EP0688954B1 - Controlled replenishment device for high pressure membrane pumps - Google Patents

Description

The invention relates to a hydraulically driven high-pressure diaphragm pump.

A diaphragm pump is known from GB-A-887.774. However, this is a conventional diaphragm pump, which is only suitable for low pressures. A Supply of a hydraulic fluid that may need to be filled is only possible in the end position of the drive piston.

From FR-A-1,122,901 is a hydraulically driven Diaphragm pump known, which is also only for low Prints is suitable. The hydraulic fluid reservoir sits directly on the cylinder of the drive piston and enables hydraulic fluid supply when the drive piston releases the inlet.

A diaphragm pump can be found in DE-A-1 453 579, in which a timed relationship to the drive piston operated slide is provided, the one Connection between the hydraulic pressure chamber and the reservoir open for the hydraulic fluid and can close. A sniffer valve is in this diaphragm pump not provided.

In the case of diaphragm pumps, there is usually a leakage a so-called sniffing device, provided which is a sniffer connection in the form of a connecting channel between the pressure chamber and the storage room. This connection channel is normally controlled by a vacuum spring-loaded sniffer valve closed. The sniffer valve then responds or opens then the connection between the pressure room and the storage room, if the piston suffers from a lack of hydraulic fluid during the suction stroke caused excessive vacuum in the hydraulic system generated. This negative pressure in the work area will detected by the sniffer valve, so that then the missing Hydraulic fluid in the pressure chamber above that from the reservoir coming connection channel can be supplemented.

With such a leak supplement, the problem arises that vacuum peaks in the hydraulic system at the beginning of Suction strokes of the piston occur, leading to an early response of the sniffer valve. Such a pronounced one Vacuum peak, the so-called Joukowsky shock, occurs preferably with large high-pressure diaphragm pumps at the beginning the suction phase when the liquid column in the suction line accelerated suddenly when opening the suction valve becomes. The resulting early response of the Sniffer valve has overfilled the pressure chamber with Hydraulic fluid result, which in turn is too strong Deflection or stress on the membrane during the Pressure stroke causes.

For such a premature response of the sniffer valve due to the occurring vacuum peaks - and this as a result caused overfilling of the hydraulic pressure chamber with Hydraulic fluid - to avoid it is already known the leakage supplementation by means of a so-called membrane control system to influence. The membrane itself does this Actuation of a control valve, one from the diaphragm controlled control slide the membrane in the area of Sucking stroke end position scans and in this suction stroke end position the membrane the connection from the storage room to the pressure room opens. The leak is only supplemented if the Membrane a predetermined limit position at the end of the suction stroke has reached.

A modified membrane control system is also already available known, by means of which also a premature Leakage supplementation can be prevented. Here too is one influenced by the respective membrane system Control system provided that with spring-loaded control pins is working. These usually hold the leakage valve mechanically closed. However, if by the diaphragm is movably guided in the suction stroke end position Perforated plate against the force of springs accordingly is moved, this also moves the control pins, so that the leakage valve is released.

However, such known membrane control systems have the Disadvantage that they are structurally complex. They also have to be set very precisely in order to small diaphragm strokes, especially in high pressure diaphragm pumps occur with metal membranes to function exactly.

The invention is therefore based on the object, the diaphragm pump of the generic type for the elimination of the described To design disadvantages such that with little constructive effort to address the Sniffer valve, especially during the occurrence of the Coupling vacuum peak, is prevented and thus avoided is that such negative pressure peaks already at the beginning trigger the sniffer valve during the suction stroke.

The features of the invention created to achieve this object result from claim 1. Advantageous refinements of these are described in the further claims.

The invention is based on the essential idea that Sniffer connection between pressure room and storage room not by the membrane structure, but by the location of the Control the displacer yourself. This is done in such a way that the piston as a control element, in particular as a control slide, serves the at least at the beginning of the suction stroke Sniffer connection between pressure room and storage room interrupts and only releases this connection when he has covered part of his suction stroke. The piston preferably provides the sniffing connection then free when he has traveled about half of his stroke Has.

