US2339105A - Carburetor for internal combustion engines - Google Patents

Description

, 1944- c. G. PlCKERlNG ETOR FOR INTERNAL COMBUSTION ENGINES Jan. 11

GARBUR Filed March 12, 1941 4 Sheets-Sheet 1 FIG 1 Invent! CHIYQLES GEEENBHNK P KERiNq Jm 1944- c. G. PICKERING' 3 5 CARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed March 12, 1941 4 Sheets-Sheet 2 F'IGZ.

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C'ARBURETOR FOR INTERNAL COMBUSTION ENGINES Filed March 12, 1941 4 Sheets-Sheet 3 FIGS.

3:. I II g l7 2s 7 Inocnbr CHFIRLEj GEEEHBHNK PICKERINq Jan. 11, 1944. c. G. PICKERING' 1 CA'RBURETOR FOR INTERNAL COMBUSTION ENGINES rch 12, 1941 4 Sheets-Sheet 4 Filed Ma Patented Jan. 11, 1944 CARBURETOR FOR INTERNAL COMBUSTION ENGINES Charles Greenbank Pickering, Maidstone, England, assignor to Pickering Carburetters Limited, Westminster, London, England Application March 12, 1941, Serial No. 382,991 In Great Britain March 18, 1940 8 Claims.

This invention relates to carburetors for internal combustion engines, with more especial reference to those of the kind in which a mixture of fuel and primary air is. heated and is then admixed with cold secondary air to make up the charge.

In the specification of co-pending application Serial No. 262,008 (now Patent No. 2,262,904), a method of carburation is described consisting in heating a mixture of fuel and primary air, adinitting secondary air for admixture therewith through a suction controlled aperture, regulating the heated mixture of fuel and primary air by positively varying the effect of the primary air {on the nozzle to give a relatively richer mixture as the throttle is opened and simultaneously regulating the maximum aperture for the inlet of secondary air in consonance with the throttle opening.

The particular construction of carburetor described and illustrated in the aforementioned specification employs a heated mixing chamber for fuel and primary air bolted to the carburetor body opposite the float chamber, with the mixture inlet on the atmospheric side of the main throttle. It has now been found that equally satisfactory, if not enhanced, results are obtained with a simplified and more cheaply constructed carburetor where the heated mixing chamber is separate from the carburetor body, being located, say, on the exhaust manifold and "where the mixture inlet to the induction pipe is -located on the engine or suction side of the main throttle. i In this simplified construction, a single butterfly, advantageously with its fulcrum offset from I the centre of the choke tube so as to be responsive to the engine suction serves the dual function of main throttle and secondary air inlet, the heated and regulated mixture of fuel and pri- 'mary air providing the supply when the throttle "is closed, e. g., during slow running, with or without the assistance of a pilot jet.

Q, The heated mixing chamber may be a separate flanged casting bolted direct to the exhaust manifold and is connected to the carburetor body .by feed and return conduits the cross-sectional area of the return pipe being-as described in the aforementioned specification-sufficient to accommodate the increased volume of the gases resulting from the higher temperature imparted (.to them in the heated mixing chamber but in contreriistinction to my. earlier arrangement the return pipe is connected to the main induction pipe on the engine side of the throttle.

For positively varying the effect of the primary air on the nozzle to give a relatively richer mixture as the throttle is opened, the primary air in itspreferably downwardpath through the carburetor body to the heated mixing chamber traverses part-annular passages around a rotatable jet or nozzle fed with fuel from the float chamber, rotation of this jet or nozzle towards the direction in which the primary air is flowing increasing the effect of such primary air to give a relatively richer mixture and the rotatable nozzle being connected to the main throttle through an appropriate linkage or cam thus to effect a richening of the mixture as the throttle is opened.

In the annular space or passage around the nozzle, a pair of segments are disposed and are partially rotated so as to regulate the mixture and to function as a choke for starting purposes, while axially of the nozzle there may be placed a needle or other valve controlling the total fuel supply.

As aforementioned the inlet of the mixture passing to the engine from the heated mixing chamber enters the induction pipe on the suction or engine side of the main throttle. This valve is conveniently a butterfly valve-with its fulcrum offset in relation to the choke tube when the throttle lever is closed the butterfly valve is held closed by co-operating abutments on the lever and the throttle spindle respectively.

' When the lever is moved to open the throttle, say

from an idling position, the suction is insufficient to open the butterfly valve and owing to rotation of the jet a rich mixture is fed to the engine as desired, while on the suction increasing the valve opens as far as it is permitted to do so by the position of the main throttle lever to admit a proportionof cold secondary air as required.

Preferably, a resilient connection is interposed between the controlling cam and the main throttle valve spindle, affording the latter the facility of opening still further to a limited extent should the suction be sufficient as when the throttle lever or pedal is eased from a wide open position so that the mixture is still further weakened by the increased proportion of secondary air, and in conjunction with this resilient connection a dashpot may also be furnished to prevent fluttering of the throttle or valve.

Thevinvention will be further described with reference to the accompanying drawings which illustrate by way of example the preferred embodiment of carburetor and in which Fig. 1 is a front elevation of the carburetor with the float chamber removed.

