JP7689898B2 - Screw driver - Google Patents

Description

This disclosure relates to a screw driver that strikes a screw in the direction of the screw axis and rotates it around the screw axis to tighten it.

Patent Document 1 discloses a screw driver that uses compressed air as its power source. The screw driver is equipped with a piston that is operated by compressed air, a driver bit that is screw-connected to the piston, and an air motor that rotates the driver bit in the screw tightening direction. This screw driver allows the driver bit to be replaced without disassembling the screw-driving nose by locking the piston's rotation around the screw shaft from the outside and allowing the driver bit to rotate in the loosening direction.

JP 2003-236766 A

In the screw driver of Patent Document 1, the air motor is placed coaxially with the driver bit on top of the main body, and the rotational torque of the air motor is transmitted to the piston side, causing the driver bit to rotate in the screw tightening direction. For this reason, a round bar with a circular cross section is sufficient for the driver bit, and no special part is provided to directly receive the rotational torque in the screw tightening direction from the air motor.

In addition to this coaxial air motor type, there is also a separate air motor type screw driver, which has an air motor located separately on the side of the main body. In a separate air motor type screw driver, a roller is placed in sliding contact with a driver bit that is a hexagonal rod with a hexagonal cross section, and the roller is revolved around the screw shaft by the air motor while allowing displacement in the impact direction, so that the rotational torque in the screw tightening direction is directly transmitted to the driver bit.

In the latter type of screw driver with separate air motor, the rollers must be precisely in linear contact with the outer surface (six flat surfaces) of the driver bit. If the driver bit is misaligned around the screw shaft and the ridges (corners of the hexagon) come into point contact with the rollers, the downward movement of the driver may be locked. The objective of this disclosure is to ensure that the rollers are in linear contact with the flat outer surface of the driver in a screw driver with separate air motor.

According to one aspect of the present disclosure, a screw driver strikes a screw in the screw axis direction and rotates it around the screw axis to tighten it. The screw driver has, for example, a piston that moves in the screw axis direction and a driver that has a rod-shaped polygonal cross section and is connected to the piston. The screw driver has, for example, a bit that is detachably connected to the tip of the driver and engages the screw. The screw driver has, for example, multiple rollers that are in sliding contact with the flat outer surface of the driver and guide the movement of the driver in the screw axis direction. The screw driver has, for example, a motor that revolves the multiple rollers around the screw axis to rotate the driver around the screw axis. For example, multiple guide surfaces are formed at the tip of the driver to make the tip of the driver tapered, and the circumscribing circle of the tip surface of the driver is made smaller in diameter than the inscribing circle of the multiple rollers.

As a result, when the screwdriver moves downward to enter between the rollers, the entry movement of the screwdriver is guided by the multiple guide surfaces. As a result, the screwdriver is smoothly guided between the rollers while being guided around the axis, so that the rollers are guided in a state where they make linear sliding contact with the flat outer surface of the screwdriver. This eliminates the problem of the screwdriver's downward movement being locked by the rollers.

FIG. FIG. 2 is a perspective view of a driver rotation mechanism. 3 is a perspective view of the vicinity of a joint between the driver and the bit, as viewed from the direction of arrow III in FIG. 2. 4 is a cross-sectional view taken along line IV-IV in FIG. 3, and is a vertical cross-sectional view of a joint between the driver and the bit. 5 is a cross-sectional view taken along line VV in FIG. 4, showing a cross-sectional view of the joint between the driver and the bit. 6 is a perspective view of the tip portion of the driver as viewed from a direction VI in FIG. 5 . 6 is a perspective view of the tip portion of the driver as viewed from a direction VII in FIG. 5 . FIG. 8 is a view taken along the arrow IX in FIG. 7 and shows a tip end surface of the driver. FIG.

In one or more embodiments, for example, the tip of the driver has multiple ridges. For example, when the tip of the driver passes between multiple rollers, a guide surface is formed so that when one of the multiple ridges hits one of the multiple rollers, a moment is generated in the driver around the screw axis.

The guide surface guides the driver around the axis, and each roller is guided so that it slides against the flat outer surface rather than against the ridges. This allows the rotational torque around the screw shaft to be efficiently transmitted to the driver via the rollers.

