Dec. 24, 1946. T. NELSON 2,413,189. STUD WELDING MACHINE ~ Filed March 27, 1944 2 Sheets-Sheet l INVENTOR 'xr Ted Ne/son BY 6M, .-4 @w H15 ATTORNEY ` Dec. 24, 1946. T. NELSON 2,413,189 STUD WELDING MACHINE Filed Ma?ch 27, 1944- 2 sheets-sheet 2 INVENTOR Tea’ IVe/.son MMM@ HIS ATTORNEY Patented Dec. 24, 1946 ahsisi UNITED STATES PATENT OFFICE 2,413,189 STUD WELDENG MACHINE Ted Nelson, San Leandro, Calif. Application March 27, 1944, Serial No. 528,196 18 Claims. l (Cl. 219-4) 2 My invention relates to welding machines and particularly to welding machines for welding ' and carrying the chuck in which the stud is held studs to a base such as a Wall or ceiling or floor movable in the longitudinal axis of the barrel and responsive to electrically energized means, is provided for drawing the plunger into the barrel to move the stud away from the plate to which it is to ‘ce fused, so that the welding arc is established. Spring means is provided for thrusting the plunger in the opposite direction to seat the heated stud, when the energizing circuit is broken. ri‘he electrically energized means in cludes coils of a heavy electrical conductor, em bedded in the wall of the housing barrel. This plate. The general object of the invention is the pro vi-sion of a machine for making such welds with automatic and perfect control of the several vari ables which determine the soundness of the union, the most important of which are amount of sepa ration of electrode elements, length of period of heating, the instant of physical union ci the elec trode elements, and the control ci the arc. The result of such control is an enormous speed-up in the number of perfect welds which the operator can make in s, given period. ’ during the welding operation. An armature also is an important feature of my invention for a 15 variety of reasons which will become apparent Another object of the invention is the provi when the entire construction is understood. The sion of a Welding machine oi such light weight armature carries a pick-up device or clutch incoh and compact arrangement that it may be dis anisin, operating to seize the plunger in whatever posed. in a cylindrical housing having a pistol position it lies when the stud is ñrst seated on the grip in which the manual control is placed, so that 20 plate; and then move it a predetermined distance the whole instrument somewhat resembles an automatic pistol, with characteristic ease and facility in handling. My invention possesses other objects and fea tures of value, some of which with the foregoing will be set forth in the following description oi the invention. It is to loe understood that I do not limit myself to the showing made by the said description and the drawings as i may adopt variant forms of the invention within the scope of the appended claims. In the drawings: Figure i is a partial sectional view taken in a plane lying in the main central axis. A short section of a plate to which the stud is to .he weide is included; and the gun is shown in position against it. A portion of the cover plate on the grip is shown. Figure 2 is a `side elevation of the instrument, taken in a direction opposite to that oi Figure l. Figure 3 is a wiring diagram showing the elec trical circuits and controls. In terms ci broad inclusion the welding ma chine or gun ci my invention comprises a gener» ally cylindrical barrel and grip of a dielectric or electrically nonmconducting material, which to so that the arc gap is always the same despite variation-s in stud and welding surface. 4Coils are provided for creating a magnetic field around the welding arc so as to stabilize it; and stud, stabilizer coils and energizing coils are pref erably in series connection with the conductor supplying the Welding current which preferably enters the housing through the butt of the handle. Appropriate devices outside the housing provide the welding current and make and break the welding circuit, under the control of a timer mechanism7 which is put into operation by a manually operated switch or trigger arranged in the housing grip, so that by the pressure of a iinger, the operation of the welding cycle may be initiated. Means are also provided for giving a visual signal to the operator, when during the positioning of a stud, physical electrical contact is made between the electrodes, and the welding cycle may he started. This signal is preferably located on the side oi the housing barrel, Within the held of vision of the operator. In greater detail, my stud Welding machine or gun comprises a generally cylindrical hollow bar rel 2, adjacent one end of which is an integrally :formed hollow hand grip 3, closed on one side 'oy a screw~held cover plate ll. These portions gether furnish the housing in which the operat ing parts and manual control are disposed. The comprise the housing in which the parts of the weight shape are not greatly different from gun are arranged, and are formed of a thermo those or" a large automatic pistol, but have the hi) setting type of plastic, preferably a phenol-form advantages in manipulation and control which broadly characterize the pistol shape. The op erating mechanism within the barrel portion of the housing comprises a plunger mounted for movement in the longitudinal axis of the barrel, aldehyde resin which is strong and light, easily made, and of high dielectric