JP2575593B2 - Method and apparatus for generating reciprocation by fluid pressure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for generating reciprocation by fluid pressure which can be used as a driving device for a pneumatic automatic cutter tool or the like.

[0002]

2. Description of the Related Art FIG. 7 is a diagram schematically showing a sectional structure of a conventional pneumatic automatic cutter tool 100. As shown in FIG. In the pneumatic automatic cutter tool 100, a spindle 104 having pistons 105 and 106 at both front and rear ends is slidably housed in a cylinder 103 surrounded by a front wall 101 and a rear wall 102. A slider valve 116 having front, center, and rear annular ribs 111, 112, and 113 circumferentially in contact with the inner wall of the cylinder is slidably fitted in the middle of the spindle 104 so as to be slidable back and forth. The spindle 104 includes the front wall 101 of the cylinder 103 and the front piston 1.
05 and the cylinder 10
3 is stopped and held in a state in which the elasticity of the rear spring 108 provided between the rear wall 102 and the rear piston 106 is balanced. The front end of the spindle 104 penetrates the front wall 101 of the cylinder 103 and projects forward.
The cutter blade 120 is attached to this protruding end.

[0003] The slider valve 116 has a forward air supply passage 114 extending from a peripheral surface between a central annular rib 112 and a rear annular rib 113 to a front surface of the slider valve 116.
A rearward air supply passage 115 is formed from the peripheral surface between the front annular rib 111 and the central annular rib 112 to the rear surface of the slider valve 116. In addition, cylinder 10
3, a main air supply passage 109 is formed so as to match the forward air supply passage 114 of the slider valve 116 in the neutral stop state. Reference numeral 110 denotes an exhaust path, which opens into the cylinder 103 at a predetermined position.

[0004] The conventional pneumatic automatic cutter tool 100 constructed as described above operates as follows. First, the forward air supply passage 114 of the slider valve 116 extends from the air supply main passage 109.
, When air is sent between the slider valve 116 and the front piston 105, the slider valve 116 reverses vigorously, hits the rear piston 106 on the rear surface, and moves the spindle 104 backward. At this time, the rearward supply passage 115 of the slider valve 116 is
And the air sent to the backward air supply passage 115 is sent between the slider valve 116 and the rear piston 106. Therefore, the slider valve 116 moves forward vigorously, and the front piston 10
Hitting 5 causes the spindle 104 to move forward.
At this time, the forward air supply passage 114 of the slider valve 116 comes to coincide with the main air supply passage 109 again, so that the above operation is repeated at a high speed, and the cutter blade 120 reciprocates with the spindle 104 in the front-rear direction. It has become.

[0005]

Each time the slider valve 116 repeatedly moves forward and backward, the front spring 107 and the rear spring 1
08 repeats shocking and instantaneous compression and expansion, so that the front spring 107 and the rear spring 108 are liable to be deteriorated or broken, and need to be replaced relatively frequently. Further, the air supply flow path is switched by moving the slider valve 116 forward and backward. However, the balance of the resilience of the front spring 107 and the rear spring 108 is poor (including the case where the above-described deterioration occurs). ) Has a problem in that the stop position (reverse rotation position in the traveling direction) of the slider valve 116 varies, which adversely affects the forward / backward movement, and the reciprocating motion of the cutter blade 120 cannot be obtained smoothly. there were. Furthermore, the operating speed of the spring is
And cannot be driven at a higher speed.

The present invention has been made in view of the above circumstances, and does not require frequent replacement of a front spring, a rear spring, and the like, and can smoothly reciprocate a cutter blade and the like. And compared to the spring type
It is an object of the present invention to provide a method and an apparatus for generating reciprocation by fluid pressure capable of driving at a higher speed .

