US3546420A

US3546420A - Stud welding apparatus having stud position responsive means

Info

Publication number: US3546420A
Application number: US715353A
Authority: US
Inventors: Donald H Ettinger; Engelbert A Meyer
Original assignee: Warren Fastener Corp
Current assignee: USM Corp
Priority date: 1968-03-22
Filing date: 1968-03-22
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08

Description

United States Patent lnventors Appl. No.

Filed Patented Assignee STUD WELDING APPARATUS HAVING STUD POSITION RESPONSIVE MEANS 12 Claims, 10 Drawing Figs.

U.S. Cl 219/98 Int. Cl B23k 9/20,

823k 1 1/26 Field of Search 219/98 Primary Examiner-R. F. Staubly Attorney-Burton and Parker ABSTRACT: A welding gun for securing relatively small studs or buttons to panels in rapid succession, which buttons are fed to the gun by an automatic feeding mechanism through a flexible base coupled to a transfer chamber on the gun. Means are provided on the gun in the form of a switch connected in the electrical control circuit for the gun. The switch contacts being closed to enable firing of the gun when the gun is properly positioned with respect to the panel and a button is correctly oriented in the gun collet. Misalignment of the gun with respect to the panel or absence of a button properly held in the gun collet prevents closure of the switch contacts, and the gun cannot be tired.

PATENTEUUEC 8|97U 3545420 I SHEET 3 [IF 4 INVENTOR$ DONALD H. ETTINGER ENGELBERT A. MEYER mm WA.

A r romvs rs PATENTED DEB 8197B 354K420 saw u or 4 INVENTORS DONALD H. ETTINGER ENGELBERT A. MEYER ATTORNEYS STUD WELDING APPARATUS HAVING STUD POSITION v RESPONSIVE MEANS This application is a division of our copending U.S. Pat. application, Ser. No. 485,007, filed Sept. 3, 1965, which in turn was a consolidation of our prior copending US. Pat. applications, Ser. No. 378,507, filed June 29, 1964, and Ser. No. 451,958, filed Apr. 29, I965, and a continuation-in-part of each.

The invention relates to the provision of sensing mechanism for a welding gun which is operable to enable actuation of the gun only when certain conditions are present which will insure a proper welding operation, and comprises a support having means for limiting its approach toward a panel to which a button is to welded, an electrode on the support having means for holding a button in welding position, means coupled to the electrode for delivering welding current thereto, and sensing mechanism responsive to proper engagement of a button on the electrode with the panel tov enable actuation of the current delivering means.

While the term welding gun? has been used throughout the specification, it is to be understood that such is not intended to be restricted to a construction embodying a barrel, pistol grip handle, etc. Rather it is intended in a broad sense to include shapes other than the commonly known pistol configuration.

Other objects, advantages and meritorious features will more fully appear from the following specification, claims and accompanying drawings, wherein:

FIG. 1 is a side elevation, partially in section to show details, of a welding gun embodying the invention;

FIG. 2 is a longitudinal cross sectionof the gun shown in FIG. 1; T

FIG. 3 is a side elevation, partly in section, of the gun mechanism showing the position and relationship of the parts during welding;

FIG. 4 is a front elevation of the gun shown in FIGS. 1-3;

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

FIG. 6 is a horizontal cross section taken through the forward end portion of the gun;

FIGS. 7 and 8 are enlarged perspective views of the guide members through which buttons are delivered to the gun electrode;

FIG. 9 is an enlarged'perspective schematic showing the relationship among the gun electrode rod, the button-delivery passages in the gun, and a button being delivered; and

FIG. 10 is a schematic wiring diagram of the electrical control circuit for the gun. I

In general there is shown in FIGS. 1 through 8 of the drawings what may be referred to as a welding gun in the generic sense including a support and an electrode assembly 22, which gun is adapted to weld buttons B to a panel P (FIG. 3).

