Electric power tool with replaceable head having a safety mechanism

Abstract

The present invention provides a replaceable-head power tool with a safety mechanism. It solves the problem that there is a large gap between the existing body and the working head and compensation cannot be carried out, which easily leads to damage to the body and the working head. In the present invention, a locking device sleeved on the outer periphery of the working head engaging device and rotatably arranged in the body housing drives the working head engaging device and the working head to move towards the body housing direction and locks the working head engaging device. When the working head is installed on the body housing, by means of a screwing rib fixedly arranged on the outer periphery of the locking device and a screwing groove fixedly arranged on the installation ring groove and cooperating with the screwing rib, the locking device is rotated from the engaging state to the locking state. While the locking device rotates circumferentially, it drives the working head engaging device and the working head to move towards the body housing direction along the axial direction of the locking device to complete the locking of the working head. The button is locked through the safety mechanism, and the button cannot be pressed, effectively avoiding accidental startup of the tool.

Description

Technical Field

[0001] The device of the present invention belongs to the technical field of power tools, and particularly relates to a replaceable-head power tool with a safety mechanism. Background Art

[0002] As is well known, multi-head power tools include multiple replaceable working heads. There is a known disclosed power tool, such as US9956677B2. Such a working head power tool is used to quickly remove different working heads to meet the requirements of different working occasions. There are deficiencies in the connection between the working head component and the tool body disclosed in the above-mentioned document. Especially when using a reciprocating saw working head, for example, as shown in the attached Figure 10 , Figure 14 , Figure 22, the connection end between such a working head and the tool body must be kept in close fit during operation. When in use, once a fatigue wear gap appears at the connection part between the working head and the tool body, the working efficiency of such a working head will be greatly reduced. When the connection end between the working head and the tool body of this disclosed multi-head power tool is connected, it relies on an open steel ring arranged inside the tool body. The open steel ring realizes two states of opening and closing through its own elastic deformation. The working head is quickly inserted into the tool body to forcibly guide the open steel ring to open. After connection, it relies on the elastic recovery of the open steel ring to return to the closed state. When closed, it bites the card slot arranged on the connection part of the working head. Since the cooperation form between the steel ring and the card slot is in line contact, the connection mating surface between the working head and the open steel ring is small, and the closing locking force is small. There is a hidden danger of loosening of the connection between the working head and the tool body. Moreover, during use, the gap at the connection end between the working head and the tool body will become larger, and in serious cases, the connection surface of the connection end will be damaged and deformed. The connection mating surface between the working head and the tool body is small. When the working intensity increases, the gap at the connection surface between the working head and the tool body becomes larger, thereby affecting the connection and cooperation between other working heads and the tool body. Moreover, this gap cannot be compensated, and the practical efficiency and service life of the tool are greatly reduced.

[0003] Another known multi-head power tool, such as a power tool system disclosed in CN103722537 B, also has multiple quick-release working heads. This disclosed multi-head power tool utilizes a rotatable limit ring disposed within the tool body. Wedge blocks are provided on the inner ring surface of the limit ring. This limit ring has an unlocking position and a connecting position. During connection, a pushing block on the working head is inserted into the tool body, causing the wedge block on the inner surface of the limit ring to rotate to the unlocking position. After being connected in place, the limit ring automatically returns to the connecting position by relying on a return spring. At this time, the wedge block is axially engaged with the pushing block. Although the pushing block on the working head is provided with a tapered mating surface to achieve a locking fit between the working head and the limit ring, the cooperation between the pushing block and the wedge block is still in line contact. During high-intensity operation, the mating surface between the pushing block and the wedge block is prone to fatigue wear and produce a mating gap. Since the limit ring needs to be rotatably disposed within the tool body flexibly, a rotational gap between the two must be artificially set in terms of structure. Although the connection end of the disclosed tool body and the working head increases the area of the mating surface of the connection end, due to the existence of the rotational gap between the limit ring and the tool body, there is still a connection gap after the working head is connected to the tool body during normal use. This gap will expand when using a reciprocating saw working head, resulting in reduced efficiency and lifespan during long-term operation.

