Abstract:
The present disclosure provides a power tool having a clamping device for a working element. The power tool includes an output shaft, a fastening piece having a flange portion for clamping the working element and a protruding shaft substantially perpendicular to the flange portion. A locking assembly comprising a locking member having a first position in which the protruding shaft is locked and a second position in which the protruding shaft is loosened is provided, wherein a pressing member can press the working element between the pressing member and the flange portion when the locking member is in the first position. The power tool can fasten the working element to the output shaft in a simple and reliable manner without the necessary use of such auxiliary tools as a spanner etc. and can achieve a stronger clamping force even under impact conditions.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Chinese Patent Application Nos. CN201010515143.8, filed Oct. 9, 2010, and CN201010574780.2, filed Nov. 24, 2010, each of which are incorporated herein by reference in their entirety. 
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to a power tool comprising an output shaft for driving the tool and a fastening piece for clamping a working element to an end of the output shaft. The tool further comprises a moving device for enabling the fastening piece movable between a released position and a clamped position. At the released position, the fastening piece can be removed from the output shaft by being disengaged from the moving device, and conversely at the clamped position, the fastening piece can lean against the end of the output shaft by locking with the moving device and cooperating with an elastic element such that the working element is firmly clamped. 
     BACKGROUND OF RELATED ART 
     A power tool having a quick clamping device is generally known from US 006569001 B2. The described hand-held tool is an angular grinder equipped with a hollow output mandrel therein, wherein a clamping device is mounted in the hollow mandrel and is movable between a clamped position and a released position along the axial direction of the mandrel. The described clamping device includes a clamping flange which is provided with a threaded pin in the middle thereof and is used for cooperating with an opposite flange on the end of the hollow mandrel shaft to clamp a working element therebetween. A thrust component mated with the threaded pin is further arranged in the hollow mandrel. At the clamped position, the threaded pin is screwed into the thread of the trust component and is held in the clamped position under the action of the spring force, and at the released position, the thrust component pushes the threaded pin so as to drive the clamping flange to overcome the spring force and disengage from the surface of the clamped working element. Because there is no frictional force between the clamping flange and the clamped working element when they rotate relative to each other, the threaded pin of the clamping flange can be manually screwed out of the thrust component without the aid of any accessories so that the working element can be replaced conveniently. 
     Though, for this kind of clamping device, the working element can be substantially clamped to the output shaft of the hand-held tool without any auxiliary tools, however, this clamping device is only suitable for clamping the rotatably driven working element. If the working element is driven by a vibration device such that the working element sways forward and rearward along a longitudinal axis of the output shaft, then this results in a greater transilient torque and a very great impaction occurring in the two rotation directions and it is effectively impossible to ensure the working element to be clamped sufficiently and firmly by means of a known clamping device. 
     SUMMARY 
     To improve upon the deficiencies noted in the above prior art, the present disclosure provides a power tool, which can fasten the working element to the output shaft in a simple and reliable manner without the use of such auxiliary tools as a spanner etc. and can achieve a stronger clamping force. Even under impact conditions, which occur in the tool driven by a vibration driver, for example, this clamping force is sufficient enough to ensure the working element to be clamped reliably and firmly. 
     In order to solve the above technical problem, the present disclosure introduces the following technical solution: 
     A power tool having a clamping device for a working element, comprising: an output shaft for driving the working element; a fastening piece having a flange portion for clamping the working element and a protruding shaft substantially perpendicular to the flange portion; and a locking assembly comprising a locking member having a first position in which the protruding shaft is locked and a second position in which the protruding shaft is loosened, wherein the power tool further comprises a pressing member, and the working element can be pressed between the pressing member and the flange portion when the locking member is in the first position. 
     The locking member can move between the first position and the second position and its moving direction is substantially perpendicular to the protruding shaft. 
     The power tool further comprises a movable device for moving the locking member. 
     The movable device is partially arranged on the pressing member. 
