US2547070A - Thermostatic expansion valve - Google Patents

Description

April 1951 c. L. AUGHEY ET AL THERMOSTATIC EXPANSION VALVE 2 Sheets-Sheet 1 Filed March 26, 1947 INVENTORS.

April 3, 1951 c. L. AUGHEY ET AL 2,547,070

THERMOSTATIC EXPANSION VALVE Filed March 26, 1947 2 Sheets-Sheet 2 Faten ted Apr. 3, 1951 7 2,547,070 THERMOSTATIC EXPANSION VALVE Clarence L. Augliey and Lourdes V. McCarty, Milwaukee, Wis., assignors to A P Controls Corporation, a corporation of Wisconsin Application March 26, 1947, Serial No. 737,352

10 Claims. 1

This invention relates to improvements in expansion valves for refrigerating systems of the compressor-condenser-evaporator type employing a liquefiable and vaporizable refrigerant and particularly to a valve actuatedby a limit pressure charge in thermally responsive means actuating the valve.

The phrase pressure limit charge designates such charge in the thermal element of an expansion valve that the pressure in the element remains substantially constant when the temperature of the charge (and of the space to which the element is responsive) reaches a given value. Hence increase in the temperature of the refrigerated space, even above the pro-determined limit, does not cause opening of the expansion valve. Therefore, the evaporator pressure cannot exceed a pre-determined value and the compressor motor cannot be overloaded. In the use of limit charged expansion valves, the coldest spot to which the limit charge is subjected, is the spot controlling the action of the valve. Such spot, heretofore, was in the valve itself where the liquid refrigerant expands into vapor and is a considerable distance from the thermal element bulb which should be in the cold spot. Hence it was heretofore necessary to insulate the expansion chamber within the valve from any adjacent chamber forming a part of the thermal element.

A further problem in the use of refrigerating systems with an expansion valve is the so-called unloading of the compressor which is the condition in which the valve bypasses the refrigerant on the off cycle until the pressure in the condenser is approximately equal to that in the evaporator, thus avoiding overloading the compressor during pull-down of the system and permitting the use of a low-starting torque motor. Both the initial and the operating costs of a refrigerator are thus decreased. Another difficulty with the usual expansion valve is the adjustment of the superheat value of the valve which requires thevariation by small increments, of arelatively large and heavy spring. The term superheat defines the increase of tempera ture of the vapor at a given pressure, above the temperature at the same pressure when the vapor is in contact with the liquid.

It is therefore one object of the present invention to provide an expansion valve which will avoid development therein and adjacent a portion of the thermal element actuating the valve, of a lower temperature than the space about the portions of the thermal element.

Another object of the invention is to provide an expansion Valve in which the refrigerant expansion is divided into two steps to reduce the cooling resulting from expansion to such extent as will hav no effect on any of the thermal element portions adjacent the locations at which either of the expansion steps take place.

Another object of the invention is to provide a multi-chamber expansion valve with means for equalizing the pressures in the several chambers in which expansion occurs, with the evaporator pressure thereby unloading the valve during the off portion of th system cycle.

A further object of the invention is to provide a refrigerant expansion valve in which expansion is divided into a relatively large pressure drop and a relatively small pressure drop which makes it possible to unload the system compressor.

Another object of the invention is to provide an expansion valve with a superheat adjustment which will be more sensitive and variable by smaller increments than is possible in valves used heretofore.

And a further object of the invention is to employ a spring for determining the super-heat setting of a refrigerant expansion valve, other than the spring urging a first or main valve closed in opposition to the action of a thermally responsive element, and which is more accurately adjustable than was heretofore possible by adjustment of the valve spring.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 is a cross-sectional view taken substantially on a central plane through the longitudinal axis of one embodiment of the present invention;

Fig. 2 is a View similar to Fig. 1. of another embodiment of the invention; and

Fig. 3 is a view similar to Fig. 1 of a third embodiment of the invention.

Generally, the present invention provides an expansion valve for a compression type refrigerating system, the valve receiving liquefied refrigerant and partially expanding the refrigerant in a first step through a first valve into a first chamber adjacent a portion of a thermal element controlling valve operation. The partially expanded refrigerant is held in such chamber under pressure until the refrigerant is further expanded in a second step through a second valve into a second chamber which forms threaded into the casing ll.

