US3552888A

US3552888A - Arrangement in pumps

Info

Publication number: US3552888A
Application number: US782061A
Authority: US
Inventors: Alf Anders Anselm Eriksson
Original assignee: Svenska Precisionsverktyg AB
Current assignee: Svenska Precisionsverktyg AB
Priority date: 1967-12-11
Filing date: 1968-12-09
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05
Also published as: FR1597793A; DE1813676B2; GB1251686A; DE1813676C3; SE333506B; DE1813676A1; JPS4947321B1

Abstract

A PUMP PARTICULARLY FOR LIQUIDS CONTAINING ABRASIVE SOLID PARTICLES AND DESIGNED SO AS TO PREVENT THE SOLID PARTICLES FROM PENETRATING BETWEEN THOSE PACKING SURFACES OF THE PUMP THAT SEPARATE THE PUMP SHAFT BEARINGS AND THE INTERIOR OF THE PUMP DRIVING MOTOR FROM THE PUMP CHAMBER BY MEANS OF A SECOND, READILY REPLACEABLE PACKING.

Description

Jan. 5, 1971 Filed Dec. 9. 1968 A. A. A. ERICKSSON 3,552,888

ARRANGEMENT IN PUMPS 3 Sheets-Sheet 1 Fig.1

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Unimd tates Patent 01 fine 3,552,888 Patented Jan. 5, 1971 ABSTRACT OF THE DISCLOSURE A pump particularly for liquids containing abrasive solid particles and designed so as to prevent the solid particles from penetrating between those packing surfaces of the pump that separate the pump shaft bearings and the interior of the pump driving motor from the pump chamber by means of a second, readily replaceable packmg.

7 Claims BACKGROUND OF THE INVENTION Field of the invention This invention refers to pumps, particularly of the centrifugal type and intended for conveying liquids containing solid particles. An important field of application of the invention is in so-called drainage pumps having the purpose of pumping water which often is contaminated by sand, gravel, clay or similar materials.

Description of the prior art The pump in accordance with the invention is of the general type having an impeller operating in a pump chamber, a shaft carrying said impeller, driving motor means connected to said shaft, and a packing-a main packingseparating the shaft bearings and the interior of the driving motor means from the pump chamber, in addition to which the rear side of the impeller is provided with a slot facing a stationary portion of the pump housing, such as a pump housing cover.

Said packing normally takes the form of a flat packing or a rubber cuff packing for providing a resilient pressure seal for the highest static liquid pressure occurring in the pump chamber. In order to have satisfactory endurance the packing requires lubrication, and therefore for instance a flat packing usually operates in an oil bath. In this case it is important that a higher pressure exists at the inside of the packing than at its outside facing the pump chamber. When the pump is in operation a negative pressure may be created in the above-mentioned slot at the rear side of the impeller so as to make the pressure lower at the outside of the main packing facing the pump than at its inside, so that correct lubrication of the packing will be assured. However, when the lifting height (counterpressure) of the liquid which is to be pumped from the pump chamber exceeds a predetermined value the relative negative pressure cannot be retained in the slot. Naturally the same applies when the impeller is at standstill. It has turned out that in known structures solid particles cannot be prevented from penetrating with the water between the packing surfaces in the main packing, with the result that those parts of the packing that rotate relatively to each other are rapidly worn out and therefore must be replaced at comparatively short intervals, which causes high maintenance costs and decreases the effective operating time of the pump.

The abrasive wear caused by the solid particles in the liquid on the surfaces contacted by the liquid, and particularly those surfaces on the rear side of the impeller and the pump housing cover, which together form the slot or space in which the lower pressure is generated outside the main packing, contributes to the inevitable penetration of solid particles into the packing surfaces that rotate with respect to each other. As the result of this abrasive Wear the width of the slot increases, resulting in a decrease of the centrifugal force urging the liquid outwards, which centrifugal force determines the decrease in pressure. Therefore, in all of these cases detrimental particles penetrate to the main packing, whereupon the particles settle, and after a certain time the packing breaks down. This is particularly true of pumps starting and stopping automatically and having a great many operating changes per time unit.

SUMMARY OF THE INVENTION The invention proposes to eliminate the disadvantages set forth above by providing an arrangement that can keep the surfaces of the main packing that rotate relative to each other free from detrimental particles for an eX- tended period. This is achieved substantially by a second packing-a secondary packing-made of elastic material and connected to the pump housing portion, and being adapted to separate the space outside of the first-mentioned packing from the slot in cooperation with a surface rotating with the shaft. The secondary packing is preferably adapted to exert a pressure against said rotating surface, with said pressure varying with the variations in the slot or the pressure difference between said slot and said space. The secondary packing, which, as will be understood, lies closest to the water liquid containing the particles, is subjected to relatively fast wear and is therefore designed and positioned such that it may readily be replaced and may be manufactured at low cost. The secondary packing may preferably be replaced without the main packing and the shaft, respectively, being disassembled. It is particularly advantageous to position the secondary packing and the surface cooperating therewith in those portions of the pump which under all circumstances have to be replaced at relatively short intervals as the result of their being subjected to abrasive wear by the flowing liquid that is contaminated with solid particles.

