WO1992010117A1

WO1992010117A1 - Improvements relating to chairs

Info

Publication number: WO1992010117A1
Application number: PCT/GB1991/002182
Authority: WO
Inventors: Timothy James Gluyas; Simon Charles Albert Hobbs; Anthony Wilson Evans
Original assignee: Acf International Limited
Priority date: 1990-12-13
Filing date: 1991-12-09
Publication date: 1992-06-25
Also published as: GB9027090D0; AU9034791A

Abstract

A chair comprises a base (4), a seat (18) mounted on the base and providing a seating surface (20), and a back mounted on the base and providing a surface (24) supporting part at least of the back of the user. The back and base are linked together so that the chair may be moved from a forward tilt position through a median position to a rear tilt position, such movement being restrained by a restraining mechanism (40). The restraining means acts through an adjustable mechanism (48, 50, 78, 80, 82) which may be adjusted to vary the mechanical advantage of the restraining means (40) so that the resistance provided to such movement of the chair can be adjusted to meet the requirements of the user.

Description

Title: "Improvements relating to chairs" Description of Invention

This invention is concerned with improvements relating to chairs particularly of the kind [hereinafter referred to as being of the kind specified] comprising a base, a seat providing a seating surface and a back providing support for part at least of the back of a user of the chair, the back of the chair at least being mounted for movement relative to the base, restraining means being provided to restrain movement of the back against such movement.

The present invention has been devised particularly for use with office chairs: it is however to be appreciated that the invention may be used in relation to other chairs of the kind specified, including arm chairs or car seats.

Conventionally a chair of the kind specified is provided with adjustment mechanism which is operative to vary the effect of the restraining means, whereby to vary the effort required to move the back of the chair. For example, the restraining means may comprise spring means operative to restrain movement of the back, the adjustment mechanism being operative to increase or decrease a frictional force which is applied to movement of the back.

In general operation of the adjustment mechanism of conventional chairs requires a significant degree of effort to be exerted, such as tightening or loosening a hand-wheel, to achieve a desired degree of restraint, and it is one of the various objects of this invention to reduce this difficulty.

According to this invention there is provided a chair comprising a base, a seat mounted on the base and providing a seating surface, a back mounted on the base and providing a surface supporting part at least of the back of a user, at least the back of the chair being mounted for movement relative to the base, and restraining mechanism to restrain the back of the chair against such movement, wherein the restraining mechanism acts through a mechanism which may be to vary the mechanical advantage of the restraining mechanism in restraining movement of the back. Preferably the restraining mechanism provides a force, which may be substantially constant, urge the back of the chair from a forward position through an intermediate position to a forward position, or said force may vary over the range of movement of the chair. Preferably the restraining mechanism comprises a constant pressure fluid-operated piston/cylinder device.

Preferably in addition to the back of the chair being movable, preferably the seat is also mounted for movement relative to the base, the restraining mechanism being operative to restrain the seat against such movement, and acting to so restrain through the adjustable mechanism whereby said adjustable mechanism is effective to act at the same time to vary the restraint to movement of both the back and the seat.

Advantageously the chair comprises linkage mechanism linking the back and the seat and to cause the back and the seat to move synchronously.

Preferably the linkage mechanism is operative to cause the seat and the back to move at disparate rates, and conveniently the restraining mechanism is connected to the linkage mechanism by the adjustable mechanism.

Conveniently the adjustment mechanism comprises apivotally mounted connecting lever pivotally connected to the restraining device on one side of the pivotal mounting and pivotally connected to the linkage mechanism on the other side of the pivotal mounting, means, conveniently manually operable, being provided to move one of the pivotal mountings between said connections.

Advantageously the means to move said pivotal mounting is provided by a screw-thread adjustment device which may be in the general form of a worm and worm wheel, or equivalent.

In this manner, by adjustment of the pivotal mounting in a direction longitudinal of the connecting lever, the mechanical advantage of the restraining means may be varied without any significant input of force, allowing the tilting stiffness of the chair to be conveniently adjusted.

