Abstract:
A burner includes a motor driven blower, an air tube having an inlet end portion and an outlet end portion, a housing forming an air flow path between the blower and the air tube, a nozzle for spraying liquid fuel or orifice for dispersing gas toward the outlet end portion of the air tube and a conduit for feeding the fuel to the nozzle or orifice. An air flow control device and method enable air flow and pressure to be regulated at locations near the nozzle and between the blower and the nozzle.

Description:
FIELD OF THE INVENTION 
     The present invention is directed to burners whose air is supplied by a fan and motor. These include oil burners, gas burners and dual-fuel (gas/oil) burners of any practical size and having air flow adjustment mechanisms. 
     BACKGROUND OF THE INVENTION 
     Conventional burners generally include an air tube having a fuel supply conduit (or two for dual fuel) extending axially within the tube. Each fuel supply conduit is connected at one end to a fuel supply pump or gas manifold and terminates at the other end near the end of the air tube where the fuel is dispensed as an oil spray or gas. The fuel is mixed with the air which has been delivered by a motor powered blower. A burner-mounted ignition system is connected to an ignition apparatus that is located adjacent to the fuel nozzle near the exit end of the air tube where it ignites the fuel-air mixture. 
     Burners of these types employ various mechanisms for adjusting air flow. For example, an oil burner disclosed in U.S. Pat. No. 5,184,949 employs an air gate disposed downstream of the blower for controlling the flow through an air flow passage. This fails to disclose a mechanism to control the total flow while simultaneously controlling the pressure behind the flame retention head, which pressure is important for reliable ignition and flame stability. 
     SUMMARY OF THE INVENTION 
     In general, the present invention is directed to a burner comprising a motor driven blower in a housing. An air tube has an inlet end portion and an outlet end portion and may be mounted to the housing. The housing forms an air flow path between the blower and the air tube. In an oil burner, a conduit feeds liquid fuel under pressure to the nozzle at the outlet end portion of the air tube where it sprays the fuel. 
     One aspect of the invention includes two throttling devices affixed to the fuel conduit coaxial to the air tube, each consisting of a tapered ring and a disk located within the ring and coaxial with it. Throttling together they control the air flow to a value proper for the fuel-input rate. The upstream throttle ring is configured to reduce the upstream pressure to a value determined to provide air to the second plate (the retention plate) to an exit velocity just low enough for reliable ignition and flame stability. 
     Both throttle rings may have tapers that are converging or diverging. Both minimum and maximum firing rates may be achieved by configuring the cones properly. The adjustment direction for converging and diverging cones should be opposite to one another however. 
     A mechanism is connected to the fuel conduit (a portion of which is preferably external to the housing) to accurately move it axially, thereby controlling the positions of the rigidly affixed throttle plate and the retention plate simultaneously. Consequently, only a single adjustment setting is needed for any firing rate within the range of the burner. 
     Referring to more specific features of the invention, the air flow control device adjusts the flow rate and two pressures in the air tube, P1 and P2. P1 is the pressure delivered by the blower. It is high at low flows and diminishes more or less uniformly as the flow increases. P2 is the pressure after the first air flow restrictor, and should be quite low at low rates and gradually higher at higher rates to assure good ignition and stability as the air accelerates through the second air flow restrictor to the flame zone where the pressure is near zero. This means that the throttle ring should close down to the throttle plate at the minimum setting where P1 is high, and should open up rapidly with the flow rate as P1 falls while P2 needs to rise. 
     A preferred configuration of the first air flow restrictor consists of a round throttle plate surrounded concentrically by a throttle ring, forming a venturi which is carefully configured to maintain P2 as described above. A preferred configuration of the second restrictor consists of a round retention head surrounded by a conical retention ring, forming a venturi, which is tapered to produce the minimum and the maximum flow rates required while P2 varies as specified for stability. In the preferred embodiment, the throttle plate and the retention plate are affixed to the fuel conduit and concentric with the air tube and at a fixed axial distance apart. Also, the throttle ring and retention head are affixed to the air tube at the same fixed axial distance apart. As the adjusting mechanism moves the fuel conduit axially, the throttle plate and retention plate are displaced equally within their respective concentric rings to accurately control the flow and maintain P2 for stable combustion and reliable ignition. 
