Field of the Invention

The present invention relates to a locking mechanism for connecting together two parts of a chair, such as a wheelchair, and allowing at least one of the two parts to hinge and translate relative to the other. The locking mechanism may be particularly useful for attaching parts of a backrest of a chair, such as a wheelchair, and for attaching lateral/body supports (such as torso supports, shoulder supports, hip supports, or head supports) that support/stabilise an occupant of a chair to a backrest, arm rest or frame of the chair or wheelchair. The invention also relates to a backrest and to body supports that include the locking mechanism of the invention, and to a chair comprising a locking mechanism of the invention.

Background of the Invention

A chair, such as a wheelchair, for a physically disabled person often comprises a seating portion/seat base on which an occupant of the chair can sit, and a backrest that comprises one part for supporting the lumbar and thoracic regions of the torso of the occupant of the chair, often referred to as an upper back support, and that comprises another part for supporting the upper thoracic torso and shoulder girdles of the occupant, often referred to as a shoulder support. The upper back support and shoulder support are often jointly referred to as the back support or sagittal support surface.

In some forms, the chair may comprise at least two lateral supports, one on either side of the seating portion of the chair, such as lateral/torso supports to provide support forthe trunk/torso, hips supports to provide lateral support to the pelvis and thighs, shoulder supports to provide lateral support to the shoulders, and/or head supports to provide lateral support to the head of the occupant of the chair.

Where the chair occupant is severely physically disabled, a shoulder support and/or a torso support that is fixed in position can make it difficult to transferthe person to orfrom the chair and/or to adjust the position of the person/occupant in the chair. It would be useful to be able to hinge or fold the shoulder or torso supports away from the occupant of the chair when needed. It may also be useful to hinge or fold away at least a portion of the backrest to provide better access to the occupant of the chair and/or to create a more compact arrangement for storage, such as when storing a wheelchair within a vehicle. Such arrangements would be particularly useful where the chair is for a severely physically disabled occupant, such as a wheelchair for a high needs occupant. It is therefore an object of the present invention to provide a locking mechanism to attach together first and second parts of a chair in a hinged relationship, or to at least provide the public with a useful alternative to known locking mechanisms.

Summary of the Invention

In a first aspect, the invention provides a locking mechanism for a chair comprising a first part and a second part, the first and second parts being hingedly attached together, and the locking mechanism comprising: a first pivot joint that is rotatably attachable to the first part; a second pivot joint that is rotatably attachable to the second part; and at least one linking member rotatably attached to the first pivot joint and the second pivot joint. The first pivot joint or the second pivot joint is also slidably attachable to the respective first or second part. The locking mechanism is moveable between a locked position, in which movement of the at least one linking member is prevented in order to lock the first and second parts in a first position, and an unlocked position, in which the at least one linking member is free to rotate about the first and second pivot joints, and in which the slidably attached first or second pivot joint is slidably movable toward and away from the other pivot joint, to allow the first part to hinge relative to the second part.

In some forms, the first pivot joint comprises a first pivot shaft comprising a longitudinal axis about which the first pivot joint is rotatable, and the second pivot joint comprises a second pivot shaft comprising a longitudinal axis about which the second pivot joint is rotatable. The locking mechanism further comprises two linking members, each of the linking members being attachable to the first pivot shaft and to the second pivot shaft.

In some forms, the first pivot joint is rotatably attachable to the first part via a first attachment member and the second pivot joint is rotatably attached to the second part via a second attachment member. Preferably, each of the first and second attachment members comprise a pair of opposing clamping arms to clamp against the respective pivot shaft in a locked position to prevent rotation of the respective pivot shaft.

Optionally, the opposing clamping arms of each pair of clamping arms are spaced apart from each other. A hollow may be defined between the opposing clamping arms within which the respective pivot shaft is located.

Optionally, each pair of opposing clamping arms is moveable between a clamped position, in which at least one of the clamping arms moves toward the opposing clamping arm to apply a clamping force to the respective pivot shaft to clamp the respective pivot shaft in position, and an unclamped position, in which at least one of the clamping arms moves away from the opposing clamping arm to release the clamping force on the respective pivot shaft. In some forms, each pair of opposing clamping arms are connected together by at least one fastener. Tightening the at least one fastener urges at least one of the clamping arms toward the opposing clamping arm to clamp against the respective pivot shaft in the clamped position. Conversely, loosening the at least one fastener urges at least one of the clamping arms away from the opposing claiming arm to allow the respective pivot shaft to rotate in the unclamped position.

Preferably, the at least one fastener is a threaded fastener.

In some forms, at least one of the first and second attachment members slidably engages with at least one slot, located on the second part, to slide along the slot. Optionally, the at least one of the first and second attachment members comprises at least one projecting memberthat projects through the at least one slot from one surface of the second part and engages with a stopper on an opposing surface of the second part.

In some forms, the at least one projecting member comprises a fastener that extends through the opposing clamping arms of the respective attachment member and that is tightened to clamp the clamping arms against the respective pivot shaft. The fastener may be loosened to release clamping pressure from the clamping arms to allow the respective pivot shaft to rotate and to allow the respective attachment member to slide along the at least one slot provided on the second part.

In some forms, the locking mechanism further comprises a bracket that is fixedly attached to one of the first and second parts and that comprises at least one slot, and the respective attachment member engages with the at least one slot to slide along the slot.

In some forms, one of the first and second attachment members comprises a slidable bracket that is attachable to the first or second part in a sliding arrangement. Optionally, the slidable bracket comprises at least one slot, and the respective attachment member engages with the at least one slot to slide along the slot.

In some forms, each linking member is fixedly attached to the first or second pivot shaft such that rotation of the respective pivot shaft causes simultaneous rotation of the linking member.

In some forms, the locking mechanism is a self-locking mechanism and the at least one linking member comprises a locking arm and a translation arm hingedly attached together at a third pivot joint. The locking mechanism may further comprise at least one engagement member rotatably attached to the translation arm of the linking member via the first pivot joint. The locking arm may engage with the engagement member when the locking mechanism is in a locked position to lock the first and second parts in a first position and the locking arm may disengage with the engagement member in an unlocked position to allow at the first part to hinge relative to the second part. In some forms, the third pivot joint is located between first and second ends of the locking arm. Optionally, the third pivot joint is located substantially centrally between the first and second ends of the locking arm.

In some forms, the locking arm comprises an elongate member.

In some forms, a first end of the locking arm may rotate about the second pivot joint. An engagement feature may be provided at or near a second end of the locking arm to engage with the engagement member to lock the first and second parts in the first position.

In some forms, the engagement member comprises a catch and the locking arm engages with the catch to lock the first and second parts in the first position. Optionally, the catch comprises a rotating lever that is fixedly attached to the engagement member and rotatable about the first pivot joint, such that the rotating lever is rotatable in a first direction to rotate the engagement member away from the locking arm to disengage with the locking arm in an unlocked position.

In some forms, the locking mechanism of the invention further comprises a pull bar rotatably attached to the first pivot joint and fixedly attached to the engagement member, such that the pull bar is rotatable in a first direction to rotate the engagement member away from the locking arm to disengage with the locking arm in an unlocked position.

Alternatively, the locking mechanism of the invention further comprises a lever connected to a cable connected to the engagement member and that is moveable to cause the engagement member to disengage with the locking arm in an unlocked position.

In some forms, the engagement member comprises a pawl and the translation arm comprises a recess in which the pawl is received. The engagement member may be rotatable about the first pivot joint until the pawl abuts a stop within the recess.

In some forms, the pawl is located at or near a first end of the engagement member and the catch is located at or near a second end of the engagement member.

In some forms, the locking mechanism further comprises a biasing member to bias the locking mechanism to the locked position.

In some forms, the biasing member comprises a torsion spring that engages with both the engagement member and the translation arm. Preferably, the biasing member biases the engagement member toward the locked position in a self-locking arrangement.

In a second aspect, the invention provides a backrest for a chair, the backrest comprising a first part and a second part-attached together by a hinge and a locking mechanism according to the first aspect of the invention. In a third aspect, the invention provides a lateral support for a chair, the lateral support comprising a first part and a second part-attached together by a hinge and a locking mechanism according to the first aspect of the invention.

In a fourth aspect, the invention provides a chair comprising a backrest or a lateral support according to the second or third aspect of the invention.

In a fifth aspect, the invention provides a locking mechanism for a chair comprising a first part and a second part, the first and second parts being hingedly attached together, and the locking mechanism comprising: a first pivot joint that is rotatably attachable to the first part; a second pivot joint that is rotatably and slidably attachable to the second part; and at least one linking member rotatably attached to the first pivot joint and the second pivot joint. The locking mechanism is moveable between a locked position, in which movement of the at least one linking member is prevented, and an unlocked position, in which the at least one linking member is free to rotate about the first and second pivot joints, and in which the second pivot joints is slidably movable toward and away from the first pivot joint.

In some forms, the locking mechanism is a self-locking mechanism that automatically self-locks when in the first position.

