Folding cutting system

Abstract

A cutting instrument is provided which includes a frame member, a blade body member, a blade element, an acute angle end point, a pivot element and a blade retention cavity. The body member can provide a blade element which is concave and through which a lifting edge which cuts and a retention edge which cuts can both combine to provide a centering feature. This centering feature can be enhanced by blade body designs which also center through the use of an offset concave element. The frame member can include a thumb rest as well as a rotational restraining element which are diametrically opposed and which can present roughly orthogonal forces.

I claim:  
     
         1 . A cutting system comprising: 
 a frame member;    a blade body member which is responsive to said frame member;    a blade element connected to said blade body member which is held by said blade body member wherein said blade element is removable and has a straight cutting edge and an end;    an acute angle end point presented at said end of said blade element;    a pivot element connected to said frame member and said blade body member which permits said blade body member to pivot with respect to said frame member; and    a blade retention cavity on said frame member wherein said blade retention cavity is configured to shield at least a portion of said cutting edge of said blade element when said blade body member is pivoted with respect to said frame member.    
     
     
         2 . A cutting system as described in  claim 1  wherein said an acute angle end point presented at said end of said blade element comprises a dual straight edge element.  
     
     
         3 . A cutting system as described in  claim 1  and further comprising a retaining element that holds said blade element with respect to said blade body member and wherein said retaining element is positioned approximately equidistant between said pivot element and said acute angle end point.  
     
     
         4 . A cutting system as described in  claim 1  and further comprising a releasable pivot lock to which said blade body member is responsive and which detachably prevents said blade element from pivoting with respect to said frame member.  
     
     
         5 . A cutting system as described in  claim 4  wherein said releasable pivot lock locks said blade element at three roughly orthogonal positions.  
     
     
         6 . A cutting system as described in  claim 4  wherein said blade element and said blade body are pivoting elements, and wherein said releasable pivot lock comprises: 
 a locking mechanism to which said blade element is responsive; and  
 a spring element which yieldably urges said locking mechanism against at least one of said pivoting elements.  
 
     
     
         7 . A cutting system as described in  claim 4  wherein said blade element and said blade body are pivoting elements, and wherein said releasable pivot lock comprises: 
 a pin to which said blade element is responsive; and  
 a spring element which yieldably urges said pin against at least one of said pivoting elements.  
 
     
     
         8 . A cutting system as described in  claim 1  wherein said blade retention cavity is adapted for insertion of a replaceable blade, and further comprising a retaining element wherein said replaceable blade is adapted to be held against said blade body member by said retaining element.  
     
     
         9 . A cutting system as described in  claim 8  wherein said retaining element comprises a single retaining element.  
     
     
         10 . A cutting system as described in  claim 1  wherein said frame member has an external frame surface, wherein said blade body member has an external blade body surface, and wherein said external frame surface and said external blade body surface present aligned shapes when said blade body member is pivoted with respect to said frame member so that at least a portion of said cutting edge of said blade element is shielded by said blade retention cavity.  
     
     
         11 . A cutting system as described in  claim 1 , wherein said frame member comprises a frame member having at least one finger hole.  
     
     
         12 . A cutting system as described in  claim 11 , further comprising an enhanced friction rotational restraint element located on said frame member adjacent at least one finger hole and substantially diametrically opposed with respect to said thumb rest.  
     
     
         13 . A cutting system as described in  claim 1 , wherein said cutting edge comprising: 
 a lifting edge; and    a retention edge configured such that said lifting edge and said retention edge form an edge concave feature with respect to each other.    
     
     
         14 . A cutting system as described in  claim 1 , and further comprising a cut material centering element behind at least a portion of said cutting edge.  
     
     
         15 . A cutting system as described in  claim 14 , wherein said cut material centering element comprises a concave feature.  
     
     
         16 . A cutting system as described in  claim 14 , wherein said blade body member is tapered and wherein said cut material centering element comprises said tapered blade body member.  
     
