US2808784A - Submerged booster pump - Google Patents

Description

Oct. 8, 1957 J. F. D1 STEFANO 2,808,784

SUBMERGED BOOSTER PUMP A Filed Feb. 17. 1851 2 shegtS-sheet 1 wat lll y 14'! i 52d 361K` 1 .52 f2 Z7 2% 48W $2@ 49a z 55j 2 j jy' 50 f/ Z6 Z450 535 49h 22 I './IUVEHFM JofzzzfZD/tgazza United States Patent SUBMERGED BOOSTER PUMP John F. Di Stefano, Lyndhurst, OhioLassignor to Thomplxi Products Inc., Cleveland, Ohio, a corporation of Application February 17, 1951, Serial No. 211,556

8 Claims. (Cl. 10S-113) This invention relates to a multiple inlet helicoidal type pump especially adapted for submerged mounting in a fuel cell.

Specifically, this invention relates to a submerged booster pump having an impeller assembly with screw vanes which circulate fluid from two opposed pump inlets to a central radial irnpeller assembly which centrifuga'lly discharges the liquids to a surrounding volute chamber.

While this invention will be hereinafter described as embodied in a submerged booster pump and motor unit for pumping fully liquid fuel from the aircraft fuel cell to a conduit while `releasing bubbles of gas and vapor back to the fuel cell, it should be understood that the principles of this invention are, i-n general, related to helicoidal pumps and, therefore, the invention is not to be limited to the preferred disclosed embodiment.

ln accordance with this invention, an electric motor and pump unit having a base for mounting the unit in upright position in a fuel cell, has an open ended vertical chamber surrounded by an annular volute chamber. An irnpeller is mounted in the open ended chamber and has opposed helixes for inducing the flow of liquid from the top and bottom ends of the chamber into the central portion of the chamber. These opposed helixes blend into radial pumping vanes aligned with the volute chamber. The liquid from the helixes is centrifugally discharged by these radial irnpeller vanes into the volute chamber from which it is removed through a peripheral outlet to an upstanding conduit socket formed integrally with the pump. Each opposed helix stage of the irnpeller i-ncludes a plurality, preferably three, of blades. These blades have a relatively at inlet pitch to move the liquid fuel into the pump with a minimum amount of shock. These helix stages are designed to deliver more fuel to the central portion of the open ended chamber than the rated discharge capacity for thepump, so that a recirculation of fuel occurs in the helix paths. The irnpeller is operated at relatively high speeds and a'cts as a liquid and gas separater with the lighter gaseous material tending to collect at the axis of the irnpeller where some of it is axially discharged through a hub portion of the irnpeller back to the interior of the fuel cell. Since the recirculation induced by the over-capacity of the helix blades will flow the vapor laden lighter fuel from the axis toward the periphery of the irnpeller, some vapors and gases are removed from the ends of the impeller chamber around the periphery of the irnpeller and deectors or guides are preferably provided at the open ends of the chamber to prevent comrningling of the discharging vapor rich fuel with the incoming fuel.

It is, then, a feature of this invention to provide a double helicoidal pump which impels fluid through opposed inlets toward a central outlet.

Another important feature of this invention resides in the provision of a vapor escape path from the axis of a double entry helicoidal pump.

A further and important feature of the invention resides in the blending of a radial pumping stage with op- 2,808,784 Patented Oct. 8, 19,57

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2 posed helicoidal pumping stages to provide a double entry helicoidal pump with a radial discharge stage.

An object of the invention is to vprovide a double entry helicoidal pump with a central radial stage and a vapor release path at said central radial stage.

A further object of the invention -is to provide a double entry helicoidal piunp wherein screw vanesfeed fluid from opposed pump inlets to a central radial irnpeller for discharge into a surrounding pumping chamber.

A still further object of the invention is to provide a double entry helicoidal pump with a central radial impeller stage and with Vapor separating paths discharging around the peripheries of the pump inlets and also through the axial portion of the irnpeller.

Other and further objects of this invention will be apiparent to those skilled in the art from the following detailed description of the annexed sheets which, by way of a preferred embodiment only, illustrate one pump and motor unit according to this invention.

On the drawings: Y

Figure l is a side elevational view, with parts broken away and shown in vertical cross section, of a submerged double entry Vhelicoidal booster pump and motor unit according to this invention mountedk in a tank such as a fuel cell.

