US3307012A

US3307012A - Miniature spotwelder

Info

Publication number: US3307012A
Application number: US541621A
Authority: US
Inventors: John W Ryan; Richard L May; Citron Manning
Original assignee: Mattel Inc
Current assignee: Mattel Inc
Priority date: 1966-04-11
Filing date: 1966-04-11
Publication date: 1967-02-28
Anticipated expiration: 1984-02-28
Also published as: DE1962123U; DE1690595A1; GB1154271A

Description

Feb. 28, 1967 J, W RYAN' ETAL 3,307,012

MINIATURE SPOTWELDER Filed April 1l, 1965 5 sheets-Sheet i FledvApril 11, v196e;

RYAN ETAL 3,3(922012 MINIATURE sPoTwELDER 3 Sheets-Sheet 2 Feb. 28, 1967 J. W. RYAN ETAL 3,307,012'- MINIATURE SPOTWELDER Filed April ll, 1966 5 Sheets-Sheet 3 United States Patent Oiice 3,307,012 MINIATURE SPOTWELDER John W. Ryan, Bel-Air, Richard L. May, Manhattan Beach, and Manning Citron, Los Angeles, Calif., assignors to Mattel, Inc., Hawthorne, Calif., a corporation of California Filed Apr. 11, 1966, Ser. No. 541,621 Claims. (Cl. 219-86) The present invention relates and more particularly to such a sive to manufacture and which to use.

Miniature spotwelders designed for home use by inexperienced operators are known. While generally satisfactory, such spotwelders do have certain disadvantages.

One disadvantage resides in the fact that, as is the case with all spotwelders, the parts to be welded must be heated to a glow in the area to be welded resulting in sparks sometimes being given olf. These conditions are likely to surprise an inexperienced operator causing him to drop a red-hot piece of metal on the floor. This creates a safety hazard which is greatly magnified when the spotwelder is being used in a carpeted room, as is often the case.

Another disadvantage with prior art miniature spotwelders resides in the fact that some of them are comparatively expensive to manufacture and complicated to operate.

Yet another disadvantage resides in the fact that some prior art miniature spotwelders will soon become inoperative through electrode oxidation.

In view of the foregoing factors and conditions characteristic of miniature spotwelders, it is a primary object of the present invention to provide a new and useful miniature spotwelder not subject to the disadvantages enumerated above and having spark arrestor and electrode means especially designed for making simple welds eliiciently, safely and expeditiously.

Another object of the present invention is to provide a bus bar for a miniature spotwelder which connects a swingable electrode to the secondary winding of a transformer in such a manner that the bus bar not only carries current to the electrode, but also biases the electrode to a predetermined, elevated position upon removal of welding pressure therefrom.

Yet another object of the present invention is to provide new and useful electrodes for a miniature spotwelder which are conductive even though they may become oxidized during use.

A further object of the present invention is to provide an actuating lever for a miniature spotwelder which not only lowers a swingable electrode into engagement with workpieces on a fixed electrode, 'but also exerts a modulated clamping pressure in proportion to the thickness of the workpieces.

A still further object of the present invention is to provide easily replaced, long-life electrodes for a miniature spotwelder.

Another object of the present invention is to provide a new and useful wire cutting and bending ldevice for a miniature spotwelder.

Another object of the present invention is to provide a spark arrestor for a spotwelder which is penetrable by a workpiece while completely surrounding the workpiece to hide the welding area from view.

According to the present invention, a miniature spotwelder is provided which includes a transformer having a primary winding and a secondary winding. The transformer is designed to have a maximum rise of 60 C., when operated as is intended. The primary winding operates on 117 volts A C. and draws approximately 13 amperes at full load. The secondary winding operates at to a miniature spotwelder Welder which is inexpenis economical and safe 3,307,012 Patented Feb. 28, 1967 1.7 volts at no load and at approximately 1.0 vol-t at' approximately 600 amperes.

