FIELD OF INVENTION

The present invention relates to tilting chairs .

BACKGROUND ART

Hitherto, tilting chairs have generally incorporated a tilt mechanism independent of the frame, the tilt axis of which was located approximately midway along and underneath the seat, or otherwise substantially distant from the anterior end of the seat. These chairs respond to the backward leaning of the seated occupant by simultaneous movement of both the seat portion and the back portion. This often causes the occupants knees (bent over the anterior end of the seat) to rise upwardly to a height where they collide with an accompanying desk, and the lower trunk of the occupants body to sink into the posterior part of the seat, so restricting the further stretching out of the occupant. Furthermore, the leaning back of the seated occupant on such chairs causes additional pressure to the underside of the thighs of the occupant, so restricting blood circulation.

It would therefore be advantageous to develop a chair that would allow the back, and particularly the region of the back above the lumbar, of the seated occupant to be stretched or arched backwards comfortably without causing simultaneous lifting of the legs and feet of the user.

It is an object of the present invention to overcome or substantially ameliorate the abovementioned disadvantages of the prior art.

DISCLOSURE OF INVENTION

In accordance with the present invention, there is provided a chair comprising:-

(i) a frame having a seat portion and a back portion adapted to support the trunk of the body of an occupant, said frame being supported on a base, and (ii) means for allowing that part of the back portion supporting the upper trunk of the body of the occupant to tilt relative to that part of the back portion supporting the lower trunk of the body of the occupant and seat portion. Preferably, the chair further comprises means for allowing the seat portion to tilt relative to the base, wherein the tilt axis is located underneath and substantially adjacent to the anterior end of the seat portion.

According to another aspect of the invention there is provided a chair having a seat mounted on a base and including means for allowing the seat portion to tilt relative to the base, wherein the tilt axis is located underneath and substantially adjacent to the anterior end of the seat portion.

Preferably, the seat tilting means includes a pair of vertically spaced apart substantially U-shaped support members, the upper support member supporting the anterior end of the seat portion, the lower support member being supported by the base, each free arm of the upper support member being connected to its corresponding free arm of the lower support

member by a flexible U-shaped connecting member, the ' arrangement being such that with the application of weight b the seated occupant, the upper support member will move through an arc relative to the fixed position of the lower support member by bending of both of the connecting members.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings in which:-

Fig 1 is a perspective view of the frame and base of a chair according to a preferred embodiment of the invention. Fig 2 is an isometric side view of the frame and base of the chair of Fig 1 with the seat portion partially cut-away to show the seat tilting means and showing the means for tilting of the back portion. Fig 3 is a perspective view of two adjoining chair frames, each chair frame operating according to the embodiment of Fig 2. Fig 4 is a partly cross-sectional side view of the joining assembly for the adjoining chair frames of Fig 3. DESCRIPTION OF PREFERRED EMBODIMENTS

The frame and base of Fig 1 has a main frame 10 mounted on a base 11 upon which the main frame 10 is adapted to swivel about shaft 12. The main frame 10 supports the

backing fabric 13 by way of pins 14 which are hooked at both ends. The site of attachment of each pin 14 to .fabric 13 and frame 10 is specially selected to maintain the contour of the backing fabric 13 with respect to the main frame 10. The "backing fabric 13 is divided into five parts, the outermost parts 15 and 16 and the innermost part 17 consist of a polypropylene mesh, whilst the regions 18 and 19 consist of a rubber strip heat sealed to the adjacent meshwork for reinforcement of the backing fabric. The main frame 10 which is comprised of side members

10a, 10b connected together by cross piece 10c is divided into two parts capable of limited independent movement; these are the upper part of the back portion 20 and the lower part of the back portion with seat portion 21. The role of these two parts of the main frame 10 will be described with reference to Fig. 2.

The seat tilting means 22 shown in Fig 2 includes two substantially U-shaped support members 23 and 24. The upper support member 23 is adapted to move through an arc relative to the fixed position of the lower support member 24 by the weight of the seated occupant, the movement occurring through bending of U-shaped connecting members 25 and 26. The upper support member 23 is fixedly connected to the frame 10 through a base plate 27 (partly shown) . The lower support member 24 is fixedly connected to the shaft 12.

