Grit Pickup Apparatus And Method
A grit pickup apparatus and method, and a grit pickup member used therewith that avoids the difficulties encountered with conventional devices. In accordance with certain embodiments, the grit pickup member includes an elbow-shaped preferably tubular member, having an aperture or slot formed in a wall thereof that allows communication between grit pickup media and the interior of the grit pickup member. The pickup member is submerged in the media such as granular material (e.g., sand), and as high velocity fluid travels by the aperture, the media is drawn into the interior region of the pickup member through the aperture and becomes entrained in the high velocity air stream, which carries it to the nozzle where it is expelled and directed toward a substrate to be cleaned.
The embodiments disclosed herein relate to a grit pickup device and method typically used to direct media such as granular material at an object surface to clean the same, or, for example, to strip the same of paint, dirt, grease or other coating, for example.
BACKGROUNDConventional grit pickup devices are used to clean surfaces for a variety of reasons, including polishing, degreasing, removing coatings such as paint so that the surface can be painted again, for example. These devices typically accomplish this by propelling abrasive media such as particles of sand using a high velocity fluid such as air against the surface to be cleaned, degreased, decoated, etc. For example, an air stream containing the abrasive media is created using pressure, and is directed out of a nozzle towards the substrate of interest. Preferably the abrasive media stream is ejected from the nozzle in a controlled manner, and damage to the underlying substrate is minimal or non-existent.
Known types of grit pickup devices have several drawbacks. For example, some must be adjusted based on the weight of the media being transferred. Some siphon material off the side of the media pile, causing erratic performance as the media pile erodes and is then replenished. Some cause airflow to change direction abruptly, causing poor air velocity. Most are susceptible to avalanches of media which temporarily reduces or even blocks the airflow, again causing erratic performance.
A disadvantage of this design is that the air must completely reverse direction (as shown by the arrows in the exploded insert) between the outer and inside tube which causes a drop in air velocity at exactly the point where it should be the highest. This results in poor performance.
Accordingly, it is an object of the embodiments disclosed herein to provide an improved apparatus and method for cleaning, finishing or the like surfaces of articles with a pressurized flow of media that reduces or eliminates the problems associated with conventional devices.
SUMMARYThe problems of the prior art have been overcome by the embodiments disclosed herein, which relate to grit pickup apparatus and method, and a grit pickup member used therewith that avoids the difficulties encountered with conventional devices. In accordance with certain embodiments, the grit pickup member includes an elbow-shaped preferably tubular member, having an aperture or slot formed in a wall thereof that allows communication between grit pickup media and the interior of the grit pickup member. Suitable media includes aluminum oxide, silicone carbide, garnet, glass bead, crushed glass, steel shot, sand, chilled iron, steel grit, walnut shells, corn cob, baking soda, plastic beads, polystyrene beads, cut wire shot, sawdust, rice hulls, pumice, slag, resin, or any other material which may abrade, polish or remove dirt or discoloration from a substrate. The particle size should be small enough so that it can pass through the nozzle without particles jamming together and clogging the nozzle. The nozzle is typically double the size of the air jet. The air jet size is determined by the available airflow (or fluid flow where air is not used as the carrying medium) capacity of the compressor or hose (whichever flows less). In use, the pickup member is submerged in the media such as granular material (e.g., sand), and as high velocity fluid travels by the aperture, the media is drawn into the interior region of the pickup member through the aperture and becomes entrained in the high velocity air stream. The air stream carries the granular material to the nozzle where it is expelled and directed toward a substrate to be cleaned.
Turning now to
Although air is the preferred fluid used to pick up, carry and expel the grit, other fluids, including water, also may be suitable. Although air is used as an example of a suitable fluid below, the embodiments disclosed herein are not limited to air as the fluid.
The member 10 includes an aperture 12. The aperture 12 extends through the thickness of a wall of the member 10, leads to the internal cavity 11, and is preferably oval-shaped, although other shapes are suitable and within the scope of the embodiments disclosed herein. In accordance with certain embodiments, the aperture is formed at the vertex of the angle of the member 10, and preferably the center of the aperture is formed there. In certain embodiments, the aperture is about ¾″ long at its longest dimension “L”, and ½″ wide at its widest dimension “W”. In certain embodiments, the aperture is symmetrically located with respect to the ends 13, 14. The aperture 12 can be formed by any suitable means, such as by drilling, or, for example, the member 10 can be molded with the aperture 12 formed during the molding process.
The inside diameter of the member 10 is sized based upon available airflow (e.g., the compressor size, air hose size, air et size, nozzle size, and blast hose size), and the particular diameter chosen is within the skill 1n the art. In general, the component sizes will either be determined by the available air flow or the grit size required to carry out the job effectively.
