US2679141A

US2679141A - Defrosting refrigerating apparatus

Info

Publication number: US2679141A
Application number: US247799A
Authority: US
Inventors: Lawrence A Philipp
Original assignee: Nash Kelvinator Corp
Current assignee: American Motors Corp
Priority date: 1951-09-22
Filing date: 1951-09-22
Publication date: 1954-05-25
Anticipated expiration: 1971-05-25

Description

l.. A. PHILIPP DEFRosTING REFRIGERATINC APPARATUS May 25, 1954 2 Sheets-Sheet l Filed Sept. v22, 1951 om w m m May 25, 1954 L, A, PHMPP 2,679,141

DEFROSTING REFRIGERATING APPARATUS Filed Sept. 22, 1951 l 2 Sheets-Sheet 2 71' a. j' INVENTOR.

Trae/wey Patented May 25, 1954 peut 6i' fnyl eeepending feppneatierm serial: Ne. 'zszyosgmeazoeteef 29,1941,fforT Refrigeremngmifeifeuiuevemy semer-Ne; 1783596, -lea :August the system including the evaporator is gtly Figo. 2 is e. view'fnkenfelong the une miy Fig. 3' s a fragmentary view takena1ongtiief compartment, formed by the sheet metal evaporator is preferably closed at the front thereof by an interior door t2. The evaporator 32 may, if desired, be constructed like that shown in Patent Number 2,325,706 issued August 3, 1943.

During normal operation of the refrigerator, liquid refrigerant is delivered from the condenser 3e* to the evaporator 32 under the control of a small diameter or capillary tube 54. The motor compressor unit te is connected to the header 5G above the liquid level therein by a return conduit dii through which gaseous refrigerant returns to the motor compressor unit. As shown, a portion of the return conduit 55, as at 5B, is preferably arranged in heat absorbing relationship with a portion 6E of the supply conduit 5t to cool the refrigerant passing through the latter. Accordingly, refrigeration during normal operation is produced by delivering the correct amount of liquid refrigerant to the avaporator under the control of a small diameter or capillary tube. rihe liquid evaporates in the evaporator and passes to the compressor which compresses it and delivers same to the condenser wherein it is liqueed and from which it is delivered to the small diameter or capillary tube.

A defrosting system is provided for the refrigerator, including a refrigerant supply conduit 62 and a refrigerant return conduit til. The refrigerant supply conduit 62 connects the refrigerant condenser to the evaporator 32 and is normally closed to new therethrough by a control or solenoid valve 66. This refrigerant supply conduit has a relatively large flow capacity compared to the fiow capacity of the conduit 64. A second and normally open solenoid valve 58 is provided in the return conduit 5t tocontrol flow therethrough. The defrosting system return conduit is connected to the evaporator below the outlet of the return conduit 56. As shown, the conduit tt by-passes the valve @E and connects into the return conduit 56 between the valve and the motor compressor unit 3S or conduit 65 may be a separate return line, if desired. Return conduit has a relatively small flow capacity, compared to the return conduit 56, to effect an increase in pressure in the evaporator 32 when valve ES is closed on defrosting operation of the evaporator. To insure against drainage of liquid refrigerant from the evaporator during normal operation of the system, I form the return conduit ed with a loop portion le extending above the evaporator outlet connection of the return conduit 5t. Thus, when the valve 68 is in open position during norma1 operation gas is withdrawn from the header et to the compressor whereas the liquid in the lower part of the header does not drain through the return conduit 64 because of theloop portion 'dil which extends above the liquid level in the evaporator whereas the inlet to the return conduit til is positioned in the lower part of the header and below the liquid level therein. ln practice l have found that the tube'i may be approximately 3 feet long by .031 of an inch internal diameter. Drainage of liquid from the evaporator during the defrost period is advantageous in that said liquid flows to the motor compressor unit 36 wherein it is evaporated and this latent heat of evaporation is utilized to increase the vapor` pressure and temperature in the system including the evaporating element 32. This is caused by the sensible heat stored in the motor compressor unit and casing, which heat is generated by mechanical friction and additional heat by electrical losses which are effective to evaporate the liquid which is, returned to the motor compressor unit and returned to the evaporator in the form of hot gases which are condensed in the evaporator and the latent heat of condensation provides for rapid defrosting of the evaporating element. Thus, when the system is on defrost, the valve 63 is in closed position and the conduit @t receives liquid from the lower part of the header and, due to the high pressure in the evaporator, the liquid is conducted or forced back to the motor compressor' unit throughout the defrost period. The motor compressor unit may be any of the Well known units having a motor nad a compressor enclosed in a sealed casing. Such units are well known to those skilled in the art and are used extensively. One of such units may be of the type disclosed and claimed in my Patent No. 2,199,415 dated May '7, 1949.

