Gaseous fuel injection system for internal combustion engines

A gaseous fuel injection system for internal combustion engines features a "variable-pressure-controller" which translates a varying negative pressure, sensed in the engine's air intake system by means responsive to the rate of flow of the intake air, into a proportionately varying amount of gaseous fuel at a positive pressure. That fuel is then injected into the engine's air intake system upstream or downstream of the throttle valve through flow restrictor means which cooperate with the variable-pressure-controller to provide an amount of fuel proportionate to the rate of air flow through the engine's air intake system. The invention is entirely mechanical-pneumatic in operation and readily adapted to a wide variety of liquid fueled engines, carbureted as well as fuel injected, or to one for gaseous fuel only.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
The present invention concerns internal Combustion engines and, more 
particularly, a gaseous fuel injection system for same utilizing 
mechanical and pneumatic means. 
(b) The Prior Art 
Internal combustion engines that operate on gaseous fuel only or 
alternately on liquid fuel are long and well-known. Typical such fuel 
systems employ a negative or less than ambient atmospheric pressure to, in 
effect, suck the gaseous fuel from a zero pressure governor. Usually the 
negative pressure is created by a venturi and the gaseous fuel enters the 
throat of the venturi from the zero pressure governor in amounts 
proportional to the decreases in the ambient pressure at the throat of the 
venturi which, in turn, is proportional to the rate of air flow through 
the venturi itself. In these systems, thus, the pressure of the gaseous 
fuel entering the engine's air intake system is always less than that of 
the ambient atmosphere. When a supercharger is also used, the foregoing is 
still true if "ambient" is considered to be the air pressure at the inlet 
of the engine's carburetion system, assuming the supercharger is upstream 
of the latter. 
The venturis used in the foregoing systems are relatively large in diameter 
in order to minimize pressure loss, since the length of the typical 
venturi employed, such as that in a carburetor, is relatively short and 
therefore pressure recovery is not the best. The relatively large venturi 
diameter, however, impairs the strength of the "signal", as it were, 
transmitted to the zero pressure governor, especially at lower air speeds 
through the venturi, and so impairs control over the air-to-fuel ratio. 
Unlike the situation in the case of liquid fuels it is not possible to 
increase the strength of that "signal" by the use of a secondary or 
booster venturi within the main venturi in the case of gaseous fuels. This 
is because the gaseous fuel in conventional systems is introduced at the 
very point where the "signal" is taken, namely, the throat of the venturi, 
and unlike the situation with liquid fuels, a booster venturi is too small 
to be able to introduce enough gaseous fuel into the air to provide a 
proper air-to-fuel ratio (about one part fuel to fifteen parts air by 
weight in the case of hydrocarbon fuels) in view not only of the quantity 
of air through the booster venturi itself but also in view of the physical 
size needed to conduct fuel in the gaseous state in sufficient quantities. 
The foregoing difficulties persist whether the engine is to operate on 
gaseous fuel alone or alternately on liquid fuel. In latter instances 
sometimes the venturi of the liquid fuel carburetor is used to introduce 
the gaseous fuel, or a separate venturi immediately upstream of the liquid 
fuel venturi is employed for the gaseous fuel, as in U.S. Pat. No. 
4,375,798, for instance. Yet in both these cases the gaseous fuel is still 
introduced at the very point from which the "signal" to the zero pressure 
governor is generated and thus at a pressure less than that of the ambient 
atmosphere. The same is true in a liquid fuel injection system where an 
alternate gaseous fuel system uses a venturi to measure and introduce the 
gaseous fuel, as mentioned in the foregoing patent. If, in order to employ 
a longer venturi for better pressure recovery, which in turn allows a 
smaller venturi diameter for better fuel metering, that is, a better 
"signal", the venturi for gaseous fuel is placed in an air intake trunk 
well upstream of the liquid fuel carburetor, or in an alternate intake 
trunk in the case of a liquid fuel injection system, a safety hazard 
arises in the case of an engine backfire since the entire air trunk 
downstream of the venturi is filled with a combustible mixture of air and 
fuel. 
So the chief object of the present invention is the provision of a gaseous 
fuel system for internal combustion engines which avoid the deficiencies 
and hazards mentioned. 
Another object is to do so in a manner which is readily adapted to either 
liquid fuel carbureted or injected systems having a wide variety of air 
induction shapes and designs. 
