GB1572909A - Carburettor - Google Patents

Description

(54) CARBURETOR (711) We, BLAKEWAY INDUS TRIES LTD., a company incorporated under the laws of the province of British Columbia, Canada, 1112 East 3 Street, North Vancouver, British Columbia, Canada V7J 1B8, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be par ticularly described in and by the following stateenent:- This invention concerns improvements in or relating to the mixing of air and fuel prior to comibustlion in an internal combustion engine.

Carburettors have been known for many years, the common type of carburettor having a throat with a venturi and being provided with a butterfly valve for controlling air flow through the throat Fuel is drawn by suction at the venturi to discharge through a jet as a fine spray into the throat. For automotive applications, usually the carburettor has several jets and fuel delivery oircuits to maintain desired airsfuel ratios for all engine conditions.

Normally a separate choke and a rich fuel circuit is required for starting, and for acceleration an accelerator pump to inject a measured amount of fuel into the throat is commonly provided. Modern automobile carburettors are relatively complex and are prone to blockage from dirty fuel and, with increasingly strict air pollution standards, are known to be relatively inefficient for atomisation and mixing of the fuel.

According to the present invention there is provided fuel atomising means, or constructed and arranged for use in, a carburettor having a body with a throat having a throat central axis and a throat sidewall, valve means for controlling air flow through the throat, and fuel supply means to supply fuel to the atomising means; the fuel atomising means comprising a fuel spray tube extending or adapted to extend through the sidewall into the throat substantiallly perpendicularly to the throat central axis; wherein said fuel spray tube has jet means comprising an air bleed jet means positioned to face substantially upstream towards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around the tube; wherein said jet means is fixed and is arranged longitudinally of the spray tube so as to extend transversely across a major part of the width of the throat; and wherein the fuel atomising means is arranged so that fuel supplied to the fuel atomising means is conveyed longitudinally within the spray tube through the sidewall to a fuel orifice without mixing with the air, and is then discharged through the fuel orifice sub stantially mid-way along the jet means to mix within the spray tube with air entering the spray tube via the air bleed jet means to form a rich fuel and air mixture, which mixture is discharged from the spray tube via the discharge jet means.

The present invention also provides a carburettor having a body with a throat having a throat central axis and a throat sidewall, a gate valve assembly for controlling air flow through the throat, and fuel metering means to meter a supply of fuel to the atomising means; the fuel atomising means comprising a fuel spray tube extending through the sidewall into the throat substantially perpendicularly to the throat central axis; wherein said fuel spray tube has jet means comprising an air bleed jet means facing substantially upstream towards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around the spray tube; wherein said jet means is fixed and is arranged longitudinally of rhe spray tube so as to extend transversely across a major part of the width of the throat; and wherein the fuel atomising means is arranged so that fuel supplied to the fuel atomising means is conveyed longitudinally within the spray tube through the sidewall to a fuel orifice without mixing with the air, and is then discharged through the fuel orifice substantially mid-way along the jet means to mix within the spray tube with air entering the spray tube via the air bleed jet means to form a rich fuel and air mixture, which mixture is discharged from the spray tube via the discharge jet means.

In a preferred embodiment the carburettor includes a body having a throat with a throat central axis and a sidewall; fuel atomising means having a fuel spray tube extending into the throat generally normally to the throat cenral axis, and adapted to receive fuel and to discharge fuel into the throat; and a valve assembly. In preferred embodiments, the valve assembly has a valve axis extending across the throat and nonnally to the throat central axis, first and second sliding gate valve members, and a complementary valve guide means to mount the valve members for generally trans verse sliding along the valve axis between closed and wide open positions.Each valve member has an inner portion having an inner edge disposed generally syntmetrically about the valve axis and shaped so as to correspond to approxirnately one half of the sidewall of the throat when in the wide open position. The valve members are adapted to cooperate with each other so that inner portions thereof over lap each other to dose essentially the throat in the closed position, and also to co-operate with jetmeansofthefuel spray tube. The car burettor also includes valve actuating means and fuel metering means.The valve actuating means co aperates with the valve members to move the valve members concurrently in opposite directions between the respective open and dosed positions in response to an operator control so that movement of the members controls the jet means. The fuel metering means is responsive to valve position and meters fuel prior to being discharged from the fuel spray tube. The fuel atomising means co-operates with the jet means of the fuel spray tube so as to discharge into the throat an acceptable fuel mixture for combustion for all valve positions.

The fuel atomising means includes the fuel spray tube extending into the throat and is characterised by discharge jet means extending substantially across the throat and positioned so as to. be exposed to suction resulting from air flowing around the spray tube. The fuel spray tube includes a manifold extending sub stantially across the throat and communicating with the discharge jet means, and a fuel orifice positioned midway across the throat to dis charge metered fuel into the manifold for distribution to the discharge jet means.

The fuel atornising means can also be used, with suitable modifications, in a conventional carbuxettor with a known valve means for con trolling air flow through the throat, for example a butterfly valve.

A detailed disdosure following, related to the accompanying drawings, describes preferred exnbodiments of the invention which, however, is capable of expression in structures other than those particularly described and jihistated.

In the drawings: Figure 1 is a simplified fragmented section through a portion of a carburettor of the invention, portions of the carburettor being removed to show valve actuating mechanism and valve members in open positions, Figure 2 is a simplified section on Line 2-2 of Figure 1 showing the valve members in wide open positions, Figure 3 is a simplified section on Line 7.2 of Figure 1, the valve members being shown in closed positions, Figure 4 is a simplified transverse section on Line 44 of Figure 1, Figure 5 is a simplified perspective showing valve members separated beyond the wide open position, Figure 6 is a simplified perspective showing the valve members co-operating in a partially open poistion, Figure 7 is a simplified section on Line 7-7 of Figure 2 showing fuel atomising means, and showing the valve members and fuel metering means in half open positions, Figure 8 is a simplified top plan of a first alternative carburettor, valve members thereof being shown in half open positions, Figure 9 is a simplified section generally on Line 9-9 of Figure 8, the valve members being shown in the half open positions, some portions being removed, Figure 10 is a simplified section generally on Line 1010 of Figure 8, a fuel metering means being shown in a halfzpen position, some portions being removed, and Figure lii is a simplified section of a second alternative carburettor.

