Abstract:
Agricultural forced air heaters marketed for use in farm buildings which house poultry, swine, and livestock are quite susceptible to the accumulation of dust and other particles. These heaters are gas fired units having combustion, air mixing, blower and blower motor components assembled in a parallelepiped housing. To admit incoming air for their blowers and burners the heaters have multiple openings in the form of grid-like air intake ports on various heater sides. In the environments in which they are used the extensive use of air intake holes is a disadvantage. In the heater herein panels form four distinct chambers, a blower chamber, an air mixing chamber, a motor chamber, and a combustion chamber. Air inlets open into the motor chamber as the only air inlets in the heater housing. These air inlets provide all of the air for the heater. The airflow within the heater thus is unidirectional, flowing, when the blower is operating, from the motor chamber into both the mixing chamber and the combustion chamber, and then into the blower chamber.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     There are no applications related to this application. 
     FIELD OF THE INVENTION 
     In its broader aspect this invention pertains to agricultural building heaters, that is, heaters, frequently called agricultural heaters, designed for use in farm buildings which house poultry, swine, livestock, and, in some instances, grains. More specifically the invention relates to gas fired circulating heaters having burner-fan assemblies widely used, among other buildings, in poultry or brooder houses. 
     BACKGROUND OF THE INVENTION 
     Since the most important use of the heaters provided herein will be their installations in poultry houses where chickens and turkeys are grown, that aspect of the invention will be emphasized herein. The aim in poultry growing is to provide conditions that enable chicks to expend energy to increase body weight. Such a goal desirably results in larger, more saleable birds which resist disease. Temperature variations, however, cause chicks to expend energy to sustain their body temperatures rather than to increase their body weights. Such poultry house temperature variations thus lead to smaller, less desirable chickens and turkeys. Temperature variations can also create conditions during which weaker chicks contract diseases that can spread to healthier chicks. Obviously poultry farmers desire to maximize productivity by producing as much meat as possible for the feed consumed. Maintaining proper temperatures, then, is very important in effective poultry growing. It is desirable to keep poultry warm so that the food energy provided produces a gain in weight rather than body heat. To this end, for years the poultry industry has recognized the importance of allowing growing birds to choose their most comfortable areas. In order to provide such microclimates to precisely control them at the growing level, the poultry industry has relied on gas fired heating systems that typically include a plurality of gas burner assemblies in poultry houses. By strategically locating those heating assemblies throughout a poultry house, it is possible to provide an environment which is conducive to the growth of the birds in the flock. 
     There are two types of heating assemblies currently provided for poultry houses, radiant heaters, and forced air or fan heaters. However only radiant heaters appear to have found their way into the patent art. These radiant gas burner assemblies resemble outdoor yard gas lights, except that they are adapted to be suspended by chains and the like above the flock rather than being mounted on posts like the light fixtures. The most popular radiant heaters are the radiant screen type burners, a few examples being found in such patents as U.S. Pat. Nos. 5,964,214, 5,950,615, 5,328,357, and 4,614,166. 
     Radiant heaters are not completely satisfactory because they warm the growing birds but not the air. They heat only the side of the body that is within the reflective zone of the heater&#39;s parabolic reflector. Humans can rotate their bodies to obtain some measure of comfort using the heat emanating directly from such heaters. But it is unlikely that chickens and turkeys will flip over to balance their heat intake. In addition since a radiant heater&#39;s heat and light intensity are directly proportional to the gas input, it is impossible to maintain total darkness when the heaters are in operation. These disadvantages have led to the use of forced air heaters in poultry houses. Since a forced air heater is essentially a very hot flame with a fan behind it pushing large amounts of cold air passed the hot flame there is little room for improvement in such apparatus. This may account for our failure to find them in the patent art. The prior art, then is in the form of brochures published by the companies producing the heaters now on the market, such as the Airstream and Cumberland divisions of GSI of Assumption, Ill., Shenandoah Manufacturing Co., Inc. of Harrisonburg, Va., and Hired-Hand of Bremen, Ala. These heaters have numerous air inlets to admit those large amounts of air. Another popular gas fired heater, the L B White heater, sold by such companies as Gas Works in Yalesville, Conn., and Fort Recovery Equipment Co on line, is also provided with multiple air inlet ports. Fan heaters are generally mounted, not near the ceiling, but a few feet above poultry house floors in order to blow the heat generated by the burner close to the growing birds. 
     It is difficult to keep the ground warm when heavier colder air settles on it naturally. This has led poultry growers to attempt to lower, even more, their heaters, say to within inches of the floor to supply sufficient air to warm the dirt floors, especially when baby chicks are first introduced into a poultry house. The lowering of the heaters prevents the bedding area from becoming too cold, but it introduces other problems. As will become apparent, agricultural forced air heaters currently marketed for use in poultry houses are not totally satisfactory when used close to the floor. 
