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Publication numberUS3743254 A
Publication typeGrant
Publication dateJul 3, 1973
Filing dateDec 10, 1970
Priority dateDec 10, 1970
Publication numberUS 3743254 A, US 3743254A, US-A-3743254, US3743254 A, US3743254A
InventorsC Tuckey
Original AssigneeWalbro Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Diaphragm carburetor
US 3743254 A
Abstract
A carburetor construction of the type utilizing a diaphragm controlled inlet valve wherein a pressure regulator valve is interposed between a fuel pump and a controlling diaphragm and an accelertor pump is provided to be normally expanded by a resilient bias and adapted to be pulsed by engine crankcase pressure upon the opening of a throttle valve by reason of a valving arrangement of said crankcase pressure responsive to said opening movement. Another feature of the carburetor construction disclosed is the use of an idle passage receiving fuel supply from a diaphragm chamber and leading to idle jets at the mixing passage, the idle passage passing a central area of the diaphragm chamber from which it is fed and being joined at that central area by an air bleed passage wherein the head of fuel at said point of joinder is substantially constant regardless of the position of the carburetor, thereby making it possible to balance out the control of the carburetor for varying positions of rotation in use.
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Description  (OCR text may contain errors)

United States Patent 1191 Tuckey 1 July3, 1973 [54] 3,262,433 7/1966 Jordan 123/73 3.265.050 8/1 66 Tuckey 123/119 [75] Tuck, Cass 3,275,306 9/1966 Phillips 261/95 1 w 3,361,120 1/1968 Schneider... 123/73 [73] Asslgnee 222 Corporation Cass City 3,454,265 7/1969 Phillips 261/41 3,453,994 7/1969 Nutten 61 a]... 26l/D1G. 68

22 Filed: Dec. 10, 1970 3,262,433 7/1966 Jordan 123/73 Appl. No.: 96,850

Related US. Application Data Continuation-impart of Ser. No. 853,597, Aug. 19, 1969, abandoned, which is a continuation-in-part of Ser. No. 586,231, Oct. 12, 1966, abandoned.

ABSTRACT A carburetor construction of the type utilizing a dia- [52] Cl 17 phragm controlled inlet valve wherein a pressure regu 51 l t Cl 6 17/04 lator valve is interposed between a fuel pump and a l d 41 D controlling diaphragm and an acc elertor pump is pro- 1 121 vided to be normally expanded by a resilient bias and adapted to be pulsed by engine crankcase pressure upon the opening of a throttle valve by reason of a valv- [56] Reerences Cited ing arrangement of said crankcase pressure responsive UNITED STATES PATENTS to said opening movement. Another feature of the car- 1,624,024 4/1927 Sevensson et al..' 219/469 buretor construction disclosed is the use of an idle pas- 2,215,683 9/1940 Wirt h 261/41 sage receiving fuel supply from a, diaphragm chamber 21377-607 6/1945 Bodme: 123/127 and leading to idle jets at the mixing passage, the idle 215511719 5/195; 'f k g 43 3; passage passing a central area of the diaphragm cham- 6 fli er 2 61 1 ber from which it is fed and being joined at that central 3:003:7s4 10/1961 Phillips Ir 3.1:: 260/37 s air W 3 F the head of fuel 3,037,751 6/1962 Phillips D 261,35 at sa1 point Of 0llldel 1s su stant1a y constant regard- 3,065,957 11/1962 Phillips 2 1 less of the pos1t1on of the carburetor, thereby making 3,072,390 1/1963 Phillips 261/35 it possible to balance out the control of the carburetor 3,090,608 5/1963 Phillips 261/41 for varying positions of rotation in use. 3,160,681 12/1964 Johnson 261/35 3,181,843 5/1965 Brown et al. 261/67 14 Claims, 13 Drawing Figures 64 J25 474 f a 22 4,; Jo Ea 4 a a 27' 32 7 j ='1 51,--

TE 1 m 1 36 -34 3 FUEL 52 do .20 TANK u .94 l5; 9; Ma 04 /2o 96 Joe m4 #2 t 2 i Mes Kifi h. 1

l 2 P 13: 74 001 X [/VE/AIf/fiV/VAOVJ! a .Iji.

Patented July 3, 1973 3,743,254

6 Sheets-Shut 2 INVENTORS CHARLES H. TUCKEY ATTORNEYS Paten ted July 3, 1973 3,743,254

6 Sheets-Shoot 3 INVENTORS CHARLES H. TUCKEY ATTORNEYS Patented July 3, 1973 3,743,254

6 Sheets-Shut 5 (Mr- 274 mu 1121' f 346 CHARLES H. TUCKEY MMKWE' ATTORNEYS Patented July 3, 1973 3,743,254

6 Sheets-Shut 6 F' l6. l3

INVENTOR. CHARLES H TUCKEY M,KAM,M% M

ATTORNEYS DIAPHRAGM CARBURETOR This application is a continuation-in-part of my application Ser. No. 853,597, filed Aug. 19, 1969, now abandoned which was a continuation of my application Ser. No. 586,231, filed on Oct. 12, 1966 and now abandoned.

This invention relates to a Diaphragm Carburetor and more particularly to a carburetor which is utilized for operating small power devices such as chain saws and the like where an all-position carburetor is desirable. In these circumstances, a chain saw, for example, may have to operate in any of many positions with the saw pointed up or down or sideways in either direction. Thus, the carburetor must be reasonably free from gravity influence so that it can furnish the necessary fuel for any position requirement and also while being moved from one position to another.

In addition, the carburetor engine combination must be such that it will operate over long periods of time without stalling out and this dependable operation must occur in ambient temperatures which may be extremely hot or extremely cold. Another requirement is that the carburetor engine combination continue to operate even under heavy load sometimes called. lugging operation and further in addition the carburetor should be such that the control may be moved suddenly from idle to a full throttle without interruption in operation and again from full throttle to idle.

It is with the object of meeting these many requirements for such a carburetor that the present invention has been developed.

It is an object to provide a carburetor which has a large a mixing passage as possible to get as much power as is possible out of the engine and still provide fuel enough during the heavy load cycles and proper acceleration from idle.

It is a further object to provide a carburetor which will provide fuel for an engine so that a sharp shut-off from open throttle to idle under varying load conditions will not cause stalling from an overly rich mixture.

It is thus a further object to provide a carburetor which may be adjusted to have a lean enough fuel mixture at low speeds and still not overly rich at the high speed open throttle condition, or, in the alternative, to have a rich mixture at open throttle to prevent run away when no governor is used. I

It is a further object to provide a carburetor which will prevent excessive accumulation of fuel (puddling) in the carburetor passage and in the engine chambers at idling speeds so that if the engine attitude is changed, the puddle will not enter the combustion chamber and kill the engine with an overrich mixture and also upon opening the throttle there will not be an overrich mix ture which will kill the engine. In other words, it is an object to prevent what is called puddling," especially in cold weather when the fuel is more susceptible to condensation.

