Note: Descriptions are shown in the official language in which they were submitted.
1036~41
This invention relates to a motor vehicle carburetor
and more particularly to a system for supplying cranking fuel
to the engine.
A conventional downdraft carburetor has an idle
speed channel that bypasses the induction passage around the
throttle valve to permit a supply of fuel and air when the
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103644~
throctle valve is closed, such as during engine idling speeds
and starting. For starting in cold weather below say 25F, a
choke valve is rotated towards a closed position as a function
of temperature changes to restrict the air inlet and thereby
draw in the richer mixture necessary for cranking at these
temperatures.
This invention relates to a variable area venturi
carburetor in which at least one wall of the venturi is moved
to enlarge the venturi. Tapered fuel metering rods attached
to the movable wall are wi~hdrawn from fuel jets to simultan-
eously change fuel flow~ The engine cranking position and
idle speed position of the venturi are the same, and this type
of carburetor has no choke valve. However, it is still
necessary during cold engine operation, to supply the carburetor
with extra fuel and in amounts that increase as the temperature
drops.
In accordance with the present invention,
there is provided an engine cranking fuel supply
system comprising, a carburetor having an induction passage
; ~0 connected to Presh air at one end and adapted to be connected
to the engine intake manifold at the other end, a fuel port
opening into the passage, and dual fuel supply means connected
to the port for the induction of varying amounts of cranking
fuel to the port as a function of changes in tempera~ure from
a predetermined level, the dual fuel supply means including
~irst and second fuel passages each containing a temperature
responsive flow control means variably movable to decrease the
cranking fuel flow as temperature increases towards a pre-
¦ determined level, a flow-noflow valve in the second passage
variably movable to a flow position in response to an engine
.
~036~1
cranking operation to permit Llow through the second passage
and variably movable to a non-flow position in response to
the engine attaining a running condition whereby fuel flow for
eold engine operation is supplied in varying amounts to the
~- 3
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3~;~4~
fuel port from both passages below the predetermined tempera-
ture level during engine cranking, and from only the first
passage after the engine has attained a running condition.
In this way, a fuel cranking system is provided
that is operative below a predetermined temperature to supply
quantities of fuel to the carburetor that are in addition to
fuel inducted in the normal manner.
The invention is described further, by way of
illustration, wi~h reference to the accompanying drawings,
in which:
- Figure 1 is a plan view of a portion of a
variable area venturi type carburetor embodying the invention;
Figure 2 is a side elavational view taken on a
plane indicated by and viewed in the direction of the arrows
2-2 of Figure l;
Figure 3 is a cross sectional view taken on a
plane indicated by and viewed in the direction of the arrows
.3~3 of F~gure l;
Figures 4 and 5 are enlarged cross sectional views
taken on planes indicated by and viewed in the direction of
the arrows 4-4 and 5-5 of Figure l;
Figure 6 is a cross sectional view taken on a
plane indicated by and viewed in the direction of the arrows
6-6 of Figure l;
Figure 7 is a bottom view taken on a plane
indicated by and viewed in the direction of the arrows 7-7
of Figure 6, and looking up at the underside portion of the air
horn portion of the carburetor and appears on the same sheet
of drawings as Figures 9 and 10.
30 . Figure 8 is a cross sectional ~iew taken on a
plane indicated by and viewed in the direction of the arrows
r~ 3 A
36~41
8-8 of Figure 6 and looking down on the main or central body
portion of the carburetor; and,
Figures 9 and 10 are cross sectional views taken
on planes indicated and viewed in the direction of the arrows
9-9 and 10-10 of Figure 8.
Figure 1, which is essentially to scale, i5 a
plan view of a variable area venturi carburetor of the down-
draft type. It has a pair of rectangularly shaped induction
passages 10, each having one end wall 12 which is pivotally
movable and has the profile (Figure 3) of one-half of a
venturi 13. Each opposite fixed cooperating wall 14 is
formed with the mating profile of a portion of a venturi.
The airflow capacity, therefore, varies in proportion to the
opening movements of walls 12 of the induction passages.
.
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~ 3~i441
1 As seen more clearly ln Figure 3, movahle walls 12
2 are plvotally mounted at 15 on a statlonary pln. The pin
3 actually i~ rlxed to a ~trut, not shown, that depends ~rom
4 a sectlon o~ the upper body of the carburetor. Pivotally
attached to each Or the wall bodles i3 a fuel metering rod
6 16 that cooperates wlth a maln fuel meterlng Jet 18. The
7 needles have a controlled taper to provlde a rlcher alr/fuel
8 mixture at the lower and hi~her ends of the venturl opening
9 range~ Each ~et is located ln an aperture inside wall 14 at
approximately the throat or mo~t constrlcted ~ectlon of
11 venturi 13. A fuel float bowl or reservolr 20 has a palr
12 of identlcal passages 22 conducting ~uel to the main metering
13 Jets 18. Downstream of the venturis, the carburetor throttle
14 body portlon 23 rotatably mounts a sha~t 24 on which are
rixed a pair (only one shown) Or conventional throttle plates
16 25 that aontrol the rlow Or alr and fuel through induction
passages 10.
