Abstract:
A hand held tool for the tensioning and severing of cable ties, including reciprocating means for tensioning the cable tie tail, locking means to prevent further tensioning upon the attainment of a preselected tension level in the tie tail, and severing means to sever the tie tail from the cable tie head.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/503,403 entitled “Cable Tie Tensioning and Cut-Off Tool and Method of Using”, filed 30 Jun. 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to hand held tensioning and cutting tools, and particularly to an improved hand tool for tensioning and cutting cable ties. 
     Cable ties are widely used in a variety of environments and applications. They may be used, for example, to bundle a plurality of elongate wires, cables, or other elongate articles. Cable ties may also be used to secure elongate articles to rigid structures or used as hose clamps, by way of example. Such cable ties typically include an elongate tail portion which is threaded through an integral head portion to encircle the articles to be bound and the tie tail is drawn through the cable tie head to tightly bind the elongate articles into a bundle. After the tie is tensioned around the bundle, the excess length of the tie tail which extends out of the head portion is then severed by the tool close to the head. Ties are often applied in high volumes and to precise tensions. 
     One disadvantage of many presently available tie tensioning and severing tools is that those tools require an operator to apply an excessive force on their triggers which leads tool operator fatigue after only a relatively small number of cables ties have been installed by the operator. Additionally, many prior art tie tensioning and severing tools have their tool triggers mechanically linked to the tensioning and severing mechanisms in a manner that the actual tension attained in the cable tie immediately prior to severing of the cable tie tail varies with the position of the operator&#39;s grip on the trigger during operation of the tool. Tools which rely upon mechanical linkages often increase the tension in the cable tie above the preselected value immediately prior to severing due to the movement of the linkages during the tensioning operation. This can cause stretching, weakening or breakage of the tie during severing. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a hand-held tensioning and severing tool which avoids the aforementioned shortcomings. 
     In accordance with an important aspect of the present invention, an improved hand-held tie tool is provided which includes reciprocating means for tensioning the cable tie tail, means for locking the tensioning means once a predetermined tension is met, and means for severing the cable tie tail from the cable tie while the tension is locked. 
     In accordance with another principal aspect of the present invention selective tension adjustment system is provided in the form of an acme thread cam and knob for selectively changing the preselected tie tension to a selected tension value. 
     Accordingly, it is a general object of the present invention to provide a new and improved hand held tie tensioning and severing tool capable of reliable operation which consistently severs the cable tie tail at substantially uniform tension levels and greatly reduces recoil impact from the system. The tool may further sever the cable tie tails of successively tensioned cable ties consistently at uniform tension levels, irrespective of user generated tool trigger force. 
     Another object of the present invention is to provide a hand tool for tensioning and severing cable ties which includes rotatable selective tension adjustment means for rapidly and reliably selecting a number of preselected tension levels. Further, the cutoff cam system of the present invention provides enhanced cutoff performance and durability with the tension cut off range being increased to approximately 20-200N. 
     Still another object of the present invention is to provide a hand-held tool having improved ergonomics at user/tool interfaces to thereby reduce musculoskeletal injury to the user and improve work environment safety. 
     Yet another object is to provide an improved blade nosepiece interface whereby error in blade installation by the user is greatly reduced. 
     These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a cable tie tensioning and cut-off tool according to the present invention. 
         FIG. 2  is a left side view of the tool illustrated in  FIG. 1 . 
         FIG. 3  is a top view of the tool illustrated in  FIGS. 1 and 2 . 
         FIG. 4A  is a view similar to that of  FIG. 2 , but with a portion of the housing removed with cable tie and bundle shown in phantom. 
         FIG. 4B  is a view similar to that of  FIG. 4A  and showing initiation of the tensioning and cut-off process, with tool parts moving the direction of arrows. 
         FIG. 4C  is a view similar to that of  FIG. 4B  and showing continuation of the tensioning and cut-off process, with tool parts moving the direction of arrows. 
         FIG. 4D  is a view similar to that of  FIGS. 4B and 4C  showing conclusion of the tensioning and cut-off process, with tool parts moving the direction of arrows and cable tie tail severed. 
         FIG. 5  is a perspective view of a control knob on the tool shown in  FIGS. 1-4D  that provides tension adjustment. 
