GB2070697A - Fluid pump - Google Patents

Abstract

A fluid pump particularly suited for manual operation and fitting easily into a cylindrical well casing 18 made of plastics material has a piston 30 and a check valve, both also made of plastics material. Both piston and valve have the same body structure so that the piston and the check valve may be used interchangeably by simply removing or adding minor components. These components incude a plate valve member 46 freely slidable along a coupling rod or stem 44 integral with the body structure, sealing rings 56, 58 to provide adequate sealing and sliding contact with the internal wall of the well casing 18, and an adapter which is mounted to the lower part of the body to form a check valve to secure it to the well casing. <IMAGE>

Description

SPECIFICATION Fluid pump The present invention relates to fluid pumps of the type which includes a piston arranged to be reciprocated in a cylinder by means of a piston rod.

Many existing pumping installations, especially in developing countries, are notoriously unreliable and most imported hand pumps or small power pumps, originally designed for discontinuous use in single family households in developed countries, breakdown after few months of continuous use in villages of developing countries. It has been observed that the original hardware is often inappropriate and hard to maintain; spare parts and tools to maintain the pumps are either missing or too costly and there is a lack of local institutions or business of willing or capable of servicing these pumps. A further problem is cost: power pump installations are expensive and require sophisticated support services.

It is an object of the present invention to provide a simple and reliable pumping system, especially designed for complete fabrication in developing countries; which can be produced at a cost which will enable such countries to expand rapidly the availability of safe drinking water supplies on a large scale.

This object is achieved by providing a pump which can be installed, operated and serviced by rural residents in developing countries and others and which can overcome the problems often experienced with traditional hand pumps or'open wells.

The present invention concerns a pump that, contrary to the expensive conventional design with metal well casing, uses a plastic well casing or plastic lined metal casing which acts as the pump cylinder itself. The provision of a plastic pipe for a well casing results in smooth walls, thus vastly reducing friction between pipe and piston and allowing pumping with minimal physical efforts or other forms of energy supply. Such construction lessens wear on piston rings which is a prime cause of pump failure. Another advantage of the plastic pump is that there is no chemical reaction between the pump and the water or ground, making it pollution-free.Further, in addition to being less expensive that other types of pumps, most components of the present system can be readily available in developing countries where plastic pipes, such as pipes made of polyvinyl chloride, can be produced. Furthermore, a pump made of plastic as in the present invention is light and its components can be shipped easily and economically to remote locations.

The present invention is also concerned with providing an improved design for a piston and a check valve for use with a plastic well or plastic lined metal casing. These components are made of plaStic thus allowing for maximum hydraulic efficiency, minimum drag and wear through friction, while allowing for mass production at low cost.

The present invention is therefore directed to a device which can be used interchangeably as a piston and/or a check valve in a cylindrical well casing made of plastic material; the deive comprises: a cylindrical body made of plastic material, including a top wall, a side wall and an opened base; aperture means in the top wall; peripheral groove means in the side wall; the body including upper and lower inner cavities defining a hollow lower chamber and a plurality of constricted upper chambers; a coupling rod, made of plastic material, integrally mounted to the body and extending axially with respect to the wall casing; a plate valve axially and freely mounted about the coupling rod and adapted to cover the aperture means when resting on the top wall; sealing means, made of plastic material, mounted to the body providing sealing and sliding contact with the internal wall of the well casing.

This device can be used as a piston or a check valve as both components are basically identical. When the device is used as a piston, in one preferred embodiment of the invention, the groove means comprise a pair of vertically spaced recesses, in at least one of which is received a correspondingly shaped ring of plastic material therein. When the device is used as a check valve, the lower recess engagedly receives an adapter which will allow the check valve to be pushed downward into the well casing but which will prevent it from moving upwards when the pump is actuated and seals peripherally.

Other objects and statements of the invention will become apparent from the detailed description given hereinafter; however, it should be understood that this description while indicating preferred embodiments of the invention, is given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art in reading this description.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of a well using a pump made in accordance with the present invention; Figure 2 is a cross-sectional view of a piston used with the pump made in accordance with the present invention; Figure 3 is a cross-sectional view taken along lines 3-3 of Fig. 2; Figure 4 is an exploded view, partly crosssectional, of a chech valve used in a pump made in accordance with the present invention; and Figure 5 is an enlarged sectonal view showing another embodiment of a check valve.

DESCRIPTION OF PREFERRED EMBODI MENTS Referring to Fig. 1, there is shown a pumping system using the present invention; it shows a brick pylon 10, mounted on a con crete base 2 and equipped with a handle 14 and a spout 16. A cylindrical well casing 18 extends into a drilled borehole 20; the well may also be hand-dug. A pump rod 22 extends axially in the casing 1 8 and connects a piston 26 to the handle 1 4. A well screen 24 is provided at the bottom of the borehole while a check valve 28 is provided at the bottom of casing 18.

