Abstract:
A device for supplying an alternate gas fuel to a gas-burning apparatus such that the gas-burning apparatus will receive and burn the alternate gas fuel, the gas-burning apparatus being of a type intended to burn a gas fuel which is different from the alternate fuel and is supplied at a pressure substantially different from that of the alternate fuel. The inventive device comprises: an inlet coupling attachable to a discharge fitting provided on the alternate fuel container and an outlet coupling downstream of the inlet coupling and attachable to an inlet fitting provided on the gas-burning apparatus. When the pressure of the alternate gas fuel is significantly greater than that of the intended fuel, the inventive device preferably also includes a restricting element for restricting flow of the alternate fuel through the device from the inlet coupling to the outlet coupling.

Description:
FIELD OF THE INVENTION 
     This application relates to devices for converting gas-burning devices from the use of intended gas fuels to other gas fuels. More particularly, but not by way of limitation, this invention relates to devices for converting from the use of intended gas fuels to the use of alternate gas fuels supplied at substantially different pressures. 
     BACKGROUND OF THE INVENTION 
     Portable gas stoves, lanterns, and other appliances used for camping, backpacking, etc., are typically fueled by either propane or butane. Most such appliances purchased and used in the United States are designed to burn propane. However, throughout the rest of the world, most of these devices are designed to burn butane. 
     Portable butane appliances operate at much lower pressures than do portable propane devices. Typical propane supply pressures can be greater than two, two and one-half, three, and even greater than four times higher than typical butane supply pressures. The pressure of a butane supply container used for portable butane burning devices will typically be in the range of from about 30 to about 60 psig. However, the pressure of a propane supply container used for portable propane-burning devices will typically be in the range of from about 125 to about 200 psig. 
     In addition, the discharge fittings provided on small propane containers used for camping, backpacking, etc., are typically different from those used on butane containers. Moreover, the inlet fittings on butane-burning devices are typically different from those used on propane-burning devices. 
     It would be very beneficial to convert the U.S. camping market from propane burning devices to butane burning devices. Because they operate at much lower supply pressures, butane devices are safer and more economical than propane devices. Additionally, unlike propane appliances, butane devices can be used substantially worldwide. Unfortunately, however, a switch to butane devices in the United States has not been practical in view of the fact that butane canisters for camping and backpacking are not readily available. Moreover, it is not foreseeable that such compact butane supply canisters will become available in the U.S. market until a substantial number of butane devices are placed in use. 
     Thus, a need presently exists for a device for converting gas burning devices from the use of intended gas fuels to other gas fuels. In particular, a need presently exists for a very compact device which will allow portable butane stoves, lanterns, and other appliances for camping, backpacking, etc., to receive and burn propane supplied from the small, camp-type fuel containers presently available on the market. The availability of such a device would allow butane-burning devices sold in the U.S. market to be powered by propane until such time as appropriate butane supplies are readily available. Additionally, the device would allow butane devices to be used in any region of the world where propane is the predominate fuel of choice. 
     SUMMARY OF THE INVENTION 
     The present invention provides a device which addresses the needs and alleviates the problems discussed above. The device is operable for supplying an alternate gas fuel to a gas-burning apparatus constructed to receive and burn an intended gas fuel, wherein the alternate gas fuel is different from and is supplied at a pressure significantly greater or significantly less than that of the intended gas fuel. The device comprises (a) an inlet coupling attachable to a discharge fitting provided on a fuel source for the alternate gas fuel and (b) an outlet coupling, downstream of the inlet coupling, which is attachable to a gas inlet fitting provided on the gas-burning apparatus. Thus, the inventive device is operable such that the gas-burning apparatus will receive and burn the alternate gas fuel. 
     In one aspect of the present invention wherein the source pressure of the alternate gas fuel is significantly greater than the supply pressure of the intended gas fuel, the inventive device further comprises limiting means for limiting flow of the alternate gas fuel through the device from the fuel source to the gas-burning apparatus. 
     In another aspect, the present invention provides a device for supplying propane fuel to a butane-burning apparatus such that the butane-burning apparatus will receive and burn the propane fuel. The butane-burning apparatus is an apparatus constructed to receive and burn butane from a butane container having a butane supply pressure which is substantially less than the propane supply pressure. The inventive device comprises: an inlet coupling attachable to a propane discharge fitting provided on the propane container; an outlet coupling downstream of the inlet coupling and attachable to a butane inlet fitting provided on the butane-burning apparatus; and limiting means for limiting flow of the propane through the device from the inlet coupling to the outlet coupling. 
