WO2000013551A1

WO2000013551A1 - Tilting device for a seat

Info

Publication number: WO2000013551A1
Application number: PCT/DK1999/000463
Authority: WO
Inventors: Henry Jørgen HANSEN; Jens Frost
Original assignee: Mh Stålmøbler A/S
Priority date: 1998-09-03
Filing date: 1999-09-02
Publication date: 2000-03-16
Also published as: AU5408399A; WO2000013551B1

Abstract

A tilting device for allowing tilting of a seat (11) of a chair in relation to a frame (10) of the chair comprises a rod or supporting member (20) mounted to the seat in a way that allows selective tilting movement of the seat in relation to the frame (10) in various directions from a starting position. The device further comprises spring means including a spiral spring (30) and a rubber washer (31) for counteracting the tilting movement and for biasing the supporting member towards its starting position. Tightening or adjustment means (26) are provided for selectively tightening and/or relaxing the spring means so as to selectively adjust the counteraction of the tilting movement of the supporting member (20) and the chair seat (11). The device is, e.g., applicable to work chairs, office tools or swivel chairs.

Description

TILTING DEVICE FOR A SEAT

TECHNICAL FIELD

The present invention relates to a tilting device for allowing tilting of the seat of a chair in relation to the frame of the chair.

BACKGROUND OF THE INVENTION

A great variety of chairs having tiltable seats are known. In most cases the chair seats are able to perform a rocking movement in forward and backward directions.

A chair of the latter type is disclosed in the German utility model DE 29705296 U1. This prior publication discloses a chair seat having a supporting stud fastened to and extending from the bottom surface of the seat. The stud is surrounded by a body, which is made from an elastic material, such as foamed rubber, and also fastened to the bottom surface of the seat. The free end of the supporting stud may abuttingly engage with a supporting surface defined by the frame of the chair. This structure allows tilting of the chair seat in any desired direction, and the elastic body is counteracting such tilting and is biasing the seat towards its neutral position.

DESCRIPTION OF THE INVENTION

For ergonomic reasons it may be advantageous that the user of a chair may tilt the chair seat in any desired direction by changing the location at which the weight of the user is applied to the seat, and that the seat reverts to a neutral or starting position when the weight load has been removed from the seat.

It has been found that a disadvantage of a chair using a elastic material as described in the prior art is that the elastic force counteracting tilting of the seat may not be adjusted once the chair has been designed to a user of a certain weight, such as normally an average weight. Therefore, the chair may be uncomfortable and inconvenient for a user having a weight diverging substantially from the average. Furthermore, the elastic properties of the elastic material may change with time of use. An object of the present invention is to provide an improved tilting device for a chair seat in which the above-mentioned disadvantages are overcome. Thus, the invention provides a tilting device comprising, a supporting member having a first end portion adapted to be connected to the bottom surface of the seat and a second, opposite end portion adapted to engage with a supporting surface, the supporting member being mounted in a way that allows selective tilting movement thereof in relation to the frame in various directions from a starting position, and spring means co-operating with the supporting member so as to counteract said tilting movement and so as to bias the supporting member towards its starting position, and means for selectively tightening and/or relaxing the spring means so as to selectively adjust said counteraction of the tilting movement of the supporting member and the chair seat possibly connected to said first end portion of the supporting member. Such tightening means allow individual user-adjustment of the counteraction to the seat tilting. Moreover, the device is advantageous in that the counteraction of the tilting movement does not change with time. It is a further advantage of the device according to the present invention that it allows for rocking movement not only in forward arid v backward directions but also in all other directions which improves the ergonomic comfort for the user of the chair incorporating the device.

The tilting mechanism is preferably formed so that the supporting member extends transversely from the seat and downwards therefrom, the second, opposite end portion being adapted to engage with the supporting surface.

The spring means is preferably formed and arranged so as to bias the supporting member into a initial position as well as to keep the second end portion of the supporting member into abutting engagement with the supporting surface. Thereby it is prevented that the supporting member is moved out of engagement with the supporting surface, and it is ensured that the seat is safely connected to the chair frame while the user continuously has the feeling that the seat is safely connected to the frame.

