US2509670A - Centrifugal casting means - Google Patents

Description

y 1950 E. R. CAPITA ETAL 2,509,670

CENTRIFUGAL CASTING MEANS Filed April 14, 1947 s Sheets-Sheet 1 .IJFTURNEY May 30, 1950 E. R. CAPITA EI'AL CENTRIFUGAL CASTING MEANS 3 Sheets-Sheet 2 Filed April 14, 1947 May 30, 1950 E. R. CAPITA E'IAL CENTRIF'UGAL CASTING MEANS 5 Sheets-Sheet 3 Filed April 14, 1947 g MH mi N Z a M f atented May 30,

UNITED STATES PATENT OFFICE 2,509,670 CENTRIFUGAL CASTING MEANS Emil R. Capita, North Bergen, and Thomas A. Feehan, Allendale, N. J. said Feehan assignor to Ecco High Frequency Electric Corp., North Bergen, N. J., a corporation of New Jersey Application April 14, 1947, Serial No. 741,222

Claims.

true of those manufacturers who are interestedin commercially producing articles by centrifugal casting methods, this method being a special type of casting in which a mold and its flask are whirled or revolved so that metal is thrown outwardly by centrifugal force and shaped in accordance with the form of the particular mold held within the flask. Articles formed by centrifugal casting are desirable as they have a minimum of shrinks or blowholes and the metal has a relatively dense structure.

One of the dilficulties with available centrifugal casting mechanisms is their extremely limited field of use; most of them are designed and built to perform some particular casting task and are restricted almost solely to repeated performance of only that task. Existing means for heating and melting a metal charge are limited generally to use with a particular crucible or furnace. With other mechanisms there is lacking a most desirable or optimum passage of molten metal from a crucible into a flask mold.

The present invention aims to overcome or minimize the above and other disadvantages or objections by providing a new and improved centrifugal casting device which is adapted to be utilized with various flasks and crucibles and which embodies new and improved means for heating and melting metals. The invention further contemplates the provision of means adapted to facilitate foolproof operation of the present new and improved centrifugal casting mechanism and to facilitate passage of molten metal from a crucible into the mold of a flask.

An object of the present invention is to provide a new and improved centrifugal casting mechamsm.

Another object of the invention is to provide a new and improved centrifugal casting mechanism adapted to be used with various sizes of molding flasks.

Another object of the invention is to provide a new and improved centrifugal casting mechanism which is foolproof in operation.

Still another object of the invention is to provide for improved passage of molten metal into a mold.

A still further object of the invention is to provide a new and improved heating means for use with a centrifugal casting mechanism.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will" be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings, forming a part of the specification, wherein:

Fig. 1 is a perspective View illustrating a preferred embodiment of the invention;

Fig. 2 is a top plan view illustrating a preferred embodiment of the present invention;

Fig. 3 is a fragmentary sectional view taken along the line 33 of Fig. 2;

Fig. 4 is a sectional view showing certain of the parts in heating relationship; and

Fig. 5 is a view of a wiring diagram showing a preferred form of electrical hook-up.

Referring again to the drawings and more particularly to Fig. 1 thereof, there is shown a cabinet 1 adapted to contain any suitable mechanism for creating a high frequency current for use with the centrifugal casting mechanism to be hereinafter described.

The high frequency current creating means is.

shown connected by suitable cables 2, 4, and 5 with the cabinet "I at the left side of Fig. 1. These various connections will be hereinafter described in greater detail. The centrifugal casting mechanism itself is contained within an outer casing 8 at the upper part of the cabinet 1 and is shown more particularly in Figs. 2, 3 and 4. of the drawings.

The mechanism shown in detail in Figs. 2 and 3 comprises a platform or base it] of asbestos through which extends a rotatable shaft I! that connects beneath the platform ill with a motor l3 (Fig. 4) The shaft Ii is shown extending; through a suitable bearing i4 secured by bolts to, the base ii] and it may be provided adjacent the upper part thereof with a flanged plate It to which is secured, by bolts IT, a bracketlike mem-. ber i8. An arm l9, secured by bolts 20 to one, side of the bracketlike member I8, is shown provided with a plurality of notches or apertures 22 for receiving the end of a threaded key 23 to lock or maintain in desired position an adjustable counterweight 25. The counterweight 25 has an aperture therein for receiving the counterweight arm 19 and may be moved to a suitable position along the arm, the particular position in which. it is locked or secured depending upon the weight of objects located at the opposite side of the bracketlike member I8.

