DRIVE TOOL

Abstract

Immediately before the driving operation, a wheel (28) is displaced away from a drive unit (15) by a compression spring relative to a lifting device shaft (27). A final engagement area (P5) slides away from the last rack tooth (L5). This rapid movement of the final engagement area (P5) away from the last rack tooth (L5) reduces wear on the last rack tooth. The drive unit (15) returns to a ready position, and the wheel (28) can move away from the drive unit (15) against the compression spring (29). This prevents the engagement area (P) from engaging with and locking onto the rack tooth (L).

Description

BACKGROUND This disclosure relates to a driving tool for driving drive-in components, such as nails or staples, into a wooden material, etc. US 2022 / 0 143 798 A1 (Publication No. 798) and US 2022 / 0 291 301 A1 (Publication No. 301) disclose gas spring-operated driving tools that utilize the thrust of a compressed gas as a striking force. The gas spring-operated driving tool has a piston that moves up and down within a cylinder and a striker connected to the piston that moves integrally downward to strike a driving component. The piston and striker move downward in a driving direction by gas pressure in a storage chamber. The driving component is struck by the striker, which moves downward within a driving nose, and is then ejected through an ejection port. After striking the driving component, the piston and striker are returned from a lower end-of-travel position in a reverse driving direction by a lifting mechanism. The lifting mechanism uses an electric motor to rotate a lifting wheel, which has engagement sections. These engagement sections sequentially engage with a series of rack teeth on the driver. The driver is moved (pushed) upwards in a counter-driving direction as the engagement sections of the lifting wheel sequentially engage the rack teeth of the driver. This upward movement compresses a gas in the storage chamber, causing the pressure to increase. When the driver reaches its end position, the last engagement section of the lifting wheel disengages from the last rack tooth. The built-up gas pressure then pushes (moves) the driver back downwards, thus completing the driving operation. When the drive unit is moved upwards to the upper end-of-travel position and the final engagement area of ​​the last rack tooth is unlocked, both components slide against each other, resulting in relatively significant wear at the tip end of the last rack tooth. Publication No. 798 provided a freely rotating roller body at the final engagement section to prevent wear of the last rack tooth. Publication No. 301 reduces wear of the last rack tooth by displacing the lifting wheel in the driving direction relative to the drive shaft at a stage when the final engagement area of ​​the last rack tooth is unlocked. Previously, it was necessary to ensure that the last engagement area could easily detach from the last rack tooth and that wear on the last rack tooth was more reliably reduced, without the need for additional components, such as the roller body mentioned above. BRIEF SUMMARY The above-mentioned problem is solved by a driving tool according to claim 1. According to one aspect of the present disclosure, a driving tool uses gas pressure to drive a driver, which strikes a driving component. The driving tool has a series of rack teeth on the driver that are aligned with the driving direction of the strike. To operate, the driving tool uses a wheel, a lifting shaft, and a biasing element to control the striking sequence. The wheel has multiple engagement areas that sequentially engage with the rack teeth on the driver as the wheel rotates. The lifting shaft holds and supports the wheel, allowing it to rotate and be displaceable in one direction, toward and away from the driver.The preloading element, such as a spring, displaces the wheel relative to the lifting device shaft in a direction away from the driver, so that a final engagement area of ​​the engagement areas of the last rack tooth among the majority of rack teeth, which is positioned at an extreme end in the driving direction, unlocks. Furthermore, the preloading element deforms elastically when the wheel is displaced in the direction away from the driver relative to the lifting device shaft as the driver strikes the driving element and moves against the gas pressure. Therefore, the last engagement area is easily released from the last rack tooth, and wear on the last rack tooth is more reliably reduced. The wheel is mounted so that it can rotate around the lifting device shaft and be displaced (slidable) in one direction towards and away from the driver. The wheel is preloaded against the lifting device shaft by the preloading component. The preloading component deforms elastically when the wheel is displaced away from the driver relative to the lifting device shaft as the driver strikes the component and moves against the gas pressure. This prevents the wheel from locking due to misalignment of the engagement area with the rack tooth, for example, if a nail jams. By configuring the mechanism to avoid a jammed and locked state at the start of lifting, the last engagement area of ​​the last rack tooth slides away immediately before the impact action begins, as the wheel is biased away from the drive relative to the lifting device shaft. This reduces wear on the last rack tooth. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a left side view of a driving tool. Fig. 2 is a front view of the driving tool as seen from arrow II in Fig. 1. Fig. 3 is a top view of the driving tool as seen from arrow III in Fig. 1. Fig. 4 is a left side view of the driving tool as seen from arrow IV in Fig. 3. This figure shows the driving tool with a left housing half removed. Fig. 5 is a right side view of the driving tool in Fig. 3 as seen from arrow V in Fig. 3. This figure shows the driving tool with a right housing half removed. Fig. 6 is a vertical sectional view of a lifting mechanism along line VI-VI in Fig. 1. Fig. 7 is a top view of a nose and the lifting mechanism as seen from arrow VII in Fig. 5.Figure 8 is a vertical sectional view of a lifting device shaft, a first gear, and a gear along line VIII-VIII in Figure 7. Figure 9 is a cross-sectional view of the lifting device shaft and the gear along line IX-IX in Figure 7. Figure 10 is a vertical sectional view along line XX in Figure 3 and shows the movement of a tool body. This figure shows the driver in a ready position. Figure 11 is a vertical sectional view showing the movement of the tool body. This figure shows the driver being moved to a retraction position. Figure 12 is an enlarged view of a final engagement area engaged with a final rack tooth. Figure 13 is a vertical sectional view showing the movement of the tool body.This figure shows a state in which the wheel has returned to a reference position and the last engagement area of ​​the wheel is unlocked from the last rack tooth of the driver. Fig. 14 is a vertical sectional view showing the movement of the main tool body. This figure shows a state in which a first engagement area of ​​the wheel is engaged with a first rack tooth of the driver and the driver has started to return to its ready position. Fig. 15 is a vertical sectional view showing the movement of the main tool body. This figure shows a state in which a second engagement area of ​​the wheel is engaged with a second rack tooth of the driver and the driver's return to its ready position continues. Fig. 16 is a vertical sectional view showing the movement of the main tool body.This figure shows a state in which the second engagement area is engaged with the second rack tooth and the wheel is displaced in a retraction direction relative to the lifting device shaft. Fig. 17 is a vertical sectional view showing the movement of the main tool body. This figure shows a state in which the first engagement area of ​​the wheel is engaged with the second rack tooth of the driver, which has been stopped before a forward end position, and the wheel is displaced in a direction away from the driver (in the direction of a retraction position). Fig. 18 is a perspective view of only the wheel. Fig. 19 is an enlarged partial view of Fig. 11. This figure shows the engagement state of the last engagement area with the last rack tooth when the driver has been moved to the retraction end position. This figure shows a state in which the wheel has been displaced in the direction of the retraction position.Figure 20 is a cross-sectional view of the lifting mechanism according to a second embodiment. This figure shows the engagement state of the last engagement area with the last rack tooth when the drive has been moved to the retraction end position. This figure shows a state in which the wheel is displaced towards the retraction position. Figure 21 is a cross-sectional view of the lifting mechanism according to the second embodiment. This figure shows a state in which the last engagement area is unlocked from the last rack tooth when the drive has been moved to the retraction end position. This figure shows a state in which the wheel has been returned to the reference position. DETAILED DESCRIPTION One embodiment of the present disclosure has a guide surface for a wrench size range provided on a lifting device shaft. The wheel moves slidably in the radial direction with respect to the lifting device shaft along the guide surface. Therefore, the wheel moves slidably in the radial direction with respect to the lifting device shaft over the