Abstract:
The invention relates to a tool for connecting cable cores, in particular of insulated telecommunication and data cables, to an insulation-piercing contact element, with a ram, which is formed with a ram head, by means of which the cable cores can be pressed into the insulation-piercing contact, the ram head being shaped in such a way that at least two cable cores can be pressed in simultaneously into at least two insulation-piercing contact elements lying next to each other.

Description:
TECHNICAL FIELD 
   The invention relates to a tool for connecting cable cores, in particular of insulated telecommunication and data cables, to an insulation-piercing contact element. 
   BACKGROUND 
   EP 0040307 B1 discloses a tool for connecting insulated electrical conductor wires. This tool comprises a hollow two-shell grip, in which a striking mechanism with a spring-loaded hollow slider and a ram which can be longitudinally displaced against spring force are arranged. Arranged on the part of the ram protruding out of the front end of the grip, on the head of the ram, is a wire cutter comprising two scissor legs, one of the scissor legs being pivotably movable and having at the rear end, located in the interior of the grip, an inclined longitudinal slot, in which a pin fastened in the grip is guided. A longitudinal displacement of the ram consequently leads to a pivoting movement of the movable scissor leg. For connecting an insulated cable core into an insulation-piercing contact arranged in a terminal strip, the ram head is first placed on the terminal strip. Then the grip is manually pressed in the direction of the terminal strip, until the cable core is pressed into the contact slot of the insulation-piercing contact. The advancing force exerted on the grip brings about a relative movement between the ram and the grip and also between the scissor leg of the wire cutter and the pin fastened to the grip, which then slides into the inclined longitudinal slot and thereby pivots the movable scissor leg in such a way that the cutting edge formed on its front end cuts off the cable core. 
   EP 0329917 B1 also discloses a tool for connecting cable cores to insulation-piercing contacts, with a ram which is longitudinally displaceable in the tool housing and with a cutter for the cable cores, which is arranged on the ram head, the longitudinal displacement of the ram serving for triggering the cutter. Also arranged on the ram is a latching lock, which blocks the longitudinal displacement of the ram with respect to the housing, and arranged on the ram head is a sensor, which is connected to the latching lock and only releases the longitudinal displacement of the ram in the tool housing, and consequently the cutting-off operation, when there is actuation by the insulation-piercing contact or a component surrounding it. 
   A disadvantage of the tools known from the prior art is that satisfactory handling of the respective tool by the installation engineer is either not possible or else significantly restricted in the case of confined space conditions during the installation operation. In particular when organizing generally bifilar telecommunication and data lines on an already occupied terminal strip, difficulties frequently occur if—as is generally usual—the already occupied insulation-piercing contact elements of a terminal strip are provided with safety connectors, in order to ensure overvoltage protection, for example against lightning strikes. As a result, the space conditions at an insulation-piercing contact element to be newly occupied are restricted by the spatial extent of the surrounding safety connectors alone, which has the effect on the one hand that the line to be organized can no longer be positioned correctly at the contact slot of the insulation-piercing contact element before the actual connecting and pressing-in operation and on the other hand that the connecting tool required for the installation can no longer be brought close enough to the insulation-piercing contact element that is to be newly occupied to press the line in and cut it off. The only solution remaining for the installation engineer is often to pull off all those surrounding safety connectors that are hindering the installation operation, to make it possible in the first place for the line that is to be organized to be connected. However, on the one hand this means additional work for the installation engineer and on the other hand also does not correspond to the desirable procedure from safety aspects. Moreover, re-fitting of the safety connectors may be forgotten. Optimizing a tool for connecting cable cores to an insulation-piercing contact element when there are reduced space conditions on the terminal strip consequently represents a problem which has so far not been solved satisfactorily by the customary methods and devices that are known from the prior art. 
   SUMMARY 
   The invention is therefore based on the technical problem of providing an improved tool for connecting cable cores to an insulation-piercing contact element. 
