Reclining chair mechanism.

BACKGROUND TO THE INVENTION

Tilting and reclining chairs are known in which a chair frame supports a chair seat and back and the invention is particularly concerned with a reclining chair in which the seat and the back are formed of one piece but which are made so that the seat and back can rock in unison about a rocking point. Such chairs generally have a spring assisted mechanism so that the tilting movement of the chair is resisted by the spring biassing in order that the occupant can be seated in the chair and can lean backwardly in the chair with the movement being partly offset by the spring mechanism. The spring assistance also has another benefit in that, particularly for the elderly and the infirm, the assistance provided by the spring helps the user to rise from the chair.

A desirable feature of such spring assisted reclining chairs is the provision of a locking means, generally operated by a lever accessible to the user, in order that the chair can be locked in the desired reclining position. The spring tension of such chairs is generally arranged so the reclining mechanism has sufficient strength that it can compensate for the weight of the person occupying the seat. When the occupant wishes to leave the chair the stop mechanism is released and provided the spring tension is sufficient this will return or assist to return the chair to its upright position and thereby facilitate the exit of the occupant from the chair. To enable this to occur the spring pressure must be quite high and if the chair is not occupied and it is in a reclining position and if the stop mechanism is released, it is possible for the chair

to return violently to its raised position and this can cause injury to a person or persons who might be adjacent to the chair.

Some known reclining type chairs also include a feature whereby the amount of the spring pre-load can be adjusted so the user, by manipulation of an appropriate adjustment means, usually a hand wheel or a lever, can alter the spring loading while occupying the seat, to provide the desired amount of spring assistance. Because the amount of spring loading is high, it can be difficult to operate the adjustment means and this is a disadvantage particularly for the elderly and the infirm who might not have sufficient physical strength to comfortably operate the adjustment means. This disadvantage is particularly apparent when the adjustment means is a hand wheel. A further problem with known adjustable pre-load mechanisms is that as the spring tension is being increased, this generally results in for even more physical force being required to rotate the hand wheel or move the lever.

KNOWN PRIOR ART

A basic form of tilting seat is disclosed in New Zealand Patent Specification 161613 which utilises a torsion bar to provide spring biassing with the torsion bar being connected to an arm which can be moved to vary the amount of torsion. A further basic form of spring biasing means is described in New Zealand patent specification 180978 which discloses a tilting mechanism for a chair seat with the tilting mechanism being spring biased by a coil spring tensioned by the rotation of a wing nut threaded on a shank which has a hook to which one end of the coil spring is attached. New Zealand Patent Specification 194150 discloses a mechanism using a similar concept wherein a coil spring has one leg anchored to a shank on which a

hand wheel is threaded so that rotation of the hand wheel will increase or decrease the spring tension.

Another form of spring biasing is described in New Zealand patent specification 220502 which illustrates a seat mounting assembly for a chair which utilises a parallelogram linkage and includes a spring means in conjunction with the linkage to bias the back rest to an upright position.

One such type of mechanism which includes a mechanism whereby the tension of the spring can be varied to suit the particular requirements of the occupant is disclosed in New Zealand patent specification 209165. The specification describes a tilting mechanism for a chair which has a cam which engages levers to allow the lever to be disengaged from a quadrant to thereby enable the tilt to be adjusted. When disengaged, the cam can be activated to allow a control lever to reengage in the quadrant.

Mechanism for reclining type chairs are also known which include stop mechanisms whereby the degree of tilt imparted to the chair can be maintained by operating the stop mechanism. One such mechanism is described in New Zealand patent specification 194150 which discloses another form of adjustable and tiltable chair in which a torsion spring is arranged to enable the seat to be tilted with an adjustable stop means being provided which will control the rest position of the seat. The spring means comprises a coil spring, the tension of which is adjusted by rotating a knob attached to a threaded shaft.

