US2677250A - Freezer of the top opening type - Google Patents

Description

May 4, 1954 c. F. ALSIN'G ETAL FREEZER OF THE TOP OPENING TYPE l t e 9 h s .1 e 9 h iv 4 2 2 i p 2 L 5 9 l 1- 2 m. u A d e l 1. F

2a a? a? 34.

/ II I INVENTORS Carl z'flas 'n BY Char/652.12; W 5% M fliiorvz ey May 4, 1954 c. F. ALSING EI'AL FREEZER OF THE TOP OPENING TYPE 4 Sheets-Sheet 2 Filed Aug. 21, 1952 l I I 1: 1/ I 1 1 l Mam ME T n NB I r E3 5 CC W Y y 1954 c. F. ALSING ETAL 2,677,250

FREEZER 01-" THE TOP OPENING TYPE Filed Aug. 21, 1952 4 Sheets-Sheet 3 INVENTORS. CarZ K141511229 BY AZZZOT'IZQIJ May 4, 1954 c. F. ALSING EIAL FREEZER OF THE TOP OPENING TYPE 4 Sheets-Sheet 4 Filed Aug. 21, 1952 INVENT 4 Patented May 4, 1954 2";6'77',25&

FREEZERNOE THEZTOP OBENINGxTYBE;

Carl F; Alingend Gharles= R2 DilL Evansvillfl Ind; assignors-to Seeger- Refrigerator Com pany; .SitLPa'ul; Minm, acomoration otzlvfin'neasota:

Application August.21; 1952;: Serial No; 3051676.

31i0laims: (01. 62-116) 1' 2-" The-present invention re1ates=to-freezers of-th'e' characters of reference indicate similar parts top-opening type, and=isparticu1arly concerned throughouvtlie'several views with the provision of an improved freezer of the Referringto thedrawings; of which there are flooded type, in which the outer shell maybe" four-sheets;

utilized-as aheat radiating-surfaceforthe com Fig; 1 isasideelevational view of aireezer'of densercoils; the open top type embodying the invention;

One oftheob-jects of the-invention is the-prm- Fig.- 2' is anend elevational' view 'of' thefreezer: vision of an improved freezer having semi-flooded Fig. 3-is'a-diagrammatic-sectional view, taken" evaporator coils for-the purpose of providing a on-the'planeofthe line--3'-3of" Fig: Zishowihg? more efii'cient' evaporator design,- while still inthe a-rrangement of the compartments within the corporating the wrapper coil method" of. fabricafreezer;

tion; Fig: 4 -is=a sim-ilar diagrammatic'sectional'fview;

Another objectof'the invention isth'e'provision taken on-thep-laneof'the lihe-l -l-of'Figt 1;

of an improved-evaporator ccnstruetion for open Fig; 5 is adiagrammatio-view"oftheevaporator" top freezers which maybe provided with a greater" system, showing the arrangementof 'the'coi-l's with charge of refrigerant in the system WithOIlt"th8 respect tothe'header;

refrigerant slugging outatlow ambient tempera- Fig. 6 is a similar diagrammatic viewtof aimodi= ture opera-tion'. fication of the arrangementof the cooling coils;

Anotherobject of .the-invention is the provie Fig: Tis a-side'eleva-tional view of the'liner'of .a

sion of'an improved-evaporator construction for freezer bo y 't' e a e ts F openr-top freezers'provided withxareceiver which Wand shown'with the-coils-securedto th'e'outside stores a variable h'eadiof refrigerant that is aug: f thelinerj' mented-during-continuous operating conditionsiso is a e d el v t o al View Of the liner'and' thatwhen the oil' i cold ,at'the beginning of the S'0f F g cycle the coils; which are .connected' to the re? ig; is'ai'bbttom plan'viewtaikelffrom e'bOt ceiver; may be flooded by; hydrostatic pressure in tOXIFOf thereceiver'tank; Thusthereis sufi'icient'refrig S"a" e P spective, ShOWiDEthB erant in: the evaporator systemzso; that it begins. mode ofsecurillgthe'coilsrto'thefli i to load'up'the compressor at the: beginning oflthe. F g: 11 is-atsideelevationalwiew"oftne outer cycle of operation; 3o shell of the "freezer, shown withit condenser coils th bj t of t m t s t provisiom andsecuringdevisesin :dotted'lines'on theinside of an ir'nprovedsemi-fioodd evaporator.system-. Of'said Shell; for open top freezers which is simple in construe lTiSa pip n View Of the Outer Shell'of C pable of feconomical manufacture. efficient, 1

