Patent Publication Number: US-2007108250-A1

Title: Fastening element feeding device for a hand-held power drive-in tool

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a hand-held power drive-in tool including a drive-in channel having a receptacle for receiving fastening elements stored in a magazine, and in particular, to a fastening element feeding device for such a drive-in tool and having a transporting device for transporting the fastening elements into the receptacle.  
      2. Description of the Prior Art  
      Fastening element feeding devices for hand-held power drive-in tool such as, e.g., screwdriving tools or setting tools serve for feeding fastening elements such as, e.g., screws, nails, bolts and the like into a drive-in channel of a drive-in tool in which a drive-in working tool is displaceable. The fastening elements are stored in a magazine attached to the drive-in tool, with the fastening elements being lined up parallel to each other on an elongate carrier material (e.g., strip, wire, or plastic strip) and forming a rigid or flexible string-shaped connection. With a flexible strip, the strip can be coiled-up to form a roll so that a so-called coil magazine is provided on the drive-in tool.  
      German Utility Model DE 203 09 492 U1 discloses a screwdriving tool with a screw feeding device and which has a holder provided on a housing flange of the screw-driving tool. A screw guide is arranged on the holder with a possibility of displacement relative thereto, with its end, which faces in the operational direction of the drive-in tool, being placed against the workpiece. On the screw guide, a swivel disc is supported on which a pawl is provided. The pawl has an arm that extends from the swivel disc and carries at its opposite end a fixing pin. The pin extends through a first arc-shaped opening of a link of a drive block and extends through a guideway in the holder. When the screw guide is pressed into the holder upon the screwdriving tool being pressed against a workpiece, the fixing pin is displaced along the guideway, with the pawl being pivoted by the arc-shaped opening. This causes the displacement of screws through the screw guide and toward the screwdriver.  
      The drawback of the above-described solution consists in that the operational energy for the transportation of the screw strip must be provided by the user, which adversely effects the user&#39;s comfort during the operation. Another drawback consists in that the screws should be spaced from each other on the screw strip by the same distance because the transportation path over the swivel disc is always the same. Therefore, only fastening elements having a certain diameter can be used.  
      U.S. Pat. No. 6,422,447 discloses a fastening device for driving a fastening element in a workpiece that includes a drive-in mechanism located in the housing. The drive-in mechanism includes a striker for the fastening element. The fastening device has a nose assembly placeable on the workpiece and displaceable relative to the guide of the fastening device. A transportation device feed a fastening element from a magazine with fastening elements to the nose assembly before the fastening element is driven by the striker into the workpiece. The transportation device uses, directly or indirectly, the press-on energy with which the user presses the fastening device against the workpiece.  
      The drawback of the fastening device of the U.S. patent consists in that the operational energy for transporting a fastening element is again provided by the user, which creates discomfort for the user. Here again, the fastening elements must be spaced from each other by the same distance in the magazine strip because the displacement path, over which a fastening element is transported is always the same. Therefore, only fastening elements having a certain diameter can be used.  
      Accordingly, an object of the present invention is to provide a hand-held power drive-in tool with a fastening element feeding device in which the above-discussed drawbacks of the known drive-in tools are eliminated and which insures a wide flexibility in its use.  
     SUMMARY OF THE INVENTION  
      This and other objects of the present invention, which will become apparent hereinafter, are achieved by electrically driving the transporting device of the fastening element feeding device. As a result, the energy for transporting fastening elements need not be provided by the user but can be supplied in very simple manner from a battery, an accumulator, or a network. In most of the drive-in tools, such an electrical power source is already available because a drive-in power tool is already driven by an electrical main drive. Therefore, no additional costs are involved for providing the electrical energy. A further advantage consists in the flexibility of the electrical drive that can be provided at different points along the length of the displacement or transportation path and, therefore, permit transportation of fastening elements having different diameters.  
      According to an advantageous embodiment of the present invention, the electric drive of the transportation device is located in the tool housing and can also be used for driving the drive-in tool.  
      Advantageously, the electrical drive of the transporting device is controlled by an electronic control unit, which provides for a timely and position-precise transportation of the fastening elements.  