         FIG. 6  is an exploded view of the control knob shown in  FIG. 5 . 
         FIGS. 7A-7C  are cross sections of the control knob illustrated in  FIG. 5  and taken along lines  7 A thereof showing further details of the form and function of the control knob and operation of the control knob. 
         FIGS. 8A and 8B  are, respectively, fragmentary, partially exploded and fragmentary views of a locking mechanism on the tool shown in  FIGS. 1-4D . 
         FIG. 9  is a left side view of the tool with a portion of the housing removed and showing an optional low tension feature. 
         FIGS. 9A-9D  are enlarged, fragmentary views of the low tension feature illustrated in  FIG. 9  and showing movement of the associated parts. 
         FIG. 10  is a left side view of the tool with a portion of the housing removed. 
         FIGS. 10A and 10B  are, respectively, fragmentary perspective and exploded views of a linkage on the tool shown in  FIGS. 1-4D . 
         FIGS. 11A-11D  are left side, fragmentary, views of a tool according to the present application, but with a portion of the housing removed, and showing the tension-lock-cut linkage system in use with movement of the tool parts shown with arrows. 
         FIG. 12  is a view similar to those of  FIGS. 11A-11D , but showing the barrel portion and the cut step of the tension-lock-cut linkage system. 
         FIG. 13A  is a left side, partial phantom, exploded view of a removable handle boot for use with the present tool. 
         FIG. 13B  is a view similar to that of  FIG. 13A , but showing the handle boot in place on the tool. 
         FIG. 13C  is a cross sectional view of  FIG. 13B  and taken along lines  13 C- 13 C thereof, and illustrating the handle air bladder. 
         FIG. 14A  is a left side, partial phantom, exploded view of a removable trigger boot for use with the present tool. 
         FIG. 14B  is a view similar to that of  FIG. 14A , but showing the trigger boot in place on the tool. 
         FIG. 14C  is a view similar to that of  FIG. 14B , but showing the trigger in cross section to illustrate the trigger boot in place. 
         FIG. 15A  is a fragmentary, exploded view of the nosepiece and blade member of the present tool. 
         FIG. 15B  is a fragmentary view of the nosepiece of the present tool and showing the blade member affixed in phantom. 
         FIGS. 16A and 16B  are perspective views of a calibration tool for use with the present device. 
         FIGS. 17A and 17B  are fragmentary, cross sectional views of the tension adjustment system and use of a tension calibration tool. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention. 
     Referring now to the drawings and in particular to  FIGS. 1 and 2 , an embodiment of the cable tie tensioning and cut-off tool  10  incorporating the principles of the present invention is shown as having a housing  12  in the shape of a pistol or gun and having a handle or grip portion  14 , a barrel portion  16 , and a trigger  18 . The trigger  18  is located forwardly of the grip  14  and under the barrel portion  16  where it fits naturally in the hand of a user (not shown). The tool  10  is typically used to install cable ties  20  (seen in phantom in  FIGS. 4A-4D ) around elongate bundles  22 , such as wire cable or the like. As mentioned earlier, cable ties are widely used in a variety of environments and applications, and may be used, for example, to bundle a plurality of elongate wires, cables, or other elongate articles  22 , as shown in the Figures. However, it is to be understood that the tool  10  of the present invention may be used to secure cable ties  20  in other applications, such as to secure elongate articles to rigid structures or used as hose clamps (not shown), by way of non-limiting example. As illustrated, a tie  20  includes a head portion  24  and a tie tail portion  26 . The tool  10  grips the tail portion  26  of the tie  20  and pulls it through the head  24  until a predetermined tension is achieved. The tool  10  then locks the tension and automatically cuts off the excess tail portion  26  adjacent the head  24 . 
     As seen in  FIGS. 4A-4D , one housing  12  sidewall has been cut away to show the opposite housing  12  sidewall and the internal parts and mechanism of the present tool  10 . The tool  10  generally contains a reciprocating tension mechanism, such as the pawl link  28  shown, located in the barrel portion  16  of the tool  10 . The tension mechanism  28  further includes a gripping mechanism, such as the tie-gripping pawl  30  shown, for gripping the tail portion  26  of a tie  20 , and a locking mechanism, such as the rack  32  and pinion shown for locking the tension mechanism  28  at a predetermined tension prior to activating a cutoff mechanism. In operation, the tensioning mechanism pulls the gripped tail portion  26  rearwardly to a predetermined tension. Upon reaching the predetermined tension, the locking mechanism locks the tension. A cutoff mechanism, such as the illustrated cutter link  118 , also located at the forward end of the barrel portion  16 , then activates to cause a blade member  160  to cut off the tie tail  26  closely adjacent the head portion  24 . The predetermined tension is set or adjusted by way of a tension adjustment mechanism located at the rear of the tool  10 , as will be discussed in detail. 