in operation, and'which producesla more uniform 1338' a fiegm yv View, iaken,

cooling eff'ectth'roughout the entire wall :area of. through the Wall of a freezer emb'ody ez-theliner the freezer, of Fig, '7 andtheshell offiFigw 11, showingthc de- Another object oftheinvention istheiprotvision t ils of construction;

of an improved freezer system in which :thetcon- Eigi.,14isiafragmentaryisectionalview, taken on. densertcoilsoare .securedvon the inside of theflouter theiplaneof th'evline'lld-lfllofjfige 13, looking-11L shellofrthe ,f1'eeze1'.in such .manner. as.,to. main-- theedirectionmoiftheharrowswandshowing theem:

taint thecondenser coils inintimateheatcontact bossments' in the..- vertical reinforcing members with. the outer. sh'elliand .to.. utilize the outenshell which secureethe-condensen tubesw tor theouter asla heat radiating surfacefor the condenserw coils, shell; t, also.,elim'mating. any; possibility. oftcondensatione Eigtliisawerticalfragmentary-Sectional View:

on the outer shell. of .thecouter linertaken von. the plane of: the line;

Another object of the invention iSt'thQpIOViSiOm 5l5 0f=F g. 12,5:

ofimprovedmodesof construction-forsecuringvthe Fig; 16 iSrflmIiQhi'x-hfifldliHSidG elevational-zview condenser .C0i1S:$0' thezinside surface-pf:ithesouterr ofsEi'g. 15; and." I

shell,. which; involveaa minimumeamountzoilabors Fig.2 1''! .is' -aasectionalwiew lookingsupwarct taken 1.

and'ma-terials; 0I1' th'e5 plane of the line-H 41 o'ffFig: 165

Other obj acts-andadvantages-of -i'th'e invention Referring to Fig; 1; 20*; indicates -in=its-= entirety' will-*beeapparent from i the =-followingdeseriptiom a freezer-of -the=open ton type;-in wh ich *the--operr and the accompanyingdrawingspin which similar top insulatedwabinet 21 is 'provideel'-with arr=in=- sulated cover 22 provided with suitable hinges and counter-balance springs 23 and a latch actuating handle 24. The cover is provided with the usual resilient, compressible rubber seal 25, which engages a combined breaker and finishing strip 26, covering the upper edges of the cabinet wall all around the top of the open type freezer.

The cabinet 2| is preferably formed with a smaller quick freezing compartment 21 located at the right end in Fig. 3 above a machine compartment 28, which is outside the insulation 2 9. The cabinet also has a relatively large frozen food storage compartment 36 extending from top to bottom at the other end; and the two compartments 2! and 3e are preferably formed by providing a smaller liner 3| (Fig. 7) of box-like shape open at the top, and a larger liner 32 of box-like shape open at the top, these two liners being side by side and having their top edges flush.

The liners are provided with an outwardly projecting flange 33 extending all around the top opening of the liners 3|, 32 to provide a seat for the finishing strip and breaker 26.

The compartments 2'! and may be provided with any convenient form of wire racks 34 (Fig. 3), 35, 36, the first two being supported by laterally projecting supporting wires 3'! engaging the top edge of the cabinet, and the latter one being supported by legs on the floor of the larger liner 32. The two liners 3|, 32 are preferably separated at their point of contact 31a (Fig. '7) by a sheet of insulating paper for preventing noise through the metal to metal contact of the liners and aiding in establishing a slight differential in temperatures between the quick freeze compartment 2! and the frozen food compartment 30.

.The two liners 3|, 32 may each be formed of a rectangular sheet of steel bent to box-like form with the ends welded together and capped at the bottom by means of a sheet metal rectangular cap 38 having an upwardly extending border flange 39.

' The liners 3|, 32 may be provided with either of the coil arrangements shown diagrammatically in Figs. 5 and 6. In Fig. 5 the evaporator liner is indicated by a rectangle 3 32 hearing certain coils and a vertical header or receiver 46.

