GB2478705A

GB2478705A - Lockable joint for a bed chair

Info

Publication number: GB2478705A
Application number: GB201004180A
Authority: GB
Inventors: Kevin Robert Nash
Original assignee: Catchum 88 Ltd
Current assignee: Catchum 88 Ltd
Priority date: 2010-03-15
Filing date: 2010-03-15
Publication date: 2011-09-21
Anticipated expiration: 2030-03-15
Also published as: GB2478705B; GB201004180D0

Abstract

An elbow joint for a bed chair comprises two discs or plates 12, 14 having rotationally symmetrical interlocking teeth 20, 22 on opposed mating surfaces to enable the discs to be locked or engaged relative to one another at a plurality of different angles. A hand wheel or grip 30 is coupled to one of the plates via a screw thread 32, and coupled to the second plate so that the hand wheel may rotate but not move axially relative to said second plate. Rotation of the hand wheel can therefore be used to move the discs apart as well as clamp them together.

Description

ADJUSTABLE BED CHAIR ELBOW JOINT

Field of the invention

The present invention relates to an adjustable elbow joint for use in a folding bed chair, especially bed chairs used by anglers.

Background of the invention

Folding bed chairs employ elbow joints to allow the inclination of the back rest to be adjusted and to be locked in many positions. Thus the backrest can be set in a horizontal or fully reclined position to allow the bed chair to be used as a bed, in a near vertical position to allow the bed chair to be used as a chair, as well as several positions in between.

Known adjustable bed chair elbow joints comprise two vertical parallel disc of which one is secured to the frame of the backrest and the other is secured to the frame of seat portion. The two discs are concentric and can rotate relative to another to allow the backrest to be inclined relative to the seat portion of the bed chair. To allow the backrest to be locked in a set position, interlocking formations are formed on the mating faces of the two discs, which may be shaped as teeth with vertical flanks (i.e. normal to the plane of the discs) or shaped as ratchet teeth with one inclined and one vertical flank. A screw operated by a hand wheel is turned to clamp the discs to another. The screw is threaded into the disc remote from the hand wheel and passes with clearance through the hole in the disc adjacent the hand wheel.

The formations have at least one vertical flank because a strong turning moment is applied to the discs when the bed chair is occupied and an inclined flank would risk the elbow joint failing unless considerable pressure is applied by the hand wheel to force the discs together.

A disadvantage of this design of the elbow joints is that the back rest is difficult adjust while the bed chair is occupied. This is because when the elbow joints are under tension, the discs do not separate from one another when the hand wheel is unscrewed.

Summary of the invention

With a view to mitigating the foregoing disadvantage, the present invention provides an elbow joint for a bed chair comprising two coaxial mutually rotatable discs having rotationally symmetrical interlocking formations on opposed mating surfaces to enable the discs to be locked relative to one another in a plurality of different relative angular positions, a screw engaged in one of the discs and a hand wheel for rotating the screw to lock the discs relative to one another, wherein the hand wheel is additionally coupled to the other disc in such a manner that the hand wheel may rotate but not move axially relative to said other disc.

In the present invention, because the hand wheel cannot move axially relative to the other disc as it is rotated to unscrew it from the first disc, it does not merely permit the discs to separate but it forcibly prises them apart. As a result even when vertical flanks of the interlocking formations are under pressed against one another, the hand wheel permit the formations to disengage so that the position of the back rest may be reset.

In a preferred embodiment of the invention, the hand wheel serves to rotate a screw in threaded engagement with the disc nearer to the hand wheel and the end of the screw remote from the hand wheel is secured to the disc located further from the hand wheel in such a manner as to permit the screw to rotate but not to move axially relative the latter disc.

Preferably, the hand wheel is formed integrally with an axially extending shaft of non-circular section fitted with a sleeve having a screw on its radially outer surface that is in threaded engagement with a screw threaded aperture in the disc located nearer the hand wheel, the other disc being axially clamped to the end of the shaft remote from the hand wheel.

Conveniently, the disc located further from hand wheel is clamped to the shaft by means of a nut and a bolt passing through the non-circular shaft.

The nut advantageously has an outer flange and a shaft received within end of the externally screw threaded sleeve remote from the hand wheel, the disc located further from the hand wheel being rotatable relative to the nut but sandwiched between the outer flange of the nut and the ends of the externally screw threaded sleeve.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawing, which is a section through an elbow joint embodying the present invention.