     The locking assembly further comprises an intermediate element that can abut against the locking member, wherein the pressing member is provided with a position A and a position B, and there is a height difference between the position A and the position B in the radial direction perpendicular to the protruding shaft, and the intermediate element is selectively placed on the position A or the position B. 
     The intermediate element is a steel ball or a cylindrical pin. 
     The radial height difference between the position A and the position B on the pressing member is configured as a stepped plane or a groove. 
     A biasing element acts on the pressing member for biasing the pressing member toward the flange portion. 
     The biasing element comprises a first spring. 
     The power tool further comprises an operation device for moving the pressing member toward a direction to overcome the force exerted by the biasing element. 
     The operation device comprises a lever element rotatable about a pivot shaft, wherein one end of the lever element abuts against a cam spanner and the other end thereof selectively abuts against an actuating portion provided on the pressing member. 
     The operation device comprises a rotatable shaft and an operation element for rotating the rotatable shaft about the axis thereof, the rotatable shaft being provided with an eccentric convex surface which can selectively abut against or disengage from the actuating portion arranged on the pressing member. 
     The locking member and the protruding shaft are respectively provided with formed locking structures for matching with each other. 
     The formed locking structures comprise a toothed portion arranged on the protruding shaft and a matching toothed portion arranged on the locking member. 
     An elastic element acts on the locking member and biases the locking member toward a direction D in which the protruding shaft is inserted into a cavity. 
     A projection is formed on an end surface mated with the flange portion. 
     The power tool further comprises a disengagement-proof element for preventing the protruding shaft from falling out of the cavity. 
     The locking assembly further comprises a locking shaft connected with the output shaft, wherein the locking shaft is provided with a first groove mated with the locking member. When the locking member is at a first position to lock the protruding shaft, the locking member is at a first end of the first groove; when the locking member is at a second position to loosen the protruding shaft, the locking member is at a second end of the first groove. 
     A slidable sleeve is enclosed outside of the locking shaft, wherein the slidable sleeve is provided with a second groove which is mated with the locking member and drives the locking member to move between the first end and the second end. 
     A second spring acts on the slidable sleeve, and the pressing member can abut against the slidable sleeve such that the slidable sleeve moves in a direction to overcome the spring force of the second spring. 
     The power tool further comprises an operation spanner which cooperates with the first spring such that the pressing member moves along the direction of the axis of the output shaft. 
     The operation spanner selectively contacts with or disengages from the pressing member. 
     The operation spanner is hinged to a housing of the power tool. 
     An elastic support is arranged between the operation spanner and the housing of the power tool. 
     By utilizing the above technical solution, the power tool according to the present disclosure has a quick clamping device for the working element, so its usage is convenient and effort-saving, and the structure is simple and compact, and the cost may be largely reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a power tool according to a first example of the present disclosure, wherein a clamping device for clamping a working element is in a clamping state. 
         FIG. 2  is a sectional view of a power tool according to the present disclosure, wherein the clamping device for clamping working element is in a releasing state. 
         FIG. 3  is a structural schematic view of a fork of the clamping device for moving a pressing block. 
         FIG. 4  is a structural schematic view of a pressing block of the clamping device for pressing the working element to a flange portion of a fastening piece. 
         FIG. 5  is a schematic view of an output shaft mounted with a locking assembly thereon, wherein a spring is mounted on one end of the locking member such that the locking member can be floated. 
         FIG. 6  is a sectional view of the power tool in  FIG. 1  but another form of the pressing block is utilized. 
         FIG. 7  is a structural schematic view of the pressing block in  FIG. 6 . 
         FIG. 8  is a schematic view of the power tool in  FIG. 1 , but another form of spanner is utilized. 
         FIG. 9  is a schematic view of the exterior of the power tool in  FIG. 8 . 
         FIG. 10  is an axonometric view of the power tool according to a second example of the present disclosure, illustrating a head area for driving and clamping the working element. 
