SEAT

Abstract

A seat with a contoured pan comprised of two concavely shaped pads adapted to support the thighs of a user at an optimal selected angle of 27 degrees to the horizontal plane. The combined features enable a user to be directed into a comfortable seating position that emulates the shape of the spine when standing.

Description

FIELD OF THE INVENTION

The present invention relates to a seat; particularly a seat for use in an office chair, task chair, aircraft seat, bicycle, vehicle, wheelchair, pushchair, child's seat/car seat or bench. Specifically, the invention is a seat that actively directs the sitter into a correct sitting position as hypothesised by the inventor, i.e. a position that emulates the position that the sitter's spine and pelvis would achieve if they were standing.

BACKGROUND

Traditional chairs with near horizontal seat pans (both forward to back and side to side) force people to sit in a posture that is detrimental to proper functioning of their spines and associated tissues, which can lead to strain, injury and, in some cases, spinal degeneration. Specifically, horizontal seat pans force a sitting position with a curved back and reduced thoraco-abdominal space, so causing compression of the abdominal viscera, diaphragm and lungs which can result in hindered digestion and breathing. They also put strain on the sitter's side-to-side spinal curves (scoliosis).

Since the 1970s, following the work of A. G. Mandal and others, designers have developed sitting devices that allow the thighs to be lower at the knee than buttock. However, these devices all have their drawbacks. For example:

“Kneeling Chairs”: e.g. U.S. Pat. No. 3,863,978 (Gillings 1975), U.S. Pat. No. 3,669,493 (Vowles 1972), EP0017450 (Mengshoe11980), SE8600691 (Opsvick 1986) and NO320859 (Mengshoel 2006), were the first attempt to increase sitting thigh angle. In many cases this involved a thigh-to-horizontal angle of up to 45 degrees. The user was prevented from slipping forward in the seat by ‘locking’ the leg into shin supports just below the knees. There have been several papers reporting knee strain (anterior cruciate ligaments) due to the unnatural pressure on the knee joint caused by such strain. They can also restrict the free movement of the legs and feet which is uncomfortable for the user.

“Ergonomic Chairs”: chief amongst these (developmentally) being the Aeron (Herman Miller 1994), Leap (Steelcase 1999) and Freedom Chair (Humanscale 1999). These and their imitators can have seat pans tilted but this leads to the user sliding slowly forward. To counter this movement the user tightens leg and trunk muscles so sitting soon becomes uncomfortable. The designers of these chairs advocate movement, rather than advising on a beneficial position. The chairs have numerous adjustments for the user; however, research shows unequivocally that the majority of users rarely bother to adjust their chairs. If adjustments are made they are usually limited only to height.

“Saddle Stools/Chairs”: e.g. WO0154545 (2001), NO20003763 (Mengshoel 2002), US2002167206 (2002), and NO320859 (Mengshoel 2006), use a saddle-like form and achieve the desired thigh angle by allowing the legs to drop either side. These seats work in the same way as a bicycle saddle wherein the weight of the body is taken by the ‘hammock’ of muscles that form the perineum. This diamond shaped sheet of muscles (containing the reproductive and excretory organs) hangs over the saddle seat, transferring the weight of the body through the muscle insertions at the ischial tuberosities, pubis and coccyx. Such seats have similar drawbacks to bicycle saddles, i.e. discomfort experienced after prolonged use.

“Improved Bicycle Saddles”: e.g. GB611899 (Scoular, 1946); address perceived problems of conventional bicycle saddles as mentioned above by including a modification to improve comfort in use. Devices such as GB611899 propose that two seat pads mounted on a lateral bar include a forward tilt of 20 to 30 degrees, but this is only the initial position. The pads are mounted for spring-biased rotation around the lateral bar (horizontal axis) as a user's thighs move up and down to pedal the bicycle. The initial angle is provided for ease of mounting the seat which aids buttock comfort.

“Sittings Balls”: are currently popular and, depending on the size of the ball, may allow the user to gain an advantageous thigh angle as well as providing cushioning and some intended instability, which can all be beneficial. However, such devices do not fit well into a conventional office environment.

