screw gun

Abstract

To provide a screw driving machine impacting a screw in a screw shaft direction and rotating around the screw shaft to be fastened in which durability of a driver bit impacting and rotating the screw is improved.SOLUTION: A driver bit 30 is a bit separation type whose tip side bit 32 is detachable. The bit 32 includes: a screw shaft part 32c which has screw connection with a driver 31; a small diameter part 32b; and a tip side 32a of the bit. The small diameter part 32b works as torsion bar so that a so-called cam-out is decreased to improve durability of the tip side 32a of the bit.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a screw driving machine that strikes a screw in the screw axis direction and rotates it around the screw axis to tighten it.

Background Art

[0002] Patent Document 1 discloses a screw driving machine using compressed air as a power source. The screw driving machine includes a piston operated by compressed air, a driver bit screw-coupled to the piston, and an air motor that rotates the driver bit in the screw tightening direction. In this screw driving machine, by locking the rotation of the piston around the screw axis from the outside so that the driver bit can be rotated in the loosening direction, the driver bit can be replaced without disassembling the driving nose portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a screw driving machine, it is necessary to improve the workability during driver bit replacement and to improve the wear resistance of, for example, the tip portion of the driver bit against so-called cam-out. The present disclosure aims to enhance the durability of the driver bit.

Means for Solving the Problems

[0005] According to one aspect of this disclosure, a screw driver tightens a screw by striking it in the direction of the screw axis and rotating it around the screw axis. The screw driver includes, for example, a piston that moves in the direction of the screw axis and a driver having a rod shape with a polygonal cross-section and coupled to the piston. The screw driver also includes, for example, a bit that is detachably coupled to the tip of the driver and into which a screw is engaged. The bit includes, for example, a screw shaft portion that is screw-coupled to the driver, a smaller diameter portion that extends from the screw shaft portion and has a smaller diameter than the screw shaft portion, and a bit end provided at the end of the smaller diameter portion into which a screw is engaged.

[0006] Therefore, the narrow diameter portion of the bit functions as a torsion bar, allowing the bit to be subjected to elastic twisting relative to the screwdriver. This suppresses so-called cam-out during screw tightening, thereby increasing the bit's durability.

[0007] According to another aspect of the present disclosure, a screw driver fastens a screw, for example, by striking it in the direction of the screw axis and rotating it around the screw axis. The screw driver has, for example, a piston that moves in the direction of the screw axis and a driver coupled to the piston that rotates around the screw axis. For example, the tip of the driver is equipped with a bit that is detachably screw-coupled by the screw shaft. For example, an elastic body is interposed between the driver and the bit. For example, the elastic body is elastically deformed so that the bit can be displaced in the direction of the screw axis relative to the driver.

[0008] Therefore, in the final stage of screw tightening, the screwdriver rotates relative to the screw axis around the bit while the tightening torque causes the elastic body of the screwdriver to elastically deform. This suppresses so-called cam-out during screw tightening, thereby increasing the durability of the bit. [Brief explanation of the drawing]

[0009] [Figure 1] This is a vertical cross-section of a screw gun. [Figure 2] This is an objective view of the driver rotation mechanism. [Figure 3] This is a perspective view of the area near the connection point between the driver and the bit, as seen from the direction of arrow III in Figure 2. [Figure 4] Figure 3 shows a cross-sectional view taken along the line IV-IV, which is a longitudinal cross-sectional view of the connection between the driver and the bit. [Figure 5] Figure 4 shows a cross-sectional view taken along the VV line, which is a cross-sectional view of the connection between the driver and the bit. [Figure 6] Figure 5 is a perspective view of the driver's tip as seen from direction VI. [Figure 7] Figure 5 is a perspective view of the driver's tip as seen from direction VII. [Figure 8] This is an exploded view of the driver's tip. [Figure 9] This is a view from arrow IX in Figure 7, and is a top view of the driver's tip. [Figure 10] This is a side view of the driver's tip. [Figure 11] This is a longitudinal cross-sectional view of the connection portion between the driver and the bit according to the second embodiment. [Figure 12] This is a longitudinal cross-sectional view of the connection portion between the driver and the bit according to the third embodiment. [Modes for carrying out the invention]

[0010] In one or more embodiments, for example, the driver has a mounting hole into which the screw shaft and the smaller diameter portion of the bit are inserted. For example, the length of the mounting hole in the axial direction of the screw is long enough to cover the entire length of the smaller diameter portion. Therefore, when the screw gun is powered by compressed air, leakage of compressed air supplied to the tool body is suppressed. In particular, leakage of return air is suppressed because the area around the smaller diameter portion is covered by the wall surface of the mounting hole.

[0011] In one or more embodiments, for example, the driver has a mounting hole into which the screw shaft and the smaller diameter portion of the bit are inserted. For example, the bit has a seating portion that extends from the screw shaft in the opposite direction to the smaller diameter portion. For example, the seating portion abuts against the bottom of the mounting hole. Thus, when the bit is screw-coupled to the driver, the smaller diameter portion effectively functions as a torsion bar. This reliably increases the durability of the bit.

[0012] In one or more embodiments, the elastic body is interposed, for example, between the rear end surface in the screw axis direction of the bit and the bottom of the female screw portion of the driver. Thereby, at the final stage of screwing where the screw is tightened with a constant torque, the driver elastically deforms the elastic body in the screw axis direction and relatively rotates in the screwing direction with respect to the bit, thereby suppressing the cam-out of the bit with respect to the recess of the screw.

[0013] In one or more embodiments, for example, the bit has a bit end portion where the screw is engaged. The bit end portion has an annular rear surface facing the front end surface of the driver. The bit end portion has a gap between its rear surface and the front end surface of the driver. This gap allows the elastic body to be elastically deformed and the bit to be displaced in the screw axis direction with respect to the driver. Therefore, the displacement of the bit in the screw axis direction with respect to the driver is smoothly allowed. Thereby, excessive tightening torque around the screw axis of the bit is absorbed and cam-out is more reliably avoided.

