GB2393904A - Chair with locking height adjuster and locking rotational control - Google Patents

Abstract

A swivel chair (10) has a seat (13) of variable height, with means for releasably locking the seat height, and selecting one of a plurality of predetermined swivel positions by engagement of a spring loaded trigger mechanism (82). A footrest (39) may be provided of variable height with means to vary its radial deployment from the axis of the swivel seat. A similarly adjustable step (40) may be provided, with telescopic feet (50) that are independently adjustable for height. Arms (41) of specific shape may be provided, which can be moved and clamped laterally across the seat. A removable, wheeled carriage (99) may be provided to assist transportation, and extended legs (24) may be provided to improve stability. In an alternative embodiment means is provided to enable the chair to be moved and a failsafe mechanism is included to ensure that the seat is never used when the wheels are deployed.

Description

A CHAIR 2393904

This invention relates to a chair, and more particularly a swivel chair, with one or more supports for trunk and feet.

Backoround Chairs are well known devices used for rest, leisure or work purposes, often in conjunction with a workstation such as a table or desk. An able bodied person when sitting, will typically draw out the chair from the workstation, move in front of it, then draw the chair in as they sit, finally lifting their feet and moving them further under the workstation to complete the operation.

However, this task may be beyond the capability of disabled individuals who may lack the strength, stature, co-ordination or balance to perform this multi function task. As a consequence the act of sitting on a conventional chair may require the assistance of a second party for lifting, drawing the chair in or out, steadying the person and/or to ensure the safety of an individual. When such assistance has to be paid for - as may be the case with support workers in schools and colleges - a heavy financial burden is placed upon the responsible authority.

The present invention a rose in order to provide a chair which overcame the aforementioned disadvantages and which could readily be used by persons with restricted growth, limited motor ability and/or strength.

Summarv of the Invention According to a first aspect of the invention there is provided a chair having at least one support for trunk and feet, the chair having means for varying the height of the seat with respect to a ground level; means for releasably locking the seat height; and means for selectively locking the seat in swivel positions.

Because a user is able to climb onto the chair, sit on the seat and then swivel the seat to a position where the user is comfortably sat at a desk or table,

without having to lift or move the chair, the invention offers benefits over existing types of chairs for users with restricted growth, limited physical strength or mobility.

There are preferably a plurality of predetermined swivel positions, each of which may be selected by way of an engagement mechanism, said engagement mechanism conveniently includes a resiliently deformable device, such as for example a spring loaded trigger. The device is dimensioned and arranged to be retracted so as to permit swivelling of the seat of the chair with respect to a central axis and to engage in order to lock the seat with respect to an axis of the chair.

Seat height is adjustable and means is ideally provided for selectively locking the seat in one of a plurality of positions.

One or more steps or footrests are preferably provided. The, or each, footrest or step may be adapted to vary its height with respect to the floor on which the chair is supported. Ideally means is also provided to vary the radial deployment of the step and/or footrest. That is the distance from the axis about which the chair swivels, so that the distance between the seat and the footrest may be altered, for example to ease stowage.

Preferably the adjustable step and/or footrest is/are supported on telescopic fooVfeet, each of which is ideally adjustable in dependence upon the height of a user.

A removable carriage, which is ideally fitted with wheels, is advantageously provided to assist transportation. The carriage is preferably equipped with a handle, which may retract or fold away. When extended the handle is able to lift the chair, using the wheels as a fulcrum, and move the chair.

In a further embodiment a castor base incorporating a lift mechanism may be included in the chair in order to assist with deployment and ease relocation of the chair.

Fixed feet are provided where a non-moving chair is required. A typical example being a high stool for drafting purposes, whilst castors are provided for a moveable or mobile chair, such as is commonly used at an office desk.

An advantage of castors is that the chair can be easily moved to a new location without the need for lifting the chair.

However, to use a mobile chair, with a castor base requires a relatively high degree of dexterity and physical co-ordination when sitting down or getting off the chair. Failure to approach or leave the chair properly can result in the chair striking out sideways under the influence of non vertical forces acting upon it, for example by incorrect body posture or uncontrolled application of forces. Arms of a specific shape are provided so as to assist a user to climb into and get out of the chair. The arms of the chair may be vertically adjustable.

According to a second aspect of the present invention there is provided a chair having arms that are easy to grip, the arms are round and shaped so that the user may always find a part of the armrest that offers itself at a near right angle to the users arm, irrespective of the users elevation and attitude when gripping it.

Preferably arms are curved so that they can be moved and clamped laterally across the seat so that a portion of the arm is always presented substantially at a right angle to a users arm; thereby ensuring that a portion of the arm of the chair is always readily available, and easy, to grip. Ideally the surface of the arm of the chair is also curved so that it resembles a slightly curved sausage. Also, because the arm is moveable, thereby enabling it to move laterally - towards and away from the users body when seated - a greater downward component force is obtained by the user, when pushing down on the arms, so as to assist the user stand, when the arms are positioned close to the user.

Preferably each arm is able to slide laterally and independently across the body of the seat, being mounted on an arm slide rail, which is mounted beneath the seat.

