US2915886A

US2915886A - Hermetic pumps for use in refrigeration systems

Info

Publication number: US2915886A
Application number: US670531A
Authority: US
Inventors: Jr Louis H Leonard
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 1957-07-08
Filing date: 1957-07-08
Publication date: 1959-12-08
Anticipated expiration: 1976-12-08
Also published as: GB843313A

Description

Dec. 8, 1959 L. H. LEONARD, JR

HERMETIC PUMPS FOR USE IN REFRIGERATION SYSTEMS Filed July 8, 1957 2 Sheets-Sheet 1 0000 0000 ooo8 oo OOOOOOOOOOO 0000000000 INVENTOR. LOUIS H. LEONARD, JR. BY WJ'M FIG.

ATTORNEY.

HERMETIC PUMPS FOR USE IN REFRIGERATION SYSTEMS Filed July 8. 1957 Dec. 8, 1959 L. H. LEONARD, JR

2 Sheets-Sheet 2 FIG. 3

FIG. 2

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ATTORNEY.

United States Patent HERIVIETIC PUMPS FOR USE IN REFRIGERATION SYSTEMS "15 Claims. (Cl. 62494) N.Y., assignor to a corporation of This invention relates to absorption refrigeration systems and, more particularly, to pumps for use in absorption refrigeration systems for circulating solution.

In absorption refrigeration systems of the type disclosed in my Patent No. 2,722,805, granted November 8, 1955, employing saline solutions such as a mixture of water and lithium bromide as an absorbent and water as a refrigerant, in which the system operates with a minimum practical amount of air leakage, I have found that metal plating such as copper plating occurs in many parts of the system, particularly on moving parts such as pump seal faces, pump bearings, etc. The phenomenon is not fully understood but it is believed that lithium bromide dissolves small amounts of copper from the cuprinickel or copper elements employed in the system which are exposed to solution. After limited solubility is reached, it is believed the metal plates out in the form of pure copper. The phenomenon does not appear to occur in systems which are substantially air tight so that oxygen is not present in the system. In spite of the use of many different types of material for bearings, it has been found that the pump bearings soon seized as a result of plating on the bearing surfaces.

Many attempts have been made to solve the problem by isolating the pump and motor bearings from solution. For example, it has been suggested that mercury seals be employed, that very long shafts be employed in an attempt to locate the motor and bearings above the solution level, that internal pump seals be used which would permit the motor and bearings to operate in water or octyl alcohol, etc. However, all of these various arrangements present serious problems, the most important problem residing in the fact that under certain circumstances, it is impossible to prevent solution from contacting the bearings of the pump.

The present invention solves the problem of metal plating by accepting the fact and providing a pump structure which automatically moves one of the cooperating bearing surfaces away from the other while continuing operation of the pump thereby preventing seizure of the bearing and failure of the pump.

The chief object of the present invention is to provide an absorption refrigeration system including a pump structure for circulating solution so designed that the usual metal plating of the bearing structure during operation of the system will not interfere with operation of the pump.

An object of the present invention is to provide a pump for use in a location in which it is exposed to a metal plating action such as an absorption refrigeration system employing a salt solution as an absorbing medium so designed that as metal plating occurs, the rotating assembly of the pump will move upward away from the stationary members of the structure thus maintaining a desired clearance between the cooperating surfaces of the bearing structure to prevent seizure of the bearing.

A further object is to provide a method of operation of an absorption refrigeration system. Other objects of the ice invention will be readily perceived from the following description.

This invention relates to an absorption refrigeration system which comprises, in combination, an absorber, an evaporator, vapor from the evaporator flowing to the absorber to be absorbed by solution therein, a condenser, a generator, vapor from the generator flowing to the condenser to be condensed therein, condensate from the condenser passing to the evaporator, and means to circulate solution, said means comprising a pump assembly including a pump housing having an inlet and an outlet, an impeller in said housing, a motor for actuating said impeller, a shaft carrying said impeller and connected to said motor, a bearing supporting the shaft in desired position to permit rotation thereof, the bearing including a fixed member and a movable member, one of said members having a tapered surface whereby upon plating of the bearing the movable member of the bearing tends to move in a direction away from the impeller housing.