quality. The last is important from the viewpoint of safety of the operator, and because certain of the electrical conductors may he ñxed in place and insulated 2,413,189 3 4 _and stud are electrically connected in series. Connection through the stabilizer coils is secured by terminating the conductor 3i in an eye 33, held tightly between a fiber washer 3è and the cost. Extending laterally from the barrel at the end Ul ñrst coil 32 by the engagement of the chuck against a steel washer 36, brazed to the last coil opposite the grip, are lugs 5 in which threaded 32. The coils 32, except the two end surfaces metal bushings or thimbles t are incorporated left for contact, are embedded in and insulated when the gun housing is molded. Preferably by a thermo-setting resin 3l; and of course the three of these lugs are equispaced about the bar conductor 3i is also heavily insulated. Because rel, and the thimbles serve as mountings for the the end of the conductor must move back and legs 'l which are made adjustable in length by forth with the plunger assembly, the conductor is the threaded extensions 8. given one complete loop 38 to give flexibility to Slidably'mounted in the barrel 2 ci the housing by embedding them in the housing wall, thus achieving maximum values of space, lightness of Weight, security, insulation and economy at low is the plunger assembly, including the plunger 9, at the outer end of which is iixed the flanged the whole. collar lll, which in turn, at its outer end, is threaded to mount the chuck Il, split at its hol arc at the low outer end to form resilient jaws l2 to hold spattering the stud I3. Thus the plunger, collar, chuck and Slidably stud are fixed rigidly together; and in the op 20 half of the eration of the tool, reciprocate as one. The outer surface of the chuck is formed with shallow threads or grooves to form a readily ad justable mounting for the spring la, in the oppo site end of which is carried the porcelain ferrule l5, which surrounds the end of the stud during its welding to the plate i6. The spring seats the ferrule resiliently against this plate. The plunger 9 is held centrally in the barrel by the cylindrical ilange Il, forming a sliding fit in . ` The welding current through the stabilizer coils 32 generates a powerful magnetic ñeld about the welding aro, tending to confine and stabilize the location of the weld, and preventing l and waste of the molten metal. mounted in approximately the inner thickened housing wall containing the solenoid coils, is a core or armature lli, the move ment of which into the coils (to the left of Fig ure l) is determined by the ñxed core @2. This has a threaded engagement in the housing wall and in the yoke shaped steel reinforcing tie d3, which ties the wall in which the solenoid coilsv are embedded into a mechanically strong block able to resist the stresses placed thereon in the operation of the gun. Movement of the armature under the influence of the energized solenoid the bore of the barrel, and prevented from rotacoils determines the distance the stud is moved tion therein by a key fitting the keyway I8. The to draw the welding arc; and since this distance inner end of the plunger forms a sliding ñt with is a predetermined value, the position of the lixed the stop ring le, fixed inV the barrel against a shoulder by oppositely disposed set screws 2Q, one 35 core may be varied by the use of shims ¿ill under the head of the ñxed core. It will be observed that of which is indicated in Figure 1. the ñxed core becomes a powerful magnet when A iiange 2l on the ring is provided, against the coils are energized, so that when the arma Which the shoulder 22 of the plunger seats to limit ture is stopped by it, the armature is strongly the outward movement of the plunger assembly; and this outward position is normally maintained 40 held in the retracted position, until the current is interrupted. , by the heavy spring 23, which also serves to effect Clutch means are provided for connecting the the recovery movement to this position of the armature to the plunger assembly for movement plunger assembly after it has been retracted. together as one, when the armature moves under The spring 23 constitutes secondary means for the iniiuence of the magnetic ñeld created by the moving the plunger in one direction or outwardly. coils, and for maintaining this connection so long Primary means are provided for moving the as there is any stress tending to separate the two. plunger and its connected parts in the opposite This clutch connection however is released and direction or inwardly. The inward movement the parts are Tree of each other when the arma separates the electrodes, that is, pulls the stud ture moves in the other direction; that is, toward away from the plate or base to establish the the plunger assembly, or the plunger assembly welding arc; and the outward movement plunges is -moved inwardly of the housing and toward the the heated stud down into -the heated plate to armature. The latter happens when a stud is set fuse them together. When the stud is loaded into in position to be welded. As already mentioned the chuck, the adjustment of the parts is such as to allow the stud to project a small amount be- ' the adjustment oí the three legs is preferably such as to allow the stud to extend somewhat be yond the plane of the