Production method for a combination component with a PTFE material and combination component produced by means of said production method

Abstract

The present invention relates to a production method for a combination component with a PTFE material integrally joined thereto and to a combination component produced by means of said production method. The aim of the invention is to improve a production method for a combination component with a PTFE material such that the molded part is manufactured more quickly and more economically with less material use while greater reliability in continuous operation is obtained. To achieve this aim, the part made of the material having higher temperature resistance is inserted or laid into a lower part (10) of a sintering mold (11) such that a portion of the part that is widened and / or provided with undercuts (8) protrudes freely into a space between the lower part (10) and an associated upper part (12) of the sintering mold (11), and a predefined amount of a pulverous PTFE material is introduced into the lower part (10) of the sintering mold (11), the sintering mold (11) is closed, pressed and then, while at a specific pressure, heated up to a melting temperature of the PTFE material over a process time in a specified way and subsequently cooled while at a defined pressure, and finally the combination component (1) is removed from the opened sintering mold (11).

Description

[0001] Manufacturing process for a combination component with a PTFE material and combination component manufactured thereafter

[0002] The present invention relates to a manufacturing method for a combination component with a PTFE material and a part made of a higher temperature-resistant material as a so-called insert, which is integrally connected to the PTFE material, as well as a combination component manufactured according to this method.

[0003] PTFE materials have become a very important material for numerous technical applications in recent years, as they are chemically and mechanically very resistant from very low to high temperature ranges, are non-adhesive, and at the same time, can withstand high mechanical stress. Furthermore, the properties of PTFE can be tailored to a specific application through various measures and / or additives. Therefore, countless applications for molded parts made of PTFE material are known.

[0004] In addition to the many advantages in technical applications, PTFE materials also have disadvantageous properties, such as poor adhesive properties and poor weldability. Since PTFE materials cannot be processed using injection molding, particular challenges arise in the manufacture of molded parts in which a PTFE material has to be joined to another component or insert to form a combination component, in particular with a component made of a material with a higher temperature resistance, for example a metal, which has to be at least partially enclosed as an insert by the PTFE material for permanent fixation under force and / or form closure.The object of the present invention is to improve a manufacturing process for a combination component with a PTFE material and a component made of a higher temperature-resistant material such that a combination component can be manufactured more quickly, more cost-effectively and with greater resource conservation while maintaining greater mechanical reliability in continuous operation. Particularly in light of discussions about a potential threat to public health posed by per- and polyfluorinated alkyl substances, PEAS for short, and an impending ban on at least a widespread use of this group of substances in technology, as little PTFE as possible should be used to manufacture combination components of the type mentioned.

[0005] The above-mentioned object is achieved according to the invention by the features of claim 1 in that the part made of the higher temperature-resistant material is inserted or placed into a lower part of a sintering mold in such a way that a widened and / or undercut section of this part projects freely into a space between the lower part and an associated upper part of the sintering mold. A predetermined amount of a powdered PTFE material is then filled into the lower part of the sintering mold. The sintering mold is then closed, the PTFE material is pressed and then heated under a certain pressure in a predetermined manner over a predetermined process time up to a melting temperature of the PTFE material and then cooled under a defined pressure. Finally, the combination component can be removed from the opened mold.

[0006] The present invention is based on the discovery that a PTFE material attains a gel-like consistency when heated above a certain temperature and is therefore sufficiently malleable and flowable in a closed mold during a sintering process under pressure to sufficiently enclose another component introduced into a sintering mold as a so-called insert for mechanically permanent fixing. This means that a multi-material combination component can be manufactured in one piece in a single process step with a reduced number of process steps. Using this method, several parts of largely any shape made of higher temperature-resistant materials can be at least partially enclosed or enclosed as inserts by a PTFE material in a manner predetermined by a particular type of accommodation in the sintering mold to form a one-piece combination component.The general omission of prefabricated PTFE components in a process according to the invention leads to a comparatively lower use of materials with shorter process times and energy savings compared to a known production method.

