US3442105A - Fastener setting device - Google Patents

Description

May 6, 1969 E. J. SOSNOWICZ ET AL 3,442,105

FASTENER SETTING DEVICE Filed Jan. 19, 1966 Sheet of 5 EDWARD J. SOSNOWICZ FRANK M. WILLIS BY WW ATTORNEY Ma 6, 1969 J, sosmow cz ET AL 3,442,105

FASTENER SETTING DEVICE Filed Jan. 19, 1966 Sheet 2 of 5 FIG. r

FIG. 4

INVENTORS EDWARD J. SOSNOWICZ FRANK M. WILLIS ATTORNEY May 6, 1969 w z ET AL 3,442,105

FASTENER SETTING DEVICE Shee t Filed Jan. 19, 1966 M N I... mm my M s w M D A z 2 M E 2 i M wfi I I li a \N 2 a a s 2 2 ATTORNEY y 6, 1959 E. J. SOSNOWICZ E Al. 3,442,105

FASTENER SETTING DEVICE Filed Jan. 19, 1966 Sheet 4 of 5 I 1 is 7. 7101'" II I I INVENTORS EDWARD J. SOSNOWICZ ATTORNEY May 6, 1969 E. J. SOSNOWICZ ET L FASTENER SETTING DEVICE Sheet Filed Jan. 19, 1966 INVENTORS United States Patent 3,442,105 FASTENER SETTING DEVICE Edward J. Sosnowicz, Colwyn, Pa., and Frank M. Willis, Sewell, N.J., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Jan. 19, 1966, Ser. No. 521,641 Int. Cl. 1321i /00; B21d 26/08 US. Cl. 7256 11 Claims ABSTRACT OF THE DISCLOSURE A device for setting electrically fired explosively-actuated fasteners comprising a current-sensitive explosive in contact with a first electrode and a second electrode. The device comprises a supporting body for two electrodes one of which acts as a positioner for the device with respect to the fastener and is yieldably mounted in the body. The second electrode is mounted in the body for independent movement with respect to the positioning electrode in a direction parallel to the direction of yieldable movement of the positioning electrode.

head portion and a shank portion having a central longitudinal recess. The recess holds an explosive charge which conventionally is one capable of ignition merely by the application of heat. In use, the shank of the fastener is pressed through aligned holes in two panels which are to be joined, with the explosive charge located in the portion of the shank positioned slightly beyond the far surface of the metal plate most removed from the head of the fastener. When the explosive charge is actuated, i.e., detonated or deflagrated, the walls of the fastener in the vicinity of the charge are bulged out and the fastener thereby holds the metal plates tightly together.

While various methods have been suggested to fire the explosive charge in the fastener, viz, percussion, safety fuse, or high voltage static discharge, by far the most commonly used method is by means of an electric heating device which is applied to the fastener head and, by thermal conductance, raises the temperature of at least the head of the rivet until the ignition temperature of the explosive charge is attained. The necessity for the use of a cumbersome-heat-producing tool in such work is a distinct disadvantage and results in increased labor costs or, where the space surrounding the head of the fasteners is restricted, often precludes their use. The presently used tools are heavy, require a bulky power source trailing behind the operator, build up considerable heat in use, adding to the operators frustrations, and require a high degree of adjustment and maintenance of the heating tip. Further, considerable pressure must be applied in using the conventional heating tools.

An explosive fastener now has been developed which does not depend upon heat transfer through the head for actuation of the explosive charge, but rather employs a charge which is actuated in microseconds by low electric current passing therethrough. These new fasteners, which can be rivets, bolts, screws, nails, pins, or the like, are described more thoroughly in copending application Ser. No. 393,550, by W. E. Schulz, filed Sept. 1, 1964,

Patented May 6, 1969 which was abandoned in favor of continuationdn-part application SJN. 521,599, filed Jan. 19, 1966, and now US. 3,332,311, issued July 25, 1967, which is incorporated herein by reference. The expanding explosive charge therein comprises a detonating explosive compo sition such as, typically, lead azide in intimate admixture with particles of an electrically conductive, semiconductive, or voltage-sensitive material, preferably carbon and typically graphite in admixtures with amorphous carbon. The fastener is provided with an opening, preferably through its head, into the recess containing the explosive charge, and an electrode, which is insulated along its entire length but has bare ends, is inserted into the recess. A portion of the electrode within the recess is contoured, e.g., headed, to preclude forceful eject-ion of the conductor upon actuation of the explosive charge. The surface of the electrode within the recess is peripherally coextensive with the walls of the recess. The conductive, semiconductive, or voltage-sensitive particles dispersed in the explosive charge are believed to provide a plurality of conducting paths (bridges) of microscopic cross-section but measurable resistance preferably of, e.-g., 1 to 1000 ohms, between the electrode and the body of the fastener. The passage of an electric current supplied by a (1 to microfarads) capacitor charged by a (nominal 30 to volts) direct current source is sufficient to effect actuation of the explosive charge and expansion of the walls of the shank of the fastener within microseconds, at rates many times faster than that required to fire conventional heat actuated fasteners. However, there still remains a need for a lightweight, nonhazardous tool to set, i.e., bring about actuation of, the explosive charge of the recently developed fasteners and, in some embodiments, to eliminate any protrusion of the electrode above the fastener head after firing.

