US3132009A - Petroleum gas-air mixer and metering means - Google Patents

Description

May 5, 1964 c. BOYD 3,132,009

PETROLEUM GAS-AIR MIXER AND METERING MEANS Filed Dec- 20, 1960 2 Sheets-Sheet 1 FIGJ.

INVENTOR 2 CLARENCE BOYD ATTORNEYS May 5, 1964 c. BOYD PETROLEUM GAS-AIR MIXER AND METERING MEANS 2 Sheets-Sheet 2 Filed Dec.

INVENIOR CLARENCE BOYD ATTORNEYS United States Patent 3,132,009 PETROLEUM GAS-AIR MIXER AND METERING MEANS Clarence Boyd, 504 Denham Road, Rockville, Md. Filed Dec. 20, 1960, Ser. No. 77,068

' 10 Claims. (Cl. 48l80) gines. As a fuel, LPG is less expensive and it materially reduces the amount of lubricating oil used and the cost of engine maintenance. In these uses, special types of carburetors or mixers must be employed to mix the fuel with air since the fuel is a gas at' ordinary temperatures, rather than a liquid, as in the case of gasoline and conventional carburetors are unsatisfactory. The fuel pump used with gasoline is replaced by Vaporizers and pressure.

regulators to control the evaporation and flow of the to the fuel-air mixers.

The simplest mixer is a long tube through which air is drawn by engine vacuum which has a side opening for introduction of fuel.. A choke valve is at the top of the tube and a throttle valve at the bottom. This type of mixer has been found unsatisfactory in the need for using a choke which must be readjusted as the engine warms, in its inability to permit low speed idling, in low fuel efiiciency and in giving slow engine response to changes in the throttle opening. Engines operated with such mixers must be idled at relatively high speeds and will become rough-operating and will stall when the throttle opening is reduced in an effort to idle at slower speeds. Sudden changes in throttle opening are not followed by instantaneous engineresponse and there is a delay before the engine changes speed when the throttle opening is increased or decreased The problem is particularly serious with small one and two cylinder engines such as fuel used in floor cleaning equipment, lawn mowers and the like, which are usually the most diificult engines to opcrate smoothly.

In an: effort to overcome these difficulties, this type of mixer. has been modified by the inclusion of various types of bafiles or homogenizers in the mixer between the fuel inlet opening and the throttle and by providing a plurality of fuel inlet holes around a venturi tube, but only limited improvement has resulted.

' The pressureregulators used to control the fiow of gas to the mixers have also presented problems. The amount of fuel flow needed varies as the motor is accelerated or decelerated and the simple forms of pressure regulator do not respond rapidly enough to meet changes in fuel demand. When the engine is accelerated by. opening the throttle, and gas is drawn ,into the carburetor more rapidly, gas pressure in the line between the regulator and the carburetor drops and flow through the regulator must increase to meet this demand, but the more simple pressure regulators do not respond rapidly enough. Similar delays are experienced on deceleration.

The present invention overcomes these difficulties by providing a liquid propane-air mixer capable of supplying fuel at all engine speeds, responding instantaneously to changes in the throttle valve opening and operating without a choke valve, and a pressure regulator metering valve for use with this mixer. The mixer of this invention is a long narrow venturi tube with a plurality of inlet ports, angularly spaced about a point in the interior of the tube. The venturi tube is smooth-walled and funnel-shaped at top and bottom with a substantially straight central portion, interrupted only by an abrupt increase 5 in diameter along a ridge which is adjacent the up stream edge of the inlet ports and preferably coincides with them.

Passageways from the inlet'ports connect to an annular chamber to which fuel is supplied at a controlled pressure about equal to atmospheric pressure and these passageways descend toward the inlet ports and are inclined toward the venturi throat and around it at a compound angle of about 12 30 to give a slight swirling motion to the fuel as it enters the venturi. There are small grooves in the wall of the venturi tube at the lower ends of the inlet ports so that the bottom corner of the ports are slightly rounded, and these grooves, together with the overhang atthe top of the ports along the ridge, tend to guide the fuel close tothe wall of the venturi tube. There is a throttle at the lower end of the venturi tube, but no choke is required.

