Methods and apparatus using microwaves for material characteristics measurements

Claim 2

In a method of determining the characteristics of a material containing a volatile ingredient, the steps of providing an enclosed chamber and a source of microwave energy coupled to said chamber, placing a sample of said material in said chamber, supplying microwave energy from said source into said chamber to generate heat within said sample and to volatilize an ingredient of said sample while establishing at a certain point a microwave field which varies in strength as a function of the degree of the volatilization of said ingredient of the sample, and monitoring the microwave field strength at said certain point to continuously measure the degree of volatilization of said ingredient of the sample.

Claim 3

In a method as defined in claim 1, wherein the material is such that the strength of said field at said certain point levels off when said ingredient of the sample is substantially volatilized, determining the content of said ingredient by measuring the difference between the weight of the sample prior to heating thereof and the weight of the sample after the strength of said field at said certain point levels off.

Claim 4

In a method as defined in claim 2, said ingredient of said sample being the moisture therein.

Claim 5

In a method as defined in claim 2, placing said sample on a platform within said chamber connected to weighing means outside said chamber, and performing said weight difference measurement with said weighing means.

Claim 6

In apparatus for determining characteristics of a material containing volatile ingredients, metal wall means defining an enclosed chamber for receiving a sample of said material, a source of microwave energy, wave guide means for supplying microwave energy from said source to said chamber to generate heat within said sample and to volatilize an ingredient of the sample while establishing at a certain point a microwave field which varies in strength as a function of the degree of volatilization of said ingredient of the sample, probe means at said certain point for developing a signal proportional to the microwave field thereat, monitoring means for monitoring the amplitude of said signal, microwave stirrer means for directing microwave energy from said wave guide means into said chamber at continUally varying directions, and means for stopping said stirrer means at a certain position to provide a uniform condition permitting accurate measurement of said microwave field.

Claim 7

In apparatus for determining characteristics of a material containing volatile ingredients, metal wall means defining an enclosed chamber for receiving a sample of said material, a source of microwave energy, wave guide means for supplying microwave energy from said source to said chamber to generate heat within said sample and to volatilize an ingredient of the sample while establishing at a certain point a microwave field which varies in strength as a function of the degree of volatilization of said ingredient of the sample, probe means at said certain point for developing a signal proportional to the microwave field thereat, monitoring means for monitoring the amplitude of said signal, microwave stirrer means for directing microwave energy from said wave guide means into said chamber at continUally varying directions, and means for stopping said stirrer means at a certain position to provide a uniform condition permitting accurate measurement of said microwave field.

Claim 8

In apparatus for determining characteristics of a material containing volatile ingredients, metal wall means defining an enclosed chamber for receiving a sample of said material, a source of microwave energy, wave guide means for supplying microwave energy from said source to said chamber to generate heat within said sample and to volatilize an ingredient of the sample, weight measuring means for measuring the weight of said sample prior to and after heating thereof to determine the contents of the volatilized ingredient, said weight measuring means comprising a platform within said chamber and a weighing mechanism outside said chamber coupled to said platform, said metal wall means having an opening therethrough, an elongated member of dielectric material coupling said platform to said weighing mechanism, and gland means at said opening surrounding said elongated member of dielectric material and arranged for minimizing transmission of microwave energy from within said chamber and out through said opening to the surrounding space, said gland means comprising a metal tube surrounding said elongated member and mounted in and extending inwardly through said metal wall means, said tube having a length and cross-sectional dimensions such as to be tuned beyond cut-off at the frequency of said microwave energy, and a hollow annulus of plastic material extending outwardly from the outer end of said tube in concentric relation thereto and in surrounding concentric relation to said elongated member of dielectric material, and a liquid filling said hollow annulus and having high microwave absorptive characteristics.

Claim 9

In apparatus for determining characteristics of a material containing volatile ingredients, metal wall means defining an enclosed chamber for receiving a sample of said material, a source of microwave energy, wave guide means for supplying microwave energy from said source to said chamber to generate heat within said sample and to volatilize an ingredient of the sample, weight measuring means for measuring the weight of said sample prior to and after heating thereof to determine the contents of the volatilized ingredient, said weight measuring means comprising a platform within said chamber and a weighing mechanism outside said chamber coupled to said platform, said metal wall means having an opening therethrough, an elongated member of dielectric material coupling said platform to said weighing mechanism, and gland means at said opening surrounding said elongated member of dielectric material and arranged for minimizing transmission of microwave energy from within said chamber and out through said opening to the surrounding space, said gland means comprising a metal tube surrounding said elongated member and mounted in and extending inwardly through said metal wall means, said tube having a length and cross-sectional dimensions such as to be tuned beyond cut-off at the frequency of said microwave energy, and a hollow annulus of plastic material extending outwardly from the outer end of said tube in concentric relation thereto and in surrounding concentric relation to said elongated member of dielectric material, and a liquid filling said hollow annulus and having high microwave absorptive characteristics.

Claim 10

In apparatus for determining characteristics of a material containing volatile ingredients, metal wall means defining an enclosed chamber for receiving a sample of said material, a source of microwave energy, wave guide means for supplying microwave energy from said source to said chamber to generate heat within said sample and to volatilize an ingredient of the sample while establishing at a certain point a microwave field which varies in strength as a function of the degree of volatilization of said ingredient of the sample, probe means at said certain point for developing a signal proportional to the microwave field thereat, said probe means being mounted in said wave guide means and being arranged for measuring the forward flowing current in said wave guide means, monitoring means including meter means for indicating the amplitude of said forward flowing current and for establishing a value at which the amplitude of said forward flowing current levels off for a substantial time interval following complete volatilization of said one ingredient and prior to volatilization of other ingredients, means associated with said meter means and arranged to be manually set to develop an output signal when said forward pulling current levels off at said certain value, signal means operable in response to said output signal, and means responsive to said output signal for disabling said source of microwave energy.

Claim 11

In apparatus for determining characteristics of a material containing volatile ingredients, metal wall means defining an enclosed chamber for receiving a sample of said material, a source of microwave energy, wave guide means for supplying microwave energy from said source to said chamber to generate heat within said sample and to volatilize an ingredient of the sample while establishing at a certain point a microwave field which varies in strength as a function of the degree of volatilization of said ingredient of the sample, probe means at said certain point for developing a signal proportional to the microwave field thereat, said probe means being mounted in said wave guide means and being arranged for measuring the forward flowing current in said wave guide means, monitoring means including meter means for indicating the amplitude of said forward flowing current and for establishing a value at which the amplitude of said forward flowing current levels off for a substantial time interval following complete volatilization of said one ingredient and prior to volatilization of other ingredients, means associated with said meter means and arranged to be manually set to develop an output signal when said forward pulling current levels off at said certain value, signal means operable in response to said output signal, and means responsive to said output signal for disabling said source of microwave energy.