Abstract:
An adaptable hand operated tool for tensioning safety cable to a predetermined tension limit, crimping a ferrule onto the cable, and cutting the cable. The tool comprises a body for adapting the tool to a hand operated hydraulic tool, a cable tensioner, and an elongated, removable nose. The cable tensioner comprises a wheel for applying tension to a cable wrapped around the wheel, and a clutch for prohibiting a rotational force from being applied to the wheel when a predetermined cable tension is applied. The elongated has an aperture for receiving a ferrule and passing the cable therethrough. A plunger is reciprocally operative in the nosepiece to crimp the ferrule on the safety cable and simultaneously severing a free end of the cable. The plunger is actuated by a piston of a hand operated hydraulic base tool.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an apparatus for attaching safety cables to releasable fasteners and, more particularly, to an adaptable apparatus for tensioning, locking and terminating safety cables. 
   BACKGROUND OF THE INVENTION 
   Various types of machinery are subject to vibration that can loosen nuts and bolts. Safety wire has long been used as protection to resist such loosening. In such use, safety wire secures two or more parts together so that loosening of one part is counteracted by tightening of the wire. Typically, a single wire is passed through an aperture in a nut or bolt, the free ends twisted together up to another part, one of the ends inserted through an aperture in the another part and the ends again twisted. The standards for utilization of safety wire are critical and are set forth in Aerospace Standard AS567, entitled “General Practices for the Use of Lockwire, Key Washers and Cotter Pins,” available from the Society of Automotive Engineers, Inc., 400 Commonwealth Dr., Warrendale, Pa. 
   Safety wire or lockwire, as it is sometimes known, has several known problems. More recently, there has been developed an improved locking system using safety cable. Safety cable is a stranded cable having a termination on one end allowing the cable to be pulled to a predetermined tension through the aforementioned apertures in nuts and bolts. After tensioning, the free end of the cable must be terminated to hold the tension and cleanly severed to minimize any possibility of snags on loose wires. One such tool to perform this operation is commercially available under the trade name “Safe-T-Cable™” from the assignee of the current application, Daniels Manufacturing Corporation, and is described in U.S. Pat. No. 5,345,663. 
   Safety cable is utilized on bolts and fasteners that are often located in cramped or minimally accessible locations. Accordingly, it is also desirable to provide a tool which is modular to provide interchangeable tool lengths and is reduced in size to access cramped locations. Further, in typical applications, the installation of safety wire involves a considerable amount of time and manual operation of a tool, resulting in operator fatigue. Accordingly, it is desirable to provide a tool where the required hand force to operate the tool is reduced. 
   SUMMARY OF THE INVENTION 
   A tool for tensioning safety cable to a mechanically set tension limit and for terminating the cable when the cable has been tensioned to the mechanically set limit is described herein as including a manual actuator for gripping and pulling the cable to the tension limit, and a hydraulically assisted actuator for crimping a ferrule onto the cable when the tension limit has been reached, the hydraulically assisted actuator being operative to sever a free end of the cable concurrently with crimping of the ferrule. The toll may also include a tensioning wheel for retaining cable wrapped around the wheel and allowing tension to be applied to the cable by manual rotation thereof, and a clutch for transferring a rotational force to the wheel, the clutch preventing rotational force from being applied to the wheel when a predetermined cable tension has been reached. The tool may further include a plunger for progressively crimping the ferrule as the hydraulically assisted actuator is operated and a shearing edge, operative in conjunction with a ferrule edge, for severing the free end of the cable as the ferrule edge is forced past the shearing edge by the plunger as the ferrule is being crimped. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which: 
       FIG. 1  is a top planar view of a tool according to the present invention. 
       FIG. 2  is a cross-sectional top view of the tool of  FIG. 1 . 
       FIG. 3  is a cross sectional side view of the tool of  FIG. 1 . 
       FIG. 4  is an enlarged view of the distal end of the nosepiece of the tool of  FIG. 1 . 
       FIG. 5  is a partial exploded view of the tool of  FIG. 1  including the tool body, the cable tensioner assembly, and an exemplary hydraulically operated base tool. 
