Patent Abstract:
A dual fuel vent free gas heater. In one implementation the heater includes a gas burner adapted to receive one of a first type of gas or of a second type of gas with a first pilot burner intended to receive the first type of gas and a second pilot burner intended to receive the second type of gas. A first temperature sensor is located adjacent the first pilot burner and a second temperature sensor is located adjacent the second pilot burner. A normally closed thermal switch is coupled to the first temperature sensor and located in the electrical flow path between a voltage source and a gas control valve actuator, the thermal switch configured to open when the temperature detected by the first temperature sensor exceeds a predetermined temperature indicative that the second type of gas is being delivered to the first pilot burner.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. Pat. No. 7,766,006 and U.S. application Ser. Nos. 12/643,880, 12/237,131 and 12/237,136. 
     FIELD OF THE INVENTION 
     The present invention relates generally to gas heaters and, more particularly, to unvented gas heaters. 
     BACKGROUND 
     Unvented gas heaters are designed to be used indoors without pipes, ducts, or other conduit to vent the heater&#39;s exhaust to the exterior atmosphere. Vent free gas heaters typically include one or more gas burners and optionally one or more ceramic containing heating elements in a housing. The gas and air mix in the heater where combustion takes place. These heaters may have a blower to force air flow through the heater providing the release of heated gases or convective heat. 
     Unvented gas heaters have been designed to be free standing, mounted on a wall, or in a decorative housing such as a vent free fireplace. The housing providing a vent free fireplace is typically substantially the size of a fireplace and has artificial logs above the burners. Some have even been designed with a glass front to provide the appearance of an enclosed fireplace. 
     The unvented heaters of the prior art are typically designed to use either natural gas or liquid propane gas as a fuel source. It is not permitted for a manufacturer to supply a conversion kit for an unvented gas heater to convert from one fuel source to another. Even if such a conversion kit were permitted, as is the case with vented gas heaters, to change fuel source gas type on a heater in the field, requires the installer to change the regulator, pilot orifice and burner orifice for the alternate gas type. 
     SUMMARY OF THE DISCLOSURE 
     A dual fuel gas burner is provided for use in a vent free heater. Embodiments of the dual fuel vent free gas burner can be used in free standing heaters, wall mount heaters, gas fireplaces, or other vent free heaters as is known in the art. A dual fuel vent free gas heater provides convective and/or radiant heat preferably to an indoor environment. The heater may be designed to use natural convective air currents and may optionally have a fan enhancing the natural convective currents within the heater. Alternatively, a fan may be used to force the gases and/or air within the heater at desired flow patterns which may be counter to natural convective forces. 
     This gas heater can be operated with multiple fuels such as liquid propane or natural gas. In some embodiments, an installer turns a selector valve plumbed in the product gas train. This selection sends the correct gas type to the correct fuel injector and pilot burner. Preferably, all plumbing connections are performed at the factory rather than onsite by the user or installer. 
     Embodiments of the gas heater can be operated on liquid propane or natural gas by connecting the fuel supply to the correct regulator on the heater. The installer or user then turns a selector valve, in selected embodiments, plumbed in the product gas train. This selection sends the correct gas type to the correct injector and pilot burner for the supply gas. Optionally, an oxygen detection system is incorporated within the heater. Advantageously, the heater is thermostatically controlled. 
     In one implementation a dual fuel vent free gas heater is provided comprising: a gas burner adapted to receive one of a first type of gas or of a second type of gas, a first pilot burner located adjacent the gas burner and intended to receive the first type of gas, a second pilot burner located adjacent the gas burner intended to receive the second type of gas, a normally closed control valve comprising an actuator and adapted to open upon a predetermined electrical voltage being applied to the actuator, the control valve situated to permit either the first type of gas or the second type of gas to flow through the control valve toward the gas burner when the control valve is in the open position, a first temperature sensor located adjacent the first pilot burner, a second temperature sensor located adjacent the second pilot burner, and a normally closed thermal switch coupled to the first temperature sensor and not couple to the second temperature sensor, the thermal switch located in the electrical flow path between a voltage source and the control valve actuator, the thermal switch configured to open when the temperature detected by the first temperature sensor exceeds a predetermined temperature indicative that the second type of gas is being delivered to the first pilot burner. 
