GB2125234A - An explosion- or flame-proof electrical coupling - Google Patents

Abstract

An explosion- or flame-proof electrical coupling comprises a plug 16 provided with contact pins 54 to be received in bushes 20 in a socket, the plug having a cylindrical collar 140 formed with an internal annular surface which, following insertion of the plug into the socket, surrounds an annular surface on the socket so as to form an air gap 150. A shutter ring 48 having openings 56 correspond in number to the bushes 20 is provided in the socket 14 to cover the bushes 20 before insertion of the plug into the socket and is locked in this position by spring-urged pins 68 engaging in the openings 56. To insert the plug into the socket, the plug is moved axially so that the pins 54 engage in the openings 56 to displace the locking pins 68. The plug and, therefore, the disc 48 is rotated to align the pins 54 with the bushes 20 and, finally, the plug 16 is moved axially. In one embodiment, this movement is guided by a radial lug on the collar 140 engaging in a first axial groove, a part- circular groove and a second axial groove offset from the first groove. <IMAGE>

Description

SPECIFICATION An explosion- or flame-proof coupling plug device The invention related to an explosion- or flameproof coupling plug device according to the classifying part of Claim 1.

Coupling plug devices which are used in areas endangered by explosion or underground must be constructed so as to prevent the removal of the plug from the socket leading to en electric arc.

This is obtained in the majority of coupling plug devices of the above-mentioned type by providing the socket with a switch which is switched on once the plug has been inserted in the socket and locked, the prongs being inserted in the bushes without voltage and an electric coupling only being effected by switching on the switch following insertion and the establishment of the mechanical connection between the socket and the plug. In order to separate the coupling plug device, the switch disposed in the plug is firstly switched off, so that the bushes or prongs are no longer live. The plug device can then be unlocked and the plug removed. Electric arc phenomena, which can lead to the ignition of an explosive mixture, do not occur between the prongs and the bushes in either case.

Plug devices with switches of this type are used when the plug device is designed for a current > 1 OA or for a voltage > 250VN/60V=.

Depending on the construction of the plug device, switches are not necessary in the case of fairly low voltages and currents.

A plug device of the above-mentioned type is known in which the bush comprises a cylindrical extension, on which inwardly directed pins are provided. The plug, which is formed as a separate metal structure, comprises a collar with Z-shaped grooves. The outer diameter of the collar is of a size such that the collar fits exactly into the cylindrical extension of the socket. The Z-shaped grooves extend parallel to the central axis of the plug over a certain distance, then at right angles thereto and then parallel again.These grooves engage with pins at the inner surface of the cylindrical extension, as a result of which plugs which are not adapted to the socket cannot be inserted in the socket and the adapted plug device is inserted in a special manner: firstly in a linear manner, until a sufficient air gap, corresponding to specifications 0170/0171 of the Verband deutscher Elektrotechniker (Association of German Electrical Engineers), is formed between the inner surface of the cylindrical extension and the outer surface of the collar at the plug, thus forming a pressure-resistant space, containing the plug contacts and bushes between the plug and the socket (at this point the prongs and the bushes are not yet in alignment, so that the plug cannot be inserted further into the socket), after which the plug is rotated by guiding the pins in the vertical grooves, or vice versa, until the prongs and the bushes are in alignment, and the plug is finally completely inserted in the socket. Any electrical arcs drawn between the bushes and the prongs cannot cause any damage, as the space as such is pressure-resistant and hot gases which could lead to the ignition of the surrounding airgas mixture cannot leave the air gap. The coupling plug device is then also locked, so that the plug can no longer be removed from the socket.

The plug is then removed from the socket in a reverse manner: the two live parts are firstly separated by withdrawing the prongs from the bushes until the pins come into contact with the vertical groove. The plug is then rotated, so that the prongs are no longer in alignment with the bushes after which the plug can finally easily be removed from the socket.

This construction requires special socket and plug designs in order to obtain optimum guideance and locking of the socket and plug.

Furthermore, it is not possible to prevent the live bushes from being accessible from outside.

The object of the invention is to provide a coupling plug device of the above-mentioned type in which, even when the plug is removed, the bushes are provided with a cover, such that they are not accessible by means of a normal tool.

This object is sovled according to the invention by the characterising feature of Claim 1.

The disc according to the invention is formed in a manner similar to that of a so-called child-proof device in conventional sockets, which are designed to prevent children pushing pointed metallic objects into sockets without permission.

A conventional, commercial lug on the projection or collar of the plug can be used in order to guide the latter, which lug is guided in grooves in a Z-shaped manner in the direction of the longitudinal axis and transversely thereto. It is also possible to provide a similar guide by appropriately shaping the inner surface of the collar and the outer surface of the cylindrical extension, over which the collar engages, at the socket. This guide is characterised in the features of Claims 1 to 5.

