US2572073A

US2572073A - Electric furnace and feeding means and the controls therefor

Info

Publication number: US2572073A
Application number: US2615A
Authority: US
Inventors: Jr Harold A Strickland; Donald W Riddell
Original assignee: Ohio Crankshaft Co
Current assignee: Ohio Crankshaft Co
Priority date: 1948-01-16
Filing date: 1948-01-16
Publication date: 1951-10-23
Anticipated expiration: 1968-10-23

Description

H. A. sTRlcKLAND, JR., ET AL 2,572,073

ELECTRIC FURNACE AND FEEDING MEANS AND THE'CONTROLS THEREFOR 7 Sheets-Sheet l Oct. 23, 1951 Filed Jan. 16, 1948 H. A. sTRlcKLAND, JR., ET AL 2,572,073

7 SheetsLSheet 2 INVENTOR f HAROLD A. Svmcxmno, Ik. BY DoNALo W. RmoELL. www

Oct. 23, 1951 ELECTRIC FURNACEI AND FEEDING MEANS AND THE CONTROLS THEREFOR Filed Jan. 16, 1948 Oct. 23, 1951 H. A. sTRlcKLAND, JR., ETAL 2,572,073

ELECTRIC FURNCE AND FEEDING MEANS AND THE CONTROLS THEREFOR INVENTOR BY .DONALD W. Rmoau.

'W ATTO H. A; sTRxcKLAND, JR., ETAL 2,572,073

Oct. 23, 1951 ELECTRIC FURNACE AND FEEDING MEANS AND THE CONTROLS THEREFQR Filed Jan. 16, 1948 7 Sheets-Sheet 4 N LDW Rmoeu.

OC- 23, 1951 H. A. s'rRlcKLAND, JR., ET Al. 2,572,073

ELECTRIC FURNACE AND FEEDING MEANS AND THE CONTROLS THEREFOR 7 Sheets-Sheet 5 Filed Jan. 16, 1948 INVENTOR HARoLD A. TmcKLAND IR. BY DoNA o \.\J. Rumen. AWGN@l Octf 23, 1951 H. A. sTRlcKLAND, JR., ET AL ELECTRIC FURNACE AND FEEDING MEANS AND THE CONTROLS THEREFOR '7 Sheets-SheetI 6 Filed Jan. 16, 1948 INVENTOR HARoLo A. EvTmcKLAND, IR. Y DONAD W. Rm ELL.

ATTORN@ Oct. 23, 1951 H. A. sTRlcKLAND, JR., ET AL 2,572,073

ELECTRIC FURNACE AND FEEDING MEANS AND THE CONTROLS THEREFOR Filed Jan. 16, 1948 '7 Sheets-Sheet '7 WATER-slur opr- Sm DELAY TIMER :Ik PRESSURE o' z i 8 llo HEAT PILQT RELAY Patented Oct. 23, 1951 ELECTRIC EURNACE AND FEDING MES AND THE CONTROLS THEREFOR Harold A. Strickland, Jr., and Donald W. Riddell, Detroit, Mich., assignors, by mesne assignments, to The Ohio Crankshaft Company, Cleveland,

Ohio, a corporation ot Ohio Application January 16, 1948, Serial No. 2,615

12 Claims. 1

This invention relates to heating furnaces, particularly to through-feed or continuous heating furnaces of the high frequency induction heating type disclosed in the patent to Strickland 2,325,638 of August 3, 1943, and has for an object a provision of improvements in this art.

One of the particular objects of the invention is to provide safety mechanism for such a furnace which Will with certainty guard against overheating of billets in the furnace by cutting ofi the heating current when certain prescribed conditions are not observed.

Another object is to provide in connection with the heating means and certain stock feeding means used in connection therewith, time sequence controls which maintain the furnace in fully automatic operation as long as a supply of workpieces or billets is maintained in the feeding means and other prescribed conditions are observed.

Another object is to provide certain selective controls whereby the feeding means may be perated without the heating means.

Another object is to provide timing controls which will shut down the heating means in case the feeding means has not operated within a predetermined time, thus assuring that the current will be cut ofi to avoid overheating workpieces in the furnace in case the feeding means should jam for any reason.

Another object is to provide means for energizing each of a plurality of heating coils in a prescribed sequence in order that the drain on the current supply will not be too sudden.

Another object is to provide means for reapplying the current after a shut down, as for example, a shut down when a supply of billets for the feed means is exhausted, whereby all of several heating coils are reenergized at once in case the shut down has existed for less than a predetermined time and to reenergize the coils serially in case the shut down has existed for longer than a predetermined time.

Another object is to maintain the flow of cooling fluid to the heating coils for a predetermined time after the current has been cut o in order to avoid overheating by hot billets which still remain in the furnace.