[0014] In one or more embodiments, the lead of the screw shaft portion is smaller than that of the double-start screw. Therefore, at the final stage of screwing, the driver relatively displaces more greatly around the screw axis with a slight displacement in the screw axis direction with respect to the bit than in the case of a double-start screw. Thereby, a larger buffering width by the elastic body of the bit is ensured, and the cam-out of the bit with respect to the recess of the screw is more reliably suppressed.

[0015] In one or more embodiments, for example, the driver has a bar shape with a polygonal cross-section. In this case, for example, it has a plurality of rollers that abut against the flat outer surface of the driver and guide the movement of the driver in the screw axis direction, and a motor that revolves the plurality of rollers around the screw axis to rotate the driver around the screw axis. Therefore, while the driver is guided in the screw axis direction by the plurality of rollers, the driver rotates around the screw axis when the motor is activated.

[0016] In one or more embodiments, for example, the bit is different from the driver in at least one of material, surface treatment, and heat treatment. Therefore, the bit is formed of a material more durable than the driver, or the bit is subjected to a surface treatment or heat treatment more durable than that of the driver. Thereby, while reducing the cost of the driver, the durability of the bit can be enhanced.

[0017] In one or more embodiments, for example, the driver has a lock hole for inserting a lock pin that restricts rotation around the screw axis of the driver. Therefore, the driver is prevented from rotating, facilitating the bit replacement operation.

[0018] In one or more embodiments, for example, the driver has a roller that transmits rotational torque around the screw axis. For example, the bit has a bit end portion where a screw is engaged. For example, at the upper movement end position of the driver, the bit end portion of the bit is located below the roller, and the screw shaft portion of the bit is located above the roller. Therefore, the short bit is firmly screwed to the driver.

Example

[0019] FIG. 1 shows a compression air-driven screw driving machine 1 according to this example. The screw driving machine 1 is used for the operation of tightening a screw (bolt) 2 into a clamped material 3 such as a gypsum board or wood. The screw driving machine 1 includes a tool main body portion 10, a grip portion 4 that a user holds, and a magazine 5 that houses a large number of screws 2.

[0020] The tool main body portion 10 has a cylindrical main body housing 11. A cylindrical cylinder 12 is installed inside the main body housing 11. A piston 13 is installed inside the cylinder 12. A long bar-shaped driver bit 30 is coupled to the piston 13. The screw 2 is struck in the screw axis S direction by the driver bit 30 and is rotated around the screw axis S and tightened. In the following description, the screw driving machine 1 is held in a vertical posture, and the driving direction (tightening direction) of the screw 2 is downward.

[0021] A driver guide 6 is provided at the lower part of the tool body 10 to guide the driver bit 30 so that it can reciprocate up and down. The driver guide 6 extends downward from the tool body 10. The inside of the driver guide 6 is an injection passage 6a that runs vertically through it. The driver bit 30 is guided to reciprocate up and down within the injection passage 6a.

[0022] A contact arm 7 is provided at the lower part of the driver guide 6 so as to be able to move up and down relative to it. By pushing the tool body 10 downward while the contact arm 7 is in contact with the material to be fastened 3, the contact arm 7 is displaced upward relative to the driver guide 6 and is activated. The driving and fastening operations are performed by both the activation of the contact arm 7 and the pulling operation of the switch lever 8, which will be described later.

[0023] A grip portion 4 for the user to hold is provided on the side of the tool body 10. The grip portion 4 extends laterally from the tool body 10. A hose connection portion 4a for connecting an air hose for supplying compressed air is provided at the tip of the grip portion 4. The inside of the grip portion 4 is a pressure accumulation chamber 4b. Compressed air is stored in the pressure accumulation chamber 4b. The air pressure in the pressure accumulation chamber 4b is maintained at an appropriate pressure by a pressure regulating valve 4c. The compressed air from the pressure accumulation chamber 4b is supplied to the tool body 10. A trigger-type switch lever 8, operated by the user with their fingertips, is provided below the base of the grip portion 4.

[0024] A cylindrical magazine 5 is provided straddling the driver guide 6 and the grip section 4. The magazine 5 houses numerous screws 2. These screws 2 are housed in a connected screw strip, temporarily fastened to each other in parallel via a resin connecting material. The connected screw strip is loaded into the magazine 5 in a coiled state. The diagram omits the illustration of the connected screw strip.

[0025] The magazine 5 is connected to the injection passage 6a of the driver guide 6 via the feed mechanism 9. The feed mechanism 9 supplies one screw 2 at a time into the injection passage 6a in conjunction with the driving operation. A single screw 2 supplied into the injection passage 6a is struck by the driver bit 30 in the direction of the screw axis S and rotated around the screw axis S.

[0026] An air motor 15 is positioned above the magazine 5. The air motor 15 is started by compressed air that is branched off from a portion of the compressed air supplied from the pressure accumulator chamber 4b to the tool body 10. The rotational output of the air motor 15 is transmitted to the bit rotating unit 20 via a gear train 16. The bit rotating unit 20 is interposed between the tool body 10 and the driver guide 6. The bit rotating unit 20 is supported so as to be rotatable around the central axis J of the driver bit 30.

[0027] The bit rotation unit 20 is rotated by the air motor 15, causing the driver bit 30 to rotate around its central axis J. The central axis J of the driver bit 30 coincides with the screw axis S, which corresponds to the tightening direction of the screw 2.

[0028] The bit rotating section 20 is equipped with an annular roller holder 21. The upper side of the roller holder 21 is closed by a cover 22. As shown in Figure 2, a gear 21a is provided on the outer circumference of the roller holder 21. The gear 21a is provided around the entire circumference. A gear train 16 meshes with the gear 21a. The rotational torque of the air motor 15 is transmitted to the roller holder 21 through the meshing of the gear 21a and the gear train 16. As a result, the roller holder 21 rotates around the central axis J of the driver bit 30.