“Moving/Movement-control/exercise chairs”: e.g. U.S. Pat. No. 5,588,704 (Harza, 1996); U.S. Pat. No. 7,090,303 (Kropa, 2006); US2009/0079243 (Kunzler et al, 2009); US2009/0135133 (Kunzler et al, 2009), can involve movement for either exercise or health and the possibility to control other apparatus. Movement is often beneficial to humans and its complete absence for extended periods is detrimental, however, the addition of poorly controlled or poorly guided movement in a work seat will often lead to distraction and discomfort. It is erroneous to think that by providing ample free movement in a sitting device that the body will find the best position for comfort and health.

“Dual-pad/tilting/Shaped Chairs”: e.g. U.S. Pat. No. 4,387,925 (Barker et al, 1983); U.S. Pat. No. 4,552,404 (Congleton, 1985); GB2226756 (National Research Development Corporation, 1988); U.S. Pat. No. 5,580,128 (Johnson et al, 1996); WO 2006/073019 (Train Corp et al, 2006); WO 01/76420 (Hansen, 2001); (U.S. Pat. No. 7,387,339 (Bykov et al, 2008); U.S. Pat. No. 7,063,386 (Dowty et al, 2006); U.S. Pat. No. 6,357,827 (Brightbill et al, 2002); U.S. Pat. No. 5,024,485 (Berg et al, 1991); U.S. Pat. No. 5,713,632 (Su, 1998); WO2009040861 (Manzini Roberto, 2009); WO 94/08491 (Bustanate Serrano, 1994) are primarily concerned with the comfort of the sitter. Shaped pads often resemble early, shaped “tractor-type” seats. These seats, which keep a central anterior to posterior ridge, create the same problems of discomfort after a little while as the previously mentioned saddle seats. Dual pads are an improvement but providing these without any contouring will not allow adequate forward tilting of the seat pads without the movement of the sitter, the same is true for flat, tilting seats. To be truly comfortable, the inventor has noted, the pads should allow for a small degree of roll, pitch and yaw.

SUMMARY OF THE INVENTION

By observing patients the present inventor concluded that humans have not evolved to sit and, therefore, any work chair must be designed to emulate the position that the pelvis and spine achieve in the standing posture of the individual. A detailed anatomical knowledge and expertise in spine, pelvic and musculo-skeletal structure and function led to a hypothesis in how best to achieve this improved seated position.

In studying spines for many years the inventor realised that when an individual moves from the standing to sitting position there is dramatic change in spinal and pelvic posture. Firstly, as most seats have horizontal or slightly downward sloping seat pans this does not allow the lumbar spine to achieve a stable position and so requires the overuse of insufficient spinal and paraspinal muscles to maintain an upright position. These muscles are not meant to maintain an upright position for a sustained period. Secondly, the human body is full of asymmetries, no place more so than in the legs, as they are the longest parts of the body. Most people have a leg length difference and hence a difference in pelvic height. This uneven pelvic height causes side to side curves (scoliosis) in the spine. When sitting on a normal, fixed, non-adaptive chair the pelvis is usually forced into a horizontal position, hence creating changes, stresses and discomfort on the spinal scoliosis.

Through an extended process of prototyping and empirical testing resulting in the present invention, it has been possible to reproduce the pelvic and spinal positions achieved when standing.

The invention produced is counterintuitive, as it looks uncomfortable but, nevertheless, is extremely comfortable. Furthermore, it looks simple but has a high level of complexity and is a practical innovation.

Following the conclusions reached above, the present invention seeks to provide a seat that actively directs the sitter into a sitting position wherein the sitter's spine and pelvis have a similar structural and postural position as when the sitter is standing. In order to achieve this the seat must allow a considerable downward slope of the thighs (from hip to knee), without the sitter sliding forward, and each side of the pelvis must be helped to achieve the same relative height to the other as they have when standing.

In a broad aspect of the invention there is provided a seat with a contoured pan adapted to support each ischial tuberosity of a user and enabling the thighs of a user to be supported at a position between 15 and 45 degrees to the horizontal plane.

The contoured seat pan provides a cup-like support (i.e. concave around at least two axes) such that, even when at an angle, a user will sit comfortably and not slide forward. The function of preventing a user from sliding forward may be achieved through other means that are equivalent to a contoured seat pan, such as ridges, a non-slip rubber surface or even adhesive/straps. These functional equivalents may be incorporated instead of a strictly “contoured” seat pan.

