TECHNICAL FIELD OF THE INVENTION

This invention relates to a chair, or seat base for a chair, which includes articulated seating elements. In particular, this invention relates to chair, or seat base for a chair, which in use promotes a more comfortable seating posture and/or provides a relaxing support for a user when in a semi-supine position. BACKGROUND

Many people find it hard to sit comfortably for long periods when using a hard or office type chair. Strain can develop in the neck shoulders and back and it is often a challenge to maintain good posture because it is either tiring or hard to keep in awareness, especially when concentrating on detailed work. These common problems of strain and rounded posture while sitting are in marked contrast to the effortless good posture which is near-universal for young, pre-school age children. And although there are a number of exercises and processes to help restore and maintain a better back and sitting posture they usually take a certain amount of work and or mindfulness to keep the benefits going. This invention is based on a physical reflex whereby if the arms or legs are outwardly braced and pulling against each other it works to brace the back and make it less prone to slumping and generally stronger. For example, this can be experienced by holding the left and right hand and pulling softly outwards with the elbows and then checking the difference in one's proneness to slumping. In this configuration most people find that they do not have to make their customary effort to hold their back up to avoid any tendency to slump.

Also when the limbs are outwardly braced the core strength of the back and abdominal and pelvic support muscles is enhanced. This can be seen for example by the difference in a simple test of balance and back strength whereby a person tries to resist another person pushing them in the small of the back. In normal circumstances the majority of people find that they have little resistance to this push, whereas when they link hands and pull outwards with their arms their backs can push back more effectively and resist lateral movement. The extent to which the back can push back with more strength when braced is mirrored in how much easier to sit comfortably and with less effort when braced. Obviously a person cannot sit at a desk with their hands linked and arms braced to enjoy more comfortable sitting but the same bracing and back strengthening effect can be achieved by bracing the legs, and this is what the present invention seeks to achieve.

To try to bring about this physical effect a number of seat bases or chairs have been proposed in which the seat is split into two parts and when the user sits on the seat base, the left and right halves of the seat are able to pivot or rotate in an opposing manner, i.e. one half rotates anti-clockwise and one half rotates clockwise. The prior art described in CN201492023U shows a superficially similar split seat where the two halves rotate about a position proximate to the sitting bones but the crucial difference is that the two halves of the seat are linked by a cog mechanism. This means that there can be no free and independent movement of the left and right legs. Also the legs do not brace against each other when they turn out. On the contrary the cog link means that when the left leg turns out clockwise it turns the right leg out anti-clockwise, and there is no opposition in the two movements. In other words the apparatus described in the prior art cannot create the same effect of free movement and oppositional bracing of the legs as the apparatus described here.

Whilst the apparatus set out in CN201492023U seeks to alleviate the problems of seated posture as outlined above, it certainly has not solved the problem. Therefore, a need exists for a chair, or seat base for a chair, which promotes an advantageous bracing of the user's core and back muscles to maintain an upright posture when seated or when in a semi-supine position.

It is an object of the present invention to provide a chair, or seat base for a chair, with articulated seating elements which overcomes or reduces the drawbacks associated with known products of this type. The present invention provides a seat base which is split in two and when the user sits on the chair, the left and right halves of the seat rotate anticlockwise and clockwise, respectively. The front part of the seat halves move away from each other and the back parts of the seat move towards each other. Such a seat base allows for independent movement of the left and right seat halves and correspondingly the left and right legs and follow a tendency for the legs to splay out on sitting. In typical use, the back part of the seat halves begin to press on each other after approximately 5° to 10° outward rotation of the legs and this effectively creates the same limb against limb outward bracing described above that causes the back and body to brace overall and engage a different kind of strength. This effect is also mirrored in the outward motion of similarity configured armrests, when the arms rest upon them.

It is an object of the present invention to provide an articulated seat base and armrests of the chair described are intended to help the user find and maintain a comfortable, well- aligned and fully self-supporting spine while sitting to work and also to enable the body to rest when the user sits back in the chair.

