Abstract:
A cutting tool with first and second pivoted shearing blades has a guide member mounted to the first blade for transverse movement relative to the first blade and toward and away from the second blade. The guide member has a transverse restraining surface that confronts a transverse guided surface of the second blade during cutting of a workpiece to resist axial separation of the cutting edges away from the cutting plane. A yieldable, resettable mechanism enables release of an uncut cable captured by the guide member in the event the planned cut is in error or must be postponed. Examples include a ball detent, a magnet, an over-center extension spring arrangement and a torsion spring.

Description:
FIELD OF THE INVENTION 
     The invention relates to cutting tools, in particular, to scissor-action tools having pivoted shearing blades for cutting cables and similar workpieces. 
     BACKGROUND OF THE INVENTION 
     Scissor-action tools for cutting cables and similar workpieces have cutting blades that typically are guided when cutting so they do not bend away from each other and from the cutting plane they define. The shearing blade tips must be able to open wide enough to allow a cable to enter through the front of the tool (thus enabling lateral cable engagement) and then travel through the cable until it is severed. Ideally, the blades should travel from fully open to the “guided” position before cutting begins. 
     SUMMARY OF THE INVENTION 
     The invention facilitates release of an uncut cable captured by the actuated blade guide of a scissor-action cutting tool in the event the planned cut is in error or must be postponed. An example of a cutting tool having a cable-capturing, actuated blade guide is disclosed as the first embodiment (FIGS. 1-6d) in commonly owned application Ser. No. 13/554,028, filed Jul. 20, 2012 and titled “Cutting Tool with Actuated Blade Guide,” which is incorporated by reference herein in its entirety. 
     The invention broadly encompasses a cutting tool comprising first and second shearing blades and a guide mechanism that resists axial separation of the blades during cutting. The first and second blades are mounted for relative pivotal movement about a blade pivot axis and have respective cutting edges defining therebetween a transverse cutting plane substantially normal to the pivot axis. The first and second blades have respective first and second distal blade portions that define a workpiece-admitting gap and converge transversely as the blades relatively advance from an open position to engage a workpiece disposed between the blades. 
     A guide mechanism carried by the first blade includes a guide member extending toward the second distal blade portion and constrained to move transversely along a prescribed path relative to the first and second distal blade portions between a fully extended position, in which the guide member spans at least a portion of the gap, and retracted positions in which the guide member occupies lesser portions of the gap. The guide member has a distal end and a transverse restraining surface configured to confront a transverse guided surface of the second distal blade portion during cutting to resist axial separation of the cutting edges away from the cutting plane. A spring biases the guide member toward its fully extended position and allows the guide member to retract when its distal end is urged against a workpiece, the guide member thereafter returning to its fully extended position to capture the workpiece between the cutting blades after the workpiece clears the distal end. 
     A resettable catch enables tool release from a captured but uncut workpiece in the event the planned cut is in error or must be postponed. The catch normally maintains constrained movement of the guide member along its prescribed path but is yieldable to allow the guide member to move away from its prescribed path and away from the gap between the blades when the guide member is urged forcefully against the uncut captured workpiece, thereby releasing the tool from the workpiece. 
     The guide mechanism preferably is pivotally attached to the first blade and the resettable catch can yield to allow the guide mechanism to swing transversely from its normal captive position when the tool is to be removed from an uncut captured workpiece. The guide member preferably is supported by and slides along a transversely extending rail. 
