FIELD OF THE INVENTION

This invention relates to apparatus for preparing, classifying, and metering particle media useful for various purposes and especially for particle blast cleaning and treating systems. BACKGROUND OF THE INVENTION

Sand blast technology has been well developed and widrly used and acceptable cleaning results are able to be obtained with crude systems and low cost abrasives. However, many types of surfaces of materials are not able to be cleaned in this way because of damage to the surfaces and possible effect on the integrity of the objects being cleaned . Also, aside from environmental considerations nearby ob^-.cts ars often inconvenienced or damaged by over sp- -yy e: ts and clean-up is normally time consuming anc .osti_ Over the last few years the use of other abrasive materials such as plastic chips and frozen liquids such as water (H20) ice, dry ice (C02) , and pellets of the. •- mixed with certain chemical materials have been proposed for use in air blast technology to clean, wash, decor aminate or otherwise treat surfaces of a wide range of objects and materials. The following are j atents that show methods and apparatus using these types of materials:

British Patent No. 1,397,102 filed March 22, 1972

Published June 11, If"5 U.S. Patent No. 4,703,590 issued November 3, 1987 U.S. Patent No. 4,769,956 issued September 13, 1988 French Patent App. 80-03099 filed February 8, 1980

Publication No. 2,475, ?5 French Patent App. 80-2437E .led November 17 1980 Publication No. 2,494,_.o0 British Patent App. GB 2,171,624A Published September 3, 1986

Japanese Public Disclosure No. 97533 dated August 2, 1975 U.S. Patent No. 3,676,963 issued July 18, 1972 United States patent 4,769,956 is an example of a sand blast machine employing two or more blast nozzles for propelling abrasive sand at interior and exterior exposed surfaces of a component to be treated. Control is exercised on the respective blast nozzles to vary the pressure, as opposed to energy, delivered to the surface from low to high levels to thereby vary the extent of abrasion on various surfaces interior and exterior of the workpiece being treated.

The remaining patents disclose various devices which employ ice particles in blast nozzles for treatment of work surfaces. All of these systems function on the basis of propelling the ice particles through the blast nozzle in the same manner that sand blasting is achieved such as, for example, in the aforementioned United States patent 4,769,956. No consideration is given to controlling relative flows and mass ratios in transporting the ice particles to the blast nozzle in a manner to minimize degradation of the ice particles in the transport stream. Hence as is characteristic of previously known ice blasting equipment, the effectiveness of the ice particles in doing work on the surface to be treated is not commercially effective. It has been found, in accordance with this invention, that suitable control of mass flow rates, fluid flow rates and ratios thereof provide a commercially viable form of ice blast technology for treating and cleaning various surfaces.

Of the above patents and published patent applications, U.K. application 2,171,624 is representative of the types of equipment used in ice blast technology.

The input particles are fed by gravity into a charging chamber which is a cylindrical shell with a

rotating bladed rotor therein to carry the particles to an output leading to an auger which drives them in a continuous manner into an entraining air jet stream. Control of the air and particle amounts and ratios is very imprecise and it would seem to be difficult to obtain good cleaning effects from the system described especially for a wide spectrum of surface types and conditions. The blade rotor or plodder would be difficult or impossible to seal against substantial pressure differences and control shear which could damage delicate particle media. The system is gravity dependent and therefore limiting for media which tends to pack and plug up the system. The quantity of media passed by the plodder and that by the receiving auger cannot be matched in a practical way and necessitates an overflow to the receiver. The design of the screw or auger does not due to its design seal against pressure. SUMMARY OF INVENTION

In accordance with an aspect of the invention, an apparatus for delivering a controlled volume of sized ice particles comprises: i) means for storing a supply of ice chunks; ii) means for crushing ice chunks into ice particles, said crushing means having an inlet which is in solid/fluid communication with an outlet of said storing means; iii) means for classifying ice particles into a desired size range, said classifying means having an inlet which is in solid/fluid communication with an outlet of said crushing means; iv) means for fluidizing a volume of classified ice particles with pressurized fluid, an inlet of said fluidizing means being in solid/fluid communication with an outlet of said classifying means, said fluidizing means having an outlet through which fluidized classified ice particles travel under fluid pressure; and

