GB2304036A

GB2304036A - Seat with adjustable back

Info

Publication number: GB2304036A
Application number: GB9616424A
Authority: GB
Inventors: Wolfgang Rothe; Schuttler Oliver; Michael Hewel
Original assignee: Stabilus GmbH
Current assignee: Stabilus GmbH
Priority date: 1995-08-04
Filing date: 1996-08-05
Publication date: 1997-03-12
Also published as: ITMI961578A1; FR2737396A1; DE19528649C2; IT1283514B1; ES2148018A1; JPH09103336A; GB9616424D0; ITMI961578A0; ES2148018B1; DE19528649A1

Description

2304036 1 SEAT The invention relates to a seat of the kind comprising a

seat support, a seat surface connected to the seat support about a pivotal axis, a seat back angularly movable relative to the seat surface and a fluid pressure spring means for controlling the angular position of the seat back, the fluid pressure spring means being manually lockable through an actuating device. The invention relates particularly to a stool, where the fluid pressure spring means comprises a gas spring.

A seat of the kind set forth is known from EP 0 022 933. The adjustment of the back of the seat through a locking gas spring is generally regarded as very desirable. A seating layout with large rows of seats in a conference room or at a bar can seem disorderly when the seats have a non-uniform setting when not in use. Restoring devices which return the seat to a definite angular starting position when it is vacant have been known for a substantial time.

It is the aim of the present invention to produce a seat of the kind set forth in which the adjustable back moves to a predetermined position when the scat is vacated.

According to the present invention, in a seat of the kind set forth the seat surface is pivotable about the axis between a first position in which it is under load, and a second position in which it is relieved of load, the pivotal movement from the first to the second position causing a switching movement of a switching device operative to release the fluid pressure spring means from the locked position to move the seat back into a rest position.

2 Preferably, the pivotal movement of the seat surface is provided by an energy-storing device. The energy-storing device may comprise a simple coil spring which is sufficiently pre-loaded in each position of the seat surface. When an energy-storing device is used it has been found to be particularly advantageous if the pivotal axis is arranged in the region of the front edge of the seat. Instead of an energy-storing device, the product of the mass and the lever length of the part of the seat surface between the front edge of the seat surface and the pivotal axis is greater than the produce of the mass and the lever length of the part of the seat surface between the pivotal axis and the rear edge adjacent the seat back.

It is important that the pivotal axis is not placed at the rear edge of the seat surface. It is always possible that the user of the seat loads the part of the seat surface lying rearwardly of the pivotal axis very heavily, and only lightly loads the front portion of the seat surface. In this load situation, with the pivotal axis which lies at the rear, the direction of action could reverse and the second position could be arrived at, causing the fluid pressure spring to be unlocked. If then the seat back is used as a support the person sitting on the stool could fall over together with the stool. However, with the pivotal axis adjacent the front edge of the seat surface this situation cannot arise. An unloaded rear portion of the seat surface can also form a clear indication that the stool is unloaded, and excludes the possibility, with a forwardly disposed pivotal axis, that the seat could be under load and simultaneously the fluid pressure spring could be automatically unlocked.

Preferably the actuating device comprises an actuating handle member acting through a force -transmitting element on a release lever for the fluid pressure spring means, the f orce- transmitting element having a predetermined lost motion for a position in which the actuating handle 3 member moves the fluid pressure spring means into the locked position and simultaneously the seat surface is unloaded, making it possible for the switching device to move the fluid pressure spring means to the unlocked position without the actuating handle member having to be moved from the position it currently occupies. In all events the lost motion prevents the switching device and the actuating device being put under stress in the second position of the seat surface.

To simplify construction the actuating device and the switching device engage the same release lever for the fluid pressure spring means.

Preferably the switching device includes a bell crank lever comprising two limbs, the lever being controlled by the seat surface and acting on the release lever of the fluid pressure spring means. The bell crank lever may be pivotally mounted on the seat surface at the intersection of the limbs and with the fluid pressure spring means released is held in a predetermined position by one limb through the release lever, which is under pressure loading of the fluid pressure spring means. The other limb of the bell crank lever forms a sliding bearing with a guide track on the seat support through a guide device on this limb. The limb having the guide device is preferably longer than the limb engaging the release lever. A relatively small angular movement of the' seat surface then leads to a relatively large switching movement for the switching device.

Advantageously the force-transmitting element comprises a Bowden cable. The seat surface may engage a resilient buffer at the end opposite the pivotal axis when under load.