,The receiver 40 has its suction outlet conduit at 4| extending into the top of the receiver, where it is more likely to suck gaseous refrigerant from the receiver 40; and the receiver 46 is provided with a series of sinuous coils 42, which may be arranged sinuously or in the wrap-around arrangement on the liners 3|, 42, which have both ends 43 and 44 in communication with the receiver 40.

The lower end 44 of these coils 42 communicates with the receiver 40 adjacent its bottom and is supplied with a supply of refrigerant in liquid form under a hydrostatic liquid pressure indicated by the letter h and shown by the refrigerant level 45 in the receiver 40.

"The upper end 43 of the tubing 42 communicates with the receiver 40 above the level 45 of liquid and permits the gaseous refrigerant to pass into the receiver 40 as it bubbles up through the tubing 42, which preferably has a continuous upward slope toward the discharge end 43.

The evaporator of this freezer is preferably provided with another series of coils 46, which may be arranged sinuously, or in the wraparound manner, butalso preferably have a continuous slope downward from the inlet 4! to the lowest point 48 in this system of coils 46, from 4 which the outlet conduit 49 extends upward to carry gas to the top of the receiver 40.

The operation of this type of coil arrangement is such that the lower coils 42 will be flooded by the hydrostatic pressure in the receiver tank 40; and a head of liquid h is maintained under all operating conditions such that liquid refrigerant flows into the lower coils by gravity.

The refrigerant evaporated continues to float up through the tubing and returns to the upper section of the receiver tank. As soon as the compressor starts there is refrigerant in the evaporator system, which begins to load up the compressor, which in turn helps to increase the rate of warming up of the oil and pump parts, which assist the high side compressor in delivering refrigerant to the entering series coils 46.

These series coils 46 are refrigerated; and the excess refrigerant is delivered to the receiver tank after only traversing a portion of the space around the freezer. The result of this type of system is that both the lower and the upper parts of the refrigerator are refrigerated simultaneously; and the resulting suction pressure on the unit is maintained at a higher level during the refrigerating cycle. This results in a higher efficiency and lower kilowatt consumption for a given freezer temperature.

Referring now to Fig. 6, this shows diagrammatically a modification of the arrangement of the coils with respect to a rectangle 3|, 32, indicating the two liners. In this type the freezer is provided with a vertical header or receiver 50, which has its suction take-off conduit 5| at the 7 top.

The inlet to the coils is indicated at 52, leading to a series of sinuous or spirally wrapped coils 53, which are preferably arranged on the bottom of the quick freeze compartment liner This gives the coils 53 at the bottom of the quick freeze compartment 21 a sufficient supply of refrigerant so that food placed in contact with the bottom of the liner 3| is quickly frozen.

The side walls of the two liners 3|, 32 are covered sinuously or by the wrap-around method with a series of coils 54, which have both ends 55 and 56 communicating with the vertical receiver 50. The coils 54 have their inlet from coils 53 at the T joint 51; and the coils 54 discharge gas into the receiver 50 at the upper end 55, and may discharge a portion of liquid or gas through the tube 56 during portions of the cycle.

The first-mentioned series of coils 53 on the bottom of the quick freeze compartment communicate with the coils 54 at the point 51 by means of a T joint at a point spaced from the receiver 50. Thus the outlet 5'! from the coils 53 serves to promote circulation upward through the coils 54.

In each of these cases the receiver 40 or 5D is, of course, several times the diameter of the tubing employed for the coils so that bubbles form in the refrigerant, and have the tendency to fill the tubing used for coils; but bubbles are much smaller than the space inside the receivers, where they rise in the liquid, which has a definite hydrostatic head.

The operation of this type of coil arrangement is more efficient than the continuous tube type of freezer coils, especially under low ambient conditions. By providin such a vertical header a greater charge of refrigerant may be used in the system without the refrigerant slugging out under low ambient operation.

ae'rmsw Pressure in theheader isequali-zed entire 011' cycle by having both endsof the-wrapper section 54 of'the'coils connected to'the header; allows the header and the evaporator coils" 54 tobecome filled withli'quidonthe same-level, on the Off cycle.

The joint 5? between the continuous-section 53 and the i'iooded section E i-should be-made ata lowpointof the system to assure'a-liqui-d seai and thus prevent any bypassing of the coils to berefrigerated.