     A problem which is somewhat unique to the poultry industry is that dry feed, feathers and excrement which accumulate on dry poultry house dirt floors produce a remarkably dusty environment. To their disadvantage agricultural forced air heaters on the market are quite susceptible to the accumulation of such dust and other particles. Because of the accumulation of debris the heaters being marketed cannot be used very close to the poultry house floors. Whether the air born contaminants are kicked up by the young birds or emanate from the birds themselves, they can be ingested by the heaters. Contaminated air drawn into commercially available heaters results in accumulations which are detrimental to the burner, the fan motor, and other parts of the heater. Debris settles on horizontal surfaces within the heater, as well as on various other heater surfaces. Since these surfaces must be cleaned, the resulting maintenance of such systems adds significantly to the overall costs of raising the young chickens or turkeys. If the maintenance is deficient debris can gradually diminish the burner flame. The debris also settles on the motor and blower wheel within the heater causing the motor to run at temperatures above its design temperature. Given this environment it can be appreciated that prior art heaters are subject to improvement. It is these improvements which are within the contemplation of this invention. 
     As will be explained in greater detail hereinafter in conjunction with FIGS. 1 and 2 of the drawings, in order to admit incoming air the for their blowers and burners the commercial heaters have multiple openings for incoming air in the form of grid-like air intake ports on various heater sides. Other forced air agricultural heaters on the market are provided with similar grids for incoming air, but they are spaced across the heater floor. In the environment described the extensive use of air intake holes is quite disadvantageous. The incorporation of inlet air openings such as those shown in FIGS. 1 and 2 in the drawings leads to the debris problems alluded to. The inclusion of numerous air inlet openings does provide for greater air flow, and does produce the amount of heat desired. However it is to be realized that the intake holes require compensating adjustments. For instance, the large number of holes render it more difficult to ignite the burner within the time period set by the sensor. A higher gas pressure is required to initiate ignition. Low gas pressures lead to unreliable or failed ignitions due to lean mixtures. After ignition a high gas pressure is also required to compensate for the high air volume that flows through the burner. Since the air-to-fuel mixture required to sustain combustion subjects the heater surfaces to higher temperatures, the outsides of the heaters are hotter to the touch. A higher gas pressure requirement can also be a drawback because some actual field conditions may not be adapted to provide such a high gas pressure demands. 
     Due to the amount of wet litter and natural perspiration associated with such animals as chickens, turkeys, and pigs, the air within these animal confinements frequently becomes humid. Under these humid conditions it is virtually impossible to prevent the accumulation of debris on the motor and on the blower wheel, as well as around inlet openings and air passageways. Over time the heater&#39;s internal air paths become restricted by accumulation, forcing the airstreams to make sharp turns. When this occurs there is a tendency for larger and heavier particles to fall out of the airstream as its velocity drops during changes in direction. If not removed, the deposits build up and become hardened by exposure to damp air. Eventually accumulations tend to form around the inlet openings and on critical surfaces. The buildup often decreases the air volume by obstructing the air passageways. The decrease in air volume, as previously noted, then causes the motor to overheat and run more slowly. In addition, since the heater&#39;s gas valve generally is not designed for variable operation, the reduced inflowing air yields a richer fuel which produces a longer, larger, flame which burns hotter and more erratically. This resulting flame increases the combustion chamber temperature, and often activates the heater&#39;s high limit switch or harms the inner working parts of the heater. As the debris continues to accumulate the motor will run less and less efficiently. By this invention forced air heaters for poultry houses are improved so that they do not permit accumulations such as those described. The result is that the heater, in effect, is self-cleaning. In addition the flame is not allowed to enter the blower wheel. The improvement herein also permits the poultry house heater herein to be suspended closer to the dirt floor than existing heaters. 
     Considering now one additional aspect, the eating habits of poultry are highly influenced by daylight hours. To take advantage of this, modern poultry growing techniques embody the practice by growers of simulating the passing of days by periodically darkening their poultry houses to create night-like conditions. The practice has been found to simulate different days. Undertaking this several times a day deceives the birds so that they eat more. This light control practice helps the birds grow faster. As an example, a free-range chicken usually requires up to ten months to attain a five and one-half pound dressed size. When light control techniques are employed chickens reach their five and one half pound dressed size in forty-two to forty-five days rather than the normal ten months. The net affect is that a grower can bring forth eight or nine flocks a year, thus greatly increasing the return on his investment. 