Herein there will be described certain stock feeding details, coil hoods, soaking chamber hood, heat shields for the coils, certain time sequence controls of general application, and various other details which form the subject matter of applications of one or the other of the present coinventors; namely, application Serial No. 790,154 filed December 6, 1947, on an invention entitled Heating and Work-Handling Apparatus by the present inventors; application Serial No. 2,613 filed January 16, 1948, now Patent Number 2,563,883, on an invention entitled Workpiece Support and Guide for Induction-Heating Furnaces, the inventor there being Harold A. Strickland, Jr., as the sole inventor and Serial No. 2,614 filed January 16, 1948, on an invention entitled Electric Furnace and Stock-Feeding Means Therefor, the inventor there being Harold A. Strickland, Jr., as the sole inventor.

The above and other objects and advantages of the invention will be apparent from the following description of an exemplary embodiment of the invention, reference being made to the accompanying drawings thereof, wherein:

Figure 1 is a right side elevation, with some of the cover panels or doors removed and part of the coil hood cut away, of a three-coil furnace and related feeding apparatus embodying the present invention;

Figure 2 is a left side elevation of the same apparatus, with the doors in place and with the hood in raised position;

Figure 3 is a top plan view, with the hoods closed and with the soaking chamber hood swung out to one side;

Figure 4 is an enlarged partial vertical section of the rear or discharge end of the furnace, the section being taken on the line 4-4 of Fig. 3 but with the soaking chamber hood returned to its normal operating position;

Figure 5 is a transverse vertical section and elevation taken on the line 5-5 of Fig. l;

Figure 6 is a partial vertical transverse section taken on the line 6-6 of Fig. 2;

Figure 7 is a left side elevation and section taken on the line 1-'1 of Fig. 6;

Figure 8 is an inclined longitudinal section and elevation, taken about on the line 8--8 of Fig. 5;

Figure 9 is a transverse vertical section taken on the line 9-9 of Fig. 8;

Figure l0 is a perspective view of the cooled stock guide rails and related parts;

Figure l1 is a schematic view and wiring diagram; and

Figure 12 is a cycle diagram.

The furnace herein shown comprises a supporting frame or multiple unit cabinet IU with three units Illa, IIJb and Ic, associated with a skeleton framework Il which is welded or riveted up from angle, channel or other standard pieces of metal as needed for the number of heating units to be used. Mounted above and in association respectively with each of the cabinets are a like number of electric induction heating coils I2, here distinguished as l2a, l2b and I2C. From front to rear end, or right to left in Fig. 2, these heating coils are also referred to as #L #2 and #3. Preferably high frequency heating current is used for heating.-

In the upper part of each cabinet there are placed a number of capacitors I3 and in the lower part of each cabinet there are placed suitable contactors i4. There are two contactors'for each coil and one of these is shown in side elevation in Fig. 5. Y

Suitable bus bars and connections, all indicated generally by the numeral l5, are shownA for serving the contactors, capacitors and coils.

Common cooling uid conduits I6 are provided for the several coils.

A beam Il, here of I-section, extends 'above' the entire furnace, thatA is above all of the coils `in Whatever number provided,thebeam being "supported at its ends by end supports-l8. At veach side of the beam H there is'hinged one or more coil hoodmembers i9 which may be closed, as shown in Fig. l, or opened, as shown in Fig. 2.

HAside from the main frame Il, the bus bars '15, the beam il, Vand the hoods I9, the apparatus has no parts which extend between units 'except control circuit wiring, and the self-contained and identical heating units comprising coil, capacitors, contactors and relate-d parts'may be readily assembled in any desired number.

In each unit the coil l2 is mounted as a removable unit on insulating end support plates 2l which are detachably secured to bottom brackets 22 secured on the frame Il. Each coil unit carries With ita Vbus assembly 23 which is detachablysecured to fixed adjustable bus connections 24, and each unit also carries cooling fluid manifolds A25 which aredisconnectible fat hose connections 23 leading to the long fluid conduits I6.

4As shown in'Figs.'4; 8, 9 and'lO, each heating coil is provided with stock supporting and guide rails 29 which project out of each end to such distance' that in the open space between coils, the

rails'are very close'together to form, in effect, continuous surfaces over whichthe work'may move. However, the rails of adjacent coils can move laterally relative to each Aother so as'not to interfere with the movement 'of 'af 'coil when l'being removed cr replaced. yThe details'ofthe guide rails and associated'parts will'be described later. In this particulaigthe present Vapplication is a continuation-impart of the application of Harold A.' Strickland, Jr., Serial'No. 681,996; filed July 8, 1945, now Patent Number2,54l,l23.

At'the front end of the furnace, another Ycabinet ld is provided'toliouse apparatus of ageneral nature whichserves all coils -in common, the apparatus here shown, Fig. l, comprising transformers 3l and operating pressure fluid-'pumping and controlling apparatus 32.

