US1984252A - Carburetor - Google Patents

Description

D. COLLINS Dec. 11, 1934.

CARBURETOR Filed July 15, 1932 IN VEN TOR. Pol/GL4: COLL/N5 "4. Q 5% A TTORNEY 66. ll, i884 Patented 7 Claims.

This invention relates to carburetors, and more particularly to acceleration devices for carburetors.

An object of the invention is to provide an acceleration device which utilizes the pressure in the fuel line produced by the mechanical fuel pumps now in common use.

A further object of the invention is to provide an acceleration pump of the character referred to having means for compensating for varying pressures in the fuel line.

Further objects and advantages of the invention will be apparent from the following description, taken in connection with the appended drawing, in which:

Figure 1 is a side elevation of a carburetor embodying the invention;

Figure 2 is an enlarged fragmentary sectional view showing the fuel connections to the float chamber;

Figure 3 is a sectional view showing the acceleration fuel nozzle and associated parts; and

Figure 4 is an enlarged sectional view taken on the line 4--4 of Figure 1.

The carburetor shown in Figure 1 is of the down draft type, although the invention is equally applicable to other types. As illustrated, it comprises an air horn 10, a float chamber 12, and a mixing chamber 14 controlled by a throttle 16. The throttle is controlled in the-usual manner by a lever 18 which has connected thereto a manually operable rod 20.

The float chamber is provided with the usual float 22 controlling an inlet valve 24 which governs the admission of fuel from a pump 25 or other suitable source of pressure through a pipe 26. The pipe 26 discharges into an auxiliary fuel chamber 28 in which is positioned the usual strainer 30. A tube 32 leads from the fuel chamher to the acceleration nozzle 34 which discharges into the mixing chamber at the venturi A tube 38 leads to a control unit 40, and a tube 42 leads to a compensating device 44, both of which are described in detail below.

The control unit 4-0 comprises a chamber 46 containing oil, glycerine or other suitable liquid and closed at one side by a flexible diaphragm 48. The diaphragm is designed to be flexed by a compression spring 49 positioned between the diaphragm and one end of a rod 50. The other end of rod 50 contacts with a cam 52 formed on the throttle axis 54, so that as the throttle is opened the diaphragm is yieldingly pressed inwardly by spring 49, thus compressing the liquid in the chamber 46.

The chamber 46 is provided with a relief chamber, or dome 56, of such capacity as to accommodate nearly all, but not all, of the liquid displaced by the maximum throw of cam 52. Cormnunication between chamber 46 and dome 56 is controlled by a relief valve unit comprising a hinged flap valve 58 which is so mounted that it obstructs upward flow of liquid when in its uppermost position. The fiap valve is actuated by gravity, and normally rests in the position indicated by dotted lines in Figure 4, in which position it permits free flow of liquid between the chamber and the dome. If desired, a poppet valve 60 may be mounted in valve 58, and held on its seat by a thermostatic spring 62 which expands when heated to permit the liquid to pass through the valve 58 even when the latter is in its closed position.

It will be seen that when the throttle is opened suddenly valve 58 will be closed by the upward surge of liquid, and pressure will be created in the chamber 46, but when the throttle is opened slowly the valve 58 will remain open and allow the displaced liquid to pass upwardly into dome 56. When the temperature of spring 62 is relatively high, as when the engine has been run long enough to warm up, the liquid will pass into the dome whether the throttle is opened quickly or slowly. If a liquid such as lubricating oil is used in chamber 46, however, the valve -60 may be dispensed with, since the viscosity of the liquid, and hence its effect in closing valve 58, will vary with temperature, so that at low temperatures but little of the liquid will pass very slowly into dome 56 and at higher temperatures it will pass more rapidly. At low temperatures 'the viscosity of the liquid would tend to prevent quick opening of the throttle, but this is avoided by the interposition of spring 49, which permits the diaphragm 48 to flex gradually even when the throttle is opened quickly. .At wide open throttle, however, the capacity of dome 56 is insufiicient to accommodate the liquid displaced, and the liquid will be slightly compressed even after the dome is filled.

