Pumps – Expansible chamber type – Valved piston
Patent
1998-05-04
2000-03-28
Freay, Charles G.
Pumps
Expansible chamber type
Valved piston
13754319, F04B 5312
Patent
active
060423501
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a piston pump for a hydraulic system including a cylindrical bore, a pump piston adapted to reciprocate in the cylindrical bore and bounding as a movable wall a working chamber, and an inlet valve which closes in the way of a non-return valve and has a closure member and a valve seat, the closure member being preloaded by a valve spring which is arranged in a spring housing that cooperates with the pump piston, on the one hand, and with a compression spring preloading the pump piston, on the other hand.
German patent application No. 42 42 420 discloses a pump of this type. The disadvantage of the prior art pump is that it comprises many individual parts, which refers especially to the pump piston. This renders the assembly difficult because mainly the valve spring urges the individual parts apart.
Therefore, an object of the present invention is to further improve upon a generic piston pump so that its assembly is facilitated and its manufacture is thus reduced in costs. An additional objective is to improve the operation of the piston pump.
SUMMARY OF THE INVENTION
This object is achieved by a pump piston with a spring housing attached to one end of the pump piston and with one end of a compression spring attached to the spring housing, wherein the end of the pump piston attached to the spring housing includes a joint chamfer which passes over into a sharp recess accomodating elements of the spring housing.
The pump piston of the pump according to the present invention can be preassembled most easily, and the inlet valve (preferably comprised of a spring housing, a closure member and a valve spring) is directly connected to the pump piston. A complete construction unit is thereby achieved which can be tested, stored and mounted into the piston pump in one part, without splitting into single parts or requiring to be supported in special mounting devices. Further, the compression spring which biasses the pump piston is secured to the piston or to the spring housing. An additional advantage is thereby achieved because the complete unit composed of the compression spring, the inlet valve and the piston can be drawn at the spring out of the housing. The connection of the individual functional elements takes place in the assembled condition by the functional elements themselves, and in first place by the pump piston, the spring housing and the compression spring which is used as a piston resetting spring. Preferably, at least one of these connections is frictional or operative. For example, the compression spring in its area connected to the spring retainer cup may be radially undersized with respect to the abutment surface on the spring retainer cup. A corresponding frictional or operative connection may also be provided between the spring retainer cup and the piston.
In order to establish a positive connection as an alternative or in addition, form-lock elements may be provided which snap into an undercut in the pump piston. To this end, the spring housing is manufactured so as to be radially undersized, and the form-lock elements may be radially outwardly or inwardly stamped projections which permit an engagement with the pump piston and the end of the compression spring.
In an aspect of the present invention, the spring housing includes web elements which carry the form-lock elements at their free ends. The web elements have a radially resilient, yielding design, thereby preventing plastic deformations when the spring housing is mounted on the pump piston. The free spaces between the web elements have correspondingly large dimensions.
It is ensured by a special surface treatment that the inwardly disposed form-lock elements will not wear off during the assembly and that frictional resistance is minimized. Favorably, the surface of the spring housing is hardened, however, in a way that the core ductility is not changed. This avoids a possible rupture of the web elements.
Advantageously, in a positive engagement between the spring housing and th
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patent: 4365648 (1982-12-01), Grothe
patent: 5823639 (1998-10-01), Zinnkann et al.
patent: 5915927 (1999-06-01), Kuromitsu
Evora Robert Z.
Freay Charles G.
ITT Manufacturing Enterprises Inc.
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