Expansible chamber devices – Displacement control of plural cylinders arranged in... – Having motor-operated adjustment
Reexamination Certificate
2000-11-01
2002-02-05
Lopez, F. Daniel (Department: 3745)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Having motor-operated adjustment
C092S013400, C092S013600
Reexamination Certificate
active
06343537
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a dual stroke cylinder for stopping a piston in an intermediate position of a stroke and more specifically to a dual stroke cylinder for stopping a piston in an intermediate position of a stroke in a fluid pressure cylinder that is used for lifting such that a load is pushed up or pulled up by a rod of the piston or not for lifting such that the rod does not directly receive a weight of the load.
PRIOR ART
In a normal fluid pressure cylinder, a rod moves from a beginning to an end of a stroke at a single stroke. However, it is desired that the rod is once stopped in an intermediate position of the stroke with certain operation being done by that time and that the rod is then moved to the stroke end where operation in the next stage is done.
If the fluid pressure cylinder is controlled by a solenoid valve, energization of the solenoid valve may be interrupted by an unexpected accident. In such a case, a part of an operator's body may be pinched by a workpiece or the like mounted to the rod at the beginning or end of the stroke of the rod. As a safeguard for preventing such a problem, it is more advantageous to use a fluid pressure cylinder in which a rod can stop in an intermediate position that is a non-energized home position than to use a lock mechanism or a three-position valve.
FIG. 8
shows an example of a known dual stroke cylinder in which a rod can stop in an intermediate position of a stroke. In the dual stroke cylinder, a first cylinder
1
A having a first piston
2
A with a stroke S
1
and a first rod
3
A and a second cylinder
1
B having a second piston
2
B with a stroke S
2
that is larger than the stroke S
1
and a second rod
3
B are concentrically connected in series and a tip end of the first rod
3
A airtightly passes through covers of the cylinders
1
A and
1
B to come in contact with the second piston
2
B.
In this dual stroke cylinder, in a state shown in
FIG. 8
in which the first and second pistons
2
A and
2
B and the first and second rods
3
A and
3
B are in return stroke end positions, if compressed air is supplied from a port
5
A to a head-side cylinder chamber
7
A of the first piston
2
A, the first piston
2
A and the first rod
3
A move leftward in
FIG. 8
by the stroke S
1
and stop and the second piston
2
B and the second rod
3
B are pushed by the first rod
3
A and move leftward by the stroke S
1
.
Then, if compressed air is supplied from a port
5
B to a head-side cylinder chamber
7
B of the second cylinder
1
B, the second piston
2
B and the second rod
3
B further move leftward by a stroke (S
2
-S
1
) and stop.
Therefore, it is possible to stop the rod
3
B of the second cylinder
1
B in an intermediate position of the stroke S
1
.
If compressed air is supplied respectively from a port
6
B to a rod-side cylinder chamber
8
B of the second cylinder
1
B and from a port
6
A to a rod-side cylinder chamber
8
A of the first cylinder
1
A and compressed air in the head-side cylinder chambers
7
A and
7
B of the cylinders
1
A and
1
B is discharged to an outside, the second piston
2
B and the second rod
3
B move rightward by the stroke S
2
and the first rod
3
A and the first piston
2
A move rightward by the stroke S
1
, thereby returning to the state shown in FIG.
8
.
The port
6
A on a rod side of the first cylinder
1
A may be a breathing port.
Although the rod
3
B can stop in the intermediate position of the stroke in the above dual stroke cylinder, the cylinder is formed by connecting the two cylinders
1
A and
1
B in series, which complicates the structure and increases the number of parts and cost. Moreover, it is necessary to control supply and discharge of compressed air to and from at least the respective ports
5
A,
5
B, and
6
B of the two cylinders
1
A and
1
B and a structure of a system for controlling supply of the compressed air including pipe connection is complicated.
DISCLOSURE OF THE INVENTION
It is a main object of the present invention to provide a dual stroke cylinder in which a structure and a structure of a system for controlling supply of compressed air are simple, the number of parts is small, and cost can be reduced.
It is another object of the invention to provide a dual stroke cylinder in which a rod can stop not only in full-stroke positions but also in an intermediate stop position only by supply of compressed air to two ports.
To achieve the above objects, according to the invention, there is provided a dual stroke cylinder having a sleeve for intermediate stop and passing for sliding through a rod hole in a cylinder body, with a rod passing for sliding through the sleeve.
A base end portion of the sleeve is positioned in a rod-side pressure chamber and has a pressure receiving portion with a diameter smaller than that of the piston. The sleeve is stopped by stop means in the position when the sleeve moves to a forward end. Between the rod and the sleeve, first lock means for locking the rod and the sleeve to each other at a rearward end when the rod moves rearward relatively to the sleeve and second lock means for locking the rod and the sleeve to each other at a forward end when the rod moves forward relatively to the sleeve are provided.
According to a concrete embodiment of the invention, the stop means is a flange portion formed on an outer periphery of the base end portion of the sleeve and the flange portion is locked to an inner end of the rod hole in the cylinder body at the forward end.
According to another concrete embodiment of the invention, the first lock means is a large-diameter portion formed at the tip end of the rod, the large-diameter portion comes into contact with the tip end portion of the sleeve at the rearward end of the rod, the second lock means is the piston, and the piston comes into contact with a rear end portion of the sleeve at the forward end of the rod.
The dual stroke cylinder can be used for lifting such that a load is lifted or lowered by pushing the load up or by pulling the load up by the rod. The dual stroke cylinder can be used not for lifting such that the piston does not directly receive a weight of the load in the intermediate stop position.
If the cylinder is used as a lift for pushing up, pressure fluid of equal pressure is supplied to the head-side pressure chamber and the rod-side pressure chamber through the ports. If the cylinder is used as a lift for pulling up, pressure fluid of lower pressure is supplied to the head-side pressure chamber, pressure fluid of higher pressure is supplied to the rod-side pressure chamber, and a difference between the pressures of the fluid is maintained at such a value that the piston can stop in the intermediate stop position. If the cylinder is used not for lifting, the pressure fluid of lower pressure is supplied to the head-side pressure chamber, pressure fluid of higher pressure is supplied to the rod-side pressure chamber, and a difference between the pressures of the fluid is maintained at such a value that the piston can stop in the intermediate stop position.
REFERENCES:
patent: 4072087 (1978-02-01), Mueller
patent: 4773300 (1988-09-01), Klatt et al.
patent: 82/03896 (1982-11-01), None
Hirano Akihiro
Iida Kenji
Lopez F. Daniel
SMC Corporation
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