[0007]

According to the present invention, the following technical measures have been taken in order to achieve the above object. That is, the method for generating reciprocation according to the present invention employs a drive take-out head in a cylinder.
To supply fluid to the first chamber with a drive plunger integral with
And move forward by supplying fluid to the second chamber.
Slidable back and forth as well as switching inside the cylinder
The plunger is supplied with the fluid to the third chamber so that the plunger is in the first posture.
And the second chamber is brought into the second posture by supplying fluid to the fourth chamber.
So that when the switching plunger is in the first position,
The working fluid is supplied and driven to the second chamber of the plunger.
The fluid in the first chamber of the plunger is discharged out of the cylinder and turned off.
When the replacement plunger is in the second position, the first position of the drive plunger
The working fluid is supplied to the chamber, and the second
The fluid inside the chamber is discharged out of the cylinder, and the drive plunger is
The switching plunger after moving forward a predetermined amount from the limit position
To switch from the first position to the second position by fluid pressure.
The working fluid is supplied to the four chambers, and the drive plunger is
Fluid pressure the changeover plunger after reverse a predetermined amount from that position
In the third room to switch from the second position to the first position
This is to supply a moving fluid.

Further , the reciprocating motion generating apparatus of the present invention
Integral drive plunger and drive take-out head in Sunda first
The vehicle moves backward by supplying fluid to the chamber and supplies fluid to the second chamber.
The plunger is slidably moved back and forth so as to move forward by feeding , and a switching plunger is provided in the cylinder in the third chamber.
Is supplied to the first posture and fluid is supplied to the fourth chamber.
Provided such that the second posture by supercharging, when switching plunger is in the first position, a rear supply passage for supercharged the working fluid to the second chamber of the drive plunger, the drive plunger
A front discharge passage for discharging the fluid in one chamber to the outside of the cylinder is formed, and when the switching plunger is in the second posture, a front supply passage for supplying working fluid to the first chamber of the drive plunger; A fluid passage is provided in the cylinder and the switching plunger so that a rear discharge passage for discharging the fluid in the second chamber to the outside of the cylinder is formed.
A working fluid is supplied to the fourth chamber so as to switch the switching plunger from the first position to the second position by the fluid pressure after the drive plunger has advanced a predetermined amount from the position at the reverse limit, and
Fluid is supplied to the cylinder and the switching plunger so that working fluid is supplied to the third chamber in order to switch the switching plunger from the second position to the first position by fluid pressure after the driving plunger has moved backward by a predetermined amount from a position at the forward limit. A channel is formed .

The switching plunger is slidably provided in the cylinder behind the driving plunger so that the switching plunger is in the first position when the switching plunger moves backward, and is in the second position when the switching plunger moves forward. It is preferable to keep it.

[0010]

According to the present invention , a driving plan is used without using a spring.
Jaws can be reciprocated smoothly at high speed,
Driving at high speed without being limited by operating speed
As well as durability because there is no breakage of the spring
You. In addition, since the flow path of the working fluid is formed in the cylinder and the switching plunger, while having a compact structure,
The above operation can be achieved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a pneumatic automatic cutter tool 2 in which a reciprocating motion generating device 1 according to the present invention is incorporated in a main body 3, 4 is a drive take-out head of the reciprocating motion generating device 1, and 5 is A cutter blade 14 is attached to the drive take-out head 4 and reciprocates. Reference numeral 14 denotes a hose joint for connecting the main body 3 to a hose 6 having an air supply system and an exhaust system. An operation switch for intermittently supplying air in the apparatus 14.

FIG. 2 is a side sectional view showing the reciprocating motion generator 1 by enlarging and breaking the main body 3. The reciprocating motion generator 1 includes a front cylinder 10 having a front wall 11 and a front cylinder 10. The cylinder 15 is composed of a rear cylinder 12 connected to a rear part of the front cylinder 10 and a rear wall 13 which closes the rear part of the rear cylinder 12 as a part of the hose joint 14. Front cylinder 1
A front plunger 20 (drive plunger) is housed in the rear cylinder 12 so as to be slidable back and forth, and a rear plunger 21 (switching plunger) is housed in the rear cylinder 12 so as to be slidable back and forth. A rear plunger 21 is provided on the rear wall 13.
Cushioning material 17 is embedded with its front part exposed in the rear cylinder 12.

The front plunger 20 is formed so as to protrude to the full inner diameter of the front cylinder 10, and has a flange portion 20a whose front and rear surfaces are pressure receiving surfaces;
Oa is formed so as to have an H-shaped cross section by a cylindrical peripheral wall 20b provided to protrude forward and backward from the outer peripheral end of Oa. A drive shaft 22 that penetrates through the front wall 11 of the front cylinder 10 and protrudes forward from the main body body 3 is connected to the flange portion 20a. An ejection head 4 (see FIG. 1) is provided.

