Patent Application
20190093652
The present invention relates to a diaphragm pump with a functionally safe diaphragm position control.
Diaphragm pumps have a delivery chamber with a suction connection and a pressure connection and a working chamber which is separated from the delivery chamber by a diaphragm. In order to deliver a medium, the diaphragm is moved to and for in an oscillatory manner between a first and a second position, in which the working chamber is filled with a hydraulic fluid to which an oscillating pressure is applied. The two positions of the diaphragm are normally designated as the pressure stroke position and as the suction stroke position.
Usually, the pressure connection is connected to the delivery chamber via a pressure valve formed as a check valve, and the suction connection is connected to the delivery chamber via a suction valve, likewise formed as a check valve. During the movement of the diaphragm from the first to the second position, the so-called suction stroke, the volume of the delivery chamber is enlarged, which means that the pressure in the delivery chamber falls. As soon as the pressure in the delivery chamber falls below the pressure in a suction line connected to the suction connection, the suction valve opens and medium to be delivered is sucked into the delivery chamber via the suction connection. As soon as the diaphragm moves from the second position in the direction of the first position again (this is the so-called pressure stroke), the volume in the delivery chamber decreases and the pressure in the delivery chamber rises. The suction valve is closed in order to prevent the medium to be delivered from flowing back into the suction line. As soon as the pressure in the delivery chamber exceeds the pressure in a pressure line connected to the pressure connection, the pressure valve is opened, so that the delivery medium in the delivery chamber can be forced into the pressure line.
The diaphragm itself can be preloaded in a sprung manner in the direction of the suction stroke position. The diaphragm will always assume a position in which the forces acting on the diaphragm cancel one another out. The forces generated by the fluid pressure in the delivery chamber and those generated by the sprung preload in the direction of the suction stroke position counteract the forces generated by the fluid pressure in the working chamber.
The application of an oscillating pressure to the hydraulic fluid thus leads to an oscillating movement of the diaphragm and, associated with this, to an oscillating pumping process of the delivery fluid from the suction line into the pressure line.
Hydraulically operated diaphragm pumps are preferably used in the delivery of delivery fluids under high pressures, since, as a result of the hydraulic fluid, uniform loading of the diaphragm is carried out and the latter thus has a long service life.
Here, the application of the oscillating pressure to the hydraulic fluid is normally carried out by means of a moving piston. It is possible that, in the event of severe contamination of the suction valve or flow past the piston, the quantity of fluid in the working chamber will deviate from the desired quantity. In this case, either too much hydraulic fluid can be collected in the working chamber, so that the diaphragm is deflected beyond its pressure stroke position, or there can be too little hydraulic fluid in the working chamber, so that the diaphragm cannot reach the pressure stroke position. In the first case there is the danger of excessive loading of the diaphragm, which reduces its service life and can lead to damage. In the second case, the delivery volume per stroke is undesirably reduced.
Solutions for this problem are described in the prior art, for example DE 10 2013 105 072 A1 discloses a solution according to which a movement of the diaphragm beyond the pressure stroke position opens a passage to a storage chamber of the hydraulic fluid, so that the pressure in the working chamber is automatically reduced.
Ideally, the supply of the diaphragm pump should be ensured under all load and operating conditions, in order to avoid damage to the diaphragm pumps and in particular to the diaphragm itself. The problem here is, in particular, faults which, for example, can occur as a result of a closed or contaminated suction line. In this case, there is too little or no delivery fluid in the delivery chamber. As described, the forces generated by the fluid pressure in the delivery chamber and the forces generated by the sprung preload in the direction of the suction stroke position counteract the forces generated by the fluid pressure in the working chamber. However, if there is no or too low a quantity of delivery fluid in the delivery chamber, the diaphragm can be deflected beyond the pressure stroke position, since the fluid pressure in the delivery chamber is too low.
To solve this problem, it is known, for example in the prior art, to fall back on powerful return springs. However, these have the disadvantages that severe cavitation arises in the delivery chamber, which is associated with foam formation and the development of noise, and the diaphragm is subjected to extreme loadings, above all at the clamping points.
The object of the present invention is therefore to overcome the disadvantages of the prior art and in particular to supply a diaphragm pump which prevents damage to the diaphragm in the event of a fault, with the development of noise and foam formation preferably being prevented.
This object is achieved by a diaphragm pump having a delivery chamber and a working chamber, wherein the delivery chamber comprises a pressure connection and a suction connection, and wherein the working chamber can be or is filled with a hydraulic fluid and is operatively connected to a pressure generating device in order to apply an oscillating pressure to the hydraulic fluid, further comprising a diaphragm having at least one diaphragm layer and a diaphragm core, which separates the delivery chamber and the working chamber from each other and which can be transferred from a pressure stroke position into a suction stroke position and back again, wherein the volume of the delivery chamber in the pressure stroke position of the diaphragm is smaller than in the suction stroke position, and wherein the diaphragm is or can be operatively connected to a diaphragm return device comprising a pull rod, which applies or can apply a return force on the diaphragm in the direction of the suction stroke position, and further comprising a storage chamber for holding the hydraulic fluid, and wherein the working chamber and the storage chamber are connected to each other by means of a return flow channel closed by means of a closure element, and wherein the closure element is operatively connected to the diaphragm core and the diaphragm return device, so that the return force and a pressure force counteracting the return force as a result of the fluid pressure in the working chamber act on the closure element, and wherein, when a predetermined triggering force is exceeded as a sum of the return force and the pressure force on the closure element, the return flow channel is opened. The invention is based on the surprising finding that, as a result of the inventive design of a closure element operatively connected to the diaphragm core and the diaphragm return device, the forces acting on the diaphragm can be limited effectively to a predetermined value in that, when a triggering force is exceeded, a return flow channel is opened and the fluid pressure in the working chamber is reduced, in that the fluid can flow out of the working chamber into the storage chamber. If two forces act in opposite directions, then the result is that the magnitude of the overall force is reduced by the fact that the greater force magnitude is reduced by the smaller. However, this assumes that the forces act at the same point of action. In the diaphragm pump according to the invention, the return force acts on or in the region of the end of the pull rod of the diaphragm return device located opposite the diaphragm, and the pressure force acts in the region of the diaphragm. The points of action of return force and pressure force are thus located, according to the invention, on opposite sides of the closure element, so that the addition of return force and pressure force acts on the closure element itself. If, according to the invention, this sum exceeds a predetermined triggering force, the closure element is opened and the pressure force is reduced. Thus, the diaphragm is protected against excessively high loads. The delivery pressure in the delivery chamber, by contrast, counteracts the pressure force directly, since both forces act directly on the diaphragm on one side of the closure element. The pressure force is therefore reduced in its magnitude by the force of the delivery pressure in the delivery chamber acting against the former. If the delivery pressure in the delivery chamber falls abruptly, the magnitude of the pressure force conversely rises sharply, so that the resultant sum of pressure force and return force can lie above the triggering force, this initially being independent of the deflection of the diaphragm between suction stroke position and pressure stroke position. However, provision can in particular be made that, in the event of a deflection of the diaphragm away from the suction stroke position beyond the pressure stroke position, the closure element and the return flow channel are opened. In order to generate the return force, according to the invention spring elements are preferably used. If the diaphragm is moved away from the suction stroke position beyond the pressure stroke position, the return force of the spring element acting in the direction of the suction stroke position increases. At the same time, the pressure force counteracting the return force, generated by the fluid in the working chamber and acting on the diaphragm in the opposite direction, rises. By means of a suitable choice of the triggering force, the maximum deflection of the diaphragm can thus be determined. According to an inventive embodiment of the present invention, this can also be done irrespective of the delivery pressure in the delivery chamber. According to an embodiment of the present invention, it has proven to be particularly advantageous if the return flow channel extends partly in the diaphragm return device. According to the invention, the closure element is operatively connected to the diaphragm core and the diaphragm return device. It has transpired here that the return flow channel particularly suitably extends partly in the diaphragm return device, so that an integrated solution of diaphragm core, diaphragm return device, closure element and return flow channel can be provided. This configuration has proven to be particularly compact and reliable. In addition, it may be preferred for diaphragm core and pull rod to be detachably connected to each other, wherein, when the diaphragm core and pull rod are connected, the return flow channel is closed, and when they are not connected, the return flow channel is opened. Provision can be made where the closure element is formed by the diaphragm core.
