ADJUSTABLE LOCKING MECHANISM FOR A CHAIR

DESCRIPTION

The present invention relates to mechanisms for locking a first part of a device in a plurality of positions relative to a second part of a device, and particularly but not exclusively to mechanisms for use in adjustable chair supports. It is known in the art to provide office chairs with moveable supporting parts. For example, it is well known to provide a chair having an armrest which is moveable relative to a seat of the chair to accommodate users of different proportions. Such moveable supporting parts are often locked in position using an adjustable arm mechanism of the type disclosed in US 5393125 and US 6398309. The adjustable arm mechanism disclosed in each of these documents comprise an actuator having a cam-like profile

for urging at least one ball-bearing into one of a plurality of indentations formed on a locking surface, the actuator being moveable by a user between an unlocked position in which the ball-bearing may move out of the indentation and a locked position in which the ball bearing is urged into the indentation. The actuator is biased in the locked position by means of a spring in order to maintain the relative position of the supporting part relative to the seat. It is also known in the art to provide an adjustable arm mechanism comprising a gas strut for selectively varying the height of an arm relative to seat. Advantageously, the use of the gas strut allows for quiet or near silent operation. However, the cost of incorporating such a mechanism into a chair may be prohibitive in many applications.

The present applicant has identified the need for an improved locking mechanism which overcomes, or at least alleviates, problems connected with the prior art. In accordance with a first aspect of the present invention, there is provided a mechanism for locking a first part of a device in a plurality of positions relative to a second part of the device, comprising: a locking member moveable between an operative configuration in which movement of the first part relative to the second part is prevented and an inoperative position in which movement of the first part relative to the second part is permitted; and an actuator for moving the locking member

from the inoperative position to the operative position as the actuator moves from a first configuration to a second configuration; wherein the locking member is biased in the inoperative position when the actuator is in the first configuration.

In this way, there is provided a mechanical locking mechanism in which the locking member is drawn away from a locking surface of the mechanism during adjustment of the position of the first part relative to the second part. Thus, the present invention provides for quiet or even near-silent operation without resorting to the use of a mechanism comprising a gas strut.

The mechanism may comprise a chamber for engaging the locking member when in the inoperative position. In one embodiment, the mechanism is configured for use in a predetermined orientation relative to gravity and the locking member is configured to drop into the chamber under its own weight when the mechanism is deployed in the predetermined orientation. For example, the chamber may have a lower surface for supporting the locking member as it moves from the operative configuration to the inoperative configuration and the lower surface extends below a mouth of the chamber. In this way, the mechanism may be configured to draw the locking member away from the locking surface of the mechanism automatically when the locking member is in the inoperative position and without the need for spring means .

The actuator may be biased in its second configuration to maintain the locking member in the operative position.

The actuator may comprise a profile defining a cam surface for moving the locking member from the inoperative position to the operative position.

In one embodiment, the locking surface comprises a plurality of discrete locking profiles and a leading portion of the locking member engages one of the plurality of discrete locking profiles of the locking surface when in the operative configuration.

In a further embodiment, the chamber is configured to force the locking member against the locking surface when a downward force is applied to the actuator whilst the locking member is in the operative configuration. For example, the chamber may have an upper surface opposing the lower surface, the upper surface being configured to force the locking member against the locking surface when a downward force is applied to the actuator whilst the locking member is in the operative configuration.

In this way, when the locking mechanism is used to adjustably lock a support member (e.g. a support member of a chair) , an external force applied to the actuator via the support member will advantageously act to maintain the first part in its locked position relative to the second part .

The locking member may be a ball-bearing. However,

another embodiment the locking member is a roller bearing.

Advantageously, use of a roller bearing as opposed to a conventional ball-bearing allows use of plastics materials in place of relatively stronger metals since the outer periphery of the roller bearing will typically present a face contact against mechanism parts rather than the equivalent point contact of a ball-bearing. In addition, the use of a roller bearing advantageously allows the use of lower tolerances in manufacture than would otherwise be required with a ball-bearing for precisely the same reasons .

In accordance with a second aspect of the present invention, there is provided a mechanism for locking a first part of a device in a plurality of positions relative to a second part of the device, comprising: a locking surface comprising a plurality of discrete locking profiles; a locking member housed in a chamber, the locking member being moveable between an operative configuration in which a leading portion of the locking member engages one of the plurality of discrete locking profiles of the locking surface for preventing movement of the first part relative to the second part and an inoperative position in which the locking member disengages the locking surface for permitting movement of the first part relative to the second part; and an actuator for moving the locking member from the inoperative position to the operative position as the actuator moves from a first configuration to a second

configuration; wherein the chamber is configured to force the locking member against the locking surface when a force is applied to the actuator whilst the locking member is in the operative configuration. In one embodiment, the chamber has a lower surface for in use supporting the locking member and an upper surface opposing the lower surface, the upper surface being configured to force the locking member against the locking surface when a downward force is applied to the actuator whilst the locking member is in the operative configuration .