The vextreme front cabinetie houses the timers, switchboard,switches, relays, and -other control apparatus. Some of the controls 'are mounted on a panel te on the side atthe Yfront where thy will be accessible'to anoperator 'when in his usual position for feedingworkpieces or billets to the machine.

The cabinets i3d andy I @e and theirv'equ'ipment are provided for all-furnacesfwhether'assembled as jone-coil heaters or as multi-coil heaters. Mounted upon the-top o f thecabinets vl-I'ld'i-and "we isa work-feed unit-'X35 whichf is# movable 4 axially of the furnace upon guides 3E and is adjusted as a unit by a screw 3l' threaded into a sleeve 38 mounted on the feed unit. The screw is rotatable but held against endwise movement in a support bearing 39 and is turned by a crank 4D. y

The feed vmechanism comprises spaced end supports 42 which are permanently secured at a fixed distance apart on a base 43 which slides on the guides 36. The end supports are further held in xedspaced relation by an inclined chute Vsupport piece 44 and an upper cross bar 45 which is held in vertically adjusted positions on the end supports by set screws 45. Chute guides 4l are adjustably-securedto the support piece 44 by set screwsl to'provide for billets or workpieces W of different lengths. At the upper end the chute guides are further held in adjusted positions by a slottedpiece 49 and s et screws 5S. The upper cross bar 45 carries a clamp device 5i for clamping'billets in the chute andthe vertical adjustment of the cross bar accommodates for billets of different thicknesses.

The support piece 44 has mounted thereon a gate device'53 which controls the down-feed of billets to loading position. `Both the clamp de'- viceV 5l an-d the gate device 53 are here formed as' cylinder-pistondevices operated by pressure iiuid.

From the chute a billet, when released by the opening of the gate 53, falls upon a V-shaped feed trough 54 which is'adjustably held on a cross piece 55 by bolts 56 so -as to be adjustable endwise to stand close to theprojecting rails ofthe #i coil. When the feed device is adjusted, the trough is readjustedfto bring Vit near the furnace rails. The V-trough plates are slottedfrom their ends to avoid inductance from the furnace coil.

A pusher device Bil, comprising pistonand cylinder parts and a ram 5i, is mounted on the outer end plate'42, vas by aring 62. Onrone side the ram carries a valve cam barv 53 having a 34 for operating thestems of a clamp valve CV and a gate valve GV respectively. The valve devices 'are mountedfonasupport bracket car'- ried by an endY-'plate42- A switch plate G3i-hinged iat 6? (Fig. 6),*has its lower end located where it will be raised a billet in the lo'werniost position just above the gate plate 68. The vupper end of the-switch plate, when raised by the dropping of the lower end, operates micro-switches W-i, W-2, later to be described.

The valve lcam bar '53, when the `piston isi-at the forward' end ofits stroke,l operates a switch actuator YES'for switches RS-l landfRS-2 which will be 'described-later. v

The exit or delivery end of the furnace beyond the rear end of the last heating coil has vmeans for supporting a'workpiece for a pause period to'allow heat to'penetrate-toward thecenter. The coils heat so-rapidly-on-the outside byinduction that this soaking time-is useful Yin preparing the workpiece for-forging. `As aimatterof fact, the spaces between adjacent 'coils alsoiprovide a soaking time. It-is -to Ybe understoodthat the current characteristicsl will be chosen so Las to best serve the conditions-iiri-posed-,forexample, a single coil furnace heating-more deeply-than a multi-coil furnace, butthere is usuallyso'me need for a soakingtime Y Surrounding -the furnacej exit vand covering what may be termed a 'soaking chamber, there is provided a-heatinsulated-hood 15 :Which com- -prises afmetal casin'gl I6l andraheatiinsulating lining 11.- The hood is supported for swinging movement on a vertical axis on one side of the furnace by hinges 18 and is held in closed position by a latch pin 19 on the other side.

At the bottom, the hood is provided with swinging doors 80, which may be referred to as bomb bay doors,- these being mounted on hinge shafts 8| in bearing brackets 82 and being urged to closed position, as by a spring 83 secured between arms 84 carried by the door shafts 8|. When a workpiece is pushed out from the soaking chamber, it drops upon the doors to open them and pass through them, whereupon the spring 83 causes the doors to close again. At the end of the furnace and in line with its chamber axis, the hood 'I5 is provided with a transparency-covered sight opening 8G. Another sight opening 81 is provided in the top of the hood. A billet deflector 88 is provided in the top of the hood to cause an end billet to break away from the next billet in case they may be slightly fused together. At the sight opening 81 or at some other location in the hood, a heat or light responsive device, which may be referred to as an electric eye or photo relay, is provided to control the temperature of the emerging billets, more particularly to shut off the heat if billets are near the melting point to endanger the heating coils. This device is indicated only in the wiring diagram where it is designated at PR.