      Advantageously, there is provided means for detecting an object in the receptacle of the drive-in channel, which is connected to the control unit. This measure permits to communicate to the control unit a signal that a fastening element, which is fed by the transporting device, has been received in the receptacle, so that the control unit can turn off the electric drive of the transportation device. Thereby, the control unit can also recognize when the receptacle is empty and is ready to receive another fastening element for a new drive-in process. The detecting means also permits to recognize failed positions of the drive-in working tool. E.g., the detecting means permits to determine when a driving piston of a setting tool has not completely returned in is initial position after completion of a drive-in process and, therefore, blocks the receiving space. In this case, the control unit would block the displacement of a fastening element by the transporting device until the failed position of the drive-in working tool is eliminated, and the receptacle becomes free.  
      Instead of or in addition to the detection means, means, e.g., for determining the distance between two adjacent fastening elements in the magazine can be also provided, which also would be connected with the control unit. Based on the data communicated by this means, the control unit can calculate the necessary displacement of the fastening element by the transporting device and turn off automatically the electric drive of the transporting device after a fastening element has been displaced, without receiving a turn-off signal of a detecting device.  
      According to a technically low-cost solution, the detecting means is formed as a capacity sensor. Alternatively, other switching means or sensors can be used such as, e.g., photosensors or electromechanical switches.  
      Advantageously, the electric drive is formed as a servo motor that can be driven in different directions and that is particularly suitable to be controlled by the electronic control unit, and that further provides for a rapid sequence of alternative displacement steps. Of course, other electrical drives such as, e.g., unidirectional motors, solenoids, or the like can be used.  
      Advantageously, the servo motor is connected with a transporting member elastically pivotable in a direction opposite a displacement direction of the transporting device. In this way, the transportation displacement of the electric drive can be transmitted to the magazine strip with fastening elements in a technically low-cost manner. A transporting member which is, e.g., formed as a claw, can easily engage the magazine strip or a separate fastening element. Because of the pivotability of the transporting member in the direction opposite the transportation direction of the transporting device, the transporting member can be easily displaced by the electric drive in the opposite direction past the magazine strip for engaging the following fastening element to subsequently transport it.  
      Alternatively, the transporting member can be formed, e.g., as a transporting or split gear driven by an electric drive formed as a servo drive.  
      The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS:  
      The drawings show:  
       FIG. 1 a  side partially cross-sectional view of a hand-held drive-in tool formed as a setting tool and equipped with a fastening element feeding device according to the present invention;  
       FIG. 2 a  cross-sectional view of the fastening element feeding device shown in  FIG. 1  along line II-II in  FIG. 1 ;  
       FIG. 3 a  cross-sectional view of the fastening element feeding device shown in  FIG. 2  at an increased, in comparison with  FIG. 2 , scale; and  
       FIG. 4 a  cross-sectional view of a hand-held drive-in tool formed as a screwdriving tool and equipped with a fastening element feeding device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIGS. 1 through 3  shows a hand-held power drive-in tool designated generally with reference numeral  20  which is equipped with a fastening element feeding device according to the present invention and designated generally with a reference numeral  10 . The drive-in tool  20  includes a housing  21  in which there is arranged a drive of the drive-in tool, not shown in the drawing. The drive-in tool  20 , which is shown in  FIGS. 1-3 , is formed as a setting tool with which a fastening element  41  is driven in a workpiece with a drive-in working tool  15  that is formed as a driving ram or a driving piston. The drive-in piston can be driven in per se known manner, e.g., by expandable gases (combustion gases, compressed air, etc.) or electrically, e.g., by an electrically driven flywheel. The drive-in tool  1  is displaceable in a drive-in channel  12  having a receptacle ( 118 ) for the fastening element  41 .  
      On a head portion  11  of the drive-in tool  20 , there is arranged a magazine  40  formed as a coil magazine which forms part of the fastening element feeding device  10  and which carries fastening elements  41  in form of nails arranged in a magazine strip  42 .  
      The fastening element feeding device  10  forms an integral part of the drive in tool  20 . However, the fastening element feeding device  10  can also be formed as a separate unit and replaceably secured on a flange of the drive-in tool  20 , e.g., with a coupling section.  