       FIG. 6  is a partial exploded view of the cable tensioner assembly of  FIG. 5  with some details omitted for clarity. 
       FIG. 7  depicts a cross sectional view of the cable tensioning assembly of  FIG. 5  taken along a rotation axis. 
       FIG. 8  is a partial exploded view of the tool of  FIG. 1  including the tool body and the nose. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a functional hardware diagram of one form of the present invention. Referring to the figures in general, and in particular to  FIGS. 2 and 3 , there is illustrated a top view and a cross-sectional side view of a safety cable tool  10 , respectively. The safety cable tool is capable of being operatively attached to a hydraulically operated base tool  26 , such a hydraulic pump assembly, part number HD38, available from Daniels Manufacturing Corporation, and generally includes a body  28 , a cable tensioner assembly  30 , and a nose  32 .  FIG. 1  includes a safety cable  12  passing through apertures in each of the bolt heads  14  and  16 . A ferrule  18  is clamped at one end of cable  12  to prevent it from being pulled through the bolt apertures. A second ferrule  20  is seated in an aperture  21  in the nosepiece  22  of tool  10  in a position to be crimped onto cable  12  when a predetermined tension has been pulled on cable  12  by a cable tensioner assembly  30 . The free end  24  of cable  12  is coupled to the cable tensioner assembly  30  and to apply tension to the cable  12 . Specifically, the free end of the cable is wrapped around the cable tensioner assembly  30  and wedged so that tension can be tangentially applied by rotating the cable tensioner assembly  30  in the same direction as the cable  12  is wrapped. For example, if the cable  12  is wrapped clockwise around the cable tensioner assembly  30 , the assembly  30  is rotated clockwise to further wrap the cable  12  and apply increased tension. When a predetermined tension (such as a tension between 15and 25 pounds) is applied to the cable  12 , the cable tensioner assembly  30  prevents further tensioning to be applied, while maintaining the predetermined tension on the cable  12 . The wrapping of the cable  12  about the cable tensioner assembly  30  also prevents the cable from loosening while the ferrule  18  is being crimped. 
   The cable tensioner assembly  30  will now be described in further detail with respect to FIGS  2 ,  5 ,  6 , and  7 .  FIG. 2  depicts a cross-sectional top view of the tool of  FIG. 1  and  FIG. 5  is a partial exploded view of the tool of  FIG. 1  including the tool body, the cable tensioner assembly, and an exemplary hydraulically operated base tool. Fig  6  is a partial exploded view of the cable tensioner assembly  30  of  FIG. 5  with some details omitted for clarity, and  FIG. 7  depicts a cross sectional view of the cable tensioning assembly  30  of  FIG. 5  taken along a rotation axis. The cable tensioning assembly  30  further includes a knob  80 , a clutch tensioning force wheel  82  that includes an axle  90 , a clutch ring  84 , and a faceplate  86 . The cable tensioner assembly  30  is rotatably mounted in the tool body  28  generally perpendicular to the elongate axis of the nose  32 , so that the axle  90  of the wheel  82  extends substantially through an opening  70  in the body  28 , allowing access of the axle end  102  at the opposite side of the body. In an embodiment, the axle  90  rides in a ring bearing  106  mounted within the body  28  and sandwiched between two bearing washers  108 . In addition, a circumferential groove is formed in the axle near the end  102  to allow fastening of a retaining ring  104  to rotatably retain the axle  90  in the body  28 . 
   On the body side  110  of the wheel  82 , the surface of the wheel  82  has a flat portion  113  extending radially away from the axle  90 , then the surface assumes a sloping profile extending from the flat portion  113  to a rim  81  of the wheel  82  forming a flared portion  114 . The flat portion  113  is configured to allow attaching a faceplate  86  thereto, with, for example, screws  136 . An attachment portion  88  of the faceplate  86  is a raised cylindrical platform having a height perpendicular to a face  87  of the faceplate  86 . In an aspect of the invention, the height may be slightly smaller than the diameter of the safety cable  12 . When the faceplate  86  is attached to the wheel  82 , the face  87  of the faceplate  86  and the flared portion  114  forms a gripping slot  115  tapering to a relatively smaller width toward the axle  90 . Accordingly, the flared portion  114  acts to wedge a safety cable  12  wrapped circumferentially in the gripping slot  115 , thereby retaining the cable  12  so that tension can be applied by rotating the knob  80 . 
