Air Tools

Abstract

To provide a relief valve whose O ring is hardly detached from a valve rod.SOLUTION: A driving tool comprises: a chamber 33 which stores compressed-air; and a relief valve 2 which is arranged in the chamber 33. The relief valve 2 includes: an inflow passage 7a which is communicated to the chamber 33; and a discharge passage 7b which is formed at the downstream side of the inflow passage 7a and whose diameter is larger than that of the inflow passage 7a. A valve rod 3 moves along the inflow passage 7a. An O ring 6 is attached to an annular groove in an outer periphery of the valve rod 3 to seal the inflow passage 7a. The valve rod 3 has an air escaping groove. The air escaping groove include: an inlet part which is open to an inner peripheral chamber; and an outlet part which is open to the discharge passage 7b. The air escaping groove discharges the compressed-air from the inner peripheral chamber to the discharge passage 7b when the compressed-air is entered into the inner peripheral chamber between a wall surface of the annular groove and an inner peripheral surface of the O ring 6 while the O ring 6 is shifted by inner pressure of the chamber 33 to be in the middle of passing through the inflow passage 7a and going to the discharge passage 7b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tool. [Background technology]

[0002] Pneumatic tools use compressed air to perform their work. For example, compressed air is supplied to the pneumatic tool from an air supply source (air compressor). An example of a pneumatic tool is a driving tool, which uses compressed air as power to drive fasteners such as nails, screws, and staples into a mating material. The driving tool has a chamber that stores compressed air, a piston that moves up and down using the compressed air, and an air motor that obtains rotational force using the compressed air. The air motor rotates the driver bit, while the piston lowers the driver bit. This causes the driver bit to drive a screw into the mating material.

[0003] Conventionally, the chamber of such a pneumatic tool is provided with a relief valve that opens the chamber to the atmosphere when the internal pressure becomes abnormal (see, for example, Patent Document 1). The relief valve has, for example, an O-ring attached to a valve stem, and the O-ring seals the flow path that connects the chamber to the outside air. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-237374 Summary of the Invention [Problem to be solved by the invention]

[0005] Relief valves normally return to their original state when the chamber is opened to the atmosphere and the pressure inside the chamber returns to normal. However, if the pressure inside the chamber is extremely high, the O-ring may come off the valve stem during operation. Therefore, in order to use the relief valve again, the O-ring must be reattached to the valve stem. In other words, the relief valve must be restored. For this reason, there has traditionally been a need for relief valves in which the O-ring is less likely to come off the valve stem. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, a pneumatic tool includes a chamber for storing compressed air and a relief valve provided in the chamber. The relief valve has an inlet passage communicating with the chamber and an outlet passage formed downstream of the inlet passage and having a larger diameter than the inlet passage. A valve stem moves along the inlet passage. An O-ring sealing the inlet passage is attached to an annular groove on the outer periphery of the valve stem. An air release path is formed in the valve stem. The air release path has an inlet opening into the inner periphery chamber and an outlet opening into the outlet passage so that when compressed air enters an inner periphery chamber between the wall surface of the annular groove and the inner periphery of the O-ring while the O-ring is moving beyond the inlet passage toward the outlet passage due to internal pressure of the chamber, the compressed air is released from the inner periphery chamber to the outlet passage.

[0007] Therefore, the O-ring expands when it reaches the exhaust flow path, and the compressed air that enters the inner chamber can encourage further expansion of the O-ring. However, at the same time, the compressed air is discharged from the inner chamber to the exhaust flow path through the air release path. This prevents the O-ring from expanding and becoming dislodged from the valve stem. As a result, there is no need to perform the restoration work of re-inserting the O-ring onto the valve stem in order to reuse the relief valve. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] FIG. [Figure 4]FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] FIG. 10 is a diagram showing a state in which the relief valve is activated and the O-ring seal is released. [Figure 6] FIG. 10 is a diagram illustrating the effect of the air release groove. [Figure 7] FIG. 10 is a partial cross-sectional view of a relief valve according to another embodiment. [Figure 8] FIG. 10 is a diagram showing a state in which an O-ring expands in diameter in a relief valve that does not have an air release groove. [Figure 9] 9 is a diagram showing a state in which the O-ring has come off the valve stem in the relief valve of FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] According to another feature of the present disclosure, the air release path is formed by a groove formed in the downstream wall surface of the annular groove, which supports the O-ring from the downstream side of the compressed air. The groove extends radially of the valve stem. Therefore, compared to a structure in which a through-hole is formed in the valve stem and the inner circumferential chamber and the exhaust flow path are connected through the through-hole, the air release path can be easily obtained.