In the coil hoods I9 there are provided vent openings 89 above the open space between coils to release heat, gases or smoke from the billets resting in the space between coils. It will be noted from Figs. 4, 8, 9 and l0, that the guide rails 29 are tubular and are cooled by fluid from disconnectible feed and return lines at one end. The cooling tubes are returned outwardly as at 90 at one end and have an outer run 9| which is located within the confines of the coil insulating lining 92 to keep it and the heating coil cool. The double rail construction with interconnecting supports 93 also provides strength for holding the insulation in place. The cooling rails are mounted on the coil end plates 2| by

bolts

94, 95 and adjustable connectors 96. It will be noted that the line-connected ends of the rails are returned through a coil support plate 2| and have their line connections above the outside of the coil and between its supporting plates, where there will be protection from heat. The inner run of the cooling rail is coated with a wearresisting liner fused thereon. There are a number of suitable materials, one such being a composition of tungsten 12-17 chromium 30-35%, carbon 2.25-2.75%, cobalt, substantially the balance, this being known commercially as Stellite The outer run 9| is provided with wings 91 which are fused thereon to hold the heat insulating lining of the coil.

For such coils or portions of coils as are subject to unusual heat from billets after they have been heated to high temperature, there is provided a special heat dissipating means, for example, of the type shown in Figs. 8, 9 and 10. Here an extensive area of a highly heat rconductive material, such as copper, is soldered to the outer run 9| of the rails so as to lie outside the heat insulation and inside the coil lining. The fins or plates 98 thus provided are slitted as at 99 to avoid buckling or other objectionable features of continuous sheets for such a use. It.

is found that if the heat shields are coextensive with the last approximately one-fifth of the total heating coil length, they will provide ade- 6 quate coi-l protection and prolong coil life to a remarkable degree.

Between the ends of adjacent coils, inclined plates |02 may be provided for directing scale and dirt toward the outside of the cabinet assembly, the plates being supported upon brackets |03 on the coil end plates 2|.

The operation of the apparatus will be described in connection with the circuit diagram, Fig. 11.

The ram 8| normally stops in its forward position, that is toward the rear end of the machine as a whole. It is shown slightly back of forward position to illustrate its switches RS-l and RS-Z in their non-operated position. In the normal full forward stopped position of the ram, its switch RS-I is closed and its switch RS-2 is open. RS-l opens and RS-2 closes as soon as the ram starts to move back.

A ram pause timer T| causes the ram to rest at the front end of its stroke. It is settable for a wide range of time merely by moving a fixed contact hand which is engaged after the predetermined time lapse by a movable hand driven by a synchronous motor. This represents one form of timer which may be used. The end of the preset timer period is registered by closurev of its switch TI-I. Its motor is represented by the reference character T|-M. By providing; the pause timer Tl, a number of control advantages are obtained, including the ability to` adjust for diiferent feed rates for billets of dif-- ferent size, different coils, different heats desired. and matching of delivery periods to suit the needs`- of the forging machines which use the billets:-

heated by this machine.

The ram cylinder is provided with a valve RV' The arrangement is; such that when the solenoid SO2 is not energized,

operated by solenoid SO2.

the ram stays in its forward position and whenz the solenoid is energized, the ram returns to its. rear position.

The ram cam bar 63J which carries the cam 64 for operating the valves CV and GV for the clamp 5| and gate 53 respectively, is shown also in Fig. 11. As the ram approaches the rear end of its travel, the associated Valve CV causes the clamp 5| to hold the billet which is in next to last position. Later, near the rear end of the ram travel, the associated valve GV causes the gate to be lowered to drop the billet from last position to the V-trough 54. When the ram moves forward again, it first replaces the gate in the chute and later releases the clamp to allow the stack of billets in the chute to slide down against the gate.

When the billet in last position drops, it opens switches W-I and W-2, and when another billet drops to the last position, it closes these switches. If no billet drops down, the machine is stopped after a certain lapse of time. Whenever TR3 or TR3 becomes deenergized, the auxiliary switches open immediately.

To prepare for the start of operations, the main line switch S-I of Ll, L2 is closed. For heating, as well as ram operation, a switch S-2, which may be referred to as a safe run switch, is closed. For operation of the ram only, S-2 is left open. The cooling water for the coilsV is turned on. This closes water shut-off valve switch VS, pressure switch PS and flow switches FS to the coils (three here). The temperature at the coils is assumed to be not excessive so temperature switches TS are closed. The panels or doors of the cabinet are closed so their safety asi-,suesse aeidsea. "toss blqsid so hood safety switches HS are closed. The yram is I to 'be "actuatedLand-not heldto -a rear rposition so Athe fr arn return switch is opened.

