Housing part for a housing with flameproof encapsulation comprising a porous body

Abstract

A housing part for an explosion-protected housing (10) with flameproof encapsulation. The housing part comprises a porous body (20) in a passage (15) of the housing part. The passage (15) is closed in a flameproof manner by means of the porous body (20). The porous body (20) comprises an inner side (21) assigned to the interior of the housing (10) and an outer side (22) assigned to the surrounding area (12) comprising the explosive atmosphere. A gas volume flow can pass through the porous body (20), entering the porous body (20) on the inner side (21) and escape on the outer side (22) or vice versa. To prevent the penetration of water or of other aqueous liquids into the interior of the housing (10), the porous body (20) comprises a hydrophobic surface (B) in at least one area (31).

Claims

1. An explosion-protected housing (10) with flameproof encapsulation comprising: a housing part (16), said housing part having a passage (15) into which a flameproof porous body (20) is inserted for defining a pressure release device to limit an explosion pressure in an interior of the housing (10), said porous body (20) having an inner side (21) assigned to an interior of said housing (10) and an outer side (22) assigned to a surrounding area (12) of the housing (10), said porous body (20) being made of an alloyed steel which is temperature resistant up to at least 400 C. said porous body (20) having hydrophobic coating that forms a hydrophobic surface (B) for preventing the passage of water from the surrounding area and into the interior of said housing, and said porous body (20) providing a gas-permeable connection between said inner side (21) and outer side (22) for permitting the passage of high pressure gas from the interior of said housing, through porous body (20) and hydrophobic coating and to the surrounding area (12) in the event of an explosion within the housing while preventing the passage of sparks and flames.

2. The explosion-protected housing (10) according to claim 1 in which said hydrophobic surface (B) contains or adjoins the outer side (22) of the porous body (20).

3. The explosion-protected housing (10) according to claim 1 in which said hydrophobic surface (B) contains or adjoins the inner side (21) of the porous body (20).

4. The explosion-protected housing (10) according to claim 1 in which said hydrophobic surface is formed by a hydrophobic coating (B) which contains a fluorocarbon and/or a silane.

5. The explosion-protected housing (10) according to claim 1 in which said hydrophobic surface is formed by a hydrophobic coating (B) which contains a fat and/or a wax.

6. The explosion-protected housing (10) according to claim 1 in which said porous body (20) comprises fibers which have a diameter of at least 70 micrometers and maximally 130 micrometers.

7. The explosion-protected housing (10) according to claim 6 in which said fibers (29) of the porous body (20) have a hydrophobic surface (B).

8. The explosion-protected housing (10) according to claim 1 in which said porous body (20) defines pores having a pore size (P) of at least 80 micrometers and maximally 250 micrometers.

9. The explosion-protected housing (10) according to claim 1 in which said porous body (20) has a porosity () of at least 60% and maximally 80%.

10. The explosion-protected housing (10) according to claim 1 in which said porous body (20) is made of stainless steel.

11. The explosion-protected housing (10) according to claim 1 in which said porous body (20) is disposed in a passage (15) of a nozzle (16).

12. The explosion-protected housing (10) according to claim 11 in which said nozzle (16) has a splash water protector (35) at the outer side (22) of the porous body (20).

13. The explosion-protected housing (10) according to claim 1 in which said porous body has a transverse thickness of at least 5 millimeters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective of an illustrative explosion-protected housing with flame-protection encapsulation in accordance with the invention;

(2) FIG. 2 is a perspective of an alternative embodiment of an explosion-proof housing according to the invention;

(3) FIG. 3 is a is an enlarged vertical section of a pressure release device for the explosion-protected housing shown in FIG. 1;

(4) FIG. 4 is an enlarged vertical section of an alternative embodiment of pressure release device according to the invention;

(5) FIGS. 5-7 are perspectives of alternative exemplary embodiments of porous bodies for use in an explosion-protected housing in accordance with the invention;

(6) FIG. 8 is a cross section of a porous body, such as shown in FIGS. 5-7; and

(7) FIG. 9 is a schematic illustration of the mode of operation of a hydrophobic surface of the porous body according to the exemplary embodiments.

(8) While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) Referring now more particularly to FIG. 1 of the drawings, there is shown an illustrative explosion-protect housing with flameproof encapsulation 10 in accordance with the invention. The explosion-protect housing with flameproof encapsulation 10 in particular provides an ignition protection type pressure-resistant encapsulation (Ex-d). It comprises a flow-through device 11 in a housing bottom 10a, a housing wall 10b, or a housing top 10c of the housing 10. Exemplary embodiments for the flow-through device 11 are illustrated in FIGS. 3 and 4.