Briefly, the objects of the invention are accomplished by providing a small and compact carburetor with a fuel pump operating on crankcase pulse in combination with a pressure regulator device controlling fuel to a metering diaphragm and the provision of an accelerator pump adjacent the main fuel jet again responsive to crankcase pulses to increase fuel flow upon movement of the controlling throttle to open position. The acceleration pump acts also in cooperation with the idle system and the main jet system to lean out the idle system as the throttle is closed, the idle system having an air bleed which meets it as it passes the central part of the fuel diaphragm chamber to maintain a constant liquid fuel head up to the point that air is mixed in to form an emulsion going to the idle jets.

Other objects and features of the invention will be apparent in the following description and claims wherein the best mode contemplated for carrying out the invention is described as well as the principles of operation.

Drawings accompany the disclosure and the various views thereof may be briefly described as:

FIG. I, a diagrammatic view of the various elements of the carburetor presented in a single plane for purposes of ready comprehension of the invention.

FIG. 2, a top view of an actual carburetor body with the top plate removed.

FIG. 3, a view of the underside of the'top plate as it is rotated off the main body shown in FIG. 2.

FIG. 4, an end view of the carburetor taken from the throttle side of the mixing passage.

FIG.. 5, a bottom view of the carburetor body reversed from the view shown in FIG. 2.

FIG. 6, a view of the body side of the bottom plate as it has been rotatedvoff the main body shown in FIG. 5.

FIG. 7, a side view of the carburetor in an upsidedown position.

FIG. 8, a sectional view taken on line 8-8 of FIG. 5 and FIG. 6.

FIG. 9, a sectional view through the mixing passage of the carburetor taken on line 9--9 of FIG. 4.

FIG. 10, a perspective view of a modified carburetor intentionally elongated vertically to facilitate understanding of the passages.

FIG. 11, a perspective view of a chain saw showing the relative location of the carburetor.

FIG. 12, a small view of the air mixing passage at the idle ports and throttle valve.

FIG. 13, a section of the schematic presentation of FIG. 10 showing the air bleed juncture.

REFERRING TO THE DRAWINGS The carburetor embodiment to be described actually is composed of a central block housing 20 with a cap plate 22 and a bottom plate 24 which will be described in detail in connection with the various figures of the drawings. In the diagrammatic showing in FIG. 1 presented in one plane to facilitate an understanding of the entire circuit, the body portion is shown generally at 20 with a cap portion 22 and a bottom plate 24.

FUEL INLET AND PUMP With reference to FIG. 1, a fuel inlet connector 26 admits fuel through a passage 28 to a small surge chamber 30 formed in the top surface of the body 20, this chamber 30 connecting through a passage 32 to a riser passage 34 spaced from a similar :riser passage 36 connecting to a pumping chamber 38 through a short passage 40. The pumping chamber connects through a passage 42 to a short riser passage 44 spaced from a reservoir recess 46. The cap plate 22 holds two diaphragm gasket members 48 and 50 in position on the main block 20, the top diaphragm member having suitable openings to cooperate with valve tab 52 above the passage 34 and valve tab 54 above the passage 44. This is a known method of valving passages in carburetors of this kind, the openings in diaphragm gasket 48 providing sufficient clearance to allow the valve tabs to operate to open and close the passage 34 and 44 respectively.

The undersurface of the cap plate 22 is provided with shallow grooves 56 and 58 respectively above the two valve tabs 52 and 54 to assure free action of the tabs and a small chamber 60 is formed in plate 22 to permit fluctuation of a diaphragm portion 62 in the diaphragm gasket sheet 50. Through a passage 64, the chamber 60, which may be called a pulsing chamber, above the diaphragm area 62, connects to passages 66 and 67 in the housing block 20, these passages ultimately being connected to the crankcase of an engine by reason of the mounting of the carburetor block directly on an engine housing. Thus, with respect to this particular portion of the carburetor which may be entitled a supply pump, pulses through the passages 66 and 67 will fluctuate the diaphragm area 62 and cause respective enlargement and ensmallment of the pusling chamber 38 which draws fuel from the supply passage 28 through the valve 52 to the chamber 38 and forces fuel out of this chamber through the valve 54 to the reservoir 46.

PRESSURE REGULATOR AND METERING VALVE Moving now to the pressure regulator area of the carburetor, it will be seen that the fuel reservoir 46 is connected to a downwardly extending passage 70 leading to a spring-pressed check ball 72 mounted in a small threaded insert 74, this insert having formed therein a seat for the ball in communication with a passage beyond said seat leading to a chamber 76. Opposite the chamber 76 in the bottom plate 24 is a recess 78 separated from chamber 76 by a diaphragm area 79 in a gasket 80 backed by a spring 82. This spring exerts pressure through said diaphragm on a small disc 84 having an actuating pin 86 which extends through the insert 74 to the ball check 72.

Chamber 78 is vented to atmosphere through a passage 88 and chamber 76 has an outlet passage 90 leading to a recess 92 above a short valve pin 94 commonly referred to as a needle valve or metering valve having a valve area 96 cooperating with a valve seat in a screw insert 98. The valve pin 94 is backed by a spring 100 and is actuated through a pin extension 102 on the seat side of the valve by a lever 104 pivoted at 106 extending through a composite chamber formed by a recess 108 in the body 20 and a recess 110 ip the bottom plate 24. The lever 104 has a relatively long flat extension 112 which bears against a diaphragm area 114 in the diaphragm gasket 80. Chamber 110 is connected to atmosphere through a small hole 116 and chamber 108 has an outlet passage 120 leading to a main jet control needle valve 122 having an actuating post 124 to control adjustment.

The metering valve 96 operates by the lever 104 and the diaphragm 114 operates in a manner known in present day carburetors in response to mixing passage vacuum, and the pressure regulator valve controls the pressure behind the valve pin 94 in chamber 92 so that it will not build up over a cerain predetermined closure is resisted by the coil spring 82 and resisted also by actual pressure in the chamber 76 so that a fairly steady pressure on the fuel in chamber 76 can be maintained permitting valve pin 94 to operate without undue resistance regardless of the actuation of the supply pump or pressure build up in the fuel tank in hot weather.

MAIN AND IDLE JETS AND ACCELERATION PULSE DIAPHRAGM Fuel reaching the main jet control needle valve 122 passes through a passage 126 to a chamber 128 connected to a main jet opening 130 in the mixing passage 132. A check valve disc 134 held in place by a retaining cage 136 permits flow into the mixing chamber through passage 130 but closes against back flow through this passage. Extending also off from the fuel recess 128 is another check valve 140 held in place by a retaining cage 142 leading to a passage 144 controlled by an idle control needle valve 146 adjusted by a threaded actuating post 148. Valve 146 controls idle fuel through a small passage 150 (See FIGS. 1, 5) leading to an idle feed tube 152 which extends into the engine housing 149 to a point beyond the reed cage 151; this tube has a reduced calibrated outlet 153. The juncture A where an air bleed 260 meets the passage 150 is at the center of the diaphragm chamber 108 as shown in FIG. 5.

Below the check valve 142 and the entrance to passage 144 is a diaphragm area on the diaphragm gasket 80, this diaphragm area being urged downwardly by a coil spring 162 and overlying a shallow pulse chamber 164 in the bottom plate 24. This pulse chamber 164 is connected through a passage 166 and a restriction 192 to the passage 66 leading from the engine crankcase. A throttle shaft 170 intercepts this passage 166 and, when rotated to a certain position (the open position of the throttle valve), connects this passage and the recess 164 to the pulse from the crankcase of an engine. Both the check valves 134 and 140 are provided to prevent back bleeding when the particular main jet or idle jet is not in use.

Referring now to FIG. 2 where the actual design structure of the carburetor is shown, the various parts and passages will be related to the diagrammatic showing of FIG. 1 wherever possible with the same reference characters as has been used. In FIG. 2, the body 20 has the inlet 26 shown leading to passage 28, surge chamber 30 and to riser passage 34 which is controlled by valve flap 52 in the valve gasket diaphragm 48.

Fuel passing the tab check valve 52 (FIG. 3) enters the short cross passage 56 in the bottom surface of the top plate-22, to follow the dotted arrow shown in FIG.

. 2, to the passage 36 leading through passage 40 entering the fuel chamber 38. This fuel chamber has an outlet 42 leading to passage 44, the top of which is controlled by the tab 54 (FIG. 3), which when lifted by the pressure in the chamber 38, will permit fuel to pass through the passage 44 and a short cross passage 58 in the undersurface of the top plate 22 to the reservoir 46 (see dotted arrow in FIG. 2). This reservoir has a passage 70 extending downwardly from the bottom surface thereof which leads to the pressure regulator valve 72 backed by spring 73 (see sectional view, FIG. 8). A check valve 72 is mounted in the threaded insert 74 above the chamber 76 in body 20, the check valve being controlled by the pin 86 on the disc 84 backing against the diaphragm area 79 of the combined diaphragm gasket 80.

Fuel which passes the pressure valve controlled by the disc 84 and the diaphragm area 79 moves through passage 90 to the chamber 92 (FIG. 8) above the metering control valve 94 having the valve portion 96 which cooperates with the seat in the threaded insert 98. Fuel passing through this metering valve reaches the chamber 108 overlying the diaphragm area 114 which controls the position of the lever arm 104 which in turn cooperates with the actuating pin 102.

The pulsing pressure for actuating the diaphragm portion 62, shown in FIGS. 1 and 3, is received through a passage 66 which terminates at the end face of the carburetor which is mounted directly on the engine housing (FIGS. 2 and 4). This passage connects with the interior of the crankcase of the engine so that the pulsations in that crankcase are reflected through pas-- sage 66 to a short riser passage 67 (FIG. 2) and then through a passage 64 (FIG. 3) in the bottom surface of the top plate 22 to the chamber 60. The passage 66, as shown in FIG. 4, is also connected across the face of the carburetor by a groove 180 which leads to an in wardly extending passage 182 intersecting an opening 184 which carries a throttle shaft 170 controlling a throttle valve 188. An actuating lever 190 controls the position of the throttle valve.

The passage 182 is closed by a plug which is perforated. to provide a calibrated restricted opening 192 and the throttle valve shaft 170 is provided with a cross passage 194 so that the pulsing power received in passage 66 can be transmitted to the diaphragm 160 when the throttle valve 188 is moved to open position. As

viewed in FIG. 4, the body is provided with two drilled holes 196 and 198 to permit holding bolts to pass through the carburetor to an engine housing. Also projecting from the face of the carburetor illustrated in FIG. 4, is the idle feed tube 152 which extends past the reed cage to the engine crankcase as previously described.

To continue with the fuel flow in the carburetor, as the carburetor is now inverted from the position shown in FIG. 2, and the bottom plate 24 removed and turned over, the parts will appear as illustrated in FIGS. 5 and 6. Here, we see the control disc 84 of the pressure regulator valve, the bottom of the insert 98 and the control lever 104 which is pivoted at 106 on a pin 200. The oval-shaped chamber 108 which is overlaid with the diaphragm area 114 of the gasket member has a passage 120 extending from one end thereof which connects through a short passage 202 to a needle valve port 204 controlled by the needle valve 122. The port 204 connects through a short passage 126 to chamber 128 at the periphery of which is mounted the check valve assembly 136 leading to the main port 130 connecting with the mixing passage 132 as shown in FIG. 9.

The chamber 128 (FIGS. 5 and 9) also carries centrally the check valve assembly 142 (FIG. 1) leading to the idle passage 144 controlled by needle 146 and leading to the passage 150 connected to the projecting idle tube 152. Viewing the bottom side of the bottom plate 24 in FIG. 6, which is overlaid by the diaphragm gasket 80, it will be seen that there is a chamber similar in shape to the recess 108 which is connected to atmo-,

sphere through the short passage 116. There is also a circular recess 78 which carries the coil spring 82 which registers with a recess 76 (FIG. 5) in which is mounted the operating disc 84 of the pressure regula- 101'.

The pulsing pressure for the chamber 128 comes from the basic opening 66 (FIG. 4) through the surface channel 180 to the passage 182 shown in FIG. 4 which has the small calibrated opening 192 opening to a cross passage 166 in the block 20 (FIG. 7.), this passage extending across to a riser passage 166A leading upwardly to plate 24 and a small port 210 connected through a small cross passage 21 1 to the pulse chamber 164 shown in FIG. 6. A portion ofthis chamber 164 with a deepened chamber 214 overlaps the diaphragm area 160. Thus, pulsations from the crankcase of the engine will reach the diaphragm area 160 through the above-described passages under the control of the throttle valve shaft 170 and the cross passage 194.

Also, in the mixing passage on the air inlet side is a choke valve 216 controlled by a shaft 218 and a short, actuating lever 220 (FIG. 2) to provide the normal function of a choke valve used particularly in starting an engine.

With respect to size, .the modification above described is dimensioned to occupy approximately 2 cubic inches for the body 20 and the two plates 22 and 24. Thus, the entire arrangement is extremely small and compact while permitting a reasonably large mixing passage.

