US2711886A - Downdraught carburetors - Google Patents

Description

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J. BlvER DOWNDRAUGHT CARBURETORS Fic - 4 4 4 O 9 2 Mu. A f v f 4A w 1 1 f [LMI 3 /w 5 l. l .1 l \5 M|m| 4 7 3 l 5 3 G /7 V IH `Fume 2%, 1955 Filed June 12, 1951 June 28, 1955` J. BlvER ZHLSS DOWNDRAUGHT CARBURETORS Filed June 12, '1951 2 sheets-sheet 2 sited bidi@ DWNDRAUGHT CARBURETORS -iean Biver, Paris, France, assigner to Societe dEtudes de Carburation lAutomobile et lAviation-S. E. C. A. A., Levallois-Perret, France Application Enne 12, 1951, Serial No. 231,206

6 Claims. (Cl. 261--75) iy falling into the mixing chamber have the disadvantage of causing jerks in the running of the engine at certain speeds.

The object of the invention is to do away with this discontinuous tiow by successive drops and to produce a continuous fiow of fuel under running conditions wherein drops of fuel would have a tendency to be formed. By means of the invention, the ruiming of the engine is rendered more regular and its .smoothness is increased.

According to the invention a downdraught carburettor for internal combustion engines supplied with liquid fuel comprises a mixture passage wherein the tiow takes place downwardly, a mixing chamber in said passage and a tubular outlet for primary mixture wherein the ow takes place and opening into said mixing chamber, a deiiector forming a substantially continuous path between the outlet edge of said tubular outlet and the wall of said mixing chamber being so disposed that it guides the liquid particles running along the walls of the said outlet towards the wall of the said mixing chamber.

By a deflector forming a substantially continuous path, it is meant that the interruptions which might exist in the said path, have a width less than the diameter of a drop of the liquid fuel. Thus, the formation of a drop along the lower edge of the tubular outlet for primary mixture is impossible. The liquid fuel spreads itself as a thin and continuous film on the surface of the said deiiector and flows regularly and without jerks towards the wall of the mixing chamber.

In a preferred manner of embodiment of the invention, the said deilector comprises several arms interposed between the said tubular outlet and the wall of the mixture passage.

Preferably, the said arms join in their lower part to an annular edge projecting slightly relative to the downstream part of the mixture passage.

Preferably the said arms have a considerable slope along the whole of their length and may be formed with a vertical part followed by a sloping part.

The upper extremities of the said arms may be connected together by a ring disposed opposite to the said tubular outlet in immediate proximity to the latter and may be connected to the said ring by curves.

The lower extremities of the said arms may also be connected to a ring.

rlibe said deiiector may form a separate member, the said ring connected to the lower extremities of the said arms being fastened between a projection made in the Patented x.lune 28, 1955 body of the Carburettor and an added choke tube surrounding the said tubular outlet.

In a modification, the said arms are formed by ribs forming one with the added choke tube surrounding the said tubular outlet.

The said ribs are preferably hollowed at their upper part over part of their height so as to reserve a free annular passage in the waist region of the said choke tube.

In combination with the various embodiments above mentioned, the said tubular outlet advantageously consists of a tube having approximately the form of a venturi open at its upper part to receive primary air and receiving aerated fuel by a lateral conduit, a rib with an inclined lower edge being transversely disposed in the said tube in the plane of the said lateral conduit and above the opening of the latter.

The description which follows, taken in connection with the accompanying drawings, will give, by way of example, a ready understanding of several ways of realizing the invention.

Fig. l illustrates, in a vertical section, a Carburettor embodying the invention.

Fig. 2 illustrates, on a larger scale, a section on line lI-iI of a part of the Carburettor illustrated in Fig. l.

Fig. 3 illustrates, in a vertical section, a modification of the embodiment of the members illustrated in Fig. 2.

Fig. 4 illustrates in a section on line IV-IV the arrangement illustrated in Fig. 3.

Fig. 5 illustrates in a vertical section a modified embodiment of the arrangement illustrated in Fig. 3.

Fig. 6 illustrates a section on line Vl-VI of the arrangement illustrated in Fig. 5.

The Carburettor illustrated in Fig. 1 is, as a whole, a Carburettor of the usual type comprising a body 1 and a cover 2. A oat chamber 3 formed in the body 1 receives the liquid fuel through a passage 4 connected to a fuel supply conduit 5 through a filter 6. The fuel rises to level X-X in the float chamber 3 owing to a float 7 controlling a needle valve 8 which co-operates with a seat 9. Float chamber 3 feeds a well iii through a passage 11 and a calibrated jet 12.

The Carburettor comprises a mixture passage 13 fed with air through an air intake 14 and connected, at its lower part to the induction pipe of the engine (not illustrated). The Carburettor is fixed to the said induction pipe by means of a flange 15.

