Housing with a rotational friction welding seam

Abstract

A housing (10) which has a first part (14) with a first wall (22) having an outer wall surface (28) and a second part (18) with a second wall (24) having an inner wall surface (30). The wall surfaces can have for example a cylindrical casing shape at least in some sections. Portions of the first wall (22) and the second wall (24) overlap in an overlap region (26). The first wall (22) and the second wall (24) are connected along the circumference of the wall surfaces (28, 30) by means of a rotational friction welding seam (32) arranged in the overlap region (26). The rotational friction welding seam (32) has a compact zone (48) with a first elastic modulus and a mixing zone (44) with a different second elastic modulus.

Claims

1. An explosion protected housing (10) for an electrical operating device (12) comprising: a first part (14) made of plastic having a first wall (22) with an outer wall surface (28) about an axis of said first part (14), a second part (18) made of plastic having a second wall (24) with an inner wall surface (30) about said axis, said first wall (22) and said second wall (24) have an overlap region (26), and said first part (14) and said second part (18) being connected to each other by a rotational friction welding seam (32) located in the overlap region (26) along circumferences of said wall surfaces (28, 30) of said first and second walls (22, 24) so as to form an explosion-proof enclosure for the electrical operating device satisfying the protection level of pressure-proof encapsulation (Ex-d) and/or the protection level of increased safety (Ex-e), said rotational friction welding seam (32) having at least one compact zone (48) formed of fully fused plastic material and one mixing zone (44) formed by partially fused plastic material that exhibits a higher resilience than the fully fused plastic material of said compact zone, and said mixing zone (44) being in an axial edge region (46) of the overlap region (26) where there is a transition from the overlap region (26) to a side wall surface of one of said parts.

2. The explosion protected housing (10) of claim 1 in which said rotational friction welding seam (32) has two of said mixing zones (44) that are separated by said compact zone (48) along said central axis (R) of the rotational friction welding seam (32).

3. The explosion protected housing (10) of claim 1 in which at least one of the first part (14) and the second part (18) has grooves (50) or pockets (50) in the wall surface (28, 30).

4. The explosion protected housing (10) of claim 3 in which said grooves (50) or pockets (50) of the first part (14) and/or of the second part (18) are arranged peripherally along the circumference of the wall surfaces (28, 30) in the overlap region (26).

5. The explosion protected housing (10) of claim 1 in which at least one of the first part (14) and the second part (18) is a cap or a stopper.

6. The explosion protected housing (10) of claim 1 in which at least one of the first wall (22) and the second wall (24) consists of amorphous plastic material.

7. The explosion protected housing (10) of claim 1 in which said first wall (22) and said second wall (24) consist of different materials.

8. The explosion protected housing (10) of claim 1 in which at least one of the first wall (22) and the second wall (24) consist of polycarbonate.

9. The explosion protected housing (10) of claim 1 in which at least one of the outer wall surface (28) of the first wall (22) and the inner wall surface (30) of the second wall (24) has a conical form within the overlap region (26).

10. The explosion protected housing (10) of claim 1 in which the first part (14) and the second part (18) are further welded to each other at one end surface (34, 36) of the first part and one end surface (34, 36) of the second part.

11. The explosion protected housing (10) of claim 1 in which the first part (14) and the second part (18) are connected to each other along their circumferences solely by a rotational friction welding seam (32) on the wall surfaces (28, 30) having a cylindrical casing shape.

12. The explosion protected housing (10) of claim 1 in which said mixing zone (44) of said rotational friction welding seam (32) has first elastic modulus, and said compact zone (48) of said rotational friction welding seam (32) has a second different elastic modulus greater than said first elastic modulus.

13. The explosion protected housing (10) of claim 1 in which the compact zone (48) of the rotational friction welding seam (32) has a more homogeneous material distribution than that of the mixing zone (44).

14. The explosion protected housing (10) of claim 1 in which said compact zone (48) of said rotational friction welding seam (32) has a greater material density than that of the mixing zone (44).