In some forms, the at least one linking arm comprises a jointed arm comprising a locking arm and a translation arm hingedly attached together at a third pivot joint; at least one engagement member is rotatably attached to the translation arm via the first pivot joint; and the locking arm engages with the engagement member when the locking mechanism is in a locked position.

In a sixth aspect, the invention provides a chair, wheelchair, backrest, or lateral support comprising a locking mechanism of the fifth aspect of the invention.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements, or features. Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated within this specification as if individually described.

The term 'comprising' as used in this specification (including the claims) means 'consisting at least in part of. When interpreting statements in this specification and claims that include the term 'comprising', other features besides those prefaced by this term can also be present. Related terms such as 'comprise' and 'comprises' are to be interpreted in a similar manner.

It is intended that reference to a range of numbers disclosed in this specification (for example, 1 to 10) also incorporates reference to all rational numbers within that range and any range of rational numbers within that range (for example, 1 to 6, 1.5 to 5.5 and 3.1 to 10). Therefore, all sub-ranges of all ranges expressly disclosed in this specification are hereby expressly disclosed.

As used in this specification, the term '(s)' following a noun means the plural and/or singular form of that noun.

As used in this specification, the term 'and/or' means 'and' or 'or', or where the context allows, both.

Brief Description of the Drawings

Figure 1 is an isometric rear view showing one form of multi-part backrest for a wheelchair in which each part of the backrest is connected to an adjacent part by a lockable locking mechanism according to one form of the invention;

Figure 2 is a side view of another form of backrest for a chair in which the shoulder support is connected to the adjacent upper back support by one form of self-locking mechanism according to the invention and the upper back support is connected to the adjacent lower back support by a lockable locking mechanism of the invention and in which both the shoulder support and lower back support are hinged forward in a first position to support a chair occupant with a substantially C- shaped spine;

Figure 3 is a side view of the backrest and locking mechanisms of Figure 2, but in which the lower back support is hinged rearward to support a person with a substantially S-shaped spine;

Figure 4 is a side view of the backrest and locking mechanisms of Figure 2, but in which both the shoulder support and the lower back support are hinged rearward to support a person with a substantially arched spine;

Figure 4a is a side view of another form of locking mechanism in which the locking/clamping member is configured to allow for discrete positioning of the pivot shaft and therefore of the first part relative to the second part;

Figure 5 is an isometric view from the rear showing one form of backrest with one form of self-locking mechanism according to the invention;

Figure 5a is an isometric view from the rear of another form of backrest in which a locking mechanism of the invention is slidably attached to a first part and to a second part of a backrest;

Figure 6 is a side view of the backrest of Figure 5 in which both the backrest is in a first position and the self-locking mechanism is in a locked position;

Figure 7 is a semi-exploded isometric view showing one form of biasing member that engages with an engagement member and a translation arm of the self-locking mechanism to bias the locking mechanism, and therefore the first and second parts of the backrest, to the locked position; Figure 7a is a cross-sectional view of one form of self-locking mechanism of the invention, showing a biasing member, in the form of a torsion spring, engaging with an engagement member and a translation arm;

Figure 8 is an isometric rear view of one form of backrest comprising a self-locking mechanism comprising a rotating lever to unlock the mechanism;

Figure 9 is an isometric rear view of one form of backrest comprising a self-locking mechanism comprising a pull handle to unlock the mechanism;

Figure 10 is an isometric rear view of one form of backrest comprising a self-locking mechanism comprising a lever and cable arrangement to unlock the mechanism;

Figure 11 is an enlarged rearview of the first and second parts of the backrest and self-locking mechanism shown in Figure 6;

Figure 12 is an enlarged side view of the first and second parts of the backrest and self-locking mechanism shown in Figure 6;

Figure 12a is an enlarged isometric rearview of the self-locking mechanism shown in Figure

12 in the locked position;

Figure 13 is a side view of the backrest and self-locking mechanism of Figure 6 and in which the engagement member has been pulled upwardly to disengage with the locking arm and release the locking mechanism;

Figure 13a is an enlarged isometric rearview of the self-locking mechanism shown in Figure

13 at the point at which the engagement member and locking arm disengage to unlock the locking mechanism and to allow the first part of the backrest to hinge rearwardly relative to the second part;

Figure 14 is a side view of the backrest and self-locking mechanism of Figure 13 and in which the locking arm has fully disengaged with the engagement member, releasing the locking mechanism and allowing the first part of the backrest to hinge rearwardly relative to the second part of the backrest;

Figure 14a is an enlarged isometric rear view of the self-locking mechanism shown in Figure

14, showing the locking mechanism in the unlocked, collapsed position and showing the backrest in the hinged position;

Figure 15 is an enlarged side view of the backrest and self-locking mechanism of Figure 14 and in which the second part of the backrest has been pushed slightly forward to cause the distal, second end of the locking arm to rotate and abut the engagement member;

Figure 15a is an enlarged isometric rear view of the self-locking mechanism shown in Figure

15, showing the locking arm of the locking mechanism pressing against the catch of the engagement arm as the locking mechanism moves towards the locked position; Figure 16 is a side view of the backrest and self-locking mechanism of Figure 15 and in which the second part of the backrest has been pushed further forward, causing the distal end of the locking arm to press against and slide against the catch of the engagement member, pushing the engagement member overthe distal end of the locking arm, as the locking mechanism moves toward the locked position;

Figure 16a is an enlarged isometric rearview of the self-locking mechanism shown in Figure 16, showing the distal end of the locking arm pushing against the catch and pushing the catch upwardly as the locking arm slides beneath the catch;

Figure 17 is a side view of the backrest and self-locking mechanism of Figure 16 and an enlarged view of Figure 12, in which the first part has been pushed forward to the first position, pulling the locking arm closer to the rear surface of the backrest, so that the locking arm is trapped between the catch and the first pivot joint and presses rearwardly against the catch so that the engagement feature of the locking arm engages with catch the in the locked position;

Figure 18 is a rear view of one form of self-locking mechanism according to the invention, the locking mechanism comprising two linkage bodies, each comprising a pair of locking arms, linking members and engagement members, and in which the two linkage bodies are connected together by a shaft that extends across the bodies and that forms a catch for the locking mechanism and also forms a gripping member for a user to lift the catch away from the locking arms;

Figure 19 is an isometric rear view of the self-locking mechanism of Figure 18 and in which the locking mechanism is in the locked position;

Figure 20 is an isometric rear view of one form of backrest comprising lateral shoulder supports, lateral torso supports, and lateral pelvic and thigh supports, each comprising a self-locking mechanism of the invention and also showing a lockable locking mechanism between the upper back support and the lower back support of the backrest;

Figure 21 is a top view of a backrest comprising a lateral support on either side of the backrest, the lateral supports being locked in a first position in which the support member of each support is substantially aligned with the first portion of the bracket of each lateral support;

Figure 22 is a top view of the backrest of Figure 21 in which the lateral supports are locked in a first position, in which each support is hinged rearwardly relative to the first portion of the support bracket;

Figure 23 is a top view of the backrest of Figure 21 in which one of the lateral supports is locked in a first position, in which the support is hinged forward relative to the first portion of the support bracket, and the other lateral support is in an unlocked, second position; Figure 24 is an isometric view of a wheelchair having a backrest bearing locking mechanisms of the invention; and

Figure 25 is an isometric view of a chair having a backrest bearing locking mechanisms of the invention.

Detailed Description of Preferred Embodiments of the Invention

As shown in Figures 1 to 25, the present invention provides a locking mechanism 400, 400' for locking and unlocking the angular position of a first part of a chair 2000 relative to a second part of the chair 2000, where the first and second parts are hingedly attached together by a hinge and by the locking mechanism 400, 400'. The locking mechanism of the present invention comprises different embodiments, including a physically lockable locking mechanism 400 and a self-locking mechanism 400'.

In some forms, the locking mechanism 400, 400' of the invention is for use with a multi-part backrest 1000 for a chair 2000, such as a wheelchair, the backrest 1000 comprising at least two parts that are hingedly attached together. In other forms, the locking mechanism 400, 400' of the invention may be used with a multi-part lateral support 500 to laterally support the head, shoulder region, torso/trunk region, pelvic and thigh region, or lower leg region of an occupant of a chair 2000. Typically, the locking mechanism 400, 400' will be used with a wheelchair, a commode chair, or any other chair that provides customised postural support to the occupant of the chair. Such chairs may be specially configured to support the posture of an occupant with high physical needs, such as a severely physically disabled an occupant with Spina bifida for example.

The invention will first be described in relation to use with a multi-part backrest 1000 and will then be described in relation to use with a multi-part lateral support 500. The use of the locking mechanism 400, 400' of the invention with a multi-part backrest 1000 and a multi-part lateral support 500 are illustrative only. It is envisaged that the locking mechanism 400, 400' may be used to attach any two parts of a chair 2000 together in a hinged arrangement in which the angular position of at least one of the two parts needs to be adjustable and locked and unlocked relative to the other of the two parts of the chair. The present invention also relates to a backrest, a lateral support, and a chair (such as a wheelchair) comprising the locking mechanism of the invention.