FIG. 3 is a side view showing the rear plunger 21. The rear plunger 21 has a small diameter portion 21a,
It has a middle diameter portion 21b and a large diameter portion 22c.
A is provided with a first constricted portion 24, and a middle constricted portion 21b is provided with a second constricted portion 25 and a third constricted portion 26. Front end portion of middle diameter portion 21b (step portion with small diameter portion 21a)
Is provided with a chamfer 27. And the small diameter portion 21
Inside a is formed an air passage 39 that communicates the outer peripheral surface of the first constricted portion 24 with the front end surface.

4A and 4B show the front cylinder 10, wherein FIG. 4A is a rear view, FIG. 4B is a sectional view taken along the line AA (in the same direction as FIG. 2), and FIG. FIG. 4 is a cross-sectional view taken along line B. The front cylinder 10 is provided with a guide cylinder 23 for holding the drive shaft 22 at the front of the front wall 11. In this guide cylinder 23, a bush or packing for bearing is mounted. Are formed. The inner diameter of the front cylinder 10 is formed so as to be able to slidably hold the outer peripheral surface of the above-mentioned front plunger 20 while contacting the outer peripheral surface of the front plunger 20 except for a partial area 10a near the front wall 11. , A partial area 10 near the front wall 11 with respect to this inner diameter.
The inner diameter of “a” is formed slightly larger. On the other hand, three air passages 30, 31, 32 are formed inside the peripheral wall (inside the thickness) of the front cylinder 10 so as to extend in the front-rear direction. Each of the air passages 30 to 31 has one end opened at a different position in the front-rear direction and the circumferential direction of the cylinder inner wall, and the other end opened at the rear end surface of the front cylinder 10.

For convenience of the following description, each air passage 30
Openings on the inner wall side of the cylinder in the air passages 30 to 32 are similarly defined as holes a, c, and e.
The openings on the rear end face side of 0 are holes b, d, and f. 5A and 5B show the rear cylinder 12, wherein FIG. 5A is a front view, FIG. 5B is a right side view, and FIG. 5C is a cross-sectional view taken along line CC (FIG. 2).
(D) is a sectional view taken along line DD, (e)
Is a sectional view taken along line EE. The front end portion of the outer peripheral portion of the rear cylinder 12 is closer to the front end portion.
The diameter is reduced so as to be smaller than the inner diameter on the rear side of the cylindrical peripheral wall 20b. On the outer peripheral portion behind the reduced diameter portion, opposing peripheral surfaces are recessed in a semicircular groove along the front-rear direction, and their rear ends are opened but the front ends are not opened. The thus formed concave portion 38 is provided. The inside of the rear cylinder 12 has a small-diameter portion 12a and a medium-diameter portion 1 that extend from the front to the rear.
2b and a large diameter portion 12c. These parts (1
The inner diameters of 2a, 12b, 12c) are such that the outer peripheral surfaces of the small-diameter portion 21a, the intermediate-diameter portion 21b, and the large-diameter portion 22c of the rear plunger 21 can be held in a slidable manner while being in airtight contact therewith. Is formed. In addition, medium diameter part 1
A boring portion 12d slightly larger than the inner diameter of the middle diameter portion 12b on the rear side is formed at the front end of the 2b (close to the step portion with the small diameter portion 12a). The hole u penetrating in the radial direction at the portion overlapping the small diameter portion 12a and the hole x, y penetrating radially at the portion overlapping the middle diameter portion 12b in the meniscus groove-shaped concave portion 38, and the large diameter portion A hole z penetrating in the radial direction is formed at a portion overlapping with 12c. Five air passages 33 to 37 are formed inside the peripheral wall (inside the thickness) of the rear cylinder 12 along the front-rear direction. Among these, the ventilation passages 34 to 36 have one ends opened at different positions in the front-rear direction and the circumferential direction of the inner wall of the cylinder, and the other end is opened at the front end surface of the rear cylinder 12. Of the other two, one of the air passages 33 has two front and rear openings corresponding to the middle diameter portion 12b, and the other end has an opening at the rear end face of the rear cylinder 12. Has become. And the other air passage 37
Have both ends opened to the inner wall of each cylinder so that the middle diameter portion 21b and the large diameter portion 22c communicate with each other. Of course, the ventilation paths 33 and 37 are also positioned differently in the circumferential direction from the ventilation paths 34 to 36 described above.

