EP0174750A1

EP0174750A1 - Pump

Info

Publication number: EP0174750A1
Application number: EP85305787A
Authority: EP
Inventors: Sing Yau Goh
Original assignee: Universiti Malaya
Current assignee: Universiti Malaya
Priority date: 1984-08-17
Filing date: 1985-08-14
Publication date: 1986-03-19
Also published as: MY100511A; PH25261A; GB2163220B; GB2163220A; IN165632B; GB8420909D0

Abstract

A force pump is disclosed that requires no stuffing box. The pump has a riser pipe (1) and a delivery pipe (2) branched off the riser pipe between upper and lower piston assemblies (12A, 12B) that operate together in the riser pipe. There are one-way valves (14A, 14B), respectively below the lower piston assembly (12B) and at the foot of the delivery pipe (1). The lower piston assembly (12A) incorporates a one-way bypass (21 '22).

The one-way bypass (21/22) in the lower piston assembly (12A) and the one-way valves (14A, 14B) are set to open and close as fluid is pumped such that on each upstroke of the piston assemblies (12A, 12B) the one-way bypass (21 22) and the one-way valve (14B) in the delivery pipe (2) are closed and the one-way valve (14A) in the riser pipe is open so that by the action of the lower piston assembly (12B) fluid is drawn into the riser riser through the one-way valve (14A) therein, and such that on each downstroke of the piston assemblies (14A, 14B) the one-way bypass (21/22) and the one-way valve (14B) in the delivery pipe are open and the one-way valve (14A) in the riser pipe is closed so that by the action of the upper piston assembly (12A) fluid from the riser pipe is passed through the one-way valve (14B) in the delivery pipe to be delivered from this pipe.

In addition to requiring no stuffing box, the total work input is performed during two separate strokes so that the maximum effort required of an opertor is reduced. When the pump is used to deliver water to an elevated position, or under pressure, the delivery pipe is under pressure but the resultant flooding which might otherwise occur above the upper piston assembly (12A) due to water leaking past this piston assembly (12A) when both assemblies are stationary or operating at low speeds is prevented by the foot valve assembly (14B) at the foot of the delivery pipe (2).

Description

This invention relates to pumps required to lift water from a depth to be delivered to an elevated position or under pressure.
In British Patent Specifications Nos. 730,097 and 1,479,595 there are disclosed pumps in each of which there is a riser pipe (19/21 in 730,097 and 20 in 1,479,595) containing upper (30 in 730,097 and 27 in 1,479,595) and lower (32 and 34 respectively) piston assemblies fast (by means of screw threading in 730,097 and by pins 30 and 35 in 1,479,595) on a common piston rod (31 in both specifications). There is a one-way bypass (34 in 730,097 and 36 in 1,479,595) in the lower piston assembly. A delivery pipe (18 in 730,097 and 38 in 1,479,595) is branched off the riser pipe from a zone between the piston assemblies, and there is a one-way valve (28 in 730,097 and 32/33 in 1,479,595) in the riser pipe below the lower piston assembly. If a pump constructed in this manner were to be used with it delivery pipe normally under pressure, as is the case where water is being pumped to a water tank at an elevated position so that the delivery pipe is supporting the water column leading to the tank (and the volume of water supported could be substantial as the delivery pipe should be of large diameter to minimise friction losses during delivery strokes) there would be a tendency for the water in the delivery pipe to leak back past the seals of the upper piston assembly in the piston assemblies stationary or operating at low speed conditions. Extra work would then be required to refill the delivery pipe before water could be delivered to the delivery point. Furthermore, if loss of water were to be minimised a stuffing box (such as at 15/16 in 730,097) serving as a water seal between the sliding piston rod and the top of the pump body would have to be of good quality, leading to problems of construction and maintenance.
According to the present invention there is provided a pump comprising a riser pipe; upper and lower piston assemblies fast on a common piston rod in the riser pipe, the lower piston assembly incorporating a one-way bypass; a delivery pipe branched off the riser pipe from a zone that is between the upper and lower piston assemblies; and a one-way valve that is in the riser pipe below the lower piston assembly; characterised in that said one-way valve is a first one-way valve, and in that there is a second one-way valve that is in the delivery pipe; the one-way bypass in the lower piston assembly and the one-way valves being set to open and close as fluid is pumped such that on each upstroke of the piston assemblies the one-way bypass and the one-way valve in the delivery pipe are closed and the one-way valve in the riser pipe is open so that by the action of the lower piston assembly fluid is drawn into the riser pipe through the one-way valve therein, and such that on each downstroke of the piston assemblies the one-way bypass and the one-way valve in the delivery pipe are open and the one-way valve in the riser pipe is closed so that by the action of the upper piston assembly fluid from the riser pipe is passed through the one-way valve in the delivery pipe to be delivered from this pipe. When this pump is used to deliver water to an elevated position, or under pressure, so that the delivery pipe is under pressure, the second one-way valve in the delivery pipe serves to prevent water leaking back past the upper piston assembly, thus preventing flooding where the piston rod enters the riser pipe when the piston assemblies are stationary or operating at low piston speed. As stated above, if flooding were to occur above the upper piston assembly, extra work would be required upon the next operation of the pump to refill the delivery pipe. Also, as flooding does not occur above the upper piston assembly, and as in this pump the upper piston assembly is inactive during the upstroke, and fluid is delivered from the delivery pipe, by the action of the upper piston assembly, only during the downstroke, a stuffing box sealing the piston rod where it enters the riser pipe is not required, thus simplifying the construction. Furthermore, as the total work input is performed during two separate strokes - the upstroke to lift the fluid and the downstroke to deliver the fluid - the maximum effort required of the operator is reduced as compared with conventional pumps and also the maximum loading on load bearing components is reduced resulting in reduced wear and tear.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 is a sectional side view of a first form of pump,
Figure 2 is a sectional side view of a second form of pump,
Figure 3 is a side view, to a larger scale and partly in section, of a piston assembly incorporated in the pumps of Figures 1 and 2, and
Figure 4 is a view similar to Figure 3 of a valve assembly incorporated in the pumps of Figures 1 and 2.

