US2496496A - Turbine pump - Google Patents

Description

Feb. 7, 1950 J-. M. ROTH ET AL I 2,496,496

TURBINE PUMP Filed Feb. 15, 1946 2 Sheets-Sheet l [FIVE HZUFE (/A) IV. Ear/i E. dusros fiooews/z'ae ZQZ/ lw M 7 5.

Feb. 7, 1950 J. M. ROTH ETAL 2,496,496

TURBINE PUMP Filed Feb. 15, 1946 2 Sfieets-Sheet 2 FF q 2. as

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5 c/usrw Booavs/ E cz Patented Feb. 7, 1950 TURBINE PUMP Jay M. Roth and E. Justus Bodensieck, Cleveland, Ohio, assignors to Thompson Products, Inc., Cleveland, Ohio, a. corporation of Ohio Application February 15, 1946, Serial No. 647,757

14 Claims. (Cl. 103-109) This invention relates to turbine pumps for building up high pressures at relatively low rates of flow Without requiring excessive driving effort.

Specifically, the invention deals with a turbine pump having a rotor with fluid passages at spaced intervals around the periphery thereof and stator vanes alongside of the rotor for directing fluid flow to the inner ends of the rotor passages and out of the outer ends of the rotor passages in such a manner as to produce a series of incremental pressure boosts or increases of pressure on the fluid to obtain an efficient multi-stage pumpthe effect on the fluid.

Heretofore, turbine pumps have included impeller wheels or rotors running in a continuous channel or race having a barrier only between the inlet and outlet ports of the pump. In such turbine pumps, 2. continuous ring of fluid surrounds the rotor in the pumping channel or race, and is subjected to a number of impacts or impulses by the rotor vanes to be forced for substantially a complete revolution in the channel between the inlet and outlet ports. The impacts or impulses given to the fluid by the blades of the rotor produce a multi-stage pumping effect but, since no dividing walls are provided in the channel or race between the inlet and outlet ports of the pump, all of the stages of thepump are in full communication with each other around the entire periphery of the rotor and the pressure increase obtained in each stage is, therefore, necessarily quite small. Further, in such pumps, both sides of the rotor or impeller are exposed to the same pumping channel or race, and fluid advances in parallel communicating paths on opposite sides of the impeller and is at the same pressure in each path at any particular section of the channel. The pressure build-up thereby produced by the pump is thus limited to the number of impacts or impulses that can be given to the fluid in a single continuous channel or race. Thus, while known turbine pumps develop higher pressures than are obtainable in centrifugal pumps having equal impeller diameters and operating at the same speeds, prior to this invention turbine pumps were incapable of efficiently developing such high pressures at very low delivery rates.

According to the present invention, a high pressure, low delivery turbine pump is provided in a very compact, lightweight arrangement suitable for use in aircraft. The pumps of this invention are capable of developing from 500 to 1000.1bs. per square inch pressure on fluids such as gasoline at low delivery rates and are especially useful to feed the jets of gas turbine fuel systems.

The pumps of this invention have fluid-directing stator vanes arranged alongside of the rotor to guide the fluid and to actually separate the pumping channel or race into a plurality of individual effects or stages. These stator vanes receive fiuid centrifugally discharged from the outer ends of the rotor passages and guide the fluid to the inner ends of the rotor passages at advanced points in the pumping channel. A definite multi-staged pumping efiect is thereby obtained.

A feature of the invention resides in the provision of fluid-directing vanes on opposite sides of the rotor in the pumping channel or race of a turbine pump, and the provision of alternate oppositely inclined bores through the rotor at spaced intervals therearound and each having an outer end discharging through one side face of the rotor and an inner end receiving fluid through the opposite side face of the rotor. Fluid is discharged by centrifugal iorce from the outer ends of the bores and is directed by the vanes into the inner ends of the oppositely sloping adjacent bores for further staging or pumping back to the outer ends of these bores. A criss-cross staging of the fluid is thereby obtained to produce a series build-up of pressure in alternating stages on opposite sides of the rotor. In effect, two separate vaned pumping channels are provided, one on each side of the rotor, but pumping progresses alternately from one channel to the other in series of stages. Higher pressures at lower rates of flow are thereby obtained.