A further object is to accomplish the foregoing with relatively little 
complexity and at relatively small cost. 
SUMMARY OF THE INVENTION 
The objects of the invention are achieved essentially by a 
mechanical-pneumatic system which separates the point at which the 
"signal" is generated from the point at which the gaseous fuel is admitted 
into the engine's air intake system. The "signal" itself is a negative 
pressure which reduces in proportion to the increase in air flow in the 
engine's air intake passage. That increasingly negative pressure in turn 
results in supply to the engine of a proportionately increasing amount of 
gaseous fuel at a positive pressure (above that of the ambient 
atmosphere). In short, the fuel is injected into the engine's air intake 
system at a positive pressure instead of being sucked into the engine at a 
negative pressure, as in the case of the systems referred to above. 
The ensuing advantages of the foregoing are immediate and significant. 
First, the gaseous fuel can be injected at any place in the engine's air 
intake system rather than being restricted to the same point at which the 
"signal" is generated. Second, and perhaps even more important, it allows 
the use of a relatively small booster venturi to provide the "signal" 
since that venturi is thereby relieved of having also to introduce the 
fuel. And, as previously noted, the use of a booster venturi provides a 
stronger and thus better "signal" for better control of the air-to-fuel 
ratio. Third, electronic controls can be used to make adjustments in the 
relatively small "signal" line from the booster venturi in order to alter 
the main fuel delivery system and thus provide a "closed loop" system with 
an O.sub.2 sensor in the exhaust stream. In the prior systems referred to 
that can only be done by controls inserted into the quite large main fuel 
consequently requires much larger or elaborate components than those 
necessary for the much smaller "signal" line in the present instance. 
The "signal" itself may be generated by a booster venturi, which includes a 
sensing port opening into its throat, located in turn in the throat of a 
main venturi which may be placed upstream of the liquid carburetor or 
upstream of the throttle valve in the case of liquid fuel injection 
installations. In vehicles which incorporate an air intake passage in the 
form of a trunk either upstream or downstream of the air cleaner, the main 
venturi is simply placed within the air trunk itself, thus allowing the 
use of a much longer venturi for excellent pressure recovery than is 
possible with carburetor venturis. The "signal", in the form of a varying 
pressure differential generated by the booster venturi, is applied to a 
"variable-pressure-controller" which, together with a flow restrictor 
placed in the fuel delivery line, provides fuel at a proportionately 
varying positive pressure and thereby a proportionately varying amount of 
fuel to the engine's air intake system. 
In a preferred embodiment the variable-pressure-controller consists 
essentially of four chambers axially stacked in a cylindrical housing, the 
first two chambers being separated by a first diaphragm, and the second 
two chambers by a second diaphragm, the second and third chambers in turn 
being divided by a rigid partition. The centers of the two diaphragms are 
associated through the partition in such a manner that movement of one in 
one direction results in movement of the other in the same direction, that 
movement in turn being transmitted to a fuel inlet valve opening into the 
fourth chamber. Fuel from a primary regulator, which is preferably 
incorporated into the variable-pressure-controller, is applied to the 
normally closed inlet valve at above atmospheric pressure. The first 
chamber is connected to the engine's air intake passage upstream of the 
main venturi and the second chamber to the sensing port of the booster 
venturi. Hence a pressure differential is created between the first and 
second chambers proportionate to the rate of air flow through the two 
venturis. The fourth chamber is connected into the engine's air intake 
system, either upstream or downstream of the throttle valve, through an 
adjustable flow restrictor producing a pressure loss proportionate to the 
pressure differential between the first and second chambers, the greater 
that pressure differential the greater that pressure loss and vice versa. 
Finally, the third chamber is connected either to the ambient atmosphere 
or into the engine's air intake system upstream of the throttle valve. 
The operation of the variable-pressure-controller will be explained in more 
detail later, but briefly the pressure differential between the first and 
second chamber creates a first force on the first diaphragm and thus also 
on the second diaphragm which tends to open the fuel valve and allow fuel 
to flow into the fourth chamber and thence into the engine's intake system 
through the restrictor. The action of the flow restrictor in turn causes a 
rise of pressure in the fourth chamber proportionate to the pressure 
differential between the first and second chambers. The rise of pressure 
in the fourth chamber creates a second, counter force, balanced against 
tee pressure in the third chamber, on the second diaphragm which tends to 
close the inlet valve. When the two forces reach equilibrium, the fuel 
valve remains in a stationary open position and fuel under pressure is 
thereby injected into the engine. In that manner does a varying negative 
pressure sensed by the booster venturi produce an injection pressure and 
therefore a proportionately varying amount of fuel at a positive pressure 
into the engine, the air-fuel ratio being determined by adjusting the flow 
restrictor. 
