DE102018109933A1 - Process-oriented tensioning of a membrane package - Google Patents

Abstract

The present invention relates to a membrane pump with a membrane package and a membrane return device comprising a pull rod, the membrane package comprising a membrane and a membrane holding device fixing the membrane, the membrane package and the pull rod being non-positively connected to one another by means of a magnetic adhesive force.

Description

The present invention relates to a membrane package for a membrane pump.

Diaphragm pumps have a delivery chamber with a suction connection and a pressure connection, as well as a working chamber that is separated from the delivery chamber by a membrane. In order to convey a medium, the membrane is oscillated back and forth between a first and a second position in which the working space is filled with a hydraulic fluid which is subjected to an oscillating pressure. The two positions of the membrane are usually referred to as the pressure stroke position and the suction stroke position.

Hydraulically operated diaphragm pumps are preferably used when pumping conveying fluids at high pressures, since the hydraulic fluid places a uniform load on the diaphragm and this therefore has a long service life.

The quality of the diaphragm and its precise processing are of paramount importance for the operation of diaphragm pumps. To manufacture the membrane, a blank, usually based on PTFE (polytetrafluoroethylene), is initially provided and provided with a central locking hole, which is also referred to as the center.

If a high-quality membrane is provided, it must be integrated into a membrane package for use in a membrane pump. The highest precision is also required here. The membrane is usually clamped between two core components of the membrane core and centered by means of a guide element and the center.

The problem here is that the PTFE layer of the membrane has a thermal expansion coefficient that differs greatly from the other elements of the membrane package and thereby follows a non-linear thermal expansion. The reason for this is recrystallization at about 23 ° C. Between 10 ° C and 40 ° C this results in an increase in volume of approx. 6% in the PTFE layer, which leads to problems especially when it is braced.

In practice, there are temperature differences of up to 60 ° C between the assembly and the operation of membrane packages with correspondingly large volume changes in the PTFE layers. It should be noted that the core tension does not change linearly with the change in volume, but proportionally with a higher factor of, for example, 3 and more.

Several methods are therefore known in the prior art for such bracing. These are based on the fact that the membrane packs are either generated by means of a press bond under very high forces or that the bracing is provided by screwing the two core components together.

A press connection has the disadvantage that the setting and checking of the bracing is very complex and, moreover, such membrane packages have only a limited pressure resistance.

The membrane packages produced by screwing also have disadvantages. In order to ensure tension, the screw usually has to be tightened up to a fixed stop. The bracing process is usually completed in a certain time, since the provided screw lock, e.g. an adhesive that hardens. Since high forces are also required for clamping, a key width for gripping a tool is usually provided on the core components, which later poses a risk of deposits in the dosing room.

Thus, two methods are known, each of which has the particular disadvantage that only a certain amount of tension can be provided without a change to the membrane packet elements to be assembled and braced. In addition, the assembly itself is complex and not very flexible and must take place within a time specified by the assembly process (press bond, adhesive). Due to the different thermal expansion coefficients of membrane and core components described, a decrease in the PTFE volume of the membrane is disadvantageous, since the sealing effect in the clamping zone of the core is reduced. This is aggravated by the fact that, as already stated, the flow behavior of the membrane during pressing cannot be influenced directly, but is determined by the times specified for the respective processes.

In order to prevent the membrane from failing, the core must always be tightened so tightly during assembly that a sufficient amount of tension is maintained under all process conditions. This is complex and due to the high forces that are necessary for the bracing not always possible to a sufficient extent.

The object of the present invention is therefore to overcome the disadvantages of the prior art and, in particular, to provide a membrane package which, without variations on the components, allows simple and safe clamping with an adjustable amount of clamping for allows different process conditions, whereby the assembly process is additionally simplified and time-variable.

This object is achieved by a membrane package for a membrane pump, comprising at least one membrane holding element with a first connecting section, a membrane with at least one membrane system, and a clamping element with a second connecting section, the membrane being arranged in sections between the connecting sections of the membrane holding element and the clamping element, wherein a guiding element protruding from the diaphragm holding element is included, and the clamping element is connected to the guiding element of the diaphragm holding element by means of a fastening means without thread, the diaphragm being clamped with a tension force X between the connecting sections, and wherein the tension force X is not set by the fastening means.