     In another implementation a dual fuel vent free gas heater is provided comprising: a gas burner adapted to receive one of a first type of gas or of a second type of gas, a first pilot burner located adjacent the gas burner and intended to receive the first type of gas, a second pilot burner located adjacent the gas burner and intended to receive the second type of gas, a first temperature sensor located adjacent the first pilot burner and adapted to generate an electrical voltage deliverable to the control valve upon being heated by a pilot flame emitted by the first pilot burner, a second temperature sensor located adjacent the second pilot burner and adapted to generate an electrical voltage deliverable to the control valve upon being heated by a pilot flame emitted by the second pilot burner, a normally closed control valve comprising an actuator and adapted to open upon a predetermined electrical voltage being applied to the actuator, the control valve situated to permit the first type of gas or the second type of gas to flow through the control valve toward the gas burner when the control valve is in the open position, and a normally closed thermal switch situated between the first temperature sensor and the control valve actuator and not situated between the second temperature sensor and the control valve actuator, the thermal switch configured to open when the temperature detected by the first temperature sensor is indicative that second type of gas is being delivered to the first pilot burner. 
     In another implementation a dual fuel vent free gas heater is provided comprising: a gas burner adapted to receive one of a liquid propane gas or a natural gas, a first pilot burner located adjacent the gas burner and intended to receive the natural gas, a second pilot burner located adjacent the gas burner and intended to receive the liquid propane gas, a normally closed control valve comprising an actuator and adapted to open upon a predetermined electrical voltage being applied to the actuator, the control valve situated to permit either the natural gas or the liquid propane gas to pass through the control valve towards the gas burner, a first temperature sensor located adjacent the first pilot burner, a second temperature sensor located adjacent the second pilot burner, and a normally closed thermal switch coupled to the first temperature sensor and not coupled to the second temperature sensor, the thermal switch located in the electrical flow path between a voltage source and the control valve actuator, the thermal switch configured to open when the temperature detected by the first temperature sensor is indicative that liquid propane gas is being delivered to the first pilot burner. 
     In another implementation a dual fuel vent free gas heater is provided comprising: a gas burner adapted to receive one of a liquid propane gas or a natural gas, a first pilot burner located adjacent the gas burner and intended to receive the natural gas, a second pilot burner located adjacent the gas burner and intended to receive the liquid propane gas, a first temperature sensor located adjacent the first pilot burner and adapted to generate an electrical voltage deliverable to the control valve upon being heated by a pilot flame emitted by the first pilot burner; a second temperature sensor located adjacent the second pilot burner and adapted to generate an electrical voltage deliverable to the control valve upon being heated by a pilot flame emitted by the second pilot burner; a normally closed control valve comprising an actuator and adapted to open upon a predetermined electrical voltage being applied to the actuator, the control valve situated to permit the natural gas or the liquid propane gas to flow through the control valve toward the gas burner when the control valve is in the open position, and a normally closed thermal switch situated between the first temperature sensor and the control valve actuator and not the second temperature sensor and the control valve actuator, the thermal switch configured to open when the temperature detected by the first temperature sensor is indicative that liquid propane gas is being delivered to the first pilot burner. 
     In one implementation the first and second temperature sensors comprise thermocouples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an embodiment of a dual fuel vent free showing heater components thereof assembled within a housing; 
         FIG. 2  is a cut-away view of the dual fuel vent free heater of  FIG. 1  showing an oxygen detection system; 
         FIG. 3  is schematic view of the dual fuel vent free heater of  FIG. 1  showing flow connection of component parts; 
         FIG. 4  is schematic view of a dual fuel vent free heater having a single multiuse injector and a thermal switch; 
         FIG. 5  is schematic view of a dual fuel vent free heater having a dual burner configuration; 
         FIG. 6  is schematic view of a dual fuel vent free heater having a dual burner and dual thermostatic control valve configuration; 
         FIG. 7  is a schematic view of a dual fuel vent free heater having a multi-positional manual control valve, a thermal switch, and a thermostatic control valve; 
         FIG. 8  is a blow-up view of the multi-positional manual control valve of  FIG. 7 ; 
         FIG. 9A  is a schematic view of a dual fuel vent free heater having a multi-positional manual control valve, a thermal switch, a thermostatic control valve, and pilot burners; 
         FIG. 9B  is a schematic view of a dule fuel vent free heater having a multi-positional manual control valve, a thermal switch, a thermostatic control valve, and a pilot burners according to another implementation; 
         FIG. 10  is schematic view of the dual fuel vent free heater having a first burner, a second burner, and a cross-over burner for use in a vent free fireplace unit; and 
         FIG. 11  is a schematic view of a dual fuel vent free heater having a multi-positional manual control valve directly controlling the flow of fuel into the heater. 
