EP0061706A1 - Air-pressure actuated double-diaphragm pump - Google Patents

Abstract

A double-diaphragm pump having a novel air-pressure reversal device is described, in which there is assigned to a valve controlled piston (52) for reversing the compressed air supplied to the two air chambers (20) of the diaphragm pump a mechanical energy storage device (238) which drives the valve control piston mechanically at the instant of reversal in such a way that even in the case of very slow pump operation the valve is quickly reversed by the stored mechanical energy, so that undefined intermediate positions, possibly accompanied by losses of compressed air, cannot occur. Owing to these measures in conjunction with novel sealing devices (132) for the moving parts, the pressure losses are reduced, and thus the efficiency of the pump is increased, and moreover special lubricating devices are avoided. According to a development, there is provided for the purpose of reversing the compressed air supplied to the two air chambers of the diaphragm pump a pilot valve control device (70) which drives the (main) valve control piston (52) pneumatically in such a way that the main valve is delayed at approximately half the length of stroke, at which position the main valve control piston disconnects the two air chambers both from the compressed air connection and from the exhaust connection, and connects them to one another instead for the purpose of pressure compensation. Owing to these measures, the pressure losses are even further reduced, and the efficiency of a pump thereby increased, and moreover the risk of icing during egress of air is diminished. <IMAGE>

Description

..The invention relates to a pneumatically driven double diaphragm pump comprising a pump housing having two spaced juxtaposed housing chambers, each having a _M embraneinrichtung and divided by this into a pump chamber and an air chamber, wherein the air chambers of the two housing chambers are aligned with each other and between have a compressed air reversing device that supplies compressed air to the two air chambers and alternately relieves the pressure on the air chambers, the pump chambers being connected via valve devices to a suction port and a pressure port, via which the material to be conveyed is sucked into the pump chamber due to the membrane movement generated by the compressed air is pressed out of the pump chamber, the compressed air reversing device having a main valve control piston for reversing the air chamber connection paths.

Compressed air driven double diaphragm pumps of this type are already known in various embodiments.

For example, the applicant's information document LP 004 shows a diaphragm pump of the type shown in FIG. 1. Such pressure Air diaphragm pumps are particularly suitable for rough pump operation, for example for pumping sludge, pastes, powders and the like. The advantage of such diaphragm pumps is that they require no rotating parts and no shaft seals and are completely dry-running. Diaphragm pumps of this type are self-priming and can optionally be used in over- and underwater operation. In particular, operation against closed pressure lines is also possible without an additional overflow valve.

The compressed air drive eliminates the need for separate drive devices with the base plates and couplings that are then required. Diaphragm pumps of the type described above are particularly compact and easy to transport and can be used independently of other energy sources, such as electrical energy in particular.

Since no tightly tolerated sliding or rotating parts are necessary and the movement speeds are low, abrasive, viscous and shear-sensitive media can also be conveyed without difficulty.

The pump can also be regulated in a simple manner by changing the air quantity of the supplied operating compressed air, without the need for expensive and complicated regulator drives.

Up to now, however, the compressed air reversal device, which is shown in FIG. 2, was problematic. The valve control piston used according to the figure in the known device works as a two-position valve, which either the in.Fig. Connects 1 air chamber shown on the left through the outlet with the free atmosphere, or relieves the right air chamber after switching.

The abrupt discharge in each case leads to strong flow noises and thus to the diaphragm pump working quite loudly. Another environmentally harmful fact is that the working air from the oil reservoir been pressed oil mist can be used as interfering admixture of the exhaust lead to the lubrication of the piston to a contamination of the surroundings of the diaphragm pump in the area of the outlet unless the need for expensive collecting and _F iltereinrichtungen be provided. Finally, in certain positions of the valve control piston, there is a direct path from air areas under working pressure to the areas of the pressure reversing device under atmospheric pressure, so that an undesired loss of compressed air occurs in these positions.

Compressed air losses also occur due to the tolerances between the piston and the housing, which cannot be reduced arbitrarily, which, despite the oil lubrication, cannot completely prevent the passage of compressed air.

In summary, it can be said that the known compressed air-driven double diaphragm pump shown in FIGS. 1 and 2 has an extremely simple construction and is very robust, but has a rather poor efficiency and, in addition, is highly polluting to the environment through noise and oil mist.

The object of the invention is to provide a double diaphragm pump of the type mentioned in the introduction, in which the compressed air reversing device is designed in such a way that the disadvantages described above are avoided.

The object is achieved in that the valve control piston is driven by a mechanically operating drive system with a mechanical energy store, the mechanical energy store in turn being actuated by the movement of the membrane devices.

Efficiency and noise reduction can be further improved with a slightly greater design effort by using a pneumatically operating pilot control system with a pilot valve control piston as the drive system for the valve control piston is used, the pilot valve control piston in turn being actuated by the movement of the membrane device. On the one hand, this results in a direct lock between the working air and outside air, and on the other hand the reversing of the main valve control piston can be carried out in such a way that there is pressure equalization between the two air chambers. This pressure equalization results, on the one hand, in a further improvement in the efficiency, namely in that the inevitable dead space in the air chambers is not acted upon by the working air itself, but rather by the relief air from the other air chamber, before the air chamber is supplied with the working air by the main valve control piston is associated. Furthermore, the pressure compensation also reduces the noise development, which is particularly evident at the outlet.

The new construction also makes it possible to use plastic-metal sealing surfaces instead of metal-metal sealing surfaces, so that lubrication with oil mist is unnecessary.

This not only prevents the environmental pollution caused by oil mist, the air losses due to tolerances between the valve piston and valve housing can be largely eliminated, since the metal-plastic seals are much denser than the metal-metal sealing surfaces, which improves efficiency.

As a result of the pressure relief during the draining process, which is reduced by the pressure compensation, the risk of icing at the air outlet is also reduced in the pump with a pilot valve, so that work can be carried out with increased performance without the risk of icing. However, the pilot valve pump tends to operate in extreme operating conditions, e.g. B. with very slow operation, to get stuck in the end positions. This mode of operation can result if the pump works against pressure, e.g. B. against a normally closed filling valve, with which the material to be conveyed should only be removed for a short time if necessary. In the This danger does not exist for pumps with mechanical energy storage devices that can be suddenly discharged. Depending on the application, one or the other embodiment will therefore be preferred.