3 .1 a part of the passage to the evaporator. A bypass is provided in connection with one of the valves to unload the system by equalizing the pressures in the chambers. The second valve is a pressure-reducing valve and is under the action of a spring which is more accurately adjustable to vary the superheat setting of the valve than was possible heretofore.

Referring particularly to the drawing, number designates a casing having an inlet passage I l in which a strainer I2 is held by a nut i3, The passage H terminates in an enlarged portion l6 connectible with a chamber 11 by an opening in a valve seat member including a mounting is threaded into the opening andsupporting a valve seat member I9. The valve seat mounting I8 extends into chamber H as a-"hollow cylinder with holes through the wall thereof and with a slot 28 in the end of the cylinder wall. The slot receives one of two ears 23 extending from a valve body 2.4., the other ear slidin on the wall of the mounting, and the ears guide such valve body in its movement in 'the valve seat mounting l'8 to bring the needle point of the valve 2'4 into and out of seating position in the valve seat It.

The valve 24 is mounted in a cup-shaped carrier 25 with a lip flange 2'6 and 'is movably supported therein by a spring 27. The valve carrier is adjustably supported on a spring 36 seated at one end under the carrier lip 'flange and seated at the other end on a ring 3l threaded on a cylindrical block 32 secured against relative rotation on a stem 33 and extending through a closure member 34 The stem 33 is sealed into the closure 34 by packing 35 compressed by a nut '36, and the end of the stem protruding beyond the nut is protected by a cap 31.

The valve carrier supports a plurality of pushpins 40 extending from chamber ll through the end of the casing into a chamber 4! defined by a flexible diaphragm 42 fixed on the casing II, the pu'shpins bearin on a pad 43 held in contact with the diaphragm by the .pushpin's. The passages in which the pushpins slide, are materially larger than the pushpins so that the pressures in chambers H and 4| are always substantially equalized. An apertured 'cap 46 encloses the diaphragm 42 and coacts therewith 'to form a chamber 41, the cap also serving to hold the di'aphragm on the casing in gas-tight relation. Chamber 4'! is closed bya plug 48 in which is fixed a conduit 49 connected'with a bulb 58 which is to be located adjacent the evaporator in the space to be refrigerated. A spring 5! acts between the cap 46 and a pad 52 bearing on'the diaphragm 42. Chamber 41, conduit 49 and bulb are limit charged with a liquid (such as methyl chloride when the system is charged e. g. with difluoro dichloro methane) which is partially l:

evaporated at a given temperature and which produces such pressure, at the given temperature, as will raise the vaporization point of the liquid suficiently to prevent further vaporization thereof and further increase in pressure so long as the space to be refrigerated is at the given temperature.

The casing l I has connected therewith an outlet fitting 56 of substantially'T shape, which provides an outlet chamber and passage 51 to an evaporator (not shown) and receives means guidin and adjusting a valve 58 which separates the chamber [1 from the chamber '51. Such valve seats on a'portion of the casing wall definingthe chamber l1 and is movably held in seated position by a spring 59 acting between the valve and a thimble-like guide 60 forming a seat for one end of the spring. The position of the guide 60 is adjusted by movement'of a stem 6| threaded into the outlet fitting and sealed therein by packing 62 through which the stem extends for adjustment, the protruding end of the stem being protected by a cap 63.

The action of the described structure can best be understood by consideration of the temperature values prevailing in the several chambers. It is assumed that the temperature at the evaporator inlet is to be 0 F. and that the refrigeran't will absorb sufficient heat in the evaporator to raise the refrigerant temperature to 10 F. The coldest spot in the usual refrigerating system employing an expansion valve, is the chamber H of the valve and it is accordingly usually necessary to insulate such chamber from the chamber 41 (and the bulb 50) which should be responsive only to the evaporator temperature. But in the present construction the temperature in chambers l1 and 4i can be made higher than the evaporator temperature because the usual refrigerant expansion is divided into two steps between chambers ii and 5?. The temperature in chamber I! may be made 15 F. which is 5 higher than the desired temperature of the evaporator and the bulb "50 (rather than lower than such bulb temperature). But chambers l1 and 4.1 are connected by the pushpin passages and chamber 4| is also at the temperature of 15. Hence it is no longer necessary to insulate chamber 41 from chamber if? to avoid a cold space in the valve itself.