The pump of Figure 1 is a force pump for raising water and delivering it to an elevated position, or under pressure. A riser pipe 1 has a delivery pipe 2 branched off from a zone intermediate its ends, the two pipes 1, 2 depending from a mount 3. Above the mount 3 the delivery pipe 2 has a connection 4 for receiving a pressure delivery pipe, and a delivery outlet 5 which is at an elevated position. Selection between pressure delivery, or de-livery at the outlet 5, is effected by making good the connection 4 and closing a hand-operated valve 6, or closing-off the connection 4 and opening the valve 6. The mount 3 is supported from the ground by a stand 7.
The riser pipe 1 terminates at the mount 3. A piston rod 8 having its upper end fast in a block 9 pivoted to an operating lever 10 passes through the mount 3 and into the riser pipe 1. The operating lever 1C is pivotally supported by a post 11 upstanding from the mount 3. Within the riser pipe 1 the piston rod 8 carries upper and lower piston assemblies 12A, 12B, each fast with the rod so that they move together. The upper piston assemply 12A operates above the zone at which the delivery pipe 2 is branched off the riser pipe 1. The lower pistor assembly 12B operates below this zone. At the top of the riser pipe 1 there is an overflow outlet 13.
At the foot of the riser pipe 1 there is a one-way foot valve assembly 14A. A similar one-way foot valve assembly 14B is at the foot of the delivery pipe 2.
The piston assembly shown in Figure 3 is the lower assembly 12B. A bolt 15 passed through the barrel 16 of the piston carries at its upper end a socket 17 in which is engaged the piston rod 8 (not shown in Figure 3). The rod 8 is made fast in the socket 17 by a pin (not shown passed through a hole 18 in the socket 17, through a corresponding bore in the piston rod 8, and through a further hole in the socket 17. Bolt and socket are locked relative to the barrel by lock nuts 19.
Around the barrel 16 there are piston rings 20. Through the barrel 16 there are axial bores 21, for example there are six such bores equally spaced around the barrel on a common pitch circle, and at the top of the barrel 16 a flap valve member 22 co=operates with the bores 21 so that the bores 16 and the valve member 22 constitute a one-way bypass through the lower piston assembly.
The upper piston assembly 12A is similar to the lower piston assembly 12B except that it has no through bores such as the bores 21 (and therefore no flap valve member) or the bores are permanently blocked off. Sockets such as the socket 17 are provided above and below the upper piston assembly 12A so that the assembly can be made fast between upper and lower runs of the piston rod E.
The two one-way foot valve assemblies 14A, 14E are identical, and are best seen in Figure 4. Each foct valve assembly 14A, 14B conveniently has a barrel 16' which is identical with the barrel 16 of the lower piston assembly 12B except that the piston rings are replaced by a double-tip seal 23 mounted in a groove that is provided intermediate the grooves that receive the piston rings when the barrel is to serve as the barrel of a piston assembly. The through bores 21 and the flap valve member 22 form the valve assembly as a one-way valve. A pin 24 is permanently mounted in the opposed holes in the socket 17 for receiving a hook (nct shown) if lowered down the pipe i or 2 for recovering the foct valve assembly.
Conveniently the pipes 1 and 2 are of polyvinylchloride, solvent-welded together; the stand 7 is of mild steel; and the mount 3, block 9, lever 10 and support post 11 are of timber. In the pumps illustrated, the barrel 16(16') of the piston assemblies and the foot valve assemblies are of polyvinylchloride; the piston rings 20 are of polyethylene; and the flap valve members 22 and the double-tip seal 23 are of natural or synthetic rubber.
When mounted for operation, as shown in Figure 1, the foot of the stand 7 is set in concrete 25 at ground level, and the riser pipe 1 extends down inside a casing pipe 26 to the water 27. The foot valve assembly 14A at the foot of the riser pipe 1 is below water.
Operation is as follows from the condition lower piston assembly 12B at lowest position/no water above this assembly.

