US2754396A - Workpiece supply fixture for induction heating apparatus - Google Patents

Description

July 10, 1956 w. B. ALBRECHT WORKPIECE SUPPLY FIXTURE FOR INDUCTION HEATING APPARATUS Filed June 5, 1953 2 Sheets-Sheet l July 10, 1956 w. B. ALBRECHT 2,754,396

WORKPIECE SUPPLY FIXTURE FOR INDUCTION HEATING APPARATUS Filed June 5, 1953 2 Sheets-Sheet 2 WORKPIECE SUPPLY FIXTURE FQR INDUCTION HEATING APPARATUS William B. Albrecht, Wauwatosa, Wis, assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis.

Application June 5, 1953, Serial No. 359,744

9 Claims. (Cl. 21910.69)

This invention relates in general to induction heating apparatus and more specifically to an improved fixture for automatically supplying workpieces to the heating station in a consecutive manner.

The heat treating of various kinds of objects by a high frequency current is well known and has proved successful in producing therein desired metallurgical characteristics. The object to be heated, commonly referred to as the workpiece, is positioned in a heating station, defined by a portion of an induction heating work coil, for a predetermined period of time, depending on the size and shape of the workpiece and the heat treating operation being performed.

In some suggested apparatus the work coil which defines the heating station comprises a hairpin like inductor, the workpieces passing through the inductor in a direction parallel to the lengthwise direction of the inductor while they are being heated. In other suggested apparatus the work coil comprises a number of conductor turns which define a vertical passage, the workpieces being positioned in the passage so that the conductor turns substantially surround it during the heating cycle. Of the two types of work coils it has been found that the work pice is heated more uniformly when it is substantially surrounded by the work coil.

Previously suggested induction heating apparatus which utilized a work coil that substantially surrounds the workpiece have not proved satisfactory for some types of heat treating operations. Specifically, in annealing thin wall cylindrically shaped workpieces, such as shell castings where the time required to heat the workpiece is relatively short, the apparatus does not supply workpieces to the work coil with sufficient speed to operate efificiently.

To overcome this disadvantage it is proposed, according to the present invention, to provide an improved induction heating apparatus which includes a fixture for positioning workpieces rapidly in the heating station. This fixture comprises a pair of substantially parallel fiat movable plates disposed transverse to and on opposite ends of the heating station. One plate provides a support for the workpiece in the station and the other plate provides a support for the workpieces to positioned in the station. The plates cooperate with each other on being moved to allow the workpieces to be fed by gravity to the heating station in a consecutive manner. in addition to supporting the workpiece in the heating station the lower plate provides means for rotating the workpiece to insure an even distribution of heat.

It is therefore an object of the present invention to provide an improved induction heating apparatus for heat treating workpieces in a consecutive manner.

Another object of the present invention is to provide an improved induction heat treating apparatus which includes a fixture for simultaneously supplying workpieces in a consecutive manner to a plurality of heating stations.

A further object of the present invention is to provide an improved induction heating apparatus including a fixture which automatically positions the workpiece in the States Patent 2,754,396 Fatented July 10, 1956 heating station and rotates the workpiece while it is being heated.

A still further object of the present invention is to provide an induction heating apparatus for consecutively annealing a plurality of thin wall cylindrical workpieces, the apparatus including a fixture having a pair of movable members which cooperate with each other to allow the workpieces to be positioned rapidly by gravity in the heating station in a consecutive manner.

Objects and advantages other than those mentioned above will become apparentfrom the following description when read in connection with the drawings in which:

Fig. 1 is a front view partly in section of the induction heating apparatus embodying the present invention;

Fig. 2 is a partial plan view of the apparatus shown in Fig. 1; and

Figs. 3 and 4 are schematic views of the apparatus shown in Fig. l.

The apparatus shown in Fig. 1 comprises generally a source of high frequency current shown schematically as a generator 12 which is connected to an induction heating work coil 13 for heat treating workpieces being supplied to work coil 13 by fixture i4.

