Positionable linear friction lock assembly

Abstract

An infinitely positionable linear friction lock assembly utilizes a single friction spring coaxially disposed about a translating rod within an elongated housing. A bias bushing is provided for slidably supporting the rod. The bushing defines a sloped shoulder against which the friction spring hears, with the angle of the shoulder calibrated to provide an increased holding force up to a predetermined axial force on the rod, and permitting the rod to slip at greater axial forces without disturbing the integrity of the spring or its coils. The assembly includes a release or actuation lever having a cap bushing integrated therein to support the rod and keep the actuation lever in alignment.

What is claimed is:  
     
         1 . An infinitely positionable linear friction lock assembly having a predetermined axial slip force, the lock comprising: 
 a housing;    a bias bushing engaged to said housing, said bushing defining a bore therethrough, the bore defining a longitudinal axis, and said bushing further defining a spring seat at one end of said bore, said spring seat including a sloped shoulder;    a rod slidably extending through said bore of said bushing along said longitudinal axis;    a coil spring positioned around and coaxial with said rod, said spring having a normal inside diameter smaller than the diameter of said rod, said spring having a first end in contact with said sloped shoulder;    said sloped shoulder inclined relative to said longitudinal axis at an angle sized to asymmetrically compress said spring on said rod, upon application of an axial force on said rod in a first direction less than a predetermined axial slip force, said angle further sized to maintain the integrity of the spring while allowing the rod to slip through the spring upon application of an axial force or said rod greater than said predetermined axial slip force.    
     
     
         2 . The infinitely positionable linear friction lock assembly of  claim 1 , wherein: 
 said predetermined sloped shoulder is between 10 and 30 degrees.    
     
     
         3 . The infinitely positionable linear friction lock assembly of  claim 2 , wherein: 
 said sloped shoulder is preferably less than 25 degrees from perpendicular to axis of said rod.    
     
     
         4 . The infinitely positionable linear friction lock assembly of  claim 2 , wherein: 
 said sloped shoulder is approximately 25 degrees from perpendicular to axis of said rod.    
     
     
         5 . The infinitely positionable linear friction lock assembly of  claim 2 , wherein: 
 said coil spring has a first tang at said first end of said spring, said first tang protruding radially outward from said spring; and    said bias bushing has a first catch, said first catch engaging said first tang.    
     
     
         6 . The infinitely positionable linear friction lock assembly of  claim 5 , wherein: 
 said first catch is an axial slot defined in said spring seat.    
     
     
         7 . The infinitely positionable linear friction lock assembly of  claim 6 , wherein: 
 said bias bushing is fixedly engaged at one interior end of said housing; and    
     
     
         8 . The infinitely positionable linear friction lock assembly of  claim 7 , further comprising: 
 a release mechanism defining an opening for engaging a second end of said spring and having a lever for actuating said release mechanism, to applying an unwinding torsion to said spring.    
     
     
         9 . An infinitely positionable linear friction lock assembly comprising: 
 a housing;    a bias bushing engaged to said housing, said bushing defining a bore therethrough and defining a counterbored spring seat at one end of said bore;    a rod located through said bore of said bushing;    a coil spring positioned around and coaxial with said rod, said spring having a normal inside diameter smaller than the diameter of said rod, said spring having a first end in contact with said spring seat; and    a release mechanism defining an opening for engaging a second end of said spring and having an actuator for applying an unwinding torsion to said spring.    
     
     
         10 . The infinitely positionable linear friction lock assembly of  claim 9 , wherein: 
 said coil spring has a first tang at said first end of said spring and a second tang at said second end, said tangs protruding radially outward from said spring ends;    said bias bushing defining a first catch for receiving said first tang;    said release mechanism defining a second catch for contacting and rotationally displacing said second tang upon actuation of said actuator, whereby said second catch applies an unwinding torsion to said spring, increasing the inside diameter of the spring, and permitting axial translation of said rod.    
     
     
         11 . The infinitely positionable linear friction lock assembly of  claim 10 , wherein 
 said release mechanism further comprises: 
 a C-shaped tube portion for receiving said second spring end, said tube portion having a first slotted notch protruding across an interior segment of said tube portion and contacting said second spring end; and  
 wherein said actuator is a lever portion attached to said tube portion.  
   