     
    
    
     DETAILED DESCRIPTION 
     The following description describes embodiments of a dual fuel vent free heater. In the following description, numerous specific details and options are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details or optional components and that such descriptions are merely for convenience and that such are selected solely for the purpose of illustrating the invention. As such, reference to the figures showing embodiments of the present invention is made to describe the invention and not to limit the scope of the disclosure and claims herein. 
       FIGS. 1 ,  2  and  3  show a dual fuel vent free heater  100 .  FIG. 1  shows the component parts of dual fuel vent free heater  100  in a housing  180  and  FIG. 3  shows the flow diagram of heater  100 . Dual fuel vent free gas heater  100  comprises a gas burner  132  having a plurality of gas outlet ports  155  (shown in  FIG. 3 ) in an upper surface thereof. Gas outlet ports  155  are in flow communication with pilot flame burners  120  and  122 . Brackets  139  hold pilot flame burners  120  and  122 , piezometric igniters  157  and  159 , and temperature sensors  152  and  154  proximate burner  132 . Piezometric igniters  157  and  159  are in flow communication with pilot flame burners  122  and  120  respectively. Fuel injectors  126  and  128  are in flow communication with the interior portion of gas burner  132 . Bracket  124  holds fuel injectors  126  and  128  at an injection angle with respect to a longitudinal axis of gas burner  132  other then 0.degree. Non-concentric alignment of injectors  126  and  128  with a burner venturi within burner  132  with hat bracket  124  controls angle of injectors which may be varied depending on the size of burner  132 . Optionally, an oversized venturi may accommodate non-concentric injectors  126  and  128 . Preferably, bracket  124  has threaded apertures for accommodation of injectors having a threaded outer annular surface. Therefore, any size burner  132  may used. Preferably, the injection angel of each injector is of the same magnitude. Fuel supply lines  134  and  136  are in flow communication with fuel injectors  126  and  128  respectively. Fuel supply line  134  and injector  126  have a composition and configuration for transporting a fuel such as natural gas or liquid propane at a desired flow rate and fuel supply line  136  and injector  128  have a composition and configuration for transporting a different fuel such as the other of natural gas or liquid propane at a desired flow rate. 
       FIG. 2  is a cutaway portion of dual fuel vent free heater  100  showing an oxygen detection system. The oxygen detection system has temperature sensors  152  and  154  in proximity to oxygen detection gas outlet ports  153  in gas burner  132 . Oxygen detection gas outlet ports  153  extend down a cylindrical wall in gas burner  132  from the plurality of gas outlet ports  155  on the upper surface of burner  132 . Oxygen detection control system  131 , shown schematically in  FIG. 3 , is in electronic communication with temperature sensors  152  and  154  and thermostatic control  130  wherein thermostatic control  130  has valves controlling the flow of fuels to injectors  126  and  128  and pilot flame burners  120  and  122 . Oxygen detection control system  131  sends an electronic signal to thermostatic control  130  directing thermostatic control  130  to close the valves shutting off the flow of fuel when a temperature sensor  157  or  159  indicates a temperature less than a control temperature. 
     Dual fuel vent free gas heater  100  comprises two regulators  112  and  114  in flow communication with “T” connector  110  via fuel lines  148  and  150  respectively. Fuel line  146  extends from “T” connector  110  to thermostatic control valve  130 . Pilot line  144  leads from thermostatic control valve  130  to pilot control valve  118 . Injector line  142  leads from thermostatic control valve  130  to injector control valve  116 . Fuel lines  138  and  140  lead from pilot control valve  118  to pilot flame burners  122  and  120  respectively. Fuel lines  136  and  134  lead from injector control valve  116  to injectors  126  and  128  respectively. Control valves  118  and  116  are manually adjusted for the fuel type being connected to regulator  112  or  114 . Typically control valves  118  and  116  each have a setting for natural gas and a setting for liquid propane gas and are adjusted according to the fuel connected to regulator  112  or  114 . 