v) means for cooling to ice freezing temperatures internal surfaces of said storing means, said crushing means, said classifying means and said fluidizing means. According to another aspect of the invention, apparatus for preparing, classifying, and metering particle media useful for various purposes including blast cleaning and treating systems comprises: a) means for taking a media input having a working particle size range and sending the media particles along with a fluidizing air input through a scroll, b) a classifier/surge tank acting as a cyclone separator connected to the fluidized particle/air stream output of the scroll, c) means for taking the lighter portions of the particles from the cyclone separator and transporting this to recovery or utilization means, d) means for taking the heavier portions of the particles from the cyclone separator and transporting this to the utilization means or recovery, e) metering means for taking the lighter or heavier portion of the particles from the cyclone separator in a controlled manner, and f) means for taking the metered particle stream from the metering means and providing along with a pressurized air input, a fluidized air/particle output in a controlled manner such that the air/particle ratios are controlled and the particles are in a steady or pulsed flow as desired. According to another aspect of the invention, apparatus for preparing, classifying, and metering particle media useful for various purposes including particle blast cleaning and treating systems comprises: a) means for sizing a media input to a working particle size range, b) means for taking the particle output from the sizing means and sending the particles along with a

fluidizing air input through a scroll to initiate cyclonic action by pneumatic or mechanical action, c) a classifier/surge tank acting as a cyclone separator connected to the fluidized particle/air stream output of the scroll, d) means for taking the lighter portions of the particles from the cyclone separator and transporting this to recovery or utilization means, e) means for taking the heavier portions of the particles from the cyclone separator and transporting this to utilization or recovery means, f) metering means for taking either the lighter or the heavier portion of the particles from the cyclone separator in a controlled manner, g) means for taking the metered particle stream from the metering means and providing along with a pressurized air input, a fluidized air/particle output in a controlled manner such that the air/particle ratios are controlled and the particles are in a steady or pulsed flow as desired.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention are shown in the drawings wherein:

Figure 1 is a schematic flow diagram of a particle media preparation system for particle blast cleaning and other purposes,

Figure 2 is a cross-section of apparatus for the system of Figure 1,

Figure 3 is an end view of the apparatus of Figure 2,

Figure 4 is of a partially broken view of the apparatus of Figure 2,

Figure 5 is a cross-section view of the crusher and classifier impeller, Figure 6 is a cross-section on VI-VI of Figure 2 of the crusher and scroll,

Figure 7 is a cross-section of the flow metering screw,

Figure 8 is a cross-section of the rotary metering pump, Figure 9 is a top view of the rotary metering pump,

Figure 10 is a cross-section of the rotary cylinder showing the individual chambers,

Figure 11 shows detail of the labrynth seal for purposes of maintaining and isolating pressure in incremental steps,

Figure 12 is a schematic diagram of the particle media preparation apparatus in a complete particle blast cleaning and treating system,

Figure 13 is a cut-away isometric view of the portable ice blast treating equipment,

Figure 14 is a schematic view of the components of the portable system which provide a fluidized stream of ice particles,

Figure 15 is a section through apparatus for crushing ice chunks to form ice particles,

Figure 16 is a perspective view of the ice crushing apparatus,

Figure 17 is a section through a diverter valve for use in diverting the flow of ice particles, Figure 18 is a perspective view of the apparatus for fluidizing ice particles,

Figure 19 is a section through the fluidizing device of Figure 18,

Figure 20 is a top view of the diverter valve of Figure 17, and

Figure 21 is a longitudinal section through the fluidizing apparatus of Figure 18. DESCRIPTION OF THE INVENTION

As discussed in applicant's co-pending PCT application S.N. CA90/00174, a judicious selection of the process and apparatus parameters is required in order to deliver ice particles to and expel them from a blast

nozzle with sufficient velocity to do the desired degree of work on the work face. In accordance with the principles of the process and apparatus, as set out in the co-pending application, particular embodiments of the invention are set out in the following Figures to achieve an effective cleaning of the surfaces using particle blast technology and, in particular, ice particle blast technology. Two overall systems are set out in the Figures wherein Figures 1 through 12 address various features of one aspect of the invention, whereas Figures 13 through 21 address other aspects of the invention.

Figure 1 is a schematic flow diagram of the system wherein the input media material is fed into crusher (sizer) 1 which has a fluidizing air input. The air is added to fluidize and prevent temperature rise of the media due to the energy introduced for size reduction and air for cyclonic action. A mechanical impeller 2 which may run at the crusher/sizer speed or at other desired speeds to introduce a spin to the sized material and send the material and the fluidizing air through scroll 3 to initiate cyclone action in classifier/surge tank 4. In addition to providing surge volume and level control, this vessel provides media size control by cyclonic action (settling rate difference between larger heavier and smaller lighter particles) . An eductor 5 generates a forced vortex and a velocity which entrains the finer particles having slower settling rates and fluidizes the entrained media for transport. Velocities and therefore selection of the fineness of the particles withdrawn are adjustable via an eductor (motive) air rate control which controls the total entrained air flowing through the system. Crusher/sizer speed control provides further adjustment of fines to coarse particle ratios.

