Chair support mechanism and chair including the same

Abstract

A chair support mechanism 1 comprises a base support 2, a seat support 3, a backrest support 4, and at least one lever arm 8 having a first and second ends. The seat support and backrest support are c

Description

Field of the Invention The present invention relates to a support for a chair, in particular to a support on which a chair seat and chair back are mounted which facilitates relative movement between the chair seat and chair back, and a chair including such a support. Background of the Invention Support mechanisms for chairs on which a chair seat and chair back are mounted are well known in the art. Typically these are either by a spring resisting the recline of the chair back or, where such support mechanisms provide a resistance for a reclining motion of the chair back by generating a lifting motion of the chair seat coupled to a lesser spring. These latter support mechanisms utilise the weight of the person sitting in the chair to generate the supporting motion described. Generally, support mechanisms of the type described above comprise three components, those being: a component that is static and fixed to the base of the chair, usually by a pillar connected to a base that includes a plurality of legs, a part to which the chair seat is mounted and a part to which the chair back is mounted. These three parts are connected together by linkages and pivots and guides. US2008 / 0136239 describes a synchronising mechanism comprising a base carrier for attachment to a column, a seat carrier and a backrest carrier. A first link connects the backrest carrier to the base carrier and a second link connects the backrest carrier to the seat carrier, such that a pivoting movement of the backrest carrier in a rearward direction induces a raising movement of the rear region of the seat carrier. The seat carrier is connected to the base carrier such that a raising movement of the forward region of the seat carrier takes place and the same time. CN115120053 describes a chair support mechanism that includes a locking mechanism so that the seat may be locked such that the chair back may not recline. US10,143,306 describes a mechanism for an office chair comprising a base support for attachment to a column. A seat support is arranged on the base support and is moveable relative thereto. A backrest support is coupled pivotably to the seat support and the base support. A lever extends from the base support to the seat support and is coupled pivotably to these components. The connection of the lever to the base support comprises a slot, so that the lever 1 may not only pivot relative to the base support, but also to provide for relative sliding motion between the base support and the lever. It would be desirable to provide a chair support mechanism where reclining movement of the backrest causes the seat to both lift and move forwards to provide both a counterbalance and improve stability of the chair, and which has a minimum number of parts and is simple to manufacture and assemble. Summary of the Invention According to a first aspect of the invention there is provided a chair support mechanism comprising a base support, a seat support, a backrest support, and at least one lever arm having a first end and a second end, wherein: the seat support and backrest support are connected to each other by a pivot connection having a fixed axis; the base support and the seat support are both connected to the first end of the at least one lever arm, said at least one lever arm rotatable relative to each of the base support and the seat support, the backrest support connected to the second end of the at least one lever arm for rotation therebetween; the first end of the lever is connected to the seat support for sliding and rotation therebetween; the base support is connected to the seat support for sliding and rotational motion therebetween; characterised in that a reclining force on the backrest support causes the seat support to move forwards and upwards and release of the reclining force causes the seat support to move backwards and downwards. Preferably, the seat support includes forward and rearward pairs of slots, respective individual slots of each pair disposed on opposing sides of the seat support and aligned with each other, and each slot receiving a projection extending from the base support. Advantageously, a forward shaft is mounted in the forward part of the base support and extends to each side thereof, the ends of the shaft forming the projections that engage in the forward pair of slots. Preferably, a rearward shaft is mounted in the rearward part of the base support and extends to each side thereof, the ends of the rearward shaft forming the projections that engage in the rearward pair of slots, and wherein the at least one lever is mounted on the rearward shaft. The forward and rearward slots may lie on an axis that extends downwardly with respect to the axis of an upper surface of the seat support at an angle that generates both forward / backward and upward / downward motion. The forward and rearward slots may lie on axes that are at a different angle with respect to the axis of the upper surface of the seat support. Preferably, the forward slot lies at an angle of 45 degrees with respect to the axis of the upper surface of the seat support and the rearward slot lies at an angle of 30 degrees with respect to the axis of the upper surface of the seat support. The chair support mechanism may further comprise biasing means arranged to bias the mechanism into the upright configuration. The biasing means may comprise one or more elastic members. An elastic member may be a spring. Preferably, the biasing means is attached to the base support and the seat support. Advantageously, the seat support comprises a member that extends from one side of the seat support to the other, one end of the biasing means being attached to the member, and wherein the other end of the biasing means is attached to a member extending across the base support. The member may be removable from the seat support, the seat support providing a plurality of locating slots for receiving said member. The member extending across the base support may be the rearward shaft. The base support and lever arm together may provide a first end stop comprising a wall formed in the base support that is aligned with the at least one lever arm and engages therewith to prevent further movement of the base support relative to the at least one lever arm. Preferably, the back rest support and lever arm together provide a second end stop comprising a wall formed in the backrest support that is aligned with the at least one lever arm and engages therewith to prevent further reclining movement of the backrest support relative to the base support. The chair support mechanism, may further comprise a lock arranged to selectively lock the mechanism in the upright configuration or permit full reclining of the mechanism. Advantageously, the lock is arranged to selectively lock the mechanism in a configuration that permits limited reeling of the mechanism. Preferably, the lock comprises a lever attached at one end to the base support and being rotatable relative to the base support between a reclining position in which the other end of the lever is disengaged from the seat support and a locked position in which said other end of the lever is engaged with the seat support. Advantageously, the lock further provides a partial reclining position in which a part of the lever engages with the seat support when the mechanism is partially reclined. The chair support mechanism may further comprise a lock operating mechanism comprising a handle mounted rotatably on the chair support mechanism and a cam mounted on the handle, the cam arranged to engage with an underside of the lever, the underside of the lever comprising a cam follower, wherein rotation of the handle in a first direction causes the cam to move along the cam follower so as to cause the lever to lift from the reclining position to the locked position. Preferably, the lock operating mechanism comprises a detent and at least two recesses, each recess arranged to receive the detent. Advantageously, the lock operating mechanism comprises three recesses, one for receiving the detent when the lever is in the locked position, one for receiving the detent when the lever is in the reclining position and the other for receiving the detent when the lever is in the partially reclining position. According to a second aspect of the invention there is provided a chair comprising a chair support mechanism of the first aspect of the invention. Brief Description of the Drawings In the Drawings, which illustrate preferred embodiments of the invention, and which are by way of example: Figure 1 a schematic representation of a chair support mechanism according to the invention in a non-reclined configuration; Figure 2 a schematic representation of the chair support mechanism illustrated in Figure 1 in a reclined configuration; Figure 3 is a top plan view of the chair support mechanism illustrated in Figure 1; Figure 4a is a cross-section on the axis E-E in Figure 3 with the chair support mechanism in a non-reclined configuration; Figure 4b is a cross-section on the axis B-B in Figure 3 with the chair support mechanism in a non-reclined configuration; Figure 4c is a cross-section on the axis C-C in Figure 3 with the chair support mechanism in a non-reclined configuration; Figure 5a is a cross-section on the axis E-E in Figure 3 with the chair support mechanism in a reclined configuration; Figure 5b is a cross-section on the axis B-B in Figure 3 with the chair support mechanism in a reclined configuration; Figure 5c is a cross-section on the axis C-C in Figure 3 with the chair support mechanism in a reclined configuration; Figure 6 is a partial cut-away schematic representation of the chair support mechanism in a non-reclined configuration; Figure 7 is a side view of the partial cut-away representation of the chair support mechanism in a non-reclined unlocked configuration illustrated in Figure 6; Figure 8 is a side view of the partial cut-away representation of the chair support mechanism illustrated in Figure 6 in a fully reclined unlocked configuration; Figure 9 is a side view of the partial cut-away representation of the chair support mechanism illustrated in Figure 6 in a partially reclined unlocked configuration; Figure 10 is a side view of the partial cut-away representation of the chair support mechanism in a non-reclined locked configuration illustrated in Figure 6; Figure 11 is an exploded view plan view illustrating a locking system; Figure 12 is a cut-away schematic representation of the chair support mechanism illustrating the locking system; Figure 13 is an exploded a cut-away schematic representation of the locking system; and Figure 14 is a cut-away schematic representation of the locking system. Detailed Description of the Preferred Embodiments Referring now to Figures 1 and 2, a chair support mechanism 1 includes a base support 2, a seat support 3 and a back rest support 4. The base support 2 comprises a hole 2g configured to receive a support pillar S (shown in Figures 12 and 13) which is itself attached to a chair base (not shown). The seat support 3 and the back rest support 4 are attached to the base support 2 so as to pivot with respect thereto, and with respect to each other. Hence, when an occupant of the chair leans backwards, the back rest support 4 tilts backwards, which causes the seat support to move forwards and upwards, stretching the springs 5. One end 5a of each spring 5 is attached to a bar 6 that extends between two spaced apart side walls 3a of the seat support 3. The ends of the bar 6 sit in slots 3b. As can be appreciated from Figures 3, 4c and 5c, the slots 3b lie on an angle to the vertical so that a force exerted on the bar 6 by springs 5 pulls the bar 6 into the slots 3b. The other end 5b of each spring 5 is attached to a bar 7, which extends through the base support 2 and is fixed with respect thereto, as described in greater detail below. Each free end of the bar 7 is located in a slot 3d formed in a wall of the seat support 3. The slot 3d has a longitudinal axis X-X which lies at an angle of approximately 30 degrees to the plane Y-Y of the seat support 3. Hence, the bar 7 may move within the slot 3d along the axis X-X. Two spaced apart lever arms 8 are mounted on the shaft 7 for relative rotation thereto. The lever arms 8 are attached at their other ends to the backrest support 4, again in a manner that permits the lever arms 8 to rotate relative to the backrest support 4. In the illustrated example bolts 8a pass through respective holes in a wall 4a to fasten the lever arm 8 to the backrest 4. As can be seen in Figure 4b, the lever 8 engages with a wall 2b of a part 2a of the base support 2, engagement of the lever 8 with the wall 2b listing rotation of the lever 8. The back rest support 4 is pivotally attached to the seat support by means of a pin 4b that is attached to the wall 4c of the backrest support 4 and the seat support 3 in holes 3c, so as to permit relative rotation between the seat support 3 and the backrest support 4 about the pin 4b. A bar 9 is mounted in the base support 2, the bar 9 extending through holes 2e formed in collars 2e’ which extend from walls 2d of said base support 2. The free ends of the bar 9 locate in slots 3e in the seat support 3. The longitudinal axis Z-Z of the slots 3e lies at an angle of approximately 45 degrees to the plane Y-Y of the seat support 3. The bar 9 is therefore free to slide between the ends of the slot 3e. Springs 5 are attached to the bars 6 and 7, the springs 5 biasing the chair support mechanism into the configuration shown in Figures 1 and 4a to 4c. The chair support mechanism functions as follows: When a person sitting in a chair leans back on a backrest attached to the backrest support 4 the backrest support rotates about the pins 4b, as can be appreciated from Figures 4a to 4c and Figures 5a to 5c. The above-described rotation of the backrest support 4 causes the levers 8, which are attached to the backrest support 4 for relative rotation there between, to rotate in a clockwise manner and at the same time for the shaft 7 to which the lever arms 8 are attached to slide in slots 3d from the position shown in Figure 4c to the position shown in Figure 5c. The base support 2 remains stationary and hence the bar 7 remains stationary. As such, the sliding motion of the bar 7 in the slots is a result of the seat support 3 in which the slots 3d are formed moving upwards and to the left from the position shown in Figure 4c to the position shown in Figure 5c. The front part of the seat support 3 moves upward more than the rear part as a result of the longitudinal axis Z-Z of the slot 3e lying at a steeper angle to the plane Y-Y that