A further effect is obtained whereby when the two sides of the pelvis and the lower limbs are able to move and articulate freely around the respective sitting-bones this has a beneficial effect on the spine both in the sitting and semi-supine position when the user lays on their back with their knees drawn up and the feet on the floor. It also has an effect when the user sits on the apparatus and sits back in a tiltable chair - when the chair tilts more than approximately 15° the back stops holding itself up, and with the postural system much less active than when sitting up, the effect is then similar to lying flat.

Testing of the present invention has revealed that users report that when using the apparatus as a seat they involuntarily sit straighter and feel their back actively relaxing. The sitting experience often shifts from a person tending to slump and peer at their work to tending to sit straight and relaxed in an effortless unconscious way. And when they lean back in the chair, there is a different kind of experience, often reported as a sense of releasing of tension and weight into the chair.

These effects are achieved by the user sitting with the sitting-bones, or more formally known as the ischial protuberances or tuberosities, directly on two separate halves of the seat that are free to rotate and tend to move apart when the user sits down and their legs slightly splay out. Thus the legs and the two sides of the pelvis are able to move more freely relative to each other than with a normal chair. The optimal effect is found when the two halves of the seat rotate at a point proximate the position of the ischial tuberosities or at points located between these two points of the body, or at one rotation point approximately corresponding to the midpoint between them.

This effect is also mirrored when the user rests their elbows on a similarly articulating armrest and the forearms are able to both ground their weight on the armrest and also move freely in the horizontal plane. SUMMARY OF THE INVENTION

The present invention is described herein and in the claims.

According to the present invention there is provided a seat apparatus, comprising:

a base section;

a split seat comprising two separate seat platforms positioned side-by-side on the base section for supporting a seated person; and

means, connected between the base section and the split seat, for allowing rotational motion of each of the seat platforms generally in the same plane as the base section, the seat platforms being independently rotatable relative to one another.

An advantage of the present invention is that it can be used to promote or bring about a bracing effect on the seated person's core and back muscles to improve their posture when seated or in a semi-supine position. Preferably, the left and right top parts of the seat are mounted on bearings that allow them to rotate in the horizontal plane. Firstly two axial bearings are positioned such that their centres are generally positioned in alignment with the sitter's sitting-bones. Thus the rotary bearing mechanisms are positioned towards the back of the chair in the same position where a person would normally rest their sitting-bones and the same distance apart as the ischial tuberosities. Two ball joint or radial bearings on each side of the top elements of the seat positioned at the front allow for free movement of the front of the seat and also keep the front of the apparatus stable. When the user sits on the seat the two top elements of the seat are free to rotate when the person's legs move. When a person sits on a chair or lets their weight of their thighs rest on a supporting apparatus there is some natural splaying out of the legs. Thus when the user sits or rests on the apparatus the top elements of the seat will tend to rotate apart at the front of the seat in accordance with how the legs splay out.

The two top elements of the chair may be made from wood, plastic or other composite materials. They can be mounted on the base by a number of different mechanisms that allow low-friction rotation such as axial bearings under the sitting bones with radial or ball-joint bearings or Teflon ^® type or low-friction pads or opposing strong permanent magnets to facilitate the support and free movement of the front of the chair. The preferred embodiment includes axial bearings and radial bearings because they minimise friction and stiction or initial resistance to motion when the user sits on the chair. The two top halves may be further padded with cushioning material to make them softer and more comfortable to sit on. It is important that the sitting-bones are well-aligned relative to the seating halves so the chair moves in a way that mirrors the small subtle movements of the legs and pelvis. Typically, the distance between the ischial tuberosities is 10 cm to 14 cm so various sizes of chair can be built to accommodate different sizes of user. With this configuration the chair moves in an arc very similar to the natural outward arc of the legs.

