US2781442A - Apparatus for riveting - Google Patents

Description

Feb. 12, 1957 2,781,442

w. G. FLEssNER ErAL APPARATUS FOR RIVETING Filed March 9, 1953 mll l2 Sheets-Sheet l 35 Z *d l l Feb. 12, 195'/A w. G. FU-SSNER Em 2,781,442

APPARATUS `FOR RIVIEITINGv 2 Sheets-Sheet 2 Fil-ed March 9, 1953 SEO Dwi SMQ NGN United States l Patent C) APPARATUS FOR RIVETING William G. Flessner, Skokie, and Ernest W. Luke, Waukegan, Ill., assignors to Fansteel Metallurgical Corporation, a corporation of New York Application March 9, 1953, Serial No. 341,074

Claims. (Cl. 219--150) This invention relates to an apparatus for and method of welding small metal articles, and more particularly, relates to the Welding of contact buttons or points upon metal arms, made particularly of spring material, by application of a forging action which intimately joins each contact button to its associated arm.

Contact buttons or points are available in a number of sizes and thicknesses and may be of any one of a number of different metals. The active contact material, which may consist of tungsten, silver or other relatively expensive material, usually comes With a backing of copper, iron, steel, or other relatively cheap metal. The backing generally is constructed in the form of a rivet having a shank of smaller diameter than the head of the button, which may be spread for the purpose of attaching the contact to the contact arm. The contact arm, which may be of thin metal, such as spring steel or spring copper or bronze', is generally apertured to accommodate the shank of the rivet-shaped contact backing part.

It `is clear that Va satisfactory contact and contact arm assembly should have perfect mechanical and electrical contact therebetween so that all mechanical movement n will be concentrated or localized at the contact face, and also so that the circuit making and breaking function will be localized at the contact face. A contact assembly where the button or point is not tightly joined to the contact arm will be a fertile field for both mechanical and electrical difficulties. Mechanically, the repeated hammering to which contacts are subjected, as for example in the distributor points of an automobile engine, will tend to wear the backing of the contact button against the hard material of the contact arm. Electrically, any looseness between the contact button and arm will permit -arcing to occur therebetween. Such arcing is, of course,

destructive to the contact assembly. The improper functioning of the contact assembly in both mechanical and electrical senses will thus tend to reduce greatly the life expectancy of the contact assembly.

In certain present day methods and apparatuses for making contact assemblies, substantial difficulty is occasioned by the tendency cf the spring arm to pull away from the contact button just at the instant when Welding or riveting is to occur. This pulling is usually caused by the action of intense magnetic fields set up by heavy Welding currents and the resiliency of the spring arm. At this instant, the shank metal is soft and has not been spread, so the contact button cannot be considered as riveted to the arm.` In other present day methods and apparatuses for making spring contact assemblies, there kis a tendency to crack or damage the contact button.

This occurs when the button is gripped in a chuck and the shank is spun or staked. The center of the contact button is not supported against the spinning or staking force and the contact button frequently cracks.

In accordance with this invention, a method and `apparatus is provided wherein the assembly of contact button and contact arm and the subsequent Welding thereof is facilitated. The new method and apparatus are positive 2gsm-t2 Patented Feb. l2, 1957 2 in action and render the manufacture of contact assemblies fool-proof and effective, While making it practically impossible to produce defective or damaged assemblies or parts.

In general, the new apparatus provides a Welder having top and bottom electrodes. For convenience, a vertical orientation of the Welder Will be assumed; it is possible, however, to have other Welder positions. The bottom electrode is recessed to accommodate a contact button, the button being disposed with the contact face down and the rivet shank up. An apertured spring arm for the assembly is disposed over the bottom electrode so that the contact shank will project through the aperture in the spring arm. The top electrode of the new Welder is provided with a resilient member extending therefrom and bearing upon the spring arm to prevent the spring arm from pulling away from the contact button shoulder formed at the point where the shank joins the head of the contact button.

Additionally, the top welding electrode has the active part thereof of refractory material. 'Ihe Welder itself is of the resistance type with the electrodes and Work being tightly in contact during the welding. Such Welders customarily have the active electrodes of relatively soft material such as copper. By contrast, the new Welder has the active part of the top electrode, and in some instances both electrodes, of refractory material. As a result, a Welder embodying the present invention makes it possible to develop a forging action upon the Work during welding. In the case of a contact button having a Vrivet-like shank, the forging action is advantageous in venting the thin metal piece from leaving the shoulder at the rivet head upon electrode separation. The current passing through the rivet shank serves to soften the shank metal to facilitate the forging action which intimately joins the spread rivet shank to the thin metal piece.

vFor a more complete understanding of the invention, both in its specific and general forms, reference will now be made to the drawings, wherein exemplary embodiments of the invention are illustrated. It is understood that variations within the skill of those versed in the art may be made Without departing from the scope or spirit of the invention.

