METHOD AND SEALING ELEMENT FOR SEALED LEADING OF CABLES THROUGH AN OPENING IN A WALL OF A CABINET CONTAINING ELECTRICAL EQUIPMENT, AND USE OF A TOOL FOR LEADING A CABLE THROUGH A SEALING ELEMENT

Abstract: An element for sealed leading of a cable (6) through a wall (2) of a cabinet (1) containing electrical equipment, consists of a plate (7) of elastic material, such as rubber or plastic, and of uniform thickness, which is adapted to completely cover an opening in the wall (2) and in which optionally positionable slits (20) are cut, without removing any material, the cables (6) being passed through said slits, while the surrounding elastic material is being pressed aside and compressed.

Description: METHOD AND SEALING ELEMENT FOR SEALED LEADING OF CABLES THROUGH AN OPENING IN A WALL OF A CABINET CONTAINING ELECTRICAL EQUIPMENT, AND USE OF A TOOL FOR LEADING A CABLE THROUGH A SEALING ELEMENT Background of the invention For mounting electric cables in different kinds of conventional casings, such as switch boxes, switch cabinets or switchboards, not only a variety of casing models are required but also a great number of lead- in flanges for each such model. The reason is that according to the special use of the individual casing, different numbers of cables and differently dimensioned cables may have to be connected to one and the same casing. Since the lead-in flanges consist of metal plates in which prefabricated holes for the cables are formed, flanges having different hole patterns must be used for different combinations of cables. This is extremely inconvenient since each wholesaler and each retailer must store a great number of different types of flanges for each type of casing. A further drawback of conventional lead-in flanges is that they require a special fitting and a matching rubber seal for each hole and cable. The diameter of such fittings is fairly large, and to tighten the fittings a big space around each cable is necessary. As a result, only a limited number of cables can be passed through a flange of a given size. The fittings further demand a great deal of work for mounting of the cables. Besides, if additional cables are to be mounted in the casing afterwards, the flange first used must be replaced by a flange having a different, matching pattern of holes. Brief description of the inventive idea The present invention aims at obviating the above drawbacks of conventional lead-in flanges in cabinets containing electrical equipment, and at creating oppor¬ tunities for simple, quick and conveniently performed leading-in of electric cables or other conductors. According to the invention, this is achieved by a method which is characterised in that a plate of elastic material, such as rubber or plastic, and preferably of uniform thickness is used as a sealing element completely covering the opening in the wall of the cabinet, and that for each cable, there is cut, without removing any material, a slit in said elastic plate, and that each cable is forced through said slit, while pressing aside and compressing the elastic material in the area of the slit. In addition to the method as such, the invention also relates to a sealing element for carrying out the method and a tool for leading a cable through the sealing element. The characteristic features of the sealing element and the tool are stated in the appended claims. By using, according to the principle of the invention, a sealing element in the form of a plate of elastic material, particularly rubber, the advantage is achieved that lead-in slits can be rapidly and readily cut in the plate in optional patterns, the slits as well as the cables being positioned closely together, which means that a very large number of cables can be led even through a plate of limited size. A further essential advantage is that one or more cables already mounted can be removed- from the installation by simply being withdrawn from the plate which because of its elastic properties then automatically fills up the cavity earlier occupied by the cable. If one or more cables are removed, the sealing plate itself thus need not be replaced, which results in great cost savings both in storing of sealing elements and in dismounting and remounting of cables in the installation. Brief description of prior art FR 1,540,647, FR 2,171,021, SE 354,387 and DE 2,109,548 disclose plates or elements which are adapted to lead cables to switch cabinets or the like and which are at least partly made of elastic material. However, a common feature of these prior art lead-in plates is that for each cable they are provided with a preformed membrane or thin part which is readily penetrated to leave a permanent hole. This means that the hole remains open if