US2975713A - Liquid fuel supply apparatus - Google Patents

Description

March 21, 1961 G. w. WRIGHT 2,975,713

LIQUID FUEL SUPPLY APPARATUS Filed June 9, 1955 4 Sheets-Sheet 1 U 71o 714 INV NToR.

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` LIQUID FUEL SUPPLY APPARATUS Filed June 9, 1955 4 Sheets-Sheet 2 102 1 118 i af IN VEN TOR. GEORGE W p/awz;

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I''/P/VEXS- United States Patent vC) LIQUID FUEL SUPPLY APPARATUS George W. Wright, Fort Wayne, Ind., assigner to Tokheim Corporation, Fort Wayne, Ind., a corporation of Indiana Filed June 9, 1955, Ser. No. 514,221

Claims. (Cl. 10S-87) This invention relates to apparatus for supplying liquid fuel to a combusion engine, especially for automotive use, and particularly to a submerged centrifugal fuel pump and the combination thereof with a fuel tank and other related fuel-supply apparatus.

lt is an object of the invention to provide a centrifugal fuel pump unit for submerged operation in a body of liquid fuel such as the gasoline in a fuel tank, especially an automotive fuel tank, which will be gravity-fed from the body of liquid and will deliver fuel substantially free of air and vapor and in liquid state under pressure from such tank to the fuel feeding device of an engine, and will avoid vapor lock problems which occur with pumps `which draw iluid from the tank by suction; which will pump adequate quantities of fuel to the engine at proper pressure under the widely varying and dilicult conditions of automotive use, and will continue to pump when the fuel level in the tank is low and will substantially empty the tank of its gasoline; which will expel gas (such as air or Vapor) from admixture with liquid passing through the pump and will not become gas-bound as by vapor in the pump or by air admitted by exposure of the pump inlets to air, as from the sloshing of gasoline in the tank; and which will prevent the accumulation of water in the pump, as from condensation in the tank, and will allow water to drain from the pump and adjacent lines when the pump is at rest and will thus reduce the danger of fuel supply failure from ice formation.

It is an object of the invention to provide a small centrifugal pump which is elfective at the pumping rates used in automotive fuel systems, which rates, being usually of the order of less than or 30 gallons per hour, are quite small in terms of usual centrifugal design; and to do so in the face of the known fact that the design of such small capacity centrifugal pumps is both perplexing and unpredictable. It is a further object of the invention to provide a fuel pump unit which avoids use of the short-lived pumping diaphragms common in presently used pumps; which will operate with minimum powerconsumption from the electrical system of the automotive vehicle, and will .operate reliably and effectively under the varyingpconditions which occur in such systems; which will supply 'adequate fuel at suicient but not excessive pressures under all conditions, and will quickly purge the fuel system of any vapor accumulation, such as that which strongly tends to occur in the fuel line immediately after a hot engine is stopped. It is a further object of the invention to provide such a fuel pump unit which is compact and adapted to fit a variety of fuel tanks, including the shallow tanks commonly used in passenger cars andthe tall narrow tanks commonly used in trucks; which will be highly reliable in operation and have a long life and require a minimum of service; and which will have such reliability under the adverse mounting and operating conditions of a vehicle which is normally in motion and which may be in relatively rough motion and is subject to Vvarious adverse road and weather conditions.

ICC

It is a further object of the invention to provide a fuel-pump unit and system adapted for mass production at relatively low cost.

lt is a further and specic object of the invention in a preferred form, as for automotive use, to provide a pump which causes a minimum of disturbance of the fuel in which the pump is submerged. The pump may be made to cause agitation and beating and recirculation of the fuel in the tank, to separate vapor and lightends from the fuel prior to its passage through the pump,

as in the manner of the Curtis Reissue Patent No. 22,739; but for many uses such disturbance is desirably avoided and the light-ends or highly volatile constituents of the fuel are preserved and delivered in liquid state for utilization by the engine.

It is an object of the invention to combine the fuel pump with a motor in an interrelated unit, and to combine the pump with a tank and other related parts of a fuel system, in a manner to provide a more effective and advantageous fuel system, especially for automotive use.

Further and more specific objects of the invention will appear from the following specification.

ln accordance with the invention, the fuel pump is a ldouble-inlet centrifugal pump, desirablycombined in a unitary assembly with an electrical driving motor with the unit arranged to operate in a generally upright or vertical position with the pump at the bottom, and in normal use the pump is mounted in submerged position close to the bottom of the tank or of a sump formed in the bottom wall of the tank.

The pump comprises a casing which has both top and bottom inlet throats and which forms a thin, annular, and desirably outwardly tapering, pumping chamber extending outward from between the throats. The chamber communicates with an outer volute connected to a pump discharge conduit. A centrifugal impeller on a central shaft carries impeller blades which revolve in the pump casing. Preferably, the blades are supported on the hub by structure which lies between the throats in a medial plane of the pump chamber, and the blades are desirably of the open unshrouded type operating with running clearance between the opposite walls of the pumping chamber. Preferably, the pump has no rotary seals between the impeller and the casing. The blades may have some forward or rearward sweep, but substantially straight blades are found to produce a relatively constant discharge pressure over the range of delivery rates which occur in automotive systems, and straight blades the bottom throat to the top throat, and which permit the pump to be filled by liquid from either throat. Such openings may be wholly or partially within the projected area of one or both throats, and may comprise a central bore on the axis of the impeller. The openings may also be wholly or partially outward of the peripheries of one or both throats, and for reasons which will appear the openings are preferably outward of the peripheries of both throats.

The blades of the impeller may extend inward to Within the throats to act onthe liquid before it enters the pumping chamber, and in such case the blades exposed through the throat may cause a beating and agitating eifect in the entering liquid and a reciijculating movement diverging conical stream outward from the periphery of f the throat in which the action occurs, as in the manner' disclosed in the Curtis Reissue Patent No. 22,739. Such beating and agitating and recirculation can occur at either or both the top and bottom throats, depending on the relation between the throat periphery and the adjacent mner end portions of the blades, and can be made to occur in one throat and be avoided in the other, for example, to occur in the top throat and not in the bottom throat.

