GB1565121A - Screw pump - Google Patents

Description

(54) SCREW PUMP (71) We, CPC ENGINEERING COR PORATION of Box 36, Route 20, Sturbridge, Massachusetts 01566, United States of America, a corporation of the Commonwealth of Massachusetts, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The basic principle of the screw pump dates from the time of Archimedes. In fact, these pumps are commonly referred to in the art as Archimedes Screw Pumps.Fundamentally, the screw pump consists of a tubular member containing a helically arranged elevator, so that when the pump is inclined with its lower end in water and the elevator is rotated about its longitudinal axis, water is lifted from stage to stage within the tubular member, and, in many relatively inefficient arrangements, water can be lifted to heights of 10 or 20 feet in a single pass. While such pumps leave much to be desired in terms of their efficiency, they do constitute a useful means for lifting water in many types of situation, because they are of relatively simple construction, and maintenance is easy.

A variety of improvements have been devised and the pumps are currently relatively popular for such uses as moving sewage sludge from a collection pit to an elevated area. Their performance at intake and outlet is ragged. That is, there is a considerable amount of splashing of liquid and sludge which makes the operation considerably untidier than it need be. Shaft deflection and "screw to housing" clearance have reduced pump efficiency and limited pump lift height and capacity.

According to the present invention there is provided a conveyor for elevating liquids, the conveyor comprising: a cylindrical tube; and a conveyor screw within said tube, said screw having - one or a plurality of flights, each flight having a generally helical form and being mounted around the central longitudinal axis of said tube with the flights, where there are more than one, being arranged to form a multiple helical screw, said conveyor screw having the outer edge of the or each helical flight integrally joined to said tube, and the liquid-elevating helical surfaces of the or each flight of said conveyor screw canted towards the outlet end of said cylindrical tube, and said tube being supported for rotation about said longitudinal axis.

In order that the invention may be more fully understood, some preferred embodiments in accordance therewith will now be described, by way of example only, with reference to the accompanying drawings, wherein Figure 1 is an elementary side elevation showing the relationship of two pools of liquid at different levels with a conveyor for liquids, in the form of a pump in accordance with the invention, mounted in place for delivery of liquid from the lower level to the upper; Figure 2 is a section longitudinally through the pump showing the construction of part of two of the helical cones which form the flight within the structure; Figure 3 illustrates the manner of assembly of the helical cones at the discharge end of the structure, showing a flanged outer anti-spatter shroud for use on the delivery end of the pump;; Figure 4 shows the structure of the delivery end of the pump; Figure 5 shows the improved intake end of the pump, wherein the modified curve of the cylindrical cone contributes to an improved efficiency in the take up and delivery of liquid; Figure 6 illustrates a cleaning apparatus; Figure 7 is a longitudinal section showing geometrically how a conventional screw pump would be formed; Figure 8 is a longitudinal section showing geometrically how the screw of a pump in accordance with this invention is formed; and Figure 9 is a side elevation showing an alternative method of supporting and/or of driving a cylinder of a pump in accordance with the invention, by means of a center shaft, positioned at either or both ends.

Referring now to Figure 1, 10 represents concrete trough or basin in which liquid water, or sewage containing a certain amount of sludge, is collected. The concrete basin or trough 10, in which the liquid is collected has walls 11 and a base 12 to form an incline or deep intake area 13. Adjacent the edge of the trough is a mound 14 on which a typical roller bearing 15 carried by the cylindrical body (or cylinder) 30 of the pump rides.

At the other end of the pump, a base 16 carries an upright 17 mounted thereon, which upright at its upper end 18 carries a bearing means 19 for the cylindrical pump.

A structural member 20 is connected to the mound 14, to the upper end 18 of the upright 17, and also to a support 21, for a platform 22, which in turn supports a drive gear 23 which, by way of a motor 24, functions to drive the cylinder 30.

An alternative means of support for pump cylinder 30 is shown in Figure 9. This means eliminates the necessity of a full length supporting structure and is comprised of a center shaft 108, a main bearing 104, and a support bracket 111. A drive motor 113 may be directly coupled to the pump shaft 108 with a flexible coupling 114. The pump shown in Figure 9 will be described more fully hereinafter.

The pump shown in Figure 1 discharges into an elevated trough or discharge container 25 which may be of concrete and of any conventional form. Thus, this pump extends from the trough 10 to the edge 26 of the receiving trough 25. Its details of construction are better understood by reference to Figures 2 and 3, which show it in partial longitudinal section.