18 The size Or venturis 13 and the movement of walls
19 12 ls controlled in thls case by a spring returned, control
vacuum actuated, diaphra~m type servo 26. The servo consl~ts
21 or a hollow two-piece casting dlvlded into two chambers 28
22 and 30 by an annular flexlble diaphragm 32. The dlaphragm is
23 sealingly mounted along it~ edge in the casting. Chamber 28
24 18 an alr chamber, connected to amblent or atmospherlc pressure
through a passage 34 (lndlcated also ln Flgures 1, 6 and
26 8). Chamber 30 ls a vacuum chamber connected to inductlon
27 pa8sage8 10 at a point below the throat but stlll ln the
28 venturl 13. This subJects chamber 30 to changes in a control
29 vacuum that varies wlth alrflow but at a rate that is
sllghtly dlfferent than true venturi vacuum. The exact
31 location o~ the tap of cour3e is a matter of choice. Chamber
32 3 also ls connected to be actuated by ported intake manifold
~ 3644~L
1 vacuum, for cold weather operation, as wlll be described in
2 more detail later.
3 Completlng the construction, servo 26 has fixed
4 to one side of diaphragm 32, by a retainer 35, a plunger or
actuator 36. The plunger is plvotally connected to a ~haft
37 interconnecting cast portions o~ the movable walls 12.
7 Flxed to the other side of diaphragm 32 is a retalner 38
8 against whlch is seated a sprlng 39. The other end of the
9 sprlng bears agalnst a seat 40 axially ad~ustable to vary the
sprlng preload.
11 Figure 3 indlcates schematically ln dotted llnes a
12 passage "p" between chamber 30 and lnductlon passages 10.
13 In actuality, as best seen ln Figures 5, 8, 9 and 10, servo
1l~ chamber 30 is connected by a restricted line 41 (Flgure 8)
to an lntersectln~ passage 42 (Flgures 8-10). Passage 42
16 lntersects wlth a vertlcally downwardly extendln~ pa~age 44
17 (Flgure 10) containlng a flow restrlctor or orlflce 46 and
18 termlnatln~ ln a chamber 48. Chamber 48 ls connected by a
19 port 50 to lnductlon passage 10 at a polnt below the edge of
throttle valve 25 when it ls in lt~ closed positlon shown.
21 In the posltlon shown, therefore, as the throttle valve 18
22 rotated to an open posltion, port 50 ls progresslvely sub~ected
23 to the lncreased pressure above the throttle valve to bleed
24 the vacuum in passage 42.
Passage 42 also intersects with a ri~ht angled
26 passage 52 (Figures 8, 9 and 5) that connects to a passa~e
27 54 (Flgure 5). The latter passe~ vertlcally through the main
28 body portlon of the carburetor lnto a horlzontal passage 56
29 ~ locat~d ln the carburetor alr horn sectlon. Pas~age 56 in
turn is connected by a palr of passages 58 and 60 to the well
31 62 (Flgure ~) ln which is arcuately movable one of the mountlng
32 members 70 (Fi~ure 3) for movable wall 12. While not shown,
4~
l the well 62 in Figure 8 and the adJacent lnduction passage
2 10 are lnterconnected by a depressed porklon of the main
3 body between the two so that the openlng 63 shown ln Flgure 5
4 sen~es the control or venturl-llke vacuum connected by the
passa~es named to servo chamber 30.
6 Looklng now at Fl~ure 5, the openlilg 63 to the
7 control vacuum ln this case is adapted to be alternately
8 restricted or progressively opened by a needle type valve 72.
9 me valve is movable into and out of the seat 63 ln response
to a temperature sensltlve element, in a manner that wlll
ll be described more clearly later. Suffice it to say at thls
12 polnt~ that durlng normal englne operatlng temperatures,
13 the needle valve 72 is completely wlthdrawn from opening 63
14 thcreby permlttln~ venturl-like vacuum to be sensed through
passa~es 60, 58, 56, 54, 52, 42 and 40 to chamber 30 Or the
16 servo, the ported manlfold vacuum ~lmultaneously beln~ sensed
17 through port 50, chamber 48, line 42 to llne 41 and ~ervo
18 chamber 30.
l9 It should be noted that the slze of the venturi-
like vacuum pasBages 60~ 58, 56, 54 and 52 are conslderably
21 larger than that of the ported manifold vacuum passage 44,
22 coupled wlth the oriflce 46, so that when the needle valve
23 72 is in the up posltion, the manifold vacuum is bled to the
24 level of the venturl-like or control vacuum and, therefore,
has e~sentlally no effect on the movement of ~ervo 26. The
26 manifold vacuum ls used during cold weather operatlons to
27 modulate the venturi-like or control vacuum to schedule the
28 opening o~ the venturi 13 to regulate the richness of the
29 fuel/air mixture. When the needle valve 72 is in the closed
or nearly closed position, the venturl vacuum flow will be
31 es~entlally blocked and manifold vacllum will be the prlme force
32 acting on servo ~hamber 30. This will cause the movable
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~03~
l venturi wall3 12 to be moved to a larger area venturl pulllng
2 the fuel meterlng rods 16 out further.