leg ends so that when plac yond them, so that the plunger assembly is pushed ing the gun in the position of parts shown in Fig slightly back into the barrel against the resist ure 1, the stud is pressed back from its free posi ance of the spring 23, when the stud is in posi tion, shown in the dotted lines, and is held tion and the three legs seated to insure per resiliently against the plate. In a similar fashion pendicularity of the stud. During this movement ~ the spring lll is adjusted so that when the stud is of the plunger assembly, which varies with varia seated in the position or” the weld, the ferrule is tions in the stud and in the surface to which the also held resiliently against the plate. stud is to be welded, the assembly is free of the Embedded in the inwardly thickened wall of armature, but with the power movement of the the housing at the grip end are the coils 26 of a armature, the clutch acts instantly to engage the solenoid. One end of the coil terminates in a plunger, so that the entire plunger assembly in connector socket within the grip chamber 2l, cluding the stud is retracted against the resist and to which. the end of the welding current con ance of the spring 23, the exact amount of the ductor 2S is ñxed by the screw 2S. The other end terminates in a connector socket on the outside 70 armature movement. This is always the same for a given setting of the lixed core. Thus irrespec of the barrel, and to which the end of the con ductor 3l is fixed. . tive of variations in stud or the plate to which it The other end of the conductor 3l is connected is tobe welded, the stud is always retracted the'Y through- the stabilizer coils 32 to the chuck, so same'predetermined distance determined >by the that solenoid coils 25, stabilizer coils 32, chuck 75 fixed core setting. This distance is of course the ' 5 2,413,189 one best suited for the arc required for the stud used. The clutch means required for this duty com prises a link e6, disposed longitudinally of the barrel and against the upper wall thereof, and having a flange @l rigidly fixed by the screw 68 to the end of the armature. A tongue da, pressed out of the link forms a key which, engaging in the keyway 5l formed in the barrel, prevents transverse movement of the link while permitting its rectilinear movement back and forth with the armature. The free end of the link is provided with a short hook flange 52, which engages the ñxed stop ring i9 to limit the recovery movement of the arma ture after its power stroke. A spring 53 inter posed between the nxed core and the armature in aligned axial recesses tends to return the ar mature and link to the recovered position as shown in Figure l. The air pocket formed be tween the core and armature may be ignored, since the volume changes but little due to the central recesses, and passage of air occurs past the armature. The hook flange 52 has another important function. It is hooked over one side of the clutch ring all surrounding the inner end of the plunger. rfhe clutch ring is so sized and proportioned that when it is perpendicular to the plunger there is no engagement; and plunger and clutch ring may be freely moved relative one to the other. A diameter of plunger about .093 of an inch less than the diameter or the hole in the clutch ring gives a satisfactory result. To pre vent fleë-íure in the ring, it is preferably provided with a short peripheral flange 55. Tipping the clutch ring out of perpendicularity with the plunger causes an instant seizure of the plunger by the ring. A boss 53 in the stop ring, on the opposite side from the hook 52, supports the clutch ring in the inactive or non-seizingpo sition, into which it is resiliently pressed by the coil spring 5l, the end coils of which are disposed about the heads of the plunger and screw 48. rllhe inner end of the plunger head is recessed as shown, both for lightness and to receive the pro jecting head of the screw 48 upon the extreme movement of the plunger. From the foregoing it will be clear that both retracting and extending movement of the plunger assembly may occur without disturbing the perpendicularity of the clutch ring to the cylindrical plunger head which it encircles, but that the least power move of the armature and link tips the clutch ring to seize the plunger, which then moves with the armature and against the spring 23, to the end of the armature move ment where it is held until the circuit is broken, whereupon spring 23 effects the rapid recovery movement of the plunger assembly, spring 53 ef 6 the solenoid however the stud is lifted or retract ed from the plate to establish the welding arc and thereafter until the circuitis broken the current jumps the gap between stud and plate heating both to the degree required for fusing. Upon the breaking of the circuit through the solenoid coils, the plunger assembly released; and the spring effects its r cover-y movement, plunging Lhe stud into the heat softened area on the plate, The fused material cools almost instantly, at which time the gun is pulled free, leaving the stud welded in place. Manually operated means in the grip portion of the gun housing are provided for initiating the Welding cycle of operations. After the in itial setting of the spark gap interval (deter mination of ïniature travel by setting the ñXed core) which need be changed