   The invention is based here on the recognition that on the one hand simultaneous connection of two cable cores of a bifilar line to two insulation-piercing contact elements lying next to each other in a single working step offers the possibility of better utilizing the installation space that is available, and consequently being able to dispense with pulling out the surrounding safety connectors, if a specially configured tool is used. On the other hand, temporary fixing of the cable cores to be connected to the ram head of the tool before the actual connecting and pressing-in operation facilitates the reliable pre-positioning of the cable cores. This is achieved according to the invention by proposing a connecting tool in which the ram head is shaped in such a way that at least two cable cores can be connected and pressed in at least two insulation-piercing contact elements lying next to each other. This also allows quick, positionally accurate and reliable connecting of cable cores even when there are very confined space conditions on the terminal strip, which are caused for example by safety connectors attached to the surrounding insulation-piercing contact elements, without having to pull further safety connectors out of the terminal strip for installation purposes apart from the safety connector provided for the double core that is to be installed. 
   In a preferred embodiment, the ram protrudes through an opening in an end face of a tool housing, in which the ram is arranged in a longitudinally displaceable manner. Arranged on the ram head is a cutter for the cable cores, the longitudinal displacement of the ram serving for triggering the cutting-off operation. As a result, connecting, pressing-in and cutting-off take place in one operation, the defined cutting-off of the cable cores allowing the transmission properties at the contacts to be reproduced in terms of quality. 
   In an advantageous embodiment, the part of the ram protruding from the tool comprises a ram head and a ram shank. In this case, the ram head primarily serves for attaching the subcomponents of the tool that are required for the connecting, pressing-in and cutting-off of the cable cores and are in direct engagement with the insulation-piercing contact element during the installation operation. The function of the ram shank, on the other hand, is mainly based on the idea of producing an operative connection between the mechanical subcomponents accommodated in the tool housing and the subcomponents attached to the ram head and also of increasing the range of the tool by its length. The ram head preferably differs here from the ram shank by a greater extent in the circumferential direction. In the case of those embodiments in which the cutter is formed by two scissor blades which are movable with respect to each other and are pivotally mounted with respect to each other about a common axis, the ram is divided into the ram head and the ram shank precisely by that vertical plane which runs perpendicularly in relation to the longitudinal direction of the tool and includes the pivot axis of the cutter. 
   In a further advantageous embodiment, the cutter arranged on the ram head comprises two scissor blades which are movable with respect to each other, one of the two scissor blades having at least one shearing surface and the other scissor blade having at least two shearing surfaces. In this case, the at least two shearing surfaces located on one scissor blade are provided for the purpose of respectively shearing off simultaneously and separately from one another one of the cable cores that are to be connected to an insulation-piercing contact element and cut off. 
   In a further advantageous embodiment, at least one of the shearing surfaces is part of a u-shaped indentation of one of the scissor blades. This u-shaped indentation serves the purpose of enclosing the cable cores that are to be cut and avoiding slipping away or escaping of the cable core during the cutting-off operation. 
   In a further preferred embodiment, at least one of the shearing surfaces has a beveled cutting-edge geometry. Such a shearing surface, configured for example in the form of a beveled edge (chamfer), offers the advantage of an optimum shearing action in combination with the opposite shearing blade during the cutting-off of the cable core. 
   In a further embodiment, the scissor blades are arranged lying flat on the ram, one over the other, an inner scissor blade being arranged between the ram and an outer scissor blade and the outer scissor blade not being in contact, by at least one of its outer surfaces, either with the ram head and/or ram shank or with the other scissor blade. An embodiment of this type, in which the cutter is attached to a certain extent such that it lies freely on the ram and the outer scissor blade is not restricted by the geometry of the ram, makes particularly simple assembly of the tool possible and similarly, if need be, uncomplicated exchange of one of the scissor blades. 
   In a further embodiment, the outer scissor blade has a u-shaped indentation and two shearing surfaces with beveled cutting-edge geometry, the one shearing surface being part of the u-shaped indentation and the other shearing surface being formed by part of the narrow outer surface of the scissor blade running in the longitudinal direction. In this case, the u-shaped indentation serves the purpose of enclosing one of the cable cores that is to be cut and avoiding slipping away or escaping of the cable core during the cutting-off operation, while the beveled cutting-edge geometry, for example in the form of a beveled edge (chamfer), ensures an optimum shearing action in combination with the opposite shearing blade during the cutting-off of the cable cores. 