A control or thermostatic switch 72 is provided to control operation of the solenoid valves t6 and The switch l2, preferably a bi-metal blade, is cooperable with a contact lli to control operation of the solenoids. A resistance heater in series circuit with the bi-metal blade l2, is energized when the blade is in engagement with its contact 'M and is arranged to influence the bi-metal blade to remain in closed circuit position. Preferably a. push-button "iS is provided for manually moving the bi-inetal blade into engagement with its cooperating contact l'l. A second thermostatic switch or bi-metal blade S is provided to control operation of the solenoids 65, S3 and of the heater 'It and is arranged to respend to te temperature of the evaporator 32. This thermostat Si? is in closed circuit position engaging a cooperable contact 82 during normal operation of the refrigerating apparatus. The thermostat contact 82 is connected to a main lead wire 8d and the thermostat blade 38 is connected in series with the solenoid valve coil 56 and with the heater 'i5 by a lead wire 28. A lead wire @d connects the thermostat contact 'i4 in series circuit with the coil of the solenoid valve which in turn is connected to a main lead wire te.

When it is desired to defrost the evaporator 32, the thermostatic blade 72 is moved manually into engagement with its cooperable Contact 74 by means or" the pushbutton 58. This closes the circuit of the solenoids 55, and of the heater since thermostat 5Fl is closed in response to the low temperature of the evaporator 32. Upon closing of the thermostat 'i2 the heater i8 is energized and acts to hold the thermostat l2 in closed circuit-position. Also, upon closing of the circuit by thermostat l2, the solenoid valve 65 is energized and opens the refrigerant supply line $2 and the other solenoid EB is energized and closes the refrigerant return line 5d. When this occurs, refrigerant flows into the supply conduit d2 and is delivered thereby in gaseous form into the evaporator 32 wherein the refrigerant condenses in this cold region and gives up its heat to raise rapidly the temperature of the evaporator E2. Liquid refrigerant is withdrawn from the evaporator by the motor compressor unit 3E through the return conduit iid which because of its small fiow capacity causes an increase in refrigo-rant pressure in the evaporator 32. When the temperature of the evaporator 32 has increased to the temperature at which ice and frost have been removed therefrom or to the temperature for which the thermostat has been set, the thermostat t opens the circuit of the solenoids lili',V 6B -andof the heater 16. When this occursy thesolenoid 5t returns to closed position and solenoid 68 'returns to open position placing the refrigerating apparatus in condition for continuation of normal operation.- Also, When the thermostat Si? responds to a predetermined increase in the evaporator temperature, the heater 16 is deenergized, allowing thermostatV 'I2 to return automatically to its normal, open circuit position.

From the foregoing description, it will be noted that-I have provided an improved refrigerating apparatus which may be quickly defrosted without shutting down the system and onewhich automatically returnsto normal operation upon completion of the defrosting operation. It will also be noted that on the defrosting operation, the evaporator in effect has the function of a condenser, the heat of Condensation quickly raising-the temperature of the evaporator to remove ice and'frost therefrom. In addition, I have provided a refrigerating apparatus in which the system itself functions in reverse to remove ice from the evaporator.. includes a small flow capacity return line which acts to increase the pressure in the evaporator and decrease the time required to defrost the evaporator; a portion of the defrosting system return conduit being arranged to prevent drain'- ing of liquid refrigerant therethrough from. the evaporator during normal operation of the system-while the tube during defrosting serves to conduct liquid to the motor compressor unit which evaporates` same to increase the vapor pressure in the evaporator due to the latent heat of evaporation.

