Abstract:
The invention related to a multi-functional power tool, comprises an housing, a motor set in the housing, a main shaft driven through the rotation of the motor, a working shaft extended outside the housing, an active impact block, which can rotate with and make axial motion with respect to the main shaft, is configured on the main shaft, a passive impact block which rotates with the working shaft and can alternatively make axial motion with respect to the working shaft is mounted on the working shaft, the active impact block rotates to drive the passive impact block through the coordination of the first end tooth set on the active impact block and the second end tooth set on the passive impact block; the power tool further includes a function shifting button which can move between the first location and the second location to alternatively limit the passive impact block&#39;s axial motion with respect to the working shaft, in this way to realize the shifting between the first function and the second function of the power tool. This function shifting mechanism features simple structure, low manufacturing cost, convenient and efficient operation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to and all the advantages of International Application No. PCT/CN2008/000648, filed on Mar. 31, 2008, which claims priority to Chinese Patent Application No. 200710021300.8, filed on Apr. 18, 2007. 
     FIELD OF TECHNOLOGY 
     The present invention relates to a power tool, and more especially, to a multi-functional power tool capable of realizing impact wrench function and electric drill function or electric screwdriver set function or impact drill function. 
     BACKGROUND OF THE INVENTION 
     Among the existing power tools, the impact wrench is used to tighten the screw fastener to work piece. It generally comprises a main shaft driven by the rotation of the motor, impact block connected with the main shaft through spiral scroll and ball, and working shaft fit for the impact block through the end tooth and located in front of the impact block. An impact spring is configured in the back of the impact block, which compresses the impact block to enable the impact block to keep reliable coordination with the working shaft. During working, the rotation movement of the main shaft directly outputs to the screw piece through the impact block and working shaft so as to secure the screw piece to work piece. During the tightening, the load on the working shaft gradually increases. When the load exceeds the preset value, the impact moves toward the motor relative to the working shaft through the rolling of the ball in the spiral scroll, and compresses the spring behind it. At the moment that the impact block and the end tooth of the working shaft are unfitted, under the action of the impact spring, the impact block moves forward in axial direction and beats the working shaft in rotation direction, so as to enable the working shaft to keep tightening the screw piece in the direction of rotation. In such cycles, through endless intermittent beating of the impact block, the screw piece can be secured to a work piece in the end. Electric drill is used to drill holes in work piece. However, the user generally requires tightening screw pieces onto the work piece or drilling holes in work piece during working. In this way, it is very inconvenient when the user is required to change tools again and again for operation. 
     US patent application No. 2005/0199404A1 discloses a power tool capable of realizing impact wrench and electric drill functions in one tool. The power tool secures the impact block ( 7 ) and working shaft ( 8 ) on the outer circumference through function shifting mechanism (the function shifting button  33  and connecting piece  25  shown in  FIG. 1  and  FIG. 4  of this patent for application) to keep the impact and working shaft relatively fixed, in this way, to realize the shifting between impact wrench function and electric drill function. With this structure, the user is only required to adjust the function shifting button to shift between impact wrench function and electric drill function. European patent application No. EP 1050381 A2 discloses another power tool with both impact wrench function and electric drill function. The power tool secures the impact block ( 5 ) and working shaft ( 6 ) along the axis through function shifting mechanism (Drawing  15 ,  16 ,  24 ,  35  and  36  attached to the patent for application) to keep the impact and working shaft relatively fixed, in this way, to realize the shifting between impact wrench function and electric drill function. However, the power tool disclosed by the abovementioned US patent for application uses a round sleeve with relatively large size as the connecting piece, in this way to increase the overall volume of the power tool, improve manufacturing cost; while the function shifting mechanism of the power tool disclosed by the abovementioned European patent for application requires multiple components&#39; cooperation, and the reliability is reduced due to the complicated structure. 