3 As thus ~ar described~ durlng norMal engine operating
4 temperatures, the operation ~s as follows. The rotatlve
movement of throttle valves 25 controls total airflow through
6 both passages lO to lncrease as the throttle valves are moved
7 from thelr closed positlon. An increase ln alr~low provldes
8 e~sentially a proportional lncrease in the control vacuum in
9 chamber 30 from port 63 until the dlaphragm 32 1~ moved
towards the cup 40. This moves both walls 12 to open inductlon
11 passages lO and increase the area of venturls 13 whlle
12 simultaneously retractlng the fuel meterlng rods 16 to increase
13 fuel flow. Thus, the total airflow and ~uel flow vary wlth
14 changes in throttle valve settlng up to a maxlmum.
Returnlng now to the general construction shown
16 ln Figure l, durlng cold englne operatlon, as stated prevlously,
17 it is de~lrable to provlde an addltional supply of fuel to
18 the lndu¢t~on passages to assure sufriclent fuel vapor both
l9 ror startlng the engine as well as a dlfferent schedule Or
addltlonal fuel for runnlng the cold englne prlor to its
21 reachlng normal operatlng temperature level. The~e requlrements
22 are sati~fled by providing a comblnatlon fuel enrlchment system,
23 a cranking fuel enrlchment system embodylng the lnventlon~
24 as well as a throttle plate posltloner devlce to crack open
the throttle plates an addltlonal amount durlng cold starting
26 operations.
27 More speclflcally, Flgures 5J 6 and 8 show portions
28 Or both the cold running enrlchment system as well as the
29 cold start cranking fuel system. The body portlon of the
carburetor 15 cast with a ~uel bowl 20 containlng fuel
31 dellvered thereto past a conventlonal inlet needle valve 80
32 from a supply llne 82. The needle valve 80 is moved vertlcally
~364~
1 ln a bore 84 by the tab 86 secured to a float member B8
2 plvotally mounted at 90 on a depending portlon of the air
3 horn ~ectlon o~ the carburetor.
4 ~ The lnlet valve 80 operates in a known manner.
Movement Or float 88 downwardly as a result of lowering of
6 the liquid ruel level causes the needle 80 to drop. This
7 permlts ~uel under pres~ure to enter the reservolr from
8 llne 82 to rlll it agaln to the deslred level. Raising of
9 the rloat rai~es the inlet valve agalnst the conlcal seat shown
to 3hut orf the upply when the desired level ha~ been reached.
11 The lower portion of fuel bowl 20 contains a needle
12 like cranking fuel supply valve 100 (Flgure 5). The latter
13 has a conical ~alve portlon 102 that cooperates wlth the
14 upper edges 104 o~ a ~uel well 106. Valve 100 is connected
to a temperature respon~ive device to be moved lnto and out
16 Or the wall wlth changes ln temperature, ln a manner to be
17 descrlbed, to control the rate of rlow Or ruel rrom reservolr
18 20 lnto ~uel well 106. Well 106 13 connected to an intersecting
19 passage 112 tFlgure 8) that connect~ wlth a cross passage 114
to rlow ruel into another pas~age 116 past a solenold controlled
21 valve unlt 118.
22 As best seen ln Flgure 69 unlt 118 conslsts
23 esRentlally o~ a valve 120 ~ormed on the end o~ the armature
24 of a solenold 122. A sprlng not shown normally blases valve
120 to close communlcatlon between pas3ages 114 and 116.
26 The solenold normaliy would be powered from the starter relay
27 Or the motor vehlcle lgnltlon system so that the solenold ls
28 - rendered operatlve only durlng en~ine startlng conditions.
.
29 That is, when the lgnltlon key ls turned to the st~rt positlon,
the solenold 118 would be energized and cause valve 120 to
31 be retracted rlghtwardly to open communlcatlon between pa~sa~es
32 114 and 116. A rlow Or startlng ~uel would then be permltted
.
~1~36~
1 rrom ~uel bowl 20 into passage 116.
2 As soon as the englne attained runnlng condltion,
3 return o~ the lgnltion switch to the on positlon would
4 de-energize solenold 122 and again block pa~sage 114 rrom
con~unlcating wlth passage 116. The solenold unit could
~6 lnclude a manlrold vacuum swltch so the solenold ls not
7 energized above a vacuum level o~ say 2"Hg., for example.