Fig. 2 is a cross-section through the mixture regulating jet on the line IIII of Fig. 3 looking from the right,

Fig. 3 is a vertical section looking from the rear of the carburetor, Fig. i is a general view to a smaller scale showing the carburetor and the preferred form of exhaust heated mixing chamber and Referring now to the drawings, 6 generally designates the carburetor body, having a primary air inlet 2, main air inlet 3 and mixing chamber l in which is disposed a venturi or diffuser tube 5.

The throttle or butterfly valve disposed in the main inlet 3 is designated 5 being shown open in the full lines and in its closed position by the dotted lines and is carried by a spindle I which in this embodiment is offset from the centre of the main inlet 3 for the purpose hereinafter more fully explained.

Formed integral with the body I of the carburetor is a boss 8 housing a rotatable nozzle I1 and its associated mixture regulating mechanism, the primary air passing downwardly through the inlet pipe 2 and the hollow centre of the boss 8 through a flange connection 9 to a pipe I which leads to the heated mixing chamber 44 shown as a jacket surrounding the exhaust manifold 45 although it may be of any conventional form, or resort may be had to a volute chamber similar to that described in the specification of co-pending application Serial No. 262,008 or the chamber may be electrically heated as desired. The heated and volatilised mixture of fuel and primary air returns to the carburetor through a rising pipe H which has a flange connection I2 bolted to the carburetor body I and which opens to the interior of the mixin chamber 4 through a port I3 and the aforementioned venturi or dilfuser tube 5.

M represents a throttle lever mounted on the spindle l and connected through appropriate linkage to the accelerator pedal, hand lever or -.other conventional control, While I represents a cam also carried by the throttle spindle with which cam co-operates an arm I6 mounted on a stem 29 of the rotatable jet or nozzle I! to richen the mixture as the throttle is opened.

The construction of the parts associated with resenting the main jet which is replaceable and to which fuel is fed from a float chamber I9, through a bracket 23 having a central cavity 2I closured by a screw plug 22, removal of the latter giving access to the jet. 23 and 24 are bolts securing the bracket 23 carrying the float chamber iii to the boss 8 of the carburetor body I, these bolts serving also to secure the rotatable let I? with its operating mechanism and its associated choke lever 33 for starting purposes.

The boss 8 is formed with a circular bore 25 into which open the primary air inlet 2 and from which a short duct 2a communicates with the pipe I3 passing the mixture of fuel and primary air, to the heated mixing chamber.

Within the circular bore 25, that is to say, in the space between the rotatable jet I1 and circular wall of the bore are disposed a pair of segments 26 and 2'! forming the extremity of a bush 23 surrounding the. stem 29 of the rotating nozzle II', the segments being partially rotated to regulate the effect of the primary air on the nozzle to vary the mixture or to function as a choke for starting purposes. The aforementioned lever 30 is provided to rotate the bush 28 and segments 26 and 21.

The rotatable nozzle I1 is shown furnished with two radial apertures 3| and 32 (see Fig. 3) to facilitate dissemination and volatilisation of the fuel particles in the primary air stream passing to the heated mixing chamber 44 although a single aperture may be utilised and as will be understood rotation of the nozzle so that its apertures 3I and 32 move towards the direction in which the primary air is passing downwardly through the inlet 2 and pipe l0 increases the effect of such primary air to give a relatively richer mixture, this movement being effected by clockwise movement of the arm I6 as the throttle lever I4 is moved in a counterclockwise directionv to open the butterfly valve 6, against the resistance of a spring 39.

In the particular embodiment illustrated, the butterfly 6 serves both as the main throttle and to regulate the supply of secondary air, and to this end its spindle I is offset from the centre and the inlet pipe 3 so that a larger area of the valve is open to the engine suction on one side of the spindle I than on the other, and conse-- quently the suction tends to open the valve.

Moreover, the throttle lever I4 is not secured to the spindle 'I but is a riding fit thereon being free to move between abutments 33 and 34 on the cam I5. This cam is also a free fit on the spindle I and as will be seen more clearly from Fig. 1, a short arm 35 is secured to the end of the throttle spindle I externally of the cam I5 and to co-operate with thi arm there is furnished on the surface of the cam the second pair of abutments 36 and 31 which allow limited relative movement between the arm 35 and the cam I5, a spring 38 being interposed between such arm and the abutment 37 so that the arm is normally maintained in contact with the other abutment 36. Limited relative movement is thus permitted (a) between the throttle lever I 4 and the cam I5 within the range afforded by the abutments 33 and 34 and (12) between the cam I5 and the spindle I of the butterfly 6 within the range afforded by the abutments 36, 37.

With the throttle lever I4 in the position illustrated in Fig. 1, the cam I5 is pushed clockwise by the abutment 34 to the zero (weak position) of the rotatable nozzle I1 and the spring 38 urges the arm 35 on the throttle spindle into contact with the abutment 33 thus to close the throttle Valve 6.

