GB2369563A - Sofa/chair with extendable cushion - Google Patents

Abstract

A sofa or chair comprises a seat back 4 spaced from a seat base 1 and a cushion 3 received on base 1 wherein the position of cushion 3 can be adjusted to alter the length of cushion 3 projecting forward of seat back 4. Preferably the chair/sofa comprises a plurality of separately adjustable cushions. Cushion 3 may be raised at an angle of 10-20{ and can be adjusted by motors or manually by lifting or sliding along car seat runners. Seat back 4 is preferably angularly adjustable and has a forwardly curved, height adjustable, lumbar support 5, a vertically, angularly and horizontally adjustable headrest 9 and a tapered pillow 8 below headrest 9.

Description

Supportive sofa or chair Description This invention relates to a seat, or a plurality of seating units forming a sofa or seating system, which supports people of different sizes in a comfortable and healthy posture.

In order to sit comfortably and without risk to the health of the spine, people need to sit fully back in a seat, with the lumbar spine supported in a forward curve against the seat back. However this is only possible if the occupants'upper leg length (from the back of the buttocks to the back of the knee) is no greater than the length of the bottom-cushion, since otherwise the backs of the knees hook the nose of the cushion before the pelvis can be fully at the back of the cushion.

A difficulty arises in that people vary in the length of the upper leg, so that a bottomcushion which is short enough to enable most people to sit correctly is too short for long-legged people to enjoy support under the front of the thigh, and also too short to allow occupants to lie comfortably on one side on a sofa. The compromise thus forced is generally resolved in favour of taller people, causing discomfort and health risks for many seat occupants. It is a further difficulty with conventional sofas that two people of significantly different leg lengths cannot properly be accommodated by any single cushion length.

In addition the dimensions of the pelvis and spine vary between people, and in existing seats the shape, location and hardness of the lumbar support are generally either absent, inadequate, uncomfortable, or complicated by being adjustable.

A further difficulty is that the anatomical construction of the spine and pelvis produces a geometrical tendency for the pelvis to rotate, which rotation bends the lumbar spine into a backward curve. Living-room seating such as sofas and upholstered chairs generally have bottom-cushions which are more or less horizontal, making it easy for the pelvis to rotate and slide along the bottom-cushion away from the seat-back.

It is a further difficulty with conventional sofas that seat-backs are too low to offer head support to occupants who sit upright.

A yet further impediment to comfort is that in conventional living-room seats the seatback is arranged at an angle of 90'-100'to the bottom-cushion, creating a correspondingly acute angle at the hip of occupants who sit fully back against the seat-back. Such angles at the hip are uncomfortable over long periods. Furthermore the upright angle of these seat-backs means that they take little of the weight of the occupant's torso, arms and head, causing that weight to fall on the pelvis, thereby increasing pressure under the pelvic bones and muscles.

Thus, through a combination of traditional characteristics, seating, and living-room seating in particular, generally both assumes and promotes a slumped sitting posture.

Slumped sitting postures, in which the lumbar spine is in a reverse curve and the buttock muscles are under high pressure, are bad for the health of the spine and its supporting tissues, and are uncomfortable.

Prior Art W09809552A1 discloses a couch (a sofa-bed) with sliding seat, in which a range of cushion length adjustment is quoted as 24.75 inches to 33.73 inches, and an advantage is claimed that the forward cushion adjustment allows the back of the knees to be supported among longer-legged occupants. However, 24.75 inches is already longer than the corresponding upper leg length (from the rear of the buttocks to the back of the knee) of 99.95 percent of US adults. A further limitation is that the one-piece seat cannot be adjusted to suit two different occupants simultaneously.

The Invention The present invention provides a solution to these problems, comprising a seat with a bottom-cushion having means of adjustment of its length to suit the thigh lengths of individual occupants (whether several occupants of a sofa or a single occupant of a chair). Optionally provided are a bottom-cushion sloping upwards back-to-front, a seat-back which is so angled, shaped and constructed as to provide apt lumbar and head support for most adult occupants, and a simple means of providing adjustment for a range of postures and degrees of lumbar support, including leisure postures such as watching television.

