Patent Publication Number: US-8123198-B2

Title: Ignition system for a pulse fog generator

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/860,798, filed Aug. 20, 2010, now U.S. Pat. No. 8,006,959, which is a divisional application of U.S. patent application Ser. No. 12/042,604, filed Mar. 5, 2008, now U.S. Pat. No. 7,798,474, both of which are hereby incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     The present invention generally relates to the field of fogging devices. In particular, the invention is directed toward fogging devices utilizing the pulse-jet, or resonant intermittent combustion, principle. 
     Fogging devices, used to generate an insecticide fog, for example, and utilizing the pulse-jet or resonant intermittent combustion principle, are well known in the prior art. Examples of such devices are disclosed in U.S. Pat. No. 3,993,582 to Curtis, U.S. Pat. No. 4,030,695 to Curtis, and U.S. Pat. No. 4,343,719 to Stevens et al. Each of these patents disclose a fogging apparatus utilizing a resonant, intermittent combustion device, a fuel supply, a formulation supply, a formulation control device, and a starting device. In such prior art devices, the resonant intermittent combustion device is shut off by way of a valve located in the carburetor. 
     Fogging devices disclosed in U.S. Pat. No. 4,811,901 to Stevens et al. (“the &#39;901 patent”) and U.S. Pat. No. 4,934,601 to Stevens et al. (“the &#39;601 patent”), both of which are hereby incorporated by reference into the present application, provide an improved starting system for the resonant intermittent combustion device, an improved combustion device shut off system, and an improved formulation control device over previous fogging devices. These fogging devices utilize ignition systems that generally require at least 12 volts DC for supplying power to ignite the fogging device. Additionally, these ignition systems are typically grounded via a single grounding means. However, there are potential safety concerns that exist with having only a single grounding means. 
     Accordingly, a need has arisen for improving the design of these fogging devices by implementing a secondary grounding means. In particular, there is a need for a pulse fog generator with an ignition system operating from a low voltage power source and at least one additional grounding means, which in combination, would reduce the overall weight of the machine, lower the cost of the machine, and eliminate wasted energy required for starting the machine. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention provides an ignition system for a pulse fog generator in which the engine has a carburetor, a pump for pumping air into the carburetor, and a priming pump for directing a quantity of fuel into the carburetor. The ignition system includes an igniter which operates on low voltage and a frequency between 10-20 Hz, a switch for activating and deactivating the igniter, and a grounding connection for grounding the igniter to the carburetor. 
     In another embodiment, an ignition system for mounting to a chassis of a pulse fog generator is provided in which the pulse fog generator has a carburetor, a pump for pumping air into the carburetor, and a priming pump for directing a quantity of fuel into the carburetor. The ignition system comprises an igniter assembly having a switch for activating and/or deactivating the ignition assembly, an igniter bracket for grounding the igniter assembly to the chassis, and an ignition wire assembly that includes a first end and a second end. The first end of the wire assembly couples to the igniter assembly and the second end couples to a spark plug near the carburetor. Additionally, an igniter cap may couple to the igniter assembly and a low voltage power supply may supply power to the igniter assembly. 
     In a different embodiment of the present invention, a method is provided for igniting a pulse fog generator that comprises a carburetor, a pump for pumping air into the carburetor, a priming pump for directing a quantity of fuel into the carburetor, and an ignition system that includes an igniter which is operable on 1.5 volts DC at a frequency of 10 Hz. In this embodiment, the method includes actuating a lever on the carburetor to an open position, directing air and fuel to flow into the carburetor for ignition, triggering a switch on the ignition system, and igniting the pulse fog generator. 