At the rear end of the support 20 there may be provided a pistol grip type handle shown partially at 24, the upper portion of which includes a housing 26'within which is enclosed certain standard components well known in the art. The gun shown is particularly designed to be used in conjunction with a welding system commonly" referred to as "drawn arc," wherein the stud or button isinitially placed in contact with the workpiece, the stud is momentarily withdrawn from the workpiece while current is passed to strike an arc therebetween, and thereafter the stud is plunged against the workpiece while welding current is passed therebetwecnto effect the-weld. The withdrawal of the stud is accomplished by the provision of an electrical solenoid in the gun housing rearwardly of the electrode assembly, whereby energization of the solenoid provides the lift" during the welding cycle, and the stud is spring-returned to the workpiece when the solenoid is deenergized. If some other type of welding operation, for example percussive or resistance welding, is employed, no lift" is required, and the solenoid may be eliminated. It will become apparent to those skilled in the art as the specification proceeds that the subject matter of the invention may be utilized with any of the known types of welding methods.

Projecting forwardly from the handle 24 are a pair of elongate members 28 comprising a portion of the support 20, upon the forward end of whichis mounted an upstanding block 30. Secured to the forward face of block 30 is an insulating member 32 which may be properlytermed both a panel locator and an arc shield, comprising a base portion 34 and a hollow sleeve 36. Member 32 may be mounted on block 30 by means of cap screws or the like 38 as shown in FIG. 4. Block 30 and member 32 have aligned internally threaded apertures therethrough 40 within which is threaded an adjusting screw 42 described in more detail hereinafter.

Mounted atop block 30 and secured thereto as by capscrews 44 (see FIGS. 4 and 5) are a pair of

smaller blocks

46 and 48 arranged in faceto-face abutment and cut away to define a passage 50 through which buttons are delivered to the gun. The blocks are held in face-to-face abutment by a cap screw 52. Preferably the

blocks

46 and 48 are machined to conform to the configuration of the buttons to be delivered, which will more fully appear as the specifications proceed.

The electrode assembly" 22 is mounted for limited reciprocable movement on the support 20 and includes coaxially aligned

members

54 and 56 secured together as by screws 58, the rear member 54 being a hollow shell open at the bot tom to accommodate an electrical cable 60, and the forward member 56 comprising a fluid pressure cylinder. Projecting forwardly from member 56 and'preferably integral therewith is a tubular electrode member 62 having a forward end portion defining a button-holding chuck or collet 64. The chuck 64 may be a longitudinallysplit sleeve forming three resilient fingers as shown in front elevation in FIG. 4, cooperating'to hold a button in position to be welded. Disposed for reciprocation within electrode member 62 is a rodlike electrode element 66 which extends completely through cylinder 56, projecting out the rear end thereof and connected at its rear end to the electric cable 60 as by a nut 68.

A fluid pressure piston 70 in'cylinder 56 provided with a surrounding sealing ring 72 has a rearwardly extending sleeve 74 encircling rod 66. With nut 68 threaded on the rod entrapping cable 60 against the end of sleeve 74, rod 66 is rigidly connected to piston 70 for conjoint movement, and a currentconducting connection is established between the cable and the rod electrode, which is of course electrically conductive. Cylinder 56 is provided with fluid-conducting

passages

76 and 78 opening into opposite ends of the cylinder respectively. Fluid under pressure is delivered to the

passages

76 and 78 through conduits 80 and 82 connected thereto through suitable fittings 84. The conduits are coupled to a source of fluid under pressure (not shown), and fluid supply to the cylinder 56 is controlled by a solenoid operated valve schematically shown in FIG. 10, described in greater detail hereinafter.

Adjacent its rear end tubular electrode member 62 is provided with an upwardly opening cavity 86 within which are disposed a pair of

guide blocks

88 and 90 shown in enlarged perspective in FIGS. 7 and 8. The blocks are received in the cavity 86 in face-to-face abutting relation, and are axially bored as at 92 to accommodate a button B and the electrode element 66. As can be seen from FIGS. 6, 7 and 8, the

blocks

88 and 90 are machined to provide a passageway 94 opening into bore 92, which passageway 94 conforms to the configuration of button B with the walls of the passageway closely embracing the button to insure proper orientation thereof within the bore 92 for subsequent delivery by rod electrode element 66 to the holding chuck 64. In FIGS. 18 inclusive, the button B is shown as being generally H shaped in profile, and the ment by electrode 66.

