US2541123A - Control system for inductionheating apparatus - Google Patents

Description

Feb. 13, 1951 H. A. STRIQKLAND, JR

CONTROL SYSTEM FOR INDUCTION-HEATING APPARATUS 4 SheetsSheet 1 Original Filed May 1'7, 1945 1N VEN TOR Harold A. Strickland, d1.

ATTORNEY Feb. 13, 1951 H. A. STRICKLAND, JR 2,541,123

. CONTROL SYSTEM FOR INDUCTION-HEATING APPARATUS Original Filed May 17, 1945 4 Sheets-Sheet 2 lll llllllllllllllllm mmmm K maxim 1m 2 ;g 1 3 INVENTOR Hamid A. Smck/and J1? 4Q4Z..-:?EZZZL Z:L

ATTORNEY Feb. 13, 1951 H. A. STRICKLAND, JR

CONTROL SYSTEM FOR INDUCTION-HEATING APPARATUS Original Filed May 1'7, 1945 4 Sheets-Sheet 3 [Hamid Siffcfdmid, 1/

Feb. 13', 1951 H. A. STRICKLAND, JR

CONTROL SYSTEM FOR INDUCTION-HEATING APPARATUS 4 Sheets-Sheet 4 Original Filed May 17, 1945 E IG: 7

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A TTGENEY Patented Feb. 13, 1951 CONTROL SYSTEM FOR INDUCTION- HEATING APPARATUS Harold A. Strickland, J r., Detroit, Mich., assignor, by mesne assignments, to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Original application May 17, 1945, Serial No. 594,329. Divided and this application July 8, 1946, Serial No. 681,996

2 Claims. (01. 219-13) This invention relates to apparatus for heating inductively workpieces adapted to move progressively through the heating coil of the apparatus and is an improvement over the apparatus shown in applicants Patent No. 2,325,638, filed September 19, 1941. This application is a divisional of Serial No. 594,329, filed May 17, 1945, now abandoned.

An object of this invention is to provide a highfrequency induction furnace of the type shown Figure 2 is a section of the furnace taken along the line 2-2 of Figure 1;

Figure 3 is a view indicating the transfer point between coil sections in the furnace;

Figure 4 is an end view of the workpiece guide element;

Figure 5 is a side view of the workpiece guide; Figure 6 is a view of a part of the workpiece guide; and

Figure 7 is a wiring diagram.

The sectional elevation of Figure 1 illustrates.

the general setup and arrangement of the apparatus for machine generally designated by the numeral I. On the base 2 there is mounted a frame 3 for enclosure of the capacitor bank I v and for support of the induction furnace workpiece feed apparatusand power means. For aid 'in description the power mechanism will be designated by the letter A, the workpiece feed apparatus by the letter B. and the induction furnace by the letter C, these units being positioned as shown in Figure 1 from left to right of the machine. These various units A, B and C are enclosed by a casing 5 preferably of non-magnetic material; as aluminum, the casing extending Qn'om enclto end of the machine and nnboth sides and ends as shown in Figures 1 and 2. Preferably the casing is divided transversely into sections 5a and 5b, section Go enclosing the induction furnace and section 5b the feed mechanism and power unit.

Referring first to the workpiece feeding unit B there is provided a chute 6 which extends angularly from the top casing 5 in position to receive a number of workpieces which for purposes of description will be referred to as billets. These billets have a length corresponding to the width of the chute and are adapted for placement side by side in the chute for feeding into the billet channel 1 at the base of the chute. A supply chute switch 83 opens the power circuit when the supply of billets fails. As fully described in applicants patent above-mentioned the channel 1 is open at either end and from the power side is adapted to receive power application from the A unit including the plunger element 8 pivotally connected to a connecting rod 9 adapted for reciprocation by the pulley and belt mechanism shown. A motor [0 is connected to the shaft of the lower pulley, the screw shaft l I and hand wheel I2 affording means for adjusting the tension of the belt.