[0010] According to another feature of the present disclosure, multiple grooves are formed on the downstream wall surface of the annular groove. Therefore, compared to when a single groove is formed, compressed air that has entered the inner peripheral chamber is quickly discharged to the discharge passage. This makes it possible to more effectively suppress the diameter expansion of the O-ring.

[0011] According to another feature of the present disclosure, the pneumatic tool has a grip that is held by a user and that houses a chamber. The relief valve is provided on a tip surface of the grip. Therefore, the direction of compressed air discharged from the relief valve is oriented in the axial direction of the grip. Therefore, even when compressed air is discharged from the relief valve, the compressed air is less likely to hit an operator.

[0012] According to another feature of the present disclosure, a pneumatic tool includes a pressure regulating valve that reduces the pressure of externally supplied compressed air and supplies it to a chamber. The pneumatic tool includes a driving tool body equipped with a driver that uses the compressed air from the chamber to drive fasteners. Therefore, the externally supplied compressed air is reduced in pressure by the pressure regulating valve to an appropriate pressure for operating the driver.

[0013] According to another feature of the present disclosure, a pneumatic tool includes a chamber for storing compressed air and a relief valve provided in the chamber. The relief valve has an inlet passage communicating with the chamber and an outlet passage formed downstream of the inlet passage and having a larger diameter than the inlet passage. A valve stem moves along the inlet passage. An O-ring sealing the inlet passage is attached to an annular groove on the outer periphery of the valve stem. The tool has an O-ring disengagement prevention structure that prevents the O-ring from expanding radially and becoming detached from the valve stem when the O-ring is forced beyond the inlet passage toward the outlet passage due to internal pressure of the chamber.

[0014] Therefore, the O-ring fall-off prevention structure prevents the O-ring from expanding radially and coming off the valve stem. This eliminates the need for restoration work, such as re-inserting the O-ring onto the valve stem, in order to reuse the relief valve.

[0015] 1, the driving tool 1 is a handheld screw tightening tool, known as a screw driver, for example. The driving tool 1 includes a tool body 20 incorporating a striking mechanism, a grip portion 30 that is held by the user, a magazine 40 capable of storing a large number of screws B, and an air motor 45.

[0016] As shown in Figure 1, the tool body 20 has a cylindrical body housing 21. The body housing 21 houses a striking mechanism having a cylinder 22 and a piston 23. A long, rod-shaped driver bit 24 is connected to the underside of the piston 23. The driver bit 24 extends downward. The driver bit 24 protrudes from the cylinder 22 past the inner periphery of a lower moving end damper 25 disposed at the bottom of the cylinder 22.

[0017] 1, a driving nose 27 is provided at the bottom of the tool body 20. The driving nose 27 extends downward. The driver bit 24 is inserted into the interior of the driving nose 27 (driving passage 27a).

[0018] As shown in Figure 1, the grip portion 30 extends laterally from the side of the tool body 20. A chamber 33 for storing compressed air is provided inside the grip portion 30. An activation valve 32 is provided on the underside of the base of the grip portion 30. A trigger 31 is provided below the activation valve 32 and on the side of the tool body 20.

[0019] As shown in Figure 1, trigger 31 is pulled upward with the fingertips of the hand holding grip portion 30. Pulling trigger 31 turns on activation valve 32. When activation valve 32 is turned on, compressed air is supplied from chamber 33 to tool body 20. The supplied compressed air moves piston 23 downward within cylinder 22. The downward movement of piston 23 moves driver bit 24 downward within driving passage 27a.

