Abstract:
Automatic feeding blind rivet guns and method facilitating rapid installation of blind rivets with good freedom of movement of the operator. The blind rivet guns receive a carrier holding a substantial plurality of blind rivets in close side by side proximity and automatically sequentially loads and sets the blind rivets in response to operator control. The blind rivets are preferably supplied on an inexpensive disposable plastic carrier ready for use with the rivet installation gun. The installation gun itself is pneumatically powered, though other sources of power, such as electrical power, could be used.

Description:
This application is a continuation-in-part of application Ser. No. 09/753,836, filed Jan. 3, 2001, entitled “Rivet Gun” and claims the benefit of U.S. Provisional Patent Application No. 60/275,337, filed Mar. 12, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to blind rivet installation equipment. 
     2. Prior Art 
     Blind rivets are well known in the prior art, being settable from one side of the work pieces to be joined by the rivet without requiring bucking or other access to the opposite side of the work pieces. Blind rivets are characterized by a hollow-headed shank with a stem extending therethrough, the stem having some provision for expanding the shank as the stem is pulled from the head-end of the rivet. In some types of rivets, the stems are pulled all the way through the rivet, leaving a hollow installed rivet. In other cases, the stem will first form an expanded tail on the shank as if it had been bucked, then intentionally break, usually with some form of locking provision so that the portion of the stem remaining in the installed rivet becomes a permanent and secure part of the installed rivet. 
     Installation tools for blind rivets of various types are also well known. Such tools include hand powered devices, compressed air powered devices and electrically powered devices, including devices powered by rechargeable batteries. In the prior art, these devices are single shot devices, requiring the manual loading of each rivet prior to the installation of the rivet. While an experienced riveter can fairly quickly load each rivet into the gun, the manual loading requirement still reduces the rate at which the blind rivets may be installed. 
     Finally, installation systems are known which automatically feed the rivets to the gun for higher speed installation. Such a system used for a proprietary tacking rivet manufactured by Allfast Fastening Systems, Inc., the assignee of the present invention, is the Allfast TackMatic™, sold by the assignee of the present invention. That system utilizes a console unit that automatically feeds the rivets to a handgun, sets the rivets, and then collects the spent stems. The handgun is tethered to the console unit by a line through which the rivets are fed and by a high pressure air hose for powering the handgun. The console unit may be made relatively mobile by placement on a wheeled cart, though limitations on the length of the flexible rivet feeding tube, etc. limit the range of motion of the installation gun. Consequently, while such systems work well on assembly lines for individual assembly of products that are not particularly large, they are generally not used in aircraft manufacture because of the mobility required because of the size of the assembly on which the rivet installation system would have to be used. 
     BRIEF SUMMARY OF THE INVENTION 
     Automatic feeding blind rivet guns and method facilitating rapid installation of blind rivets with good freedom of movement of the operator. The blind rivet guns receive a carrier holding a substantial plurality of blind rivets in close side by side proximity and automatically sequentially loads and sets the blind rivets in response to operator control. The blind rivets are preferably supplied on an inexpensive disposable plastic carrier ready for use with the rivet installation gun. The installation gun itself is pneumatically powered, though other sources of power, such as electrical power, could be used. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of an exemplary embodiment of a blind rivet gun in accordance with the present invention. 
     FIG. 2 is an illustration of an operator using the blind rivet gun of FIG.  1 . 
     FIGS. 3 a  through  3   d  illustrate the blind rivet and the rivet carrier used with the preferred embodiment of the present invention. 
     FIG. 4 is an exploded view of the pulling head actuator of the present invention. 
     FIG. 5 is across sectional view of the pulling head used with the preferred embodiment of the present invention. 
     FIG. 6 is a perspective view of the pulling head and rivet. 
     FIGS. 7 a  through  7   e  illustrate the relative positions of the mechanisms of the preferred embodiment rivet gun with a rivet in the pulling position. 
     FIG. 8 is perspective view showing the rivets on a rivet carrier in the magazine of the preferred embodiment. 
     FIG. 9 is a perspective exploded view of a part of the rivet loading system of the preferred embodiment. 
     FIG. 10 is a perspective view of the pulling head with a rivet in the pulling position. 