For many uses of the pump, particularly in automotive and other systems which are not subject to the low pressures of high-altitude flying, such beating and agitating and recirculating and bubble formation is desirably avoided, in order to preserve all constituents of the fuel in liquid state and to deliver them for utilization by the engine. To this end, in the preferred form of pump for such uses, the blades of the impeller do not extend into the throats, and their inner ends lie at or outwardly beyond the peripheries of those throats. To this same end, the central portion of the impeller, within the throats, is desirably formed with non-agitating surfaces, for example, with smooth and uninterrupted surfaces of revolution, to produce a minimum of agitation and swirling of the entering liquid, and the openings through the irnpeller (except possibly a circular axial bore) are arranged wholly outward of the peripheries of the throats.

In the pump preferred for automotive use, the mpeller comprises a relatively small hub sufficient for mounting on the pump shaft, ywith a smooth-surfaced and uninterrupted circular web extending outward from that hub to the periphery of the largest of the throats, and the impeller blades are formed as circumferentially spaced blades projecting outward in the pumping charnber from the edge of that web and lying wholly outward from the throats with no blade portions extending into or exposed through the throats. The circumferential spacing of the blades leaves open spaces between them in the pumping chamber, especially at the inner portions of the chamber, to permit both the desired gas escape iiow from the bottom to the top throat and the desired cross flow of liquid from one throat to the opposite side of the pump. In the pumping chamber, the impeller is open both in the sense that it carries no shroud and in the sense that its blades are circumferentially spaced to permit free fluid flow and pressure transmission axially across the blades.

Preferably, the impeller blades are tapered outwardly and the opposite walls of the pumping chamber are correspondingly dished. The clearance between the bladesJ and the walls need not be an extremely close clearance, and may be relatively large in proportion to blade width, for example, of the order of 0.015 to 0.025 with blades having a tip width of the order of 1,66. l

kIt will be evident from the foregoing that certain relationships between the throats and the inner ends of the blades are preferred but that variations are contemplated depending on the effects desired. Thus, the periphery of either throat may lie even with the inner ends of the blades, or may lie either inward or outward therefrom; the relationship at the ,two throats may be different; and the difference may result from different positioning either of the inner ends of the .blades or of the peripheries of the throats.

The blade-supporting web of the impeller desirably lies in a medial plane of the pumping chamber, with the blade edges standing axially both upward and downward therefrom toward the top and bottom chamber walls. The medial plane is desirably the central medial plane. The top kand bottom halves of the blades may differ, but desirably the opposite blade halves are of Vequal height and length and the impeller is symmetrical with respect to a central radial plane, which tends to eliminate end thrust and Ipositions the blade-supporting structure cen-` trally between and spaced from the casing walls. This arrangement and the absence of shrouds on the blades avoids any need for running seals between the pump rotor and the pump casing, and reduces the power consumption over what the pump would require if shrouds and seals were used. With unshrouded blades any reverse leakage ilow along the walls of the pumping chamber is in Contact with the uid being pumped, but this is believed to be advantageous to the dispelling of gas from the pump.

The top and bottom inlet throats of the pump are in substantially open communication with the body of liquid in which the pump is submerged, and in a pump-motor unit the pump and motor are spaced to provide such communication at the top throat. The inlets are desirably screened with screen which admits fuel but excludes solid particles larger than the pump clearances. The top screen should be of a character to permit the escape of gas through it. The screens may be of a character to exclude water from the pump,

In accordance with present automotive practice, the pump motor is a direct-current motor. It desirably operates at a speed of the order of 4000 r.p.m. to 5000 r.p.m. lt may be a wet motor, i.e., one which is filled by the fuel or through which the fuel is circulated for cooling and lubrication. Preferably, however, the motor is an enclosed dry motor, and motion is transmitted from it to the pump by a magnetic coupling operating through an imperforate wall in accordance with the teachings of the co-pending application of William L. Hudson, Serial No. 538,753, iiled October 5, 1955, now U.S. Patent No. 2,885,126. v

The pump-motor unit is mounted in the fuel tank to position the pump at as low a level as possible which still permits free access of liquid to the bottom throat. When a sump is used, the sump is desirably of sufficient size and depth to position the top throat substantially at or below the level of the surrounding tank bottom wall. The sump may be surrounded by relatively upright walls to baille lateral iiuid flow from the sump.

When the pump inlet screens are of a type which pass water, the pump is desirably positioned with its bottom throat immediately above the lowest point in the tank, i.e., that point where water of condensation tends to collect.

Pumps embodying the invention continue to pump effectively even when the liquid level in the tank falls to or even below the top throat opening. While the top throat is then exposed to air, the pump is suliiciently filled with liquid from the bottom throat to maintain effective pumping and to prevent and oppose passage of air into the pumping chamber. Accordingly, with the pump mounted close to the bottom of the tank, it will continue to pump until the tank is substantially empty.

When both throats are exposed to air, by reason, for example, of the sloshing of fuel in the tank, pumping is of course interrupted so long as such exposure continues. But when the fuel flows back to the pump, the pumping action immediately resumes. Any air or gas which is caught in the pump or bottom throat upon thc resubmergence of the pump passes through the impeller openings and is released through the top throat. Gas which may occur in the pump or bottom throat for any other reason, as from vaporization or cavitation under extreme temperature and pressure conditions, is released from the pump in like manner, and the pump does not become gas-bound.

The pressure conditions in the pump are believed to cooperate with its structural features to produce this releaseY of gas and to avoid gas binding. in the direction of progression through the pump from the throats to the volute, the pressure rises increasingly toward the tips of the blades, to produce a relatively*high-pressure zone swept by the outer ends of the blades. The discharge head or back-pressure against which the pump normally operates tends to hold liquid in this high-pressure Zone; and if the pump is only partially lille'd, the liquid present collectsin this outer or high` pressure zone, where it blocks escape of air to the volute, and any air which is present separates inward toward the throats. The openings between the blades in the pumping chamber permit the liquid from either throat to freely fill the chamber across its whole height, and permit the air or gas to rise through the impellcr to the top of the pump. Liquid entering the bottom throat will progressively fill the pump, and the air orgas is displaced inward and upward to and through the top throat.

With the pump close to the bottom of the tank and with a screen which admits water, water of condensation which occurs in the tank is discharged therefrom by the pump as it occurs; for as small quantities of water drain to a point below the pump, they are picked up and entrained with the entering fuel and are discharged by the pump with the fuel. Water will then be discharged as a relatively small proportion of the total liquid delivered by the pump, and can pass through the engine without interfering with its normal operation; and water will not accumulate to enter the pump in large proportions. Because the pump has both top and bottom openings, not only does it permit any gas to escape upward, as has been noted, but it also permits any water in the pump or in the adjacent lines to drain from the pump back to the tank when the pump is stopped. Because of such draining and because the accumulation of water is prevented, 'the fuel system substantially avoids any danger that it will be rendered inoperative by the freezing of water in the pump or in the lines.

