KR20080083205A - Pneumatic reciprocating tool - Google Patents

Abstract

A pneumatic reciprocating tool having increased durability against impact by a piston that reciprocates. The pneumatic reciprocating tool has a tubular housing (12), first and second pistons (14, 16) placed in the housing so as to be displaceable in the axial direction of the housing, and a tool installation member (18) extending forward from the second piston. Compressed air from a compressed air source is supplied between the first and second pistons to drive the first and second pistons to rearward and forward, respectively. A braking member (22) is placed in front of the second piston. The braking member has a piston braking chamber (24) having an opening facing rearward. The braking member receives from the opening a front part of the second piston that is driven and displaced forward a predetermined distance by the compressed air, and thus the braking member brakes and stops the second piston by air in the piston braking chamber compressed by the front part of the second piston.

Description

Pneumatic Reciprocating Tool {PNEUMATIC RECIPROCATING TOOL}

The present invention relates to a pneumatic reciprocating tool such as a handheld saw that is driven by compressed air.

This type of pneumatic reciprocating tool extends forward from, for example, a cylindrical housing, first and second pistons disposed in the housing so as to be displaceable in the axial direction of the housing, A tool mounting member for mounting a tool such as a saw at the front end, compressed air supply passage means for communicating a compressed air source between the first and second pistons, and elastically supporting the first and second pistons toward the front and the rear, respectively Having first and second springs, and supplying compressed air from the compressed air source between the first and second pistons so that the first and second pistons resist the first and second springs, respectively, and There is a type in which the tool mounting member is driven forward by displacing forward.

However, in such a type of reciprocating tool, the weight of the second piston with the tool mounting member is large, and even when the second spring is used, since the collision with the housing during the forward drive occurs, the urethane rubber inside the housing A cushioning material formed by the back is provided. However, when the pressure of the compressed air for driving becomes high, it becomes impossible to maintain the durability with such a shock absorbing material.

Patent Document 1: Japanese Unexamined Patent Publication No. 2005-205514

In view of such a point, an object of this invention is to provide the pneumatic reciprocating tool which made it possible to moderately brake and stop a 2nd piston, even if the driving compressed air becomes high pressure, and to relieve the impact force.

That is, the present invention,

Cylindrical housing,

A first piston provided in the housing so as to be displaceable in the axial direction of the housing;

A second piston provided in the housing, aligned in the axial direction with the first piston, and displaceable in the axial direction;

A tool mounting member extending forward from the second piston and mounting a tool such as a saw to the front end;

A compressed air supply means for supplying compressed air from a compressed air source between the first and second pistons, and supplying compressed air from the compressed air source between the first and second pistons to In a pneumatic reciprocating tool in which the two pistons are moved rearward and forward, respectively, to drive the tool mounting member forward,

A braking member provided in the housing at a front position of the second piston, the braking member having a piston braking chamber having a rearward facing opening, the front portion of the second piston being driven and displaced forwardly by a predetermined distance by the compressed air; A braking member which stops the second piston by the air of the piston braking chamber compressed by the front portion by taking in from the opening;

A pneumatic reciprocating tool is provided, having atmospheric communication means for communicating a space between the first and second pistons to the atmosphere when the second piston enters the piston braking chamber.

In this pneumatic reciprocating tool, braking is performed by air compressed by the second piston in the piston braking chamber of the braking member, thereby eliminating the durability problem of the cushioning material such as urethane rubber generated in the conventional tool. Can be.

Specifically, it is preferable to form a means for communicating the space between the second piston in the housing and the braking member to the compressed air source. That is, by doing in this way, since the air pressure in a piston braking chamber can always be raised, when a 2nd piston drives forward and enters into the piston braking chamber, a big braking force can be exerted.

It is also preferable to provide a spring for elastically supporting the braking member in the axial rearward direction thereof.

That is, by doing in this way, since the braking force by air in the piston braking chamber with respect to a 2nd piston can be made small, the said braking member can be made small.