     The present device provides consistent tension and cutting performance such that uniform tension per setting across all tools is achieved. The device target goal is no scatter in tension force per setting. Present devices have tolerances of up to +/−25N. Tolerance range is greatly reduced with the present device. 
     Tension Adjustment System 
     The present tool  10  includes a novel tension adjustment mechanism. As will be seen, the tension control and adjustment mechanism of the present tool  10  functions to provide a controlled tension to the rear of the cutoff cam  36  (see  FIGS. 4A-4C ). This, in turn, determines the point at which the cutoff cam  36  pivots to actuate the locking mechanism and the cutoff mechanism, to thereby cutoff the tie tail  26 . 
     The tension adjustment system of the present device is simple to use and eliminates the use of two knobs, as in known devices, through the use of an acme thread cam action and knob as will be discussed. With reference particularly to the view of  FIGS. 5-7C , it may be seen that the tension control mechanism includes a U-bracket  38  positioned horizontally, and slidably moveable, within the housing  12  at the rear end of the barrel portion  16 . The forward ends  40  of the U-bracket  38  are pivotally coupled to the rear end of the cutoff cam  36  by means of a tension pin  42  extending through the forward ends  40  of the U-bracket and through an elongated slot  44  formed in the cutoff cam  36  (see particularly  FIG. 10B ). The rearward end of the U-bracket  38  is biased toward the rear of the housing  12  by means of the inner and outer tension springs,  46 ,  48  respectively. The tension springs  46 ,  48  are confined between a tension shaft  50  and a tension nut  52 . A rotating cam  54  is coupled to a tension adjustment knob  56  by way of tessellated portions  58  which engage corresponding interlocking splines  60  in the adjustment knob  56 . The rotating cam  54  further includes a threaded portion  62  adapted to threadingly engage fixed cam  64  and its housing  66 . As the adjustment knob  56  is turned, the rotating cam  54  either draws the tension shaft  50  closer to the rear of the housing  12  or drives the tension shaft  50  farther from the rear of the housing  12  depending on the direction in which the adjustment knob  56  is turned. Accordingly, the tension applied by the U-bracket  38  to the cutoff cam  36  is increased as the adjustment knob  56  is turned so as to compress the tension springs  46 ,  48  and is decreased as the adjustment knob  56  is turned to decompress the tension springs  46 ,  48 . 
     As seen in  FIG. 7A , the tessellated portions  58  of rotating cam  54  mate with and slide on splines  60 . This features allows the threaded portion  62  to rotate and move longitudinally along the splines, while the adjustment knob  56  remains stationary. This feature allows the overall tool  10  length and overall ergonomics to remain constant throughout its adjustment range. 
     Preferably, the adjustment knob  56  includes indicia  68  to designate selected tension settings. The indicia  68  may correspond to the incremental tension ranges provided by detents  70  on the adjustment knob  56  in which a ball  72 , or other suitable device, rides. The present tension adjustment system further includes capability to calibrate, hold and lock. A locking latch  74  is slidingly located on the housing  66  of the fixed cam  64 . As seen particularly in the view of  FIGS. 6-8B , the locking latch  74  includes a switch  76  and a locking pin  78 , seen as a screw in these views. To adjust tension, the hold switch  76  on the top of the tool  10  is moved to an unlocked position; the adjustment knob  56  is rotated to the desired tension setting; the hold switch  76  is released to the lock position. The precise tension setting is accomplished by rotating the adjustment knob  56  across multiple discrete detent stops  70 . The tension adjustment system preferably includes the Mil Spec 1 through 8 settings, including ½ and ¼ increments. Further, the tension adjustment system may be calibrated at the point of manufacture or may be calibrated in the field. When the device  10  is to be calibrated in the field, a calibration tension tool  80 , may be used, as will be discussed later with reference to  FIGS. 16A-17B . 