In accordance with this invention, there is now provided a device for setting the aforementioned electrically fired, explosively actuated fasteners, which is characterized by its simplicity, compactness, reliability, and rapidity of setting.

The devices of this invention for setting the aforementioned electrically-fired, explosively-actuated fasteners comprise:

(a) positioning means which is yieldably mounted for movement parallel to the axis of said fasteners during setting and which engages the body of the fasteners and forces them into the workpiece,

(b) a conductive electrode independently movable with respect to (a) in a direction parallel to the direction of yieldable movement thereof to engage an electrode in said fasteners, and

(c) a power source which is connected to electrode (b) and thus to one electrode, usually a central electrode, of the fasteners.

The positioning means is preferably tubular, of metal or other conductive material and substantially coaxial with electrode (b). Preferably, the positioning means is in the portion of the device circuit connected to one pole of the power source, usually through the body of the device, and engages the body electrode of the fasteners. Alternately, however, the positioning means can be non-conductive plastic or other insulating material, the fastener bodies being merely grounded, e.g., on the workpiece together with the device body. The positioning means also provides the force necessary to draw parts of the workpiece together, e.g., in the blind fastening of panels.

After the positioning means in devices of this invention is brought into contact with a fastener and the body thereof is pushed farther toward the workpiece, electrode (b) is brought into contact with the fasteners completing the circuit therethrough, actuating the explosive therein and setting the fasteners. During this forward body movement, pressure applied by the positioning means on the fastener and workpiece increases. This force on the fastener and workpiece is preferably applied by a spring, preferably a coil spring, abutting the positioning means, i.e., either the electrode per se or an appurtenance thereto, and also abutting some stationary element in this body of the device. Alternately, for example, the force applied to the positioning means urging it toward the workpiece can be supplied by having the rearward portion of the positioning means-tubular electrode act as a piston in an air cylinder or by applying some other yieldable force against the positioning means in the direction of the workpiece, e.g., by placing a yieldable elastomeric cushion abutting the rear of the positioning means and the device body.

In a preferred embodiment of the invention fasteners are supplied atuomatically in front of the electrodes by a pneumatically driven feeding head mounted and axially movable along the nosepiece bearing the positioning means-tubular electrode. In one preferred embodiment, this feeding head is actuated to supply each fastener by the current which sets the preceding fastener. Alternately, however, a separate switch, e.g., a switch in the pistol grip handle, can be used to actuate the feeding of each fastener to the feeding head. In one other embodiment of the invention particularly useful with fasteners having central electrodes with protruding heads, the devices contains a means for driving the electrode (b) forward rapidly to peen the head of the fasteners.

The power source is preferably of the capacitive type usually of 1 to 100 microfarad capacity and preferably with a battery recharger coupled therewith. Alternately, the firing current or the recharging current can be supplied directly from any conventional D.C. or rectified A.C. source. In order to lengthen the life of the batteries in the manual device and control charging time of the capacitor, preferably a resistance, usually of 8000 to 20,000 ohms, is connected in series with the power source, preferably on the probe (electrode (b)) side.

The conductive elements of the devices of this invention can be of brass, bronze, steel, aluminum or other metals including any of the conductive materials commonly used in hand tools. For non-conductive elements, plastics including nylon, polytetrafluoroethylene, polyethylene, polypropylene, acetal resins, the phenolic and aminoplast thermosets, as well as laminates thereof can be used.

-In the accompanying drawings which illustrate the invention:

FIGURE 1 is a schematic, cross-sectional view of an electrically fired, explosively actuated fastener being fired by a device of this invention,

FIGURE 2 is a cross-sectional view of the manual device of this invention, the parts therein being shown in the at rest position,

FIGURE 3 is a cross-sectional view of a finger-manipulated device in accordance with this invention,

FIGURE 4 is a schematic diagram of the basic electric circuitry involved in the devices of this invention,

FIGURES 5 and 6 are cross-sectional elevational and partial top views, respectively, of an automatically fed device of this invention.

FIGURE 7 is a schematic diagram of electric circuitry which can be employed in accordance with this invention to correlate feeding of fasteners with setting of a preceding fastener.

FIGURES 8 and 9 are views of a device of this invention adapted to set fasteners and instantaneously thereafter to peen any portion of the electrode protruding above the fastener head flush therewith.