Overall, this effectively prevents the vacuum peak occurring at the beginning of the suction stroke Sniffer valve triggers prematurely because of this time the sniffer connection between the pressure chamber and the storage room is still inevitably closed by the piston.

Such, controlled by means of the respective piston position Sniffing disability can be done with simple constructive Realize funds while ensuring at the same time is that it works effectively.

In an embodiment of the invention, it is possible to use the piston to act directly or indirectly as a spool, but in any case with a membrane control system associated design effort is avoided. The Control is according to the low pressure side provided so that here by the piston each a channel on the pantry side is closed is held or opened in a controlled manner.

In the principle according to the invention set out above, according to which the piston has a channel on the storage space side the sniffing connection for a certain time at the beginning holds its suction stroke closed, the design be taken such that the pantry side Channel of the sniffer connection in the cylinder bore for the piston opens. This canal-side canal then with a piston channel that opens into the storage space, associated when the piston is part of its Suction stroke.

As a modification of this, it is also possible to indirectly use the piston to act as a control, for example the piston at its rear end with a parallel running Auxiliary control slide is connected. This is in a part of the sniffer connection channel on the storage room side displaceable and because it is hollow or is designed as a sleeve, the connection to the storage room interrupt depending on the stroke position of the displacer or release.

Overall, the invention is simple prevents that at the beginning of the suction stroke in the hydraulic system occurring vacuum peak a premature response of the snifting valve causes an overfill of the pressure chamber with hydraulic fluid.

Fig. 1

schematisch im Schnitt eine hydraulisch angetriebene Membranpumpe mit einer durch den Kolben bewirkten hochdruckseitigen Steuerung der Schnüffelbehinderung; diese ist jedoch nicht Gegenstand der Erfindung;

Fig. 2

schematisch in Form zweier Diagramme (1. Druck über Hubweg = Indikatordiagramm und 2. Druck über Zeit) den Kurvenverlauf charakteristischer Daten beim Druckhub sowie Saughub der Membranpumpe zur Darstellung der beim Beginn des Saughubes auftretenden Unterdruckspitze;

Fig. 3

eine Ausführungsform der Erfindung mit einer niederdruckseitigen Steuerung der Schnüffelbehinderung;

Fig. 4

eine gegenüber Fig. 3 abgewandelte Ausführungsform mit niederdruckseitiger Steuerung und

Fig. 5

eine weiterhin abgewandelte Ausführungsform mit einer einen zusätzlichen Steuerkolben (Hilfssteuerschieber) verwendenden niederdruckseitigen Steuerung.

The invention is explained below with reference to the drawing. This shows in:

Fig. 1

schematically in section a hydraulically driven diaphragm pump with a high-pressure control of the sniffing obstruction caused by the piston; however, this is not the subject of the invention;

Fig. 2

schematically in the form of two diagrams (1st pressure over stroke = indicator diagram and 2nd pressure over time) the curve of characteristic data during the pressure stroke and suction stroke of the diaphragm pump to show the vacuum peak occurring at the start of the suction stroke;

Fig. 3

an embodiment of the invention with a low-pressure control of the sniffing disability;

Fig. 4

an alternative to FIG. 3 embodiment with low-pressure control and

Fig. 5

a further modified embodiment with an additional control piston (auxiliary control slide) using low-pressure control.

In the hydraulically driven shown in Fig. 1 Diaphragm pump is a high pressure diaphragm pump, in which a metal membrane 1 is used. This is between two perforated plates 2, 3 - a perforated plate 2 with flat inner surface and a perforated plate 3 with concave Inner surface - clamped. These in turn are between a pump housing 4 and one detachable on the front side fixed pump cover 5 clamped.

The membrane 1 separates a delivery chamber 6 from one Hydraulic fluid filled pressure chamber 7.

The diaphragm pump shown has a hydraulic one Diaphragm drive in the form of an oscillating displacement piston 8 on, which is sealed in the pump housing 4 between the Pressure chamber 7 and a reservoir 9 for the hydraulic fluid is movable. In the illustrated embodiment here the piston 8 is sealed by means of a so-called joint seal.

