JPH0570725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a pneumatic cylinder for clamping a workpiece.

[Prior Art] Pneumatic cylinders in which a piston rod reciprocates by the action of compressed air pressure have been widely known. Further, in general, this pneumatic cylinder is also widely used to fix workpieces and the like.

[Problems to be Solved by the Invention] However, when compressed air is no longer supplied to such conventional pneumatic cylinders, for example, when a pipe is disconnected or the compressor is stopped due to a power outage, etc., the pressing force is lost. Therefore, in a clamping device using a pneumatic cylinder, there is a problem in that when the pushing force is removed, the workpiece cannot be securely fixed, which may be dangerous, for example, during cutting of the workpiece.

Also, when using pneumatic cylinders,
The cylinder diameter is selected based on the required maximum pushing force. However, in general, the maximum pushing force is often required for only a portion of the stroke. For example, when used in a clamp device, the maximum pushing force is required only when the workpiece is contacted and fixed. Therefore, even when the maximum pushing force is not required, such as during a stroke, compressed air corresponding to the cylinder diameter selected based on the maximum pushing force is consumed, resulting in a problem that the amount of compressed air consumed is large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and to provide a pneumatic cylinder that maintains the pushing force of a piston rod without supplying compressed air and consumes less air.

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following structure as a means for solving the problems. That is, in a pneumatic cylinder that reciprocates a piston rod by the acting force of compressed air pressure, clamps a workpiece when the piston rod moves in one direction, and unclamps it when it moves in the other direction, the piston rod is arranged in an annular shape in contact with the outer periphery of the piston rod. a plurality of steel balls; a holder rotatably holding the plurality of steel balls and slidably mounted on the piston rod in a clamping direction from a predetermined open position; a small compression spring that biases the piston rod in the unclamping direction so as to return the piston rod to the piston rod;
A tapered hole whose diameter is reduced in the unclamping direction and circumscribes the steel ball moves from the open position where it does not press the steel ball in the clamping direction, thereby pressing the piston rod via the steel ball and releasing the compression spring. a main piston formed to be able to transmit the urging force of the piston rod to the piston rod and having a main pressure chamber formed on the side opposite to the compression spring; a sub-piston having a sub-pressure chamber formed on a side opposite to the main piston, and a connecting member disposed between each of the pistons and slidably attached to the piston rod, By supplying compressed air to the pressure chamber, the main piston is moved to a position where the tapered hole does not press the steel ball against the biasing force of the compression spring, and when the supply of compressed air is stopped, the biasing force of the compression spring is reduced. This is the configuration of the pneumatic cylinder characterized in that the piston rod is biased in the clamping direction by the piston rod.

[Function] The pneumatic cylinder of the present invention having the above configuration has the following features:
By supplying compressed air to the main and sub-pressure chambers, the pistons connected by the connecting members cooperate to move the main piston against the biasing force of the compression spring to a position where the tapered hole does not press the steel ball. Therefore, the piston rod reciprocates due to the acting force of the compressed air pressure. When the supply of compressed air is stopped, the compression spring moves the main piston in the clamping direction due to its biasing force, presses the piston rod via the steel ball, transmits the biasing force of the compression spring to the piston rod, and the piston rod moves in the clamping direction. Hold the pushing force.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

Fig. 1 is a partial sectional view of a pneumatic cylinder which is an embodiment of the present invention, Fig. 2 is a sectional view along AA of Fig. 1,
Figure 3 is a view from arrow B in Figure 1, Figure 4 is a view from Figure 1.
It is a CC sectional view.

The other pneumatic cylinder includes a pushing force holding part 1 and a small diameter cylinder part 2.

The small diameter cylinder part 2 is fitted to both ends of its cylinder tube 4 and includes a head cover 10 and an intermediate cover 12 having ports 6 and 8, and a piston 14 is slidably fitted inside the cylinder tube 4. At the same time, a piston rod 16 is fixed to the piston 14. This piston rod 16 is slidably inserted into an insertion hole 18 provided through the intermediate cover 12 and extends toward the pushing force holding portion 1 side. Furthermore, a cylinder tube 22 of the pushing force holding section 1 is fitted into the outer circumferential recess 20 of the intermediate cover 12 . In this embodiment, as shown in FIG.
By moving the piston rod 16 in the direction of protruding it,
In FIG. 1, the piston rod 16 is arranged to clamp a workpiece W, which will be described later, by moving to the left, and unclamp the workpiece W by moving the piston rod 16 in the opposite direction (rightward in FIG. 1). .

