GB2057067A - High pressure pump - Google Patents

Abstract

A pump includes a tubular member (46) which preferably is double walled, inside a pressure chamber (44) which is divided into three compartments (52, 54, 56). One end of the tubular member is connected to a source of material and the other end is the discharge end of the pump. The lengths of the tubular member in the first (52) and third (56) compartments function as inlet and outlet valves respectively and the length in the second compartment (54) functions as the displacement member of the pump. The compartments are pressurised by means of an hydraulic fluid in the following cycle: the third compartment (56) is pressurised to close the outlet valve and the source material is moved through the inlet valve (52) into the displacement member (54); the first compartment (52) is pressurised to close the inlet valve and then the second compartment (54) is initially pressurised; the third compartment (56) is depressurised to open the outlet valve and then the second compartment (54) is fully pressurised to collapse the enclosed length of tubular member and so force the material through the discharge end of the pump. The cycle is repeated for continuous pumping. The cycle can be reversed to pump in the opposite direction. Two or more pumps (40, 42) in parallel provide a smoother pumping rate. <IMAGE>

Description

SPECIFICATION High pressure pump This invention relates to a high pressure pump which is suitable for pumping flowable materials such as fluids which may contain a high proportion of solids.

The invention provides a method of pumping a flowable material which includes the steps of introducing some of the material through an inlet into a collapsible container and pressurising the container externally so as to collapse the container at least partially and thereby cause material to be expelled from the container through an outlet.

The container may be pressurised by any suitable means but preferably use is made of a pressurised fluid which may be gaseous or liquid, e.g. water or hydraulic fluid.

In accordance with one form of the invention the container outlet is connected to an outlet conduit through which the material is expelled from the container, the method including the step of placing the container interior in communication with the outlet conduit only when the pressure inside the container exceeds a predetermined level.

Further according to the invention the container inlet is connected to an inlet conduit through which the material is introduced into the container, the method including the step of sealing the container interior from the inlet conduit after introducing the material into the container.

One advantage of the invention lies in the fact that in a preferred embodiment of the invention the entire container is pressurised and consequently there is a minimal pressure differential between the inner and outer surfaces of the container. This enhances the life of the container.

The method of the invention may be carried out at two or more locations, in parallel, with the outlet conduits merging into a common line. The inlet conduits may be connected to separate input lines or to a common input line.

The invention also provides a pump which includes a pressure chamber, a collapsible container inside the chamber, the container including an outlet, and an inlet through which a flowable material is introduced into the container, and means to pressurise the chamber externally of the container so as to collapse the container at least partially and thereby cause material to be expelled from the container through the outlet The pump may include means to seal the inlet when the material is expelled from, and means to seal the outlet when material is introduced into, the container.

The material may be introduced by mechanical means, for example, an auger, or by reducing the pressure in the chamber so that the material is forced in by the resulting differential pressure between the chamber interior and atmosphere. If the collapsible container is elastic or resilient, use may be made of its memory, which causes it to expand when the chamber is depressurised, to draw material from the input line.

The latter example is particularly applicable where the material is a liquid. On the other hand an auger or other mechanical device would be used when the material contains a high proportion of solids.

In a preferred embodiment of the invention the pump includes a flexible member which is located inside the pressure chamber and outside the container so that when the chamber is pressurised a force which collapses the container at least partially is exerted on the container by means of the flexible member.

This embodiment of the invention may advantageously be implemented by forming the flexible member from at least one tubular section and the collapsible container from at least one tubular segment which is located inside the tubular section.

The pump of the invention expels the material intermittently and consequently surges of the material are experienced on the delivery side of the pump. The surges may be compensated for to some extent by operating at least two of the pumps in parallel with the pumps drawing from a common input line and discharging into a common output line, and synchronising the operation of the pumps so that generally while material is being introduced into one pump material is being expelled from another pump.

Thus the pumps are worked alternately, or successively.

When two or more pumps are operated in parallel, discharging into a common outputline, it is by no means essential for the pumps to be connected to a common input line. Thus each pump could be connected to a separate input line.

This arrangement is particularly effective if two or more materials are to be blended or mixed, for each pump could then be used to pump one of the constituent materials and a substantial amount of mixing would take place when the constituent materials flow into the common output line.

Another advantage of the combination lies in the fact that by controlling the extent of collapse of the collapsible containers the proportions of the constituent materials are controlled. The extent of collapse is easily regulated by means of relatively simple valving which enables one to control the quantity of pressure fluid introduced into the pressure chamber during each pumping cycle. The valving may be adjusted as desired either manually or automatically.