In FIGURE 1, an electrically fired rivet having a body 1 of aluminum, bronze, brass or other conventional fastener metal is positioned already for setting in aligned holes in parts 2 and 3 to be joined. Body 1 has a recess passing axially through the head and shank thereof. At the upper part of this recess is an electrode 4, usually of metal similar to body 1, bare at its upper and lower ends but insulated from body 1 by an insulating layer 5, e.g., a. coating of Formvar polyvinyl-methylal resin. Within the aforementioned recess adjacent the inner end of electrode 4 is an electrically fired explosive charge 6, e.g., of, by weight, 65% of 25p. dextrinated lead azide, 16% of 2-l0a micronized graphite, 4% nitrostarch, 13% tetracene and 2%-29p. oil furnace black pin set at 35,000 p.s.i. The bottom of the recess in body 1 is closed with a rubber spacer 7 and soft carbon steel plug 8. After charge 6 is detonated as will be presently described, the shank of body 1 expands to the position shown by the dotted lines 9.

The device of this invention shown in FIGURE 1 comprises annular metal electrode 10 which engages the head portion of the body 1 of the rivet and central metal electrode 11 which engages electrode 4 in the rivet. Annular electrode 10 is positioned to engage the rivet first and then plastic or other insulating base 12 is depressed to move electrode 11 into engagement with electrode 4 of the rivet. Electrode 10 is held in engagement with the rivet by spring 13 as electrode 1 lis moved into engagement. When both electrodes 10 and 11 have engaged the fastener, current from a power source comprising battery 14 and capacitor 15 passes through the electrodes and explosive charge 6 as shown by the arrows in FIGURE 1, detonating charge 6 and setting the rivet.

In FIGURE 2, a tool, i.e., a gun, is shown which has a tubular, barrel-like body which is of an electrically conductive material, typically a metal, having a hollow barrel 20 and a hollow handle 21. A nosepiece 22, also of a conductive material and having a central aperture therethrough is mounted for reciprocal forward and backward movement in the muzzle of the gun barrel parallel to the longitudinal axis of the barrel. Nosepiece 22 forms one electrode in the device of this invention. Spring 23, which is mounted on stationary dielectric spacer and guide 24 near the rear of the barrel, extends substantially the length of the barrel into contact with the rearward surface of nosepiece 22, restricting its rearward motion. The forward portion of dielectric spacer and guide 24 forms a cylindrical chamber portion 25. The extremity of the chamber portion toward the muzzle is abutted by electrode 26 which is mounted along the longitudinal axis of the barrel, the forward portion of the electrode 26 extending into and being axially aligned with the aperture 27 in nosepiece 22. The diameter of electrode 26 is slightly less than the diameter of the aperture to allow its smooth passage through aperture 27 during reciprocal movement of nosepiece 22, relative to the barrel. Spring 28, which is mounted on insulator guide 29 and extends into the rear of cylindrical chamber portion 25, biases the contact means forward and acts as a cushion to prevent overtravel of and damage to electrode 26. Electrode 26 is insulated from nosepiece electrode 22 by dielectric sleeve 30, which is in close peripheral contact with the cylindrical surfaces of both components.

The electrical components of the gun, i.e., device or tool, conveniently are contained in the cavity in the handle 21 of the gun. These components make up the energy package, i.e., power source, which comprises, basically, capacitor 31, which usually is of about from 1 to microfarad capacitance, preferably about 10 to 20 microfarads, and preferably has positive and negative terminals as designated in the drawing, charged by a negative 30 to volt DC. power source 32, i.e., a bat tery or batteries. Resistor 33 (connected between the negative side of the battery 32 and negative side of capacitor 32 of about from 8000 to 20,0009 resistance prevents a current flow in excess of the battery manufacturers recommendation. Lead 34 from the negative side of capacitor 31 is connected to mount 29 and is in electrical contact with spring 28 which is, in turn, in electrical contact with electrode 26. Thus, electrode 26 is connected electrically in circuit with capacitor 31. Nosepiece electrode 22 is connected to the positive side of capacitor 31 through barrel and housing 20 and lug 35- in the hollow handle of the gun body. Jack 39 provided in the handle of the gun for attachment of the hand device hereinafter described is connected to the negative side of the capacitor.