Referring therefore to the drawings:

Figure l shows an exploded view of the upper welding electrode and base block, with a contact button and spring arm between the electrode and base block in preparation for assembly.

Figure 2 shows, partly in section, the Welding electrodes and the parts of a contact button assembly just prior to the initiation of welding.

Figure 3 is a View ygenerally similar to Figure 2, but showing the electrodes pressed tightly together to weld the contact button and contact arm into a unitary assembly.

Figure 4 is a perspective elevation of a lower electrode.

Figure 5 is a detail, partly in section, of a modified form of lower electrode provided with a removable tip.

Figure 6 shows a modified form of resilient member to engage the contact arm.

Figure 7 shows partially in section a modified base block which'may be used with the present invention.

' Figure 8 is a diagrammatic view of a Welding system embodying the present invention.

Referring first to Figures l to 5 inclusive, the significant portions of the Welder comprise the electrode structures. Thus, the Welder includes base block 10 of rigid insulating material, 'such as fibre, Bakelite, or wood. Block 10 may be supported in any suitable fashion and has bore 11 with counterbore 12, the 'latter extending 'upwardly from the bottom of block toward the top. Bore 11, together with the top face of the bottom electrode to be described later, cooperates to provide a shallow recess for accommodating contact button 13. Y l y y Contact button 13 has reduced shank portion 15, this contact button being assembled with contact Varm or metal reed 16 to provide a contact assembly. Reed ,16 islapertured at 17 `to accommodate Contact button shank 15, the length of the shank being somewhat greater than the thickness of reed 16. This is shown in Figure2 where, prior to welding, the shank material extendsl throughthe reed aperture and `has apart above the top surface ofthe reed. Where assembliesjother than contact, assemblies are to be joined, ,the contact button may be Va simple rivet having a head Vand shank.

linsulating block 1t) `supports a bottom electrode, generally indicated by ,numeraltl The bottom electrode has body portion 2 1 andreduced electrodeportion 22. The lateral dimensionsV of parts 251 and and 22 of bottom electrode 2i) are so proportioned that the electrode snugly ts bore 11 of insulating block 10., Lowerelectrode 2t) has portion 24 threaded lso that nuts ZS'and 26vmay be used to adjust the electrode heightl inl block 10 and for engaging the bottom surface of block 10 to withstand the welding pressure. Between vnuts 25 and 26 a connector may be disposed Afor establishing a circuit connection to the lower electrode. ,s v v,

lt will be understood that the, bottom electrode may be removed from block 10 and replaced by another electrode having a diiferent sized electrode portion 22 for rthe purpose of accommodating different thicknesses of contact buttons. The bottom electrode is preferably of silver or copper, having excellent heat and electrical conductivities, and has the active electrode part of silver orof refractory material, as will be explained later.

Blockli) is preferably stationary in the -welding machine and is adapted to have a movable electrode assembly, Vgenerally indicated by numeral 28, bear down upon the parts for performing a welding operation. Movable electrode vassembly 28 includes insulating block 30 carryingl the electrode proper.

The top electrode comprises bolt portion 32, beloytl which is body portion 33 carrying pin 34. Bolt portion 32 is Vthreadedinto a threaded part of block 30 and has nut 35 to lock the top electrode in desired vertical position. Block 30 may be made of a suitable conducting material, Isuch as copper, to provide a convenient connecting surface for the end of a conductor (notlshow'n) `leading to a terminal of a source of current. Pin 34 maybe integral with or attached to body portion "33.of the electrode structure,"and the active tip face thereof is larger in area than the contact or. rivet shank face.

The top electrode is preferably `of 'silver orcopper Ito provide excellent heat and electrical conductivities. 'Pin portion 34 may be of silver'or copper lwith a removable tip 3.4' made-preferably of arefractory materialgsuch as tungsten. Tip 34' may be threaded into v`a boreprovided Ain the end of pin 34. If desired, the removabletip may beomitted and the entirepin 34 may be made 'of the refractory material, although this is not preferred.

