ALTERNATE LIQUID/GASEOUS FUEL OPERATION OF ENGINES

Abstract: An attachment for operating an internal combustion engine (10) on either gaseous or liquid fuel incorporates a modified air cleaner-intake assembly (20) having spaced cover (38) and adapter (21, 27) plates between which is sandwiched a typical annular filter element (33). An annular diaphragm (51) connects an inner plate (53) to the cover plate (38) to form a chamber (62) therewith on one side of the inner plate (53) into which gaseous fuel is admitted. During gaseous fuel operation gas pressure in the chamber (62) maintains the inner plate (53) adjacent the adapter plate (27) to form therewith an annular venturi (58) into which gaseous fuel from the chamber (62) is admitted through a ring of ports (63) through the inner plate (53) at the venturi (58). During liquid fuel operation incoming air lowers the pressure in the chamber (62) sufficiently so that the inner plate (53) automatically moves away from the adapter plate (27) to provide an unobstructed air only path to the engine (10).

Description: ALTERNATE LIQUID/GASEOUS FUEL OPERATION OF ENGINES Technical Field The invention relates to apparatus for alternate liquid or gaseous fuel operation of internal combustion engines. Background Art Dual fuel operation of internal combustion en¬ gines, though long known and practiced, is nowadays becoming more and more to the fore in view of the growing shortage and cost of liquid fuel, particularly petrol. Especially in the cases of larger vehicles, such as lorries, motor cara¬ vans and the like, their innate higher fuel consumption has made the ability to operate them either on liquid or gaseous fuel increasingly attractive owing to the relatively plen¬ tiful supplies and lower cost of gaseous fuels, such as propane, compared to petrol. Currently, several schemes to this end are in practice. Some replace the typical air filter assembly with one which incorporates a fixed venturi arrangement for metering the gaseous fuel. A separate arrangement, exterior of the air cleaner assembly, is usually also fitted for slow-run operation. Some other approaches attempt to incor¬ porate both the main and slow run systems into the air cleaner assembly. These employ, for instance, a diaphragm operated valve which controls a small variable venturi for slow run and a separate fixed large venturi for high speed operation, or a diaphragm operated air valve in conjunction with a fuel valve which together meter both air and fuel throughout the engine speed and load range including slow- run. Examples of these two latter approaches are found in U.S. patents 2,927,848 and 2,983,592, from which it will be readily seen that both are fairly intricate and thus expen¬ sive and elaborate to manufacture. In any event, since all the prior art devices whatever their nature, fit upstream of those means in the engine air intake passage which meter liquid fuel and air in carburetted and fuel injected engines, their paraphernalia of Venturis, air valves and the like would improperly throttle air supply and upset functioning of the liquid fuel metering means downstream of air filter assembly when oper¬ ating on liquid fuel. Hence, the foregoing systems neces¬ sarily incorporate some manner by which the incoming air can bypass the gaseous fuel metering and mixing means when the engine operates on liquid fuel. Typically the bypass con¬ stitutes a separate or alternate air intake route which is closed off during gaseous fuel operation and opened during liquid fuel operation either manually, as by a handworked cable, or electrically as by a solenoid operated valve. Such a manual approach, of course, requires extra parts and the running of the cable from the engine to the driver's station. The electrical approach, while it can be arranged to operate automatically when the engine is shifted from one fuel to the other, also requires additional, not inexpensive parts. Disclosure of Invention The present invention overcomes the disadvantages of the prior art by a modified air cleaner assembly which incorporates within it an annular venturi formed between an adapter plate, which encircles the engine air intake, and one side of a reciprocally movable diaphragm plate when dis¬ posed adjacent the adapter plate. The diaphragm plate is surrounded and suspended by a thin flexible diaphragm con- nected at its outer margin to a cover plate to form a cham¬ ber with the other side of the diaphragm plate, a typical air filter element being also sandwiched between the adapter and cover plates. Gaseous fuel is supplied to the chamber from the customary zero pressure governor and is drawn from the chamber through a ring of outlet ports through the dia¬ phragm plate at the venturi formed when the latter plate is adjacent the adapter plate. During gaseous fuel operation, gas pressure in the chamber maintains the diaphragm plate in its venturi forming position, but during liquid fuel opera- • tions when supply of gaseous fuel to the chamber is closed off, the diaphragm plate automatically retreats from the adapter plate to open up the venturi and provide a substan¬ tially unobstructed passage for air only to the engine. The latter movement of the diaphragm plate occurs by virtue of the rush of incoming air past the aforesaid outlet ports in the diaphragm plate which in turn decreases the pressure in the chamber on one side of the diaphragm plate below that exerted on the other side of the latter plate by the in¬ coming air. Hence the need for an alternate air passage and means to open and close it is entirely eliminated. The parts required are few and rudimentary insofar as materials and manufacture are concerned, being stamped or spun from simple sheet stock, so cost is low and reliability and efficiency high. For slow-run operation a separate system is employed, such as one admitting the gaseous fuel through a metering valve directly into the engine's intake manifold below the throttle plate, or one in which the fuel is admitted into the aforesaid chamber through a separate inlet and valve controlled by intake manifold vacuum. The present invention is suitable for all types of gaseous fuels and, while hereafter shown and described for use with a downdraught carburettor, it can be readily adapted for side- draught and updraught carburettors or even fuel injection applications in either petrol or diesel versions. Brief Description of Drawings Figure 1 is a diametrical cross-section of an air cleaner assembly incorporating the invention mounted on the airhorn of a downdraught liquid fuel carburettor. Figure 2 is a sectional plan view taken along the line 2-2 of Figure 1. Figures 3 and 4 are enlarged sectional views taken respectively along the lines 3-3 and 4-4 of Figure 2 an illustrating in more detail the mounting of the diaphragm to the cover and diaphragm plates. Figure 5 is a sectional view taken along the lin 5-5 of Figure 2. Best Mode For Carrying Out The Invention Figure 1 depicts an internal combustion engine 10 equipped with a multi-choke, downdraught carburettor 11 having liquid fuel metering venturi 12 and throttle plates 13 surmounted by a carburettor air inlet horn 14. The air horn 14 includes an annular seat 15 for the lower end of an air cleaner assembly which is retained thereon by a typical hold-down post 16 extending centrally upright from the mouth of the air horn 14, being threaded at 17 at its upper end and provided with a stop collar and gasket 18. The air cleaner- assembly of the present invention, generally indicated at 20, includes an inner annular adapter 21 whose lower end 22 is inwardly flanged to press against a gasket 23 about the air horn seat 15 and whose upper end 24 is outwardly flanged and surmounted by a gasket 25. The neck 26 of an outer annular adapter 27 seats atop the gasket 25, its inner edge being downwardly flanged at 28 to locate the adapter 27 within the upper mouth of the inner adapter 21. (The inner and outer adapters 21 and 27 are preferably separate parts so that the air horns of different carburet¬ tors or other air intakes can be more easily and economi¬ cally accommodated.) The upper annular surface 29 of the outer adapter 27 slopes downwardly from its neck 26 to a shelf 30, the outer edge of the latter having an upturned flange 31 to form an upwardly facing annular seat 32 for the lower end of a typical annular air filter element 33 having gasketed end caps 34. The upper end of the filter element 33 is received in a complementary opposed seat 35 formed by a downturned flange 36 on a shelf 37 at the outer margin of a removable cover 38. The latter cover includes an annular wall 39 sloping upwardly from the shelf 37 and a central concavity 40 up through which extends the hold-down post 16. The latter post is fitted with a thumbnut 41 in order to retain the adapters 21 and 27, the filter element 33 and the cover 38 assembled atop the carburettor air horn 14. De- spite the concavity 40, which is to improve underhood clear¬ ance by in effect lowering the upper end of the post 16, the cover 38 is essentially of inverted dished configuration and its sloped wall 39 is apertured to provide a large main gaseous fuel inlet 42 from a hose fitting 43 in the form of an aluminum casting bolted at 44 with a gasket 45 to the exterior of the wall 39. The upper end of the filter element 33 suspends a diaphragm assembly 50 comprising an annular diaphragm 51 of thin flexible material whose outer margin is sandwiched between the upper filter end gasket 34 and an additional gasket 52 (see Figure 3) in the filter upper end seat 35. The radially intermediate portion of the diaphragm 51 is sinuously disposed as shown in Figure 1. Its inner margin is sandwiched in turn between the outer margin of a rigid circular diaphragm plate 53 and the outer face of a channel section, annular clamp ring 54, a pair of gaskets 55 (see Figure 4) being interposed on each side of the diaphragm 51 and the parts secured, for instance, by rivets 56. Radially inward from the clamp ring 54 the diaphragm plate 53 is shaped to form an annular depression 57 whose lower convex face lies closely adjacent the adapter neck 26 where, when the diaphragm assembly 50 is in its position shown in full lines in Figure 1, it forms an annular venturi passage 58 therebetween having an intermediate section or portion con- stituting a throat 59. The immediate central area of the diaphragm plate 53 is dished at 60 and provided with an upwardly coined aperture 61 which slidably receives the mid- section of the post 16 for guided reciprocal movement of the diaphragm assembly 50 along the post 16, as indicated in Figure " 1. The cover 38 and the diaphragm assembly 50 thus define a chamber 62 into which gaseous fuel is admitted through the inlet 42. Through the diaphragm plate 53 at the throat 59 is a ring of spaced gaseous fuel outlet ports 63 from the chamber 62 into the venturi passage 58. The upward travel of the diaphragm assembly 50 is limited by contact of the coined aperture 61 with the stop collar 18, and in order to limit the downward travel of the diaphragm assembly 50, and thus also to adjust the width of the venturi throat 59, the diaphragm plate 53 is fitted with several adjusting screws 64 evenly spaced around the throat 59. The lower ends of the screws 64 engage the adapter neck 26 therebelow, the screws 64 being threaded through nuts 65 (see Figure 5) crimped in apertures in the diaphragm plate 53 between the outlet ports 63. Conical springs 66 encom¬ pass the screws 64 and seat against the under face of their heads 67 to secure the adjustment. When operating on gaseous fuel, the latter is sup- plied to the chamber 62 through the inlet 42. The pressure of the gas in the chamber 62 above the diaphragm assembly 50, which is typically in the range of -2.50 to -76.20 mm of water column, maintains the assembly 50 in its lowermost position with the ends of the adjusting screws 64 sitting atop the adapter neck 26 to form the venturi passage 58 since that pressure is greater than the pressure of the incoming air below the assembly 50, which is typically in the neighborhood of -2.50 and -17.80 mm of water column respectively upstream and downstream of the throat 59 and -762 mm at the latter. Accordingly, the low air pressure at the throat 59 draws gaseous fuel from the outlet ports 63 into the incoming air stream. The annular shape of the venturi passage 58 and the distribution of the outlet port 63 around it especially enhance gas distribution and mixture with the air. For slow-run operation a typical separate slow-run system may be incorporated into the engine mani¬ fold, as previously mentioned, or, as also mentioned, a slow-run system in which a valve 70, controlled by manifold vacuum, introduces gaseous fuel into the chamber 62 through an inlet 71 in the cover wall 39 opposite the main inlet 42. When operating on liquid fuel, the gaseous fuel supply to the inlet 42 (and the inlet 71) is, of course, closed off. The chamber 62 thereby becomes closed except for the outlet ports 63. The incoming air to the carburet¬ tor 11 past the outlet ports 63 lowers the pressure in the chamber 62 against the upper face of the diaphragm assembly 50 below that against-- the lower face of the latter, where¬ upon the diaphragm assembly 50 automatically rises, as indicated in broken lines in Figure 1, toward its uppermost limit against the stop collar 18 depending upon the air demand of the engine. The venturi passage 58 is thus "de- stroyed" and the incoming air passes substantially unimpeded to the carburettor 11. In short, the assembly 20 then func¬ tions just as would a normal air cleaner assembly, as if the diaphragm assembly 50 were wholly absent. It will be appre¬ ciated by those skilled in the art that for the diaphragm assembly 50 to rise as aforesaid, its effective diaphragm area, whose diameter is indicated by the line A-A in Figure 2, must be sufficient to enable the pressure differential between the opposite sides of the diaphragm assembly 50 to overcome the weight and friction of the latter. This is readily achieved by constructing the diaphragm assembly 50 of light-weight materials. As will be apparent, the parts of the air cleaner assembly 20 are all simple and straightforward. The adapt¬ ers 21 and 27, the cover 38 and the diaphragm plate 53 can all be stamped or spun from sheetmetal such as aluminum. The diaphragm 51 is preferably a 0.20 mm thick sheet of Dacron or Nylon impregnated with epochlorhydron. The overall size of the assembly 20 is also modest, an overall diameter of about 356 mm, a height of about 100 to 130 mm between the air horn 14 and the top of the post 16, a dia¬ meter of the diaphragm plate 53 between the outlet ports 63 of about 160 mm, and an outer free diameter of the diaphragm 51 of about 280 mm all being adequate for engines as large 8.20 litres displacement. The diameter of the outlet ports 63 is preferably between about 4.0 and 4.80 mm and their number vary from 4 to 20 or so depending upon engine dis¬ placement. Different sized engines can thus be accommodated simply by different diaphragm plates 53 as well as by ad- justment of the width of the throat 59 by the screws 64. For sidedraught and updraught applications, especially the latter, a light coil spring around the post 16 between the stop collar 18 and the coined aperture 63 may be necessary to maintain the diaphragm assembly 50 in its position for gaseous fuel operation.

Claims: What is claimed is: 1. Mixing means for operating an internal com¬ bustion engine having an air inlet on liquid or alternately on gaseous fuel, the mixing means being characterized by: a housing having fixed first and second wall means, said air inlet opening into the housing through the first wall means and being surrounded by a first surface portion disposed on a face of the first wall means, the second wall means par¬ tially defining a gaseous fuel chamber and disposed in spaced relation to and opposite said first surface portion of the first wall means; intermediate wall means disposed in spaced relation to and between both the first and second wall means and further defining said chamber, a face of the intermediate wall means including a second surface portion disposed in opposed spaced relation to said first surface portion and also surrounding said air inlet, the intermedi¬ ate wall means being reciprocally movable relative to and between the first and second wall means between first and second limit positions respectively adjacent and remote from the first wall means during engine operation on respectively gaseous and liquid fuel, said first and second surface por¬ tions when the intermediate wall means is in its first limit position defining therebetween a passage of venturi shape in cross-section surrounding said air inlet for controlling supply of gaseous fuel to the engine, the venturi passage having an intermediate throat portion for communicating at an upstream end with the atmosphere and for communicating at a downstream end with said air inlet, the intermediate wall means when in its second limit position providing for a substantially unimpeded flow of air past said surface por- tions; a plurality of gaseous fuel outlet ports spaced around said throat portion and communicating with said cham¬ ber through the intermediate wall means ; and inlet means for supplying gaseous fuel to said chamber. 2. The mixing means of claim 1 further charac¬ terized by a periphery of the intermediate wall means being articulately connected to a periphery of the second wall means to allow said reciprocal movement of the intermediate wall means. 3. The mixing means of claim 2 further charac¬ terized by the second wall means being a circular cover member facing the intermediate wall means to form therewith said chamber; by the intermediate wall means being a circu- lar inner member having an annular face portion of generally convex cross-section configuration disposed radially inward of the marginal area of said inner member, said convex face portion forming said second surface portion; and by said articulate connection being an annular flexible diaphragm having its inner marginal area sealingly connected to the marginal area of said inner member and its outer marginal area sealingly secured to the marginal area of said cover member. 4. The mixing means of claim 3 further charac¬ terized by the first wall means being an annular adapter member coaxial with said cover member and said inner member and having a face portion of a cross-section configuration to form at least part of said first surface portion; and by adjusting means carried by said adapter member or said inner member and engaging the other member for adjustably varying the distance between said face portions when said inner member is in its first limit position. 5. The mixing means of claim 4 further charac¬ terized by guide means extending slidably through said inner member to confine said movement thereof to a linear path. 6. The mixing means of claim 5 further charac¬ terized by the peripheral margins of said cover and adapter members additionally defining opposed annular seat portions for receiving an annular air filter element therebetween upstream of said venturi passage. 7. The mixing means of claim 6 further charac¬ terized by the adapter member having interfitted separate outer and inner portions, the inner portion being adapted for engaging said air inlet opening. -11- 8. The mixing ' means of claims 1, 2, 3, 4, 5, 6 or 7 further characterized by said gaseous fuel inlet means including first and second inlets opening through the second wall means. 9. An internal combustion engine operable on liquid fuel or alternately on gaseous fuel in which the engine has an engine air supply passage terminating in an engine air inlet disposed upstream of means in said passage for controlling the supply of liquid fuel and/or air to the engine and intake means disposed at said air inlet for mixing air and gaseous fuel from a supply source in proper proportions and supplying the mixture to the engine when operated on gaseous fuel and for providing for a substan- tially unimpeded supply of air only to said air inlet when the engine is alternately operated on liquid fuel charac¬ terized by the intake means including: first, second and third closure members, the first closure member having an opening therethrough communicating with the engine air inlet and a first configured surface surrounding said opening, the second closure member having opposite faces, one of said faces including a second configured surface in opposed spaced relation to the first configured surface, the second and third closure members being articulately connected to each other around respective peripheral portions to provide a gaseous fuel chamber on the other face of the second clo-r sure member, said articulate connection providing for move¬ ment of the second closure member relative to and between the first and third closure members between a first limit position adjacent the first closure member and a second limit position adjacent the third closure member, said first and second configured surfaces when the second closure member is in its first limit position defining therebetween an annularly disposed passage of venturi shape in cross- section around and adjacent said opening for flow of mixed air and gaseous fuel to said opening, said venturi passage having an intermediate throat section, the second closure member when in its second limit position providing for a substantially unrestricted flow of air only past said con- figured surfaces to sai opening; a plurality of gaseous fuel outlet ports spaced around said venturi throat section and opening into said chamber through the second closure member; and inlet means carried by the third closure member for supply of gaseous fuel to said chamber at a pressure sufficient to maintain the second closure member in its first limit position during operation of the engine on gas¬ eous fuel, the second closure member being effective to be automatically disposed toward its second limit position when supply of gaseous fuel . to said inlet means is closed off during operation of the engine on liquid fuel. 10. The engine of claim 9 further characterized by the first closure member including a generally annular adapter plate formed to a cross-sectional configuration pro¬ viding at least part of said first configured surface; by the second closure member including a circular diaphragm plate having an annular portion radially intermediate there¬ of of generally dished configuration in cross-section, the diaphragm plate being disposed coaxially with the adapter plate, the convex face of said annular portion forming said second configured surface with said gaseous fuel outlet ports being disposed therearound; and by guide means for the diaphragm plate for confining said movement thereof to a linear path. 11. The engine of claim 10 further characterized by said articulate connection between the diaphragm plate and the third closure member being a flexible diaphragm sheet sealingly secured to and between said peripheral portions thereof. 12. The engine of claim 11 further characterized by the third closure member being a removable circular cover plate of generally dished configuration in cross-section and coaxially disposed with the adapter and diaphragm plates, the concavity of the cover plate facing the diaphragm plate and diaphragm sheet to form said chamber therebetween; and by a plurality of adjusting means carried by said annular portion of the " diaphragm plate and extending through said venturi throat section to the adapter plate in order to adjust the spacing between said configured surfaces and thus the first limit position of the diaphragm plate. 13. The engine of claim 11 further characterized by the outer peripheral margins of adapter and cover plates including opposed annular seats for receiving an annular air filter element therebetween; and by said guide means includ- ing a longitudinal member extending coaxially through the diaphragm and cover plates, the diaphragm plate being recip¬ rocally slidable along said guide member during said move¬ ment thereof, said guide member having an end adjacent the exterior of the cover plate carrying releasable means to maintain the adapter and cover plates and an air filter element assembled in their aforesaid relationship. 14. The engine of claim 13 further characterized by the adapter plate including a separate inner annular portion fittingly engagable with an engine air inlet of the aforesaid nature. 15. The engine of claims 8, 9, 10, 11, 12, 13 or 14 further characterized by valve controlled second inlet means carried by the third closure member for supply of gaseous fuel to said chamber.

Inventors: GARRETSON K
Applicants: GARRETSON EQUIP CO INC
Application year: 1980
Main classification: F02M21
IPC codes: F02B3, F02B69, F02M13, F02M21, F02M35