     FIG. 11 is an exploded view of a part of the rivet loading system of the preferred embodiment. 
     FIGS. 12 a  through  12   c  illustrate the relative positions of the mechanisms of the preferred embodiment rivet gun when a rivet has just been pulled. 
     FIGS. 13 a  through  13   h  illustrate the next rivet loading sequence of the preferred embodiment of the present invention. 
     FIGS. 14 through 16 illustrate the ejection sequence of the preferred embodiment of the present invention for ejecting the stem of the previously pulled rivet from the pulling head. 
     FIG. 17 is an exploded view of the pulling head and rivet holding members of the preferred embodiment. 
     FIG. 18 is an exploded perspective view of a housing with rivet stem retention capability. 
     FIGS. 19 and 20 illustrate the relative positions of the mechanisms of an embodiment rivet gun with a rivet proceeding to the pulling position. 
     FIG. 21 is an illustration of portions of an alternate embodiment, primarily the barrel assembly of an alternate embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention comprises a rivet gun operable with a cartridge holding multiple blind rivets, and controllably operable by an installer to install individual rivets and automatically load successive rivets for installation. For purposes of explanation and not by way of limitation, a specific embodiment is disclosed in detail herein to illustrate one implementation of the broad concepts of the present invention. Further, for purposes of explanation only, the specific rivet illustrated is the Allfast FASTACK™ tacking rivet manufactured by Allfast Fastening Systems, Inc., assignee of the present invention, under Allfast&#39;s U.S. Pat. No. 5,689,873 “Tacking Fastener” patent. 
     First referring to FIGS. 1 and 2, an illustration of an exemplary embodiment of the present invention rivet gun and a rivet installer using the rivet gun may be seen. The rivet gun itself is characterized by what will be referred to herein as a barrel assembly  30 , and a magazine assembly  32  for automatically feeding rivets into the installation position. The rivet gun in the exemplary embodiment is powered by pressurized air provided through air hose  33 , with the operation of the barrel assembly  30  and the magazine  32  being coordinated through air lines  34  and  35 . The rivet gun also includes a handle assembly  36  with trigger  44 . 
     In the exemplary embodiment, the rivets illustrated and for which the exemplary rivet gun is adapted are illustrated in FIGS. 3 a - 3   d.  The rivets are characterized by a shank  37  with integral head  38 , in this embodiment a conical head, with a stem  39  extending through the head and shank and having a tail-former  40  adjacent the end of the shank  37 . In use, the tail-former  40  and shank  37  are inserted through a mating hole in the workpieces to be joined so that the head  38  abuts the surface of the outer workpiece, then the stem  39  is pulled with respect to head  38 . The tail-former  40  forms a bulbous end on the shank  37 , pulling the workpieces together, until the tail-former  40  deflects inward and is pulled entirely through the shank and head  38 . This leaves the installed shank and head as a hollow tack rivet for later drilling out for installation of a permanent rivet. The tack rivet shown, however, is used as exemplary only, as the present invention may readily be used with blind rivets of other designs, including but obviously not limited to, blind rivets wherein after the workpieces have been pulled together and the stem end expanded in some form, a portion of the stem is locked to the head or shank of the rivet, after which the stem fractures adjacent the head end of the installed rivet and is disposed of. 
     In the exemplary embodiment, the rivets generally indicated by the numeral  41  are held in parallel close side by side disposition by a plastic U-shaped  42  having pockets  43  therein retaining the stems  39  of the rivets. The rivets on the carrier preferably are spaced as close together as reasonably possible to maximize the number of rivets on the carrier, and as will subsequently be appreciated, are spaced closer than would allow the passage of a pulling head (with or without a housing around the pulling head) concentric with one rivet to engage that rivet without disturbing or dislodging at least one other rivet on the carrier. In some cases the rivets may be touching each other. In other cases, the rivets may be spaced slightly apart, though usually not by as much as to allow the inclusion of another rivet on the carrier if the rivets had been placed closer together. In any event, the rivets will be spaced closer together than will allow the passage of the pulling head with or without housing as described above. The plastic carrier  42  is preferably injection molded using a somewhat rigid though malleable plastic so that the rivet stems are firmly held, but may be forced out of the pockets in the plastic carrier without chipping or breaking the carrier. 
