A wide variety of fuel-air mixing devices are known. Nearly as well known is the fact that inadequate mixing of fuel and air frequently results in the generation of undesirable combustion by-products such as carbon monoxide. Such by-products from internal combustion engines are undesirable and in free-standing home heating devices can be fatal.

Among the several objects of the present invention may be noted the provision of a device which thoroughly mixes fluids passing therethrough; the provision of a gas- fired space heater requiring no external vent; the provision of a high efficiency heat generating device; and the provision of a fuel burning system which in which fuel and air is mixed to a highly homogeneous state prior to combustion thereby promoting more complete combustion. These as well as other objects and advantageous features of the present invention will be in part apparent and in part pointed out hereinafter.

In general, a multi-chambered mixing device has a spheroidal chamber, a toroidal chamber partially surrounding the spheroidal chamber and a cylindrical chamber having an outlet opening at one end and a flared inlet opening at the other end. The toroidal chamber functions as a manifold and is optional. Multiple direct inlets are sometimes preferred in which case, the mixing device is typically two-chambered. The cylindrical chamber is partially surrounded by the spheroidal chamber and the flared inlet opening is located within the spheroidal chamber while the outlet opening is located outside the spheroidal chamber. The spheroidal chamber is formed from two hemispheroidal shells each having a rim for joining to the rim of the other, and the toroidal chamber is formed between one hemispheroidal shell and a truncated hemispheroidal shell having a rim for joining to the rim of said one hemispheroidal shell. There is an inlet opening into the toroidal chamber for accepting a fluid mixture and a plurality of apertures in the one

hemispheroidal shell for passing a fluid mixture from the toroidal chamber to the spheroidal chamber.

Also in general, a high efficiency free-standing gas fired space heater has a pre- heated gaseous fuel mixed with air in a multi-chamber mixer, and the resulting homogeneous, highly combustible mixture fed to a screen-enclosed combustion area to be burned.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a cross-sectional view of a mixing device illustrating my invention in one form; Figure 2 is a view in cross-section in the direction of arrows 2-2 of Figure 1; Figure 3 is a schematic illustration of one application for the mixing device of Figures 1 and 2; Figure 4 is an enlarged cross-sectional view of the rim where the device portions join; Figure 5 is a schematic illustration of another application for the mixing device of Figures 1 and 2; Figure 6 is a cross-sectional view of a mixing device similar to Figure 1 illustrating my invention in another form; Figure 7 is a view in cross-section in the direction of arrows 7-7 of Figure 6; Figure 8 is a schematic illustration of a further application for the mixing device of Figures 1 and 2; Figure 9 is a cross-sectional view of a functional implementation of the system depicted in Figure 8 in the form of free-standing space heater incorporating the present invention in one form; Figure 10 is a more detailed cross-sectional illustration of the burner portion õf the heater of Figure 9; Figure 11 is a view in cross-section along line 11-11 of Figure 10; Figure 12 is a cross-sectional view of a variation on the burner head suitable for use in conjunction with any of Figures 3,5,8 or 9; Figure 13 is a top plan view of one form of the burner head of Figure 11; and Figure 14 is a top plan view of another form of the burner head of Figure 11.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawing.

The exemplifications set out herein illustrate a preferred embodiment of the invention in one form thereof and such exemplifications are not to be construed as limiting the scope of the disclosure or the scope of the invention in any manner.

DESCRIPTION OF THE PRFFFRRED FMBODIMEN The mixing device of the present invention is generally spheroidal in shape. It may take on a substantially spherical interior configuration, be formed as an oblate or prolate spheroid, be ellipsoidal, or have some other similar generally globe-like configuration all hereinafter referred to as spheroidal or, in the case of its halves, hemispheroidal.

Referring to Figures 1,2 and 4, the mixing device 11 is formed as a generally spheroidal multiple chambered enclosure from two hemispheroidal shells 13 and 15. The shells each have a rim (16 and 18 in Figure 4) for joining to the rim of the other as indicated at 19 to form the generally spheroidal chamber 33. There is a further truncated hemispheroidal shell 17 which also has a rim 20 for joining to the rim 18 of hemispheroidal shell 17 again as indicated at 19. The rims may be joined by a series of rivets such as 47, by welding, or by some other suitable technique.

The truncated hemispheroidal shell 17 is larger than and nests with hemispheroidal shell 15 when they are joined to form a generally toriodal chamber 34.