In accordance with a third aspect of the present invention, there is provided a mechanism for locking a first part of a device in a plurality of positions relative to a second part of the device, comprising: a locking member moveable between an operative configuration in which movement of the first part relative to the second part is prevented and an inoperative position in which movement of the first part relative to the second part is permitted; and an actuator for moving the locking member from the inoperative position to the operative position as the actuator moves from a first configuration to a second configuration; wherein the locking member comprises a roller bearing. In accordance with a fourth aspect of the present invention, there is provided a chair comprising: a body; support means mounted on the body for supporting a part of a user's body when a user is seated on the chair, the

support means being moveable relative to the body for adjusting a configuration of the chair; and a mechanism according to any of the preceding aspects of the present invention, wherein the first part is coupled to the support means and the second part is coupled to the body.

The support means may comprise one of: an arm rest; a backrest ; and a seat .

The chair may be a freestanding chair, e.g. an office chair or the like. The chair may be mounted on castors. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic cross-sectional side view of a mechanism in accordance with the present invention in a locked configuration;

Figure 2 is a schematic cross-sectional side view of the mechanism of Figure 1 in an unlocked configuration.

Figures 1 and 2 show a mechanism 10 for locking a first part 20 of a device 30 in a plurality of positions relative to a second part 40 of the device 30. The first part 20 may be for attachment to a support member (e.g. an arm) of an office chair (not shown) ; the second part 40 may be for attachment to a body (e.g. a seat) of an office chair (also not shown) . The mechanism 10 comprises: a pair of locking surfaces 50 each comprising a plurality of discrete indentations or locking profiles 52 for locking the first part 20 in a plurality of discrete positions relate to the

second part 40; a pair of roller bearings 60, each associated with a respective locking surface 50; and an elongate actuator 70 positioned between the pair of the roller bearings 60, the actuator 70 being moveable between a first position (as shown in Figure 2) and a second position (as shown in Figure 1) .

Each roller bearing 60 is housed in a respective inclined chamber 80 and is moveable between an operative configuration (as shown in Figure 1) in which a leading portion 62 of each roller bearing 60 snugly engages one of the plurality of discrete locking profiles 52 of its respective the locking surface 50 for preventing movement of the first part 20 relative to the second part 40; and an inoperative position (as shown in Figure 2) in which each roller bearing 60 disengages the locking surface 50 for permitting movement of the first part 20 relative to the second part 40.

The actuator 70 comprises a profile defining a pair of cam surfaces 72 each for moving a respective roller bearing 60 from its inoperative position shown in Figure 2 to its operative position shown in Figure 1 as the actuator 70 moves from the first position shown in Figure 2 to the second position shown in Figure 1. The actuator is biased in its second position by means of a spring 90 to maintain the roller bearing 60 in the operative position once the first part 20 is positioned as required relative to the second part 40. In order to release the roller bearings 60 from their respective locking surfaces

50, a force is applied (e.g. by a user) to overcome the biasing force of spring 90.

The mechanism 10 is configured for use in a predetermined orientation relative to gravity, with the first part 10 being positioned directly above the second part 40 (as shown in Figures 1 and 2) . Each chamber 80 comprises a lower surface 82 for supporting its respective the roller bearing 60 and each lower surface 82 extends below a mouth 84 of its respective chamber 80. In this way, each roller bearing 60 is configured to disengage from its respective locking surface 50 and drop fully into its respective chamber 80 under its own weight when the actuator 70 is in the first position and the mechanism 10 is deployed in the predetermined orientation shown. In this way, the mechanism is configured to automatically draw each roller bearing 60 away from its respective locking surface 50 when each roller bearing 60 is in its inoperative position in order to avoid noise-inducing contact between the roller bearings 60 and their respective locking surfaces 50 during repositioning of the first part 20 relative to the second part 40.

Each respective chamber 80 further comprises an upper surface 86 opposing the lower surface 82, the upper surface 86 being angled to force its respective roller bearing 60 against its respective locking surface 50 when a downward force is applied to the actuator 70 whilst the roller bearings 60 are in the operative configuration. In this way, when the mechanism 10 is used to adjustably lock

a support member of a chair, an external force applied to the actuator 70 via the support member (e.g. a part of a user's body pressing down against the support member) will advantageously act to maintain the first part 20 in its locked position relative to the second part 40.