Further advantageous developments of the invention are contained in the subclaims.

An embodiment of the invention and further advantageous developments and improvements thereof are illustrated and described in detail with reference to the drawing, which shows two embodiments of the invention and in which: Figure 1 is a longitudinal sectional view through a plug device according to the invention, Figure 2 is a sectional view, similar to that of Figure 1, in the position in which the prongs are just unlocking the plate, Figure 3 is a rolled out sectional view in the region of the plate, Figures 4 to 9 are different sectional views of a further arrangement of the invention, Figure 5 being a sectional view along the line V-V of Figure 4, Figure 6 a sectional view along the line VI--VI of Figure 4, Figure 7 a plan view of the socket along the line VII of Figure 4 and Figure 8 a sectional view along the line IX-IX of Figure 9.

Figure 1 is a longitudinal sectional view of a coupling plug device 12 according to the invention which is mounted in a housing 10, of which only the lower part is shown. This coupling plug device 12 consists of a bush part 14 and a plug part 1 6, which are illustrated in the joined state.

The bush part comprises a bush housing 18, in which the individual bushes 20 are inserted.

Figure 1 shows only one bush. These bushes 20 penetrate the housing 1 8 and end in a connecting lug 22, to which a cable connection 26 is clamped by means of a clamping screw 24. The bush housing 1 8 continues into a collar 28, which surrounds the bushes 20 in a cylindrical manner, and an intermediate housing 30, which is connected to the bush housing 1 8 by means of a screw connection 32. The head 34 of the screw connection 32 is integrally cast in the intermediate housing 30 by means of casting resin 36. For this purpose the intermediate housing 30 comprises a cylindrical extension 38, through which the screw 32 passes and at the free end of which the screwhead 34 is cast in a recess 40 by means of the casting resin 36.

The bushes 20 end in a plane 46, which extends radially on at a right angle to the longitudinal axis L-L and adjoins the collar 28.

An intermediate part 44 is non-rotatably mounted in the plane 46 at the bush housing 18, on which part 44 a ring 48 is mounted which comprises a central recess 50, which is penetrated by an extension 52 at the bush housing 18 in the plane 46, thus guiding the ring 48, so tht the ring 48 can rotate about the longitudinal axis L-L. The extension 52 projects in the same direction as the collar 28 to the plug part 16. The ring 48 is of plane construction and comrises openings 56, which correspond in number to the prongs 54 of the plug part 1 6 and which are surrounded by annular collars 58, which project from the surface of the ring 48 by approximately half the thickness of the ring and end in a flush manner in the plane containing the edge of the collar 18.At the side opposite the collar 58, the ring 48 also comprises an annular rim 60 in the vicinity of its outer circumference, by means of which it is mounted on the intermediate part 44.

On its side facing the bush housing 18, the intermediate part 44 also comprises annular collars 62, which engage in blind-end bores 64 in the bush housing 1 8 and are thus held and guided in these blind-end bores 64. The annular collar 62 surrounds a bore 66, in which a pin 68 for locking the ring 48 is guided. The pin 68 is subject to the pressure of a spring 70, which is supported at one end of the base 72 of the blind-end bore 64 and at the other end at a flange 74 on the pin 68 and thus tends to push the pin out of the recess or bore 66. The method of operation of the arrangement is described below in detail.

A receiving cylinder 78 is secured to the housing 10, and a flange 80, which is formed onto the bush housing 18, is in contact with the front surface, disposed inside the housing, of the cylinder 78 and is secured thereto by means of screws 82. An enlarged portion 84, which permits the plug part 1 6 to be inserted, is formed onto the receiving cylinder, a lid 90 being hinged to the portion 84 by means of an eyelet 86 and a spindle 88.

The plug part 16 comprises a plug housing 100, in which the prongs 54 are in each case guided in a bore 102 in the plug housing, the outer surface of the prongs 54 and the inner surface of the bore 102 forming an air gap in accordance with the VDE specifications 0170/0171. On the side of the plug housing 100 remote from the direction of insertion, the prongs 54 continue so as to form a connecting lug 104, to which a connection cable 108 is secured by means of a clamping screw connection 106. After penetrating the plug housing 100, the connecting lug 104 comprises an enlarged portion 110, by means of which it comes into contact with the front surface of a cylindrical extension 112 with the bore 102.