[0029] A driver bit 30 is inserted through the center of the bit rotating part 20 so as to be able to reciprocate up and down. The driver bit 30 is provided so as to be able to reciprocate up and down, passing through the center of the roller holder 21 and the center of the cover part 22.

[0030] As shown in Figure 2, three rollers 23 are held inside the roller holder 21. The three rollers 23 are rotatable around the axis of the pivot shafts 23a, which protrude from both sides. The three rollers 23 are positioned at three equal divisions (120° intervals) around the central axis J of the driver bit 30. The driver bit 30 is inserted through the center of the three rollers 23, and the three rollers 23 slide against the flat outer surface (flat outer surface F) of the driver bit 30 in a line contact state. This guides the driver bit 30 so that it can move up and down by the three rollers 23. As the bit rotation part 20 rotates with the three rollers 23 sliding against the flat outer surface F of the driver bit 30 in a line contact state, rotational torque around the central axis J is transmitted to the driver bit 30. This causes the driver bit 30 to rotate around the central axis J (around the screw axis S).

[0031] As shown in Figures 3 and 4, the driver bit 30 has a driver 31 integrally coupled to the center of the lower surface of the piston 13, and a bit 32 coupled to the lower part of the driver 31. The bit 32 is detachably (replaceable) coupled to the lower part of the driver 31. The driver 31 has a long hexagonal rod shape with a regular hexagonal cross-section. The six flat outer surfaces of the driver 31 correspond to the flat outer surface F.

[0032] Bit 32 is shorter than driver bit 31 and constitutes a very short area at the tip of driver bit 30. Bit 32 has a round bar shape with a circular cross-section. The tip of bit 32 is the bit tip portion 32a that engages with the recess of the screw head 2.

[0033] A screw shaft portion 32c is integrally provided on the upper part of the bit 32 via a narrow diameter portion 32b. A mounting hole 31a is provided in the center of the lower surface of the driver 31, coaxial with the central axis J. A female screw portion 31b is provided at the back of the mounting hole 31a. The bit 32 is coaxially coupled to the driver 31 by screwing the screw shaft portion 32c into the female screw portion 31b.

[0034] The narrow-diameter portion 32b of the bit 32 is formed to have a smaller diameter than the screw diameter of the screw shaft portion 32c. Therefore, the narrow-diameter portion 32b functions as a torsion bar that allows elastic displacement (torsion) of the bit 32 around the central axis J relative to the driver 31. The function of the narrow-diameter portion 32b as a torsion bar suppresses so-called cam-out during screw tightening operations, thereby increasing the durability of the bit 32.

[0035] The bit 32 has a seating portion 32d that extends from the screw shaft portion 32c in the opposite direction to the narrow diameter portion 32b. The screw shaft portion 32c of the bit 32 is tightened until the seating portion 32d abuts against the bottom 31c of the mounting hole 31a of the driver 31. As a result, a small gap 30a is created between the stepped surface 32e of the bit 32 and the tip surface of the driver 31. This ensures that the function of the narrow diameter portion 32b as a torsion bar is reliably performed.

[0036] The length (depth) of the mounting hole 31a of the driver 31 in the direction of the screw axis S is long enough to cover almost the entire length of the narrow diameter portion 32b. As a result, the area around the narrow diameter portion 32b is surrounded by the wall portion of the mounting hole 31a. This allows the roller 23 to slide in line contact with the flat outer surface F of the driver 31 even around the narrow diameter portion 32b. Furthermore, when the driver bit 30 is returned to near the upper moving end, the compressed air (so-called return air) supplied to the lower side of the piston 13 (lower piston chamber) is prevented from leaking out from around the narrow diameter portion 32b. This ensures that the piston 13 and driver 31 are reliably returned to the upper moving end position by a sufficient amount of return air.

[0037] When the driver bit 30 reaches the upper moving end position or near the upper moving end, as shown in Figures 2-4, the tip portion 32a of the bit 32 is located below the roller 23, and the screw shaft portion 32c of the bit 32 is located above the roller 23. Therefore, the short bit is firmly screwed to the driver.

[0038] Bit 32 is made of a different material than driver 31. Bit 32 is made of a more durable material than driver 31. In addition, bit 32 is subjected to a different surface treatment, a different heat treatment, or both compared to driver 31. Bit 32 is subjected to a surface treatment that is more wear-resistant than driver 31, and a heat treatment that increases its hardness, etc. This allows for lower costs for driver 31 while increasing the durability of the necessary part (bit 32).

[0039] As shown in Figure 4, the driver 31 has a locking hole 31d into which a locking pin 35 for preventing rotation is inserted. The locking hole 31d is located above the mounting hole 31a. As shown in Figure 1, the driver guide 6 is provided with an insertion hole 6b corresponding to the locking hole 31d. When changing bits, the driver bit 30 is moved downward to align the locking hole 31d with the insertion hole 6b. In this state, the locking pin 35 is inserted through the insertion hole 6b into the locking hole 31d, preventing the driver bit 30 from rotating. This improves the convenience of bit changing, which is performed by rotating the bit 32 relative to the driver 31. As shown in Figure 4, a bit changing jig 36 can be used to rotate the bit 32 relative to the driver 31 when changing bits. By engaging the bit tip 32a with the recess 36a of the bit changing jig 36 and rotating it around the screw shaft S, the screw shaft portion 32c is tightened and loosened relative to the female screw portion 31b. By using the locking pin 35 and the bit replacement jig 36, the bit 32 can be replaced quickly and easily.

