US2943785A - Internally powered compressor - Google Patents

Description

July 5, 1960 e. E. MALLINCKRODT 2,943,735

' INTERNALLY POWERED COMPRESSOR Filed Jan. 25, 1957 3 Sheets-Sheet 2 July 5, 1960 a. E. MALLINCKRODT 2,943,735

INTERNALLY POWERED COMPRESSOR Filed Jan. 25, 1957 s Sheets-Sheet s 7 2,943,785 INTERNALLY POWERED COMPRESSOR George E. Mallincltrodt, St. Louis, Mo-, assignor to Elliot Enterprises, Incorporated, St.Louis, Mo., a corpo-.

ration of Missouri Filed Jan. 25, 1957, Ser. No. 636,415

6 Claims. (Cl. 230-139) displacement, although havinga variable compression ra-. tio for combustion; the provision of an efficient internally powered compressor of the class described having su-' perior pressure-speed characteristics determined by said variable compression ratio; the provision of a compressor of the class. described in which each piston-is operative for both power and compressing events, thus minimizing the number ofpartsrequired and resulting, for a given capacity, in a comparatively compact, light-weight and low-cost machine; and the provision of a compressor of this class havinginherent substantialdy'namic balance between its rotating parts. Other objects and featnreswill be in part apparent and in part pointed out hereinafter. 'The invention accordingly comprises the elements and combinations of-elements, features of construction, and

* arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of which will be indicated in the following claims.

In the accompanying drawings, in which several of various possible embodiments of the invention are illus; trated,

Fig. this a diagrammatic axial-section of an eighte.

piston machine illustrating one formpf the invention; Fig. 2, is a cross sectiontakenjonline 2:-.-2 o' f Fig'.. 1;

Fig.3 is a diagrammatic view'simila'rto .Fig ;,2 but showing a subsequent position of parts and including a showing of a turbine to be supplied with-gas;

Fig. 4 is a cross section takenon line 4-4 of Fig. 1;

Fig. 5 is a view similar to Fig. Zbut illustratinga modified six-piston form of the invention;

Fig. 6 is a diagrammatic view similar to Fig, 5 but showing a subsequent position ofparts; and,

Fig, 7 is a cross section similar to Fig, 4 but illustrating parts correspondingto the modified formof theinvention shown in Figs. 5 and 6.

Corresponding reference. characters indicate" corresponding parts throughout .theseveral views oithe dra w.

ings. Diagrammaticviews are used hereinfor clarity,

further detailed features of certain subcombinations of parts used having beendisclosedin my various prior patents, including 2,638,880; 2,680,430; 2,687,609 2,736,-

and 2,756,728. Various sealing means between relatively moving parts, known, to the art, are not shown.

Also for purposes of clarity and description andeaselof reading the drawings, certain sets of, pistons are identified by arbitrary stippling, and others are not. This stippling has no other significance.

Various machines, such as gas turbines, for example, require a substantial volume ofa working medium such as a hot compressed gas, apart of whichmay beair. Reciprocating positive displacement compressors,-because nite States. Patent 9 F 2. of their complexities, are not ideal for producing such a medium in quantity. Nor are centrifugal compressors advantageous, because of-their noupositive displacement characteristics. By means of the present invention, the advantages are obtained of an inherently dynamically balanced comparatively small and eflicient rotary machinev having a single set of positive displacement elements for production of power and compression, having characteristics of quick response to variations in requirements for a supply of hot operating gas, by other units.

Referring now more particularly to Figs. 1-4, which show a preferred form of the-apparatus, there is shown in general at numeral 1 a toroidal or annular cylinder formed by an outside ring 3, to which are bolted internallyfiat side checks 5 and 7. The latter haveextensions forming sleeve bearingportions 9 and 11, respectively, for rotatablequills 13 and 15. Adjacent ends of the quills 13 and 15 are formed as abuttingrings 17 and 19,. respectively, which have suitable running sealing by the inside face of thering 3, the inside planes of the cheeks 5 and 7, and the coextensive outside cylindric forms of the rings 17 and 19. Ring 17 carries four pistons A, B, C, D, spaced at intervals. These-pistons are of substantially the same rectangular cross-sectional form as the cylinder 1 and have sealing means (not shown, but see Patent 2,756,728). Ring 19 carries four pistons W, X, Y, Z, spaced at 90 intervals. These pistons are also of substantially the same rectangular cross-sectional form as the cylinder 1 and carry similar. suitable piston ring sealing means. Thus the pistons A, B, C, D on ring 17 interdigitate-with pistons W, X, .Y, Z on ring 19 (see Fig. 2).