Where the locking mechanism of the invention is used with a multi-part backrest for a chair, the locking mechanism attaches to two adjacent first and second parts of the backrest that are connected by a hinge. The locking mechanism is configured to lock the first and second parts together in a locked, first position, and to unlock the two parts to allow the first part to hinge/rotate relative to the second part to adopt a second position. Typically, the second position is one in which the first part is rotated away from the second part to allow better access to the occupant of the chair or to help the occupant enter or exit the chair for example. When improved access to the occupant is no longer required, the two parts can be returned to the first position where the two parts are locked in position, preferably automatically and without a user, such as a caregiver, needing to make adjustments to reach the first position.

The first position is the preferred default / return position. When the locking mechanism 400, 400' is used with a backrest, the first position may be any position in which the two parts of the backrest are arranged to usefully or best support the posture of an occupant of the chair in a seated position. The embodiment of the invention that relates to a self-locking mechanism is particularly useful because the mechanism may be set to self-lock only when the first and second parts are in the first position. Therefore, even after releasing the locking mechanism and moving the first part out of the way in a second position, a user can rotate the first part to return to the first position and the locking mechanism will automatically lock the first and second parts in the first position without requiring a user, such as a caregiver, to physically adjust the resulting angle or to lock the two parts together.

The first position is therefore a selected position that denotes the angular position of the first and second parts of the article relative to each other when in the locked position. The selected first position of the first and second parts may vary between occupants of a chair, depending on the postural support needs of the particular occupant. In effect, the first position is adjustable to meet the postural support needs of the occupant of the chair. For example, in relation to a backrest, the first position may be one in which the first and second parts of the backrest are substantially aligned to provide a substantially flat backrest. In this form, the angle between the first and second parts is about 180° (a straight angle). In another form, the first position may be one in which one of the parts is hinged forward relative to the other part to provide an acute angle or an obtuse angle of between 0° and 180°. In other forms, the first position may be one in which the first part is hinged rearwardly relative to the second part to provide the front surface of the backrest with a reflex angle of between 180° and 360°. The locking mechanism of the invention is useful in that it allows a multi-part backrest and a lateral support to be readily adjusted to meet the postural support needs of an occupant of the chair without needing to create a one-off customised chair.

Preferred features of the locking mechanism 400, 400' of the invention will now be described. By way of exemplification only the features of the locking mechanism 400, 400' are described when used to attach the first and second parts of a backrest together, and in which the first part may hinge relative to the second part and may be locked in position relative to the second part. Flowever, it should be appreciated that these features of the locking mechanism 400, 400' also apply when the locking mechanism is used to attach first and second parts of a lateral support arrangement together, in which the first part may hinge relative to the second part and may be locked in position relative to the second part, or when used to attach other first and second parts of a chair together.

Figures 1 to 19 show some forms of locking mechanism 400, 400' of the invention that may be used with a multi-part backrest of a chair, such as a wheelchair. The multi-part backrest 1000 comprises at least two parts, a first part and a second part, that are hingedly attached together by a hinge 250 and by a locking mechanism 400, 400' according to the invention. The hinge 250 allows at least the first part to hinge/rotate forwardly or rearwardly from the second part, so that the angle between the first and second parts can be adjusted to account for the length and curvature of the occupant's spine.

The backrest 1000 shown is a three-part backrest that comprises a shoulder support 100, an upper back support 200, and a lower back support 300. The shoulder support 100 supports the shoulder girdle of the chair occupant, the upper back support 200 supports the torso of the occupant, and the lower back support 300 supports the pelvis and sacrum of the occupant.

Adjacent parts of the backrest that are hinged together may be referred to herein as a 'first part' or a 'second part', depending on the orientation of the locking mechanism of the invention. In effect, the first part is arranged to hinge / rotate relative to the second part, which remains in a fixed position. For example, in Figure 1, the shoulder support 100 hinges /rotates from the upper back support 200, which remains in a fixed position. Therefore, the shoulder support 100 may be considered to be the first part and the upper back support 200 may be considered to be the second part. That is to say, the first part is capable of rotation, while the second part remains in a fixed position. If the arrangement was reversed so that the upper back support 200 hinged/rotated from the shoulder support 100 then the upper back support 200 may be considered to be the first part and the shoulder support 100 may be considered to be the second part. Similarly, in the arrangement illustrated in Figure 1, the lower back support 300 hinges/rotates from the upper back support 200, so in this arrangement, the lower back support 300 may be considered to be the first part and the upper back support 200 may be considered to be the second part. If the arrangement was reversed so that the upper back support 200 hinges/ rotates from the lower back support 300 then the upper back support 200 may be considered to be the first part and the lower back support 300 may be considered to be the second part.

In some forms, as shown in Figures 1 to 19, the locking mechanism 400, 400' of the invention comprises a first pivot joint 440 that is rotatably attachable to the first part of the backrest, and a second pivot joint 460 that is rotatably attachable to the second part. At least one of the first and second joints 440, 460 is slidable toward and away from the other pivot joint 440, 460 to enable rotation of one of the first and second parts relative to the other. In the embodiments shown in Figures 1 to 19, the second pivot joint 460 is slidable along a portion of the second part. For example, as shown in Figure 1, the locking mechanism 400 may comprise a first pivot joint 440 that is rotatably attached to the shoulder support 100 (the first part) and a second pivot joint 460 that is rotatably and slidably attached to the upper back support 200 (the second part). In other forms, the locking mechanism 400 may comprise a first pivot joint 440 that is rotatably attached to the lower back support 300 (the first part) and a second pivot joint 460 that is rotatably and slidably attached to the upper back support 200 (the second part). In another form, as shown in Figure 5a, the locking mechanism 400 may comprise a first pivot joint 440 that is rotatably and slidably attached to the lower back support 300 (the first part) and a second pivot joint 460 that is rotatably and slidably attached to the upper back support 200 (the second part). In yet other forms, as shown in Figures 20 to 23, the first pivot joint 440 is rotatably and slidably attached to the support member of a lateral support (the first part) and the second pivot joint 460 is rotatably attached to the attachment bracket of the lateral support (the second part).

In some forms, as shown in Figures 1 to 5, the first pivot joint 440 is attached to the first part of the backrest 1000 at a fixed location and the second pivot joint 460 is slidably attached to the second part of the backrest such that the second pivot joint 460 is slidable toward and away from the first pivot joint 440.

Both the first and second first pivot joints 440, 460 are configured to adopt a locked position and an unlocked position. In some forms, as shown in the locking mechanism 400 of Figure 1, when both pivot joints 440, 460 are in the locked position, each pivot joint is substantially immovable and the first part of the backrest is unable to hinge relative to the second part. When both the first and second pivot joints 440, 460 are in the unlocked position, each pivot joint 440, 460 is rotatable and the second pivot joint 460 is slidable toward and away from the first pivot joint 440 to allow the first part of the backrest to hinge/rotate relative to the second part.

In other forms, as shown in Figures 20 to 23, the first pivot joint 440 is slidably attached to the first part to move toward and away from the second pivot joint 460, which is attached to the second part at a fixed location. Again, in this arrangement, the first part may hinge/rotate relative to the second part. In these forms, the features and operation of the locking mechanism are the same as those shown in Figures 1 to 19, except that instead of the second pivot joint 460 being slidably attached to the second part, the first pivot joint is slidably attached to the first part.

In yet other forms, as shown in Figure 5a, the first pivot joint 440 is slidably attached to the first part (in this case lower backrest 300) and the second pivot joint 460 is slidably attached to the second part (in this case central backrest 200) so that each of the first and second pivot joints are movable toward and away from the other.

In some forms, the first pivot joint 440 comprises a first pivot shaft 441 rotatably attached or attachable to the first part of the backrest 1000 by a first attachment member 445.

The first attachment member 445 may comprise a first mounting block, which is attachable to a rear surface of the first part of the backrest at a fixed location.

The first pivot shaft 441 may be at least partially held within the first attachment member 445, such as within an opening, such as a channel, of the first attachment member. The first attachment member 445 is configured to hold the shaft 441 in a locked position and to release the shaft 441 in an unlocked position. The first pivot shaft 441 comprises a longitudinal axis about which the first pivot shaft 441 (and therefore the first pivot joint 440) is rotatable in the unlocked position.