The components of the invention are all relatively simple in nature and 
correspondingly economical to produce, especially compared to electronic 
liquid and gaseous fuel injection systems. Other features and advantages 
of the invention will become apparent from the drawings and the more 
detailed description which follows.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
(a) Structure of the System 
In FIG. 1 the air intake system, generally designated at 10, of a typical 
carbureted engine includes an air intake passage or trunk 11 leading to an 
air cleaner 12 atop a two-barrel carburetor 13 having throttle valves 14 
feeding the engine's intake manifold 15. The air cleaner 12, of course, 
could be at the forward end of the air trunk 11. As noted, the "signal 
generator", generally designated at 20, may consist of a relatively long 
main venturi 21 secured within the air trunk 11. Within the throat 22 of 
the latter and appropriately supported as indicated is a small secondary 
or booster venturi 23 having a sensing port 24 opening into its throat 25 
from which leads a small tubular elbow 26 (see FIG. 4). 
The particular "variable-pressure-controller" illustrated, generally 
referred to at 30, comprises a cast, cylindrical housing 31 diametrically 
split along its axis at 31a and 31b, the housing 31 being held together by 
a surround of screws 32 through integrally cast, exterior bosses 33 (see 
FIG. 2). One end of the housing 31 forms a cover 34 which, together with 
the intermediate housing section 35, suspends a first flexible 
intermediate section 35 includes an integrally cast wall 37 which together 
with the cover 34 forms a pair of first and second chambers, A and B, 
separated by the diaphragm 36 which is free to move in either axial 
direction. The cover 34 is provided with a port 38 into the chamber A and 
the intermediate section 35 with a pair of ports 39 and 40 into the 
chamber B. The intermediate section 35 and the body 41 of the housing 31 
suspend a second flexible diaphragm 42 between a second set of annular 
gaskets, thus forming a pair of third and fourth chambers, C and D, 
separated by the diaphragm 42. Both diaphragms 36 and 42 are provided on 
their opposing faces with large, thin stiff discs 43 in order to increase 
their effective diaphragm area, and the housing wall 37 is axially bored 
to receive a floating pin 44 which bears against the two discs 43. The 
intermediate section 35 is provided with a port 46 into the chamber C and 
the body 41 with a large fuel outlet 47 from the chamber D. 
The body 41 includes a cast partition 48, which forms the other end of the 
chamber D, screwed at 49 (see FIG. 2), to an annular seat 50 within the 
body 41. Referring now to FIGS. 1-3, the orifice 51 of a fuel valve, 
generally designated a 52, passes through the partition 48 adjacent the 
fuel outlet 47 and is opened and closed by a valve operating lever 54, 
fulcrumed at 55 on the partition 48, having an elastomeric disc 56 at one 
end which engages the seat 53 to close the valve 52. The disc 56 is 
disposed on the lower face of an elongated fibreboard tab 57 separated 
from the underface of the lever 54 by a smaller disc 58 which bears 
against a boss 54a on the underside of the lever 54 (see FIG. 3). The two 
discs 56 and 58 and the tab 57 are connected by a thin wire retainer 59 
which passes centrally up through the discs 56 and 58 and swivelly through 
the valve lever 54. The retainer 59 is then bent at right angles and 
loosely located between a pair of upstanding tangs 60 atop the lever 54 
(see FIG. 3). The swivel connection of the discs 56 and 58 and the tab 57 
to the lever 54 thus assures an even pressure of the disc 56 on the valve 
seat 53 when the valve 52 is closed. Furthermore, as seen in FIG. 2, the 
tab 57 includes a nose having a notch 11 directed toward the fuel outlet 
47 and offset to the right of the longitudinal center line of the tab 57, 
the notch 61 receiving and riding along a headed pin 62 upstanding from 
the partition 48. As the valve lever 54 opens the nose of the tab 57 abuts 
the head of the pin 62 causing the tab 57 and thus the disc 56 to tilt, 
owing to their swivel connection to the lever 54 and the boss 54a of the 
latter, so that the left side of the disc 56 as viewed in FIGS. 2 and 3 is 
higher above the seat 53 than is its right side, all for purposes to be 
described. The valve 52 is biased to its closed position by a compressible 
coil spring 63 up through a bore 64 in the body 41, the spring 63 engaging 
the underside of the valve lever 54 between its far end and the fulcrum 
55. The spring 63 is retained by a plug 65 threaded into the bore 64 in 
order to adjust the spring pressure on the valve lever 54. Finally, the 
far end of the lever 54 is swivelly attached to the lower end of a pin 66 
whose upper end in turn is swivelly attached to a small, thin metal disc 
67 secured to the adjacent face of the diaphragm 42. 
