GB2167947A

GB2167947A - Tilt mechanism for chairs

Info

Publication number: GB2167947A
Application number: GB08526487A
Authority: GB
Inventors: Philip Denman
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-10-27
Filing date: 1985-10-28
Publication date: 1986-06-11
Also published as: GB8526487D0

Abstract

A tilt mechanism for a chair to allow tilting movement of a seat portion (2) with respect to a base portion (4), the tilt mechanism being operable to permit tilting movement in at least two different directions from a null position. The mechanism can be arranged to tilt forward and backwards from a null position, or from side to side from the null position, or a combination of all four movements. The mechanism comprises a cam (7) rigidly attached to arms (5) attached to the seat, and a spring biased plate (11) movable within a housing (8). Slots (15) in the wall of the housing allow the lobes (9) of the cam to project therethrough on tilting of the seat. <IMAGE>

Description

SPECIFICATION Tilt mechanism for chairs This invention relates to a tilt meachanism for chairs, and chairs embodying the same, which enable the user of the chair to tilt from a null or central position.

Tilt mechanisms for chairs are well known but conventionally, the mechanisms only allow tilting movement in one direction from the null position.

Typically, this direction is backwards and does not always provide the relevant tilting movement which is required by the occupant of a chair.

According to the present invention there is provided a tilt mechanism for a chair and adapted to interconnect a seat portion and a base portion of the chair, the tilt mechanism being operable to permit tilting movement in at least two different directions from a null position.

The two different directions may be forward and backward, or side to side and indeed, the tilt mechanism may be arranged to allow tilting movement in all four directions, i.e. forward, backward, and side to side.

The tilt mechanism may comprise a resiliently loaded cam plate adapted for attachment to the base portion or the seat portion of a chair, and a cam adapted for attachment to the seat portion or the base portion, respectively, the cam plate being moveable against the resilient acfion when relative movement takes place between the cam and cam plate to control the tilting movement of the seat portion relative to the base portion which thus takes place.

Means may be provided for compensating for the body weight of the occupant of the chair to which the tilt mechanism is fitted, whereby the preload on the cam plate is increased for heavier users, so as to make the effort required to tilt the seat portion generally related to the body weight of the user. The weight compensation means may comprise a pin carried by the cam and mounted for sliding movement in a spaced pair of opposed slots, provided in a housing for the plate, whereby the pins will be moved downwardly in the slots, so as to increase the preload on the cam plate when the weight of an occupant of the chair exceeds the nominal preload. The pin may also serve to control sideways tilting movement and may carry resilient means to stabilise this movement. The resilient loading of the cam plate may be implemented by a compression spring or by a gas spring.

Chair tilt mechanisms in accordance with the present invention will now be described in greater detail, by way of example, with reference to the company drawings, in which: Figure lisa diagramatic side view of a first embodiment of tilt mechanism fitted to a chair, Figures 2 and 3 are similar to Figure 1,with certain components removed, showing forward and backward tiltings of the chair, respectively, Figure 4 is a partial view in the direction of arrow IV of Figure 1.

Figure 5 is a side view of a second embodiment of a tilt mechanism, Figure 6 is a view similar to Figure 5 but showing forward tilting of the mechanism, Figure 7 is a view in the direction of arrow VII of Figure 6, and Figure 8 is a view similar to that of Figure 7 but showing a sideways tilting movement.

Referring first to Figures 1 to 4, the tilt mechanism comprises two portions, the first being indicated generally at 1 and being adapted for attachment to a seat portion 2, and the second being indicated generally at 3 and being adapted for attachment to a base portion 4 of the chair. The first portion 1 of the tilt mechanism is in the form of a "U" shaped bracket, the depending arms 5 of which taper towards their free ends and are rigidly connected to a shaft 6. The intermediate portion of the "U" shaped bracket is connected to the underside of the seat portion 2 of the chair. The shaft 6 has rigidly attached at its centre a cam 7 contained within a housing 8 which forms part of the second portion 3 of the tilt mechanism.The cam is symmetrical and comprises two lobes 9 both of which in the null or central position of the tilt mechanism engage a cam plate 11 which is also contained within the housing 8 and forms part of the second portion 3 of the tilt mechanism. The cam plate 11 is spring loaded by a compression spring 12. The housing 8 is generally rectangular and the shaft 6 extends through one pair of opposed walls 13, the other plate of opposed walls 14 being slotted at 15 in order to allow the lobes 9 of the cam 7 to move therethrough on rotation thereof. The base of the housing 8 has an inwardly directed tapered mounting 15 to receive a complementary shaped portion of the base 4 of the chair.

When the chair is occupied, if the occupant moves his body weight forward, then this will rotate the bracket 5 which in turn will rotate the shaft 6 and hence the cam 7. Accordingly, the right hand lobe 9 of the cam, as seen in Figures 1 and 2, will move downwardly and hence depress the cam plate 11.