A movable electrode is connected to the secondary winding by a bus bar having sucient resiliency and a predetermined shape for biasing the swingable electrode to a predetermined position spaced sufficiently from a xed electrode that workpieces may be admitted between the electrodes. Both electrodes are made from a silverplated, copper-chromium alloy. 'Ihe electrodes are silver plated because .the oxide of silver is almost as conductive as the silver. The bus bar for the swingable electrode is mounted inside an arm which is pivotally mounted on a housing. The arm may be pivoted by depressing'an actuating handle including a steel lever which is formed integrally with a crank member and a bight portion. The crank member is connected to the arm for swinging it when the lever is depressed downwardly. The lever, when it reaches the bottom of its stroke, actuates an electrical switch completing a circuit to the electrodes. The switch is permanently alhxed to the welder in a position sufiiciently below the lever so that it must ybe sprung downwardly after the electrodes have firmly clamped a workpiece to be welded. The amount the lever is sprung for thick workpieces is greater than the amount it is sprung for thin workpieces. Thus, the operating handle has a torsion effect which results in approximately the same p.s.i. being applied to a thick piece as that applied to a thin piece.

The bus bar which connects the swingable electrode to the secondary winding is made of hard-drawn copper and serves as a return spring returning the swingable electrode to its upper position.

A new and useful spark arrestor of the present invention is permanently connected to each elect-rode. Each spark a-rrestor completely surrounds its associated electrode and not only arrests sparks, but also hides the electrodes from view during a welding operation to prevent an inexperienced operator from becoming surprised by the appearance of sparks which might cause him t-o drop a red-hot workpiece on the floor causing damage thereto.

In addition, a new and useful wire cutting and bending device is provided. This device may be readily attached to the housing of the spotwelder for use in combination therewith.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings in which like reference characters refer to like elements in the several views.

In the drawings:

FIG. l is an exploded, perspective view of a miniature spotwelder constituting a presently preferred embodiment of the invention in combination with a new and useful wire cutting and bending device of the present invention;

FIG. 2 is an enlarged, partial cross-sectional view taken along line 2 2 of FIG. 1;

FIG. 3 is an enlarged, partial wire cutting and bending device operation;

FIG. 4 is an enlarged cross-sectional View taken along line 4 4 of FIG. l with parts shown in elevation;

FIG. 5 is a cross-sectional view taken along line 5 5 of FIG. 4;

FIG. 6 is an enlarged, partial cross-sectional view taken along line 6 6 of FIG. 5;

FIG. 7 is a cross-sectional view taken along line 7 7 of FIG. 5;

plan view showing the during a wire bending FIG. 8 is a partial elevational view of the spotwelder of FIG. 1 with parts broken away to show internal construction;

FIG. 9 is a partial cross-sectional view of the electrode portion of the spotwelder shown in FIG. 8 being taken at right angles thereto;

FIG. 10 is a schematic view showing a portion of a spark arrestor shown in FIG. 9 during one step in the manufacture thereof; and

FIG. 11 is a view similar to FIG. 10 showing the spark arrestor during a second step in the manufacture thereof. Referring again to the drawings, a miniature spotwelder constituting a presently preferred embodiment of the invention, generally designated 101, includes a housing 12 having an upper housing half 14 and a lower housing half 16. The upper housing half 14 includes a closed top wall 18, a front wall 20, a rear wall 22, side walls 24 and an open bottom 26. The open bottom 26 is encompassed by a peripheral lip 28 for properly positioning the upper housing half 14 on the lower housing half 16.

