CA1092913A - Carburetor - Google Patents

Abstract

CARBURETOR
Abstract of the Invention A carburetor for internal combustion engines having a stationary metering element and a rotor assembly which is movable and rotatable with respect to the metering element to control the fuel-air mixture and to thoroughly admix the fuel and air before its passage to the engine.

Description

Background o~ the Inventlon ;
Carburetors ~hich are no~ ~n general use ~or lnternal combustion engines emplo~ conventional ~enturl kype ~uel-air ratio control s~stems which are quite complex ln construction and ad~ustment. This t~pe o~ s~stem is such that it can be designed ~or maximum e~icienc~ onl~ within a relatively limited range ~ith the result that e~ficienc~ is sacri~lced outside such range. Additionall~ 3 a supplemental supply o~
fuel is in~ected under certain conditions, such as a rapid acceleration ~rom idling position, ~hlch ~urther complicates the apparatus involved in the s~stem. The net result o~ these conventional s~stems is ine~ficient combustion which not only affects engine operation but also causes some of the unburned ~uel to be discharged through the engine exhaust.
The above deficiencies in the carburetors now in use have long been recognized and various attempts have been made to design car~uretors ~herein the fuel supply i5 automatically - ad~usted to actual air intake regardless of the position o~ the air flo~ control means. These prior art car~uretors have taken the ~orm o~ a ~uel val~e ~hich coacts in one manner or another ~ith an air ~lo~ control assembly 50 that theoreticall~, any motion o~ the air flo~ control assembl~ also ad~usts the ~lo~
o~ ~uel accordingl~. Additionall~, some o~ these de~ices ha~e rotated the air flo~ control assembl~ and ha~e discharged the .. . .. -. ...
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fuel into the air stream to enhance the mixture of the fuel with the in-coming air. Examples of these prior art carburetors are exempliEied by l).S. Patents No. 1,439,573, 1,484,577, 3,2~5,374 and 3,339,900. Although showing the basic concept of an air flow assembly controlled by engine suct-ion and coacting with a fuel valve, these prior devices have failed to accomplish accurate control of fuel-air mixture for various reasons, such as improper mounting of the air flow control assembly or of the fuel control valve, undesirable location of fuel and air inlets or an ineffective shape of the fuel-air mixing chamber. As a result, none of the prior art carbur-etors accomplish proper control of the air-fuel mixture throughout all ranges and loads of engine operation.
Summary of the Invention .
One of the objects of this invention is to provide a carburetor in which the fuel supply is automatically adjus*ed to the actual air intake regardless of *he position of the air flow control means.
According to the invention there is provided a carburetor for an internal combustion engine having, a housing with a fuel-air mixing chamber in a first portion and a fuel inlet in a second portion, an air inlet into the mixing chamber, a rotor assembly movable axially within said housing and coacting with the air inlet to substantially close the same when said assembly is at the end of its travel in one direction relative to the housing and to open said inlet upon movement of the assembly in the opposite direct-ion of travel, resilient means between the rotor assembly and the housing for urging the rotor assembly in that direction which substantially closes ; the air inlet, a metering valve within the housing having a metering element mounted in a stationary position in the housing and a metering orifice car-ried by the rotor assembly, means for conducting fuel rom the fuel inlet to said metering valve, the metering orifice of the rotor assembly coacting with the stationary metering element to control passage of fuel past the valve in accordance with the relative axial position of the rotor assembly

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with respect to the housin~, such axial position of the rotor assembly being responsive to the air pressure differential across the rotor assembly, means for conducting the fuel which passes the metering valve through the rotor assembly and into the mixing chamber to mix with the admitted air, whereby axial position of the rotor assembly determines the relative volumes of air and fuel to form the fuel-air mixture which is thereafter conducted to the engine being operated, and characterized by means for positively guiding the rotor assembly i.n its axial movement within said housing to maintain accurate axial align-ment of the metering orifice about the metering element through-out the entire axial travel of the rotor assembly with respect to said metering element, said means for positively guiding said rotor assembly including an elongate non-deformable guide surface forming part of the rotor assembly located between :
the rotor assembly and the metering element and having sliding contact with the exterior of the metering element, whereby said elongate guide surface functions to prevent any lateral move-ment of the rotor assembly relative to said metering element during movement of the rotor assembly with respect to the element. ~

