Abstract:
A portable controlled heating unit providing for recirculating heated air to obtain better control of exit temperature from a heating unit. Temperature sensors of exit temperature control vaned entrances and exits under one single unit to control the recirculation.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention pertains to portable devices for providing heated air to any particular desired point. In many instances such devices may use a heat producer such as that of applicant&#39;s U.S. Pat. No. 5,819,724, issued Oct. 13, 1998, but they may also be used where the heat is produced by some other type of heater. Usually the transmission of heat is a heated oil or similar fluid. Ordinarily the heater is driven by an engine and is enclosed in a housing having an inlet and a directed outlet. 
     Particularly in very cold climates where the ambient air is drawn into the heat exchanges, there may be times when the air is not adequately heated for use in heating the desired area or where the heated air needs to be better controlled. 
     In order to do that added heating or to get improved control, this invention proposes a fairly simple recirculating device. Controls are necessary and provide for the appropriate outlet temperatures and amounts of flow. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a side elevational view of the portable recirculating unit, 
     FIG. 2 is a top plan view of the unit of FIG. 1 with parts being broken away to show underlying parts, 
     FIG. 3 is an end elevational view of the unit from the intake end, 
     FIG. 4 is a partial sectional view of the intake end of the unit, with the recirculating shutter closed, and 
     FIG. 5 is a view similar to claim  4  with the shutter opened 
    
    
     DESCRIPTION 
     Briefly this invention comprises a portable recirculating device for heated air together with controls to provide an appropriate output. 
     More specifically and referring to the drawings, the heating unit is supplied with heat by a heater of the type described in applicant&#39;s U.S. Pat. No. 5,819,724 as noted above. The heating unit is mounted on a pair of wheels  10  supporting the entire device and making it readily moveable from place to place wherever needed. A tongue  11  may be used to allow towing and placement of the unit. 
     Customarily, the unit comprising a housing  12  within which is located an engine which drives a heat generator of the type described in applicant&#39;s patent noted above and which may also drive a fan adapted to blow air through the unit and out through nozzles  13  at the exit end of the housing  12 . The entire interior of the device as well as the housing  12  itself are customary installations, and therefore none of the details are shown. The usual heating unit contains the engine, heat generator and often a fan although the radiator fan of the engine may displace any separate fans. 
     Normally the air is taken into the housing  12  at the end opposite the nozzles  13  through an open grill  15 . From the grill, the air flows through the housing  12  over the engine and through its radiator. If an auxiliary fan is used, the air may be drawn through the fan and impelled to the exit nozzle  13 . The engine is used to drive the heat generator which normally heats oil which then is circulated through tubes in a heat exchanging coil near the exit thus providing heated air to be expelled through nozzle  13 . One side may be hinged near its top edge as to provide access to the interior. This structure is conventional and is not shown in detail for that reason. 
     The problem solved by this invention arises chiefly in very cold weather when the intake air is so cold that the rise in temperature caused by the system is inadequate to provide the desired heating. To sense that inadequacy, a sensor  18  is positioned in the general area of the heat exchanger or its exit. This sensor measures the temperature of air coming out of the heat exchange and then controls the recirculating mechanism which forms the principal structure of the embodiment of the invention. The control system includes a line  19  running from the sensor  18  to a thermostat  20  on a control panel  21  in the interior of the housing  12 . The thermostat then causes a motorized control device  28  to control the inlet as described below. 
     That principal structure is placed at the entry end of the device. It consists of a chamber  22  enclosed by walls  23  (FIGS.  4  and  5 ). The bottom of the chamber is open and guarded by the inlet grill  15  through which the ambient air is pulled into the chamber  22 . 
     A bank of shutters  24  divides the chamber  22  into an inlet chamber  25  and a recirculation chamber  26 . In normal operation, the air enters through the grill  15  into the inlet chamber  25 , passes through the open shutter  24  shown in FIG.  5  and thence runs into the housing  12  and out of the nozzles  13 . 
     In the preferred embodiment, the shutters  24  include a series of vanes pivoted on axles  27  and linked together by links  28 . Thus the shutters can assume positions ranging from closed as shown in FIG. 4 to fully open as shown in FIG.  5 . It will be obvious to those skilled in the art that other forms of shutters could be used. As an example, a pair of plates having openings which could be either matched in an open position or blocked in a closed position could be used. Other types of shutters may also be considered for a similar installation. 
     When the ambient air is very cold, the sensor  18  activates a powered control device  29  which may be a small motor, a solenoid or similar device to move a control rod  30  to move the shutters  24  to or toward the closed position (FIG.  4 ). 
     The recirculation occurs because the housing  12  is constructed with a duct  31  above the engine compartment. This duct leads from the exit end of the housing  12  back to the recirculation chamber  26  from which it can be recirculated through the engine compartment and out through the nozzle  13 . 
     The sensor  18  and the control device  29  control the flow of air though the engine compartment by adjusting the shutters  24  by means of the rod  30 . The volume of recirculated air flow is controlled by a closing vane  32 . A rod  33  leads from the back of shutters  24  to the vane  32  so that when the shutters open, the vane  32  is closed. When the shutters are closed as in FIG. 4, the vane  32  will then be open. 
     Thus in normal use (FIG. 5) when the air at the outlet is sufficiently warmed, the shutters  24  are opened and the air flows freely through the grill  15  and into the housing to be continually warmed and blown out through the nozzle  13 . The vane  32  is substantially closed so that no air flows through the duct  31  and all the heated air flows straight through the system. 
     If the air entering the grill is very cold and the heat exchanger in the compartment  12  is inadequate to raise the temperature to an acceptable figure, the sensor  18  activates the control device  29  to move the shutters  24  toward the closed position. This also raises the vane  32  to open the duct  31  into the recirculation chamber  26  so as to allow air to recirculate from the discharge end of the housing to be additionally heated by passing through the heat exchanger another time. Eventually, the air is properly tempered so that the sensor  18  and control device  29  reads a correct balance and the entire unit is conditioned to deliver air from the nozzles  13  at a satisfactory temperature. 
     It is therefore apparent that by the use of the recirculating function and its controls that a more satisfactory heater can be made available.