The variable-pressure-controller 30 preferably also incorporates a primary 
regulator of the gaseous fuel, which regulator in this case is disposed in 
the body 41 on the other side of the partition 48. For this purpose the 
end wall of the body 41 is bored and threaded to receive a primary fuel 
valve, generally designated at 70, consisting of an annular fitting 71 
which spacedly surrounds a typical needle valve 72 operative in an orifice 
73 at the inner end of the fitting 71. A light, compressible coil spring 
74, backed b an annular threaded plug 75, urges the valve 72 into sealing 
engagement with the orifice 73. The latter orifice opens into a primary 
fuel chamber 76 in communication with the orifice 51 of the valve 52. The 
nose of the needle valve 72 abuts a small metal disc on one face of an 
elastomeric, circular diaphragm 77 clamped between the partition 48 and 
its annular seat 50 in the body 41. The effective area of engaging the 
other face of the diaphragm 77 and co-axial with the needle valve 72. The 
disc 78 is laterally located by a central boss 79 upstanding from its 
other face and encompassed by a strong, compressible coil spring 80 
received in turn in the well of a plastic plug 81 threaded into an 
integral boss 82 on the partition 48. The plug 81 thereby adjusts the 
pressure of the spring 80 on the disc 78 and thus on the needle valve 72 
which is normally held off its seat on the orifice 73 by the pressure of 
the spring 80. A port 83 (see FIG. 2) opens through the partition 48 onto 
the disc 78 through a fitting 84 from which a small metal tube 85 leads 
adjacent the left side, as viewed in FIGS. 2 and 3, of the valve seat 53 
of the valve 52. Finally, the body 41 about the inlet valve 70 and the 
primary chamber 76 are cast with water passages 86 (not needed in the case 
of fuels already in a gaseous condition) for supply of hot water from the 
engine's cooling system to assist passage of the fuel entering the primary 
fuel valve 70 and chamber 76 from a liquid to a gaseous state. 
The operation of the primary regulator will be apparent to those skilled in 
the art, but briefly the gaseous fuel in liquid form or high pressure 
gaseous state is led from the tank T and solenoid shut-off valve V1 
through a line 87 to the inlet fitting 71, thence around the needle valve 
72, and through the orifice 73 into the primary chamber 76. The spring 80 
is set to provide a nominal 3 psi in the chamber 76. When that pressure is 
reached the diaphragm 77 and disc 78 compress the spring 80 allowing the 
needle valve 72 to seat on the orifice 73 until the pressure in the 
chamber 76 falls when the fuel valve 52 opens, whereupon the spring 80 
reopens the needle valve 72 and the cycle repeats itself. In order to 
compensate for the decrease in the force of the spring 80 as it expands 
which, when the fuel valve 52 opens, may allow the pressure in chamber 76 
to drop below 3 psi, as well as advantageously to provide a pressure in 
chamber D somewhat greater than 3 psi when the fuel valve 52 is open, the 
aforementioned tilt of the disc 56 of the valve 52 directs gas under 
pressure from the orifice 51 into the tube 85 and then through the port 83 
into the area between the partition 48 and the disc 78. The sum of the 
forces provided by the gas pressure and the spring 80 thus holds the 
needle valve 72 off the orifice 73 until the pressure in the primary 
chamber 76 stabilizes at a new higher pressure. 