According to this invention there is also provided a chair comprising a base, a seat providing a seating surface mounted on the base for generally pivotal movement in a generally horizontal disposition, a back providing a surface to support part at least of the back of a user and mounted on the base for generally pivotal movement in a generally vertical disposition, linkage mechanism linking the seat and the back so that the back and the seat undergo pivotal movement in relation to one another, and restraining mechanism to restrain the seat and back against movement, wherein the restraining mechanism acts through a mechanism which may be adjusted to vary the mechanical advantage of the restraining mechanism in resisting movement of the back and seat.

In this manner a desired tilt stiffness may be obtained relatively easily, simply by varying the mechanical advantage.

Conveniently the restraining mechanism acts to restrain parallel pivotal axes of the chair against relative movement, preferably either of approach or separation, and preferably the restraining mechanism so acts through the intermediary of the adjustment mechanism.

Difficulty is also encountered in that, where a chair of the kind specified is operating under a specific tilt stiffness, whether or not that tilt stiffness is variable, the same tilt stiffness is encountered in relation both to moving the chair between its forward tilt position and its median position, and to moving the chair between its median position and its rear position. However in use it is significantly iΛoτe difficult for a user of the chair to control movement of the chair from the forward tilt position to the median position than it is to control movement from the median position to the rearward position.

Thus according to this invention there is also provided a chair comprising a base, a seat providing a seating surface movably mounted on the base a back movably mounted on the base, linkage mechanism linking the seat and the back so that the back and the seat undergo movement in relation to one another, the chair being movable between a first, forward position, a second, neutral or intermediate position and a third, rear position, restraining mechanism being provided to urge the seat and back towards said first position, differential means being provided whereby the force required to move the chair from the second to the third position is greater than the force required to move the chair from the first to the second position.

The restraining mechanism may comprise a device for exerting a substantially constant or a variable force, and said differential means may be operative to vary the mechanical advantage by which the restraining means moves the chair between said positions.

The invention may be used in a chair comprising adjustment means as above described, to vary the overall tilting stiffness of the chair, the differential means being effective to [for example] reduce the tilting stiffness encountered on movement of the chair between the forward position and the median position, irrespective of the level of tilting stiffness as set by the adjusting means.

The features set out in the last preceding paragraph are advantageously used with other features of the invention, described herein above. According to this invention there is also provided a chair of the kind specified, comprising means releasably to secure the chair in its median position, said means conveniently being provided by a retractable stop, conveniently which is manually movable between advanced and retracted positions. Thus in the advanced position the retractable stop adopts a position in which part -of the linkage mechanism of the chair is prevented from moving beyond a certain position, which is necessary for the chair to be moved from the median to the forward position.

There will now be given a detailed description, to be read with reference to the accompanying drawings, of three chairs which is are preferred embodiments of this invention, having been selected for the purposes of illustrating the invention by way of example. In the accompanying drawings:

FIGURE 1 is a side elevation of the chair which is the first embodiment of the invention in a central rest position;

FIGURE 2 is a side elevation of the chair in a forward tilt position; FIGURE 3 is a side elevation of the chair in a rearward tilt position; FIGURE 4 is an underside view of the chair, wherein restraining mechanism and adjusting mechanism thereof;

FIGURE 5 is an elevational view, parts being broken away, of a detail of the adjustment mechanism;

FIGURE 6 is a view corresponding to Figure 4 wherein the adjustment mechanism in a different position;

FIGURE 7 is a schematic perspective view showing part of the mechanism of the chair which is the second embodiment of the invention;

FIGURES 8, 9 and 10 are schematic elevational views showing parts of a mechanism in positions corresponding to the rear, intermediate and forward tilt positions; and

FIGURE 11 and 12 are views showing the forward and rear tilt positions respectively of the chair which is the third embodiment of the invention; and Figure 13 is a view corresponding to Figure 8, showing the restraining mechanism and adjustable means of the third embodiment.