It will thus be seen that all of the elements shown in the diagrammatic view of FIG. 1 have a counterpart in the actual block carburetor structure illustrated in FIGS. 2 to 9 and mounted on the induction system of an internal combustion engine shown in part in FIG. 7.

In the operation of the carburetor and engine combination, fuel from a suitable tank supply is pumped by the supply pump diaphragm 62 through inlet valve 52 and outlet valve 54 to reservoir 46 where it feeds the pressure regulator valve 72 which in turn supplies fuel at a substantially constant pressure to metering valve 94. The diaphragm chamber 108 is responsive to pressure in the mixing passage 132 such that a lowered pressure will cause valve 94 to open, admitting fuel to passage and the main fuel jet through the main needle valve 122.

Idle fuel also reaches the passage 144 and control needle 146 from the same source. During the idle stages of operation with the throttle valve substantially closed, fuel will flow through valve and needle 146 to the idle projection tube 152 and move directly into the engine without having to pass through the reed cage. The air bleed passage 260 (FIGS. 1 and 5) bleeds air to the idle passage at the central area of the diaphram chamber 108 in a manner described in detail later.

Any fuel passing into the idle passage during open throttle conditions will move directly into the engine and will not accumulate or puddle in the engine passages or ahead of the needle valve as has been common in the past. Thus, in open throttle conditions, the idle passages will be substantially exhausted of fuel. Then, upon sudden closing of the throttle, residual fuel in the main fuel jet and at the engine chambers will keep the engine going in what is called a comedown." The sudden closing of the throttle also throws a high vacuum on the idle passages and, accordingly, the passages 144, and 152 will be again filling with fuel which will reach the engine after a slight delay as the engine throttles down. This tends to prevent flooding in the sudden throttle cut-off action and insures against an overly rich comedown which may unduly slow or kill the engine.

For example, an engine operating at 6,000 R.P.M. which is suddenly cut off should idle out to approximately 2,000 to 2,300 R.P.M. An overly rich mixture at this point may cuase it to go down as far as 1,400 R.P.M. and below this it may well cut out. The above system is, therefore, designed to prevent this overrich comedown which will slow the engine down to the point that it may stall.

Another factor of the system which assists in this operation is the pump diaphragm 162. In close throttle condition, of course, the port 194 in throttle shaft 170 is closed from passage 166 so that there is no action of the engine pulses on the diaphragm 160. It is preferable that a bleed slot 230 (FIG. 1) be provided longitudinally in the surface of the throttle shaft extending to the mixing passage to prevent leadage of the pulse effect around the shaft to passage 166 when the shaft is rotated to closed throttle, condition. An atmospheric bleed hold 232 also is provided to the pulse side of the diaphragm 160 (FIGS. 1 and 6).

In the operation of the diaphragm 160 when the throttle valve is opened and the port 194 connects the engine crankcase with passage 166, there will be a sudden charge of pressure to the diaphragm 160 which will drive an acceleration charge of fuel from chamber 128 through the main jet opening 130. The pressure from the engine crankcase at high speed tends then to keep the spring 162 compressed and the diaphragm in a substantially bottomed-out position. When, however, the throttle valve is closed to cut-off passage 166, then the spring 162 starts to move the diaphragm 160 back away from the idle passage 144 and tends to reduce the pressure in the passage 128. This tends to slow down the movement of fuel into the idle passage 144 and further delays the idle fuel reaching the outlet 153 of the idle tube 152. Thus, there is a further delay in idle fuel reaching the engine after throttlecut back and an insurance that there will not be an overly rich mixture to the engine which will reduce its speed unduly or cause it to stall.

Another factor of the carburetor is the permitting of a reasonably rich mixture at high speeds to prevent what is called run-away action. For example, if the macine is being used to drive a chain saw which is operating under load with the engine running at about 6000 R.P.M. and the saw breaks out of the piece in which it is working with the throttle open, the full fuel charge may drive the engine up to a run-away speed such as I 1,000 or 12,000 R.P.M. which is, in most cases, undesirable. With a rich mixture at this high speed, the fuel charge to the engine is such that it will break into what is called a four-cycle operation in that instead of one firing every revolution of the crankshaft, the engine will start to miss and may be fired only every two revolutions. This causes drastic reduction in power and serves as an automatic governor action. If, on the other hand,

a governor is actually installed on the machine, then a leaner mixture can be used for the open throttle situation.

The effect of the diaphragm 160 can be regulated by calibration of the restriction aperture 102 to increase or decrease the conditions above described.

When the engine is operating at a high R.P.M., the pulse effect through passage 166 to diaphragm 160 is essentially nullified by the restriction 192 and bleed-off hole 232 since the rapid pulses are damped to the point of relative ineffectiveness. When the engine is loaded, however, in an open throttle position so that gate valve 194 is open, the longer and slower pulses from the crankcase will move effectively through the restriction 192 and cause a fluctuation of the diaphragm to move additional fuel into the main jet to prevent stalling out under load.

FIG. 10 illustrates a modified carburetor design eliminating the pressure regulator but retaining the accelerator pump and incorporating a unique idlepassage and air bleed arrangement located relative to the fuel supply such that practically perfect balance, that is, adjustment to tilt, is achieved. In addition, this modification achieves the essential capacity to drop full throttle to idle in any position without stalling, and also the ability to go from idle to full throttle without stalling.

In FIG. 10, the small block carburetor housing, which in actuality may be about 2 inches cubic dimension, has been stretched vertically to promote a ready understanding of the various passages and recesses in the carburetor.

The carburetor consists primarily of a main body 240 having a top plate 242 which will be suitably fastened on the body by screws. A composite diaphragm-gasket 244 is interposed to seal the parts and to provide a diaphragm for a pump recess as well as integral pump valves in a standard fashion. Certain connecting passages in plate 242 are shown in dotted lines arched to designate location in the plate. On the bottom of the carburetor is a plate 245, also covered with a diaphragm-gasket 246. The plate 245 has a depressed area to form a diaphragm chamber in conjunction with the housing 240 and the diaphragm carries a round plate 248 on which is mounted a central headed pin 250 to cooperate with a valve actuator to be later described. On the side of the carburetor block is an accelerator pump plate 253 which covers an accelerator pump recess and clamps a small diaphragm 255.

The carburetor body has a mixing passage 261, sometimes referred to as a venturi paSsage, which at one end receives input air and, at the other end, discharges a mixture of air and fuel.

A choke valve 262 is conventionally mounted on an actuator shaft 24 and a throttle valve 266 is similarly mounted on a throttle shaft 268. This throttle shaft 268 has a corss passage 270 which, in full throttle position, connects to inersection passages in the carburetor body as will be described.

