AU2016101420A4 - Combination of attachment device and power tool - Google Patents

Abstract

An attachment device for a power tool with a cooling fan includes a connection device for connecting the attachment device with the power tool, a dust collecting device which is provided with a dust inlet, an air flow outlet and a collecting chamber disposed between the dust inlet and 5 the air flow outlet, and a suction device being capable of creating suction at the dust inlet when the cooling fan of the power tool being rotated. When the cooling fan is rotated, the suction device creates suction at the dust inlet so as to drive the air to enter the collecting chamber from the dust inlet and exhaust from the air flow outlet. |213 21 __ _ _% 131 214 m21 41 212 S3--------------------------------I

Description

COMBINATION OF ATTACHMENT DEVICE AND POWER TOOL RELATED APPLICTION INFORMATION

[0001] This application claims the benefit of Chinese Patent Application No. CN 201520616807.8, filed on August 14, 2015, Chinese Patent Application No. CN 201510502263.7, filed on August 14, 2015, all of which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to an attachment device and its combination with a power tool.

BACKGROUND OF THE DISCLOSURE

[0003] During the operation of a power tool, it will inevitably produce dust. For example, when an electric drill, an impact drill or an electric hammer is used to drill holes on a wall, a lot of dust is produced at a wok head thereof. The dispersing dust may affect the visibility in the working area so as to affect the operation of a power tool. Further, the dispersing dust may enter the eyes of a user to harm the human body.

[0004] In order to solve the problem above, it is needed to make the power tool have a dust collecting function. However, the currently known dust collecting devices have complex structure, the manufacturing cost is high and the effect of dust collecting is not so good.

[0005] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

SUMMARY

[0006] In one aspect of the disclosure, an attachment device for a power tool with a cooling fan includes a connection device for connecting the attachment device with the power tool, a dust collecting device which is provided with a dust inlet, an air flow outlet and a collecting chamber disposed between the dust inlet and the air flow outlet, and a suction device being capable of creating suction at the dust inlet when the cooling fan of the power tool being rotated. When the cooling fan is rotated, the suction device creates suction at the dust inlet so as to drive the air to enter the collecting chamber from the dust inlet and exhaust from the air flow outlet.

[0007] In another aspect of the disclosure, a combination includes a power tool and an attachment device. The power tool includes a prime mover, a cooling fan driven by the prime mover to rotate about a rotation axis, and a tool housing for containing the prime mover and the cooling fan, the tool housing including vents allowing an air flow generated by the cooling fan to exhaust from an inside of the tool housing. The attachment device includes a dust collecting device which is provided with a dust inlet, an air flow outlet and a collecting chamber disposed between the dust inlet and the air flow outlet, a suction device being capable of creating suction at the dust inlet when the air flow exhausting from the vents, and a connection device for connecting the attachment device with the power tool. When the cooling fan is rotated and the air flow exhausting from the vents, the suction device creates suction at the dust inlet so as to drive the air to enter the collecting chamber from the dust inlet and exhaust from the air flow outlet.

[0008] Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG 1 is a schematic view of an exemplary combination of a power tool and an attachment device.

[0010] FIG 2 is a schematic view of the power tool and the attachment device in FIG 1, wherein they are separated.

[0011] FIG 3 is a part sectioned view of the attachment device in FIG 1, wherein a device housing of the attachment device is partially removed.

[0012] FIG 4 is a schematic view of the attachment device in FIG 1.

[0013] FIG 5 is a schematic view of a containing chamber of the attachment device in FIG 1.

[0014] FIG 6 is a schematic view of a driving fan and a driven fan of the attachment device in FIG 1.

[0015] FIG 7 is a left view of the combination of the power tool and the attachment device in FIG 1.

[0016] FIG 8 is a schematic view of another embodiment of a combination of a power tool and an attachment device.

[0017] FIG 9 is a schematic view of the power tool and the attachment device in FIG 8, wherein they are separated.

[0018] FIG 10 is a schematic view of the attachment device in FIG 8.

[0019] FIG 11 is a part sectioned view of a part of the attachment device in FIG 10.

[0020] FIG 12 is a part sectioned view of another part of the attachment device in FIG 10.

