Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF THE INVENTION
i The present invention relates to improvements in
fluid pumps of the type which includes a piston arranged
~ to be reciprocated in a cylinder by some means, usually
- 5 manual, connected to the piston rod.
BACKGROUND OF THE INVENTION
It has been noted that existing pumping instal-
- lations, especially in developing countries, are notori-
ously unreliable and most imported hand pumps or small
~` 10 power pumps, originally designed for discontinuous use
in single family households in developed countries, break-
down 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
15 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 willing or capable of
, servicing these pumps. A further problem is cost; power
` pump installations are expensive and require sophisticated
support services.
; OBJECTS AND STATEMENT OF THE INVENTION
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~'' It is an object of the present invention to
provide a simple and reliable pumping system, especially
;~ designed for complete fabrication in developing countries;
`;~ 25 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.
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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
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; metal casing which acts as the pump cylinder itself. The
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- 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 con-
~ 5 struction lessens wear on piston rings which is a prime
; cause of pumps 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 than other
;- lO 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 minimal cost.
` The present invention is therefore directed to
a device which can be used interchangeably as a piston
' 25 and/or a check valve in a cylindrical well casing made
` of plastic material; the device 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
- 30 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 well 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
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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
~ 5 valve as both components are basically identical. When
- the device is used as a piston, in one preferred embodi-
ment 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
` 25 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
-~ 30 lines 3-3 of Fig. 2;
Figure 4 is an exploded view, partl~v cross-
sectional, of a check valve used in a pump made in
accordance with the present invention; and
Figure 5 is an enlarged sectional view showing
another embodiment of a check valve.
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DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Fig. 1, there is shown a pumping
~;~ system using the present invention; it shows a brick
pylon 10, mounted on a concrete base 12 and e~uipped with
; 5 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 18
and connects a piston 26 to the handle 14. A well screen
24 is provided at the bottom of the borehole while a check
; 10 valve 28 is provided at the bottom of casing 18.
A position of the casing 18 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, poly-
15 ethylene 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
stabilizer which are widely used in the polyvinyl chloride
compounds are entirely unacceptable. The plastic material
- 25 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 it floats.
' 30 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.
- 35 The well screen 24 is preferably a slotted poly-
vinyl chloride member which is inserted in the bottom of
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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 impo~tant feature of the present invention,
is that piston 26 and check valve 28, which are sub-
merged 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 cylindri-
cal 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
~-~ 15 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
p positions shown in Fig. 2. The plate valve has an outer
diameter or shape to close apertures 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 portion 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 44 if both are glued together.
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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 optimum
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 relatively low coefficient of friction with poly-
vinyl 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 into the casing. However, 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
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- and another check valve is inserted 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.
: 10 It has been said above that wear is negligeable
between the piston rings and the pipe casing when a poly-
vinyl 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 e~ual to the length of the stroke. With
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repeated strokes, water eventually 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 repair by
one person onlyO 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.
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. Although the present invention is directed to
a hand pump and is primarily designed for manual operation,
. it can be easily understood that this pump can be used
~- with animal, wind, electric or diesel power. Hence, any
~; 5 reference to a hand pump should not be interpret~d as
`. being limiting.
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