,Slidable over pin 34 is insulatingbushing 38 khaving bottom flange 39 extending outwardlytherefrom. :Bushing 33 is of insulating mateiialsuch as"Bakelite,glass, ceramic or Aother rigid insulatingrnaterial. Disposed'over body 33 of the top electrode is exible sleeve 41of rubber, plastic or similar resilient material. `Sleeve 41 'extends down farenough 'so that it encloses pin 34 and engages the outer surface` of bushing 33. vSleeve 41 land lbody 33 are so proportioned that the sleeve hugs ,the'bodytightly. Bushing 3S is also large enough so that the-flexible sleeve will'tightlygrip the bushing. Flexible sleeve 41 is'normally long enough so that in the normal `position ofthe sleeve, bushing 38 will telescope with the end'of' pin 34, the lower part of the bushing extending beyond the pin illustratedin Figure 2.

Bushing 38 functions as an extension of sleeve 41. It is possible to omit the bushing and rely upon the sleeve alone, although the embodiment just described is preferred.

Upon downward movement of the top electrode, bushing 38 will be telescoped over pin 34, the active face 34' of pin 34 pressing down against the top face of shank 15 of the contact button. V1t is understood, of course, that the means for supporting either block 1G 4or block 30, or both, will include suitable 'springs yso that when the top electrode presses down upon the button shank there will be predetermined pressure exerted upon the end faces of the contact'buttonor rivet, as the case may be.

By adjusting the pressure of the electrodes upon the contact assembly and the amount of electric current passing through the shank of Vthe contact, adesired forging action 'will result. vinasmuch as the top electrode face is preferably-made `of refractory material, such as tungsten, and since shank '15 Vis usually "of copper or other metal 'having a melting point whi'chis low-compared to tungsten, there will be little diculty in Isecuring a sufficiently high ltemperature for effecting a softening of the button or rivet shank metal without serious damage to the tungsten electrode face. The upper electrode initially makes Contact with the button shank, which protrudes slightly above Vthe reed 16, and only the button shank is heated to a suticiently high temperature to be softened as the current is concentrated in the button shank.

The bottom electrode may be constructed similar to top electrode 2S. Thus, referring to Figure 5, electrode 45 has recess'47 into which may be pressed electrode tip dii. When this construction is used tor thc lower electrode, tip 48 may have reduced portion 5h corresponding to reduced portion 22 of the electrode shown in Figure 3. `trode ltip 43 has depending part 49' extending into recess ,a elec-- '47. A bayonet or screw joint, as shown for the top electrode, between the insert and electrode body may be provided to facilitate speedy change.

`While silver may be used as an active electrode ma- {terialat the electrode tip, it wears relatively fast, and no forging action is possible on copper. Tungsten, iron, nickel, or anyimetal having a melting point higher than copper-or the shank metal, may be used as the active top electrode Yfor obtaining forging as well as Welding, this beingatt'achedfto Vthe-silver or copper electrode body, as

`is tip 34. In the specic example shown, only the shank `end ofthe rivet is heated-and forged. Hence, Vthe top electrode will-have a'refractory-metal-tip, such astungsten. However, there may be instances where the bottom 'of the 4rivet'is to be -heated-andforged, in which case :the bottom electrode will Valso include a tip made of a refrzuztory material.

As shown, however, the vbottom Aelectrode yneed only .conductrcurrent to the contact butt-on and the largearea 4'of the vcontact buttonwill assure goed conduction yof the current Yto the shank.

During a welding or forging operation, V lleirible lsleeve 41, Willyield fand permit hanged bushing 38 to slide upwardly. The spring of sleeve 41 will retain flanged bush- A ingr33against reed'1'6 and prevent any movement of the reed upwardly away from the contact button.

Instead of a exible sleeve, a coilrspring maybeused. Thejspring is insulated either from `the reed or from the Rrnoyable electrode body, `or both. Suchja construction is shown in Figure 6 where helical spring 41', havinga itapered cross-section, 'embraces part 34 of the electrode l and is retained against upward movement by insulator 33].-A j The movable electrode-may'also be tapered withthe ,largerl end up` and thus-permit theuse of a simple coil dramas' of the electrode pin and not necessarily surround the electrode pin as the rubber sleeve and springs do. It is true that the force on reed 16 would be on one side only of the aperture; however, reed 16 is usually stii enough so that if one part of the reed near the aperture is restrained from upward movement, the remainder of the reed Will be restrained.

Instead of a contact point assembly, the contact button may be a rivet, and reed 16 may be replaced by two or more articles to be riveted together.

Suitable means for cooling the electrodes may be provided. Thus, Water-jacketed electrodes are Well known in the art and may be used.