[0007] Advantageous further developments are the subject of the dependent claims. Accordingly, the combination component is manufactured with the exact final contour, i.e., in compliance with previously agreed tolerances of the respective dimensions upon removal from the defined, cooled press mold. This means that a combination component freshly removed from a sufficiently cooled sintered mold does not require any further machining by peeling, milling, grinding, etc. In addition to saving process time in the manufacture of a ready-to-use product, this also saves PTFE material and reduces a large amount of production-related waste.

[0008] According to a preferred embodiment of the invention, the part made of the higher-temperature-resistant material is positively integrated into the combination component with a PTFE material. Therefore, no additional auxiliary materials are required for this mechanical connection.

[0009] According to a further development of the invention, in the manufacturing process, a melting temperature of the PTFE material is maintained at approximately 375°C under a pressure of approximately 100 bar to approximately 800 bar for a duration dependent on a maximum wall thickness, which duration generally amounts to a few minutes. Cooling under a defined pressure to approximately ambient temperature then takes place with essentially linear temperature control for a duration which, as with heating and maintaining the temperature, depends on a maximum wall thickness of the respective PTFE component.

[0010] As a combination component within the meaning of the present invention, in a preferred embodiment, a known valve diaphragm comprises a clamping edge enclosing a diaphragm surface, wherein the diaphragm surface has a sealing lip and an actuator tappet formed from a metallic pin, via which the diaphragm surface installed in a valve is mechanically movable between adjustable open positions and a closed position. To meet ultra-high purity requirements with the highest chemical and mechanical resistance over a wide range of operating temperatures, one side of the valve diaphragm that is in contact with a fluid medium in an application is formed with a sealing lip made of a PTFE material. A known manufacturing process provides for the assembly of such a valve diaphragm from the following separately prefabricated components:

[0011] - a circuit board as a stamped part from a PTFE film;

[0012] - an actuator plunger or pin made of corrosion-resistant steel with a widened base part;

[0013] - a hollow cone or dome as a turned part made from a sawn PTFE plate and a PFA disc as a turned part made from a PFA rod material.

[0014] To produce this valve diaphragm, the PFA disc is currently placed on the center of the PTFE board in the lower part of a sintering mold, onto which the base of the pin is placed. The dome is then pushed over the pin to enclose the base of the pin together with the PFA disc. The sintering mold is then closed with an upper part, with the described arrangement then passed through a furnace under pressure and heating up to the melting temperature of the PTFE material for a predetermined time and then cooled under a defined pressure. The finished combined component removed from the sintering mold, made up of the individual parts mentioned, is then subjected to further machining if necessary.

[0015] EP 3 825 089 A1 discloses a method for producing a fluororesin molded article. This method involves pressing different PTFE powders using a primary mold to produce a preformed article composed of regions or layers of different PTFE powders. Here, too, a metal part can be inserted into the preformed article. Following sintering of this preformed article in a secondary mold with subsequent cooling of the preformed article sintered in the secondary mold during pressing, the workpiece can be removed and reworked.

[0016] Process engineering advantages are achieved by specifically applying a manufacturing method according to the invention with the features described above, in that an actuator tappet or pin is inserted into a recess in a lower part of a compression mold in such a way that a widened and / or undercut foot part projects freely into a space between the lower part and an associated upper part of the compression mold, a predetermined amount of a powdered PTFE material being filled into the lower part of the compression mold, the compression mold then being closed and heated under a certain pressure in a predetermined manner over a predetermined process time up to a melting temperature of the PTFE material and then cooled under a defined pressure. The finished combination component is then removed from the opened sintered mold and does not need to be reworked because it is finished to its final contour.

[0017] Since, according to the described prior art, each individual component generally had to be machined separately, the process according to the invention not only saves labor and time, but also saves a considerable amount of material. In particular, the additional use of PFA is eliminated, and the use of PTFE powder, regardless of its grain size or admixtures, can be essentially limited to the weight of a respective PTFE component without waste or waste.

[0018] In a preferred embodiment of the invention, the combination component is manufactured as a membrane with a membrane surface made of a PTFE material and an actuator tappet integrally connected to it by a form-fitting connection, as a single part made of a higher-temperature-resistant material, according to predetermined final contours. This eliminates the need for subsequent machining steps.

[0019] According to an advantageous development of the invention, the diaphragm surface extends into a sealing ring that radially surrounds the diaphragm surface. Preferably, the sealing ring has a plurality of closed sealing lips. Furthermore, in one embodiment of the invention, the diaphragm surface has at least one additional sealing lip extending through a center of the diaphragm surface.

[0020] Further features and advantages of embodiments of the invention are explained in more detail below with reference to an exemplary embodiment based on the drawing. In this drawing, a schematic representation shows:

[0021] Figures 1a and 1b: perspective views of an embodiment of a membrane designed as a combination component from above and below;

[0022] Figure 2 : a sectional view of a plane AA of Figure 1b ;

[0023] Figure 3 : a sectional view of a membrane manufactured according to known methods.

[0024] The same reference numerals are used for the same elements throughout the various illustrations in the drawing. Without limiting the invention, the following describes only one use of exemplary embodiments of the invention against the background of a use of a combination component in the form of a diaphragm component of a diaphragm valve for clean room applications. However, it is obvious to a person skilled in the art that a combination component described below can also be adapted to other external shapes and a different material selection is possible in the same way in order to correspond to different applications and / or other areas of use. Almost any geometry with a finished net shape, from oval to square, can be produced using a method according to the invention, with or without inserts.

[0025] The illustrations in Figures 1a and 1b show perspective views of a diaphragm 2 designed as a combination component 1, obliquely from above and below, as is basically known from the prior art and, viewed superficially from the outside, can also be produced according to the present invention. Such a diaphragm 2 is installed in a diaphragm valve housing (not shown in detail here) in order to adjust the opening width of a flow opening between a maximum open position and a reliably sealing closed position in order to control the flow of a fluid medium, as a rule, continuously. For this purpose, this combination component 1 is connected in one piece to a diaphragm surface 3 which is active for this control and to an actuator tappet 4 which is mechanically moved or adjusted accordingly in order to set a flow opening of the diaphragm valve.

[0026] According to the prior art, a manufacturing process for producing a membrane 2 of the type mentioned comprises assembling several separately prefabricated components. A circuit board 5, from which the actual membrane surface 3 is subsequently formed, is punched from a PTFE film. An insert in the form of an actuator tappet 4 or pin made of a corrosion-resistant metal, such as nickel-chromium steel, is produced with a widened base part 6 as a turned and / or milled part. A hollow cone 7 or dome adapted to the outer contour of the actuator tappet 4 and having a chamfer for receiving a widened base part 6 of the actuator tappet 4 is also provided as a turned part, the starting material here being a sawn PTFE plate. Alternatively, in this embodiment, a base part 6 of the actuator plunger 4 is provided with a groove 8 for forming an undercut.Finally, a thin, profiled PFA disk 9 is manufactured as a turned part from a PFA bar. The production of the blank 5, hollow cone 7, and PFA disk 9, in particular, is very material- and time-consuming due to the various machining steps involved.

[0027] The circuit board 5 is first inserted into a lower part 10 of a sintering mold 11 in a manner not shown in more detail. The PFA disk 9 is then placed on the center of the circuit board 5, and the base part 7 of the pin 4 is arranged vertically on this disk 9. The dome 8 with a recess is then pushed over the pin 4 such that the dome 7 encloses the base part 6 of the pin 4 together with the PFA disk 9. The sintering mold 11 is then closed by an upper part 12, wherein a recess is provided in the upper part 12 for part of the pin 4, in which recess the pin 4 is received over a predetermined length. After sintering and cooling, the combination component 1 is removed from the opened sintering mold 11, measured at certain test points and usually reworked by deburring, peeling, milling or grinding.

[0028] A sectional view of the known membrane component 2 as a finished combination component 1 consisting of a membrane 2 made of a PTFE material with an actuator tappet 4 made of nickel-chromium steel is shown in Figure 3. Accordingly, after completion of the press-sintering process, the hollow cone 7 with the PFA disc 9 and the membrane 2 form a composite body with a predetermined shape, which encloses the base part 6 of the actuator tappet 4 as an insert in a form-fitting manner.

[0029] In addition to the high expenditure on material and process time with high offcuts and waste, the membrane 2 described above as a combination component 1 also has the problem that the membrane surface 3 formed from the circuit board 5 is connected to the formed hollow cone 7 via the PFA material of the disk 9. Experience has shown that this connecting surface therefore represents a mechanical weak point in the known membrane 2 because the combination component 1 can tear at the interfaces between the PTFE materials and the PFA material. In addition to possible air inclusions at the said interfaces, the different thermal expansion coefficients of steel and PTFE also lead to the formation of defects at these connection points and material failure.

[0030] Using the known sintering mold 11, a method according to the invention will now be described with reference to the illustration in Figure 2, by the implementation of which a combination component 1 is manufactured more quickly and cost-effectively with greater mechanical reliability in continuous operation. For this purpose, the actuator plunger 4 is positioned and inserted as an insert in a recess in the lower part 10 of the sintering mold 11 in such a way that a widened foot part 6 of the actuator plunger 4 provided with an undercut or, in this example, with a groove 8, projects freely into a space between the lower part 10 and an associated upper part 12 of the sintering mold 11. A predetermined amount of a powdered PTFE material is then poured into the lower part of the sintering mold 11, which powder remains in the lower part 10 under the effect of gravity, regardless of whether the PTFE material is free-flowing or not.The sintering mold 11 is then closed and heated under a specific pressure in a predetermined manner over a process time to a melting temperature of the PTFE material, and held there for a specific time to homogenize the molten PTFE material. The described arrangement is passed through a furnace under a pressure of approximately 100 to approximately 800 bar, depending on the material and heating, up to the melting temperature of the PTFE material at approximately 375°C over a predetermined time of a few minutes, and then cooled under a defined pressure.

[0031] In a specific embodiment of a membrane component 2 with a diameter D of the PTFE component of approximately 100 mm and a maximum material thickness d of approximately 8 mm, a time of up to 8 minutes is set for the melting process under 250 bar at a temperature of 375 °C, whereby greater maximum material thicknesses also require longer heating, holding, and cooling times in the described manufacturing process. After cooling under pressure to an ambient temperature of the assembly at approximately 30 °C, the membrane 2 is finally removed from the open sintering mold 11 as the finished combination component 1.

[0032] The diaphragm 2, with the diaphragm surface 3 made of a PTFE material and the actuator tappet 4 connected to it in one piece as a part made of a higher temperature-resistant material, forms a combination component 1 manufactured according to predetermined final contours, so that at least in the area of ​​the diaphragm surface 3 no further post-processing steps are required. This also makes designs on such a combination component 1 possible which, depending on the external shape, would make post-processing very difficult. Here, the diaphragm surface 3 runs into a sealing ring 13 which surrounds the diaphragm surface 3 in a radially closed manner and is accommodated in an installation position like a flange seal in a valve housing (not shown). The sealing ring 13 for this purpose comprises a plurality of radially closed sealing lips.In addition, the diaphragm surface 3 has a sealing lip 14 running through its center M with a length corresponding to a diameter of the diaphragm surface 3, which serves in an installed position of the combination component 1 to ensure a secure blocking effect of a diaphragm valve in a finally closed position.

[0033] The present invention has been described only by way of example with reference to a membrane 2 as a combination component 1, wherein particular features deviating from a radial symmetry, such as the sealing lip 14, have been emphasized in order to provide, in addition to the effective and material-saving production, new, expanded design options for a final-shape finished combination component

[0034] 1, which can be realized by this invention. The same applies to the use of several inserts or pins to be fixed in or on the membrane surface 3 instead of the only one actuator tappet 4 described here. With an oval or round outer shape, an exemplary embodiment of a membrane on a pin with an M5 threaded section was realized, which has an outer diameter D of approximately 100 mm. In an area around an approximately 10 mm wide base part 6 of the T-shaped pin, the membrane measures

[0035] 2 a thickness d of approx. 8 mm, which decreases towards an outer edge to approx. 1.3 mm. As a series, membranes with diameters D from approx. 40 mm to approx. 150 mm with thicknesses d of approx. 1.05 to approx. 1.6 mm are manufactured according to a process described above. List of reference symbols Combination component Membrane Membrane surface Insert, actuator tappet / pin made of corrosion-resistant metal Plate Base part Hollow cone or dome Chamfer / undercut on the base part 6 of the pin 4 Thin profiled disc made of PFA 0 Lower part of the sintered mold 11 1 Sintered mold 2 Upper part of the sintered mold 11 3 Sealing ring 4 Sealing lip d Thickness of a membrane 2

[0036] D Outer diameter of a membrane 2

[0037] M center of membrane surface 3

Claims

Claims 1. Manufacturing method for a combination component with a PTFE material and a part made of a higher temperature-resistant material, which is connected in one piece therewith and is known as an insert, characterized in that the part made of the higher temperature-resistant material is inserted or placed into a lower part (10) of a sintering mold (11) in such a way that a widened section of the part and / or a section provided with an undercut (7) projects freely into a space between the lower part (10) and an associated upper part (12) of the sintering mold (11), wherein a predetermined amount of a powdered PTFE material is introduced into the lower part (10) of the sintering mold (11), the sintering mold (11) is closed, pressed and then heated under a certain pressure in a predetermined manner over a process time up to a melting temperature of the PTFE material and then cooled under a defined pressure and the combination component (1) is finally removed from the opened sintering mold (11).

2. Manufacturing method according to the preceding claim, characterized in that the combination component (1) is manufactured with exact final contour.

3. Manufacturing method according to one of the preceding claims, characterized in that the part made of the higher temperature-resistant material in the combination component (1) is connected to a PTFE material under positive locking.

4. Manufacturing method according to one of the preceding claims, characterized in that a melting temperature of the PTFE material is kept at approximately 375°C under a pressure of approximately 100 to approximately 800 bar for a period of a few minutes, with cooling under a defined pressure to approximately an ambient temperature taking place essentially linearly over a period of a few minutes depending on a maximum wall thickness of the respective PTFE component.

5. Manufacturing method according to one of the preceding claims, characterized in that it is used to produce an integrally connected combination component (1) in the form of a membrane (2) with a membrane surface (3) made of a PTFE material and an actuator tappet connected in one piece thereto (4) made of a higher temperature-resistant material is used as an insert, wherein the actuator tappet (4) is inserted into a recess in a lower part (10) of a sintering mold (11) in such a way that a widened and / or undercut (8) provided foot part (6) of the actuator tappet (4) projects freely into a space between the lower part (10) and an associated upper part (12) of the sintering mold (11), wherein a predetermined amount of a powdered PTFE material is filled into the lower part (10) of the sintering mold (11), the sintering mold (11) is then closed and heated under a certain pressure in a predetermined manner over a process time up to a melting temperature of the PTFE material and then cooled under pressure in a defined manner and the membrane (2) is finally removed from the opened sintering mold (11) as a finished combination component (1).

6. Combination component (1) made of a PTFE material and a part made of a higher temperature-resistant material, characterized in that it has predetermined final contours is manufactured according to a manufacturing method according to one of the preceding claims.

7. Combination component (1) according to the preceding claim, characterized in that the combination component (1) forms a membrane (2) with a membrane surface (3) made of a PTFE material and an actuator tappet (4) connected thereto in one piece with a form fit as a part made of a higher temperature-resistant material.

8. Combination component (1) according to the preceding claim, characterized in that the membrane surface (3) runs into at least one sealing ring (13) which surrounds the membrane surface (3) in a radially closed manner.

9. Combination component (1) according to the preceding claim, characterized in that the sealing ring (13) has a plurality of closed sealing lips.

10. Combination component (1) according to one of the four preceding claims, characterized in that the membrane surface (3) has at least one sealing lip (14) which is formed by a Center (M) of the membrane surface (3).

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