     In one embodiment the resettable catch is in the form of a spring-loaded ball carried by the guide mechanism; in the normal captive position the ball is retained in a recess in the first blade. In another embodiment the resettable catch is in the form of a magnet that keeps the guide mechanism in the captive position. In a further embodiment the resettable catch is in the form of an over-center extension spring arrangement that normally biases the guide mechanism toward the captive position but reverses its bias away from the captive position when the guide mechanism is displaced beyond a null position. In yet another embodiment the guide mechanism is constantly urged toward the captive position by a torsion spring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Several embodiments of the disclosed invention, including the best mode for carrying out the invention, are described in detail below purely as examples, with reference to the accompanying drawing, in which: 
         FIG. 1  is a perspective view of a first embodiment of cutting tool according to the invention; 
         FIG. 2  is a front elevational view thereof; 
         FIG. 3  is a right side elevational view thereof; 
         FIG. 4  is a perspective view of the guide mechanism thereof; 
         FIG. 5  is an exploded view of the guide mechanism of  FIG. 4 ; 
         FIGS. 6 a -6 c    are a front elevational views of the cutting tool of  FIG. 1  shown in sequential stages of use in preparation for cutting a workpiece; 
         FIG. 7  is a front elevational view of the cutting tool of  FIG. 1  shown as it is freed from an uncut workpiece; 
         FIG. 8 a    is a front elevational view of the cutting tool of  FIG. 1  shown in an initial stage of removal from an uncut workpiece; 
         FIG. 8 b    is a sectional view thereof taken along line  8   b - 8   b  in  FIG. 8   a;    
         FIG. 9 a    is a front elevational view of the cutting tool of  FIG. 1  shown in an intermediate stage of removal from an uncut workpiece; 
         FIG. 9 b    is a sectional view thereof taken along line  9   b - 9   b  in  FIG. 9   a;    
         FIG. 10 a   , which is similar to  FIG. 7 , is a front elevational view of the cutting tool of  FIG. 1  shown in a final stage of removal from an uncut workpiece; 
         FIG. 10 b    is a sectional view thereof taken along line  10   b - 10   b  in  FIG. 10   a;    
         FIG. 11  is a front elevational view of a second embodiment of cutting tool according to the invention; 
         FIG. 12  is a front elevational view of a third embodiment of cutting tool according to the invention; and 
         FIG. 13  is a front elevational view of a fourth embodiment of cutting tool according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Each of the disclosed embodiments of the invention is shown in the drawing figures as a cutting head per se having a pair of pivoted jaws, each jaw supporting a replaceable shearing blade having a cutting edge. The jaw and blade components are substantially identical in all embodiments, so the same reference numbers are used to identify the common parts. The cutting head is adapted to be mounted to a manual or a powered actuator that supplies a force to cause relative pivotal movement of the jaws and, hence, the shearing blades, in a manner well known in this art. As used throughout this application, including the claims, the terms “first blade,” “second blade” and “blade” are intended to cover the blades per se as well as their supporting structures, such as their jaws, unless otherwise indicated or implied. 
     Referring to  FIGS. 1-3 , a first embodiment of cutting tool according to the invention comprises a first jaw  2  pivoted to a second jaw  4  for relative movement about a pivot axis  6 . The cutting end of the tool comprises a first shearing blade  8  bolted to first jaw  2  and a second shearing blade  10  bolted to second jaw  4 . Blade  8  has a cutting edge  12 , blade  10  has a cutting edge  14 , and the two cutting edges  12 ,  14  define between them a transverse cutting plane substantially normal to pivot axis  6 . The powered end of the tool comprises inner surfaces (not shown) on jaws  2 ,  4  that are spread apart by an advancing actuator member in a manner known in the art, which causes blades  8 ,  10  to converge and cut through a workpiece (e.g., cable) placed between them. A helical tension spring (not shown) extending between the jaws at the powered end of the tool biases the blades to the open position as shown, also in a manner known in the art. The jaws  2 ,  4  are shown mounted in a clevis  16 , which would be mounted to an actuator. 
