US3160106A

US3160106A - Centrifugal pumps

Info

Publication number: US3160106A
Application number: US262980A
Authority: US
Inventors: Stewart I Ashworth
Original assignee: Abrasive Developments Ltd
Current assignee: Abrasive Developments Ltd
Priority date: 1962-03-08
Filing date: 1963-03-05
Publication date: 1964-12-08
Anticipated expiration: 1981-12-08
Also published as: GB960736A

Description

Dec. 8, 1964 s. l. ASHWORTH 3,160,106

CENTRIFUGAL PUMPS Filed March 5, 1963 Y 2 Sheets-Sheet 1 /NVEMTOZ.

5 Teumzrlvzs HSHL/OETH pseN-r 8, 1964 s. l. ASHWORTH 3,

CENTRIFUGAL PUMPS Filed March 5, 1963 2 Sheets-Sheet 2 l/vue/v-roz.

STEWHIFT /v s Raga/ gr AGENT United States Patent Oflice 3,153,1hh Patented Dec. 8, 1964 3,16%,1M CENTRIFUGAL PUMPS Stewart I. Asliworth, Studiey, England, assignor to Abrasive Bcvelopments Limited, Henley in-Arden, Solihuil, England, a company of Great Britain Filed Mar. 5, 1963, Ser. No. 2623$ Claims priority, application Great Britain, Mar. 8, 1962,

,923/62 3 Claims. (Cl. 103-193) This invention relates to centrifugal pumps for pumping a mixture of solid particles and liquid, such as mixture of abrasive particles and water. It is particularly concerned with such pump, hereinafter referred to as a pump of the kind specified, in which a vertical impeller shaft extends upwardly from the impeller in an upper housing and through sealing means in the upper end of the housing, which sealing means comprise a sleeve concentric with and providing an annular space about the shaft, and there is provision for liquid from the back of the impeller to enter the annular space and form the seal therein. In accordance with a previous proposal the seal has been formed of substantially the abrasive mixture itself. One object of this invention is to provide for a liquid seal which will contain considerably less abrasive than hitherto; a second object is to provide a simpler construction of the sealing means.

In accordance with the invention the sleeve extends downwardly from the upper annular closing wall of the upper housing, the entry to the annular space is provided by the lower end of the sleeve, there is provided means for setting up whirling motion of the liquid about the axis of the sleeve and shaft at least in the region of the entry to the annular space and there is further provided an outlet in the upper housing wall above the level of the entry.

By creating the whirling motion about the axis of the sleeve and shaft at least in the region of the entry, the abrasive particles tend to be thrown outwards to leave clarified liquid in the central region; thus substantially clarified liquid enters the sleeve to form the seal, thereby reducing the degree of erosion of the impeller shaft by abrasive particles otherwise carried into the sealing sleeve.

The whirling motion may be set up by subsidiary impelling means provided on the back of the impeller or on the shaft at or near its junction with the impeller. Alternatively deflectors may be provided at the lower end of the sleeve. Preferably however the upper housing is formed as a tornado-chamber, being an annular vessel, with an annular entry provided between the back of the impeller and the lower end of the chamber wall. The liquid is projected by the impeller through the annular entry at considerable pressure and angular velocity into the lower end of the tornado-chamber, setting up the characteristic whirling motion throughout the generally rising body of liquid in the chamber. The angular ve locity is greatest at the lower end of the chamber, giving rise to the steepest radial pressure gradient near the opening to the sleeve; it is thus in this lower region of the chamber that the major clarification occurs, the larger proportion of particles going to the outside of the whirl and substantially clear liquid passing into the sealing sleeve.

The whirling motion becomes less violent in the upper part of the tornado chamber, that is above the entry to the sealing sleeve. Through the outlet in the upper part of the tornado chamber, the mixture of abrasive particles and liquid can be returned to the main source of supply to the pump.

In the process of blasting metal and other surface with abrasive particles in a liquid, for instance glass pellets in water, some of the particles are broken and there is also introduced into the abrasive liquid small particles removed from the eroded surface. It is desirable to separate out the smaller particles and this may be effected by a separate device, forming no part of this invention, included in the liquid circulating system.

The presence of the aforementioned tornado chamber provides however a supplementary means for effecting such a separation of the mixture of particles from the liquid which has been forced into it. As the intensity of the whirling motion is reduced at the upper end of the chamber, there tends to be a greater proportion of the larger particles in the radially outer part of the whirl and a greater proportion of the smaller particles near the axis. Thus there may be provided a further outlet, the inner end of which is extended to a radially intermediate position in the upper part of the tornado chamber. This outlet may lead to waste or it may be led to a clarifying means from which clarified liquid may be led back to the main circulating system.

