US2686251A - High-frequency heating - Google Patents

Description

Patented Aug. 10, 1954 HIGH-FREQUENCY HEATING Theodore P. Kinn,

Baltimore, Edward M. Wharfl,

Jr., Ellicott City, and Milton P. Vore, Catonsville, Md., assignors to Westinghouse Electric Corporation, East P tion of Pennsylvania ittsburgh, Pa., a corpora- Application August 12, 1950, Serial No. 179,072

9 Claims. 1

Our invention relates to high-frequency heating systems, and more particularly to high-frequency heating systems of a type having a plurality of work-treating stations, each including a high-frequency work-heater, the stations being energized from a single source of high-frequency in a sequence which can be repeated indefinitely.

It is recognized that a high-frequency source of power, such as a tube-oscillator generator, can be more economically employed when its duty cycle, that is the ratio of its active work time to its idle time, is as high as possible. When a plu rality of work-treating stations are to be alternating or sequentially energized by the same generator, certain problems arise because of the high frequency and the high currents involved. Difficulties that may be encountered are set forth in Dravneek Patent No. 2,321,189, dated June 8, 1943 and in Zottu Patent No. 2,419,307, dated August 22, 1947.

These patents, representative of the prior art, show systems for selectively energizing a plurality of work-treating stations by means of a circuit selecting means involving a transfer switch which selectively connects the high-frequency generator to whatever work-treating station is to be energized, the remaining work-treating stations being disconnected and deenergized during such connection. As one work-treating station is energized, the other or others are unloaded and re" loaded. The energized work-treating station is then deenergized by operation of the transfer switch, and the high-frequency generator connected to a second work-treating station. In this manner a system of high capacity is provided which can economically utilize a high-frequency generator of comparatively small rating because most of the energy which the generator is called upon to supply is that demanded by a single work-heating station. However, the use of a switching means requires engageable and disengageable contacts, so that a complicated switching mechanism must be used because it is necessary to transfer high-frequency currents and voltages from a circuit including a first work-treating station to a different circuit including another work-treating station.

An object of our invention is to provide a system in which a high-frequency generator can be sequentially effective on a plurality of work-treating stations without the use of transfer switching means having make-and-break contacts.

A further object of our invention is to provide an induction heating system in which a single high-frequency generator and a plurality of highfrequency worktreating stations are connected in a single circuit that has no transfer switching means; the system nevertheless including means which permits the energy to be selectively supplied from the generator to any grouping of work-treating stations, less than all of them.

An ancilliary object of our invention is to provide a system of the type described in which a single high-frequency tube-oscillator source of power is connected selectively to each of a plurality of work-treating stations through a single circuit which is not altered while the different work-treating stations are selectively operated.

A further object of our invention is to provide a system of the type described in which a single tube-oscillator generator selectively energizes each of a plurality of induction-heating coils connected in a single circuit; the selective operation being such as to maintain the electrical characteristics of the load presented to the highfrequency tube-oscillator generator substantially constant. v

An over-all object of our invention is to provide a high-frequency heating system of the type described in which the tube-oscillator generator may be operated as nearly continuously as possible.

The principles of our invention are of broad application but are herein described in connection with preferred forms thereof, having a plurality of high-frequency work-treating stations, each of which includes a work-heater in the form of an induction-heating coil. The work-treating stations are connected in a common circuit that has no transfer switching means such a used in the prior art. Each work-treating station also includes work-holder means which holds work that is to be heated by the associated induction-heating coil.

When the induction-heating coils are selectively operable, those which are not supplied Wtih work are instead supplied with a piece of metal, in the form of a coil or block or other similar form; the metal being of high conductivity such as copper or silver, for example. The piece or pieces of metal are closely coupled to the nonworking induction-heating coils. Physically, each piece of metal is as near as practical to the associated coil without touching it or introducing the danger of park-over. The close coupling and high conductivity of the metal-pieces practically nullifies the inductance of the non-working induction-heating coils without the absorption of a great deal of power.

