FR2465905A1 - ALTERNATIVE DIAPHRAGM PUMP WITH PNEUMATIC CONTROL AND DIRECTION INVERSION MECHANISM FOR ALTERNATIVE PUMP - Google Patents

Abstract

THE INVENTION RELATES TO AN ALTERNATIVE DIAPHRAGM PUMP. ACCORDING TO THE INVENTION, TWO PUMPING DIAPHRAGMS ARE MOUNTED AT THE OPPOSITE ENDS OF A SHAFT ON WHICH A CALIPER WHICH CARRIES SPRINGS 36 MOUNTED AROUND THE AXLES 37. WHEN THE SHAFT CARRIING THE DIAPHRAGMS IS MOVED DUE TO THE TRANSMISSION. OF AIR COMPRESSED FROM A FIRST SIDE OF THE DIAPHRAGM, THE SHAFT MOVES AND, NEAR THE END OF ITS TRAVEL, DRIVES A CALIPER SO MUCH THAT THE SPRINGS 36 ARE QUICKLY RELEASED AND PUSH THE CALIPER WHICH THEN COMMANDS A DISTRIBUTOR WHO REVERSE ENGINE COMPRESSED AIR TRANSMISSION TO DIAPHRAGMS. APPLICATION TO FOOD SYRUP PUMPS.

Description

The present invention relates to a diode pump

  pneumatically operated diaphragm, used in the instal-

  syrup dispensing section, and more specifically it relates to an alternative pump comprising a spring-loaded inversion mechanism for changing the direction of operation of a pump

  alternative at the end of races in opposite directions.

  The diaphragm pumps are used a lot,

  especially for pumping solutions into

  and very viscous materials, and they are used

  under conditions in which the viscosity of the fluid

  pumped, the applied pressure on the suction side of

  the pump and the backpressure applied on the side of the

  may vary when the operating conditions of the pump vary. The speed of these pumps is generally regulated by mounting an adjustable valve in the pipe transmitting air to the pump. However, this arrangement requires that the operation of the pump is constantly observed and that the valve is constantly adjusted according to the variable conditions, otherwise, the speed of the pump could vary significantly depending on the

  Working conditions. For example, if the counter

  pressure exerted on the pump increases or decreases for any reason or if the viscosity of the pumped liquid

  varies, the speed of operation and the quantity of

  pumped per unit of time vary in a similar way.

  ponding. Accordingly, it is highly desirable that the pump be controlled in such a manner that its speed is substantially constant while the conditions vary. In addition, it is essential that the cycle of

  pumping is carried out in its entirety so that the

  pumped be distributed consistently with a concentration

  constant consistency or consistency. For this purpose, the patent

  United States of America No. 4,008,984 suggests the use of

  a device in which springs

  opposing dales are intended to assist the shutter of a

  corresponding valve at the end of the pumping cycle.

  These coil compression springs, having

  identical characteristics when using the system.

  pneumatic system, facilitate the complete execution of the

  First, they are pumped in one direction and cause a positive change of direction when one or other of the springs is fully compressed. Although

  this system constitutes an inversion mechanism for the pom-

  pe double-acting described in the aforementioned patent, it pre-

  feels disadvantages. For example, when for any reason the pressure circuit operates in such a way that back pressure is created or established and prevents pumping before the end of the cycle or

  change the direction of pumping, nothing prevents this inde-

  sirable and the state in which the spring is fully compressed is not reached. So, it is possible that the

  pumping changes meaning, regardless of the presence of.

  compression springs before the end of the cycle, so that

  the yield is reduced if even the operation of

  seems the alternative pump is not prevented himself.

  The invention therefore relates to an alternative diaphragm pump for dispensing a syrup under constant pressure to a beverage dispensing installation.

  concentrated, does not have the aforementioned drawbacks.

  It also relates to an alternative pump with

  effect for pumping syrups in

  concentrated beverage dispensing systems, in which an inversion device changes the direction of operation

  pump at the end of each alternative race.

  It also relates to a diaphragm pump with

  pneumatic control, comprising a special distributor

  characterized by an organ driven by springs and mounted on a common shaft, this member alternately controlling the transmission of a compressed gas to two

diaphragms.

  It also concerns a pneumatic alternative pump

  double-acting technique for dispensing a syrup through a dispensing outlet, such as the system

  inversion of the pumping direction includes a device for in-

  snap-action version that ensures execution

complete pumping races.