It will he understood that household refrigerators are controlled in response to change in temperature of the evaporator and accordingly any'suitable thermostat control (not shown) now in use, may be used with the ahove described refrigerator. Therefore, when the present system is placed in condition for defrosting, the

usual thermostat control of the system will cause continuous operation until the defrosting is over and the system has again reached normal operating condition. When this occurs, warm refrigerant will be passed directly to the 'evaporator from the condenser to quickly defrost the evaporator, and liquid refrigerant from theevaporator header will now through the restrictive passage- Way 6d to the motor compressor unit. When the evaporator temperature reaches a predetermined temperature, the auxiliary control Si! will interrupt the defrosting condition and lallow the normal control to cause the system to return to normal function.

In a modified form shown in Fig. 5, the system is diagrammatically illustrated disclosing a system somewhat like that shown in Fig. 4. `How-'- ever, the modified system shown in Fig. 5 provides for icy-passing refrigerant gas leaving the compressor so that it flows directly into the evaporator and not only ley-passes the liquid supply and control Aconduit but also ley-passes the condenser. In all other respects the system is the saine as that shown in Fig. 4. The system shown in Fig. 5 wherein the gaseous refrigerant flows directly from the compressor to the evaporator hasbeen found to rapidly defrost the evaporator.

In Fig. 5 reference numerals applied are the same as those applied to Fig. 4 with the addition of -100addedto each numeral. Thus the evaporator 132 includes the passages 148 and headerv 115.0 and is supplied with refrigerantfrom the- Furthermore my system` 6 condenser |38 by a small diameter or capillary tube i548 lwhich controls flow of liquid to thev evaporator. Gaseousrefrigerant is during normal operation `Withdrawn from the evaporator |32 by a motor-compressor unit i311 through the vapor lreturn conduit ist, which conduit is controlled by a solenoid valve les. The vapor return conduit l5@ includes a portion E58 which is in heat exchange relation with the conduit.

E54 and itil. In this embodiment the solenoid valve` EGB functions the same as valve 55 in Fig. 4, however, the outlet of the valve its allows refrigerant to i'iow into conduit 62 which flows directlysinto the evaporator thereby conducting the hot gases from the compressor to the evaporator and bfi-passing thel condenser ist and control conduit l 54. push-button i'lil, heating element Il@ and contact llt, operates the same as the switch 'l2 in Fig. 4. Likewise the switch lll with Contact 132 functions the same as switch t@ and contact 82 in Fig. 4. Likewise the electric conduits its and |38 are connected in series circuit the saine as conduits te and 3S are connected in the circuit shown in Fig. 4. In other words, the systenisv disclosed for refrigeration and defrosting are the same in Figs. 4 and 5 with the exception that the solenoid valve which controls the flow of gaseous refrigerant to the evaporator causesv the refrigerant to flow immediately from the compressor to the evaporator, icy-passing the condenser and capillary supply conduit whereas in Fig. 4 the solenoid valve @E controls the flow of gaseous refrigerant to the evaporator after therefrigerant passes through the condenser. The description applying to Fig. 4 also applies to that in Fig. 5. It will also be noted that in Fig. 5 a liquid return conduit its which is the same as that shown in Fig. 4 designated and serves to conduct liquid from the lower part of the header in the evaporator to the suction or vapor return conduit which conducts the liquid to the compressor where vapcrated and the vapor pressure increased to increase the pressure and temperature in the evaporator where such evaporated refrigerant is again condensed and re-circulated to thus effectively and quickly defrost the evaporating element.

Likewise the system shown in Fig. 5 may be controlled by the same type of thermostatic control referred to as controlling the system disclosed in Fig. 4 in response to changes of temperature in the refrigerant evaporator disclosed in said system.

In Fig. 6 I have shown an enlarged vier.7k of the motor-compressor unit 33 which is a conventional type well known in the art. This unit 35 includes a casing 2te which houses a cornpressor 2&2 and motor Zini. The motor 29d includes a stator 2&6 and rotor 2Enl. rEhe rotor 2538' is provided with holes or slots 2 lil. Refrigerant returned from the evaporator 32 through conduit 56 enters Ycasing'zll Where the refrigerant passes in direct Contact with the compressor 2932 andmotor 2M before passing to the compressor inlet 2 l2y and' passes through the slots 2l@ of the rotor 28v before ventering the inlet ft2. The conipressor 22 has an outlet 2 ifi which leads to the condenser 38. Accordingly any liquid refrigerant which is conducted through conduit 5t into casing 20o comes into direct contact with both the motor and compressor to cause evaporation thereof-and since the refrigerant passes through the holes 2m any liquid particles are separated. from the gaseous refrigerant by centrifugal force The switch' lf2 which includesdue to the rotation of the rotor. Thus only gas passes to the compressor inlet 2I2. This unit 35 may also be used in connection with the system shown in Fig. 5. Further details of this type of motor-compressor unit utilizing a rotor having holes or slots therein may he found in said Patent No. 2,199,415.