Preferably the seat pan supports a thigh angle of 22 to 32 degrees (but optimally the pan is selected to support the thighs at 27 degrees) to the horizontal plane, which causes the lumbar spine to replicate the anterior facing curve (lordosis) it achieves when a person is standing. In other words, the present invention directs (and maintains) the body to replicate the position of the pelvis and spine as occurs when standing. During use the sitting thigh angle does not alter significantly.

When the standing lordosis is achieved it is the natural positioning of the vertebral structures that hold the body upright, not the muscles of the back. When the natural standing lordotic posture is lost, as with a horizontal seat pan, the muscles of the back attempt to support the person in an upright position. These muscles soon tire and allow the lumbar spine to curve (slump) forward which has a detrimental effect to the rest of the spine, shoulders, neck, arms and forearms.

Preferably the seat pan is comprised of two separate, at least partially concave, shaped seat pads for each side of a user, wherein each pad supports the tissues and shapes around each ischial tuberosity. This structure enhances the body's natural cushioning features and so reduces the need for wasteful/excessive cushioning.

The seat pan could be formed in a single integrated piece that performs the function of the two seat pads otherwise described herein.

By focusing on the support of ischial tuberositites and understanding that for the most part, the variation of their distance apart in the adult human population is only approximately 12% it becomes possible to produce seats that support a far wider range of users than standard seats.

In a preferred form of the invention each seat pad is attached to a base/pedestal structure by a lug with an internal silicon bush at the front and is also connected by a pivoting leaf-spring and another silicon bush at the back. This allows each seat pad to vary its height, towards the back, in a linked way, relative to the other pad. This addresses the fact that it is essential for comfortable sitting that one side of the pelvis might be higher than the other as in most standing people.

As mentioned, the pads are concave around two axes (not one as in some prior art, e.g. GB611899) and are preferably able to move around at least four axes and two fulcra (again, distinguished from GB611899 which has only one axis).

The leaf spring also allows the springing movement of a back post, a movement that helps in the treatment of hypertonicity in the back muscles provided by a series of “back balls” located on a seat back portion. The pads also have a silicon mounting bush within the lug at the front and between the mountings at the back, which allow for a controlled amount of roll in the seat pad.

Preferably the back portion is self adjusting in response to a user sitting on the contoured pan. The self adjusting back component of the invention can be used to treat hypertonicity (elevated tone) in the postural back muscles. Furthermore, the seat is preferably manually adjustable in height only; with the result that many superfluous and wasteful manual adjustment mechanisms (as found in the prior art) can be discarded.

The seat can be used in an adapted form for use in bicycle and motorcycle seats. Research has shown that use of standard bicycle saddles can lead to low fertility and erectile dysfunction in males. The standard saddle is also irritating to haemorrhoids. Many people do not ride bicycles as they find them uncomfortable and this is because much of the body weight is transferred through the perineum rather than the ischial tuberosities as outlined by the present invention.

A seat according to the invention, specifically for bicycle use, may be modified by cutting off approximately half of the pad to reduce its size. In other words, some uses of the seat of the invention may necessitate utilising only part of each pad.

The invention is also anticipated for use in wheelchairs and integrated into other seat structures, such as a bench. Indeed the invention could also be in the form of a portable or retrofit insert for any seat/chair.

It is noteworthy that, other than a height-from-ground adjustment, the seat of the invention is intended to automatically adapt to a user and does not require numerous user adjustments/customisation to find a comfortable position. Prior art seating devices are known to provide manual adjustments that may, coincidentally, locate a seating position which would emulate a standing position and, in such a case, the prior art seat may achieve the same benefits as the present invention for that user. However, such a seat cannot adapt to future changes in the user or other users the way the present invention can.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a side view of a seat according to the invention in a raised position;

FIG. 2 shows a side elevation view of the seat in a lowered position;

FIG. 3 shows a rear elevation view of the seat in the lowered position;

FIG. 4 shows a general perspective view of the seat of the invention;

FIG. 5 shows a closer view of the seat when the seat back has been loaded;

FIG. 6 shows a closer view of the seat when in a resting position;

FIG. 7 shows a detailed rear view of the seat;

FIG. 8 shows a detailed underneath view of the seat;