This invention further relates to a pump for use in a location in which it is exposed to a metal plating action such as an absorption refrigeration system employing a salt solution as an absorbing medium comprising, in combination, a pump housing having an inlet and an outlet, an impeller in said housing, a motor for actuating said impeller, a shaft carrying said impeller and connected to said motor, a bearing supporting the shaft in desired position to permit rotation thereof, the bearing including a fixed member and a movable member, one of said members having a tapered surface whereby upon plating of the bearing the movable member of the bearing tends to move in a direction away from the impeller housing.

This invention further relates to a method of operation of an absorption refrigeration system employing a pump for circulating solution in which the solution is capable of metal plating the bearing surfaces of the pump, the steps consisting in rotating the pump impeller to circulate solution, and, as plating of the bearing surfaces occurs, automatically moving one of the cooperating bearing surfaces to prevent seizure of the bearing and failure of the pump.

The attached drawings illustrate a preferred embodiment of the present invention, in which Figure 1 is a flow diagram of an absorption refrigeration system including the pump structure of the present invention;

Figure 2 is a sectional view of the pump structure;

Figure 3 is a fragmentary sectional view of an absorber shell modified to receive the improved pump structure;

Figure 4 is a fragmentary sectional view of a modified bearing structure; and

Figure 5 is a fragmentary sectional pump assembly.

Referring to the attached drawings, there is illustrated diagrammatically in Figure 1 the absorption refrigeration system of the present invention. The system comprises a shell 2, containing a plurality of tubes 3, which cooperate with the shell to form an absorber. Placed in shell 2 above absorber 3 is a pan-like member which cooperates with shell 2 to form an evaporator 4. A plurality of tubes 5 extend longitudinally of the shell above the pan-like member. Medium to be cooled passes through these tubes in heat exchange relation with liquid refrigerant sprayed thereover. A vapor condensate return header 6 is placed over the tubes 5 and serves to discharge condensate thereover.

A second shell 7, preferably, is placed above the first shell. Tubes 8 extend in the power portion of shell 7 and cooperate with shell 7 to form a generator. A plurality of tubes 9 are placed in the upper portion of shell 7 to form a condenser. The tubes 9 cooperate with a pan-like member 10 to form the condenser. Both shells view of a modified tion may be discharged in stantially constant.

3. are, supported in desired position on supports (not shown).

Pump 11 withdraws weak solution from absorber 3 through line 12. Pump '11 forwards weak solution through line 13 to heat exchanger 14 in which the weak solution'is placed in heat. exchange'relation with strong solution returning from the generator as hereinafter de-' scribed. The weak solution is then forwarded from heat exchanger 14 through line 15 to generator '8. Strong solution flows from generator'8 through overflow arrangement 16, line 17, heat exchanger 14, and line 18 to the absorber, preferably, being discharged therein adjacent one end of shell 2. Strong solution flows through forces of gravity from the genator to the absorber. It will be understood, or" course, if desired, the strong 'solu the absorber over the tubes of solution'through the generator is sub- The specific construction of pump 11 is hereinafter described.

Pump 19 serves as an absorber pump and is employed to withdraw a solution of intermediate concentration from absorber 3 through line 21. The specific construction of pump 19 is hereinafter described. Preferably, pump 19 is enclosed in the absorber shell; the solution of intermediate concentration through line 22 to the absorber. Spray arrangement 23 serves to distribute the recirculated solution over the tubes throughtherein. Flow out the length of the absorber 3. It will be understood that the strong solution mixes to some extent with'solution in the absorber and that further mixing occurs as the pump 19 forwards the tion having a concentration intermediate the concentra- Pump 19 forwards mixed solution so that a solution of the strong and weak solutions is circulated.

Reference is made to co.pending application, Serial No. 505,369, filed April 8, 1955, now Patent No. 2,840,977 in the name of Louis H. Leonard, Jr., for a more detailed description of the flow of solution in the system.

Condensing water is forwarded by a pump (not shown) through line 25 to the tubes3 of the absorber. The condensing water passes from the tubes 3 of theabsorber through line 26 to the tubes 9 of the condenser. Condensing water leaves the tubes 9 of the condenser through line 27.

A modulating valve 29 is placed in line 27 to regulate flow of condensing water through the condenser. Valve 29 is actuated in response to the temperature of chilled medium leaving the evaporator. A suitable control system is disclosed and claimed in my Patent No. 2,722,805, granted November 8, 1955. Under some circumstances, if desired, a bypass line 27 may be provided about the condenser, a manual valve 27" being placed in line 27'. Line 27 permits an initial adjustment of the flow of condensing water through the condenser so that the proper condensing temperature is maintained for full load operation.