     
         17 . A cutting system as described in  claim 1  and further comprising a thumb rest to which said frame member is responsive and which in use acts to cause a force which is substantially perpendicular to at least a portion of said blade element.  
     
     
         18 . A cutting system as described in  claim 11 , wherein said frame member presents a spatial relation with respect to a cutting surface when used with a finger through said at least one finger hole in said frame member, and further comprising a substantially planer lifting edge and a substantially planer retention edge each form an angle with respect to said cutting surface when said frame member is positioned in said spatial relation, and wherein said angle of said substantially planer lifting edge with respect to said cutting surface is less than 90 degrees while the angle of said substantially planer retention edge with respect to said cutting surface is about 90 degrees.  
     
     
         19 . A method of operating a cutting instrument comprising the steps of: 
 manually holding a cutting instrument, having a frame member and having a blade element removably inserted into a blade body member wherein said blade element has a straight cutting edge and an end;    presenting an acute angle end point at said end of said blade element to at least a portion of a material;    cutting at least a portion of said material through action of said cutting instrument;    removing said cutting instrument from proximity to said material;    pivoting said blade element and said blade body member with respect to said frame member;    inserting said straight cutting edge of said blade element into said frame member; and    shielding at least a portion of said straight cutting edge of said blade element by said frame member.    
     
     
         20 . A method of operating a cutting instrument as described in  claim 19  wherein said step of presenting said acute angle end point at said end of said blade element to at least a portion of a material comprises the step of presenting said acute angle end point having a dual straight edge element at said end of said blade element to at least a portion of a material.  
     
     
         21 . A method of operating a cutting instrument as described in  claim 19  wherein said step of pivoting said blade element and said blade body member with respect to said frame member establishes a pivot point and further comprising the step of retaining said blade element by a retaining element that holds said blade element with respect to said blade body member and wherein said retaining element is positioned approximately equidistant between said pivot point and said acute angle end point.  
     
     
         22 . A method of operating a cutting instrument as described in  claim 19  wherein said cutting instrument has a blade back portion and a frame front portion and wherein said step of pivoting said blade with respect to said frame member comprises the step of aligning at least a portion of said blade back portion and said frame front portion.  
     
     
         23 . A method of operating a cutting instrument as described in  claim 19  and further comprising the step of locking said blade with respect to said frame member.  
     
     
         24 . A method of operating a cutting instrument as described in  claim 23  wherein said step of locking said blade with respect to said frame member comprises the steps of: 
 biasing a locking mechanism in the vicinity of said blade element; and  
 positioning at least a portion of said locking mechanism against at least a portion of said blade element.  
 
     
     
         25 . A method of operating a cutting instrument as described in  claim 23  wherein said step of locking said blade with respect to said frame member comprises the steps of: 
 biasing a pin in the vicinity of said blade element; and  
 positioning at least a portion of said pin against at least a portion of said blade element.  
 
     
     
         26 . A method of operating a cutting instrument as described in  claim 23  and further comprising the step of releasing said lock after accomplishing said step of locking said blade with respect to said frame member.  
     
     
         27 . A method of operating a cutting instrument as described in  claim 19  wherein said cutting instrument has a blade and a blade body member having a slit adapted for insertion of a replaceable blade and a retaining element, and further comprising the steps of: 
 removing said blade from said blade body member;  
 replacing said blade with a replacement blade;  
 inserting said replacement blade in said slit in said blade body member; and  
 retaining said replacement blade in said blade body member.  
 
     
     
         28 . A method of operating a taxidermy and field-dress cutting instrument as described in  claim 19 , further comprising the step of pressing a finger against a frictionally enhanced portion on said cutting instrument adjacent at least one finger hole and diametrically opposed with respect to said portion of said cutting instrument to which a thumb is pressed.  
     
     
         29 . A method of taxidermy and field-dress cutting as described in  claim 28  further comprising a step of pressing a thumb against a portion of said cutting instrument and wherein said step of pressing a finger against a frictionally enhanced portion of said cutting instrument act to accomplish the step of creating roughly orthogonal forces on said cutting instrument.