The quills '13 and 15 have extensionsll and 23, respectively, to which are splined hubs 25 and.27, re-

spectively, the same being locked in proper splined positions,-by fastening nuts 29. The splines are numbered 2. The hubs 27 and25 carry identical flywheel elements 31 and 31' which, if desired, may be of the variable inertia type such as shown, for example, in'rsaid Patent 2,638,880; or these flywheels may be of the constant inertia type such as shownin-said Patent 2,687,609. The; hubs :25 and 27'also respectively carrygidenticalspiders; 33 and ;35,,one ofwhich (35) is shown in solid .end 'ele-. vation in-Fig. 4 and one'ofwhich.(33) is shown in dotted E elevation,-

The reverse-lacing parts attached to spider 351 areto'be deseribedbelow, and those on spider 33 are to be: understood tobe identical inform-and operation. The-- indexcharacters employed for describing those; on spider 33 will be the samewas thosefor the-parts on spider 35; exceptthat the former will be primed. Detailed, descrip tion-ofthe parts associated. with-spider 35 .willtherefore arm49 of each bell crank, is slotted, as ShOWI'l fill; 51,-

and contains a .drawbolt 53, A coil. spring 55 'is wound;

around oppositeends ofeach pin and anchored at' its ends by studs 57. A bale portion 59 of each spring. ,reacts against the respective arm. of spider- 35. Each pin carries a. polygonal head 61, adapted to be engaged, by,

aiyvrench: Thus, by looseningthe ,drawbolt 53,. the pin 37-maybe wound, so as to wind or tension the. springv 55; After winding, the drawbolt istightened, whereupon each bell crankxtl becomes biased in a clockwise direction (Fig. 4)

i atented July 5,- 1.960

This forces eachfollower roller 47 against". a cam track 71, further described below, 1

Bearing sleeve 11 is flanged, as shown at 63, for receiving a bolted assembly of ring parts 65, 67 and 69 for supporting an inwardly directed camtrack 71. Correspondingly indexed but primed parts are attached to the bearing sleeve 9 for supporting an inwardly directed cam track 71'. The cam tracks 71 and 71 are preferably mounted, so that their shapes are axially aligned. The spider 3-3, bell cranks 41 and follower rollers 47' are mounted to be as shown by the dotted lines in Fig. 4 when the groups of pistons A, B, C, D and W, X, Y, Z are related as shown in Fig. 2.

Ring 65 also carries a bearing 66, for supporting the extension 23 of quill 15. A corresponding bearing 66' in ring 65' supports the extension 21 of quill 13. Thus it may be seen from Fig. .4 that the springs 55 and 55" bias the respective sets of follower rollers 47 and 47 against the respective cam tracks 71 and 71', the latter showing in Fig. 1.

Each cam track 71 and 71', as illustrated in the case of cam track 71 in Fig. 4, is essentially square in form, having four flats 73 and four rounded or filleted corners 75. It will be understood that cam track 71' being located directly behind cam track 71 as viewed in Fig. 4, is not visible in that figure but appears in Fig. 1. The relationship of the parts is such (Fig. 4) that clockwise rotation of the spiders 35' and 33 is permitted, but each has a reverse-locking position. The reverse-locking position of spider 35 appears in solid lines in Fig. 4. Thus ring or rotor 19 (to which the spider 35 is attached) and its pistons W, X, Y, Z are reverse-locked. This is for the reason that thrusts on the follower rollers 47, due to any tendency toward reverse rotation in the Fig. 4 solid-line position, are at (or so near) aright angle with respect to one of the flats 73 as to prevent anticlockwise rotation of each bell crank41 (in the case of spider 35. At this time the corresponding connected spider 33 and follower rollers 47' pass through the dotted-line position shown in Fig. 4 and the pistons W,.X, Y, 'Z

on ring 19 are in the intermediate position shown in Fig. 2.