The clutch coil 'I2-"C of Water "shuteof Ddelay timer T2 s-keptenergized logas sj-'l isgigept closed. It holds outthe timerelutchb@ When SLI i"s ""`opened,'tl'e`c lutch iserr'gagedad'after a time "delayfp'eriod, lthe timer 'switch is actuated to actuate solenoidSO| toshut off Waterjto by- .a delay lto allotv bubbles jto be removed from the .c-eoligfnuid iinesits Switch'frRl-l is closed. The .circuit irvclve'd `is; LI, conductor |05, P S, VS,' conduc tor `|05a, to-L2.

The time-delay relays' are Y'repr eeseifled'by separate coils forinstantaneous and"de l ay s witch op'- eratiom'andthedday switch is represented as carrying hinged varies vvhich can fold together and move rapidly in a fluid lin one direction o f rriovemen't but which spread and "cause slow movement-in the other direction. This is-rnerely symbolic. Delay-'actionl timers which Yare settable for timedperiods of any predeterrninedlengthare available on the'markett It Will be assumed that tire photo-electric relay PR vvill be used in the soakingjchamber to indicate 'Whenfbillets areoverheated. Its svqitch PR-I in yseri es With the `door and hood safety s'WitchesDS and'l- IS To"starto'perationsthe start push-button-PB is pressed to'close PB- I and Y13B-2.

Closure 'of 13B-4| ener ges relay Rljfand 'the relaylocks in on its svvitchERL-A. The circuit completed hei'eis; LI, conductor |00, "coil RI-C, conductor PB'-|, 'conductor |08, stop push button Cs' vv itchPB 2'-`|', conductor |09, to L2. Clos 'ure of'Rlga shorts vmit m1,-PBAaQjg-ns. R1 alsocloses 'R|`| in the line 'to heat pilot relay R3 but this has no eiectas yet because he circ uit is open elsewhere. The circuitinvoivedjs: Ll, cbndutor H u, Ra-Cycondujcop in, PR-e, DS, HS, conductor l2, vR|| conductor |13, conductor H4, conductor |5, to R3i|[whichv is open (or from ||3 to conductor I| 6 and PBLZ which also leads to oper 1 p c' ints). Rl also closesjR|2 to connect the'ram pause timerrelay T| tojLZ'. The circuit involved I'S: 'L|, conductor'il'l, conductor 8, T |#M,` 'Conductor |'|9,' R|'2, conductor |20, to L2.A The c losureof PB-2 has no eiiect'jat this tirneas the circuit `is open at lboth TR2 and TRB.

`When the rain is fully at front end o fjits stroke, its switch RS-I is closed and RS- Z'opfened vRS- L b'eingc1osed tirner Tl is sei-,'intojact'ion and after aiti'nie'd period,l theram pilot relay R2 is energized.v 'The'circuitlinvolved is` jL|, corimiuctor |23, R2-3, conductor 120, Wl ('now ,fr-closed), conductor |25, Rslfcoductor |26, con"- At the sani'e time, timer TI `erlerg'iz-es tirii'e fdelayijelaYTRS. The' circuit involvedis: LL LU, @adapter 133, Tag-creases n, conductor |34, ','l, FI-il, ||9,"'R|l2,' 120,'130 E2.

'Energizationpf T83 opens T R'3-"2 and closes 'msj-fa. 'ras-1 delays 1in opening, being timl to open'after the ramha'sreturned 'andthe lgate hjsfpe'ed'and l'Sd.

Asfthe ram "approaches y'the rear end of `its stroke,its cam bar 4causes clamp, valve CV tob'e actuated jtofcl'am'p 'a 'billet 'in the nekt to last position in the :1' 1ute; l At the rear end ofv its stroke itopens bthe"'gate to feed down a billet upontheguide. Y

Dropping downofa billet from the last posi; tion opensswitchesjW-I andW-2. Y

Opening Aof Wfl deenergize's R2 and 'causersftie ram to move forward. It should here be Inoted that 'when the `machine 'vvas energized by closing S-I ,and assumihg'a billet to be inthe last or feed; down position to keep W-2 closed, a time-delay relay TR2 v vill at once Abe 'energized Vand `Wil1 be keptjenergizedwas long Yas W-2 is kept closed. The circuit involved is: Ll, conductor |31, TR2; o2, TR2-or, opductor ras, W-2',`conuuctr re, to L2. Opening of W-Z -deenergizes TR2 'and causes itto open TR2-2 andclose TR2LI, both Withoutdelay.

As the `ram movesgforwarijits vcam bar iiist causes the gate oclosethe bottom 'endrthe chute and later causes the "clam'p'to release billet vto allow the Whole :stack to descend. The lowermost billet V4closes switches Wil 'and WLZ.

mesure -of Welghasno mmejdiate elrct but the closure of VV- 2 en ergizes TR2 again.