only when change of size of stud requires a diiîerent spark gap, loading the chuck with a stud, placing the stud on the mars: where it is to be welded, and press ing the trigger is all that is required for a per feet weld. Disposed in the grip of the housing in a po sition conveniently under e. finger is a trigger, preferably a push button ill, bearing at its inner end against the spring switch arm t2, which is spaced a short distance from the 'spring switch arm §53. These arms are insulated from each other; and form the terminals of the conductors Sil and lit respectively, carried in a flexible con duit 6l of convenient length to the stationary electrical devices which effect and control the operation of my gun. The conduit lil enters the butt end of the grip along with the conduit 68 the welding current conductor. This t together with the placing of the solenoid coils well back in the “breach” of the barrel, and placing and proportions or" the other parts, contributes heavily to the balance of the gun in the hand of the Welder. While my gun relatively light in Iweight when compared to previously known welding tools, it is of very great importance tc the oper ator after a few hours or use, whether the in strument balances easily in the hand, or whether a muscular effort is required to position the gun in addition to the necessary overall support. My gun has been designed to insure balance about the grip; and this is directly reflected in the number of studs which can be welded by an op erator after the first few hours of the day. The remote controls and connecting circuits of my tool are shown in diagram in Figure 3. ri‘he control devices are standardized and well known and only the circuits which I prefer to use re quire detailed eXplälR-ÈÍOIL The welding current is derived from a direct current generator it, having a conductor ‘il for fects the recovery of the armature and link, and (il) grounding its positive side on the plate or wall spring 5l presses the clutch ring back into its in “it to which the studs are to be welded, The active or free perpendicular position against the negative side of the generaoäoin is connected by hook 52 and boss 55. conductor lil to one pole of the switch al, the Thus irrespective the position of the plunger other pole being connected by conductor run when the gun has been placed to make a weld ning through conduit to the gun. and with the stud pressing against the plate, The welding current control 1switch which operation of the solenoid and clutch results in normally open is operated by the relay 82, seizing the plunger assembly and retracting it supplied by the conductors and connect the fixed predetermined distance traveled by the ed through the normally twin switches 8S armature, the energizing current passing in series El with the coi luctors and 535i respec through the solenoid coils conductor 3i, sta tively, connected in turn to a source of A. C. bilizer coils 32, chuck, and stud. Since the stud is current. The twin switches,.- Sfâ and 3l are oper in physical contact with the plate when the cir~ ated by the relay Sil in the circuit including the cuit is ñrst established, the flow is at first di conductors Q2 and S3 connected by the normally rectly from plate to stud. With the action of closed switch Sil, which is controlled by the timer 2,413,189 7 8 closed by the relay |05, supplied by conductors means on the plunger for holding a stud, a sole the armature and plunger for seizing the plunger 9S. The conductor 93 is fed from the conductor when the armature is actuated, and a spring car 64 extending to the terminal 62 of the trigger ried by the armature and plunger for releasing switch, as also is the conductor 97 which sup the clutch means when the plunger is moved by plies the timer. The other terminal 63 0f the the first-named spring. trigger switch is supplied by the conductor 65, 3. A stud welding machine comprising a cy connected to the conductor 88. lindrical housing, a plunger slidably arranged in Means are provided for indicating to the op the housing and substantially coaxial with the erator while positioning the stud the establish long axis thereof, means on the plunger for hold ing of electrical contact between stud and plate; ing a stud substantially coaxial with the plunger, and this is preferably done by a red neon light primary means for moving the plunger in one di 98 disposed on the side of the gun and which rection, secondary means for moving the plunger glows when the circuit is completed. The lamp in the other direction, and mechanism including is supplied by conductors |û| and |62, the lamp a spring pressed clutch ring, interposed between ends of which are carried into the gun through the conduit 6l. The other end of conductor llii 15 the plunger and the primary means for seizing the plunger when the primary means is actuated is connected to conductor 8S; and the other end and for releasing the plunger when the plunger of conductor |82 terminates in one pole of the is moved by the secondary means. . switch ID3, the other pole of which is connected Ll. A stud welding machine comprising a hous to conductor 38 by conductor lilli. The switch §03 which is normally open, is 20 ing, a plunger slidably arranged in the housing, noid core slidable in the housing, an energizing |91 and |98 in parallel with a resistance |û9, coil