In Figs. 7 and 8 I have shown two modied forms of motor-compressor units which may be used in connection with the systems disclosed herein. Under certain operating conditions it may be desirable to use these units.

In Fig. 7 there is shown a motor-compressor unit 22@ having a casing 222 provided with an inlet 224 which receives the refrigerant from the evaporator of the refrigerating system. In the casing is shown a motor 226 in the upper portion thereof and a compressor 227 is positioned in the lower part of the casing and is provided with inlet 223 and outlet 23B. Refrigerant entering' casing 222 comes into contact with baiile 232 which causes liquid to now into contact with the motor 22%, compressor 22'! and the inside casing walls to evaporate said liquid due to the heat of the motor and casing which receives heat from both the motor and the compressor. Thus only refrigerant gas enters inlet 228.

In Fig. 8 a motor-compressor unit 2&6 includes a casing 2112 having an inlet 2513. Within the casing 242 is a motor 2M. having a rotor 2aB which carries a cup-shaped fan 248. Below the motor 244 is positioned compressor 2% having an inlet 25e and an outlet 252. Relrigerant entering the casing 2&2 moves in the direction of the fan 242i and any liquid refrigerant so entering drops into said fan and due to the rotation or" the rotor such liquid is thrown upwardly into contact with the dome portion of casing 2&2 which causes evaporation of said liquid due to the heat of the casing which receives its heat from both the motor and compressor. Thus only gaseous refrigerant enters inlet E56.

From the foregoing it will De readily apparent that I have provided refrigerating systems such as disclosed in Figs, 1i and 5 wherein refrigerant gases are passed from the compressor into the evaporator wherein such gases are condensed and due to the latent heat of condensation the evapo rators of such systems are readily deirosted. Also. it will be noted that liquid refrigerant during the defrost period is drained or caused to flow into the motor compressor casing wherein sensible heat stored is utilized to vaporize the liquid refrigerant to increase the vapor pressure and temperature in the system including the evaporators by the latent heat of evaporation to also aid in rapidly defrosting the refrigerant evaporators so that defrosting takes place so rapidly that frozen foods and the like stored therein do not have an opportunity to warm up to a point which would cause melting thereof.

Furthermore, in systems of this type it is com mon practice to place the thermal bulb of a thermostat in contact with the surface of an evaporator so that the temperature of the evapforator will actuate the thermostat to open close the circuit to the motor compressor unit to thereby control the operation of the system in accordance with the temperature of the evaporator. Accordingly, when the defrost switches are actuated to place the systems on defrost operation the thermostat which controls the motor compressor circuit will continue to demand refrigeration and keep the motor compressor circuit closed until the defrost cycle has been com pleted and the system has operated sufficiently to lower the temperature in the evaporator to actuate the thermostat to open the motor compressor circuit connections. Such thermostats cause the system to operate during normal oper ation so as to maintain the temperatures in the evaporator, and in the food storage compartment within predetermined limits.

Although only preferred forms of the invention have been illustrated, and those forms described in detail, it will be apparent to those skilled in the art that various modifications may be made therein Without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

l. Refrigerating apparatus comprising a refrigerant condensing element including a motorcompressor unit and an evaporator having a liquid collecting vessel at its outlet, supply means for controlling the flow of liquid refrigerant from the condensing element to said evaporator to maintain the pressure at the discharge of the compressor higher than the pressure in said evaporator during a certain period of operation, conduit means for ley-passing said supply means during another period of operation to increase the pressure in said evaporator, and return conduit means arranged to conduct liquid refrigerant from said vessel into direct contact with said motor-compressor unit only when said conduit means is open to kay-pass said supply means and cause said increase in pressure in said evaporator.