[0020] As shown in Figure 1, screws B are supplied one by one from a magazine 40 into the driving passage 27a. The magazine 40 is loaded with a large number of screws B connected by, for example, a resin connecting band in a wound state. The magazine 40 is connected to the driving nose 27 via a screw feed mechanism 40a. The screw feed mechanism 40a supplies the screws B into the driving passage 27a in conjunction with the driving operation. The driver bit 24 strikes one screw B supplied into the driving passage 27a.

[0021] As shown in Figure 1, an annular bit rotation part 26 is interposed between the tool body 20 and the driving nose part 27. The bit rotation part 26 is provided so as to be rotatable about the axis of the driver bit 24. The driver bit 24 is always inserted into the inner periphery of the bit rotation part 26. The bit rotation part 26 has the function of rotating the driver bit 24 about the bit axis (in the bit tightening direction) while allowing the driver bit 24 to reciprocate up and down.

[0022] As shown in Figure 1, the bit rotation part 26 is rotated in the bit tightening direction by an air motor 45. A multi-stage gear train 28 is interposed between the bit rotation part 26 and the air motor 45. The gear train 28 transmits the rotational power of the air motor 45 to the bit rotation part 26. This causes the bit rotation part 26 to rotate around the axis of the driver bit 24. As the bit rotation part 26 rotates, the driver bit 24 inserted into its inner periphery rotates integrally in the screw tightening direction.

[0023] 1, the driver bit 24 moves downward in the driving passage 27a due to the downward movement of the piston 23, while being rotated in the bit tightening direction by the bit rotation part 26. As a result, one screw B is struck against the workpiece W and rotated to tighten it.

[0024] As shown in Figure 1, a contact arm 27b is disposed below the driving nose 27 so that it can move up and down relative to the driving nose 27. By pressing down on the driving tool 1 with the contact arm 27b in contact with the fastening portion of the workpiece W, the contact arm 27b moves up relative to the driving nose 27. The driving operation of the tool body 20 is performed on the condition that both an ON operation, which moves the contact arm 27b up, and a trigger 31 are pulled. This prevents accidental driving operations.

[0025] As shown in Figure 1, a lid 50 that airtightly closes the chamber 33 is attached to the tip of the grip 30. A connection coupler 52 for connecting an air hose H is provided on the lid 50. The connection coupler 52 is connected to the chamber 33 via a pressure regulating valve 51. Compressed air at an appropriate pressure is supplied to the chamber 33 by the pressure regulating valve 51.

[0026] 2, the pressure regulating valve 51 has a small-diameter cylindrical portion 51a and an intermediate cylindrical portion 51b. A valve stem 51c, a valve element 51d, a valve seat 51e, a first spring 51f, and a second spring 51g are provided in a flow path formed in the small-diameter cylindrical portion 51a and the intermediate cylindrical portion 51b. Compressed air supplied to the pressure regulating valve 51 from the connection coupler 52 moves the valve element 51d away from the valve seat 51e against the biasing force of the first spring 51f. Therefore, the compressed air is decompressed by the first spring 51f and supplied into the chamber 33.

[0027] As shown in Figure 1, the cover 50 is provided with one relief valve 2 adjacent to the pressure regulating valve 51. The relief valve 2 opens the chamber 33 to the atmosphere, maintaining the inside of the chamber 33 at an appropriate pressure. Details of the relief valve 2 are shown in Figure 2 and subsequent figures.

[0028] As shown in Figure 2, the relief valve 2 has a valve body 7 formed with a flow path that communicates with the chamber 33. The valve body 7 is provided with a valve stem 3 that is movable along the flow path and a compression spring 8 that biases the valve stem 3 in the closing direction. An O-ring 6 is provided on the outer circumferential surface of the valve stem 3.