     Tension-Lock-Cut System 
     The tension-lock-cut system embodying various features of the invention, and its operation, may be seen in  FIGS. 9-12 . The tension-lock-cut system of the present invention reduces the tool  10  backlash perceived by a user, eliminates dynamic tension on the cable tie  20  during the tension and cut phases, and standardizes cut-off force during the cut phase. To these ends, the tension-lock-cut system includes a tension-lock-cut linkage  82  (see  FIGS. 10A and 10B ). 
     Linkage 
     As seen, the linkage  82  includes a pawl link  28  mounted for horizontal, linear reciprocal movement relative to the housing  12 . The pawl link  28  is supported for linear movement within the housing  12  by way of channels (not shown) formed in the interior wall the housing  12 . A tie gripping pawl  30  is carried at the forwardmost end  84  of the pawl link  28  (see  FIG. 10 ) and is pivotally attached to the pawl link  28 . The gripping pawl  30  is upwardly pivotable, as will be discussed later in greater detail. 
     Referring further to  FIGS. 10A and 10B , the pawl link  28  is reciprocated within the housing  12  by way of an actuating structure located in the trigger  18 , a short link  86 , and a handle link  88 . The trigger  18  includes an elongate, rigid trigger handle link  90  that extends upwardly into the barrel portion  16  of the housing  12 . As seen, the trigger handle link  90  includes two substantially parallel spaced arms  92  at its upper end. Each of the arms  92  includes an aperture  94 . A pair of trigger bearings  96  dimensioned to be closely received in the apertures  94  serves to pivotally mount the trigger handle link  90  within the housing  12  for movement around a substantially horizontal pivot axis  98 . When thus mounted, the trigger  18  is movable from a forward or initial position shown in  FIG. 11A , to a rearward or final position adjacent the handle  14 , as shown in  FIG. 11D . 
     A pair of trigger inner links  100  extends upwardly into the barrel portion  16  of the housing  12  alongside the trigger handle link  90  between the arms  92 . The lower ends  102  of the trigger inner links  100  are pivotally joined to the trigger handle link  90  for pivoting movement around a substantially horizontal pivot axis  104 . The upper ends  106  of the trigger inner links  100  further include apertures  108 . The upper ends  106  support a horizontally disposed dog bone cam shaft  110  that is concentrically aligned with the apertures  94  in the upper ends of the trigger handle link  90  and apertures  108  in the inner trigger links  100 . Intermediate links  112  each comprise rigid, elongate, substantially parallel member that are of arcuate form. The intermediate links  112  are each pivotally joined at their lower ends  114  at a rearward point  116  of the cutter link  118 . The intermediate links  112  are further pivotally joined at their upper ends  120  to the upper ends  106  of the trigger inner links  100  by way of dog bone cam shaft  110 . 
     A rack member  32  having a plurality of upstanding teeth  31  is affixed to the rearwardmost end  122  of pawl link  28 . The rack member  32  is adapted to engagingly support pinion member  34 . Pinion member  34  includes a plurality of teeth members  33  adapted to engage the corresponding teeth members  31  in the rack member  32 . The pinion member  34  further includes an upstanding arm member  124  and pivot members  126 . Pivot members  126  are adapted to support pinion torsion spring  128  (see  FIGS. 10B and 11A ). The pinion torsion spring  128  pivotally biases the pinion  34  toward the cutoff cam  36 , such that the upstanding arm member  124  is in contact with the cutoff cam  36 . 
     The cutoff cam  36  is pivotally mounted for pivotal movement around a substantially horizontal pivot axis  130  and includes a cradle  132  in its upper surface. The dog bone cam shaft  110  ordinarily rests in the cradle  132 . The cutoff cam  36  is preferably further formed with a pair of spaced apart blocks  134  which form a channel  136  at a rearward portion of the cutoff cam  36 . The channel  136  is adapted to receive the upstanding arm member  124  of pinion  34 . It is to be noted that the width of the cradle  132  is preferably of a width great enough to enhance toll longevity and consistent repeatability. 