Medium to be cooled is forwarded by a pump (not shown) through line 30 to the tubes of coil 5 of evalporator 4. The cooled medium leaves the tubes S-through line 31 and is forwarded to a place of use such as the central station of an air conditioning system. The medium, after passing through the central station, returns to the evaporator 4 through line 30 to be againcooled and reused.

Condensate leaves condenser 9 returned to header 6 in the evaporator and discharged in the evaporator over the tubes 5 to wet. thetubes. It will be appreciated the refrigerant is flashed or vapor ized to cool the same upon its discharge in the evaporator and is vaporized by its heat exchange relation with medium passing through the tubes of the evaporator. The flashed vapor passes to absorber '3 to be absorbed by the solution therein.

Pump 35 serves to recirculate liquid refrigerant collected in the evaporator. evaporator by line 36 through line 32 and isneed for solution pump seals.

. 110 and a movable member 111 secured to the shaft104.

. the impeller greater I the impeller so'that Pump 35 isconnected tothe' to withdraw liquid refrigerant aerasae therefrom. Pump 35 forwards the liquid refrigerant through line 37 to spray arrangement 38 of the evaporator, the liquid refrigerant flash cooling upon discharge in the evaporator, remaining liquid refrigerant wetting the tubes to cool medium passing through the tubes. The heat exchange relation between medium passing through the tubes and the liquid refrigerant on the exterior of the tubes cools the medium and evaporates the liquid refrigerant. The vapor passes to the absorber as previously described. 7

A suitable purge arrangement indicated generally at 42 is provided to remove non-condensible gases from I the absorber. The ejector 43 of purge arrangement 42 is connected by line 44 to a purgeline 45 extending longitudinally of the absorber. 'The cooling coil 46 of purge arrangement 42 is connected to line 30 by line 46' and to line 31 by line 47, permitting medium to be employed for cooling solution in the purge tank 48. The purge arrangement 42 is disclosed and claimed in co-= pending-application, Serial No. 565,324, filed February 14, 1956, in the name of Louis H. Leonard, Jr., and reference is made to such application for a more complete description of the purging arrangement.

A more detailed description of the absorber and the evaporator are disclosed and claimed in co-pending application Serial No. 580,052, filed February 3, 1956, in the name of Louis H. Leonard, Jr.

Steam is supplied to the generator through line 51 and is condensed in the tubes of the generator 8 in heat exchange relation with solution in the generator, the condensate leaving the generator through line 52, a steam trap 53 being placed in line 52.

The preferred absorbing solution is a solution of lithium bromide and water. The preferred refrigerant is water. Preferably, the solution concentration leaving the generator is about 66%. As stated above, a greater concentration may permit crystallization to occur, causing solidification in the heat exchanger and perhaps in other portions of the system.

The term weak solution is used herein to describe a solution weak in absorbing power. The term strong solution is used'herein to define a solution strong in absorbing power.

As shown in Figure 1, absorber pump 19, preferably, is placed in the absorber shell in a position in which at least the greater portion of the pump assembly is surrounded by solution in the absorber thus' eliminating the Absorber pump 19 (refer to Figure 2) includes a housing having an inlet} 101 and an outlet 102. An impeller 103 is placed in thehousing 100 and is carried by a vertically extending shaft} 104 connected to the rotor 105 of a motor 106. When the motor is stopped, forces of gravity keeps the assembly located properly. On start-up, thrust pulls the assem-' bly downward, maintaining the cooperating bearing sur faces hereinafter described in contact with each other. It will be appreciated the motor stator and rotor are encased in a material resistant to the solution such as an epoxy resin.

Bearings

107 and 108 are provided to support the shaft position in a substantially vertically extending direc- 109 sup- 1n tion as hereinafter explained. Support members port the

bearings

107, 108 and the motor in the assembly.

Each of the

bearings

107, 108 includes a fixed member The cooperating surfaces 112, 113 of members 110, 111 are tapered, as shown in Figure 2, themovable member. 111 having an area at its end away from the impeller greater than the area at its end adjacent the impeller."