The top wall 18 is provided with a plurality of elongated openings 30 adjacent the side walls 24 permitting the free flow of air from a plurality of louvers 32 provided in the bottom wall 34 of the lower housing half 16. The top wall 18 is also provided with a pair of rectangular,

recessed lands

36, 38 and a circular, recessed land 40 which may be used for supporting suitable nameplates or other indicia. In addition, the top wall 18 is provided with a substantially square recessed portion 42 adapted to non-rotatably receive a wire bending block 44 for a purpose and in a manner to be hereinafter described. Also, a substantially rectangular recessed portion 46 is provided in the top Wall 18 for receiving a wire cutter bar 48 having a rst notch 50 provided along its lower edge 52, a second notch 54 provided along its first side 56 and a third notch 58 provided along its other side 60. The notch 50 is adapted to engage a transverse web 62 provided in the bottom of the recessed portion 46 and the notches 54 and 58 are adapted to engage pads 64 and'66, respectively, formed on a wall 68 of the recessed portion 46 during the forming of the upper housing half by a molding operation which also forms an elongated opening 68 (FIG. 2) in the top wall 18 subjacent each pad 64, 66. The openings 68 facilitate extending suitable means upwardly within a mold to form the pads 64 and 66 without Irequiring a second step in the molding operation.

During this molding operation, an island 70 is also formed integrally with the top wall 18 forming a housing for pivotally receiving the end 72 of a swingable, electrode-holding arm 74. In addition, a fixed, electrodeholder housing '76 is formed integrally with the front wall 20 during the molding operation and a U-shaped slot 78 is provided in Ithe front wall 20 in alignment with a similar U-shaped slot 80 provided in the front wall 82 of the lower housing half 16. Additionally, the rear wall 22 is provided with a notch 84 (FIG. 7) which cooperates with a similar notch 86 formed in the rear wall 88 of the lower housing half 16 for receiving a rubber grommet 90 carrying an electrical conductor 92 which connects the spotwelder 10 to a source of electrical power.

A cored, hollow boss 94 is provided on each corner of the bottomy wall 34 on the lower housing half 16 for the reception of suitable rubber-like foot pads 96 which prevent the spotwelder 10 from sliding around on a work bench. The hollow interiors of the bosses 94 pierce the inner surface 98 of the bottom wall 34 on a reduced diameter for receiving suitable wood screws, not shown, for permanently aiixing the spotwelder 10 to a Work bench. An upstanding pedestal 100 may be affixed to the inner surface 98 of the bottom wall 34 by screws 101 and carries an upstanding pin 102 (FIG. 4) at its upper end 104 for a purpose to be hereinafter stated.

The bottom wall 34 is also provided with a pair of apertures 106 which communicate with associated hollow bosses 108 extending upwardly from the inner surface 98.

4 When the housing half 14 is placed lon housing half 16, the bosses 108 are in alignment with similar bosses 110 depending from the top wall 18 for the reception of suitable bolts 111 which may be inserted through the apertures 106 in the bottom wall 34 and threaded into engagement with internal threads 112 provided in the bosses for securing the

housing halves

14 and 16 together.

A frame 114, having four corner posts like the ones shown at 116, depends from the under side 118 of the top wall 18 for supporting a welding transformer 120. The transformer 120 may be secured to the frame 114 by suitable stove bolts 122 which pass through each corner of transformer laminations 124 and threadedly engage an associated post 116.

The transformer 120 is designed to have a maximum temperature rise of approximately 60 C. and includes concentrically wound primary and

secondary coils

126 and 128, respectively. Under full load, the transformer 120 changes 13 amperes of 117 volt house current into approximately 600 amperes of about 1 volt welding current. The primary winding 128 may be connected to such house current by the conduct-or 92 which includes a first lead 130 having a first end 132 connected to one side of a normally open, single-pole switch 134 and a second lead 136 having an end 138 connected to one side of an automatic circuit breaker 142. A lead 144 con nects the other side of the circuit breaker 142 to the primary winding 126. The other side of the switch 134 is connected by a lead 148 to the primary winding 126. The circuit breaker 142 may be of any suitable type which senses overloads in both heat and current. Such overloads cause circuit breaker 142 to open and stop the How of current; however, after a short time the circuit breaker 142 cools and resets itself automatically.