To set one of the electrically fired, explosively actuated fasteners 36, i.e., to actuate (detonate or deflagrate) the explosive charge 37 therein, the gun is applied to the head of the fastener with aperture 27 substantially centered over the insulated electrode 38 in the fastener head. With the gun in position and capacitor 31 charged, the operator pushes the gun against the head of the fastener 36 and toward the surface of the parts to be joined by the fastener, thereby exerting push-down force on the parts. Contact of nosepiece 22 with the head of the fastener 36 connects, electrically, the fastener body to the positive side of the capacitor 31. As push down force is exerted, nosepiece 22 moves back into the muzzle of the barrel against the resistance presented by spring 23. The compression force (resistance) of spring 23 is selected and/or adjusted to regulate the total push down exerted to move nosepiece 22 back into the muzzle of the barrel and to bring electrode 26 into electrical contact with the electrode 38 in the head of the fastener 36. As the nosepiece electrode 22 moves back into the muzzle 20 the forward tip of electrode 26 protrudes through the insulating guide 30 in the nosepiece to contact the electrode 38. Contact of electrode 26 with the electrode of the fastener places the electrode 38, which becomes connected to the negative side of the capacitor 31 and the conductive particles in the explosive charge 37, in the electric circuit described above. The energy in the capacitor 31 is discharged through spring 28, chamber 25, and electrode 26 to electrode 38, from electrode 38 through microscopic bridges provided by conductive particles in the explosive composition 37 to the body of the fastener 36 which is connected in the electric circuit, i.e., to the positive side of capacitor 31, through nosepiece electrode 22, housing 20 and lug 35, as described above. The explosive composition is actuated, e.g., is detonated or deflagrates, in microseconds, typically 1 to 15 0 microseconds, after contact is made. Actuation of the explosive composition, as detected by a click, radially expands the fastener body without rupturing it. When the gun is removed from the panels, the compression force in spring 23 is released and nosepiece electrode 22 is pushed forward in the muzzle by the spring 28. The gun can be made to fit in the operators hand in a position designed for minimum fatigue and manipulated by body and shoulder motion, minimizing wrist action. Jack 39 can be used to connect the power source of the gun to a hand device of this invention, e.g., of the type shown in FIGURE 3, by a coaxial cable.

As shown in FIGURE 3, devices of this invention can be made small enough to fit in a thimble-like holder which can be slipped onto the tip of an operators finger and particularly adapted for use in locations where there is small clearance. In this embodiment, housing 41 is a tubular metal body and nosepiece 42 is mounted for movement along the longitudinal axis of the housing against the resistance presented by spring 43 which biasses it forward. Electrode 44 is, in this embodiment, stationarily mounted in the housing and insulated by dielectric sleeve 45.

A small coaxial cable, such as RG 178B/U (military designation number) extends into the opposite extremity of housing 41. The center conductor 47 of the cable, which is protected and insulated by the coaxial cable dielectric 48, is attached to a washer-like piece 51, typically of brass, which is insulated from body 41 by a machined piece 50 of a hard dielectric such as a polyoxymethylene (Delrin) or nylon. The conductive washer-like piece 51 is in physical contact with electrode 44. The braided shield 52 of the coaxial cable is attached to the washer-like piece 49. The assembly is held in place in housing 41 typically by a snap-ring 53 and provides a means of electrically connecting the body of the finger tool in circuit with the power source, e.g., those of FIGURES l and 2. Conveniently, a power source comprising the batteries, a capacitor, and a current limiting resistor can be stored in the operators pocket or afiixed to a holster by a clip.

Operation of the finger-tool is basically the same as that of the devices of FIGURES 1 and .2. In the operation of this tool, the operators finger action serves to cushion electrode 44 and to preclude its overtravel when contact is made with the head of the fastener in a similar way to the action of springs 13 and 23 in FIGURES 1 and 2, respectively.

The electric circuitry employed to actuate the conductive explosive composition within the fastener can be seen more readily by reference to FIGURE 4. In this figure, the designation of electric components is as described above for FIGURE 2. To repeat somewhat the discussion of FIGURE 1, in the operation of the gun, the capacitor 31 is charged to battery voltage through resistor 33. When the electrode 26, which is connected in the electric circuit directly as in FIGURE 3, or through a spring as in FIG- URES 2 and 5, is in contact with the electrode of the fastener, the capacitor is discharged through electrode 26, the conductive explosive mixture within the fastener, the fastener body, and the body of the gun. The resistance value for resistor 33 is selected to limit the current from the power source 21 to preselected value, e.g., 5 to 10 milliamperes, which regulates the recharge time for capacitor 31.

FIGURES 5 and 6 show a gun adapted to receive fasteners automatically and pneumatically fed to it and to aid in positioning the fasteners in aligned holes in panels to be joined. The nosepiece 60 shown in these figures replaces the nosepiece 22 of the manual gun shown in FIGURE 2. The increased length of the nosepiece 60 over that of the nosepiece 22 of FIGURE 2 is required to accommodate the Y-feeding head 61 of the pneumatic feeding and positioning mechanism. The nosepiece 60 has a lip 62 providing a piston for operation in cavity 63. Electrode 76, which is movable in nosepiece 60 in a similar manner to its motion in nosepiece 22 in the manual gun, is lengthened to correspond to the increased length of the nosepiece 60.

The body of assembly 61 fits about the nosepiece 60 and peripherally engages lip 62. Cavity 63 is coaxial with nosepiece 60 and with the barrel of the gun. Tubular passage 64 which intersects passage 65 with an included angle, e.g., of 20 to 40, being formed between the longitudinal axes of passage 64 and the exit passage 65 in assembly 61 leading from cavity 63, an enlarged rear portion of passage 65. Cavity 63 defines an air cylinder within which lip 62 acts as a piston. Tap 72 is provided to connect the air cylinder with an external source of compressed air.

