Abstract:
The invention provides a device that joins together several metal sheets in a single step. The device features a mechanism which simultaneously punctures a plurality of substrates and folds back extrusions produced when the substrates are punctured. The mechanism automatically retracts from the metal sheets once the folding of the extrusions occurs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/250,624 filed on Oct. 12, 2009, currently pending. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to the field of devices for joining metal objects and, more particularly, to a device used in riveting together studs and thin sheets of metal. 
         [0004]    2. Background of the Invention 
         [0005]    Devices for attaching or riveting together studs and thin sheets of metal have been available. However, they suffer from several disadvantages. To begin with, their use requires that the operation be carried out in three steps: first the studs or sheets of metal must be perforated at the junction point; second a rivet or the like must be inserted through the perforation; and third the rivet must be compressed or, at the very least, the extrusions or hanging chads resulting from the perforation of the metal sheets must be hammered down. 
         [0006]    Quite often, another device serving as an anvil must be placed on the side opposite to that where the perforating device engages the work pieces. If the workpiece is large and therefore unwieldy, positioning of the workpiece on an anvil or other support structure may require several workers. 
         [0007]    A need exists in the art for a device that rivets a plurality of plates in one single step without recourse to a support structure such as an anvil. The device should be modular such that it is easily carried. Also, the device should be comprised of common materials so as to minimize cost. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of this invention is to provide a metal-plate riveting device that overcomes many of the disadvantages in the prior art. 
         [0009]    Another object of the invention is to provide a labor-saving metal-plate riveting device that rivets a plurality of plates. A feature of this invention is a combination of a puncturing device with a means to automatically fold back extrusions, burrs and hanging chads produced as the plates are punctured. An advantage of this invention is that it provides a riveting device that rivets a plurality of substrates such as plates in one single step. 
         [0010]    Yet another object of the invention is to provide a riveting device that enables the joining of multiple substrates through folded extrusions and the insertion of a plurality of rivets into the substrates without recourse to any backstop or support structure or other device positioned on the back side of the substrate (i.e., the side opposite to the side initially contacted by the invented device). A feature of this invention is that it comprises a combination of a puncturing device and a means to fold substrate-extrusions, chards or hanging chads (which are produced when the plates are punctured) to the back side of the plates. This folding means engages the substrate on the same side as does the puncturing device. An advantage of this invention is that it provides a riveting device that is capable of being operated from solely one side of the substrates to be riveted such that no substrate support or backstop is required during use. 
         [0011]    Another object of the invention is to facilitate permanent attachment of a plurality of metal substrates at points away from the edge of the substrates. A feature of the invention is that the puncturing device may fasten the substrates at any location on the surface of the substrates. A benefit of the invention is that it may join substrates at any accessible location, especially with access to only one surface, and not merely the edge of the substrates. 
         [0012]    In brief, in one embodiment, this invention provides a device for fastening together a plurality of substrates having a front side and a back side in one step by combining a puncturing mechanism means with a means to fold back extrusions produced when the plates are punctured wherein said puncturing mechanism and said folding back means operate from only one side of each of said substrates. In another embodiment, this invention provides a method for fastening a plurality of substrates in a single step said method comprising combining a puncturing mechanism with a means for folding back extrusions produced when said substrates are punctured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0013]    The foregoing and other objects, aspects, and advantages of this invention will be better understood from the following detailed description of the preferred embodiments of the invention with reference to the drawing, in which: 