This slide arrangement is much as described for the footrest and step, and is provided with a clamp to ensure that an armrest is both rigid in use and prevented from sliding laterally.

Persons of normal intellect, but with physical disabilities, may be precluded from manual handling of the chair, or its associated equipment, operational, or safety devices.

Persons with a disability, particularly of balance or co-ordination, may have difficulty sitting in a mobile chair. To overcome this problem certain types of castors have been fitted with brakes. However, even the provision of brakes has not always been suitable, as if the brakes were not deployed, for example if an attendant forgot, accidents may have resulted. Also such brakes often needed to be engaged before use. A user or supervisor sometimes overlooked engagement of a brake. Often users with impaired ability did not possess necessary fine motor skills to engage (or release) a brake. In extreme cases the failure to engage brakes may have resulted in injury.

According to a further aspect of the present invention there is provided a chair having means for varying the height of the seat with respect to a ground level; means for releasably locking the seat height; and means for selectively locking the seat in swivel positions; the chair including transport means to assist in moving the chair from one location to another and a plurality of feet on which the chair is adapted to rest; and means for engaging a transport mechanism and means for disengaging the transport mechanism.

It is a pre-requisite of the user, that the chair is safe for use as a user approaches the chair. This was not always possible where castors were fitted. To overcome this a retractable mechanism is provided. Because it is

not possible for a user to climb onto the chair without the use of the retractable footrest, this preferred aspect of the invention ensures that as soon as the footrest is deployed the chair is reset to stand on the ground on its fixed feet; not on its castors and is therefore unable to move inadvertently.

Notwithstanding this requirement a castor base sometimes needs to be used in order to move the chair, for example to a new location in a classroom.

Preferably the transport mechanism includes one or more castors or wheels arranged, so that when engaged, the chair can be pushed or rolled by an assistant, for example. When the transport mechanism is disengaged the chair is unable to be moved. In practice this may mean that a brake has been applied or the position of the chair has been lowered from being supported by castors to a position where it is supported by a solid base.

To ensure that an unsafe situation cannot exist, as a result of mischief or forgetfulness, safe provision is made for ensuring that the chair cannot be left unsafe. That is, with the chair left raised upon the castor base. This is achieved by the provision of a tripping mechanism attached to the castor base lifting mechanism.

A preferred example of a means for disengaging the transport mechanism includes the deployment of one or more selected accessories, essential to the use of the chair. Typically deployment causes a castor base lift mechanism to be tripped, returning the chair immediately to its fixed feet. Such accessories include the step, the retractable footrest and the flip-up footrest. Furthermore, the mechanism cannot be reset whilst the appropriate accessory is deployed for use, except whilst deliberately deployed by human intervention. As soon as a lever or other default trip mechanism is activated, the chair returns to a safe mode i.e. resting upon its fixed feet.

This aspect of the invention provides a foolproof means to ensure that a user is never able to use a chair, if it is not safely and firmly located on the floor.

For the chair to be safe it must rest upon its default, fixed feet. It must not be possible to use the chair whilst raised on its castor base, as were this case,

the chair might strike out, resulting in the user falling or possibly injuring themselves. Given that the user is of normal intellect it would be apparent to the user considering use of the chair, that the chair was potentially unsafe because: Firstly a person was holding the lever in the "chair raised" position; and secondly one, or all of the essential accessories, required for use of the chair were not deployed for use, thus the chair may not be safe, but in this circumstance, the user could not use the chair.

According to a yet further aspect of the invention there is provided a chair having means for varying the height of the seat with respect to a ground level; characterized in that a fixed portion is provided on which is mounted at least one accessory and a movable portion is provided, on which the seat of the chair is mounted, there being means for moving the fixed and moveable portions relative one to another and locking them.

Accessories include: a step, a retractable footrest, a wheeled carriage, independent support legs or a flip-up footrest. An advantage of this aspect of the invention is that, depending upon the nature of the accessory, such as the footrest or step, it does not have to be repositioned, once set to a particular position (height), upon the appropriate portion of the chair. This aspect of the invention ensures that accessories that do not need to be reset (for example the step, carriage or support legs) may be attached to a fixed portion of the chair; whereas those accessories that are required to move cooperably with the seat (e.g. footrest) may be arranged to be attached to the moving portion of the chair.

Brief Description of the Fioures

Preferred embodiments of the invention will now be described by way of examples only, and with reference to the Figures in which: Figure 1 shows a front elevation of a preferred embodiment of the chair;

Figure 2 shows a plan view of the chair shown in Figure 1, with the seat removed; Figure 3 shows side and end elevations of the seat and arms; Figure 4 is a side elevation view of the chair with an alternative base mechanism; Figure 5 shows a cross section through a trip and lift mechanism; Figure 6 is a plan view of the base of the chair shown in Figure 4; Figure 7a is a side elevation of an alternative embodiment of a chair with a flip-up footrest; Figure 7b is a plan view showing a trip mechanism for a retractable footrest or retractable step; Figures 8 and 9 are side and end elevations respectively showing a lift and trip mechanism for a castor base for use with the chair; and Figures 10 and 11 are side and plan elevations respectively of an alternative embodiment of a chair having relatively slidable attachment supports.