     As further shown, the linkage  82  also includes a handle link  88  having an upper end extending upwardly and forwardly toward the rear end  122  of the pawl link  28 . A pair of substantially parallel spaced short links  86  is pivotally joined at their forward ends  138  to the trigger inner link  100  at pivot axis  140 . The short links  86  are further joined at their rearward ends  130  to the handle link  88  for pivoting movement around substantially horizontal axis  142 . 
     As mentioned previously, the linkage  82  is coupled to the tension adjustment system through the U-bracket  38 . Forward ends  40  of the U-bracket  38  are pivotally coupled to the rear end of the cutoff cam  36  by means of a pin  42  extending through the forward ends of the U-bracket  38  and through the elongated slot  44  formed in the cutoff cam  36 . 
     Tension Operation 
       FIG. 11A  shows the linkage in its initial, un-actuated state. In this position, the trigger handle link  90  and trigger inner links  100  are fully forward and away from the handle member  14 . The cutoff cam  36  is pivoted in its full clockwise position around the pivot axis  130  under a predetermined tension developed and controlled by the tension adjustment system. This seats the dog bone cam shaft  110  into the cradle  132  and aligns the dog bone cam shaft  110 , the upper end  106  of the inner trigger links  100 , and the upper ends  120  of the intermediate links  112  with pivot axis  144 . 
     As viewed in  FIG. 11B , cable tie tensioning beings when the trigger  18  is squeezed toward the handle or grip portion  14  in the direction of arrow A. As the trigger  18  begins moving, the short link  86  pivots the handle link  88  in a clockwise direction around the pivot axis  146  and against handle torsion spring  148 . At the same time, the handle link  88  draws the pawl link  28  away from the nose piece  150  (see  FIGS. 4 b    and  4 C). As the pawl link  28  begins to move back in the direction of arrow B, the pawl  30  disengages from the nose guide block  152  and begins to pivot upwardly in response to its spring bias, thereby trapping the tie tail  26  between itself and the nosepiece backing plate  154 . This grips the tie tail  26  and pulls the tie tail  26  back along with the pawl  30  and pawl link  28 . This has the further effect of pulling the tie tail  26  through the head portion  24  to tighten the tie  20  around a bundle  22 . 
     When the tie  20  is initially installed and the tie tail  26  is first pulled back, it generates little resistance to being pulled. As the tie  20  draws up against the bundle  22 , the tie tail  26  begins to resist being pulled. The resistance is felt by the pawl link  28  and is transferred through the handle link  88 , the short link  86  and inner trigger link  100  to the dog bone cam shaft  110 . As long as the tie tail  26  does not resist being pulled by the pawl link  28 , little resistance is felt by the handle link  88  as it is pushed back by the short link  86 . As the tie tail  26  begins to resist being pulled, the resistance felt by the pawl link  28  is transferred back through the handle link  88 , the short link  86 , the inner trigger link  100 , and to the dog bone cam shaft  110 . The resistance force transferred by the short link  86  to the inner trigger link  100  tends to pivot the inner trigger link  100  in a clockwise direction about the pivot axis  140 . Such pivoting movement on the inner trigger link  100  is impeded by the dog bone cam shaft  110  that is held in position by the cutoff cam  36 . 
     The resistance force that is transferred to the dog bone cam shaft  110  through inner trigger link  100  tends to rotate the cutoff cam  36  around the cam pivot axis  130 . The cutoff cam  36  resists such rotation due to the restraining force applied to it by the tension control mechanism. The force increases as the tie tail  26  is pulled more snugly, until the resistance force becomes great enough to overcome the force applied to the cutoff cam  36  by the tension control mechanism. When this occurs, the cutoff cam  36  rotates in the counterclockwise direction shown by arrow C in  FIG. 11D . 
     An alternative, low tension arrangement may be seen in the views of  FIGS. 9-9D . When the tool  10  is used in low tension operation, the possibility exists that tension is insufficient to disengage the cutoff cam  36 . In this context, and as shown, the tool  10  may be provided with a cavity  200 , having a spring biased ball bearing  202 . When engaged, the ball bearing  202  provides biasing pressure against the cutoff cam  36  to thereby provide the additional tension necessary for proper tool  10  function in low tension applications. As illustrated, a slidable low tension latch  204  may be moved from a first position to a second position to thereby change the degree of compression on the spring  206  and thereby adjust the degree of ball  202  bias against the cutoff cam  36 . 