BRIEF DESCRIPTION OF THE DRAWING The invention will be more specifically described below with reference to the accompanying drawings that illustrate embodiments as examples, wherein furthermore additional features characterizing the invention will be disclosed.

FIG. 1 shows a longitudinal section through the lower portion of a drainage pump, FIG. 2 shows a portion of a pump housing cover in a longitudinal section, FIG. 3 shows part of this portion in a similar section but on an enlarged scale, FIGS. 4-6 and 810, inclusive, show fragmentarily different embodiments of the secondary packing and the portions of the pump housing cover supporting said packing in the same section as FIGS. 1 and 2 and FIG. 7, finally, shows a portion of the packing of FIG. 6 viewed axially.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 the designation 10 refers to a pump housing which at its lower portion, which may consist of an individual bottom section 12, which is provided with inlets 14 for the slimy water to be pumped. A pump chamber 16 is provided with an impeller 18 having blades 20 of known type on the overhanging end of a shaft 22. A diffusor bowl 24 defines the passage in which the blades 20 operate and forms, together with a pump housing cover generally deisgnated 26, a discharge channel 28, which proceeds as a riser channel 30. The lower portion of the latter may be provided with a so-called wear ring 32.

The shaft 22 carries the rotor 34 of an electric motor and is mounted in bearings on both sides of the motor, with the lower bearing 36 being illustrated in FIG. 1. The designation 38 refers to the stator of the electric motor. The bearing 36 is positioned in a partition 40 of the housing 10 and is retained against a shoulder in said partition by means of a cover 42.

The pump housing cover 26 is provided with a disc element 44 made of metal and fit into the housing 10 and its partition 40, respectively, and is affixed by means of screws 46. The pump housing cover will thus define an oil chamber 48- wherein between the shaft 22 and the cover a main packing is positioned in the form of a fiat packing generally designated 50 and comprising a stationary packing ring 52 connected to the cover as well as a packing ring 54. Ring 54 is composed of two elements and is made to provide a seal for the shaft 22 and is carried along in the rotation of the latter by means of a sheath 56 of elastic material such as rubber and a retainer 58 of more rigid material. The rings 52 and 54, respectively, are provided with fiat sealing surfaces that may slide relatively to each other. A spring 60 maintains the rotating packing ring 54 against the stationary packing ring 52. The packing 50 and its various portions are known in the prior art and will therefore not be described in detail here.

Furthermore, the pump housing cover 26 is provided with a disc 62 of rubber or similar elastic material, which may be provided with a circular recess 64, in which the impeller 18 is introduced. The disc 62 is strengthened or reinforced on its rear side, which faces upwards in FIG. 1, by means of a metal disc 66, to which it is cured or glued, respectively. This disc 66 provides the disc 62 with the necessary mechanical rigidity with respect to any occurring bending strains, etc. The disc 62 extends radially past and above the cover element 44 and is provided with an annular protrusion 68 (FIG. 3) which is adapted to snap into a mating groove at the outer edge of the element 44. In addition, the protrusion 68 may be reinforced by means of a spring, for example a helical spring 70, which preferably is cured in the disc '62. The disc 62 afiixed to the plate 66 is rigidly mounted to the cover element 44 by means of a number of screws 72 distributed along its circumference. These screws are positioned as close to the shaft 22 as possible. Due to the reinforcing plate 66 and the snap means 68, 70 the disc 62 is held firmly in position with repect to the cover element 44, in spite of the manner in which the screws 72 are mounted, said screws being permitted to be unprotected as the abrasive wear of the solid particles in the water is low at this small radius.

In operation of the pump, the water containing the particles is drawn in through the openings 14 of the housing to the pump chamber 16 and is raised by the impeller 18 through a discharge hose (not illustrated) connected to the channel 30. A positive pressure varying with the height the water must be raised will thus be created on the pressure side of the pump chamber. Between the rear side of the impeller 18 and the disc 62 a slot or space 74 is formed and communicates with the pressure side of the pump chamber 16 and will therefore contain water having solid particles dispersed therein. In order to prevent this water from penetrating to the packing 50 it is known in the prior art to let the rear side of the impeller operate as a pump in miniature, so that a lower pressure than on the pressure side of the pump chamber will be produced in the space 76 radially inside of the slot. For this purpose the rear side of the impeller is often provided with ridges or the like forming extensions of pump blades but having insignificant height.