For the sake of convenience in the following description, each air passage 33
Through 37 are holes g, h, j,
n, p, s, and t; similarly, openings k, m, and r at the front end face side of the rear cylinder 12 in the ventilation paths 34 to 36, and openings at the rear end face side of the rear cylinder 12 in the ventilation path 33. Is a hole i. Between the front cylinder 10 and the rear cylinder 12, the ventilation paths 30 and 34 are in communication with the holes b and k, the ventilation paths 31 and 35 are in communication with the holes d and m, and the 36 are connected so that the holes f and r communicate with each other, and this connected state is held by positioning means (not shown) such as a knock pin. Each of these connected ventilation paths is sometimes used as a circulation path and sometimes as a supply path for switching. Also, as shown in FIG. 2, the front cylinder 10 and the rear cylinder 12 are housed in the main body 3,
When the hose joint 14 is connected to the hose joint 14, the hole i of the air passage 33 communicates with the air supply main passage 16 provided in the hose joint 14 to form a supply passage.
In addition, the semicircular groove-shaped concave portion 38 forms a direct discharge path for exhaust between the inner peripheral surface of the main body 3 and this direct discharge path is connected to an exhaust system (not shown) in the hose joint 14. It is designed to communicate. In FIG. 2, the ventilation paths 31, 3
5 and the ventilation paths 32, 36, and the ventilation path 37 are illustrated in a position deviated from the actual formation position, and the parts other than the ventilation path 37 are indicated by broken lines to avoid confusion with others.
The holes u, x, y, and z are indicated by two-dot chain lines.

Next, a method for generating reciprocating motion according to the present invention will be described with reference to FIG.
A description will be given based on (a) to (c). As shown in FIG. 6A, the front plunger 20
At the rear stop position of the front / rear sliding area, and the rear plunger 21 in the rear cylinder 12 at the front stop position (second posture) of the front / rear sliding area (that is, the rear plunger 21 is brought into a state of mutual proximity). The operation is started from this state.

After pressing the operation switch 7 (see FIG. 1), the supply air from the air supply main passage 16 and the ventilation passage 33 is first divided into the holes h and g. The air reaches the hole j via the second constricted portion 25 of the rear plunger 21, and is supplied from the hole a to the first chamber formed in front of the front plunger 20 through the ventilation paths 34 and 30. Thus, the ventilation path 33, the second constricted portion 25 and the ventilation path 34,
30, the front chamber (first chamber) of the drive plunger 20
Is formed with a front supply passage for supplying a working fluid.

On the other hand, what flows into the hole g is a step formed between the small diameter portion 21a and the medium diameter portion 21b of the rear plunger 21 and the small diameter portion 12a and the medium diameter portion 12b of the rear cylinder 12. Both the step portion provided between the two and the step portion are supplied to the portion in close contact with each other. In this part, the chamfered portion 27 of the rear plunger 21 (see FIG. 3)
And the boring portion 12d (see FIG. 5) of the rear cylinder 12 are in agreement with each other, so that air is divided between them and acts to push open the stepped portions. Therefore, the rear plunger 21 moves backward while the third chamber is formed between the steps. Then, due to the thrust caused by the rearward movement of the rear plunger 21, the air which has been filled in the fourth chamber formed behind the rear plunger 21 has passed from the hole n through the ventilation passages 35 and 31 to the hole c. From the second plunger between the rear plunger 21 and the front plunger 20. The excess air in the fourth chamber passes through the ventilation passage 37 from the hole s to the hole t, and further passes through the third constriction 26 of the rear plunger 21 from the hole y to the concave portion 38 outside the hole.
(Direct discharge path) and is exhausted to the hose joint 14 side.

As shown in FIG. 6B, the rear plunger 2
After the hole 1 is moved backward, the hole h is closed, and after the supply of air to the first chamber is cut off, air flowing into the third chamber from the hole g flows from the first constricted portion 24 of the rear plunger 21 to the inside thereof. As described above, the air flows into the passage 39 and is supplied to the second chamber together with the air circulated from the fourth chamber (the switching plunger 21 in this state is referred to as a first posture). Thus, the rear chamber of the drive plunger 20 (the second chamber) is formed by the air passage 33, the first constricted portion 24 and the air passage 39.
A rear supply passage for supplying working fluid to the chamber is formed. As a result, the front plunger 20 is advanced.

