GB2365761A

GB2365761A - Adjustable telescopic strut

Info

Publication number: GB2365761A
Application number: GB0019792A
Authority: GB
Inventors: Jonathan Edward Fagg
Original assignee: CHUB LEISURE Ltd
Current assignee: CHUB LEISURE Ltd
Priority date: 2000-08-12
Filing date: 2000-08-12
Publication date: 2002-02-27
Also published as: GB0019792D0

Abstract

An adjustable telescopic strut suitable for use as a leisure chair leg has outer and inner tubular members 10,11 which are telescopically slideable and lockable at any required selling. A pair of angled locking plates 14,15 are provided in apertures 16,17 in the outer member 10, the locking plates 14,15 each having a bore through which the inner member 11 passes and a spring 19 urging the locking plates 14,15 to opposed inclined locking settings. A control sleeve 26 encircles the locking plates and includes profiles 31,36 to move the locking plates 14,15 to lie in generally radial planes when the sleeve 26 is appropriately turned thereby freeing the inner member 11 for sliding movement relative to the outer member 10.

Description

<Desc/Clms Page number 1> ADJUSTABLE TELESCOPIC STRUT This invention relates to an adjustable telescopic strut. In particular, but not exclusively, the invention concerns such a strut suitable to serve as an adjustable leg for a chair, a bed-chair or a table, such as may be employed on uneven ground.

A well-known problem associated with a four-legged chair, bed-chair or table is that if the ground is uneven, then the chair or table will not stand uniformly on all four legs, unless some form of adjustment for those legs is provided. A particular problem arises in the case of a chair or bed-chair intended 'for use out of doors - a so-called leisure chair. Such leisure chairs very frequently are used on uneven ground and so can be uncomfortable to sit upon. Leisure chairs are very widely used by anglers, who try to place the chairs on the most even ground they can find on a river bank, the side of a lake or the like. Unfortunately, the ground very often is. sloping as well as being uneven immediately adjacent a river or lake, and so it is difficult securely to position a leisure chair there.

In an attempt to overcome the above problem, it is known to provide a leisure chair with independently adjustable legs. Most designs have some kind of telescoping leg arrangement together with a locking mechanism which allows a leg to be secured at a selected one of a number of spaced positions. This may be achieved by having a peg resiliently mounted on one member making up the telescopic leg and which may pass through a selected hole of a row thereof in the other member of the leg.

Generally, the locking mechanisms used on leisure chairs are either difficult to use or not very reliable, in practice. Further, most of those do not

allow adjustment to an exact selected position, but rather only to any one of a number of possible positions. There is thus a need for a locking mechanism for an adjustable telescopic leg which is reliable in use, easy to operate and which permits a leg incorporating the mechanism to be adjusted to an exact length.

Accordingly, this invention provides an adjustable telescopic strut, comprising an inner member, an outer tubular member within which the inner member is slidably disposed, and a locking mechanism to secure the inner member at least against collapsing movement a desired position with respect to the outer member, which locking mechanism comprises a locking plate mounted in an aperture defined at or adjacent one end of the outer member and having an opening through which the inner member passes, said aperture being configured to permit the plate to move between a free position where the plate lies generally in a radial plane and a locked position where the plate lies at an acute angle to the radial plane and resists at least collapsing sliding movement of the inner member, a spring arranged to urge the plate to its said locked position, and a control member rotatably mounted on the outer member and having an internal thrust surface which engages the plate and moves the plate away from its locked position to its free position upon rotation of the control member in the appropriate sense.

It will be appreciated that when a leisure chair incorporates an adjustable telescopic strut of this invention as at least one, but preferably all, of the legs of the chair, it is possible to adjust the chair so as to rest in a secure manner on uneven ground. If all the legs are adjustable in this way, it is also possible to adjust the chair so that the seat is at a required angle to the horizontal. Adjustment of each leg is very easy to perform, requiring no more than turning

of the control member followed by axial adjustment of the inner member with respect to the outer member, whereafter the control member may be turned back to its initial position so securing the leg. Further, accidental operation, for example when the chair is being used, is highly unlikely.