Yet another form of stop mechanism is described in New Zealand patent specification 166593 which discloses a mechanism which prevents the chair from being rocked when it is in the reclining position. A further form of locking mechanism is described in New Zealand patent specification 206638 which discloses a stop mechanism whereby the rocking of the chair can be blocked against movement until the blocking mechanism is released. New Zealand Patent Specification 237530 also describes a toggle linkage which inhibits movement of the carriage when it is in an upright position.

The necessity for a weight responsive locking mechanism is recognised for instance in the teachings of New Zealand Patent Specification 212280.

Reclining chairs are of particular benefit to the elderly and the invalid but the difficulty experienced with such chairs is that when the occupant is seated on the chair, if the chair should be in its reclined position then unless there is some form of spring assistance built into the chair, it is difficult for the occupant to leave the chair and consequently such chairs are often not satisfactory for the elderly or the invalid.

Another problem with the known reclining mechanisms is that the adjustment means for the spring biassing is often difficult to operate because it is necessary to add or subtract tension to springs which have a comparatively heavy pre¬ load tension and to this end generally a screw type mechanism or the like is provided with the mechanism terminating in a hand wheel or similar which is positioned so that the occupant can, while seated on the chair, rotate the hand knob to thereby increase or decrease the tension on the springs as required. Rotation of the hand

knob requires a moderate physical effort and consequently the elderly and the invalid are often not able to utilise this aspect.

OBJECT OF THE INVENTION It is therefore an object of this invention to provide an improved mechanism which will minimise the above disadvantages.

STATEMENT OF THE INVENTION Accordingly, one form of the invention comprises a mechanism to provide spring bias to a reclining type chair having a chair frame and a reclining seat pivoted to the chair frame, said mechanism comprising:

pivot means attachable between the chair frame and the said seat to enable the seat to pivot on the chair frame, and spring assist means associated with the pivot means to spring assist the pivotal movement of the pivot means, wherein

the spring assist means includes a coil tension spring having a first leg which extends from the body of the spring and which bears on an anchor member and a second leg which bears on a rotatable cam which can be manipulated to increase or decrease the tension in the tension spring, and

releasable stop means to inhibit pivotal movement between the chair frame and the seat when the seat is in a reclined position unless a greater than predetermined weight is exerted on the seat.

Preferably the spring assist means includes a plurality of coil tension springs.

Preferably the rotatable cam comprises an adjustment rod having a cam face, said rod being rotatable by actuating means which is located externally of the seat.

Preferably the means located externally of the seat is a lever.

Preferably means are provided which at least partially compensate the rotatory force imparted to the adjustment rod by the tension spring.

Preferably the means to at least partially compensate the rotatory force comprises a neutralising coil spring having one leg anchored to the anchor member and the other leg bearing on the adjustment rod substantially opposite the point of contact of the tension spring with the cam face of the adjustment rod.

Preferably means are provided to substantially prevent rotation of the adjustment rod except by the actuating means.

Preferably the means to substantially prevent rotation of the adjustment rod comprises a spring actuated clutch which will maintain the adjustment rod substantially locked against rotation until the actuating means is operated.

Preferably the releasable stop means includes a pawl comprised of an elongated member having a distal end which moves in an arcuate path said movement being determined by the relative reclining position of the seat to the chair frame, said

distal end being provided with engagement means engageable by a detent to releasably maintain the pawl with the seat in a selected reclined position, said detent having release means operable to engage the pawl to positively maintain the detent in engagement with the pawl or to be disengaged from said pawl, the detent also including means to retain the detent in engagement with the pawl after the release means has been operated to disengage the release means from the pawl, until more than a predetermined minimum weight is exerted on the said seat.

Preferably the engagement means comprises a toothed rack on the distal end of the pawl and complementarily shaped teeth on the detent.

Preferably the detent is pivoted in a manner that it can pivot to engage with or be disengaged from the pawl and wherein the pivotal point of the detent is offset from the main axis of the detent.

Preferably the detent is spring urged to spring assist the detent out of engagement with the said pawl.

Preferably the detent release means comprises a rotatable release cam operable to contact the detent to maintain it in contact with the pawl and to be rotated to be disengaged from the detent.

