Method and apparatus for ice blasting

Abstract

The invention provides an apparatus and method for partitioning continuously produced ice particulates and delivering them at a high velocity onto a substrate for treating the surface of the substrate. The apparatus includes a refrigerated curved surface that is brought into contact with water to form a thin, substantially uniform, ice sheet on the surface. This ice sheet is of such thickness as to contain stresses so that the sheet is predisposed to fracture into particulates. A harvesting blade is mounted to intercept a leading edge of the ice sheet and to fragment the ice sheet to produce ice particulates. These ice particulates enter into an inlet where they are fluidized and drawn into a manifold that extends substantially along the length of the harvesting blade. The manifold partitions the particulates into separate delivery tubes where they are ejected from nozzles to the workpiece. The manifold can be created to either evenly or unevenly distribute ice particulates to the delivery tubes. The flow of particulates through the nozzles can also be individually controlled by using a pressure regulator to control the amount of pressurized air entering the nozzles.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:  
     
         1 . A method of partitioning a stream of continuously produced particulates, the method comprising: 
 (a) continuously producing ice particulates using a rotary cooling member having a surface on which ice is formed and an ice removal blade;    (b) positioning a manifold inlet adjacent to the ice removal blade, the manifold inlet supplying at least two nozzles via delivery tubes;    (c) introducing a flow of air into the at least two nozzles to draw the particulates into the manifold in a fluidized stream;    (d) partitioning the fluidized particulate stream through the manifold and into the at least two nozzles; and    (e) dispensing particulate streams of fluidized particulates from the at least two nozzles.    
     
     
         2 . The method of  claim 1 , wherein the ice particulates are formed by continuously freezing water on the surface of the rotary cooling member, the surface being curved and producing a thin, curved sheet of ice subject to self fragmentation; and rotating the rotary cooling member causing the leading edge of the thin, curved sheet of ice to impact the removal blade.  
     
     
         3 . The method of  claim 1 , wherein the fluidized particulates are ejected at different rates from the at least two nozzles.  
     
     
         4 . The method of  claim 1 , wherein the particulates ejected from each of the nozzles are directed at a workpiece at a different orientation.  
     
     
         5 . A method of partitioning a continuously produced stream of ice particles, the method comprising: 
 (a) continuously freezing water into a thin, curved sheet of ice subject to self-fragmentation, the self-fragmented ice providing a source of ice particulates;    (b) introducing a flow of air into at least two nozzles each being in fluid communication with the source of ice particulates via a delivery tube, the flow of air being sufficient to develop a suction force along at least a portion of each of the delivery tubes, the suction force drawing the ice particulates into the nozzles via the delivery tubes;    (c) continuously harvesting at least a portion of the self-fragmented thin, curved sheet of ice in the form of ice particulates directly into a fluidized stream of particulates in air that is partitioned to flow through the at least two delivery tubes; and    (d) ejecting the ice particulates from the end of each nozzle.    
     
     
         6 . The method of  claim 5 , wherein the nozzle is able to control the velocity of particulates therethrough.  
     
     
         7 . The method of  claim 5 , wherein the nozzles supply particulates at different velocities.  
     
     
         8 . The method according to  claim 5 , wherein the supply of air introduced to each nozzle is provided from a common source.  
     
     
         9 . The method according to  claim 6 , wherein the pressure of the air supplied to one nozzle is different from any other nozzle, the difference in nozzle air pressure being used to control the velocity of the ice particulates exiting the nozzle.  
     
     
         10 . The method according to  claim 5  further comprising directing an air supply at the harvested ice particulates to help promote ice particulate fluidization.  
     
     
         11 . The method according to  claim 5  further comprising vibrating the manifold to promote fluidization.  
     
     
         12 . An apparatus for partitioning ice particles, the apparatus comprising: 
 (a) a rotary cooling member having an outer surface, the rotary cooling member being cooled by refrigerant such that liquid freezes on the outer surface;    (b) a harvesting blade disposed adjacent to the outer surface to remove frozen particulates from the surface;    (c) a manifold having an inlet disposed to collect frozen particulates from the harvesting blade, and an outlet;    (d) at least two delivery tubes, said delivery tubes having a receiving end fluidly coupled to the outlet of the manifold and a delivery end, the delivery end having a nozzle for ejecting frozen ice particulates from the end of each of said delivery tubes; and    (e) an air stream supply that introduces an air stream into each of said nozzles, said stream of air producing a suction force to draw harvested frozen particulates from the manifold, through the delivery tube, into the nozzle and eject them from the nozzle when said stream of air is directed through said nozzle.    
     
     
         13 . The apparatus of  claim 12 , wherein the surface of the rotary cooling member is curved, and the frozen particulates are ice particulates formed from a thin, curved sheet of frozen water on the surface of the rotary cooling member, the sheet of ice being subject to self-fragmentation.  
     
     
         14 . The apparatus of  claim 12 , wherein the manifold has at least two harvesting chambers; each harvesting chamber having an inlet end and an outlet end, the inlet end directed at the source of frozen particulate and located adjacent to the source of particulate such that a suction force created in said nozzle draws a portion of the ice particulate into a chamber of the manifold, and the outlet end being connected to the receiving end of said delivery tube.  
     
     
         15 . The apparatus of  claim 12 , wherein the ice particulates are directed at a workpiece at different orientations.  
     
     
         16 . The apparatus of  claim 12  further comprising a single source of air supplying said nozzles.  
     
     
         17 . The apparatus of  claim 12 , further comprising a means for directing an air supply across the outer surface of the rotary member to promote fluidizing of the harvested the ice particulates.  
     
     
         18 . The apparatus in  claim 12 , further comprising a means for vibrating the manifold to promote fluidization of the harvested ice particulates.  
     
     
         19 . An apparatus for directing ice particles at a workpiece, the apparatus comprising: 
 (a) a rotary cooling member having an outer surface, the rotary cooling member being cooled by refrigerant to at least 0° C., the rotary cooling member being rotated in a bath of water, a thin sheet of ice being formed on the cylindrical surface when water contacts the surface;    (b) a harvesting blade disposed adjacent to the outer surface of the rotary member, the harvesting blade extending along the length of the outer surface of the rotary member, the harvesting blade oriented to enable fragmenting the thin sheet of ice to form ice particulates;    (c) a manifold having an inlet disposed adjacent to the harvesting blade to collect ice particulates and having an outlet that distributes the ice particulates, the manifold having at least two chambers, each of the chambers having a gathering end and a discharge end, the gathering end being located adjacent to the harvesting blade, the discharge end distributing partitioned ice particulates; and    (d) at least two delivery tubes, the at least two delivery tubes having a receiving end and a delivery end, the receiving end fluidly coupled to the discharge end of the manifold chamber to receive the partitioned ice particulates into the delivery tube, the delivery end connecting to a nozzle to deliver the ice particulate to the workpiece;    (e) an air stream supply that introduces an air stream into each of the nozzles, the stream being introduced between the nozzle and the delivery end of the at least two delivery tubes, said stream of air producing a suction force to draw harvested frozen ice particulates from the manifold and through the delivery tube and eject them from the nozzle when said stream of air is directed through said nozzle.    
     
     
         20 . The apparatus in  claim 19  wherein the ice particulates are ejected out of each of the nozzles towards a workpiece at a different orientation.  
     
     
         21 . The apparatus in  claim 19 , further comprising a pressure regulator to control the air stream supply entering the at least two nozzles, said regulator controlling the pressure of the air stream into the nozzles.