FIG. 9 illustrates a side view where the seat pads have been tilted by a load;

FIG. 10 illustrates a front view where the seat pads have been loaded as in FIG. 9;

FIG. 11 illustrates a rear perspective view of the seat;

FIG. 12 illustrates a detailed rear view, comparable to FIG. 7, where the seat pans are tilting;

FIGS. 13 a and 13b illustrate a perspective view of an alternative seat design;

FIG. 14 illustrates a perspective view of a bracket and joint for mounting the seat pads; and

FIG. 15 illustrates a cross-section through the bracket and joint of FIG. 14; and

FIG. 16 illustrates an exploded perspective view of the bracket and joint of FIG. 14.

DETAILED DESCRIPTION

FIG. 4 best illustrates a general view of a seat according to the present invention incorporated into an office chair which has a base with feet and/or wheels 11 converging into a central pedestal 12. Such a base with wheels is relatively conventional and it should be noted that any recognisable configuration of chair with ground contacting parts could implement the invention. A height adjustment means 13 is incorporated into the pedestal 12, which may be in the form of a screw thread (as shown) or a pneumatic/spring cylinder. FIGS. 1 and 2 illustrate relatively raised and lowered positions of the seat by virtue of the height adjustment means 13. Height of the seat from the ground is adjusted for comfort dependent on the length of a user's legs, e.g. so feet will be flat on the floor.

The seat itself includes a seat pan preferably formed from two pads 14 which have an at least partially concave construction and are a mirror-image of each other. These pads 14 are preferably independently mounted onto a frame structure 15 at the upper end of the pedestal 12 that supports each pad and a back portion 16, pivotally attached at an axis 17 (best seen in FIG. 6).

Seat back 16 also features a series of padded supports 18 or “back balls” that, in use, contact a user's back.

FIG. 6 illustrates a side view of a seat according to the invention in its initial unloaded or “resting” state, i.e. without the weight of a person applied. The seat pads 14 rest at a relatively high angle and it will be apparent that seat back 16 is reclined at an angle over vertical in this first resting position, before a person sits on the seat.

As illustrated in FIG. 5, when a force F is applied to the seat pan 14 (e.g. by a person sitting down), pressure in the vicinity of the pivot 17 causes the seat back 16 to move in a direction L toward vertical.

FIGS. 5 and 6 generally show a relative linkage arrangement of the seat pads where the frame structure 15 is connected to the pedestal and the spine-shaped seat back 16 is connected at a second pivot 19 (located between the first pivot 17 and the upwardly curving back portion of seat back 16) by a link arm 20 to a front lug 21 extending from the underside of a seat pad. The lugs include an internal silicon bush that provides some flexibility (i.e. “give”) to the pad movement.

The distal end of the curved seat back terminates in the first pivot connection point 17 where a leaf spring 22 is mounted and spans between the two seat pads 14 as best seen in FIG. 7. A further set of resilient bushes 23 (made of silicon or equivalent) are mounted with and extend from the rear underside of the seat pads 14 to connect with the leaf spring 22 spanning therebetween. The resilient nature of the bushes 23 provide a limited degree of yaw movement in the pads.

FIG. 8 illustrates an underneath view of the seat where a lateral bar 24 passing through the (inboard) lugs 21 at the front side of the seat pads 14 provides a horizontal axis about which the front side of the pads have a degree of movement. The lateral bar 24 is stabilised by outboard lugs 25 extending underneath the pads 14.

In totality the mechanism is designed to articulate each pad using a rose joint pivot system, accompanied by a leaf spring/bush arrangement. Each pad, therefore, has a limited degree of movement in several directions to adapt to a sitting person, but yet direct said person into an optimum position based around the incline angle of the seat pads. Once seated a person is maintained in an optimal and comfortable position which, so far as the shape of the spine is concerned, emulates standing.

Particularly, by virtue of the seat pads being attached to the base/pedestal structure 15/20 by a lug 21 with an internal silicon bush at the front and also connected by the pivoting leaf-spring 22 and another silicon bush 23 at the back; each seat pad is able to vary its height, towards the rear, in a linked way, relative to the other pad. This addresses the fact that it is essential for comfortable sitting that one side of the pelvis might be slightly higher than the other as in most standing people.