does the longitudinal axis X-X of the slot 3d. Springs 5 are caused to extend when the occupant of the chair leans backwards on the backrest 4 as described above. When the occupant leans forwards, releasing the force on the backrest the springs 5 return the chair support mechanism from the configuration shown in Figures 5a to 5c to the configuration shown in Figures 4a to 4c. The chair support mechanism 1 includes a lock means comprising a lever 10. The lever 10 is best illustrated in Figures 6 and 10 to 12. The lever 10 is attached to the bar 7 to pivot thereabout, between a first position, a second position and a third position. The lever 10 comprises an end portion 10a, a recess 10b and a stepped portion 10c. When the lever 10 is rotated about the bar 7 such that the end portion 10a sits below the bar 6, the chair support mechanism 1 is free to move as described above, when an occupant leans backwards on the chair back or leans forwards from a backward leaning position. The lever 10 provides two locking conditions. When the lever 10 is rotated towards the bar 6 such that the step 10c sits below the shaft 6, but the end portion 10a is in the path of the shaft 6, the chair support mechanism 1 may move in the manner described above, but such movement is restricted by the end wall 10a coming into 7 contact with the shaft 6. Hence, a short range of movement of the backrest and set support is provided. When the lever 10 is rotated such that the bar 6 sits in the recess 10b, then the chair support mechanism 1 is locked against movement. Figures 6 to 13 illustrate a mechanism that is configured to operate the lever 10, that is to move the lever between the three positions described above. The mechanism comprises a component 20, a part of which engages directly with the lever 10, and a handle 30. The handle 30 includes a vertical shaft part 30a, a horizontal shaft part 30b and a plate 30c, which is attached to the shaft 30b and extends therefrom. The component 20 is mounted on the vertical and horizontal shaft parts 30a, 30b. The component 20 includes a block 20a. The end wall of the block 20a mounts a detent 20b which comprises the first part of a locking mechanism. The detent 20b is mounted to slide within the block 20a and is biased by a spring (not shown) into the position shown in Figure 13. In Figure 13, the detent 20b is located in a recess 2f. Two further recesses 2f’ and 2f” are provided in the base support 2 as can be seen from Figure 11. The component 20 includes an arm 20c which extends over the plate 30c and provides a sprung bias on the plate 30c, keeping the plate 30c in contact with the upper end of seat column S maintaining the position of the handle 30 in the base support 2. The base support 2 includes a wall 2h which sits under the component 20, supporting the component as it is rotated by handle 30. A peg 20e extends from the upper surface of the component 20. As shown in Figure 14, the free end of the peg 20e has an outwardly extending portion 20f which engages with a slot 20g in the base support 2. The peg 20e, the outwardly extending portion 20f and slot 20g together support the component 20 against vertical forces when control lever 30 is used. The component 20 also includes a wall 20d that extends towards and beneath the lever 10. A cam 20d’ is provided on an upper part of the free end of the wall 20d. The cam 20d’ is hemi-spherical in shape. The cam 20d’ sits under the lever 10 and is in contact with the underside thereof, the underside of the lever 10 acting as a cam follower. As can be seen from Figure 13, the underside of lever 10 comprises an enlarged portion 10d. This enlarged portion 10d provides for the cam 20d’ to maintain contact with the underside of the lever 10 as the cam 20d’ moves through an arc when the handle 30 is rotated. Further, the underside of the lever 10 includes a first portion 10d’ that is substantially horizontal, and a second portion 10d” that extends downwardly relative to the first portion. When the handle is rotated, the cam 20d’ moves from engaging with the first portion 10d’ to engaging with the second portion 10d”, causing the lever to lift. As the handle 30 is rotated the cam 20d’ moves part way along the second portion 10d” of the lever 10, which lifts the lever 10. The detent 20b moves into the second recess 2f’ when the handle 30 is rotated sufficiently. With the detent in the second recess 2f’ the lever 10 is positioned such that the bar 6 is aligned with the stepped portion 10c, thereby permitting only partial movement of the chair support mechanism 1. When the handle 30 is rotated further, the cam 20d’ moves further along the second portion 10d” of the lever 10, lifting the lever 10 further. The detent 20b moves into the third recess 2f” when the handle 30 is rotated sufficiently. With the detent in the third recess 2f” the lever 10 is positioned such that the bar 6 is situated in the recess 10b, thereby locking the chair support mechanism 1 against movement.