A flat, wide copper strip 152 extends from the secondary winding 128 and is connected to one end 153 of a copper bus-bar 154 by a bolt-washer-and-nut assembly 156. The other end 158 of the bus-bar 154 includes a narrow portion 160 which is engaged by a xed electrode holder 162. The fixed electrode holder 162 is mounted in the housing 76 and includes an internallythreaded, frusto-conical end portion 163 extending up through an aperture 164 provided in the top wall 166 of the housing 76. The electrode holder 162 also includes a passageway 166 extending through the body portion 168 thereof for reception of the reduced portion 160 of the end 158. The xed electr-ode holder 162 is firmly affixed in electrical contact with the bus-bar 154 by a fixed electrode 17 t) having a comparatively broad spherical tip 172, a wrench-engaging body portion 174, an externally threaded end portion 176 and a bus-bar engaging tip 178. The electrode 170 may be conveniently made from a copper-chromium alloy which is silverplated for taking advantage of the conductivity of silver oxide when the tip 172 becomes oxidized during use of the spotwelder 10.

The electrode 170 is surrounded by a spark arrestor 182 which is preferably permanently affixed to the top wall 166 of the housing 76 by spinning-over the end 183 of the frusto-conical portion 163 of electrode holder 162 against a dished plate 184 provided in the spark arrestor 182. Since it is desired that the spotwelder 10 be safe to use in a home, on a rug for example, sparks must not only be prevented from leaving the area of the electrode 170, but must be kept from view of an operator of the welder 10 at all times during a welding operation to prevent the operator from being surprised by the appearance of sparks which might cause him to drop a red-hot workpiece on the rug. With this in mind, the spark arrestor 182 includes a plurality of looped tufts 186 made of filament glass to resist the heat given off by sparks during welding operations. The tufts 186 must be penetrable by Va workpiece 187 (FIG. 9) being welded while co1npletely surrounding the workpiece by flexing around it. It is necessary to form the tufts 186 with looped ends prevent the ends from a braiding away The looped ends 188 may be formed by stitching the tufts 186 as shown in FIG. 10 by using glass threads 190. However, the looped ends 188 will take a substantially circular shape which will not satisfactorily prevent sparks from passing through the tufts 186. This may be remedied by giving the loops 186 a substantially flat shape by sewing them together with cotton threads 192 and then by firing the tufts 186 in suflicient heat to burn the cotton threads away while tempering the loops 188 so that they will take a set in this substantially Hat shape, as shown in FIG. 1l.

This firing does not burn the threads 190 leaving them in place to bind the ends 196 of tufts 186 together. These bound ends are then aixed to an annular collar 197 which also carries the plate 184. The tufts 186 are then treated with a material containing graphite so that they will be lubricated to minimize wear when they are brought into engagement with the tufts 186 of an upper, identical spark arrestor 194 and the workpiece 187, as shown in FIG. 9.

A flat, wide copper lead 198 connects the secondary winding 128 to one end 200 of a hard-drawn copper bus-bar 204 having a crook 206 connecting the end 200 to a straight portion 208 extending through the larm 74 to its end 210 where the end 212 of the bus-bar 204 includes a narrowed portion 214 to which a swingable electrode holder 216, which may be identical to the fixed electrode holder 162, is affixed by a swingable electrode 218 which, in turn, may be identical to the fixed electrode 170.

The swingable electrode holder 216 includes a passageway 166 and a frusto-conical portion 163, both of which may be identical to corresponding portions of the fixed electrode holder 162. The end 183 of the portion 163 may be spun over into engagement with the dished plate 184 of the upper spark arrestor 194 to permanently ax it to the swingable arm 74.

The natural resiliency of the bus-bar 204 combined with its shape, including the crook 206, biases the arm 74 to the position shown in FIG. 4 wherein the swingable electrode 218 is suiiiciently spaced above the iixed electrode 170 to permit insertion of workpieces, such as the workpiece 187, between the

electrodes

218 and 170. When the arm 74 is swung to overcome the bi-as of the bus-bar 204, in a manner to be hereinafter described, the end 200 is prevented from moving by the pedestal 100 provided in the lower housing half 16. This is accomplished by engaging the pin 102 in a dielectric tting 220 having a shank portion 222 engaged in an aperture 224 provided in the end 200 and a head 226 adapted to seat on the upper end 104 of the pedestal 100.