(10) The flow-through device 11 serves as pressure release device and/or as pressure compensating device. In its function as pressure compensating device, pressure differences between the interior of the housing 10 and the surrounding area 12 outside of the housing 10 are compensated, in that a gas volume can flow through the flow-through device 11 from the interior into the surrounding area 12 or vice versa. Such pressure differences can result because of pressure fluctuations, for example, in particular if the solar radiation acts on the explosion-protected housing 10 with flameproof encapsulation.

(11) In the ignition protection type pressure-resistant encapsulation, the explosion-protected housing with flameproof encapsulation must be able to withstand an explosion pressure in the interior of the housing 10. The flow-through device 11 serves as pressure release device for limiting the explosion pressure in the interior of the housing 10. For this purpose, a sufficiently large volume flow through the flow-through device 11 is ensured if the pressure in the interior of the housing 10 rises in response to an explosion. Due to the pressure limitation by means of the flow-through device 11, the housing 10 can be constructed less stable in response to expected explosion pressures, whereby material, costs and weight can be saved.

(12) The flow-through device 11 comprises a passage 15 which connects the interior of the housing 10 to the surrounding area 12 and which provides for a gas flow. The cross section of the passage 15 can be designed in an arbitrary manner. In the case of the exemplary embodiments illustrated herein, the passage 15 has a circular cross section.

(13) According to the exemplary embodiment, the passage 15 penetrates a nozzle 16. The nozzle 16 can be fastened in an opening of the housing 10 in the housing bottom 10a, in a housing wall 10b or in the housing top 10c. In this case, the nozzle 16 has an external thread 17 by means of which the nozzle 16 can be screwed into an internal thread in the opening of the respective housing part. The nozzle 16 can also be arranged and fixed in a non-positive manner and/or in a positive manner and/or in a firmly bonded manner in the opening of the housing 10 or any other manner.

(14) Electrical and/or electronic components, which are not illustrated, are arranged in the housing 10 in a conventional manner. Such components can serve as ignition sources for an explosive atmosphere in the surrounding area 12 of the housing 10. The passage 15 of the flow-through device 11 thus may not have a spark gap. A porous body 20 is thus inserted in the passage 15. Due to its porosity, the porous body 20 allows for a gas flow through the porous body 20, but ensures simultaneously that flames or spark gaps cannot reach through the passage 15 out of the interior of the housing 10 into the surrounding area 12.

(15) The porous body 20 can be fastened in the passage 15 in a firmly bonded manner and/or in a non-positive manner and/or in a positive manner. For example, it is advantageous, if the porous body 20 is placed into a casting mold during production of the nozzle 16 and establishes a firmly bonded connection to the nozzle 16 when material is filled into the casting mold. As an alternative to this, the porous body 20 can be held in the passage 15 by means of an interference fit, wherein an elastic clamping force is created between the wall of the nozzle 16 which defines the passage 15 and the porous body 20. In this embodiment, the porous body 20 can additionally be secured against being displaced or pushed out of the passage 15, respectively, by means of securing means in the direction of extension of the passage 15.

(16) In the exemplary embodiment, the porous body 20 has the shape of a disc. It comprises an inner side 21, which is assigned to the interior of the housing 10, and an outer side 22, which is assigned to the surrounding area 12 outside of the housing 10. For example, gas can enter into the porous body 20 on the inner side 21, and can escape on the outer side 22 or also vice versa. The inner side 21 and the outer side 22 are connected to one another via a peripheral surface 23. The peripheral surface 23 is closed in a ring-shaped manner. In top view onto the inner side 21 or the outer side 22, the porous body 20 has a contour or shape, which is adapted to the contour or shape of the cross sectional surface of the passage 15 such that a spark gap-free connection between the wall, which defines the porous body 20 and the wall, which defines the passage 15, is possible. In the exemplary embodiment, the porous body 20 has a circular contour.

(17) Preferably, the porous body comprises fibers 29 which are intertwined with one another in an unordered manner. The porous body 20 thus comprises a randomly oriented fiber structure part (FIG. 7) or is formed by such a randomly oriented fiber structure part 30.

(18) The fibers preferably consist of metal and, in the case of the exemplary embodiment, of a chromium alloyed steel or stainless steel. Preferably, all of the fibers 29 have the same diameter. The diameter is at least 70 micrometers and maximally 130 micrometers.