[0029] As shown in FIG. 2, the valve box 7 has two flow paths: an inlet flow path 7a that communicates with the chamber 33, and an outlet flow path 7b that communicates with the downstream side of the inlet flow path 7a. The inlet flow path 7a extends linearly from one side of the lid portion 50 and has a smaller cross-sectional diameter than the cylindrical inner circumferential surface 7f of the outlet flow path 7b. The outlet flow path 7b has a tapered surface 7d on its upstream side that increases in diameter from upstream to downstream. The upstream portion of the tapered surface 7d connects to the inner wall of the inlet flow path 7a. The outlet flow path 7b has a cylindrical inner circumferential surface 7f on its downstream side that is larger in diameter than the inlet flow path 7a. Because the diameter of the cylindrical inner circumferential surface 7f is larger than the diameter of the downstream portion of the tapered surface 7d, a step is formed between the tapered surface 7d and the cylindrical inner circumferential surface 7f. The step forms an abutment surface 7e that restricts the upstream movement of the stopper portion 3d of the valve stem 3. A seat 7c for a compression spring 8 is provided at the downstream portion of the cylindrical inner peripheral surface 7f. The inlet flow path 7a and the outlet flow path 7b are arranged substantially on a straight line.

[0030] As shown in Figure 3, the valve stem 3 comprises, from upstream to downstream, a sliding portion 3a, a stopper portion 3d, and a leg portion 3e. The sliding portion 3a is generally cylindrical, and an annular groove 4 in which an O-ring 6 (shown in Figure 2) is installed is formed on its outer circumferential surface. The sliding portion 3a has a head portion 3b on the upstream side of the annular groove 4. The downstream side of the head portion 3b forms the upstream wall surface 4a of the annular groove 4. The sliding portion 3a has a sliding body portion 3c on the downstream side of the annular groove 4. The upstream side of the sliding body portion 3c forms the downstream wall surface 4b of the annular groove 4. Fillets are provided between the upstream wall surface 4a and the bottom surface 4c, and between the downstream wall surface 4b and the bottom surface 4c. The annular groove 4 has a bottom surface 4c, and the depth of the annular groove 4 is shallower than the diameter of the O-ring 6.

[0031] As shown in Figures 3 and 4, an air release groove 5 is formed on the downstream wall surface 4b. A plurality of air release grooves 5, for example, four air release grooves 5, are formed on the downstream wall surface 4b. The plurality of air release grooves 5 are arranged at approximately equal intervals in the circumferential direction. Each air release groove 5 has an inlet 5e near the bottom surface 4c of the annular groove 4 and extends radially. The inlet 5e is located, for example, near the end point of the fillet between the bottom surface 4c and the downstream wall surface 4b. Each air release groove 5 has an outlet 5f on the radially outer side. The outlet 5f is located radially outward from the center of a partial orthogonal cross section of the O-ring 6 and opens into the inlet flow path 7a (or the outlet flow path 7b). The end of the outlet 5f opens into the outer circumferential surface of the sliding portion 3a. The width of the air release groove 5 is, for example, approximately half the wire diameter of the O-ring 6. The depth of the air release groove 5 is, for example, half the diameter of the O-ring 6 or less.

[0032] As shown in Figures 3 and 4, the stopper portion 3d is approximately a rectangular parallelepiped. The four corners of the stopper portion 3d are chamfered to form curved surfaces. The four corners of the stopper portion 3d are sized to abut against the abutment surface 7e, and by interfering with the abutment surface 7e, they restrict the movement of the valve stem 3 toward the upstream side. An end of a compression spring 8 abuts against the downstream surface of the stopper portion 3d.

[0033] As shown in Figures 2 and 3, the leg 3e is a substantially hollow cylinder, and from upstream to downstream, it has a main body 3f, a middle portion 3g, and a tip portion 3h. The diameters of the main body 3f, the middle portion 3g, and the tip portion 3h decrease in this order. The tip portion 3h is always inserted into the through-hole of the base 7c. This prevents the tip of the leg 3e from moving significantly. The middle portion 3g has a larger diameter than the through-hole of the base 7c. Therefore, when the valve stem 3 moves downstream, the middle portion 3g abuts against the upper surface of the base 7c. This restricts downstream movement of the valve stem 3. The leg 3e has multiple, for example, four, slits 3i formed along its entire axial length. This allows the leg 3e to elastically contract in diameter. A compression spring 8 is attached to the outer periphery of the leg 3e.

[0034] As shown in FIG. 2, the compression spring 8 is a coil spring. A first end on the upstream side of the compression spring 8 abuts against the downstream surface of the stopper portion 3d. A second end on the downstream side of the compression spring 8 abuts against the upstream surface of the pedestal 7c. The pedestal 7c is fixed near the outlet of the discharge flow path 7b. Specifically, a pin hole 7g is formed near the outlet of the discharge flow path 7b. A spring pin (not shown) is fitted into the pin hole 7g, and the pedestal 7c is fixed by the spring pin.