It is within the scope of this invention to provide a single outlet which is radially adjustable whereby its inner end may be adjusted to open into any desired position between the outer wall of the chamber and the sleeve.

Beyond the upper end of the tornado chamber or other upper housing the upper end of the sleeve opens into an open top vessel provided with a side outlet for the liquid rising through the sleeve.

A supplementary impeller may be mounted on the shaft in this vessel, to assist in the upper movement of liquid through the sealing sleeve and the expelling of the liquidthrough the outlet from the vessel.

In use the pump may be installed in such a position that the lower end of the sleeve is below the normal level of liquid supply to the pump so that when the pump is stationary, there will be maintained an effective liquid seal.

The impeller shaft may be coupled to a motor mounted on top of the apparatus, the weight of the shaft and impeller being entirely supported by a bearing incorporated with the motor and thereby above the liquid level.

The invention will be further described with reference by way of example to one form of the preferred embodiment and to the accompanyng drawings, wherein:

FIGURE 1 is a section through the vertical axis of the pump; and,

FIGURE 2 represents an enlargement of part of FIG- URE 1.

The centrifugal pump, having its axis vertical comprises the volute pump casing 1 with its tangential outlet 2 and a lower central inlet 3 which opens out of a feed chamber 4 in a base support 5 on which the casing 1 is mounted. On the top of the casing 1 is provided a supporting frame 6 for a motor 7 of which only part is represented diagrammatically.

The end of the motor spindle 8 is coupled to the upper end of the impeller shaft 9 by engaging in a socket formation 16 of the end of the impeller shaft and being fixed therein by a key ll (FIGURE 2). To the lower end of the shaft 9 is bolted the impeller 12, the diameter of the impeller being greater than a circular central opening 13 in the top of the pump casing 1 and there being provided an annular passage 14 leading from the interior of the pump casing 1 around the back of the peripheral part of the impeller 12 to that central opening 13. In addition to the main impeller blades 15 on the front face of the impeller, there are also provided some smaller blades 16 on its rear face.

To the top of the pump casing 1 is bolted a structure 17 comprising a downwardly divergent frusto-conical wall 18, open at its lower end and having at that end an outer bolted to the top of the pump casing. The motor spindle 8 and the impeller shaft Q extend axially within the structure 17, the spindle 8 passing freely through an opening bounded by a short inwardly directed radial flange 21 at the upper end of the wall 13. Alittle more than midway from the lower end of the structure 17 the wall 18 is formed integral with an internal radially inward extending annular web 22 and a cylindrical sleeve, the sealing sleeve 23, extends downwardly from the inner boundary of the web 22 to terminate above the level of the lower end of the wall 18 of the structure 17. The coupling socket 10 at the upper end'. of the impeller shaft 9 is entirely above the annular web 22 and towards its lower end the socket formation It) carries smallrradial extensions constituting the supplementary impeller 24.

The internal diameter of the sealing sleeve 23 is greater than the diameter of the shaft 9, to form between them an annular passage 25 (FIGURE 2) of uniform dimensions. The lower part 26 of the interior of the structure 17 below the annular web 22 constitutes, and will hereinafter be called, the tornado chamber; the part 27'above the web 22 willbe called the water outlet chamber. It will be seen that the annular passage 25 opens at its upper end into the water outlet chamber 27 and at its lower end into the lower end of the tornado chamber.

The pump is intended to be used with a mixture of abrasive Particles and water. The interior walls of the pump casing 1 and also the insides of the outer and upper walls of the tornado chamber 26 are lined with a rubber composition28 which is replaceable and provides a protection against erosion by the abrasive particles.

When the pump is working some of the water/ abrasive mixture is forced at considerable pressure and with high angular momentum through'the annular passage 14 at the back of the impeller 12 into the lower end and near the peripheral boundary of the tornado chamber 26, giving rise to a violent swirl which extends throughout the tornado chamber and is centred on the axis of the cham her. The rotary action is most violent at the lower end of the chamber 26, where the radial pressure gradient is steepest in the radiallyinner region and the greater part of the abrasive particles are thrown towards the wall of the chamber, as indicated at A, leaving in the central region B, that is at the lower end of the sealing sleeve 23, a mass of comparatively-clear water at raised pressure. This clear water ascends the annular sealing passage 25 to the water outlet chamber 27 from which it passes through a side clear water outlet opening 29 and pipe 30. v The supplementary impeller 24 assists the movement of water up the annular sealing passage 25 and its escape through the outlet 29.