UPSTROKE

Lower piston assembly 12B rising with flap valve member 22 closed draws water into riser pipe 1 through the foot valve assembly 14A which opens to allow passage of water. Upper piston assembly 12B rising but inactive. Foot valve assembly 14P is closed.

DOMNSTROKE

Flap valve member 22 cf lower piston assembly 12B opens so this assembly inactive. Foot valve assembly 14A closes. Upper piston assembly 12A active tc force water through foot valve assembly 14E and out through delivery pipe 2.
Repetition of upstrokes and downstrokes repeats above cycle. As the upper piston assembly is inactive during the upstrokes, and fluid is delivered from the delivery pipe, by the action of the upper piston assembly, only during the downstrokes, no stuffing box sealing the piston rod where it enters the lift pipe is required.
By using pistons of polyvinylchloride with polyethylene sealing rings frictional resistance is minimised. Water leakage past the sealing surfaces acts to lubricate these surfaces, further to minimise frictional resistance.
It can be demonstrated that leakage rate past the sealing rings is directly proportional to the delivery water head. During the downstrokes, the water flow rate past the rings of the upper piston assembly 12A is proportional to the delivery water head. This water accummulates above this piston assembly. During the upstrokes, the water flow rate downwards past the rings of the lower piston assembly 12B is proportional to the lifted water head, whilst the water accummulated above the upper piston assembly 12A tends to flow back downwards past the rings of this assembly. If the rings of the two piston assemblies 12A, 12B are identical, progressive accummulation of water above the upper piston assembly 12A occurs but only when the delivery water head exceeds the lifted water head. It is for this condition that the overflow outlet 13 above the upper piston assembly 12A is provided. If, on the other hand, the delivery water head is less than the lifted water head, there is a negative accummulation of water above the upper piston assembly 12A, that is air from above this piston assembly flows downwards pas: the rings of the assembly during the upstrokes. Baring the downstrokes, this air is expelled upwards past the rings of the upper piston assembly 12A before the build-up of delivery pressure and no overflow outlet is therefore necessary for situations where the delivery water head is equal to or less than the lifted water head.
It is also pcssible to remove the requirement for an overflow outlet for all combinations of lifted anc delivery water heads, by using nen-identical piston rings. The rings of the lower piston assembly 12B may be made to have a better or worse sealing efficiency than those of the upper piston assembly 12A, for example by varying the thickness of material cf the rings or by rutting leakage grooves in the rings, tc compensate fcr the difference in leakage past the piston assemblies arising from a difference in lifted and delivery water heads.
An alternative "pressure-suction" configuration as shown in Figure 2 may be used to raise water from depths which are less than the "maximum suction depth" and to deliver the water to an elevated position or under pressure.
In the pump of Figure 2, the majority of the components are as shown in the pump of Figure 1, as indicated by the use-of like numerals as used in Figure 1. The riser pipe 1' in this pump has a full bore portion terminating some way above the bottom of the pipe 1', the pipe 1' being continued below the full bore portion by a portion 1'A of reduced diameter bore. The foot valve 14A is disposed at the bottom of the full bore portion and the piston rod 8' is shorter than the piston rod 8 of the pump of Figure 1 so that the piston assembly 12B is accommodated above the portion 1' A of reduced diameter bore.
In the pump of Figure 2 the lower piston assembly 12B and the foot valve 14A are more readily accessible for servicing and repair than is the case in the pump of Figure 1.
In both pumps no stuffing box is required, as already discussed. Furthermore, as the total work input is performed during two separate strokes - the upstroke to lift the fluid and the downstroke to delivery the fluid - the maximum effort required of the operator is reduced as compared with conventional lift pumps and also the maximum loading on load bearing components is reduced resulting in reduced wear and tear. When the pump is used to deliver water to an elevated position, or under pressure, the delivery pipe is under pressure but the resultant flooding which might otherwise occur above the upper piston assembly due to water leaking past this piston assembly when both assemblies are stationary or operating at low speeds is prevented by the foot valve assembly 14B at the foot of the delivery pipe 2.