guide surface of the wrench size range. In one embodiment of the present disclosure, a preloading component is arranged between guide surfaces of the wrench-width area. Thus, the preloading component is compactly arranged on the lifting device shaft. In one embodiment of the present disclosure, the last engagement area is located at the front in the direction of rotation of the wheel with respect to a virtual plane that contains the guide surface of the wrench size area. Therefore, the wheel is easily slideable in the radial direction immediately before the last engagement area is unlocked by the last rack tooth. In one embodiment of the present disclosure, the plurality of engagement areas includes a first engagement area on which it first engages with a plurality of rack teeth when the driver is moved against the gas pressure. At least part of the first engagement area is located between two virtual planes that have the guide surfaces of the wrench size area. Therefore, the wheel is easily slidable in the radial direction at the stage when the first engagement area is engaged with the second rack tooth of the driver.In one embodiment of the present disclosure, the last rack tooth has engagement surfaces that sequentially come into contact with the engagement area and extend in different directions. After the last engagement area has moved from an initial engagement surface to a different engagement surface, the wheel is displaced in one direction away from the driver due to the preload force of the preloading component. Therefore, as the last engagement area moves from the initial engagement surface to the different engagement surface, which has a different direction of extension, the external force applied to the last engagement area of ​​the last rack tooth changes.Consequently, immediately before the driving process, the wheel slides away from the driver due to the preload force of the preloading component, thereby reducing wear on the last rack tooth. In one embodiment of the present disclosure, a plurality of engagement surfaces of the last rack tooth have a flat surface and a circular arc surface. After the last engagement area has moved from the flat surface to the circular arc surface, the wheel is displaced due to the preload force of the preloading element. Therefore, when the direction of the external force applied by the last rack tooth changes as the last engagement area moves from the flat surface to the circular arc surface, the wheel moves easily away from the driver due to the preload force of the preloading element. In one embodiment of the present disclosure, the wheel has a lubricant sump between the plurality of engagement areas and the lifting device shaft. Lubricant is supplied from the lubricant sump to at least one of the plurality of engagement areas. Therefore, the lubricant flows due to the centrifugal force generated by the rotation of the wheel and is supplied to at least one of the plurality of engagement areas. In one embodiment of the present disclosure, the lubricant sump extends in a circular arc shape. A lubricant filling hole extends from a rear end of the lubricant sump in the direction of rotation of the wheel towards the last engagement area. Therefore, the lubricant is efficiently supplied to the last engagement area through the lubricant filling hole. In one embodiment of the present disclosure, the final engagement area has a flat surface and a circular arc surface with different directions of extension. As the final engagement area moves from the flat surface to the circular arc surface and then leaves the circular arc surface, the guide surface of the lifting device shaft is substantially parallel to the flat surface of the final engagement area. Therefore, due to the preload force, the wheel moves easily away from the driver, thus reducing wear on the final engagement area. In one embodiment of the present disclosure, the lifting device shaft has two guide surfaces extending in a direction perpendicular to the axis of rotation of the lifting device shaft and slidably holding the wheel in the direction of extension. The lifting device shaft has force points at which each of the two guide surfaces contacts the wheel when the lifting device shaft transmits rotational power to the wheel. The lifting device shaft is located on the opposite side of the engagement area, where the center of the two force points is located towards the wheel with respect to the axis of rotation. Therefore, even if the last engagement area is arranged towards the rear in the direction of rotation, the wheel can be displaced away from the driver by the preload force of the preloading component when the last engagement area moves away from the last rack tooth. In this way, if the wheel is configured to slide towards the retraction position both when the first engagement area engages with the first rack tooth at the start of the lifting movement and when the last engagement area disengages from the last rack tooth at the end of the lifting movement, the wheel diameter can be made smaller while maintaining the lifting range of the drive tool. Reducing the wheel diameter allows the lifting device shaft and wheel to be positioned closer to the side of the drive tool. This, in turn, allows the drive tool to be made smaller by reducing the size of the inner housing that accommodates the wheel. In one embodiment of the present disclosure, one of the two guide surfaces is located closer to the last engagement area and closer to the centerline passing through the axis of rotation and extending in the direction of the guide surface than the other guide surface. Therefore, it is possible to bring the wheel closer to the driver by placing the last engagement area further back in the direction of rotation. In one embodiment of the present disclosure, the centerline of the preloading element, which extends through the center of the preloading element in the preloading direction, is located on the opposite side of the engagement area with respect to the axis of rotation of the lifting device shaft. Therefore, the preloading element is offset to the rear side in the direction of rotation with respect to the axis of rotation of the lifting device shaft. Consequently, since the preloading element shifts to the same side in response to the displacement of the force center of the last engagement area among the two engagement areas, away from the last engagement area, the wheel can easily shift radially with respect to the lifting device shaft. In one embodiment of the present disclosure, the preloading element is a coil spring. The lifting device shaft has two guide surfaces. One guide surface is located on the inside of a lateral region of the coil spring. The other guide surface is located on the outside of the lateral region of the coil spring. Therefore, the preloading element is compactly arranged over a region between the two guide surfaces. In one embodiment of the present disclosure, an effective part having a guide receiving surface which slidably contacts the guide surface located within the width range of the helical spring is provided on the wheel. Thus, a force point is defined on the side of the last engagement area between the guide surface and the guide receiving surface. [Versions] An example of the present teachings is described below. In this embodiment, a gas spring-operated driving tool 1 is shown as an example of a driving tool 1, which uses gas pressure in a storage chamber as a thrust force for driving in components n. The following description describes an example in which a user holds the driving tool 1 in a forward-facing position. Accordingly, a driving direction of the component n is defined as a forward direction, and a counter-driving direction is defined as a rearward direction. The user of the driving tool 1 is located on a rear side (essentially the right side of the driving tool 1 in Fig. 1). A direction upward, downward, left, and right is defined with reference to the user. As shown in Figs. 1, 2, 3, 4, 5 to 6, the driving tool 1 has a main tool body 10. The main tool body 10 has a cylinder 12 which is received in a substantially cylindrical main body housing 11. The main body housing 11 has a split structure, divided into a left and a right half. The main body housing 11 is formed by joining a left housing half 11L on the left side and a right housing half 11R on the right side. A piston 13 moves back and forth inside the cylinder 12 in a forward-backward direction. A rear section of the cylinder 12, behind the piston 13, is connected to a storage chamber 14, which holds a sealed, compressed gas such as air. The pressure of the gas in the storage chamber 14 acts as a thrust force that pushes the piston 13 forward in the direction of travel. As shown in Fig. 10, a front part of the cylinder 12 is connected to a drive passage 2a of a drive nose section 2, which is provided on a front part of the main tool body 10. A magazine 50, loaded with drive components n, is coupled to the drive nose section 2. The drive components n are fed one after the other from the magazine 50 into the drive passage 2a. The drive components n are fed in a position extending in the front-back direction. A contact arm 3, which can move relative to the drive nose section 2 in the front direction, is provided on a front part of the drive nose section 2. The contact arm 3 retracts relative to the drive nose section 2 when it comes into contact with a workpiece W. A driver 15, which is long in the front-back direction, is coupled to a front face of the