JP5630309B2 - Impact tool - Google Patents

Description

  The present invention relates to a striking tool, and in particular, is capable of effectively adjusting a change in atmospheric pressure in a sealed space of a striking mechanism.

  A hammer drill is known as an impact tool for drilling or drilling holes in work pieces such as concrete and bricks by being driven by an electric motor and applying rotational force or impact force to the tip tool, or both. Yes. An example of a conventional electric hammer drill will be described with reference to FIG. FIG. 6 is a side view of a conventional hammer drill, and shows a main part in a sectional view. The hammer drill 101 intermittently collides with the second hammer 20 by reciprocating the piston 14 back and forth using the motor 31 as a driving source, and the striking force is transmitted from the second hammer 20 to a tip tool (not shown). The housing part forming the outline of the hammer drill 101 includes a crankcase 102 that houses a power transmission mechanism from the motor 31, a motor housing 108 that is provided below the crankcase 102 and houses the motor 31, and a rear side of the crankcase 102. And a cylinder case 4 holding a cylindrical cylinder 17 that defines a moving space of a reciprocating piston 9. These can be formed in a divided structure by, for example, plastic. A power cable 30 is connected to the lower end of the handle housing 3, and a trigger 29 is provided at the grip portion. By operating the trigger 29, the amount of power supplied from the external power source to the motor 31 can be adjusted, and the rotation speed of the motor 31 can be adjusted.

  The motor 31 is provided below the crankcase 102, and the output shaft 32 that outputs the rotational driving force is disposed so as to be perpendicular to the axial direction of the cylinder 17. A pinion gear 35 is attached to the upper end of the output shaft 32 extending upward from the motor 31. The output shaft 32 is rotatably held by a bearing 34. The output shaft 32 is provided with a cooling fan 33 for cooling the motor 31. A crankshaft 38 is disposed vertically on the rear side of the pinion gear 35 and is rotatably supported by a bearing 39 and a metal 36. A gear 37 that meshes with the pinion gear 35 is coaxially fixed to the lower end of the crankshaft 38, and the crank weight 10 is fixed to the upper end.

  A connecting rod 12 is fixed to the crank weight 10 by a crankshaft 11. A piston 14 is fixed to the front end of the connecting rod 12 in the axial direction by a piston pin 13, and a rotational movement of the motor 31 is converted into a reciprocating movement of the piston 14 by a drive transmission unit constituted by these members. The piston 14 is slidably provided inside the cylinder 17. A striker 19 is provided on the front end side in the cylinder 17, and the striker 19 can also slide in the front-rear direction inside the cylinder 17. An air chamber 15 is defined between the piston 14 in the cylinder 17 and the striker 19, and a space in which the striker 19 moves is connected to the cylinder peripheral portion 18 by communication holes 17 a and 17 b. Since the internal pressure of the air chamber fluctuates due to the reciprocating motion of the piston 14, the striker 19 reciprocates back and forth in the cylinder 17 due to the fluctuation of the internal pressure and intermittently collides with the second hammer 20. The striking force is transmitted to the tip tool that does not.

  The retainer sleeve 22 forms a cylinder portion together with the cylinder 17 and is attached to the front side of the cylinder 17. A tool holding portion 7 is provided at the distal end portion of the retainer sleeve 22, and a distal end tool (not shown) is detachably attached to the attachment hole 24. The striking force generated when the striker 19 moves forward is transmitted to the tip tool. Due to the impact force due to this collision, a tip tool (not shown) crushes the work material and creates a hole in the work material. A retainer sleeve 22 that houses the front side of the striker 19 is held by the case 5 and the grip 6.

  Next, the operation of the conventional hammer drill 101 will be described. The operator presses a tip tool (not shown) against a work material (not shown) while holding the handle housing 3 by hand. Next, the operator pulls the trigger 29 and rotates the motor 31. The rotational driving force of the motor 31 is transmitted to the crankshaft 38 via the pinion gear 35 and the gear 37. The rotation of the crankshaft 38 is converted into the reciprocating motion of the piston 14 in the cylinder 17 by the crank weight 10, the crankshaft 11, the connecting rod 12, and the piston 14 that constitute a drive transmission portion (reciprocating motion converting portion). By the reciprocating motion of the piston 14, the pressure of the air in the air chamber 15 repeatedly rises and falls, and a striking force is applied to the striker 19 by this pressure change. The striker 19 moves forward and collides with the rear end of the second hammer 20, and the second hammer 20 imparts a striking force to the tip tool.