[0035] As shown in FIG. 2, the O-ring 6 is made of, for example, rubber and has an annular shape. The O-ring 6 is annular and can elastically expand in diameter. The inner diameter of the O-ring 6 is smaller than the diameter of the bottom surface 4c of the annular groove 4 at the sliding portion 3a in its natural state. The outer diameter of the O-ring 6 is larger than the outer diameter of the sliding portion 3a (head portion 3b and sliding body portion 3c). Therefore, when the O-ring 6 is installed in the annular groove 4, the inner peripheral surface 6a abuts against the bottom surface 4c of the annular groove 4, and the outer peripheral surface 6b protrudes from the annular groove 4. This allows the O-ring 6 to cooperate with the valve stem 3 to seal the inlet flow path 7a.

[0036] When the internal pressure of the chamber 33 is below a predetermined level, the relief valve 2 causes the valve stem 3 to tightly contact the O-ring 6 with the inlet passage 7a, as shown by the imaginary line in Figure 5. This seals the inlet passage 7a. Here, the O-ring 6 is elastically deformed by being pressed by the inner wall of the inlet passage 7a. As a result, the O-ring 6 elastically deforms toward the bottom surface 4c of the annular groove 4. As a result, the area where the O-ring 6 abuts against the bottom surface 4c of the annular groove 4 increases. Furthermore, the pressing force between the O-ring 6 and the bottom surface 4c of the annular groove 4 increases. When the internal pressure of the chamber 33 exceeds a predetermined level, the valve stem 3 moves downstream against the biasing force of the compression spring 8.

[0037] As shown in Figures 5 and 6, the O-ring 6 moves downstream along with the valve stem 3, passing through the inlet passage 7a and reaching the tapered surface 7d. At the tapered surface 7d, the force pushing the O-ring 6 radially inward is weaker than that exerted by the inner wall of the inlet passage 7a, so the O-ring 6 attempts to return to its original natural state due to its own elastic force. In other words, the outer peripheral surface 6b of the O-ring 6 expands in diameter. As the O-ring 6 moves downstream, it is pushed downstream by the internal pressure of the inlet passage 7a. Therefore, the downstream side of the O-ring 6 is pressed against the downstream wall surface 4b of the annular groove 4. Meanwhile, the upstream side of the O-ring 6 moves away from the upstream wall surface 4a of the annular groove 4. At least the upstream side of the O-ring 6 moves away from the upstream wall surface 4a of the annular groove 4 when it reaches the tapered surface 7d.

[0038] As shown in Figures 5 and 6, the outer peripheral surface 6b of the O-ring 6 abuts against the tapered surface 7d. Therefore, compressed air in the inlet flow passage 7a passes between the upstream side of the O-ring 6 and the upstream wall surface 4a of the annular groove 4 and enters the inner peripheral surface 6a of the O-ring 6. The compressed air then pushes the inner peripheral surface 6a of the O-ring 6 radially outward, expanding the diameter of the O-ring 6. This causes the inner peripheral surface 6a of the O-ring 6 to move away from the bottom surface 4c of the annular groove 4. As a result, the compressed air flows downstream of the O-ring 6 through the gap between the inner peripheral surface 6a of the O-ring 6 and the bottom surface 4c of the annular groove 4. That is, the compressed air flows into the inner peripheral chamber 4d, which is surrounded by the bottom surface 4c of the annular groove 4, the downstream wall surface 4b, and the inner peripheral surface 6a of the O-ring 6. The compressed air then attempts to further expand the diameter of the O-ring 6. To address this, an air release groove 5 is formed in the valve stem 3.