It will be apparent that the preferred seat pads of the invention have some degree of movement about at least four axes and two fulcra. Particularly, the pads move around three axes (pitch, roll, yaw) and a fourth, being the anterior-posterior axis between the back of the seat pads around which the leaf spring rotates.

FIGS. 9 to 12 illustrate the linked articulated movement of the rear of the seat pads 14 where the right-hand seat pad 14A (see FIG. 10) is depressed lower than the left-hand pad 14B by the weight/physiology of a person (not illustrated) sitting on the seat.

FIG. 12 particularly shows the tilting (rolling/seesawing curved arrows S) nature of the seat pads by virtue of the leaf spring 22 wherein, as one pad lowers, the other rises.

The linked articulated movement can be incorporated into a seat independently of the optimum sitting angle provided by the contoured pads because it addresses variations in pelvic shapes that are not solved by the sitting thigh angle alone.

The leaf spring 22, being resilient, also allows springing movement of the seat back 16 via its pivotal connection 17, a movement that helps in the treatment of pain in the back muscles provided by the series of “back balls” 18 located on a seat back portion. As mentioned, the pads have a silicon mounting bush within the lug at the front and between the mountings at the back, which allow for a controlled amount of roll in the seat pad.

A more conventional seat back (as in an office chair) may be incorporated with the seat which is not necessarily pivotally linked to the seat pads, e.g. it could extend from elsewhere on the base/pedestal and be movable or adjustable independently.

While a leaf spring is illustrated in the presently preferred embodiment of the invention, such biased movement could be provided by other spring types or pneumatic cylinders.

FIGS. 13 a and 13b show a further embodiment of a seat 130 comprising two seat pads 131, 132 for seating a user in a comparable way to the other embodiments described herein.

Each of the seat pads 131, 132 is mounted at respective ends 133, 134 of a “U” or “horseshoe” shaped bracket 135. Bracket 135 is mounted on a chair base system as appropriate for the particular application. For example, the embodiment shown in FIG. 13 utilises a base 136 with wheels and a height adjustment.

As noted hereinbefore it is a feature of the embodiments of this disclosure to support the user in a position which mimics the standing position. This typically results in the height of the seat pads from the floor being larger than for a conventional seat. For example, the point of the pads supporting the ischial tuberosities may be positioned in the range of 450 mm to 650 mm from the floor.

The joint arrangement between the bracket 135 and base 136 of the seat allows movement of the bracket 135 relative to the base 136. In particular the joint allows limited rotation about a front-to-rear axis through the joint such that as one seat pad 131, 132 rises the other falls relative to a horizontal plane. The joint may also allow the bracket to rotate around an axis perpendicular to that front-to-rear axis to allow the angle of the bracket arms and seat pads 131, 132 to vary to the horizontal plane.

FIG. 14 shows a perspective view of the bracket 135 which comprises a ball joint arrangement 140 and two mounting arms 141, 142 extending from the bracket to ends 133, 134 for mounting the seat pads. Although the bracket is shown having a relatively smoothly curved horseshoe shape, any shape which connects the ball joint arrangement to mounting points for the seat pads may be utilised. The term horseshoe shaped does not thus require a continuous curve, but rather simply requires a generally curved component extending around a curve and to two ends on which the seat pads are mounted. Furthermore, in alternative embodiments the bracket can be any shape that mounts the seat pads in the required location. For example, a substantially straight bracket may be utilised to mount the seat pads either side of the ball joint 140.

In a particular group of embodiments, including that shown in FIGS. 13-15, the ball joint is located to the rear of the seat pad attachment points such that the seat pads tip forwards when weight is applied to the seat pads.

Ball joint 140 comprises a mounting point for mounting the bracket to a seat base to form a complete seat.

FIG. 15 shows a cross-section through the bracket 135 and FIG. 16 shows an exploded view of the components of the bracket. A ball 150 has a mounting point 151 for attaching the bracket to a seat base. In this example the mounting point comprises a pair of pins 152, 153 for location in sockets on the seat base, but as will be appreciated any appropriate method of attachment may be utilised.

Ball 150 may be formed of any material suitable for bearing the weight of the seat and sitter, for example steel, or other suitable metal.

