A STRAIN RELIEF DEVICE FOR ELECTRIC CABLES, PREFERABLY IN AN APPARATUS OR TERMINAL BOX

Abstract: A strain relief device for electric cables in general and in particular in an apparatus or terminal box comprising a load-absorbing relieving member (3.1) with the aid of which a cable can be clamped against a counter-support (1). The relieving member (3.1) is displaceable in a direction towards the counter-support (1) in a guide arrangement (2.3) and can be locked in inserted position with the aid of a locking member (2.5), against a cable inserted through a cable opening (2.2). The relieving member (3.1) may be arranged on the inside of an apparatus or terminal box in direct connection with a cable opening (2.2). The relieving member may consist of a disk (3.1) with saw teeth (3.2), directed towards the wall (2) of the box and being in communication with corresponding teeth (2.4) on the locking member, which in turn consists of a locking tongue (2.5) forming a part of the wall (2) of the box.

Description: A STRAIN RELIEF DEVICE FOR ELECTRIC CABLES, PREFERABLY IN AN APPARATUS OR TERMINAL BOX Technical Field The present invention relates to a strain relief device for electric cables in general and in particular in an apparatus or terminal box comprising a bottom surrounded by sidewalls. The strain relief device comprises a load-absorbing relieving member with the aid of which a cable can be clamped against a counter-support, possibly consisting of the bottom of the box or some other fixed component in the box or on another apparatus. Background Art Strain relief devices in apparatus or terminal boxes, as also in other electrical devices, usually consist of a bush cap secured at each end to a base by means of screws. Strain relief is achieved by inserting the cable beneath the bush cap between the screws, which are then tightened and clamp the cable to the base, the latter thus constituting a counter-support. In conventional terminal boxes this type of strain relief is placed on the outside of the box which means that it is not easily accessible when the box is recessed in a wall, for instance. The use of strain relief devices in the form of bush caps requires the use of tools, e.g. a screwdriver, and entails several work phases consisting of shifting the hold on cable, bush cap, screws and tools when connecting a cable to a terminal block or the like in the box. This is time-consuming, particularly since it is easy to drop a screw or the cap or the tool, for instance, in cold weather when the fin- gers are stiff. Furthermore, if a screw is lost the first box is often discarded and replaced with a new instead of looking for the lost screw. Description of the Invention The object of the present invention is to provide a strain relief that is more easily accessible than current strain reliefs, and also to eliminate the need for tools such as screwdrivers, when fitting the strain relief. The object is achieved by means of the present invention which relates to a strain relief device for electric cables in general and in particular in an apparatus or terminal box, but which may also have other applications, e.g. apparatus in ge- neral such as computers, printers, copiers and the like, and which comprises a load-absorbing relieving member with the aid of which a cable can be clamped against a counter-support. The reliever member is displaceable towards the counter-support in a guide arrangement and can be locked in inserted position against a cable inserted through a cable opening, with the aid of a locking member. The relieving member is preferably arranged on the inside of the apparatus or terminal box in direct connection with a cable opening in the wall of the box, and displaceable in guide members constituting a part of the wall of the box. The strain relief member may consist of a relieving disk with saw teeth, arranged in the direction of movement of the disk and directed towards the wall of the box, and in engagement with corresponding teeth on the locking member, which in turn consists of a locking tongue forming a part of the wall of the box. The locking tongue is provided with a groove directed towards the opening of the box, extending in the direction of movement of the relieving disk and directed towards the latter, whereby the locking tongue can be released from the relieving disk by pressing down a screwdriver, for instance, into the groove and causing the locking tongue to spring outwards from the box so that its teeth are released from engagement with the teeth of the relieving disc, thereby releasing the relieving disk. However, it lies within the scope of the invention to achieve locking between the locking tongue and the relieving disk in some other way, e.g. by providing each member with a co-operating shoulder that can be released from the other in the manner described above. In a particular embodiment in which the strain relief device according to the invention is arranged in a terminal box, the actual relieving member is arranged in one of the corners of the box that is provided with a recessed flat section perpendicular to the bottom of the box and intersecting its sides at an angle of 45°, or in some other way. The reason for arranging the strain relief device in this way is so as not to encroach on the interior space of the terminal box or the like, which space is needed for connectors such as a terminal block. Further details and features of the invention are revealed in the description of the drawings and in the claims. Description of the Drawings The invention will be described in the following by way of an example with reference to the accompanying drawings. Figure 1 shows a terminal box, square in shape, seen from the side in a diagonal direction. Figure 2 shows the terminal box according to Figure 1 , seen from above towards its open end. Figure 3 shows a cross section of the terminal box along the line l-l in Fig Figure 4 shows an enlargement of the lower corner of the terminal box shown in Figure 2. Figure 5 shows a cross section along the line 11-11 in Figure 4. The terminal box illustrated in Figures 1 and 2 has a bottom 1 surrounded by four side walls 2. Two adjacent corners of the box are provided with recessed, flat sections 2.1 that are perpendicular to the bottom 1 and intersect the adjacent sides at an angle of 45°. Each flat section 2.1 extends some way up from the bottom of the box and has a cable opening 2.2 for a cable to be drawn into the box. In Figure 1 the cable opening is shown covered by a plate that can be broken off. This has been removed in Figure 3. A strain relief 3 is arranged inside the box at each cable opening 2.2. One such strain relief 3 is shown in a view towards the inside of a flat section 2.1 in Figure 3 and another strain relief 3 is shown in cross section in the same figure. An enlargement of the cross section of the de- tensioner is shown in Figure 5. The strain relief 3 comprises a load-absorbing relieving disk 3.1 which is displaceable perpendicularly to the bottom 1 of the terminal box, along guide members 2.3 that form a part of the wall 2 of the box at the flat section 2.1. The relieving disk 3.1 is provided with saw teeth 3.2 extending perpendicularly to the direction of movement of the relieving disk 3.1 and being directed towards the flat section 2.1. The teeth 3.2 of the relieving disk 3.1 are in engagement with corresponding teeth 2.4 arranged on a resilient locking tongue 2.5 that constitutes a part of the wall in the flat section 2.1 and which is also shown in Figure 1. The teeth 3.2 of the relieving disk 3.1 are provided with upwardly facing flat surfaces, whereas the teeth 2.4 of the locking tongue 2.5 are provided with downwardly di- rected flat surfaces, as shown in Figure 5. When the relieving disk 3.1 is pressed down against a cable, not shown in the drawings, which has been inserted through the cable opening 2.2, the locking tongue 2.5 springs out and permits the teeth 3.2 of the relieving disk to pass the teeth 2.4 of the tongue since the cooperating teeth only prevent movement of the relieving disk 3.1 in the opposite di- rection. In order to release a cable that has been inserted into the terminal box and clamped there, the locking tongue 2.5 is first caused to spring out by inserting the tip of a screwdriver, for instance, into a groove 2.6 extending downwardly in the locking tongue 2.5. The tongue then springs outwards thereby releasing the teeth 3.2 of the relieving disc 3.1 from the teeth 2.4 of the locking tongue 2.5 so that the relieving disk 3.1 can be pulled up from its abutment with the cable. The cable can then be removed from the terminal box.

