Dec. 17, 1946. D. PACKARD ¿TAL WELDING SYSTEM rim nec. 1v. 194s 2,412,745 Patented Dec. 17, 1946 2,412,745 UNITED STATES PATENT oFFlcE 2,412,745 WELDING SYSTEM David Packard, Palo Alt 0, and Noel EI Porter, Berkeley, Calif., assignors to Hewlett-Packard Company, Palo Alto, Calif., a copartnership consisting of William R. Hewlett and David Packard Application December 17, 194s, serial No. 514,648 4 Claims. This invention relates generally to electric arc welding systems of the motor generator type, and particularly to welding systems adapted for au tomatic control. In welding systems of the above type it is con ventional practice to make use of a starter switch in the alternating current supply lines to' the motor, and with this switch having control cir cuits conditioned by start and stop contacts for Control causing automatic closing of the starter switch with resultant starting of the motor generator in operation responsive to snorting the welding rod upon the work preparatory to striking an arc. Systems of» this type which have been developed in the past have been unduly complicated, and have generally required direct interruption of the welding circuit by means of heavy duty switch contacts. Furthermore prior systems have not been readily adaptable to various prevailing com mercial types of motor generator welding equip ment. f It is an object of the present invention to pro vide a simple and effective system of the above (ci. 1v1-_97) tion, but in general it consists of contact sets I, 2, 3 and 4 which are moved to closed position upon energizing the operating coil Il. Manually operated start and stop contacts I'I and Il serve to initiate closing and opening of the main switch contacts through the action of coil I3. In addition it is customary to provide overload re lease contacts I9 in series with contacts I3. In the present instance the control circuits ci' 10 the starter switch are electrically related to the welding circuit through means including the transformer C, and the magnetic relay or switch D. In addition supplemental relays E, F and G are provided for functions which will be presently 15 explained. The relay D is constructed with an operating coil 2| of relatively low resistance and reactive impedance, whereby it can be connected perma nently in series with the welding circuit I2. In practice a magnetic core 22 has been employed, with the heavy Welding conductor I2 simply looped through one leg of this core, as illustrated diagrammatically. One side of the coil for relay G is s_hown con 25 nected to contact 3 of relay» A, and the other side of this coil connects to conductor 23, which ex tends to the line LI. Contact 2 of relay G is connected by conductor 24 to one of the set of character, which is characterized by an absence of contacts for interrupting the welding circuit. 30 contacts 4 of the starter switch B. Contact 5 Another object of the invention is to provide a of relay G is connected by conductor 25 to the system of the above character which can be read other side of the contact set 4. ily applied to prevailing types of welding equip Transformer C has its primary terminals con nected to conductors 23 and 24 by conductors 2l and 28. One side of the secondary of this trans former is grounded, and the other side connects through conductor 29 with the welding circuit conductor I2. Contacts I and 2 of relay E are ment. A further object of the invention is to provide a novel arrangement for indicating or‘registering the total arc time of the system over an extended time period of operation. . Further objects and features of the invention connected in series with conductor 29. Also a series protective fuse 30 can be provided. will appear >from the following description in which the preferred embodiment has been set 40 The operating coil of relay E has its one side forth in detail in conjunction with the accom connected to conductor 28, and- its other side to panying drawing. v . the contact 2 of relay F. Contact I of relay F is in' turn connected to conductor 24.’ Contact 3 of relay F is connected by conductor 32 to con drives the direct current welding generator II. 45 tact I of relay D. The operating coil Alternating current supply lines LI, L2 yand L3 F has its one side grounded and its other side The system as illustrated in the drawing con sists of an alternating current motor I II which supply current to the motor I0 through the line connected «by conductor 33 to the we1ding`con switch A and starter switch B. One side of the generator I I is shown grounded and the other ductor I2. side is connected to the welding conductor I2, switch and is in series with the stop contact I8, is connected to contact 2 of relay G. Contact I of this relay is connected to conductor 25. which extends to the welding wire or rod I3. The - ' v .` Conductor 34, which leads from the starter work or object III being welded is likewise shown In addition to the equipment referred to above as grounded to complete the welding circuit. The starting switch B may vary in construc 55 the system preferably includes a tctalizing de vice 36 connected by conductors 3l and 33 to y, anarco 3 and _to open its contacts I and 2. Opening of _ conductor 28 and to contact l of relay D. This » totalizer can be any suitable counting or time in l . . 4 contacts I and 2 insures deenergization of relay E irrespective of momentary deenergization of » dlcating device, consisting for example of a con relay D. stant speed synchronous motor driving suitable counting means. When the motor generator reaches normal speed the operator draws an arc between the work Relay G is a time delay device constructed so and the welding rod I3, and proceeds with nor that upon energizing its operating coil the con mal Welding operations. The welding current tacts I and 2 are opened after a predetermined maintains the relay D energized, with contacts time period of continuous excitation. Should 10 I and 4 closed to supply alternating current to current through the coil of this device be in-` the totalizer 36, but the winding of delay relay ` terrupted momentarily, the device is automati G is deenergized by virtue of contacts I and 3 cally reset, whereby thereafter continuous ex being open. The welding equipment remains in citation for the entire period of delay is required. this condition as long as normal welding pro Time delay relays of this typexare well known in ceeds. Should