Detailed Descrintion of Preferred Embodiments of the Invention Referring to the Figures and particularly Figure 1, there is shown a chair 10 having a base 11 with a telescopic strut 12 centrally and vertically mounted upon it. The strut 12, is typically, but is not limited to, a gas spring type, of the common piston 17a and cylinder 17b configuration, atop which seat 13 is mounted. Base 11 is typically, but is not limited to, the common five star base type, having separate legs on which are fixed feet 50. Alternatively, or in addition to feet, the chair may be fitted with castors or wheels 25 or a

combination thereof. Castors and wheels 25 may be arranged to be of the free or locking type.

Coaxial with strut 12 is a support frame hereinafter referred to as attachment support 14 which has at its lowest end an end clamp 16, which when operated by any suitable arrangement such as a pinch screw or clamp, grips an outer surface of the telescopic strut 12, thus preventing any relative movement (rotation or axial shift) between the attachment support 14 and the strut 12.

When end clamp 16 is released however, both axial movement and rotation of the attachment support 14 along, and rotatably about, strut 12 is possible.

As mentioned above, seat 13 sits atop strut 12, which is free to rotate within the cylinder 17b and can be extended or retracted when operated by a suitable mechanism (not shown). The attachment support 14 is therefore effectively coupled to the seat 13 by way of a rotary coupling means. A suitable arrangement is shown whereby the attachment support 14 is retained in a groove in a circular collar 18, which is fixedly attached to an underside of seat 13. The collar 18 permits the attachment support 14 to rise and fall with the seat 13, as the piston of the strut 12 extends or retracts within the cylinder, generally in the direction of double headed arrow M'. Collar 18 also allows free rotation of the seat 13 and attachment support 14 relative to one another. However, when attachment support clamp 16 is applied against the cylinder 17b of strut 12, vertical movement of the attachment support 14, and thus the seat 13, is prevented.

Attachment support 14 incorporates an indexing device, hereinafter referred to as index 27 mounted beneath the seat 13. Hinging on a fulcrum bracket 19 is a lever operated, trigger 20, the handle of which trigger 20 extends laterally to the side of the seat 13 and is shaped in such a way that a knob or grip is easily reached and activated by the user. The trigger 20 is held in contact with a surface of the index 27 by a spring 21 or similar device, unless moved away from the index 27 by the user. Index 27 has notches, holes, grooves, indents or similar devices (not shown), at intervals along a radial path of contact between trigger 20 and index 27. These are intended to cooperate

with sympathetic engagement means in order to lock the seat 13. The spring-

loaded trigger 20 is able to drop into notches, for example, when a notch and trigger 10 come into alignment, thus locking seat and attachment support 15 together, thereby preventing relative rotation therebetween. When attachment support clamp 16 is also employed; seat 13 and base 11 are effectively locked together, both axially and radially.

A plurality of notches or indents (not shown) are distributed about index 27 to suit the application but, for the purposes of the present preferred embodiment, are four in number, arranged at ninety degrees one to another. For convenience these are referred to as being at the four points of a compass -

North, South, East and West. Referring to Figure 2, the main body of the attachment support 14 is provided with at least one, but typically four vertical slide means 28a, in the form of, but not limited to, a tee slot, beam, gutter, dovetail slide, channel or groove. Each slide means 28a are located at ninety degrees one to another. The slide means 28a is substantially parallel to the axis of strut 12 and receive a tee-bolt. Means is provided to prevent rotation of bracket 22 about attachment support 14. This may be in the form of tees running within the slot 28 or concave and convex surfaces or any other common means as shown in Figure 2. Each slide means 28a is capable of receiving a bracket 22. Each bracket 22 locates in the slide means 28a, and all able to move along the axis of the slot 28 and may be clamped to the attachment support 14 in any desired position along their length, by suitable clamp means such as a tee bolt or by utilising other tightening means such as nut, handle 33, lever, cam lock. More than one such bracket 22 may be fitted to a slide means.

Brackets 22 provide support for a variety of accessories or may be a part of the accessory itself as in the example of the wheeled carriage 99 on which the chair 10 may be optionally mounted in order to assist in relocating it. Such a wheeled carriage 99 may be adjustable, as described for the bracket 22, such that its wheels 25 are level with, or slightly above, the base 11 feet or castors, but outboard of them such that when the chair 10 is tilted sideways, in the direction of arrow B. the chair weight is transferred to the wheels 25 in the

manner of a sack truck. The chair 10 can then be moved between locations.

A notch of the index 27 is so arranged to align the back of the chair, with the wheeled carriage 99 such that the seat back or a suitable handle(s) mounted on it (not shown), may be used to support and push along the chair 10 when tilted. Suitably shaped footplate(s) 40, for example as shown in Figure 1, are provided to assist the user to climb into the chair and provide support for the users feet. The footplates 40 may pivot (so are retractable) or may slide towards and away from the telescopic strut 12, along at least one horizontal slide. One or more footplate(s) 40 may be incorporated into the bracket 22.

