JP2019107723A - Driving machine - Google Patents

Abstract

To solve such a problem that a driving machine with use of compressed air is provided with a cushion member for absorbing an impact of a piston at a driving dead point, and when there is a gap between a tip of the piston in a driving direction and a cylinder, the cushion member tends to tear or accelerate deterioration as the same tries to approach the gap, and further, a driver is inclined by a brake force which is received by the piston from the cushion member, and the piston may contact and scrape an inner peripheral part of the cylinder, whereby sealability of a seal member, which seals between the piston and the cylinder, is reduced and the seal member becomes easy to be worn, and therefore, in the driving machine with use of compressed air, improvement in durability of the cushion member and suppression of contact between the piston and the cylinder at an inclination time of the driver are required.SOLUTION: A piston 11 has a tip 11b which faces and contacts a cushion member 18, and a base end part 11d which receives a pressure of compressed air. A maximum outer diameter Da of the tip 11b is larger than a maximum outer diameter Db of the base end part 11d.SELECTED DRAWING: Figure 21

Description

  The present invention relates to a driving machine such as a nailing machine for driving a nail using compressed air.

  Patent Documents 1 to 3 disclose a nailing machine using compressed air. The driving machine using compressed air includes a tool body in which a cylinder and a piston are installed, a handle portion held by a user, and a driving tool supply unit. The tool body is loaded with a magazine loaded with a number of driving tools. The driving tool supply unit supplies one driving tool from the magazine to the nose of the tool body. A piston reciprocates in the cylinder, and a striking driver attached to the piston ejects from the injection port the driving tool supplied in the driving passage of the nose portion.

  The tool body is provided with a cushion member that absorbs the impact of the piston at the driving dead point of the piston. Patent Document 2 discloses a cushion member which is deformed by an impact when it moves to a driving dead center of a piston. The deformed cushion member comes in close contact with the end face of the piston. The cushion member which has lost the relief place tries to enter toward the side where there is a gap.

Patent No. 6211398 Patent No. 5716395 gazette JP, 2013-208661, A

  If there is a gap between the piston and the cylinder at the end of the piston in the driving direction, the deformed cushion member tends to enter the gap. Moreover, the piston is instantaneously moved by being pushed by the compressed air. Therefore, the cushion member momentarily tries to enter the gap. This makes the cushion member easy to tear or prematurely degrades.

  The piston disclosed in Patent Document 3 has a flange portion protruding in the driving direction on the peripheral edge portion of the tip surface thereof. The buttocks prevent the cushion member from entering the gap between the piston and the cylinder. However, since the tip of the cushion member directly collides with the buttocks, there is little space for the cushion member to escape. Therefore, the suppression of the deterioration of the cushion member is not very effective.

  The driving machine using compressed air is also required to have the following structure. The driver is supported at few points to reduce friction. The proximal end side of the driver with respect to the piston is supported by being attached to the piston by welding or screwing. The tip of the driver is supported by penetrating a driver support hole provided in a bottom cap at the tip of the cylinder. When the piston moves in the driving direction, the piston supporting the driver approaches the driver support hole. When the piston reaches the movement dead center, the driver is easily inclined with the driver support hole as a fulcrum by the braking force that the piston receives from the cushion member. When the gap between the piston and the cylinder is small, the proximal end of the piston, which is the side that receives the compressed air, easily contacts the inner peripheral portion of the cylinder by the driver being inclined.

  The piston is formed of a relatively strong material such as, for example, iron, in order to enhance the resistance to the impact upon reciprocating. The cylinder is formed of a relatively lightweight material, such as, for example, aluminum, in order to make the tool body lightweight. Therefore, the inner circumferential portion of the cylinder may be scraped by the contact of the piston with the inner circumferential portion of the cylinder. When the inner periphery of the cylinder is scraped, the sealing performance of the sealing member for sealing between the piston and the cylinder is reduced. In addition, the seal member is apt to be worn out by rubbing the seal member with the scraped portion of the inner peripheral portion of the cylinder.

  As described above, a driving machine using compressed air is required to increase the durability of a cushion member that absorbs an impact in the driving direction of the piston. The driving machine using compressed air is also required to suppress the contact between the piston and the cylinder when the driver is inclined.

  According to one aspect of the present invention, a driving machine includes a cylinder installed in a tool body, a piston that reciprocates in the cylinder using compressed air, a driver that moves with the piston and drives a driving tool, and It has a cushion member located forward in the driving direction and absorbing the impact of the piston. The piston has a distal end facing the cushion member and abutted against the cushion member, and a proximal end receiving the pressure of compressed air. The largest outer diameter of the tip is greater than the largest outer diameter of the proximal end.

  Therefore, since the maximum outer diameter of the tip of the piston is large, the gap between the tip of the piston and the inner circumferential portion of the cylinder can be reduced. Thereby, the cushion member which has been deformed into the gap between the piston and the cylinder is prevented from entering. Thus, tearing of the cushion member can be suppressed, and the durability of the cushion member can be enhanced. On the other hand, the maximum outside diameter of the proximal end of the piston is small, and the proximal end of the piston is separated from the inner periphery of the cylinder. Therefore, when the driver inclines with the tip end thereof as a fulcrum, it is possible to prevent the proximal end of the piston from coming into contact with the cylinder. Thus, the piston can be prevented from scraping the inner peripheral portion of the cylinder.

