Abstract:
Pliers ( 20 ) include first and second pivotally interconnected plier arms ( 22, 32 ) each having a handle ( 24, 34 ) and a jaw ( 26, 36 ). The plier handles ( 24, 34 ) are operable to manipulate the plier jaws ( 26, 36 ). The pliers ( 20 ) also include a latch mechanism ( 300 ) for alternately latching the pliers ( 20 ) in a closed condition and releasing the pliers to an open condition in response to successive applications of squeeze to the plier arms ( 22, 32 ).

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/736,751, filed Dec. 13, 2012, which is hereby incorporated by reference in its entirety. This application also claims the benefit of U.S. Provisional Application Ser. No. 61/736,725, filed Dec. 13, 2012, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a hand tool for twisting safety wires. More particularly, the invention relates to a safety wire twisting hand tool that includes a rotating device adapted for a quick release connection with pliers having different configurations. The invention further relates to safety wire twisting hand tool that includes a latch mechanism for latching the pliers in a closed condition. 
     BACKGROUND OF THE INVENTION 
     Wire twisting pliers are used to twist safety wires that are typically used by aircraft mechanics to secure safety wire bolts from accidentally loosening from vibrations, such as those caused by aircraft engines. Safety wire nuts and bolts are used in a number of other applications as well, such as auto racing and industrial equipment. Wire twisting pliers typically include a conventional pair of pliers that is fitted with a locking mechanism and a rotating device. The locking mechanism locks the pliers on the wires that are to be twisted. The rotating device is manually operable to impart rotation of the pliers to thereby twist the wire. Such devices are disclosed in U.S. Pat. Nos. 4,842,025, 5,211,209, and 5,560,402 
     Wire twisting pliers twist a variety of wire sizes or gages depending on the job requirements. The most common sizes are 0.012″, 0.020″, 0.025″, 0.032″, 0.041″, and 0.051″. As the wire size increases, however, excessive jaw pressure is placed on the wire in order to lock the handles, making the handles difficult to lock and causing damage to the safety wire. This damage to the wire can cause premature failure of the safety wire in its application. 
     Additional problems can be encountered with the use of common wire twisting pliers. For example, wire twisting pliers are often used on wire bolts that are hard to reach, which causes the user to extend his or her hand/fingers/thumb beyond limitation in an effort to access portions of the tool. Also, during use, wire ends can be left spinning loose, which allows the wires to thrash around during twisting and potentially cause damage to the work piece or injuring the user. Additionally, standard teeth on plier jaws often distort and mar the wire, causing potential failure points in the wire strength. Moreover, safety wires are typically terminated by cutting the twisted wire, folding it over, and then crimping it in a tight loop known as a “pigtail.” Pigtails are difficult to accomplish with the bulky nose of existing wire twisters. Furthermore, when cutting the wire prior to twisting, care must be exercised so that the cut-off pieces do not fall into the surrounding machinery. 
     SUMMARY OF THE INVENTION 
     The invention relates to pliers that include first and second pivotally interconnected plier arms each having a handle and a jaw. The plier handles are operable to manipulate the plier jaws. The pliers also include a latch mechanism for alternately latching the pliers in a closed condition and releasing the pliers to an open condition in response to successive applications of squeeze to the plier arms. 
     According to one aspect of the invention, the latch mechanism comprises a cam connected to the first plier arm and a cam receiver connected to the second plier arm. The latch mechanism has a latched condition in which the cam receiver retains the cam to latch the pliers in the closed condition. The latch mechanism has an unlatched condition in which the cam receiver releases the cam to permit placing the pliers in the open condition. 
     According to another aspect of the invention, the cam is adapted to enter the cam receiver upon closure of the pliers. The cam receiver is adapted to latch onto the cam to place the latch mechanism in the latched condition in response to a predetermined amount of squeeze being applied to the plier arms. The cam receiver is adapted to release the cam to place the latch mechanism in the unlatched condition in response to a subsequent application of the predetermined amount of squeeze. 
     According to another aspect of the invention, the cam comprises a cylindrical body mounted on the first plier arm for rotation about an axis. The cam comprises a recess on a cylindrical outer surface of the cam. The cam receiver comprises at least one member that enters the recess on the cylindrical surface of the cam. An engagement between the at least one member and portions of the cam defining the recess placing the latch mechanism in the latched condition. 
     According to another aspect of the invention, the portions of the cam defining the recess comprise an upper cam surface and a lower cam surface. The at least one member engages at least one of the upper cam surface and the lower cam surface to cause the cam to rotate about the axis. The at least one member engages the lower cam surface in the latched condition of the latch mechanism. The at least one member passes through an opening in the lower cam surface when transitioning from the latched condition to the unlatched condition. 
