Portable electric heater

Abstract

A portable heater that provides a relatively large heat output for its size in either of a natural convection mode or a forced convection mode. The heater may include an electric heating element inside of a housing. A vertical baffle in the housing may be positioned between the heating element and a front of the housing. The heater may have a housing with a volume of less than 18,000 cubic centimeters and a heat output of about 1500 Watts. Less than about 25 percent of the surface of the housing may be open to allow air flow through the housing. The heater may have a ratio of heat output to housing volume of at least 0.082, and up to 0.1

What is claimed is:  
     
         1 . A portable heater comprising: 
 a housing having an air inlet, an air outlet, an exterior surface and a front;    a plurality of baffles located within the housing; and    a heating element located within the housing, the heating element capable of heating air flowing from the air inlet to the air outlet in a natural convection mode;    wherein the baffles are constructed and arranged to help maintain at least a portion of the exterior surface of the housing at or below a threshold temperature during heating in at least a natural convection mode and at least one of the baffles is positioned between the front of the housing and the heating element.    
     
     
         2 . The heater of  claim 1  wherein the plurality of baffles comprises at least two substantially vertical baffles.  
     
     
         3 . The heater of  claim 2  wherein the heating element includes an electric heating element positioned between the two substantially vertical baffles near the air inlet.  
     
     
         4 . The heater of  claim 1  further comprising a safety device that causes heat output by the heating element to be reduced when an overheat condition is detected.  
     
     
         5 . The heater of  claim 4  wherein the safety device comprises one of a bimetal strip, a thermistor, and a thermal fuse.  
     
     
         6 . The heater of  claim 1  wherein at least a portion of the air inlet is located on a bottom portion of the housing and at least a portion of the air outlet is located on a top portion of the housing.  
     
     
         7 . The heater of  claim 1  further comprising a fan that urges air to move into the housing through at least a portion of the air inlet in a forced convection mode.  
     
     
         8 . The heater of  claim 1  wherein the heating element comprises an electric resistance heating element.  
     
     
         9 . The heater of  claim 1  wherein the threshold temperature is about 170 degrees Celsius.  
     
     
         10 . The heater of  claim 1  wherein the housing is substantially a rectangular box that is less than about 30 cm tall, less than about 60 cm long and less than about 20 cm wide.  
     
     
         11 . The heater of  claim 1  wherein the housing comprises structural components capable of being manufactured by a roll forming process.  
     
     
         12 . The heater of  claim 1  wherein the heating element is an electric heating element arranged for a heat output up to about 1500 Watts, and the threshold temperature is about 150 degrees Celsius.  
     
     
         13 . The heater of  claim 1  further comprising at least one end cap that supports the housing.  
     
     
         14 . The heater of  claim 1  wherein at least one of the air inlet and the air outlet are formed in or included in a grill capable of being formed in a punch press process.  
     
     
         15 . A portable heater comprising: 
 a housing having an exterior surface;    a heating element positioned inside the housing and constructed and arranged to heat air; and    at least two substantially vertical baffles positioned inside the housing and defining an interior zone enclosing at least a portion of the heating element and defining a secondary zone defined by an area outside of the interior zone and inside the housing;    wherein the at least two baffles, the housing and the heating element are arranged to operate in a natural convection heating mode while maintaining the exterior surface of the housing below a threshold temperature.    
     
     
         16 . The heater of  claim 15  further comprising a safety device that causes heat output of the heating element to be reduced when an overheat condition is detected.  
     
     
         17 . The heater of  claim 16  wherein the safety device comprises one of a bimetal strip, a thermistor, and a thermal fuse.  
     
     
         18 . The heater of  claim 15  wherein the housing has an air inlet, and further comprising a fan that urges air to move into the housing through at least a portion of the air inlet in a forced convection mode.  
     
     
         19 . The heater of  claim 18  wherein the heating element is an electric heating element positioned substantially between the at least two substantially vertical baffles near the air inlet.  
     
     
         20 . The heater of  claim 15  wherein the heating element comprises an electric  20  resistance heating element.  
     
     
         21 . The heater of  claim 15  wherein the heating element has a heat output at least 750 Watts.  
     
     
         22 . The heater of  claim 15  wherein the housing has a volume of less than about 16,500 ccm.  
     
     
         23 . The heater of  claim 15  wherein the housing has a volume of about 15,000 ccm.  
     
     
         24 . The heater of  claim 15  wherein the housing is substantially a rectangular box that is less than about 30 cm tall, less than about 60 cm long and less than about 20 cm wide.  
     
     
         25 . The heater of  claim 15  wherein the threshold temperature is about 170 degrees Celsius.  
     
     
         26 . The heater of  claim 15  wherein the housing has a volume of about 15,000 ccm, the heating element has a heat output of about 1500 Watts and the threshold temperature is about 150 degrees Celsius.  
     
     
         27 . A portable heater comprising: 
 a housing having an exterior surface, an air inlet and an air outlet, both the air inlet and the air outlet comprising less than about 25% of a surface area of the housing, the housing having a volume of less than about 18,000 ccm; and    a heating element located within the housing;    the heater capable of sustained operation in a natural convection heating mode while maintaining the exterior surface of the housing below a threshold temperature of about 170 degrees Celsius.    
     
     
         28 . The heater of  claim 27  wherein at least a portion of the air inlet is located on a bottom portion of the exterior housing and at least a portion of the air outlet is located on a top portion of the exterior housing.  
     
     
         29 . The heater of  claim 27  further comprising a safety device that causes the heating element to reduce heat output when an overheat condition is detected.  
     
     
         30 . The heater of  claim 27  further comprising first and second substantially vertical baffles positioned within the housing, the first baffle extending along at least a portion of a front of the housing and the second baffle extending along at least a portion of a rear of the housing, the heating element being positioned between the first and second baffles such that the first baffle is positioned between at least a portion of the heating element and the front of the housing, and the second baffle is positioned between at least a portion of the heating element and the rear of the housing.  
     
     
         31 . The heater of  claim 27  further comprising a fan that urges air to move into the housing through at least a portion of the air inlet in a forced convection mode.  
     
     
         32 . The heater of  claim 27  wherein the heating element comprises an electric resistance heating element.  
     
     
         33 . The heater of  claim 27  wherein the housing is substantially a rectangular box that is about 25 cm tall, about 55 cm long and about 13.5 cm wide.  
     
     
         34 . The heater of  claim 27  wherein the housing comprises structural components capable of being manufactured by a roll forming process.  
     
     
         35 . The heater of  claim 27  wherein at least one of the air inlet and the air outlet are formed in or included in a grill capable of being formed in a punch press process.  
     
     
         36 . The heater of  claim 27  wherein the threshold temperature is about 150 degrees Celsius.  
     
     
         37 . The heater of  claim 36  wherein the housing has a volume of about 15,000 ccm.  
     
     
         38 . The heater of  claim 37  wherein the heater has a heat output of at least about 1500 Watts.  
     
     
         39 . A portable heater comprising: 
 a housing having an exterior surface, an air inlet, an air outlet and a total volume in cubic centimeters; and    an electric heating element located within the housing;    wherein the heater has a heat output of at least 750 Watts in a natural convection mode while maintaining the exterior surface of the housing below a threshold temperature of about 170 degrees Celsius, a ratio of the heat output to the total volume of the housing being at least about 0.082.    
     
     
         40 . The heater of  claim 39  wherein the heater has a heat output of up to 1300 Watts in a natural convection mode.  
     
     
         41 . The heater of  claim 39  wherein the heater has a heat output of up to 1500 Watts in a natural convection mode.  
     
     
         42 . The heater of  claim 39  wherein the threshold temperature is about 150 degrees Celsius.  
     
     
         43 . The heater of  claim 42  wherein the ratio of the heat output to the total volume of the housing is at least about 0.09.  
     
     
         44 . The heater of  claim 43  wherein the heater has a heat output of at least about 1500 Watts.  
     
     
         45 . The heater of  claim 39  wherein the ratio of the heat output to the total volume of the housing is approximately 0.1.  
     
     
         46 . The heater of  claim 39  wherein the plurality of baffles comprises at least two substantially vertical baffles.  
     
     
         47 . The heater of  claim 39  wherein at least a portion of the air inlet is located on a bottom portion of the exterior housing and at least a portion of the air outlet is located on a top portion of the exterior housing.  
     
     
         48 . The heater of  claim 39  further comprising a safety device that causes the heating element to reduce heat output when an overheat condition is detected.  
     
     
         49 . The heater of  claim 48  wherein the safety device comprises one of a bimetal strip, a thermistor and a thermal fuse.  
     
     
         50 . The heater of  claim 39  wherein the plurality of baffles comprises first and second substantially vertical baffles positioned within the housing, the first baffle extending along at least a portion of a front of the housing and the second baffle extending along at least a portion of a rear of the housing, the heating element being positioned between the first and second baffles such that the first baffle is positioned between at least a portion of the heating element and the front of the housing and the second baffle is positioned between at least a portion of the heating element and the rear of the housing.  
     
     
         51 . The heater of  claim 39  further comprising a fan that urges air to move into the housing through at least a portion of the air inlet in forced convection mode.  
     
     
         52 . The heater of  claim 39  wherein the heating element comprises an electric resistance heating element.  
     
     
         53 . The heater of  claim 39  wherein the housing has a volume of about 15,000 ccm.  
     
     
         54 . The heater of  claim 39  wherein the housing comprises structural components capable of being manufactured by a roll forming process.  
     
     
         55 . The heater of  claim 54  wherein all of the structural components are capable of being manufactured by a roll forming process.  
     
     
         56 . The heater of  claim 39  further comprising a supporting structure to elevate the housing.  
     
     
         57 . The heater of  claim 56  wherein the supporting structure includes at least one end cap.