On the lever It being moved counter-clockwise, e. g., by depression of the throttle, the spring 38 pushes the cam It in a counter-clockwise direction and thus moves the nozzle arm I6 to a position giving a richer mixture, maintaining the abutment 34 against the lever I4. If the suction is sufiicient the valve 3 will open to a limited extent against the resistance of the spring 38 to admit a proportion of cold secondary air into admixture with the heated mixture 01' fuel and primary air returning upwardly through the pipe I I and port I3 into the mixing chamber 4 and choke tube 5 which has circumferential distributing apertures 5a to ensure a uniform admixture.

Further movement of the throttle lever I4 in the counter-clockwise direction positively opens the butterfly valve 6 and as will be appreciated,

if the suction is sufficient, the valve is afforded an opportunity of opening still further against the resistance of the spring 38.

During the return, i. e., clockwise movement of the throttle lever l4 such as would occur on deceleration, the conditions are reversed, that is to say, the lever H! in contact with the abutment 34 moves the cam I5 in a clockwise direction thus releasing the nozzle arm [6 for the spring 39 to rotate the nozzle H, to weaken the mixture, and the spring 38 interposed between the abutment 31 and the short arm 35 on the throttle spindle l gradually closes the butterfly valve 6, although under these conditions the suction would normally be sufficient to cause the butterfly to lag in closing, thus allowing the admission of a higher proportion of cold secondary air through the main inlet 3, while the primary mixture passing from the nozzle [1 through the heated mixing chamber to the port I3 is being simultaneously weakened.

In the event of the suction being insuflicient to open the butterfly 6, the spring 39 co-operating with the lost-motion connection between the lever 14 and the cam 15 prevents the primary mixture which constitutes the sole supply under these conditions from becoming too rich.

To obviate any tendency of the butterfly valve 6, which as just described is not fixed for movement with the throttle lever M, to oscillate or flutter in response to momentary fluctuations in the engine suction, a dash-pot stabiliser is provided and comprises a dashpot cylinder 40 pivoted to the main body of the carburetor at 4|, and having a piston rod or plunger 42 extending upwardly and coupled to an arm 43 on the end of the spindle 1 remote from the lever l4.

By the present invention an improved and simplified form of carburetor is obtained.

I claim:

1. A carburetor for internal combustion engines including a heated mixing chamber for fuel and primary air, a rotatable fuel jet or nozzle having fuel apertures on its peripheral surface, part annular passages around said nozzle traversed by the primary air on its way to the heated mixing chamber, a secondary air inlet, a throttle for said inlet and a lever regulating aid throttle,

and means linking the throttle lever to the nozzle so as to effect rotation of the latter so that its apertures move towards the direction in which the primary air is flowing as the lever is moved to open the throttle or butterfly whereby a relatively richer mixture is obtained under these conditions.

2, A carburetor according to claim 1 including a suction operated butterfly valve regulating the supply of secondary air for admixture with the primary air and fuel mixture and an offset stem for said valve wherein a resilient connection is interposed between the stem of the butterfly and the means linking the throttle lever with the rotary nozzle.

3. A carburetor according to claim 1 including a secondary air inlet, an offset pivot stem and a butterfly valve mounted on said stem for partial rotation to control the passage of air through said inlet, wherein the linkin means comprises a cam co-operating with an arm for rotating the nozzle said cam having abutments between which rides a projection on the butterfly stem with the interposition of a spring urging the butterfly valve in the closing direction.

4. A carburetor according to claim 1 including a secondary air inlet, an offset pivot stem and a butterfly valve mounted on said stem for partial rotation to control the passage of air through said inlet, wherein th linking means comprises a cam co-operating with an arm for rotating the nozzle said cam having abutments between which rides a projection on the butterfly stem with the interposition of a spring urging the butterfly valve in the closin direction and a second pair of abutments on said cam adapted to be engaged by the throttle lever to operate the cam said second abutments permitting a limited relative movement between the throttle lever and the cam for the purpose specified.

5. In a carburetor means for varying the fuelair mixture comprising a radially disposed nozzle for fuel a passage surrounding said nozzle and a pair of segments defining a part annular space around such nozzle for the passage of air and means to rotate the segments in relation to the nozzle thus to regulate the mixture and to function as a choke for starting purposes.

6. A carburetor for internal combustion engines having a heated mixing chamber for fuel and primary air, a throttle valve for secondary air, a lever for said throttle valve, the mixture of fuel and primary air passing to the induction pipe on the engine side of such throttle valve and means for positively varying the effect of the primary air on the nozzle to give a relatively richer mixture as the throttle lever is opened, comprising a rotatable jet or nozzle traversed by the primary air and having a peripheral fuel aperture whereby rotation of the jet to move the aperture towards the direction in which the primary air is flowing, richens the mixture.

7. A carburetor having means for positively varying the effect of the primary air on the nozzle according to claim 6 wherein the nozzle is cylindrical and a plurality of fuel apertures is furnished in different radial positions on the peripheral surface of the nozzle.

8. In a carburetor having means for positively varying the effect of the primary air on the nozzle according to claim 6 the provision of segments defining a part circular passage for the primary air around the nozzle such segments being rotatably adjustable to vary the effect of the primary air on the nozzle to regulate the mixture.

CHARLES GREENBAN K PICKERING.

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