US 5,318,754 A · Microwave ashing apparatuses and components

Abstract

An apparatus for use in analyzing materials for ash content includes a walled chamber which retains microwave radiation therein, a source of microwave radiation, such as a magnetron, for radiating onto contents of such chamber, and an ashing furnace in the chamber which includes a heat resistant wall of low thermal conductivity, which is transmissive of microwave radiation, and a microwave absorptive material which is capable of being heated by microwave radiation to an ashing temperature. The furnace includes a passageway through it for the entry into the furnace cavity of a gas, such as air, and for venting gas, such as combustion products, from the furnace cavity, and preferably also includes a removable trapezoidally shaped door in a front wall thereof, which, when the chamber door is open, is readily removable from the furnace by hand, without burning the operator's fingers, despite the high internal temperature in the furnace cavity. Air flows through the chamber and around the furnace, helping to cool the exterior, of the furnace walls. It is preferred that the operation of the furnace and the ashing temperature be controlled by a combination of a temperature sensor, preferably a thermocouple, and a control mechanism, which turns the magnetron on and off as the temperature in the furnace cavity falls below or rises above a desired set temperature, respectively.

Claims17

Dependent claims

An apparatus for ashing ashable materials which comprises:

a walled microwave retaining chamber;
a source of microwave radiation for radiating onto contents of said chamber, which contents include said ashable material;
an ashing furnace within said chamber having a furnace wall of heat resistance material about an internal furnace cavity, with an opening in said furnace wall for insertion and removal of said ashable material, a door of heat resistant material for closing and opening said opening in said furnace wall, a microwave absorptive material which has a surface thereof exposed to said furnace cavity, which microwave absorptive material is capable of being heated to an ashing temperature by microwave radiation, and a passageway through said furnace for passing gas into the furnace cavity and for venting gas from said cavity, which passageway includes an upper portion through which gas is removed from an upper portion of the furnace cavity, with the furnace wall and furnace door being of heat resistant material of low thermal conductivity which is essentially transparent to microwave radiation;
a temperature sensor;
for sensing the temperature in the ashing furnace, which sensor is located in said upper portion of said passageway through the furnace and is of a size that allows passage of gas past it from the furnace cavity to the chamber through a clearance in the passageway;
and controlling means, responsive to the temperature sensor, for controlling the source of microwave radiation and thereby controlling the temperature in the ashing furnace.

3 more elements

An apparatus for ashing ashable materials which comprises:

a walled microwave retaining chamber;
a source of microwave radiation for radiating onto contents of said chamber;
an ashing furnace within said chamber having a furnace wall of heat resistant material about an internal furnace cavity, with an opening in said furnace wall for insertion and removal of an ashable sample, a door of heat resistant material for closing and opening said opening in said furnace wall, a microwave absorptive material which has a surface thereof exposed to said furnace cavity, which material is capable of being heated to an ashing temperature by microwave radiation, and a passageway through said furnace for passing gas into the furnace cavity and for venting gas from aid cavity, with the furnace wall and furnace door being of heat resistant material of low thermal conductivity which is essentially transparent to microwave radiation;
a temperature sensor, for sensing the temperature in the ashing furnace, which sensor is located in said passageway through the furnace and which is of a size to allow passage of gas from the furnace cavity to the chamber through a clearance in the passageway;
controlling means, responsive to the temperature sensor, for controlling the source of microwave radiation other thereby regulating the temperature in the asking furnace;
and inlet and outlet openings in the microwave retaining chamber wall for passage of gas into and out of said chamber, around said furnace.

3 more elements

An apparatus for ashing ashable samples which comprises:

a walled microwave retaining chamber;
a source of microwave radiation for radiating onto contents of said chamber;
an ashing furnace within said chamber having a furnace wall about an internal furnace cavity, with an opening in said furnace wall for insertion therein and removal therefrom of an ashable sample, a door for closing and opening said opening in said furnace wall, a microwave absorptive material which has a surface thereof exposed to said furnace cavity, which absorptive material is capable of being heated to an ashing temperature by microwave radiation, a passageway through said furnace for passing gas into the furnace cavity and for venting gas from said cavity, said passageway comprising an opening in an upper portion of the heat resistant wall of the asking furnace for passage of gas from the furnace cavity to the chamber, with the furnace wall and furnace door being of heat resistant material of low thermal conductivity which is essentially transparent to microwave radiation;
a thermocouple;
a controlling means, responsive to said thermocouple, for controlling the source of microwave radiation and thereby regulating the temperature in the ashing furnace;
and electrically conducting means for connecting the controlling means and the thermocouple;
with the thermocouple being located in the opening in the upper portion of the wall of the ashing furnace and with said opening being larger than the thermocouple so as to allow passage of gas from the furnace cavity to the chamber through a clearance between said opening and said thermocouple;
and inlet and outlet openings in the microwave retaining chamber wall for passage of gas into and out of said chamber, around said furnace.

5 more elements

Dependencies are inferred from the claim text.

Microwave ashing apparatuses and components

Life of this patent

Microwave ashing apparatuses and components

Life of this patent

Abstract

Claims17