The plug housing 100 is rigidly connected by means of a screw connection 114 to a holding housing 116, which comprises a column-like extension 118 through which the screw bolt 114 passes. The free end of the column-like extension 118, which extends parallel to the longitudinal axis L-L and at a spacing from the latter, is connected to a traction relief support plate 120, through which the screw 114 passes, so that the traction relief support plate 120 is firmly clamped between the screw head and the free end of the column-like extension 118.This traction relief support plate is rigidly connected to an outer housing 124 by means of a screw connection 122, which is not shown in detail in Figure 1, so that the support plate 120 at the same time serves to secure the combination of the plug housing 100 and the holding housing 11 6, which are held together by means of a screw connection 114, in the outer housing 124. For this purpose the plug housing 100 comprises a radially extending flange 128, onto which a rim 126 is formed which projects in the axial direction towards the cable inlet and rests against the free front surface of the pot-like outer housing 124.

The pot base 130 comprises an opening 132, which is closed on the outside in a manner known per se by means of an anti-kink sleeve 136, which is secured to the pot base by means of screw connections 134. The cable inlet is disposed at this point. A traction relief device 138 is disposed on the plate 120. The traction relief device and the anti-kink sleeve are part of the prior art which is known per se and are not important to the invention.

On the side directed towards the direction of insertion, the plug housing comprises a cylindrical collar 140, which surrounds the prongs 54 or projects slightly beyond them. The collar 140 engages round the collar 28 of the brush housing 18.

There will now be a description of Figure 2, which shows a further longitudinal section. The collar 140 of the plug part comprises a radially projecting lug 142. When the plug is inserted in the bush part the lug 142 moves along the inner surface of the receiving cylinder 78 in a groove 144 extending in the longitudinal direction. This longitudinal groove 144 passes in the region of the plane 54 into a radial groove 146, which extends at the circumference of the receiving cylinder 78 and adjoins a further groove, which is not shown in the drawing, extends in the axial direction and is angularly offset with respect to the groove 144. Owing to the guidance of the lug 142 in the longitudinal groove 144, the radial groove 146 and the other longitudinal groove, the lug 142 describes a Z-shaped movement.In other words, when the lug 142 is guided in the groove 144, the plug is firstly inserted in the bush in a linear manner, until the lug comes to rest against the plane 1 54. The lug 142 is then rotated in the groove 146, during which movement the plug is not moved in the longitudinal direction. Once the lug 142 has reached the other longitudinal groove, the plug can be completely inserted, as can be seen from Figure 1, and the prongs 54 form an electrical-galvanic connection with the bushes 20. The space containing tbe bush parts and the prongs is then a pressure-resistant space.

The air gaps required for this purpose are the gaps 148, 1 50 and 102'. The gap 148 is formed by the interspace between the outer surface of the bush and the inner surface of the duct 1 52 in the bush housing 18. A metal ring 1 56 is inserted in the intermediate housing 30 in order to form the air gap 1 50. The outer surface of the metal ring 1 56 and the inner surface of the extension 140 form the air gap 1 50. The third air gap is the gap between the prongs and the opening 102.

The required length of the air gap 150 is obtained once the plug has been inserted to the extent shown in figure 2. The air gap lengths 148 and 102 are fixed.

As can be seen from figure 2, the ring 48 is designed to cover the bushes 20. The ring is locked by means of the pin 68. This illustrated more clearly in Figure 3, which shows a rolled out section in the region of the ring at the circumference of the circle on which the bushes or prongs are disposed. The ring accordingly comprises three openings 56, which are indicated by the reference numbers 56', 56" and 56t", in Figure 3 for the purpose of differentiation. The bush housing 1 8 contains three blind holes 64', 64" and 64"', in which the locking pins 68', 68" and 68"' are inserted. These penetrate the intermediate plate 44 in the bores 66', 66" and 66"'. Figure 3 shows that the pin 68" is pushed into the opening 56".The position shown in the centre corresponds to the position before the plug is inserted in the bush part. When the plug is inserted, the prong 54tut pushes the pin 68tut into the blind-end bore 64"', as a result of which the pin 68tut or 68"', respectively, is pushed out of the bore 56"', so that it is possible to rotate the ring 48. The locking effect of the pin 68 is thus discontinued. The position at the bottom of Figure 3 is shown in Figure 2. In accordance with the guidance of the lug 142, the plug can now be rotated in the groove 146 until the openings or recesses 56, in which the prongs 54 are disposed or engaged, lie directly above the bushings 20.

The lug 142 is at the same time disposed in a line with the second longitudinal groove. As the prongs 54, the bores 56 and the bushes 20 are in alignment with one another and as the lug is in alignment with the second longitudinal groove, the plug can be completely inserted into the bushing part. The ring 48, which is guided in a rotatable manner in the bush part, thus serves, in the same way as a child-proof device, to cover the bushes when the plug is removed, and the fact that it is practically impossible to rotate the ring without using the prongs prevents a metallic object being inserted in the bushes.