surrounding the core, clutch means between shunted around the switch 8|. Both relay wind the core and plunger for seizing the plunger when ings and resistance are calculated to pass only a fraction of the available direct current, as only 25 the core is moved in one direction by the ener gized coil, a spring for moving the plunger in the the operation of the relay |06 to close the switch other direction, and means on the solenoid core |63 in the neon lamp circuit, is desired when the for releasing the clutch means when the plunger stud closes the circuit through the ground, thus moved by the spring. indicating that the closing of the trigger switch 5. A stud welding machine comprising a hous will start the flow of the full volume of welding 30 ing, a plunger slidably arranged in the housing, current. means on the plunger for holding a. stud, a sole The instant the trigger switch is closed, the re noid core slidable in the housing, an energizing lay 9! closes the twin switches 85 and 8l to supply coil surrounding the core, a ring slidable on the the relay 82, which then closes the switch 8l , per mitting the full direct current to flow through the 35 plunger when normal to the plunger axis and en gaging the plunger when tipped from the normal welding circuit. This, it will be recalled, ener position, means pressing the ring into normal po gizes the solenoid coilsl 2S, and pulls the stud sition, means connecting the core to one side of away from the plate to» establish the welding arc. the ring whereby movement of the core by the Simultaneously with the energizing of the relay 9|, the timer 9S starts its predetermined timed 40 energized coil tips the ring and moves the plunger in one direction, and a spring for moving the cycle, at the end oi which it opens the switch 94, plunger in the other direction. thus allowing the twin switches 86 and- 8l to open, 6. A stud welding machine comprising a hous which in turn cause the opening of the switch 8| ing, a plunger slidably arranged in the housing, in the welding circuit, ending the arc and releas ing the plunger assembly from the pull of the 45 means on the plunger for holding a stud, a plunger-moving spring interposed between solenoid so that the stud is seated against the plunger and housing, a clutch ring on the plunger plate by action of the spring 23. and engaging the plunger when tipped from nor With the generator running and the location mal position, means normally retaining the clutch in which the studs are to be welded easily ac cessible, a welder can easily load with stud and 50 ring in disengaged position, a link engaging one side of the clutch ring to tip it from normal ferrule, position the stud, press and release the position when the link is moved, and electrically trigger, pause, and then pull the gun chuck free actuated means for moving the link to move the of the perfectly welded stud in ten seconds or plunger to compress the spring. less, and can maintain a rate of 250 to 300 welded 7. A stud welding machine comprising an elec studs an hour. Positions reached with diñîculty, 55 trically non-conducting housing, a plunger slid or bent or other special studs will of course slow ably arranged in the housing, means on the up production. plunger for holding a stud, a, plunger-moving I claim: spring interposed between plunger and housing, l. AA stud welding machine comprising a hous ing, a plunger slidably arranged in the housing, 60 a clutch ring on the plunger, means normally re taining the clutch ring in disengaged position, an means on the plunger for holding a stud, primary armature, a link connecting the armature to one means for moving the plunger in one direction, side of the clutch ring, and an electric conductor secondary means for moving the plunger in the disposed to energize the armature and embedded other direction, means interposed between the plunger and primary means for seizing the plunger 65 in the wall of the housing. 8. A stud welding machine comprising an elec when the primary means is actuated, and means trically non-conducting housing, a plunger slid located between the plunger and primary means for releasing the plunger when the plunger is ably arranged in the housing, means on the moved by the secondary means. plunger for holding a stud, a plunger-moving 2. A stud welding machine comprising a hous 70 spring interposed between plunger and housing, ing, a plunger slidably arranged in the housing, an armature slidably arrangedv in the housing, a core adjustable to limit movement of the arma means on the plunger for holding a stud, an elec tricallyoperated armature for moving the plunger ture, coils of an electric conductor embedded in in one direction, a spring for moving the plunger the housing around the armature and core, and a in the' opposite direction, clutch means between 75 clutch for connecting the armature and plunger. 9 2,413,189 10 9. A stud Welding machine comprising a gen erally cylindrical housing of electrically non-con ducting material, a plunger slidably arranged in the housing, means on the plunger for holding a stud, a spring interposed between plunger and housing for moving the plunger in one direc tion, an armature slidably arranged in the hous . ing, an electric conductor embedded in the Wall from the plate to establish the welding arc and including coils of an electric conductor embedded in the wall of the housing. 