The invention is explained in more detail below on the basis of exemplary embodiments which are illustrated in the drawings.

• Fig. 1 in einer Schnittansicht eine bekannte Doppelmembranpumpe;
• _Fig. 2 eine herkömmliche Druckluftumsteuereinrichtung, wie sie bei einer Doppelmembranpumpe gemäß Fig. 1 verwendet werden kann;
• _Fig. 3 eine mit der Doppelmembranpumpe gemäß Fig. 1 anwendbare, erfindungsgemäß verbesserte Druckluftumsteuereinrichtung in einer Längsschnittansicht, die durch den Ventilsteuerkolben gelegt ist;
• Fig. 4 eine Seitenansicht auf die Auslaßseite des Gehäuses der erfindungsgemäßen Druckluftumsteuereinrichtung;
• Fig. 5 eine quer zur Ventilachse verlaufende Schnittansicht durch die Umsteuereinrichtung, wobei der Schnitt längs der Linie V-V der Fig. 4 gelegt ist;
• Fig. 6 eine Seitenansicht von links auf die in Fig. 4 dargestellte Umsteuereinrichtung;
• Fig. 7 eine Seitenansicht von rechts auf die in Fig. 4 dargestellte Umsteuereinrichtung;
• Fig. 8 und 9 eine Teilradialschnitt- sowie eine Axialschnittansicht in vergrößerter Darstellung zur Erläuterung des Aufbaus des Kolbenzylinders;
• _Fig. 10 eine ebenfalls vergrößerte Axialschnittansicht des zugehörigen Kolbens;
• Fig. 11, 12, 13, 14 und 15 Einzelteile des Ventilsteuerkolbens;
• Fig. 16 eine Teilschnittansicht längs der Linien XVI-XVI der Fig. 5;
• Fig. 17 eine Schnittansicht längs der Linien XVII-XVII der Fig. 7;
• Fig. 18 eine Schnittansicht ähnlich der Fig. 1 zur Darstellung der Gesamtanordnung;
• Fig. 19 eine andere Ausführungsform der erfindungsgemäß verbesserten Druckluftumsteuereinrichtung in einer Längsschnittansicht, die durch den Hauptventilsteuerkolben gelegt ist;
• Fig. 20, 21, 22, 23 die wesentlichsten Teile der in Fig. 19 dargestellten Umsteuereinrichtung als einzelne Teile, wobei in Fig. 21 ein Axialschnitt und in'Fig. 22 verschiedene Radialschnitte des in Fig. 21 dargestellten Teils wiedergegeben ist;
• Fig. 24 eine durch die Pilotventilachse verlaufende Schnittansicht durch die neuartige Umsteuereinrichtung, wobei der Schnitt längs der Linie XXIV-XXIV der Fig. 19 gelegt ist;
• Fig. 25 einen gleichfalls durch die Pilotventilachse verlaufenden Schnitt, jedoch senkrecht zur dem Schnitt der Fig. 24, wobei dieser Schnitt längs der Linie XXV-XXV der Fig. 19 verläuft;
• Fig. 25a - 25c die einzelnen Teile der in Fig. 25 dargestellten Anordnung, wobei die Schnittansicht der Fig. 25a auch entlang der Linie XXVa-XXVa der Fig. 28 entspricht;
• Fig. 26 eine zum Schnitt der Fig. 25a parallele Schnittansicht längs der Linie XXVI-XXVI der Fig. 29;
• Fig. 27 eine zum Schnitt der Fig. 26 parallele Schnittansicht längs der Linie XXVII-XXVII der Fig. 29;
• Fig. 28 eine Seitenansicht auf die erfindungsgemäße Druckluftumsteuereinrichtung von rechts gemäß Fig. 24 in Richtung der Pfeile XXVIII-XXVIII;
• _Fig. 29 eine Seitenansicht von links gemäß Fig. 24 in Richtung der Pfeile XXIX-XXIX; und
• Fig. 30 in einer schematisierten Darstellung drei verschiedene Arbeitsstellungen des Hauptventils zur Erläuterung der Arbeitsweise der erfindungsgemäßen Druckluftumsteuereinrichtung gemäß der weiteren Ausführungsform.

It shows:

• Figure 1 is a sectional view of a known double diaphragm pump.
• _F ig. 2 shows a conventional compressed air reversal device, as can be used in a double diaphragm pump according to FIG. 1;
• _F ig. 3 shows a compressed air reversing device which can be used with the double diaphragm pump according to FIG. 1 and is improved according to the invention in a longitudinal sectional view which is laid through the valve control piston;
• 4 shows a side view of the outlet side of the housing of the compressed air reversing device according to the invention;
• FIG. 5 shows a sectional view running transversely to the valve axis through the reversing device, the section being taken along the line VV of FIG. 4;
• Fig. 6 is a left side view of the reversing device shown in Fig. 4;
• Fig. 7 is a right side view of the reversing device shown in Fig. 4;
• 8 and 9 are a partial radial sectional view and an axial sectional view in an enlarged view to explain the structure of the piston cylinder;
• _F ig. 10 is an enlarged axial sectional view of the associated piston;
• 11, 12, 13, 14 and 15 individual parts of the valve control piston;
• Fig. 16 is a partial sectional view taken along lines XVI-XVI of Fig. 5;
• Fig. 17 is a sectional view taken along lines XVII-XVII of Fig. 7;
• FIG. 18 is a sectional view similar to FIG. 1 to show the overall arrangement;
• 19 shows another embodiment of the compressed air changeover device improved according to the invention in a longitudinal sectional view which is laid through the main valve control piston;
• 20, 21, 22, 23 the most essential parts of the reversing device shown in FIG. 19 as individual parts, with an axial section in FIG. 21 and FIG. 22 different radial sections of the part shown in FIG. 21 are shown;
• 24 is a sectional view through the pilot valve axis through the novel reversing device, the section being taken along the line XXIV-XXIV of FIG. 19;
• 25 shows a section likewise running through the pilot valve axis, but perpendicular to the section of FIG. 24, this section running along the line XXV-XXV of FIG. 19;
• 25a-25c the individual parts of the arrangement shown in FIG. 25, the sectional view of FIG. 25a also corresponding to the line XXVa-XXVa of FIG. 28;
• FIG. 26 is a sectional view parallel to the section of FIG. 25a along the line XXVI-XXVI of FIG. 29;
• FIG. 27 shows a sectional view parallel to the section of FIG. 26 along the line XXVII-XXVII of FIG. 29;
• 28 shows a side view of the compressed air reversing device according to the invention from the right according to FIG. 24 in the direction of the arrows XXVIII-XXVIII;
• _F ig. 29 shows a side view from the left according to FIG. 24 in the direction of the arrows XXIX-XXIX; and
• 30 shows a schematic representation of three different working positions of the main valve to explain the mode of operation of the compressed air reversing device according to the invention in accordance with the further embodiment.