The swirling action becomes progressively less violent towards the top of the tornado chamber 26 so that the distribution of abrasive particles is less concentrated in the radially outer region as is progressively indicated at A1 and A2 in FIGURE 2.

At the upper end of the tornado chamber the mixture of abrasive particles and water passes out through a side opening 31 and pipe 32.

As is diagrammatically shown in FIGURE 2 the larger particles tend to be concentrated in the radially outermost zone and to some extent the finer particles could be selectively removed by means of an outlet pipe terminating at an appropriately selected inner radial position at or towards the upper end of the tornado chamber 26.

Due to the diflerent pressure conditions and speeds of rotation of the contents of the tornado chamber 26 which are set up between the top and bottom of the chamber, the movement of the contents is complex. In addition to the inflow at the bottom of the chamber, the outflow of clarified water into the lower end of the sealing sleeve 23, and the outflow of abrasive/Water mixture at the upper outlet 31, the tornado" effect can also be represented, as

by the broad arrows in FIGURE 2, as an elongated loop 4' when seen in a radial plane. The particles tend to be drawn downwards from a radially inner region at the top of the chamber in an approximation to a downwardly divergent envelope, the diameter of that envelope increasing as the centrifugal forces increase, until at its lower end it tends to be concentrated almost at the annular entry at the back of the impeller 12. Thus it appears that there is an upward flow of particles near the wall of the chamber and a return flow from the radially inner region at the top of the chamber towards the radially outer region of the lower end of the chamber. Superimposed on this movement there is the effect of centrifugal force tending to urge-the heavier particles to the radi ally outer regions at all levels and to concentrate the lighter particles into the radially outer regions more strongly at the bottom than at the top. There is apparently an outflow as well as an inflow of particles through the annular passage 14 at the back of the impeller; the broad arrows shown in this'position in FIGURE 2 are intended only to generally indicate this double direction flow and not precise paths of flow.

The auxiliary impellers 16 on the back of the impeller must undoubtedly tend to set up or at least accentuate the flow pattern described above, and it is found that when they are used the degree of clarification of water passing out of the annular sealing passage 25 is greater than when they are not used.

The highest water level in the circulatory system or the liquid sump with which the pump is used is normally above the upper end of the sealing sleeve 23, as indicated at W in FIGURE 1. Thus when the pump stops, water remaining in the water outlet chamber will still provide the required seal, it being obvious that when the pump stops there may be at least some slight reverse flow which, in the absence of the clarified water seal, could result in abrasive/water mixture rising into the sealing sleeve.

The water may discharge from the upper pipe 3% to an automatic device for maintaining the water level at the required height in the vessel or other part of the system to which the water is returned. I This may be a device in the form of an automaticvalve which is held in one condition by water discharging through the pipe 30 and is biased to return to another condition when that flow stops.

The arrangement has the advantage that it eliminates waste of abrasive through possible overflow from a vessel to which, in the present case, only clean water need be discharged. It is an additional advantage in some circumstances under which the pump may be used to be able to obtaina source of comparatively clean water.

What I claim then is:

1. A centrifugal pump comprising a vertical driving shaft, an impeller mounted on the lower end of the driving shaft, a pump housing including a lowerrimpeller housing and an upper housing through which said shaftextends, an upper annularclosing wall for said upper housing and a cylindrical sleeve extending downwardly from the radially inner annular boundary of said closing wall, said sleeve having an internal diameter greater than the external diameter of said shaft to define an annular open-ended passage between said shaft and said sleeve, a lower entry to said annular passage being provided by the lower end of said sleeve, an annular entry to said upper housing from said impeller housing being defined-between said impeller and the lower end of said upper housing, an outlet from said upper housing above the level of said lower entry, means for generating whirling motion of liquid entering said upper housing from said impeller housing, an outlet chamber above said upper housing, at least one radial impeller blade on said shaft within said outlet chamber, said upper annular closing'wall for said housing being also the lower annular wall of said outlet chamber, said sleeve opening at its upper end into said outlet chamber, and a side outlet being provided in said outlet chamber for escape of liquid therefrom.

