Patent Publication Number: US-8991516-B2

Title: Electric tool

Description:
RELATED APPLICATION DATA 
     This application claims the benefit of CN 201010253482.3, filed on Aug. 8, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The subject disclosure generally relates electric tools and, more particularly, to a leakage-preventing and sealing device for the grease lubricating the moveable members inside an electric tool. 
     In electric tools, most of the moveable members need to be lubricated by grease. The lubricating effect of the grease is, however, often diminished with use of the electric tool. This is particularly true for electric tools having high-speed-rotating moveable members. Moreover, if the grease leaks out to an electrical connection part, the electric connection quality could be affected. 
     SUMMARY 
     To solve the above-mentioned problems, the following describes an electric tool equipped with a leakage-preventing device. 
     More particularly, described hereinafter is an electric tool having a gripping portion, a working portion rotatably connected to the gripping portion about an axis, a gear box accommodated within the gripping portion and having an opening, and an output shaft movably accommodated within the working portion in a reciprocating manner with the output shaft being rotated and displaced from one end to the other end of the opening along with the working portion. A leakage-preventing device is arranged at the opening. 
     In a described embodiment, the leakage-preventing device comprises a bushing rotatably arranged within the gear box, and the bushing is provided with a hole through which the output shaft may pass. Generally, the hole extends along the axis direction of the output shaft. 
     Further, the bushing may be provided with a notch and a grease-gathering portion, shaped as a barb, may be arranged at a first end or/and a second end of the notch where it protrudes to the inside of the bushing. 
     Still further, a transmission gear may be contained in the gear box and the transmission gear is provided with a groove within which the first end and/or the second end of the notch can be engaged. 
     Yet further, impact components may also be contained in the gear box and an isolating rib portion, for avoiding grease leaking, may be arranged between the transmission gear and the impact components. 
     Yet further, the working portion may be provided with a light source with a scraping device being arranged on an electric connection device of the light source. 
     Yet further, the electric connection device may comprise a moveable connecting piece arranged on the working portion and a stationary connecting piece connected with the moveable connecting piece and disposed on the gripping portion with the scraping device having scraping pieces disposed on the two sides of the moveable connecting piece respectively and with one end of a scraping piece contacting with the stationary connecting piece. 
     Yet further, the scraping device may include grease-gathering grooves disposed on two ends of the stationary connecting piece. 
     By adopting one or more of the above mentioned technical solutions, the following technical effects can be obtained: 
     1) with the bushing disposed at the opening of the gear box for avoiding grease leaking, the opening of the gear box can be covered no matter how the bushing is displaced along with the output shaft, so that leaking of the lubricating grease can be avoided; 
     2) the isolating rib portion disposed between the transmission gear and the impact components can decrease the flowing diffusion of the lubricating grease from the transmission area to the striking area; and 
     3) if the connecting piece of the light source is adhered with the leaked lubricating grease, the scraping piece can scrape away the leaked lubricating grease to ensure the unobstructed contact between the connecting pieces and the grease-gathering grooves disposed on the ends of the scraping piece respectively along the rotation direction thereof can be used for gathering the scraped grease. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An electric tool will be further explained hereinafter with reference to the accompanying drawings, wherein: 
         FIG. 1  is a schematic view of an exemplary electric tool constructed according to the description that follows showing an operating state for striking a nail; 
         FIG. 2  is a schematic view of the electric tool showing another operating state for striking a nail; 
         FIG. 3  is a partial sectional view seen from the front of the electric tool; 
         FIG. 4  is a sectional view taken along the axis C shown in  FIG. 3 ; 
         FIG. 5  is a partial sectional view seen from the side of the electric tool showing a working portion being rotated 180 degrees with respect to a gripping portion; 
         FIG. 6  is a partial sectional view seen from the side of the electric tool showing the working portion being rotated 90 degrees with respect to the gripping portion; 
         FIG. 7  is a schematic view illustrating an exemplary electric connection of a light source on the electric tool; 
         FIG. 8  is a schematic view illustrating an exemplary oil scraping device disposed on the device for electrically connecting with the light source; 
         FIG. 9  is a schematic view illustrating an exemplary leakage-preventing device disposed on the electric tool wherein the leakage-preventing device comprises a bushing disposed at the opening of a gear box, and an output shaft is connected to the inside of the axle hole provided on the bushing and drives the bushing to move from a first end position (a) to a second end position (b) of the gear box opening; 
         FIG. 10  is a schematic view illustrating a further technical feature of the leakage-preventing device in  FIG. 9  wherein a notch is provided on the bushing for keeping the device away from the gear transmission position of a transmission gear; and 
         FIG. 11  is a schematic view illustrating a still further technical feature of the leakage-preventing device in  FIG. 9  wherein a groove is provided at the gear transmission position. 
