GB2074643A

GB2074643A - Clamping device for locking two telescopically movable members

Info

Publication number: GB2074643A
Application number: GB8111936A
Authority: GB
Original assignee: Hunter Douglas Industries BV
Current assignee: Hunter Douglas Industries BV
Priority date: 1980-04-26
Filing date: 1981-04-15
Publication date: 1981-11-04
Also published as: FR2481386A1; ES257841Y; BE888553A; DE3114516A1; NL8002465A; IT8121349A0; IT1137054B; ES257841U; GB2074643B

Abstract

A clamping device is provided for locking together two telescopically movable parts 11, 12, such as telescopic tent pole, the outer of which has a widening 13 at its outermost end, the widening having an orifice 14 therein. The clamping device includes a removable hair pin shaped spring 18, a loose internally threaded element 15 and a cooperating externally threaded element 16. One arm 21 of the spring part passes into the widening and the other arm 20 can be sprung, in the longitudinal direction of the tube, on the outside of the widening of the tube wall. In this way, in the assembled state, the internally threaded element 15 is held in place in the orifice 14 and the externally threaded element 16, for example an eyebolt, is screwed into the internally threaded element and bears against the one arm of the spring part 21 which is within the outer tube, forcing it against the inner tube 11. <IMAGE>

Description

SPECIFICATION Clamping device for locking two telescopically movable members The present invention relates to a clamping device for locking two telescopically movable members, such as two tubes, or a tube and a rod.

One example of such telescopically movable members is a telescopic tent pole, which contains an internally threaded element, which can be pushed from inside into an appropriate orifice provided in a widening on one side of the outermost end of the outer tube, and can be fastened therein. The threaded element also contains a screw element interacting with an internal thread to effect the clamping connection.

A conventional clamping device for tent poles consists of internally threaded element welded or riveted to the outer tube and of an eyebolt serving for locking. As a result of the moderately high specific pressure which is exerted by the end of the eyebolt on the tube to be locked, deformation and/or damage concentrated at one point of the inner tube tends to occur. Moreover, the manufacture of a clamping device of this type is complicated, because the internally threaded element has to be fitted manually, after which the screw element has to be turned on a lathe before the tube can be painted. If the screw element is not first turned on a lathe, then the thread becomes clogged during painting, thus giving rise to subsequent difficulties.

According to the present invention, we provide a clamping device for locking together two telescopically movable members, one of which forms an outer tube, which is provided on one side with a widening at its outermost end, the widening having an orifice therein, said clamping device comprising a removable hairpin shaped spring part, a loose internally threaded element and a cooperating externally threaded element, the spring part being shaped so that, at the location of the widening at the end of the outer tube, one arm passes into the widening and the other arm can be sprung, in the longitudinal direction of the tube, on the outside of the widening of the tube wall, in such a way that, in the assembled state, the internally threaded element is retained in its position in the orifice and so that when the externally threaded element is screwed into the internally threaded element, it bears against the one arm of the spring part.

Such a construction makes it possible to avoid the above difficulties by providing three loose individual parts which can be supplied with the tent poles, so that the user can fit the clamping device himself. Since there are virtually no projecting parts on the tubes any longer, less damage to the tent poles also occurs between packaging and transport.

The function of the spring part is to hold the loose internally threaded element in its position relative to the orifice, whilst falling out is prevented without a permanent fastening method, for example riveting or welding, being necessary for this purpose. To counteract any rotation of the internally threaded element, it can be provided with a flange adapted to engage the sides of the widening. Owing to the presence of the flange on the internally threaded element, the latter is held in the orifice by the spring element pressing the flange against the sides of the widening, which may have, for example, the form of a trapezium.

The rotation of the internally threaded element can be counteracted, if a square or rectangular form is given to the flange, which can then no longer rotate within the appropriately designed trapezoidal widening.