In addition, the braking member may be connected to the first piston so as to be integrally displaced with the first piston, and a spring may be provided to elastically support the first piston axially forward. That is, in this way, the first piston and the braking member are positioned in the axial direction when compressed air is not supplied between the first and second pistons by the first elastic support force, and the first and second pistons When compressed air is supplied in between, the braking member is driven rearward with the first piston. Thus, when the second piston is driven forward by the compressed air, the second piston and the braking member come close to each other, and when the second piston enters the piston braking chamber of the braking member, the movement of the braking member to the rear, thus, Movement backward of the first piston is subject to braking. Therefore, not only the shock relief of the second piston but also the shock relief of the first piston can be obtained. Moreover, the stroke length of a 1st and 2nd piston can be shortened.

More specifically,

The first piston has a rear wall and a cylindrical wall extending forward from the rear end wall,

The second piston is capable of sliding in the axial direction within the cylindrical wall of the first piston,

The atmospheric communication means having an opening formed to penetrate the cylindrical wall of the first piston, and an air passage formed in the housing and communicating with the opening to communicate with the atmosphere,

The opening of the atmospheric communication means can allow the second piston to open and close by sliding relative to the first piston.

In addition, in the above pneumatic reciprocating tool,

From the rear end of the housing and having a fixed axis extending forward in the housing,

The rear end wall of the first piston has a hole through which the fixed shaft is inserted, and the first piston is slidable along the fixed shaft,

The compressed air supply means can have a through hole penetrating the fixed shaft in the axial direction, and a compressed air introduction passage allowing one end to communicate with the rear end of the through hole and the other end to communicate with the compressed air source. The pneumatic reciprocating tool further includes a valve having a first cross section communicated between the first and second pistons through the through hole, and a second cross section having an area smaller than the first cross section. When the force exerted by the compressed air on the second end face is greater than the force exerted on the first end face by the compressed air, the compressed air inlet passage leading to the rear end of the through hole of the fixed shaft is closed and the second end face is closed. And a valve which is displaced to open the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft when the force acting by the compressed air is smaller than the force acting by the compressed air on its first end face. Can be.

By doing this, when the second piston is driven forward by the compressed air and displaced forward by a predetermined distance, when the first and second pistons are reduced to atmospheric pressure or a value close thereto by the atmospheric communication means, The supply of compressed air between the first and second pistons can be cut off so that the braking stop of the second piston can be performed efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a longitudinal sectional view of a compressed pneumatic reciprocating tool according to the present invention and shows a state in which it is not operated.

FIG. 2 is an enlarged cross-sectional view illustrating a compressed air supply path of the compressed pneumatic reciprocating tool of FIG. 1.

Fig. 3 is the same view as Fig. 1 but shows the state in which the compressed pneumatic reciprocating tool is operated so that the tip of the second piston starts to enter the piston braking chamber of the braking member.

FIG. 4 is a view along the line IV-IV in FIG. 3. FIG.

FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 3.

FIG. 6 is the same view as FIG. 1, but the compressed pneumatic reciprocating tool is operated to show a state in which the second piston enters the piston braking chamber of the braking member and is braked.

Explanation of symbols on the main parts of the drawings

10 pneumatic reciprocating tool 12 housing

14: first piston 16: second piston

18: Tool mounting member 19: Supply passage (through hole)

20: fixed shaft 22: braking member

24: piston braking chamber 26: front part

27: sealing ring 28: rear wall

30: cylindrical wall 32: through hole

34: first coil spring 36: second coil spring

40: hose 42: rear wall

44: first trailing member 46: second trailing member

45, 47: packing 48: horizontal passage

50: opening and closing valve 51: spring setting member

52: valve setting hole 53: compression coil spring

54: reverse L-shaped passage 58: first vertical passage 58

59: small diameter horizontal passage 60: large diameter horizontal passage

62: second vertical passage 64: rear flange portion

66: horizontal through hole 68: spool valve

70 valve holding member 72 large diameter sliding portion

74: small diameter sliding portion 76: large diameter hole portion

78: small diameter hole 79: passage

80: upward horizontal through hole 82: circular recess

84: first recessed portion 86: second recessed portion

88: radial hole 90: compressed air communication path

92 liner 94 radial through hole

96 radial hole 98 space

100: annular sliding portion 104: exhaust passage

110: lever

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the pneumatic reciprocating tool which concerns on this invention is described in detail based on an accompanying drawing.