The arm 74 is swingably connected to the island 70 by a pivot pin 228 mounted in apertures 230 provided in the side wall portions 232 of the island 70 and are insulated therefrom by cylindrical inslators 234 which are positioned in the apertures 230. The arm 74 includes a right housing half 234 and a left housing half 236 which are joined together by stove bolts 238 to encase the bus-bar 204. Free flow of air through the arm 74 is assured by providing it with an open bottom 240 and a iinned top wall 242 having a plurality of heat-radiating iins 244. The pivot pin 228 is connected to the end 72 of arm 74 by a pair of hollow transition members 246 which are mounted in a rectangular opening 2418 provided in the top wall 250 of the island 70 and which are provided with an opening 249 through which the crook 206 extends. The members 246 each include a bifurcated portion 252 which extends downwardly from the housing half 14 into the lower housing half 16. The members 246 are connected together by a stove bolt 254 so that the bifurcated portions 252 form ,a U-shaped trackway 256 for a dielectric roller 258 having a peripheral iiange 260 engaged in a slot 262 for preventing lateral displacement of the roller 258 as it is rolled along the trackway 256 by a crank 264 provided on the end 266 of an operat- 188 (FIG. l1) to during use.

ing handle 268. The operating handle 268 includes another end 270 which extends through the

U-shaped openings

78 and 80. The end 270 carries a grip portion 274 adjacent which an aperture 276 is provided in the operating handle 268 for the reception of one end 278 of a cord 280 having its other end 282 attached to a treadle 284 for actuating the operating handle 268 by a foot control 285.

The operating handle 268 includes a bight portion 286 which is pivotally mounted in the frame 114 in a pair of spaced, U-shaped notches, one of which is shown at 288 in FIG. 6. The bight portion 286 is retained in position in the notches 288 by the laminated portion 124 0f the transformer 120. The operating handle 268 also includes a lever 289 extending from the bight portion 286 to the grip 274 superadjacent an actuating button 290 extending upwardly from the switch 134. The oper- Iating handle 268 may be depressed to swing the arm 74 downwardly so that the electrode 218 will engage the workpiece 187 with the ixed electrode 170 with an optimum pressure, regardless of the thickness of the workpiece 187. This is accomplished by making the operating handle 268 out of steel and forming the lever 289, the bight portion 286 and the crank 264 integrally so that, when the lever 289 reaches the bottom of its stroke, it contacts button 290 actuating the switch 134 completing a circuit to the transfermer 120. The switch 134 is aiixed to a plate 291 by screws 292 in a position sufficiently below the lever 289 that the lever 289 must be sprung downwardly after the electrodes 218 and have rmly clamped the workpiece 187. Thus, the amount the lever 189 is sprung for thick workpieces is greater than the amount it is sprung for thin pieces and, therefore, the operating handle 268 has a torsion effect which results in approximately the same p.s.i. being applied to a thick workpiece as that applied to a thin workpiece.

Although many uses for the spotwelder 10 will manifest themselves, it is primarily a hobby tool for spotwelding wire shapes. During such welding operations, it is quite often desirable to cut and bend the wire. For this purpose, the end 52 of the cutter bar 48 may be inserted into the recess 46 with the notch 50 engaging the web 62 and the notches 54 and 58 engaging the pads 64 and 66, respectively. The cutter bar 48 may then be wedged into position by a wedge assembly 294 having a grip portion 296 and a wedge-shaped end 298. The end 298 is provided with a notch 299 engageable with the web 62. A cutter handle 300, having a first end 301 forming a grip portion and a second end 302, may then be assembled to the cutter bar 48. This is accomplished by engaging a button 304, provided on the end 302 of the cutter handle 300, in a keyhole-type aperture 306 provided in the cutter bar 48 adjacent its end 308 in such 4a manner that a crook 310 formed in the end 308 will face a similar crook 312 formed in the end 302 of the cutter handle 300. This forms a small aperture 314 adapted to receive the wire workpiece 187 so that it may be severed by pushing downwardly on the grip portion 301.