At numeral 77 is shown a drive shaft carried on sets of bearings 79 and 81 within the quills 13 and 15. Bolted to the hub 35 is a gripping assembly 83 for one end of a drive spring 85. A second gripping assembly 87 is provided for the opposite end of this spring, said as-,

sembly 87 being attached to the shaft 77 by the set screw gripping arrangement shown at 89. Corresponding parts indexed with primed numbers connect the hub 25 with the other end portion of shaft 77. The springs 85 and 85' are in neutral or unstressed position when the parts are in the positions illustrated in Figs. 2 and 4. This position of parts will hereinafter be referred to as a neutral position. The shaft 77, with the operating parts of the auxiliaries connected thereto, has sulficient moment of inertia that it will maintain a substantially constant angular velocity while delivering or receiving energy from the rotor systems with which it is connected by springs 85 and 85.

Referring to Figs. 2 and 3, there is shown diagrammatically at numeral 91 an ignition device'such as a constantly energized glow plug, countersunk into the inner face of cheek so as to allow the pistons to pass. Further details regarding such ignition devices are unnecessary, since such are known in the art. At numeral 93 is a fuel inlet port, to which a suitable carburetor or fuel injection device is attached, not shown because it may be any of known type. At numerals 95 and 97 are shown air inlet ports, connected to the atmosphere. At 99 is shown an exhaust gas outlet port, and at numerals 101 and 103, air exhaust ports. The ports 99, 101 and 103 are connected to a gas manifold 105 supplying appropriate apparatus 107 for using the gas and air from ports 99, 101 and 103. This may be a gas turbine, such as illustrated diagrammatically at 107. At numeral 109 is shown a scavenging auxiliary exhaust port connected to the atmosphere. 7 r

Referring to Fig. 2, the bracketing arrow P indicates the 180 portion of the machine, throughout which power events occur, and bracketing arrow G indicates the 180 portion of the machine throughout which air compression events occur. Ports 93 and 99 subtend the power section P. Ports 103' and 95 subtend the compressor section G. Ports 103 and 97 subtend what will be called a subsection of section G and ports 95 and 101 subtend what will be called another subsection of section G. Operation is as follows, referring to Figs. 2 and 3, assuming that the machine is in operation:

Pistons W, X, Y, Z are reverse-locked, in view of the reverse-locking of spider 35 and follower rollers 47 (Fig.

- 4). This is due to the back pressure on piston W caused by an explosion event occurring between pistons W and B. This pressure is in excess of compression pressure between pistons A and W. The ignition means 91 has previously ignited fuel and caused said explosion event.

But means 91 is shielded from igniting fuel under compression between pistons A and W. The pistons A, B, C, D are being advanced clockwise, their corresponding spider 33 and follower rollers 47 having moved from a prior reverse-locked position thereof to the dotted-line position shown in Fig. 4. Thus the explosion event occuring between pistons W and B drives pistons A, B, C, D, reaction being provided by piston W, which is reverselocked. Spent gas from a previous explosion event is being compressed between pistons B and X, and travels out of port 99 to the turbine 107. A suction event (through port 93) is also occurring between pistons A and Z, drawing in carbureted fuel gas or vapor through port 93. 1 a

An air suction event is occurring between pistons X y and C, air being drawn in through port 95. Air is also the turbine 107. Air is also being compressed between pistons D and Z and being driven out through port 103 to the turbine 107 Thus'at the instant under discussion, pistons A, W, B are engaged in gas power events in the arcuate power section P of the machine, and pistons D, Y, C are engaged in air compression events in the arcuate compressor section G of the machine. Pistons Z and X are engaged in both sets of events, respectively, being interposed between ports 93 and 103 on the one hand and 99 and on the other hand. Piston X also covers scavenging port 109. 'As will appear, each piston passes successively and repeatedly through all gas power and air compression events.

As the explosion between pistons W and B progresses, its pressure decreases but the compression between pistons A and W increases, so that ultimely the reverselocked position of piston W (and connected pistons X, Y,,Z) becomes driven clockwise from the position shown in Fig. 2 to the position shown in Fig. 3, wherein the positions of the pistons W, X, Y, Z and A, B, C, D have been interchanged. This is due to the gas-buffered collision event between pistons A and W. For further particulars, if desired regarding such action, said prior patents may be consulted, particularly Nos. 2,638,880 and 2,680,430. .During this interchange, piston W has been pushed from its reverse-locked position and piston A has assumed it, while at the same time the compressed gas between pistons A and W has been exposed to ignition from the temporarily unshielded plug 91, resulting in an explosion event between pistons A and W in Fig. 3, with a gaseous'oompression event between pistons A and Z. Pistons A, B, C, D are then reverse-locked (Fig. 3). At this time, spent or exhaust gas is being driven from between pistons W, 'B into port 99, and compressed air is senses cs e n i occurring. through t n bewar tonsD and 2', Air sucticnevents are occurring through ports 95 and 97, between pistons X and B and Y and C respectively. I In the positionof parts' shown in Fig. 3, the spider 33, attached to pistons A F, C, D, has advanced to the reverse-locked. position .shown in Fig. 4 for spider 35. Spider 35, along with its pistons W, X, Y, Z, has receded froma reverse-locked position.