It Will be assumed that the l` ti`rfn'e'delay vrelay TRI wurhavejqiqsed its switch TRA compl@tmg a line to o neside-'eah of TR2-I and TRSf'L Tle line establishedis as follovvsz L2, |05a, VS, S, TS, FS, conductor I l||, TRlfl, lconductor "|052, |43 t0 andlll t0 TRS-. s

Energizauonef TR2 closes yTR2-2 at' ocejaiid begins a timing period lforZLRZ-I to open. It is ser to "qpenfa'fter therein has mve-d forward and paused at'the outer 'end forits'presetwaiting perio d Y, Y The CfSfd .Conditqebf ,both Swithesl'of TR2 has no Vimmediate effect because TR3 is "still energized `and TRB-2 is closed and TRS-1 not yet timed outjif `set properly.

At end o i l its forward stroke, 'the ramclose's RS-Iya'nd @penses-z- Opening Qf. RS# ideeergizes ,malate this closes TRS-(fand TRS-s2 and lopens, 'mal-'3, "au withoutdelay. Y

,Closureof R3-'2 veergizes #I contacter Yrelay R4 which closes the switches R4-'L Rit- 2 and R4-4`o f the"' cohtactors and these, When` closed,

Closure of C|| and C|2 energizes TR4 which, after a delay period, closes TR4-I. The circuit involved is: LB|, conductor |60, TRA-C (pilot lamp |6| in parallel), conductor |62, CI-Z, C|-|, conductor |63, to LB2.

Closure of TRS-I energizes #3 contacter relav R6 which. through its switches R-I, Eli-2, R6-4, actuates the #3 contactors and these, when closed, close #3 contactor interlocks C3| and C3-2. The circuit involved to energize R5 is LBI, conductor |11, R6-C. conductor |18, S- (closed to |18 but shiftable to open), conductor |19 (connected by conductor |80 to |51 of S-5), TR5-I, conductor |8|, |1I, |56, R3-2, |51, S-Z, |58. to LB2.

Closure of TRB-I energizes relay R1. The cir cuit involved is: LBI, conductor |88, R1-C, conductor |89, TRE-I, conductor |90, |1|, |56, R3e2, |51, S-2, |58, to LB2.

Heat is thus placed successively on all three heating coils.

If the heat goes olf and remains off for less than a predetermined period and R3-2 is closed, this will nd the delay switch TRS-l closed and this will cause R1 to be energized which immediately closes R1-|, R1-2 to supply current to the #2 and #3 coils. R3-2 causes current to be supplied to coil #I so all coils will be energized at one time. The circuit involved to supply current to the #2 coil is as follows: LBI, |65, RS-C, |66, S5, |68, |69, |54, conductor |92, R1-I, conductor |93, conductor |94, |1|, |56,'R3-2, |51, S2, |58, to LBZ; and for current to #3 coil is as follows: LBI, |11, R6-C, |18, S-B, |19, |80, conductor |96, R1-2, conductor |81, conductor |98, |1|, |56, R3-2, |51, S-2, |58, to LB2. i

At the end of the waiting period, the timer Tl energizes ram pilot relay R2 to cause the ram to return, as before. It also energizes TR3, as before.

Energization of TR3 closes TRS-3 and leaves TRS-I closed (until later opened) so heat pilot relay R3 is held in when TR2-I shortly opens. If TR2-| opens rst, R3 will be deenergized to open R3| so that the later closure of TR3-3 will be ineffective to keep the heat on. However, operation of PB-2 would restore heat.

Similarly if TRS-I opens (as it should shortly after the gate closes) before TR2-2 closes when the gate closes, R3 will be deenergized and closure of TR2-2 (TR3 still being energized and TR3-2 open) will not energize R3. Again, closure of PB-2 would apply` heat.

Hence, this allows the operator to put in bi1- lets and start the heat aga-in without waiting.

The failure of W-l to close again after the last billet is fed down would prevent the ram from being returned from the outer end of its stroke, 1

The insertion of billets inthe chute closes W-I and W-2 and causes `the ram to start operating again.

The heat contacter circuits are of known type and it is here only necessary to know that there are two contactors for each coil and that they supply the coils with high frequency current,

derived from an independent source, by way of conductors 208, 20| for coil #1, 282, 283 for coil #2. and 204, 285 for coll #3. Suitable control of multilcoil furnaces mat7 be provided by using a transformer for one coil only, for example, coil #I asillustrated;

A solenoid MSOI is provided for starting the hydraulic pump motor when current is turned on at S-l, orerload devices OL being provided vin connection therewith.

A p'lot lamp 201 indicates when the switch S-l is cosed.

'The timing 'of operations wil be clear-er from consideration of Fig. 12, showing the cycle diagram. The duration of one complete cycle is represented by theV top horizontal line 2|!) which extends between the vertical start line 2|| and the vertical nish line 2|2.l The second horizontal yline 2| 3 represents the ram movements. It starts back at line 2|| and completes its backstroke at a vertical line 214. It starts again at the Vertical line 2|5 and completes its forward stroke at the vertical line 2|8. The ram waits at the forward end of its stroke, as represented by the distance between the lines 2 |6 and 2|2. The third horizontal line 2|1 represents the gate operation, which opens approximately at the line 2| 4 to feed down a billet, and closes approximately at the line 2 l 5.