Generator 12 and work coil 33 may be of any suitable type known in the art. As shown, work coil 13 comprises a plurality of fiat plate inductors 17, i8 and 19 which are disposed in parallel spaced relationship with each other and which are connected together electrically by cooling conduit 2% in a suitable manner. The inductors are provided with two cylindrical openings each, which form two passages 21 and 22 when the inductors are assembled with corresponding Openings in axial alignment.

Fixture 14, which operates to position workpieces automatically in passages 21 and 22, comprises a frame having a base 23 and a panel 24 disposed substantially perpendicular to base 23 and secured thereto by braces 26, 27. A shelf 23, disposed parallel to base 23 and rigidly secured to panel 24 in a suitable manner, serves to support a holding device 29 and a control switch 30 for generator 12. A centrifugal switch 31 is mounted on a top flange 25 positioned above shelf 28. Device 29 and switches 34) and 31 are all actuated by rotation of shaft 32 whose axis of rotation is parallel to the axes of passages 21 and 22 of work coil 13 and is spaced from each axis a predetermined distance. Shaft 32 is suitably journaled in portion 33 of bracket 34, which is rigidly bolted to panel 24.

Shaft 32 may be actuated by any suitable known means to cause it to either rotate or oscillate about its axis. In the preferred embodiment of the apparatus, shaft 32 is rotated about its axis by means of a variable speed motor 36 which has its shaft 37 connected to shaft 32 through a spring biased slip clutch 38.

A plate 39 is disposed on shaft 32 immediately below shelf 28 and is fixedly attached to shaft 322 by a key 41. Plate 39 when suitably moved to one position operates to support two columns of workpieces which are stacked in vertically disposed guide tubes 48 and 49, portions of which are shown in Fig. 1, and when plate 39 is moved to another position it is inoperable to support the workpieces. Guide tubes 48 and 49 are positioned above passages 21 and 22, respectively, of work coil 13 and aligned therewith so that the columns of workpieces rest on plate 39, the columns extending upward through openings 51, 52 in holding device 29 into guide tubes 48, 49 which are attached to device 29. In order to allow workpieces to be supplied to the heating station by gravity plate 39 is provided with an opening through which the lowermost workpieces may pass when the plate is suitably actuated. If desired a plurality of such openings may be provided in the plate, the openings being spaced cireumferentially .withrespect to each other. If the work coil has aplurality of heating stations the plate may also be provided with other openings which are in radial alignment with the circumferentially spaced openings. As

shown-in Eig.,3 plate 39 is substantially circular and is provided with two circumferentially elongated openings 42 and43 which-are disposed diametrically opposite each other and are located with 'theircenter lines an equal distance from the center of plate .39. Also since work coil 13 :has;two heating stations, the circumferential edge 4412f plate ,39 is recessed radially inward oppositeopenlugs ;42 and 43 to provide two othertopenings 416 and :47 which are radially aligned with openings42, .43, respectively.

.Assecond plate 53 is spacedaxiallybelowplate 39 cm shaft 32'and' fixedly attached to the latter by. a set screw 54. :Platei53 is similar to plater39 andoperates to sup port :the workpieces inpassages21 and 22of work coil 13 during theiheatingcycle. As shown in Fig. 3 plate 53 differs from plate 39 in that it has twoannular recesses 56 and 57. 'Recess 56 forms a-pair of circular edges 58 on the upper face of plate 53 and recess 57 forms alike pair of edges 59. One edge of each pair liesson circles which are concentric with shaft 32 and pass through the axes of passages 21 and 22. When plate 53 is rotated recess 56 passes under only the half of passage 21 which is nearest the axis of rotation of shaft 32, the radius 'ofone of the circular edges-58 being equal to'the distance between the axes of shaft 32 and'passage '21. Recess 57 issimilarly positioned with respect to passage 22. 'Therefore, while the workpieces are being supported in passages '21, 22 by plate 53, only half of the workpieces are in contact with the plate atany one'timeythe otherhalf'extending over one of the annular recesses 56-or 57.