It is, then, an important feature of this invention to provide a turbine pump wherein fluid is circulated in series back and forth to opposite sides of the pump rotor, thereby eliminating the heretofore parallel operation of both sides of a conventional turbine pump to increase the pres- ,sure developed by turbine pumps and, at the pressures but vented back to a selected lower pressure area of the pump for limiting the pressure on the seal.

An object of the invention is to increase the discharge pressure capacity of turbine-type pumps without increasing the flow rate of the pump.

Another object of the invention is to provide a series type turbine pump that will develop very high pressures at very low delivery rates.

A still further object of the invention is to provide a small, lightweight, compact turbine pump suitable for aircraft usage and capable of developing sufficiently high pressures at low delivery rates for supplying the feed jets of an aircraft turbine engine.

A still further object of the invention is to provide a turbine pump with stator vanes or guide vanes coacting with the pump rotor in the pumping channel or race of the pump for dividing the race into distinct pumping stages.

A still further object of the invention is to provide a pump seal arrangement for high pressure pumps that is maintained at a predetermined pressure less than the full pressure developed by the pump.

Other and further objects of the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which, by way of a preferred example only, illustrate one embodiment of the invention.

n the drawings:

Figure 1 is an axial cross-sectional view, with parts in elevation, of a turbine pump according to this invention.

Figure 2 is a transverse cross-sectional view, with parts in end elevation, taken substantially along the line IIII of Figure 1 and having some parts broken away to show underlying structure.

Figure 3 is a transverse cross-sectional view taken substantially alon the line III-III of Figure -1.

Figure 4 is a fragmentary phantom diagrammatic view illustrating operation of the pump of Figures 1 to 3.

Figure 5 is a plan view of a stator vane for the right hand side of the rotor of the pump shown in Figure 1.

Figure 6 is a plan View of a stator vane for the left hand side of the rotor of the pump shown in Figure 1.

As shown on the drawings:

As best shown in Figure 1, the pump III of this invention includes a'cylindrical metal casin II having a cylindrical bore I2 extending inwardly from its back face to a front or end wall Ila. The front wall IIa has a central forwardly projectlng pilot portion IIb to center the casing in the aperture of a mounting pad of a motor (not shown) for driving the pump. This front wall IIa has a stepped bore through the central portion thereof including a major diameter bore portion I3 communicating with the chamber provided by the bore I2, an intermediate reduced bore I4 extending concentrically from the bore I3, and a smaller bore I5 extending concentrically from the bore I I through the front face of the pilot portion III). A shoulder I6 is provided between the bores I3 and I 4. A second shoulder ll 7 is provided between the bores I4 and I5.

A drilled hole It is formed through the front wall II a of the casin II and communicates at its inner end with the chamber provided by the bore II. The outer end of this hole I8 is closed 4 by a screw plug P threaded into the casing. A drilled hole Is in the front wall or end wall Ila intersects the inner end of the hole II as shown for a purpose to be more fully hereinafter described.

A groove" is formed around the bore l2 of the casing II near the open rear end face of the casing for a purpose to be hereinafter more fully described.

A ring block 2I snugly fitting the bore I2 of the casing II is seated in the casing against the end wall Ila thereof. This ring block 2I has a central aperture 22 lined with a cylindrical bushing or bearing 23. This cylindrical bushing or bearing 23 is also bottomed on the end wall IIa of the casing II.

The ring block 2I has an annular groove 2| of semicircular cross section between the aperture 22 and the periphery thereof. This groove 24 extends inwardly from the flat face 2Ia of the ring 2I which is opposite the flat face 2Ib seated on the end wall Ila of the casing. A hole 23 is provided through the ring block 2| to join the hole I! with the groove 24 at a point in the pump near the inlet port thereof for a purpose to be more fully hereinafter described.

A rotor 26 having a flat faced circular disk or wheel portion 26a with central hollow hub portions 26b and 23c extending from opposite faces thereof is mounted in the bore I2 of the casing II with the hub 23b thereof rotatably supported in the bushing or bearing 22 carried by ring block 2I and with one flat face of the disk portion 26a thereof in close-running clearance relation with the face 2 la of the ring block 2 I. The disk or wheel portion 22a of the rotor 26 is of smaller diameter than the bore I2 but of a sufllciently great diameter to extend radially beyond the groove 24.