piston 13. A front part of the driver 15 enters the driving passage 2a. The driver 15 advances in the driving passage 2a due to the gas pressure in the storage chamber 14, which acts on a rear face of the piston 13. A front end of the driver 15 strikes a single driving component n, which is fed into the driving passage 2a. The struck driving component n is ejected from an ejection opening 2b of the driving nose area 2. The ejected driving component n is driven into a workpiece W. A front damper 17 is arranged at the front of the cylinder 12 to dampen an impact at the front end of the piston 13. The driver 15 enters the inner circumference of the front damper 17. When the driver 15 reaches the front end and the driving process is initiated, the piston 13 collides with the front damper 17. When the piston 13 strikes the front-end damper 17 and stops in the front-end position, a lifting mechanism 20 returns both the piston 13 and the drive unit 15 to a rear ready position. Fig. 10 shows the state when the piston 13 and the drive unit 15 have returned to the ready position. When the drive unit 15 is further retracted to the retraction end position by rotating a wheel 28 in the ready position, a final engagement area P5 of the wheel 28 disengages from a final rack tooth L5 of the drive unit 15. After disengagement from the final rack tooth L5, the piston 13 moves forward due to the gas pressure acting on the rear. Thus, the drive unit 15 moves forward in the driving direction to initiate the driving process. The driver 15 has five rack teeth L arranged on its upper surface. The rack teeth L are spaced at a constant distance from each other along the longitudinal (front-to-back) direction of the driver 15. Each rack tooth L is in a position where it projects upwards. The five rack teeth L are referred to below as the first rack tooth L1, the second rack tooth L2, the third rack tooth L3, the fourth rack tooth L4, and the last rack tooth L5, in order from the rear. The last rack tooth L5 is located at the outermost end in the driving direction. During operation, the driver 15 is pulled backwards from its front-end position to the rear ready position when the engagement areas P of the lifting mechanism 20 (described later) sequentially mesh with each of the five rack teeth L. As shown in Fig. 1, a handle 4 for the user is provided approximately in the center of the main tool body 10 in the front-back direction. A push button 5 for the user to press with their fingertips to actuate the push button 5 is provided on the upper front surface of the handle 4. The contact arm 3 is pressed against the workpiece W and moved relative to the rearward of the drive nose area 2, thereby activating (making effective) the push button 5. A battery mounting area 6 is provided on a lower part of the handle 4. A battery pack 7 can be removably attached to a lower surface of the battery mounting area 6. The battery pack 7 can be removed from the battery mounting area 6 by sliding it rearward relative to the battery mounting area 6. The removed battery pack 7 can be reused by charging it with a separately provided charger.The electrical power of the battery pack 7 is supplied to the lifting mechanism 20. A lower housing 48 is connected to a front part of the battery mounting area 6. The lower housing 48 is designed to project forward. A rectangular, flat-plate-shaped controller 49 is installed inside the lower housing 48. As shown in Fig. 6, the controller 49 is mounted in an upright position. The controller 49 primarily controls the operation of the electric motor 30. An upper part of the lower housing 48 is open. A lower part of the electric motor 30 is held against an upper opening 48a of the lower housing 48. The lifting mechanism 20 is arranged transversely over an area extending to the right and upwards from the driving nose area 2. The lifting mechanism 20 has a function of returning the piston 13 and the driving nose 15 integrally to the rear ready position after striking. When the piston 13 is returned rearward by the lifting mechanism 20, the gas pressure in the storage chamber 14 is increased. As shown in Fig. 6, the lifting mechanism 20 is located inside a lifting device housing 21, which is on the right side of the right housing half 11R. The lifting device housing 21 is open at the bottom, and the opening is covered by a right lifting device base 22. An electric motor 30 is mounted on the right lifting device base 22. An upper opening 48a of the lower housing 48 is located opposite the lower opening of the lifting device housing 21. The electric motor 30 is held such that it is inserted between the opening of the lifting device housing 21 and the upper opening 48a of the lower housing 48. The electric motor 30 is mounted in an orientation where one axis (motor axis J) of an output shaft 31 is aligned with the top-bottom direction. Therefore, the motor axis J is perpendicular to the direction of travel (the direction perpendicular to the plane of the blade in Fig. 6). The electric motor 30 is activated by pressing the trigger 5, using the electrical power of the battery pack 7 as a power source. The magazine 50 is located along the left side of the electric motor 30. As shown in Fig. 6, the output shaft 31 of the electric motor 30 is rotatably mounted on the motor housing 32 via bearings 33 and 34. A drive bevel gear 35 is provided on an upper section of the output shaft 31. The drive bevel gear 35 meshes with a large-diameter output bevel gear 36. The output bevel gear 36 is supported by an intermediate shaft 37. The intermediate shaft 37 is rotatably mounted about its axis via bearings 38 and 39. The axis of rotation of the intermediate shaft 37 is perpendicular to the motor axis J and the direction of input. The left bearing 38 is attached to the right lifting device base 22. The left bearing 39 is attached to a round, plate-shaped cover 40, which is positioned to cover the opening of the right lifting device base 22. An annular elastic component 41 is inserted between the cover 40 and the lifting device housing 21. The vibration of the lifting mechanism 20 is dampened by the elastic component 41. As shown in Figures 6 and 7, a one-way coupling 42 is inserted (arranged) between the intermediate shaft 37 and the right-hand lifting device base 22. The one-way coupling 42 has a plurality of roller bodies 42b that are inserted between the right-hand lifting device base 22 and a coupling plate 42a that is coupled to the intermediate shaft 37. Although not shown in the figure, each roller body 42b is located in a recess provided between the coupling plate 42a and the right-hand lifting device base 22. The depth of each recess changes gradually in the direction of rotation. When the intermediate shaft 37 rotates in the direction that causes the drive 15 to return to the ready position (clockwise rotation when viewed from the left), each roller body 42b of the one-way coupling 42 is displaced to the deeper part of the recess.Therefore, the rotation of the intermediate shaft 37 is not blocked by the one-way clutch 42, and the wheel 28 and the lifting device shaft 27 rotate in the direction (counterclockwise when viewed from the left side) which causes the driver 15 to retract, thereby bringing the driver 15 back to the rear. When an external force causing rotation in the opposite direction (rotation opposite to arrow R in Fig. 9) is applied to the wheel 28 and the lifting device shaft 27, e.g., by the rack teeth L of the drive 15 during forward movement, each roller body 42b of the one-way clutch 42 is displaced to the flat part of the recess. Consequently, the rotation of the clutch plate 42a relative to the right lifting device base 22 is blocked, thus blocking the rotation of the intermediate shaft 37. This prevents a strong external torque from being applied to the electric motor 30, thereby improving the durability of the electric motor 30. A left portion of the intermediate shaft 37 projects to the left of the right lifting device base 22. A left lifting device base 23 is coupled to the left side of the right lifting device base 22. The right lifting device base 22 is located in the right housing half 11R of the main body housing 11, and the left lifting device base 23 is located in the left housing half 11L of the main body housing 11. A second gear 37a is provided on the left side of the intermediate shaft 37. The second gear 37a meshes with a first gear 24. A spur gear is used for both the second gear 37a and the first gear 24. As shown in Fig. 8, the first gear 24 is rotatably mounted relative to a connecting sleeve 43. The connecting sleeve 43 is rotatably mounted on the left lifting device base 23 via two bearings 44 and 45. A drive ring 25 is mounted on the connecting sleeve 43. The drive ring 25 is received in a recess 24a in the thickness direction of the first gear 24. The drive ring 25 is integrally rotatable with the connecting sleeve 43 via a plurality of steel balls 25a. A plurality of ribs 24b, projecting in the thickness direction, are provided in the recess 24a of the first gear 24. A plurality of ribs 25b, projecting in the thickness direction, are provided on a right-hand side of the drive ring 25. A damping element 26 is inserted between each rib 24b of the first gear 24 and each rib 25b of the drive ring 25. The impacts in the direction of rotation between the first gear 24 and the drive ring 25 are absorbed by a plurality of damping elements 26 arranged around the axis of rotation of the first gear 24. A splined hole 43a is formed on an inner circumference