Referring nowto Figs. Tto 9; these a-re-views showing the two liners provided -with coils accord-- ing to the-arrangement of Fig; 6. The two-liners are preferabijrprovided-with a multiplicity-ct vertically-extending coil securing strips 58-; these being in the form of'sheet metalangles'ofthe type shown in'Fig. 10.

The coil securing'strips 58 have-an-attachi-ngflange 58 which iswelded-totheside of *the liner in substantially vertical position; These*-strips-* 58', are, of course, shorter on-"the' shorter liner 3| of the quick freeze compartment; and in each case preferably run substantially fromthe top-t0 thebottom of the liner;.

Each coil securing stripis'" has an outwardly projecting coil supporting-flange 60, which is provided with a plurality of" regularly spaced inwardly extendingslots 61, which have a-straight' edge'fiion'one side: and a-circularedges-31* which engages about three-fourths'of a" tube 64; shown as an example; The tube-securing flange til-has a longitudinally extending retaining flange 65 curved Ol'lits lowerside' in Fig. complementarily to the tube Mybut-all. of the retaining flanges are bentlaterally; as-indicated at a in Fig. 10 to open the slotsfil for receiving the tube and any of the other. tubes ofthe system.

Thus the tubing maybe wrappedtightly around the two assembled linersand placed in appropriate slots 6! of the securing 'devices'58 so 'tha-tth-e tubing slopes continuously downward: fromits uppermost portions andjso that the bubbles maytravel upward in the tubing, After-a tube is placed in the slot 61; the bent flange SSa'ofthatslot is bent over to the position BEFto-retainthe tubing, as shown in Fig. 10.

show the header 5B of Fig. G'and 'tlie'coils-b lar ranged in the wrap-around mannerabout the two liners 3i and 32' and .communicatingvwith"the header 59 at the bottom, indicated. at 56, and at the top, indicated at55.

The, header being thus connected to'thetubing, it is supported on the liner by means of the tubing.

Referring now to Fig. 9; the section 53. of tubing of. 6 is shown to extend from its ,inlet 521 to its outlet 5?, which is a T'-shapedconnection'to the coils 55 at a low point spaced from themtrance 56 of this tubing and from the receiver 50.

Similar securing metal'strips. 58" may extend across the bottom of the liner 3| for securing thecoils 53, as shown in Fig. 9'.

The. motorcompressor unit 6B- ofFiggB', is; ofcourse, supported in the machine compartment outside the insulation 29; which is: preferably arrangedinrigid rectangular blocks, as shown in' Fig. 3; filling the space between the liners and theouter shell 5?, shown in Fig 1l'. The-connec= tions to the condenser are shown in Fig. '7, where- 68. indicates the. inletifrom the" condenser to" a capillary tube, 59, which is coiled in" heat. con ductingcontact with a suction tube 10; extending to the upper part of the receiver 50 at'55.

This a Referring'to-Figs: I'D-14, theses-are; views slrowe ing the arrangement; of the a condenser coils on.

the inside ofthe outer shell' ofz'thefreezen. The:

outer shell 61 comprises:arectangularxmetal box having two sides 68; 69=Land two ends .HI; Wand provided with a'bottom'portion 1 2: offreducedsize: joined tothe. upperportion by anzoifsetrfiangec 13 andprovided with abottom panel 1 k.

The bottom 72 is provided-with-tfour rectanguw lar stamped sheet" metal pads IE5 welded thereto and serving as feet; and these pads maysbesproavided with the usual levelers;

The inside ofthe shell 6Tiszprovidedxwith ai plurality of spaced channelled reinforcing rmeme bers 76 extending verticallyrof" the side andiendz.

walls and'removably attached tothe side and 'endi walls. Each of'the channelled reinforcing-meme bers- 16 isofthe construction'ishown in- Eigzxl, having a body flange' 'l' i whichengages the v of the'shell 61 and having-side flanges-l8 joined} tothe laterally extending fianges'lil.

in tight heat conducting contact withzthe shell.

The reinforcing members T6 are'not' weldedtm.

the shell wall, b'ut'areremovably heldlat'therton and the bottom by means 0f-thebrackets.:8l: a-lii the bottom and the bendable flanges :82' at-the: tops The shell is provided at its upper end withuan: inwardly projecting flange 83 extendingall:- aroundthe'top of the shell and- -formingz'a seat for the breaker strip 26: This inwardly projecte -ing flange 83 is deformed at-two spaced points;

as shown in Fig. 15a-nd Fig; 16 at 814: tonextend downward behind backwardly turned end flanges- 85 on the reinforcing members-16"."

