Fluid handling – Systems – Supply and exhaust
Reexamination Certificate
1999-04-27
2001-02-27
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Supply and exhaust
C060S460000, C091S420000, C091S446000, C091S518000, C137S596100
Reexamination Certificate
active
06192929
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a hydraulic controller in hydraulic valves used in construction equipments, and more particularly to a hydraulic controller with low pressure loss, superior responsibility, high stability, and in complex-operability.
The hydraulic control valve as shown in
FIG. 4
has been known as hydraulic controllers.
Thus hydraulic control valve as illustrated in
FIG. 4
has the following elements. A switching spool
12
is accommodated in a valve body
10
. A compressed oil is supplied from a supplying passage
14
of a hydraulic pump to a cylinder port
16
a
or
16
b
. In connection with a relative movement of the switching spool
12
to the valve body
10
, a passage from the supplying passage
14
to an oil chamber
18
is opened, whereby, the compressed oil having entered into the oil chamber
18
, is reached to an oil chamber
20
, so that when the switching spool
12
is in a neutral position, a plunger
24
is moved upwardly, which blocks passages
22
,
22
extending between the oil chamber
20
and a cylinder port
16
a
or
16
b
positioned in downstream side of the oil chamber
20
, before the pressured oil enters into the passages,
22
,
22
and then into the cylinder port
16
a
or
16
b.
In a back chamber
25
of the plunger
24
, when the compressed oil applying onto plunger
24
is passed from the oil chamber
20
to the passage
22
, almost constant pressure drop appears such as to allow the plunger
24
to act as a pressure compensation means as well as the plunger
24
to exhibit a certain operation. For these purposes, a spring
26
is provided to apply its elastic force to the plunger
24
, whereby the oil chamber
20
is shut from the passage
22
. If, however, this spring
26
is not provided, the plunger
24
has no stable balanced position, thereby making it difficult to stabilize the pressure compensation function.
The back chamber
25
of the plunger
24
is connected to the outside through a communication passage
28
which may optionally be further connected to the tank circuit
29
trough the throttle.
For the well-known hydraulic control valves, other than the above, in order to supply the compressed oil from the supplying passage of the hydraulic pump, a movable member is provided as a pressure compensation valve on the passage of the compressed oil, and further in order to cause a constant pressure reduction in the upstream and downstream sides of the movable member, the spring force is designed to work on the movable member in such a way to close the passage to the cylinder port from the supplying passage.
However, there had remained various problems with the conventional hydraulic control valves, which should have to be solved.
In the prior art mentioned above, the pressure compensation valves are provided between the supplying passage and the cylinder port, and the pressure compensation valves are free from a compressed fluid action applied with the spring force such as to close the supplying passage to the a cylinder port from the hydraulic pump. Therefore, in order to operate the switching spool for causing the compressed oil to be flowed into the cylinder port, it is necessary that the pressure compensation valve is kept open against the spring force. In order to provide the function as the pressure compensation valve, it is also necessary that the spring force is not so faint, whereby the pressure loss corresponding the spring force is caused, making it difficult save energy.
Furthermore, in the hydraulic control valve as shown in
FIG. 4
, the back chamber of the plunger is connected to the tank circuit through the throttle. When the switching spool is in a non-operating state, the hydraulic control valve is kept closing the passage to the cylinder port from the supplying passage of the hydraulic pump. If the hydraulic control valve is used in a cold district, then the hydraulic oil has an extremely high viscosity. For this reason, if the high viscosity hydraulic oil is used for quick start, then the hydraulic oil in the valve chamber of the hydraulic control valve is exhausted to the outside through the throttle.
This exhaust takes some time during which the plunger remains in position, whereby the movement of the plunger as the pressure compensation valve for opening the upstream and downstream passages is likely to be delayed in response.
In this case, this response may be improved by widening the opening degree of the throttle. In order to but in order to keep the pressure compensation valve in good performance, it is however necessary to increase the quantity of the discharged oil from the throttle. This may raise another problem in difficulty to save energy for the whole system.
Furthermore, in concurrent operations of two spools, all of the pressure compensation valves must be equilibrated individually in the respective neutral positions between the closed and opened positions. Accordingly, these values tend to be influenced mutually, and thus it is required to consider the safety enough well.
In the prior art, a flow rate regulating device is connected between a switching valve and a cylinder port, that is, an actuator is connected to a hydraulic control device.
In this case, by limit the supply of the oil from a hydraulic pump to an actuator, namely by the flow rate control is made by the meter-in control. When the hydraulic control unit is used in the construction equipment, the following problem is raised. Though the load reduced with empty weight should be under the meter-out control, the degree of opening on the side of the meter-in control is limited as described above, whereby a cavitation is formed due; to insufficient supply of the compressed oil to the actuator, thereby making difficult a smooth operation of the load.
Upon repeated earnest studies and investigations the inventor could confirm the following facts.
SUMMARY OF THE INVENTION
An object of the present invention to provide a novel hydraulic controller with a reduced pressure loss and good responsibility and stability as well as good operability of operating plural switching spools.
The present invention provides a hydraulic controller comprising: a plurality of switching spools; a plurality of cylinder ports of a switching valve; a compressed oil passage common to, the switching valves having an intermediate chambers, at least a check valve in correspondence with at least a part of said switching spools, and said check valve being positioned between said intermediate chambers and said cylinder ports, so that said switching spools being positioned in a neutral position to close said passage and also being movable to adjust opening degree of said passage, wherein auxiliary ports are provided between the cylinder ports and a tank line; flow rate adjusters are also provided between the auxiliary ports and the tank line for adjusting an opening degree of the passage; pressure detectors are provided in the switching valves for detecting pressures of oils in the intermediate chambers; a maximum pressure selector operatively linked to said pressure detectors for selecting a maximum pressure from the detected pressures by the pressure detectors; whereby the pressures of said intermediate chambers are applied to the flow rate adjusters in an opening direction, whilst the selected maximum pressure selected by said maximum pressure selector is applied to the flow rate adjusters in a closing direction.
REFERENCES:
patent: 4020867 (1977-05-01), Sumiyoshi
McGinn & Gibb PLLC
Michalsky Gerald A.
Toshiba Machine Co. Ltd.
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