Abstract:
A gas phase of LPG such as propane is used to power a small internal combustion engine driving or powering a preselected device such as a powered lawnmower, weed whacker, string trimmer, leaf blower or the like and the fuel system is provided with heating arrangements that insure the gas phase of the LPG is discharged from the LPG tank for all operating conditions of the device.

Description:
INCORPORATION BY REFERENCE 
     Applicants incorporate by reference the teaching and technology as disclosed in pending application Ser. No. 11/702,381, filed Feb. 6, 2007 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to Liquified Petroleum Gas (LPG) fueled internal combustion engine powered arrangements and, more particularly, to such arrangements in which the internal combustion engine is powered by the gas phase of the LPG at all times and may be as utilized in lawnmowers, weed whackers, leaf blowers, string trimmers and the like 
     2. Description of the Prior Art 
     Utilization of LPG as a fuel for internal combustion engines has been heretofore been known for use in large internal combustion engine powered arrangements such as forklifts, trucks, buses and other such arrangements and devices. As such, the tank capacity of the LPG is quite large: on the order of 5 gallons or larger and in which the LPG is withdrawn from the LPG tank in liquid phase form and this requires that the LPG tanks be mounted in a particular orientation so that only liquid phase LPG is withdrawn therefrom during operation of the internal combustion engine  12 . Further, the LPG tank is, generally, mounted in regions remote from the engine or any normally occurring heat source during operation and/or storage of the device. 
     During operation of such devices, the liquid phase LPG travels through transfer lines to either a vaporizer or a vaporizer/regulator structure. The vaporizer or vaporizer/regulator causes the liquid phase LPG to be converted to the gas phase LPG. The latent heat of vaporization of the liquid phase LPG as it is converted to the gas phase LPG would cause the vaporizer or vaporizer/regulator to get extremely cold and in many applications would freeze the liquid phase LPG to a solid phase and thus stop the flow of LPG to the engine unless means are provided to heat the vaporizer or vaporizer/regulator. Various structural arrangements have heretofore been utilized to supply heat to the vaporizer or vaporizer/regulator. In liquid cooled internal combustion engines the hot engine coolant was often routed to pas through or adjacent to the vaporizer or vaporizer/regulator in order to transfer heat thereto. In air cooled internal combustion engines some or all of the hot exhaust products may be forced over the vaporizer or vaporizer/regulator by the engine cooling fan. In other prior art applications, the LPG transfer lines may be placed in close proximity to the exhaust manifold or the vaporizer or vaporizer/regulator may be close coupled to the exhaust manifold for receiving heat therefrom. 
     In yet other prior art devices, an electrically powered heater was provided at the vaporizer or vaporizer/regulator. 
     Thus, such prior art applications and devices utilizing the large tanks of LPG often required many complex structural arrangements and components in order to insure that the liquid phase LPG was converted to the gas phase LPG. 
     In many other applications, the use of a large, e.g., 5 gallon LPG tank and its attendant complexity is not needed or desired. For example, in many smaller internal combustion engine powered devices, it is often desired to utilize a small LPG tank such as one containing one or two pounds of LPG. Such devices include, but are not limited to lawnmowers, leaf blowers, string trimmers, or the like. The one or two pond LPG tanks are readily available as such LPG tanks are widely utilized in the camping industry to provide LPG for portable for stoves, lamps and the like. However, in such applications, the LPG tank is oriented to provide that only the gas phase LPG exits the LPG tank and, therefore, the freezing of the LPG would occur in the LPG tank rather than external the LPG tank. Depending on the rate of flow of the gas phase LPG from the LPG tank, the freezing of the LPG occurs in the LPG tank. 
     However, in many applications it is desired that the mounting of the LPG tank be such that no specific orientation of the LPG tank is required for the internal combustion engine to operate on the gas phase of the LPG. 
     Accordingly, there has long been a need in an It is another object of the present invention provide an LPG fueled internal combustion engine apparatus utilizing propane as the LPG from a conventional one to two pound LPG propane tank for the supply of the LPG and which does not require a particular orientation of the LPG tank with respect to gravity for satisfactory operation. 