     Lock Operation 
     The lock operation may be best viewed in the illustration of  FIG. 11D . As seen, operation of the device has progressed to the point at which the resistance force transferred through the pawl link  28 , the handle link  88 , the short link  86  and inner trigger link  100  to the dog bone cam shaft  110  has become great enough to overcome the force applied to the cutoff cam  36  by the tension control mechanism. As seen, the cutoff cam  36  rotates in the counterclockwise direction shown by arrow C around the cam pivot axis  130 , thereby allowing the dog bone cam shaft  110  to move forwardly, in the direction of arrow D, out of the cradle  132  in the cutoff cam  36 . When this occurs, the pinion  34  rotates in a counterclockwise direction, shown by arrow E, through the biasing action of pinion torsion spring  128 . The pinion  34  continues to rotate in the direction of arrow E until the plurality of pinion teeth members  33  engage corresponding teeth members  31  in the rack  32 . The engagement of pinion teeth members  33  and rack teeth members  31  effectively locks further rearward tensioning of the component parts. It will be appreciated that the advantage provided by the locking of rearward tensioning just prior to the cutoff operation causes the tool  10  to accurately tension the tie tail  26  each time a cut is performed. Further, blade  160  life is increased since the tie tail  26  is stationary during cutoff. This eliminates inadvertent drag of the tie tail  26  across the blade  160  sharp edge which occurs when the tie tail  26  is constantly tensioned during cutoff operation. 
     Cutoff Operation 
     Cutoff of the tie tail  26  and movement of cooperating parts may be viewed in  FIGS. 4D and 12 . As seen, once the pinion  34  and rack  32  have engaged one another and rearward tensioning ceases, intermediate link  112  moves in the direction of arrow F (see  FIG. 12 ). As it does so, it pushes the rear end  116  of the cutter link  118  down in the direction of arrow G (see  FIG. 11D ). This movement pivots the cutter link  118  around the cutter link axis  162  thereby causing the cutter link  118  to raise the blade member  160  in the direction of arrow H, and thereby cut off the tie tail  26 . When the tie tail  26  is cut, it no longer applies a resisting force to the pawl link  28  and the tool  10  returns to the original condition seen in  FIG. 4A . 
     Ergonomics 
     The present device  10  is further provided with certain features designed to improve the ergonomics of the device. As may be viewed particularly in  FIGS. 13A-14C , the device  10  may include protective coverings, or boots  170 , over certain areas of user interface. 
     With particular reference to  FIGS. 13A-13C , it may be seen that the handle portion  14  may include a handle boot  170 . The handle boot  170  is preferably fabricated of soft, elastomeric material, such as rubber, or other suitable resilient material that will conform to the user&#39;s hand (not shown). The boot  170  may be joined to the handle member  14  by way of a key lock system as is shown, wherein key members  172  are molded as a part of the boot  170 , with key members  172  adapted to be engaged in lock apertures  168  in the handle member  14 . As may be seen with particular reference to  FIG. 13C , while in the installed position, the handle boot  170  and the handle member  14  interact to create a air bladder  174 . The air bladder  174 , in conjunction with the soft characteristic of the handle boot  170 , creates a trampoline effect during use of the tool  10 . For example, as the user&#39;s hand pushes against the handle boot surface  171 , the air bladder  174  and boot  170  conform to the user&#39;s hand thereby reducing user fatigue and discomfort. 
     As may be viewed in  FIGS. 14A-14C , the device  10  is seen to further include a trigger boot  170 A. Similar to the handle boot  170 , the trigger boot  170 A is preferably formed of a soft, elastomeric material, such as rubber, or other suitable resilient material that will conform to the user&#39;s hand. As in the handle boot  170 , the trigger boot  170 A may be joined to the trigger member  18  by way of a key lock system. In the case of the trigger boot  170 A key members  172  may be formed as a part of the trigger member  18 , which are adapted to be engaged in lock apertures  168  formed in the trigger boot  170 A. 