The Carburettor is of the downdraught type, that is to say that the mixture flows downwardly in the mixture passage 13. A mixing chamber 16 formed in the mixture passage 13 receives a primary mixture from a tubular outlet 17 wherein the flow takes place downwardly and having approximately the form of a venturi. The tubular outlet 17 is designated, in accordance with usage, by the term venturi The venturi 17 is fed with primary air at its upper part 18 by the air intake 14 and with aerated fuel by a lateral conduit 19.

The conduit 19 is fed with fuel by the well 1t) with which it communicates. The fuel supplied by the well 16 is aerated by means of a tube Ztl pierced with holes 21 in stages and fed with air at its upper part through an orifice 22 opening into a space 23 which communicates with the air intake 14. The conduit 19 receives supplementary emulsion air through an orifice 2d also opening into the space 23.

The upper part of the float chamber 3 itself communicates with the space 23 through an oriice 25.

The quantity of mixture delivered to the engine is controlled by a throttle valve 26.

When the throttle Valve is in the neighbourhood of the closed position, the fuel is supplied by a slow running arrangement of the usual type comprising for example an idling hole 27 adjusted by means of a screw valve 2S and a progression hole 29 opening into the mixture passage in the neighbourhood of the edge of the throttle valve 26 when the latter is closed. The orifices Z7 and 29 are supplied with aerated fuel through a channel 30 receiving air through an air-bleed orifice 31 communicating with the air intake 14 and fuel through an idling jet 32 communicating with the well through a duct 33.

The venturi 17 opens into the waist 34 of a choke tube 35 mounted in the body of the Carburettor and having approximately the form of a venturi. A rib 36 comprising an inclined edge 37 in its lower part is disposed across the venturi 17 in the plane of the lateral aerated fuel conduit 19.

According to the invention, a deflector 3S is disposed in the mixing chamber 16 and its detail is clearly shown in Fig. 2, where the air intake 14 is supposed to be removed.

The deflector 3S comprises a lower ring 39 and an upper ring 4t) connected together by several arms 41. In the drawing, a deflector with four arms has been illustrated, but the number of arms may be different. The lower ring 39 rests on a shoulder 4Z of the body of the Carburettor and is secured between this ring and the choke tube 35.

The outlet edge 43 of the lower ring 39 has a diameter slightly less than the diameter of the downstream part 34 of the mixing passage. These arms comprise a vertical part followed by a sloping part of which the slope is considerable. The upper edge 46 of the ring 40 is opposite and immediately adjacent the outlet edge 47 of the venturi 17. However, preferably, contact between the two edges 36 and 37 is avoided, on the one hand because a narrow slot 48 between these two edges allows of factory and fitting tolerances and on the other hand because such a slot improves the functioning of the device as will be hereinafter explained. The slot 4S should have a width less than the diameter of the drops of fuel susceptible of being formed along the edge 47.

The deflector 48 may be a die cast member or a member cut out and pressed.

The operation of the device is as follows:

When the engine is idling, the throttle valve 26 being almost completely closed, the suction at the outlet of the venturi 17 is practically nothing and the engine is fed with fuel through the idling hole 27 and the progression hole 29.

When the throttle valve 26 is slightly opened, a slight depression is created in the waist 34 of the choke tube 35 and said depression initiates a flow of fuel in the venturi 17, the function of the progression hole 29 being to ensure the continuity between the fuel feed through the slow running arrangement and the fuel feed through the venturi 17 which forms the normal running device.

Under the effect of this slight depression, the fuel is sucked in from the well 10 into the venturi 17 through the lateral conduit 19, but the velocities of flow are too small for the fuel to be suitably atomised by the emulsion air entering through the hole 24 or by the primary air admitted through the inlet 18 of the venturi 17. The fuel then has a tendency to run in the form of a liquid skin along the internal wall of the venturi 17. In the absence of the deffector 38, the fuel would tend to assemble in a large drop at a point on the lower edge 47 of the venturi 17 and the drop would be detached after having reached a certain size. It has been ascertained that successive drops of fuel thus falling into the mixture passage give rise to discontinuous feed of the engine, which produces jerks in the running of the latter.

By means of the deector 38, if a drop of fuel tends to be formed at a point on the lower edge 47, this drop will make contact with the upper edge 46 of the ring 40 of the deflector before being sufficiently heavy to be detached. The fuel forming the growing drop then spreads in a thin layer and flows by gravity along one of the arms 41 of the deflector 38 towards the wall 44 of the mixing passage. In practice as the fuel is sucked in in a continuous manner into the venturi 17 through the duct 19, once the flow has been started along one of the arms of the deflector 38, this flow goes on in a continuous manner. The detlector 38 forms a continuous path for fiow of the liquid fuel, in spite of the interruption formed by the slot 48 between the lower edge 47 of the venturi 17 and the upper edge 46 of the deflector 38, the two edges of the slot being connected by a liquid bridge, and the defiector guides the ow of the liquid fuel towards the wall 44 of the mixture passage.

