This invention relates to adjustable chairs, and adjustable furniture items incorporating a chair portion.

It is well understood that in order to avoid health problems for the user as well as to improve his or her performance, it is desirable to provide a degree of adjustment for chairs on which those working at a table or desk sit. A myriad of complex designs have been produced in connection with the standard 'typist's' chair and there is a wealth of patent literature relating to such items. Examples are US-A-4854641 and WO 97/22282.

Most chairs have some sort of height adjustment, often provided using some form of gas spring or the like and, in addition, the relative positions of the seat and the back may often be changed, as well as their angle with respect to the floor on which the seat is placed. In the field of office furniture, in particular to avoid loss of productivity due to back pain or discomfort, there is a clear justification for investing in an appropriate chair. However, because the positions of the parts may all be changed independently, it is possible to adjust such chairs to a very un-ergonomic position which, while it may feel comfortable to the user, in fact strains their back.

In a quite different scenario, that of the schoolroom, the desirability of providing seating appropriate to the person who is going to sit on the chair is just as great, but there are several major differences:

The first is that the amount of money that can be spent on each chair is nowhere near as much as is justified in an office environment. Secondly, chairs for use in schools need to cover a very wide range of pupil size. Thirdly, specific chairs may not always be used by the same pupil and fourthly the chairs may be moved around as the schoolroom is reconfigured for different group activities, or for use by pupils from a different age group. Fifthly, even if the problem of cost of an adjustable chair could be overcome, it would be particularly undesirable to provide a chair which could be mis- adjusted, not only because it might cause health problems, but because it might tempt the mischievous or wayward pupil purposely to make it adopt an inappropriate configuration. And young children particularly cannot be expected to know what the proper configuration should be. Finally, adult visitors or others such as teaching assistants may wish to sit, and it is inconvenient and expensive to provide separate chairs for that.

US-A-5667274 discloses a chair designed for use in schools and with an adjustable seat and adjustable back. The two adjustments are independent.

In recent years, the question of appropriate seating in schools has been addressed at both national and European level. In particular, European Standard prEN1729 Part 1 and British Standard BS5873 Part 1 specify functional dimensions, identification and finish of chairs and tables for educational institutions. In particular, the Standard provides a range of sizes which are to be accompanied by a colour coding and corresponding size mark. For example, the seat height varies from 210 mm for the smallest to 510 mm above the floor for the largest size, and other dimensions vary proportionally.

We have now found that, by the use of an inventive design, adjustable chairs may be produced which may be easily and simply preadjusted to correspond with one of the chair sizes set out in the standard, and which may thereafter be readjusted within a range of such sizes so that, in purchasing terms, a school or similar institution may only need to buy a single model of an adjustable size chair, in order to be able to cover the entire size range they need to have available. Each chair can be adjusted simply and straightforwardly to the relevant chair size by the pupil concerned within its range of possible sizes. In a development of the inventive design, the present invention also provides furniture units including a table or desk portion and an attached adjustable chair.

According broadly to the present invention, there is provided an article of furniture designed to rest on a floor, and incorporating a seat portion, and a seat back portion, and means for supporting the seat and seat back portions relative to the floor, wherein the seat and back portions are both movable relative to the supporting means and wherein the movable seat and seat back portions engage with one another in such fashion that upward movement of the seat portion relative to the floor or to a footrest mounted on the supporting means imparts rearward movement to the seat back portion, and vice versa.

According to a specific aspect of the present invention, there is provided a chair having a floor-engaging base and two pairs of elongate members extending upwards from the base, a seat back slidably mounted on one pair of such members and a seat portion slidably mounted on the other, and wherein the elongate members intersect each side of the chair and the seat portion and seat back portion incorporate means for linking the movement of the seat back and seat portions relative to one another when they are moved relative to the base.