8 It also could oontain a thermal swltch to prevent operation
9 above 120~F., ~or example, when extra cranklng fuel usually
ls no* needed.
11 From passage 116 the ruel passes upwardly through
12 the carburetor main body passage 124 (Flgure 6) where it
13 flows into a plenum 126, shown also ln Flgure 7. From the
14 plenum, the ~uel ls divided equally to be lnducted out through
passages 128 into each Or the induction passages 10 at a
16 location adJacent the venturi but spaced from the fuel ~ets
17 18. Thu~, lt wlll be seen that ~or startlng operations,
18 energlzatlon o~ the solenold by turnlng Or the vehlcle lgnltlon
19 swltch cause~ addltlonal ~uel to be added at times to the
lnductlon passages, ror startlng purposes.
2~ The quantlty Or cranklng fuel to be added to the
22 inductlon passages, or, on the other hand, the positlon of
23 crankln~ valve 100, 19 controlled by the connectlon o~ valve
24 100 to the lower end o~ a needle valve 140 (Flgure 5). The
needlo Yalve rorms a portlon Or the engine running fuel
26 enrlc}lment system. More speclflcally, needle valve 140 is
27 tapered a~ lts lower end as shown at 142, ror a purpose to
28 be descrlbed, and ha~ a unlversal connectlon 144 to the
29 plastlc con~cal valve 100. The latter defines a varlable ~low
srea 145 between the Yalve and wall Or well 106 that varies
31 ~n slze as a ~unction of the vertlcal movement o~ valve 100.
32 Thererore~ vertical movement Or valve 100 modulates the rate
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~q~369~
1 O~ ~low Or ruel rrom reservoir 20 lnto well 106 when solenold
2 valve 120 i~ opened. The needle valve 140 moves upwardly and
3 downwardly wlth changes in temperature, as will now be descrlbed.
4 The needle valve 140, ln thi3 case, ls vertlcally
movable ln a well 146 in the upper body portlon. It ls axially
6 aligned by a seal 148 and a valve seat 150 with whlch it
cooperates to meter fuei. The seal and seat deflne a chamber
a 152 ~hlch is c~nnected by an angled passage 154 to the end 156
9 of a worm-like passage 158 best seen in Flgure 7. The opposite
end 1~0 of pas~age 158 connect3 wlth a vertlcal passage 162
11 (Flgure 6) that lnter~ects an angled passage 164 leadln~ to
12 the plenum 126. As stated previously, plenum 126 also receives
13 ~uel from ths cranking fuel passage 124. Together then,
14 the ~uel passes into each lnductlon passage 10 through the
slde passage3 128. It wlll be seen then that, dependlng upon
16 the vertlcal position o~ needle valve 140, a quantity of fuel
~7 will rlow past the tapered portlon 142 of the needle valve
18 lnto tlle varlous passages lnto lnduction passages 10 to supply
19 addltional ruel durlng cold runnlng operation of the engine.
The vertlaal movement of needle valve 140 1~ controlled
21 by a temperature sensltlve element that moves the needle
22 valve 14Q upwardly to increase ruel rlow a3 the temperature
23 decreases below the normal operating level, and moves the
24 needle valve 140 to a downward position to shut orf the fuel
enrlchment when the temperature reaches the normal operatlng
26 level. Concurrently9 the downward movement Or needle valve
27 140 as the temperature lncreases will move the cranklng fuel
28 valve 100 downwardly in proportlon to the temperature lncrea~e.
29 There~ore, when the normal operating level is reached? cranklng
Yalve 100 wlll provide a maximum restrictlon to flow through the
31 area 145, and Yery llttle addltional ruel will then be added
32 during startin~ of the englne.
33 The upper end o~ needle valve l4n 19 plvotally
34 connected to the end Or a lever 16~. The lever ls pivotally
- 10 --
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~1113~
1 mounted on a pln 168 proJecting through an aperture ln a boss
2 170 proJecting from the carburetor upper body. The opposlte
3 end of lever 166 ls pivotally connected to an ad~ustable nut 172
4 on the upper end o~ a dependlng llnk 174. The lln~ 174 is
adapted to be connected to a thermo~tatically responsive movable
6 elemen~ to be dç~crlbed. Ad~ustlng the upper en~l 172 of course
7 wlll vary the operating characteristics o~ the system. Downward
8 movement of lin~ 174 is limlted by abutment Or the nut 172
9 agalnst a stop washer 176. Pro~ecting horlzontally or laterally
from link 174 18 a connector 178 plvotally engaging the threaded
11 upper end 180 of needle valve 72. The upper end 180 contains a
12 yoke member 182 adJustably threaded to the end of needle valve
13 72 as ~hown to determine the upward and downward llmits o~
14 movement Or the needle valve.
