Power plants – Pressure fluid source and motor – Input pump and rotary output motor system having...
Reexamination Certificate
2001-11-28
2003-03-04
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Input pump and rotary output motor system having...
Reexamination Certificate
active
06526748
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to hydraulic pumps, although other uses will be apparent from the teachings disclosed herein. In particular, the present invention relates to Bantam Duty Pumps (BDP) which can be combined with motors and other remotely-located units. When used in this manner, these BDP units provide an infinitely variable flow rate between zero and maximum in both forward and reverse modes of operation.
Pumps discussed herein are of the axial piston design which utilize spherical-nosed pistons, although variations within the spirit of this invention will be apparent to those with skill in the art and the invention should not be read as being limited to such pumps. One such prior art pump is shown in FIG.
1
. The pump is a variable displacement pump
10
designed for vehicle applications. A compression spring
12
located inside each piston
14
holds the nose
16
of the piston
14
against a thrust-bearing
18
. A plurality of such pistons positioned about the center of the cylinder
20
forms a cylinder block kit
22
. The variable displacement pump
10
features a cradle mounted swashplate
24
with direct-proportional displacement control. Tilt of swashplate
24
causes oil to flow from pump
10
; reversing the direction of tilt of the swashplate
24
reverses the flow of oil from the pump
10
. The pump is fluidly connected with a motor to form a pump-motor circuit having a high pressure side and a low pressure side through which the oil flows. See generally FIG.
4
C. Controlling the oil flow direction, i.e. changing the high and low pressure sides, controls the motor output rotation. Tilt of the swashplate
24
is controlled through operation of a swashplate control shaft
26
(also referred to herein as trunnion arm). The trunnion arm is connected to a slide which connects with the swashplate. Generally, movement of the trunnion arm
26
produces a proportional swashplate movement and change in pump flow and/or direction. This direct-proportional displacement control (DPC) provides a simple method of control.
A fixed displacement gerotor charge pump
28
is generally provided in BDP units. Oil from an external reservoir (such as reservoir
200
in
FIG. 4C
) and filter is pumped into the low pressure side by the charge pump
28
. Fluid not required to replenish the closed loop flows either into the pump housing
30
through a cooling orifice or back to the charge pump
28
inlet through the charge pressure relief valve. Charge check valves
32
are included in the pump
10
and end cap
34
(cap
34
) to control the makeup of oil flow of the system. A screw type bypass valve
36
is utilized in the pump
10
to permit movement of the machine (tractor, vehicle, etc.) and allow the machine to be pushed or towed. Opening a passage way between fluid ports with bypass valve
36
allows oil to flow, thereby opening the pump-motor circuit, which allows the motor to turn with little resistance because the vehicle wheels will not back drive pump
10
.
While such pumps are useful, they have the disadvantage of having a preferred alignment direction. More particularly, the housing
30
has a preferred alignment with the end cap. This preferred alignment direction is created by the hose coupling, or connections, between the motor
38
and the pump end cap
34
(see FIGS.
2
and
3
). The placement of the system ports
40
determines the preferred alignment of the housing
30
. This is particularly troublesome when one desires to control a hydraulically powered vehicle with pumps positioned on either side of the vehicle and where the control arms for the individual pumps also must be mounted to the outer sides thereof. A control arm for the left pump
10
L (FIG.
2
), for instance, can be conveniently connected to the trunnion arm
26
to provide control of the swashplate from the left. However, to connect a control arm to the right pump
10
R, for instance, the pump must be rotated to place the trunnion arm
26
nearer to the right side of the vehicle. Costly hose fittings are then required to connect the hoses
44
to the pump
10
R. Alternatively a cumbersome and costly U-shaped control linkage
46
may be connected to the trunnion arm
26
while maintaining the pump end cap in its preferred orientation, as shown in FIG.
3
.
An improvement on the earlier pumps having preferred alignment is shown in
FIG. 4C
; the corresponding end cap
156
is shown in FIG.
14
A.
FIGS. 4C and 14A
disclose a prior art pump wherein the end cap
156
may be connected to the housing in one of two orientations. Specifically, end cap
156
is rotatable 180° with respect to the housing. This permits the trunnion arm
26
to be placed on opposing sides. This improved “symmetric pump” has shortcomings, however, which the present invention overcomes. The advantages of a symmetric pump according to the present invention over the prior art “symmetric pump” will be apparent to those with skill in the art from the teachings herein.
SUMMARY OF THE INVENTION
The present invention overcomes these and other problems by providing a pump which does not have a preferred mounting alignment. One object of the present invention is to provide a new and improved pump. A further object is to provide a symmetric pump having a symmetric housing and a symmetric end cap.
Another object of the present invention is to provide an improved hydrostatic vehicle.
Another object of the present invention is to provide means for utilizing a hydraulic pump in multiple directions without the cost of expensive fittings and accessories.
Accordingly, the present invention includes a pump having a housing and an end cap. The housing includes a pump shaft rotatably supported therein. The end cap may be connected to the housing in either a first position or a second position rotated relative to the housing from the first position about an axis through the pump shaft.
Another embodiment of the invention includes a pump comprising an end cap and a housing connectible to the end cap in either a first position relative to the end cap or a second position rotated relative to the first position. The second position is rotated relative to the end cap (and the first position) about an axis through the housing and the end cap. The housing is connected to the end cap in one of the first or second positions.
Another embodiment of the invention includes a pump comprising a housing and a swashplate rotatably supported in the housing. A pump shaft is supported by the housing and extends through the swashplate. A trunnion arm is extended from the housing and positioned to vary or act upon the operation of the swashplate. An end cap is connected to the housing. The end cap has a system port opening external thereto in a first orientation. The pump further comprises connection means for connecting the housing to the end cap in one of a first position and a second position such that the trunnion arm extends in a first direction and the system port opens in the first orientation when the housing is connected to the end cap in the first position. The connection means also provides connection such that the trunnion arm extends in a second direction and the system port opens in the first orientation when the housing is connected to the end cap in the second position.
The invention includes an end cap for a hydraulic pump, wherein the pump includes a housing adapted to connect to the end cap.
The end cap comprises a first edge and a second edge separated by a third edge. A first check plug and a first case drain are positioned in the first edge. A second check plug and a second case drain are positioned in the second edge. A pair of system ports are positioned in the third edge.
The invention also provides a control device for a hydraulic pump having a housing and a swashplate operably supported therein and a trunnion arm engaging the swashplate. The control device comprises a control arm attached to the trunnion arm and a stud mounted in and extending from the housing a spaced distance from the trunnion arm. The stud
Altheimer & Gray
Hydro-Gear Limited Partnership
Leslie Michael
Look Edward K.
LandOfFree
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