On the side of the billet channel 1 adjacent the furnace a channel extension (3 is provided into which billets are moved by the projector 8 from the channel I as they are fed downwardly in the chute 6 by gravity. This feeding action is intermittent in accordance with the reciprocation of the plunger 8 and the projected billets are lined by this action of the mechanism end to end in the channel I3. As the movement continues the billets are moved through the guide grid" to the heating chamber of the furnace. The guide grid is of special construction comprising two right angled sections 15 and it, one of which is shown in Figure 6, which, on being united, form a member with a square contour having a solid base of flat stock from which extend projecting fingers I1. These fingers are roughly triangular in shape with the flattened sides of the plates in a given unit each parallel with each other. The inner edge [8 of these plates is preferably formed of hardened material as these edges constitute the bearing surface of the grid and may be formed of separate strips attached to the plates 11. The bearin edge or. the pla e I. i bs antia sections :25, 26 and .21.

-' i'tFig. 1'3). the lugs 33 with a cutoff corner on the'end at a parallel with the axis of the furnace and so positioned relative to this axis that the center of the exit opening of the grid is coincident with the heating channel axis. Adjustment of the grid, so as to permit centering thereof in relation to the coil axis, is possible from the construction of the grid in two sections, the attachment bolts i9 being of lesser diameter than the attachment apertures 20 on the grid to permit relative movement .of the sections with reference to each other. By such movement the center of the grid axis opening may be shifted laterally.

The induction furnace C is positioned in extension of the grid 14 as shown in'Figu-ne 1; This unit includes three sections 25, 26 and 21 in common alignment and formed :as compl'ete Iuriits independent of each other andseparably remov able. Each unit comprises a heating -coil -28 wound in square formation of square sectioned copper tubing, the turns =of the coil being insulated from each other. Interiorly :of the cell are a plurality of insulation blocks 29 (Fig. 2) supported in place by metal tubes or rails 31) provided with butterfly supporting plates 31. 'These plates are attached to the rails 33 on the inner -sides thereof with lateral extensions adapted to "overlie the-adjacent edges --'of the refractory iire brick or other material used as hea'ting insulation material, thus reta'ining this material :in

place.

The rails 39 function as cooling rneans', :the profleeting ends thereof b'e'ing -ou't'turn'ed and attached to supply sources 32 of a :coolant. "The also serve to support lugs '33 :consisting of small plates edge-attached at displaced points along the inner =usrface :of the rails :as shown in oo-pending application :Serial No. 384,503, filed March 21, 1 941, new Patent "No. 2,408,350

deited :Septemb'er 2l4, 1946. 1A5 will :be seen from inspection :of .Figure T2 the rlugs 35 are in close proximity to the billets on ail :sijdes thereof so =tha tbuckling "of the train of billets ininovement through theifurnace chamber is prevented. The :lugs '33 .shoul'dloe of heat :resistant metal so as ito withstand high temperatures present in the 5fiurnace during operation.

:Externalto the "coil =28 :there ;-is :a layer -01" insuilat'mg slabs BQ-Whichmay be of Transite. At the sends :of :the co'iLsupport plates -,%5 are provided to which the heating .coil -unit is attached byfmeans of rods 36, there being four of these .redsshown Figure *2 extending external 'to the coil from :end to endand retained by means of hookedsup- .iports 3:! on the outer-face of theend plates 35.

Coil connections from each coil for supply icf electrical power is iby means of :the coil taps 2i, '0 qconnecting traps 3'8 and bus bars :33, Ali-and 41 "The "capacitors -42 are :connected by straps :43 to and F45 mounted on the :coolant tubing -;inter- .mediate "the end plates 35 :of :adjacentsections These lugs :are :in general similar to which the billet approaches but the "lug 46 is formed with a flatter andmoreextendedtfacexon In :order to insure 'con- At the rear or exit end of the section 21 of the furnace a second guide grill 58 is provided leading into a chute section 5|. A further chute section 52 at the end of the first chute section provides a channel for carrying the heated billet to a receptacle external of the machine. A door switch 53 comprising a pivoted plate hinged on the side of the chanel so as to be actuated by the :movement of :a passing billet isprovlided. Also in line with the axis of the furnace ra photo-cell unit 54 containing switch means 98 (Fig. 7) is secured to the casing section 5a at the end of the ma- .chine, an aperture being made in the casing so thatl'ig'ht from the furnace may penetrate the unit to modify the resistance of the cell.