1 shows a somewhat schematic sectional view of a conventional compressed air-driven double membrane pump 10, consisting of a pump housing 12 with two housing chambers 14 arranged at a distance from one another, each of which has a membrane 16 and is divided into a pump chamber 18 and an air chamber 20 , wherein, as can be readily seen, the two air chambers 20 are aligned with one another and a compressed air reversing device 22 between them have the air from above supplied pressurized _A rbeits-, see arrow 24, the two air chambers 20 feeds (arrow 26).

The pump chambers are connected via ball valve devices 30 to a common suction port 32, which in turn is connected to a storage container supplying the medium to be conveyed, and via further valve devices 28 to a common pressure port 34, which is connected to the device, which is connected to this promotional good is to be delivered.

The membrane devices 16 each comprise annular membrane support plates 36, which are each screwed onto the end of a membrane piston 38 and hold an annular membrane 40 made of resilient material on their inner border between them in a pressure-tight manner, while the outer border of the annular membrane part 40 between the edges of correspondingly shaped parts of the pump housing 12, see e.g. B. the housing part 21 is kept pressure-tight.

2 shows in greater detail the compressed air reversing device 22 used in the double diaphragm pump according to FIG. 1, which consists of an air control valve housing 42 which can be screwed to the pump housing 12 and which has an inlet 44 for working air and an outlet 46 for exhaust air. The outlet 46 opens into a silencer 48 which is intended to dampen at least part of the flow noise of the escaping compressed air.

The known air control valve housing according to FIG. 2 has an oil container 50, and the working air flowing past at the upper end of a tube extending into this oil container sucks oil from the oil container 50 and atomizes it, so that the working air then entering the reversing device carries fine oil droplets with it serve to lubricate the moving parts of the air control valve housing. These moving parts around include a metal piston 52 which is displaceable between two end positions in a corresponding cylinder 54 formed by the housing 42 and made of metal.

In the position shown in FIG. 2, working air reaches the right air chamber 20 on the rear side of the membrane device 40 along the flow direction of the arrow 26 in FIG. 1, whereupon the air presses the membrane outward into the position shown in broken lines and thus the material to be conveyed out the pump chamber 18 promotes via the upper ball valve 28 in the pressure port 34.

At the same time, the other membrane on the left-hand side is pulled inward, and thus new product is sucked out of the suction port 32 through the lower ball valve 30 shown on the left into the left-hand pump chamber 18. During this time, the left air chamber is connected via a channel to the outlet space 64, which channel is formed by corresponding openings in the air control valve housing 42, designated by the reference numbers 60 and 62, to a respective opening bridge 58 which is located within the piston 52. At the same time, the space 66 located above the piston 52 is vented, so that, despite this space, the piston on this side is relieved of pressure by means of pressurized working air fed through narrow nozzles. The lower side of the piston 52, on the other hand, is not vented, so that the working air supplied leads to a build-up of pressure and finally moves the piston 52 away from the position shown in FIG. 2 and upwards, as a result of which the connection 58 present in the piston 52 now Openings 68 and 56 bridged and thus connects the right air chamber with the outlet space 64. At the same time, the corresponding connection of the left air chamber to the discharge space 64 is interrupted, as a result of which pressure can now build up in the left air chamber due to the working air, so that the working cycle is repeated in the opposite direction.

The known air control valve thus supplies both air chambers with working air under all operating conditions and in any position of the membranes. The membrane movement takes place by venting the air chamber.

This construction of the air control valve requires a piston, which is identified by the reference number 52 in FIG. 2. A disadvantage of this overall simple construction is the fact that the consumption of compressed air is high, as already explained at the beginning. In addition, the piston 52 must be lubricated by oil mist, which the incoming working air pulls out of the oil tank 50.

In FIG. 3, the essential structure of the pilot control system according to the invention according to a first embodiment can be seen in an axial sectional view parallel to the axis of the diaphragm piston 38 and the valve control piston 52. The view shown in FIG. 3 essentially corresponds to that of FIG. 1, so that here too the membrane 40 becomes visible, which is attached by membrane plates 36 by means of a screw 72 to the end of the membrane piston 38. The end of the diaphragm piston 38 also carries a stop plate 74, the inner annular surface 76 of which comes into contact with the front end of the valve control piston 52 and shifts the latter into the respective other position as soon as the diaphragm piston 38 reaches its respective end position. 3, it is the leftmost position in which the valve spool 52 is shifted to the left, as shown. FIG. 3 essentially represents a schematic view, while the further FIGS. 4 to 17 represent a practical exemplary embodiment, FIG. 4 representing a side view of the air outlet side of the housing 42 of the reversing device 22, while FIG. 5 shows a view of the piston axis vertical sectional view along the arrows VV, again through the housing 42 of the reversing device 22, without inserted individual parts.

In detail, the air pressure control device 22 comprises a _G e- _h äuse 42 having an inlet 44 for supply air and an outlet 46 for exhaust air. A muffler, not shown here, can be screwed into the exhaust air opening 46 in order to dampen the flow noise of the compressed air even more. An oil container is not shown here since the piston 52 is mounted in its cylinder 54 and in guides 232, see FIG. 3, in such a way that no metal-to-metal friction occurs, as will be explained in more detail later.

The piston 52, as can be seen, is parallel to the membrane piston 38 and can therefore be actuated very easily. Mechanically by the movement of, for example, the membrane support plate or the membrane plate, as has already been briefly explained in connection with FIG. 3.