110 has an area at its end adjacent The fixed member 7 than its area at the 'end away from pered surfaces during operation of the absorption refrigeration system the movable member and shaft carry-.1

106 in position upon plating of the cooperating ta-.

ing the impeller tend to ride upward or to move in a direction away from the impeller housing carrying the impeller closer to the upper wall of the housing. In other words, the movable member in effect is in the form of a cone or, preferably, the frustum of a cone so placed that its smaller end is adjacent the housing. The impeller, shaft, movable bearing member and motor rotor form a movable assembly which is pulled downward by the thrust of the impeller in operation, the assembly moving upward upon plating of the cooperating surfaces of the bearings. It will be appreciated that under some circumstances wear of the fixed member 110 or the movable member 111 may occur due, of course, to length of time the bearing is in use. Under these circumstances, upon wear of the cooperating surfaces, the movable member 111 tends to move downward or in a direction toward the impeller housing to assure desired clearance between the cooperating surfaces of the bearing structure.

A line 115 connected to the discharge of the impeller 103 communicates by

lines

116, 117 with the cooperating surfaces of the bearings thus providing solution between the cooperating surfaces to lubricate the same. Suitable wear rings 118, 119 are provided about the shaft and impeller to seal the housing. I have found that the copper plating deposits or plates substantially uniformly on all rubbing surfaces so that the cooperating

surfaces

112, 113 at least are uniformly plated during operation of the system.

While I have described the absorber pump 19 as being of a desired construction, it will be appreciated pump 11 likewise exposed to solution may be constructed similarly. If desired, all pumps in the system exposed to solution may be so constructed. Under some circumstances, pump 11 and pump 19 may be combined as a single pump for supplying weak solution to the generator and for recirculating solution in the absorber.

In Figure 3, I have shown a modification of the invention. In this case the shell of the absorber is provided with a sump 125 which extends below the shell. Pump assembly 19 is placed in sump 125 below the coil bundle or tubes 3. It will be noted generally that the solution level in the sump 125 is below the motor 106 so that the bearings 107 operate in a pool of solution. Drops of cooled solution spray or drip from the tubes 3 over motor 106 thus cooling the motor; it will be appreciated that the coolest solution in the system is thus employed to cool the pump motor. Since the bearings 107 operate in a pool of solution, it is not necessary usually to provide lines connecting the outlet of the impeller with the bearings for lubrication purposes.

In Figure 4, I have shown the movable member 111 of bearing 107 provided with an extended surface 126. This may be of value during operation of the system over a long period of time for it assures that adequate contacting surfaces are provided even when the movable assembly of the pumps has moved upward a substantial distance.

In Figure 5, I have shown means for raising the stator of the motor when the rotor moves upwardly which may be desirable in certain types of motors due to the magnetic center of the motor. A yoke 130 is placed about the shaft 104 between rings 131. A rod 132 carrying yoke 130 is fulcrumed at 133 and is connected by suitable linkage 134 to a rod 135 fulcrumed at 136 carrying a support 137 for the stator 106. Thus, as the shaft 104 carrying rotor 105 moves upward, through

rods

132, 135 and linkage 134, stator 106' similarly moves upward thus maintaining the magnetic center of the motor.

In operation, the system is started, pump 19 recirculating solution in the absorber. Refrigeration is provided by chilling medium passing through the tubes of the evaporator. During continued operation, the bearing surfaces of the pump are copper plated. As the cooperating surfaces of members 110, 1511 are plated, member 111 6 together with shaft 104, rotor 105 of the motor and impeller 103 automatically move upward bringing the impeller closer to the top wall of housing and thereby preventing seizure of the bearings and failure of the pump.

The present invention eliminates an extremely difficult problem in absorption refrigeration systems employing a saline solution as an absorbent and water as a refrigerant by taking advantage of the fact that uniform metal plating occurs on the rubbing surfaces of the pump bearings exposed to the absorbent. Preferably, the bearings are constructed of a material which will be plated easily by copper thus permitting lubrication of the bearings with the solution and cooling of the pump motor by solution. Since the pump thrust pulls down the entire assembly, it will be appreciated the cooperating surfaces of the bearing rest on one another and as such surfaces are plated the movable pump assembly members are moved upward automatic lly thereby preventing seizure of the bearings.

An extremely simple, economical pump assembly is provided by taking advantage of What at first glance appears to be an inherent defect of the system and turning such defect into an advantage which permits economies in construction of the system to be effected and eliminates the disadvantages heretofore deemed inherent in the use of pumps in the system.