Welding operations be interrupted the art, and can consist for example of a small 15 relay D is deenergized with the result that con» self-starting synchronous motor, geared to open tacts I and ii are closed, and contacts I and f3, the contact after a predetermined period of con together with contacts 2 and E, are opened. This tinuous operation, and with provision for auto results in energizing the delay relay G, but does matically interrupting the gear train to permit not immediately alter the closed condition of immediate resetting when excitation is inter 20 the starting switch B. Should welding be re sumed before a sumcient time has lapsed ior rupted. The relay F, which can be termed a protective relay G to open its contacts I and 2, then relay D is again energized, and the winding of delay relay relay, is adapted for direct current operation at a potential below that normally maintained across G deenergized whereby the motive element of the the welding arc. For example with a welding 25 same is restored to its initial position. If the generator adapted to maintain about 25 volts welding current is interrupted for a period of across the arc during normal welding operations, time equal to that to which the delay relay G is the relay can be wound to operate at a potential adjusted, then the contacts I and 2 oi’ the delay relay are opened, with the result that flow of of about 10 volts. „ Operation of the system described above can 30 current through coil Ie is interrupted, and the starting switch B is immediately opened to dis be outlined as follows: With the line switch A openthe system is completely deenergized. Upon continue supply of current to the motor III. Be closing the line switch A. transformer C is ener gized, relay E is energized to maintain its con , fore the motor generator comes to rest the voltu age applied to the winding of relay F drops suf 35 ficiently to cause opening oí contacts I and 3 tacts I and 2 closed, and potential from the sec ondary of transformer C is applied to the welding and closing of contacts I and 2. The system is conductor I2. The circuit for energizing the now ready for restarting in the manner previously described, that is by shorting the rod I3 upon transformer C can be traced from line LI, con ductor 23, conductors 2l and 28, conductor 25, the work IQ. contacts I and 2 of delay relay G, conductor 36 40 It Will be noted from the above that the total and contacts I8 and I9 which connect vto line L3. izer 3S is connected and is in operation only dur~= The coil of relay E is energized in that its one ing periods of arc welding, when normal weld ing current is flowing through the welding cir side connects with conductor 28, and its other closed contacts I and 2"-~ cuit. Therefore over a considerable period of of relay F, conductor 2li, and coil I6, which in 45 time the readings of this device will be cumu turn connects to conductor 21. The impedance lative and will shc'f': the total period of arc weld of the coil for relay E is such that the current ing time for which the machine was in use. It iiow through coil I6 is insumcient to operate the is necessary that there be a substantial voltage starter switch. Relay D remains deenergized, across the arc, as well as a ñow of welding cur and totalizer 36 is not energized because contacts 50 rent, for the totalizer to operate. This is be I and II are open. Y ' To start the motor generator in operation the operator short circuits the welding rod I3 upon the work II. This causes a momentary surge of current from transformer C through the coi1 2I 55 of relay D, thereby causing the closing of con tacts I and 4, and also contacts 2 and 5. Closing of contacts 2 and 5 of relay D effectively short circuits the starting contacts I'I. This causes the coil I6 of the starting switch to be energized 60 with sufficient current to cause the contact sets, I, 2, 3 and 4, to be closed. Closing of contacts 4 short circuits or locks out the starting contacts I1, and also the contacts 2 and 5 of relay D.'` Thus' ' while the motor is being started in operation, the 65 transformer. C need not continue to supply suñ'i cient current to coil 2| to maintain relay D en ergized. Simultaneously with relay D being en ergized the coil of relay E is deenergized to open cause relay F must be energized as well as relay D, for current to be supplied to the totalizer. Relay F is deenergized if the welding rod is short ed to the"work, because at that time the voltage across the arc is reduced to zero or to a value so low that relay F is not energized. Thus the totalizer does not count or record time when the arc is not in actual working operation. The complication of. a breaker switch inl the Welding circuit itself is completely eliminated with the present system, and relay D may be of rela tively light construction, with its contacts de signed tc handle the relatively small current: required. Relay F in conjunction with relay l insures an open secondary circuit for the trans former C during normal welding operations, thu protecting the transformer against unduly heav: loads by virtue of the low impedance of the weld ing circuit to ground. its contacts I and 2 and thus interrupt the sec 70 It will be evident that our invention is appli ondary circuit of transformer C. This occurs cable to various makes of motor generator equip because the coil of relay E is shorted out by the . ment having various types of starting switcha closing of contacts 2 and 5 of relay D. .As the Such circuit changes as are required for differ direct current potential from generator I I builds ent typesof starting switches will be apparenti up, relay F is energized to close its contacts I and 75 2,412,745 those skilled in the art, and will not alter the principle of operations. We claim: 1. In a welding system of the type having a motor connected to alternating current supply Ul provision for automatically closing and opening the same in response to the closing and opening of control circuits, a relay having a low imped ance energizing coil in series with the welding 2. In a. welding system of the type having a nected to receive direct current from the weld ing circuit and adapted to interrupt the energiz ing circuit of the last named relay. 3. In a. welding system of the type having a motor connected to alternating current supply lines through a starter switch and a direct cur- 70 cuit. DAVID PACKARD. NOEL E. PORTER.