US2589859A

US2589859A - Suction line liquid return trap

Info

Publication number: US2589859A
Application number: US59693A
Authority: US
Inventors: Harry A Phillips
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-11-12
Filing date: 1948-11-12
Publication date: 1952-03-18
Anticipated expiration: 1969-03-18
Also published as: US2641281A

Description

March 1952 H. A. PHILLIPS SUCTION LINE LIQUID RETURN TRAP Filed Nov. 12, 1948 4 Sheets-Sheet l March 18, 1952 Filed Nov. 12, 1948 H. A. PHILLIPS SUCTION LINE LIQUID RETURN TRAP 4 Sheets-Sheet 2 ikz/eflor. firryj 5.

- '44" eva M tlay'a March 18, 1952 Filed Nov. l2,- 1948 H. A. PHILLIPS SUCTION LINE LIQUID RETURN TRAP 4 Shee'tS -Sheet 3 fivezz 021 @mwwzw a March 18, 1952 H. A. PHILLIPS 2,589,859

SUCTION LINE LIQUID RETURN TRAP Filed Nov. 12, 1948 4 Sheets-Sheet 4 Patented Mar. 18, 1952 UNITED STATES PATENT OFFICE SUCTION LINE LIQUID RETURN TRAP Harry A. Phillips, Chicago, Ill.

Application November 12 1948, Serial No. 59,693

Claims.

The invention relates and has reference more particularly to improvements especially designed for such systems for protecting the compressor thereof from liquid refrigerant such as would otherwise return to the compressor in the suction line.

An object of theinvention is to provide improved apparatus for accumulating liquid refrigerant that may be returning in the suction line of a refrigerating system and in utilizing the high pressure refrigerant gas to deliver the accumulated liquid refrigerant to the high pressure side of the system, thereby by-passing and protecting the compressor of the system.

More specifically an object of the invention is to provide a suction line return device for accumulating liquid refrigerant returning in the suction line and which will be automatic in its operation of utilizing high pressure refrigerant gas from the discharge side of the compressor to pump said liquid refrigerant from its point of accumulation to a trap above the receiver so that the liquid refrigerant can be delivered to the receiver by a gravity feed augmented by pressure.

.A further object of the invention is to provide apparatus as described for protecting the come pressor of refrigerating systems fom an overflow of liquid refri erant and which will employ the ejector method for pumping the liquid refrigerant to the trap above the receiver.

Another object of the invention is to provide a suction line return trap for liquid refrigerant which will operate automatically by employing electric means controlled by the level of the liquid in the trap for controlling the pumping action of the high pressure refrigerant gas.

With these and various other objects in view,

to refrigerating systems I the invention may consist of certain novel feati'on'of the modified structure to aconventional refrigerating system; I

- Figure 3 is-an elevational view of a refrigerating systenr'incorporating the improvements of:

to and from the trap; and

the invention modified by a novel type way valve for controlling the gaseous refrigerant 1 Figure 4 is a longitudinal sectional view of the new three-way valve showing the structure of the same.

Referring to Figure 1 of the drawings, which shows a preferred embodiment of the invention, 1

, and by operation of the compressor the pressure of this gaseous refrigerant is increased with a corresponding increase in temperature. The high pressure discharge side of the compressor has connection at I4 with the high pressure gaseous refrigerant line I5, said line having interposed therein the hand valve I6 and which connects with receiver IT.

The cyliinder ll forms a combination receiver and condenser so that the high pressure gaseous refrigerant from the discharge line I5 is condensed to a liquid form and stored in the receiver until ready for use, for which purpose the receiver is provided with a liquid refrigerant line I8 connecting with the receiver at the bottom thereof and which is provided with the hand valve IS. The line I8 conducts the liquid refrigerant to the evaporatcrs of the refrigerating system and fol-' lowing evaporation of the refrigerant to produce the desired refrigerating effect the same is returned to the compressor through the suction line It, thus completing the cycle.

