EP2997261A1 - Diaphragm pump having position control - Google Patents

Abstract

The invention relates to a diaphragm pump, comprising a pumping chamber, a suction connection and a pressure connection, which are both connected to the pumping chamber, a working chamber, which is filled with a hydraulic fluid, a device for applying an oscillating pressure p1 to the hydraulic fluid, a diaphragm, which separates the pumping chamber and the working chamber from each other and can be moved back and forth between a pressure stroke position and a suction stroke position, wherein the volume of the pumping chamber is smaller in the pressure stroke position of the diaphragm than in the suction stroke position of the diaphragm, and a storage chamber for accommodating hydraulic fluid at the pressure p2, wherein the storage chamber and the working chamber are connected to each other by means of a valve having a closing part. According to the invention, in order to provide a diaphragm pump of the type mentioned at the beginning that has a simple construction and reliably ensures that the diaphragm cannot move too far beyond the pressure stroke position, the diaphragm is coupled to the closing part in such a way that the valve is opened when the diaphragm moves from the pressure stroke position to a position that is farther from the suction stroke position.

Description

 Diaphragm pump with position control

The present invention relates to a hydraulically driven diaphragm pump. Such diaphragm pumps have a delivery chamber, both a suction port and a pressure port, which are both connected to the delivery chamber, a working space which is filled with a hydraulic fluid, a device for pressurizing the hydraulic fluid with an oscillating pressure pi, a diaphragm separating the delivery chamber and the working chamber from one another and between a pressure stroke position and a suction stroke position, the volume of the delivery chamber being smaller in the pressure stroke position of the membrane than in the suction stroke position of the membrane, a reservoir for receiving the hydraulic fluid at the pressure p2, wherein the storage space and working space are connected to one another via a valve with a closure part.

In operation, the suction port and pressure port are each connected via check valves to a suction line or a pressure line.

The membrane may be resiliently biased in the direction of the suction stroke position. The membrane will assume a position in which the forces acting on the membrane, i. the force applied by the fluid pressure in the delivery chamber and optionally by the resilient bias in the direction of suction stroke position on the one hand and the force applied by the fluid pressure in the working space in the direction of Druckhubposition force on the other hand, cancel each other.

Therefore, if the fluid pressure in the working space is reduced and thereby becomes smaller than the pressure in the delivery chamber, this leads to a movement of the diaphragm in the direction of the suction stroke position. Due to the associated increase in the delivery chamber volume and the pressure in the delivery chamber decreases. If the fluid pressure in the delivery chamber falls below a value predetermined by the pressure in the suction line (usually ambient pressure) and the check valve, the check valve on the suction line opens and delivery fluid is sucked out of the suction line into the delivery chamber via the suction connection.

On the other hand, if the pressure in the working space increases, the diaphragm is moved from the suction stroke position in the direction of the pressure stroke position, whereby the pressure in the delivery chamber is increased and the delivery fluid in the delivery chamber is forced into the pressure conduit via the pressure connection. The pressurization of the hydraulic fluid with an oscillating pressure thus leads to an oscillating movement of the diaphragm and, associated therewith, to an oscillating pumping action of the delivery fluid from the suction line into the pressure line.

Such hydraulically driven diaphragm pumps are used in particular in the promotion of conveying fluid under very high pressures, since the membrane is evenly loaded by the hydraulic fluid and has a longer service life.

The pressurization of the hydraulic fluid with an oscillating pressure is usually carried out by means of a moving piston. Even with the best processing of the individual moving parts can still come to flow around the piston with hydraulic fluid, so that the amount of fluid in the working space deviates from the optimum amount, which means that the membrane is either moved beyond the Druckhubposition, resulting in a perforation or Destruction of the membrane may result, or the membrane no longer reaches the Druckhubposition, whereby the delivery volume per stroke is reduced. Both are undesirable.

In EP 0 547 404 a hydraulically driven diaphragm pump is described. In this pump, the working space is connected via a leak-relief valve to the reservoir. When the pressure in the working space falls below a predetermined hydraulic pressure, the leak-relief valve opens and hydraulic fluid can flow from the working space into the storage space. Moreover, in EP 0 547 404 the diaphragm is connected to a spool which, in the event that the diaphragm moves beyond the pressure stroke position away from the suction stroke position, is connected to a valve member which provides the hydraulic connection from the part of the working space in which the oscillating pressure-generating piston is arranged, and the part of the working space in which the membrane is arranged interrupts.