The pressure created in chamber 46 by the opening movement of the throttle is transmit ted through tube 38 to a Bourdon tube 64 which is connected to tube 38 and which carries at its free end a valve member 66 cooperating with'a valve seat 68 to control tube 32. The Bourdon tube tends to straighten under pressure, and in so doing lowers member 66' from its seat and permits fiow of fuel (under the head produced by the pump) to the acceleration nozzle 3e. Such flow, however, will gradualiy decrease as the liquid in chamber 46 lealzs around valve 58, which is provided with clearance for this purpose. Such clearance is augmented by valve 62 when the engine is hot, thereby further shortening the time of injection.

At wide open throttle, as explained above, the dome 56 cannot relieve all the pressure in chamber 46, and as a result the valve 66 will remain slightly open, permitting a relatively slow discharge of fuel therefrom. Under these conditions, the device acts as an economizer, in that the supply of fuel can be adjusted for maximum economy for ordinary speeds, but the additional discharge will give maximum power at wide open throttle.

In order to compensate for variations in the fuel pressure, nozzle 34. is provided with a needle valve 70 having threaded stem engaging a correspondingly threaded bore in the wall '72 of the carburetor At its outer end the needle valve is provided with an arm I l to which is attached a Bourdon tube 76 connected to tube 42. The parts are so arranged that at the imum pressure furnished by the pump the needle valve will be withdrawn from the nozzle 3 to permit an unobstructed flow therethrough, but at higher pressures the needle valve will he moved inwardly by the Bourdon tube 76 to restrict, more or less, the flow of fuel. In this way the acceleration discharge is maintained constant in spite of varying fuel pressures.

It will be appreciated that the invention herein disclosed may be varied in various ways without departing from the spirit thereof, and is not to be limited except as defined by the following claims.

I claim:

3.. In a fuel feed system, a float chamber, an acceleration nozzle, means for supplying fuel under pressure to the float chamber and to the acceleration nozzle, a manually operable valve controlling the flow of fuel to the acceleration nozzle, and means for compensating for variations in the pressure of fuel supplied to the acceleration nozzle.

2. In afuel feed system,-.-a carburetor, a fuel pump therefor, an acceleration nozzle supplied with fuel under pressure from the fuel pump,

means operated by opening movement of the minthrottle to control the discharge from the acceleration nozzle, means for compensating for variations in the fuel pressure, and means for compensating for variations in temperature.

3. In a fuel feed system, a carburetor having an acceleration nozzle, means for supplying fuel to said carburetor and to said nozzle under pressure, a liquid chamber having a flexible wall arranged to be deformed by opening movement of the throttle to put the liquid under compression, a normally open relief valve adapted to be closed only by sudden opening movement of the throttle, and means responsive to pressures existing in said chamber for controlling the flow of fuel to the acceleration nozzle.

A device as defined in claim 3, having in addition a member operative upon increase in the pressure of fuel to partially close the acceleration nozzle.

5. In an acceleration device for carburetors, a pressure fluid chamber having a flexible wall, means connected to the throttle whereby opening movement of the throttle flexes said wall to compress the fluid, a relief chamber connected to the pressure fluid chamber, and having in sufiicient capacity to receive the liquid displaced by the flexing of said wall, a normally open check valve between the chambers adapted to he closed by sudden increase in pressure in the pressure fluid chamber, and a. thermostatically operated auxiliary valve in the check valve.

6. In an acceleration device for carburetors, a pressure fluid chamber having a flexible wall, yielding means connected to the throttle whereby opening movement of the throttle yieldingly flexes said wall to compress the fluid, a relief chamber connected to the pressure fluid chamber, and having insufiicient capacity to receive the liquid displaced by the flexing of said wall, a normally open check valve between the charmbers adapted to be closed by sudden increase in pressure in the pressure fluid chamber, and a thermostatically operated auxiliary valve in the check valve.

7. In a fuel supply system, a float chamber, a throttle, an acceleration nozzle, means for supplying fuel under pressure to the float chamher and to the acceleration nozzle, means operated in accordance with throttle movement for controlling the flow of fuel to the acceleration nozzle, and means for compensating for variations in the fuel pressure.

DOUGLAS COLLINS.

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