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- 3 -,. ~ ,, ~ ther obJects and ad~antages o~ the present invention are hereina~ter set forth and are explaIned in dekail wlth re~er-ence to the drawings wherein:
~ igure 1 is a side ele~ation o~ a carburetor constructed in accordance with the in~ention and showing an air cleaner mounted thereon;
~ igure 2 is a plan view o~ ~igure 1 with the air cleaner omitted and sho~ing certain parts in dotted lines and other parts partiall~ in elevation, ~igure 3 is a vertical sectional ~Ie~ taken on the line 3-3 of ~igure 1 with the rotor assembl~ raised and the ~uel inlet val~e closed;
~igure 4 is a partial vertical sectional ~iew similar to ~igure 3, ~ith the rotor assembly mo~ed downwardl~ and the fuel assembl~ moved down~ardl~ and the fuel inlet ~al~e open;
~igure 5 is a horizontal cross-sectional ~iew taken on the line 5-5 o~ ~igure 3;
~igure 6 is a plan view of the rotor illustrating the disposition o~ the fins on the upper surrace; and . ~ :
~igure 7 is a detail ~iew of the last motion connection between the butter~l~ val~e sha~t and the primer rod.
Description_o~ Pre~erred Embodiment . . . _ _ In the drawings, the numeral 10 designates the lower portion o~ the carburetor housing which is generally cylindri-cal in shape and formed G~ two sections connected ~ suitable scre~s. The upper portion lOa o~ the carburetor housing is o~
reduced diameter and have the bore lOb ~ormed therein; also ~ ~
said portion is provided with a circular ~lange 11 at its upper ~-end which is connected to the lower portion o~ the housing through elongate tie bolts 12. ~he tie ~olts extend through spacer sleeves 13 and 13a which are interposed between ~lange 11 and said lower portion 10 o~ the housing. ~n air cleaner 14

-4-of an~ suitable design is mounted to surround the housing and is o~ usual construction to ~ilter the air which ~ill be drawn into the carburetor. ~n~ suita~le rneans (not shown~ may be utilized to secure the air cleaner in place.
The lo~er portion Or the housing 10 has an adapter flange 15 ~hich is adapted to be connected to the intake mani~ld o~
the engine ~not sho~n~. ~s is clearl~ shown in ~igure 3, the ~lange 15 and lo~er end o~ the housing has an outlet bore 16 ~hich estaalishes communication bet~een the engine mani~old and a fuel-air mixing chamber 18. Said chamber is de~ined b~v an overhanging inclined ~all surface 18a, an inclined wall sur~ace 18b o~ increasing diameter, and an inclined ~all sur~ace 18c o~
decreasing diameter; the ~all sur~ace 18c terminates at the upper end o~ the bore 16. A circular air inlet 18d is located in the central portion of the upper overhanging wall of the lo~er housing.
Any suitable throttle val~e ~hich is herein sho~n as the usual butter~l~ valve 19 is mounted upon a throttle valve sha~t 20, one end o~ ~hich has a connector 21 for connecting said sha~t with the usual accelerator- control o~ the engine to be operated. When the throttle valve 19 is opened, the engine suction ~ill act ~ithin the mixing chamber 18 through the bore 16 to dra~ the air-fuel mixture into such chamber.
Mounted ~ithin the mixing chamber 18 is a rotor assem~ly generall~ indicated by 22 and such assembl~v includes the rotor ~-~
23 mounted upon suitable aearings 24 which, in turn, are sup-ported b~ an annular or tuaular bod~ 25. The bod~ 25 is sup~
ported bet~een the lo~er housing 10 and the upper housing lOa o~ the carburetor b~ means o~ ~lat springs 26 ~hich ~ear 3~ against the underside o~ an external flange 27 ~ormed integral ~ith the central porti~n o~ body 25. The outer ends o~ the springs are con~ined ~et~een the spacer sleeves 13 and 13a th:rough which the tie rods extend and said springs urge the rotor assembl~ upwardly to move the upper surface of the rotor 23 into its upper position relative to the wall surface 18a.
The use of ~lat springs is pre~erable because such sprin~s have much ~etter linearit~ than the standard coil springs and also reduce the o~erall height o~ the carburetor. Althou~h three flat spr~ngs have been shown ~lg. 5~, more or less may be provided.
Rotor assembly 22 consisting of' rotor 23 and the tubular body 25 and associated parts are most clearly shown in ~igures 3 and 4. In ~igure 3, the rotor assembly ls in lts uppermost position within the upper housing lOa with the upper surface of the rotor in close proximit~ to the wall surface 18a. The annular bod~ 25 o~ the rotor assembl~ has an upper extension 25a which is slidable within the bore lOb formed within the upper housing lOa. The lower portion of the body 25 below the annular flange 27 is reduced as shown at 25b, and the bearings 24 surround such reduced portion with the upper surfaces of the bearing rings engaging annular horizontal shoulders 28 on the bod~ 25 and on the rotor 23; the bearings are retained in position ~ retainer rings 25c to rotatably mount the rotor on the ~ody 25. Upward displacement of the rotor with respect to the bearlngs and the ~ody 25 is prevented by retainer 25d.
A bore 29 extends completely through the body 25 and is reduced at its lower end as lndicated at 29a to form an annular support shoulder 33. An annular ~alve seat 31 is supported on this shoulder and ls sealed ~ith the bore of the body 25 by a suitable sealing ring 32. The upper surface 33 of the valve `~
seat is flat ~hile the ~ore Or the val~e seat is tapered and enlarged ln a do~n~ard direction to form a metering orifice 34.
Secured ~ithln the bore 29 o~ the bod~ 25 abo~e the val~e seat 3I is a guide slee~e 35 ha~ing a bore 35a. The lower end ~0~