The chamber A is fluid connected by a line L1 from its port 38 to a port 90 
in the air trunk 11 upstream of the signal generator 20, and the chamber B 
in turn by a line 22 from its port 39 to the elbow 26 of the booster 
venturi 23. The chamber C for best control of the air-fuel ratio is 
preferably fluid connected by a line L3 from its port 46 to a port 91 in 
the air horn of the carburetor 13 of the carbureted version of the 
invention shown in FIG. 1. Alternately the chamber C could be connected 
into the air intake system 10 at any place upstream of the throttle valve 
14 or simply vented to the atmosphere. The fuel outlet 47 from the 
variable-pressure-controller 30 and thus its chamber D is fluid connected 
by a large line L4a to an adjustable flow restrictor, generally designated 
at 100, and thence by lines L4b to a pair of fuel nozzles 92, one for each 
throat of the carburetor 13, preferably disposed adjacent the port 91. The 
fuel valve 52, the chamber D, the line L4a, the flow restrictor 100, and 
the lines L4b thus all constitute a fuel passage from the primary 
regulator or other source of fuel to the engine's air intake system 10. 
The nozzles 92 are of any suitable construction which serves to spray the 
fuel generally radially in order to obtain excellent mixing of the gaseous 
fuel with the incoming air, better than that obtained when gaseous fuel is 
merely sucked into the throat of a venturi as in the prior art 
arrangements previously mentioned. 
The flow restrictor 100 (see FIG. 5) consists of a hexagonal fitting 101 
having an inlet 102 for connection to the line L4a and a pair of outlets 
103 for connection to the two lines L4b in the carbureted version of FIG. 
1. Within the fitting 101 between the inlet and outlet 102 and 103 is a 
chamber 104 into which through the side of the fitting 101 is adjustably 
threaded a sleeve 105 at one end of a fitting 106 having an enlarged 
annular chamber 107 at its other end closed by a threaded end cap 108. 
Once the proper intrusion of the sleeve 105 into the chamber 104 is 
roughly determined (as hereafter set forth), it is held there by a large 
lock nut 109 on the sleeve 105 operative against the fitting 101. The 
sleeve 105 receives a sliding piston 110 having a head 111 in the chamber 
107 against whose end bears a bellows 112 secured between the fitting 106 
and the end cap 108. A compressible coil spring 113 encompasses the piston 
head 111 between the bellows 112 and the other end of the chamber 107. A 
screw 114, encompassed by a compressible coil spring 115, for adjustment 
of the stroke of the piston 110 relative to the sleeve 105 is threaded 
axially through the end cap 108 and bears against the inner end of the 
bellows 112 through a small metal disc 116. The interior of the bellows 
112 is open to the atmosphere through a port 117 in the end cap 108 and 
the chamber 107 is ported through a fitting 118. The latter fitting is 
fluid connected by a line L5 to the second port 40 of the 
variable-pressure-controller chamber B and by a line L6 to a port 119 into 
the engine's intake manifold 15 downstream of the throttle valves 
(b) Operation of the System in the Carbureted Version 
When the ignition key is turned to its "start" position, a primer solenoid 
120 on the exterior of the variable-pressure-controller cover 34 is 
activated. The solenoid 120 includes a plunger 121 extending through the 
cover 34 centrally into the chamber A adjacent a small disc 122 attached 
to the diaphragm 36. The plunger 121 is held in its retracted position (as 
shown in FIG. 1) by a spring 123 and its stroke is controlled by a hand 
screw 124 which adjusts the distance between a stop collar 125 on the 
plunger 121 and the housing of the solenoid 120. When the solenoid 120 is 
activated its plunger 121 moves the diaphragm 36 to the right in FIG. 1, 
and through the pin 44, diaphragm 42 and pin 66, thus depresses the valve 
lever 54 to open the fuel valve 52. If the engine turns over, as detected 
at the distributor or elsewhere, the solenoid shut-off valve V1 on the 
tank T is opened allowing fuel to flow through the line 87 into the 
primary fuel inlet valve 70, thus pressuring the primary chamber 76 with 
gaseous fuel at a nominal 3 psi in the manner previously set forth. It 
will be understood, of course, that the pressure of the valve spring 63 on 
the valve lever 54 is adjusted by the plug 65 to just hold the valve 52 
closed against the 3 psi pressure at the valve seat 53. A small quantity 
of fuel then flows through the open valve 52 into the chamber D and thence 
through the flow restrictor 100 to the fuel nozzles 92. When the engine 
starts, the ignition key is returned from its "start" position, the 
solenoid 120 is deactivated and its plunger 121 returned to its retracted 
position. 