   In a further advantageous embodiment, the inner scissor blade has two u-shaped indentations and two shearing surfaces, the two shearing surfaces respectively being part of one of the two u-shaped indentations. In this case, the distances between the u-shaped indentations preferably correspond to the spacing pitch of the insulation-piercing contact elements in the terminal strip to which the cable cores are to be connected. The u-shaped indentations, and in particular the two shearing surfaces, in this case respectively form a complementary cutting edge with respect to the shearing surface of the outer scissor blade and in this way permit secure enclosing of the cable cores that are to be cut and an optimum shearing action. In this case, the cutting-edge regions of the inner scissor blade preferably correspond to the opposite cutting-edge regions of the outer scissor blade and preferably cover one another completely, or at least partly, in the course of their shearing movement with respect to each other. 
   In a further preferred embodiment, the outer scissor blade is movable and pivotable with respect to the inner scissor blade. In this case, the inner scissor blade is fixed, while the outer scissor blade can perform a pivoting movement with respect to the inner scissor blade, it preferably being possible for the pivoting movement to be triggered by means of an inclined groove with the aid of a spring-loaded slider in the tool housing. This embodiment allows a particularly simple, low-cost, stable and low-maintenance construction of the connecting tool. 
   In a further preferred embodiment, the scissor blades are mounted pivotably with respect to each other about a common axis. On account of the lever action produced during the shearing operation, depending on the arrangement of the pivot point, this allows a particularly favorable ratio of forces between the manual force applied by the installation engineer and the shearing forces acting, which can in this way be made to suit exactly the thickness of the wire to be cut off with the tool. 
   In a further preferred embodiment, the common axis is formed by a connecting element which connects the two scissor blades pivotably to each other and to the ram. As a result, a particularly simple and stable construction of the tool is ensured. 
   In a further preferred embodiment, the connecting element is formed as a screw. This allows a particularly simple and stable construction of the tool and, if need be, uncomplicated exchange of the scissor blades. In principle, apart from this preferred configuration, however, other fastening means are also conceivable as the connecting element, such as rivets for example. 
   In a further preferred embodiment, the ram shank is at least just as long as the ram head. A ram shank which is of the same length as the ram head or longer in this case serves the purpose of increasing the range of the tool. In particular when bifilar lines are being connected simultaneously to two insulation-piercing contact elements lying next to each other of a terminal strip, there are particularly confined space conditions on the terminal strip if the neighboring insulation-piercing contact elements are all fitted with safety connectors. In this case, an extension of the ram shank can be deliberately used to increase the distance between the safety connector and the tool housing in particular, which otherwise often proves to be a problem during the installation operation. This has the consequence that, even if the intermediate space between two surrounding safety connectors is just narrow enough to allow the ram of the tool to pass through, satisfactory connecting and pressing-in of the cable cores in the terminal strip is nevertheless possible with the aid of the connecting tool and there is no collision between the tool housing and safety connectors during the installation operation. 
   In a further preferred embodiment, a latching lock which blocks the longitudinal displacement of the ram with respect to the tool housing is arranged on the ram, and a sensor which is connected to the latching lock and releases the latching lock when there is actuation by a terminal strip which comprises the insulation-piercing contact elements is arranged on the ram head. In this case, the sensor which is arranged on the ram head and is connected to the latching lock only releases the longitudinal displacement when the cable core that is to be connected has fully reached the end position in the contact slot of the insulation-piercing contact element and a satisfactory connection has been established. This ensures that the end of the cable core is only cut off after contacting has taken place. It is in this case also conceivable that the latching lock can be manually unlocked independently of the sensor by means of an unlocking device, for example for the case in which two cable cores are to be connected into the same contact slot of an insulation-piercing contact element. 
   In a further preferred embodiment, the sensor acts via a sensor rod on a spring-loaded pawl of the latching lock. This corresponds to a particularly simple, stable and maintenance-free type of construction of the tool. In this case, when a reference point, which may be formed for example by part of the terminal strip, is reached, a mechanically acting sensor exerts a force via a sensor rod on the spring-loaded pawl of the latching lock, in this way signals the correct pressing-in depth of the cable cores into the contact slot of the insulation-piercing contact element and only then releases the cutting movement for cutting off the ends of the cable cores. 