Conventional needle valves are threadingly inserted in the body 240, an idle adjustment valve 272 and a main jet adjustment valve 274. Also a fuel inlet flow valve 280 is controlled in the inlet passage by a lever 282 pivoted on an anchored pin 284. A spring 283 serves to urge the valve 280 to a closed position against fuel pressure. A small headed pin 286 mechanically associates, by a bifurcate portion 288, the needle valve 280 and one end of lever 282. The other end 29 of lever 282, similarly shaped, engages the headed pin 250 previously referred to as fastened to diaphragm plate 248.

With this background of the mechanical parts of the carburetor of FIG. 10, the passages will be described starting with the fuel inlet and terminating in the function of the device.

A fuel inlet connection 300 leads through a passage 302 to a vented surge chamber 304 in the top of body 240 and on through a passage 306 to an inlet flap check valve 307 in diaphragm 244 to a connecting passage 308 in top plate 242. The flow continues to passage 310 leading to pump recess 312 and out of recess 312 to outlet passage 314 and a flap check valve 316 in an overpassage 318 in plate 242 leading to a fuel sieve 320 in a control valve passage 322. This passage has a valve seat 324 controlled by needle valve 280 and lever 282 connected to diaphragm plate 248. A small atmospheric opening 326 in plate 245 is provided.

From valve 280 fuel is conducted to a circular recess 330 above diaphragm 246A where there is provided a fuel outlet 332 controlled by the needle end 334 of main jet adjustment screw 274. Fuel flowing past the needle enters a main fuel pocket 336 which opens through a check valve 338, preferably of the disc type shown in FIG. 1, to the main jet or fuel nozzle 340 in the fuel mixing passage.

Fuel is also available to an idle fuel pocket 342 above diaphragm recess 330 through passage 344 around needle 334, a cross passage 346, idle needle passage 348 controlled by idle needle 350 and a suitable valve seat. Idle fuel continues through an elongated idle fuel passages 352, 354, and 356 to pocket 342 where it can reach the mixing passage through three longitudinally spaced idle ports 357, 358 and 359. See FIG. 12.

Port 357 is the main idle port with throttle closed while ports 358, 359 serve asair bleed ports. As the throttle opens port 358 can also admit fuel, and in full throttle these ports will not function at all.

The junction point A on FIG. is an important location. At this point beyond the idle adjustment valve 350 an air bleed passage 360 connects to the idle fuel passage. This junction point is at the center area of the diaphragm chamber to assure fuel balance in rotated positions of the carburetor as described later. The center line of the diaphragm recess 330 and the diaphragm area 246A is illustrated on the drawing (FIG. 10, FIG.

13) and it will be noted that the juncture point A is right on this center line and adjacent the center of the recess. It can be spaced a little to one side of the center point of the diaphragm area, toward the choke side of the carburetor, for purposes to be described later with use on a chain saw application.

The passages 352 and 354 are described as elongated" and this means that they are not designed to follow the shortest distance between idle needle passage 348 and juncture A. They are intentionally circuitous between these two points to lengthen the passage dis tance. The exact length can easily be determined in calibrating a carburetor for a particular installation, the purpose being to prevent an overrich comedown from full throttle to idle, and to provide a source of said fuel for the accelerator pump to be described in more detail as it returns to a storage position after the initial movement to full throttle position.

The regular fuel pump at pocket 312 and the accelerator pump are controlled by fluid pulsations from the engine crankcase. The engine side of the carburetor, facing away from the device as viewed in FIG. 10, has a surface groove 370 (Passage 180 in FIG. 4 shows a corresponding passage in the FIG. 1 embodiment.) which is connected to a passage from the crankcase on which the carburetor is mounted. This surface passage leads to a passage 372 in the carburetor body and an overpassage 374 in plate 242 to pump chamber 312 divided by a diaphragm area 376 formed by the interposed diaphragm 244. Thus, the fuel pump is pulsed to furnish fuel to passage 32 2 and valve 280. Another end of surface passage 370 is connected to an inwardly directed passage 378 which intercepts the throttle shaft bore 380 at the location of the cross passage 270 in throttle shaft 268. Passage 378 rises to a small chamber 382 with a restriction 384, this chamber being con nected through passages 386, 388 and 389 to a dry side chamber 390 in accelerator pump plate 253. A small diaphragm gasket 255 separates chamber 390 from an opposed chamber 392 in the side wall of the carburetor. A small coil spring-394 on the inside of the diaphragm urges the diaphragm outward.

The inside or wet side of the diaphragm, and thus chamber 392, is connected through internal passages 396, a short L-shaped surface passage 397, and a further internal passage 398 to the open side of idle needle valve passage 348.

Thus, it will be seen that a fluid. pulse through throttle shaft 268 on the dry side of the diaphragm 255 will compress spring 394 and urge fuel in chamber 392, previously drawn in by action of spring 394, into the main jet pocket 336. While this pulSe acts alos on the idle system, the course of least resistance is the main jet 340. Accordingly, a sudden opening of the throttle valve 266 will cause an initial supply of fuel to effect immediate response.

During this throttle operation, the diaphragm 255 remains depressed and the air bleed 360 makes possible an exhausting action on the idle passages by the main jet. When the throttle valve 266 is suddenly closed, the spring 394 acting on diaphragm 255 at chamber 392 creates a vacuum which draws fuel into chamber 392 from the main fuel pocket 336 and the idle passages 352, 354, 356 depleting these passages. There is also an exhausting action on the idle passages by the main jet itself since there is no unidirectional valve in the idle passages. In other words, the idle passage is designed for unrestricted flow in both directions so it can function during idle position of the throttle to furnish fuel to the idle openings and also be purged during full throttle operation. The air bleed 360 makes this possible. As a result, when the throttle valve 266 is suddenly closed, the accumulated fuel in the mixing chamber and intake manifold will supply the engine for a limited time while the idle passages are refilling. Thus, an overrich condition will not obtain and there will be no stalling of the engine. This avoids what isknown in the trade as an overrich comedown.

It will be understood that the action of the diaphragm 246A is convention]. The engine suction exerted through the main nozzle and the idle holes acts on this diaphragm to pull it upward against spring 283, thus opening valve 280 to admit fuel from the pump to chamber 330 and fuel opening 332.

During idle, fuel originates at high speed adjustment opening 332 and flows through passages 334, 346, past idle needle 350, passage 348 and passages 352, 354 to juncture A. At this point, idle fuel picks up air from air bleed 360, restricted in the neighborhood of 0.025, inch, and the emulsion or mixture passes to the idle pocket 342 where it picks up more air from bleed ports 359, 358 and finally discharges on the outside of throttle valve 266 through main idle port 357. During part throttle, the ports 358 and 359 may progressively serve to discharge the mixture of air and fuel called emulsion to the mixing passage. Check valve 338 in the main nozzle acts to prevent back bleed.

