Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
2000-10-13
2002-06-25
Rivell, John (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C137S596140, C060S427000, C060S445000
Reexamination Certificate
active
06408876
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to a control valve, which is arranged in a hydraulic system to be arranged in a construction machine or the like and is operable responsive to a pilot pressure to control a flow of pressure fluid to be supplied to an actuator.
2. Background Art
Hydraulic apparatuses, for example, construction machines and the like often make use of a system that a flow rate of working fluid is controlled by a control valve operable responsive to a pilot pressure and the pilot pressure is outputted, as is, as a control pressure to control a pressure and flow rate of pressure fluid to be delivered from a hydraulic pump. In this instance, it is a common practice to control plural spools, which are arranged in association with a single hydraulic pump and are housed within the control valve, to effect distribution of a flow rate. Adopted here is a system that the highest one of pilot pressures for actuating the plural spools, respectively, is transmitted to a delivery control device for the hydraulic pump by way of a shuttle valve or the like. It is generally a hydraulic remote control valve that controls the plural pilot pressures, and as is shown in JP 3-59502, the shuttle valve which selects the highest one of the pilot pressures is generally arranged as an integral element inside the hydraulic remote control valve.
FIG. 3
is a circuit diagram of a conventional technique of this sort, namely, of a hydraulic system including a conventional control valve.
The conventional technique shown in
FIG. 3
is provided with a variable displacement hydraulic pump
61
, a control valve
62
having spools
57
,
59
for controlling flows of hydraulic fluid delivered from the hydraulic pump
61
and supplied to unillustrated actuators such as hydraulic cylinders, and a hydraulic remote control valve
70
for producing pilot pressures for actuating the spools
57
,
59
in the control valve
62
.
The hydraulic remote control valve
70
includes a control lever
50
for controlling the spool
57
, a control lever
51
for controlling the spool
59
, hydraulic pilot valves
50
a
,
50
b
operable in association with pivotal control of the above-mentioned control lever
50
, and hydraulic pilot valves
51
a
,
51
b
operable in association with pivotal control of the above-mentioned control lever
51
.
The pilot valve
50
a
and a pressure fluid port, which is in communication with one
57
a
of pressure fluid control compartments in the spool
57
, are connected to each other through a pilot line
56
a
, while the pilot valve
50
b
and a pressure fluid port, which is in communication with the other pressure fluid control compartment
57
b
in the spool
57
, are connected to each other through a pilot line
56
b
. Similarly, the pilot valve
51
a
and a pressure fluid port, which is in communication with one
59
a
of pressure fluid control compartments in the spool
59
, are connected to each other through a pilot line
58
a
, while the pilot valve
51
a
and a pressure fluid port, which is in communication with the other pressure control compartment
59
b
in the spool
59
, are connected to each other through a pilot line
58
b
. Of the above-mentioned pilot lines
56
a
,
56
b
,
58
a
,
58
b
, portions exposed to the outside of the hydraulic remote control valve
70
make up external lines and are formed, for example, of pressure fluid hoses having flexibility.
Further, the above-mentioned hydraulic remote control valve
70
is of a construction that includes, as integral elements, a first shuttle valve
52
for selecting fluid on a side of higher pressure one of the pilot lines
56
a
,
56
b
, a second shuttle valve
53
for selecting fluid on a side of higher pressure one of the pilot lines
58
a
,
58
b
, and a third shuttle valve
54
for further outputting higher one of the pilot pressures outputted from the first and second shuttle valves
52
,
53
, respectively.
In addition, the conventional hydraulic system is also provided with a line
60
for transmitting the pilot pressure, which has been outputted through the third shuttle valve
54
, as a control pressure for the hydraulic pump
61
. This line
60
is also in the form of an external line, and comprises a pressure fluid hose having flexibility.
The hydraulic remote control valve
70
is generally arranged on a left-hand or right-hand side of the driver's seat. According to the conventional art, there is a tendency that, as shown in
FIG. 3
, more pressure fluid hoses tend to be connected to the hydraulic remote control valve
70
, so that a limitation tends to be imposed on a space for its arrangement. In other words, the arrangement and design tolerance of the hydraulic remote control valve
70
tends to become smaller. Incidentally, five external lines extend out as pressure fluid hoses in total in the embodiment illustrated in
FIG. 3
, including the four pilot lines from the hydraulic remote control valve
70
and the single line from the third shuttle valve
54
.
As apparatuses making use of the hydraulic remote control valve
70
of this type, on the other hand, there are, for example, mini power shovels such as that disclosed in JP 8-137567. In mini power shovels of this type, control levers for operating a remote control valve are arranged movably in many instances in view of operator's convenience upon ingress to and egress from the operator's seat. An example of these mini power shovels is illustrated in FIG.
4
.
As is shown in
FIG. 4
, the mini power shovel is provided with a travel base
101
, which includes a pair of crawler treads, and a swivel superstructure
102
arranged on the travel base
101
. On the swivel superstructure
102
, an operator's seat
103
is disposed, and a canopy
104
is arranged above the operator's seat
103
such that a roof
104
a
covers the operator's seat
103
. A swing post
105
is arranged on a front part of the swivel superstructure
102
. A boom
106
is connected to the swing post
105
. The boom
106
is turnable in a vertical direction, and is also turnable in a horizontal plane by way of the swing post
105
.
Arranged in front of the operator's seat
103
are a left drive lever
107
a
and a right drive lever. The left drive lever
107
a
is used to operate an unillustrated left drive motor which serves to drive the left-hand crawler tread of the travel base
101
, while the right drive lever is employed to operate an unillustrated right drive motor which serves to drive the right-hand crawler tread of the travel base
101
. Arranged on a forward left-hand side of the driver's seat
103
is a left control device for operating, for example, unillustrated boom and bucket cylinders adapted to drive the boom
106
and an unillustrated bucket, respectively; namely, a left console
108
having a left control lever
108
a
. Arranged on a froward right-hand side of the operator's seat
103
is a right control device for operating, for example, unillustrated arm cylinder and swivel motor adapted to drive an unillustrated arm and the swivel superstructure
102
, respectively; namely, a right console having a right control lever. In addition, a left gate lock lever
110
a
which makes up a jump lifter is arranged on the side of the left console
108
, and a right gate lock lever which makes up another jump lifter is disposed on the side of the right console.
In the mini power shovel constructed as described above, an operator who has operated it in the operator's seat
103
turns the left gate lock lever
110
a
in a clockwise direction as viewed in
FIG. 4
(to a position indicated by alternate long and short dash lines in the figure) when the operator wants to egress, for example, from the left side where the left console
108
is located. When the left gate lock lever
110
a
is caused to turn as mentioned above, the control lever
108
a
is also caused to jump up rearward so that a foot area, specifically the space on a forward left-hand area of the operator's seat
103
becomes wider, ther
Nishimura Yoshizumi
Nozawa Yusaku
Takahashi Kinya
Tougasaki Mitsuhisa
Crowell & Moring LLP
Hitachi Construction Machinery Co. Ltd.
Rivell John
Schoenfeld Meredith H.
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