The pump cover 5 has a spring-loaded in the usual way Inlet valve 10 and a spring-loaded outlet valve 11 on. These two valves 10, 11 are above one Inlet channel 12 and an outlet channel 13 with the Delivery chamber 6 in connection that the medium is at the 1 to the right according to FIG. 1 suction stroke of the displacer 8 and thus the membrane 1 in the direction of the arrow the inlet valve 10 and the inlet channel 12 into the delivery chamber 6 is sucked in. In contrast, the pumped medium in the pressure stroke to the left according to FIG. 1 of the piston 8 and thus the membrane 1 via the outlet channel 13 and the outlet valve 11 metered in the direction of the arrow from the Delivery chamber 6 pushed out.

In order to overfill the pressure chamber 7 with hydraulic fluid to prevent and so that the membrane 1 before too strong Deflection or stress during the pressure stroke too protect, a pressure relief valve 14 is provided, the via corresponding channels 15, 16 with the pressure chamber 7 and communicates with the storage room 9; it is so set that when an undesirable occurs large overpressure in the pressure chamber 7 at the end of the pressure stroke of the piston 8 opens, so that the excess Hydraulic fluid via the channels 15, 16 in the storage room 9 is discharged.

In a corresponding manner at the end of the membrane suction stroke To prevent cavitation from occurring and for that to ensure the leakage loss necessary to supplement the leakage, a leak supplement device 17 is provided. This has a conventional spring-loaded, vacuum-controlled Sniffer valve 18, which via a channel 19 with the Storage room 9 communicates. The connection of the leak supplement device 17 or the sniffer valve 18 with the pressure chamber 7 takes place via a further channel 20 which, 1, from the snifting valve 18 leads directly into the cylinder bore 21 for the piston 8 or flows there. In the illustrated embodiment This channel 20 on the pressure chamber side opens at one point the piston cylinder bore 21, which is about half the stroke h of the piston 8, i.e. in the middle between whose front and rear dead center lies.

As can be seen, the piston 8 holds the pressure chamber side Channel 20 of the leak supplement device 17 at the beginning of its Suction strokes are closed, so that the sniffer connection interrupted between pressure chamber 7 and storage room 9 is. This connection is only then through the piston 8 released when he has covered part of his suction stroke Has. Only then is the leak supplement device 17 or the sniffer valve 18 is able to when a Excessive negative pressure caused by leakage losses for refilling hydraulic fluid from the storage room 9 to worry about.

The arrangement shown, in which the controlled Sniffing on the high pressure side is suitable are particularly suitable for stroke-controlled diaphragm pumps with constant Piston center position. As already stated, the piston 8 as a spool for temporarily blocking the Leakage supplement 17 used to their premature To prevent response at the beginning of the piston suction stroke. To The beginning of the suction stroke is the piston 8 in the Position according to Fig. 1, in the front face approximately flush with the corresponding wall of the pressure chamber 7 completes. In this piston position, that of position 3 2 corresponds to the two diagrams, is the Channel 20 of the leakage supplement device 17 on the pressure chamber side closed by the piston 8. After the piston 8 in the course of its suction stroke to position 4 in the respective 2 has moved, the generated is sufficient Suction pressure ps from opening the inlet valve 10. Subsequently need the liquid column in the inlet line 12, the inlet valve 10 and the membrane 1 accelerated be, creating a vacuum peak with the amplitude Δp is generated as in position 4 in the respective Diagrams according to FIG. 2 can be seen. This as a Joukowsky push designated vacuum peak would normally be a early response of the sniffer valve 18 and thus an undesirable overfilling of the pressure chamber 7 with Effect hydraulic fluid from the reservoir 9. While this time, however, is the channel 20 on the pressure chamber side still closed by the piston 8, so that due to this purely piston-controlled sniffing obstruction the sniffer valve 18 do not respond to the vacuum tip mentioned can. Not until the end of the suction stroke, after that the piston 8 the distance h shown in FIG. 1 (= Suction stroke) has passed, the end face passes of the piston 8, the opening of the channel on the pressure chamber side 20 and releases it. So now during one remaining short piston stroke distance the addition of Hydraulic fluid from the reservoir 9 through the channels 19, 20 possible in the pressure chamber 7.

In the embodiment shown in FIG. 3 the invention is - in contrast to the high-pressure control of the Sniffing disability according to FIG. 1 - a low-pressure side Control of sniffing disability provided. This is suitable are particularly suitable for diaphragm pumps with constant stroke length, the seal of the piston 8 within its cylinder bore 21 also - just like the one previously described Embodiment according to FIG. 1 - by means of a Single joint seal is formed.

3 as can be seen from that of the snifting valve 18 of the leakage supplement 17 outgoing pressure chamber side channel 20a arranged such that it is not in the cylinder bore 21 of the displacer 8 opens out, but runs to the pressure chamber 7 and on whose end wall opens out.

The duct 19 on the storage room side, which, starting from the sniffer valve 18, runs in the direction of the pantry, is also intended. However, the sniffer valve 18 opens opposite end not directly in the storage room 9, but as it were only indirectly. For this purpose, the channel 19 on the storage room side with its sniffer valve 18 opposite end in an additional channel 19a, the - across extending to the axis of the displacer 8 - in one bush-like insert part which slidably guides the piston 8 22 runs and in turn into the storage room 9 flows out.

The piston 8 points at a certain point on it Longitudinal extension of an annular groove 23, this point is selected such that it is at a distance h (piston stroke) to the additional channel 19a when the piston 8 is 3 front dead center position (pressure stroke end) having. This means that the piston 8 in the illustrated Location, which is also the beginning of the suction stroke - accordingly position 3 in the two diagrams according to FIG. 2 - Indicates, keeps the additional duct 19a closed and hence the sniffer connection between the storage room 9 and pressure chamber 7 interrupts. Then if the piston 8 in Course of its suction stroke from left to right according to FIG. 3 moved and position 4 in the two diagrams 2 passes through, the occurring vacuum peak not to trigger the sniffer valve prematurely 18 lead because the annular groove 23 of the piston 8th is still at a distance from the additional channel 19a, so that the sniffer connection to the storage room is interrupted is.

Then when the piston 8 has reached the end of its suction stroke is and according to position 1 in the two 2 the dash-dotted line 3, the annular groove is located 23 of the piston 8 at the level of the additional channel 19a. Thereby is the sniffer connection via channels 19a, 19 and 20a produced between the storage space 9 and the pressure space 7, so when in the hydraulic system due to a defect there is an excessive vacuum in hydraulic fluid, the sniffer valve 18 responds and automatically the missing Hydraulic fluid from the reservoir 9 supplemented. Then when the piston 8 starts again with the pressure stroke and from position 1 to position 2 according to the two 2 moves, the ring groove shifts 23 of the piston 8 immediately out of alignment with the additional channel 19, so that it is closed immediately and the Sniffer connection interrupts.

In the modified embodiment according to FIG. 4, the configuration is similar to that of the embodiment 3 taken. What is different, however, is that the Piston 8 in its bore 21 not by means of a single-joint seal, but sealed by means of piston rings 24 is in the usual way on the piston 8th are set.

In addition, the piston 8 instead of an annular groove 23 with a provided reduced diameter piston part 8a, so that thereby between this reduced diameter piston part 8a and the associated cylinder bore 21 an annular space 23a is formed, the function of that of the annular groove 23 corresponds.

As can be seen, it is the one with the canal-side duct 19 connected additional channel 19a formed such that it transverse to the axis of the piston 8 - not the whole Insert 22 penetrates, but only in the cylinder bore 21 of the piston 8 opens out. The connection between the additional channel 19a and the storage room 9, at corresponding piston position, manufactured in that in the insert 22 is a further channel 19b provided by the Storage space 9 extends to the cylinder bore 21 of the piston 8 and there at a point that is offset from the mouth of the additional channel 19a, opens out.

As can be clearly seen from Fig. 4, is shown in the Position of the piston 8, the position at the end of Pressure stroke or at the beginning of the suction stroke according to the Corresponds to position 3 in the two diagrams according to FIG. 2, the sniffer connection between the storage room 9 and the pressure chamber 7 interrupted. The same also applies if the piston 8 in the course of its suction stroke the position 4 in the two diagrams according to FIG. 2, because here the two channels 19a, 19b still through the Pistons 8 are closed, so that in this position occurring vacuum peak does not lead to a premature response of the snifting valve 18 can lead. Only, when the piston 8 is in the course of its further suction stroke the position 1 in the two diagrams according to FIG. 2 approximates or reaches this position, the piston 8 comes along its reduced-diameter piston part 8a in the area of the two mouths of channels 19a, 19b. This will then the connection between these two via the annular space 23a Channels 19a, 19b made, so that hereby Sniffer connection between the storage room 9 and the Pressure chamber 7 is released and any required Leakage supplementation via the snifting valve 18 is made possible.

In the further modified embodiment according to FIG. 5 is also a low-pressure control of the Sniffing disability provided. For this purpose the Piston 8 parallel at its storage chamber end trending auxiliary spool in the form of an additional Control piston 25 on. This is on a piston 8 attached flange 26 arranged in the vicinity of its circumference and runs in such a way that it runs in a corresponding Channel 27 of the housing 4 is immersed. This housing channel 27 stands, as shown, on the one hand with the channel 19 of the leakage supplement device on the storage room side 17 in connection and on the other hand opens into the storage room 9 out.

The additional control piston 25 is hollow or as a sleeve ends open on both sides. This will, on the one hand in the position shown of the piston 8, which the End of the pressure stroke or the start of the suction stroke according to the Corresponds to position 3 in the two diagrams according to FIG. 2, the sniffer connection between the pantry 9 and the Pressure chamber 7 interrupted, since the control piston 25 largely is completely immersed in the housing channel 27 and thus closes the channel 19 on the storage room side. On the other hand, the additional control piston 25, if the piston 8 is near or in its suction stroke end position according to position 1 in the two diagrams Fig. 2 - is, together with the piston 8 accordingly moved so that the connection between the storage chamber-side channel 19 and the housing channel 27 is released. So then the sniffing connection between the storage room 9 and the pressure chamber 7 - over the hollow control piston 25, the housing channel 27, the storage room side Channel 19 and the pressure chamber side channel 20a-manufactured, so that with a corresponding negative pressure in the pressure chamber 7 the sniffer valve 18 responds and for an automatic Leakage supplement from the storage room 9 ensures.

Then when the piston 8 starts again with the pressure stroke and from position 1 to position 2 according to the two 2 moves, the plunges synchronously the piston 8 shifting control piston 25 again in the Housing channel 27 and closes the storage room side again Channel 19.

Claims (5)

1. A hydraulically driven high-pressure diaphragm pump having

   a metal diaphragm (1) clamped on the edge side between pump housing (4) and pump cover (5) and separating a delivery space (6) from a hydraulic pressure space (7),

   a hydraulic diaphragm drive in the form of an oscillating displacing piston (8) which is displaceable in a cylinder bore (21) of the pump body (4) between the pressure space (7) and a reservoir (9) for the hydraulic fluid, and

   a replenishment device (17) having a breather connection in the form of a connecting channel (19, 20) between pressure space (7) and reservoir (9) which is normally closed by a vacuum-controlled, spring-loaded blow valve (18), whereby

   the blow valve (18) divides the connecting channel into a channel (19) on the reservoir side and a channel (20) on the pressure space side, and

   the channel (19) on the reservoir side is adjustable by the position of the piston (8) such that the channel (19) on the reservoir side is closed at least at the beginning of the filling stroke, and released only when the piston (8) has covered part of its filling stroke path.
2. The high-pressure diaphragm pump of claim 1, characterized in that the piston (8) releases the breather connection between pressure space (7) and reservoir (8) about after half of its filling stroke path.
3. The high-pressure diaphragm pump of claim 1 or 2, characterized in that the piston (8) has a tapered-diameter portion (23, 23a) serving to release the channel (19, 19a) on the reservoir side when the piston (8) has covered part of its filling stroke path.
4. The high-pressure diaphragm pump of claim 1, characterized in that the piston (8) is connected at its reservoir side end with a parallel extending auxiliary slide valve (25) which is displaceable in a housing channel (27) forming part of the channel on the reservoir side and serves to release the channel (19) on the reservoir side.
5. The high-pressure diaphragm pump of claim 4, characterized in that the auxiliary slide valve (25) is formed as a sleeve.

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