Plastic article or earthenware shaping or treating: apparatus – Reshaping – resizing or vulcanizing means for tire – tire...
Reexamination Certificate
2000-07-31
2002-02-12
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Reshaping, resizing or vulcanizing means for tire, tire...
C425S047000, C425S451900
Reexamination Certificate
active
06345970
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic actuator used for various mechanisms of a hydraulic type tire press, and a hydraulic system for a tire curing press for supplying pressure oil to a hydraulic control valve.
2. Description of the Related Art
A press frame of a tire vulcanizer (a tire press) comprises, as shown in
FIG. 3
, an upper frame
31
, a lower frame
32
, and a side frame
33
, and a metal mold
35
is secured to the lower frame
32
through a lower mold mounting member
34
. An upper metal mold
36
is secured to an upper mold mounting member
37
, and is closable with respect to the lower metal mold
35
. A piston rod
38
is secured to the mounting member
37
, the mounting member
37
being moved up and down along a vertically elevating guide
39
by operation of an elevating cylinder
26
. A pressurizing and transmitting rod
40
is stood upright on the mounting member
37
, and a clamping cylinder
27
for transmitting a pressurizing force to the pressurizing and transmitting rod
40
is fixedly mounted on the upper frame
31
.
The tire vulcanizer repeats the inserting step for inserting a green tire prior to vulcanization between the upper and lower metal molds
35
and
36
to close the upper and lower metal molds
35
and
36
, the vulcanizing step for loading the clamping force to the upper and lower metal molds
35
and
36
so that the tire is not forced out during vulcanization to vulcanize the tire, and the taking out step for opening the mold in order to take out the vulcanized tire to vulcanize the tires sequentially. As shown in
FIG. 5
, the inserting step and the taking out step are referred to as “dry cycle”, and the step for loading the clamping force to vulcanize the tire is referred to as “vulcanizing cycle”. That is, the operating cycle of the tire vulcanizer is divided broadly into the dry cycle and the vulcanizing cycle.
The conventional hydraulic unit in the tire curing press is generally designed so that as shown in
FIG. 4
, a large capacity, 100 l/min, variable capacity pump
43
with cut-off pressure set to 125 kgf/cm
2
, and a large capacity, 170 l/min, fixed capacity pump
44
are respectively driven by a 22 kw motor to supply pressure oil to five presses
48
to
52
. An unload valve
45
having 140 kgf/cm
2
of set pressure is connected to the variable pump
43
, and an unload valve
46
having 100 kgf/cm
2
of set pressure is connected to the fixed pump
44
. These unload valves
45
and
46
have a relief function for protecting line pressure, and a role for compensating for operating pressure of the press, and are designed so that pressure oil discharged from the pumps is switched to the press sides
48
to
52
and the tank side
53
. In the conventional hydraulic unit
47
, in the press closing operation during the dry cycle, pressure oil is supplied to the press sides
48
to
52
by the variable pump
43
and the fixed pump
44
; and during the vulcanization, necessary flow rate is supplied to the presses
48
to
52
sides merely by the variable pump
43
to compensate for pressure. The dry cycle in the presses is approximately 1/10 of the vulcanizing cycle, and the variable pump
43
is continuously operated in order to compensate for pressure.
The variable pump
43
is always in the on-load state during the dry cycle and during the vulcanization as well, and pressure oil discharged from the pump
43
is supplied to the presses
48
to
52
sides. However, during the vulcanization, pressure oil is merely necessary for the clamping cylinder and a part of actuators such as a clamp portion, and the flow rate necessary for the presses
48
to
52
sides is lessened as a whole. Therefore, the discharge flow rate of the variable pump
43
is automatically adjusted to the minimum discharge flow rate to supply pressure oil.
However, since the variable pump always supplies pressure oil to the press sides, pressure is always applied to hydraulic lines on the press sides after the hydraulic pump to cause a leakage of the about 5 to 10 l/min mark from the hydraulic valve. Further, the flow rate necessary for the presses is variable as shown in
FIG. 5
, and the constant flow rate is not always necessary, and therefore, the fixed pump is in the unload state during the vulcanization, and the discharged pressure oil is thrown into the tank. As described above, in the conventional hydraulic system, the motor of the hydraulic unit is continuously operated despite the fact that the most machineries stop during the vulcanization so that two pumps are being operated without stopping. Further, since the leakage from the hydraulic valve is incontinent, there poses a problem in that power (energy) is used wastefully so that consuming electric power of the hydraulic unit is wasted.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a hydraulic system for a tire curing press for limiting operation of a hydraulic unit during vulcanization by which machineries are stopped.
The present invention provides a hydraulic system for a tire vulcanizer in which various hydraulic cylinders of a tire vulcanizer for vulcanizing and molding tires and a hydraulic unit for supplying pressure oil having a fixed pressure are connected by hydraulic lines, comprising the one or more tire vulcanizers operated by said various hydraulic cylinders, a hydraulic unit for supplying pressure oil of fixed pressure, an accumulator circuit for supplying the accumulated pressure oil to said various hydraulic cylinders, and check means provided every said tire vulcanizer so that during vulcanization of said tire vulcanizer, pressure oil of said hydraulic unit and said accumulator circuit is cut off, and in the operation of said tire vulcanizer, the cutting off is released to cause the pressure oil of said hydraulic unit and said accumulator circuit to pass.
In this case, during the dry cycle, pressure oil is supplied from the hydraulic unit and the accumulator; and during the vulcanization, a master valve constituting the check means is closed to cut off a supply of pressure oil from the accumulator and the hydraulic unit to the various hydraulic cylinders. The hydraulic unit supplies pressure oil to the accumulator to accumulate it during the time pressure oil is cut of a supply to the various hydraulic cylinders. Thereby, pressure oil can be supplied at a stretch from the hydraulic unit and the accumulator to the various cylinders during the dry cycle, and a pump having a smaller capacity than that of conventional pumps without delaying the dry cycle time for about 1 to 2 minutes. When a supply of pressure oil from the hydraulic unit and the accumulator is cut off by the master valve constituting the check means, it is not necessary to always supply pressure oil of fixed quantity in order to compensate for a leakage from the hydraulic valve in each vulcanizer but a supply quantity of pressure oil during the vulcanization can be reduced, thus enabling reduction of consuming electric power of the hydraulic unit.
The present invention further provides, in addition to the above-described constitution, a hydraulic system in which every said tire vulcanizer is provided an auxiliary accumulator for accumulating the remainder of the discharged flow rate of said hydraulic unit, if the discharged flow rate of said hydraulic unit and said main accumulator exceeds the necessary flow rate of said tire vulcanizer, to compensate for pressure of said various hydraulic cylinders during the vulcanization.
In this case, since pressure oil can be supplied to clamps or the like requiring pressure oil during vulcanization by the auxiliary accumulator without throwing out the remainder of the discharged flow rate of the hydraulic unit as in prior art, and therefore, the effective utilization of pressure oil can be achieved, and the consuming electric power of the hydraulic unit can be further reduced.
Further, according to the present invention, in addition to the above-described constitution, the hydraulic unit tu
(Kobe Steel, Ltd.)
Mackey James P.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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