Figures 4 to 8 show a further way of guiding the plug part with respect to the bush. Only the collar 1 60 of the plug part is shown in figure 8, which collar 1 60 corresponds to the collar 140 and surrounds the prongs 54. At the inner side of its free end the collar 1 60 comprises a secant-like narrow portion 162, the inner surface 1 64 of which is straight and extends parallel to the horizontal plane.

The bush part is schematically illustrated in Figure 4, which shows the extension 28 having a diameter D,. The intermediate part 164, which adjoins the latter, has a diameter D2. This region 164, which is surrounded by the collar 160, comprises a plurality of flat portions, as can be seen from Figures 5 to 7. Along the lines V-V there is a flat portion 166, which passes in the axial direction into a flat portion 168, the smallest diameter of which is the outer diameter D1 of the collar 28. A circular transition section 1 70 is disposed between the flat portions 1 66 and 1 68.

The plug 1 60 is inserted as follows: The surface 1 64 passes into the flat portion 1 68. The flat portion 164 can be turned through an angle a in the region of the connecting surface 1 70, so that this edge-like narrow portion 1 62 of the plug is in alignment with the flat portion 166 and can accordingly be inserted further up to the stepped surface 172.The arrangement according to Figures 4 to 9 achieves the same effect as the arrangement according to Figure 1 with the lug: the plug is firstly inserted in a linear manner up to the end edge 1 74 of the flat portion 168, after which it can be rotated by way of the connecting surface 170 and, owing to the boundary surface 176, which defines the connecting surface 170 and the flat portion 166, it can no longer be removed. The ring 48 is unlocked and-when the prongs 54, the bore 56 and the bushes 20 are in alignment-the plug is completely inserted. This is also shown in Figure 7. The prong is inserted in the plane of the diagram at a right angle thereto in the direction of the arrow F1, until the front surface of the collar 1 60 comes into contact with the boundary 174. The plug is then turned through the angle a in the direction of the arrow F2, after which it can again be completely inserted in the direction of the arrow F1 up p to the stepped surface 172.

Claims (8)

Claims

1. An explosion- or flame-proof electrical coupling plug device comprising a socket provided with bushes, a plug provided with prongs and surrounded by a cylindrical collar, at the inner surface of which an annular surface is provided which, following the insertion of the plug in the socket, surrounds an annular surface at the outer surface of the socket, thus forming an air gap according to the VDE specifications 0170- 0171, and a pressure-resistant space, which is formed after the plug has been inserted in the socket in a linear manner and in which the contact points are disposed between the bushes and the prongs, the plug also being rotated in the socket following the linear insertion of the plug, so as to bring the prongs and the bushes into alignment, characterised in that a ring (48), comprising openings (56), which correspond in number and position to the bushes (20), is arranged on the socket (14), covers the bushes before the plug (16) is inserted and is locked in this position, that the openings are arranged such that they receive the prongs following the insertion of the plug and the unlocking action thus caused, and that the ring can be rotated with the plug.

2. A device, according to Claim 1, characterised in that blind-end bores (64) are provided in the bush housing (18) of the socket and contain locking pins (68) which engage in a respective opening (56) in the ring (48) in the locked position and are pushed against the pressure of a spring (70) into the blind-end bore (64) by the pronghs (54) and then by the ring (48) in the unlocked position.

3. A device according to Claim 2, characterised in that the bush housing (18) is covered at the bush insertion side by a stationary intermediate part (44), which serves to guide the locking pins (68).

4. A device according to Claim 3, characterised in that the intermediate part (44) comprises cylindrical collars (62), which partially engage in the blind-end bores (64) and surround an opening (66) in which the guide pins (68) are guided.

5. A device, according to Claim 4, characterised in that the ring (48) comprises collar-like projections (58) which surround the openings (56) and the height of which corresponds approximately to the thickness of the ring (48).

6. A device, according to Claim 5, characterised in that a cylindrical projection (52) is provided at the bush housing and surrounds the ring (48) in a central bore (50), thus serving to guide the said ring.

7. A device, according to one of the preceding claims, characterised in that a thickened portion (162) is provided at the inner surface of the end of the collar of the plug (16) which surrounds the prongs and that flat portions (1 66, 1 68), which extend at an angle (a) and are axially offset with respect to one another, are provided at the bush part (12) and are defined in the axial direction by projections (174, 176), the spacing of which corresponds to the thickness of the thickened portion (162) at the plug in the axial direction, such that, following the insertion of the plug with the thickened portion (162) up to the flat portion (168) as far as the boundary (174) thereof, the subsequent rotation in the region between the two boundaries (174, 176) and the further insertion along the flat portion (166), the bushes and the prongs are coupled.

8. A device, according to one of the preceding claims, characterised in that the recesses (29), which are disposed in the intermediate housing (30) and through which the prongs can be inserted towards the bushings, are in the shape of an oblong hole, such that they permit the prongs to be rotated about the longitudinal axis L-L.