Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
2002-05-28
2003-09-30
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S102000
Reexamination Certificate
active
06626738
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to improved blast nozzles for removing adherent material such as paint, scale, dirt, grease and the like from solid surfaces with abrasive particles propelled by air. In particular, the present invention is directed to a novel blast nozzle having a specified shape and dimensions to improve blast-cleaning efficiency.
DESCRIPTION OF THE PRIOR ART
In order to clean a solid surface so that such surface can again be coated such as, for example, to preserve metal against deterioration, or simply to degrease a solid surface such as surfaces contacting food or building structures which contain food serving or food processing operations, it has become common-practice to use an abrasive blasting technique wherein abrasive particles are propelled by a high pressure fluid against the solid surface in order to dislodge previously applied coatings, scale, dirt, grease or other contaminants. Various abrasive blasting techniques have been utilized to remove the coatings, grease and the like from solid surfaces. Thus, blasting techniques comprising dry blasting which involves directing the abrasive particles to a surface by means of pressurized air typically ranging from 30 to 150 psi, wet blasting in which the abrasive blast media is directed to the surface by a highly pressurized stream of water typically 3,000 psi and above, multi-step processes comprising dry or wet blasting and a mechanical technique such as sanding, chipping, etc. and a single step process in which both air and water are utilized either in combination at high pressures to propel the abrasive blast media to the surface as disclosed in U.S. Pat. No. 4,817,342, or in combination with relatively low pressure water used as a dust control agent or to control substrate damage have been used.
A typical dry blasting apparatus as well as a wet blasting apparatus which utilizes highly pressurized air to entrain, carry and direct the abrasive blast media to the solid surface to be treated and low pressure water for dust control comprises a dispensing portion in which the blast media typically contained in a storage tank is entrained in highly pressurized air, a flexible hose which carriers the air/blast media mixture to the blast nozzle and which allows the operator to move the blast nozzle relative to the surface to be cleaned and the blast nozzle which accelerates the abrasive blast media and directs same into contact with the surface to be treated. The blast nozzle is typically hand-held by the operator and moved relative to the targeted surface so as to direct the abrasive blast media across the entire surface to be treated.
The blast media or abrasive particle most widely used for blasting surfaces to remove adherent material is sand. Sand is a hard abrasive that is very useful in removing adherent materials such as paint, scale and other materials from metal surfaces such as steel. While sand is a most useful abrasive for each type of blasting technique, there are disadvantages in using sand as a blast media. For one, sand, i.e. silica, is friable and upon hitting a metal surface will break into minute particles that are small enough to enter the lungs. The minute silica particles pose a substantial health hazard. Additionally, much effort is needed to remove the sand from the surrounding area after completion of blasting. Still another disadvantage is the hardness of sand itself. Thus sand cannot readily be used as an abrasive to remove coatings from relatively soft metals such as aluminum or any other soft substrate such as plastic, plastic composite structures, concrete or wood, as such relatively soft substrates can be excessively damaged by the abrasiveness of sand. Moreover, sand cannot be used around moving parts of machinery inasmuch as the sand particles can enter bearing surfaces and the like.
An alternative to non-soluble blast media such as sand, in particular, for removing adherent coatings from relatively soft substrates such as softer metals such as aluminum, composite surfaces, plastics, concrete and the like is sodium bicarbonate. While sodium bicarbonate is softer than sand, it is sufficiently hard to remove coatings from aluminum surfaces and as well remove other coatings such as paint, dirt, and grease from non-metallic surfaces without harming the substrate surface. Sodium bicarbonate is not harmful to the environment and is most advantageously water-soluble such that the particles that remain subsequent to blasting can be simply washed away without yielding environmental harm.
Sodium bicarbonate blast media has been directed to the targeted surface by means of venturi-type blast nozzles typically used for directing harder abrasive media such as sand. Such blast nozzles include a hollow converging inlet portion, a venturi orifice and a diverging hollow outlet portion downstream of the orifice. Since the sodium bicarbonate blast media is less dense than sand or other hard abrasive media, the blast nozzles used to direct sand do not necessarily have the proper dimensions for accelerating the sodium bicarbonate media there through to provide the optimum velocity and most productive cleaning. It therefore, would be advantageous to design a blast nozzle which would be most useful for blast cleaning with less dense media such as sodium bicarbonate so as to obtain optimal cleaning productivity with such blast media.
It has been suggested previously that by increasing the length of the nozzle, productivity can be increased at least with respect to blasting with sand. Unfortunately, the blast nozzles used for propelling sand against a targeted surface must be formed of very heavy ceramic material to withstand the abrasive nature of the sand. Longer nozzles simply are not practical since by lengthening the nozzle, the weight of the nozzle would be greatly increased making hand-held operation of such nozzles extremely difficult. In addition, the cost would be excessive and the nozzles would be fragile and subject to breakage. Using a softer sodium bicarbonate blast media, however, allows the use of substantially lighter materials of construction to form the blast nozzle. For example, very thin stainless steel can be used to form the blast nozzle. The blast nozzle can now be lengthened without adding excessive weight thereto. Hand-held operation is now practical and a substantially improved productivity can be achieved whether dry blasting or atomized water blasting is used. The present inventor has disclosed in U.S. Pat. No. 5,484,325 that in those blast nozzles comprising a converging inlet, a venturi throat and a diverging outlet, providing the blast nozzle with a total length of at least about four times, preferably at least five times and, more preferably, at least about six times the length of the inlet, substantially improved production can be achieved by blasting with sodium bicarbonate. This improved productivity has been found whether during dry blasting or utilizing dry blasting with atomized water for dust control.
Further disclosed in aforementioned U.S. Pat. No. 5,484,325 is that optimal productivity for blast cleaning a surface with a softer, less dense blast media such as sodium bicarbonate can be achieved by a venturi-type blast nozzle characterized more specifically than by the mere relative total length to inlet length of the blast nozzle. As disclosed therein, it was found that optimal productivity can be achieved if the outlet length, that being the length of the venturi-type nozzle immediately downstream of the orifice (throat) to the outlet of the nozzle is approximately 20 times the diameter of the orifice. Generally, it was found that an outlet length that is 18 to 24 times the orifice diameter provides optimal productivity. At outlet lengths below the range cited, productivity is adversely affected. At lengths above the range, productivity is no longer improved or may be adversely affected. Along with the outlet length, optimal productivity is achieved if the outlet diameter is approximately 1.5 times the orifice diameter. Deviat
Frenkel Stuart D.
Hail III Joseph J.
Shank Manufacturing
Thomas David B.
LandOfFree
Performance fan nozzle does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Performance fan nozzle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Performance fan nozzle will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3072082