     Given the foregoing details relative to poultry house heaters it can be seen that militating against the light control practice is the fact that under certain less-than-optimum operating conditions, the higher gas pressure in prior art agricultural heaters causes a portion of the flame to be drawn into the blower wheel. The elongated portion of the flame entering the blower housing results in visible light which is then emitted through the heater&#39;s exhaust opening, precluding total room darkness. In addition, the prior art heaters in FIGS. 1 and 2 do not offer double-wall combustion chamber protection in the case of light and heat since they utilize one or more of the exterior housing panels as part of the combustion chamber. Total darkness is further compromised because combustion light is emitted through the multiple air intake openings that are incorporated in prior art exterior housing panels. The gas fired agricultural heater provided herein does not emit any light at its sides or bottom, thus allowing for total nocturnal or simulated nocturnal darkness conditions in the poultry house. Further, by the improvement herein the poultry house heater, unlike those in the art, does not permit conditions which cause richer fuel flames. 
     SUMMARY OF THE INVENTION 
     A widely used type of agricultural heater is improved by this invention. The type of heater improved is a gas fired, forced air or fan heater having combustion, air mixing, blower and blower motor components assembled in a box-like or parallelepiped housing. The improvement herein includes interior heater compartment-forming panels which in combination with roof and floor panels form four distinct chambers within the housing. One of these chambers is a center blower chamber provided with a hot air outlet. On one side of the blower chamber, with a common wall between them, is an adjacent incoming cool air-heated air mixing chamber. On the other side, also separated by a common wall, is an adjacent motor chamber, such that the three chambers are in series. The fourth chamber is a combustion chamber whose location depends upon whether the chamber houses a vertical burner, or horizontal burner, which is new to this art. A blower is supported in the center blower chamber with its axis perpendicular to the common walls. A blower motor is mounted in the motor chamber on the common wall between the motor chamber and the blower chamber with its drive shaft extending into the blower chamber to be coupled to the blower. Air inlets open into the motor chamber, and as the only air inlets in the housing, those air inlets provide all of the air for the heater. Incoming air then initially cools the blower motor. Air passageways are provided to allow air to be drawn from the motor chamber into the air mixing chamber when the blower is operating. An opening in the common wall between the air mixing chamber and the blower chamber allows mixed ambient temperature air and hot air to flow into the blower. Openings leading from the motor chamber to the combustion chamber also allow incoming air to be drawn into the combustion chamber when the blower is operating. A passageway leading from the combustion chamber to the mixing chamber directs hot air from the combustion chamber into the mixing chamber to be mixed with incoming, ambient temperature air, to produce additional heated air to be drawn into the blower. The airflow within the heater thus is unidirectional, flowing, when the blower is operating, from the motor chamber into both the mixing chamber and the combustion chamber, and then into the blower chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In addition to FIGS. 1 and 2, included to illustrate how air is drawn into prior art forced air agricultural heaters, additional drawings are included herein to illustrate the invention, and the best mode presently contemplated for carrying out the invention, as well as additional embodiments thereof. 
     FIG. 1 is an isometric view illustrating the air inlet ports in one type of gas fired forced air agricultural heater currently on the market. 
     FIG. 2 is an isometric view illustrating another type of currently marketed agricultural heater with its housing removed to reveal the air inlet ports. 
     FIG. 3 is an isometric view showing the external appearance of the agricultural heater of this invention as it will be marketed. 
     FIG. 4 is an isometric view, partially cut away, showing internal portions of one form of the heater of this invention. 
     FIG. 5 is an isometric view, partially cut away, showing internal portions of the preferred form of the heater of this invention. 
     FIG. 6 is an enlarged side view illustrating the flame flowing from the horizontal burner depicted in FIG.  5 . 
     FIG. 7 is an isometric view, similar to FIG. 3 but showing added outlet deflecting plate and viewing port embodiments. 
     FIG. 8 is an isometric view, partially cut away to show, in greater detail, an entire deflecting plate assembly. 
     FIG. 9 is a side view of the heater of the invention showing a vortex created by the deflecting plate assembly of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The prior art has been discussed quite fully, but for the sake of clarity, prior art FIGS. 1 and 2 have been included herein. FIG. 1 is an isometric view which illustrates the general configuration of agricultural heaters of the type usually suspended above floors in poultry and livestock houses. In its as-sold form, designated by the reference numeral  9 , this class of heaters has its components assembled in a framework within a box-like or parallelepiped housing  20  preferably fabricated of metal. 
     Shown in FIG. 1 are side panels  11  (one being not visible), front panel  13  and a rear oppositely disposed panel, also not visible, along with top panel  15  and bottom panel  16  that form the parallelepiped housing  20 . FIG. 1 is a view of forced air heaters widely sold by a well-known manufacturer. The extensive use of inlet air openings can be seen in the figure. This type of heater is provided with rectangular ports  17  in at least two of its panels, such as side panel  11 , its oppositely disposed side panel, not shown, front panel  13 , and its back panel, which also is not visible. As shown in FIG. 1, in this commercially available agricultural heater, even bottom panel  16  of housing  20  is provided with a number of air inlet openings or ports. 