According to the present invention, the seat-back has a gap underneath and behind, into which the cushion may be inserted. The position of the bottom-cushion can be varied forwardly of the seat back, by inserting it to various extents into the gap, so that varying proportions of the cushion length may be used according to the occupant's upper leg length. The protruding length of the cushion is adjustable preferably between 400 and 600 mm (15. 7" and 23.6"), in order on the one hand to suit the corresponding body dimensions of at least 99% of European and US adults, yet on the other hand not gratuitously to invite slumped postures by providing unnecessary length. The structure of the seat is correspondingly short, so that when the cushion is in its most rearward position no part of the seat structure beneath protrudes to the front. Various means of enabling this adjustment are disclosed below. The adjustment is preferably either continuous or in steps of no more than 20 mm, in order to enable fine adjustment to match the length of the leg.

Optionally the bottom-cushion is at an angle of 0-25 degrees to the floor, sloping upward back-to-front, preferably 10-20 , preferably 15 , so that gravity helps to keep the occupant's pelvis at the back of the cushion. An additional benefit of this angle is that short-legged occupants benefit from decreasing height of the front of the cushion as it is shortened, in the ratio of approximately 25 mm drop in height for 100 mm shortening (in the case of a 150 angle). This gives some automatic allowance for the tendency of people who have short upper legs also to have short lower legs, and conversely for long-legged people to have both long thighs and long lower legs. The shortness of the seat structure disclosed above enables occupants to place their feet rearward towards the torso when rising out of the seat, so making rising easier by bringing their feet closer to the body's centre of gravity.

The upper surface of the bottom-cushion at the front is at a height between 350 and 500 mm from the floor, in the most rearward and forward position respectively, preferably 380-450 mm, preferably 390-440 mm.

A seat-back is optionally provided which is angled at between 350 and 650 to the vertical, preferably 50-60 , preferably 55 , and dimensioned and curved so that occupants'backs are supported in a forward curve in the lumbar region. This lumbar support comprises a shape which in cross-section is approximately a section of a circle (i. e. a curve of constant radius), definable by the radius of that circle and the length of a line or flat side linking its ends (the chord). The lumbar support disclosed is made substantially effective for more than 98% of adult European and US occupant sizes by its radius of curvature of 950-1200 mm, preferably 1000-1100 mm, preferably 1050 mm, and chord length of 350-600 mm, preferably 400-500 mm, preferably 450 mm (in cross-section). This extended curve gives support wherever the occupant's individual contact area may be, without high pressures which would be uncomfortable.

The angle of the seat-back to the bottom-cushion allows a comfortably obtuse angle through the hip joint, as measured between a line drawn through the hip in the plane of the femur and another line drawn through the hip in the plane of the sacrum. Hip angles more acute than approximately 100 degrees become progressively less comfortable and more associated with work postures than relaxed seated postures.

Preferably the present invention gives hip angles of 100'or more.

A head support structure is preferably provided extending upwardly from the seat

back at an angle of between 250 rearwards and 50 forwards from the vertical, preferably between 100 rearwards and vertical, preferably 5'rearwards, in order to support the occupant's head and shoulders in an attitude which is suitable for leisure activities such as watching television. This headrest structure is 250-370 mm in height (vertical length), preferably 280-350 mm, preferably 320 mm, in order to be high enough for at least 99% of European adults without being unnecessarily high.

A moveable cushion or pillow on the seat-back is optionally provided, which the user may place higher or lower, to obtain more or less lumbar support respectively, and also or alternatively to sit less or more upright respectively, and also or alternatively to obtain more or less support behind the head. This pillow is deployed in front of the headrest structure, to provide a very soft, yielding surface and to enable fine adjustment of the thickness of support actually behind the head, so that the very light forces needed to support the head while looking forwards can be set with precision by the occupant. Such support enables the neck muscles to be relaxed while occupying the seat.

Thus the invention is designed to facilitate a seated posture which is relaxed, and yet comfortable and healthy, for the large majority of European and US adults.

