Patent Publication Number: US-2013247385-A1

Title: Compound wire rope cutter

Description:
CLAIM OF PRIORITY 
     This application claims priority from Provisional Application Ser. No. 61/614,702, filed on Mar. 23, 2012, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     This disclosure relates to wire rope cutters. More particularly, this disclosure relates to wire rope cutters with a compound mechanical advantage. 
     Existing cutting tools which may use a mechanical advantage are sometimes used in the arbor industry for cutting small diameter wire rope. Some existing cutters supposedly utilizing a compound mechanical advantage so that the cutting jaws are better enabled to open further. The opposite is actually the case. The handles must be opened further than with a single stage cutter in order to open an equivalent amount to a single stage cutter. 
     An example of an existing compound lever cutter is shown in U.S. Pat. No. 92,092. However, the cutter mechanism in U.S. Pat. No. 92,202 is used in the arbor industry and does not save space or overall length. 
     Existing cutting tools utilize a fulcrum method to generate additional force for the purpose of cutting through wire rope. (See  FIG. 1 ). This results in a mechanical advantage which is typically defined as the ratio of the output force created by a mechanism divided by the applied input force. However, due to the length of a handle from a pivot compared to the length of the cutting jaw, a single mechanical advantage is developed. The mechanical advantage (MA) is defined as the pivot handle length divided by the pivot jaw length or: 
         MA =Pivot Handle Length/Pivot Jaw Length 
     Thus, there exists a need for a wire rope cutter which has a compound mechanical advantage. There also exists a need for a compound cutter which is nested and has a reduced overall length. 
     Other benefits and aspects of the disclosure will become apparent upon a reading and understanding of the following detailed description. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the disclosure, a wire rope cutter has a first handle and a second handle; a first lever and a second lever; a first cutting jaw and a second cutting jaw; wherein the first cutting jaw is formed at a distal end of said first lever; said second cutting jaw is formed at a distal end of the second lever; a first pivot for pivotally connecting the first handle and the second handle; a second pivot for pivoting connecting the first lever to the first handle; a third pivot for pivotally connecting the second lever to the second handle; and a fourth pivot for pivotally connecting the first lever to the second lever. 
     In accordance with another aspect of the disclosure, a compound wire rope cutter assembly has a first handle and a second handle having a first pivot connecting the first and second handles; a first cutting jaw half and a second cutting jaw half, wherein the first cutting jaw half is connected to the first handle via a second pivot; wherein the second cutting jaw half is connected to the second handle via a third pivot; and wherein the first cutting jaw half and the second cutting jaw half are connected by a fourth pivot; wherein a compound mechanical advantage is defined by a first mechanical advantage defined by a pivot lever length and a pivot jaw length, and a second mechanical advantage defined by a handle length and a pivot handle length. 
     Another aspect of the disclosure is a compound mechanical advantage formed by a first mechanical advantage and a second mechanical advantage. 
     Other aspects of the disclosure will become apparent upon a reading and understanding of the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an existing cutter which uses a fulcrum method to generate additional force; 
         FIG. 2  illustrates a perspective view of a compound wire rope cutter in accordance with a preferred embodiment of the present disclosure; 
         FIG. 3  illustrates a top plan view of the compound wire rope cutter of  FIG. 2 ; 
         FIG. 4  illustrates a partial top plan view of the cutter in an opened position; 
         FIG. 5  illustrates a perspective view of the cutter of  FIG. 2  cutting a wire rope; 
         FIG. 6  illustrates a top plan view of the cutter of  FIG. 2  in a fully opened position; 
         FIG. 7  illustrates an exploded perspective view of the cutter of  FIG. 2 ; 
         FIG. 8  illustrates a top plan view of a forward toggle cutter in accordance with another aspect of the disclosure; 
         FIG. 9  illustrates a chart illustrating a mechanical advantage between an existing cutter, a reverse toggle and a forward toggle cutter; 
         FIG. 10  illustrates a chart showing maximum handle forces of a cutter in accordance with the present disclosure versus an existing cutter; 
         FIG. 11  illustrates a perspective view of a cutter jaw with a grease port option in accordance with another aspect of the disclosure; and 
         FIG. 12  illustrates a transparent perspective view of the cutter jaw of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The present disclosure relates to wire rope cutters. More particularly, it relates to a wire rope cutter having a compound mechanical advantage. 
     Existing cutter tools typically use a single fulcrum method to generate additional force for the purpose of cutting through wire rope. Referring to  FIG. 1 , an existing cutter tool has a pivot handle  10  which has a pivot handle length (L 1 ) of e.g., about 18.25 inches. A jaw  12  has a pivot jaw length (L 2 ) of e.g., about 0.562 inches. The force applied at the jaw is shown as Fj and the force applied at the handle is shown as Fh. The force is applied as pounds force. Due to the length of the handle from the pivot when compared to the length of the cutting jaw to the pivot a mechanical advantage (MA) is developed as the pivot handle length (L 1 ) divided by the pivot jaw length (L 2 ), or: 
     
       
         
           
             MA 
             = 
             
               
                 L 
                  
                 
                     
                 
                  
                 1 
               
               
                 L 
                  
                 
                     
                 
                  
                 2 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             32.44 
             = 
             
               18.25 
               0.562 
             
           
         
       
     
     Thus the mechanical advantage is 32.44. 
     Referring now to  FIGS. 2-7 , a compound wire rope cutter in accordance with a preferred embodiment of the disclosure is shown. A compound mechanical advantage is defined as a mechanical advantage combined with or superimposed onto another mechanical advantage. The force applied at the jaw is shown as Fj and the force applied at the levers is shown as Fl and the force applied at the handle is shown as Fh. The force is applied as pounds force. 
     Referring to  FIG. 2 , the cutter in accordance with one aspect of the disclosure has handles  20 ,  22  which are preferably symmetrical and preferably made of aluminum and are corrosion resistant. Each handle has an angled or curved portion  21 ,  23  ( FIG. 7 ) which are angled in opposite directions to which the levers  32 ,  34  are pivotally mounted. Ends of the curved portions  21 ,  23  curve each other in an assembled configuration. 
     Referring to  FIG. 7 , portion  21  a pair of openings  25 ,  27 , wherein opening  25  aligns with opening  29  of portion  23  to form handle pivot  36 . A bolt, flange washer and nut assembly  37  is used to pivotably retain portion  21  to portion  23  via openings  25 ,  29 . Opening  27  of portion  21  aligns with opening  39  of lever  32  to form lever pivot  30 . Nut  33 , flange washer  35 , bolt  43  and washer  17  retains portion  21  to pivot  32  to form lever pivot  30 . 
     Opening  31  of portion  23  aligns with opening  41  of lever  34  to form lever pivot  28 . Bolt  43 , nut  33  and flange washer assembly  35 ,  17  pivotably retains portion  31  to lever  34 . 
     Opening  45  of jaw  42  and opening  47  of jaw  44  together form pivot  40  for cutting jaws  42 ,  44 . Bolt, nut and washer assembly  19  pivotably retain jaw  42  to jaw  44  to form jaw pivot  40 . 
     Lever  34  has a first curved portion  49  and a second curved portion  51  which form the jaw  44 . Curved portion  51  is curved in an opposite direction to a curved portion  49 . Similarly, lever  32  has a first curved portion  53  and a second curved portion  55  which forms jaw  42 . Portion  53  curves in an opposite direction to portion  55 . 
     Due to lower handle forces, lighter weight material such as aluminum can be used. The handles can have grips  24 ,  26  formed of a suitable grippable material such as an extruded Santoprene™. However, other materials are also contemplated by the disclosure. 
     There are two lever pivots  28 ,  30  for levers  32 ,  34  and handle pivot  36  for handles  20 ,  22 . A jaw pivot  40  is used for pivoting cutting jaws  42 ,  44 . Cutting jaws  42 ,  44  are symmetrical and are preferably made of a steel alloy. The pivots  28 ,  30 ,  36 ,  40  form the nested compound force multiplier section of the cutter. 
       FIGS. 3-7  and the discussion below illustrate approximate dimensions for the various lengths. These dimensions are provided for illustrative purposes and show one example of the calculation of a mechanical advantage. Other sizes, configurations and dimensions are contemplated by the disclosure. 
     Referring now to  FIG. 3 , the handle length L 3  can be about 16.925 inches from an end of the handle (where force Fh is applied) to the handle pivot  36 . The pivot lever length L 4 , i.e., the distance between jaw pivot  40  and lever pivots  28 ,  30  (where force Fl is applied) is about 2.144 inches. The pivot jaw length L 5 , i.e., the distance between jaw pivot  40  and an inner edge of the jaw (where force Fj is applied) is about 0.622 inches. The pivot handle length L 6 , i.e., the distance between handle pivot  36  and lever pivots  28 ,  30  is about 1.200 inches. Thus, the first mechanical advantage MA 1  is calculated as follows: 
     MA 1  is the pivot lever length L 4  divided by the pivot jaw length L 5 , or: 
     