In some forms, the first attachment member 445 comprises a first clamping member configured to hold the first pivot shaft 441 in the locked position and to allow the shaft 441 to rotate about its longitudinal axis in the unlocked position. The first clamping member may comprise at least one clamping arm that moves toward and away from an opposing surface to clamp the first pivot shaft 441 in an opening, such as a channel, in between. In some forms, the first clamping member comprises a first pair of clamping arms 443 that are spaced apart from each other in an opposing arrangement to form an opening in between. The clamping arms 443 are moveable between a clamped/locked position and an unclamped/unlocked position. In the clamped position, at least one or both of the clamping arms 443 moves toward the opposing clamping arm to apply a clamping force to the first pivot shaft 441 to clamp against the first pivot shaft 440 in order to prevent rotation of the first pivot shaft 441 and to hold the first pivot shaft 440 in position and to prevent the first pivot joint from sliding along the first part (in embodiments where the first pivot joint is both rotatably and slidably attached to the first part). In the unlocked position, at least one of the clamping arms 443 moves away from the opposing clamping arm to release the clamping force on the first pivot shaft 440 so that the first pivot shaft may freely rotate between the clamping arms 443.

The first pivot shaft 441 may be at least partially held between the first clamping arms 443 and may extend in the direction of its longitudinal axis. In some forms, the first pivot shaft 441 is located within a hollow defined between the opposing clamping arms 443 to prevent the shaft 441 falling out. In some forms, the hollow comprises a channel formed by curved interior surfaces of the clamping arms 443.

In some forms, the first clamping arms 443 may comprise a pair of generally u-shaped arms that are connected together near the ends of the 'U' (i.e. near the distal ends of each clamping arm). In some forms, the ends of the U-shaped claiming arms are joined together with a cross-piece 443a, as shown in Figure 1. Preferably, the first clamping arms 443 are connected together by at least one fastener 50 or by a pair of threaded fasteners 50, such as screws or bolts or the like. For example, the first clamping arms 443 may be attached together at a first end/side and each of the clamping arms 443 may have a distal end/side that engages with the fastener(s) 50. Tightening the fastener(s) 50 urges at least one of the clamping arms 443 toward the opposing clamping arm to clamp against the first pivot shaft 441 in the clamped/locked position. Loosening the fastener(s) 50 urges at least one of the clamping arms 443 away from the opposing claiming arm to allow the first pivot shaft 440 to rotate in the unclamped/unlocked position.

In some forms, the second pivot joint 460 comprises a second pivot shaft 461 comprising a longitudinal axis about which the second pivot shaft 461 (and therefore the second pivot joint 460) is rotatable.

In some forms, the second pivot joint 460 is rotatably and slidably attached or attachable to the second part by a second attachment member 465. The second attachment member 465 may comprise a first mounting block, which is attachable to a rear surface of the second part of the backrest.

The second attachment member 465 may be slidably attached to the second part such that the second attachment member 465 is moveable along at least a portion of the second part of the backrest in a direction that is substantially perpendicular to the second pivot shaft 461. The second pivot joint 460 is therefore both rotatable and slidable along at least a portion of the second part of the backrest. In the embodiments 400, 400' shown in Figures 1 and 5, the second pivot shaft 461 lies substantially horizontally and the second attachment member 465 is slidable in a substantially vertical direction.

The second pivot joint 460 may be configured to adopt a locked position and an unlocked position. For example, the second pivot shaft 461 may be at least partially held within in an opening, such as a channel, of the second attachment member 465, which is configured to hold the shaft 461 in a locked position and to release the shaft 461 in an unlocked position. The shaft 461 extends in the direction of its longitudinal axis.

In some forms, the second attachment member 465 comprises a second clamping member configured to hold the second pivot shaft 461 in the locked position and to allow the shaft 461 to rotate about its longitudinal axis in the unlocked position. The second clamping member may comprise at least one clamping arm that moves toward and away from an opposing surface to clamp/lock the second pivot shaft 461 in an opening, such as a channel, in between.

In some forms, the second clamping member comprises a second pair of clamping arms 463 that are spaced apart from each other in an opposing arrangement to form an opening in between. The clamping arms 463 are moveable between a clamped/locked position and an unclamped/unlocked position. In the clamped/locked position, at least one or both of the clamping arms 463 moves toward the opposing clamping arm to apply a clamping force to the second pivot shaft 461 to clamp against the second pivot shaft 461 in orderto prevent rotation of the second pivot shaft 461 and to hold the second pivot shaft 461 in position and to prevent the second pivot joint from sliding along the second part (where the second pivot joint is both rotatably and slidably attached to the second part). In the unlocked position, at least one of the clamping arms 463 moves away from the opposing clamping arm to release the clamping force on the second pivot shaft 461 so that the shaft 461 may freely rotate between the clamping arms 463 and to allow the second pivot joint to slide along the second part.

The second pivot shaft 461 may be at least partially held between the second clamping arms 463 to prevent the second pivot shaft 461 from falling out of the second attachment member 465. In some forms, the second pivot shaft 461 is located within a hollow defined between the opposing clamping arms 463. In some forms, the hollow comprises a channel formed by curved interior surfaces of the clamping arms 463.

In some forms, the second clamping arms 463 may comprise a pair of generally u-shaped arms that are connected together near the ends of the 'U' (i.e. near the distal ends of each clamping arm). In some forms, the ends of the U-shaped claiming arms are joined together with a cross-piece 463a, as shown in Figure 1. Preferably, the second clamping arms 463 are connected together by at least one fastener 50, or by a pair of threaded fasteners 50, such as screws or bolts or the like. For example, the second clamping arms 463 may be attached together at a first end/side and each of the clamping arms 463 may have a distal end/side that engages with the fastener(s) 50. Tightening the fastener(s) 50 urges at least one of the clamping arms 463 toward the opposing clamping arm to clamp against the second pivot shaft 461 in the clamped/locked position. Loosening the fastener(s) 50 urges at least one of the clamping arms 463 away from the opposing clamping arm to allow the second pivot shaft 461 to rotate in the unclamped/unlocked position.

In some forms, as shown in Figure 4a, the first or second clamping member comprises a pair of clamping arms 443', 463' that each comprise an inner surface comprising a series of channels 444 for receiving the first or second pivot shaft 441, 461 therein. The pivot shaft 441, 461 can be moved between the clamping arms 443', 463' until it reaches the desired position, at which point a fastener passing through the clamping arms 443', 463' is secured to clamp the arms 443', 463' against the pivot shaft 441, 461 to lock the pivot shaft 441, 461 in position. In this form, the pivot shaft 441, 461 can be clamped in discrete positions to adjust the angle between the first and second parts. In some forms, the second part of the backrest comprises at least one angle adjustment slot 700 that extends substantially perpendicular to the first and second pivot shafts 441, 461. For example, the angle adjustment slot 700 may extend substantially vertically along a portion of the second part of the backrest, so that the second attachment member 465 can slide up and down the slot 700. In preferred forms, the second part of the backrest comprises at least two substantially vertically extending angle adjustment slots 700. The second attachment member 465 engages with the angle adjustment slot(s) 700 and is moveable along the length of the slot(s) 700 in the unlocked position.

In some forms, the second attachment member 465 comprises at least one engagement element that slidably engages with the slot(s) 700 to attach the second attachment member 465 to the second part and to allow the second attachment member to slide along the slot(s) 700. In some forms, the engagement element comprises at least one projecting member, such as a fastener 50, that projects through the at least one slot 700, from one surface of the second part, and engages with a stopper on an opposing surface of the second part. By sliding the second attachment member 465 along the angle adjustment slot 700, the second pivot joint 460 is caused to slide toward and away from the first pivot joint 440. The second attachment member 465 may be slid along the length of the respective slot 700' until the desired angle between the first and second parts of the backrest is reached, at which point the engagement element 50 is fastened to the second part to hold the second attachment member 465 and second pivot joint 460 in position. Preferably, the engagement element 50 is the same fastener that clamps the second clamping arms 463 against the second pivot shaft 461, so that by tightening the fastener 50, the pivot shaft 461 is held in place and the second attachment member 465 and second clamping arms 463 are prevented from sliding along the angle adjustment slot 700.

In some forms, the second attachment member 465 comprises a bracket 490 that is attached or attachable to a rear surface of the second part of the backrest in a fixed or sliding arrangement. In some forms, the bracket 490 comprises one or more angle adjustment slots 700' for engaging with the second attachment member 465. For example, where the bracket 490 is fixedly attached to the second part, the second attachment member 465 may slide along one or more angle adjustment slots 700' provided on the bracket 490. In some forms, the slidable bracket 490 may comprise at least one angle adjustment slot 700' that lies substantially perpendicular to the first and second pivot shafts 441, 461 and along which the second attachment member 465, and therefore the second pivot joint 460, can slide toward and away from the first pivot joint 440. Where the locking mechanism is used with a backrest, the bracket 490 may comprise at least two substantially vertically extending angle adjustment slots 700' and the second attachment member 465 engages with the angle adjustment slots 700' and is moveable alongthe length of the slots 700' in the unlocked position. The second attachment member 465 may comprise at least one engagement element that engages with the at least one slot 700' of the bracket to slidingly attach the second attachment member 465 to the bracket 490.