[0004] For the above-disclosed multi-head power tool, the connection structure between the working head and the tool body is not perfect and reliable. The multi-head power tool disclosed in CN103722537 B seemingly solves the mating gap between the working head and the limit ring, but the anti-fatigue wear ability of this mating structure is poor. At the same time, there is still a mating gap between the limit ring and the tool body. Since there are multiple working heads and the mating gaps between each working head and the tool body are inconsistent, more importantly, the mating gaps between the two can never be compensated and adjusted. There are areas for improvement in the prior art. Summary of the Invention

[0005] Aiming at the deficiency that there is a large gap between the existing body and the working head and it cannot be compensated, which easily leads to damage to the body and the working head, the device of the present invention provides a replaceable-head electric tool with a safety mechanism that is not prone to loosening at the connection position during operation, has a large strength of the connection mating surface, reliable connection stability, strong anti-fatigue wear ability of the connection mating structure, a compensation function for the connection mating gaps of different working heads, a long service life of the connection structure, and can prevent the connection position from accidentally triggering to the unlocking position.

[0006] The inventive objective of the present invention is achieved through the following technical scheme: it includes a tool body and at least one working head that can be quickly disassembled and assembled therewith, the tool body includes a body shell, a motor installed in the body shell and a working head coupling device that can quickly disassemble and assemble the working head and is arranged at the output end of the tool body, a switch body for controlling the start of the tool body is fixedly arranged on the tool body, and a button is movably arranged on the switch body, characterized in that the tool body is also provided with a locking device for axially locking the working head, the main body of the locking device is arranged in the body shell and outside the working head coupling device, the locking device and the inner wall of the body shell are connected by a threaded connection or a bevel connection, and a safety mechanism for locking the button is arranged between the tool body and the working head.

[0007] Preferably, the working head has a working head connecting end connected to and cooperating with the tool body, the working head connecting end has an axially extending extension step, the extension step is provided with an external engaging unit, the working head coupling device has a coupling outer ring surface, the coupling outer ring surface has an outer ring step, the outer ring step has a rotating flank and an axial abutment surface, the inner surface of the working head coupling device has a protruding internal engaging unit, the internal engaging element has a guide bevel and an axial locking surface, the working head coupling device is also provided with an axially extending axial boss, when the working head coupling device is connected to the working head, the guide bevel is axially pushed by the external interlocking unit to realize the circumferential rotation of the working head coupling device, the output end of the motor is also fixedly provided with a motor bracket, the motor bracket is provided with a limiting groove for axially inserting the axial boss of the working head coupling device, a reset element is provided in the limiting groove, and the rotational reset of the axial boss in the positioning groove is realized by the support of the reset element.

[0008] Preferably, the locking device can rotate circumferentially around the output shaft and has at least three working states of unlocking, engaging and locking. The locking device can switch between the three working states. When the locking device is in the unlocking state and the engaging state, it is linked with the circumferential rotation of the working head engaging device. When the locking device is in the locking state, it is linked with the axial rotation of the working head engaging device.

[0009] Preferably, a locking inner ring surface and a locking outer ring surface are provided on the locking device, and at least one section of screw-in rib is provided on the locking outer ring surface. The locking inner ring surface of the locking device is axially sleeved with the engaging outer ring surface of the working head engaging device. An inner ring step is also provided on the locking inner ring surface, and a conducting surface and a groove are provided on the inner ring step. The conducting surface and the axial abutment surface on the working head engaging device are axially displaced and abutted against each other when the locking device is in a locked state, and the groove is axially sleeved with the rotating flank, and is linked to the rotation of the working head engaging device when the locking device is in an unlocked state and an engaged state.

[0010] Preferably, a lever is provided on the outer locking surface of the locking device. The lever is circumferentially rotatable about an axis and is disposed in a notch in the body housing.

[0011] Preferably, a mating groove is provided on the inner wall of the body housing to cooperate with the mating rib of the locking device. The mating groove and the mating rib are in close contact when the locking device is in the locked state and are separated when the locking device is in the unlocked state.

[0012] Preferably, a mounting notch is provided on the body housing, and a fastening element for locking the above-mentioned locking device is fixed on the mounting notch. At least one locking groove cooperating with the above-mentioned fastening element is provided on the outer ring surface of the locking device. The locking groove contacts the fastening element when the locking device is in the locked state.