the associated cable is later removed, and the lead-in plate must thus in its entirety be replaced by a new plate, in case the wiring of the installation need be rearranged. In these prior art structures, the lead-in membranes are further prefabricated in given patterns which restrict the electrician's liberty to arrange the wires in any desired manner when leading the wires into the cabinet. GB Patent Specification 1,507,027 discloses a sealing device for electric cables or conductors, which is based on the use of a rubber plate having one or more holes and mounted in a sleeve-coupling comprising at least two parts which via a screw joint can be tightened relative to each other, while the material of the rubber plate is being compressed to cause the rubber to sealingly engage the conductor! s) passed through the respective holes in the rubber plate. Although this publication mentions that the holes can be provided just prior to use, the inventive idea which can be read from the publication, is entirely limited to the concept of providing, in one way or another (by drilling, cutting or punching), precisely holes, i.e. areas in which material has been removed, in the rubber plate. After the holes have been made, they remain irrevocably in the rubber plate which thus must be discarded and replaced by a new lead-in plate in case of rearrangement of the wires. It should also be mentioned that SE 7809750-8, 8002044-9 and 8002047-2 disclose the leading of cables through elastic bodies at optional points. In these cases, the elastic lead-in bodies are, however, made of a f re-resistant foam material. Brief description of the accompanying drawing •In the drawing: Fig. 1 is an exploded view of different parts included in the sealing or lead-in element according to the invention, and Fig. 2 is a perspective view of the same element mounted in a cabinet. Detailed description of the invention In the drawing, a casing containing electrical equipment is designated 1. The casing may consist of a simple switch box, a cabinet or a large switchboard. In a wall 2 of the cabinet 1 , there is formed an opening 3 which can preferably be of standard design having a rectangular shape with bevelled corners. In the same way as for conventional metal lead-in flanges, the wall 2 is provided with four threaded holes 4 for a corresponding number of fixing screws 5. As an element sealing the opening 3 and allowing leading-in of wires 6, a plate 7 of elastic material, particularly rubber, which preferably is of uniform thickness and in this case is rectangular, is used according to the invention. This lead-in plate 7 may preferably have a thickness of 10-15 mm and be made of pure rubber in which a reinforcement layer 8 suitably consisting of tow or ' woven textile fabric of some suitable kind is embedded or vulcanised. This reinforcement layer 8 gives the rubber plate 7 excellent rigidness and stability ensuring that each cable or wire 6 is automatically retained in its mounted position, without the tendency of the rubber to return to its original shape being lost. Four holes 9 are formed in the rubber plate 7 which match the holes 4 in the wall 2 of the cabinet 1. The plate 7 is adapted to coact with a frame 10 of metal or rigid plastic which has a through opening 11 of the same shape, in this case substantially rectangular, as the opening 3 in the cabinet 1. The frame 10 also has four holes 12 whose mutual positions correspond to the positions of the holes 9 in the plate 7 and the holes 4 in the cabinet 1. The frame 10 itself can suitably be made of thin metal sheet which is compression moulded, while forming both inner edge portions 13 which extend perpendicular away from the planar sheet metal web and are pressed into the rubber plate 7 as the fixing screws 5 are being tightened, and slightly more shallow outer edge portions 14 em¬ bracing and protecting the edge portions of the rubber plate 7 in the mounted state. In Fig. 2, a tool generally designated 15 comprises a handle 16 and, extending therefrom, a metal blade 17 of arcuate cross section which tapers successively from the handle 16 to a narrow front tip 18. In connection with the metal blade 17, the handle 16 is formed with a successively tapering rounded recess 19 along which a cable 6 can easily slide. The leading in of a cable 6 by means of the tool 15 is carried out in the following manner. When the tool blade 17 of arcuate cross-section is pressed into and through the rubber plate 7 in the desired position, an arcuate slit 20 is formed which widens as the tool moves through the plate. Preferably at the same time as the tool, the cable 6 is passed through the slit 20 thus cut, the cable being kept in engagement with the inside of the blade 