  According to another feature, the piston has an annular groove at the outer periphery between the distal end and the proximal end. An annular sealing member for sealing between the piston and the cylinder is mounted in the groove. Therefore, when the driver tilts with its tip as a fulcrum, the tip of the piston is located closer to the fulcrum than the seal member. Therefore, the seal member serves as a buffer between the piston and the cylinder, and the tip end is prevented from coming into contact with the inner periphery of the cylinder. On the other hand, the proximal end of the piston is located farther from the fulcrum than the seal member. Therefore, the proximal end is more reliably prevented from coming into contact with the inner periphery of the cylinder. Thus, the sealability between the piston and the cylinder by the seal member can be maintained, and wear of the seal member can be suppressed.

  According to another feature, the maximum outer diameter of the distal end and the maximum outer diameter of the proximal end have a step via the groove. Therefore, the seal member can be easily assembled to the groove. Moreover, the tip end of the piston can be closer to the inner periphery of the cylinder, and the base end can be separated from the inner periphery of the cylinder. Further, by relatively simplifying the structure of the piston, it can be molded relatively inexpensively.

  According to another feature, the tip of the piston has a tip surface that is perpendicular to the direction of movement of the piston and that strikes the cushion member, and the tip surface is annular with the largest outer diameter. Therefore, the tip of the piston pushes the cushion member in the moving direction, and the cushion member easily escapes in the direction intersecting the moving direction. In other words, the deformed cushion member hardly escapes in the direction of movement of the piston. As a result, it is difficult for the deformed cushion member to enter the gap between the piston and the cylinder.

  According to another feature, the proximal end of the piston has a chamfer that decreases in diameter away from the tip. When the driver tilts, the rear end in the moving direction of the piston easily contacts the inner circumferential portion of the cylinder. On the other hand, the piston has a chamfer at the rear end in the moving direction, and the rear end in the moving direction of the piston is separated from the inner circumferential portion of the cylinder. Therefore, it is more effectively suppressed that the piston cuts the inner peripheral portion of the cylinder.

It is a longitudinal cross-sectional view of a driving machine. It is a longitudinal cross-sectional view of the tool main body of an initial state (non-operating state). It is an enlarged view of the III section in FIG. It is a longitudinal cross-sectional view of the tool main body of the step in which the head valve began to move downward by pulling the switch lever. It is an enlarged view of V part in FIG. It is a longitudinal cross-sectional view of the tool main body of the step in which the head valve is moving downward. It is an enlarged view of the VII section in FIG. It is a longitudinal cross-sectional view of the tool main body of the stage in which compressed air was supplied to the piston upper chamber by closing the exhaust passage and opening the head valve and the piston started to move downward. It is an enlarged view of the IX section in FIG. It is a longitudinal cross-sectional view of the tool main body in the stage in which the piston has reached the driving dead center by the head valve being fully opened and the driving operation has been completed. It is an enlarged view of the XI part in FIG. After completion of the driving operation, the pull operation of the switch lever is released, whereby the head valve starts to ascend. FIG. 13 is an enlarged view of a portion XIII in FIG. 12 in a state where the exhaust passage is shut off and the head valve is open but the piston is still at the driving dead center. It is a longitudinal cross-sectional view of the tool body in a state in which the head valve is closed, the exhaust passage is opened, and the piston starts to rise from the driving dead center. It is an enlarged view of the XV part in FIG. It is a longitudinal cross-sectional view of the tool main body in a state in which the piston has been returned to the initial position but the head valve has reached the initial position. It is an enlarged view of the XVII part in FIG. It is a perspective view of a piston and a driver. It is a side view of a piston and a driver. It is sectional drawing of a piston, and a side view of a driver. It is an enlarged view of the XXI section in FIG. FIG. 22 is a partial enlarged cross-sectional view of the second embodiment of the driving machine corresponding to FIG. 21. FIG. 22 is a partial enlarged cross-sectional view of a third embodiment of the driving machine corresponding to FIG. 21.

  One embodiment of the present invention will be described based on FIGS. As shown in FIG. 1, the driving machine 1 is a nailing machine for driving nails using compressed air. The driving machine 1 comprises a tool body 10, a driving nose portion 2 extending downward from the lower portion of the tool body 10, a handle portion 3 gripped by a user, and a magazine 4 loaded with a number of driving tools (not shown). , And the driving tool feed mechanism 5 is provided. The driving tool feeding mechanism 5 feeds driving tools one by one from the magazine 4 into the driving path of the driving nose portion 2 in conjunction with the driving operation. In the following description, the driving direction of the driving tool in the vertical direction is the downward direction. The direction in which the handle portion 3 extends with respect to the tool body 10 in the front-rear direction is taken as the rear.