According to this preferred embodiment, diaphragm core and pull rod together form the closure element. The two are detachably connected to each other, wherein the connection is released only when the triggering force is exceeded. Once the connection has been released, the working fluid can flow into the storage chamber through the return flow channel preferably partly integrated into the pull rod, so that the pressure in the working chamber decreases. According to an embodiment of the present invention, it may be preferable that the closure element comprises a magnet and/or is operatively connected thereto, wherein direction and intensity of the magnetic force correspond to the predetermined triggering force and, when the triggering force is exceeded the return flow channel is opened. According to the invention, provision can be made for the diaphragm core to comprise a magnet, which is operatively connected to the pull rod of the diaphragm return device and is designed and configured to keep the diaphragm core connected to the pull rod until the triggering force has been exceeded. If the triggering force is exceeded, the diaphragm core is detached from the pull rod and the two elements are present separately. In this state, the return flow channel preferably integrated in the pull rod is opened and the working fluid can flow into the storage chamber, so that the pressure in the working chamber, and thus the pressure force, is reduced. A magnetic connection according to the invention of diaphragm core and pull rod has in particular the advantage that a reversible solution is provided. As soon as the triggering force is undershot, diaphragm core and pull rod can be connected again and the diaphragm pump according to the invention can continue its operation without the diaphragm having been damaged. Of course, provision can also be made for the magnet to be comprised by the pull rod, by another element of the diaphragm return device and/or a further element of the diaphragm pump. Alternatively, provision can also be made where the closure element comprises an intended breaking point as overload protection, which resists the triggering force until the latter is exceeded and, when the triggering force is exceeded, breaks and the return flow channel is opened. Such an intended breaking point as a constituent part of the connection of diaphragm head and pull rod prevents the same re-coupling and thus leads to the situation where, in the event of a protective event occurring for the diaphragm, the corresponding component must be replaced before re-commissioning. Provision can also be made where the working chamber is arranged in a housing, wherein the return flow channel extends partly through the housing in the region of the pull rod. The working chamber of a diaphragm pump according to the invention is usually separated from the storage chamber by means of a housing. To provide the return flow channel which makes it possible for the working fluid to flow from the working chamber into the storage chamber, said channel must necessarily lead through the aforesaid housing. According to the invention, it has proven to be particularly positive if the return flow channel which extends partly in the pull rod is continued in the region of the housing adjacent to the pull rod. As a result, it is possible to dispense with hoses, lines and the like, so that an efficient and reliable solution is provided.
It may be particularly preferred that the diaphragm return device is guided partly through a region of the housing that is formed as a guide section, wherein the return flow channel has on its side facing the diaphragm return device an elongated connecting section along the deflection of the diaphragm return device, so that, irrespective of the deflection position of the diaphragm return device, the section of the return flow channel that is located in the diaphragm return device and the section of the return flow channel that is located in the housing are operatively connected.
