NO157875B

NO157875B - HYDRAULIC PUMP PUMP FOR PUMPING UP OF FLUID.

Info

Publication number: NO157875B
Application number: NO85854946A
Authority: NO
Inventors: Evald Isaksson
Original assignee: Evald Isaksson
Priority date: 1984-04-09
Filing date: 1985-12-09
Publication date: 1988-02-22
Also published as: EP0179793B1; SE8401969D0; DK564285D0; DE3561110D1; NO157875C; EP0179793A1; WO1985004691A1; DK564285A; SE439807B; NO854946L

Description

Den foreliggende oppfinnelse vedrører en hydraulisk stempelpumpe for oppumping av av væske, innbefattende såvel en første pumpedel, som nedenfor betegnes som den nedsenkede pumpedel, beregnet på å senkes ned i væsken, som en andre pumpedel, som nedenfor betegnes drivpumpedelen, beregnet på å drive den nedsenkede pumpedel, idet den nedsenkede pumpedel via en ledning kommuniserer med et i drivpumpedelen anordnet sylinderkammer, som er utstyrt med en ventil som er beregnet på å åpne en forbindelse mellom sylinderkammeret og et avtapningssted på stempelpumpen, idet drivpumpedelen er anordnet til ved en drivfase, ved hjelp av et drivstempel å mate en mengde av væsken fra sylinderkammeret ned gjennom nevnte ledning til den nedsenkede pumpedel, og idet den nedsenkede pumpedel er anordnet til i løpet av en pumpefase, ved hjelp av et arbeidsstempel å mate den væske som skal pumpes opp i motsatt retning opp gjennom nevnte ledning. The present invention relates to a hydraulic piston pump for pumping up liquid, including both a first pump part, which is referred to below as the submerged pump part, intended to be lowered into the liquid, and a second pump part, which is referred to below as the drive pump part, intended to drive it submerged pump part, the submerged pump part communicating via a line with a cylinder chamber arranged in the drive pump part, which is equipped with a valve intended to open a connection between the cylinder chamber and a draining point on the piston pump, the drive pump part being arranged for at a drive phase, at using a drive piston to feed a quantity of the liquid from the cylinder chamber down through said line to the submerged pump part, and as the submerged pump part is arranged during a pumping phase, using a working piston to feed the liquid to be pumped up in the opposite direction direction up through said wire.

Slike kjente pumper, se f.eks. SE patent 7903469-0, kan utformes med en bøyelig slange som forbindelse mellom den nedsenkede pumpedel og sylinderkammeret i drivpumpedelen. Væske-søylen i slangen utnyttes derved som "pumpestang". Drivpumpedelens drivstempel presser væsken nedover i slangen, idet væske-trykket påvirker hovedstempelet i den nedsenkede pumpedel. Such known pumps, see e.g. SEE patent 7903469-0, can be designed with a flexible hose as a connection between the submerged pump part and the cylinder chamber in the drive pump part. The liquid column in the hose is thereby used as a "pump rod". The drive pump part's drive piston pushes the liquid down the hose, as the liquid pressure affects the main piston in the submerged pump part.

Når trykket fra drivstempelet opphører, trykkes væsken opp gjennom slangen ved hjelp av hovedstempelet. When the pressure from the drive piston ceases, the liquid is pushed up through the hose by means of the main piston.

De kjente pumper har imidlertid flere ulemper. Blant annet gir de ofte en langsom væskeoppumping pga. at drivpumpedelens drivstempel bremser væskestrømmen i pumperetningen. Kjente utførelser av drivpumpedelens drivstempel gir heller ikke optimal tetning av stempelets ventil, da en forbedret tetningsfunksjon ytterligere ville bremse pumpeslaget. However, the known pumps have several disadvantages. Among other things, they often provide a slow fluid pumping due to that the drive pump part's drive piston slows down the liquid flow in the pump direction. Known designs of the drive pump part's drive piston also do not provide optimal sealing of the piston's valve, as an improved sealing function would further slow down the pump stroke.