     FIG. 4 is an exploded view of the exemplary rivet gun of the present invention, particularly showing the barrel assembly  30  in exploded form. In general, this Figure will not be described specifically, but the corresponding parts labeled in other Figures will similarly be labeled in FIG. 4 for further reference. 
     Now referring to FIG. 5, a cross-section of the pulling head used with the present invention may be seen. The pulling head includes a draw bolt  45 , coupled at one end to a draw bolt extension  46  and at the other end to a collet  47  holding jaws  48  therein. Jaws  48 , typically three in number each spanning on the order of 120°, are serrated on their inner diameters to grip the complimentary serrations on the stem  39  of the rivet, being encouraged to a closed position by an O-ring  49  in a groove in the jaws. The jaws are also encouraged toward a left-most closed position by a spring  50  acting between the end of the draw bolt  45  and the larger end of the jaws. With this construction, and the cooperative shape of the serrations on the rivet stem and the jaws, a rivet stem may be relatively easily pushed into (and even through) the jaws from the left side as viewed in FIG. 5, though may not be pulled back out of the jaws from that direction. 
     The collet  47  and draw bolt  45  have a sliding fit within housing  51  which has an extension  52  engaging the rivet head during the pulling to hold the rivet in the hole in the workpieces as the stem of the rivet is pulled to form the end of the shank and to then pass through the rivet shank and rivet head. Housing  51  and its integral extension  52  are positioned within holding members  53 , which may also be seen in FIG.  6 . These two members, separated along a vertical plane, are elastically encouraged toward each other by O-rings  54 , visible in both FIGS. 5 and 6. As may be seen perhaps best in FIG. 6, the forward part of members  53  are relieved in region  55  so as to provide a tapered vertical entry for a rivet into the position shown in FIG. 6, with members  53  initially holding the shank of the rivet as shall subsequently be described in greater detail. 
     Also visible in FIG. 6 is one of a pair of pins  56 , one on each side of the collet  47 , extending into cooperatively disposed slots in housing  51  and members  53 . As shall subsequently be seen, these pins, together with the associated slots, define the limits of the relative motion between the collet  47 , the housing  51  and the members  53 . 
     FIGS. 7 a,    7   b  and  7   c  illustrate the relative position of the various parts in the pulling head, barrel assembly and magazine assembly when a rivet is in position ready for pulling. In FIG. 7 a,  the magazine assembly is shown detached and slightly dropped with respect to the barrel assembly for better clarity in the explanation to follow. As shown in FIG. 7 a,  a portion of which is shown in expanded scale in FIG. 7 b,  the barrel assembly  30  includes a forward barrel member  57  and a cylindrical barrel member  58  threaded thereto. Within the barrel assembly is housing  51  and draw bolt  45 , as well as draw bolt extensions  46  and  67  (see also FIG. 5 for an expanded view of some of these parts). The barrel assembly  30  includes a first pressure barrier  59  trapped between forward housing member  57  and snap ring  60 , a second pressure barrier  61  trapped between snap rings  62  and  63 , and a third pressure barrier  64  trapped between snap rings  65  and  66 , the snap rings being of conventional design, snapping into complementary grooves in the inside diameter of cylindrical housing member  58 . These pressure barriers have an O-ring seal at their outer periphery and a sliding seal on their inner periphery to allow linear translation of the housing  51  and draw bolt extensions  46  and  67 . 
     Also located within cylindrical housing member  58  are a number of pistons, one being fastened to housing  51  and the other two being fastened to drawbolt  45 /drawbolt extensions  46  and/or  67 . In particular, piston  68  is fastened to housing  51 , and accordingly, moves in translation along the barrel assembly in unison therewith. Piston  69  is coupled to drawbolt  45 /drawbolt extension  46  so as to move in unison therewith, piston  69  being limited in motion with respect to piston  68  by pins  70 , with sliding seals between the piston  69  and pins  70  preventing significant leakage of air. In that regard, FIG. 7 a  suggests two pins  70 , or at least an even number of pins, though in the preferred embodiment three pins spaced 120° apart are actually used as shown in FIG.  4 . Also coupled to drawbolt extensions  46  and  67  is another piston  71 . 