15. The explosion protected housing of claim 1 in which at least one of said parts has an end wall, and said compact zone is adjacent said end wall and said mixing zone is separated from said end wall by said compact zone.

16. A method for manufacturing the explosion protected housing of claim 1 comprising the steps of: connecting the first wall (22) and the second wall (24) along their circumferential surfaces (28, 30) by rotational friction welding through rotation of one of said parts relative to the other of said parts to form rotational friction welding seam (32) having said compact zone (48) and said mixing zone (44).

17. The method of claim 16 in which said rotational friction welding forms a rotational friction welding seam (32) having said compact zone (48) with a greater elastic modulus than the elastic modulus of said mixing zone (44).

18. The method of claim 16 in which said rotational friction welding forms a welding seam (32) having a compact zone (48) with a greater material density than the mixing zone (44).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a vertical section of an illustrative housing in accordance with the invention containing an electrical operating means;

(2) FIG. 2 is an enlarged vertical section of the detail S shown in FIG. 1 of the illustrated housing;

(3) FIG. 3 is a vertical section of an alternative embodiment of housing in accordance with the invention; and

(4) FIG. 4 is a depiction of a method of manufacturing a housing in accordance with the invention.

(5) 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

(6) Referring now more particularly to FIG. 1 of the drawings, there is shown an illustrative housing 10 in accordance with the invention, in this case containing a lamp 12 and being configured in an explosion-proof manner satisfying the safety level of a pressure-proof encapsulation (Ex-d) and, additionally, being waterproof. By its cylindrical shape, the housing 10 defines an axis of rotation R. The housing 10 comprises a first part 14 that is tubular or cylindrical and has a bottom 16. The first part 14 has an outside diameter A of approximately 60 mm. A second part 18 having the form of a cap is welded onto the first part 14. The first part 14 and the second part 18 are in this case each produced by injection molding and consist of an amorphous transparent polycarbonate. However, the first part 14 and the second part 18 may also consist of different materials. For example, one of the parts may consist of glass or steel or of a plastic material other than polycarbonate.

(7) The cap 18 has an end surface 20 that is oriented transversely to the axis to rotation R. One section of the first wall 22 of the first part 14 overlaps with a second wall 24 of the cap 18, said second wall extending around the first part 14. The first wall 22 has an outer wall surface 28 that has the shape of a cylindrical casing. It is connected to an inner wall surface 30 of the second part 18 that has the shape of a cylindrical casing via a rotational friction welding seam 32. The outer wall surface 28 and/or the inner wall surface 30 may also have a casing shape deviating from a cylindrical form. For example, the wall surfaces may taper conically and/or be provided with facets, and be configured as multi-edge surfaces. On the end of the first wall 22 of the first part 14 arranged in the second part 18, the first part 14 has an annular end surface 34. Between the annular end surface 34 extending in circumferential direction and the end surface 36 of the end wall 20 of the second part 18, there is a welding zone 38 with solidified melt. The solidified melt in the welding zone 38 has formed due to friction of the cover surface 34 on the end wall surface 36. The melt may also be fused material of the outer wall surface 28 or the inner wall surface 30, which material has arrived by capillary action or by material advance in the region of the welding zone 38 and forms a heat bond at that location.

(8) FIG. 2 shows a detail S of the housing. The second wall 24 of the second part 18 has, in a first section 40 remote from the end wall 20, a form that conically tapers in the direction of the end wall 20. In a second section 42 located closer to the end wall 20 along the axis of rotation R, the inner wall surface of the second wall 24 has a constant diameter. In an edge region 46 of the overlap region 26 at the of the overlap region to the first part 14 along the axis of rotation R, the rotational friction welding seam 32 has a mixing zone 44 with an inhomogeneous material distribution. In the exemplary embodiment, the mixing zone 44 is, in particular, a fine-pore foam. This foam provides mechanical securing in this edge region 46. In this manner, it is possible, for example, to create a buffer zone that yields in particular to forces that could be due to an explosion inside the housing 10. Otherwise such forces could lead to a shearing off of the first part 14 over the edge of the second part 18 in the edge region 46.