The degree of tension in the bending of the upper support member 23 with respect to the lower support member 24 can be adjusted by spring tensioning means 28. A cross-

member 29 fixedly connects the two arms of the lower support member 24. An L-shaped member 30 is fixedly connected to the upper support member 23 and projects outwardly such that its base end extends beneath and abuts against the cross member 29. Moulded to the cross member 29 is a shaft 48 which extends downwardly through an aperture (not shown) in the base end of the member 30. The shaft 48 has a threaded portion (not shown) at its end remote of the cross member 29 which screwably engages the correspondingly threaded bore of a screw cap 49. The screw cap 49 has a dished plate 50 concentrically housed about a portion of its bore. The dished plate 50 is engaged to the bore of the screw cap 49 in such a way that it will travel longitudinally with the bore along the threaded portion of the shaft 48 whilst remaining rotationally stationary. A coiled spring 51 envelopes the shaft 48 and its uppermost end abuts against the lower surface of the base end of the L-shaped member 30 and its other end abuts against the depressed surface of the dished plate 50. With this arrangement the pressure applied by the base end of the L-shaped member 30 against the cross member 29 may be adjusted by turning of the screw cap 49, thereby allowing the spring tensioning means 28 to adjust the tension between the upper and lower U-shaped support members 23 and 24, and allowing for variation in the tilting tension of the lower part of the back portion with seat portion 21.

As also shown in Fig 2, the means for tilting the upper part of the back portion 20 relative to the lower part of the

back portion with seat portion 21 consists of a pair of coiled springs (only 31 shown) located tightly within opposite arms or side members 10a and 10b of the frame 10 that supports the occupant's back. The opposite tubular arms 10a and 10b of the frame 10 are discontinuous at a point that corresponds to the position supporting the lumbar region of the seated occupant. Extending across each of the discontinuous points is the respective inserted coiled spring, and the discontinuous gaps (only 32 shown in Fig. 2) that exist are of sufficient dimension to allow that part of the frame 10 above the gaps, (the portion 20), to tilt relative to that part of the frame 10 below the gaps, (the portion 21). Ideally, the gaps should be covered by flexible protective material such as masking tape. A pair of elongated spring members in the form of spring steel wires 33 and 34 are secured to the frame 10 as shown by having their ends bent slightly acutely into holes located at the anterior face of the frame 10 and immediately above and below the corresponding location of each inserted spring (only 31 shown). For each spring wire (such as 34), the position of the two holes by which it is secured to the frame 10 and the degree to which the ends of the spring wire entering the bore of the frame are bent backwards are such as to ensure that the adjacent inserted spring 31 does not wander up or down the bore of the frame that houses it under the effect of continued bending of the upper part of the back portion 20 with respect to the lower part of the back portion with seat portion 21.

As well, the spring steel wires 33 and 34 serve to ensure that the upper part of the back portion 20 remains at a constantly fixed distance from the lower part of the back portion with seat portion 21 whenever there is no backward pressure applied to the portion 20, as a gradual slipping away of the portion 20 from the portion 21 along the inserted spring (only 31 shown) may otherwise occur with continued bending of these parts.

The portion of each spring wire 33 and 34 that emerges from the holes in the frame 10 is arched slightly outwardly from the anterior surface of the frame adjacent thereto. The maximum clearance between each spring wire and frame is of such magnitude that it sets the desired range of angulation between the upper and lower parts of the back portion 20 and 21 respectively. As the upper part of the back portion 20 bends with respect to the lower part of the back portion with seat portion 21, each spring wire will similarly bend but only to the extent where the arched portion of each wire rigidly contacts against the anterior face of the frame 10. In this way, the maximum angulation between the portions 20 and 21 is determined, in the main, by the clearance of the spring wires 33 and 34 from the frame 10.

The two adjoining chair frames of Fig 3 are connected in part through the threaded projections 35 and 36 shown in Fig 1. In the embodiment of Fig 1, these projections would be used to secure arm rests (not shown in Fig 1), but the position of such arm rests 37 and 38 can be seen in Fig 3. A single joining assembly 39 for the adjoining chair

frames of Fig 3 is shown in detail in Fig 4. The two adjacent frames 10 and 40 have threaded projections 35 and 41 that receive the partly threaded bore of sleeves 42 and 43 (shown in section) . Each sleeve also has an unthreaded narrowed portion which, in the configuration shown, faces the narrowed portion of the other sleeve. The unthreaded narrowed portion is separated from the threaded portion of each sleeve by a circumferential wall 44. In their opposing juxtaposition, the unthreaded portions receive a hollowed cylindrical member 45 therebetween (shown in section) that is threaded only on its inner surface. Two screws 46 and 47, separately inserted against the walls of each sleeve and threaded within the joining cylinder 45, secure the two sleeves 42 and 43 together, thereby providing firm connection between any two adjoining chairs.

Various modifications may be made in details of design and construction without departing from the scope or ambit of the invention. For example, the main frame could consist of a sole upright member rather than the two spaced apart upright members 10a and 10b.