  As shown in FIG. 1, the tool body 10 includes a piston 11 and a cylinder 12 which movably accommodates the piston 11. The piston 11 is made of, for example, iron, which is high in strength and high in impact resistance. The cylinder 12 is made of, for example, aluminum, which is relatively lightweight in order to make the tool body 10 lightweight. As shown in FIGS. 18, 19 and 20, a striking driver 13 is provided at the center of the tip 11 b in the driving direction of the piston 11. The driver 13 is provided integrally with the piston 11 by welding. As shown in FIG. 1, a head valve 20 for opening and closing the accumulator 8 with respect to the upper chamber (piston upper chamber 11U) of the piston 11 is provided on the upper outer periphery of the cylinder 12. The driving machine 1 does not exhaust the compressed air flowing into the piston upper chamber 11U as it is after the driving operation but returns it to the lower chamber (piston lower chamber 11D) side of the piston 11 to drive the piston 11 back to its initial position from the dead point. It has a structure that makes it a recycling system.

  As shown in FIGS. 1 and 2, the handle portion 3 extends laterally from the side of the tool body 10. A trigger valve 6 for switching between supply and exhaust of the tool body 10 is accommodated in the lower surface on the base side of the handle portion 3. The switch lever 7 is disposed below the trigger valve 6, and the switch lever 7 is tiltably attached to the tool body 10. As a result, the user can pull (switch on) the switch lever 7 with the fingertip of the hand holding the handle portion 3. As shown in FIG. 4, by pulling the switch lever 7, the pin of the trigger valve 6 is pushed, and the trigger valve 6 is turned on. When the trigger valve 6 is turned on, the head valve lower chamber 20D is opened to the atmosphere through the air switching passage 9. As shown in FIG. 6, after the head valve lower chamber 20D is opened to the atmosphere, the head valve 20 moves downward and is opened. Thus, the driving operation is started.

  When the pull operation of the switch lever 7 is released as shown in FIG. 2, the pin of the trigger valve 6 is protruded from the valve body by the spring, and the trigger valve 6 is turned off. When the trigger valve 6 is turned off, compressed air is supplied into the head valve lower chamber 20D via the air switching passage 9. The compressed air in the head valve lower chamber 20D moves the head valve 20 in the closing direction (upward). The head valve 20 closes the communication passage between the piston upper chamber 11U and the accumulator 8. As a result, the supply of compressed air to the piston upper chamber 11U is shut off.

  As shown in FIG. 1, a joint 3 a for connecting an air hose (not shown) for supplying compressed air is provided at the rear end of the handle portion 3. Compressed air from the air hose is supplied and stored to the accumulator 8 in the handle portion 3 via the joint 3a. The compressed air in the accumulator 8 always flows into the head valve upper chamber 20U. The compressed air in the head valve upper chamber 20U acts to open the head valve 20.

  As shown in FIG. 1, between the rear end side of the handle portion 3 and the driving nose portion 2, the magazine 4 and the driving tool feeding mechanism 5 are provided in a bridging state. The driving tool feed mechanism 5 feeds driving tools one by one from the magazine 4 to the driving nose portion 2 in conjunction with the driving operation of the tool body 10. The driving nose portion 2 is provided with a driving passage. The driver 13 moves in the driving direction in the driving path by the driving operation of the tool body 10. As a result, one driving tool is driven out from the injection port 2a.

  As shown in FIG. 1, the tool body 10 includes a cylindrical main body housing 14. An upper portion of the main body housing 14 is airtightly closed by a top cap (first cap) 15. The lower portion of the main body housing 14 is airtightly closed by a bottom cap (second cap) 16. A top cushion (first cushion) 17 is attached to the lower surface of the top cap 15. A cushion member (second cushion) 18 is attached to the top surface of the bottom cap 16. The cushion member 18 extends substantially parallel to the driving direction of the piston 11 and is substantially cylindrical. The cushion member 18 is formed of an elastic member, for example, rubber.

  As shown in FIG. 21, an annular groove 11 a to which an annular seal member 35 is attached is provided on the outer periphery of the piston 11. The seal member 35 has a circular cross-sectional shape in the radial direction. The seal member 35 radially seals between the piston 11 and the cylinder 12. Therefore, the seal member 35 seals between the piston lower chamber 11D and the piston upper chamber 11U. The piston 11 has a tip end 11b in the driving direction (downward) from the groove 11a, and has a base end 11d in the opposite direction (upper) from the driving direction.

  As shown in FIG. 21, the distal end portion 11b has a distal end surface 11c at the distal end in the driving direction. The distal end surface 11 c is disc-shaped, is orthogonal to the driving direction, and faces the cushion member 18. The tip surface 11c contacts the cushion member 18 in a direction perpendicular to the driving direction during the driving operation. The tip portion 11 b has a cylindrical shape and a region having the same diameter (maximum outer diameter Da) in the axial direction with a predetermined length. The tip end face 11c is formed in an annular flat shape having a maximum outer diameter Da in one plane.