     FIG. 2 is an isometric view of a highly commercial agricultural heater. These heaters carry their air intake openings  19  in the bottom or floor panel  21 . The housing encasing the heater components has not been shown so that these ports can be seen. Ports  19  extend in rows all the way across the floor panel as shown and are so close together they resemble a grid-work. With the housing removed burner  22 , flame deflecting baffles  23  and blower  24 , with its inlet  25 , are visible. Because of the huge number of air intake ports there is no separate mixing zone. The grid-work in the floor beneath the burner  22  is provided for heated air-cooled air mixing. The floor of motor area  26  is also provided with air intake ports  19 . From this view of the grid-work it can be seen that the poultry house dusty environment is a matter of concern. 
     Referring now to FIG. 3, shown in that figure is one embodiment of the forced air heater of this invention. It can be seen that the heater  10  is in the form of a parallelepiped structure formed by housing  20 . The rectangular front panel  30   a , a back panel (not shown), a rectangular side panel  31 , the other side panel (not shown) and the top panel  32  are illustrated in FIG. 3, with the bottom panel not being visible. Front opening  33  is the hot air outlet, a modified form of which is to be discussed hereinafter. Also shown in the housing of heater  10  of the invention are rows  34  of inlet air ports in the side panel  31 , which encloses the blower motor chamber. It is again emphasized that this series of openings  34  is the only air intake opening to the heater. It follows that the incoming air must flow from the motor area into all of the other functional areas. To achieve this flow the functional areas have been divided into chambers. This array of chambers will become clear by referring to FIG.  4 . 
     FIG. 4 is an isometric view, partially cutaway, to show the internal portions of the heater of this invention. By the use of vertical panels  36  and  37  the heater herein has been divided into three separate chambers. Panels  36  and  37  are disposed as common walls parallel to the side panels, such as side panel  31 , to form these three chambers. Between panels or common walls  36  and  37  blower  39  is mounted in blower chamber  40 . It should be stressed at this juncture that the ignition system, the controls, the burner, the other heater components, and the blower are not the essence of this invention. Rather, they are those used in the prior art heaters mentioned hereinbefore. Thus the blower is a standard squirrel cage blower or fan chamber capable of delivering hot air at a rate of 520 to 2,000 CFM. Panel  36  serves as a common wall between blower chamber  40  and mixing chamber  42 . In mixing chamber  42  incoming cool air, that is, ambient temperature air, mixes with hot air generated by the burner  50  in combustion chamber  52 . The inner wall of mixing chamber  42  is the other side of common wall  36  between the mixing chamber and the blower chamber. The other common wall  37  is placed between blower chamber  40  and the motor chamber ( 44 ). Motor chamber  44  is fabricated to form an enclosure so that incoming air, before traveling through passageways to the mixing chamber, and through ports to the combustion chamber, first cools the motor. Motor  46  is mounted on a motor plate  47  so that the entire motor and plate assembly can be mounted/removed from common wall  37  as a unit. Motor  46 , then, is mounted on the motor chamber side of common wall  37  with the drive shaft of motor  46  extending through common wall  37  in alignment with the axis of blower  39 . The motor drive shaft is coupled to the blower so that blower  39  is driven by the motor, say, a standard one-eighth, one-fourth or one-third horsepower electric motor. 
     Vertical burner  50  is housed in a separate combustion chamber  52  which is formed by sidewalls  53  and  54  and a back wall  59  behind burner  50 . Burner  50  can be a readily available gas-fired (LP or natural gas) direct spark or hot surface ignited burner having an output of 5,000 to 250,000 BTUH. Combustion chamber sidewalls  53  and  54  are provided with air intake ports  56  for the passage of air from the motor chamber  44  where it is first drawn in through ports  34  of FIG.  3 . Combustion chamber  52  includes the area enclosed by chamber walls  53  and  54 , burner  50 , and baffle  57 , beneath which the flame is ignited. The baffle diverts the burner flame from a vertical flame to a horizontal flame. Air openings  56  supply the air from motor chamber  44  for ignition. The ignited burner flame is deflected by arcuate baffle  57  into channel  61  and is then drawn around baffle  63  by blower  39  into mixing chamber  42  as will be explained further in conjunction with FIG.  6 . In FIG. 4 heater top  32  has been cut away to show baffle  57  which confines and diverts hot air emanating from the burner so that it can be directed through channel  61  to the mixing chamber ( 42 ). Channel  61  is formed by inner combustion chamber sidewalls  65  (only one being visible), a channel bottom  64  and a channel top  66 . It has been found that the long flame path provides additional burn time, leading to greater combustion efficiency and low carbon monoxide emission. One of the features of this embodiment is the provision of a long flame. To this end channel  61  is part of combustion chamber  52  as it extends across the tops of the three chambers  44 ,  40 , and  42 . Because of the long flame path, additional air, flowing from motor chamber  44 , is supplied to the flame through openings  58   a  and  58   b . This ensures complete combustion and provides a gas force partially lifting the flame above panel  64 . The air entering combustion chamber  52  must be slowed down and reduced in volume so that dilution of the fuel mixture within burner  50  chamber is minimized. This downstream metering of air by ports  58   a  and  58   b  ensures that a rich fuel and air mixture is available for ignition, even when supplied gas pressure is lower than normally recommended. 