In one preferred form of such a chair, it comprises a base frame, a first pair of side members inclined upwardly and rearwardly from the front of the base frame and a second pair of side members extending upwardly from the base frame from a position to the rear of the first pair of side members, and sufficient to reach the rearwardly extending side members, the seat back is telescoped on the first pair of side members and the seat portion is telescoped on the second pair of side members. In order to achieve the linking of the seat member movement and the seat back movement, an appropriate mechanism is provided at the region of intersection of the first and second pairs of side members, and a variety of mechanisms may be provided. One simple and inexpensive mechanism is to mesh the seat back and seat portions together with a pair of inter-engaging racks so that, as one is moved up or down on the side members, the racks, the teeth of which are angled relative to the direction of such movement, mesh with one another to ensure that both back and seat portions move together, either to move the seat back upwards and rearwards as the seat portion is moved upwards and forwards or vice versa.

An alternative is to provide an angled mount on each of a pair of supports forming part of the seat back portion, and means each side of the seat portion slidably engaged in the angled mounts.

In place of telescoping the seat portion and seat back portion on to the respective pairs of side members, each may be slidably mounted thereon via a suitable pair of sleeves; this can enable a more rigid connection between the pairs of side members where they intersect, so providing a very stable and supportive chair.

The precise relationships between the relative movements of frame, seat portion and seat back portion will depend on the geometry and engineering of the particular design, but, as can easily be seen, the appropriate inclinations of the upwardly extending members of the seat portion may be moved up and forward and the seat back portion up and back to maintain a comfortable relationship between the two and relative to the floor on which the chair is set. The relationship is desirably always a fixed proportional one, i.e. the seat height, seat depth and lumbar support height are always at the same ratios one to another, and the engineering should preferably ensure that this is the case.

Preferably the chair includes means for locking one or other of the seat portion and seat back portion in one of a number of spaced positions relative to the frame, in order to be able to set the chair to a given size. As the three parts of the chair move relative to one another during size adjustment, it is easy to provide a simple indication as to the size at which the seat is set.

If desired, means may be provided to adjust the width of the seat and/or seat back portion as these are raised and lowered relative to the base portion.

Where the chair is part of an article of furniture in accordance with the present invention, the article preferably includes a desk or table portion. This may be mounted at a fixed height above the floor - so providing a standard height desk in a classroom, with the seat and seat back, and a linked footrest, then all adjusting as set out above to match the size of the chair portion to the intended occupant.

The present invention is explained in more detail with reference to the accompanying drawings in which: Figure 1 is a perspective exploded view of a first exemplary embodiment of a chair in accordance with the present invention;

Figure 2 is a side exploded view of the chair of Figure 1 ;

Figures 3, 4 and 5 are perspective views of the chair of Figure 1 from the front, side and back, with an enlarged detail showing the intermeshing of seat back and seat portion in the area of intersection of the two legs of the frame;

Figure 6 is an exploded view in perspective of a second embodiment of a chair according to the present invention;

Figure 7 is a perspective view from below and behind showing two components of the chair of Figure 6;

Figure 8 is a perspective view from behind of the chair shown in Figure 6 with an enlarged portion showing the interaction between two of its components;

Figures 9 and 10 are perspective views showing how the chair may be adjusted to position its seat and back higher and more to the rear compared with its base;

Figures 11, 12 and 13 are diagrammatic views showing the chair of Figure 6 adjusted to three different positions, each Figure showing the chair from above, in front, behind and from each side;

Figure 14 is a diagrammatic side view of a combined chair and desk for school use in accordance with the present invention;

Figure 15 is an exploded view of a further embodiment of a chair in accordance with the present invention;

Figure 16 is a diagrammatic view from behind and below of the chair shown in Figure 15; and

Figure 17 is a diagrammatic view of the chair of Figure 15 from above and from the front and showing a magnified detail of the adjustment indicator incorporated therein.

Referring to Figures 1 to 5 of the drawings, the frame of the chair shown in these Figures is a simple base structure of metal tube or rod, e.g. of steel rods welded together. As can be seen in the drawing, the major portion of the frame can be made of a single bent piece of rod 1 with forwardly extending rear frame members 2 welded thereto and located with reference to the longer rearwardly extending parts of rod 1 by way of a short welded post 5. The frame may have four clip-on feet 6 so that it does not sit direct on the floor.

A back portion 3 consists of a moulded engineering grade plastics back having a pair of downwardly projecting extensions 4, each of which is in the form of a tube having an internal bore slightly larger than the diameter of the steel rod used to make the base, and having a slot extending from its open end to accommodate post 5.