Referring now to Figures 2 and 3, the cylindrical pump body 30 is shown in section to reveal conical helical turns 31 arranged therein. The central opening 32 formed by the inner edge of the conical turns 31 is approximately one-fourth of the diameter of the cylinder 30.

The significance of the term conical helical turns will be observed in Figure 3, wherein several turns 31 of the flight are shown, and it will be apparent that the liquid-elevating helical surface of the flight is canted towards the outlet end of the cylinder 30. This forms a "V" shaped, cone-shaped, depression between the flight and the cylinder wall to carry water.

At the lower or intake end the last turn 38, is extended about one-half a revolution by carrying it around the circumference to the point where the flight carries beyond the end 39 of the cylinder. The amount extending outside the cylinder 30 by this mechanism is shown by the flight 38 which extends outside the cylinder for at least about one-third of its circumference to give a forward cutting edge 38' which is held in appropriate relation to the rest of the helix by the extension of the cylinder wall 30.

To permit discharge of fluid from the cylinder, the helix at the discharge end is shaped as though it had been extended beyond the end of the cylinder, to the point at least where the outer edge of the helical flight comes to the edge of the circumference of the upper end of the cylinder 30, and then cut in a plane passing across the end of the open cylinder, normal to the axis, so as to shear off that portion of the helical flight extending beyond the end. That is, in the inclined position, the final portion of the flight, in the direction of rotation, is of continuously reducing height, a truncated conical helix 60 so that water captured within the flight can spill over the edge and uniformly and easily pass over the final discharge edge of the pump. This is shown in greater detail in Figure 4.

As a final convenience at the discharge end for receiving liquid and sludge, without generating a large amount of splashing around the end of the pump, a stationary shroud is formed thereon. This can be best seen in Figure 3, and consists of an "L" sectioned collar 40 extending around and beyond the end of the cylinder 30, and spaced therefrom a short distance. The end of the cylinder is turned back on itself as shown at 30'. The shroud 40 is also turned back on itself, so as to extend into the space thus formed to form a lip seal as shown at 40'. It will be appreciated that this seal prevents liquid emerging from the outlet end of the pump from dripping down the outside of the pump, and acts without being in contact with the rotating body of the pump, so that it does not absorb power from the pump in the way in which a seal relying on frictional contact would.

Referring back now to Figure 2, two methods of fabrication of the device can be made apparent from the inspection thereof.

In the first method, the cylinder 30 is rolled and butt welded to form a full cylinder. The individual turns of the flight are preformed to a conical helix so as to easily slide into cylinder 30 and are then welded in position.

The second method is primarily for use on the smaller diameter pumps. The cylinder 30 is formed as a partial cylinder having its side open to the extent of about one-third of the circumference. The turns 31 are preformed; each as a cone having the proper inclination, having the proper outer circumference and inner circumference or inner opening. The turn is thus insertable into the cylinder itself by having a slight compression and is also relatively easily movable within the main cylinder. Once it is moved into place it can be allowed to spring back to full diameter whereupon it is welded, or otherwise integrally joined, along the edge 31' where it contacts the inner surface of the cylinder. The second turn, and third, etc., on through the length of the flight can be equally conveniently fitted into place, held in place and welded.Thereupon, upon completion of the assembly of the tube with its inner flight, a sealing plate to cover the exterior can be set in place and plug welded along the line of contact with the flight within.

It will be apparent from the construction which has been thus outlined that the advantage of the rolled and butt welded drum with the screw in the form of a single flight formed from conical helical turns welded to the inner wall, is a structure which, in operation, is of improved efficiency over conventional screw type pumps.

The section modulus and moment of inertia obtained by use of the external pump cylinder provides structural stability not within the capability of conventional screws of the center-shaft construction. This results in increased lift potential and permits higher pump speeds thus boosting capacity. Leakage between screw and stationary housing in the conventional pump causes a severe drop-off in efficiency when the level in the intake pool is low. The efficiency of the cone pump can remain substantially constant at all intake levels, owing to zero leakage between the screw and the cylinder.

The conical helical configuration of the screw reduces turbulence within the pump and minimizes spill or splashback of liquid through the center hole. In addition, this conical helix maximizes the total volume per turn and permits the use of a wide range of pump inclination angles without material adverse effect on the capacity of the pump.