Formålet med den foreliggende oppfinnelse er derfor å tilveiebringe en hydraulisk stempelpumpe av den innledningsvis angitte type, hvor ovennevnte ulemper er unngått. The purpose of the present invention is therefore to provide a hydraulic piston pump of the type indicated at the outset, where the above-mentioned disadvantages are avoided.

Dette formål oppnås ved at stempelpumpen ifølge oppfinnelsen er utformet med de i patentkrav 1 angitte trekk. This purpose is achieved by the piston pump according to the invention being designed with the features specified in patent claim 1.

Ytterligere fordeler ved oppfinnelsen fremgår av den følgende beskrivelse samt av underkravene, som angir videre- Further advantages of the invention appear from the following description as well as from the sub-claims, which state further

utviklinger av oppfinnelsen. developments of the invention.

Oppfinnelsen skal beskrives nærmere nedenfor under hen-visning til den vedlagte tegning som viser en foretrukket ut-førelsesform for oppfinnelsen. Fig. 1 og 2 viser en første, henholdsvis en andre funksjonsstilling ved en drivpumpedel ifølge oppfinnelsen. Fig. 3, 4 og 5 viser en første, andre henholdsvis tredje funksjonsstilling for den pumpedel ifølge oppfinnelsen som er beregnet på å nedsenkes i væsken. The invention shall be described in more detail below with reference to the attached drawing which shows a preferred embodiment of the invention. Fig. 1 and 2 show a first, respectively a second functional position of a drive pump part according to the invention. Fig. 3, 4 and 5 show a first, second and third functional position for the pump part according to the invention which is intended to be immersed in the liquid.

Stempelpumpen ifølge oppfinnelsen innbefatter såvel en første pumpedel 1 beregnet på å nedsenkes på det lavere nivå, fra hvilket væsken skal pumpes opp, som en drivpumpedel 2 som er beliggende på det høyere nivå, vanligvis over jord, dit væsken skal pumpes opp.. Delene 1 og 2 kommuniserer med hverandre ved hjelp av en ledning, som kan være utformet som et rør eller som i det viste utførelseseksempel i form av en bøyelig slange 3 . The piston pump according to the invention includes both a first pump part 1 intended to be submerged at the lower level, from which the liquid is to be pumped up, and a drive pump part 2 which is located at the higher level, usually above ground, where the liquid is to be pumped up.. The parts 1 and 2 communicate with each other by means of a line, which can be designed as a pipe or, as in the embodiment shown, in the form of a flexible hose 3 .

Drivpumpedelen 2, se fig. 1 og 2, innbefatter et på en bunnplate 4 montert pumpehus 5, som er utstyrt med et avtapningssted i form av et rør 6. Slangen 3 munner i et vertikalt sylinderkammer 7 i en på bunnplaten 4 montert sylinder 8. Et hult, hylseformet første stempel 9 er forskyvbart i sylinderkammeret 7. Stempelet 9 er avtettet mot veggen i sylinderkammeret 7 ved hjelp av en tetningsring 10, f.eks. en O-ring, Drive pump part 2, see fig. 1 and 2, includes a pump housing 5 mounted on a base plate 4, which is equipped with a drain point in the form of a tube 6. The hose 3 opens into a vertical cylinder chamber 7 in a cylinder 8 mounted on the base plate 4. A hollow, sleeve-shaped first piston 9 is displaceable in the cylinder chamber 7. The piston 9 is sealed against the wall in the cylinder chamber 7 by means of a sealing ring 10, e.g. an O-ring,

som er innført i et spor i veggen til sylinderkammeret 7. which is inserted into a groove in the wall of the cylinder chamber 7.