The circular disk portion 26a of the rotor 26 has alternate oppositely inclined bores 21 and 20 therethrough around the peripheral portion thereof. The bores 23 register with the radially inner portion of the groove 24 in the ring block 2I. The bores 21 have outer ends registering with the radially outer portion of the groove 2Q in the ring block 2|.

A spacer sleeve 2! is mounted in the bore I2 of the casing II and is bottomed on the face 2Ia of the ring block 2I. This spacer sleeve 2! surrounds the disk portion 26a of the rotor 26 in spaced relation.

A second ring block 33 snugly fitting the bore I2 of the casing II is inserted through the open rear face of the casing I I and is bottomed on the spacer sleeve 23. This sleeve 29 separates the rin blocks 2I and 33 to maintain desired operating clearance for the rotor disk portion 26a between the ring blocks.

The ring block 33 has a central aperture 3| therethrough lined with a cylindrical bushing or bearing 32. The hub 26c of the rotor is rotatably mounted in this bushing or bearing 22.

The ring block 30 has an annular groove 33 of semicircular cross section between the aperture 3| and the periphery thereof. This groove 33 extends inwardly from the flat face 30a of the ring block which is bottomed on the spacer sleeve 29. The holes 21 in the rotor disk 26a communicate at their inner ends with the radially inward portion of the groove 32 while the holes 28 through the rotor disk 22a communicate at their outer ends with the radially outward portion of the through the bottom of the ring block 30 to communicate with the radially inward portion of the between the inlet and outlet ports to separate these ports. A similar partition wall (not shown) is provided in the groove 24 of the ring block 2| in axial alignment with the partition wall 36.

A closure disk or end plate 31 is seated in the bore |2 of the casing H to close the back of the casing. A peripheral groove 38 is provided around the disk 31 to receive an 0" ring seal 35 for sealing the periphery of the disk 31. A second groove 40 is provided around the inner face of the closure disk 31 to receive another 0 ring seal 4| to seal against the face 30b of the ring block 30.

A third groove 42 is provided in the face of the ring 31 to receive a third 0 ring 43 for sealing against the bearing 32.

The space between "0 rings 4| and 43 is open through holes such as 33a in the ring block 30 extending from the groove 33 at such pressure stages as is necessary to hold the ring blocks 30 and 2| tightly against the spacer 29, thus maintaining close operating clearance between the rotor and the ring blocks 2| and 30.

In addition, grooves such as 44 are provided in the face b of the ring block 30 around the inlet and outlet ports 34 and to receive 0 ring seals 45 for sealing against the closure disk 31.

The disk 31 has nipples such as 45 extending axially outward from its outer face. These nipples 4B are joined through bores such as 41 with the inlet port 34 as shown and also with the outlet port 35.

The closure disk 31 is retained in the casing II by a snap ring 48 seated in the groove 20 of the casing and extending radially inward from this groove to thrust against the outer face of the disk 31.

Before the ring block, rotor and closure disk are seated in the casing a sealing ring 49 composed of graphitic carbon or other material affording a good bearing and sealing surface, is seated in the bore H of the end wall Ha against the shoulder l1 to present a sealing face extending inward from the bore l4 adjacent the bore l2.

A drive shaft 50 is provided for driving the rotor 23. This drive shaft 50 has a splined end portion 50a projecting beyond the pilot portion Ilb to be coupled with a driving motor (not shown). A collar portion 50b is provided on the shaft '50 to carry a sealing rib 500 on one face thereof to ride on the sealing face 49a of the ring 49. The shaft 50 extends through the hollow hub of the rotor 26 and has an inner splined end 50d splined to the splined interior 26d of the rotor hub 260. The splined teeth 26d extend radially inward into the hollow hub 250 to provide abutment shoulders 26c.

A coil spring 5| surrounds the shaft 50 in the hollow hub portion of the rotor 28 and is bottomed at its opposite ends on the shoulders 26c and collar 53b. The spring 5| is effective to urge the shaft 50 toward the end wall ||a for holding the rib 50c in sealing engagement with the face 49a of the ring 49. Leakage through the bores in the end wall He in the casing is thereby stopped.