Referring to Figure 5, extention of the intake end or blades of the helix as at 50 for the purpose of cutting and capturing such solid matter as might be carried by a liquid, such as sewage, is most useful. To allow for the fact that some of these materials might be quite hard, the leading edge 51 can be made serrated or of an extra hard grade of steel, and is supported by an arcuate extension 52 of the cylinder 30. The amount of this extention may be as much as half a revolution.

At the discharge end of the device the truncated or disappearing helix 60 at the plane of the end of the cylinder 30 eliminates pulsation of delivery of liquid from the outlet end and gives effectively a good continuous outlet flow. That is, by the time the liquid contents of one turn have been discharged, the liquid contents of the next turn have climbed into place for discharge.

This cutting of the top turn of the conical helix spirally, starting at a point slightly below the center hole and progressing outwardly to the cylinder 30 means the spiral should encompass approximately 360" for a single helix pump, 1800 for a double helix pump and 1200 for a triple helix pump.

While it is preferred to leave the center of the apparatus open (by arranging that the or each helical flight is spaced from the longitudinal axis of the cylinder so as to define a longitudinal void which is centrally disposed within the cylinder), it is useful to install a central tube in this opening. When added to the center hole, as indicated, it increases pump volume by, of course, reducing any possibility of splash-back from flight to flight. Generally this can be done by welding a light weight tube in position in the center hole, or by merely fastening it into position in the center hole, to allow for removal to provide access for cleaning purposes. A modification is to provide a heavy duty, inflatable, adjustable diameter center tube of a material such as neoprene, for example, so that it can be deflated and dropped out readily for cleaning purposes.

For cleaning, the apparatus shown in Figure 6 may be used. This consists merely of a center shaft 70 with a single, or plurality of radial arms 71, 72, 73, 74 positioned so as to match the pitch of the pump. The device can then be passed through the center hole and allowed to pass axially inside the pump and either the cleaning device or the pump body itself may be rotated to cause relative motion of the cleaning arms with respect to the flights.

The general construction of the device may be from structural steel, welded seams, and welded joints. The turns can be individually fabricated or an entire helix can be preformed and wrapped in an appropriate tube. In one embodiment the pump is supported at both ends of the cylinder by conventional bearings. However, we prefer roller type bearings, in contact with external races, fastened to the pump cylinder. Alternatively, peripheral type ball or roller bearings can be used. The supporting structure, as used in the field can be whatever is necessary to suit the purpose, as illustrated in Figure 1. As a drive unit, the pump cylinder can be rotated by means of a direct connection to a gear box, using a flat driving belt, or a "V" belt, coupling, or a chain.It is preferred to use a reversible main drive motor, so as to provide a means by which liquids can be trained from the pump for shut down. This also will permit purging of the pump from the upper end.

Reference will now be made to Figures 7 and 8, which are auxiliary drawings useful for the purpose of classifying the geometry of the device. Figure 7 shows the conventional helix. This may be visualized as the locus of the hypotenuse of a right triangle, A, as it is wrapped around a circular cylinder, with its axis parallel to one side.

This is the mathematical helix. Its pitch, the distance between points on the helix per revolution, and other properties have been described in detail in mathematical terms, as is well known. In the development of screws, based on the helix, the thread follows this line. Drill bits for digging in the earth and, actually, the Archimedean screw, are based on the helix as the surface generated by a line normal to the axis of the cylinder and having one end trace the helix on the surface of the cylinder. This is illustrated in Figure 7.

Our departure from the conventional helix, or the conventional Archimedean screw, as shown in Figure 8, resides in having the line trace the helix, while being canted towards the outlet end of the cylinder, so that it is set at an angle (preferably of 20 to 45 ) to the axis of the cylinder. (It may be observed that this angle as shown in the schematic figures of the drawings is somewhat above (or, in the case of Figure 8, at the upper end of) this range.) In this way, the turns of the conical helix are developed and any single revolution is much like a cone, except that on the completion of the surface of revolution, the surface has advanced, in the direction of the longitudinal axis of the cylinder, by an amount equal to the pitch of the helix.The canting or inclination of the surface towards the central axis contributes markedly to the capacity of the screw in moving liquid and sludge.