The system may be run such that the fines are the rejects to be sent to recovery and the coarser material the product. Alternatively, the fines may be the product and the coarser recycled for additional size reduction.

This arrangement may preclude the need for multiple crushers and size reduction steps which is the current industrial practice.

Delicate or difficult to handle media (dry, abrasive, etc.) cannot be easily handled without shear in pumping through any appreciable pressure rise in known suitable apparatus. Output from classifier/surge cyclone or tank 4 is sent via flow metering pump 6 to a rotary cylinder metering pump 8 which is designed to raise the metered particles to the desired pressure with near zero shear by passing cylinder chambers through progressive pressure increments with air or their fluid added in a controlled manner to raise the pressure as required and also fluidize the particles. The chambers in the rotary pump may be fully or partially loaded at the inlet and the output rate controlled by the rate of chamber deliveries (by the R.P.M. of the drive motor) . For more control and providing for pulse rate of delivery, the pump chambers are oversized with respect to the desired maximum rate and the R.P.M. independently controls the pulse rate.

Figures 2, 3, and 4 illustrate the above system in more detail. A sizer/crusher 1 is driven by crusher speed control motor 10. Input media is supplied to the crusher through opening 13 by screw or auger drive 11 driven by motor 12 (see Figure 4) and classifying air is introduced as well at port 13. From crusher 1 the crushed material and classifying air is driven by impeller 2 through scroll 3 into classifier/surge tank 4 to act as a cyclone classifier. Scroll 3 also has classifying air injected into the air stream by air injection devices 3a and 3b positioned as shown in Figure 4. These are known devices and serve to provide an enhanced rotating air stream to the cyclone classifier. The crusher 1 and impeller 2 (shown in section in Figure 5 and in cross-section in Figure 6) may be driven at the same speed or at differing speeds by a suitable drive

shaft arrangement. A cut (portion) of the media particles can be taken from the cyclone classifier by eductor nozzle assembly 5 having an eductor air input 5a. This material which would be the lighter, finer portion can be taken to reject, recycled, or if required as an input to a cleaning, treating, or other utilization system. The heavier portion of the material from the cyclone is taken to a metering device 6 (Figure 2) preferably a screw device 6b such as shown in Figure 7. This is driven by a controllable motor drive (see Figure 3) . The metering screw is precisely machined and has direct feed entry from the cyclone (via fluidizing and gravity) through a large open throat and discharges directly into a rotary metering pump 8. The metered material from the screw which would be at or near atmospheric pressure is fed into the rotary chamber pump driven by a controllable motor 8a. This pump 8 is shown in more detail in Figures 8, 9, 10, and 11. As seen in cross-section in Figure 8 and in top view in Figure 9, the device comprises a cylindrical housing 15 having a top plate 16 and a bottom plate 17. An input port 18 which would be connected to the output of the cyclone classifier via the metering screw serves to introduce the particle material into the device. A process air injection nozzle introduces fluidizing and transporting air into the device and a fluidized process feed is taken at nozzle 20. A rotating cylinder 21 containing a series of chambers 22 as shown in Figure 10 is shaft mounted inside housing 15. These chambers which are cylindrical in shape are sealed top and bottom by a labrynth or annular ring type seal shown in detail in Figure 11 and these provide good sealing action without direct contact between the rotary cylinder and the housing walls. As the rotary cylinder rotates each of the chambers comes in turn under port 18 and is filled either fully or partially as desired with the particle material. The chamber then moves to a position under pressurized air

inlet port 25 (see especially Figure 9) which raises the pressure in the chamber to a first level. Further pressure levels are realized by the introduction of pressurized air in step-wise fashion as the chamber moves past ports 26, 27, and 28 until it reaches port 19 where an increased pressurized air input fluidizes and transports the material to the desired output at port 20 (see Figure 8) . The chambers then pass under air outlet ports 29 and 30 which serve to drop the pressure to the- working level for the chambers when they pass to inlet port 18. This pressurized air output may be reused by injecting back into the system at suitable positions.

