Field of the invention

The present invention relates to the pumping of ground water for drinking.

Background to the invention

Accessing groundwater through a borehole or well is a common technique used to obtain water for drinking or other purposes. Particularly in semi-arid areas of remote regions this is an important way to obtain drinking water. Also common is the use of a pump in order to transport water present in ground water to the surface.

The present disclosure addresses how to obtain potable water in a reliable manner from a borehole in an isolated environment.

Areas in which water is accessed through a borehole are often rural and remote. Infrastructure relating to the reliable provision of power is often not be available. The use of locally generated power, for example power from a renewable power source such a solar powered source, may play an important aspect. However, renewable power sources are often relatively low power and they typically fluctuate. The present invention seeks to solve this problem. The Apollo-AC Electric Pump from Blackhawk Technology Company is a known pump suitable for pumping liquid from a borehole up to the surface. This known pump has a vertically reciprocating piston with a vertically reciprocating drive rod and a motor located at the surface. Any vertically reciprocating element has to overcome gravity and this is done at the expense of energy.

Summary of the invention

In an aspect the invention relates to a pump system for use in a borehole, the pump system comprising a pumping chamber having a piston configured to reciprocate in a direction substantially perpendicular to the borehole axis. The pump system comprises a renewable power source, or an electrical interface for receiving energy from a renewable power source, to drive said motion of the piston. Typically, the system comprises an electrical motor which drives said motion of the piston. The electrical motor is typically configured to be located down the borehole.

The invention also extends to a pump system for use in a borehole, the pump system comprising a pumping chamber having a piston, and an electrical motor configured to be located down (typically within) the borehole to drive the said motion of the piston. Typically, the pump system comprises a renewable power source or an interface for receiving energy from a renewable power source. Typically, the piston is configured to make a reciprocating motion in a direction substantially perpendicular to the borehole axis.

The invention also extends to a method of pumping subsurface groundwater up through a borehole to above the ground, the method comprising: receiving power above the ground (typically by collecting renewable energy using a renewable energy generator); and transmitting said power down the borehole to drive a pump with a substantially horizontal reciprocating motion, to thereby pump water to the surface level. Typically the pump comprises a pumping chamber having a piston, and an electrical motor down (typically within) the borehole which is powered by the said power. Typically, the piston is configured to reciprocate substantially horizontally.

The motion of the piston relative to (typically within) the pumping chamber pumps water upwards, to the surface, in use, typically through a pipe. The pumping chamber, piston and typically also the electric motor, may be installed in a borehole. The borehole is typically substantially vertical. The borehole typically has an axis. The borehole is typically circular in cross section.

The electrical motor is typically located down the borehole, in use. The electrical motor is typically located within the borehole, in use. The electrical motor may be a submersible motor, that is one capable of operating in an aqueous environment, such as in water.

The pump system typically comprises a housing which retains the pumping chamber and the piston. Typically, the electrical motor is located within or attached to the housing. However, the electrical motor may be located separately to the housing but within the borehole.

Typically, the housing is elongate having a major dimension. The housing may have a longitudinal axis. In use, the housing is fitted within the borehole with its major dimension (and longitudinal axis) parallel to the length of the borehole. Typically, the piston is configured to reciprocate substantially perpendicular to the major dimension of the housing. Thus, where the borehole is vertical, the piston will reciprocate substantially horizontally.

A borehole made to access ground water generally passes vertically down into the Earth. It is not unknown that a borehole needs to be made to a depth of 200m in order to access water. A borehole may even need to be made to a depth of 350m. Typically the pumping chamber is located at least 1m underground. The pumping chamber may be located less than 350m or less than 250m or less than 100m or less than 50m underground.

By configuring a system comprising a piston which makes a reciprocating motion perpendicular to the vertical borehole axis, i.e. a piston which reciprocates backwards and forwards in a horizontal motion, vertical motion of the piston is avoided. Raising a piston vertically requires energy. Even if gravitational potential energy is returned, raising the piston requires a greater force to be exerted than is the case with a piston which reciprocates horizontally in use, leading to greater energy consumption and a requirement for a high power energy source. Energy can therefore be saved, and potentially a lower-power energy supply used, by avoiding vertical piston motion. Substantially perpendicular to the length of the borehole, or the major dimension of the housing, may be at an angle of less than 10° or less than 5° to orthogonal to the length of the borehole. Substantially horizontal may be at angle of less than 10° or less than 5° to horizontal.