However, this structure is relatively complicated and is also error-prone if, due to the formation of the valve element, a hydraulically tight separation of the piston from the membrane working space is not ensured. In addition, in the part of the working space in which the piston is arranged, an additional pressure relief valve must be provided which allows escape of the hydraulic fluid in the case of closing the connection to the diaphragm working space with the valve member. Based on the described prior art, it is therefore an object of the present invention to provide a diaphragm pump of the type mentioned above, which is simple in construction and reliably ensures that the membrane can not move too far beyond the Druckhubposition also. According to the invention, this is achieved in that the membrane is coupled to the closure part in such a way that upon movement of the membrane from the pressure stroke position to a position farther away from the suction stroke position, the valve is opened.

Therefore, should, for example, because too much hydraulic fluid in the working space, the membrane move beyond the Druckhubposition also, the coupling of the membrane with the closure element to a valve opening and hydraulic fluid can escape from the working space in the storage room, resulting in a significant reduction of Pressure in the working space leads and therefore prevents further movement of the diaphragm on the Druckhubposition. Instead, due to the decrease in pressure in the working space, the diaphragm will move back towards the pressure stroke position, closing the valve again due to the coupling of the diaphragm with the closure member. By this measure, it is ensured that a movement of the membrane is significantly prevented beyond the Druckhubposition out into a position which is farther away from the suction stroke position.

For example, a pull rod, which is attached to the membrane may be provided, wherein the closure part is connected to the pull rod.

In a preferred embodiment, it is provided that the closure member is movably secured to the pull rod so that the closure member can be reciprocated relative to the pull rod between two positions designed such that in the push stroke position of the diaphragm, when the closure member in the first position, the valve is closed and, when the closure member is in the second position, the valve is open.

In a further preferred embodiment, the closure part is resiliently biased in the first position.

By this measure, thus, the membrane can perform a certain movement without the closure part opens the valve. Only when the membrane is in a position farther away from the suction stroke position than the pressure stroke position, the closure member is moved out of the valve seat due to the mechanical connection with the diaphragm, so that the valve is opened.

In a further preferred embodiment, the resilient bias of the closure member is dimensioned such that, if for the pressure difference between the pressure in the reservoir and the pressure in the working space is: p ₂ - ρ _λ > a, where a is a predetermined pressure, the closure part is moved from the first position towards the second position and the valve is opened. In this case, a is determined by the choice of the spring constant of the resilient bias. This measure ensures that, in the event of fluid loss in the working space, fluid can be replenished from the storage space as soon as the pressure in the working space falls below a predetermined value.

In a further preferred embodiment, the membrane is resiliently prestressed in the direction of the suction stroke, this being preferably effected by a spring-biased pull rod.

By this measure, the return movement of the membrane from the Druckhubposition is ensured in the suction stroke position even if in the delivery chamber no or too low a delivery fluid pressure is applied. In most applications, the pump at the suction port must suck delivery fluid so that then the delivery fluid pressure drops in the delivery chamber and the bias is required to move the membrane in the direction of suction stroke.

In a further preferred embodiment it is provided that the working space is arranged in a housing, wherein the housing has a wall element with a passage to the reservoir and a valve seat, wherein preferably the wall element is movably arranged in an opening of the housing.

In other words, the valve can also be opened without movement of the closure part in which the wall element and thus the valve seat is moved relative to the closure part.

Due to the movable arrangement of the wall element and thus the valve seat, the additional provision of a pressure relief valve can be avoided. If the pressure in the working space rises too much, this will lead to a movement of the wall element and thus the valve seat in the opening, with the result that the closure part is moved out of the valve seat and thus the valve is opened, so that the pressure in Working space lowered again by the connection to the storage room.

Preferably, the wall element is resiliently biased in the direction of the housing opening, wherein preferably in the opening a stop element is arranged, against which the wall element is resiliently biased. In this case, the resilient bias of the wall element is advantageously dimensioned such that, if, for the pressure difference between the pressure in the working space and the pressure in the reservoir: ρ _λ - p ₂ > b, where b is a predetermined pressure, the wall element of the Moves the closure part and thereby the valve opens.

Further advantages, features and applications of the present invention will become apparent from the following description of a preferred embodiment. Show it:

FIG. 1 shows a schematic representation of an embodiment according to the invention of a diaphragm pump in the pressure stroke position,

FIG. 2 shows a schematic illustration of an embodiment of a diaphragm pump according to the invention in the suction stroke position, FIG. 3 shows a schematic representation for the case where there is too much hydraulic fluid in the working space,

Figure 4 is a schematic representation for the case that too little hydraulic fluid in the working space, and Figure 5 is a schematic representation to illustrate the overpressure function.

