Патент USA US2405985код для вставки
Aug. 2o, 1946. 2,405,985 H. A. STRICKLAND, JR INDUCTION HEATING APPARATUS Filed Sept. 2, 1945 4v Sheets-Sheet E." Haroîd .5., Sim' líZandJí: ' INVENTON B V.. ATTORNEY AUS- 20, 1946» H.~A. s'rRlcKLAND, JR 2,405,985 INÈUCTION HEATING APPARATUS Filed Sept. 2, 1943 I 4 Sheets-Sheet 3 Harold ß. «S'Zrz'cìîla‘mdJìr " INVENToR KM ATTORNEY Aug- 20, 1946» ~2,405,985 H. A. sTRlcKLAND, JR INDUCTION HEATING APPARATUS Fiied sept. 2, 1943> 4 Sheets-Sheet 4 MÃ m@ /m2 <2 i».Í E@E ñE:. L N w d!! «E` Q\? T@ @w wm f@EQT xd «NC E@ \_a A@@SNEœ: @GEW .iluwm2 IOÑLV wë; ëÉmE _Qi m:a NQ„owE fl( y ëS. »21H Um . @8 E@m:@ON@n omw È «Q m8 DON ._ n“@Owjó,li’ tr ANl @i w ¿NIN m . ,@Ef4152|@ n: È+\ IN VEN TOR d «l. y 1m,ETf. v2,405,985 Patented Aug. 20, 1946 UNITED STATES PATENT OFFICE 2,405,985 INDUCTION HEATING APPARATUS Harold A. Strickland, Jr., Detroit, Mich., assign or, by mesne assignments, to The Budd Com pany, Philadelphia, Pa., a corporation of Penn Sylvania Application September 2, 1943, Serial No. 500,903 16 Claims. (Cl. 219-13) 1 This invention relates to induction heating ap paratus. More particularly the invention relates to heating apparatus provided with mechanism adapted for holding workpieces of varying lengths including an extreme length beyond that of the furnace casing. In induction heating apparatus such for exam Z closure means for the feed opening, but capable of independent movement of said closure means; and to provide simplified construction for the operation of the induction heating apparatus. Other objects will appear on examination of the following description of the invention taken with the accompanying drawings, in which: Fig. 1 is a side elevation of the upper portion ple as described in my co-pending application, of the heating apparatus showing the furnace Serial No. 384,503, filed March 21, 1941, use is made of an induction heating coil within which 10 casing and associated control apparatus; Fig. 2 is a front elevational view showing the a workpiece is inserted, the feed opening of the heating coil being normally closed in the heat ing cycle by a pivoted hood which functions to initiate the heating operation and also to pre feed opening closure mechanism, partly in sec tion; Fig. 3 is a vertical section taken through the vent access for removal of the workpiece while 15 control box showing the means for initiating the heating cycle; the heating current is effective. This is of im . Fig. 4 is a vertical section taken along the lines portance in order to protect the workmen from .4-4 of Fig. 3; possible electrical breakdown and shock and also Fig. 5 is a horizontal section taken just below to prevent removal and re-insertion of the work piece during the continuance of the heating cycle. 20 the top casing wall of Figs. 3 and 4 and illus \trating the control mechanism; A disadvantage of this construction resides in the Fig. 6 is a detail showing the relationship of fact that the furnace cannot operate with a work ì«workpiece and holding means at the front open ?¿ing or mouth of the furnace; tends outwardly beyond the hood thus preventing closing of the hood and the initiation of the heat 25 Fig. '7 is a section along the lines `I--1 of Fig. 6, piece of such length that a portion thereof ex ing action. One of the primary objects of the present in and ' Fig. 8 is a wiring diagram of the electric cir cuit. vention is to provide a holding or electrical Referring to Fig. 1, I have shown in outline grounding device and closure means for a work 30 an electrical induction heating apparatus hav piece in an induction heating coil furnace which ing particular adaption to the heating of bars is effective to clamp a workpiece of extreme length or the like. The construction of the apparatus is without interfering with the normal heating in general similar to that shown in my co-pend ing application above referred to and includes workpiece in the apparatus which also provides a 35 three sections, the numeral I0 being applied to the furnace section proper, the numeral Il to ground in case the workpiece should be removed `the section including the control mechanism and during the heating cycle. Still another object ‘the numeral I2 to the section containing con is to provide a clamping means for workpieces, _densers and bus bar connections. which is automatically adjustable to workpieces The furnace section I0 is provided with a cas of different diameter. Still another object is to ing I3 and a front end plate UI within which is provide a clamping means for a workpiece which shown in dash outline the base plate I5 support in the case of a short workpiece moves to close ing C-brackets I6 the latter in turn supporting the feed opening to prevent removal of or con the induction heating coil unit I1. The feed tact with the piece while heating is in progress. An additional object is to provide a clamping « opening or mouth I8 formed in a. plate 