Objects, features and innovations of our in- 3 vention, in addition to the foregoing, will be discernible from the following description of preferred embodiments thereof, to which our invention is obviously not limited. The description is to be taken in conjunction with the accompanying drawings. Both the description and drawings are highly simplified for clearly setting forth the principles of our invention, without the use of excessive detail. In the drawings:

Figure 1 is a sectional view substantially on the line 1-1 of Figure 2;

Fig. 2 is a vertical view, partly in section and partly in elevation, of a high-frequency heating system embodying the principles of our invention;

Fig. 3 is a vertical view, partly in section and partly in elevation, of a modified part for a system such as shown in Figs. 1 and 2; and

Fig. 4 is a schematic wiring diagram of a further modification for a system embodying the principles of our invention.

A high-frequency tube oscillator generator unit is represented in Fig. 1 by the reference numeral 2. As is known to the art, such a unit usually comprises a housing which contains suitable electronic tubes, circuits, transformers and further equipment for the generation and over-all control of high-frequency energy which is delivered to a pair of connectors or terminals 4 and 6 carried by a shelf 8 on the outside of the unit. Secured to the terminals 4 and 6 are a pair of highfrequency power-supply conductors Ill and [2 to which a plurality of Work-treating stations are connected. Two such stations I4 and [6 are indicated in the preferred embodiment, each comprising as many work-receiving induction-heating coil-units or openings as desired. The coils of each work-heating station are similar and may be either individual coils or a unit equivalent to several coils, as is known to the art.

In the present embodiment being described, the induction-heating coil at each work-heating station is constructed as a unit by providing in a well-known manner, work-receiving holes or cut-out portions I8 and 20 in a plate 22 for the work-treating station l4, and work-receiving holes or cut-out portions 24 and 26 in a plate 28 for the work-treating station 16. As is customary in such constructions, slots 30 are provided between the cut-out portions and a single end of the associated plate so that in efiect each work-treating station comprises two work-receiving induction-heating coil-parts connected in series. Preferably the plates are made of copper orother highly conductive material.

For convenience and to allow a single operator to supervise both work-treating stations, the induction-heating coil-unit 22 is endwise alongside the induction heating coil-unit l6, and both are connected in series to the power supply conductors l and I2. For such connection, the slotted ends of the coil- units 22 and 28 are edgewise adjacent, and the power supply conductors l0 and I2 are electrically intimately connected to one side of facing end portions thereof, respectively. The other facing side portions of the plates are electrically intimately connected by a jumper conductor 32 in the form of a small copper plate. Consequently, the coil- units 22 and 28 are connected in a series circuit which passes directly, without interruption, from and between the two terminals 4 and 6.

In accordance with our invention, the induction-heating coil- units 22 and 28 are alternately repeatedly operated for'heat-treating work therein, without the use of make-and-break transfer switches. To this end, our system comprises a power-selecting means, or power-selector, which is external to the induction-heating coils and the power supply conductors, and is in no way mechanically connected thereto.

7 The power-selecting means is in the nature of a power-transfer means rather than a circuittransfer switch, and preferably has as many power-transfer means as there are work-treating stations, and as many power-transfer devices as there are work-receiving holes. Each powertransfer device comprises a metal coil or block, or the equivalent, made of a metal of high conductivity, such as copper or silver. Each powertransfer device is arranged to move between a position inside of the associated work-receiving hole that is in inductive relation therewith, and a position outside thereof that is out of inductive relation therewith. More specifically, the powerselecting means is indicated in its entirety by the reference numeral 42, and comprises. a plurality of power-transfer means 44 and 46 respectively associated with the work-treating stations 14 and I6. The power-transfer means 44 comprises power- transfer devices 48 and 50 associated with the induction-heating coil-unit 22; and the power-transfer means 46 comprises power- transfer devices 52 and 54 associated with the induction-heating coil-unit 28. The power- transfer devices 48, 50, 52 and 54 are shown for simplicity as having the shape of solid cylinders, each of which closely fits into a work-receiving hole of an induction-heating coil without contacting the walls defining such holes. More specifically, the

power- transfer devices 48, 50, 52 and 54 are associated respectively with the cutout portions 18, 26, 24 and 26 of the induction-heating coil- units 22 and 28 of the work-treating stations I4 andl6.

