A CHAIR

Abstract: A chair (10) comprising at least one leg (21, 23) depending from a seat (30), a backrest (40) mounted on a support (41) and a backrest adjustment mechanism (45, 80), said chair (10) being characterised by said backrest adjustment mechanism (45, 80) being adjustable from a first position to a second position to control the depth of said seat (30), said backrest adjustment mechanism (45, 80) being releasably prevented from backward movement, with forward movement being performed by a single force.

Description: A CHAIR The present invention relates to an improved chair, particularly but not exclusively for musicians. The chairs of the present invention also provide growing children a chair which they can use through to maturity. Traditionally, chairs for orchestras, children and the like have been of a standard size, perhaps with some minimal adjustments possible. Accordingly, such an "average" chair was generally unsuitable for all users. Further, musicians must habitually adopt specific postures when playing, be it erect, bending slightly forward or backwards, sitting on the front, rear, or middle of the chair or twisting to conform with their instrument. This commonly leads to back and other skeletal and muscular problems as a result of continuing and sustained poor posture, which is exacerbated by the variety of chairs used. Indeed, it is common for musicians to carry with them a variety of cushions, wedges and the like in an effort to rectify the deficiencies of the seating. It is an object of the present invention to provide a chair which substantially ameliorates or overcomes at least one of the disadvantages of prior art chairs. According to one aspect of the present invention there is disclosed a chair comprising at least one leg depending from a seat, a backrest mounted on a support and a backrest adjustment mechanism, said chair being characterised by said backrest adjustment mechanism being adjustable from a first position to a second position tc control the depth of said seat, said backrest adjustment mechanism being releasably prevented from backward movement, with forward movement being performed by a single force. - According to another aspect of the present invention there is disclosed a backrest adjustment mechanism which is adjustable from a first position to a second position, said backrest mechanism being releasably prevented from backward movement, with forward movement being performed by a single force. Preferably each of said legs are separately extendable, whilst the backrest is mounted upon a backrest bracket which includes a ratchet mechanism to control the forward movement. Preferably the forward movement occurs in discrete increments. It is also preferable that the dimensions of the backrest are such that the width is relatively smaller when compared to conventional backrests. The backrest is preferably able to rotate around at least one axis. The backrest is preferably shaped so as to be concave forward whilst being vertically convex forward to fit comfortably and supportively into the natural contour of the lower spine. Other objects and aspects of the present invention will be apparent from the following illustrations of a particular embodiment, in which: Figure 1 is a perspective view of a chair according to the invention; Figure 2A and 2B are side views showing two positions of the lumbar bracket; Figure 3 is a schematic view from below of the adjustment mechanism according to this embodiment; Figure 4 is a sectional view of a leg extension device; and Figure 5 is a side view of another adjustment mechanism of the backrest forward-backward mechanism. Referring to figure 1, a chair 10 embodying the invention has a seat portion 30 of a relatively large area. The upholstery is of reasonably firm resilience without being too deep. The relatively large seat area 30, comfortably accommodates of persons of larger girth. The downward curve on the front 31 of the seat is also noted. In Figure 1 , the relative slope of the chair 10 is illustrated. It is possible within the scope of the invention for the chair to slope backwards or be level or tilt forward, however, it is sometimes preferred that a forward slope be provided where use is to be by musicians. This is most conveniently and securely provided by shortening the front legs 21, and 22. This aspect is more apparent from figures 2A and 2B. Most preferably, the slope is between 1 in 20 and 3 in 20, when unextendable legs are utilised. The height of the chair is also of significance where extendable legs are not used. A seated height of between say 38 cm and 54 cm at the front enables comfortable seating for virtually all users, utilising the depth adjusting mechanism described below. A backrest 40 is secured by bracket 42. The backrest 40 includes vertical adjustment means 41 , preferably a screw type adjustment mechanism cooperating with the bracket and a passage provided in the bracket. A user can thereby adjust the backrest height as is most comfortable. The backrest 40, is of a relatively small size when compared to conventional backrests. Musicians of various kinds, for instance violinists, need to be able to move their arms without striking the back of the chair. The backrest 4C of the present invention enables this, while still providing effective support. Preferred dimensions of the backrest are between say 28 and 34 cm wide and between say 14 and 26 cm high. The adjustment mechanism 41 does not hold the backrest 40, rigid, but allows limited rotational movement around an axis indicated as arrow 2 of figure 1 , so as to maximise user comfort. The back rest 40 is able to accommodate some rotation 5 around arrow 1 by means of the softness of the cushion material used in the backrest 40. The backrest 40 is held by a pivot pin (not shown) and biased by a spring (not shown) towards a backward-leaning position ie. the top of the backrest 40 is rearward of the bottom. The backrest 40 thus moves when a user is seating himself to conform to the appropriate position when seated. 