Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Patent
1994-11-28
1996-04-02
Bertsch, Richard A.
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
417273, 91491, F04B 106
Patent
active
055035353
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to positive displacement rotary radial piston hydraulic machines, and is particularly directed at a more economical and efficient form of housing structure for such machines. In the radial piston type of hydraulic machine, a cylinder-barrel is mounted for rotation on a ported pintle-valve, and is provided with a number of generally radial cylinders. Each cylinder contains a piston and each piston engages a slipper which contacts a surrounding annular track-ring. The arcuate-ports in the pintle-valve are connected to fluid inlet and outlet passageways in the housing and thus rotary movement of the cylinder-barrel is accompanied by radial displacement of the pistons and corresponding displacement of fluid through these passageways. The control-system acts in determining the degree of eccentricity required between the track-ring and pintle-valve, in order to supply the desired rate of fluid to a hydraulic circuit.
DESCRIPTION OF THE PRIOR ART
Fixed-displacement gear-pumps currently account for about 80% of all hydrostatic pump sales, with the more versatile, but more expensive variable-displacement type of piston pump taking most of the balance.
Despite widespread agreement that variable-displacement hydraulic systems provide significant efficiency advantages over fixed-displacement ones, no existing variable-displacement piston pump design is capable of competing with fixed-displacement pumps on cost.
In part, this is due to the many quite complex internal components required in a variable-displacement piston pump, such as the pistons and the cylinder barrel. Nowadays with modern CNC production machinery and using inexpensive processes such as sintered powder-metallurgy, these components are no-longer significantly more expensive to produce than the intermeshing spur gears and associated floating bearings of a gear pump.
However, the bulk of the differences in cost is largely due to the complex and high-precision housing structures which have been required throughout the 100 year history of variable-displacement piston pumps. Typically, the housing structure comprises two or more broadly cylindrical or circular elements.
U.S. Pat. No. 3,750,533 shows an example of such a housing for a piston machine, and where each housing element is provided with a central aperture in order to support the drive-shaft and pintle-valve respectively. However, the multitude of machining operations required to produce all the necessary features in the housing amounts towards a significant proportion of the total manufacturing cost of the pump.
Alternatively, the housing structure for a piston machine may comprise four members as shown in U.S. Pat. No. 3,200,762, where two of such members are of part cylindrical form which engage with two circular housing members to achieve the complete housing structure for the machine. However, this form of more elaborate housing structure still requires a multitude of machining operations in order to be effective.
By contrast with such piston devices as mentioned above, the housing structure for a gear pump is comparatively simple requiring much less machining.
Therefore, what is required is an inexpensive housing structure for variable-displacement piston pumps which is as simple and efficient to produce as the typical housing structure presently used for gear pumps.
SUMMARY OF THE INVENTION
From one aspect the invention consists in a housing for a radial piston hydrostatic machine having a drive-shaft, comprising two shells connectable together along a parting plane in which the rotating axis of the drive-shaft lies and wherein the interior of each said shell is formed with a number of generally semi-circular formations and/or recesses, respective pairs of said formations and/or recesses form apertures or pockets to receive and/or support internal elements of said hydrostatic machine.
It is one feature of the invention to support the drive-shaft in a bearing or bearings which are held between the two shells. Rotation of the cylinder-barrel
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Arnold George D. M.
Blair Arthur A.
Thoma Christian H.
Bertsch Richard A.
Korytnyk Peter G.
Unipat AG
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