Hence in the description of our invention, we have used the term conical helix to refer to this form of development of the pumping surface or the flight (or flights) of the screw.

Referring now to Figure 9, there is shown therein in diagrammatic form, in a side elevation, a full assembly of a pump built in accordance with the principles herein developed. For clarity and reference, a new sequence of numbers, commencing with 100, is used. Thus, the inlet hold tank 100 for the sludge is below ground level 101 and the outlet tank 102, to which the sludge is to be moved, is at a higher level from the lower by several feet. The base load bearing member 103 carries lower main bearing 104 in which the body of the pump cylinder 105 is carried. The lower end of the pump cylinder 105 is submerged in sludge in the inlet tank.

At the upper end 107 the structure is identified by the employment of the center shaft 108 which enters the structure to between one-third to and one-half its total length. It is integrally joined to the flight 109 which is the conveyor screw of the unit.

Splash shroud 110 is held in place on supporting bracket 111.

Supporting bracket 111 is fastened at an appropriate level to a support base 112 and supports the main drive motor 113 which is connected through a flexible coupling 114 to the upper main bearing 115.

In this fashion the principles of the design of the inclined helical flight of the screw pump cylinder are built into the structure and the design advantage of a lower main bearing merely taking the weight of the bearing with the upper main bearing connected to a shaft to absorb the thrust and torque, is apparent. That is, the pump cylinder can, for example, be fabricated (a) with no center shaft and the drive formed as illustrated in connection with Figure 2; or (b) with a partial center shaft and drive as shown in Figure 9, this with or without a lower center shaft.

From the foregoing description of the pumps shown in the accompanying drawings, it will be appreciated that a conveyor in accordance with preferred embodiments of the invention may be in the form of a screw pump, fundamentally in design based on an Archimedes screw, comprising a tubular member having a helical screw mounted therein, integrally joined thereto, the turns of the screw being radially inclined to the longitudinal axis of the tube, the entire structure having a central longitudinal opening, the end discharge being characterized by a liquid tight seal, the structure being designed to have its lower or intake end immersed in liquid, and carrying solids such as watery sewage sludge and, by rotation, to lift the sludge through elevations as high as 20 and 30 foot (6 to 10 meters). These pumps can lift sludge through an angle of elevation of from 30 to 50 or more, the preferred range being 36 to 450.

WHAT WE CLAIM IS: 1. A conveyor for elevating liquids, the conveyor comprising: a cylindrical tube; and a conveyor screw within said tube, said screw having one or a plurality of flights, each flight having a generally helical form and being mounted around the central longitudinal axis of said tube with the flights, where there are more than one, being arranged to form a multiple helical screw, said conveyor screw having the outer edge of the or each helical flight integrally joined to said tube, and the liquid-elevating