Furthermore, it has been found that certain dimensions of this mixer are critical and that the dimension of the various openings and passageways are strictly controlled by the engine for which the mixer is used. The internal diameter of the venturi tube above the ridge is about onefourth the bore of a one cylinder engine or the sum of the bores of larger engines. Preferably, there are eight inlet ports and the sum of the diameters of the passageways, which should be equal diameter, is equal to the diameter in the upper portion of the venturitube. The depth of the ridge is not greater than the diameter of one of the passageways and probably is about one-half so that the increase in diameter of the venturi tube at the ridge is equal to no more than twice the diameter of a'passageway and preferably is equal to it. The annular fuel supply channel should have a depth of one-half the diameter of the venturi tube above the ridge, although this dimension probably is not too critical.

This mixer has been used with one cylinder engines, using commercial fuel metering equipment and it has been found possible to idle an engine at 350-360 rpm. Using the best commercially available mixers, the lowest idle speeds are 600-800 rpm. In addition, substantial fuel savings have been found. A one cylinder engine which runs only 40 to 44 hours with 4.7 gallons of fuel using a commercial fuel mixer has been operated for 60 to 62 sure reduction and metering. The first is similar to a the valve.

conventional pressure regulator and has a piston or diaphragm controllingthe opening of a valve in response to the pressure differential between a dead air space behind the piston and the pressure of 'LPG emerging from The second stage is a small metering valve such as a needle valve and the third stage is a gate valve opened and closed in synchronism with the throttle valve of the mixer.

The invention can be more fully understood from the following detailed description of a preferred embodiment of one part of the metering apparatus; and

FIGURE 7 is an enlarged partial section showing an inlet port.

The mixer 1 is an assembly of two parts, a venturi tube 2 and an outer shell 3, separated by an annular fuel distribution channel 4. The interior of the venturi tube 2 is smooth-walled and funnel shaped at top 5 and bottom 6 with a substantially straight central section 7, interrupted only by a ridge 8. There are eight inlet ports 9, spaced about the central section 7, the tops of which coincide with ridge 8 and passageway 10 lead downwardly to these ports from annular fuel distribution channel 4. There is a butterfly type throttle valve 11 atthe lower end of central section 7 mounted on shaft 12 which is journalled in the venturi tube'2 and the outer shell 3, and a stop screw 21 is threaded through the body to engage the throttle and limit its closing for idling the engine. The outer wall of the venturi tube is recessed in the upper portion to provide the fuel distribution channel 4 and has a shoulder 13, below which the outer diameter of the venturi tube is reduced, and this shoulder rests on a corresponding shoulder 14 of the outer shell.

The outer shell 3 is tubular, with a shoulder 14 at the center of its inner wall so that the inner diameter. of the lower portion of the shell is less than that of the upper portion. At the lower end of the shell there is an outwardly extending flange l5 withscrew holes 16 and 16' for securing the mixer to the inlet manifold or other input to an engine.

In the preferred embodiment of the invention, the venturi tube extends beyond flange and the lower end of the shell 3. Thus the high velocity of air-fuel mixture through the venturi tube is continued as far'into the engine as possible. I

The upper portion of the shell encloses the fuel distribution channel 4 and there is a pipe 17 extending laterally from the wall of the shell and passing therethrough which communicates with channel4. The outer end of the pipe is internally threaded for attachment to a pres' sure regulated source of propane gas such as by tube 18 as shown in FIGURE 3.

A course metering needle type valve (notshown) may be included in the shell 3 to regulate the flow of fuel gas from pipe 17 into fuel distribution channel 4 and this may be particularly important when not using the pressure regulator and metering apparatus forming a part of this invention. v The angle of offset of the passageways 10 is one of the most critical features of the invention and 12 30' has been found to be the proper angle for one and two cylinder engines. a plane through the radius drawn to the inlet port along the longitudinal axis and 12 30 to a plane along the longitudinal axis and perpendicular to that radius. Small variations of as much as a few degrees have been found to result in the problems previously discussed in connection with the mixers in current use. For example, when the angle was 16, the response of the engine was not satisfactory.