of the connecting sleeve 43. A splined shaft section 27d of the lifting device shaft 27 is inserted into the splined hole 43a. The lifting device shaft 27 and the connecting sleeve 43 are integrally rotatable via a splined fit between the splined shaft section 27d and the splined hole 43a. A left portion of the lifting device shaft 27 is rotatably mounted on a round, plate-shaped cover 47 via a bearing 46. As shown in Fig. 6, the cover 47 is held on the inner surface of the left housing half 11L on the left side. The axis of rotation of the lifting device shaft 27 is perpendicular to both the motor axis J and the direction of insertion. As shown in Figs. 7, 8, and 9, a wheel 28 is mounted on the lifting device shaft 27. The wheel 28 has two flange regions 28f that cover approximately half of its circumference. The two flange regions 28f are arranged opposite each other on the left and right sides. Five identical engagement regions P (first engagement region P1, second engagement region P2, third engagement region P3, fourth engagement region P4, and last engagement region P5) are positioned at substantially equal intervals around the circumferential edge of the wheel 28 and extend between the two flanges. The five identical engagement regions P are made of metal shafts of the same diameter and length. When the wheel 28 rotates, the five engagement regions P sequentially engage with the five rack teeth L on the drive pin 15, thereby retracting the drive pin 15 from its forward end position to the rear ready position. As shown in Fig. 9, a wrench-width portion (a portion with flats across its width) 27a is formed on the lifting device shaft 27. Two guide surfaces 27b, parallel to each other, are provided on the wrench-width portion 27a. A single retaining hole 27c is provided between the two guide surfaces 27b. The retaining hole 27c is designed with the radial direction of the lifting device shaft 27 as its depth direction. A single preload element 29 is held in the retaining hole 27c. Thus, the preload element 29 is arranged between the two guide surfaces 27b of the wrench-width portion 27a. In this embodiment, a compression spring (coil spring) is used as the preload element 29. The wheel 28 is mounted on the wrench-sized section 27a of the lifting device shaft 27. An elongated bearing hole 28a is provided at the center of rotation of the wheel 28. Two bearing surfaces 28b, parallel to each other, are provided in the bearing hole 28a. By inserting the wrench-sized section 27a into the bearing hole 28a, the wheel 28 is mounted such that it is rotatable integrally with the lifting device shaft 27. The guide surfaces 27b of the lifting device shaft 27 are each slidably in contact with the two bearing surfaces 28b of the bearing hole 28a. Consequently, the wheel 28 is mounted such that it is slidable relative to the lifting device shaft 27 within a certain range in the radial direction (sliding direction S). The sliding direction S of the wheel 28 is aligned with the direction in which the first engagement area P1 moves towards and away from the lifting device shaft 27. The preloading element 29 pushes the wheel 28 in the direction that separates (removes) the first engagement area P1 from the lifting device shaft 27. Fig. 8 shows a state immediately after an impact, in which the wheel 28 has been displaced in the direction (upwards in Fig. 8) to separate (separate) the first engagement area P1 from the lifting device shaft 27 under the preloading force of the preloading element 29. Fig. 9 shows a state immediately before the impact, in which the wheel 28 was displaced in the direction (downwards in Fig. 9) in which the first engagement area P1 approaches the lifting device shaft 27, against the preload force of the preloading component 29 due to the thrust force in the driving direction of the driver 15, which is applied by the last engagement area P5.In the following, with regard to the relative positions of the lifting device shaft 27 and the wheel 28, the position in which the wheel 28 has been displaced in a direction to separate the first engagement area P1 from the lifting device shaft 27 due to the preload force of the preloading element 29 (the position in which the compression spring 29 is extended) is referred to as the “reference position”, as shown in Fig. 8. As shown in Fig. 9, a position in which the first engagement area P1 has been displaced in the direction in which the first engagement area P1 approaches the lifting device shaft 27 opposite to the preloading element 29 (the position in which the preloading element 29 is compressed) is referred to as the “retraction position” (“retracted position”). The last engagement area P5 is located in the direction of rotation R of the wheel 28 with respect to a virtual plane K which has the guide surface 27b of the wrench size area 27a, on the front side (to the right in Fig. 9 ). When the driver 15 is moved backwards against the gas pressure, at least part of the engagement area P1, which first engages with the majority of rack teeth L, is located between two virtual planes K, each of which has the guide surface 27b of the wrench size area 27a. As shown in Fig. 9, almost the entire first engagement area P1 is located between the two virtual planes K. When the electric motor 30 is started, the lifting device shaft 27 of the lifting mechanism 20 and the wheel 28 rotate integrally in the direction indicated by arrow R in Fig. 9. As the wheel 28 rotates in the direction of arrow R, the drive pin 15 is returned to the rear from its front-end position. The five engagement areas P of the wheel 28 are located in a region smaller (narrower) than half the circumference of the wheel's circumferential edge. With respect to the direction of rotation R of the wheel 28, the second engagement area P2 is adjacent to the opposite side of the first engagement area P1. The third engagement area P3, the fourth engagement area P4, and the last engagement area P5 are successively adjacent to their respective opposite sides. The remaining area of ​​the wheel's circumferential edge (the area between the first engagement area P1 and the last engagement area P5) is defined as a relief section 28c. The relief section 28c is located opposite the driver 15, thus preventing interference between the engagement areas P of the wheel 28 and the rack teeth L of the driver 15. This allows the driver 15 to move smoothly in the driving direction (driving operation). When the rack tooth L of the driver 15 disengages from the engagement area P of the wheel 28, the wheel 28 is positioned in the reference position due to the preload force of the preloading component 29. As shown in Figs. 9 and 17, a circular arc groove-shaped lubricant sump 28d is formed in the wheel 28. The lubricant sump 28d is located between the bearing hole 28a (lifting device shaft 27) and the engagement areas P. Lubricant is pre-filled in the lubricant sump 28d. During operation of the driving tool 1, the lubricant flows from the lubricant sump 28d towards the engagement areas P due to the centrifugal force generated by the rotation of the wheel 28. The lubricant sump 28d is designed to pass through the left and right flange regions 28f. The lubricant sump 28d primarily directs lubricant outwards from both ends of the sump 28d to the ends of each engagement region P. A lubricant filling hole 28e is located at the retraction end of the lubricant sump 28d in the direction of rotation R of the wheel 28 and leads towards the last engagement region P5. The lubricant filling hole 28e, which is positioned between the left and right flange regions 28f, allows the lubricant from the lubricant sump 28d to flow directly to the last engagement region P5 through the lubricant filling hole 28e. This ensures that the last engagement region P5 receives sufficient lubrication, significantly improving its wear resistance. Fig. 10 shows the drive unit 15 stopped in the ready position. In the ready position, the last engagement area P5 of the wheel 28 is engaged with a front surface of the last rack tooth L5 of the drive unit 15. In the ready position, a thrust force in the driving direction of the drive unit 15 is applied to the wheel 28 through the last engagement area P5. In the ready position, the thrust force of the drive unit 15 is applied to the last engagement area P5 as an external force directed forward or downward in a diagonal direction. In the ready position, the sliding direction of the wheel 28 relative to the lifting device shaft 27 (the extension direction of the guide surface 27b) is oriented downward in a diagonal direction.For this reason, the wheel 28 slides to a retracted position, in which it approaches the driver 15, against the preload force of the preloading component 29 relative to the lifting device shaft 27. When the electric motor 30 is started from the standby position shown in Fig. 10, the wheel 28 rotates in the direction of arrow R. Consequently, as shown in Fig. 11, the drive pin 15 and the piston 13 move to the retraction end position. The rotation of the wheel 28 shifts the last engagement area P5 rearward and obliquely upward (away from the drive pin 15). Therefore, during the movement from the standby position to the retraction end position, the last engagement area P5 slides into contact with the front surface (engagement surface 15a) of the last rack tooth L5. As shown in Fig. 12, the engagement surface 15a of the last rack tooth L5 has a flat surface 15b and a circular arc surface 15c. The flat surface 15b extends in a direction that is