Rivet injector system for an automatic riveting machine

Abstract

The rivet injector system includes a set of grasping spring-loaded rivet fingers which are mounted on a rivet ram portion of an automatic riveting machine. The rivet injector assembly receives a rivet from a feed tube into a chamber in the assembly. A stopper pin and a moveable forward end stop within the chamber are operated to hold the rivet axially, the rivet being supported on a rivet pad in the chamber. A tower portion of the injector assembly is slidably mounted to raise the rivet, forcing it between the spring-loaded rivet fingers, which firmly grasp the rivet. The forward end stop and the stopper pin are then retracted and the tower portion lowered, leaving the rivet grasped by the rivet fingers, permitting the rivet to be moved forwardly into a hole in the workpiece.

1 . A system for transporting rivets, for use in an automatic riveting machine, provided from a feed tube, comprising:
 a set of rivet fingers mounted on a ram portion of the automatic riveting machine for grasping a rivet; and   a rivet injector assembly for receiving a rivet by air pressure from a feed tube, holding the rivet first at opposing longitudinal ends of the rivet, moving it into the grasp of the rivet fingers and then releasing the rivet so that the ram portion can move the rivet held by the rivet fingers into a drilled hole in a workpiece.   
   
   
       2 . The system of  claim 1 , wherein the rivet injector assembly is mounted on the automatic riveting machine but away from the ram portion, permitting the ram portion to pass by the injector assembly to insert the rivet in the hole in the workpiece. 
   
   
       3 . The system of  claim 1 , wherein the rivet is positively held at all times by either or both of the rivet injector assembly and the rivet fingers. 
   
   
       4 . The system of  claim 1 , wherein the rivet fingers are spring-loaded on the ram portion. 
   
   
       5 . The system of  claim 1 , wherein the rivet fingers are horizontally positioned on the ram portion and are spring-loaded in a closed position. 
   
   
       6 . The system of  claim 1 , wherein the rivet injector assembly includes a chamber into which the rivet is moved from the feed tube by compressed air, the chamber being partially defined by a slidable cover having an internal cavity defining upper and side surfaces of the chamber. 
   
   
       7 . The system of  claim 6 , wherein the rivet injector assembly includes a moveable forward end stop mounted at a forward end of the chamber, wherein a rivet fed into the chamber is forced against the forward end stop by compressed air, the rivet injector assembly further including a stopper pin positioned in the vicinity of a rear end of the chamber, the stopper pin being mounted so that it is in a retracted, lowered position when a rivet is moved into the chamber, and then is moved to an extended, raised position following a rivet being fed into the chamber against the forward end stop, wherein subsequent movement of the forward end stop rearwardly toward the stopper pin results in the rivet being held axially at its respective ends between the stopper pin and the forward end stop. 
   
   
       8 . The system of  claim 7 , wherein the stopper pin is at a fixed axial location relative to the ram portion of the automatic riveting machine, such that a rear end of the rivet is always at the same position relative to the ram portion regardless of the length of the rivet. 
   
   
       9 . The system of  claim 7 , including a rivet sensor positioned around the feed tube in the vicinity of the rivet injector assembly for determining movement of the rivet in the feed tube and a signal system which raises the stopper pin a selected time following recognition of a rivet by the rivet sensor. 
   
   
       10 . The system of  claim 1 , wherein the rivet injector system includes a chamber and a rivet pad positioned within the chamber, the rivet pad configured with a central longitudinal groove therein such that a rivet entering the chamber is supported by the central groove, the rivet pad arranged to support the rivet along a side opposite from a side of the rivet which initially contacts the rivet fingers. 
   
   
       11 . The system of  claim 10 , wherein the rivet pad is plastic. 
   
   
       12 . The system of  claim 7 , wherein the rivet injector assembly includes a tower portion which includes the chamber and which moves upwardly with the rivet held in the chamber, following movement of the slidable cover to the rear which exposes the rivet, such upward movement sufficient to force the rivet between the spring-loaded closed rivet fingers, wherein the rivet is thereafter released by the forward end stop and the stopper pin and the tower portion lowered sufficiently that the ram and the rivet fingers grasping the rivet can move forwardly to insert the rivet into the hole in the workpiece. 
   
   
       13 . The system of  claim 1 , wherein the distance between the forward end stop in its retracted position and the stopper pin in its raised position is greater than the length of a single longest rivet used in the system but less than the combined length of two shortest rivets used in the system, and wherein the system removes rivets present in the chamber when the stopper pin cannot be moved to its raised position by opening the chamber and blowing the rivets present out of the chamber. 
   
   
       14 . The system of  claim 1 , wherein the workpiece is an aircraft wing panel. 
   
   
       15 . The system of  claim 1 , including a circuit, which includes a linear potentiometer, for determining the length of the rivet when it is held between the stopper pin and the forward end stop. 
   
   
       16 . A system for use with an automatic riveting machine for transporting rivets provided from a feed tube, comprising:
 a grasping finger assembly for moving rivets to a drilled hole in a workpiece; and   a rivet injector assembly for receiving a rivet under air pressure from a feed tube, the rivet injector assembly including axial rivet holding elements and a control system therefor for holding a received rivet at the ends thereof, the rivet injector assembly being movable to force the rivet into the grasping finger assembly and then releasing the rivet after the finger assembly has grasped the rivet so that the rivet can thereafter be moved into the drilled hole in the workpiece.   
   
   
       17 . The system of  claim 16 , wherein the rivet injector assembly is mounted on the automatic riveting machine but is movable sufficiently away from a ram portion thereof to permit the ram to pass by the injector assembly to insert the rivet in the hole in the workpiece. 
   
   
       18 . The system of  claim 16 , wherein a received rivet is grasped positively at all times as it is moved into the grasping finger assembly.