15. In a machine for welding a stud to a plate, a housing, stud holding means carried by the housing, electro-magnetic means for moving the stud holding means to establish the welding arc between stud and plate, and arc stabilizing means of the housing to energize the armature to move including a plurality of coils of an electric con in the opposite direction, and means for con 10 ductor arranged on the machine adjacent the necting the armature and plunger. stud and connected in series with the electro l0. A stud welding machine comprising a gen magnetic means, and means for energizing the erally cylindrical housing of electrically non-con electro~magnetic means and coils. ducting material, a plunger slidably arranged in 16. A stud welding machine comprising a hol the housing, means on the plunger for holding a stud, a spring interposed between plunger and housing for moving the plunger in one direction, an armature slidably arranged in the housing, an electric conductor embedded in the wall of the housing to energize the armature to move in the opposite direction, means for connecting the armature and plunger, and an electric con ductor about the stud-holding means and in series with the conductor embedded in the hous ing wall. 11. A stud welding machine comprising a hous ing of dielectric material, coils of an electric con ductor embedded in the housing wall at one end, a plunger slidably arranged at the other end, means on the plunger for holding a stud, an armature energized by the coils and slidably ar ranged in the housing, means operating to connect the plunger and armature when the latter moves in one direction, and a spring compressed by such movement for moving the plunger in the opposite direction. l2. A stud welding machine comprising a hous ing of dielectric material, coils of an electric con ductor embedded in the housing wall at one end, a plunger slidably arranged at the other end, means on the plunger for holding a stud, an armature energized by the coils and slidably ar ranged in the housing, means for connecting the plunger and armature when the latter moves in one direction, a spring compressed by such move ment for moving the plunger in the opposite di rection, and a plurality of coils of an electric con ductor about the stud holding means and in series low generally cylindrical housing of dielectric material, a metal coil embedded in the wall of the housing adjacent one end thereof and form ing both an electric conductor constituting the coil of a solenoid and a mechanical reenforcement for the wall, the wall constituting insulating and mounting means for the coil, a solenoid core slid able within the coil, an adjustable stop for limit ing the travel of the solenoid core, a plunger slid ably arranged in the housing at the end opposite the solenoid coil, means on the plunger for hold ing a stud, and means disposed between the sole noid core and plunger for connecting the two for coextensive movement as one when the solenoid is energized to move the core and for releasing 30 the plunger from the solenoid core when the solenoid is deenergized. 17. A stud welding machine comprising a hol low generally cylindrical housing of dielectric l material, a metal coil embedded in the wall of the housing adjacent one end thereof and form ing both an electric conductor constituting the coil of a solenoid and a mechanical reenforcement for the wall, the wall constituting insulating and mounting means for the coil, a solenoid core slid 40 able within the coil, a plunger slidably arranged in the housing at the end opposite the solenoid coil, means on the plunger for holding a stud, means for connecting the solenoid core and plunger when the core moves in one direction, and a spring compressed by such movement for mov ing the plunger in the opposite direction. 18. A stud welding machine comprising a hol low generally cylindrical housing of dielectric ma with the conductor embedded in the housing wall. terial, a metal coil embedded in the wall of the 13. A stud welding machine comprising a hous 50 housing adjacent one end thereof and forming ing, a plunger slidably arranged in the housing, both an electric conductor constituting the coil means on the plunger for holding a stud, a spring of a solenoid and a mechanical reenforcement for interposed between the plunger and housing for the wall, the wall constituting insulating and moving the plunger in one direction, electro mounting means for the coil, a solenoid core Slid magnetic means including coils of an electric 55 able within the coil, a plunger slidably arranged conductor arranged in the housing to move the in the housing at the end opposite the solenoid plunger in the opposite direction, a plurality of coil, means on the plunger for holding a stud, coils of an electric conductor about the stud said solenoid coil and core and said plunger and holding means and in series with the coils of the stud holding means being in axial alignment and electro-magnetic means, and means for supply 60 coaxial with said cylindrical housing, and means ing an electric current to the coils, for connecting the solenoid core and plunger 14. In a machine for welding a stud to a plate, a housing of dielectric material, and elec tro~magnetic means for moving the stud away when the core moves in one direction. TED NELSON.