As shown in Figs. 1 and 3, a key 5| is seated in an axial groove 52 in the bore l2 of the casing H and projects therefrom into corresponding grooves in the ring blocks 2| and 3|] and in the spacer sleeve 29 to hold these members against relative rotative movement to each other' the casing As best shown in Figs. 1 and 6, the groove 24 of the ring block 2| has a plurality of radially extending stator vanes 53 at spaced intervals therearound. These vanes 53 have semi-cylindrical outer edges 53a snugly fitting the groove 24 and semi-cylindrical inner edges 53b receiving a solid ring 54. The ring 54 has a flat face 540. substantially flush with the face 2|a of the ring block 2| and with the end portions of the vanes. As shown in Fig. 6, these end portions of the vanes are curved in opposite directions with portions 530 disposed in the radially outer part of the groove 24 and arranged to scoop fluid out of the outer ends of the bores 21 of the rotor as the rotor is driven in the counter-clockwise direction shown by the arrows in Figs. 1 and 3. The oppo-.

sitely inclined portions 53d of the vanes 53 are bent or curved to direct fluid into the inner ends of the bores 28 of the rotor. As shown in Fig. l, the vanes 53 are arranged on the left hand side of the rotor.

The ring block 30 has a plurality of stator vanes 55 in the groove 33 thereof. These vanes extend radially around the groove and have semi-cylindrical outer edges 55a snugly fitting the groove wall together with semi-cylindrical inner edges 55b receiving a ring 56 similar to the ring 54. The ring 56 has a flat face 55a substantially flush with the face 30a of the ring block 30 and flush with the adjacent edges of the vanes 55.

As shown in Figs. 1 and 5, the vanes have oppositely bent or curved end portions 550 and 55d with the portion 550 lying in the radially outward portion of the groove 33 and arranged to scoop fluid out of the outer ends of the bores 25 and with the portions 55d lying in the radially inward portion of the groove 33 and arranged to direct fluid into the inner ends of the bores 21 when the rotor is driven in the counter-clockwise direction indicated by the arrows in Figs. 1 and 3.

The vanes 53 and 55 cooperate with the groove walls in which they are seated and with the rings 54 and 56 which they carry to define a series of radially extending passages or stages in the grooves communicating respectively with the outer ends of one set of inclined bores in the rotor and with the inner ends of the other set of oppositely inclined bores in the rotor. The vanes extend completely around the grooves except where the grooves are blocked off by the par tit on well such as 36 shown in Fig. 2. The oppositely bent or offset inner and outer end portions of the vanes are arranged so that fluid which is discharged centrifugally out of the outer ends of the rotor bores is directed into the passages to flow radially inward and be directed into the inner ends of adjacent bores having their outer ends communicating with the radially outer ends of the opposite set of vanes. Fluid thus flows in a somewhat figure 8 path from the passages in one ring block to the passages in the other ring block.

Operation of the pump can be better understood by reference to Fig. 4 which is a phantom view showing the vanes 55 in the ring block 30 and showing the overlying rotor 26. As illustrated in Fig. 4, fluid from the inlet port 34 is received in the inner end of the first rotor hole 21 and is centrifugally discharged through the outer end of this hol 21 into passages provided by the vanes 53 in the groove 24 (not shown). These and to.

vanes then direct the fluid to the inner end of next adjacent hole 2! of the rotor. Fluid is then centrifugally discharged through the outer end of this hole 28 into the passages provided by the vane 55 in the groove 33 of the ring block 3|. These vanes 55 scoop the fluid out of the outer end of the hole 28 and direct it to the inner end of the next hole 2'! which in turn discharges it through its outer end into the passages provided by vanes in the groove 24. These vanes in turn direct the fluid to the inner end of the next hole 28 from which the fluid is centrifugally discharged at the outer end of the hole 28 into passages provided by the vanes 55 in the groove 33. It will be noted that while only about two outer ends of the vanes communicate at any one time with the outer ends of the holes, more than two of the inner ends of the vanes communicate with the inner ends of the holes. This arrangement efiects circumferential advancement of fluid in the pumping channel in addition to the advancement provided by rotation of fluid in the holes of the rotor.

After making substantially a complete path around the circumference ofthe pumping channels, the fluid is discharged out of the outlet port 35 adjacent the barrier 36.

The fluid thus receives a series of centrifugal force impulses each time it is directed into a hole of the rotor. Since adjacent holes of the rotor are inclined in opposite directions, the fluid is picked up first from the right hand side of the rotor, is discharged through the left hand side of the rotor, is directed into the inner ends of the oppositely sloping bores and is centrifugally discharged back through the right hand side of the rotor at a point circumferentially advanced from the inlet port. The fluid traverses through the rotor many times during its course of travel between the inlet and outlet ports and opposite sides of the rotor are under the same fluid pressure so that end thrusts on the bearings 21 and 32 are eliminated.