     The overall design and mentioned ergonomic improvements to the tool  10  are known to improve measurable applied grip force, thereby reducing musculoskeletal injury to the user and improving work environment safety. For example, when rated on the Borg-10 rating of perceived exertion scale, users consistently rated the tool  10  as requiring less than “moderate” effort as compared to other prior art tools. (See Borg, G. A.,  Psychophysical Bases of Perceived Exertion, Med Sci Sports Exerc.  1982; 14(5): 377-81 for discussion of the Borg-10 scale). Further, when evaluated using the Strain Index, (see Moore J S, Garg A.,  The Strain Index: A Proposed Method to Analyze Jobs for Risk of Distal Upper Extremity Disorders, Am Ind Hyg Assoc J.  1995 May; 56(5): 443-458), the present tool  10  resulted in more “low risk” scenarios as compared to other prior art tools. The Strain Index is a semi-quantitative evaluation method that considers several exposure variables to determine the risk of user musculoskeletal disorders. Variables include intensity of effort, efforts per minute, percent duration of exertion, among others. 
     Blade Interface 
     With attention now to  FIGS. 15A and 15B , it may be seen that the forwardmost end of the device  10  barrel  16  carries a nosepiece  150 . The nosepiece  150  preferably includes a blunt, substantially vertical planar face  151  adapted to butt up against the head  24  of a cable tie  20  (not seen in these views) when the tie  20  is tensioned. The nosepiece  150  further includes an upper, horizontal portion  153  that, in cooperation with the face  151  defines a slot  156  for receiving the tie tail portion  26  of the cable tie  20 . As may be further seen, the slot  156  may be open toward the left side of the device  10  so that the tail  26  may be inserted into the device  10  from the side. A nose guide block  152  positioned behind the nose piece  150  defines a lower surface for supporting the underside of the tie tail  26 . 
     As further viewed in  FIGS. 15A and 15B , the sharpened blade member  160  is located immediately behind the nose piece  150  and the nose guide block  152 . Blade member  160  is confined between a pair of vertical channels  157  defined between the nosepiece  150  and the housing  12  which permit the blade member  160  to reciprocate vertically behind the nosepiece  150 . As further seen, the blade member  160  includes a blade link aperture  161  arranged to secure the forward end  119  of the cutter link  118  therethrough and thereby carry the blade member  160  on the cutter link  118  during reciprocation of the cutter link  118  while cutting. 
     With specific reference to  FIG. 15A , it may be seen that the blade member  160  further includes a blade perimeter  158  having a beveled portion  159 . As seen, the beveled portion  159  corresponds to a respective beveled area  164  on the housing  12 . The blade beveled portion  159  is configured to allow single directional mounting of the blade  160  by the user. This feature alleviates improper blade  160  mounting during replacement or repair. Correct blade  160  mounting further increases the longevity of both the blade member  160  and the tool  10 . Further, the beveled portion  159  gives a well understood indication to users of correct blade  160  placement, thereby increasing user efficiency during blade replacement. 
     Calibration 
     As mentioned previously, the tension adjustment system may be calibrated at the point of manufacture or may be calibrated in the field. Calibration sets the base tension point from which the further tension adjustments, discussed previously, may be made. During calibration, a calibration tension tool  80  may be used. 
     With specific reference to  FIGS. 16A-17B , a calibration tension tool  80  for use with the present device  10  may be seen. As seen, the calibration tension tool  80  includes a first side  180  and a second side  182 . As viewed particularly in  FIG. 16A , the first side  180  preferably includes a plurality of upstanding protuberances  184 . Illustrated in  FIG. 16B  is the second side  182  of calibration tension tool  80  and showing an upstanding, elongate key device  186 . As shown, the key device  186  may further include at least one pin portion  188 . Use of the calibration tension tool  80  may be viewed in  FIGS. 17A and 17B . As seen in  FIG. 17A , the first side  180  of calibration tool  80  may be used to remove the calibration cap  190 . As seen, the protuberances  184  engage corresponding detents  191  in the calibration cap  190  while the calibration tool  80  rotates in the direction of arrow F to twist off the calibration cap  190 . With the calibration cap  190  removed, and as seen in  FIG. 17B , the key device  186  on the second side  182  of calibration tool  80  along with pin portions  188  engage the tension calibration nut  52  in corresponding detents  192 . The calibration tool  80  is then rotated in the direction of arrow G to thereby rotate the tension shaft  50  and rotating cam  54  to a predetermined tension position. It is to be noted that rotation of the tension shaft  50  may be in clockwise or counterclockwise direction, depending on whether the user wishes to set calibration at a higher or lower set tension. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention.