Abstract:
The present invention discloses a power tool having a main body portion and at least one interchangeable cutting tool carrier. A motor and a transmission mechanism are mounted in the main body portion and the cutting tool carrier includes a cutting tool assembly which includes a connection mechanism. The transmission mechanism includes a driving device which is mounted on the driving shaft and may be coupled with the connection mechanism. The transmission mechanism also has a stationary element and a movable element, each having a magnet mounted on a surface. Due to the magnetic force, the moving element and the driving device are able to move relative to the stationary element to allow for automatic alignment of the driving device and the connection mechanism of the cutting tool elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to CN 200920045162.1 filed May 8, 2009, which is hereby incorporated by reference. 
       FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       TECHNICAL FIELD 
       [0003]    The present invention relates to a power tool, and more specifically, to an adaptable power tool that can be used with different types of interchangeable cutting tool attachments. 
       BACKGROUND OF THE INVENTION 
       [0004]    Many power tools are adaptable to allow for their use across different purposes. The adaptability increases convenience and reduces expenses for a user of the power tool. Specifically, a main body of a power tool can be connected with different cutting tool attachments to allow for many different uses of the power tool. For example, a garden tool may have a main body portion and a plurality of different cutting tool carriers. Each cutting tool carrier can be equipped with several different types of cutting tool attachments, such as short blades for cutting grass and long blades for pruning shrubs. Each of the various cutting tool carriers can be interchangeably connected to the main body portion to provide a multi-use garden tool. 
         [0005]    As explained above, the garden tool can accomplish many different functions by connecting the main body portion with different cutting tool carriers. As a result, a user is able to accomplish many different gardening tasks by purchasing only one machine. However, the above mentioned garden tool of the prior art does not adequately provide for the alignment of the main body portion with the connection mechanism when the cutting tool carrier is installed on the main body portion. Specifically, in the prior art, the user must first rotate a driving shaft of the driving device to a predetermined position and then move the blade of the attachment to a corresponding position to allow for installation. This tedious connection and alignment process can be very cumbersome and time-consuming for a user of the power tool. 
       SUMMARY OF THE INVENTION 
       [0006]    In order to overcome the disadvantages and deficiencies in the prior art, this invention provides an improved power tool which has an automatic alignment function when interchanging the cutting tool elements and thus can be operated conveniently. 
         [0007]    The power tool provided in the present invention includes a main body portion and at least one interchangeable cutting tool carrier. A motor and a transmission mechanism are mounted in the main body portion, and the cutting tool carrier includes a cutting tool assembly which includes a connection mechanism. The transmission mechanism includes a driving device which is mounted on the driving shaft and cooperates with the connection mechanism. The transmission mechanism also has a stationary element and a moving element which can move together with the driving device and can provide mutual repulsion force therebetween. 
         [0008]    Under effect of the repulsive force, the moving element may be moveable relative to the stationary element, and the driving device can be moveable relative to the stationary element since the moving element can be moved together with the driving device. Upon assembling the main body portion and the cutting tool carrier of the power tools, the driving device used for driving the cutting tool elements can move to allow for the automatic alignment of the driving device and the connection mechanism of the cutting tool. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will be further described with reference to accompanying figures and preferred embodiments. 
           [0010]      FIG. 1  is an illustrative view of a preferred embodiment of a garden tool according to the present invention. 
           [0011]      FIG. 2  is an illustrative view of an interchangeable cutting tool carrier. 
           [0012]      FIG. 3  is an illustrative view of partial internal structure of the garden tool shown in  FIG. 1 . 
           [0013]      FIG. 4  is a plan view of a gear shown in  FIG. 3 . 
           [0014]      FIG. 5  is a cutaway view of the gear shown in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  shows a preferred embodiment of a garden tool according to the present invention. The garden tool  100  can be used for cutting grass, pruning shrubs and cutting other types of vegetation. The garden tool  100  includes a main body portion  1  which can be connected with different cutting tool carriers to achieve different functions. As shown in  FIGS. 1 and 2 , a long cutting tool carrier  2  used for pruning shrubs and a short cutting tool carrier  3  for cutting grass, respectively, are shown. Each of cutting tool carriers  2  and  3  includes a base  4  and a cutting tool element installed thereon. The cutting tool carrier  2  for pruning shrubs is provided with a pair of longer blades  20  which can move relative to each other in a linear reciprocating motion along a front-rear direction. The cutting tool carrier  3  for cutting grass is provided with a pair of shorter blades  30  where at least one blade can swing relative to the other blade in a swinging motion. 
         [0016]    As shown in  FIG. 3 , the main body portion  1  of the garden tool  100  has a motor  10  installed therein. A deceleration mechanism is connected to the output end of the motor  10  to reduce speed output from the motor  10 . The deceleration mechanism is a gear transmission mechanism including four gears  12 ,  13 ,  14  and  15 , wherein the gear  12  is mounted on the output shaft of the motor  10 , the gears  13  and  14  are mounted on the shaft  16 , and the gear  15  is installed on the shaft  11 . The gear  12  and the gear  13  are installed to engage with each other and the gear  14  and the gear  15  are also installed to engage with each other. The shafts  16 ,  11  are arranged parallel to each other and are conical at the free ends. The two shafts  16  and  11  extend out from the main body portion  1  so they may be connected with the cutting tool carrier. The shaft  11  is coupled with a driving device for driving the blades. In this embodiment, the driving device is an elliptical device which includes a large elliptical wheel  17  and a small elliptical wheel  18 . The large and small elliptical wheels  17 ,  18  are fixed on the gear  15  and overlap with each other, and the relative position between the two elliptical wheels is permanent. In other embodiments, the two elliptical wheels can be made integrally. The large and small elliptical wheels  17 ,  18  can be respectively mated with the connection mechanisms of the blades  20 ,  30 , i.e. oval-shaped holes, so as to drive the blades to move. 