As shown in FIG. 1 and FIG. 2, the pneumatic reciprocating tool 10 according to the present invention includes a cylindrical housing 12 and a first piston 14 provided in the housing so as to be displaceable in the axial direction of the housing. ), A second piston 16 installed in the first piston and displaceable in the axial direction, extending forward from the second piston, and a tool mounting member for mounting a tool S such as a saw at the front end thereof. Compressed air supply means having a fixed shaft (20) formed with a supply path (19) for supplying compressed air between the first and second pistons and extending forward from the rear end of the housing (12); Have

Between the first and second pistons 14 and 16, by supplying compressed air from the compressed air source (not shown) and displacing the first and second pistons 14 and 16, respectively, backwards and forwards, The tool mounting member is driven forward.

The pneumatic reciprocating tool 10 also has a braking member 22 provided in its housing at the front position of the second piston 16. The braking member 22 has a piston braking chamber 24 having an opening facing rearward, the front portion having a small diameter of the second piston 16 driven and displaced forward by a predetermined distance by compressed air ( By taking 26 from the opening, the second piston 16 is braked by the air in the piston braking chamber 24 compressed by the front portion 26. In the example shown, a seal ring 27 is provided in the front portion 26 of the second piston 16, and the seal ring 27 has entered its piston portion 24 into the piston braking chamber 24. When the piston braking chamber 24 is sealed. The first piston 14 has a rear end wall 28 and a cylindrical wall 30 extending forward from the rear end wall, and the through wall 32 is formed in the cylindrical wall 30. The through hole communicates with the atmosphere as described later, and as shown in FIG. 3, when the front portion 26 of the second piston 16 enters the piston braking chamber 24 of the braking member 22, The through hole 32 is opened from the closing by the second piston 16 to allow air between the first and second pistons 14 and 16 to the atmosphere.

In the example shown, the braking member 22 is screwed to the first piston 14 and is adapted to be displaced in the axial direction together with the first piston 14. Further, the first piston 14 is elastically supported forward by the first coil spring 34 set between the rear end portion of the housing 12, and the braking member 22 is a front end of the housing 12. It is elastically supported backward by the 2nd coil spring 36 set between the parts.

As shown in FIG. 2, the compressed air supply means through which the supply path 19 of the fixed shaft 20 communicates with the 1st and 40 which were attached to the rear end wall 42 and the rear end wall 42 of the housing 12, and It is comprised by the fluid flow path formed in the 2nd rear-end member 44,46. In addition, in FIG. 2, 45 and 47 represent the packing.

The second rear end member 46 accommodates the horizontal passage 48 to which the hose 40 is connected and the opening / closing valve 50 which is formed to be orthogonal to the horizontal passage 48 and is displaceable in the vertical direction. It has a valve setting hole 52 and an inverted L-shaped passage 54 formed near the lower end of the valve setting hole 52. The on-off valve 50 is elastically supported in the closed position by the compression coil spring 53 set between the spring setting member 51 set in the valve setting hole 52, and is squeezed by the second rear end member 46. It pushes the lever 110 in a clockwise direction to move to the open position.

The first rear end member 44 includes a first vertical passage 58 communicated with the inverse L-shaped passage 54, a small diameter horizontal passage 59 connected to an upper end of the vertical passage 58, and a small diameter horizontal line. The large diameter horizontal passage 60 connected to the vertical passage 58 at a position below the passage 59 and the second vertical passage 62 to be described later are included. 4 is a left cross-sectional view of the first rear end member viewed along the line IV-IV in FIG. 3.

The rear end wall 42 of the housing 12 has a horizontal through hole formed to a diameter that receives the circular rear end flange portion 64 of the fixed shaft 20 shown in FIG. 5, which is a cross-sectional view taken along the line VV of FIG. 3. Has 66. The spool valve 68 and the valve holding member 70 for slidably holding the spool valve in the horizontal direction are set in the horizontal through hole. The spool valve 68 has a large diameter sliding part 72 and a small diameter sliding part 74, and correspondingly, the valve holding member 70 has the large diameter hole which supports the large diameter sliding part 72 so that sliding is possible. A central horizontal through hole having a portion 76 and a small diameter hole 78 is formed. The valve holding member 70 further has an upper horizontal through hole 80 in an upper portion thereof, and the horizontal through hole 80 has a small diameter horizontal passage 59 of which the right end thereof is the first rear end member 44. In communication with On the left end surface of the valve holding member 70, a circular concave portion 82 having a diameter larger than that of the left end opening is formed concentrically with the left end opening of the central horizontal through hole 77, and the upper horizontal through hole 80 is formed. ) Is connected to the circular recess 82. The spool valve 68 is formed with first and second recesses 84 and 86 from its left and right sides in the radial center portion thereof, and radially from the second recess 86 with the spool valve. A penetrating radial hole 88 is formed. On the other hand, the passage reached to the position which communicates with the 2nd vertical path 62 of the 1st rear-end member 44 in the part of the center horizontal through-hole 77 mentioned above rather than the small diameter hole part 78 is mentioned. 79 is formed, and the passage 79 communicates with the radial hole 88.