The chair which is the first embodiment of this .invention, and which has been selected for the purposes of illustrating the invention by way of example, is an office chair, comprising a base 4 consisting of a stand 6 mounted on Castors 8, the stand providing a cylinder -9 from which a piston 10 extends, the degree of extension of the piston being adjustable by control means [not shown] in conventional manner.

Carried by the piston 10 is a base member afforded by a forward stirrup 12, to which a rear stirrup 16 is pivotally mounted by coaxial pivots 14.

The chair comprises a seat 18 providing a seating surface 20, a back 22 providing a surface 24 for supporting the lumber region at least of a user, and arm supports 26.

Secured to a forward region of the seat 18 is a bracket 22 pivotally connected to the forward stirrup 12 by a pivotal axle 28, whilst secured to the underside of the seat at a rearward portion is a bracket 30, said bracket 30 being slidable in the forward and reverse directions of the seat such as in dovetail formations, and being connected to the rear stirrup 16 by a pivot axle 32.

The back 22 of the chair is supported by a bracket 34 fixedly secured to the rear stirrup 16.

In use, the seat 18 may be pivotally moved about the pivotal axle 28 between a rest or intermediate position shown in Figure 1, a forward tilt position shown in Figure 2, and a rearward tilt position shown in Figure 3. Such movement of the seat causes the distance between the pivotal axles 28 and 32 to be altered, causing the bracket 30 to move across the underside of the seat in the dovetail formation, and causes the rear stirrup 16 to rotate about the pivotal axis 14, causing the back of the chair to vary its inclination to the vertical, generally as shown in Figures 1 to 3. As will be seen, an 11° rearward tilt of the seat from the rest position produces a 21° rearward tilt of the back, whilst a 4° forward tilt of the seat from the rest position produces a 10° forward tilt of the back, although these angles, and the ratio between them, may be varied if desired.

Secured at a forward region to the pivot axle 28 and extending beneath the chair rearwardly of the pivot 28 is a carrier in the form of a tray 39, the tray being unconnected at the rear other than as is described hereinafter.

Pivotally connected to the underside of the tray 39 [Figure 4] is restraining mechanism, said restraining mechanism acting through the intermediary of adjusting mechamsm to restrain movement between the tray and the pivot axle 32, and in consequence between the pivot axle 28 and the pivot axle 32. In this manner the restraining mechanism is effective to restrain movement of the chair, i.e. movement of the seat about the pivot axis 28 and of the back about pivot axis 14.

The restraining mechanism comprises a gas spring 40, i.e. a cylinder 42 filled with pressurised gas, having a piston 44 extending therefrom, which acts in the same manner as a constant force spring - the piston 44 being connected at 45 to the tray 39 adjacent to the pivot axis 28, and the cylinder being pivotally connected at 46 to a connecting lever 48, the opposite end of the lever 48 being connected to the pivot axis 32 by a rear link 49.

In conventional manner the gas spring 40 is provided with a locking lever 41 which may be operated to prevent extension or retraction of the piston 44, and hence lock the chair in a desired inclined position.

The lever 48 is pivotally mounted on a principal fulcrum device 50: thus pressure exerted on the chair to produce rearward tilt [corresponding to a separation of the pivot axles 28 and 32] is restrained by the resistance of the gas spring 40 to extension, whilst pressure exerted on the chair to produce a forward tilt [corresponding to movement of approach between the pivot axles 28 and 32] is restrained by resistance of the gas spring 40 to compression.

It will be appreciated that such movement may be accomplished either by exerting pressure on the seat, or by exerting pressure on the back, or a combination of the two, and that during such movement, movement of the knee point [alternatively known as the "waterfall"] of the chair is minimal.

The principal fulcrum 50 forms part of the adjustment mechamsm of the preferred embodiment, and the tilting stiffness of the chair may be varied by movement of the principal fulcrum 50 in a direction longitudinally of the connecting lever 48.

