Motors: expansible chamber type – With motive fluid valve – Relatively movable serial valves
Reexamination Certificate
1999-10-27
2001-10-23
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Relatively movable serial valves
Reexamination Certificate
active
06305264
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuator control circuit which makes it possible to control, for example, the displacement speed of an actuator such as a cylinder.
2. Description of the Related Art
In recent years, an pneumatic actuator, for example, a cylinder is widely used to transport a small object or the like especially in electronic and electric industries as well as in other industries. The cylinder includes a piston which makes rectilinear reciprocating movement along a cylinder chamber of a cylinder tube. Concerning such a cylinder, those generally known to be used when the displacement speed of the piston is controlled include a meter-in circuit
1
(see
FIG. 19
) which controls the flow rate of the pressure fluid flowing through a passage disposed on the supply side for supplying the pressure fluid into the cylinder chamber, and a meter-out circuit
2
(see
FIG. 20
) which controls the flow rate of the pressure fluid flowing through a passage disposed on the discharge side for discharging the pressure fluid from the cylinder chamber.
In
FIGS. 19 and 20
, reference numeral
3
indicates a speed control valve comprising a check valve
4
and a variable throttle valve
5
. Reference numeral
6
indicates a switching solenoid-operated valve. Reference numerals
7
a
and
7
b
indicate first and second cylinder chambers respectively.
However, for example, when a pneumatic actuator such as a cylinder is operated at a low speed in order to transport, for example, a small object or the like, if the meter-in circuit
1
is used, then the displacement state and the stop state are intermittently repeated. As a result, an inconvenience occurs in that the so-called stick-slip phenomenon takes place, in which a step-shaped characteristic curve appears, which represents the relationship between the time and the displacement amount.
Further, the meter-in circuit
1
concerning the conventional technique is inconvenient in that the so-called delay of response time occurs, in which the time required to start the displacement of the piston is delayed when the operation of the cylinder is started again after the operation of the cylinder is stopped for a long period of time.
On the other hand, the meter-out circuit
2
is inconvenient in that the so-called jumping out phenomenon occurs, in which the piston makes quick displacement along the cylinder chamber
7
a
(
7
b
) due to any adhesion of the piston when the operation of the cylinder is started again after the operation of the cylinder is stopped for a long period of time.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide an actuator control circuit which makes it possible to control the displacement speed of an actuator at a low speed in a stable manner by excluding the occurrence of the stick-slip phenomenon and the jumping out phenomenon.
A principal object of the present invention is to provide an actuator control circuit which makes it possible to improve the delay of response time which appears when the operation of a cylinder is started again after the operation of the cylinder is stopped for a long period of time.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.
REFERENCES:
patent: 3954046 (1976-05-01), Stillhard
Hosono Masayuki
Yang Qinghai
Leslie Michael
Look Edward K.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Kabushiki Kaisha
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