Bracket 135 is provided with a concave opening on the lower side, in the centre of the horseshoe shape. The concave opening is lined with a liner 152 formed of, for example, plastic. An example of a suitable material is Nylon. The opening and liner 152 are sized to match the outer face of the ball 150 such that the liner is in substantially even and continuous contact with the surface of the ball.

Ring piece 153 is attached to the bottom of bracket 135. The central opening 154 of ring piece 153 is shaped to match the outer surface of the ball 150. When attached to the bracket 135 the ring piece 153 holds the liner in place and contacts the ball 150 in the same way as the liner. The size of the opening 154 decreases from the side proximal to the bracket towards the side distal to the bracket, thereby holding the ball 150 within the opening 151. The inner surface of the liner 152 and the inner surface of the opening of the ring piece thus form a spherical surface in contact with the spherical surface of the ball 135. The liner is sized to provide solid, stable, support on the ball 150, but to allow movement of the bracket relative to the ball. The ball can thus rotate with the socket, but translation movement is prevented. The liner may be formed of an appropriate material, for example Nylon.

The ring piece 153 is shaped such that its thickness reduces with distance from the centre of the ring piece 153. In the embodiment of the figures the ring is shaped such that the surface proximal to the bracket is perpendicular to the axis of symmetry of the ring, but the surface distal to the bracket is not perpendicular such that the ring piece becomes thinner towards the outer edge of the ring. The distal and proximal surfaces of the ring are thus not parallel.

When the bracket 135 is mounted on a seat base as shown in FIG. 13 the tapered ring enables the bracket to move with respect to the base and ball, but that movement is limited by the surface of the ring coming into contact with the upper surface of the seat base. The amount of movement of the bracket on the ball is thus defined by the shape of the surface. The amount of movement increases as the difference in thickness between the inner and outer edges of the ring piece increases.

The shape of the ring piece may vary around the ring. For example, the difference in thickness may be greater at the front of the ring that at the side. This provides greater movement front to back, but less movement side-to-side.

The upper surface of the seat base may be provided with a resilient material to provide a spring effect to the movement of the bracket. This resilient material may hold the bracket in a predefined position (for example horizontal) when the seat is unoccupied, and return it to that position as a person leaves the seat, but allows movement of the seat when it is loaded with a person.

The ball joint described with reference to FIGS. 13 to 15 thus allows roll movement of the bracket about a front-to-back axis of the seat such that one pad is lowered and the other raised, thereby accommodating asymmetries in the sitters body. The amount of movement is limited by the shape of the ring piece and may be controlled by the use of a resilient element. The typical leg-length difference, and hence required difference between the points of the seat pads that support the ischial tuberosities, is in the range 5-35 mm. The roll movement of the bracket is preferably limited to allow this amount of movement, but not substantially more. Using typical skeletal sizing it can be calculated that an angular rotation of the bracket by 21 degrees from the horizontal position provides the required difference in height.

The ball joint also allows rotation of the bracket around a side-to-side axis such that the pads are raised and lowered and the angle of the pads is changed. In an exemplary embodiment the joint may allow 5-10 degrees of rotation below the horizontal about this axis. The ring may thus be configured to only permit rotation in one direction about this axis—the bracket cannot rotate to raise the seat pads, but can rotate to lower the seat pads.

In the example of the figures, the arms 141, 142 of the bracket are formed of multiple layers of material to provide a leaf-spring. Although not shown in the figures, the lower layers of material may be shorter, and not reach as far towards the ends of the arms as the upper layers. These leaf springs allow movement of the pads relative to the seat base to allow the seat pads to adapt their position depending on the weight and positioning of the sitter.

Preferably the back portion 16 is self adjusting in response to a user sitting on the contoured pan 14. The self adjusting back component of the invention can be used to treat pain in the postural back muscles or for the general accommodation thereof. Furthermore, it should be noted that the seat is preferably manually adjustable in height only; with the result that many superfluous and wasteful manual adjustment mechanisms (as found in the prior art) can be discarded.

Preferably, when loaded with the weight of a person, seat pads 14 should accommodate and support a user's thighs at an angle selected to be substantially 27° below the horizontal while the curved and contoured nature of the seat pads 14 comfortably prevent a user from sliding forward.