Preferably the rotatory movement of the cam is controllable by means located externally of the seat.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred forms of the invention will now be described with the aid of the accompanying drawings wherein;

Figure 1 is a diagrammatic side view of a typical reclining type chair incorporating the mechanism of this invention and showing the combined seat and back in an upright position.

Figure 2 is a similar view to that of Figure 1 but showing the combined seat and backrest in a partially reclined position.

Figures 3, 4 and 5 are diagrammatic sectional views of part of the tension spring tension adjusting mechanism.

Figures 6, 7, 8 and 9 are diagrammatic views of different stages of operation of the reclining and locking mechanism.

Figure 10 is a plan view of one end of the spring tension adjustment mechanism and the stop mechanism associated with the reclining mechanism.

Figure 1 1 is a view of part of a shaft locking mechanism, and

Figure 12 is a view rotated through 90° of the mechanism illustrated in Figure 1 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figures 1 and 2 of the drawings, a typical chair as illustrated comprises a frame which has legs 1 , a pair of arms 2, and side rails 3 joined together to form the usual type of chair frame. The seat 4 and backrest 5, in the highly preferred form of the invention, may be manufactured as an integral unit, such as by having a combined moulded base, or else can be manufactured from component parts suitably joined together. The base may be upholstered in a known manner. The combined seat and backrest is pivoted to the chair frame by the apparatus of the present invention which includes a frame having two side arms 10 (one of which is shown in Figure 10) which is provided with suitable holes so that the side arms 10 of the frame can be attached to the rails 3 of the chair in a known manner.

The underside of the seat 4 is attached by suitable screws or the like to a seat strut 1 1 which may be a metal channel section or the like. The seat strut 1 1 is more particularly illustrated in Figures 3 through 9 and in Figure 10 a sectional view only of the seat strut 1 1 is illustrated. Each side arm 10 is provided with a boss 10a which has a bore in which a link rod 13 is engaged in a manner that the link rod can pivot in the bores and extend between the two side arms 10 which are attached to the chair rails 3. The seat strut 1 1 is attached to the link rod 13 and consequently the pivotal point between the chair frame and the chair seat is at the junction of the link rod 13 with the side arms 10. The link rod 13 is stabilised by arms 20 which extend from a plate 6 which spans between the side arms 10. The arms 20 are provided with bearing holes through which the link rod 13 extends.

The spring biassing mechanism will enable the seat to be spring urged into an upright position and comprises two essentially duplicate modules, one of which is

illustrated in Figure 10. One module is located at one side of the seat and the other module is located at the other side with both modules being joined so they will act in unison on the seat. Unless otherwise specified, the description following applied to both modules. The spring biasing is obtained by utilising a number of tension springs 16 which are located on the link rod 13. In the embodiment illustrated four tension springs are utilised, but it will be understood the number of tension springs can vary to suit the particular circumstances. One leg 16a of each tension spring 16 bears against an anchor member 17 which in the embodiment illustrated is a length of angle section steel joined to and extending between the seat struts 1 1. The anchor member 17 can include a number of cut outs 17a to aid the assembly of the mechanism. Preferably means, (not shown in the drawings), are provided on the anchor member to positively locate the ends 16a of the legs on the anchor member. The other leg 16b of each tension spring 16 bears against an adjustment rod 19 which is pivotally located in bearings 22 which are supported by the arms 20 which extends from the plate 6, in a manner that the adjustment rod 19 can rotate in relation to the frame.

The adjustment rod 19 is provided with a cam face or a number of cam faces, which in the embodiment illustrated is formed by a radially offset portion 21. It will be understood other methods of forming a cam face as will be apparent to those skilled in the art may also be employed. For instance the cam face 21 can comprise a number of independent radial cams located on the adjustment rod. The leg 16a of each tension spring 16 bears on the cam face 21 and preferably anti-friction means 21a, which may for instance be a nylon block is interposed between the leg 16a of the tension spring and the cam face to reduce friction. Rotation of the adjustment rod 19 in a clockwise or anti-clockwise manner will tension or relax the tension spring

16 by the action of the cam face moving the leg of the tension spring to further tension the tension spring or to relax the tension. The rate of each tension spring and consequently the combined rate of the tension springs will depend upon the amount of spring tension and the graduation in spring tension required.