     Additionally, many of the prior art LPG fueled internal combustion engine powered devices have utilized butane as the LPG. Such devices are common in many foreign countries such as Japan and Korea. In the United States and in Europe, on the other hand, propane LPG tanks are quite readily available. The physical properties of propane as compared to butane makes the propane LPG tanks more attractive as a fuel for the small internal combustion engine applications. For example, for an equivalent amount of LPG, a butane fueled device would run for about one half hour while for a propane fueled device would run for about three to four hours. Also, the butane LPG tanks that are readily available in Japan and Korea provide for only gas phase butane to be withdrawn from the bottle and are provided with an internal tube to insure that only gas is withdraw and thus require a preferred orientation with respect to gravity. Since liquid phase butane becomes a gas phase butane at about 31 degrees F. which is only about 39 degrees F. different from the conventionally stated standard operating temperature of a nominal 70 degrees F., there is little cooling effect due to the evaporation and freezing in the LPG tank or in the system is not likely by utilization in a small internal combustion engine. Liquid phase propane, on the other hand, becomes gas phase propane at about minus 44 degrees F. which is about 114 degrees F. different from the conventionally stated standard operating temperature of a nominal 70 degrees F. Therefore, the propane would freeze to the solid phase in the LPG tank or elsewhere in the delivery system long before the LPG tank is empty depending on the consumption rate and the temperature. As contrasted to butane, the propane requires structure to prevent freezing to the solid phase. 
     Therefore, it is an object of the present invention to provide an LPG fueled internal combustion engine apparatus utilizing propane as the LPG. 
     It is another object of the present invention to utilize a conventional one to two pound LPG propane tank for the supply of the LPG. 
     It is another object of the present invention provide an LPG fueled internal combustion engine apparatus utilizing propane as the LPG and in which the propane is provided from a conventional one to two pound LPG propane tank for the supply of the LPG. 
     It is another object of the present invention provide an LPG fueled internal combustion engine apparatus utilizing propane as the LPG from a conventional one to two pound LPG propane tank for the supply of the LPG and which does not require a particular orientation of the LPG tank with respect to gravity for satisfactory operation. 
     It is another object of the present invention provide an LPG fueled internal combustion engine apparatus utilizing propane as the LPG from a conventional one to two pound LPG propane tank for the supply of the LPG which does not require a particular orientation of the LPG tank with respect to gravity for satisfactory operation and in which the possibility of freezing of the liquid phase LPG to the solid phase LPG is substantially prevented in both the LPG tank and in the gas phase supply system to the internal combustion engine. 
     It is yet another object of the present invention to provide an LPG fueled internal combustion engine apparatus utilizing propane as the LPG from a conventional one to two pound LPG propane tank for the supply of the LPG which does not require a particular orientation of the LPG tank with respect to gravity for satisfactory operation and which insures that only gas phase LPG propane is withdrawn from the LPG tank regardless of the orientation thereof during operation. 
     SUMMARY OF THE INVENTION 
     The above and other objects of the present invention are achieved, in a preferred embodiment thereof as utilized in a LPG gas phase fueled internal combustion engine lawnmower. This embodiment has an LPG tank containing propane which has both a liquid phase LPG and a gas phase LPG therein mounted in a vertical orientation with respect to gravity so that liquid phase LPG is at the discharge valve of the LPG tank for the conventional operation of the lawnmower on a relatively flat surface though operation will also satisfactorily occur for any other orientation of the lawnmower such as, for example, on a sloping surface of lawn even though the gas phase LPG may be at the discharge valve. 
     The LPG tank is mounted by a mounting bracket on the internal combustion engine so as to be in both heat transfer relationship to a portion of the internal combustion engine from which the mounting bracket receives heat as well as in vibration receiving relationship to the internal combustion engine. The heat and vibration from the mounting bracket is transferred to the LPG tank and thus into the LPG in the LPG tank. The mounting bracket is also coupled to the discharge valve of the LPG tank so as to provide heating to the discharge valve. 