The power-selecting means 42 also comprises a plurality of reciprocable plates or supports 56 and 58 that are movable on fixed vertical guide rods 60 and 62 respectively. The plate 56 is associated with the power-transfer means 44, and has secured thereto depending supports or rods 64 for the power- transfer devices 48 and 50; and the plate 53 is associated with the power-transfer means 46 and has secured thereto depending supports or rods 66 for the power- transfer devices 52 and 54.

Each work-treating station also comprises one or more work-holders adapted to place work to be heat-treated in the associated induction-heating coil. As represented in Fig. 2, the work-treating stations l4 and I6 are provided with workholders 6B and 16, respectively, below the induce: tion-heating coil- units 22 and 28, respectivelyponthe side of the last which is opposite to the side at which the power-transfer devices are located. The work- holders 68 and 10 comprise work-supporting plates 12 and 74, respectively; each worksupporting plate having means for receiving;-

work-receiving adapters corresponding to the number of work-heating holes at the associated;-

work-treating station- As shown in Fig. 2 the support-plates l2 and 14 removably receive workreceiving adapters l6 and I8, respectively.- Each adapter comprises a seat for receiving a piece of work W and a central work-centering stem 80. This centering piece extends a significant distanceabove any work that might be placed on the ass sociated adapter. q

The work-treating stations [4 and It also comprise work-reciprocating means 82 and 84: for operating the work- holders 68 and 16, respectlvely. The reciprocating means 82 and 84 comprise reciprocable piston rods 86 and 88, respectively, operable in suitable pneumatic cylinders. These cylinders ar controlled either manually or automatically through any suitable controls represented by valves 94 and 86 for work- holders 68 and 10, respectively.

In the operation of the equipment thus far described, it may be assumed that the equipment is in the position shown in Fig. 2 where the work-treating station I6 is in the condition having its work-holder 10 loaded with ferrous or iron work-pieces W and its reciprocating means 84 holding the work-holder raised so that the work W is in the holes 26 and 24 of the induction-heating coil-unit 28; and where the worktreating station I4 has its work-holder 68 and reciprocating means 82 in lower position where work can be loaded on its adapters I8.

In such condition, it is to be observed that at the work-treating station I 6, the centering stems 80 of the work-holder I0 has raised the powertransfer devices 52 and 54 to a position well above the induction-heating coil-unit 28 of the associated work-treating station I6. In this position, the power-transfer devices are, for practical purposes, out of inductive relation with the induction heating coil-unit.

At the other work-treating station I4 the power- transfer devices 48 and 50 fall, by gravity, into a position in which they are fully immersed in the magnetic fields of the holes I8 and 0f the induction-heating coil-unit 22 of the worktreating station I4. Th highly conductive devices" 48 and 50 are in full inductive relation with the coil-unit 22, and the inductance of the coilunit is materially decreased with closed coupling between the devices and the coil unit.

If now the high-frequency tube oscillator generator 2 is energized to supply high-frequency energy to th power-supply conductors I0 and I2, current will new in a. single complete circuit, starting at a terminal 4 and passing successively through the power-supply conductor I0, along the coil-unit or plate 22 of the work-treating station I4, across the connection plate 32, along the coil-unit or plate 28 of the worktreating station I6, to the power-supply conductor I2, and to the other terminal 8. The inductance of this circuit is determined by the inductance of the conductors I0, I2 and 32 which remains unchanged, and the inductance of the two coil- units 22 and 28. These two coil-units are alike except for the material in their work-receiving holes. This material comprises the work-pieces W in the holes 22 and 24' of the coil-unit 28, and the power- transfer devices 48 and 50 in the holes I8 and 20 of the coil-unit 22.

Assume now that th work-pieces at the worktreating station I8 have been heated. The power to the generator 2 may be cut oil and the workpieces may b quenched if desired, by means not shown. The reciprocating means 82 and 84 are operated so that the position of the work- holders 68 and 10 are reversed, that is the work-holder I0 is lowered and the work-holder 68 is raised. When the work-holder 10 of the work-treating station I6 has dropped fully, the treated work can be removed therefrom, and new work placed thereon.

