Laminar air flow, low temperature air heaters using thick or thin film resistors

Abstract

An elongate heating element that includes an insulative substrate and a resistive coating that heats to a predetermined temperature when an electrical current is passed through the coating. The insulative material forming the substrate is preferably a ceramic such as cordierite, but the invention is not limited to any particular insulative material.

1 . A heater comprising: 
 an insulative substrate;    a resistive film on the substrate having first and second spaced apart portions;    first and second connectors in communication with the respective first and second spaced apart portions of the resistive film, and adapted for directing an electrical current from an electrical source through the resistive film; and,    an air moving device for directing an air stream over the resistive film.    
   
   
       2 . A heater according to  claim 1  further comprising the insulative substrate including an insulative film formed on a substrate.  
   
   
       3 . A heater according to  claim 1  further comprising the insulative substrate being at least one hollow tube.  
   
   
       4 . A heater according to  claim 1  further comprising the insulative substrate being a plurality of hollow tubes.  
   
   
       5 . A heater according to  claim 3  further comprising a housing and the at least one hollow tube mounted in the housing.  
   
   
       6 . A heater according to  claim 4  further comprising a housing and the plurality of hollow tubes mounted in the housing.  
   
   
       7 . A heater according to  claim 5  further comprising the housing having at least one mounting bracket protruding from an inner surface of the housing and the at least one hollow tube mounted in the at least one mounting bracket.  
   
   
       8 . A heater according to  claim 6  further comprising the housing having a plurality of mounting brackets protruding from an inner surface of the housing and the plurality of hollow tubes mounted in the mounting brackets.  
   
   
       9 . A heater according to  claim 7  further comprising the at least one mounting bracket in communication with the electrical source and the first and second connectors.  
   
   
       10 . A heater according to  claim 8  further comprising the mounting brackets in communication with the electrical source and the first and second connectors of the plurality of hollow tubes.  
   
   
       11 . A heater according to  claim 5  further comprising the at least one hollow tube having inner and outer heat transfer surfaces, the outer heat transfer surface comprising the resistive film.  
   
   
       12 . A heater according to  claim 6  further comprising the plurality of hollow tubes each having inner and outer heat transfer surfaces, each outer heat transfer surface comprising the resistive film.  
   
   
       13 . A heater according to  claim 5  further comprising the at least one hollow tube having a longitudinal axis and being disposed in the housing with the longitudinal axis parallel to a direction of airflow through the housing.  
   
   
       14 . A heater according to  claim 5  further comprising the at least one hollow tube having a longitudinal axis and being disposed in the housing with the longitudinal axis perpendicular to a direction of airflow through the housing.  
   
   
       15 . A heater according to  claim 1  further comprising the insulative substrate including at least one plate.  
   
   
       16 . A heater according to  claim 1  further comprising the insulative substrate being a plurality of plates.  
   
   
       17 . A heater according to  claim 15  further comprising a housing and the at least one plate mounted in the housing.  
   
   
       18 . A heater according to  claim 16  further comprising a housing and the plurality of plates mounted in the housing.  
   
   
       19 . A heater according to  claim 17  further comprising the housing having at least one mounting bracket protruding from an inner surface of the housing and the at least one plate mounted in the at least one mounting bracket.  
   
   
       20 . A heater according to  claim 18  further comprising the housing having a plurality of mounting brackets protruding from an inner surface of the housing and the plurality of plates mounted in the mounting brackets.  
   
   
       21 . A heater according to  claim 19  further comprising the at least one mounting bracket in communication with the electrical source and the first and second connectors.  
   
   
       22 . A heater according to  claim 20  further comprising the mounting brackets in communication with the electrical source and the first and second connectors of the plurality of plates.  
   
   
       23 . A heater according to  claim 15  further comprising the at least one plate having first and second heat transfer surfaces, the first heat transfer surface comprising the resistive film.  
   
   
       24 . A heater according to  claim 16  further comprising the plurality of plates each having first and second heat transfer surfaces, each first heat transfer surface comprising the resistive film.  
   
   
       25 . A heater according to  claim 17  further comprising the at least one plate disposed in the housing with a first surface parallel to a direction of airflow through the housing.  
   
   
       26 . A heater according to  claim 17  further comprising the at least one plate being disposed in the housing with a first surface perpendicular to a direction of airflow through the housing.  
   
   
       27 . A heater according to  claim 1  wherein the resistive film comprises a thin film.  
   
   
       28 . A heater according to  claim 27  wherein the thin film is formed by a process selected from the group consisting of chemical vapor deposition and physical vapor deposition methods.  
   
   
       29 . A heater according to  claim 1  wherein the resistive film comprises a thick film.  
   
   
       30 . A heater according to  claim 29  wherein the thick film is formed by a process selected from the group consisting of screening and spraying.  
   
   
       31 . A heater according to  claim 3  wherein the at least one hollow tube includes at least two concentric tubes, each tube having the resistive film formed thereon.  
   
   
       32 . A heater according to  claim 3  wherein the at least one hollow tube includes at least one hollow, conical tube.  
   
   
       33 . (canceled)  
   
   
       34 . A heater according to  claim 15  wherein the resistive film comprises a trapezoidal resistive film.