The invention provides improved apparatus for collecting liquid refrigerant in the suction line of the system and returning the same to the receiver, thus protecting the compressor of the refrigerating system which is not adapted to handle slugs of liquid refrigerant with any degree of success. More particularly, the apparatus of the invention employs the'high pressure re-' f'rigerant gasas a pumping medium to facilitate' of'the invention and which illustrates applicaconveyance of the liquid refrigerant from the suctionline to they receiver. Asshown in Figure,

1, an accumulator drum designated by'nuineral 2B is interposed in the suction line H] at a point conveniently in advance of the compressor and' t e returning liquid refrigerant in the suction l. c I0 isv thus collected by the accumulator drum ofthreee with the evaporated refrigerant, however, continuing on and being returned to the compressor. The accumulator is provided with the drain 2i having the hand operated valve 22 for draining oil from the drum. The pipe 23 has connection with the accumulator drum 2!! at a point adjacent the bottom thereof, said pipe including the hand valve 24 and a check valve 25. The depending end of the pipe 23 connects with the top of a trap 26 which initially receives the liquid refrigerant from the accumulator drum 20. The drain 2'! leading from the bottom of the trap 26 is equipped with the check valve 28 and a hand valve 36. The drain connects with the receiver 17.

From the foregoing it will be seen that the accumulator drum and the receiver are connected by means in the form of pipes and conduits for conveying the liquid refrigerant accumulating in the drum to the receiver, thus icy-passing the compressor. The liquid from the drum 2!) naturally drains to the trap 26, it being understood that the hand valve 24 is open to permit such drainage. Also the check valve 25 is constructed to permit the liquid refrigerant to drain downwardly into the trap 26, the check valve closing only upon pressure developing in trap 26 so that the pressure can be maintained in the trap and leakage to the drum 2'3 prevented. The liquid refrigerant in the trap 26 will also have a tendency to drain through the check valve 28 in the drain 2'! to the receiver. However, to augment such drainage the invention provides apparatus utilizing the high pressure refrigerant gas in line l5.

Said apparatus, as shown in Figure 1, essentially consists of an auxiliary line 3| equipped with the hand valve 32, a solenoid operated valve 33, and a three-way valve 34. A pipe depends from hand valve 32 and enters the line [5, said pipe having its end bent in a direction upstream toward the flow of the high pressure refrigerant gas in line It. The three-way valve 34 includes a horizontal connection 36 which joins the valve to the trap 26. The pipe 37 provides the vertical connection for the three-way valve, the same including the hand operated valve 38 and a bent terminal end 40 having location within suction line It with said bent end being directed down stream as regards the flow of the refrigerant gas in the suction line.

The solenoid valve 33 in the auxiliary line 3| is controlled by the photo switches 4| and. 42. Such switches are located on the trap 26 and are actuated in accordance with the level of the liquid refrigerant in said trap. When the level of the liquid refrigerant reaches switch 4| said switch is actuated to cause energization of solenoid 33, opening the valve associated therewith.

With the solenoid valve open it will be seen that the high pressure refrigerant gas from line i 5 will be permitted to flow through the'auxiliary line 3] and upon reaching the three-way valve 3 3 the action of the gaseous refrigerant is such as to close off line 31 so that the high pressure gas flows through line 35 to the top of trap 26. The action of the high pressure gas on the check valve 25 is also such as to close the check valve with the result that pressure is applied to the liquid refrigerant in the trap, causing the same to flow;

through the drain 2? into the receiver. When the level of the liquid refrigerant reaches the 130-.

sition of switch 42 the switch is actuated to cause de-energization of the solenoid valve 33 with the result that the valve is caused to close. The flow above described operations are repeated.

In the modification shown in Figure 2 the operation of the apparatus is basically similar to that disclosed in Figure 1. However, it will be seen that the trap and receiver have a location above the accumulator and in this modification the high pressure refrigerant gas from the discharge line of the compressor is additionally employed to pump the liquid refrigerant from the accumulator drum to the trap.

Referring more particularly to said figure, suction line {36 has connection at 5! with the compressor 52 driven by the electric motor 53 by means of'the endless belt 54. The high pressure discharge side of the compressor has connection at 55 with the high pressure gaseous refrigerant line 56, said line having interposed therein the hand valve 51 and which connects with receiver '58. Said receiver may comprise a combination condenser-receiver. In any case, the high pressure gaseous refrigerant front discharge line 56 is condensed and stored in the receiver until ready for use, for which purpose the receiver is provided with the liquid refrigerant line 66, having the hand valve BI.