FIG. 1 shows a schematic representation of part of a diaphragm pump. The diaphragm pump according to the invention has a delivery chamber (not shown), a suction connection (not shown) connected to the delivery chamber and a pressure connection (not shown). A working space 7 is filled with a hydraulic fluid. The hydraulic fluid can be acted upon via the channel 12 with an oscillating pressure pi.

Furthermore, a membrane (not shown) is provided, which separates the delivery chamber and the working space 7 from each other. The membrane is clamped between the delivery chamber housing (not shown) and the component 3. This membrane is by means of the head 2 of a pull rod

1 held in their position. The delivery chamber is then in the figure 1 left of the head

2 of the drawbar 1.

In Figure 1, the tie rod 1 is shown in its Druckhubposition, ie, that this is the position which the tie rod 1 and thus the membrane should take at the end of the print stroke. This position is usually achieved by the pressure pi is increased in the working space 7, so that the pressurized fluid through the channels 18 pressure on the with the head 2 of the drawbar. 1 exerts connected membrane and this in the direction of the delivery chamber, ie to the left in Figure 1, presses.

The pull rod 1 and thus the connected via the head 2 with the pull rod 1 membrane is by means of the spring 4, which is supported on the one hand on the component 3 and on the other hand on a collar-shaped extension of the tie rod 1, resiliently in the direction of the suction stroke, i. in the figure 1 to the right, biased. Therefore, decreases the pressure pi in the working space 7, so the spring 4 ensures that the pull rod 1 and thus the membrane is moved in the direction of suction stroke, whereby the volume is increased in the delivery chamber. The corresponding suction stroke position is shown in FIG. In this position, the membrane (not shown) bears against the conical surfaces of the component 3.

By the oscillating pressure, which is passed through the channel 12 to the working space 7, the pull rod 2 moves alternately against the spring force of the spring 4 in the direction of Druckhubposition (shown in Figure 1) and due to the spring force of the spring 4 in the direction of the suction stroke (shown in Figure 2).

An optimal function of the diaphragm pump is only ensured if the right amount of hydraulic fluid is present in the working space 7, since only then the diaphragm and thus the pull rod 2 completely perform the desired movement.

The pull rod 2 is connected to a closure part 5, which cooperates with a valve seat inserted in the wall element 9. The wall element 9 has a connection 17, via which the working space 7 is filled with a reservoir 8, in which hydraulic fluid at the pressure p2 (this is essentially the ambient pressure).

In the pressure stroke position and suction stroke position shown in FIGS. 1 and 2, during the proper operation of the pump, the closure element 5 is positioned in the valve seat of the wall element 9, so that the connection 17 between the work space 7 and the reservoir 8 is closed. To ensure this, the closure element 6 is movably arranged within the pull rod 1. The pull rod has corresponding slots 15, in which a pin 14 which is fixed to the closure element 6, engages. By this construction, the shutter member 6 can be reciprocated relative to the pull rod 1 in the longitudinal direction between two positions. These positions are selected so that during a movement between the pressure stroke and the suction stroke, ie during a movement between the two normal extreme positions shown in FIGS. 1 and 2, the closure element 5 can keep the connection 17 between the working space 7 and the reservoir 8 closed. To ensure this, there is an additional one Spring 6 is provided, which presses the closure element in the direction of the wall element 9, ie in the direction of the valve seat. The spring 6 is supported for this purpose on the tie rod 1.

Due to always existing leaks, however, it can happen that there is too much hydraulic fluid in the working space 7. As a result, the membrane moves further away from the suction stroke position shown in FIG. 2 via the print-stroke position shown in FIG. This is not desirable, as it can lead to damage or even destruction of the membrane.

In the embodiment shown, a movement of the membrane beyond the Druckhubposition leads to the situation shown in Figure 3. Since the membrane and thus the pull rod 1 has moved too far to the left, the construction shown causes the pin 14 connected to the closure element in the slot 15 on one side of the stop and due to the movement of the membrane to the left the closure element 5 is lifted from the valve seat in the wall element 9. As a result of this measure, the connection 17 between the working space 7 and the storage space 8 is opened and fluid can escape from the working space 7 into the storage space 8. This happens until the pressure pi has dropped again, i. until the excess amount of fluid has drained via the connection 17 into the reservoir, so that the spring 4 is again able to move the diaphragm back into the Druckhubposition. In principle, the case may occur that too little hydraulic fluid is contained in the working space 7. This then leads to the fact that the pump can no longer reach the Druckhubposition shown in Figure 1 and therefore each pump stroke no longer the intended amount can be transported. Too little hydraulic fluid in the working space 7 also causes at least at the end of the suction stroke, i. essentially in the suction stroke position shown in FIG. 2, the pressure pi in the working space drops sharply. While such a pressure drop does not adversely affect pump operation, it can be used to provide a leak supplement.