The accompanying drawings illustrate the invention. In such drawings:

Fig. l is a somewhat schematic diagram of an automobile fuel system embodying the invention;

Fig. 2 is a vertical section of a fuel pump and motor unit in accordance with the invention, in the form of a built-up assembly adapted for automotive use;

Fig. 3 is a bottom section taken on the line 3 3 of Fig. 2, i.e., a bottom plan view of the pump of Fig. 2 with the bottom half of the pump casing removed;

Fig. 4 is a top plan view of the assembly shown in Fig. 2;

Fig. 5 is a vertical section on the line 5-5 of Fig. 6 of a preferred modification of pumpmotor unit adapted for quantity production for automotive vehicle use,v ass ociated with a preferred mounting;

Fig. 6 is a bottom plan view of the pump-motor unit and mounting shown in Fig. 5;

Fig. 7 is a vertical section taken generally on the line 7--7 of Fig. 5 and more specifically on the line 7-7 of Fig. 8, Aand showing a mounting clip on an enlarged scale;

Fig.- 8 is a section taken on the line 8 8 of Fig. 7;

Fig. 9 is a vertical section of another modification of a pump-motor unit in accordance with the invention, in which the pump motor is a wet motor;

Fig. l() is a section taken on the line 10-10 of Fig. 9;

Fig. ll is a fragmentary vertical section similar to Fig. 2, showing an impeller and casing arrangement adapted to produce beating and agitating and recirculation of liquid in the body of liquid in which the pump operates;

Fig. 12 is an enlarged half-section of a pump casmg and impeller, showing the preferred blade and throat relationship fory automotive use; and

Figs. 13 and 14 are similar half-sections illustrating modified blade and throat relationships.

The system shown in Fig. l includes a pump and motorV assembly 1i! mounted as a depending unit in a fuel tank 12 and connected by a fuel line 14 through a iilter 16 to the float-controlled inlet valve 18 of the carburetor 20 for an automotive engine 22. The pump operates against back-pressure resulting from the static discharge head andthe friction head in the line 14 and filter 16, and especially from the restrictionrvnormally provided by the valve 18.

The ignition system of the engine 22 is controlled by a key-actuated switch 24 having amovable contact 26 connected to a battery 27, and having a fixed contact 2&z connected to the ignition circuit 30. The switch may alsov have a second fixed contact 32 connected to the actuating relay for the engine starter 34. In normal running, the movable contact 26 closes an ignition circuit to the first.A fixed contact 28. For starting, the movable contact 26 is moved beyond this normal running position to engageV both the first contact 28 and the second fixed contact 32, and then closes both the ignition circuit and the starter relay circuit. The motor of the fuel pump 10 is energized by Ia line 36 in parallel with the ignition circuit 30, and preferably includes a switch wln'ch is responsive to engine operation, for example, responsive to intake vacuum, to oil pressure, to generator output, to rotation of some engine part, or to some other engine or accessory function. As shown, this switch is a normally open switch 38 actuated to closed position by a sensitive vacuum-responsive motor 4t), responsive to intake vacuum of the engine 22. With a suitably sensitive vacuum motor, such vacuum is suficient both under starting conditions and under al1 running conditions to effect the closing of the pump energizing switch. If desired, however, the pump can also be energized in response to switch actuation. For this, the switch 24 may be provided with an additional fixed contact 31, positioned to be energized concurrently with or ahead of the starter contact 32, and such contact may be connected by a line 44 (shown in dotted lines) to energize the pump 16 independently of the switch 38 during actuation of the starter relay.

The pump and motor assembly shown in Figs. 2 through 4 comprises a mounting plate Si) secured about the edges of an opening in the top wall 52 of the fuel tank- 12. .A central depending collar 54 on the plate 50 carries a cylindrical motor housing shell 56, sealed to the collar 54 by an O-ring gasket 58. A motor support casting 60' .is received and secured in the lower end of the tube 56,

and sealed thereto by an O-ring gasket `62. The upper end of the casting 69 is formed to receive the bearing boss 66 at the lower end of the motor 63, Iand the motor is supported by the casting 60 and is secured in place by' bolts 69.

The motor shaft 7i) is carried by radial and thrust bear, ings in the motor, and projects downward. Its lower end slidably receives the hub 72 of the driver member 74 of a magnetic coupling and is drivingly connected thereto by a cross pin 76 engaged in a slot in the hub 72. The shaft thus centers and drives the driver member 7 4, but neither member transmits or receives thrust from the other. The lower end of the motor support casting 60 is closed by an imperforate wall or diaphragm 80, sealed thereto by an IJ-ring gasket 82 and clamped in place by a housing 84 for the driven member 86 of the magnetic coupling.

A pump body 9b is secured to this assembly below the. housing S4, and is spaced therefrom by a series of spacing posts 192. The body 9i) forms the upper wall 92 of the pump casing, and such wall carries one or more struts 94 extending diagonally upward and inward to support a central bearing sleeve 95 which fits into a cen-trai opening in the housing S4 and houses a pair of spaced sleeve bearings 98 for the pump shaft 100. A passage in one of the struts 94 carries fuel from the pressure side of the pump to the space between the bearings 98 for lubrication. A pump cover 104 forms the bottom wall 106 of the pump casing.

The two pump casing walls 92 and 106 have central openings to form axially opposite top and bottom inlet throats 16S and 116, and define a thin annular pumping chamber 112 which extends outward from between the throats. Such chamber openly communicates with a volute 114 formed in the body and cover, and this leads tangentially through a pump delivery passage 116 to a socket 118 for the lower endof a pump discharge pipe' 120. The pipe is received between that socket 118 and;

savana d" sealed to each socket by an O-ring gasket. The top socket 122 connects with av discharge fitting 124 adapted to be joined to the fuel line 14.

One side of the motor d8 is grounded, and the other side is connected by a lead lijdr to `a terminal post 126 extending through an insulating tting on the mounting plate. The pump-motor line 3d may be connected to the post 126, and the connection is protected by an enclosing shield 13o.