Figure 2 is an enlarged horizontal cross-sectional view taken along the line Il-II of Figure 1.

Figure 3 is a cross-sectional View similar to Figure 2 but taken at a level just below the section line II-f-l'l of Figure l to show the full length of the radial blades.

Figure 4 is a fragmentary enlarged vertical cross-sectional view,.witl1 parts in elevation, taken along the line lV-IV of Figure 1.

Figure 5 is a top plan view, with a portion in horizontal cross section, of the irnpeller in the pump of Figure 1.

Figure 6 is a transverse cross-sectional view taken along the line Vl-VI of Figure 3.

As shown on the drawings: p

The pump and motor unit 10 of Figure l is mounted in a fuel cell 11 in alignment with an opening 11a in the bottom wall of the cell; This unit 10 includes an electric motor 12 mounted on top of a casing 13 which has a conical head portion 14` receiving the bottom of the motor to provide an end head for the motor. This head portion 14 has depending posts, such as 15, carrying an integral annular pump casing 16 in spaced relation beneath the head 14.

The casing 16 is formed with an integral upstanding discharge head 17 and the bottoms ofthe posts, the casing 16, and the head 17, terminate in flush relationship to cooperate with a base plate 18 which is positioned against the under side of the bottom wall of the fuel cell 11 to span the opening 11a thereof for supporting the entire assembly ofthe casing 13 and motor 12 in the -fuel cell. A gasket 19 is interposed between the base plate 18 and the casing and head part, and a second gasket 20 is interposed between the peripheral portion of the base plate' 18 and the bottom wall ofthe fuel cell 11; A mounting ring 21 is positioned Iagainst the upper side of the bottom wall of the fuel cell around the opening 11a thereof and cap screws 22 extending through the periphery Yof the base plate 18 and through the bottom wall of the fuel cell are secured in the mounting ring 21 to attach the base plate rigidly to the fuel cell. Screws (not shown) are also provided for seeming the unit .13 to theA base plate-18.

The base plate 18 provides a sump 23 in free open communication with the bottom of the fuel cell 11to receive fuel therefrom. Anopening 24 is also Yprovided s in the base 18 in alignment witha passage 25 through the discharge head'17 of the casing 16. A cap 26 isheld in seated relationship, closing the opening 24, by means of an elongated bolt 27 which extends through the cap and passage and is threaded into the wall of a conduit nipple 28 mounted on top of the head 17. The upper end of the bolt 27 is threaded into a boss portion 28a of the nipple 28 so that a single bolt serves to hold the cap and nipple on opposite ends of the head 17. If an outside nipple mounting is desired, the positions of the cap and nipple can be reversed.

The head 14 o f'gthe casing 13 contains a well 14a mounting a bearing 29 for the motor armature shaft 30. A pair of llame trap sleeves 31 surround the shaft 3i) beneath the bearing 29 and are disposed in a passage 14h from the well. A seal Iassembly 32 is mounted in a lsecond well 14e of the head 14. This seal assembly 32 includes a stationary seal ring 32a anchored in the well 14C and a rotating seal ring 32b mounted on the shaft 30 to ride against the bottom face of the ring 32a.

The shaft 30 extends through an open ended vertical passage or chamber 33 of the casing portion 16 and has a nut 34 threaded on the bottom end thereof.

The cylinder 33 is, in effect, a cylindrical bore through the casing 16 and has the intermediate portion thereof surrounded by an annular volute chamber 35 with a penpheral discharge passage 35a entering the passage 25 of the head 17. The bore thus has axially opposed open ends with the bottom open end facing the sump 23 and the top open end facing the space between the casing 16 Vand the head 14.

An impeller 36 is mounted on the shaft 30 in the chamber or bore 33. This impeller 36 includes a first or bottom helicoidal stage 36a, a second or top helicoidal stage 36h, and a third or central radial stage 36 aligned With the volute chamber 35, each radiating from an axial hub 36a' mounted on the shaft 30.V

As best shown in Figures 1, 2, and 5, each helicoidal stage 36a and 36h has three helix or screw blades 37, 38, and 39, each having about three-fourths of a full turn and defining therebetween helical paths of opposite pitch from the opposite ends of the chamber 33 to the radial stage 36C. The blades 37, 38, and 39 have inlet edges terminating slightly beyond the respective ends of the chamber 33 and discharge or trailing edgesV terminating in fiat planes at the radial impeller stage 36e. The helical paths between the blades therefore feed the fuel from the opposite ends to the central portion of the passage.