The snout 67 on assembly 61 is of frustro-conical configuration continuing, and being coaxial with, passage 65. The snout provides an aperture 68 whose diameter is slightly larger than the shank of the fastener with which the gun is to be used but less than the head thereof. The frustro-conical snout is bisected (split) longitudinally and the two portions thus formed mounted on body 61 and held closed by fiat springs 69. These springs permit halves of snout 67 to spread and move apart radially providing sutficient clearance for the head of the fastener to pass through aperture 68. The wall thickness of the snout diminishes from a maximum at the section mounted adjacent body 61 to a minimum at the aperture. The interior of the snout is highly polished and the edges rounded slightly to provide a smooth surface which will build up minimal friction during passage of the fastener.

The feeding head 61 is shown in FIGURES 5 and 6 slidably mounted on nosepiece electrode 60 by a pair of springs 70 which can extend from the muzzle of the barrel to the feeding head. The springs are bent around pedestals which prevents the springs from becoming straight. The springs exert neither a push or pull-force but act to insure return of the nosepiece attachment to its at rest rearward position during actuation of the gun.

FIGURE shows a fasener 73 being fed into section 65 of the attachment through the bore of section 64. Pressure applied to air cylinder 63 through tap 72 displaces the head 61, forcing it forward with respect to the nosepiece 60 so that the path between section 64 and the interior of snout 67 is unobstructed.

The dotted lines in FIGURE 5 show the lip 62, electrode tip of nosepiece 60, and the fastener 73 in the sno t 67 in position to be inserted in parts to be joined. After the initial pulse of air is exerted, air pressure is vented from the air cylinder 63 primarily by leakage of air around lip 62, allowing the head 61 to move back toward the handle of the gun. The time between the pulsing of air that blows a fastener to the head 61 and the time the air vents overlaps. The pulse of air and air pressure in the head assembly and the force of springs 69 trap and hold the fastener in place in the nose of the attachment until contact is made between the head of the fastener 73 and the tip of nosepiece electrode 60 in functioning of the gun, no matter what the position of the gun might be, i.e., there is little or no dependence on gravity ,or pawls (dogs). The two portions of the snout are held together by the force of springs 69, trapping the head of the fastener.

In FIGURE 6 snout 67 and the tip of nosepiece electrode 60 are shown in position to set the fastener 73. The snout 67 and fastener 73 are in the position shown by dotted lines in FIGURE 5. At the time the shank of the fastener is inserted into aligned holes in the parts. As increased pushdown force is exerted, the two portions of the snout spread apart to free the head of the fastener and the head attachment moves back toward the barrel of the gun permitting the tip of nosepiece electrode 60 to push the fastener 73 all the way into the holes in the parts as shown in FIGURE 6. With the application of still greater pushing force, the nosepiece 60 itself moves rearward in body 75 against the force of spring 74, thereby causing electrode 76 to come forward with respect to nosepiece 60 and to protrude through the aperture in the snout, making electrical contact with the electrode of the fastener 73.

The power source comprising capacitor 80 and resistor 81 is grounded through lug 83 to body 75 and electrodenosepiece 60 while the negative terminal of the power source is connected to electrode 76 through spring 77 in dielectric housing 78 abutted against stationary abutment 79. All of the aforementioned elements function like the corresponding elements in FIGURE 2. Resistor 81 and the positive side of capacitor 80 are connected to the central circuitry of FIGURE 7 described hereafter through a BNC connector 84 at the base of the hollow handle of the gun. Batteries are not provided in the handle of this gun since rectified A.C. current from the circuitry of FIGURE 7 is the power source.

Alternatively, the adaptor for receiving and holding the fasteners supplied from a hopper can be one which 'has means providing a first barrier to obstruct passage through its snout of a fastener and second barrier means upstream of the first barrier to obstruct movement of the fastener away from the snout, the first barrier yieldable by the movement of the probe to free the obstructed fastener.

The fasteners are conveyed to the automatic gun pneumatically from a hopper by a combined pneumatic-electric mechanism whose functioning can be correlated with firing of the fastener and the positioning and discharging of a fastener in the muzzle of the gun.

An example of a suitable device for supplying fasteners t0 the feeding head 61 of device of this invention is shown in U.S. Patent 3,026,000 (see particularly FIGURE 1) which is incorporated herein by reference. Other feeding mechanisms which could be used to provide fasteners to the passage 64 in the feeding head 61 are shown in U.S. Patents 2,304,572, 2,534,140, 2,706,504, 2,886,076, and 2,886,077 which are incorporated herein by reference.

The timing of the release mechanism and feeding of a fastener to the head 61 assembly of the gun in FIGURE 5 can be correlated with setting of a fastener by the gun in accordance with this invention through the electric circuitry shown in FIGURE 7 in which the elements are as shown below. Typical ratings of these elements for a firing circuit are as shown in parentheses.