     
     
         12 . The infinitely positionable linear friction lock assembly of  claim 11 , further comprising: 
 a window defined by an axial wall portion of said housing, said lever portion protruding from an interior of said housing through said window.    
     
     
         13 . The infinitely positionable linear friction lock assembly of  claim 12 , wherein: 
 said lever defines a slot for engaging an actuating cable.    
     
     
         14 . The infinitely positionable linear friction lock assembly of  claim 12 , further comprising: 
 a cap bushing engaged to said housing and having an interior lip at a first end, said lip coupled with said tube portion of said lever, and said tube portion positioned between said second spring end and said cap bushing.    
     
     
         15 . The infinitely positionable linear friction lock assembly of  claim 14 , wherein said lock assembly measures less than 31 millimeters in length.  
     
     
         16 . The infinitely positionable linear friction lock assembly of  claim 12 , wherein: 
 said first tang is located 180° relative to said second tang.    
     
     
         17 . An infinitely positionable linear friction lock assembly comprising: 
 a housing;    a bias bushing attached at one interior end of said housing, said bushing defining a bore therethrough and defining a counterbored spring seat at one end of said bore, a base of said spring seat defining a sloped shoulder;    a rod located through said bias bushing bore;    a coil spring positioned around and coaxial with said rod, said spring having a first end in contact with said spring seat;    a release mechanism defining a tube portion for receiving a second end of said spring;    said release mechanism further defining a lever portion attached to said tube portion and for actuating said tube portion; and    a cap bushing attached at an opposite interior end of said housing, said cap bushing defining a bore therethrough and defining an interior lip at a first end of said bore, said lip coupled with said tube portion of said release mechanism, and said tube portion positioned between said second spring end and said cap bushing.    
     
     
         18 . The infinitely positionable linear friction lock assembly of  claim 17 , wherein: 
 said housing is cylindrical;    said cap bushing is positioned in said housing to align said tube portion coupled to said lip with the axis of said housing and to prevent contact of said tube portion with said housing; and    said cap bushing is further positioned in said housing to align said cap bushing bore with said bias bushing bore, thereby providing smooth movement of said rod through said bores.    
     
     
         19 . The infinitely positionable linear friction lock assembly of  claim 18 , wherein: 
 a lock assembly comprised of at least said housing, said bias bushing, said cap bushing, and said coil spring, measures less than 31 millimeters long.    
     
     
         20 . An infinitely positionable linear friction lock assembly having a predetermined axial slip force, the lock comprising: 
 a cylindrical housing, said housing defining a window in an axial wall portion of said housing;    a mounting bracket attached to said housing;    a bias bushing engaged to a first end of said housing, said bushing defining a bore therethrough and defining a counterbored spring seat at one end of said bore, a base of said spring seat defining a sloped shoulder, said slope shoulder between 10 and 30 degrees from a perpendicular axis to said bore;    a rod located through said bore of said bushing, said rod defining a flange end;    a coil spring positioned around and coaxial with said rod, said spring having a normal inside diameter smaller than the diameter of said rod, said spring having a first end in contact with said sloped shoulder, said coil spring having a first tang at the first end of said spring and a second tang at a second end of said spring, said tangs protruding radially outward from said spring;    said bias bushing having a first catch for engaging said first tang;    said sloped shoulder inclined high enough relative to said first spring end to asymmetrically compress said spring on said rod, inhibiting translation of said rod relative to said spring upon application of an axial load on said rod in a first direction, while inclined low enough relative to said first spring end that said rod slips through said spring upon application of an axial force that exceeds the predetermined axial slip force;    a release mechanism defining a tube portion for receiving said second end of said spring, said tube portion have a second catch for contacting and rotationally displacing said second tang, said release mechanism also having a lever portion for actuating said tube portion and protruding from an interior of said housing through said housing window; and    a cap bushing attached at a second opposite interior end of said housing, said cap bushing defining a bore therethrough and defining an interior lip at a first end of said bore, said lip coupled with said tube portion of said release mechanism, and said tube portion positioned between said second spring end and said cap bushing.    
     
     
         21 . The infinitely positionable linear friction lock assembly of  claim 20 , wherein said lock measures less than 31 millimeters long.