[0013] Preferably, the safety mechanism includes a locking element movably disposed in the tool body and used for locking the above-mentioned button. A mounting shaft is fixedly provided on the locking element. The locking element is rotatably disposed in the tool body through the mounting shaft. A biting portion is fixedly provided at the upper end of the button. One end of the above-mentioned locking element is buckled on the biting portion, and this end is the rear end of the locking element. A matching convex portion for driving the front end of the locking element to rotate about the mounting shaft so that the rear end of the locking element disengages from the biting portion is provided at the lower end of the working head. An unlocking block capable of driving the locking element to rotate is provided on the matching convex portion. A return spring for driving the front end of the locking element to rotate about the mounting shaft so that the rear end of the locking element can be reset and locked on the biting portion is provided in the tool body.

[0014] Preferably, a biting surface is provided at one end of the biting portion cooperating with the locking element. A locking surface for locking on the biting surface is provided at the rear end of the locking element. A trigger surface contacting the above-mentioned unlocking block is provided at the front end of the locking element. A clamping groove for clamping the above-mentioned unlocking block is provided on the trigger surface.

[0015] Preferably, a commutation block for adjusting the current direction in the switch body is rotatably provided on the switch body. A swing boss is fixedly provided at one end of the commutation block away from the switch body. A commutation dial for driving the commutation block to rotate is movably provided on the tool body. A translation groove sleeving the swing boss is formed on the commutation dial. The swing boss is clamped in the translation groove. A yaw element for locking the commutation dial is rotatably provided on the tool body. A translation boss is fixedly provided on the commutation dial. A yaw groove for clamping on the translation boss is formed at the rear end of the yaw element. The commutation dial can move along the length direction of the commutation dial and drive the yaw element and the commutation block to rotate. A yaw trigger surface for clamping on the matching convex part is formed at the front end of the yaw element. A fixing block for locking the yaw element is fixedly provided on the matching convex part. The yaw trigger surface on the yaw element can only be located on one side of the fixing block. The unlocking block can move along the length direction of the matching convex part and drive the locking element to rotate. A working head safety spring for driving the unlocking block away from the matching convex part is further provided on the matching convex part.

[0016] Compared with the prior art, in the present invention, the working head is installed on the body housing through the working head engaging device. The locking device sleeved on the outer periphery of the working head engaging device and rotatably provided in the body housing drives the working head engaging device and the working head to move towards the body housing and locks the working head engaging device. The locking device has three states: unlocking, engaging, and locking. When the working head is installed on the body housing, the locking device is in the connecting and engaging state. Through the screwing convex ribs fixedly provided on the outer periphery of the locking device and the screwing grooves fixedly provided on the installation ring groove and matching with the screwing convex ribs, the locking device is rotated from the engaging state to the locking state. While the locking device rotates circumferentially, it drives the working head engaging device and the working head to move towards the body housing along the axial direction of the locking device to complete the locking of the working head, effectively reducing the gap between the working head and the body housing, greatly reducing the loss during the use of the working head, and greatly prolonging the service life of the working head and the body housing. The button is locked through the safety mechanism, and the button cannot be pressed, effectively avoiding the accidental startup of the tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the overall structural view of the present invention;

[0018] Figure 2 is the exploded view of the structure of the present invention;

[0019] Figure 3 is the overall structural view of the motor bracket, the working head engaging device, and the locking device;

[0020] Figure 4 is the sectional view of the motor bracket, the working head engaging device, and the locking device;

[0021] Figure 5 is a sectional view of the fuselage housing;

[0022] Figure 6 is an overall structural view of the working head engaging device;

[0023] Figure 7 is an overall structural view of the locking device;

[0024] Figure 8 is a front view of the locking device;

[0025] Figure 9 is a schematic diagram of the unlocking device in the unlocked state;

[0026] Figure 10 is a schematic diagram of the unlocking device in the engaged state;

[0027] Figure 11 is a schematic diagram of the unlocking device in the locked state;

[0028] Figure 12 is an internal view of the safety mechanism;

[0029] Figure 13 is an exploded view of the structure at the button and the locking element;

[0030] Figure 14 is an internal structural view after the unlocking block is pressed;

[0031] Figure 15 is Figure 14 an enlarged view of location A in

[0032] Figure 16 is an overall structural view of the yaw element.