     According to another aspect of the invention, the pliers include a rotating device that is manually actuatable to rotate the pliers. The plier jaws can comprise a blade for cutting a wire and a wire grasper for grasping the wire cut by the blade. The plier arms are deflectable and resiliently return to their original form in response to the successive applications of squeeze. The resilient return to original form actuates the latch mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the invention will become apparent to one skilled in the art to which the invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, in which: 
         FIG. 1  is a plan view of a wire twisting tool illustrating a first condition of the tool, according to the invention. 
         FIG. 2  is a plan view of the wire twisting tool illustrating a second condition of the tool. 
         FIGS. 3 and 4  are perspective views of the wire twisting tool. 
         FIG. 5  is a magnified perspective view illustrating a portion of the wire twisting tool. 
         FIG. 6  is a is a magnified plan view illustrating a portion of the wire twisting tool. 
         FIG. 7  is a partially schematic plan view illustrating another portion of the wire twisting tool. 
         FIGS. 8A-8F  illustrate another portion of the wire twisting tool. 
         FIGS. 9A-9F  are schematic views that illustrate the operation of a portion of the wire twisting tool. 
         FIGS. 10 and 11  are magnified views illustrating another portion of the wire twisting tool. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention relates to a wire twisting tool for twisting safety wires, such as those commonly used in the aviation industry. Referring to  FIGS. 1-4 , the wire twisting tool  10  includes pliers  20  and a plier rotating device  50  for imparting rotation of the pliers about an axis  12 . 
     The pliers  20  include a first plier arm  22  and a second plier arm  32 . The first plier arm  22  includes a handle portion  24  and a jaw portion  26 . The second plier arm  32  includes a handle portion  34  and a jaw portion  36 . The handle portions  24  and  34  define a handle  42  of the pliers  20 , and the jaw portions  26  and  36  define a head  44  of the pliers. The plier arms  22  and  32  are connected to each other at a pivot joint  40  by means, such as a fastener or press pin. The pliers  20  are operable in a conventional manner to apply a wire gripping force with the plier head  44  via operation of the plier handle  42 . 
     The rotating device  50  includes a housing  60  and a shaft  80  terminated with a knob  82 . The shaft  80  is movable along the axis  12  relative to the housing  60  by pulling on the knob  82 , which actuates a rotation mechanism in the housing that, in turn, imparts rotation of the housing and the pliers  20  relative to the shaft about the axis  12 . The direction of spindle rotation (i.e., the direction of wire twisting) can be selected by the user via rotation selection switch/sleeve  72 . To actuate the switch  72 , the user rotates the sleeve relative to the housing  60 , which switches the direction in which the rotation mechanism rotates the housing  60  in response to the user pulling on the knob  82 . For example, rotating the sleeve  72  counterclockwise may result in counterclockwise wire twisting; and rotating the sleeve  72  clockwise may result in clockwise wire twisting. 
     The rotation mechanism of the rotating device  50  operates to impart rotation of the pliers  20  in a manner that is similar or identical to the manner in which other known rotating devices associated with other wire twisting tools. For example, the rotating device may be configured with a general construction and mode of operation that is similar or identical to the general construction and mode of operation of the wire twisting tools disclosed in U.S. Pat. Nos. 4,842,025, 5,211,209, and 5,560,402, individually or in combination. The disclosures of U.S. Pat. Nos. 4,842,025, 5,211,209, and 5,560,402 are hereby incorporated by reference in their entireties. In operation, the user can lock the plier head  44  onto a wire and pull on the shaft  80  via the knob  82  to effectuate rotation of the pliers  20  to thereby twist the wire. 
     As another feature of the invention, the head  44  of the pliers  20  is configured to permit grasping wires while at the same time helping to prevent marring or otherwise damaging the wire. To achieve this, tips  180 ,  182  of jaws  26 ,  36 , respectively, are configured with waved wire grasping surfaces  184 ,  186 . This is best shown in  FIGS. 5 and 6 . Utilizing the waves of the surfaces  184 ,  186  to aid in grasping wires allows for the reduction or elimination of grooves or knurling on the surfaces, which can mar or otherwise damage the wires. 
     Additionally, the tips  180 ,  182  have a tapered width configuration (shown best in  FIG. 5 ) such that the terminal end portions of the jaws  26 ,  36  are narrow and well-suited for improved folding and shaping wire ends to form pigtail terminations. The tips  180 ,  182  widen beyond the terminal end portions, and the waved surfaces  184 ,  186  continue through the taper and into the widened portions of the jaws  26 ,  36 . The widened portions of the tips  180 ,  182  can thus be used primarily for wire gripping, and the narrow portions can be used primarily to terminate wires. 