Referring particularly to Figures 1 to 3, a carburettor 10 for mixing air and fuel prior to combustion includes a body 12 having a throat 13 with a cylindrical sidewall 14. Air enters the carburettor from an intake stack in the direction of an arrow 15, in response to reduced induction pressure. A fuel spray tube 16 extends across and between opposed portions of the throat and has a fuel inlet 17 at one end to receive fuel and a plug 19 at an opposite end and is adapted to discharge fuel into the throat by means to be described. The carburettor has a throat central axis 18 and a valve assembly 20 having a valve axis 21 extending across the throat on a diameter thereof.

Thus, the spray tube 16 and the valve axis 21 extend normally to the throat axis 18. The tube 16 forms part of fuel atomising means as hereinafter described.

The valve assembly is controlled by the valve actuating means 23 coupled by a valve control link 24 to an operator control (not shown). The valve assembly includes first and second sliding gate valve members 25 and 26 and a complementary valve guide means 27 to mount the valve members for generally transverse sliding along the valve axis between an open position of the valve shown in Figure 2 and a closed position shown in Figure 3.

The valve members 25 and 26 have inner portions 31 and 32 provided with concave inner edges 33 and 34 respectively, the inner edges being disposed generally symmetrically about the valve axis and being shaped to correspond to approximately one half of the sidewall 14 of the throat when in the wide open position.

As seen in Figure 2, when the carburettor is open the inner edges 33 and 34 are not necessarily flush with the throat sidewall, but can project into the throat from the sidewall to produce turbulence in the air flow which improves the mixing of the fuel with the air. If maximum air flow through the throat is a major consideration the inner edges 33 and 34 should retract to be flush with the throat sidewall in the wide open position. The guide means 27 has oppositely extending valve guide projections 28 and 29 to receive and support outer portions of the valve members 25 and 26 respectively in the wide open position, and to support outer portions of the tube 16.

As best seen in Figures 4, 5 and 6, the valve meter 25 has first and second portions 37 and 28 having thicknesses 35 and 36 respectively, the thickness 36 being approximately twice the thickness 35. The first portion is a generally rectangular slab having a pair of spaced parallel side edges 41 and 42 adapted to slide in the valve guide means 27, and the concave inner edge 33. The first portion 37 has a face 43 with an axial groove 44 to accept approximately one-half of the fuel spray tube 16, the face having a periphery defined in part by portions of the second portion, the edges 33, 41 and 42 and an outer edge 48 of the valve member. The face 43 also has a pair of gear racks 46 and 47 extending parallel to and adjacent the side edges 41 and 42 of the member between spaced inner edges of the inner portion 31 and the outer edge 48.

The second portion 38 has an axially disposed passage 45 aligned with the groove 44 in the face 43 so as to accept the fuel spray tube 16 which passes through the second portion to the outer edge 48. The second portion has a convex semi-cylindrical inner wall 50 spaced outwards from the inner edge 33 a distance 51 as measured along the valve axis, which distance defines valve overlap. Thus the groove 44 extends between mid-positions of the convex inner wall 50 and the concave inner edge 33.

The second valve member 26 is generally similar to the first valve member and has first and second portions 57 and 5;8 and a passage 53 in the second portion aligned with a groove 55 extending across a face 56 of the first portion 57, forming a valve overlap. The passages 45 and 53 and the grooves 44 and 55 of the valve members are mutually aligned for all positions of the valve members to permit free sliding of the members along the fuel spray tube 16. The first portion 57 has parallel side edges 59 and 60 with gear racks 61 and 62 extending parallel to and adjacent the side edges 59 and 60.

The valve members 25 and 26 are mounted in the valve guide means 28 in opposite rela tionship to each other, so that faces 34 and 56 of the respective first portions are positioned so as to be adjacent to each other. As best seen in Figure 6, the concave inner edge 34 of the first portion 57 of the valve member 26 is complementary to the convex inner wall 50 of the second portion 38 of the valve member 25. Similarly, the second portion 5.8 of the valve member 26 has a convex inner wall 63 (shown in Figures 1, 2 and 3) which is complementary to the inner edge 33 of the valve members 25.Because the concave inner edge and convex inner wall of one valve member is complementary to the concave inner edge and convex inner wall of rhe other valve member, when the valve is closed, air flow through the carburettor is restricted. The degree of restriction can be adjusted by changing equally on each valve member the width of the valve overlap and degree of fit of the complementary portions d the valve members. When closed a relatively small amount ob air can flow around the side edges of the valve members between the guide means and this is sufficient to provide cool air for cooling the cylinder after the engine has been switched off but is still rotating.The air flowing around the edges of the valve member remote from the throat thus bypasses the fuel spray tube and does not draw fuel into the engine which, in some cases, would orherwise tend to initiate ignition even when the engine has been switched off. Thus this is an air bypass means and the amount of air being bypassed can be adjusted by selecting particular clearances between the valve members and guide means. It is important that negilgible air by-passes the fuel spray tube when the valve members are open and the engine is operating as this would cause erratic running due to undesirable variations in airsfuel ratio.

As best seen in Figure 4, a pair ob similar gear wheels 65 and 66 are journalled on pins 67 and 68 extending inwards from the valve guide means 27, the gear wheels meshing with the opposed racks 46 and 61, and 47 and 62 respectively of the valve members, to provide a simple rack and pinion mechanism on each side of the fuel spray tube. The rack and pinion mechanisms automatically couple the valve members together so as to move equal amounts in opposite directions. The valve members and gear wheels can be made from injection moulded plastic so that lubrication problems are reduced and the tolerances obtainable with precision injection mouldings permit economical mass production of the major components of the valve mechanism.

For a given movement of one valve member, change in opening between the valve members is twice that that would be obtained if only one valve member moved. Thus the valve assembly has a particularly fast response for a given control movement when compared with a single plate valve. Furthermore, the movement of the valve members is symmetrical relative to the throat for all valve positions, which also contrasts with a single plate valve.

The valve control link 24 includes a sheathed control cable 70, such as a Bowden cable, having an outer end 71 of the sheath thereof secured to the projection 28 of the valve guide means, and an outer end 73 of an inner wire thereof secured to the valve mem ber 25. Inner ends (not shown) extend to an operators throttle control, for example, the hand grip of a motor cycle, or the accelerator pedal linkage of an automobile. Compression spring means 75 enclose a portion of the fuel spray tube 16 and extend between the valve guide means and the outer edge 48 of the member 25 to apply a closing force to the valve member tending to move it to the closed position. The closing force is applied along the axis 21 and aligned with the tube 16 which also is a guide and thus jamming tendency is reduced.The throttle is opened by drawing the wire outer end 73 outwards, thus compressing the spring means 75 and moving the valve member 25 outwards which, through the gear wheels 65 and 66 concurrently moves the valve member 26 outwards, i.e. in the opposite direction. Thus the gear wheels 65 and 66, the gear racks 46, 47, 61 and 62 and the control cable 70 serve as valve actuating means co-operating with the valve members to move the valve members concurrently in opposite directions between the respective open and dosed positions in response to an operator control. It is noted that the gear wheels are rotatable means journailed for rotation relative to the carburettor, and alternative and equivalent valve actuating means and rotatable means are disclosed with reference to Figures 8 and 9.

As best seen in Figures 1 and 4, the valve guide means 27 includes open rectangular recesses 77 and 78 on opposite sides of the spray tube, and recess 77 having opposed parallel walls 80 and 81 which restrict the valve members against rodcing relative to the valve axis as the valve members move between extreme positions. Additional support for the valve members is obtained by opposed inner faces 83 and 84 of the valve guide projections 28 (shown in Figure 1 only), which inner faces engage upper and lower faces respectively of inner and outer portions of the valve members.

Similarly, inner faces 85 and 86 of the valve guide projection. 29 engage upper and lower faces respectively at opposite ends of the valve members. It can be seen that the valve members are thus supported along the side edges ier flor for positions of the valve members wftt aditionsl support of the inner and outer pro of the valve members when in extreme positions. This produces smooth sliding of the valve members along the guide means and also along the fuel spray tube with little tendency to jam through non alignment.

Referring mainly to Figure 7, fuel spray tube 16 has air bleed jet means comprising a plurality of air bleed jets 91 spaced along the tube and facing generally upstream to inlet air flow, shown as the arrow 15, so as to receive a portion of ram air entering the carburettor. The fuel tube also has discharge jet means comprising a plurality of discharge jets 93 spaced along the tube and positioned so as to be exposed to suction resulting from air flowing around the spray tube. In some con ditions suction can also be generated by air flow around the inner portions 31 and 32 of the valve members which augments suction pxduced by air flowing around the tube. The air bleed jets and discharge jets extend in rows between opposite portions of the sidewall of the throat and are equally spaced.The air bleed jets are larger, spaced further apart and fewer in number than the discharge jets for reasons to be described As best seen in Figure 4, the discharge jets are positioned on the periphery of the tube at about 45 degrees to the main direction of air flow at a position where suction is generated as air flows past the tube 16. Preferably most of the air entering the air bleed jets 91 cannot pass directly out through the discharge jets 93 and thus the discharge jets are non-aligned with the air bleed jet means.

As best seen in Figure 6, portions of the valve members having the passages 45 and 53 and the grooves 44 and 55 respectively partially enclose portions of the fuel spray tube adjacent opposite portions of the throat Thus, as the valve assembly closes, the valve members move towards each other and the air bleed jets and the discharge jets adjacent opposite portions of the throat are progressively closed by the valve members. It is noted that as the valve member 25 moves inwards, the valve overlap of the member 25 closes the discharge jets ahead of the air bleed jets. Likewise as the member 26 moves inwards, its valve overlap closes the air bleed jets ahead of the discharge jets.

The fuel spray tube 16 is aharacteriséd by an outer sleeve 96 having a central bore 95 and the rows of air bleed and discharge jets 91 and 93 respectively, and an inner tube 97 which is a snug fit within the central bore 95.

The inner tube 97 has a central bore 99 which serves as a passage for receiving fuel from a fuel line (not shown) connected to the fuel inlet 17 and entering the bore in direction of an arrow 100. The fuel line receives fuel from a constant head device such as a common float chamber or constant pressure delivery pump (not shown). The central bore 99 has a restriction 101 defining a fuel flow jet 102 which communicates with a discharge chamber 104 on a side of the restriction remote from the inlet 17. An inner end 98 of the tube 97 has an annular groove 106 extending therearound, which defines with a portion of the central bore 95 of the outer sleeve 96 and opposed shoulders of the groove 106 an annular mixing manifold 107 within the tube 116.The manifold 107 extends between the upstream and downstream portions of the bore 95 and along the spray tube between extreme outer positions of the air bleed and discharge jets and connects the air bleed jets to the discharge jets. A fuel orifice 109 passing through an inner wall 110 of the manifold connects the discharge chamber 104 to a downstream portion of the manifold and thus is disposed relative to rhe air bleed jet means so as to be essentially sheltered from direct flow of air entering the air bleed jet means. The fuel orifice 109 is on the throat axis 18 and thus is disposed approximately mid-way across the throat 13 to ensure central distribution of fuel into the manifold, i.e. at a mid-position of the manifold to provide generally even distribution of fuel to the discharge jets.Thus fuel passes along the bore 99, through the fuel jet 102, into the discharge chamber 104, through the fuel orifice 109 and then generally equally to opposite ends ob the manifold 107. Ram air that enters the air bleed jets 91 flows around the annular groove 106 and mixes with fuel discharged from the fuel orifice 109. Some atomisation of the liquid fuel may take place here, but mostly air is mixed with fuel droplets to form a relatively rich primary air/fuel mixture which is then drawn through the fuel discharge jets 93 to atomise in the suction adjacent the jets 93. This subsequent atomisation at the jets 93 is assisted by air turbulence and suction resulting from air flow passing the inner portions 31 and 32 of valve members.

The air bleed jets preferably have a total area greater than the discharge jets so as to pass an adequate volume of air to initiate primary mixing of the metered fuel. The discharge jets are relatively fine openings to improve atomisation. Thus, the tube 16, the air bleed jets 91, the fuel orifice 109, the manifold 107 and discharge jets 93 serve as fuel atomising means '111.

A fuel needle 112 has a tapered outer end 1t13 passing through the fuel flow jet 102 and an inner end 115 releasably connected to an inner end of an arm 116. The arm 116 has an outer end fitted in an opening 118 in the valve member 26, and a portion of the outer sleeve 96 has a longitudinal slot 120 to provide clearance for the arm 116 to pass therethrough.

As can be seen, as the valve member 26 moves axially between open and closed positions in directions shown by a dotble-headed arrow 122, the tapered end 113 of the fuel needle moves axially through the fuel flow jet 102 varying degree of restriction of the fuel jet thus serving as a fuel metering means 121. The slot 120 thus has a length equal to at least total stroke of one valve member to accommodate full movement of the valve member between extreme positions. An "0" ring seal 124 encircles an inner parallel portion of the fuel needle essentially to prevent loss of fuel through an outer end of the discharge chamber 104. Thus the arm 116 serves as a coupling means 125 which connects the fuel needle to an adjacent valve means so that axial movement of the valve member is reflected by the needle.The plug 19 has an opening 123 to accept a screw driver (not shown) for engagement with a screw driver slot 126 at the inner end 115 of the needle 112 for turning the needle in the arm 116 for axial adjustment of the needle. The needle B12 can thus be moved axially relative to the arm 1116 for "zeroing" the needle relative to the jet 102.

As best seen in Figure 4, the needle has a flat portion 127 inclined to a central axis of the needle, so that cross-sectional area of the needle varies along the length thereof. Thus when the needle 112 co-operates with the jet 102, with a constant fuel supply pressure, the fuel flow through the fuel jet is metered an amount dependent on cross-sectional area of that portion of the needle which co-operates with the jet. The tapered needle 112 thus serves as a variable fuel flow restrictor which co-operates with the fuel jet to vary degree of restriction of the fuel jet. Because the needle is connected to the valve member 26, relative position of the flow restrictor in the jet is dependent on position of the valve member, which is related to volume of air flowing through throat.The flat portion 127 is pre ferably disposed adjacent the fuel orifice 109 so as to provide a relatively direct route be tween the fuel jet and fuel orifice, and this relative disposition can usually be attained after rotation of the needle 112. The fuel orifice is no smaller than the jet 102 when fully open so as not to restrict flow from the chamber 104. It is seen that as the needle moves in the jet 102, it would tend to clean it of a blockage, thus making the carburettor sel-cleaning to a limited extent.

In suinmary, it can be seen that the car burettor has the fuel metering means 121 posi tioned within the fuel spray tube, in which the fuel metering mearrs is responsive to Valve position to meter fuel discharged from the fuel spray tube, and the gate valve cooperates with the fuel spray tube so that as the valve doses, volume flow of air entering the air bleed orifices is controlled by selectively closing air bleed jets simultaneously with the discharge jets. It is noted that the air bleed jets com municate with the discharge jets and a supply of metered fuel so that the metered fuel and the ram air in the manifold discharge simul taneously through the discharge jets.

A portion of ram air entering the carburettor throat enters the fuel spray tube through the air bleed jets 91 and passes through the mani fold 107 to leave the fuel spray tube through the discharge jets 93. This portion of air concurrently mixes initially with metered fuel passing through the fuel orifice 109 to form the relatively rich primary air/fuel mixture in the material 107, which then discharges through the discharge jets 93 for subsequent mixing with air in the throat downstream from the spray tube to produce a desired leaner air/ fuel mixture for combustion.It can be seen that, as the carburettor closes, air bleed and discharge jets are closed progressively from each end of the tube, thus proportioning ram air fed into the jets and fuel discharged from the jets in an amount generally proportional to air flowing through the carburettor. Note that fuel metering is determined primarily by position of the fuel needle 112 in the fuel jet 102, with some adjustment being possible by varying ram air fed into the mixing manifold.

The spray tube 16 has the plurality of air bleed jets 91 and discharge jets 93 spaced along the tube between the sidewall of the carburettor throat If required, size and spacing of the jets can be varied to accommodate air flow variations across the throat, or to acoinmodate different air/fuel mixtures for different valve positions. Two rows of discharge jets can be provided snmmetrically on opposite sides of the fuel spray tube so as to be exposed to the suction, and if desired can be.staggered relative to each other for even dispersion of fuel into the air stream.

'tematively, the air bleed jet means can be a narrow axial slit extending along an up portion portion of the spray tube and the dis- charge jet means can be a similar narrow slit extending along a portion of the fuel spray tube exposed to suction. This would produce a coniinuously varying area of air bleed jet means or discharge jet means exposed to air flow, contrasting with the plurality of jets which is discontinuous or incremental. The slits could taper to provide non-linear area characteristics to attain desired air/fuel ratios for all valve positions. Alternatively, one air bleed jet can be provided at the middle of the tube, i.e. mid-way across the throat.This latter alternative does not have extensive or progressive closing of the air bleed jet means as the valve closes, from the wide open positions until the valve members approach edges of rhe jets. The air bleed jet means and discharge jet means are collectively referred to as jet means.

The fuel atomising means can be nosed also as a substitute for at least some of rhe fuel jets in a conventional carburettor having blown valve means for controlling air flow through the throat, for example a butterfly valve.

Referring initially to Figure 8, an alternative cnarettor 130 having a throat 13t1 has an aiternative gate valve assembly 132 actuated by an alternative valve actuating means 133, alternative fuel atomising means and aitema- tive fuel metering means 135. The valve assembly 132 has a valve axis 1316, and first and second valve members 137 and 138 mounted in valve guide means 139 and adap- ted for the transverse sliding along the valve axis between closed and wide open positions.

The valve members and the valve guide means are generally similar to the valve guide means of Figure 1, with differences as follows. As seen in Figure 8, a major difference from the carburettor 10 of Figure 1 relates to rhe fuel atomising means having a fuel spray tube 134 which extends diametrically across the throat perpendicular to the valve axis 136 of Figure 8, in contrast to the tube 16 of Figures 2 and 3 which extends parallel to the valve axis. The tube 134 receives fuel in direction of an arrow 142 from a fuel supply (not shown).Inner portions 140 and 141 of the members 137 and 138 have additional clearance 143 and 145 to receive the fuel spray tube 134 transversely so as to extend over downstream and upstream sides of the tube respectively so as to sandwich the fuel tube. Thus the passages 45 and 53 and grooves k4 and 55 of the valve members 25 and 26 of Figures through 6 are eliminated. The fuel spray tube 134 has a plurality of air bleed jets 144 and discharge jets (not shown) on the upstream and downstream sides of the tube respectively, which are generally similar to the jets 91 and 93 of the fuel spray tube 16 of the carburettor 10.The fuel spray tube 134 coqerates with the valve members 1137 and 138 so that jets adjacent opposite portions of the throat are progressively closed by the valve members as the valve assembly closes, similarly to the structure of Figure 1.

The tube 134 has a manifold and a related centrally disposed fuel orifice (neither of which are shown) similarly to the tube 16.

The valve actuating means 133 eliminates and is a substitute for the rack and pinion mechanism of the means 23 of Figure 1.

Referring also to Figure 9, the means 133 has a lever mechanism 146 which includes a lever d48 secured at a midpoint thereof to an axle 1150 which is journalied for rotarion about an axis 149 disposed diametrically to the, carburettor throat. The axis 149 is shown to be aligned with the fuel spray tube 134 although alternative locarions are envisaged. A pair of links 1511 and 152 have inner ends 153 and 1154 connected to opposite ends of the lever ,148, and outer ends 155 and 156 journailed on pins 157 and 158 extending transv ly from the valve members 137 and 138 as own. The pins 1517 and 158 extend through axial slots 161 and 162 in the valve guide means and are thus constrained to move in planes parallel to the valve axis. As can be seen in Figure 9 rotation of the axle 150 rotates the lever 148 between its valve open position 1164 and its valve dosed position 1165 resulting in con current mutual sliding of the valve members equal amounts in opposite directions.A control arm 166 secured to an outer end of the axle 150 is connected to an operator control, for example the throttle lever, through control link means (nowt shown), with return spring means (also not shown) as required.

The fuel metering means 135 is positioned remote from the throat 131 and within one portion of the guide means 139. As seen in Figures 8 and 10, the means 135 includes a tapered fuel needle 169 which co-operates with a longitudinal bore of the tube 134 to meter flow to the fuel orifice through the longitudinal bore which serves as a passage to conduct fuel to the fuel orifice. The needle has a tapered outer end 173, and an inner end 170 threaded on to an arm 171 extending from the valve member 138 into a clearance slot 172 in the valve guide means. The valve guide means has a parallel bore 175 adapted to receive the end 173 and the fuel spray tube 134 passes through that portion of the valve guide means and is pierced by the bore 175.

Thus the outer end 175 of the needle passes transversely across the longitudinal bore of the fuel spray tube to meter fuel flow therethrough.

The end 170 has a screw driver slot and the valve guide means 139 has a clearance bore 177 to accept the screw vcr for rotatEonTh the needle for axial adjustment of the needle.

As can be seen, movement of the valve member 138 in direction of an arrow 178 to close rhe valve moves the fuel needle inwards, increasing restriction of the fuel spray tube 134, thus decreasing flow of fuel through the metering means 135 in an amount proportional to movement of the valve members.

A second alternative carburettor 184 shown in Figure 11 has an alternative valve assembly 1.83 having first and second valve members 18,7 and 188 formed from flat plates, outer edges of which are adapted to run in valve guide means 189 which are generally similar to the previously described valve guide means.

The carburettor has an alternative fuel atomising means 191 characterised by a fuel spray tube 193 extending across the throat parallel to movement of the valve members. The fuel spray tube has a plurality of air bleed jets 194 and discharge jets 193 spaced along the tube on upstream and downstream sides thereof similarly to the previously described embodiments. The tube 193 is positioned adjacent to and downstream of the valve members so that the valve members close the air bleed jets as required. The first and second portion of the previously described valve members are thus eliminated, together with the passages and grooves to accept the fuel tube. Valve actuating means (not shown) such as the lever mechanism 146 of Figure 8, move the valve members concurrently in opposite directions as previously described.The fuel spray tube is positioned in turbulence produced in the air flow past the valve members to improve atonusation and mixing of the fuel. The valve mem;bers only restrict entry of ram air into the upstream facing air bleed jets,. and provide no restriction for discharge from the discharge jets on the lower surface thereof. A fuel needle 196 werates with a fuel jet (not shown) within the tube 193 and is threaded onto an arm 197 extending from the valve member 187 into a clearance slot 198 in the tube 193. Thus fuel metering is proportional to valve opening as in the previous embodiments.

Alternatively, the first and second valve members can be fitted on the downstream side of the fuel spray tube 193 as shown generally in broken outline at 187.1 and 188d. In this alternative position the air bleed jets 194 remain unobstructed for all valve positions, and suction at some of the discharge jets 195 is reduced by the valve members when par tially closed. The alternative carburercor 184 provides a simpllified structure which could have applications where atomisation is less critical.

Thus in all alternative embodiments as above, the fuel needle coqerates with the bore of the fuel spray tube to serve as a van- aible flow restrictor which co-operates with the fuel jet to vary degree of restriction of the fuel jet The flow restrictor is connected to the valve means so that relative position of the flow restrictor in the jet is related to volume of air flowing through the carburettor throat.

In all embodineents, the fuel atomising means discharges fuel symmetrically relative to the throat, and, in some cases, also distributes the fuel diametrically across the throat prior to discharge.

The fuel atomising means may be supplied as a conversion kit for an existing known carburettor to give the advantages of essentially even diametrical distribution of atomised fuel which has been metered in an amount dependent on throat suction.

WHAT WE CLAIM IS: 1. Fuel atomising means in, or constructed and arranged for use in, a carburettor having a body with a throat having a throat central axis and a throat sidewall, a valve means for controlling air flow through the throat, and fuel supply means to supply fuel to the atomising means; the fuel atomising means comprising a fuel spray tube extending or adapted to extend through the sidewall into the throat 'substantially perpendicularly to the throat central axis; wherein said fuel spray tube has jet means comprising an air bleed jet means positioned to face substantially upstream to ,wards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around the spray tube; wherein said jet means is fixed and is arranged longitudinally of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (38)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   current mutual sliding of the valve members equal amounts in opposite directions. A control arm 166 secured to an outer end of the axle 150 is connected to an operator control, for example the throttle lever, through control link means (nowt shown), with return spring means (also not shown) as required.

   The fuel metering means 135 is positioned remote from the throat 131 and within one portion of the guide means 139. As seen in Figures 8 and 10, the means 135 includes a tapered fuel needle 169 which co-operates with a longitudinal bore of the tube 134 to meter flow to the fuel orifice through the longitudinal bore which serves as a passage to conduct fuel to the fuel orifice. The needle has a tapered outer end 173, and an inner end 170 threaded on to an arm 171 extending from the valve member 138 into a clearance slot 172 in the valve guide means. The valve guide means has a parallel bore 175 adapted to receive the end 173 and the fuel spray tube

   134 passes through that portion of the valve guide means and is pierced by the bore 175.

   Thus the outer end 175 of the needle passes transversely across the longitudinal bore of the fuel spray tube to meter fuel flow therethrough.

   The end 170 has a screw driver slot and the valve guide means 139 has a clearance bore 177 to accept the screw vcr for rotatEonTh the needle for axial adjustment of the needle.

   As can be seen, movement of the valve member 138 in direction of an arrow 178 to close rhe valve moves the fuel needle inwards, increasing restriction of the fuel spray tube 134, thus decreasing flow of fuel through the metering means 135 in an amount proportional to movement of the valve members.

   A second alternative carburettor 184 shown in Figure 11 has an alternative valve assembly 1.83 having first and second valve members 18,7 and 188 formed from flat plates, outer edges of which are adapted to run in valve guide means 189 which are generally similar to the previously described valve guide means.

   The carburettor has an alternative fuel atomising means 191 characterised by a fuel spray tube 193 extending across the throat parallel to movement of the valve members. The fuel spray tube has a plurality of air bleed jets 194 and discharge jets 193 spaced along the tube on upstream and downstream sides thereof similarly to the previously described embodiments. The tube 193 is positioned adjacent to and downstream of the valve members so that the valve members close the air bleed jets as required. The first and second portion of the previously described valve members are thus eliminated, together with the passages and grooves to accept the fuel tube. Valve actuating means (not shown) such as the lever mechanism 146 of Figure 8, move the valve members concurrently in opposite directions as previously described.The fuel spray tube is positioned in turbulence produced in the air flow past the valve members to improve atonusation and mixing of the fuel. The valve mem;bers only restrict entry of ram air into the upstream facing air bleed jets,. and provide no restriction for discharge from the discharge jets on the lower surface thereof. A fuel needle 196 werates with a fuel jet (not shown) within the tube 193 and is threaded onto an arm 197 extending from the valve member 187 into a clearance slot 198 in the tube 193. Thus fuel metering is proportional to valve opening as in the previous embodiments.

   Alternatively, the first and second valve members can be fitted on the downstream side of the fuel spray tube 193 as shown generally in broken outline at 187.1 and 188d. In this alternative position the air bleed jets 194 remain unobstructed for all valve positions, and suction at some of the discharge jets 195 is reduced by the valve members when par tially closed. The alternative carburercor 184 provides a simpllified structure which could have applications where atomisation is less critical.

   Thus in all alternative embodiments as above, the fuel needle coqerates with the bore of the fuel spray tube to serve as a van- aible flow restrictor which co-operates with the fuel jet to vary degree of restriction of the fuel jet The flow restrictor is connected to the valve means so that relative position of the flow restrictor in the jet is related to volume of air flowing through the carburettor throat.

   In all embodineents, the fuel atomising means discharges fuel symmetrically relative to the throat, and, in some cases, also distributes the fuel diametrically across the throat prior to discharge.

   The fuel atomising means may be supplied as a conversion kit for an existing known carburettor to give the advantages of essentially even diametrical distribution of atomised fuel which has been metered in an amount dependent on throat suction.

   WHAT WE CLAIM IS: 1. Fuel atomising means in, or constructed and arranged for use in, a carburettor having a body with a throat having a throat central axis and a throat sidewall, a valve means for controlling air flow through the throat, and fuel supply means to supply fuel to the atomising means; the fuel atomising means comprising a fuel spray tube extending or adapted to extend through the sidewall into the throat 'substantially perpendicularly to the throat central axis; wherein said fuel spray tube has jet means comprising an air bleed jet means positioned to face substantially upstream to ,wards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around the spray tube; wherein said jet means is fixed and is arranged longitudinally of the

   spray tube so as to extend transversely across a major part of the width of the throat; and wherein the fuel atomising means is arranged so that fuel supplied to the fuel atomising means is conveyed longitudinally within the spray tube through the sidewall to a fuel orifice without mixing with the air, and is then discharged through the fuel orifice substantially mid-way along the jet means to mix within the spray tube with air entering the spray tube via the air bleed jet means to form a rich fuel and air mixture, which mixture is discharged from the spray tube via the discharge jet means.
2. 2. Fuel atomising means in, or constructed and arranged for use, in a carburettor having a body with a throat having a throat central axis and a throat sidewall, valve means for controlling air flow through the throat, and fuel supply means to supply fuel to the atomis ing means; the fuel atomising means compris ing a fuel spray tube extending or adapted to extend through the sidewall into the throat substantially perpendicularly to the throat central axis; wherein said fuel spray tube has a jet means comprising an air bleed jet means positioned to face substantially upstream to wards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around the spray tube; wherein said jet means is fixed and is arranged longitudinally of the spray tie i so as to extend transversely across a major part of the width of the throat; and wherein the fuel atomising means includes a mixing manifold extending within the spray tube along the length of the jet means to connect the air bleed and discharge jet means, and includes a fuel orifice disposed within the manifold substantially midway along the jet means to connect the manifold with a fuel passage extending longitudinally within the fuel spray tube, so that in aperation, fuel is supplied unmixed with air along the fuel pass age through said sidewall to the fuel orifice, and a portion of air flow entering the car burettor throat enters the fuel spray tube through the air bleed jet means and passes through the manifold to leave the fuel spray tube through the discharge jet means, which portion of air mixes with the fuel, discharged into the manifold via the fuel orifice, to form a relatively rich primary air and fuel mixture in the manifold, which mixture then discharges through the discharge jet means for subsequent mixing with the air in the throat downstream of the spray tube to produce a leaner air and fuel mixture for combustion.
3. 3. Fuel atomising means as claimed in claim

   1 or 2, wherein rhe fuel orifice is disposed in a position substantially sheltered from the direct flow of the air entering the air bleed iet means
4. 4. Fuel atomising means as claimed in claim 1, 2 or 3, wherein the air bleed jet means is disposed relative to the discharge jet means so that most of the air entering the fuel spray tube is caused to move in a non-linear path to the discharge jet means.
5. 5. Fuel atomising means as claimed in claim 2, or claim 3 or 4 as appended to claim 2 including fuel metering means to control the flow of fuel along said fuel passage, wherein said fuel metering means comprises a fuel flow jet in or connected to said fuel passage, and a variable flow restrictor co-operative with the fuel flow jet to vary the restriction of the latter.
6. 6. Fuel atotnising means as claimed in claim 3, wherein the variable flow restrictor is in the form of a needle having a cross-sectional area which varies along the length of the needle, the needle being longitudinally movable relative to the fuel flow jet to vary the restriction of the latter.
7. 7. Fuel atomising means as claimed in claim 6, wherein the fuel flow jet is disposed in said fuel passage, wherein the needle extends longi tudnally of the fuel spray tube and into said fuel flow jet.
8. 8. Fuel atomising means as claimed in claim 7, wherein the needle has a flat portion which is incl'ined to the longitudinal axis of the needle, said flat portion confronting the fuel orifice.
9. 9. Fuel atoonising means substantially as hereinbefore described with reference to Figlures 4 and 7, or Figures 8 and 10 of the accompanying drawings.
10. 10. A carburettor having a body with a throat having a throat central axis and a throat sidewall, a gate valve asseibly for controlling air flow through the throat, and fuel metering means to meter a supply of fuel to the atomising means; the fuel atomising means comprising a fuel spray tube extending through the sidewall into the throat substantially perpendicularly to the throat central axis; wherein said fuel spray tube has jet means comprising an air bleed jet means facing substantially upstream towards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around the spray tube; wherein said jet means is fixed and is arranged longitudinally of the spray tube so as to extend transversely across a major part of the width of the throat; and wherein the fuel atomising means is arranged so that fuel supplied to the fuel atomising means is conveyed longitudinally within the spray tube through the sidewall to a fuel orifice without mixing with the air, and is then discharged through the fuel orifice substantially mid-way along the jet means to mix within the spray tube with air entering the spray tube via the air bleed jet means to dorm a rich fuel and air mixture, which mix ture is discharged from the spray tube via the discharge jet means.
11. 1\1. A carburettor having a body with a ;throat having a throat central axis and a throat sidewall, a gate valve assembly for controlling air flow through the throat, and fuel metering means to meter a supply of fuel to the fuel atomising means; the fuel atomising means comprising a fuel spray tube extending through the sidewall into the throat substantially per pendicularly to the throat central axis; wherein said fuel spray tube has jet means comprising an air bleed jet means facing substantially up stream towards the air flow through the throat so as to receive a portion of the air flow, and discharge jet means positioned so as to be exposed to the suction which results from air flowing around" the spray tube; wherein said jet means is fixed and is arranged longi tudinally of the spray tube so as to extend transversely across a major part of the width of the throat; wherein the gate valve assembly comprises first and second gate valve mem bers cable in unison in opposite directions parallel to a valve axis substantially perpen dicular to the throat axis between open and dosed positions to open and close substantially the throat and at least part of said jet means; wherein said fuel metering means is respon sive to the position of the gate valve mem bers to meter the fuel flow; and wherein the fuel atomising means is arranged so that fuel suppLied to the fuel atomising means is con ,veyed longitudinally within the spray tube through the sidewall to a fuel orifice without mixing with the air, and is then discharged through the fuel orifice substantially mid-way along the jet means to mix within the spray ,tube with air entering the spray tube via the air bleed jet means to form a rich air fuel and air mixture, which mixture is discharged from the spray tube via the discharge jet means.
12. 12. A carburettor as claimed in claim 1'1, wherein each valve member has an inner por tion having an inner edge disposed substan tially symmetrically about the valve axis and shaped to correspond to one half of the throat sidewall in the open position, and wherein the ,valve members are arranged so that said inner portions overlap each other in the closed posi tion.
13. 13. A carburettor as claimed in claim 11 or 12, wherein the gate valve assembly serves to vary the opening of both the air bleed jet means and the discharge jet means.
14. 14. A carburettor as claimed in claim 11, 12 or 13, wherein the valve members are shaped to accommodate the fuel spray tube therebetween.
15. 15. A carburettor as claimed in any one of claims 10 to 14, wherein the fuel spray tube extends the width of the throat and the jet means extends across most of the width of the throat.
16. 116. A carburettor as claimed in any one of claims 10 to 15, wherein the air bleed jet means comprises a plurality of jets.
17. 17. A carburettor as claimed in any one of claims 10 to 16, wherein the discharge jet means comprises a plurality of jets.
18. b8. A carburettor as claimed in any one of claims 10 to 17, wherein the fuel atomising means comprises a mixing manifold disposed within the spray tube so as to connect said air bleed and discharge jet means.
19. 19. A carburettor as claimed in claim 18, wherein the fuel orifice is disposed in the manifold in a position substantially sheltered from the direct flow of the air entering the air bleed jet means.
20. 20. A carburettor as claimed in any one of claims 10 to 19, wherein the air bleed jet means is disposed relative to the discharge jet means so that most of the air entering the fuel spray tube is caused to move in a non-linear path to the discharge jet means.
21. 21. A carburettor as claimed in any one of claims 10 to 20, wherein the fuel metering means comprises a fuel flow jet and a variable flow restrictor in the form of a needle having a cross-sectional area which varies along the length of the needle, the needle being longi tudinally movable by the gate valve assembly relative to the fuel flow jet to vary the restriction of the latter.
22. 22. A carburettor as claimed in claim 21 as appended to claim 11, wherein the fuel flow jet is disposed in the fuel spray tube, wherein the fuel spray tube extends along the valve axis; and wherein the needle extends through said jet and is movable by an arm which extends through a slot in the fuel spray tube to connect the needle with one of said gate valve members.
23. 23. A carburettor as claimed in claim 21 as appended to claim 111, wherein the fuel spray tube is perpendicular to the valve axis, and is connected to the variable flow restrictor outside the throat; and wherein the needle extends transversely of the fuel spray tube parallel to the valve axis and is connected to one of said gate valve members by an arm.
24. 24. A carburettor as claimed in claim 11 in which: (a) each valve member has first and second portions, each first portion having a face with an axial groove to accept approximately one-half of the fuel spray tube, the face extending inwards from the second portion to the inner edge of the valve member; each second portion having an axially disposed passage aligned with the respective groove in the face of the first por tion so as to accept the fuel spray tube, (lib) the valve members are mounted in the valve guide means in opposite relationship to each other so that when the carburettor is closed, faces of the first portions are positioned so as to be complementary to each other and the passages and grooves of the valve members are mutually aligned for all positions of the valve members, thus permitting free sliding of the valve members along the tube to open and close the air bleed and the discharge jet means, and to permit essential closure of the valve due to overlapping of the inner portions of valve members.
25. 25. A carburettor as claimed in claim 24 in which: (a) the carburettor throat has a cylindrical sidewall, (b) the spray tube is disposed diametrically across the throat, and in which each valve member is further characterised by: (c) the first portion having a pair of spaced parallel side edges adapted to slide in the valve guide means, and the inner edge of the first portion having a concave semi-circular inner edge similar to the cylindrical sidewall of the throat, (d) the second portion having a convex semi-cylindrical inner wall spaced inwards from the inner edge of the first portion a distance on the valve axis defining valve overlap, the groove on the face of the first portion extending between mid-positions of the convex and concave end wall, thickness of the second portion being approximately twice thickness of the first portion, the valve members being disposed in the valve guide means so that when the carburettor is dosed the concave inner edge and convex inner wall of one valve member are complementary to the convex inner wall and concave inner edge respectively of the other valve member.
26. 26. A carburettor as claimed in claim 11 in which the fuel atomising means is characterised by the fuel spray tube having: (a) a plurality of air bleed jets serving as the air bleed jet means and spaced along the tube and facing generally upstream to inlet air flow so as to receive a portion of ram air entering the carburettor, (b) a plurality of discharge jets serving as the discharge jet means and spaced along the tube and positioned so as to be exposed to suction resulting from air flowing around the spray tube, (c) a manifold connecting the air bleed jets to the discharge jets and discharge jets and extending substantially across the throat; and wherein: the fuel orifice connects the manifold with the fuel metering means and is disposed sub stank'ally mid-way across the throat so as to supply metered fuel from the metering means to a mid position of the manifold to provide a generally even distribution of fuel to the discharge jets, so that, in operation, a portion of air entering the carburettor throat enters the fuel spray tube through the air bleed jets and passes through the manifold to leave the fuel spray tube through the discharge jets, which portion of air concurrently mixes initially with metered fuel passing through the fuel orifice to form a relatively rich primary air/fuel mixture in the manifold, and then discharges through the discharge jets for subsequent mixing with air in the throat downstream of the spray tube to produce a desired leaner air/fuel mixture for combustion.
27. 27. A carburettor as claimed in claim 26 in which the fuel metering means has a fuel inlet connected to a fuel supply and further includes: (a) a fuel flow jet connecting the fuel inlet with the fuel orifice, (b) a variable fuel flow restrictor co-operating with the fuel flow jet to vary degree of restriction of the fuel flow jet, the flow restrictor being connected to a valve member so that relative position of the flow restrictor in the fuel flow jet is dependent on position of the valve members.
28. 28. A carburettor as claimed in claim 27 in which: (a) the fuel flow restrictor is a needle having a cros,-'sectional area which varies along the length of the needle so that when the needle co-operates with the fuel flow jet the fuel flow is metered an amount dependent on cross-sectional area of a portion of the needle co-operating with the jet, the carburettor further including: (b) coupling means to connect the needle to the valve means, so that relative position of the needle in the jet is related to the valve position.
29. 29. A carburettor as claimed in claim 28 in which: (a) the fuel flow jet and the fuel flow restrictor are positioned within the fuel spray tube, the tube having a longitudinal slot having a length at least equal to total stroke of one valve member, (b) the coupling means is an arm extending from the needle and passing through the longitudinal slot to connect an adjacent valve member to the needle, so that axial movement of the valve member is reflected by the needle.
30. 30. A carburettor as claimed in claim 11, having valve actuating means which includes: (a) rotatable means joumalled for rotation relative to the carburettor and co-operating with the valve members so that rotation of the rotatable means moves the valve members concurrently equal amounts in said opposite directions.
31. 31. A carburettor as claimed in claim 30 in which: (a) the rotatable means is a gear wheel journalled for rotation, (b) the valve members have opposed inner faces provided with gear racks complementary to and on opposite sides of the gear wheel for forming a rack and pinion valve mechanism.
32. 32. A carburettor as claimed in claim 30 in which: (a) the rotatable means is a lever journalled for rotation at the mid-point thereof, the valve actuating means further including: (b) a pair of links having inner ends connected to the lever and outer ends constrained to move in planes parallel to the valve axis, each outer end co-operating with a respective valve member.
33. 33. A carburettor as claimed m claim 11 in which the fuel atomising means is characterised by the fuel spray tube having: (a) air bleed jets serving as the air bleed jet means, which jets are spaced along the tube and face generally upstream to inlet air flow so as to receive a portion of a ram air entering the carburettor, (b) discharge jets serving as the discharge jet means, which jets are spaced along the tube and poistioned so as to be exposed to suction resulting from air flowing around the spray tube, the discharge jet means communicating with the air bleed jet means and a supply of metered fuel so that the metered fuel and the portion of ram air are discharged simultaneously through the discharge jet means, the discharge jet means being non aligned with the air bleed jet means so that most of the air entering the air bleed jet means cannot pass directly out through the discharge jet means, and the carburettor is further characterised by: (c) the fuel spray tube extending normally to the valve axis and co-operating with the valve members so that jet means adjacent opposite portions of the.throat are progress ively closed by the valve members as the valve assembly closes.
34. 34. A carburettor as claimed in claim 11 in which: (a) the first and second valve members are generally flat plates, (b) the fuel atomising means is characterised by the fuel spray tube having a plurality of jets spaced along the tube, and the fuel spray tube is positioned adjacent the valve members so that the valve members close the jets as required, so that the jets adjacent opposite portions of the carburettor throat are progressively closed to the valve members as the valve assembly closes.
35. 35. A carburettor as claimed in claim 10 in which the fuel atomising means is characterised by: (a) the air bleed jet means extending sub stantially between the throat sidewalls, (b) the discharge jet means extending be tween the throat sidewalls and being non aligned with the air bleed jet means so that most of the air entering the air bleed jet means cannot pass directly out through the discharge jet means, (c) the fuel spray tube having an internal manifold connection with the air bleed and discharge jet means and extending along the spray tube between extreme outer positions of the air bleed jet means and the discharge jet means, and (d) the fuel orifice connecting the manifold with the fuel metering means and disposed relative to the air bleed jet means so as to be essentially sheltered from direct flow of air entering the air bleed jet means, so as to supply metered fuel from the metering means to a midzposition of the manifold to provide a generally even distribution of fuel to the discharge jet means.
36. 36. A carbauttor as claimed in claim 27 in which the needle has: (a) a tapered outer end passing through the fuel flow jet, (b) a flat portion inclined to a central axis of the needle so that cross sectional area of the needle varies along the length thereof, the flat portion being disposed adjacna: the fuel orifice so as to provide a relatively direct route between the fuel jet and the fuel orifice.
37. 37. A carburettor substantially as hereinbefore described with reference to Figures 1 to 7, Figures 8,9 and 10, or Figure 11 of the accoinpenying drawings.
38. 38. A carburettor incorporating fuel atomising means as claimed in any one of claims 1 to 9.