6 at tached to the end plate I4 is in extension of the or closure means for a heating coil which func heating chamber I9 of the heating coil and with tions in time sequence in relation to the means in this chamber and extending outwardly be for initiating the heating cycle. Additional ob yond the feed opening is a workpiece 20. Feed jects are to provide a holding means for a work piece in an induction furnace which functions 50 ppening guide ring 2| functions to assist in the support of the workpiece 20 as well asA to aid in normally in conjunction with the means for ini guiding the workpiece into the end of the coil, tiating the heating cycle but which may func Aas described in my co-pending application Se tion independently thereof without disturbance rial No. 506,016, filed October 13, 1943, now Pat of the cycle initiating means; to provide means for closing a relay circuit simultaneously with the 55 ent No. 2,400,660, dated May 21, 1946. function of the apparatus. Another important object is to provide means for clamping a long 2,405,985 Means for grounding the workpiece or alter nately for preventing removal thereof where the workpiece is of such a length as to be included within the casing, is illustrated particularly in Figure 2 of the drawings. In this figure there is shown in horizontal alignment with thecenter of the workpiece >2i) and on either side of the same, clamping mechanisms 22 and‘23, each con sisting of a cylinder 24 secured by bolts 25 to the outer face of the end plate It. These cyl inders are each provided with pistons 26 having projecting piston rods 2ï, the pistons normally being urged outwardly in relation t0 the Work- Adapted for axial movement also within the casing ¿i3 is the valve rod 56 which is axially hollowed at the end adjacent the valve member 5|) to form a channel 51 extending from the free end of the rod 56 to a point 58 where a lateral duct opens from the rod into a transverse duct 59 formed in a stationary member 50 within which the rod 5t is movable' and communicat ing with the exhaust 44. A chamber 6| sepa rates the rubber plate of member '50 and the end of the valve rod 56, said chamber communicat ing with the outlet port 45. Within this chamber also is a coil spring S2 surrounding the end of piece by coil springs 28. The inner ends of the the valve red for retaining the packing in place piston rods terminate in lateral yokes 29 having 15 as shown in Figurey 5,. In this position fluid under pivot rods 3Q on which are mounted rollers 3| forming the clamping or closure elements for the workpiece. Rollers are required because of axial expansion of the workpiece while heating. ' In op- ’ ~ressure in the clamping mechanisms 22 and 23 will havefree exitythrough the conduits 32 and chamber 6| and duct 57 to the exhaust port d4, thus relieving the pressure in the cylinders 24 eration, when pressure is led into the cylinder 20 of the holdingunits and permitting movement chamber, as by pipe lines 32, the pistons are ofthe holding member away from the workpiece. movedVA inwardly, carrying the holding elements In Figures 4 and 5 the adaptation of the valve 3| into engagement with the workpiece 20 if ex means is shown for use in connection with the tending through the feed opening of the furnace, operation of electric switches |24 and |25. These thepressure of the pistons being such as to main 25 switches are included in the casings 63 and 61|v tain they rollers- iixedly in position against the and utilize spring operating plates S5 and 66. workpiece, effectively> grounding the same These spring plates, as shown, are fastened by through the all-metal structure of the machine screws to the switch casings and hence are freely frame. In the case of a workpiece included en movable to operate switch plungers intermediate tirely within the furnace casing, the contact roll . the spring plat-es and the casings 63 or 54. The ers «move-into close-position with each other and free ends of these spring plates underlie the an present an effective barrier against removal or nular flange 5l formed on the inner end of the Contact with a workpiece. Cross guide plates 33 hollow push button ft2, so that axial movement of » are welded to the inner edges of the yokes 29 to the push button causes movement of the spring prevent-'rotation of the roller suspensions on the 35 members and consequent actuation of the otherwise rotatable piston rods, as well as for sup switches within the casings 63 and 611. In order plementation of the rollers in coacting as a bar to secure this vswitch actuation to some degree rier for the feed opening. - Control apparatus for initiating the movement independently of the actuation of the three-way valve, the push button is'slidingly mounted on of »the holding or closure means 3| as hereinabove 4.0.; the end of an extension of the valve casing 43, described is shown in detail in aFigures 3 through so as to have a limited