(19) The porosity of the porous body 20 can be calculated as follows:

(20) $=\left(1-\frac{}{{}_0}\right).Math.100\%,$ with : porosity in percent : molded density of the body .sub.0: true density of the body In the exemplary embodiment of the porous body 20 illustrated in FIG. 6, the porosity is substantially constant across the entire porous body 20. In contrast, the porosity is smaller in an edge area 24, which comprises the peripheral surface 23, in the exemplary embodiments according to FIGS. 5 and 6. In addition to its porous material, the porous body 20 also comprises a ring part 25, which surrounds the porous material or the randomly oriented fiber structure part 30 in a ring-shaped manner and which thus forms a peripheral surface 23 of the porous body 20, which is substantially closed in a gas-tight manner, in the embodiment illustrated in FIG. 7. A gas penetration or a gas escape, respectively, is only possible on the inner side 21 or on the outer side 22, respectively.

(21) The porosity of the porous body 20 or of the randomly oriented fiber structure part 30, respectively, is at least 60% and maximally 80%. The pore size P of the porous body 20 or of the randomly oriented fiber structure part 30, respectively, lies at least in one spatial direction and preferably in at least two spatial directions in a range of at least 80 micrometers to maximally 250 micrometers. In particular, the pore size P in the two spatial directions lies within the specified range, in which the inner side 21 and the outer side 22 extend at a right angle to the gas flow direction G. The pore size P is illustrated schematically in FIG. 9.

(22) The thickness D of the porous body 20 between the inner side 21 and the outer side 22 is at least 5 to 10 mm.

(23) The porous body 20 or the randomly oriented fiber structure part 30, respectively, comprises a hydrophobic surface B. This hydrophobic surface B is illustrated in FIG. 8 in a highly schematic manner and is formed there by means of a coating, for example. As an alternative, the hydrophobic surface can be created by activating and/or treating the material of the porous body 20 or of the randomly oriented fiber structure part 30, respectively. For example, an activation of the hydrophobic characteristics is possible by means of a laser interference structuring or by creating nanostructures.

(24) The hydrophobic surface B is attached directly at the randomly oriented fiber structure part 30 or the porous body 20, respectively. In the exemplary embodiment, the fibers 29 are provided with the hydrophobic surface B at least in one area 31 of the porous body 20 or of the randomly oriented fiber structure part 30. According to the example, this area 31 contains at least the outer side 22. In the alternative or additionally, the area 31 could also contain the inner side 21 and could adjoin it. It further is possible to provide a plurality of areas 31 or the entire porous body 20 or the entire randomly oriented fiber structure part 30, respectively, with a hydrophobic surface B. For example, the fibers 29 can be provided with the hydrophobic surface B prior to the intertwining to form the randomly oriented fiber structure part 30. Preferably, the hydrophobic surface B, however, is first applied as coating to the porous body 20 or the randomly oriented fiber structure part 30 in at least one area 31 or is created at the porous body 20 or the randomly oriented fiber structure part 30.

(25) As is illustrated in FIG. 8, at least one layer of the randomly oriented fiber structure part 30 or of the porous body 20, respectively, which contains the outer side 22 and which adjoins this outer side 22, is provided with the hydrophobic surface B. This has the advantage that in the event of an explosion in the interior of the housing 10, the hot gases, which permeate on the inner side 21, are cooled down initially, until they reach the area 31 comprising the hydrophobic surface B. The hydrophobic surface B or the coating can thus be less temperature-resistant than the material which is used to produce the porous body 20.

(26) Preferably, the material, which is used to produce the porous body 20 or the randomly oriented fiber structure part 30 according to the example the fibers 29 have a temperature resistance of at least 400 C. In the exemplary embodiment, the material, which is used for the hydrophobic surface B, which is formed by means of a coating, contains a fluorocarbon. For example, the surface B can contain polytetrafluoroethylene or can be formed from it. Other materials comprising a fluorocarbon and/or one or a plurality of silanes can also be used. The fluorocarbons and/or silanes have the advantage that they not only prevent the penetration of water through the porous body 20 into the interior of the housing 10, but also impede or hinder the penetration of oily fluids. Fluorocarbons furthermore impede the adhesion of particles to the porous body 20, so that the pores do not clog with dirt particles and impede or reduce the gas volume flow through the porous body 20. As an alternative or in addition to a fluorocarbon and/or a silane, the material of the hydrophobic surface B can also contain a fat and/or a wax.

(27) In the area 31 comprising the hydrophobic surface B, the porosity or the pore size P, respectively, can be smaller than outside of this area 31. Preferably, the porosity and/or the pore size P is nonetheless within the respective above-specified range, that is, the pore size P is at least 80 micrometers and maximally 150 micrometers and/or the porosity is at least 60% and maximally 80%.