  The second hammer 20 mounted inside the cylinder 17 constitutes a striking mechanism and is disposed so as to be in contact with an end of a tip tool (not shown). The striking mechanism portion is filled with a lubricant, and oil seals and O-rings 16 and 21 are disposed on the respective shafts to form a predetermined sealed space together with the cylinder peripheral portion 18. The sealed space is shielded from the outside air and prevents the lubricant from flowing out. FIG. 7 shows the range of the sealed space. FIG. 7 is a view for explaining a sealed space in the conventional hammer drill 101. A portion indicated by a thick line is a sealed space 70. Although the front end position of the sealed space is a portion of the O-ring 21, the second hammer 20 moves back and forth, so the front end position of the sealed space is not fixed.

  When the conventional impact tool described above is operated, the internal temperature of the airframe rises due to the heat generated by the impact mechanism, the air inside the sealed space 70 expands, and the internal pressure rises. At this time, the expanded air flows out of the fuselage with the lubricant from somewhere in the seal. If the motor is stopped and left after the operation of the striking tool, the temperature of the main body, which has been high, is lowered to room temperature, and the pressure inside the striking mechanism is also lowered accordingly. At this time, the pressure inside the striking mechanism is negative compared to before using the main body because air flows out from the sealing material of the second hammer 20 to increase the pressure inside the striking mechanism when using the main body. Become. Further, since the sealing material is highly airtight, air does not flow from the outside into the striking mechanism portion due to a pressure difference at room temperature. Accordingly, when the impact tool is reused, the compression force is reduced due to the decrease in the air pressure in the air chamber 15, the amplitude of the reciprocating motion of the striker 19 is reduced, and the striker 19 returns without going to the impact point. There is a risk. Alternatively, since the speed at the strike point of the striker 19 is small and the rebound speed is small, there is a possibility that the striking force may be reduced without the vibration energy of the striker 19 being amplified.

  As a technique for reducing the influence of the internal pressure fluctuation of the sealed space 70 in the conventional hammer drill 101, for example, the technique of Patent Document 1 is known. In Patent Document 1, a sub chamber is provided in a crank case, a through hole is provided in a wall between the crank case (blow mechanism part) and the sub chamber, and a valve is provided in the through hole. The sub chamber is provided with a breathing hole communicating with the outside air, and a felt is provided on the outside air side of the breathing hole to adsorb the lubricant and prevent the lubricant from flowing out to the outside. With this configuration, the influence of the pressure fluctuation in the sealed chamber is removed by the movement of air between the crankcase (striking mechanism) side and the sub chamber.

JP 2007-987 A

  However, in the technique of Patent Document 1, a pressure adjustment mechanism is provided between the crankcase (striking mechanism portion) side and the sub chamber, and the pressure adjustment mechanism is disposed at a position in contact with the rotationally driven connecting rod. Since it is configured to operate in conjunction with the rotational motion, there is a risk that in a situation where the connecting rod does not rotate, the compression force in the air chamber may remain reduced when the impact tool is reused without opening the pressure adjustment mechanism. .

  The present invention has been made in view of the above background, and an object of the present invention is to provide a striking tool that can prevent a striking defect and can stably perform striking.

  Another object of the present invention is to provide a striking tool capable of effectively adjusting a change in air pressure in the sealed space of the striking mechanism.

  Still another object of the present invention is to realize an internal pressure fluctuation suppressing mechanism that can adjust the change in atmospheric pressure in the sealed space of the striking mechanism portion at a low cost while minimizing the parts to be changed.

  The characteristics of representative ones of the inventions disclosed in the present application will be described as follows.

  According to one aspect of the present invention, a motor, a piston that reciprocates in the cylinder by the driving force of the motor, and the piston is struck via pressure fluctuations in the air chamber in the cylinder, and the striking force is applied to the tip tool. In the impact tool having a striker for transmitting and configured as a sealed space by blocking the space in which the piston and the striker are accommodated from the outside air, pressure adjusting means is provided to allow air to pass only from the outside air to the sealed space. The pressure adjusting means is a valve that allows air to pass only in one direction when a pressure difference of a predetermined value or more is generated, for example, a rubber one-way valve.