Connected with opposite ends of the bracketlike member is by nuts 26 and 29 are spaced arms or shafts 3| and 32, each of which is provided with threaded end portions 33 and 3t and relatively smooth guide surfaces 35 and 36. The shafts or arms 3| and 32 are preferably electrically insulated by any suitable means, such as insulating members 3!! this avoids induced electrical circuit through arms 3| and 32, counterweight arm l9, and mold holding means 32 and 43f A pair of channel-like structures 31 and at. are shown carried in spaced relationship on the threaded portions 33 and Met the spaced shafts 3| and. 32, each of the channel-like structures having apertures at opposite sides thereof through which extend the spaced shafts arena 32. The channel-like structures may be'rtained in desired position by nuts 40 and 4| located at opposite sides of the flanges throu h w ich extend the. spaced shafts 3| and 32 Positioned within the grooves or channels of: the channellike. structures 3! and 38. are. substantially U; shaped flask receiving members 42 and 4.3.. A mol flask 44 may be lowered into the openin of the upwardly disposed U-shaped portions of the flask receiving members 42 and 4.3. with one end. of the dash in abutting relationship with a plate member it. carried at the outer side. of the channel-like structure. 3.8; the opposite end of. a mold in the. flask is open so that metal from. a crucible 50 may be transferred into the mold when the. device is in operation.

The crucible 5.0 is shown retained Within a opening. of a transverse member 52 carried. at opposite sides thereof by inwardly extendingportions. 53. and 55 of tubular support members 55 and 51. The hollow portions of thetuhular meme, hers. 56. and. 1. are shown extending about the spaced arms at and 32. and they. may mevealong, these; arm. members inconnection with the operation. of the mechanism, as will be laterdescribed.

The. transverse member .52 is. shown provided with an extension 58 adapted to be received by, acut-out. portion of. the bracketlilre. member. it to assist in limiting movement of the transverse. member. in. the direction of the vertical shait H. In some instances it may also. be. desirable to provide a collar member 59. on one. of. the shafts St or 32. for limting thev extent of. movement .01- thetransverse member. 52 along. the. supporting shafts. The purpose of the collar 59 or. outwardly extendingv portion 58 is tofacilitate alignment of the lower part 55 of thecrucib1e5fl with a heating device ti. When the transverse member 52 and-crucible Fifiare. moveclto position a'djacent' the upright shaft H- these. stops tend to correctly position the lower part 55 of thecru ci-ble 50- accurately with respect to" the heating means 6t so that danger of damaging any of the operating parts in connection with the operation ofthe mechanism is minimized.

A light spring or other resilient-means 6251s shown extending about one of the shafts. 3|. and is adapted to normally urge the transverse member 52 and crucible 5|] outwardly towardthe open endrof a flask it carried by the supporting. brackxets- 42- and t3 so. that a dischargeopening at. the side ofthe crucible will. move into contiguous re lationship with an entrance. opening to amold carried within the flaskv M. Thereasonior this spring 62 and its outward urging effect will be hereinafterv explained in. greater detail.

' The crucible. 50., ispreferably provided Withan 4 outwardly extending flange 64 adapted to rest against adjacent edges of the aperture in the transverse member 52 and the crucible extends downwardly through the opening 5| so that the major portion 55 thereof is positioned beneath the transverse portion 52. The upper part of the crucible 5B is shown provided with a charging opening 5| for facilitating insertion of material and with an exit or discharge opening 65 at a side wall thereof facing toward the flask 44. Preferably the side walls of the refractory material B! with which the crucible 59 is lined are inclined at the discharge side of the crucible toward the exit opening 65 to provide an improved flow of molten metal to and through the discharge opening upon operation of the mechr e -v The means for heating the crucible and melting metal in it is shown more particularly in Fig. 4. The heating means is shown in Fig. 4 in l vated h ating osition s rroundi t downwardly. x en n Horton or the rucible; and in Fi s.- 2 nd. 3 in a. owe non-heatin Position. As how beheat i mean 6'. s m prises an ndu tio il; 13 mou ted. on a. P ate. m mber 10 car ed. y aba r o sho ts... v ti al r disposed ho w sha s Q8 an 6 Shai s 6. and 6 x end rou h an e ectri al insulatin bushi H. fit ed i t he a be tos ba "2; a c mercially v i able mate l n n. by t e trade name My a ex as br r n sat s acto or he bu hin H; but. any su table materi l. be used. The in ct on h atin coi a be. car ed on: the brack or plate in. y clam and o rangement. e c l tse f pr i rabl commieing a length of substantially helically; arranged pper tub n form d o sumoi nt diam er to rec iv with the ce ter rt on or once a the e: of. he depen in or i n o the oruo ble .0-. panddown mo m n o th hollow h fts it and 6 9. elevates. and lowers the heating. coil 1 :3