Figure 12 illustrates the media preparation system described above in a complete particle blast cleaning and treating system. The raw media supply is fed to crusher 32 having a fluidizing air input 33 from air source 34, with the media particles passing through impeller 35, scroll 36 having air injection inputs 36a and 36b to cyclone classifier 37. The fines portion is taken by eductor 38 and sent to recycle. The heavier portion of the particles passes to metering screw 19 controlled by motor 39a and then to rotary cylinder 40 which as described above sends a controlled fluidized air and particle stream to fluidizer 41 having a pressurized air input from air source 34 via control valve 44. The output air and particle stream from the fluidizer are transported through line 42 to blast head 43 having accelerating air inlet nozzles 43a and 43b supplied from the air source via lines 45 and 46 and controlled by control valves 47 and 48. This system provides complete control of all the parameters required to give excellent cleaning and treating action to a wide range of surface conditions.

The control valves are adjusted to provide a range of flow rates for pressurized fluid to various points in the system design. It is appreciated that the control valves may be manually adjusted or controlled by

electronic valve controllers which respond to signals from a central controller. The valves are adjusted to control the respective air flows to the crusher, the separation cyclone, the fluidizer and the blast head. By appropriate control of these flow rates of pressurized fluid to these devices, the optimum work efficiency of the particles employed in the media can be achieved to provide the desired de-ree of surface cleaning and/or treatment. This is particularly advantageous when the particles employed for the media are derived from a supply of ice. Ice particles and other types of particles, such as plastic chips and glass beads, are sensitive to break-down c— deterioration during the fluidization and transpc stage This significantly alters the effectiveness of the particles as they pus- through the blast head to perform work on the surface to be treated. It is therefore desirable to control the flow rates of pressurized fluid which may be used in the various devices particularly in t ^~ - ^~ fluidizing pump device 40 and 41. To effect ade .te fluidization of the particles in the pressurized fl _.u stream for purposes of transport of the particles to the blast head. It has been determined that the ratio of flow rates of the pressurized fluid to the fluidizer and other upstream equipment, such as the pressure and metering device and the like, should be controlled in a manner so thε " he ratio of flow rate of pressurized fluid to these upstream devices relative to the flow rate of pressurized fluids to the blast head is in the range of 0.1 to 1.5. As applied to ice particles, it has been determined that the ratios of flow rates in this range provide for fluidization and transport of the ice particles in a manner which minimizes degradation of the ice particles upon delivery to the blast head. The additional pressurized fluids then required at the blast head 43 is adequate to sufficiently accelerate the particles, particularly ice particles, to a velocity which develops

the necessary pressure at the work face to effect the desired degree of surface treatment and/or cleaning. It is appreciated that the longer the pipe or hose required to transport the fluidized particles from the fluidizer- pump 40/41 to the blast head 43, usually results in the ratio being in the range of 1 up to perhaps 1.5. For standard lengths of hose in transporting the fluidized particles to the blast head, that is in the range of 22 to 80 feet, it has been found that a ratio of the flow rates in the range of 0.1 to 0.5 is useful and ensures that the ice particles have maintained their size distribution as classified before being propelled through the blast head.

According to an alternative embodiment of the invention, a mobile ice blasting system is shown in

Figure 13. The ice blast system 50 is transported on a flat bed trailer 52 having tandem wheels 54 with a hitch at the front 56 of the trailer. When the trailer is standing alone, front jacks 58 are provided to support the trailer in a relatively horizontal position. The ice particle supply system generally designated 60 provides in line 62 sufficient pressurized air to power the blast head (not shown) and fluidized ice particles in line 64. When the blast head is not in operation, ice particles are directed to recycle or waste in line 66. Entrance to the mobile unit is through door 68 and where necessary steps 70 are provided.

The ice making system and air cooling systems have significant power requirements. In view of total mobility of the system, the unit has its own electrical power generating apparatus. In the rear portion of the flat bed trailer 52 is a diesel electric generator system 72 having a diesel motor 74 and en electric generator 76. The generator 76 develops power which is controlled by the control panels 78 and 80 to distribute electrical power to the various onsite devices. An air compressor generally designated 82 develops the necessary air

pressure to transport, fluidize and power the blast head. Air enters the system at air inlet 84. The air is filtered and passed through two refrigeration systems 86 and 88. Refrigeration system 86 cools the incoming air to approximately 35°F. The second refrigeration unit 88 cools the air down to 15°F to 0°F before entry through duct 90 to the compressor 82. The compressor 82 steps the pressure of the incoming air up to approximately 100 to 150 psig in line 92. The temperature of the compressed air is in the range of 60°F to 95°F. The air at this point is dry due to dehumidification in coolers 86 and 88. The warm dry air is directed through pipe 96 to post cooler 94. The post cooler 94 cools the air down to approximately 5°F to 0°F. A major portion of this air is directed to line 62 which, in turn, leads to the blast head. A minor portion of this air is directed to post cooler 98 to cool the air further. This cooler air is used in the ice particle making system 60 which will be discussed in more detail with reference to the subsequent drawings.