vThe cyclic action as deseribed continues indefinitely, each piston successivelypas'singthrough all gas suction, compression, explosionand exhaust events in section I of the machine, and then successively through all air suction and compression events in section G, the equal rotor systems connectedwith pistons A, B, C, D and W, X, Y, Z, respectively, alte r nate'ly assuming reverse-locked positions. The result is a substantially continuous pulsing of both fuel exhaustgas and air to the turbine 107.

T p of e l a y s xhausti e 09 which is connected to atmosphere, isto permit scavenging during the gas exhaust event of any excess of gases not a ept by t t b r m sX a fp irtw a which might otherwiseintenfere with an efiicient completion of the exhaust event, g, Assuming that the machine isin operation as above described, there is then theoretically no requirement for the shaft 77. The. practical purpose ofthe shalftis to effect starting and to drive any auxiliaries needed, such as generators fuel, .oil, pumps, or cooling fans and the like (not shown because conventional onesmay be employed). The alternately rotary and diiferentially moving systems. drive the shaft 77 through the respective spring connections 85 or 85, the springs winding and unwinding to eflectdriving, and perrnitting the relative or differential motions between pistons w X, Y, Z and A, B,. C, D during their cyclic action-s above described. Further details as to this type of differential driving ac: tion may be found insaid Patent 2,736,328. Other gear or hydraulic differential drivingrneans may also be used (see Patents 2,638,880 and 2,686,43Qfor gear means, and 2,756,728 for hydraulic means). ,The, flywheels 3.1; serve both to aid in bringing the successive pistons into re verse-locked positions and to minimize velocity changes in shaft 77. When the shaft is used for'startingp liboses,

the starter at'tac jhed to it; (notshown) iscaused simply t r a t s ta stink .sq ..itb htth ous springs 85' and $5 initiates anyone actions described. The required relative motions between'the systems of iqis: tons A, B, C, Djand W, X, Y, ipiently'initiated b a r ss i st iis s have j lower rollers 47 and 47" in passing ar n {thei 'respeo tive cam tracks 71' and 71'. At thi cr calcranking speed, corresponding to the natural ir quencies of oscillatorymotions between the rotary systems thev shaft, the relative oscillations of the rotor 'sys'ie'ms build up until power events are initiated and anama in response to repeated explosive action. A u 7 In Figs. 5-7 is illustrated a six pisto'n form of the machine, which in proper section appears essentially such as shown in Fig. 1, and a redrawing of that figure is therefore unnecessary, particularly inasmuch as all of the points of departure of this form can be described irom said Figs. S -7. In this case, rotor 17 carrieson'ly three pistons L, M, N, ,andgrotor. 19 carries only three pistonsR, S ,'T, the. machinebeing-divided intoa240" power's'ection U and a 120". compressing sectionV; Said angles define angles of action l Thesame type of ignition device 91 is used in cheek 5. 1 However, a fuel inlet port 111, agas exhaust port 1 13 and a scavengerport 119 are changed in position, as shown. The number of air inlet and outlet ports is halved, an air inlet port 115 being adjacent ports 113, 119 and an. air outlet port,117. being adjacent ports 111;" Ports 11 1, 113 subtend the power section Ujand ports11 5, I17fsubtendcompress6r section V. The ports 111* and 117 are spacedto accepfa piston 6 between them when the piston is reverse-locked (see piston T, for example); and ports 113 and 115 are spaced toaccept a piston between them when the piston is reverse-locked (see piston S, for example).

