Expansible chamber devices – Piston – With separable means for pivotally mounting connecting rod...
Patent
1996-12-23
1998-07-28
Denion, Thomas E.
Expansible chamber devices
Piston
With separable means for pivotally mounting connecting rod...
92248, 92128, 92 71, 74 60, 403140, F16J 114
Patent
active
057849510
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A piston with a slide shoe for a hydraulic piston engine, as well as a method of manufacturing same.
The present invention relates to a piston with a slide shoe for a hydraulic piston engine, where the slide shoe comprises a ball socket, and where the piston is arranged with a corresponding ball head, whereby these are connected in a ball-and-socket joint.
Hydraulic piston engines with such pistons with slide shoes may function for example according to the axial piston or radial piston principle. In both cases are the pistons placed slidingly in a cylinder block, and the slide shoe is held in contact against a guide surface in such a manner that the piston is moved in the cylinder block as a result of a relative movement of the cylinder block in relation to the guide surface, whereby the slide shoe slides across the guide surface.
In order to reduce friction between among other things the piston and the slide shoe, several constructions are known where one of the contact surfaces in the ball-and-socket joint connecting the piston and the slide shoe is made at least partially of a friction-reducing material.
U.S. Pat. No. 5,601,009 describes a piston with a slide shoe of the type described in the introduction, where the piston is provided with a ball head, which is connected to a slide shoe, on which slide shoe a ball socket is moulded on, so that together the ball socket and the ball head form the ball-and-socket joint between the piston and the slide shoe. Here the ball socket is moulded together with a second surface on the slide shoe, which forms the sliding surface of the slide shoe in relation to the guide surface, whereby an effective fixation of both the ball socket and the slide surface on the slide shoe is obtained.
SUMMARY OF THE INVENTION
The present invention is based on the preceding technology according to U.S. Pat. No. 5,601,009, and is a further development of same. The invention is particular by the fact that the ball head on the piston is constituted at least partially of a spherical surface of a friction-reducing material which is moulded on and held in relation to the piston.
By this method, as a consequence of the subsequent shrinking of the moulded-on, friction reducing material, a possibility is obtained of good fixation of the ball head on the piston, while at the same time a gap can be created between the ball socket and the ball head, which is not immediately obtainable by the technology according to U.S. Pat. No. 5,601,009, where, due to thermal shrinking of the material, the ball socket moulded on to the slide shoe will tend to dissociate itself from the slide socket and press against the ball head on the piston, which in the worst case may cause fracture of the moulded-on layer on the slide shoe during operation, because the moulded-on layer is constantly deformed in the areas abutting on the ball head.
In addition, the present invention makes it simpler to dimension the gap established between the moulded-on ball head on the piston and the slide socket. Among other things, this is important when low-viscosity pressure media such as water are used, where a relatively large gap is often required to obtain a satisfactory lubricating and cooling effect on the ball-and-socket joint.
The shrinkage of the moulded-on ball head on the piston is uniform over the whole spherical surface, because the moulded-on ball head can have a uniform layer thickness on the part of the ball formed on the piston.
However, according to the present invention it is possible to mould the ball head on so that it is secured in relation to the piston in or on a simple recess or similar, which is arranged on the piston, which can render production of the piston cheaper.
Furthermore, it is advantageous to fix the moulded on ball head in relation to the piston by geometrical locking.
The slide shoe is provided with moulded-on surfaces of friction reducing material on the sliding surface of the slide shoe against the guide surface and against a pressure unit holding the slide shoe
REFERENCES:
patent: 3261216 (1966-07-01), Woolfenoen
patent: 3874275 (1975-04-01), Cunningham et al.
patent: 4043255 (1977-08-01), Cunningham
patent: 4610195 (1986-09-01), Cunningham et al.
patent: 4938121 (1990-07-01), Melchior
patent: 5392693 (1995-02-01), Engel et al.
patent: 5490446 (1996-02-01), Engel
patent: 5601009 (1997-02-01), Jepsen et al.
Danfoss A/S
Denion Thomas E.
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