Patent Publication Number: US-8978951-B2

Title: Auto hammer

Description:
RELATED APPLICATION INFORMATION 
     This application claims the benefit of CN 201120093131.0, filed on Mar. 29, 2011, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present disclosure relates to a power tool and, more particularly, to an auto hammer for striking a fastener such as a nail. 
     An auto hammer is a commonly used hand-held tool, which has various types. According to the power source, the auto hammer can be divided into two types: pneumatic and electric. The pneumatic auto hammer must be equipped with an air compressor as a power supply, thus the use of the pneumatic auto hammer is limited in some occasions. The electric auto hammer comprises a transmission mechanism for converting the rotating motion of a motor into the linear motion of an impact rod arranged in a nozzle. When a switch on the auto hammer is turned on, the electric power energy is converted into the mechanical energy of the reciprocating motion. 
     Both U.S. Pat. No. 6,431,430 and PCT Publication No. WO 2006/008546 disclose an electric auto hammer powered by a battery pack. The described electric auto hammer comprises a slider-crank mechanism for converting the rotating motion into the linear motion. However, one disadvantage of the described auto hammer is that the slider-crank mechanism substantially performs the push actions, but not the strike actions. The efficiency of such push actions is much lower than that of the strike actions when the auto hammer is provided with the same motor power. Another disadvantage is that the stroke of a pushing rod driven by the slider-crank mechanism is a constant, so when the nail meets a hard object, the resistance force produced thereby may cause the rotor of the motor to be locked. A further disadvantage is that the motor is arranged in front of or behind the handle so that the connection between the motor and the transmission mechanism takes a lot of space which make the auto hammer relatively larger and inconvenient for a user to operate and carry. 
     Chinese Patent No. 1769010 discloses an auto hammer which comprises a rack and pinion mechanism for converting the rotating motion of a motor into the biasing force of a compression spring, and then the compression spring is released by a releasing mechanism to produce a striking force. The described auto hammer can carry out a single-strike action under the spring force, but not a continuous strike action. So the work efficiency is still relatively low, and the auto hammer cannot be used frequently. Furthermore, the motor is arranged in a housing below a head and separated from a handle, thus the structure of the auto hammer is still not compact. 
     SUMMARY 
     To overcome the limitations and disadvantages noted above, the following describes an auto hammer which has a compact structure, a small size, and one which can be easily gripped. More particularly, the following describes an auto hammer having a motor arranged in a housing, a striking device arranged in a nozzle portion of the housing and a transmission mechanism for converting the rotating motion of the motor into the striking motion for the striking device, wherein the transmission mechanism includes a striking assembly for exerting a striking motion onto the striking device, and the striking assembly further includes a rotational driving member and a rotational striking member enclosing the rotational driving member, and the rotational striking member is provided with at least one striking portion for striking and contacting the striking device. The auto hammer also has a gripping portion suitable for palm-gripping that is arranged on the back side of the housing opposite to the striking device, and the motor is arranged on the same side as the striking assembly relative to the axis of the reciprocating linear motion of a striking shaft of the striking device. 
     Further, the auto hammer also includes a battery pack for supplying power to the motor, and the battery pack and the motor are arranged on the same side of the striking device. 
     Further, the battery pack is arranged parallel to the motor. 
     Alternatively, the auto hammer further includes a battery pack for supplying power to the motor, and the battery and the motor are arranged on the two opposite sides of the striking device respectively. 
     Further, the battery pack is arranged substantially parallel to the striking device. 
     By adjusting the relative position between the battery pack, the motor and the striking device, for example, as compared with such an arrangement in which the battery pack is provided coaxially behind the motor and where the device has a long gripping handle, the subject auto hammer significantly reduces the length of the whole auto hammer by arranging the battery pack parallel to the motor, so that the subject auto hammer is small and portable. In addition, the gripping portion is arranged on the back side of the housing opposite to the striking device, so that it can be gripped more comfortably; meanwhile, the striking assembly and the motor are arranged on the same side of the striking device, which is helpful for striking the nails at a corner position of the work piece. 
     As will become apparent, the auto hammer described hereinafter includes one or more of the following: 
     The rotational driving member is provided with an actuating portion for driving the rotational striking member to rotate, and the rotational striking member is provided with a linkage portion which can mate with the actuating portion and move in the direction of the rotating axis of the striking assembly relative to the actuating portion. 
     The actuating portion is configured as a groove or a projection, and the linkage portion is configured as a projection or a groove which can correspondingly mate with the groove or the projection of the actuating portion. 
     The rotational driving member and the rotational striking member are respectively formed with corresponding grooves with an engaging member mounted therein. 