  As shown in FIG. 21, the base end 11d is located in the piston upper chamber 11U, receives pressure of compressed air in the piston upper chamber 11U, and moves the piston 11 in the driving direction. The base end portion 11 d is generally disc-shaped, and has a cylindrical recess in a circular center region. The bottom of the recess is located at the height at which the groove 11a is located. A chamfered portion 11 e is formed on the outer periphery (upper surface outer periphery) of the end face of the base end portion 11 d. The chamfered portion 11 e has a tapered shape in which the diameter decreases with distance from the tip end portion 11 b (as moving upward). The proximal end 11 d has a maximum outer diameter Db at or near the distal end in the driving direction. The maximum outer diameter Db of the proximal end 11d is smaller than the maximum outer diameter Da of the distal end 11b.

  The upper piston chamber 11U located in the upper region of the cylinder 12 as shown in FIG. 2 is opened and closed by a cylindrical head valve 20. A cylindrical valve guide 21 is disposed on the outer periphery of the cylinder 12, and a head valve 20 is disposed on the outer periphery of the valve guide 21. The valve guide 21 supports the head valve 20 so as to be able to move up and down. A compression spring 23 is disposed between the lower portion of the head valve 20 and the lower portion of the valve guide 21 in the head valve lower chamber 20D. The compression spring 23 always biases the head valve 20 upward (in the closing direction).

  When the trigger valve 6 is turned off (in a non-operation state), compressed air is supplied through the air switching passage 9 into the head valve lower chamber 20D. When compressed air is supplied into the head valve lower chamber 20D, the head valve 20 moves upward by the air pressure and the biasing force of the compression spring 23, and is held at the initial position (closed position). When the head valve 20 is closed, the piston upper chamber 11U and the accumulator 8 are airtightly shut off. When the trigger valve 6 is turned on, the head valve lower chamber 20D is vented to the atmosphere through the air switching passage 9. As a result, the head valve 20 is moved against the compression spring 23 in the driving direction by the compressed air of the head valve upper chamber 20U. The upper piston chamber 11U is open to the accumulator 8.

  A cylindrical sheet holder 19 is attached to the lower surface of the top cap 15 as shown in FIGS. The seat holder 19 is located radially outward of the top cushion 17. The upper portion of the cylinder 12 is inserted into the inner periphery of the sheet holder 19. A urethane rubber valve seat 22 is attached along the outer peripheral surface of the seat holder 19. The valve seat 22 also has a cylindrical shape. The valve seat 22 has a base portion 22a protruding in the radial direction, and a cylindrical inner peripheral side cylindrical portion 22b extending axially downward from the inner peripheral side of the base portion 22a. The head valve 20 moves upward and the upper end thereof abuts on the lower surface of the base 22 a of the valve seat 22. As a result, the movement of the head valve 20 is restricted and held at the initial position, and the piston upper chamber 11U is airtightly shut off from the accumulator 8.

  As shown in FIG. 2, an exhaust passage 24 is provided between the head valve 20 and the valve guide 21. The exhaust passage 24 is branched into the recycle passage 28 through an air hole 21 a formed in the valve guide 21. The plurality of vent holes 21 a are formed in the valve guide 21 at predetermined intervals in the circumferential direction. A recycle passage 28 is formed between the cylinder 12 and the valve guide 21. After the impacting tool strikes, the compressed air in the upper piston chamber 11U is returned to the lower piston chamber 11D through the recycle passage 28 and the exhaust passage 24 in the upward movement process of the piston 11. The piston 11 returns to the initial position by the compressed air returned into the lower piston chamber 11D.

  As shown in FIGS. 2 and 3, the exhaust passage 24 is airtightly shut off from the piston upper chamber 11U by a seal ring 25 mounted on the upper inner peripheral surface of the head valve 20. The upper end portion of the head valve 20 abuts on the base portion 22 a of the valve seat 22 in the initial position (closed position). The seal ring 25 is located above the seal portion 21 c of the valve guide 21 and is separated from the seal portion 21 c. As a result, the exhaust passage 24 and the recycle passage 28 are opened with respect to the piston upper chamber 11U (exhaust passage open state). The outer peripheral surface of the inner peripheral side cylindrical portion 22 b of the valve seat 22 abuts on the inner peripheral surface of the head valve 20. Therefore, the exhaust passage 24 is airtightly shut off with respect to the accumulator 8.

  As shown in FIGS. 8 and 9, when the head valve 20 is moved downward from the closed position, the seal ring 25 abuts on the outer peripheral surface of the seal portion 21 c of the valve guide 21. As a result, the exhaust passage 24 and the recycle passage 28 are airtightly closed with respect to the piston upper chamber 11U (exhaust passage blocked state).

  As shown in FIGS. 10 and 11, the head valve 20 moves downward, and the valve seat 22 separates from the inner peripheral surface of the head valve 20. Thus, the piston upper chamber 11U is opened to the accumulator 8. Therefore, compressed air is supplied from the accumulator 8 to the piston upper chamber 11U. When the piston upper chamber 11U and the accumulator 8 are opened, the exhaust passage 24 and the recycle passage 28 are shut off (exhaust passage shut-off state). Therefore, the flow of compressed air from the accumulator 8 into the exhaust passage 24 and the recycle passage 28 (initial leakage) is suppressed.