' Fixedly mounted on the support 20 as by securement to one of the members 28 through screws '96 is an upwardly extending arm 98 carrying switch means 100, in this case a microswitch. The switch 100 is actuated by means of an actuating arm 102 projecting therefrom and having a roller 104 at its outer end. Roller 104 normally rests upon the forward end of member 54, in which position the switch contacts remain open. However, as the electrode assembly 22 is shifted rearwardly with respect to the support to its position shown in FIG. 3, roller 104 engages a projection 106 provided on cylinder 56, shifting actuating arm 102 to close the contacts of switch 100. As will become clear from the description following, switch 100 will be actuated to energize the welding circuit only if a button B is properly positioned in the holding chuck 64 when the forward end of the gun is forced against the panel P, and if the button axis is substantially perpendicular to the panel P. In the absence of a button B in proper position for welding, the amount of relative movement between support 20 and electrode assembly 22 will be insufficient to actuate switch 100.

As shown in FIGS. 1 and 2, member 54 has a rearmost end portion 108 guidably received in housing 26, with a coil spring 110 in the housing bearing against member 54 urging the electrode assembly 22 to a normally forwardly projecting position. The electrode assembly is yieldably shiftable against the tension of spring 110 with respect to the support 20 to the position shown in FIG. 3, at which switch 100 is actuated to enable delivery of welding current to the gun and effect welding of the button B to panel P.

To describe the operation of the welding gun, we assume that a button B has been delivered through tubular electrode 62 to the button-holding chuck 64, with the rod-like electrode element 66 engaging the button, as shown best in FIG. 2. Fluid under pressure is being supplied through conduit 82 and passage 78 to urge piston 70 forwardly in cylinder 56 against the forward end wall 112 thereof, which serves as a positive stop for the piston and hence positively determines the limit of stroke of electrode 66. The entire electrode assembly 22 is biased forwardly by spring 110 so that the button B projects a predetermined distance beyond shield 36, which distance may be conveniently set by position of screw 42 which the electrode assembly abuts in forward position.

Assuming all phases of the control circuit are operative, when the button B is brought against a panel P, and the gun urged against the panel, relative movement occurs between the electrode assembly 22 and the support 20 until the forward face of shield 32 abuts the panel P as shown in FIG. 3. In this position, the projection 106 has struck switch roller 104, moving switch arm 102 toactuate switch 100 just as the forward extremity of shield 32 abuts the panel P. Adjustment screw 42 may be shifted to provide exact projection of the button B with respect to shield 36 so that switch 100 is actuated when the shield abuts the panel P with a button B properly positioned in the collet 64, as shown in FIG. 3. Actuation of switch 100 energizes the control circuit shown schematically in FIG. 10, and the welding operation continues automatically.

The actual welding circuit for effecting current supply to the button B to be welded is shown partially in the upper portion of FIG. 10, and includes a transformer 120 for stepping the line voltage down to a suitable value, a diode rectifier 122, a control relay CR-l and a condenser 124 connected in parallel with relay DR-l. It is to be understood that these elements comprise only a portion of the complete welding circuit, and are shown only to afford an understanding of the subject matter of the instant invention. Such are well known components in the electric welding art and need not be described in further detail.

Referring to the remaining portion of FIG. 10, there is shown a control circuit supplied with 110 volts alternating current from a suitable source (not source). With the parts of the circuit as shown in FIG. 10, the gun is as shown in FIGS. I and 2, i.e., conduit 82 is pressurized forcing piston 70 and electrode 66 forwardly engaging button B releasably held in holding chuck 64, and switch contacts 100 are open. When the welding gun is shifted toward the panel P. Button B first abuts the panel, interrupting movement of the electrode as- -sembly 22 theretoward, and support 20 moves forwardly against the force of spring 110 until the forward extremity of shield 32 abuts the panel. At this point the relationship between support 20 and electrode assembly is as shown in FIG. 3, and contact of roller 104 against projection 106 closes switch 100.