     The rotational driving member is provided with a pair of slant grooves, and the rotational striking member is provided with a pair of guide grooves corresponding to the pair of slant grooves. 
     The rotational striking member has a hollow portion and encloses the rotational driving member via the hollow portion. 
     The rotational striking member is provided with a protruding shaft portion which is enclosed into the hollow portion of the rotational driving member. 
     The transmission mechanism also includes a transmitting portion for vertical turning. 
     An output gear of the transmitting portion is connected fixedly with or integrally made with the rotational driving member. 
     With the above arrangements, the subject auto hammer has a compact structure, small size, comfortable gripping and good portability while allowing the device to be used to strike fasteners, such as nails, etc., periodically and continuously. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary auto hammer constructed according to the description that follows; 
         FIG. 2  is a view illustrating the inner structure of the auto hammer in  FIG. 1  with half of the housing removed; 
         FIG. 3  is a sectional view of the auto hammer in  FIG. 2  along a plane perpendicular to the view of  FIG. 2 ; 
         FIG. 4  is a perspective view of a rotating shaft shown in  FIG. 3 ; 
         FIG. 5  is a perspective view of a striking wheel shown in  FIG. 3 ; 
         FIG. 6  is a view of the rotating shaft and the striking wheel shown in  FIG. 3  as assembled together; 
         FIG. 7  is a sectional view of the auto hammer in  FIG. 2  along a plane perpendicular to the view of  FIG. 2  showing a further embodiment; 
         FIG. 8  is a perspective view of a rotating shaft as shown in  FIG. 7 ; 
         FIG. 9  is a view of the rotating shaft and a striking wheel as shown in  FIG. 7  as assembled together and in a first position; 
         FIG. 10  is a view of the rotating shaft and a striking wheel as shown in  FIG. 7  as assembled together and in a second position; 
         FIG. 11  is a view of the auto hammer in  FIG. 2  along a plane perpendicular to the view of  FIG. 2  showing a still further embodiment wherein a housing, a motor and a part of a transmission mechanism are removed; 
         FIG. 12  is a perspective view of the device shown in  FIG. 11  partially sectioned; 
         FIG. 13  is a perspective view of the auto hammer wherein the battery pack, the motor, the transmission mechanism and the striking device are arranged in a first position; 
         FIG. 14  is a perspective view of the auto hammer wherein the battery pack, the motor, the transmission mechanism and the striking device are arranged in a second position; and 
         FIG. 15  is a perspective view of the auto hammer wherein the battery pack, the motor, the transmission mechanism and the striking device are arranged in third position. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be explained in details with reference to the drawings. 
     As shown in  FIG. 1 , an auto hammer  1  includes a housing  3  which consists of two half-housings. The housing  3  has a body portion which forms a gripping handle  31  in the longitudinal direction. A switch  6  is mounted on the gripping handle  31  for turning on/off a motor arranged in the housing  3 . A battery pack  5  is mounted on the lower end of the housing  3 . A nozzle portion  4  is provided on a head portion  32  on the upper end of the housing  3  for receiving a striking device  7  for striking a fastener such as a nail. 
     In the present embodiment, the battery pack  5  is substantially coaxial with the gripping handle  31 . The casing of the battery pack  5  is adjacently smooth to, e.g., aligned with, the housing  3 . At least a portion of the battery pack  5  is inserted into the housing  3 , so that the connection between the battery pack  5  and the housing  3  is more stable. In other embodiments, the battery pack  5  can be arranged parallel or perpendicular to a longitudinal axis of the gripping handle  31 . The auto hammer  1  is not limited to be supplied by the battery pack, and an AC power supply is feasible. 
       FIG. 2  shows a view of the inner structure of the auto hammer  1 . A motor  2  is arranged in the housing  3 . The rotating motion of the motor  2  is converted into the impact motion for the striking device  7  by a transmission mechanism  10 . The transmission mechanism  10  includes a gear transmission portion  10  which rotates and an impact assembly  8  for impacting the striking device  7 . The striking device  7  includes a striking shaft  9  which performs linear reciprocating motions. Referring to  FIG. 3-7 , the impacting assembly  8  includes a rotating shaft  11  and a striking wheel  12  which have the same rotating axis X. The rotating shaft  11  is supported in the head portion  32  of the housing  3  via the bearings on the two ends. The rotating shaft  11  is driven to rotate by a pair of bevel gears  101  and  102 . In the present embodiment, the rotating shaft  11  is connected fixedly to the big bevel gear  102 . In other embodiments, referring to  FIGS. 11 and 12 , the rotating shaft  11  can be integrated with the big bevel gear  102 . The striking wheel  12  has a plate shape and encloses the rotating shaft  11  via a hollow portion. The striking wheel  12  is provided with at least one striking portion  121 , preferably two striking portions  121  which are arranged symmetrically relative to the rotating axis X and protruded outwards from the outer circumference of the striking wheel  12 . During the rotation of the striking wheel  12  driven by the rotating shaft  11 , the striking portion  121  of the striking wheel  12  strikes a struck portion of the striking shaft  9  continuously and periodically. Thereby the front end of the striking shaft  9  strikes a fastener such as a nail continuously and periodically, and the nail is struck gradually into a work piece to be processed. 