     The handle assembly  36  is connected to an airhose (not shown in FIG. 7 a ) with a trigger  44  determining the porting of the air under pressure, typically on the order of 90 psi, to the pneumatic actuator in the barrel assembly just described. The trigger  44  is coupled to member  74  that couples the center of three ports to either the left port or the right port, with the remaining of the three ports being coupled to the high pressure air. As shown in FIG. 7 a,  the left port is coupled to the center port, and the right port is coupled to the high pressure air. If, on the other hand, when the trigger  44  is depressed, member  74  will slide to the right, coupling high pressure air to the left port and coupling the center port to the right port. In this porting, the center port is a vent to atmosphere, being vented thereto through opening  75  in the manifolding. 
     With the trigger released as shown in FIG. 7 a,  the high pressure air is ported to the region between piston  69  and pressure barrier  61 , forcing piston  69  forward against piston  68 , holding both housing  51  and members  53  (see also FIG. 7 b ) in their forward-most position. In this position, rivet  41  is ready for insertion into the hole in the workpieces to be joined, and then pulled. FIG. 7 c  is a cross-section taken looking upward toward the axis of the rivet and draw bolt assembly. This Figure illustrates the relative position of the various parts as viewed from beneath the pulling head, and further illustrates the then existing relative position of pins  56  with respect to the slots in housing  51  and member  53 . 
     Referring again to FIG. 7 a,  in the rivet ready for setting condition of the rivet gun, the high pressure air is also ducted to the top of an actuator  80  in the magazine assembly, holding the actuator member  81  in its lower-most position. The magazine assembly itself receives carrier  42  with a plurality of rivets  41  thereon (see FIG.  8 ), with a spring acting against the rivet stem of the lowest rivet to encourage the rivets and carrier upward. The carrier of rivets is loaded into the magazine assembly from the bottom thereof, the removable bottom cover  82  providing access for the loading of the rivets. Details of the spring assembly, etc. are not shown, as the same are similar in certain respects to a handgun cartridge clip. 
     The actuator  80  has mounted thereon a top assembly, shown in an end view in FIG.  7 D and in perspective in FIG. 9, an exploded view for illustration purposes. As shown in these two Figures, the piston rod  83  has a cam plate  84  and a pusher plate  85  mounted thereon. Cam plate  84  controls slide plate  86 , which as shown in FIGS. 7 d  and  9 , is yieldably encouraged to its right-most position by springs  87 . Immediately above slide plate  86  is a fixed plate  88  having an opening therein directly below the axis of the pulling head and members  53 . As may be seen in FIG. 7 d,  with the slide plate  86  in the right-most position, the top-most rivet  41  has been encouraged upward by the magazine spring into the complementary opening (see FIG. 9) in the slide plate, the groove in fix plate  88  providing clearance for the rim of the rivet head. Slide plate  86  and the fixed plate  88  are also shown in plan form in FIG. 11, illustrating the complementary nature of the openings in the plates relative to the outline of the rivet with which the rivet gun will be used. The relative position of the rivet carrier  42  and slide plate  86  in this embodiment may be seen in FIG. 8, the carrier  42  passing at one side of the slide plate  86  as rivets are removed from the carrier and installed. The relative position of various parts are also illustrated in the perspective view of the head region of the gun of FIG. 10, showing the carrier  42 , a rivet  41  in the pulling position and the relative position of members  53 . 
     Now referring to FIGS. 12 a  through  12 C, the initial motion of the various parts of the rivet gun upon pulling of the trigger control  44  may be seen. FIG. 12 a,  like FIG. 7 a,  is a partial cross-section of the entire gun illustrating the porting of the high pressure air and the position of the pistons in the barrel assembly  30  and the actuator  80  in the magazine. FIG. 12 b  is a portion of the assembly of FIG. 12 a  taken on an expanded scale, and FIG. 12 c  is a cross-section of much of the assembly of FIG. 12 b,  though presented as a view looking up at the pulling head, as opposed to the side view of FIG. 12 b.    