The helix blades 37, 38, and 39 have the same relatively ilat pitch so as to gently accelerate the fuel from the ends of the chamber 33 without agitation tending to release bubbles of gas and vapor from the liquid. The

blades slice the liquid in the inlet and gradually accelerate it along three separate helical paths. Each helical path is blocked at its inner or delivery endby the radiai stage 36C of the impellervwhich, as shown in Figures 3 and 6, includes three radial vanes 40, 41, and 42 radiating from the hub 36d and projecting across the discharge ends of the helical paths to centrifugally discharge the fluid in a radial direction from the helical paths into the volute chamber 35. As best shown in Figure 6, each vane 40, 41, and 42, such as the illustrated vane 42, has an active abutment face 43 between merging helix blades from the helix stages 36a and 36h. These faces 43 will effect radial discharge of the uid out of the helical paths into the volute chamber.

As shown in Figure 4, the two helicoidal stages 36a and 36b merge so that common walls such as 45 are formed between the stages. Apertures 46 as shown in Figures 2 and 4 are provided through each of these common walls 45 thereby joining the paths between the opposed blades such as the illustrated blades 37.

The apertures 46 are closely disposed to the hub 36d and serve to vent vapors and vapor rich liquid hugging the axial portion of the bottom helicoidal stage 36a into the top helicoidal stage 36b.

As best shown in Figures 4 vand 5, the hub 36d has a plurality of passages47 extending axially through th vapor rich fluid and the vapors to the axial outlets 47 so that the vapors can be discharged out of the open upper end of the hub 36d.

Since the helicoidal stages 36a and 36h are designed to feed more liquid to the radial stage than can be discharged through the volute 35, a recirculation of liquid occurs in the helical paths resulting in a flow of vapor rich huid separated at the axial portion of the impeller to the periphery of the impeller. This vapor rich fuel is thereupon discharged out of the open ends `of the chamber 33 around the periphery of the impeller. As shown in Figure 1, the peripheral portion of the lower end of the chamber 33 discharges into the bottom of a cup-shaped deflector 49.- This deector 49 has a cylindrical side wall 49u surrounding the pump casing part 16 and extending to a level above the casing. The cup'has a bottom 4% underlying the bottom of the casing 16 and held in spaced relation therefrom by spacers 50 interposed between thc bottom of the casing and the bottom of the cup around screws 51 which mount the cup on the casing. The bottom 49h is apertured and has an upturned lip 49e facing the open bottom of the chamber 33 and coacting there- With to provide a bottom inlet to the pump. This lip 49C is spaced from the bottom Wall of the casing 16 so as to provide a gap which will receive the vapor rich iluid from the peripheral portion of the bottom end of the chamber -`33. This vapor rich liquid will thereupon flow through Lthe cup around the casing 16 to be discharged back into the fuel cell at a level above the casing.

The upper end of the chamber 33 also discharges vapor rich fuel around the peripheral portion thereof by the recirculation of the liquid in the helicoidal stage 36b. To

Aprevent a Vcommingling of this vapor rich liquid with the incoming liquid to the top of the chamber 33, the casing 16 has a guide cone or deilector 52 mounted on the top thereof. This cone 52 has an outturned mounting flange 52a around the lower open end thereof which is anchored to the top of the casing 16 by screws 53. An apertured ring portion 52h projects over the peripheral portion of the top open end of the chamber 33 and converges to an opstanding .cylindrical portion 52o of the deilector. This cylindrical portion merges intoa diverging conical portion 52d which terminates substantially flush with the top of thecup 49. Apertures 54 in the ring 52h form paths for the discharge of the vapor rich tluid into the upper end of the cup 49 around the conical portion 52d lof the deflector 52 so that the vapor rich liquid is discharged out of the top of the cup with the vapor rich liquid from the bottom end of the chamber 33. The conical portion 52d of the dellector 52 provides a converging entrance mouth for the liquid entering the upper endof the chamber 33.