In Figs. 8, 9 and 10 of the valve control = part 53 of the piston 52 in an axial section (Fig. 10) and the associated _K olbenzylinder 54 in a cross-sectional view (Fig. 8) and also an axial cross-sectional (Fig. 9) in reproduced on a scale that corresponds to that of FIG. 3, while the parts in FIGS. 4, 5, 6 and 7 are shown only about half as large.

The valve control piston device is now designed such that the piston cylinder 54 forms, together with the pistons 52, 53, annular spaces 202, 204 and 206, which serve to bridge different channels, which in turn end in openings, which can partly be seen in FIG. 3, but can be seen more clearly from FIG. 9.

In particular, the annular space 204 in the position of the piston 52 within the cylinder 54 shown in FIG. 3 is connected to the opening 208, which in turn opens via an annular space 212 - formed by the cylinder 54 - in a channel 210, which in turn is in the cast housing 42 5, 6 and 7. This channel 210 is in turn connected to a bore 213, see FIG. 16, which in turn is connected to the air chamber 20 in a manner not shown, see the bore 23 in the housing part 21 in FIG. 1.

However, the annular space 204 is also connected to bores 218, which can be seen in FIG. 9 and establish a connection with an annular space 220 formed by the cylinder 54, see also FIG. 3. This annular space 220 formed by the piston cylinder 54 protrudes a relatively narrow duct connection 222 in connection with the outlet space 64, from which exhaust air reaches the outlet 46, see FIGS. 4 and 5.

Thus, in the position of the piston 52 shown in FIG. 3 within the cylinder 54, there is an air connection between the outlet and the one air chamber 20, while the opposite air chamber 20 via the associated bore 213 and the associated channel 210 with the in FIG. 3 bores 208 shown on the right and are connected to the annular space 206. However, this space is also connected to bores 224 according to FIG. 9, which open to a further annular space 226 formed by the cylinder 54. Instead of the bores 224, incisions 225 starting from the end edge 227 can also be provided, as can be seen in FIGS. 8 and 9 and is also shown in FIG. 3. This annular space 226 is in turn connected to channels 211, see FIG. 17, which in turn open into the supply air space 216, as can be seen in FIGS. 5, 6 and 7. This means that the latter air chamber 20 communicates with the pressure inlet 44.

The situation is exactly the opposite when the piston 52 shown in FIG. 3 is not in the position shown, but in the position, not shown, shifted to the right.

He reaches this position in the following way: first, the connection between the air chambers 20 and the supply air or exhaust air is such that the membrane 40 moves to the right (as seen in FIG. 3). The plate 74 thus moves away from the end 228 of a plunger 230, which is inside a cap-like Guide 232 is axially slidably mounted, wherein an annular seal 234 effects a seal between the plunger 230 and the guide 232. The plunger 230 is screwed onto a threaded rod 236 which in turn has a plunger 230 at its other end, which is mounted in the same way as the plunger 230 already described. Arranged around the threaded rod 236 is a compression spring 238, which at its ends rests on driving disks 240, which in turn are supported on an annular shoulder 242, which is formed by the end face of the plunger 230, into which the threaded rod 236 is screwed. The drive plate 240 is shown in FIG. 14 in a sectional view and a top view, its particular shape being explained in more detail later. The drive plate 240 is designed so that it can slide on the threaded rod 236 in the axial direction, as well as within a bore 244 formed inside the part 53, which is closed at the two ends of the part 53 by inwardly pointing ring-like projections or ring shoulders 246 and which is interrupted in the middle by a further ring projection 248, see FIG. 3. The ring projection 248 as well as the ring projections 246 have such an inner diameter that the compression spring 238 pushed onto the threaded rod 236 can be pushed through it unhindered, but that the drive plate 240 can bear against the ring shoulders 250 and 252 formed by the ring projections 246 and 248, respectively.

So that the driving disk 240 shown in FIG. 14 can be introduced through the circular openings formed by the ring projections 246, it has the flattening 254 which can be seen in FIG. 14.

However, it is also possible, instead of the flattening of the driving plate 240 into the annular projections 246, to provide two opposing incisions through which a circular driving plate can be inserted, although this latter option is usually more complex in terms of construction.

In both cases, however, it is possible to insert a drive plate 254 into the corresponding cavity 256 of the piston 52 and then to place it against the associated ring projection 246. After the introduction of the first drive plate 240, the compression spring 238 can then be inserted from the other side and compressed to such an extent that the second drive plate 240 can also be inserted and placed against the associated annular shoulder 246. Then the threaded rod 236 can then be pushed through and the plunger _^ 23O then screwed on.

On the outer circumference of part 53, see FIG. 10, piston ring beads 136 can be seen, into which ring grooves 258 are made, into which sealing rings 132 can be inserted. These sealing rings 132 can be of a conventional type, for example they could be commercially available jacket rings which comprise an inner O-ring made of a rubber material and an outer race made of PTFE (Teflon). Compared to purely rubber-elastic sealing rings, jacket rings have lower running friction and lower breakaway forces even after long downtimes, and they also have high wear resistance even when completely dry. The PTFE is usually filled with powdered bronze, so that the z. B. also from bronze alloys existing metal parts of the valve piston 54 give favorable dry-running properties.

Between the two beads 136 with the annular grooves 258 there is a further bead 260, which is formed from a flat roof part 262 and two flanks 264 sloping down from the roof part 262, which again merge into a flat peripheral part 266, which is then inclined again by one Rising flank part 268 is limited, which is formed by the associated bead 136. This creates a cam track 261 on which balls 270 can slide or roll. More specifically, see FIGS. 3, 9 and 11, for example. B. a total of six four balls 270, which lie in corresponding bores 272, which, see FIG. 9, are mounted in the cylinder 54. These balls are by means of spring devices 274 (Fig. 11) against the Piston 52 formed cam track 261 pressed. The spring devices 274 can expediently be a correspondingly shaped ring spring, as is shown in perspective in FIG. 11.

With the help of this cam track 261 and the balls 270 sliding on this cam track and by means of the compression spring 238, the energy store for the valve changeover mentioned at the outset is implemented. The piston part 53 is initially held by the balls 270 in the position shown in FIG. 3, for example, so that a clearly defined position of the piston part 53 within the cylinder 54 and thus clear air duct connections are created. If the diaphragm piston 38 moves with the stop plate 74 to the right from the position shown in FIG. 3, the stop plate located on the left, not recognizable, will reach the plunger 230 there. (In the meantime, the right stop plate 74 has released the right tappet 230.) As the diaphragm piston 38 continues to move to the right, the left tappet 230 and thus also the threaded rod 236 and the right tappet 230 are now displaced to the right. The left tappet 230 presses the compression spring 238 together with its shoulder 242 and the drive plate 240 resting thereon, whereby it is supported on the right side against the drive plate 240 arranged there, which is held in place by the associated annular projection 246 of the piston part 53. The spring forces of the ring spring 274 for the balls 270 and the compression spring 238 are matched to one another in such a way that the piston part 53 is not released by the slowly increasing pressure of the spring 238. The piston part 53 will therefore remain in the position shown until, with the plunger 230 shifting further to the right, the driving disk 240 shown on the left finally reaches the annular shoulder 252 of the central annular projection 248. The compression spring 238 has now stored potential energy, but its compression force is still not sufficient to push the balls 270 up against the force of the ring spring 274 over the inclined surface 264. But now if the plunger 230 due to the very strong pressure of the stop plate 74 is shifted further to the right, this spring force of the spring 238 is supplemented by the force of the stop plate, which is also transmitted to the piston part 53 via the drive plate 24 ₀ and the shoulder surface 252. These common forces are sufficient to help the ball 27 ₀ over the hurdle of the flank 264. At the moment when the ball 270 has reached the flat surface of the roof part 262 of the cam track, relatively small forces are sufficient to move the piston part 53 further to the right, so that the force of the spring 238 is now independent of the further movement of the diaphragm piston 38 moves the piston part 53 to the right until the ball 270 passes through the flank 264 on the left and has reached the subsequent flat part 266. The piston part 53 has thus reached its second stable position in which the air chamber previously connected to the compressed air source is now connected to the exhaust air line, while conversely the air chamber previously connected to the exhaust air line is now connected to the compressed air source.

It can be seen that no undefined intermediate positions of the piston part 53 can occur due to this construction, so that in particular a sticking of the reversing device which is sometimes perceived as disadvantageous does not occur in an undefined intermediate position.

With regard to the piston-cylinder device 54 shown in FIG. 9, it should be added that it has ring projections 276, which form a plurality of receiving grooves 278 for sealing rings 280, the latter being recognizable in FIG. 3 and used to serve the various annular spaces formed by the cylinder 54, e.g. B. 212 to separate from each other pressure-tight.

As can also be seen from FIG. 3, the cylinder 54 is inserted into a corresponding bore 282 of the valve housing 42 and then held in place on both sides by the cap-like guides 232. The cap-like guide 232 is in turn festge by means of a holding plate 284 3, where a sealing washer 286 can also be seen. The holding plate 284 is in turn suitably secured to the side surfaces 288 of housing 42, see _F ig. 4, for example screwed together with the housing plate 21 of the pump chamber 18 resting on the reversing device, for example with the aid of screw bolts passed through bores 290 (FIG. 5).

The use of a cylinder insert bushing 54 which is inserted in a housing 42, permits the production of the housing 42 from _M etalldruckguß and so results in a very simple and cost saving manufacturing process without complicated metal processing steps.

The openings arranged in the valve cylinder sleeve 54, see for example the reference numbers 208, 224, 218, can also be formed in the form of elongated holes arranged in the circumferential direction, but several round holes arranged next to one another can be produced more easily and also result in better support of the sealing rings when they are passed over openings.

The reversing device according to the invention can be designed for different operating pressure ranges, it only being necessary to ensure that appropriately dimensioned spring devices are provided. At higher operating pressure, for example, the friction between the piston 52 and the cylinder wall of the cylinder 54 caused by the sealing devices 132 is higher, so that the spring 238 accordingly also receives a greater spring force in order to carry out the switching of the valve safely and quickly in the event of a trigger. Correspondingly, the ring spring 274, which is shown in one embodiment in FIG. 18, must then be dimensioned to be larger, so that the piston 52 is held securely until the drive plate 240 reaches the shoulder 252 for the purpose of triggering the changeover.

With the compressed air reversing device for a double diaphragm pump described above, a higher degree of efficiency is thus achieved above all, since air losses during the pump stroke practically do not occur, in particular also not when the pump is operated against higher pressures of the material to be conveyed (for example for pressures of several bar) and also not at a standstill under full air pressure with the pump pressure line closed (pressure maintenance). The improved sealing of the valve piston in the valve cylinder also contributes to this increase in efficiency because of the avoided air losses due to leaks.

Since lubrication is not required, the associated maintenance of an oil reservoir is also eliminated and, in particular, there is also no contamination of the pumped medium and the environment of the pump by exhaust air oil mist.

Due to the special design, the compressed air reversing device can also be maintained relatively easily, since the individual parts, in particular also the piston cylinder, can be easily replaced, the same applies to the valve piston and the various sealing rings, which may be subject to wear.

The membrane piston can also be mounted in exchangeable guide rings. Alternatively, storage can also take place in a bearing bush 37 with sealing sets, one of which (reference number 35) is shown in more detail in FIG. 18, which FIG. 18 shows the overall structure of the compressed air reversing device. Such interchangeable seal sets can be constructed similarly to the sealing rings used for the piston 52, i. H. e.g. B. from a bronze-loaded PTFE sealing ring and an O-ring made of z. B. synthetic rubber exist as an extrusion ring.

The overall construction of the compressed air reversing device 22 according to this and the embodiment of the present invention to be described later is designed so that it can be used for diaphragm pump units of different sizes. In particular, lets use the reversing device for any travel of the diaphragm, because the reversal always takes place in the last part of the respective stroke, ie that the valve travel of the pilot valve is independent of the travel of the membrane and in particular can be kept much smaller than the travel of the membrane. This not only increases the versatility of the reversing device, it also reduces wear.

The further embodiment working with a pilot control valve will now be discussed, reference being made to FIGS. 19 to 30.

In a longitudinal section in FIG. 19, a compressed air reversing device improved according to the invention is shown in a longitudinal sectional view, which essentially corresponds to the sectional view of FIG. 2, that is to say is laid through the axis of the main valve control piston 52 and at the same time perpendicular to the membrane piston 38 rigidly connecting the two membrane devices 60 to one another cuts.

This compressed air control device 22 also includes an air control valve housing 42 with an inlet 44 for supply air and an outlet 46 for exhaust air. A silencer can also be provided here, but it is not absolutely necessary because of the significantly lower flow noise of the compressed air according to the invention. An oil container is also missing here, since the piston 52 is mounted in its cylinder 54 in such a way that metal-metal friction no longer occurs, as will be explained.

The compressed air reversing device 22 shown in FIG. 19 now has, in addition to the main valve control piston, which is driven by compressed air as in the prior art, a pneumatically operating pilot control system serving to control this compressed air, consisting of a pilot valve control piston 70, which according to FIG. 19 is arranged perpendicular to the main valve 52 so that it is parallel to the diaphragm piston 38 and thus mechanically, for example, in a very simple manner from the movement the membrane support plates or membrane plate 36 can be actuated.

This can be seen more clearly in FIG. 24, which shows a sectional view through the membrane piston 38 and the pilot valve 70 according to the line XXIV-XXIV in FIG. 19. . Thus, the illustrated in Fig 24 view substantially corresponding to that of Figure 1, so that here too ^-. Diaphragm 40 is visible, which is secured of membrane plates 36 by a screw 72 at the end of the membrane piston 38. The end of the diaphragm piston 38 also carries a stop plate 74, the inner annular surface 76 of which comes into contact with the front end of the pilot valve control piston 70 and shifts the latter into the respective other position as soon as the diaphragm piston 38 reaches its respective end position. 24, it is the rightmost position in which the pilot piston 70 is shifted to the right, as shown. The pilot valve control piston 70 is shaped such that in this position it connects a central opening 78 in the pilot piston cylinder 80 with an opening 82 to the right of it according to FIG. 24, which can also be seen in FIG. 25, which figure is perpendicular to the sectional view of FIG 24 is a section through the pilot valve axis, see also arrows XXV-XXV of FIG. 19. The opening 78 can also be seen in FIG. 19, which is a longitudinal section through the main valve 52 and thus a section along the line IXX- IXX of FIG. 25. As can be seen, working air supplied to the inlet 44 thus flows, for example, via a dust filter 84 into the supply air space 86 and from there into the duct 88, from where the air passes through the opening 78 into the annular space 90 formed by the pilot valve 70. From there, the air then passes, see FIG. 25, according to the position of the pilot valve 70 shown in FIG. 25, through the opening 82 into a duct 92 which opens into a duct 94, which in FIG. 20 only contains the air control valve housing 42 19, can be seen in a sectional view similar to that in FIG. 19 and ends in an opening 96 at the right end of the cylinder 54. The right side of the main valve 52 shown in FIG. 19 is therefore under the pressure of the working air and the main valve therefore takes the pressure in _F ig. 19 shown position shifted to the left. This position is also shown schematically in FIG. 30 above, this schematic illustration simultaneously showing the two valve pistons 52 and 70 lying perpendicular to one another in their longitudinal extent.

Similar to the pilot valve, the main valve 52, together with its cylinder, forms 54 annular spaces, 98, 100 and 102, which are used to bridge different channels, which in turn end in openings which are partially recognizable in FIG. 19. overall, however, can be seen from the various radial sectional views in FIG. 22.

In addition to these three fairly wide annular spaces 98, 100 and 102, the main valve 52 also forms two narrow annular spaces 1 ₀ 4 and 106, which pass through a bore 108 running inside the valve piston 52 and through a radial bore 110 and 112, respectively, emanating from this axial bore 108 communicate with each other.

As can be seen from FIG. 19, the channel 88 and thus the pressurized supply air is connected via openings 114 to the annular space 98, which in turn is connected via an opening in the cylinder 54 above the drawing plane in FIG. can be seen in section D of FIG. 21/22 and provided with the reference number 116) and a further channel extending from this opening is connected to the left air chamber according to FIG. 24. The data associated with the connection to the right air chamber openings in the cylinder 54 are opposed strength in the _F. 19 recognizable, see reference number 118. These openings 118 open, see FIG. 20, in the channel 120, which can also be seen in FIG. 25, which is connected to the right air chamber. _Since , on the other hand, the annular space 100 is connected to the exhaust air space 124 via an opening 122 in FIG. 19 above the plane of the drawing, see section G of FIG. 21/22, this results in a desired ventilation of the right air chamber. The corresponding openings 126 for the other air chamber are in Fig. 19, in turn, can be seen as well as the conces- örige _h, leading to the exhaust chamber 124. Channel 128, see FIG. 20.

The situation described above will not be maintained for long. As a result of the supply air flowing through the central channel 108 of the main valve 52 and entering the left air chamber, the pressure in the left air chamber will increase and, when the pressure prevailing in the associated pump chamber, the left diaphragm and thus the associated diaphragm plate and the piston rod 38 will follow move left. This lifts the diaphragm plate from the end of the pilot valve piston rod 70. However, the pilot valve remains in its position since the right diaphragm with the associated diaphragm plate only reaches the right end of the pilot valve piston 70 at the end of the pump stroke and shifts it to the left. As can be seen in FIG. 30, a switchover takes place in such a way that the supply air entering through duct 78 no longer reaches the right duct 94 and thus the right end of the main valve 52, but instead via the left one, with the Reference number 194 provided channel to the opening 196 and thus to the left side of the main valve 52. The main valve 52 thus begins to shift to the right, but only with a delay, since the air on the right side of the main valve piston 52 passes through the opening 96 and the channel 94 must flow past a constriction into the right air chamber, which is currently vented, the constriction being formed by a ring 128 which is carried by the pilot valve control piston and which is only slightly smaller in diameter than the inside diameter of the pilot piston cylinder 80 the annular wall 130 resulting from the cylinder wall and the outer circumference of the nozzle ring is dimensioned such that under the operating conditions, the main valve moves in the other direction at a predetermined decelerated speed. There is a special reason for this.