Preferably, said aperture is formed by two opposed perforations in the outer member, through the wall thereof at or adjacent its one end. One perforation may have a greater axial length than the other, whereby the locking plate will lie at an angle to the radial plane when the locking plate bears on the circumferential edges of the apertures.

The opening in the locking plate may have a pair of arcuate opposed edges which bear on the outer surface of the inner member, through the aperture in the outer member, when the locking plate is in its locked position. Movement of the inner member in the sense which will tend to increase the angle of inclination of the locking plate with respect to the axis of the strut will serve more securely to lock together the two members. Conversely, axial sliding movement in the opposite sense will tend to decrease the angle of inclination of the locking plate and so may be permitted. The curvature of said arcuate edges may be substantially equal to the diameter of the inner member. Between and symmetrically disposed with respect to the arcuate edges may be two opposed parallel linear edges. The spacing of these edges may be slightly greater than the diameter of the outer member, so that the locking member may be slid over the outer member, for positioning in the aperture.

Advantageously, a second locking plate is mounted within an aperture defined at or adjacent the free end of the outer member, which second locking plate is similarly disposed and arranged to the first-mentioned locking plate

except that when in its locked position, the second locking plate resists at least expanding movement of the inner member. In this case, the control member may have a second internal thrust surface which engages the second locking plate and moves that second locking plate away from its locked position to its free position, upon rotation of the control member in the appropriate sense.

The second locking plate advantageously is mounted in the same aperture as is the first-mentioned locking plate. Further, the second locking plate may be moved to its free position upon rotation of the control member in the same sense as frees the first-mentioned locking plate. On the other hand, the control member could be arranged so that rotation thereof in one sense frees one locking plate and rotation in the other sense frees the other locking plate.

In order further to minimise the likelihood of accidental release of the locking mechanism, a detent may be provided which tends to retain the control member in its position where both locking plates are in their respective locked positions, movement of the control member requiring a positive rotational force, in order to free the locking plates.

By way of example only, one specific embodiment of an adjustable leg constructed and arranged in accordance with the present invention will now be described in detail, reference being made to the accompanying drawings, in which:- Figure 1 is a side view of the lower part of the leg; Figure 2 is a sectional view through the locking mechanism of the leg; Figures 3A and 3B show the locking mechanism respectively in its locked and free positions, but with the control sleeve removed for clarity;

Figure 4 is a side view on the control sleeve; Figure 5 is a cross-section through the main body of the control sleeve; Figures 6A and 6B are respectively axial and side views on an end cap for the main body of the control sleeve; Figure 7 is an axial cross-section through the end cap; Figures 8A, 8B and 8C are respectively a side view on the outer member, a second side view taken at 90 to Figure 8A, and an end view on the outer member; and Figure 9 is an axial view on a locking plate.

Referring initially to Figures 1 and 2, there is shown a telescopic strut intended to serve as a leg for a bed chair, a fishing chair, or the like. At least three of the legs of that chair should be adjustable, in order to allow levelling of the seat of the chair, despite any unevenness in the ground on which the chair stands. To that end, at least three (but preferably all) of the legs are telescopic to permit adjustment of their effective lengths, and may be secured against collapsing movement at a desired position.

In Figures 1 and 2, there is shown a tubular outer member 10 within which is slidably received a tubular inner member 11. A locking mechanism 12 is arranged to secure the inner member with respect to the outer member, against axial sliding movement. At its lower end, the inner member 11 is provided with a rubber foot 13 and at the upper end (not shown) of the outer member 10, the leg is rigidly fixed or hinged to a seat frame of the chair.

The locking mechanism 12 is formed by a pair of locking plates 14,15 disposed in a pair of apertures 16,17 in the outer member 10, the plates 14,15 being similar and each having a central opening 18 (Figure 9) through which is

slidably received the inner member 11. A compression spring 19 is disposed between the two locking plates 14,15, to urge those plates apart and so towards the axial ends of the apertures 16,17 in the tubular member 10.