Provided in the tray 39, specifically in a plate 60 thereof (Figures 4 and 4) is an elongate slot 62. Secured to the plate 60 is a bearing assembly 64 of the principal fulcrum, a spindle of which extends through the slot 62 whereby the bearing assembly 64 is slidable along the plate 60. The connecting lever 48 is in the form of a housing 68 [Figure 5] which carries at its ends forks 69, 70 which are respectively pivotally secured to the gas cylinder 42 and the rear link 49. Extending longitudinally through the housing 68 is a bore 72, part of which is threaded, as shown at 74. Opening into the bore 72 on the underside of the housing, as seen in Figure 5, is an elongate slot 76, through which a head 78 of the bearing assembly 64 extends into the bore 72. Mounted on the head 78 is an exteriorly threaded, cylindrical adjustment member 80, said adjustment member being capable of rotation about its longitudinal axis within the bore 72, and being retained axially in positionally relationship to the head 78 by a pin. Specifically the adjustment member 80 is provided with an interior key formation 82 [Figure 4] into which an adjusting element may be entered to rotate the adjustment member, causing the adjustment member, and hence the head 78 to be moved longitudinally of the bore 72 in threaded engagement with the threads 74 thereof. Such movement of the head 78 causes the bearing assembly 64 of the principal fulcrum 50 to move relative to the carrier plate 60.

In this manner the velocity ratio between the pivots 69 and 70 may be changed, and hence the mechanical advantage between the gas spring and the pivot axle 32. By movement of the bearing assembly 64 towards the link 49 [i.e. into the position shown in Figure 4] the force exerted by the restraining mechanism is maximised, requiring greater force to be exerted to move the seat and back of the chair, whilst movement of the bearing assembly 64 away from the link 49 [i.e. into the position shown in Figure 6] the force exerted by the restraining mechanism is minimised, allowing easier tilting movement of the back and seat.

In this manner the tilting stiffness of the chair may be varied with minimal exertion of force. Particularly if desired an adjustment element [e.g. indicated at 84, shown in dotted lines in Figure 4] may be arranged such that it may be engaged with the key formation 82 only when the chair is in its median position.

Figure 6 shows the position of the principal fulcrum 50 in its position of lowest load, and also illustrates, in broken lines, the position of various elements of the restraining mechanism and the adjustment mechanism in the positions of forward tilt [indicated A], and rearward tilt, indicated [B], the median position being shown in full lines. The chair which is the second embodiment of the invention, shown in Figures 7 to 10, is similar to the first embodiment above described, and will be described hereinafter inasmuch as the second embodiment differs from the first embodiment. Unless otherwise stated, the second embodiment is constructed and arranged to operate in a manner substantially the same as the first embodiment, and similar numerals, with the suffix a, have been used to denote corresponding parts.

In the second embodiment, a connecting lever 48a is mounted on the tray 39a_. for rotation about a principal fulcrum 50a, the connecting lever 48a. being attached by a pivot link 69a. at one end to the gas cylinder [not shown] and carrying on the other side of the principal fulcrum a positionally adjustable slide block Ul from which a pin 110 extends. The pin 110 extends between slots 112 of a rear link 114 which has an integral sleeve 116 through which the rear axle 32a. extends. Thus by positional adjustment of the pin 110, by rotation of an adjustment element 83a, the mechanical advantage of the force acting on the rear link 69a. may be changed, varying the tilting stiffness of the chair.

However in the second embodiment the primary fulcrum 50a is carried by a pivot member 120 which is pivotally mounted on the tray 39a. on a secondary fulcrum 122 positioned in relation to the primary fulcrum 50a on the side thereof opposite to the pin 110. Thus on movement of the lever arm by the gas cylinder, the connecting lever 48a will move primarily about the primary fulcrum 50a.

The pivot member 120 is provided with an abutment 124 which is engaged by the connecting lever 48a. as it moves from its rearward tilt position to its median position. Having engaged the abutment, the connecting arm 48a cannot then move relative to the pivot member 120, and extension of the gas cylinder causes the connecting lever 48a. to move with the pivot member 120 about the secondary fulcrum 122. The pin 124 is located so that engagement occurs in the median position (Figure 9), Figure 8 illustrating the rear tilt position and Figure 10 illustrating the forward tilt position. In this manner the mechanical advantage, in addition to being capable of being varied overall by the adjustment means 83a, also differs between tilting movement from the forward to the median position, and from the median position to the rearward tilt position, in particular allowing control of the movement of the chair from its median to its forward tilt position to be resisted and hence controlled by a user of the chair, more easily than movement of the chair from its rear tilt position to its median position. This is consistent with a user of the chair being more easily able to move the chair rearwardly from the median position than from the forward position.

