FR2465902A1 - MEMBRANE PUMP FOR DETERMINING TWO COMPONENTS OF A MIXTURE AND PUMP ASSEMBLY COMPRISING TWO PUMPS - Google Patents

Abstract

DOSING PUMP 10 WHICH THE BODY 21 INTERNALLY SHAPES A HYDRAULIC TANK 22 CONTAINING AND SUPPLYING TWO PISTON PUMPS 40, 41 WHICH EACH ACTIVATING A DIAPHRAGM PUMP 28 OR 29 IN ORDER TO SUCTION AND DELIVER THE TWO COMPONENTS OF SUITABLE DOSAGE INTO A MIXER ' A MIX. THE CYLINDERS 56, 57 OF THE PISTON PUMPS 40, 41 HAVE HOLES 56.2, 57.3 WHICH MAKE THEM COMMUNICATE WITH THE RESERVOIR 22. ONE OF THEM 56 CAN BE MOVED LONGITUDINALLY BY MEANS OF A CONTROL 59, 60 TO MAKE VARIABLE THE FLOW OF THE CORRESPONDING DIAPHRAGM PUMP 28. THE TRANSMISSION OF THE PUMP 10 MOTOR IS AT VARIABLE SPEED. APPLICATION TO PUMPS INTENDED IN PARTICULAR FOR DELIVERY IN A MIXER OF PROPERLY DOSED PRODUCTS.

Description

The present invention generally relates to diaphragm metering pumps

  and variable flow, and in particular a pump adjustable so as to dispense at will accurately metered quantities of the two components of a fluid mixture.

  Pumps of the above type are commonly used

  dosed to dispense the components of a fluid mixture, for example a paint, a resin, a floor covering, as well as to mix with water small amounts of a concentrated product for example a fertilizer or a herbicide intended to be

sprayed in the fields.

  It is obvious that, because of the variety of uses mentioned above, the pumps in question must satisfy

to many imperatives.

  There are already pumps of the type considered, but their structure obviously limits their possibilities in some cases. As described, for example, in U.S. Patent No. 3,612,727, their metering function is provided by mechanical limitation of the return stroke of their piston, the latter being stopped.

  brutally by a stop that dampens its kinetic energy

  as well as the sets to which it is connected and pressurized oil which moves the pump diaphragm. A cam that makes a revolution first deviates from the stopped piston, then hits it again

  to put it back suddenly in motion. According to the

  this cam and the moment o, during each cycle of operation, it comes into contact with the piston, its repeated shocks against the latter as well as those of the piston against the stop can make strongly vibrate

the pump.

  There are also diaphragm metering pumps

  who aspire and repress only one product and

  attempt a mechanism of another type to vary their flow. For example, the piston of one of these pumps comprises an orifice intended, at the end of the effective stroke of this piston, to suddenly relax the pressurized liquid contained in the cylinder as this orifice passes in front of the end of the piston. a fixed and adjustable rod (see United States Patent No. 3,285,182). U.S. Patent 3,374,750 discloses another pump in which the length of the stroke is varied.

  piston by varying the eccentricity of its transmission.

  The principle of varying this eccentricity and using an expansion of the liquid under pressure to the

  end of the effective stroke of the piston, requires for its

  cation a rather complicated mechanism and the generalization of depressions during the-return stroke of the piston,

  which presents serious difficulties.

  U.S. Patent Nos. 2,578,746, 3,075,468, 3,254,845, and 3,680,981 disclose other types of diaphragm pumps, the operation of which is based on the separation of the pressurized oil that sucks and pushes the piston back and forth and the other liquid that sucks and pushes the diaphragm of the pump. In some cases, the relaxation of the liquid under too much pressure is done in different ways, and it is obviously necessary after this relaxation to fill

the cylinder.

