US3819293A

US3819293A - Centrifugal pump for corrosive liquids

Info

Publication number: US3819293A
Application number: US00260291A
Authority: US
Inventors: F Zitzmann
Original assignee: ZUR FORDERUNG DER WISSENSCHAFT
Current assignee: ZUR FORDERUNG DER WISSENSCHAFT; ZUR FORDERUNG DER WISSENSCHAFTEN EV DT
Priority date: 1971-06-07
Filing date: 1972-06-06
Publication date: 1974-06-25
Anticipated expiration: 1991-06-25
Also published as: DE2128265A1; GB1379267A; FR2141225A5

Abstract

There is described a centrifugal pump having a sealed glass housing provided with an inlet and an outlet, a glass shaft disposed in the housing and rotatably supported by a cylindrical wall portion thereof, an impeller fastened to one end of the shaft and a ferromagnetic body fastened to the other end of the shaft within a sealed jacket thereof. The pump is associated with external means that generate a rotary magnetic field which, by virtue of its interaction with said ferromagnetic body, causes rotation of the shaft.

Description

United States Patent [191 Zitzmann June 25, 1974 CENTRIFUGAL PUMP FOR CORROSIVE LIQUIDS [75] Inventor: Fritz Zitzmann, Garching, Germany [73] Assignee: Max-Planck-Gesellschaft Zur Forderung der Wissenschaften e.V., Gottingen, Germany [22] Filed: June 6, 1972 [21] Appl. No.: 260,291

[30] Foreign Application Priority Data June 7, 1971 Germany 2128265 [52] US. Cl 415/200, 417/420, 415/214 [51] Int. Cl. F04d 29/42, F04h 17/00 [58] Field of Search 415/200, 197, 196, 214,

[56] References Cited UNITED STATES PATENTS Clifton .7. 417/420 3,558,238 1/1971 Van Herpt 415/169 A FOREIGN PATENTS OR APPLICATIONS 901,160 7/1962 Great Britain 415/200 Primary ExaminerHenry F. Raduazo Attorney, Agent, or Firm-Edwin E. Greigg [5 7 ABSTRACT There is described a centrifugal pump having a sealed glass housing provided with an inlet and an outlet, a glass shaft disposed in the housing and rotatably supported by a cylindrical wall portion thereof, an impeller fastened to one end of the shaft and a ferromagnetic body fastened to the other end of the shaft within a sealed jacket thereof. The pump is associated with external means that generate a rotary magnetic field which, by virtue of its interaction with said ferromagnetic body, causes rotation of the shaft.

10 Claims, 3 Drawing Figures PATENTEHm-zs 1914 Sam 3 or 3 m Fig. 3

50o I =2500 RPM 400 n =2ooo RPM Q 0 IO 20 30 7 liter min I 1 CENTRIFUGAL PUMP FOR *CORROSIVE LIQUIDS This invention relates to a centrifugal pump for corrosive liquids and is of the type that has a housing which contains an inlet opening and an outlet opening as well as an impeller which is secured to a shaft which, in turn, is coupled to a drive means.

The particular purpose of the present invention is to provide a circulating pump for liquid lasers which work with POCl and SeOC1 as the stimulating medium. In view of the fact that these laser media are very corrosive and furthermore, since impurities have to be carefully avoided, these materials can be allowed to contact only glass or possibly polytetrafluoroethylene.

The glass centrifugal pumps available in commerce are not adapted for the aforenoted use since the delivered medium may contact materials other than glass. In such pumps only the pump housing, the impellerand the closure plates provided with sealing rings are made of glass. The shaft to which the impeller is affixed is brought out of the housing through a sealing assembly and is directly connected to a drive motor.

It is an object of the invention to provide a centrifugal pump which ensures that the liquid delivered thereby can contact only glass.

Briefly stated, according to the invention, the centrifugal pump has a glass housing which is sealed except for a liquid inlet at the low pressure side and a liquid outlet at the high pressure side, a glass shaft rotatably supported within the housing and carrying an impeller, a ferromagnetic body sealed into said shaft and means arranged externally of the pump housing for generating a rotary magnetic field to impart rotation on said ferromagnetic body, said shaft and said impeller.

In a centrifugal pump constructed according to the invention,-there is ensured with absolute security that the liquid to be delivered by the pump can contact only glass.

The invention will be better understood as well as further objects and advantages become more apparent from the ensuring detailed specification of a preferred, although exemplary embodiment taken in conjunction with the drawing wherein:

FIG. 1 is an axial sectional view of the preferred embodiment;

FIG. 2 is a front elevational view of the preferred embodiment as seen from the right-hand side of FIG. 1 and FIG. 3 is a diagram illustrating the pressure head as a function of the output flow rate of a pump according to the invention.