The imperforate wall or diaphragm {d} is made of nonrnagnetic material, such as stainless steel, brass, or a noncoriductive material. As shown, the wall Sti is a stili disk of synthetic resin material reinforced with fiber. lt is completely imperforate, and the entire assembly above it isv completely closed and sealed from the fuel in the tank. Both the driving member 74 of the magnetic coupling and especially the motor 68 are thus isolated from the tank and operate dry, with suitable lubrication., in an atmosphere free of fuel. The motor chamber may be vented in the atmosphere through a screened opening 132 in the mounting plate Sil. Alternatively, the clos-ed assembly may be sealed, and tilled with gas to provide a controlled atmosphere.

The driving member 74 of the magnetic coupling is of circular shape, and carries two spaced depending annular walls, which form a seat for an annular permanent magnet 14). This has chamfered lower-corners and is fixed in its seat by deforming the walls over those chamfered corners. The magnet is magnetized, preferably after assembly, to provide spaced magnetic poles at its bottom face. Preferably, four such poles are used, of alternate polarity. The member 74 may carry fan blades 75 on its top surface, to circulate air through the motor. The driven member S6 of the magnet coupling is of similar construction, with a central hub 142 and two upstanding spaced annular walls which form a magnet receptacle. A companion annular permanent magnet 144 is secured therein, and is magnetized like the magnet 143% but with its poles at its top face.

Each coupling member 74 and 86 has a central thrust bearing seat 146, and thrust balls are interposed between such seats 146 and a pair of thrust plates 14g inserted in a thickened portion at the center of the wall 8G. The thrust arising from the traction between the permanent magnets 14d and 144 is taken directly by this central thrust bearing structure and is not imposed on the housings or on either the motor bearings or the pump shaft bearings. The driven coupling member 36 is fixed on the pump shaft 100 and is centered thereby, and the magnetic traction holds the coupling and shaft upward in the position determined by the bottom thrust insert 14S of the Wall 80.

The pump impeller shown in Figs. 2 and 3 (and similarly in Fig. l2) comprises a small central hub 1150 threaded onto the pump shaft 19d, with a circular web 152 extending radially therefrom in the central plane of the pumping chamber,` and with a series of circumferentially spaced impeller blades d carried at the edge of the web. The blades shown are T-shaped in cross section. Their reinforcing central ribs are integral with the web 152 and extend in its plane along the leading faces of the blades. From the central rib of each blade, the blade edges stand upward and downward into running clearance with the pumping chamber walls 92 and 106. The top and bottom blade halves are of the same height and of the same radial length. The impeller is thus symmetrical with respect to the central plane of the pump. The blades are tapered outwardly, and the pumping chamber walls SF2 and 1% have a corresponding shallow conical shape. The circumferential spacing of the blades about the circular web 152 leaves relatively large open spaces between them, and such spaces extend inward to the inner 'ends of the blades. With such spacing', liquid from either throat can freely cross the centralplane of the pumpto till the impeller, pressure willw be equalized across the whole axial width of each blade, and any air or gas in the pumping chamber can freely rise to the top of that chamber for escape through the top throat 108.

As has been noted, an automobile fuel pump desirably avoids beating and agitating the fuel, and desirably produces a minimum of recirculation or swirling or other movement in the surrounding liquid in the tank. To this end, the inner ends of the blades 154 lie at or outwardly from the peripheries of the throats, with no portions of the blades directly exposed through either throat to the surrounding liquid. To this same end, the central hub 15) and the web 152 of the impeller in Figs. 2 and 3 are formed with smooth uninterrupted surfaces of revolution over the whole surface area which is exposed through the throats, and the at smooth web 152 extends outward to the periphery of the largest of the throats 108 and 110. The two throats may be of the same size, but in the preferred relation shown, the top throat is of the size as the circle of the inner ends of the blades, and the bottom throat is somewhat smaller.

The blades may have some forward or rearward sweep, but preferably are substantially straight. As shown, the leading edge of the central rib of each blade has a slight rearward sweep, while the blade edges lie radially of the impeller axis. The pump pressure should remain fairly constant over the whole range of delivery rates called for by the engine, and especially should remain within the range of pressures which can be controlled reliably' by the inlet valve of the fuel mixing device. A desirable discharge pressure range is below about 5 pounds per square inch as a maximum and above about 3 pounds per square inch as a minimum, with normal voltage in the motor supply circuit. Moreover, effective output pressure should be maintained over a wide range of delivery rates despite voltage drops which are likely to occur in the automotive electrical system from which lthe pump motor is energized. The preferred straight blades are found to give ythese desired characteristics.

The pump of Figs. 2 to 4, with an impeller of 1.5" diameter and 1/15 blade-tip width, operating at 4000 r.p.m. to 5000 r.p.m., is found to have an output capacity ranging up to about 25 gallons of gasoline per hour in a pressure range of from 3 to 5 p.s.i. With the pump operating at normal delivery conditions, the smooth-centered impeller has no beating or agitating effect on the entering liquid and hence does not produce vaporization or volatile constituents of gasoline even when the gasoline is -under boiling conditions. While some swirling of liquid occurs adjacent the inlet throats, the movement is relatively mild. Even under substantially boiling conditions, the swirling does not normally produce a hollow vortex with gas occurring along its axis and does not produce a recirculating stream or current of bubbles in the liquid. All constituents of the gasoline entering the pump are thus preserved and delivered in liquid state under pressure to the fuel mixing device of the engine.

When the tank in which the pump is operating contains a relatively low level of fuel, movement of the tank will slosh the liquid away from the pump and temporarily expose the inlets to air.

While such exposure of the throats to air interrupts pumping, the delivery line is maintained full of fuel and pumping resumes immediately upon resubmergence of `the throats, and the pump does not become gas-bound.

The assembly shown in Figs. 5 and 6 is adapted for quantity production as a substantially permanently assembled unit. The main body of the assembly comprises a tubular shell 2%, conveniently made of commercial tubing. A diaphragm 2&2 is inserted in its lower end, and is fixed and sealed in 4place as by soldering. The center of the diaphragm Zo?. carries a thrust bearing insert 234 and a depending sleeve bearing 2da, which are 9 secured and sealed to the diaphragm as by welding or soldering. Above the diaphragm 202, the shell 200 receives a motor-supporting spacer 208 which may be molded'from a synthetic resin material such as nylon and is generally cylindrical in shape. It rests on the diaphragm, and its upper portion tits closely within the shell 200. At three spaced points around its upper edge, it is provided with upward extensions 209 to center the motor 210 within the shell 200.