of the sleeve is slightl~ ~lared and rests upon the ~alve seat 31 and said sleeve is retalned in place by a snap ring 36 secured within the bore o~ the tubular bod~ 25 and engaging the upper end of sleeve 35. An 0-ring or other static seal 35b seals between the sleeve and the bore of bod~ 25.
The intermedlate portlon of the sleeve 35 is reduced to form an annular space 37 surroundlng the sleeve, which space communicates with a radiall~ directed tubular fuel inlet 38.
Such tubular inlet is connected to a flexi~le fuel line 38a which permits ~ertical movement of the sealed inlet 38 with the rotor assembl~ to which the inlet is attached. ~uel ports 39 are formed in the lower end of the slee~e 35 and provide a communicatlon ~etween the fuel inlet 38 and annular space 37 with the meterlng oriflce 34 of the valve seat. The fuel ports 39 are so sized with respect to the total fuel suppl~ s~stem that the~ create sufficlent constrlction to support a back pressure in the s~stem to there~y mlnimize the possibilit~ of so-called ~apor lock~l in the s~stem.
~or controlling the admission of fuel past the valve seat 20 31 and through the meterlng oriflce 34, a meterlng rod 40 is provided. The rod ls generall~ c~lindrical throughout its length but near its lower end ~s formed ~ith an annular seatlng surface 41 adapted to ~e engaged b~ the upper surface 33 of the ~alve seat. ~elow the shoulder 41 ls a metering pin 42 which ma~ ~e tapered in an~ desired manner to control the volume of ~uel ~hich will pass through the metering orlflce 34 when the valve se~t moves downwardl~ a~a~ from the seating surface 41.
The meterlng rod 40 is securel~ positioned ~ithin the upper housing through threads 43 ~hi`ch engage the threaded ~ore ~;
30 of a metering rod retainer element 411 secured to the up~er ;
central portion of the upper housing lOa. Because the car-~uretor has ~een found to ~e extremel~ sensiti~e, ~t is de-g . . ....

~%~3 sirable that the threads 43 be of a ~ine pitch to obtain desirable mInute ad~ustment changes. An annular seal 45, such as an 0-ring, surrounds the intermediate portion o~ the mete-r-ing rod 40 and provides a seal between the exterior o~ the rod and the bore 35a o~ the sleeve 35. When the rotor assembly 22 moves downwardly within the housing o~ the carburetor, the upper sur~ace 33 o~ the ~alve seat 31 mo~es away ~rom the seating sur~ace 41 o~ the meterlng rod. Upon this occurring, ~uel entering through the inlet 38 passes through the annular space 37, ports 39 and flo~s through the metering ori~ice 34 ~ormed b~ the bore o~ the val~e seat.
Since the guide sleeve 35 is o~ substantial length, said slee~e is guided during its entire vertical movement to main tain proper alignment o~ the bod~ 25 and o~ the metering ori~ice 34 axially with respect to the metering pin 42 o~ the metering rod. B~ properl~ shaping the orifice 34 and the external surface of the metering pin 42, a ~er~ accurate control o~ ~uel admitted ma~ be maintained throughout the entire movement o~ the rotor assembl~. It is noted that there is onl~ one seal, namel~ the 0-ring 45, ~hich is sub~ected to an~ sliding motion; the seal 32 associated with the ~al~e seat and the seal 35b associated with the slee~e 35 are static seals ~hich ha~e no e~ect upon the moving parts.
~ ith the rotor assem~l~ moved down~ardl~ to permit the admission of ~uel past the ori~ice 34, said ~uel ~lows into a chamber 23a ~ormed within the lower end o~ the rotor 23, which chamber is closed except ~or radial passages 46 formed in the upper sur~ace o~ a plate 47 suita~ly secured to the ~ower end o~ the rotor. The outer ends o~ passages 46 communicate with 3C the mixi:ng chambe:r 18 so that the ~uel which passes through the ori~ce is discharged into said chamber.