At their lower ends-the bracketsB-I are welded on the inside of the shellin-such' position as to confine the body I? of the-reinforcing member '55 between the bracket-andthe shell. Thus the: reinforcing -members ft'are heldat the-top and the bottomagainst the inside of 'the'shellj and these reinforcing members hold the' coils-=8! of thecondenser in tight'eng-agement with-the-in-.- side of the-shell. arranged in a plurality of passesirr wraparound manner; beginningat tlie point 8-6 (Fig;

- 11) and extending about the inside of the shelli with the first turn 81; and thereafter havin diagonally extending portions 88 and equivalent horizontal portions extending about the" whole volume of the shell on the inside At the lower part of the liner the-coils 8! are arranged about the'inside of that portion-of 'the'- shell which surrounds the longer liner 32; ending: at the bottom at a discharge-conduit 89; which leads from the condenser to the-capillary-tube, and thence to the-evaporator.

The-inlet to the condenser is shown at- 90- (Fig. 12) extendingfromthemachines compart ment 28 to the inside 'of the-bottom=panel14 of the shell slat the longer liner.

Thereafter the condenser tube extends from-90 inward at 91 toward thecenter of-the-bottompaneland isarranged in rectangular, spiral for mation untila pluralityot turns brings the -tubing 92 over near the side wall. It is bent upwardly I,

at 93; and the vertical tubei!zftcommunicates with the other turns of the condenser at86i- Thus the compressed refrigerant enters the condenser at'90 and'is first'directed to the bottom of the shell, where-itusesthe bottom'pa-nel dora radiation surface. Thereafter the condensed--re-- The'coils 8 are preferably 7 frigerant or partially condensed refrigerant is carried through a plurality of wrap-around turns of condenser tubing arranged on the inside of the outer shell, and terminating at the bottom.

The spiral turns 9|, 92 of condenser tubing secured to the bottom panel by a multiplicity of small metal brackets 95, each having one flange welded to the bottom panel and the other flange curving about the tube.

In additio to the metallic securing devices for the condenser tubing and the evaporator tubing, the tubing is preferably covered with a layer of heat conducting mastic intimately engaging the liner or the shell, as the case may be; and this mastic may contain aluminum fillings, which aid in conducting the heat from the tubing to the shell and from the liner to the tubing.

,The present freezer construction utilizes a minimum amount of steel because it uses the outer shell as the radiating surface for the condenser. It permits the use of a greater charge of refrigerant which accumulates in the header and the flooded coils, and produces a more efiicient distribution of the refrigerating effect in a more eflicient manner.

.While we have illustrated a preferred embodiment of our invention, many modifications may be made without departing from the spirit of the invention, and we do not wish to be limited to the precise details of construction set forth, but desire to avail ourselves of all changes within the scope of the appended claims.

Having thus described our invention, what We claim as new and desire to secure by Letters Patent of the United States, is:

1. In an open top freezer, the combination of a pair of inner metal liners of rectangular boxformation open at the top and of the same width but of different height, said liners being joined together at two adjacent sides, in heat-conducting relation with each other, and with the top edges flush with each other to form a liner assembly, the shorter liner forming a quick freeze compartment with space below it for a machine compartment, and the longer liner forming a food storage compartment, an outer metal shell of complementary form spaced from the liner assembly on all sides and bottom and insulated from the liner assembly by blocks of insulation, an insulating cover closing said open top, a breaker strip connecting the top of the liner assembly and the shell about the open top, a motor compressor in said machine compartment, a condenser coil carried on the inside of said shell in heat-conducting relation with the shell and connected to the compressor outlet, a capillary tube connected to the condenser and extending to an evaporator coil, said evaporator coil having a bottom portion in heat-conducting relation with the bottom of said shorter liner and extending downward on the longer liner; and being wrapped about said longer liner and proceeding upwardly and being wrapped about both said liners and proceeding upwardly to he top of the liner assembly, a vertically extending cylindrical receiver of substantially larger size than said evaporator coil carried by said longer liner and extending vertically on said longer liner, said wrapped liner coil having its lower end connected to the bottom portion of said receiver and having its upper end connected to the upper portion of said receiver, a suction tube from the top em} of said receiver to the compressor inlet, and said bottom coil on said shorter liner having a T-connection to said wrapped coil adjacent the lower end thereof but spaced from'said receiver, and a charge of refrigerant in said receiver extending well up in the receiver above said short liner bottom coil to flood said latter coils and cool the evaporator quickly and thoroughly on starting of the motor compressor.