     Another improvement in this embodiment stems from the location of the heater air inlet openings ( 34  in FIGS. 3) relative to the air inlet openings ( 56  in FIG. 4) leading to the combustion chamber. As can be seen these openings are positioned at an angle to each other, and in close proximity. Inlet openings  34  are situated beside combustion chamber openings  56 . Fast moving airstreams within an enclosed structure cannot make abrupt ninety degrees turns without slowing down or undergoing deceleration forces. To take advantage of this fact, air intake ports  56  (FIG. 4) are positioned at a 90□ angle relative to the main airstream entering the heater through openings  34 . With this arrangement most of the incoming air does not make the ninety degrees transition through inlet ports  56 . Rather, the larger quantity of incoming air drawn by the blower bypasses combustion intake ports  56  and moves on to inlet ports  55   a ,  58   a ,  58   b , and  58   c . (See FIG.  4 ). Most of the incoming air, thus, flows naturally upwardly around burner  50  toward baffle  57 , with only a portion being drawn into the burner to mix with the supplied fuel vapor. Because of the small surface area of air inlet ports  34  relative to the heater&#39;s exhaust flow rate, a high airflow rate or velocity is achieved by this invention. For instance, with an exhaust rate of 800 to 1100 cubic feet per minute the average inlet air velocity through ports  34  in FIG. 3 will be increased to about 3200 to 4200 feet per minute due to the smaller surface area of inlet ports  34 . An inlet air velocity of this caliber can lead to burner control problems. However herein, instead of injecting a high velocity air inlet stream directly into combustion chamber  52  a portion of the turbulent high velocity airstream is siphoned off by the arrangement of the two air inlets  34  and  56 . The stream introduced into the combustion chamber through inlets  56  is a low pressure, slower moving, lower volume airstream in order to provide a desirable fuel mixture for ignition. 
     As implied in the preceding discussion of the increase in air velocity within the heater herein, one of the goals of the design of the heater is to create highly energized turbulent flow within it. A high velocity flow is important for both cooling and air metering functions. The generation and regulation of a turbulent airflow within the heater&#39;s interior plays an important role in keeping the exterior panels cool to the touch. Turbulent fluid flow is, thus, a desired flow characteristic. It is more effective than laminar flow at removing heat because it tends to break up the thin boundary layer that exists between a moving fluid and a surface. Its control not only promotes cooling, but that control also allows for an air metering capability inside combustion chamber  52 . For this reason, inlet ports  34  (FIG. 3) are divided into smaller ports. Similarly, inlet ports  56  (FIG. 4) are divided into even smaller openings, preferably about one-half the size of ports  34 . Since the path taken by the airstream from combustion  52 , through channel  61 , and finally to mixing chamber  42 , is longer and more restrictive than the side and bottom channels of the heater, it is natural that the vacuum created in the combustion chamber by blower  39  is lower. 
     As indicated hereinbefore still another feature of this invention is the provision of a heater whose housing surfaces are not hot to the touch. In addition to the velocity aspect discussed, to accomplish this various air spaces or air gaps and built-in heat sinks (to be described) are included in the heater design. There is, for example, an air space  55   a  between panel  55   c  and the housing front wall  30   a . A similar air space is fabricated along the back of the heater. Another air space is provided between housing top  32  and the tops  66  and  67  of combustion channel  61 . In general these air gaps function as built in heat shields or heat barriers between the hot inner surfaces within the heater, and the exterior housing surfaces. The air gaps are sized for the amount of air that will be passing through them at the designed air throughput speed. As a guide, the air gap must not be so small that it generates a backpressure when the system is operating. 
     In addition to the cooling achieved by the air spaces, strips or dividers can be fabricated between various adjacent openings within the heater to function as heat sinks. An example is divider  90  in FIG. 4 between openings  58   c  which will lower the temperature of panel  37 . Not shown are similar cooling webs or strips on panel  36 . Though not shown, webs  90  in the preferred embodiment may be rotated in any included angle normal to the direction of airflow from plus 90-degree to minus 90-degree. In addition, by alternating the angle from one web to the next such that any two consecutive webs are at some included angle other than zero or 180 degrees, both heat transfer and turbulence generation are greatly enhanced. 