Ac thus far descrlbed, therefore, wlth respect to the
16 runnln~ ~ue~ enrlchm2n~ ~ystem, wi'h the 'hrc~tle plate~ ln the
17 ldle speed positlons, when link 174 1~ ln the po~ltion shown
18 indiaatlng that the temperature is at the lowest below normal
19 englne operating level, the needle val~e 140 will ha~e been
~0 moved to lt~ upwardmo~t posltlon to provide maxlmum rate of
21 ~uel ~low. Needle valve 72 also wlll have moved to its downward-
22 mo3t positlon re~tricting the port or outlet 63 to the lnductlon
23 passage ~hown in Figure 8. Thu8, ported mr~rilfold vacuum in
24 port 50 (Fl~ure 10) wlll act ln servo chamber 30 to move walls
12 to enlarge the venturl areas, w~lch decreases the ~uel
26 meterlng slgnal actlng on both outlet passages 128 and Jet 18.
27 ~h18 leana the mixture a~ compared to the cranking mlxture and
28 what lt would be under accelerative condltlon3.
29 Slmultaneously, maxlmum addltlonal ruel quantlty
wlll rlow ~rom the fuel enrichment well 152 lnto the lnductlon
31 passage~ 10 through the lnterconnectlng~outlet passages 128.
32 As soon as the temperature lncreases rrom its lowest settlng,
33 the llnk 174 wlll move vertlcally upwardly from the posltlon
34 ~hown. Thl~ will ~radually and progressl~ely ralse the venturi-
1 1
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1 llke vacuum control needle ~alve 72 and lower progre~slvely the
2 needle valve 140. Thus, the venturi-like control vacuum
3 be~ln~ to bleed lnto passage 60. The vacuum force acting Oll
4 serYo chamber 30 will progresslvely decrease to permit servo
sprlng 3g to ~lowly close the venturl towards the normal engine
6 ldle ~peed posltion. The addltlonal ~uel nrlc~ant will
7 decrease as the tapered port~on 142 o~ needle valve 140 closes
8 the openin~ to the ruel bowl.
9 Turnlng now to the teMperature re~ponsive control
of the movement Or llnk 174 and the throttle valve positioner,
11 F~gures 1, 2 and 4 show the same more clearly. As best seen
12 ln Figure 4, the lower end of link 174 is plvotally connected
13 to one end o~ a lever 216 that ls fixed on a shaft 218. T~,e
14 ot~er end Or lever 216 ad~u~tably supports a screw 220 that
bears agalnst the end 222 of an essentially conventlonal fast
16 ldle cam 224. The cam 18 rotatably mounted on sha~t 218 and
17 ha3 a wei~hted lower end 223. The end has a peripheral edge
18 portion ~ormed with a serie~ Or clrcumferentially contl~uous
19 steps 224, 226 and 228 and a hlg~ cam step 230. Each 3tep
progre8~ively in the order named ls o~ greater radial extent
21 than the pre~ious. ~ -
22 Cooperating with fast idle cam 224 to locate or
23 posltlon the throttl~ plàtes 25 ls a lever or throttle stop
24 232 ~ormed at lts outer end with a cur~ed engaging portion
234. Le~er 232 is rotatably mounted on throttle shaft 24. ~-~
26 It has a dependlng tang portion 236 engaged by the end of
27 an adJu~tably mounted screw 238 carrled by a lln~age 240 rlxed
28 to the throttle ~ha~t 24. A throttle return coll sprlng
29 242 has one end 244 ancnored under a pln 246 exten~lng
,. from a ~lxed portion of the car~uretor throttle flange.
31 The opposlte end of the sprlnæ ~ears agalnst an angled tane
32 250 of linka~e 240 thereby blasing the linka~e and screw ~38
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l ln a clockwise directlon against the tab end 236 Or lever
2 232. The le~er 232 thus i3 constantly biased in a clockwlse
3 directlon towards the edge surrace of fast idle cam 224.
4 The cam steps thererore c~nstitute abutment means or stops
ln the path o~ movement Or lever 232 to determine the idle
6 speed positlon o~ throttle plate~ 25.
7 Insertable at tlmes between the end 234 of lever
~8 232 and the ed~e of fast idle cam 224 is the ~lnger portion
9 252 Or an arcuately movable link 254. The latter 15 plvotally
connected at 256 to the end Or a lever 258 rotatably mounted
ll on shart 218. Lever 258 ls connected at its upper end at
12 260 to an actuatlng llnk 262. The opposlte end o~ link
13 262 ls connected to one end of a bell crank lever 264 plvotally
14 mounted at 266 on the ears of an extension of a servo houslng
268.
