POSITIVE-DISPLACEMENT PUMP

Abstract: A submersible positive-displacement pump comprises a pump housing (10A/10B) having an inlet (11) at its lower portion and an outlet (17-19) at its upper portion, a variable-volume pump chamber (21) which is provided at the lower portion (10A) of the pump housing and communicates with the inlet through an annular passage (29) having a one-way inlet valve (23) and communicating with the outlet through an opening (20) controlled by a one-way outlet valve (30). A displacement member (27) below the pump chamber (21) is connected with a lifting member (28) which extends upwardly from the pump housing and is connected to a driving device. By means of the lifting member the displacement member can be reciprocated vertically for reducing and increasing the volume of the pump chamber. The pump chamber (21) is defined partly by a circumferentially extending pump housing wall (22) and partly by a sealing coolar (23) which bridges the annular passage (29) and one circumferential end of which is movable in the pump chamber towards and away from the pump housing wall (22) in order to open and close the passage under the influence of a pressure differential between the pump chamber (21) and the inlet (11).

Description: Positive-displacement pump This invention relates to a positive-displacement pump and more particularly to a positive-displacement pump, comprising: (I) a submersible pump housing having at the lower portion thereof an inlet for liquid to be pumped, having at the upper portion thereof an outlet for liquid being pumped, and having a variable volume pump chamber communicating with the inlet and the outlet, (II) a pumping mechanism including a displace¬ ment member which is disposed in the pump housing and movable therein, and a driving device by means of which the displace¬ ment member can be actuated to reduce repetitively the volume of the pump chamber and which comprises a lifting member connected with the displacement member, (III) a one-way inlet valve provided between the inlet and the pump chamber, and (IV) a one-way outlet valve provided between the pump chamber and the outlet. Primarily, the pump according to the invention is useful as a submersible pump, i.e. a pump submerged in the body of liquid from which the liquid being pumped is taken and, accordingly, a pump which operates without suction head. For example, the pump may be lowered below the water level in a well, a pond or other water supply or in a tank or other liquid reservoir from which water is to be taken by means of the pump. An object of the invention is to provide a simple and inexpensive submersible positive-displacement pump the pump chamber of which can be filled very rapidly by gravity flow from the surrounding body of water. According to the invention, the pump is primarily characterised in that the inlet communicates with the pump chamber by way of an annular gap between the displacement member and a circumferentially extending pump housing side wall which defines the pump chamber, and in that the one-way inlet valve includes a flexible sealing collar which bridges the annular gap throughout the circumferential extension thereof and one circumferential end of which is sealingly affixed to the pump housing or the sealing member and the other circumferential end of which is movable in the pump chamber towards and away from the said pump housing wall under the influence of a pressure differential between the inlet and the pump chamber. The invention is described in greater detail hereinafter with reference to the accompanying drawings, the two figures of which show an exemplary embodiment of the pump according to the invention in vertical axial section, Fig. 1 showing the pump during filling of the pump chamber and Fig. 2 showing the pump during expulsion of water from the pump chamber. The illustrated pump is adapted for use as a well pump and, more particularly, is intended to be lowered to a posi¬ tion below the water table in a drilled well. The pump comprises a housing which is circular in cross- section and comprised of a base part 10A and a top part 10B secured to the base part. The base part 10A forms a generally cylindrical cage into which water may flow freely (without any significant pressure drop) from the body of water in which the pump is submerged. Openings 11 through which the water enters may be provided with a straining cloth (not shown) or may themselves form strainer apertures in the side wall of the base part. A waist 13 is formed in the upper portion of the base part and retains within it the lower portion of the top part 10B; to this end the lower portion of the top part is provided with a comple ental waist 14. In order that the waist 14 may readi- ly be positioned within the waist 13 of the base part, the last-mentioned waist may be split so that it can readily be expanded. A retaining ring 15 applied after the top part 10B has been mounted secures the top part reliably. The waist 14 of the top part merges upwardly with an intermediate portion 16 which initially widens and then tapers upwardly towards.an outlet throat 17. A riser tube or hose 18 is connected to the latter. Above the waist 14 the interme¬ diate portion 16 defines an outlet chamber 19 which chamber communicates with the base part 10A by way of the central circular opening 20 defined by the waist 14 of the top part. Directly beneath the opening 20 a pump chamber 21 is provided in the pump housing 10A/10B. Laterally or horizontal¬ ly, the pump chamber is defined partly by the inner side 22 of the lower portion of the waist 14 and partly by a sealing collar 23 which forms part of a bowl-shaped body 24 of flexible material and serves as an inlet valve. The bottom wall 25 of the bowl-shaped body 24 is domed and delimits the pump chamber