In one or more embodiments, the driver has a hexagonal rod shape with, for example, six ridges. The tip of the driver has, for example, six guide surfaces extending from the six ridges and twelve tip ridges formed by the six guide surfaces. For example, when the tip of the driver passes between a plurality of rollers, when three of the twelve tip ridges hit the plurality of rollers, the six guide surfaces are formed so that the three points of contact are the vertices of a scalene triangle. As a result, the direction of action of the reaction forces received from the three points is a direction away from the center of the driver, and the reaction forces in the three directions are not balanced with each other. Therefore, all the reaction forces in the three directions act on the driver as moments around the central axis. When the three points are the vertices of an equilateral triangle, the reaction forces all act as forces toward the center of the driver, and no moment is generated. Also, when two points are the vertices of an isosceles triangle, the reaction forces in the two directions are balanced and sufficient moment is not generated. With the three points forming the vertices of a scalene triangle, a moment around the screw shaft is efficiently generated on the driver, guiding the driver to an appropriate position around the screw shaft. This allows the rollers to be guided into linear contact with each flat outer surface.

In one or more embodiments, for example, multiple guide surfaces located on the semicircular side around the central axis of the driver are arranged at different angles to each other around the screw shaft. This ensures that the driver is guided to the appropriate position around the screw shaft.

In one or more embodiments, for example, the multiple guide surfaces located on the semicircular side around the central axis of the driver have different widths in a cross section perpendicular to the screw axis. This allows the driver to be more reliably guided to the appropriate position around the screw axis.

In one or more embodiments, for example, the guide surfaces are parallel to each other with respect to an angle about the central axis of the driver, with the guide surfaces on opposite sides of the central axis of the driver being parallel to each other. This allows the driver to be efficiently guided to the appropriate position about the screw axis.

In one or more embodiments, for example, multiple guide surfaces are arranged at the same angle relative to one another in the screw axial direction. This allows the driver to smoothly guide around the screw shaft as the driver advances in the screw axial direction.

In one or more embodiments, for example, the bit has a round bar shape with a circular cross section. In this case, the bit rotates around the screw shaft by rotating the driver around the screw shaft with the rotational torque transmitted by the revolution of multiple rollers. This makes it possible to connect a round bar-shaped bit to the driver without having to consider its position around the screw shaft, making it even easier to replace the bit.

Figure 1 shows a compressed air-driven screw driver 1 according to this embodiment. The screw driver 1 is used to drive screws 2 into a material 3 such as plasterboard or wood. The screw driver 1 comprises a tool body 10, a grip 4 that is held by the user, and a magazine 5 that holds a large number of screws 2.

The tool body 10 has a cylindrical body housing 11. A cylindrical cylinder 12 is fitted inside the body housing 11. A piston 13 is fitted inside the cylinder 12. A long rod-shaped driver bit 30 is connected to the piston 13. The driver bit 30 strikes the screw 2 in the direction of the screw axis S and rotates it around the screw axis S to tighten it. In the following explanation, the screw driver 1 is held in a vertical position, and the driving direction (tightening direction) of the screw 2 is downward.

A driver guide 6 is provided at the bottom 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 penetrates vertically. The driver bit 30 is guided within the injection passage 6a so that it can reciprocate up and down.

A contact arm 7 is provided below the driver guide 6 so that it can be displaced up and down relative to the workpiece 3. By pressing the tool body 10 downward with the contact arm 7 in contact with the workpiece 3, the contact arm 7 is displaced upward relative to the driver guide 6 and turned on. The driving and tightening operations are performed by turning on the contact arm 7 and pulling the switch lever 8, which will be described later.

A grip portion 4 is provided on the side of the tool body 10 for the user to grip. The grip portion 4 extends laterally from the tool body 10. A hose connection portion 4a is provided at the tip of the grip portion 4 for connecting an air hose for supplying compressed air. The inside of the grip portion 4 is a pressure accumulator chamber 4b. Compressed air is accumulated in the pressure accumulator chamber 4b. The air pressure in the pressure accumulator chamber 4b is maintained at an appropriate pressure by a pressure regulating valve 4c. The compressed air in the pressure accumulator chamber 4b is supplied to the tool body 10. A trigger-type switch lever 8 is provided below the base side of the grip portion 4, which the user pulls with his or her fingertip.

A cylindrical magazine 5 is provided between the driver guide 6 and the grip portion 4. A large number of screws 2 are stored in the magazine 5. The large number of screws 2 are stored in the form of a connected screw band in which the screws are temporarily fastened in parallel to each other via a resin connecting material. The connected screw band is loaded into the magazine 5 in a coiled state. The connected screw band is not shown in the figure.