  As shown in FIG. 3, the lower portion of the exhaust passage 24 communicates with an exhaust chamber 26 provided around the valve guide 21. As shown in FIG. 2, the exhaust chamber 26 is in communication with the exhaust passage 27 through an exhaust hole 20 a provided at the lower part of the head valve 20. The plurality of exhaust holes 20 a are formed at predetermined intervals in the circumferential direction with respect to the head valve 20. A check valve 21 b is provided at the lower part of the recycle passage 28, and the recycle passage 28 is in communication with the return air chamber 30 via the check valve 21 b. The check valve 21 b prevents the compressed air from flowing from the return air chamber 30 to the recycle passage 28. The return air chamber 30 is formed by airtightly dividing the lower portion of the cylinder 12 and the main body housing 14. The return air chamber 30 is in communication with the piston lower chamber 11D through an air passage 31 provided in the lower portion of the cylinder 12.

  Hereinafter, a series of driving operations of the driving machine 1 will be described in order. In the initial state (non-operational state) shown in FIGS. 2 and 3, compressed air is supplied from the accumulator 8 to the head valve lower chamber 20D through the air switching passage 9, and the piston 11 is moved upward by the compressed air. The head valve 20 abuts against the valve seat 22 by the compression spring 23 and shuts off the piston upper chamber 11 U and the accumulator 8. The seal ring 25 is located above the seal portion 21 c of the valve guide 21 and is separated from the seal portion 21 c. Therefore, the exhaust passage 24 and the recycle passage 28 are opened to the piston upper chamber 11U.

  As shown in FIG. 4, the switch lever 7 is pulled upward, and the trigger valve 6 is turned on. As a result, the air switching passage 9 communicates with the atmosphere, and the compressed air in the head valve lower chamber 20D is exhausted through the air switching passage 9. The pressure in the head valve lower chamber 20D is lower than the pressure in the head valve upper chamber 20U. As shown in FIG. 5, since the valve seat 22 abuts on the inner peripheral surface of the head valve 20, the piston upper chamber 11 U is shut off from the accumulator 8. Since the seal ring 25 is still separated from the seal portion 21c of the valve guide 21, the exhaust passage 24 and the recycle passage 28 are opened to the piston upper chamber 11U. The air pressure in the exhaust passage 24 causes the head valve 20 to move downward against the compression spring 23.

  As shown in FIGS. 6 and 7, the head valve 20 moves further downward, and the exhaust throttle portion 20c provided on the inner peripheral surface of the head valve 20 cooperates with the outer peripheral surface of the valve guide 21 to discharge the exhaust passage 24 and the exhaust. The flow passage area of the air flow passage communicating with the chamber 26 is narrowed to substantially block the air flow passage. The valve seat 22 still abuts on the inner peripheral surface of the head valve 20, and the piston upper chamber 11U is airtightly shut off from the accumulator 8.

  As shown in FIGS. 8 and 9, the head valve 20 moves further downward, and the seal ring 25 abuts on the seal portion 21 c of the valve guide 21. Thus, the exhaust passage 24 is airtightly shut off from the piston upper chamber 11U. Thereafter, the valve seat 22 is separated from the inner peripheral surface of the head valve 20. Thus, the piston upper chamber 11U is opened to the accumulator 8. The compressed air is supplied to the piston upper chamber 11U, and the piston 11 starts to move in the driving direction.

  As shown in FIGS. 10 and 11, the head valve 20 is driven to reach the dead point and the driving operation is completed. The seal ring 25 is maintained in contact with the seal portion 21c of the valve guide 21 until the piston 11 reaches the driving dead point. As a result, the exhaust passage 24 and the recycle passage 28 are maintained in a state of being airtightly shut off from the piston upper chamber 11U and the accumulator 8. The piston lower chamber 11D, the return air chamber 30, the recycle passage 28 and the exhaust chamber 26 are maintained in the exhaust state (the open state of the atmosphere) while the piston 11 is moved from the initial position to the driving dead point.

  When the piston 11 reaches the driving dead point, the driving operation of one driving tool is performed. By releasing the pull operation of the switch lever 7 after the driving operation, the trigger valve 6 is turned off. As a result, the air switching passage 9 and the accumulator 8 communicate with each other, and compressed air is supplied from the accumulator 8 through the air switching passage 9 to the head valve lower chamber 20D. The air pressure in the head valve lower chamber 20D moves the head valve 20 upward. 12 and 13 show a state in which the head valve 20 has started to move upward. In this state, the exhaust passage 24 and the recycle passage 28 are closed with respect to the piston upper chamber 11U and the accumulator 8. Therefore, return air for moving the piston 11 located at the driving dead center upward is not supplied to the piston lower chamber 11D. Thus, as shown, the piston 11 is still located at the driving dead center.

