Technical Field

This invention relates to improvements to chairs. This invention relates to improvements to chairs and in particular to an improved seat design and support means therefore. The present invention has particular but not exclusive application to chairs of the type which have a forwardly tilted seat or a seat which allows for some degree of forward tilting movement and particular reference will be made to such arrangements. However not all aspects of this invention are limited to such seat arrangements.

A seated person's weight is largely born on and balanced over the ischial tuberosities of the pelvis and their seated posture is largely determined by the front to rear rotation of the pelvis. If the knees are elevated higher than the hips, the pelvis is tilted back and a less desirable posture results. Background Art

Chairs of many different designs are currently available. In chair designs, the most common seat configuration is one in which the seat is substantially horizontal or of a slightly backward tilt. Users of such chairs often develop a poor posture and associated neck or back pain. Some chairs also encourage persons to adopt an anatomically undesirable positions when leaning forward.

In improved chair designs, the seat is provided with a forward tilt to encourage a more erect posture. Using such chair designs, the knees are lower than the hips and the normal curve of the spine is encouraged. As the tilt of the chair seat increases however, a stop or knee rest is required to be provided to prevent a person seated on the chair from sliding off the seat. The use of stops or knee rests however applies pressure to the knees which can thus be aggravated. Furthermore, chairs of this design reduce the freedom of movement of the person's posture and additionally the chairs themselves are generally cumbersome.

A further disadvantage of known chairs is that the

design of the seat and/or backrest limits twisting or sideways pivoting movement. This disadvantage often results from excessive frictional restraint between the user and the chair through the incorporation of various cushion configurations in the chair or because of the backrest width and nature of construction.

Commonly chairs used in office situations, for example by typists or other office workers have a central pedestal and a plurality of legs which extend radially outwardly from the central pedestal and which are provided with castors at the free ends thereof. Generally, however, there is no provision for a footrest in chairs of the above type, or if there is provision the footrest is not particularly suited to general office use. For example, some chairs have an elongated pedestal which supports a base ring on the radial legs which serves the purpose of a footrest. However chairs of this type have only limited application.

Also many prior chairs are formed with tilting seats as these are considered desirable. In this respect it is believed that small amplitude tilting movements of the spine stimulate nutrient secretion to the spine. However most chairs use conventional tilting arrangements which result in the user's body being raised and lowered with the tilting action. This changes the body's height in relation to an associated desk which is most undesirable. Thus the desired relationship between hip and knees and the desk at which the person is seated is varied with the tilting.

Furthermore when in a tilted position, offset pressure must be applied to the seat in order to maintain the desired tilted attitude. This further reduces the relaxed attitude of the user's body and increases stress.

Various aspects of the present invention aim to alleviate at least one of the above disadvantages or at least provide a viable alternative to the known chairs. Summary of the Invention

With the foregoing in view, this invention in one aspect resides broadly in a chair having:-

a forwardly inclined seat providing a lowered front portion and a rear portion, and recess means in said rear portion for receiving the ischial tuberosities of a user's pelvis and forming a raised portion in front of the ischial tuberosities of a seated user.

The recess means may be formed as a single shallow recess. However in the preferred form, the recess means is in the form of spaced apart recesses for receiving and supporting respective ischial tuberosities in an anatomically correct position, the recesses being disposed at opposite sides of and symmetrically located relative to the fore and aft centreline of said rear portion.

The recesses may be formed as shallow indentations in a one piece seat moulding or they may be formed as deep indentations or apertures supporting padded inserts into which the ischial tuberosities of a seated person extend.

Preferably the recesses are separated by a groove extending along the fore and aft centreline of the rear portion. The groove may be relatively shallow and may be flared in width at each end. Where only a single recess is used, the groove is arranged centrally of the seat and recess. This groove is adapted to prevent unwanted pressure being applied to the user by ensuring that the user's weight is substantially evenly taken by the user's ischial tuberosities and the underside of the legs which contact the front portion of the seat.

The seat may be of a generally square or rectangular configuration with the side edges thereof rounded or curved downwardly for minimising lines of pressure which may be otherwise applied by the front edge across a user*s legs.