The system typically does not include a drive rod which extends from the surface to the housing, particularly one which reciprocates vertically. This may be highly significant, particularly in the case of a deep borehole, for example one of 200 m depth.

The reduction of the energy required to operate an arrangement in which a piston makes a reciprocating motion substantially perpendicular to the borehole axis, renders the pumping arrangement suitable to be powered by a renewable power source, which may be lower power and/or fluctuating. The renewable power source is typically located above ground in use.

The renewable power source may for example be a solar powered generator, a wind powered generator, a geothermal energy powered generator or an anaerobic digester. The renewable power source may have a maximum power of less than 10kW or less than 5kW.

A solar powered power source may be particularly suitable for powering a pump system in an arid or semi-arid environment associated with strong sunlight.

Typically, the renewal power source is a standalone power source which is not connected to an electrical grid. Typically, the pump system is located on land but not connected to an electrical grid.

The electrical motor may drive the reciprocating motion directly, or it may drive the reciprocating motion indirectly.

The pump system may comprise a rotatable shaft, also called a pump shaft. The electrical motor may be coupled to the rotatable shaft. The electrical motor may drive rotation of the rotatable shaft in use. Typically the rotatable shaft has an axis of rotation which is parallel to the borehole. The rotatable shaft may be located within the housing. The rotatable shaft may extend from the motor (within the borehole) into or within the housing. Typically the rotatable shaft has an axis of rotation which is parallel to a major dimension of the housing. The rotatable shaft is typically driven by the electrical motor in use.

The pump system may be configured such that rotation of the pump shaft translates to the reciprocating motion of the piston. The axis of rotation of the pump shaft is generally along the longitudinal axis of the pump shaft. In other words, the axis of rotation of the pump shaft is generally vertical, where there is space.

Typically, there is no pump shaft extending between the surface and the housing.

Actioning reciprocating motion of the piston through rotation of a pump shaft has the effect that the energy required to move the pump shaft is limited to that required for rotational motion. This is generally a significant reduction on the energy required to move the pump shaft in a vertical direction and/or the maximum power required.

The pump system may comprise a converter for converting rotational motion of the pump shaft to translational motion of the piston.

For example, the pump system may comprise a cam, a connecting rod, or a slotted link mechanism, such as a Scotch yoke, to translate rotation of the pump shaft to said reciprocating motion of the piston.

In a cam arrangement an eccentric disk or other suitably shaped element rotating with the pump shaft may be used to provide a translational force to the piston head.

The system may comprise a connecting rod arrangement to translate rotational movement of the pump shaft to translational movement of the piston head. A connecting rod may be attached with rotational freedom at one end to a body, such as a disc, which rotates together with the pump shaft. The other end of the connecting rod may be attached with rotational freedom to the piston.

Typically, the piston comprises a piston head. The piston is typically constrained to a reciprocal piston motion. The motion of the piston head may be constrained by one or more piston guide formations within the housing. The motion of the piston head may be constrained by the pumping chambers. The pumping chamber may be a cylinder within which the piston slides. The motion of the piston head may be constrained to be in a direction perpendicular to the axis of rotation of the pump shaft. In this way, as the pump shaft rotates, the disc rotates with the pump shaft and the connecting rod transmits this movement to the piston head which translates in a reciprocating manner. Thus, the motion of the piston head is constrained to be horizontal in use, in a vertical borehole.