[0021] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

[0022] The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0023] Referring to FIGS. 1-2, a combination 10 includes a power tool 100 and an attachment device 200. The power tool 100 includes a prime mover 110, a cooling fan 120 and a tool housing 130.

[0024] The tool housing 130 is a main component of the power tool 100, and the prime mover 110 and the cooling fan 120 are assembled as a whole through the tool housing 130. As shown in FIG. 2, the prime mover 110 and the cooling fan 120 are contained in the tool housing 130. Here, the word ‘contain’ includes totally contain and partially contain. The tool housing 130 is formed with a handle 131 for a user to grip it and operate the power tool 100. Specifically, the power tool 100 is a hand held power tool.

[0025] The prime mover 110 supplies power to the power tool 100, which can be an engine or a motor. As shown in FIG. 2, the prime mover 110 is a motor which is more environmentally friendly than the engine, and the power tool 100 is an electric power tool. Specifically, the power tool 100 is an electric drill or an electric hammer. In the working process of the prime mover 110, it generates a lot of heat, and the temperature of the prime mover 110 may further rise because of the heat congregation, which may cause the power tool 100 to fail eventually and affect the normal use. In order to reduce the temperature, the tool housing 130 is provided with vents 132, and the internal of the tool housing 130 communicates with the external air through the vents 132 so as to reduce the temperature in the tool housing 130.

[0026] As shown in FIG. 2, in order to dissipate the heat quickly, speed up the air flow and improve the cooling effect, the power tool 100 includes the cooling fan 120, and the cooling fan 120 is driven by the prime mover 110 to rotate about a rotation axis S3. The cooling fan 120 can generate an air flow which flows through the vents 132 and exhausts from the internal of the tool housing 130. Specifically, the cooling fan 120 is a centrifugal fan, which is mounted on an output shaft of the prime mover 110.

[0027] The power tool 100 further includes a control element 140 for controlling the prime mover 110. As shown in FIG. 2, the control element 140 is a trigger. The user can operate the control element 140 to control the prime mover 110 when he grips the handle 131.

[0028] A traditional attachment for sucking dust includes a collecting chamber, which uses the cooling fan of the power tool as a power source. The cooling fan is rotated to suck air into the collecting chamber, and the air with dust may be sucked to the cooling fan, which may pollute or damage the cooling fan, and even the power tool. The working life of the power tool may be reduced, and the use may be affected.

[0029] Referring to FIGS. 3-4, in order to solve the problem above, a dust collecting device 210 is provided with a dust inlet 211 and an air flow outlet 212. The attachment device 200 has the dust collecting effect so that it can avoid harming the human body. The dust collecting device 210 is further provided with a collecting chamber 213. For the air flow path, the collecting chamber 213 is disposed between the dust inlet 211 and the air flow outlet 212. The air enters the collecting chamber 213 from the dust inlet 211 and then exhausts from the air flow outlet 212. As shown in FIG. 3, the dust collecting device 210 includes a filter 215. Specifically, the filter 215 includes a filter paper. The air entered the dust collecting device 210 is filtered by the filter 215, so the dust is deposited in the collecting chamber 213, and then the air exhausts from the air flow outlet 212.

[0030] A suction device 220 is capable of creating suction at the dust inlet 211 when the air exhausts from the vents 132. Referring to FIGS. 3-4, the suction device 220 includes a device housing 221, a driving fan 222 and a driven fan 223. As shown in FIG. 5, the device housing 221 is provided with a containing chamber 2211. As shown in FIG. 6, the driving fan 222 is capable of rotating about a first axis S1 relative to the device housing 221, and the driven fan 223 is capable of rotating about a second axis S2 relative to the device housing 221. As shown in FIG. 3, the driving fan 222 and the driven fan 223 are contained in the containing chamber 2211. Here, the word “contain” includes totally contain and partially contain. In this embodiment, the driving fan 222 and the driven fan 223 are totally contained in the containing chamber 2211. As shown in FIG. 4, the device housing 221 is provided with an air inlet 2212 and an air outlet 2213. The air inlet 2212 is connected with the vents 132 so as to allow the air flow to enter the containing chamber 2211. The air outlet 2213 allows the air flow generated by the driven fan 223 to flow out of the containing chamber 2211. When the cooling fan 120 is rotated, the driving fan 222 is driven to rotate by the air flow generated by the cooling fan 120, and the driven fan 223 is driven to rotate by the driving fan 222, so the suction is created at the air flow outlet 212.