The apertures 16,17 are diametrically opposed in the outer member 10, aperture 16 having a greater axial length than aperture 17. The two apertures are symmetrically disposed with reference to a central radial plane, so that the locking plates 14,15 will tend to take up the positions shown in Figures 2 and 3A, under the action of the compression spring 19. Each plate 14,15 has a circular external profile (Figure 9), the opening 18 in that plate having a pair of diametrically opposed arcuate sections 21,22 which together define a part of a circle which is a close sliding fit over the outer diameter of the inner member 11. Further, the opening 18 has two generally linear portions 23,24, disposed parallel to one another symmetrically with respect to the arcuate sections 21,22. The spacing of the linear portions 23,24 is slightly greater than the outer diameter of the outer member 10. Thus, each locking plate 14,15 may be located in the two apertures 16,17 by positioning one arcuate section in aperture 16, and then hinging the plate round to have the other arcuate section in aperture 17. For this purpose, the end part of the outer tube is cut away as shown at 25.

When the two locking plates 14,15 are disposed parallel to one another, as shown in Figure 313, the inner member 11 is a free sliding fit within the outer member 10. When the locking plates 14,15 are moved by the action of compression spring 19 to their respective positions shown in Figure 3A, the arcuate portions 21,22 of the locking plates engage and bite into the material of the inner member 11, such that plate 14 resists collapsing telescopic movement

of the inner and outer members 10,11 and plate 15 resists expanding telescopic movement of those members 10,11.

A control sleeve 26 is rotatably arranged on the end portion of the outer member 10, to effect movement of the plates 14,15 away from their respective positions shown in Figure 3A, to the positions shown in Figure 3B. This control sleeve 26 has a main body 27 (Figure 5) to which is fitted an end cap 28 (Figures 6A, 6B and 7). The main body 27 is tubular and at one end defines a bore 29 which is a rotational fit on the outer diameter of the outer member 10. Adjoining the bore 29 is a tubular part 30 the internal diameter of which is slightly greater than the diameter of the plates 14,15, to permit those plates to lie within the main body when disposed in radial planes as shown in Figure 3B.

An abutment 31 projects inwardly from the tubular part 30, adjacent the bore 29, and lies on the side of the upper locking plate 14 remote from the free end of the outer member 10. The end cap 28 is snap-fitted into the end of the tubular part 30, shoulder 32 of the end cap being received in an internal annular groove 33 formed in the main body 27. A peg 34 is provided on the end cap 28, which peg locates in a recess 35 in the end face of the main body 27, to locate the end cap in a fixed relative disposition with respect to the main body 27. The end cap 28 has a leg 36 which projects axially into the main body 27, against the inner surface of the tubular part 30 and in axial alignment with the abutment 31. As shown in Figure 2, the upper end of this leg 36 lies closely adjacent the lower surface of the lower locking plate 15 - that is, the surface thereof nearer the lower end of the outer member 10.

A notch 38 is formed in the end region of the cutaway part 25 of the lower end of the outer member 10. A spring-loaded plunger 39 is mounted in

the end cap 28, and runs on the cutaway end face of the outer member 10. When the plunger 39 is disposed in the notch 38., the plunger tends to hold the control sleeve in that position until a positive rotational force is applied to the control sleeve 26 to lift the plunger out of the notch 38. Further, the plunger limits rotational movement of the control sleeve, by engaging the end portion 37 of the outer member.

As shown in Figures 8B and 8C, the outer surface of the tubular member 10 is provided with a lug 40, formed for example by punching outwardly the material of the tubular member, with access being gained through the larger aperture 16. This lug 40 serves to prevent the control sleeve 26 coming off the outer member 10, by engaging the shoulder between tubular control sleeve 30 and bore 29.

The normal position of the locking mechanism is shown in Figure 2, where the plunger 39 is located in notch 38 and so restrains the control 26 against rotation unless a sufficient turning force is applied thereto. In this normal position, the two locking plates 14,15 are urged apart by compression spring 19 and serve to lock the inner member 11 against axial movement, with respect to the outer member 10. Collapsing movement is resisted by the upper locking plate 14, whereas expanding movement is resisted by the lower locking plate 15.