In this modification the accumulator drum 6'2 is interposed in the suction line 56 at a convenient point in advance of the compressor and it will be seen that said accumulator drum has a position below the receiver and the trap. It is therefore necessary to pump the liquid refrigerant from the drum to the trap for which purpose the present invention utilizes the high pressure gaseous refrigerant in line 56. Said line 56 is tapped by the auxiliary line 63 at 66, the said auxiliary line adjacent the accumulator drum including the solenoid operated valve 65 and having connection with the ejector 66. The ejector is connected by pipe 6'! with the accumulator drum 62 so that the liquid refrigerant in the drum naturally drains through pipe 61 into the ejector 66. Upon reaching the ejector the liquid entrains with the high pressure refrigerant gas supplied by line 63 and the same is conveyed through line 16 which connects the ejector 66 with the trap I l. The check valve 12 interposed in line 10 facilitates the maintenance of pressure in the trap. The check valve therefore opens normally in a direction permitting flow of the gaseous refrigerant and entrained iiquid refrigerant from the ejector to the trap but automatically closes when a predeterminedpressure develops in the trap. The trap H is provided with the conventional drain similar to that shown in Figure 1, in luding drain pipe '13 having check valve 14 and the hand operated valve '55. The liquid refrigerant from the trap draining through '53 isdelivered to the receiver 58.

The liquid refrigerant draining from trap H is augmented by the high pressure gaseous refriS- erant in line 56 in a manner similar in all respects to that as disclosed in connection with Figure 1. The auxiliary line it is equipped with a solenoid actuated valve Ti and said auxiliary line has connection with the threeway 1 valve 18. At the right hand end of the auxiliary line 16 the same is provided 'with a depending pipe 19 which enters the high pressure gaseous refrigerant line 56 and has its end bent in a direction upstream toward the fiow of the high pressure refrigerant gas. The three-way valve ii; at the opposite end of the auxiliary line 16 includes a vertical connection 80, which connects the three-way valve to the trap II. The third connection for the valve is provided by the line 8i which joins the valve to the suction line 50, the same entering the suction line and having its terminal end 82 bent in a direction downstream, as regards the how of the refrigerant in the suction line.

In operation of the apparatus as shown in Figure 2, it will be understood that the solenoid valve 65 is controlled by the photo switches 83 and 84, being supported on the wall of the accumulator drum and having location within the drum so that the level of the liquid refrigerant actuates said switches. When the liquid refrigerant in the drum reaches switch 83 the solenoid valve 65 is energized and caused to open, admitting the high pressure gaseous refrigerant from line 56 to the ejector 66. The liquid refrigerant passed to the ejector by line 51 is thus conveyed to the trap II and the operation continues until the liquid level within the accumulator drum reaches switch 84. When this takes place switch 84 is actuated to de-energize the solenoid actuated valve 65, causing the same to close, whereupon the pumping of the liquid refrigerant to trap H is terminated.

The application of pressure to the liquid refrigerant in trap II is also automatically controlled by

photo switches

85 and 86 supported by the trap and having location within the same so that the switches are actuated by the level of the refrigerant. When the liquid refrigerant in trap 'lI reaches the level of switch 85 the solenoid actuated valve T7 is energized, causing opening of said valve and the admission of the high pressure refrigerant gas from line 56 to the trap. With the opening of valve i! the three-way valve 18 automatically closes line 8! so that the pressure is prevented from escaping to the suction line. The pressure within the trap also automatically closes check valve 72, thus permitting the pressure to build up within trap i! and effect drainage of the liquid refrigerant through it to reservoir 53. When the level within the trap reaches switch 86 the switch is actuated, causing de-energization of the solenoid actuated valve l1 whereupon the valve closes, terminating the flow of gaseous refrigerant from line 56.

The automatic draining of trap 'II as above described will alternate with the automatic pumping of the liquid by the ejector 56. To a large extent this is controlled by check valve I2 since the valve automatically closes line 10. when a predetermined pressure exists in the trap.

In Figure 3 a modified form of apparatus is shown, basically similar to Figure 1 but employing an improved form of three-way valve for controlling the flow of high pressure refrigerant gas into and from the trap. As shown in said figure the suction line 50 has connection at M with the compressor 92 driven by the electric motor 93 by means of the endless belt 9, 5. The

high pressure gaseous refrigerant line 85 has connection with the discharge side of the compressor and said line conducts the gaseous refrigerant to receiver 95, there being interposed in the.line a hand valve 91 for controlling the now of the gaseous refrigerant to the receiver.-

trap IIJI.