[0031] As shown in FIG. 1, a connection device 230 is configured to connect the attachment device 200 with the power tool 100. Specifically, the connection device 230 is connected with the tool housing 130 of the power tool 100 by means of sliding.

[0032] Referring to FIGS. 3 and 5, the containing chamber 2211 includes a first containing portion 11 and a second containing portion 12. The first containing portion 11 is configured to contain the driving fan 222, and the second containing portion 12 is configured to contain the driven fan 223. The air inlet 2212 is disposed at the first containing portion 11. When the cooling fan 120 is rotated, the air exhausts from the vents 132, then enters the first containing portion 11 from the air inlet 2212, and drives the driving fan 222 to rotate about the first axis S1. The air outlet 2213 is disposed at the second containing portion 12. When the driven fan 223 is rotated, the air flow generated flows out of the second containing portion 12 from the air outlet 2213.

[0033] The containing chamber 2211 is provided with two different containing portions to contain the driving fan 222 and the driven fan 223, so that the driving fan 222 and the driven fan 223 are fixed at the different positions in the containing chamber 2211 through the different containing portions. Thus, the fixation is reliable. Further, the air flow generated by the driving fan 222 can’t interfere the suction created by the driven fan 223. As shown in FIG. 3, the first containing portion 11 is provided with vents 2214. The air flow generated by the driving fan 222 enters the first containing portion 11 from the air inlet 2212 and exhausts from the vents 2214. That is, the air flow generated by the driving fan 222 doesn’t flow through the second containing portion 12. So, the air flows of the driving fan 222 and the driven fan 223 are isolated and prevented from interfering.

[0034] As shown in FIG. 3, in order to make the driving fan 222 be capable of driving the driven fan 223, the suction device 220 further includes a transmission assembly 224 for transmitting between the driving fan 222 and the driven fan 223. The transmission assembly 224 is disposed between the driving fan 222 and the driven fan 223. This arrangement uses the space reasonably. So, when the attachment device 200 is assembled to the power tool 100, the size in a direction is not too long. Further, the arrangement of the transmission assembly 224, the driving fan 222 and the driven fan 223 make the gravity distribute reasonably. So, when the attachment device 200 is assembled to the power tool 100, the weight of any end of the power tool 100 is not too heavy to make the user feel inconvenient to operate. As shown in FIG. 5, in order to fix the transmission assembly 224 and prevent it from damage, the containing chamber 2211 further includes a third containing portion 13 for containing the transmission assembly 224. The third containing portion 13 is located between the first containing portion 11 and the second containing portion 12.

[0035] As shown in FIG. 6, the transmission assembly 224 is a connecting shaft 2241. The driving fan 222 and the driven fan 223 are mounted on the connecting shaft 2241. The attachment device 200 further includes a bearing 2242 which is located between the driving fan 222 and the driven fan 223. The connecting shaft 2241 passes through the bearing 2242. The driving fan 222 and the driven fan 223 are rotated coaxially, so the structure is simple and it avoids multi-stage transmission which may cause energy loss, reduce the efficiency of the fan and affect the effect of dust collection eventually. As shown in FIG. 3, the dust collecting device 210 includes a duct 214. The duct 214 includes a linear portion 2141 which is parallel to the first axis SI of the driving fan 222. The linear portion 2141 forms an air flow channel which is relatively straight and facilitates the flow of the air. The linear portion 2141 is constituted by a telescopic structure or several slidable parts. The attachment device 200 further includes a biasing element 216 for restoring the telescopic structure to the initial non-retraction position. The air flow outlet 212 is disposed at one end of the linear portion 2141. The second containing portion 12 is provided with a duct connector 2211a for connecting with the air flow outlet 212. The driven fan 223 is disposed between the duct connector 2211 and the driving fan 222. The duct connector 221 la is substantially extended along the second axis S2. Comparing with the duct connector 2211a being arranged in the radial direction of the driven fan 223, the arrangement aforementioned can create larger suction and provide higher dust collecting efficiency. As shown in FIG. 6, the driving fan 222 and the driven fan 223 are centrifugal fans. The driven fan 223 has a diameter which is less than a diameter of the driving fan 222. The driven fan 223 produces load when it is rotated. When the driving fan 222 is directly connected with the driven fan 223 through the connecting shaft 2241, if the diameter of the driving fan 222 is less than the diameter of the driven fan 223, the driven fan 223 produces too large load, and the driving fan 222 can’t drive the driven fan 223 to rotate. Thereby, the diameter of the driving fan 222 is greater than the diameter of the driven fan 223.