The free end of the second end portion of the supporting member may have a concavely curved shape, such as the shape of spherical segment. It has been found, however, that an improved tilting behaviour of the chair seat may be obtained when the supporting surface and the adjacent free end surface of the supporting member define a relatively large contacting area, which is encircled by an annular, preferably circular edge defined on the supporting member and/or the supporting surface. Thus, the second end of the supporting member is in connection with the supporting surface at the relatively large contacting area in the starting position or neutral position so that this position is rather stable. However, when the chair seat is tilted, connection between the second end of the supporting member and the supporting surface is reduced to a rather small length of the annular edge. In a first embodiment of the tilting device, the supporting surface and the second end portion of the supporting member engaging therewith comprise a substantially circularly cylindrical male portion extending into a complementary shaped recess defined by a female portion. Thus a circular edge is defined at the free end of the cylindrical male portion. Alternatively, the supporting surface engages the second end portion of the supporting member through an axial ball bearing, so that the recess defined by the female portion is formed by the axial ball bearing on the second end portion of the supporting member, so that both the supporting surface and the second end portion of the supporting member comprises a substantially circularly cylindrical male portion, each fitting into respective ends of the bearing that have the complementary shaped female portion. In the latter embodiment, the axial ball bearing is adapted to counteract axial forces, and as the supporting member in general substantially vertical, the bearing substantially counteracting vertical forces, preferably any and all vertical forces.

The spring means may comprise any kind of springs being able to provide the desired counteraction to the tilting movement of the chair seat. Thus, the spring means may comprise a spiral spring, a rubber spring or disc springs. In a preferred embodiment, two spring elements which are arranged in series, the elements comprising, e.g., a metal spiral and a flexible disc, such as a rubber disc or washer.

The metal spiral may be made from steel wire, such as DIN 17223-B. The diameter of the steel wire may be 6-10 mm, such as 6.5 - 7.5 mm, preferably nominal 7 mm. The inner diameter of the spiral may be 20 - 40 mm, such as 25 - 35 mm, usually 28 - 32 mm, such as most nominally 30 mm. The overall straight-line length of the spiral when not compressed may be 30 - 70 mm, such as 45 - 55 mm, such as nominally 50 mm. The number of windings in the spiral may be 2 - 10, such as 3 - 7, such as 4 - 6, such as between 5.2 and 5.8, such as 5.4. In a presently preferred embodiment, the diameter of the steel wire is nominally 7 mm, the inner diameter of the spiral spring is nominally 30 mm, the overall straight-line length of the spiral when not compressed is nominally 50 mm, the spring having 5.4 windings.

The spring means may surround the supporting member, and the tightening means may be adapted to compress the spring means in the axial direction of the supporting member. The counteracting force may be increased and reduced by tightening and relaxing or loosening the spring means, respectively. When the spring means is tightened to a defined maximum, the tilting mechanism will preferably be locked in a non tilting mode.

The tilting device according to the invention may further comprise a housing surrounding the spring means. The supporting member may extend axially into the housing through an opening defined in a first housing end wall. Preferably, means are provided for limiting the tilting movement of the supporting member and the chair seat connected thereto. The maximum tilting movement may be defined by an edge portion of the first housing end wall defining the opening therein.

Opposite ends of the spring means may be in abutting engagement with said first housing end wall and a radially extending collar part formed on said second end portion of the supporting member. Consequently, the spring means is biasing the supporting member towards its neutral or starting position and is at the same time biasing the second end portion of the supporting member into abutting engagement with the supporting surface.