       FIG. 4  shows a schematic view of dual fuel vent free heater  400  having a single burner  132  and a thermal switch  458 . Gas burner  132  has a plurality of gas outlet ports in an upper surface thereof, fuel injector  426  is in flow communication with fuel supply line  134  and an interior of gas burner  132 . Fuel injector  426  has a manual control valve therein for controlling the flow of a fuel to burner  132 . Injector  426  has at least two settings for adjustment to alternate between at least two different fuels being fed from regulator  112  or regulator  114  through fuel supply line  134 . Fuel supply line  134  is in flow communication with thermostat control  130 . Fuel line  140  is in flow communication with thermostat control  130  and pilot burner  120  and has regulator  456  inline therewith. Regulators  114  and  112  each have back flow prevention systems or a plug  411  in allowing a single fuel tank to be connected to either regulator leaving the other regulator without a fuel source. Regulators  112  and  114  are each in flow communication with a “T” connector via fuel lines  148  and  150  respectively. Fuel inlet line  146  extends from the “T” connector and feeds into thermostat control valve  130 . Thermal switch  458  is in electronic communication with thermostat control valve  130  and temperature sensor  159 . Temperature sensor  159  is in proximity to pilot burner  120 . Thermal switch  458  sends an electronic signal to thermostat control valve  130  shutting off fuel flow to fuel supply line  134  and pilot burner supply line  140  in the event that an incorrect setting is made with injector  426  with respect to the fuel being fed to regulator  112  or  114 . 
       FIG. 5  shows dual fuel vent free heater  500  having a dual burner configuration. Two regulators  112  and  114  are in flow communication with a “T” connector via fuel lines  148  and  150  respectively. Fuel line  146  extends from the “T” connector to thermostatic control valve  130 . Pilot burner supply lines  138  and  140  lead from control valve  130  pilot flame burners  122  and  120  respectively. Fuel injector lines  134  and  136  lead from thermostatic control valve  130  to injectors  126  and  128  respectively. Burner  132   a  has first pilot flame burner  122  proximate gas outlet apertures therein and injector  126  proximate an axial opening. Burner  132   b  has pilot flame burner  120  proximate gas outlet apertures and injector  128  proximate an axial opening therein. 
       FIG. 6  is schematic view of dual fuel vent free heater  600  having a dual burner and dual thermostatic control valve configuration. Regulator  112  is in flow communication with control valve  130   a  via fuel line  148 . Regulator  114  is in flow communication with control valve  130   b  via fuel line  150 . Pilot supply line  140  leads from control valve  130   a  to pilot flame burner  120  and pilot supply line  138  leads from control valve  130   b  to pilot flame burner  122 . Injector supply line  134  leads from control valve  130   a  to fuel injector  126 . Injector supply line  136  leads from control valve  130   b  fuel injector  128 . Burner  132   a  has pilot flame burner  120  proximate gas outlet apertures and fuel injector  126  proximate an axial opening. Burner  132   b  has pilot flame burner  122  proximate gas outlet apertures and fuel injector  128  proximate an axial opening therein. 
       FIG. 7  shows a schematic view of dual fuel vent free heater  700  having a multi-positional manual control valve  800 . Regulators  112  and  114  are in flow communication with a “T” connector via fuel lines  148  and  150  respectively. Fuel line  146  extends from the “T” connector to thermostatic control valve  130 . Pilot line  142  and injector line  144  lead from thermostatic control valve  130  to multi-positional manual control valve  800 . Multi-positional manual control valve  800  directs flow from pilot line  142  and injector line  144  to pilot supply line  140  and injector supply line  136 , or pilot supply line  138  and injector supply line  134 , or blocks the flow from pilot line  142  and injector line  144 . Burner  132  has injectors  126  and  128  held at an axial opening with bracket  124 . Pilot burners  120  and  122  are proximate the outer surface of burner  132  and are in flow communication with pilot supply line  140  and  138  respectively. Thermal switch  158  is in electronic communication with T/C block  756 . T/C block  756  is in electronic communication with a thermocouple proximate each pilot burner  120  and  122 , via T/C lines  154  and  152 , and control valve  130 . In the event an incorrect setting is made with respect to the fuel being fed to the correct injector and pilot burner, thermal switch  158  or control valve  130  shuts off the flow of gas to heater  700 . 