           [0014]      FIG. 1  is an overall cross-sectional view of an exemplary embodiment of a device for perforating and riveting metal plates, in accordance with features of the present invention; 
           [0015]      FIG. 2  is a perspective view of a piston component of an embodiment of a device for perforating and riveting metal plates depicted in  FIG. 1 , in accordance with features of the present invention; 
           [0016]      FIG. 3   a  is a perspective view of a riveting component of an embodiment of a device for perforating and riveting metal plates depicted in  FIG. 1 , in accordance with features of the present invention; 
           [0017]      FIG. 3   b  is a perspective view of a plate in the rivet component of an embodiment of a device for perforating and riveting metal plates depicted in  FIG. 1 , in accordance with features of the present invention; 
           [0018]      FIG. 3   c  is a plan view of a base for a rivet component of an embodiment of a device for perforating and riveting metal plates depicted in  FIG. 1 , in accordance with features of the present invention; 
           [0019]      FIG. 4   a  is a profile view of a hammer component of an embodiment of a device for perforating and riveting metal plates depicted in  FIG. 1 , in accordance with features of the present invention; 
           [0020]      FIG. 4   b  is an elevation view of a hammer component of an embodiment of a device for perforating and riveting metal plates depicted in  FIG. 1  in accordance with features of the present invention; 
           [0021]      FIG. 4   c  is a view of  FIG. 1  taken along line  4   c - 4   c , in accordance with features of the present invention 
           [0022]      FIG. 4   d  is a detailed view of a hinge arrangement for an embodiment of the invented device depicted in  FIG. 1 , in accordance with features of the present invention 
           [0023]      FIG. 5   a  is an overall cross-sectional view of the invented device during perforation of a plurality of substrates, in accordance with features of the present invention; 
           [0024]      FIG. 5   b  is an overall cross-sectional view the invented device in post-perforation stage, in accordance with features of the present invention; 
           [0025]      FIGS. 6   a  through  6   c  are schematic views of stages in the operation of the invented device, in accordance with features of the present invention; 
           [0026]      FIG. 7   a  is a perspective view of an alternate embodiment of the invented device, in accordance with features of the present invention; 
           [0027]      FIG. 7   b  is a perspective view of a piston component of the device depicted in  FIG. 7   a , in accordance with features of the present invention; 
           [0028]      FIG. 7   c  is a perspective view of a rivet component of the device depicted in  FIG. 7   a , in accordance with features of the present invention; 
           [0029]      FIG. 7   d  is a cross-sectional view of  FIG. 7   a , taken along lines  7 - 7 ; 
           [0030]      FIG. 7   e  is a perspective view of a deployed configuration of the device depicted in  FIG. 7   a , in accordance with features of the present invention; 
           [0031]      FIG. 8   a  is a perspective view of another embodiment of the invented device, in accordance with features of the present invention; 
           [0032]      FIG. 8   b  is a perspective view of a piston component of the device depicted in  FIG. 8   a , in accordance with features of the present invention; 
           [0033]      FIG. 8   c  is an exploded view of a riveting component and a piston component for the device depicted in  FIG. 8   a , in accordance with features of the present invention; 
           [0034]      FIG. 8   d  is a cross-sectional view of  FIG. 8   c  taken along lines  8 - 8 ; and 
           [0035]      FIG. 9  is a perspective view of another embodiment of the cap of the invented device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    The present invention provides a labor-saving metal plate riveting device that rivets a plurality of plates in one single step. It combines a puncturing device with a means for folding back extrusions produced when the plates are first punctured. 
         [0037]    The present invention discloses a method and a device such that given an unsupported side of a stack comprising a plurality of substrates coplanarly arranged, the user can, by applying the invented tool to the other side of the configuration, perforate the entire configuration transversely and rivet the substrates together in a single step. 
         [0038]    The present invention is a substrate-piercing device comprising a piercing mechanism and a riveting mechanism. Initially, upon positioning of the device upon a plurality of substrates to be fastened together, a charge deploys a piston outwardly toward the substrate. Suitable charges are those originating from coiled spring, voltage potential, compressed air, fluid or a chemical charge such as propane or gunpowder. 
