Previously is known a telescopically adjustable tube, in which a tube with a smaller outer diameter slides inside a tube with a larger diameter. This type of a tube is locked to the desired length by means of a bolt pin, which is pushed through holes made in both tube parts. However, when the tube is moved, the bolt pin detaches easily, which is why this type of an arrangement is mainly suitable for stationary products, such as the adjustable support structures of furniture and certain types of sports equipment. In the patent publication US 4,257, 591, for example, the detachment problem concerning the bolt pin has been solved by means of a separate locking spring.

Previously is also known a sleeve joint by means of which tube extensions are connected to each other by means of a friction joint. For example, in the patent publications US 4, 585, 367 and GB 2 158 865 are shown eccentric surfaces which press the friction attachment surfaces against the outer surface of the inner tube by rotating the outer sleeve. In this type of a telescopic arrangement the problem is that it is difficult to generate a friction-locking force so strong that it would suffice, for example, in ski pole or walking pole use where strong axial forces are directed at the tube.

The aim of the present invention is to provide a sleeve joint for a tube with telescopic length adjustment, by means of which joint the above-mentioned disadvantages can be eliminated or substantially reduced.

This aim is achieved by means of the present invention in such a way that inside the second sleeve part is a friction-locking sleeve surrounding the inner tube, the said sleeve being axially compressible and thus expandable to friction- locking attachment when screwing the sleeve parts with respect to each other.

The advantage of the invention is that the joint is strong enough for the tube to be stressed with a considerable axial force. The telescopic tube with a sleeve joint according to the invention can be applied especially to the length adjustment of ski poles and walking poles. The strength and ease of use of the joint also make it possible to use the tube as a tool shaft. The tube can be used, for example, as a broom or mop handle. If necessary, the attachment at the end of the tube can be exchanged. For example, the tube part of a ski pole, which comprises a ring and a tip part, can be exchanged for a tube part which comprises the rubber tip of a walking pole. Furthermore, the tube relating to the invention takes up little space when stored or transported. The adjustment of the tube is in addition stepless.

As tube material can be used composite materials, that is, reinforced fibres bound with resin, such as carbon and/or glass fibres. Metal is also a suitable tube or pole material. The sleeves of the sleeve joint are hard, injection moulded plastic.

Preferred embodiments of the invention are disclosed in the dependent claims.

The invention is described in greater detail in the following, with reference to the appended drawings, in which Figure 1 shows diagrammatically a three-part telescopic tube with two sleeve joints.

Figure 2 shows the sleeves of the sleeve joint in cross-section.

Figure 3 shows a slide ring from above and from the side.

Figure 4 shows the friction-locking sleeve from above and from the side.

Figure 5 shows a cross-sectional view of the sleeve joint.

Figure 1 shows diagrammatically a tube which is telescopically adjustable by means of a sleeve joint, the tube being denoted by reference numeral 1. In this embodiment there are two sleeve joints 10, 20, but their number may vary.

Depending on the application, their number is typically 1 to 3. At the sleeve joint, the tube 1 is comprised of an outer tube 2 and an inner tube 3, which is pushed inside the outer tube 2.

Figure 2 shows the first sleeve part 10 and the second sleeve part 20 which form the sleeve joint. The first sleeve part 10 of the sleeve joint is fixed permanently on its upper part 11 around the end of the tube with the larger diameter, that is, the outer tube 2, for example, by means of injection moulding.

On the outer surface of the lower part of the first sleeve part 10 is formed an external thread 14. In the second sleeve part 20 is, on the other hand, formed an internal thread 25, preferably on the inner surface of its upper part 21, whereby the first sleeve part 10 and second sleeve part 20 are interlocked by means of the said threads 14 and 25. The inner diameter of the middle part 22 of the sleeve part 20 is slightly smaller than the diameter of the thread part and corresponds to the outer diameter of the lower end 15 of the sleeve part 10.

The outer diameter of the inner tube 3 (see Figure 5) is formed in such a way that it is able to slide inside the first 10 and second 20 sleeve parts forming the outer tube 2 and the sleeve joint. For this purpose, in the lower parts of the sleeve parts 10 and 20 are formed sections 12 and 23 with the smallest inner diameters, which correspond to the outer diameter of the inner tube 3 in slide fit.

Figure 4 shows a friction-locking sleeve 40. It is preferably made of rubber or plastic or a similar elastically compressible material such as silicone, polyurethane, etc. In conjunction with the second sleeve part 20, on its inner surface, is arranged a shoulder 24, against which the friction-locking sleeve 40 rests at its first end. As seen in Figure 5, when installed in place, the axially compressible friction-locking sleeve 40 is located essentially as an axial extension to the internal thread 25 of the second sleeve part 20 and surrounds the inner tube 3 led through the second sleeve part 20. Thus the friction-locking sleeve 40 rests preferably with its other end, via the slide ring 30 shown in Figure 3, on the end 15 of the first sleeve part 10. The slide ring 30 facilitates the tightening of the joint and spares the end of the joint 40 of abrasion.

When attaching the sleeve parts 10 and 20 to each other, the screw joint 14, 25 is first screwed only so far that the friction-locking sleeve 40 is not axially compressed. After this, the position of the inner tube 3 is adjusted as desired with respect to the outer tube 2. The sleeve parts 10 and 20 are then connected to their final locking position by screwing them further with respect to each other by means of the threads 14 and 25. At the same time, the slide ring 30 resting against the end 15 of the first sleeve part 10 compresses the friction-locking sleeve 40 arranged in the second sleeve part 20 against the shoulder 24, whereby the friction-locking sleeve compresses axially as shown in Figure 5. At the same time, the wall thickness of the friction-locking sleeve 40 tends to increase, which means that a friction-locking attachment is formed between its inner wall 41 and the outer wall 3. 1 of the inner tube 3. This attachment locks the inner tube 3 tightly into the desired position with respect to the outer tube 2.

The inner tube 3 must obviously extend sufficiently far past the friction-locking sleeve 40, preferably sufficiently deep inside the outer tube 2, to prevent the pole 1 from breaking or collapsing at the joint or otherwise breaking in a similar manner.

To obtain a sufficient attachment area, the axial length of the friction-locking sleeve 40 in rest position is preferably greater than its diameter. The length of

the friction-locking sleeve 40 changes by more than 15%, however preferably by more than 25%, between the friction-locking attachment and the rest position.

This change in length ensures that the friction-locking sleeve 40 will tend to expand sufficiently and effect a high surface pressure against the outer surface 3.1 of the inner tube 3 to achieve sufficiently tight friction-locking attachment.

The diameter of the tube 1 changes in such a way that it is conical in the axial direction. One or more of the separate tube parts may also be slightly conical.

Thus also the dimensions of both of the sleeve joints of the tube 1, such as the diameters of the threads 14 and 25 and the diameter of the friction-locking sleeve 40, vary in accordance with the diameter of the pole 1.