A seat portion 8 is likewise a moulded engineering plastics seat having a pair of downwardly projecting extensions 9, each of which again is in the form of a tube having an internal bore of diameter slightly greater than the outer diameter of the steel rod 1 used to form the base, and with a slot 12 to accommodate post 5.

On the sides of the extensions 4, 9 on the seat back and seat moulded portions 3, 8 are sets of teeth denoted 10 and angled so that the teeth on an extension may be meshed with those on the other when the seat and seat back are fitted on to the base frame by putting the tubular extensions 4, 9 on to the projecting steel rods.

Assembly is easy and straightforward and, once done, the chair can be locked against disassembly by using some appropriate form of catch or clip which means that the chair cannot be so easily taken apart as it can be assembled. However, the catch, clip or the like ought to be removable in case, for example, it is desired to replace one of the seat and back without replacing the other, for example if one part has become damaged.

With the base stationary, lifting the back 3 causes the seat 8 to rise and move forward because of the intermeshing teeth 10 and the chair has a fixing mechanism which can be actuated to hold the three parts of the chair together in fixed position once the desired size has been set. In terms of the matching of the size to the given European Standard, it is straightforward to provide that there is a colour-coded strip on some part of the chair which is, for example, progressively exposed or covered up as the chair varies in size or, for example, as one part changes its position relative to another part of the chair.

The precise configuration of the frame, seat and back may vary to suit the particular design. It is noteworthy that the design can be produced in stackable fashion so that the seats can be stacked in compact fashion when not needed for use.

Referring now to Figures 6 to 13, this shows a second embodiment of a chair constructed in accordance with the present invention.

As shown in Figure 6, the base of the chair consists of a bent tube 20 having a generally U-shaped portion which is set on the floor and two end parts integrally connected with the tops of the U-shape which extend upwards and rearwards. Across the U-shape is welded a second U-shaped member 21, likewise formed of a bent tube welded between the tubular portions 20 and 21 are two latching bars 30. Located underneath tube portion 20 are four floor pads 22 e.g. of hard-wearing plastics material.

The remainder of the chair consists of a seat moulding 25, a seat back moulding 26 having a pair of depending support rods 27, a pair of adjustment sleeves 28, and a pair of torsion springs 29 which locate in the top ends of sleeves 28 and in the seat back moulding 26. The seat moulding 25, seat back moulding 26 and the adjustment sleeves 28 may all be made from moulded plastics material having an appropriate strength and finish.

The seat moulding 25 consists of a horizontal seat portion 31 integrally moulded with two downwardly dependent hollow support posts 32. These are a sliding fit over the upstanding portions of U-shaped tubular member 21. As can be seen from Figure 6, each has a slot 33 running down its front in order to enable the passage of latching bar 30, and each is split at the bottom with a cutaway part 35 to flex the bottom of post 32 open as it is telescoped over portion 21.

On the sides of the seat portion 31 are two sets of parallel ribs 34 which essentially form a rack member.

Each sleeve 28 is capable of being slid over the upwardly and rearwardly inclined straight portion of tube 20 and, as can be seen from Figure 7, it has an elongate slot 36 extending from near one end to just past the middle and, at the side of slot 36, there are six spaced recesses 37 which are sized to accommodate latching bar 30. The central portion of sleeve 28 has on it a moulded rack formed by a set of ribs 38 which have the same pitch as the ribs 34 on the sides of seat portion 31. Again, the sleeve is split at the lower end of slot 36 so it may be flexed to enable the sleeve 28 to be telescoped on to portion 20 past bar 30.

The seat back support rods 27 are dimensioned so that they can fit inside the upwardly and rearwardly inclined straight portions of tube 20. Springs 29, which engage with seat back 26 and sleeve 28, bias the tubes 28 to rotate (viewed from the top) anti-clockwise in the case of the bar on the right-hand side of the chair and clockwise in the case of the bar on the left-hand side of the chair.

When the seat is assembled, as shown in Figure 8, it can be seen that the two racks 34 and 38 come to engage during assembly, with the lowermost of the recesses 37 fitting around bar 30. By rotating the two sleeves in opposite senses against the bias of springs 29 and pushing down, the seat and seat back portions may be moved to their lowermost position with the latching bar 30 then being located in the uppermost recess 37 at the end of slot 36.