The present invention eliminates the solution pump seal problem which confronted the industry since it does not attempt to prevent solution from contacting the pump bearings or it is necessary to provide the expensive mechanical seals, seal water assemblies and make-up water lines, etc. heretofore employed. The operation of the system is more quiet for motor noises are confined in the system and are muflled by the walls of the shell and solution.

While I have described a preferred embodiment of the invention it will be understood that the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim:

1. In a pump for use in a location in which it may be exposed to a metal plating action such as an absorption refrigeration system employing a salt solution as an absorbing medium, the combination of a pump housing having an inlet and an outlet, an impeller in said housing, means for actuating said impeller, a shaft carrying said impeller and connected to said actuating means, a bearing supporting the shaft in desired position to permit rotation thereof, the bearing including a fixed member and a movable member, one of said members having a tapered surface whereby upon wear of the bearing during operation the movable member moves to maintain a desired clearance with the fixed member while upon plating of the bearing during operation the movable member of the bearing tends to move in a direction away from the impeller housing.

2. In a pump for use in a location in which it is exposed to a metal plating action such as an absorption refrigeration system employing a salt solution as an absorbing medium, the combination of a pump housing having an inlet and an outlet, an impeller in said housing, means for actuating said impeller, a shaft carrying said impeller and connected to said actuating means, a bearing supportingthe shaft in desired position to permit rotation thereof, the bearing including a fixed member and a movable member secured to the shaft, said members having cooperating tapered surfaces whereby upon plating of the bearing during operation of the system the shaft and movable member tend to move in a direction away from the impeller housing carrying the impeller closer to a wall of the housing.

3. In a pump for use in a location in which it is exposed to a metal plating solution such as an absorption re frigeration system employing a salt solution as an abher having an area I greater than the area at the end adjacent the impeller, the fixed member having an area at its end adjacent the sorbing medium, the combination of a pump housing impeller greater than the area at the end away from the impeller whereby upon plating of the cooperating tapered surfaces during operation the shaft and movable member tend to move in a direction away from the impeller housing carrying the impeller closer to a wall of the housing.

4. In a pump for use in a location in which it is exposed to a metal plating solution such as an absorption re- 'rrigeration system employing a salt solution as an ab-- sol-hing medium, the combination of a pump housing having an inlet and an ing, a motor for actuating said impeller, a shaft carrying said impeller and connected to said motor, means for supporting the bearing member and the motor, the bearing member including a stationary member held in substantially fixed position and a rotating member secured to said shaft, said membershaving cooperating surfaces, the cooperating surface of the rotating member being tapered and the rotating member having a diameter at its end away from the impeller greater than the diameter of its end adjacent the impeller whereby upon plating of the cooperating surfaces during operation the 'rotat move in a direction away ing member and shaft tend to from the impeller housing.

5. A pump according to claim 4 including means to supply medium from the impeller to the cooperating bearing surfaces to lubricate the same,

6. In a pump for use in a location in which it is exposed to a metal plating action such as an absorption refrigeration system employinga salt solution as an absorbing medium, the combination of a pump housing having an inlet and an outlet, an impeller in said housm vertically extending shaft carrying said impeller and connected to said motor, a bearing supporting the shaft in substantially'vertical position to permit rotation thereof, the bearing including a fixed member and a movable member secured to the shaft, said members having cooperating tapered surfaces whereby upon plating of the bearing during operation the shaft and movable member tend to move in a vertical direction from the housing.

7. In a pump for use in a location in which it may be exposed to a metal plating action such as an absorption refrigeration system employing a salt solution as an absorbing medium, the combination of a pump housing having an inlet and an outlet, an impeller in said housing, a motor for actuating said impeller, a shaft carrying said impeller and connected to said motor, abearing supporting the shaft in desired position to permit rotation thereof, the bearing including a fixed member and a movable member secured to-the shaft, said vmembers having cooperating tapered surfaces, the impeller, shaft, movable bearing member and motor rotor forming a movable assembly capable of being pulled in one direction by the thrust of the impeller, so that upon wear the assembly moves in one direction to maintain a desired clearance between the cooperating moving in the opposite direction operating surfaces of the bearing.

8. A, pump according to claim 7 in which means are provided to move the stator. of the motor. in the same direction as therotor of the motor upon plating ofv the copon plating of the cooperating surfaces.