[0036] In a direction perpendicular to the first axis SI, the cooling fan 120 and the driving fan 222 are rotated in opposite directions, and the driving fan 222 and the driven fan 223 are rotated in the same direction. The rotation axis S3 is substantially parallel to the first axis SI.

[0037] As shown in FIG. 3, the collecting chamber 213 and the handle 131 are in the same side of the rotation axis S3. The handle 131 is mirror symmetrical relative a third plane P3. The plane in which the second axis S2 and the rotation axis S3 are located is defined as a first plane PI, and the plane which passes through the rotation axis S3 and is perpendicular to the first plane PI is defined as a second plane P2. In one embodiment, the second axis S2 is located in the third plane P3, and the third plane P3 and the first plane PI are overlapped. As shown in FIG. 7, in another embodiment, the second axis S2 is not located in the third plane P3, and there is an angle between the third plane P3 and the first plane P1. The collecting chamber 213 and the handle 131 are in the same side of the second plane P2. Specifically, the handle 131 is not parallel to the rotation axis S3, and there is an angle between the handle 131 and the rotation axis S3. The collecting chamber 213 is disposed in the angle between the handle 131 and the rotation axis S3. When the user operates the power tool 100, the collecting chamber 213 can’t protrude a spatial scale defined by the tool housing 130. Comparing with another arrangement that is the collecting chamber 213 and the handle 131 are disposed in the two sides of the rotation axis S3 and further another arrangement that is the collecting chamber 213 and the handle 131 are disposed in the same side of the second plane P2, this arrangement has smaller volume when the attachment device 200 is assembled to the power tool 100, which facilitates the user to operate the power tool 100.

[0038] As shown in FIG. 2, in the direction of the rotation axis S3, the cooling fan 120 is disposed between the dust inlet 211 and the handle 131. As shown in FIG. 3, in the direction of the second axis S2, the containing chamber 2211, the driven fan 223, the driving fan 222 and the handle 131 are arranged in turn. The cooling fan 120 is close to a working area of the power tool 100, and the driven fan 223 is further close to the working area. So the air flow path in the dust collecting device 210 is shortened, and the volume and weight of the dust collecting device 210 is reduced. Further, because the air flow path is shortened, the resistance acting on the air flow is decreased, and it is only needed a relatively small force to push the air flow to move.

[0039] Referring to FIGS. 8-9, a combination 10’ includes a power tool 100’ and an attachment device 200’. The power tool 100’ includes a prime mover 110’, a cooling fan 120’ and a tool housing 130’.

[0040] The tool housing 130’ is a main component of the power tool 100’, and the prime mover 110’ and the cooling fan 120’ are assembled as a whole through the tool housing 130’. The prime mover 110’ and the cooling fan 120’ are contained in the tool housing 130’. Here, the word ‘contain’ includes totally contain and partially contain. The tool housing 130’ is formed with a handle 131’ for a user to grip it and operate the power tool 100’. Specifically, the power tool 100’ is a hand held power tool. The prime mover 110’ can be an engine or a motor. As shown in FIG. 8, the prime mover 110’ is a motor which is more environmentally friendly than the engine, and the power tool 100’ is an electric power tool. Specifically, the power tool 100’ is an electric drill or an electric hammer.

[0041] In the working process of the prime mover 110’, it generates a lot of heat, and the temperature of the prime mover 110’ may further rise because of the heat congregation, which may cause the power tool 100’ to fail eventually and affect the normal use. As shown in FIG. 9, in order to reduce the temperature, the tool housing 130’ is provided with vents 132’, and the internal of the tool housing 130’ communicates with the external air through the vents 132’ so as to reduce the temperature in the tool housing 130’. In order to speed up the air flow and improve the cooling effect, the power tool 100’ includes the cooling fan 120’. The cooling fan 120’ can be rotated to drive the air to pass through the vents 132’.