Thereafter, as the throttle valves 14 are opened, air flows through the air 
trunk 11 and the signal generator 20, whereby the booster venturi 23 
creates a first pressure differential between the pressure at the port 90 
and the pressure at the sensing port 24 of the booster venturi 23, which 
pressure through the air trunk That pressure differential is communicated 
through lines L1 and L2 to chambers A and B of the 
variable-pressure-controller 30, thus creating a first force which moves 
the diaphragms 36 and 42 to the right in FIG. 1 and further opens the 
valve 52 in the manner just explained. Additional fuel then flows into the 
chamber D at greater than atmospheric pressure and thence through the flow 
restrictor 100 to the fuel nozzles 92 for injection into the engine at a 
positive, above atmospheric pressure. The increased rate of fuel flow 
causes a rise in pressure in chamber D owing to the action of the flow 
restrictor 100 inasmuch as the restriction or pressure drop provided by 
the latter increases with the increase in the rate of flow through it, 
which increase is proportionate to the increase in the first pressure 
differential between the chambers A and B created by the increase in the 
rate of air flow through the signal generator 20. A second pressure 
differential is thereby created between the chambers C and D since the 
pressure in chamber C is substantially only atmospheric or slightly less 
depending upon whether that chamber is vented to the atmosphere or 
connected into the air intake system 10 upstream of the throttle valve 14. 
The second pressure differential imposes a second force on the diaphragm 
42 counter to that of the first force imposed thereon by the diaphragm 36, 
which second force owing to the pins 44 and 66 tends to move the 
diaphragms 36 and 42 to the left in FIG. 1 and thus to close the valve 52. 
When the two forces equalize, the valve 52 assumes an open position 
consonant with the rate of air flow through the signal generator 20 which 
in turn of course is determined by the setting of the throttle valves 14. 
The two forces rise and fall and the valve 52 thus opens and closes in 
proportionate synchronization with the changing flow in the air trunk 11. 
The chamber B is also preferably subjected through the lines L5 and L6 to 
the subatmospheric pressure in the intake manifold 15 in order to hold the 
valve 52 open at engine idle speeds when the rate of air flow through the 
signal generator 20 is insufficient for that purpose, an adjustable needle 
valve V2 being inserted in the line L5 to vary the amount of vacuum 
applied to the chamber B. This is merely one of several ways in which that 
can be accomplished in the present instance and is not critical to the 
essential operation of the system. 
The air-fuel ratio is adjusted at the flow restrictor 100. The screw 114 is 
first turned to bottom the piston 110 in the chamber 177 of the fitting 
106. Then a "cruise" setting is made by loosening the lock nut 109 and 
turning the fitting 106 one way or the other while the engine is running 
in order to vary the intrusion of the piston 110 into the chamber 104, and 
thus the restriction provided by the restrictor 100. That in turn 
increases or decreases the pressure in the chamber D of the 
variable-pressure-controller 30 and thus the opening of the valve 52 for a 
given rate of air flow through the signal generator 20, i.e., engine 
speed. Adjustment of the stroke of the piston 110 is then made by 
backing-off the screw 114 which allows the piston 110 to retract relative 
to the sleeve 105 of the fitting 106. The flow restrictor 100 thence 
functions as an "economizer" valve at light engine loads. Intake manifold 
vacuum is applied through the lines L5 and L6 to the restrictor chamber 
107 through the fitting 118, whereby the pressure in the chamber 107 is 
less than the atmospheric pressure within the bellows 112 owing to the 
port 117. When that vacuum rises to a predetermined value, based on the 
effective area of the bellows 112 and the strength of the spring 113, the 
bellows 112 moves the piston 110 further into the chamber 104, thus 
increasing the pressure drop across the restrictor 100 and reducing the 
opening of the valve 52 in the manner described. 
(c) The Fuel Injected Version 
Turning to FIG. 6, the invention and its operation as incorporated into a 
typical liquid fuel injected engine is essentially the same as in the 
carbureted version and primed, identical reference numerals have been used 
for corresponding parts. The incoming air passes through the air cleaner 
12, at the head of the air intake passage or trunk 11', through the signal 
generator 20, in the air intake trunk 11', thence through the air meter 
AM, past the throttle valve 14', into the intake manifold or plenum 
chamber 15', and finally through individual ram-pipes RP into the engine, 
liquid fuel being introduced by injectors I at the downstream ends of the 
ram-pipes RP and the gaseous fuel injected by a nozzle 92' upstream of the 
throttle valve 14'. Alternately, a fuel line L4b" and a nozzle 92" could 
enter the air intake passage 10' downstream of the throttle valve 14', as 
indicated by broken lines in FIG. 6. Or separate lines L4b'" and nozzles 
92'" could be provided for each of the ram-pipes RP, as indicated by 
alternate broken lines in FIG. 6. However, when the gaseous fuel is 
injected downstream of the throttle valve 14', the flow restrictor 100' is 
thereby subjected to a variable negative pressure or vacuum ranging from a 
high at idle or light engine loads when the throttle valve 14' is nearly 
closed to almost zero when the throttle valve 14' is wide open. Such a 
variable vacuum would obviously upset the function of the flow restrictor 
100' and thus the amount of fuel supplied by the 
variable-pressure-controller 30'. In order to compensate for that it is 
necessary to incorporate a device such as a "vacuum regulator" 130 in the 
line L4b" or L4b'", as the case may be, entering the air intake system 10' 
downstream of the throttle valve 14', as indicated in FIG. 6. 
Such a vacuum regulator is illustrated in more detail in FIG. 7 and 
comprises a cast cylindrical housing 131 having an inlet passage 132, at 
the inner end of which is a valve seat 133, and an outlet passage 134. The 
inlet passage 132 communicates through a bore 135 with a chamber 136 
formed in the housing 131 below a flexible diaphragm 137 to whose lower 
face is attached a circular metal plate 138. Above the diaphragm 137 an 
end cap 139 clamps the diaphragm 137 in place and forms with it a second 
chamber 140 which is connected through a port 141 and a line L7 into the 
air intake system 10' at 149 between the throttle valve 14' and the signal 
generator 20'. Above the valve seat 133 a plastic plug 142 is threaded 
into a bore in the housing 131 communicating with the chamber 136. The 
stem 143 of a disc valve 144, engageable with the seat 133, passes up 
through a bore in the plug 142 into the chamber 136 just below the plate 
138 and is sealed against leakage through the plug 142 by a small O-ring 
145. A compressible coil spring 146 around the plug 142 and stem 143 is 
captured between the floor of the chamber 136 and a metal disc 147 secured 
to the upper end of the stem 143 by a suitable retainer 148, the spring 
146 biasing the valve 144 to its openmost position shown in FIG. 7. The 
inlet passage 132 is connected to the outlet 103' of the flow restrictor 
100, and the outlet passage 134 to the fuel nozzles 92" or 92'", as the 
case may be. 
The flow restrictor 100' is subjected to the variable negative pressure or 
vacuum downstream of the throttle valve 14' through the regulator 
passages 132 and 134 and the open valve 144. When that vacuum reaches a 
prescribed amount, which is determined by the effective area of the 
diaphragm 137 and the strength of the spring 146, it is communicated 
through the bore 135 to the chamber 136 below the diaphragm 137, thus 
causing the latter to decrease the opening of the valve 144 inasmuch as 
the chamber 140 above the diaphragm 137 is at a greater pressure owing to 
the connection through the line L7 into the air intake system 10' at 149. 
Since there is then a greater restriction between the regulator inlet and 
outlet passages 132 and 134, pressure builds up in the inlet passage 132 
and thus in the chamber 136 through the bore 135 owing to the fact that 
fuel is being supplied from the flow restrictor 100' at above atmospheric 
pressure. As the pressure in chamber 136 rises the diaphragm 137 increases 
the opening of the valve 144 until the pressure once again decreases in 
the chamber 136. The valve 144 thus cycles back and forth with the result 
that a substantially constant pressure, substantially equal to that in the 
air intake system 10' between the throttle valve 14' and the signal 
generator 20', is maintained in the inlet passage 132 and thus at the flow 
restrictor 100', a pressure independent of whatever may be the pressure 
downstream of the throttle valve 14'. In both cases in which the gaseous 
fuel is injected downstream of the throttle valve 14', the connection 91' 
of the chamber C of the variable-pressure-controller 30' remains upstream 
of the throttle valve 14' in order not to upset the function of the 
variable-pressure-controller 30'. Obviously similar alternatives could be 
applied pipes are used in conjunction with one or more carburetors. 