substantially perpendicular to the driving direction. Therefore, as the driver 15 moves from the ready position to the retraction end, the last engagement area P5 moves from a sliding contact state with the flat surface 15b (position indicated by a solid line in Fig. 12) to a sliding contact state with the circular arc surface 15c (position indicated by a phantom line in Fig. 12). As shown in Figs. 11 and 12, at a stage in which the last engagement area P5 moves from the flat surface 15b to the circular arc surface 15c, the guide surface 27b of the lifting device shaft 27 is essentially parallel to the flat surface 15b of the last rack tooth L5. Therefore, as shown in Fig. 13, when the drive 15 reaches the retraction end and the last engagement area P5 moves away from the circular arc surface 15c over the flat surface 15b, the thrust force of the drive 15 decreases, causing the wheel 28 to displace directly away from the drive 15 with respect to the lifting device shaft 27 (reference position) due to the preload force of the preloading component 29. Consequently, the last engagement area P5 moves directly away from the last rack tooth L5.Since the last engagement area P5 moves directly away from the last rack tooth L5, the wear on the last rack tooth L5 is reduced. As the last engagement area P5 moves away from the last rack tooth L5, the drive 15 moves forward due to the thrust force acting on the rear surface of the piston 13, thus effecting the driving operation. The wheel 28 continues to rotate in the direction indicated by arrow R. As shown in Fig. 14, when the drive unit 15 reaches its foremost position and a normal impact has occurred, the first engagement area P1 of the wheel 28 engages with the front surface of the first rack tooth L1. This action initiates the return movement of the drive unit 15 to its ready position. After the last engagement area P5 disengages from the last rack tooth L5, the wheel 28 is held in the reference position relative to the lifting device shaft 27 by the preloading element 29. The wheel 28 remains in this reference position during the forward impact of the drive unit until the first engagement area P1 re-engages with the rack tooth L1 (during the driving operation of the drive unit 15). For example, as shown in Fig. 17, an abnormal driving process may occur. This could involve, for instance, nail jamming or insufficient driving force. In this case, the driver 15 may stop just before reaching the front-end position, and the piston 13 may stop at the rear position of the damper. Simultaneously, the first engagement area P1 is retracted away from the rack tooth L, thus preventing an interference state (mesh and blocked state) between the first engagement area P1 and the rack tooth L. For example, as a result of the driver 15 stopping just before reaching the front-end position due to nail jamming or the like, the first engagement area P1, indicated by the phantom line in the figure, interferes with the head of the second rack tooth L2 instead of the first rack tooth L1.Simultaneously, the wheel 28 is displaced to the retraction position opposite the preloading component 29 due to the gas pressure in the storage chamber 14, which is applied to the wheel 28 via the first engagement area P1, as shown by the solid line in the figure. Consequently, the first engagement area P1 is displaced to the position shown by the solid line in the figure, thus preventing interference between the first engagement area P1 and the second rack tooth L2. By avoiding interference with the second rack tooth L2, the first engagement area P1 is brought into suitable engagement with a leading edge of the first rack tooth L1. Therefore, after the interlocking and jamming condition is avoided, the drive 15 is returned upwards to a normal engagement position. This facilitates the removal of the jammed nail. After a normal driving operation has been performed, the first engagement area P1 of the wheel 28 engages with the front surface of the first rack tooth L1, and the return movement of the drive 15 to the ready position begins. The wheel 28 rotates approximately half a revolution to move the drive 15 from the front end position to the ready position and then upward to the upper end of the movement position. During this time, the gas pressure in the storage chamber 14 acts on each engagement area P of the wheel 28 via each rack tooth L of the drive 15. Of the total thrust force of the gas pressure, the component in the sliding direction between the bearing surface 28b of the bearing hole 28a and the guide surface 27b of the lifting device shaft 27 acts in the direction to move the wheel 28 closer to the drive 15. Therefore, as shown in Fig.As shown in Figure 14, at the time when the return movement of the drive 15 starts, the wheel 28 is in the reference position due to the thrust force of the gas pressure and the preload force of the preloading component 29. During one rotation of the wheel 28 (one driving operation), the wheel 28 moves once between the reference position and the retraction position due to the gas pressure acting on each engagement area P. In the rotation from the retraction end position shown in Fig. 13 to the position shown in Fig. 14, the thrust force of the gas pressure does not act on the wheel 28. The retraction end position shown in Fig. 13 is the position at which the last engagement area P5 moves away from the last rack tooth L5. In the position shown in Fig. 14, the first engagement area P1 meshes with the first rack tooth L1. Simultaneously, the wheel 28 is held at the reference position by the preload force of the preloading element 29. As shown in Fig. 15, after the return movement starts, the wheel 28 continues to rotate in direction R, and the first engagement area P1 meshes with the first rack tooth L1. Then the second engagement area P2 meshes with the second rack tooth L2. Simultaneously, the thrust force of the gas pressure acting on the wheel 28 increases. For this reason, as shown in Fig. 16, the wheel 28 is displaced to the return position opposite the preloading element 29. Consequently, the engagement of the first engagement area P1 with the first rack tooth L1 and the engagement of the second engagement area P2 with the second rack tooth L2 both become weak (shallow). As the wheel 28 continues to rotate in direction R and the last engagement area P5 meshes with the front surface of the last rack tooth L5, the drive unit is returned to the ready position shown in Fig. 10. The wheel 28 continues to rotate in direction R while remaining in the retraction position. In the ready position shown in Fig. 10, a gas pressure acts on the last engagement area P5 in a direction that pushes the wheel 28 downwards towards the retraction position, opposite the preloading element 29. In this way, during a normal driving operation, the wheel 28 is displaced from the reference position to the retraction position during the return movement of the driver 15. Then, in the retraction end position, the last engagement area P5 moves away from the last rack tooth L5. At this stage (driving start stage), the wheel 28 is returned from the retraction position to the reference position. During a normal driving operation, the displacement of the wheel 28 from the reference position to the retraction position is caused by the thrust force of the gas pressure, which is applied by normal meshing between the engagement area P of the wheel 28 and the rack tooth L of the driver 15.On the other hand, in the case of abnormal driving processes, such as nail jamming, the displacement of the wheel 28 from the reference position to the retraction position is caused by a reaction that is accompanied by an abnormal meshing (interference) between the engagement area P of the wheel 28 and the rack tooth L of the driver 15. According to the embodiment described above, the lifting mechanism 20 pre-tensions the wheel 28 in the direction away from the drive 15 (towards the reference position) with respect to the lifting device shaft 27, such that the last engagement area P5 moves away from the last rack tooth L5 in the retraction end position of the drive 15. Then, when the drive 15 is moved from the forward end position to the ready position against the gas pressure, the pre-tensioning component 29 is elastically deformed as the wheel 28 is displaced in the direction away from the drive 15 with respect to the lifting device shaft 27 (towards the retraction position). Therefore, in the retraction end position of the drive 15, the last engagement area P5 easily disengages from the last rack tooth L5, thus reliably reducing wear on the last rack tooth L5. The wheel 28 can rotate around the lifting device shaft 27 and move towards and away from the drive 15. The wheel 28 is pre-tensioned towards the lifting device shaft 27 by the pre-tensioning element 29. The pre-tensioning element 29 deforms elastically when the wheel 28 moves away from the drive 15 relative to the lifting device shaft 27. When the driver 15 strikes the driving component n and is pushed (moved) backwards against the gas pressure, the preload component 29 bends. This mechanism helps to prevent the wheel 28 from locking, e.g. during a nail jam, by allowing the engagement area P to be displaced from alignment with the rack tooth L. By configuring the mechanism to avoid meshing and locking at the start of lifting, the last engagement area P5 quickly slides away from the last rack tooth L5 immediately before the driving process begins, when the wheel 28 is biased away from the driver 15 (towards the