16 The servo hou~in~ is hollow and divideu into tWG
17 chambers 270 and 272 by an edge mounted annular flexlble
18 diaphragm 274. Chamber 270 1B an alr chamber communicating
l9 to the atmosphere through an openlng 276. Chamber 272 is
a ~acuum chamber communlcating by a passage not shown with
21 ~he lnductlon passages at a loca~ion below the throttle valves
22 25. A plunger 278 ls rlveted at one end 280 to a hat shaped
23 spri~g retalner 282, and pro~ects through a stop 284 ~or
24 connection to the opposIte end 286 of bell crank le~er 264.
A oompresslon sprlng 288 normally blases the plunger 278
26 upwardly to move bell crank 264, llnk 262, lever 258 and
27 ~lnger portion 254 in a clockwise dlrection.
28 Appllcatlon o~ engine vacuum to the servo chamber
29 272 when the englne ls runnlng is suf~iclent to counteract
the ~orce Or spring 288 and cause the plunger 278 to move
31 ~ertlcally downwardly. Thls moves lever 258 and flnger portlon
32 254 in a counterclockwise dlrectlon to withdraw or retract
33 the finger portlon rrom between the lever end 234 and the fast
- 13 -
l ldle cam steps. ~ ~ 4
2 Thus, lt will be seen that when the ~n~ine 15 o~f
3 preparato~ to starting operatlon, depresslon o~ the vehlcle
4 accelerator pedal wlll rotate throttle shaft 24 and lever
232 ln a GounterclockwIse dlrectlon away from the end 252
6 of fin~er portlon 254. Slnce there ls no manl~old va¢uum in
7 chamber 272 of servo 269, ~pring 288 wlll posltion the ~inger
8 portion 254 to the positlon shown 80 that upon relea~e Or
9 the accelarator pedal, coil spring 242 will cause a clockwise
return movement of the throttle valve lever 232 untll lt
11 engage~ the arcuate portion 290 Or the end 252 of the rlnger
12 portlon 254, whl~h ln turn abuts the edge of the fast idle
13 cam 2240
14 Once the englne has attalned runnlng operatlon
beyond cranking vacuum level, then openlng o~ the throttle
16 valves 25 by depresslon of the a¢celerator pedal, pivot3 lever
17 232 downwardly and permits retraction or movement of finger
18 portion 254 to an ~noperatlve positlon to the right by the
l9 vacuum ln servo 268. Lever 232 then 18 permltted to engage
the edge of the fast ldle cam directly and the positlon of the
21 throttle plates will be determlned strlctly by the rotatlve
22 posltion of the rast ldle cam 224.
23 The fast ldle cam i3 controlled ln its rotation
24 by a lever 292 flxed on shaft 218. The lever ls located '~
wlthln a hollow cup-shaped houslng 294 that ls cast integ,rally,
26 wlth the throttle body portlon 23. Lever 292 has an uptu~ne.d
27 slotted end 296 in whlch i8 located the outer end 297 of,.a
28 thermostatlcally re~ponslve blmetalllc sprln~ coll 298. The
29 lnner end Or the spring i~ flxed on a stub shaft 300 proJec~ing
from an insulated cover 302. The cover is fastened by
31 screw~ to the houslng 294 with an lnsulating gasket 302
32 between. The gasket has an arcuate slot 304 along whloh th~
-
1~36~4~
l end 296 moves wlth temperature changes. The gasket also has
2 a hole 306 through which pro~ectR the end 308 of a tube
3 connected by a pair of passages 309 and 310 to the lnductlon
4 passages lO at a locatlon ~not shown) below the throttle
valves. For clarity, the cover 302 has been removed ln
6 Figurs 2, and Figure 4 show~ the outllne of the houslng ln
7 phantom, for orlentatlon purpose~. Completlng the constructlon,
8 ~he housing has a hot air lnlet tube 312 connected by a passage
9 314 to the lnterior of houslng 294 on the far ~ide of ga3ket
302. ~he tube would emanate from a known type Or exhaust
ll mani~old heated stove ln whlch alr flowlng past the manlfold
2 18 warmed.
13 In operatlon, once the en~ine 18 operatlng, wlth
14 gasket 302 in place and cover 304 applied9 manlrold vacuum
actlng ln pa~sages 309 and 310 oauses hot alr to Plow into
16 tube 312 to the far slde of gasket 302. The air is then drawn
17 throuKh the slot 306 and out through passages 309 and 310,
18 warmlng the coll 298 as it passes lt. Thus, the coll wlll
l9 bo progre~slvely warmed as the englne temperature rlses,
resultlng in a clrcumferentlal movement of the end 297 of
21 the ooll to rotate lever 292 in the same directlon. This
22 rota~es lever 216 away ~rom the ~aat idle cam and permlts the
23 ~ast ldle cam to rotate counterclockwlse by gravlty. Slmilarly,
24 upon englne shutdown, coollng of the coll wlll cause lt
to rotate levers 292 and 216 in the opposlte dlrection. This
26 of course 31multaneously rotates the fast ldle cam 224 by
27 the screw 220~ so that, dependlng upon the temperature level,
28 one of the steps 225, 226, 228 or the hlgh cam atep 230 will
29 be presented opposite the end 234 of throttle lever 232.