The pushing force holding part 1 includes a rod cover 24 provided opposite to the intermediate cover 12, and an insertion hole 26 is bored in the center of the rod cover 24, so that the piston rod 16 can slide into the insertion hole 26. It has been inserted. Further, a screw hole 28 is formed in the rod cover 24, and an O-ring 29 is fitted into the screw hole 28 to prevent leakage, and one end of the cylinder tube 22 is screwed into the screw hole 28. A threaded portion 30 is formed at the other end of the cylinder tube 22, and a nut 32 is screwed into this threaded portion 30 to be fixed to the intermediate cover 12.

Furthermore, the rod cover 24 is provided with figures 2 and 3.
As shown in the figure, a return port 34 is formed, and a manual lever 38 having a convex portion 36 at its tip is swingably inserted. Further, the rod cover 24 is provided with two clevises 42 into which bushes 40 are inserted.

Inside the cylinder tube 22 of the pushing force holding part 1,
A main piston 44, which is slidably mounted on the piston rod 9, is also slidably inserted into the cylinder tube 22. A tapered hole 46 whose diameter decreases toward the unclamping direction is bored in the center of the main piston 44. As shown in FIG. 4, a plurality of steel balls 48 are arranged in an annular shape between the tapered hole 46 and the outer periphery of the piston rod 16 in contact with the outer periphery of the piston rod 16. It is rotatably held and arranged in the container 50. The retainer 50 is the intermediate cover 12
The piston rod 16 is fitted around the piston rod 16 so as to be slidable in the clamping direction from a predetermined open position where it abuts the piston rod.
In addition, when the main piston 44 is in contact with the intermediate cover 12, the tapered hole 46 that circumscribes the steel ball 48 is not pressing the steel ball 48, and from that state it moves to the left (moves in the clamping direction). steel ball 4
The taper hole 46 is formed with an inclination angle of about 10 degrees on one side, for example, so that the piston rod 16 can be pressed through the taper hole 46. Furthermore, a small compression spring 52 is provided between the retainer 50 and the main piston 44 and is attached to the piston rod 16, which biases the retainer 50 in the direction of contacting the intermediate cover 12 and returns it to the open position. It is like that.

A recess 54 is formed on the outer periphery of the main piston 44, and a recess 56 is also formed on the outer periphery of the intermediate cover 12.
4 and 56 are provided with compression springs 58 that bias the main piston 44 in the clamping direction. The main piston 44 on the opposite side where this compression spring 58 is disposed
A recess 60 is formed in the center of the piston rod 16, into which one end of a connecting pipe 62, which is a connecting member, is inserted around the piston rod 16 with a gap. A through hole 64 is bored in the radial direction at the end of the connecting pipe 62 on the main piston 44 side. Note that a passage 66 is formed by the gap between the piston rod 16 and the connecting pipe 62.

Further, inside the cylinder tube 22, a sub-piston 68 is disposed in parallel with the main piston 44 and is encircled with a gap in the piston rod 16.
is slidably inserted. A recess 70 is formed in the center of the sub-piston 68 on the main piston 44 side, and the end of the connecting pipe 62, which is leak-proofed with an O-ring 72, is inserted into the recess 70. In addition, this piston rod 16 and the sub-piston 6
A passage 74 is formed by the gap between the two.

Further, a partition cover 78 is provided between the main piston 44 and the sub-piston 68, and is sealed with an O-ring 76 and slidably mounted around the connecting pipe 62. This partition cover 78 is held between two retaining rings 82 that are fitted into two grooves 80 formed in the cylinder tube 22. Therefore, the partition cover 78 does not move in the axial direction.

In addition, the main piston 44, the connecting pipe 62, the partition cover 78, and the cylinder tube 22 are included in the pushing force holding part 1.
A main pressure chamber 84 surrounded by the sub piston 6 is formed.
8, a sub-pressure chamber 86 is formed surrounded by the piston rod 16, the rod cover 24, and the cylinder tube 22. This auxiliary pressure chamber 86 is connected to the return port 34
It communicates with In addition, the through hole 64, the passage 66,
74 communicates the main pressure chamber 84 and the sub-pressure chamber 86. Compressed air is supplied to the main pressure chamber 84 and the sub-pressure chamber 86, and an acting force corresponding to the compressed air is generated on the main piston 44 and the sub-piston 68. This acting force on the main piston 44 and the auxiliary piston 68 are generated. This acting force of the main piston 44 and the sub piston 6
8 and the biasing force of the compression spring 58, the biasing force of the compression spring 58 is set to be slightly smaller.

