Blasting air tube with sleeve, and method

Abstract

An inflatable air tube includes a sleeve member arranged concentrically about the upper end portion of the air tube to define a receptacle chamber for receiving a quantity of bulk explosive blasting powder, thereby to add weight to the air tube for positioning and stabilizing the same in the bulk explosive powder during the depositing of the powder into a blasting hole drilled into the ground. According to the method of the present invention, a plurality of accurate blasting patterns may be provided in the blasting powder column by timing the manual or mechanical insertion of the air tubes into the bulk blasting powder relative to the rate of supply of the powder from a source thereof.

1 . An air tube adapted for insertion within a bulk explosive blasting powder during the loading thereof into a blast hole formed within the ground, comprising:
 (a) an inflatable generally cylindrical vertically arranged air tube formed of flexible synthetic plastic material and operable between collapsed and inflated conditions, said air tube in said inflated condition including upper and lower generally dome-shaped convex end portions, and a cylindrical intermediate portion connected between said end portions, thereby to define a central chamber, said air tube in said inflated condition having a longitudinal axis extending vertically between said end portions, said air tube in said collapsed condition being diametrically compressed toward a flat configuration defining a pair of parallel adjacent flat side walls;   (b) inflation stem means for introducing air into said air tube chamber to transform the same from said collapsed condition to said inflated condition; and   (c) means operable when said air tube is in said inflated condition to define an open-topped blasting powder receptacle in concentrically spaced relation about said upper dome-shaped end portion, whereby when said air tube is positioned within the flow of blasting powder into the blast hole, the receptacle is filled with powder, thereby to increase the weight of the air tube.   
   
   
       2 . An air tube as defined in  claim 1 , wherein said air tube upper end has a generally arch-shaped configuration when said air tube is in said collapsed condition; and further wherein said receptacle defining means comprises:
 (1) a sleeve member formed of flexible synthetic plastic material, said sleeve member being operable between a tubular configuration and a radially compressed flat configuration when said air tube is in said inflated and collapsed conditions, respectively; and   (2) connecting means connecting said sleeve member with at least one of said air tube side walls when said air tube is in said collapsed condition.   
   
   
       3 . An air tube as defined in  claim 2 , wherein the length (l) of said sleeve member is between about 12% and 20% of the length (L) of said air tube. 
   
   
       4 . An air tube as defined in  claim 3 , wherein said sleeve member has a top edge that is even with the bottom edge of said air tube upper end portion when said air tube is in said collapsed condition. 
   
   
       5 . An air tube as defined in  claim 2 , wherein said sleeve connecting means has a length of about 3″. 
   
   
       6 . An air tube as defined in  claim 5 , wherein said sleeve connecting means comprises a heat-sealed connection. 
   
   
       7 . An air tube as defined in  claim 5 , wherein said sleeve connecting means comprises an adhesive strip. 
   
   
       8 . An air tube as defined in  claim 5 , wherein said sleeve connecting means includes a layer of adhesive. 
   
   
       9 . An air tube as defined in  claim 2 , wherein the width of the sleeve member, when said air tube and said sleeve member are in the collapsed condition, is no less than the corresponding width of the air tube. 
   
   
       10 . An air tube as defined in  claim 9 , wherein the diameter of said sleeve member, when in the expanded condition, is such as to cause the inner periphery of said sleeve member to be in frictional engagement with the outer periphery of said air tube intermediate portion. 
   
   
       11 . An air tube as defined in  claim 2 , wherein the diameter of said air tube when in the inflated condition is no greater than about 60% of the diameter of the blast hole. 
   
   
       12 . The method of blasting a hole in the surface of the ground, which comprised the steps of:
 (a) drilling a blast hole in the surface of the ground, thereby to define a blast hole mouth;   (b) arranging a source of explosive blasting powder in spaced relation above said blast hole mouth;   (c) depositing from said source a flow of explosive blasting powder in bulk form at a given density and at a given loading rate downwardly into said blast hole;   (d) placing in the blasting powder flow a vertically-arranged air tube having at its upper end an open-topped receptacle, thereby to introduce blasting powder into said receptacle to increase the weight of the air tube; and   (e) releasing said weighted air tube in the blasting powder flow for insertion by said flow into said bore hole.   
   
   
       13 . The method for blasting a hole in the surface of the ground as defined in  claim 12 , including the steps of successively introducing a plurality of said air tubes into the blasting powder flow in a predetermined timed relation relative to the rate of flow of the powder, thereby to produce a desired accurate blasting pattern in the resultant blasting powder column.