A Scotch yoke, otherwise known as a slotted link mechanism, may provide a means for transmitting and transforming the rotational motion of the pump shaft to a reciprocating motion of the piston head. The system configuration is such that the axis of rotation of the pump shaft generally coincides with the longitudinal axis of the pump shaft. The inclusion of a Scotch yoke arrangement may be associated with the pump shaft comprising an off-axis shaft portion which engages with a sliding yoke attached to the piston shaft. The off-axis shaft portion acts as a shaft slider and resides in a channel of the piston. The shaft slider slides within the channel, which extends horizontally. As the pump shaft rotates, the shaft slider navigates a circular path. The circular navigation of the shaft slider, together with the constraints of the piston cylinder and possibly also by any piston support mechanism on the piston, thereby force the piston into a translational motion, which reciprocates as the shaft slider rotates in a circular fashion. The shaft slider may comprise bearings to reduce friction between the shaft slider and the channel. An increase in efficiency is thereby achieved.

The pump shaft may take the form of a rod. The pump shaft may take the form of a plurality of rods aligned along a single axis. This may be necessary if a continuous rod would interfere with the converter mechanism for converting rotational motion of the pump shaft to translational motion of the piston.

The power source may be arranged to drive a motor configured to drive said motion of the piston. Preferably, configuration of the system is such that the motor drives rotation of the pump shaft. The rotation of the pump shaft then causes the motion of the piston. In this way, the motor drives the motion of the piston via rotation of the pump shaft.

This has the advantage that the motor may be located distant from the piston. This is particularly advantageous if the piston is placed down a borehole, which is an inconvenient location should maintenance of the motor be required. Thus there may be embodiments in which the motor is located at or above ground level in a convenient location for maintenance and the pump shaft extends down the borehole from the motor to the piston.

It may be that the piston head is elongate having a major dimension. It may be that the pumping chamber is elongate having a major dimension. Typically the piston head and pumping chamber are each elongate in the same direction. Typically, the major dimension of the piston head is substantially parallel to the major dimension of the housing. It may be that the major dimension of the pumping chamber is parallel to the major dimension of the housing. Thus, the major dimension of the piston head is typically substantially vertical. Thus, the major dimension of the pumping chamber is typically substantially vertical. The major dimension of the piston head is typically substantially parallel to the axis of rotation of the rotatable shaft. The major dimension of the pumping chamber is typically substantially parallel to the axis of rotation of the rotatable shaft. The major dimension of the piston head may be greater than 50%, greater than 75% or even greater than 100% the maximum diameter of the housing. The major dimension of the pumping chamber may be greater than 50%, greater than 75% or even greater than 100% the maximum diameter of the housing.

Thus pump capacity is maximised within the confined space of a borehole. The stroke volume of the piston within the pumping chamber can be greater than would be the case if the piston head and pumping chamber were not extended along the length of the borehole in this way.

The pump system may comprise a piston head which is rectangular or oval in shape. In this case, the major dimension will typically be the long axis of the rectangle or oval.

A rectangular piston head may offer relative ease of manufacture. A piston head which is oval in shape offers several advantages. A piston head which is oval in shape lacks sharp corners, with the result that there is decreased wear of any seal around the piston head edge and increased seal durability.

The piston head may have a major dimension which is along the length of the borehole axis. The piston head may have a major dimension which is along the length of the housing axis. The piston head may have a major dimension parallel to the length of the pump shaft.

The pump system (e.g. the housing) may comprise at least one piston support. A piston support may take the form of a rod which is attached to the rear side (side opposite the pumping chamber) of the piston and which engages with a corresponding support channel. The corresponding support channel may be mounted on a housing or a housing of the pump. A support channel may comprise guided bearings for bearing, supporting and guiding the piston support rod.

There may be more than one piston support rod, each with a corresponding support channel. Each support channel may comprise guided bearings. For example, there may be four piston support rods arranged around the piston head, and four corresponding support channels each with guided bearings.

A piston support rod attached to the piston, and in an engaged arrangement with a corresponding support channel comprising guided bearings for bearing, supporting and guiding the rod, provides the piston with structural support beyond that of the piston shaft. This has the effect of reducing the mechanical stress within the piston head, the piston head otherwise being responsible for transferring any force from (or to) the piston shaft.

At least one piston support may connect to the piston head in a filleted connection.