     An added advantage of this invention relates to the improved uniformity and higher combustion efficiency of the flame. This results from improved air distribution in the air tube after the throttle where air approaches the flame retention head. To enhance this, several holes are incorporated in the throttle plate. 
     The present invention advantageously enables air pressure to be simply yet precisely controlled with the air flow control device. A user need not make an adjustment near the blower and a separate adjustment in the air tube. Instead, one air flow control device may be used to meter air pressure and air flow at locations near the nozzle and between the blower and the nozzle. This advantageously achieves a desirable range of pressure near the nozzle and results in uniform air flow. The present invention advantageously may adjust air pressure and flow to a desired level using only the air flow control device, although additional adjustment mechanisms may be used, if desired. 
     In a preferred embodiment of the present invention, the burner includes an air flow control device comprising a first air flow restrictor disposed between the blower and the nozzle, a second air flow restrictor disposed downstream of the first air flow restrictor relative to the direction of air flow, and a mechanism adapted to adjust the position of both the first and second restrictor plates to control air flow. The mechanism comprises a component connected to the conduit and a member that engages the component so as to move it precisely in either direction. The mechanism and the connected portion of the conduit are preferably external of the housing. 
     In one aspect of the invention the mechanism comprises an apertured support that extends outwardly from the housing. The mechanism component comprises an arm that is pivotally connected to the housing. A protrusion extends outwardly from the arm. The member comprises a threaded rod carried in the aperture of the support. Stops may be threadingly fixed on the rod so as to flank the protrusion, wherein rotation of the rod causes the stop members to engage the protrusion and pivotally move the arm. 
     In another aspect of the invention the mechanism comprises an apertured support that extends outwardly from the housing. The component comprises a threaded rod carried in the aperture of the support and fastened to the conduit. The member comprises internal threads that engage the rod, wherein rotation of the member against the support causes movement of the rod. 
     In another aspect of the invention, the mechanism comprises an arm that is pivotally connected to the housing. The member comprises a rack and pinion, one of the rack and pinion being connected to the housing and the other of the rack and pinion being connected to the arm. Motion that is imparted relative to the rack and pinion pivotally moves the arm. 
     Yet another aspect of the invention is directed to the component comprising at least one plate connected to the conduit. The member is eccentric such that movement of each plate is effected by rotating the member. The mechanism preferably comprises a plurality of plates each containing a conduit opening for receiving the conduit and an opening for receiving the member. A location of the conduit opening in one of the plurality of plates may be offset from a location of the conduit opening in another of the plurality of plates. Each plate comprises an oblong shaped opening that receives the member. Rotation of the member in the oblong shaped opening enables movement of the plate within a predetermined range of distance. 