     The discharge valve of the LPG tanks utilized in the present invention has a spring biased poppet that is moved from a spring biased closed position to an open position when coupled to a standard mounting plug. The standard mounting plug has a probe that unseats the poppet when the mounting plug is attached to the discharge valve. As liquid phase propane starts to flow from the LPG tank under the force produced by the gas pressure in the LPG tank, the small size of the orifice at the poppet causes the liquid phase to vaporize into the gas phase. Since, depending on the flow rate of the liquid phase LPG through the poppet orifice, the latent heat of vaporization might cause the discharge vale to become so cold as to freeze the liquid phase LPG into the solid phase LPG, heat is supplied to the mounting plug at the discharge valve so as to heat the discharge valve and thus prevent freezing of the LPG. Such heating of the discharge valve may be provided by coupling a portion of the mounting bracket to the mounting plug. 
     The supply of gas phase LPG is passed from the mounting plug through a shutoff valve, through a pressure regulator and into the carburetor of the internal combustion engine. The carburetor is preferably a chokeless carburetor of conventional design and may, if desired, be incorporated as a single unit with the pressure regulator. The vacuum generated in the carburetor by the operation of the internal combustion engine draws the gas phase LPG into the carburetor. At substantially zero vacuum, no liquid phase LPG is drawn into the carburetor. Gas phase LPG is drawn into the carburetor commensurate only with the vacuum thereby providing that the gas phase LPG flow rate is at the rate demanded by the internal combustion engine. 
     Thus, according to the principles of the present invention regardless of whether the liquid phase of the LPG or the gas phase of the LPG is at the discharge port, satisfactory operation of the apparatus is insured. 
     In another embodiment of the present invention achieving the objects as stated above, the LPG tank may be mounted on an LPG fueled internal combustion engine driven leaf blower or a string trimmer. As such, in operation the leaf blower or string trimmer and, consequently, the LPG tank, may be in any orientation with respect to gravity. For the technological advances as described above, satisfactory operation is achieved by having only gas phase propane LPG flow from the LPG tank into fuel supply system to the internal combustion engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The above and other embodiments of the present invention my be more fully understood from the following detailed description taken together with the accompanying drawing wherein similar reference characters refer to similar elements throughout and in which: 
         FIG. 1  is an exploded view of a preferred embodiment of the present invention as utilized in an LPG fueled internal combustion engine powered lawn mower; 
         FIG. 2  is a sectional view showing the attachment of the LPG tank to the internal combustion engine in the embodiment illustrated in  FIG. 1 ; 
         FIG. 2A  is a block diagram illustrating the flow path of the fuel supply system of the present invention; 
         FIG. 3  illustrates another embodiment of the present invention as utilized in a string trimmer, leaf blower or the like; and 
         FIG. 4  is an exploded view of the attachment of the LPG tank to the embodiment illustrated in  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawing, there is shown on  FIGS. 1 and 2  an embodiment, generally designated  10 , of an LPG fueled internal combustion engine apparatus utilizing the gas phase of propane as the LPG from a conventional one to two pound LPG propane tank for the supply of the gas phase LPG and which does not require a particular orientation of the LPG tank with respect to gravity for satisfactory operation. In embodiment  10 , an internal combustion engine  12  is incorporated on a powered lawnmower  14 . An LPG tank  16  is provided in a vertical orientation mounting position with respect to both gravity as indicted by the arrow  11  and the lawnmower  14  in the most common orientation of the lawnmower  14  during use which is generally horizontal. The LPG tank  16  contains a liquified petroleum gas  18  such as, preferably, propane, though the LPG propane may include a mixture of propane with small amounts of additives such as butane, propylene or other desired additives The LPG  18  in the tank  16  does not fill the tank completely so that there is both a liquid phase  20  and gas phase  22  of the LPG  18  in the tank  16 . According to the principles of the present invention, the LPG utilized to fuel the internal combustion engine  12  is provided from the liquid phase  20  of the LPG which is vaporized to the gas phase at the discharge of the LPG tank and thus prior to introduction to the internal combustion engine  12 . 