  The present invention thus relates to an improved pump assembly which, driven by a transmission and containing in tandem two diaphragm pumps and a simple control intended to easily vary the flow of at least one of these, is capable of a part to dose very precisely and very often the relative quantities and proportions of the two components of a liquid mixture which it directs to a dispensing nozzle, on the other hand, in normal operation, to maintain under pressure the oil that operates the aforementioned pumps while they flow to the nozzle, and to ensure the relaxation of this hydraulic pressure if these

  pumps suddenly stop debiting.

  This pumping assembly is essentially

  its two tandem diaphragm pumps operated by two independent piston pumps driven by the same transmission, the cylinder of one of the latter being a sleeve that can be moved longitudinally to determine the relative proportions. desired liquids from the diaphragm pumps. This sleeve, well embedded in the single hydraulic tank of the assembly, tank with the contents of which it is in contact externally, is pierced with a filling hole which makes it communicate with this tank, and it contains the piston of the pump in

question.

  This pumping assembly is also characterized by its operating speed which is variable, which makes it possible to vary the flow rate of the two diaphragm pumps, and by a control which makes it possible to vary these flow rates with respect to each other. in order to obtain a correct dosage of each of the two components of the final mixture; by the double threading of the adjustment device of the aforementioned sleeve; by the laminated structure of the diaphragms of its diaphragm pumps, the sheet which is in contact with the pressurized oil being made of "Buna-N" elastomer, while the one on the other side is made of "Teflon" in order to not be damaged by the liquid components of the final mixture; these membranes also form at their periphery and around their central hole beads which fit into complementary grooves of the

  body of the pumping assembly and the stem that is solidified

  diaphragm by its return which can be either a rotary shaft with eccentric, or another transmission capable of making the pistons come and go quickly, by

  example a pneumatic piston engine.

  One of the main advantages of the pumping assembly according to the invention is the precision with which it can vary to a great extent the relative proportions of the components of the final mixture, and this without vibrating undesirably regardless of its speed of operation and the pressures generated. It allows easy and repeated dosing with precision

quantities of liquids pumped.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting examples and in which Figure 1 shows schematically in plan a pump assembly according to the invention; Figure 2 is a longitudinal and vertical section along the line 2-2 of Figure 3; Figure 3 is a longitudinal section along the line 3-3 of Figure 2; Figure 4 is an enlarged section on the line 4-4 of Figure 3; FIG. 5 is a diagrammatic plan view of a variant of the pump assembly according to the invention; and

  Figure 6 shows in elevation and partial-

  another section of the dosing pump

according to the invention.

  In FIG. 1, reference numeral 10 designates

  pumping system according to the invention, together for the purpose of first pushing a mixer 11, then the latter, by a long pipe 12 in a spray tank 13 without air, the two components of the spray mixture , in this case the resin contained in a reservoir 14 and a catalyst contained in a reservoir 15. It is obviously possible to use an additional apparatus between the pump 10 and the mixer 11, for example to

reheat and filter the mixture.

  A motor 16 rotates the driving shaft 20 of the assembly 10 via a transmission to

pulleys 17 and 19 and belt 18.

  As represented in FIGS. 2 and 3, the assembly 10 comprises a body or casing 21 which internally forms a hydraulic reservoir 22. Bearings or bearings 23 and 24 support the shaft 20, including an eccentric section 26 that surrounds a ball bearing 27 is an eccentric 25, the peripheral surface 27a J0 of the outer ring of this bearing 27 making an orbicular movement around the axis of rotation of

the tree 20.

  The pumping assembly 10 contains two pumps

  28 and 29 with diaphragm and two pumps 40 and 41 with piston.

  Both diaphragm pumps 28 and 29 are practically

  identical and their constituents therefore bear the same references. The body of the casing 21 of the assembly 10 internally forms the housings 21.1 and 21.2 of the solid bodies 30 of these pumps. Head screws clamp against the housing 21 of the end covers 31 which immobilize

  in their housing these pump bodies 30.

