Abstract:
The invention relates to a pliers-type tool and to a method for cutting through optical fibre cables (OF). According to the invention, the OF cable is received between the jaws of the pliers precisely, in a specific position, and is securely and precisely held and supported there. The invention uses a novel round blade ( 14 ) which is accommodated in a separately operated cutting device ( 23 ). A switching mechanism ( 26, 28, 31, 32 ) is allocated to the cutting device for measuring the duration of use of the cutting blade.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a pliers-type tool and a method for cutting through optical waveguide cables. 
     2. Prior Art 
     Pliers-type tools and methods for cutting through cables, including such for optical waveguides, are known (DE 3406917; DE 3436668; DE 3509991; DE 3802577). 
     These tools, predominantly in the form of manually operable pliers and designed for cutting through and, in some cases, also for stripping away cable insulations, no longer meet the requirements, in respect of the functional characteristics of the cutting devices used in them, that apply to the quality of the parting or cutting site on optical waveguide cables. 
     This is because, in the parting of optical waveguide cables, it is not sufficient to perform a simple parting cut, as is usual in the case of electric cables. Rather, in this case, it is a matter of executing the highest quality of parting cut in respect of the condition of the cut face on the optical waveguide fibre. The quality requirements in this case consist in realizing the cut face absolutely smoothly and perpendicularly relative to the longitudinal axis of the fibre and, at the same time, producing its surface with an optimum surface quality. 
     The cutting or parting device, previously proposed by the applicant in DE-OS 19842122, in a tool, to be handled in the manner of pliers, for performing various types of work on optical waveguide cables is also no longer capable of adequately fulfilling the current requirements in respect of the quality of the cut face in macrometric and micrometric scales. 
     SUMMARY OF THE INVENTION 
     Finally, for the purpose of further improving this cutting technology, a cutting device was proposed by the applicant (DE 10056780.0) in which, in different method steps, the locating of the optical waveguide cable, as well as its holding and clamping, determining its position, have been effected in a new manner and the cutting blade has been designed for executing more precise parting cuts. 
     This procedure proposed therein, together with the functional refinement of the cutting device, have opened up new possibilities in cutting technology for optical waveguide cables which have already been positively endorsed in practical application in the processing of optical waveguide cables. 
     Although, with these refinements, obvious improvements have been achieved, when it is a matter of ensuring or guaranteeing a constantly good quality of the parting or cut face on the optical waveguide cable, when such special tools are handled by technicians one factor remains outside the control required in this case. 
     Since the quality of cut is largely dependent on the condition and quality of the blade edge, it appears to be absolutely essential to take measures to ensure that a usable, sharp blade edge is always available to the user or fitter, in the constantly repeated use of the cutting device, without this requiring any active operation or action on the part of the user through adjustment of the cutting blade to a different, new cutting zone. 
     For other reasons, also, this hitherto subjective assessment should not continue to be left to the user or fitter. Rather, it should be characteristic of the pliers tool, taking effect automatically, in the form of a control mechanism integrated into the tool, which stops the latter after appropriate use. 
     This requirement for improved, objectively more effective control of the cutting characteristics of the cutting blade constitutes a further object of the present invention. 
     On the basis of the stated intended purposes, the object of the invention is to indicate a tool with a cutting device, as well as a method for parting optical waveguide cables, which is integrated, in a manner known in principle, into a manually operated pair of pliers, which can be brought into effect by a likewise known purchase device which can be operated independently of the closing movement of the pliers, and which, in a refining manner in respect of method, permits the achievement of a precise parting cut of a quality not hitherto achieved, running perpendicularly to the cable axis and producing a high surface quality at the cut face, and which, for the purpose of ensuring these quality standards, is furthermore to be provided with a forced-action control mechanism by means of which the duration of use of the edge can be predetermined, by limitation of the number of cuts of a cutting portion of the cutting blade, before the cutting device is completely and forcibly stopped. 
     To achieve this object, a tool is proposed which has the features characterized in the claims and, with the cutting device described more fully therein, on a manually operated pair of pliers, permits the execution of the proposed procedure. In a first set of solutions to the defined problem, the preconditions for a high-quality parting cut are fulfilled with the exact locating of the optical waveguide cable, defining its position, its holding, securing its position, and the novel, advantageous supporting of the optical waveguide cable between the bit jaws of the pliers, while, in a second set of solutions to the defined problem, the high operating quality of the cutting blade is assured, with a ratchet mechanism actuated independently of the operator during the cutting or parting operation, through the provision of a constantly new, unused cutting portion on the circumference of the cutting blade. 
     This ratchet mechanism belonging to the cutting device has the effect that, after a determined number of cutting strokes with the cutting device initiated by a purchase device, the cutting blade is rotated further, or indexed, by a partial step proportioned to the circumference in each case, in order to provide on the cutting blade circumference in each case a hitherto unused, new cutting portion. The advantages resulting from this are self-evident and obviously do not need to be described separately. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The technical solution according to the invention, together with its solution elements, are characterized more fully in the claims and in the embodiment example with reference to the associated drawing, wherein: 
         FIG. 1  shows the cutting and crimping tool, to be handled in the manner of pliers, with a cutting device in perspective side view; 
         FIG. 2  shows the side view of a detail, representing the pair of clamping jaws with the cable clamping device for the novel, advantageous method steps; 
         FIG. 3  shows the top view on to the lower clamping jaw with the cutting device in the operated position; 
         FIG. 4  shows the side view of the locator and clamping holder of the cutting blade; 
         FIG. 5  shows the cross-section of the cutting-blade edge, in greatly enlarged scale, corresponding to the detail “A” in  FIG. 4 ; 
         FIG. 6  shows the head part of a pair of optical waveguide cutting and crimping pliers with an integrated ratchet mechanism for the cutting blade; 
         FIG. 7  shows a detail from  FIG. 6 , representing the pawl and latching tooth; 
         FIG. 8  shows, in section along the line I—I in  FIG. 6 , the front view of the pair of cutting and crimping pliers with the cutting blade and the ratchet mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The design of the cutting device on a pair of manually operable pliers  1 , by means of which various work can be performed on optical waveguide cables, such as removal of insulation, parting and crimping, provides for a special cutting technology by which the cable end can be parted in an exact manner, i.e., perpendicularly to the longitudinal axis of the fibre and with a good surface quality of the cut face. 
     This pair of pliers  1  is of a design which is known in principle. It consists of a fixed bit jaw  2 , a movable bit jaw  3  and of handles  4  and  5 , and can be brought into an open or closed position through a conventionally functioning and designed toggle lever mechanism  6  and  7 . 
     Attached to the bit jaws  2  and  3  in a fixed, but replaceable, manner are specially designed clamping jaws  8  and  9 , which each carry a clamping profile appropriate to the size of the optical waveguide cable, as shown by FIG.  2 . 
     The strip-type clamping profile  10  mounted on the upper, relatively fixed clamping jaw  8  has a concave clamping face  11  running transversely relative to the bit of the pliers. The clamping profile  12  mounted on the lower, relatively movable clamping jaw  9  is in the form of a groove  13  and, together with the clamping face  11 , forms a round circular cross-section in which the optical waveguide cable is located with a full form-fit. 
     The form-fit represented in  FIG. 2  is precisely matched to the diameter of the optical waveguide cable so that, when the pliers are closed, the cable is located without any play in the longitudinal and transverse directions. In addition, upon closing of the bit or clamping jaws  8  and  9 , it is tensioned in its location in such a way that, under the effect of the cutting pressure by the cutting blade  14 , it cannot change the spatial position apportioned to it. 
     A further particularity of the cutting technology according to the invention also consists in that, with the aforementioned clamping position, the clamping profile  12  disposed on the clamping jaw  9  is laterally cleared towards the cut-off end of the optical waveguide cable, i.e., away from the cutting blade  14 , as has been indicated by the clearance  15  in FIG.  2 . In this outer region, therefore, the optical waveguide cable is not fully enclosed by the clamping profiles  11 ;  12 , but only supported on the lower portion of the clamping profile  12 , as indicated by a bold line in FIG.  2 . It is therefore able to yield to the appropriate extent to the laterally acting cutting pressure by the cutting blade  14 , actuated by swivelling-in of the purchase device “H”, but without being able to change its spatial position. Moreover, for a smooth cutting operation, the outer portion of the clamping profile  12 , or the groove  13 , is inclined slightly outwards, i.e., towards the free end of the optical waveguide cable, as has been shown to be advantageous in the cutting operation, depending on the type and size of cable. 
     Further features of the cutting technology according to the invention also consist in the design of the cutting blade  14  which, for the cutting or parting operation to be performed on optical waveguide cables, enables novel and advantageous effects to be achieved in respect of the quality of the parting face on the functional part of the cable. 
     Firstly, the locating and holding device for the cutting blade  14  provides for an axial bracing provided in the plane of the blade, as indicated in a greatly enlarged representation in FIG.  4 . This bracing, by means of a strain washer  16 , provides the cutting blade  14  with an inner stability in the cutting plane which is greater than in the normal state, so as to prevent the blade from bending away. 
     In addition, the axial bracing of the cutting blade  14  on the shaft  17  against the bearing flange  18 , together with the edge bevel  19 , produces advantageous effects in that, during the execution of the parting cut on the firmly clamped optical waveguide cable, an axially inwardly directed pressure component becomes effective on the so-called cable core. This results in an effect which has a polishing action and which smoothes the surface of the cable core in a desirable manner. In order to increase this effect further, the edge bevel  19  is provided with a cutting lip  20 , executed in the micro range, the effect of which is to smooth the cut face of the core of the optical waveguide cable by pressure polishing, in order to prevent any scattering losses of the light energy to be transmitted at the contract face smoothed in this way. Moreover, the cutting lip  20  can be slightly curved, a factor which has proved to have further advantage. 
     The procedure and handling of the cutting device for parting optical waveguide cables with a pair of pliers of the indicated design is as follows: 
     Starting from the task of placing a new contact on an optical waveguide in a technically correct manner and of executing a parting cut for this purpose, following the opening of the two bit jaws  2 ;  3 , the cable end, as shown in  FIG. 2 , is inserted in the clamping jaws  8 ;  9 , where it is precisely inserted in the clamping profile  12 , in order then to be pressed, by the closing movement of the handles  4 ;  5  of the pliers, against the similarly shaped clamping profile  11  of the clamping profile  10  belonging to the fixed bit jaw  2 , or clamping jaw  8 . This produces an immovably fixed seating of the cable, this seating being fixed in the end position by means of the lever mechanism which is usual for such pliers. 
     The optical waveguide cable is then cut, or parted, using the cutting device which is to be operated when the pliers are closed, for which purpose the purchase device H, in the form of a swivel arm, is swivelled in the known manner by the finger of the operating hand in the cutting direction “S”. 
     In the course of this swivelling movement, the cutting blade  14  first comes laterally to the cut edge  21  of the clamping jaw  9 , where it is supported with a controllable initial tension so as to allow no play whatsoever at the cut edge  21  during cutting. Since the cutting blade  14  is in any case pretensioned in the axial direction, see  FIG. 4 , as the cutting movement progresses further, a parting of the cable is achieved which is fully free from play and with the surface effects mentioned above. 
     Following completion of the cutting or parting operation, the swivel arm, with the cutting blade  14 , returns automatically to its initial position under spring tension. The pliers can then be opened in the usual manner and the optical waveguide cable removed from the clamping profiles. 
     In a further refinement of this type of pliers, a ratchet mechanism has been assigned the integrated cutting device for the optical waveguide cable. This ratchet mechanism is designed to count or register the number of parting cuts to be executed with one edge portion of the circular cutting blade  14  and to ensure, with the control mechanism thereby created, that only a predefined number of parting cuts can be executed with one edge portion on the cutting blade  14  before a new, unused edge portion is made available through the rotating indexing of the cutting blade  14 . 