(9) Furthermore, the rotational friction welding seam 32 has a compact zone 48 that is located in a section of the rotational friction welding seam 32 along the axis of rotation R closer to the end wall 20. The rotational friction welding seam may also have an additional melting zone that is separated in axial direction, by the compact zone 48, from the mixing zone 44. Compared with the mixing zone 44, the compact zone 48 has a more homogeneous material distribution with a greater density. The rotational friction welding seam 32 has a radial thickness d that, due to the conical progression in some sections of the otherwise conical progression of the inner wall surface 30 having the shape of a cylindrical casing, can assume different values along the axis of rotation R. In addition, the depicted housing 10 has grooves 50 that are provided in the second wall 24 and extend around the periphery of said wall. The grooves 50 are disposed to receive the melt for the control of the melt flow and as undercuts for mechanically securing the housing. The first wall 22 and the second wall 24 are connected along their entire circumference by means of the rotational friction welding seam. The recesses or grooves 50 may also be configured as pockets that are regularly or irregularly arranged at some points along the circumference and that, for example, are disposed for receiving excess melt or for mechanical securing.

(10) FIG. 3 shows another housing 10 according to the invention, said housing containing an electrical operating means 12. The first part 14 is configured as a massive stopper that closes the second part 18. At the same time, the electrical operating means 12 is fastened to the stopper. The first part 14 has a first wall 22 that has an outer wall surface 38 having the shape of a cylindrical casing. The first part 14 and the second part 18 are connected only by a rotational friction welding seam 32 between the outer surfaces 28 having the shape of a cylindrical casing and the inner wall surface 30 of the second part 18 having the shape of a cylindrical casing.

(11) The rotational friction welding seam 32 has a mixing zone 44 that is provided at the transition from the first part 14 to the overlap region along the direction of the axis of rotation in an edge region 46 of the overlap region 26. The elastic modulus of the mixing zone 44 is greater than that of the compact zone 48 that is provided next to the mixing zone 44 at a distance from the edge region 46. At this location, the mixing zone 44 reduces the risk of a tearing off of the second wall 24 during an explosion in the interior of the housing 10. The compact zone 48 of the rotational friction welding seam 32 has a homogeneous material distribution and is disposed to seal the housing 10. There are no recesses provided in the overlap region 26, so that the rotational friction welding seam is formed without undercuts.

(12) FIG. 4 illustrates the method of the invention with the use of a device 52 for the manufacture of a housing with a friction welding seam.

(13) The device for the manufacture 52 shown by FIG. 4 comprises a first holder 54 into which a first part 14 of polycarbonate is clamped so as to be non-rotational relative to the first holder 54. A shaft 56 is arranged on the first holder 54, whereby said shaft can drive the holder by means of a rotational drive to rotate about an axis of rotation R. In addition, the first holder 54 can be moved along an infeed axis Z toward a second holder 58 of the device 52 or away therefrom in a translatory manner.

(14) A second part 18 of polycarbonate having the shape of a cylindrical cap is clamped into the second holder 58 of the device. The second holder 58 comprises a swivel bearing 60 that can be locked against rotation. The second part 18 has a second wall 24 whose jacket-shaped inner wall surface 30 has initially the shape of a cylindrical casing and widens conically toward an end 62 of the second wall 24 remote from the end wall 20. Other than that, the second wall 24 has the shape of a cylindrical casing and is straight. The second inner wall surface 30 of the second wall 24 having the shape of a cylindrical casing has a first inside diameter I1 in the straight region of the second wall 24 having the shape of a cylindrical casing. In the conically tapering end 62, the second wall 24 has a second inside diameter I2, wherein the second inside diameter I2 is greater than the first inside diameter I1 in the straight region having the shape of a cylindrical casing due to the conically inclined wall surface at the end 62. Due to a second inside diameter I2 that is greater than the outside diameter A of the first part and a conically tapering form of the second part, it is possible to create a stop slope at an angle . Preferably, the angle is at most 3 degrees. For example, a lamp whose receptacle is indicated in FIG. 4 may be arranged in the second part 18.