         [0039]    Upon deployment, the piston simultaneously transversely pierces the substrates while causing the rivet mechanism to laterally bend the shards defining the resulting aperture upon the back of the last substrate. For example, when air pressure deploys the piston toward a first surface of a stack of plates, a polygonal aperture is formed transversely through the stack, whereby the tip of the rivet mechanism acts as a punch. Said polygonal aperture is bounded by triangular extrusions or shards extending through the aperture and toward the rear of the stack of plates. Simultaneous with the tip of the riveting mechanism forming the aperture, mid portions of the riveting mechanism defining hammer heads laterally force the shards against the back surface of the stack so that the shards establish intimate irreversible contact with the back surface of the stack. This deployment is achieved when the piston, coaxially arranged with a sleeve defining the rivet mechanism is thrust in the sleeve so as to cause the hammer heads to deploy laterally. The hammer heads are defined by longitudinally extending portions of the sleeve which are separated from each other by longitudinally extending slits. 
       Structure of the One Embodiment of the Device 
       [0040]      FIG. 1  shows a cross-sectional view of the invented device  10  removably received by a means for actuating the device in an axial direction. The aforementioned actuating means includes, but is not limited to, pressurized air, chemical charge, mechanical actuation, such as spring loading, and a combination thereof. 
         [0041]    The device defines a first or distal end  16  and a second or proximal end  18  when it is enclosed in a housing  11 . The device  10  comprises a piston portion  25  coaxially aligned with a riveting tool portion  40 . This coaxial arrangement is spring biased toward the proximal end  18  of the device by one or a plurality of springs  20  and  30 . The proximal end  18  of the housing  11  snaps on or is otherwise removably received by said actuation device or is fully integrated into another device. 
         [0042]    At this juncture, it should be noted that the device  10  can be seamlessly integrated into existing nail guns, such as those pneumatically actuated or electrically actuated. The housing  11  of the invented device in such instances is defined by the nailing end of such guns. For example, the nailing end of pneumatically-or electrically-actuated guns typically encircle a piston within the gun, that piston charged by air, a voltage potential, or coiled spring. 
         [0043]    A proximal facing surface  36  of the piston is adapted to contact the effect of the actuating means, such as a bolus of fluid from a pressurized line or chemical charge, or mechanical contact with a rapidly expanding spring, 
         [0044]    For example,  FIG. 1  depicts a piston spring  30  positioned between the base of the piston  25  and the base of the riveting tool  40 . Specifically, the pertinent portion of the base of the piston defines a distally facing surface  27  while the pertinent portion of the base of the riveting tool defines a proximally facing surface  28 . These surfaces, when placed in opposition to each other, form a chamber  33  in which the piston spring  30  resides. 
         [0045]    A second spring  20 , dubbed herein as a rivet spring, is positioned between a distally facing surface  38  of the rivet portion and medially extending surface of the generally perpendicular to the longitudinal axis a of the device. In an embodiment of the device, the medially extending surface is defined by a proximally-facing surface  14  of a threaded collar  17  which is adapted to be threadably received by the distal most end of the housing  11 . This collar provides a means for axial adjustment of the device to vary the protrusion of the riveting mechanism from the distal end of the device. In one embodiment, this inside surface defines a circumferentially arranged, medially extending ring surface  12 . 
         [0046]    In operation of one embodiment of the device, pressurized air (e.g. 50-150 psig) impacts the resting position of the proximal facing surface  36  of the piston to propel the piston in a distally extending direction. A circumferentially extending groove  19  along a proximal periphery of the piston  25  is adapted to receive an o-ring gasket  21  so as to provide a means for hermetically sealing the proximal end of the barrel to the proximal end of the piston while maintaining slidable communication between the piston and the barrel, similar to the configuration of a piston in a cylinder of an engine. At the opposite (i.e., distal) end of the device, the stop  12  limits motion of the riveting tool  40  by contacting distal surface  38 . A threaded surface  24  of the distal end  16  of the housing is adapted to receive the complementary threaded spacer  17  so that one may adjust the distance the tip  39  of the rivet portion  40  protrudes from the first end  16  of the housing  11  after compressed air is applied by varying the length of the spacer  17 . This spacer  17  may also communicate with the housing  11  in a snap fit arrangement or some other reversible attachment means. 