  It also relates to a dual-acting pneumatic reciprocating pump comprising an inverting device which includes a distributor, a dispenser actuator and a snap-action spring member and reliably directs the compressed gas to the surface. of one or other of the diaphragms, cyclically.

  It also concerns a pneumatic alternative pump

  diaphragm apparatus comprising an inverting device which allows fluid to be dispensed through either of two diaphragm-delimited chambers formed at

  ends of the pump, in a systematic and regulated manner.

  More specifically, the invention relates in a

  generally a pumping device comprising two diaphragms

  my hoses mounted at the ends of a common tree.

  The outer surface of the diaphragms is in contact with the

  to be distributed by the pumping device, more pre-

  a syrup intended for a distribution installation

  concentrated drink. The chamber delimited in the pump casing has an inner wall in which are

  formed passages intended to transmit to the over-

  faces of the diaphragms of the compressed air introduced into the alternative pump. The air flow is controlled by an inversion slide intended to return the flow of compressed air to the appropriate diaphragm at the end of each stroke of the pump in a cyclic manner. A stirrup or actuator member of the dispenser cooperates with the shaft,

  in the inner chamber of the pump casing, and

  place when moving the tree. The stirrup is made

  in such a way that it cooperates with the distributor

  during the terminal phase of the pumping stroke so that it then controls the distributor and reverses the direction of movement of the pistons of the pump. This inversion device of the pump further comprises a device

  snap action actuator, co-

  with the yoke mounted on the shaft and centered in the inner chamber of the pump housing, the actuator being mounted so that it can pivot

  below the shaft connecting the diaphragms. The distribution

  tor has O-rings placed in a body and arranged with respect to the compressed air passage formed in

  the distributor in such a way that, during the first

  half of the alternative pumping cycle, a combined gas

  award-winning penetrates through the corresponding passages and arrives

  to the air chamber of one of the diaphragms. Yes-

  simultaneously, a passage allows the discharge of the gas discharged by the chamber defined by the remaining diaphragm. During the interaction between the shaft-mounted yoke and the spring-mounted actuator, the connection of the distributor ports that transmit the compressed gas to the diaphragm surfaces is changed at the end of the stroke. pumping so that the pump changes direction. The snap action mechanism prevents the pneumatic reversing device from sticking to the intermediate position. In operation, compressed gas enters through a passage in a dispenser and is directed by another passageway formed in the inner wall of the pump housing to the chamber for containing air and limited by one of the diaphragms, inside the pump. When the diaphragm, acting like a piston,

  repels the syrup from the chamber that it delimits by

  wise, to the distribution exit, the move

  the shaft also causes the displacement of the

  diaphragm remaining in a direction that corresponds to the absence of application of pressure. This same displacement of

  the tree also causes cooperation with the stirrup.

  When it moves, it triggers the pivoting of two sudden-action compression springs

  which, before turning in the off-center position, are

  pushed against each other. When -esorts turn

  in the off-center position, they unfold and repel the

  bre and the stirrup in the direction of the established movement. The

  operation of the spring mechanism ensures the

  diaphragm, caused initially by compressed air, due to the sudden release of the compression springs and simultaneously the flow of air

  compressed tablet in the dispenser is reversed. The opera-

  ration is repeated as long as the dispensing outlet

  is opened and the syrup is dispensed as a pressurized stream. When the dispensing outlet is closed, the counterpressure applied to the diaphragm is

  enough for the tree not to move.

  During the implementation of the

  It is an object of the invention to provide an alternative diaphragm pump suitable for pumping syrup in a concentrated beverage dispensing system so that the liquid is discharged to a controlled pressure reliably. An inverting distributor cooperates with two compression springs resting on each other so that they do not apply pressure to the bearing surfaces of the pump shaft. Since the pistons of the diaphragm pump are driven by compressed gas, it is still possible that a backpressure or

  condition of malfunction occurs and

  premature inversion of the pumping cycle, before the end of a race, with interruption of the distribution of the desired syrup at the dispensing outlet. Due to the mounting of the device controlled by springs according to the invention, this premature inversion is eliminated

  thanks to the sudden triggering due to the

  particular and with the particular assembly of

  pressure in the distributor inversion device.

  Other features and advantages of the

  come out better from the following description.