If it is required to adjust the effective length of the telescopic leg, the control sleeve 26 is turned typically through 180 . During this, the abutment 31 acts on the upper locking 14 and the leg 36 on the lower locking plate 15, so moving those locking plates to a parallel disposition as shown in Figure 3B. Then, the inner member 11 may be moved freely with respect to the outer

member 10. Once set at the required position, the control sleeve may be returned back to its initial position, with plunger 39 located in notch 38, so once more securing together against axial movement the inner and outer members 10 and 11.

In the described embodiment, both locking plates 14,15 are moved simultaneously to a parallel disposition by rotation of the control sleeve 26. In an alternative embodiment (not shown) rotation of the control sleeve in one sense moves one of the locking plates into a radial plane, and rotation of the control sleeve in the other sense moves the other locking plate into a radial plane.. Thus, the length of the leg may be adjusted selectively to be either longer or shorter, but held against movement in the opposite sense.

Claims

CLAIMS 1. An adjustable telescopic strut, comprising an inner member, an outer tubular member within which the inner member is slidably disposed, and a locking mechanism to secure the inner member at least against collapsing movement a desired position with respect to the outer member, which locking mechanism comprises a locking plate mounted in an aperture defined at or adjacent one end of the outer member and having an opening through which the inner member passes, said aperture being configured to permit the plate to move between a free position where the plate lies generally in a radial plane and a locked position where the plate lies at an acute angle to the radial plane and resists at least collapsing sliding movement of the inner member, a spring arranged to urge the plate to its said locked position, and a control member rotatably mounted on the outer member and having an internal thrust surface which engages the plate and moves the plate away from its locked position to its free position upon rotation of the control member in the appropriate sense.
2. An adjustable telescopic strut as claimed in claim 1, wherein said aperture is formed by two opposed perforations through the wall of the outer member, at or adjacent its one end.
3. An adjustable telescopic strut as claimed in claim 2, wherein one perforation has a greater axial length than the other, whereby the locking plate lies at an angle to a radial plane when the plate bears on the circumferential edges of the perforations.
4. An adjustable telescopic strut as claimed in any of the preceding claims, wherein the opening in the locking plate has a pair of arcuate opposed edges

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which bear on the outer surface of the inner member when the locking plate is in its locked position.
5. An adjustable telescopic strut as claimed in claim 4, wherein the spacing of said pair of parallel opposed edges is substantially equal to the outer diameter of the outer member.
6. An adjustable telescopic strut as claimed in any of the preceding claims, wherein the outer member has a projection from its outer surface which projection engages a shoulder formed in the control member to retain the control member on the outer member.
7. An adjustable telescopic strut as claimed in any of the preceding claims; wherein a second locking plate is mounted within an aperture defined at or adjacent the free end of the outer member which second locking plate is similarly disposed and arranged to the first-mentioned locking plate except that when in its locked position the second locking plate resists at least expanding movement of the inner member, and the control member has a second internal thrust surface which engages the second locking plate and moves the second plate away from its locked position to its free position upon rotation on the control member in the appropriate opposite sense.
8. An adjustable telescopic strut as claimed in claim 7, wherein the second locking plate is mounted in the same aperture as is the first-mentioned locking plate.
9. An adjustable telescopic strut as claimed in claim 7 or claim 8, wherein the second locking plate is moved to its free position upon rotation of the control member in the same sense as frees the first-mentioned locking plate.

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10. An adjustable telescopic strut as claimed in claim 7 or claim 8, wherein the second locking plate is moved to its free position upon rotation of the control member in the opposite sense to that which frees the first-mentioned locking plate, whereby the locking plates may selectively be moved to their respective free positions.
11. An adjustable telescopic strut as claimed in any of the preceding claims, wherein detent means is provided to maintain the control member at its position where the or each locking plate is at its locked position.
12. An adjustable telescopic strut substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.