A portion of the casing 1 8 functions as a pump cylinder and at least that portion has a smooth internal surface to minimize wear.

Most widely used thermoplastics for pipe production are rigid polyvinyl chloride, polyethylene and ABS. The advantage of a polyvinyl chloride pipe is that it can be easily joined in the field without special tooling or skill and also because the current state of commercial practice is such that a polyvinyl chloride pipe is generally freer of ovality.

Since the pipe is to be used for the supply of potable water, it should not contain material which are potentially injurious to health.

In particular, lead stablizers which are widely used in the polyvinyl chloride compounds are entirely unacceptable. The plastic material should be absent of toxic ingredients or coverings.

The pump rod 22 should preferably be buoyant enough to neutralize its own weight in water. This has the advantage that if the rod inadvertedly falls into the well, it can be retrieved easily because if floats. A pump rod of polyvinyl chloride has many advantages over alternative wooden or metal rods. It is light and easy to transport; it is not subject to corrosion and does not swell or rot. It is not attacked by micro organisms and is sufficiently strong to activate the pump piston.

The well screen 24 is preferably a slotted polyvinyl chloride member which is inserted in the bottom of the borehole 20 to provide influx of clean water to the displacement pump. This screen acts as a filter and may be provided in various sizes.

An important feature of the present invention, is that piston 26 and check valve 28, which are submerged in casing 18, are identically shaped. Referring to Figs. 2 and 4, respectively showing a piston and a check valve, each component includes basically a cylindrical body 30 including a top wall 32, a side wall 34 and an opened base 36. Each body 36 includes upper and lower cavities defining a hollow lower chamber 38 and a plurality of constricted upper chambers 39. In the embodiment shown, there are three chambers 39, each of which gradually reduces in cross-section area from the lower chamber 38 to a respective aperture 40 on the top wall of the body. The upper part of the body includes a central conical portion 42 so as to allow a coupling rod 44 extending up from the top wall to form an integral part therewith, thus providing a unitary and homogeneous structure.

Coaxially mounted to the rod 44 is a plate valve 46, preferably made of polyvinyl chloride, which is adapted to reciprocate along the rod in the two positions shown in Fig. 2. The plate valve has an outer diameter or shape to' close aperatures 40 on the top wall of the body when the plate valve rests on the top wall; a pin 48 on the rod limits the upward movement of the plate valve 46. This pin may be fixed at an angle to the axis of the coupling rod allowing plate valve 46 to be tilted in the casing for increase flow area around the plate valve. the upper portion of the rod 44 has a tapered porton 50 to facilitate connection to the pump rod 22 and to compensate dimension tolerances. The taper section 50 allows the use of a variety of inner diameters of pump rods.The material of pump rod 22 should be compatible with that of rod 4,4 if both are glued together. In one variant of the present invention, the lower edge of the pump rod 22, once installed on the coupling rod 44, may also serve as a stop for limiting the upwards movement of the plate valve, in which case a pin 48 would not be required.

The outer side wall 34 of cylindrical body 30 has two peripheral grooves 52,54 vertically spaced from one another and of varying width, upper groove 52 being larger than lower groove 54. In Fig. 2, where the body is to be used as a piston, a pair of rings 56,58 are respectively mounted in grooves 52,54.

These rings are split to provide easy installation to a groove and to adjust to a pipe diameter. These rings allow for any ovality in the structure of the internal wall of the cylindrical well casing by self-rotation in the opti mum location by a play of forces acting thereon. Hence, the rings provide sealing and sliding contact with the internal wall of the casing. The rings are made of polyethylene.

This material is preferred because of its rela- tively low coefficient of friction with polyvinyl chloride. This reduces the pumping force required. In cases where only one ring should be used, ring 58 is omitted.

In Fig. 4, where the device is to be used as a check valve, groove 54 serves to engagedly connect an adapter 60 which itself has an internal groove 62 into which fits the lower extremity 64 of body 30. The adapter is made of polyethylene and its connection to body is by a snap-on engagement. The outer lower edge of adapter 60 has a peripheral sealing skirt 66 which engages and slides on the internal wall of the well casing when the check valve is positioned int the casing. How ever, the particular shape of the skirt prevents any upward movement of the check valve in the casing during pumping. Since the check valve is made of plastic and is inexpensive, should it be required to replace the check valve, the latter is simply pushed down into the borehole and another check valve is in serted as a replacement. Ring 56 may or may not be used with the check valve.

In the design of the present invention, the piston and the check valve remain below the surface of water in the well; this means that the piston rings are always wet and thus water lubricated. The particular shape of the inner chambers allows improved flow characteristics, reducing turbulence and providing less restriction during reloading; also, there is minimum back pressure.