One example of a suitable slide means, on which the footplate 38 may rest, is shown in Figure 2, and comprises at least one slot 42 along the bracket 22 upon which the footplate 38 rests. At least one threaded clamp bolt 26 passes through the slot 42 and a hole in the footplate 38, with a suitable tightening means such as lever, knob, nut, cam-lock being provided to tighten footplate 38 and slide together. When the tightening means is released the shank of the clamp bolt(s) 26 and thus the footplate 38, may freely slide towards and away from the strut 12.

Referring again to Figure 2 typically two footplates 38 are mounted, each on a different bracket 22 and usually on different vertical slides of attachment support 15. The footplates 38 are ideally arranged at different heights, and when on different slides, are angularly displaced one from another, typically by ninety degrees as shown. However, the location or number of footplates is not limited to that configuration, deployment, angle nor number.

The higher footplate (i.e. one farthest from ground level) hereinafter referred to as footrest 39, is typically bracketed on the North facing vertical slide and moves, North South, as a consequence. Its height is set such that when the user is comfortably seated at a workstation their feet rest upon the north facing footrest 39.

The lower footplate, hereinafter referred to as a step 40, is similar to the footrest 38 in that it may also be elevated and slide towards and away from strut 12, but if the footrest 38 were facing north, the step 40 would typically be bracketed upon a west, south or east facing bracket 22. The purpose of the step 40 would then be that of a transitional step to assist the user in mounting the seat 13 of the chair. This is because a typical example of a chair 10 for an achondroplaisic person (a person of short stature) is relatively high and at least one step may be needed for that person to attempt to sit at a high desk, such as might be found in an industrial or educational science laboratory.

Persons of low muscle tone, balance and, or co-ordination might also find it difficult to climb onto a relatively high chair. Thus step 40 and footrest 39, used in combination, and at different heights and angular displacements; with the seat 13 rotating between them is a highly desirable feature and makes the use of the invention particularly advantageous. The fact that the chair 10 does not need to move during the operation is also of great benefit to some users. In use a user aligns the seat 13 with the step 40, ensuring against inadvertent rotation by locking the seat with the trigger 20 and clamp 16. The user then climbs onto the step 40, turning their back to the seat 13 before sitting down.

The height of the step 40 may also be adjusted to a suitable elevation so as to enable the user to sit from this advantageous position, or at the very least make it much easier for them to do so.

When safely seated, the user releases trigger mechanism 20, thereby enabling the seat to rotate, and turns the seat 13 to the north, whereupon the users feet are correctly positioned over the footrest 39 as previously described. The user may now commence work at the bench, desk or table.

Unseating is effectively a reversal of the procedure. It will be appreciated that no drawing in or out of the chair is necessary to complete this seating operation and this too is advantageous for the user.

Though essentially similar to the footrest 39, the step 40 is additionally supplied with telescopic legs 49. Referring again briefly to Figure 1 telescopic leg(s) 49 are mounted on the underside of the step 40 and can be vertically adjusted to suit the chosen height of the step 40. Locking of the telescopic components of the leg is by suitable and common means such as button clip, clevis pin, screw, spring plunger, split clamp or any other suitable means (not shown). Such telescopic legs 49 may be provided with a variety of feet 50 to suit the application, including wheels 25 and castors, both locking and freewheeling. These feet 50 may be individually adjustable, for example by utilising a threaded shank with lock nut as its means of attachment to the leg.

When fully deployed both step 40 and footrest 39 may extend beyond the footprint of the base 11 and its limits of stability, and as such may present a tipping hazard. As previously described the step 40 is provided with legs which when attached ensure its stability at all times, irrespective of its deployment. However, the footrest may be elevated to such a height that the legs appear ungainly, or actively obstruct table parts. Referring to Figure 2 an independent extended support leg 24 is provided, that commonly attaches to the same slide rail as the footrest 39, but beneath it, such that the feet 50 of the support leg 24 are at the same level as the level of the base feet 50. For clarity only, Figure 2 shows the extended leg on the opposite slide. The extended support leg 24 is provided with at least two feet 50, which may be independently adjusted for height and are spaced as wide apart as the width of the footrest 39 and extend as far out as the furthest deployment of the footrest 39 from the strut 12.

Referring to Figure 3, arms 41 are provided to give support whilst seated, and also to assist the user in getting on and off the chair. Most chair armrests are mounted to the side of the seat 13 and are spaced at seats width or greater.

However, much advantage is gained by having arms 41 that fit closely against the flanks of the users body as such arms 41 provide lateral support where balance is poor, and additionally minimise the effort required to lift body weight, by keeping the users arms close to the body and nearly vertical so

that when climbing from the seat the force exerted by the user is confined to a lifting force.

Where it is required to move the chair for stowage or to a new location, means of transportation are provided. The transportation means may include either wheels 25 attached to attachment support 14, as described above, or by provision of an independent castor base, cooperably mounted within the footprint of the fixed base as show, for example in greater detail in Figures 4, 5 and 6.

A type of chair, commonly known as an "office chair" has a base of preferably five horizontal legs, each of which radiates from a central column upon which the chair seat is mounted. A fixed foot or castor is provided at each leg extremity. Fixed feet are provided where a nonmoving chair is required, a typical example being a high stool for drafting purposes, whilst castors are provided for a moveable chair, such as is commonly used at an office desk.