Some specific embodiments of the invention will now be described by way of example, with reference to the accompanying drawing, in which: Fig 1 is a side elevation of a seat in accordance with the invention.

Fig 2 is cross-section through an alternative bottom-cushion for use with the seat of Fig 1, and Fig 3 is a perspective view of an alternative lumbar support means for use with the seat of Fig 1.

Example 1.

Referring to Fig 1 of the drawing, in its most preferred embodiment the seat-back consists of a flat supporting structure (4), such as a board, inclined at 55 degrees to the vertical, onto which is fastened a lumbar support (5) made of soft foam (for example a polyurethane foam of density 55 kg/m3 and hardness 110 N, foams to such specifications being available from foam suppliers. This lumbar support extends across the width of the seat-back, and is positioned vertically so that its bottom edge is adjacent to the surface of the bottom-cushion (3). The lumbar support extends upwards and rearwards in the plane of the seat back through a linear distance of 450 mm. At a height approximately 50 mm above the top of the lumbar support (measured in the plane of the seat-back structure) the seat-back structure (4) becomes, or is attached to, a head-rest support structure (9), extending upwardly at an angle of 50 from the vertical (leaning backwards). This headrest structure is about 320 mm in height. The means of making this transition from sloping to nearly vertical structure will be readily apparent to the person skilled in the art, for example by use of a bracket. To the front of the headrest structure is provided a pillow as disclosed above. In this preferred embodiment the whole seat-back is further covered in a layer of polyurethane or similar foam (6) of similar specification to the lumbar support, in a constant thickness of approximately 50 mm, then in a further layer of very soft foam (7) (for example hardness approximately 70 N) in a thickness of approximately 20 mm. The purpose of this topmost layer is to absorb surface irregularities such as clothing creases without creating high pressures on the skin. The bottom-cushion (3) is supported on and optionally fastened (for example by hook-and-loop fastening) to a base or subframe (1), which is mounted to the main structure of the sofa via sliding or wheeled elements such as runners (2), such as car seat runners which can be obtained from car accessory suppliers. The cushion, base and runners slope upwards from the back to the front of the seat at an angle of 15'to the floor. In this preferred embodiment the bottom-cushion base or subframe (1) is linked by a spring or other energy-storing device to the seat frame, to facilitate forward adjustment by the user while seated by partially counteracting the pull of gravity which acts down the slope.

The spring preferably exerts a force of 130 +/-30 N, in order to be suitable for both light and heavy users. In this preferred embodiment the height of the upper surface of the bottom-cushion at the front is about 390 mm when the cushion is at its minimum working length, to enable the feet of shorter-legged occupants to be fully supported on the floor.

Example 2 As Example 1, but the bottom-cushion (3) includes a stiffer reinforcing layer (10), in the underside, which supports the front of the cushion when it overhangs the front of the support structure (see Fig 2). The reinforcing layer may be made of a sheet material such as plywood, or may be a hard and stiff grade of foam, or may comprise a plurality of bars, rods or struts. By these means the support structure is not required to extend all the way forward.

Example 3 As Examples 1 or 2, but the cushion together with any stiffening structure that may be found desirable (for example, a board on the underside) is attached to the seat frame with hook-and-loop or a similar fastening, so that users adjust the cushion length by lifting the cushion and refitting it. This embodiment is suitable for environments where the same individuals habitually sit in the same seat, so that frequent adjustment is not required.

Example 4 As Examples 1,2 or 3, but the underside of the cushion (3) and the upper surface of the support structure (1) have areas which, together, create high friction to resist translational movement of the cushion unless it is lifted.

Example 5 As any preceding example, but the lumbar support (5) is adjustable in height and/or protrusion and/or length and/or hardness. Many mechanisms exist for providing adjustment, for example air inflation, and will be known to the person skilled in the art.

Example 6 As any preceding example, but a motor is provided to facilitate adjustment of working cushion length. The motor can act through a chain, drive belt, screw drive or similar drivetrain, or can be bought as an actuator complete with screw drive and linkage.

Such mechanisms will be known to the person skilled in the art.

