Abrading – Machine – Sandblast
Reexamination Certificate
2000-04-11
2002-05-21
Banks, Derris H. (Department: 3723)
Abrading
Machine
Sandblast
C451S100000
Reexamination Certificate
active
06390898
ABSTRACT:
FIELD OF INVENTION
The invention relates to a method for treating and, especially, for the cleaning, abrasive stripping or clearing of coatings, graffiti or other superficial contamination on parts, workpieces or surfaces made of stone, concrete, wood, metal, plastic, glass, ceramic or paper, whereby a blasting agent is gravity fed from a supply container to a carrying air stream which is guided inside a hose system consisting of incoming and outgoing lines, transported by means of negative pressure through the same and blasted from a blasting chamber through a blasting lance against the surface to be treated, and from there transported back into the carrying air stream, so that the blasting agent in recirculated.
The invention relates also to a device for implementing the method with a supply container with a conically shaped lower end as a discharge funnel provided with an outlet opening for feeding a fine-grained and/or coarse-grained blasting agent, which by gravity reaches the outlet opening of the discharge funnel, which via a flexible incoming line for the transport of the blasting agent is connected with a blasting chamber, which can be evacuated by means of an underpressure-producing aggregate and accommodate the parts and surfaces, which in turn is connected with an outgoing underpressure line, whereby through an opening in the blasting chamber a blast lance connected with the incoming underpressure line provided with a nozzle is guided.
The invention relates also to the use of sodium hydrogen carbonate, thermoset plastic particles, ash, comminuted fine-grained slag, corundum, quartz, metallic particles, glass beads, vegetable/organic particles or mixtures thereof for the removal of paint, spray paint, graffiti or other contaminants.
BACKGROUND OF THE INVENTION
It is known to remove coatings or other contaminants such an deposits from walls with a blasting treatment with grains blasting agents which are blasted with an overpressure of 10 to 300 bar against the object to be blasted. The blasting agent, mostly fine-grained sand or metal particles, is transported to the blasting location with a copressed air stream (see DE 31 27 012 A1, DE 34 13 576 A1, DE 37 38 246 A1, DE 40 03 324 A1, DE 40 14 085 C1, DE 41 43 113 C; DE 42 01 860 C1).
From DE-OS 29 16 131 a surface is treated with the aid of a container provided at its lower end with a discharge funnel with an outlet for a grinding agent, with a pistol guiding the grinding agent unto the surface to be treated. The pistol is traversed by a channel at whose end a compressed-air source is connected. An incoming line connects the outlet of the container with the channel in the pistol at a point upstream of the connection with the compressed-air source. An opening is provided in the incoming line close to the outlet, through which the atmospheric pressure is in communication with the incoming line, so that the compressed air which flows through the pistol channel and over the end of the incoming line generates a negative pressure in the incoming line which sucks air through the opening, whereby the grinding agent is aspirated through the outlet and blasted against the surface to be treated at the other end of the pistol channel.
The barrel of the pistol is surrounded by a hood, which can be positioned on the surface to be treated. From the hood a return line leads to the container, on which also a vacuum source is connected, which generates a negative pressure over the stored grinding agent, which aspirates from the hood the materials blasted against the surface to be treated.
With this known system two circuits are established, a negative pressure circuit for the aspiration of the used blasting material and an overpressure circuit which accelerates the blasting material to the necessary blasting velocity, whereby the addition of the blasting material in the overpressure circuit is performed with the negative pressure created by the overpressure. Both circuits are separated from each other by the blasting material stored in the container acting as a pressure barrier.
Finally for the production of the necessary blasting velocity, this known system also works with an overpressure which must be delivered to the blasting pistol and is energy consuming. The additionally required negative pressure generator in the collection container complicates matters even more.
Due in part to the considerable overpressure the blasting agents have a high impact energy, which in the case of a sensitive substrate, for instance plastic surfaces, can lead to damage or even destruction. A gentle detachment without damage to the substrate is not possible.
A further disadvantage in that a separation of the detached lacquer layer from the blasting material does not take place, i.e. the contaminated blasting material has to be discarded and replaced.
From the DE-OS 44 07 956 a sand blasting box is known for the surface treatment of preferably flat material surfaces, which on its frontal side has an opening whereinto the frontal end of a sand blasting pistol connected to a compressed-air source is introduced. The rear side of the sand blasting box has a treatment window with an elastic sealing strip, which can be positioned over the material surface to be treated. The blasting sand is directed by means of compressed air, i.e. under overpressure, onto the surface to be treated. A commercially available household vacuum cleaner in connected to the sand blasting box. which produces a negative pressure in the blasting box and aspirates the blasting material. The barrel of the blasting pistol is guided in the blasting box by means of a rubber diaphragm arranged at the end and is capable of swinging motion in order to project the blasting material at various angles and distances onto the treatment surface.
Also in this known solution the blasting material receives its blasting and moving energy through overpressure. Again two separate circuits are required, namely an overpressure circuit in the form of a compressed-air stream for the transport of the sand to the pistol and a negative pressure circuit for the aspiration of the sand exiting the pistol. Therefore the costs are high.
After blasting the blasting material is contaminated with the removed matter. There is no separation, so that also in this system the blasting material has to be discarded or separately processed again. The stream of blasting material created by the overpressure is extremely energy-rich and not suited for the detachment of coating from problematic soft substrates, because it in not possible to adjust the blasting energy.
The DE 36 29 623 A1 discloses a device for cleaning of surfaces of large objects with a granular blasting agent, with a blasting basket movable parallel to the object surface, wherein over an open side a blast against the surface of the object can be created and which captures and evacuates the particles of blasting material with the detached dirt particles ricocheting from the material surface. This apparatus is connected with an operator cabin equipped with observation windows, so that the installation is in plain view of the operator and forms a mobile work unit together with the cabin. The blasting space is connected via a flexible line with a negative pressure space, wherein separating devices for the separation of the exhaust air, recyclable blasting agents and residuals are provided. The recycled blasting agent is guided towards a spinner, whose rotational velocity sets the blasting intensity.
A recirculation of the blasting agent is achieved, but here too a circuit for the aspiration of used blasting agent through negative pressure and a circuit for the actuation of a blasting turbine with a spinner are required. The blasting agent receive its energy through the rotation of the spinner, which in expensive from the point of view of equipment and control technology. For the removal of for instance graffiti such a construction is much too complicated and consumes too much energy.
DE 196 14 555 A1 describes a device and a method for the abrasive blasting, parti
Banks Derris H.
Dubno Herbert
Shakeri Hadi
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