2. Refrigerating apparatus comprising in combination a refrigerant evaporator having a liquid collecting vessel at its outlet, a refrigerant condensing element for circulating a refrigerating medium into said vessel and through said evaporator, said condensing element having a motorcompressor unit, means for defrosting said evaporator including conduit means for conducting liquid refrigerant from said evaporator into thermal contact with said motorwcompressor unit to cause evaporation of said liquid and conduit means for conducting the latent heat of such evaporation by means of the evaporated refrigerant into said evaporator.

3. Refrigerating apparatus comprising a motorcompressor unit, a condenser and an evaporator conducting a level of liquid therein adjacent its outlet, conduit means connecting the evaporator with said motor-compressor unit, supply means connecting said condenser with said evaporator, oy-pass means for lay-passing said supply means, and said conduit means including an inlet portion below said liquid level and being arranged to conduct liquid refrigerant from said evaporator into direct contact with said motor-compressor unit when said ny-pass means is in operation.

Ai. In a refrigerating apparatus having a refrigerant evaporator having a reservoir containing a quantity of liquid refrigerant at its outlet and a refrigerant condensing element operatively connected by refrigerant supply and return conduits, said element having a motor-compressor unit, a defrosting system for the apparatus cornprising, a second refrigerant supply conduit connecting the condensing element to the evaporator, said second refrigerant suppiy conduit seing arranged to deliver gaseous refrigerant to the evaporator, a normally closed valve controlling flow through said second supply conduit, and said return conduit having a portion at least of its inlet positioned on said evaporator below the liquid level therein atleast during defrosting to receive liquid refrigerant from said evaporator when said valve is opened and the pressure in the evaporator is thereby increased and the liquid is conducted into direct contact with said motorcompressor unit to .be yevaporated thereby and the latent heat of evaporation is conducted to said evaporator.

5.l In a refrigerating apparatus having a `refrigerant evaporator and a condensing element operatively connected by a refrigerant supply conduit and a refrigerant return conduit, a defrosting control system for the evapora-tor com-- rising, a refrigerant supply conduit to deliver gaseous refrigerant from the condensing element to andcondense the refrigerant in the evaporator, a normally closed solenoid valve controlling flow through said second refrigerant supply conduit, a normally open solenoid valve controlling flow through said refrigerant return conduit, a thermostat responsive tothe temperature of the evaporator controlling operation of said valves, a manually closed thermostatic switch controlling operation of said valves, a resistance heater to influence and Vhold said thermostatic switch closed and being controlled by said thermostat.

6. In a refrigerating apparatus having a refrigerant evaporator and a condensing element operatively connected by a refrigerant supply conduit and a refrigerant return conduit, a clefrosting control system for the evaporator comprising, a refrigerant supply conduit to deliver gaseous refrigerant from the condensing element to and condense the refrigerant in the evaporator, a normally closed solenoid valve controlling flow through said second refrigerant supply conduit, a normally open solenoid valve controlling flow through said refrigerant return conduit, a thermostat responsive to the temperature of the evaporator controlling operation of said valves, a manually closed thermostatic switch controlling operation of said valves, a resistance heater to infiuence and hold said thermostatic switch closed and being controlled by said thermostat, and a by-pass conduit connected to the evaporator below the return conduit outlet and connected to said return conduit between said normally open valve and said condensing element.

7. In a refrigerating apparatus, a refrigerant evaporator, a refrigerant condenser, a relatively small flow capacity conduit delivering liquid refrigerant from said condenser to said evaporator during normal operation of the system, a relatively large ow capacity conduit connected to deliver refrigerant from said condenser to said evaporator to defrost the evaporator by heat of condensation, a refrigerant compressor operatively connected to said condenser, a refrigerant return conduit delivering refrigerant from said evaporator to said compressor, a normally closed electrically operated valve controlling flow through said relatively large flow capacity conduit, a valve controlling flow through said refrigerant return conduit, a control responsive to a condition of the refrigerant controlling operation of said valves, a thermostatic switch controlling said valves, and a resistance heater arranged to heat and hold said thermostatic switch in closed position and controlled by said control.