It has already been said that it is favorable to balance the pressure between the two air before changing the stroke of the diaphragm pump to produce chambers, because on the one hand this makes better use of pressure energy and thus increases the efficiency, on the other hand the exhaust air then blown off into the free atmosphere has a lower pressure than the working air, so that the blowing noise is reduced and the risk of icing is reduced.

This pressure equalization is achieved by an intermediate position which is maintained for a sufficiently long time due to the slow changeover movement of the main valve 52 and which is shown under 2 in FIG. 30. In this intermediate position, the central bore 108 connects the openings 116 and 118 with their annular spaces 104 and 106, while the openings 132 connected to the exhaust air chamber and the openings 114 connected to the supply air chamber in annular spaces 100, 102 and 98 are blind end and are closed, as indicated by the crosses. This leaves only a connection between the left air chamber and the right air chamber, so that the desired pressure equalization between the two air chambers takes place via the openings 116 and 118 together with the associated connecting channels and the axial bore 108 of the main valve 52. _D a are provided in this communication path no constrictions, results in a sufficiently rapid pressure equalization, so that the main valve must not be moved very slowly, it must merely a sudden Across shooting can be prevented, as would occur without regard to the pilot valve 70 described constriction 130 .

The energy gained through pressure equalization depends on the size of the dead volume of the air chamber in the end position of the diaphragm pump. With the help of the pressure compensation, this dead space, which is initially at atmospheric pressure, is raised to a pressure by the right air chamber under working pressure, which depending on the volume ratio between the dead space and the maximally large other air chamber is either only slightly below the working pressure (with a very small dead space), or it drops a little more if the dead space is larger Takes up part of the usable space. In both cases, pressure equalization saves filling the dead space with valuable working air under pressure, so working air is only required to carry out the actual working stroke. Depending on the size of the dead space, efficiency improvements of between 10 and 30% can be achieved with the usual double diaphragm pumps.

Another advantage is that there is no direct connection path between the connection for working air and the outlet at any position of the membrane piston, as in the prior art, so that if the membrane piston rod stops at any point due to, for example, a blocked material flow, no working air is consumed. In the prior art, it could happen that this position was available at certain positions of the diaphragm piston rod, so that the result was a constant discharge of working air with correspondingly high operating costs.

30, three of the main valve pistons 52 have finally reached the other position shown on the right, the situation with respect to illustration 1 has just reversed, so that now the left air chamber is connected to the exhaust air chamber and thus to the atmospheric pressure that the remaining residual pressure, which is greatly reduced by the pressure compensation, is now released into the free atmosphere, while the right air chamber is supplied with supply air until the pressure in the right air chamber again reaches the pressure of the medium, whereupon the pump executes its next stroke.

The bores in cylinder 54 for the main control piston and the annular spaces of the main control piston are aligned with each other so that when the pilot valve is switched over and thus the drive air for the main control piston is reversed, the main control piston initially progresses quickly on the first half of its path and that in Fig. 30 , 2 position shown reached. In the meantime, however, an air cushion has built up on the exhaust side of the main control piston due to the throttling in the pilot valve (annular gap 130), so that the main valve piston 52 is decelerated pretty much in this central position and thus remains in the position in which the Pressure equalization can occur through the overflow of air from one air chamber into the other. At the same time, supply air and extract air are blocked, only the two air chambers are connected. In the other position finally reached, the filling of the previously relieved air chamber and the relieving of the previously filled and partially relieved by pressure equalization other air chamber then begins.

The savings in compressed air consumption due to the pressure equalization described above are even greater if the diaphragm pump is only operated with a reduced stroke length for various reasons. When the stroke length is reduced, the dead spaces increase.

Another advantage can be seen in the fact that the air chambers are no longer suddenly emptied from the full working pressure when switching, but only from the reduced pressure achieved by the pressure equalization, so that hard pressure peaks are avoided, which not only adversely affect the noise level, but also load the individual parts of the pump.

It has already been stated that the new construction works without oil mist. This can be achieved in that the main valve and the pilot valve are formed by cylinder sleeves 54 and 80, in which the valve pistons 52 and 70 slide, which have annular grooves (for example the wide annular grooves 98, 100 and 102 of the piston 52 and its narrow one Ring grooves 104 and 106 and the ring groove of the pilot piston 70, which is provided with the reference number 90), which are closed by sealing rings made of flexible material. These sealing rings, which have the reference number 132 in FIG. 3, are in corresponding grooves 134 inserted in piston ring beads 136, see FIG. 23. In the case of the pilot piston, a corresponding sealing ring 132 is pushed onto an annular surface 138 (see FIG. 25c) against a shoulder 140 and then held in place by the throttle ring 128 which is then pushed on, see also FIG. 25.

These sealing rings 132 can be of a conventional type, for example it can be commercially available jacket rings which / an inner O-ring made of a rubber material and an outer race made of PTFE (Teflon). Compared to pure rubber-elastic sealing rings have a lower shrouds _L attrition and reduced breakaway forces on even after long standstill times, they also have high resistance to wear even with a completely dry operation. The PTFE is usually filled with powdered bronze, so that the z. B. also from bronze alloys existing metal parts of the valve devices result in cheap dry-running devices.

The ring 128 serving as a throttling device can also be made of PTFE and, for example, form a gap of approximately 0.2 mm between its outer circumference and the inner surface of the piston insert 80, which gap is usually sufficient to achieve the desired air throttling effect and thus the deceleration of the main valve.

The described sealing rings make it possible to avoid any air loss between the piston and piston housing, although no oil lubrication is provided.

The use of cylinder insert bushes, which are inserted into a housing 42, allows the production of the housing 42 - from die-cast metal and thus results in a very simple and cost-saving manufacturing process without complex metalworking steps.

The openings arranged in the valve cylinder sleeves 54 and 80 (in FIG. 21, for example 114, 118, 126) could also be in shape are formed by elongated holes arranged in the circumferential direction, but several round holes arranged next to one another can be produced more easily and also result in better support of the sealing rings when these openings are passed over.