[0040] The three rollers 23 need to be precisely line-contacting and sliding against the three flat outer surfaces F of the driver 31. To achieve this, the tip of the driver 31 is provided with six guide surfaces C (C1 to C6). Figure 8 shows the tip of the driver 31 unfolded around the central axis J on the flat outer surface F6, and Figure 9 shows details of the tip surface of the driver 31. In Figures 8 and 9, the six flat outer surfaces F are labeled F1 to F6, and the six ridges R are labeled R1 to R6. The six ridges R1 to R6 are located at 60° intervals around the central axis J.

[0041] The three rollers 23, which are arranged at 120° intervals around the central axis J of the driver 31, are in sliding contact with the flat outer surfaces F1, F3, and F5, or with the flat outer surfaces F2, F4, and F6, thereby achieving an appropriate state in which the rotational torque of the bit rotating part 20 is efficiently transmitted to the driver 31.

[0042] Triangular guide surfaces C extend from the tip of each ridge line R1 to R6. Guide surface C1 is provided at the tip of ridge line R1. Guide surface C2 is provided at the tip of ridge line R2. Guide surface C3 is provided at the tip of ridge line R3. Guide surface C4 is provided at the tip of ridge line R4. Guide surface C5 is provided at the tip of ridge line R5. Guide surface C6 is provided at the tip of ridge line R6. The six guide surfaces C1 to C6 are provided at an angle in the direction of tapering at the tip. As a result, the tip of the driver 31 is formed in a tapered shape. The six guide surfaces C1 to C6 correspond to a chamfer created by tapering (removing) the tip of each ridge line R1 to R6 in the direction of tapering.

[0043] The circumscribed circle D2 of the tip surface of the driver 31, which includes the bases C1a to C6a of the six guide surfaces C1 to C6, has a smaller diameter than the inscribed circle D1 of the three rollers 23. As a result, the tip of the driver 31 is reliably positioned between the three rollers 23, regardless of its relative position around the central axis J of the driver 31.

[0044] Three adjacent guide surfaces C1, C2, and C3 around the central axis J are located within one half-circumference of the central axis J (first axis range H1), while the remaining three guide surfaces C4, C5, and C6 are located within the other half-circumference (second axis range H2). The three guide surfaces C1, C2, and C3 located within the first axis range H1 have different shapes and different sizes of scalene triangles. The three guide surfaces C4, C5, and C6 located within the second axis range H2 have different shapes and different sizes of scalene triangles.

[0045] Therefore, the three guide surfaces C1, C2, and C3 in the first axial range H1 are arranged at mutually different angles around the central axis J (screw axis S, hereafter the same). The three guide surfaces C4, C5, and C6 in the second axial range H2 are arranged at mutually different angles around the central axis J. The three guide surfaces C1, C2, and C3 in the first axial range H1 have mutually different widths in a cross-section perpendicular to the central axis J. For example, the bases C1a, C2a, and C3a of guide surfaces C1, C2, and C3 have mutually different lengths. Similarly, the three guide surfaces C4, C5, and C6 in the second axial range H2 also have mutually different widths in a cross-section perpendicular to the central axis J. For example, the bases C4a, C5a, and C6a of guide surfaces C4, C5, and C6 have mutually different lengths.

[0046] The guide surfaces C1, C2, and C3 in the first axis rotation range H1 and the guide surfaces C4, C5, and C6 in the second axis rotation range H2 are arranged point-symmetrically with respect to the central axis J. Therefore, the guide surface C1 in the first axis rotation range H1 and the guide surface C4 in the second axis rotation range H2 have triangles of the same shape and size. Similarly, the guide surface C2 in the first axis rotation range H1 and the guide surface C5 in the second axis rotation range H2 have triangles of the same shape and size. Furthermore, the guide surface C3 in the first axis rotation range H1 and the guide surface C6 in the second axis rotation range H2 have triangles of the same shape and size. In addition, with respect to the inclination angle around the central axis J, the guide surfaces C1 and C4 are arranged parallel to each other, the guide surfaces C2 and C5 are arranged parallel to each other, and the guide surfaces C3 and C6 are arranged parallel to each other.

[0047] Because guide surfaces C1, C2, C3 and guide surfaces C4, C5, C6 are arranged point-symmetrically, the bases of guide surfaces C on opposite sides of the central axis J (180° apart) are parallel to each other. The base C1a of guide surface C1 and the base C4a of guide surface C4 are parallel. The base C2a of guide surface C2 and the base C5a of guide surface C5 are parallel. The base C3a of guide surface C3 and the base C6a of guide surface C6 are parallel.

[0048] The six guide surfaces C1 to C6 are arranged with the same angle α in the tapering direction relative to the central axis J. Figure 10 shows the state in which guide surface C1 is tilted at an angle α with respect to the central axis J. This allows the driver 31 to smoothly guide itself into the space between the three rollers 23 while suppressing axial wobble.

[0049] Each of the six guide surfaces C1 to C6 has two tip edges (C1b, C1c), (C2b, ​​C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), and (C6b, C6c) corresponding to the two sides excluding the bases C1a to C6a. Therefore, the tip of the driver 31 is provided with a total of 12 tip edges (C1b, C1c), (C2b, ​​C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), and (C6b, C6c).

[0050] As shown in Figure 9, when the tip of the driver 31 passes between the three rollers 23, if three of the 12 tip edges (C1b, C3b, C5b) from (C1b, C1c), (C2b, ​​C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), (C6b, C6c) hit the rollers 23, six guide surfaces C1 to C6 are formed such that the three points 23A, 23B, 23C that hit the rollers are the vertices of a scalene triangle. In addition to (C1b, C3b, C5b), there are a total of four possible combinations of the three tip edges: (C1c, C3c, C5c), (C2b, ​​C4b, C6b), and (C2c, C4c, C6c). The sizes of the six guide surfaces C1 to C6 and their inclination angles around the central axis J are appropriately set so that the triangle formed by connecting the contact points 23A, 23B, and 23C of the roller 23 with respect to the three leading edges of each pattern is a scalene triangle.