Operation When the unit 10 is submerged in liquid fuel such as gasoline in the fuel cell 11, the bottom open end of the impeller chamber 33 receives the liquid from the sump 23 through the apertured bottom 49b of the deflector cup 49. The top of the impeller chamber 33 receives liquidvfrom the fuel cell through the guide cone 52. When the motor 12 is operated to rotate the shaft 311 in a screw advancing direction, the bottom helicoidal stage 36a of the impeller 36 will slice into the liquid at the bottom of the chamber 33 to gradually accelerate the liquid and cause the same to flow to the central portion of the passage. At the same time, the top helicoidal stage 36h of the impeller 36 will slice oif the liquid in the top end kof the chamber 33 to accelerate the liquid and cause the same to ow downwardly to the central portion of the chamber. The liquid will ow in three helical paths in each helicoidal stage, and these paths will merge at the radial stage 36C, whereupon the abutment faces 43 of theradial vanes 40, 41, and 42 will radially discharge the lluid into the volute 35. The liquid will swirl through the volute chamber 35 to discharge through the outlet 35a into the passage 25 for ow through the nipple 28.

The impeller 36 acts as a centrifugal gas and liquid separator to lling 'out the heavier fully liquid material toward the periphery thereof, while accumulating the lighter vapor rich liquid at the axial center thereof. Any bubbles of gas and vapor which are trapped under the walls 45 formed by the merging helical blades will ow through the apertures 46 to be discharged through the ports 48 into the passages 47 where they will freely rise out of the open top of the impeller hub. This arrangement provides for an axial discharge of bubbles of gas and vapor.

A peripheral discharge of vapor rich fuel is also obtained by designing the helicoidal stages 36a and 36h so as to have a lluid displacement capacity which is greater than the discharge capacity of the pump, whereupon fluid will recirculate in the helical paths in each stage to force the vapor rich uid from the axial center-of the stage to the periphery of the stage. The recirculation pressure will thereupon force the vapor rich liquid out of the peripheral portions of the open ends of the chamber 33, whereupon the vapor rich liquid discharging out of the bottom end of the chamber will be deflected into the cup 49, while the vapor rich liquid discharging out of the top end of the chamber will be deflected into the cup 49 around the guide cone 52. The streams of vapor rich liquid issuing from the peripheral portions of the open ends of the chamber 33 are therefore not merged with the liquid entering the open ends of the chamber through the apertured bottom ofthe cup and the guide cone of the top deilector.

From the above description it will therefore be understood that this invention provides a double entry two stage helicoidal pump including two inlet stages cornposed of a plurality of helix blades of opposite hand blending into a common discharge stagel composed of a plurality of radial blades. Recirculation within the inlet stages, effected by over capacity of the helicoids, effects vapor separation at the clearances between the impeller and the pump body, which clearances can be adjusted to give maximum vapor separation. The vapors are educted by means of vapor separators or deectors which also serve as separating Walls to prevent commingling of the incoming liquid and the outgoing vapor rich fluid. An axial discharge is also provided for vapors which are not recirculated. lf desired, a relief valve can be provided in the discharge head ofthe pump to cut down electric current consumption when the pump is being operated under partial or no flow conditions.

lt will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

l. A submerged vapor expelling pump comprising, a casing having an annular volute pumping chamber formed therein, said casing further providing cylindrical pumping chambers on opposite sides of said volute pumping chamber, a multi-stage impeller having a first stage comprising screw vanes in each of said cylindrical pumping charnbers moving uid axially with minimal shock from opposite ends inwardly toward said volute pumping chamber, said cylindrical pumping chambers having walls of suciently greater diameter than the outer diameter of said screw vanes to form an annular running clearance gap at the periphery of said screw vane, said impeller having a second stage of a lesser capacity than said first stage to promote recirculation in the helix path of the screw vanes and to produce a counteriiow of bubble-rich fluid in said gap at the periphery of said screw vanes comprising intermediate centrifugal pumping vanes for discharging bubble-freed liquid into said annular volute chamber, said casing having decctor baies carried at oppositey ends thereof each having a cylindrical portion v .of the same diameter as said screw vanes and providing a centrally disposed inlet for respective ones of said screw vanes, said 'baffles forming throats in axial register with the corresponding gaps for discharging bubble-rich fluid outside of said casing.

2. In an aircraft fuel system of the type including a fuel cell, a submerged electric motor and a booster pump mounted on one wall inside of said cell, the improvement of a pump body having an outlet and opposed inlets on different sides of said outlet, an impeller rotatably mounted in said pump body and driven by said motor, said impeller having radial vanes providing a centrifugal pumping stage delivering fluid to said outlet, and helical screw vanes on each side of said radial vanes to provide a double helicoidal pumping stage for moving iluid from each inlet to said centrifugal stage, said impeller having a hub portion formed with passage means extending axially therethrough Vand adapted to open into therfuel cell outside said pump body, said hub portion having ports `formed therein communicating said passage means to the helical paths provided by the screw vanes for venting vapors trapped adjacent the hub portions of the impeller.

