Abstract:
A method for cutting an outer cladding or tube of a light waveguide cable to form a gap includes removing material on the opposite lateral portions of the outer cladding to produce flattened areas, forming an annular cut on each end of the flattened area and then splitting the cladding in the flattened areas to enable removal of the portion. To accomplish the production of the flattened areas, a milling unit having guide rollers for the cladding and a pair of milling wheels engaging opposite sides of a cladding of a cable held in the guide rollers is used.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a method and an apparatus for cutting light waveguide cables with a tubular outer cladding. 
     In the cutting technique for light waveguide bundle leads, which comprise, for example, a plastic or synthetic cladding, the exposure of the light waveguide leads can occur with a simple cutting tool. The cable cladding is sliced along a cladding line and then removed for a corresponding length. However, in cable cladding having a metal tube, which is used in a microcable, this cutting technique is not possible, because these microcables consist of mostly metal tubes in which the light waveguides are accommodated in a loose fashion. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a method in which the cable cladding of metal, particular metal tubes of microcables, can be detached and removed at a prescribed length from a piece of cable in what is known as a cutting technique. This object is achieved with a method in which the tubular outer cladding of the light waveguide cable has material removed along two opposite cladding lines to form flattened portions and then an annular incision or cut is constructed at least at one end of the resulting flattened portions so that the tubular outer cladding can be separated and removed along these flattened areas. 
     Another object of the invention is to provide an apparatus for removing the material to form the flattened thin web portions, which apparatus comprises a milling unit, guide rollers for guiding the cladding while milling opposite sides of the cladding to form the flattened portions. 
     An advantageous result of the method is that the cutting technique can be used even with bundle leads or, respectively, light waveguide cables with metal tubes, for example microcables or cladding-only cables. The outer metal tube of the microcable is then stripped or removed along two opposite lines to form two flattened areas and then the tube can be subsequently separated or, respectively sliced in this region in a simple fashion and removed after forming at least one annular incision at the end of the flattened areas. The annular incision or cuts are preferably constructed at both ends. In this way, the intermediate region of the microcable is exposed to such an extent that the light waveguide leads, which are loose in the cladding, are now accessible. The material strippings, which form flattened portions on the tube of the light waveguide cables, are produced by milling, wherein both of the opposing cladding regions are appropriately simultaneously processed. In this method, the light waveguide cable is, thus, first led in a device between guide rollers and then successively pushed into a milling unit acting on both sides. This unit consists of at least two opposed milling wheels or cutters. The intervals between the guide rollers as well as between the milling cutters can be adjusted to the diameter of the employed cable type and potentially also controlled, so that tolerances can be balanced out. In this step, the tube is stripped to such an extent that narrow webs still remain, preferably with a thickness in the order of magnitude of 0.1 mm. This is necessary in order to assure that the light waveguide leads that are inside the cable are not damaged by the removal of the material. In another step, an annular incision is introduced in the tube at least at one end of the resulting flattened regions in order to separate the region which is to be exposed from the rest of the cable. In another step, the resulting thin webs are then split along a respective cladding line and the outer cladding, which is now split longitudinally, is removed. The individual functioning parts of the device which are used in this method can consist of component parts which are used in succession. However, the guide unit, the milling unit, the annular cutter and removal devices can also be put together into a single structural unit. The control unit and regulating unit for driving the guide rollers and the milling wheels or cutters can then also be integrated in this structural unit. 
     Other advantages and features of the invention will be readily apparent from the following description of the preferred embodiments, the drawings and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a light waveguide cable constructed as a microcable; 
     FIG. 2 is a cross-sectional view of the microcable of FIG. 1 after removal of material to produce lateral flattened areas; 
     FIG. 3 is a perspective view of a microcable after construction of the first annular incision; 
     FIG. 4 is a perspective view of a microcable after the completed cutting process to remove portions to obtain access to the fibers; 
     FIG. 5 is a plan view of an apparatus for producing the lateral milled portions on the cladding; and 
     FIG. 6 is an end view of the device of FIG. 5 showing regulating means. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The principles of the present invention are particularly useful for obtaining access to the interior of a microcable, generally indicated in FIG. 1. The microcable of FIG. 1 is a light waveguide cable which consists of a tube 2 of metal, which surrounds light waveguide leads or fibers 3, which are loosely received inside the tube 2. If a branching or junction or a cable sleeve is to be set up for such a microcable, then the microcable must be cut, which means that the tube 2 must be opened so that the light waveguide leads located inside are accessible. Care must be taken that the sensitive light waveguide leads 3 are not damaged during the opening of the tube 2. The exposed light waveguide leads 3 are then spliced with other light waveguide leads in the branching or junction and are laid down or, respectively, lead through uncut in a cable sleeve in the lead-throughs or continuations. The unprotected light waveguide leads are therein surrounded over the entire length of the gap by a longitudinally slit hose, which is clamped onto the tube a clamping device, such as a helical spring clamping arrangement, so that the light waveguides are protected from buckling with impermissible bends. 