     Further objects, features, and advantages of the present invention will be apparent upon examining the accompanying drawings and upon reading the following description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 provides an exploded view of an embodiment 2 of an adaptor provided by the present invention. 
     FIG. 2 provides a perspective inlet end view of inventive adaptor  2 . 
     FIG. 3 provides a perspective outlet end view of inventive adaptor  2 . 
     FIG. 4 provides a cutaway, elevational side view of inventive adaptor  2  wherein the outlet valve  104  thereof is in closed position. 
     FIG. 5 provides a cutaway, elevational side view of inventive adaptor  2  wherein outlet valve  104  is in open position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment 2 of the inventive adaptor is depicted in FIGS. 1-5. Embodiment 2 is particularly well suited for adapting a butane-burning device to the use of propane fuel. Inventive adaptor  2  comprises: a housing  4  including an inlet fitting/coupling  6  removably attached to an outlet fitting/coupling  8 ; a probe  10  projecting from inlet fitting  6 ; a valve assembly  12  projecting from outlet fitting  8 ; a flow passage  14  extending through probe  10  and housing  4  to valve assembly  12 ; and an orifice element  16  positioned in flow passageway  14  between probe  10  and valve assembly  12 . 
     Inlet fitting  6  and probe  10  are of a type structured for attachment to and activation of most of the small, camping-type propane canisters available on the market. However, as will be apparent, generally any type of attachment structure and activation element can be used depending upon the structure of the fuel supply container to which inventive adaptor  2  is to be attached. 
     The inlet fitting  6  depicted in FIGS. 1-5 comprises: a larger diameter, cylindrical rearward section  8  having a rearward end  20 ; a large diameter rearward bore  22  having internal threads  24  formed therein for releasable attachment to an externally-threaded propane discharge fitting; a threaded second bore  26  extending from the forward end of large bore  22 ; a threaded third bore  30  extending from the forward end of second bore  26 ; an externally threaded forward section  34  extending from rearward section  18  and having an external diameter smaller than that of section  18 ; a bore  36  extending into the forward end  38  of externally threaded section  34 ; a small, frusto 15  conical counter bore extending from forward bore  36  to third bore  30 ; and a groove  40  formed in the forward end  38  of inlet fitting  6  for receiving an O-ring  42  or other sealing element. 
     Inlet fitting  6  further includes a raised lip or hub  44  provided around the rearward end of second bore  26 . Thus, a flat radial groove  46  is formed at the forward end of large bore  22  for receiving a rubber gasket  48  or other sealing element. When the discharge fitting of the propane canister is threadedly received in large bore  22 , gasket  48  seals against the end of the propane discharge fitting. 
     Probe  10  comprises: an elongate segment  50  which projects from the rearward end  20  of inlet fitting  6 ; a threaded forward segment  52  which is threadedly received in second bore  26 ; an enlarged segment  54  between rearward segment  50  and forward segment  52  and having flats  56  provided thereon for tightening threaded segment  52  into second bore  26 ; a longitudinal flow channel  58  extending through probe  10 ; and a cap  60  provided on he distal end of rearward segment  50 . A lateral slot  62  is provided across cap  60  in fluid communication with the rearward end of longitudinal flow channel  58 . When the forward end  52  of probe  10  is received in interior threaded bore  26  of inlet fitting  6 , a washer  64  is preferably positioned between the enlarged segment  54  of probe  10  and the end of the lip/hub  44  formed in large bore  22 . Washer  64  preferably extends radially a sufficient distance to hold gasket  48  in groove  46 . 
     The discharge fittings of propane canisters of the type used for camping will typically include a valve stem which is surrounded by an externally threaded coupling. Propane is released from the canister when the valve stem is depressed inwardly. Thus, probe  10  is constructed to interact with valve elements of this type such that, as the large threaded bore  22  of inlet fitting  6  is screwed on to the discharge fitting of the propane canister, the cap  60  of probe  10  contacts the forward end of the propane valve stem and eventually depresses the propane valve stem a sufficient distance to cause propane to be released from the canister. The released propane flows through the lateral slot  62  of probe cap  60  and into longitudinal flow channel  58 . 