  The membranes 34 of the pumps 28 and 29 separate from each other their internal compartments, the first 32 is intended to suck and discharge one of the components of the final mixture, while the second 33 is fed with liquid under pressure by one of the pumps

piston mentioned above 40 and 41.

  A rod 35 whose base is clamped against the edge of the central hole of each annular membrane 34 enters a supply line 36 which, provided

  in the pump body 30, communicates its compartment

  33 with one of the piston pumps 40 and 41. The pipe 36 contains a fixed sleeve 35.1 which supports and guides the rod 35 which a support in the form of a cross keeps spaced from the pump body 30. On this rod 35 is threaded a compression spring 37 whose one end is in contact with a shoulder of the body 30, while its other end is in contact with a washer 38 secured by means of a screw to the free end of the rod 35. The annular membranes 34 have a laminated structure, their sheet 34.1 which is on the side of the chamber 33 being made of "neoprene", while their opposite sheet 34.2 is made of a plastics material resistant to the action of chemicals, for example

  of "Mylar" or "Teflon", and more specifically polytechnic

  trafluoréthylène. Each membrane 34 has a peripheral bead 34.4 and a bead 34.3 around its hole

central.

  Its peripheral bead 34.4 fits into a complementary annular groove 30.1 of the pump body 30, while its inner bead 34.3 engages in an annular groove 35.2 formed in the base 35.3 of the rod 35. A disc 39 clamps by means of a screw 39.1 against the base 35.3 of the rod 35 the edge of the hole

central of each membrane 34.

  Fittings 42 and 43, which respectively contain

  44 of the diaphragm pumps 28 and 29 are connected to the compartments 32 of the diaphragm pumps 28 and 29 with supply pipes 46 and 47 respectively connected to the tanks 14 and 15 containing the components of the final mixture. And on the other hand

  the pipes 48 and 49 through which these components reach

blender 11.

  It is the fluid under pressure coming out of

  Piston 40 and 41 which operates diaphragm pumps 28 and 29. The carcasses 50.1 and 51.1 of the pistons and 51 of the pumps 40 and 41 are in contact on the one hand with the peripheral surface 27a of the eccentric 25 and on the other hand with one end of a coil spring 52 or 53 whose other end is in contact with a shoulder of the housing 21 'of these pumps 40 and 41, these springs permanently holding these pistons against the peripheral surface 27a of the eccentric 25. The cylinders 54 and 55 in which the pistons and 51 come and go are sleeves 56 and 57, the second 57, stationary in its housing 21 ', is clamped by the body 30 of the diaphragm pump 29 so as to enter a shoulder 57.1 of this sleeve against a shoulder complementary to this dwelling. This sleeve 57

  is deeply sunk into the hydrau-

  22 whose content is thus in contact with the peripheral surface 57.2 of its deep end. The side wall of this sleeve 57 is pierced with two holes 57.3 which communicate with its internal cylindrical chamber

with this tank 22.

  It should be noted that the spring 53 encloses the

  peripheral surface of the cylindrical sleeve 57.

  The cylinder or sleeve 56 of the pump 40 is also largely depressed in the reservoir 22, and it is pierced with holes 56.2 which make it communicate with this

  internal chamber 54 which it delimits externally.

  surely. It slides exactly and longitudinally in a bore 21.1 of its housing 21 'and its yoke 56.3 forms a longitudinal groove 56. 4 in which protrudes the end of a key 58 which, screwed into the wall of its housing 21', the guide longitudinally

by preventing it from turning.

  The cylinder head 56.3 of the cylinder 56 is prolonged

  by a rod 56.5 which, having a circumferential thread

  56.6, is screwed into a tubular element 59 of a rotary knurled control 60. This element 59 has a peripheral thread 59.1 and is screwed into

  a complementary threaded projection 61 of the housing 21 '.

  The internal and peripheral threads of the

  59 of the order are both entitled to their

  not are different. The diametral pitch of the peri-

  The aforementioned phérique, which has the shape shown, is 18, while that of the internal threads of the element 59 and peripheral of the rod 56.5 is 24. As a result, a consequent rotation of the control 59, 60 does not move longitudinally very little rod 56.5 and the

sleeve of cylinder 56.

