Manufacturing process for a combination component with a PTFE material and the combination component manufactured thereafter

Abstract

The present invention relates to a manufacturing process for a combination component with a PTFE material and a combination component manufactured thereunder. To improve a manufacturing process for a composite component with a PTFE material in such a way that the molded part is manufactured faster and more cost-effectively with lower material usage while offering higher reliability in continuous operation, it is proposed that the part made of the higher temperature-resistant material be inserted or placed into a lower part (10) of a sintering mold (11) such that an expanded and / or undercut section (8) of the part projects freely into a space between the lower part (10) and an associated upper part (12) of the sintering mold (11), wherein a predetermined quantity 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 specific pressure in a predetermined manner over a process time until the PTFE material reaches a melting temperature, and subsequently cooled under defined pressure, and the combined component (1) is finally removed from the opened sintering mold (11).

Description

[0001] 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, as well as a combination component manufactured according to the method.

[0002] 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, non-adhesive, and at the same time, highly mechanically resilient. Furthermore, the properties of PTFE can be tailored to suit a specific application through various measures and / or additives. Therefore, countless applications for molded parts made of PTFE material are known.

[0003] Despite their many advantages in technical applications, PTFE materials also exhibit disadvantageous properties, such as poor adhesive properties and poor weldability. Furthermore, since PTFE materials cannot be processed using injection molding processes, particular challenges arise in the production of molded parts in which a PTFE material must be combined with another component or insert to form a combined component, particularly with a component made of a higher temperature-resistant material, such as a metal, which must be at least partially enclosed by the PTFE material as an insert for permanent fixation under force and / or form closure.

[0004] The present invention aims to improve a manufacturing process for a combination component comprising 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-efficiently, and more resource-efficiently, while maintaining greater mechanical reliability in continuous operation. Especially in light of discussions regarding a potential threat to public health posed by per- and polyfluorinated alkyl substances (PFAS) and the 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 this type.

[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 protrudes 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 poured into the lower part of the sintering mold. The sintering mold is then 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. Finally, the combination component can be removed from the opened mold.

[0006] The present invention is based on the finding that a PTFE material achieves a gel-like consistency when heated above a certain temperature and is therefore sufficiently malleable and flowable during a sintering process under pressure in a closed mold to sufficiently enclose another component introduced into a sintering mold as a so-called insert for mechanically permanent fixation. 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 largely arbitrarily shaped parts made of higher temperature-resistant materials can be at least partially surrounded or enclosed by a PTFE material as inserts in a manner predetermined by the respective 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 results in a comparatively lower material usage 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 mold. This eliminates the need for subsequent machining by peeling, milling, grinding, etc., of a combination component freshly removed from a sufficiently cooled sintered mold. In addition to saving process time in the manufacture of a ready-to-use product, this also saves PTFE material and reduces a significant amount of production-related waste.

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

[0009] According to a further development of the invention, the manufacturing process involves maintaining a melting temperature of the PTFE material at approximately 375°C under a pressure of approximately 100 bar to approximately 800 bar for a duration dependent on the maximum wall thickness, which typically amounts to a few minutes. Cooling under a defined pressure to approximately ambient temperature then occurs with a substantially linear temperature control over a duration that, like the heating and temperature maintenance, depends on the 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 during use 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: - a circuit board as a stamped part from a PTFE film; - an actuator plunger or pin made of corrosion-resistant steel with a widened base part; - a hollow cone or dome as a turned part made of a sawn PTFE plate and - a PFA disc as a turned part from a PFA rod material.

[0011] To manufacture this valve diaphragm, the PFA disc is currently placed on the center of the PTFE plate in the lower part of a sintering mold, onto which the base of the pin is placed. The mandrel 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, and the described assembly is then moved through a furnace under pressure and heating until the PTFE material reaches its melting temperature for a predetermined time, and then cooled under a defined pressure. The finished, one-piece combined component, removed from the sintering mold, is then subjected to further machining if necessary.

[0012] 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 preform article composed of regions or layers of different PTFE powders. Here, too, a metal part can be inserted into the preform article. Following sintering of this preform article in a secondary mold with subsequent cooling of the preform article sintered during pressing in the secondary mold, the workpiece can be removed and reworked.

[0013] Process-related advantages are achieved by applying a manufacturing method according to the invention in accordance 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 such that a widened and / or undercut foot part protrudes freely into a space between the lower part and a corresponding upper part of the compression mold. A predetermined amount of a powdered PTFE material is poured into the lower part of the compression mold. The compression mold is then 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 subsequently cooled under a defined pressure. The finished combination component is then removed from the opened sintering mold and, due to its completion in its final contour, does not require any further processing.

[0014] Since, according to the described prior art, each individual component usually 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 can be dispensed with, 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.

[0015] 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-fit 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.

[0016] According to an advantageous development of the invention, the diaphragm surface tapers into a sealing ring that radially encloses the diaphragm surface. The sealing ring preferably has several 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.

[0017] Further features and advantages of embodiments of the invention are explained in more detail below with reference to an exemplary embodiment and the drawings. In the drawings, a schematic representation shows: Fig. 1a and Fig. 1b: perspective views of an embodiment of a membrane designed as a combination component from above and below; Fig. 2: a sectional view of a plane AA of Fig. 1b; Fig. 3: a sectional view of a membrane manufactured by known methods.

[0018] The same reference numerals are used for identical elements throughout the various illustrations of the drawing. Without limiting the invention, only one use of exemplary embodiments of the invention is described below 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, in the same way, an adaptation of a combination component described below to other shapes and a different selection of materials is possible in order to correspond to different applications and / or other areas of use. Almost any final-shape geometry can be produced using a method according to the invention, with or without inserts.

