Method for producing an explosion-proof line bushing, and explosion-proof line bushing

Abstract

An explosion-proof line bushing and method for producing the line bushing. A prespecified amount of elastomeric material is applied to a line and completely surrounds the line in a flat section in the circumferential direction. The line is inserted into a passage opening of a bushing body. The bushing body is preferably plastically deformed. After the plastic deformation, the elastomeric material substantially fills the volume remaining between the formed bushing body and line. The elastomeric material is elastically deformed and presses both against the line and the formed bushing body so that flame-proof gaps are formed between the bushing body and the line. The applied mass of the elastomeric material is determined depending on the inner volume between the formed bushing body and the line remaining.

Claims

1. A method for manufacturing an explosion-proof line bushing, the method comprising: providing a plastically deformable bushing body with a passage opening; applying a predefined amount of elastomeric material on a surface section of an outer surface of a line, wherein the amount of the elastomeric material is predefined depending at least on the outer dimension of the line; arranging of the surface section of the line with the elastomeric material in the passage opening of the bushing body; and plastically deforming the bushing body such that a deformed central section of the bushing body elastically deforms and presses the elastomeric material against the outer surface of the line such that between the deformed bushing body and the elastomeric material as well as the elastomeric material and the line a flameproof gap is formed respectively, wherein the elastomeric material is applied on the surface section of the outer surface of the line prior to the complete vulcanization of the elastomeric material.

2. The method according to claim 1, wherein the elastomeric material is applied in multiple layers on the surface section of the outer surface of the line.

3. The method according to claim 2, wherein due to direct contact with each other the layers of the elastomeric material connect with each other to a singular elastomeric body.

4. The method according to claim 1, wherein the elastomeric material is applied on the surface section without formation of a substance bond with the line.

5. The method according to claim 1, wherein the elastomeric material completely surrounds the surface section in circumferential direction.

6. The method according to claim 1, wherein the elastomeric material is provided as band shaped material and is wrapped on the surface section of the outer surface of the line.

7. The method according to claim 1, wherein the elastomeric material fills the space between the deformed bushing body and the line substantially completely.

8. The method according to claim 1, wherein the bushing body is deformed such that the deformed axial end sections have a smaller outer dimension than the deformed central section of the bushing body.

9. The method according to claim 1, wherein the bushing body is deformed such that the deformed axial end sections have a smaller inner dimension than the deformed central section of the bushing body.

10. The method according to claim 1, wherein the end sections of the deformed bushing body abut directly against the outer surface of the line.

11. The method according to claim 1, wherein the deformed bushing body has a larger axial length than the elastomeric material.

12. The method according to claim 1, wherein the bushing body has a hollow cylindrical shape in its non-deformed initial condition.

13. A method for manufacturing an explosion-proof line bushing, the method comprising: providing a plastically deformable bushing body with a passage opening; applying a predefined amount of elastomeric material on a surface section of an outer surface of a line, wherein the amount of the elastomeric material is predefined depending at least on the outer dimension of the line; arranging of the surface section of the line with the elastomeric material in the passage opening of the bushing body; and plastically deforming the bushing body such that a deformed central section of the bushing body elastically deforms and presses the elastomeric material against the outer surface of the line such that between the deformed bushing body and the elastomeric material as well as the elastomeric material and the line a flameproof gap is formed respectively, wherein the end sections of the deformed bushing body abut directly against the outer surface of the line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1-5 each show a step during the manufacturing of an explosion-proof line bushing by use of an embodiment of a bushing body as well as elastomeric material and

(2) FIGS. 6 and 7 the manufacturing of another explosion-proof line bushing by use of the bushing body of FIGS. 1-5 with a different line of larger diameter.

DETAILED DESCRIPTION

(3) In FIGS. 1-5 the manufacturing of an explosion-proof line bushing 10 is schematically illustrated. The explosion-proof line bushing 10 serves to feed a line 11 in an explosion-proof manner through a wall or a wall section 12. The wall or wall section 12 separates an explosion-proof area or space from an explosive atmosphere. For example the wall section 12 can be part of an explosion-proof housing, particularly of flameproof enclosure (Ex-d).