In some forms, where the bracket 490 is attached to the second part in a sliding arrangement, the slidable bracket 490 may slide along one or more angle adjustment slots 700 provided on the second part, so as to slide relative to the second part. The slot(s) 700 may extend substantially perpendicular to the first and second pivot shafts 441, 461. In these forms, the slidable bracket 490 is slidably attachable to the second part and comprises at least one engagement element that slidably engages with at least one angle adjustment slot 700 to slide along the slot 700 and attach the second attachment member 465 to the second part. In some forms, the second part comprises at least two angle adjustment slots 700 and the slidable bracket 490 engages with each of the angle adjustment slots 700. The slidable bracket 490 is moveable along the length of the slots 700 in the unlocked position to allow the second pivot joint 460 to slide toward and away from the first pivot joint 440. In some forms, the at least one engagement element may comprise at least one projecting member, such as a fastener 50, that projects through the at least one slot 700 from one surface of the second part and engages with a stopper on an opposing surface of the second part.

In other forms, the slidable bracket 490 comprises at least one angle adjustment slot 700' and the second part comprises at least one angle adjustment slot 700, each slot 700, 700' extending substantially perpendicular to the first and second pivot shafts 441, 461. The slidable bracket 490 may be slidably attachable to the second part by a first engagement element that slidably engages with an angle adjustment slot 700 located on the second part, as described above. The second attachment member 465 may be slidably attachable to the slidable bracket 490 by a second engagement element that slidably engages with the angle adjustment slot 700' of the slidable bracket 490, as described above. Therefore, the slidable bracket 490 is slidable along the slot(s) 700 relative to the second part, and the second attachment member 465 is slidable along the slot(s) 700' relative to the slidable bracket 490. This arrangement allows for the first and second parts to be distanced from each other to a greater extent than if only the slidable bracket 490 or only the second part comprises an angle adjustment slot.

In some forms, the slidable bracket 490 is a substantially plate-like member.

In some forms, the hinge 250 attaching the first and second parts is located on the slidable bracket 490. For example, the first part may hinge from the slidable bracket via a hinge 250, as shown in Figures 2 to 4 and 6, and the slidable bracket 490 may slide relative to the second part. The slidable bracket 490 allows for the distance between the first and second parts of a backrest to be adjusted for people of different heights and torso contours.

In other embodiments, the first attachment member 445 and the first pivot joint 440 may be slidable relative to the first part of the backrest, as shown in Figure 5a. Optionally, the first attachment member 445 may be slidably attached to the first part or to a bracket (such as bracket 490) attached to the first part in a fixed or sliding arrangement, as described above. In other forms, the first attachment member 445 may be fixedly attached to a bracket, which is slidably attached to the first part of the backrest, as described above.

To lock one or both pivot joints 440, 460, it is important that the locking mechanism prevents each joint 440, 460 from sliding relative to the attached first or second part. It is preferred, but not essential, that the pivot shaft 441, 461 of each joint 440, 460 is also prevented from rotating in order to reduce slop in the connection.

As shown in Figures 1, 5 and 6, for example, the locking mechanism 400, 400' also comprises at least one linking member 405, 405' that is rotatably attached to both the first pivot joint 440 and the second pivot joint 460, to connect the first and second joints 440, 460 together.

In some forms, the linking member 405, 405' may comprise first and second ends. The first pivot joint 440 may be attached to the first end of the linking member 405, 405' and the second pivot joint 460 may be attached to the second end of the linking member 405, 405'.

In some forms, as shown in Figure 1, the linking member 405 of the physically lockable locking mechanism 400 is curved or angled to provide a concave or hollow region facing toward a rear surface of the first and second parts. The forward-facing curve or angle of the linking member 405 allows the first part to hinge forward relative to the second part. The extent to which the first part can hinge forward may be determined by the location of the second part relative to the first part, as the second part will, at some point, obstruct further forward rotation of the first part.

Where the locking mechanism is a physically lockable locking mechanism 400 (i.e. where a user, such as a caregiver, is required to manually lock the locking mechanism), as shown in Figure 1, the linking member 405 may comprise an abutment stop 406 located on a front surface of the linking member 405. The abutment stop 406 contacts a rear surface of the second part, such as a rear surface of the second part 200 of the backrest, when the linking member is at its maximum point of forward rotation. In this way, the abutment stop 406 prevents over-rotation of the first part of the backrest, which could otherwise cause damage to the backrest, the hinge 250, or the locking mechanism 400. The curved or angled linking member 405 and abutment stop 406 are not necessary where the locking mechanism is a self-locking mechanism 400', as will be described later in this specification. In some forms, as shown in Figures 1, 5 and 6 for example, the locking mechanism 400, 400' comprises two linking members 405. Each of the linking members is attachable to the first pivot shaft 441 and to the second pivot shaft 461. Optionally, one end of each linking member 405 is attached at or near each end of the first pivot shaft 441 and the other end of each linking member 405 is attached at or near each end of the second pivot shaft 461, so that the two linking members 405 extend between the first and second shafts 441, 461 at either end of the shafts 441, 461. In some forms, each linking member 405 is fixedly attached to at least one of the pivot shafts 441, 461 such that rotation of the respective pivot shaft 441, 461 causes simultaneous rotation of the linking members 405 and vice versa. For example, each linking member 405 may be fixedly attached to a respective end of the second pivot shaft 461.

The locking mechanism 400, 400' is moveable between a locked position and an unlocked position. In the locked position, movement of each linking member 405 is prevented in order to lock the first and second parts in a first position, such as by locking the angular position of the lower back support 300 relative to the upper back support 200 or by locking the angular position of the shoulder support 100 relative to the upper back support 200. In the unlocked position, each linking member 405 is free to rotate about the first and second pivot joints 440, 460, and at least one of the pivot joints 440, 460 is slidable toward and away from the other pivot joint 440,460, to allow the first part to hinge relative to the second part.

Operation of the lockable locking mechanism 400 will now be described according to an embodiment in which the second pivot joint 460 and second attachment member 465 of the mechanism 400 is slidable along the second part of a backrest. Flowever, in embodiments where the first pivot joint 440 and first attachment member 445 are slidable along the first part of the backrest, or both the first and second pivot joints 440, 460 and first and second attachments members 445, 465 are slidable along the respective first and second parts of the backrest, the locking mechanism will operate in the same way, except that the sliding components are different.

To hinge the first part of the backrest relative to the second part, when the first and second parts are connected by a lockable locking mechanism 400 of the invention, the fasteners 50 of the first and second attachment members 445, 465 are loosened to the unlocked position. The first part (such as the lower back support 300) is then angled forward or backward relative to the second part (such as the upper back support 200), by rotating about the hinge 250 to adopt the desired first position. As the first part (300) rotates, the first pivot shaft 441 rotates within the first attachment member 445, causing the linking member(s) 405 to rotate simultaneously in the same direction. The linking members 405 are also attached to the second pivot joint 460 and, depending on the desired angle between the first and second parts, the linking member(s) 405 may pull or push on the second pivot joint 460 to cause the second attachment member 465 (and therefore the second pivot joint 460) to slide up or down along at least one of the angle adjustment slots 700, 700' to accommodate the desired angle.

For example, when the first part (300) is rotated forward to adopt the maximum forward facing position, as shown in Figures 2 and 3, the abutment stop 406 may abut the rear surface of the backrest 1000 or the slidable bracket 490 and the second pivot joint 460 may be located at or near a bottom end of the angle adjustment slot(s) 700, 700'. Conversely, as shown in Figure 4, when the first part (300) is rotated rearward to adopt the maximum rearward facing position, the abutment stop 406 is spaced from the rear surface of the second part and the second pivot joint 460 is slid upward along at least one of the angle adjustment slot(s) 700, 700' to accommodate the rearward angled position. In this way, the locking mechanism 400, 400' translates and rotates relative to the first and second parts of the backrest 1000.

Once the desired angle between the first and second parts is reached, the fasteners 50 of the second attachment member 465 are tightened to prevent the second attachment member from sliding along the angle adjustment slot(s) and optionally also to prevent rotation of the second pivot joint 460. The fasteners 50 of the first attachment member 445 are also optionally tightened to prevent rotation of the first pivot joint 440. The locking mechanism 400 is now locked in the first position.

The locking mechanism 400 may also be readily released to an unlocked position so that the first part can be rotated to a second position, in which the first part is rotated rearwardly relative to the second part. To release/unlock the locking mechanism 400, the fasteners 50 of the first and second attachment members 445, 465 are loosened to allow the linking arm(s) 405 to rotate about the first and second pivot joints 440, 460 as the first part is rotated rearwardly, as shown in Figure 4.