         [0047]      FIG. 2  is a perspective view of an exemplary embodiment of the piston portion  25  depicted in  FIG. 1 . Preferably, this piston section  25  is manufactured from a single piece of high impact resistant material such as SAE Grade S Tool steel. The piston portion  25  comprises a cylindrical shaft  29  emanating from a base  32 . The shaft  29  defines a longitudinally extending portion  29   s  having a polygonal cross-section bounded by planes  23 . A distal portion  29   c  defines a circular cross-section. The shaft terminates in a tip  26 , which is depicted as a hemisphere in  FIG. 2 . However, the tip can also be frusto-conical as depicted in  FIG. 1 . A hemispherical tip  26  reduces frictional wear on the piston. (See Operation of the Device infra). 
         [0048]    While in general the cross-section of the portion  29   s  can be an arbitrary polygon, for illustration purposes, in the remainder of this description this cross-section will be taken to be a square and in some embodiments (such as the one depicted in  FIG. 2 ) this square cross-section excludes sharp corners. A medially facing surface of the base  32  defines a channel  31  circumscribing the shaft  29  and adapted to receive the piston spring  30  and a peripheral wall  34  comprising the o-ring groove  19 . As noted supra, the floor of the channel (i.e., the distal facing surface  27  of the piston portion) is adapted to support the piston spring  30 . 
         [0049]      FIG. 3   a  is a perspective view of an exemplary embodiment of the riveting portion. The riveting portion comprises a base  57  and four hammers  59  emanating from the base  57  and attached to the base  57  as described infra. The base  57  comprises a top plate  82  and a bottom plate  84 , with the top plate  82  secured to the bottom plate  84  by fastening means  83  such as screws.  FIGS. 4   a  and  4   b  provide profile and face views of a hammer  59 . Each hammer  59  comprises a cam surface  45  at its proximal end, a hammer head  53  at its distal end, and a generally elongate flat substrate or panel  47  positioned intermediate, and integrally formed with, the cam surface and the hammer head. A plurality of hammers are symmetrically arranged about the longitudinal axis a of the device to form a sleeve  49  defining a longitudinally extending interior surface. This surface is adapted to slidably receive the portion  29   s  of the piston. (See  FIG. 1 ). 
         [0050]    Each panel terminates in a hammer head  53  such that when four hammer heads  53  are symmetrically arranged about the longitudinal axis, the resulting configuration resembles a pyramid  48 . Each hammer head has an interior face  51  so that the four hammer heads  53  form within the pyramid  48  an interior cavity  46  configured to receive the piston tip  26 . 
         [0051]    Each pyramid face comprises a base edge  50 , two slanted edges  71 , and a mid-face section  77 . As shown in  FIG. 4   a , the base-edge  50  is rounded. (See Operation of the Device infra concerning this feature.) To facilitate use of the device to perforate metal plates, the pyramid faces are concave with edges  71  protruding from the face and the mid-face section  77  being recessed, as is shown in  FIG. 4   c  which is a cross-sectional view of  FIG. 1  along the line  4   c - 4   c.    
         [0052]      FIG. 4   d  depicts a hinge arrangement for a hammer  59  (shown in  FIG. 3   a ). The cam surface  45  and the panel leg  54  are positioned between the shaft  29   s  and a peripheral region  81  of the top plate  82  of the piston portion. An L-shaped substrate or rubber elbow  89  is positioned intermediate the cam surface and the top plate region  81 , with a horizontally disposed region  98  of the elbow further positioned in an annular channel formed by a depending surface of the top plate  82  which is overhanging an upwardly facing surface of the bottom plate  84  of the piston base. The cam surface  45  is supported by a peripheral portion  92  of the bottom plate  84  not overhung by the top plate  82 . The rubber elbow  89  consists of reversibly deformable material. The elbow  89  further comprises a vertically disposed section  99  that is sandwiched between the top plate region  81  and the hammer leg  54  and cam surface  45 . The horizontally disposed section  98  (which is perpendicular the vertical section  99 ) is frictionally held or sandwiched between the plate  82  and the surface  92  by means of one or more fasteners  83 . A torque T applied to the hammer  59  results in a swing in the direction T by the hammer but the laterally biasing force provided by rubber elbow  89  forces the hammer  59  to return to its original substantially vertical position once the torque T terminates. 