     SUMMARY OF THE INVENTION 
     The present invention provides a multi-functional power tool which can realize the shifting between impact wrench function and electric drill function or functions. This function shifting mechanism features simple structure, low manufacturing cost, convenient and efficient operation. 
     Aimed to realized the above features, the present invention provides: A multi-functional power tool, characterized in that: the power tool comprises an housing, a motor set in the housing, a main shaft driven through the rotation of the motor, a working shaft used to connect corresponding working head when running, wherein an active impact block, which can make axial motion with respect to the main shaft, is configured on the main shaft, a passive impact block which rotates with the working shaft and can alternatively make axial motion with respect to the working shaft is mounted on the working shaft, the active impact block rotates to drive the passive impact block through the coordination of the first end tooth set on the active impact block and the second end tooth set on the passive impact block; the power tool further includes a function shifting button which can move between the first location and the second location to alternatively limit the passive impact block&#39;s axial motion with respect to the working shaft, in this way to realize the shifting between the first function and the second function of the power tool. 
     As an improvement of the invention, the power tool further comprises a compression piece set on the passive impact block and away from the side of the active impact block, wherein the compression piece compresses the passive impact block so that the passive impact block is apt to make movement toward the active impact block. 
     Aimed to realized the above features, the present invention also could provides: A drilling tool, characterized in that: the power tool comprises an housing, a power source, a main shaft driven by the power source and a working shaft fit for the working head, the main shaft is provided with impact storage block making axial movement with respect to the main shaft, wherein the working shaft is provided with the passive impact block in axial movement, the first working mode and the second working mode exist between the impact storage block and passive impact block, wherein there is no relative axial displacement between the impact storage block and passive impact block in the first working mode, while there is relative axial displacement between the impact storage block and passive impact block in the first working mode, a function shifting button is set on the housing, which includes a location limiting part alternatively limiting the axial movement of the passive impact block. 
     Aimed to realized the above features, the present invention also could provides: A power tool, comprising: 
     An housing; 
     A power source, set in the housing and outputting rotation power; 
     A working shaft, extending toward the front of the housing and capable of connecting the external working head; 
     A gear reduction mechanism, set between the power source and working shaft and transmitting the rotation output of power source to the working shaft; 
     An active impact block, driven by the rotation of output shaft of the gear reduction mechanism; 
     A passive impact block, capable of engaging with the active impact block and driven by the rotation, the passive impact block is set on the working shaft and rotates to drive the working shaft, and the passive impact block can make axial motion with respect to the working shaft, wherein the active impact block can alternatively ungear the passive impact block when the load on the working shaft increases to the specific value, then mesh with the passive impact block again under the output shaft&#39;s rotation driving, thus to exert intermittent impact on the working shaft in the direction of rotation. 
     An impact shifting piece, capable of alternatively limiting the passive impact block&#39;s axial motion with respect to the working shaft, so as to make the impact mechanism shift between the impact status that the active and passive impact blocks can ungear each other and the limiting status that the active and passive impact blocks cannot ungear each other. 