To return to the idle system arrangement, one of the problems has been to prevent stalling in return from full throttle, and also during idle when the carburetor is in any of a multitude of positions i.e., on either side, or either end, upside down, etc. In the present embodiment, the juncture A is important. Since this is on the center line of the diaphragm opening 330 and substantially at the center of the chamber, there is solid fuel in the idle lines up to this point. Thus, the head of fuel is substantially equal at fuel outlet 332 and at juncture A regardless of the position of the carburetor. The emulsion in passage 356 and fuel pocket 342 is lighter and not especially responsive to gravity so that offcenter position beyond point A is not critical. It will be noted also that the idle control valve is in the solid fuel area of the idle passage which improves control.

In FIG. 11, a chain saw 410 is shown with carburetor body 240 mounted therein. The carburetor is so mounted that juncture A is preferably as close as possible to the center line of the crankcase of the engine. With the nose down, that is chain 412 down, it is preferable to have leaner than average idle mixture since all flow by gravity is toward the engine. Thus, juncture A can be spaced a little on the operator side of center of the diaphragm recess to lean out the idle a little in this position.

The idle system above described in connection with FIG. finds its counterpart in the previously described embodiments. In FIG. 1 (and FIG. 5) in the lower portion thereof a small atmosphere passage 260 connects to the idle passage 150 at the juncture A. This passage 260 is shownin the actual structure in FIGS. 5 and 9 where above the chamber 108 is a small chamber 252 terminating in a short passage 254 which may be called a part-throttle feed hole. Also, a passage 256 connects the chamber 252 to the main jet opening 130. In addition, the chamber 252 is connected through a small bleedpassage 260, previously referred to, to the idle passage. This bleed passage can be, for example, about 0.01 8 inch in diameter but this may vary with the particular calibration of the carburetor. These passages are shown also in FIG. 5. It will be seen that the juncture A of passages 150 and 260 is substantially at the center of the oval diaphragm chamber so that in any position ofrotation the liquid head in the idle passage up to the point of air bleed will be essentially the same.

The above-described idle passages are provided to participate in what is called a partially open throttle auxiliary feed for fuel. It is desirable in a carburetor of the kind above described to have what is referred to as a tight idle circuit. This means that the flow through the idle circuit is cut down by the control passages to a minimum in order that changes in the rotative position of the carburetor which will change the head on the available fuel to the idle system will not affect the flow through the idle passages. With such a tight system, however, it is sometimes difficult to obtain enough flow through the idle system alone to carry the engine on what is called partial throttle.

The passages 252, 254, 256 above described make it possible to supplement the fuel feed by the connection to the main fuel circuit above the check valve of the main circuit and not connected with the normal idle bleed to the mixing chamber. When the throttle valve is partially open, this system can provide fuel to supplement the supply and thus keep the engine running smoothly. Air flow through the small bleed line 260 to chamber 252 from the idle passage permits the exhaustion of the chamber 252 when the main nozzle takes over as the throttle opens.

The pressure regulator valve described in the circuit with respect to the embodiment of FIG. 1 protects the system against an oversupply of fuel which again might cause stalling. Particularly, in high ambient temperatures which may cause a build-up of pressure in a fuel tank which has a pressure vent cap, the regulator valve will keep a substantially constant pressure in diaphragm chamber 108 to allow normal fluctuation in response to engine action.

The carburetor is designed to operate in any position of tilt from right side up to upside down. This is necessary in many applications and most particularly in chain saws where an operator must maneuver his machine into many positions to accomplish the necessary cutting.

I claim:

I. In an all-position carburetor system for moving liquid fuel from a supply to an engine including a carburetor body to be mounted on an engine having a mixing passage with a venturi portion and a diaphragm chamber, an inlet control valve, a diaphragm acting on said valve in said chamber for controlling the opening and closing of said valve, and supply passages leading from a fuel supply inlet to a main jet opening at the venturi portion of said mixing passage, that improvement which comprises:

a. means forming a pulse chamber connected to said supply passages,

b. means in said pulse chamber resiliently biased to a position enlarging said chamber and movable to a position ensmalling said chamber,

0. a pneumatic passage in said carburetor body having one end to serve as an inlet adapted to be connected to the crankcase of an engine to convey crankcase pressure from an engine and another end connected to said last-named biased means,

d. a throttle valve in said mixing passage movable from an open throttle position to a closed throttle position,

e. means responsive to movement of said throttle valve to open said pneumatic passage when said throuttle is moved to open positon to cause ensmalling of said pulse chamber thereby pushing an accleration charge into said main jet opening, and to close said pneumatic passage to effect enlarging of said pulse chamber when said throttle is closed thereby restoring a charge of fuel in said pulse chamber,

f. means forming an extended passage for liquid idle fuel from said supply passages to said mixing passage adjacent said throttle valve, a portion of said passage for idle fuel passing through an area in said body transfixed by the axis line perpendicular to and passing through the center of said diaphragm,

g. an air bleed passage connecting atmospheric air from a point spaced from the venturi portion of the mixing passage to said idle fuel passage at a juncture point at said portion of said idle fuel passage, and

h. an idle fuel adjustment means positioned in said liquid idle fuel passage ahead of said air bleed passage whereby the liquid hydraulic head pressure at said juncture point is substantially equal regardless of the tipped or rotated position of said carburetor.

2. An all-position carburetor system for moving liquid fuel from a supply to an engine which comprises:

a. a carburetor body to be mounted on an engine having a mixing passage and supply passages leading from a main fuel supply reservoir to a main jet opening to said mixing passage,

b. means forming a chamber to provide a supplemental fuel reservoir adjacent said main jet connected to said supply passages, whereby said main jet can receive fuel from said chamber,

c. means in said chamber resiliently biased to a position enlarging a fuel receiving portion of said chamber and movable to a position ensmalling said chamber,

d. a pneumatic passage in said carburetor body having one end to serve as an inlet adapted to be connected to the crankcase of an engine to convey crankcase pressure from an engine and another end connected to said last-named biased means,

e. a throttle valve in said mixing passage movable from an open throttle position to a closed throttle position, and

f. valve means in said pneumatic passage movable in response to movement of said throttle valve to open said pneumatic passage when said throttle is moved to open position to cause ensmalling of said chamber thereby pushing an acceleration charge of fuel into said main jet opening, and to close said penumatic passage to effect enlarging of said chamber when said throttle is closed thereby restoring a charge of fuel in said chamber.

3. A carburetor system as defined in claim 2 in which means is provided to form an idle jetpassage leading from said main supply reservoir to a position to be open to an engine, passage means connecting said idle jet passage to said supplemental fuel chamber and to said main jet whereby to be exhausted of fuel during an open throttle period when said main jet is subject to aspiration pressure, said idle jet passage being subject alsothrough the passage connection to said chamber to partial vacuum when said resiliently biased means moves in the direction of bias to enlarge said chamber thereby to delay idle fuel flow to an engine from the idle passage upon the closing of said throttle.