(4) In the wall section 12 a wall opening 13 is provided (FIG. 5). The wall opening has a wall opening in a surface 14 that preferably corresponds to a cylinder skin surface. A bushing body is part of the line bushing 10. In case of a completely established explosion-proof line bushing 10 the bushing body 15 is plastically deformed and/or worked (FIG. 5) and thus forms a bushing outer surface 16 that is assigned to the wall opening 13 or the wall opening inner surface 14. When arranging the section of the bushing body 15 in the wall opening 13 the wall opening inner surface 14 and the bushing outer surface 16 commonly limit an outer flame-proof gap 17. The outer flame-proof gap 17 can be closed in a ring shaped manner. It is also possible that the bushing body 15 abuts at one or more locations at the wall inner surface 14 such that the outer flameproof gap 17 is not completely closed in a ring-shaped manner and comprises an irregular gap thickness with view in cross section.

(5) In case the flameproof connection between the bushing body 15 and the wall section 12 is established means can be provided in order to guarantee and maintain the positioning of the bushing outer surface 16 in the wall opening 13. For example fastening means or locking means can be provided in order to retain or secure the bushing body 15 in the required relative position at the wall section 12. For example the bushing body 15 can be secured or retained in a material bond manner and/or in a force fit manner and/or in a form fit manner at the wall section 12 or in the wall opening 13.

(6) For manufacturing of the line bushing 10 in a first step (FIG. 1) an elastomeric material is applied and according to the example wrapped on the outer surface 21 of the line 11. For example the outer surface 21 can be formed by an outer surface of a line sheath. The line 11 can comprise at least one electrical conductor and/or at least one optical conductor and/or at least one fluidic conductor. It can be a multicore cable, for example.

(7) The elastomeric material 22 is provided in the form of an elastomeric band according to the example or in an other appropriate form that allows a stepless variation of the amount or mass of the elastomeric material. The elastomeric band 23 is wrapped on a surface section 24 of the outer surface 21 in circumferential direction around the outer surface 21 such that the elastomeric material 22 completely surrounds the line 11 in the surface section 24 in circumferential direction.

(8) The elastomeric material 22 is applied in multiple layers 25 in the surface section 24 on the line 11. According to the example each layer 25 is formed by one or by multiple windings of the elastomeric band 23 that are arranged axially adjacent to each other. The wrapping of the line 11 with the elastomeric band 23 is schematically illustrated in FIG. 1 by arrow P.

(9) Preferably each layer 25 has the same thickness radial to the extension direction of the line 11 or with view in an axial direction A, which can be achieved for example in that the width of the elastomeric band corresponds to the axial length of the surface section 24 in which the elastomeric material 22 is applied.

(10) The elastomeric material 22 is preferably not completely vulcanized if it is applied on the line 11. During the application of the elastomeric material 22 directly adjacent layers 25 get into contact with each other and connect with each other. In doing so an elastomeric body 26 emerges that is manufactured from elastomeric material 22 that has a hollow cylindrical shape or sleeve shape and surrounds the line 11 in the surface section 24. Thereby an adhesive bond or substance bond between the elastomeric body 26 and the line 11 is not created (FIG. 2). The elastomeric material 22 can comprise polyisobutylen, for example.

(11) In the next step the line 11 with the elastomeric material 22 or the elastomeric body 26 is passed through a passage opening 30 of the bushing body 15 (FIG. 2). The passage opening 30 extends completely through the bushing body 15 in an axial direction A and has a cylindrical shape in the embodiment. FIG. 2 illustrates the bushing body 15 in its non-deformed initial condition. In the embodiment it has a substantially hollow cylindrical shape or sleeve shape with a cylinder skin surface shaped outer and inner surface. The bushing body 15 has in its non-deformed initial condition an outer diameter that corresponds to a first diameter d1 and an inner diameter that corresponds to a second diameter d2. The outer dimension or the outer diameter of the elastomeric body 26 is at most as large and preferably smaller than the second diameter d2. In the embodiment the line 11 comprises an outer diameter that corresponds to a third diameter d3.