This movement of the cam plate 11 increases the spring loading thereon by the spring 12 so that the tilting movement of the seat portion 2 of the chair relative to the base portion 4 is controlled. As seen in Figure 2, this rotational movement of the cam 7 results in the left hand lobe 9 of the cam extending through the associated slot 16 in the housing wall 14.

Once the body weight of the occupant is moved backwards, then the tilt mechanism will return to the null position of Figure 1. If the bodyweight is now moved backwards from the null position, then backward tilting of the seat portion 2 occurs as illustrated in Figure 3. In this mode of operation, the left hand lobe 9 of the cam 7 engages and depresses the cam plate 11, with the right hand lobe extending through its associated slot 16 in the housing wall 14.

Turning now to Figures 4 to 8,thetilt mechanism is generally similar to that of the first embodiment, except that the cam 20 is generally rectangular as seen in side view in Figure 5, with the front and rear edges or corners 21 serving as the cam lobes equivalent to the lobes 9 of the cam 7 of the first embodiment. The cam is carried by a shaft 6 as before, the shaft extending through a pair of vertically extending slots 23 in a pair of opposed walls 24 of the housing 25 containing the cam plate 11 and associated spring 12. Rocking movement of the cam 20 about the axis of the shaft 6 to allow forward and backward tilting of the mechanism is accommodated by a slot 26 in the top 27 of the housing 25.

Forward and backward tilting of the seat portion 2 (not shown in Figures 4 to 8) of the chair is accomplished in a manner similar to that described in respect of the embodiment of Figures 1 to 4.

However, the provision of the slot 23 in which the shaft 6 is free to slide vertically enables automatic compensation to be effected for the weight of the occupant of the chair. For a heavier occupant, the shaft will move vertically downwards in the slot 23 in order to increase the preload on the cam plate 11 by way of the spring 12 so that rotational movement of the cam 20 will take a greater effort than with a less heavy occupant. Consequently the effort required to effect tilting movement is generally related to the body weight of the chair occupant. In this embodiment, it is also possible for sideways tilting to be acommodated as indicated in Figure 8.If the seat portion 2 of the chair is tilted sideways, the cam 20 is rocked about an axis at right angles to the axis of the shaft 6, whereby the latter is tilted, as seen in Figure 8, this tilting movement being accommodated by the slot 23. The sideways tilting movement is stabilised by the provision of springs 28 fitted to the shaft 6 on either side of the cam 20.

The springs may be replaced by cylindrical members of an elastomeric material.

In each of the disclosed embodiments the spring 12 may be replaced by a gas spring.

It will be seen that the present invention allows tilting movement of a chair seat relatives to its base in at least two different directions from a null position. In terms of backward and forward tilting, this is a distinct advantage from the conventional arrangement of backward tilting only because very often, one needs to tilt forwards. Likewise, the ability to tilt sideways also represents a significant advance in the art.

Claims

1. A tilt mechanism for interconnecting a seat portion and a base portion of a chair, the tilt mechanism being operable to permit tilting in at least two different directions from the null position.

2. A tilt mechanism according to claim 1, wherein the two different directions of tilting movement are forwards and backwards.

3. A tilt mechanism according to claim 1, wherein the two different directions of movement are from side to side.

4. A tilt mechanism according to claim 1, wherein the mechanism is capable of tilting movement in four different directions from the null position.

5. A tilt mechanism according to any of the preceding claims, wherein the mechanism comprises a resiliently loaded cam plate adapted for attachment to the base portion or the seat portion of a chair, and a cam adapted for attachment to the seat portion or the base portion, respectively, the cam plate being moveable against the resilient loading when relative movement takes place between the cam and cam plate to control the tilting movement of the chair seat portion relative to the base portion which thus takes place.

6. A tilt mechanism according to claim 5, wherein means are provided for compensating for the body weight of the user of the chair to which the mechanism is fitted, whereby the preload on the cam plate is increased for heavier occupants, so as to make the effort required to tilt the mechanism generally related to the body weight of the user.

7. Atilt mechanism according to claim 6, wherein the weight compensation means comprises a pin carried by the cam and mounted for sliding movement in a pair of opposed slots provided in a housing containing the cam plate.

8. A tilt mechanism according to claim 7, wherein the pin also serves to control sideways tilting movement of the mechanism.

9. Atilt mechanism according to claim 8, wherein the pin is provided with resilient means to control sideways tilting movement.

10. A tilt mechanism according to any of claims 2 to 9, wherein the resilient loading of the cam plate is implemented by a compression spring.

11. A tilt mechanism according to any of claims 2 to 9, wherein the resilient loading of the cam plate is implemented by a gas spring.

12. Stilt mechanism substantially as herein particularly described with reference to Figures 1 to 4 or Figures 5 to 8 of the accompanying drawings.

13. A chair embodying a tilt mechanism in accordance with any of the preceding claims.