(d) Summary 
From all of the foregoing it will be clear that the components of the 
system of the invention are all relatively "simple" in structure and thus 
readily manufactured at relatively small cost, especially compared with 
electronic systems. Furthermore, the system is far more versatile than 
electronic ones because it is readily adaptable to a wide variety of 
engine sizes, that is, the same components can be used without change 
(except in some instances for the size of the signal generator 20), 
something impossible in the case of electronic systems. It can be applied 
as an alternate to a liquid fuel system (as shown) or to an engine 
operable on gaseous fuel alone. And it is easy and economical to install 
and service. Moreover, the components are all of modest size and weight, a 
suitable signal generator 20 having its main venturi 21 spun from aluminum 
and about 7 inches in length and 21/2 inches in diameter. The 
variable-pressure-controller housing 31 is an alloy casting with an 
overall length oof about 41/2 inches and a diameter of about 61/2 inches, 
the total weight of the variable-pressure-controller 30 being a bit over 5 
pounds. The system will function with most any liquefied or compressed 
petroleum or gaseous fuel: propane, butane, natural gas, even with 
hydrogen gas. 
(e) Variations of the Invention 
The invention is also capable of different embodiments without altering its 
essential function. For instance, the primary regulator need not be 
incorporated into the variable-pressure-controller 30. The diaphragms 36 
and 42 could instead be bellows or even pistons. Nor need the diaphragms 
36 and 42 be of the same size inasmuch as it will be obvious that the 
necessary opposing forces on the valve 52 could be provided without 
requiring the diaphragm or like areas producing those forces to be equal 
since it is their effective areas multiplied by the pressures concerned 
that are important. The four chambers A-D could be arranged other than as 
shown, for instance, chambers A and B could be more remote from chambers C 
and D and other linkages arranged between them to operate the fuel inlet 
valve 52. That valve itself could be of some other design as well. The 
variable-pressure-controller 30 will also function if the chamber A simply 
communicates with the atmosphere instead of the air trunk 11 upstream of 
the signal generator 20 which is preferable in order to compensate for the 
increased air pressure in a forwardly directed air intake trunk owing to 
vehicle movement. Furthermore, the valve 52 and the flow restrictor 100 
could be located in a fuel line or passage leading directly from the 
primary regulator to the engine's air intake system 10, the fuel passing 
first through the valve 52 and thence through the restrictor 100 without 
passing through the chamber D of the variable-pressure-controller 30. The 
chamber D in that case would then need only communicate with the fuel 
passage between the valve 52 and the flow restrictor 100 since it is the 
pressure upstream of the restrictor 100 which must be applied to the 
chamber D in order for the variable-pressure-controller 30 to function, 
all without altering the essential nature and operation of the invention. 
If in addition in that case the fuel valve 52 were to take the form of a 
shuttle-type spool valve disposed in the fuel passage downstream of the 
flow restrictor 100 and connected at its ends to the diaphragms 36 and 42, 
the chamber C were to connect into the fuel passage between the spool 
valve and the flow restrictor 100, and the chamber D were to connect into 
the fuel passage between the primary regulator and the restrictor 100, the 
variable-pressure-controller 30 would also function as a differential 
pressure regulator and eliminate the need for a vacuum regulator 130 in 
those instances in which the fuel is injected downstream of the throttle 
valve. 
The signal generator 20 itself can be placed elsewhere in the air intake 
system 10 or 10', such as downstream of the throttle valves 14 or 14', and 
the system still essentially function as described. Indeed, the signal 
generator 20 could be of some other nature, such as a Pitot tube, or a 
single, very long venturi with a small throat and sensing port thus 
eliminating the need for a booster venturi, in short, any turbulent 
(non-laminar) flow device which will produce a pressure differential 
proportionate to the rate of air flow into the engine. The flow restrictor 
100 could be incorporated into the variable-pressure-controller 30. It 
could even be a simple fixed orifice, though that would require different 
sized orifices for different engines, or some other turbulent 
(non-laminar) flow device producing a restriction proportionate to the 
pressure differential created by the signal generator 20 could be used. 
Other aspects of the essential operation and parameters of the invention 
will be apparent to those of skill in the art. Hence, though the invention 
has been described in terms of a particular embodiment, being a best mode 
known of carrying out the invention, it is not limited to that embodiment 
alone. Instead, the following claims are to be read as encompassing all 
adaptations and modifications of the invention falling within its spirit 
and scope.