Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Reexamination Certificate
2001-06-04
2002-06-25
Yuen, Henry C. (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
C251S035000, C137S460000
Reexamination Certificate
active
06409142
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hose rupture control valve unit (hose rupture valve), which is provided in a hydraulic machine, such as a hydraulic excavator, for preventing a drop of a load upon rupture of a cylinder hose.
BACKGROUND ART
In a hydraulic machine, e.g., a hydraulic excavator, there is a need for preventing a drop of a load even if a hose or steel pipe for supplying a hydraulic fluid to a hydraulic cylinder, serving as an actuator for driving the load, e.g., an arm, should be ruptured. To meet such a need, a hose rupture control valve unit, also called a hose rupture valve, is provided in the hydraulic machine.
FIG. 14
is a hydraulic circuit diagram showing a typical conventional hose rupture control valve unit, and
FIG. 15
is a sectional view of the hose rupture control valve unit.
Referring to
FIGS. 14 and 15
, a hose rupture control valve unit
200
comprises a housing
204
provided with two input/output ports
201
,
202
and a reservoir port
203
. The input/output port
201
is directly attached to a bottom port of a hydraulic cylinder
102
, the input/output port
202
is connected to one of actuator ports of a control valve
103
via a hydraulic hose
105
, and the reservoir port
203
is connected to a reservoir
109
via a drain hose
205
. Within the housing
204
, there are provided a main spool
211
operated with a pilot pressure supplied as an external signal from a manual pilot valve
108
, a check valve
212
for fluid supply, a poppet valve body
214
controlled by a pilot portion
213
which is provided on the main spool
211
, and an overload relief valve
215
for releasing an abnormal pressure.
In the conventional hose rupture control valve unit
200
having the above-described construction, a hydraulic fluid is supplied to the bottom side of the hydraulic cylinder
102
by supplying the hydraulic fluid from the control valve
103
to the bottom side through the fluid-supply check valve
212
in the valve unit
200
. Also, the hydraulic fluid is discharged from the bottom side of the hydraulic cylinder
102
by operating the main spool
211
of the valve unit
200
with the pilot pressure, as an external signal, so as to first open the poppet valve body
214
controlled by the pilot portion
213
which is provided on the main spool
211
, and to then open a variable throttle portion
211
a
also provided on the main spool
211
, thereby draining the hydraulic fluid to the reservoir
109
while controlling a flow rate of the hydraulic fluid.
The poppet valve body
214
is provided in series with the main spool
211
, and has the function (load check function) of reducing the amount of leakage in a condition of holding the load pressure on the bottom side of the hydraulic cylinder
102
.
The overload relief valve
215
functions to drain the hydraulic fluid and prevent hose rupture in case that an excessive external force acts upon the hydraulic cylinder
102
and the hydraulic pressure supplied to the bottom side of the hydraulic cylinder
102
is brought into a high-pressure level.
Also, if the hydraulic hose
105
leading from the control valve
103
to the input/output port
202
should be ruptured, the check valve
212
and the poppet valve body
214
are closed to prevent a drop of a load supported by the hydraulic cylinder
102
. In such an event, by operating the main spool
211
with the pilot pressure from the manual pilot valve
108
and adjusting an opening area of the variable throttle portion
211
a
, it is possible to slowly contract the hydraulic cylinder
102
under action of the weight of the load itself and to move the load to a safety position.
Numerals
107
a
and
107
b
denote main relief valves for limiting a maximum pressure in the circuit.
Further, JP, A 3-249411 discloses a hose rupture control valve unit utilizing a proportional seat valve to reduce an overall size of the valve unit.
FIG. 16
shows the disclosed hose rupture control unit.
Referring to
FIG. 16
, a hose rupture control valve unit
300
comprises a housing
323
provided with an input port
320
, a work port
321
and a reservoir port
322
. The input port
320
is connected to one of actuator ports of a control valve
103
, the work port
321
is connected to a bottom port of a hydraulic cylinder
102
, and the reservoir port
322
is connected to a reservoir
109
via a drain hose
205
. Within the housing
323
, there are provided a check valve
324
for fluid supply, a proportional seat valve
325
, an overload relief valve
326
, and a pilot valve
340
. The pilot valve
340
is operated with a pilot pressure supplied as an external signal from a manual pilot valve
108
(see FIG.
14
), and the proportional seat valve
325
is operated with the operation of the pilot valve
340
. The overload relief valve
326
is incorporated in the proportional seat valve
325
.
A hydraulic fluid to the bottom side of the hydraulic cylinder
102
is supplied by supplying the hydraulic fluid from the control valve
103
to the bottom side through the fluid-supply check valve
324
in the valve unit
300
. Also, the hydraulic fluid is discharged from the bottom side of the hydraulic cylinder
102
by operating the pilot valve
340
of the valve unit
300
with the pilot pressure, as an external signal, to open the proportional seat valve
325
, thereby draining the hydraulic fluid to the reservoir
109
while controlling a flow rate of the hydraulic fluid. The proportional seat valve
325
has the function (load check function) of reducing the amount of leakage in a condition of holding the load pressure on the bottom side of the hydraulic cylinder
102
.
The overload relief valve
326
functions to open the proportional seat valve
325
for draining the hydraulic fluid and preventing hose rupture in case that an excessive external force acts on the hydraulic cylinder
102
and the hydraulic pressure supplied to the bottom side of the hydraulic cylinder
102
is brought into a high-pressure level.
Also, if a hydraulic hose
105
leading from the control valve
103
to the input port
320
should be ruptured, the check valve
324
and the proportional seat valve
325
are closed to prevent a drop of a load supported by the hydraulic cylinder
102
. In such an event, by operating a spool
341
of the pilot valve
340
with the pilot pressure and adjusting an opening area of the proportional seat valve
325
, it is possible to slowly contract the hydraulic cylinder
102
under action of the weight of the load itself and to move the load to a safety position.
DISCLOSURE OF THE INVENTION
However, the above-described prior arts have a problem that it is difficult to reduce a pressure loss and to cut down an overall size and production cost of the valve unit.
More specifically, in the prior art shown in
FIGS. 14 and 15
, various components, i.e., the check valve
212
for fluid supply, the main spool
211
, the poppet valve body
214
controlled by the pilot portion
213
provided on the main spool
211
, and the overload relief valve
215
, are separately provided corresponding to the respective functions. Therefore, incorporating all those components in the housing
204
of a certain restricted size imposes a limitation on sizes of the individual components. Also, there has been a difficulty in reducing the production cost.
On the other hand, since all of the hydraulic fluid discharged from the hydraulic cylinder
102
passes through the main spool
211
, a spool valve body of the main spool
211
is required to have a larger diameter. Further, because of the main spool
211
and the poppet valve body
214
being provided in series, the hydraulic fluid passes through these two valve elements at a large flow rate. Accordingly, when those parts are incorporated in the housing
204
of the certain restricted size, their sizes are necessarily limited, which may result in that a sufficient flow passage is not ensured and a pressure loss is increased. In addition, a pressure loss is also inevitably produced with such a construction that the hydr
Kariya Masao
Sugiyama Genroku
Bastianelli John
Hitachi Construction Machinery Co. Ltd.
Mattingly Stanger & Malur, P.C.
Yuen Henry C.
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