In the early usage of the seat it is possible that users may find it comparatively tiring to use the seat for long periods as it tends to activate the postural muscles in a different way that they are used to. Also when used as a chair in public or shared environments the effect may not be to every user's liking, so the apparatus would preferably include a feature that immobilises the movement of the seating halves which would allows the chair to be used as both a conventional fixed seat and in a mode where the two halves of the seat are free to move in the way described here.

When used as a seat the chair may include a tilt mechanism in the base that allows the user to both tilt the chair forward by approximately 0° to 5° and tilt back by up to approximately 15° or more. The chair should also have adjustable height so the user can ground their feet on the floor when they are tilted back or forward. The apparatus can be built into a variety of chairs from hard chairs to office chairs and stools to wheelchairs and vehicle seats.

This configuration has a parallel dynamic configuration intended for when the user's arms rest on the armrests. The armrests are comprised of a mobile upper and static lower armrest parts connected by an axial bearing positioned approximately where the elbow would rest and a ball joint or radial bearing that lays approximately under the user's wrists. This means that the upper armrest part can move in an arc similar to the way the way the forearm would rotate about the elbow joint. The movement is restricted to approximately 10° in either direction similar to the range of motion of the top seating elements of the seat.

In a further embodiment the two seat halves rotate at a point approximate to the midpoint between the ischial tuberosities.

In a further embodiment the apparatus is configured as a vehicle seat with the seat halves articulated by means of a servomotor controlled axial bearing.

The principle purpose of the present invention is to allow the upper and lower limbs both to rest on the seat base and armrests respectively and to also be free to move in the horizontal plane with the chair following a similar movement arc to the natural rotation of the legs and arms.

It is believed that a chair, or seat base for a chair, which includes articulated seating elements in accordance with the present invention at least addresses the problems outlined above.

It will be obvious to those skilled in the art that variations of the present invention are possible and it is intended that the present invention may be used other than as specifically described herein.

BRIEF DESCRIPTION OF THE DRA WINGS

The present invention will now be described by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows a schematic plan of how the two top parts of the seat base are mounted and positioned on the lower surface of a seat base;

Figure 2 shows a side section of an apparatus configured to be used as a chair without armrests and shows the detail of the articulating seat base;

Figure 3 shows a side elevation of the apparatus when it is configured as a chair with armrests and shows the detail of the articulating seat base and also the articulating armrest;

Figure 4 shows a sectional front elevation of the articulating armrest in accordance with the present invention;

Figure 5 shows a side elevation of the apparatus when it is configured to be used as a standalone seat base;

Figure 6 shows a side section of an apparatus when it is configured to be used as a leg or foot support;

Figure 7 shows a schematic plan of a split seat base where the two seat halves are mounted and positioned on the lower surface of a seat base and where the seat halves have a single shared point of rotation;

Figure 8 shows a side plan cutaway view of the split seat base of Figure 7 which provides a single shared point of rotation via a three race axial bearing;

Figure 9 shows a schematic plan of a vehicle seat with articulating split seats; and

Figure 10 shows a side elevation of a vehicle seat fitted with the articulating split seats.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention has adopted the approach of a chair, or seat base for a chair, which includes articulated seating elements and when the user sits on the chair the left and right halves of the seat rotate anti-clockwise and clockwise, respectively. The front part of the seat halves move away from each other and the back parts of the seat move towards each other. Such a seat base allows for independent movement of the left and right seat halves and correspondingly the left and right legs and follow a tendency for the legs to splay out on sitting. Such a configuration promotes or brings about a bracing effect on the user's core and back muscles to improve posture when seated or in a semi-supine position.

Referring now to the drawings, a seat base (100) for a chair (17) according to the present invention is illustrated in Figures 1 to 4. In Figure 1, the split chair seat (100) has a two part support area, each seat half comprising of a lower base (3) upon which are mounted two cushioned elements (1) mounted on two load bearing upper elements (2) which rotate in the horizontal plane by means of posterior positioned axial bearings (4) and two anterior and one posteriorly positioned radial bearings (5) which connect the upper support elements (1, 2) with the lower base (3) of the seat base (100).