The seat is suitably moulded of plastics material such as being formed for example of laid fibreglass reinforced plastics or it may be injection moulded plastics. The seat may be provided with an array of apertures to improve ventilation and assist in providing a non-slip surface. The seat may also be supported so as to be able to deflect slightly from its normal position under the influence of an

applied load.

In a further preferred form, the seat is formed integrally with a backrest or support which extends upwardly from the rear portion of the seat. The backrest is suitably inwardly recessed on opposite sides adjacent to its junction with the seat so as to minimise backrest distortion, to provide less restriction to movement of a seated person and to provide ventilation to the seat and backrest surfaces, and it may also be provided with an opening aligned with the fore and aft centreline of the seat. This opening is suitably of such a size as to allow the seat to be gripped and lifted.

Preferably the backrest is of a concave configuration in cross section, the concavity increasing from the bottom to the top of the backrest. The backrest may also taper upwardly from the side recesses to a blunt apex. As with the seat, the backrest may be provided with a series of through apertures for ventilation.

In another aspect this invention resides broadly in footrest means for chairs of the type having a central supporting strut extending from a base having legs extending outwardly from the strut and terminated by feet or castors, said footrest means including:- a footrest member having a rest portion which extends between the outer ends of adjacent said legs, and securing means for securing said footrest member to said respective legs.

Preferably the footrest member has an outer arcuate rim which forms the rest portion and which, in use, is positioned substantially equidistant from the strut extending from the base and the securing means provides anti-twist support for the footrest member whereby the arcuate rim is maintained in a substantially horizontal plane.

In one preferred arrangement, the footrest member is adapted to be secured to the respective legs of the chair by the respective castor wheel assemblies. Other fastening arrangements however may be provided for securing the footrest member to the respective legs of the chair.

For example the footrest member may be a formed as a sector supported on the upper edges of adjacent splayed legs and with its arcuate base forming the rest portion. In a further arrangement, the footrest member may be permanently secured between respective legs such as by welding.

The footrest means may provide a rest portion which extends between the outer ends of only two adjacent legs and may be formed so that its ends may overlap with a further footrest means and join to a common leg and extend to opposite legs adjacent the central leg.

Alternatively the footrest means may be a one-piece member which extends to opposite sides of a central leg to the adjacent legs at each side thereof. If desired the footrest means may comprise a plurality of footrest members which extend between adjacent pairs of legs so as to extend circumferentially of the base of the chair.

In one arrangement the footrest means is formed for use with a seat base having feet or castors provided with upstanding shafts which are received in sockets in the ends of the respective legs and the footrest means is captured by the shaft and located between the body of the respective feet or castor the underside of the respective legs. For this purpose, ends of the footrest member and or an intermediate portion thereof are apertured to receive the capturing shaft. The footrest members may be adjustable in length to enable them to adapt to chair bases of different form. For this purpose, the footrest members may be of a telescopic construction. The footrest means may be formed integrally with the base assembly and/or may be incorporated into new chairs or attached to existing chairs.

In yet another aspect this invention resides in a chair seat support of the type utilising a leaf or torsion spring having upper and lower end portions which connect to the seat base and the support means respectively to springedly support the seat base relative to the support means, and hereinafter referred to collectively as "U-shaped spring means", said chair support including:- support means providing an elevated seat support;

U-shaped spring means having a lower end portion fixed to the support means and an upper end portion fixed to the seat base, and characterised in that the portion of the U- shaped spring means which spans between the upper and lower end portions, hereinafter referred to as the spanning portion, is disposed substantially centrally of the seat base to permit a user to move when supported by the seat base to a position at which the seat base is tilted forwardly while its medial position above the spanning portion remains at a substantially constant elevation. The spanning portion may be a U-shaped portion or it may be a coiled portion.

Preferably the support means is a central strut type support which is height adjustable and the U-shaped spring means comprises a pair of laterally spaced apart U-shaped springs in which the spanning portion between the upper and lower end portions is a substantially part-cylindrical springing portion. The use of U-shaped springs is preferred over the use of torsion springs as, in addition to providing spring for the tilting action, U-shaped springs also provide minimal vertical springing for the supported seat.