In any case the high pressure densed and stored in the receiver until ready for use, whereupon it is withdrawn by the liquid refrigerant line 98 having the hand valve 99.

In this modification the accumulator drum I00 is interposed in the suction line 90 at any convenient point in advance of the compressor, at which point the accumulator drum will have a position above the receiver and above the trap It, the said trap having a connection with the accumulator drum by means of the pipe I02 which is provided with the hand valve I03 and the check valve I04. The returning liquid re frigerant in the suction line 90 is collected by the accumulator drum I00 and drawn off by pipe I02 which delivers the liquid refrigerant to the A drain pipe I05 connects the bottom of the trap with the receiver 96 so that the liquid refrigerant is periodically pumped from the trap and delivered to the receiver through said drain pipe which is equipped with the check valve I06 and-hand valve I 01.

In the modification of Figure 3 any liquidre frigerant overflowing the evaporator and returning with the gaseous refrigerant in the suction line 90 will be collected by the drum and caused receiver in advance of the same, all as particularly pointed out in connection with the appara-- tus of Figure 1. For periodically pumping the liquid refrigerant from trap I GI, using high pressure gaseous refrigerant in accordance with the invention, the present modification employs an improved form of three-way valve identified by numeral H0 and which is shown in sectional detail in Figure 4. An auxiliary gaseous refrigerant line II I is provided with a depending pipe II2 which enters the gaseous refrigerant line 95 and has its end bent in a direction upstream toward the flow of the refrigerant in said line. The

hand valve II3 controls the fiow of gaseous refrigerant from pipe I I2 to the auxiliary line III. Said auxiliary line has connection at II4 with the three-way valve IIO, which valve discharges to a delivery line I I5 leading to the trap I0 I. The

' valve also has an exhaust line II6 which enters the suction line having its end bent downstream with respect to the flow of the gaseous refrigerant in said; suction line. Accordingly with respect to the three-way valve IIO the auxiliary line II I constitutes the inlet supplying the valve with high pressure gaseous refrigerant. According to actuation of the valve mechanism within the three-way valve the gaseous refrigerant is delivered to line I I5 and thus produces a pumping action on the liquid refrigerant in the trap I0 I, causing the same to flow to the receiver 98. Eventually the gaseous refrigerant in trap I 0! is vented by actuation of the valve mecha-- nism which connects the trap with the line II6. For control purposes the exhaust line I I5 is'provided with a hand operated valve I I1.

Actuation of the valve mechanism within the three-way valve can be controlled by the valve IE5 which is operated electrically by the solenoid IZI. The valve I20 islocated in the bypass conduit I22 and in order to understand the utility of this bypass conduit it is necessary to under! stand the construction and operation of the improved three-way valve which will now be described. Feferring to Figure 4, the three-way valve includes a hodyportion I25 provided with an inlet opening I26 to which the conduit III "is secured and an outlet opening I21 to which the line H6 is secured. The thirdopening of the three-way valve is indicated by numeral I28 and the line 'I I has connection with said opening. The partition I29 located within housing I25 provides a high pressure valve seat I32 located between the high pressure chamber I3I and the delivery opening I28 and a low pressure valve seat-I32 located between the low pressure'chamber I33 and the delivery opening I28. The piston I34, having location in the high pressure chamber I35, is relatively small in diameter compared tothe much larger diameter piston I35 located in the low pressure chamber I31. The chambers are located in opposed relation at the respective ends of the valve body I25 and said pistons are operatively connected by the rod I38 which extends through the central openings in the valve seats I30 and I32, the valve rod at I40 having threaded connection with piston I34 and at I4I having threaded connection with piston I35. The piston I34 is centrally cored for receiving the coil spring I42 which at one end has contact with the piston and at its other end is supported by the adjustable support I43 threaded at I44 in its respective end 545 of the valve body portion I25. This end of the body portion is provided with the passage I48 to which is connected the bypass conduit I22.