The bearings (4, 5) enable the two upper seat parts (1, 2) to rotate parallel to the lower base (3) and thus allow the sitter's femur bones to move freely apart from one another when seated. The upper seat elements (1, 2) and seat base (3) and other supporting elements not shown can be made from any rigid and durable material such as wood, metal, fibreglass or moulded plastic and materials with similar tensile strength. The rotational effect can be achieved with various kinds of mechanisms that both connect and support the load bearing elements (2, 3) and facilitate rotational movement such as Teflon ^® or low friction upper and lower parts and opposing permanent magnets.

The skilled person will appreciate that the radial bearings (5) which are provided as spindled rollers disposed in the seat base section (3) abut against a steel or glass reinforced plastic (GRP) plate or panel disposed on the underside of each seat element (2). This provides a hard wearing surface to allow rotational movement of the seat elements (2) over the base (3), but for reasons of clarity these panels are not shown in the drawings. The skilled person will also appreciate that the radial bearings (5) could be replaced with one or more ball joint bearings which supports rotational movement of the seat halves (2) about the axial bearings (4) disposed at the posterior of the seat base (100).

The anterior part of the foam cushioning and upper seat parts (1, 2) are shaped and cut away at a level corresponding with the centre point of the axial device (4). This means that when the user sits on the apparatus and their legs naturally slightly splay legs open, the left and right seat upper elements (1, 2) and the user's legs can rotate apart.

The cushioning layer (1) is shaped such as to feel most comfortable for the majority of users such that the sitter is positioned with their sitting bones near to the rotation points of the seat elements (1, 2). This is achieved by small additional support elements which are not shown which support the anterior part of the pelvis most comfortably in a position corresponding with the ischial tuberosities approximately within around 1.5 cm of the rotation points (4) of the seat elements (1, 2).

The rotation points (4) of the seat elements (1, 2) being located approximately 15 cm ± 2.0 cm from the nearest point of the lumbar support area of the chair back (17), the overall intention being that the most comfortable and normal way to sit on the chair would result in the sitter sitting with the ischial tuberosities located close to, or on, the rotation points (4).

Also the cushioning and support layers (1, 2) would ideally feature additional support in the form of either extra padding and a slight upward incline respectively to the distal side of the front of the leg. This would help enhance the action whereby when the legs move outwards as part of the natural slight splaying of the legs when sitting the seat halves (1, 2) move correspondingly. And it minimises the possibility that the legs might roll outwards and the seat halves (1, 2) move less. The optimal effect is achieved when the seat halves (1, 2) effectively move as one. A detachable stopper (6) can fit into a number of recessed holes (7) which lets the user adjust how much the upper seat parts (1, 2) move apart before the stopper (6) restricts the outward movement of the user's legs. Optionally, a two part spring-loaded catch (8) enables the left and right seat halves (1, 2) to be immobilised or free to move. The catch (8) is operable by pushing the two seat halves (1, 2) together to immobilise them and clicked together again to release the two seat halves (1, 2).

Figure 2 shows a cushioned upper element (1) and load-bearing upper element (2) mounted on the base part (18) of a chair (17) via two anterior positioned ball joint or radial bearings (5) and one posterior positioned radial bearings (5) and a posterior positioned axial bearing (4). The two top elements (1, 2) are free to rotate in the horizontal plane parallel to the lower base (3) because the bearings (4, 5) enable them to rotate with respect to the chair base (18).

The axial bearings (4) are positioned with the centres approximately 10 cm to 14 cm or less apart which is similar to the distance between the sitting-bones for most adults. The centre of the axial bearings (4) are also approximately 12 cm to 15 cm from the back of the chair (17) which approximates to where the sitting bones are usually positioned while sitting on a seat.