In order to manufacture the main piston 52 according to FIG. 23, in particular its axial bore 108, the component is either first produced from two parts 152 and 153, see FIG. 23, or a one-piece component is cut at point 154 and then the axial bore 108 is introduced, after which the two parts 152 and 153 are connected to one another, for example by welding.

The main valve arrangement, consisting of the cylinder 54 and the piston 52, is fixed after insertion into the housing by double-sided sealing and retaining screws 1-38, 140, see FIG. 19.

In the pilot valve, the valve sleeve 80 and the piston 70 are held by the housing walls 142 of the diaphragm pump, see FIG. 24, to which the air control valve housing 42 can be screwed in with the interposition of a sealing washer 144. Corresponding threaded holes can be seen in FIGS. 28 and 29 and are given the reference number 144.

The storage of the membrane piston 38, see for. 24, takes place in interchangeable guide rings, three of which are shown in FIG. 24 and have the reference number 146. Also interchangeable seal sets 148, which are constructed similarly to the seal rings 132, i.e. between two of these guide rings 146. H. from a bronze-loaded PTFE sealing ring and an O-ring made from e.g. B. synthetic rubber as a pressure ring.

With the compressed air reversing device according to the two embodiments described above, a higher degree of efficiency is thus achieved, above all, since there are no air losses during a stroke of the pump and in the changeover phases, especially not when operating the pump against higher pressures of the material to be pumped (for example of a few bar) and also not at a standstill under full air pressure with the pump pressure line closed (pressure maintenance). The improved sealing of the valve pistons in their valve cylinders also contributes to this increase in efficiency due to the avoided air losses due to leaks.

As a result of the reduced pressure level of the blown-off air, the risk of freezing and noise are also reduced. _D a lubrication is not required, eliminating the associated maintenance of an oil reservoir, and in particular also be dispensed with impurities of the conveying medium and the outside of the pump through the exhaust air-oil mist.

Due to the special design, the compressed air reversing device can be mass-produced in a relatively inexpensive manner, the individual parts, in particular the piston cylinders of the valves, can be easily replaced, as can the valve pistons and their sealing rings.

Claims (16)

1. Compressed air driven double diaphragm pump (10) consisting of a pump housing (12) with two spaced apart housing chambers (14), each having a membrane device (16) and divided by this into a pump chamber (18) and an air chamber (20) , the air chambers (20) of the two housing chambers (14) being aligned with one another and having a compressed air reversing device (22) between them which supplies compressed air to the two air chambers (20) and alternately relieves the pressure on the air chambers, the pump chamber (18) via valve devices ( 28, 30) with a suction nozzle (32) and a pressure connection (34) are in connection through which the pumped _G ut sucked due to the generated by the compressed air diaphragm movement or pushed out of the pump chamber (18) into the pump chamber (18) The compressed air reversing device (22) has a valve control piston (52) for reversing the air chamber connection paths chnet that the valve control piston (52) via a mechanically operating drive system (238, 240, 242, 250, 252, 261, 270, 274) is driven with a mechanical energy store (238), the mechanical energy store (238) is in turn triggered by the movement of the membrane devices (16). 2. Double diaphragm pump according to claim 1, characterized in that the drive of the valve control piston (52) by means of the drive system by means of a rising edge (264) of a cam track (261) on which a spring-loaded ball (270, 274) rests is delayed. 3. Double diaphragm pump according to claim 1 or 2, characterized in that the drive system represents a changeover switch which can be actuated when the end positions of the diaphragm devices (16) are reached. 4. Double diaphragm pump according to one of claims 1 to 3, characterized in that the energy store is formed by a pressure spring (238) arranged inside the valve control piston (52). 5. Double diaphragm pump according to claim 4, characterized in that the compression spring (238) is arranged axially around a connecting rod (236), and is supported with its ends on a drive plate (240) which on the connecting rod (236) and within of the piston (52) is slidably arranged and the ends thereof on the one hand on a radially outwardly pointing annular shoulder (242) formed at the associated end of the connecting rod (236), on the other hand at the associated end of the piston (54) on one radially from the inner surface of the piston internal ring shoulder (250) can be supported. 6. Double diaphragm pump according to claim 5, characterized in that the piston inner surface has two further, approximately centrally arranged, radially inwardly facing annular shoulders (252) as further contact surfaces for the drive plates (240). 7. Double diaphragm pump according to claim 5 or 6, characterized in that the connecting rod (236) is part of the piston rod of the valve control piston (52). 8. Double diaphragm pump according to one of claims 1 to 7, characterized in that the valve from a in an injection molded housing (42) insertable cylinder sleeve (54) is formed, in which the valve control piston (52) is slidably received. 9. Double diaphragm pump according to claim 8, characterized in that the valve control piston (52) has annular grooves (258) which are closed by sealing rings (132) made of flexible material. 10. Double diaphragm pump according to claim 1, characterized in that a pneumatically operating pilot control system with a pilot valve control piston (70) is used as the drive system for the valve control piston (main valve control piston) (52), the pilot valve control piston (70) in turn from the movement of the Membrane devices (16) is actuated. 11. Double diaphragm pump according to claim 10, characterized in that the pneumatic drive of the main valve control piston (52) by the pilot control system (70, 80) by means of a constriction (130) in the channel for the drive air and / or the air displaced by the main valve control piston (52) is delayed is. 12. ' Double diaphragm pump according to claim 10 or 11, characterized in that the pilot control system (70, 80) is a pneumatic switch which can be actuated when the end positions of the diaphragm devices (16) are reached. 13. Double diaphragm pump according to one of claims 10 to 12, characterized in that the main valve control piston (52) passes through a central position in which the air chambers (20) are separated from the working air or the atmospheric air. ₁ 4. Double diaphragm pump according to claim 13, characterized in that the two air chambers (20) are connected to one another in the central position of the main valve control piston (52). 15. Double diaphragm pump according to one of claims 10 to 14, characterized in that the main valve and the pilot valve of in an injection molded housing (42) insertable cylinder sleeves (54, 80) are formed, in which the valve pistons (52, 70) are slidably received. ₁₆ . Double diaphragm pump according to claim 11, characterized in that the constriction (130) is formed by a ring (128) pushed onto the pilot valve control piston (70) and the wall of the pilot piston cylinder (80).

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