ll'tiha's been previously mentioned that the casrings'irhas been divided into two sections 5a, and 5b. Theinnenenfisfif these two casings adjoin each other and are supported by an intercepting transverse .plate 55 extending across the upper casing :chamber. This plate also supports the grid [4. iCon-nectionrbetween the plate 55 and the casing ends is by means of brackets 55 and 51 which are "bolted respectively to the plate and casing. The

plate is lined, preferably with insulation matesrial :in illhe :form pf insulation :sheets, upper .edge of which extends 'between the adjoining redgesaof :casings :5a and '5?) and between :the brackch58 and the plate 55580135 zto:insulatecelectrically sboth ca-sings from -:.each other and from the brackets 15.6. Insulation also surrounds the bolts .58 securing {the bracket :56 to -the plate 55. ,Ad-

ditional insulation of the casingi'is -proyided inan :insulation get-rip :59 placed :between the .bracket 26%] and :the casing plate 61 rasishown in Figure 2. The attaching screw bolt .is also insulated from the bracket 69. In {this manner the electrical including the casing and the plate .5! is interrupted whereby eddyscurrents, .due .to .flux transmitted by the heating coils, are eliminated.

It is pointed out .f-urther-asrshown-in Figure 2 that there is provided flux return paths ior the .-coil in the 52 secured along the inner :suriface of the casing 5a. These .fiux .return units comprise laminated strips 63 placed in :slotted "tubes 64 where they are retained .bythe :fiber linking 65 and plate 68. These aextend longitudinally of the leasing parallel to the heating .coil and reducethe eddy currents .in the casing ;-to such :an extent that heating .efiects therein are practically eliminated. Without these flux meturn units the-casing becomes sohot thatit is a source of danger to the attendants.

InFigure 5710f the drawing is indicated a wiring diagram of the circuit which is applicable :to the machine as hereinabove described. The :use of :threemhase alternating purreut is indicated as being applied to inlet source terminals 10, 1i and 12. From source .10 :the circuit leads through a gmainzmanualiswitch 1-.3,-nnd2a. relay iSWitGh .74 to the motor :15 .for operating the equipment. ,Enom source J1 the .circuit leads through manual switch 16 to the mainiconductor 1,1 andirom'source J2 through manual switch 1-8 to the main :conductor 39. The circuit involves .six sections referred .to :as :sections 113 G, .H :and vI. ;S,ection 134mmprises the :motor ;;pilo.t :circuit and includes the rpilotrizelay coil :80, the manual motongstantrswitch 8; l, th'ezmanual motor .stopningnwitch 2 ,:the nor- 7 :mally "open supply phute -switch $3., the :normally closed line switch ".84 and "the normally open :timer .chute "manual zswitch :85. A pilot lamp :86

:is provided "also in parallel with .thcpilot coil 7.80 to indicate. ,current :fiow .in ?this branch icircnit.

manual switch II is provided. The E branch circuit includes the motor 15, the relay switch 14, the relay switch 81 between the motor and the main conductor 11 and the relay switch 80 between the motor and the main conductor 19. These switches are normally open and on closure cause the motor to function.

Branch F of the circuit is the timer section. The timer may be of any known construction such as the Eagle timer and includes a clutch coil 09 a motor 90 and a normally closed relay switch 9i, the motor and switch being in series across the main conductors I1 and 19. The clutch coil is in series with the normally open delivery switch 53 between the conductors I1 and I9. The timer circuit also includes the timer switch 93 which normally is open but remains closed during the operation of the machine unless the movement of billets is interrupted.

Branch G of the circuit includes the intermediate contactor coil 94 in parallel with the indicating lamp 95, the normally open manual switch 96, the normally closed manual switch 91, the normally open door switch Ill, the normally closed photo-cell switch 98, the normally open coolant pressure switch 99 and the normally open flow switch I00, each of these elements being connected in series from the conductor 11 to a point between the pilot coil 80 in the D circuit and the manual motor starting sw tch 8|. A normally open relay switch IOI shunts the manual switch 90 in the intermediate contactor circuit.