[0033] Markings in the figure: 10, tool body; 11, body housing; 12, motor; 14, motor bracket; 15, reset element; 16, tool head engaging device; 17, locking outer ring surface; 18, tool head connection end; 19, extending step; 20, tool head; 21, locking device; 22, screwing rib; 23, guiding inclined surface; 24, axial boss; 25, rotating flank; 26, axial abutting surface; 27, outer ring step; 28, axial locking surface; 29, groove; 30, lever; 31, outer engaging element; 32, limiting groove; 33, conducting surface; 34, locking inner ring surface; 35, notch; 36, inner ring step; 37, inner engaging element; 38, engaging outer ring surface; 41, screwing groove; 42, fastening element; 43, mounting notch; 45, locking groove; 46, switch body; 47, button; 48, engaging part; 49, reset spring; 50, triggering inclined surface; 51, locking element; 52, yaw element; 53, matching convex part; 54, yaw groove; 55, swinging boss; 56, translation groove; 57, reversing lever; 58, translation convex platform; 59, tool head safety spring; 60, yaw triggering surface; 61, locking surface; 62, support shaft; 63, engaging surface; 64, unlocking block; 65, clamping groove; 66, reversing block; 67, fixed block; 68, safety mechanism. Detailed implementation mode

[0034] The present invention will be further described below in conjunction with the embodiments shown in the accompanying drawings: As Figure 1-16 shown, a replaceable-head power tool with a safety mechanism includes a tool body 10 and at least one tool head 20 that can be quickly disassembled and assembled with it. The tool body 10 includes a body housing 11, a motor 12 installed in the body housing 11, and a tool head engaging device 16 that can quickly disassemble and assemble the tool head 20 provided at the output end of the tool body 10. A switch body 46 for controlling the start of the tool body 10 is fixedly provided on the tool body 10. A button 47 is movably provided on the switch body 46. A locking device 21 for axially locking the tool head 20 is also provided on the tool body 10. The main body of the locking device 21 is arranged in the body housing 11 and outside the tool head engaging device 16. The locking device 21 is connected to the inner wall of the body housing 11 through an inclined surface. After the tool head 20 is installed, the tool head 20 is axially displaced and locked by a gold-breaking device to reduce the gap between the tool head 20 and the body housing 11. A safety mechanism 68 for locking the button 47 is provided between the tool body 10 and the tool head 20.

[0035] The described working head 20 has a working head connection end 18 that is connected and fitted to the tool body 10. The working head connection end 18 has an axially extending extension step 19, and an outer engagement element 31 is provided on the extension step 19. The working head engaging device 16 has an engaging outer ring surface 38. The engaging outer ring surface 38 has an outer ring step 27, and a rotating flank 25 and an axial abutting surface 26 are provided on the outer ring step 27. The inner surface of the working head engaging device 16 has a protruding inner engagement element 37. The inner engagement element 37 has a guiding inclined surface 23 and an axial locking surface. The working head engaging device 16 is also provided with an axially extending axial boss 24. When the working head engaging device 16 is connected to the working head 20, the guiding inclined surface 23 is axially pushed by the outer engagement element 31 to achieve circumferential rotation of the working head engaging device 16. The output end of the motor 12 is also fixedly provided with a motor bracket 14. A limiting groove 32 for axially inserting the axial boss 24 of the working head engaging device 16 is provided on the motor bracket 14. A reset element 15 is provided in the limiting groove 32, and the axial boss 24 is supported by the reset element 15 to rotate and reset in the positioning groove.

[0036] The described locking device 21 can rotate circumferentially around the output shaft and has at least three working states of unlocking, engaging, and locking. The locking device 21 can be switched between the three working states. When the locking device 21 is in the unlocking state and the engaging state, it is circumferentially rotationally linked with the working head engaging device 16. When the locking device 21 is in the locking state, it is axially linked with the working head engaging device 16. A locking inner ring surface 34 and a locking outer ring surface 17 are provided on the locking device 21. At least one section of a screwed rib 22 is provided on the locking outer ring surface 17. The locking inner ring surface 34 of the locking device 21 axially sleeved on the engaging outer ring surface 38 of the working head engaging device 16. An inner ring step 36 is also provided on the locking inner ring surface 34. A conduction surface 33 and a groove 29 are provided on the inner ring step 36. The conduction surface 33 axially abuts against the axial abutting surface 26 on the working head engaging device 16 when the locking device 21 is in the locking state. The groove 29 axially sleeved the rotating flank 25 and is rotationally linked with the working head engaging device 16 when the locking device 21 is in the unlocking state and the engaging state. A lever 30 is provided on the locking outer ring surface 17 of the locking device 21. The lever 30 can rotate circumferentially around the axis and is arranged in a notch 35 on the body housing 11. A screwed groove 41 that cooperates with the screwed rib 22 of the locking device 21 is provided on the inner wall of the body housing 11. The screwed groove 41 and the screwed rib 22 are closely fitted when the locking device 21 is in the locking state and are separated when the locking device 21 is in the unlocking state.