The horizontal line 2|8 represents the action of time-delay relay TR3. It is energized at ord'nate 2| and deenergized at the line 2|6 'but its time-delay switch TR3-| is set for actuation at a point 2|5a which is. a short time after the ram is supposed to start forward. Hence, if there is any jam in the ram return or in the billet feed, the heating current will be shut off. If there is no work-piece or billet in the feed-down position to close switches W-I, W-2, the ram also will stop when it reaches the front end of its stroke, assuming that the ram did not jam on its backstroke but merely failed to get back on time.

The line 2|9 represents the action of timedelay relay TR2. It is energized at the ordinate 2|5 where the ram starts forward and remains energized until the ram returns. Its switch TR2-I, however, is timed for actuation at the point 2||a which is slightly after the ram is scheduled to start its return movement. Hence, if there is any jam in the forward movement of the ram or if the proper pause at the front end of the ram stroke has not been observed, the heating current is cut oil.

To make the original setting, it is only necessary to place the movable contact element of lthe relay at a point some distance beyond the point requiredbye.thegoperations .to -fbe1-matched f and supervisedf` and'athen gradually ifto movei the l contact backLuntil-.only aslg'ht marginzofsaifety v:lfisi-left. "Inthisway thessupervisory;response may v-be`made as fine orcoarse as.may'be;desired.

It is thus seerrthat ithezinvention provides imv-.proved controls for. azwork-heaiting furnacegparticularly for van induction fheating furnace. :The 1time:.delay Aelements arezin` part linterposed as .fl/delay; elements .inthe actionrof work-feedingfden A:fvices and in .pa-rt' are-matched with ,thev 1 actions of the feeding devices in a supervisory capacity :tm-provide safety? in .operation .in .case .the 'feed devices'ido notfunction properly. rAlso* there are provided means for applying current-,.ato-a "plu-i.

.-ralitv ofcoils consecutivelyfat-:time 'intervals or applying-currentitofall ofthe coils simultaneously iin caseA current has not been .oft long enough: to .-@alloW-workpieces :to cool beyondadesired amount.

There are also provided means for selectiveiycut-'i :ting any of the coils'in or out of action yand means for shutting downzthe V.furnace incase the :emerging workpieces are iihotter f than desired. i Also means are providedforcausing 4cooling fluid to iiow to the coils until theyandthe 'load-ofi.;

`'i-vtiorp'ieces Vhave cooled; There: are A'various zimprovements iin detailszofconstmiction' andgopera- .tion Which proviegreatj'rapidityfand-facility in changing from one type ofmperationto-another.

to be supplied to the heating coil fora-predetermined vperiod of timeY after thecurrent is -cut offl andifth'en` tozacutfoi ithesflowaorfcoolingfnid ais described and claimed incmyfcopending appliycation Serial. No.^;202;6;lf6 ledvDecernber 14s-11950. s.

` ','Whileeone embodiment has? beenvdescribed -f or epurposeslo'f illustrationojt is to-irbenunderstood ethattthere may hermans-:embodiments within dahef-lim'itsof fthe :p1-rior Aart fand the i-scrivimiofY the aisubjoinedclaims.

^Whatisclaimedrisz i l.y An electricfurnaceppomprsngaheating #coil '-f'havingeaeworkpiecezpassage therethroughpmech- .-a'n'ism for:reedingzaworkpieuehroughsaid:coil

and movable-ainadirectionfito feedaworkpiece andereturn;ztimeiiresponsiveeapparatus .setrinto operation :whenisaid @feedingmechanism 1 commences feeding a Workpiecerandl azswitchf-'coniitrolledf-py saidrtimeresponsive apparatus.' forcutftingecurrent fromisaid'vcoil ifzsaidfeedingnnech- .fanism has not :started"snif-returnl withinaxpref-vdetenminedtime.

T2: An:electriciurnacecomprismg a heating coil shaving 'aa :workpiece-:passage therethrough; fa

:pusherforffeeding workpieces through saidf'coil, f

fa" first timer for:causingfsaid'ipusher 'to pause: at fthefforwardlendaof rits stroke-and Iaseeond 'timer set into actionfiwhenfthe pusheristartsforward "for cutting lofi" currerrtfromrfsaid.v coil `if said -f-workpieces therethrough, means .fing :means-.providing aV through passageforwork- VVpieces, mechanism -for .through said-passagafanditiming: apparatusassofeeding nWorkpieces ciated with secondz'mechanism;including rateeoflmovementV determining equipment; said .equipment` acting to cutvo the heat ifzvvorkpiecesf` are not fed forward at ar predetermined rate.

f5. A11-electric furnace comprisingfelectric: heat- .ing means providing 'a through passage Vfor-.workgv-pieces, reciprocating mechanism ffor pushing workpieces through saidpassa-ge;y anditiniingrapparatus operativelyassociated iwi-th said `recipv`-rocatory mechanism: andsensitive to movement :thereof in either directionpsaidfapparatusacting v'tto 'cutoi heat nif ,the reciprocatingomechanism :'ffails to' move Veither forward: or backward y:Within predetermined time limits.

