GB2119639A

GB2119639A - Tilting mechanism for a chair

Info

Publication number: GB2119639A
Application number: GB08213781A
Authority: GB
Inventors: Jurek Buchacz
Original assignee: Ring Mekanikk AS
Current assignee: Ring Mekanikk AS
Priority date: 1982-05-12
Filing date: 1982-05-12
Publication date: 1983-11-23

Abstract

Seat regulating mechanism for a chair, preferably a workman's chair, for adjusting the seat angle with the centre of gravity g of the user in the axis X-X of the chair supporting spindle independent of the angle of the seat plane in relation to said axis, the seat being displaceable along an arc having its centre in the users centre of gravity g, and determined by the formula L=R.tan alpha wherein L horizontal displacement of the seat, R= the radius from the centre of gravity of the user to the plane of displacement, alpha =angle of displacement in relation to the vertical axis through said centre of gravity and the displacement being controlled by a control plate 9 and manually operable worm gearing 10, 11, characterised in that the after surface of the control plate 9 forms an angle less than 90 DEG with the horizontal plane in order to produce the arcuate displacement of the seat during the rotation of the control plate about the eccentric axis X-X. A control groove on the plate surface receives control balls 5 on the seat 1, and rods 15 on the chair support 8 engage in slots 16 in the seat. <IMAGE>

Description

SPECIFICATION Tilting mechanism for a chair The present invention relates to a tilting mechanism for a chair and more particularly to an adjustable chair mechanism, especially a mechanism for adjusting the seat angle of a chair for a person at work.

There is known (from German Off.leg.schrift 2323018) an adjustable chair mechanism that permits regulation of the seat angle, but that has several substantial drawbacks, such as that the centre of gravity of the chair varies for different positions of the seat, that it is not possible to achieve fine adjustment of the seat position, that the chair must be counter-balanced and that the regulating mechanism requires a separate locking device.

It is an object of the invention to provide a chair mechanism of the kind referred to above, by means of which the seat angle may be adjusted in a simple manner to that most suitable to the work of the user and that giving the user the best possible and most comfortable sitting position during work. It is also an object of the invention to provide such a mechanism which is self-locking in any position.

The invention will be better understood through the following more detailed description with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a portion of the chair mechanism; Figure 2 is a front view of the mechanism; Figure 3 is an illustration of the control curve determining the movements of the seat; and Figure 4 is a purely schematic drawing of one form of chair according to the invention.

Referring to Figure 1, a supporting column 6 is attached at its lower end to an undercarriage (not shown) of the chair and has its upper portion inserted into a sleeve 7 beneath the chair mechanism. The sleeve 7 is welded to a plate 8 extending substantially horizontally and carrying on its upper side a movable control plate 9. The control plate 9 is mounted on a shaft (not shown) centred on the axis X-X carried through the plate 8 and provided with a worm gear (not shown) on the underside of the plate in a housing 10, the worm gear being rotatable by means of a worm (not shown) engaging the worm gear through an opening in the housing 10.

The worm may be rotated manually by means of a knurled handwheel 11. These elements for the operation of the control plate 9 may be of a commonly known type and are not shown or described in greater detail here. It is stressed, however, that this driving method provides a selflocking adjustment of the control plate 9.

The control plate 9, which is circular in top plan view, is eccentrically mounted on its vertical drive shaft and will rotate in a horizontal plane when the worm is rotated by means of the handwheel 11. (The axis of the worm is shown in Figure 2 by the chain-dotted line 12.) On its upper surface the control plate 9 is provided with a control groove 13 (see Figure 3), the shape of which is determined by a formula to be further explained later.

The plate 8 is reinforced on both of its longitudinally extending edges by rods 14 welded to the plate which rods are angled upwards at both ends and termined in short transverse rods 15.

The rods 1 4 and transverse rods 1 5 support a seat base plate 1 serving to carry a chair seat proper 2, for instance, as shown in Figure 4, through engagement of the transverse rods 1 5 with slots 1 6 in brackets 1 7 provided in pairs on the underside of the seat base plate 1. The slots 1 6 have a slightly arcuate form and thus allow movement of the seat base plate 1 on the supporting structure consisting of the plate 8 and the rods 14.

The seat base plate 1 carries on its lower surface a reinforcing rib 3 forming a support for two control pins 4 having ball heads 5 spaced apart in the direction of the said movement of the chair seat.

The operation of the mechanism is as follows: By rotation of the handwheei lithe worm 12 is rotated and consequently the worm gear in the housing 10 is rotated. The worm gear is situated on the same shaft as the control plate 9 on opposite sides of the plate 8. As a result the control plate with its control groove 1 3 will rotated around the-axis X-X which does not pass through the centre of the plate 9 and the control pins 4 with their ball heads 5 will be subjected to a reciprocal movement owing to the form of the groove 13.The control plate 9 at the same time has a slanting surface, as is best shown in Figure 2 at 9a, and as the control plate rotates this will produce a lifting of that one of the ball pins 4 and that part of the seat base plate 1 that is moving outwards from the axis X-X along the slot 1 6 especially, because of the shape of the groove 13, in the extreme positions of its travel.

The movement of the seat base plate 1 (and of a chair seat 2, with or without a back rest, that may be mounted on it) by operation of the worm, obeys the equation: L=R.tan a where: L=horizontal displacement of the seat; R=radius from the centre of gravity of a notional user to the plane of displacement; and angle of displacement in relation to the vertical axis through the said centre of gravity.

In practice, the maximum value of the angle a may be arranged to be 200 and the control groove 13 will then be determined as shown in Figure 3. In the drawing the control plate 9 is shown in the two extreme positions, but the control groove 13 is shown in full in the upper position and only indicated by a line of points in the lower position.

Claims

1. A seat-regulating mechanism for adjusting the seat angle of a chair while maintaining a point on the axis of the chair supporting spindle corresponding to the centre of gravity of a notional user independent of the angle of the seat plane in relation to the said axis, the,seat being displaceable along an arc having its centre at the said notional centre of gravity and determined by the formula L=R.tan a where: L=horizontal displacement of the seat; R=the radius from the said centre of gravity to the plane of displacement; and a=angle of displacement in relation to the vertical axis through the said centre of gravity and the displacement being controlled by a control plate and by means of mechanical elements, and wherein the surface of the control plate forms an angle with the horizontal plane in order to produce the arcuate displacement of the seat during rotation of the control plate.

2. A seat-regulating mechanism as claimed in claim 1 and substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

3. A chair having a seat-regulating mechanism as claimed in claim 1 or claim 2.