In some forms, as shown in Figures 5 and 6 to 23, the locking mechanism of the invention is a self-locking mechanism 400', which comprises a first pivot joint 440 and a second pivot joint 460 to attach together first and second parts of an article (such as a backrest or to attach a lateral support to a backrest, seat base, or chair frame for example), as described above. The self-locking mechanism 400' also comprises at least one linking member 405', and preferably comprises at least two linking members 405' in a spaced apart configuration along the length of the respective pivot shaft 441, 461, again as described above. Flowever, the self-locking mechanism 400' differs from the physically lockable locking mechanism 400 in that the at least one linking member 405' of the self-locking mechanism 400' is a jointed linking member 405'. In some forms, the linking member 405' comprises a locking arm 410 and a translation arm 420 that are hingedly attached together at a third pivot joint 450. The self-locking mechanism 400' also comprises at least one engagement member 430 that is rotatably attached to the translation arm 420 of the linking member 405' via the first pivot joint 440. In this arrangement, both the translation arm 420 and the engagement member 430 are rotatable about the first pivot joint 440.

In some forms, the locking arm 410 is hingedly attached to or attachable to the second part of the backrest, via the second pivot joint 460. In some forms, the locking arm 410 comprises an elongate member comprising a first end 410a and a second, distal end 410b, as shown in Figure 7a. The first end 410a of the locking arm 410 is rotatably attached to the second pivot joint 460, such that the first end 410a of the locking arm 410 is rotatable about the second pivot joint 460.

The translation arm 420 is rotatable about the first pivot joint 440 and the third pivot joint 450. The third pivot joint 450 is located between the first and second ends of the locking arm 410. In some forms, the third pivot joint 450 is located substantially centrally between the first and second ends 410a, 410b. In other forms, the third pivot joint 450 is located closer to one end of the locking arm 410, such as closer to the second end 410b of the locking arm 410.

In some forms, each translation arm 420 comprises an elongate member comprising a first end 420a and a second end 420b. The translation arm 420 may be attached to the third pivot joint 450 at or near its second end 420b to rotate about its second end 420b. The translation arm 420 may be attached to the first pivot joint 440 at or near the first end 420a so that the translation arm is also rotatable about its first end 420a.

The locking arm 410 engages with the engagement member 430 when the self-locking mechanism 400' is in a locked position to lock the first and second parts in a first position. The locking arm 410 disengages with the engagement member 430 in an unlocked position to allow the first part to hinge relative to the second part.

The rotatable translation member 420 connects the locking arm 410 with the first pivot joint 440 so that rotational movement of the locking arm 410 translates to rotational movement of the first part of the backrest, when the locking mechanism 400' is unlocked. In this arrangement, the translation arm 420 transfers movement between the locking arm 410 and the first part of the backrest.

In some forms, the locking arm 410 comprises an engagement feature 415, as shown in Figure 12a, which may be provided at or near the second, distal end 410b of the locking arm 410, to engage with the engagement member 430. The engagement feature 415 may be any suitable feature that engages with the engagement member 430 to lock the first and second parts of the backrest in a first position and that disengages with the engagement member 430 to allow the first part to hinge relative to the second part. In some forms, the engagement feature 415 comprises a hooked portion, such as a scalloped edge or recess, that engages with the engagement member 430 in the locked position to lock the first and second parts in the first position.

In some forms, the engagement member 430 comprises a first end 430a and a second, distal end 430b, as shown in Figure 12. The engagement member 430 may be attached to the first pivot joint 440 at or near its first end 430a. In some forms, the engagement member 430 may rotate about the first pivot joint 440 so that the distal end 430b of the engagement member 430 may rotate toward and away from the translation arm 420 to move between an engage position and a disengage position respectively.

In some forms, as shown in Figure 12a, the engagement member 430 comprises a catch 480 that projects from the engagement member 430 to engage with the locking arm 410 in the locked position. The catch 480 may be of any suitable form to engage with and lock the position of the locking arm 410. In some forms, the catch 480 is provided at or near the distal end 430b of the engagement member 430. The engagement member 430 is rotatable about the first pivot joint 440 to engage with the locking arm 410 in the locked / engage position and to disengage with the locking arm 410 in the unlocked / disengage position. In this arrangement, the engagement member 430 (and catch 480) can be rotated away from the distal end of the locking arm 410 to disengage with the locking arm. The engagement member 430 (and catch 480) may also be rotated in the other direction to engage with the locking arm 410 in the locked position.

In some forms, as shown in Figure 7, the catch 480 comprises an elongate member, such as a rod, that extends in a direction substantially parallel to the longitudinal direction of the first and second pivot shafts 441, 461.

The self-locking mechanism 400' may comprise a pair of linking members 405', preferably one at each end of the pivot shafts 441, 461, such that the mechanism 400' comprises a pair of locking arms 410, a pair of translation arms 420 and a pair of engagement members 430. In these forms, the elongate rod of the catch 480 may extend between the distal ends of each engagement member 430, so that rotation of the engagement members 430 about the first pivot shaft 441 causes the catch/rod 480 to rotate toward the third pivot joint 450 (for engagement with the locking arm 410) or to rotate away from the translation arm 420 (for disengagement with the locking arm 410). In some forms, the catch/rod 480 comprises a gripping region that extends between the two engagement members 430. The gripping region allows a user to grip the catch 480 and pull the catch away from the locking arm 410 to unlock the self-locking mechanism 400'.

In some forms, the self-locking mechanism 400' comprises a quick release component by which a user can readily release the engagement between the locking arm 410 and the engagement member 430 in order to unlock the mechanism 400'. The quick release component may take any suitable form.

For example, in some forms, as shown in Figure 8, the self-locking mechanism 400' comprises a quick release component comprising a rotating lever 481 for actuating by a user to readily release / disengage the locking arm 410 from the engagement member 430. The rotating lever 481 may be connected to the engagement member 430, either directly or indirectly. In some forms, the rotating lever 481 is rotatably attached to the first pivot joint 440 and fixedly attached to the engagement member 430 so that rotation of the rotating lever 481 about the first pivot joint 440 causes simultaneous rotation of the engagement member 430 in the same direction. The rotating lever 481 is rotatable in a first direction, away from the locking arm 410, to rotate the engagement member 430 and catch 480 away from the locking arm 410 in order to disengage from the locking arm 410.

In other forms, as shown in Figure 9, the quick release component comprises a pull handle

482 for actuating by a user to readily release / disengage the locking arm 410 from the engagement member 430. The pull handle 482 may be connected to the engagement member 430, either directly or indirectly. In some forms, the pull handle 482 is rotatably attached to the distal end of the engagement member 430 so that the pull handle 482 can be actuated by pulling in a direction away from the catch 480, which causes the engagement member 430 to rotate away from the locking arm, disengaging the locking arm 410 from the catch 480 in the unlocked position.

In yet other forms, as shown in Figure 10, the quick release component comprises a lever

483 connected to a cable 484 that is connected to the engagement member 430, either directly or indirectly. In some forms, the cable is connected to a pull handle 482, as described above. In some forms, the lever 483 is mounted on a handle of the chair. The lever 483 may be actuated by pulling on the lever 483, which pulls on the cable 464, which in turn pulls the pull handle 482 in a direction away from the catch 480 to cause the engagement member 430 to rotate away from the locking arm 410 to disengage from the locking arm 410.

In other forms, the cable 484 is directly connected to the engagement member 430 or the catch 480 so that pulling on the lever 483 causes the cable to pull the engagement member 430 and catch 480 away from the locking arm 410 to disengage the locking arm.

Therefore, by actuating the lever 483, the cable 484 is moveable toward and away from the engagement member 430 to cause the engagement member 430 to respectively engage with the locking arm 410 in a locked position and to disengage with the locking arm 410 in an unlocked position. In some forms, the self-locking mechanism 400' further comprises a biasing member 470 to bias the locking mechanism 400' to the locked position. In some forms, as shown in Figures 7 and 7a, the biasing member 470 comprises a torsion spring. Optionally, the biasing member 470 engages with both the engagement member 430 and the translation arm 420 to bias the engagement member 430 toward the locked position in a self-locking arrangement, as shown in Figure 7a. Where the self locking mechanism 400' comprises a pair of linking members 405, a torsion spring 470 may be located between each adjacent translation arm 420 and engagement member 430.

The biasing member 470 may urge the engagement member 430 and therefore the catch 480 toward the engage position, so that after rotating the engagement member and catch 480 away from the locking arm 410 to disengage the locking arm (by actuating the rotating lever 481 / pull bar 482 / lever 483), the engagement member 430 (and catch 480) will rotate in the other direction and return to the engage position as soon as the engagement member 430 and catch 480 are released. In the engaged position, the catch 480 of the engagement member 430 is positioned to engage with the locking arm 410 when the locking arm is rotated to the locked position. Using this arrangement, the self-locking mechanism 400' automatically locks the first and second parts of the backrest together when the first and second parts are returned to the first position and the locking arm 410 re-engages with the engagement member430. The self-locking nature of the locking mechanism 400' avoids the risk of a user, such as a caregiver, forgetting to lock the two parts together or failing to adequately lock the two parts together before an occupant of the chair applies pressure or weight to the unlocked or ineffectively locked parts, putting the safety of the occupant at risk.