For example, a compressor capable of delivering 45 CFM @90 PSI, ⅜″ I.D. air hose, a 7/32″ I.D. airjet, a 7/16″ I.D. nozzle, a ½″ I.D. blast hose and a grit pickup member 10) with an I.D. of ½″ is a suitable combination. The size of the aperture can vary considerably with little or no effect on performance, because the lower pressure inside of the grit pickup is what determines how much grit can be conveyed to the blast gun. The lower pressure area will pick up grit until the weight of the grit in suspension exceeds the available lift. At that point, the air speed will start to slow and subsequently the lower pressure will start to moderate. The lack of strong low pressure will cause less grit to be picked up, until the airspeed recovers or the low pressure recovers, at which point full grit pickup will resume. One suitable aperture is ⅔ as wide and equal in length to the internal diameter of the tubular elbow. The size of every component can be determined by how much airflow is available and how much of that airflow is to be used. For example, an air jet that flows at 45 cfm cannot be used effectively with a compressor or air hose that can only deliver 30 cfm as air pressure will drop off instantly. However, an air jet that flows at 45 cfm (or less) can be used with a compressor/hose combination that that is capable of delivering 500 cfm. The air jet should have the lowest flow rate of all components in the system. In certain embodiments, the nozzle internal diameter is twice the internal diameter of the air jet. It will be appreciated by those skilled in the art that although in the embodiment shown the member 10 is tubular and the internal diameter is of circular cross-section, other shapes are within the scope of the present invention, and the term “diameter” as used herein is not limited to circular shapes. An internal diameter of ½ inch has been found to be suitable (for the typical application). A very large compressor could use a ¾″ I.D. or even 1″ I.D. or larger grit pickup for increased productivity. A small compressor should use a ⅜″ I.D. or ¼″ I.D. grit pickup due to low air flow capacity.
As seen in
In accordance with certain embodiments, the member 10 could be integral with the pipe 20 and/or the hose 25; e.g., formed with one or both as a single unitary unit, thereby eliminating any necessity for attachments.
In operation, the member 10 with pipe 20 and hose 25 are positioned in a material hopper 1, preferably in an orientation such that the aperture 12 in the member 10 is facing downward toward the bottom of the hopper 1, as shown in
The velocity should be sufficient to propel grit from the gun and reach the substrate.
In certain embodiments, a screen or sieve 35 may be placed over the source of granular material to allow grit to pass through but not allow clumps through. This would be helpful in keeping foreign objects from clogging the grit pickup or nozzle. The size of the screen or sieve openings 36 is within the skill in the art. The screen 35 is preferably removable to enable service or to replace it with a different size screen. Because the nozzle is always smaller than the blast hose or the aperture, the screen or sieve size must be small enough to allow only particles to pass which will not jam or clog the nozzle.
Preferably the screen 35 is high enough in the material hopper 1 so that all or at least most of the grit is screened as soon as it is introduced into the hopper 1. This allows the user to see and remove clumps or foreign items before blasting is commenced. In the embodiments where the material hopper 1 is shaped like an inverted cone or pyramid, the higher the screen is (i.e., the closer it is to the top or inlet of the hopper), the more surface area it will have, which aids in unobstructed flow. In certain embodiments, the screen can be positioned from just over the grit pickup to several feet above the grit pickup. An example of the screen being feet above the pickup would be in a large blast cabinet. The screen could act as the floor which supports the parts to be blasted. As blast proceeds, the screen filters out coating or rust particles which are too big to pass through but allows the grit to fall through to the hopper where it can be picked up and used again. The advantage of this design is foreign matter can be easily cleaned out through the cabinet door with a brush and dustpan. The downside is if it is a fine screen the grit will erode it and it will require frequent replacement.
Claims
1. A grit pickup device, comprising an angled pickup member having a wall defining an interior cavity and an aperture in said wall, a first end extending in a first direction from said aperture, and a second end extending in a second direction from said aperture, and a nozzle in fluid communication with said angled member via said second end.
2. The grit pickup device of claim 1, further comprising a source of granular material, and wherein said angled pickup member is submerged in said granular material.
3. The grit pickup device of claim 2, wherein said nozzle is in fluid communication with a high pressure fluid, which causes a high velocity air stream to enter said first end and travel past said aperture, causing said granular material to enter said interior cavity through said aperture and become entrained in said high velocity air stream.
4. The grit pickup device of claim 3, further comprising a source of granular material, and a screen between said source of granular material and said angled member.
5. The grit pickup device of claim 1, wherein said aperture is oval-shaped.
6. The grit pickup device of claim 1, wherein when said angled member is oriented so that said aperture is at the bottom of said member, said first end is angled at about 45° from horizontal.
7. The grit pickup device of claim 6, wherein when said angled member is oriented so that said aperture is at the bottom of said member, said second end is angled at about 45° from horizontal.
8. A method of directing granular material against a substrate, comprising:
- providing a source of granular material;
- submerging a pickup member in said granular material, said pickup member comprising a wall defining an interior cavity and an aperture in said wall, a first end extending in a first direction from said aperture, and a second end extending in a second direction from said aperture;
- causing said first end to be in fluid communication with ambient air unobstructed by said granular material;
- providing a nozzle in fluid communication with said second end;
- creating a high velocity air stream in said pickup member, causing said granular material to enter said interior cavity through said aperture and become entrained in said stream; and
- ejecting said entrained granular material out of said nozzle and towards said substrate.
9. The method of claim 8, wherein said aperture is oval-shaped.
10. The method of claim 8, wherein when said angled member is oriented so that said aperture is at the bottom of said member, said first end is angled at about 45° from horizontal.
11. The method of claim 10, wherein when said angled member is oriented so that said aperture is at the bottom of said member, said second end is angled at about 45° from horizontal.
Type: Application
Filed: Sep 13, 2011
Publication Date: Mar 14, 2013
Inventor: Christopher Surdam (Pomfret Center, CT)
Application Number: 13/231,142
International Classification: B24C 1/00 (20060101);