Abstract:
A pliers-type stripping tool includes a base, a pair of pivot levers pivotally connected with the base, a pair of clamping members connected for relative longitudinal displacement on one of the pivot levers, a pair of cutting members connected for relative longitudinal displacement on the other of the pivot levers, a first spring biasing the clamping jaws apart, a second spring biasing the cutting jaws apart, and a first operating arrangement operable by a pair of pivotally-connected handles to displace the clamping and cutting jaws together from their normal separated conditions toward adjacent positions in clamping and insulation-piercing engagement with an insulated conductor positioned therebetween. The cutting members sever a length of the insulation layer that extends concentrically around the conductor, and a second operating arrangement is operable by the handles to separate the pivot levers, thereby to strip the severed insulation layer from the bare conductor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A pliers-type stripping tool includes a base, a pair of pivot levers pivotally connected with the base, a pair of clamping members connected for relative longitudinal displacement on one of the pivot levers, a pair of cutting members connected for relative longitudinal displacement on the other of said pivot levers, first and second spring means biasing apart the clamping jaws and the cutting jaws, respectively, and first operating means including a pair of pivotally connected handles operable to displace the clamping and cutting jaws together from their normal separated conditions toward adjacent positions in engagement with an insulated conductor positioned therebetween. Owing to the spring biasing means, a certain degree of tolerance is provided to compensate for variations in the diametric dimensions of the insulated conductor components. The cutting members sever a length of the insulation layer, and second operating means are operable by the handles to separate the pivot levers, thereby to strip from the bare conductor the length of severed insulation. 
     2. Brief Description of the Prior Art 
     Insulation stripping tools of the pliers type are well known in the prior art, as evidenced, for example, by the German patent No. DE 79 33 957 U1. This tool includes two clamping jaws and two stripping knives which operate in a pulling manner, that is to say, one clamping jaw each and a stripping knife are pulled in case of activation against a fixed clamping jaw and a fixed stripping knife. The movable clamping jaw and the stripping knife are not coupled together so that the movable clamping jaw and the stripping knife can be applied against the conductor independently of each other. 
     It is also known that one can provide a two-knife arrangement including two stripping knives each on stripping pliers that are arranged “back to back” with adjacent cutting areas. This can be advantageous because one does not leave any imprint of the clamping jaws on the conductor, which, under certain circumstances, could even damage the conductor, and because the very sharp knives can securely prevent the conductor from slipping through. On the other hand, separation with the two knife arrangement, positioned back to back, consisting of two stripping knifes each, is not always advantageous because that can result in an unsightly cutting result. The known stripping tools of this pliers design have the disadvantage that they have an extensively asymmetrical structure, something that makes production more expensive due to the large number of required parts and, moreover, the user finds handling this device to be rather difficult. 
     The present invention was developed to provide an improved pliers-type insulation stripping tool by means of which, using appropriate handling procedures, it is possible in a simple manner to provide a tolerance compensation for varying conductor diameters. Preferably, as an alternative, there is provided both a design with two clamping jaws and two stripping knives as well as an arrangement with an arrangement including two knives lying next to each other with two stripping knives each. 
     A certain degree of play is provided between the clamping and/or the cutting jaws due to the resilient action of a spring means with some degree of play in each case, which play is so designed that conductor tolerances, when clamping a conductor or when cutting the insulation end, can be equalized in a resilient manner. 
     According to manufacturer&#39;s data, conductors with the same nominal cross-section also differ somewhat from each other individually because, for instance, a single-wire, fine-wire, or multi-wire conductor may display a somewhat varying diameter. Therefore, the additional resilient arrangement also of the upper clamping jaw and the upper stripping knife or two stripping knives will have an advantageous effect in terms of “tolerance equalization.” 
     It is possible to combine the advantages of a clamping jaw arrangement and a stripping knife arrangement with each other because, on the one hand, it is advantageous to cut the conductor only with one stripping knife pair in order to avoid an unsightly double cut and, on the other hand, it is advantageous to hold the conductor in a defined fashion with one clamping jaw pair. However, according to the state of the art, the absence of tolerance equalization for conductors that allegedly have the same cross-section turned out to be a problem. These problems are solved by the present invention in a simple and effective way. The pliers are distinguished by comfortable handling capability. 
     The present invention makes it possible also to provide a dual knife arrangement with two movable and two fixed stripping knives each or—in a particularly preferred manner—one clamping jaw arrangement with two clamping jaws and one knife arrangement with two stripping knives. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide a pliers-type insulation stripping tool including a pair of pivot levers that are connected with a base, a pair of clamping jaws mounted for relative displacement longitudinally of one pivot lever, a pair of cutting jaws being mounted for relative displacement longitudinally of the other pivot lever, spring means normally biasing said clamping jaws apart and said cutting jaws apart, and first operating means operable by pivotally connected handle means for clamping the insulated conductor and for severing the insulation layer. The resilient mounting of the clamping jaws and the cutting jaws provides a certain degree of tolerance, thereby to compensate for dimensional variations in the components of the insulated conductor. 
     According to another object of the invention, second operating means are provided that are operable by the handles to separate the pivot levers and thereby strip the severed length of insulation from the bare conductor. 
     A further object of the invention is to provide an insulation stripping tool wherein the cutting jaws consist of a plurality of spring-biased sections that are relatively laterally displaceable to a limited extent, thereby to provide a degree of tolerance to compensate for variations in the dimensions of the conductor components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawings, in which: 
         FIGS. 1–3  are side elevation views illustrating the insulation stripping tool of the present invention in the initial conductor receiving condition, the conductor clamping and cutting position, and the final insulation stripping position, respectively, and 
         FIGS. 4–6  are corresponding views with certain parts removed; 
         FIGS. 7 and 8  are detailed perspective views of the of the clamping and cutting means when in the initial conductor receiving condition and the clamping and cutting position, respectively; 
         FIG. 9  is a detailed side elevation view of the tool when in the clamping and cutting condition of  FIG. 8 ; 
         FIG. 10  is a detailed perspective view of the tool when in the final stripping condition of  FIGS. 3 and 6 ; 
         FIGS. 11 and 12  are exploded views of the handle and pivot lever components of the insulation stripping tool, respectively; 
         FIGS. 13–15  are detailed front, side and rear perspective views, respectively, of the clamping jaw, cutting jaw and support assemblies; 
         FIGS. 16 and 17  are front and rear exploded perspective views of a second embodiment of the cutting jaw and support assembly; 
         FIGS. 18 and 19  are side elevation views of another embodiment of the insulation stripping tool when in the clamping and stripping positions, respectively; 
         FIGS. 20   a  and  20   b  are detailed perspective front and rear views, respectively, of the clamping and cutting jaw assemblies when in the initial conductor introducing condition; 
         FIGS. 21   a – 21   d  are detailed side elevation and perspective views illustrating the clamping and cutting jaw assemblies when in the stripping condition; and 
         FIGS. 22   a  and  22   b  are front and rear exploded perspective views of another embodiment of the clamping and cutting jaw assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first more particularly to  FIGS. 1–6 , the insulation stripping tool  1  of the present invention includes a pair of pivotally connected handles  2  and  3 , and a pair of pivotally connected pivot levers  19  and  20 . As shown in  FIG. 11 , the handle  2  includes an integral base portion  4  that carries the pivot pins  7   a  and  7   b  that define the pivot axes P 1  and P 2  of the pivot levers  19  and  20 , respectively, as best shown in  FIG. 6 . The handle  2  includes a pair of parallel spaced sheet metal plates  5  and  6  that are separated by spacer pins  7  and cylindrical sleeves  8  to define a gap. A handle cover  11  formed of soft synthetic plastic material is mounted upon the handle portions  9  of the handle plates. Similarly, the pivot lever  19  ( FIG. 12 ) includes a pair of parallel spaced metal lever plates  21  and  23  that contain at one end a first pair of aligned openings that define the first pivot axis P 1 , and a second pair of aligned openings that define a third pivot axis P 3  ( FIG. 6 ) about which the handle  3  is pivotally connected with the lever  19 . 
     Referring now more particularly to  FIGS. 7–10 , in accordance with the present invention, there are mounted on the pivot lever  19  a fixed upper clamping jaw  26  and a relatively moveable lower clamping jaw  37 . Mounted on the other pivot lever  20  are a fixed upper cutting jaw  28  and a relatively moveable lower cutting jaw  38 . The upper jaws are supported by retainers  25  and  27  that are fixed by pin or screw means to the upper ends of the pivot levers  19  and  20 , respectively. The lower clamping jaw  37  is supported by retainer  31  that is guided for movement by guide pins  33  and  34  that extend into the opposed longitudinal guide slots  29  contained in the lever plates  21  and  23  of  FIG. 12 . The lower cutting jaw  38  is supported by a retainer  32  that is similarly guided by guide pins  35  and  36  in longitudinal guide slots  30  ( FIG. 7 ) contained in the spaced plates of the pivot lever  20 . Helical springs  39  and  40  mounted in the gaps between the spaced plates of the pivot levers  19  and  20  bias the lower retainers  31  and  32  downwardly toward their separated conductor receiving positions of  FIGS. 1 ,  4  and  7 . The springs are supported by L-shaped supports  41  ( FIG. 12) and 42  that support spring retainers  66  and  67 , respectively. Eccentric pin means  43  and  44  ( FIG. 4 ) are provided that cooperate with the lower ends of the L-shaped spring supports  41 , thereby to provide means for adjusting the tensions of the helical springs  39  and  40 , respectively. As will be described in greater detail below, the pivot levers  19  and  20  are biased by compression spring means  49  and  50  ( FIG. 5 ) toward the closed condition of  FIGS. 4 ,  5 , and  7 – 9 . 
     In accordance with an important feature of the invention, first operating means are provided that are operable by the handles  2  and  3  to displace the moveable clamping and cutting jaws  37  and  38  upwardly against the biasing force of springs  39  and  40 , respectively, toward their clamping and cutting positions of  FIGS. 2 ,  5 ,  8 , and  9 . These first operating means include a pair of cooperating cam plates  45  and  46  that are connected with the lower retainers  32  and  31 , respectively, for operation by the handle  3  via an integral portion  14  that projects outwardly from the handle upper end. Thus, as best shown in  FIGS. 4–10 , when the handle  3  is pivoted about pivot axis P 3  toward the intermediate position of  FIGS. 2 ,  5 ,  8 , and  9 , the projecting portion  14  on handle  3  engages the lower surface of the cam portion  47  of cam plate  45 , and the upper surface of the cam portion  47  engages the corresponding lower cam surface  48  on the cam plate  46 , as shown in  FIG. 10 , whereupon the moveable clamping and cutting jaws  37  and  38  are displaced upwardly toward their closed clamping and cutting positions against the restoring force of the biasing springs  39  and  40 , respectively. During this pivotal separation of the pivot levers  19  and  20 , the clamping jaws grip and firmly clamp the conductor  16 , and the cutting edges on the cutting jaws sever the insulation in a circular pattern extending concentrically about the conductor. 
     According to another important feature of the invention, second operating means are provided for pivoting the pivot levers  19  and  20  apart from their closed positions of  FIGS. 2 ,  5 ,  8 , and  9  toward their separated stripping positions of  FIGS. 3 ,  6  and  10  when the handles are pivoted from their intermediate positions of  FIGS. 2 and 5  toward their fully closed positions of  FIGS. 3 and 6 . These second operating means include a further cam member  51  ( FIG. 12 ) fastened in the gap between the lever plates  21  and  23  of pivot lever  19  for cooperation with a corresponding cam lug  53  fastened to the pivot lever  20 . During this pivotal movement of the pivot levers toward the fully closed condition, the insulated conductor  16  remains clamped between the clamping jaws  26  and  37 , and the severed insulation length  17  ( FIG. 10 ) is stripped from the bare conductor  18 , as shown in  FIG. 10 . Upon release of the gripping pressure on the handles  2  and  3 , the springs  39  and  40  bias the moveable lower retainers  31  and  32  downwardly together with the plates plates  45  and  46 , thereby to effect engagement of the cam portion  47  of plate  45  with the cam surface  15  on the lever projecting portion  14  ( FIG. 10 ), whereby pivot lever  3  is pivoted outwardly toward its initial open position of  FIGS. 1 and 4 . 
     In accordance with another feature of the invention, conductor cutting means  54  ( FIG. 1 ) are provided for transversely completely cutting the insulated conductor. These cutting means include a slot  59  contained in handle  2  for receiving an insulated conductor arranged transversely of the tool, and a knife member  55  pivotally connected intermediate its ends with the base  4  for pivotal movement about the first pivot axis P 1 . At one end, the knife contains an arcuate slot  56  that receives an operating pin  57  mounted on the handle  3 . Thus, as shown in  FIGS. 1–3 , as the handle  3  is pivoted toward the closed position relative to the handle  2 , the free end  58  of the knife is displaced upwardly, thereby to completely cut an insulated conductor that has been inserted within the slot  59 . These cutting means may be provided with a protective cap  60  formed of a synthetic plastic material, which cup is fastened to the handle  2  as shown in  FIG. 11 . 
     Referring again to  FIG. 12 , in order to permit a limited degree of play between the upper jaws and their respective pivot levers, the attachment holes  68  contained in the pivot levers are oversized relative to the fastening pins  69  for the upper retainers  25  and  27 , respectively. 
     Operation 
     In operation, a conductor  16  is placed between the separated clamping jaws  26 ,  37  and the separated cutting jaws  28 ,  38  ( FIGS. 1 and 4 ), and then the two handles  2 ,  3  are compressed together. In the process, handle portion  14  engages cam portion  47  and cam surface  48  of the cam plates  45 ,  46  (that can also be molded directly upon retainers  31 ,  32 ) in the longitudinal slots  29 ,  30  away from handles  2 ,  3  and upward, while the screw springs  39 ,  40  are compressed. Furthermore, conductor  16  is clamped by clamping jaws  26 ,  37  and the insulation of the conductor  16  is cut ( FIG. 9 ). Upon continued operation of handle  2 , pivot levers  19 ,  20  move away from each other because the fixed cam member  51  of one pivot lever  19  cooperates with an additional radial cam surface  52 , specifically, in this case, an additional cam lug  53  on the second pivot lever  20 , whereby cam member  51  and this radial cam are so designed that upon further compression of the handles  2  and  3 , the pivot levers  19 ,  20  will move away from each other or will be opened. During this opening process, the severed insulation  17  is stripped off conductor  16  ( FIG. 10 ). 