       FIG. 8  shows a blow-up view of multi-positional manual control valve  800 . Multi-positional manual control valve  800  comprises a control block  804  and a control cylinder  802 . Control block  804  has a cylindrical aperture  850  extending from a front surface to a rear surface. The front surface of control  800  has fuel selection and cut off indicators LP, NG, and OFF. Three fuel injector apertures  820 ,  824  and  830  extend from cylindrical aperture  850  at about 90.degree. intervals to a left side, top, and right side of control block  804 . A pilot aperture is axially aligned about cylindrical aperture  850  with each fuel injector aperture, pilot aperture  822  is axial aligned with injector aperture  820 , pilot aperture  826  is axial aligned with injector aperture  824 , and pilot aperture  828  is axial aligned with injector aperture  830 . Control cylinder  802  has an outer circumference proximate the circumference of cylindrical aperture  850  in control block  804  wherein control cylinder  802  is closely received within. Control cylinder  802  has “L” shaped flow through fuel injector aperture  812  and an axially aligned “L” shaped flow through pilot aperture  814 . Control cylinder  802  has a first, second, and third, position within the cylindrical aperture in control block  804 . The front surface of control cylinder  802  has a selection arrow pointing to an appropriate indicator on the front surface of control block  804 . At a first position, fuel injector aperture  820  and pilot aperture  822  are in flow communication with fuel injector aperture  824  and pilot aperture  826 . At a second position, as shown in  FIG. 8B , fuel injector aperture  824  and pilot aperture  826  are in flow communication with fuel injector aperture  830  and pilot aperture  828 . At the third position, one end of the “L” shaped flow through fuel injector aperture  812  and axially aligned “L” shaped flow through pilot aperture  814  are blocked by the wall of cylindrical aperture  850  in control block  804  cutting off the flow of fuel. 
       FIG. 9  shows a schematic view of dual fuel vent free heater  900 . Dual fuel gas heater  900  comprises two regulators  112  and  114  in flow communication with a “T” connector via fuel lines  148  and  150 . Fuel line  146  extends from the “T” connector to thermostatic control valve  130 . A pilot line  142  and an injector line  144  lead from thermostatic control valve  130  to multi-positional manual control valve  800 . Multi-positional manual control valve  800  has a first, second, and third control position as indicated with LP, NG, and OFF. The first control position creates a flow communication between the pilot line  144  and injector line  142  leading from thermostatic control valve  130  with pilot flame burner  120  and injector  128  through pilot feed line  140  and injector feed line  136  respectively. The second control position creates a flow communication between pilot line  144  and injector line  142  leading from thermostatic control valve  130  with pilot flame burner  122  and injector  126  respectively. The third position cuts off fuel flow from pilot line  144  and injector line  142  leading from thermostatic control valve  130 . Thermal switch  935  is in electrical communication with a temperature sensor proximate pilot flame burners  120  and  122  via electrical connectors  154  and  152  respectively. Thermal switch  935  sends a shut off signal to a control valve when a first set temperature is exceeded in pilot flame burner  120  or a second set temperature is exceeded in pilot flame burner  122  cutting off the flow of fuel to heater  900 . 
     In one implementation the thermal switch  935  is in electrical communication with the temperature sensor proximate pilot flame burner  122  and not with the temperature sensor proximate pilot flame burner  120 . In one implementation, the thermal switch  935  is configured to transition from a closed state to an open state when a temperature at or near the pilot flame burner exceeds a predetermined temperature indicative that an LP gas is being supplied to the NG gas pilot flame burner. In one implementation, upon transitioning from the closed state to the open state, electrical power to a gas supply valve (e.g., thermostatic control valve  130 ) is interrupted resulting in the flow of fuel to heater  900  being terminated. 
       FIG. 10  shows a schematic view of dual fuel vent free heater  1000  having burner  132   a ,  132   b , and cross-over burner  171 . Such a configuration provides a blue flame burner and a yellow flame burner as is often desirable in a vent free fireplace heater. The configuration of heater  1000  is similar to the configuration of heater  900  with the addition of burners  132   b , cross-over burner  171 , two fuel line “T” connectors, and fuel injectors  126   b  and  128   b . Crossover burner  171  is in flow communication with burners  132   a  and  132   b . Burner  132   b  has fuel injectors  126   b  and  128   b  held by bracket  124   b  proximate an axial end and is situated substantially parallel burner  132   a . Fuel supply line  134   b  feeds injector  126   b  with a “T” connector in flow communication with fuel supply line  134   a . Fuel supply line  136   b  feeds injector  128   b  with a “T” connector in flow communication with fuel supply line  136   a.    
       FIG. 11  is a schematic view of dual fuel vent free heater  1100  having a multi-positional manual control valve  800  directly controlling the flow of fuel into heater  1100 . The configuration of heater  1100  is similar to that of heater  900  but does not have thermostatic control  130 . Rather, fuel from either regulator  112  or regulator  114  is fed through fuel line  148  or  150 . Fuel lines  148  and  150  “T” into pilot line  142  and injector line  144  which lead directly to multi-positional manual control valve  800 . Therefore, the amount of heat produced by heater  1100  is manually controlled with multi-positional manual control valve  800  without any thermostatic control.

Technology Classification (CPC): 5