Such a shaft is protected by a tube which is mounted on the rotating parts such that the driver cannot make contact with the rotating parts. The problem with these shafts is that the cover extending over the universal joints must normally take a wide form in order to enable the angular displacement of the joint. These large covers leave much clearance, whereby there is still a hazard for the user because he can still make unintentional contact with the rotating parts.

The invention has for its object to obv-ate these drawbacks, particularly in wide-angle joints, and provides for this purpose a coupling shaft which is distinguished in that the cover is formed from two shell-like parts, wherein the mutually opposite edges of the covers are provided with releasable coupling elements, and wherein a flexible sleeve is carried by one of the shell-like parts, which sleeve extends over the bearing ring of the protective tube and extends as far as the outer surface thereof.

Owing to the divided cover, the shells of which can be separated by means of releasable coupling elements, the joint remains accessible for maintenance purposes

but the universal joint or wide-angle joint; ully protected in the closed position.

This divided embodiment also makes it possible to fixedly mount the one shell-like part thereof on the driven or driving vehicle round the coupling shafts thereof, so that full protection is then also ensured.

The coupling means are preferably embodied in the form of a bayonet fitting which can be secured by means of a releasable snap member.

The invention further relates to a coupling shaft for transmitting a torque from the power take-off shaft of a driving implement, for instance an agricultural tractor, to the'input shaft of a driven implement, for instance an agricultural machine, wherein the shaft ends are each provided with at least one universal joint such as a cross-link, wherein the hollow and telescopically embodied shaft is protected by a telescopic tube of suitable material which is mounted on the shaft by means of a bearing ring arranged at each end and wherein a cover extends over the universal joint, which is characterized according to the invention in that a lubrication pipe extends through the hollow shaft, which pipe communicates close to one end with a transverse bore through the wall of the shaft closed by a lubricating nipple and on the other end connects to one or more transverse bores which debouch into the space between the telescopic parts thereof.

The telescopic parts of the coupling shaft can in this way be lubricated in simple manner.

The invention will be further elucidated hereinbelow in the figure description of two embodiments. In the drawing: figure 1 shows a standing cross-section of the coupling shaft according to the invention provided with a wide-angle joint, figure 2 shows a cross-section along the line II-I- in figure 1,

figure 3 shows a standing cross-section corresponding with the left-hand part in figure 1 of an embodiment variant of the safety cover, figure 4 is a perspective view of the embodiment of figure 1.

Designated with the numeral 1 in the figures is the coupling shaft which consists of a non-round inner tube 2 and a non-round outer tube 3 fitting therearound. The two parts are mutually slidable in lengthwise direction so that coupling shaft 1 is telescopic and can have different lengths.

The one and the other end of the inner tube are embodied with a part of the first cardan joint 4 which is provided with a coupling body 5 which then bears a second cardan joint 6. This joint is provided with a connecting bush 7 for mounting on a power take-off shaft of the driving respectively the driven implement on the other side.

The universal joint consisting of two cardan joints 4 and 6 forms a so-called wide-angle joint enabling a large angle of articulation between bush 7 and shaft i.

It is known to close the universal joints by means of covers and sleeves which connect onto a l-kewise telescopic protective tube 8, which also consists of an inner tube 9 and an outer tube 10. these tube parts are connected to an annular flange part 11 which acts as a slide bearing on the bush 12 of the inner cardan joints 4 of the coupling shaft.

Arranged according to the invention round the universal joint is a safety cover 13 which consists of two shell-like parts 14,15 which are provided on the coupling means 16 to enable forming of a spherical closed cover 13.

Each shell part 14,15 is mounted via a bearing 17 onto the body of universal joint 5 so that when the joint and the shaft 1 rotate the spherical cover 13 can remain stationary. Extending between cover 13 and

protective tube 8 is a flexible sleeve 18 which is likewise stationary when the coupling shaft rotates.

Figure 4 shows that the coupling means between shells 14,15 each consist of hammer-shaped elements16, the protruding portions of which interlock through a small angular displacement of the two shells, see 19, 20.

In order to prevent unintentional reverse rotation of the shells, the remaining gap on the other side of coupling elements 16 can be filled with a suitable shaped part 21 which is connected via a flexible strip 22 to one of the shell parts, here 15. In order to enable release of the cover shells the shaped part 21 must therefore first be removed, and remains hanging on flexible strip 22 to prevent loss. The cover shells can then be rotated back again a short distance and taken apart, so that the universal joint can be accessed for lubrication purposes or maintenance.

Figure 3 shows an embodiment wherein the left-hand shell part 15 of cover 13 is lengthened with a cylindrical part 25 which is extended as far as a cylindrical part 26 mounted on housing part 27 of the driven or driving implement, so that after mounting of coupling shaft 1, i. e. mounting of bush 7 on power take- off shaft 28, the joint can be wholly covered by mounting the right-hand shell part 14 against the fixed shell part. A complete covering of the universal joint is ensured in this way.

The invention further relates to a lubricating system for the hollow telescopic coupling shaft 1.

Extending through the hollow space of the inner tube is a lubrication pipe 30 which is connected at one side to a transverse bore into which is placed a lubricating nipple 31 which ends in lubrication pipe 30. The hollow space of the hollow shaft is closed at that position by a plug 32.

The other end, see on the right in figure 1, is received in a plug 32 and connects onto transverse bores which lead to the space between inner shaft 2 and outer shaft 3, see figure 2. The bores 33 thus provide the through-feed of lubricant from lubricating nipple 31 and lubrication pipe 30 to the space between the inner and outer shaft.

In order to prevent loss of lubricant the left-hand side of the space between the inner and outer shaft is closed by a ring 34, see on the left in figure 1, respectively a blind flange 35, see on the right in figure 1.

The invention is not limited to the above described embodiments.