There is at least one and frequently a plurality of apertures such as 21,23 and 31 in the hemispheroidal shell 15 which form passageways between the chamber 34 and chamber 33. Finally, there is a pipe 29 forming, on its interior, a cylindrical chamber and, on its exterior, a surface which influences the flow directions within the chamber 33. The pipe passes through the hemispheroidal shell 13 to provide an outlet from the chamber 33.

This pipe 29 passes substantially through the spheroidal interior of chamber 33 and terminates in a flared end near the flattened inner surface 27 of hemispheroidal shell 15.

Thus, there is a planar surface portion 27 adjacent the flared pipe end. In one implementation, the central angle subtended by the flattened surface area 27 was about 20 degrees. In that same implementation, the central angle subtended by the apertures, e. g., between 21 and 31 was about 60 degrees. The flared pipe end and the flattened surface 27 cooperate to induce a helical tornado-like flow through the pipe. A surface tension reducing polytetrafluoroethylene coating (45 in Figure 4) may be applied to the inner surfaces of the hemispheroidal shells. A similar coating may be applied to the inner surface of the truncated hemispheroidal shell 17 if desired.

There is a generally circular opening 25 formed where the truncated hemispheroidal shell is truncated for receiving a fuel-air mixture, for example, from the piezoelectric evaporator 37 of Figure 3. The pipe 29 extends from the hemispheroidal shell 13 a distance sufficient to provide a connection for conveying a homogeneous combustible mixture from the device to a fuel utilization device such as the combustion chamber 41 of Figure 3.

The method of operation of the mixing device should now be clear. Fuel and air enter the inlet opening 25 with the fuel-air mixture flowing laminarly through that opening. The mixture then moves somewhat radially through the toriodal chamber 34 and from that chamber through the plurality of apertures into the spheroidal chamber 33. The mixture flows turbulently through the chamber 33 and into the flared end of the pipe 29. Flow continues to be turbulent (actually tornado-like) through the pipe 29 and finally becomes a laminar flow as the extremely well mixed fuel-air exits the pipe 29. The tortuous path and turbulent flow contributes significantly to intimate mixing of the fuel with the air thereby improving combustion.

As one example of a system utilizing the mixing device 11, the combustion device or system of Figure 3 includes a liquid fuel source 12 and a piezoelectric evaporator for agitating the fuel and changing the liquid fuel into a gaseous phase. The mixing device 11 as heretofor described receives the fuel vapor and air from source 10 and combines the gaseous fuel with air to form a homogeneous fuel-air mixture. The laminar flow output end of the pipe 29 conveys the fuel-air mixture from the mixing device by way of a blower 39 and one or more fire screens 43 to a combustion chamber 41. The fire screens 43 are present merely as a precaution against combustion moving upstream in the system.

As a second example of a system utilizing the mixing device 11, an engine driven generator 49 of Figure 5 which may be, for example, of the emergency or"back-up" variety, receives its fuel-air mixture from pipe 29 of mixing device 11. The fuel, typically gasoline, is fed from supply 12 to an evaporating unit 51 and then to the inlet 25 of mixing device 11.

If the mixing device 11 is too large for a given application, the flow rate through it is too slow to induce the desired turbulence and the degree of mixing suffers. If the mixing device is too small for a given application, the throttling effect limits flow and performance suffers. In one implementation, a 51/2"diameter mixing device was found

to work well with engines having displacements between 60 cc and 300 cc, but performance was poor outside that range.

Inlet manifold 34 may be replaced by individual inlet lines such as 53,55 and 57 as shown in the modified mixing device 11 a of Figures 6 and 7. These individual inlet lines 53,55 and 57 may be coupled together and to a source of fuel such as the evaporator 51 or 37, or may be coupled to different sources so that the mixing device may function to homogenize a plurality of different materials. Eight different materials could be mixed by the illustrated mixing device, but more or fewer inlets could be provided. Also, the inlets may be elongated slots rather than circular. Generally twelve inlets is preferred.

As one more example of a system utilizing the mixing device 11, the combustion device or system of Figure 8 includes a gaseous fuel source 61 such as natural or LP gas.

The mixing device 11 as heretofor described receives the fuel and air from source 10 and combines the gaseous fuel with air to form a homogeneous fuel-air mixture. The laminar flow output end of the pipe 29 conveys the fuel-air mixture from the mixing device by way of a blower 65 and one or more fire screens 67 to a combustion chamber 71. Again, the fire screens 67 are present merely as a precaution against combustion moving upstream in the system.