Thus, the throttle plate ldle speed setting wlll be determined
31 by which step is engaged by lever 232, during runnlng operations
32 of the englne. Durlng cold start operations, as described
~364~
1 prev~ously, the rlnger portion 254 will be inserted between
2 the end 234 of lever 232 and whatever step or rota~ive cam
3 posi~lon the fast idle cam 224 has attained ~o that the
4 throttle plates are opened more for ~tartlng purposes th~n
durin~ normal cold runnlng conditions.
6 It will be ~een, therefore, that regardless of
7 what po~ltlon the ~ast ldle cam 224 assumes because of the
8 prevaillng ambient temperature, the throttle plates wlll be
9 oponed an additlonal amount ror startlng purposes. The
a~ditlonal amount will vary to agree wlth the amblent temper-
11 ature le~el so that a ¢orrect startlng air/ruel mlxture 1~
12 obtalned. This is in contrast to the conventlonal constructlons
13 in which thare is only one rast ldle start posltlon, accomplished
14 only by po~itlonlng the slngle high step 230 agalnst the
throttle lever end 234~ At the lnbetween temperature levels,
16 thls i8 too high and results ln too fast an idle speed, and
17 one that may provide undesirable emlsslons.
18 The overall operatlon of the carburetor ls belleved
19 to be clear ~rom the above descrlptlon and by reference to
th~ drawlngs. Thererore, lt wlll be repeated now only briefly.
21 Aasume that the engine is Orr and the ambient temperature
22 18 ~ssentlally 0F. ~he colled bimetalllc sprin~ 2g8 will have
23 contraoted a maxlmum amount rotatlng lever 292 clockwlse ~rom
24 th~ posltlon shown in Figure 2 to posltlon the end 297 of
25 ` the le~er at the left end 316 of the slot 306. Thls wlll
26 rotate lever 216 to mo~e the rast ldle ¢am 224 clockwise to
27 locate the hlgh cam ~tep 230 opposlte the end 234 of throttle
28 lever 232. Simultaneously~ by openlng the throttle platesJ
29 lever 232 wlll move away from the fast ldle cam and permlt
the s~rvo sprlng 288 to move the finger portion 254 between
31 the rast idle cam step 230 and lever 232. The throttle plates
32 now will be opened a maximum amount for the coldest start
- 16 -
~364~
1 posltions, The induction passage~ 10 at thls tlme are at
2 th~ir smallest cross section because the servo sprlng 39 ha~
3 moved wall~ 12 to thls po4itlon. This, therefore, exposes the
4 pa~sages to a larger cranklng vacuum slgnal 80 that the alrflow
a~ro~s the ~uel metering Jets 18 ls lncreas~d.
6 Slmultaneously, the rotation of lever 216 moves link
7 174 downw~rdly to its extreme posltion untll the stop 172
8 shown ln Flgure 5 abut~ the washer 176. This plvot needle
9 valv~ 140 to its uppermost positlon allowlng a maximum amount
or fuel from ~uel bowl 20 through the space between the ~eat
11 150 and the tapered lower portlon of valve 140. Thls upward
12 posltion also moves the cranking valve 100 upwardly to open
13 wlde the pas~age 145 to flow fuel to passage 112. ~lerefore,
14 whon the ignltlon swltch 1~ turned to an on or start posltlon,
tho solenoid 118 will wlthdraw the valve 120 to permlt a maximum
16 rate Or fuel to Plow from passage 114 to 116.
17 When the engine ls cranked ~or ~tartlng purposes,
18 th~ cranking vacuum slgnal 18 ~urrlclent actlng across the
19 inductlon passage outlets 128 (Flgure 7) ~o draw fuel up
cranking fuel aircult passage 124 into plenum 126. Slmultan-
21 eously~ fuel ls drawn past the engine runnlng ~uel circult
22 noedle ~alve 140 into the worm passage 158 (Figure 7) to
23 plenum chamber 126, where both clrcults combine and the fuel
24 lndusted to provide the necesAary startlng richness. On¢e the
englne has been started, release Or t}~e lgnltlon switch
26 to tho englne runnln~ position de-energlze~ ~olenold 118 to
27 then agaln block the connection between the cranking supply
28 line 114 and the line 116. However, with the llnk 174 ln lts
29 downwardmost coldest positlon, the valve 72 will also be down
os~ntially blocklng off port 63. Accordlngly, the higher
31 ported englne running manl~old vacuum will act ln servo chamber
32 3 and draw the wall~ 12 of the venturis to open or enlarge
- 17 -
l the venturi area. ~3~44~
2 Wlth the throttle plates unmoved from the ~ast ldle
3 speed position, the openlng of the venturls wlll decrease
4 the alr velocity across the fuel ~et 18 to decrease the fuel
metering slgnal while at the same time enlarglng the fuel
6 Jet orlfices. Simultaneously, the area of dlscharges 128
7 being constant, lowerlng the air velocity decreases the fuel
8 meterlng signal to decrease fuel output tllrough these passages.
