The invention relates to a length-adjustable shaft, comprising an outer and inner axial part which cooperate with one another in the manner of a telescope. Such shafts are cardan shafts which are used in rolling mills for driving rollers. Shafts of this kind are also used in the construction of vehicles, e.g. in wheelsets of rail vehicles (see SE 0702642). The invention is based on this state of the art.
The shaft comprises two parts, which are an outer sleeve-like axial part and an inner axial part. The inner axial part is displaceable in a telescopic fashion within the outer axial part in the axial direction in a limited way. The length of the entire shaft can thus be changed within certain limits.
A bearing is provided between the two axial parts. It can comprise three or more rolling bearings for example. The bearings are arranged with their longitudinal axis perpendicularly in relation to the rotational axis of the roller. Each bearing is carried by an inner axial part and engages in a longitudinal groove of the sleeve-like outer axial part. The bearings are lubricated with a lubricant, e.g. with oil. The inner axial part has an expansion chamber and further a face wall which immerses into the space which is enclosed by the sleeve-like axial outer part.
A vent opening is provided in the face wall. It produces a conductive connection between the two mentioned cavities. When the shaft is shortened by pushing the inner axial part into the outer axial part, the air is displaced into the cavity. The air is compressed and thus exerts a damping effect.
One problem is that lubricant will deposit over time in the vent opening and will seal the opening. This is caused by the fact that during operation lubricant vapors will accumulate in the space enclosed by the outer axial part, which vapors will deposit in the vent opening.
The invention is based on the object of providing a length-adjustable shaft according to the preamble of claim 1 in such a way that the vent opening will not get blocked at all or will remain open for a longer period of time than previously.
This object is achieved by the features of claim 1.
Accordingly, the vent opening comprises at least one bore, the longitudinal axis of which extends eccentrically in relation to the rotational axis of the shaft or is offset in relation to the same in the radial direction. The longitudinal axis of the bore will generally extend parallel to the rotational axis of the shaft.
This leads to the following result during operation of the shaft:
Lubricant will still deposit in the bore from the air laden with the lubricant mist. As a result of the eccentricity of the longitudinal axis of the bore in relation to the rotational axis of the shaft, the lubricant will only deposit in the radially outer region of the bore, so that the radial inner region of the bore will remain free. No closed lubricant ring will thus be produced in the bore. Rather, the deposit of lubricant is formed like the crescent of a moon, when seen in a sectional view perpendicular to the longitudinal axis of the bore. It has been seen that the deposited lubricant will flow in the embodiment in accordance with the invention from the bore into the cavity of the inner axial part where it cannot cause any damage.
Instead of a single bore it is also possible to provide two or more bores which are grouped about the rotational axis of the shaft.
The state of the art and the invention are now explained in closer detail by reference to the drawings, wherein the following is shown in detail:
The wheelset for a rail vehicle as shown in
A universal joint 6 is provided before each wheel 2, 3. The shaft 1 comprises an outer axial part 7 and an inner axial part 8. The axial part 7 is sleeve-like. It rests on the inner axial part 8 via three bearings. The three bearings (tripods) are shown in the sectional view of
The three rolling bearings 10 thus roll off in the longitudinal grooves during a telescopic movement of the outer and inner axial part 7, 8.
The shaft comprises the outer axial part 7 and the inner axial part 8. A universal joint 6 each is disposed at the end of the shaft.
The inner axial part 8 protrudes to a substantial part into the space enclosed by the outer axial part 7, so that only a residual cavity 7.1 remains. The inner axial part 8 encloses a buffer space 8.1. Cavity 7.1 and buffer space 8.1 are in conductive connection with one another, namely through a vent opening 11. A bore insert 12 is screwed into the same.
One of the three journals 9 with the associated rolling bearing 10 can be seen, which rolling bearing is lubricated with oil.
Cavity 7.1 contains a mixture of air and lubricant mist.
The arrangement of the bore insert 12 can be seen in
Lubricant deposits on the surface of the bores 12.2, 12.3 and 12.4 from the mentioned lubricant mist during operation of shaft 1. Since the two axial bores 12.3 and 12.4 are offset against the rotational axis 13, the lubricant deposits only in the radially outer surface area of the bores 12.3 and 12.4 as a result of centrifugal force. The gradual blocking of the bores is prevented or at least delayed.
The two axial bores 12.3, 12.4 can be inclined in relation to the rotational axis 13 of shaft 1, in the sense that they move away from the rotational axis 13 towards the buffer space 8.1. This promotes the flowing off of deposited lubricant towards the buffer space 8.1.
Number | Date | Country | Kind |
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10 2008 007 153.6 | Jan 2008 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2009/000099 | 1/10/2009 | WO | 00 | 9/28/2010 |