As may be understood from the above this measure is not sufiicient to effectively counter-act the penetration of particles of slime or sludge into the sealing surfaces of the main packing 50. In accordance Withthe invention. and the embodiment of FIGS. 1-3, respectively, the disc 62 is formed with an annular sealing lip 78 at its central portion, with said lip comprising a sealing surface 80 that for instance may be fiat and that cooperates with a similar surface on the impeller 18. Said lip is designed such that the surface 80 will extend slightly below the flat bottom side of the disc 62 when the lip in uncompressed condition as may be seen in FIG. 2. Due to an annular recess 82 in the disc 62 the radial extension of the lip 78 will decrease in the direction away from the surface 80. The bracing disc 66 backs up the lip 78 by means of a backing ring 84 if desired. Also, the lip 78 may be made as a separate element of elastic material, such as rubber, which is connected to the disc 62 if desired.

The lip 78 is normally urged against the fiat surface of the impeller 18 under a predetermined force. The degree of compression of the lip may be made high, so that there are good abrasion tolerances on the lip and on the impeller, respectively. During rotation of the impeller a negative pressure is produced in the space 76 adjacent the lip 78. As the result of its design the lip will then be affected by a force tending to draw it away from the impeller 18 during operation. By proportioning the area and initial pressure of the lip against the impeller at standstill it is possible either to make the seal open entirely and to evacuate the sealing space 86 situated inside thereof and in communication with the flat sealing surface of the main packing 50 to the same pressure as that existing outside, or otherwise to provide a negative pressure in the space 86, with said negative pressure having a slightly higher absolute value than the pressure in the space 76 in order to prevent both sides of the packing 50 from being subjected to an unnecessarily high pressure difference with a resulting high consumption of oil in the tank 48.

When the pump stops, the negative pressure in the inner space 86 will be retained. On the other hand, the negative pressure in the space 76 Will terminate, and instead a positive pressure will be produced with the effect of urging the lip 78 against the sealing surface of the impeller 18 as the result of the undercut form of the lip 78.

If it is not possible to maintain a sufiicient negative pressure in the space 76 during operation of the pump, the sealing effect will be reached by the lip being urged against the sealing surface of the impeller 18, with said lip releasing again as soon as a new negative pressure is produced. Under normal operating conditions a negative pressure exists, and the lip will therefore dynamically beprotected against a large engagement pressure and thus against wear. The secondary packing disclosed above may be defined as a packing functioning hydrodynamically and making possible a pressure reduction in the space 86 but not a positive pressure therein. Furthermore, self-control is provided for balancing the pressure of the lip against the impeller 18. The secondary packing will thereby prevent outer abrasive particles from penetrating into the chamber 86 and further on to the main packing 50, and in addition favorable pressure .conditions are insured on both sides of the main packing for providing an appropriate amount of lubricant supply to the packing surfaces.

The impeller 18 and the disc 62 are subjected to continuous abrasion as the result of contact with the solid particles in the form of slime or sludge .in the water. This is true even if the rubber material of whichdisc 62 is made has particularly great resistance in this respect. However, these elements may be removed insimple manner and replaced with new ones. Thus it is not necessary to disassemble the shaft 22 and the main packing 50, respectively. The impeller 18 is affixed tothe shaft by readily removable means, generally designated 88, in a manner that is known in the prior art. The diffusor bowl 24 and the wear ring 32being subjected to the solid particles in the water are also made of'a material, such as rubber, having high resistance against the abrasive effect of said particles. These components may also be replaced conveniently after the lower bottom section 12 has been removed.

In FIG. 1 the designation 90 refers to a conduit containing necessary components for the automatic functioning of the pump and being of no interest in this connection.

In the embodiment of FIG. 4 the secondary packing is provided with an annular flange 92 that appropriately may be slightly conical and that is composed of resilient material such as rubber and suitably is integral with the disc 62. The rear side of flange 92 engages the rigid disc 66. In this embodiment the packing only operates to continuously engage the impeller 18 with a predetermined initial pressure.

In the embodiment of FIG. 5 the lip 94 is free on its rear side as the result of the disc 66 having a greater bore diameter than in the preceding embodiment, and thus diaphragm operation is achieved. The packing lip 94 has a wiping function with respect to solid particles wanting to penetrate the same. It may be given a high initial pressure against the impeller, and thus pressure may also be amplified by another resilient element, for instance an elastic washer lying behind the lip 94. It will then be possible to enclose a liquid, for example oil, in the space 86 in accordance with FIG. 1, even though the volume will be small in this case. If the lip 94 is not provided with a high initial pressure it will open and admit the liquid that is to be pumped into the space 86 when a predetermined positive pressure exists in chamber 16. When the pressure returns to negative in the slot 74 again the liquid will remain in the interior space 86, and said negative pressure will effectively be prevented from being equalized outwardly over the secondary packing as the result of diaphragm action of lip 94 in combination with the positive pressure retained in the space 86. If the positive pressure does not have a detrimental level for the main packing 50 or if the latter can operate in water, repeated inwardly directed floods of the conveyed liquid and any resulting harmful production of sediments of solid particles adjacent the main packing are prevented in this embodiment.

