GB2322907A

GB2322907A - Lockable hinge particularly for collapsible chair

Info

Publication number: GB2322907A
Application number: GB9704429A
Authority: GB
Inventors: Jonathan Fagg; Mark Fagg
Original assignee: CHUB LEISURE Ltd
Current assignee: CHUB LEISURE Ltd
Priority date: 1997-03-04
Filing date: 1997-03-04
Publication date: 1998-09-09
Anticipated expiration: 2017-03-04
Also published as: GB9704429D0; GB2322907B

Abstract

A hinge 10 for pivotally connecting first and second members 11, 12, such as a chair base and a chair back, about a common axis 13 allows the first and second members 11, 12 to be releasable locked in a selected angular disposition. The hinge 10 comprises a first plate 14 attached to the first member 11 and a second plate 17 attached to the second member 12. The first plate 14 and the second plate 17 are formed, respectively, with through bores 15 and recesses 18 spaced circumferentially about the axis 13. A locking member 27 is formed with a plurality of circumferentially spaced locking pins 28 and a cam surface 33 that interacts with a cam surface 36 formed on an operating knob 34. Rotation of the operating knob 34 and subsequent interaction of the cam surfaces 33, 36 causes the locking pins to be either inserted into or withdrawn from the recesses 18 under the action of spring 31, thereby locking or unlocking the hinge 10.

Description

LOCKING DEVICE This invention relates to a locking device, for clamping in some pre-selected angular disposition two members which are pivoted together. Though the invention may be employed in a variety of different circumstances, the invention finds a particular application for the locking of the backrest of a collapsible leisure chair (or bed) at some preselected angle, with respect to the chair base. The invention therefore further relates to such a collapsible leisure chair or bed when provided with a locking device of this invention.

A known form of collapsible leisure chair1 widely used for example by anglers, has a metallic frame which defines at least a base portion and a backrest portion, a cover being suitably connected to the frame to allow a user to sit on the base portion and lean back against the backrest portion. To enhance the comfort of using such a chair, it is also known to provide a locking mechanism which permits the backrest portion to be secured at one of a number of pre-set angular dispositions with respect to the base portion. Such a locking mechanism is usually provided on both sides of the chair, in the vicinity of the pivotal connection between the base portion and the backrest portion, so as not to inhibit collapsing movement of the backrest portion to a fully-folded setting, to permit the chair to be carried from place to place. A further similar arrangement is often provided on a collapsible leisure bed, which in effect has a further hinged portion at the opposite end of the base portion to the backrest portion and which further portion may be locked at a selected angular position with respect to the base portion.

A person sitting in the chair (or bed) and leaning back on the backrest portion may exert a relatively high load on that backrest portion.

As the known form of locking arrangements for this kind of chair are provided in the vicinity of the pivotal connection between the backrest portion and the base portion, the locking mechanism may be subjected to very high loads. As a result, such mechanisms as have been conventionally employed with collapsible leisure chairs have been prone to wear or breakage, leading to unreliable operation and possible unintentional release when the chair is in use.

Many of the known forms of locking mechanisms intended for use with collapsible leisure chairs as have been described above employ some form of screw-threaded mechanism arranged to perform the locking action. Such a mechanism will normally require a significant number of turns on a nut, to effect locking or release of the mechanism. The tuming of a nut to perform this function is not a particularly convenient action for a user1 especially if the user is already sitting in the chair. Consequently, there is a tendency for the user insufficiently to tighten the nut when locking the backrest at some pre-set disposition. In tum, this leads to further wear or an increased likelihood of breakage of the mechanism.

It is a principal aim of the present invention to address the disadvantages of the known forms of locking mechanisms as described above, particularly as applied to a leisure chair or bed, and thus to provide a mechanism which is both reliable in operation and also relatively easy to use.

According to the present invention, there is provided a locking device for first and second members pivoted together about a common axis, to lock the members at a selected angular disposition, comprising: - a first plate secured to the first member and defining a plurality of through-bores on a pitch circle centred on said axis; - a second plate secured to the second member and defining a multiplicity of recesses on the same pitch circle centred on said axis, the angular spacing of the through-bores being a multiple of the angular spacing of the recesses; - a locking member having a base from one face of which projects a plurality of locking pins on the same pitch circle and arranged so that each pin projects through a respective through-bore of the first plate for reception in a recess of the second plate; - an operating knob rotatably mounted about said axis adjacent the other face of the locking member; and - a face cam mechanism formed between the opposed face of the base and the adjacent face of the knob, whereby rotation of the knob drives the locking pins from an unlocked position where the pins are free of the recesses to a locked position where the ends of the pins remote from the base are located in the recesses.