The spring tightening means may comprise any means allowing the user to selectively tighten or relaxing the spring means so as to increase or decrease the spring bias, respectively. The spring tightening means preferably comprise an axially displaceable tightening member extending axially into the housing through a second housing end wall opposite to the first housing end wall, said supporting surface being defined at the free end of the tightening member. The tightening member may be of any type by means of which the spring means may be tightened or loosened continuously or incrementally. For example, the tightening member may comprise a screw engaging with a threaded bore formed in the second housing end wall. A cone shaped flange may be fixed on the supporting member, so that when the supporting member is tightened towards the first end portion, the flange is pressed against the edge of the hole in the first end portion, whereby the seat may be locked and tilting movement prevented. Preferably, the free end of the tightening member defines the supporting surface, and the cylindrical male portion may then be formed on the inner free end of the tightening member.

The present invention further relates to a chair having a tiltable seat, which is mounted on a chair frame by means of a tilting device as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described with reference to the drawings, wherein

Fig. 1 is a side view and partially sectional view of a first embodiment of a chair according to the invention incorporating a first embodiment of a tilting device according to the invention, Fig. 2 is a fragmentary view of the tilting device of the chair of Fig. 1 shown in an enlarged scale,

Fig. 3 is a side view and partially sectional view of a second embodiment of a chair according to the invention incorporating a second embodiment of a tilting device according to the invention, and Fig 4. is a exploded view of a tilting device according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a chair incorporating a first embodiment of a tilting device according to the invention. The chair has a chair frame generally designated 10 on which a seat 11 has been mounted by means of a tilting device generally designated 12. The chair frame comprises a foot part 13 having a tubular post 14 extending upwardly therefrom. The frame 10 further comprises a base member 15 having a downwards extending shaft 16, which is telescopically received in the tubular post 14, and an upwardly extending chair back support 17 on which a chair back 18 is adjustably supported.

The tilting device 12 by means of which the seat 11 is mounted on the base member 15 of the frame 10 comprises a housing 19, which is fastened to the base member 15. The upper end of a supporting member 20 is fastened to the bottom surface of the seat 11 by fastening means 21 , and the lower end portion of the shaft section 20 extends into the housing 19 through an opening 22 formed in the upper end wall thereof. A spring 23, such as a spiral spring, is arranged within the housing 19 so as to surround the shaft section 20. The opposite ends of the spring 23 are in abutting engagement with the inner side of the upper end wall of the housing 19 and with a radial collar or flange 24 formed at the free end of the shaft section 20, respectively. A threaded bore 25 is formed in the lower end wall of the housing 19. An adjustment screw 26 with a screw head or knob 27 is received in the threaded bore 25, and an enlarged cylindrical head 28 is formed at the free end of the screw 26. The inner free end of the enlarged head 28 is received en a shallow recess 29 formed in the lower end surface of the supporting member 20, and a substantially plane end surface of the enlarged head 28 is in abutting engagement with the bottom surface of the recess 29.

The spring 23 applies a downwards directed force to the peripherally extending collar or flange 24 tending to maintain the supporting member 20 and the seat fastened thereto in a neutral, stable position in which the total inner peripheral edge formed on the enlarged head 28 is engaging with the bottom surface of the recess 29. When a user of the chair moves on the chair seat 11 such that his centre of gravity is positioned on a vertical line, which is spaced substantially from the vertical axis of the supporting member 20, the supporting member 20 and the seat 11 will be caused to tilt. The pivot point for such tilting is defined by a small length of the inner circular edge of the enlarged head 28 remaining in contact with the bottom surface of the recess 29. Such tilting movement is counteracted by the spring 23, which tends to move the supporting member 20 back to its neutral position. Therefore, as soon as the chair seat 11 is unloaded it is moved back to its stable, neutral position by the spring 23.This means that a user may tilt the seat 11 against the spring bias to any angular position within limits determined by the rim of the opening 22 which limits the tilting movements of the supporting member 20.

The bias of the spring 23 may be adjusted to the needs of the individual user of the chair. Thus, when the screw 26 is screwed further into the housing 19 so as to further compress the spring 23, the bias of the spring is increased. Similarly, the bias of the spring may be decreased by screwing the adjustment screw in the opposite direction.