By the thrust accompanying the forward movement of the front plunger 20, the air which has been filled in the first chamber is pushed out from the hole e to the hole p via the ventilation passages 32 and 36 (see FIG. 6 ( In b), the front plunger 20 is already in the hole e
), And the rear plunger 21 is in a state of being coincident with the hole p at this time.
Through the second constricted portion 25 and the hole x of the
8 (direct release path) and exhausted to the hose joint 14 side. Thus, the ventilation chambers 32, 36, the second constriction 25, and the recess 38 allow the front chamber of the drive plunger 20 (first chamber).
A front discharge passage for discharging the fluid in the chamber (chamber) to the outside of the cylinder 15 is formed.

At this time, a part of the air being supplied to the second chamber reaches the hole n from the hole c via the ventilation paths 31 and 35, and is circulated into the fourth chamber. Therefore, by the time the rear plunger 21 collides with the cushioning member 17 due to the reverse movement, the internal pressure in the fourth chamber starts to increase, inducing a force for reversing the traveling direction of the rear plunger 21 and moving the rear plunger 21 forward. After such an operation, the front plunger 20 reaches the front stop position of the front and rear sliding area, and the rear plunger 21 reaches the rear stop position of the front and rear sliding area (that is, the mutual plunging state). ) Has become.

As shown in FIG. 6C, the rear plunger 2
1 starts to move forward by reversing the traveling direction, the first constricted portion 24 eventually becomes the small-diameter portion 12a of the rear cylinder 12.
And the air supply to the second chamber is cut off, and the hole h is opened instead. The air from the hole h passes through the second constricted portion 25 of the rear plunger 21 to the hole j, and is sent into the hole a through the ventilation paths 34 and 30. At this time, the front plunger 20 is configured to overlap the hole a as shown in FIG. 6B, but a partial area 10a of the front cylinder 10 near the front wall 11 (see FIG. 6B). 4) is formed to have a large diameter, so that air flows into the first chamber from the hole a, and the front plunger 20 can be moved backward. On the other hand, the second chamber is reduced by the thrust when the front plunger 20 moves backward and the thrust of the rear plunger 21 that is moving forward as described above. The filled air reaches the hole n from the hole c via the ventilation paths 31 and 35 and is circulated to the fourth chamber, and flows from the fourth chamber into the hole s, passes through the ventilation path 37, and from the hole t. Further, at this time, the third constricted portion 26 and the hole y of the rear plunger 21 in the matching state are set.
After that, the air is discharged to the concave portion 38 (direct release path) on the outside thereof and is exhausted to the hose joint 14 side. Thus, the vent passages 31, 35, 37, the third constriction 26 and the recess 38 form a rear discharge passage for discharging the fluid in the rear chamber (second chamber) of the drive plunger 20 to the outside of the cylinder 15. I have.

Therefore, after such an operation, the front plunger 20 reaches the rear stop position in the front-rear sliding area, and the rear plunger 21 reaches the front stop position in the front-rear sliding area. The operation returns to the stage shown in FIG. 6A, and thereafter, these operations are repeated at a high speed. As a result, the drive take-out head 4 (see FIG. 1) reciprocates.

In the present invention, a liquid such as water can be used as a working fluid other than air. In addition, by appropriately replacing a component (for example, a saw blade, a hammer, a ratchet wrench, etc.) attached to the drive take-out head 4,
Its versatility can be enhanced.

[0027]

According to the reciprocating motion generating method of the present invention and the reciprocating motion generating device of the present invention, the driving plunger does not use the front spring or the rear spring, and the switching plunger does not use the spring.
Without, it is possible to smoothly reciprocate the plunger by the fluid pressure, the high speed that exceeds the operation speed of the spring forward
It is possible to make a return movement, and the spring may be damaged.
Since no occurrence occurs, the durability can be improved.

[Brief description of the drawings]

FIG. 1 is a side view of a pneumatic automatic cutter tool incorporating a reciprocating motion generator according to the present invention.

FIG. 2 is a side sectional view showing a reciprocating motion generator by enlarging and breaking a main part of FIG. 1;

FIG. 3 is a side sectional view of the rear plunger (slightly reduced from FIG. 2).