     As shown in FIG. 12 a,  when the trigger control  44  is depressed, region  89  is vented to atmosphere and regions  90  and  91  are coupled to the high pressure air. The pressure in chamber  91  acts against piston  71 , pulling the drawbolt extension  46  and thus the drawbolt  45  to pull the stem of the rivet to set the rivet. At the same time, the pressure in chamber  90  acts against piston  68  to hold the extension  52  on the housing  51  against the head of the rivet, so that the head of the rivet is not pulled away from the adjacent workpiece. While piston  69  is also connected to the drawbolt assembly, the primary pulling of the rivet stem is believed to be done by piston  71 , the pressure in chamber  89 , though decreasing during the pulling because of the venting of the chamber through vent port  92 , minimizes at least the initial pulling force provided by piston  69 . When the pulling is complete, piston  69  will move to the position shown in FIG. 12 a,  namely at its right-most limit of its travel with respect to piston  68  to engage the pins  70  on piston  68 . As may be seen in FIG. 12 b,  the distal end of the shank  37  of the rivet has been formed and the rivet stem  39  has been pulled all of the way through the rivet shank and head. Of course, in alternate embodiments intended for use with blind rivets wherein during the pulling of the rivet the stem is locked in position after pulling and the remaining stem fractures adjacent the head, only the fractured part of the stem will then remain engaged by the pulling head. 
     Once pulling is complete, as illustrated in FIGS. 12 a  and  12   b,  the pressure in chamber  91  will continue to move piston  71 , and thus the drawbolt assembly, further to the right. Referring to FIG. 12 c,  a cross-sectional view from below, it may be seen that pins  56  in collet  47  are at their right-hand most position with respect to the slots in housing  51 . Accordingly, any further movement of piston  71  to the right, as shown in FIGS. 12 a  and  12   b,  will also pull housing  51  to the right. Thus, the entire piston assembly and pulling head will move to the right-hand extreme of their travel, as illustrated in FIGS. 13 a  and  13   b,  the air in chamber  93  (FIG. 12 a ) being vented to atmosphere during this motion by vent  94 . 
     Referring again to FIG. 12 a,  it will be noted that upon depression of the trigger control  44 , high pressure air is also ported to the bottom of actuator  80 , forcing the cam plate  84  and the pressure plate  85  upward (see FIG.  9 ). As shown in FIG. 13 d,  slide plate  86  with the rivet captured by the opening therein (see FIG. 11) is forced to the left of the upward motion of the cam plate  84 , stripping the rivet from the carrier  42  and moving the same to a position directly under members  53 . Continued upward motion of the cam plate  84  and the pusher plate  85  causes the pusher plate to force the rivet upward through the opening in plate  88  and through the tapered region  55  of members  53  (FIG.  6 ), to be retained by members  53  as. shown in FIG. 13 e,  a view looking upward, and as shown in FIG. 13 c,  the side view of FIG. 13 f  and perspective of FIG. 13 h.  In that regard, FIGS. 13 b,    13   c  and  13   f  also show the remaining stem from the previously pulled rivet. 
     When the trigger control  44  is released, regions  91  and  100  (FIG. 13 a ) are vented to atmosphere and the region between piston  69  and pressure barrier  61  is pressurized. Pressure remains, however, between piston  69  and piston  68  so that piston  69  will remain against the ends of pin  70  as the entire assembly moves to the left, the region between pistons  68  and  69  finally being vented through port  101  (FIG. 7 a ) in the final motion of the outer seal in piston  68  moving to the left of the port. At the same time, as may be seen in FIG. 7 a,  the top of actuator  80  is pressurized and the bottom vented to atmosphere, first withdrawing the pusher plate from fixed plate  88  and slide plate  87  as shown in FIG. 13 g,  and then further withdrawing the cam plate  84  to allow springs  87  to push the slide plate  86  to its right-most position (see FIG. 7 d ) to allow the next rivet on the carrier  42  to become engaged in the complementary opening of the slide plate in readiness for loading on the next operating cycle. 
     When the pulling actuator assembly is in the fully withdrawn position, as shown in FIGS. 13 a  and  13   b,  members  53  are also retracted (see FIG. 13 c ) by the engagement of pins  56  with the ends of the slots in members  53 . As may be seen in FIG. 13 c,  a rivet  41  is retained by members  53  while the stem  39  of a previously pulled rivet remains in the jaws of the pulling head. 