Closure of switch contacts 100, as shown in'FIG. 10, immediately energizes relay CR-3, thereby closing relay contacts CR-Sa, CR-3b and CR-3C. Closure of CR-3a completes the welding circuit, and therefore current is supplied to button B initiating the welding cycle immediately upon actuation of switch 100. While switch 100 may be used as the sole control switch for initiating the cycle of operation, a conventional trigger switch which is manually operated may be placed in series with the switch contacts 100, requiring closure of both switch contacts to start the cycle. Closure of CR-3b energizes relay CR-Z, opening contacts CR-2a and closing contacts C R- 2b. Relay CR-2 is thus locked in by CR-Zb while relay CR-3 is deenergized by opening of CR-2a. As CR-3 cannot be reenergized through CR-2a until CR-2 is deenergized, and CR-2 is only deenergized by the opening of 100, the welding circuit cannot be reinitiated unless the gun is pulled away from the panel P to allow electrode assembly 22 to shift forward with respect to support 20, opening switch 100. Thus the provision of relays CR-2 and CR-3 in the control circuit positively prevents double welding of a button, as the gun must be retracted from the panel to open switch before the welding circuit can be reenergized.

Energization of relay CR-3 closes contacts CR-3C, which energizes time delay relays TD- l and TD-2. Relay contacts TD-la are closed instantaneously, locking in the time delay relays. At the expirationof the time period of TD-l, its contacts TD-lb close, energizing solenoid S to shift the fluid pres sure valve (not shown) controlling the flow of fluid pressure to cylinder 56. Closure of TD-lb also energizes relay CR-4, which includes a set of contacts in the button-delivery system (not shown), closure of which contacts causes a button to be delivered through delivery conduit 116

passages

50 and 94 to the tubular electrode. Reversal of the valve exhausts line 82 and pressurizes line 84 (see FIG. 2) supplying fluid pressure through passage 76 to the front face of piston 70, moving the piston rearwardly against the positive stop comprising cylinder end wall 114, as shown in dotted outline at 70' in FIG. 2. Electrode rod element 66 shifts with the piston, and in its rearmost position the front extremity of the rod lies in alinement with the rear wall of button passage 94, forming a continuation of such wall so that upon entry of a button there is no possibility of the button becoming misaligned in the tubular electrode 62.

Upon the energization of solenoid S to retract piston 70 and rod 66, the button-delivery system (not shown) coupled to passageway 50 through conduit 116, is actuated by energization of relay CR-4 to deliver another button to the tubular electrode 62 forwardly of electrode rod 66. After a predetermined time interval sufflcient to insure button delivery to electrode 62, the time period of relay TD-2 expires, opening normally closed contacts TD-2a, deenergizing relay TD-1, opening contacts TD-lb, and thus deenergizing solenoid S. When the solenoid is deenergized, the fluid pressure control valve (not shown) shifts to its position pressurizing line 82 to shift piston 70 and electrode 66 forwardly, with the electrode carrying the button just delivered through tubular electrode 62 to its position in holding chuck 64 as shown in FIGS. 1 and 2. Even if the gun has not been retracted from panel P, i.e., has been held against the panel during the entire operation, the welding circuit cannot be energized to cause welding current to flow through cable 60 and electrode 66 to the button because of the provision of the safety interlock comprising relays CR-3 and CR-Z described above.

It should be noted that the above-described operation of the circuit shown in FIG. 10 is not specifically concerned with the particular type of welding operation being employed. A condenser 124 is shown, but for purpose of illustration only, and

the gun may be of the drawn arc type, which is preferred, or the resistance or percussive type.