Precisely the same technique may be employed for proportioning the rate of flow from a single pump in accordance with any control parameter.

The invention is further described by way of examples with reference to the accompanying drawings in which: Figures 1 to 4 illustrate the principle of operation of a pump according to a first form of the invention, Figure 5 illustrates two pumps according to a second form of the invention which are connected to operate automatically in parallel, and Figures 6 to 8 illustrate in section different methods of construction employed in the pump of the invention.

Figure 1 illustrates a pump according to a first form of the invention, in a condition of non-use.

The pump consists of a metallic tubular casing 10 which forms a pressure chamber, a flexible tube 14 which is made from steel reinforced rubber inside the casing 10, seals 16 and 18 at opposed ends of the casing which connect the tube 14 to the casing 10 in a leak-proof manner, an inlet pipe 20 connected to one end of the tube 14, an outlet pipe 22 connected to the opposing end of the tube 14, and two pinch valves 24 and 26 which act on the tube 14 near its ends respectively, and which are operable externally of the casing 10.

The casing 10 has a pressure fluid port 28 which is connected to a pressure fluid source, not shown, which is used to pressurise the casing 10 externally of the tube 14 with water or another suitable hydraulic fluid.

The inlet pipe 20 may be connected to an auger, not shown, used for transporting material into the tube 14. The auger would be used if the material to be pumped contains a high proportion of solids. The auger may, however, be dispensed with if the material is a liquid which then preferably should be under a slight pressure.

One cycle of operation of the pump of the invention is illustrated in Figures 2 to 4. As shown in Figure 2 the valve 26 is closed to prevent material from the pipe 22 re-entering the tube 14 and the valve 24 is opened so that the auger may feed material through the pipe 20 into the tube 14. When the tube 14 is filled the valve 24 is closed and the volume around the tube is pressurised by pumping pressure fluid through the port 28. The pressure exerted by the fluid on the tube 14 raises the pressure of the material in the tube and, when the pressure inside the tube is equal to the pressure in the pipe 22, the valve 26 is opened. This situation is shown in Figure 3. The pressure in the chamber is increased and the tube 14 is thereby collapsed causing the material in the tube to flow into the pipe 22, as shown in Figure 4. The degree of collapse of the tube 14 controls the pumping rate.The degree of collapse is easily controlled by controlling the maximum pressure in the pressure chamber and consequently it is a relatively simple matter to control the pumping rate.

Once the tube 14 has been collapsed to the requisite degree, the valve 26 is closed, sealing the tube 14 off from the material in the pipe 22.

Fluid is then exhausted from the pressure chamber through the port 28 and once the pressure inside the chamber has dropped to a predetermined level the valve 24 is opened so that the auger can again feed material through the inlet pipe 20 into the tube 14, as shown in Figure 2. The pumping cycle then recommences. Alternatively, the valve 24 may be opened while the chamber is still pressurised and the material is then introduced through the pipe 20 while the fluid is being exhausted through the port 28.

In the preceding description reference is made to an auger which is used to feed material through the pipe 20 into the tube 14. The auger would be used if the material contains a high proportion of solids but it may be dispensed with, depending on the flowability of the material, by creating a reduced pressure in the casing 10 around the tube 14 when the valve 24 is opened. Use is then made of the differential pressure existing between the chamber and the atmosphere and, in effect, the atmosphere is used to drive the material through the pipe 20 into the tube 14.

If the material is a liquid under a slight pressure created, for example, by a pressure head, it would readily flow under gravity action into the tube 14 from the pipe 20. If the tube 14 is resilient the suction effect of its natural expansion when the pressure chamber is depressurised tends to draw material into the tube and this effect may be sufficient to enable a gravity feed to be dispensed with.

When a single pump of the type shown in Figures 1 to 4 is employed the material in the outlet pipe 22 is moved stepwise. To eliminate surging or pulsation in this pipe two or more of the pumps of the invention can be employed in parallel and be arranged so that generally as the tube 14 of one of the pumps is being collapsed the tube 14 of a successive pump is being filled.