As can be seen in FIG. 4, a drop in the pressure pi below a predetermined value, however, causes the fluid pressure p2 prevailing in the reservoir 8 to be able to lift the closing element 5 out of the valve seat against the force of the spring 6 so that even in this situation the connection 17 between the working space 7 and the storage space 8 is opened and as long as fluid flows from the storage space 8 into the working space 7, until there the pressure rises again and the spring 6 ensures that the closing element 5 the connection 17 locked again. Finally, it may happen in the diaphragm pumps described that, for some reason, the pressure on the pressure line increases sharply, so that it is no longer possible to move the membrane with the oscillating pressure pi in the working space 7 to the Druckhubposition shown in Figure 1. Instead, the pressure pi in the working space 7 increases sharply, which also leads to a Damage to the membrane may result. For this reason, it is provided in the embodiment shown that the wall element 9, in which the passage 17 are incorporated together with the valve seat, can be moved in an opening in the housing 1 1 of the working space 7. A spring 10, which on the one hand abuts against the storage space housing 13 and on the other hand against the wall element 9, ensures that the wall element 9 is pressed into the opening of the working space housing 11 in the direction of a stop 16. However, if a situation is reached in which the pressure pi in the working space 7 exceeds a predetermined value, although the Druckhubposition has not yet been reached, this leads to the fact that the wall element 9 moves against the force of the spring 10 of the stopper 16 and thereby the closure element 5 is disengaged from the valve seat and the connection 17 between the working space 7 and the storage space 8 is opened, whereby the overpressure pi can be relieved in the working space. As a result, the membrane moves into its suction stroke position shown in FIG. Since the membrane rests in this position on the conical surfaces of the element 3, the membrane is protected.

LIST OF REFERENCE NUMBERS

pull bar

 head

 component

 feather

 closure element

 feather

 working space

 Storage room

 wall element

 feather

 casing

 channel

 Pantry housing

 spigot

 Long hole

 attack

 connection

 channels

Claims

P a n t a n s p r e c h e Diaphragm pump with a pump room, a suction connection and a pressure connection, which are both connected to the delivery chamber, a working space which is filled with a hydraulic fluid, a means for pressurizing the hydraulic fluid with an oscillating pressure PL a diaphragm which separates the delivery chamber and the working chamber from each other and is movable back and forth between a pressure stroke position and a suction stroke position, the volume of the delivery chamber being smaller in the pressure stroke position of the membrane than in the suction stroke position of the membrane, a reservoir for receiving hydraulic fluid at the pressure p2, wherein the storage space and working space are connected to one another via a valve with a closure part, characterized in that the membrane is coupled to the closure part in such a way that upon movement of the membrane from the Druckhubposition to a position which is farther away from the suction stroke position, the valve is opened. Diaphragm pump according to claim 1, characterized in that a pull rod, which is fixed to the membrane, is provided, wherein the closure part is connected to the pull rod. A diaphragm pump according to claim 2, characterized in that the closure member is movably secured to the pull rod so that the closure member can be reciprocated relative to the pull rod between two positions adapted to be in the push stroke position of the diaphragm when the closure member in the first position, the valve is closed and in the second position of the closure part, the valve is open. Diaphragm pump according to claim 3, characterized in that the closure part is resiliently biased in the first position. Diaphragm pump according to claim 4, characterized in that the resilient bias of the closure part is dimensioned such that, if for the pressure difference between the pressure in the reservoir and the pressure in the working space p ₂ - ρ _λ > a, where a is a predetermined pressure, the closure member is moved from the first position toward the second position and the valve is opened. Diaphragm pump according to one of claims 1 to 5, characterized in that the membrane is resiliently biased in the direction of the suction stroke, wherein this is preferably effected by a resiliently biased pull rod. Diaphragm pump according to one of claims 1 to 6, characterized in that the working space is arranged in a housing, wherein the housing has a wall element with a valve seat, wherein preferably the wall element is arranged to be movable in an opening of the housing. Diaphragm pump according to claim 7, characterized in that the wall element is resiliently biased in the direction of the housing opening, wherein preferably in the opening a stop element is arranged, against which the wall element is resiliently biased. Diaphragm pump according to claim 8, characterized in that the resilient bias of the wall element is dimensioned such that, if for the pressure difference between the pressure in the working space and the pressure in the reservoir ρ _λ - p ₂ > b, where b is a predetermined pressure, the Wall element moves away from the closure part and thereby opens the valve.