     Many additional features, advantages and a fuller understanding of the invention will be had from the accompanying drawings and the detailed description that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a burner constructed in accordance with the present invention; 
     FIG. 2 is an exploded perspective view depicting a portion of the burner shown in FIG. 1; 
     FIG. 3 is a cross-sectional view showing components at an air tube portion of the burner and one embodiment of an air flow control mechanism that operates pivotally; 
     FIG. 3A is a perspective view showing another aspect of the air flow control mechanism of FIG. 3; 
     FIG. 4 is a view as seen along the lines designated  4 — 4  in FIG. 3; 
     FIG. 5 is a view depicting another embodiment of the air flow control mechanism that operates using a rack and pinion; 
     FIG. 6 is a cross-sectional view as seen from the lines designated  6 — 6  in FIG. 5; 
     FIG. 7 is a view depicting another embodiment of the air flow control mechanism; 
     FIG. 8 is a cross-sectional view as seen along the lines designated  8 — 8  in FIG. 7; 
     FIG. 9 is a cross-sectional view as seen along the lines designated  9 — 9  in FIG. 7; 
     FIGS. 10 and 11 depict movement of a plate of the air flow control mechanism of FIG. 7; 
     FIG. 12 is another embodiment of the air flow control mechanism that moves linearly; 
     FIG. 13 is a cross-sectional view as seen along the lines designated  13 — 13  in FIG. 12; and 
     FIG. 14 is a cross-sectional view as seen along the lines designated  14 — 14  in FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1-3 of the drawings, the present invention is a “gun type” oil burner generally shown at  10 . The burner includes a housing  12 . Contained in the housing is a motor  14  and a blower  16  that is powered by the motor, the locations of which are generally shown in FIG. 1. A fuel pump  18  that is also powered by the motor is attached to the housing and has various inlet and outlet fittings as are known in the art. An air tube  20  is fastened to the housing and has an inlet end portion  22  and an outlet end portion  24 . The air tube has two restrictive sections  26  and  28  connected to a body  30  of the air tube. The housing forms an air flow path from an air inlet  31  to the blower and then through the air tube. The air flow path is depicted generally by dotted lines D. A nozzle  32  sprays oil toward the outlet end portion of the air tube. Oil from a fuel supply is pumped by the fuel pump through the conduit  34 . The conduit extends within the housing and bends so as to extend out of a slot  36  formed in the housing. The housing may be formed of a plastic material or of metal (e.g., aluminum). A portion of conduit  38  leads from an outlet coupling  40  of the fuel pump and is connected to the conduit  34  with coupling  42  or one of the other couplings described hereafter. 
     An air flow control device  44  comprises a first or throttle plate  46  disposed at a location between the blower and the nozzle and fitting and moving inside throttle ring  28  and a second plate or retention head  48  disposed near the nozzle and fitting and moving inside retention ring  26 . The throttle plate and retention head are connected to the conduit  34 . The air flow control device also includes a head adjustment mechanism  50  for moving the conduit and thereby adjusting the position of the throttle plate and retention head within the throttle and retention rings, respectively, for controlling air flow and pressure. 
     A transformer  52  or other ignition device is mounted to the burner. Also included is an electrical controller  54  with a safety mechanism that regulates the operation of the burner in a well known manner. A back door  56  is pivotally mounted to the housing with fastener  58  and can be locked with fastener  60 , once swung in place. The back door enables easy access to the interior of the burner. Electrodes  62  extend near the nozzle for igniting the fuel-air mixture into flame. The fuel may be any suitable combustible gaseous or liquid fuel such as oil. Although the burner shown in the drawings utilizes oil as the fuel, modifications to the burner suitable for enabling the use of gaseous fuel would be apparent to one skilled in the art in view of this disclosure. 
     As shown in FIG. 3, the throttle plate is fitted onto the conduit and held in place such as against the back of interiorly threaded member  63   a  which is threaded onto the conduit. A spider  63   b  is held in place on the member  63   a  and holds the retention head to the conduit by fingers that extend into openings in the retention head  48 . Insulators of the electrodes  62  are connected to the throttle plate. The electrodes (only one of which is seen in FIG. 3) extend to a point near the nozzle for igniting the spray of oil to produce flame. The electrodes are electrically connected to the transformer or other ignition device. 
     The throttle ring  28  is disposed around the periphery of the throttle plate  46  and fixed to the air tube. The retention ring  26  is disposed around the periphery of the retention head  48  and fixed to the air tube. The throttle and retention rings each form a venturi in the air tube. The throttle plate and retention head move within the respective venturis. As shown in FIG. 3, the throttle and retention rings have tapered cross-sectional surfaces that extend from near the air tube progressively inwardly relative to the air flow direction. Each of the throttle plate and retention head has a circumferential surface that is sized so as to form apertures of various widths with the tapered cross-sectional surfaces of the throttle ring and retention ring, respectively. The circumferences of the throttle plate and retention head are held concentrically within the throttle ring and retention ring, respectively, by ribs C disposed about the circumference of the rings. The ribs C are concentric and their innermost portions C1 extend parallel to the central axis of the air tube for guiding the retention head and the throttle plate. A first aperture B1 begins to be formed between the surface of the throttle plate that is closest to the air tube outlet, and the corresponding surface of the retention ring, and a second aperture B2 begins to be formed between the surface of the retention head that is closest to the air tube outlet, and the corresponding surface of the retention ring. These apertures B1 and B2 are variable and increase in size when the retention head and throttle plate are moved away from the outlet end portion of the air tube. The apertures may be formed by a tapered surface in the ring and mating surface in the plate or by other shapes of these components, as long as the apertures achieve the desired pressure and flow characteristics in accordance with the present invention. 
     The throttle plate  46  has openings  66 , some of which are shown in FIG. 2, for enabling sighting of the flame and for contributing to desired metering of air pressure and flow downstream of the throttle plate. The retention head  48  has a plurality of vaned openings  68  that provide for desirable air flow downstream of the retention head near the nozzle. The purpose of the vanes is for air/fuel mixing and flame shaping, as known to those skilled in the art. The retention head is also provided with an opening  70  for sighting the flame. 
     The inventive air flow control device advantageously enables air to be metered to a desired pressure and flow. In particular, the air flow control device is designed to achieve a desired pressure in the region R2, for example, a pressure of about 1 inch water column. Air in a first region R1 between the blower and the throttle plate is at a pressure P1 ranging from 1.75 to 4.50 inches water column (depending on flow). The pressure P1 is directly reduced by a first flow restrictor, (e.g., the throttle plate and ring) to a pressure P2 ranging from 0.4 to 1.1 inches water column (depending on flow). The pressure P2 in the region R2 is obtained in accordance with the present invention as a result of the air flow and pressure drop across the throttle plate and ring as well as across the retention head and ring. 
     The present invention advantageously meters the flow of air so that the air has a desired pressure near the nozzle in the region R2. The invention contemplates various ways to accomplish this result such as the use of multiple air flow restrictors or portions thereof that may move together or independently of one another, flow restrictors or portions thereof connected to the conduit that move upon movement of the conduit, and flow restrictors or portions thereof that are moved with mechanisms that do not rely upon movement of the conduit. In addition, the flow restrictor portions need not be plate shaped, but rather, may be any shape that enables air to be metered to a desired pressure near the nozzle in the region R2 downstream of the first air flow restrictor. 
     More specifically, the present invention preferably moves the throttle plate and retention head to enable the desired pressure and flow to be achieved. A preferred aspect of the invention moves the throttle plate and retention head simultaneously. The simultaneous movement of both the throttle plate and retention head with the air flow control device, enables the air flow and pressure to be conveniently controlled with a single adjustment. However, it will be appreciated by those skilled in the art in view of this disclosure that more than two plates may be used, that the plates may have different numbers and shapes of openings, and that the plates and rings may employ different geometric shapes. 
     The throttle ring and throttle plate meter air pressure and flow that are delivered to the retention ring and retention head. The retention ring and retention head meter air and provide mixing of air with fuel from the fuel nozzle for combustion. The throttle plate and retention head are moved toward the outlet end portion of the air tube to decrease air flow and control air pressure for decreased fuel firing rates such as those ranging from ½ gallon (gal) to ¾ gal per hour. The throttle plate and retention head are moved back away from the outlet end portion of the air tube to increase air flow and control air pressure for increased fuel firing rates such as those ranging from 1{fraction (1/10)} gal to 1¾ gal per hour. The throttle plate and retention head can also be moved back to increase air flow for excess combustion air, if desired. 
     The head adjustment mechanism comprises a component connected to the conduit and a member that moves so as to impart motion to the component and thus, the conduit. A portion of the conduit  34  that extends externally of the housing is connected to the component of the mechanism. One form of the head adjustment mechanism is shown in FIGS. 3 and 4. The mechanism comprises an anchor or support  74  that extends outwardly from the housing and is connected to an intermediate plate  164 . The component  70  comprises an arm  76  that is pivotally connected to the intermediate plate  164  such as by stud  78  and nut  79  as will be described in more detail hereafter. The arm preferably has a pointer portion  84  that points to readings on an indicator  86  that correspond to desired firing conditions. A coupling  87  is threaded onto a portion of the conduit  34  to lock the conduit to the arm. A cam shaped, apertured protrusion  88  extends outwardly from the arm and is disposed between nuts or stops  90   a ,  90   b  that are fixed in place on a threaded rod or bolt  90  carried by the support  74 . Rotation of a head  92  of the rod causes the stop members to engage the protrusion and pivotally move the arm in view of the cam shape of the protrusion. When the bolt is rotated so as to pull the nut  90   a  against the protrusion to the right in the view shown in FIG. 3, the arm and conduit are retracted away from the air tube outlet to enable greater air flow in the air tube at the first and second air flow restrictor areas. Conversely, when the bolt is rotated so as to push the nut  90   b  and move the protrusion to the left in the view shown in FIG. 3, the arm and conduit are moved toward the air tube outlet to restrict more air flow. The bolt may be turned by relatively small increments to enable precise air flow and pressure control as shown on the indicator. 
     Another head adjustment mechanism shown in FIGS. 5 and 6 comprises a component  70  that includes an arm  94  that is pivotally connected to the housing such as by a bolt  96 . The bolt  96  extends through an opening  98  in the arm and into a threaded opening  100  formed in the housing. The arm includes a pointer portion  102  that points at readings on an indicator that correspond to desired firing conditions. The member  72  comprises a rack  104  and pinion  106 . The rack is connected to the housing. A rotatable component  108  includes a shaft  110  that extends through an opening  112  in the arm and the pinion  106  that is configured so as to engage the rack. When a dial  114  is rotated, it causes the pinion to move along the rack, which pivots the arm and, in turn, moves the conduit. Clockwise rotation of the dial causes the arm to pivot to the left as depicted in the view of FIG.  5  and moves the conduit toward the air tube outlet, resulting in more restricted air flow. Counterclockwise rotation of the dial causes the arm to pivot to the right as seen in the view of FIG.  5  and retracts the conduit from the air tube outlet, resulting in more air flow. 
     Another embodiment of the head adjustment mechanism is shown in FIGS. 7-11 and comprises at least one plate  116 , one of which is connected to the conduit at a time. The member  72  is in the form of an eccentric  118 . Rotation of the eccentric moves each plate. The mechanism preferably comprises a plurality of plates  116  (only one of which is shown) each containing an opening  120  for receiving the conduit and an opening  122  for receiving the eccentric. The eccentric may be received in an opening  124  in the housing and at an inward end may include a shoulder  126 . Between the shoulder  126  and the housing is a snap-fit ring  128  or the like for rotatably securing the eccentric to the housing. The eccentric has a socket  130  disposed in an offset location so as to form a major plate engaging section  132 . A coupling  134  may be threaded onto threads  136  of the conduit  34  to lock the conduit to the plate. The plate may be received by upper and lower guides  138 . A pointer  140  extends from one of the guides and indicates the fuel firing rate with readings printed on each plate. 
     A location of the conduit opening  120  in one of the plates is offset from a location of the conduit opening  120  in another of the plates. For example, the conduit opening may be displaced in succession from the eccentric opening by a distance of ⅛ inch from a previous plate in the series of plates. The plates are used one at a time. Therefore, a first plate in the series of plates with its conduit opening all the way to the left enables the lowest fuel firing rate with a range determined by the degree of movement of the eccentric. A second successive plate in the series of plates with the conduit opening displaced ⅛ inch further right than the first plate would have a higher fuel firing rate compared to the first plate with the same range of fuel firing rates as the first plate, and so on for successive plates. For example, when a higher fuel firing rate is desired, the plate would be replaced by one in which the conduit opening is spaced further to the right away from the eccentric opening. 
     As shown in FIG. 10, the plate is in a neutral position that is not being moved by the eccentric. Counterclockwise rotation of the eccentric moves its plate engaging section  132  and, in turn, moves the plate to the right from a position L1 to a position L2 shown in FIG.  11 . This moves the conduit out and increases the amount of air flow. Conversely, clockwise rotation of the eccentric from the position shown in FIG. 10 moves the engaging section and, in turn, moves the plate to the left from the position L1 to the position L3 shown in FIG.  11 . This moves the conduit in toward the air tube outlet and increases the restriction of air flow. 
     Yet another embodiment of the head adjustment mechanism is shown in FIGS. 12-14 and comprises a support  142  that extends outwardly from and is connected to the housing. The component  70  comprises a threaded rod  141  carried in an aperture of the support. An internally threaded member such as a nut  146  is rotatably secured to the rod such as with a snap-fit ring  147  on a collar of the nut, or the like. A plate  148  is secured to the housing between upper and lower guides  150 . A slot  151  is formed in the housing. A pointer  152  may include an aperture  154  that receives the conduit. An indicator plate  156  may be secured to the housing as shown in FIG.  12 . The conduit  34  is connected to the housing by an interiorly threaded coupling  158 . A collar member  160  is disposed between the coupling and the plate  148 . The rod  141  is fastened to the collar  160  such as by welding. Rotation of the nut  146  on the rod  141  and against the support  142  causes the rod and, in turn the conduit, to move linearly either to the left or right as depicted in FIG.  12  and causes the conduit to move in and out, respectively. As shown in FIG. 12, movement of the rod to the left increases restriction of air flow whereas movement to the right increases air flow. The plate  148  may move with the arm and covers portions of the slot  151 . 
     The head adjustment mechanism is zeroed in using the mechanism of FIGS. 3 and 4, for example, by a procedure that includes inserting the conduit-head-electrode subassembly all the way to the outlet end of the air tube where it engages the ring  26  and stops. A back plate  161  of the mechanism includes a portion  162  that bends around the corner of the burner and is trapped by the door  56 . The back plate  161  has a slot S1 that corresponds to the slot  36  formed in the housing. Disposed on the back plate is an intermediate plate  164 , which includes a bent portion  166  that forms the indicator  86 . Another aspect of the air flow control mechanism is shown in FIG. 3A which is similar to FIG.  3  and where like numerals designate like parts. A pointer portion  84   a  is bent to extend through an opening  165  in a bent portion  166   a  of indicator  86   a  that forms a part of the intermediate plate  164   a . The intermediate plate has a slot S2 that corresponds to the slot  36  in the housing but is shorter. A zeroing slot  168  is disposed in the intermediate plate  164 , for accommodating variations in tolerance. The stud  78  passes through the opening  80  in the arm, is staked in countersunk opening  172  in the intermediate plate, and held in place with nut  79  to act as a pivot point for the arm. With the conduit furthermost toward the air tube outlet, the arm and intermediate plate are moved together as an assembly on the fixed backplate so as to position the pointer at the zero position on the indicator of the plate. A zeroing nut  176  threadingly engages a stud  177  that is passed through the slot  168  in the intermediate plate  164  and is staked into an opening  170  in the backplate  161  to lock the plates in position. Any of the mechanisms described may be adapted to utilize the zeroing procedure described above. 
     The mechanism is operated in the manner described to regulate air flow and pressure in the second region R2. The air flow control device regulates air at a pressure P1 in the first region R1 to reduce the pressure P1 to a pressure P2 in the second region R2. This is accomplished by moving the conduit either in or out of the air tube into the flow restricting or flow increasing positions. Therefore, the invention advantageously enables easy, consistent and precisely controlled air pressure and uniform air flow in the burner. 
     Many modifications and variations of the invention will be apparent to those skilled in the art in light of the foregoing disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the invention can be practiced otherwise than has been specifically shown and described.