The rotor which is mounted upon the bearings 24 is a _8-.. . .... . . . . . ..

circular member generall~ conical in shape with its upper surface su~stantiall~ conformlng to the o~erhanging wall sur-~ace 18a of the mixlng cham~er of the housing. The upper surface of said ~otor is formed with groo~es 22a (Figure 6) which are cut at an angle relative to a radial direction extending from the rotor center. Each groo~e extends from the periphery~ of the rotor and terminates at a point short of the hua of said rotor so that the area ad~acent the hub is an annular smooth surface 22~. The cutting of the groo~es 22a forms a pluralit~ o~ upstanding fins or blades 48 on the upper surface of the rotor and such fins or blades also extend from the rotor peripher~ to the smooth sur~ace 22b at an angle to a true radial direction. The groo~es pro~ide air channels or passages in the upper surface of the rotor ~hich channels are open at both ends.
Since the inclination of the upper surface of the rotor generally conforms, or is generall~ parallel to the upper over-hanging ~all surface 18a, the rotor coacts therewith durlng ;~
initial do~n~ard movement of the rotor to control the admission 23 o~ air into the mixing cham~er 18. It is noted, however, that ~hen the rotor is in its uppermost position, the air channels or passages formed by the groo~es 22a are not completely ~;
closed; at this time, the peripheral surface 22c of the disk is closely ad~acent the inclined ~all 18~ and su~stantiall~, although not completel~ shuts off air flo~r into the chamber.
Because the peripheral sur~ace 22c is the closest point to the inner wall surface 18~ of the chamber ~hen the rotor i5 in it,s uppermost position, the spacing between the periphery and ~rall determine the minimum air ~lo~ into the cha~er at this time.
~30 ~hen the rotor ~nitiall~ mo~es downwardl~ ~rom its u~per--most position, the air entering through air inlet 18d is ~orced to a~ruptl~ change direction of flo~r in order to follo~r the air channels. This applies a substantial ~orce to the ~ins or blades 48 because Or the lnertia ~orce developed by said rapid change o~ direction of ~low ~hich assures immediate and rapid rotation of the rotor. As the rotor mo~es downwardly, its peripheral sur~ace 22c mo~es axiall~ of the chamber and by reason o~ the inclined wall 18b o~ increasing diameter, an additional volume o~ a~r is admitted to the chamber. By properl~ selecting the strength of the springs 26 and predeter-mlning the angle o~ inclination o~ the wall 18b with respect to the diameter o~ the disk, the exact volume o~ air entering the chamber at various engine speeds is controlled. Such air volume is also related to the predetermined angle o~ taper on the ~uel metering pin 42 and in this manner, the proper ~uel-air mixture is deli~ered to the engine being operated in all positions o~ the rotor assernbly relati~e to the metering rod 40.
~ hen the rotor is pulled downwardly by the suction o~ the engine, due to opening o~ the butter~l~ val~e l9, air enters the mixing chamber through the air inlet 18d and through the air channels in the top sur~ace o~ the rotor 23. This incoming air, upon striking the ~ins 48, imparts a rotation to the rotor ~hich e~ects a spinning o~ the rotor so that the ~uel ~hich is discharging ~rom the ~uel passages 46 in the lower portion o~
the rotor is caused to disburse or entrain and admix ~ith the air ~lo~ing into the c~amber 18 bet~een the rot~r and the ~alls Or the lo~er housing lO.
The mixing chamber 18 is relativel~ shallo~ in hei~ht and has the out~ardly inclined ~all 18b of increasing diameter ex-tending ~rom the o~erhanging ~all surface 18b to the lower -~
inclined ~all 18c of decreasing diameter ~hich terminates at the u~per end o~ the Dore 16 in the lo~er ~ortion o~ the housing. This con~iguration o~ the chamber creates a lo~
pressure area at the outer peripheral edge o~` the rot~r member -la_ and draws the ~uel ~hich is being centrl~ugally discharged through the ports 46 ~nto intimate entrainment with the alr.
As the ~uel and air admix and travel along the wall 18k, the mixture suddenly encounters the inclined wall 18c to change its direction and further turbulence is created to assure that a thorough mixing of the fuel with the air and a total distribu-tion of such fuel throughout the mixture ~111 be effected.