Claims

1. A pump comprising a riser pipe (1); upper and lower piston assemblies (12A,12B) fast on a common piston rod (8) in the riser pipe, the lower piston assembly incorporating a one-way bypass (16/22); a delivery pipe (2) branched off the riser pipe from a zone that is between the upper and lower piston assemblies; and a one-way valve (14A) that is in the riser pipe below the lower piston assembly; characterised in that said one-way valve (14A) is a first one-way valve, and in that there is a second one-way valve (14B) that is in the delivery pipe (2); the one-way bypass (16/22) in the lower piston assembly (12B) and the one-way valves (14A,14B) being set to open and close as fluid is pumped such that on each upstroke of the piston assemblies (12A,12B) the one-way bypass (16/22) and the one-way valve (14B) in the delivery pipe (2) are closed and the one-way valve (14A) in the riser pipe (1) is open so that by the action of the lower piston asembly (12B) fluid is drawn into the riser pipe (1) through the one-way valve (14A) therein, and such that on each downstroke of the piston assemblies (12A, 12B) the one-way bypass (16/22) and the one-way valve (14B) in the delivery pipe (2) are open and the one-way valve (14A) in the riser pipe (1) is closed so that by the action of the upper piston assembly (12A) fluid from the riser pipe (1) is passed through the one-way valve (14B) in the delivery pipe (2) to be delivered from this pipe (2).

2. A pump as claimed in claim 1, wherein the upper and lower piston assemblies (12A,12B) are substantially identical, and wherein there is an overflow outlet (13) from the riser pipe (1) above the upper piston assembly (12A) for releasing fluid accummulating above the upper piston assembly (12A).

3. A pump as claimed in claim 1, wherein the sealing efficiency of the upper piston assembly (12A) to the riser pipe (1) differs from that of the lower piston assembly (12B) to the riser pipe (1).

4. A pump as claimed in claim 1, 2 or 3, wherein the one-way valve (14A) in the riser pipe (1) is positioned to be below the fluid to be pumped in use of the pump.

5. A pump as claimed in claim 1, 2 or 3, wherein the one-way valve (14A) in the riser pipe (1) is positioned to be above the fluid to be pumped in use of the pump.

6. A pump as claimed in any one of the preceding claims, wherein the riser pipe (1), the delivery pipe (2) and sealing rings (20) carried by the piston assemblies (12A,12B) are of synthetic plastics material.

7. A pump as claimed in claim 6, wherein the riser pipe (1) and the delivery pipe (2) are of polyvinylchloride.

8. A pump as claimed in claim 6 or 7, wherein the sealing rings (20) of the piston assemblies (12A,12B) are of polyethylene.