The magazine 5 is connected to the injection passage 6a of the driver guide 6 via a feed mechanism 9. The feed mechanism 9 feeds the screws 2 one by one into the injection passage 6a in conjunction with the driving operation. Each screw 2 fed into the injection passage 6a is struck in the direction of the screw axis S by the driver bit 30 and rotated around the screw axis S.

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

When the bit rotating part 20 is rotated by the air motor 15, the driver bit 30 rotates 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.

The bit rotation unit 20 is equipped with a circular roller holder 21. The top side of the roller holder 21 is closed by a lid 22. As shown in FIG. 2, a gear 21a is provided on the outer circumferential surface of the roller holder 21. The gear 21a is provided around the entire circumference. The 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 with the gear train 16. This causes the roller holder 21 to rotate around the central axis J of the driver bit 30.

The driver bit 30 is inserted into the center of the bit rotation part 20 so that it can move back and forth up and down. The driver bit 30 passes through the center of the roller holder 21 and the center of the lid part 22 so that it can move back and forth up and down.

As shown in FIG. 2, three rollers 23 are held inside the roller holder 21. The three rollers 23 are arranged to be rotatable around the axis of the support shaft 23a via the support shaft 23a protruding on both sides. The three rollers 23 are arranged at three equal positions (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 are in linear contact with the flat outer surface (flat outer surface F) of the driver bit 30. This allows the driver bit 30 to be guided vertically by the three rollers 23. When the bit rotating part 20 rotates with the three rollers 23 in linear contact with the flat outer surface F of the driver bit 30, a 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).

As shown in Figures 3 and 4, the driver bit 30 has a driver 31 that is integrally connected to the center of the underside of the piston 13, and a bit 32 that is connected to the lower part of the driver 31. The bit 32 is connected to the lower part of the driver 31 in a detachable (replaceable) manner. 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.

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

A screw shaft portion 32c is integrally provided on the upper part of the bit 32 via a thin-diameter portion 32b. A mounting hole 31a is provided at the center of the underside of the driver 31, coaxially with the central axis J. A female thread portion 31b is provided at the back of the mounting hole 31a. The screw shaft portion 32c is tightened into the female thread portion 31b, thereby coaxially connecting the bit 32 to the driver 31.

The thin-diameter portion 32b of the bit 32 is formed with a diameter smaller than the thread diameter of the screw shaft portion 32c. Therefore, the thin-diameter portion 32b functions as a torsion bar that allows the bit 32 to elastically displace (twist) around the central axis J relative to the driver 31. The thin-diameter portion 32b functions as a torsion bar to suppress so-called cam-out during screw tightening operations, thereby improving the durability of the bit 32.

The bit 32 has a seat 32d that extends from the threaded shaft 32c in the opposite direction to the thin-diameter portion 32b. The threaded shaft 32c of the bit 32 is screwed in until the seat 32d abuts against the bottom 31c of the mounting hole 31a of the driver 31. This creates 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 thin-diameter portion 32b functions as a torsion bar.

The length (depth) of the mounting hole 31a of the driver 31 in the screw axis S direction is long enough to cover almost the entire length of the thin-diameter portion 32b. Therefore, the thin-diameter portion 32b is surrounded by the wall of the mounting hole 31a. This allows the roller 23 to slide in a line contact state against the flat outer surface F of the driver 31 around the thin-diameter portion 32b. In addition, when the driver bit 30 is returned to the upper end of the movement, the compressed air (so-called return air) supplied to the lower surface side (piston lower chamber) of the piston 13 is prevented from leaking out from around the thin-diameter portion 32b. This ensures that the piston 13 and the driver 31 are returned to the upper end position with a sufficient amount of return air.

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

The bit 32 is made of a different material than the driver 31. The bit 32 is made of a material that is more durable than the driver 31. In addition, the bit 32 is subjected to a different surface treatment, a different heat treatment, or both, than the driver 31. The bit 32 is subjected to a surface treatment that is more wear-resistant than the driver 31, and is also subjected to a heat treatment that increases its hardness, etc. This reduces the cost of the driver 31 while increasing the durability of the necessary area (the bit 32).