The mechanism also includes a neutralising spring 50 which in the preferred form is a coil spring located on the adjustment rod 13. One leg 51 of the spring 50 is anchored to the arm 20 and the other leg 53 bears on the reverse side of the cam face 21 of the adjustment rod 19. Anti-friction means 54 which may be a nylon block is interposed between the leg 53 and the cam face 21. The purpose of the neutralising spring is to partly offset the rotatory moment that is tended to be imparted to the adjustment rod 19 by the tension of the tension springs 16.

Figure 3 indicates the position of the tension springs when the seat is in the rest mode, that is without any weight on the seat and with the tension springs also in the rest position. In this position the angle of the legs of the tension spring is indicated by the arrows A - B. When the adjustment rod is rotated so the legs of the tension springs ride up the cam face 21 , additional tension is applied to the legs of the tension spring and the legs now adopt the angle A -C as illustrated in Figure 4. Figure 5 indicates the angle A - D which is the relative movement between the side arm 10 and the seat strut 1 1 when the seat is occupied, while the angle A - E indicates the maximum angle that can be reached by the reclining mechanism. It will be apparent that reverse rotation of the adjustment rod will allow the tension in the tension springs to relax. The rotation of the adjustment rod 16 is preferably effected by a crank lever 27 which has an extension arm 28 such as indicated in Figure 2 so that the arm will extend outside of the chair for convenient movement by the operator.

Because of the rotatory forces exerted on the adjustment rod 13 by the tension springs 16, although this is partly offset by the neutralising spring 50, means are also preferably provided to positively lock the adjustment rod against unwanted rotation. One preferred means of arranging this is by a clutch arrangement 59 indicated generally in Figure 10 and shown more particularly in Figures 1 1 and 12.

The clutch arrangement in this particular embodiment may consist of a coil tension spring 60 which is a friction fit on a sleeve 61 which projects from an annular collar

62. The collar 62 and the sleeve 61 have a bore through which the adjustment rod

19 passes. The annular collar 62 is suitably joined to an arm 10 (not shown in Figures 1 1 and 12 which extends from the plate 6 to prevent rotation of the collar. In its relaxed state the spring 60 will grip onto the outside of the sleeve 61. The spring 60 has two legs 63 and 64 which project substantially radially from the spring and are spaced apart a distance approximately equal to the width of a lug 66 which is attached to the adjustment rod 19 in a manner that it will extend parallel to the axis of the rod but is spaced from the surface of the rod. A bifurcated saddle 68 is attached to the lever 23 and the arms of the saddle which extend substantially parallel to the surface of the adjustment rod 19, are spaced apart to accommodate the legs 63 and 64 of the spring 60.

The clutch arrangement operates in a manner that if rotatory force is applied to the adjustment rod 19 in either direction, this will result in the lug 66 contacting either the leg 63 or the leg 64 of the spring depending upon the direction of possible rotation. This contact, if continued, will tend to move the leg of the spring and this will tend to further tighten the grip of the spring on the sleeve 61 and thereby prevent further rotation of the adjustment rod. If the lever 27 is moved to rotate the adjustment rod 19, one of the arms of the bifurcated saddle 68 will contact a leg 63

or 64 as appropriate of the spring and this will tend to relax the spring on the sleeve

61 , so that rotation of the adjustment rod can occur. Consequently until the lever 27 is actually moved, the adjustment rod is locked against rotation.

A releasable stop mechanism is also included with the apparatus and is depicted diagrammatically in Figures 6, 7, 8 and 9. The purpose of the stop mechanism is to ensure the chair cannot be returned from a reclined position to an upright position unless there is more than a predetermined weight resting on the seat of the chair, such as would occur when a person is sitting on the chair. Figure 6 illustrates a preferred form of the mechanism with the stop mechanism in a disengaged position and the chair vacant. Figure 7 is a view similar to that of Figure 6 but with the chair occupied. Figure 8 is a view of the mechanism with the stop mechanism engaged and with the chair occupied. Figure 9 is a view of the mechanism with the stop mechanism in a released position and with the chair occupied.