T e ho lo coppe ubin ompos n h c i 13 may beo neote at he end thereo b @9 pl nss 63: w th the h l w h ft n a d lower nds. of he haf may e conn ct d.

by u be r other x e onn ti nsw t a. su ply of cooling water so that heating eitects gen erated in the. coil by eddy currents or the likemay be removed.

The. hafts; 68; a 6.9. ma b con e ted: n suitable manner with the cables 4 and 5 net-erred to in connection with Fig. l of the drawings-the latter cablesextending into the cabinet I and bee ing connected with a suitable high frequency. Q1112! rent generating means, therein.

Adjacent one endof, the plate-lilis shownahole low block member. l5, preferably. on iasbestoseor the like having an aperture T5 at .itslupper part. The aperture 15 is adapted to. receive a. pin if! care I ried by and extending downwardly: from. one of the arms 5:4. of a tubular member 511. movably mounted on a shaft 3|. lhe spaced shafts. 68 and 69 are. adapted to move. vertically so that the coil 13 may be'moved'upwardly. to a; position surrounding or extending, about: the downwardly extending part 55 of the crucible 55; As'gthe. coil 13; plate. 10 and block 75.1;move. upwardly; the downwardly extending pin-H. may be guided into the aperture 16, tothus facilitate. correct: align..- ment of the parts. and positioning ofrthe. heating coil about the lower: part; of; the crucible. When the coil is elevated surrounding the, crucible, as shown, in. Fig. 4, high frequencycurrent may be suppliedtothecoil to heat by induction and melt a chargaof-rmaterialcarriedin the crucible; such heating is rapid and eficient and favorably increases the rate of production over ordinary resistance elements of the type used in irons or toasters.

' After a charge of metal in the crucible 50 has been melted, the coil .13 may be quickly lowered to the position indicated in Figs. 3 and 4 of the drawings. As pin 1'! moves out of aperture 16 in block member 15, the spring 62 urges the transverse arm 52 and crucible 58 outwardly toward a mold carried within flask 44. The spring 62 urges the crucible outwardly immediately upon freeing of the crucible but not so as to objectionably slam the crucible against flask 44 or its mold. The spring is preferably of such length as to become extended to full length when the crucible discharge opening is in proximity to the mold inlet opening, but it may be such as to become fully extended when the crucible exit opening is spaced about one inch from the mold inlet opening. With the latter spring the action is as follows: since the shaft H normally commences to rotate when coil 13 reaches its lower position, centrifugal force moves the crucible the remaining one inch and when the crucible is stopped by the flask, molten metal is thrown outwardly through the crucible discharge opening 65 into a mold cavity within the flask. Thus, with the shorter spring, the crucible moves outwardly quickly and centrifugal force is utilized to move the crucible only a short distance; this feature means that metal may pass from the crucible to a mold within a short period of time after the shaft l I commences to rotate. Where the spring is of a length to move the mold into contact with the flask, centrifugal force promptly effects movement of the metal into the mold. Any suitable number of springs may be utilized and they may be used on the shaft 32 as well as on the shaft 3 I.

It is desirable to minimize the possibility of damage to the present mechanism by inadvertent rotation of the shaft ll during intervals when the heating mechanism BI is in elevated position with the coil 13 extending about the crucible 50. In the preferred embodiment of the present invention, such accidental damaging is prevented by interlocking connections between the heating mechanism BI and the motor 13 which is connected with and effective to rotate the shaft H. When the heater coil is raised to elevated position about the crucible 50 by the lever or arm 18 (Figs. 1 and 4), the contacts 19 and 88 are closed by the bar Bl so that the coil 13 may be energized by high frequency current supplied through the leads 4 and 5. It will be noted that when the contacts 19 and 80 are in closed relationship the contacts 82 and 83 are open by reason of the fact that the bar 84 is out of contact therewith and hence closing the motor switch 86 against the contacts 81 and 88 is ineffective to admit current to the solenoid 89 for moving the motor contactor 9| to close the contacts from a power line to the motor l3.