     The opening movement of clamping jaws  26 ,  37  and of cutting jaws  28 ,  38  takes place on the basis of the geometry of the radial-cam surface  15  of one cam plate  45  prior to the opening of the handles  2 ,  3 . In the process, the screw springs  39 ,  40  operate upon the lower clamping jaw  37  and the lower cutting jaw  38  and bias the same back toward their starting positions. Compression springs  49 ,  50  also cause the return opening movement of handles  2 ,  3 . 
     Because the upper cutting jaw  28  and especially also the upper clamping jaw  26  are resiliently supported with some play upon pivot levers  19 ,  20 , one can in a simple manner provide tolerance compensation for the individual conductor geometry in spite of slightly inaccurate insertion of a conductor into the clamping jaw arrangement. 
     Here, first of all, both clamping jaws  26 ,  37  and the cutting jaws  28 ,  38  contain a plurality of recesses  61   a ,  61   b , . . . as well as  62   a ,  62   b , . . . of different size or with different diameter. In this way, one can accommodate various conductors in accordance with their diametric size. 
     According to manufacturer&#39;s information, conductors  16  with the same cross-section will differ from each other individually to some extent, because, for example, single-wire or multi-wire conductors have a somewhat different diameters where the additional “resilient” arrangement also of the upper clamping jaw  26  and the upper cutting jaw  38  will have a tolerance-compensating effect. 
     Theoretically, it is also conceivable that one might insert two cutting jaw pairs into the retainers. The design with one clamping jaw pair and one cutting jaw pair, however, is definitely preferred. 
     As shown in  FIG. 16 , at least one of the cutting jaws  28 ,  38  can also in a particularly advantageous manner have a multipart sectional structure including a pair of metal plates  64 ,  65  of which one has the actual cutting edges  63 , while the other plate has corresponding recesses  62   a ′,  62   b ′ matching the recesses  62   a ,  62   b , . . . of section  64 , or of the actual cutting jaw that guides and positions the conductor  16 . Preferably, the recesses  61   a ,  61   b , . . . of at least one of the clamping jaws and/or recesses  62   a ,  62   b  of the stripping knife have a semicircular configuration or in a particularly advantageous manner (or according to a segment by segment modification), can also have a greatly tapering geometry (for example, an acute-angle shape, as shown in  FIGS. 13–16 ) in order thus advantageously to influence the procedure of centering the conductor and to create the spaces for conductor insulation (below the projections). 
     The handles of the pliers-type tool are not completely symmetrical, of course, especially with regard to handles  2 ,  3 , but they are also distinguished by a pleasant operating sensation that can be compared to a symmetrical pair of pliers. 
     Referring now to  FIGS. 18 and 19 , another embodiment of the stripping pliers is disclosed having certain structural differences relative to the embodiment of  FIGS. 1–17 , especially with regard to the design of the cutting knives. According to  FIGS. 18 to 22 , both the upper and the lower cutting jaws  28 ,  38  of the second pivot lever  20  comprise two cutting jaw sections  70 ,  71 , one of which has the actual cutting edge  72  with several recesses  73  placed next to each other for several conductors having the same diameter or for conductors having different diameters (depending on the design), and in each case other corresponding recesses  74  that guide and position the conductor. Recesses  73  on the cutting edge preferably are designed essentially in a semicircular manner at least on their bottom so that, in particular, a thin conductor will be guided, fixed and cut in an optimum fashion. 
     The essential point here is that cutting jaw section  71  works as a guide plate that rests contiguously against cutting edge  72  of the actual cutting jaw or of the cutting jaw section plate  70  with cutting edge  72 . As a result, the conductor cannot slip away evasively during cutting and is positioned in an optimum fashion and is cut precisely.  FIG. 18  additionally shows the provision of a conductor stop  75  on the second clamping jaw that is adjustably arranged on a measuring scale  76  so that the length of the insulation layer  78  that is to be removed from conductor  77  can be variably adjusted in a simple manner. The upper and lower clamping jaws  80 ,  81  in the first hand lever do not have any contour that would be adapted to the conductors in a form-locking manner, but instead, they have flat recesses or steps  82  that essentially have a rectangular cross-section and that in each case are somewhat wider than the diameter of conductor  77  that is to be stripped of its insulation so that the latter, prior to firm clamping, are somewhat movable in the area of the clamping jaws and automatically will take up or find the particular optimum clamping position. 
     While in accordance with the provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes may be made without deviating from the inventive concepts set forth above.