     A tank support bracket  24  is utilized for supporting the LPG tank  16  on the internal combustion engine  12 . In the embodiment  10 , the bracket  24  is mounted on the cylinder head  26  by head bolts  28 . The tank support bracket  24  preferably incorporates a quick release, such as an over center clamp for coupling the LPG tank  16  to the tank support bracket  24 , though other types of coupling arrangements such as an elastic band, a snap on latch, or even a hook and loop band or the like may be utilized as desired for particular applications. The tank support bracket  24  is fixed to the cylinder head  26  of the internal combustion engine  12  by, for example, cylinder head bolts  30 . 
     The tank support bracket  24  is, in preferred embodiments of the present invention, closely coupled to a part of the internal combustion engine  12  so that it receives both vibration and heat from the internal combustion engine  12  during operation of the internal combustion engine  12 . The vibration transferred from the internal combustion engine  12  to the tank support bracket  24  and thus to the LPG tank  16  and the LPG  18  provides agitation to the LPG  18  so as to aid in keeping the LPG  18  from freezing as the temperature thereof drops during the withdrawal of the LPG  18  therefrom, as described below in greater detail. Further, such agitation of the LPG  18  increases the surface area  34  of the LPG  18  in the tank  16  thereby causing an increase in the gas phase  22  of the LPG in the tank  16 . 
     As shown more clearly in  FIG. 2 , in the conventional one to two pound propane LPG tanks utilized in the present invention is provided with a discharge valve  32 . The discharge valve  32  has a spring biased poppet  34  normally biased into the closed position by spring  36 . The discharge valve  32  is threaded into a mounting plug  38  having a probe  40  that unseats the poppet  34  against the bias of the spring  36  to allow the start of the flow of liquid phase LPG therethrough. However, the flow orifice  42  around the poppet is so small that the liquid phase propane  20  is vaporized into the gas phase propane  22   a  at the discharge valve  32  as it flows through the mounting plug  38 . The probe  40  of the mounting plug  38  has walls defining a gas flow passage  40 ′ therethrough. 
     A clamping nut  44  having walls  46  defining a gas storage volume  48  therein is provided and the gas volume  48  is in gas flow communication with the gas flow passage  40 ′ and contains the gas phase propane  22   a  until gas phase propane is required by the internal combustion engine  12 . The clamping nut  44  threadingly engages the mounting plug  38  at  44   a  and clamps a heating portion  24   a  of the mounting bracket  24  between the clamping nut  44  and the mounting plug  38 . The heating portion  24   a  of the mounting bracket  24  heats the mounting plug  38 , the discharge valve  32  and the clamping nut  44  to prevent any freezing of the gas phase propane flowing through the orifice  42  of the discharge valve. An “O” ring  50  may be provided between the clamping nut  44  and the mounting plug  38 . 
     The gas phase propane  22   a  flows through a connector assembly  52  as indicated by the arrow  54 . 
     A tank heating portion  24   b  of the mounting bracket  24  is in heat and vibration transfer relationship to the LPG tank  16  to heat and agitate the liquid phase LPG therein. 
       FIG. 2A  illustrates a block diagram the flow path of the fuel system according to the principles of the present invention. As shown on  FIG. 2A , the gas phase propane  22   a  flows from the storage volume  48  into a gas phase transmitting tube  61 , through a shutoff valve  60  and for the shutoff valve in the open position thereof, into a gas phase transmitting tube  61 , through a pressure regulator  62  and into a chokeless carburetor  64  for transmission to the internal combustion engine  12  as indicated by the arrows  54   a ,  54   b , and  54   c . The shutoff valve  60 , pressure regulator  62  and chokeless carburetor  64  may be of any desired commercially available gas phase design suitable for the purpose. When the shutoff valve  60  is opened, gas phase propane  22   a  from the storage volume  48  of the clamping nut  44  is allowed to flow to the internal combustion engine  12  in the amount as demanded by the vacuum created by the internal combustion engine  12 . 
