WO2000008975A1

WO2000008975A1 - Locking mechanism

Info

Publication number: WO2000008975A1
Application number: PCT/GB1999/002387
Authority: WO
Inventors: Gordon Dennis Hobb
Original assignee: Northeastern Components (International) Ltd
Priority date: 1998-08-11
Filing date: 1999-07-22
Publication date: 2000-02-24
Also published as: GB9817339D0

Abstract

A locking device (10) for adjusting the relative inclination of two parts of a chair is disclosed. The device comprises a housing (19) having a top plate (13) having an aperture (22). A slide bar (11) has a series of partially spherical recesses (17) arranged adjacent the aperture (22). A ball bearing (23) is partially received in the aperture (22) and engages one of the partially spherical recesses (17) to prevent the slide bar (11) moving relative to the top plate (13). An actuator member (24) can move between a first position in which it urges the ball bearing (23) into engagement with the recess (17), and a second portion in which it does not prevent sliding relative movement of the slide bar (11) and top plate (13). The actuator member (24) is prevented from moving from the first position to the second position when the locking device (10) is subjected to a load tending to cause sliding relative movement of the slide bar (11) and top plate (13).

Description

LOCKING MECHANISM

The present invention relates to a locking mechanism, and relates particularly, but not exclusively, to a locking mechanism for enabling adjustment of the inclination of the back and/or seat of an office chair.

Mechanisms for adjusting the inclination of the back and seat of an office chair relative to each other and to the ground are known in which pivoting movement of the seat relative to the ground and/or of the back relative to the seat is controlled by locking the seat or back in position by means of one or more small pressurised gas cylinders. Alternatively, it is known to utilise a multi-plate clutch arrangement in which sets of parallel plates are placed under compression to prevent them from moving relative to each other, which in turn prevents rotation of the back and/or seat of the chair. The chair back and/or seat are generally biased by springs towards the upright position of the chair, and the desired orientation of the chair is chosen by releasing the locking mechanism, moving the back and/or seat of the chair to the desired inclination, and locking the chair in that orientation.

Locking mechanisms of the gas cylinder type generally suffer from the disadvantage that the gas cylinders are expensive and need to be purchased from specialist manufacturers, and have a relatively short life expectancy, typically two to three years in normal use of the chair. The locking mechanisms of the multi-plate clutch type suffer from the disadvantage that they are also costly because of the significant number of parts involved, thus making assembly more difficult, and the locking action of the locked mechanism can often be overcome if sufficient force is applied to the chair. In addition, because such locking mechanisms usually form an integral part of the main mechanism of each individual chair, it is difficult to produce a single mechanism that can be used in several different types of chair. Furthermore, locking mechanisms of the multi -plate clutch type require an eccentric cam to be attached to the mechanism, and the locking mechanism often requires a considerable force to operate the cam, which in turn makes the mechanism difficult to operate.

A potentially more serious disadvantage of office chairs containing locking mechanisms of both the gas-cylinder and clutch types is that when the back of a chair is locked in a reclined position, it can be inadvertently released by a person not sitting fully back against the back of the chair. As a result, because the chair back is generally biased by springs towards the upright position of the chair, the back of the chair can be projected forwards under the biasing force of the springs with sufficient force to cause injury.

It is known to address this problem by providing a locking mechanism in which push-pull rods or bars slot into one or more holes or slots incorporated into the main chair mechanism to lock the back of the chair in one or more inclinations relative to the seat . Because the back of the chair is still biased by springs towards the upright position of the chair, when the occupant is not sitting fully back against the chair back, the locking mechanism is placed under load by the springs, thus making it difficult to remove the rod or bar from the hole or slot. It is therefore difficult to release the locking mechanism unless the occupant leans back against the spring pressure to remove the load from the locking rod or bar.

However, such devices suffer from the drawback that the locking bar is generally part of the main chair mechanism, which makes it difficult to produce a locking mechanism suitable for several different types of chair, and can also make the chair difficult to operate. In addition, it can be difficult to correctly locate the rod or bar in a corresponding slot, as a consequence of which the chair may be noisy and not very smooth in operation..

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art .

According to an aspect of the present invention, there is provided a device for adjusting the relative inclination of two parts of a chair, the device comprising:

a body member having an aperture and adapted to be fixed relative to a first part of the chair;

a sliding member having an engaging portion arranged adjacent said aperture in use, wherein the sliding member is adapted to be fixed relative to a second part of the chair and to slide relative to the body member to adjust the relative inclination of said first and second parts;

an engaging member partially received in said aperture and adapted to engage said engaging portion to prevent sliding relative movement of said body member and said sliding member; and

an actuator member adapted to move between a first position in which the actuator member urges said engaging member into engagement with said engaging portion and a second position in which said engaging member does not prevent sliding relative movement of said body member and said sliding member, wherein said actuator member is prevented from moving from said first position to said second position when the device is subjected to a load tending to cause sliding relative movement of said body member and said sliding member.

By providing a device in which an engaging member is partially received in an aperture in the body member and an actuator member does not directly lock the body member and sliding member relative to each other, this provides the advantage of improving the ease of use of the device and making operation of the device smoother in comparison with prior art devices having locking rods or bars cooperating with holes or slots. In addition, it is easy to construct the device of the present invention as a self-contained unit that can be used with a variety of chair mechanisms without the necessity of designing a separate locking device for each type of chair. Furthermore, because the device is operated simply by movement of the actuator member between the first and second positions, the device can be operated by a variety of different means, such as push buttons, cable releases or rotating handles. The provides the advantage of enabling separation of the operation of the locking mechanism from the body of the device, thus giving chair designers considerably more freedom than in the case of the prior art .

The sliding member may be received in a slot in the body member.

In a preferred embodiment, the engaging member comprises a ball bearing, and the engaging portion comprises a plurality of recesses, wherein each said recess is adapted to partially receive said ball bearing to prevent sliding relative movement of said body member and sliding member.

The actuator member is preferably arranged adjacent said aperture and is adapted to slide between said first and second positions .

The actuator member may include an inclined portion for abutting said engaging member to urge said engaging member into engagement with said engaging means as the actuator member moves from said second position to said first position. In a preferred embodiment, the actuator member is at least partially received within a further aperture in said body member, wherein when the actuator member is in said first position and the device is subjected to a load tending to cause sliding relative movement of said body member and said sliding member, the actuator member is urged into engagement with said body member to prevent movement of the actuator member to said second position.

According to another aspect of the present invention, there is provided a chair comprising a first part, a second part, and a device as defined above for adjusting the relative inclination of said first and second parts.

The first part may be a back of the chair and the second part may be a seat of the chair.

Alternatively, or in addition, the first part may be a back of the chair and the second part may be a support of the chair.

The chair preferably further comprises biasing means tending to cause sliding relative movement of said sliding member and body member.

As an aid to understanding the invention, a preferred embodiment thereof will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which :-

Figure 1 is a schematic cross-sectional elevation view of part of an office chair embodying the present invention;

Figure 2 is a detailed cross-sectional view of a locking mechanism shown in Figure 1; and

Figure 3 is a view along the line A-A of Figure 2. Referring in detail to Figure 1, an office chair 1 of the forward pivot or knee tilt type comprises a back 2 and a seat 3 attached to a seat frame 4. A supporting frame 5 is mounted to a support 6 and hinged to the seat frame 4 about pivot axis 7. The seat back 2 and seat 3 are urged in the direction of arrow B in Figure 1 between a rest position I and a reclined position II by means of a heavy duty torsion spring 8 which is sufficiently strong to counterbalance the weight of the occupant as the chair is reclined and to return the chair bearing the weight of the occupant to its rest position. A hand wheel 9 is used to adjust the pre-tension of torsion spring 8.

A locking device 10 is located between the seat frame 4 and the supporting frame 5 and comprises a sliding member 11 hinged to the seat frame 4 by means of pivot pin 12, and a top plate 13 attached by a pivot pin 14 to the supporting frame 5. The locking mechanism 10 is actuated by pulling on knob 15 which causes cable 16 to release the device 10 to enable the seat frame 4 to be pivoted relative to the supporting frame 5 between positions I and II (shown in dotted lines in Figure 1) in the direction of arrow C under the weight of the occupant.

Referring the Figures 2 and 3, the locking mechanism 10 is shown in greater detail. The mechanism 10 comprises a sliding member in the form of a slide bar 11 having an engaging portion comprising a series of partially spherical recesses 17, and includes an aperture 18 for receiving pivot pin 12. The slide bar 11 is received in a slot in housing 19 and slides in the slot between limits defined by dowel 20 sliding in slot 21. The slot 21 serves to determine the "stroke" of the device and to prevent the slide bar 11 from being pulled out of the housing 19.

A top plate 13, forming part of the housing 19, has an aperture 22 through which a ball bearing 23 extends such that the ball bearing 23 is partially accommodated in the aperture 22. The ball bearing 23 has a radius of curvature corresponding to that of recesses 17.

An actuator member 24, to which cable 16 (not shown in Figures 2 and 3) is attached, is received in a slot 25 in housing 19 defined by an upper part 26 of housing 19. The actuator member 24 has an inclined portion 27 for defining a space 28 between the actuator member 24 and the top plate 13 and is adapted to slide relative to the top plate in the direction of arrow D shown in Figure 2. The housing 19 also includes an aperture 29 for receiving pivot pin 14.

In the position shown in Figure 2, the actuator member 24 urges the ball bearing member 23 into engagement with one of the recesses 17 to prevent sliding movement of the slide bar 11 relative to the top plate 13. As the actuator member 24 is moved in the direction of arrow D, the space 28 is located above aperture 22. As a result, sliding movement of the slide bar 11 relative to the top plate 13 causes the ball bearing 23 to rise out of engagement with recesses 17 into space 28.

The operation of the mechanism of Figures 2 and 3 will now be described.

When no occupier is sitting on the chair, or the occupier is sitting too far forward to counteract the effect of torsion spring 8, the torsion spring 8 urges the slide bar 11 in the direction of arrow E shown in Figure 2. This causes one or more of the recesses 17 to urge the ball bearing 23 upwards against inclined portion 27 of actuator member 24, as a result of which the ball bearing 23 cannot move upwards, and sliding movement of the slide bar 11 relative to the top plate 13 is prevented. The ball bearing 23 urges the actuator member 24 upwards against the upper plate 26 of the housing 19, as a result of which it is very difficult to slide the actuator member 26 in the direction of arrow D shown in Figure 2 by means of cable 16 to release the locking mechanism. When the occupier is sitting correctly on the seat 3, the occupier's weight counterbalances the torsion spring 8, as a result of which there is no force urging the ball bearing 23 upwards against the actuator member 24. Consequently, the actuator member 24 can be slid in the direction of arrow D by means of cable 16 to locate the space 28 above the aperture 22 to allow sliding movement of slide bar 11 relative to top plate 13.

It will be appreciated by persons skilled in the .art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

Claims

1. A device for adjusting the relative inclination of two parts of a chair, the device comprising:

a sliding member having an engaging portion arranged adjacent said aperture in use, wherein the sliding member is adapted to be fixed relative to a second part of the chair .and to slide relative to the body member to adjust the relative inclination of said first and second parts;

2. A device according to claim 1, wherein the sliding member is received in a slot in the body member.

3. A device according to claim 1 or 2 , wherein the engaging member comprises a ball bearing, and the engaging portion comprises a plurality of recesses, and wherein each said recess is adapted to partially receive said ball bearing to prevent sliding relative movement of said body member and sliding member .

4. A device according to any one of the preceding claims, wherein the actuator member is arranged adjacent said aperture and is adapted to slide between said first and second positions .

5. A device according to any one of the preceding claims, wherein the actuator member includes an inclined portion for abutting said engaging member to urge said engaging member into engagement with said engaging means as the actuator member moves from said second position to said first position.

6. A device according to any one of the preceding claims, wherein the actuator member is at least partially received within a further aperture in said body member, wherein when the actuator member is in said first position and the device is subjected to a load tending to cause sliding relative movement of said body member and said sliding member, the actuator member is urged into engagement with said body member to prevent movement of the actuator member to said second position.

7. A chair comprising a first part, a second part, and a device according to any one of the preceding claims for adjusting the relative inclination of said first and second parts .

8. A chair according to claim 7, wherein the first part is a back of the chair and the second part is a seat of the chair.

9. A chair according to claim 7 or 8 , wherein the first part is a back of the chair and the second part is a support of the chair.

10. A chair according to any one of claims 7 to 9, further comprising biasing means tending to cause sliding relative movement of said sliding member and body member.