Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
1999-09-09
2001-08-21
Ryznic, John E. (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S452000, C060S486000
Reexamination Certificate
active
06276133
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pressure fluid supply and delivery apparatus that is adapted to supply and deliver pressure fluid into a plurality of fluid operated actuators having different loads or load pressures, or to feed such actuators with pressure fluid delivered or distributed. In particular, the invention relates to improvements in such a pressure fluid supply and delivery apparatus.
BACKGROUND ART
A conventional apparatus of the type described is shown in FIG.
7
.
The apparatus shown includes a hydraulic pump
1
having a discharge or delivery passage la to which a first and a second operating valve
1
and
3
are connected in parallel with each other. The first operating valve
2
has a first fluid operated actuator
4
connected thereto via a pressure compensating valve
6
. Likewise, the second operating valve
3
has a second fluid operated actuator
5
connected thereto via a pressure compensating valve
6
′. A shuttle valve
7
is also connected as shown for selectively sensing the one of the respective load pressures (maximum load pressure) in the actuators
4
and
5
that is higher than the other. The maximum load pressure sensed by the shuttle valve is imported into the pressure compensating valves
6
and
6
′.
The pressure compensating valves
6
and
6
′ have a set pressure determined by a maximum load pressure that develops in the actuators
4
and
5
. The pressure compensating valves
6
and
6
′ on the set pressure determined operates to maintain constant the difference in pressure across the inlet and outlet sides of each of the first and second operating valves
2
and
3
. This permits the first and second actuators
4
and
5
to be fed with pressure fluid in respective volumetric flows proportioned in accordance with the amounts of operation for (thus the openings in) the first and second operating valves
2
and
3
.
In the prior pressure fluid supply and delivery apparatus described above, if, for example, the second actuator
5
is lower in load while the first actuator
4
is higher in load, the pressure compensating valve
6
′ on the low load side becomes smaller in the area of opening than the pressure compensating valve
6
on the higher load side. As a consequence, with a given pressure of fluid discharged from the hydraulic pump
1
prevailing up to both the pressure compensating valves
6
and
6
′, a large loss (loss in pressure) develops in the fluid of an elevated pressure that passes through the pressure compensating valve
6
′ on the lower load side.
DISCLOSURE OF THE INVENTION
It is accordingly an object of the present invention to provide an improved pressure fluid supply and delivery apparatus that has a pressure compensating function and yet has a reduced loss (loss in pressure).
This and other objects which will become more readily apparent hereinafter are attained in accordance with the present invention by a pressure fluid supply and delivery apparatus which comprises: a variable displacement hydraulic pump unit having a plurality of fluid discharge ports independent each other and a common drive shaft; a plurality of fluid circuits connected to the said plural discharge ports, respectively; a plurality of fluid operated actuators connected via respective operating valves to the said plural fluid circuits, respectively; a displacement control means operable in response to discharge pressures in the said plural fluid discharge ports and load pressures in the said plural actuators for controlling discharge fluid pressure of the said variable displacement hydraulic pump unit; and a combining valve means disposed between the said plural fluid circuits and operable to block fluid communication between the said plural fluid circuits when the said plural fluid discharge ports have an equal pressure and operable to establish fluid communication between the said fluid circuits via a constriction when a difference in pressure develops between the said fluid discharge ports.
As the improved apparatus is so constructed as described above, those pressures develop respectively in the plural discharge ports which are independent of each other and that correspond to external loads for the respective actuators. A difference developing between load pressures in the plural actuators causes the combining valve to take its position of fluid communication to allow the plural fluid circuits to communicate with each other via a constriction. Thus, if pressure fluid is being supplied and delivered concurrently into a first actuator having a lower load pressure and with a larger volumetric flow required and a second actuator having a higher load pressure and with a smaller volumetric flow required, a portion of fluid being supplied and delivered into the second actuator is shunted and supplemented into fluid being supplied and delivered into the first actuator via the constriction. If pressure fluid is being supplied and delivered concurrently into fluid being supplied and delivered into a first actuator having a lower load pressure and with a smaller volumetric flow required and a second actuator having a higher load pressure and with a larger volumetric flow required, the combining valve is simply switched to take its fluid blocking position and its position of fluid communication alternately.
A plurality of actuators are therefore allowed to operate simultaneously with fluid of pressure compensated for in a reduced loss in pressure while satisfying volumetric flow requirements for the plural operating valves.
Specifically in the improved construction described above, the said plural fluid operated actuators may be connected in parallel to each of the said plural fluid circuits via a plurality of operating valves and a plurality of pressure compensating valves, respectively. Then, the said plural pressure compensating valves connected to each of the said plural fluid circuits may have a set pressure determined by a highest of the load pressures in said actuators connected to each of said plural fluid circuits.
As the improved apparatus is so specifically constructed as described above, a parallel connection of a plurality of actuators is established to each of the plural fluid circuits via respective operating valves and respective pressure compensating valves. The plural pressure compensating valves connected to each of the fluid circuits have a compensating pressure level established by a highest of the load pressures in the plural actuators connected to each of the fluid circuits.
This specific apparatus arrangement permits the actuators more in number than the number of the fluid circuits to be operated simultaneously.
Preferably in the first mentioned improved apparatus construction, the said variable displacement hydraulic pump unit has a plurality of groups of cylinder bores with the groups consisting of a plurality of cylinder bores formed in a plurality of concentric circular arrangements in a cylinder block of a swash plate hydraulic pump, positioned closer to its outer and inner peripheries, respectively, and a plurality of sets of pressure ports with the sets consisting of a plurality of high pressure ports and a plurality of low pressure ports formed in a plurality of concentric circular arrangements in a valve plate, positioned closer to its outer and inner peripheries, respectively.
Alternatively, the said variable displacement hydraulic pump unit comprises a plurality of hydraulic pumps of variable displacement type, having their respective drive shafts mechanically coupled together and their respective displacement control members connected to each other so that these plural hydraulic pumps have an identical displacement.
Preferably in the improved apparatus constructions described above, the said combining valve includes a spring, a first pressure receiving portion connected to one of the said plural fluid circuits, and a second pressure receiving portion connected to another of the said plural fluid circuits, the said combining valve being operable to take its flu
Endo Hiroshi
Yoshida Nobumi
Armstrong, Westerman, Hattori, McLeland & Naughton, LLP.
Komatsu Ltd.
Ryznic John E.
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