  1, a section of the pump according to the invention, corresponding to the initial position of the compression stroke, in the direction indicated; FIG. 1A is a plan view of the pump of FIG. 1, showing the details of the fluid inlet and outlet manifolds and the inlet and outlet valves of the pump according to the invention; - Figures 2A and 2B are respectively a section and a bottom view of the pump of Figure 1, and they represent the spring reversing device according to the invention, in the trigger position to the right; FIGS. 3A and 3B are respectively a partial section and a bottom view of the pump of FIG. 1, showing the spring reversing mechanism

  according to the invention just after the triggering position

  shown in FIGS. 2A and 2B, causing the

  change of direction of the pump shaft and the de-

placement to the left;

  FIG. 4 is a sectional view of the distributor of

  version according to the invention, in the position it occupies when the pump shaft of Figure 1 is driven to the right;

  FIG. 5 is a sectional view of the distributor of

  version according to the invention in the position it occupies when the pump shaft of FIG. 1 is driven to the left

  FIG. 6 is an exploded perspective

  feeling the details of the assembly of the stirrup according to the invention.

on the pump shaft; and

  FIG. 7 is a partial section representing

  so another diaphragm embodiment of a

pump according to the invention.

  FIGS. 1 and 1A represent, in section in elevation and in plan respectively, the reciprocating pump according to the invention which is generally referred to as 10 and

  which comprises a housing 11 having a collector 12a of

  and an outlet manifold 12b in its upper wall

  These collectors are intended to transport the syrup to be pumped from the inlet SI to the outlet SO of the pump via the chambers described below.

  of this memoir. A shaft 14 is placed in a chamber

  13 of the pump and it connects diaphragms and 16. A stirrup 17 or actuating member having extensions or arm 17a can slide on the shaft

  14 which passes into a longitudinal bore 17b (Figure 6).

  An inverting distributor 40 is attached to the inner wall

  21 of the housing 11, in the inner chamber 13 of the

  pump. A pin 25 is force-fitted in the

  14 and, during operation of the pump, it moves with the shaft a predetermined distance before cooperating with an end of a slot 26 formed in

  the stirrup 17. The shaft 14 is mounted in tori joints

  at its ends so that it can slide. A spring actuating member 27 (FIGS. 2A, 2B, 3A, 3B) is mounted under the stirrup, in the chamber 13 of the housing, so that it can pivot under the stirrup with which it cooperates. The inversion effect of the dispenser is facilitated by the cooperation of the stirrup 17

  and the activation device 27, and the distribution

  alternatively transmits the compressed gas

  through passage 22 to pneumatic chambers, for

  through passages 23 and 24 so that a pres-

  be applied to diaphragms 15 and 16 corresponding to

  dent. The dispenser 40 has a body 41 and a spool 42 bearing O-rings 43. The operation of this inverting dispenser is described in more detail with reference to FIGS. 2A, 2B, 3A, 3B, 4 and 5. Each diaphragm of the pump is formed of a flexible material such as rubber, attached to the inner walls of the

  pump housing as indicated by reference 20.

  In an advantageous embodiment of the invention,

  vention, the diaphragms further comprise a piston

  metal on the outer face of the diaphragm and a cape

  metal retainer on the inside of the diaphragm

  me, as shown in Figure 7 described in more detail

in the following.

  The pumping cycle of a pump according to the invention and the circulation of the fluid appear more clearly in FIG. 1A. The fluid to be pumped enters via an inlet EI into the inlet manifold 12a which is arranged at the upper part of the pump and which communicates with the

  chambers 28 and 29 of fluid, through

  Retention pets 31L and 31R that are normally closed.

  When the fluid pressure of the inlet manifold 12a exceeds that of the chamber 28 or 29, the flaps 31L, 31R open. As the pump according to the invention is of alternative type, the pressures in the chambers 28, 29

  always experience opposite variations. Thus, when

  that the shaft shown in Fig. 1A moves to the right, the chamber 28 is at a higher pressure than the manifold 12a and the chamber 29 contains fluid at a lower pressure than the manifold

  12a. Under these conditions, the valve 31L opens and introduces

  fluid in the chamber 29 while the valve 31R is closed. Thus, during operation, the valves 31L

  and 31R open and close alternately.