   The axle  90  includes an axle bore  92  open on the axle end  102  and intersecting radial passageways  94  extending from the axle bore  92  radially outward and opening at the rim  81  of the wheel  82 . The axle bore  92  is partially internally threaded on the axle end  102  to accommodate a threaded adjustment screw  100 . Elongated clutch tensioning force pins  116  are slidingly installed in the radial passageways  94  so that an end  121  of the clutch tensioning force pin  116  protrudes from the rim  81  of the wheel  82 , and the other end  117  protrudes into the axle bore  92 . In an aspect of the invention, the end  121  of the clutch tensioning force pin  116  may be hemispherically shaped. A spring actuator  98 , having an angled tip  99 , such as a  45  degree chamfer, is positioned in the bore  92  so that the angled tip  99  contacts the ends  117  of the tensioning force pins  116  extending radially into the bore  92 . In an aspect of the invention, the ends  117  may be angled, such as with a 45 degree chamfer, to complementarily abut the angled tip  99  of spring actuator  98 . A compression spring  96  followed by an adjustment screw  100  (forming an adjustable spring seat) are positioned in the bore  92  to adjustably maintain an axial force on the spring actuator  98  that is transferred, by the angled tip  99  of the spring actuator  98 , to a radial force acting radially outward on ends  117  of the clutch tensioning force pins  116 . 
   The clutch ring  84  fits rotatably around the rim  81  of the wheel  82  and, as more clearly shown in  FIG. 6 , includes indentations  120  laterally formed and uniformly spaced in the inner diameter of the ring  84 . The indentations  120  movably accommodate the ends  121  of the clutch tensioning force pins  116  radially protruding from rim  81  of the wheel  82 . For example, the indentations may have a circular cross section sized to engage a hemispherically shaped end  121  of the clutch tensioning force pin  116 . The ends  121  of the clutch tensioning force pins  116 , forced into the indentations  120  by action of the spring actuator  98  and the compression spring  96 , prevent rotation of the clutch ring  84  around the wheel  82  until a rotational force is applied sufficient to overcome the force of the compression spring  96  communicated through the spring actuator  98  to the clutch tensioning force pins  116  lodged in respective indentations  120 . When sufficient rotational force, or tension, is applied to the clutch ring  84 , the sides of the indentations  120  act to radially displace the protruding clutch tensioning force pins  116  in a direction towards the axle bore  92  and out of the indentations  120 , so that the clutch ring  84  rotates about the wheel  82  as long as sufficient rotational force is applied. The force acting on the clutch tensioning force pins  116  to keep the pins  116  lodged in the indentations  120 , and, correspondingly, the rotational force required to overcome the radial force on the pins  116 , can be adjusted by threading the adjustment screw  100  in or out of the axle bore  92  to alter the compression of the spring  96 , accessed via an axle bore  92  opening at the axle end  102  as shown  FIG. 5 . For example, as the adjustment screw  100  is tightened, increasing pressure is exerted on the spring actuator  98  corresponding to the compression on the spring. The force on the spring actuator  98  is transferred longitudinally to the tensioning force pins  116 . 
   In one form, the spring actuator  98  may have a 45 degree conical tapered end to contact the ends of the tensioning force pins  116  positioned within the axle bore  92 . In another aspect, the ends of the tensioning force pins  116  positioned within the axle bore  92  may have a 45 degree conical taper corresponding to the 45 degree conical taper of the spring actuator  98 . The longitudinal force applied to the respective ends of the tensioning force pins  116  positioned within the axle bore  92  is then transferred to the indentations  120  in the clutch ring  84 , resulting in increased tensioning force required to force the ends of the tensioning force pins  116  from respective indentations  120 . Accordingly, the clutch tensioning force pins  116 , the spring actuator  98 , the compression spring  96 , and adjustment screw  100  comprise, with clutch tensioning force wheel  82 , the tension setting means for controlling tension in cable  12 . 