     The structure and functioning of the ratchet mechanism on the cutting device are as follows: 
     Disposed in the region of the head part of the pliers, is the cutting device  23 , together with the cutting blade  14 , which is equipped with the purchase device “H” including the swivel arm  22  and is pivotally mounted on a pin  24  for the purpose of being swivelled in, by means of the purchase device “H” with the swivel arm  22 , towards the bit jaws  2  and  3  between which the optical waveguide cable to be cut is located and partially clamped, for the purpose of executing the cutting or parting operation in the arrow direction “S”. 
     The swivel arm  22 , which is mounted in the head part of the pliers with the pin  24 , is initially held out of cutting engagement by a spring  25 , as shown in FIG.  1  and FIG.  6 . 
     At the same time, there is disposed on this swivel arm  22  the ratchet mechanism assigned, according to the invention, to the cutting device  23 , for the intermittent further rotation or indexing of the cutting blade  14 , which ratchet mechanism serves the purpose, as explained, of replacing the portion of the blade edge hitherto in use by an unused, new edge portion after a certain number of parting cuts. 
     This ratchet mechanism is formed, firstly, from a pawl  26  located eccentrically on the pin  24  ( FIGS. 6 and 8 ) and from a ratchet wheel  28 , attached to the bearing pin  27  of the cutting blade  14  and joined to it in a rotationally positive manner. 
     The pawl  26 , acted upon by a retaining spring  29 , is in constant active contact with the said ratchet wheel so that, upon actuation of the swivel arm  22  for the purpose of executing the cutting and parting operation, the ratchet wheel  28  is indexed at the same time by one tooth division by means of the eccentrically moved pawl  26 . 
     Depending on the number of teeth on the ratchet wheel  28 , in the embodiment example preferably 30 teeth, 30 indexing steps and then, consequently, 30 indexings are performed on the ratchet wheel  28  by the pawl  26  before a tooth division is indexed on the indexing wheel  32  by the cam  31 . The ratchet mechanism in this case provides for a further mechanism before the intended stoppage of the cutting device is effected. 
     Following each full rotation of the ratchet wheel  28 , the cam  31  engages with the indexing wheel  32 , as shown, as a result of which the indexing wheel  32  is indexed by one tooth division. This means that, in the case of an assumed tooth number of, for example, 42 teeth, the ratchet mechanism allows 30×42=1260 change operations before it is stopped by an appropriately provided index pin  33 , which is not accessible from the outside, and the cutting device is fully blocked in a deliberate manner. 
     The cutting capacity of the cutting blade  14  is to be rated, or limited, according to these 1260 change operations which are possible with the ratchet mechanism and which thus correspond to the number of parting cuts that can be executed with this cutting device. The cutting device should then be opened, and the cutting blade changed, only by an authorized workshop. 
     The created limitation and control over the duration of use of a cutting blade to be observed according to the invention assures, to a large degree, the required constantly good surface quality on the cut or parting face of the optical waveguide cable and, consequently, the effective energy transmission sought by means of the latter. 
     LIST OF REFERENCES 
     
         
           1  Pliers, head part of pliers 
           2  Fixed bit jaw 
           3  Movable bit jaw 
           4  }Handles 
         
           5 
         
           6  }Toggle lever 
         
           7 
         
           8  }Clamping jaw 
         
           9 
         
           10  Clamping profile as clamping forcer 
           11  Clamping face 
           12  Clamping profile 
           13  Groove on clamping jaw  9   
           14  Cutting blade 
           15  Clearance 
           16  Strain washer 
           17  Blade locating shaft 
           18  Bearing flange 
           19  Edge bevel 
           20  Cutting lip 
           21  Cut edge on clamping jaw  9   
           22  Swivel arm 
           23  Cutting device 
           24  Pin 
           25  Spring 
           26  Pawl 
           27  Bearing pin 
           28  Ratchet wheel 
           29  Retaining spring 
         
           30 
         
           31  Cam 
           32  Indexing wheel 
           33  Index pin 
         “A” Detail in  FIG. 6   
         “H” Purchase device 
         “S” Cutting direction by cutting blade  14