US 3738623 A
A diaphragm-controlled carburetor having a pressure pump actuated by engine pulses wherein a pump diaphragm is supported by a pan-shaped side mount spring to assist pressure pulses of the engine in a manner to improve the pump efficiency at both low speed and high speed conditions.
Description (OCR text may contain errors)
Unite Tuckey States Patent 1 June 12, 11973 DIAPHRAGM CARBURETOR [7 5] Inventor: Charles H. Tuckey, Cass City, Mich.
 Assignee: Walbro Corporation, Cass City,
 Filed: 'Jan. 13, 1971  Appl. No.: 106,178
- U'.S. Cl 261/35, 261/D1G. 68, 261/69 A  Int. Cl. F02m 17/04  Field of Search 261/35, DIG. 68,
261/69 A; 123/139 AH, 73 A, DIG. 6; 417/395, 413, 470, 471; 48/184  References Cited UNITED STATES PATENTS 2,745,390 5/1956 Heidner et a1. 123/73 A 2,823,905 2/1958 2,835,239 5/1958 943,848 12/1909 1,647,768 11/1927 2,297,653 9/1942 Horton et a1. 417/395 2,307,566 1/1943 Browne 417/395 2,653,552 9/1953 Geeraert 417/395 2,831,758 4/1958 Warner et a1. 48/184 3,182,601 5/1965 Johnson 261/DIG. 68 3,250,224 5/1966 Phillips et a]. 261/DIG. 68 3,308,765 3/1967 Mutschler et a1 417/413 X FOREIGN PATENTS OR APPLICATIONS 1,188,366 3/1965 Germany 261/DIG. 68
Primary Examiner-Tim R. Miles Att0rneyBarnes, Kisselle, Raisch & Choate  ABSTRACT A diaphragm-controlled carburetor having a pressure pump actuated by engine pulses wherein a pump diaphragm is supported by a pan-shaped side mount spring to assist pressure pulses of the engine in a manner to improve the pump efficiency at both low speed and high speed conditions.
2 Claims, 2 Drawing Figures DIAPHRAGM CARBURETOR This invention relates to aDiaphragm Carburetor and more particularly to an improvement in a fuel pump for such a carburetor.
It is an object of the invention to provide a return spring for a diaphragm of a fuel pump to improve efficiency at both low speed conditions, idle, and at high speed, full throttle.
Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claims in which the principles of operation of the invention are set forth together with the best mode presently contemplated.
Drawings accompany the disclosure and the various views thereof may be briefly described as:
FIG. 1, a sectional view of a diaphragm carburetor having a fuel pump and a vapor pump incorporated therein.
FIG. 2, a plan view of a diaphragm control plate.
Referring to FIG. 1, a main carburetor housing 120 has a mixing passage 122 with a choke valve 124 an a throttle valve 126. A main fuel passage 130 controlled by a needle valve 132 leads to a fuel well 134 which is connected to a tube 136 a leadingupwardly through the venturi portion of the mixing passage. The tube has multiple outlets 138a for fuel. The well 134 also has an air inlet 136 and a feed port 138 leading to an intermediate fuel supply chamber 140 with suitable fuel passages 142. An idle recess 144 has some intermediate passages 146 connecting to the mixing passage and also a main idle port 148 controlled by a needle valve 150.
In the bottom of the housing 120 is formed a diaphragm chamber 160 closed by a diaphragm 162 which acts on one end of a lever 164 pivoted in the housing and carrying at its other end a fuel inlet valve 166 operating in a suitable seat thimble 168 which has a top port opening to a recess 170. A small flexible member 172 provides an anti-back bleed check valve 174 for the entrance of fuel into the main fuel passage 130 and this member also has a small port 176 which furnishes fuel from the diaphragm chamber to the idle recess 144. The diaphragm 162 is held in place by a first intermediate plate 178 which has a top recess 180 below diaphragm 162 and a bottom recess 182 which serves as a part of a pumping chamber above a diaphragm 184 which is controlled in its motion by a leaf spring member having a pan support portion 186 with a side extension anchoring portion 188 provided with locating tabs 190 clamped against the bottom of the housing 178 by a second intermediate housing plate 192. The pumping chamber 189 is defined by the diaphragm 184 and the shallow opening below it in plate 192.
tion of the pump, the vacuum pulse will draw fuel into.
the chamber and the spring is intended to assist the pressure pulse to return the diaphragm in the pump-out portion of the cycle. It has been found that the pan-type spring shown in FIGS. 1 and 2 assists the weak pressure pulse at low throttle or idle conditions. On the other hand, when at wide open throttle when vacuum pulses are weaker, the pan type spring does not hinder the vacuum action, that is, it does not subtract from the weaker vacuum pulses. The shape of the spring also gives support to the diaphragm, the edges being panned to prevent cutting into the flexible portion thereof. Accordingly, the pump performs well at the low end idle and, in contrast to the coil spring, does not detract from operation at the high end full throttle. The diaphragm member 184 also has a valve flap 196 backed by a suitable coil spring to control a passage which will be described below.