A filleted connection between a piston support rod and the piston head further helps to spread the stress burden on the piston head. The fillets distribute the stress over a broader area, reducing stress concentration on the piston head and effectively making the piston head more durable.

The pump system (e.g. the housing) may comprise a biasing means, for example a sprung arrangement, configured to return the piston head after a discharge stroke.

The sprung arrangement configured to return the piston head after a discharge stroke may take the form of a spring or a plurality of springs. The sprung arrangement may exert a force on the piston head which is opposite in direction to the force exerted on the piston head originating from the pump shaft. The sprung arrangement may exert a force on the piston head which is opposite in direction to the force exerted on the piston head originating from the pump shaft and transferred to the piston head through a cam. The cam may be on the pump shaft. Typically, the housing defines the pumping chamber. Typically, the piston reciprocates within or around the pumping chamber. The pumping chamber typically has a cross- section which cooperates with the shape of the piston.

The pump shaft may pass through the housing.

The pump system may comprise a pipe extending along the borehole. The pipe may transport the liquid being pumped, typically water, from a source to the surface. The housing may be configured so that it is connectable to this pipe. The housing may comprise an inlet to which the pipe is connectable (or connected in use) and into which water is intended to pass when being pumped from a water source. The housing may comprise an outlet to which the pipe is connectable (or connected in use) and from which water is intended to pass when being pumped to the surface. Alternatively, the inlet for the water and the outlet for the water may form part of the pipe, which pipe may be configured to be attachable to the housing.

The housing may comprise housing support for the at least one piston support. A housing support may take the form of a channel within which a piston support fits. The channel may be fixedly attached to the housing. Bearings may be provided to facilitate a low friction motion of a piston support within a housing support as the piston reciprocates.

The pump system may comprise at least one bearing supporting rotation of the pump shaft.

The housing may comprise at least one bearing supporting or intended to support rotation of the pump shaft. A bearing may be positioned where the pump shaft traverses an outer wall of the housing. The pump shaft may pass through the housing, in which case the pump shaft may pass through an outer wall of the housing twice. A bearing intended to support rotation of the pump shaft may be present at each position where the pump shaft traverses the housing wall. One of more bearings intended to support rotation of the pump shaft may be present within the housing. Bearings within the housing may be additional to bearings present at the housing walls, or they may be alternative to bearings present at the housing walls.

The piston head may be connected to a connecting rod, which connecting rod drives motion of the piston head. The connecting rod may be filleted. That is, the cross-sectional area of the pump shaft may increase approaching the piston head, reaching a maximum area at the contact surface. A pump shaft which is filleted in this way distributes the stress exerted on the piston head over a larger area effectively increasing durability of the elements.

The pump shaft may be filleted, typically in the vicinity of the off-axis shaft portion. Filleting of the pump shaft strengthens the mechanical structure.

Typically power may be collected at the surface level using a renewable power source. This may typically deliver power in a fluctuating manner. Examples of a fluctuating renewable power source are a solar powered generator, a wind powered generator, and a geothermal energy powered generator.

In addition to the advantages already mentioned above, the system and method of the present disclosure eliminates the requirement for components traditionally found in piston pump systems, such as transmission gears, connecting-rods and stuffing boxes. Furthermore, as the motor can be connected with the piston through a rotating pump shaft, a long drive rod can be avoided. The system and method of the present disclosure are thus well suited to a remote rural environment.

Description of the Drawings

An example embodiment of the present invention will now be illustrated with reference to the following Figures in which:

Figure 1 shows a pump unit comprising a piston and piston chamber attached to the piping. The circumference of the borehole is indicated.

Figure 2 shows the pump system of Figure 1 stripped of components to illustrate a filleted fitting between pump shaft and the Scotch yoke mechanism for transferring motion, as well as bearings supporting the pump shaft.

Figure 3 shows the Scotch yoke mechanism for transferring rotational motion to piston displacement motion. Figure 4 is a view of the rear side of a piston head including the piston cylinder, the yoke, supporting panels and piston supports.

Figure 5 shows the main housing body including the piston cylinder and support channels for the piston supports.

Figure 6 shows a connecting rod mechanism for transferring rotational motion to piston displacement motion.