The workpiece 187 may be bent to various shapes by placing the bending block 44 into the square opening 42 in such a manner that a cylindrical, bifurcated member 316 provided on the bending block 44 extends above the top wall 18. The cutter handle 300 may then be mounted on the cylindrical member 316 by engaging an aperture 318 provided therein adjacent the button 304 with the cylindrical member 316 in such a manner that the button 304 is uppermost. The workpiece 187 may then be inserted into the bifurcated portion 320 of the member 316 in such a manner that the end 322 of the workpiece 187 extends past the button 304. The handle 300 may then be rotated bending the end 322 of workpiece 187 about the bending block 44.

Operation of the device will be readily understood. If the cord 280 and the foot control 285 are not being used, the spotwelder 10 may be placed on a suitable level surture of internal parts of the welder face and plugged into a convenient 117 volt A C. house outlet. No other large appliances should be operated at the same time on the circuit servicing the spotwelder 10. If it is desired to use the foot control 285, the spotwelder 10 should be placed near the edge of a table so that the grip 274 on the operating handle 268 extends over the edge of the table. The end 278 of cord 280' may then be placed through the aperture 276 in the operating handle 268 and down through the treadle 284. The treadle 284 may then be adjusted to a convenient angle after which the end 282 of the cord 280 is tied off.

A cooling tray should then be lled with Water and, if desired, a sponge may be placed in the water.

The

electrodes

170 and 218 may be cleaned by sanding them lightly with emery cloth. If it is desired to weld wire, steel wire up to 1/8 inch diameter may be used. The areas to be welded should be cleaned with emery cloth and any non-conductive coating, such .as paint, rust or the like, should be removed. The two parts to be welded together should be centered between the

electrodes

170 and 218 Vafter which the control lever 268 may be pressed down to clamp the workpieces between the electrodes. The lever 268 must be pressed down until it bottoms out in slot 80 so that the button 290 will be depressed closing the circuit to the transformer 120. The control handle 268 is held in its down position for up to 2 seconds, depending upon wire sizes. The welding cycle starts only when control lever 268 is pressed all the way down. The metal from the two wires will fuse together only after it is red hot. After the weld has been completed, the handle 268 may be released whereupon the resilience of bus-bar 204 will return the arm 74 lto its elevated position separating the

electrodes

170 and 218. The workpiece may then be removed and cooled by placing it on the wet sponge in the tray.

The spotwelder 10 may also be used for welding steel sheets having a thickness no greater than 0.015 inch. Such sheets may be welded by cleaning the areas to be welded with emery cloth. The areas to be welded should then be dimpled with a 16 penny common nail on a wood block. The dimple is used to locate the weld on the lower electrode 170 after which the control handle 268 may be lowered to clamp the workpieces between the

electrodes

170 and 218 and to actuate the switch 134.

During a welding operation, or otherwise, should the secondary circuit become shorted, the circuit breaker 142 will open the primary circuit in less than one second. The circuit breaker also controls the maximum temperato a maximum rise of 65 C. when the spotwelder 10 isoperated at maximum rated duty cycle of 8%. In addition, the circuit breaker 142 controls overloading, overheating and undesirable combinations of both within stated maximum temperature and amp branch circuit limitations.

While the particular spotwelder herein shown and described in detail is fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiment of the invention and that no limitations are intended to the details of construction or design hereinshown other than as dened in the appended claims.

