US2732191A - smitley - Google Patents

Description

Jan. 24, 1956 Filed Aug. 4, 1953 M. L. SMITLEY 2,732,191

DUAL CARBURETOR 2 Sheets-Sheet 1 ooe-olo'LEnx smxsn INTO 55m 46 )QY 17M X Marion 1/. Sm iil y' IN VEN TOR.

Jan. 24, 1956 M. L. SMITLEY 2,732,191

DUAL CARBURETOR Filed Aug. 4, 1953 2 Sheets-Sheet 2 Fig: 2

Maria)? L. Smiil 0 7 IN VEN TOR.

BY M,

United States Patent F DUAL CARBURETOR Application August 4, 1953, Serial No. 372,325

1 Claim. (Cl. 261-23) The object of this invention is to improve the operation of a two-stage carburetor. Carburetors of the progressive type have been known for fifty years (e. g. Bollee #871,320; Lancia 1,180,483; Friz 1,449,664; Ball & Ball of 1916 and the 1941 Buick). However, for these fifty years no one has ever produced an entirely satisfactory two-stage carburetor and each attempt, after a brief life, has been abandoned. Y

The transition from the first to the second stage has not been sufliciently smooth to be accepted by the public.

The object of this invention is, therefore, to improve this transition and satisfy the public.

Figure 1 shows diagrammatically the preferred form of my invention.

Figure 2 shows an actual reduction to practice on the exact lines laid down in Figure 1.

In Figure l:

is the air entrance of the venturi 12 and into which discharges a fuel nozzle 14. The venturi is controlled by a choke valve 16 as shown in Patent #2,547,873, located in the throat of the venturi 12 so that the nozzle is always under suction in all positions of the choke 16.

18 is the throttle which controls the discharge of air and fuel to the engine from the primary carburetor.

28 is the second throttle for the secondary carburetor.

20 is the primary throttle lever which is manually controlled.

21 and 23 are the two primary low speed fuel. outlets that insure a smooth transfer from idle to low speed operation.

22 is the throttle link which insures that the secondary throttle 28 is closed whenever the primary throttle 18 is closed, but permits the secondary throttle 28 to remain closed after 18 is opened.

24 is a slot in the lever 26 which controls the secondary throttle 28 to permit this one-way control of the secondary throttle 28.

30 is the secondary venturi into which the secondary fuel nozzle 32 discharges.

34 is the eccentrically controlled throttle shaft for the secondary throttle 28.

The eccentricity of this throttle shaft 34 is 0.055 inch on the downstream side of the inclined throttle 28. This insures that engine suction when the throttle 18 is closed will positively close the secondary throttle 28 and will overcome any friction which otherwise would allow an air leakage to disturb idling.

The secondary throttle lever 26 is connected by a link 36 with the diaphragm 38 which forms the right hand wall of the diaphragm suction chamber 40. The suction chamber 40 is maintained at subatmospheric pressure by means of the pipe 42 which is in restricted communication with the venturi 12 of the primary carburetor in all positions of the choke valve 16 at the opening 44.

Check valve 46 is supported by the spring 48 located in the body 43 of the chamber 50.

This check valve 46 is not exactly tight on its seat. A leak having a dimension of around 7 or 8 thousandths of P I Cc I 2,732,191

Pa terned Jan. 24, 1956 an inch in diameter is put into the seat so that when the valve is seated, suction will slowly build up in the chamber 40. r

The spring 50 is provided to normally keep the secondary throttle 28 closed and to permit the secondary throttle to open slowly under the influence of suction in the venturi 12 but to permit the throttle 28 to close promptly when entering on a hill and slowing down.

In Figure 2:

Similar parts having similar numbers; for example, 116 is the choke valve in the primary carburetor located in the primary venturi 112. 114 is the nozzle for the primary venturi. 118 is the throttle to the primary carburetor. 115 is a passage for air and fuel from the float chamher 117 (see Patent #2,547,873 referred to above).

132 is the nozzle for air and fuel for the secondary carburetor discharging into the secondary venturi 130.

126 is the slotted throttle lever for the secondary throttle 128.

124 is the slot in lever 126.

As before, the throttle 128 is 0.055 inch off center and its diameter is 1%(;''.

136 is the rod connecting diaphragm 138 (which has a diameter of 1%") with the lever 127 which is rigidly mounted on the throttle shaft 129 as is the slotted lever 126. 1

A loose link 131 connects in the slot 124 with the primary throttle lever so that if primary throttle 118 is closed, then secondary throttle 128 will also be closed; but the throttle 118 can be opened and the secondary throttle 128 will remain closed.

A spring 150 located in the chamber 140 tends to keep secondary throttle 128 closed.

A spring 148 tends to seat the ball check valve 146 against a seat 147 which is provided with a leak so that the pressure in chamber-140 can fall only slowly, but can rise rapidly.

b 121, 123, 125, 127 are four low speed outlets controlled y 11ga The position of the upstream lip of the throttle (b) The lowest orifice 127 is controlled by the low speed idling control valve 129.

This is the low speed control system.

A passage 142 connects the left hand side of check valve 146 through the leak with the restriction 144 in throat 112.

Operation As before, if the load is reduced, as when running downhill, then all the power needed is derived from the primary carburetor and the secondary throttle 128 remains closed. Again, if the throttle 118 is wide open as when climbing a hill, then the suction in the primary venturi 112 is too low to overcome the spring 150. The throttle 128 still remains closed by the pressure exerted by the spring 150. Now, if the flow through venturi 112 exceeds a safe top limit, suction at 144 in the throat is transmitted through the pipe 142 past the leak around the check valve 146 to the chamber 140. The pressure in chamber 140 slowly falls and eventually, the throttle 128 opens. If the throttle 118 is suddenly closed, the link 131 engages the left hand end of slot 124 and the secondary throttle 128 is positively closed. The spring 148 is selected so as to permit the ball valve 146 to move easily to the left so that the diaphragm 138 can also easily move to the right.

What I claim is:

In a two stage carburetor having a primary and a secondary venturi, mixing chambers and two mixture outlets in parallel, two butterfly throttles, one in each outlet, means for positively opening the throttle controlling the primary mixture outlet; said secondary throttle being oftset so that the upstream lip is longer than the downstream lip by approximately ".where the throttle has a diameter of about 1.31 inches so as to be held closed by inlet manifold suction, a oneway lost motion connectionfromthe primary to said secondary throttle so that the primary throttle positively closes said secondary throttle when the primary throtde is closed, a chamber, a moving wall therein positively connected to said secondary'throttle lever, a passage from said chamber to the throat of the primary venturi of said primary mixing chamber, a check valve therein, a valve seat thencfor, a light spring pushing said valve on said seat and a restricted by pass around said valve to admit air freely to said chamber when said secondary throttle is positively closed and to delay the automatic opening of said secondary throttle by delay: ing the admission of low pressure air to said chamber through said restricted by pass, said moving wall being responsive to the suction admitted past said check valve to said chamber and positively connected to the secondary throttle.

References Citedinthe file of this patent UNiTED STATES PATENTS 2,376,732 Strebinger May 22, 1945 2,609,807 Winkler Sept. 9, 1952 2,647,502 Braun Aug. 4, 1953

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