[0042] The prime mover 110’ drives the cooling fan 120’ to rotate about a rotation axis 101.

Generally, the prime mover 110’ drives the cooling fan 120’ to rotate through a transmission device. Specifically, the cooling fan 120’ is a centrifugal fan, which is approximately located in the middle portion of the power tool 100’.

[0043] The power tool 100’ further includes a control element 140’ for controlling the prime mover 110’. As shown in FIG. 9, the control element 140’ is a trigger. The user can operate the control element 140’ to control the prime mover 110’ when he grips the handle 131 ’.

[0044] As shown in FIG. 9, the attachment device 200’ is used to collect dust. The attachment device 200’ includes a connection device 210’ and a dust collecting device 220’. The dust collecting device 220’ is configured to collect dust. The attachment device 200’ is connected with the tool housing 130’ through the connection device 210’. Here, the word ‘connect’ includes fixedly connect and detachably connect. Specifically, the connection device 210’ is fixed to the tool housing 130’ by means of sliding. FIG. 8 shows a situation that the attachment device 200’ is assembled to the power tool 100’, and FIG. 9 shows another situation that the attachment device 200’ is removed from the power tool 100’. When it is not needed to collect the dust, the attachment device 200’ can be removed from the power tool 100’. When it is needed to collect the dust, the attachment device 200’ can be connected with the power tool 100’.

[0045] Referring to FIGS. 10-12, the dust collecting device 220’ includes a dust inlet 22Γ, a collecting chamber 223’ and an air flow outlet 222’. The dust inlet 221’ allows the dust to enter the collecting chamber 223’, which corresponds to a head portion of the power tool 100’.

[0046] The collecting chamber 223’ is used to deposit the dust. The air with dust passes through the dust inlet 221’ and then enters the collecting chamber 223’. As shown in FIG. 12, the dust collecting device 220’ further includes a filter 225’. Specifically, the filter 225’ includes a filter paper. The air entered the dust collecting device 220’ is filtered by the filter 225’, so the dust is deposited in the collecting chamber 223’, and then the air exhausts from the air flow outlet 222’. As shown in FIG. 10, the dust collecting device 220’ includes a duct 224’. The duct 224’ includes a compressing portion 224Γ. The compressing portion 2241’ has a section which contracts along an extending direction of the duct 224’. The minimum section of the compressing portion 224Γ is closest to the air flow outlet 222’.

[0047] In order to make the dust enter the dust collecting device 220’, it is needed to create suction at the dust inlet 22Γ. Referring to FIGS. 10-11, the attachment device 200’ further includes a suction device 230’which is capable of creating the suction at the dust inlet 221 ’. The suction device 230’ is formed with a suction duct 231’. The suction duct 231’ is formed with an air flow inlet 232’. The air flow outlet 222’ of the dust collecting device 220’ is disposed on the duct wall of the suction duct 23Γ. When the cooling fan 120’ of the power tool 100’ is rotated, the cooling fan 120’ generates the air flow, and the air flow passes through the suction duct 231 ’. Here, the word ‘pass through’ means the air flow flows through the vents 132’ and the suction duct 231 ’ in turn or reversely. In this embodiment, the air flow generated by the cooling fan 120’ flows through the vents 132’ and the suction duct 231’ in turn. When the air flow generated by the cooling fan 120’ flows through the suction duct 231 ’, the suction is created at the dust inlet 22Γ. So the air enters the collecting chamber 223’ from the dust inlet 221 ’, and goes through the filter 225’ and the duct 224’, and then enters the suction duct 231 ’ from the air flow outlet 222’.