  Output check valves 32L, 32R placed in an outlet manifold 12b have a substantially similar operation. Thus, when the outlet manifold 12b is at a pressure lower than that of one of the chambers 28, 29, the valve of this chamber opens and delivers fluid to the outlet SO of the pump. In the example considered, when the shaft 14 moves to the right, the pressure in the chamber 28 is

  so that the flap 32R opens and allows the fluid to

  to flow to the pump outlet SO through

median of the collector 12b.

  The check valves 31L, 31R, 32L, 32R are

  virtually identical, apart from the orientations.

  They are all formed of rubber and comprise a central rod A fixed in the wall of the pump, and a seat B in the form of a disc which normally bears against fluid flow holes C. When pushed by the pressurized fluid to their open position, the seats B bend away from the orifices C and allow the passage of the fluid. The valves described above occupy the highest positions in the chambers 28, 29 so that

  it can not form pockets of air that

  should be sucked in by the pump outlet SO and which

  It would cause an irregular circulation of the fluid.

  FIG. 6 represents in more detail the stirrup 17 or actuating member which is mounted on the shaft 14 on which it moves. The stirrup 17 has two arms 17a

  above, described above and described above.

  to cooperate with the distributor 40, so that they

  switch it from one state to another. A long bore

  17b is formed in the stirrup 17 and houses the shaft 14. When it has been introduced into the bore 17b, the pin 25 indicated above is force-fitted into a hole 17a formed in the shaft 14. lower plate 17c is similarly fixed under the stirrup 17 and supports two axes 39. As described below, the axes 39 support a first pair of spring ends of the trigger mechanism

  abruptly shown in Figures 2B and 3B.

  FIGS. 2A and 2B show the pumping mechanism of FIG. 1, for a stroke of the pump in the direction indicated at the location of engagement of the pin carried by the shaft with one end of the slot formed in 17. At this moment, the stirrup is driven by the pin 25 and begins to move with the shaft and the actuator 27, connected to the stirrup, begins to pass beyond his unstable equilibrium position. The diaphragm 16 exerts a pressure on the liquid of the chamber 28 which is discharged via the valve 32R into the passage] 2bet which escapes through the outlet SO to the corresponding distribution stations. Figures 2B and 3B show the position of the diaphragm, the shaft and the stirrup at the end of the stroke. When the inversion mechanism with the general reference 27 moves beyond the unstable equilibrium position, a trigger

  suddenly causes the thrust of an arm 17a of the

  sort against the protruding end of the spool 42 so that the positions of the dispenser O-rings

  are changed and the current of compressed air is brutal-

  reversed in the distributor 40, at the end of the race so that the piston effect of the pump is reversed. Figures 2B and 3B show the details of the reversing mechanism 27. This, in one embodiment, comprises a coil spring 36 wound

  around an axis 37 and articulated by an axis 38 on the housing

  and after an axis 39 on the stirrup 17. After cooperation with the shaft, the stirrup 17 moves in the direction of travel of the pump and then causes the rotation of the axes 37 beyond the equilibrium positions. unstable,

  around the axes 38 so that the springs 36 pushes

  feel the stirrup in the direction of movement established, at a speed greater than that of the displacement of the shaft, until the stirrup comes knocking the drawer 42 of the

  distributor mechanism and reverse the direction of circulation.

  compressed air in the circuit, the pumping

  then in the opposite direction. The position of the compression springs and the stirrup at the ends of the stroke is shown in FIG. 3B. The presence of the axes 37 in the springs 36 prevents the buckling of the springs

  during the movement of the piston during operation

  pump. In a variant, the torsion springs 36T, shown in phantom, may replace the helical springs represented in the device.

  triggering action according to the invention

  tion. The stirrup 17 slides along the shaft and is pushed by the mechanism 27 first in one direction then in

  opposite direction depending on the inversion of the distributor 40.