         [0053]      FIG. 3   b  is a perspective view of the top plate  82  of the base  57  (appearing in  FIG. 3   a ) while  FIG. 3   c  is a face view of the bottom plate  84  of the base  57 . The top plate  82  defines a centrally disposed bore  87  having an x-shaped cross section. The center of the cross section defines a square bore  85  adapted to slidably communicate the piston shaft  29   s  (See  FIG. 3   c ). As depicted in  FIG. 3   c , rectangular bores  88  are contiguous to the square bores  85 . Each rectangular bore  88  is designed to accommodate the vertically disposed section  99  of the rubber elbow  89  and the hammer leg  54  depicted in  FIG. 4   d . Also, the plate  82  defines clearance countersunk bores  97  dimensioned to receive the fasteners  83 . 
         [0054]    The bottom plate  84  defines a square through bore  85  to allow slidable communication with the piston shaft  29   s . The bottom plate also defines four shallow rectangular cavities  86  bordering the bore  85 , each of said bordering cavities designed to accommodate a cam surface  45 . The cavities  86  are contiguous to cavities  88  of the same depth, each designed to accommodate the horizontally disposed section  98  of a rubber elbow  89 . Also the plate  84  comprises threaded bores  91  dimensioned to receive the fasteners  83 .  FIGS. 5   a  and  5   b  depict the base  57  assembled with the rubber elbows and the cam surface. 
       Operation Details 
       [0055]    The device is intended for piercing simultaneously one or more sheets of metal or other suitable material, folding back extrusions produced when the sheets are pierced, and pressing back the extrusions on the back side of the last sheet being riveted. With two or more sheets so acted upon, the sheets are crimped to each other so that they cannot be separated nor rotated with respect to the other. 
         [0056]    As shown in  FIG. 1  the device is operated with an air gun. Alternatively, one may use a device where an air-fuel mixture is ignited by an ignition source. Such a device provides much higher pressure than standard compressed air devices. A spring gun or a rod and lever are also suitable. For the sake of specificity, an air gun is assumed in the remainder of this description. 
         [0057]    When pressure is applied between the piston base  32  and the proximal end  18  of the housing  11 , the piston is propelled forward, i.e., towards the distal or first end  16  of the barrel. This forward piston motion actuates the axial and lateral movement of the hammerheads of the rivet portion. The axial movement of the rivet portion terminates when the spring  20  is fully compressed and distal facing surface  38  contacts stop  12 . Simultaneously, the rivet tool pyramid  48  pierces the sheets of metal  41 ,  42 , forming roughly triangular extrusions  43  or chads. (See  FIG. 5   a ) 
         [0058]    The axial-extending length of the spacer  17  is chosen so that the edge  50  of the hammer head comes to rest at a medial position  44  in the extrusions  43 . At this point the tapered tip  26  of the piston is instantaneously at rest with respect to the mating cavity  46  in the riveting portion and the piston spring  20  is fully compressed while the rivet spring  30  is at or near equilibrium. Yet at this point the region  13  in the gun barrel is still pressurized and this pressure acting on the base  32  is transmitted to the section  26  of the piston which in turn acts on the cavity  46 . 