3. A submerged vapor expelling pump comprising, a casing having an annular pumping chamber formed therein, said casing further providing a cylindrical bore adjacent to and coaxial with said pumping chamber, a multi-stage rotatable, impeller having a lirst stage comprising screw vanes in said cylindrical bore moving fluid from one end of said bore to said pumping chamber, said impeller having a second stage comprising centrifugal radial pumping vanes for discharging bubblefreed liquid into said annular volute chamber, and a deflector bae in said one end of said bore providing a centrally disposed inlet for said screw vanes and an annular radially outwardly spaced throat concentric with said inlet and forming a flow path extending outwardly from the peripheral portion of said inlet for discharging bubble-rich fluid outside of said casing, said screw vanes comprising helix blades having trailing edges terminating in a ilat plane and merging with said radial vanes in a blended together relation, said impeller having a hub portion formed with passage means extending axially therethrough and having ports communicating said passage means to an area immediately adjacent said hub portion in the helix paths for venting vapor-rich iiuid collected in said area outwardly of the casing.

4. In a pump having an inlet and an outlet, a rotary two-stage impeller having a hub, radial vanes on said hub providing a centrifugal pumping stage delivering Huid to the outlet, and screw vanes on said hub on the top and bottom side of said radial vanes to provide a double helicoidal pumping stagefor moving fluid from the inlet to `said centrifugal stage, said screw vanes including circumferentially overlapped helix blades merging at common walls formed between the stages, said common walls having Aa plurality of circumferentially spaced apertures formed therethrough closely adjacent said hub and intercommunicating the oppositely extending helix paths to vent vapors and vapor-rich liquid hugging the axial path of the bottom helix blades into the top helix blades, said impeller hub having passage means formed therein and extending axially therethrough and having ports formed therein communicating said passage means to an area immediately adjacent said apertures for venting vapor-rich fluid from the helix paths through said hub passage means.

5. In a submergedtype pump, a multi-stage impeller having a lirst stage comprising screw vanes with cylindrical outer peripheral edges and terminating at one end in a second stage comprising centrifugal pumping vanes, a casing having a volute pumping chamber with an outlet for said centrifugal pumping stage and a cylindrical 7. pumping chamber with an inlet for said screw vanes, said cylindrical pumping chamber having walls of a suiciently greater diameter than the outer diameter of said screw vanes to form an annular running clearance gap at the periphery of said screw vanes, said impeller being rotatable on a given axis to move uid through said cylindrical pumping chamber axially with minimal shock toward said volute pumping chamber, said second stage being of a lesser capacity than said first stage to promote recirculation in the helix path of the screw vanes and to produce a countertlow of bubble-rich fluid in the gap at the periphery of the screw vanes, and a delector baii'le having a cylindrical portion of approximately the same diameter as the outer diameter of said screw vanes and being positioned by said casing at the end of said cylindrical chamber to form a throat in axial register with said gap, through which bubble-rich fluid is discharged outside of the casing, while said centrifugal pumping vanes ydischarge bubble-freed fluid into said volute chamber.

6. A submerged vapor expelling pump comprising, a casing having an annular volute pumping chamber formed therein, said casing further providing cylindrical pumping chambers on opposite sides of said volute pumping chamber, a multi-stage impeller having a rst stage comprising screw vanes in each of said cylindrical pumping chambers moving iiuid axially with minimal shock from opposite ends inwardly toward said volute pumping chamber, said cylindrical pumping chambers having walls of a sutliciently greater diameter than the outer diameter o1 the corresponding screw vanes to form annular running clearance gaps at the peripheries of said screw vanes, said impeller having a second stage of a lesser capacity than said first stage to promote recirculation in the helix path of the screw vanes and to produce a counterow of bubble-rich iiuid in said gaps at the peripheries of said screw vanes, said second stage comprising intermediate centrifugal pumping vanes for discharging bubble-freed liquid into said annular volute chamber, said casing having detlector bathes carried at opposite ends thereof each having a cylindrical portion of the same diameter as the outer diameter of said screw vanes to provide a centrally disposed inlet for respective ones of said screw vanes and forming a throat in axial register with a corresponding gap for discharging bubble-rich uid outside of said casing, said impeller having a hub portion formed with passage means extending axially therethrough and adapted to open outside said casing, said hub portion having ports formed therein communieating said passage means to the helical paths provided by the screw vanes for venting vapors trapped adjacent the hub portions of the impeller.