Claims: CLAIMS 1. A strain relief device for electric cables in an apparatus or terminal box comprising a load-absorbing strain relief member (3.1) arranged on the inside of the apparatus or terminal box in direct connection with a cable opening (2.2) in the wall (2) of the box, and displaceable in guide members (2.3) constituting a part of the wall (2) of the box, against a counter-support (1 ) and lockabie in inserted position with the aid of a locking member (2.5), against a cable inserted through a cable opening (2.2), characterized in that the strain relief member consists of a relieving disk (3.1) with saw teeth (3.2), arranged in the direction of movement of the disk and directed towards the wall (2) of the box in engagement with corresponding teeth (2.4) on the locking member, which in turn consists of a locking tongue (2.5) forming a part of the wall (2) of the box. 2. A strain relief device as claimed in claim 1 , characterized in that the locking tongue (2.5) is provided with a groove (2.6) directed towards the opening of the box and extending in the direction of movement of the relieving disk (3.1) and directed towards the latter, whereby the locking tongue (2.5) can be released from the relieving disk (3.1) by pressing down a screwdriver, for instance, into the groove (2.6) and causing the locking tongue (2.5) to spring outwards from the box so that its teeth (2.4) are released from engagement with the teeth (3.2) of the relieving disc (3.1), thereby releasing the relieving disk (3.1). 3. A strain relief device as claimed in claim 1 or claim 2, characterized in that it is arranged in at least one of the corners of the box that is provided with a recessed flat section (2.1) perpendicular to the bottom (1 ) of the box and intersecting its sides at an angle of 45°.

Inventors: BOTVIDSSON LARS, ERIKSSON STAFFAN, BOTVIDSSON, LARS, ERIKSSON, STAFFAN
Applicants: BOTVIDSSON LARS, ERIKSSON STAFFAN, THORSMAN & CO AB, BOTVIDSSON, LARS, ERIKSSON, STAFFAN, THORSMAN & CO. AB
Application year: 2000
Main classification: H02G15
IPC codes: H01R13