       FIG. 3-6  show views in which the rotating shaft  11  of the auto hammer drives the striking wheel  12  to rotate, and the periodic striking actions thus can be achieved. The striking wheel  12  encircles the rotating shaft  11 . The rotating shaft  11  is provided with a pair of slant grooves  111  at the engaging position with the striking wheel  12  which are oblique relative to the rotating axis X. Preferably, to facilitate assembling, one end of the slant groove  111  extends to one end surface of the rotating shaft  11 . Correspondingly, a pair of projections  122  is provided at the engaging position of the striking wheel  12  which can be engaged with the slant grooves  111  respectively. When the switch  6  is turned on initially, the projections  122  are positioned at the bottom of the slant grooves  111 , and the striking wheel  12  is driven to rotate by the rotating shaft  11 . While one of the striking portions  121  of the striking wheel  12  strikes the striking shaft  9 , the striking portion  121  is stopped by the striking shaft  9 , so that the rotation of the striking wheel  12  is blocked temporarily. However, the rotating shaft  11  still continues rotating, which forces the projections  122  to move in the slant grooves  111 . Thus the striking wheel  12  is driven to move axially towards an energy storage spring  13  and compress the spring  13  till the striking portion  121  of the striking wheel  12  staggering from the striking shaft  9 . Once the blocking of the striking wheel  12  by the striking shaft  9  is eliminated, the striking wheel  12  rotates at a speed in excess of the rotation speed of the rotating shaft  11  under the biasing force of the energy storage spring  13 , and the projections  122  are forced to move along the direction of the pushing force of the energy storage spring  13  in the slant grooves  111 , so that the position of the striking wheel  12  corresponds to the position of the striking shaft  9  again. When the other striking portion  121  strikes the struck portion of the striking shaft  9 , another striking action is accomplished. The above process will be repeated to strike the nail into the work piece. 
     In the present embodiment, the energy storage spring  13  is arranged in the housing  3 , and exerts a pushing force to the striking wheel  12  along the direction of the axis X. One end of the energy storage spring  13  abuts against one side of the striking wheel  12  directly or indirectly, and the other end abuts against a gasket  18  enclosing the rotating shaft  11 . The gasket  18  is positioned in the axis direction of the rotating shaft  11  by a retainer ring  19  embedded in an annular groove  20  of the rotating shaft  11 . In other embodiments, the retainer ring  19  can be replaced by an annular flange or shaft shoulder (not shown in the drawings) which is directly formed on the rotating shaft  11  and can serve as a stopper. 
       FIGS. 7-10  show another embodiment in which the rotating shaft  11  of the auto hammer drives the striking wheel  12  to rotate, and the periodic striking actions thus can be achieved. The operational principle of this embodiment is the same as the embodiment described above and, as such, need not be described in greater details herein. The difference only lies in that at the place where the rotating shaft  11  encircles the striking wheel  12 , the slant grooves and the projections mated with each other in the above embodiment are replaced with each other, that is, the slant grooves  123  are arranged in the striking wheel, while the projections  112  are arranged on the rotating shaft. 
     In the above two embodiments, the striking wheel  12  is formed with a hollow portion to encircle the rotating shaft  11 . However, the connecting form of the striking wheel  12  and the rotating shaft  11  of the present invention is not limited to the above two embodiments. For example, the striking wheel  12  is formed with a protruding shaft which is enclosed into a hollow portion of the rotating shaft. Correspondingly, the grooves and the projections mated with each other at the enclosing position are respectively arranged on the outer cylindrical surface of the protruding shaft and the inner cylindrical surface of the hollow portion of the rotating shaft, which can also achieve the object of the present invention. 