   The clutch ring  84  also includes lateral grooves  124  formed in the outside diameter for installing knob mounting pins  118 . The clutch ring  84  and wheel  82  fit within a circular recess  122  formed in one side of the knob  80 . The knob  80  includes lateral grooves  125  on the inside diameter of the recess  122  corresponding to the lateral grooves  124  on the clutch ring  84  to tangentially fix the clutch ring  84  within the recess  122  by inserting appropriately sized pins  118  into the grooves  124 , 125  when the clutch ring  84  and wheel  82  are installed. Accordingly, the knob  80  can move coaxially with respect to the elongate axis of the axle  90  as can be seen in  FIG. 5 . The axle stub  132  is circumferentially grooved to accept a retaining ring  134  to rotatably retain the knob  80  on the axle stud  132 . 
   In an aspect of the invention depicted in  FIG. 7 , ball keepers  128  are provided to retain a cable  12  wrapped around the tensioner assembly  30  and forced into the gripping slot  115  as the tensioner assembly  30  is rotated to apply tension to the cable  12 . The ball keepers  128  are positioned circumferentially in bores  130  transversely formed in the wheel  82  so that the ball keepers  128  partially extend from the bores on  130  on the body side of the wheel  82 , and are in movable contact with the face  87  of the faceplate  86 . The ball keepers  128  are urged through the respective bores  130  towards the face  87  by springs  126  held in place by a face of the recess  122  of the knob  80  when the knob  80  is assembled to the wheel  82  on an axle stub  132 . The ball keepers  128  retain the safety cable  12  in the gripping slot  115  as the safety cable  12  is forced into the slot during a tensioning process. The springs  126  allow the ball keepers  128  to move perpendicularly away from the face  87 of the faceplate  86  to allow passage of the cable  12  into the gripping slot  115  as the cable  12  is drawn tighter around the tensioning assembly  30  during tensioning. After the safety cable  12  is cut, a cut off portion of the cable can be unwound from the gripping slot  115  for removal. 
   When sufficient tension is applied to a cable  12  wrapped around the tensioner assembly  30 , the clutch ring  84  and, correspondingly the knob  80 , will slip around the rim  81  of wheel  82  by forcing the ends  121  of the clutch tensioning force pins  116  out of the indentations  120  in the clutch ring  84 . Accordingly, when the proper tension has been applied to the cable  12 , further tensioning of the cable  12  is prevented by allowing the knob  80  and clutch ring  84  to slip tangentially about the clutch tensioning force wheel  82 . 
   The nose  32  of the tool will now be described in further detail with respect to  FIGS. 2 ,  3 , and  8 .  FIG. 2  depicts a cross-sectional top view of the tool of  FIG. 1 , and  FIG. 3  depicts a cross-sectional side view of the tool of  FIG. 1 .  FIG. 8  is a partial exploded view of the tool of  FIG. 1  including the tool body and the nose. The nose  32  of the tool generally includes a nosepiece  22 , an indenter  34 , a push rod  44 , a nose extension  52 , a spring  56 , and an adjustment barrel  60 . The indenter  34 , push rod  44 , and adjustment barrel  60  together form a plunger assembly  33 , while the nosepiece  22 , nose extension  52  and spring  56  together form a nosepiece assembly  62 . It should be noted that when referring to parts comprising the nose assembly  32 , the “distal end” of a part is the end that, when assembled in the tool, points away from the tool. Conversely, the “proximal end” of a part is the end that, when assembled in the tool, points towards the tool. As described earlier, a ferrule  20  fits within aperture  21  in the distal end of nosepiece  22 . When the plunger assembly  33 , is actuated by a piston  27  on the base  26  tool, the distal end of indenter  34  is pushed into the aperture  21 , thereby crimping the ferrule  20  about the cable  12 . The depth of the crimp may be adjusted using the adjustment barrel  60 . The aperture  21  is larger on an entrance side of the nosepiece than it is on the exit side. 