  The sleeve 56 is also pierced with large holes

  62 which cause it to communicate via line 36 with the com-

  Part 33 of the neighboring diaphragm pump 28.

  In the housings 21 'of the pumps 40 and 41 are

  formed ducts 63 and 64 for disengaging or

  which allow the pressurized liquid to iron internal chambers 54 and 55 of these pumps in the

  tank 22, for example when the user closes abruptly

  Only the spray tip 13 prevents the components of the final mixture from leaving the compartments 32 of the diaphragm pumps 28 and 29. These ducts 63 and 64

  contain relief valves 65 which are sensitive to

  identical and each comprise a shutter 66 that a spring 67 recalls against its seat 68 to keep the valve closed as the pressure in the chamber

  neighboring 54 or 55 does not exceed a minimum value

  determined. A threaded member 68 screwed into a plug 69,

  itself screwed into a projection 70 of the housing 21 'corres-

  laying, allows to adjust and maintain the tension of the

spring 67.

  A collector annular groove 71 formed in the housing 21 'of the pump 40 all around the

  cylinder 56 and near its orifices 62 makes

  connect its inner chamber 54 on the one hand with the valve that contains the conduit 63, on the other hand with the pipe 36 which feeds the compartment 33 of the pump

  28 to membrane in liquid under pressure.

  The cylinder or sleeve 57 is pierced with similar holes 62.1 which communicate its internal chamber with a collector annular groove 71. 1 of its housing 21 'to allow the underpressure liquid to pass through the conduit 64 by passing through the valve 65

  in case the pressure becomes excessive.

  To operate the pumping assembly se-

  In the invention, its engine 16 is started.

  adjusts pulley 17 at variable speed to

  the shaft 20 between 200 and 1200 rpm approximately. It is possible to vary the flow of the two diaphragm pumps 28 and 29 a great deal by varying the rotational speed of the shaft 20, these two variations being almost directly proportional to one another. It is furthermore possible to vary the flow rate of the diaphragm pump 28 by means of the manual control 59, 60 which moves longitudinally the cylinder or sleeve 56 and by

therefore its holes 56.2.

  When the shaft 20 rotates, its eccentric 25 reciprocates the pistons 50 and 51 of the pumps 40 and 41, these pistons being almost entirely housed in the cantilevered ends of the sleeves or cylinders 56 and

  57, ends protruding into the reservoir 22.

  When the piston 50 sinks into the cylinder 56 from its position shown in Figures 2 and 3, its deep end passes in front of the holes 56.2 of the cylinder by blocking them, and it is only from

  from this moment that his efficient run begins, that is

  that is, it causes the liquid under pressure to escape from the chamber 54 through the holes 62 into the line 36 and from there into the compartment 33 of the pump 28 by displacing the membrane 34 thereof, which

  has the effect of expelling the liquid contained in the

  32 as long as the eccentric 25 pushes the piston 50 into the chamber 54 of the pump 40. As soon as the piston 50 stops then begins to return in the opposite direction under the action of the spring 52, the spring 37 of the pump 28 tends to return its membrane 34 to its rest position at the same time that the liquid from the reservoir 15 refills the compartment 32 of the pump 28. While the piston 50, driven by the eccentric, makes the go and return above, the piston 51 of the pump 41, released by the eccentric 25 and under the action of the spring 53, begins to move towards the middle of the housing 21 thus allowing the spring 37 to

  the pump 29 to draw its membrane 34 into its compartment

  33 and thereby enlarge its other compartment 32 which draws the liquid from the reservoir 14. When the pump assembly is operating normally and its spout 13 is open, the two diaphragm pumps 28 and 29 operate at full flow , the valves 65 remain closed and no liquid flows in the bypass ducts 63 and 64. No flow of pressurized liquid also passes through the holes 57.3 and 56.2 of the sleeves or cylinders 57 and 56, because

  the internal chambers 54 and 55 of these cylinders

  There is no escape of pressurized liquid when the pumps 40 and 41 are operating normally. The small possible losses of liquid under pressure, which result for example from a seepage along the pistons 50 and 51, are compensated in the chambers 54 and 55 of the cylinders

  56 and 57 by the liquid under pressure passing from the reservoir

  see 22 in these cylinders by their holes 56.2 and 57.3

  during each stroke of the pistons 50 and 51.