The present invention is based on the surprising finding that a membrane package enables optimum tensioning of the membrane when the tensioning of the membrane is separated from the locking of the membrane package in the tensioned position.

According to the methods known from the prior art, the bracing and locking always take place in one step, be it in the known press connection or in the known methods with clamping screws.

The disadvantages of these solutions are completely eliminated according to the invention; rather, for the first time it is possible for a membrane package to be set without different mechanical changes to the tension.

For this purpose, the membrane is brought into contact with the first connecting section of the membrane holding element, then the clamping element is brought into contact with the membrane in sections under the action of force, and finally, after tensioning, the clamping element is firmly connected and fixed to the guide element by the fastening means.

For this purpose, it is advantageous according to the invention that the clamping element is connected to the membrane holding element with a threadless fastening means, since this threadless connection enables the clamping element to be freely positioned relative to the membrane holding element.

It is thus possible, as stated, to decouple the clamping force X provided by the membrane holding element and clamping element from the fastening means, so that this is not adjusted by the fastening means.

It is irrelevant which degree of tension is set. The clamping force X is freely selectable. External aids such as hydraulic presses can also be used, for example, in order to be able to provide particularly high assembly forces. It is particularly advantageous that the bracing can be set to different process conditions directly and without modifications to the individual elements of the membrane aspect, the particular coefficient of thermal expansion of the PTFE layers being able to be fully taken into account.

Furthermore, there is no time limit on the duration of the tightening process, since no hardening speed of a screw locking device has to be observed. The membrane flow process required for sealing can thus be further optimized and, if necessary, carried out slowly or with breaks. The operational reliability of the membrane package can thus be further increased.

It is also provided according to the invention that the membrane package is assembled fully or partially automatically. This is particularly advantageous since human sources of error, such as tightening the clamping screws too strongly or too weakly, are avoided according to the prior art. In addition, it is advantageous that the clamping element can have a surface that is as smooth as possible, so that, in comparison to the previous clamping screws, there are no points of attack for accumulation of dirt or deposits.

According to an embodiment of the invention, it can be provided that the first and / or the second connecting section comprises depressions which are arranged in particular in the form of concentric circles around the center of the membrane holding element and / or the clamping element.

Such depressions increase the mechanical resistance of the connection of membrane and membrane holding element or clamping element and can also serve to improve the seal.

Furthermore, it can be provided that the membrane and the clamping element each comprise a, in particular central, recess, so that the membrane and the clamping element are plugged onto the guide element and are guided by the latter in two axes of movement.

Such a design of a guide element has the advantage that, similarly to a clamping screw, centering of the membrane and clamping element with respect to the membrane holding element can be ensured.

It can be particularly advantageous that the guide element forms a receiving collar for the central receiving of the clamping element.

With such a receiving collar, the clamping element can be brought exactly into the desired contact with the guide element.

Furthermore, it can be provided that the clamping element is connected to the guide element by means of welding, gluing, crimping and / or pinning.

In contrast to the clamping screws known from the prior art, welding, gluing, crimping and / or pinning the clamping element and guide element enables a predetermined clamped position to be maintained without the fixing of the two elements having an influence on the degree of clamping. The welding, gluing, crimping and / or pinning obviously forms the fastening means according to the invention

It can be particularly advantageous here that the clamping element forms a groove for a weld seam in the connected state with the guide element of the membrane holding element, the groove being formed in particular on the side of the clamping element facing away from the membrane.

This formation of a weld seam has proven to be advantageous with high forces, since a stable and secure connection between the clamping element and the guide element is thereby achieved.

It can also be advantageous according to one embodiment of the present invention that the fixed connection of the guide element and the clamping element takes place exclusively in an area spaced apart by at least the thickness of the membrane in the fixed state from the connecting section to the end of the membrane holding element on the guide element side.

Regardless of the spacing around the thickness of the membrane in the fixed state, the fixed connection of the clamping element and the guide element in the context of the present invention differs from the prior art in that the connection is always made in the area of the clamping element on the guide element and not in Area of the membrane holding element, as would be the case with a clamping screw screwed into this.