     Referring further to  FIGS. 4 and 5 , the blade guide mechanism includes a guide member in the form of an L-shaped arm  22  having a transversely extending flange  24 , the inner surface  26  of which confronts the outer surface of blade  10  during cutting. Arm  22  also has a laterally projecting boss  28  with a bore  30  surrounding and slidable along a transversely extending rail (pin)  32 . Rail  32  is supported between the front ear  34  and the rear ear  36  of a mounting bracket  38 , which is attached to the distal portion of blade  8  as described below. A coil spring  40  surrounds rail  32  between boss  28  and rear ear  36  to bias arm  22  forward toward the distal portion of blade  10 . In addition to rail  32 , several other structures stabilize arm  22  to keep its flange  24  parallel to the cutting plane: the lower surface  29  of boss  28 , which abuts the upper surface  39  of mounting bracket  38 ; and the inner surface  42  of arm extension  40 , which abuts the outer surface  44  of mounting bracket  38 . 
     As seen in  FIGS. 2 and 6   a , which show the blades in their fully open state with arm  22  fully extended, arm  22  extends farther from pivot axis  6  than opposing blade  10  so as to facilitate the arm&#39;s engagement with a workpiece W (see  FIG. 6 b   ). In this state, arm  22  spans a substantial portion (e.g., at least half) of the gap defined by the distal portions of blades  8 ,  10 . Preferably, arm  22  spans about 75% of the gap, as shown, so that the arm begins to perform its blade-guiding function very soon after the blade tips begin to converge. In its retracted state with the blades open (see  FIG. 6 c   ), arm  22  opens the gap sufficiently to allow entry of the largest diameter workpiece specified for cutting. Arm  22  is retracted by urging its free end against a workpiece W (see  FIG. 6 b   ); and once the arm retracts sufficiently to allow the workpiece to pass between the distal blade portions (see  FIG. 6 c   ) the tool is simply pushed onto the workpiece, whereupon spring  40  returns the arm to its initial, fully extended position (see  FIG. 6 d   ), capturing the workpiece between the blades. As the cutting operation commences, inner guide surface  26  of arm  22  promptly confronts the outer surface of blade  10  to resist deflection of the blades away from the cutting plane. 
     Cable cutting often involves selecting the right cable from among many at a particular job site. If the wrong cable is captured or if the cut must be postponed after cable capture, the tool must be removed from the uncut cable for further use. If the blades are reachable by hand, the guide can be retracted manually along its prescribed linear path. However, cutting tools of this type often are mounted on long handles or poles to afford the reach needed to access overhead or other remote cables. In those instances manual retraction of the guide would be very difficult if not impossible and the tool would then be rendered unusable, hanging from the uncut cable. The invention includes an easily operable quick-release feature that enables removal of the tool from an uncut workpiece. In the present example, this feature is afforded by the yieldable nature of the attachment of mounting bracket  38  to blade  8 . 
     Referring to  FIGS. 5 and 6   b , mounting bracket  38  is attached to blade  8  by a cap screw  50  threaded into a hole  51  in blade  8  (see  FIG. 5 ). The cylindrical head of cap screw  50  closely resides in a recess  52  in mounting bracket  38  and serves as a pivot (release axis) about which the bracket can swing. Mounting bracket  38  is held in the normal (captive) position shown in  FIGS. 2 and 6   c  by a spring-loaded ball catch (ball detent)  54 , which is snugly held in a hole  56  in bracket  38  and serves as a pivot for the bracket. The spring of ball catch  54  urges the ball toward blade  8 , where it normally rests in a retention recess in blade  8  during normal cutting use (see  FIG. 8 b   ). The retention recess can be a blind hole or a through hole  58 , as shown. The retention force afforded by ball catch  54  should be strong enough to support the weight of the tool and any pole to which it is attached so that the tool can hang from an overhead cable and not inadvertently release from the cable. 