  In the process of moving the head valve 20 further upward, the upper inner peripheral surface of the head valve 20 abuts on the valve seat 22, and the communication between the accumulator 8 and the piston upper chamber 11U is closed. The exhaust passage 24 and the recycle passage 28 are kept shut off.

  As shown in FIGS. 14 and 15, after the communication between the accumulator 8 and the piston upper chamber 11U is closed, the head valve 20 is further moved upward. As a result, the seal ring 25 is disengaged from the seal portion 21 c of the valve guide 21 and the exhaust passage 24 is opened. Thus, at the stage where the head valve 20 is closed, the exhaust passage 24 is opened after the accumulator 8 is closed. Therefore, so-called back leakage, which is the flow of compressed air from the accumulator 8 to the exhaust passage 24, is also prevented.

  At the stage shown in FIGS. 14 and 15, the seal ring 25 is disengaged from the seal portion 21c, and the exhaust passage 24 and the piston upper chamber 11U communicate with each other. On the other hand, the communication passage between the exhaust passage 24 and the exhaust chamber 26 is narrowed by the exhaust throttle portion 20c. Therefore, compressed air in the piston upper chamber 11U preferentially flows from the exhaust passage 24 into the recycle passage 28 via the vent hole 21a. The compressed air that has flowed into the recycle passage 28 flows into the return air chamber 30, and is further supplied to the piston lower chamber 11D through the air passage 31. Thereby, the piston 11 starts to move toward the initial position as shown in FIG. This state is continued until the head valve 20 reaches the initial position, as shown in FIGS.

  While the piston 11 is moving upward, the compressed air in the piston upper chamber 11U is recirculated to the return air chamber 30 through the recycle passage 24. Thus, the return air is continuously supplied to the piston lower chamber 11D. The piston 11 thus reached the driving dead point is returned to the initial position by recycling (reusing) the compressed air in the piston upper chamber 11U through the exhaust passage 24 and the recycling passage 28.

  The piston 11 returns to the initial position, and the head valve 20 returns to the initial position, thereby returning to the initial state shown in FIGS. When the head valve 20 returns to the initial position, the space between the exhaust throttle portion 20c of the head valve 20 and the valve guide 21 becomes large, and the exhaust throttle portion 20c is opened. When the exhaust throttle portion 20c is opened, compressed air in the piston upper chamber 11U and the exhaust passage 24 is exhausted to the atmosphere through the exhaust chamber 26, the exhaust hole 20a and the exhaust passage 27.

  As shown in FIG. 3, an exhaust hole 12 a is provided at the top of the cylinder 12. The exhaust hole 12a is located below the seal member 35 attached to the piston 11 returned to the initial position. Therefore, the remaining compressed air flowing into the piston lower chamber 11D through the return air chamber 30 is also exhausted to the upper piston chamber 11U through the exhaust hole 12a. Thus, the remaining compressed air is finally exhausted to the atmosphere through the exhaust passage 27. Thus, a series of driving operations by one pulling operation of the switch lever 7 is completed.

  According to the driving machine 1 configured as described above, as shown in FIG. 21, since the maximum outer diameter Da of the tip end portion 11b of the piston 11 is set as close as possible to the inner diameter of the cylinder 12, the tip end portion 11b and the cylinder The clearance of the inner circumference of 12 can be reduced. Thereby, the cushion member 18 deformed into the gap between the piston 11 and the cylinder 12 is prevented from entering. Thus, tearing of the cushion member 18 can be suppressed, and the durability of the cushion member 18 can be enhanced. On the other hand, the maximum outer diameter of the proximal end 11 d of the piston 11 is smaller than the maximum outer diameter Da of the distal end 11 b, and the proximal end 11 d is separated from the inner circumferential portion of the cylinder 12. Therefore, when the driver 13 is inclined with the driver support hole 16 a as a fulcrum, the base end portion 11 d can be prevented from contacting the cylinder 12. Thus, it is possible to suppress the piston 11 from scraping the inner peripheral portion of the cylinder 12.

  As shown in FIG. 21, the piston 11 has an annular groove 11a on the outer periphery between the tip end 11b and the base end 11d. An annular seal member 35 for sealing between the piston 11 and the cylinder 12 is mounted in the groove 11a. The distal end portion 11 b is positioned closer to the driver support hole 16 a than the seal member 35, and the proximal end 11 d is positioned farther from the driver support hole 16 a than the seal member 35. Therefore, when the driver 13 is inclined with the driver support hole 16 a as a fulcrum, the seal member 35 serves as a shock absorbing material between the piston 11 and the cylinder 12, and the tip 11 b is prevented from contacting the inner periphery of the cylinder 12 . Further, the proximal end 11 d is more reliably prevented from coming into contact with the inner peripheral portion of the cylinder 12. Thus, the sealability between the piston 11 and the cylinder 12 by the seal member 35 can be maintained, and wear of the seal member 35 can be suppressed.

