IES58057B2 - A chair tilting mechanism - Google Patents

Abstract

In a chair tilting mechanism (10), a seat support (25) pivots about a fixed support (20) at a pivot pin (26). Rotation is biased by a spring unit within a control handle (11). A backrest support (41) is directly pivotally connected to the fixed support (20). The backrest support (41) is additionally connected to the seat support (25) by a connector (42) comprising an upper round bar (42a) and a lower round bar (42b). The connector (42) allows both rotational and sliding motion of the backrest support (41) with respect to the seat support (25). Thus, the seat and backrest supports are connected together in a manner which allows synchronised tilting of the seat and backrest of a chair whenever one or other is tilted.

Description

A chair til-ting mechanism The invention relates to a chair tilting mechanism which provides for tilting of components of a chair such as an office Chair.

U.S. Patent Specification No. 4,555,085 (Bauer et al) describes such a mechanism. This mechanism provides for tilting of a seat support about a fixed support which is fixed to the pedestal or the spindle of an office chair. Bias is provided between the two supports by a coil spring, the tension of which is adjustable. A problem with this arrangement is that while the seat may tilt backwards and forwards under the control of the seated person, the positions of the chair are not particularly comfortable because the backrest moves with the seat.

European Patent Specification No. EP 265782 (Volke) describes a tilting mechanism whereby a pelvic support is pivoted to a rocker arm, which is in turn pivoted to a fixed support. There is a complex mechanism comprising synchronising levers to control the mutual tilting angles of the pelvic support and of the seat. Because of the large leverage involved in movement of components of chairs, there are large stresses developed in a chair mechanism and it appears that a complex mechanism such as that described in EP 265782 would not be particularly reliable.

The invention is directed towards providing a chair tilting mechanism with relatively few parts so that stress in the mechanism may be accommodated relatively easily. Another object of the invention is that the mechanism be inexpensive and simple to produce and to transport. • _>·' <·'* '-· Ο - 2 A further object of the invention is that the mechanism provide for synchronised tilting of a backrest and seat so that at all positions of a seat, the backrest is at an ideal position for the user and vice versa.

According to the invention, there is provided a chair tilting mechanism comprising a fixed support, a seat support pivotally connected to the fixed support by a pivot, a backrest support, and a bias means connected between at least two of the supports to provide bias during tilting, characterised in that, the backrest support is pivotally connected to the fixed support at a pivot, and is connected to the seat - support by a connector which allows both rotational and longitudinal mutual motion.

In one embodiment, the pivot connecting the backrest and fixed supports is at a forward extremity of the backrest support, and the connector engages the backrest support rearwardly of said pivot.

Preferably, the bias means acts between the seat and fixed supports. In this embodiment, the bias means preferably acts on the seat support forwardly of the pivot between the seat and fixed supports.

In another embodiment, the connector comprises members having mutually engaging surfaces on the backrest and seat supports allowing rotational and sliding motion. In this embodiment, the members may include a transverse member having a curved surface on one support engaging a longitudinally-directed portion of the other support. The transverse member is preferably on the seat support, and in one embodiment is in the form of a round bar.

In an alternative embodiment, the connector is a link arm pivotally connected at one end to the seat support, and pivotally connected at the other end to the backrest support.

In another embodiment, the mechanism further comprises means for pre-setting a location of the pivot between the backrest and fixed supports so that the initial rake angle of the backrest support may be pre-set.

In a further embodiment, the pre-setting means comprises a slot in one support engaging a pivot pin in the other support and a lock for locking the pivot pin at one position in this slot.

According to another aspect, the invention provides a chair incorporating a mechanism as described above.

The invention should be more clearly understood from the following description of some preferred embodiments thereof, given by way of example only with reference to the accompanying drawings in which:Fig. 1 is a side view showing a chair incorporating a tilting mechanism of the invention; Fig. 2 is a perspective view from above of the tilting mechanism; Fig. 3 is a diagrammatic cross-sectional side view of the mechanism in one position; Fig. 4 is a similar view of the mechanism in a different tilting position; Figs. 5a and 5b are diagrammatic side views showing an alternative construction of mechanism at two positions; and Fig. 6 is a diagrammatic side view showing another mechanism.

Referring to Fig. 1, an office chair 1 is shown which has a central pedestal or spindle 2 mounted on legs 3 on which there are casters 4. The chair 1 also comprises a seat 2, and a backrest 6 mounted on a back stem 7. The seat 5 and the -back stem 7 are connected to a tilting mechanism 10 which is supported on the spindle 2. The tilting mechanism 10 has a hand-operated knob 11 housing a spring unit for spring bias control during tilting of components of the chair 1. The mechanism 10 and all of the chair components which are connected to it are movable in the vertical direction on the spindle 2 which is gas-operated by a control handle 12 extending transversely from the mechanism 10.