In the forward end of the trailer 52, ice chunks are made in two banks 100 and 102 of independent ice makers. Each ice maker has its own refrigeration unit and water supply. The ice makers are of standard design which develop normal sized ice cubes. Bank 100 of ice makers drop the ice cubes into a trough 104 having an auger 106. Bank 102 of the ice makers drops ice cubes into trough 108 which has an auger 110. Troughs 104 and 108 are tilted downwardly slightly towards the front 56 of the trailer to ensure that any moisture which may drop into the troughs from the ice maker is moved away from the ice cul^s. The augers 106 and 110 move the ice cubes along the troughs 104 and 108 upwardly thereof to drop the ice cubes into hopper 112. An auger (not shown) is provided in hopper 112 to move the ice cubes over towards hopper side wall 114. The ice cubes, or ice chunks, are then fed into an ice crusher 116. The ice crusher produces a

range of ice particle sizes which are fed into a particle size classifying unit 118 to a fluidizing device 120 which fluidizes the ice particles and propels them through hose 122. A diverter valve 124 is connected to hose 122. The diverter valve 124 directs the flow of fluidized ice particles either through line 64 towards the blast head or line 66 to recycle or waste when the blast head is shut down. The minor portion of cool air from post cooler 94, which is fed through line 97, is introduced to post cooler 98 to further cool the air to approximately -5°F to -25°F for various uses in the ice making, crushing, sizing, classifying and fluidizing steps. The refrigeration compressor system 126 also provides refrigeration for the various ice particle making devices of the system 60 to be discussed in the subsequent drawings. Similarly with post cooler 94, a refrigeration system 128 is provided to develop the necessary coolant to cool the warm compressed air in line 92. With reference to Figure 14, the ice particle making and fluidizing system is schematically shown. An ice maker bank 100 makes ice chunks 130 which are dropped into the trough 104. The auger 106 rotates in a direction to move the ice chunks along the trough 104 in the direction of arrow 132. As explained with reference to Figure 13, the trough 104 may be sloped slightly downwardly towards the back portion 143 of the trough. This allows any water existing the ice maker 100 in the direction of arrow 136 to run down the trough 134 and out through release valve 138. At the extremity 140 of the trough 104, the ice chunks 130 are advanced by the auger 106 into the hopper 112. The hopper 112 has an auger 142 to move the ice chunks therealong towards its outlet 144 adjacent side wall 114 (shown in Figure 13) of the hopper. The ice chunks are fed into the ice crusher 116. The ice crusher 116 or sizer breaks the ice chunks 130 into ice particles. The operation of the ice sizer will

be discussed with respect to Figures 15 and 16. The ice chunks 130 are fed into the inlet 146 of the ice crusher. The ice particles 148 are removed from the ice crusher through outlet 150 and dropped into the classifying unit 118 where the particles are classified into the desired particle size for fluidizing by the fluidizing device 120. The classifier 118 may select particle sizes by a variety of techniques, such as the cyclone system already discussed. According to this embodiment, the sizing is accomplished by a series of screens and secondary crushing units to provid: at the outlet 152 of the classifier the, desired particle size.

The sized particles 148 from the ice crusher 116 are fed into an inlet 151 of the classifier 118. The particles 148 fall onto a first classifying screen 154. An auger 156 is positioned within the semi-circv „ar screen 154 and on top thereof so as to advance the particles 148 in the direction of arrow 158. The first classifying screen 154 has the opening size which defines the split between the -arse and fine particles. The preferred particle si-., is in the 1 to 5 mm range. Hence the opening size for "-^e screen 54 may be 1 mm or less, or in the British sy^ , the screen size may be in the range of 0.132 inchet The fines fall through the openings in screen 154 in the direction of arrow 160 and fall into a trough 162. The fines 164 as they collect in the trough 162 are remove- _* therefrom for other uses or simply discarded. The preferred technique for removal of fines from trough 162 is by use of an air blast. Air from the post cooler 98 is delivered in the direction of arrow 166 through pipe 168. The air is introduced through the trough end wall 170 at outlet 172. The air is directed in the direction of arrow 174 to blow the fines 164 along the trough and through suitable hosing or the like to waste or other uses. The air, which is introduced to the trough through opening 172, is cool and dry. This provides some of the air in the classifying

