The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The use of dry ice for blast cleaning is well known in the art. In dry ice blast cleaning systems, pieces of dry ice (solidified Carbon Dioxide, CO2) are drawn into a fluid stream (typically compressed air) and moved through a blast gun. The pieces of dry ice are entrained into the gas stream and propelled out of the gun to impact against the surface to be cleaned. After the dry ice pieces collide with the surface, the dry ice pieces sublimate into gaseous CO2 and become part of the ambient atmosphere. Generally, the only remaining residue from this process is the removed surface debris.
The sizing of the dry ice pieces used in the dry ice blast cleaning system varies with the method used to produce the pieces and the items to be cleaned. One of the most common sizes approximates the size of rice grains. Another form or size of dry ice pieces are rod-shaped dry ice generally called nuggets. Dry ice nuggets generally have a larger size than previously used dry ice pieces but have a much longer shelf life than smaller-sized forms of dry ice pieces available in the market. The problem presented by the use of dry ice nuggets is that their size must be reduced for efficient use in a dry ice blast cleaning system.
One problem with conventional dry ice blast cleaning systems is that the systems are affected by ambient atmospheric conditions. In particular, operation of the conventional dry ice blast cleaning systems can be difficult in environments having high humidity or where the cleaning requires prolonged storage of the dry ice pieces. In such conditions, moisture in the ambient air in and around the system can condense around the dry ice pieces as liquid water or water ice, causing the dry ice pieces to adhere to one another and to clog the system. When operating in adverse ambient atmospheric conditions, it would be advantageous to have a dry ice cleaning blast system having a hopper formed to reduce clogging and increase user safety and to prevent the formation of ice around the dry ice pieces.
In conventional dry ice blast cleaning systems, the hopper includes welded portions having one or more weld lines. The weld lines, specifically those in the lower portion of the hopper and those between the discharge end and the lower portion, can accumulate residue of the dry ice pieces, reducing the flow through of the dry ice pieces and clogging the lower portion. This accumulation of dry ice residue is commonly referred to in the art as “bridging.” The dry ice pieces can break down in the hopper, the smaller dry ice pieces or residue are then vibrated together in the hopper which can also cause “bridging.” Typically, a user will chisel out the “bridged” dry ice residue. In some cases, a user has been known to keep the dry ice blast cleaning system in an “ON” operating state, risking bodily harm and equipment damage while chiseling out the bridged dry ice pieces or dry ice residue. Additionally, damage to the dry ice blast cleaning system may result from tools or debris falling into the hopper and into the mixing chamber.
There remains a need for a dry ice blast cleaning system which increases the efficiency of the drive ice blast cleaning system by allowing better flow of the dry ice pieces through the system.