downwardly. As is apparent from the figures, the rotationally sym¬ metrical sealing collar 23, when viewed in axial diametrical section, has an arcuate, outwardly convex contour such that the largest diameter of the collar is about halfway between the upper, free end or rim 23A of the collar and the lower end 23B which merges with the bottom wall 25 and such that the two ends 23A, 23B are of approximately equal diameters. The shape and dimensions of the sealing collar 23 and the properties of the material the collar is made of are chosen and matched such that the collar moves away inwardly from the pump housing wall 22 as soon as the pressure of the liquid surrounding the collar exceeds the pressure within the pump chamber and is moved into sealing engagement with the surrounding pump hous¬ ing wall 22 as soon as the pressure of the liquid within the pump chamber exceeds the pressure outside it. In other words, a very small pressure differential across the collar is suffi¬ cient to open or close the flow passage controlled by the collar. As is appreciated, the material of the collar has to possess such a strength and such a degree of inextensibility that the collar can endure the hydrostatic pressure resulting from the column of water in the riser hose. Some elasticity of the material may be advantageous, but preferably at least the top or free end 23 is extendable only to a small extent. The bowl-shaped body 24, which preferably is made of plastic by blow moulding, vacuum moulding or any other suit¬ able process for making thin-walled plastic articles, is supported by, and preferably is secured to, the upper side of a displacement member in the form of a relatively heavy body 27 which is vertically movable in the base part 10A of the pump housing. This body serves during its upward movement to contract the pump chamber 21, and thereby to displace liquid therein upwardly through the opening 20, and during its down¬ ward movement to cause the pump chamber to expand. The displacement member 27 in turn is supported by a lifting element 28 in the form of a rod or cable extending centrally upwardly through the pump housing 10A/10B, the outlet throat 17 of the pump housing and the riser hose 18 to a driving device D which is not shown in detail. By means of the driving device the lifting element 28 and, accordingly, the displacement member 27 are reciprocated vertically over a certain distance in operation of the pump. Abutments (not shown) may be provided on the pump housing to limit the verti- cal movement in both directions. During its vertical movement the displacement member 27 varies the height, and thereby the flow-through cross-sectional area, of the annular gap 29 which is defined by the displacement member and the pump housing wall 22 and which is bridged by the sealing collar 23. How- ever, the gap 29 is wide enough to permit filling of the pump chamber 21 rapidly and substantially with no pressure drop even when the displacement member is in its uppermost posi¬ tion. In the outlet chamber 19 there is an outlet valve member 30 which is slidably movable along the lifting member 28 and comprises a tubular stem 31 and a valve disc 32 made integral¬ ly with the lower portion of the stem. The valve disc 32 is adapted to be in sealing engagement with the inner side 33 of the upper portion of the waist 14 of the housing part 10B under the influence of the weight of the valve member and the hydrostatic pressure in the outlet chamber 19 when that pressure exceeds the pressure in the pump chamber 21. The valve member 30 may be made of any suitable material, such as plastic, of greater density than water. Operation of the illustrated pump is explained below, it being assumed that the pump is lowered to a position some distance below the water table in a well pipe or well hole B the wall of which is indicated by vertical phantom lines in the drawing. The pump housing is clamped against the wall of the tube or hole at the intermediate portion 16 of the top part 10B of the pump housing under the influence of the hydro¬ static pressure in the pump housing resulting from the column of liquid, in the riser hose 18. To this end, the intermediate portion 16 can be expanded elastically in the radial direc- tion. In order that water may flow relatively freely past the pump between the pump housing and the well pipe or hole the intermediate portion 16 of the pump housing is formed with vertical grooves defining passages which extend between the upper and lower end of the intermediate portion and are always open. Fig. 1 shows the pump in a phase of operation in which the lifting member 28, and thus the displacing member 27 and the bowl-shaped body 24, are near the end point of the downward stroke. Accordingly, the pump chamber 21 approaches its condi¬ tion of maximum volume, but water may still enter the pump chamber through the housing openings 11 and the annular passage 34 between the pump housing wall 22 and the sealing collar 23. The pressure resulting from the overlying column of liquid maintains the valve member 30 in closed position against the valve seat formed by the wall 33. As soon as the lifting member 28 is raised and moves the displacement member 27 upwardly so that the contraction of the pump chamber begins, the sealing collar 23 is pressed outward- ly into sealing engagement with the wall 22 of the pump hous¬ ing. As a consequence of the upward movement of the displace¬ ment member 27 the water in the pump chamber 21 is expelled upwardly through the opening 20 past the valve disc 32 into the outlet chamber 19 whereby a corresponding volume is driven upwardly in the riser hose 18. This is shown in Fig. 2. When the lifting member 28 and the displacement member 27 are then allowed to move downwardly, the valve member 30 again closes against the seat 