To more readily adapt the Welding apparatus of the present invention for use With contact buttons of varying size, the base lblock shown in Figures l, 2 and 3 is modified in the manner shown in Figure 7. The block herein comprises a lower portion 10a made of an insulating material as in Figures 1, 2 and 3, and an upper portion 10b made of a suitable metal, such as a nickel-alloy material. Base block portions 10a and 10b have* apertures 12' and 11' respectively, corresponding to apertures 12 and 11 in the embodiment of Figures 1, 2 and 3. Aperture 11 snugly receives the head of a oontactbutton 13. The upper and lower portions 10a and 10b are held together by suitable fastening means, as by thread-ed bolts (not shown), so that the upper portion 10b may be readily changed in order to accommodate contact buttons of different sizes, requiring aperture 11 to be of a different Width or depth.

The lower electrode construction shown in Figure 5 is utilized in the embodiment of Figure 7 4so that the tip 48 may -be readily changed when necessary.

Referring now to Figure 8, there is shown a Welding system for carrying out Welding. The Welding comprises base 50 upon which is supported the lower electrode structure previously described. Base S0 has post 51 and arm 52 carrying head 53. Within head 53 is the movable top electrode previously described and for convenience generally indicated by numeral 54. Top electrode 54 is carried 4by a suitable piston operating within an air cylinder of a conventional press. A Winding, generally indicated by numeral 56, controls the air applied to the piston. Excepting for the detailed construction of the two electrodes as previously described, the Welder shown in Figure 6 and so far described is conventional.

The -top and bottom electrodes are connected by Wires to a power source generally indicated by 58. The power source Iis adapted to supply heavy alternating or direct currents at a low voltage of the onder of about l or 2 volts. Power source 58 has wires 59 and 60 for controlling the energization of the power source.

Movable electrode assembly 54 carries trip arm 62 which is adapted to cooperate With switch nger 63 of switch 64 secured to a suitable part of the Welder, such as for example post 51. Means not shown are provided for adjusting the closure of switch 64 at a predetermined point in the `downward travel of the movable electrode assembly. The timing is such that switch 64 is closed just prior to the impact of electrode pin 34 upon contact shank 15. v

Switch 64 has one terminal connected by Wire 66 to the top terminal of winding 67 of relay 68. Relay 68 is of the type having a delayed opening and closing, such relays being Well known and available in a variety of forms. The delay in the relay operation is of the order of ybetween about one tenth and about one third of a second, although this may vary depending upon various factors.

Winding 67 has its `lower terminal connected by Wire 69 to fixed contact 71 of an operating relay 72. Fixed contact 71 cooperates with movable contact 73, this latter contact also cooperating with fixed contact 74. It is understood that movable contact 73 bridges X-ed contacts 71 and 74, when the relay `is closed, to connect these 6 xed contacts. Contact 74 is connected by wire 75 t junction 76. Junction 76 is connected to one terminal of Winding 77 of relay 72, the other terminal of this Winding lbeing connected by Wire 78 to the remaining terminal of switch 64.

Wires 59 and 60 are connected to fixed contacts 80 and 81 respectively of relay 72. Movable contact 82 is provided for bridging contacts and 81. Both the movable contacts are mounted on a suitable plunger 84 which is actuated by Winding 77. The relay is normally biased to the open position as shown, from which position energization of Winding 77 Will close the relay contacts.

Winding 56 for operating the press part of the Welder has center 87 grounded. Winding 56 has terminals 88 and 89, the winding consisting of two parts, one Winding for driving the movable electrode in one direction and Vthe other Winding for driving the movable electrode in the other direction. Terminal 88 of the air control Winding is connected by Wire 91 through manual switch 92 to fixed contact 93 of delay relay 68. Terminal 89 of the air control Winding is connected by Wire 94 to xed contact 95 of delay relay 68. Delay relay 68 has movable contact 96 normally biased against contact 93. Upon energization of the relay winding 67, movable contact 96 will be pulled against off normal contact 95.

Movable contact 96 of delay relay 68 is connected by Wire 97 to transformer secondary 98, the other terminal of the secondary being grounded. Secondary 98 is part of transformer 99 having primary 100 connected across supply Wires 101 and 102. Wires 101 and 102 are connected to junction 76 and to wire 66 respectively. A double pole single throw switch 103 is provided for cutting olf power to Wires 101 and 102 in case the system is to be shut down.

The operation of the system shown in Figure 7 is as follows: It is assumed that a contact button is seated in block 10 and that reed 16 is disposed over shank 15. Suitable automatic means for feeding contact buttons and reeds to the Welder may be provided. l'n the normal position of the Welder, the top electrode will be clear of reed 16 so that both the Contact button and reed may be properly positioned in the lower electrode structure.