The vanes 53 separate the right hand pumping channel into a series of radial stages or passageways around the circumference of the channel. The vanes 55 separates the left hand pumping channel into a series of radial passages around the channel. While two separate pumping channels are provided each on opposite sides of the rotor, these channels are connected in series through the bores of the rotor and the fluid flows in a spiral path from one channel through the rotor to the opposite channel and thence back through the rotor to the first channel.

Since leakage from the pumping channels into the hollow interior of the rotor hub may occur, the collar 50b may have its inner face subjected to very high pressures urging the rib We too tightly against the seal ring 4!. This invention, however, limits the maximum pressure in the hollow hub by venting the hub interior back to a low stage pressure area of the pump through holes i8, i8, and 25. Thus the hub interior can be maintained under any desired maximum pressure by venting into a selected pressure area of a pumping channel. The selected area is preferably adiacent the pump inlet. Any leakage through the vent is thus returned to the pump and the pump seal will not drag or be damaged by excessive pressures.

From the above description it should be understood that this invention now provides a turbine pump with pumping channels on opposite sides of the rotor arranged in series relationship by passages through the rotor and each containing radially extending stator vanes to better separate the pumping channels into distinct stages.

It will. Of course, be understood that various details of construction may be v i throush 8 wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of th appended claims.

We claim as our invention:

1. A pump comprising a rotor with a plurality of spaced alternate oppositely inclined bores deflning fluid passages around the circumference thereof, said passages having inner fluid receiving ends and outer discharge ends in radially spaced relationship, vanes adjacent said rotor defining fluid passageways for feeding fluid to the inner ends of said rotor passages and for receiving fluid from the outer ends of said rotor passages, said rotor passages being constructed and arranged to eifect a series of incremental pressure increases on fluid as the rotor is rotated relative to the vanes to centrifugally discharge fluid from the outer ends of the rotor passages.

2. A pump comprising a turbine rotor having fluid passages spaced around the periphery thereof with inner fluid receiving ends and outer centrifugal force discharge ends, a pump casing defining a pumping channel adjacent each side of said rotor and communicating with the inner and outer ends of said rotor passages, one of said channels having inlet and outlet ports, a partition in both of said channels separating said ports, and vanes in said channels arranged for directing fluid centrifugally discharged from the outer ends of preceding rotor pasages to the inner ends of succeeding rotor passages whereby rotation of the rotor relative to the vanes will effect a series of pressure enhancing impacts on fluid from the inlet port to discharge the fluid out of the outlet port.

3. In a turbine type pump including a rotor, the improvements of a pumping channel adjacent said rotor, and fluid directing vanes in said pumping channel separating the channel into a plurality of stages.

4. In a turbine type pump including a rotor, the improvements of pumping channels on opposite sides of the rotor and adjacent thereto and fluid directing vanes in said channels separating the channels into a plurality of pumping stages.

5. In a turbine type pump including a rotor, the improvement of a separate pumping channel on each side of the rotor and passages through the rotor connecting the radially inner portion of one channel with the radial outer portion of the other channel.

6. In a pump including a rotor and a pumping channel on each side of the rotor, the improvement of alternate oppositely inclined bores defining fluid flow passages in said rotor connecting the radially inner end of one pumping channel with the radial outer end of the other pumping channel, and fluid flow directing vanes in said channels arranged to receive fluid from the outer ends of the rotor passages and direct fluid into the inner ends of other rotor passages.

7. In a turbine type pump including a rotor having passages with radially inner fluid receiving ends and radially outer fluid discharge ends, said passages being efl'ective to centrifugally discharge fluid received through their inner ends, a pumping channel along side of said rotor, and vanes in said pumping channel arranged for directing fluid to the inner ends of said rotor passages and for receiving fluid from the outer ends of said rotor passages, said vanes being constructed and arranged with oppositely bent inner and outer ends to cause liquids to be drawn into the inner ends of the passages and to scoop liquid out of the outer ends of the passages.