     FIG. 4  is an enlarged view of the nosepiece  22  showing the entrance side having a large open area, while the exit side has a small opening  21 A just suitable for passage of cable  12 . The entrance side opening has an oval configuration extending toward the distal end of nosepiece  22 . Accordingly, as plunger assembly  33  is actuated, it not only crimps ferrule  20  but drives the edge of the ferrule  20  past the exit side opening  21 A. The ferrule edge and exit side opening edge combine to act as a shear to automatically sever the free end portion  24  of the cable  12  extending out of the ferrule  20 . The tool  10  thereby crimps the ferrule  20  and severs the free end  24  of the cable in a single operation. In one aspect of the invention, shearing of the free end of the cable  24  occurs at fixed, predetermined crimp depth that is less than crimp depth required to maintain a minimum required tensile strength of the installed safety cable  12 , but more than a minimum depth of crimp necessary to prevent the cable  12  from pulling out of the ferrule  20  as the cable  12  is sheared during crimping. Accordingly, the distance of the exit hole  21 A in relation to an edge of a ferrule  20  positioned in the aperture  21  is fixed so that an initial crimping depth is applied by the indenter  34  before shearing of the cable  12  between the hole  21 A and the edge of the ferrule  20  is initiated. Once the initial crimping depth is applied so the cable  12  will not pull out of the initially crimped ferrule  20 , shearing occurs as the indenter  34  crimps the ferrule  20  to a final desired depth so that a minimum required tensile strength is maintained. As a result, shearing takes place at the same crimp depth regardless of the final crimp depth that can be adjusted using the adjustment barrel  60 . 
   In one aspect of the invention, the proximal end of the nosepiece  22  has two alignment ears  38  configured to slidably interlock with flat portions  40  of the indenter  34  to align the plunger assembly  33  in a fixed angular orientation with respect to the aperture  21  of the nosepiece  22  for proper crimping of the ferrule  20 . The proximal end of the nosepiece  22  is externally threaded to mate with internal threads on a nose extension  52  so that the nosepiece  22  can be screwed into the distal end of the nose extension  52 . 
   Returning now to  FIGS. 2 ,  3 , and  8 , the proximal end of the indenter  34  is formed to receive a stud  48  on the distal end of the push rod  44  so that the indenter can be attached to the pushrod  44 . A bore  36 , transversely piercing the indenter  22  and the stud  48 , allows insertion of pin  42  to firmly affix the indenter  34  to the distal end of the push rod  44 . A middle portion of the push rod is cut out into a waist  50  to accommodate a reciprocal movement limiting set screw  54  when the pushrod  44  is slidably mounted within the nose extension  52 . The proximal end of the push rod  44  is threaded externally to mate with internal threads on adjustment barrel  60 , so that when the proximal end of the pushrod  44  is passed through the nose extension  52  and spring  56 , the pushrod  44  can be screwed into the adjustment barrel  60 . 
   The nose extension  52  includes a passageway  53 , extending from the distal end to the proximal end, wherein the internal diameter of the passageway  53  is slightly larger than the outside diameter of the pushrod  44  to allow reciprocal movement of the pushrod  44  when the pushrod is assembled within the nose extension  52 . As previously described, the distal end of the nose extension  52  is threaded to receive the complementarily threaded proximal end of the nosepiece  22 . The proximal end of the nose extension  52  includes a circumferentially enlarged cylindrical head  64  to provide a contact surface  63  for the compression spring  56 , and a flange  65  to prevent the nose extension  52  proximal end from being forced out of the tool body  28  when the plunger assembly  33  is activated. In addition, the head  64  is radially bored and tapped to accommodate a setscrew  54  for reciprocally retaining the push rod  44  at the waist  50  when the pushrod  44  is installed in the nose extension  52 . The set screw  54  is screwed in so that the end of the set screw  54  is just short of touching the waist  50  of the push rod  44 . Accordingly, the plunger assembly  33  is restrained within the nosepiece assembly  62  by the set screw&#39;s  54  interference with the waist  50  of the pushrod  44 . 
