System for heating materials with electromagnetic waves

Claim 2

A process for preparing frozen material for excavation comprising the steps of: (a) inserting longitudinally elongate electromagnetic energy applicators into said material at spaced locations, each said applicator being constructed for radiation of electromagnetic energy along a substantial portion of its length; (b) sensing the temperature of said material a selected distance from at least one applicator; (c) radiating electromagnetic energy through said applicators; (d) ceasing to radiate electromagnetic energy through said applicators when said sensed temperature reaches a predetermined temperature, said predetermined temperature being at about the freezing point of said material, said selected distance being chosen so that portions of said material are heated to their freezing point and other portions of said material remain substantially unheated by said electromagnetic energy.

Claim 3

The process of claim 1 wherein said predetermined temperature is 0° centigrade.

Claim 4

The process of claim 1 including the step of: (e) thereafter intermittently radiating electromagnetic energy through said applicators to maintain portions of said material at their freezing point.

Claim 5

A process for preparing frozen material for excavation comprising the steps of: (a) inserting longitudinally elongate electromagnetic energy applicators into said material such that adjacent applicators are spaced at least a first distance apart, each said applicator being constructed for radiation of electromagnetic energy along a substantial portion of its length; (b) sensing the temperature of said material a second distance from at least one of said applicators, said second distance being less than one half of said first distance; (c) initiating radiation of electromagnetic energy through said applicators when said sensed temperature falls below a predetermined temperature, said predetermined temperature being at about the freezing point of said material; (d) interrupting radiation of electromagnetic energy through said applicators when said sensed temperature rises to a second predetermined temperature, said second predetermined temperature being at least as high as the freezing point of said material, so that portions of said material are heated to their freezing point, and other portions of said material are substantially unheated by said electromagnetic energy.

Claim 6

A process for preparing frozen material for excavation comprising the steps of: (a) inserting longitudinally elongate electromagnetic energy applicators into said material such that adjacent applicators are spaced at least a first distance apart, each said applicator being constructed for radiation of electromagnetic energy along a substantial portion of its length; (b) sensing the temperature of said material a second distance from at least one of said applicators, said second distance being less than one half of said first distance; (c) initiating radiation of electromagnetic energy through said applicators when said sensed temperature falls below a predetermined temperature, said predetermined temperature being at about the freezing point of said material; (d) interrupting radiation of electromagnetic energy through said applicators when said sensed temperature rises to a second predetermined temperature, said second predetermined temperature being at least as high as the freezing point of said material, so that portions of said material are heated to their freezing point, and other portions of said material are substantially unheated by said electromagnetic energy.

Claim 7

The process of claim 4 wherein said applicators comprise coaxial slotted antennas.

Claim 8

The process of claim 4 wherein said predetermined temperature is 0° centigrade.

Claim 9

The process of claim 4, including the step of: (e) sensing the temperature in the vicinity of at lease one of said applicators and interrupting radiation of electromagnetic energy through said applicators while said temperature in the vicinity of at least one of said applicators exceeds a predetermined temperature indicative of the overheating of said applicators.

Claim 10

The process of claim 7, further including the step of: intermittently activating and deactivating the radiation of electromagnetic energy through said applicators in response to a timer after said sensed temperature has risen to said second predetermined temperature to maintain said material at about said second predetermined temperature.

Claim 11

The process of claim 7, wherein the step of sensing the temperature of said material includes measuring the temperature at three different depths in said material, one measurement being taken at the surface, one at a depth of one-half the depth of said elongate applicators, and one at the full depth of said elongate applicators.

Claim 12

Apparatus for preparing frozen material for removal comprising: (a) a plurality of cylindrical coaxial electromagnetic wave applicators slotted along a substantial portion of their length for insertion into said frozen material; (b) electromagnetic energy generator means coupled to said applicators; (c) at least one temperature sensor for insertion into said frozen material a selected distance from said applicators; (d) first control means to initiate electromagnetic energy generation from said generator; (e) second control means for interrupting electromagnetic energy generation from said generator when the temperature sensed by said temperature sensor exceeds a predetermined temperature, said selected distance being such that, when said apparatus is in operation, portions of said material remain frozen.

Claim 13

Apparatus for preparing frozen material for removal comprising: (a) a plurality of cylindrical coaxial electromagnetic wave applicators slotted along a substantial portion of their length for insertion into said frozen material; (b) electromagnetic energy generator means coupled to said applicators; (c) at least one temperature sensor for insertion into said frozen material a selected distance from said applicators; (d) first control means to initiate electromagnetic energy generation from said generator; (e) second control means for interrupting electromagnetic energy generation from said generator when the temperature sensed by said temperature sensor exceeds a predetermined temperature, said selected distance being such that, when said apparatus is in operation, portions of said material remain frozen.

Claim 14

The apparatus of claim 10 wherein said first control means initiates electromagnetic energy generation when said temperature sensor senses a temperature below a second predetermined temperature.