Turning now to FIGS. 1 and 2, the centrifugal pump shown comprises a pump unit and a drive unit 12. The pump unit 10 has a glass housing 14 which, with the exception of an inlet opening 16 at the low pressure side and an outlet opening 18 at the high pressure side is closed in a vacuum tight manner. Entirely within the housing 14 there is disposed a glass shaft 20 which,

along a central part, is rotatably supported by a tubular mid portion 14a of the housing 14. The contacting cylindrical faces of the shaft and the housing are coaxial with the shaft axis and are preferably polished. To one end of the shaft 20 there is welded a glass impeller 22 which is centered with respect to the shaft 20 and which has a hollow'hub portion 22a axially open at one side towards the inlet opening 16. The hub portion 220 2 supports a plurality of integral radial impeller tubes 22b.

The pump impeller is located in an enlarged cylindrical housing portion 14b which contains the outlet opening 18. The latter is so positioned that the arcuately ground open ends of the impeller tubes 22b register sequentially therewith during operation of the pump. The distance between the outer end of each impeller tube 22b and the internal wall of the cylindrical part 14b is preferably small; in case of an internal diameter of the cylindrical part 14b of mm, it may be approximately 0.2 mm.

The cylindrical housing portion 14b continues in a conical housing portion into which merges the inlet opening 16. To the conical portion 140 there is welded an axial glass pin 24 which limits a rightward axial displacement of the shaft 20.

In a jacket-like enlargement 28 of that end of the shaft 20 which is remote from the impeller 22, there is disposed a ferromagnetic (for example, ferrite) body 26. Preferably, the jacket 28 has a ground, cylindrical outer face coaxial with the shaft axis and the housing portion l4e surrounding the jacket 28 has a ground cylindrical inner face, also coaxial with the shaft axis. An axial protrusion 30 provided on the enlargement 28 cooperates with a housing portion 14d to limit a leftward axial displacement of the shaft 20. The housing 14 is sealed closed in a vacuum tight manner at the housing portion 14d. Instead of such a seal it is feasible to provide, for example, a removable polytetrafluorethylene closure so that the portion of the housing 14 that contains the ferromagnetic body 26 may be easily emptied and cleaned.

The pump unit is supported by a stand 31 which is connected with the mid portion 14a of the housing. The pump shown in the drawing is preferably operated in a horizontal position.

The drive unit 12 contains a second ferromagnetic body 32 which is supported in a cup-shaped member 34 which, in turn, is coupled to a motor means, not shown. At least one of the two

bodies

26, 32 is a permanent magnet, so that the rotary motion of the body 32, by virtue of the rotating magnetic field, can be transmitted through the glass housing 14 and the jacket 28 to the body 26 and thus to the shaft 20 and the impeller 22. It is seen that the pump 10 and the drive assembly 12 are separate, unconnected units; accordingly, they are replaceable independently of one another.

The shaft 20'has a relatively large axial play (for example, 3 mm) and the impeller 22 is so positioned with respect to the outlet opening 18 and the body 26 with respect to the body 32 that during the operation of the pump the impeller tubes 2212 will be in axial alignment with the outlet opening 18 as they sequentially register therewith and, at the same time, the means that limit the axial displacement of the shaft 20 remain out of contact therewith.

In operation, the pump housing is filled with the medium to be delivered which, at the same time, serves to lubricate the bearing faces of the shaft 20 and the tubular housing portion 14a.

The shaft 20 or the inner wall of the tubular part 14a may have one or more generally axially extending longitudinal grooves to permit a more rapid vacuumization of the pump housing, a more uniform lubrication of the shaft 20 and, if necessary, removal of foreign bodies.

3 The aforedescribed preferred embodiment may be built in different sizes. Three exemplary sets of dimensions are given in the table below.

components 151 example 2nd example 3rd example part 14b 75 mm inner dia. 64 mm inner dia. 90 mm inner dia.

a. outlet opening mm inner dia. 9 mm inner dia. 14 mm inner dia.

18 shaft 20 16 mm dia.

At an operational rpm of approximately 3,000 the pressure head reached a maximum 5.5 m. water column at a flow rate of 7.5 lit/min. for the pump built according to example 1, and a maximum 5.1 m. water column at a flow rate of 7.2 lit/min. for a pump built according to example 2.

Even after an operational period of more than 2,000 hours of a pump according to example 2, there were no wear or other defects observable.

The relationship of the pressure head (cm water column) of the pump built according to example 3 with respect to the flow rate (liter/minute) is graphically illustrated in FIG. 3 for two different rpms.

What is claimed is:

l. A centrifugal pump particularly for corrosive liquids, comprising A. a glass pump housing having 1. an inlet at its low pressure side,

2. an outlet at its high pressure side, 3. a tubular bearing face forming one part of the inner wall of said housing,

said pump housing being permanently sealed in a vacuum tight manner over its entire area, except for said inlet and outlet,

B. a glass pump shaft situated in its entirety inside said housing and rotatably supported by said tubular bearing face,

C. a glass impeller fastened to said shaft,

D. a ferromagnetic body fixedly enclosed within said shaft and E. means disposed externally of said housing for generating a rotating magnetic field to impart rotation to said ferromagnetic body for driving said pump shaft.