         FIG. 11  is a sectional view of the power tool in  FIG. 10 , wherein the working element is in a state of being clamped by the clamping device, and at the same time, the locking member is at a first position to lock the protruding shaft of the fastening piece. 
         FIG. 12  is a sectional view of the power tool in  FIG. 10 , wherein the working element is in a state of being released by the clamping device, and at the same time, the locking member is at a second position to release the protruding shaft of the fastening piece. 
         FIG. 13  is an exploded view of parts of the locking assembly of the power tool in  FIG. 10  which can axially lock the fastening piece. 
     
    
    
     DETAILED DESCRIPTION 
     Next, various examples of the power tool according to the present disclosure will be further explained with reference to the drawings. 
     A First Example 
     As shown in  FIGS. 1 ,  2  and  6 , the present disclosure will be illustrated with a power tool  100  as an example which drives a working element  1  in an oscillating manner. A power output shaft  6  of the power tool  100  is supported by bearings and sways back and forth about its axis Y with a small deflection angle and a high frequency under the action of a vibration bracket  5 . The power output end of the output shaft  6  is connected with a clamping device  200  for clamping a working element  1 . The clamping device  200  comprises a fastening piece  8 , a pressing block  4  cooperating with the fastening piece  8  to clamp the working element  1 , and a locking assembly for locking the fastening piece  8 . The fastening piece  8  is configured to have a flange portion  82  able to clamp the working element  1  and have a protruding shaft  81  substantially perpendicular to the flange portion  82 . 
     The locking assembly comprises a locking shaft  10 ′, a locking member  12 ′ and steel balls  14 , wherein the upper end of the locking shaft  10 ′ is connected with the output shaft  6 , the shaft-core portions of the locking shaft  10 ′ and the output shaft  6  are configured to have a hollow cavity  61  for receiving the protruding shaft  81 . The protruding shaft  81  can be inserted into the cavity  61  and clamped or released by the locking assembly. The output shaft  6 , the locking shaft  10 ′ and the protruding shaft  81  locked in the cavity  61  have a common axis Y. The protruding shaft  81  is provided with a toothed portion  85  thereon, and the locking member  12 ′ is provided with a matching toothed portion  123  mated with the toothed portion  85  on the protruding shaft  81 ; a pressing block  4  is arranged out of the locking shaft  10 ′ and the inner surface of the pressing block  4  is provided with a groove  43  for the steel balls  14  falling into or sliding out. The locking member  12 ′ can move radially under action of the steel balls  14 . When the steel balls  14  are placed within the groove  43 , the steel balls  14  can partially protrude out of the inner surface of the pressing block  4 , and when they slide out of the groove  43 , they can abut against the locking member  12 ′ and press the locking member  12 ′ onto the protruding shaft  81 . The groove  43  is provided with an inclined plane for the steel balls  14  sliding in or out conveniently. It can be easily understood that, in other examples, the steel balls  14  also can be replaced by the cylindrical pins, and the above groove  43  also can be substituted by other structures such as an inclined plane, a stepped plane and the like, as long as it can achieve an height difference in the direction perpendicular to the radial direction of the protruding shaft  81 . It also could be easily known for a person of ordinary skill in the art that, the above inclined plane also can be configured as the shape with the function of self-locking for enhancing reliability of the inclined plane. 
     The upper end of the pressing block  4  is provided with a spring  3 . Under action of the spring  3 , the pressing block  4  is biased toward the flange portion  82  of the fastening piece  8 . The pressing block  4  is provided with a flange  42  thereon. A shifting end  152  of the fork  15  rotatable about a pivot shaft (the axis X is substantially perpendicular to the axis Y) can abut against the lower surface of the flange  42  so that the pressing block  4  can be pushed to overcome the force of the spring  3  to move away from the flange portion  82 . The shifting fork  15  is hingedly supported on the housing  7  by a shaft  153 , and a cam spanner  2  acts on an end  151  opposite to the shifting end  152 . The clamping device  200  can be easily manipulated by arranging an operation handle of the cam spanner  2  out of the housing  7 . Further, the housing  7  is provided with a limit pin  18  for preventing the cam spanner  2  from excessive rotation. It can be easily understood that, in other examples, the flange  42  also can be replaced by other structures such as a recess, a stop block and the like, which also can achieve the function that the pressing block  4  moves along the direction to overcome the force of the spring  3  under the action of the fork  15 . 
     As shown in  FIG. 5 , a spring  19  is axially placed in the holes of the locking member  12 ′. With reference to  FIG. 2 , the other end of the spring  19  abuts against the inner end surface of the locking shaft  10 ′. The axial height of the locking member  12 ′ is slightly smaller than that of the installation space thereof, thus, under the action of the force of the spring  19 , the locking member  12 ′ can be slightly displaced in the axial direction and its function is that: when the teeth of the locking member  12 ′ do not engage with the teeth of the protruding shaft  81  exactly, the locking member  12 ′ can be floated axially such that the teeth are engaged exactly. 
     With reference to  FIGS. 1 ,  6  and  7 , the projections  105  for transferring torque and driving the working element  1  to deflect can be arranged on the retaining end surface of the locking shaft  10 ′ corresponding to the flange portion  82  of the fastening piece  8  and also can be arranged on the pressed end surface  44  of the pressing block  4 . In this example, the pressing block  4  is enclosed outside of the locking shaft  10 ′ by a biasing position in such a manner that the pressing block  4  and the locking shaft  10 ′ can&#39;t rotate relative to each other. Moreover, the working element  1  can be clamped between the pressed end surface  44  of the pressing block  4  and the flange portion  82  of the fastening piece  8 . 
       FIGS. 8 and 9  illustrate another example, wherein the pressing block  4  can be manipulated to move. By pulling a big spanner  2 ′, an eccentric shaft  16  can be rotated along therewith and act on the pressing block  4  by the convex surface  161  having different center distances and arranged on the eccentric shaft  16 , so as to achieve the purpose that the pressing block  4  moves in the direction of the axis Y to release and clamp the working element  1 . While clamping the working element  1 , the convex surface  161  of the eccentric shaft  16  disengages from the pressing block  4 , and the pressing block  4  biases toward the working element  1  under the action of the force of the spring  3 . While releasing the working element  1 , the convex surface  161  of the eccentric shaft  16  moves upward against the pressing block  4 , and then the working element  1  can be taken down when the spring force exerted on the working element  1  is withdrawn. 
     In order to prevent the fastening piece  8  from disengaging from the clamping device  200  in a free-falling state when the protruding shaft  81  of the fastening piece  8  is loosened by the locking member  12 ′, a disengagement-proof element  17  such as a damping rubber ring, an elastic piece and the like can be arranged on the inner wall of the cavity of the locking shaft  10 ′. The disengagement-proof element  17  also can be a magnetic element and further can be arranged on the retaining end surface of the locking shaft  10 ′ that is used for mating with the flange portion. 
     In this example, the output shaft  6  and the locking shaft  10 ′ are press-fitted together in such a manner that they can&#39;t rotate relative to each other, which facilitates the manufacturing and assembling of the clamping device. In other examples, the output shaft  6  and the locking shaft  10 ′ also can be integrally formed by the same shaft. 
     According to the above examples the manner of manipulating the power tool to clamp or release the working element will be described as follows. 
       FIG. 1  is a schematic view illustrating the clamping device  200  in the clamped state. A short diameter eccentric surface of the cam spanner  2  abuts against one end  151  of the fork  15 , and at the same time, the shifting end  152  opposite to the end  151  is in the state of disengaging from the flange  42  of the pressing block  4 . Accordingly, under the action of the force of the spring  3 , the pressing block  4  biases toward the working element  1 , and meanwhile the downward movement of the pressing block  4  pushes the steel balls  14  to press toward the locking member  12 ′ such that the matching toothed portion  123  of the locking member  12 ′ engages with the toothed portion  85  of the protruding shaft  81 , thus, the protruding shaft  81  is limited in the axial direction (i.e. the direction of the axis Y) and further the working element  1  is clamped between the flange portion  82  of the fastening piece  8  and the pressing block  4 . 
       FIG. 2  is a schematic view illustrating the clamping device  200  in the released state. The cam spanner  2  is shifted to one end  151  of the fork  15  toward which the long diameter eccentric surface of the cam spanner  2  is pressed, then the shifting end  152  opposite to the end  151  abuts against the flange  42  of the pressing block  4  so as to lift the pressing block  4 . With the upward movement of the pressing block  4 , the force exerted on the working element  1  is withdrawn, and the groove  43  arranged on the pressing block  4  is just moved to the position corresponding to the steel balls  14  with the upward movement of the pressing block  4 . At this time, the fastening piece  8  is pulled downwardly so that the two locking members  12 ′ can be separated radially. Simultaneously, the two steel balls  14  roll into the groove  43  of the pressing block  4  to vacate the space for radially opening the locking member  12 ′, such that the toothed portion  85  of the protruding shaft  81  of the fastening piece  8  disengages from the matching toothed portion  123  of the locking member  12 ′. In this way, the fastening piece  8  can be pulled out successfully and then the working element  1  can be removed therefrom. 
     A Second Example 
     As shown in  FIGS. 10 to 14 , a power output shaft  6  of a power tool  100  is supported by the bearings and sways back and forth about its axis Y with a small deflection angle and a high frequency under the action of a vibration bracket  5 . The power output end of the output shaft  6  is connected with a clamping device  200  that is used for clamping a working element  1 . The clamping device  200  comprises a fastening piece  8 , a pressing block  4  for cooperating with the fastening piece  8  to clamp the working element  1 , and a locking assembly for locking the fastening piece  8 . The fastening piece  8  is configured to have a flange portion  82  able to clamp the working element and have a protruding shaft  81  substantially perpendicular to the flange portion  82 . 
     The locking assembly comprises a locking shaft  10 , a slidable sleeve  11  and a locking member  12 , wherein the locking shaft  10  is configured as a hollow member in which the hollow cavity  61 ′ is used for receiving the protruding shaft  81 , and the upper end of the locking shaft  10  is connected with the output shaft  6 . The output shaft  6 , the locking shaft  10  and the protruding shaft  81  locked in the locking shaft  10  have a common axis Y. The locking shaft  10  is further provided with a first grooves  102  and  102 ′ which are mated with the locking member  12  and have a first end  103  near the axis Y and a second end  104  away from the axis Y. In the present example, the first grooves  102  and  102 ′ are arranged as slanted grooves which form an angle with the axis Y and have a self-locking function. The slidable sleeve  11  is enclosed outside of the locking shaft  10  and can slide along the direction of the axis Y and is provided with second grooves  111  and  111 ′ mated with the locking member  12 . 
     In this example, the locking member  12  includes two rollers arranged symmetrically relative to the axis Y, which are provided with a mounting portion  121  and a clamping portion  122 , wherein the mounting portion  121  is simultaneously mated with the first grooves  102 ,  102 ′ and the second grooves  111 ,  111 ′ and the clamping portion  122  is mated with a flat plane  84  on the protruding shaft  81 . When the slidable sleeve  11  moves toward the direction of the axis Y, the locking member  12  is driven by the second grooves  111 ,  111 ′ to move between the first end  103  and the second end  104  of the first grooves  102 ,  102 ′. When the locking member  12  is placed on the first end  103  of the first grooves, the protruding shaft  81  of the fastening piece is clamped so as to lock the fastening piece  8  axially. When the locking member  12  is placed on the second end  104  of the first grooves, the protruding shaft  81  of the fastening piece is loosened so that the fastening piece  8  can be taken out of the locking shaft  10 . 