[0051] When the contact points 23A, 23B, and 23C of the roller 23 with respect to the tip ridge form the vertices of a scalene triangle, the direction of action of the reaction forces received from the three contact points 23A, 23B, and 23C is off-center from the central axis J of the driver 31, and the three reaction forces are not balanced. As a result, all three reaction forces act on the driver 31 as moments around the central axis J. When the three contact points 23A, 23B, and 23C form the vertices of an equilateral triangle, the direction of action of the reaction forces is all directed toward the central axis J of the driver 31, resulting in no moment M being generated. Also, when the three contact points 23A, 23B, and 23C form the vertices of an isosceles triangle, the reaction forces in two directions are balanced, and no sufficient moment is generated. When the three contact points 23A, 23B, and 23C form the vertices of a scalene triangle, a moment M around the screw axis is efficiently generated on the driver. This allows the driver 31 to be positioned quickly and reliably around its central axis J, guiding it to a state where the rollers 23 slide against each flat outer surface F in a line contact manner.

[0052] According to the first embodiment illustrated above, the driver bit 30 has a bit 32 that is detachable from the driver 31. The bit 32 has a screw shaft portion 32c for screw coupling to the driver 31. There is a narrow diameter portion 32b between the screw shaft portion 32c and the bit tip portion 32a. The narrow diameter portion 32b of the bit 32 functions as a torsion bar that allows elastic twisting of the bit tip portion 32a relative to the driver. This suppresses so-called cam-out during screw tightening work and increases the durability of the bit 32.

[0053] In the illustrated first embodiment, the length (depth) of the mounting hole 31a of the driver 31 in the direction of the screw axis S is formed to be long enough to cover almost the entire length of the small diameter portion 32b. As a result, the area around the small diameter portion 32b is surrounded by the wall portion of the mounting hole 31a. This prevents the return air supplied to the piston lower chamber from leaking out from around the small diameter portion 32b. As a result, the piston 13 and the driver 31 are reliably returned to the upper moving end position by a sufficient amount of return air.

[0054] According to the first embodiment illustrated, the screw shaft portion 32c of the bit 32 is tightened until the seating portion 32d abuts against the bottom portion 31c of the mounting hole 31a of the driver 31, creating a small gap 30a between the stepped surface 32e of the bit 32 and the tip surface of the driver 31. This ensures that the function of the small diameter portion 32b as a torsion bar is reliably performed, increasing the durability of the bit 32.

[0055] In the first embodiment illustrated, the bit 32 is made of a material that is more durable than the driver 31. Furthermore, the bit 32 is subjected to a surface treatment, heat treatment, or both that makes it more wear-resistant than the driver 31. This increases the durability of the required part (bit 32) and reduces the cost of the driver bit 30.

[0056] According to the first embodiment illustrated, the replacement of the bit 32 is made easier. During replacement, a locking pin 35 is inserted into the locking hole 31d of the driver 31 to prevent the driver from rotating. At the same time, by attaching the bit replacement jig 36 to the bit tip 32a and rotating it, the screw shaft portion 32c can be easily loosened and tightened against the female screw portion 31b. Thus, the replacement of the bit 32 is made more convenient.

[0057] According to the first embodiment illustrated, when the driver bit 30 is in the upper moving end position, the bit tip portion 32a of the bit 32 is located below the roller 23, and the screw shaft portion 32c of the bit 32 is located above the roller 23. This allows for a strong screw connection to the driver 31 while shortening the bit tip portion 32a.

[0058] Various modifications can be made to the first embodiment illustrated. For example, although a hexagonal rod-shaped driver 31 with a hexagonal cross-section was illustrated, the illustrated bit separation structure can also be applied to a rod-shaped driver with a polygonal cross-section having three or more flat outer surfaces F.

[0059] Although a round bar-shaped bit 32 with a circular cross-section was used as an example, the illustrated thin diameter portion 32b can also be applied to a rectangular bar-shaped bit with a polygonal cross-section, similar to the driver 31.

[0060] Although the example shows a configuration in which a locking pin 35 is inserted into a locking hole 31d to prevent the driver 31 from rotating during bit replacement, the driver 31 can also be prevented from rotating by inserting a locking pin into the bit rotating part 20 or the gear train 16, thereby locking their rotation.

[0061] Although an air motor-separated screw gun 1, in which the air motor 15 is positioned to the side of the tool body 10, has been illustrated, the illustrated bit coupling structure and the small diameter section 32b can also be applied to an air motor-coaxial screw gun, in which the air motor is positioned coaxially with the driver bit on the upper part of the tool body. In the case of the latter air motor-coaxial screw gun, both the driver and the bit can be round bars with a circular cross-section.

[0062] In the first embodiment, the bit 32 is provided with a small diameter portion 32b, and cam-out is suppressed by the elastic deformation of the small diameter portion 32b around the screw axis S. This cam-out suppression structure can be modified. Components and components that do not require modification are denoted by the same reference numerals and their descriptions are omitted.

[0063] Figure 11 shows a driver bit 40 according to the second embodiment. The driver bit 40 according to the second embodiment has a driver 41 integrally coupled to the center of the lower surface of the piston 13, and a bit 42 coupled to the lower part of the driver 41, similar to the first embodiment. The bit 42 is detachably (replaceable) coupled to the lower part of the driver 41. The driver 41 has a long hexagonal rod shape with a regular hexagonal cross-section.

[0064] The tip of the bit 42 is a bit tip portion 42a that engages with a recess in the head of the screw 2. A screw shaft portion 42b is integrally provided above the bit tip portion 42a. A fine-pitch screw with a smaller lead than a coarse-pitch screw is used for the screw shaft portion 42b. A female screw portion 41a is provided coaxially with the central axis J at the center of the lower surface of the driver 41. The bit 42 is coaxially coupled to the driver 41 by screwing the screw shaft portion 42b into the female screw portion 41a.