When the arm or lever 18 is moved so as to lower the coil '13, the bar 84 closes the contacts 82 and 83 and hence current may flow to energize the solenoid 89 and move the motor contactor 9| into position to admit current from a power line to the motor l3.

When the motor push-button 88 is pressed, the motor contactor circuit is partially closed, depending upon whether or not the bar 84 is in position to connect the contacts 82 and 83. Ifthe coil 13 is in elevated position and the bar 84 away from the contacts 82 and 83, the motor l3 will not operate. Conversely when the coil 13 is in lowered position the contacts 82 and 83 will be closed and the motor may start. This interlocking arrangement normally prevents operation of the motor unless the coil assembly is clear of the rotating parts.

Any suitable speed regulator may be connected, in known manner, into the motor circuit so that actuation of the controlling handle or wheel 92 is effective to vary the speed of the motor and hence the revolutions per minute of the shaft II and mechanism carried thereby. A suitable speed indicating pointer and plate 94 may be provided to facilitate adjustment of the speed to that required.

When the switch 95 is closed across the contacts 91 and 98, the high frequency current generating means within the cabinet I is so connected with the heating coil 13 by the cables 4 and 5 that when the heating coil 13 is in elevated position, with the bar 81 connected across the contacts 19 and 80, the current may operate the heating coil 13; thus the switch 95 and bar 8| are interlocked with each other and high frequency current flows through the coil 13 when it is in elevated position around a crucible. Pressing the switch I00 is effective to operate the relay and switch construction shown at I03 and to cease supplying high frequency current to the heating coil '13 even though it is in the elevated position.

In connection with the operation of the above described mechanism, a charged crucible may first be placed into the holder or aperture of the transverse member 52, the supporting shafts 3| and 32 rotated over the heating means GI, and then the downwardly extending part 55 of the crucible placed into alignment with the coil 13 by pressing it inwardly toward the shaft I I. As the coil 13 is elevated by raising the lever or arm 18, the guide pin 11 moves into the aperture 16 in the block member 15 and insures correct alignment of the parts. When the heating mechanism BI, is thus raised to elevated position the lever or arm 18 may be rotated slightly to one side so that it may rest upon a ledge 12 (Fig. l) to hold the heating mechanism 6| in elevated position.

The flask 44, which usually consists of a metal tube in which is placed a prepared refractory mold, may next be placed into the openings of the flask holders 42 and 43, with the outwardly disposed end of the flask 44 resting against a plate member 46. The high frequency current to the coil 13 may next be turned on by pressing the push-button 95 to close the contacts 96 and 98.

When a metal charge in the crucible has been brought to a molten condition and is ready for castinathe motor push-button 86 may be closed to connect the contacts 81 and 88. This partially closes the motor contactor circuit; however, since this circuit is also controlled by a limit switch used in connection with the coil raising mechanism, the motor I3 will not commence to rotate the shaft ll until the arm 18 is moved to its lower position with the bar 84 connecting the contacts 82 and 83. This interlocking arrangement minimizes the possibility of accidental rotation of the shaft ll until such time as the coil assembly has moved to its downward position, as shown in Figs. 2 and 3.

When the heating mechanism 6| is movedto its "lower position, the relatively lightifs'pring 62 may urge the crucible '50 and its carrying mechanism outwardly toward the open end of a mold carried within the flask M. This quickly places the crucible discharge opening 65 adjacent orin proximity 'to'th'e entrance opening of a mold and as the shaft l l commences to rotate, 'cen-t-rifugal force causes the molten metal to flow outwardly and upwardly along the inclined side walls of the crucible 50 adjacent the "discharge, opening 65 in the side of the crucible. The molten metal will tend to acquire some such position :as is indicated in the dotted lines in Fig. 3. Since the molten metal thus leaves the crucible through the "discharge aperture 65 in the side of the crucible, a bottom pour effect is obtained so that clean metal tends to first enter. the mold cavity and the lighter residue oxides or impurities to enter the mold lastly and to form in and uponthe sprue, which is generally removed from the article subsequent to the casting operation.

The revolutions of the motor 13 and shaft 11 per unit of time may be selectively determined by means of the Wheel '92 and indicating means 94.

