The present invention relates generally to electric heaters and more specifically to positive temperature coefficient (PTC) electric heaters.
Two well-known types of electric heaters are the resistance-wire heater and the positive temperature coefficient (PTC) heater. In a resistance-wire heater, heat is produced by passing current through an electric wire. In a PTC heater, heat is produced by passing current through a plurality of electrically interconnected PTC (ceramic)pellets. The primary drawback of the resistance-wire heater is its propensity for overheating, which can often result in a fire if there are flammable items within the heater""s immediate vicinity. More specifically, the heat source in a resistance-wire heater can often reach temperatures as high as 1600 degrees fahrenheit, well above the limit of combustible materials. Without installing a an effective safety mechanism in the resistance-wire heaters, the possibility of overheating and fire is present.
In contrast to the resistance-wire type heaters, the possibility of overheating and fire in a PTC heater is not present. This is a result of the self-limiting characteristic of the PTC element""s temperature. Due to the physical chemistry of the doped ceramic material of which the PTC elements are made in a PTC heater, the PTC elements effectively shut off at a relatively low temperature. Typically, once a PTC element""s temperature rises to approximately 340 degrees fahrenheit, the resistance of the element rises to a point to completely eliminate the flow of current through it, thereby preventing any further rising of the FTC element""s temperature. This physical characteristic of a ceramic FTC heater element prevents overheating and eliminates the possibility of fire.
In addition, FTC heaters are more durable than resistance-wire heaters. A limitation of PTC heaters, however, is that the heat produced is directed over a relatively small area. This is due primarily to the size and shape of the heater assembly containing the ceramic pellets.
Some pertinent patents include U.S. Pat. Nos. 5,245,692, 5,197,112, 4,965,432, 4,737,616, 4,703,153, 4,518,847, and 4,459,466.
It is an object of the present invention to provide a new and improved PTC heater.
It is another object of the present invention to provide a PTC heater which is small in volume and which can generate a large amount of heat.
It is still another object of the present invention to provide a PTC heater which disperses the heat emitted over a large area.
It is yet another object of the present invention to provide a PTC heater which can be mass produced, has a minimal number of parts, and can be easily assembled.
In furtherance of the objects broadly set forth above, a positive temperature coefficient (PTC) heater is provided which comprises a housing having a front and a rear, the front and rear each having at least one opening therein, a fan mounted within the housing for producing a flow of air in from the opening in the rear and out through the opening in the front, a pair of positive temperature coefficient (PTC) heater assemblies disposed in the housing in front of the fan in side by side relationship and angled relative to each other, and a plenum mounted in the housing for directing the air flow produced by the fan toward the PTC heater assemblies.
Additional objects, as well as features and advantages, of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.