-single throw single pole toggle switch 101 and 113rectifier (type 1N2071) 102-resistor (18000 at 2 watts) 103-resis.or (10,0000 at 1 watt) 104-potentiometer (10,0000 at /2 watt) 105-variable resistor (25000, /2 watt) 106fixed resistor (5600, /1 watt) 107current-sensitive relay (0.53 milliamps) 108medium power relay (16000, volts A.C.)

109-se1f-timing air solenoidregulates flow of air to escape mechanism 110solenoid air valve (l0-watts)-regulates flow of air to nosepiece 111capacitor (10 fd., 150 volts D.C.)

112fuse amp) 114-capacitor (40 ,ufd., 150 volts, D.C., electrolytic) In operation, switch 100 is closed so that volts AC. is applied to operate the hopper of the mechanism feeding fasteners to the gun of FIGURE 5 and current is applied to contacts b of relays 107 and 108 and to the cathode side of diode 101. Diode 101 rectifies the 120 volts A.C. current through voltage- divider resistors 102 and 103 to provide a negative (90 volts) DC. power source for the capacitor discharge circuit in the gun.

When capacitor 80 in the gun is discharged by the firing of the explosive charge in a fastener or by actuating a test switch (not shown) in the gun, the current needed to recharge capacitor 80 flowing from the voltage divider through relay 107 and resistors 104 and 81 actuates relay 102. Resistor 81 limits the maximum current in the system, e.g., to approximately 68 mililamperes, and resistor 104 controls the length of time that the relay 102 remains actuated by providing a shunt path of variable resistance, variations therein resulting in raising or lowering of the current threshold for actuation and drop-out of relay 102. Capacitor 111 smooths out the (60 cycle) ripple in the circuit and precludes chattering in relay 111.

Since relay 111 has a light power contact rating, medium power relay 108 is used to perate air solenoids 109 and 110 and is timed by relay 102. The timing of air solenoid 110, which delivers air through tap 72 to extend the feeding head and to open the fastener path therein, is regulated (timed) by relay 108. Air solenoid 109, which regulates the pulsing of air to the mechanism feeding the fasteners 73 is self timing but requires a short pulse of 120 volts AC. to start its cycle. It is possible to omit air solenoid A5 in some embodiments; if such is the case, resistors 105 and 106, rectifier 113, and capacitor 114 make up a delay circuit which controls the actuation of relay 108. Resistors 105 and 106 control the charging rate of capacitor 114 which regulates the actuation time of relay 108, the magnitude of delay increasing with increasing resistance.

Actuation of air solenoid valve 110 admits compressed air into the pressure tap 72 of the gun to open the passage for the fastener in the attachment as shown in FIGURE 5. Actuation of air solenoid 109 admits compressed air into the feeder mechanism (not shown) and conveys a fastener through flexible tubing (not shown) and passage 64 into the head 61 of the gun.

By the time that the fastener is in the snout 67 of the attachment, compressed air is sufficiently vented from the air cylinder 63 and the positioning of the end of nosepiece electrode 60 with respect to the head 61 becomes that shown by the dotted lines. The operator manipulates the gun so that the shank of the fastener is inserted and positioned in the aligned holes in panels to be joined and presses the gun toward the panels as described above. In response of this pressure, the sections of snout 67 spread apart allowing the head of the fastener to pass through the snout and contact is made with the end of nosepiece 60, as described above and as shown in FIGURE 6. Contact of electrode 76 with the electrode of the fastener and subsequent setting of the fastener act as a switch in the electric circuit, triggering the feeding (escape or release) of a subsequent fastener.

As stated, firm contact of the electrode of the tool (gun) with the electrode of the fastener is sufficient to set the fastener wihin about 150 microseconds. The gun, as described, can be used to set fasteners in which the electrode is substantially flush with the head of the fastener or recessed in a chamfered section of the fastener as long as there is suflicient clearance in the chamfered section to allow the electrode to contact the uninsulated (bared) end of the electrode of the fastener. However, the gun can be modified as described below to not only set the fastener, i.e., by connecting the fastener body and conductive charge in electric circuit with the charged capacitor, upon contact of the electrode of the tool with the electrode of the fastener, but to instantaneously peen any portion of the electrode which may protrude above the head of the fastener flush with the head.