         [0059]    Stop  12  prevents the over-extension of the rivet portion  40 . The rivet portion  40  is not stopped by a substrate external to the device nor is the operation of the device dependent on any of the puncture elements resting against or impacting an external substrate. When the forward motion of the rivet portion  40  is stopped by the stop  12 , the pressure in the housing  11  urges the piston assembly further forward. This forces the tip section  26  of the piston to force its way into the cavity  46  in the pyramid  48  in the rivet portion. (See  FIG. 5   b ). This action imparts a lateral force to interior surfaces of the four hammer head sections  53  and the sleeve panels  47 , thereby leading to their separation (akin to the opening of flower petals) so as to form a four-pronged hydra. The hammer heads  53  of the pyramid sections in turn apply a lateral force on the extrusions  43  and in a direction that is approximately perpendicular from the longitudinal axis of the piston. This action causes the hammer heads to thereby slide laterally across proximal ends of the extrusions, thereby folding the extrusions back against the surface of the last sheet of metal in the stack. (Note that the sliding of the hammer heads  53  on the extrusions  43  is facilitated by the fact that the edge  50  of the hammer heads  53  is rounded.) At this point air pressure is lost from the housing  11  through exhaust slots  35  (See  FIG. 5   b ) in the cylinder or via an external bypass valve. This allows the piston spring  30  to exert a force backward (i.e. towards the end  18  of the housing). This causes the four hammer heads  53  to retract towards the axis. Then the springs bring back the rivet/piston combination to the position depicted in  FIG. 1 . 
         [0060]    Experimentation by the inventor has determined that a hemispherical shape for the piston tip  26  minimizes frictional wear on that tip. With a hemispherical tip  26 , as the tip  26  advances in the rivet cavity  46  different regions  26   a ,  26   b ,  26   c  of the tip  26  (See  FIG. 2 ) come into contact with the inner face  51  of the hammer head  53  so that different regions of both the tip  26  and the hammer heads  53  experience wear in a single stroke. (See  FIGS. 6   a ,  6   b ,  6   c ) 
       Alternative Embodiments 
       [0061]    Alternative embodiments may differ in several respects from the preceding embodiment. 
         [0062]      FIG. 7   a  depicts an alternate exemplary embodiment  110  comprising a piston portion  125  and a rivet portion  140 . The piston portion  125 , which is manufactured from a single piece of high impact resistant material such as steel, is depicted in  FIG. 7   b . The piston portion  125  comprises a shaft  129  emanating from a base  132 . The shaft  129  comprises a section  129   s  with a polygonal cross-section and a proximal section  129   c  with a circular cross-section, the latter terminating in a frusto-conical section  128  followed by a narrower shaft  127  which in turn terminates in a cone tip  126 . (A circle  133  defines the transition between the shaft  127  and the cone  126 ). The base  132  comprises a channel  131  circumscribing the shaft  129  and adapted to receive a piston spring  30  and a peripheral wall  134  comprising an o-ring groove  119 . The shaft portion  129   s  with a polygonal cross-section is bounded by planes  123  and the tip  126  is a pyramid  126   s  the faces of which are aligned with the planes  123 . While in general the cross-section of the portion  129   s  can be an arbitrary polygon, in the remainder of this description this cross-section will be taken to be a square. 
         [0063]      FIG. 7   c  is a perspective view of an exemplary embodiment of the rivet portion  140  which is intended for use with the square cross-section piston portion  125  depicted in  FIG. 7   b . The rivet portion  140  is manufactured from a single piece of high impact reversibly deformable material such as tool steel. The rivet portion  140  comprises four sections separated by slits  162 . Each section comprises a panel  161  and a head  153 , such that the four sections form a hollow cylindrical shaft constituting a sleeve  149  emanating from the base  157  with the sleeve terminating in a pyramid  148 . The rectangular panels  161  originate from the base  157  at regions  158  at the base of each panel. The panel regions  158  are very thin and since they are composed of reversibly deformable material they serve as reversible hinges. The slits  162  extend the entire length of the rivet section above its base and into the pyramid  148 , to allow for separation of the four heads  153  upon actuation of the piston which is received by internal surfaces of the rivet portion. 
         [0064]      FIG. 7   d  shows a cross-section of the device  110  taken along the line  7 - 7  in  FIG. 7   a . The rivet portion comprises a longitudinally extending bore  151  adapted to slidably receive the shaft  129  of the piston. As such, the bore and the shaft have similar cross sections, with the shaft dimensioned slightly smaller to facilitate substantially frictionless sliding within the bore. 