Referring to Fig. 7, it will be seen thatin this case the'hub 27 carries a three-legged spider 121, carrying three sets of spring-pressed follower roller systems 55, 41, 47 such as above described. Correspondingly, the hub 25 at theother end of the machine (not appearing in Fig. 7) carries a three-legged spider 123, carrying three sets of spring-pressed follower roller systems 55, 41, 47', such as above described. In this case the cam tracks (the one shown in Fig. 7 being numbered and 'there being another coaxially positioned behind it) have onlythree flats 127 and three filleted corners 129, providing three reverse-locking positions such as shown in solid lines in Fig. 7. The intermediate positions are shown by the dotted lines in Fig. 7 representing parts 55, 41 and 47. The gas exhaust port 113 and air exhaust port 117 are connected by means of manifold 131 with the gas turbine 107.

Operation of the alternate form of the invention is as follows, referring to Figs. 5 and 7:

Pistons R, S, T, connected with spider 121, are in reverse-locking positions, while pistons L, M, N are moving clockwise. A suction event drawing in fuel through port 111 is occurring between pistons T and L. A gas compression event is occurring between pistons L and R. The explosion event is occurring between pistons R and M which holds system R, S, T reverse-locked to provide the necessary reaction. Gas is being exhausted from between pistons M and S through exhaust port 113 and is being delivered to the turbine 107. At the same time, air is being compressed between pistons T and N and driven out of the air exhaust port 117 to turbine 107..

In time, the pressure between pistons R and M decreases and the compression between pistons L and R increases sufiiciently toremove pistons R, S,.T from their reverse-locked positions shown in Fig. 5, pistons L, M, N taking up reverse-locked positions, as shown in Fig. 6. In the meantime, the compressed gas between pistons L and Ruhas been exposedto theignition plug 91 tov produce anexplosionj (Fig. 6) between pistons L and R in Fig. 6. Gas is being exhausted .betweenpistons R and M throughport 113 ,for delivery to turbine 107. Fuel gas compression at this time occurs between pistons T and L. Fuel gas suction .occurs through port 111 into the space between relatively receding pistons T and N. Air is being. drawn into port 115 between relativelyreceding pistons M and S, and compressed air is being drivenfrom between relatively approaching pistons S and N through port 117.

The preferred fornrof the invention, as shown in Figs. .2-4, is used in those cases in which for a given power consumption a larger amount of air is desired at relativelylower maximum pressures; whereas the form of theinvention shown in Figs. 5 and 6 is employed where for a given power consumption a smaller amount of; air is. required at relatively higher maximum pressures. The reason is that for a'given' set of power events in Figs. 2-4, two air compression events are brought about by one explosion event; whereas in the case of Figs. S -7, only one air compression event is brought about by one explosion event. Other things being equal, substantially more air is being moved by the same power in the form of Figs. 2-4 as compared to the air being moved in the form of Figs. 5-7; therefore the ability to produce higher air pressure in the latter case. Also, in the Pigs. 5 7 form of theinventiomahigher compression ratio'may .be maintained in the power section U than is the-casein the p'owersection P in the form It will be seen that rotary systems are constituted on the one hand by parts 19 (including the pistons carried thereby), quill 15, extension 23, hub 27, spider 35, springpressed follower members 43, and follower rollers 47; and on the other hand, by parts 17 (including the pistons carried thereby), quill 13, extension 21, hub 25, spider 33, spring-pressed follower members 43, and the follower rollers 47. Since these systems are identical in construction, their moments of inertia and natural frequencies of oscillation are the same, provided, as is the case, springs 85 and 85 are identical.

The term free pistons may be applied to the sets of pistons described because the relative motions between the groups of pistons on the respective rotors are determined by the algebraic sums of the compressive and expansive forces of the gaseous charges between them, and not by any geometrically determined motions imposed by any kinematically constrained linkage between them. This is irrespective of the fact that an average substantially constant velocity may be delivered from the pistons to the shaft 77 in view of the substantial moment of inertia of theshaft and parts driven thereby. Thus by the term free piston compressor, as used in the claims below, is meant a compressor having gascontrolled relative piston movements characterized by the absence from between the rotors carrying the pistons of any kinematically constraining linkage which might geometrically constrain the relative motions between the pistons. Their only constraint in my apparatus is variable and due to the actions of the reverse-locking mechanisms as determined by the momentums of the rotor systems, the gas buffering occurring during. the collision events between pistons and the explosive forces.