It will be seen that thepresent inventionprovides a new and improved mechanism for cen- '-ti'ifugall-y casting metals. The induction heating :means, which is readily movable into and out of -operative position about a crucible, provides .a "very rapid and eliicien't heating means. The Imechanism or device embodies. great flexibility o'f :usein that the flask holding means may-be selecitivly positionedtohold flasks of various sizes :and lengths. 'The crucible and its carrying memfloe'r may be readily positioned at appropriate ilocations along "the supporting arms to permit Lrapid insertion and removal offiasks of the same or 'differe'nt sizes. "The 'cruci'bl'emoves into opera.- "tive relationship with a fiask mold regardless of whether the'moldis "of relatively short or long dimensions. A new and improved "interlocking feature minimizes the possibility of accidentally damaging the machineand injuring an operator 1 by reason of-the fact that the heating 'means -is so connected "as to requirem-ovement of the heating means out "of heating position prior to actuation "of the rotating parts of the "mechanism; the present centrifugal casting mech- "anism is thus rendered substantially foolproo in operation.

As various changes may "bemade "in the form, construction and arrangement of the parts herein vvrithout departing from the spirit "and. "scope of- -th-e invention and without sacrificing any of it's-'advant'ages,'- it is to beunderste'od -'-that all matter herein is to' "be interpreted *as illustrative and not in a limiting sense.

Having "thus described our =invent-ion, w

c aim:

"'1. ln'a -device of'the' class describe'd,'the-comloihat-ion' of a mem'ber rota-table about a-central "axis, crucible "supportingmeans slidably fitted on and rreely*reciprocable along said rotatable tion ofsaid rotatable member,--and mean's tor "encircling :said c'ruc'ible 'with athe :he'atmgecoil, whereby 1 material within the crucible nmay .abe

- emitec.

2.1111 adevice of the class described,- the com bination of a member rotatable about a central axis, crucible supporting means slidably fitted on and freely reciprocable along said rotatable memberbetween an inward heating position adjacent said central axis to an outward position on the member, an open-ended heating coil located adjacent said central axis out of heating relationship with respect to a crucible supported by said supporting means and with its axis out of alignment with that of the crucible during .rotation of said rotatable member, complementary pin and recess means carried by said cruci- :ble supporting means and heating coil for aligningthe open end, of the coil with the crucible during movement of one toward the other, and means for encircling said crucible with the heating coil, whereby material within the crucible may belmelted.

3.. In a device of the class described, the com- .bination of a rotatable member, .a crucible bracket. slidably mounted on and freely movablea'long said rotatable member from a heating location adiacent its center of rotation to an outwardlw cation thereon, a crucible carried by and movable withzsaid bracket having a portion depending below said bracket, an open ended heating :coil adjacentrsaid center of rotation located out ofproxim-ity to the depending portion of said crucible :during in'onelheating periods and movable to encircling position around the. depending portion of the crucible for heating material within the crucible, and means for elevating said heating coil-around the depending portion of the crucible.

4. Inc device of the. class descrihed, the combination ofv a revolvable arm, crucible supporting means slidably mounted on and itreely movable along said revolvable arm, an open ended heating coil adjacent .an .inner end of said revolvable arm and movable into position around a CIllCiblcdJ-ll'w ing periods when the revolvable arm is at restiand said crucible is adjacent said inner end of the revolva'ble arm, said coil being movable away from said position around said crucible .prior torevclution of said farm, :means formcving the heating coil into "position around the crucible and for moving it away therefrom, and interlocking means preventing initiating revolution "of said 'arm while the crucible is encircled by sa'id' heab ing coil.

5. In a device of the class described, t-he combination of .a irevolvable arm, crucible supporting means slidably fitted on .said arm and normally freely reciprocable therealongbetweena crucibleheating -positicn and material-transferring posi- .tion, a crucible (carried by and movable with .said supporting means, an open-ended heating coil below saidirevolvable arm and vertically movable between a.heating position around said crucible and a positionclear of said'crucible, a-cooperat- Ling guide pin :and recess .for aligning thezcrucible. with the open end of the coil during movement .of the coil toward the crucible, means Ffor elevatingthe heating 'coilto said position around-a portion of said crucible, and interlocking means adapted .to prevent initiating revolution :of said arm while theheating coil iselevatedand around .the crucible.

