Motors: expansible chamber type – Fluid supply through diverse paths to single expansible chamber – Second path activated in response to pressure or flow in...
Patent
1996-04-01
1998-11-10
Nguyen, Hoang
Motors: expansible chamber type
Fluid supply through diverse paths to single expansible chamber
Second path activated in response to pressure or flow in...
91 31, 91435, 91436, 91437, F15B 1304, F15B 1108
Patent
active
058328050
DESCRIPTION:
BRIEF SUMMARY
1. TECHNICAL FIELD
The present invention relates to a method and apparatus for controlling the speed of a hydraulic cylinder used as the injection cylinder of, e.g., a die casting machine or an injection molding machine.
2. BACKGROUND ART
It is conventionally known to incorporate a flow regulating valve described in, e.g., U.S. Pat. No. 4,586,539 in the hydraulic circuit of the injection cylinder of, e.g., a die casting machine.
This flow regulating valve is a single compact valve serving as four valves, i.e., a flow regulating valve and an opening/closing valve for low-speed injection, and a flow regulating valve and an opening/closing valve for high-speed injection. This valve can perform a smooth and quick operation with a comparatively small driving force and valve open state holding force and thus has a high practical value.
On the other hand, it is conventionally known to incorporate a run-around circuit that connects a rod-side chamber and a head-side chamber in the injection cylinder unit of, e.g., a die casting machine, in order to economize the amount of hydraulic operating fluid supplied from the hydraulic source to the head-side chamber of the cylinder, so that the piston is moved forward with as a minimum amount of hydraulic operating fluid. In the forward movement, the hydraulic operating fluid discharged from the rod-side chamber is introduced into the head-side chamber, and the piston is moved forward together with the hydraulic operating fluid supplied from the hydraulic source, e.g., an accumulator or a hydraulic pump.
Conventionally, when the flow regulating valve is incorporated in the hydraulic circuit of an injection cylinder having a run-around circuit, a meter-in or meter-out circuit is constituted.
FIG. 3 shows a meter-in circuit in a simplified manner. Referring to FIG. 3, reference numeral 1 denotes a cylinder; 2, a piston, 3, a piston rod integrally formed with the piston 2; 4, a head-side chamber; 5, a rod-side chamber; 6, a run-around circuit connecting the rod-side chamber 5 and the head-side chamber 4; 7, a pilot check valve which is closed when the piston 2 is moved backward; and 8, a hydraulic source, e.g., an accumulator.
Reference numeral 9 denotes a known flow regulating valve described in, e.g., U.S. Pat. No. 4,586,539 mentioned above. The flow regulating valve 9 is incorporated between the hydraulic source 8 and the head-side chamber 4. In this case, since the flow regulating valve 9 is incorporated in the hydraulic operating fluid input side of the cylinder 1, the entire structure is called a meter-in circuit.
FIG. 4 shows a meter-out circuit in a simplified manner. In this case, no flow regulating valve is provided between a hydraulic source 8 and a head-side chamber 4, and a flow regulating valve 9 is provided at the output side of a rod-side chamber 5. Thus, the entire structure is called a meter-out circuit.
3. DISCLOSURE OF INVENTION
In the meter-in circuit shown in FIG. 3, during high-speed forward movement, as the valve opening degree of the flow regulating valve 9 is large, the movement of the piston 2 is stabilized. On the other hand, during low-speed forward movement, as the valve opening degree of the flow regulating valve 9 is decreased, the fluid immediately after being output from the hydraulic source 8 is restricted. Thus, the pressure of the hydraulic operating fluid becomes very low during low-speed forward movement. As a result, a quick response cannot be obtained, and the movement and speed of the piston 2 become unstable.
As shown in FIG. 5, the pressure of the hydraulic operating fluid can be increased by interposing a stationary restrictor 10 in a run-around circuit 6. When, however, the speed is to be increased, the pressure loss of the stationary restrictor 10 portion becomes large. Then, it is difficult to increase the speed.
In the meter-out circuit shown in FIG. 4, since the pressure of the hydraulic operating fluid of the hydraulic source 8 directly acts on the head-side chamber 4, the pressure of the hydraulic operating fluid of th
REFERENCES:
patent: 4141280 (1979-02-01), Lorimor
patent: 4432270 (1984-02-01), Kyster et al.
patent: 4566477 (1986-01-01), Barker et al.
patent: 4586539 (1986-05-01), Veno
patent: 5251705 (1993-10-01), Waggoner et al.
Kurashima Yasuhiro
Yamane Takashi
Nguyen Hoang
Ube Industries Ltd.
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