US 3824042 A
A submersible pump suitable for the transfer of liquid comprising a cylindrical shaft of mean radius R1 and length L connected at one extremity to a drive mechanism and at the other extremity to an impeller located within an impeller housing provided with a liquid inlet and outlet, the shaft being free to rotate within a guide tube of mean radius R2 such that the ratio of R1 to R2 is in the critical range 1:1.15 to 1:2.0 and the ratio of L to R1 is greater than 80:1.
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Description (OCR text may contain errors)
United States Patent Barnes et al.
SUBMERSIBLE PUMP Inventors: Edward Barnes, Speldhurst; Ian
Douglas Fergusson, Godstone, both of England BP Chemicals International Limited, London, England Filed: Nov. 16, 1972 Appl. No.: 306,987
Foreign Application Priority Data Nov. 30, 1971 Great Britain 55555/71 U.S. Cl 417/424, 415/176, 415/204 Int. Cl. F04d 13/06, F04d 17/00 Field of Search 415/170 A, 175, 176, 214,
References Cited UNITED STATES PATENTS 8/1937 Tighe 415/214 [451 July 16, 1974 3,160,106 12/1964 Ashworth 415/212 3,211,101 10/1965 Ashworth et al. 415/176 3,394,660 7/1968 Ohmann et al. 415/214 FOREIGN PATENTS OR APPLICATIONS 809,510 7/1951 Germany 417/424 Primary ExaminerHenry F. Raduazo v Attorney, Agent, or Firm Brooks Haidt & Haffner [5 7 ABSTRACT A submersible pump suitable for the transfer of liquid comprisipg a gylindfical shaft of mean radius R 1 and length L connected at one extremity to a drive mechanism and at the other extremity to an impeller located within an impeller housing provided with a liquid inlet and outlet, the shaft being free to rotate within a guide tube of mean radius R such that the ratio of R to R is in the critical range 121.15 to 1:2.0and the ratio of L to R is greater than 80:1.
6 Claims, 1 Drawing Figure SUBMERSIBLE PUMP The present invention relates to a submersible pump for the transfer of liquid.
When handling liquid in containers the need often arises to transfer the liquid from one container to another or supply the liquid to a process by means of a pump. In the case of containers that are too large to handle or more particularly in instances where the liquid in question has dangerous properties, then it is convenient if the design of the pump is such that it is capable of emptying the container without the need to resort to inversion of the container. There are a number of such pumps available whose design is essentially based upon a centrifugal or axial flow impeller arranged in such a way that the impeller is mounted on a shaft extension of sufficient length to enable the impeller to work at the bottom of the container whilst the motor remains external to the container. Such pumps normally include a relatively complicated gland or wet bearing arranged in such a manner that any leakage is directed back into the liquid container. These designs of pump have a number of disadvantages not least of which is the excessive wear that can occur when the unit is running dry, a situation that might arise when the pump is left running after the container has become empty.
It is an object of the present invention to provide a submersible pump which obviates the need for glands and wet bearings and as a result leads to improvements in the cost, useful lifetime and hazard risk of the unit.
Accordingly the present invention is a submersible pump suitable for the transfer of liquids which pump comprises a substantially cylindrical shaft of mean radius R and length L connected at one extremity to a drive mechanism and at the other extremity to an impeller located within an impeller housing provided with means for the discharge and entry of liquid, the shaft being free to rotate within a guide tube of mean radius R such that the ratio of R to R is in the critical range of l:l.l5 to 112.0 and the ratio ofL to R, is greater than 80:1.
In a particular embodiment of the imvention the ratio ofR to R may be in the range l:l.l5 to 1:1.5.
It is preferred that the shaft is centrally mounted within the guide tube for a distance of at least R and preferably ZOR into the tube.
Although the drive mechanism may be any mechanism capable of rotating the shaft it is preferred to use an electric motor.
The material from which the shaft is fabricated is suitably one which is substantially dimensionally stable and, for applications involving corrosive fluids, one which is chemically stable. The preferred material is stainless steel.
Whilst the guide tube may be fabricated from any substantially rigid and corrosion resistant material it is preferred, for reasons of economy in construction, to use a thermoplastic such as polypropylene which is readily produced in tubular form by extrusion.
It is preferred to rigidly support the impeller housing and guide tube. A form of support found suitable for this purpose is a rigid outer tube which serves also to form an outer protective casing for the submersible part of the pump. However other forms of support may be used. Whilst any rigid, non-corrosive material may be used in the fabrication of the outer tube it is preferred to use a plastics material e.g. polyethylene or polypropylene.
The ratio of the radius of the shaft R to the radius of the tube R is critical in the performance of the invention, particularly at high rotational speed e.g. 6,000 rmp. If this ratio is too high the rotational friction causes excessive heat generation which leads ultimately to seizure of the pump since there is no means for conducting the heat away from the moving parts. On the other hand if the ratio R, R is too low there is too much lateral movement of the drive shaft which detracts from the efficient operation of the pump by causing the impeller to collide with the housing. It is believed that ratios of R R within the specified range are effective because there is just sufficient lateral movement of the shaft to cause random contact of the shaft and guide tube, thus preventing localised heat aaccumulation, without detracting from the operation of the impeller.
The impeller itself may be fabricated from any suitable chemically resistant material and may be any shape necessary to achieve the necessary transfer of liquid.
The impeller housing provided with means'for the discharge and entry of liquid is suitably injection moulded from a plastics material and may be attached to the outer tube by, for example, screws or adhesive. The liquid may be discharged from the pump without any control on the flow but for process purposes it is usually desirable to provide a metered flow rate, which may suitably be achieved for, example by a variable area meter.
An embodiment of the invention is illustrated with reference to the accompanying drawing which shows a sectional view of a pump according to the invention.
With reference to the drawing an impeller 1 is secured at one end of a substantially cylindrical stainless steel shaft 2, of length 36 inches and outer diameter one-eighth inch, suitably threaded, by a stainless steel nut 9. The shaft is driven by an electric motor 4 and runs in a polypropylene guide tube 3 of substantially circular cross-section and of 3/16 inch internal diameter. The guide tube terminates a short distance above the impeller housing 6 and the shaft enters the impeller housing through the aperture 11 which is concentric with the guide tube. The impeller housing incorporates a hose nozzle 7 to which is fitted a hose 8.
The design of impeller housing facilitates construction in a single unit from plastics material by injection moulding A rigid polyethylene tube 5 serves as an outer casing for the submersible part of the pump in addition to providing support for the guide tube at 12A and both the guide tube and impeller housing at 128. The supports 12A and 12B attached to the guide tube are secured by bolts 13A and 138 respectively. The hose 8 for a large part of its length is contained within the outer tube and exits from the pump via a discharge connection (not shown in the Figure) and a flow meter 10. The outer tube is cut away for a short distance at its lower end 15 to allow ingress of fluid to the region of the impeller. Finally the impeller housing is closed by the plastics disc 14 secured by adhesive. Although not shown in the Figure it is found convenient to house the electric motor in PVC housing which not only prevents accidental spillage of liquids on the motor but also servesas an insulator. Apart from the advantage that the pump contains no glands or wet bearings and construction is such that the pump is formed of a number of easily replaceable integral units.
in operation the impeller end of the pump is submerged in the liquid to be transferred and the electric motor 4 is switched on driving the impeller 6 which thereby draws fluid through the aperture 11 into the inpeller housing whereupon the centrifugal action of the impeller forces the liquid through the hoze nozzle 7 out through the hose 8. The liquid is finally discharged through the meter 10 which is adjusted to provide the required flow rate.
1. A'submersible pump for the transfer of liquids comprising a drive mechanism, a substantially vertically depending cylindrical shaft extending from and rotable around its axis by said drive mechanism, said shaft having a length which is greater than eighty times the means radius of its outer surface and having a free end remote from said drive mechanism and said shaft being free of support bearings between said drive mechanism and said free end, a stationary impeller housing at said free end of said shaft-and extending around the axis of said shaft, said housing having fluid inlet and outlet openings, an impeller in only said housing and mounted on said shaft at the free end thereof for rotation therewith and a stationary guide tube intermediate said housing and said drive mechanism and depending from the drive mechanism housing, said guide tube being co-axial with and surrounding said shaft and having an inner surface mean radius which is greater than said mean radius of said outer surface of said shaft, the ratio of said latter outer surface radius to said inner surface radius being in the critical range of 1:1.15 to 1:20 and said shaft otherwise being free of contact with stationary bearings and glands from said free end thereof to said drive mechanism.
2. A submersible pump as set forth in claim 1, said ratio of said outer surface radius to said inner surface radius is in the range from 121.15 to 121.5.
3. A submersible pump as set forth in claim 1, wherein the length of said guide tube which surrounds said shaft is at least 10 times said means radius of the outer surface of said shaft.
4. A submersible pump as set forth in claim 1, wherein the length of said guide tube whichsurrounds said shaft is at least 20 times said mean radius of the outer surface of said shaft.
5. A submersible pump as set forth in claim 1, wherein the drive mechanism is an electric motor.
6. A submersible pump for the transfer of liquids comprising a drive mechanism, a substantially vertically depending cylindrical shaft extending from and rotatable around its axis by said drive mechanism, said shaft having a length which is greater than eighty times the mean radius of its outer surface and having a free end remote from said drive mechanism, a stationary impeller housing at said free end of said shaft and extending around the axis of said shaft, said housing having a wall extending transversely to said axis and an opening therethrough larger than the diameter of said shaft so as to provide space around said shaft intermediate it and said wall and said housing having an outlet opening, an impeller in said housing on the side of said wall opposite from said drive mechanism and mounted on said sjaft at the free end thereof for rotation therewith and a stationary guide tube intermediate said wall and said drive mechanism and depending from the drive mechanism housing, said guide tube being coaxial with and surrounding said shaft and having its end nearer said wall spaced from said wall in the direction of said drive mechanism, said guide tube also having an inner surface mean radius which is greater than said mean radius of said outer surface of said shaft, the ratio of said latter outer surface radius to said inner surface radius being in the critical range of l;l.l5 to 1:20 and said shaft otherwise being free of contact with stationary bearings and glands from said free end thereof to said drive mechanism.
Patent No. 3,824,042 I Da e July 16, 1974 Inventor) Edward Barnes and Ian Douglas Fergusson It is certified that error appears'in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 1, line 44 "imvention" should read --invention- Column 2, line 7 "rmp" should read -rpmline 51 after "moulding" insert a period Column 3, line 20 "means" should read --meanline 24 deletehyphen between "shaft" and "and" Column .4, line 3 "means" should read ---mean-- I line 27 "sjaft" should read -shaf t- Signed and sealed this 8th day of October 1974.
MCCOY M. GIBSON JR. I c. MARSHALL 'DANN Attesting Officer 4 Commissioner of Patents F ORM 5 0-1050 (10-69) U5COMM-DC 60376-P69 9 U 5 GOVERNMENY PRINTING OFFICE 1959 03S6-]3l