     Orifice element  16  comprises: an externally threaded rearward section  66  which is received in the small, threaded, bore  30  of inlet fitting  6 ; a larger diameter forward section  68  having flats  70  provided on the exterior thereof for tightening orifice element  16  into threaded bore  30 ; a longitudinal flow channel  72  provided through orifice element  16 ; and an end wall, cap, plug or other element  74  provided at the forward end of, or elsewhere in, orifice element  16  and having a small flow restriction orifice  78  formed therethrough. Orifice  78  is in fluid communication with the flow channel  72  of orifice element  16 . Orifice  78  is sized to restrict the flow of propane from the propane canister and reduce the pressure of the flowing propane sufficiently to enable the propane fuel to be used in the butane-burning device to which the other end of inventive adaptor is attached. 
     The outlet fitting/coupling  8  and the valve assembly  12  of embodiment 2 of the inventive adaptor  2  are structured to attach to a gas inlet fitting of a type commonly employed on butane-burning camp devices. Outlet fitting  8  includes a radial flange  80  on the forward end  82  thereof. A slot  84  is provided in radial flange  80  for receiving a post which will typically be included in the appliance fitting. Outlet fitting  8  can thus be secured to the appliance by positioning the post of the appliance in slot  84  and rotating the inventive adaptor a quarter turn. As will be understood by those skilled in the art, the appliance fitting will typically include a plurality of fingers or latches which contract onto and grasp flange  80  as the adaptor is turned. 
     Outlet fitting  8  further comprises: a rearward segment  86  having an internally threaded bore  88  for threadedly receiving the forward end  34  of inlet fitting  6 ; an interior radial wall  90  provided at the forward end of threaded bore  88 ; a forward bore  92  extending into the forward end  82  of outlet fitting  8 ; an annular groove  94  formed in forward bore  92  for receiving an O-ring or other sealing element associated with the appliance fitting; a hub  96  extending from interior radial wall  90  into forward bore  92 ; a passageway  98  extending through interior wall  90  and hub  96 ; and a radial lip  100  provided at the forward end of hub  96  and projecting into passage  98 . Internal threads  102  are provided in at least the rearward portion of passage  98 . 
     Valve assembly  12  comprises: a valve stem  104  which projects from the forward end of hub  86 ; a valve cage  106  which slidably receives and retains an enlarged rearward portion  121  of valve stem  104  and which includes an externally threaded forward portion  110  which is received in threaded hub  96 ; an O-ring or other sealing element  112  positioned in hub  96  between hub lip  100  and the forward end of valve cage  106 ; a cap  114  threadedly secured over the rearward end of valve cage  106 ; and a spring  116  contained within cage  106  between cap  114  and the enlarged rearward portion  121  of valve stern  104 . Spring  116  continuously urges valve stem  104  outwardly. Cap  114  has a port  118  provided therethrough which allows gas to flow from orifice element  16  into valve cage  106 . 
     Valve stem  104  includes a flow passage  124  having an outlet port  120  provided at the forward end of valve stem  104  and an inlet port  122  provided through the side wall of the valve stem. Inlet port  122  is positioned such that, when inventive adaptor  2  is not attached to the gas burning device and valve stem  104  is thus held fully outward by spring  116 , valve inlet port  122  will be positioned forwardly of O-ring  112 . Thus, inlet port  122  will not be in fluid communication with the remainder of adaptor flow passage  114  so that valve assembly  12  will be closed. Valve assembly  12  is depicted in closed position in FIG.  4 . As adaptor  2  is attached to the inlet fitting of the appliance, valve stem  104  is automatically pushed rearwardly to an open position wherein inlet port  122  is positioned within cage  106  behind O-ring  112 . The open position of valve assembly  12  is depicted in FIG.  5 . 
     Thus, when inventive adaptor  2  is fully assembled with inlet fitting  6  secured to the discharge coupling of a propane canister and outlet fitting  8  attached to the inlet fitting of a butane appliance, the entire flow passage  14  of inventive adaptor  2  is open such that the propane fuel flows into and through the flow channel  58  of probe  10 , the flow channel  72  and flow restriction orifice  78  of orifice element  16 , the aperture  118  of cap  114 , the interior of valve cage  106 , and the inlet port  122  of valve stem  104 . 
     As will be apparent, the inlet  6  and outlet  8  fittings of inventive adaptor  2  could be configured to mate with any common type of gas discharge and appliance fittings. Additionally, other types of restriction elements suitable for restricting the flow and reducing the pressure of the gas flowing through the inventive adaptor will be apparent to those skilled in the art. Examples of such elements include needle valves or other types of valve elements, adjustable or fixed regulators, tubing of a length and inside diameter sufficient to obtain a desired restriction in flow, multiple orifice elements, etc. 
     Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.