By correctly synchronising the pumping action of each pump and by merging the outlets of each of the pumps a substantially smooth flow of material through the common outlet pipe can be achieved. Figure 5 shows a combination for achieving this which employs two pumps 40 and 42 respectively according to a second form of the invention. Each of these pumps has an outer metallic casing 44, a first inner tube 46 of steel reinforced rubber and a second inner tube 48 which is of similar material but which is axially segmented and which is located around the tube 46. Seals 50 inside the casing 44 which are engaged with the segmented tube 48 form three pressure compartments 52, 54 and 56, and 58, 60 and 62, respectively in each pump. The pumps have changeover valves 64, 66, 68 and 70, and pilot valves 72, 74, 76 and 78 connected to them.

The pumps, which are connected on their upstream sides, i.e. the left-hand side in the drawing, to a supply of the material to be pumped, and on their downstream sides, i.e. the right-hand side in the drawing, to a common line, operate as follows: hydraulic fluid flows through the valve 68 into the compartment 52. The compartment 52 is pressurised and the enclosed segment of the tube 48 collapses causing the tube 46 inside the compartment 52 to collapse as well. The tube 46 is sealed thereby. When the pressure inside the compartment reaches a predetermined level the pilot valve 76 is switched, operating the changeover valve 66. Hydraulic fluid then flows into the compartments 54 and 62 and is dumped from the compartments 56 and 60. The lengths of tube inside the compartment 54 are collapsed and the material inside is expelled, moving to the right in the drawing.The compartment 62 is simultaneously pressurised and sealed.

Once the tubes inside the compartment 54 are practically completely flattened the pressure in the compartment 54 builds up and eventually exceeds a level at which the pilot valve 72 is switched. This valve causes operation of the changeover valve 68 and hydraulic fluid is then directed into the compartment 58, eventually collapsing the tube lengths inside the compartment. The increasing pressure in the compartment 58 reaches a level at which the pilot valve 74 is switched and the changeover valve 66 is operated. Consequently fluid is dumped from the compartments 54 and 62, causing the enclosed tubes to be opened, and diverted into the compartments 56 and 60. The increasing pressure in the compartment 60 collapses the enclosed tube lengths, expelling material to the right, through the tube inside the compartment 62.Similarly, the tube lengths in the compartment 56 are collapsed, sealing the tube lengths in the compartment 54 from the discharge line. As the pressure builds up in the compartment 56 a level is reached at which the changeover valve 64 is operated and fluid is then dumped from the compartment 52 via the valve 64 causing the enclosed tube lengths in the compartment 52 to be opened. Material is then moved into the inner tube length inside the compartment 54.

When the pressure inside the compartment 60 exceeds a predetermined level the pilot valve 78 is switched, causing changeover of the valves 68 and 64. Fluid is again introduced into the compartment 52. Since the valve 64 is closed the compartment 52 is pressurised, and, as before, the pilot valve 76 is switched. Fluid is then admitted into the compartment 54 and drained from the compartment 56.

The pumping cycle then recommences. The operation of the upper pump is identical to that of the lower pump with the valves 70, 74 and 78 being analogous to that of the valves 64, 76 and 72 respectively.

The valves 64 and 70 are also used, i.e. in addition to fluid from the valve 68, to provide auxiliary pressure fluid which is used to pressurise the compartments 52 and 58 respectively.

Consequently, when the valve 68 is switched, removing the main source of pressure fluid from either of the compartments, the enclosed tube lengths are maintained in their collapsed states by the auxiliary pressure fluid.

Another refinement is the use of bypass valves 80 and 82 between the compartments 52 and 54, and 58 and 60, respectively. These valves are used to pre-pressurise the compartments 54 and 60 respectively before the introduction of the main source of pressure fluid from the valve 68.

The pumping rates of the two pumps 40 and 42 are effectively controlled by means of the settings of the pilot valves 78 and 72 respectively.

The pressure of the hydraulic fluid could also be regulated to control the pumping rates. The pumps could be connected to a common input line or a common source of material but if the combination of pumps is to be used for mixing or blending each pump would be connected to a separate line.

A further point is that by reversing the sequence in which the compartments are pressurised pumping takes place. in the reverse direction. This is also the case with the pump of Figures 1 to 4.

Figure 6 illustrates a suitable method of sealing a single flexible tube 100 inside a tubular metal casing 102. A seal formed by means of a piston 104 with a peripheral O-ring seal 106 is located in the casing 102 and locked in position by means of screws, not shown, extending through the wall of the casing. The piston has a tapered hole 108 through which the tube 100 passes. A tapered, segmented collet 110 is bolted to the piston 104 providing a fluid tight seal around the outer surface of the tube adjacent the piston.