  According to another feature of the present invention, the crank chamber is provided with an opening for supplying lubricating oil in a crank chamber that houses a crankshaft that forms part of the sealed space and reciprocates the piston. A cover is provided, and a valve that allows air to pass only from the outside air to the sealed space is provided in the crank cover. Furthermore, a plate for holding the valve was provided, and an air hole communicating with the opening of the valve was provided in the plate. Instead of using a plate, a circular groove is provided on the inner wall of the through hole where the valve of the crank cover is mounted, and an annular convex portion is provided on the valve so that the convex portion is inserted into the circumferential groove. It may be attached to the crank cover.

According to the present invention, since the pressure adjusting means for passing air only from the outside air to the sealed space is provided, it is possible to suppress the pressure drop in the sealed space, and the impact failure caused by the negative pressure in the sealed space is prevented. Can be prevented, and a stable product can be provided. Further, since the pressure adjusting means is a valve that allows air to pass only in one direction when a pressure difference of a predetermined value or more is generated, the structure is simple and can be stably operated.

According to the present invention, since the valve is a rubber one-way valve, it can be manufactured at low cost, and the cost increase can be minimized. In addition, since the valve that allows air to pass only in one direction operates only with a pressure difference and does not require power for the operation, the pressure can be adjusted effectively even when the impact tool is stopped. Furthermore, since the valve is provided in the crank cover, the valve can be easily attached only by changing the configuration of the crank cover. Furthermore, it is possible to prevent the assemblability from being deteriorated by attaching the valve to the crank cover.

According to the present invention, since the plate for holding the valve is provided, it is possible to prevent the valve from dropping off. Further, since the air hole communicating with the opening of the valve is provided in the plate, the air flow from the valve is not obstructed. In addition, a circumferential groove is provided on the inner wall of the through hole where the valve of the crank cover is mounted, and the valve is mounted on the crank cover by inserting the convex portion of the valve into the circumferential groove, so the structure of the crank cover is changed. The present invention can be easily realized only by this.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

It is sectional drawing (partial side view) which shows the whole structure of the impact tool (hammer drill 1) which concerns on the Example of this invention. (1) is a sectional view of the valve 60 of FIG. 1, and (2) is a partial sectional view of the vicinity of the valve 60. It is a perspective view which shows the shape of the crank cover 50 of FIG. It is sectional drawing (partial side view) which shows the whole structure of the impact tool (hammer drill 1 ') based on the 2nd Example of this invention. It is the elements on larger scale near the valve | bulb 60 of FIG. It is sectional drawing which shows the whole structure of the conventional impact tool (hammer drill 101). It is a figure for demonstrating the sealed space 70 in the conventional impact tool (hammer drill 101).

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same parts as those in the conventional hammer drill 101 shown in FIGS. 6 and 7 are denoted by the same reference numerals, and the repeated description is omitted. Further, in this specification, description will be made assuming that the front-rear, up-down, left-right directions are the directions shown in the drawing. FIG. 1 is a cross-sectional view (partial side view) showing the overall configuration of an impact tool (hammer drill 1) according to an embodiment of the present invention.

  The hammer drill 1 rotates the crankshaft 11 by the rotational force of the motor 31, converts the rotational force of the motor 31 into a reciprocating motion by the connecting rod 12, and reciprocates the piston 14 provided in the cylinder 17 in the front-rear direction. In the cylinder 17, the striker 19 is moved in conjunction with the pressure in the air chamber 15 increasing or decreasing, and at the same time a second that can come into contact with the end of the tip tool detachably held in the cylinder 17. Hammer 20 is hit. The striking mechanism that transmits the striking force to the tip tools is filled with a lubricant such as grease, and each shaft is provided with an oil seal, O-rings 16 and 21, etc., and a sealed space 70 (see FIG. 7). Shut off the inside and outside air to prevent the lubricant from flowing out.

  In the present embodiment, a through hole is provided in the crank cover 50 that defines the sealed space 70 so that the inside of the airframe and the outside air can be ventilated, and a valve 60 that allows air to pass only in one direction is attached to the through hole. The valve 60 is, for example, a rubber valve, and is a one-way valve that allows the outside air to pass through the sealed space when the air pressure in the sealed space is lower than the outside air, but does not flow air in the opposite direction. In the sealed space, since the internal pressure largely fluctuates due to the reciprocating motion of the piston 14, a pressing plate 65 is provided as a retaining member so that the valve 60 does not fall out of the through hole. One end of the plate 65 is fixed by the crankcase 2 with a bolt 68. The crankcase 2 is formed with a screw boss 2a in which a screw groove for screwing the bolt 68 is formed.