[0039] For reference, a relief valve 90 without an air release groove 5 will be described using Figures 8 and 9. Without the air release groove 5, the compressed air entering the inner circumferential chamber 4d would have no escape route. Therefore, the compressed air in the inner circumferential chamber 4d would press against the inner circumferential surface 6a of the O-ring 6, causing the O-ring 6 to further expand in diameter. If the O-ring 6 were to move away from the tapered surface 7d or the downstream wall surface 4b of the annular groove 4, the compressed air would be discharged into the discharge passage 7b, preventing further expansion of the O-ring 6. However, if the O-ring 6 continues to expand without moving away from either of these surfaces, there is a risk that the O-ring 6 will become misaligned axially with respect to the annular groove 4, as shown in Figure 9. In this case, the worker would have to reinsert the O-ring 6 onto the valve stem 3, interrupting the operation.

[0040] Meanwhile, as shown in Figure 6, the air release groove 5 allows the compressed air that has entered the inner peripheral chamber 4d to be discharged to the discharge passage 7b. Therefore, the O-ring 6 is prevented from expanding in diameter due to the compressed air pressing against the inner peripheral surface 6a. Meanwhile, the valve stem 3 moves further downstream, reaching the position shown by the solid line in Figure 5. Thus, the inlet passage 7a and the outlet passage 7b are connected to each other on the radially outer side of the O-ring 6, and the chamber 33 is opened to the atmosphere. Therefore, the O-ring 6 is prevented from coming off the annular groove 4 in the axial direction.

[0041] As described above, the driving tool 1 has a chamber 33 that stores compressed air and a relief valve 2 provided in the chamber 33, as shown in FIGS. 1 and 2. The relief valve 2 has an inlet passage 7a that communicates with the chamber 33, and an outlet passage 7b that is formed downstream of the inlet passage 7a and has a larger diameter than the inlet passage 7a. As shown in FIG. 5, the valve stem 3 moves along the inlet passage 7a. An O-ring 6 that seals the inlet passage 7a is attached to an annular groove 4 on the outer periphery of the valve stem 3. An air release path (e.g., air release grooves 5a to 5d) is formed in the valve stem 3. When the O-ring 6 is forced by the internal pressure of the chamber 33 to move beyond the inlet flow path 7a toward the outlet flow path 7b and the compressed air enters the inner chamber 4d between the wall surface of the annular groove 4 and the inner surface 6a of the O-ring 6, the air escape path has an inlet portion 5e that opens into the inner chamber 4d and an outlet 5f that opens into the outlet flow path 7b so that the compressed air is discharged from the inner chamber 4d to the outlet flow path 7b.

[0042] Therefore, the O-ring 6 moves with the valve stem 3 and reaches the discharge flow path 7b, expanding in diameter, and the compressed air that has entered the inner circumferential chamber 4d can encourage further expansion of the O-ring 6. However, at the same time, the compressed air is discharged from the inner circumferential chamber 4d to the discharge flow path 7b through the air release path. This prevents the O-ring 6 from expanding in diameter and becoming detached from the valve stem 3. As a result, there is no need for restoration work to re-insert the O-ring 6 onto the valve stem 3 in order to reuse the relief valve 2.

[0043] 4, the air release path is formed by a groove (e.g., air release groove 5a) formed on the downstream wall surface 4b, which supports the O-ring 6 from the downstream side of the compressed air, out of the wall surfaces 4a and 4b of the annular groove 4. The groove extends in the radial direction of the valve stem 3. Therefore, compared to a structure in which a through-hole is formed in the valve stem 3 and the inner circumferential chamber 4d and the discharge flow path 7b communicate with each other, for example, an air release path can be obtained more easily.

[0044] As shown in Figure 4, multiple grooves (for example, four air release grooves 5a to 5d) are formed on the downstream wall surface 4b of the annular groove 4. Therefore, compared to when a single groove is formed, compressed air that has entered the inner peripheral chamber 4d is quickly discharged to the discharge flow path 7b. This makes it possible to more effectively suppress the diameter expansion of the O-ring 6.

[0045] As shown in Figure 1, the driving tool 1 has a grip portion 30 that is held by a user and houses a chamber 33. The relief valve 2 is provided on the tip surface of the grip portion 30. Therefore, the direction of the compressed air discharged from the relief valve 2 is in the axial direction of the grip portion 30. Therefore, even when compressed air is discharged from the relief valve 2, it is less likely that the compressed air will hit the operator.