      The transporting device  30  of the fastening element feeding device  10  is located adjacent to the magazine  40  and is designed for displacing the magazine strip  42 . The transporting device  30  includes an electric drive  31  which is formed as a servo mechanism having a drive shaft  32  on which a transporting member  33  is arranged. The transporting member  33  extends into a guide space  43  of the magazine  40  for the magazine strip  42 . The transporting member  33  is formed as an elastically pivotable pawl which is held by a spring  39  in a position in which it projects radially a way from the shaft  32  of the drive  41 .  
      In the region of the receptacle  18 , there is arranged object detection means  13  for detecting objects such as a fastening element  41  or the drive-in working tool  15 . The object detection means  13  is formed as a capacity sensor that is connected by a first conductor  14  with a control unit  35 . The detection means  13  detects presence or absence of a fastening element  41  or the drive-in working tool  15  in the receptacle  18  and communicates a corresponding signal to the control unit  35  over the first conductor  14 . The control unit  35  and other electrical components, which are associated with the control unit  35 , are supplied with electrical energy from a voltage source  16  such as, e.g., at least one battery or at least one accumulator, over a second conductor  17 . The electric drive  31  is supplied with electrical energy from the voltage source  16  via a third conductor  34 . A fourth conductor  36  connects the control unit  35  with the electric drive  31  for controlling the same. The drive-in tool  20  is further equipped with optical and/or sound signal means  37  that is are connected with the control unit  35  by a fifth conductor  38 .  
      In the embodiment of the drive-in tool  20  shown in  FIGS. 1-3 , the electric drive  31 , the voltage source  16 , and the control unit  35  are all arranged in the housing  21  of the drive-in tool  20 . It is, however, possible to arrange them directly in an independent fastening element feeding device  10  such as e.g., a magazine unit mountable on a drive-in tool.  
      The transportation of the fastening element  41  with the transporting device  30  in the fastening element feeding device  10  takes place after a fastening element  41  has been driven in a workpiece (not shown in the drawings. The drive-in working tool  15  is then displaced from the receptacle  18  which is detected by the detection means  13 , and a corresponding signal is transmitted to the control unit  35  over the first conductor  14 . As shown in  FIG. 3 , the electric drive  31  displaces the transporting member  33 , under control of the control unit  35 , in the direction of arrow  53 , shown with dash lines, in a first position  51 , and the transporting member  33  pivots past a fastening element  41 . 1  against the biasing force of the spring  39 . After reversal of the drive direction of the electric drive  31  by the control unit  35 , the transporting member  33  engages the fastening element  41 . 1  from behind, and the fastening element  41 . 1  is transported by the transporting member  33  in the direction of arrow  54  over a path shown in  FIG. 3  by angle “a,” with the transporting member  33  being displaced to a second position  52 . In the second position  52  of the transporting member  33 , a new fastening element  41 . 2  is located in the receptacle  18  of the drive-in channel  12 .  
      The presence of the fastening element  41 . 2  in the receptacle  18  is detected by the detection means  13  and communicated to the control unit  35 . A further drive-in process can be effected with the drive-in tool  20 . When there is no fastening element  41  to be transported by the transporting member  33 , the transporting member  33  idles, in response to which, the control unit  35  actuates the signal means  37  that generates an optical and/or acoustic signal. Another signal can be generated by the signal means  37 , under control of the control unit  35 , when the receptacle  18  is not empty after a completion of a drive-in process, e.g., when the drive-in working tool  15  is not withdrawn, as required by a proper operation of the drive-in tool  20 .  
      The angle “a” that defines the transportation path, can have different values which depend on the distance of the fastening elements  41  to each other and/or on their diameter.  
      Alternatively or in addition to the detection means  13 , there can be provided a detection device that senses the distance between two fastening elements  41  in the magazine strip  42  and which is transmitted to the control unit  35  which, based on these data, predetermined the transportation width.  
      The fastening element feeding device  10 , which is shown in  FIG. 4 , is mounted on a drive-in tool  20  formed as a screw-driving tool and differs from that described above only in that the drive-in working tool  15  displaceable in the drive-in channel  12  is formed as a screwdriver.  
      Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as limitations thereof and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.