Referring now to FIG. I, it can be seen how switch 100, in addition to actuating the circuit, is provided as shown for safety purposes, positively preventing the welding cycle from being initiated unless a button is properly positioned in the chuck 64 to be welded and the button is substantially perpendicular to the panel P. In order to actuate switch 100, suffrcient relative motion must occur between projection 106 and switch roller 104 to shift actuating arm 102, and this relative movement is accomplished by forcing the gun against a panel. Thus when the shield 32 abuts panel P, the electrode assembly 22 must have shifted a predetermined distance relative to support 20 and the switch 100 to actuate the arm 104. As button B projects beyond the endof electrode assembly 22, if no button is present, the relative shiftable movement will be insufficient to actuate switch 100, and the circuit will not be energized; Similarly, the axes of button and gun must be substantially perpendicular to the panel for the requisite movement to occur. 1

As piston and electrode rod 66 come up against a positive stop defined by end wall 112 of cylinder 56, button B is positioned exactly with respect to the electrode assembly. In addition, screw 42 serves as a positive stop determining the exact position of the electrode assembly 22 with respect to the support 20. Thus the exact relative positions of all the parts of the gun are positively located to insure proper operation of the gun. Stop screw 42 also makes it possible to exactly aline the passageway 94 in electrode 62 with the delivery passage 50 in

members

46 and 48 to insure proper button delivery to the electrode, as can be most. clearly seen in FIG. 2.

We claim:

1. A welding gun for welding buttons to a panel comprising: a support movable toward andfrom the panel and including a front end portion for abutting the panel and thus limiting the approach of the support toward the panel, an electrode mounted for movement on the support having means at one end for holdinga button thereon against the panel in position to be welded thereto, and means coupled to the electrode for delivering a welding current thereto and including sensing means which is responsiveto predetermined relative movement between the electrode and the support upon engagement of a button on the electrode with the panel and abutment of the front end portion of the support against the panel with the electrode substantially perpendicular to the panel to condition the delivery means for delivery'of a welding current to the electrode.

2. ln a welding gun for welding buttons to a panel: an electrode projecting from the gun and yieldably supported thereon and having means at its projecting end for supporting a button to be welded to the panel, means coupled to the gun for delivering a welding current .to the electrode, and control mechanism including sensing means in the gun operatively coupled to the current delivery means and responsive to predetermined movement of the electrode when a button on the electrode is engaged with the panel and the gun is forced against the panel with the electrode substantially perpendicular to the panel to actuate the control mechanism and condition said delivery means to deliver a welding current to the electrode.

3. In a welding gun for welding buttons to a panel: an electrode projecting from the gun and supported thereon yieldingly biased to an extended position and having means at the forward end of the electrode for releasably retaining a button in position for welding to the panel; means on the gun normally spaced rearwardly of the-weldable end of a button held by the electrode when the electrode is in its extended position and engageable with the panel for limiting movement of the gun toward thepanel; current delivery means coupled to the gun for delivering welding current to the electrode; and a control circuit coupled to the current delivery means and including a sensing means responsive topredeterrnined retraction of the electrode with a button retained thereon when said panel means to deliver welding current to the electrode.

4. In a welding gun for welding buttons to a panel: an electrode assembly yieldably biased toward the front end of the gun and including a tubular outer member normally projecting forwardly of the gun front'end and a rodlike inner element, said tubular member having a button-holding chuck at its forward end and a button-delivery aperture opening laterally through a side wall thereof spaced rearwardly of the chuck, said rod element being supported for reciprocation within the tubular member to engage a button delivered through said aperture and carry the button to a welding position projecting from said chuck; means coupled to the rod-like element for shifting the same; means for delivering weldingcurrent to said electrode; and control means coupled to said rod shifting means and to said current delivery means and including a part responsive to predetennined relative movement of the electrode assembly with respect to the gun when the front end of the gun is forced into substantially perpendicular contact with the panel and a button is in welding position projecting from the chuck to render said current delivery means operative to deliver welding current to said electrode.

