Expansible chamber devices – With guide or seal on cylinder end portion for piston or... – Non-metallic seal means between piston or member and end...
Patent
1997-01-13
1998-05-05
Denion, Thomas E.
Expansible chamber devices
With guide or seal on cylinder end portion for piston or...
Non-metallic seal means between piston or member and end...
921701, 417454, F16J 1518
Patent
active
057461112
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention relates to a piston pump which is intended as a return pump for a hydraulic unit of an anti-lock brake system and/or as a feed pump of a traction control system for motor vehicles.
Such a piston pump is known from German Patent Disclosure DE 41 33 391 A1. In the known piston pump, the relative motion between the piston and cylinder can cause running scratches, that is, roughened places or scoring, to develop on the circumference of a piston or a cylinder bore during use of the piston pump. These scratches can damage a ring seal that seals off the piston from the cylinder, if they come into contact with the piston in its reciprocating motion.
ADVANTAGES OF THE INVENTION
In the piston pump of the invention, the piston is axially guided in the cylinder bore outside the region that comes into contact with the ring seal during piston reciprocation. In the region in which the ring seal comes into contact with the piston circumference or the cylinder bore, the piston and cylinder bore, or a filler piece inserted into the cylinder bore, do not touch one another. A sealing face on the piston or cylinder, along which the ring seal slides during the reciprocation of the piston, is separate from a piston guide. This prevents the possibility of scratches developing in a region that comes into contact with the ring seal. This is true regardless of whether the ring seal moves along with the piston, or is inserted in stationary fashion in the cylinder bore.
The invention has the advantage that the ring seal, during the reciprocation of the piston, always slides along only a sliding and sealing face that the ring seal sweeps over; consequently this face maintains its original, low-friction machined state during the entire service life of the piston pump. The ring seal is not significantly worn down and is not damaged; good sealing between the piston and the cylinder bore is assured for a virtually unlimited time.
The invention relate to further aspects and advantageous features of the piston pump of the invention.
BRIEF DESCRIPTION OF THE DRAWING
The invention is described below in further detail in terms of an exemplary embodiment shown in the drawing. The sole FIGURE of the drawing shows a longitudinal section through a piston pump of the invention.
The piston pump 10 according to the invention, shown in the drawing, is accommodated in a hydraulic block 12, which is provided for hydraulic control of an anti-lock system and a traction control system of a motor vehicle brake system. The only portion of the hydraulic block 12 shown is the region that receives the piston pump 10. It forms a cylinder bore 16 for the piston pump 10 of the invention.
A piston 14 is guided displaceably in a longitudinal direction in the cylinder bore 16. In the exemplary embodiment shown, a roller of a needle bearing, which is hardened, ground and polished, is used as the piston 14. This piston 14 is quite economical, since it is a mass-produced part. Because of its surface quality, it assures a low-friction, very good sealing cylindrical face.
One end of the piston 14 protrudes into an eccentric tang chamber 18 in the hydraulic block 12, where with one end face 20 the face end meets a circumferential face 22 of an eccentric tang 24, which is seated integrally, with an eccentricity, on a face end of an eccentric tang shaft 26, which is disposed at right angles to the piston 14 and is supported rotatably in the hydraulic block 12. By driving the eccentric tang shaft 26 to rotate, by means of an electric motor not visible in the drawing, the piston 14 can be driven via the eccentric tang 24 to reciprocate in the cylinder bore 16.
A helical compression spring 28, as the piston restoring spring, engages an end face 30 of the piston 14 remote from the eccentric tang 24 and keeps the piston in contact with the circumferential face 22 of the eccentric tang 24. The piston restoring spring 28 is braced against a closure cap 32, which is inserted into a mouth of the cylinder bore 16, on a side remote from the eccentric tang
REFERENCES:
patent: 2330781 (1943-09-01), Langmyhr et al.
patent: 3916771 (1975-11-01), Nendzig et al.
patent: 4417857 (1983-11-01), Sudbeck
patent: 4527957 (1985-07-01), Dettinger et al.
patent: 4716924 (1988-01-01), Pacht
patent: 4768933 (1988-09-01), Stachowiak
Alaze Norbert
Mueller Erwin
Ott Harald
Schmidt Klaus
Wetzel Gerhard
Denion Thomas E.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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