"Disposed intermediate plate 39 and plate 53 is a U-shaped channel 61 which is secured to bracket 34 and which serves as a holding means for ceramic bushings 62. Ceramic bushings 62 are disposedon both ends of passages'21 and 22 of work coil 13 and are fitted into suitable recesses of channel 61. Thesetbushings when axially aligned with passages 21 and '22 act aslgnides for-centering the-workpieces in the passages and for preventing'the workpieces from coming in contact with any part of work coil 13.

"Holding device 29 operates .to hold each column of workpieces-in a fixed position when plate 39 is rotated to a nonsupporting position, for example, when any of t'heopeningsin plate 39 are positioned below passages 51, 52'of-device29. Device 29 comprises an actuating arm :63 having one end pivotally attached to a ,pivot pin 64 secured to top flange 25, and the other end operable'to hold the'columns of workpieces stationary. Since the diameters of the workpieces may vary slightly means are-provide'd-to-allow one column to beheld with aforce independent of the force on the other column. This holdingaction is obtained through spring 66 which biases arm 63 against cam,,67 that is positionedon. shaft32in apre'determined relationship with platet39. The-endof arm 63-which'acts to clamp the second lowermost workpiece 68 of-each column againstthe walls .of openings 51 and 52, includes two pins .71 and '72 whichjbear againstthe workpieces 68 when arm 63 isint'heholding position, pin 71 being rigidly fixed in arm .63 .whilepin 72 isbiasedI'by-a spring 73. This arrangementallows, the workpiece-*inteach column to beheldjfirmlylbecausethe holding'force'of .pins 771, 72 are independent of each other. When plate 39 is in a position to s,upp.ort .the column of workpieces, cam ,67 :opposes thebiasingr-actionsof spring'66-and allows the workpiecesto drop; and. rest ;on p'late39. I

--'Control switch 130 is actuated ,by a cam 76 which .is suitably positioned on shaft "32 to open switch 30 and cause =work -coil 13 to be-energized whenthe workpieces arcvpositione'd in passages 21 "and "22 :of work coil 13.

Cam 76 is a butterfly type cam and may be adjusted to .va y th time switch 30 remains n h open posit on- Likewise, centrifugal switch 31 is mounted on top flange 25 and suitably coupled to shaft 32 by a chain drive to prevent work coil 13 from being energized by switch 30 while shaft 32 is rotating below a predetermined speed.

The various electrical connections for the apparatus are shownin Figs. 3 and 4 which represent Schematic views of the apparatus shown in Fig. 1. Motor 36 is connected to a suitable voltage supply circuit 79 through a manually operated switch 80. Generator ,1'2'is also connected across circuit 79 through manually operated switch 81. Control switch 30 is connected to generator 12 through suitable control means 83, and centrifugal switch 31 is connected in shunt with switch 30. Control means 83 operates to cause work coil 13 to be energized from generator 12 only when both switches 30 and 31 are open.

The operation of the apparatus, shown in Fig. l in the deenergized position, is as follows. Switch 81 is move to the closed position to energize generator 12, and switch 89 is moved to the closed position toenergize'motor 36 and cause shaft 32 to rotate clockwise, as shown in the drawings. Rotation of shaft 32 opens centrifugal switch 31 which allows the energizing of work .coil 13 to be controlled by switch 39.

As shown in Fig. 1 the stacks of workpieces in guide tubesdii and 49 are supported by plate 39 and remain supported by the plate until immediately before the openings idZ and 46 in plate 39 are positioned below passages 51 and 52 in device 29, at which time arm 63 is moved to the clamping position by action ofbiasing spring 66 and cam 67. Arm 63 when in the clamping position causes pins 71 and 72 to force the second lowermost workpiece 6'8 of each stack against the walls of passages 51 and '52 thereby holding the stack of workpieces in a-stationary position. Arm 63 remains in this position as shaft 32 continues to rotate causing openings 42 and 46 of plate 39 to pass under passages 51 and 52 which allows the lowermostworkp-iece 89 in each stack to drop into passages *21 and 22.