     Compared with the existing technology, the present invention has the following favorable effects: the power tool is additionally provided with independent passive impact block, and limits the passive impact block&#39;s movement together with the active impact block through function shifting button, thus to realize impact wrench function; moreover, this function shifting button can also cancel the limitation to the passive impact block, so as to make it move together with the active impact block, thus to realize drilling function, wherein the abovementioned function shifting mechanism features simple structure, relatively low manufacturing cost, convenient and efficient operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is further detailed in combination with the drawings attached and embodiments hereinafter, wherein: 
         FIG. 1  is the front view of the multi-functional power tool in the embodiment for the present invention; 
         FIG. 2  is the exploded view of working parts of the multi-functional power tool shown in  FIG. 1 ; 
         FIG. 3  is partial and sectional scheme of the multi-functional power tool shown in  FIG. 1 , mainly disclosing the realizing mechanism of impact wrench function and drilling function, and function shifting mechanism; wherein the power tool is in the low resisting moment status of the impact wrench function status; at this time, the function shifting button is at the first location, and the passive-active impact block is compressed by the sub-passive-active impact block to deviate from function shifting button location; 
       Similar to  FIG. 3 ,  FIG. 4  shows the power tool in high resistant status of the impact wrench function status; at this time, function shifting button is at the first location, the active-active impact block has deviated from the passive-active impact block under the driving of the motor, while the passive-active impact block is incapable of following the active impact block to make axial movement due to the limitation of function shifting button, thus to realize impact function; 
         FIG. 5  is similar to  FIG. 3 , but the difference lies in that the function shifting button is at the second location, the passive-active impact block can move together with the active-active impact block, this power tool then realizes drilling function accordingly; 
         FIG. 6  is sectional scheme along A-A line direction in  FIG. 4 ; 
         FIG. 7  is sectional scheme along B-B line direction in  FIG. 6 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1-7  show an embodiment of the multi-functional power tool for the present invention. In this embodiment, the power tool is provided with impact wrench function and drilling function. As shown in  FIG. 1 , the power tool  100  comprises an housing  1  distributed horizontally, a handle  6  arranged to form certain angle with the housing and the detachable battery pack  8  at the bottom of the handle. A tool gripper  52 , set in the front of the housing  1 , used to hold different working heads (no drawings) respectively for realizing different functions. If gripping fastener when realizing impact wrench function, hold twist drill while realizing drilling function. A switch  7  is mounted on the handle  6 , through which the operator can start up the power tool through pressing this switch. 
       FIG. 2  shows the working parts of the power tool configured in the horizontal housing. As shown in  FIG. 2 , from right to left of the figure, working parts include a motor  11  and motor output shaft  12  extended from the front of the motor. A gear reduction system is set in front of the motor  11 . In this embodiment, the reduction system is planetary gear reduction system which comprises gearbox  21  and planetary carrier  22 . Internal gear  213  is set in front of the gearbox  21  and several planetary gears  23  are mounted on the planetary carrier  22 . The motor output shaft  12  is in the center of several planetary gears  23  and is engaged with various planetary gears, while the periphery of the planetary gear  23  and internal gear  213  mesh. When the motor runs, the motor output shaft  12  drives the planetary gear  23  to run inside the internal gear  213 , so as to transmit the rotation speed of motor output to the main shaft  24  linking the planetary carrier  22  through certain reduction ratio. A distribution board  13  is set between the motor and gear reduction system, and secured with the main body of the motor  11  through screw stud  14 . A pair of clamping arms  131  extends forwards from the both sides of the distribution board  13  in a symmetrical way, which is firmly clamped on the lug  211  projecting from the back of the gearbox  21 , wherein the inner recess in the outside of the lug  211  forms a notch  212  which can house the lug projecting from the internal wall of the housing  1  (not shown in the drawings). With this structure, the motor  11  and gear reduction system can be reliably secured inside the housing  1 . In front of the gear reduction system sets a mechanism used to realize the impact wrench function, comprising a set of active impact block  31  on the main shaft  24 , impact spring  32  between active impact block  31  and gearbox  21 , and spiral scroll impact mechanism of internal ball located at the junction of active impact block  31  and main shaft  24 , wherein the impact mechanism consists of outer spiral scroll  241  formed by the depression of the surface of main shaft  24 , ball  25  capable of rolling in the outer spiral scroll  241 . In this embodiment, the ball is steel and set in the inner ring of active impact  31  to house the internal spiral scroll  312  of the ball  25 . A pair of the first end teeth  311  protrudes in the front of active impact block  31  in a radial and symmetrical way. Gaskets  33 ,  34  are set between impact spring  32  and gearbox  21 , impact spring  32  and active impact block  31 . 