Suitably the substantially part-cylindrical spanning portion has a radius of between 1 1/8" and 3 1/4". In a preferred embodiment each U-shaped spring is formed as a spring steel leaf spring having a width of between 1" to 2", a thickness of between 1/8" and 1/4", and a spanning portion radius of between 5/8" and 1 h " • Suitably the thinner sectioned springs are used for supporting average weight adults and the thicker section springs are used for supporting heavy adults. It is also preferred that the upper and lower end portions diverge outwardly from the spanning portion and that they be mounted to extend rearwardly of the spanning portion so that the seat base is freely supported in an inclined attitude. Suitably the upper and lower end portions diverge outwardly from the spanning portion with an included angle of between 5° and 10°. However if desired the spanning portion can be disposed at the rear of the end portions which would then preferably converge towards one another away from the

spanning portion.

Furthermore it is preferred that the spanning portion be disposed forwardly of the axis of the strut and suitably about 2" in front of the strut. The end portions may also be provided with movement limiting means which limits the tilting extent afforded by the U-shaped spring, such as a buffer for limiting compression and a stay for limiting recoil and preferably the limiting means are adjustable.

In still another aspect, this invention resides in a chair assembly having a selected combination of; the chair according to one aspect of this invention as defined variously above; the footrest means according to another aspect of this invention as defined variously above, and/or the chair seat support according to yet another aspect of this invention as defined variously above. 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 which illustrate a preferred embodiment of the invention and wherein:-

FIG. 1 illustrates a chair incorporating a seat and backrest according to one aspect the invention;

FIG. 2 illustrates the seat and backrest of the chair with profile lines indicating the shape thereof;

FIG. 3 is a plan view of the seat of the chair;

FIG. 4 is a side elevational view of the seat of the chair;

FIG. 5 is a sectional view of the seat along line A-A of FIG. 3;

FIG. 6 is a sectional view along line B-B of FIG.3;

FIG. 7 is an elevational view of the backrest of the chair;

FIG. 8 is a perspective view illustration a seat provided with padded inserts for supporting the ischial tuberosities and incorporating a footrest assembly according to the present invention;

FIG. 9 is a typical cross-section through an insert;

FIG. 10 illustrates the footrest assembly prior to attachment to a chair.

Fig. 11 is a sectional view along line A-A, showing the configuration of the footrest assembly; Fig. 12 is an enlarged side elevational view, showing the manner in which the footrest members are secured in position to the legs of the chair;

FIG. 13 diagra matically illustrates the seat in use supported by a preferred for of support, and FIG. 14 is a perspective view of a preferred form of torsional mounting seat spring. Detailed Description of the Embodiments

Referring to the drawings and firstly to Fig. 1 there is illustrated a chair 10 according to the present invention including a body support portion 11 which includes an integral seat 12 and backrest 13. The seat 12 is of generally rectangular form in plan view and includes a rear portion 14 and a front portion 15.

The rear portion 14 as shown in Figs. 2 to 6 includes a pair of shallow recesses 16 arranged symmetrically on opposite sides of the fore and aft centerline 17 of the seat 12, the recesses 16 being adapted to received the ischial tuberosities of a person seated on the chair 10.

The recesses 16 are slightly curved in cross section as is apparent in Fig. 6. A shallow groove 19 extends along the centerline 17 of the seat 12 and is flared outwardly in width at its opposite ends 20 and 21.

As shown in Fig. 5, the recesses 16 increase in depth rearwardly from the front portion 15 and the junction between the recesses 16 and the front portion 15 of the seat forms a raised portion 22 extending in front of and being formed by the recesses 16.

The body support portion 11 is normally supported on a pedestal 23 as shown in Fig. 1 such that the seat 12 is tilted downwardly and forwardly. This may be a fixed inclination or may be adjustable such as by pivotally mounting the body support portion 11 to the pedestal of the chair. When a person is seated on the body support portion

11, the ischial tuberosities of the pelvis are located in the recesses 16 which forms an effectively level surface therefor.

Furthermore the raised portions 22 prevent a person sliding forward on the seat 12. This enables a user to sit comfortably with the muscular and skeletal structures placing the upper legs sloping downward to encourage the slightly forward tilted position of the pelvis required for maintaining the normal spinal curvature in a balanced sitting posture.

The outer periphery 24 of the seat 12 is preferably curved outwardly and downwardly to provide minimum resistance to twisting or turning on the seat 12.

Referring now to Figs. 7 and 8 there is illustrated the preferred backrest 13 for the chair 10 of the invention. The backrest 13 extends upwardly from the rear of the seat 12 and includes adjacent the seat 12 a pair of opposite inwardly directed curved recesses 25. The opposite sides 26 of the backrest 13 extend upwardly from the recesses 25 and converge towards each other to an apex 27 at the upper end of the backrest 13.

The backrest 13 as shown in Fig. 8 has a concave configuration 28 in cross section to provide support to the back of the user and comfort. The concavity 28 increases upwardly towards the apex 27 as will be more apparent in Fig. 2.

The lower portion of the backrest 13 is also provided with an opening 29 aligned with the groove 19. The opening 29 provides for ventilation and additionally provides a convenient gripping recess to enable lifting of the chair 10. Further ventilation of the seat 12 and backrest 13 may be achieved by providing an array of apertures 30 therethrough as illustrated.

The chair 10 of the invention has a number of advantages over the prior art. The seat 12 enables a person to bend forwardly or rearwardly without moving on the seat 12. Thus a user may lean forward on the seat in order to create the appropriate lordosis without tipping the chair 10 about its

base support. In conventional seats many users tilt their seat about the forward edge of the supporting base or they sit at the front edge of the seat in order to create the desirable lordosis. Such practices may lead to accidents. The backrest 13 which is complementary to the seat 12 provides good spinal support whilst allows movement and rotation of the trunk without strain. The shape of the seat 12 and backrest 13 are such that padding is not required for comfortable seating. Padding however may be used and may for example be in the form of a thin layer of resilient material or in the form of, or associated with inserts as described below.

The apertures 30 through the seat 12 and backrest 13 as well as allowing for ventilation, provide a degree of anti- slip on the chair 10. Where the seat 12 is supported on a central pedestal support 23 as in Fig. 1, the material forming the seat 12 is such as to deform to a limited degree under the weight of a person sitting thereon thereby providing additional comfort to the user. The body support portion 11 of the seat 10 may be formed of any suitable material such as timber, metal or plastics however preferably the body support portion is formed of a stiff material such as plastics or fibreglass reinforced plastics. The chair 10 is most suitable for use as a school chair in class rooms however it may equally be used in other environments such as an office chair or other general seating chair. Of course other supports other than a pedestal support 23 as shown in Fig. 1 may be used for supporting the seat 12 and backrest 13. Referring to Figs. 8 and 9 it will be seen that the chair 40 in lieu of the recesses 16 contains padded inserts 41 symmetrically disposed at opposite side of the fore and aft centreline in the rear seat portion 42. The inserts 41 fit into inwardly flared annular recesses 43 having upper edges contiguous with the shallow recesses 44 into which the ischial tuberosities of the pelvis extend so and which form the upstand portions 45. A central groove 46 extends between the recesses 43.

The padded inserts deform under the weight of a user and provide a more comfortable support for the ischial tuberosities. The covering 47 is suitably vinyl or the like of a type which has a relatively high frictional coefficient for assisting in the restraint of a user on the seat 40 when it is tilted forwardly.

Chairs with a pedestal support extending from a five star type base may utilise a footrest according to this invention, as illustrated in Fig. 8. As illustrated the chair 40 includes a seat and backrest portion 51 supported on a pedestal 52 including a central spindle 53 which may be vertically adjustable, for example by means of a screw adjustment or a pneumatic adjustment. The pedestal 52 includes at its lower end a plurality of radially extending legs 54, each of which is provided at its free end with a respective castor wheel assembly 55.

Each castor wheel assembly 55, as shown more clearly in Fig. 12 includes an upstanding shaft 56 which is receivable in a socket 57 in the end of the leg 54, the shaft 56 being detachable from the socket 57 for repair or replacement of the caster wheel assembly 55.

The footrest assembly 60 according to the present invention includes in this embodiment, two footrest members 62 which extend at an obtuse angle relative to each other and which in this embodiment are integrally formed. The footrest assembly 60 is provided with apertures 63 in respective bosses 64 formed at the ends of the footrest assembly 60 and between the footrest members 62. The apertures 63 are sized to receive the shaft 56 of the castor wheel assemblies 55. The footrest members 62 between the hubs 64 may be shaped in any suitable manner and for example may be provided with a non-slip upper surface. In the embodiment illustrated, the footrest members 62 have an arcuate outer edge 65 and an inner linear edge 66, however the linear edge may if desired be also of a curved configuration. Similarly the outer edge of the member 62 may be of a linear configuration. The footrest assembly 60 may be formed of metal and/or plastics.

To secure the footrest assembly 60 to a chair 50, the castor wheel assemblies 55 of three adjacent legs 54 are removed and the footrest assembly 60 positioned such that the apertures 63 are aligned with respective sockets 57 in the ends of the legs 54. The shafts 56 of the castor wheel assemblies 55 are then inserted through the apertures 60 and into the sockets 57, such as to capture the footrest assembly 60 to the legs 54 as shown in Fig. 12.

The chair 50 may thus be used with the facility of the footrest assembly 60 which may be positioned in any attitude desired simply by rotating the pedestal 53.

In the embodiment described and illustrated, the footrest assembly 60 includes two footrest members 62, however, the footrest assembly 60 may include only one member which spans a pair of adjacent legs 54 or alternatively the footrest assembly 60 may include a plurality of members 62 as shown in dotted outline in Fig. 11 which may extend circumferentially of the pedestal 53.

The footrest assembly 60 may be incorporated into a chair during the manufacture thereof or simply added to pedestal type chairs by removing its castor wheel assemblies 55 and thereafter locating the footrest assembly 60 between the castor wheel assemblies 55 and the ends of the legs 54. Where incorporated during manufacture, the footrest members 62 may be manufactured integrally with the legs 54 of the pedestal 53 extending between the outer ends of the legs 54. The central boss 64 may provide a pivoting between the footrest members 62 whereby the angle therebetween may be adjusted for different forms of chair, for example a chair with only four legs 54 or a chair with more than five legs 54.

Referring to Figs. 13 and 14 it will be seen that the torsional mounting or pivot 67 of the supporting seat 69, which could be a seat having an integral backrest of the type described above, but which is preferably includes separate backrest 68, upon a supporting base 70 is suitably achieved by providing a pair of U-shaped springs 71 laterally spaced apart and disposed with the spring fulcrum substantially in

line with the support axis 74 of a person comfortably seated on the seat 69. This axis 74 or the transverse plane in which it is contained passes through the skull, neck, lower backbone and ischial tuberosities of the pelvis. It will be seen that each U-shaped spring 71 has an upper end portion 72 and a lower end portion 73 which are apertured to enable them to be bolted to the seat base 69 and the supporting base 70 respectively. These portions are interconnected by a part circular spanning portion 75 having a radius of about 3/4". The spring 71 is formed from spring steel leaf which is 2" wide and 1/8" thick and the end portions diverge at 5°.

This arrangement provides an operative springing movement, which is translated into pivoting and minimal vertical spring of the seat base, of between 1 3/4" between end portions when unloaded and 3/4" when loaded by a normal weight adult. The included angle between the portions 72 and 73 is 5°.

A user may pivot the seat base 69 to a forward tilt which suits them without effectively raising or lowering of the seat portion above the spanning portion 75 on which the ischial tuberosities is supported. In addition a user may easily rotate to and fro about the axis of the chair strut 76 without adversely affecting their good posture or comfort. Furthermore, a seated user may also readily rotate and tilt their hips either simultaneously or independently.

The pivot 67 may be locked in a selected tilted position if desired. For this purpose the seat base 69 is provided with a threaded shaft 77 suspended pivotly therefrom to pass through an aperture 78 in the supporting frame 70. A finger nut 79 is engaged on the shaft 77 and may be adjusted along the shaft 77 to hold the seat base 69 in the desired tilted attitude. Other locking mechanisms may of course be utilised if desired. The backrest 68, which is suitably profiled to accommodate the natural lordosis of a user's back, is also provided with a soft foamed plastic lumber support roll 80 which is suitably fitted into a shallow recess 81 formed in

the backrest 68. The lumber support roll 80 is attached to the backrest by releasable hook and loop fastening means whereby it may be it may be readily changed with another support roll of a different density or profile to suit the individual. The padded inserts 41 may likewise be interchanged to suit the user.

Whilst the above has been given by way of illustrative embodiment of the invention, all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as defined in the appended claims.