7. A submerged vapor expelling pump comprising, a

casing having an annular volute pumping chamber formed f therein, said casing further providing cylindrical pumping chambers on opposite sides of said volute pumping chamber, a multi-stage impeller having a rst stage comprising screw vanes in eachf said cylindrical pumping chambers moving iiuid axially with minimal shock; from opposite ends inwardly toward said volute pumping chamber, said impeller having a second stage of a lesser capacity than said first stage, said cylindrical pumping chambers having walls of a sutticiently greater diameter than the outer diameter of said screw vanes to form annular running clearance gaps at the peripheries of said screw vanes, said second stage of said impeller comprising intermediate centrifugal pumping vanes for discharging bubble-freed liquid into said Vannular volute chamber while promoting the recirculation of fluid in the helix path of the screw vanes which produces a counterow of bubble-rich uid in said gaps at the peripheries of said screw vanes, said casing having deflector bailies carried at oppositeends thereof each having a cylindrical portion y of said screw vanes to provide a centrally disposed inlet and a throat in axial register with each corresponding gap through which bubble-rich fluid is discharged outside of said casing, said screw vanes comprising helix blades having trailing edges terminating in a flat plane and merging with said radial vanes in a blended together relation, said impeller having a hub portion formed with passage means extending axially therethrough and having ports communicating said passage means to an area immediately adjacent said hub portion in the helix paths for venting vapor-rich uid collected in said area outwardly of the casing.

8. Ina pump having an inlet and an outlet, a rotary two-stage impeller having a hub, radial vanes on said hub providing a centrifugal pumping stage delivering huid to the outlet, screw vanes on said hub on the top and bottom side of said radial vanes to provide a double helicoidal pumping stage for moving Huid from the inlet to said centrifugal stage, said screw vanes including circumferentially overlapped helix blades merging at common walls formed between the stages, said common walls having a plurality of circumferentially spaced apertures formed therethrough closely adjacent said hub and intercommunicating the oppositely extending helix paths to vent vapors and vapor-rich liquid hugging the axial path of the bottom helix blades into the top helix blades, said impeller hub having passage means formed therein and extending axially therethrough and having ports formed therein communicating said passage means to an area immediately adjacent said apertures for venting vapor-rich uid from the helix paths through said hub passage means, and a casing having a volute pumping chamber for said centrifugal pumping stage and a cylindrical pumping chamber for each ofthe top and bottom screw vanes, each cylindrical pumping chamber having walls of a suiiciently greater diameter than the outer diameter of said screw vanes to form annular running clearance gaps at the peripheries of said screw vanes, said impeller being rotatable to move tluid through said cylindrical pumping chambers axially with minimal shock toward said volute pumping chamber, said centrifugal pumping stage being of a lesser capacity than the combined helicoidal pumping stages to promote recirculation in the helix paths of the screw vanes and to produce a counterflow of bubble-rich uid inthe gaps at the peripheries of the screw vanes, and deliector baffles each having a cylindrical portion of approximately the same diameter as the outer diameter of the corresponding top and bottom screw vanes, said baffles being positioned by said casing at the respective ends of said cylindrical chambers to form throats in axial register with the corresponding gaps through which bubble-rich fiuid is discharged outside of the casing, while said centrifugal pumping stage discharges bubble-freed uid into said volute chamber.

A References Cited in the tile of this patent UNITED STATES PATENTS 1,089,770

Kerr Mar. 10, 1914 1,213,461 Cooper Jan. 23, 1917 1,586,978 Dorer June l, 1926 2,134,686 De Lancey Nov. 1, 1938 2,306,298 Curtis Dec. 22, 1942 2,312,526 Curtis Mar. 2, 1943 2,463,251 Curtis Mar. 1, 1949 2,480,435 Aspelin Aug. 30, 1949 2,575,568 Topanelian Nov. 20, 1951 2,581,055 Wahle Jan. 1, 1952 FOREEGN PATENTS 4,016 Great Britain 1884 574,140 Great Britain Dec. 12, 1945 585,505 Great Britain Aug. 14, 1945 607,830 Great Britain Sept. 6, 1948

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