US 5,756,975 AGranted

Apparatus and method for microwave curing of resins in engineered wood products

AssigneeEwes Enterprises

InventorsGeorge M. Harris, Peter Robicheau, Leonard J. Groves, Deepay Mukerjee

Life of this patent

Estimating the term…

Loading patent…

Abstract

An apparatus, system, and method, for using circular mode magnetic microwave energy to heat the interior regions of a work piece of wood fiber and glue. The microwaves are generated and transmitted as rectangular waveguide mode microwave energy, and are converted by mode converter to circular magnetic mode microwave energy. As circular magnetic mode microwave energy, the microwave energy passes through a work piece or billet of material is reflected on the other side, and travels through the billet a second time. Reflected microwave energy from the main reflected wave as well as reflections from other structures, surfaces and layers in the system travel back toward the microwave source. They are sensed, and a computer tuning system causes capacitive probes to generate offsetting microwave reflections, which are opposite in phase and equal in magnitude to the sum of all of the reflected waves. These induced reflections cancel and negate the reflected microwaves, resulting in optimum utilization of microwave energy to heat the wood in the billet.

Claims26

Dependent claims

A system for producing dimensioned material using a fibrous component and a binder material which are organized in layers into a billet, where the billet has a longitudinal axis in which said system utilizes microwaves to heat the billets in a press with platens or in a preheating stage before the billet is pressed, by illuminating the billet with an incident traveling wave of microwave energy which passes through the billet, is reflected back through the billet as a reflected wave, the reflected wave is sensed, and tuned to cancel a reflected microwave energy, said system comprising:

one or more microwave sources for generating microwave energy and directing the microwave energy into a wave guide network;
a wave guide network for guiding a microwave traveling wave from the microwave source to the billet as microwave energy in the form of a rectangular wave guide mode;
one or more mode converters located in the wave guide network which convert rectangular wave guide mode microwave energy to a form of microwave energy called circular magnetic mode microwave energy;
one or more circular magnetic mode microwave applicators connected to the wave guide network for directing the circular magnetic mode microwave energy from the mode converters to the billet;
a heating chamber, through which the billet is passed and in which the billet is irradiated with circular magnetic mode microwave energy, from the circular magnetic mode microwave applicators;
one or more microwave reflecting surfaces mounted in the heating chamber on a side of the billet opposite the microwave applicators, for sending a reflected microwave energy wave which exits an opposite side of the billet directly back into the billet and toward the microwave applicators;
one or more sensors of microwave energy for measuring reflected microwave energy which is traveling toward the microwave source in the wave guide network, and for reporting measured energy as reflected microwave energy measured to a computer tuning system;
a computer tuning system which uses the reflected microwave energy measured by the sensors of microwave energy to calculate adjustments in a means of tuning the microwaves which are required to reduce the reflected microwaves traveling toward the microwave source to approximately zero;
a means for tuning the microwaves based on control signals from the computer tuning system;
and
a press with platens for pressing layers of the fibrous component and the binder together while the billet is being irradiated with microwave energy or after the billet has been irradiated with microwave energy.

8 more elements

An apparatus for generating heat in a billet, in which the billet has a longitudinal axis and a transverse axis, and consists of a fibrous component and a binder material, in which the billet is to be placed in a press while the binder material cures, and the heat is generated by illuminating the billet with a traveling wave of microwave energy which passes through the billet, is reflected back into the billet, is sensed, and is tuned to cancel a reflected microwave energy, the apparatus comprising:

one or more microwave sources for generating microwave energy in the form of a traveling wave and directing the microwave energy into a wave guide network;
a wave guide network for guiding a microwave traveling wave from the microwave source to the billet as microwave energy in the form of rectangular wave guide mode;
one or more mode converters located in the wave guide network which convert the rectangular wave guide mode microwave energy generated by the microwave sources to circular magnetic mode microwave energy;
one or more circular magnetic mode microwave applicators connected to the wave guide network, for directing the circular magnetic mode microwave energy from the mode converters to the billet;
a heating chamber through which the billet is passed and in which the billet is irradiated with circular magnetic mode microwave energy from the circular magnetic mode microwave applicators;
one or more microwave reflecting surfaces mounted in the heating chamber on a side opposite the billet from the microwave applicators for reflecting the circular magnetic mode energy which exits an opposite side of the billet directly back into the billet and toward the circular magnetic mode microwave applicators;
one or more sensors of microwaves for measuring the reflected microwave energy in the wave guide network which has passed through the billet after exiting the billet and being reflected back into the billet and is traveling toward the microwave generator, as well as other reflected microwave energy, and for reporting the reflected microwave energy measured to a computer tuning system;
a computer tuning system which uses the reflected microwave energy measured by the sensors of microwaves to calculate adjustments in a means of tuning the microwaves which are required to reduce the amount of reflected microwaves passing toward the microwave source to approximately zero;
and
a means for tuning the microwaves generated based on one or more control signals from the computer tuning system.

7 more elements

A method of making dimensioned material using a fibrous component and a binder material component which cures, and in which a rate of curing is accelerated by heat, these two components being arranged in a billet with a center and a longitudinal axis, in which the method comprises:

combining the fibrous component and the binder material into a billet, for subsequent curing;
generating microwave energy from a microwave source, for heating the billet and curing the binder material;
conducting the microwave energy through a rectangular microwave wave guide network as rectangular wave guide mode microwave energy from the microwave source to one or more mode converters, for application of the microwave energy to the billet in a microwave energy field;
converting the microwave energy sent from the microwave source from rectangular wave guide mode to a traveling wave of circular magnetic mode using a microwave energy mode converter;
illuminating the billet with the traveling wave of circular magnetic mode microwave energy, for heating the billet and curing the binder material;
reflecting that portion of the traveling wave of circular magnetic mode microwave energy which passes through the billet, back into the billet after it has passed through the billet by the use of a reflecting surface, for the purpose of maximum utilization of microwave energy for producing heat;
sensing the reflected microwave energy which travels back through the billet and toward the source of the microwave energy from a reflecting surface, so that it can be tuned to reduce reflected microwave energy;
tuning the microwave energy in the microwave wave guide network so that the reflected microwave energy traveling toward the microwave source is canceled by induced reflections of an opposite and equal nature in the microwave energy traveling from the microwave source and reduced to approximately zero;
passing the billet through the microwave energy field in a continuous motion;
passing the billet through a press which applies pressure to the billet for a period of time during which the binder material completes curing;
and
passing the billet out of the press.

9 more elements

Dependencies are inferred from the claim text.