The depth of the ridge 8 is also important and it must be less than the diameter of one of the passageways, preferably about one-half the diameter ofthe passageway. As described, the lower edge of each inlet port is grooved or rounded out to a depth of about a few thousandth of an inch as shown at 19 in FIGURE 7 so as to smooth flow of the fuel into the venturi tube. These grooves and the overhang of ridge 8 are believed to guide the fuel along the wall of the lower portion of the straight-walled central section 7 of'the venturi tube.

As a fuel source, a tank of liquid propane is connected through a vaporizer and a metering pressure regulator to the inlet pipe 17. The liquid fuel is evaporated by passing it'through connecting lines although, in some cases, it may be necessary to employ a heat exchanger of conventional type, perhaps heated by exhaust gases Pressure in the fuel distribution channel is maintained This is a compound angle of 12 30' to.

at about atmospheric pressure. This prevents substantial amounts of fuel from flowing through the small di-- ameter passageways when the engine is not operating.

To control the pressure, conventional pressure regulators have been used with the above mixer, and improvements over conventional mixers have been observed. However, this equipment is bulky and not as satisfactory as the pressure regulator-metering device forming part of a this invention.

v 55. The outlet is shown generally at 61, leading from cavity 56and an additional outlet opening having threaded walls is at 62, closed by a threaded cap 63 screwed into the opening. The latter opening provides for removal of water and other materials condensed and trapped in chamber 56. The first stage 51 may generally be described as a piston type pressure reducer. There is a small chamber 64 below the cavity and a passageway 65 connects this chamber 64 with cavity 55. The walls of this passageway are threaded and a bushing 66 having an opening 67 through its center is screwed into it. The lower surface of the bushing is flat and serves as a valve seat for a valve controlling the flow of fuel gas upwardly into cavity 55. The valve also includes a core 68, having a central shaft 69 and a sealing flange 7 0 extending outwardly therefrom. The shaft passes upwardly through the opening67, and theflange lies below the bushing so that the valve is closed by raising the flange against the bushing. The upper face of the flange may be leather or plastic or some other resilient material to improve the seal. A compression spring 71 is beneath the flange and tends to urge the valve core against the lower surface of the bushing to prev ent fuel gas from flowing from the inlet upwardly into chamber 55. Means are provided above this in the cavity 55 to counteract this spring and depress the valve core and permit fuel to flow upwardly through opening 67 at a rate dependent upon pressure in the cavity 55.

As a convenience in machining, the lower chamber 64 is generally cylindrical in shape and extends to the lower wall of the block 54. At the bottom of the chamber the wallsar'e threaded and a cap 72 is screwed into the chamber to make a gas-tight seal. The center of this cap is bored out to form an opening 73 and a slightly wider shallow recess at its upper end. Opening 73 is sufiiciently wide to receive the shaft 69 when the valve core is depressed and the shallow recess receives the compression spring'71.

The upper chamber 55 is closed by an inverted cupshaped closure member 74 which is threaded on its outer wall at75. The upper wall of the cavity 55 is also threaded and the closure member is screwed into the cavity. The inner walls of at least the lower part of the closure member are straight to form a cylinder in which the piston 76 moves.

- The piston 76 may be of aluminum or other suitable metal and has a rubber gasket 77 secured to its lower end and of the same outside diameter as the inner diameter of closure member 74 so as to be in sliding contact with it. Depending from the lower side of the piston 76 is a plunger 78 which is aligned with the shaft 69 of the valve. This pin presses down onthe valve core and tends to keep the valve open.

At the top of the closure member 74, there is a threaded opening 79 and a cap 80 having a downwardly-extendingthreaded rod 81 screwedintothis opening. The lower end of rod 81 is rounded at 82 and the piston carries anupwardly extending boss 83, the top of which is recessed toreceive the rounded bottom of rod 81. Beneath the piston 76 is a compression spring 84 which tends to urge the piston upwardly-toward the rod 81.

In operation, the position of piston 76 will depend upon the back pressure of airabove it and the pressure of fuel gas below. If the pressure of fuel gas rises or falls the piston will move up or down, compressing or relaxing the air above it until its pressure is the same as that of the fuel gas. Since the lower end of plunger78 depresses the valve core 68, an increase in pressure of fuel gas beneath the piston will force the piston up and permit the valve core to rise. This in turn will reduce the rate of flow of propane through the valve and will tend to reduce the pressure of fuel gas beneath the piston. The piston will then fall towardits equilibrium position, so that the pressure in the cavity 55, beneath the piston 76, will tend to remain constant. Raising and lowering the cap 80 will provide an upper limit to the height of the piston and hence of the Valve core 69. This provides a minimum opening for the valve and a minimum pressure of propane in the lower portion of chamber 55 which is varied by adjusting the cap.