It will be appreciated that by providing a significant number of pins arranged on a common pitch circle around the axis of pivotal connection of the two members, the load on the locking mechanism may be distributed amongst all of the pins. In addition, by providing a face cam mechanism acting between the operating knob and the base of the locking member, operation of the mechanism may simply be effected by turning the operating knob through less than 360" and typically through about 120 . This action may shift the mechanism from fully released to fully locked and thus is easy to perform, even when a user is sitting in the chair.

In a preferred embodiment, the first plate defines the same number of through-bores as there are locking pins on the locking member, and the second plate defines twice as many recesses as there are pins and through-bores. In the alternative, the second plate could define the same number of recesses as there are pins and throughbores, or some other multiple of the number of pins and through-bores.

The appropriate arrangement should be selected having regard to the strength requirements of the locking device and the number of different settings at which a user might wish to lock one member with respect to the other, but in a preferred embodiment, there are ten pins and throughbores and twenty recesses.

The locking device preferably includes a screw-threaded fastener which may suitably be tightened in order to hold the first and second plates with their adjacent faces in engagement with each other, but free to rotate about the common axis. For this purpose, it is preferred for a bolt to extend through a hole formed on the centre of the pitch circles of the through-bores, pins and recesses, with the locking member, the operating knob and at least one of the plates all being mounted for rotation about that bolt.

In order to ensure release of the locking device, a compression spring may be mounted to act between the first plate and the locking member, to urge the locking member to the unlocked position with the locking pins free of the recesses in the second plate. Operation of the knob to move the locking pins to their locked position will thus be against the action of the spring.

In a preferred arrangement, the face cam formed on the opposed face of the base has three separate ramp portions, equi-spaced therearound. The operating knob has three corresponding followers which engage the three ramp portions respectively, in order to effect movement of the locking member to the locked position, upon rotation of the knob in the appropriate direction. Preferably, a stop arrangement is provided to prevent the operating knob being turned beyond a position at which the pins are in their locked position.

This invention extends to a collapsible leisure chair or bed having a frame defining a base portion and a backrest portion pivoted to the base portion, two locking devices of this invention as described above being provided one on each side of the chair or bed at the pivotal connection of the backrest portion to the base portion. In this arrangement, for each locking device, the first plate is secured to a frame member of either one of the base portion or the backrest portion and the second plate is secured to a frame member of the other of the base portion and the backrest portion.

By way of example only, one specific embodiment of locking device of this invention will now be described in detail, reference being made to the accompanying drawings, in which: Figure 1 is an exploded view, partially in section, of the embodiment of locking device; Figures 2 and 3 are respectively side and plan views of the locking device of Figure 1; Figure 4 is an isometric view of the locking member; and Figures 5 and 6 are side views of the first and second plates, respectively.

In the drawings there is shown a locking device 10 arranged to lock together in a desired angular setting two tubular members 11 and 12, pivoted together about an axis 13. Member 11 is connected to a first plate 14 having ten through-bores 15 arranged in an equi-spaced circular manner about a central aperture 16, with the plane of the plate 14 parallel to the length of member 11. In a similar way, member 12 is connected to a second plate 17, that second plate having twenty recesses 18 also arranged in an equi-spaced circular manner about a central aperture 19, the pitch circle of the through-bores 15 being the same as the pitch circle of the recesses 18. Each of the central apertures 16 and 19 is counter-bored in order to provide a respective shoulder 16A and 19A directed away from the other plate, when the two plates are clamped together with their inwardly directed faces 20 and 21 in sliding engagement.

A bush 23 is located in the smaller diameter regions of apertures 16 and 19, and a bolt 24 passes through that bush with a nut and washer 25 threaded on to the bolt. In this way, members 11 and 12 may pivot about axis 13, with surfaces 20 and 21 of the first and second plates 14 and 17 in sliding engagement with each other.

Also carried on the bolt 24 is a second bush 26, on which is rotatably mounted a locking member 27. The locking member has ten pins 28 projecting parallel to the bolt axis, the pins being equi-spaced and arranged on a common pitch circle with the through-bores 15 so that one pin may locate in each through-bore. The pins are of such a length so that when base 29 of the locking member 27 bears on outwardly directed face 30 of the first plate 14, the pins project from the inwardlydirected face 20 of the first plate, and are received in ten alternate recesses 18 of the second plate 17. A spring 31 acts between shoulder 16A of the first plate 14 and the locking member 27, washer 32 being disposed between bushes 23 and 26, to locate against shoulder 16A of the first plate 14.

On the side of the base 29 opposed to pins 28 are three arcuate ramp surfaces 33, each in the form of a face cam. A knob 34 is rotatably mounted on bush 35, the knob 34 having follower surfaces 36 arranged to engage the ramp surfaces 33 of the locking member 27. Also formed on the locking member 27 is a skirt 37 surrounding the ramp surfaces, a pair of stops 38 upstanding from the skirt and arranged to limit the angular movement of the knob 34 relative to the locking member 27, to approximately 100 . For this purpose, an annular discontinuous groove 39 is formed in the knob, to receive the stops 38. Washers 40 are provided to each side of bush 35, to retain knob 34 on the bolt 24.

In use, the locking device is assembled as best appreciated from Figure 1, with the nut and washer 25 tightened on to the bolt 24 so as to hold together all of the components. Bush 23 has an axial length slightly greater than the combined axial lengths of the smaller diameter portions of apertures 16 and 19, so that the first and second plates are not clamped together on tightening the nut and washer 25 on the bolt 24, but instead may slide over one another so permitting members 11 and 12 to pivot about bolt 24. When locked, knob 34 thrusts the locking member 27 against the action of spring 31, to engage the end portions of pins 28 in alternate recesses 18 of the second plate 17. To release the locking device so as to permit the members 11 and 12 to pivot, the knob 34 is turned counter-clockwise through about 100 , so allowing the locking member 27 to move under the action of spring 31 away from second plate 17 until the pins 28 come free of recesses 18. Once the members 11 and 12 have been set at the desired angular position, the knob 34 may be turned clockwise through 100 , so that the follower surfaces 36 push on the ramp surfaces 34 to move the locking member 27 back to the position where the free ends of the pins 28 are engaged in recesses 18.

The free end of each pin 18 is rounded so as to facilitate the entry of the pin into a recess 18. Thus, there is no need accurately to pre-set the relative positions of members 11 and 12, before starting to use the knob 34 to lock the relative position.

The locking device described above is particularly suitable for use with a collapsible portable leisure chair constructed from tubular frame members with canvas or sheet nylon coverings. Such a chair may have a base section and a backrest section, the base section having a pair of parallel frame members one on each side of the chair, and the backrest section also having a pair of parallel frame members each pivoted to one of the base section frame members respectively. In this case, two such locking devices as described above advantageously are employed, one at each pivotal connection between the respective frame members of the base section and the backrest section. The pivoting action of the backrest section will take place about the axis of bolt 24, with the knobs 34 located externally of the seat to facilitate easy use for adjustment of the angle of inclination of the backrest.

Claims

1. A locking device for first and second members pivoted together about a common axis, to lock the members at a selected angular disposition, comprising: - a first plate secured to the first member and defining a plurality of through-bores on a pitch circle centred on said axis; - a second plate secured to the second member and defining a multiplicity of recesses on the same pitch circle centred on said axis, the angular spacing of the through-bores being a multiple of the angular spacing of the recesses; - a locking member having a base from one face of which projects a plurality of locking pins on the same pitch circle and arranged so that each pin projects through a respective through-bore of the first plate for reception in a recess of the second plate; - an operating knob rotatably mounted about said axis adjacent the other face of the locking member; and - a face cam mechanism formed between the opposed face of the base and the adjacent face of the knob, whereby rotation of the knob drives the locking pins from an unlocked position where the pins are free of the recesses to a locked position where the ends of the pins remote from the base are located in the recesses.

2. A locking device as claimed in claim 1, wherein the first plate defines the same number of through-bores as there are locking pins on the locking member, and the second plate defines the same number of recesses as there are pins and through-bores.

3. A locking device as claimed in claim 1, wherein the first plate defines the same number of through-bores as there are locking pins on the locking member, and the second plate defines twice as many recesses as there are pins and through-bores.

4. A locking device as claimed in claim 3, wherein there are ten locking pins and through-bores and twenty recesses.

5. A locking device as claimed in any of the preceding claims, wherein there is provided a screw-threaded fastener extending through the axis of the device, to hold together the first plate, second plate, locking member and knob.

6. A locking device as claimed in any of the preceding claims, wherein a compression spring is arranged to act between the first plate and the locking member, to urge the locking member to the unlocked position with the locking pins free of the recesses in the second plate.

7. A locking device as claimed in any of the preceding claims, wherein the face cam is formed on the face of the base of the locking member opposed to the pins and has three ramp portions, equi-spaced around the locking member.

8. A locking device as claimed in claim 7, wherein the operating knob has three cam followers disposed to engage the three ramp portions respectively, so as thereby to effect axial movement of the locking member.

9. A locking device as claimed in any of the preceding claims, wherein there is provided a stop arrangement for the operating knob to limit the angular movement of the knob with respect to the locking member.

10. A locking device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

11. A collapsible leisure chair or bed having a frame defining a base portion and a backrest portion pivoted to the base portion, two locking devices each as claimed in any of the preceding claims being provided one on each side of the chair or bed at the pivotal connection of the backrest portion to the base portion.

12. A collapsible leisure chair or bed as claimed in claim 11, wherein at each locking device, a frame member of either one or the base portion or the backrest portion is secured to the first plate and a frame member of the other of the base portion and the backrest portion is secured to the second plate.