reference position) relative to the lifting device shaft 27. This reduces wear on the last rack tooth L5. According to the embodiment, the lifting device shaft 27 has the guide surface 27b of the wrench size range 27a, and the wheel 28 moves sliding in the radial direction with respect to the lifting device shaft 27 along the guide surface 27b. Therefore, the wheel 28 moves sliding in the radial direction with respect to the lifting device shaft 27 over the guide surface 27b of the wrench size range 27a. According to the embodiment, the preloading component 29 is arranged between the guide surfaces 27b of the wrench size area 27a. Thus, the preloading component 29 is compactly arranged on the lifting device shaft 27. According to the embodiment, the last engagement area P5 is located at the front in the direction of rotation R of the wheel 28 with respect to a virtual plane K, which has the guide surface 27b of the wrench size area 27a. Therefore, the wheel 28 can easily slide in the radial direction immediately before the last engagement area P5 is released from the last rack tooth L5. According to the embodiment, the plurality of engagement areas P includes the first engagement area P1, which engages first with the plurality of rack teeth L when the driver 15 is moved against the gas pressure. At least part of the first engagement area P1 is located between the two virtual planes K, each of which has the guide surfaces 27b of the wrench size area 27a. Therefore, the wheel 28 is easily slidable in the radial direction at the stage when the first engagement area P1 is engaged with the rack tooth L of the driver 15. According to the embodiment, the last rack tooth L5 has a flat surface 15b and a circular arc surface 15c, which sequentially come into contact with the engagement area P and have different directions of extension. Therefore, as the engagement area P moves from the flat surface 15b of the last rack tooth L5 to the circular arc surface 15c, the external force applied to the engagement area P of the last rack tooth L5 changes. Consequently, immediately before the driving operation, the wheel 28 slides away from the driver 15 (towards the reference position) due to the preload force of the preloading element 29, thereby reducing wear on the last rack tooth L5. According to the embodiment, the engagement surface 15a of the last rack tooth L5 has a flat surface 15b and a circular arc surface 15c. When the last engagement area P5 moves from the flat surface 15b to the circular arc surface 15c, the wheel 28 moves due to the preload force of the preloading element 29. Therefore, when the direction of the external force applied to the last rack tooth L5 changes as the last engagement area P5 moves from the flat surface 15b to the circular arc surface 15c, the wheel 28 moves freely away from the driver 15 (towards the reference position) due to the preload force of the preloading element 29. According to the embodiment, the wheel 28 has the lubricant sump 28d between the plurality of engagement areas P and the lifting device shaft 27. The lubricant is supplied from the lubricant sump 28d to at least one of the plurality of engagement areas P. Therefore, lubricant flows due to the centrifugal force generated by rotation of the wheel 28 and is supplied to at least one of the plurality of engagement areas P. According to the embodiment, the lubricant sump 28d extends in a circular arc shape. The lubricant filling hole 28e extends from a rear end of the lubricant sump 28d in a direction of rotation R of the wheel 28 towards the last engagement area P5. Therefore, lubricant is efficiently supplied to the last engagement area P5 via the lubricant filling hole 28e. According to the embodiment, the last rack tooth L5 has the flat surface 15b and the circular arc surface 15c with different directions of extension. When the last engagement area P5 moves from the flat surface 15b to the circular arc surface 15c and the last engagement area P5 leaves the circular arc surface 15c, the guide surface 27b of the lifting device shaft 27 is essentially parallel to the flat surface 15b of the last rack tooth L5. Therefore, the wheel moves rapidly away from the driver 15 due to the preload force of the preloading element 29, thereby reducing wear on the rack tooth L5. Various modifications can be made to the embodiments described above. Figures 20 and 21 show a lifting mechanism 60 according to a second embodiment. The lifting mechanism 60 has been modified with respect to a lifting device shaft 61 and a wheel 62. Figure 19 is an enlarged partial view of Figure 11 and shows an enlarged view of the lifting mechanism 20 of the first embodiment. As shown in Fig. 19, in the first embodiment the wheel 28 is mounted on the wrench-sized section 27a of the lifting device shaft 27. The two guide surfaces 27b of the wrench-sized section 27a extend in a direction perpendicular to the axis of rotation G of the lifting device shaft 27. The bearing surfaces 28b on the side of the wheel 28 are each slidably abutting the two guide surfaces 27b. Therefore, force points 65 and 66 are provided at which each of the two guide surfaces 27b contacts the wheel 28 when the lifting device shaft 27 transmits the rotational power in the direction of arrow R of the wheel 28. The two guide surfaces 27b are arranged in a line-symmetric relationship with respect to the center line that passes through the axis of rotation G (center of rotation of the lifting device shaft 27). The two force points 65 and 66 are arranged in a point-symmetric relationship about the axis of rotation G. Force point 65 is located on the lower part of the guide surface 27b on the side closest to the last engagement area P5, and force point 66 is located on the upper part of the guide surface 27b on the side furthest from the last engagement area P5. Thus, in the first embodiment, a force line Z1, connecting the two force points 65 and 66, passes through the axis of rotation G. In the first embodiment, the last engagement area P5 is located on the front side in the direction of rotation with respect to the force line Z1. Consequently, an external force acts to displace the wheel 28 to the retraction position with respect to the last engagement area P5. As shown in Fig. 20, the lifting mechanism 60 according to the second embodiment has the modified lifting device shaft 61. Components and configurations that do not require modification compared to the first embodiment are not described again using the same reference numerals. In the second embodiment, the lifting device shaft 61 has an increased width on both the front and rear sides about a virtual axis G1, which passes through the axis of rotation G and is perpendicular to the direction of movement of the driver 15. The axis of rotation G of the lifting device shaft 61 passes through an intersection of a virtual axis G2, which is parallel to the direction of movement of the driver 15, and a virtual axis G1, which is perpendicular to the direction of movement of the driver 15. The lifting device shaft 61 has a reduced width at the end (the side near the last engagement area P5) that is closer to the last engagement area P5, thereby creating a projecting area 61b at one side end of the lifting device shaft 61 that extends parallel to the virtual axis G1. A guide surface 61c is provided on the rear side (the side opposite the engagement area P) of the projecting area 61b. The other guide surface 61a is provided on the front side (the side furthest from the engagement area P) of the lifting device shaft 61 and has the projecting area 61b. The guide surfaces 61a and 61c are arranged parallel to each other. Together, the guide surfaces 61a and 61c form a wrench-width area 61d. The other guide surface 61a is slidably in contact with a guide hole 62a of the wheel 62. Therefore, a force point 68 is provided on the upper part of the other guide surface 61a. A guide receiving surface 71a of an operating element 71 is in contact with the guide surface 61c on the side near the engagement area P. The operating element 71 is integrally formed with the bearing hole 62a of the wheel 62. The operating element 71 is designed such that it projects in the direction of the axis of rotation G. The guide receiving surface 71a is located on the front side of the operating element 71. The guide surface 61c of the lifting device shaft 61 is slidably in contact with the guide receiving surface 71a. Thus, a force point 67 is provided on the lower part of the guide surface 61c. In the second embodiment, the guide surface 61c is displaced on the side of the engagement area P in a direction away from the engagement area P with respect to the virtual axis G1. Therefore, in the second embodiment, the guide surface 61c is further away from the engagement area P than the guide surface 27b in the first embodiment. Consequently, the force point 67 on the side of the engagement area P is displaced in a direction away from the engagement area P with respect to the virtual axis G1. In the second embodiment, the lifting device shaft 61 is designed to be wide, such that the guide surface 61a is shifted laterally away from the engagement area P to a position further away from the engagement area P. Consequently, the force point 68 is shifted to a position further away from the engagement area P than the force point 66 in the first embodiment. Figure 20 shows the force points 65 and 66 and the force line Z1 of the first embodiment for comparison with the force points 67 and 68 and the force line Z2 of the second embodiment. The