Instead of the conventional surface pressure caused by the externally threaded screw element, pressing force is, with the construction of the invention, now exerted on the relatively large pressure face of the first arm of the spring part, as a result of which damage to the tube surface at that point is reduced or eliminated. At the same time, an additional advantage arises since, in the conventional screw clamping a deformation of the tube cross-section can easily occur, as a result of which it becomes more difficult to push the telescopic members in and out. This is no longer the case with the construction of the invention, because of the lower surface pressure exerted by means of the face of the spring part.Although the spring part can, on the outside of the outer tube, either hook into the orifice enlarged for this purpose or find a purchase in a notch or groove intended for this purpose, it is appropriate to provide the second arm of the spring part with an insertion orifice for the internally threaded element. Furthermore, another appropriate construction to prevent rotation of the internally threaded element can also be applied, in that the insertion orifice for the internally threaded element and the element itself are designed to fit one another and have a non-circular cross-section.

Also, it is favourable, in order to avoid damage to the already painted or not yet painted tube surface, if the two outermost ends of the spring part are each bent in the same direction, with the end of the first arm being bent towards the second arm. The second arm of the spring part can thereby comfortably be brought over the internally fitted element, whilst the first arm of the spring part makes it easier to push the inner tube in and out and, moreover, cannot seize on the material of the tube with its free end as a result of a sharp severing burr which is virtually always present.

According to the invention we also provide an assembly of two telescopically movable members in which one member is tubular at least at its end and forms the outer part of the two parts, wherein said part is provided on one side with a widening at its outer end, the widening having an orifice therein and a clamping device according to the invention mounted with one arm of the spring part passing into the widening and the other arm sprung on the outside of the widening to retain the internally threaded element in the orifice.

The invention will be more fully understood from the following description, which is given merely by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a cross-section through a telescopic tent pole combination, showing a conventional clamping connection; Figure 2 is a side elevation, partly in section, of a telescopic tent pole combination, using one embodiment of clamping device according to the invention; and Figure 3 is a cross-section along the line Ill-Ill of Figure 2.

In Figure 1, an inner tube 1 is telescopically movable in an outer tube 2, the tubes both having a circular cross-section, whilst the outer tube is provided close to its outermost end with a trapezoidal cross-section widening 3 (see also Figures 2 and 3). An orifice 4 is formed in this part of the tube and an internally threaded element 5 is welded firmly therein. A screw element 6 can be screwed into this internally threaded element, said screw element exerting, after tightening, such a pressure against the outer surface of the inner tube 1, that the inner tube is clamped. The construction of this type for the clamping device of the two tubes 1 and 2 is well known. Likewise the outer tube 2 can have a circular cross-section extending to its end, and a plane nut can be welded on the tube end, so that, finally, the same clamping is achieved.

The disadvantages described above are now eliminated by means of a clamping device as shown in Figures 2 and 3. Figure 2 shows an inner tube 11 which is telescopically movable in an outer tube 12, and Figure 3 shows that a certain clearance exists between the two tubes. As may also be seen in Figure 1, the end of the outer tube 12 has a trapezoidal cross-section widening 13 arranged at the location of the clamping device. In the outer tube 12 is formed an orifice 14 in which a loose internally threaded element 15, into which is screwed an externally threaded screw element 16, is provided. The internally threaded element 15 can be made round or angular and is provided with a rectangular flange 17.As Figure 2 shows, this flange 17 falls into the upper part of the trapezoidal widening 13 and is held there, in its place, by a spring part 18 which is bent in the form of a hair pin to have a first arm 21 and a second arm 19 which is provided with an orifice 20 for the internally threaded element 1 5. When the screw element 1 6 is screwed into the internally threaded element 15, to an extent in which the lower end of the screw element 16 does not project below the flange 17 thereof, then, in the marked position of the second arm 1 9 of the spring part 18, the first arm 21 of the spring part 1 8 is pressed against the flange (as is shown by the broken lines). As a result, the flange, which is integral with the internally threaded element 15, is retained in the orifice 14.When the screw element 1 6 is tightened further, its lower end projects below the flange and thereupon presses the first arm 21 of the spring part 18 downwards against the inner tube 11 into the position indicated in Figure 2. The clamping connection is effected by a further tightening of the screw element 16. Even if greater pressure is exerted on the surface of the inner tube 11 with further tightening, the face of the hair pin shaped spring part 1 8 ensures the distribution of the screwing pressure occurs and, consequently, no undesirable deformation and/or permanent damage to the inner tube 11 can arise at the location of the clamping connection.

Although the spring part is drawn in Figures 2 and 3 with an orifice 20 so as to be pushed over the internally threaded element, this Iastfeatureis not absolutely essential. If the outermost end of the second arm 1 9 is bent, for example, in the form of a hook (not shown), this can also engage into the orifice 14 of the outer tube 12 or, for example, into a groove which is recessed in the internally threaded element and which serves to provide a point of engagement for the outer end, so that the latter does not spring loose after the spring part 1 8 has been fitted.However, the preferred construction illustrated in Figures 2 and 3 seems, in this respect, to be the simplest and the most appropriate for good fastening of the spring part relative to the outer tube 12 and to the internally threaded element 15, and also has the advantage that a suitable non-circular construction is obtained as a result of the combination of the orifice and the internally threaded element To avoid damage caused by scratching of the usually painted surface of the tent pole, two outermost ends of the spring part are bent upwards somewhat, at the points 22 and 23, so that the sharp spring edges (burns) which are virtually always present, cannot cause any damage. The user of the tent poles, or of the telescopic tubes for other purposes, can now fit the clamping device in the outer tube himself and, if desired, effect the clamping connection.It goes without saying that the circular cross-section of the tubes, which are shown, is not obligatory, but that angular cross-sections can also be used, and also that more than one clamping device on the same outer tube, depending on the clamping pressure required and/or the desire to centre a tube with a significantly smaller cross-section than a tube with a larger cross-section than the tube shown. Because the pressures which arise are effective on a large friction surface in the clamping connection, the trapezoidal widening 13 only needs to be large enough for sufficient height to remain for the thickness of the flange of the internally threaded element 15, for the clearance between the telescopically movable tubes and for the height of the first spring arm 21 of the spring part 18, with the bent edges at 22 taken altogether. Because of the smaller space taken up by an outer tube in this way, the total advantages provided by means of a clamping device according to the invention are considerable, especially with regard to its assembly and fitting.

Claims

1. A clamping device for locking together two telescopically movable members, one of which forms an outer tube, which is provided on one side with a widening at its outermost end, the widening having an orifice therein, said clamping device comprising a removable hair pin shaped spring part, a loose internally threaded element and a cooperating externally threaded element, the spring part being shaped so that, at the location of the widening at the end of the outer tube, one arm passes into the widening and the other arm can be sprung in the longitudinal direction of the tube, on the outside of the widening, in such a way that, in the assembled state, the internally threaded element is retained in its position in the orifice and so that when the externally threaded element is screwed into the internally threaded element, it bears against the one arm of the spring part.

2. A clamping device according to claim 1, wherein the internally threaded element is provided with a flange adapted to engage the sides of the widening of the outer tube to prevent, in the assembled state, any rotation of the internally threaded element.

3. A clamping device according to claim 1 or 2, wherein the spring part consists of a leaf spring which is bent in the form of a hair pin substantially through an angle of 1 800 about an axis transverse to the longitudinal direction, the first arm which is adapted to be introduced into the tube being of such a length that it extends over the threaded bore in the internally threaded element and its width corresponds at least to the diameter of said threaded bore.

4. A clamping device according to claim 3, wherein the two outermost ends of the spring part are each bent in the same direction, with the end of the first arm being bent towards the end of the second arm.

5. A clamping device according to any preceding claim, wherein the second arm of the spring part is provided for attaching to the outside of the outer tube, with an insertion orifice for the internally threaded element.

6. A clamping device according to claim 5, wherein the insertion orifice of the internally threaded element and the internally threaded element itself are designed to fit one another and have a non-circular cross-section.

7. A clamping device for locking together two telescopically movable members, said device being substantially as hereinbefore described, with reference to and as illustrated in, Figures 2 and 3 of the accompanying drawings.

8. An assembly of two telescopically movable members in which one member is tubular at least at its end and forms the outer part of the two parts, wherein said part is provided on one side with a widening at its outermost end, the widening having an orifice therein and a clamping device according to any preceding claim, mounted with one arm of the spring part passing into the widening and the other arm sprung on the outside of the widening to retain the internally threaded element in the orifice.