Because the horizontal seating surface 41 of the meterlng rod engages the ~lat upper surface of the valve seat 33, there is a positive shuto~ oP fuel when the parts are in the posi-tion sho~n in ~igure 3. In order to provide ~or easy starting, an actuating arm 50 is attached to the throttle shaft 20 wlth a lost motion connection as best shown ln ~igure 8. The shaft 20 has a pin 120 which engages within a slot 50a provided in the arm 50 so that the butterfly valve must be opened a substantial distance before the arm 50 ls moved. The outer end o~ this arm is adapted to extend over the adapter flange 15 and is held in a predetermined position ~ith respect thereto by an adJusting scre~ 51. A primer rod 52 has its lo~er end engaged by the arm 50 and its upper end engages the underside Or an actuating fork 53. ~ ~ t The actuating fork 53 extends through a retainer blQck 54 (~igure 22 and overlies the upper end of the external flange 27 ~hich is formed on the tubular bod~ 25 of the rotor assembly.
When the throttle valve of the engine is opened suf~iciently beyond the lost motion connection, the shaft 20 is rotated and the outer end of arm 50 is raised ~hich, due to the fulcrum action, causes the fork 53 to urge the rotor assembly in a do~n~ard direction against the strength of the support springs 3~ 26. As soon as a do~n~ard motion o~ the rotor assembly occurs, the upper surface 33 o~ the ~alve seat 31 ~ill mo~e dc~n~ardly a~a~ from the seating surface 41 of the metering rod, khereby ~.0~g~3 permitting fuel to pass through metering orifice 3LI into chamber 2~a ~ithin the rotor 23 and to be discharged outwardl~
through the radial passages 46. With this arrangement, upon a ~ide opening of the throttle, fuel -ls introduced into the engine for starting.
As pre~iousl~ explained, the annular bod~ o~ the rotor assembly is movable within the bore lOb of the upper hous~ng lOa. Moving with the bod~ 25 is the gulde sleeve 35 and upward movement o~ the parts is stopped when the upper portion of the valve seat engages the seating surface 41 of the stationary metering rod 40. Because there may be some accumulation or condensation occurring above the annular bod~ 25 and its attached guide sleeve 35, it is desira~le to vent the upper end ;
of the space within which the annular bod~ moves. For this purpose, an incl~ned port 55 (~ig. 3~ is formed within the upper housing lOa and has a ~ent tube 56 connected thereto.
The ~ent tube preferably extends into the area ~ust above the rotor so as to discharge within the air channels of said rotor and thereby be discharged into chamber 18.
In operation, when the rotor assembly is in its uppermost position C~igure 3) there is a positive shutoff of the fuel because the flat seating surface 41 of the metering rod is engaged ~ the upper flat surface 33 of the ~alve seat 31. In -~
this position, the a~r inlet to the mixing chamber 18 is sub-stantiall~ closed because the peripheral position 22c of the rotor is in close proximit~ to the ~all 18~ of the miYing cham~er. It is understood that the taper of the metering pin 42 and it~ relationship to the metering orifice 34, as well as the size of the rotor and the air channels and the force of 3 springs 26, have becn predetermined in accordance ~ith the engine to be operated. -A5 is ~ell known, all ~utterfl~ ~al~es in car~uretors have a preset opening when the engine is not operat~ng. This prese'c opening is for the purpose of' permitting a ~low of air and ~uel immediatel~ upon s~tarting o~ the engine to provide f'or su~fi-cient air-~uel m~xture at idling speed. In the present car-huretor, the butter~ alve has such preset opening. When such preset opening is not su~ricient to produce en~ine start-ing, the accelerator can be depressed ~e~ond khe lost motion connection consisting o~ the pln 120 and slot 50a, ~hich actuate the primer rod 52 to mechanically increase the ~uel lO supply and thereby enrich the m~xture. ;
When the engine is started by opening the butter~ly ~alve 19~ a suction acts upon the rotor assembly to move it down~
~ardl~ and permlt f'uel to ~low through the metering ori~ice 34 in the valve seat. At the same time, the rotor is moved a~ay from the inclined upper inner ~all sur~ace 18a of the over~
hanging wall of the lo~er housing. Such movement permits air ; ~ to enter the air inlet 18~ and because of` its abrupt change in direction in order to pass through the air channels, such incoming air instantaneousl~ imparts rotation to the rotor.
Since f'uel is discharging through the passages 46, the rotation of the rotor centrifugal~y discharges the ~uel into the air passing into the mixing cham~er over the periphery of the rotor. Assisting the mixture o~ the ~uel and air is the de~elopment of' a low pressure zone immediatel~ below the rotor's peripheral portion, ~ollowed b~ the extremely turbulent zone ~hi:ch is created as the air ls caused to again change direction by its contact ~ith the inwardly dtrected ~all sur~ace 18c. ~s the rotor assembl~ moves further in a down~ard direction the air velocit~ increases and the f'uel discharge becomes greater and more violent to thereb~ increase the dis-tri~ution and entrainment of' ~uel within the air. Because the rotor size, the metering pin and orif'ice sizes and the spring , .