     
    
    
     DETAIL DESCRIPTION 
     A preferred embodiment of an electric tool will be explained in detail hereinafter wherein the electric tool is embodied in an electric hammer for striking a nail. It is to be understood, however, that this illustrative embodiment is not intended to be limiting. Rather, those of skill in the art will readily understand how to utilize the various components described hereinafter in other electrical devices to achieve the same results. 
     As shown in  FIGS. 1-6 , an electric hammer comprises a gripping portion  20  having a first axis A and a working portion  10  having a second axis B, the working portion  10  being rotatable with respect to the gripping portion  20  about a third axis C which is perpendicular to a plane defined by the first axis A and the second axis B. The intersection between the second axis B and the first axis A is closer to the tip end of the gripping portion  20  than the intersection between the third axis C and the first axis A, so that the working portion  10  can be operated in a narrower space. 
     As shown in  FIG. 1 , when the electric hammer is operated at a corner area formed by two workpieces that are disposed perpendicular to each other, the nail is struck into one workpiece at an angle of 45 degrees relative to the surface of the other workpiece so as to connect the two workpieces. In this case, the working portion  10  is rotated by 135 degrees relative to the gripping portion  20  and the hand of the operator grips the upright gripping portion, so that it is labor-saving and comfortable for operation. To enhance the light brightness in the working area  50  during striking of a nail, a light source  30  may be further disposed on the rotatable working portion  10 . As shown in  FIG. 2 , when one workpiece at the top needs to be operated upon, it is unnecessary for the operator to adjust the orientation of the gripping portion  20  manually but, instead, the operator need only rotate the working portion  10  to a position that is 180 degrees relative to the gripping portion  20 , so that the operation of the device remains convenient. 
     As shown in  FIGS. 3-6 , the working portion  10  has positioned therein working parts  1  which mainly comprises an output shaft  7  for striking a nail, a bushing  6  exteriorly mounted on the output shaft  7 , a cover  12  and a nail-receiving opening  11 , etc. The gripping portion  20  comprises a housing  2  for supporting a gear box  5  and the working parts  1 . A transmission gear  9  and impact components  8  are supported within the gear box  5 . A releasing button  3  is further provided on the housing  2  for locking and releasing the working parts  1 , which can be restored by a biasing member  4 . 
     The operation principle of rotation is that: the releasing button  3  has a discontinuous surface on the periphery thereof, accordingly, the housing  2  and the working parts  1  also have discontinuous surfaces for mating with that of the releasing button  3 . When the releasing button  3  is located between the housing  2  and the working parts  1 , the working parts  1  are locked and can not be rotated. When the releasing button  3  is pressed, the discontinuous surface of the releasing button  3  disengages from the housing  2  and entirely enters into the working parts  1 , so that the working parts  1  can be rotated. Due to the biasing member  4 , the releasing button  3  has a tendency of disengaging from the working parts  1  and entering into the housing  2 . When the releasing button  3  is rotated by a certain angle, the discontinuous surface thereof is consistent with the discontinuous surface on the housing  2 , as a result, the releasing button  3  enters into the housing and the working parts  1  is locked. 
     When the working parts  1  rotate, the output shaft  7  mounted thereon is substantially tangential at its axle center to the peripheral circle of the rotating impact components  8 . 
     As shown in  FIGS. 4 and 7 , the connection mode of the light source  30  (preferably, a LED light) is schematically shown. For the convenience of the user after rotating the working parts  1 , the LED light is configured to be rotated along with the working parts  1 . The LED is mounted on the working parts  1  so that the light emitted therefrom can illuminate the working area  50  in front of the nail-receiving opening  11 . The wiring takes the form of: the positive and negative wires are led out from the LED at one end thereof and soldered onto the moveable positive and negative connecting pieces  34 ,  32  at the other end thereof, respectively. The wires are arranged along the inside surface of the cover  12  in the form of an arc. The moveable positive and negative connecting pieces  34 ,  32  are fixed on the cover  12  respectively, and the stationary positive and negative connecting pieces  35 ,  31  are fixed on the front and rear sides of the gear box  5  respectively. When the cover  12  is mounted on the gear box  5 , the moveable positive and negative connecting pieces  34 ,  32  contact with the stationary positive and negative connecting pieces  35 ,  31 , respectively. Another two positive and negative wires  36  are connected to the stationary positive and negative connecting pieces  35 ,  31  at one end thereof and to the PCB assembly at the other end thereof, respectively. The stationary positive and negative connecting pieces  35 ,  31  are longer in length than the movable positive and negative connecting pieces  34 ,  32 , so that the moveable positive and negative connecting pieces  34 ,  32  can slide on the positive and negative static connecting pieces  35 ,  31  when the working portion  10  rotates relative to the gripping portion. 