Innerveggen til det hylseformede stempel 9 danner et vertikalt sylinderkammer 11 for et drivstempel 12. Dette har et utenfor stempelhylsen 9 beliggende sylindrisk hode 13 med større diameter enn sylinderkammeret 11. Hodet 13 er via en skjematisk vist veivstang 14 operativt forbundet med en hylseformet veivaksel 15. Denne er montert på en drivaksel 16, som på ikke vist måte kan drives f.eks. på manuell eller elektrisk måte. Drivakselen 16 er anordnet til ved hjelp av en medbringerknast 17 å kunne ta med veivakselen 15 ved hjelp av en motsvarende knast 18 på veivstangen 15. The inner wall of the sleeve-shaped piston 9 forms a vertical cylinder chamber 11 for a drive piston 12. This has a cylindrical head 13 located outside the piston sleeve 9 with a larger diameter than the cylinder chamber 11. The head 13 is operatively connected to a sleeve-shaped crankshaft 15 via a schematically shown crank rod 14. This is mounted on a drive shaft 16, which can be driven in a manner not shown, e.g. manually or electrically. The drive shaft 16 is arranged to be able to carry the crankshaft 15 with the help of a carrier cam 17 by means of a corresponding cam 18 on the crankshaft 15.

Stempelets 12, nærmest hodet 13 beliggende mantelflate omgis av en tetningsring 19, f.eks. i form av en O-ring. Denne er beregnet på å kunnes tette mot den øvre kant 2 0 på stempelet 9. Kanten 20 er avfaset innover ca. 45°, hvorved tetningsringen 19 av hodet 13 vil bli komprimert både nedover og innover mot stemplenes sentrum, slik at en meget god tetningseffekt oppnås, som er avhengig av hodets 13 trykk mot stempelet 9. The mantle surface of the piston 12, located closest to the head 13, is surrounded by a sealing ring 19, e.g. in the form of an O-ring. This is designed to taper tightly against the upper edge 20 of the piston 9. The edge 20 is chamfered inwards approx. 45°, whereby the sealing ring 19 of the head 13 will be compressed both downwards and inwards towards the center of the pistons, so that a very good sealing effect is achieved, which is dependent on the pressure of the head 13 against the piston 9.

Stempelet 12, som har form av en hul, sylindrisk hylse, har i sin øvre hylsedel, rett under hodet 13 et antall hull eller kanaler 21 for væskepassasje, som er anordnet til å blok-keres henholdsvis frilegges av stempelet 9. The piston 12, which has the form of a hollow, cylindrical sleeve, has in its upper sleeve part, directly below the head 13, a number of holes or channels 21 for liquid passage, which are arranged to be blocked or exposed by the piston 9.

Stempelet 9 har nedentil en bunn i form av en mot stempelet 9 fastskrudd metallskive 22. Denne har et sentralt, gjennomgående hull 23 for en metallisk pinneskrue 24, hvis diameter underskrider hullets 23 diameter, samt et antall kransformet, rundt hullet 23 anordnede, gjennomgående hull 25 for væskepas-sas je . The piston 9 has a bottom in the form of a metal disc 22 screwed against the piston 9. This has a central, through hole 23 for a metallic pin screw 24, whose diameter is smaller than the diameter of the hole 23, as well as a number of wreath-shaped, through holes arranged around the hole 23 25 for liquid passage.

Stempelet 9 danner derved en ventil med mulighet for The piston 9 thereby forms a valve with the possibility of

å åpne en forbindelse mellom sylinderkammeret 7 og avtapningsstedet 6. to open a connection between the cylinder chamber 7 and the drain point 6.

Pinneskruens 24 ene ende er fastgjenget i et gjenget hull i hodet 13. I pinneskruens 24 andre ende er det gjenget på en metallmutter 26. Denne har større diameter enn hullet 23, slik at mutteren 26 kan medbringe skiven 22 og stempelet 9 One end of the stud screw 24 is threaded into a threaded hole in the head 13. A metal nut 26 is threaded into the other end of the stud screw 24. This has a larger diameter than the hole 23, so that the nut 26 can carry the disc 22 and the piston 9

når stempelet 12 har beveget seg oppover en forutinnstilt len-gde, slik det fremgår av fig. 2. when the piston 12 has moved up a preset length, as can be seen from fig. 2.