If the user now wants the chair to be suitable for a larger child than when the chair is set at its lowest seat position, the chair may be adjusted as shown in Figures 9 and 10. The user places a foot on the base, twists the two sleeves 28 outwards as shown by arrows 40 and this moves the latching bars out of a recess 37 and into slot 36. Pulling the sleeves upwards as shown by arrows 41 in Figure 10 then the seat and seat back move as shown by the arrows 42, upwards and slightly forwards in the case of the seat and upwards and slightly back in the case of the seat back, thus making the seat more suitable for a larger occupant.

When the grip is released on the two sleeves 28, springs 29 turn them back and both seat portion and seat back portion drop slightly until the latching bar 30 drops into the first recess 37 it encounters. The seat may thus usually be adjusted up or down to cover a range of possible sizes. This is clearly evident in Figures 11, 12 and 13 which show the same chair at its lowermost position in Figure 11, an intermediate position in Figure 12 and an uppermost position in Figure 13. These may correspond, for example, to recommended sizes 3, 5 and 6 in accordance with the standard referred to above.

Referring now to Figure 14, this shows diagrammatically an article of furniture being a desk/seat unit for school use. A desk portion 50 is mounted on a base frame 51, on which is also mounted a variable height footrest 52, a variable height seat portion 53 and a seat back portion 54. By means of suitable mechanical linkages, footrest 52, seat portion 53 and seat back portion 54 may be moved to the positions shown in shading 52', 53' and 54' respectively to accommodate a larger child. The desk portion 40 is shown horizontal, but it may slope if desired, and means to adjust its slope may be incorporated. When horizontal, two or more such units may be abutted to provide a uniform larger horizontal desk surface, for example for group work among a selection of pupils of different sizes.

Referring now to Figures 15 to 17, these show diagrammatically a further embodiment which is similar in many ways to the second embodiment shown in Figures 6 to 13, but, on account of the design of the frame, it is somewhat more robust. The telescoping arrangements between the frame on the one hand the seat portion and back portion on the other have been replaced in the case of the seat portion by a sliding sleeve arrangement.

Referring in more detail to these figures, Figure 15 shows the chair in exploded view. The base consists of two bent tubular frame members 61, 62 which are welded together at four points to provide a stable rigid frame. A seat portion 63 has two depending legs 64 which are in the form of semi-circular section 'half tubes' of internal diameter fitting the external diameter of frame member 62 with sufficient play to enable easy sliding thereon. The legs 64 are held captive on the frame member 62 by means of two half sleeve members 65 which may be affixed to the legs 64 by any appropriate means. As can be seen from Figure 16, the bottom part of each leg 64 constitutes a sleeve sliding on frame member 62.

A seat back portion 70 consists of a seat back having two forwardly and downwardly directed legs 71, each of which is a sliding fit over the top section of frame member 61. As can be seen from Figure 16, the rear sides of legs 71 are relieved by a long slot which receives the top portions of the two parts of frame member 62 where they are welded to the frame member 61.

Each of the legs 71 carries a slide block 73 fixed in position on the leg 71 and having a groove running at an angle to leg 71 and running essentially horizontally. To either side of the seat portion 63 are elongate flanges 75 which fit in slide blocks 73. As can be seen from Figure 16, the seat back portion 70 may slide up and down on frame member 61 and simultaneously the seat portion 63 slides up and down on frame member 62. As this happens, the flanges 75 on the edge of the seat 63 slide in the blocks 73 and, as can be seen most clearly in Figure 7, this moves the seat size markings 76 along with the size marking corresponding to the adjustment being visible through an aperture in slide block 73.

As shown in Figure 15, frame member 61 has a row of spaced holes in it on either side and these may co-act with a sprung latch pin (not shown in the drawings) attached to legs 71 to lock each of legs 71 into a given position relative to frame member 61 and corresponding to one of the range of sizes to which the chair may be adjusted. The release of such latch pins may be achieved by any convenient mechanical system, for example a push button release, trigger release or release via some form of linkage actuated, for example, when pulling the back rest upwardly.