The fluid pressure spring means preferably comprises a gas spring.

4 Two embodiments of the invention are illustrated by way of example, in the accompanying drawings, in which:- Figure 1 shows a seat with its seating surface unloaded; Figure 2 shows the seat of Figure 1, but loaded; Figure 3 shows a gas spring; and Figure 4 shows a modified version of the seat of Figure 1.

Figure 1 shows the important part of a scat in the form of a stool, in a first position in which the seat is under load, that is in use. The seat comprises a seat support 3 secured on a support column 1 which, if required, can rotate, as shown in EP 0 483 806. The seat support 3 provides a pivotal axis 5 for a seat surface 7. The pivotal axis 5 is arranged in the neighbourhood of the front edge 9 of the seat surface 17. The rear part of the seat surface is engaged on its underside by an energy- storing device 11 comprising a coil spring which rests on the seat support 3 and which tries to pivot the seat surface 7 about the axis 5 into a second, unloaded position.

The seat also includes a seat back 13, angularly movable relative to the seat surface 7, the angular movement taking place about a bearing 15 at the rear edge of the seat surf ace 7. The seat back 13 is adjusted angularly by a fluid pressure spring means in the form of a gas spring 17 which can be released or locked manually as desired through an actuating device 19. In order to alter the position of the seat back 13 the gas spring 17 engages at one end against the seat back 13 and of the other end engages a lug 21 on the seat surface 7. With the gas spring in its released condition the force of the gas spring is operative to cause a piston rod 23 of the gas spring 17 to extend so that the seat back 13 performs an angular movement about the bearing 15 in a direction towards the seat surface 7.

The actuating device 19 for manual locking of the gas spring 17 includes a force-transmitting element 25 in the form of a Bowden cable extending between a manually operable actuating handle member 27 mounted on a bracket 29 and a release lever 31. The release lever 31 is part of a release head 33 which is secured to the piston rod 23 of the gas spring 17. As shown in Figure 3 an actuating plunger 35 is axially displaceable within the piston rod 23 of the gas spring and its inner end acts on a valve pin 37 which controls a connection between working chambers 39; 41 which contain gas under pressure and are separated by a piston 43 carried by the piston rod 23. The plunger 35 is always urged by the gas pressure in addition to extend the piston rod 23, that it, urging it outwardly of the cylinder.

The seat also has a switching device operative to release the gas spring 17 from the locked position when the seat surface moves into its second position.

The switching device includes a bell crank lever 47 pivoted on the lug 21 about a pivot bearing 45 and comprising two limbs 47a; 47b, the bearing 45 being at the intersection of the two limbs. The limb 47a is longer than the limb 47b, and has a guide device 49, in the form of a roll pin, forming a sliding bearing engaging a guide track 51 on the underside of the seat support 3. The shorter limb 47b is acted on by the force of the gas pressure in the gas spring 17 acting through the release lever 31, which engages the limb 47b. If the released condition of the gas spring 6 17 is selected by the actuating handle member 27 then the shorter limb 47b still bears against the release lever 31 as the longer limb 47a exerts a torque about the pivot 45 on the bell crank lever because of its greater length, ensuring the shorter limb 47b remains in contact with the release 5 lever 31.

With the seat surface under load and therefore in its first position shown in Figure 1, its rear position rests on at least one rubber buffer 53.

As soon as the seat is relieved of load that, is vacated by the user, the seat surface 7 takes up the second position shown in Figure 2. The seat surface 7 pivots into the second position about the axis 5 under the influence of the energy-storing spring 11 and in this position the spring exerts a counter-clockwise torque about the axis 5. As a result of this pivotal movement the lug 21 together with the bearing 45 also moves in an arc in a counter-clockwise direction. The bell crank lever 47, which is connected to the lug 21 by the pivot bearing 45, performs a counterclockwise movement about the bearing 45, causing the guide device 49 to slide on the track 51 towards the gas spring 17. The pivotal movement of the seat surface causes a switching movement of the bell crank lever 47. The movement of the lever 47 causes the guide device 49 to perform a purely translatory movement and the short limb 47b performs a counter- clockwise rotary movement about the bearing 45. The relative lengths of the limbs of the bell crank lever are such that a relatively small pivotal movement of the seat surface 7 results in a relatively large switching movement of the bell crank lever 47. This switching movement is transmitted to the release lever 31 which moves the actuating plunger 35, and as a consequence the valve pin 37 (see Figure 3) axially within the piston rod 23, opening the connection within the piston 43 of the gas spring 17 and releasing the gas spring 17 from its locked position. In the 7 released position, the gas spring 17 causes an extension force which displaces the piston 43 and the piston rod 23 in an extending direction. This extending movement increases the length of the gas spring 17 which engages through its release head 33 against the lug 21 on the seat surface.