The bypass conduit I22 extends to the opposite end I41 of the body portion and in connecting'therewith has communication with passage I48 leading to chamber I31. The solenoid actuated valve I20 is located in the bypass conduit I22 to control the flow of gaseous refrigerant from chamber I35 to chamber I31. The piston I36 in said chamber I37 is cored for receiving the coil spring I49 which is confined between the end of the body. portion and the piston. It will be observed that the coil springs I42 and I49 oppose each other and in accord- I ance with the invention coil spring I42 is a relatively strong spring, whereas spring I49 is considerably weaker so that under normal conditions spring I42 controls and maintains the pis ton I34 in a direction toward the left, Figure 4, to thus hold the piston in contact with the valve seat I30, thereby closing off the chamber IBI and preventing the flow of high pressure gaseous refrigerant to the delivery pipe H5. The piston I34 may be provided with an insert I50 of steel or other suitable hard material for contact with the valve seat so as to take up wear and insure good sealing contact with said valve seat. With the spring I42 extended to maintain the piston I34 in contact with its seat it will be seen that piston I35 is located to the rear of its chamber with coil spring I49 under compression and the hardened insert I5I carried by the piston being located in spaced relation with the seat I32. Accordingly under normal conditions this low pressure side of the valve is open and the ex haust conduit III; has connection with delivery pipe II5 and with the trap IOI.

In accordance with the invention the piston I34 is provided with a bleed or leakage passage I52 connecting the interior of the piston and thus the chamber I35 with the high pressure gas chamber I 35. Under normal conditions with the solenoid valve I20 closed, the high pressure gas will flow through the bleed passage I52 into chamber I35 and into the bypass conduit I22 connecting with this end of the body portion. -I-Iowever, chamber I31.isimaintained at a low high and low sides of the valve.

pressure when the solenoid valve is closed since the bleed or leakage passage I53 in piston I35 connects the said chamber with the exhaust conduit H6. The bleed or leakage passages I52 and I53 in the pistons, respectively, may take other forms, as, for example, the pistons may have a loose fit in their respective chambers such as to allow flow of the gas past the pistons.

When the solenoid valve I is opened flow of gaseous refrigerant at an intermediate pressure will take place in the bypass conduit I22. This intermediate pressure builds up in chamber I31 behind piston I36 and said pressure acting in the same direction as the coil spring I49 will overcome spring I42, causing a movement of the pistons so that the valve seat I32 is closed and I is opened. It is of course understood that the coil springs are so adjusted that this intermediate pressure will accomplish reciprocating movement of the pistons in a direction toward the'right as described. It will be found that the intermediate pressure of the gas flowing through the bypass conduit I22 will be approximately half the difference between the pressure on the Since the valve seat I30 is opened by movement of piston I34 to the right, the high pressure gaseous refrigerant will flow through opening i255 to the delivery pipe II5 which discharges the same to the trap IOI. the liquid in the trap is to force the liquid refrigerant in the trap through check valve I06 and into the liquid receiver G5. The high pressure gaseous refrigerant is not admitted to the exhaust line H5 since the valve seat I32 is closed.

Opening and closing of valve I20 is controlled electrically in accordance with the level of the liquid refrigerant in the trap IIlI. A source of electric current indicated by conductors L1 and L2 has connection through conductors I54 and I55 with the solenoid I2I which actuates said valve I20. A photo switch I is provided for energizing the solenoid when the liquid refrigerant in the trap reaches the level of said switch. A deenergizing photo switch I 51 is provided for opening the electric circuit to the solenoid when the liquid refrigerant in the trap descends to the low level indicated by the position of this switch. The control of the valve I20 in the bypass I22 is therefore automatic and said valve functions to control the internal mechanism of the three-way valve III! as described. Upon deenergization of the solenoid I2I valve I20 will close and the pistons I34 and I36 will be reciprocated to their initial left hand position. This takes place since the intermediate pressure existing within chamber I31 is terminated by the closing of valve I20. The gas within the chamber I31 is constantly bled through passage I53 to the exhaust line I I6 and immediately upon closing of valve I20 this intermediate pressure is terminated so that the stronger coil spring I42 takes over and moves the pistons to their ini-'- tial left hand position. The supply of the high pressure gaseous refrigerant is cutbff and simultaneously the interior of trap I00 is connected to the exhaust line H3. With the parts in normal position again the apparatus repeats another cycle wherein the liquid refrigerant from the accumulator drum I00 drains to trap IOI gradually filling the trap to the level of the photo switch I50 whereupon the three-way valve is again actuated.