At the above temperatures, the pressure relations in the several valve chambers are such as to .produce another useful result. At the above temperatures, the absolute pressure in chamber I7 is 32.44 and in chamber '5? is 23.87, all pressures being in lbs. per sq. in. absolute. There being a difference of only 8.57 lbs. pressure between the first chamber l l and the second chamber 51, a small bypass may now be provided in or around valve 58 to equalize the pressures in such chambers during the oif portion of the system cycle. Such bypass is shown herein as a small opening 64 through valve 58. Even when valve 58 is closed, the pressure in chamber 1! causes flow of partially expanded refrigerant into chamber 5.! (and into the evaporator) until the pressure in the several chambers is'equalized thus unloading the valve. The opening -64 .is sufficiently small (of the order of a ..Oi)B-..02 inch in diameter per ton of refrigeration) so as not to interfere with the pressure-reducing or second expansion step of valve 58. The small opening is, however, non-clogging and has .such character- .istic only because of the low pressure difference The temperatures of chambers l? and 4| are controlled by valve 58 which is under a pressure difference of only 8.57 lbs. and the spring S'S-urging the valve to seat the position need exert only that force. Hence such spring may be made with a relativelysmall'diameter and is'more accurately adjustable by small increments than was pos:

sible with the relatively "large and heavy spring 5 30 heretofore used for the super-heat adjustment.

At 10 F. the pressure in chamber 41 is 23.60 lbs. and the pressure in chamber I! at I5 is 32.44 lbs. These pressures require a spring 5| to exert aforce of 8.44 lbs. per sq. in. of diaphragm area plus spring 30. Spring 30 which is now used only as a valve-closing spring can accordingly be made much softer. It is obvious that by selecting the proper charge and temperature relations, spring 5| may be eliminated.

In the several modifications shown the structures are generally similar to those above described but are materially simplified. In Fig. 2, a casing 61 provides an inlet passage 68. A valve seat member 69 receives a valve I controlling flow of refrigerant into a first chamber H, such chamber being partially defined by a partition I2 with an opening therethrough and a bead about the opening to form a valve seat.

The first valve It is mounted on a plate "I3 movable in contact with the walls of the first chamber II and is supported on a spring I4 seating on the partition 72. A second chamber 71 also forming the passage to the evaporator, receives refrigerant from chamber ll under the control of a second valve 70 with an opening I9 therethrough and supported on a spring 80, the other end of the spring being seated on a plate BI supported on a stem 82 for adjustment of the spring force. The stem 82 is mounted in a' gland 83 threaded into the valve housing and sealed therein by a packing BA with a follower 85. The stem projects beyond the follower 85 for adjustment and such projecting stem portion is enclosed by a cap 86.

A diaphragm 90 is mounted on the casing 61 to define a chamber 9i into which pushpins 92 extend from their support on the valve plate I3, the pushpin passages again connecting chambers TI and SI. The pushpins engage with a pad 93 and hold such pad in contact with the diaphragm 90. A cover 94 is fixed on the valve casing and coacts with the diaphragm 90 to provide a chamber '95 with the diaphragm serving as a flexible wall thereof, the chamber being closed by a plug 96. The diaphragm is held in contact with the pad 93 by a spring 9'! seating between the cover and a pad 58 resting on the diaphragm. A tube 99 extends through the cover 94 in gastight relation and is connected with a bulb similar to bulb 50 and also located in the space to be refrigerated. Flexure of the diaphragm is under the action of the limit charge in such chamber, tube and bulb as is wellknown.

- -In Fig. 3, a casing I02 is provided with an inlet passageway 93 culminating in an enlarged portion I04 having an. opening through a wall thereof communicating with a first chamber IE5, flow 'of liquid between inlet #03, IM and chamber I05 being controlled by a valve I 06. The stem of valve I05 has a plate I0! mounted thereon and the end of the stem extends into a passage in a cap I08 threaded into the valve casing, the plate and the stem guiding movement of the valve which is urged toward closed position by a spring I09 acting between the plate and the cap.

The chamber N35 is separated from a second chamber H3 also forming the outlet passage to an evaporator (not shown), by a valve II I having an opening I i 5 therethrough and urged toward seated position by'a spring IIB acting between the valve and a plate H1. Th plate II I is adjustably positioned by a stem II8 threaded in a gland- I I9 which is itself threaded into thevalve 6. casing. The stem is sealed in the gland by pack ing I20 which is compressed by a packing fol lower I2I and the end of the stem II8 extending beyond the packing follower is enclosed by a cap I22.