On the other hand, the spring storage chamber 88 surrounded by the recess 54 of the main piston 44, the recess 56 of the intermediate cover 12, and the cylinder tube 22 is constantly communicated with the atmosphere through an exhaust hole 90 formed in the cylinder tube 22. Further, a chamber 92 surrounded by the sub-piston 68, the connecting pipe 62, the partition cover 78, and the cylinder tube 22 is constantly communicated with the atmosphere through an exhaust hole 94 formed in the cylinder tube 22. A filter 96 is inserted into each of these exhaust holes 90, 94.

In this embodiment, the main piston 44 and one sub-piston 68 form a tandem type single-acting cylinder, but for example, a plurality of sub-pistons 68 are provided, and a plurality of connecting pipes are connected between them. 6
2, the thrust can be further increased, and the biasing force of the compression spring 58 can also be increased.

Next, the operation of the pneumatic cylinder of this embodiment will be explained.

First, when compressed air is supplied to the return port 34, the compressed air flows into the auxiliary pressure chamber 86 via the return port 3. Subsequently, compressed air also flows into the main pressure chamber 84 via the passages 74 and 66 and the through hole 64. Therefore, an acting force in the right direction in the drawing according to the compressed air pressure is generated on the main piston 44 and the sub-piston 68, respectively, and the acting force generated on the main piston 44 and the sub-piston 68 connected to the main piston 44 through the connecting pipe 62 are When the sum of the acting forces generated in and of the biasing force of the spring 58 overcomes the biasing force of the spring 58, the main piston 44 and the sub piston 68 move to the right.

The main piston 44 and the sub piston 68 move to the right,
When the main piston 44 comes into contact with the intermediate cover 12,
Rightward movement is stopped. At this time, the retainer 50 is brought into contact with the intermediate cover 12 due to the biasing force of the small compression spring 52. Moreover, between the tapered hole 46 and the steel ball 48 or between the steel ball 48 and the piston rod 16,
There is a slight gap, and the steel ball 48 is in a state where it can rotate freely. In this state, by supplying and discharging compressed air to the ports 6 and 8, the piston rod 16 can freely reciprocate.

Furthermore, when the supply of compressed air to the return port 34 is stopped, the main piston 44 and the sub piston 68 connected to the main piston 44 through the connecting pipe 62
It moves to the left in the figure due to the biasing force of the compression spring 58. As the main piston 44 moves to the left, the tapered hole 46 comes into contact with a plurality of steel balls 48, and the steel balls 4
8, the piston rod 16 is pressed and gripped with a strong force corresponding to the biasing force of the compression spring 58 and the inclination angle of the tapered hole 46, and the steel ball 48 is wedged into the piston rod 16. Also, at this time,
The steel ball 48 is connected to the cage 50, the piston rod 16,
The main piston 44 can move together with the main piston 44 until it abuts against the retaining ring 82 . Therefore, the main piston 44 has a stroke until it hits the retaining ring 82, but as shown in FIG. 5, the piston rod 16 that is clamping the work W moves further in the clamping direction (see FIG. Then move left). Therefore, in order to maintain the clamped state of the workpiece W, the piston rod 16
There is no need to move it in the clamping direction, and it is sufficient to have a pushing force, so the stroke may be small. In this state, move the piston rod 16 to the steel ball 4.
8 to the left (clamping direction), the biasing force of the compression spring 58 is transmitted to the piston rod 16, and the clamped state is maintained by the biasing force of the compression spring 58.

Again, as described above, when compressed air is supplied to the return port 34, the main piston 44 moves to the right, and the pressing and gripping of the piston rod 16 by the taper hole 46 via the steel ball 48 is released.

On the other hand, when compressed air is not supplied to the return port 34, that is, when the piston rod 16 is pressed and gripped by the tapered hole 46 via the steel ball 48,
When the manual lever 38 is rotated clockwise, the convex portion 36 of the manual lever 38 comes into contact with the sub-piston 68,
Sub piston 68, connecting pipe 62, main piston 44
is moved to the right against the biasing force of the compression spring 58.
Therefore, the pressing and gripping of the piston rod 16 via the steel ball 48 by the taper hole 46 can also be released.

As mentioned above, the pneumatic cylinder of this embodiment is
By supplying compressed air to the main pressure chamber 84 and the sub-pressure chamber 86, the piston rod 16 can be freely reciprocated by supplying and discharging the compressed air to and from the ports 6 and 8. Furthermore, since the main piston 44 and the sub-piston 68 form a tandem cylinder, the sum of their acting forces can be made very large compared to the cylinder diameter.
The biasing force of can also be set to a very large value. Therefore, when there is no compressed air supply,
Due to the strong biasing force of the compression spring 58, the main piston 44 and the sub-piston 68 move to the left, and press and grip the piston rod 16 with a strong force corresponding to the biasing force of the compression spring 58 and the inclination angle of the tapered hole 46. As the piston rod 16 is pushed to the left, the piston rod 16 maintains the pushing force in the left direction.