Figure 7 illustrates one sealing method employed in the pump of the invention when use is made of a first inner tube 112 and a segmented tube 114 around the tube 112. Adjacent ends of the segmented tube 114 are frictionally engaged with barbed spigots 11 6 of a piston 11 8 which has a peripheral O-ring 120 and which is located in a metal casing 122. The piston is locked in position as before. The sections on either side of the piston form compartments of the type 52 and 54, or 54 and 56, etc. With this sealing method the inner tube 112 passes freely through the pump interior. The use of two tubes has the advantage that the inner tube 112, which is subjected to abrasion, may be removed from the pump when worn without dismantling the seals formed by the pistons.

Figure 8 illustrates a sealing method employed in the pump at its delivery end.

The tube 114 is engaged with a barbed spigot 116 of a piston 11 8. The piston is locked in the metal casing 122 by means of a locking screw 124. A flange 126 is welded on the outer surface of the casing 1 22. The inner tube 112 has its end engaged with spigot 128 of a flange 130. A ring 132 with a tapered hole 134, through which the tube 112 passes, is bolted by means 136 between the flanges 126 and 130.

In use a discharge pipe, not shown, is connected to the flange 130. It is found that this form of construction is particularly effective at providing a fluid tight seal inside the pump. In addition, when the tube 112 is worn it may be easily replaced by loosening the bolts 136 and then withdrawing the flange 130 and the attendant tube 112.

On the supply side of the pump the inner tube 11 2 simply extends outside the casing 122, i.e.

the flange 1 30 is dispensed with, and the tube is engaged directly with a suitable coupling device.

The advantage of the pump of the invention lies in the fact that it is simple yet is able to provide very high pumping pressures relatively inexpensively. The pump when worn is easily repaired. The tubes used for the pump are not subjected to high differential pressures for the mode of operation is such that the pressures inside the tubes are substantially equal to and balanced by the pressures outside the tubes. Thus the pressure differentials are effectively borne by the metallic casing of the pump.

The synchronisation of the pumps of Figure 5 is effected automatically by hydraulic means.

Clearly, the control could be effected by pneumatic, electrical or other suitable means.

Further, use could be made of more than two pumps in parallel. By these means a substantially constant pumping rate may be achieved.

The pump may also be used to pump in either direction and the pumping rate is easily controlled according to requirement.

Claims (12)

1. A method of pumping a flowable material which includes the steps of introducing some of the material through an inlet into a collapsible container and pressurising the container externally so as to collapse the container at least partially and thereby cause material to be expelled from the container through an outlet.

2. A method according to Claim 1 wherein the container outlet is connected to an outlet conduit through which the material is expelled from the container, the method including the step of placing the container interior in com'munication with the outlet conduit only when the pressure inside the container exceeds a predetermined level.

3. A method according to Claim 1 or 2 wherein the container inlet is connected to an inlet conduit through which the material is introduced into the container, the method including the step of sealing the container interior from the inlet conduit after introducing the material into the container.

4. A pump which includes a pressure chamber, a collapsible container inside the chamber, the container including an outlet, and an inlet through which a flowable material is introduced into the container, and means to pressurise the chamber externally of the container so as to collapse the container at least partially and thereby cause material to be expelled from the container through the outlet.

5. A pump according to Claim 4 which includes means to seal the inlet when material is expelled from the container, and means to seal the outlet when material is introduced into the container.

6. A pump according to Claim 4 or 5 which includes a flexible member which is located inside the pressure chamber and outside the container so that when the chamber is pressurised a force which collapses the container at least partially is exerted on the container by means of the flexible member.

7. A pump according to Claim 6 wherein the flexible member comprises at least one tubular section and the collapsible container comprises at least one tubular segment located inside the tubular section.

8. A pump according to any one of Claims 4 to 7 in which the pressurising means includes fluid which is introduced into the pressure chamber under pressure, and, after the container has been collapsed, is exhausted from the pressure chamber.

9. A pump according to any one of Claims 4 to 8 which includes means to control the degree of collapse of the container thereby to regulate the pumping rate of the pump.

10. A combination which comprises at least two pumps, each pump being according to any one of Claims 4 to 9, the material from each pump being expelled into a common line, and means to synchronise the operation of the pumps so that generally while material is being introduced into one pump material is being expelled from another pump.

11. A method of pumping a flowable material substantially as herein described with reference to Figures 1 to 4, or Figure 5, of the accompanying drawings.

12. A pump substantially as herein described with reference to Figures 1 to 4, or Figure 5, modified in accordance with Figure 6, 7 or 8.