center point Z0, which lies on the force line Z2 connecting the two force points 67 and 68 and is centered in the sliding direction (extension direction of the guide surfaces 61a and 61c) of force points 67 and 68, is displaced away from the engagement area P with respect to the axis of rotation G. The center point Z0 is located on the virtual axis G2. Therefore, the force line Z2 of the second embodiment is displaced away from the engagement area P with respect to the force line Z1 of the first embodiment. In the second embodiment, the force line Z2 is displaced to the rear of the direction of rotation R of the wheel 62, as indicated by arrow Z. This allows the last engagement area P5 to be positioned further back in the direction of rotation R. In the first embodiment, shown in Fig. 19, the last engagement area P5 is located at the front in the direction of rotation R of the wheel 28 with respect to the force line Z1. In the second embodiment, shown in Fig. 20, the last engagement area P5 is shifted to the rear in the direction of rotation R with respect to the force line Z1 of the first embodiment. By extending the installation area of ​​the last engagement area P5 rearward in the direction of rotation R, the diameter of the wheel 62 can be reduced by positioning each engagement area P further inward with respect to the axis of rotation G of the lifting device shaft 61, while the circumferential length of the engagement area P within the installation area (lifting range of the drive 15) remains unchanged. By reducing the diameter of the wheel 62, the axis of rotation G of the lifting device shaft 61 can be positioned closer to the drive 15.This makes it possible to design the left lifting device base 23 (inner housing), which accommodates the wheel 62, with a smaller diameter. A lateral side of the lifting device shaft 61 on the side of the engagement area P, which is wider than the lifting device shaft 27 in the first embodiment, is defined as an additional side surface 61e. The additional side surface 61e is slidably fitted into the bearing hole 62a of the wheel 62. As in the first embodiment, a coil spring (compression spring) is used as the preloading element 70. Unlike the first embodiment, in the second embodiment the preloading element 70 is offset to the side away from the engagement area P with respect to the virtual axis G1. Therefore, the preloading element 70 is displaced from an intermediate position between the guide surface 61a and the additional side surface 61e of the lifting device shaft 61 towards the guide surface 61a. A center line C of the preloading element 70, which extends through the center of the preloading element 70 in the preloading direction, is substantially aligned with the guide surface 61c. Therefore, the preloading element 70 is located on the side away from the last engagement area P5 with respect to the axis of rotation G of the lifting device shaft 61. As in the first embodiment, the wheel 62 is pre-tensioned in the direction of the reference position with respect to the lifting device shaft 61 by the pre-tensioning component 70. The guide surface 61c is located within the width area (radial inside) of the pre-tensioning component 70, and the guide surface 61a is located outside the width area (radial outside) of the pre-tensioning component 70. The guide receiving surface 71a of the working part 71 of the wheel 62 is slidably in contact with the guide surface 61c, which is located within the width area of ​​the pre-tensioning component 70. According to the lifting mechanism 60 of the second embodiment, when the wheel 62 rotates in the direction of arrow R, the last engagement area P5 meshes with the front face of the last rack tooth L5, causing the drive 15 to return to its ready position (shown in Fig. 20). The rotational movement of the lifting device shaft 61 is transmitted to the wheel 62 via force points 67 and 68. During the return of the drive 15, the wheel 62 moves from its reference position to the retraction position. The wheel 62 continues to rotate in the direction of arrow R while remaining in the retraction position. In the ready position (shown in Fig. 20), the gas pressure pushes the wheel 62 downward to the retraction position and acts against the preload force 70 at the last engagement area P5. When the wheel 62 rotates in the direction of arrow R and reaches the retraction end position from the ready position, the last engagement area P5 slides into contact with the engagement surface 15a (flat surface 15b and circular arc surface 15c) of the last rack tooth L5, as in the first embodiment. As the last engagement area P5 passes over the flat surface 15b and leaves the circular arc surface 15c, the wheel 62 is immediately displaced away from the driver 15 with respect to the lifting device shaft 61 (reference position) by the preload force of the preloading component 70, as shown in Fig. 21, because the thrust force of the driver 15 ceases to act. Consequently, the last engagement area P5 moves rapidly away from the last rack tooth L5. The wear on the last rack tooth L5 is reduced if the last engagement area P5 moves quickly away from the last rack tooth L5. As the last engagement area P5 moves away from the last rack tooth L5, the relief area 62b is opposite the drive unit 15 and allows the drive unit 15 to move forward due to the gas pressure acting on the rear of the piston 13, thus initiating the driving operation. The wheel 62 continues to rotate in the direction of arrow R while being returned to the reference position. When the drive unit 15 reaches the lower end of its travel, the first engagement area P1 engages with the front of the first rack tooth L1, and the drive unit 15 is raised toward the ready position.As in the first embodiment, if a nail jamming or the like occurs, the first engagement area P1 is displaced from the reference position to the retraction position by an external force acting on the first engagement area P1 opposite the preloading component 70, thereby preventing abnormal combing (engagement) of the first engagement area P1. In the second embodiment, the lifting device shaft 61 has two guide surfaces 61a and 61c that extend in a direction perpendicular to the axis of rotation G of the lifting device shaft 61 and allow the wheel 62 to slide in the direction of extension. The lifting device shaft 61 has these two guide surfaces 61a and 61c, each of which has a force point 68 and 67 that comes into contact with the wheel 62 when the lifting device shaft 61 transmits rotational power to the wheel 62. The force line Z2, which connects the two force points 68 and 67, is located further away from the axis of rotation G on the opposite side of the engagement area P provided on the wheel 62. Consequently, the center point Z0 of the two force points 68 and 67 is located on the opposite side of the engagement area P with respect to the axis of rotation G in the sliding direction.Therefore, even if the last engagement area P5 is arranged further back in the direction of rotation R, the wheel 62 can be displaced in the direction away from the driver 15 by the preload force of the preloading component 70 when the last engagement area P5 leaves the last rack tooth L5. Accordingly, the wheel 62 slides towards the retraction position both at the point where the first engagement area P1 engages with the first rack tooth L1 at the beginning of the lifting movement, and at the point where the last engagement area P5 disengages from the last rack tooth L5 at the end of the lifting movement. This configuration allows the wheel diameter to be reduced while ensuring the lifting range (stroke) of the drive tool 15. By reducing the wheel diameter, the lifting device shaft 61 and the wheel 62 can be positioned closer to the side of the drive tool 15. Consequently, the inner housing that accommodates the wheel 62 can be made smaller, which in turn reduces the size of the drive tool 1. According to the second embodiment, among the two guide surfaces 61a and 61c, the guide surface 61c that is closer to the last engagement area P5 is closer to the virtual line G1, which passes through the axis of rotation G and extends in the direction of extension of the guide surfaces 61a and 61c, than the other guide surface 61a. Therefore, even if the last engagement area P5 is arranged further back in the direction of rotation R, the wheel 62 can be separated from the driver 15 by the preload force of the preloading component 70. In the second embodiment, the center line C of the preloading component, which extends through the center of the preloading component 70 in the preloading direction, is positioned further away from the last engagement area P5 with respect to the axis of rotation G of the lifting device shaft 61. Therefore, the preloading component 70 is offset to the rear side in the direction of rotation R with respect to the axis of rotation G of the lifting device shaft 61. Consequently, the lifting device shaft 61 shifts the force point 67 on the side of the last engagement area P5 of the two force points 68 and 67 to the side away from the last engagement area P5. The wheel 62 is then easily displaced in the radial direction with respect to the lifting device shaft 61. In the second embodiment, the preloading element 70 is a coil spring. As shown in Fig. 20, the guide surface 61c is located on the front side in the direction of rotation R with respect to the projecting area 61b. The guide surface 61a is located on the rear side in the direction of rotation R with respect to the projecting