     The incorporation of an airstream temperature barrier can be better exemplified by a, discussion of the airflow through heater  10  of the invention. As explained in conjunction with FIG. 3 all of the air for the heater  10  enters motor chamber  44  through ports  34 . When the blower is operating the incoming airflow divides so as to circulate in several airstreams flowing through various passageways toward the mixing chamber as will now be described in conjunction with FIG.  4 . Since all of the incoming air drawn in through air intake ports  34  will be drawn toward the blower, it flows first into the mixing chamber ( 42 ). One airstream passes through openings  56  into the combustion chamber  52  as described hereinbefore in conjunction with ports  58   a  and  58   b . This stream then splits into two components. One component flows into burner  50 , and then into combustion channel  61 . Channel  61  directs the heated gas stream into mixing chamber  42 . The other component flows in a passageway  45  which is formed between the top side of combustion chamber roof  66 , as well as  67 , and the underside of heater top panel  32 . After cooling the inside surface of housing top panel  32  the airstream component flows across the combustion chamber roof  66  and  67 , and finally into mixing chamber  42  through ports  60   a . Another airstream carries a greater quantity of air from the motor chamber through openings  58   c . This stream flows beneath blower chamber  40  and behind inner panel  55   c  into the mixing chamber. The front and back passageways can be visualized by referring to  55   c  in FIG.  4 . The incoming airstream flows into this passageway  55   a  between an inner panel wall  55   c  and housing front panel wall  30   a  on its way to mixing chamber  42 . To adequately cool the front panel wall  30   a  of the heater airflow passageway  55   a  extends upwardly as far as top panel  67  (FIG.  4 ). After cooling the front heater housing wall, the air flows into mixing chamber  42  through ports  60  and  60   a . A similar arrangement (not shown) exists along the back side of heater  10 . The cooling of the heater floor is accomplished by the air entering the motor chamber  44  which then flows through ports  58   c  along the floor until it enters the mixing chamber. It is to be understood that the use of similar inner cooling passageways also prevents the side walls of the housing from becoming overly hot. It can now be seen that flow of air through the heater herein is indeed virtually unidirectional. It can also be seen that cooling streams flow in passageways or channels formed along the inside walls of all six sides of the parallelepiped housing of this invention. 
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     In its preferred form the heater of this invention includes a horizontal burner. A horizontally disposed burner, new to this art, permits a longer than conventional flame path to be employed while also allowing for a controllable, compact, heating unit. By controllable we mean that with a horizontal burner the flame path can be so adjusted that it can be set to end just short of the blower entrance. Flame entering a blower is not only detrimental to the blower impeller, by unduly heating the blades, but the resulting flame is a source of light. In prior art heaters the numerous air intake openings are not fabricated to dispel light when darkness is desired in order to simulate the end of a day. By the same token light emanating because the tip of a flame entered a blower has not been dealt with. 
     For a better understanding of a horizontal burner heater FIG. 5 is given. Referring to that figure it can be seen that combustion chamber  72  lays across the tops or roofs of motor chamber  44 , blower chamber  40 , and mixing chamber  42 . Air intake openings or ports  71   a  and  71   b  provide air for ignition and combustion as did ports  56 ,  58   a  and  58   b  in the heater shown in FIG.  4 . Burner  70  is supported in its horizontal position by brackets  73  and  75  which support the burner above the combustion chamber floor so that it can receive air from below through ports  71   a  and  71   b . Also shown in FIG. 5 are an electronically actuated gas valve  76 , an igniter  77 , a gas pipe  78 , a high temperature limit or automatic shut-off switch  80 , and gas orifice unit  82 . A flame probe  84  detects the presence of a flame. All of these components, for example, the electronically actuated gas valve  76 , gas pipe  78 , and the other heater parts shown are well known and, being readily available, are incorporated in the majority of the agricultural heaters of this type. 
     As can be visualized by viewing FIG. 5 the flame actually emanates beneath bracket  73  just above the common wall  36  between the blower chamber  40  and the mixing chamber  42 . This means that there is no flame above motor chamber  44 , and blower chamber  40 . Their housing walls, then, need not be heat protected. Hence the housing front and rear walls  30   a  and  30   b  can serve as the walls of those chambers. Accordingly front heat barrier wall  55   c  and the corresponding back barrier wall terminate at the blower chamber common wall  36 . Downstream from the blower flame the front and rear housing walls  30   a  and  30   b  are heat protected by inner heat barrier walls  55   c  and airflow passageway  55   a  as explained in conjunction with FIG.  4 . The housing top panel  32  of the heater above the flame area is heat protected by heat shield or heat barrier panel  67  which is installed in the area above combustion chamber  72 . 
     On further considering FIG. 5 it is to be realized that the motor, blower, and mixing chambers beneath combustion chamber  72  are structurally and functionally similar to those in the heater previously described in connection with FIG.  4 . To repeat, then, all of the air for heater  10  first enters the motor chamber  44  through a single entry panel, that is, ports  34  in panel  31 . In this embodiment also, the airstream divides to flow as several streams passing through various passageways, all in the direction of mixing chamber  42 . As in the embodiment with the vertically disposed burner the airstream passes into the combustion chamber  72 , this time through openings  71   a  and  71   b  which are similar in location to ports  58   a  and  58   b  in FIG.  4 . Thus the arrangement and sizing of openings  71   a  and  71   b  serve the same basic functions as ports  58   a  and  58   b  in FIG.  4 . They are designed to provide the same means for low gas pressure operation by slowing down the stream of air and reducing its volume. Concomitantly flame from burner  70  is drawn around the top of baffle  63  by blower  39  during operation. In prior art heating units the flame is deflected into the mixing area by a baffle. Rather, herein the flame travels horizontally and then makes almost a 180 degree downward turn across baffle  63  as it enters the mixing chamber. Slot  74  in baffle  63  is merely an expansion joint. In order to increase the quantity of hot air entering mixing chamber  42 , another airstream carrying a greater quantity of air flows from the motor chamber  44 , through openings  58   c  in the base of common wall  37 . This airstream flows beneath blower  39 , and, passes through openings, not visible, but similar to  58   c  in common wall  36  as it enters mixing chamber  42 . 
     An additional feature herein is the provision of means for heat protecting the barrier walls themselves (See walls  55   c , FIG.  5 ). To cool these front and back interior walls  55   c , while further protecting front and rear housing walls  30   a  and  30   b , additional passageways or channels are incorporated in the heater to direct airstreams on both sides of walls  55   c . Returning to FIG. 5 it can be seen that in addition to passageway  55   a  directing air across the front of interior wall  55   c  as in the embodiment in FIG. 4, an additional passageway or channel  55   b  is included in this preferred embodiment. As can be seen the added passageway  55   b  emanates just below blower  39 , and it directs a flow of air along the backside of inner wall  55   c  to protect the metal from which that inner wall is fabricated. The passageway formed behind barrier panel  55   c  thus allows air to protect both sides of that panel, and then to flow upwardly as far as top panel  67  before passing into the mixing chamber  42  through ports  60  and  60   a . As in the vertically disposed embodiment, panels  36  and  37  also have cooling heat sink strips  90  formed between adjacent openings  58   c.    
     An especially unique feature of the preferred agricultural house heater of this invention is its inclusion of not only a horizontal flame path, but a horizontal burner. Prior art heaters produce horizontal flames from burners having gas ports directed vertically with the resulting flame deflected ninety degrees into a horizontal flow. Such diverted flames are sensitive to disruptive flows of air. The horizontal burner of this invention, although illustrated in FIG. 5, is shown in greater detail in FIG. 6, which is a partially cut away side view of the portion of the heater, showing the horizontally disposed burner  70  as it is supported by bracket  73 . Burner  70  lies across the top of panel  64  so that its flame is drawn across the top of arcuate panel  63 , disposed in mixing chamber  42  adjacent blower chamber  40 . It is to be pointed out that even after vertical flames in existing heaters are directed into horizontal flow, the flame is guided by a baffle above the flame to divert it downwardly into an ambient air-hot air mixing area. In other words the flame flows along the underside of a baffle, whereas, during operation, the flame herein is drawn across the top surface of the panel or baffle  63  as shown at  115   a  in FIG.  6 . The distance of the burner element above the combustion floor panel, and the length of the baffle plate arc are such that the burner flame terminates at the end of the baffle rather than in the blower. 
     Referring now in greater detail to the disruptive flow aspect, the diversion of a flame, say from the vertical to the horizontal, can lead to an erratic flame. Bracket  73  (FIG. 6) serves not only as a mounting platform for igniter  77 , but for a high-limit switch  80  which causes the gas valve to close when the flame becomes erratic. Whether the flame is disrupted by a gust of air, or whether the disruption is caused by some restriction, it will loose its normal disposition, such as  115   a , and assume some erratic disposition, such as  115   b , shown by the phantom lines in FIG.  6 . Some outside heaters employ various additional baffles, and even adjustable shutters, to ensure that unwanted gusts of wind do not disrupt their flames. Such precautionary measures are necessary to prevent an erratic flame from tripping the high-limit switch or the flame probe. Since the flame emanating from the burner illustrated in FIG. 6 is not diverted from a vertical to a horizontal disposition, but is ejected horizontally it is more stable. It is, therefore, less subject to disruption, and readily drawn across the top surface of arcuate panel  63 . 
     Most prior art heaters have a high-limit switch mounted facing the flame some distance away from the burner&#39;s opening. However, as the flame travels away from a burner&#39;s opening, it is transformed from a coherent flame into an incoherent flame that resembles ends of paper streamers fluttering in the wind as can be seen by observing flame  115   a  in FIG.  6 . Since their high-limit switch is often mounted only a few inches away from the incoherent portion of the flame, the flame can activate the high-limit switch initiating an overheating alarm which is false. As seen in FIG. 6, igniter  80  herein is strategically mounted very close to the origin of the flame  115   a , and perpendicular thereto. There are two reasons for this. One, by mounting high-limit switch  80  close to the opening of burner  70  where the flame is more coherent, the switch is less likely to be affected by the incoherent end of the flame. Second, since the high-limit switch is mounted perpendicular to flame it receives a smaller amount of heat from the flame by convection and radiation, and therefore runs cooler. On the other hand, when a disruption causes flame  115   a  to rise upwardly as illustrated by phantom lines  115   b , it will contact the sensing surface  116  of high-limit switch  80  and bring the sensor to its activation temperature in less than a second, safely shutting of the gas valve before internal components are subjected to destructive overheating. 
     Also unique to the agricultural heater of this invention is the disposition of the deflection plate or awning  92  illustrated in FIG.  7 . For this embodiment we refer now to FIGS. 7,  8 , and  9 . Through testing and test results it was discovered that unexpected advantages were obtained by the use of a heater outlet deflection plate, the entire assembly  91  of which is shown in FIG. 8 as an enlarged portion of the heater outlet partially cut away. As can be seen in FIG. 8 deflection plate  92  is attached along the top edge of hot air outlet  33  in front panel  30   a . Supported in hot air outlet  33 , the angular deflection plate  92  formed from a single piece of sheet metal or fabricated as a short awning made of plastic. When the inclusion of a deflection plate was planned it was intended merely to deflect the outlet hot air downwardly to compensate for the elevation of the heater. However, instead of merely deflecting the hot air downwardly, to then rise because of its lighter weight and loss of forward momentum, it was found that when the deflection panel  92  herein was curved downwardly to form an angle of about 30 degrees with the horizontal it generated a flow resembling a horizontal vortex, diagrammatically illustrated in FIG.  9 . The vortex  96  emanated at the tip just below deflection plate  92  and rotated along the floor  97  as seen in FIG.  9 . It was also found that the vortex enhanced the mixing of hot air flowing out of the heater with ambient air in the poultry house. Having made this discovery, we devised a series of tests to better quantify the flow pattern and relative strength of these horizontal vortices. By placing streamers or paper strips and small 1″×1″×4″ rectangular foam blocks on their ends at two feet increments along the floor, we were able to observe the flow pattern and force of the vortex. With the heater suspended at a height of 28 inches from the floor, the mixed hot air-ambient air vortex knocked over rectangular blocks placed as close as six feet from the heater outlet, and those as far away as 28 feet as it rolled along the floor. It then remained to observe how the horizontal vortex enhanced the mixing of hot and cold air at the ground level. In order to create a colder and denser air ground level atmosphere similar to that in a poultry house on a typical winter day, a three-inch thick fog blanket was created using dry ice and water. To prevent ambient air from skewing the results, cold air was introduced into the test area for fifteen seconds prior to the test. Within seconds, the heated air from heater outlet  33  began rotating in a cyclonic manner, quickly dispelling the fog blanket and knocking over all of the foam blocks within sixteen feet of the heater. Fifteen seconds or so later the rotating airstream or vortex knocked over foam blocks positioned as far away as the twenty-eight foot marker. Even though the force of the vortex had decreased so that it did not knock over the remaining foam blocks, it continued to disperse the fog and dust particles on the floor for at least six additional feet. In the same tests, using commercially available heaters, the hot airstream leaving the heater quickly rose from its twenty-eight inch baseline to approximately six feet by the time it reached the twelve-foot mark. It did not knock over a single foam block or cause any of the paper streamers to flutter. These observations and test results showed that the rotational momentum induced by the deflection plate prevented the hot airstream from rising naturally toward the ceiling. 
     Having been given the teachings of this invention modifications will occur to those skilled in the art. Thus, instead of being fabricated so that it is integral with the front heated wall, deflection plate  91  can be made as an assembly with a portion extending into, or forming a part of air outlet  33  as illustrated in FIG.  8 . The assembly can also be adapted to be secured to the blower housing roof. The top of blower housing  39  and the inner portion of the deflection plate can be provided with a series of mounting holes  95  (two being visible) arranged to allow for front-to-back adjustments. Slots  94  on blower housing top  39  can also be included to provide fine adjustments for deflection plate assembly  91 . While deflection plate assembly can be clearly visible when in its fully extended position as in FIG. 8, it can be retracted and hidden from view. As another variation a peephole with or without a glass or clear plastic window, such as  64  in FIG. 7, can be installed for observing the flame and the mode of operation of the heater as well as for other purposes. As still another modification, in lieu of two rows of incoming air inlet ports  34  as illustrated in FIG. 3, any arrangement of incoming air inlet ports can be employed, one example being the rows of inlet ports  34  also shown in FIG.  7 . In addition none of the air ports need be configured as shown, but can be circular, triangular, or in any other desired shape. Likewise the vertical burner need not be adjacent the motor chamber, but can be placed in any of several other locations. Other such ramifications which will be obvious to those skilled in the art are deemed to be within the scope of this invention.