2. In an open top freezer, the combination of a pair of inner metal liners of rectangular boxformation open at the top and of the same width but of different height, said liners being joined together at two adjacent sides, in heat-conducting relation with each other, and with the top edges flush with each other to form a liner assembly, the shorter liner forming a quick freeze compartment with space below it for a machine compartment, and the longer liner forming a food storage compartment, an outer metal shell of complementary form spaced from the liner assembly on all sides and bottom and insulated from the liner assembly by blocks of insulation, an insulating cover closing said open top, a breaker strip connecting the top of the liner assembly and the shell about the ope top, a motor compressor in said machine compartment, a condenser coil carried on the inside of said shell in heat-conducting relation with the shell and connected to the compressor outlet, a capillary tube connected to the condenser and extending to an evaporator coil, said evaporator coil having a bottom portion in heat-conducting relation with the bottom of said shorter liner and extending downward on the longer liner; and being wrapped about said longer liner and prceeding upwardly and being Wrapped about both said liners and proceeding upwardly to the top of the liner assembly, a vertically extending cylindrical receiver of substantially larger size than said evaporator coil carried by said longer liner and extending vertically on said longer liner, said wrapped liner coil having its lower end connected to the bottom portion of said receiver and having its upper end connected to the upper portion of said receiver, a suction tube from the top end of said receiver to the compressor inlet, and said bottom coil on said shorter liner having a T-connection to said wrapped coil adjacent the lower end thereof but spaced from said receiver, and a charge of refrigerant in said receiver extending well up in the receiver above said short liner bottom coil to flood said latter coils and cool the evaporator quickly and thoroughly on starting of the motor compressor, the said liner assembly being provided with a plurality of vertically extending angular members having one flange welded to its sides and the other flange provided with partially circular grooves close to the liner for receiving the coils, said grooves being blocked by an integral tab extending outside the coils but bendable in the direction of the coils to admit the coils into said grooves.

3. In an open top freezer, the combination of a pair of inner metal liners of rectangular boxformation open at the top and of the same width but of different height, said liners being joined together at two adjacent sides, in heat-conducting relation with each other, and with the top edges flush with each other to form a liner assembly, the shorter liner forming a quick freeze compartment with space below it for a machine compartment, and the longer liner forming a food storage compartment, an outer metal shell of complementary form spaced from the liner assembly on all sides and bottom and insulated from the liner assembly by blocks of insulation, an insulating cover closing said open top, a

breaker strip connecting the top of the liner assembly and the shell about the open top, a motor compressor in said machine compartment, a condenser coil carried on the inside of said shell in heat-conducting relation with the shell and connected to the compressor outlet, a capillary tube connected to the condenser and extending to an evaporator coil, said evaporator coil being wrapped about said liner assembly and engaging the bottom of the shorter liner and having both of its ends connected to the ends of a vertical receiver, said condenser coil starting at the top of said shell and extending around inside the shell in one continuous coil from top to bottom with a spiral portion inside the bottom of said longer shell, said coil being held in heat-exchange engagement with the shell by channeled, vertical frame members inwardly open, and having outer transverse embossed grooves for receiving said condenser coil turns, said channeled members being unattached to the shell except at the top and the bottom ends thereof, said members having an inwardly turned retaining flange at the bottom 10 engaged under an outwardly extending bracket attached to said shell, and said shell having its upper edge formed with a U-bend on itself and with an inwardly extending flange deformed downwardly and outwardly at spaced points engaging below and inside the edge of an inwardly extending top flange on each channeled member, a charge of refrigerant in said vertical receiver extending well up into the receiver above the bottom evaporator coils of the shorter liner to flood the coils which are below the refrigerator level in the receiver and cool the evaporator quickly upon starting of the motor compressor.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,172,129 Phillip Sept. 5, 1939 2,302,051 Phillip Nov. 17, 1942 2,446,686 Behrens Aug. 10, 1948 2,599,733 Whitmore June 10, 1952

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