     By referring to  FIG. 3 , the working parts further comprise function adjusting mechanism in front of the active impact block  31 , working shaft  51  extending from the front of the housing  1 , and tool gripper  52  set around the front of the housing  1 . The function adjusting mechanism consists of passive impact block  41 , function shifting button  44  and compression piece  42 , wherein the function adjusting block  41  is set in the face of active impact block  31 , the second end tooth  411  capable of being engaged with the first end tooth  311  of the active impact block  31  extends from the back in a radial and symmetrical way, a shoulder  412  forms in the front and is set between the shoulder  412  and the second end tooth  411  at certain interval. Several key slots  414  are arranged on the circumference of the inner ring of passive impact block  41 , which can correspondingly house several raised keys  511  formed on working shaft  51 . With this structure, the passive impact block  41  can run together with the working shaft  51 , and the passive impact block  41  can make axial movement with respect to the working shaft  51 . It is easy to figure out the solution for common technicians in this field that key slot and raised key can be interchanged, namely, key slot can be set on the working shaft and raised key can be set on passive impact block. In this embodiment, the compression piece  42  is a spiral spring, wherein the back props up the passive impact block through a gasket  43 , and the front props up the inner wall of the housing  1 . Certainly, the compression piece can be also composed of plate spring or other elastic elements. In front of the working shaft  51  sets housing slot  512  capable of housing corresponding working heads when realizing different functions and being clamped and secured firmly through the tool gripper  52 . 
     By referring to  FIG. 6  and  FIG. 7 , in this embodiment, the function shifting button  44  comprises the operating part  441  outside the housing  1  and the location limiting part  442  capable of extending into the housing  1 , wherein the operating part  441  is a sliding block and capable of sliding on the outer circumference of the housing  1 . A slide way  443  is arranged on the operating part  441  along the vertical direction. The operating part  441  and location limiting part  442  are connected through a movable pivot  444  which (the movable pivot  444 ) can roll in the slide way  443  of the operating part  441 . The upper part of the location limiting part  442  is connected with the movable pivot  444  to allow the pivot to rotate around the movable pivot. The location limiting part  442  can extend into the housing through the opening in the wall of the housing  1 , and can be alternatively located in the spacing area  413  between the shoulder  412  of the passive impact block  41  and the second end tooth  411 , and can be against the shoulder  412  at a specific location. The fixed pivot  445  is set in the opening area of the housing  1 . The middle part of the location limiting part  442  is connected with the fixed pivot  445  to allow the pivot to rotate around the pivot. With this structure, the user is only required to glide the operating part  441  on the surface of the housing  1 , in this way, the location limiting part  442  can alternatively enter into the spacing area  413  between the shoulder  412  of the passive impact block  41  and the second end tooth  411 , or stay outside the spacing area  413 , such as in the opening area of the housing. Certainly, it is easy to figure out the solution for common technicians in this field that the function shifting button is made into simple plug-in type element, namely, located in the spacing area after plugging through the housing opening, or outside the spacing area after unplugging. 
       FIG. 3  and  FIG. 4  disclose the working situation when the power tool realizes impact wrench function, wherein  FIG. 3  shows the low resisting moment status when the tool is in the impact wrench function status,  FIG. 4  shows the high resisting moment status when the tool is in the impact wrench function status. When realizing the impact wrench function, the function shifting button  44  is adjusted to the first location as shown in  FIG. 6 , at this time, the function shifting button  44  and the passive impact block fit each other, namely, the location limiting part  442  is located in the spacing area  413  of the passive impact block. The passive impact block  41  is apt to make movement toward the active impact block  31  under the compression of the compression piece  42 . However, the pressure from the impact spring  32  makes the first end tooth  311  of the active impact block  31  and the second end tooth  411  of the passive impact block mesh with each other, so as to limit and stop the movement of the passive impact block  41 . When the power tool runs, the main shaft  24  is driven by the rotation of the motor output shaft  12 . Through the driving of the ball  25  included in inner and outer spiral scrolls  312 ,  241 , the active impact block  31  follows to rotate, then the passive impact block  41  rotates as well, and then tightens the nuts (no shown in the drawings) rapidly through the working shaft  51  and tool gripper  52  to drive the working head (now shown in the drawings). 