unit to ensure that moisture is removed from the system and also to fluidize to some extent the ice particles 148 as they move along the first classifying screen 154. After this first split in the particle size, particles larger than the mesh of screen 154 are advanced by auger 156 to a second classifying screen 176. Screen 176 has an opening size which is at the upper limit of the desired range of particle size. According to a preferred embodiment, this is in the range of slightly less than 5 mm or in the British system, the screen size is preferably of an opening of approximately 0.181 inches. Hence the desired blast particles 178 fall through the opening of secondary classifying screen 176 onto a deflecting plate 180 which directs the accepted particles 178 in the direction of arrow 182 onto a third classifying screen 184.

The third classifying screen 184 is required to separate any unwanted fines from particles developed by secondary ice crushing device 186. The larger particles of ice 188, which are retained on the screen 176, are advanced by the auger 156 into the secondary crushing device 186. The secondary crushing device consists of a truncated cone having apertures 190 in the periphery thereof which are of a size range of a desired particle size. This may be in the preferred range of 1 to 5 mm. A paddle 192 is rotated in the direction of arrow 194 so as to crush and urge particles of sizes less than the opening size 190 outwardly thereof to direct a stream of particles 192 onto the third classifying screen 184. An auger 194 is provided on top of the classifying screen 184 to advance the ice particles 178 and 192 in the direction of arrow 196. The third classifying screen 184 preferably has an opening size the same as that of classifying screen 154. Hence the unwanted fine particles 198 fall in a direction of arrow 200 into receiving trough 202. As with the fines rejection system of the first classifying unit, the unwanted fines 198 are

removed from the trough 202 by use of an air blast directed through nozzle 204 in the direction of arrow 206. Such cool, dry air as obtained from the second post cooler 98 also provides a degree of fluidization and drying air for the third classifier 184 to maintain solid particle.3 of the desired size range. The auger 194, as it displaces the ice particles along the third classifying screen 184, drops the classified particles 178 in the direction of arrow 208 through a funnel 210, the opening of which defines the outlet 152 for the classifier 118. The funnel 210 is connected to the inlet 214 of the ice particle fluidizing device 120. The operation of .e ice particle fluidizing device will be discussed with respect to Figures 18, 19 and 21. The ice particles, as fluidized, travel through a hose in the direction of arrows 216 to the diverter valve 124. The diverter valve 124 directs the ice particles either in the direction of arrow 218 to the supply hose 64, or in the direction of arrow 220 to the waste hose 66. The inner surfaces of the various devices of the ice preparation and classifying system should be kept cool and dry. It is therefore desirable to provide cooling for all interior surfaces of the troughs 104 and 108, the hopper 112, the ice crusher 116, the classifier 118, the fluidizer 120. This can be readily accomplished by providing cooling jackets on each of these units. Details of the cooling jack t for the ice crusl- ^j r 116 and fl- ^izer 120 will be discussed with respect to su. uen- drawings. Similar cooling jackets may be pro iβd on the troughs 104 and 108 and on and in the classifier 118. The cooling jackets usually consists of a series of walls which define annular or outer chambers or p -urns about the inner surfaces of the equipment. Preferably a heat sink liquid is provided in these chambers to readily conduct heat away from the interior surfaces of the devices. The heat sink liquid, which accc ng to a preferred embodiment may be ethylene

glycol, is cooled by passing coolant through the annular chambers. The coolant may be in the form of Freon ^® which passes through tubing placed within these chambers to take heat away from the heat sink liquid thereby maintaining the surfaces at the necessary temperatures which produce and/or retain the solid structure for the ice particles.

In addition to cooling provided by the system, particularly operated by the secondary cooling unit 126, cool dry air is also directed into the various units of the ice preparation and classifying system 60. Cool dry air may be directed along the troughs 104 and 106 . With reference to Figure 14, the air may be directed in the direction opposite to arrow 132 to remove any moisture from the system and direct it towards the drain 138.

Cooling air may also be introduced into the hopper 112 to remove any moisture from the air and again maintain a temperature within the hopper such that the ice chunks remain in solid state. In the ice crusher 116, air may be introduced to partially fluidize the ice particles as they are being formed and remove the moisture therefrom. Air, as already discussed, is introduced to the classifying system through the fines troughs. Air is introduced to the fluidizing system 120 to fluidize the ice particles in the manner to be discussed with respect to the subsequent Figures.