Such a configuration of a return flow channel according to the invention makes it possible that no hoses, lines or the like are needed for a connection of the section of the return flow channel that is arranged in the pull rod and the section of the return flow channel that is located in the housing. Instead, irrespective of the deflection of the diaphragm return device, a secure connection of the section of the return flow channel extending in the latter to the stationary section which extends in the housing is made possible. Furthermore, provision can be made for the pull rod to be operatively connected to a spring element, so that the diaphragm is sprung preloaded in the direction of the suction stroke. It has proven to be advantageous, to provide the return force, to fall back on a spring element, which is connected to the end of the pull rod opposite the diaphragm. It may in particular be advantageous that the deflection of the pull rod is limited by means of a fixed stop, so that the pull rod cannot be moved from the suction stroke position beyond the pressure stroke position or a predetermined position further removed from the suction stroke position than the pressure stroke position. This has the advantage in particular that, in the event of an overfilling that occurs slowly, for example as a result of an increasingly contaminated suction line, a maximum deflection of the diaphragm can be defined. If the diaphragm is deflected beyond this point, the sum of return force and pressure force rises significantly and the return flow channel is opened. It has also proven to be advantageous that the working chamber and the storage chamber are connected to each other via a return flow channel closed by a further closure element, wherein the further closure element is connected to the pull rod so as to be movable relative to the latter, so that the further closure element can be transferred from a closed position into an open position and back, and wherein the further closure element comprises a force generating element and/or is operatively connected to the latter, which locks the further closure element in the closed position, and wherein the further closure element is transferred into the open position and the further return flow channel is opened when it is true of the pressure difference between the pressure in the storage chamber p2 and the pressure in the working chamber p1 that p2−p1>a, where a is a predetermined pressure.
Provision can be made where the further return flow channel extends partly in the diaphragm return device, in particular in the pull rod, and wherein the further return flow channel is preferably connected to the return flow channel.
It is thus possible to ensure that, in the event of a fluid loss in the working chamber, fluid can be topped up from the storage chamber as soon as the pressure in the working chamber falls below a predetermined value.
It is particularly advantageous that, according to the invention, the leakage compensation is integrated directly in the diaphragm return device and can be operatively connected to the same return flow channel, so that the number of apertures through the housing is minimized. Each connection extending through the housing is associated with the risk of a lack of tightness, in particular when there are high pressures in the working chamber, so that a housing that is closed as far as possible is fundamentally preferred.
Further features and advantages of the invention can be gathered from the following description, in which exemplary embodiments of the invention will be explained by way of example by using schematic drawings, without restricting the invention as a result.
Here:
In
The working chamber 5 is filled with a hydraulic fluid and is operatively connected to a pressure generating device, not shown, in order to apply an oscillating pressure to the hydraulic fluid.
The diaphragm 11 has at least one diaphragm layer 13 and a diaphragm core 15, wherein the diaphragm 11 can be transferred from a pressure stroke position into a suction stroke position and back again.
As shown in
The diaphragm 11 is additionally connected to a diaphragm return device 17, comprising a pull rod 19 which applies a return force on the diaphragm 11 in the direction of the suction stroke position.
Furthermore, a storage chamber 21 for holding the hydraulic fluid is shown, wherein the working chamber 5 and the storage chamber 21 are connected to each other by means of a return flow channel 25 closed by means of a closure element 23.
As can be seen in
The magnet 27 is designed and configured to maintain the connection between diaphragm core 15 and pull rod 19 until a triggering force is exceeded. The connection of diaphragm core 15 and pull rod 19, which together form the closure element, is acted on firstly by the return force R, which acts through the spring element 39 on the end of the pull rod 19 opposite the diaphragm. The return force R is counteracted by the magnitude of the pressure force D and the delivery pressure F of the delivery fluid in the delivery chamber 3. The pressure force D acts on that end of the pull rod 19 which faces the diaphragm 11. Thus, the sum of pressure force D and return force R acts on the connection of diaphragm core 15 and pull rod 19.
Furthermore, it is shown in
This elongated connecting section 37 is used for the purpose that, irrespective of the deflection position of the diaphragm return device 17, the section of the return flow channel 25 that is located in the diaphragm return device 17 and the section of the return flow channel 25 that is located in the housing are operatively connected, so that at any time the connection between the working chamber 3 and the storage chamber 21 can be produced.
An alternative embodiment of the present invention is illustrated in
A further embodiment is shown in
The further closure element 41 is operatively connected to a force generating element 45 which, in the embodiment according to
The features of the invention described in the preceding description, the claims and the drawings can be important, both individually and also in any desired combination, for the implementation of the invention in its various embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| DE 2017 122 270.7 | Sep 2017 | DE | national |
