Multi-piston hydraulic pump for a free piston engine

The invention relates to a multi-piston hydraulic pump for a free-piston engine, comprising two engine pistons (2) mounted on a common piston rod (1) which is also fitted with pin-shaped pistons (5a, 5b) of the hydraulic pump at a radial distance from the piston rod (1). Mounting blocks (6a,6b) for the hydralic punp pistos (5a, 5b) extend from the engine piston rod (1) crosswise relative to each other at an axial distance from each other. The hydraulic pistons (5a and 5b) fastened to different mounting blocks (6 and 6b and 6b) are located for the most part side by side over the same section of the axial length of the engine piston rod and the free ends thereof point in opposite directions.

The present invention relates to a multi-piston hydraulic pump for a
 free-piston engine, comprising two engine pistons mounted on a common
 piston rod which is also fitted with pin-shaped pistons of the hydraulic
 pump at a radial distance from the piston rod, and mounting blocks for the
 hydraulic pump pistons extend from the engine piston rod at a distance
 from each other and the free ends of the hydraulic pistons point in
 opposite directions.
 This type of free-piston engine with its multi-piston hydraulic pump is
 prior known from the Patent publication U.S. Pat. No. 4,097,198. An object
 of the invention is to improve this prior known mechanism in view of
 optimizing the space utilization of a hydraulic pump and, thus, for
 reducing the overall length of an engine.
 This object is achieved by the invention on the basis of the characterizing
 features set forth in the appended claim 1.
 The invention is further capable of achieving the additional advantage that
 the mounting blocks of hydraulic pump pistons can be used as pistons for
 the scavenger pumps of engine cylinders.

A free-piston engine includes two engine pistons 2 mounted on the opposite
 ends of a piston rod 1. The piston rod 1 has its mid-section provided with
 axially spaced scavenger pump pistons 6a and 6b, which are T-shaped blocks
 whose T-stems are parallel and against each other and T-heads are
 crosswise, in the present case at an angle of 90.degree. relative to each
 other. Pin-shaped hydraulic pump pistons 5a are fastened to the mounting
 block 6a. Respectively, two hydraulic pump pistons 5b are fastened to the
 mounting block 6b. The hydraulic pistons 5a and 5b fastened to different
 mounting blocks 6a and 6b are located for the most part side by side over
 the same section of the axial length of the engine piston rod 1 and the
 free ends of pistons 5a point in the direction opposite to that of the
 free ends of pistons 5b. By virtue of this arrangement, it is possible to
 employ a multi-piston hydraulic pump having a length which is as short as
 possible. Naturally, the number of pistons 5a and 5b may vary.
 The mounting blocks 6a and 6b of the hydraulic pistons can also be used for
 another purpose. They can also serve as pistons for the scavenger pumps of
 engine cylinders. In this case, the scavenger pump pistons constituted by
 blocks 6a and 6b operate in cylinder spaces 7a and 7b made in the engine
 body, said spaces being connected by way of scavenging ducts 8a and 8b to
 respective engine cylinders.
 The piston rod 1 extends through holes bored centrally in blocks 6a and 6b
 and the blocks 6a and 6b are fastened to the piston rod 1 by means of
 crosswise fastening pins 9. The pin pistons 5a and 5b are secured to
 blocks 6a and 6b by means of crosswise fastening pins 10. Receiving holes
 11 for the bases of pin pistons 5a and 5b are made loose and filled with
 resilient packings, whereby the pin pistons 5a and 5b are able to find
 their way into pump cylinders 5 without setting unreasonably strict
 tolerances for manufacturing.