The main contactor circuit H includes the bridge rectifier I02 connected directly to the conductor l1 and, through the relay switch I03 and resistor I04, to the conductor 19. A normally open relay switch I05 by-passes the resistor I04. The rectified c rcuit comprises the normally open relay switch I and the main contactor coil I01 which functions to close the heating circuit. The armature of this coil when closing also closes switch I after the first current surge through the H circuit. The heating circuit I includes the normally open relay switch I00 and the heating coil I09 energized from the high frequency power source IIO.

Additionally, the circuit includes the lamp indicator I I I to indicate power in mains I1 and I9, and lamp I I2 and normally open pressure switch I I3 to indicate proper coolant pressure in the furnace tubing.

In operation, with the door switch II4 closed, the coolant circuits for the support rails and heating coils are supplied with coolant under pressure thereby causing closure of pressure and flow switches 99, I00 and H3 in the G branch circuit. Billets are placed in billet chute 0, closing switch 83. The motor switch 8| is then closed manually thereby completing a circuit through the pilot coil 80 and lamp 88. Energization of coil 80 closes relay switch II5 locking the coil 00 and permitting starting switch 8i to be opened. Also relay contacts I4, 81 and 88 are closed to energize the motor I5 and start the feeding mechanism. Billets are consequently intermittently moved fro-m the base of the chute into the furnace for heating by the heating coil. Simulta neously the intermediate contactor manual switch 96 is closed energizing coil 94 and causing closure of relay switch IOI to lock in the coil circuit, Also the contact switches I03 and I06 are closed in the H contactor circuit supplying direct current to contactor coil I01 to close switch I05 and the heating circuit I. If there is no obstruction in the movement of the billets it will be continuous and uniform and as each successive billet leaves the exit grid 50 and moves down the chute 52 it will operate the stock delivery switch 53 causing closure of the same and energization of the timer clutch coil 89. Thereupon timer switch 93 closes and the timer begins a cycle which is substantially in excess of the time necessary to bring a billet to the required temperature in moving through the furnace. Consequently the billet will pass out of the furnace and down chute 53 before the timer cycle is completed and in so doing operates the delivery switch 53 to cause a resetting of the timer, the timer switch 93 remaining closed. After another time interval and before the timer completes its new cycle another billet emerges from the exit grid and operates the chute stock delivery switch. This sequence of operations will continue indefinitely as long as the supply of billets in the supply chute is maintained and as long as there is no interruption in the movement of billets through the furnace. Should the supply of billets fail or should a stoppage occur in the furnace for any reason or should the power mechanism for supplying billets to the furnace be interrupted the timer will then tune out, switch 93 will open and motor 15 will stop through opening of the associated switches '14, 81 and 88. On the opening of timer switch 93 timer motor switch 9i also opens.

After stoppage due to any of the causes mentioned, a restarting of the machine can be accomplished only by actuating the stock delivery switch 53, assuming that the supply, pressure and flow switches are closed. When this occurs timer switches 9i and 93 close and the timer resets for anew cycle.

In the event that through excess voltages or other causes the heat in the furnace becomes excessive the photo-cell switch 98 opens thereby deenergizing the heating circuit but not interrupting the motor circuit so that the billet movement continues until the temperature has fallen in the furnace to a normal value.

Modifications in structure and circuit may be made within the scope of the claims hereto appended.

What is claimed is:

1. In a machine for progressive heating of a train of workpieces; an induction heating chamber therefor, means for supplying a train of individual workpieces, power means for moving said train through said chamber, a high-frequency power source for heating workpieces in said chamber, means for interrupting the power means and power source on failure of said train of workpieces to move upon actuation by said power means, and additional means for interrupting the power source alone on development of abnormal heat in said chamber, said last-mentioned means comprising controls actuated in response to the temperature of emerging workpieces.

2, In a machine for progressive heating of a train of workpieces; an induction heating chamber therefor, means for supplying a train of individual workpieces, power means for moving said train through said chamber, a high-frequency power source for heating workpieces in said chamber, means for interrupting the power means and power source on failure of said train of workpieces to move upon actuation by said power means, and additional means for interrupting the power source alone on development of abnormal heat in said chamber and for connecting the power supply on reduction of heat to normal in said chamber, said last-mentioned means oom-

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