  As shown in FIG. 21, the maximum outer diameter Da of the distal end portion 11b and the maximum outer diameter Db of the base end portion 11d have a level difference via the groove portion 11a. Therefore, the seal member 35 can be easily assembled to the groove 11a. Moreover, the tip end portion 11 b can be made closer to the inner peripheral portion of the cylinder 12. On the other hand, the proximal end 11 d can be separated from the inner circumferential portion of the cylinder 12. Further, by relatively simplifying the structure of the piston 11, it can be molded relatively inexpensively.

  As shown in FIG. 21, the distal end portion 11 b has a distal end surface 11 c that is orthogonal to the moving direction of the piston 11 and that contacts the cushion member 18. Therefore, the tip end portion 11b pushes the cushion member 18 in the driving direction, and the cushion member 18 easily escapes in the direction intersecting the driving direction. In other words, the deformed cushion member 18 hardly escapes in the moving direction of the piston 11. As a result, it is difficult for the deformed cushion member 18 to enter the gap between the piston 11 and the cylinder 12.

  As shown in FIG. 21, the proximal end 11 d has a chamfered portion 11 e whose diameter decreases with distance from the distal end 11 b. When the driver 13 tilts, the rear end in the moving direction of the piston 11 easily contacts the inner peripheral portion of the cylinder 12. On the other hand, the piston 11 has a chamfered portion 11 e at the rear end in the moving direction, and the rear end in the moving direction of the piston 11 is separated from the inner circumferential portion of the cylinder 12. Therefore, scraping of the inner peripheral portion of the cylinder 12 by the piston 11 is more effectively suppressed.

  Instead of the driving machine 1 described above, a driving machine 40 having a piston 41 shown in FIG. 22 may be used. As shown in FIG. 22, an annular groove 41 a to which an annular seal member 35 can be attached is provided on the outer periphery of the piston 41. The seal member 35 radially seals between the piston 41 and the cylinder 12. A tip 41 b is formed on the side of the groove 41 a in the driving direction (on the lower side of the piston chamber 41 D). The tip end surface 41c of the tip end portion 41b in the driving direction faces the cushion member 18 in a direction perpendicular to the driving direction. The side surface of the distal end portion 41b has a tapered shape in which the diameter decreases with increasing distance from the distal end surface 41c.

  As shown in FIG. 22, a base end 41d is formed above the groove 41a (on the upper piston chamber 41U). The side surface of the proximal end portion 41d has a tapered shape in which the diameter decreases with distance from the distal end surface 41c toward the upper side. The side surfaces of the tip end portion 41 b and the base end portion 41 d are provided flush with the groove portion 41 a interposed therebetween. The distal end portion 41 b has a maximum outer diameter Dc in the vicinity of the distal end surface 41 c. The base end 41d has a maximum outer diameter Dd near the groove 41a. The maximum outer diameter Dc of the distal end surface 41c is larger than the maximum outer diameter Dd of the proximal end 41d.

  The piston 41 shown in FIG. 22 has a tapered shape in which the diameter decreases as the side surfaces of the tip end portion 41b and the base end portion 41d move away from the tip end surface 41c, and is flush with the groove portion 41a interposed therebetween. When the driver 13 tilts, the rear end in the moving direction of the piston 41 easily contacts the inner peripheral portion of the cylinder 12. On the other hand, the piston 41 is separated from the inner peripheral portion of the cylinder 12 as it goes to the rear end in the movement direction. Therefore, scraping of the inner peripheral portion of the cylinder 12 by the piston 41 is more effectively suppressed. Further, by making the side surfaces of the distal end portion 41 b and the proximal end portion 41 d flush with each other, the structure of the piston 41 is relatively simple and can be molded relatively inexpensively.

  Instead of the above-described driving machine 1, a driving machine 50 having a piston 51 shown in FIG. 23 may be used. As shown in FIG. 23, on the outer periphery of the piston 51, an annular groove 51a to which the annular seal member 35 can be attached is provided. The seal member 35 radially seals between the piston 51 and the cylinder 12. A tip 51 b is formed on the side of the groove 51 a in the driving direction (on the lower piston chamber 51 D side). The end surface 51c of the end portion 51b in the driving direction faces the cushion member 18 in a direction perpendicular to the driving direction. The tip end surface 51c contacts the cushion member 18 during the driving operation. Between the front end surface 51c and the groove 51a, an annular lightening portion 51f is provided in parallel with the groove 51a.

  As shown in FIG. 23, a base end 51d is formed above the groove 51a (on the upper piston chamber 51U side). Above the lightening portion 51f and below the groove 51a, an intermediate projecting portion 51g radially protruding from the lightening portion 51f and the groove 51a is formed. That is, the groove 51a is formed so as to be sandwiched between the base end 51d and the middle overhang 51g. A chamfered portion 51e is formed on the upper end portion of the base end portion 51d. The chamfered portion 51e has a tapered shape in which the diameter decreases with distance from the tip end portion 51b toward the upper side. The distal end portion 51b has a cylindrical portion in the vicinity of the distal end surface 51c, and the cylindrical portion has a maximum outer diameter De. The base end portion 51 d and the middle overhang portion 51 g have the maximum outer diameter Df in the vicinity of the groove portion 51 a. The maximum outer diameter De of the distal end portion 51b is provided larger than the maximum outer diameter Df of the base end portion 51d.