33 so that the pump chamber 21 is isolated from the hydrostatic pressure in the outlet chamber 19. The water around the pump housing 10A/10B can therefore displace the upper portion of the sealing collar 23 inwardly and flow through the annular passage 34 into the pump chamber 21 with substantially no pressure drop (see Fig. 1) . Because of its annular configuration, and because the surface area of the sealing collar 23 acted on by the inward water pressure is large, the passage 34 opens over a very large flow-through cross-sectional area. Since, in addition, the flow path of the water is very short, the pump chamber 21 is filled very rapidly; for practical purposes the filling time may always be taken as equal to the time the displacement member requires for its downward stroke. In practice, the pump can therefore always operate without filling problems at the rate at which the driving device is capable of moving the lifting member and the displacement member. Because the hori¬ zontal cross-sectional area of the pump chamber 21 can be nearly as large as the interior cross-sectional area of the base part 10A of the pump housing, the stroke volume may be large even when the stroke length is short. In the illustrated embodiment, the pump housing wall 22 serves as a stationary valve seat which coacts with the reci¬ procating sealing collar 23. This arrangement is normally preferred, but it is possible within the scope of the inven¬ tion to affix the sealing collar 23 to the pump housing wall 22 and arrange for its lower annular end 23B to coact with the displacement member 27 which then serves as a movable valve seat. Naturally, other modifications are also possible within the scope of the invention. During inoperative periods of the pump, water may slowly leak between the valve member 30 and the lifting member 28 under the influence of the hydrostatic pressure resulting from the column of water in the riser hose 18. This leakage is not sufficient, however, to increase the pressure within the pump chamber 21 and thereby cause the sealing collar 23 to engage the pump housing wall 22. Instead, the leaking water may flow past the sealing collar into the body of water around the pump. The water column in the riser hose 18 may therefore sink slowly so that the pressure in the outlet chamber 19 is equa¬ lised and the clamping of the intermediate portion 16 against the wall of the well tube or well hole gradually disappears.

Claims: Claims 1. A positive-displacement pump, comprising a submersible pump housing having at the lower portion thereof an inlet (11) for liquid to be pumped, having at the upper portion thereof an outlet (17) for liquid being pumped, and having a variable volume pump chamber (21) communicating with the inlet and the outlet, a pumping mechanism including a displacement member (27) which is disposed in the pump housing and movable therein, and a driving device by means of which the displacement member can be actuated to reduce repetitively the volume of the pump chamber and which comprises a lifting member (28) connected with the displacement member, a one-way inlet valve (23) provided between the inlet (11) and the pump chamber (21) , and a one-way outlet valve (30) provided between the pump chamber (21) and the outlet, characterised in that the inlet (11) communicates with the pump chamber by way of an annular gap (29) between the displacement member (27) and a circumferentially extending wall (22) of the pump hous¬ ing (10A/10B) which surrounds the displacement member and defines the pump chamber (21) , and the one-way inlet valve includes a flexible sealing collar (23) which bridges the annular gap (29) throughout the circum¬ ferential extension thereof and one end (23B) of which is sealingly affixed to one of the pump housing (10A/10B) and the displacement member (27) and the other end (23A) of which is movable in the pump chamber (21) under the influence of a pressure differential between the inlet (11) and the pump chamber (21) . 2. A pump according to claim 1, characterised in that the pump chamber (21) is delimited downwardly by a wall (25) which is formed by or disposed on the displacement member (27) and with which said one end of the sealing collar is joined, the sealing collar (23) and the wall (25) preferably being inte¬ gral. 3. A pump according to claim 1 or 2, characterised in that the sealing collar (23) as seen in axial diametrical section has an arcuate, outwardly convex contour, its largest diameter being at a position intermediate the circumferential ends (23A,23B) thereof. 4. A pump according to claim 2 or claims 2 and 3, charac- terised in that said wall (22) of the pump housing forms a side wall of an upwardly tapering space (21) in the pump housing and in that the sealing collar (23) is adapted under the influence of pressure in the pump chamber (21) to engage sealingly the inside of the wall (22) at that space. 5. A pump according to claim 4, characterised in that the upwardly tapering space (21) merges upwardly, by way of a circular opening (20) , with an outlet chamber (19) provided in the pump housing (10A/10B) and forming part of the outlet, and in that the one-way outlet valve comprises a vertically mov- able valve member (30) disposed in the outlet chamber and a valve seat (33) which is provided at the transition between said tapering space and the outlet chamber and surrounds the opening. 6. A pump according to claim 5, characterised in that the valve member (28) is slidably guided on the lifting member (28). 7. A pump according to claim 5 or 6, characterised in that the outlet chamber (19) is elastically expandable hori¬ zontally.

Inventors: LUNDBAECK STIG, LUNDBAECK, STIG
Applicants: LUNDBAECK STIG, LUNDBAECK, STIG
Application year: 1990
Main classification: F04B47
IPC codes: F04B43, F04B47