The lug 21 together with the pivot bearing 45 comprise a double-function bearing which cannot alter its position on the seat surface 7. In contrast to this the point of engagement of the gas spring 17 on the seat back 13 moves relative to the seat support 3, causing the seat back 13 to restore the seat back 13 to a rest position by angular movement about the bearing 15.

Taken together, the energy-storing device 11, the seat surface 7 and the bell crank lever 47 form a switching device which automatically ensures that the seat, when unloaded, adapts a predetermined rest position of the seat back. As can be seen by a comparison of Figures 1 and 2 the position of the actuating handle 27 has no influence on the automatic restoration of the rest position of the seat back 13. There is a predetermined lost motion provided in the force transmitting element 25, for example by making the outer part of the Bowden cable short in relation to its core, so that the position of the actuating handle member 27 can be bridged when the gas spring 17 is locked.

Figure 4 shows a modification of the embodiment of Figure 1 and corresponding reference numerals have been applied to corresponding parts. In Figure 4, instead of an energy-storing device 11 the pivotal axis 5 is chosen so that the product of the mass times the length of the lever (11) of the part between the front edge 9 of the seat surface 7 and the pivotal axis 5 is greater than the product of the mass and the lever length (12) of the part from the axis 5 to the rear edge of the seat surface 7 in order to ensure that the seat surface 7 pivots as required between the first 8 and second positions. The construction and operation of the embodiment of Figure 4 is otherwise the same as that of Figure 1.

Finally it should be pointed out that the seat back 13 does not have to be connected to the seat surface 7 but could instead be connected to the seat support 3 through a bearing 15.

9

Claims

1. A seat of the kind set forth, in which the seat surface is pivotable about the axis between a first position in which it is under load, and a second position in which it is relieved of load, the pivotal movement from the first to the second position causing a switching movement of a switching device operative to release the fluid pressure spring means from the locked position to move the seat back into a rest position.

2. A seat as claimed in claim 1, in which the pivotal movement of the seat surface is provided by an energy-storing device.

3. A seat as claimed in claim 2, in which the energy-storing device comprises a coil spring.

is

4. A seat as claimed in any preceding claim, in which the pivotal axis is arranged in the region of the front edge of the seat surface.

5. A seat as claimed in claim 1, in which the product of the mass and the lever length of the part of the seat surface between the front edge of the seat surface and the pivotal axis is greater than the product of the mass and the lever length of the part of the seat surfacie between the pivotal axis and the rear edge adjacent the seat back.

6. A seat as claimed in any preceding claim, in which the actuating device comprises an actuating handle member acting through a force- transmitting element on a release lever for the fluid pressure spring means, the force -transm itti ng element having a predetermined lost motion for a switching position in which the actuating handle member moves the fluid pressure spring means into the locked position and simultaneously the seat surface is unloaded.

7. A seat as claimed in claim 6, in which the actuating device and the switching device engage the same release lever for the fluid pressure spring means.

8. A seat as claimed in any preceding claim, in which the switching device includes a bell crank lever which has two limbs, the lever being controlled by the seat surface and acting on the release lever of the fluid pressure spring means.

9. A seat as claimed in claim 8, in which the bell crank lever is pivotally mounted on the seat surface at the intersection of the limbs and with the fluid pressure spring means released is held in a predetermined position by one limb through the release lever which is under pressure loading from the fluid pressure spring means.

10. A seat as claimed in claim 9, in which the other limb of the bell crank lever forms a sliding bearing with a guide track on the seat support through a guide device on this limb.

11. A seat as claimed in claim 10, in which the limb having the guide device is longer than the limb engaging the release lever.

12. A seat as claimed in any of claims 6 to 11, in which the forcetransmitting element comprises a Bowden cable.

11

13. A seat as claimed in any preceding claim, in which the seat surface engages a resilient buffer at the end opposite the pivotal axis when under load.

14. A seat as claimed in any preceding claim, in which the fluid pressure spring means comprises a gas spring.

15. A scat of the kind set forth substantially as described herein with reference to and as illustrated in Figures 1 to 3 of the accompanying 10 drawings.

16. A seat of the kind set forth substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings.