US3572976A

US3572976A - Fluid takeoff device for canned motor driven pump

Info

Publication number: US3572976A
Application number: US764242A
Authority: US
Inventors: Ryuichi Sato
Original assignee: Nikkiso Co Ltd
Current assignee: Nikkiso Co Ltd
Priority date: 1967-10-09
Filing date: 1968-10-01
Publication date: 1971-03-30
Anticipated expiration: 1988-03-30

Abstract

A fluid takeoff device for canned motor driven pump in which a part of the circulation fluid for cooling and lubricating motor rotors and bearings is led through the back wall of the pump impeller chamber so that a flow rate of the circulation fluid is always stabilized without being influenced by the variation in a discharge rate of the pump.

Description

United States Patent [72] Inventor RyuichiSato Tokyo, Japan [21] Appl. No. 764,242 [22] Filed Oct. 1,1968 [45] Patented Mar. 30, 1971 [73] Assignee Nikkiso Co., Ltd.

Tokyo, Japan [32] Priority Oct. 9, 1967 Japan [31] 42/6 4,837

[54] FLUID TAKEOFF DEVICE FOR CANNED MOTOR DRIVEN PUMP 2 Claims, 4 Drawing Figs.

[52] U.S. Cl 417/369, 310/63, 310/90, 418/102,415/1 12 [51] Int. Cl ..F04d 13/02, H02k 9/00, H02k 5/16 19 10 I f f -i',,-' & Z 16 1.

[50] Field ofSearch ..103/87(D), 87 (consulted), 87 (art), 87; 230/1 17, 209, 210; 310/54, 63, 90

[5 6] References Cited UNITED STATES PATENTS 2,925,041 2/1960 Sigmund 103/87 3,135,211 6/1964 Pezzillo 103/87 3,220,349 11/1965 White 103/87 Primary Examiner-Robert M. Walker Attorney-Blum, Moscovitz, Friedman and Kaplan ABSTRACT: A fluid takeoff device for canned motor driven pump in which a part of the circulation fluid for cooling and lubricating motor rotors and bearings is led through the back wall of the pump impeller chamber so that a flow rate of the circulation fluid is always stabilized without being influenced by the variation in a discharge rate of the pump.

Patented March 30, 1971 3,572,976

2 Sheets-Sheet 1 FIG-.1

INVENTOR ATTORNEY BACKGROUND OF THE INVENTION This invention relates to a fluid takeoff device for canned motor driven pump.

Generally, the canned motor driven pump has such characteristic features that an interior of the stator and an external surface of the rotor of the driving motor are welded and sealed with an anticorrosive sheet metal of nonmagnetic responsive property, and a part of the fluid is taken off from an outlet and then led through a circulation tubing into the rear side of the rotor chamber to permit a. further circulation of the fluid throughout passageways provided in the inner peripheries and the outer ends of the bearings, a spacing between the rotor and the stator, a passageway provided in an inner periphery and the outer ends of the front bearing, a clearance formed between shaft and a sleeve and an impeller balance hole so that the rotary parts of the rotor and'the impeller are all immersed in the liquid without remaining any movable portion passing through the liquid contacting portion and the outer portion, which enables to provide a perfect nonleakage pumping operation since there is no shaft sealing portion.

in the canned motor driven pump heretofore used, the circulation fluid for cooling and lubricating the motor and the bearing is taken ofi from the pump delivery connection through an auxiliary fluid takeoff pipe connected to the filter or screen provided along the tubular outlet.

According to this construction, however, a flow velocity at the nozzle portion is relatively changed with variation of the static pressure in proportion to the discharge rate of the pump so that flow rate of the circulation fluid is abruptly reduced in accordance with a rise of the discharge rate of the pump as is shown by a dotted line in HG. 4.

This defect makes it impossible to obtain an apparatus for removing an axial thrust of the motor rotor and, therefore, adversely affects to the duration of the thrust bearing in the fluid of the canned motor driven pump which does not always possess lubricity.

Further, when a flow rate of the circulation fluid is reduced less than a constant level, the motor is likely heated with a risk of heat deterioration.

SUMMARY OF THE lNVENTlON it is thus a principal object of the invention to eliminate the fatal defects in the conventional canned motor driven pump and to provide a new fluid takeoff device for canned motor driven pump which is simple in construction and operable with constant circulation fluid and without being influenced by the variation in the discharge rate of the pump.

Another object of the invention is to provide a new fluid takeoff device for canned motor driven pump in which a part of the circulation fluid for cooling and lubricating motor rotors and bearings is led through the back wall of the pump impeller chamber so that a flow rate of the circulation fluid is stabilized without being influenced by variation in the discharge rate of the pump.

Still another object of the invention is to provide a fluid takeoff device which comprises an impeller chamber surface of partition wall partitioning the impeller chamber and the motor chamber, a circular groove provided at a predetermined distance from the center of said impeller chamber surface with a given width and depth, a screen member covering said circular groove in such way that the surface of said screen member comes in flat with the plane of the impeller chamber surface, a fluid chamber formed of a spacing between the wall of circular groove and the screen member, an inner slot provided in the partition wall to communicate with the fluid chmber and a circulation tubing connected to said inner slot outside the partition wall.

These and other objects and advantages of this invention will become readily apparent and understood from the following nonlirnitative description and accompanying drawings in which the same reference numerals designate the same or similar parts throughout the drawings.

BRIEF DESCRIPTION OF THE DRAWKNGS:

FIG. 1 is a longitudinally sectioned lateral view, in partially broken away, of a canned motor driven pump with a fluid takeoff device applied in accordance with the invention;

FIG. 2 is a fragmentarily enlarged sectional view of the fluid takeoff device of !FIG. 1;

FIG. 3 is a fragmentarily enlarged sectional view of a fluid takeoff device taken along the line A-A of F KG. 2; and

FIG. 4 is a diagrammatic view showing the relation between the discharge rate and the circulation rate of the conventional takeofi connection in comparison with the fluid takeoff device according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, the reference numeral 1 designates a covering of the canned motor driven pump and 2 stands for a cylindrical inner sleeve of nonmagnetic responsive property in which a motor rotor chamber 3 is provided. A shaft 4 is rotatably supported in spaced bearings 5a andSb between which a motor rotor 6 an outer surface of which being sealed with a sheet metal of nonmagnetic responsive property issecured to the shaft 4.

An impeller casing 7 is provided with an inlet 8 for flowing the fluid to the center axial direction, an impeller chamber and with a delivery outlet 10.

The shaft 4 is extended to the impeller chamber 9 and fitted with an impeller 11 so that a rotor axis and an impeller axis are of a coaxial relation.

()n the impeller chamber surface 12 of a partition wall 14 partitioning the impeller chamber 9 and the motor chamber 13 is provided with a circular groove l5 having a predetermined width and depth at the predetermined distance from the center of said impeller chamber surface 12.

The circular groove 15 is coated with a detachable screen member 116, material and mesh size of which may be determined in accordance with nature of the fluid being pumped and particle size of slurry included in said fluid.

it is important that the screen member to should be fixed to the circular groove 15 so that the surface of the screen member l6 resides in the same plane as the impeller chamber wall 12.

By this construction, it has been appreciated that the screen member according to the invention may have a greater area and also a superior self-washing ability as compared with the conventional cylindrical screen since it is always washed with the fluid flowing in parallel with the plane of the screen.

The spacing between the wall of the circular groove 35 and the screen 16 constitutes a fluid chamber 17 which is communicated with an inner slot llil provided in a common partition wall 14 partitioning the impeller chamber 9 and the motor chamber 13.

The inner slot 18 is connected to the circulation tubing 1% of the known structure at outside the common partition wail 14 When the shaft 4 is rotated by the driving operation of the motor, the liquid being pumped by the impeller it is sucked through the inlet 8 and a majority of said liquid is fed to the outlet 10 under an increased velocity. A part of sucked fluid, however, is subjected to a boost pressure by means of the same impeller 11 to permeate into the space formed in the rear side of the impeller l1. between said impeller ii and the impeller chamber wall 12. While, a part of said liquid is iiitered off through the screen its to remove the slurries and then taken off into the fluid chamber l7.

The thusly filtered clean fluid is led through the inner slot l8 and the circulation tubing iii connected thereto at outside of partition wall into the motor rotor chamber to cool and lubricate the rotor and the bearing with the following circulation of the fluid through the clearance between the shaft and the outer sleeve to the impeller chamber. In this case, the flow rate of the circulation fluid is satisfactorily stabilized without being influenced by the variation in the pump discharge rate as is shown by the solid line in FIG. 4.

According to the invention, a stable supply of the circulation fluid can be attained without suffering any influence of the variation in the pump discharge rate and the plugging by the slurries is perfectly prevented owing to the superior selfwashing capacity as the filter member is mounted in the same plane as the impeller chamber wall and therefore a performance of the canned motor driven pump is greatly increased.

While certain preferred embodiments of the invention have been illustrated by way of example in the drawings and particularly described, it will be understood that various modifications may be made in the methods and constructions and that the invention is no way limited to the embodiments shown.

Iclaim:

1. In a canned motor driven pump, takeoff means of fluid for cooling and lubricating motor rotors and bearings, which comprises circular groove means provided with a predetermined width and depth in an impeller chamber surface of a partition wall partitioning impeller chamber and motor chamber and at a predetermined distance from the center of impeller chamber surface, filtering means mounted on the circular groove means for filtering off slurries, fluid chamber means formed between walls of the circular groove means and the filtering means, and slot means provided in the partition wall and connected at its one end to the circular groove means and at its the other end to the circulation connection for feeding a part of circulation fluid.

2. Takeoff means of fluid for cooling and lubricating motor rotors and bearings according to claim 1, wherein filtering means is fitted to circular groove means so that surface of said filtering means resides in the same plane as the impeller chamber surface.