     To ensure a reliable connection between the connecting pieces, an elastic member  33  is disposed on the moveable positive and negative connecting pieces  34 ,  32  respectively for assisting them into contact with the stationary positive and negative connecting pieces  35 ,  31 . 
     Referring to  FIGS. 1 and 2 , it is preferred to dispose the light source  30  at the lower portion of the working portion  10 . The light source  30  is controlled by a switch controlling the motor M and is supplied with power from a battery package  40  disposed at the bottom portion of the gripping portion  20 . 
     In the illustrated embodiment, to prevent the lubricating grease inside the device from leaking out due to the motion of the members, a leakage-preventing device for controlling the grease is provided in the electric tool. As shown in  FIGS. 9 ,  5  and  6 , the gear box  5  has an opening  51 , hence, when the impact components  8  in the gear box  5  are driven to rotate in the gear box  5  by the transmission gear  9 , two tabs formed on the periphery of the impact components intermittently strike the output shaft  7  protruding to the inside of the opening  51  on the gear box. As a result, the output shaft  7  can move in a straight reciprocating manner within the working portion  10  to strike the nails or the like. In addition, since the working portion  10  of the electric hammer in this embodiment can be rotated relative to the gripping portion  20  to drive the output shaft  7  disposed therein to change its position, the opening  51  of the gear box serves to provide a space for the displacement of the output shaft  7 . 
     To avoid the leakage of the lubricating grease in the gear box  5  from the opening  51 , the bushing  6  is disposed at the opening  51  of the gear box. The profiles of the bushing  6  and the gear box  5  are concentric circles, wherein the bushing is encompassed by the gear box  5 . The output shaft  7  is connected to the bushing  6  through the axle hole  62  formed on the bushing so that the bushing  6  can be driven to rotate along the inner surface of the gear box  5 . As a result, the bushing  6  can move between the first end position (a) and the second end position (b) of the opening  51  on the gear box. It is noted that, the bushing  6  can cover the opening  51  on the gear box  5  no matter how it rotates, so that the leakage of the lubricating grease can be avoided. 
     As shown in  FIG. 10 , since the bushing  6  may interfere with the transmission gear  9  protruding into the gear box  5 , in order to keep away from the gear transmission position of the transmission gear, a notch  60  is formed on the bushing  6 , which has a first end  61  and a second end  61  separated from each other. To enhance the sealing effect for grease, it is preferred for the above leakage-preventing device to provide a barb-shaped grease-gathering portion on the first end  61  and/or the second end  61  of the bushing protruding to the inside of the bushing  6 . In order to make the length of the bushing  6  overlapping with respect to the inner surface of the gear box at one end of the opening  51  on the gear box when the bushing  6  is rotated to the other end, it is preferred for the above leakage-preventing device to form a groove  91  at the gear transmission position where the two ends of the notch  60  on the bushing  6  may be touched, and one end of the notch  60  on the bushing  6  can be embedded into the groove  91  as illustrated in  FIG. 11 . 
     Since the outer surface of the bushing  6  is engaged with the inner surface of the gear box  5 , the grease coming off the impact components  8  to the inner surface of the bushing  6  will flow back to the gear box  5  along this inner surface and is not likely to flow out of the gear box along the engagement surface. Certainly, it may be easily conceivable for those skilled in the art that the outer diameter of the bushing  6  may be slightly larger than the inner diameter of the gear box  5  so as to enhance the leak tightness of the seal. Referring to  FIG. 4 , another embodiment of the leakage-preventing device can be seen. Rib portions  52  are arranged on the gear box  5  for isolating the transmission gear  9  from the impact components  8 , so that the flowing diffusion of the lubricating grease from the transmission area to the striking area can be reduced. 
     To avoid a failure of connection of the LED due to the leakage of the grease, in the present embodiment a scraping device is disposed on the positive and negative connecting pieces of the circuit respectively. Referring to  FIG. 8  and taken the scraping device disposed on the negative connecting piece for example, a scraping piece  38  is disposed on two sides of the moveable negative connecting piece  32  along the rotation direction thereof respectively, with one end of each scraping piece  38  being mounted on the cover  12  and the other end thereof being contacted by the stationary negative connecting piece  31 . When the working parts  1  rotates and the stationary negative connecting piece  31  is adhered with the leaked lubricating grease, the scraping piece  38  can scrape away the grease immediately to ensure the unobstructed contact between the LED connecting pieces. Moreover, a grease-gathering groove may be formed on the ends of the scraping piece  38  along the rotating direction respectively for gathering the scraped grease. The scraping device disposed on the positive connecting piece is the same as the scraping device on the negative connecting piece. 
     While various concepts have been described in detail, it will be appreciated by those skilled in the art that modifications and alternatives to those concepts could be developed in light of the overall teachings of the disclosure. Therefore, it will be appreciated that the particular concepts disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any equivalents thereof.