As shown in FIG. 4, the driver 31 has a lock hole 31d into which a lock pin 35 for preventing rotation is inserted. The lock hole 31d is provided above the mounting hole 31a. As shown in FIG. 1, the driver guide 6 has an insertion hole 6b corresponding to the lock hole 31d. When changing the bit, the driver bit 30 is moved downward to align the lock hole 31d with the insertion hole 6b. In this state, the lock pin 35 is inserted into the lock hole 31d through the insertion hole 6b to prevent the driver bit 30 from rotating. This improves the convenience of the bit change work performed by rotating the bit 32 relative to the driver 31. As shown in FIG. 4, when changing the bit, a bit change tool 36 for rotating the bit 32 relative to the driver 31 can be used. The bit tip 32a is engaged with the recess 36a of the bit change tool 36 and rotated around the screw shaft S, thereby tightening and loosening the screw shaft 32c relative to the female screw part 31b. By using the lock pin 35 and bit replacement jig 36, the bit 32 can be replaced quickly and easily.

The three rollers 23 need to be precisely in sliding contact with the three flat outer surfaces F of the driver 31 in a line-contact state. 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 developed around the central axis J with the flat outer surface F6, and Figure 9 shows the 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 positioned at 60° intervals around the central axis J.

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 the flat outer surfaces F2, F4, and F6, creating an appropriate state in which the rotational torque of the bit rotating portion 20 is efficiently transmitted to the driver 31.

A triangular guide surface C extends from the tip of each of the ridgelines R1 to R6. A guide surface C1 is provided at the tip of ridgeline R1. A guide surface C2 is provided at the tip of ridgeline R2. A guide surface C3 is provided at the tip of ridgeline R3. A guide surface C4 is provided at the tip of ridgeline R4. A guide surface C5 is provided at the tip of ridgeline R5. A guide surface C6 is provided at the tip of ridgeline R6. The six guide surfaces C1 to C6 are provided at an incline in the tapering direction. This forms the tip of the driver 31 in a tapered shape. The six guide surfaces C1 to C6 correspond to C-chamfers in which the tips of the ridgelines R1 to R6 are cut away in the tapering direction (tapered shape).

The circumscribing 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 inscribing circle D1 of the three rollers 23. This ensures that the tip of the driver 31 can be inserted between the three rollers 23 regardless of the relative position of the driver 31 around the central axis J.

The three guide surfaces C1, C2, C3 adjacent to each other around the central axis J are arranged in one half-circumference range (first axis range H1) around the central axis J, and the remaining three guide surfaces C4, C5, C6 are arranged in the other half-circumference range (second axis range H2). The three guide surfaces C1, C2, C3 located in the first axis range H1 have mutually different shapes and different large scalene triangles. The three guide surfaces C4, C5, C6 located in the second axis range H2 have mutually different shapes and different sized scalene triangles.

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

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. Furthermore, 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. Furthermore, with respect to the inclination angle around the central axis J, the guide surface C1 and the guide surface C4 are arranged parallel to each other, the guide surface C2 and the guide surface C5 are arranged parallel to each other, and the guide surface C3 and the guide surface C6 are arranged parallel to each other.

The guide surfaces C1, C2, C3 and the guide surfaces C4, C5, C6 are arranged point symmetrically, so that the bases of the guide surfaces C on opposite sides 180° from the central axis J are arranged parallel to each other. The base C1a of the guide surface C1 and the base C4a of the guide surface C4 are arranged parallel to each other. The base C2a of the guide surface C2 and the base C5a of the guide surface C5 are arranged parallel to each other. The base C3a of the guide surface C3 and the base C6a of the guide surface C6 are arranged parallel to each other.

The six guide surfaces C1 to C6 are arranged with the same inclination angle α in the tapering direction relative to the central axis J. Figure 10 shows the state in which the guide surface C1 is inclined at angle α relative to the central axis J. This allows the driver 31 to be smoothly guided as it enters between the three rollers 23 while suppressing axial wobble.

The six guide surfaces C1 to C6 each have two tip edges (C1b, C1c), (C2b, C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), and (C6b, C6c) that correspond to two sides excluding the base sides C1a to C6a. Therefore, the tip of the driver 31 has a total of 12 tip edges (C1b, C1c), (C2b, C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), and (C6b, C6c).

As shown in Figure 9, when the tip of the driver 31 passes between the three rollers 23, six guide surfaces C1 to C6 are formed so that when three of the twelve tip edges (C1b, C1c), (C2b, C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), and (C6b, C6c) (C1b, C3b, C5b) come into contact with the rollers 23, the three contact points 23A, 23B, and 23C form the vertices of a scalene triangle. There are four possible combinations of the three tip edges: (C1b, C3b, C5b), (C1c, C3c, C5c), (C2b, C4b, C6b), and (C2c, C4c, C6c). The size of the six guide surfaces C1 to C6 and the angle of inclination around the central axis J are appropriately set so that the triangle connecting the contact points 23A, 23B, and 23C of the roller 23 with the three tip ridges of each pattern is a scalene triangle.