sliding movement relative 6, and «is referred to generally by the numeral 35. tothe valve `casing before engaging the valve rod This unit is enclosed in a casing 36 attached by 5Bwhen-mo'ved .toward the rod. To this end the adjustable screw bolts 5 to the end plate I4 above tubular casingtß is screw threaded within the andY toone side of the feed opening of the work „ push button head, this casing extending to and piece and heating coil and directly above the having slidable engagement with the outer end pressure cylinder 23 as shown in Fig. 2. The cas Geef. a coupling 'le screw threaded to the Valve ing~36 is box-shaped and is provided on its outer casing 43. The inner end of this tube 68 is closed face 3l lwith enlarged spaced openings 38 and 39, byan inwardly extending annular ñange except one above the other. Within the casing 36 and 50k fora central aperture within which the stem of ñxed to the end plate I4 is a base plate el) to a vheaded member li placed withinA the tube 68 which at the upper end thereof is ñxed a three is movable. A coil spring l2 is positioned within the casing GQ which normally urges the headed the base-plate 4i! through the opening 38 in the member 'Ii into the extreme inward limit of move control casing and terminating-in a push button ment with sufñcient initial pressure so that the 52 whereby the valve is operated. spring is compressed further ‘only after the valve >The three-way valve structure is shown more rod ,56 is pressed against its rubber seat 55. clearly in Fig. 5, the valve comprising a casing Thel protruded stem of the member 1| is ¿i3 having an exhaust port 44, and inlet port 45, normally adjacent but out of contact with and an outlet port 55. The inlet port is coupled 60 the outer end of the valve rodtt. The guiding to an-inlet pressure conduit ¿l1 and the outlet collar ‘F3 on the Valve rod 56 'holds the end of the port, through a conduit 98, to the pipe line 32 valve rod in position and also provides a seat for associated with the pressure units 22 and 23. the inner 'and outer coil springs 'M and 'l5 where Within the casing 43 of the valve adjacent the bythe head and the attached valve stem are.` inlet port 45 is a chamber 49 in which a freely 65 normally urged to outward position and packing floating valve member 5e is adapted to have axial is pressed around'the valve rod 55. movement. 'This valve member is formed as a The periphery of the annular ñange 6l is in way valve unit 4| extending horizontally from circular plate 5| with axially extending edges 52 clined toward the axis of the valve in a direction forming depressions on either side of the plate 5|, awayfrom the cap of the button to form a cam- , the end of the plate adjacent the base 40 form 70 ming surface l5. Adapted to cooperatively en ing a'recess for a coil spring 53 which normally gage' this camming surface is a similar surface urges the valve member 50 axially against the formed on the member Tl mounted on the pivot other side '54 of chamber 49. The other recess pin` T8, supported beneath the extension casing ofthe valve member 50 holds a soft rubber plate 'lil :of the valve. In operative position of the 55. 75 mechanism the camming surface of thev member 2,405,985 11 engages the camming surface of the ilange 61 Ã and is held in this position by means of a coil pivot spring 19. It now appears that when pres sure is applied to the push button 42 the initial ders 24, so that this switch and the holding mech anisms are directly related and act simultane ously. Similarly on release of the pressure in the holding cylinders the pressure switch is operated action will be to forcel the pivotal member 11'l to open and break the circuit. Terminal bar |00 mounted on angle plates |04 downwardly until the cam surfaces override each is also positioned within the casing and attached other, whereupon the spring 19 will force up the through the angle plates to the base plate 40. pivotal member, so that its end engages the edge The wiring diagram of the heating apparatus _of the flange 61 thereby holding the push button in a predetermined fixed position inwardly of its 10 is shown in Fig. 8 the power source supplying alternating current being indicated at ||0, and normal inoperative position. The push button is the main circuit lines at ||| and ||2. The cir maintained in this inward position until thepiv otal member is forced outwardly to such an ex cuits may be roughly classified in live sections in this frame and secured to the base plate 40 is an electro-magnet 3 having an armature 85 mov able therein in an approximately vertical direc B is based on a pilot contactor relay |2| which on energization is adapted to close the contacts of switches |22 and |23. In addition to the basic tion, the outer end of the armature terminating in the double arch-shaped member 81 having apertures adapted to receive the cross pin 84. Spacing tubes 88 are placed on said cross pin