1 0 In figures 2A and 2B, the effect of relative movement (in the direction of arrows 3 of figure 1 ) between the seat 30 and bracket 42 is illustrated. In the configuration of figure 2B, seat depth, i.e. the distance between the front 31 of the seat 30 and the backrest 40, is a maximum. This will accommodate a tall person, or a shorter person who wishes to lean back a great " deal. Sliding the bracket 42 inwardly reduces the 1 5 effective seat depth progressively to the configuration of figure 2A. This position would normally accommodate a shorter person, or someone who wishes to sit on the front 31 of the chair. The backrest 40 can move inwardly up to a maximum of half the length of the seat 30, much more than is illustrated, for people who wish to sit very far forwards in this chair. This is a feature partly accomplished by the depth of traverse of the bracket 2 0 42, and the angulation of the bracket. A particular feature of the present invention is the large extent of travel possible for the backrest 40, and hence large range of effective seat depths provided. This enables appropriate seating for persons of a variety of heights, and a variety of required seating positions. 25 It should be noted that the curve of bracket 42 is such that the backrest 40 considerably overhangs the seat 30 in the figure 2A position. This ensures that a user's back contacts only the backrest 40 and not, for instance, the middle of the bracket 42. When the backrest 40 traverses in a forward or backward direction, the backrest does not change its orientation relative to the seat 30. 30 The angle of the bracket and preferred seat slope, together with depth adjustment as described above, provide an ergonomically desirable structure. Referring to figure 3, one mechanism for the operation of the depth adjusting arrangement is illustrated. The seat 30, and bottom plate 43, covers the entire mechanism, but this is not illustrated in figure 3. Bracket 42 includes a toothed region 35 44 corresponding to the permitted travel. A substantially U-shaped member 46, open at either end but of small depth to prevent wobble at the bracket 42, receives the toothed end 44 of the bracket 42. An opening 49 receives a lever 45, having a handle surface at one end and a surface for engaging the teeth 52 of toothed region 44. The engaging end is tapered on the edge facing rearward and relatively fiat on the edge acing forward. Hence. 5 in use, the bracket 42 may be slid in without using lever 45 to the desired position in this way, only a single force is needed to effect adjustment. In use, the chairs for an orchestra are generally set up in the fully out position of figure 2B, a musician is then seated and slides the bracket in to reach the desired position using only one hand for the simple movement. 1 0 The bracket is held firmly by the teeth 42 cooperating with the flat surface of lever 45. The lever is biased by bias spring 47 secured by projection 48 of member 46. It will be apparent that any other bias arrangement which is mechanically equivalent may be employed within the scope of the invention, including pivoting the lever 45 and relying on gravity to drop the stop 49A into the opening 49. 1 5 It is preferred but not essential that the lever be on the right side, to suit the majority of users. The lever preferably protrudes beyond the seat for easy access. Illustrated in figure 4 is a leg extension mechanism 70. The extension mechanism 70 can be located in the front and/or rear tubular legs 21 , 23 and consists of 20 an inner tube 71 which closely fits the internal diameter of legs 21 , 23. Where inner leg portion 71 engages the ground a suitable leg termination can be placed such as a plastic or rubber stop. The inner leg 71 has located therein a spring which biases a stc * member 73 in a radially outward direction. In this instance, the spring 72 is of a leaf type construetion however any suitable biasing member can be utilised. The stop member 25 73 has a dome or taper shaped top and substantially straight sides. The legs 21 , 23 have a series of apertures 74 whilst inner leg 71 has a single aperture 75 through which stop 73 protrudes. When stop 73 is in position, the hole 75 and hole 74 on the inner and outer legs respectively engage the sides stop 73 a: right angles. In operation one simply forces the stop 73 inwardly allowing the inner leg 0 to be moved relative to the outer leg. One of the advantages of having legs which are individually height adjustable is that this ensures that, particularly for musicians, the angle of tilt is as desired, either forward or backward depending upon the musician e.g. cellist. violinist.etc. Also, some musicians prefer to sit on sides of chairs rather than the front 5 and because each leg is individually extendable any angle or orientation can be achieved by the user. An alternative ratchet arrangement is illustrated in figure 5. This differs from the apparatus of figure 3 in that a series of holes 81 are located in a plate which is bolted under the seat of the apparatus