     When the nut end face contacts the surface of the working piece (not shown in the drawings), the resisting moment rapidly increases. After reaching a certain value, the active impact block  31  and passive impact block  41  engaged with each other are both held back. The passive impact block  41  stops rotation, but the main shaft  24  keeps rotation under the driving of the motor output shaft  12 , in this way, to force the ball  25  to roll along the scroll by overcoming the friction force between the inner and outer spiral scrolls  312 ,  241 , so as to push the active impact block  31  to move toward the motor and compress the impact spring  32 . In this process, the early-stage passive impact block  41  makes axial movement at a tiny distance along with the active impact block  31  under the action of the compression piece  42 . However, when the location limiting part  442  of the function shifting button  44  is propped up, further movement is impossible. Therefore, the active impact block  31  is gradually away from the passive impact block  41  in the axial direction. When the axial movement distance of the active impact block  31  exceeds the height of the second end tooth  411  of the passive impact block, namely, at the moment the active impact block  31  and passive impact block  41  ungear each other, the main shaft  24  drives the active impact block  31  to rotate so that the first end tooth  311  slides over the second end tooth  411  of the passive impact block. At the moment of sliding, due to the impact spring  32 , the ball  25  returns to the original location along the spiral scrolls  312 ,  241  again. The active impact block  31  is pushed forwards, and impacts the second end tooth  411  of the passive impact block due to the accelerated rotation of the main shaft  24  so that the passive impact block  41  keeps movement in the rotation direction. In such cycles, the screw piece can be secured under the force of impact. It is easy to figure out the solution for common technicians in this field and the outer ball spiral scroll impact structure can be also adopted to realize the function of impact wrench. The working process and principles are the same to the inner ball spiral scroll impact structure disclosed in this embodiment, so they are not detailed herein. 
     When realizing the abovementioned impact wrench function, it is required that the active impact block  31  rotates intermittently to impact the passive impact block  41  so as to enable the working head (fastener) capable of tightening the nuts. However, when realizing the drilling function, it is only required that the working head (twist drill) keeps drilling, while the intermittent impact of the active impact block is not required any more. By referring to  FIGS. 5 and 7 , when the function shifting button  44  is adjusted to the second location as shown in  FIG. 7 , namely, the location limiting part  442  is located outside the spacing area  413  of the passive impact block  41 . At this time, the power tool is in the working status of drilling function. During drilling, since the resisting moment of the working shaft  51  gradually increases, the active impact block  31  moves toward the motor. At this time, due to the lack of the limitation of the function shifting button  44 , the passive impact block  41  makes axial movement along with the active impact block  31  under the compression of the compression piece  42  with respect to the working shaft  51 . Meanwhile, active impact block  31 , passive impact block  41  and working shaft  51  moves together in the rotation direction. Since the passive impact block  41  and active impact block  31  cannot ungear each other, namely the two blocks cannot form an impact, continuous drilling of the working head can be ensured. 
     In other embodiments, when the function shifting button is at the second location, namely the passive impact block moves together with the active impact block, the clutch structure added between the planetary gear reduction system of the power tool and inner ball spiral scroll impact structure can realize the electric screwdriver set function correspondingly, while the active impact block structure of dynamic, static end teeth in the front of the working shaft can realize impact drill function correspondingly. The abovementioned functions can be set separately and form double-functional power tool in combination with the impact wrench function, form tri-functional power tool or quarter-functional power tool by means of overlying setting. Since the abovementioned functional mechanism added is the existing technology and it has been described in detail in the reference document cited by the background technology of this application, it is unnecessary for the applicant to give details herein.