[0046] 1, the driving tool 1 has a pressure regulating valve 51 that reduces the pressure of externally supplied compressed air and supplies it to the chamber 33. The pneumatic tool has a driving tool body 20 equipped with a driver (e.g., driver bit 24) that uses the compressed air from the chamber 33 to drive a fastener (e.g., a screw B). Therefore, the externally supplied compressed air is reduced in pressure by the pressure regulating valve 51 to an appropriate level for operating the driver.

[0047] 1 and 2, an O-ring 6 that seals the inlet flow path 7a is attached to the annular groove 4 on the outer periphery of the valve stem 3. The O-ring 6 has an O-ring detachment prevention structure (e.g., air release grooves 5a to 5d) that prevents the O-ring 6 from expanding radially and becoming detached from the valve stem 3 when the O-ring 6 passes through the inlet flow path 7a and heads toward the outlet flow path 7b due to the internal pressure of the chamber 33.

[0048] Therefore, the O-ring fall-off prevention structure prevents the O-ring 6 from expanding in the radial direction and from coming off the valve stem 3. Thus, in order to reuse the relief valve 2, the restoration work of re-inserting the O-ring 6 onto the valve stem 3 is not required.

[0049] Embodiment 2 will be described with reference to Fig. 7. Embodiment 2 is formed in substantially the same manner as the above-described embodiment 1. The driving tool 1 of embodiment 2 has a valve stem 70 shown in Fig. 7 instead of the valve stem 3 shown in Fig. 6.

[0050] As shown in FIG. 7 , an air release hole 75 is formed in the downstream wall surface 4b of the valve stem 70. The air release hole 75 is, for example, a drilled hole that penetrates from the downstream wall surface 4b to the outer circumferential surface of the sliding body portion 3c. An inlet portion 75e of the air release hole 75 is located near the bottom surface 4c of the annular groove 4. As a result, the inlet portion 75e opens into the inner circumferential chamber 4d on the inner circumferential side of the center of the partial orthogonal cross section of the O-ring 6. The inlet portion 75e is located, for example, near the end position of the fillet between the bottom surface 4c and the downstream wall surface 4b. An outlet 75f of the air release hole 75 opens into the outer circumferential surface of the sliding body portion 3c. As a result, the inlet portion 75e opens into the flow paths 7a and 7b on the outer circumferential side of the center of the partial orthogonal cross section of the O-ring 6.

[0051] Instead of the above-described configuration, the following configuration may be used. The air release hole 75 may have an orthogonal cross-sectional shape of, for example, an ellipse or a polygon, as long as it connects the inner circumferential chamber 4d to the flow paths 7a and 7b. To further increase the amount of compressed air that escapes, a plurality of air release holes 75, for example, four, may be formed in the downstream wall surface 4b.

[0052] As shown in Figure 1, the driving tool 1 uses compressed air to strike and rotate a screw B against a workpiece W to fasten it. Alternatively, it may be, for example, an air nailer. In other words, the driving tool 1 may be any pneumatic tool with a relief valve in the chamber, and may also be, for example, an air impact driver, air hammer, air wrench, etc.

[0053] 6, the end of the discharge port 5f of the air release groove 5 opens at the outer peripheral surface of the sliding portion 3a. Alternatively, the end of the discharge port 5f may open at the downstream wall surface 4b. That is, it is sufficient that the air release groove 5 opens at a position on the outer peripheral side of the center of the partial orthogonal cross section of the O-ring 6 to the flow paths 7a, 7b, and the air release groove 5 may extend radially from the inlet portion 5e beyond the center, so that the end of the discharge port 5f opens at the downstream wall surface 4b.

[0054] 4, the air release groove 5 has four air release grooves 5a to 5d. Alternatively, only one air release groove 5a may be formed. Also, five or more air release grooves 5 may be formed by forming a groove in addition to the four air release grooves 5a to 5d.

[0055] As shown in Figure 2, the driving tool 1 has a chamber 33 equipped with a pressure regulating valve 51 as well as a relief valve 2. Alternatively, the chamber 33 may be equipped with only the relief valve 2. In other words, compressed air is supplied directly to the chamber 33 from an external air supply source. The relief valve 2 operates when abnormal pressure occurs in the chamber 33 due to a malfunction of the air supply source or the like.