4. A carburetor system as defined in claim 3, said carburetor being shaped to be mounted on an engine having a fuel and air inlet vavle positioned to receive a mixture of fuel and air from said mixing passage, said idle jet passage being designed for flow in both directions of its length and terminating in a passageway extending from said carburetor such that it can project into an engine to a point adjacent and outside a fuel and air inlet vavle of an engine.

5. An all-position carburetor system for moving liquid fuel from a supply to an engine having a fuel and air inlet mainfold and a fuel and air inlet valve therein which comprises:

a. a carburetor body adapted to be mounted on an engine manifold having a mixing passage positioned to discharge into said manifold and supply passages leading from a fuel supply inlet to a main jet opening to said mixing passage and idle jet passages leading to the engine manifold,

b. means forming a first chamber adjacent said main jet and the origin of said idle jet passage at the end of and connected to said supply passage,

c. a fuel pump, a pressure regulator valve, and a fuel supply valve in series in that order in said supply passage between said fuel inlet and said chamber, means including a diaphragm operating said fuel supply valve influenced by fluctuations in said mixing passage reflected through said supply passage,

d. means forming a second chamber open to said main jet and said idle jet passages and second diaphragm means having an inside for closing one side of said second chamber and means resiliently biasing said second diaphragm to enlarge said chamber,

e. a pneumatic passage adapted to connect the outside of said second diaphragm to the mainfold of an engine to subject it to the pulse pressures of an engine on which it is mounted,

a throttle valve in said mixing passage, and

. means to coordinate the action of said second diaphragm with said throttle valve to cause acceleration fuel to reach said main jet upon opening of said throttle and to delay fuel flowing into said idle jet upon closing said throttle comprising a valve in said pneumatic passage operable to open said passage upon opening of said throttle and to close said passage upon closing of said throttle.

6. A carburetor system as defined in claim 5 in which said idle jet passages leading from said chamber are designed for flow in both directions of length and terminate at the end of a passageway leading from said carburetor body to deliver idle fuel to an engine beyond said fuel and air inlet valve. v

7. An all-position carburetor system for moving liquid fuel from a supply to an engine which comprises:

a. a carburetor body to be mounted on an engine having a mixing passage and a diaphragm chamber, an inlet control valve, a diaphragm acting on said valve in said chamber for controlling the opening and closing of said valve, and supply passages leading from a fuel supply inlet to a main jet opening at said mixing passages,

b. means forming a pulse chamber connected to said supply passages,

c. means in said pulse chamber resiliently biased to a position enlarging said chamber and movable to a position ensmalling said chamber,

d. a pneumatic passage in said carburetor body hav ing one end to serve as an inlet adapted to be connected to the crankcase of an engine to convey crankcase pressure from an engine and another end connected to said last-named biased means,

e. a throttle valve in said mixing passage movable from an open throttle position to a closed throttle position,

f. means responsive to movement of said throttle valve to open said pneumatic passage when said throttle is moved to open position to cause ensmalling of said pulse chamber thereby pushing an acceleration charge into said main jet opening, and to close said pneumatic passage to effec enlarging of said pulse chamber when said throttle is closed thereby restoring a charge of fuel in said pulse chamber,

g. means forming an extended passage for liquid idle fuel from said supply passages to said mixing passage adjacent said throttle valve, said passage for idle fuel passing through an area in said body transfixed by the axis line perpendicular to and passing through the center of said diaphragm,

liquid idle fuel passage ahead of said air bleed pasing of said idle passage under closed throttle operation. 10. An all-position carburetor system for moving liquid from a supply to an engine which comprises:

h. an air bleed passage connecting air to said idle fuel a. a carburetor body to be mounted adjcent an engine passage at said area, wherein the liquid head in said having a throttle-controlled mixing passage and, idle fuel passage transmitted from said diaphragm supply passages leading from a fuel supply inlet to chamber to the air bleed juncture will assure bala main jet opening at said mixing passage, anced fuel feed in rotated positions of said carbureb a f l i l t control valve,

and c. a relatively flat diaphragm chamber formed in said i. an dle fuel manual ad ustment positioned in said body adjacent said mixing passage, 3 diaphragm1o llquld ldle fuel Passage ahead of Sald bleed P cated in said chamber subject to pressure fluctua- Sagetions in said mixing passage and associated with an'posmon carburetor system f movmg said fuel inlet control valve to actuate said control uldfuel from a Supply to an engine whlci} comprises: valve in response to said pressure fluctuations, said a. a carburetor body to be mounted ad acent an enchamber being connected in Said Supply passage gmejhavmg a mlxmg passzige and PP Y Passages between said fuel supply and said main jet, ieadmg f f Supply mlet to a mam J open d. manual control means for limiting the fuel flow mg at sflld P from said chamber to said main jet,

f Inlet control vfilvei e. means forming a passage for idle fuel from said a daPhYaEgm iocated m afelatwely flat dfaphragm chamber to an idle fuel outlet, said passage being chamber sald body actmg said fuel connected to said main jet downstream of the main 9 W m response m pressure flucmatms m jet relative to the fuel supply inlet and diaphragm Said fg Piassage, saldghamber ig f l chamber and extending in a direction of the plane i Sal P pilss'flge etween Sal ue Supp y of the diaphragm to an idle adjustment valve and d m at mam g d f d1 from said valve back over the diaphragm to a posifg i e gngate f zf i i tion overlying a central area on the perpendicular mm Sal c am an I ue Sal axis of said diaphragm chamber and then to the idle fuel passage extending over said chamber to an mixing passage, area at the center of said chamber before passing f. means forming an air bleed passage leading to a to said mixing chamber,

uncture with said idle fuel passage at said central e. means forming an air bleed passage extending over area of said diaphragm,

said chamber to connect air to said idle fuel paswhereby aspiration of fuel through said main et sage at said area wherein solid fuel flows through a t th f 1 said idle fuel passage from said chamber to said Sal b g p j empdy .5. i area and an air and fuel mixture flows through said passage 3 wleen Sal c i an Sal i idle fuel passage from said area to the idle fuel outpassage urmg open t e 9 an let and thereby cause delayed filling of said idle passage f. an idle fuel manual adjustment positioned in said under F i operatlon' 40 11. In an all-position diaphragm carburetor having a throttle-controlled mixing passage, a diaphragmcontrolled fuel inlet valve, a main jet, idle jets, and adjustment control valves for said jets,

a. a diaphragm chamber in said carburetor and a diaphragm in said chamber positioned to act on and sage.