An advantage of castors is that the chair can be easily moved to a new location without the need for lifting the chair. However to use a chair with a castor base requires a high degree of physical co-ordination when sitting down, or the chair may strike out sideways under the influence of non vertical forces acting upon it, for example by incorrect body posture.

Persons with a disability, particularly of balance or co-ordination, may have difficulty sitting in a mobile chair such as that described. To overcome this problem certain types of castors may be fitted with brakes, however even this provision may not be suitable as it is not foolproof. For example, it requires the brakes to be engaged before use. This essential requirement may be forgotten or may require such fine motor skill as to be beyond the capability of a person with a disability, such that use of such a device may render them liable to injury or accident.

An alternative embodiment of the invention is shown in Figures 4, 5 and 6 and depicts the base portion only of a chair 10 with a transport mechanism, such as castors, for moving the chair. The transport mechanism is desirable as

the chair can be relatively heavy and therefore difficult to lift and move. In use the chair 10 is in the dropped position (not shown) and stands on fixed feet of a 5-star base, as seen in Figure 6, in plan view. In this configuration it will be appreciated that the transport mechanism is disengaged. Figure 4 shows the chair 10 in the raised position, i.e. with the transport mechanism engaged or deployed, so that the chair 10 may be moved on the castors 55.

When the engagement mechanism is deployed, castors 55 rest on the floor at all times and support the castor base 11. Base 11 and castor base 51 are independent one from another in the vertical plane but, because of post(s) 58, (typically two in number) main base 11 and castor base 51 are obliged to move co-operably when moving sideways or turning on the floor. Posts 58 are located in base 11 by way of sockets or hole in 53.

Screwed to the top of pillars on 54 is a tubular ring 56. In the default position the ring passes between each post 58 over each leg of the main base 11 with a clearance of say 10mm. It can be seen that were the main base 11 to be lifted it can therefore only rise by about 10mm before contacting the ring at all points, preventing further lifting.

When the chair 10 is being moved, it is necessary to lift the fixed feet 50 of the main base 11, (and thus the weight of the chair), from the floor and to transfer the weight of the chair 10 to the castor base thereby permitting movement and relocation of the chair. The chair is lifted through a height of around 10mm previously described, by way of a lift mechanism until ring 56 contacts the main base 11 on all 5 legs whereat further lifting is prevented. During the lifting process the chair 10 is free to topple in any direction as it lifts within the restraint of the 10mm gap between ring 56 and leg. This arrangement is provided in orderthat no vertical slides or other complex and accurate device is required to guide and manage the separation, however when the chair 10 assembly reaches its maximum elevation it is solid with, and fully supported by the castor base 51.

Figure 4 also shows the mechanism for engaging the relocation means -

namely the means whereby separation is achieved with a lift mechanism for

lifting the feet 50 from the floor and permitting castors 55 to engage the ground. Beam 61 is hinged at one end in a clevis type fulcrum block 62. An adjustment in the form of a screw 63, supported by the castor base 51, is provided. A locking mechanism, such as a locking nut (not shown), is also provided to prevent accidental rotation and thus inadvertent adjustment of the beam 61. Beam 61 presses upwards on a pad 64, which locates against the underside of the main base 11 when the beam 61 is caused to lift by lever 59.

An elbow lever 59 is attached to beam 61 by way of a pivot 80. At the upper end of elbow lever 59 is a hinge whose support pin 67 is secured to a handle 68 at a given radius from the fulcrum point of the handle at 66a. This pivot point is arranged near the end of the fork handle 68 and is supported by the castor base 55a. The handle 68 at pivot point 66a is in the form of a fork or clevis. A knob 70 or other suitable grip is provided at its free end. The lift lever 59 sits inside the fork or clevis, with the pin 67 passing through one side of the fork, then lift lever 59 then the other side of the fork.

In operation the handle lies approximately horizontal, but when the main base is lifted the handle moves through an arc to a point where pivots 66, 67 and 80 are all collinear. A cut out is provided in lift lever 59 such that the pivot 66 does not impede the progress towards colinear alignment of lift lever 59. The cut out is made slightly deeper than is necessary for colinear alignment so that the pivot 67 may pass beyond alignment by a few degrees only, before pivot 66 impedes the continued progress of lift lever 59. This "over centre" arrangement ensures that when the knob is released the mass bearing down upon lift lever 59 through the weight of the chair 10, bearing on beam 61, causes the mechanism to remain in the "active" or deployed position until the knob 70 is moved in reverse.

The radial displacement of pivot 67 from pivot 66 is such that the legs of the main base 11 are brought into firm contact with the underside of the ring 56 when the knob 70 is fully raised to its over centre position.

The fork 68 of the knob 70 pivots within a close gap between two flanges of the castor base 51, such that all lateral movement of the handle is prevented

as is shown in Figure 5. Figure 5 shows how pivot pin 67 is equal in length to the width of the fork 68. Because the flanges within which fork 68 sits are of a certain size, the pivot pin 67 is similarly constrained by the two flanges such that it cannot move laterally.