  Figures 4 and 5 are simplified sections

  and enlarged of the inverting distributor 40 according to the invention.

  vention, shown in the form of a spool valve movable in translation, comprising a body 41, the spool 42 having three O-rings 43 disposed along its length, in the cavity 44 of the distributor. Air circulation passages 45 formed in the upper part of the distributor body are connected to the passage 22 of FIG. 1 and introduce the compressed air into the cavity 44, and passages 46 and 47 are connected to the passages 23, 24. of Figure 1 and transmit the air that has circulated

  in the distributor to the surface of the diaphragms cor-

  corresponding to the pump. The distributor 40 shown

  indicates that compressed air is introduced into the cabin

  44 by passage 45 in such a way that

  during the first half of the alter-

  native, the air reaches one of the rooms through the passage 46 and the passage 24 (Figure 1) while simultaneously, the other passage 47 allows the evacuation of the gas to be rejected and which comes from the other chamber containing air. After contact of the stirrup 17 with the left end protruding from the slide 42, it is pushed to the right so that, at the end of the pumping stroke, the O-rings 43 take the positions shown in FIG. 4 and the compressed gas is transmitted in the other direction so that it enters the other chamber delimited behind the other diaphragm, and the pump is driven in the other direction. In this position, the left end of the slide then protrudes from the cavity 44 and waits to be in contact with an arm 17a of the stirrup,

  when operating in the opposite direction of the pump.

  During operation, the distributor 15 alternately transmits air to the passages 23 and 24, to the chambers delimited behind the diaphragms.

  and 16. The springs 36 or 36T, mounted on the caliper,

  constantly push the pump shaft first in one direction and then in the other, depending on the position of the stirrup 17 along the shaft. The compressed air enters the chambers delimited behind the diaphragms 15 and 16 and moves the diaphragms so that the liquid is discharged from the chambers. As indicated above, the stirrup 17 mounted on the shaft 14 moves initially during the displacement of the shaft by cooperation of the pin with one end of the slot 26. The springs 36 or 36T which, at the time of cooperation, bear against each other, with practically no resulting force applied transversely to the shaft, pivot beyond the stable equilibrium position and apply another driving force to the stirrup which then moves rapidly , because of the sudden release of the springs 36, so that the arms 17a of the stirrup 17 come against the slide 42 which protrudes from the body 40. In this way, the positions of the O-rings inside the body

  of the distributor change and the flow of air

  The award winning interior is modified so that the first half of the pump cycle is over. The introduction

  continuous compressed air in the distributor 40 trigger

  the pump by the pistons mounted on the shaft in the other direction, with initial compression of the springs 36 or 36T, the process described above being repeated in the other direction, the compressed springs not ensuring a thrust in the other way. The inversion mechanism operates in such a way that the displacement of

  one or the other of the diaphragms, caused by the air

  awarded, is completed so that the pumping stroke can not be reversed prematurely or the distributor

  can not stick in central position.

  FIG. 7 is a section of a pump part similar to that described with reference to FIGS. 1 and 1A, except for the structure of the diaphragms as

  indicated by reference 16a. These diaphragms 16a comprise

  in addition, metal plates 52 in the form of

  shovels on the outer face of the diaphragm and a cup 54 retaining cup-shaped, on the inner face. This consideration prevents the formation of cracks in the

flexible diaphragm.

  Preferably, the pump housing is formed of molded plastic as shown in Fig. 1, so that the valves are mounted in the pump and all lines or passages are formed within the housing. This construction eliminates superfluous joints and external piping, so

  that the set has greater reliability. As indicated

  in FIG. 1, the internal wall of the housing comprises

  a continuous organ that surrounds all the elements of the

  inversion. The outer walls of the housing 11 are also formed of molded plastic, so that the entire diaphragm pump according to the invention has

  a very advantageous overall construction.

  It is understood that the invention has not been

  as a preferred example and that any technical equivalence can be

  constituent elements without departing from its scope.

Claims (15)