[0065] A pressing shaft portion 42c is coaxially and integrally provided on the upper part of the screw shaft portion 42b of the bit 42. A retaining hole 41b is provided on the upper part of the female screw portion 41a of the driver 41. The pressing shaft portion 42c of the bit 42 is inserted into the retaining hole 41b. When the bit 42 is removed from the driver 41, the pressing shaft portion 42c is released from the retaining hole 41b.

[0066] An elastic body 43 is interposed between the upper surface of the pressing shaft portion 42c (the rear end surface 42e of the screw shaft portion 42b) and the bottom surface 41c of the retaining hole 41b. The elastic body 43 is made of a rubber material that forms a sphere with relatively high hardness. When the bit 42 is screwed onto the driver 41, the elastic body 43 is pre-entered into the retaining hole 41b. By screwing the screw shaft portion 42b into the female screw portion 41a and screwing the bit 42 onto the driver 41, the elastic body 43 is sandwiched between the rear end surface 42e of the pressing shaft portion 42c and the bottom surface 41c of the retaining hole 41b. As a result, the bit 42 is connected to the driver 41 with an appropriate elastic force applied to it around the screw shaft S.

[0067] When bit 42 is attached (elastically coupled), a small gap 44 is provided between the annular tip surface 41d of the driver 41 and the annular rear surface 42d of bit 42 that faces the tip surface 41d. The gap 44 allows for relative displacement of the screw shaft portion 42b with respect to the female screw portion 41a in the tightening direction (relative displacement in the direction of the central axis J). As a result, the elastic body 43 is elastically deformed by the screw tightening torque.

[0068] During screw tightening, the screw tightening torque around the screw axis S is applied to the bit 42 via the driver 41, thereby driving the screw tightening process. The screw tightening torque of the driver 41 acts automatically on the screw axis portion 42b of the bit 42. In the final stage of screw tightening, when the screw 2 has been tightened to a constant torque, the driver 41 rotates relative to the bit 42 in the screw tightening direction, while elastically deforming the elastic body 43 in the direction of the screw axis S. This suppresses the so-called cam-out of the bit 42 relative to the head of the screw 2. This increases the durability of the bit 42.

[0069] Similar to the first embodiment, the bit 42 is made of a different material than the driver 41. The bit 42 is made of a more durable material than the driver 41. In addition, the bit 42 is subjected to a different surface treatment, a different heat treatment, or both, than the driver 41. The bit 42 is subjected to a surface treatment that is more wear-resistant than the driver 41, and is also subjected to a heat treatment that increases its hardness, etc. This makes it possible to reduce the cost of the driver 41 while increasing the durability of the necessary part (bit 42).

[0070] The bit 42 is attached and detached using the lock pin 35 and bit replacement jig 36, as in the first embodiment. The driver 41 is provided with a lock hole 41e for inserting the lock pin 35. Also, as in the first embodiment, torque for tightening screws is applied to the driver 41 by the bit rotation section 20, which includes three rollers 23.

[0071] According to the second embodiment, the driver bit 40 has a bit 42 that is detachable from the driver 41. The bit 42 has a screw shaft portion 42b for screw coupling to the driver 41. An elastic body 43 is interposed between the bottom portion 41c of the driver 41 and the rear end surface 42e of the bit 42. The elastic deformation of the elastic body 43 allows the bit 42 to be displaced relative to the driver 41 in the screw axis S direction. This suppresses so-called cam-out during screw tightening work and increases the durability of the bit 32.

[0072] According to the second embodiment, a fine-pitch screw with a smaller lead than a coarse-pitch screw is used for the screw shaft portion 42b. Therefore, in the final stage of screw tightening, the driver 41 is displaced more significantly around the screw shaft S with only a slight displacement in the direction of the screw shaft S than in the case of a coarse-pitch screw. This ensures a larger buffer width for the elastic body 43 of the bit 42, and more reliably suppresses the cam-out of the bit 42 relative to the head (recess) of the screw 2.

[0073] Modifications can be made to the second embodiment. A cylindrical elastic body can be used instead of the spherical elastic body 43. In this case, the clamping position of the elastic body may be a vertical position with the axis of the cylinder aligned with the screw axis S, or a horizontal position with the axis of the cylinder perpendicular to the screw axis S. Alternatively, a configuration in which multiple elastic bodies are clamped may be used. Alternatively, a torsion spring may be used instead of a rubber elastic body.

[0074] Figure 12 shows a driver bit 50 according to the third embodiment. The driver bit 50 according to the third embodiment has a driver 51 integrally coupled to the center of the lower surface of the piston 13, and a bit 52 coupled to the lower part of the driver 51, similar to the first and second embodiments. The bit 52 is detachably (replaceable) coupled to the lower part of the driver 51. The driver 51 has a long hexagonal rod shape with a regular hexagonal cross-section.

[0075] The tip of the bit 52 is a bit tip portion 52a that engages with a recess in the head of the screw 2. A screw shaft portion 52b is integrally provided above the bit tip portion 52a. A fine-pitch screw with a smaller lead than a coarse-pitch screw is used for the screw shaft portion 52b. A female screw portion 51a is provided coaxially with the central axis J at the center of the lower surface of the driver 51. The bit 52 is coaxially coupled to the driver 51 by screwing the screw shaft portion 52b into the female screw portion 51a.

[0076] In the third embodiment, the screw shaft portion 52b of the bit 52 does not reach the bottom of the female thread portion 51a of the driver 51. As a result, a gap 54 of sufficient size in the direction of the screw axis S is always maintained between the rear end face of the screw shaft portion 52b and the bottom of the female thread portion 51a. This gap 54 allows for constant displacement of the bit 52 in the direction of the screw axis S.