The motor assembly 210 is inserted within the shell 200 to rest on the upper face of the spacer 208. It is held down, and its upper end is centered, by a stabilizing plate 212 molded of synthetic resin such as nylon. The stabilizing plate is held in place, and the upper end of the shell 200 is closed, by a cap 214 which has a central tubular upward extension 216. This receives a grommet 218 through which the motor leads are passed. Such leads include a live lead 219 and a ground lead 220, the latter being connected to one of the bolts 222 which hold the motor assembly 210 together. The tubular extension 216 of the cap 214 is connected and sealed to a conduit 224 which carries the motor leads and serves to stabilize the mounting described below. The conduit may be sealed, as with a mass of sealing-compound 225.

The motor shaft 226 is carried by radial and thrust bearings in the motor 210 and its lower end projects downwardly and is provided with a drive pin 228. The driver member 230 of a magnetic coupling is slidably and dvingly mounted on the end of the shaft 226, and carries an annular magnet 232. The magnet is conveniently a pressed ferrite magnet, magnetized after assembly to provide for circumferentially spaced poles at its lower face.l The member 230 may be an anodized aluminum casting provided at its center with a hardened cup-shaped thrust bearing insert 234 which rides on a thrust ball between itself and the diaphragm insert 204.

The shell 200 projects a short distance below the diaphragm 202, and receives a pump body casting 240. Such casting forms the upper wall 242 of the pump casing, and has a rim 244 which abuts the lower edge of the shell 200. Three circumferentially spaced posts 246 extend upward from the pump body 240 and iit closely Within the lower end of the shell 200. Their upper ends abut the lower face of the diaphragm 202, and support a shroud 248 which forms a housing for the driven member 250 of the magnetic coupling. The pump body 240 is conveniently secured in place by one or more pins 252 pressed into aligned holes in the shell 200 and the legs 246. f

The lower end of the shell 200, between the posts 246,

y lis punched to provide inlet openings 254, and these are covered by a screen 256 wrapped around the lower end of the shell 200 and overlapping the rim 244 of the body 240.

- The'lower half lof the pump casing is formed by a cover 260, which may be molded of a synthetic resin material such as nylon. It provides the lower wall 262 of the pump housing. A volute 264 is formed by the pump body and cover, around the pump chamber, and leads to a socketV in the pump body 240 which receives the lower end of the discharge pipe 266.

The bottom throat of the pump is formed in the bottom pump casing wall 262, and is bridged by a spider 272 which supports a bearing sleeve 274 for the lower end of the pump shaft 276. The bearing sleeve may be integral and homogeneous with the cover 260 when that cover isrmade of a bearing material such as nylon. The bottom throat is protected by a screen 270 fitted within a tapering collar 268 on the body260 and held in place by a snap ring 269.

The pump shaft 276 is journaled at its ends in the sleeve bearing 206 on the diaphragm and in the bearing sleeve` 274 of the pump cover. Itsupper end face forms a thrust 10 bearing riding against a thrust ball received between it and the diaphragm insert 204.

The driven member 250 of the magnetic coupling is similar in construction to the driver member 230, and carries a companion magnet 251 magnetized after assembly to provide magnetic poles at its upper face in positions for alignment with the poles of the driving magnet 232. The driven member 250 is fixed on the upper end of the pump shaft 276, as by a press fit on a knurled section of the shaft, and the magnetic traction holds the shaft upward against the thrust bearing and fixes its axial position. The shroud 248 encloses the driven member 250 to prevent agitation and stirring of the liquid in the tank by the rotation of that member 250.

The pump impeller in Fig. 5 is generally similar to that shown in Figs. 2 and 3, both in construction and in its relationship to the top and bottom throats of the pump casing. It has a central hub which is pressed on a knurled section of the pump shaft 276, and has a circular central web of smooth and uninterrupted surface configuration within the throats of the pump, and such web supports spaced impeller blades which revolve in the pump chamber defined by the walls 242 and 262.

The pump body 240 and cover 260 are provided with peripheral anges 241 and 261 and are secured together by four rivets 280 passed through such flanges at spaced points around the periphery of the pump. The flanges may be used as a mounting for the pump and motor assembly.

In the mounting shown in Figs. 5 to 8, the pumpmotor unit is carried by its flanges 241 and 261 on a bracket 300 secured to the bottomwall of a tank. The bracket has a raised mounting plate 302, with downwardly oifset feet at its end edges which support theplate above the bottom of the tank. The pump lianges'.

241 and 261 are of unsymmetrical peripheral shape, andmounting plate 302 is punched to provide an opening of.4 generally similar unsymmetrical shape. To orient the pump with respect to the bracket 300, the plate 302 carries four upturned guide posts 304, and the flanges of. the pump are provided with tiat outer faces in comple-- mentary relationship with the inner faces of those posts 304. The relationship permits the pump to be insertedlY in only a single position, and the posts 304 loosely re-Y ceive and guide the pump housing as it is inserted.

The pump is secured in place on the bracket by snap fasteners, comprising clips carried by either the pump or bracket and` engaged with retainers carried by the other.. As shown, the assembled iianges 241 and 261 are pro-- vided with three circumferentially spaced rectangular openings 306, with that portion of each opening which lies in the flange 241 being slightly wider than the por-- tion which lies in the cover 260. A generally U-shaped spring clip 308 is inserted upwardly in each of the openings 306'. At the outer side of the central plane of each clip, its side walls are deformed outward to form clipretaining fingers or lugs 310 which engage over the upper edges of the pump body iiange 261 to retain the clip in its opening 306. At the inner side of the central plane of each clip 30S, its side walls are deformed inward to form spring latches 312. For cooperation with the three clips 308, the bracket plate 302 carries three upturned retaining fingers 314 which have notches 316 in their side edges, as shown in Fig. 7, to receive the spring latches 312. The guide posts 304 orient the pump in proper relationship with the bracket, and align the clips 308 with the retaining fingers 314, and when the pump is then pressed downward to its mounting position, the spring latches312 engage over the retaining lingers 314 and in the notches 316 to secure the pump assembly on the mounting bracket 300.