Also pivoting about pivot 66 is a trip trigger 82 (shown in Figures 5 and 8) similarly arranged within the fork 68 or clevis. This trigger 82 is normally held clear of pivot pin 67 by a spring 83 attached at its other extremity. This spring 83 is so arranged to hold the trigger clear of pivot pin 67 allowing the handle to be latched in the chair raised position when required.

Also attached to the trigger 82 is a means of moving the lever in an opposite direction to that caused by the spring and in so doing causes a tripping of the handle. This means may be in the form of an electrical solenoid, a hydraulic cylinder, a pneumatic cylinder or solenoid, or any other suitable linear motion device, however for the purpose of this example a Bowden (Trade Mark) type cable is considered by way of illustration.

When the cable or other device is activated, i.e. drawn in the opposite direction to spring tension, the trigger 82 is caused to move against the spring tension. Continued movement will cause the trigger 82 to bear upon pin 67 and if movement continues to push the handle of fork 68 and link lever 59 in the reverse direction until fork 68 moves to a point whereby pivot points 66, 67 and 80 move first into alignment - the point of theoretical equilibrium - and then beyond to a point of instability.

Moving beyond alignment to this point of instability will cause the mass of the chair bearing upon the beam to pull down upon the link lever, which being unrestrained returns to the default position of safety, i.e. with handle horizontal and the weight of the chair resting upon the fixed feet. In this manner any mechanism causing the trigger 82 to move the pin 67 as described will cause tripping of the castor base, so that the chair returns to its fixed feet.

Mechanisms that activate the tripping mechanism in this way can include a manual lever, however, for foolproof activation, the transport mechanism should be operated by deployment of a device or accessory essential to the user, for example a step, retractable footrest or a flip-up footrest. Because these devices have to be deployed in order that the chair can be used, and deploying the accessory causes the lift mechanism to trip, the chair becomes safe against all eventualities. Figure 7 shows an example of a chair with such a means for deploying the location mechanism, which comprises a flip up footrest. Cable is attached to footrest bracket 105 at a point offset from pivot 106 at pivot point 109. Outer casing 110, of a Bowden (Trade Mark) cable arrangement is socketed at a suitable fixed point, for example upon bracket 107 as shown. An adjuster 111 is provided at a suitable point along the cable length, e.g. at a socket of bracket 107. The other end of outer casing is similarly attached at a fixed point in the area of a trip mechanism and may be provided with similar adjustment means as required (not shown).

Adjusters are provided with the usual locking means.

Considering either a retractable step, or retractable footrest as shown in Figure 7b, when the footrest 104 is deployed in the direction of arrow X by being slid along its guide rails (or slots), it pushes upon arm 120, which is pivoted at a suitable fixed point, such that the arm 120 is caused to revolve about its pivot point, and in so doing draws upon the inner wire of the Bowden (Trade Mark) cable previously described for the flip-up footrest. All other arrangements being as for the flip-up footrest, the trip mechanism is caused to operate in a similar manner.

When the trip mechanism is activated in this way the lift device can still be lifted manually by knob 70 however the trigger position will ensure that the trigger 82 can never latch into the raised position until the accessory is stowed in the retracted - undeployed position or mode.

Though the trip mechanism is described for one accessory only, there is no limit to the number of accessories, which may individually, cumulatively, or independently trip the mechanism.

The height of the seat is predefined by both the users physique and the height of the table in question, therefore the footrest may well need to be lower than that achievable by the retractable footrest, there being a limit to how low the retractable footrest can be set.

The retractable footrest eventually impinges against the base with the result that it cannot drop lower than about 0.15 m above ground level. Flip-up footrest on the other hand, operates outside the footprint of the base mechanism and can therefore be as low as 0.05m above the floor.

Referring to Figure 7a there is shown a chair with a flip-up footrest.

Removably attached to attachment support 14 is a bracket 101, provided for the purpose of mounting flip up footrest 104. Bracket 101 is attached by suitable means 102 such as a bolted flange or clamp running within a channel section of the channel section of the attachment support 14. Additional support may be provided by brackets 103 attached to 101, which extend to at least one foot of the base. Attachment is in the form of a hole in the bracket through which the post of the castor or foot passes before entering the leg of the base. In this manner, lateral or radial movement of the bracket 101 is prevented and when employed in cooperation with clamps 102 provides a very rigid support for the attached footrest 104.

Flip up footrest 104 is attached to hinged bracket 105 in such a manner, for example by slots within the hinged brackets construction, that footrest 104 can slide co operable with the hinged bracket, away from and towards the central column of the chair. Clamp means is provided in the manner of a bolt or screw with knob, nut or the like, such that the chosen position of the footrest can be releasably fixed upon the footrest. Hinged bracket 105 pivots about a pin 106, which passes through flanges of a sliding clamp bracket 107.

Pin 106 provides a fulcrum point for 105 supported by sliding clamp bracket 107. Sliding clamp bracket 107 slides co-operably with bracket 101 within a channel or slot or other suitable guide means. This arrangement only allows movement of sliding clamp bracket 107 in the direction of arrows X.