As can be seen from the above, the area of the spool valve 68 is larger than the area of the surface oriented to the right, and when the pressure of the compressed air source is applied to both sides, the spool valve 68 is right. It is supposed to move.

The housing 12 is formed with a compressed air communication path 90 extending in the axial direction along the lower portion as seen in FIGS. 1 and 2, and the front end of the passage 90 is formed on the inner circumference of the housing 12. The second piston through the radial through hole 94 formed in the liner 92 formed so that the first piston 14 slides and the radial hole 96 formed in the cylindrical wall 30 of the first piston 14. It is in communication with the space 98 between the 16 and the braking member 22. As shown, annular sliding parts 100 and 102 are provided on both sides of the radial hole 96 formed in the cylindrical wall 30 of the first piston 14, and the liner 92 is provided. The compressed air that enters from the radial through hole 94 formed in the chamber is prevented from leaking to both sides.

In addition, the through-hole 32 formed in the cylindrical wall of the 1st piston 14 is formed between the liner 92 and the 1st piston, and extends back, As shown in FIG. 5, the fixed shaft 20 Is communicated with the atmosphere by an exhaust path 104 extending between the flange portion 64 of the s) and the rear end wall 42 of the housing 12 and extending to the first rear end member 44.

In order to operate this pneumatic reciprocating tool 10, the lever 110 is pushed clockwise as shown in FIG. 1 to open and close the valve 50. Thereby, compressed air is supplied from the compressed air source through the hose 40, the passages 48, 54 of the second rear end member 46, and the passages 58, 59, 60 of the first rear end member 44. On the left and right sides of (68). As described above, the left-facing side of the spool valve 68 has a larger area than the right-facing side. Therefore, when compressed air acts on these faces, the spool valve 68 is elastically supported to the right, Compressed air passes through the through hole 19 of the fixed shaft 20 and is supplied between the first and second pistons 14 and 16. In the state shown in FIG. 1, the second piston 16 closes the through hole 32 formed in the cylindrical wall 30 of the first piston 14, and thus is supplied between the first and second pistons. Compressed air drives the first and second pistons rearward and forward, respectively.

3 shows that the first and second pistons 14, 16 are driven as such, so that the front end of the front portion 26 of the second piston 16 has the piston braking chamber 24 of the braking member 22. The state which started to enter the right end opening is shown. At this time, the second piston 16 opens the through hole 32 formed in the cylindrical wall 30 of the first piston 14 to exhaust the space between the first and second pistons 14 and 16. Communication with the furnace 104. For this reason, the 1st piston 14 is stopped by the action of the 1st coil spring 34, and then moves forward.

However, the second piston 16, by inertia, continues to move forward at a higher speed than the braking member integral with the first piston 14, so that the front portion 26 of the second piston is again It enters into the piston braking chamber 24 of the braking member 22 and compresses the air in the braking chamber (at the time when the front portion 26 of the second piston enters the piston braking chamber 24, the first and the second Since the space between the pistons 14 and 16 communicates with the atmosphere, the spool valve is displaced to the left, so that the upper horizontal through-hole 80 of the valve holding member 70 and the supply passage 19 of the fixed shaft 20 are closed. )). The air compressed in the braking chamber 24 brakes against the second piston 16 so that the second piston finally stops, and then the compressed air communication path 90 radially penetrates. It is pressed back by the compressed air supplied to the space 98 through the hole 94 and the radial hole 96, whereby the second piston 16 is the cylindrical wall 30 of the first piston 14. ), The through hole 32 is closed, and the movement continues further to the rear, the space 98 is communicated with the through hole 32, and the space 98 is communicated with the atmosphere. At the same time, the volume between the first and second pistons 14, 16 is reduced so that the internal air pressure rises, and the spool valve 68 is moved again to the right, so that the compressed air from the compressed air source is fixed shaft 20 It is supplied between the first and second piston through the through hole 19 of.