[0077] An annular rear surface 52c is provided around the base of the screw shaft portion 52b. An annular elastic body 53 is attached to the base of the screw shaft portion 52b. The elastic body 53 is attached along the rear surface 52c. In the third embodiment, an O-ring with relatively high hardness is used as the elastic body 53.

[0078] An annular tip surface 51c is provided around the opening of the female screw portion 51a on the lower surface of the driver 51. When the bit 52 is screw-connected to the driver 51, the elastic body 53 is sandwiched between the rear surface 52c of the bit 52 and the tip surface 51c of the driver 51.

[0079] The elastic body 53 is pre-attached to the screw shaft portion 52b when the bit 52 is screwed onto the driver 51. By screwing the screw shaft portion 52b into the female screw portion 51a and screwing the bit 52 onto the driver 51, the elastic body 53 is sandwiched between the rear surface 52c of the bit 52 and the tip surface 51c of the driver 51. As a result, the bit 52 is connected to the driver 51 with an appropriate elastic force applied to it in the direction of the screw axis S.

[0080] During screw tightening, the screw tightening torque around the screw axis S is applied to the bit 52 via the driver 51, thereby driving the screw tightening process. The screw tightening torque of the driver 51 acts automatically on the screw shaft portion 52b of the bit 52. In the final stage of screw tightening, when the screw 2 has been tightened to a constant torque, the driver 51 rotates relative to the bit 52 in the screw tightening direction, while elastically deforming the elastic body 53 in the direction of the screw axis S. This suppresses the so-called cam-out of the bit 52 relative to the head of the screw 2. This increases the durability of the bit 52.

[0081] Similar to the first embodiment, the bit 52 is made of a different material than the driver 51. The bit 52 is made of a more durable material than the driver 51. In addition, the bit 52 is subjected to a different surface treatment, a different heat treatment, or both, than the driver 51. The bit 52 is subjected to a surface treatment that is more wear-resistant than the driver 51, and is also subjected to a heat treatment that increases its hardness, etc. This makes it possible to reduce the cost of the driver 51 while increasing the durability of the necessary part (bit 52).

[0082] The bit 52 is attached and detached using the lock pin 35 and bit replacement jig 36, as in the first and second embodiments. The driver 51 is provided with a lock hole 51d for inserting the lock pin 35. Also, as in the first and second embodiments, torque for tightening screws is applied to the driver 51 by the bit rotation section 20, which includes three rollers 23.

[0083] According to the third embodiment, the driver bit 50 has a bit 52 that is detachable from the driver 51. The bit 52 has a screw shaft portion 52b for screw coupling to the driver 51. An annular elastic body 53 is interposed between the tip surface 51c of the driver 51 and the rear surface 52c of the bit 52. The elastic deformation of the elastic body 53 allows the bit 52 to be displaced relative to the driver 51 in the screw axis S direction. Excess torque is absorbed by the elastic deformation of the elastic body 53 in the final stage of screw tightening. This suppresses so-called cam-out and increases the durability of the bit 52.

[0084] According to the third embodiment, a fine-pitch screw with a smaller lead than a coarse-pitch screw is used for the screw shaft portion 52b. Therefore, in the final stage of screw tightening, the driver 51 displaces more relative to the bit 52 with a slight displacement in the direction of the screw axis S than in the case of a coarse-pitch screw. This ensures a larger buffer width for the elastic body 53 of the bit 52, and more reliably suppresses the cam-out of the bit 52 relative to the head (recess) of the screw 2.

[0085] Although the configurations using fine-pitch threads for the screw shaft portion 42b in the second embodiment and the screw shaft portion 52b in the third embodiment have been illustrated, the lead of the screw shaft portion may be changed within a range smaller than that of a coarse-pitch thread.

[0086] The screw gun 1 in the first to third embodiments is an example of a screw gun in one aspect of this disclosure. The piston 13 in the first to third embodiments is an example of a piston in one aspect of this disclosure. The driver 31 in the first embodiment, the driver 41 in the second embodiment, and the driver 51 in the third embodiment are examples of drivers in one aspect of this disclosure. The bit 32 in the first embodiment, the bit 42 in the second embodiment, and the bit 52 in the third embodiment are examples of bits in one aspect of this disclosure. The roller 23 in the first to third embodiments is an example of a roller in one aspect of this disclosure. The air motor 15 in the first to third embodiments is an example of a motor in one aspect of this disclosure.

[0087] The screw shaft portion 32c of the first embodiment is an example of a screw shaft portion in one aspect of the present disclosure. The screw shaft portion 42b of the second embodiment is an example of a screw shaft portion in another aspect of the present disclosure. The screw shaft portion 52b of the third embodiment is an example of a screw shaft portion in another aspect of the present disclosure. The small diameter portion 32b of the first embodiment is an example of a small diameter portion in one aspect of the present disclosure. The bit tip portion 32a of the first embodiment, the bit tip portion 42a of the second embodiment, and the bit tip portion 52a of the third embodiment are each examples of bit ends in one aspect of the present disclosure.

[0088] The elastic body 43 in the second embodiment and the elastic body 53 in the third embodiment are the positions of elastic bodies in another aspect of the present disclosure, respectively. [Explanation of symbols]