Next, a clamp device to which the pneumatic cylinder of this embodiment is applied will be explained with reference to FIG.
FIG. 5 is a front view of the clamp device.

This clamp device includes a fulcrum pin 10 inserted into a bush 40 of a clevis 42 of this pneumatic cylinder.
0 is fitted into a support stand 104 attached to the side surface 102a of the base 102, and the present pneumatic cylinder is swingably supported. Further, a joint 106 is screwed into the tip of the piston rod 16, and the joint 106 is rotatably engaged with one end of a lever 110 by a fulcrum pin 108. The lever 110 is supported by a fulcrum pin 112.
It is rotatably engaged with a support stand 114 attached to the upper surface 102b of the base 102. Further, a workpiece W is placed below the other end of the lever 110.

When this clamping device supplies compressed air to the return port 34 and port 6, the piston rod 16
is raised together with the joint 106, and the lever 11
0 swings counterclockwise around the fulcrum pin 112, the other end of the lever 110 comes into contact with the workpiece W,
Clamp the workpiece W. When the workpiece W is clamped, the piston rod 18 is stopped while maintaining an upward pushing force due to the acting force of the compressed air pressure. At this time, when the supply of compressed air is stopped, the biasing force of the compression spring 58 causes the main piston 4 to
4 moves, and the taper hole 46 strongly presses and grips the piston rod 16 via the steel ball 48, and pushes the piston rod 16 upward. At this time, the piston rod 16 does not move, but is urged upward by the urging force of the compression spring 58.

Therefore, according to the present clamping device, even if the supply of compressed air is stopped during clamping, the piston rod 16 is biased by the compression spring 58 and maintains its pushing force, thereby maintaining the clamped state of the workpiece W.
Therefore, even if the compressor or the like stops while cutting the work W, for example, the work W will not come off the clamp and pose a danger. Furthermore, a pressing force sufficient to swing the lever 110 is sufficient for the small diameter cylinder portion 2, and the cylinder diameter of the small diameter cylinder portion 2 may be small. Therefore,
The amount of air consumed for clamping operation is small.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

Effects of the Invention As detailed above, according to the pneumatic cylinder of the present invention, the compression spring strongly presses and grips the piston rod, and the piston rod maintains a pressing force in the clamping direction. Therefore, even if the supply of compressed air is stopped due to a failure or the like, the clamped state of the workpiece can be maintained, and the amount of air consumed can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a pneumatic cylinder showing an embodiment of the present invention, Fig. 2 is a sectional view along AA of Fig. 1,
Figure 3 is a view from arrow B in Figure 1, Figure 4 is a view from Figure 1.
The CC sectional view and FIG. 5 are front views of a clamp device to which the pneumatic cylinder of the present invention is applied. 16...Piston rod, 44...Main piston, 46...Tapered hole, 48...Steel ball, 68...
Sub-piston, 84...Main pressure chamber, 86...Sub-pressure chamber.

Claims (1)

[Scope of Claims] 1. In a pneumatic cylinder that reciprocates a piston rod by the acting force of compressed air pressure, clamps a workpiece by moving the piston rod in one direction, and unclamps it by moving the piston rod in the other direction, the piston rod is in contact with the outer circumference of the piston rod. a plurality of steel balls arranged in an annular shape; a holder rotatably holding the plurality of steel balls; and a holder ring-mounted on the piston rod so as to be slidable in a clamping direction from a predetermined open position; a small compression spring that biases in the unclamping direction so as to return the device to the open position; a small compression spring that is slidably mounted on the piston rod and is biased in the clamping direction by the compression spring;
A tapered hole whose diameter is reduced in the unclamping direction and circumscribes the steel ball is moved from the open position where it does not press the steel ball in the clamping direction, thereby pressing the piston rod via the steel ball to release the compression spring. a main piston formed to be able to transmit the urging force of the piston rod to the piston rod and having a main pressure chamber formed on the side opposite to the compression spring; a sub-piston having a sub-pressure chamber formed on a side opposite to the main piston, and a connecting member disposed between each of the pistons and slidably attached to the piston rod, By supplying compressed air to the pressure chamber, the main piston is moved to a position where the tapered hole does not press the steel ball against the biasing force of the compression spring, and when the supply of compressed air is stopped, the biasing force of the compression spring is reduced. The pneumatic cylinder is characterized in that the piston rod is biased in the clamping direction by the piston rod.