8. A turbine type pump comprising a rotor having opposed faces, annular pumping channels adjacent each opposed face of the rotor, alternate oppositely inclined passages through the rotor connecting the radially inner end of one pumping channel with the radial outer end of the other pumping channel, and fluid directing vanes in said channel separating the channels into a plurality of stages and arranged to scoop liquid out of the outer ends of the rotor passages and feed the liquid to the inner ends of the passages.

9. In a turbine type pump the improvement of means defining an annular pumping channel, radially extending fluid directing vanes at spaced intervals in said channel, and barrier means intermediate the ends of said vanes cooperating with the vanes to direct fluid from the inner ends to the outer ends of the vanes.

10. A high pressure developing low delivery rate turbine pump which comprises means defining opposed annular pumping channels, radially extending vanes in said channels arranged to advance fluid around the channels, a rotor between said channels, and passages in said rotor connecting said channels in series whereby rotation of the rotor will eflect incremental pressure boosts on the liquid and liquid will flow through the passages and between the vanes in a figure eight path around said pumping channels.

11. A turbine pump comprising a casing having a bore extending inwardly from one end thereof to an end wall, said end wall of the casing having an axial bore therethrough, opposed ring blocks in said bore of the casing having central apertures aligned with the aperture of said end wall of the casing, annular grooves in the opposed faces of said ringblocks, said annular grooves having semicircular cross sections, bearings in the apertures of said ring blocks, a sleeve in said bore of the casing separating the grooved faces of said ring blocks, a rotor having an aperture therethrough, a disk portion between said ring blocks and hollow hubs rotatably mounted in said bearings, said disk portion of the rotor having alternate oppositely inclined bores therethrough joining the radially inner end of one groove with the radially outer end of the other groove, radially extending fluid flow directing vanes in said grooves of the ring blocks, ring members carried by said vanes on their inner edges intermediate the radially inner and outer end portions thereof, a closure plate in said bore oi. the casing, means venting the groove of the ring block adjacent said closure plate to the space between said ring block and closure plate to pressure the ring block against the sleeve, said closure plate and said adjacent ring block having aligned inlet and outlet ports, the inlet port 01' said ring block opening into the radially inner portion of the annular groove in said ring block, the outlet port or said ring block opening into the radially outer portion of said annular groove, a partition wall extending across the grooves of said ring blocks between the inlet and outlet ports, a drive shaft extending through the aperture in said end wall 'of the casing and into the aperture of said rotor, means connecting said drive shaft with said rotor, seal means on said drive shaft, cooperating seal means carried in the aperture of said end wall of the casing, a spring urging the seal means of the drive shaft against the cooperating seal means carried by the end wall of the casing, and means providing a passage connecting the hollow interior of said rotor with a groove in one of said ring blocks to vent the interior of the rotor to a low pressure area of the pump.

12. A turbine type pump comprising a rotor, a separate annular pumping channel on each side of said rotor, an inlet port in one of said channels, an outlet port in said one channel, a barrier wall separating the inlet and outlet ports, said channels having a plurality of flow paths with outer inlet ends and inner outlet ends and fluid flow passages through said rotor having alternately arranged oppositely inclined paths connecting the radially inner ends of the flow paths in one channel with the radially outer ends of the flow paths in the other channel for directing fluid in crisscross relation between the channels to advance through the flow paths in the channels to effect a series of incremental pressure boosts on liquid introduced through the inlet port and to discharge the liquid under high pressures out of the outlet port.

13. Ina pump a rotor having a hollow hub, a casing defining a pumping channel, a drive shaft extending into the hollow hub of the rotor, coacting seal means respectively carried by the drive shaft and the pump casing, and means venting the hollow hub of the rotor back to a low pressure stage of the pump to limit pressure on the seal means to a predetermined pressure.

14. In a turbine type pump a rotor having a hollow internally splined hub, a casing defining opposed pumping channels rotatably supporting the hollow hub of said rotor, a drive shaft extending into said casing having a splined end coupled to the splined portion of the hollow hub of the rotor, coactlng seal means carried by the pump casing and the drive shaft for sealing the hollow hub of the rotor, and means providing passageways connecting the hollow hub of the rotor with a low pressure stage of a pumping channel to limit pressure exerted-on the cooperating sealing means.

JAY M. ROTH. E. JUSTUS BODENSIECK.

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

Germany Oct. 16, 1933

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