In the embodiment of the tilting device according to the invention described above with reference to the drawings the spring 23 serves a double purpose. Thus, the spring is not only biasing the supporting member 20 and the seat 11 towards the neutral position, but also maintains the enlarged head 28 in abutting engagement with the adjacent end surface of the supporting member 20.

Fig 3 illustrates a chair having incorporating a second embodiment of a tilting device according to the invention. The chair comprises a chair frame 10 on which a seat 11 has been mounted by means of a tilting device 12. The chair frame comprises a foot part 13 having a tubular post 14 extending upwardly therefrom. The frame 10 further comprises a base member 15 having a downwards extending shaft 16, which is telescopically received in the tubular post 14, and a supporting and adjusting member 40 which is supporting an upwardly extending and horizontally adjustable chair back support 17 on which a adjustably supporting member for a chair back 18 is mounted. The chair back is hereby adjustable in both vertical and horizontal direction to provide comfort for the chair user.

The tilting device of Figs. 3 and 4 comprises two spring elements 30,31 in the form of a spiral spring 30 and a flexible washer 31. The washer 31 is placed on the bottom collar or flange 24, around a reduced diameter portion 24a of the collar or flange 24, so that there is no direct connection between the supporting member 20 and the washer 31. The spiral spring 30 is placed on top of the washer 31. The spiral spring 30 is engaging with the top flange 34, the top flange 34 engaging with a top end wall 37 of the housing 40 . The collar or flange 24 is placed tiltably in the housing 12, the collar or flange 24 being fixed in a radial direction by the supporting member 20 and in a downwards direction by an axial bearing 32, whereby the axial bearing 32 is supported by the screw 26. The screw 26 is in engagement with the bottom end wall of the housing 38. A conical flange 33 is placed on the supporting member 20, the flange resting on and being supported by a locking ring 35 mounted in a recess 39 on the supporting member 20.

The spiral spring 30 may be made from a metal, such as steel, or from reinforced plastic. The flexible washer 31 may be made from rubber or flexible plastic. In a preferred embodiment, the washer 31 is made from natural rubber. The housing 12 may be made from a combination of metal and plastic, in a preferred embodiment the bottom 38 and the sides 40 being made from steel, and the top 37 which has a more complex design being made from PA plastic.

In the embodiment of the tilting device of Figs. 3 and 4, the supporting member 20 is biased towards a neutral position by the spiral spring 30 and the flexible washer 31 , the spring elements 30,31 also loading the axial bearing 32 and keeping the bearing 32 in engagement with the bottom collar or flange 24 and the screw 26.

A preferred embodiment of the tilting device comprises a locking member 33 with a conical portion, the locking member 33 being mounted on the supporting member 20 so that the axes of symmetry of the locking member 33 and the supporting member 20, respectively, are coincident. A locking ring 35 is placed in a recess 39 on the supporting member 20, the locking member 33 resting on a surface of the locking ring 35, so as to prevent the locking member 33 from moving downwards in relation to the supporting member 20. The locking member 33 is mounted in such a way in relation to the housing 19 that the conical portion of the locking member 33 abuts the first housing end wall 37 when the spring 30,31 is tightened to a maximum by the tightening means 26, whereby the supporting member 20 and thus the seat 11 may be locked in a non-tilting position.

When turning the screw 26 clockwise with the screw handle 27, the screw 26 is moved upwards, and thereby the supporting member 20 is moved upwardly. Thus, the spring elements 30,31 are caused to be compressed and tilting is impeded. When the compression of the spring elements 30,31 is at its maximum, the conical flange 33 is in engagement with the top end wall 37 of the housing 40 ,thereby causing the supporting member 20 to be fixed in a non tilting mode.

The axial ball bearing 32 counteracts substantially all the radial forces from the supporting member which facilitates turning of the screw 26 and the screw handle 27.

It should be understood that various modifications and changes of the embodiment described above might be made within the scope of the present invention. As an example, separate spring means may be used for biasing the supporting member 20 to the neutral position and for maintaining the enlarged head 28 in abutting engagement with the adjacent end surface of the supporting member 20, respectively.