[0056] As shown in Figure 3, the air release groove 5 is formed on the wall surface 4b of the annular groove 4 in the valve stem 3. Alternatively, the air release groove 5 may be formed on the tapered surface 7d of the discharge passage 7b in the valve body 7. The air release groove 5 formed on the tapered surface 7d can prevent the formation of the inner circumferential chamber 4d itself. As a result, the O-ring 6 will not be pushed by the compressed air that has entered the inner circumferential chamber 4d and expand in diameter. For example, the air release groove 5 extends from the upstream portion to the downstream portion of the tapered surface 7d, with the inlet portion 5e opening into the inlet passage 7a and the discharge port 5f opening at the abutment surface 7e, functioning as a structure to prevent the O-ring from falling off. [Explanation of symbols]

[0057] 1. Driving tool 2 Relief valve 3 Valve stem 3a Sliding part 3b head 3c Sliding body 3d Stopper part 3e Legs 3i Slit 4 Annular groove 4a Upstream wall 4b Downstream wall 4c Bottom 4d inner chamber 5a~5d Air release groove (5) 5e, 75e entrance section 5f, 75f outlet 6 O-rings 6a Inner surface 6b Outer surface 7 Valve box 7a Inlet channel 7b Discharge flow path 7c pedestal 7d Tapered surface 7e Contact surface 7f Cylinder inner surface 7g pinhole 20 Tool body 21 Main body housing 22 cylinders 23 Piston 24 driver bits 25 Lower moving end damper 26-bit rotating unit 27 Nose 27a Drive-in Passage 27b Contact arm 28 Gear train 30 Grip section 31 Trigger 32 Start valve 33 Chamber 40 Magazines 40a Screw feed mechanism 45 Air Motor 50 Lid 51 Pressure regulating valve 52 Connection coupler 70 Valve stem 75 Air release hole 90 Relief valve B Vis H Air Hose W Fastening material

Claims

1. A pneumatic tool, a chamber for storing compressed air; A relief valve is provided in the chamber, and the relief valve an inlet channel communicating with the chamber; a discharge flow path formed downstream of the inlet flow path and having a diameter larger than that of the inlet flow path; a valve stem that moves along the inlet flow path; an O-ring fitted in an annular groove on the outer periphery of the valve stem to seal the inlet flow passage; the annular groove has a bottom surface located on an inner circumferential side of the O-ring and a downstream wall surface that supports the O-ring from the downstream side of the compressed air, the discharge flow path has a tapered surface whose diameter increases from the downstream end of the inlet flow path toward the downstream side, When the O-ring is positioned in the inflow passage, an outer peripheral surface of the O-ring abuts on an inner wall of the inflow passage over the entire circumference, and an inner peripheral surface of the O-ring abuts on the bottom surface over the entire circumference, an O-ring detachment prevention structure that prevents the O-ring from expanding radially and coming off the valve stem while the O-ring is moving toward the discharge flow path beyond the inlet flow path due to the internal pressure of the chamber; The O-ring falling-off prevention structure is a pneumatic tool having: an air escape path that is provided on the downstream wall surface and has an inlet that opens into an inner chamber between the bottom surface and the inner surface of the O-ring and an outlet that opens into the discharge flow path; the tapered surface with which the outer surface of the O-ring abuts over the entire circumference; and the downstream wall surface with which the downstream side of the O-ring abuts.

2. The pneumatic tool according to claim 1, The air release path is formed by a groove formed in the downstream wall surface, the groove extending in a radial direction of the valve stem.

3. The pneumatic tool according to claim 2, A pneumatic tool in which a plurality of the grooves are formed in the downstream wall surface of the annular groove.

4. The pneumatic tool according to claim 3, a grip extending laterally from a side of the tool body, which is grasped by a user and which houses the chamber; The relief valve is provided on a tip surface of the grip located on the opposite side of the tool body.

5. The pneumatic tool according to claim 4, a pressure regulating valve that reduces the pressure of the compressed air from the outside and supplies it to the chamber; A pneumatic tool having the tool body with a driver that utilizes compressed air from the chamber to drive fasteners.

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