of figure 1. The holes 81 in plate 82 are positioned in a lower most arrangement for the purpose of hiding the working components of the ratchet mechanism 80. The plate 82 can be fabricated from a U shaped channel which is subsequently bolted to the seat 30 or may even be a flat sheet which is bolted to the under portions of the seat 30 by means of space. Sufficient clearance must be provided for backrest bracket 83 and the rest of mechanism 80. The mechanism 80 comprises a lever portion 84 having stop means 85 at one end and a manual control portion 86 on the other side of fulcrum 87. The lever portion 84 acts under the influence of gravity to engage holes 81 , however this letter can be biased if desired. The stop 85 has an angled face and substantially perpendicular face 88 which engages the rearward side of holes 81. Thus, from this arrangement it can be seen that the seat will move in the forward direction by the application of the single force applied to backrest bracket 83 via contact with any portion of the backrest 83 or the backrest itself. However once stop 85 engages a hole 81 rear perpendicular face 89 will ■ engage the side of a hole 81 thus preventing the backrest bracket 83 from moving in the rearward direction which is in direction of arrow 90. Preferably the bracket 83 is of a bar type skeletal construction with lever 84 being suspended between two such bars so that the lever 84 is in the middle of the bracket 83. in a preferred form, the backrest of the present invention is shaped so as to be slightly convex anteriorly. They are further shaped so as to be horizontally concave forwards, whilst vertically convex forwards. Lumbar support can be added to the backrest. This is done by the use of thick outside soft paddling preferably soft density polyethylene foam, with the lumbar support being formed from a half tear drop shaped (in cross section)roll of thicker denser foam being located inside the soft padding approximately 2/3 of the way down the backrest, and positioned right across the backrest horizontally and within the contours of the backrest padding. The chair may be constructed of any suitable material. One embodiment employs tubular steel for the frame, steel for the bracket and ratchet, resilient foam for the upholstery, with a woven fabric covering. Alternative materials may be employed, for instance plastic materials for the ratchet to reduce the level of noise produced thereby, and modern plastics for almost all components. The desαibed ratchet arrangements provide a secure, easily operable function with a minimum of effort namely a single force being required, which and is easier to use and more positive in action than alternative mechanisms. It is noted that the chair is shown with stationary configuration, as would normally be most stable, but a version with castors or wheels may be easily provided. Variations within the spirit of the invention will be apparent to those skilled in the art.

Claims: CLAIMS: 1. A chair comprising at least one leg depending from a seat, a backrest mounted on a support and a backrest adjustment mechanism, said chair being characterised by said backrest adjustment mechanism being adjustable from a first position to a second position to control the depth of said seat, said backrest adjustment mechanism being releasably prevented from backward movement, with forward movement being performed by a single force. 2. A chair comprising four legs depending from a seat and a backrest, said chair being characterised by each of said legs being separately extendable. 3. A chair as claimed in claim 1 wherein the or each of said legs are separately extendable. 4. A chair as claimed in any one of claims 1 ,2 or3 wherein said backrest is mounted on a bracket which includes a ratchet mechanism to control said forward movement. 5. A chair as claimed in any one of claims 1 ,2 or 3 wherein said backrest is mounted ona bracket which includes a screw, clamp or geared mechanism to control said forward movement. ^ 6. A chair as claimed in any one of the previous claims wherein said forward movement is performed in discrete increments. 7. A chair as claimed in any one of the previous claims wherein said forward movement is performed in continous increments. 8. A chair is claimed in any one of the preceding claims wherein said backrest is of a width dimension which is relatively small. 9. A chair is claimed in any one of the previous claims wherein said backrest is adapted for rotational movement around at least one axis. 10. A chair is claimed in any one of the previous claims wherein said backrest is shaped concave forwards horizontally , and or convex forwards vertically . 11. A chair is claimed in any one of the previous claims wherein said backrest includes a lumbar support being formed from a tear drop shaped roll of denser padding being located inside the backrest approximately 2/3 of the way down the backrest, and extending right across the backrest. 12. A chair is claimed in any one of the previous claims wherein said first position and said second position are any positions ranging from over the seat in the region of half the depth of said seat to clear of said seat. 13. A backrest adjustment mechanism which is adjustable from a first position to a second position , said backrest mechanism being releasably prevented from backward movement, with forward movement being performed by a single force.

Inventors: OWEN EARL, OWEN, EARL
Applicants: OWEN EARL, OWEN, EARL
Application year: 1992
Main classification: A47C3
IPC codes: A47C1