X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
2000-11-09
2003-09-30
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S068000, C250S453110
Reexamination Certificate
active
06628750
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the irradiation arts. It finds particular application in the field of product sterilization and will be described with particular reference thereto. However, it is to be understood that the present invention is also applicable to other applications and is not limited to the aforementioned application.
X-rays and electron beams have been found to be useful in the irradiation of products. This type of high energy radiation, in sufficient doses, destroys most all types of parasitic bacteria and viruses which have the potential of making people ill. This is useful for sterilizing food meant for consumption, as well as other products such as medical instruments. Of course, with x-rays and electron beams the product is free from residual radiation. High energy irradiation is used for numerous other applications including polymer modification, material treatment, and the like.
X-rays are high energy photons that are produced as a result of accelerated electrons interacting with a target. Both x-rays and electrons penetrate solid material, depositing energy along the way. In living organisms, these types of radiation interact with the tissue and can destroy it, or destroy its capability to reproduce, effectively destroying it. In polymers, the radiation breaks chemical bonds.
Electron beams are generally more effective than x-rays when destroying harmful organisms. Electrons have a higher linear energy transfer (LET) than x-rays. That is, they deposit significantly more energy per distance traveled. However, they do not penetrate as far as x-rays. Most of the electron energy is transferred near the surface of the product. Generally, effectiveness is traded for range or depth when going from electrons to x-rays. X-rays penetrate much deeper into objects but do not interact as much as electrons. Both modalities are useful, depending on the application.
The present invention provides a new and improved method and apparatus for the irradiation of product. The present invention presents a new method and apparatus that overcomes the above referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, an irradiation treatment system is given. Multiple conveyers convey product through a region to be sterilized by radiation of varying energy levels. Multiple scan horns emit either x-rays or accelerated electrons into the product.
According to a more limited aspect of the present invention, a single accelerator supplies electrons to scan horns and x-ray targets of the system.
In accordance with another aspect of the present invention, a method of irradiation is given. Products are passed in parallel through a region to be sterilized. The products are scanned by beams of electrons as they pass.
According to another aspect of the present invention, a method of product sterilization is given. A product type is manually input into a product sterilization system, variables are determined to discern optimum performance of the system, and products are fed through the system.
One advantage of the present invention is that it supports a wide range of electron potentials.
Another advantage of the present invention is that it irradiates a wide variety of consumer products.
Another advantage of the present invention is that it has both electron beam and x-ray capability.
Yet another advantage of the present invention is that it requires only one electron accelerator.
Still further benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the preferred embodiments.
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Dunn Drew A.
Fay Sharpe Fagan Minnich & McKee LLP
Kiknadze Irakli
Steris Inc.
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