9. A pump according to claim 7 in which means are outlet, an impeller in said hous- I a motor for actuating said impeller, a substantially 1 tapered surfaces while provided to supply medium from the impeller to the cooperating bearing surfaces to lubricate the same.

10. A pump according, to claim 7 in which themovable bearing member comprises a frustum of a cone placed in a position such that its smaller area i adjacent the housing. a v

ll. A pump according to claim 10 in which the frustum is provided with an extended portion so that the movable member has a greater length than the fixed member.

12. in the method of operation of an absorption-wrefrigeration system employing a pump for circulating solution in which the solution is capable of metal plating the bearing surfaces of the pump and in which the pump impeller, the impeller shaft, a tapered bearing member and the motor rotor comprise an assembly, thcmsteps which consist in actuating the impeller to circulate solution, supplying solution from the impeller to cooperating bearing surfaces to lubricate the same, and, as plating of the bearing surfaces occurs, automatically moving the assembly in a vertical direction to prevent seizure of the bearing and failure of the pump.

13. In the method of operation of an absorption refrigeration system including an absorber having a plu-' rality of tubes therein through which a cooling medium is passed to cool solution exteriorly of the tubesv and employing a pump for circulating solution in which the solution is capable of metal plating the bearing surfaces of the pump, the steps which consist in rotating the pump impeller to circulate solution, dripping cooled solution from the tubes of the absorber upon the pump motor to cool the same, and, as plating of the bearing surfaces occurs, automatically moving one of the cooperating bearing surfaces to prevent seizure of the bearing and failure of the pump.

14-. In an absorption refrigeration system, the combination of an absorber having tubes therein through which a cooling medium passes to cool solution exteriorly of the tubes, an evaporator, vapor from the evaporator flowing to the absorber to be absorbed by solution therein, a condenser, a generator, vapor from the generator flowing to the condenser to be condensed therein, condensate from the condenser passing to the evaporator, and means to circulate solution, said means comprising a pump assembly placed in the absorber below said tubes and including a pump housing having an inlet and an outlet, an impeller in said housing, a motor for actuating said impeller disposed above the solution level in the absorber and in a position exposed to cooled solution dripping from the tubes thus cooling the motor, a shaft carrying said impeller and connected to said motor, a bearing supporting the shaft in desired position to permit rotation thereof, the bearing including a fixed member, and a movable member secured to the shaft, said members having cooperating tapered surfaces, the impeller, shaft, movable bearing member and motor rotor forming a movable assembly capable of being pulled in one direc tion by the thrust of the impeller, the assembly moving in the opposite direction upon plating of the cooperating surfaces of the bearing.

15. In an absorption refrigeration system, the combination of an absorberthaving tubes 'th'erein'through which a cooling medium passes to cool solution exteriorly of the tubes, an evaporator, vapor from the evaporator flowing to the absorber to be absorbed-by solution there'- in, a condenser, a generator, vapor from the generator flowing 'to the condenser to be condensedthereinjcondensate from the condenser passing to the evaporator, means to supply strong solution from the generator to the absorber, means to supply weak solution from the absorber to the generator, and means to recirculate solution in the absorber, said recirculating means comprising a pump assembly placed in the absorber below said tubes including a pump housing having an inlet and an outlet, an impeller in said housing, a motor for actuating said im- 10 pellet, disposed above the solution level in the absorber movable assembly capable of being pulled in one direcand in a position exposed to cooled solution dripping tion by the thrust of the impeller, the assembly moving in from the tubes, thus cooling the motor, a shaft carrying the opposite direction upon plating of the cooperating said impeller and connected to said motor, a bearing surfaces of the bearing.

supporting the shaft in desired position to permit rota- 5 tion thereof, the bearing including a fixed member and References Cited in the file of this patent a movable member secured to the shaft, said members having cooperating tapered surfaces, the impeller, shaft, UNITED STATES PATENTS movable bearing member and motor rotor forming 2. 2,722,805 Leonard Nov. 8, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2915 886 December 8 1959 Louis [-10 Leonard Jro It is hereby certified thafi error appears in the printed specification of the above numbered patent requiring correction and that the said,Let Lers Patent should read as corrected below Column 2 line 68 for "power" read lower -o Signed and sealed this 5th day of July 1960,,

(SEAL) Atfiest:

KARL H. .AXLINE I ROBERT C. WATSON Attesting Officer 7 1 Cmrmissioner of Patents