(28) The contact angle between a drop of water 34 and the surface on the outer side 22 of the porous body 20 or of the randomly oriented fiber structure part 30 is increased by means of the hydrophobic surface B and is larger than 90, and preferably larger than 120, and more preferably larger than 160. It is attained through this that smaller drops of water, which are smaller than the pore size P, combine to form larger drops of water 34 and cannot pass through the pores into the interior of the housing 10. The area 31 comprising the hydrophobic surface B is thus not permeated by drops of water. It is irrelevant thereby, whether the area 31 is present directly on the outer side 22 or at a different section of the porous body 20 or of the randomly oriented fiber structure part 30.

(29) In the exemplary embodiment according to FIG. 4, the flow-through device 11 comprises a protective cover 35 on the side which is assigned to the surrounding area 12. The protective cover 35 is arranged at a distance to the outer side 22 of the porous body 20 and in this case is connected to the nozzle 16. The protective cover 35 comprises a closed protective wall area 36 which is arranged at a distance to the outer side 22 and which completely covers the outer side 22. The protective wall section 36 is connected to the nozzle 16 by means of at least one holding element 37. The at least one holding element 37 extends away from the nozzle 16 and thus holds the protective wall section 36 at a distance from the outer side 22 of the porous body 20 and a distance to the opening of the passage 15. In the exemplary embodiment, a single holding element 37, which is ring-shaped, is provided, which surrounds the outlet of the passage 15 on the side of the nozzle 16, which is assigned to the surrounding area 12. As a modification for this, provision could also be made for a plurality of individual holding elements 37, which are distributed around the periphery.

(30) The holding element 37, which, according to the example, is closed in a ring-shaped manner, comprises a plurality of discharge channels 38, which are located about the periphery. Water, which accumulates in a space 39 between the protective wall section 36 and the porous body 20, can drain from the intermediate space 39 through these discharge channels 38. The protective wall section 36 protects the porous body 20 or the outer side 22 thereof from splash water or a water jet hitting the porous body 20 directly. The protective cover 35 thus forms a jet and splash water protection.

(31) In the exemplary embodiment illustrated herein, the inner surface 40 of the protective wall section 36, which faces the intermediate space 39, does not extend in a plane, but rather has a convex shape. An incline is formed through this so that water, which collects in the space 39 on the inner surface 40, flows in the direction of the discharge channels 38. This is advantageous when the flow-through device 11 is attached to a housing bottom 10a, as is illustrated schematically in FIG. 1.

(32) In the exemplary embodiments according to FIGS. 1, 2 and 3, the passage 15 is arranged in a housing part, which is formed by the nozzle 16. As an alternative to this, it is also possible to provide the passage 15 directly in a housing wall 10b, a housing bottom 10a or a housing top 10c and to arrange the porous body 20 directly at that location. In such case, the nozzle 16 is not necessary.

(33) It is furthermore possible to embody entire housing parts, for example housing walls 10b, housing tops 10c or housing bottoms 10b from the porous body 20, which is illustrated in FIG. 2. A housing door or a cover could also be formed by a porous body 10 as an alternative to this illustration. A gas communication between the interior of the housing 10 and the surrounding area 12 is thereby possible by means of all of the housing parts 10a, 10b, 10c,which are formed by a porous body 20.

(34) In the case of all of the embodiments, at least one area 31 of each porous body 20 is provided with the hydrophobic surface B.

(35) From the foregoing, a housing part is provided for an explosion-protected housing 10 with flameproof encapsulation. The housing part can be formed by a nozzle 16 of a flow-through device 11 and/or by a housing wall 10b and/or by a housing bottom 10a and/or by a housing top 10c. This housing part comprises a porous body 20, which sits in a passage 15 of the housing part. The passage 15 is closed by means of the porous body 20 in a flameproof manner. The porous body 20 comprises an inner side 21, which is assigned to the interior of the housing 10 and an outer side 22 which is assigned to the surrounding area 12 comprising the explosive atmosphere. A gas volume flow can flow through the porous body 20. Gas can enter into the porous body 20 on the inner side 21 and can escape on the outer side 22 or vice versa. To prevent the penetration of water or of other aqueous liquids into the interior of the housing 10, the porous body 20 comprises a hydrophobic surface B in at least one area 31.

LIST OF REFERENCE NUMERALS

(36) 10 housing 10a housing bottom 10b housing wall 10c housing top 11 flow-through device 12 surrounding area 15 passage 16 nozzle 17 external thread 20 porous body 21 inner side 22 outer side 23 peripheral surface 24 edge area 25 ring part 29 Fiber 30 randomly oriented fiber structure part 31 Area 34 drop of water 35 protective cover 36 protective wall section 37 holding element 38 discharge channel 39 space contact angle p porosity d thickness b hydrophobic surface g gas flow direction p pore size