On movement of the chair from its forward towards its rearward tilt position, a stop 130 is provided which is engaged by the pivot member 120 at the position corresponding to the median position, ensuring that the connecting lever then commences to rotate about the principal fulcrum 50a..

Additionally, if desired means may be provided conveniently to restrain movement of the chair into its forward tilt position when unoccupied, under the action of the gas cylinder. Thus a manually retractable or advancable secondary^" stop 132 may be provided, as is shown in Figure 9, which may be advanced into a position behind the pivot member 120, and prevent movement thereof as is necessary to move the chair from its median from its forward tilt position. In this manner, when the chair is unoccupied, for example when being displayed for sale, the chair will conveniently adopt and remain at rest in its median position rather than adopting its forward tilt position. Conveniently, the stop 132 may be brought into operation by a specific movement of the control lever 83a.

Whilst in the first and second embodiments the back 22 of the chair is connected directly to the rear stirrup 16, in the third embodiment, in which similar numerals with the suffix b_have been utilised to indicate similar parts, the back 22b. is fixed to a bracket 140 which is pivotally connected to the tray 39b_by a supplementary pivot 142. The rear axle 32b_ mounted on rear stirrup 16b_ passes through angled slots 144 in the tray 39b. (see Figures 11 and 12), movement of the rear stirrup 16b. being transmitted to the back 22b_ by a supplementary roller 132 of the bracket 140 which passes through angled slots 244 in the stirrup 16b. By location of a pivot for the back of the seat which is located somewhat more rearwardly than the pivot 14b_ of the rear stirrup, the degree of widening of the gap X between the back of the chair and the seat as the chair is moved to its rear tilt position is reduced.

In the third embodiment the restraining mechanism 40b_. comprises a constant pressure gas cylinder 42b. in conjunction with a pair of compression springs 150, each mounted on a tie rod 152, the mechanism being pivotally mounted at a rear end on pivot 45b, and being attached at its other end by pivot 69b. to bracket 48b, said bracket 48b_ being mounted on a fixed primary fulcrum 50b.

A bracket assembly 116b_. carries two pairs of rollers 154, 156 which embrace the shaft 32b, said bracket assembly carrying at its forward end a pivot 110b_ which extends through slots 112b. provided in the plate 48b.

Thus outstroking movement of the restraining means 40b. causes the plate to pivot in a clockwise direction (Figures 13) about the primary fulcrum 50b, drawing the rear axle 32b_ to the left, and moving the chair into its forward tilt position.

As with the second embodiment, the mechanical advantage of operation of the restraining means 40b. may be varied by movement of the fulcrum 110b, by operation of an adjustment lever 83b_.

Additionally, whilst rotation of the lever 83b positionally adjusts the fulcrum 110b_ longitudinally of the slots 112b, varying the mechanical advantage, by movement of the lever 83b_ in an axial direction, a stop 132b. may be moved into a position in which it restrains further movement of the lever 48b. in a clockwise direction beyond the- position illustrated in Figure 13, effectively preventing movement of the chair from the median position to the forward tilt position.

Further, by virtue of the construction and operation of the restraining means 40b, the effective force exerted by the restraining means reduces with outstroke, and thus the force exerted by the restraining means on movement of the chair from the rear tilt position to the median tilt position will be greater than the force exerted by the restraining means on movement of the chair from the median to the forward tilt position. Thus, with the second embodiment, this enables a user of the chair to move the chair between the median and forward tilt positions more easily than he may move the chair the median to the rear tilt positions.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in the terms or means for performing the desired function, or a method or process for attaining the disclosed result, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A chair comprising a base [4], a seat [18] mounted on the base and providing a seating surface [20], a back [22] mounted on the base and providing a surface [24] supporting part at least of back of the user, at least the back being mounted for movement relative to the base, and restraining means [40, 42, 44, 45, 46, 48, 49] to restrain the back against such movement, wherein the restraining means acts through a mechanism [48, 50, 64, 78, 80, 82] which may be adjusted to vary a mechanical advantage of the restraining means in restraining movement of the back [22].