[0037] The body housing 11 is provided with a mounting notch 43, and a fastening element 42 for locking the locking device 21 is fixed on the mounting notch 43. At least one locking groove 45 cooperating with the fastening element 42 is arranged on the outer circumferential surface of the locking device 21. The locking groove 45 contacts the fastening element 42 when the locking device 21 is in the engaged state and the locked state. The locking device 21 in the engaged state and the locked state is fixed by the fastening element 42, avoiding the situation that the locking device 21 is reset due to vibration and the locking device 21 is disengaged from the locked state.

[0038] The working head 20 is mounted on the body housing 11 through a working head engaging device 16. The locking device 21 sleeved on the outer periphery of the working head engaging device 16 and rotatably arranged in the body housing 11 drives the working head engaging device 16 and the working head 20 to move towards the body housing 11 and locks the working head engaging device 16. The locking device 21 has three states: unlocking, engaging and locking. When the working head 20 is mounted on the body housing 11, the locking device 21 is in the engaged state. The locking device 21 is rotated from the engaged state to the locked state through a screwing rib 22 fixedly arranged on the outer periphery of the locking device 21 and a screwing groove 41 fixedly arranged on the mounting ring groove and cooperating with the screwing rib 22. While the locking device 21 rotates circumferentially, it drives the working head engaging device 16 and the working head 20 to move towards the body housing 11 along the axis of the locking device 21 to complete the locking of the working head 20, effectively reducing the gap between the working head 20 and the body housing 11, greatly reducing the loss during the use of the working head 20, and greatly prolonging the service life of the working head 20 and the body housing 11.

[0039] The safety mechanism 68 includes a locking element 51 movably arranged in the tool body 10 and used for locking the button 47. A support shaft 62 is fixedly arranged on the locking element 51. The locking element 51 is rotatably arranged in the tool body 10 through the support shaft 62. An engaging portion 48 is fixedly arranged at the upper end of the button 47. One end of the locking element 51 is buckled on the engaging portion 48, and this end is the rear end of the locking element 51. A matching convex portion 53 for driving the front end of the locking element 51 to rotate around the support shaft 62 so that the rear end of the locking element 51 is disengaged from the engaging portion 48 is fixedly arranged at the lower end of the working head 20. An unlocking block 64 capable of moving along the length direction of the matching convex portion 53 and driving the locking element 51 to rotate is movably arranged on the matching convex portion 53. A working head safety spring 59 for driving the unlocking block 64 away from the matching convex portion 53 is arranged on the matching convex portion 53. A reset spring 49 for driving the front end of the locking element 51 to rotate around the support shaft 62 so that the rear end of the locking element 51 is clamped on the engaging portion 48 is also arranged in the tool body 10.

[0040] One end of the engaging portion 48 away from the locking element 51 is provided with an engaging surface 63, and the rear end of the locking element 51 is provided with a locking surface 61 for being clamped on the engaging surface 63. The locking element 51 is buckled on the engaging surface 63 of the engaging portion 48 through the engaging surface 63.

[0041] The front end of the locking element 51 is provided with a trigger inclined surface 50 that contacts the unlocking block 64. During the movement of the unlocking block 64 towards the locking element 51, it first contacts the starting inclined surface on the locking element 51. The locking element 51 is driven to rotate around the support shaft 62 through the trigger inclined surface 50, so that the rear end of the locking element 51 is separated from the engaging portion 48 to complete unlocking, making the action of the unlocking block 64 driving the locking element 51 to complete unlocking smoother.

[0042] The trigger inclined surface 50 is provided with a clamping groove 65 for clamping the unlocking block 64. After the unlocking block 64 drives the locking element 51 to rotate to complete the unlocking of the engaging portion 48, the unlocking block 64 is clamped in the clamping groove 65, preventing the unlocking block 64 from sliding after unlocking, and being safer and more reliable during use.

[0043] By rotating the locking element 51 arranged in the tool body 10 to be clamped on the engaging portion 48 of the button 47, when the working head 20 is not installed or after the working head 20 is installed, if the user accidentally touches the button 47, the locking element 51 is buckled on the engaging surface 63 of the engaging portion 48 through the locking surface 61, realizing the locking of the button 47, and the button 47 cannot be pressed, effectively avoiding the accidental start of the tool. When the tool body 10 needs to be used, the working head 20 is installed on the tool body 10, and the unlocking block 64 is pressed to make the unlocking block 64 move towards the locking element 51 and contact the trigger inclined surface 50 on the locking element 51. The unlocking block 64 drives the front end of the locking element 51 to rotate around the support shaft 62, so that the rear end of the locking element 51 is separated from the engaging portion 48. At this time, pressing the button 47 can start the tool body 10, which is safer during use and effectively protects the safety of the user and the tool body 10.

[0044] A commutation block 66 for adjusting the current direction in the switch body 46 is rotatably provided on the switch body 46. A swinging boss 55 is fixedly provided at one end of the commutation block 66 far away from the switch body 46. A commutation dial 57 for driving the commutation block 66 to rotate is movably provided on the tool body 10. A translation groove 56 sleeving the swinging boss 55 is formed on the commutation dial 57. The swinging boss 55 is clamped in the translation groove 56. A yaw element 52 for locking the commutation dial 57 is rotatably provided on the tool body 10. A translation boss 58 is fixedly provided on the commutation dial 57. A yaw groove 54 for clamping on the translation boss 58 is formed at the rear end of the yaw element 52. The commutation dial 57 can move along the length direction of the commutation dial 57 and drive the yaw element 52 and the commutation block 66 to rotate. A yaw trigger surface 60 for clamping on the matching convex portion 53 is formed at the front end of the yaw element 52. A fixing block 67 for locking the yaw element 52 is fixedly provided on the matching convex portion 53. The yaw trigger surface 60 on the yaw element 52 can only be located on one side of the fixing block 67. The current direction is adjusted by the commutation dial 57. After the adjustment is completed, the working head 20 is installed on the tool body 10. At this time, the yaw trigger surface 60 on the yaw element 52 is only located on one side of the fixing block 67 in the matching convex portion 53. The yaw element 52 and the commutation dial 57 are locked by the fixing block 67, avoiding damage to the tool body 10 caused by accidental touch of the commutation dial 57 during the use of the tool body 10, and being relatively safe and reliable in use.

[0045] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A replaceable-head power tool with a safety mechanism, comprising a tool body and at least one working head that can be quickly disassembled and assembled with it. The tool body includes a body housing, a motor installed in the body housing, and a working head engaging device that can quickly disassemble and assemble the working head provided at the output end of the tool body. A switch body for controlling the start of the tool body is fixedly provided on the tool body, and a button is movably provided on the switch body. It is characterized in that, A locking device for axially locking the working head is further provided on the tool body. The main body of the locking device is arranged inside the body housing and outside the working head engaging device. The locking device is connected to the inner wall of the body housing by a threaded connection or an inclined surface connection. A safety mechanism with a locking button is arranged between the tool body and the working head; The working head has a working head connection end for connecting and cooperating with the tool body. The working head connection end has an axially extending extension step. An external engagement unit is arranged on the extension step. The working head engaging device has an engaging outer ring surface. The engaging outer ring surface has an outer ring step. The outer ring step has a rotating flank and an axial abutting surface. The inner surface of the working head engaging device has a protruding inner engagement element. The inner engagement element has a guiding inclined surface and an axial locking surface. The working head engaging device is also provided with an axially extending axial boss. When the working head engaging device is connected to the working head, the guiding inclined surface is axially pushed by the external engagement unit to realize the circumferential rotation of the working head engaging device. A motor bracket is fixedly arranged at the output end of the motor. A limiting groove for axially inserting the axial boss of the working head engaging device is arranged on the motor bracket. A reset element is arranged in the limiting groove, and the axial boss is supported by the reset element to realize rotational reset in the positioning groove; The locking device can rotate circumferentially around the output shaft and has at least three working states: unlocking, engaging, and locking. The locking device can be switched between the three working states. When the locking device is in the unlocking state and the engaging state, it is circumferentially rotated and linked with the working head engaging device. When the locking device is in the locking state, it is axially linked with the working head engaging device; A locking inner ring surface and a locking outer ring surface are arranged on the locking device. At least one section of engaging rib is arranged on the locking outer ring surface. The locking inner ring surface of the locking device axially sleeved the engaging outer ring surface of the working head engaging device. An inner ring step is also arranged on the locking inner ring surface. A conducting surface and a groove are arranged on the inner ring step. The conducting surface axially abuts against the axial abutting surface on the working head engaging device when the locking device is in the locking state. The groove axially sleeved the rotating flank and is rotationally linked with the working head engaging device when the locking device is in the unlocking state and the engaging state; A lever is arranged on the locking outer ring surface of the locking device. The lever can rotate circumferentially around the axis and is arranged in the notch on the body housing.