By means of the slot 4S when a drop tends to be formed at a point on the edge 47 of the venturi 17, this drop, under the effect of the capillary forces, spreads as a ring over all the circumference of the slot 4S or at least over a large part of this slot, so that the fuel tends to flow along all the arms or at least along several arms of the defiector, whilst, if the edges 46 and 47 of the deflector 38 and of the venturi 17 were in contact, the flow would perhaps have a tendency to take place along a single arm of the deflector. The slot 43 has therefore for effect more regularly to distribute the fuel over the periphery of the wall of the mixture passage.

Experiment has shown that the device is more emcient if the outlet edge 43 of the deflector is of a diameter slightly less than the diameter of the passage 44, than if this outlet edge 43 were to be of the same diameter as the passage 44, Although the phenomenon has not been analysed it may be supposed that a projecting edge 43 has for effect to give rise to a circular spread of liquid fuel along the said edge and thus to favour the distribution of the fuel on the periphery of the mixture passage 44.

The connecting curves 45 between the arms 41 of the deflector and the upper ring have for effect to avoid the formation of drops at certain points on the lower edge of the said ring, which formation is to be feared if this lower edge were horizontal and connected by a sharp angle with the free arms 41.

The rib 36 disposed across the venturi 17 has the following function. Under certain running conditions where the suction is still insuilicient to give rise to a satisfactory atomisation of fuel in the conduit 19 and the venturi 17, but where it suffices already to give rise to the division of the fuel in the form of drops in the conduit 19, these drops may be drawn by the current of air into the venturi 17 without touching the wall of the latter, thus producing the disadvantages mentioned above. Because of the rib 36, such drops are projected onto the lower oblique wall 37 of the said rib which channels them towards the wall t of the venturi 17. This rib, known per se, is advantageously combined with the defiector which forms the main subject of the invention, because it avoids the projection of the drops into the interior of the venturi, whilst the deflector avoids the formation of drops along the lower edge of the venturi.

Owing to the deflector according to the invention, the running of the engine is rendered more regular at the speeds whereat the flow of fuel would have a tendency to be formed by drops. Accelerations are also improved, because, when accelerating, the output of fuel by the main feed arrangement has a tendency to start drop by drop and there again the ow drop by drop is displaced by a continuous flow.

As a general rule, in known carburettors, effort is made to prevent particles of liquid fuel coming into contact with the wall of the mixture passage, in order to avoid formation of a liquid skin on said wall, whilst, according to the present invention, on the contrary, effort is made under certain running conditions, to guide the drops of. fuel towards the wall of the mixture passage. l t will be noted that in the arrangement illustrated in Figs. l and 2 the drops of fuel are only led towards the wall of the mixture passage at small depressions. When the depression is substantial, that is to say under normal running conditions, the atomisation of the fuel is suicient for the latter not to iiow in the form of a liquid sheath along the walls of the venturi 17. Furthermore the velocity of the mixture in the mixing chamber 16 sutlcies for the liquid particles, which would be able to ow along the arms 41 of the deilector to become detached from these arms before reaching the wall 44 of the mixing passage. The arrangement of the arms 41 formed by a vertical part followed by a sloping part favours the detachment of the liquid particles at the end of the vertical part of the said arms under the effect of their vis viva.

In the modification illustrated in Figs. 3 and 4 the deflector 49 forms one with the body of the added choke tube 50 which rests on the shoulder 42 of the body of the Carburettor.

The deiiector properly so called is formed by ribs 51 connecting the wall of the choke tube S0 to a ring 52 of which the upper edge is disposed opposite and immediately adjacent the lower edge of the venturi 17. The lower edge of the ring 52 comprises curved recesses 53 between the successive ribs 51.

Preferably, the outlet edge 54 of the choke tube 50 has a diameter slightly less than the diameter of the downstream part of the mixture passage like the outlet edge 43 illustrated in Fig. 2.

The choke-deiiector unit 51)-49 may be die cast in one piece.

The operation of the arrangement illustrated in Figs. 3 and 4 is exactly like the operation of the device illustrated in Figs. 1 and 2.

The ribs, like those illustrated in Figs. 3 and 4, have the disadvantage of partially obstructing the choke tube 50 in the region of the waist of the latter.

ln the modiiication illustrated in Figs. 5 and 6, the ribs 55 are recessed at their upper part over a part of their height at 56 so as to reserve an annular free passage 57 in the neighbourhood of the waist 58 of the choke tube 59.