In FIGURES 8 and 9, an embodiment of the device of this invention is shown which is adapted to set a fastener and instantaneously thereafter to peen the head and any electrode protruding therefrom. This gun also has a barrel-like body 120 which may be of an electrically conductive material, e.g., a metal. Nosepiece electrode 121 of a conductive material is mounted for movement in the muzzle of the body 120 parallel to the longitudinal axis of the barrel against the resistance of tension spring 122. Contact striker head 123 rides in chamber 124 and electrode 125, in the chamber portion forwardly therefrom, is mounted in the barrel for movement along the guns longitudinal axis. The extent of rearward movement of contact-striker head 123 and electrode '125 is restricted and controlled by spring 126 mounted on stationary spring support 127 which is mounted in bushing 128 near the breech of the barrel, the spring extending substantially the entire length of the barrel portion of the gun body. The forwward portion of spring 126 extends into the cylindrical chamber portion 119 and urges striker head 123 toward the workpiece. Movement of electrode 125 within the nosepiece 121 during relative movement of the two is regulated by insulated guide 129, which is movable in the nosepiece against the resistance of spring 130. Striker head 123 is separated from the nosepiece 121 by an insulating sleeve 131 which is in close peripheral contact with the surface of both components. The rear of sleeve 131 engages latch retainer 132.

As may be seen in FIGURE 9, latch 133, having a central aperture which is of larger inner diameter than the outer diameter of striker 123 is held in groove 134, which extends circumferentially about striker 123 with its rearward surface in contact with the forward surface of the latch retainer 132. Insulating cam 135 and insulating guide 136 are provided in the walls of the gun barrel as means of regulating movement of the latch 133 as the nosepiece 121 is moved toward the rear of the barrel. Guide 136 has an insulated leaf spring 137 designed to provide positive return of the latch 133 to groove 134 as the striker mechanism moves forward to fire the fastener. Cam 135 is an inclined plane, i.e., a wedge, which is designed to move the latch 133 on an axis perpendicular to its forward travel. Compression spring 122, referred to earlier, opposes the rearward movement of the nosepiece 121, striker head 123 and the latch 133.

The electrical components of the tool, which are basically those described for the gun of FIGURE 2, again conveniently are contained in a cavity in the handle of the gun. However the circuitry is modified to include, as a circuit checking means, a neon pilot light.

Neon pilot light 145 (FIGURE 8), which is an electric circuit with a voltage dropping resistor 147 (preferably of 68,000 ohms when the power source is a 90-volt battery), with a push button switch having normally open contacts for momentary action, and with a current limiting resistor 138 (nominally of 200 ohms when the power source is a 90-volt battery for protection of the push button switch contacts), provides a means of testing the batteries 139, under load conditions. When the pushbutton switch 140 is actuated, capacitor 141 discharges through resistor 138 and switch 140 and appears as a near short circuit simulating rivet firing conditions and causing nearly maximum current to flow through resistor 142. Substantially full battery voltage (nominally 90 volts) is thus impressed across resistor 142, causing the neon indicator to be illuminated. Thus, the operator can be assured that suflicient power is available to charge capacitor 141 in a selected time, e.g., desirably, /2 to second, to the voltage required to fire the explosive mixture in the fastener. If the neon pilot light is not illuminated, insuflicient power is available to charge the capacitor 141, and the power source should be replaced or recharged.

To fire (actuate) the explosive charge in the recently developed fasteners with this gun and instantaneously peen the set fastener, the gun is applied to the fastener with the opening in the insulating guide 129 substantially centered on the electrode of the fastener. With the gun in position and the capacitor charged, the operator presses the gun against the surface of the parts to be joined. As the pushing force is exerted, the insulated guide 129 moves back into electrode nosepiece 121, permitting the nosepiece 121 to make contact with the head of the fastener, and the nosepiece 121 itself moves rearwardly into the barrel, thereby moving back latch 133, latch retainer 132, and striker head 123. The nosepiece 121, latch retainer 132, latch 133, and the striker head 123 move toward the rear of the barrel against the combined resistance of spring 122 and spring 126. The tension (resistance) in each of the springs is preset and adjusted to regulate the amount of energy stored in striker spring 126 and the total force exerted by both springs is combined to provide the resistive effort or force required to bring the striker 123 into contact with the electrode of the fastener (this force is resisted by the structural strength of the parts to be joined). Spring 122 will be strong enough to return the nosepiece to the forward position and to maintain good contact with the parts and fastener head even after latch 133 trips and the energy (force) for spring 126 is released. The force, and, accordingly, the size of spring 126 is determined by the energy required to peen the fastener head by fiat-faced electrode 125. The force and, accordingly, the size of spring 122 will be determined by the minimum requirements mentioned, i.e., the push-down force desired to be exerted on the panels and firmly to seat the fastener in the hole.

As the nosepiece 121, striker head 123 and latch 133 move back, latch 133 is urged in a direction perpendicular to its rearward travel and to the axis of the striker head 123 by cam 135. Latch 133 moves upward along the inclined plane of cam 135, becoming displaced with respect to the groove 134 until, at a release point near the apex of cam 135, the latch 133 is released from the groove, thus releasing the striker head 123. The tension in spring 126 then is released, and the striker mechanism moves forward with respect to the nosepiece 121. Since latch 133 has a central aperture larger than the maximum outer diameter of striker head 123, the striker head 123 can pass through the latch 133 without being reengaged. As the tension in spring 126 is released, the striker head 123 :moves forward, so that the forward surface of electrode fixed thereto protrudes through 1 1 insulated guide 129 to contact the electrode of the fast-ener. Contact of the electrode 125 with the electrode of the fastener incorporates the electrode and the conductive particles in the explosive charge in the electric circuit.