T16. AA heatingfurnac'e comprising heating means vproviding `a 'through passa-ge for yfwor'kpie'ces, :mechanismfor'i'feedmg Workpieces' through-fsaid passage, equipmentA for Ysupplyingcworkpiecesfvto Asaid feeding mechanism, and',time-controlled apparatus operatively associated withsaid feed mechanism and` said workpiece supplyv equipment,

1 said apparatus shutting oitheheating means rif the feeding means fails tofeed'forward atapredetermined ratepandalsoif the supply meansfails to supply workpieces at agpr'edeterminedrate.

f7. Aheating furnace comprisingheatingmeans Yproviding a through passage vfor fworkpieces,

y--reciprocatory means for ytpushin'g lworkpeces -:ith-rough, said passage, andV timer apparatus operatively associated 'with theposition` of :'saidpu'shing means and separately set linto timing action '.at'thestartnof thev strokelo'f the pushing tmeans in each direc-tion, said apparatus shutting-'oil' the heating means if "the pushing means `has .notereversed and started moving in the other direction within a predetermined time.

8,'An electric furnacecomprising velectric'lieat- -ing means having A'a ypassage 4r'for "workpieces therethrough, means "for `feeding workpieces at :a`

predetermined rate throughlsaid passage; timing meansfor cutting oi the ycurrentto `the/:heating means .if Lworkpieces Aare; not -fed at :the 4predetermined rate, andmeans1i-for resupplyingffull heating current to the heating #means if :proper :feeding conditions'a-re reestablishedvwithin a predetermined time after shut-down; and Yforresupplying current in stages :if -properffeedingconj-ditions Vare .notl reestablishedx within i .the predez-termined time.

i 9.1 An electric furnaceycomprising a lplurality-nf telectric heating units vvproviding a passage Vfor Workpieces therethrough, time-responsive means for energizing said heating units-sequentiallyat predetermined time intervals, and means for feeding workpieces through said passage.

10. A'n electric furnace comprising a plurality of electric heating units providinga passage yfor for feeding workpieces .through saidgpassage, 1 and time-responsive means energizing saidv heating -iunits sequentially vat predetermined `time intervals if they have been deenergized for :more thana pre- :determined time and for `energizing them'more @rapidly if they have been deenergized for less than the predetermined time.

11. An'electric induction "furnace comprising ivi-combination, a plurality of^separate induction .heating coils-arranged innaXial series'and providnga thTOUEh passage'longthe axis for Workpieces, areciprocatoryworkpiecepusher, a Work- .,piece yhopper` and escapement means timed with the pusher @action forssupplyingf workpieces l:to

said pusher, time-responsive means for halting the pusher at the forward end of its stroke for a predetermined time, time-responsive means for cutting current from said coils if the pusher fails to start yback within a predetermined time,time responsive means for cutting current fromvsaid coils if the pusher fails to start forward within a predetermined time, means for cutting current from said coils if the feed-down position of said workpiece hopper is empty, means including time-delay means for energizing said coils serially at predetermined time intervals if deenergized for more than a predetermined time and for energizing the coils at one time as a group if deenergized for less than said predetermined time.

12. An electric induction furnace comprising, in combination, a plurality of separate inductionheating coils arranged in axial series and providing a through passage along the axis for workpieces, a reciprocatory workpiece pusher, a workpiece hopper and escapement means timed with the pusher action for supplying workpieces to said pusher, time-responsive means for halting the pusher at the forward end of its stroke for a predetermined time, time-responsive means for cutting current from said coils if the pusher fails to start back within a predetermined time, timeresponsive means for cutting current from said coils if the pusher fails to start forward within a predetermined time, means for cutting current from said coils if the feed-down position of said workpiece hopper is empty, said coil having cooling means associated therewith, cooling-fluid supply mea-ns for said coil and means for causing cooling iiuid to be supplied to said coil for a predetermined period of time after said current is cut oi to said coil and then to shut oi the ow of cooling fluid to the coil.

HAROLD A. STRICKLAND, JR.

DONALD W. RIDDELL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,281,335 Somes Apr. 28, 1942 2,325,638 Strickland Aug. 3, 1943 2,325,810 Strickland Aug. 3, 1943 2,408,350 Strickland Sept. 24, 1946