The piston may be replaced by a diaphragm but this is less satisfactory, both in operation and in the need for frequent diaphragm replacement.

A second stage of metering is provided by a needle valve 85 controlling fuel gas flow through passageway 57.

The valve includes a stern threaded into an opening in the block 54 which can be turned, down against a seat (not shown) adjacent the passageway 57.

The third stage of regulation, shown at 52, the rate of flow of fuel gas is regulated in accordance with the throttle opening 'of the fuel air mixer. The cavity 56 is subdivided by a cup member 86 which is threaded on the upper portion of its outer wall at 87 and screwed down into threads at the upper end of the wall of cavity 56. There are small openings 88 and 88' in the bottom of the cup which are covered with screens to trap undesired particles. Fuel gas flows into the lower portion of the cavity 56 and up through these openings into sub-chamber 89.

There is a window valve 90 in this sub-chamber leading to tube 18 extending through the lower wall of the cup and the lower wall of block 54 to connect with the LPG air mixer. The window valve 90 comprises a hollow body 91 which may be an enlargement of the upper end of the tube 18 and a shaft 92 within the body and extending upwardly through sub-chamber 89. The lower end of the shaft is hollow as shown at 93 and has a lateral opening 94 through its wall leading toits hollow center. A Teflon or other plastic gasket 95 surrounds the lower end of the shaft 92 to seal the space between the shaft and the inner wall of the body and has an opening aligned with the opening 94 in the shaft. There is another opening 96 in the wall of the valve body 91 which also is aligned with these openings so that fuel gas may. flow from the subchamber 89 through the valve into the tube 18.

A bushing 196 with a central opening to accommodate the shaft 92 is screwed into an opening in the top of the valve body. A cover 97 seals the upper end of the block 54 and screws onto the threads 87 of cup 86. It has a threaded opening through its center and a bushing 197 is screwed into the opening. The bushing also has a central opening of the same diameter as the shaft 92 through which the shaft passes. An additional shaft seal is shown generally at 98 within sub-chamber 89. It is a round plate 99 having an annular groove 100 and a large synthetic rubber O-ring 101 in the groove in contact with the inner Wall of the cup 86. The diameter of cup is enlarged in its upper end to provide a shoulder 102 on which the plate rests. There is an opening 103 in the center of plate 99 and the shaft 92 passes through this opening. An O-ring can also seal at this point. A safety valve 104 of conventional design is also provided in the plate to release any excess pressure in sub-chamber 89.

are pins 105 extending upwardly from the body of the valve and there is another pin 106 passing through the shaft 92 which engages with pins 105 as the shaft turns.

A modified form of valve is shown in FIGURE 6 and in this case the upper part of the valve body is designated 107 and the opening in the body as 103. The upper end of the opening is enlarged into a tapered recess 109 which serves as a valve seat. The shaft of the valve is indicated at.110 and it carries a frustro-conical valve plug 111 at its lower end which mates with recess 109. The shaft is raised and lowered to open and close the valve and a simple mechanism for this is the cam member 112 secured to the shaft and a pin 113 on which it rests. As the shaft turns, the cam reciprocates the shaft.

The valve shaft 92 is connected through suitable linkages to shaft 12 which carries the butterfly valve throttle. A simple arrangement is shown in FIGURES l and 2.

.. Lever arms 114 and 115 are rigidly secured to shaft 12 and a shaft 116 respectively. The lever arms are pivotally joined at their distal ends by a pin 117. There is a vertical opening through block 54 and shaft 116 extends up- Wardly through the opening. At the top, a lever 118 is secured to shaft 116 and another lever 119 to valve shaft 92. Levers 118 and 119 are in turn joined by a connecting rod 120 pivotally mounted on the distal ends of the levers by bearings 121 and 122. The lengths of the various levers and connecting rods must be such that window valve or its equivalent is fully open when the throttle valve 11 is open and that both valves close together. Preferably, the length of connecting rod 120 is adjustable so that the valves may be synchronized.