Briefly, the mechanism 10 of the invention allows the seat 5 to be tilted forwardly or backwardly about a transverse axis (as indicated by the arrows A). At the same time, the mechanism causes the backrest 6 to tilt (as indicated by the arrows B) in synchronism with the seat so that both are at an optimum position at all times. This is referred to in the specification as synchronised tilting. The tilting movement is biased by the spring unit inside the control knob 11 and the default position caused by the spring unit is that shown in Fig. 1.

Referring now to Figs. 2 to 4 inclusive, the mechanism 10 is shown in detail. The mechanism 10 comprises a fixed support 20 having a vertically-extending aperture 21 for reception of the chair spindle 2. As already discussed, a control handle 12 (not shown in Fig. 2) extending above the aperture 21 allows for control of the gas spindle 2 for vertical movement of the fixed support 20 and thus of the mechanism 10 and of the components connected to it. Thus, the term fixed support” in this specification means fixed with respect to the mechanism and not in the absolute sense. Indeed, it is also envisaged that the fixed support of the mechanism of the invention may be controlled by an external mechanism to tilt. However, with respect to the other parts of the mechanism and the seat and backrest, it is to be regarded as being fixed in position. The fixed support 20 has a pair of integral spindle control brackets 22, each having an aperture to allow the control handle 12 pass through. The fixed support 20 also has a stop member 23.

The mechanism 10 also comprises a seat support 25 which is channel-shaped having upper flanges 27 which are, in use, bolted to the underside of the seat 5. The fixed support 20 nests within the seat support 25 and is pivotally connected to it by a transverse pivot pin 26. This connection is shown most clearly in Figs. 3 and 4. Thus, the seat support 25 may pivot with respect to the fixed support 20 about the pivot pin 26. This pivotal motion is controlled by the spring unit within the control handle 11 which comprises a solid cylinder 28 seated in a bracket 32 on the seat support 25. The cylinder 28 is threaded to a bolt 29. The bolt 29 carries a disc at its lower end, which in turn supports a spring 30 held against a bracket 31 on the fixed support 20. Thus, the spring 30 acts between the bracket 31 on the fixed support and the bracket 32 on the seat support to provide bias between these two supports to in effect balance the weight of the user. The extent of pivotal motion is controlled by abutment of the stop member 23 against the seat support 25.

The fixed support. 20 carries a transverse pivot pin 40 to which a backrest support 41 is pivotally connected. Thus, the backrest support 41 is pivotally connected directly to the fixed support 20. The backrest support 41 is designed to be bolted to the back stem 7 shown in Fig. 1. It may thus be regarded as an integral part of the backrest structure .

In order to achieve synchronised tilting of the backrest and seat supports with respect to the fixed support, the backrest support 41 is additionally connected to the seat support 25 by a connector 42 which allows both Longitudinal and rotational motion. In this embodiment, the connector 42 comprises an upper round bar 42a and a lower round bar 42b mounted across and forming a part of the seat support 25. The upper bar 42a engages an upper surface of the backrest support 41 and the lower bar 42b engages a lower surface of the backrest support 41.

Referring specifically to Figs. 3 and 4, the manner in which the mechanism 10 provides for synchronised tilting is clearly shown. If, say, the backrest support 41 is tilted by the seated person in the anti-clockwise direction about the fixed support 20 at the pivot pin 40, the seat support 25 will also pivot in the anti-clockwise direction about the pivot pin 26 under the action of the support 41 pushing the lower bar 42b. On the other hand, when the seated person leans forwardly, the seat support 25 tilts in the clockwise direction about the fixed support 20 at the pivot pin 26 and the lower bar 42b causes the seat support 41 also to tilt in the clockwise direction about the pivot pin 40 (and thus about the fixed support 20). This latter action is either aided or caused entirely by the spring 40. The only function of' the upper bar 42a is to prevent the backrest being pushed forwardly on its own.

The angular relationship of the tilting motion is determined by the positioning of the pivot pins 26 and 40 and of the bar 42b. If these three components are equidistant, then the backrest support tilts through double the angle of the seat support.

It will be appreciated that the connector 4 2 comprising the bars 4 2a and 4 2b provide for both rotational and longitudinal (in this embodiment sliding) motion of the bracket 41 with respect to the seat support 25. To put it simply, both the seat support and the backrest support rotate with respect to the fixed support, while the backrest support moves with respect to the seat support in both a rotational and a longitudinal manner. This provides synchronised tilting. In this embodiment the components 26, 40 and 42b are located for a 2:1 backrest: seat tilting relationship. In Fig. 4, the backrest support has tilted 17°, while the seat support has tilted 9°.