     The present invention is explained in more detail hereinafter on the basis of advantageous embodiments shown in the figures. The special features shown therein may be used individually or in combination to provide embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned aspects of the present invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention, taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a pulse fog generator; 
         FIG. 2  is an exploded view of the pulse fog generator of  FIG. 1 ; 
         FIG. 3  is a partial perspective view of the first side of the pulse fog generator of  FIG. 1 ; 
         FIG. 4  is a partial perspective view of the second side of the pulse fog generator of  FIG. 1 ; 
         FIG. 5  is an exploded view of an ignition system of a pulse fog generator; 
         FIG. 6  is an exploded view of a carburetor and antechamber assembly of a pulse fog generator; 
         FIG. 7  is a schematic view of a prior art ignition system for a fogger device operating with at least 12 VDC; 
         FIG. 8  is a schematic view of an embodiment of an ignition system for a pulse fog generator operating with a low voltage power source; 
         FIG. 9A  is a side view of a carburetor with a lever in a fully closed position; 
         FIG. 9B  is a side view of the carburetor of  FIG. 9A  with the lever at the tipping point; and 
         FIG. 9C  is a side view of the carburetor of  FIG. 9A  with the lever in a fully open position. 
     
    
    
     Corresponding reference numerals are used to indicate corresponding parts throughout the several views. 
     DETAILED DESCRIPTION 
     The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention. 
     A pulse fog generator with a novel ignition assembly is shown in  FIG. 1 . The pulse fog generator  2  comprises an engine mounting assembly  6  and a carburetor (not shown) which is enclosed by a carburetor cover assembly  8 . The pulse fog generator  2  may operate from various types of fuel including propane, JP-8 jet fuel, kerosene, methanol, ethanol, diesel, and other special blends of fuel which facilitate the ignition process of the pulse fog generator  2 . A fuel tank assembly  12  may be mounted to the pulse fog generator  2  for holding the fuel. 
     In addition to fuel supply, an air supply assembly  4  may be mounted to the pulse fog generator  2  for supplying air to the ignition system  16  (see  FIG. 2 ). The air supply assembly  4  may include any means known to one skilled in the art for supplying air. In one embodiment, the air supply assembly  4  may be an air compressor or an electrically-powered air pump. In a different embodiment, the air supply may be manually operated. In an advantageous embodiment, the air supply assembly  4  will supply the proper amount of air to mix with the fuel for igniting and operating the pulse fog generator. 
     In the pulse fog generator of  FIG. 1 , a formulation tank assembly  14  is provided and may be mounted to the pulse fog generator  2 . One embodiment of the formulation tank assembly  14  that may be mounted to the pulse fog generator  2  is described in detail in U.S. Pat. No. 4,811,901, which as mentioned above, is incorporated by reference. As also shown in  FIG. 1 , a wire guard assembly  10  is provided for directing contents from the formulation tank assembly  14  to the surroundings. The wire guard assembly  10  may extend from the engine mounting assembly  6  and surround a tubular member  15  that dispenses the formulation. 
     An exploded view of the pulse fog generator  2  of  FIG. 1  is illustrated in  FIG. 2 . Besides the components described above, the pulse fog generator  2  further comprises an ignition assembly  16  that will be described in greater detail below. In the embodiment of  FIG. 2 , the ignition assembly  16  includes an igniter  18  that may be powered by a low voltage power supply  22  that may provide less than 12 volts DC. In another embodiment, the low voltage power supply may provide between 1-5 volts DC. In a specific embodiment, the low voltage power supply provides 1.5 volts DC. In the various embodiments in which the power source is a battery, as in  FIG. 2  for example, the igniter  18  may operate from a single AAA battery. The ability to start the pulse jet generator with a lower voltage power supply reduces waste consumption, saves energy, and helps with efforts geared toward recycling and improving the quality of the environment. In contrast, other fogger devices known in the art generally require 12 volts DC or more, because lower input to output voltage ratios cannot be used to ignite a pulse jet generator without tuning the engine to a proper range. Additionally, fogger devices known to those skilled in the art rely on pressurizing the fuel system, which prevent such fogger devices from being ignited using low input voltages. In contrast, the present invention incorporates a carburetor and primer bulb setup as described in U.S. Pat. No. 4,934,601, which as stated above, is incorporated by reference. 