Of course, separate connections from the valve shaft 92 and the throttle shaft 12 to the accelerator are permissible but less expedient.

While preferred embodiments have been described it will be appreciated that various changes canbe made in the details of construction and mode of operation without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A mixer for air and vaporized petroleum gas comprising a venturi tube having a plurality of vaporized petroleum gas inlet ports in the wall thereof and passageways to each of said ports through said wall, each passageway being inclined inwardly and toward the downstream end of the venturi at an angle to a first plane along the longitudinal axis of the venturi tube and through a line joining the center of the venturi tube with the port to which the passageway connects and to a second plane along said longitudinal axis and perpendicular to said line such that the vaporized petroleum gas initially travels within said tube peripherally thereof, the diameter of said venturi tube increasing abruptly along a ridge adjacent the upstream edge of said inlet ports, the depth of said ridge being less than the diameter of said passageway.

2. A mixer as set forth in claim 1 in which the depth of said ridge is about one-half the diameter of said passageway.

3. A mixer as set forth in claim 1 having a plurality of inlet ports and passageways, the total diameter of said passageways being equal to the diameter of said venturi tube.

4. A mixer as set forth in claim 3 in which there are eight passageways and inlet ports.

5. A mixer as set forth in claim 1 in which the wall of said venturi tube is grooved at the lower end of said inlet ports to smooth the downward swirling motion of fuel gas along the inner wall of the venturi tube.

6. A mixer as set forth in claim 1 in which said angle is about 12 30'.

7. A mixer as set forth in claim 1 including a flange fitting near the outlet end thereof for attachment to an internal combustion engine, said venturi tube extending beyond said flange fitting to continue the high velocity of fuel-air mixture therethrough into the engine.

8. A mixerias set forth'in claim 1 including a throttle valve between said inlet port and the outlet end of the venturi tube. 3

9. A mixer as set forth in claim 1 including a fuel gas distribution channel communicating with the outer end of said passageway and means for supplying fuel gas to said channel at a controlled pressure of about one atmosphere.

way, a throttle valve in said venturi tube to control the flow of fuel-air mixture therethrough, said fuel gas supply means including a fuel valve, and means operatively connecting said throttle valve with said fuel valve to open and closesaid valves in synchronism.

References Cited in the file of this patent UNITED STATES PATENTS 732,016 Uhlin June 23, 1903 1,410,909 Garvey Mar. 28, 1922 1,973,712 Justheim Sept. 18, 1934 2,233,523 Forgar Mar. 4, 1941 2,353,865 Armstrong July 18, 1944 2,650,081 Rockwell Aug. 25, 1953 2,924,514 Neubauer Feb. 9, 1960

Claims (1)

1. A MIXER FOR AIR AND VAPORIZED PETROLEUM GAS COMPRISING A VENTURI TUBE HAVING A PLURALITY OF VAPORIZED PETROLEUM GAS INLET PORTS IN THE WALL THEREOF AND PASSAGEWAYS TO EACH OF SAID PORTS THROUGH SAID WALL, EACH PASSAGEWAY BEING INCLINED INWARDLY AND TOWARD THE DOWNSTREAM END OF THE VENTURI AT AN ANGLE TO A FIRST PLANE ALONG THE LONGITUDINAL AXIS OF THE VENTURI TUBE AND THROUGH A LINE JOING THE CENTER OF THE VENTURI TUBE WITH THE PORT TO WHICH THE PASSAGEWAY CONNECTS AND TO A SECOND PLANE ALONG SAID LONGITUDINAL AXIS AND PERPENDICULAR TO SAID LINE SUCH THAT THE VAPORIZED PETROLEUM GAS INITIALLY TRAVELS WITHIN SAID TUBE PERIPHERALLY THEREOF, THE DIAMETER OF SAID VENTURI TUBE INCREASING ABRUPTLY ALONG A RIDGE ADJACENT THE UPSTREAM EDGE OF SAID INLET PORTS, THE DEPTH OF SAID RIDGE BEING LESS THAN THE DIAMETER OF SAID PASSAGEWAY.

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