In this way, the reciprocating action of this pneumatic reciprocating tool is continued.

In addition, when the on-off valve 50 is opened, the compressed air source is connected to the passage 54 of the second rear end member 46, the passages 58 and 60 of the first rear end member 44, and the radial direction of the spool valve 68. Through the hole 88 and the second recess 86, the passage 79, the passage 62 of the first rear end member 44, and the passage 90 of the housing 12, the second piston 16 and It is always in communication with the space 98 between the braking members 22, so that the piston braking chamber 24 is filled with compressed air, so that the second piston 16 has intruded into the piston braking chamber 24. A large braking action can be performed with respect to the second piston 16 at the time.

Further, when the on-off valve 50 is opened, the second piston 16 is positioned at the position shown in FIG. 3 with respect to the first piston 14, that is, the through hole 32 of the cylindrical wall 30 of the first piston 14. In the case where the gap between the first and second pistons is in communication with the atmosphere, the compressed air is supplied to the space 24 between the second piston 16 and the braking member 22 as described above. Since the 2nd piston 16 is in the state as shown in FIG. 1 with respect to the 1st piston 14 by the action of the compressed air, it moves the spool valve 68 to the right, and the above-mentioned In the same manner, the reciprocating action of the pneumatic reciprocating tool is performed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this Example, It can change variously within the scope of this invention prescribed | regulated by the claim. For example, in the illustrated example, the braking member 22 is separated from the housing 12 to slide in the housing, but can be fixed to the housing by integrally forming the housing.

Claims (13)