     The ignition assembly  16  of  FIG. 2  further comprises an ignition wire assembly  24  in which one end couples to a sparkplug (not shown) near the carburetor and a second end couples to the igniter  18 . An igniter bracket  26  and igniter cap  28  are also provided, wherein the bracket  26  is generally used for grounding the ignition assembly  16  and the cap  28  may be depressed to ignite the ignition assembly  16 . As will be described below with reference to  FIG. 5 , the igniter bracket  26  may function as a single means for grounding the ignition assembly  16 , but mounting the igniter  18  to the igniter bracket  26  does not always produce the most optimal grounding condition. Therefore, to ground the pulse jet generator  2  in a more favorable manner, a ground wire assembly  20  may be used as a secondary or “emergency” means for grounding the ignition assembly  16 . 
     In the embodiment of  FIG. 3 , a partial perspective view of the pulse fog generator  2  of  FIG. 1  is shown. In this embodiment, the carburetor cover assembly  8  is removed and the ignition bracket  26  is shown mounted to the chassis  30  of the generator  2 . The ignition switch  32  is also visible and it includes the igniter cap  28  as described with reference to  FIG. 2  above. The ignition switch  32  may include any type of mechanism for igniting the ignition assembly  16 . In the embodiment of  FIG. 3 , the ignition switch  32  may be pressed inwards. Other embodiments of the switch  32  may comprise levers, knobs, flip switches, turn-key, and other forms of switches known to the skilled artisan. 
     In the embodiment of  FIG. 3 , a typical fuel filter  34  is shown disposed at a location along a fuel delivery line  35 . In general, the fuel delivery line  35  may supply fuel from the fuel tank assembly  12  to the carburetor. Also shown in  FIG. 3  is a carburetor power switch assembly  36  which may be used for turning the pulse fog generator  2  on and/or off. In the embodiment shown in  FIG. 3 , this switch assembly  36  is shown as a lever, but as with the ignition switch  32 , may comprise any form of a switch known to the skilled artisan. The carburetor power switch assembly  36  will be described in further detail with regard to  FIG. 9  below. 
     With reference to the embodiment of  FIG. 4 , the fuel tank assembly  12  includes a fuel tank cap  40  and the formulation tank assembly  14  includes a formulation tank cap  42 . As for distributing formulation from the formulation tank assembly  14 , a flow-control orifice  44  and formulation on/off valve  46  may be provided to control the flow rate of formulation from the tank assembly  14 . The formulation tank assembly  14  is described in more detail in U.S. Pat. No. 4,811,901, which as stated above, is herein incorporated by reference. 
     An exemplary embodiment of the ignition assembly  16  is shown as an exploded view in  FIG. 5 . In particular, the ignition assembly  16  may comprise an igniter  18  that operates with a low voltage power supply  22  such as a battery. The igniter  18  may include a holding compartment  54  in which the power supply  22  is held. The ignition assembly  16  further includes an igniter bracket  26 . The bracket  26  may include a top surface  27 , at least one side wall  29 , and a front wall  31  that defines a bracket opening  70 . In one embodiment, the bracket  26  is made from stainless steel. In alternate embodiments, the bracket  26  may be made from other materials known to the skilled artisan that would be conducive for grounding the igniter  18 . 
     In addition to the bracket, the ignition assembly  16  further includes a cap  28 , an ignition wire assembly  24 , and a ground wire assembly  20 . As previously described, the ignition wire assembly  24  is coupled between the igniter  18  and a spark plug (not shown). The ignition wire assembly  24  includes a first end  56  that may comprise a terminal strip for coupling to the igniter  18 . A second end  58  of the ignition wire assembly  24  includes a coupler for connecting to a standard spark plug. As previously mentioned, the ground wire assembly  20  acts as a secondary means for grounding the ignition assembly  16 . The ground wire assembly  20  includes a first end  60  for coupling to the igniter bracket  26  and a second end  62  for coupling at or near the sparkplug. Although the ground wire assembly  20  is provided as a secondary means for grounding the ignition assembly  16 , it advantageously grounds the assembly  16  at a primary grounding point  158  (see  FIG. 8 ) and thus improves the grounding of the overall device. The first end  60  of the ground wire assembly  20  may be coupled to the igniter bracket  26  via a plurality of fasteners including a nut  68 , washer  66 , and screw or bolt  64 . 