   In a further preferred embodiment, the sensor rod runs at least partly in the ram head in a vertical plane running centrally through the tool and at least partly in the ram shank in a plane parallel to the vertical plane running centrally through the tool. This arrangement is of advantage in particular in the case of embodiments with scissor blades which are mounted pivotably about an axis with respect to each other, if the sensor is attached centrally in the ram head and the force is then likewise passed on substantially centrally in the longitudinal direction from the sensor via the sensor rod in the ram head. In order to avoid space problems within the ram in the case of this configuration, the sensor rod is then preferably angled away a number of times and is continued within the ram shank slightly offset laterally with respect to the vertical central plane of the tool, so that no conflict occurs with the arrangement of the pivot axis of the scissor blades, or the corresponding connecting element. 
   In a further preferred embodiment, at least two pressing-in plates are arranged parallel to each other in the ram head. These plates may be produced for example from metal and offer the advantage of particularly high stability, so that satisfactory functioning of the tool is always ensured even when there are great pressing-in forces and the tool is used frequently. Although the pressing-in plates are preferably configured as components which are separately attached in the ram head, it is also conceivable that the pressing-in plates can be formed from a single part together with the ram head. 
   In a further preferred embodiment, the end face of the ram head is provided with a longitudinally slit clamping element for receiving at least two cable cores. This allows the cable cores to be temporarily fixed to the ram head before the actual connecting and pressing-in operation, whereby particularly safe handling and more accurate pre-positioning of the cable cores at the contact slot of the insulation-piercing contact element is made possible, in particular when there are confined space conditions on the terminal strip. In this case, the means for fixing the cable cores in the clamping element are preferably configured as parallel slots, which are made slightly wider than the diameter of the cable cores to be connected. In order to ensure the fixing of the cable cores, detents are in this case preferably attached to the slot openings, which are open toward the end face of the clamping element and allow the cable cores to latch in the clamping element before the actual connecting and pressing-in operation at the contact slot of the insulation-piercing contact element. The opening left free by the detents on the end face of the clamping element is in this case just large enough that, after connecting, pressing-in and cutting-off of the cable cores has taken place in the terminal strip, the clamping forces of the insulation-piercing contact element acting on the respective cable core are greater than the clamping forces of the longitudinally slit clamping element on the ram head. This has the effect that, when the tool is withdrawn, the cable cores can be released again from the longitudinally slit clamping element and remain in the insulation-piercing contact element. The longitudinally slit clamping element preferably has a certain resilience in this case, in particular at its lateral longitudinal webs, and is made for example from plastic. The central piece of the clamping element located between the longitudinal slots is preferably configured as an extended central web, which protrudes in the longitudinal direction slightly beyond the openings of the longitudinal slots and is beveled slightly on both sides. This allows facilitated guidance of the tool and also reliable positioning of the ram head in the terminal strip in the optimum position for the connecting and pressing-in operation. 
   In a further preferred embodiment, the clamping element is formed as a separate element and is connected to the ram head. This allows particularly simple production of the tool. Furthermore, in this way it is also possible, depending on the thickness of the wire of the cable cores that are to be connected, for different clamping elements to be used on one tool. In this case, the clamping element is preferably configured as a screwed-on plate made of plastic, which is inserted in a recess of the ram head and finishes flush with the underside of the ram head. However, alternative embodiments in which the clamping element is formed from a single part together with the ram head are also conceivable. 
   In a further preferred embodiment, a swinging-out pulling hook and/or a piercing tool are attached in the tool housing. These can be swung out of their position of rest in the tool housing laterally from corresponding side slots in the tool housing into their operating position. With the pulling hook, already connected cable cores can be pulled out again from the contact slot of the insulation-piercing contact element. With the piercing tool it is possible for example to release latching connections between the terminal strip and its holder, for example by engaging behind formed-on lugs. 
   In an alternative embodiment there is proposed a connecting tool which, in a way similar to the tool previously known from EP 0329917 B1, has a ram which is longitudinally displaceable in the tool housing and protrudes through an opening in the end face of the tool housing, and which also has a cutter arranged on the ram head for cutting off cable cores, the longitudinal displacement of the ram serving for triggering the cutting-off operation. As a difference from the device known from EP 0329917 B1, however, in the case of the proposed connecting tool the ram head is shaped in such a way that the end face of the ram head is provided with a longitudinally slit clamping element for receiving at least one cable core. This allows the cable core to be temporarily fixed to the ram head before the actual connecting and pressing-in operation, whereby particularly safe handling and more accurate pre-positioning of the cable core at the contact slot of the insulation-piercing contact element is made possible. This allows quick, positionally accurate and reliable connecting of cable cores. In this case, the means for fixing the cable core in the clamping element is preferably configured as a slot, which is made slightly wider than the diameter of the cable core to be connected. In order to ensure the fixing of the cable cores, a detent is in this case preferably attached to the slot opening, which is open toward the end face of the clamping element and allows the cable core to latch in the clamping element before the actual connecting and pressing-in operation at the contact slot of the insulation-piercing contact element. The opening left free by the detent on the end face of the clamping element is in this case just large enough that, after connecting, pressing-in and cutting-off of the cable core has taken place in the terminal strip, the clamping forces of the insulation-piercing contact element acting on the cable core are greater than the clamping forces of the longitudinally slit clamping element on the ram head. This has the effect that, when the tool is withdrawn, the cable core can be released again from the longitudinally slit clamping element and remains in the insulation-piercing contact element. The longitudinally slit clamping element preferably has a certain resilience in this case, in particular at its lateral longitudinal webs, and is made for example from plastic. The clamping element is preferably formed as a separate element and is connected to the ram head. This allows particularly simple production of the tool. Furthermore, in this way it is also possible, depending on the thickness of the wire of the cable core that is to be connected, for different clamping elements to be used on one tool. In this case, the clamping element is preferably configured as a screwed-on plate made of plastic, which is inserted in a recess of the ram head and finishes flush with the underside of the ram head. However, alternative embodiments in which the clamping element is formed from a single part together with the ram head are also conceivable. Otherwise, this alternative embodiment is based on the tool described more precisely in EP 0329917 B1, so that reference is made to the comments made there in their entirety. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below on the basis of a preferred exemplary embodiment. In the associated drawings: 
       FIG. 1  shows an oblique view of the tool in a three-dimensional representation, 
       FIG. 2  shows an oblique view of the front part of the tool in a three-dimensional representation, 
       FIG. 3  shows an oblique view of the opened tool in a three-dimensional representation without the cutter and the upper half-shell of the tool housing, 
       FIG. 4  shows a schematic representation of the clamping element attached to the ram head, in a view from below, and 
       FIG. 5  shows a perspective representation of the tool when connecting two cores. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a tool  1 , which comprises a tool housing  12  which is formed by two plastic half-shells  14 ,  15  and forms a grip  16 . The two housing half-shells  14 ,  15  are connected against each other by means of screws  17 . Arranged in the grip  16 , which is provided with an opening  33  at one end face  32 , is a longitudinally displaceable ram  2 , which is provided with a striking mechanism and protrudes through the opening  33  in the end face  32  of the tool housing  12 . The part of the ram  2  protruding from the tool  1  comprises a ram head  5 , located at the front end of the ram  2 , and a ram shank  7 , located between the ram head  5  and the opening  33  of the tool housing. Arranged on the ram head is a cutter  29  for cutting off cable cores, the longitudinal displacement of the ram  2  serving for triggering the cutting-off operation. The cutter  29  in this case comprises two scissor blades  4 ,  8 , which are movable with respect to each other and are arranged lying flat on the ram head  5 , one over the other, an inner scissor blade  8  being arranged between the ram  2  and an outer scissor blade  4 . In this case, the inner scissor blade  8  is fixed, while the outer scissor blade  4  can perform a pivoting movement with respect to the inner scissor blade  8 , it being possible for the pivoting movement to be triggered by means of an inclined groove and the pin  42  sliding in the inclined groove with the aid of a spring-loaded slider in the tool housing  12 . The scissor blades  4  and  8  are mounted pivotably with respect to each other about a common axis. The common axis is formed by a screw  20 , which connects the two scissor blades  4 ,  8  pivotably to each other and also to the ram  2 . The outer scissor blade  4  is not in contact, either by its upper outer surface or by its two narrow outer surfaces running in the longitudinal direction of the tool  1 , either with the ram head  5  or with the ram shank  7 . The cutter  29  is therefore attached to a certain extent such that it lies freely on the ram  2  and movement of the outer scissor blade  4  is not restricted by the geometry of the ram  2 . In addition, a rotary knob  21  is provided as a fixing means in the grip  16  and a latching lock  3  is arranged between two side walls  24 ,  25  of the ram  2 . The latching lock  3  comprises a spring-loaded pawl  10 , which is pivotably arranged in the ram  2 . The pawl  10  assumes a defined position under spring loading, in which part of the pawl  10  that is formed in the shape of a hook engages behind the end wall  34  of the housing half-shell  15 . Such a tool with a ram, slider, cutter, rotary knob and latching lock is described more precisely in EP 0329917 B1, to which reference is expressly made. As a difference from the tool known from EP 0329917 B1, however, in the tool  1  the ram head  5  and cutter  29  are shaped in such a way that two cable cores can be introduced simultaneously into two insulation-piercing contact elements lying next to each other and the overhanging ends of the wire can be cut off. 