(12) Bushing body 25 is arranged in axial direction A relative to the elastomeric body 26 such that the elastomeric body 26 is substantially centered in the passage opening 30 as schematically shown in FIG. 2. In the next step the bushing body is plastically deformed. With a suitable crimping tool (not illustrated) a deformation force F is applied on the bushing body 15 at multiple locations uniformly distributed in circumferential direction around the bushing body that is orientated radially inward to the line 11. The deformation force F is schematically illustrated in FIG. 3 by block arrows.

(13) During the deformation the shape of the bushing body 15 is changed. The deformed bushing body 15 (FIG. 3) has several axial sections the shape of which is different from the directly adjoining axial section. According to the embodiment the deformed bushing body 15 has at each axial longitudinal end an end section 31 and a central section 32 between the two end sections 31. Each end section 31 can be connected with the central section 32 by a radially expanding or conical connecting section 33.

(14) The central section 32 of the non-deformed bushing body 15 has an outer diameter that corresponds to a fourth diameter d4 and that is smaller than first diameter d1 in the initial condition of the bushing body 15. The central section 32 of the deformed bushing body 15 has an inner diameter that corresponds to a fifth diameter d5 and that is smaller than the second diameter d2 in the initial condition of the bushing body 15. The fifth diameter d5 is larger than third diameter d3 of the line 11.

(15) In the embodiment the bushing body 15 is deformed from its initial condition such that the outer diameter of the end section 31 is smaller than the fourth diameter d4 of the central section 32. In addition the inner diameter of the end section 31 is smaller than the fifth diameter d5 of the central section 32. At the end sections 31 the deformed bushing body 15 can abut directly against the outer surface 21 of the line 11 and can apply a clamping force on the line 11. In doing so an axial locking of the bushing body 15 and the elastomeric body 26 relative to the line 11 is achieved.

(16) The elastomeric material 22 applied on the line 11 in the first step has a defined mass that is preset such that the volume between the deformed bushing body 15 and the line 11 is substantially filled. The remaining volume or the remaining space is preferably filled by at least 95% and further by preferably by at least 97% and further preferably by at least 99%. The mass of the elastomeric material 22 is particularly predefined such that it completely fills the area between the central section 32 of the deformed bushing body and the line 11.

(17) In other words the amount or mass of the elastomeric material 22 that is applied on the line 11 is determined and predefined depending on the outer diameter of the line 11 (here: third diameter d3) and the inner diameter of the deformed bushing body 15 at least in the central section 32 (here: fifth diameter d5) and the axial length of the central section 32 of the deformed bushing body 15. In doing so it is possible to use a bushing body 15 that has in its initial condition the same outer diameter and inner diameter for different line diameters of the line 11 and to that the mass of the elastomeric material 22 to be applied accordingly during the manufacturing of the line bushing 10. It has shown that in doing so lines with outer diameters from about 8 mm to 25 mm can be crimped in an explosion-proofed manner with only 8 or 10 or 12 different sizes of the bushing body 15.

(18) After the plastic deformation of the bushing body the elastomeric body 26 is elastically deformed and presses against the inner side of the central section 32 of the deformed bushing body and against the outer surface 21 of the line 11. In doing so remaining interstices are at least partly closed such that between the deformed bushing body 15 and the elastomeric body 26 as well as between the elastomeric body 26 and the line 11 an inner flameproof gap 34 is formed respectively.

(19) If the elastomeric material was applied in several layers 25 and one layer 25 consists of several axially adjacently applied individual windings that axially overlap slightly each layer 25 can have a larger radial thickness in the at least one overlapping area of the individual windings than outside the overlapping area. For this reason or due to other manufacturing related reasons the resulting skin surface of the elastomeric material 22 or of the elastomeric body 26 can have height deviations, particularly elevations, compared with an ideal target cylinder skin surface. In this case it is advantageous if all elevations have a height measured radially to the axial direction relative to the target cylinder skin surface that is smaller than the radius change of the passage opening in the central section 32.