     In accordance with the present invention, a cutting of the light waveguide microcable 1 is done by producing flattened portions 5 on opposite sides of the tube 2, as shown in FIG. 2, by stripping the material away, such as by milling. In fact, the material is removed to such an extent that only an extremely small wall or, respectively, thin webs 4 and 6 remain in order to minimize the danger of damaging the light waveguide leads 3, which are inside of the tube 2. Given a wall thickness of the tube 2 of 1 mm to 2 mm, the residual wall thicknesses at the webs 4 and 6 should be smaller than 0.1 mm. On one hand, the webs 4 and 6 should still offer protection and, on the other hand, however, their slicing into two half-tubes and their removal should be possible with a simple extraction device, according to the length of the webs. 
     As shown in FIG. 3, the next step following the production of the lateral flattenings 5 is to produce an annular incision or cut 14, which extends completely around the circumference of the tube 2 and can be produced with a ring or annular tube cutter 24 (see FIG. 5). It is preferably produced at the end of the flattened region 5, which has a length 4&#39;. Thus, a ring-shaped severing through the tube will occur. It is advantageous that the microcable 1 with the tube 2 is held in a holder on both sides of the cuts prior to the severing by the annular cut 14. Thus, the fibers are protected from impermissible bending if the tubes on both ends of the flattened region are being held. 
     As shown in FIG. 4, the next step is a second ring incision or annular cut 16 that is spaced at the other end of the flattened webs 4 and 6 and the webs 4 and 6 have longitudinal cuts so that two half-tubes 17 are produced and can be lifted out from the microcable 1 to form a gap which provides access to the leads 3. It is appropriate to begin the severing first along one web starting from an annular incision 16. The uncut light waveguides 3 located therein are thus accessible and can be brought into a cable sleeve, for example, branched there or led therethrough. 
     An apparatus, generally indicated at 7 in FIG. 5, is the simplest form for forming the flattened portions 5 on the tube 2 of the microcable 1. The apparatus includes guide rollers 11 and 12, which are arranged with the two rollers 11 on one side and the second roller 12 on the opposite side. The roller 12, as illustrated, is mounted to be adjustable in a controlled fashion in a direction of the double-arrow 9 so as to compensate for changes in the size or diameter of the tube 2 of the microcable 1. This adjustment also allows for compensating for tolerance in the diameter due to movement of the cable. To produce the flattenings, two opposed milling wheels or cutting rollers 8 are arranged in a milling unit, whose rollers have an interval which can be adjusted in the direction indicated by the double-arrow 9, in correspondence with the requirement removal of the material. The arrow 13 indicates the direction of rotation of each of the milling wheels 8 for production of the flattened portions 5 on the microcable 1. Thus, both wheels rotate in the same direction but cut the tube in opposite directions. The illustration is based on the assumption that the device 7 is pulled along the microcable 1 in the direction of the arrow 10. It is also possible, however, to hold the device or apparatus 7 in place and to pull the microcable 1 through the guide channels between the guide rollers and the milling wheels in a direction opposite to the arrow 10 so that relative movement is in the direction of the arrow 10. 
     The device 7 can be provided with regulating units, as illustrated in FIG. 6. For example, the microcable 1 consisting of the tube 2 and the light waveguide leads 3 is led in a guide channel 21 of the device 7 perpendicular to the direction of the drawing. The stripping or removal of material has already been conducted by the milling wheels 8, which are mounted on supports 18 on both sides, so that the flattened portion 5 have already occurred. In addition, the two milling wheels 8 are driven by a controllable drive unit 19. A justifying device 20 is indicated, through which the microcable 1 is correspondingly guided and controlled in the guide channel 21, which is between the guide rollers, which are not illustrated in this Figure. A plurality of milling units 8 or guide units can also be arranged one behind the other or, respectively, successively in the device if a more exact guidance and removal of material in a plurality of layers is desired. 
     It is advantageous if the interval of the opposing milling wheels 8 is adjusted according to the interval of the opposite guide rollers 11, independently according to the respective diameter of the tube 2. In the device, the milling wheels 8 and the guide rollers 11 on one side can be assembled on a drive unit 19, which is pressed in a biased manner against a drive unit 22 with a milling wheel and the guide roller 12 on the opposite side. In this way, tolerances and thickness fluctuations of the tube 2 can be compensated. 
     FIG. 5 shows splitting or severing devices 25 for making the longitudinal cuts in the flattened regions 5 along a respective cladding line, with which device the tube 2 is split in the flattened regions into two half-tubes 17, as illustrated in FIG. 4. However, such a cutting device can be a conventional cutter. It is also possible to use conventional tools for cutting each of the half-tubes or bending them and removing them from the microcable adjacent each of the annular cuts, such as 14. Preferably, the apparatus 7 is constructed so that it can be pulled or moved along arbitrarily-shaped microcables without the remaining webs 4 and 6 with a residual thickness of 0.1 mm being compromised. 
     Although various minor modifications may be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent granted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.