After firing the explosive charge, electrode 125 travels the distance corresponding to the length of electrode or other part to be peened protruding above the fastener head within about 100 microseconds, thus peening the electrode flush with the fastener head. During forward travel of the striker head 123, the tension of spring 122 insures contact of the head of the fastener and the nosepiece 121 and with the parts to be joined. A delay in the peening action may be provided by placing a spring 143 within the nosepiece axially aligned with electrode 125 and referenced against striker head 123.

When the gun is removed from the parts to be joined, the tension in spring 122 is released and nosepiece 121 and latch 133 are pushed forward. As the elements move forward, guide 136 and spring 137 assure that the latch is returned to groove 134 and the gun is readied for another cycle. Spring 130 in nosepiece 121 pushes the insulated guide 129 forward.

We claim:

1. A device for setting electrically-fired explosivelyactuated fasteners, said fasteners comprising a currentsensitive explosive in contact with a first electrode and a second electrode that is insulated from said first electrode, said device comprising a body,

(a) positioning means for engagement with said fasteners and yieldably mounted in said body for reciprocal movement therein parallel to the axis of the fasteners during setting,

(b) an electrode independently movable with respect to said means (a) in a direction parallel to the direction of yieldable movement thereof, for engagement with said first electrode of said fasteners, and

(c) a power source connected through said electrode (b).

2. A device of claim 1 wherein said means (a) is a conductive tubular electrode substantially coaxial with said electrode (b), said power source (c) being connected to said electrode (b) and said tubular electrode.

3. A device of claim 2 wherein said tubular electrode is held in engagement against said fastener by a spring which exerts a force on said tubular electrode in an axial direction toward the fastener as said electrode (b) is brought into contact with the insulated electrode in the fastener.

4. A device of claim 3 wherein said power source cornprises at least one battery and a capacitor connected in parallel.

5. A device of claim 4 wherein at least one resistor is hooked in series with said capacitor to limit the charging rate of said capacitor.

6. A device of claim 3 wherein said electrode (b) is spring loaded to limit the maximum force which can be exerted by the tip thereof in a forward direction.

7. A device of claim 3 comprising a nosepiece includ ing the tubular electrode, said tubular electrode being urged forward by a coil spring coaxial with said tubular electrode and abutting a stationary abutment within said body, said electrode (b) being opposed in its rearward movement relative to said body by a second coil spring within said first mentioned coil spring, said electrode (b) being substantially coaxial with, insulated from and axially movable within said tubular electrode and having its forward tip disposed rearward of the forward tip of said tubular electrode when said device is in the at-rest condition.

8. A device of claim 7 wherein said tubular electrode is connected to the positive terminal of said power source through said body, and said electrode (b) is connected to the negative terminal of said power source, said power source being housed within said body and comprising a capacitor and at least one current limiting resistor connected in parallel with at least one battery.

9. A device of claim 7 bearing a feeding head mounted on said nosepiece comprising said tubular electrode, said feeding head having an axial passage through which said tubular electrode and electrode (b) pass when said device is abutted against a workpiece and said body of said device is moved forwardly, and a passage which intersects said axial passage near its forward terminus through which fasteners can be pneumatically fed, and means to feed air to an enlarged portion of said axial passage in front of a piston-like enlargement of said nosepiece slideably mounted within said enlarged portion to thereby withdraw said electrodes rearward and clear said intersection for feeding of another fastener.

10. A device of claim 9 additionally comprising means for automatically feeding each fastener in response to the setting of the next preceding fastener which comprises a relay responsive to passage of current through said electrodes, said relay activating said air fed to said enlarged portion of said axial passage and to a fastener feeding mechanism on passage of said current.

11. A device of claim 7 additionally comprising means for simultaneously contacting said first electrode of said fasteners and peening the head thereof which comprises latching means which compresses said second coil spring as said body is moved forward with respect to said electrodes and means to release said latching means when said body and electrodes have reached a given position with respect to each other to thereby release said second coil spring and drive said electrode (b) rapidly and forceably against the head of said fasteners.

References Cited UNITED STATES PATENTS 2,080,220 5/1937 Butter et a1. -37 2,387,742 10/ 1945 Burrows. 2,534,140 12/1950 Moore. 2,706,504 4/1955 Moore. 2,886,076 5/ 1959 Shinkle et al. 2,886,077 5 1959 Rafferty et al. 3,166,971 1/ 1965 Stoecker.

FOREIGN PATENTS 467,514 6/ 1937 Great Britain.

RICHARD J. HERBST, Primary Examiner.

US. Cl. X.R. 29421

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