     As a feature of the invention, the wire twisting tool  10  includes a latch mechanism  300  that facilitates a simple, quick, and reliable latching of the second plier arm  32  against pivoting movement relative to the first plier arm  22 . The latch mechanism  300  is operable to lock the pliers  20  in a closed/clamping condition ( FIG. 1 ). When the handle portions  24 ,  34  are squeezed to operate the pliers  20  from the open condition ( FIG. 2 ) to the closed condition ( FIG. 1 ), the latch mechanism  300  locks the pliers in the closed condition. When the handle portions  24 ,  34  are squeezed while the pliers  20  are latched in the closed condition, the latch mechanism  300  is released, thus placing the pliers in the open condition. The latch mechanism  300  thus provides an alternating latch/unlatch operation on successive squeezing of the handle portions  24 ,  34 . 
     Referring to  FIG. 7 , the latch mechanism  300  includes a cam  310  mounted to the second plier arm  32  and a cam receiver  330  formed in the first plier arm  22 . The cam  310  is generally cylindrical and is mounted on the plier arm  22  in a manner, e.g., via fasteners, such that it can rotate freely about an axis  312 . The connection between the cam  310  and the plier arm  22  can be such that it can be there is some resistance to rotation so that the cam can be rotated during use, but resists rotation in response to external forces such as normal use of the pliers  20  or the rotating device  50 . For example, a leaf spring  318  can bias the cam  310  in a manner that maintains the rotational position of the cam. This spring  318  could deflect when pressure is exerted on the cam  310  in response to a squeezing force applied to the plier arms  22 ,  32 , allowing the cam  310  to rotate about the axis  312  in the manner described below with reference to  FIGS. 9A-9F . 
     The cam receiver  330  includes one or more pins  332  positioned in an opening  334  in the first plier arm  22 . The cam  310  moves into the opening  334  when the pliers  20  are placed in the closed condition. When the cam  310  enters the opening  334 , it engages the pin  332 , which causes the cam  310  to operate in the manner described below with reference to  FIGS. 9A-9F . 
     The cam  310  is illustrated in  FIGS. 7-8F . The cam  310  has a generally cylindrical outer surface  314 . A recess  316  in the surface  314  extends circumferentially around the cam  310 . The recess  316  defines a first or upper cam surface  320  and an opposite second or lower cam surface  322 . The recess  316  intersects a surface  324  of the cam  310  and thereby forms an opening  326 . In this configuration, there are two such openings  326  (see  FIGS. 8A and 8B ) positioned on radially opposite sides of the cam  310 .  FIGS. 8C-8F  illustrate the side elevation of the cam  310  at 90-degree intervals of rotation and therefore illustrate the entire profile for the upper and lower cam surfaces  320  and  322 . 
     Operation of the latch mechanism  300  is illustrated in  FIGS. 9A-9F . In these figures, the cam  310  and the pin  332  of the cam receiver  330  are illustrated schematically. Additionally, for purposes of simplicity in illustration and explanation, the cylindrical cam  310  in  FIGS. 9A-9F  is illustrated in a generally rectangular form as if the cylindrical cam was cut vertically, “unrolled,” and laid flat on a surface. Thus, in  FIGS. 9A-9F , opposite ends of the rectangularly illustrated cam  310  meet in its contiguous, cylindrical form. 
     Referring to  FIG. 9A , the pin  332  is initially positioned above or outside the cam  310 , as is the case when the pliers  20  are in the opened condition (see  FIG. 14 ). As the pliers  20  are moved toward the closed condition, the in moves into the recess  316  of the cam  310  through the opening  326 , as indicated generally by the arrow in  FIG. 9A . In  FIGS. 9A-9F  the operation of the latch mechanism  300  is illustrated with a single pin  332 . The cam receiver  330  could, however, be fit with two pins that are received in openings  328  on radially opposite sides of the can  310 . 
     Referring to  FIG. 9B , as the plier handles  24 ,  34  are closed, the pin  332  enters the recess  316  through the opening  326  and moves along a path indicated generally by the dashed lines in  FIG. 9B  until it engages the lower cam surface  322 . Further closure of the handles  24 ,  34  causes the pin  332  to slide along the inclined portion of the lower cam surface  322 . As a result, the cam  310  rotates, as indicated generally by arrow B in  FIG. 9B . The pin  332  eventually reaches the pin  332  in the final position illustrated in solid lines. This further closure movement of the handles  24 ,  34  is facilitated through the deflection of the handles, once the jaws  26 ,  36  have closed and clamped onto a work piece, such as a wire. 