       FIGS. 11 and 12  show views of further another embodiment, in which the rotating shaft  11  of the auto hammer drives the striking wheel  12  to rotate, and the periodic striking actions thus can be achieved. The striking wheel  12  is provided with a protruding shaft portion  124  which is enclosed into a hollow portion  114  of the rotating shaft  11 . At the enclosing position, an inner cylindrical surface of the rotating shaft  11  and an outer cylindrical surface of the protruding shaft  124  are respectively formed with a pair of slant grooves  115  arranged oblique relative to the axis X and a pair of guide grooves  125 . The position of each guide groove  125  corresponds to that of each slant groove  115 . A pair of steel balls  14  is respectively arranged in a cavity formed by the slant groove  115  and guide groove  125 , and move with the change of the position of the cavity caused by the change of the relative position of the slant groove  115  and the guide grooves  125 . Then, when the rotating shaft  11  rotates, the striking wheel  12  can be driven to rotate as a result of the steel balls  14  arranged in the slant grooves  115  exerting a pressure to the guide grooves  125 . The energy storage spring  13  is mounted in the housing  3 , one end of which is fixed and the other end of which abuts against one side of the striking wheel  12 . The energy storage spring  13  exerts a pushing force to the striking wheel  12  in the axis direction of the striking wheel  12 , so that when the rotating shaft  11  and the striking wheel  12  are immobile or rotate without load, the steel balls  14  are located at the top of the slant grooves  115  and the bottom of the guide grooves  125 , and the striking wheel  12  is located in a first axial position relative to the rotating shaft  11 . When the motor is started, the striking wheel  12  rotates together with the rotating shaft  11  until the striking portion  121  of the striking wheel  12  strikes the striking shaft  9  to achieve a striking action to the striking shaft  9 . Meanwhile, because the end of the striking shaft  9  in contact with the striking wheel  12  would temporarily stop the further rotation of the striking wheel  12 , the striking wheel  12  is forced to move axially towards a second position compressing the energy storage spring  13  relative to the rotating shaft  11  under the interaction of the grooves  115 ,  125  and the engaging element (for example, the steel balls  14 ) therein. When the striking wheel  12  moves to stagger from the striking shaft  9  and disengages from blocking, it will rotate at a speed in excess of the normal rotation speed of the rotating shaft  11  under the action of the elastic potential energy released by the energy storage spring  13 , and move to the first position again, which causes the striking wheel  12  to strike the striking shaft  9  powerfully by its rotation potential energy again. 
       FIGS. 13-15  are views showing an appearance of the auto hammer of the present invention with a palm-shaped gripping portion and the inner structure of the auto hammer. The battery pack  5  and the motor  2  are arranged parallel to each other, so that the dimension of the auto hammer  1  in the longitudinal direction is reduced significantly while the dimension in the radial direction is broadened. Thus, the gripping portion is shifted from the long gripping handle  31  to the back gripping portion  31 ′ of the housing  3  opposite to the striking device  7 , and the gripping manner is changed from gripping with the palm surrounding the gripping handle  31  to palm-gripping with a majority of the palm flat-pressing on the back gripping portion  31 ′, thereby providing for more comfortable gripping. Further, the striking assembly  8  and the motor  2  are respectively arranged on two sides of an axis defined by the linear reciprocating motion of the striking shaft  9  of the striking device  7 , so that the centre of the gripping portion  31 ′ is closer to or passes through the axis of the reciprocating linear motion of the striking shaft  9  of the striking device  7 , which reduces the striking moment of the gripping portion  31 ′ and provides for more comfortable gripping which minimizes fatigue of an operator and which is therefore more suitable for longer operational times. Meanwhile, the arrangement results in a device that is more compact and more portable. When the auto hammer is gripped in the palm, the auto hammer  1  may be further provided with a band (not shown in the drawings) for tightly binding the hand of an operator to the back gripping portion  31 ′, which efficiently reduces the operating force on the wrist of the operator and the working intensity of the operation. 
     The battery pack  5  and the motor  2  of the present invention may also be arranged on opposite sides of the striking device  7  respectively, to enhance balance of the whole machine with respect to the working position where the striking shaft  9  of the striking device  7  strike the nail in a linear reciprocating motion. At this time, in order to enable the auto hammer  1  to have a smaller shape and be suited for gripping, the battery pack  5  can be arranged at an angle relative to the mounting axis of the motor  2 . Preferably, the battery pack  5  and the striking device  7  are arranged parallel to each other. 
     The motor  2  and the striking assembly  8  of the present invention may also be arranged on the same side of the striking device  7  so that the striking device  7  is closer to the head portion  32  of the housing  3 , thus it is more helpful for striking nails which are closer to the corners of a work piece. 
     The auto hammer of the present invention is not limited to the contents described in the above embodiments and the structure represented in the drawings. For example, one of the rotating shaft  11  and the striking wheel  12  can also rotate by enclosing a stationary shaft which is supported in the housing (not shown) by the bearings on the two ends of the stationary shaft. Anyway, the obvious changes, replacements and modifications to the shape and position of the components based on the present utility model are contained within the protection scope of the present utility model.