The chair base (18) is in turn mounted on a tilting mechanism (19) that enables the chair to tilt both forwards by approximately 5° and also tilt backwards by a minimum of approximately 15°. Whilst not shown in Figure 2 for reasons of clarity, the skilled person will appreciate that the chair (17) also includes a mechanism to raise and lower the chair support (20) so the user can rest their feet on the ground when in the different sitting up and reclining positions.

Figure 3 is similar to Figure 2 and shows a chair (17) with the addition of an upper armrest (21) which rests on an armrest base (24) and is connected by an axial bearing (22) and a ball joint or radial bearing (23). The armrests (21, 24) connect to the base element of the chair (18) via a height adjustable support (25). The axial bearing (22) is located with the central turning point approximately 10 cm from the back of the chair which allows the elbows to be positioned directly above the turning point of the armrest (21) when sat in a normal position. The ball joint or radial (23) is positioned approximately 10 cm from the front end of the armrests (21, 24). The position of the axial bearing under the elbow means the movement of the upper armrest (21) follows approximately the same arc as the free movement of the forearm. The action of the axial bearing (22) and ball joint or radial bearing (23) is such that the user's arms can freely rotate anti-clockwise and clockwise by approximately 10° in either direction while they are resting on the upper armrest (21).

Figure 4 shows the mechanism for restricting the movement of the upper armrest (21) and ensuring that the upper armrest (21) does not slip off the armrest base (24) when the upper armrest (21) rolls over it via the ball joint or radial bearing (23). Two flanges (26) are positioned on either side of the upper armrest (21) to restrict the movement to approximately 3 cm on either side of the midline of the armrest base (24).

Figure 5 shows a second embodiment of the seat base (100). The construction of the second embodiment is very similar to that of the first embodiment and corresponding features have been given the same reference numerals. The second embodiment differs from the first embodiment in that the seat base (100) can be angled to allow a user to be supported in a tilted or semi-supine position.

In Figure 5 an upper cushioned element (1) mounted on a weight supporting upper element (2) which are connected by an axial bearing (4) and ball-transfer bearings (5) which allow the free movement in the horizontal plane of the upper seat elements (1, 2) over the base part (3), as described above. These elements (1, 2, 3) are positioned on a supporting block (14) which is angled at approximately 10° to 15°, so that when the apparatus is used as a seat the user sits at a slight angle to the horizontal.

A folding flap (9) which articulates via a hinge (10) is fixed under the base element (3). The upper elements (1, 2, 3) are connected to the lower base element (13) by means of a piece of similar material (11) articulated by two hinges (12, 15). This mechanism helps the top elements (1, 2, 3) of the seat apparatus (100) stay in place when used as a seat.

In Figure 6, which shows the seat base (100) of Figure 5 extended, the two articulating top elements (1,2) are connected to a supporting top element (3) by means of an axial bearing (4) and ball transfer joint (5), enabling the top elements (1, 2) to rotate parallel to the supporting upper part (3). The apparatus is positioned at a relatively shallow angle to the vertical by means of folding the back plate (11) onto the same plane as the lower base (13) by means of hinges (15, 12). The top elements (1, 2, 3) are made secure by means of an articulated flap (9) and hinge (10) and can be positioned at different angles by the base of the flap (9) butting against different railings (16) which are secured on the lower base (13).

Detachable cushioned leg supports (32) fix on the underside of the top supporting part (2) and help keep the user's legs from splaying out and spilling over the edge of the apparatus when the anterior part of the top elements (1, 2) rotate outwards when the user's legs rest upon the apparatus when the user is in a semi-supine position.