`The top wall 52 of the fuel tank is provided with a suitable opening for insertion of the pump-motor assembly, and such opening is closed by a cover plate 320. Such cover plate has a central opening containestarlo ing an elastic srommet 3.22 to closely embrace the. upper end of the conduit 22d at the top of the motor and. pump assembly. The upper end of the grommet 322 is closed by a terminal shield 324 through which the leads 219 and 220 are passed. The plate 320 also carries a pump discharge fitting 326, in communication with a depending socket 328 which receives the upper end of the. pump discharge pipe 266. The upper end of such pipe desirably carries an elastic grommet 330 which fric,- tionally engages the wall of the socket 32S.

ln mounting the pump, the pumpmotor assembly, including adischarge pipe 266 carried in the socket of the pump` body, is inserted through the opening in the tank top wall, is properly oriented with respect to the bracket Sili). by engagement of the flanges 241 and 261 between the posts 364, and is then pressed firmly downward to engage the retaining posts 314 in the clips` 36S carried in the openings 30.6 of the pump ilanges. This substantially locks the pump to the bracket 300, although the engagement can be released when it is desired to remove the pump from the tank. After the pump has been locked on the bracket 303, the cover plate 32h is ap plied to the top tank wall. The motor leads 219 and 229 are led up through the grommet 322, and that grommet is then engaged over the end of the:` Conduit 224, and the socket 32S is engaged over the end of the grommet 330 carried by the discharge pipe Zoo. The plate is then pressed downward to its seated position on the tank top wall and is secured in place. The conduit 224 serves av supplementary mounting function, as noted above, for its engagement in the grommet 322 stabilizes the upper end of the assembly, to suppress vibration` and prevent rocking movements which might tend tov dis.- 'lodge the pump from its mounting bracket 300. The grommets 322 and 330 prevent transmission of vibration to the top wall of the tank.

The conduit 224- and discharge pipe 266 can be made of any desired length to suit the depth of the tank in. which the assembly is mounted. Thus, in a shallow pas songer car tank, the conduit 224 will usually be relatively short,` and the relationship may be substantially that shown in Fig. while in a tall tank such'as is commonly used in trucks, the conduit 224i and pipe 265 may be quite long.

In the modification shown in Figs. 5 through 8, the motor Zit? and the driving member 23@ of the coupling are completely enclosed in the compartment formed above the imperforate wallk or diaphragm 262, and suchcompartment is lrerrnetically sealed from the tank. The compartment may be permitted to breathe to the at mosphere outside the tank, by providing for leakage past the grommet 218 in the conduit 224 and along the wire; leads 2E@ and 229 where they pass through the terminal: shield. Preferably, however, the assembly is sealed' as, by applying a sealing compound 225, Such as litharge,. around the wire leads inthe conduit 224,. and. in such. case, thev motor compartment may be filledJ with a con.- trolled atmosphere favorable to motor operationV and. life.

Operation of the motor rotates the driver 23@ of themagnetic coupling, and the driven member 25%, being4 magnetically coupled thereto, isdrivenfatthe samel speed; The torque required for normal operation: of theA small centrifugal pump isreadily transmitted by, the coupling, and the coupling et'fect is desirably limited to a, value sufficient for normal pump operation but less thanI the normal torque of the motor, and less, than sufficient to reestablish itself during operation once it is broken.. If. the pump should beeornelocked, thel coupling effect would, then be` broken and theA motor wouldl run free, without danger of overheating or burningy out.r v Y The pump of Figs. 5 andi 6vk operates in substantially thesame way as the pump of Fig. 2. lts surfaces ex-. posed throughthe throats are nonfagitating surfaces and` produce no heating and vaporization of the enteringy liquid and but; little swirling or other movement in the surrounding body of liquid. Swirling movement at the lower throat is further reduced by the spider supporting the bearing 274 below the bottom throat. The pump does not become gas-bound even when its throats are exposed to air by the sloshing of fuel in the tank, and resumes pumping immediately on resubmergence of the throats. Air or gas caught in the bottom throat or in the pump is displaced upwardly between the spaced blades and escapes through the top throat. The pump produces effective pumping until the liquid level in the tank (or sump) falls below the top throat of the pump casing, and thus will substantially empty the tank in which it is mounted.

The pump-motor unit shown in Figs. 9 and l() is made substantially entirely of sheet-metal stampings, and utilizes a wet motor, i.e., a motor through which fuel is circulated for cooling and lubrication. The unit includes a mounting plate 410 by which it is. carried by the top `wall 412v of a fuel tank.v Like the other modifications, the pump may be positioned in a sump 414 formed, in the. bottom wall of the tank. The mounting plate 410 carries a depending collar 416 on which a hanger tube 4l?) is supported. The lower end of the tube 418 is closed by a motor supporting plate 426 which has a central depending cup L22 for the reception of the lower bearing boss of the motor unit 424. The motor unit is desirably disposed with its commutator 426 at the bottorn, to insurek lubrication of the commutator under all conditions, and the motor is secured to the mounting plate 421) by bolts, 44S. One side of the motor is grounded', and the other side is connected by a lead 430 to aY terminal' post 432 like that shown in Fig. 2.

. The depending cup 422 of the motor support plate 420 has inlet openingsv 434 in its side wall, and such openings are desirably covered' by a, cylindrical screen. The pump housing isV formed of' a pair of sheet-metal stampings 436 and' 438 which are secured together at their peripheries and are supported` from an inturned flange at the bottom of the cup 422. The casing walls form top and bottom inlet throats a pumping chamber extending outward from betweensuch throats, and a volute at the periphery of the pumping chamber. The outer end of the volute connects'with a` socket for the reception of the'lower end of a pump discharge pipe 442, Whose upper end` is received in a socket in Van outlet fitting 444 carried by the mounting plate 410.

The motor shaft 45S extends downward from the motorl into the pump casing, and the pump impeller 452 is mounted directly on its lower end. In this case the top and bot-tomA throats of the pump casingare relatively larger than those shown in the modifications described above, and the impeller blades extend inward into the throatm. With the blades thusexposed through the throats, the impeller produces an agitating effect on the entering liquid and a relatively violent swirling both in the entering: liquid and in the surroundingbody of liquid. Such agitationy and` swirling tend to separate the more volatile constituents4 from tbe fuel as gas bubbles,. and such gasbubbles may be discharged from the throats in outward. conical streams. Gas may also tend to collect at the center of the vortex or swirling body of liquid. Any bubbles which occur at, the. top throat Vare free to risc, therefrom and' to escape back to the tank through the openings 434,. and; to this end the openings extend upward to a point'labove the bottom of the motor bearing boss. BubblesV which are discharged with the recirculating liquid from theperiphery ofthe bottom throat are free to-riseabout the pump casing to the top of thetank. Bubbles which collecty at the center of the vortex at'the bottom throat aredesirably led off from the center of the vortex, and for this purpose, the pump shaft 455).