An implementation of the system shown in Figure 8 appears in Figures 9,10 and 11. In Figure 9, the shroud 69 has air admitting apertures in a base portion 105 as well as in base support plate 103. Cool air enters the apertures and is heated in the shroud.

Hot air exits through an open or apertured top. The unit rests on legs such as 101. The combustion chamber 71 is supported by a central tubular support 107 from which wires or rods 109 extend upwardly. The combustion chamber 71 includes a screened-in region 115.

In Figure 9, a gaseous fuel source 61 such as a natural gas meter, LP gas tank or the like supplies fuel through the conduit 73 which extends along a circuitous path first upwardly, then along the bottom of the outer chamber 69, and finally back downwardly and to one inlet to mixer 11. The conduit may extend along the bottom of chamber 69 or may be otherwise disposed in close proximity to the outer chamber 69. Thus, heat from the combustion chamber 71 provides the fuel preheating function 63. A source of combustion air 10 provides another inlet to the mixer 11. A motor 75 drives blower 65 forcing the fuel-air mixture from the mixer 11 upwardly through fire screen 67 and into the conduit 77. The open end 81 of conduit 77 functions as a burner outlet within the

combustion chamber 71 and is shown in greater detail in Figure 10. Electrically energizable igniter electrodes 79 and 84 similar to those employed on conventional home gas furnaces is positioned closely adjacent the burner outlet 81. Also closely adjacent the burner outlet is a flame detector 87 of conventional type which functions as a safety device to shut off the flow of fuel when a flame should be present, but is not detected.

An automatic shut-off solenoid 85 operates a butterfly valve 89 or similar control valve within pipe 77 to close the pipe 77 when the burner shuts off. Thus, an intentional or fail- safe shutdown of the burner causes valve 89 to close as well as disconnecting fan motor 75 and closing a control valve (not shown) in the fuel supply line 73. This traps a fuel-air mixture within the system facilitating subsequent re-ignition. There is also a vane 83 within the pipe 77 open end formed generally from a flat sheet of metal which has been twisted so the edges are generally helical where they contact the inside wall of the pipe 77. This vane is for introducing a swirling turbulence into the fuel-air mixture as it exits the burner outlet 81. A metal enclosure or burner head 71 has screen 115 which surrounds the burner outlet 81, igniter 79 and vane 83. The region within the metal screen 115 is the combustion region or chamber while the outer chamber or shroud 69 is rather larger and may be enclosed by one or more glass or metal plates as desired.

Screen 115 functions somewhat like a lantern mantle and takes on a red glow during operation. Little or no flame appears beyond the confines of the metal screen.

Figures 12-14 illustrate yet another variation on the combustion chamber of the present invention. Here, a highly temperature resistant combustion chamber is formed as a ceramic or stainless steel globe 117 open at the top and at the bottom and having generally serpentine shaped sidewalls. Beginning at the bottom, there is a relatively narrow region 125 and then the globe widening into an intermediate region 127 and finally narrows near the top at 129. The uppermost region of the globe is a flared mouth region 131 at the top. Figure 14 is a top view and illustrates the ceramic globe as an elongated generally racetrack shape while the top view of Figure 13 illustrates an alternative configuration where the globe is a surface of revolution.

Fuel is conveyed to the combustion chamber of Figures 12 and 13 by a fuel conveying tube 119 which extends centrally upwardly into the bottom of the globe. The fuel conveying tube 119 has wires or rods 121 which support a conical diverter 123 which urges the hot gasses outwardly so as to follow the serpentine contour of the globe inner sidewalls. As with the embodiment of Figures 9-11, combustion chamber 117 may be disposed within a shroud having an air inlet and an air outlet along with convection or some other means for circulating cool air into the inlet, through the shroud and hot air

out of the outlet. If the globe 117 is elongated, the fuel may be supplied by an elongated manifold 133 similar to burner units found on home barbecue devices. A V-shaped spreader similar to the diverter 123 may be positioned over the manifold 133 if desired.

From the foregoing, it is now apparent that a novel fluid mixing device as well as a novel arrangement utilizing that device have been disclosed meeting the objects and advantageous features set out hereinbefore as well as others, and that numerous modifications as to the precise shapes, configurations and details may be made by those having ordinary skill in the art without departing from the spirit of the invention or the scope thereof as set out by the claims which follow.