A diaphragm I25 closes one end of easing I02 to define a first expansion chamber I05 from which partially expanded refrigerant may pass to a second expansion chamber through valve II4 and the passage II5 therein. The diaphragm is enclosed in a cover I2! coacting with such diaphragm to define a chamber I28 having an opening therein closed by a plug I29 into which is set a tube I30 connecting the chamber I28 with the interior of the tube and with a bulb similar to bulb 50 of Fig. 1. The chamber I28, the tube 29 and the bulb of the present modification are charged as above described, and the bulb is so placed as to be responsive to the temperature of the evaporator in the space to be refrigerated.

A pushpin I33 bears on valve I06, through the aperture in valve seat member I35 for such valve, and is connected with a pad I34 bearing on the under side of the diaphragm #25 under the pressure of the spring I09. A pad I35 rests on diaphragm I25 to provide a seat for a spring I31 acting between plug I29 and the pad to aid the pressure of the charge in the thermal element in keeping the diaphragm thereof under pressure in the direction for opening valve I05.

It will thus be seen that the present invention provides a structure in which a limit charged valve does not require heat insulation of the thermal element from the refrigerant expansion chamber in the valve, in which the valve is made unloading in a simple and practical manner and in which the super-heat adjustment is made on a spring more readily adjusted than the usual valve supporting spring.

The present structure provides a casing receiving an expansible refrigerant which is liquefied under pressure. The liquid refrigerant is expanded and vaporized in a plurality of chambers in the casing and connectible in series. Vaporiz'ation of the refrigerant into the several chambers is under the control of a valve for each chamber thereby dividing the expansion into a plurality of stages or steps of which the first stage results in a large decrease in pressure from the compressor discharge pressure at which the liquid refrigerant is held in the condenser receiver and of which the second stage provides a relatively small decrease in pressure. The valve controlling the first expansion stage is urged toward seated position by aspring which may-be adjustable either at the factory only or may be adjustable in the field also. Such spring op" posed by the pressure in a chamber forming a portion of a thermal element carrying a limit charge responsive to the temperature of space to be refrigerated and usually associated with the evaporator. The valve controlling the second expansion stage is also urged toward seated position by a spring which is however relatively small and easily adjustable and such spring acts only against the pressure in the first expansion stage. The thermally responsive ele ment includes a diaphragm subjected on the one side to the pressure of the thermal element charge varying as the evaporator pressure varies and subjected on the other side to the pressure of the partially expanded refrigerant in the first expansion chamber. The pressure relations in the several expansion chambers may accordingl-y be readily so adjusted that the temperature in the first expansion hig e than aporator t mperatu e thereby mak ng the mit charge of the thermal element zesnons ve to the evaporator temperatu e- With pressure relations in the several chanp hers adjusted to obtain the r su t a et e d scribed, the and .see nd e ans members ay be interconnected by 'llni pntrfilled 11 8 5 sa so that the :pressu such membe w ll equ uze when the firs valv is losed a d these-- \by permit unloadin of th comp ss r 'Sueh nti us connection oi the ex an ion 'eh m hers is practical because the djfierence in pres.- sure "between :the first and second pharnbers is l iv ly small and s ch ii er nee in pres u e does not .0102; the relativ l s a pas a ethe nlo ding passa e is .h r in hown an pe ture through the second valve but-,rnay of course be .a passage through the ca ing itself,

In the :present construction, the hi-as spring for the first valve is required only to'he vadjusted to rcoact with the pressure of the thermal element limit charge a a given temperatu e and need not :be as large ,as heretofore. fiuoh spring may now be adjusted in the factory and a relatively small spring which is easily ad uste b relatively small increments and opposes only the pressure in the first expansion chamber, may now be employed for any field ard Stm mS fine?- essary to set the .degree of expansion the first chamber tor ob aini g the empe ature ther determined by rartieul r sys m d t ns int h field, which wil b hi her h eveperet m rature o a ven sy t m- The division of the expansion action into {a p r y f s ps, the provi ion of an passage and the adjustment of superheat by use of the spring acting on the second valve, are each separate features which :may be sepa ately incorporated in .a valve, or any two or more of such features mayibe combinedin thesameyalve.