Plate 53 is positioned on shaft 32 with its openings circumferentially offset from corresponding opening'in plate 39 so'that by the timethe'bottom of the workpieces 89 have reached the plane of plate 53, the latter is in a position to supportworkpieces -89 in passages 21 and 22. This condition is shown schematically in Fig. 3 where the Workpieces 89 which were lowermost in each tube have fallen through the radially aligned openings 42 and 46 in plate 39 into passages 21 and 22. Cam 67 is shown about to actuate arm 63 to the nonclarnping position and allow the stacks of workpieces to drop and be supported as before by plate 39. Control switch 30 as shown in Fig. 3 is actuated to the open position by cam 76 ,thus allowing work coil 13 to be energized from generator 12. 7

If desired, workpieces 89 presently positioned in passages 21 and 22 may be rotated about their respective axes by suitable means while being heated. As shown in Figs. 3 and 4 only one-half of the bottomof each workpiece-89 is in sliding contact with the plate at any one time because the other half extends ,over onetof the annular recesses 56 or 5'7. Therefore, the friction between the bottom of the workpieces 68 and the portions of the plate adjacent the annular recesses 56, 57 causes each workpiece to be turned clockwise about its axis. T 0 provide more rotation of the workpiece the .coefiicient of friction of the contacting'portion may be increasedinany suitablemanner, such as by knurling the contacting portions or inlayinga piece of material having a higher coe'flicientof friction than the plate. I

At theend-ofthe heating cycle plat e,53 hasheenn'ptated to'a position so that openings 43and47 of plate 53 are passed under paS. s 21, 2 2tof work coil .13 ftoallow the heated workpieces to ,drop thIQughjhe5e gp em This conditionis shownschematically in,Eig.i4 Where the heated workpieces are beginning to drop from passages 21 and 22, control switch 36 is then in the closed position and arm 63 has just been moved to the clamping. position by cam 67 and spring 66. Further rotation of shaft 32 brings the plates to a position similar to that shown in Fig. 3, but with shaft 32 being rotated 180 soas to position openings 43 and 47 where openings 42 and 46 are positioned in Fig. 3. The operation is then repeated.

If for some reason plate 39 or plate 53 becomes jammed by a workpiece so that shaft 32 cannot rotate, clutch 38 allows motor shaft 37 to continue rotating. However, since centrifugal switch 31 which is actuated by rotation of shaft 32, is then closed, work coil 13 will not be energized and the danger of overheating a workpiece is eliminated.

The apparatus is shown in the drawings utilizing only one work coil that defines two heating stations. However, it will be apparent to one skilled in the art that a plurality of work coils may be used in spaced relationship with each other if desired, and it will also be apparent that the work coil may define one or more heating stations.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising a work coil defining a heating station; means for positioning workpieces in said station in a consecutive manner comprising means dis-- posed above said station for stacking said workpieces, a first movable member disposed above said station and below said stacking means, said first member being operable in one position to support the lowermost workpiece of said stacked workpieces and inoperable in another position, a second movable member disposed below said sta-. tion, said second member operable in one position to sup-. port a workpiece in said station and inoperable in another position, mechanical means common to both members to move said members from said one position to said other position to cause said workpieces to be positioned in a consecutive manner by gravity in said heating station; means for energizing said work coil with a high frequency current and means to control said energizing means .in a predetermined manner with respect to said positioning means.

2. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency cur' rent, said apparatus comprising a work coil defining a heating sttaion; means for positioning workpieces in said station in a consecutive manner comprising means disposed above said station for stacking said workpieces, a first movable member disposed above said station and below said stacking means, said first member being operable in one position to support the lowermost workpiece of said stacked workpieces and inoperable in another position, a second movable member disposed below said station, said second member operable in one position to sup-. port a workpiece in said sttaion and inoperable in anotherposition, an actuating shaft connected to move said members from said one position to said other position to cause said workpieces to be positioned in a consecutive manner by gravity in said heating station, and means to move said shaft; means for energizing said work coil with a high frequency current and means to control said energizing means in a predetermined manner with respect to said positioning means.

3. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising a work coil having a workpiece receiving passage; means for positioning workpieces in said passage in a consecutive manner, said positioning means including a fixture comprising an actuating shaft having its axis of rotation parallel to the axis of said workpiece receiving passage and spaced laterally therefrom a predetermined distance, means to rotate said shaft, a first plate disposed above said passage and fixedly attached to said shaft, a second plate disposed below said passage and fixedly attached to said shaft, each said plate having an opening disposed therein spaced radially from said of rotation of said shaft said predetermined distance, and means disposed above said first plate for stacking said workpieces along said axis of said passage with the lowermost workpiece in contact with said first plate, said plates being disposed on said shaft so as to cooperate with each other on rotation of said shaft to cause each said lowermost workpiece to be positioned consecutively in said passage; means to energize said work coil with a high frequency current; and means to control said energizing means in a predetermined manner with respect to said positioning means.

4. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising a work coil having a workpiece receiving passage; means for positioning workpieces in said passage in a consecutive manner, said positioning means including a fixture comprising an actuating shaft having its axis of rotation parallel to the axis of said workpiece receiving passage and spaced laterally therefrom a predetermined distance, means to rotate said shaft, a first plate disposed above said passage and fixedly attached to said shaft, a second plate disposed below said passage and fixedly attached to said shaft, each said plate having an opening disposed therein spaced radially from said axis of rotation of said shaft said predetermined distance, means disposed above said first plate for stacking said workpieces along said axis of said passage with the lowermost workpiece in contact with said first plate, said plates being disposed on said shaft so as to cooperate with each other on rotation of said shaft to cause each said lowermost workpiece to be positioned consecutively in said passage, and means cooperating with said second plate to cause rotation of said workpieces positioned in said passage when said work coil is energized; means to energize said work coil with a high frequency current; and means to control said energizing means in a predetermined manner with respect to said positioning means.

5. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising a work coil having a workpiece receiving passage; means for positioning workpieces in said passage in a consecutive manner, said positioning means including a fixture comprising an actuating shaft journaled by said fixture with its axis of rotation parallel to the axis of said workpiece receiving passage and spaced laterally therefrom a predetermined distance, means to rotate said shaft, a first circular plate disposed above said passage and fixedly attached to said shaft, a second circular plate disposed below said passage and fixedly attached to said shaft, each said plate having a circumferentially elongated opening disposed therein and spaced radially from said axis of rotation of said shaft for said predetermined distance, a guide tube disposed above said first plate for stacking said workpieces along said axis of said passage with the lowermost workpiece in contact with said first plate, said plates being disposed on said shaft so as to cooperate with each other on rotation of said shaft to cause each said lowermost workpiece to be positioned consecutively in said passage; means to energize said work coil with a high frequency current; and means to control said energizing means in a predetermined manner with respect to said positioning means.

6. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising a work coil. having a. workpiece receivingpassage; means .for positioning workpieces in said passage in a consecutive manner, said positioning means including a fixture comprising an actuating shaft journaled by said fixture with. its axis. of rotation parallel to the axis of said workpiece receiving passage and spaced laterally therefrom a predetermined distance, means to rotate said shaft, a first circular plate disposed above said passage and fixedly attached to said shaft, a second circular plate disposed below said passage and fixedly attached to said shaft, each said plate having a circumferentially elongated opening disposed therein and spaced radially from said axis of rotation of said shaft for said predetermined distance, a guide tube disposed above saidfirst plate for stacking said workpieces along said axis of said passagewith the lowermost workpiece in contact with said first plate, said plates being disposed on said shaft so. as to. cooperate with each other on rotation of said shaft to cause each said lowermost workpiece to bepositioned consecutively insaid passage, and means to hold said workpieces in stacked position while said lowermost workpiece. is being positioned in said passage; means to energize said work coil with a high frequency current; and means to control said energizing means in a predetermined manner with respect to said positioning means.