As shown in Figure 16, the ice crusher 116 has an outer housing 222 which houses the ice crushing jaws 224 and ice crushing mandrel 226. The ice crusher enclosure 222 has jacketed cooling chamber 228 in which the coolant remains. A series of tubes 230 pass through the chamber 228 to extract heat from the fixed heat sink liquid. As already discussed, Freon may be circulated through the tubes 230 to cool the heat sink liquid which may be ethylene glycol. The ice crusher jaws 224 are mounted on a splined shaft 232 which rotates in the direction of arrow 234. Cool dry air may be introduced laterally of

the crusher through jets 236 and 238 having lines 240 and 242 connected to a supply of pressurized cool dry air from the post cooler 94. The cool dry air, as it flows through the ice crusher 116, removes moist air and moisture from the system and also introduces additional cooling into the ice crusher to maintain the ice in solid form.

With reference to Figure 15, the section shows the manner in which the ice chunks 130 are converted into ice particles 148. The ice crusher 116, as explained with respect to Figure 16, has the jacketed cooling chamber 228 with the coolant 229 provided therein through the jacketed area are the Freon cooling tubes 230. The ice crusher, has an inlet 146 through which the ice chunks 130 travel in the direction of arrow 244. The ice chunks fall onto the ice crusher mandrel 226. The ice crusher mandrel is supported by the inner wall 246 of the ice crusher by slots 248 and 250. The edges of the mandrel are shaped to be received by these slots 248 and 250 so as to secure the mandrel in place. The mandrel is sloped upwardly from slot 248 to slot 250 where the mandrel is positioned sufficiently close to the shaft 232 such that the jaws 224 pass upwardly through the openings 252 in the mandrel. As the jaws 224 pass through the opening 252, ice particles are gathered on the toothed front portions 254 of the jaw and crushed against the upwardly sloping surface 256 of the mandrel. The developed ice particles 148 are passed through the opening 252 of the mandrel. It has been found that the upward sloping of the mandrel 226 converts the ice chunks 130 into the desired particles 148 with minimal production of fines. The crusher jaws 224, as they pass through the opening 252, move the ice chunks 130 along the upward sloping face 256 of the mandrel in the direction of arrow 258. As the jaw 224 passes downwardly through the opening 252, the jaw 254 engages the ice chunks to crush them against the side

walls of the opening 252 to cause all developed particles 148 of a dimension less than the width of the opening 252 to pass therethrough. Any ice chunks which do not pass through the opening 252 are picked up by the next ice crusher jaw for recrushing so that a continuous supply of ice particles 148 is developed beneath the mandrel 226. The ice particles 148 exit the ice crusher through outlet 150 as they travel in the direction of arrow 152.

The cool dry air is injected through nozzles 236 and 238 beneath the mandrel 226 serve to remove any moisture from the surfaces of the solid chunks of ice as well as provide an upward flow of air through the ice crusher to provide to some degree fluidization of the particles 130 as they fall downwardly onto mandrel 226. After the particles are classified by classifier

118, the particles of acceptable size 178 are fed in the direction of arrow 152 into the inlet 214 of the fluidizer 120. With reference to Figure 18, the fluidizer 120 has a body portion 260 secured to plate 262. The plate 262 is in turn secured to the outlet of the classifier 118. The rotor for the fluidizer is mounted on shaft 264 which is driven by a suitable power means, such as an electric motor. The electric motor rotates the shaft 264 in the direction of arrow 266. Ice particles within the fluidizer are fluidized by pressurized, dry, cool air introduced into fluidizer chamber inlet 268 in the direction of arrow 270. The fluidized particles flow out from fluidizer chamber through outlet 272 in the direction of arrow 274. The section of Figure 19 shows that within the body portion 260, is a jacketed cooling chamber 276 which cools the inner surface 278 of the fluidizer to ensure the solid state for the ice particles. As shown in Figure 19, the fluidizer consists of a rotor 280 which has mounted thereon a plurality of vanes 282. Each vane 282 is secured in the rotor mandrel 284 where the rotor is mounted on the drive shaft 264.