  The tip end 51b of the piston 51 shown in FIG. 23 includes an annular lightening portion 51f. Therefore, by providing the piston 51 long in the vertical direction, the contact of the seal member 35 with the air passage 31 can be suppressed. Further, the weight of the piston 51 provided long in the vertical direction can be reduced by providing the lightening portion 51f. Therefore, the force applied from the piston 51 to the inner peripheral portion of the cylinder 12 when the driver 13 tilts can be reduced.

  Various modifications can be made to the embodiment described above. The configuration of the driving machines 1, 40, 50 is not limited to the nailing machine that ejects nails, and can be applied to, for example, a driving machine that ejects pin nails and staples. Instead of a compressor that supplies compressed air, for example, an electric pneumatic system may be used to generate compressed air by rotating a crank with an electric motor. The pistons 11, 41 and 51 and the driver 13 may be integrally coupled by, for example, screwing instead of welding.

  The cushion member 18 may be made of, for example, a buffer material such as an elastomeric resin instead of rubber. The shape of the cushion member can be appropriately changed, and instead of the cylindrical cushion member 18, for example, a substantially hexagonal columnar cushion member in which a hole through which the driver 13 passes may be applied. Instead of the seal member 35 having a circular cross section in the radial direction, for example, an annular seal member having a square cross section in the radial direction may be used. Further, the seal member can be appropriately selected from materials having sealing properties such as rubber and urethane. Instead of the annular lightening portion 51f, a grooved lightening portion into which a member having a two-face width for suppressing the rotation of the piston 51 can be inserted may be applied.

Da, Dc, De: Maximum outer diameter Db, Dd, Df (at the end of the piston) Maximum outer diameter 1 (at the proximal end of the piston) 1: Driving machine (first embodiment)
2 ... Drive nose portion 3 ... Handle portion 3a ... Joint 4 ... Drive tool feed mechanism 6 ... Trigger valve 7 ... Switch lever 8 ... Accumulator (accumulation chamber)
9: Air switching passage 10: Tool body 11: Piston 11a: Groove portion 11b: Tip portion 11c: Tip surface 11d: Base end portion 11e: Chamfered portion 11U: Piston upper chamber, 11D: Piston lower chamber 12: Cylinder 12a: Exhaust hole 13: Driver 14: Body housing 15: Top cap 16: Bottom cap, 16a: Driver support hole 17: Top cushion 18: Cushion member 19: Seat holder 20: Head valve 20a: Exhaust hole, 20c: Exhaustion Head portion 20U: head valve upper chamber, 20D: head valve lower chamber 21: valve guide 21a: vent hole, 21b: check valve, 21c: seal portion 22: valve seat 22a: base portion, 22b: inner peripheral side cylindrical portion 23 ... compression spring 24 ... exhaust passage 25 ... seal ring 26 ... exhaust chamber 27 ... exhaust passage 28 ... recycling Passages 30 ... return air chamber 31 ... air passage 35 ... sealing member 40 ... driving tool (Second Embodiment)
DESCRIPTION OF SYMBOLS 41 ... Piston 41a ... Groove part, 41b ... Tip part, 41c ... Tip surface, 41d ... Base end part 41U ... Piston upper chamber, 41D ... Piston lower chamber 50 ... Driving machine (3rd Embodiment)
DESCRIPTION OF SYMBOLS 51 ... Piston 51a ... Groove part, 51b ... Tip part, 51c ... Tip surface, 51d ... Base end part, 51e ... Chamfered part 51f ... Lightening part, 51g ... Middle overhang part 51U ... Piston upper chamber, 51D ... Piston lower chamber

Claims (5)

It is a driving machine,
A cylinder installed in the tool body,
A piston that reciprocates in the cylinder using compressed air;
A driver for moving with the piston to drive a driving tool;
It has a cushion member located forward in the driving direction of the piston to absorb an impact from the piston,
The piston has a tip end facing the cushion member and contacting the cushion member, and a base end receiving pressure of the compressed air, and the maximum outer diameter of the tip end is larger than the maximum outer diameter of the base end Driving machine. The driving machine according to claim 1, wherein
The piston has an annular groove on the outer periphery between the distal end and the proximal end,
And an annular seal member for sealing the space between the cylinder and the piston. The driving machine according to claim 2, wherein
The said maximum outer diameter of the said front-end | tip part and the said largest outer diameter of the said base end have a level | step difference via the said groove part. The driving machine according to any one of claims 1 to 3, wherein
The tip of the piston has a tip surface orthogonal to the direction of movement of the piston and abutting the cushion member, and the tip surface is an annular shape having the maximum outer diameter. The driving machine according to any one of claims 1 to 4, wherein
The said proximal end of the said piston has a chamfer which becomes small in diameter, so that it leaves | separates from the said front-end | tip part.

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