Mutterens 26 funksjon er tildels å dra stempelhylsen The function of the nut 26 is partly to pull the piston sleeve

9 opp til et forutbestemt arbeidsnivå/slaglengde, tildels å utgjøre en justeringsanordning, ved hjelp av hvilken pumpens kapasitet på enkel måte kan innstilles, da den er avhengig av stempelets slaglengde. 9 up to a predetermined working level/stroke length, partly to constitute an adjustment device, by means of which the pump's capacity can be set in a simple way, as it depends on the stroke length of the piston.

Stempelet 9 med tilhørende komponenter er hensiktsmessig fremstilt av rustfritt stål, men sylinderen 8 og stempelet 12 hensiktsmessig er av et plastmateriale. The piston 9 with associated components is suitably made of stainless steel, but the cylinder 8 and the piston 12 are suitably made of a plastic material.

Tetningsringen 10 virker som en glidetetning ved stempelets 9 bevegelse i sylinderen 8, og gir derfor en viss mot-stand mot bevegelse for stempelet 9. Tetningsringen 19 virker derimot som en slags anslagstetning, dvs. den hindrer ikke bevegelsen for stempelet 12 i forhold til sylinderen 11. En viss klaring kan til og med kunne forekomme mellom stempel 12 og sylinderen 11, slik at stempelet 12 kan bevege seg ubrem- The sealing ring 10 acts as a sliding seal when the piston 9 moves in the cylinder 8, and therefore provides a certain resistance to movement of the piston 9. The sealing ring 19, on the other hand, acts as a kind of impact seal, i.e. it does not prevent the movement of the piston 12 in relation to the cylinder 11. A certain clearance may even occur between the piston 12 and the cylinder 11, so that the piston 12 can move unbraked

set i denne, seen in this,

Den i væsken nedsenkede pumpedel er vist på fig. 3-5. Den innbefatter et pumpehus 27, som oventil kommuniserer med drivpumpedelen 2 via den tidligere nevnte ledning i form av slangen 3. The pump part immersed in the liquid is shown in fig. 3-5. It includes a pump housing 27, which communicates from above with the drive pump part 2 via the previously mentioned line in the form of the hose 3.

Pumpehuset 27, som har form av et vertikalt rør, innbefatter en stasjonær, vertikal sylinder 28 med et hylseformet stempel 29. Denne er avtettet mot sylinderens 28 vegg ved hjelp av en tetningsring 30, f.eks. en V-ring, som er innført i et spor i sylinderens 28 vegg. I det hylseformede stempel 29 beveger seg et hylseformet, som ventil tjenende, hult stempel 31. The pump housing 27, which has the form of a vertical tube, includes a stationary, vertical cylinder 28 with a sleeve-shaped piston 29. This is sealed against the wall of the cylinder 28 by means of a sealing ring 30, e.g. a V-ring, which is inserted into a groove in the cylinder 28 wall. In the sleeve-shaped piston 29, a sleeve-shaped, hollow piston 31 serving as a valve moves.

Rommet over sylinderen 28 danner et trykkammer 32, som sammen med trykket fra væskesøylen i slangen 3 påvirker stempelet 31 via et hode 33 på dets øvre ende. Stemplene 29 og 31 er begrenset bevegelige i forhold til hverandre mot virkningen av en fjær 34, hvis ene ende er festet i stempelet 29 og hvis andre ende er festet i stempelet 31. Mantelflaten til stempelet 31 nærmest hodet 33 omgis av en tetningsring 35, f.eks. i form av en O-ring. Denne er beregnet på å kunne tette mot den øvre kant på stempelet 29, hvilken kant er avfaset på samme måte som kanten 20 på drivpumpedelens stempel 9. The space above the cylinder 28 forms a pressure chamber 32, which together with the pressure from the liquid column in the hose 3 affects the piston 31 via a head 33 on its upper end. The pistons 29 and 31 are limitedly movable in relation to each other against the action of a spring 34, one end of which is fixed in the piston 29 and the other end of which is fixed in the piston 31. The mantle surface of the piston 31 closest to the head 33 is surrounded by a sealing ring 35, f .ex. in the form of an O-ring. This is intended to be able to seal against the upper edge of the piston 29, which edge is chamfered in the same way as the edge 20 of the drive pump part's piston 9.

