Device to lock oscillation of the backrest of armchairs with seat and backrest having synchronized variable tilting

Abstract

 A chair or armchair of the type with seat and backrest having variable tilting, in which a slider (20) connected to an oscillating support (13) moves in response to the oscillations of this and has at least one side stop toothing (24), and a positioning element (21) connected to the stationary body (11) and which can be moved angularly from a close position to a distant position to and from said slider (20) and it engages with the toothing (24) of the slider (20) when said positioning element (21) is close to said slider (20) to establish various tilting positions of the backrest.

Description

[0001] The present invention pertains in general to office chairs or armchairs of the type with seat and backrest having synchronized variable tilting, and more specifically it concerns a device locking/unlocking oscillation of the backrest of said chairs and armchairs.

[0002] Various constructions of office chairs and armchairs are known which are equipped with seat and backrest having synchronized variable tilting, that is to say susceptible to interdependent angular movements on corresponding axes of rotation oriented transversely under the seat. In practice the backrest may tilt to a various extent upwards and with respect to a fixed support body and according to the thrusts applied thereto, and the seat varies its tilt automatically in relation to the arrangement of the backrest.

[0003] It is an object of the present invention to provide a locking device which permits, on command, to stop oscillation of the backrest and to position the backrest, also with the aid of a preselector unit, according to several angles for a handier and more comfortable use of the seat.

[0004] Such an object is achieved with a locking device for seats and armchairs of the above mentioned type according to claim 1. The device is moreover described more in detail in the continuation of the description made with reference to the accompanying schematic, indicative and non-limitative drawings in which:

Figure 1 is a side view of the support unit of a seat incorporating a device according to the invention in the locked position;

Figure 2 is a view as in Fig. 1 but with the device unlocked;

Figure 3 is a view of the locking device according to arrows III-III in Fig. 1; and

Figures 4 and 5 show a preselector unit in locked and unlocked positions respectively.

[0005] In the example illustrated, the proposed device 10 is applied to a seat which comprises - in a per se known manner - a stationary body 11, fixed to the top of a supporting upright 12 with a variable height, an oscillating support 13 hinged to the fixed body and elastic means - not illustrated- connecting the fixed body and the oscillating support together.

[0006] The fixed body 11 has, in its front portion, a first transverse shaft 14 susceptible to oscillate on which a crosspiece 15 is fitted and, in its rear portion, a second shaft 16, parallel to the first one, on which the oscillating support 13, joined to a second crosspiece 17, is hinged. To the front crosspiece 15 and rear crosspiece 17 a seat 18 is fixed which comprises a seat and a backrest. The oscillating support 13 can anyhow tilt to different extents with respect to the fixed body correspondingly changing the arrangement of the seat 18. The movements of the oscillating support are opposed by elastic means -not represented- connected thereto at 19 and they can be locked with the device 10 to stop the seat in the desired position each time.

[0007] This device 10 essentially comprises a slider 20 and a positioning element 21 interacting with each other to lock oscillation of the oscillating support 13. One end of the slider 20 is connected to the bottom portion of the oscillating support 13 by means of a pin 22 placed away from the oscillating shaft 16 of the support. The other end of the slider 20 is inserted and slides in a guiding element 23 anchored, by hinging, to the front shaft 15. In this way, the slider 20 moves longitudinally coming out and going back in said guiding element 23 upon the oscillations of the oscillating support 13.

[0008] The positioning element 21 is also hinged to the front shaft 15 with the possibility of making angular movements with respect to the slider 20 to couple and uncouple therewith, preferably from above.

[0009] On at least one side of the slider 20 a rack stop toothing 24 is provided designed to interact with corresponding positioning toothing 25 provided on at least one facing portion of the positioning element 21 - see Fig. 3.

[0010] The angular movements of the positioning element 21 for its coupling and uncoupling with the slider 20 are controlled by a handle 26 placed on one side of the seat - see Figs. 3, 5. The handle 26 bears a cam 27 by way of a crank which is connected to one end 28' of a lever 28 fitted swinging on a middle pin 28a and having its opposite end jointed at 28'' with an end arm 29. This arm engages in a sliding manner with a lug 30 to the side of the positioning element 21, and, between said lug and the joint 28'' of the end arm 29, a reaction spring 31 is fitted at the swinging lever 28.

[0011] When the positioning element 21 is close to the slider 20 - see Figs. 1, 3 - the toothings 24, 25 of these components couple and interact thus preventing any longitudinal movement of the slider 20. In this way the oscillation of the oscillating support 13 is locked and the position of the seat established. Such a condition is obtained when the handle 26 with the cam 27 is turned into the position shown in Fig. 4 and the swinging lever 28 is moved in the direction to cause rotation upwards of the end arm 29. In this position the spring 31 will develop a force aimed at stably keeping the positioning element next to the slider.

[0012] For unlocking, it is necessary to move the handle 26 with the cam into the position shown in Fig. 5. Then the swinging lever 28 turns moving the end arm 29 downwards. The spring 31 compresses, but the interaction and friction of contact between the toothings 24, 25 of the slider 20 and of the positioning element 21, as well as the action of the elastic means which usually oppose the oscillation of the support 13, continue to keep the components 20, 21 locked together. The force of the spring 31 is not sufficient to cause the toothings 24, 25 to uncouple even though this coupling is unstable and therefore ready to change. Indeed, it is necessary to apply a force against the backrest to achieve such a condition and allow the toothings 24, 25 to uncouple. Only in this way is friction cancelled between the toothings and only then the action of the compressed spring 31 can cause the positioning element to move away from the slider leaving the oscillating backrest free and able to be repositioned as preferred.

[0013] Such a system has the advantage of defining varying angles of the backrest, thus preventing unwittingly unlocking the oscillation due to impact and/or improper manoeuvring of the locking/unlocking handle and preventing the backrest from violently and suddenly moving towards the occupant of the seat.

Claims

1. A chair or armchair of the type with seat and backrest having variable tilting, including a stationary body (11) fixed to the top of a supporting upright (12) and bearing the seat, an oscillating support (13) hinged onto the stationary body and bearing the backrest, and elastic means connecting the stationary body and the oscillating support to oppose the oscillations of this support, a device (10) locking the oscillations of the oscillating support in various positions and with it of the backrest, characterized by:

- a slider (20) connected to the oscillating support (13), movable in response to the oscillations of the oscillating support itself and having at least one side stop toothing (24);

- a positioning element (21) connected to the stationary body (11), movable angularly from a close position to a distant position to and from said slider (20) and having at least one side toothing (25) designed to couple in various positions with the toothing (24) of the slider (20) when said positioning element (21) is close to said slider (20); and

- a control unit (26, 29) of said positioning element (21) for movements thereof closer to and further away from said slider when locking and unlocking the oscillations of the oscillating support.

2. A device according to claim 1, wherein said slider (20) is hinged (22) to the oscillating support in an eccentric position with respect to the axis of oscillation of the support itself and is guided and telescopically sliding in a guiding element (23) hinged to the stationary body (11).

3. A device according to claim 1, wherein said control unit of the positioning element comprises: a manoeuvring handle (26) bearing a cam (27); a lever (28) swinging on a middle axis (28a) and having one end connected to said cam (27) and the opposite end turned towards the positioning element (21); an end arm (29) jointed with said opposite end of the swinging lever (28) and slidingly engaging a lug (30) to the side of said positioning element, and a reaction spring (31) contained between said lug (30) and the joint of said end arm (29) with said swinging lever, said end arm (29) causing the positioning element (21) to move towards and away from the slider (20) with the aid of said spring (31).

Drawing