  The cantilevered depression in the reservoir 22 of a large portion of the cylinders 56 and 57 of the pumps and 41 has many advantages. The filling holes 56.2 and 57.3 of these cylinders are very short because their length corresponds to the thickness of the wall of these cylinders. To fill these it is not necessary to spare in the housing 21 long and sinuous conduits. Removability of the cylinders 56 and 57 simplifies the structure of the piston pumps 40 and 41, so that it is easy to replace these cylinders to maintain them and the pistons they contain, or possibly change their dimensions. The rotary control 59, 60 makes it possible to determine with very great precision the dosage of the components of the final mixture which are pumped by the apparatus. The slightly different steps of the threads 56.6 and 59.1 make it possible to vary the longitudinal position very little. of the sleeve or cylinder 56 by means of a larger rotation of the knob 60 of the control 59, 60. By thus carefully determining the longitudinal position of the cylinder or sleeve 56 by means of this command 59, 60, it is possible to change this setting many times during successive pumping operations. As shown in FIG. 2, the knurled knob 60 of this control and the projection 61 of the casing 21 may comprise peripheral graduations giving this adjustment device the

precision of a vernier.

  The characteristics of some of the pumped liquids may vary from one batch to another or depending on the temperature, and the adjustment of the position of the cylinder 56 makes it possible to determine exactly the quantity of liquid sucked up and discharged by the pump. with membrane.

  It suffices to vary the longitudinal position

  dinal this cylinder 56 and therefore its holes 56.2 to change the moment o the piston 50 mouth the latter, which actually changes the amount of pressurized liquid that enters the compartment 33 of the pump 28 and comes out, If the spout 13 is suddenly closed to stop the two membrane pumps 28 and 29 being pumped out, the pressurized liquid leaving the chambers

  54 and 55 pumps 40 and 41 is no longer able to move

  membranes 34, which immediately has the effect of

  to generate excessive pressure in these chambers and consequently to open the relief valves 65

  which then allow the liquid under pressure to return-

  to the reservoir 22 by the bypass ducts 63 and 64-. The eccentric continues to reciprocate the pistons 50 and 51 which thus drive through these ducts a large part of the pressurized liquid contained in the

rooms 54 and 55.

  As soon as the dispensing spout 13 is reopened, the

  the liquid they contain may leave the compartments

  32 of the diaphragm pumps and the pressurized oil is sucked into the chambers 54 and 55 of the piston pumps by the holes 56.2 and 57.3 of their cylinders, which makes them work again quickly to

  full flow as well as diaphragm pumps 28 and 29.

  To make it possible to vary considerably the overall flow rate of the pump assembly as well as the appropriate dosage of the components of the mixture, it is possible to adjust the pulley 17 that supports the shaft of the motor 16 so as to vary the speed. the tree of the set 10 as well as that of

  the eccentric 25 and piston pumps 40 and 41.

  During operation of the pumps 28 and 29, the central beads 34. 3 and peripheral 34.4 of their membranes prevent any untimely movement of the latter and ensure very well their tightness with respect to the liquids that are on both sides.

contact with them.

  The chemical-resistant sheet 34.2 of each membrane 34 allows the metering pumps 28 and 29 to suck and discharge a very large number of liquids with very different characteristics. This leaflet,

  although thinner than the opposite sheet 34.1 in neo

  prene, resists very well the action of liquids pumped.