However, it has proven to be particularly advantageous that a connection is made on the end opposite the second connecting section between the clamping element and the guide element, since a weld seam can be produced there in a particularly simple and reliable manner. In the case of crimping, gluing or pins for establishing the connection, it can be particularly advantageous if these are arranged, at least by the membrane thickness in the compressed state, from the second connection area, so that the membrane does not come into contact with the connection elements.

1. a) Bereitstellen eines Membranhalteelements mit einem ersten Verbindungsabschnitt und einem aus dem ersten Verbindungsabschnitt auskragenden Führungselement;
2. b) Bereitstellen einer Membran mit mindestens einer Membranlage und mit einer zu dem Führungselement korrespondierenden Aussparung;
3. c) Aufstecken der Membran auf das Führungselement und abschnittsweises in Anlage bringen der Membran an den ersten Verbindungsabschnitt;
4. d) Bereitstellen eines Klemmelements mit einer zu dem Führungselement korrespondierenden Aussparung und Aufstecken des Klemmelements auf das Führungselement und anschließendes in Anlage bringen an die Membran;
5. e) Beaufschlagen des Membranhalteelements, der Membran und des Klemmelements mit einer Kraft zum Erzeugen einer Verspannung des Membranpakets mit einer Spannkraft X; und
6. f) anschließendes Fixierens von Membranhalteelement, Membran und Klemmelement durch festes Verbinden des Klemmelements mit dem Führungselement im verspannten Zustand.

The invention also provides a method for producing a membrane package, in particular a membrane package according to the invention, comprising the following steps, in particular in this order:

1. a) providing a membrane holding element with a first connecting section and a guide element projecting from the first connecting section;
2. b) providing a membrane with at least one membrane system and with a recess corresponding to the guide element;
3. c) plugging the membrane onto the guide element and bringing the membrane into contact with the sections in the first connecting section;
4. d) providing a clamping element with a recess corresponding to the guide element and plugging the clamping element onto the guide element and then bringing it into contact with the membrane;
5. e) applying a force to the membrane holding element, the membrane and the clamping element to generate a tension of the membrane package with a tension force X; and
6. f) subsequent fixing of the membrane holding element, membrane and clamping element by firmly connecting the clamping element to the guide element in the tensioned state.

The method according to the invention also makes it clear that the invention is based on the separation of bracing and fixing.

It can be provided that the force provided in step e) and the resulting tensioning of the membrane are adapted to the desired process conditions for the use of the membrane.

Finally, the invention provides a use of a membrane package according to the invention in a membrane pump, the tensioning of the membrane package being predetermined by the process conditions of the membrane pump.

Further features and advantages of the invention result from the following description, in which exemplary embodiments of the invention are explained by way of example with reference to schematic drawings, without thereby restricting the invention.

• 1: einen perspektiver Ansicht einer Ausführungsform eines erfindungsgemäßen Membranpakets im nicht zusammengebauten Zustand;
• 2: einen perspektiver Ansicht der Ausführungsform eines erfindungsgemäßen Membranpakets mit auf dem Membranhalteelement angeordneter Membran; und
• 3: einen perspektiver Ansicht der Ausführungsform aus den 1 und 2 eines erfindungsgemäßen Membranpakets im zusammengebauten Zustand.

It shows:

• 1 : a perspective view of an embodiment of a membrane package according to the invention in the unassembled state;
• 2 : a perspective view of the embodiment of a membrane package according to the invention with a membrane arranged on the membrane holding element; and
• 3 : a perspective view of the embodiment from the 1 and 2 of a membrane package according to the invention in the assembled state.

In 1 is an example of an embodiment of a membrane package according to the invention 1 shown for a diaphragm pump, not shown. Here are in 1 the individual components of the membrane package 1 shown in the not yet assembled state. The 2 and 3 show the following assembly steps.

The membrane package 1 comprises a membrane holding element 3 with a first connecting section and a clamping element 5 , Between the membrane holding element 3 and the clamping element 5 is a three-layer membrane 7 arranged.

The membrane holding element 3 includes a cantilevered guide element, so that the membrane 7 and the clamping element 5 can be attached to the guide element and are guided by it in two axes of movement.

It can be clearly seen that in this exemplary embodiment the guide element forms a receiving collar for the central receiving of the clamping element.

It can also be seen that the first and / or the second connecting section comprises depressions in the form of concentric circles 9 around the center of the membrane holding member 3 and the clamping element 5 are arranged.