It has been said above that wear is negligeable between the piston rings and the pipe casing when a polyvinyl chloride casing and polyethylene rings are used. Even if wear should unexpectedly occur, it is a simple operation to shorten the piston rod, so that the piston rings travel on an unworn section of the well casing.

In the embodiment illustrated in Fig. 5, an O-ring 68 is provided between body 30 and adapter 60 to further sealing purposes.

The pump of the present invention operates on a very simple principle: on the downstroke, water pressure forces the pipe valve in the piston to open and the identical plate valve in the check valve to close; on the upstroke, the configuration is reversed in that the piston valve closes, water is drawn into the pipe casing through the opened check valve and is lifted a distance equal to the length of the stroke. With repeated strokes, water eventu ally reaches the collar of the well where it remains thereafter for easy hand or power pumping.

The piston and check valve of the present invention, can be removed for inspection and rapair by one person only. In contrast conventional hand pumps often require at least two persons for inspection and repair. Also, the piston and check valve being made of identical interchangeable components, stocking of spare parts is reduced to a minimum.

Although the present invention is directed to a hand pump and is primarily designed for manually operation, it can be easily under "stood that this pump can be used with animal,-wind, electric or diesel power. Hence, any reference to a hand pump should not be interpreted as being limited.

Claims (14)

1. A piston or check valve for use in a cylindrical well casing, comprising a cylindrical body of plastics material having a top and a side wall, the body defining a lower cavity, open to the bottom of the piston, and upper cavities leading from the lower cavity to aperture means in the top wall, a stem of plastics material integral with the body and extending axially of the body, sealing means of plastics material carried by the body for making sealing contact with a well casing and a plate valve member freely mounted on the stem for axial movement into and out of contact with the top wall to respectively close and uncover the aperture means.

2. A piston or valve according to claim 1, and including stop means on the coupling rod for limiting upwards movement of the plate valve member along the coupling rod away from the top wall.

3. A piston or valve according to claim 1 or 2, wherein the upper chambers gradually increase in cross-section from said aperture means on said top wall to said lower chamber.

4. A piston according to any of the preceding claims wherein, said sealing means comprises a pair of piston rings mounted on each of a pair of spaced peripheral grooves in the body.

5. A check valve according to any of claims 1 to 4, wherein said sealing means comprises adapter means mounted to said body adjacent said base, said adapter means having means engaging a peripheral groove in the body.

6. A check valve according to claim 5, wherein said adapter means is made of polyethylene.

7. A check valve according to claim 5 or 6, including a ring in a second peripheral groove above the groove receiving the adapter means.

8. A check valve according to any of claims 5 to 7, wherein said adapter means include skirt means on the outer side wall thereof to engage the inner wall of said well casing to sealingly secure said check valve in said casing.

9. A piston or check valve according to any of the preceding claims wherein said plate valve is made of plastics material.

10. A piston or check valve according to any of the preceding claims wherein said body is made of polyvinyl chloride.

11. A device as defined in claim 4 or 7, wherein said rings are made of polyethylene.

1 2. A pump comprising: a cylindrical well casing made of plastics material, having a smooth inner wall, said well casing having a portion defining a pump cylinder; a pair of identically-shaped cylindrical bodies, made of plastics material, received in said casing, one of said bodies being fixedly mounted in said casing, the other of said bodies being slidable therein above said one body; each said body including: a top wall having aperture means thereon, a side wall having upper and lower groove means therein, and an open base; each said body including upper and lower inner cavities defining a hollow lower chamber terminating at said base and a plurality of upper chambers, leading from said lower chamber to said aperture means; a stem of plastics material, integrally mounted to each top wall of said body and extending axially with respect to said well casing; a plate valve mounted about each said stem for free axial movement thereon and adapted to cover said aperture means of the respective body when resting on said top wall; stop means on each said stem for limiting upward movement of said plate valve along said stem; ring means, made of plastics material, mounted in said groove means of said other body to provide sliding and sealing contact with said inner wall of said casing whereby said other body acts as a piston in said casing and said casing acts as a pump cylider; the stem of said other body, a coupling rod portion, and adapter means mounted to said one body and having means engaging the lower groove means of said one body to sealingly secure said one body against said inner wall of said well casing whereby said one body acts as a ckeck valve in said casing.

1 3. A pump according to claim 12, wherein the lower portion of said adapter means defines an outer skirt contacting said inner wall of said casing, said skirt allowing said one body to slide downward into said well casing but preventing upward movement thereof during pumping.

14. A pump according to claim 12 or 13, further comprising a pump rod, made of buoyant plastic material, attached at one end thereof, to said stem of said outer body.

1 5. A pump according to claim 14, having an operating handle at the upper end of said pump rod.

1 6. A piston substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

1 7. A check valve substantially as hereinbefore described with reference to Figs. 1 and 3 to 5.

1 8. A hand pump substantially as hereinbefore described with reference to the accompanying drawings.