  In FIGS. 2 and 3, the peripheral surface 27a of the eccentric 25 directly moves the pistons 50 and 51 which are in the extension of one another as are also the cylinders or sleeves 56 and 57, but it is obvious that the contact between this eccentric and these pistons can be ensured also by

  via a rod connected to the piston in question.

  Moreover, although the pumping assembly 10 shown in FIGS. 1 to 4 comprises only one piston pump 40 with a variable flow rate as a function of the variable longitudinal position of its cylinder or sleeve 56, FIG. a variant 10.1 of the pump assembly according to the invention, which variant comprises two separate pumps 40.1 and 40.2 with piston, both being identical to the pump 40 of FIGS. 1 to 3. Each

  of these pumps 40.1 and 40.2 actuates a corresponding pump.

  28.1 or 28.2 membrane, each of which is identical to that 28 shown in Figures 1 to 4. In Figure 5, the motor 16.1 also comprises a pulley 17.1 that can be adjusted to vary the operating speed of the pumps. It is therefore possible to vary the dosing of the pumped materials by regulating the operation of the piston pumps.

  with their commands 60.1 and 60.2 as above

  described with reference to FIGS. 1 to 4 about the pump

piston.

  Figure 6 shows a variant 10.2 of the

  appears to previous pumping variant which comprises the two piston pumps 40.1 and 40.2 and the two diaphragm pumps 28.1 and 28.2 of Figure 5. In this variant, however, the mechanism that moves the pistons 40.1 and 40.2 back and forth. is a pneumatic motor 75 with piston and double effect. It is of course also possible to make this pneumatic motor 75 cooperate with the piston pumps 40 and 41 and the diaphragm pumps 28 and 29.

figure 1.

  Springs 52 'permanently hold the carcasses 50.1' of the pistons 50 'of the pumps 40.1 and 40.2 against the free ends adjacent to the two rods 76 of a piston 77 which goes back and forth in a cylinder 78. The wall of the latter is pierced of holes 79 and through which enters or exits pressurized air whose regulation is provided by a four-way distributor 81 whose servocontrol members 82 and 83 move the drawer properly. Valves 84, 85 regulate, according to the position of the piston, the pressurized air supply of the servo-control members 82, 83, so as to operate the

  distributor 81 in synchronism with the movement of

  and-coming piston 77 and its rods 76.

  The pneumatic motor can be operated so that the pistons 50 'come and go at the same speed and with the same result as in the

  other embodiments of the invention.

  The housing 21a of the air motor 75 internally forms hydraulic tanks 22.1 in whose contents are immersed the cylinders of the piston pumps and their pistons 50 'and their springs 52'-, in order to feed the internal chambers of these

  cylinders in pressurized liquid as previously described

  1 to 4. It is possible, if desired, to communicate with one another

  aforesaid tanks 22.1 by means of ducts.

  In some cases, it may be advantageous to reduce the flow of one of the piston pumps by reducing the diameter of its piston and correspondingly the

  caliber of its cylinder. To balance the different efforts

  the pneumatic motor, it is then possible to give a stepped conformation to its piston 77 and to its cylinder 78, so that the effective areas of the surfaces on which the compressed air

  exerts its pressure be different.

  In another variant according to the invention, it is possible to enclose the discharge valves 65 in a cartridge or a removable capsule, which allows, without disordering, to extract them from the hydraulic circuit

during its priming.

  From the foregoing, it appears that the invention provides a pumping assembly which, intended to suck and discharge by dosing the two components of a mixture, comprises in tandem two diaphragm pumps and two hydraulic piston pumps which it is possible to move longitudinally the cylinder of one of these last to vary the effective stroke. of his piston and

  therefore the flow rate of the pump corresponding to.

  membrane. It is possible to use this assembly as a simple pump and not as a metering pump of the two components of a mixture, but in most cases it is the latter function that it provides.