What is claimed is:

1. A miniature spotwelder, comprising:

a transformer 'having a primary winding and a secondary wind-ingr a xed Welding electrode connected lwinding;

a swingable Welding electrode;

a bus-bar connecting said swingable electrode to said secondary winding, said busabar having means comprising its physical properties and shape for biasing said swingable electrode to a predetermined position spaced suiiiciently from said fixed electrode to admit workpieces therebetween; and

a swingable lever connected to said bus-bar for swingto said secondary ing said swingable electrode towards said xed electrode clamping said xworkfpieces therebetween.

2. A spotwelder as started in claim 1 including mutually engageable spark arrestor means encompassing and shielding each of said electrodes at all times during a welding operation to prevent sparks from leaving the welding area.

3. A spotwelder as stated in claim 1 including switch means controlling the flow of electrical current to said primary iwinding, said switch means being mounted in lthe path of travel of said lever and being spaced a predetermined distance from said lever at the end of its electrodeclosing stroke, said lever including means comprising its physical properties an-d shape whereby said lever may be sprung into engagement with said switch means to complete a circuit to said primary winding only after said lever has been swung sufficiently to cause said swingable electrode to exert `a predetermined pressure on said workpieces.

4. .A miniature spotwelder, comprising:

a transformer having a primary winding and a secondary Winding;

a fixed welding electrode connected to said secondary winding;

a swingable welding electrode;

a bus-:bar connecting said swingalble electrode to said secondary winding, said bus-bar having suicient resiliency and a predetermined shape for biasing said swingable electrode to a predetermined position `spaced sufficiently from said xed electrode to admit workpieces therebetween;

a swingable lever connected to said bus-bar for swinging said swingable electrode towards said fixed electrode clamping said workpieces therebetween;

Ihousing means;

an electrical switch mounted in said lhousing means in a predetermined position, said switch completing a circuit to said primary winding, said lever including a bight portion pivotally mounting said lever in said housing, a grip portion connected to one end of said bight portion and extending to the exterior of said housing for actuation by a user of `said spotwelder and a crank member extending from the other end of said bight portion; and

means connecting said crank portion to said bus-bar, said lever actuating said switch when said grip portion has been swung a predetermined amount 'by said user, said predetermined position of said switch being such that said lever must be swung suiiciently after said swingable electrode has clamped said workpieces against said fixed electrode to cause .a predetermined pressure to be exerted on said workpieces.

5. A spotwelder as stated in claim 4 including an overload device connected in said circuit between said switch and said primary winding.

6. A spotwelder as stated in claim 4 wherein said electrodes are threadedly connected to said spotwelder, whereby said electrodes may be readily removed with a wrench.

7. A spotwelder as stated in claim 4 including mutually engageable spark arrestors, one surrounding each electro-de for shielding an associated electrode in such a manner that sparks emanating from said workpieces are held captive and shielded from View, each of said spark arrestors including a plurality of spun glass tufts having flat, looped portions which are deectible by said workpieces.

8. A spotwelder as stated in claim 1 wherein said busbar comprises a hard-drawn copper unit having a straight portion and a crook, said straight portion having a free end, an electrode holder straddling said free end, said electrode holder including an internally threaded portion, said swingable electrode including external threads or threadedly engaging said internally threaded portion in suc-h a manner that one end of said swingable elecan actuating handle having a bight portion, a crank portion extending from one side of said bight portrode may be threaded into rrn engagement with said free end, thereby clamping said electrode holder to said free end.