2. The replaceable-head power tool with a safety mechanism according to claim 1, wherein, A mating groove that mates with the engaging rib of the locking device is arranged on the inner wall of the body housing. The mating groove and the engaging rib are in close contact when the locking device is in the locking state and are separated when the locking device is in the unlocking state.

3. The replaceable-head electric tool with a safety mechanism according to claim 1 or 2, characterized in that, An installation notch is arranged on the body housing. A fastening element for locking the above-mentioned locking device is fixed on the installation notch. At least one locking groove that mates with the above-mentioned fastening element is arranged on the outer ring surface of the locking device. The locking groove contacts the fastening element when the locking device is in the locking state.

4. The replaceable head power tool with a safety mechanism according to claim 1, characterized in that, The safety mechanism includes a locking element movably arranged in the tool body and used for locking the above button. A mounting shaft is fixedly arranged on the locking element, and the locking element is rotatably arranged in the tool body through the mounting shaft. A biting portion is fixedly arranged at the upper end of the button, and one end of the locking element is buckled on the biting portion, and this end is the rear end of the locking element. A matching convex portion is arranged at the lower end of the working head, which drives the front end of the locking element to rotate around the mounting shaft so that the rear end of the locking element disengages from the biting portion. An unlocking block capable of driving the locking element to rotate is arranged on the matching convex portion. A return spring is arranged in the tool body to drive the front end of the locking element to rotate around the mounting shaft so that the rear end of the locking element can be reset and locked on the biting portion.

5. The replaceable-head power tool with a safety mechanism according to claim 4, wherein, A biting surface is provided at one end of the biting portion that cooperates with the locking element. A locking surface for locking on the biting surface is provided at the rear end of the locking element. A triggering surface in contact with the above unlocking block is provided at the front end of the locking element. A clamping groove for clamping the above unlocking block is provided on the triggering surface.

6. The replaceable-head power tool with a safety mechanism according to claim 5, characterized in that, A commutation block for adjusting the current direction in the switch body is rotatably arranged on the switch body. A swinging convex platform is fixedly arranged at one end of the commutation block away from the switch body. A commutation dial for driving the commutation block to rotate is movably arranged on the tool body. A translation groove sleeved on the swinging convex platform is provided on the commutation dial, and the swinging convex platform is clamped in the translation groove. A yaw element for locking the commutation dial is rotatably arranged on the tool body. A translation convex platform is fixedly arranged on the commutation dial. A yaw groove for clamping on the above translation convex platform is provided at the rear end of the yaw element. The commutation dial can move along the length direction of the commutation dial and drive the yaw element and the commutation block to rotate. A yaw triggering surface for clamping on the above matching convex portion is provided at the front end of the yaw element. A fixing block for locking the yaw element is fixedly arranged on the matching convex portion. The yaw triggering surface on the yaw element can only be located on one side of the fixing block. The unlocking block can move along the length direction of the matching convex portion and drive the locking element to rotate. A working head safety spring for driving the unlocking block away from the matching convex portion is also arranged on the matching convex portion.

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