in termediate the member 81 and- the depending side` plates S3 to hold the frame in ñxed relationship 35 elements mentioned, the starting circuit includes the starter switches |24 and |25, pilot lamp |26 and main contactor relay switch |21, the circuit passing from main line ||2 through tap line |28, pilot lamp |26 and relay |2| in parallel, main relay switch |21, pilot contactor relay switch |23 and starter switch |24 in parallel, and starter designated as "Supply,” “Startingf’ “Load safe tent as to permit the ilange of the push'button to, escape from the detent and move to its normal 15 ty,” “Timer” and “High frequency” and iden tir-led as in the -drawings as YA, B, C, D and E outer limit. The means for releasing the push respectively. The supply section A includes fuses button and its movement‘of the pivotalmember | |3, overload disconnection heating elements | I4, 11 comprises the lever arm‘80 pivotally mounted , and lmain switches |I5. Included also are the on the pivot 18 and extending between the’mem 'ber 11 and the extension valve casing 10. On 20 main power line 60 cycle pilot lamp H6, water ’ pressure switches ||1, water pressure pilot lamp the opposite side of the pivot from the lever 8|), l |8, Water heater H9, and water thermostat |20. the arm 8|, integral with the lever, extends and ~ Main lines ||| and ||2 extend from the supply Yterminates in a pivot pin 82 to which side plates circuit A into the Starting and load protective 83 are attached extending freely downwardly to circuits B and C, these two sections being mutu engage the cross pin 84 at the base thereof, thus ally dependent for operation. Starting circuit forming a square-shaped pendent frame. With to said member. With this construction, on en ergization of the electro-magnet, the attraction switch |25 to the load safety section C. of the member 81 results in an upward movement from starter and pilot relay switches |23 and Also |24 a branch line leads through pilot relay |22 of the same. The frame is lifted thereby operat ing the arm 8| and causing the lever 80 to press 40 to a sequence or distributor switch |48, which selects the particular furnace of a bank of fur the pivot member downwardly thereby releasing naces for energization, and thence to the timer the push button from its inwardly placed posi circuit section D. tion. v ` , An alternative manual means for operating the The basic elements of the load-safety section lever 80 is also provided in a second arm 90 fixed C are the anti-reset relay |29 and load switch to the arm 8| and extending generally downward ly therefrom and toward the front side 31 of the contact elements 8a, 8b and |0|a, |0|b. Anti reset relay | 29 is adapted on energization to close ' control casing 36. The end of this arm termi anti-reset relay switches |3| and |32. y In addition to the Aenumerated basic elements, nates in a Contact plate 0| adjacent the aperture 39 in the lower side of the front control plate 3T. 50 there is included in the C section the anti-reset pilot lamp |36, and water temperature and flow Extending rearwardly from the sides of the open switches |40 and |4|. The circuit leads from ing 39 is guide casing 92 having an inner wall mainline | || through water temperature and formed with a central aperture. Movable with in this aperture is a plunger 93 having a linger ñow switches |40 and | 4|, load switch contact plate 94 and an end stop 85 attached tothe 55 elements 8a and |0|a in parallel, through anti reset relay switch |32, junction point |44, to hood plunger external to the inward aperture thereof. switch |25 of the B section. Also from main A spring 36 is coiled around the plunger within line ||2 the circuit leads through the anti-reset the guide casing 92 between the ringer plate 94 .relay coil |29 and pilot lamp |36 in parallel to and the inner edge of the plunger receiving aper ture. The action of this spring is to normally 60 a common junction |42; thence by anti-reset re lay switch |3| to a common junction point |43. maintain the ñnger plate at the outer limit of its From point |43 the circuit leads through switch Amovement but to permit yieldable inward move contact elements |0|b and 8b to point |42. ment of the finger plate whereby the end or the Switch contact elements |û|b and 8b are nor plunger is moved against the contact plate 3| of the lever 90 and thus moves the lever arm 80 65 mally closed, and switch contact elements 8_a and |0|a normally open. Y downwardly to cause release of the push button. The timer current section D is formed princi On reference to Fig. 5 it will be observed that pally of two timers of any appropriate commer `the connections from the outlet 46 through the cial make together with related elements. The pipe. line 48 terminates in a coupling 91, one end of which is connected to the pipe 98 leading into 70 function of the timer is to eiîect a timer limit, subject to adjustment, on the amount of heat the clamping pipe line 32 (Fig, 2) and the other received by the workpiece and two timers vare end connected into the pipe line 99 having con used to insure completion of a heating cycle in nection to a pressure operated switch |84 shown case one timer should fail to perform properly. in Fig. 4. This switch is adapted for actuation Whenever pressure is applied to the holding cylin Timer |50 includes the timer solenoid |5I, motor 2,405,985 v7 l 8 |52 and. magnetic timer lockswitch 1| 53.y Asso | 1.' -Usually the -powerf »source- provides >current at about 800fvolts and 3000 cycles in »the-heating v» kciated with this timer areïthe-.timer on-relayï` |54 . and, timer. on-relay<~switch |55. LA-»switch larm |56 is movable to».