2. A centrifugal pump comprising a vertical driving shaft, an impeller mounted on the lower end of the driving shaft, a pump housing consisting of a lower impeller housing and an upper housing through which said shaft extends, an upper annular closing wall for said upper housing and a cylindrical sleeve extending downwardly from the radially inner annular boundary of said closing wall, said sleeve having an internal diameter greater than the external diameter of said shaft to define an annular open-ended passage between said shaft and said sleeve, a lower entry to said annular passage being provided by the lower end of said sleeve, an annular entry to said upper housing from said impeller housing being defined between said impeller and the lower end of said upper housing, an outlet from said upper housing above the level of said lower entry, an outlet chamber above said upper housing, said sleeve opening at its upper end into said outlet chamber, an outlet in the outlet chamber for the escape of liquid therefrom, and means for generating whirling mo tion of liquid entering said upper housing from said impeller housing to direct at least some of said liquid to the outlet from the upper housing.

3. A centrifugal pump comprising a vertical driving shaft, an impeller mounted on the lower end of the vertical driving shaft, a pump housing including a lower impeller housing, an inlet and an outlet for said lower impeller housing, and an upper housing through which said shaft extends, an upper annular closing wall for said upper housing extending inwardly from the outer circumferential Wall of the upper housing, a cylindrical sleeve extending downwardly from the radially inner annular boundary of said closing wall, said sleeve having an internal diameter greater than the external diameter of said shaft to define an annular open-ended passage between said shaft and said sleeve, said sleeve being spaced inwardly from said outer circumferential wall so that the sleeve and the Wall define an annular chamber, a lower entry from said annular chamber to said annular passage being provided by the lower end of said sleeve, an annular entry to said annular chamber from said impeller housing being defined between said impeller and the lower end of the outer circumferential wall of said upper housing, an outlet from said annular chamber in the outer circumferential wall of the upper housing above the level of said lower entry, an outlet chamber above said upper housing, said sleeve opening at its upper end into said outlet chamber, an outlet in the outlet chamber for the escape of liquid therefrom, and means on the impeller for generating whirling motion of liquid entering said annular chamber through said annular entry and causing at least some of said liquid to flow upwardly within the upper housing to the outlet therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,249,572 Weitling Dec. 11, 1917 2,003,168 Allen May 28, 1935 3,024,734 Dickson et al Mar. 13, 1962 FOREIGN PATENTS 16,500 Denmark Sept. 26, 1912 1,193,200 France Apr. 27, 1959 840,671 Great Britain July 6, 1960

Claims

1. A CENTRIFUGAL PUMP COMPRISING A VERTICAL DRIVING SHAFT, AN IMPELLER MOUNTED ON THE LOWER END OF THE DRIVING SHAFT, A PUMP HOUSING INCLUDING A LOWER IMPELLER HOUSING AND AN UPPER HOUSING THROUGH WHICH SAID SHAFT EXTENDS, AN UPPER ANNULAR CLOSING WALL FOR SAID UPPER HOUSING AND A CYLINDRICAL SLEEVE EXTENDING DOWNWARDLY FROM THE RADIALLY INNER ANNULAR BOUNDARY OF SAID CLOSING WALL, SAID SLEEVE HAVING AN INTERNAL DIAMETER GREATER THAN THE EXTERNAL DIAMETER OF SAID SHAFT TO DEFINE AN ANNULAR OPEN-ENDED PASSAGE BETWEEN SAID SHAFT AND SAID SLEEVE, A LOWER ENTRY TO SAID ANNULAR PASSAGE BEING PROVIDED BY THE LOWER END OF SAID SLEEVE, AN ANNULAR ENTRY TO SAID UPPER HOUSING FROM SAID IMPELLER HOUSING BEING DEFINED BETWEEN SAID IMPELLER AND THE LOWER END OF SAID UPPER HOUSING, AN OUTLET FROM SAID UPPER HOUSING ABOVE THE LEVEL OF SAID LOWER ENTRY, MEANS FOR GENERATING WHIRLING MOTION OF LIQUID ENTERING SAID UPPER HOUSING FROM SAID IMPELLER HOUSING, AN OUTLET CHAMBER ABOVE SAID UPPER HOUSING, AT LEAST ONE RADIAL IMPELLER BLADE ON SAID SHAFT WITHIN SAID OUTLET CHAMBER, SAID UPPER ANNULAR CLOSING WALL FOR SAID HOUSING BEING ALSO THE LOWER ANNULAR WALL OF SAID OUTLET CHAMBER, SAID SLEEVE OPENING AT ITS UPPER END INTO SAID OUTLET CHAMBER, AND A SIDE OUTLET BEING PROVIDED IN SAID OUTLET CHAMBER FOR ESCAPE OF LIQUID THEREFROM.