Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
1999-08-06
2001-02-13
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C091S446000, C091S452000, C091S455000, C137S596160, C137S596200
Reexamination Certificate
active
06186172
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a directional control valve system for feeding a hydraulic actuator with pressure fluid from a pressure fluid source.
BACKGROUND ART
A directional control valve system has been known having a meter-in flow control valve, a pair of load checking valves and a meter-out flow control valve in which one of the two load checking valves is fed with pressure fluid through the meter-in flow control valve to feed pressure fluid into a first chamber of a hydraulic actuator and pressure fluid in a second chamber of the hydraulic actuator is permitted to flow out into a reservoir through the meter-out flow control valve.
In such a directional control valve system, pressure fluid is fed selectively into one of the two load checking valves by switching the meter-in flow control valve. This requires the meter-in flow control valve to be provided with a pump port, a first outlet port and a second outlet port and to be constructed so that displacement of a spool may allow the first or second outlet port to communicate with the pump port. The essential need for these three ports has thus rendered the system unduly complex in structure.
It is accordingly an object of the present invention to provide a directional control valve system that can resolve the above-mentioned problem.
BRIEF SUMMARY OF THE INVENTION
A first form of the invention provided herein is a directional control valve system, characterized in that it comprises: a meter-in flow control valve
1
for establishing and blocking fluid communication of a pump port with a single outlet port
12
; a first load checking valve
2
disposed between the said outlet port
12
and a first actuator port
72
and adapted to be held in a closed state in response to an external signal; a second load checking valve
3
disposed between the said outlet port
12
and a second actuator port
74
and adapted to be held in a closed state in response to an external signal; and a meter-out flow control valve
4
for establishing fluid communication of one of the said first actuator port
72
and the said second actuator port
74
with a tank port
71
.
According to the first form of the invention, it can be seen and should be appreciated that bringing the pump port of the meter-in flow control valve
1
into fluid communication with the outlet port
12
, holding the first load checking valve
2
in a closed state and bringing the first actuator port
72
of the meter-out flow control valve
4
into fluid communication with a first tank port
71
permits pressure fluid having flowed into the pump port to force the second load checking valve
3
to open and thereby to feed into the second actuator, and pressure fluid in the first actuator port
72
to flow out into the tank port
71
.
Also, bringing the pump port of the meter-in flow control valve
1
, into fluid communication with the outlet port
12
holding the second load checking valve
3
in a closed state and bringing the second actuator port
74
of the meter-out flow control valve
4
into fluid communication with tank port
71
allows pressure fluid that has flown into the pump port to force the first load checking valve
2
to open and thereby to feed into the first actuator port
72
and pressure fluid in the second actuator port
74
to flow out into the tank port
71
.
It thus becomes possible for pressure fluid admitted into the pump port to be furnished into the first or second actuator port
72
,
74
and for pressure fluid in the second or first actuator port
74
,
72
to be caused to flow out into a reservoir, permitting a first chamber
99
a
, a second chamber
99
b
of a hydraulic actuator
99
to be supplied with pressure fluid.
It should also be noted that the meter-in flow control valve
1
requiring no more than two ports, i.e., only the pump port and the outlet port
12
, becomes simple in structure.
A second form of the invention provided herein is a directional control valve system in which the meter-in flow control valve
1
in the first form of the invention described is constructed to include an outlet port
12
, a first pump port
13
, a second pump port
16
and a meter-in spool
19
, and to be operable to block fluid communication between the ports when the meter-in spool
19
is located at a neutral position thereof and to be operable to establish fluid communication between the ports when the meter-in spool
19
is located at a first position that is on one side of the neutral position as well as when the meter-in spool
19
is located at a second position that is on the other side of the neutral position.
According to the second form of the invention, it can be seen and should be appreciated that moving the meter-in spool
19
in either one side or the other side establishes fluid communication of both the first and second pump ports
13
and
16
with the outlet port
12
, thereby permitting pressure fluid admitted therein to flow out into the outlet port
12
.
It thus becomes possible to feed a volumetric flow that is twice as large as the spool diameter, hence to make the spool
19
smaller in diameter and compact.
It should also be noted that pressure fluid that is discharged from a first hydraulic pump and pressure fluid that is discharged from a second hydraulic pump can be combined to flow into the outlet port
12
for supply into a hydraulic actuator.
A third form of the invention provided herein is a directional control valve in which coaxially with the first load checking valve
2
adopted in the first or second form of the invention there is disposed a relief valve for a check valve
63
for permitting fluid flow from the first actuator port
72
into a relief port
59
, and coaxially with the second load checking valve
3
is so adopted that there is disposed a relief valve for a check valve
63
for permitting fluid flow from the second actuator port
74
into a relief port
59
, these relief ports
59
being connected to a single relief valve
130
According to the third form of the invention, it can be seen and should be appreciated that pressure fluid in the first actuator port
72
is allowed to flow through the relief valve for the check valve
63
disposed coaxially with the first load checking valve
2
, from a relief port
59
into the relief valve
130
. Pressure fluid in the second actuator port
74
is allowed to flow through the relief valve for the check valve
63
disposed coaxially with the second load checking valve
3
, from a relief port
59
into the relief valve
130
.
Thus, providing a single relief valve is sufficient to prevent an abnormal rise in pressure in each of the first and second actuator ports
72
and
74
. It should also be noted that if a plurality of first and/or second load checking valves
2
,
3
are provided, connecting these relief ports
59
together with a path or paths can prevent every one of them from suffering from an abnormal pressure rise in it.
A fourth form of the invention provided herein is a directional control valve system in which the meter-out flow control valve
4
of the first, second or the third form of the invention described is adapted to block fluid communication between the ports when the meter-out spool
76
lies at the neutral position and to establish fluid communication of the first actuator port
72
with the tank port
71
when the meter-out spool
76
lies at the first position and to establish fluid communication of the second actuator port
74
with the tank port
71
when the meter-out spool
76
lies at the second position.
According to the fourth form of the invention, it can be seen and should be appreciated that moving the meter-out spool
76
to take one of its first and second positions establishes fluid communication of one of the first and second actuator ports
72
and
74
with the tank port
71
.
This permits a switching operation to be performed of the meter-out flow control valve
4
with simplicity using an electromagnetic proportional pressure control valve or a hydraulic pilot valve.
A fifth form of the invention provi
Kananen Ronald P.
Komatsu Ltd.
Michalsky Gerald A.
Rader Fishman & Grauer
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