The mechanism 10 also comprises a clutch 50 having clutch leaves 51 connected between the pivot pin 40 and a clutch pin 53 on the seat support 25. The clutch leaves 50 have elongate slots 52 through which the pin 53 protrudes and there is a lock mechanism, not shown, which clamps the leaves against washers on the pin 53 to prevent synchronised tilting. This is an infinitely variable lock. Thus, the clutch 50 is only used in the exceptional situation where the person does not require tilting, but prefers the seat and backrest to remain at a fixed position for a certain time period. The normal position for the clutch 50 is to be disengaged and for synchronised tilting to occur.

It will be appreciated that the spring unit within the control handle 11 biases the tilting which is allowed. Although the spring unit is only connected between the fixed and seat supports, because of the connector 42, it also biases tilting of the backrest support 41.

It will be appreciated that the mechanism of the invention is extremely simple because there are relatively few parts. These parts are manufactured with the strength necessary to cope with the stresses which are transmitted through a mechanism. It will also be appreciated that the mechanism is extremely compact as all of the components can be fitted inside the channel-shaped seat support 25.

The mechanism need not necessarily have a connector such as that shown in Figs. 1 to 4. The connector may alternatively take the form of a link which connects the seat and backrest supports. Such an embodiment is shown in Figs. 5a and 5b in which a mechanism 60 is shown. The mechanism 60 comprises a curved backrest support 61 which is pivotally connected to a fixed support 62 by a pivot pin 65. The fixed support 62 is pivotally connected to a seat support 6 3 by a pivot pin 64. A connector 6 6 comprises a link arm 67 connected at its upper end to a pivot pin 67a on the seat support 63 and at its lower end to a pivot pin 67b on the backrest support 61. It will be appreciated that the connector 62 allows the necessary rotational and longitudinal motion as shown by the difference in the positions of the various components in Figs. 5a and 5b. In effect, the connector 66 pulls the seat support 63 when the components are moving in the anti-clockwise direction. On the other hand, when the seat support 63 tilts under action of the spring unit in the clockwise direction, the connector 66 pulls the / -· 9 backrest support 61 back to the position shown in Fig. 5a. It will be appreciated that any suitable type of connector which allows both rotational and longitudinal motion between the seat and backrest supports would suffice.

In another embodiment, the invention provides a means for pre-setting the initial rake angle between the backrest and the seat of a chair. This is achieved by allowing pre-setting of the initial angle between the backrest support and the fixed support. It will be appreciated that by setting this angle to a new value, not only is the initial rake angle of the backrest changed, but also the manner in which synchronised tilting occurs is changed because of the different relationships between the angles of the components. Such an embodiment is shown in Fig. 6 in which parts similar to those described with reference to previous drawings are identified by the same reference numerals. In this embodiment, a mechanism 70 has a fixed support 71 having a pin 7 2 with front and back flat faces. A backrest support 73 terminates in a slotted member 74 which engages the pin 72. A lock, not shown, allows the position of the slotted member 74 with respect to the pin 7 2 to be initially set. This effectively sets the initial angular relationship between the supports and thus governs the manner in which subsequent synchronised tilting occurs. The lock which is used comprises thrust washers on both sides of the slotted member 74 and an internallythreaded handle which engages the threaded end of the pin 72. Rotation of the handle allows setting of the initial angle at the desired level.

The invention is not limited to the embodiments hereinbefore described,· but may be varied in constructions and detail.

Claims (4)

1.

2.

3.

4. A chair tilting mechanism comprising a fixed support, a seat support pivotally connected to the fixed support by a pivot, a backrest support, and a bias means connected between at least two of the supports to provide bias during tilting, characterised in that, the backrest support is pivotally connected to the fixed support at a pivot, and is connected to the seat support by a connector which allows both rotational and longitudinal mutual motion. A mechanism as claimed in claim 1, wherein the pivot connecting the backrest and fixed supports is at a forward extremity of the backrest support, and the connector engages the backrest support rearwardly of said pivot. A mechanism as claimed in claim 1 or 2, wherein the connector comprises members having mutually engaging surfaces on the backrest and seat supports allowing rotational and sliding motion. A mechanism as claimed in claim 1 or 2, wherein the connector is a link arm pivotally connected at one end to the seat support, and pivotally connected at the other end to the backrest support. A chair incorporating a mechanism as claimed in any preceding claim.