Patent Publication Number: US-8109123-B2

Title: Riveting unit for electric rivet gun

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an electric rivet gun, and more specifically to a riveting unit for an electric rivet gun that can prevent excessive backward movement of a clamping jaw for ensuring the normal operation of the electric rivet gun. 
     2. Description of the Related Art 
     A conventional electric riveter comprises a housing, a driving unit mounted in the housing, and a riveting unit having a transmission unit connected to the driving unit and a clamping jaw connected to the transmission unit. The clamping jaw can be driven to move forwards and backwards through the forward and backward rotation of the driving unit caused by a trigger, thereby attaining the purpose of ejecting a blind rivet. 
     However, the operation time of the driving unit is decided by holding the trigger, that is to say, if a user presses the trigger too short, the blind rivet can&#39;t be ejected, and if the user presses the trigger too long, the clamping jaw may be locked induced by its excessive backward movement, causing the breakdown of the riveting unit. Therefore, it is desirable to provide a riveting unit that can eliminate the aforesaid drawback. 
     SUMMARY OF THE INVENTION 
     It is one objective of the present invention to provide a riveting unit for an electric rivet gun that has a sensor to detect the movement of a clamping jaw for ensuring the normal operation of the electric rivet gun. 
     To achieve the above-mentioned objective of the present invention, the riveting unit comprises a transmission unit, a clamping jaw having a locating portion driven by the transmission unit to be moveable between a first position where a blind rivet can be installed in the clamping jaw, and a second position where the blind rivet can be ejected, a first sensor configured to detect whether the locating portion of the clamping jaw is located at the first position, and a second sensor configured to detect whether the locating portion of the clamping jaw is located at the second position. 
     Once the locating portion of the clamping jaw is moved from the first position to the second position, the second sensor can allow the transmission unit to stop the movement of the clamping jaw for preventing excessive backward movement of the clamping jaw and ensuring normal operation of the riveting unit. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a perspective view of an electric rivet gun; 
         FIG. 2  is a partial exploded view of a riveting unit according to a preferred embodiment of the prevent invention; 
         FIG. 3  is a sectional view of the riveting unit; 
         FIG. 4  is similar to  FIG. 3 , showing a blind rivet is installed; 
         FIG. 5  is similar to  FIG. 4 , showing the clamping jaw is moved to the second position; and 
         FIG. 6  is similar to  FIG. 5 , showing the clamping jaw is moved back to the first position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , a riveting unit  10  in accordance with a preferred embodiment of the present invention is installed in an electric rivet gun  1 . Referring to  FIGS. 1-3 , the electric rivet gun  1  comprises a housing  3  having a chamber  4  therein, and a driving unit  5  installed in the camber  4  of the housing  3  and having a transmission shaft  6  with a first teeth portion  7 . The riveting unit  10  comprises a transmission unit  40 , a clamping jaw  50 , a first sensor  60 , and a second sensor  62 . 
     As shown in  FIGS. 2-3 , the transmission unit  40  is disposed in the chamber  4  of the housing  3 , and provided with a wheel  42  and a restricting member  44 . The wheel  42  has a first threaded portion  421  at a middle thereof and a second teeth portion  422  engaged with the first teeth portion  7  of the driving unit  5  such that the wheel  42  can be driven to rotate by the forward and backward rotation of the driving unit  5 . The restricting member  44  has a through hole  443  sleeved on the first threaded portion  421  of the wheel  42  for restricting an axial movement of the wheel  42  and allowing relative rotation between the wheel  42  and the restricting member  44 , and an elongated slot  441  communicated with through hole  443 . To deserve to be mentioned, the transmission unit  40  is not limited to be engaged with the driving unit  5  in a coaxial or non-coaxial manner. 
     As shown in  FIG. 3 , the clamping jaw  50  includes a moving rod  52  and a locating rod  54 . The moving rod  52  is inserted into the through hole  443  of the restricting member  44  and has a jaw portion  523  at one end thereof for clamping a blind rivet  70 , and a second threaded portion  521  at the other end thereof threaded with the first threaded portion  421  of the wheel  42  such that the moving rod  52  can be driven to be axially moved through the forward and backward rotation of the wheel  42 . The locating rod  54  is perpendicularly connected to the moving rod  52  so as to be moveable between a first position P 1  and a second position P 2  through the axial movement of the moving rod  52 , and provided with a locating portion  542  passing through the elongated slot  441  of the restricting member  44 . 
     The first and second sensors  60  &amp;  62  are disposed in the chamber  4  of the housing  3  and respectively configured to detect whether the locating rod  54  is located at the first and second positions P 1  &amp; P 2 . The first and second sensors  60  &amp;  62  are selected from the group consisting of a contact switch and a non-contact switch, such as a limit switch, a Hall effect sensor, or a photoelectric switch. In this embodiment, each of the first and second sensors  60  &amp;  62  is a Hall effect sensor that is actuated by a magnetic force generated by the locating portion  542  of the clamping jaw  50 . 
     As shown in  FIGS. 3 and 4 , when a user doesn&#39;t press a trigger (not shown) of the electric rivet gun, the locating rod  54  is located at the first position P 1  where the jaw portion  523  of the clamping jaw  50  is opened to allow the installation of the blind rivet  70 . 
     As shown in  FIGS. 5 and 6 , when the user presses the trigger, the transmission unit  40  can be actuated by the driving unit  5  to move the clamping jaw  50  backwards such that the locating rod  54  can be moved from the first position P 1  to the second position P 2 , and meanwhile the blind rivet  70  can be clamped and pulled by the clamping jaw  50 . Once the locating rod  54  is moved to the second position P 2 , the blind rivet  70  can be ejected due to the break of a rivet stem of the blind rivet  70 , and furthermore the second sensor  62  can allow the transmission unit  40  to stop the movement of the clamping jaw  50 . Thereafter, the user can release the trigger to move the clamping jaw  50  back to the first position P 1  through the backward rotation of the transmission unit  40  for the next ejection. 
     By means of the aforesaid, the riveting unit of the present invention provides two sensors that can detect the movement of the clamping jaw to prevent the clamping jaw from moving backwards excessively, thereby attaining the purpose of avoiding breakdown of the riveting unit and ensuring normal operation of the electric rivet gun. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.