Figures 7(a), 7(b) each show a cam arrangement for transferring rotational motion to piston displacement. The spring arrangement for returning the piston head after a discharge stroke is also seen.

Detailed Description of an Example Embodiment

Figure 1 is a schematic diagram of an assembled pump unit 1 with front cover 18, main housing body 20 (transparently shown with internal components) and back cover 22.

In this example embodiment, the circumferential lines 2 around the pump unit shows a diameter of 8.98 inches (228 mm) which means that the design is within the 1-inch (25.4 mm) tolerance for a 10-inch (254 mm) borehole size constraint. An arbitrary clearance of 1.5 mm was assumed between the rectangular channel and the housing back cover to accommodate any backward deformation within the piston and the shaft.

The pump unit comprises an inlet 13 at its base and an outlet 16 for water on its top surface. The front cover, inlet and outlet, function as a pipe section which can be integrated into a vertical water pipe within a borehole with the housing body and back cover mounted thereto.

Movement of groundwater from the inlet to the outlet and up to the surface is driven by the motion of piston head 4 which reciprocates in a horizontal direction within piston chamber 5. The reciprocating motion is perpendicular to the vertical axis of the borehole. The orientation of the pump unit and thus the piston within the borehole is determined by the elongate external shape of the pump unit and by the orientation of the outlet which is arranged to couple to a vertical outflow pipe. An advantage of the horizontal direction of movement of the piston is that the piston head can be elongate, parallel to the borehole length, within the pump, resulting in an increase in piston displacement volume with smaller stroke length and slow pump speed. A displacement of 1 litre discharge per stroke may be obtained.

The piston motion is driven by pump shaft 7 which rotates about its axis in use driven by an electric motor 3. In the embodiment example illustrated in Figure 1, the rotation of pump shaft 7 is supported by four shaft bearings 19, one at each end of the housing, and two located within the housing.

In this embodiment illustrated in Figure 1, rotational motion of the pump shaft 7 is transformed to translational reciprocating motion of the piston via a Scotch yoke mechanism. The piston head 4 is fitted to a slider or yoke 8, which can be seen in the Figure 1. The piston, comprising piston head 4, piston stem 36 and fillets 38 reciprocates in a horizontal direction within the piston cavity. A gasket around the piston head seals the piston cavity off from the inside of the housing.

Figure 2 illustrates the pump system of Figure 1 but without several externally visible features, viz. the housing, the piping and the piston chamber. Two internal shaft bearings are each supported by a mount 17 which is fixedly attached to the back cover of the housing 22.

Pump shaft 7 comprises fillets 38 adjacent to the internal bearings 19. These fillets 38 support smooth flow of stresses when load is applied, i.e. when the pump shaft rotates, particularly when it starts to rotate from a stationary situation.

Also visible in Figure 2 are four rods on the rear side (side opposite the pumping chamber) of the piston head 4. These support the piston head 4 and will be described in greater detail below.

Figure 3 shows the embodiment further stripped of features in order to expose the Scotch yoke mechanism (in this figure in combination with a rectangularly shaped piston head). As seen in Figure 3, the slider or yoke 8 is connected to the piston head 4 via a connecting rod 40. Piston stem 36 provide additional support for the piston head 4. As the pump shaft 7 rotates around its own axis, shaft pin 10 traces out a circular path and the shaft pin 10 moves back and forth within the yoke 8, driving motion of the piston 4 in the only available way, i.e. reciprocating horizontal motion, as the shaft pin moves back and forth within the yoke. The shaft pin 10 may comprise bearings to reduce friction with the yoke 8.

Piston supports help to constrain movement of the piston. In Figure 3 the four rods 34 attached to the rear side (side opposite the pumping chamber) of the piston head 4 form part of the piston support. Figure 4 illustrates the piston head 4 (oval shaped) viewed from the rear side (side opposite the pumping chamber) and shows four support rods 34. The yoke 8 of the Scotch yoke is clearly seen, as is the piston stem 36. Fillets 38 on each of the piston shaft and the support rods 34 support bending of the piston head 4 on the application of load.