Upon closure 0f manual switch 92, the left-hand half of Winding 56 will be energized. This Will cause the Welding electrode to be moved downwardly. When switch 64 has been tripped to a closed position, van energizing circuit for winding 77 will be established. This circuit will run from wire 192, along Wire 66, through switch 64, Wire 78, Winding 77 to Wire 191. Relay 72 will close. The closure of relay 72 will cause contacts 71 and 74 to complete an energizing circuit for Winding 67 of the delay relay. At the same time contacts 80 and 81 will be closed to trigger the power source. The electrodes at this time are pressing the contact 4assembly together and a heavy current will pass through the contact shank.

When heat cycle, as initiated by circuits 59 and 60, has been completed, relay 67 operates to move contact 96 against contact 9S. When contact 96 breaks from contact 93, the energizing circuit from secondary 98 to the left half of Winding 56 will be opened. When contact 96 engages contact 95, the right half of Winding 56 will be energized and this will result in air being utilized to raise the movable electrode assembly. When the movable electrode assembly moves up enough to open switch 64, relay 72 will release and open the circuit for Winding 67 of the delay relay. The delay in release of relay 63 will sullice to permit the top electrode assembly to reach the end of its travel.

It is understood that manual switch 92 is closed long enough for the movable electrode assembly to reach the bottom of its stroke. By virtue of this switch arrangement, complete control over the Welder is retained by the operator from the beginning of the downward stroke possible to 4provide trip means .forstaiting a 'Welding cycle by `a momentary closingof switch 92'afterWhich .theswitch remains closed for the downward movement of the electrode.

,After the top electrode has moved to trip switch 64, the Welderfis nolonger under'the control of the operator. Instead, the time delay relay insures that a number of c'y'clesof current (if alternating currentis used) lpas's'es through the work. The Welder of the instant invention thus provides a relatively simple and eifective means cornbining resistance welding and forgingaction in a manner which greatly reduces the human element, 'thus assuring uniformity of Work.

The term refractory material, used throughout 'the specification and claims to describe 'the 'material out of Which the electrode tips are made, should be understood tomean a Conductive material Which has a melting point apprecia'hly higher than the material being Welded.

The system for Weldingcontactbuttons above disclosed primarily utilized a forging action to weld orintimately join a contact button to its associated-arm. rIhe shank ofthe button was heated by current merely tosoften the shank to facilitate the forging action. If desired, lthe current passing through the Contact button or other Work piece may be utilized to actually melt the contact button, or other Work piece, and the associated material to provide for a fusion Welding action, as Well as a yforging action.

Numerous other variations of the specific Welding systern above described vmay be used Without deviating from 'the broader aspects of the present invention.

We claim:

l. In a Welder vfor spreading a rivet over thin meta stock, the combination of an electrode having an active face for contacting and supporting the head of a rivet, at least one apertured metal strip through which the rivet shank passes and over which the shank is to be spread, means for supporting said metal strip in proper relation to the rivet so that the rivet shank extends through the aperture, and a movable electrode assembly including an elongated movable electrode having an active tip portion carried by a larger body portion, said movable electrode having its tip normally spaced from the shank face but movable toward the same to contact the shank face and` exert pressure thereon, a resilient sleeve-like member carried by '"sad larger 'body 'portion and also surrounding "the "tip portion, `a substantial part of the sleeve surrounding said tipportion being 'free of 'any lateral support fso that said unsupported portion may 'yield substantially in a'll directions,`said member having its unsupported portion 'extending from said movable electrode assembly toward the thin metal strip, `said re'- silie'nt memberbeing Selfseating o'n said metal strip and bearing against the same prior to vany contacting of th'e movable electrode upon the 'shank face, said resilient member having lateral' clearance'from said tip 'portion and yielding upon movement ot" said electrode to engage the shank face, said electrodes contacting the rivet at opposite 'ends of the rivet and passing a heavy current lthrough the rivet to heat vthe same, 'said resilient member serving to maintain the thin 'metal strip in S'elfese'ating yposition with respect tothe rivet shoulder.

V2. The Welder- Vaccording'to claim 1 wherein'said re silient member is 'a rubber sleeve.

l3A. The Welder according to claim l wherein said resilientmember is a ilexible rubber sleeve and has a'btishing carried at the end thereof, said bushing fitting the electrode and being slidable along said electrode.

4. The Welder according to claim l wherein said rcsilient member is a'helical coil spring.

5. The Welder according to claim l wherein said resilient member is a tapered helical coil spring With the small end'of the spring 'being disposed around the larger lbody Aportion and the large end yof the spring extending in a manner to engage the thin metal strip.

Rfe'rencesCi'te'd in thele of this patent UNITED STATES PATENTS

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