Abrasive rotary cutting string manufacture and use

Abstract

A method of producing an abrasive cutting string provides for coating a plastomeric string with a solution of a solvent and the plastomeric material of the string, applying an abrasive and removing the solvent to thereby provide a cutting string with excellent abrasive bind and string coverage, that can be manufactured at high speeds, and then used on a spool in the rotary cutting assembly of a string trimmer to incrementally feed at least one extremity of the abrasive string for rotation through a cutting swath.

I claim: 
     
         1 . A method of manufacturing an abrasive cutting string for use in a rotary string trimmer comprising the steps of:
 (a) selecting a string made of a plastomeric material;   (b) coating the string with a solution comprising a solvent and the plastomeric material;   (c) applying an abrasive to the solution coated string;   (d) removing the solvent from the abrasive coated string;   (e) placing the abrasive coated string upon a spool in a cutting head assembly of a rotary string trimmer with at least one extremity of the abrasive coated string extending for rotation through a cutting swath.   
     
     
         2 . The method of  claim 1  further comprising the step of winding the abrasive cutting string upon a reel before placing the abrasive cutting string on the spool. 
     
     
         3 . The method of  claim 1  wherein the plastomeric material is polyamide. 
     
     
         4 . The method of  claim 3  wherein the polyamide is selected from Nylon 6, Nylon 66 and mixtures thereof. 
     
     
         5 . The method of  claim 4  wherein the solvent is formic acid. 
     
     
         6 . The method of  claim 4  wherein the polyamide is in the solution at a concentration of between 10 percent and 20 percent weight by volume. 
     
     
         7 . The method of  claim 1  wherein after solution is applied to the string the excess solution is brushed off the surface of the string. 
     
     
         8 . The method of  claim 1  wherein solvent vapors are captured when the solvent is removed and the solvent is recovered by condensation. 
     
     
         9 . The method of  claim 1  wherein the abrasive is selected from the group of silica, glass, fine sand, emery, marble, coarse garnet, metal particles, plastic particles, and mixtures thereof. 
     
     
         10 . The method of  claim 1  wherein the abrasive particles have a mesh size in the range from about 30 mesh to about 70 mesh. 
     
     
         11 . The method of  claim 1  wherein the string is coated with abrasive particles at a speed of at least 200 feet per minute. 
     
     
         12 . The method of  claim 1  wherein the abrasive particles cover at least 99 percent of surface area of the string. 
     
     
         13 . The method of  claim 1  wherein at least 50 percent of the abrasive particles have a bind strength in excess of half of the tear strength of the string of plastomeric material. 
     
     
         14 . The method of  claim 1  wherein the diameter of the uncoated string of plastomeric material is greater than 60 percent of the diameter of the abrasive coated string. 
     
     
         15 . The method of  claim 1  wherein the abrasive is applied to the solution coated string at a rate of about four grams per square inch of surface on the uncoated string of plastomeric material. 
     
     
         16 . The method of  claim 1  wherein the abrasive particles cover at least 95 percent of the surface areas of the string and at least half of the abrasive particles have a bind strength greater than half the tear strength of the string's plastomeric material. 
     
     
         17 . A method of manufacturing an abrasive cutting string for use in a rotary string trimmer comprising the steps of:
 (a) selecting a string made of a Nylon soluble in formic acid;   (b) coating the Nylon string with a solution of 10 to 20 percent by weight of Nylon dissolved in formic acid;   (c) applying abrasive particles of between about 30 mesh and 70 mesh size to the solution coated Nylon string;   (d) heating the abrasive coated string to a temperature of between about 100 and 150 degrees centigrade to substantially remove the formic acid;   (e) recovering formic acid by condensation;   (f) uniformly sizing the abrasive string; and   (g) winding the abrasive coated string upon a reel.   
     
     
         18 . The method of  claim 17  where the abrasive particles cover over 95 percent of the surface of the string made of a Nylon. 
     
     
         19 . The method of  claim 17  wherein the diameter of the string made of Nylon is greater than 60 percent of the diameter of the abrasive coated string. 
     
     
         20 . The method of  claim 17  wherein the abrasive is applied to the solution coated Nylon string at a rate of about four grams per square inch of surface of the string made of Nylon.