       
         
           
             
               MA 
                
               
                   
               
                
               1 
             
             = 
             
               
                 L 
                  
                 
                     
                 
                  
                 4 
               
               
                 L 
                  
                 
                     
                 
                  
                 5 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             3.45 
             = 
             
               2.144 
               0.622 
             
           
         
       
     
     Thus, the first mechanical advantage MA 1  is approximately 3.45. The second mechanical advantage MA 2  is calculated as the handle length L 3  divided by the pivot handle length L 6 , or: 
     
       
         
           
             
               MA 
                
               
                   
               
                
               2 
             
             = 
             
               
                 L 
                  
                 
                     
                 
                  
                 3 
               
               
                 L 
                  
                 
                     
                 
                  
                 6 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             14.10 
             = 
             
               16.925 
               1.200 
             
           
         
       
     
     Thus, the second mechanical advantage MA 2  is approximately 14.10. The overall compound mechanical advantage MAC, at this particular angle of handle opening, is MA 1  multiplied by MA 2  or MA 1 ×MA 2  or 3.45×14.10=48.66. Thus, compound mechanical advantage MAC is approximately 48.66. 
     Thus, the advantage of the present disclosure when compared to an existing tool is therefore 48.66/32.44=1.5. In other words, the present disclosure tool requires less force, or 1/1.5 or approximately two-thirds or about 0.67 times the amount of force required as an existing tool to cut a wire rope; again, at this particular angle of handle opening. 
     The compound mechanical advantage of the present disclosure is different when the tool is opened to allow the insertion of the largest diameter wire rope (i.e., about 10mm). That is, the opening L 11  between the jaws is about 10 mm (see  FIG. 6 ). 
     Referring now to  FIG. 4 , the handle length L 7 , i.e., the distance from an end of the handle (where force Fh is applied) to the handle pivot  36  is about 5.578 inches. The pivot lever length L 8 , i.e., the distance between lever pivots  28 ,  30  and jaw pivot  40  is about 1.780 inches. The pivot handle length L 9 , i.e., the distance between lever pivots  28 ,  30  l and pivot  36  is about 0.099 inches. The pivot jaw length L 10 , i.e., the distance between pivot  40  and the inside edge of a jaw is about 0.664 inches. The relationship between the first and second mechanical advantages is the same as before, but the torque lengths are different as shown in  FIG. 5 . Specifically, a first mechanical advantage is defined as the pivot lever length L 8  divided by the pivot jaw length L 10 , or: 
     
       
         
           
             
               MA 
                
               
                   
               
                
               3 
             
             = 
             
               
                 L 
                  
                 
                     
                 
                  