     Referring again to FIG. 13 a,  when the trigger  44  is released, regions  99  and  100  are vented to the atmosphere and pressure is ported to the region between piston  69  and pressure barrier  61 . Since high pressure air remains between pistons  68  and  69 , pistons  68  and  69  will remain separated as shown in FIG. 13 a,  though will proceed to the left, passing through the position shown in FIG.  19 . As may be seen therein, the stem  39  of the next rivet is passed through the opening in extension  52  of the housing, with the stem being grasped therein by pins  150  held in position by a spring wire ring  152 . In that regard, as may also be seen in FIG. 18, pins  150  have an angled face  154  to allow a stem  39  to proceed into the housing  52 , the angled pins  150  yieldably retracting against the spring force of spring wire member  152 , though retaining the stem so as to not allow the forcing of the stem through the front of member  52 . As pistons  68  and  69  continue to the left (FIG. 13 a ), the housing  52  pushes the rivet outward between members  53  to the pulling position, illustrated by way of example, in FIG. 7 c.  When reaching this position, the region between pistons  68  and  69  becomes vented to atmosphere through port  101  (see FIG. 7 a ), allowing piston  69  to continue forward to the position shown in FIG. 7 a,  pushing the drawbolt  45  forward so that the jaws of the pulling head engage the stem of the rivet as illustrated in FIG. 7 c,  preparing the gun and rivet for the next pulling cycle. 
     In another embodiment, when the trigger  44  is released the region between pistons  68  and  69  (see FIG. 13 a ) may be vented, together with regions  91  and  100 , in which case the pressure applied between piston  69  and pressure barrier  61  will first cause piston  69  to move to the left against piston  68  to extend the drawbolt relative to the housing, and then return pistons  68  and  69  in unison to the position shown in FIG. 7 c.  In this case, as the pulling actuator assembly moves to the left from the position shown in FIG. 13 a  to the position shown in FIG. 7 a  as previously described, housing  51 , collet  47 , jaws  48 , etc. move to the left, as shown in FIG. 14, with the stem of the rivet just loaded hitting the end of the stem still retained in jaws  48 , encouraging the jaws to the open position to push the stem of the already pulled rivet out of the jaws and causing the jaws to engage the stem of the rivet just loaded, as shown in FIG.  15 . As the pulling head moves further to the left, members  53  will follow, though reaching the limit of their travel as shown in FIG. 16, after which the extension  52  in the housing  51  and/or the head of the rivet force members  53  to separate, allowing the rivet, housing and housing extension to extend to the pulling position, as illustrated in FIG. 7 a  through  7   d.  In that regard, the travel of members  53  is limited by members  105  coupled thereto, the members separating to allow the extension of a rivet therebetween against the elasticity of the O-rings  54 , as shown in FIG.  17 . The stems of the already pulled rivets are ejected from the pulling head (see FIG. 7 e ) and out the back of the draw bolt/draw bolt extensions into a collection reservoir (not shown) screwed onto the end of the barrel assembly  30  for stem collection purposes and as an operator protection from the motion of the draw bolt extension  67 . 
     Now referring to FIG. 21, portions of an alternate embodiment, primarily the barrel assembly of an alternate embodiment, may be seen. While details of the pulling head, etc. are not shown in FIG. 21, they may be substantially the same as that shown for the previously described embodiment of FIGS. 18,  19  and  20 . As may be seen in FIG. 21, a single chamber is defined by end plates  110  and  112 . End plate  110  is held in position by forward barrel member  113  and snap ring  114 , while end plate  112  is held in position by snap rings  116  and  118 . Within the chamber are two pistons  120  and  122 , piston  120  being connected to drawbolt extension  124  and piston  122  being connected to the housing, not shown in detail in FIG. 21, but corresponding to housing  51  of the previously described embodiment of FIGS. 18,  19  and  20 . 