Claims

1. A tilting device for allowing tilting of a seat (11 ) of a chair in relation to a frame (10) of the chair, said device (12) comprising a supporting member (20) having a first end portion adapted to be connected to the bottom surface of the seat (11) and a second, opposite end portion (24) adapted to engage with a supporting surface (28), the supporting member (20) being mounted in a way that allows selective tilting movement thereof in relation to the frame (10) in various directions from a starting position, spring means (23;30,31) co-operating with the supporting member so as to counteract said tilting movement and so as to bias the supporting member towards its starting position, and means (26) for selectively tightening and/or relaxing the spring means so as to selectively adjust said counteraction of the tilting movement of the supporting member (20) and the chair seat (11) possibly connected to said first end portion of the supporting member.

2. A tilting device according to claim 1 , wherein the supporting member (20) extends transversely from the seat and downwards therefrom, the second, opposite end portion (24) being adapted to engage with the supporting surface (28).

3. A tilting device according to claim 1 or 2, wherein the spring means (23) is biasing the second end portion (24) of the supporting member (20) into abutting engagement with the supporting surface (28).

4. A tilting device according to any of the claims 1-3, wherein the supporting surface (28) and the second end portion (24) of the supporting member (20) engaging therewith comprise at least one substantially circularly cylindrical male portion (28) extending into a complementary shaped recess (29) defined by a female portion (24).

5. A tilting device according to any of the claims 1-4, wherein the spring means (23), which comprises for example a spiral spring, a rubber spring or disc springs, surrounds the supporting member (20), the tightening means (26) being adapted to compress the spring means in the axial direction of the supporting member.

6. A tilting device according to claim 5, wherein the spring means (23) comprises at least two spring elements which are arranged in parallel or in series.

7. A tilting device according to claim 6, wherein the spring means (23) comprises a spiral spring and a flexible disc which are arranged in series.

8. A tilting device according to any of the preceding claims, further comprising a housing (19) surrounding the spring means (23), the supporting member (20) extending axially into the housing through an opening defined in a first housing end wall.

9. A tilting device according to any of claims 5-8, wherein opposite ends of the spring means (23) are in abutting engagement with said first housing end wall and a radially extending collar part (24) formed on said second end portion of the supporting member (20).

10. A tilting device according to any of claims 6-9, wherein the spring tightening means comprise an axially displaceable tightening member (26) extending axially into the housing (19) through a second housing end wall opposite to the first housing end wall, said supporting surface being defined at the free end (28) of the tightening member.

11. A tilting device according to claim 10, wherein the tightening member comprises a screw (26) engaging with a threaded bore (25) formed in the second housing end wall.

12. A tilting device according to claim 4 and claims 10 or 11 , wherein the cylindrical male portion (28) is formed on the inner free end of the tightening member (26).

13. A tilting device according to claim 4 and claims 10 or 11 , wherein the recess defined by the female portion is formed by an axial ball bearing (32) on the second end portion of the supporting member (20), the axial ball bearing being adapted to counteract axial forces.

14. A tilting device according to any of claims 5-13, further comprising: a locking member (33) with a conical portion, the locking member being mounted on the supporting member (20) so that the axes of symmetry of the locking member (33) and the supporting member (20), respectively, are coincident, a locking ring (35) being placed in a recess (39) on the supporting member (20), the locking member (33) resting on a surface of the locking ring (35), so as to prevent the locking member (33) from moving downwards in relation to the supporting member (20), the locking member (33) being mounted in such a way in relation to the housing (19) that the conical portion of the locking member (33) abuts the first housing end wall (37) when the spring (30,31) is tightened to a maximum by the tightening means (26), whereby the supporting member (20) and thus the seat (11) may be locked in a non-tilting position.

15. A chair comprising a chair frame (10) and a seat (11) tiltably mounted thereon by means of a tilting device (12) according to any of the