Means of adjusting the angular attitude of 105 and thus 104 is provided by an adjustable screw 108, which passes through a bracket attachment of 105 and may be provided with locking means in the form of shakeproof device, lock nut, knob or any similar means (not shown). Adjustment is achieved by turning the screw, the end of which bears upon any part of 101 or 107 or any of their attachments.

Even when adjuster screw 108 is set and clamped, flip up footrest 104 can be lifted through an angle about pivot 106 until it comes to rest against 101 or a suitably arrange stopper mechanism (not shown) In this manner the footrest can be stowed for safety, transport of space, when not in use.

Gravity acting upon the flip-up footrest when in the stowed (generally upright) position is sufficient to hold it in place as the angle of 101 (which prevents further rotation) ensures that centre of gravity has passed through the vertical centreline of the pivot and is thus in decent.

A bias spring (not shown) may be provided to lighten the weight of the footrest when lifting for stowage. This may be in the form of a tension spring, coil spring, compression spring or torsion spring etc. arranged in a suitable manner about the pivot pin 106, co-operable with flip-up footrest bracket 105 and sliding bracket 107.

Certain accessories, for example the flip-up footrest, step and wheeled carriage 99, are not normally required to rise and fall with the seat 13 of the chair and it would be inconvenient were they to do so as they are positioned relative to the floor and not the seat. Figures 10 and 11 show an alternative embodiment having a means of attachment of such accessories. Referring to Figures 10 and 11, there is shown two attachment supports 150 and 151.

Support 150 being much as described above (with reference to support 14 of Figure 1). Support 150 rises and falls co-operably with the seat 13, whilst the other support 151, which is effectively the fixed attachment support 151, is entirely independent of any height adjustment of the seat 13.

Fixed attachment support 151 is fixed about the central support strut 12 at its lower end, in much the same manner as described for attachment support 14, i.e. a circumferential clamp which when operated by cam lock, pinch bolt etc. grips the cylinder of the support strut 12. However, unlike attachment support 14, which is provided with a rotary coupling means to the seat 13, the fixed attachment support is provided with a lateral support only at its upper end.

Typically the lateral support is in the form of a bored flange, which passes freely over either the main body of the strut 12 or over the moving piston itself.

With reference to Figure 11 it can be seen that accessories attached to the fixed attachment support 151 remain in their chosen position relative to the floor, irrespective of variations in the seat height, whilst accessories co-

operable with the seat 13 (e.g. those attached to attachment support 150 such as a footrest 39) move with the seat 13. An advantage with this is that only the part of the chair that needs to rise or fall is connected to the portion of the frame that is capable of rising and falling, and more especially, the accessories that need to remain at a constant height with respect to the floor (such as a step) remain so.

Where attachment support 150 and fixed attachment support 151 are employed together it is probable that (but not limited to) four slide means are shared by the attachment support 150 and fixed attachment support 151 in any desirable ratio. For example, three slide means may be mounted on the fixed attachment support 150 with one slide means on moving attachment support 151. However the arrangement is not limited to that ratio and two slide means may be provided with each as shown in Figure 10, or in any other ratio of any other number of slide means.

When two attachment supports are provided as described, they may be so arranged as to be co-operable with one another such that axial displacement is allowed whilst rotational displacement between both fixed 151 and movable supports 150 is restricted. An illustration of a suitable means is given in Figures 10 and 11 where it can be seen that the close proximity of adjacent

faces of attachment support 150 and fixed attachment support 151 prevent rotation of 150. Both fixed 151 and movable supports 150 are ideally located around the barrel of strut 12 and fixed attachment support 151 is clamped thereto - at its lower end - as previously described.

Vertical movement of attachment support 151 can be clamped as previously described, with a circumferential clamp or pinch screw etc. or if desired, by an arrangement whereby attachment support 150 is free to move over strut 12, but is clamped thereto by a fixed attachment or by any suitable clamping arrangement. An example of such an arrangement is shown where: clamp bar 154 is secured to fixed attachment support 151 by a screw, knob, nut, or similar device 155, and when tightened, causes clamp bar 154 to be pressed against attachment support 150 preventing axial movement between fixed 151 and movable supports 150 and thus all associated devices, accessories and mechanisms, for example, seat 13 or footrest.

The invention has been described for use by persons with limited motor ability and/or strength. As will be appreciated, the aforementioned embodiments are described by way of example only and variation may be made to them without departing from the scope of the invention, for example elderly persons may use the chair.

Claims (41)

Claims

1. A chair has a seat for supporting a user and means for varying the height of the seat with respect to a ground level; a means for releasably locking the seat height; and a means for selectively locking the seat in one of a plurality of swivel positions.

2. A chair according to claim 1 wherein a rotary coupling is provided that is fixedly attached to the seat and allows the seat to revolve with an attachment support, whilst preventing any linear separation of the seat and the attachment support along an axis parallel to the axis of rotation of the seat.

3. A chair according to claim 1 or 2 wherein an engagement mechanism, includes a resiliently deformable device, for example a spring-loaded trigger.

4. A chair according to either of claims 2 or 3 wherein the engagement mechanism is dimensioned and arranged to be retracted so as to permit swivelling of the seat with respect to a central axis and to engage in order to lock the seat with respect to an axis of the chair.