CLAIMS I   1. Alternative pump, characterized in that it com-   takes a stacker (11) having remote chambers   and members (15, 16) forming pistons in the chamber, dividing each of the chambers into a driving part and a delivery part (28, 29), the pistons   (15, 16) being mounted on a common shaft (14),   (22, 23) placed in the casing and intended to connect   the motor parts and the discharge parts of the chambers   at an inlet (SI) and an outlet (SO) of residual fluid   respectively, valves (31L, 31R, 32L, 32R) placed in   the removal parts and intended to regulate the   tion of the fluid to be pumped between the discharge parts and the collectors, and a control for directing the working fluid alternately in one or the other of   motorized parts delimited by the pistons in the chambers   side control, the control comprising a distributor (40) connected to the engine fluid source, a f17) member   in distributor action, mobile on a surface of gold-   between a first and a second position   longitudinally on the shaft 14 so that the fluid   be directed alternately to the contracting parties   these, and a device (27) with sudden release of   preventing the stopping of the actuating member (17) from   distributor between his first and second posi-   tion, this device (27) with sudden tripping   almost no resultant force in the transverse direction   Dirty to the shaft (14) against the bearing surface.   2. Pump according to claim 1, characterized in that the pistons (15, 16) are diaphragms connected by a common shaft (14), this shaft carrying a device   (27) for cooperating with the actuating member (17)   dispenser arrangement which itself controls the snap-action device (27) so that the dispenser actuator member (17) moves rapidly and thus causes the reversal of the control and the changeover.   compressed fluid direction so that the pump   alternately suitable.   3. Pump according to claim 2, characterized in that the device (25) for cooperation with the device   (17) distributor activation involves a governance   pin disposed in the shaft (14) and cooperating with one end of a slot (26) formed in the device (17)   dispenser actuation, in a pre-positioned position   determined during the displacement of the shaft (14).   4. Pump according to any one of the claims   1 to 3, characterized in that the device (27) for   abruptly includes two opposing springs of compres-   on either side of a tree that is parallel   to the longitudinal axis of the shaft (14).   5. Pump according to claim 4, characterized in   what the compression springs are springs coids (36).   6. Pump according to claim 4, characterized in that the compression springs are springs of twist (36T).   7. Pump according to claim 2, characterized in that each of the diaphragms (16a) further comprises a metal piston (52) on its outer face and a cap   metal retainer (54) at its inner face.   Pump according to claim 1, characterized in   its case is made of a plastic material   EEA. 9. Pump according to claim 1, characterized in that the check valves (31L, 31R, 32L, 32R) are placed in the highest possible position in the parts of repression.   10. Alternative pump, characterized in that it comprises a housing (11) having remote champres   laterally and containing pistons (15, 16) which divide   Each of the pistons (15, 16) is mounted on a common shaft (14), a common passage (12b) formed   in the housing and intended to connect the refolding parts   rooms to a common exit (SO) for distribution   bution, valve outlets (32L, 32R) formed in the discharge portions and for discharging pressurized liquid from the discharge portions to the common passage (12b), and control for directing fluid under pressure alternately in the motor parts delimited by the pistons (15, 16) in the   side chambers, the flap outlets (32L, 32R) occu-   the highest possible positions in the parts of repression.   11. Inverting mechanism for a fluid circulation control valve (40) that selectively directs   a fluid alternately according to one of two direc-   according to its switching between a first and a second   conde position, said mechanism being characterized in that it comprises a sliding member (17) actuating dispenser for cooperating with the distributor (40)   and switching it between his first and second po-   a bearing surface disposed along a predetermined axis along which the actuating member (17) slides, and   a device (27) with sudden triggering   to prevent stopping of the dispenser actuating member (17) between its first and second positions,   this device (27) with sudden release exercising practica-   there is no resultant force in the transverse direction   Dirty to the axis, against the bearing surface.   Mechanism according to claim 11, characterized   in that the device (27) with a sudden tripping   carries a device coupled to the actuating member (17)   dispenser and having an intermediate unstable equilibrium position, causing the passage of the organ   (17) to activate one side or the other of the   unstable situation which is practically equidistant from   first and second position.   13. Mechanism according to claim 12, characterized in that the spring device comprises two opposite compression springs (36) placed on either side of 1 axis.   Mechanism according to claim 13, characterized   in that the compression springs (36) are helicoidal spells.   Mechanism according to claim 14, characterized   in that the coil springs (36) are placed   support devices (37) which prevent flam- bage springs.   16. Mechanism according to claim 13, characterized in that the compression springs are springs torsion (36T).   17. Alternative pump, characterized in that   comprises a housing (11) having remote chambers la-   tr-.a! e-ment, containing pistons (15, 16) dividing each   cu-ne chambers in a driving part and a discharge part, the pistons (15, 16) being mounted on a common shaft (14), a common passage (12b) placed in the housing and for connecting the discharge parts rooms with a common exit (SO) distribution,   flip outlets (32L, 32R) from the discharge parts   intended to transmit a liquid under pressure   at the common passage (12b), and a command intended to   the fluid compressed alternately towards one or the other of the motor parts delimited by the pistons   in the side chambers, the pistons (15, 16)   taking soft diaphragms folded towards the parts   pressure, around the periphery of metal plates als.