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A pneumatically operated hydraulic pump includes a cylinder housing accommodating a main piston to subdivide the housing interior in two working chambers. The main piston is connected to a hydraulic piston for joint reciprocation so that the hydraulic piston can carry out a suction stroke when the m

A pneumatically operated hydraulic pump includes a cylinder housing accommodating a main piston to subdivide the housing interior in two working chambers. The main piston is connected to a hydraulic piston for joint reciprocation so that the hydraulic piston can carry out a suction stroke when the main piston moves to one end position and a pressure stroke when the main piston moves to the other end position. Arranged laterally to the cylinder housing is a control mechanism for regulating a flow of working fluid alternately to the working chambers. The control mechanism includes a plastic valve casing for accommodating a control piston having opposite end faces of different size to define different effective areas and thereby realize reciprocation of the control piston by the working fluid. A slide shoe is guided in the valve casing for conjoint movement with the control piston. A displacement of the main piston into the two end positions actuates respective pilot valves which regulate the reciprocation of the control piston and the slide shoe to thereby move the main piston between the end positions which discharging working fluid via the deflection zone in the slide shoe to the atmosphere.

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1. A pneumatically operated hydraulic pump; comprising:a cylinder housing made of plastic material, said housing defining an interior and having opposite ends; a valve bottom formed integrally with the housing at one end thereof; an end cap made of plastic material detachably mounted to the housing

1. A pneumatically operated hydraulic pump; comprising:a cylinder housing made of plastic material, said housing defining an interior and having opposite ends; a valve bottom formed integrally with the housing at one end thereof; an end cap made of plastic material detachably mounted to the housing at the other end thereof; a main piston accommodated in the housing to subdivide the interior of the housing in two working chambers, said piston being movable between two end positions in response to admission of a working fluid and having attached thereon a first hydraulic piston, guidingly received in the end cap, for joint reciprocation with the main piston so that the hydraulic piston is destined to carry out a suction stroke when the main piston moves to one of the end positions, and a pressure stroke when the main piston moves to the other one of the end positions; a control means for regulating a flow of working fluid alternately to the working chambers, said control means including a valve casing of plastic material which is mounted laterally to the valve bottom and has a chamber which contains working fluid under pressure, a solid control piston accommodated in the valve casing and having axial end faces which are different in size so as to define different effective areas and thereby permit reciprocation of the control piston by the working fluid, and a slide shoe guided in the chamber of the valve casing and having formed interiorly therein a deflection zone for conjoint movement with the control piston to thereby open a flow of working fluid to one of the working chambers of the main piston for movement of the main piston to one of the end positions and to open a flow of working fluid to the other one of the working chambers for movement of the main piston to the other one of the end positions; and a valve assembly, actuated by the main piston during displacement thereof into the two end positions, for regulating a flow of working fluid to the control mechanism to effect reciprocation of the control piston and the slide shoe, so that the main piston moves between the end positions while working fluid is discharged via the deflection zone in the slide shoe to the atmosphere, said valve assembly including a first pilot valve disposed in a stepped bore of the valve bottom, and a second pilot valve disposed in a stepped bore of the end cap.