When the contact points 23A, 23B, and 23C of the roller 23 against the tip edge are the apexes of a scalene triangle, the direction of the reaction force received from the three contact points 23A, 23B, and 23C is a direction away from the central axis J of the driver 31, and the reaction forces in the three directions are not balanced with each other. Therefore, all the reaction forces in the three directions act on the driver 31 as a moment around the central axis J. When the three contact points 23A, 23B, and 23C are the apexes of an equilateral triangle, the reaction forces all act as forces toward the central axis J of the driver 31, and as a result, no moment M is generated. Also, when the three contact points 23A, 23B, and 23C are the apexes of an isosceles triangle, the reaction forces in the two directions are balanced and sufficient moment is not generated. When the three contact points 23A, 23B, and 23C are the apexes of a scalene triangle, the moment M around the screw shaft is efficiently generated on the driver. This allows the driver 31 to be quickly and reliably positioned around the central axis J, and guides the rollers 23 into linear contact with each flat outer surface F.

According to the embodiment exemplified above, six guide surfaces C1 to C6 are provided at the tip of the driver 31. The six guide surfaces C1 to C6 are provided at the tips of the ridges R1 to R6 of the driver 31. This causes the tip of the driver 31 to be tapered, and the circumscribing circle D2, which has the smallest diameter at the tip, is smaller than the inscribing circle D1 of the three rollers 23. As a result, when the tip of the driver 31 passes between the three rollers 23, the three rollers 23 are reliably in contact with each guide surface C, and the tip of the driver 31 is smoothly guided between the three rollers 23. This prevents the downward movement of the driver 31 from being locked by the rollers 23.

Moreover, the guide surfaces C1, C2, and C3 in the first axis rotation range H1 are provided with different sizes and different inclinations relative to the central axis J, and the guide surfaces C4, C5, and C6 in the second axis rotation range H2 are also provided with different sizes and different inclinations relative to the central axis J. In addition, 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.

As a result, for example, when the tip of the driver 31 passes between the three rollers 23, if three of the 12 tip edges (C1b, C1c), (C2b, C2c), (C3b, C3c), (C4b, C4c), (C5b, C5c), and (C6b, C6c) come into contact with the rollers 23, the three contact points 23A, 23B, and 23C form the vertices of a scalene triangle. This allows a moment M around the screw shaft to be efficiently generated on the driver 31.

The generated moment M guides the driver 31 to an appropriate position around the central axis J, so that the three rollers 23 are guided in linear sliding contact with the flat outer surfaces F1, F3, and F5, or the flat outer surfaces F2, F4, and F6. This allows the rotational torque around the screw axis S to be efficiently transmitted from the bit rotating section 20 to the driver 31.

In the illustrated embodiment, 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. This allows the driver 31 to be efficiently guided around the central axis J (around the screw axis S), and quickly and reliably achieves the appropriate state in which the three rollers 23 slide linearly against the flat outer surface F.

The six guide surfaces C1 to C6 are arranged at the same inclination angle α relative to each other in the direction of the screw axis S. This allows the driver 31 to guide its movement around the screw axis S quickly and smoothly as it advances in the direction of the screw axis S.

In the illustrated embodiment, the bit 32 has a round bar shape with a circular cross section. Therefore, the bit 32 can be connected to the driver 31 without having to consider its position around the screw shaft S. This makes it even easier to replace the bit 32.

Various modifications can be made to the illustrated embodiment. For example, a driver 31 with a hexagonal cross section and a hexagonal rod shape has been illustrated, but the illustrated guide surface C can be applied to each ridge R of a driver with a rod shape having a polygonal cross section with three or more flat outer surfaces F.

The configuration shown is one in which a lock pin 35 is inserted into the lock hole 31d to prevent the driver 31 from rotating during bit replacement work, but instead, the driver 31 can be prevented from rotating by inserting a lock pin into the bit rotation section 20 or the gear train 16 to lock the rotation of these.

The screw driver 1 of the embodiment is an example of a screw driver in one aspect of the present disclosure. The piston 13 of the embodiment is an example of a piston in one aspect of the present disclosure. The driver 31 of the embodiment is an example of a driver in one aspect of the present disclosure. The bit 32 of the embodiment is an example of a bit in one aspect of the present disclosure. The roller 23 of the embodiment is an example of a roller in one aspect of the present disclosure. The air motor 15 of the embodiment is an example of a motor in one aspect of the present disclosure.

