Plant stem breaking apparatus and method

Abstract

A stem breaking apparatus includes a roller having unevenly spaced radial projections and is useful in a method of extracting bast fibers from a plant stem. The roller is one of a pair of intermeshed counter-rotating rollers between which the plant stem is passed to break the woody core of the stem for separation from the bast fibers. Pairs of adjacent projections are angularly spaced by a larger amount that the individual projections of each pair. The rollers provide a larger support span than conventional stem-breaking rollers, resulting in gentler breaking of the woody core and preventing or eliminating the kinks and inter-fiber splitting associated with conventional stem breaking. Pre-compression of the stems before breaking offers further advantages.

1 . A stem breaking apparatus comprising a roller having unevenly spaced radial projections. 
     
     
         2 . The apparatus of  claim 1 , further comprising a tooth including a plurality of the radial projections. 
     
     
         3 . The apparatus of  claim 1 , further comprising a plurality of teeth, each radial projection being provided by one of the teeth, wherein an angular spacing between adjacent teeth is greater than an angular spacing between at least one pair of the radial projections. 
     
     
         4 . The apparatus of  claim 1 , further comprising a plurality of teeth extending from a minor diameter to a major diameter of the roller, each radial projection being provided by one of the teeth and extending to the major diameter. 
     
     
         5 . The apparatus of  claim 1 , wherein each radial projection extends from a minor diameter to a major diameter of the roller, and wherein at least one radial projection has a surface that intersects an adjacent radial projection at a diameter between the minor and major diameters. 
     
     
         6 . The apparatus of  claim 1 , wherein the roller is a first roller having a plurality of teeth intermeshed with a plurality of teeth of a second roller, each roller having unevenly spaced radial projections, and wherein each radial projection is provided by one of the teeth of the respective roller. 
     
     
         7 . The apparatus of  claim 1 , wherein the roller is a first roller, the apparatus further comprising a second roller having radial projections intermeshed with the radial projections of the first roller such that a pair of the projections of the first roller lies between a pair of the projections of the second roller where the rollers oppose each other at a roller gap. 
     
     
         8 . The apparatus of  claim 1 , wherein the roller is a first roller and the unevenly spaced radial projections are arranged in an angular pattern, the apparatus further comprising a second roller having unevenly spaced radial projections arranged in the same angular pattern and intermeshed with the radial projections of the first roller. 
     
     
         9 . The apparatus of  claim 1 , wherein the roller is a first roller, the apparatus further comprising a second roller having radial projections intermeshed with the radial projections of the first roller such that a plant stem passed between the rollers is subjected to four-point bending. 
     
     
         10 . The apparatus of  claim 9 , wherein, during the four-point bending, the plant stem spans a distance between a first radial projection and a second radial projection of the first roller and additionally spans a distance between a third radial projection and a fourth radial projection of the second roller. 
     
     
         11 . The apparatus of  claim 10 , wherein the third radial projection and the fourth radial projection extend between the first radial projection and the second radial projection. 
     
     
         12 . The apparatus of  claim 10 , wherein each of the third and fourth radial projections is provided by a tooth of the second roller, and wherein each of the first and second radial projections is provided by a respective tooth of the first roller. 
     
     
         13 . A method of extracting bast fibers from a plant stem, the method comprising bending the plant stem by an amount sufficiently high to break a woody core of the plant stem and sufficiently low to prevent formation of kinks in a majority of the bast fibers surrounding the woody core. 
     
     
         14 . The method of  claim 13 , further comprising the step of subjecting the plant stem to four-point bending between a pair of rollers, during which the plant stem spans a distance between adjacent teeth of one of the rollers and spans a distance between adjacent projections of a tooth of the other roller. 
     
     
         15 . The method of  claim 13 , further comprising the step of passing the plant stem between a pair of rollers each having unevenly spaced radial projections. 
     
     
         16 . The method of  claim 15 , further comprising the step of compressing the plant stem before passing the plant stem between the pair of rollers. 
     
     
         17 . The method of  claim 16 , wherein the step of compressing is performed below a threshold compressive force to prevent damage to the bast fibers.