Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
2000-04-14
2001-11-20
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
Reexamination Certificate
active
06318238
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns the wobble drive of an axial piston machine. Such wobble drives involve a wobble or swash plate which drives via its front side at least one piston which is positioned parallel or even inclined to the axis of rotation of the wobble plate. The invention also particularly concerns high-pressure cleaning units in which such wobble drives are part of an axial piston pump.
BACKGROUND OF THE INVENTION
Known from EP-A 0242550 is a high-pressure cleaning unit in which a wobble body is mounted in a rotationally fixed manner on the drive shaft of an electric motor. Additionally provided is a wobble plate arranged at an incline to the drive shaft, the front side of the wobble plate driving several pistons positioned parallel to the axis of rotation of the drive shaft. An axial-groove ball bearing is positioned between the wobble body and the wobble plate. The axial-groove ball bearing is provided with ball grooves and balls rolling in the grooves. The increasing demands on the performance of such high-pressure cleaning units require an increase in the rotary speed of the drive shaft. At elevated rotary drive speeds, substantially increased centrifugal forces act on the balls of known axial-groove ball bearings so that there is a danger that the load distribution on the races will shift from one of uniform loading to a loading of the outer edge areas of the ball grooves. The associated wear and possibly reduced rollability of the balls is undesired. In addition, there is the danger that as a result of the increased edge loading, the races will become deformed such that the balls will be slung radially from the race path.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to further develop the wobble drive of an axial piston machine according to the introductory clause of claim
1
such that one insures that the rolling bodies are securely held in their race paths even at elevated rotary drive speeds. According to the present invention, this problem is solved as a result of the fact that the wobble plate is provided with a rim overlapping the wobble body, the rolling bodies being positioned between the rim and the wobble body. The rolling bodies are unable to the leave their race path because the rim securely holds them therein. Since wobble plates are preferably lightweight in order to reduce dynamic forces, they are usually made from thin sheet metal. The rim provided by the present invention thus fulfills a further function in addition to that of securing the balls: the wobble plate is favorably strengthened in its rigidity by the angled rim.
In the case of the ball bearing, one is preferably dealing with an angular-contact ball bearing with balls rolling in its races. The load angle is set such that the balls are simply pressed more intensely against the races even at elevated rotary drive speeds. If one is dealing with a hollow cylindrical wobble body, for example, of thin sheet metal, the end facing the wobble plate can be readily reshaped to form the ball race. This can be accomplished, for example, by stamping or using a deep-drawing process.
Preferably, the rim is joined by a corner section as one piece with the wobble plate, the corner section incorporating the ball race. In this especially favorably embodiment, no separate production step is necessary for producing the ball race.
At the end facing away from the wobble plate, the wobble body exhibits an inwardly directed radial flange forming a receptacle for a drive shaft. The radial flange advantageously increases the rigidity of the wobble body.
For reliable radial and axial support of the drive shaft, the wobble drive is provided with two angular-contact ball bearings, one being positioned between the wobble plate and the wobble body and the other between the wobble body and a housing, the bearing axis of the second angular-contact ball bearing being coaxial with the axis of rotation of the drive shaft. The end of the drive shaft facing the wobble drive is accordingly securely supported radially against the housing via the wobble body and the second angular-contact ball bearing. If both angular-contact ball bearings are incorporated in an X-arrangement in the wobble drive, axial supporting forces will not be transferred to the drive shaft, but via the second angular-contact ball bearing to the housing. In this case, it is possible to form a ball race at each end of the wobble body. This preferably occurs by reshaping such as can be accomplished, for example, by stamping or using the deep-drawing process.
Both the wobble body as well as the wobble plate of the wobble drive of the present invention are especially suited to manufacture in a non-machining process, especially a deep-drawing process, such that thin sheet metal can be employed.
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Baumann Boris
Becker Klaus
Braun Berthold
Nathan Robert
Alfred Karcher GmbH & Co.
Ryznic John E.
Volpe and Koenig P.C.
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