[0048] As shown in FIG. 11, the suction duct 231’ includes a contraction segment 233’, a expansion segment 234’ and a middle segment 235’. The middle segment 235’ is located between the contraction segment 233’ and the expansion segment 234’. The contraction segment 233’ has a minimum sectional dimension which is less than or equal to a maximum sectional dimension of the middle segment 235’. The expansion segment 234’ has a minimum sectional dimension which is less than or equal to a maximum sectional dimension of the middle segment 235’. Here, the sectional dimension of the contraction segment 233’, the expansion segment 234’ and the middle segment 235’ means a sectional dimension of an air flow channel inside the three sections. The air flow outlet 222’ of the dust collecting device 220’ is disposed on the duct wall of the middle segment 235’.

[0049] The contraction segment 233’ includes a contraction proximal end 2331’ which is closest to the middle segment 235’and a contraction distal end 2232’ which is farthest from the middle segment 235’. The section of the contraction segment 233’ contracts from the contraction distal end 2232’ to the contraction proximal end 233Γ. The expansion segment 234’ includes an expansion proximal end 2341 ’ which is closest to the middle segment 235’and an expansion distal end 2342’ which is farthest from the middle segment 235’. The section of the expansion segment 234’ expands from the expansion proximal end 2341 ’ to the expansion distal end 2342’.

[0050] When the attachment device 200’ is assembled to the power tool 100’, the collecting chamber 223’ can be disposed at different positions of the power tool 100’. In order to avoid the power tool 100’ with the attachment device 200’ affecting the normal operation, the handle 131’ and the collecting chamber 223’ are located on the same side of the rotation axis 101. This arrangement can use the space reasonably and avoids the interference.

[0051] Specifically, the vents 132’ are substantially extended along a first line Dl. The handle 131’ and the collecting chamber 223 ’ are located on the same side of a plane which goes through the rotation axis 101 and is perpendicular to the first line Dl.

[0052] In the direction of the rotation axis 101, the cooling fan 120’ is located between the dust inlet 221 ’ and the handle 131 ’.

[0053] The above illustrates and describes basic principles, main features and advantages of the present invention. Those skilled in the art should appreciate that the above embodiments do not limit the present invention in any form. Technical solutions obtained by equivalent substitution or equivalent variations all fall within the scope of the present invention.

Claims (20)

1. CLAIMS What is claimed is:

   1. An attachment device for a power tool with a cooling fan, comprising: a connection device for connecting the attachment device with the power tool; a dust collecting device which is provided with a dust inlet, an air flow outlet and a collecting chamber disposed between the dust inlet and the air flow outlet; and a suction device being capable of creating suction at the dust inlet when the cooling fan of the power tool being rotated, wherein when the cooling fan is rotated, the suction device creates suction at the dust inlet so as to drive the air to enter the collecting chamber from the dust inlet and exhaust from the air flow outlet.
2. 2. The attachment device of claim 1, wherein the suction device comprises: a device housing which is provided with a containing chamber; a driving fan contained in the containing chamber, which is capable of rotating about a first axis relative to the device housing; and a driven fan contained in the containing chamber, which is capable of rotating about a second axis relative to the device housing, wherein the device housing comprises: an air inlet allowing an air flow to enter the containing chamber; and an air outlet allowing an air flow generated by the driven fan to flow out of the containing chamber, wherein when the air flow enters the containing chamber through the air inlet, the driving fan is driven to rotate, and the driven fan is driven to rotate by the driving fan so as to create suction at the air flow outlet.
3. 3. The attachment device of claim 2, wherein the containing chamber comprises: a first containing portion for containing the driving fan; and a second containing portion for containing the driven fan, wherein the air inlet is disposed at the first containing portion, and the air outlet is disposed at the second containing portion.
4. 4. The attachment device of claim 3, wherein the suction device comprises a transmission assembly for transmitting between the driving fan and the driven fan, the containing chamber further comprises a third containing portion for containing the transmission assembly.
5. 5. The attachment device of claim 4, wherein the driving fan and the driven fan are rotated coaxially, the dust collecting device comprises a duct which comprises a linear portion substantially parallel to the first axis of the driving fan, the air flow outlet is disposed at one end of the linear portion, the second containing portion comprises a duct connector for connecting with the air flow outlet, the driven fan is located between the duct connector and the driving fan.
6. 6. The attachment device of claim 4, wherein the second containing portion comprises a duct connector for connecting with the air flow outlet, the driven fan is located between the duct connector and the driving fan.
7. 7. The attachment device of claim 1, wherein the suction device comprises a suction duct allowing an air flow generated by the cooling fan to go through, and the air flow outlet is disposed on a duct wall of the suction duct.
8. 8. The attachment device of claim 7, wherein the suction duct comprises a contraction segment, an expansion segment and a middle segment located between the contraction segment and the expansion segment, and the contraction segment has a minimum sectional dimension which is less than or equal to a maximum sectional dimension of the middle segment, and the expansion segment has a minimum sectional dimension which is less than or equal to a maximum sectional dimension of the middle segment.
9. 9. The attachment device of claim 8, wherein the air flow outlet is disposed on a duct wall of the middle segment.
10. 10. The attachment device of claim 8, wherein the contraction segment comprises a contraction proximal end which is closest to the middle segment and a contraction distal end which is farthest from the middle segment, a section of the contraction segment contracts from the contraction distal end to the contraction proximal end; the expansion segment comprises an expansion proximal end which is closest to the middle segment and an expansion distal end which is farthest from the middle segment, a section of the expansion segment expands from the expansion proximal end to the expansion distal end.
11. 11. The attachment device of claim 7, wherein the dust collecting device comprises a duct, the duct comprises a compressing portion which contracts along an extending direction of the duct, the compressing portion has a minimum section which is closest to the air flow outlet.
12. 12. A combination comprising: a power tool comprising: a prime mover; a cooling fan driven by the prime mover to rotate about a rotation axis; and a tool housing for containing the prime mover and the cooling fan, the tool housing comprising vents allowing an air flow generated by the cooling fan to exhaust from an inside of the tool housing, an attachment device comprising: a dust collecting device which is provided with a dust inlet, an air flow outlet and a collecting chamber disposed between the dust inlet and the air flow outlet; a suction device being capable of creating suction at the dust inlet when the air flow exhausting from the vents; and a connection device for connecting the attachment device with the power tool, wherein when the cooling fan is rotated and the air flow exhausts from the vents, the suction device creates suction at the dust inlet so as to drive the air to enter the collecting chamber from the dust inlet and exhaust from the air flow outlet.
13. 13. The combination of claim 12, wherein the suction device comprises: a device housing which is provided with a containing chamber; a driving fan contained in the containing chamber, which is capable of rotating about a first axis relative to the device housing; and a driven fan contained in the containing chamber, which is capable of rotating about a second axis relative to the device housing, wherein the device housing comprises: an air inlet for connecting with the vents, which allows an air flow to enter the containing chamber; and an air outlet allowing the air flow generated by the driven fan to flow out of the containing chamber, wherein when the cooling fan is rotated to generate the air flow, the driving fan is driven to rotate by the air flow, and the driven fan is driven to rotate by the driving fan so as to create suction at the air flow outlet.
14. 14. The combination of claim 13, wherein the tool housing is formed with a handle for a user to grip, and the collecting chamber and the handle are located on the same side of the rotation axis of the cooling fan.
15. 15. The combination of claim 13, wherein the tool housing is formed with a handle for a user to grip, a plane in which the second axis and the rotation axis of the cooling fan is located is defined as a first plane, another plane which passes through the rotation axis of the cooling fan and is perpendicular to the first plane is defined as a second plane, the collecting chamber and the handle are located on the same side of the second plane.
16. 16. The combination of claim 13, wherein in a direction of the rotation axis of the cooling fan, the cooling fan is located between the dust inlet and the handle.
17. 17. The combination of claim 13, wherein in a direction of the second axis, the collecting chamber, the driven fan, the driving fan and the handle are arranged in turn.
18. 18. The combination of claim 12, wherein the suction device comprises a suction duct allowing the air flow generated by the cooling fan to go through, the air flow outlet is disposed on a duct wall of the suction duct, the suction duct is provided with an air flow inlet being capable of corresponding with the vents.
19. 19. The combination of claim 18, wherein the tool housing is formed with a handle, the handle and the collecting chamber are located on the same side of the rotation axis of the cooling fan.
20. 20. The combination of claim 18, wherein the tool housing is formed with a handle, the vents are substantially extended along a direction of a first line, the handle and the collecting chamber are located on the same side of a plane which passes through the rotation axis of the cooling fan and is perpendicular to the first line.