(20) The deformed bushing body 15 has the bushing outer surface 16 in the central section 32 that comprises the shape of a cylindrical skin surface in the embodiment. In order to form the outer flameproof gap 17 commonly with the wall inner surface 14 the bushing outer surface 16 can be worked in a further step after the plastic deformation of the bushing body 15 in order to comply with a pre-defined quality or tolerance. This work is illustrated highly schematically in FIG. 4. For example a rotating grinding tool 38 or another suitable working tool can be used for this working step in order to create the required surface quality and dimensional accuracy of the bushing outer surface 16.

(21) Finally the deformed bushing body 15 attached at the line 11 can be arranged in the wall opening 13 as it has been initially described with reference to FIG. 5, and the outer flame-proof gap 17 can be formed in the wall opening 13. In doing so the line 11 can be fed through the wall opening 13 in a flameproof manner. Neither between the bushing body 15 and the line nor between the bushing body 15 and the wall opening 13 flameproof gaps 17, 34 are present such that no hot gases, sparks and flames or other ignition means can enter the explosive atmosphere.

(22) The variability of the use of the bushing body 15 for different lines 11 is schematically made clear by FIGS. 6 and 7. FIG. 6 shows the bushing body 15 of FIG. 2 in its initial condition with an outer diameter that corresponds to the first diameter d1 and with an inner diameter that corresponds to the second diameter d2. Here the line 11 has an outer diameter that corresponds to a sixth diameter d6 wherein the sixth diameter d6 is larger than the third diameter d3 of the line 11 from FIG. 2. The mass of the applied elastomeric material 22 has been adapted to the reduced volume between the line 11 and the deformed bushing body 15 (FIG. 7). In doing so it is possible to connect lines 11 with different outer diameters with a similar bushing body 15 in a flameproof manner.

(23) In the embodiment described here the outer flame-proof gap 17 is limited by two plain cylindrical surfaces 14, 16. Alternatively to this the outer flameproof gap 17 could also comprise elevations and/or depressions. For example a part of the wall opening 13 could be formed by an inner thread and a part of the bushing body 15 or a fastening means connectable with the bushing body 15 could be provided with an outer thread that can be threaded together with the inner thread of the wall opening 13.

(24) The invention refers to a method for manufacturing an explosion-proof line bushing 10 as well as such a line bushing 10. A predefined amount or mass of an elastomeric material 22 is applied on a line 11 that completely surrounds the line 11 in a surface section 24 in circumferential direction. The line 11 with the elastomeric material 22 is inserted in a passage opening 30 of a bushing body 15. The bushing body 15 is plastically deformed preferably over its total axial length. After plastic deformation the elastomeric material 22 fills the volume remaining between a deformed bushing body 15 and the line 11 substantially completely. The elastomeric material 22 is elastically deformed and presses against the line 11 as well as against the deformed bushing body 15 such that flameproof gaps 34 are formed between the bushing body 15 and the line 11. The applied mass of the elastomeric material 22 is determined and predefined depending on the inner volume remaining between the deformed bushing body 15 and the line 11 after deformation of the bushing body 15. Thus the mass of the elastomeric material 22 depends at least from the outer dimension of the line 11. Bushing bodies 15 having the same dimensions can thus be used for lines 11 with different outer dimensions.

LIST OF REFERENCE SIGNS

(25) 10 line bushing 11 line 12 wall 13 wall opening 14 wall opening inner surface 15 bushing body 16 bushing outer surface 17 outer flameproof gap 21 line outer surface 22 elastomeric material 23 elastomeric 24 surface section 25 layer of the elastomeric material 26 elastomeric body 30 passage opening 31 end section 32 central section 33 conical connecting section 34 inner flameproof gap 38 grinding tool A axial direction d1 first diameter d2 second diameter d3 third diameter d4 fourth diameter d5 fifth diameter d6 sixth diameter F deformation force