Each support rod 34 engages with guided bearings present in a support channel 31 which may be fixedly attached to the housing of the pump system. An illustration of the housing is shown in Figure 5. Figure 5 shows the cylinder cavity which is formed from the housing. Also visible are four channels 31 for receiving the support rods 34 attached to the rear side (side opposite the pumping chamber) of the piston head 4. In the illustrated embodiment the channels 31 are fixedly attached to the housing. Each of these channels may comprise a shaft guided bearing to help support and guide with minimum friction the reciprocating motion of the support rod 34. Linear shaft guided bearings are feasible for slow motion with less friction than for crossheads sliding on crossways normally found in a piston pump. For instance, using bearings, the friction is reduced due to lower coefficient of friction compared to sliding i.e. 0.0015 - 0.002 for ball bearings and 0.08 - 0.20 for steel on steel sliding. The allowable linear speed for a linear guided bearing is also high ranging 2 - 5 m/s (compact series), which means that higher revolutions from 752 - 1880 rpm can be achieved (e.g. for a 2-inch stroke). These bearings are also lubricated, sealed and made with corrosion resistant materials.

Figure 6 illustrates a connecting rod mechanism 40, this being an alternative to the Scotch yoke mechanism for converting rotational motion of the pump shaft to reciprocating translational motion of the piston head 4.

A further mechanism for converting rotational motion of the pump shaft to reciprocating translational motion of the piston head is one based on a cam 25, as illustrated in Figure 7. The cam shaft pushes forward the piston through the in-contact bearing during the piston discharge stroke. The cam mechanism requires springs 28 to pull the piston head 4 back after it has been pushed away by the cam. The reciprocating piston motion is supported by the piston-supports 34 which reciprocate within the support channels 31 containing linear bearings inside. One possible drawback of this cam system over the Scotch yoke particularly is the mismatch of the timing between the shaft rotation during discharge stroke and pulling back of the springs during intake. The deviation in cam shaft rotational speed causes rolling slippage. If the pump speed increases, the timing to pull back the piston could mismatch resulting in the incompletion of the strokes particularly the intake stroke which solely rely on springs’ retraction. If any of the four springs lose retraction force (i.e. show slow retraction or unmatched retraction than other springs set) then again jeopardising the completion of intake stroke plus one side of piston may tilt against the cylinder wall enhancing seal wear. In other words, piston motion is not strongly linked with the shaft motion and relies partially on the springs. Additionally, every forward stroke has to overcome additional initial springs’ excitation force to initiate the discharge, thus consuming additional power. These issues make the cam mechanism a less desirable one, although still usable.

In all embodiments, it is rotation of pump shaft 7 which drives the reciprocating motion of the piston which in turn leads to pumping of groundwater. A motor, typically an electrical motor, rotates the pump shaft. The motor 3 may be positioned on the housing, or near the housing. Such an arrangement is illustrated in Figure 1. Alternatively, the motor may be placed distant from the housing, for example at ground level. The power for the motor is provided by a renewable power source, such as a solar panels. Renewable power sources are typically relatively low power and typically fluctuating. Electrical cabling is typically used to transmit electricity generated by the renewable power source and the motor.

Translation of a vertical pump shaft, including reciprocating translation, requires gravity to be overcome. This is not the case for rotation of a pump shaft around its axis. Energy is thereby saved by rotating a pump shaft along its axis. The energy required to displace the piston horizontally is relatively low and the elongate nature of the piston enables a large stroke volume. Furthermore, the parts of the pump are relatively few in number and can be expected to work reliably for long period of time. Accordingly an efficient pump suitable for use with renewable energy sources in remote areas is provided.

Reference numerals 1 pump unit

2 circumferential lines

3 electric motor

4 piston head

5 piston chamber

7 pump shaft

8 slider/yoke

10 shaft pin

13 inlet

16 outlet

17 bearing support

18 housing front

19 shaft bearings

20 housing mid section

21 housing

22 housing back cover

25 cam

28 biasing means

31 channel

34 support rod

36 supporting panel

38 fillets

40 connecting rod mechanism