9. A miniature spotwelder, comprising:

a housing having an 4upper housing half and a lower 5 a free end extending externally of said housing, said housing half, said lower housing half including a operating handle `being pivotally mounted in said ybottom w-all having an upstanding pedestal provided housing by engaging said bight portion between thereon, said upper housing half including a top said transformer and said top wall, said lever extendwall having a plurality of posts depending therefrom ing along the underside of said lever extending along toward said bottom wall; 10 the underside of said top wall superjacent said a 'welding transformer connected to said posts and exelectrical switch and being engagea-ble with said tending into said lower housing half, said welding button when said lever is depressed a predetermined transformer including a primary winding connecti amount, said crank portion being connected to said able to a 117 volt A.C. electrical current source -bifurcated portion for swinging said swingable arm and being designed to draw 12 amps at full load, said 15 to lower said swingable electrode toward said fixed transformer also including a secondary winding havelectrode when said handle is depressed, said button ing a secondary voltage of approximately 1 Volt at being located a suicient distance from said lever 650 amps, said transformer converting 12 amps of portion that said lever portion must be depressed the 117 volt A.C. current into approximately 650 suciently after said swingable electrode has engaged amps of approximately 1 volt welding current under 20 a workpiece against said xed electrode to exert a full load; predetermined pressure on said wonkpiece before ak swingable arm swingably connected to said top wall, said button is contacted; and l said swingable arm including a bifurcated portion spark arrestor means surrounding said electrodes for extending through said top wall into said housing; confining sparks emanating from said workpieces to a hard-drawn copper bus-bar having one end connected the area surrounding said electrode and for hiding to said secondary winding, a crook extending from said one end up through said bifurcated portion and a straight portion extending from said crook through said arm, said straight portion including a free end tion and a lever portion extending from the other side of said bight portion, said lever portion having said sparks from the view of a user of said spot- Welder.

10. lIn combination with a spotwelder having upper and lower welding electrode means, spark arrestor means,

positioned at the free end of said arm; comprising:

a swingable electrode holder connected to said free yskirt means surrounding each of said electrode means, end of said bus-bar, said swingable electrode holder each of said skirt means including an annular collar including an internally threaded portion communiand a plurality of heat-resistant, deformable elements eating with `said free end of said bus-bar; affixed to said annular collar in overlapping relation an externally threaded, swingable electrode threadedly and being deflectilble by a workpiece being welded engaging the internally threaded portion of said by said electrode means while completely surroundswingalble electrode holder and extending iuto clarnping the portion of said workpiece at said electrodes ing engagement :with said free end; by flexing around it.

a second #busebar having one end connected to said secondary winding and a free end extending through References Cited by the Examiner sai hlusinbg toba position adjacent the free end of UNITED STATES PATENTS sal o er us-i ar; y

a xed electrode holder positioned on the free end of gllmson 219 86 elps 219-110 X said second 'bus-bar, sald xed electrode holder 1n- 1 986 512 1/1935 AMeadowcroft 219-86 cluding an lnternally threaded portion communi- 2 175 749 10/1939 Bckm t an 219-120 X catlng w1th said free end of sa1d second bus-bar; 2 194 573 3/1940 S chulz 219-86 a fixed electrode having external thread threadedly en- 2,434,025 1/1948 Wallace 219-86 gagmg sald internal threads on sald fixed electrode 268.8 0645 8/1954 Clark 219 86 holder and extending into clamped engagement with said free end of said second bus-bar;

an electrical switch connecting said primary circuit to a source of 117 volt A.C. current, said switch including an actuating button located a predetermined distance below said top wall;

FOREIGN PATENTS 482,472 3/193'8 Great Britain.

RICHA-RD M. WOOD, Primary Examiner.

Claims

1. A MINIATURE SPOTWELDER, COMPRISING: A TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING; A FIXED WELDING ELECTRODE CONNECTED TO SAID SECONDARY WINDING; A SWINGABLE WELDING ELECTRODE; A BUS-BAR CONNECTING SAID SWINGABLE ELECTRODE TO SAID SECONDARY WINDING, SAID BUS-BAR HAVING MEANS COMPRISING ITS PHYSICAL PROPERTIES AND SHAPE FOR BIASING SAID SWINGABLE ELECTRODE TO A PREDETERMINED POSITION SPACED SUFFICIENTLY FROM SAID FIXED ELECTRODE TO ADMIT WORKPIECES THEREBETWEEN; AND A SWINGABLE LEVER CONNECTED TO SAID BUS-BAR FOR SWINGING SAID SWINGABLE ELECTRODE TOWARDS SAID FIXED ELECTRODE CLAMPING SAID WORKPIECES THEREBETWEEN.