2. A centrifugal pump as defined in claim 1, wherein said bearing face engages a mid portion of said shaft, said impeller being fastened to one end of said shaft, said shaft having, at its end remote from said impeller, an integral glass jacket enclosing said ferromagnetic body.

3. A centrifugal pump as defined in claim 1, said impeller including a hollow hub portion having an axial opening oriented towards said inlet and a plurality of open-ended impeller tubes extending radially from said hub portion, said housing including a cylindrical portion accommodating said impeller, said outlet being disposed in the wall of said cylindrical portion, the open ends of said impeller tubes registering sequentially with said outlet during the rotation of said shaft.

4. A centrifugal pump as defined in claim 1, including axial abutment means adjacent both ends of said shaft permitting a limited, relatively large axial play thereof.

5. A centrifugal pump as defined in claim 3, including axial abutment means adjacent both ends of said shaft permitting a limited, relatively large axial play thereof, the position of said impeller with respect to said outlet and the position of said ferromagnetic body with respect to said means being such that upon self-centering of said impeller with respect to said outlet during operation, said axial abutment means remaining out of contact with said shaft.

6. A centrifugal pump as defined in claim 1, wherein said bearing face includes at least one lubricating groove.

7. A centrifugal pump as defined in claim 1, wherein said shaft includes at least one lubricating groove.

8. A centrifugal pump as defined in claim 1, wherein said housing in its portion surrounding said ferromagnetic body includes an opening sealed by a removable closure member.

9. A centrifugal pump as defined in claim 2, said glass jacket having a ground outer face coaxial with the axis of said shaft and said housing having a portion surrounding said jacket, said last-named portion including a ground inner face coaxial with said axis.

10. A centrifugal pump particularly for corrosive fluids comprising:

A. an all glass integral pump housing means defining an elongated tubular bearing means, a pumping chamber on one end of said tubular bearing means and having an inlet and an outlet, and closure means adjacent said tubular bearing means, said tubular bearing means and said closure means all open to the corrosive fluid in said pumping chamber, and said housing means further being completely sealed except for said inlet and said outlet so said corrosive fluid is completely contained in said housing means,

B. an all glass shaft journaled in said bearing means and having an impeller for rotation on said shaft in said pump chamber for pumping fluid entering said inlet out said outlet, and means for receiving rotational energy from a source of rotational energy en closed within said shaft so as to be sealed against the corrosive fluids in said housing means, and

C. means externally of said housing means for rotating said shaft by sending rotational energy to said means for receiving rotational energy so as to rotate said impeller to pump said corrosive fluid out said outlet.

Claims

1. A centrifugal pump particularly for corrosive liquids, comprising A. a glass pump housing having 1. an inlet at its low pressure side, 2. an outlet at its high pressure side, 3. a tubular bearing face forming one part of the inner wall of said housing, said pump housing being permanently sealed in a vacuum tight manner over its entire area, except for said inlet and outlet, B. a glass pump shaft situated in its entirety inside said housing and rotatably supported by said tubular bearing face, C. a glass impeller fastened to said shaft, D. a ferromagnetic body fixedly enclosed within said shaft and E. means disposed externally of said housing for generating a rotating magnetic field to impart rotation to said ferromagnetic body for driving said pump shaft.

2. an outlet at its high pressure side,

3. a tubular bearing face forming one part of the inner wall of said housing, said pump housing being permanently sealed in a vacuum tight manner over its entire area, except for said inlet and outlet, B. a glass pump shaft situated in its entirety inside said housing and rotatably supported by said tubular bearing face, C. a glass impeller fastened to said shaft, D. a ferromagnetic body fixedly enclosed within said shaft and E. means disposed externally of said housing for generating a rotating magnetic field to impart rotation to said ferromagnetic body for driving said pump shaft.

10. A centrifugal pump particularly for corrosive fluIds comprising: A. an all glass integral pump housing means defining an elongated tubular bearing means, a pumping chamber on one end of said tubular bearing means and having an inlet and an outlet, and closure means adjacent said tubular bearing means, said tubular bearing means and said closure means all open to the corrosive fluid in said pumping chamber, and said housing means further being completely sealed except for said inlet and said outlet so said corrosive fluid is completely contained in said housing means, B. an all glass shaft journaled in said bearing means and having an impeller for rotation on said shaft in said pump chamber for pumping fluid entering said inlet out said outlet, and means for receiving rotational energy from a source of rotational energy enclosed within said shaft so as to be sealed against the corrosive fluids in said housing means, and C. means externally of said housing means for rotating said shaft by sending rotational energy to said means for receiving rotational energy so as to rotate said impeller to pump said corrosive fluid out said outlet.