Stempelet 31 har i sin øvre, hylseformede del, rett under kanten 33 et antall gjennomgående hull 36 (hvorav to er vist) for væskepassasje. Det hylseformede stempel 29 har i sin nedre del et antall gjennomgående hull 37 (hvorav fire er vist) for væskepassasje. The piston 31 has in its upper, sleeve-shaped part, just below the edge 33, a number of through holes 36 (two of which are shown) for liquid passage. The sleeve-shaped piston 29 has in its lower part a number of through holes 37 (of which four are shown) for liquid passage.

Sylinderens 28 vegg har en horisontal kanal 38, som for-binder sylinderens 28 innside med væsken som omgir pumpehuset. Kanalen 38 danner derved en overstrømningsventil, som forhind-rer at stempelet 29 vandrer ned gjennom sylinderen 28 eller at så høyt trykk oppstår at pumpen skades. The wall of the cylinder 28 has a horizontal channel 38, which connects the inside of the cylinder 28 with the liquid that surrounds the pump housing. The channel 38 thereby forms an overflow valve, which prevents the piston 29 from moving down through the cylinder 28 or such a high pressure occurring that the pump is damaged.

Et ytterligere stempel 39, betegnet arbeids- eller hovedstempel ligger an med et oppoverrettet hode 40 mot stempelets 29 nedre kant ved hjelp av en mot stempelets 39 underside vir-kende, sterk fjær 41. Hodet 40 er stivt forbundet med hovedstempelet 39 ved hjelp av en vertikal hals 42, langs hvilken det er forskyvbar en horisontal, sirkulær ventilskive 43. Skiven 43 er beregnet på å åpne henholdsvis lukke et antall (hvorav to er vist) gjennomgående, vertikale væskegjennomstrømnings-kanaler 44 i hovedstempelet 39. A further piston 39, designated working or main piston, rests with an upwardly directed head 40 against the lower edge of the piston 29 by means of a strong spring 41 acting against the underside of the piston 39. The head 40 is rigidly connected to the main piston 39 by means of a vertical neck 42, along which a horizontal, circular valve disk 43 is displaceable. The disk 43 is designed to open and close respectively a number (of which two are shown) continuous, vertical fluid flow channels 44 in the main piston 39.

Fjæren 41 kan forspennes slik at væskesøylens tyngde The spring 41 can be biased so that the weight of the liquid column

i slangen 3 overskrides noe av fjærkraften i pumpens hvilestilling. Da justeringsanordninger for slik forspenning er ålment kjent for fagmannen på området, er slike anordninger ikke vist eller beskrevet her. in hose 3, some of the spring force is exceeded in the pump's rest position. As adjustment devices for such biasing are widely known to those skilled in the art, such devices are not shown or described here.

Stempelpumpen har følgende virkemåte. The piston pump has the following mode of operation.

Når drivstempelet 12 i en drivfase presses nedover av veivstangen 14, se fig. 1, presses væske fra sylinderkammeret 7 nedover i pilenes 45 retning gjennom slangen 3, slik at stempelet 31 i den nedre pumpedel 1 presses nedover ved hjelp av en kraft som er antydet med en pil 46 på fig. 3. Stempelet 29 trykker derved hovedstempelet 39 nedover. Når dette presses nedover, trykker væsken under hovedstempelet 39 opp ventilskiven 43, se fig. 3, slik at væske kan strømme opp gjennom kana-lene 44 i pilenes 47 retning til et rom mellom hovedstempelet 39 og sylinderen 28. When the drive piston 12 is pressed downwards by the crank rod 14 in a drive phase, see fig. 1, liquid is pressed from the cylinder chamber 7 downwards in the direction of the arrows 45 through the hose 3, so that the piston 31 in the lower pump part 1 is pressed downwards by means of a force indicated by an arrow 46 in fig. 3. The piston 29 thereby presses the main piston 39 downwards. When this is pushed down, the liquid under the main piston 39 pushes up the valve disc 43, see fig. 3, so that liquid can flow up through the channels 44 in the direction of the arrows 47 to a space between the main piston 39 and the cylinder 28.