In some forms, the first end 430a of the engagement member 430 comprises a projecting member that engages with a recess 425 provided on the translation arm 420, preferably at or near the second end of the translation arm 420 to prevent over-rotation of the engagement member 430. In some forms, as shown in Figure 7, the projecting member comprises a pawl 435 and the translation arm 420 comprises a recess 425 in which the pawl 435 is received. The engagement member 430 is rotatable about the first pivot joint 440 until the pawl 435 abuts a stop 424 within the recess 425. In some forms, the stop 424 is formed by an end wall of the recess 425. The stop 424 limits the extent of rotation of the engagement member430 and therefore prevents over-rotation of the engagement member 430.

Typically, the pawl 435 is located at or near the first end 430a of the engagement member 430 and the catch is located at or near the second end 430b of the engagement member 430.

Typically, the pawl 435 abuts the stop 424 when the engagement member 430 is rotated to the unlocked position. At this point, tension is placed on the torsion spring 470, so that the torsion spring urges the distal end 430b of the engagement member 430, and therefore the catch 480, in the opposite direction, encouraging the engagement member 430 to return to the engage position as soon as the catch 480, rotating lever 481, pull handle 482, or lever 483 is released.

It should be appreciated that although the self-locking mechanism 400' may operate using a single linking member 405' comprising a locking arm 410, a translation arm 420 and an engagement member430, it is preferred that the self-locking mechanism 400' comprises a pair of linking members 405' and therefore comprises two locking arms 410 and two translation arms 420 and a pair of engagement members 430. In these forms, the third pivot joint 450 may comprise a third pivot shaft 451 that extends between the locking arms 410 and the translation arms 420. The third pivot shaft 451 comprises opposing ends. In some forms, each locking arm 410 and translation arm 420 is rotatably attached to a respective end of the third pivot shaft 451. In these forms, the translation arms 420 and engagement members 430 may be provided at opposing ends of the first pivot shaft 441, the locking arms 410 may be provided at opposing ends of the second pivot shaft 461, and the locking arms 410 and translation arms 420 may also be provided at opposing ends of the third pivot shaft 451. This arrangement provides greater strength and stability to the locking mechanism 400' and reduces the risk that the locking mechanism 400' could twist and fail.

In some forms, as shown in Figures 1 and 11, a pair of self-locking mechanisms 400, 400' are located side by side on the backrest 1000. Each locking mechanism 400, 400' attaches to both the first part and the second part of the backrest, as described above. For example, in the embodiments of Figures 1 and 5, a total of four locking mechanisms 400, 400' are provided to attach the shoulder support 100 to the upper back support 200 and to attach the upper back support 200 to the lower back support 300. It has been found that two side-by-side locking mechanisms 400, 400' that are attached to adjacent parts of the backrest provide a stronger connection between the adjacent parts than if a single locking mechanism 400, 400' is used.

In some forms, as shown in Figures 11, and 12 to 16a, a pair of self-locking mechanisms 400' are attached together to form a dual component locking mechanism, which is attached to the rear surfaces of first and second parts of the backrest 1000. In some forms, the two self-locking mechanisms 400' are attached together by a common catch 480 that comprises a rod that extends across both adjacent self-locking mechanisms 400', as shown in Figure 12a.

In some forms, the upper back support 200 and the lower back support 300 may be attached together by a self-locking mechanism 400' according to the invention. But typically (when used with a multi-part backrest), the self-locking mechanism 400' is used between the shoulder support 100 and the upper back support 200 of the backrest 1000.

Operation of the self-locking mechanism 400' and its effect on the movement of a first part in relation to a second part of the backrest will now be described in relation to Figures 11 and 12 to 17, in which the self-locking mechanism 400' is arranged on a backrest 1000 to allow the shoulder support 100 to hinge from the upper back support 200 until a desired angular position is reached between the shoulder support 100 and upper back support 200, in order to usefully support the seated posture of the chair occupant. In this scenario, the shoulder support 100 comprises a first part of the backrest and the upper back support 200 comprises a second part of the backrest. The desired angular support position will be referred to as the 'first position'.

To select the desired angle between the first and second parts of the backrest 1000 in order to reach the first position, the fasteners 50 of the first and second attachment members 445, 465 are loosened to allow the first and second pivot shafts 441, 461 to rotate freely. Where the locking mechanism includes a slidable portion, such as by comprising a slidable bracket 490, the engagement elements 55 of the slidable portion or bracket 490 are also loosened to allow the bracket 490 to slide freely relative to the second part of the backrest. The first part may then be rotated forwardly or rearwardly to adopt a first position that helps support the posture of an occupant of the chair. Where the occupant has a substantially C-shaped spine, a substantially S-shaped spine, or a hunched shoulder region, it may be useful to hinge the first part forward relative to the second part, as shown in Figures 2 and 3. Conversely, where the occupant has a substantially arched spine, or an arched shoulder region, it may be useful to hinge the first part rearward relative to the second part, as shown in Figure 4. Alternatively, the first and second parts may be substantially aligned, as shown in Figure 5.

Where the locking mechanism 400' is attached to the backrest in a sliding arrangement, the distance between the first and second parts of the backrest may be adjusted to account for the length of the spine of the occupant of the chair.

Figures 12 and 12a show one form of self-locking mechanism 400' in a locked position to lock the first and second parts 100, 200 of the backrest in a first position. In this position, the engagement feature 415 at the distal end 410b of locking arm 410 is engaged with the catch 480. In the embodiment illustrated, the engagement feature 415 is a hooked portion and the catch 480 comprises a rod that extends between a pair of engagement members 430. The hooked portion 415 at the distal end 410b of the locking arm 410 hooks partially around the catch 480, pressing the catch 480 and the second end of the engagement member 430 away from the first pivot joint 440 to apply tension to the locking arm(s) 410 and translation arm(s) 420, such that these arms 410, 420 are held in an extended position. Simultaneously, the biasing member 470 urges the catch 480 toward the engage position. The catch 480 and engagement member 430 form a lever that does not jam under load, so the self-locking mechanism 400' may be released to the unlocked position even when under load while the occupant sits in the chair leaning against the backrest 1000.

The optional biasing member 470 of the self-locking mechanism 400' prevents the mechanism 400' from inadvertently unlocking if overloaded.

Figures 13 and 13a show the self-locking mechanism 400' during the unlocking process and in which the catch 480 of the engagement member 430 has been lifted away from the locking arm 410 to disengage from the locking arm 410. As the catch 480 is lifted, the engagement member 430 rotates about the first pivot joint 440, causing the pawl 435 of the engagement member to rotate within the recess 425 of the translation arm 420 until the pawl abuts the stop 424. The stop 424 marks the point at which, or just beyond which, the locking arm 410 disengages from the catch 480 and therefore from the engagement member 430, as shown best in Figure 13. Once the locking arm 410 disengages from the catch 480, the locking arm is free to rotate about the second pivot joint 460, removing the tension on the translation arm 420. The translation arm 420 is then able to rotate about the third pivot joint 450, allowing the first part to hinge rearwardly about the hinge 250.

Figures 14 and 14a show the self-locking mechanism 400' in the unlocked, second position, in which the first part (the shoulder support 100) of the backrest is hinged rearwardly relative to the second part (the upper back support 200). In this arrangement, the locking arm 410 has fully disengaged from the catch 480 of the engagement member 430 such that the distal, second end 410b of the locking arm projects rearwardly, free of the engagement member 430. The torsion spring 470 urges the pawl 435 away from the stop 424 so that the catch 480 and therefore the second end 430b of the engagement member 430 are rotated toward the third pivot joint 450 in the engage position. As the locking arm 410 projects rearwardly, the translation arm 420 rotates about the third pivot joint 450, collapsing the locking mechanism 400' so that the distance between the first and second pivot joints 440, 460 is reduced and so that the first part (100) of the backrest is caused to hinge rearwardly relative to the second part (200) by pivoting about the hinge 250 that connects the first and second parts of the backrest 1000 together. In this collapsed, second position, the first part of the backrest is hinged away from the second part to provide easier access to an occupant of the chair.

To return the first and second parts of the backrest 1000 to the first position, a user may push the first part 100 of the backrest forward toward the first position, causing the translation arm 420 to rotate about the third pivot joint 450 and to pull against the locking arm 410 via the third pivot joint 450. As the locking arm 410 is pulled toward the first position, the locking arm 410 rotates about the second pivot joint 460. In the embodiment orientation shown in Figures 15 and 15a, the locking arm 410 rotates upwardly toward the first position. As the locking arm 410 rotates, the distal, second end 410b of the locking arm contacts the catch 480 of the engagement member 430. In preferred forms, the distal end 410b of the locking arm is tapered to slide against the catch 480 as the locking arm 410 rotates further toward the first position.

As shown in Figures 16 and 16a, by continuing to move the first part of the backrest forward toward the first position, the distal end 410b of the locking arm 410 pushes and slides against the catch 480, pushing against the catch 480 (as shown in broken lines in Figure 16). The distal end 410b of the rotating locking arm 410 continues pushing against the catch until the catch 480 is pushed over the distal end 410b of the locking arm 410, as shown best in Figure 16.