Claims

1. A chair support mechanism comprising a base support, a seat support, a backrest support, and at least one lever arm having a first end and a second end, wherein:the seat support and backrest support are connected to each other by a pivot connection having a fixed axis;the base support and the seat support are both connected to the first end of the at least one lever arm, said at least one lever arm rotatable relative to each of the base support and the seat support, the backrest support connected to the second end of the at least one lever arm for rotation therebetween;the first end of the lever is connected to the seat support for sliding and rotation therebetween;the base support is connected to the seat support for sliding and rotational motion therebetween;characterised in that a reclining force on the backrest support causes the seat support to move forwards and upwards and release of the reclining force causes the seat support to move backwards and downwards.

2. A chair support mechanism according to Claim 1, wherein the seat support includes forward and rearward pairs of slots, respective individual slots of each pair disposed on opposing sides of the seat support and aligned with each other, and each slot receiving a projection extending from the base support.

3. A chair support mechanism according to Claim 2, wherein a forward shaft is mounted in the forward part of the base support and extends to each side thereof, the ends of the shaft forming the projections that engage in the forward pair of slots.

4. A chair support mechanism according to Claim 2 or 3, wherein a rearward shaft is mounted in the rearward part of the base support and extends to each side thereof, the ends of the rearward shaft forming the projections that engage in the rearward pair of slots, and wherein the at least one lever is mounted on the rearward shaft.

5. A chair support mechanism according to any of Claims 2 to 4, wherein the forward and rearward slots lie on an axis that extends downwardly with respect to the axis of an upper surface of the seat support at an angle that generates both forward / backward and upward / downward motion.

6. A chair support mechanism according to Claim 5, wherein the forward and rearward slots lie on axes that are at a different angle with respect to the axis of the upper surface of the seat support.

7. A chair support mechanism according to Claim 6, wherein the forward slot lies at an angle of 45 degrees with respect to the axis of the upper surface of the seat support and the rearward slot lies at an angle of 30 degrees with respect to the axis of the upper surface of the seat support.

8. A chair support mechanism according to Claim 1, further comprising biasing means arranged to bias the mechanism into the upright configuration.

9. A chair support mechanism according to Claim 8, wherein the biasing means comprises an elastic member.

10. A chair support mechanism according to Claim 8 or 9, wherein the biasing means is attached to the base support and the seat support.

11. A chair support mechanism according to Claim 10, wherein the seat support comprises a member that extends from one side of the seat support to the other, one end of the biasing means being attached to the member, and wherein the other end of the biasing means is attached to a member extending across the base support.

12. A chair support mechanism according to Claim 11, wherein the member is removable from the seat support, the seat support providing a plurality of locating slots for receiving said member.

13. A chair support mechanism according to any of Claims 10 or 13, when dependent on Claim 4, wherein the member extending across the base support is the rearward shaft.

14. A chair support mechanism according to any preceding claim, wherein the base support and lever arm together provide a first end stop comprising a wall formed in the base support that is aligned with the at least one lever arm and engages therewith to prevent further movement of the base support relative to the at least one lever arm.

15. A chair support mechanism according to any preceding claim, wherein the back rest support and lever arm together provide a second end stop comprising a wall formed in the backrest support that is aligned with the at least one lever arm and engages therewith to prevent further reclining movement of the backrest support relative to the base support.

16. A chair support mechanism according to any preceding claim, further comprising a lock arranged to selectively lock the mechanism in the upright configuration or permit full reclining of the mechanism.

17. A chair support mechanism according to Claim 16, wherein the lock is arranged to selectively lock the mechanism in a configuration that permits limited reeling of the mechanism.

18. A chair support mechanism according to Claim 16 or 17, wherein the lock comprises a lever attached at one end to the base support and being rotatable relative to the base support between a reclining position in which the other end of the lever is disengaged from the seat support and a locked position in which said other end of the lever is engaged with the seat support.

19. A chair support mechanism according to Claim 19, wherein the lock further provides a partial reclining position in which a part of the lever engages with the seat support when the mechanism is partially reclined.

20. A chair support mechanism according to Claim 18 or 19, further comprising a lock operating mechanism comprising a handle mounted rotatably on the chair support mechanism and a cam mounted on the handle, the cam arranged to engage with an underside of the lever, the underside of the lever comprising a cam follower, wherein rotation of the handle in a first direction causes the cam to move along the cam follower so as to cause the lever to lift from the reclining position to the locked position.

21. A chair support mechanism according to Claim 20, wherein the lock operating mechanism comprises a detent and at least two recesses, each recess arranged to receive the detent.

22. A chair support mechanism according to Claim 21, wherein the lock operating mechanism comprises three recesses, one for receiving the detent when the lever is in the locked position, one for receiving the detent when the lever is in the reclining position and the other for receiving the detent when the lever is in the partially reclining position.

23. A chair comprising a chair support mechanism as claimed in any of Claims 1 to 22.

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