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. preferred to use a reversible main drive motor, so as to provide a means by which liquids can be trained from the pump for shut down. This also will permit purging of the pump from the upper end. Reference will now be made to Figures 7 and 8, which are auxiliary drawings useful for the purpose of classifying the geometry of the device. Figure 7 shows the conventional helix. This may be visualized as the locus of the hypotenuse of a right triangle, A, as it is wrapped around a circular cylinder, with its axis parallel to one side. This is the mathematical helix. Its pitch, the distance between points on the helix per revolution, and other properties have been described in detail in mathematical terms, as is well known. In the development of screws, based on the helix, the thread follows this line. Drill bits for digging in the earth and, actually, the Archimedean screw, are based on the helix as the surface generated by a line normal to the axis of the cylinder and having one end trace the helix on the surface of the cylinder. This is illustrated in Figure 7. Our departure from the conventional helix, or the conventional Archimedean screw, as shown in Figure 8, resides in having the line trace the helix, while being canted towards the outlet end of the cylinder, so that it is set at an angle (preferably of 20 to 45 ) to the axis of the cylinder. (It may be observed that this angle as shown in the schematic figures of the drawings is somewhat above (or, in the case of Figure 8, at the upper end of) this range.) In this way, the turns of the conical helix are developed and any single revolution is much like a cone, except that on the completion of the surface of revolution, the surface has advanced, in the direction of the longitudinal axis of the cylinder, by an amount equal to the pitch of the helix.The canting or inclination of the surface towards the central axis contributes markedly to the capacity of the screw in moving liquid and sludge. Hence in the description of our invention, we have used the term conical helix to refer to this form of development of the pumping surface or the flight (or flights) of the screw. Referring now to Figure 9, there is shown therein in diagrammatic form, in a side elevation, a full assembly of a pump built in accordance with the principles herein developed. For clarity and reference, a new sequence of numbers, commencing with 100, is used. Thus, the inlet hold tank 100 for the sludge is below ground level 101 and the outlet tank 102, to which the sludge is to be moved, is at a higher level from the lower by several feet. The base load bearing member 103 carries lower main bearing 104 in which the body of the pump cylinder 105 is carried. The lower end of the pump cylinder 105 is submerged in sludge in the inlet tank. At the upper end 107 the structure is identified by the employment of the center shaft 108 which enters the structure to between one-third to and one-half its total length. It is integrally joined to the flight 109 which is the conveyor screw of the unit. Splash shroud 110 is held in place on supporting bracket 111. Supporting bracket 111 is fastened at an appropriate level to a support base 112 and supports the main drive motor 113 which is connected through a flexible coupling 114 to the upper main bearing 115. In this fashion the principles of the design of the inclined helical flight of the screw pump cylinder are built into the structure and the design advantage of a lower main bearing merely taking the weight of the bearing with the upper main bearing connected to a shaft to absorb the thrust and torque, is apparent. That is, the pump cylinder can, for example, be fabricated (a) with no center shaft and the drive formed as illustrated in connection with Figure 2; or (b) with a partial center shaft and drive as shown in Figure 9, this with or without a lower center shaft. From the foregoing description of the pumps shown in the accompanying drawings, it will be appreciated that a conveyor in accordance with preferred embodiments of the invention may be in the form of a screw pump, fundamentally in design based on an Archimedes screw, comprising a tubular member having a helical screw mounted therein, integrally joined thereto, the turns of the screw being radially inclined to the longitudinal axis of the tube, the entire structure having a central longitudinal opening, the end discharge being characterized by a liquid tight seal, the structure being designed to have its lower or intake end immersed in liquid, and carrying solids such as watery sewage sludge and, by rotation, to lift the sludge through elevations as high as 20 and 30 foot (6 to 10 meters).These pumps can lift sludge through an angle of elevation of from 30 to 50 or more, the preferred range being 36 to 450. WHAT WE CLAIM IS:

1. A conveyor for elevating liquids, the conveyor comprising: a cylindrical tube; and a conveyor screw within said tube, said screw having one or a plurality of flights, each flight having a generally helical form and being mounted around the central longitudinal axis of said tube with the flights, where there are more than one, being arranged to form a multiple helical screw, said conveyor screw having the outer edge of the or each helical flight integrally joined to said tube, and the liquid-elevating

helical surfaces of the or each flight of said conveyor screw canted towards the outlet end of said cylindrical tube, and said tube being supported for rotation about said longitudinal axis.

2. A conveyor according to claim 1, wherein said tube is supported at both ends thereof.

3. A conveyor according to claim 1 or claim 2, including means for rotating the tube about said longitudinal axis.

4. A conveyor according to any one of claims 1 to 3, wherein said helical surfaces are canted as aforesaid, at an angle of between 20 and 45" with respect to said longitudinal axis.

5. A conveyor according to any one of claims 1 to 4, wherein each flight is mounted around a longitudinal tube which is centrally disposed within said cylindrical tube.

6. A conveyor according to any one of claims 1 to 4, wherein the inner edge of the or each helical flight is spaced from said longitudinal axis so as to define a longitudinal cylindrical void which is centrally disposed within said cylindrical tube.

7. A conveyor according to any one of claims 1 to 6, wherein the inlet end of said conveyor screw carries an extension of the screw at the inlet end beyond the plane defining the inlet end of said cylinder.

8. A conveyor according to any one of claims 1 to 7, wherein the screw at the discharge end of the conveyor has an inner edge which is so shaped that the spacing of said inner edge from said longitudinal axis increases progressively as the discharge end of the screw is approached.

9. A conveyor according to any one of claims 1 to 8, wherein said conveyor screw terminates at the discharge end of the conveyor substantially in the plane of the discharge end of said cylindrical tube.

10. A conveyor according to any one of claims 1 to 9, where the discharge end of said device has a lip seal and an anti-spatter shroud.

11. A conveyor according to claim 1, substantially as hereinbefore described with reference to, and as schematically illustrated in, the accompanying drawings.