Example 7 As any preceding example, but the cushion is held in any position by a matching set of notches or teeth, which mesh when the cushion is resting or pressed down onto the support structure.

Example 8 As any preceding example, but the pillow or cushion (8) on the seat-back and/or headrest tapers from top to bottom (seen from the side) in a wedge shape, so that at the bottom it tapers to a point to give a smooth transition to the lumbar support, while at the top the thickness is greater, so that as the cushion is deployed lower on the seatback the amount of support increases. In the preferred embodiment the cushion is about 600 mm in length, up to about 150 mm in thickness, and filled with soft filling such as polyester hollow fibre as used in quilts and pillows. Preferably the filling is provided in a plurality of compartments within the outer cover to limit movement of the filling and so maintain the shape of the pillow in use.

Example 9 As any preceding example, but the lumbar support is created wholly or in part by a shaped support structure such as a frame. (Fig 3). In this embodiment there is a back frame with a sheet material, fabric or set of springs in tension side-to-side, so shaped as to provide a lumbar support profile similar to that described in Example 1. Being in tension side to side, the diaphragm adopts the profile of the frame, and thus tends to support the occupant's spine in the shape defined thereby, so a greater or lesser extent according to the degree of tension and elasticity of the diaphragm material.

Accordingly, a frame shaped and dimensioned in accordance with the lumbar support profile disclosed above is used to provide lumbar support.

Example 10 As any preceding example, but the lumbar support is created wholly or in part by a shaped support structure holding springs. In this embodiment, there is a back frame with a set of springs in compression or a sheet of sheet material such as plywood or steel, so shaped as to provide a lumbar support profile similar to that described in Example 1.

Example 11 As any preceding example, but the occupant's legs and/or feet are supported on a structure such as a legrest or footstool. This allows the bottom-cushion to be made higher, for ease of sitting and rising, while still allowing shorter-legged occupants to have support under their feet. In addition or alternatively it provides a posture in which the lower leg is at a less acute angle to the upper leg, and the foot is vertically nearer to the heart, compared with resting the foot on the floor, thereby improving blood flow through the knee and so health and comfort.

Claims (16)

1. CLAIMS 1. A seat comprising a seat back and a base, the base being adapted to receive a bottom-cushion, the seat also having a gap between the seat back and the base, in which the bottom-cushion may be received, and a means for adjusting the position of the bottom cushion to vary the amount of the bottom cushion extending forwardly of the seat back.
2. 2. A seat according to Claim 1, comprising a plurality of individual seating units which may be adjusted separately.
3. 3. A seat according to Claim 1 or Claim 2 wherein the bottom cushion extends at an angle, rising back-to-front, of approximately 100 to 200 to a floor surface on which the seat stands.
4. 4. A seat according to Claim 1 or Claim 2 wherein the seat back is adapted to support an occupant's back to provide a forward curve in the lumbar region.
5. 5. A seat according to Claim 4, wherein, if the start and end points of the lumbar support curve were joined by a straight line (i. e. the main plane of the seat back), the line would be inclined at an angle to the vertical of between 35 and 65 degrees.
6. 6. A seat according to any one of the preceding claims having adjustable lumbar support means on the seat back.
7. 7. A seat according to Claim 6 wherein said lumbar support means comprises a support element adjustable upwardly and downwardly in its position on the seat back.
8. 8. A seat according to any preceding claim having a seat-back which adjusts angularly.
9. 9. A seat according to any preceding claim, further having a head rest fixed to the top of the seat back supporting structure.
10. 10. A seat according to any one of the preceding claims having a vertically adjustable head rest or pillow.
11. 11. A seat according to any preceding claim wherein a pillow or soft cushion is included for use between the headrest structure and the occupant's head.
12. 12. A seat according to Claim 10 or Claim 11, wherein said head rest pillow tapers from top to bottom.
13. 13. A seat according to any preceding claim having a headrest portion which adjusts forwardly and backwardly.
14. 14. A seat according to any preceding claim having a headrest portion which adjusts angularly.
15. 15. A seating unit according to Claim 1 wherein the unit is a sofa.
16. 16. A seat substantially as described herein with reference to the accompanying drawing.