4A and 4B show a front cylinder, in which FIG. 4A is a rear view, FIG. 4B is a sectional view taken along line AA of FIG. 4A, and FIG. 4C is a sectional view taken along line BB of FIG. (Both are slightly reduced from FIG. 2).

5A and 5B show a rear cylinder, in which FIG. 5A is a front view, FIG. 5B is a right side view of FIG. 5A, and FIG.
-C line sectional view, (d) is a DD line sectional view of (a),
(E) is a sectional view taken along line EE of (a) (both are shown in FIG.
Slightly smaller).

FIG. 6 is a schematic diagram for explaining a reciprocating motion generation method according to the present invention.

FIG. 7 is a diagram schematically showing a cross-sectional structure of a conventional pneumatic automatic cutter tool.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reciprocating motion generator 2 Pneumatic automatic cutter device 4 Drive extraction head 5 Cutter blade 10 Front cylinder 11 Front wall 12 Rear cylinder 13 Rear wall 15 Cylinder 20 Front plunger 21 Rear plunger

Claims (3)

(57) [Claims] A drive take-out head in a cylinder (15)
A drive plunger (20) integral with (4) is supplied to the first chamber with fluid.
To reverse and to supply fluid to the second chamber.
Slidably forward and backward so that it moves forward with
Switching plunger (21) in Linda (15) in third room
The first position is established by supplying the fluid, and the fluid flows into the fourth chamber.
When the switching plunger (21) is in the first posture, the driving plan is provided.
The working fluid is supplied to the second chamber of the
The fluid in the first chamber of the dynamic plunger (20) is transferred to the cylinder (1).
5) The switching plunger (21) is discharged to the outside and is in the second posture.
At this time, the working fluid is applied to the first chamber of the drive plunger (20).
And the flow in the second chamber of the drive plunger (20)
The body is discharged out of the cylinder (15), and the drive plunger (20) is moved a predetermined amount from the position at the reverse limit.
After moving forward, the switching plunger (21) is
Working fluid is supplied to the fourth chamber to switch from the first position to the second position.
The drive plunger (20) is in the forward limit
After a predetermined amount of backward movement, the switching plunger (21) is
In the third room to switch from the second position to the first position
A method for generating reciprocating motion by fluid pressure, which comprises supplying a moving fluid . 2. A drive plunger (20) integral with a drive take-off head (4) in a cylinder (15) provides a fluid in a first chamber.
To reverse and to supply fluid to the second chamber.
And a switching plunger (21) is provided in the cylinder (15) .
The first posture is established by supplying fluid to the third chamber and the fourth posture is achieved.
Chamber is provided such that the second posture by supercharged the fluid, when the switching plunger (21) is in the first position, a rear supply passage for supercharged the working fluid to the second chamber of the drive plunger (20) (33 , 24, 39) and the second of the drive plungers (20) .
A front discharge passage (32, 36, 25, 38) for discharging the fluid in one chamber to the outside of the cylinder (15) is formed,
When the switching plunger (21) is in the second position, a front supply path (33, 25, 34, 30) for supplying working fluid to the first chamber of the driving plunger (20), and the driving plunger (2).
0), the cylinder (15) and the switching plunger (2) are formed such that a rear discharge passage (31, 35, 37, 26, 38) for discharging the fluid in the second chamber to the outside of the cylinder (15) is formed.
In order to switch the switching plunger (21) from the first position to the second position by fluid pressure after the drive plunger (20) has advanced a predetermined amount from the position at the reverse limit while the fluid flow path is provided in (1). The switching plunger (21) after the working fluid is supplied to the fourth chamber and the drive plunger (20) has moved backward by a predetermined amount from the position at the limit of forward movement.
To switch from the second position to the first position by fluid pressure .
Cylinder (15) so that the working fluid is supplied to the three chambers.
And a fluid pressure reciprocating motion generating device, wherein a fluid flow path is formed in the switching plunger (21). 3. The switching plunger (21) is provided slidably back and forth in the cylinder (15) behind the driving plunger (20), and assumes a first position when the switching plunger (21) moves backward. The reciprocating device according to claim 2, wherein the switching plunger (21) is configured to be in the second position when the switching plunger advances.