7. Apparatus for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising a work coil having a workpiece receiving passage; means for positioning workpieces in saidpassage in a consecutive manner, said positioning means including a fixture comprising an actuating shaft journaled in said fixture with its. axis of rotation parallel to the axis of said workpiece receiving passage and spaced laterally therefrom a predetermined distance, means to rotate said shaft, a first circular plate disposed above said passage and fixedly attached to said shaft, a second circular plate disposed. below said passage and fixedly attached to said shaft, each said plate having a circumferentially elongated opening disposed therein. with its center spaced radially rom said axis for said predetermined distance, means for stacking said workpieces along the axis of said passage above said first plate with the lowermost workpiece in contact with said first plate, said plates being positioned on said shaft with respect to each other so as to cooperate with each other onrotation of said shaft to cause each said lowermost workpiece to bepositi'oned consecutively in said passage, means to hold said workpieces inv stacked position while'said lowermost'workpiece is being positioned in said passage, and means to cause rotation of said workpiece. positionedinsaid passage comprising an annular recess disposed in said second plate concentric with said shaft to form two radially spaced circular edges on the upper face of said second plate, the radius of one of said circular edges being at least equal to said predetermined distance; means to energize said workcoil with a high frequency current; and meanscto control said energizing means a predetermined relationship with said positioning means.

8. Apparatus for consecutively heat treating a plurality of workpieces by induction from. a high frequency current, said apparatus comprising a work coil having a plurality of workpiece receiving passages; means for simultaneously positioning workpieces insaid passages in a consecutive manner, said positioning means including a fixture comprising an actuating shaft suitably journaled in said fixture with its axis of rotation parallel to the axes of said workpiece receiving passages. and spaced laterally from one of saidpassages a predetermined distance, means to rotate said shaft, afirst circular plate disposed above said passages. and fixedly attached to said shaft, a second circular plate disposed below saidpassages and fixedly attached to. said shaft, each said plate having apair of radially spaced circumferentially elongated openings having, radial widths sufiicient to allow workpieces to pass through said openings unobstructed when said openings are aligned with said passages, means for stacking said workpieces along the axes of said passages. above said first plate with the. lowermost workpieces in contact with said first plate, said plates. being positioned on said shaft with respect to .each other so .as to cooperate with each other on rotation of said shaft to. cause said lowermost workpieces to be positioned in said passages, means to hold said workpiecesin stacked position while said lowermost workpieces are being positioned in said passages, means. to energize said workcoil with a high frequency current; and means to. control said energizing means in a predetermined relationship with said positioningmeans.

9... Apparatus. for consecutively heat treating a plurality of workpieces by induction from a high frequency current, said apparatus comprising, a work coil having a plurality of workpiece receiving passages; means for simultaneously positioning workpieces in said. passages in a consecutive. manner, said, positioning means including a fixture comprising anactuating shaft suitably journaled in said fixture with its axis of rotation parallel to the axes of said workpiece. receiving passages and spaced laterally from one of said passages a predetermined distance, means to rotate said shaft, afirst circular plate disposed. above said passages a-nd fixedly attached. to said-shaft, a second circular plate disposed below said pmsages and fixedly attached to said shaft, each'sa-id plate having a pair of radially spaced circurnferentially elongated openings having radial widths suflicient to. allow workpieces to pass through said openings unobstructedwhen said openings are aligned with said passages, means for stacking said workpieces along the. axes of said-passages. above'said first plate with the lowermost workpiecesincontact with said first plate, said plates being-positioned on said shaft with respect to each other so-asto cooperate with each other on rotation of said shaft to causesaid lowermost workpieces to bepositioned in said passages, means to hold said workpieces instacked position'. while said: lowermost: workpieces are being positioned insaid passages, 31111211163118 to cause rotation of said workpiecespositionedq in said passagescomprising annular recesses; disposed'in said second plate concentric, with said shaft to. form radially spaced circular edges on the upper face of said plate, said radially spacing of two of said edgesbeingequalto the radial spacing of said elongated openings andthelradiusof one of said circular edges. being" equal to; said predetermined distance; means to energize said work coil with a high frequency current; and means. to. control said energizing means in a'predetermined relationship with said positioningmeans.

References. Cited in the file of this patent UNITED STATES PATENTS 1,776,697 McGuinness et a1. Sept. 23, 1930' 1,784,967 McGuinness Dec. 16, 1930 2,598,015 Richardson May 27, 1952 2,604,576 Collyer July 22, 1952 2,647,199 Wharfi July 28, 1953

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