     Referring to  FIG. 9C , when the closure force is removed from the plier handles  24 ,  34 , the pin  332  can move upward as viewed in  FIG. 9C  along the path indicated generally by the dashed lines in  FIG. 9C . Since the cam  310  had been rotated due to the initial closure (see  FIG. 9B ), upward movement of the pin  332  results in its engaging the upper cam surface  320 . This upward movement can be attributed to the removal of the closure force from the plier handles  24 ,  34  and their resulting resilient return to original form, having been deflected during closure. This upward movement of the pin  332  against the upper cam surface  320  causes the cam  310  to rotate further, as indicated generally by arrow B in  FIG. 9B . This further closure movement of the handles  24 ,  34  may be facilitated through the deflection of the handles, once the jaws  26 ,  36  have closed and clamped onto a work piece, such as a wire. 
     In the condition illustrated in  FIG. 9C , the pin is retained in the concave portion  340  of the upper cam surface  320 . The latch mechanism  300  is latched and the plier handles  24 ,  34  are locked in the closed condition (see  FIG. 15 ) and blocked from moving toward the open condition (see  FIG. 14 ). 
     Referring to  FIG. 9D , to unlatch the latch mechanism  300  and thereby place the pliers  20  in the open condition, the plier handles  24 ,  34  are again squeezed, which causes the pin  332  to move along a path indicated generally by the dashed lines in  FIG. 9D  until it engages the lower cam surface  322 . Further closure of the handles  24 ,  34  causes the cam  310  to rotate as the pin  332  slides along the inclined portion of the lower cam surface  322 . The rotation of the cam  310  is indicated generally by arrow D in  FIG. 9B . This eventually leaves the pin  332  in the final position illustrated in solid lines. This further closure movement of the handles  24 ,  34  may be facilitated through the deflection of the handles, e.g., once the jaws  26 ,  36  have closed and clamped onto a work piece, such as a wire. 
     Referring to  FIG. 9E , when the closure force is removed from the plier handles  24 ,  34 , the pin  332  can move upward as viewed in  FIG. 9E  along the path indicated generally by the dashed lines in  FIG. 9E . Since the cam  310  had been rotated due to the previous application of handle closure force (see  FIG. 9D ), upward movement of the pin  332  results in its engaging the upper cam surface  320 . This upward movement can be attributed to the removal of the closure force from the plier handles  24 ,  34  and their resulting resilient return to original form, having been deflected during closure. This upward movement of the pin  332  causes the pin to slide along the inclined portion of the upper cam surface  320 . This the cam  310  to rotate further, as indicated generally by arrow E in  FIG. 9E . Eventually, the pin  332  reaches the opening  326 , as indicated generally in solid lines in  FIG. 9E . 
     Referring to  FIG. 9F , the pin  332  can then exit the cam receiver  330  and the pliers can be placed in the open condition. Additionally, the exit of the pin  332  from the cam  310  has positioned the openings  326  in the cam in a position to receive the pin for a subsequent closure and latching of the pliers  20 . The latch mechanism  300  thus facilitates a sequential latched-unlatched operation on sequential application of squeezing/closure force applied to the plier handles  24 ,  34 . 
     Referring to  FIGS. 10-11 , as a feature of the invention, the pliers  20  include a wire cutting and grasping mechanism  250  for cutting a wire, e.g., a safety wire twisted onto a safety wire bolt. The wire cutting and grasping mechanism  250  is formed as a portion of the plier jaws  26 ,  36 , and includes a wire cutter  252  and a wire grasper  260 . In the illustrated embodiment, the wire cutter  252  includes a pair wire cutting blades  254 , one associated with each of the plier jaws  26 ,  36 . In a cutting condition of the pliers  20 , the blades  254  engage each other and thereby can cut a wire positioned between the blades. 
     The wire grasper  260  includes a pair of grasping elements  262 , one associated with each of the plier jaws  26 ,  36 . The grasping elements  262  are pads that are constructed of a deformable material, such as a rubber, plastic, or polymeric material. When a wire is positioned between the cutting blades  254 , a portion of the wire is also positioned between the grasping elements  262 . When the pliers  20  are closed, the cutting blades cut the wire, and the grasping elements  262  clamp onto the wire. The deformable nature of the material used to construct the grasping elements  262  may help facilitate this clamping action. Advantageously, if the user positions a free end of a wire between the grasping elements  262 , that cut portion of wire will remain held by the grasping elements after it is cut and separated from the remainder of the wire. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.