The embodiment of FIGS. 6 and 7 differs from the preceding one by the reinforcing disc 66 being provided with a number of slits 97 distributed along its circumference. If a harmful positive pressure should rise in the space 86 tending to generate a current of slimy or sludgy water through the sealing surfaces of the main packing 50 this pressure will be instantaneously relieved as soon as the pressure returns to its normal lower value in the space 76 by the portions of the rubber disc 62 situated opposite to the slits 97 being able to bend downwards so as to increase the volume of the space '86.

The secondary packing of FIG. 8 has a double lip as the result of it being provided with a central annular groove 96 on the inside. One of the diaphragm lips 98 seals axially against the impeller 18 and the other one 100 seals axially against the shoulder 102 on the shaft 22 or against a readily replaceable sheath pressed onto the same.

FIG. 9 shows an embodiment having an internal lip 104 approximately corresponding to the lip 94 in the embodiment of FIG. 5 and a lip 106 which is undercut such as the lip 78 of FIGS. 1-3. Thus the effect of this sec ondary packing will be the same as in both of the preceding embodiments.

In accordance with FIG. 10 the surface of the secondary packing facing the impeller 18 has been reinforced by means of a ring 108 of harder material, for example hard metal or ceramic material.

The invention is naturally not limited to the illustrated embodiments and it may be defined in a plurality of respects within the bounds of the scope of the idea upon which it is based.

Cir

I claim:

1. A pump, comprising a housing having an inlet for admitting liquid to a pump chamber formed in the housing adjacent one end thereof,

a motor in said housing,

a drive shaft projecting from said motor into said chamber,

an impeller removably secured to said shaft for rotation thereby in said chamber upon operation of said motor,

a vfirst packing memlber surrounding said shaft between said motor and said chamber to seal the motor from liquid in said chamber, and

a second packing member secured to said housing be tween said first packing member and said impeller, and in axially spaced confronting relation to said impeller,

said impeller being operative upon being rotated to lower the pressure in the axial space between said second packing member and said impeller, and

said second packing member having a flexible portion surrounding said shaft and operative, when said impeller is motionless, resiliently and sealingly to engage the confronting surface of said impeller with a pressure which is at maximum when the pump is not operating, and which decreases during rotation of said impeller due ot the decrease in pressure in said axial space.

2. A pump as defined in claim 1, wherein said second packing member has an axial bore surrounding ibut radially spaced from said shaft, and has in the side thereof which confronts said impeller an annular recess which communicates with said axial space, and forms a flexible, undercut, annular li-p which is responsive, during rotation of said impeller, to a predetermined reduced pressure in said axial space to be drawn radially outwardly to connect said axial space with the radial space between said shaft and the bore in said member.

3. A pump as defined in claim 1, wherein a rigid cover plate is secured to said housing to surround said shaft between said first packing member and said second packing member, and

said second packing member is removably secured to the face of said plate remote from said first packing member so that open removal of said impeller from said shaft, said second packing member may be removed without disturbing said cover plate and first packing member,

4. A pump as defined in claim 3, wherein said second "packing member is a resilient member made of an elastic material and completely covers said plate.

5. A pump as defined in claim 3, wherein a rigid reinforcing member is secured to said second packing member between said cover plate and the side of said second packing member remote from said impeller.

'6. A pump as defined in claim 5, wherein said second packing member and its reinforcing member are secured to said cover plate by a plurality of screws which extend into said plate, and

the outer, marginal portion of said second packing member is resiliently engaged by snap action in a cooperating recess formed around the outside of said cover plate.

7. A pump, comprising a housing having an inlet for admitting liquid to a pump chamber formed in the housing adjacent one end thereof,

a motor in said housing,

a drive shaft projecting from said motor into said chamber,

an impeller removably secured to said shaft for rotation thereby in said chamber during operation of said motor,

a rigid cover surrounding said shaft and fixedly secured to said housing at one end of said chamber between said motor and said impeller,

a first packing means surrounding said shaft between said motor and said cover to prevent liquid in said chamber from seeping through said cover to said motor, and

second packing means comprising a resilient member removably secured to the side of said cover remote from said first packing means and disposed in spaced, confronting relation to said impeller,

said member having a portion thereof sealingly engageable with a confronting surface on said impeller further to seal liquid in said chamber from said motor, and

said resilient member covering the entire side of said cover which faces said chamber, and being removable and replaceable, upon removal of said impeller, without necessitating removal of said cover.

References Cited STATES PATENTS ROBERT M. WALKER, Primary Examiner U .8. Cl. XJR.