In dropping, the work-holder 10 permits the power- transfer devices 52 and 54 of the powertransfer means 46 to drop into the holes 26 and e 24 of the induction-heating coil-unit 28.

f The work carried by the work-holder 68 of the 6 work-treating station I4 is now in the work-receiving holes I8 and 20 of the coil 22, and devices 48 and 50 of the power-transfer means 44 are raised to positions out of inductive relation with the coil-unit 22.

Accordingly, the conditions of the work-heating stations I4 and I6 are reversed from that shown in Fig. 2; and work in the work-treating station I4 can be heated while treated work at the work-treating station I6 is being removed and new work placed therein.

It is to be observed that the over-all inductance of the induction-heating coil- units 22 and 28 in the single circuit is not materially altered when the conditions of the two work-treating stations I4 and I6 are reversed, since electrically the inductances of the coil- units 22 and 28 have merely been transposed. Hence, the power-selecting means 42 operates to transfer power between the coil- units 22 and 28 by alternate operation of the power-transfer means 44 and 46 associated, respectively, with the coil- units 22 and 28.

In the embodiment shown in Figs. 1 and 2, the power-transfer means 44 and 46 of the powerselecting means 42 are alternately or sequentially operated by the single pair of reciprocating means 82 and 84. However, it is clear that any suitable means can be used to place and remove work from the respective induction heating coil-units and in opposite sequence to remove and place the power-transfer devices of the power-transfer means 44 and 46 in the same coil-units.

Fig. 3 illustrates an embodiment in which a separate pneumatic reciprocating means controlled by a valve 92 operates to raise and lower power transfer devices 95 and 9! into and out of a cooperating induction heating coil. To this end, the reciprocating means 90 is in the form of a cylinder that operates piston rod 98 connected to the support plate I00 from which the powertransfer devices 95 and 9'! are dependingly carried, in a manner similar to that described in connection with the power-transfer means of Fig. 1.

Any suitable means may be used to control the power supply to the terminals 4 and 6 of the tube oscillator generator 2. A simplified scheme is shown in Fig. 4 which also shows an embodiment in which the power-transfer devices of the various power-transfer means are interlocked for the case of two alternately operated work-receiving holes of an induction heating arrangement, so that both power-transfer means cannot be simultaneously immersed in the work-receiving holes of the two coil-units.

-With reference to Fig. 4, ordinary commercial power lines are represented at I02 and I04. A switch- I05 is indicative of one or more protective or other controls such as an operator-operated foot pedal. Relay contacts I08 are arranged to control the primary energizing power so that the tube-oscillator generator 2 will not be energized unless a power-transfer means has its power-transfer device immersed in the associated work-receiving hole of the associated induction-heating coil unit.

A pair of coil-units are indicated at II 0 and I I2, and they are connected in a single uninterrupted circuit I I4 that includes the power supply conductors I0 and I2 extending from a tube-oscillator generator 2. A power-transfer device H8 is associated with the induction heating coil-unit H0, and a similar power-transfer device I20 is associated with the induction heating coil-unit II,2. Each of these power transfer devices is eiceaaci 7 connected to the end of a reciprocal piston rod I22 that-passes through a pneumatic cylinder I24 for the power-transfer device I I8 and I26 for the power-transfer device I20. A mechanical interlocking arm or lever I28 is centrally pivoted be tween the two piston rods and the ends of this lever passes through a space located between pins I30 and I32 for the power transfer device H8 and pins I34 and I36 of the power transfer dearms connected to a spanning arm I44 which spans the pivot of the lever I28. When the lever pivots so that it approaches one or the other of its extreme positions, it raises the switch to close the switch 642. This switch is in an electric circuit I46 having a relay I48 which controls the relay contacts I318. During any position of the lever I28 other than its extreme positions, the bar I44 drops and opens the switch I42. Consequently, the relay I48 is deenergized and the main circuit including the power conductors I02 and I04 is open. Consequently, the tube oscillator generator 2 can only be energized while a power-transfer device is in one of the inductionheating coils and the other power-transfer device is out of the other coil.