5. A gun for welding buttons to a panel comprising: a support member; a tubular electrode member mounted for reciprocal movement within said support and having buttonholding means at a forwardly projecting end thereof; means yieldably urging said tubular member to a normally extended position; a rodlike electrode element shiftably disposed within said tubular member; motive means coupled to said rodlike element to shift the same between extreme positive end stop positions; a button-delivery conduit communicating with said tubular member for delivering buttons successively thereto; an insulated shield rigidly secured to said support spaced rearwardly of said tubular electrode member when in its extended position; means coupled to the electrode for delivering welding current thereto and including switch means response to a predetermined relative movement between said support and said electrode when the gun is thrust against the panel with a button in said holding means and the electrode substantially perpendicular to the panel to condition said current delivery means for delivery of welding current to the electrode.

6. A welding gun for welding buttons to a panel comprising: a support member; an electrode assembly mounted on the support member for limited reciprocal movement therealong and including a tubular member having a forward end portion defining a button-holding chuck with a laterally opening aperture spaced rearwardly of such end through which buttons are delivered to said member, and a rodlike element shiftably disposed within said tubular member; motive means coupled to said rod element to shift the same between positive stops at the opposite ends of the rod stroke; a sleeve-like shield fixedly mounted on said support encircling the tubular member rearwardly a predetermined distance from the forward end of the member when in its extended position; spring means yieldably urging said electrode assemblyto its extended position; means for delivering electric current to said electrode assembly; and control mechanism on the gun having a part operably coupled to said current delivery means actuatable in response to a predetermined retraction of said electrode assembly with respect to said shield with a button in said chuck to render the current delivery means operable to deliver a welding current to said electrode when the gun is forced against a panel with the electrode axis substantially perpendicular to the panel at the point of welding.

7. The invention as defined in claim 6 characterized in that positive stop means is adjustably mounted on said support engaging the electrode assembly when in its extended position to permit selective variationof the forward position of said electrode assembly with respect to said sleevelike shield.

8. The invention as defined. in claim 6 characterized in that said control mechanism includes interlock means preventing current delivery to the electrode in the absence of deactuation of said part after a previous actuation thereof.

9. In a welding apparatus for welding buttons to a panel including a welding gun and means for delivering single buttons successively to the gun, an electrode assembly shiftably mounted on the gun comprising a tubular member having a button-holding chuck at the projecting forward end thereof and a rod element reciprocably mounted within the tubular member, motive means coupled to said rod element for shifting it between opposite positive'end stop positions, said tubular member having a laterally opening aperture coupled to the button-delivery means through which buttons are delivered thereto, means for delivering a welding current to said gun, and a control system coupled to said current delivery means and said motive means and having a part responsive to predetermined retractile movement of said electrode assembly with respect to the gun upon engagement of the gun against a panel with a button in said chuck and the electrode assembly substantially perpendicular to the panel to cause said current delivery means to deliver a welding current to the electrode and operable, at the expiration of current delivery, to actuate said motive means first to shift said rod element to its retracted position immediately rearwardly of said aperture to admit a button to said tubular member and thereafter to shift the rod element to its extended position carrying a button to said holding chuck upon the delivery of a button to said tubular member by the button-delivery means.

10. A welding gun for weldingbuttons to a panel comprising: a support movable toward and from the panel and including a panel-engaging stop for limiting its approach toward the panel; an electrode movably mounted on the support having means at one end for holding a button thereon to be welded to the panel with its weldable end normally projecting beyond said panel-engaging stop; means cooperable with the electrode for yieldably uring the button-holding end thereof toward the panel; means coupled to the electrode for delivering welding current thereto and including a part responsive to predetermined retraction of said, electrode with a button thereon when the panel-engaging stop abuts the panel with the electrode substantially perpendicular to the panel to deliver a welding current to the electrode.

11. The invention as defined in claim 10 characterized in that said part includes a switch having an actuating arm pr0- jecting therefrom into the path of retractile movement of the electrode and spaced rearwardly of the electrode-when the latter is in its forward position.

12. The invention as defined in claim 1 characterized in that said support front end portion for abutting the panel has a panel-engaging end face with at least two points spaced apart on opposite sides of said electrode button holding means, with said points spaced equidistantly rearwardly of the weldable end of a button held by the holding means on the electrode 'a predetermined finite distance.