The two embodiments shown here are for a standalone device or apparatus (100) capable of being used in the sitting and semi-supine position and also with or as part of a chair (17) with articulated seat elements and articulating armrest parts (21, 24) with a tilting mechanism built into the chair (17). However the principle of two elements rotating in the horizontal plane on top of or embedded in a seating apparatus with or without armrests can be adapted for most kinds of seats and chairs to give free and separate movement of the legs and arms. Figure 7 is similar to the Figure 1 except that there is a single three race axial bearing (27) that connects to the left and right seat halves (1, 2) via the upper and middle races respectively (not shown in Figure 7) and provides a single shared rotation point for their movement. The rotation position is intended to be at the midpoint between the user's ischial tuberosities. The three race bearing (27) is shown in further detail in Figure 8, and comprises three rotational parts, namely a lower bearing part (34), an upper bearing part (35) and an inner bearing part (33) interposed therebetween. Bearing races (38) are disposed between the opposing faces of the inner (33) and lower (34) bearing parts, and the inner (33) and upper (34) bearing parts, respectively. The lower bearing part (34) abuts against the base section (3) and rotationally supports the inner bearing part (33) which is connected to one of the two seating halves (2). The other one of the respective seating halves (2) is connected to the upper bearing part (35). The two halves (2) are secured to the bearing parts (33, 35) via fixtures (36), which meet with the pear shaped and planar bearing parts (33, 35). The co-axial nature of the bearing (27) means that the inner (33) and upper bearing parts (35) rotate about a common axis upon lower bearing part (34). This common axis is positioned generally along the midpoint between the ischial protuberances of the seated user. Figure 9 shows a third embodiment of the seat base (100). The construction of the third embodiment is very similar to that of the first embodiment and corresponding features have been given the same reference numerals. The third embodiment differs from the first embodiment in that it is can be used as part of vehicle seat to allow comfort when travelling.

Figure 9 is similar to Figure 1 in dimensions, function and orientation but differs in that it represents a vehicle seat base (29) and comprises a two-part support area, each seat half comprising of a lower base (3) upon which are mounted two cushioned elements (1) mounted on two load bearing upper elements (2) which rotate in parallel with the lower base (3) by means of servomotor controlled bearings (28) and two anterior and one posteriorly positioned radial bearings (5) which connect the upper support elements (1, 2) with the lower base (3) of the seat apparatus (100).

The bearings (28, 5) enable the two upper seat parts (1, 2) to rotate in the horizontal plane and thus allow the sitter's femur bones to move freely apart from one another when seated, as described previously.

The servomotor controlled bearings (28) have however several functions that aid the comfort and safety of the user.

Firstly when the vehicle's engine is switched off the bearings (28) could be configured to return the upper seat elements (1, 2) to a central parallel position as shown in Figure 9 and for the bearing (28) and the upper seat elements (1, 2) to be immobilised. This would make it easier for the user to get in and out of the vehicle than if the seat elements (1, 2) were moveable.

Secondly, a motor controlled bearing (28) would allow the user to choose whether to have the seat elements (1, 2) in either mobile or immobilised mode for example by means of a seat mounted switch (as shown as switch (30) in Figure 10). Furthermore, the electronically controlled bearing (28) could also be linked to motion detecting devices in the vehicle (not shown) which could disable the rotation motion of the moving seat elements (1, 2) for example in the event of a sudden deceleration, collision or sudden swerve. Or alternatively, the control systems could return the seat elements (1, 2) to a parallel position in the event of any of the abovementioned events.

Figure 10, shows the vehicle seat base (29) upon which is mounted an articulated seat system comprising a two part support element of cushioning material (1) and support material (2) mounted on a lower base (3) connected by a servomotor controlled bearings (28) and radial bearings (5) which connect the upper support elements (1, 2) with the lower base (3) of the apparatus.

The bearings (28, 5) enable the two upper seat parts (1, 2) to rotate parallel to the articulated seat base (3) and car seat shell (29) and thus allow the sitter's femur bones to move freely apart from one another when seated.

As mentioned, a side-mounted switch (30) enables the user to manually mobilise or immobilise the free rotation of the articulating elements (1, 2).

The invention is not intended to be limited to the details of the embodiments described herein, which are described by way of example only. Various additions and alterations may be made to the present invention without departing from the scope of the invention. It will be understood that features described in relation to any particular embodiment can be featured in combination with other embodiments.