         [0017]    Upon assembling the main body portion  1  of the garden tool  100  and the cutting tool carrier, the garden tool  100  also includes a pair of magnets in order to achieve automatic alignment of the two elliptical wheels  17 ,  18  device and the oval-shaped holes in the blades  20 ,  30 . Referring to  FIG. 3 , a first magnet  81  is permanently installed on the shaft  11 . Referring to  FIG. 4  and  FIG. 5 , a second magnet  82  is mounted in the center hole of the gear  15  by interference fit, and the gear  15  and the second magnet  82  are movably installed on the shaft  11 . The elliptical wheels  17 ,  18  can move together with the gear  15  and the second magnet  82  due to the fixed connection between the elliptical wheels  17 ,  18  and the gear  15 . Under the assembled state, the first and second magnets  81 ,  82  are located on the shaft  11  and opposite to each other with the same magnetism. Therefore, the gear  15  and the elliptical wheels  17 ,  18  tend to move downwards under the action of the magnetic force which is repulsive due to magnetism forces of a same polarity. 
         [0018]    As shown in  FIG. 1 , a stopper  9  extends inwardly from the housing of the main body portion  1  to limit the displacement of the downward movement of the gear  15  and the elliptical wheels  17 ,  18 . In this embodiment, the stopper is a stop rod. Therefore, the gear  15  can move between the first magnet  81  and the stop rod  9  along the shaft  11 . As shown in  FIG. 3 , the height of the gear  14  is significantly larger than the height of the gear  15 . This height arrangement allows the gear  15  to engage with the gear  14  at any time during the up-down displacement of the gear  15 . 
         [0019]    The automatic alignment process for the cutting tool element of the garden tool  100  will be described hereinafter by an example of using the cutting tool carrier  3  for cutting grass. As shown in  FIG. 2 , the cutting tool carrier  3  is provided with the base  4  and the cutting tool element. The base  4  has two longitudinal arranged holes  41 ,  42 . The spacing between the two holes is equal to the spacing between the shaft  16  and the shaft  11  so that the shafts  16 ,  11  can be inserted into the holes  41 ,  42 , respectively. The base  4  further includes a rear engaging sheet  43 , left and right engaging sheets  44 ,  45  and a groove  46 . When assembling the rear engaging sheet  43  can be inserted into the hole  19  of the main body portion  1 , and the left and right engaging sheets  44 ,  45  can respectively engage with the left and right engaging slots  74 ,  75  on the main body portion  1 . The front end of the main body portion  1  is provided with a button  6  which can be operated to drive a hook  7  connected with it to rotate so as to engage with or disengage from the groove  46 . The cutting tool element  30  includes a lower blade  301  and an upper blade  302 . In this embodiment, the lower blade  301  is permanently installed on the base  4 , and the upper blade  302  is movably installed on the lower blade  301 . The upper blade  302  has an oval-shaped hole  303  as a connection mechanism at one end thereof which may be mated with the large elliptical wheel  17 , so as to drive the upper blade  302  to swing in a swinging motion to implement the action for cutting grass. 
         [0020]    When the cutting tool carrier  3  is connected to the main body portion  1  to form a grass trimmer, the rear engaging sheet  43  of the base  4  are inserted into the hole  19  of the main body portion  1  and the shafts  16 ,  11  are aligned with the holes  41 ,  42  and inserted therein. The cutting tool carrier is then further closed so that the left and right engaging sheets  44 ,  45  engage with the left and right engaging slots  74 ,  75 , and the hook  7  is mated with the groove  46 . Under this assembled state, the cutting tool carrier  3  is installed on the main body portion  1 , but the elliptical device of the main body portion  1  might not be aligned with the oval-shaped hole  303  in the blade  302 . As a result, the elliptical wheel  17  may press the edge  305  of the oval-shaped hole  303 , and the upward reaction of the oval-shaped hole  303  causes the elliptical device and the gear  15  to move upwardly by overcoming the magnetic force. When this occurs, the motor  10  is powered to drive the elliptical wheel  17  to rotate along with the gear  15 . When the elliptical wheel  17  rotates away from the edge  305  of the oval-shaped hole  303 , the elliptical wheel  17  and the gear  15  may move downwardly and fall into the oval-shaped hole  303  under the action of the magnetic field. The elliptical wheel  17  continues to rotate so as to drive the blade  302  to move. For the cutting tool carrier with only one moveable blade  302 , the small elliptical wheel  18  on the shaft  11  remains in idle state. For the cutting tool carrier with two moveable blades  20 , the large and small elliptical wheels  17 ,  18  may be mated with the large and small oval-shaped holes on the two moveable blades  20 . This allows the two blades  20  to be driven to move simultaneously. 
         [0021]    In the above-mentioned embodiments, the automatic alignment of the elliptical device and the connection mechanism of the cutting tool elements is achieved by mounting a pair of magnets with the same magnetic poles opposite to each other on the shaft  11 . However, the present invention is not limited to the magnet and it may be replaced by other materials which can produce repulsive force. In addition, those skilled in this art would easily envision that such device with the automatic alignment function for the cutting tool elements can also be used for other types of the power tools with the requirement for replacing the cutting tools elements and is not limited to the garden tool embodiments described above. 
         [0022]    The power tools disclosed in this invention are not limited to the contents mentioned above and the structures shown in the figures. Any obvious modifications, substitutions or changes to the shapes and the positions of other components based on the spirit of the present invention will be regarded as falling within the scope of this invention.