   The compression spring  56  and spring washer  58  are held in biased engagement against the head  64  of the nose extension  52  by the adjustment barrel  60  and the push rod  44 , threaded into the adjustment barrel  60  so that the spring  56  urges the plunger assembly  33  in a direction away from the aperture  21 . As a result, the longitudinal position of the plunger assembly  33  with relation to the nosepiece assembly  62  can be adjusted by threading the push rod  44  in and out of the adjustment barrel  60 . Accordingly, the depth of a crimp in the ferrule can be controlled by adjusting the effective length of the plunger assembly  33 , so the indenter  34  is adjusted to extend further distally to create a deeper crimp, or is adjusted to extend proximally to create a shallower crimp. To facilitate adjustments, the adjustment barrel  60  is radially bored with a series of openings  66  around the circumference of the adjustment barrel  60  near the proximal end to allow insertion of a longitudinal member (not shown). The longitudinal member can be inserted radially into one of the openings  66  to rotate the adjustment barrel  60  (threading the barrel onto or away from the pushrod  44 ) to perform plunger assembly positioning adjustments, such as to compensate for wear or manufacturing tolerance. 
   The plunger assembly  33  and the nosepiece assembly  62  are assembled into the nose  32  as described below. The proximal end of the nose  32  is inserted into the body  28  at the nose assembly opening  68  so that the head  64  of the nose extension is entirely inserted within the body  28 . A nose collar  72 , bored with an aperture  76  to allow the distal end of the nose extension  52  to pass through is installed over the nose extension  52  to slidably retain the proximal end of the nose  32  within the body  28  at the flange  65 . The aperture  76  can be circumferentially grooved to allow biased mounting of an appropriately sized o-ring  74  to support the shaft of the nose extension  52  as it passes through the aperture  76 . Once the nose collar  72  is installed over the nose extension  52  and the proximal end of the nose  32  is inserted in the body  28 , the collar  72  is screwed to the body  28  with screws  78 . Accordingly, the nose  32  can be rotated about an elongate axis by depressing the nosepiece  22  in a direction to compress the spring  56  to disengage the flange  65  from frictional contact with the nose collar  72  and allow the nose  32  to be rotatably positioned at a desired orientation. Advantageously, removal and replacement of the nose  32 , such as to install a different sized nosepiece  62 , can be easily accomplished by removing the nose collar  72  and installing another nose  32 . 
   The body  28  is adapted to be mounted on a hydraulically operated base tool  26  to actuate the plunger assembly  33 . Generally, the base tool  26  includes a piston  27 , mounting ears  25 , a hydraulic reservoir  27 A, a pump lever  26 A and a release lever  26 B. The piston  27  is actuated by repeatedly operating the pump lever  26 A, and the hydraulic pressure applied to the piston  27  is released by operating the release lever  26 B. The release lever  26 B causes hydraulic fluid built up behind the piston  27  during actuation to be drained off, releasing pressure on the piston  27  and allowing the piston  27  to be returned to a retracted position, such as by the spring  56  acting on the adjustment barrel  60  urging the piston  27  to the retracted position after the release lever  26 B is activated. In an aspect of the invention, the body  28  is configured to be attached to the mounting ears  25  of the base tool  26  so that the body  28  is held in fixed relation to the base tool, and the piston  27  operates coaxially with the elongate axis of the nose assembly to apply force along the elongate axis of the plunger assembly  33 . Accordingly, when the body  28  of the safety cable tool  10  is mounted on the hydraulically operated base tool  26 , the crimping of the ferrule  20  and severing of the cable  12  is accomplished by operating the pump lever  26 A of the base tool. In another aspect of the invention, the piston  27  travel is limited, for example by a stop within the base tool  26 , so that the piston  27  is prevented from pushing the indenter  34  too far into the nose  32  and keeps the spring  56  from being over compressed. 
   While the invention has been described in what is presently considered to be a preferred embodiment, various modifications and variations will become apparent to those skilled in the art. It is intended therefore that the invention not be limited to the specific disclosed embodiment but be interpreted within the full spirit and scope of the appended claims.