The guide surface C (C1 to C6) in the embodiment is an example of a guide surface in this disclosure. The circumscribing circle D2 in the embodiment is an example of a circumscribing circle of a tip surface of a driver in this disclosure. The inscribing circle D1 in the embodiment is an example of an inscribing circle of a roller in this disclosure.

1...Screw driver 2...Screw
S...screw shaft (center axis J of the driver 31)
3...material to be fastened 4...grip portion 4a...hose connection portion, 4b...pressure accumulator, 4c...pressure adjusting valve 5...magazine 6...driver guide 6a...ejection passage, 6b...insertion hole 7...contact arm 8...switch lever 9...feed mechanism 10...tool body 11...body housing 12...cylinder 13...piston 15...air motor 16...gear train 20...bit rotating portion 21...roller holder 21a...gear 22...cover portion 23...roller 23a...support shaft D1...inscribed circle of three rollers 23 30...driver bit 30a...gap 31...driver 31a...mounting hole, 31b...female thread portion, 31c...bottom, 31d...lock hole 32...bit 32a...bit tip, 32b...thin diameter portion, 32c...screw shaft portion, 32d...seating portion, 32e...step Surface D2...Circumscribing circle H1 of the tip surface of the driver 31...Range H2 around the first axis...Range F around the second axis (F1 to F6)...Flat outer surface R (R1 to R6)...Ridge line C (C1 to C6)...Guide surface C1a...Base C2a of guide surface C1...Base C3a of guide surface C2...Base C4a of guide surface C3...Base C5a of guide surface C4...Base C6a of guide surface C5...Base C1 of guide surface C6 b, C1c...tip ridgeline C2b, C2c of guide surface C1...tip ridgeline C3b, C3c of guide surface C2...tip ridgeline C4b, C4c of guide surface C3...tip ridgeline C5b, C5c of guide surface C4...tip ridgeline C6b, C6c of guide surface C5...tip ridgeline α of guide surface C...inclination angle 35 with respect to central axis J of guide surface C...lock pin 36...bit replacement jig 36a...recess

Claims (8)

A screw driver that strikes a screw in the screw axial direction and rotates it around the screw axial direction to tighten the screw,
A piston that moves in the screw axis direction;
a driver having a polygonal rod shape in cross section and coupled to the piston;
a bit that is detachably coupled to a tip of the driver and engages with the screw;
A plurality of rollers are supported rotatably about an axis on a common cross section perpendicular to the screw shaft, and have outer circumferential surfaces that are in sliding contact with the flat outer surface of the driver to guide the movement of the driver in the screw shaft direction;
a motor that revolves the rollers around the screw shaft to rotate the driver around the screw shaft;
a plurality of guide surfaces formed at a tip of the driver to cause the tip of the driver to taper;
A screw driver in which the circumscribing circle of the tip surface of the driver is smaller in diameter than the inscribing circles tangent to the outer circumferential surfaces of the plurality of rollers. The screw driver according to claim 1,
the tip of the driver has a plurality of ridges;
A screw driver in which the guide surface is formed so as to generate a moment around the screw shaft in the driver when one of the plurality of ridges hits one of the plurality of rollers as the tip of the driver passes between the plurality of rollers. The screw driver according to claim 1 or 2,
the driver has a hexagonal bar shape with six ridges;
the tip of the driver has six of the guide surfaces extending from the six ridges, and twelve tip ridges formed by the six guide surfaces;
A screw driver in which the six guide surfaces are formed so that when three of the twelve tip ridges hit the rollers as the tip of the driver passes between the rollers, the three points of contact form the vertices of a scalene triangle. A screw driver according to any one of claims 1 to 3,
A screw driver in which the multiple guide surfaces located on a semi-circular side around the central axis of the driver are arranged at different angles to each other around the screw axis. A screw driver according to any one of claims 1 to 4,
A screw driver in which the multiple guide surfaces located on a semi-circumferential side around the central axis of the driver have different widths in a cross section perpendicular to the screw shaft. A screw driver according to any one of claims 1 to 5,
A screw driver in which the multiple guide surfaces are parallel to each other with respect to an angle around the central axis of the driver, with the guide surface on the opposite side to the central axis of the driver. A screw driver according to any one of claims 1 to 6,
A screw driver in which the multiple guide surfaces are arranged at the same angle to each other in the screw axial direction. A screw driver according to any one of claims 1 to 7,
A screw driver in which the bit has a round bar shape with a circular cross section.

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