SEALING ELEMENT AND MANUFACTURING PROCESS

Abstract

A sealing element made of a plastic, which is embodied to seal against an actuator and consists of a plastic or resin that can be handled in an injection molding process. In order to significantly improve a sealing tightness of injection molded sealing elements made of a plastic, according to the invention the sealing element, as a direct product of an injection molding process, is provided with a structure in the form of a groove in the sealing surface, which groove is distributed over the periphery of the sealing surface.

Claims

1. A sealing element that is embodied to seal against an actuator, the sealing element consists of a plastic or resin, which is compatible for use in an injection molding process, wherein, as a direct product of an injection molding process, the sealing element is provided with a structure having at least one groove in a sealing surface, and the groove is distributed over a periphery of the sealing surface.

2. The sealing element according to claim 1, wherein the sealing surface has a structure with closed grooves.

3. The sealing element according to claim 2, wherein the structure of the sealing surface is a microstructure.

4. The sealing element according to claim 1, wherein an axial surface roughness throughout a groove structure of the sealing surface has an average roughness value Ra<2 m or a lower limit of an average roughness depth Rz<5 m.

5. The sealing element according to claim 1, wherein an axial surface roughness throughout a groove structure of the sealing surface has an average roughness value Ra<1 m or a lower limit of an average roughness depth Rz<2 m.

6. The sealing element according to claim 1, wherein the plastic is a thermoplastic material.

7. The sealing element according to claim 6, wherein the thermoplastic material is a fluoroplastic.

8. A process for manufacturing the sealing element according to claim 1, comprising manufacturing the sealing element using an injection molding tool in which a negative structuring has been provided to form a sealing surface with a grooved surface structure.

9. The process according to claim 8, comprising using a thermoplastic material for manufacturing the sealing element.

10. The process according to claim 9, comprising using a fluoroplastic as the thermoplastic material.

11. The process according to claim 8, wherein in the injection molding tool for manufacturing the sealing element, which is to be manufactured with a surface structure on a sealing surface, a groove structure is produced by erosion, etching, or lasers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Other features and advantages of embodiments according to the invention will be explained in greater detail below with reference to an exemplary embodiment with the aid of the drawings. In the partially simplified depictions in the drawings:

[0014] FIG. 1: shows a cross-sectional view of a sealing element in the form of a sealing ring;

[0015] FIGS. 2a to 2c: show enlarged details of a sealing surface manufactured with a known injection molding process and with a process according to the invention as well as a sample measurement of a roughness depth across a section of a sealing surface manufactured with a process according to the invention;

[0016] FIG. 3: shows a cross-sectional view of a holder of a sealing element according to FIG. 1, which can also be used in the course of a tightness test, and

[0017] FIG. 4: shows a cross-sectional view of a measuring device for the tightness test with load application using a sealing element and a holder according to the depictions mentioned above.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Throughout the various depictions of the drawings, the same reference symbols are always used for the same elements or process steps. Without limitation to the invention, a manufacturing process will be described below based on a radially symmetrical sealing element for use in a ball valve. A manufacturing process according to the invention is advantageously not limited to radially symmetrical sealing elements. In particular, it is also possible to achieve rectangular sealing surfaces with an improved tightness by means of a grooved surface structure.

[0019] FIG. 1 shows a cross-sectional depiction of a sealing element 1 in the form of a sealing ring with a height h, an inner diameter d, and an outer diameter D. A sealing surface 2 of the sealing element 1 forms an annular section of a spherical surface in adaptation to a use for sealing against a spherical actuator with a radius r. On the opposite side from the sealing surface 2, the flat cylindrical sealing element 1 has a support surface 3 with a shoulder 4. A cylindrical circumference surface 5 connects the sealing surface 2 to the shoulder 4.

[0020] The depiction in FIG. 2a shows an enlarged detail of a sealing surface 2, which has been manufactured in accordance with a known injection molding process. This surface exhibits an irregular structure composed of randomly oriented grain nubs.

[0021] By contrast, the depiction in FIG. 2b shows an enlarged detail of a sealing surface 2 of a sealing element 1, which has been manufactured with an injection molding process according to the invention using an injection molding tool in which a negative structuring has been provided to form a sealing surface 2 with a grooved surface structure. The sealing surface 2 has a surface structure, which exhibits a very uniformly constructed radial groove structure, with sections of one or more grooves R being shown by way of example in FIG. 2b. The maxima or adjacent peaks in this case are spaced apart by less than 0.1 mm or 100 m.

[0022] The graph in FIG. 2c shows an even more enlarged sample measurement of a roughness depth over a section of a sealing surface 2 provided with a grooved surface structure, with an approximately regular sequence of essentially identical maxima or peaks and minima or valleys in close proximity to one another as evidence for the microstructure that has been formed over a periphery of the sealing surface 2 of the sealing element 1.

[0023] FIG. 3 shows a cross-sectional depiction of a holder 6 for a sealing element 1 according to FIG. 1. This holder 6 has a seat 7 with a ground circumferential surface and rounded corners into which the sealing element 1 is inserted. The seat 7 is connected through the holder 6 to a pressure connection 8.

[0024] In the following, the holder 6 is used in a measuring device 9 in the course of a tightness test, which is shown in a cross-sectional depiction in FIG. 4. The holder 6 supports the sealing element 1 in the seat 7 with an elastomer O-ring 10 and is positioned in a guide 11 that is closed at the end so that the pressure connection 8 is flush with an opening 12. In this position, a plunger 13 that is supported in the guide 11 and has a hemispherical end with a ground surface presses against the sealing element 1 with an adjustable force F. Then a tightness test is performed by introducing a measurement fluid with an inlet pressure P.sub.i through a port 14 into the guide 11 and then measuring an outlet pressure P.sub.o at the opening 12.

[0025] Alternatively, a measurement of the tightness of the sealing element 1 can also be carried out by applying the inlet pressure P.sub.i through a duct 15, which is only indicated with dashed lines, along a central axis M of the plunger 13 and the outlet pressure P.sub.o is present unchanged at the opening 12. The plunger 13 is rotatable around its central axis, as indicated by the arrow. It is thus possible for a tightness at a certain pressing force F to be measured even throughout a full angle. It is thus possible to prove that a sealing element 1 manufactured according to the invention with a radially closed groove structure in the sealing surface 2 itself does not have a preferred angle with a particularly powerful sealing action. This also proves that a sealing element 1 manufactured according to the invention from a thermoplastic fluoroplastic, by means of the particular structuring on a sealing surface 2 that avoids random nubs has an improved tightness regardless of angle since the radially closed groove structure, as a cascade of micro-sealing lips, presents only a comparatively small number of leakage paths. Naturally, other configurations of a pressure measurement via the three possible connections 12, 14, 15 of the above-described measuring device 9with or without a rotation of the plunger 13yield the same positive results for a sealing element 1 manufactured according to the invention with a radially closed groove structure in the sealing surface 2.

[0026] In comparison to machined parts, injection molded parts have characteristic markings such as ejector marks or injection points. It is therefore possible to identify parts that have been manufactured by means of an injection molding process, even if they have surface structures, which are similar to those of parts manufactured by machining. In order to protect the special surface structure, these characteristic markings can be slightly displaced into a region outside of a respective sealing surface, even though a manufacturing process remains recognizable and detectable.

[0027] Thus, according to the present invention, higher-performance and more reliable sealing elements can be produced in a cheaper and faster process with good reproducibility as compared to injection molded parts while adapting to almost any shape of actuator without finishing work and in particular without time-consuming machining. On the contrary, the sealing elements removed from an injection mold can be used immediately and have a significantly improved sealing action.