The inner surface 278 of the fluidizer is cylindrica ^l 'n shape. The extremity 286 of the vanes contact the nner surface 278 of the fluidizer so that as the rotor 280 rotates in the direction of 26f5 a plurality of longitudinal circumferentia;ly moving chambers 288 are defined. The fluidizing chamber 288 is exposed to the inlet 214 into which the ice particles 178 fall. The extent to which the fluidizing chamber is filled with ice particles is dependent upon the rate at which the ice particles are fed into the inlet 214 and the rate at which the rotor 280 is rotated in the direction of arrow 266. It has been found that delivery rate in the range of 400 pounds per hour of ice, a -tational speed of approximately 20 rpm for the rotor is required. As the rotor continues rotation the chamber containing ice particles moves beneath the cylindrical interior 278 and moves towards the fluidizing air inlet 268. The manner in which the ice particles are f' .dized shall be discussed with respect to Figure 21. After the ice particles flow out of the fluidizing chamber 288, continued rotation of the rotor exposes the chamber 288 to an outlet 290 which is open to atmosphere. This allows any remaining air pressure in the chamber 288 to be exhausted before opening to the inlet 214 to receive a fresh supply of ice particles.

As shown in Figure 21, the fluidizing unit 120 ha^ a smoothly curved pressurized air inlet 268 which allow? the pressurized air to enter the chamber 288 in the direction of arrow 270. This occurs as the vane 282 passes over the enlarged inlet 292 for the chamber 288. Tfc">. pressurized air enters smoothly curved inlet 268 and rushes into the chamber 288 to fluidize the ice particles 178 and correspondingly cause them to flow through r^e smoothly cu 'ed outlet 272 in the direction of arrc 274. This provides for a gentle transfer of the ice particles to the outlet 272 without causing any significant degradation of the ice particle integrity. The use of

cool dry air for fluidizing the particles further enhances the maintenance of the solid characteristic for the ice particles. A sufficient volume of air is injected into the fluidizing chamber 288 to ensure a continued transport of the ice particles to the blast head. It is appreciated, however, that in such transport supplemental air blasts may be required should longer lengths of hose be used where the volume of air used is within the aforementioned ratio of approximately 0.1 to 1.5.

The size and distribution of ice particles for the media can greatly affect the efficiency of the ice blast in doing work on the desired surface. The classifier unit 118 is useful in providing the desired particle size in the range of 1 to 5 mm. Preferably the size range is in the 3 to 5 mm. By control of the flow rates, pressurized fluid to various devices of the ice preparation and fluidizer unit, the particle size distribution can be maintained up to the blast head at which point minimal deterioration of the particles has occurred. Hence the particles are still of the size range that will do the necessary work on the work surface. Preferably the flow rate of pressurized air for delivering the ice particles to blast head is sufficient to provide particle velocities in the transport lines in the range of 10 to 20 feet per second. The flow rate of pressurized air to the blast head is sufficient to provide particle velocities at the exit of the blast head in the range of 400 feet per second. During the operation of the blast head, or for other reasons, it may be necessary to stop flow of ice particles to the blast head. It is important, however, that the ice preparation system 60 continue to operate so that ice fines do not clog up the system. With reference to Figures 17 and 20, a suitable diverter valve 124 is provided near the outlet 272 of the fluidizer to divert the flow of ice particles to waste or recycle should the

blast head be shut down. As shown in Figure 20, the diverter valve, when in a first flow through position with the outlet 294 in position 294a, directs ice particles entering the diverter valve through inlet 296 to the blast head through line 64. The outlet 294 is on a swivel housing 298 which pivots about spindle 300. An actuator not shown is capable of pivoting the outlet 294 from position 294a to 294b where the ice particles are directed to waste or recycle in line 66. The actuator for the diverter valve may respond to a signal from the blast head where the switch is provided which allows the operator to signal the actuator to move to the diverted flow position 294b. This allows the ice preparation and classifying equipment to continue to operate in steady state until resumption of work at the blast head. Purge lines 301 and 302 are also provided to blow dry cool air through the diverter valve and through the hoses 64 and 66 to clear out any ice particles which may remain in a diverter valve and supply hoses. It is appreciated that the various devices of the ice particle preparation and classifying system may be made from various grades of plastics and metals. For purposes of heat transfer, it is preferred that the ice crusher, classifying system and fluidizer be made of a metal such as aluminum or stainless steel which will not corrode in the presence of water and have a high rate of heat conductivity. It is appreciated that the vanes of the fluidizer may be of any suitable plastics material which can withstand the colder temperatures and contact with the inner surface of the fluidizer. Preferred plastic materials include high density polyethylenes and in particular ultra high molecular weight polyethylenes. Although preferred embodiments of the invention are described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.