     Referring now to  FIGS. 3 and 4  there is illustrated another preferred embodiment generally designated  100  of an LPG fueled internal combustion engine apparatus utilizing gas phase propane as the LPG from a conventional one to two pound LPG propane tank for the supply of the gas phase LPG and which does not require a particular orientation of the LPG tank with respect to gravity for satisfactory operation. The embodiment  100  is shown as incorporated in a weed whacker, string trimmer, leaf blower or the like. The power units of such devices are often strapped onto the back of the user and in use the user may bend to various degrees so that the orientation of the LPG tank may vary during operation with respect to the direction of gravity. 
     As shown on  FIGS. 3 and 4 , many of the components described above in connection with embodiment  10  may be utilized in embodiment  100 . the LPG tank  16  is connected to the internal combustion engine  12  by the mounting bracket  24 ′ which is generally similar to the mounting bracket  24  of embodiment  10  described above. the mounting bracket  24 ′ is provided with a retaining strap  28  for securing the LPG tank  16  to the mounting bracket  24 ′. In embodiment  100  the mounting bracket  24 ′ is coupled to the crankcase  70  of the internal combustion engine  12 . The crankcase  70  is another portion of the internal combustion engine  12  which is heated during operation and thus heat and vibration are transferred from the crankcase  70  to the mounting bracket  24 ′ and thus to the LPG tank  16  by the portion  24   b ′ and to the discharge valve  32  by the portion  24   a ′ to prevent conversion of the gas phase of the LPG flowing through the discharge valve  32  to the solid phase. 
     The mounting bracket  24 ′ is retained against or in close proximity to the crankcase  70  to provide the heat transfer and vibration transfer thereto by bolts  72  and  74 . The gas phase propane from the LPG tank  16  through the shutoff valve  60  to the pressure regulator  62  as indicated by arrow  54   a , from the pressure regulator  62  to the carburetor  64  as indicated by the arrow  54   b . The gas phase propane is mixed with air flowing into the air filter  78  and to the cylinder of the internal combustion engine  12 . 
     In  FIGS. 3 and 4 , the cylinder  26 ′ of the internal combustion engine  12  may be aligned vertically with respect to the direction of gravity  11  and the LPG tank mounted horizontally or at right angles to the cylinder  26 ′. This relationship between the cylinder  26 ′ and the LPG tank  16  is maintained regardless of the orientation of the embodiment  100  with respect to the direction of gravity  11  as the user (not shown) may bend or twist during use. Thus, it is possible for either liquid or gas phase propane to be at the discharge valve  32 . However, in accordance with the principles of the present invention, it makes no difference since there is heat transfer and vibration transfer to the contents of the LPG tank  16  as well as to the discharge valve  32 . Therefore, regardless of whether the liquid phase LPG tends to freeze in the tank  16  or at the discharge valve  32  the heat and vibration transferred is sufficient to provide that there is gas phase propane flowing into the shutoff valve  60 . 
     If the liquid level of the liquid propane in the LPG tank  16  is below the discharge valve  32  gas phase propane will flow therefrom to the shutoff valve  60 . If the liquid level of the liquid phase propane in the LPG tank  16  is above the discharge valve  32 , it is converted to the gas phase propane as described above. No matter where the freezing of the propane to the solid phase might occur, the heat transfer and vibration transfer prevents such freezing regardless of the flow rate of the propane. 
     A recoil starter of conventional design as indicated at  80  may be incorporated on the internal combustion engine  12  in the embodiment  100  and, if desired a similar recoil starter may be incorporated in the embodiment  10 . 
     From the above it can be seen that there has been provided an improved gas phase fueled internal combustion engine adapted to power various types of devices. and in which only gas phase LPG flows from the LPG tank regardless of the orientation of the LPG tank with respect to gravity and regardless of whether liquid phase propane or gas phase propane is present at the discharge of the LPG tank. Such arrangements eliminate the need for costly and complex heating devices downstream from the LPG tank to convert the liquid phase propane to the gas phase propane before introduction thereof into the carburetor of the internal combustion engine. 
     Although specific embodiments of the present invention have been described above with reference to the various Figures of the drawing, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims.