The present invention relates to a post including two tubes, the respective mutually opposing end portions of which are united by a spring joint, comprising an elongate spring means extending inside the pipes and with longitudinal bias being anchored relative the tubes. Such posts are used as slalom posts, traffic and lamp posts etcetera.

The spring means is normally a coil spring. Although such a spring means serves its purpose well for heavy posts, where the spring joint seldom needs to come into action, it results in a rather complicated structure, which is accordingly expensive, inter alia, in respect of the spring mountings in both tubes.

In fields of use where the spring joint must come into action often, particularly with plastic posts of slender dimensions, e.g. slalom posts, it has been found that a coil spring is quite simply too strong, resulting in that the material in the posts in which the spring is mounted becoming fatigued, and finally results in the spring wrenching itself loose. In the French patent 2 044 032 there is proposed the use'of a rubber chord as spring means. At either end this chord has a head, which is inserted in a recess in an associated joint member. The joint members are kept urged ^" towards each other by the bias of the rubber chord, each member carrying a post tube.

With this known joint, neither the restricted transverse dimension of the chord nor the implementation of the joint members allow the application of sufficient bias for the resilience of the joint to be given enough stiffness. These known slalom posts have consequently been found to yield too much.

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The joint structure of the French patent is furthermore such as to negate the use of any kind of regulating mechanism for the bias.

The object of the present invention is to provide a spring joint for a post of the kind defined in the introduction, the embodiment of the joint being simple and cheap, even so allowing a large number of flexings at the joint without risking collapse of the joint structure. The structure shall also allow the selection of sufficiently large bias for the resilience of the joint to be very stiff as well as allowing the use of adjustment means for the bias.

In accordance with the invention this has been achieved by the post defined in the introduction being given the distinguishing features disclosed in the following claim 1. The invention will now be described in detail hereinafter, with reference to some embodiments depicted on the accompanying drawing, wherein Figure 1 is an axial section through a slalom post, Figure 2 illustrates a portion of a slalom post in axial section to clarify a modification, of the embodiment in Figure 1, Figure 3 is an axial section of a further embodiment of a slalom post and Figure 4 illustrates to a much enlarged scale a section IV of the embodiment in Figure 3 when the post is flexed at the joint.

In the embodiment of Figure 1 the joint includes a substantially rod-shaped core body 2 from polymeric material such as rubber, polyurethane etcetera. The body 2 is enclosed biassed or pretensioned in its longitudinal direction in two sleeves 4 made from steel or the like, the end surfaces 5 of these sleeves being pressed against each other by the bias. A tube 6, of hard plastics, aluminium etcetera is disposed for enclosing the sleeves 4. The core body 2 is fastened by rivets 10, 12 to said sleeves. Each tube 6 engages a shoulder 11 on the respective sleeve- 4.

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The joint may be assembled with bias in the core body 2 as follows. The lower sleeve 4 is brought over the core body 2 such that It assumes the position shown, and the core body is fixed in the sleeve by the lower rivet 10, or two crossing rivets. Thereupon the upper sleeve 4 is brought over the core body 2, and tensional stress is exercised on the core body 2 in its longitudinal direction by the lower sleeve 4 being suitably fixed and a tensional force in a direction from the sleeves 4 being applied to the projecting end of the body 2. While this tension is being applied the upper rivet 12, or two crossing rivets, are arranged through the upper end of the sleeve 4 ^" and the core body 2. When the tensional force is removed the body is thus axially pretensioned with the aid of rivets 10 and 12. Finally, the tubes 6 are put in place. A modification of the embodiment in Figure 1 is illustrated in Figure 2. Here the upper sleeve is made in two parts 14 and 16, which are in thread engagement 18 with each other. The sleeve part 14 is fixed against axial upwards movement of the upper end f the core body 2 by a pin 20, which only passes through the core body 2. The bias in the core body 2 may now be adjusted and even applied by screwing the sleeve 14 on sleeve 16 after the upper tube 6 has been slipped upwards. No corresponding rotation of the core body 2 will take place since the pin 20 does not pass through the sleeve 14. In the embodiment according to Figure 3 the core body 2 is surrounded at the joint by an upper joint sleeve 22 and a reinforcing sleeve 24. The tube 6 is slipped over both tubes 22 and 24. A rivet 26 passes through the reinforcing sleeve 24 and the tube 6 so that the core body 2 is kept fixed with respect to the latter.

A lower joint sleeve is made up from two sleeve parts 28 and 30, which are threaded to each other at 32. After pretensioning the core body 2, a rivet 34 is passed through sleeve part 30. The lower tube 6 is then slipped over the sleeve parts 28, 30. For adjusting the pretension the lower tube 6 is drawn downwardly to uncover the sleeve 30 for manipulation.

As more closely illustrated In Figure 4 the upper sleeve part 22 is terminated by a shoulder 36 surrounding a radially projecting flange 38 on the lower sleeve part 28. The shoulder 36 and flange 38 serve to locate sleeve parts 22 and 28 mutually. Figure 4 illustrates the situation when the joint comes into operation as a result of applying a lateral force to the portion of the post above the joint.

It will be understood that the bias of the core body 2 in the sleeves results in that their opposing end faces are always kept pressed against each other with a given force caused by the bias. The bias is selected such that the joint will flex when the post is subjected to forces from different directions, but will regain its straight configuration immediately afterwards. The spring movement is, of course, directly dependent on the magnitude of the bias or pretension.

Among the areas of use for the spring joint, in addition to slalom posts, traffic and lamp posts may be mentioned.