To lubricate and cool the motor, a small stream of liquid is led olf from the periphery of the pumping chamber by a tube 454 fitted into an opening in the top Wall of the pump casing 436 and leading upward into the housing of the motor 424, desirably to a point above the commutator of the motor. rl`he motor housing is substantially closed to retain liquid therein, and is provided at the top with an outlet nipple 456. Desirably, the mounting tube 4lt3 is also substantially closed below the top of the `motor, to retain a supply of liquid in cooling relation with the motor casing. Overow from within-the tube 418 is provided through one or more openings 458 adjacent the top of the motor.

Fig. 1l illustrates a modification of the pump and motor unit shown in Fig. 2, in which the pump casing and the impeller are arranged to produce beating and agitating and recirculation of the liquid. The top and bottom throats SGS and 510 of the modified pump are substantially larger than those in the pump of Fig. 2, and the impeller blades 554 are extended inward from the pumping chamber 512 substantially to the hub 550 of the impeller, so that their inner portions are openly exposed through the enlarged throats. With such exposure through the relatively large throats, the impeller tends to produce a recirculation of the liquid adjacent the pump, with liquid owing inward adjacent the axis of the pump and with liquid liowing outward from theY peripheries of the throats, and to produce `a relatively strong swirling of the liquid adjacent and outward from the pump. The agitating or'lbeating effect produced by the exposed vblades on the recirculating liquid separates volatile or gaseous constituents from it as bubbles which become entrained in the stream of recirculating liquid discharged from the peripheries of the throats. The bubbles which are so entrained, both at the top and bottom throats escape outwardly and rise through the body of liquid in the tank. Gas may also .pass through the impeller between its spaced blades, to escape `from the top throat. The swirling of the liquid forms a vortex, and gas also tends to collect at the center of such vortex. To bleed off gas from the center of the bottom throat, the pump shaft Sdi) contains a central bore which discharges past the thrust ball at the upper end of that shaft and into the housing for the driven member of the magnetic clutch. Gas so discharged displaces liquid from that housing, and provides a gaseous medium rather than a liquid medium about the driven coupling member, to reduce the frictional drag on that member.

Figs. l2 to`l4 supplement ,the other figures of the drawing to illustrate on an enlarged 'scale modifications in the relationships between the pump throats and blades. The relationships shown in Fig. l2 are likepthose of Figs. 2 and 5, and are preferred. The top and bottom halves of the impeller are symmetrical, and the inner ends 569 and Slof the top and bottom blade portions all lie the Vsame radial distance yfrom the pump axis. Therbottom throat 110 is smaller than the open area within the circle of the inner ends 561 of the bottom blade portions, and is of a size to give adequate inlet capacity. lts relationship tovthe blades is especiallyv effective to minimize swirling of the bottom inlet stream. The top throat -198 is larger than the bottom throat 110,

and ,has thesame radius as the inner ends 560 of the top blade portions, and the top wall 92 of the pump neither overhangslnor exposes the inner ends 560 of the blades. The relationship both facilitates the upward'expulsion of gas `from the pump and avoids beating and agitation of the liquid entering the throat.

In Fig. 13, the bottom throat 610 is of the same radius as Vthe circleof the inner ends 5,60%561 of the blades, while the top throat 6% is larger than that circle. With the blades separatedby open spaces which extend inward ings at the inner periphery of the pumping chamber. The upwardly exposed inner ends 560 of the blades tend to swirl the liquid in the upper throat, and to produce a recirculation to carry gas bubbles upward and outward in a conical path from the periphery of the throat.

The bottom throat 610 in Fig. 13 is the same size as the circle of the inner ends 561 of the blades, and in comparison with Fig. l2 gives a larger inlet area.

In Fig. 14, the top throat 708 and bottom throat 710 are of different radii, and the inner ends 712 and 714 of the top and bottom portions of the blades lie on different circles. This further illustrates that the top and bottom relationships may be modified to vary the pumping and gas-dispelling characteristics.

I claim as my invention:

1. A self-purging fuel pump for operation in submerged position in a fuel tank such as the gasoline tank of an automotive vehicle, comprising a pump casing adapted to be mounted in the fuel space in a fuel tank and forming an annular centrifugal pumping chamber having top and bottom walls, said top wall having a central upward-facing inlet opening for admitting liquid to the chamber and for releasing gas therefrom, said bottom wall having a central downward-facing inlet opening for admitting liquid to the chamber, said openings being in open communication with the space surrounding the pump whereby fuel can freely enter said openings from said space and gas can freely escape to said space from said upward-facing opening, a centrifugal impeller in said casing having pumping blades in said pumping chamber to pump liquid outward therein from said inlet openings, said pumping blades and the annular pumping chamber portion swept thereby being of greater radial width than axial thickness, said impeller being axially open therethrough in areas adjacent said upwardfacing inlet opening and the top surface thereof inward of such axially open areas being a substantially bladeless surface of revolution, whereby gas entering the bottom inlet can freely pass through the impeller to the top inlet and be released therethrough ahead of substantial pumping action at the top inlet.

2. A fuel pump according to claim 1 in which said impeller has pumping blades with upper unshrouded edges in running clearance relation with the top wall of the pumping chamber whereby reverse leakage flow along said wall toward the top inlet opening is in contact with fluid in the pumping chamber.

3. A selfpurging fuel pump for operation in a fuel tank such as the gasoline tank of an automotive vehicle, comprising a pump casing adapted to be mounted in the fuel space in a fuel tank and forming an annular centrifugal pumping chamber having top and bottom walls separating the chamber from the space surrounding the pump, said wall having a central upwardfacing inlet opening in open communication with the surrounding space for freely admitting liquid therefrom to the chamber and freely releasing gas thereto from the chamber, said bottom wall having a central downward-facing inlet opening communicating with such space for freely admitting liquid therefrom to the chamber, a centrifugal impeller rotatable in said casing and having a central portion between said inlet openings and having blade means supported thereby in said chamber to pump liquid outward in said chamber from said inlet openings, said pumping blades and the annular pumping chamber portion swept thereby being of greater radial width than axial thickness, said blade means being openly spaced from eachother at their inner ends yand defining uidreceiving spaces in the chamber which are in inlet communication with both inlets and kwhich provide openings through the impellerl through which gas entering the bottom inlet can freely pass upward through the irnpeller inward of the main pumping action of the impeller for release through said ltop opening.