The biasing member 470 continues to urge the catch 480 downwardly toward the second pivot joint 460, so that as soon as the locking arm 410 is located between the catch 480 and the first pivot joint 440, the catch 480 automatically rotates toward the third pivot joint 450, trapping the locking arm 410 between the catch 480 and the backrest in a self-locking arrangement. In this position, the engagement feature 415 of the locking arm 410 engages with the catch 480, as shown best in Figures 17 to 19. Once the locking arm 410 is trapped between the catch 480 and the first pivot joint 440, the self-locking mechanism 400' is locked, so that the first and second parts of the backrest are locked in the first position.

In the embodiment illustrated in Figures 12 to 17, the first part (100) of the backrest is substantially aligned with the second part (200) in the first position. In other forms, depending on the postural support needs of the occupant of the chair, the first position may require the first part of the backrest to be at an acute angle, an obtuse angle, or a reflex angle relative to a front surface of the second part, in which case the self-locking mechanism 400' will automatically lock the first and second parts in the angled first position when the first part is moved to the first position.

The locking mechanism 400' may also reduce or prevent unwanted movement between the first and second parts of the backrest, especially where two locking mechanisms are used in a side-by-side relationship with a common catch 480, as shown in Figures 7, 11, 18 and 19 for example.

The self-locking mechanism 400' therefore allows the first part of the backrest to move from the first position to a second position, in which the first part may be hinged rearwardly to its maximum extent. By allowing the shoulder support 100 to hinge far backward from the upper back support 200, a caregiver is better able to access an occupant of the chair from behind. The improved accessibility to the occupant is particularly useful where the occupant is physically disabled with high needs.

In some situations, the occupant's postural support needs may have changed since the arrangement of the two parts was set in a first position. In such circumstances, the angle between the two adjacent parts of the backrest (in the first position) needs to be adjusted to better support the posture of the occupant. The angle may be adjusted by unlocking the first and second parts from the first position, by loosening the fasteners 50, 55 that immobilise the first and second pivot shafts 441, 461 and the slidable features that attach to the backrest in a sliding arrangement, such as the slidable bracket 490 for example. The first part is then rotated about the hinge 250, and slidable along the slots 700, 700' relative to the second part until the desired support position is reached. The fasteners 50, 55 are then tightened and the self-locking mechanism 400' is locked in the new position, which becomes the first position.

It is important to note that although the locking mechanisms 400, 400' of the invention have each been shown in a particular orientation, the orientation of the locking mechanisms 400, 400' may be reversed without departing from the scope of the invention.

The invention also relates to a backrest for a chair and to a chair (such as a wheelchair) that comprises such a backrest, the backrest comprising a first part and a second part attached together by a hinge 250 and at least one locking mechanism 400, 400' of the invention.

As shown in Figures 20 to 23, the locking mechanism 400, 400' of the invention may also be used to lock a multi-part lateral support for a chair in a first position and to allow a first part of the support to rotate relative to a second part in order to adopt a second position. The lateral support is configured to support the posture of an occupant of the chair from one side (i.e. laterally). The lateral support may be a pelvic and thigh support to support the pelvic and thigh region of the occupant, a torso support to support the trunk region of the occupant, or a shoulder support to support the shoulder region of the occupant. In some forms, the lateral support may be a head support to support the head of the occupant or a leg support to support the lower legs of the occupant.

In some forms, the chair may comprise multiple lateral supports 500. For example, the backrest of the chair shown in Figure 20 comprises a lateral shoulder support 500a, a lateral torso support 500b, and a lateral pelvic and thigh support 500c on each side of the backrest 1000.

The same locking mechanisms 400, 400' of the invention, as described above, may be used with a lateral support 500 that comprises a first part of a chair and that is hingedly attached to a second part of the chair, such as the backrest, seat base orframe of the chair. The locking mechanism 400, 400' can be used to lock and unlock the position of the lateral support relative to another part of the chair, such as the backrest, seat base, or chair frame.

In some arrangements, the locking mechanism 400, 400' may be used with a lateral support 500 that comprises a first part and a second part attached together by a hinge 250. The first part of each lateral support 500 may comprise a support member 510 that is hingedly attached to a second part by a hinge 250. The locking mechanism 400, 400' may be arranged to attach to the first part and to the second part. In some forms, the second part may comprise a support bracket 520 for attaching the lateral support to the chair, such as to a backrest 1000 of the chair or to a seat base or frame of the chair. In some forms, the bracket 520 is an L-bracket comprising a first portion 520a attached to the hinge 250, and a second portion 520b that extends from the first portion 520a at an angle and that attaches to the chair, such as to the backrest, seat base, or frame of the chair. Preferably, the second portion 520b extends from the first portion 520a of the support bracket 520 at an angle of about 90°.

Where the lateral support attaches to a backrest 1000 or frame of the chair, the height of the lateral support 500 may be adjustable by attaching the support bracket 520 to the backrest/frame in a slidable arrangement. In some forms, the backrest 1000 / frame may comprise at least one slot 150 and the bracket 520 comprises at least one engagement element 60 that engages with and slides along the slot until the lateral support 500 is at the desired height. The lateral support 500 may then be secured in position at that height by fastening the engagement element 60 in the desired position. In some forms, the engagement element 60 comprises a fastener that may be tightened to secure the position of the lateral support 500 at the desired height. A similar adjustment feature can be obtained by attaching the lateral support to a seat base, such as via a support bracket with at least one adjustment slot, so that the support member 510 of the lateral support can slide toward and away from the seat base and/or to slide forward and backward along the depth of the seat base, as will be appreciated by someone skilled in the art.

In some forms, the second portion 520b of the bracket 520 may comprise at least one slot 525, and preferably at least two slots, that lie in a substantially horizontal direction. The bracket 520 may be configured to slide in the direction of the length of the slots 525 to move the lateral support 500 toward and away from the backrest 1000 to accommodate for occupants of different widths. In other words, the slot(s) 525 provide for width adjustment of the lateral support 500. In some forms, an engagement element 60, such as a fastener, extends through a respective slot 525 of the bracket 520 and through the slot 150 of the backrest so that both the height and width of the lateral support 500 can be adjusted. Once the lateral support 500 is at the desired height and distance from a virtual vertical centre line of the backrest, the fasteners 60 may be secured to hold the lateral support 500 in place.

The locking mechanism 400, 400' may be configured to attach to the lateral support and to the support bracket 520. The locking mechanism 400, 400' may be located on the lateral support 500 to allow the support member 510 to extend from the support bracket 520 at an angle that usefully supports the posture of an occupant of the chair and to lock the support member 510 and therefore the lateral support 500 in that position - the first position. The locking mechanism 400, 400' also allows the lateral support 500 to adopt a second position in which the support member 510 is hinged rearwardly relative to the bracket 520. The second position provides better access to an occupant of the chair, such as to allow a caregiver to reposition the occupant, or to remove the occupant from the chair, or to help the occupant into the chair.

Either the lockable locking mechanism 400 or the self-locking mechanism 400' of the invention may be used to lock and unlock the position of the lateral support 500. By way of example only, Figures 20 to 23 exemplify a lateral support 500 comprising a self-locking mechanism 400'. The self-locking mechanism 400' of the lateral support 500 comprises the same features as the self locking mechanism 400' of the backrest 1000, as described above. The mechanism 400' shown is arranged so that the first pivot joint 440 is attached to the support member 510 and the second pivot joint 460 is attached to the bracket 520. In preferred forms, the second pivot joint 460 is attached to the first portion 420a of the bracket 420.

In some forms, at least one of the first and second pivot joints 440, 460 is slidably attached to the lateral support 500. For example, the first pivot joint 440 may be slidably attached to the support member 510. In these forms, the support member 510 may comprise at least one angle adjustment slot 515, and preferably comprises at least two angle adjustment slots 515, extending in a direction substantially perpendicular to the longitudinal direction of the first and second pivot shafts 401, 461. The first attachment member 445 may comprise at least one engagement element, such as a fastener 50, to engage with a respective slot 515 and to slide along the slot as the angle of the support member 510 is adjusted relative to the bracket 520.

The angular position of the support member 510 (the first part) relative to the bracket 520 (the second part) can be locked by engaging the locking arm 410 with the engagement member 430, such as with a catch 480 of the engagement member 430, as described above, to lock the first and second parts in the first position. The first position may be an externally rotated position or an inwardly rotated position or a substantially aligned position, as shown in Figures 21 to 23.

Similarly, the position of the support member 510 can be released/unlocked by unlocking the mechanism 400', such as by disengaging the catch 480 from the locking arm 410, as described above in relation to use with a backrest, and as shown in Figure 23.

The invention relates to a wheelchair comprising a backrest or a lateral support that comprises a locking mechanism 400, 400' of the invention, and to a chair comprising a backrest or a lateral support that comprises a locking mechanism 400, 400' of the invention, as shown in Figures 24 and 25. It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.