     The clamping device  200  further comprises an operation spanner  2 ″ for moving the pressing block  4 , wherein the operation spanner  2 ″ is mated with a first spring  3  such that the pressing block  4  can be moved along the direction of the axis Y. One end of the first spring  3  can be placed in the circular groove  41  arranged on the pressing block  4 . The spanner  2 ″ is pivotably connected to a housing  7  about the pivot shaft  22  and surrounds outside of the pressing block  4  in the form of fork. Front and rear fork arms  25  of the spanner  2 ″ are respectively provided with a protruding column projecting out of the inner surface thereof. In the present example, the protruding column is provided by the pin column  21  that is pressed into the spanner via an interference-fit. In other examples, the protruding column also can be formed on the spanner directly, and one end of the pin column  21  projects out of the inner surface of the fork arm  25  and can cooperate with the flange  42  arranged on the pressing block  4 . A third spring  23  is provided between the spanner  2 ″ and the housing  7 . When the working element  1  is clamped and vibrates with deflection, the third spring  23  pushes the spanner  2 ″ to rotate about the pivot shaft  22  such that the pin columns  21  disengages from the flange  42 , accordingly, it can ensure the output of vibration of the tool can not be delivered to the spanner  2 ″. The spanner  2 ″ and the housing  7  are respectively provided with limiting structures  24 ,  71  for cooperating with the third spring  23  such that the spanner  2 ″ is suspended at a certain angle about the pivot shaft  22 . 
     In the present example, a boss  83  is formed on the flange portion  82  for transferring torque and driving the working element  1  to sway with deflection. In other examples, the boss for transferring torque also can be arranged on the end surface of the locking shaft mated with the flange portion of the fastening piece, or arranged on the end surface of the pressing block cooperated with the flange portion of the fastening piece. 
     Referring to  FIGS. 11 and 12 , according to the above second example, the course for operating the power tool to clamp or release the working element will be described as follows. 
     The course to install the working element is that: 
     At first, the spanner  2 ″ is lifted upwardly and rotates about the pivot shaft  22 . Accordingly, the pin columns  21  push the pressing block  4  to move upwardly. Gradually, one end of the pressing block  4  contacts with the slidable sleeve  11  and then pushes the slidable sleeve  11  to move upwardly. Subsequently, the roller-shaped locking member  12  can move upwardly along the inclined first grooves  102 ,  102 ′ on the locking shaft  10  and the two locking members  12  are separated from each other. At this time, the fastening piece  8  together with the working element  1  can be manually pressed onto the retaining end surface of the pressing block  4 . 
     Then, the spanner  2 ″ is released, the slidable sleeve  11  moves downwardly under the action of the second spring  13  and drives the locking member  12  to clamp the protruding shaft  81  of the fastening piece  8 , so that the fastening piece  8  is axially fixed. Further, the pressing block  4  continues to move downwardly under the action of the first spring  3  to press the working element  1  onto the clamping flange portion of the fastening piece  8 . 
     The course to uninstall the working element is that: 
     At first, the spanner  2 ″ is lifted upwardly and rotates about the pivot shaft  22 . Accordingly, the pin column  21  pushes the pressing block  4  to move upwardly so that the first spring  3  is compressed and the clamping force exerted on the working element  1  is withdrawn. Gradually, one end of the pressing block  4  contacts with the slidable sleeve  11  and then pushes the slidable sleeve  11  to move upwardly. Subsequently, the roller-shaped locking member  12  can move upwardly along the first inclined grooves  102 ,  102 ′ on the locking shaft  10  and the two locking members  12  are separated from each other, so that the clamping force exerted on the protruding shaft  81  is withdrawn, and at the same time the protruding shaft  8  can be taken out of the locking shaft  10  so that the fastening piece  8  and the working element  1  can be taken down. 
     After the spanner  2 ″ is released, the slidable block  11  is restored under the action of the second spring  13  and the pressing block  4  is restored to the position set by a retainer ring  9  under the action of the first spring  3 , wherein the retainer ring  9  is arranged on the locking shaft  10 .