9. In an all-position diaphragm carburetor having a throttle-controlled mixing passage, a diaphragmcontrolled fuel inlet valve, a main jet, idle jets, and adjustment control valves for said jets,

a. a diaphragm chamber in said carburetor and a diaphragm in said chamber positioned to act on and to control a fuel inlet valve between open and closed positions,

to control said fuel inlet valve and means to connect the diaphragm with the fuel inlet valve,

b. a main jet take-off port from said chamber controlled by said main jet adjustment control valve,

b. a main jet take-off port from said chamber cona firs t f from Said P to a main j leading trolled by said main jet adjustment control valve, to 531d mlxmg P c. a first passage from said port to a main jet leading a Second Passage from Sald first Passage for idle to said mixing passage, fuel leading away from said main jet take-off port d. a second passage from said first passage for idle and leading to P g i l fuel,

fuel leading away from said main jet take-off port e. a control restriction in said idle fuel passage, d l di to outlets for idlg f l, f. means forming an atmospheric air bleed indepene. a control restriction in said idle fuel passage, and dent of said outlets to connect air to said idle fuel f. means forming an atmospheric air bleed indepe passage at a point between said control restriction dent of said outlets to connect air to said idle fuel and Said Outlets, passage at a point adjacent the center f h whereby aspiration of fuel through said main jet phragm chamber and the center axis normal to the will mpty the idle fuel passage between said diaphragm therein, between said idle fuel control chamber and said air bleed passage during open restriction and said outlets, throttle operation and thereby cause delayed fillwhereby aspiration of fuel through said main jet ing of said idle passage under closed throttle opwill empty the idle fuel passage between said chamber and said air bleed passage during open throttle operation and thereby cause delayed filleration, g. means forming a pulse chamber in said carburetor connected to said second passage,

h. means in said pulse chamber resiliently biased to a position enlarging said pulse chamber and movable to a position ensmalling said pulse chamber,

i. a pneumatic passage in said carburetor body having one end to serve as an inlet adapted to be connected to the crankcase of an engine to convey crankcase pressure from an engine and another end connected to said last-named biased means,

j. a throttle valve in said mixing passage movable from an open throttle position to a closed throttle position, and

k. means responsive to movement of said throttle valve to open said pneumatic passage when said throttle is moved to open position to cause ensmalling of said pulse chamber, thereby pushing an acceleration charge into said main jet opening.

12. In an all-position diaphragm carburetor having a throttle-controlled mixing passage, a diaphragmcontrolled fuel inlet valve, a main jet, idle jets, and adjustment control valves for said jets,

a. a diaphragm chamber in said carburetor and a diaphragm in said chamber positioned to act on and to control said fuel inlet valve and means to connect the diaphragm with the fuel inlet valve,

b. a main jet take-off port from said chamber controlled by said main jet adjustment control valve, c. a first passage from said port to a main jet leading to said mixing passage,

(1. a second passage from said first passage for idle fuel leading away from said main jet take-off port and leading to outlets for idle fuel,

e. a control restriction in said idle fuel passage,

f. means forming an atmospheric air bleed independent of said outlets to connect air to said idle fuel passage at a point between said control restriction and said outlets, whereby aspiration of fuel through said main jet will empty the idle fuel passage between said chamber and said air bleed passage during open throttle operation and thereby cause delayed filling of said idle passage under closed throttle operation,

g. means forming a pulse chamber in said carburetor connected to said main jet take-off port,

h. means in said pulse chamber resiliently biased to a position enlarging said pulse chamber and movable to a position ensmalling said pulse chamber,

i. a pneumatic passage in said carburetor body having one end to serve as an inlet adapted to be connected to the crankcase of an engine to convey crankcase pressure from an engine and another end connected to said last-named biased means,

j. a throttle valve in said mixing passage movable from an open throttle position to a closed throttle position, and

k. means responsive to movement of said throttle valve to open said pneumatic passage when said throttle is moved to open position to cause ensmalling of said pulse chamber, thereby pushing an acceleration charge into said main jet opening.

13. In combination, a carburetor having a mixing passage and an unvented fuel chamber, a throttle valve in the mixing passage, a flexible diaphragm forming a wall of the fuel chamber, a fuelinlet, a valve for said inlet, means transmitting movement of the diaphragm to the inlet valve, main and secondary fuel delivery outlets opening into the mixing passage, fuel passage means between the fuel chamber and the region of the main outlet, means for regulating fuel flow through said passage means, an elongated passage means in the carburetor extending from the main delivery outlet at the fuel chamber to the secondary fuel delivery outlet, said elongated passage means including a first bore in the carburetor surrounding the means for regulating the passage means between the fuel chamber and the main outlet and a second bore leading from said first bore in the direction of the diaphragm chamber to the center of the chamber and a third bore leading from said center to the secondary fuel outlets, and air vent means for admitting atmospheric air to said second bore at the center of the chamber to delay delivery of fuel through the secondary outlet upon movement of the throttle valve to engine-idling position and to insure a balanced liquid fuel head in said elongated passage up to said air vent means. I

'14. In a carburetor having a mixing'passage and an unvented fuel chamber, a throttle valve in the mixing passage, a flexible diaphragm forming a wall of the fuel chamber, a fuel inlet, a valve for said inlet, means transmitting movement of the diaphragm to the inlet valve, main and secondary fuel delivery outlets opening into the mixing passage, a first fuel passage means between the fuel chamber and the region of the main outlet, means for regulating fuel flow through said first passage means, second fuel passage means between the fuel chamber and the region of the secondary fuel delivery outlets, means for regulating fuel flow through said second passage means, said second fuel passage means comprising a first bore originating; at said fuel chamber extending in said carburetor in a direction away from said chamber, a second bore passing back over said fuel chamber to the center, and a third bore leading to the region of the secondary fuel delivery outlets, and vent means admitting air directly into said second passage means at the center of the fuel chamber for delaying delivery of fuel from the second passage means through the secondary outlet upon movement of the throttle valve to engine-idling position, said vent means being effective upon opening movement of the throttle to promote rapid delivery of fuel to the main outlet for engine acceleration.

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Classifications
U.S. Classification261/34.2, 261/41.5, 261/69.2, 261/DIG.680, 261/35, 261/121.3
International ClassificationF02M17/04
Cooperative ClassificationY10S261/68, F02M17/04
European ClassificationF02M17/04
Legal Events
DateCodeEventDescription
Apr 9, 1991ASAssignment
Owner name: HARRIS TRUST AND SAVINGS BANK, 111 WEST MONROE ST.
Free format text: SECURITY INTEREST;ASSIGNOR:WALBRO CORPORATION A CORP. OF DE;REEL/FRAME:005660/0559
Effective date: 19910325