area 61b. Therefore, the preloading element 70 is arranged compactly over the area between the guide surfaces 61a and 61c. In the second embodiment, the guide surface 61c is located within the width range of the coil spring. The working part 71, which has a guide receiving surface 71a that is in sliding contact with the guide surface 61c, is provided on the wheel 62. Therefore, the force point 67 is located on the side of the last engagement area P5 between the guide surface 61c and the guide receiving surface 71a. Modifications can be made to the second embodiment. In the first embodiment, the force line Z1 passes through the axis of rotation G of the lifting device shaft 27. However, in the second embodiment, the force point 67 (located on the front in the direction of rotation R) is shifted further towards the rear in the direction of rotation R than in the first embodiment. This causes the force line Z2 to be shifted further towards the rear in the direction of rotation R than the force line Z1 of the first embodiment. Specifically, the force line Z2 is moved to the opposite side of the engagement area P of the wheel 62 relative to the axis of rotation G. Therefore, the force point 67 on the front in the direction of rotation R is located further towards the rear in the direction of rotation R in the second embodiment than the force point 65 in the first embodiment.This configuration allows the last engagement area P5 to move further towards the rear in the direction of rotation R. For example, the force point 67 can be fixed on the virtual axis G1. Alternatively, the force point 67 can be fixed further towards the front in the direction of rotation R relative to the virtual axis G1. Both options enable a more compact lifting mechanism 60 by reducing the diameter of the wheel 62, while maintaining the same stroke of the drive 15. The first and second embodiments described above can be further modified. For example, the wheels 28 and 62, which have five engagement areas P, and the drive unit 15, which has five rack teeth L, were described as examples. Instead, the number of engagement areas P and rack teeth L can be reduced or increased. Even in such cases, as described in the examples, the wheels 28 and 62 can be configured such that they are returned to their reference positions at the retraction end position of the drive unit 15 (moved away from the drive unit 15). Lifting mechanisms 20 and 60 were described as examples in which the axis of rotation G of the wheels 28 and 62 (lifting device shafts 27, 61) is perpendicular to the motor axis J. Alternatively, the bearing structure of the wheels 28, 62, which is described as an example, can be applied to the lifting mechanism in which the wheels are arranged coaxially with the motor axis J. A gas spring-operated driving tool that uses the thrust of a compressed gas as the driving force has been described as an example. Alternatively, the bearing structure of wheel 28, which has been described as an example, can likewise be applied to a mechanical spring-type driving tool that uses the thrust of a compression spring as the driving force. It is explicitly emphasized that all features disclosed in the description and / or the claims are to be considered separate and independent of one another for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, irrespective of the combinations of features in the embodiments and / or the claims. It is explicitly stated that all range specifications or specifications of groups of units disclose every possible intermediate value or subgroup of units for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, in particular also as a boundary of a range specification. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature US 2022 / 0 143 798 A1

[0002] US 2022 / 0 291 301 A1

[0002]

Claims

Driving tool, comprising a driver configured to drive a driving component using gas pressure, a plurality of rack teeth on the driver arranged along a driving direction, a wheel having a plurality of engagement areas that sequentially engage with the plurality of rack teeth as the wheel rotates, a lifting device shaft configured to support the wheel, wherein the lifting device shaft is rotatable and displaceable in one direction towards and away from the driver, and a preloading component, wherein the preloading component is configured to allow the wheel to displace relative to the lifting device shaft in one direction away from the driver in order to allow a final engagement area of ​​the plurality of engagement areas to disengage from a final rack tooth of the plurality of rack teeth.where the last rack tooth is located at an extreme end in the driving direction, and where the preloading component deforms elastically when the wheel is displaced in the direction away from the driver relative to the lifting device shaft, and when the driver strikes the driving component and moves against the gas pressure. Driving tool according to claim 1, further comprising guide surfaces of a wrench size range provided on the lifting device shaft, wherein the wheel is slidably movable in a radial direction with respect to the lifting device shaft along the guide surfaces. Driving tool according to claim 2, wherein the preloading component is arranged between the guide surfaces of the wrench size area. Driving tool according to claim 2 or 3, wherein the last engagement area is located at the front in a direction of rotation of the wheel with respect to virtual planes that contain each of the guide surfaces of the wrench size area. Driving tool according to one of claims 2 to 4, wherein the plurality of engagement areas has a first engagement area which first engages with the plurality of rack teeth when the driving tool is moved against the gas pressure, and at least part of the first engagement area is located between two virtual planes which each of the guide surfaces of the wrench size area has. Driving tool according to one of claims 1 to 5, wherein the last rack tooth has a plurality of engagement surfaces having different extension directions, wherein the plurality of engagement surfaces sequentially come into contact with the last engagement area, and wherein, after the last engagement area has moved from an initial engagement surface of the plurality of engagement surfaces to an engagement surface of the plurality of engagement surfaces that is different from the initial engagement surface, the wheel is displaced in a direction away from the driving tool due to a preload force of the preloading component. Driving tool according to claim 6, wherein the majority of engagement surfaces of the last rack tooth have a flat surface and a circular arc surface, and wherein, after the last engagement area has moved from the flat surface to the circular arc surface, the wheel is displaced due to the preload force of the preloading component. Driving tool according to one of claims 1 to 7, wherein the wheel has a lubricant sump between the plurality of engagement areas and the lifting device shaft, and wherein lubricant is supplied from the lubricant sump to at least one of the plurality of engagement areas. Driving tool according to claim 8, wherein the lubricant sump extends in a circular arc shape, and wherein a lubricant filling hole extends from a rear end of the lubricant sump in a direction of rotation of the wheel towards the last engagement area. Driving tool according to one of claims 2 to 5, wherein the last rack tooth has a flat surface and a circular arc surface with different directions of extension to each other, and wherein the guide surface of the lifting device shaft is substantially parallel to the flat surface of the last rack tooth when the last engagement area moves from the flat surface to the circular arc surface and the last engagement area leaves the circular arc surface. Driving tool according to one of claims 1 to 5, wherein the lifting device shaft has two guide surfaces which extend in a direction perpendicular to an axis of rotation of the lifting device shaft and slidably hold the wheel, wherein the lifting device shaft has at least two force points at which each of the two guide surfaces contacts the wheel when the lifting device shaft transmits the rotational power to the wheel, and wherein a center of the at least two force points is located on the opposite side of the engagement areas provided on the wheel with respect to the axis of rotation. Driving tool according to claim 11, wherein one of the two guide surfaces that is closest to the last engagement area is located closer to a center line passing through the axis of rotation and extending in the direction of extension of the guide surface than the other guide surface. Driving tool according to claim 12, wherein the preloading component has a center line extending in a preloading direction through the center of the preloading component and located on the opposite side to the engagement area with respect to the axis of rotation of the lifting device shaft. Driving tool according to one of claims 11 to 13, wherein the preloading component is a coil spring, wherein one of the two guide surfaces is located within a width range of the coil spring, and wherein the other is located outside the width range. Driving tool according to claim 14, which further comprises an active part having a guide receiving surface, wherein the guide receiving surface slidably contacts the guide surface which is located within the width range of the coil spring and is located on the wheel.

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