9 This leans the overall mixture ~or the closed throttle position
attained at that temperature level. At closed throttlel
11 the manifold vacuum is considerably higher than the cranking
12 vacuum. ~hls causes excess vaporlzatlon and would normally
13 lead to a richer than deslred mixture. However, the ported
l~ manl~old vacuum control ln this case compensates ~or this
by leaning the overall mixture to the desired level by openlng
16 the venturis.
17 Similarly, once the throttle plates are moved to
18 an o~f-ldle accelerative posltion, the mani~old vacuum level
19 i8 reduced so that there now iB less vaporizatlon. A slightly
richer mixture, therefore, is desired to provide acceptable
21 englne operation. This ls accomplished by the throttle plates
22 traverslng the port 50 as they move off-idle, whlch progressively
23 sub~ects the chamber 48 to more and more control vacuum
24 exlsting above the throttle plates. The manifold vacuum signal
acting on servo 30 therefore decays, and the venturl move~
26 towards a more closed posltlon to provide the richer setting
27 deslred. It is only a very short time, therefore~ berore
28 the throttle plates have completely traversed the port 50,
29 leaving control of movement o~ the venturl then strictly to
the changes in venturl-llke control vacuum. Thus, a rlcher
31 than normal ldle but less than cranking mixture is provided
32 at this time by the main ~uel metering system as well as the
~L0369L4~
1 needle valve supplemental ~eed system.
2 Concurrent with the englne attalnlng a runnlng
3 conditlon, the manl~old vacuum established in servo chamber
4 272 wlll be suf~iclent, once throttle lever 232 i5 pivoted
counterclockwise to relea~e ~lnger portio~ 254, to pivot the
flnger portlon out from between the end 234 of lever 232 and
7 the ~ast ldle cam step lt abut3. l~ow the portlon 234 will
8 move to ~irect~y abut the step o~ the ld e cam 224 and thereby
9 clo~e down the throttle plates to less open ~ast idle speed
po~l~ions~ Tbis reduces both the fuel flow and alr~low for
11 cold runn~ng operations~ whloh as stated above is deslred
12 because a less rich alr~uel mixture is requlred once the
13 engine has attalned its i~le speed horsepower.
14 As the temperature increaseR, the bimetallic oolled
1 15 sprlng 298 will rotate the lever 216 in a counterclockwise
;6 dire¢tion awa~ 4rom the 4a~t ldle cam. The cam then can
17 move in the s8me direction by gravity when the throttle
18 plates are opened beyond the rast idle position so that the
19 end o~ lever 234 graduall~ moves progresslvely clockwlse to
permit the progresslve closur~ o~ t~le throttle plates to less
21 open ldle speed posltiorls. Simultaneously, the counterclock-
22 wlse rotation o~ lever 216 efrects an upward movement of llnk
23 174 to progres3ively move the needle valve 140 downwardly and
24 thareby progre~sively clo~e Orr the addltional ruel flow past
the Yalve. Thls movement also causes an upward movement o~
26 needle valve 72 so that the venturi-llk~ vacuum decays
27 whatever ported manlrold vacuum slgnal is acting ln servo
28 c}lamb~r 30.
29 Thus, ror closed throttle pla~e~po~itlons, the
lowering ~acuum sl~nal in pre~ure chamber 30 will permlt
31 the venturl walls 12 to move to contract the venturl area
32 and move the meterlne rods 16 lnto the Jet 18. Eventually,
~ ~ .
- 19 -
~036441
1 therefore~ the throttle plates will be returned to a normal
2 closed idle ~peed posltion, the needle valve 72 wlll be drawn
3 essentially completely out of port 63 so that movement of
4 the venturi walls wlll be controlled solely by control or
venturi-like vacu~n charlges, and the supplemental fuel needle
6 valve 140 will be moved downwardly to shut o~ or es~entially
7 close off the supply o~ additlonal fuel to the system. At
8 thls time, the cranklng valve 100 wlll ~e at a mlnlmum rate
9 of flow posltion. The closlng venturi increases the alr
velocity past the fuel ~et 18. The fuel ~et, therefore, wlll
11 ha~e a smaller flow area, The total fuel ~low will be less
12 because the throttle plates are now closed more completely
13 and because no fuel is now belng lnducted ~rom ~assages 128,
14 but only that through the main Jets 18,
While the lnvention has been shown and descrlbed
16 ln its pre~erred embodlment, lt wlll be clear to those skllled
17 in the arts to which lt pertaln~ that many changes and modlflca-
18 tlons may be made thereto without depar~lng from the scope of
19 t}~e invention,
- 20 -