~0~ 3 strength has ~een predetermined, the desired and proper ~ue]-air mixture is maintained through all positions o~ t~e rotor assembly ~ith respect to the metering pin. This proper ~uel-air mixture operates- the engine at maximum e~f'icienc~ because all ~uel is burned~ an additional ad~antage is produced in lo~ering emissions o~ un~urned ~uel through the exhaust which as is ~ell known~ reduces air pollution.
The elongate slee~e 35 ~hich is secured to the rotor as-sembly housing 25 has an extended contact sur~ace with the stationar~ metering rod so tKat there 1s no chance o~ axial misalignment bet~een ori~ice 34 and metering pin 42 in an~
relative position o~ the parts with respect to each other.
Also, the 0-ring 45 is the onl~ seal ~hich is sub~ected to an~
movement and this seal is engaged by the bore 35a o~ the guide sleeve 35. The importance of maintaining proper alignment throughout all positions o~ the rotor assembl~ with respect to the metering pin is quite evident because i~ there be any mis-alignment, the proper ~uel-air mixture is not obtained.
The rotor assembl~ is maintained in its upper pcsition by the ~lat springs 26 which suspend the assembl~ and ~hich nor-mally maintain it in its raised position when the engine is not operating. This use of the ~lat springs produce a low pro~ile carburetor capable of mounting in the same space as the usual -carburetor and also provide greater linearity than standard elongate coil springs. It should be noted that the entr~ of the fuel into the ori~ice 34 fcrmed in the valve seat 31 is at the lo~er end o~ the guide sleeve 35 so that it does not in an~
w~ inter~ere ~ith the alignment guiding action o~ the sleeve.
It is desirable that the lower end o~ the guide slee~e be slightl~ ~lared out~ardl~ and that the entr~ ports 39 be pro-~ided in this area. The threading of the metering rod into its -14_ ... , . .. , " , , ~0~3'~3 support permits the metering pin to be accurately adJusted f'or idllng purposes if such is requlred.
In the event of a back-~ire of the engine, the force of the same ~ill instantaneousl~ move the rotor to its uppermost position. In such positionJ the peripheral sur~ace 22c of' the rotor is so close to the inner wall surface of' the chamber that there is insu~icient space ~or the ignlted ~uel creating the ~ack-f'~re to pass. This results in the pressure being momen-tairil~ conf`ined to the mani~old s~stem but it may be subse-quentl~ graduall~ released through the relatively small annular space around the peripher~ of' the rotor. Thus, the ~ack-fire is ef'fectivel~ snuffed out.
The foregoing disclosure and description o~ the invention are illustrative and e-xplanator~ thereof' and various changes in the size, s-hape and materials, as well as in the details of' the illustrated construction, ma~ be made ~ithln the scope o~ the appended claims ~thout departing ~rom the spirit o~ the inven-tion.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A carburetor for an internal combustion engine having, a housing with a fuel-air mixing chamber in a first portion and a fuel inlet in a second portion, an air inlet into the mixing chamber, a rotor assembly movable axially within said housing and coacting with the air inlet to substantially close the same when said assembly is at the end of its travel in one direction relative to the housing and to open said inlet upon movement of the assembly in the opposite direction of travel, resilient means between the rotor assembly and the housing for urging the rotor assembly in that direction which substantially closes the air inlet, a metering valve within the housing having a metering element mounted in a stationary position in the housing and a metering orifice carried by the rotor assembly, means for con-ducting fuel from the fuel inlet to said metering valve, the metering orifice of the rotor assembly coacting with the stationary metering element to control passage of fuel past the valve in accordance with the relative axial position of the rotor assembly with respect to the housing, such axial position of the rotor assembly being responsive to the air pressure differential across the rotor assembly, means for conducting the fuel which passes the metering valve through the rotor assembly and into the mixing chamber to mix with the admitted air, whereby axial position of the rotor assembly determines the relative volumes of air and fuel to form the fuel-air mix-ture which is thereafter conducted to the engine being operated, and characterized by means for positively guiding the rotor assembly in its axial movement within said housing to maintain accurate axial alignment of the metering orifice about the metering element throughout the entire axial travel of the rotor assembly with respect to said metering element, said means for positively guiding said rotor assembly including an elongate non-deformable guide surface forming part of the rotor assembly located between the rotor assembly and the metering element and having sliding contact with the exterior of the metering element, whereby said elongate guide surface functions to pre-vent any lateral movement of the rotor assembly relative to said metering element during movement of the rotor assembly with respect to the element.