[0019] The images of the Fig. 1a and Fig. 1b show perspective views of a diaphragm 2 designed as a combination component 1, obliquely from above and below, as is generally 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 to control the flow of a fluid medium, as a rule, continuously. For this purpose, this combination component 1 is integrally connected to a diaphragm surface 3 active for this control with an actuator tappet 4, which is mechanically moved or adjusted accordingly to adjust a flow opening of the diaphragm valve.

[0020] 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 foil. 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 of which here is a sawn PTFE plate. Alternatively, in this exemplary embodiment, a base part 6 of the actuator tappet 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 blank 5, hollow cone 7, and PFA disk 9, in particular, is very material- and time-consuming due to various machining steps.

[0021] In a lower part 10 of a sintering mold 11, the circuit board 5 is first inserted in a manner not further shown. The PFA disk 9 is then placed on the center of the circuit board 5, onto which the base part 7 of the pin 4 is arranged vertically. 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 a part of the pin 4, in which 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 specific test points and usually reworked by deburring, peeling, milling or grinding.

[0022] 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 a nickel-chromium steel is shown in Fig. 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.

[0023] In addition to the high material and processing time requirements, the above-described membrane 2 as a combination component 1 further presents the problem that the membrane surface 3 formed from the blank 5 is connected to the formed hollow cone 7 via the PFA material of the disc 9. Experience has shown that this connection surface represents a mechanical weak point of 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 these interfaces, the different thermal expansion coefficients of steel and PTFE also lead to defects at these connection points.

[0024] Using the known sintering mold 11, with reference to the figure of Fig.2 describes a method according to the invention, the implementation of which allows a combination component 1 to be 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 into a recess in the lower part 10 of the sintering mold 11 in such a way that a widened base 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 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 specified process time until the PTFE material reaches a melting temperature, where it is held for a specific time to homogenize the molten PTFE material. The described arrangement is passed through a furnace at a pressure of approximately 100 to approximately 800 bar, depending on the material and heating, until the PTFE material reaches its melting temperature of approximately 375°C over a predetermined time of a few minutes, and then cooled under pressure in a defined manner.

[0025] In a specific embodiment of a membrane component 2 with a PTFE component diameter of approximately 100 mm and a maximum material thickness of approximately 8 mm, a melting time of up to 8 minutes is set for the melting process under 250 bar at a temperature of 375°C. Larger 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 opened sintering mold 11 as the finished combination component 1.

[0026] The diaphragm 2, with the diaphragm surface 3 made of a PTFE material and the actuator tappet 4 integrally connected to it 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 enables designs on such a combination component 1 which, depending on the external shape, would make machining very difficult. Here, the diaphragm surface 3 tapers into a sealing ring 13 which surrounds the diaphragm surface 3 in a radially closed manner and, in an installed position, is accommodated in a valve housing (not shown) like a flange seal. The sealing ring 13 comprises several 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 installation position of the combination component 1 to ensure a secure blocking effect of a diaphragm valve in a finally closed position.

[0027] The present invention has been described only by way of example using a membrane 2 as a combination component 1. Particular emphasis has been placed on features deviating from radial symmetry, such as the sealing lip 14, in order to indicate not only effective and material-saving production but also new, expanded design possibilities for a final-shape combination component 1 that can be realized with this invention. The same applies to the use of multiple inserts instead of the single actuator tappet 4 described here. List of reference symbols 1 combination component 2 membrane 3 Membrane area 4 inserts, actuator plunger / pin made of corrosion-resistant metal 5 circuit boards 6 Footrest 7 hollow cone or dome 8 Chamfer / undercut on the foot part 6 of the pin 4 9 thin profiled disc made of PFA 10 Lower part of the sintering mold 11 11 Sintered mold 12 Upper part of the sintering mold 11 13 Sealing ring 14 Sealing lip M center of membrane surface 3 QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 825 089 A1

[0012]

Claims

[1] Manufacturing process for a one-piece combined component with a PTFE material and a part made of a higher temperature-resistant material as a so-called insert, characterized by , 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 and / or undercut (7) section of the part 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 specific 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 process according to the preceding claim, characterized by that the combination component (1) is manufactured with the exact final contour. [3] Manufacturing process according to one of the preceding claims, characterized by that the part made of the higher temperature-resistant material in the combination component (1) is connected with a PTFE material under positive locking. [4] Manufacturing method according to one of the preceding claims, characterized bythat a melting temperature of the PTFE material is maintained at approximately 375°C under a pressure of approximately 100 to approximately 800 bar for a period of a few minutes, whereby cooling under defined pressure to approximately an ambient temperature takes place essentially linearly over a period of a few minutes, which depends on a maximum wall thickness of the respective PTFE component. [5] Manufacturing method according to one of the preceding claims, characterized by that it is used for producing a one-piece combined component (1) in the form of a membrane (2) with a membrane surface (3) made of a PTFE material and an actuator tappet (4) made of a higher temperature-resistant material connected to it as an insert, wherein the actuator plunger (4) is inserted into a recess of 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 plunger (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 specific 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 bythat it is manufactured according to predetermined final contours by a manufacturing method according to one of the preceding claims. [7] Combination component (1) according to the preceding claim, characterized by 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 by that the membrane surface (3) runs into at least one sealing ring (13) which radially encloses the membrane surface (3). [9] Combination component (1) according to the preceding claim, characterized by that the sealing ring (13) has several closed sealing lips. [10] Combination component (1) according to one of the four preceding claims, characterized bythat the membrane surface (3) has at least one sealing lip (14) which runs through a center (M) of the membrane surface (3).

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