Cylindrical housing, A first piston provided in the housing so as to be displaceable in the axial direction of the housing; A second piston provided in the housing, aligned in the axial direction with the first piston, and displaceable in the axial direction; A tool mounting member extending forward from the second piston and mounting a tool such as a saw to the front end; Compressed air supply means for supplying compressed air from a compressed air source between the first and second pistons, and between the first and second pistons supply compressed air by the compressed air supply means, A pneumatic reciprocating tool in which the tool mounting member is driven forward by displacing the second piston backwards and forwards, respectively, A braking member provided in the housing at a front position of the second piston, the braking member having a piston braking chamber having a rearward facing opening, the front portion of the second piston being driven and displaced forwardly by a predetermined distance by the compressed air; A braking member which stops the second piston by the air of the piston braking chamber compressed by the front portion by taking in from the opening; And an atmospheric communication means for communicating the space between the first and second pistons to the atmosphere when the second piston enters the piston braking chamber. The method of claim 1, And a means for communicating a space between the second piston in the housing and the braking member to a compressed air source. The method according to claim 1 or 2, A pneumatic reciprocating tool having a spring that elastically supports the braking member to its axial rearward direction. The method according to claim 1 or 2, The braking member is connected to the first piston so as to be integrally displaced with the first piston, And a spring for elastically supporting the first piston in an axial forward direction. The method of claim 3, wherein The braking member is connected to the first piston so as to be integrally displaced with the first piston, And a spring for elastically supporting the first piston in an axial forward direction. The method according to claim 1 or 2, The first piston has a cylindrical wall extending forward from the rear end wall and the rear end wall thereof, The second piston is capable of sliding in the axial direction of the cylindrical wall of the first piston, The atmospheric communication means having an opening formed to penetrate the cylindrical wall of the first piston, and an air passage formed in the housing and communicating with the opening to communicate with the atmosphere, The opening of the atmospheric communication means is a pneumatic reciprocating tool, characterized in that the second piston is opened and closed by sliding relative to the first piston. The method of claim 3, wherein The first piston has a cylindrical wall extending forward from the rear end wall and the rear end wall thereof, The second piston is capable of sliding in the axial direction of the cylindrical wall of the first piston, The atmospheric communication means having an opening formed to penetrate the cylindrical wall of the first piston, and an air passage formed in the housing and communicating with the opening to communicate with the atmosphere, The opening of the atmospheric communication means is a pneumatic reciprocating tool, characterized in that the second piston is opened and closed by sliding relative to the first piston. The method of claim 4, wherein The first piston has a cylindrical wall extending forward from the rear end wall and the rear end wall thereof, The second piston is capable of sliding in the axial direction of the cylindrical wall of the first piston, The atmospheric communication means having an opening formed to penetrate the cylindrical wall of the first piston, and an air passage formed in the housing and communicating with the opening to communicate with the atmosphere, The opening of the atmospheric communication means is a pneumatic reciprocating tool, characterized in that the second piston is opened and closed by sliding relative to the first piston. The method of claim 5, wherein The first piston has a cylindrical wall extending forward from the rear end wall and the rear end wall thereof, The second piston is capable of sliding in the axial direction of the cylindrical wall of the first piston, The atmospheric communication means having an opening formed to penetrate the cylindrical wall of the first piston, and an air passage formed in the housing and communicating with the opening to communicate with the atmosphere, The opening of the atmospheric communication means is a pneumatic reciprocating tool, characterized in that the second piston is opened and closed by sliding relative to the first piston. The method of claim 6, Has a fixed shaft extending forward in the housing from the rear end of the housing, The rear end wall of the first piston has a hole through which the fixed shaft is inserted, and the first piston is slidable along the fixed shaft, The compressed air supply means has a through hole penetrating the fixed shaft in the axial direction, and a compressed air introduction passage whose one end communicates with the rear end of the through hole, and the other end communicates with the compressed air source, The pneumatic reciprocating tool is further provided as a valve having a first cross section communicated between the first and second pistons through the through hole of the fixed shaft and a second cross section having an area smaller than the first cross section. When the force acting on the second end face by the compressed air is greater than the force acting on the first end face by the compressed air, the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft is closed. And a valve displaced to open the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft when the force exerted by the compressed air on the second end face is smaller than the force exerted by the compressed air on the first end face. Pneumatic reciprocating tool, characterized in that. The method of claim 7, wherein Has a fixed shaft extending forward in the housing from the rear end of the housing, The rear end wall of the first piston has a hole through which the fixed shaft is inserted, and the first piston is slidable along the fixed shaft, The compressed air supply means has a through hole penetrating the fixed shaft in the axial direction, and a compressed air introduction passage whose one end communicates with the rear end of the through hole, and the other end communicates with the compressed air source, The pneumatic reciprocating tool is further provided as a valve having a first cross section communicated between the first and second pistons through the through hole of the fixed shaft and a second cross section having an area smaller than the first cross section. When the force acting on the second end face by the compressed air is greater than the force acting on the first end face by the compressed air, the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft is closed, and And a valve displaced to open the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft when the force exerted by the compressed air on the second end face is smaller than the force exerted by the compressed air on the first end face. Pneumatic reciprocating tool, characterized in that. The method of claim 8, Has a fixed shaft extending forward in the housing from the rear end of the housing, The rear end wall of the first piston has a hole through which the fixed shaft is inserted, and the first piston is slidable along the fixed shaft, The compressed air supply means has a through hole penetrating the fixed shaft in the axial direction, and a compressed air introduction passage whose one end communicates with the rear end of the through hole, and the other end communicates with the compressed air source, The pneumatic reciprocating tool is further provided as a valve having a first cross section communicated between the first and second pistons through the through hole of the fixed shaft and a second cross section having an area smaller than the first cross section. When the force acting on the second end face by the compressed air is greater than the force acting on the first end face by the compressed air, the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft is closed. And a valve for displacing the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft when the force exerted by the compressed air on the second end face is smaller than the force exerted by the compressed air on the first end face. Pneumatic reciprocating tool, characterized in that. The method of claim 9, Has a fixed shaft extending forward in the housing from the rear end of the housing, The rear end wall of the first piston has a hole through which the fixed shaft is inserted, and the first piston is slidable along the fixed shaft, The compressed air supply means has a through hole penetrating the fixed shaft in the axial direction, and a compressed air introduction passage whose one end communicates with the rear end of the through hole, and the other end communicates with the compressed air source, The pneumatic reciprocating tool is further provided as a valve having a first cross section communicated between the first and second pistons through the through hole of the fixed shaft and a second cross section having an area smaller than the first cross section. When the force acting on the second end face by the compressed air is greater than the force acting on the first end face by the compressed air, the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft is closed. And a valve displaced to open the compressed air introduction passage leading to the rear end of the through hole of the fixed shaft when the force exerted by the compressed air on the second end face is smaller than the force exerted by the compressed air on the first end face. Pneumatic reciprocating tool, characterized in that.

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