2. A carburetor for an internal combustion engine as set forth in claim 1, wherein the metering element is mounted axially within the second portion of the housing and is formed with a depending tapered metering pin, and the metering orifice formed in the rotor assembly is so located on said assembly as to be axially aligned with the metering pin in all positions of the rotor assembly relative to the housing.

3. A carburetor as set forth in claim 1, together with means mounting the metering element axially within the housing, and coacting means on the valve element and on the rotor assembly adjacent the metering orifice for positively closing the metering valve when the rotor assembly is in a position it assumes when no flow of air enters the inlet.

4. A carburetor according to claim 1 together with a rotor member rotatably mounted on the lower end of the rotor assembly and located within the fuel-air mixing chamber, means on the surface of the rotor exposed to the air flowing into said chamber and responsive to such flow for imparting a spinning motion to said rotor, and a plurality of radially extending passages in said rotor and forming part of the means which conducts fuel from the metering valve to the chamber, whereby the fuel is discharged into said chamber in a multi-tude of rotating fuel streams which are entrained, distributed and mixed with the air in said mixing chamber.

5. A carburetor according to claim 1 together with a single annular seal between the rotor assembly and the meter-ing element to minimize the frictional resistance to movement of said rotor assembly relative to the metering element.

6. A carburetor according to claim 1 wherein said resilient means comprises a plurality of flat cantilever type spring members extending between the housing and the rotor assembly.

7. A carburetor according to claim 1 including a mechani-cal connection from the engine accelerator to move the rotor assembly away from closed position to supplement engine suction for starting.

8. A carburetor according to claim 7 wherein said mechanical connection includes a fork member engaging said rotor assembly, a linkage between the accelerator and the fork member and a lost motion connection in such linkage so that when the engine butterfly valve is opened a predetermined amount further movement also opens said rotor assembly to deliver an additional volume of the fuel-air mixture to the engine.

9. A carburetor according to claim 1 wherein the meter-ing element is a rod which is cylindrical in cross-section throughout the major portion of its length and having a tapered metering pin extending from said cylindrical portion, and where-in said metering orifice is so located on the rotor assembly that the tapered metering pin extends through said orifice and has different relative positions with respect thereto as the rotor assembly moves relative to the metering element.

10. A carburetor according to claim 1 together with a flat closure surface on the metering element at the inter-section of the lower end of the cylindrical portion of the rod and the tapered metering pin and extending in a plane which is normal to the axis of the metering element, and a complementary flat surface at the upper end of the metering orifice adapted to engage the flat surface on said metering element to effect a positive closure of the orifice and shut-off of the fuel when the rotor assembly is in its closed position relative to the metering element.