It is, of course, to be understood that work is placed in the induction heating coil that does 1 not have a power-transfer device therein and the other coil having the power-transfer device therein is in non-working condition.

We have described our invention in simplified embodiments for illustrating the principles thereof. It is obvious that it has wide application for power-transfer in connection with high-frequency v currents without the use of make-and-break contacts; and that the appended claims should be given their broadest interpretation consistent with their advance over the prior art.

We claim as our invention:

l. A high-frequency heating system of a type described comprising, in combination, a' single high-frequency supply-means, a pair of terminal-connections connected thereto, a plurality of high-frequency work-treating stations each having a highfrequency work-heater and workholding means'thereat, saidhigh-frequency workheaters" being accessible for selective loading and unloading, direct non-switching connections from said pair of terminal-connections to said highfrequency work-heaters, power-selecting means comprising-a plurality of movable metallic pieces, each piece being associated with a' single oneof work-treating stations, and support means ope able on said power-selecting means for selectively moving said metallic pieces out of each respective work station that'is supplied with a workpiece.

2. A high-frequency. system comprising. in combination, a single pair of high frequency supply-conductors, a plurality of high-frequency work-treating stations, each of said: stations having a high-frequency coil associated therewith, conductor-means connecting said pair of supply conductors-and said plurality of coils in a single common circuit, and power-selector means for rendering said coils selectively operable without changing said circuit, said power-selector means comprising a plurality of highly conductive metallic pieces, a piece being associated only with a single one of said coils, and supporting means for movably supporting said metallic pieces for selective movement, said supporting means comprising a first means for placing a first of said metallic pieces inside or outside of a first of said" coils, and a second means for placing a second of said metallic pieces inside or outside of a second of said coils.

3 A system as defined in claim 2 but further characterized by each of said coils comprising an inductionheatin coil, and work-holding means for said coils at a side thereof, said supporting means supporting said metallic pieces on the opposite side of said coils.

4. A system as defined in claim 2 but further characterized by interlocking means interlocking. said first and second means so that said first metallic piece is inside said first coil at a time when said second metallic piece is outside said second coil, and vice versa.

5. An induction heating system of a type described comprising, in combination, a plurality of work-treating stations, each work-treating station comprising an induction-heatingcoil, a work-holder for each of said induction-heating coils adapted to hold a piece of work ininductive relation to the associated coil, means for relative-- ly moving'each work-holder and its associatedcoil, whereby work on each work-holder is brought" into and moved out of inductive relation with the associated coil, a piece of metal of high conductivity associated with each coil, support means for moving each metal-piece relative to its associated coil, whereby each metal-piece is brought intoand out of inductive relation with the associated coil, and common energizing'means for simultaneously applying high-frequency energy to said coils, said support means being" operative such that when a workpiece is pos itioned within any oneof said coils, the metallic characterized by" supporting means supporting said coils so that they are stationary, and means for reciprocating said work-holders and said metal-pieces.

81 A system as defined. in claim '7' but further characterized by interlocking means between a. metal-piece associated with a coil of a first worktreating station and a metal-piece associated" of work-treating, stations, each work-treating station comprising; an induction-heating coil, a work-holder for each of said induction-heating coils adaptedto hold a piece of work ininductive relation to the associated coil, means for relatively moving each work-holder and its associated coil, whereby work on each work-holder is brought into and moved out of inductive relation with the associated coil, a piece of metal of high conductivity for each coil, supporting means for said metal-pieces permitting each of said metal-pieces to be moved from a position at its associated coil to a position away from its associated coil, the latter support means being operative such that when a workpiece is positioned within the coil at any one of said work treating stations, the piece of metal associated with the latter coil is moved to a position away from the last said coil energizing means comprising a single pair of power-supply conductors and connection-conductors directly connecting said power-supply conductor and coils together in a single circuit, and supporting means supportin each of said workholders and its associated coil so as to be relatively reciprocable.

References Cited in the file of this patent UNITED STATES PATENTS

Images