‘.‘on”.position»at switchfcon tact element |51 andzto 1“oiT”.-position.atswitch contact element |56. Similarly in ktimer _|60 is included.- the solenoid. |.6|, motor |62, and mag neticlockfswitch |65. Associated with this timer |60 are timer on-relay |64, timer on-relay switch ‘» »Havingin mindthe complete organization' with associated electrical and mechanical ~features`,th'e operation of the «furnace control follows. ` The f side and» rear panel doors are closed, closing door switches |19. The water cooling system is turned - on, this »resulting »in closure of 1 pressure switch | I1 `and flow switch I4 I. ' The main switches' | | 5 are "|55 and a switch arm |66imovable to “on” posi-‘ >tion’ Contact element ‘at Y|61 and “off”-position vthen- closed, current flow being indicatedby‘the Icontact element at I 68. " The timer-section D also " VariousV current flow indicating lamps H6, ||8 '~ includes the tripping solenoid 85 -for operating the and |36. Illumination 'of~ lamp |36~indicates a mytripping latch, and> pilot lamp |10 for indicating closed-»circuit through anti-reset relay" |29, by way "completion ofthe heating cycle. 15 of Vnormally closed'load switch elements |0|b and ' The timer circuit is'traced from the sequence “ selector switch |40 through parallel lines |11 and ` |12, including timer solenoids 15| and 16| -re spectively, to the main »line ||2. A 8b. ~».Simultarieously,anti-reset re1ay'swìtch`es`l3l ~ and |32'are closed/thus locking the'anti-reset relay-'closing and lconditioning the‘circuits for To maintain application of voltage on the starter section B - power after opening of sequence switch |48, taps and theV timer section D on Vintroduction of the Yare made at |13 and |14 on lines |1| and |12 ~ workpiece. respectively at points between the sequenceswitch The workpiece is now inserted in `the'furnace .1|48 and solenoid coils |51 and I5! respectively, chamber causing the closure-of load switch ele these tap lines leading through the timer ment |0|a and thereby applying voltage to point r>switches |53and |63 respectively and :a common 25 |44 and starter -section B and timer'section'D. -return line |15 to the tap point |44 between B VVBefore the workpiece has passed completely - and C section. Line |15 also supplies power to over load switch element I0 | a itengages the ejec tor rod, thus actuating the arm of load‘switch 8. This switch'has'two circuit contact* elements 6a and '5b which are simultaneouslyactuated, normally open switch element 8a serving Aon c10 the timer switch arms |56 and |66. The timer on-relay coils |54 and |64 are connected to the main line ||2 and to points intermediate the “on” timer contacts |51 and ‘|61 and the corre sponding motor. The tripping solenoid 85 con sure to maintain a voltage on the starting‘and nects to the main line ||2 and to the “o ” timer contact elements |50 and |68. `Associated with timer section D is vthe main contactor relay | 8| with heat-on pilot lamp |82 connected in parallel therewith. Circuit connec tions with the timer section are made by exten sion of timer line |15 from point |11 through load switch 1, furnace panel door switches |19 40 associated with various side or rear panel-doors, ' on-relay timer switches |65 Vand |55 to point |80 on the relay |8|. Also the mainline |~‘|2 is extended from point |83 through point |15‘Iand starter switch |84 to the main relay |8|. »A ~‘pilot lamp IBS-indicating complete insertion of the workpiece connects the power side of the panel door switches |19 with the main line ||2. The high-frequency section'y E includes Athe main contactor relay switches and a~rectifying circuit for supplying direct current for operation ofthe high-frequency contactor operating coil. There are two main contactor» relay switches |90, |9| and the previously mentioned switch |21.y in Ythe starter section B, also operated by the relay |8|. 'The rectifying circuit is made as a conventional bridge |92 and is comprised in the» four branches |93, |94, |95 and |96 with copper oxide or equiv alent elements inserted, one in each branch, with such polarity as to produce a direct current po tential at points |91 and |90, yas indicated. Al ternating current is led to points |99 and 200 --on'the rectifier from main line ||2 at |16 and timing circuits irrespective of the action of load switch |0I. Opening of either orboth 8b~or |0| b shifts- the anti-reset relay circuit entirelywthrough anti-reset relay switch '|3I, so that should the power be _withdrawn from this _relay'permitting opening Vof the switch ISI, it cannot again be closed unless both load switch contact elements 8b and |0|b are closed,'this requiring complete unloading ofthe furnace. ' The workpiece is now moved to the rear end 'of the furnace chamber `closing load switch 1 inthe timer D section. The starter button 42 is now pushedin bringing about closure successively of starterswitches |25,` |24 and |84, the closure of switch' |24 being momentary. On the closure of switches |25 and_| 24, a closed circuit is at once established through normally closed main con tactor relay switchV |21 `and the pilot contactor relay |2| with its associated lamp |26. There upon the two pilot contactor relay switchesff|22 .and |23 are closed, switch |23 locking the pilot _relay |2|1c1osed since starter switchv |24 is closed only _momentarily vduring the hood yclosing move _ment _Also power is _applied _by way ofswitch' -| 22 to the sequence switch |48. The system of circuitsisnow conditioned for vinitiation of. aheating cycle. This will develop (ill when` the sequence switch- |48 which rcontrols the _sequence of powerapplication `in the furnacebank `establishes a closed circuitto the timersection D. When this occurs timer solenoids |5| and |'6| are»v energized, locking switches |53 and |63 are . from the C-D circuit |15 at point20l, the re ci .closed,.timer switch arms :|56 and »|06 `moveto -sultant tap line including inseries a resistance on-position at contact elements y|51 and. |61re -cut-in combination of a resistance 262 Aand nor spectively and motors A|52 and '|62 function to mally closed by-pass switch 203 on the resista-nce, start the timing cycle. Simultaneously on-posi and the main contactor relay switch 19|. The -rectiñed circuit connects in series the main con tion-relaysI |54 and l| 64 are energized, closing on tactor relay switch |90 and they high-frequency contactor operating coil 1204. Energization> of lmagnet coil 204 closes the switch 205 of the high »frequency high-voltage circuit 206 'includingf'the «power source 201, capacitor-208 and heating coil relay‘switchesL | 55 and |65, and since load switch 1, panel-door switches |19 and starter switchl |84 lare already closed, power isat once supplied from circuitl point |44 between sections B land C lthrough line |15, and from main line ||2-tò-the 2,4o5,985 v , . 9A - contact with'any part of theffurnace with >.con-i 'i main contacter relay |8| and its associated signal lamp |82. , _ , sequent damage is remote. The particular structure shown and described , AThe energization of relay |8| closes main con for accomplishing the objects of the invention have been found to be efñcacious and usable. tractor control relay switches |90 and |9|, and opens switch |21 in the'starting section circuit. However, itis apparent that modifications of th'e The effect of opening switch |21 is to de-ener- , invention as described may be made to meet spe cial conditions ef use and hence I do not desirel to be limited to the specific illustrated means ex cept in so far as required by the scope of the . claims as hereto appended, gi'ze pilot contacter coil |2| and cause the open in'g of pilot contacter relay switches |22 and |23, thus breaking the circuit through the sequence switch. Additionally, closure of main contacter relay‘switch |9`| closes a circuit from point 20| on power line |15 through` the resistance cut-in switch 203 to point |99 on the rectifier |92, thus, applying a voltage at point 200 from main line What is claimed _isi- Y, Y ,. , ‘ ' coil having a feed opening foi-,insertion vof a source and coil, a relay circuit controllingthev functioning of said circuit, including a vrelay switch |90 to energize the high-frequency con tactor coil 204. Thereupon, the switch 205 in the main induction heating coil circuit is closed and power from the source 201 _is applied to heating coil |1. `On completion of the heating cycle either timer switch, closurek means for closing said coil feed opening, and single means for closing said relayswitch and closure means, said closure means-> being adjustable independently of said relay switch. . 2. In induction heating apparatus, aheating coil having a feed opening for insertionof av work switch contact arm |56 or |66 breaks contact at and |65, thus disconnecting relay |8|` and open ing the main circuit and stopping the application of power. In addition, timer switch contact l ` workpiece, a power source, ’a circuit including said , ||2, creating a direct current voltage at points |91 and |98 which is effective through closed elements |51 or |61 and opens relay switches |55 - 1. In induction heating apparatus, a’heating- a power source for supplying power to-'said 25" piece, coil, iiuid pressure means laterally movable rela arms |55 and |66 engage contact elements |58 , tive to the coil axis to form a yieldable feed opening closure adjustable to werkpieces of dif- c, ferent diameter, said means having pressure re-. , and |68 causing functioning of tripping solenoid lease mechanism and means operably connected 30 85 to open the clamping bars 21 and star-ter switches |25 and |84. The workpiece may now be removed from the furnace by actuating of the foot pedal and/or application of tongs. with said closure means but capable of move ment independently thereof for controlling said fluid pressure means. ` ' 3. In induction heating apparatus, a heating , From the description of the structure and of th'e electrical circuit and connections as herein 35 coil having a feed opening for insertion of a work piece, a power source and circuit including a above made, the particular utility of the inven switch for supplying current to said coil, a con tion may -now be apparent. ~Operation of the trol circuit including a fluid pressure operated push button 42 to the latching point opens the switch and means for closing said power circuit valve 4| to permit air under pressure to enter the closure cylinders 24 and at the same time 40 switch, closure means for the coil feed opening, said closure means comprising two opposed, lin introduce pressure to the switch |84 to make possible energization of the main contacter relay |8| and consequent activation of the power source control relay 204. Switch |25 is closed just prier to the latching of lthe button so that in the early movable closure elements, and ñuid pres sure means for closing said control circuit switch and closure elements. ’ 4. In induction heating apparatus', a heatingv _ latched position this switch remains closed, con tinued pressure on the button causing overtravel of the flange 61 to close switch |24. When pres coil having a feed opening for insertion of a work piece, a power source, a circuit includingrsaid source and coil, a relay circuit controlling thel sequence. sure means for closing said coil feed opening, and functioning of said circuit, -including a relay sure on the button is released it returns part way to the latched position, opening switch |24 whose 50 switch, connected a starter to said switch relay circuit and circuit to permit operatively energi- . action is thus termed “momentary” It is point ed out that these three switches are closed in time ' v zation of the relay circuit and relay switch, clo It is also noted thatthe lfunctioning ' of switch |84 is fully dependent upon the appli cation of pressure to the holding cylinders 24. However, due to the fact that the holding means involve fluid pressure with its yieldable charac teristics it is also apparent that the functioning of switch' |84 is not dependent upon the degree of movement of the workpiece-engaging rollers 3| so that switch |84 functions irrespective of the size of the workpiece inserted in the feed open ing. This relationship also permits the heating of a workpiece of such length as to extend out wardly appreciably beyond the rollers 3|, in which position the rollers are spaced from each other by the inter-position of the workpiece. It is pointed out further that in the case of a long workpiece which is being subjected to a heating treatment it may be possible to remove the work piece before the heating cycle is completed but that, if such' removal is made, the piece is effec tively grounded until it is well outside of the ma chine and the chances of its making electrical single means for closing said starter switch, relay switch and closure means. 5. In induction heating apparatus, a heating coil having a feed opening for insertion of a workpiece, a power source, a circuit including said source and coil, a relay circuit controlling the functioning of said circuit, including a relay switch, a starter switch and circuit operatively connected to said relay circuit to permit ener gization of the relay circuit and relay switch, clo sure means for closing said coil feed opening, 65 single means for closing said starter switch, re lay switch and closure means, means for estab lishing a heating cycle in said heating coil on closure of said starting switch, and means for disconnecting said starting switch, relay switch and closure means on completion of said heating cycle. 6. In induction heating apparatus, a heating coil having a feed opening for insertion of a workpiece, a power source, a circuit including said source and coil, starting means for initiating 11 2,405,985 a heating'cycle in said circuit, closure means for said coil’feed‘opening, and single means’ for ener-gizing successively saidy starting "and closure' means; 7. In induction heating apparatus,- a heating , coilhaving `a feed 'opening for insertion of ya 12,4 opening only on removal ofthe workpiece during> the period of switch closure. y 12. In induction heating apparatus, a heating coil having a feed opening for insertion of a workpiece, a power source for’supplying current to said coil, a control circuit for making said power workpiece, a power source, a circuit including said sourceiand col-.starting means for initiating a source eifective in said coil during a heatingY cycle, holding means movablelaterally in rela-V heating cycle" in saidpcir'cuit, closure means for tion to the coil axis into engagement with a worksaidî‘coil feed opening,` single means for acti 10y piece positioned insaid'coil wìtha section there-, vatin'g vsaid starting and closure means, andanteofïextending out of the feed openingpenergiaá` matic timing means for bringing about deener able means for actuatingsaidholding means, andY i gization of thev starting and. closuremeans.> on movablemeans for energization of saidfenergize completionî of the heating cycle. able` means .and control circuit,` said> holding 8. 'In ‘induction heatingapparatus, a heating means being adjustable automatically to work coilï‘havi'ng a feed opening` .for insertion of a pieces Aof Vdifferent diameters and` operable only workpiece; a power source, a circuit including said during the heating cycle. source-~ and coil, "starting means for initiating-a 13. In induction Iheating apparatus, a heating. heating' cycle'in said circuit',v >closure means `for said‘c'oil feedopcnin‘g; and 'single means for »ac-' 20 coilhaving a feed opening for insertion of a work tivatingv said v‘starting and' closure means, said » starting means including" a device for restoring saidvsingle means to pre-actuating position. 9.`1nv induction‘heating apparatus, a heating piece,v a power source, la circuit .between rsaid source and coil including a switch, a controlcir-` - cuit for bringing about closure of said switch, and closure> means-for. said .coil feed opening, said» control circuitincludingmeans ffor preventing.` closure of said sourcecircuit.switch-until. clo coilhaving' ’a ‘feed ¿opening for insertion of a workpiece,->` a powïer source, and'controlicircuit connected to 'said source and coi1.,'andclosu're means for closing said/coil: opening effective only upon‘energizationof said control means, said clo sure `4means' forming'a ground connection to the sure ofthe feed opening is under wayn 14. vThe combination-according to claimv13 but including additionally- means for preventing re lease ofthe closure means >during a heat cycle. 30 workpiece.' " 15. In induction heating apparatus, a heating coil having a feedopening for insertion of a work-~` 10.' In induction" heating apparatus, a heating piece, `a power source forr supplying‘currentto ' coil having'a feed opening'for insertion "ofi a workpiece, a power source for'supplying current said coil, switchV means »f-for establishingfñow of ~ current from the source to thecoil, a‘control tosai‘d'coilfa circuîtbetween‘said coil -and Source, circuitfor causing closureof saidswitch means,- a `relayi switch 4in saidcircuit', a 'control circuit including' ,a starting 'switchan'd .a relay" coil for closure means for closing said «coil lfeed opening' initiating'a heatingl‘cycle" in 'said heatingv coil by kclosure of s‘aidrelay switch, a closure means foî‘"`said"feed opening'and me‘ans‘incorporated in means to close rsaid opening, and `single movablev said 'control"circuit for. 'activating saidl closure and energizable meansforA actuating saidclosure means for effecting energizatíon'of said energiz 40 able means and control circuit. , meansfonfclosure'ofthestarting switch" and re leasing s`aid closure îme'ans'at 'the end of the cycle.` 11; 'In' inductionmheating"apparatus,~ a heating’ coil having a feed opening for insertion of 'a work- . piece,‘"'a ‘power’ source ‘for' supplying" currentrto said coilßswitch' means controlling> current' sup-4 ply ’.from..said source,""holdingV means for 'yield`-V ably'eng‘agingî'a workpiece extending within and without said ' feed opening, l‘energi‘zable' means .for actuating >`-`said ‘holdin‘gî means, .and‘ movable mèans'for‘îenergization ‘of said energizable means' andclosure of-'saidíswitch‘means, saidholding ' means' >automatic'ally ""mo'vingtto" close saidn ‘feed ' 16. In induction heating apparatus, a heatingV coil having a feed openingifor insertion of a work piece, a power sourcel for supplying current to' said coil,f switchameans for establishing ilow- of current fromthe source to the coil, a control. circuit for causing closure- of said switch means,v closure means for closing said coil feed opening and energizable means foractuating said closure’ means to close-said-openingfand single-movable means-` for effecting - energization ofy said energiZ-I’ able means .and control circuit, said control cir cuit being dependentuponsupply of power to the closure means for closure'of the switch means. HAROLD A., STRICKLAND, J s.