The prior art presently known is disclosed in the following U.S. Pat. Nos.
______________________________________ 2 085 772 Soverhill Jul 6, 1937 2 109 279 Soverhill Feb 22, 1938 2 455 839 Walton Dec 7, 1948 2 578 819 Mast et al Dec 18, 1951 2 590 336 Mast Mar 25, 1952 2 606 274 Spierer Aug 5, 1952 2 839 657 Mast Jun 17, 1958 ______________________________________
Soverhill U.S. Pat. No. 2,109,279 shows a heater construction of the general type herein dicslosed and our invention is an improvement over such construction. An important feature of our invention resides in construction which makes the heater explosion resistant, whereby the heater may be used in hazardous areas, such as in coal mines, and coal processing areas where gas and dust particles may accumulate, as well as in areas having chemical or paint fumes which are readily ignited.
Our improved heater includes one or more heat radiating members, each cast in the form of a grid having an annular body section and integral fins radiating outwardly of the body section to dissipate heat generated by a sheathed electric heating element which is embedded within the body section for ultimate heat
The heat radiating members are disposed within a tubular casing which is open at opposite ends. A motor driven fan blows air into one end of the casing and this air is heated by passage over the heat radiating members and exits from the outer end of the casing in heated condition. An important feature of our invention resides in the construction wherein a Venturi effect is created as the air is blown over the heat radiating members, to draw air from and over the inner portion of the annular body section and thus prevent the latter from overheating. Other important aspects reside in the general construction which provides a safe and efficient heater for use in hazardous areas.