It will be appreciated that the pivot mechanism of the seat back 16 connected via the leaf spring could take several forms or, in the case of a stool-type design, be removed completely. In such a device the two seat pads 14 can be at a fixed angle of approximately 27°. Guidance for the use of the invention recommends that the users feet are flat on the floor when in the final sitting position, or at least in a position which allows the muscles thighs and legs to be relaxed. There could also be occasions when the occupier might want to use a foot rest on the lower part of the chair so that lower legs could be angled backwards or in the case of the invention being used on a higher seat such as a bar stool a higher foot rest could be incorporated to support the feet.

It should be noted that, because the two seat pads 14 are contoured to the buttocks of the user, explicit cushioning on said pads 14 can be relatively thin.

General principles of the seat according to the invention can be adapted for use in a wheelchair or other seat designs such as a bicycle or motorcycle seat. Operation is otherwise the same as described above

In all cases the seat pads (or integrated single seat pan) include a concave portion or equivalent to cup and support each ischial tuberosisty of a user in a way which does not put undue pressure on the perineum and also avoids muscle tightening which would otherwise result from a user attempting to prevent slipping forward.

The seat of the invention, in all forms, can be moulded in relatively few parts, e.g. all major elements of the office chair of FIGS. 1 to 4 can be moulded from aluminium such that it can be particularly lightweight.

Claims

1. A seat with a contoured pan, wherein: the contoured pan is supported towards the ends of a mounting bracket,the mounting bracket having a ball and socket joint positioned substantially centrally along the length of the mounting bracket,the ball of the ball and socket joint being mounted onto a chair base, wherein the ball and socket joint provides a limited range of movement of the mounting bracket relative to the chair base.

2. A seat according to claim 1, wherein the contoured pan comprises two seat pads, each seat pad mounted towards a respective end of the mounting bracket.

3. A seat according to claim 1, wherein the ball joint allows at least rotation of the mounting bracket about an axis running front-to-rear of the seat through the ball joint.

4. A seat according to claim 1, wherein the ball joint allows at least rotation of the mounting bracket about an axis laterally across the seat through the ball joint.

5. A seat according to claim 1, wherein the ball joint comprises a concave socket formed in the mounting bracket, and a ball for mounting on a chair base, the concave socket and ball being sized to prevent translation movement of the ball in the socket, but to allow rotational movement.

6. A seat according to claim 5, wherein the ball joint further comprises a ring piece mounted on the mounted bracket to retain the ball in the concave socket.

7. A seat according to claim 6, wherein the ring piece limits movement of the mounting bracket by contacting the chair base.

8. A seat according to claim 6, further comprising a resilient element between the ring piece and the chair base.

9. A seat according to claim 7, wherein the ring piece permits rotation of the bracket by up to 21 degrees from the horizontal about a front-to-rear axis through the ball joint.

10. A seat according to claim 7, wherein the ring piece permits rotation of the bracket by an angular amount to provide up to 50 mm of height difference between the parts of the seat pads supporting the ischial tuberosities.

11. A seat according to claim 7, wherein the ring piece permits rotation of the bracket by up to 10 degrees downwards from the horizontal about a lateral axis through the ball joint.

12. A seat according to claim 7, wherein the ring piece permits rotation of the bracket by up to 5 degrees downwards from the horizontal about a lateral axis through the ball joint.

13. A seat according to claim 1, wherein the contoured pan is adapted to direct the thighs of a user to be supported at a position between 22 and 32 degrees to the horizontal plane.

14. The seat of claim 1, wherein in use, when a user is seated, the seat will direct and maintain the user's spine to substantially emulate a standing position.

15. The seat of claim 13, wherein the position is substantially 27 degrees to the horizontal plane.

16. The seat of claim 1, wherein the contoured pan is adapted to support each ischial tuberosity of a user and enabling the thighs of a user to be supported.

17. The seat according to claim 1, wherein the seat pan is comprised of two at least partially concavely shaped seat pads adapted to support each ischial tuberosity of a user.

18. The seat according to claim 1, wherein the seat pan is cushioned by a relatively thin layer of padding.

19. The seat according to claim 1, wherein the mounting bracket comprises a resilient element between the ball joint and the points at which the contoured pan is attached to the mounting bracket.

20. The seat according to claim 19, wherein the resilient element is a leaf spring.