[0089] 1... Screw gun 2... Screw (screw) S... Screw shaft (center axis J of driver 31) 3…Material to be fastened 4…Grip section 4a...Hose connection, 4b...Pressure accumulator, 4c...Pressure regulating valve 5… Magazine 6…Driver Guide 6a... Injection passage, 6b... Insertion hole 7… Contact Arm 8…Switch lever 9... Feed mechanism 10…Tool body part 11…Main housing 12... Cylinder 13... Piston 15…Air motor 16...Gear train 20-bit rotation section 21... Roller holder 21a...Gear 22...Lid part 23...Laura 23a…Spindle D1... Inscribed circle of 23 rollers 30…Driver bit (First embodiment) 30a... Gap 31…Driver 31a…Mounting hole, 31b…Female threaded section, 31c…Bottom, 31d…Lock hole 32...bit 32a...Bit tip, 32b...Narrow diameter section, 32c...Screw shaft section, 32d...Seating section, 32e...Stepped surface D2...Circumscribed circle of the tip surface of driver 31 H1... First axis rotation range H2… Second axis rotation range F(F1~F6)…Flat outer surface R(R1~R6)…Ridge line C(C1~C6)…Guidance surface C1a... Base of guide surface C1 C2a... Base of guide surface C2 C3a... Base of guide surface C3 C4a... Base of guide surface C4 C5a... Base of guide surface C5 C6a... Base of guide surface C6 C1b, C1c... Tip ridge of guide surface C1 C2b, C2c... Tip ridge of guide surface C2 C3b, C3c... Tip ridge of guide surface C3 C4b, C4c... Tip ridge of guide surface C4 C5b, C5c... Tip ridge of guide surface C5 C6b, C6c... The leading edge of guide surface C6 α... Inclination angle of the guide surface C with respect to the central axis J 35... Lock pin 36…Bit changing jig 36a…recess 40…Driver bit (Second embodiment) 41…Driver 41a...Female threaded portion, 41b...Retaining hole, 41c...Bottom, 41d...Tip surface, 41e...Locking hole 42...bit 42a...Bit tip, 42b...Screw shaft, 42c...Pressing shaft, 42d...Rear surface, 42e...Rear end surface 43...Elastic body 44... Gap 50…Driver bit (Third embodiment) 51... Driver 51a...Female thread portion, 51c...Tip surface, 51d...Lock hole 52...bit 52a...Bit tip, 52b...Screw shaft, 52c...Rear side 53...Elastic body 54... Gap

Claims

1. A screw driver that tightens a screw by striking it in the direction of the screw axis and rotating it around the screw axis, The piston moves in the direction of the screw axis, A driver coupled to the piston and rotating around the screw shaft, The driver has a bit that is detachably screw-connected to the tip of the driver, The aforementioned bit is The screw shaft portion that is screw-connected to the aforementioned driver, A small diameter portion extending from the screw shaft portion and having a smaller diameter than the screw shaft portion, The end of the small diameter portion has a bit end into which the screw is engaged, The driver has a mounting hole into which the screw shaft portion and the small diameter portion of the bit are inserted, and the small diameter portion is housed along its entire length on the inner circumference side of the mounting hole. The driver has a rod shape with a polygonal cross-section, A plurality of rollers that contact the flat outer surface of the driver and guide the movement of the driver in the screw axis direction, A screw driving machine having a motor that rotates the driver around the screw shaft by causing the plurality of rollers to revolve around the screw shaft.

2. A screw driver that tightens a screw by striking it in the direction of the screw axis and rotating it around the screw axis, The piston moves in the direction of the screw axis, A driver coupled to the piston and rotating around the screw shaft, The driver has a bit that is detachably screw-connected to the tip of the driver, The aforementioned bit is The screw shaft portion that is screw-connected to the aforementioned driver, A small diameter portion extending from the screw shaft portion and having a smaller diameter than the screw shaft portion, The end of the small diameter portion has a bit end into which the screw is engaged, The driver has a mounting hole into which the screw shaft portion and the small diameter portion of the bit are inserted, and the small diameter portion is housed along its entire length on the inner circumference side of the mounting hole. The driver is a screw driver having a locking hole for inserting a locking pin that restricts the rotation of the driver around the screw shaft.

3. A screw gun according to claim 1 or 2, The driver has a mounting hole into which the screw shaft portion and the small diameter portion of the bit are inserted. The bit has a seating portion extending from the screw shaft portion in the direction opposite to the small diameter portion, and the screw driving machine has the seating portion abut against the bottom of the mounting hole.

4. A screw driver that tightens a screw by striking it in the direction of the screw axis and rotating it around the screw axis, The piston moves in the direction of the screw axis, A driver coupled to the piston and rotating around the screw shaft, A bit comprising a screw shaft portion that is detachably screw-connected to the tip of the aforementioned driver, The driver and the bit have an elastic body interposed between them, A screw driver in which the bit is displaceable in the screw axis direction relative to the driver by the elastic deformation of the elastic body due to the rotation of the bit in the screw tightening direction.

5. A screw gun according to claim 4, The elastic body is interposed between the rear end face of the bit in the screw axial direction and the bottom of the female screw portion of the driver in the screw driving machine.

6. A screw gun according to claim 4 or 5, The bit has a bit end into which the screw is engaged, The bit end has an annular rear surface facing the front surface of the driver, and has a gap between the rear surface and the front surface of the driver. A screw driver in which the gap allows the bit to be displaced in the screw axis direction relative to the driver by elastically deforming the elastic body.

7. A screw gun according to any one of claims 4 to 6, The screw driver has a screw shaft lead smaller than that of a standard screw.

8. A screw gun according to any one of claims 1 to 7, The screw driver is characterized in that the bit is made of a material more durable than the driver, or has a surface treatment that makes it more wear-resistant than the driver, or has been heat-treated to increase its hardness compared to the driver.

9. A screw gun according to any one of claims 1 or 3 to 8, The driver is a screw driver having a locking hole for inserting a locking pin that restricts the rotation of the driver around the screw shaft.

10. A screw gun according to any one of claims 2 to 9, The driver has a rod shape with a polygonal cross-section, A plurality of rollers that contact the flat outer surface of the driver and guide the movement of the driver in the screw axis direction, A screw driving machine having a motor that rotates the driver around the screw shaft by causing the plurality of rollers to revolve around the screw shaft.

11. A screw gun according to claim 1 or 10, The bit has a bit end into which the screw is engaged, A screw gun in which, at the upper moving end position of the driver, the bit end of the bit is located below the roller and the screw shaft portion of the bit is located above the roller.

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