                 8 
               
               
                 L 
                  
                 
                     
                 
                  
                 10 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             2.681 
             = 
             
               1.780 
               0.664 
             
           
         
       
     
     and
 
The second mechanical advantage is defined as the handle length L 7  divided by the pivot handle length L 9 , or:
 
     
       
         
           
             
               MA 
                
               
                   
               
                
               4 
             
             = 
             
               
                 L 
                  
                 
                     
                 
                  
                 7 
               
               
                 L 
                  
                 
                     
                 
                  
                 9 
               
             
           
         
       
       
         
           or 
         
       
       
         
           
             56.343 
             = 
             
               5.578 
               0.099 
             
           
         
       
     
     Thus, overall compound mechanical advantage MAC 2  in this case is MA 3  multiplied by MA 4  or MA 3 ×MA 4 =2.681×56.343=151.06. 
     That is, the compound mechanical advantage MAC 2  is approximately 151.06/48.66=3.1 times greater than when the tool is closed as in the previous case. 
     The tradeoff between the closed and open tool is the amount of jaw closure relative to the angle movement of the handles. For example, when the tool is opened the amount of jaw closure is proportionately smaller when the handles proceed to close. 
     This is significant since the force required to initiate the cutting is greatest for the largest diameter wire rope. From an ergonomic point of view the handles are at their further apart configuration. 
     Therefore, the compound mechanical advantage is greatest when the wire rope is of the largest diameter. This is a distinct advantage over the single mechanical advantage of many existing tools and the forward toggle design as used by others. 
     Referring now to  FIG. 8 , a “forward toggle” or jaw lever  50  which operates in an opposite fashion to a reverse toggle cutter is shown. The greatest compound mechanical advantage is when the handles are closed. At this point the cut is complete and the benefit of a high mechanical advantage is not utilized. 
     A chart illustrated in  FIG. 9  shows an approximate relationship between the three (3) different cutters, i.e., a forward toggle cutter, a reverse toggle cutter and an existing single mechanical advantage cutter. 
     While the theoretical static loading of these hand tools yield mechanical advantage factors, the actual kinematics of the cutting process is more involved. For purposes of calculations, it is assumed, for sake of convenience, that the blade shapes and swing motion when cutting are the same, when in fact they vary. Additionally the wire rope, how much it flattens during cutting and other kinematic factors as to where in the compound mechanism cutting occurs will vary from theoretical values. 
     Ultimately, the advantage of the tool of the present disclosure tool is that it yields a lower required handle force to cut the same diameter and type of wire rope. 
     Referring now to  FIG. 10 , a chart is shown illustrating the maximum measured handle forces the cutter of the present disclosure versus an existing cutter. The results were then normalized to the highest handle cutting force required with the existing tools. It is apparent from  FIG. 10  that the lower maximum cutting handle forces are required across the range of wire rope diameters in the present disclosure tool. 
     Referring now to  FIGS. 11 and 12 , the compound cutting feature of the present disclosure is improved with the addition of a lubricant film between the cutting jaws for purposes of reducing friction. With time, the grease can dissipate across wire rope cuts and travel outside the cutting jaws themselves. One option to relieve this concern is to require the customer to disassemble the compound section of the tool and reapply the lubricant film. The effort is more involved than the next mentioned alternative and is possibly prone to errors during reassembly. 
     In accordance with another aspect of the disclosure, as seen in  FIGS. 11 and 12 , a grease pocket or port  62  can be provided in and located between cutting jaw halves  60 . A threaded grease insert channel  64  extends to a grease port  66  which in turn is connected to grease pocket  62 . A threaded plug  68  is used to plug the channel  64 . 
     The channel  64  can be refilled via a provided grease supply with a threaded connector without having to disassemble the compound jaw cutting section. While grease channels  64  and pockets  62  may exist to equipment, fasteners and other components, application to a cutting tool in such in the manner shown is unique. 
     The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the above description and the appended claims or the equivalents thereof.