     As briefly mentioned above, the ignition assembly  16  includes a first manner by which the igniter  18  is grounded to the chassis or main support reference  30 , which is in addition to the ground wire assembly  20 . As shown in  FIG. 5 , the igniter  18  may include a main body  19  with a nose  21  that extends from the main body  19 . The nose  21  may comprise a plurality of clips  48 , a threaded portion  50 , and a flange  52  that protrudes from the nose  21  by approximately ⅛ inch. The flange  52  circumscribes the nose  21  and the holding compartment  54 . Although not shown in  FIG. 5 , a thin wire extends away from the flange  52  and contacts the chassis or main support frame  30  to ground the igniter  18 . In one embodiment, the wire may be 0.030-040″ in diameter. 
     As shown in  FIG. 5 , the power source  22  may be inserted into the holding compartment  54  of the igniter  18 . The igniter bracket  26  can then slide over the top of the igniter  18  such that the nose  21  slides through the bracket opening  70 . The bracket opening  70  may be configured as a round opening with square-like cutouts at two or more locations along the diameter of the opening  70 . The clips  48  of the igniter  18  may engage with these square-like cutouts in a snap-fit coupling. The nose  21  may also slide into a similarly-shaped opening  72  in the chassis  30  such that the clips  48  engage in a snap-fit coupling with the chassis  30 . As the igniter  18  couples with the chassis  30 , the thin wire may contact a metal surface of the chassis to ground the igniter  18 . Unfortunately, this type of grounding may be susceptible to a wobbly and/or loose coupling between the igniter  18 , the bracket  26 , and the chassis  30  such that the ignition assembly  16  is not properly grounded. For this reason, the ground wire assembly  20  described above is incorporated into the ignition assembly  16 . Finally, the igniter cap  28  may comprise a deformable material that allows a user to depress the cap inward and internal threads that screw onto the threaded portion  50  of the igniter  18 . Thus, the cap  28  forms a portion of the ignition switch  32 . 
     A typical carburetor and antechamber assembly known to the skilled artisan is shown in  FIG. 6 . The carburetor assembly comprises a carburetor body  94 , carburetor gaskets  92 ,  96 , an air intake bottom plate  86 , an air filter  84 , and an air injection bracket  80 . An elbow fastener  74  and nut  82  couples to the air injection bracket  80  and screws or bolts  76  secure a tube clamp  78 , the air injection bottom plate  86 , and gasket  92  to the carburetor body  94  and carburetor adapter  108 . Additional screws or fasteners  88 ,  90  mount the carburetor adapter  108 , a plurality of venturi gaskets  110 , and a petal valve assembly  112  to the antechamber/engine assembly  114 . An elbow  120 , a connector  116 , and other fasteners may be coupled to the antechamber/engine assembly  114 . A sparkplug  122  is coupled to the antechamber/engine assembly  114  with at least one o-ring  124  disposed therebetween. The assemblies may further include tubing  126  that comprise a plurality of hose clamps  128  for attaching the tubing  126 , for example, to one or more elbows  120 . As mentioned above and as will be described in further detail with regards to  FIG. 9  below, the carburetor assembly may be turned on and/or off via a lever assembly  97  as shown in  FIG. 6 . The lever assembly  97  is advantageous as it requires only a lever  98  and a spring  100 . Fasteners including bolts or screws  106  and washers  102 ,  104  may be used for coupling the lever  98  and spring  100  to the carburetor body  94 . Other embodiments of the carburetor assembly may include alternative means for turning on and off the carburetor. 
     In the schematic of  FIG. 7 , a prior art ignition system for a fogger device is illustrated. In this schematic, the ignition system  130  is operable with at least a 12 VDC battery which is held in a battery holder  134 . The battery may comprise eight D batteries, a motorcycle battery, or a similar source that supplies at least 12 VDC. A first wire  136  runs from the battery to an ignition switch  140  and a second wire  138  runs from the battery to ground. The ignition switch  140  is electrically coupled to a 12 VDC igniter  132 . The igniter  132  includes a first wire  142  which connects to an antechamber (not shown) and a second wire  144  which connects to a sparkplug (not shown). 
     An advantageous embodiment of an ignition system for a pulse jet generator is illustrated in  FIG. 8 . In this particular embodiment, the ignition system  16  is operable from a low voltage power source  152 . As described above, the low voltage power source  152  may include one or more batteries that provide less than 12 VDC. In the embodiment shown in  FIG. 8 , the low voltage power source  152  advantageously includes a single AAA battery for producing 1.5 VDC. The low voltage power source  152  reduces the overall weight and cost of the pulse fog generator. 
     The ignition system  16  of  FIG. 8  further includes an ignition switch  154 , which as described above with reference to  FIG. 5 , can be depressed to ignite the combustion process. An ignition wire assembly  24  runs between an igniter  18  of the ignition system  16  and a spark plug  122  for firing the sparkplug and igniting a carburetor  94 . The sparkplug  122  may be coupled to an antechamber  160 , which is further connected to an antechamber/engine assembly  114  and the carburetor  94 . 
     A fuel tank assembly  12  is shown in  FIG. 8  with a fuel tank cap  40 . Fuel is transported from the fuel tank assembly  12  through a fuel supply line  162  to the carburetor  94 . A fuel filter  34  is coupled at a location along the fuel supply line  162  to prevent dust, dirt, and other unwanted particles from being transported to the carburetor  94 . 
     Also shown in  FIG. 8  is a primer bulb assembly  38  which was briefly described above. The primer bulb assembly  38  is mounted to the carburetor  94 . The primer bulb assembly  38  includes a priming fuel inlet line  163  through which priming fuel is drawn, and a priming fuel outlet line  164  that opens into a carburetor throat (not shown) at an outlet port (not shown). The primer bulb assembly  38  comprises a flexible resilient bulb  39  which is mounted on a priming valve body (details of the primer bulb assembly are illustrated in  FIGS. 7   a  and  7   b  of U.S. Pat. No. 4,934,601, which is herein incorporated by reference). The fuel inlet and outlet lines  163  and  164 , respectively, are appropriately connected to the priming valve body to communicate with the proper valves of the carburetor  94 . In one embodiment, the bulb  39  may be transparent or translucent so that a visual indication is available that priming fuel is present in the bulb for injection into the carburetor. 
     The operation of the primer bulb assembly  38  is described below and in further detail in U.S. Pat. No. 4,934,601. As the priming bulb  39  is initially depressed, air or fumes in the bulb are expelled from the bulb  39  through an outlet valve (not shown in  FIG. 8 ) and priming fuel outlet line  164  and outlet port into the carburetor  94 . When the bulb  39  resiliently returns to its pre-determined undeformed shape, a vacuum is formed inside the bulb that pulls an inlet needle valve (not shown) of the carburetor  94  down and draws fuel from the fuel tank assembly  12  through the carburetor  94 , through the priming fuel inlet line  163  and into the primer bulb assembly  38 . When the bulb  39  is next depressed, the fuel within the bulb  39  is expelled through the priming fuel outlet line  164  and outlet port into the carburetor throat. When the bulb is depressed, an inlet valve (not shown) seats in its closed position, and when the bulb  39  rebounds to its undeformed shape, the outlet valve (not shown) seats in its closed position. The resilience of the bulb  39  is sufficiently great to draw a vacuum in a metering chamber (not shown) of the carburetor  94  sufficient to pull a metering needle valve (not shown) off its valve seat and to draw starting fuel from the fuel tank assembly  12 . With this embodiment, the priming fuel may be injected directly into the carburetor throat, rather than through the metering chamber. In addition, the use of the priming bulb  39  simplifies the connection between the primer bulb assembly  38  and the carburetor body  94  to eliminate pump adaptors of prior art fogger devices. 
     Referring back to the ignition system  16  of  FIG. 8 , the igniter  18  is grounded via a primary means and a secondary means. An igniter bracket  26  may be coupled to a main support reference  30  ( FIG. 5 ) of the pulse fog generator and provides a main ground contact  156 . As described above with reference to  FIG. 5 , a thin wire connected to the igniter  18  contacts the chassis and grounds the igniter  18 . A second means for grounding the igniter  18  is by coupling a ground wire assembly  20  to the igniter bracket  26  and to a primary grounding point  158  at or near the sparkplug  122 . This provides a reliable and safe means for grounding the igniter without relying on the thin wire of the igniter for contacting and/or maintaining contact with the chassis. 
     As is known with current technology for starting a pulse jet generator, three main systems are required for doing so and these include an ignition system, a fuel system, and an air system. The air system for providing air to the combustion system of the pulse jet generator may include an electrical compressor or pump and/or a mechanical, hand-operated pump. An example of an air system  4  is shown in  FIGS. 1-4 . Other potential air supply devices may also be incorporated into the design of a pulse fog generator for providing air to the combustion system. An embodiment of the fuel system assembly  12  has been shown and described above, particularly with reference to  FIGS. 1-2 ,  4 , and  8 . The ignition system, in particular with regards to the embodiments in  FIGS. 5 ,  7 , and  8 , has been described in greater detail above. The ignition system, and in particular the igniter, is generally tuned to a specific frequency or frequency range before it reaches the consumer. In some embodiments, the igniter cannot be tuned externally, while in other embodiments the igniter may be tuned externally. Igniters, which operate from low voltage power supplies, are generally tuned at different frequencies depending on various factors including the type of power source being used. For example, in standard fogging devices which include 12 VDC or more ignition systems, the frequency may be approximately 1 kHz. However, in the pulse jet generator that includes the ignition system  16  of  FIG. 8  which may operate from a 1.5 volt DC power supply, the frequency may be in the range of 10-20 Hz. Thus, the frequency may vary greatly between ignition systems that operate with different power supplies, and specifically pulse jet generators that operate with lower voltage power supplies are tuned to lower frequencies. 
     As mentioned above with regards to  FIGS. 3 and 6 , a pulse fog generator may be turned on and/or off by means of a carburetor power switch assembly  36 . An exemplary embodiment of the carburetor power switch assembly  36  is shown in  FIGS. 9A-C  as a lever assembly  97 . The lever assembly  97  is advantageous as it consists of a lever  98  and a spring  100  which mount to a standard carburetor  94 . Many carburetor power switch assemblies known to the skilled artisan require more than a dozen components, which makes the assembly and any subsequent repairs to the assembly complicated and burdensome. 
     During use, the lever  98  operates in a teeter-totter-like manner. Specifically, the lever  98  is in a fully closed position in  FIG. 9A . In order to start the pulse fog generator, the lever  98  must be pivoted to the open position of  FIG. 9C . To reach the open position, however, the lever  98  must be rotated or moved past a “tipping point” or midpoint along its travel. The spring  100  provides resistance against rotating or moving the lever  98  to the open position until the lever  98  passes the “tipping point” or midpoint of  FIG. 9B . After the lever  98  is moved past the “tipping point” or midpoint of  FIG. 9B , the spring  100  helps pull the lever  98  to the fully open position of  FIG. 9C . Once the lever  98  is positioned in the fully open position, air and fuel are permitted to freely flow into the combustion chamber. Similarly, in rotating or moving from the fully open position of  FIG. 9C  to the fully closed position of  FIG. 9A , the lever  98  must be rotated or moved past the “tipping point” or midpoint of  FIG. 9B , and once the lever  98  has done so, the spring  100  may act as a cam to further move the lever  98  to the closed position. 
     While exemplary embodiments incorporating the principles of the present invention have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.