5. A chair according to any preceding claim wherein at least one step is provided

6. A chair according to any preceding claim wherein at least one footrest is provided.

7. A chair according to either claim 5 or 6 wherein the, or each footrest, and/or the, or each step, is adapted to vary its height with respect to the floor on which the chair is supported.

8. A chair according to any of claims 5, 6 or 7 wherein means is provided to vary the radial deployment of the step and/or footrest.

9. A chair according to claims 5 to 8 wherein the adjustable step and/or footrest is/are supported on a telescopic foot, which telescopic foot is adjustable in dependence upon the height of a user.

10. A chair according to any preceding claim having a removable carriage, which carriage is fitted with wheels and assists in transportation of the chair.

11. A chair according to claim 10 wherein the carriage is equipped with a handle, which may retract or fold away.

12. A chair according to claim 10 or 1 1 wherein the carriage has a displacement mechanism that also has a failsafe.

13. A chair according to any preceding claim has a lift device and castor base mechanism incorporated in the chair in order to assist with relocation of the chair.

14. A chair according to any preceding claim has five substantially horizontal legs, each of which radiates from an axis, defined by a central column, upon which the chair seat is mounted and about which the seat is able to rotate.

15. A chair according to any preceding claim wherein arms of a specific shape are provided so as to assist a user to climb into, and get out of, the chair.

16. A chair according to claim 15 wherein the arms of the chair are laterally adjustable.

17. A chair having arms that are easy to grip, the arms being substantially circular in cross section and shaped so that a user may always find a part of the armrest that offers itself at a near right angle to the users arm, irrespective of the users elevation and attitude when gripping it.

18. A chair according to claim 17 wherein the arms are curved.

19. A chair according to either claim 17 or 18 wherein the arms are movable and clamped laterally across the seat so that a portion of the arm is always presented substantially at a right angle to a users arm; thereby ensuring that a portion of the arm of the chair is always readily available, and easy, to grip.

20. A chair according to claim 17, 18 or 19 wherein the surface of the arm of the chair is also curved so that it resembles a curved sausage.

21. A chair according to any of claims 17 to 20 wherein, in use, each arm is able to slide laterally and independently across the body of a user in the seat, said arms being mounted on an arm slide rail, which is mounted beneath the seat.

22. A chair according to claim 21 wherein the slide rail is provided with a clamp to ensure that an armrest is both rigid in use and prevented from sliding laterally.

23. A chair having means for varying the height of the seat with respect to a ground level; means for releasably locking the seat height; and means for selectively locking the seat in swivel positions; the chair including transport means to assist in moving the chair from one location to another; a plurality of feet on which the chair is adapted to rest; and means for engaging the transport mechanism and means for disengaging the transport mechanism.

24. A chair according to claim 23 wherein the transport mechanism includes one or more castors or wheels arranged, so that when engaged, the chair can be pushed or rolled by an assistant.

25. A chair according to claim 24 in which disengagement of the transport mechanism acts as a failsafe to ensure the chair is lowered from being supported by the castors or wheels to a position where it is supported by the floor directly.

26. A chair according to claim 24 or 25 wherein the transport mechanism includes a trip mechanism attached to the castor base lifting mechanism.

27. A chair according to claim 26 wherein the trip mechanism comprises a means for disengaging the transport mechanism, said trip mechanism being dependent upon the deployment of one or more accessories essential to the use of the chair.

28. A chair according to claim 27 wherein the accessory essential to the use of the chair is a step.

29. A chair according to claim 27 wherein the accessory essential to the use of the chair is a retractable footrest or flip-up footrest.

30. A chair having means for varying the height of the seat with respect to a ground level; characterized in that a fixed portion is provided on which is mounted at least one accessory and a movable portion is provided, on which the seat of the chair is mounted, there being means for moving the fixed and moveable portions relative one to another and locking them.

31. A chair according to claim 30 wherein a swivel position is selected by way of an engagement mechanism, said engagement mechanism includes a resiliently deformable device.

32. A chair according to claim 31 wherein the engagement mechanism is a spring loaded trigger.

33. A chair according to either of claims 31 or 32 wherein the engagement mechanism is dimensioned and arranged to be retracted so as to permit swivelling of the seat with respect to a central axis and to engage in order to lock the seat with respect to an axis of the chair.

34. A chair according to any of claims 30 to 33 wherein at least one step is provided

35. A chair according to any of claims 30 to 34 wherein at least one footrest is provided.

36. A chair according to either claim 34 or 35 wherein the, or each footrest, and/or the, or each step, is adapted to vary its height with respect to the floor on which the chair is supported.

37. A chair according to any of claims 34 to 36 wherein means is provided to vary the radial deployment of the step and/or footrest.

38. A chair according to claims 34 to 37 wherein the adjustable step and/or footrest is/are supported on a telescopic foot, which telescopic foot is adjustable in dependence upon the height of a user.

39. A chair according to any of claims 30 to 38 having a removable carriage, which carriage is fitted with wheels and assists in transportation of the chair.

40. A chair according to claim 39 wherein the carriage is equipped with a handle, which may retract or fold away.

41. A chair substantially as hereindescribed with reference to the Figures.