Når stempelet 12 har passert sitt nedre dødpunkt, frikobles det ved at veivakselen 15 frikobles fra drivakselen 16. Stempelets 12 nedoverrettede trykk opphører derved og fjæren 41 kan ved den såkalte pumpefase presse opp stempelet 39, slik at væsken i rommet mellom stempelet 39 og sylinderen 28 delvis presser ned ventilskiven 43, og delvis presses gjennom hullene 37 inn gjennom stempelet 29, ut gjennom hullene 36 When the piston 12 has passed its bottom dead center, it is disengaged by the crankshaft 15 being disengaged from the drive shaft 16. The downward pressure of the piston 12 thereby ceases and the spring 41 can, in the so-called pumping phase, push up the piston 39, so that the liquid in the space between the piston 39 and the cylinder 28 partly presses down the valve disk 43, and partly presses through the holes 37 in through the piston 29, out through the holes 36

i det løftede stempel 31 og opp gjennom slangen 3 i retning av pilene 48, se fig. 4. Deretter passerer væsken i retning av pilene 49 på fig. 2 inn i stemplene 9 og 12, idet stempelet 12 straks løfter ubremset, da det delvis er frikoblet og delvis ikke bremses av noe tetningselement, slik at væsken hurtig kan passere ut gjennom avtapningsstedet 6. in the lifted piston 31 and up through the hose 3 in the direction of the arrows 48, see fig. 4. The liquid then passes in the direction of the arrows 49 in fig. 2 into the pistons 9 and 12, as the piston 12 immediately lifts unbraked, as it is partly disengaged and partly not braked by any sealing element, so that the liquid can quickly pass out through the draining point 6.

Hovedstempelet 39 fortsetter deretter sin bevegelse oppover til anslag mot sylinderen 28, se fig. 5, hvoretter for-løpet gjentas, når stempelet 12 beveger seg nedover, slik at et nedoverrettet trykk, antydet med en pil 50 på fig. 5, igjen virker på stempelet 31. The main piston 39 then continues its upward movement until it abuts against the cylinder 28, see fig. 5, after which the process is repeated, when the piston 12 moves downwards, so that a downward pressure, indicated by an arrow 50 in fig. 5, again works on stamp 31.

Det er åpenbart at den beskrevne stempelpumpe kan modi-fiseres ved å bytte ut tetningsringene med andre, konvensjo-nelle tetningselementer. Videre kan ventilskiven 22 istedetfor å være gjenget fast til stempelet 9 ha samme diameter som stempelet 9, samt være pågjenget på pinneskruen 24 og således er-statte mutteren 26. It is obvious that the described piston pump can be modified by replacing the sealing rings with other, conventional sealing elements. Furthermore, instead of being threaded to the piston 9, the valve disc 22 can have the same diameter as the piston 9, as well as being threaded onto the stud screw 24 and thus replacing the nut 26.

Av beskrivelsen ovenfor fremgår at den beskrevne stempelpumpe har følgende fordeler. From the description above it appears that the described piston pump has the following advantages.

Væske kan effektivt og direkte pumpes opp uavhengig av drivanordningens posisjon, når stempelet 12 har passert sitt nedre dødpunkt, pga. at drivanordningen derved frikobles. Liquid can be efficiently and directly pumped up regardless of the drive device's position, when the piston 12 has passed its bottom dead center, due to that the drive device is thereby disengaged.

En høy og likeverdig effekt oppnås ved hvert pumpeslag/- stempelslag, uavhengig av pumpehastigheten. A high and equal effect is achieved with each pump stroke/piston stroke, regardless of the pump speed.