         [0065]    The pyramid section comprises a conical bore  146  adapted to slidably receive the conical section  128  and a cylindrical bore  156  adapted to slidably receive the shaft  127 . The pyramid  148  terminates in an aperture with rim  154  through which can protrude the shaft  127  terminating in the cone  126 . Each pyramid face comprises a base edge  150  defining a radius, two slanted edges  171 , and a mid-face section  177 . To facilitate penetration of the metal plates  41 ,  42  by the device, the pyramid faces are concave with edges  171  protruding from the face and the mid-face section  177  being recessed or depressed (See  FIG. 4   c  for an identical construction). 
         [0066]    In this embodiment, springs identical to the springs  20  and  30  depicted in  FIG. 1  are utilized. In the equilibrium situation, i.e. before the device is propelled forward, the rim  154  coincides with the circle  133 . 
         [0067]    The piston depicted in  FIG. 2  could also be used in this embodiment, in which case there is no aperture at the tip of the pyramid. 
         [0068]    The operation of this device is identical to that of the embodiment depicted in  FIG. 1 .  FIG. 7   e  is a perspective view of the embodiment  110  when the heads  153  are deployed as the piston  129  is thrust into the pyramid  146 , 
         [0069]      FIGS. 8   a ,  8   b , and  8   c  describe yet another embodiment of the present invention.  FIG. 8   a  is a perspective view of the device  200  and  FIG. 8   b  is a perspective view of the piston section. This embodiment features a circular cross-section cylindrical piston  230  that comprises a base  231  from which emanates a cylinder  233  that terminates in a first frusto-conical section  234 . Superior to and integrally molded with the first frusto-conical section  234  is a cylindrical section  235  that terminates in a second frusto-conical section  236 . Superior to and integrally molded with this second frusto-conical section is a cylindrical section  237  that terminates in a conical tip  238 . The first and second frusto-conical sections  234  and  236  have the same inclination angle and the same height. This piston  230  is intended for use with a rivet portion  210  that comprises four separate sections  211 ,  212 ,  213 , and  214  that are juxtaposed to each other and held together by o-rings or split rings  215 ,  216  received in grooves  225 ,  226 . 
         [0070]      FIG. 8   c  is an exploded profile view of the rivet portion  210  positioned superior to the piston portion  230 . Each rivet section  211 ,  212 ,  213 , and  214  comprises a base portion  241 , a sleeve portion  242  that is one quarter of a circular cross-section cylindrical sleeve and a pyramid portion  243 .  FIG. 8   d  is a cross-sectional view taken along line  8   d - 8   d  of  FIG. 8   c  of the rivet portion  210  and of the piston portion  230 . When the rivet portions are held together by the o-rings  215  and  216 , they define frusto-conical cavities  254 ,  256  dimensioned to receive piston conical sections  236  and  234 . 
         [0071]    The operation of this piston/rivet combination differs from the previous two embodiments in that when the piston  230  is thrust into the four-component rivet portion  210 , with the piston conical sections thrust into the cavities  254 ,  256  the four sections  211 ,  212 ,  213 , and  214  are forced to displace laterally, perpendicular to the axis y of the piston, with no rotational movement of the rivet sections at all. 
         [0072]      FIG. 9  is a depiction of an alternative embodiment of the invention comprising a cap  300  attached to the first or distal end  16  of the device  10  as shown in  FIG. 1 . In the alternative embodiment shown in  FIG. 9 , the cap  300  includes an integral electromagnet  310 . The electromagnet is connected to power leads  315  which can energize the electromagnet  310 . When the electromagnet  310  is energized, the cap  300  will be magnetically attracted to the metallic substrate undergoing fastening. The energized electromagnet  310  will assist to maintain the tool in place and removably engaged with the substrate, especially in instances where a high amount of lateral pressure is needed to puncture a heavy substrate. In one embodiment, the power leads  315  are connected to a direct current voltage source comprising a battery. In another embodiment, the power leads  315  are connected to an alternating current source, such as household current, wherein the alternating current source is adapted to function with the electromagnet  315 . 
         [0073]    While the invention has been described in the foregoing with reference to details of the illustrated embodiments, these details are not intended to limit the scope of the invention as defined in the appended claims.