17. When the cable is being pressed down through the slit - which has been formed without removing any rubber material - the rubber material in the area of the slit is pressed aside and compressed. This means that the cable is automatically firmly pinched by the rubber material when the cable front end has been passed through the rubber plate and the tool 15 has been removed. After mounting, the cable will thus be retained in its given position solely by the pressure applied to the cable by the compressed rubber material. Of course, this pressure also provides for an extremely tight seal between the cable and the surrounding rubber material. If an individual cable is to be removed after some time, it can be disconnected from the associated connecting means in the cabinet 1 and be withdrawn through the lead-in plate 7 in one motion. Then the rubber material which enclosed the cable returns to its original shape while filling up the space pre¬ viously occupied by the cable. In other words, the cable leaves but the arcuate cut as shown at 20. In actual practice, the cut is completely sealed, which means that after removal of the cable the sealing action of the rubber plate is intact. Conceivable modifications of the invention The invention is, of course, not limited merely - to the embodiment described above and shown in the drawing. Thus, it is conceivable to use the invention to lead in other conductors than precisely electric cables, for example pneumatic tubes of the kind which may be connected to a control equipment enclosed in a cabinet. It is further conceivable to make the inventive lead-in plate of some material other than rubber, e.g. various types of plastic. Also the shape of the lead-in plate can deviate from the one shown. The essential* thing is that the plate fully covers and seals the opening in the wall to which it is applied. It may further be pointed out that the slit which is cut in the plate can have a shape other than arcuate, e.g. a linear shape. Instead of making the fixing frame of metal, it is possible - and in practice preferred - to use plastic. It may finally be mentioned that the frame as well as the lead-in plate can be attached to the cabinet in some other manner than by screws, for example by means of so-called drivable rivets or other types of rapidly applicable fixing means.

Claims: CLAIMS 1. A method for sealed leading of cables, e.g. electric cables, through an opening (3) in a wall (2) of a cabinet (1 ) containing electrical equipment, c h a r a c t e r i s e d in that a plate (7) of elastic material, such as rubber or plastic, and prefer¬ ably of uniform thickness is used as a sealing element completely covering the opening (3) in the wall (2), that for each cable (6), there is cut, without removing any material, a slit (20) in said elastic plate, and that each cable is forced through said slit, while pressing aside and compressing the elastic material in the area of said slit. 2. A sealing element for sealed leading of cables, e*.g. electric cables, through an opening (3) in a wall (2) of a cabinet (1) containing electrical equipment, c h a r a c t e r i s e d in that said sealing element consists of a plate (7) of elastic material, such as rubber or plastic, which preferably is of uniform thickness and is adapted to completely cover the opening ( 3 ) in said wall (2) and in which optionally positionable slits (20) are cut, without removing any material, the cables being passed through said slits, while the surrounding elastic material is being pressed aside and compressed. 3. The sealing element as claimed in claim 2, c h a r a c t e r i s e d in that said plate (7) is made of pure rubber in which at least one reinforcement layer (8), consisting of e.g. tow or woven textile fabric, is embedded. 4. The sealing element as claimed in claim 2 or 3, c h a r a c t e r i s e d in that said plate (7) is rectangular and has at least four holes (9) each positioned in a corner and adapted to coact with a corresponding number of holes (12) in a frame (10) adapted to be pressed against the edge portions of said plate, as fixing screws (5) are being tightened in threaded holes (4) in said cabinet (1). 5. Use of a tool comprising a handle (16) and, extending therefrom, a metal blade (17) of arcuate cross-section, which tapers successively approximately from said handle to a narrow front tip (18) and which is adapted to lead a cable, particularly an electric cable, through a plate (7) made of elastic material, such as rubber or plastic, and serving as a sealing element for an opening (3) in a wall.

Inventors: LAERKA LENNART, LAERKA, LENNART
Applicants: RAABOMS ELEKTRISKA AB
Application year: 1988
Main classification: H02G3
IPC codes: H02B1, H02G3