2. A chair according to Claim 1 wherein the restraining means provides a substantially constant force to urge the back to a forward position.

3. A chair according to Claim 1 wherein the restraining means provides a variable force to urge the back [22] to a forward position.

4. A chair according to any one of the preceding claims wherein the restraining means comprises a fluid operated piston/cylinder device [40. 42].

5. A chair according to any one of the preceding claims comprising locking means [41] to lock the back [22] against movement.

6. A chair according to any one of the preceding claims wherein the seat [18] of the chair is additionally mounted for movement relative to the base, the restraining means being operative to urge the seat against such movement, and acting to so restrain through the adjustable mechanism [48, 50].

7. A chair according to any one of the preceding claims comprising linkage mechanism [12, 14, 16, 28, 32] linking the back and the seat and to cause the back and seat to move synchronously.

8. A chair according to Claim 7 wherein the linkage mechanism is operative to cause the back and seat to move at disparate rates.

9. A chair according to one of Claims 7 and 8 wherein the restraining mechanism [40, 42, 44, 45, 46] is connected to the linkage mechanism [28, 32] by the adjustable mechanism [48, 50, 49].

10. A chair according to any one of the preceding claims wherein the adjustable mechanism comprises a connecting lever [48] pivotally mounted [at 50] to a frame of the chair and which is pivotally connected to the restraining device [42] on one side of the pivotal mounting [50, 64] and pivotally connected to the linkage mechanism [32] on the other side of the pivotal mounting, means [74, 80, 82, 84] being provided to move one of the pivotal mountings between said connections [46, 70].

11. A seat according to Claim 10 wherein said means to move said pivotal mounting [50, 64] is provided by a screw-thread adjustment device [74, 80].

12. A chair comprising a base, a seat providing a seating surface and mounted on the base for generally pivotal movement in a generally horizontal disposition, a back providing a surface for supporting the lumber region at least of a user and mounted on the base for generally movement in a generally vertical disposition, linkage mechanism linking the back and the seat so that the back and the seat undergo pivotal movement in relation to one another, and restraining mechanism to restrain the back and the seat against pivotal movement, wherein the restraining mechanism acts through adjustment means which is operative to vary the mechanical advantage of the restraining mechanism in restraining pivotal movement of the back and seat.

13. A chair comprising a base, a seat providing a seating surface movably mounted on the base, a back movably mounted on the base, linkage mechamsm linking the seat and the back so that the back and the seat undergo movement in relation to one another, the chair being movable between a first, forward position, a second, neutral or intermediate position, and a third, rear position, restraining mechanism being provided to urge the seat and back towards said first position, differential means being provided whereby the force required to move the chair from the second to the third position is greater than the force required to move the chair from the first to the second position.

14. A chair according to Claim 13 wherein the restraining mechanism comprises a device for exerting a substantially constant force, and said differential means is operative to vary the mechanical advantage by which the restraining means moves the chair between said positions.

15. A chair according to Claim 13 wherein the restraining mechanism comprises a device for exerting a force which varies as the seat and back move from the first to the third position.

16. A chair according to any one of Claims 13, 14 and 15, also being in accordance with any one of Claims 1 to 12.

17. A chair according to any one of the preceding claims comprising means to secure the chair in its median position.

18. A chair according to Claim 16 wherein said means is provided by a retractable stop which may be moved between advanced and retracted positions.

19. A chair according to Claim 18 wherein in the advanced position said stop adopts a position in which part of the linkage mechanism of the chair is prevented from moving beyond a certain position, which is necessary for the chair to be moved from the median to the forward position.

20. A chair constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.