The invention is in no way limited to the embodiments described above by way of example and these embodiments may be modified in detail without thereby departing from the scope of the invention.

Mainly, the latter is not bound up with a particular form of embodiment of the tubular outlet' of the primary mixture. As has been indicated above, a primary mixture outlet in the form of a venturi traversed by a rib with an inclined lower edge is advantageously combined with the deector which forms the principal subject of this invention, but this combination is in no way imperative. The rib 36 which has been illustrated across the venturi 17 maybe done away with, or indeed the whole of the ..1

lateral conduit 19 and of the venturi 17 may be replaced by a simple shouldered tube terminated by a vertical part forming the tubular outlet for the primary mixture. The air inlet 1S of the venturi 17 then being done away with, the primary air would be all supplied through the orifice 24 and the holes 21 for emulsion air (Fig. 1).

The defiector itself may be modified in its embodiment. In particular, in the embodiment illustrated in Figs. 1 to 6, the ring connecting together the upper ends of the different arms of the detiector may be done away with. Also, in the embodiment illustrated in Figs. 1 and 2, the ring connecting the lower ends of the various arms of the dellector may be done away with.

I claim:

l. ln a downdraught Carburettor for internal combustion engines supplied with liquid fuel, comprising a mixture passage wherein the flow takes place downwardly, the combination of a mixing chamber in said mixture passage, a tubular outlet for primary mixture wherein the flow takes place downwardly and opening into said mixing chamber, a fuel passage and a primary air inlet both connected with said tubular outlet, an annular edge in the lower part of the wall of said mixing chamber (ifi forming a slight projection relative to the downstream part or" said mixture passage, and a plurality of arms connected at their lower ends with said annular edge and Jforming a substantially continuous path between the outlet edge of said tubular outlet and the wall of said mixture passage for guiding the particles of liquid howing along the walls of said outlet towards the wall of said mixture passage.

2. In a downdraught Carburettor for internal combustion engines supplied with liquid fuel, comprising a mixture passage wherein the flow takes place downwardly, the combination of a mixing chamber in said mixture passage, an added choke tube in said mixing chamber, a tubular outlet for primary mixture wherein the iiow takes place downwardly and opening into said added choke tube, a fuel passage and a primary air inlet both connected with said tubular outlet, and a deector comprising an upper ring disposed opposite said tubular outlet immediately adjacent the latter, a lower ring secured between a projection provided in the wall of said mixing chamber and said added choke tube, and a plurality of arms connecting said upper and lower rings.

3. In a downdraught carburettor for internal combustion engines supplied with liquid fuel, comprising a mixture passage wherein the flow takes place downwardly, the combination of a mixing chamber in said mixture passage, a venturi within said mixing chamber, a lateral conduit for aerated fuel opening into said venturi, a fuel passage and a primary air inlet both connected with said lateral conduit, a rib with a lower inclined edge disposed transversally in said venturi in the plane of said lateral conduit and above the opening ot the latter, and a deector having a plurality of arms interposed between said venturi and the wall of said mixing chamber and forming a substantially continuous path between the outlet edge of said venturi and the wall of said mixing chamber for guiding the particles of liquid iiowing along the Walls of said venturi towards the wail of said mixing chamber.

4. The invention defined in claim 1 wherein said arms are formed with a vertical part followed by a sloping part.

5. ln a downdraught Carburettor for internal combustion engines supplied with liquid fuel, comprising a mixture passage wherein the flow takes place downwardly,

the combination of a mixing chamber in said mixture passage, a tubular outlet for primary mixture wherein the ow takes place downwardly and opening into said mixing chamber, a fuel passage and a primary air inlet both connected with said tubular outlet, and an added choke tube in said mixing chamber surrounding said tubular outlet and having at its lower part an annular edge forming a slight projection relative to the downstream part of said mixture passage and a plurality of internally projecting ribs connected at their upper ends with a ring disposed opposite said tubular outlet immediately adjacent the latter.

6. The invention defined in claim 5, wherein said ribs are hollowed out at their upper part so as to provide a free annular passage in the waist region of said choke tube.

References Cited in the iile of this patent UNITED STATES PATENTS 1,453,490 Bessom May l, 1923 1,456,135 Lidholm et al May 22, 1923 1,590,059 Reents et al. June 22, 1926 1,850,532 Chambers Mar. 22, 1932 2,059,657 Sager Nov. 3, 1936 2,091,436 Emerson Aug. 31, 1937 2,127,444 Emerson Aug. 16, 1938 2,134,021 Barnes Oct. 25, 1938 2,557,111 Jorgensen et al. June 19. 1951

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