These depressions increase the mechanical resistance of the membrane connection 7 and membrane holding element 3 or clamping element 5 and can also serve as an improved seal.

According to the present embodiment, the clamping element is 5 with the guide element of the membrane holding element 3 is connected by welding, so that a weld 11 the fastener forms.

The weld seam forms a threadless connection between the membrane holding element 3 and the clamping element 5 out. It is clearly visible that the clamping element 5 in the connected state with the guide element of the membrane holding element 3 forms a groove for the weld seam, the groove on the side of the clamping element facing away from the membrane 7 5 is trained.

With regard to the 1 to 3 it is thus clear that to produce a membrane package according to the invention 1 first the membrane 7 on the diseased guide element of the membrane holding element 3 is put on and brought into contact with it. Then the clamping element 5 attached to the guide element and the membrane holding element 3 who have favourited Membrane 7 and the clamping element 5 is applied with a force for generating a tension of the membrane package with a clamping force X. The membrane package is then connected 1 through the fastener in the form of a weld 11 fixed.

It is thus clearly shown that the membrane is braced 7 from locking the membrane package 1 is separated in the tensioned position so that any clamping forces X can be set without changes to the structure of the membrane package 1 must be made.

The features of the invention disclosed in the preceding description, the claims and the drawings can be essential both individually and in any combination for the implementation of the invention in its various embodiments.

Claims (11)

Diaphragm package for a diaphragm pump, comprising at least one diaphragm holding element with a first connecting section, a diaphragm with at least one diaphragm system, and a clamping element with a second connecting section, the diaphragm being arranged in sections between the connecting sections of the diaphragm holding element and the clamping element, characterized in that one of the Diaphragm holding element projecting guide element is included, and the clamping element with the guide element of the Membrane holding element is connected threadless by means of a fastening means, the membrane being clamped with a clamping force X between the connecting sections, and wherein the clamping force X is not set by the fastening means. Membrane package after Claim 1 , characterized in that the first and / or the second connecting section comprises depressions which are arranged in particular in the form of concentric circles around the center of the membrane holding element and / or the clamping element. Membrane package after Claim 1 or Claim 2 , characterized in that at least one membrane layer of the membrane is made of a polytetrafluoroethylene-based material. Membrane package according to one of the preceding claims, characterized in that the membrane and the clamping element each comprise a, in particular central, recess, so that the membrane and the clamping element are plugged onto the guide element and are guided by the latter in two axes of movement. Membrane package according to one of the preceding claims, characterized in that the guide element forms a receiving collar for the central receiving of the clamping element. Membrane package according to one of the preceding claims, characterized in that the clamping element is connected to the guide element by means of welding, gluing, crimping and / or pinning. Membrane package after Claim 6 , characterized in that the clamping element forms a groove for a weld seam in the connected state with the guide element of the membrane holding element, the groove being formed in particular on the side of the clamping element facing away from the membrane. Membrane package according to one of the preceding claims, characterized in that the fixed connection of the guide element and clamping element takes place exclusively in an area spaced apart by at least the thickness of the membrane in the fixed state from the connecting section to the end of the membrane holding element on the guide element side. Method for producing a membrane package, in particular a membrane package according to one of the preceding claims, comprising the following steps, in particular in this order: a) providing a membrane holding element with a first connecting section and a guide element projecting from the first connecting section; b) providing a membrane with at least one membrane system and with a recess corresponding to the guide element; c) plugging the membrane onto the guide element and bringing the membrane into contact with the sections in the first connecting section; d) providing a clamping element with a recess corresponding to the guide element and plugging the clamping element onto the guide element and then bringing it into contact with the membrane; e) applying a force to the membrane holding element, the membrane and the clamping element to generate a tension of the membrane package with a tension force X; and f) subsequent fixing of the membrane holding element, membrane and clamping element by firmly connecting the clamping element to the guide element in the tensioned state. Procedure according to Claim 9 , characterized in that the force provided in step e) and the resulting bracing of the membrane is adapted to the desired process conditions of use of the membrane. Use of a membrane package according to one of the Claims 1 to 8th in a diaphragm pump, the tensioning of the diaphragm package being predetermined by the process conditions of the diaphragm pump.

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