Ailthough ilout a few embodiments of he present invention have been illustrated and described, it will be apparent to :those skilled n the art that various changes and modifiea-tions may be made therein withoutdeparting from the spirit of the invention .or from {the scope gf the appended claims.

e claim:

1. In a valve :ecntrolling expansion of a liq- :uid refrigerant under'pressure ina refrigerating system of the compression type, a easing receiving the refrigerant and defining .a first changbei in series with a second chamber, .a first and a-second valve, the first and second valves serially controlling expansion of refrigerant :intoithe first and the second chamber and dividin ex;- pansion of the refrigerant into :a plurality of steps, means responsive to the temperature of the space to be refrigerated and controlling opening of the first valve, and means responsive to pressure in the first chamber and controlling opening of the second valve, the second valve having an aperture therethrough for equalizing pressure in the chambers upon closing of the 2. In an expansion valve for refrigeratingsysternsemployin a compressed vapcrizahle retrieerant, the combination of, a :pair of valve vcontrolling :theexpansionand flow of the compressed bulb [comprising a ivaporizable liguigl which her end ertieetee t9 he tem ature 9; the space to be refrigerated, a charge in saidJ-pulb eempn ng .e va e i able liquid whi ari s be 5D. s e i said chamber mpe atuse anions n aids ace and eom eiy terror ed a a p ed te t i d emperature 9 limi t e Pres re ea q me er, e ably esmneeti g aid "di phragm one 9! sai val es, sa d en valve b ing e ulated ,ov s id-ii ap em to llow part a e pansion 9; as refrigerant to a temperature her than that in sa s ac the pa t ally expended ref ige ant a ting in opposition t the pre s e .i sais e am er nd ppes tien to th n es ng acting on the oth r valve to open -said '9 v e and all w fin l expansio o rein-sen ant.

3- en ex an en va e ere ri eratin tems mp ev e a eerop essesi v p lizeb e refug erent, the hinatien o a pa e ua ves eerit e lins th ex ans on and fl -9 th :QQmDWSfi f. ei rent hrou h t e ex ans on a e sneen b sine sa d va v s t hei eated p tiens a v ih e velum eh m i lud ng a di ph agm sex ng in r spo se to pre ur a et ens t e eh m er a e ler bu b co nected to sa d e iee ed to t e m e tur 9 t e sne 9 gereted, a :e erse .se d bul some a -varPQ i. ah e.1-iq d w c va e the n e u sa d mem it tem ra u e er et'ens in said spa e; me h h is ee nplete p iz e a e 1 eetermin em er tere oi .m1t t e pressu sa ch mber eans e .hl e enee ne sai eienhraem s ne re sai vanes said pee aite heme re ulat av said eieehr t allow a tial expansion of the refrigerantifto a-,-temper ture higher than that in said s ace, the pa tial e t nd d r te i eran ea n in e q r n ate -n es.sur e sa d chamber and n --9Pne it 9i h means actin on the o he valve [t9 O en handed refr erant le i e hi he t a perature o said rfe erhu le- :In an Kenna temsemuleuin c. .7 .r terant, the combination-oi, a hai o alves trolling the expansionand iilow of the compressed refrigerant throu the e pa sion Malta d ustable means biasing said valves {to their ted positions, a variable i lolllm fih'slmbfi fiq l t fi diaphragm :fiexing in respon e t pressu var e- 1ti0nsi-nth eheim L e .e. bu 9e eies t said lchamber and subj cted 119t tempera ur of the pace to be r eiriserateelea char e sa varies the pressure in said ichamhe .mne atu variations in sai space and on completely vapor d at a n edeterin ned tem e atu e t iimit :the pressure. in i 1than.l-he m an ove e ly c nn t ng said di a m (and one 9 said valves, said one waive being regulatedbytsaidgiaph ase; :t al ow partial ex ans on of h re us tena t at a em era ure hi her th ti w aid sp the partial y expend r fri e ant actin in pp sition to the pressureinsaidnhamhe an i pposition to the a 'ustahle meanea tine on theee h ma v :tonnensaid', th r-ra andall w final exp nsion of t e r eran th tenm n a t e ly ex rndedi e serent as hi he tha :t temperature [of said rfee er hull) i .ezspans en twe v e reirige a ine e es: :te s employ n a r mn ssed va q tiz b ef trollin therennansi an :tloxvp-i e eon pres e i refrigerant through the expansion valve, adjustable means biasing said valves to their seated positions, control means including a limit pressure charged bulb subjected to the temperature of the space to be refrigerated, one of the valves being actuated by said control means'to allow partial expansion of the refrigerant to a temperature higher than that in said space, the partially expanded refrigerant acting in opposition to said control means and in opposition to the adjustable means acting on the other valve to open said other valve and allow final expansion of the refrigerant, the temperature of said partially expanded refrigerant being higher than the temperature of said bulb, and an orifice communicating with both sides of said other valve to reduce the pressure of said partially expanded refrigerant when said one valve is closed.