  It goes without saying that many modifications can be made to the pumping assembly described

  and shown without departing from the scope of the invention.

Claims (10)

CLAIMS -   1. Hydraulic diaphragm pump, comprising a cartridge   ter (21,21 '); a membrane (34) separating one from the other its two internal compartments, the first (32) is intended to suck and discharge a fluid, while the second (33) is supplied with liquid under pressure by a pipe ( 36) communicating with an internally formed chamber (54)   in this housing (21); and a mechanism (20,25) periodically   and a piston (50) in the chamber (54), the pump being characterized in that the housing defines a reservoir (22) of hydraulic fluid under pressure; a tubular wall (56) of the sleeve-shaped cylinder communicates with this reservoir (22); the inner periphery of the wall (56) surrounds the piston and defines the chamber (54); this wall (56) is pierced with a hole (56.2) in front of which passes   the piston that closes it or releases it so that it alternates   natively pass the liquid under pressure from the tank (22)   in the chamber (54) and vice versa.   2. Pumping assembly characterized in that   comprises a hydraulic diaphragm pump according to the   cation 1, to the casing of which is connected a second pump   (29) whose membrane (34) separates one from the other a compar-   internal pump (32) for sucking and discharging a fluid, and a compartment (33) supplied with pressurized liquid by a conduit connecting the compartment (33) to a second chamber (55) for pumping liquid under pressure, arranged in the housing and containing a second piston (51) that a mechanism (21,25) is reciprocally reciprocated, the wall (56) similar to a sleeve can move in the housing to move its hole (56.2) and change the time o, and the time interval after   which, at each of its races, the piston (50) comes dear this hole.   Pumping assembly according to claim 2, characterized in that the cylindrical wall, similar to a   sleeve comprises a sleeve-shaped shutter (66),   longitudinally moving in the housing and which is pierced with a hole allowing communication with the tank for emptying and filling the pumping compartment, this hole being movable with the sleeve to vary the length of the pumping stroke and the volume of fluid moved by the pump.   Pumping assembly according to claim 3, characterized in that a single rotary variable speed motor assembly (16, 17, 19) leads the two hydraulic piston pumps. (40.41) 0   5. Hydraulic diaphragm pump according to the claim   1, characterized in that the peripheral surface of the   side wall of the cylinder (56) is in contact with the held by the reservoir (22).   6. Hydraulic diaphragm pump according to the claim   5, characterized in that the cylinder (56) and therefore its light (56.2) can be moved at will in parallel   to the stroke of the piston (50) and in that a compression device   Mande (56.5; 60), connected to the cylinder (56) and projecting out of the housing (21), allows to move this cylinder and therefore   to reposition its light (56.2) filling.   7. Pumping assembly according to claim 3, characterized in that a second wall (57) in the form of a sleeve formed in the housing, contains a second piston (51) and defines a second chamber (55) for pumping.   pressurized liquid, this second wall (57) being   pierced by a second hole (57.3) which makes   the chamber (55) with the reservoir (22).   8. Pumping assembly according to claim 7, characterized in that the second wall (57) or the second   cylinder (57) is stationary relative to the housing (21).   9. Pump according to claim 6, characterized in that the control device comprises a rotary control (59; 60) integral with the cylinder (56), screwed into the housing (21) which it partially leaves and which allows to move in the housing (21) the cylinder (56), which is extended by a threaded rod (56.5) screwed into a   element (59) of the rotary control, the complementary   (59.1) of the rotary control and the housing (21) having a pitch different from that of the rod (56.5) and the rotary control.   Pumping assembly according to claim 3,   characterized in that the transmission comprises an eccentric   (26; 27) housed in the reservoir (22) and having a peripheral surface (27a) with which the pistons (50,51)   two hydraulic pumps (40,41) are maintained in con-   tact by two coil springs (52,53) surrounding the sleeve   movable, the ends of the springs respectively taking   support on the housing (21) and on the pistons to make them   wear against the peripheral face of the eccentric.