The term alternating as applied to the pistons has the connotation, first, that the interdigitating groups of pistons alternate with one another in their interdigitated positions in the toroidal cylinder 1; second, that thepiston groups alternate in moving and reverse-locking; and, third, that each piston alternates in functioning as an engine element in performing the power events in the arcuate engine section of. the machine, and in functioning as a compressor element in passing through the arcuate compressor section of the machine. H a

It will be apparent that in both forms of the invention the toroidal orjannula'r cylinder is characterized, as the case may be, by apower section (P or U) and a compressor section (G or V)." It will also be apparent that if in either of the Fig. .3 or Fig. 6.for ms of the invention the exhaust port (99 in Fig. 3; andi113 in Fig. 6) be dis-v connected from manifold 105'or'131, respectively, .then

the output from the air compressor section of the device will be delivered without exhaust gas dilution, as, for example, to an air pressure tank. The terms toroidal and annular as used herein are intended to referto a cylinder such as 1, of any appropriate cross section.

It will be clear from the above that the invention can. be carried out in machines employing other than eight or six pistons as shown, according to the principles above outlined for constructing the eightand six-piston machines illustrated.

In view of the above, it will be seen that the several objects of the invention are achieved and other advanta-I geous results attained. V

As various changes could be made in the above con-. structions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a'limiting sense;

1. A rotary internally powered compressor compris ing an annular cylinder having fuel inlet and exhaust ports positioned substantially to subtend therein a power sector of one angle and having respectively adjacent" air exhaust and inlet ports positioned substantiallyto subtend a compressor sector of a substantially complementary angle completing a circle, piston-carrying rotors mounted for rotation relative to the cylinder and for free rotation relative to one another whereby either one of the rotors may rotate in a forward direction at any one of various angular velocities while the other remains stationary, each rotor having at least one pair of pistons interdigitatedin the cylinder with pistons of the other rotor, the members of each such pair being so angled on their respective rotor that the angle therebetween substantially equals said complementary angle, whereby said power and compressor sectors may thereby be separated by-a pair of pistons at intervals during rotor movements, each rotor having additionally at least one other piston bisecting the power sector when its said other pair of pistons is in a sector-separating position, reverse-locking means for each rotor adapted to lock it against rotation in reverse direction and inresponse toreverse-acting torque on the rotor to hold it stationary in a position wherein a said additional piston is in said bisecting position, whereby suction, compression, explosion and exhaust events may occur in said power sector when a pair of said angled pistons of the other rotor move therein, firing means adaptedto initiate an explosion event to motivate a reverse-locking event and a compression event adapted thereafter to terminate said reverse-locking event, a said additional piston of the other rotor during power events in the power sector being located for movement in the compressor sector to perform air suction and exhaust events therein.

2. A rotary internally powered compressor according to claim 1, wherein said one angle is substantially 240 and said complementary angle is substantially and wherein there are three substantially equally spaced pistons on each rotor.

3. A rotary internally powered compressor according to claim 2, including an air exhaust passageleading from said air exhaust port, and a burned-fuel exhaust passage leading from said fuel exhaust port, both of said exhaust passages being joined to form a common heated supply of air and burned fuel exhaust issuing from the compressor.

4. A rotary internally powered compressor according to claim 1, wherein said one angle and said complementary angle'both equal substantially 180 and wherein there are four substantially equally spaced pistons on each rotor. 5. A rotary internally powered compressor according to claim 4, including an additional pair of adjacent air exhaust and inlet ports located on opposite sides of a line which dividessaid compressor sector into two substantially equal parts.

6. A rotary internally powered compressor according to claim 5, including air exhaust passages leading from said air exhaust ports, and a fuel exhaust passage leading from said fuel exhaust port, all of said exhaust passages being joined to form a common supply of air and burned-fuel exhaust issuing from the compressor.

7 References Cited in the file of this patent UNITED STATES PATENTS 2,503,894 Wildhaber Apr. 11, 1950 2,544,480 Bancroft Mar. 6, 1951 2,553,954 Bancroft May 22, 1951 2,638,880 Mallinckrodt May 19, 1953 2,680,430 Mallinckrodt June 8, 1954 2,687,609- Mallinckrodt Aug. 31, 1954 2,736,328 Mallinckrodt Feb. 28; 1956 2,756,728. Mallinckrodt July 31, 1956 j FOREIGN PATENTS H g .465,211' Great Britain May 4, 1937 497,630 Great Britain Dec. 22, 1938 520,694 GreatBritain- May 1, 1940

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