  2A is a cross-sectional view of the valve 60 of FIG. 1, and FIG. 2B is a partial cross-sectional view of the vicinity of the valve 60. As shown in FIG. 2 (1), the valve 60 is composed of two opposing surfaces 60b extending on the front end side (front side) of the substantially cylindrical base member 60a, and these two surfaces 60b are hardened by the elastic force of rubber. Close contact. The two surfaces 60b are not formed separately, but are shaped like the tip of a crushed hose. On the rear end side of the base member 60a, a flange portion 60d whose diameter is increased over the entire circumference is formed. The flange portion 60d is also a convex portion that protrudes more outward than the base member 60a, and serves as a stopper to prevent the valve 60 from entering too deeply into the through hole when the valve 60 is inserted into the through hole.

  A circular opening 60 c is provided at the other end (rear side) of the valve 60. When the pressure inside the sealed space becomes lower than the atmospheric pressure, the valve 60 overcomes the force (influenced by the atmospheric pressure inside the sealed space) that keeps the two surfaces 60b in close contact with each other. The close contact state between the two surfaces is released, and the outside air flows in the direction of the arrow 61a and flows into the sealed space. When the outside air flows into the sealed space, the air pressure in the sealed space becomes almost equal to the atmospheric pressure, so that the two surfaces 60b are again in tight contact by the elastic force of the rubber. On the other hand, when the internal pressure of the sealed space is higher than the external pressure (atmospheric pressure), a strong force that presses them from the outside of the two surfaces 60b acts. Therefore, no air flows in the direction of the arrow 61b.

  FIG. 2 (2) shows a state where the valve 60 is fixed to a through hole 51 formed in the crank cover 50. The through hole 51 is a through hole formed in the wall surface of the crank cover 50 in the front-rear direction, and has a diameter substantially equal to that of the base member 60 a of the valve 60. A stepped portion 52 corresponding to the shape of the flange portion 60 d of the valve 60 is formed on the rear end side of the through hole 51. The stepped portion 52 is a recess when viewed from the inside of the through hole 51. By providing the stepped portion 52, the valve 60 inserted from the rear side of the through hole 51 does not fall out to the sealed space side. To hold. On the other hand, when the hammer drill 1 is struck, there is a case where the pressure inside the sealed space varies and the pressure on the sealed space side becomes higher than the external pressure. In that case, the rear end face is fixed by a pressing plate 65 so that the valve 60 does not fall backward from the through hole 51.

  The holding plate 65 is composed of three parts: two vertical surfaces 65a and 65c extending in the vertical direction and a horizontal surface 65b connecting one side of the vertical surfaces 65a and 65c. It is formed by bending a metal plate. A through hole 66 formed coaxially with the opening of the valve 60 is formed in the vertical surface 65a. Since the through hole 66 only needs to allow air passing through the opening 60 c of the valve 60, the size of the through hole 66 may be smaller than the opening 60 c of the valve 60. On the other hand, a through hole 67 for allowing the bolt 68 to pass therethrough is formed in the vertical surface 65 c of the plate 65. On the front side of the through hole 67, a screw boss 2a extending rearward from the wall surface of the crankcase 2 is formed, and a female screw is formed on the inner peripheral surface thereof. With the configuration described above, the plate 65 can be fixed to the crankcase 2 by the bolt 68, and the vertical surface 65a of the fixed plate presses the rear surface having the opening of the valve 60 forward, thereby allowing the valve 60 to move forward. Can be fixed to the crank cover 50 satisfactorily.

  The holding mechanism of the present embodiment only holds the opening 60c of the valve 60 from the rear side and can be fixed without using an adhesive or the like, so that the valve 60 is cranked as shown in FIGS. The crank cover 50 can be removed from the main body of the hammer drill 1 while being attached to the cover 50. Further, in order to realize the pressure adjusting means according to the present embodiment, it can be realized only by forming the screw boss 2b in the crankcase 2 and changing the shape of the crank cover 50. Other configurations of the hammer drill 1 are not limited. Since it is not necessary to add a change, the present embodiment can be realized while minimizing the cost increase.