   In this case, as shown in  FIG. 2 , the outer scissor blade  4  has a u-shaped indentation and two shearing surfaces  18 ,  19  with beveled cutting-edge geometry in the form of a beveled edge (chamfer), the one shearing surface  19  being part of the u-shaped indentation and the other shearing surface  18  being formed by part of the narrow outer surface of the scissor blade  4  running in the longitudinal direction. Furthermore, the inner scissor blade  8  has two u-shaped indentations and two shearing surfaces, the two shearing surfaces respectively being part of one of the two u-shaped indentations. In this case, the distances between the u-shaped indentations correspond to the spacing pitch of the insulation-piercing contact elements in the terminal strip to which the cable cores are to be connected. The u-shaped indentations, and in particular the two shearing surfaces, in this case respectively form a complementary cutting edge with respect to the shearing surfaces  18 ,  19  of the outer scissor blade  4 . In this case, the cutting-edge regions of the inner scissor blade  8  preferably correspond to the opposite cutting-edge regions of the outer scissor blade  4  and cover one another completely in the course of their shearing movement with respect to each other. The ram  2  of the tool  1  is divided into the ram head  5  and the ram shank  7  precisely by that vertical plane which runs perpendicularly in relation to the longitudinal direction of the tool  1  and includes the pivot axis of the cutter  29 , i.e. the screw  20 . In this case, the ram shank  7  is somewhat longer than the ram head  5 , in order to increase the range of the tool  1 . 
   Additionally arranged on the ram  2  is a latching lock  3 , which blocks the longitudinal displacement of the ram  2  with respect to the housing  12 , as shown more clearly in  FIG. 3 . Arranged on the ram head  5  is a sensor  6 , which is connected to the latching lock  3  and releases the latching lock  3  when there is actuation by a terminal strip which comprises the insulation-piercing contact elements. In this case, the sensor  6  which is arranged on the ram head  5  and is connected to the latching lock  3  only releases the longitudinal displacement when the cable core that is to be connected has fully reached the end position in the contact slot of the insulation-piercing contact element and a satisfactory connection has been established. Hooked into the spring-loaded pawl  10  is a sensor rod  9 , which is led through the ram  2  up to the front part of the ram head  5  and is formed there as a sensor  6  by being bent down by 90°. The sensor  6  is in this case mounted between two pressing-in plates  11  which are made of metal, are arranged parallel to each other in the ram head  5  and are configured as components which are separately fitted in the ram head  5 . In order to avoid a collision of the sensor rod  9  within the ram  2  with the screw  20 , the sensor rod  9  is then angled away twice in the region of the screw  20  and then continued within the ram shank  7  slightly offset laterally with respect to the vertical central plane of the tool  1 , so that no conflict occurs with the arrangement of the pivot axis of the scissor blades  4 ,  8 . The sensor rod  9  consequently runs in the ram head  5  in a vertical plane running centrally through the tool  1  and in the ram shank  7  in a plane parallel to the vertical plane running centrally through the tool. When a reference point, which may be formed for example by part of the terminal strip, is reached, the mechanically acting sensor  6  exerts a force via the sensor rod  9  on the spring-loaded pawl  10  of the latching lock  3 , in this way signals the correct pressing-in depth of the cable cores into the contact slot of the insulation-piercing contact element and only then releases the cutting movement for cutting off the ends of the cable cores. The pawl  10  of the latching lock  3  can also be manually unlocked independently of the sensor  6  by means of an unlocking device  13 , for example for the case in which two cable cores are to be connected into the same contact slot of an insulation-piercing contact element. For this purpose, a u-shaped wire clip  44  is fastened by its two leg ends  45  onto the outside of the housing half-shells  14 ,  15  of the grip  16  as a locking device  13 . By manual pivoting of the wire clip  44 , the central part of the wire clip  44  presses against the pawl  10  and consequently pivots the pawl of the latching lock  3  inward, whereby the longitudinal displacement of the ram  2  is released. If, however, the longitudinal displacement is not to be released by the unlocking device  13  or by the sensor  6 , the ram  2  can be fixed by turning the rotary knob  21 . The function of the rotary knob  21  is explained more precisely in EP 0040307 B1. Furthermore, a swinging-out pulling hook and a piercing tool are attached within the tool housing  12  between the housing half-shells  14 ,  15  and can be swung out of their position of rest from corresponding side slots in the grip  16  with the aid of a button  43  which is beveled away on its underside. 