     If the tool is to be removed from a captured but uncut workpiece, the tool is simply pulled against the workpiece forcefully (see  FIG. 8 a   ). The resulting outward force exerted on arm  22  overcomes the spring force of ball catch  54 , forcing the ball out of retention hole  58  and allowing mounting bracket  38  (with arm  22 ) to swing outwardly about cap screw  50  (see  FIGS. 9 a , 9 b   ). When the ball has cleared the outer edge of blade  8  (see  FIG. 10 b   ), the space between blades  8  and  10  is wide enough to free the tool from the workpiece (see  FIGS. 7 and 10   a ). Thereafter, manually pressing arm  22  inward (either by hand or against a stationary surface) will again overcome the spring force of ball catch  54  and reset mounting bracket  38  (and arm  22 ) to the normal (captive) position with the ball returned to hole  58 . Stops (not shown) placed at appropriate locations may be used to limit the pivot range of bracket  38 . 
     Referring to  FIG. 11 , a second embodiment of cutting tool according to the invention utilizes a permanent magnet  60  to provide a retention force that keeps the steel mounting bracket  38  in the normal (captive) position. Magnet  60  is mounted at the end of one leg of an L-bracket  62  whose other leg is secured to blade  8  by two screws  64 , which also secure blade  8  to jaw  2 . Normally the magnet engages and holds the mounting bracket in the captive position as shown. A forceful pull of the tool against a captured workpiece will overcome the magnetic retention force and release the tool. An alternative arrangement (not shown) would have the magnet secured to the mounting bracket and the magnet would engage and hold the adjacent end of the blade-mounted L-bracket or other blade-carried structure. Both arrangements are reset to the captive position manually in the manner described above for the first embodiment. In both arrangements, the retention force afforded by the magnet should be strong enough to support the weight of the tool and any pole to which it is attached so that the tool can hang from an overhead cable and not inadvertently release from the cable. 
     Referring to  FIG. 12 , a third embodiment of cutting tool according to the invention utilizes an extension spring  70  to provide a retention force that keeps the mounting bracket  38  in the normal (captive) position. Spring  70  is anchored at one end  72  to blade  8  (jaw  2 ) and at the other end  74  to mounting bracket  38 . In the captive position shown, spring  70  passes to the right of cap screw  50 , exerting a closing (clockwise) torque on mounting bracket  38  to keep it in its captive position. When the tool is pulled forcefully against a captured workpiece, mounting bracket  38  will begin to swing outwardly (counterclockwise) about cap screw  50  (as shown by the arrow) against the clockwise torque exerted on it by the extending spring  70 . When spring  70  passes to the left of cap screw  50  beyond a null position, the spring force begins to exert a counterclockwise torque on mounting bracket  38 , which quickly forces the mounting bracket to its release position where it is held by the spring force. Mounting bracket  38  is reset to the captive position manually as described above but against the counterclockwise torque exerted on mounting bracket  38  until the bracket passes the null position, whereupon the clockwise torque exerted by the spring snaps the bracket back to its captive position. The retention force afforded by the extension spring  70  should be strong enough to support the weight of the tool and any pole to which it is attached so that the tool can hang from an overhead cable and not inadvertently release from the cable. 
     Referring to  FIG. 13 , a fourth embodiment of cutting tool according to the invention utilizes a torsion spring  80  to provide a retention force that keeps the mounting bracket  38  in the normal (captive) position. Spring  80  has a lower leg  82  anchored at its end  84  to blade  8  (jaw  2 ) and an upper leg  86  anchored at its end  88  to the rear of mounting bracket  88 . In the captive position shown, spring  80  is in compression, i.e., it exerts a clockwise torque on mounting bracket  38 . When the tool is pulled forcefully against a captured workpiece, mounting bracket  38  swings outwardly (counterclockwise) about cap screw  50  (as shown by the arrow) against the clockwise torque of spring  80 . Once the tool is released from the workpiece, the spring automatically forces mounting bracket  38  clockwise back to its captive position. The retention force afforded by the torsion spring  80  should be strong enough to support the weight of the tool and any pole to which it is attached so that the tool can hang from an overhead cable and not inadvertently release from the cable. 
     While several embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.