  Next, the shape of the crank cover 50 will be described with reference to FIG. The crank cover 50 is attached to the upper side of the crankcase 2 and is formed with a cylindrical portion 53 that covers a circular opening (not shown) in the sealed space. The cylindrical portion 53 is reinforced by a plurality of ribs 54 and is firmly configured to withstand pressure fluctuations. In the present embodiment, on the rear end side of the crank cover 50, a through hole 51 that connects the inside of the cylindrical portion 53 and the outside of the crank cover 50 is formed, and the valve 60 is fitted into the through hole 51. The upper surface (ceiling surface) on the inner peripheral side of the cylindrical portion 53 is closed, an upper surface portion 50a extending from the upper surface to the left and right is formed, and the side surface 50b extends downward from both side surfaces of the upper surface portion 50a. It is formed. The crank cover 50 is made of, for example, a polymer resin such as plastic, and constitutes a part of the outer shell (housing configuration) of the hammer drill 101.

  Thus, in this embodiment, the shape of the crank cover 50 is changed, and a valve 60 that allows air to pass only in one direction is added. When the hammer drill 1 is operated in this configuration, the temperature inside the machine body rises due to heat generated by the striking mechanism, and the pressure in the sealed space rises. The increased pressure flows out from the oil seal and the O-ring to the outside, but there is no fear of air flowing out through the valve 60 at that time. Thereafter, when the operation of the hammer drill 1 is stopped, the temperature of the striking mechanism portion decreases, and the pressure in the sealed space becomes negative. When the pressure inside the sealed space becomes negative, outside air flows from the valve 60 into the impact mechanism. Thus, in this embodiment, since the pressure in the sealed space can be adjusted effectively when the hammer drill 1 is not in operation, a hammer drill that can be stably operated can be realized.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view (partial side view) showing the overall configuration of an impact tool (hammer drill 1 ') according to a second embodiment of the present invention. The second embodiment is the same as the first embodiment in that a valve 60 is provided on the crankcase cover 80. The shape and material of the valve 60 are the same as those used in the first embodiment, and air can pass only from the outside air to the inside of the sealed space. However, in the second embodiment, the shape of the crankcase cover 80 is devised so that another member for holding the valve 60, for example, the plate 65 of the first embodiment does not have to be used. Therefore, the valve 60 is fixed by performing shape processing on the inner surface of the through hole 81 so as to prevent the valve 60 from coming off.

  In the second embodiment, the inner diameter of the through hole 81 formed in the crankcase cover 80 is not constant, and a large-diameter portion 82 whose outer diameter is increased in an annular shape in a portion in front of the rear end is provided. The flange portion 60d of the valve 60 is engaged there. Therefore, when the valve 60 is attached to the crankcase cover 80, the valve 60 is pushed into the through hole 81 from the front side as indicated by an arrow 86 in FIG. Since the valve 60 is made of rubber, it has elasticity and is easily plastically deformed, so that it can be pushed into the through hole 81. Also, if the flange 60d of the valve 60 is engaged with the large-diameter portion 82 well when it is pushed in, there is no risk of disengagement. Moreover, since the mounting direction is from the inside to the outside of the crankcase cover 80 and is fixed from the side where the high pressure is applied when the hammer drill 1 ′ is operated, there is no risk of detachment due to long-term use, and stable operation is possible. An internal pressure adjustment mechanism can be realized.

Instead of maintaining the same diameter from the inside of the sealed space to the outside, the through-hole 81 is provided with a wall surface 83 so that the portion of the opening 84 inside becomes small. Since the wall surface 83 is in good contact with the opening 60c of the valve 60, it plays a major role in preventing the valve 60 from coming off from the inner side to the outer side. Similar to the first embodiment, in the second embodiment, the opening 60c of the valve 60 is not directly exposed to the outside air of the hammer drill 1 (air outside the outer portion), but inside the housing portion of the hammer drill 1. Therefore, an opening was made in the same portion 90 (see FIG. 4) as the atmospheric pressure. Since the opening on the atmospheric pressure side of the valve 60 serving as the pressure adjusting means is located in the internal space of the housing in this way, the possibility that the opening 60c of the valve 60 is clogged with dust or the like can be remarkably reduced, and for a long period of time. It can be operated stably.

