EP1291524B1 - Hydraulic diaphragm pump with prestressed diaphragm - Google Patents

Abstract

The hydraulic membrane pump has a membrane (1) clamped at the edges between a pump body (2) and a pump cover (3), which separates the discharge zone (4) from the hydraulic zone (5). The membrane is tensed by a spring in the suction stroke direction. The hydraulic membrane drive has an oscillating displacement piston (6), which slides in the pump body between a supply zone (8) for the hydraulic fluid and the hydraulic zone. The spring tension on the membrane is sufficiently strong to apply pressure to the hydraulic fluid in the hydraulic zone, to build up an overpressure against the discharge zone.

Description

The invention relates to a hydraulically driven diaphragm pump with prestressed Membrane.

In known membrane pumps of the type mentioned above (DE-1 034 030 A2, DE-25 26 925 A1), the respective membrane is biased by a compression spring. in this connection This spring is either in the delivery chamber of the diaphragm pump or in the Hydraulic space arranged, in such a way that they the movement of the membrane supported in the direction of their suction stroke.

However, since this is only a weak compression spring, As a result, only a relatively slight bias is exerted on the membrane. This has the consequence that the membrane layer control in any situation not solved satisfactorily. There are therefore additional to the membrane position control Design elements necessary, the nature of the structure of the diaphragm pump complicate and thus more expensive.

In addition, in addition, because of the exerted by the relatively weak spring low bias the gas formation in the hydraulic chamber during the suction stroke is not effectively prevented. Therefore, due to the still existing Gas formation in the hydraulic chamber the entire absorption capacity of the known diaphragm pumps limited.

In diaphragm pumps of the generic type is finally still their starting safety of great importance. Here is the diaphragm pumps in today clearly lack of safety as a disadvantage. This one is only then eliminated if additional design features are present, however additional costs. It is therefore desirable in such diaphragm pumps to have sufficient starting safety, due to which ensures that the diaphragm at standstill of the pump - due always existing internal leakage - even then not in the direction of pressure stroke moved, if there is vacuum in the pumping chamber.

In another known hydraulically driven diaphragm pump (US-A-6 086 340) is an edge between a pump body and a pump cover clamped membrane provided, which has a delivery chamber of a hydraulic chamber separates and is biased by spring force. However, this affects the Spring not in the direction of the hydraulic space, i. in the direction of the suction stroke, but in the direction of the delivery chamber and thus generates a in the hydraulic chamber undesired negative pressure in relation to the pressure in the delivery chamber.

It is also known a diaphragm pump (US-A-4,776,771), but not is designed as a hydraulically driven diaphragm pump, but a two-stage Represents diaphragm pump with purely mechanical diaphragm drive. The outer one Ring zone of the membrane (Preförderstufe) is by means of an electromagnet in Direction of pressure stroke and moved by a spring in the direction of suction stroke. Of the inner part of the diaphragm (main conveyor) is directed by an eccentric Pressure stroke and moved by a spring in the direction of suction stroke.

The invention is based on the object, the diaphragm pump of the generic Art to eliminate the disadvantages described in such a way that Nevertheless, it has a high dosing accuracy with a simple structure and that their absorbency is not limited by gas formation in the hydraulic space, so that vacuuming is also possible.

The features of the invention created to solve this problem themselves from claim 1. Advantageous embodiments thereof are in the other Claims described.

The inventively designed diaphragm pump is the essential idea on the basis of biasing the membrane by spring force so strong that they a considerable pressure force on the hydraulic fluid in the hydraulic chamber exerts and that thus in the hydraulic chamber a significant overpressure against the delivery room is constructed.

For this purpose, the membrane is biased by spring force so strong that it also follows the piston in the suction stroke when vacuum is present in the pumping chamber, and that they are at standstill of the pump due to unavoidable internal Leakage also then not moved in the direction of pressure stroke, if in the pumping chamber vacuum is applied, while still the membrane remains in its rear dead center and is supported on a nearly gap-free surface by a part the pump body and a diaphragm coupling disk is formed, wherein no additional additional elements for membrane layer control are available.

According to a preferred embodiment of the invention, the spring force is so dimensioned that the pressure in the hydraulic chamber is always at least 1 bar greater than the pressure in the pump room.