S. fn a refrigerating apparatus having a refrigerant evaporator and a refrigerant condensing element connected by supply and return conduits, an evaporator defrosting system comprising, a normally opening electrically operated valve controlling flow through said refrigerant return conduit, a refrigerant supply line of larger flowvcapacity than the rst supply line for delivering refrigerant to the evaporator to defrost the same by the heat of condensation of the refrigerant, a normally closed electrically operated valve controlling flow through said second refrigerant supply conduit, a thermostat responsive to the temperature of the evaporator to control operation of said valves, a manually operable thermostaticswitch controlling operation ofsaid valves, and a resistance heater influencing said thermostatic switch and controlled thereby. Y

9. In refrigeration apparatus, a refrigerant evaporator, a refrigerant condensing element, a relatively smali iiow capacity refrigerant supply conduit normally delivering liquid refrigerant from said condensing element to said evaporator, a refrigerant return conduit leading from an outlet of the evaporator to said condensing element, a normally open electrically operated valve operable when energized to decrease flow through said refrigerant return conduit, a relatively large flow capacity refrigerant delivering conduit connecting said condensing element and said evaporator for delivering gaseous refrigerant to said evaporator to condense and defrost said evaporator, a normally closed electrically operated valve 0perable when energized to increase flow through said relatively large ow capacity conduit, a ther- Inostatic switch manually operable to energize said valves, a resistance heater influencing and holding said thermostatic switch closed, a thermostat responsive to the temperature of said evaporator controlling said heater, and a by-pass connecting the evaporator belovv the return conduit outlet to the condensing element on the other side of the normally open valve from said outlet and having a loop portion above said outlet.

10. In a refrigerating apparatus having a refrigerant evaporator and a refrigerant condensing element operatively connected by refrigerant supply and return conduits, a defrosting control system comprising, a normally open valve controlling flovv through the return conduit, a bypass flow restricting tube from the evaporator around said valve in communication with the condensing element, a refrigerant conducting conduit of larger now capacity than said by-pass tube and connecting the condensing element and the refrigerant evaporator to deliver relatively warm refrigerant to the latter, a normally closed valve in and controlling flow through said relatively large flovv capacity conduit, a thermostatic switch controlling said valves in series circuit therewith, and a second thermostatic switch controlling said valves and said first thermostatic switch in series therewith and responsive to a condition of the refrigerant.

1l. In a refrigerating apparatus having a refrigerant evaporator and a refrigerant condensing element operatively connected by refrigerant supply and return conduits, a defrosting control system comprising, a normally open electrically operated valve controlling flow through the return conduit, a by-pass flow restricting tube from the evaporator around said valve in communication with the condensing element, a refrigerant conducting conduit of larger flow capacity than said by-pass tube and connecting the condensing element and the refrigerant evaporator to deliver relatively warm refrigerant to the latter, a normally closed electrically operated valve in and controlling flow through said relatively large iiow capacity conduit, a thermostatic switch in series circuit with and controlling said valves,

a second thermostatic switch in series with and controlling said valves and said first thermostatic switch in response to a condition of the refrigerant, and a resistance heater in series circuit with said tliermostatic switches operable to hold l said rst thermostatic switch in closed position.

12. In a refrigerating apparatus, a refrigerant evaporator, a refrigerant condenser, a relatively small iow capacity conduit delivering liquid refrigerant from said condenser to said evaporator during normal operation of the apparatus, a relatively large flow capacity conduit connecting said condenser and said evaporator, said relatively large flow capacity conduit to deliver refrigerant to said evaporator to defrost the latter by the heat of condensation, a normally closed valve responsive to temperature of the evaporator controlling flow through said relatively large iiow capacity conduit, a refrigerant compressor operatively connected to said condenser, a refrigerant return line connecting said evaporator and said compressor, a refrigerant return line of smaller flow capacity than said rst mentioned return line conduit connecting said compressor and said evaporator for restricted ow of refrigerant to the compressor during defrosting of the evaporator, said second return line being connected to said evaporator anterior to the connection therewith of said rst return line, a normally open valve responsive to the temperature of said evaporator controlling ow through said refrigerant return line, and a manually operable control for controlling operation of said valves.

13. A refrigerating system comprising, a refrigerant condensing element, a refrigerant evaporating element, a restricted passage for controlling flow of refrigerant from the condensing element to the evaporating element, an unrestricted passage for conducting evaporated refrigerant from the evaporating element to the condensing element, means for ley-passing said restricted passage, means for closing said unrestricted passage, and a continuously open restricted passage from said evaporating element to said condensing element.

References Cited in the le of this patent UNTED STATES PATENTS Number Nance Date 2,351,140 McCloy June 13, 1944 2,430,960 Soling Nov. 18, 1947