6. -In a device 10f the class described, the-combination of a base, a rotatable .shait extending upwardlyfromsa'id base, an arm carried ,by and rotatable withsaid shaft, ;a substantially radially movable crucible support slidably fitted on .and freely-movable along saidarm between an inward ,7; heating location and an outward dischargiliglo cation, resilient means pressing against said crucible support and urging it outwardly along said arm at all times from said inward heating location toward said outward discharging location, a heating coil positioned between the base and the arm adjacent said rotatable shaft and during non-heating periods spaced from a crucible carried by said support, and means for elevating said coil when the crucible support is at said inward heating location to a position surrounding part of a crucible carried by the support whereby material therein may be melted.

7. In a device of the class described, the combination of a base, a rotatable shaft extending upwardly from said base, an arm carried by and rotatable with said shaft, mold carrying means adjustably positioned on said arm adjacent an outer end thereof, an open ended heating coil adjacent said rotatable shaft, a substantially radially movable crucible support slidably fitted on and freely movable along said arm between a crucible heating position and said mold carrying means at all times other than when surrounded by a heating coil, and means for elevating said open ended coil to a position surroundin part of a crucible carried by said support when the support and crucible are positioned adjacent the rotatable shaft and the crucible is in alignment with said coil, whereby material in the crucible may be melted.

8. In a device of the class described, the combination of a base, a rotatable shaft extending upwardly from said base, an arm carried by and rotatable with said shaft, mold carrying means adjustably positioned on said :arm at a location spaced from said shaft, an open ended heating coil adjacent said rotatable shaft and movable between a low position adjacent said base and an elevated position adjacent said arm, a substantially radially movable crucible support slidably fitted on and freely movable along said arm between a crucible heating location adjacent said rotatable shaft and said mold carrying means, means for elevating said open ended coil to a position surrounding part of a crucible carried by said support when the support and crucible are positioned adjacent the rotatable shaft and the crucible is in alignment with said coil, and means operatively interconnecting said coil and said rotatable shaft and preventing rotation of the shaft while the coil is elevated and surrounding any part of the crucible.

9. In a device of the class described, the combination of a rotatable member, means adjacent the outer end of said member for holding a mold, a crucible supporting member slidably mounted on said member and freely movable substantially lengthwise along said member between an inward crucible heating position and said mold holding means, means spaced below said crucible supporting member and located adjacent the axis of rotation of said arm and elevatable to a position surrounding the lower part of a crucible carried by said support for heating and melting a material in the crucible, and resilient means for urging said crucible support along said rotatable member away from said crucible heating position toward said mold holding means and effective upon lowering of said heating means from said position surrounding the lower part of said crucible.

10. In a centrifugal casting mechanism, the combination of a pair of spaced rotatable supporting members, a pair of sleeve-like members slidably fitted on and freely movable along said spaced supporting members between an inward crucible heating position and outwardly disposed mold carrying means, a crucible supporting member extending between and carried by said pair of freely slidable sleeve-like members, a crucible carried by said supporting member having an opening at an outer side wall thereof and mold carrying means disposed adjacent the outer ends of and intermediate said pair of spaced supporting members, a heating coil positioned below said supporting members adjacent their inner ends, a portion of said mold carrying means abruptly limiting outward movement of said crucible with its supporting member and pair of freely slidable sleeve-like members, discharge of metal through the crucible opening into a mold of said mold carrying means being initiated upon striking of the crucible against the mold carrying means.

EMIL R. CAPITA. THOMAS A. FEEHAN.

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

UNITED STATES PATENTS Number Name Date 577,329 Sla-wianoff Feb. 16, 1897 1,280,289 Perry Oct. 1, 1918 1,684,800 Maximoff et al Sept. 18, 1928 1,767,036 Andresen et al. June 24, 1930 1,926,573 Willcox Sept. 12, 1933 2,011,955 Touceda Aug. 20, 1935 2,086,483 Touceda et a1. July 6, 1937 2,104,380 Touceda Jan. 4, 1938 2,140,204 Griifin Dec. 13, 1938 2,192,043 Hooper Feb. 27, 1940 2,202,473 Vickers May 28, 1940 2,216,567 Esnault-Pelterie Oct. 1, 1940 2,235,443 Steinbock et a1. Mar. 18, 1941 2,289,484 Coley July 14, 1942 2,462,259 Frei Feb. 22, 1949 2,479,610 Frei, Jr. Aug. 23, 1949 OTHER REFERENCES The Iron Age, October 31, 1946, page 49.

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