At the left-hand portion of the assembly, as shown in FIG. 1, a pump diaphragm 200 is provided between recesses in plate 178 and a second intermediate plate 192, this being a secondary vapor pump which has a disc-like inlet valve 202 and a flap-type outlet valve 204. The diaphragms 184 and 200 are pulsed by engine pulses through a connection conduit 206 leading from a crankcase connection of an internal combustion engine to the chamber 182 and thence to a connecting passage 208 to the diaphragm 200.
The bottom side of the intermediate plate 192 has two flat surface recesses 210 and 212 which serve as portions of booster chambers in conjunction with opposed recesses 214 and 216 in a third intermediate plate 220 which holds a diaphragm member 222 in position between these respective chambers. This diaphragm member 222 also provides a flap valve 224 for the pump diaphragm 184. In the bottom of the third intermediate plate 220 is a chamber 226 which provides an inlet chamber together with an annular chamber 228 which surrounds a fuel inlet 230 leading from a tank T.
A filter screen 232 serves to filter fuel entering the chamber 226 before it passes through the valve 224. The normal flow of fuel for the carburetor system will originate at the tank T and flow through the passage 230 and the filter 232 to the valve 224 in response to fluctuation of the fuel pump diaphragm 184. Fuel will then flow through passages leading to the valve 196 to an upwardly extending passage 240 terminating at the recess 170 at the top of the fuel inlet valve. Fuel will then move through the fuel inlet valve 166 in response to control of the lever 164 and the diaphragm 162 so that it is available to the main jet through the one-way valve 174 and also to the intermediate flow chamber and the idle chamber 144. Fuel will thus be available to the mixing chamber as it is called for by reason of the adjustment of the choke and throttle.
The pulse chambers formed by the respectively shallow pockets 210-214 and 212-216 serve to enhance the flow of fuel. It will be noted that chambers 214 and 212 are connected to atmosphere. Chamber 210 is connected to the fuel passage 240 and the chamber 216 is connected to the fuel recess 226.
The vapor removal system of the carburetor is under the control of the pump diaphragm 200 and its respective valves 202 and 204. The inlet valve 202 is connected through a passage 242 which leads to the diaphragm chamber directly adjacent the valve 166 which is a high point in the fuel reservoir above the diaphragm. Thus, any vapor and foam which is created in the diaphragm chamber by reason of the flow of the fuel and the vibration of the carburetor will be pulled through the inlet valve 202 and pushed to the outlet valve 204 which leads to a down passage 244 through the plates 192, 220, and the bottom plate 250 which has formed therein an outlet 252 which will be connected to a fuel tank T. Thus, the out-flow of the vapor pump to passage 244 will carry vapor from the top of diaphragm chamber 160 to the tank. This permits the diaphragm 162 and the related inlet valve 166 to control liquid fuel only and prevents a vapor build-up which interferes with the control system built for handling liquid fuel.
It will be noted that since the pump 200 is actuated by pressure pulsations from the engine, it pumps most vigorously at part or idle throttle conditions when the crankcase pulses are longer and stronger. Since this is the time that the least fuel is being pulled through the carburetor and also the least cooling is being accomplished in the engine cavity, the heat build-up at the carburetor location is apt to be greatest. This contributes to the vaporization conditions. Thus, the pump 200 is most effective when most needed.
What is claimed as new is as follows:
1. A fuel pump for use in a diaphragm-controlled carburetor comprising:
a. a first carburetor section having a pump chamber formed therein,
b. a second carburetor section overlying the first section having a pump chamber formed therein,
c. a diaphragm lying between said sections having its periphery captured therebetween and dividing said recess formed by said chambers into a pumping chamber to be connected to a source of fuel and a pulse chamber for receiving pulses from an engine crankcase, and
d. a spring assist member lying against the diaphragm on the pulse chamber side of said diaphragm comprising a circularly shaped resilient member overlying a substantial portion of the area of said diaphragm only at the center thereof and an integral, co-planar, radial extension from said member having a distal end clamped between said sections, the said member serving as the sole resilient force on the said diaphragm by reason of the inherent resilience of said radial extension.
2. A fuel pump for use in a diaphragm-controlled carburetor comprising:
a. a carburetor body having a pump chamber,
b. a diaphragm lying across said chamber to divide the chamber into a pulse chamber to receive pulses from an engine crankcase and a pumping chamber to be connected to a source of fuel,
c. a spring assist member lying on the pulse chamber side of said diaphragm comprising a circularly shaped member overlying and in contact with a substantial portion of the area of said diaphragm only at the center thereof, and
d. resilient means forming an integral part of said member co-planar therewith and extending radially from said member and rigidly mounted in said body to support said member in said chamber, the said resilient means serving as the sole resilient force on the diaphragm.