Detailed description of the preferred embodiment(s) The elbow joint 10 shown in the drawing comprises two circular discs 12 and 14 arranged coaxially and facing one another. Each of the discs 12 and 14 is formed with a respective mounting bracket 16 and 18 by means of which it is connected to a tubular frame member of a folding bed chair.

The mating faces of the discs 12 and 14 are formed with matching formations 20 and 22 that are shaped as ratchet teeth, that is to say each tooth has a vertical flank and a ramped flank. The formations 20 and 22 extend radially and are regularly spaced, in the same way as the spokes of a wheel, and can thus interlock with one another in any of a number of relative angular positions. When spaced apart from one another, as shown in the drawing, the two discs 12 and 14 can be rotated relative to one another to allow the backrest of the bed chair to be set at any desired inclination. When the two discs 12 and 14 are then clamped to one another, in the manner to be described below, the formations 20 and 22 interlock and prevent the discs from rotating, thereby holding the back rest firmly in the set position.

The mechanism used to clamp the discs 12 and 14 against one comprises a hand wheel 30 that is fast in rotation with a screw threaded sleeve 32 and can be rotated relative to the two discs 12 and 14. To prevent the sleeve from rotating relative to the hand wheel 30, the latter is formed integrally with a shaft 34 of non-circular, preferably octagonal, cross section that engages within a similarly shaped inner bore of the sleeve 34.

On the opposite side of the elbow joint from the hand wheel 30, a nut 36 is inserted in a hole in the disc 12. The nut 36, which like all the other components described so far is made of a plastics material, has a large diameter circular outer section serving as a retaining flange 38, a central circular section 40 serving as a bearing and a non-circular inner section 42 received within the inner bore of the screw threaded sleeve 32 thereby ensuring that the nut 36, the sleeve 32 and the hand wheel 30 always rotate in unison. The nut 36 has a screw threaded insert 44 which receives a bolt 46 to lock the nut 36 to the hand wheel 30.

For aesthetic reasons, the head of the bolt 46 is concealed by being mounted within a recess in the hand wheel which receives a blanking plate 48 that is pressed to glued in position.

The described clamping mechanism operates on the same principle as a bench vise. The hand wheel 30, the sleeve 32 and the nut 36 can rotate freely relative to the disc 12.

However, because the disc 12 is sandwiched between the sleeve 32 and the flange 38, the disc 12 cannot move axially relative to the hand wheel 30. As the hand wheel 30 is turned manually, it rotates the screw threaded sleeve 32 which is engages within a similarly threaded central bore in the disc 14. Thus as the sleeve 32 is rotated in one direction, conventionally clockwise, the two discs 12 and 14 are urged towards one another and as the sleeve 32 is rotated in the opposite direction the two discs 12 and 14 are pulled apart.

Because of the discs being positively driven by the sleeve 32 in both directions, they will separate from one another even if there is frictional engagement between the vertical flanks of the formations 20 and 22. This allows the inclination of the back rest of the bed chair to be adjusted even when the elbow joint is under tension from springs of the mattress or from the weight of the bed chair occupant.

Claims

CLAIMS1. An elbow joint for a bed chair comprising two coaxial mutually rotatable discs having rotationally symmetrical interlocking formations on opposed mating surfaces to enable the discs to be locked relative to one another in a plurality of different relative angular positions, a screw engaged in one of the discs and a hand wheel for rotating the screw to lock the discs relative to one another, wherein the hand wheel is additionally coupled to the other disc in such a manner that the hand wheel may rotate but not move axially relative to said other disc.
2. An elbow joint as claimed in claim 1, wherein the hand wheel serves to rotate a screw in threaded engagement with the disc nearer to the hand wheel and the end of the screw remote from the hand wheel is secured to the disc located further from the hand wheel in such a manner as to permit the screw to rotate but not to move axially relative the latter disc.
3. An elbow joint as claimed in claim 2, wherein the hand wheel is formed integrally with an axially extending shaft of non-circular section fitted with a sleeve having a screw on its radially outer surface that is in threaded engagement with a screw threaded aperture in the disc located nearer the hand wheel, the other disc being axially clamped to the end of the shaft remote from the hand wheel.
4. An elbow joint as claimed in claim 3, wherein the disc located further from hand wheel is clamped to the shaft by means of a nut and a bolt passing through the non-circular shaft.
5. An elbow joint as claimed in claim 4, wherein the nut has an outer flange and a shaft received within end of the externally screw threaded sleeve remote from the hand wheel, the disc located further from the hand wheel being rotatable relative to the nut but sandwiched between the outer flange of the nut and the ends of the externally screw threaded sleeve.
6. An elbow joint for a folding bed chair, constructed substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.