Expansible chamber devices – Relatively movable working members – Interconnected with common rotatable shaft
Reexamination Certificate
1999-11-29
2002-03-12
Look, Edward K. (Department: 3745)
Expansible chamber devices
Relatively movable working members
Interconnected with common rotatable shaft
C092S157000
Reexamination Certificate
active
06354186
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to pumps and hydraulically-actuated systems used with internal combustion engines, and more particularly to axial hydraulic pumps with wobble plates.
BACKGROUND ART
Hydraulic pumps that utilize wobble plates to drive reciprocating pistons are susceptible to wear. The wobble plate is usually the driveplate with a tilted pumping surface that pushes against the pump's pistons. As the driveplate rotates each piston is pushed away from the driveplate as the thickness of the driveplate beneath it becomes greater with the rotation, causing the piston to compress. The hydraulic pressure within the piston increases as the volume within the piston decreases. This high pressure hydraulic fluid is generally the output product of the hydraulic pump. As rotation continues and the thickness of the driveplate beneath the piston lessens, the higher hydraulic pressure within the piston allows it to expand again and refill itself with lower pressure hydraulic fluid.
There is generally friction between the driveplate and the piston as the driveplate rotates. This can cause wear to the piston and driveplate surfaces. Additionally, there is generally friction and wear against other surfaces that the rotating driveplate comes in contact with, as well.
Of course, the driveplate and whatever holds it must also be capable of bearing the loads caused by pushing against the compressing pistons. These loads may be axial (i.e., parallel to the drive shaft axis and/or perpendicular to the plaintiff rotation of the driveplate) or radial (i.e., perpendicular to the drive shaft axis), or some combination thereof.
DISCLOSURE OF THE INVENTION
A displacement pump
1
according to one aspect of the invention has a rotatable drive shaft
9
and at least one piston
20
containing a piston cavity
62
, and a piston shoe
34
flexibly connected with the piston
20
. The piston shoe
34
comprises a shoe passage
60
fluidly connected with the piston cavity
62
. The displacement pump also has a hydrostatic thrust bearing plate
40
comprising at least one thrust pad
42
, and a driveplate
12
connected with the drive shaft
9
and disposed between the piston shoe
34
and the thrust pad
42
. The driveplate
12
comprises a bearing surface
46
proximate to the thrust pad
42
, a pumping surface
38
proximate to the piston shoe
34
, and at least one communication port
48
fluidly connecting the bearing surface
46
with the pumping surface
38
. The driveplate
12
is rotatable to a position in which the piston cavity
62
is fluidly connected with the thrust pad
42
via the shoe passage
60
and the communication port.
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Gibson Dennis H.
Sommars Mark F.
Bram Eric M.
Caterpillar Inc.
Hickman Alan J.
Lazo Thomas E.
Look Edward K.
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