  According to the second embodiment, it is only necessary to attach the crankcase cover 80 according to the second embodiment instead of the conventional crankcase cover 150 (see FIG. 6) in order to newly fix the valve 60. The change of parts for implementing the present invention is minimal, and the crankcase 102 of the conventional example (see FIG. 6) can be used as it is without modification.

  As mentioned above, although this invention was demonstrated based on the Example, this invention is not limited to the above-mentioned Example, A various change is possible within the range which does not deviate from the meaning. For example, in the above-described embodiment, the valve is provided on the rear side of the crankcase cover, but the position where the valve is provided is not limited to this, and may be provided at an arbitrary position of the crankcase. Furthermore, the position where the valve is provided is not limited to the crankcase, and the valve may be provided at an arbitrary position of the boundary portion of the portion where the atmospheric pressure is reached from the sealed space.

  In the above-described embodiment, the hammer drill has been described as an example of the impact tool. However, the present invention is not limited to the hammer drill, and can be similarly applied to other impact tools having a sealed space. Furthermore, although the rubber valve is used as the pressure adjusting means in the above-described embodiments, the pressure adjusting means is not limited to this, and may be another one-way valve or a mechanical pressure adjusting means.

DESCRIPTION OF SYMBOLS 1 Hammer drill 2 Crankcase 2a Screw boss 2b Screw boss 3 Handle housing 4 Cylinder case 5 Case 6 Grip 7 Tool holding part 8 Motor housing 9 Piston 10 Crankweight 11 Crankshaft 12 Connecting rod 13 Piston pin 14 Piston 15 Air chamber 16 O-ring 17 Cylinder 17a 17b Communicating hole 18 Cylinder peripheral part 19 Striker 20 Second hammer 21 O-ring 22 Retainer sleeve 24 Mounting hole 29 Trigger 30 Power cable 31 Motor 32 Output shaft 33 Cooling fan 34 Bearing 35 Pinion gear 36 Metal 37 Gear 38 Crank shaft 39 Bearing 50 Crank Cover 50a Upper surface portion 50b Side surface 51 Through hole 52 Step portion 53 Cylindrical portion 54 Rib 60 Valve 60a Base member 60b (opposite) surface 60c opening portion 60d flange portion 65 plate 65a vertical surface 65b horizontal surface 65c vertical surface 66 through hole 67 through hole 68 bolt 70 sealed space 80 crankcase cover 81 through hole 82 large diameter portion 83 wall surface 84 opening 101 hammer drill 102 Crankcase 108 Motor housing 150 Crankcase cover

Claims (5)

A motor,
A piston that reciprocates in the cylinder by the driving force of the motor;
A striker that is struck by the pressure fluctuation of the air chamber in the cylinder by the piston and transmits the striking force to a tip tool;
In the impact tool configured as a sealed space by blocking the space in which the piston and the striker are housed from outside air,
A crank chamber that forms a part of the sealed space and houses a crankshaft for reciprocating the piston is provided with an opening for supplying lubricating oil, and a crank cover for sealing the opening is provided,
The impact tool according to claim 1, wherein the crank cover is provided with a valve that allows air to pass only in one direction when a predetermined pressure difference or more is generated between the sealed space and the outside air.   The impact tool according to claim 1, wherein the valve is a rubber one-way valve. A plate for holding the valve;
The impact tool according to claim 1 or 2, characterized in that a air hole communicating with the opening of the valve to the plate. Provide a circumferential groove on the inner wall of the through hole for mounting the valve of the crank cover,
An annular protrusion is provided on the valve,
The impact tool according to claim 3 , wherein the valve is attached to the crank cover by fitting a convex portion of the valve into the circumferential groove. A motor,
A piston that reciprocates in the cylinder by the driving force of the motor;
A striker that is struck by the pressure fluctuation of the air chamber in the cylinder by the piston and transmits the striking force to a tip tool;
In the impact tool configured as a sealed space by blocking the space in which the piston and the striker are housed from outside air,
A crankcase that defines a crank chamber that forms a part of the sealed space and houses a crankshaft for reciprocating the piston;
A one-way valve that allows air to pass only in one direction when a pressure difference of a predetermined value or more occurs between the crank chamber and the outside air;
The striking tool, wherein the one-way valve is mounted by a plate fixed to the crankcase with a bolt and having an air hole communicating with the opening of the one-way valve.

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