(15) The first part 14 and the second part 18 are preferably arranged so as to be concentric relative to each other. Between the longitudinal axes of the first part L1 and of the second part L2 that coincide with the axis of rotation R in the exemplary embodiment, there may also exist a parallel axis offset, or the longitudinal axes L1 and L2 may extend in non-parallel direction relative to each other. The first part 14 has a first wall 22 with an outer wall surface 28 having the shape of a cylindrical casing, said outer wall surface 28 having an outside diameter A. The outside diameter A is preferably greater than the first inside diameter I1, i.e., the first part represents an interference fit relative to the second part.

(16) The method for the manufacture of the housing 10 may be performed, for example, with a device for the manufacture 52 as shown by FIG. 4 as described hereinafter:

(17) The swivel bearing 60 is blocked against rotation, and the first part is rotated at a specific speed of rotation via the first holder 54, via the shaft 56 and via the driving motor. The first part 14 is moved along an infeed axis Z, said axis extending parallel to the axis of rotation R in the exemplary embodiment, back toward the second part 18 at a specific feed speed. The feed and rotation speeds can be kept constant or be varied during the friction welding process. Starting at a certain relative distance between the first part 14 and the second part 18, the first wall 22 and the second wall 24 come into contact with each other and frictional forces lead to a fusing of the material of the inner wall surface 30 and the outer wall surface 28. The feed movement is performed until the desired distance of the bottom 16 from the end wall 20 is reached. Then, the rotational movement of the first holder 54 is decelerated; in doing so, the blocking of the swivel bearing 60 counter the rotation can be eliminated, so that the second holder 58 also rotates, whereas the rotation overall comes to a stop.

(18) From the foregoing, it can be seen that a housing 10 is provided which has a first part 14 with a first wall 22 having an outer wall surface 28 and a second part 18 with a second wall 24 having an inner wall surface 30. The wall surfaces can have, for example, a cylindrical casing shape at least in some sections. Portions of the first wall 22 and the second wall 24 overlap in an overlap region 26. The first wall 22 and the second wall 24 are connected along the circumference of the wall surfaces 28, 30 by means of a rotational friction welding seam 32 arranged in the overlap region 26. The rotational friction welding seam 32 has a compact zone 48 with a first elastic modulus and a mixing zone 44 with a different, second elastic modulus.

LIST OF REFERENCE SIGNS

(19) 10 Housing

(20) 12 Electrical operating means/lamp

(21) 14 First part

(22) 16 Bottom

(23) 18 Second part

(24) 20 End wall

(25) 22 First wall

(26) 24 Second wall

(27) 26 Overlap region

(28) 28 Outer wall surface

(29) 30 Inner wall surface

(30) 32 Rotational friction welding seam

(31) 34 Peripheral end surface

(32) 36 End surface of the end wall

(33) 38 Welding zone

(34) 40 First section

(35) 42 Second section

(36) 44 Mixing zone

(37) 46 Axial edge region

(38) 48 Compact zone

(39) 50 Recess/groove/pocket

(40) 52 Device for the manufacture

(41) 54 First holder

(42) 56 Shaft

(43) 58 Second holder

(44) 60 Swivel bearing

(45) 62 End

(46) A Outside diameter

(47) d Radial thickness

(48) I1 First inside diameter

(49) I2 Second inside diameter

(50) L1 Longitudinal axis of the first part

(51) L2 Longitudinal axis of the second part

(52) R Axis of rotation

(53) S Detail

(54) Z Infeed axis

(55) Angle