Pumps – Three or more cylinders arranged in parallel – radial – or...
Reexamination Certificate
2000-02-23
2001-09-11
Freay, Charles G. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
C091S499000
Reexamination Certificate
active
06287086
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydraulic pumps, and in particular to in-line axial piston pumps.
Conventional in-line axial piston pumps have a plurality of pistons in multiple bores of a single piece cylinder barrel. The cylinder barrel is keyed to the drive shaft and is rotated by a prime mover, such as an electric motor. The cylinder barrel and the pistons are parallel to the drive shaft. As the cylinder barrel rotates within the pump housing, the pistons follow an inclined surface of a swash plate thereby reciprocating in their bores. The reciprocal motion of the pistons produces a pumping action.
The swash plate typically is a steel ring that is held at an acute angle with respect to the axis of the drive shaft. During one-half of the shaft rotation, each piston is pulled from its bore which draws fluid into that bore. Upon reaching the maximum extended position, the piston starts traveling along a portion of the inclined swash plate which pushes the piston into the bore thereby forcing the fluid to flow out of the pump.
The displacement of a given pump is determined by the number of pistons, each piston's diameter and the length of the stroke. The steeper the angle of the swash plate, the longer the piston's stroke. In a variable displacement pump, the angle of the swash plate can be changed dynamically to alter the stroke and thus the pump displacement.
Pumps of this design are well known and are commonly used in aircraft hydraulic systems. In aircraft applications, the size and weight of the pump are critical. Therefore, any improvement which reduces these factors will have benefit in aircraft usage.
SUMMARY OF THE INVENTION
A hydraulic pump according to the present invention includes a housing that has an inner chamber. A cylinder block with a plurality of piston bores is supported within the inner chamber for rotation about a longitudinal axis. During that rotation each piston bore alternately communicates with a fluid inlet and a fluid outlet in the housing. The cylinder block comprises a spherically curved element and a coupling for a drive member that produces rotation of the cylinder block. A bearing rotationally couples the cylinder block to the housing.
A socket is rotationally coupled to the housing, preferably by another bearing. The socket has an aperture with a surface that mates with the spherically curved element of the cylinder block. A drive surface, provided on the socket, is non-orthogonal to the longitudinal axis. A different one of a plurality of pistons is slidably located within each piston bore and has a head which engages the drive surface of the socket.
The drive member produces rotation of the cylinder block about the longitudinal axis. The socket rotates about an axis that is non-coaxial with the longitudinal axis. Thus as the cylinder block rotates, the pistons reciprocate into and out of the bores providing pumping action. As that rotational movement occurs the socket wobbles across the surface of the partially spherical element of the cylinder block.
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Shigley, Joseph Edward; Mechanical Engineering Design; 1977; McGraw-Hill (New York); 3rd Ed.; p. 322.
Eaton Corporation
Freay Charles G.
Haas George E.
Quarles & Brady LLP
Torrente David J.
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