Particular advantages with the invention can be achieved when the spring force is so dimensioned that in the hydraulic chamber during the suction stroke to none Time of negative pressure prevails, until the membrane mechanically on the pump body supported.

In development of the invention, the embodiment can also be made in such a way that the sum of the differential pressure generated by the spring force on the Membrane and the holding pressure of a spring-loaded leak-relief valve always at least 1 bar.

Conveniently, the dimensioning can be made, for example be that the differential pressure across the membrane with at least 0.8 bar and the holding pressure of the leak-relief valve is rated at about 0.3 bar.

In this modified embodiment of the invention, it is accordingly with Advantage possible, the absorbency of the pump - even out of the vacuum - not only by the differential pressure at the membrane, but by the sum from the differential pressure at the diaphragm and the holding pressure of the leak-relief valve to ensure.

As long as the aforementioned sum is greater than one bar, can also be pending Vacuum should not be sniffed uncontrolled. This ensures that the membrane in the suction stroke the piston even under vacuum conditions follows.

If the differential pressure at the membrane, for example, to 0.8 bar in the rear Measuring the dead center of the diaphragm is merely a holding pressure at the leak-relief valve of 0.3 bar necessary to sum the desired total differential pressure of more than 1 bar.

During the leak completion process, a vacuum of 0.3 bar. Experience has shown that such low holding pressures on the leak-relief valve in practice no disadvantages. In a corresponding manner occurs during the suction stroke and under vacuum conditions on the suction side in the hydraulic oil a negative pressure of 0.2 bar at a differential pressure of 0.8 bar at the Membrane.

Such low negative pressures bring in practice no disadvantages. The - unwanted - Gas formation of hydraulic oils is based on experience only with larger Suppress massively from approx. 0.4 bar.

This results in the overall advantage that by the possible weaker Feathering space and costs are saved.

The invention can be advantageous in design terms in various ways and realize. For example, it is possible to move the membrane in the direction the suction stroke biasing strong spring force through the membrane itself, i.e. by their shape and / or material to produce. Here comes as a material for the membrane, for example, polytetrafluoroethylene (PTFE) in question, while a suitable membrane shape, for example by a corresponding pre-deformation is formed.

In a modified structural embodiment, it is also according to the invention possible, the membrane biasing in the direction of the suction stroke strong Spring force by at least one built-in membrane spring element, for example a plate spring to produce.

A structurally particularly simple realization of the invention is based lying thought arises when the membrane in the direction of Suction stroke biasing strong spring force by a arranged in the hydraulic chamber Compression spring is generated; this can be on a connected with the membrane central guide rod on the one hand on the pump housing and on the other Support at the end of the guide rod, with respect to their strength the effective membrane area is dimensioned accordingly.

It is within the scope of the invention that the membrane in adaptation to the at her adjacent differential pressure formed as a molding membrane with a circumferential bead is, whose concave side points to the hydraulic chamber. Due to the at the Diaphragm applied differential pressure is in this case the bead of the molding membrane stabilized. This results in no tendency to buckle, so that the Membrane has a long life. In addition, there is a tendency to fretting Extremely low in sandwich membranes.

In a further embodiment of the invention, the membrane can be used as a sandwich membrane be formed with at least two membrane layers, the individual layers mechanically are coupled and the suction stroke by the spring action of the compression spring be retrieved as a complete membrane package.

• Die Saugfähigkeit der Pumpe wird nicht durch eine unerwünschte Gasbildung im Hydraulikraum begrenzt, so daß auch das Ansaugen aus Vakuum sehr gut möglich ist. Damit entspricht die Saugfähigkeit der erfindungsgemäßen Membranpumpe derjenigen einer Kolbenpumpe.
• Die erfindungsgemäße Membranpumpe weist eine hohe Dosiergenauigkeit auf, da durch den im Hydraulikraum herrschenden, erfindungsgemäß vorgesehenen Überdruck jegliche Gasbildung unterbunden wird.
• Aufgrund der erfindungsgemäßen Ausgestaltung der Hydraulikpumpe kann diese mit einem lediglich einfachen Leckergänzungsventil versehen werden, das nur eine sehr schwache oder sogar gar keine Feder aufweist, so daß während des Leckergänzungsvorgangs kaum Gasbildung auftritt.
• Aufgrund der stark verringerten bzw. vollkommen unterbundenen Gasbildung ergibt sich eine sehr vereinfachte Gasaustragung aus dem Hydraulikraum, so daß auch keine kontinuierliche Gasaustragung erforderlich ist.
• Die erfindungsgemäße Membranpumpe weist insgesamt einen einfachen Aufbau auf, so daß zur Membranlagensteuerung keine zusätzlichen Elemente erforderlich sind.
• Die Drehzahl des Antriebs der Pumpe wird nicht durch eine Gasbildung im Hydraulikraum begrenzt, so daß hohe Drehzahlen möglich sind.
• Aufgrund des im Hydraulikraum herrschenden Überdrucks wird verhindert, daß sich die Membran im Stillstand der Pumpe nach vorn in Richtung ihres Druckhubes bewegt, auch wenn im Förderraum Vakuum anliegt.
• Aufgrund des im Hydraulikraum herrschenden Überdrucks ist die Membran immer in Richtung des Förderraums ausgewölbt, d.h. vorgewölbt, so daß sie in ihrer Form stabilisiert ist.

Overall, this results in significant advantages of the invention, which can be explained only by way of example as follows:

• The absorbency of the pump is not limited by an undesirable gas formation in the hydraulic chamber, so that the suction from vacuum is very possible. Thus, the absorbency of the diaphragm pump according to the invention corresponds to that of a piston pump.
• The diaphragm pump according to the invention has a high dosing accuracy, since any gas formation is prevented by the overpressure prevailing in the hydraulic chamber.
• Due to the inventive design of the hydraulic pump, it can be provided with a merely simple leak-relief valve, which has only a very weak or even no spring, so that hardly gas formation occurs during the Leckergänzungsvorgangs.
• Due to the greatly reduced or completely suppressed gas formation results in a very simplified gas discharge from the hydraulic chamber, so that no continuous gas discharge is required.
• The membrane pump according to the invention has a total of a simple structure, so that no additional elements are required for membrane layer control.
• The speed of the drive of the pump is not limited by a gas formation in the hydraulic chamber, so that high speeds are possible.
• Due to the pressure prevailing in the hydraulic space overpressure prevents the diaphragm moves when the pump is stopped forward in the direction of its pressure stroke, even if in the pumping chamber vacuum.
• Due to the pressure prevailing in the hydraulic space overpressure, the membrane is always bulged in the direction of the delivery chamber, ie bulged, so that it is stabilized in shape.

Fig. 1

schematisch im Längsschnitt die erfindungsgemäße Membranpumpe;

Fig. 2

im Diagramm den allein aufgrund Federkraft erzeugten Differenzdruck an der Membran über deren Hubweg;

Fig. 3

gleichfalls im Diagramm den Druck im Hydrauliköl bei Vakuumbedingungen auf der Saugseite, wobei die Federkraft so bemessen ist, daß ein Differenzdruck von mindestens 0,8 bar entsteht bei einem Haltedruck des Leckergänzungsventils von 0,3 bar;

Fig. 4

im Detail schematisch im Schnitt die Membran in ihrer hinteren Totpunktlage, in der sie an einer aus Pumpenkörper und Membrankopplungsscheibe gebildeten nahezu spaltfreien Fläche abgestützt ist;

Fig. 5

die Ausbildung der Membran als Wellenmembran, deren Eigensteifigkeit zum Erzeugen einer Federkraft genutzt ist;

Fig. 6

die Ausbildung einer Membran mit einer integrierten Tellerfeder zum Erzeugen der gewünschten Federkraft und

Fig. 7

schematisch im Diagramm den nutzbaren Arbeitsbereich einer Membran, die entweder als Wellenmembran gemäß Fig. 5 oder als Membran mit integrierter Tellerfeder gemäß Fig. 6 ausgebildet ist.

The invention will be explained in more detail below with reference to the drawing. This shows in

Fig. 1

schematically in longitudinal section the diaphragm pump according to the invention;

Fig. 2

in the diagram, the differential pressure across the diaphragm caused solely by spring force over its stroke;

Fig. 3

also in the diagram, the pressure in the hydraulic oil under vacuum conditions on the suction side, wherein the spring force is dimensioned so that a differential pressure of at least 0.8 bar is formed at a holding pressure of the leak-relief valve of 0.3 bar;

Fig. 4

in detail schematically in section the membrane in its rear dead center position in which it is supported on a nearly gap-free surface formed from the pump body and diaphragm coupling disk;

Fig. 5

the formation of the membrane as a wave membrane whose inherent rigidity is used to generate a spring force;

Fig. 6

the formation of a membrane with an integrated plate spring to produce the desired spring force and

Fig. 7

schematically in the diagram the usable working range of a membrane which is formed either as a wave diaphragm according to FIG. 5 or as a diaphragm with integrated disc spring according to FIG.

As can be seen from Fig. 1, the illustrated, hydraulically driven diaphragm pump a membrane 1, the edge between a pump body. 2 and a pump cover 3 is clamped and a delivery chamber 4 of a Hydraulic chamber 5 separates.

The hydraulic drive of the membrane 1 is effected by an oscillating displacement piston 6, in the pump body 2 in a bushing 7 between the hydraulic space 5 and a reservoir 8 for the hydraulic fluid back and forth is.

The membrane 1 is in the illustrated embodiment as a three-layer sandwich membrane formed in the form of a molding membrane with a circumferential bead 9, the concave side of the hydraulic chamber 5 shows.

The individual layers of the membrane 1, not shown, are in their central Area mechanically coupled by means of corresponding discs 10, 11, the interconnected, in particular screwed, are. The in the direction of the hydraulic space 5 facing disc 11 carries a central guide rod 12, the extends axially to the rear in the hydraulic chamber 5. On this guide rod 12 is a strong compression spring 13 is arranged, on the one hand to a Shoulder 14 of the pump body 2 and on the other hand to the corresponding shoulder-like end of the guide rod 12 is supported. Due to the As a result of this exerted strong spring force, the membrane 1 is always in the direction of her Suction strokes, i. their rear dead center, biased. Here is the strength of Compression spring 13 dimensioned such that the hydraulic fluid located in the hydraulic chamber 5 a considerable pressure force is exerted, so that thus in the hydraulic chamber 5 a substantial pressure over the delivery chamber 4 constructed is. This significant overpressure in the hydraulic chamber 5 is hereby shown Embodiment always at least 1 bar greater than the pressure in the delivery chamber 4th

The diagram according to FIG. 2 schematically shows the differential pressure on the membrane Plotted over the stroke of the front dead center VT to the rear dead center HT, Here, the differential pressure on the membrane alone due to the previously described spring 13 is generated. As can be seen, the spring 13 also generates in rear dead center HT of the diaphragm a differential pressure of at least 1 bar, so that thus in the hydraulic chamber 5 is always a significant overpressure against the delivery chamber 4 is constructed.

In the diagram of FIG. 3 is at vacuum conditions on the suction side also shown the differential pressure at the diaphragm 1 (pressure in the hydraulic oil). The differential pressure is generated by spring force. In addition, the effective holding pressure of the leak-relief valve 15 shown as the sum of the differential pressure at the diaphragm 1 and the holding pressure of the leak-relief valve 15 (see Fig. 1). It is always at least 1 bar. Here, the embodiment For example, be made such that the differential pressure at the Membrane 1 is at least 0.8 bar and that the holding pressure of the leak-relief valve 15 with about 0.3 bar is measured. The effective holding pressure is then at the rear dead center HT of the membrane 1 at least 1.1 bar. At leak supplement the diaphragm 1 is earlier in its rear dead center than the piston 6 Pressure in the hydraulic oil then drops to 0.7 bar absolute or to a negative pressure of 0.3 bar.

Fig. 4 shows the membrane 1 in its hydraulic side installation, i. in her back Dead center HT. Here, the embodiment is made such that the pump body 2 together with the rear diaphragm coupling disk 11 a nearly gap-free surface for supporting the membrane 1 forms. This allows the membrane stand at standstill differential pressures of up to 400 bar without them Harm suffers.

In the embodiment shown in FIG. 5, the illustrated membrane 1 'is designed as a wave membrane, this has a due to their design Such inherent rigidity, that this the function of the compression spring described above 13 fulfilled and for applying the desired spring force on the membrane 1 ' can be used. Here, the dashed lines illustrate the work area such a wave membrane 1 '.

In the modified embodiment of FIG. 6, the illustrated Membrane 1 "integrated disc springs 16. These may, for example, in an elastomeric membrane vulcanised and also fulfill the function to that they the membrane in the direction of its suction stroke with a strong spring force Pretension. Again, the dashed lines illustrate the work area such a membrane 1 ".

Finally, FIG. 7 schematically illustrates the usable working area of one of the previously described membranes 1 'and 1 ".

Claims (10)

1. Hydraulically driven diaphragm pump having a diaphragm which is clamped in at the edge between a pump body (2) and a pump cover (3), which diaphragm divides a pumping chamber (4) from a hydraulic chamber (5) and is prestressed in the direction of its suction stroke by resilient force, and having a hydraulic drive to the diaphragm in the form of an oscillating displacing piston (6) which is movable in the pump body (2) between a supply chamber (8) for the hydraulic liquid and the hydraulic chamber (5), wherein the diaphragm (1) is so strongly prestressed by means of resilient force that, on the suction stroke, it follows the piston (6) even when there is a vacuum in the pumping chamber (4) and that, when the pump is stationary, it does not move, due to unavoidable internal leakage, in the direction of the delivery stroke even when there is a vacuum in the pumping chamber (4), wherein further the diaphragm (-1) remains in its rear end-of-stroke position and is supported against an almost gap-free surface which is formed by a part of the pump body (2) and by a diaphragm-coupling disc (11), no further, additional elements being present for the control of diaphragm position.
2. Diaphragm pump according to claim 1, characterised in that the resilient force is of a size such that the pressure in the hydraulic chamber (5) is always at least 1 bar higher than the pressure in the pumping chamber (4).
3. Diaphragm pump according to claim 1 or 2, characterised in that the resilient force is of a size such that at no time during the suction stroke does a pressure below atmospheric prevail in the hydraulic chamber (5) until the diaphragm (1) is resting physically against the pump body (2).
4. Diaphragm pump according to claim 1, characterised in that the sum of the pressure differential at the diaphragm (1) produced by the resilient force and of the holding pressure of a sprung top-up valve (15) for leakage is always at least 1 bar.
5. Diaphragm pump according to claim 4, characterised in that the pressure differential at the diaphragm (1) is sized at at least 0.8 bar and the holding pressure of the top-up valve (15) for leakage at approximately 0.3 bar.
6. Diaphragm pump according to one of the foregoing claims, characterised in that the strong resilient force which prestresses the diaphragm (1) in the direction of the suction stroke is generated by the diaphragm (1) itself, i.e. by its form and/or its material.
7. Diaphragm pump according to one of claims 1 - 5, characterised in that the strong resilient force which prestresses the diaphragm (1") in the direction of the suction stroke is generated by at least one resilient member incorporated in the diaphragm (1), such for example as a disc spring (16).
8. Diaphragm pump according to one of claims 1 - 5, characterised in that the strong resilient force which prestresses the diaphragm (1) in the direction of the suction stroke is generated by a compression spring (13) which is arranged in the hydraulic chamber (5) and which is supported, on a central mounting rod (12) connected to the diaphragm (1), on the one hand against the pump body (2) and on the other hand against the end of the mounting rod (12) and whose strength is sized as appropriate in relation to the effective area of the diaphragm (1).
9. Diaphragm pump according to one of the foregoing claims, characterised in that the diaphragm (1) is in the form of a shaped diaphragm having a corrugation. (9) extending therearound of which the concave side faces towards the hydraulic chamber (5).
10. Diaphragm pump according to one of the foregoing claims, characterised in that the diaphragm (1) is in the form of a sandwich diaphragm having at least two layers, of which sandwich diaphragm the individual layers are mechanically coupled and, on the suction stroke, can be returned as a complete diaphragm assembly by the resilient action of the compression spring (13).

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