     With trigger member  74  in the position shown, the region between pistons  120  and  122  is vented to atmosphere, while pressure is ducted through line  126  to region  128 , pushing pistons  120  and  122  to their left-most position, as shown in FIG.  18 . (The structure and operation of the trigger, as well as member  74 , may be the same as in the previously described embodiments, such as by way of example, is shown in detail in FIG. 7 a. ) When the trigger  44  (see FIG. 7 a ) is depressed, member  74  of FIG. 18 will move to the right-hand position, coupling line  126  to the vent line  130  and applying high pressure air through line  132  to the region between pistons  120  and  122 . This will cause piston  120 , coupled to the drawbolt, to move toward the right as viewed in FIG. 18, while holding piston  122  to its left-most position, the housing coupled to piston  122  holding the blind rivet in the workpiece as the drawbolt draws the stem of the rivet to set the rivet. Setting the rivet results either in the stem of the rivet being pulled all of the way through the rivet, as by way of example in a tacking rivet, or lock part of the stem in the pulled rivet, after which the remaining portion of the stem breaks off. In either event, once the stem or broken portion of the stem is free of the set rivet, the drawbolt will reach its right-hand travel limit with respect to the housing. (See the pins  56 , for instance, in FIG. 7 c  and the prior description of the operation thereof.) Thereafter, the momentum in piston  120  and the drawbolt assembly attached thereto will cause piston  122  and the housing attached thereto to move to the right in unison. This causes the peripheral seal  134  on piston  122  to move to the right of pressure port  132 , now also pressurizing the region between piston  122  and end wall  110 . This causes both pistons  120  and  122  to move to their right-most positions, also withdrawing members equivalent to members  53  of the prior embodiments to their right-hand most positions in readiness for loading of the next rivet as described with respect to the previous embodiment. At this point, the next rivet is put in position for capture by the pulling head as described with respect to the embodiment of FIGS. 18 through 20. 
     When the trigger is released, member  74  will return to the position shown in FIG. 21, pressurizing the region between piston  120  and end wall  112  and venting, at least initially, the region between piston  122  and end wall  110 . Because high pressure air is trapped between pistons  120  and  122 , the two pistons will maintain their maximum separation and will travel in unison toward the left, as shown in FIG. 21, until the peripheral seal  134  of piston  122  passes to the left of the now vented port  132 . Now the region between pistons  120  and  122  will be vented, allowing the pressure on the right side of piston  69  to force piston  69  against piston  68 , extending the drawbolt  124  to grasp the stem of the rivet in the pulling jaws in readiness for the next pulling cycle (see FIG. 7 c  for reference). When the peripheral seal  134  of piston  122  passes to the left of the vented port  132 , a small amount of air will be trapped in front of the piston. The pressure rise because of this trapped air may be held to a minimum, and/or a restricted vent to atmosphere such as a small hole in the cylinder wall or a hole filled with a restrictive filter material may be used to vent this area, as in vent  136 . The restriction preferably will not significantly interfere with the ability to pressurize this area during the rivet gun&#39;s operating cycle. 
     The advantage of the foregoing embodiment is that it facilitates a longer stroke, allowing the use of the rivet gun in closer proximity to adjacent structures in the parts being joined. In this embodiment, as in the other embodiments disclosed, the rivet stems or broken off stem parts may be collected in a receptacle at the rear of the rivet gun. 
     Thus, it may be seen that in the present invention a magazine assembly is provided for holding a plurality of rivets, with each successive rivet being loaded into the pulling position upon pulling of the preceding rivet, thereby providing an automatic rivet gun requiring only an appropriate source of power and the control of an operator for the rapid installation of blind rivets, whether by use of temporary or tacking rivets, or permanent rivets, either of the type wherein a stem is pulled entirely through the shank and head of the rivet or of other types, such as wherein, on pulling, a part of the stem is locked to the rest of the rivet while the remainder of the stem is fractured therefrom and disposed of. In the embodiment disclosed herein, pneumatic actuation is used, though other well known forms of actuators may also be used, including but not limited to, electromagnetic actuators. Similarly, different magazine assemblies and actuators may be used, whether or not the rivets are disposed on a carrier of similar or different design as in the preferred embodiment disclosed herein. Thus, it will be understood that a preferred embodiment has been disclosed herein only for purposes of specificity in the description given herein and not by way of limitation. It will be obvious skilled in the art that various changes in form and detail may be made in the invention without departing from the spirit and scope thereof.