   Furthermore, the end face of the ram head  5  is provided with a longitudinally slit clamping element  22  for receiving two cable cores, as shown more precisely in  FIG. 4  in particular, allowing the cable cores to be temporarily fixed to the ram head  5  before the actual connecting and pressing-in operation. In this case, the means for fixing the cable cores in the clamping element  22  are configured as parallel slots  26 ,  27 , which are made slightly wider than the diameter of the cable cores to be connected. In order to ensure the fixing of the cable cores, detents  30 ,  31  are in this case attached to the slot openings, which are open toward the end face of the clamping element  22  and allow the cable cores to latch in the clamping element  22  before the actual connecting and pressing-in operation. The opening left free by the detents  30 ,  31  on the end face of the clamping element  22  is in this case just large enough that, after connecting, pressing-in and cutting-off of the cable cores has taken place in the terminal strip, the clamping forces of the insulation-piercing contact element acting on the cable core are greater than the clamping forces of the longitudinally slit clamping element  22  on the ram head  5 . This has the effect that, when the tool  1  is withdrawn from the terminal strip, the cable cores that are then successfully connected to the insulation-piercing contact element can be released again from the longitudinally slit clamping element  22  and remain in the insulation-piercing contact element. The longitudinally slit clamping element  22  has a certain resilience in this case, in particular at its lateral longitudinal webs  37 ,  39 , and is made from plastic. The central piece of the clamping element located between the longitudinal slots  26 ,  27  is configured as an extended central web  41 , which protrudes in the longitudinal direction slightly beyond the openings of the longitudinal slots and is beveled slightly on both sides. The clamping element  22  is formed as a separate element in the form of a plastic plate  23  and is connected to the ram head  5  by a screw  28 . The plastic plate  23  is in this case inserted in a recess of the ram head  5  and finishes flush with the underside of the ram head  5 . 
   In  FIG. 5 , the tool  1  is represented as it is when connecting two cores  51 ,  52 , the two neighboring contacts of the terminal strip  60 , to the left and right of the insulation-piercing contacts  53  to be wired, being protected in each case by a safety connector  54 . The two cores  51 ,  52  are in this case inserted in the slots  26 ,  27  of the clamping element  22 , where they are temporarily fixed. The ram head  5  is in this case dimensioned in such a way that it fits between the two safety connectors  54 . The length of the ram  2  is in this case long enough that, when part of the ram shank  7  enters the tool housing  12  during the connecting movement, the remaining part of the ram  2  is longer than the overall height of the safety connectors. As a result, the inserted safety connectors  54  do not hinder the connecting operation. 
   LIST OF DESIGNATIONS 
   Tool for Connecting Cable Cores 
   
       
       
         
             1  tool 
             2  ram 
             3  latching lock 
             4  outer scissor blade 
             5  ram head 
             6  sensor 
             7  ram shank 
             8  inner scissor blade 
             9  sensor rod 
             10  pawl 
             11  pressing-in plate 
             12  tool housing 
             13  unlocking device 
             14 ,  15  housing half-shells 
             16  grip 
             17  screws 
             18 ,  19  shearing surfaces 
             20  screw 
             21  rotary knob 
             22  clamping element 
             23  plastic plate 
             24 ,  25  side walls 
             26 ,  27  slots 
             28  screw 
             29  cutter 
             30 ,  31  detents 
             32  end face 
             33  opening 
             34  end wall 
             37 ,  39  longitudinal webs 
             40  compression spring 
             41  central web 
             42  pin 
             43  button 
             44  wire clip 
             45  leg ends 
             51 ,  52  cores 
             53  insulation-piercing contact 
             54  safety connector 
             60  terminal strip