This application is a continuation- -in-part of my copending application Serial No. 773,843 filed The action of this gaseous refrigerant on s September 13, 1947 and entitled Suction Line Liquid Return Trap which has become abandoned.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated by the drawings as various other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. In a refrigerating system including the conventional compressor having a suction line for returning evaporated refrigerant to the compressor and having a high pressure gaseous refrigerant line connecting with a receiver, the combination of an accumulator drum interposed in the suction line for collecting. liquid refrigerant to prevent delivery of the same to the compressor, conduit means providing a passageway connecting the drum with the receiver for conveying said liquid refrigerant from the drum to the receiver, a trap included in said conduit means, ejector means utilizing the high pressure gaseous refrigerant for pumping the liquid refrigerant from the accumulator drum to the trap, and other means also utilizing the high pressure refrigerant gas by supplying the same to the trap to effect a flow of the liquid refrigerant under pressure to the receiver.

2. In a refrigerating system, as defined by claim 1, additionally including electric means located on the trap for controlling the supply of gaseous refrigerant to the same by the level of the liquid refrigerant in the trap.

3. In a refrigerating system including the conventional compressor having a suction line for returning evaporated refrigerant to the compressor and having a high pressure refrigerant line connected to a receiver, the combination of an accumulator drum interposed in the suction line for collecting liquid refrigerant, conduit means providing a passageway connecting the drum with the receiver, a trap included in said conduit means for receiving liquid refrigerant from the drum, a three-way valve having two operative positions, said valve in one position connecting the high pressure refrigerant line to the trap to supply said high pressure refrigerant thereto whereby to effect a flow of the liquid refrigerant in the trap to the receiver, and said valve in another position connecting the trap to the suction line for venting the trap.

4. In a refrigerating system including the conventional compressor having a suction line for returning evaporated refrigerant to the compressor and having a high pressure refrigerant line, the combination of an accumulator drum interposed in the suction line for collecting liquid refrigerant, conduit means providing a passageway connecting the drum with the high pressure refriger- 10 ant line, a trap in the conduit means for receiving liquid refrigerant from the drum, check valves in the conduit means on each side of the trap to permit flow in one direction only from the drum through the trap to said line, means tapping the high pressure refrigerant line at a point upstream and connecting with the trap adjacent the top thereof for supplying high pressure refrigerant to the trap, whereby to effect flow of the liquid in the trap through the passageway to said line at a point downstream of said first mentioned point, valve means associated with said high pressure refrigerant supplying means for controlling the supply of said high pressure refrigerant to the trap, said valve means operating to vent the trap to the suction line when the supply of said high pressure refrigerant is stopped, and means con trolling the operation of said valve means in accordance with the level of the liquid in the trap.

5. In a refrigerating system including the conventional compressor having a suction line for returning evaporated refrigerant to the compressor and having a high pressure refrigerant line, the combination of an accumulator drum interposed in the suction line for collecting liquid refrigerant to prevent delivery of the same to the compressor, conduit means providing a passageway connecting the drum with the high pressure refrigerant line for conveying liquid refrigerant from the drum to the line, a trap included in said conduit means for temporarily storing liquid refrigerant received from the drum, a single pipe leading from the top of the trap and which connects with the high pressure refrigerant line and with the suction line respectively, valve means in said single pipe having two operative positions, said valve means in one position connecting the high pressure refrigerant line to the trap to supply said high pressure refrigerant thereto whereby to effect a flow of the liquid refrigerant in the trap to the receiver, and said valve means in another position connecting the trap to the suction line for venting the trap.

HARRY A. PHILLIPS.

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

UNITED STATES PATENTS Number Name Date 1,000,723 Dettmar Aug. 15, 1911 1,106,244 Schliemann Aug. 4, 1914 1,106,287 Doelling Aug. 4, 1914 2,032,286 Kitzmiller Feb. 25, 1936 2,123,021 Phillips July 5, 1938 2,156,426 Brown May 2, 1939 2,164,081 Phillips June 27, 1939 2,193,261 Thomson Mar. 12, 1940 2,267,152 Gygax Dec. 23, 1941