4. A self-purging pump according to claim 3, in which the impeller comprises a central circular portion of substantially the same size as the top inlet opening with the surfaces thereof facing said opening being substantially smooth non-agitating surfaces, and said pumping blades comprise substantially free-standing arms projecting outward in spaced relation from the periphery of said circular portion.

5. A self-purgingl fuel pump for operation in submerged position in a fuel tank such as the gasoline tank of an automotive vehicle, comprising a pump casing adapted to be mounted in the fuel space in a fuel tank and forming an annular centrifugal pumping chamber having top and bottom walls, said top wall having a central upward-facing inlet opening for admitting liquid to the chamber and for releasing gas therefrom, said bottom wall having a central downward-facing inlet opening for admitting liquid to the chamber, said openings being in open communication with the space surrounding the pump whereby fuel can freely enter said openings from said space and gas can freely escape to said space from said upward-facing opening, a centrifugal impeller in saidcasing, said impeller having a central portion standing between said inlet openings, the surfaces of said central portion within the axially projected areas of the inlet openings being bladeless surfaces, said impeller having blade arms projecting substantially radially outward from said central portion and formingpumpingblades for pumping liquid outward in said pumping chamber, said blade arms and the annular pumping chamber portion swept thereby being of greater .radial width than axial thickness, said blade arms being openly spaced from each other over at least the inner radial portion of the pumping chamber and providing open liquid-receiving spaces therebetween in substantially open inlet communication with both casing inlets and in which gas in said pumping chamber can separate from liquid therein and wherein such gas and gas entering the bottom opening can freely pass upward through the impeller and be released through said top inlet.

6. A self-purging fuel pump for operation in submerged position in a fuel tank such as the gasoline tank of an automotive vehicle, comprising a pump casing adapted to be mounted in the fuel space in a fuel tank and forming an annular centrifugal pumping chamber having top and bottom walls, said top wall having a central upward-facing inlet opening for admitting liquid to the chamber and for releasing gas therefrom, said bottom wall having a central downward-facing inlet opening for ladmitting liquid to the chamber, said openings being in open communication with the space surrounding the pump whereby fuel can freely enter said openings from said space and gas can freely escape to said space from said upward-facing opening, a centrifugal impeller rotatable in said casing, said impeller having a blade supporting web in a medial plane of said pumping chamber and blade portions standing upward and downward from said structure to form pumping passages open to said casing inlet throats on opposite sides of said medial plane, the blade portions of said im aller and the annular iumninfr chamber ortion swe t thereby being of greater width radially in said medial plane than over all axial thickness of said blade and chamber portions, and said pumping spaces on opposite sides of the medial plane being in open communication with each other at the inner ends of said rlp-standing blade portions, the impeller structure exposed through the inlet openings being defined by non-agitating bladesless surfaces and the blade portions adjacent each inlet opening lying wholly outward of such opening, and the pumping spaces on opposite sides of the medial structure being in open communication with each other adjacent the inner` periphery of the pumping chamber.

7. A self-purging fuel pump'for operation in submerged position in a fuel tank such as ythe gasoline tank of an automotive vehicle, comprising a pump casing adapted to be mounted in the fuel space in a fuel tank and forming an annular centrifugal pumping chamber having top and bottom walls, said top wall having a central upward-facing inlet opening for admitting liquid to the chamber and for releasing gas therefrom, said bottom wall having a central downward-facing inlet opening for admitting liquid to the chamber, said openings being in open communication with the space surrounding the pump whereby fuel can freely enter Said openings from said space and gas can freely escape to said space from said upward-facing opening, an open impeller rotatable in said casing between said top and bottom inlets and having circumferentially spaced pumping blades in said chamber for pumping liquid outward therein, the spacing of said blades forming liquid-receiving spaces therebetween which are open axially across the whole axial width of the blades and extend inward to the inner ends of the blades and are in open communication with both casing inlets, said pumping blades and the annular pumping chamber portion swept thereby being of greater radial width than axial thickness, where by said spaces can be lled by uid from either casing inlet alone and gas in said spaces can freely rise therethrough for escape through said top casing inlet.

8. A self-purging fuel pump according to claim 7, in which said blades have unshrouded top edges in running clearance relation with the top wall of the pumping chamber whereby reverse leakage along said wall toward said top inlet is in contact with said liquid-receiving spaces to drive gas therefrom to said top inlet.

9. A self-purging fuel pump for operation in submerged position in a fuel tank such as the gasoline tank of an automotive vehicle, comprising a pump casing adapted to be mounted in the fuel space in a fuel tank and forming a centrifugal pumping chamber having a central upward-facing inlet opening for admitting liquid to the chamber and for releasing gas therefrom and having a central downward-facing inlet opening for admitting liquid to the chamber, said openings being in open communication with the fuel surrounding the pump whereby fuel can freely enter said openings from said space and gas can freely escape to said space from said upward-facing opening, said pumping chamber being in the form of a relatively thin annular chamber extending radially outward from said inlet openings a greater distance than its axial thickness, a centrifugal impeller rotatable in said casing, said impeller having blades across said annular pumping chamber for pumping liquid outward in said chamber, said blades being openly spaced from each other over a substantial portion of their length inward of their outer ends and having unshrouded top edges in running clearance relation with the top wall of said chamber, said relatively thin and wide annular pumping chamber and impeller forming an outer pressure zone swept by the outer ends of the blades and an inward zone wherein the duid-containing spaces are open through the impeller and openly communicate with both inlet openings to belled thereby and to release gas therefrom upward through the top opening.

, l0. A self-purging fuel pump according to claim 9 in which said impeller blades extend substantially radially across said pumping chamber and the axially open fluidcontaining spaces in' said inward zone are defined by impeller walls having substantially no sweep.

References Cited in the le of this patent UNITED STATES PATENTS 685,167 McKay oct. 22, 1901 748,520l Mesrravick Dec. 29, 1903 827,750 Raman Aug. 7, 1906 1,041,511 Rice et a1. ocr. 15, 1912 (Dther refrences on following page) 17 UNITED STATES PATENTS 2,430,222 Anderson etal. Apr. 7, 1914 2461'8 Davis Apr. 1o, 192s 2463'251 Lauer et al. Dec. 6, 1938 5 Summers Ian. 15, 1946 345,973 Black Oct. 15, 1946 817,077

18 Mann Nov. 4, 1947 Adams Feb. 15, 1949 Curtis Mar. 1. 1949 FOREIGN PATENTS Great Britain June 21, 1929 Germany Oct. 15, 1951

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