A shown in Figures 6 through 9, a pawl 30 is attached to the link rod 13 and extends radially from the link rod 13. The distal end of the pawl 30 is formed into a toothed rack 31 which will cooperate with a detent 32 (see also Figures 1 1 and 12) which has pivotal movement about a rod 33 and which has a face which includes teeth 34 which are complementary in shape to the toothed rack 31. A stop cam 36 is fixed to a cam rod 37 which may be suitably journalled in the seat strut 1 1 so as to extend outside the seat mechanism where it is joined to a crank 40 for convenient operation by the occupant of the chair.

Figures 6 through 9 show that the cam 36 has a flat 42 and a nose 43.

When in the position indicated in Figure 6, the rear face of the detent 32 lies against

the flat 42 of the cam 36 so that the detent can pivot under the action of a pawl spring 39 away from the toothed rack 31 to enable relative pivotal movement between the pawl 30 and the seat strut 1 1 to occur. It will be understood that because the pawl 30 is fixed to the link rod 13 which is in turn fixed to the chair frame, it will not move during any tilting action and the part which does pivot is the seat strut 1 1. Because as depicted in this view, the chair is unoccupied, the seat strut 1 1 can pivot in relation to the link rod 13 so the angle between the side arm 10 and the seat strut 1 1 can vary to provide the reclining movement to the chair seat.

When the cam 36 is rotated so the nose 43 contacts the rear of the detent

32, this will pivot the detent so the teeth 34 will engage in the teeth of the rack 31 of the pawl 30 to thereby prevent any relative movement between the side arm 10 and the seat strut 1 1 which therefore effectively locks the reclining action of the chair. To ensure the stop mechanism remains engaged until the chair is occupied, that is when a person is seated in the chair, the pivot point of the detent 32 is offset from the main axis of the detent 32. In Figure 9 which illustrates the positioning of the mechanism when the chair is not occupied, the beam will have pivoted a small degree upwardly as a result of the tension exerted by the tension springs 16 and this movement will be sufficient to tend to bind the teeth 31 of the pawl 30 with the teeth 34 of the detent 32 and thereby prevent the detent from dropping away from the pawl 30. When the seat is occupied, the tension exerted by the tension springs 16 will have been compensated sufficiently that the seat strut 1 1 will pivot downwardly a short distance and provided the cam 36 is in the position indicated in Figure 6, the detent can, under the action of the detent spring 39, drop away from the pawl to allow relative movement between the side arm 10 and the seat strut 1 1. The effect of the stop mechanism, is that if the stop mechanism is engaged, it cannot be released, until there

is a compensatory weight exerted on the seat to overcome the tension exerted by the tension springs. The lock mechanism can retain the seat in a reclined or semi reclined position, even though the lever 40 might have been moved to a release position whereby the cam face 43 is moved out of engagement with the rear of the detent 32.

Because of the particular mechanism disclosed herein, it is possible to provide a tension spring assisted reclining mechanism which can have considerable strength which can be sufficient to assist to propel a person who is seated in the chair, out of the chair. The particular purpose of this is to assist the elderly and the infirm who might otherwise find it difficult to rise from the chair. It will also be apparent, that by an appropriate adjustment of the tension on the tension springs, a person seated in the seat can partake in a relatively mild form of physical exercise by rocking the chair against the tension of the tension springs.

It will also be understood that the degree of spring assistance can be readily adjusted by the operator while sitting in the seat so that the spring assistance can vary from a light assistance to a full assistance with any intermediate degree as required.

Having disclosed the best method of putting the invention into effect it will be apparent to those skilled in this particular art that various modifications and amendments can be made to the concept of the invention and yet still fall within that concept. It is intended that all such modifications and variations be included within the scope of the present invention.