En meget effektiv tetning kan anordnes mellom stemplene A very effective seal can be arranged between the pistons

9 og 12 samt mellom stempelet 9 og sylinderen 8 uten at dette bremser væskestrømmen i pumperetning. 9 and 12 as well as between the piston 9 and the cylinder 8 without this slowing down the liquid flow in the pump direction.

Pumpens kapasitet kan enkelt innstilles etter væsketil-gangen. The pump's capacity can be easily adjusted according to the liquid supply.

Den nedre pumpedels stempler 29 og 39 må ikke nødvendig-vis være mekanisk forbundet med hverandre. The pistons 29 and 39 of the lower pump part must not necessarily be mechanically connected to each other.

Stempelet 29 kan ikke trykkes ut av sin sylinder 28 pga. overstrømningsventilen 38. Dette medfører også at pumpen ikke kan sprenges pga. et altfor høyt trykk. The piston 29 cannot be pressed out of its cylinder 28 due to the overflow valve 38. This also means that the pump cannot be exploded due to too high a pressure.

Stempelet 31 kan virke som væskedemper, når det stenger pga. at det bremses av trykkammerets 32 tak før stempelet 31 er gått helt opp til sin hvilestilling, idet væskegjennomgan-gen suksessivt minsker. The piston 31 can act as a liquid damper, when it closes due to that it is slowed down by the roof of the pressure chamber 32 before the piston 31 has moved all the way up to its rest position, as the liquid passage successively decreases.

Ventilen 31 kan fremstilles av gummi og derved virke The valve 31 can be made of rubber and thereby work

som mekanisk demper. as a mechanical damper.

Claims

1. Hydraulic piston pump for pumping up liquid, including both a first pump part (1), below referred to as the submerged pump part, intended to be immersed in the liquid, and a second pump part (2), below referred to as the drive pump part, intended to drive the submerged pump part , the submerged pump part communicating via a line (3) with a cylinder chamber (7) arranged in the drive pump part, which is equipped with a valve that can open a connection between the cylinder chamber and a drain point (6) on the piston pump, the drive pump part being arranged to a drive phase (fig. 1) by means of a drive piston (12) to feed a quantity of the liquid from the cylinder chamber down again. nom said line (3) to the submerged pump part, and as the submerged pump part is designed for a pump phase (fig.

2) by means of a working piston (39) to feed the liquid to be pumped up, in the opposite direction up through said line, characterized in that the valve consists of a displaceable hollow piston (9) in the cylinder chamber (7), in which said drive piston (12) is displaceable, and that said connection is constituted by at least one channel (21) in the drive piston (12), which channel has a first end, which communicates with the cylinder chamber (7), and a second end, which communicates with the draining point (6), and that the hollow piston (9) has the ability, by a relative displacement between the pistons (9, 12), to release or block said other end of the channel (21), i.e. to open or close said connection, in that the drive piston (12) under the influence of the liquid fed during the pumping phase for the working piston (39) will be able to be lifted and displaced in relation to the hollow piston (9), so that the other end of the channel (21) is exposed and said connection is opened.

2. Piston pump according to claim 1, characterized by an adjustable stop means (24, 26) for limiting the mutual movement between the pistons (9, 12).

3. Piston pump according to one or more of the preceding requirements, characterized in that the drive piston (12) is arranged to, during a predetermined part of its movement, carry the hollow piston (9).

4. Piston pump according to one or more of the preceding claims, characterized in that the hollow piston (9) is sealed against the wall of the cylinder chamber (7).

5. Piston pump according to one or more of the preceding claims, characterized in that the drive piston (12) seals against the hollow piston (9) only via an annular edge (20) on this.

6. Piston pump according to one or more of the preceding requirements, characterized in that the drive piston (12) is operatively connected to a drive device (16).

7. Piston pump according to claim 6, characterized in that the drive piston (12)'s ability to lift is improved by the drive device being equipped with a release device (17, 18), which is arranged to release the drive piston (12) from the drive device, when the drive piston has achieved maximum stroke length.