6. In an expansion valve for refrigerating systems employing a compressed vaporizable refrigerant, the combination of, a pair of valves controlling the expansion and flow of the compressed refrigerant through the expansion valve, means actuating one of the valves to partially expand the refrigerant, said metans including a feeler bulb subjected to the temperature of the space to be refrigerated, a charge in said bulb comprising a vaporizable liquid which varies the pres" sure in the bulb with temperature variations in said space and which is completely vaporized at a predetermined temperature to limit the pressure in said bulb, said actuating means being controlled by said partially expanded refrigerant and by pressure variations in said bulb, the other of the valves being actuated by the partially expanded refrigerant to control the pressure of the partially expanded refrigerant and to allow final expansion of the refrigerant.

7. In an expansion valve for refrigerating systems employing a compressed vaporizable refrigerant, the combination of, a pair of valves controlling the expansion and flow of the compressed refrigerant through the expansion valve, means actuating one of the valves to partially expand the refrigerant, said means including a feeler bulb subjected to the temperature of the space to be refrigerated, a charge in said bulb comprising a vaporizable liquid which varies the pressure in the bulb with temperature variations in said space and which is completely vaporized at a predetermined temperature to limit the pressure in said bulb, said actuating means being controlled by said partially expanded refrigerant and by pressure variations in said bulb, the other of the valves being actuated by the partially exthermally responsive control means including a feeler bulb subjected to the temperature of the space to be refrigerated, a charge in said bulb comprising a vaporizable liquid which varies the pressure in the bulb with temperature variations in said space and which is completely vaporized at a predetermined temperature to limit the pressure in said bulb, one of the valves being actuated by said control means to partially expand the refrigerant, the other of the valves being actuated by the partially expanded refrigerant to control and complete the final expansion of the refrigerant.

9. In an expansion valve for compression type refrigerating systems employing an expansible refrigerant, the combination of, a pair of valves controlling the expansion and flow of the compressed refrigerant through the expansion valve, thermally responsive control means including a feeler bulb subjected to the temperature of the space to be refrigerated, a charge in said bulb comprising a vaporizable liquid which varies the pressure in the bulb with temperature variations in said space and which is completely vaporized at a predetermined temperature to limit the pressure in said bulb, one of the valves being actuated by said control means to partially expand the refrigerant, the other of the valves being actuated by the partially expanded refrigerant to control and complete the final expansion of the refrigerant, the temperature of said partially expanded refrigerant being higher than the temperature of the charge in said bulb.

3.0. In an expansion valve for compression type refrigerating systems employing an expansible refrigerant, the combination of, a pair of valves controlling the expansion and flow of the compressed refrigerant through the expansion valve, limit pressure charged thermally responsive control means, one of the valves being actuated by said control means to partially expand the refrigerant, the other of the valves being actuated by the partially expanded refrigerant to control and complete the final expansion of the refrigerant, the temperature of said partially expanded refrigerant being higher than the temperature of the limit pressure charge in said control means, and an orifice communicating with both sides of said other valve to reduce the pressure of said partially expanded refrigerant when said one valve is closed.

CLARENCE L. AUGHEY. LOURDES V. MoCARTY.

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

UNITED STATES PATENTS Number Name Date 1,971,695 Ploeger Aug. 28, 1934 2,021,881 Askin Nov. 26, 1935 2,306,534 Freres Dec. 2-9, 1942 2,309,405 Matteson Jan. 26, 1943 2,335,824 Dillman Nov. 30, 1943

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