Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Patent
1989-07-24
1991-08-13
Look, Edward K.
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
91499, 92248, F01B 300
Patent
active
050386735
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a high-pressure cleaning apparatus with a wobble plate piston pump.
The pistons of such wobble plate piston pumps undergo very high accelerations in the axial direction and, therefore, the high acceleration forces occurring with the use of conventional steel pistons result in a high degree of wear in the region of contact between piston and wobble plate. In a known wobble plate piston pump, the piston is of two-piece design, with the first and smaller part of the piston being made of ceramic and extending into the pump chamber, and the second and larger part of the piston being made of metal and being in contact with the wobble plate (EP-A No. 0 149 219). Owing to this design, very large acceleration forces also occur with these pistons.
The object of the invention is to so design a wobble plate piston pump, in particular, for a high-pressure cleaning apparatus that the acceleration forces are reduced and, at the same time, the degree of wear in the region of contact remains minima.
This object is achieved in accordance with the invention in a wobble plate piston pump of the kind described at the beginning by the characterizing features of patent claim 1.
Owing to the entire piston being made of ceramic, it is possible to manufacture pistons with a low mass, which keeps the acceleration forces low. In spite of this, the wear in the region of contact can be reduced by suitable selection of the metallic material of the contact element arranged between piston and wobble plate. More particularly, the very hard ceramic material can thereby be prevented from rubbing against the wobble plate.
The cap-shaped contact element may have a central spacer element which is supported on the front face of the piston so that the remaining cap regions are spaced from the front face of the piston. These cap regions which are not in contact with the front face are then elastically deformable to a slight extent so that hard knocks occurring during the rapid pressure build-up when the valves open and close can be compensated.
It is advantageous to secure the contact element against rotation about the longitudinal axis of the piston by positive engagement in the front face or the skirt of the piston. Wear in the region of contact between contact element and piston is thereby avoided.
The disc-shaped contact element may have a central shaft which penetrates a central blind hole in the piston.
In a particularly preferred embodiment, provision is made for the piston to have at its end near the wobble plate a circumferential groove in which the contact element and/or a supporting element is held for a spring which presses the piston against the wobble plate. This circumferential groove enables positive fixing of the above-mentioned parts in the axial direction without, for example, any necessity for screw or adhesive connections. In this case, it is also particularly advantageous that the machining of the piston is considerably simplified. For example, the groove may be made in a simple cutting operation prior to the firing. Centerless and, consequently, low-cost grinding of the piston itself is carried out subsequently. Thereupon the machining of the piston itself is already completed and it is unnecessary for the piston itself to be further modified in addition for the connection of metal caps, etc. It is, of course, also possible for grinding of the circumferential groove into the piston to be carried out after the firing.
An expedient embodiment is obtained by the contact element being pressed against the front face of the piston by a holding element surrounding the piston end and by the holding element engaging the circumferential groove in order to axially fix it on the piston. A two-piece design is thereby obtained and by using a separate holding element it is possible to connect different contact elements with one and the same piston.
It is particularly advantageous for the contact element, the supporting element or the holding element to cover the circumferential groove on the outside and for
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Alfred Karcher GmbH & Co.
Lipsitz Barry R.
Look Edward K.
Verdier Christopher M.
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