US2646933A

US2646933A - Automatic carburetor choke control

Info

Publication number: US2646933A
Application number: US186286A
Authority: US
Inventors: Leonard D Boyce
Original assignee: Carter Carburetor Corp
Current assignee: Carter Carburetor Corp
Priority date: 1947-05-09
Filing date: 1950-09-22
Publication date: 1953-07-28
Anticipated expiration: 1970-07-28

Description

y 8, 1953 L. D. BOYCE 2,646,933

AUTOMATIC CARBURETOR CHOKE CONTROL Original Filed May 9, 1947 INVENTOR. LEONARD D. BOYCE ATTORNEY Q Patented July 28, 1953 AUTOMATIC CARBURETOR CHOKE CONTROL Leonard D. Boyce, Kirkwood, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Original application May 9, 1947, Serial No.

747,029, now Patent No. 2,533,551, dated December 12, 1950. Divided and this application September 22, 1950, Serial No. 186,286

4 Claims. 1

This invention relates to carburetors for internal combustion engines of the automotive type and consists particularly in a novel automatic choke control therefor. This application is a division of my copending application, Serial No. 747,029, filed May 9, 1947, now Patent No. 2,533,551 of December 12, 1950.

The present, generally used type of automatic choke control for automotive carburetors utilizes a bi-metal coiled spring which expands when the temperature is low to urge the unbalanced butterfly choke valve closed. Since the thermostat is mounted on the carburetor air horn at a point remote from the engine and, particularly the intake manifold thereof, there is a tendency for the thermostat to cool quicker than the engine. Thus, if the engine is stopped before it is fully heated and an attempt is made to restart it within a few minutes, more closing force may be applied to the choke than is desirable to obtain the proper mixture corresponding with the existing engine temperature. Accordingly, the mixture would be too rich and restarting impeded.

An object of the present invention is to provide means for counteracting the portion of the thermostat action which, at low temperatures, effects the final closing movement of the choke valve.

Another object is to avoid the premature or excessive closing of the choke valve due to excessive cooling of the thermostat, as explained above.

These objects and other more detailed objects hereafter appearing are attained by the device illustrated in the accompanying drawings in which:

Fig. 1 is a side view and section showing the upper part of a carburetor and automatic choke control embodying the invention.

Fig. 2 is a view of the parts in Fig. 1 taken at 90 thereto, parts being broken away and sectioned.

Fig. 3 is a detail section taken substantially on line 33 of Fig. 2 and showing the choke valve fully opened.

Fig. 4. is a section similar to Fig. 3 but showing the choke valve fully closed by the thermostat.

Fig. 5 is an enlarged view of a portion of the structure in Fig. 1.

Figs. 1 and 2 show the upper air horn portion I of the mixture conduit 8 of a downdraft carburetor. An unbalanced, butterfly, choke valve 9 is pivotally mounted in the air horn on a shaft I0 which projects laterally into a casing H carried at the side of the air horn. A cover i2 is adjustably and detachably secured to the casing by means of screws I3 and clips I4 and has a central pintle I5 to which is secured the inner extremity of a bi-metal thermostat coil I5. A threaded fitting I'I projecting outwardly from the. center of the casing cover provides for attachment of a tube leading to a source of heat supply (not shown). If desired, a suction connection may be provided between the thermostat casing and the mixture conduit for drawing hot air therethrough, as disclosed in Cofiey Patent No. 2,085,351.

An arm 20 is rigidly secured to the end of the choke shaft I0 within casing I and has a finger 2i projecting through an arcuate slot 22 in a baiiie plate 23 which separates the casing and cover portions. For further description of the structure and operation of these portions of the automatic choke control, reference is made to the above mentioned parent application.

Also secured to central pintle I5 on the thermostat casing cover is a flat, coiled bumper spring 24 which lies between the thermostat and cover I 2 and has its outer extremity extending through an eye 25 on the cover I2 and then bent inwardly, as at 26 (Fig. 2) so as to lie in the path of hooked, outer extremity 2! of the thermostat coil. This latter hook is disposed, upon cooling and consequent unwinding of the thermostat, to engage finger 2l on choke shaft arm 20 and urge the choke valve closed, as in Fig. 4. The thermostatic action is opposed by the direct action of air flow on the unbalanced choke.

During the closing movement of the choke valve, under the influence of the thermostat, thermostat hook 2'! in passing eye 25, engages finger 26 on bumper spring 24 so that further unwinding of the thermostat and closing of the choke is resisted by the bumper spring. Eye 25 maintains the bumper spring in a prestressed condition so that its efiect in retarding the closing influence upon the choke valve, as exerted by the thermostat, is felt immediately that the bumper spring is picked up by the thermostat. Thus, the bumper spring opposes with appreciable force the last portion of the choke-closing action of the thermostat. Preferably, the strength of spring 24 and the thermostat are adjusted so that the thermostat will fully close the choke valve against spring 24 only when the temperature is from 10 to 20 lower than that at which the choke would be closed by the thermostat if spring 24 were omitted.

The invention is of especial advantage in case the engine is stopped before being fully heated and when the outside temperature is very low. In such case, the thermostat may cool faster than the engine. To prevent such excessive expansion of the thermostat and consequent closing of the choke valve, spring 24 counteracts the portion of the thermostatic action which causes the last 10-30" of choke closing movement. Eye 25 insures proper pre-stressing of this spring which, thus, has a controlled efiect on a relatively small portion of the thermostatic action and exerts no force whatever upon the choke valve itself or when the thermostatic hook passesover eye v25 as the thermostat Winds upon itself during warm up. When the thermostat is fully heated, the choke valve hangs fully openand hook 21 leaves finger 2|, as in Fig.3.

The bumper spring feature may be applied to substantially any type of automatic choke control utilizing a thermostat wherein it is desired to retard the thermostatic action or a portion thereof. The particular form of the bumper spring, as shown, is not essential and the exact portion of the thermostatic action effected there-' by may be modified as required. The invention may'be modified in these and other respects as will occur to those skilled in the art and the exelusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim: 1. In a carburetor, a'mixture conduit having a choke valve-therein, an arm movable with said choke valve, a coiled thermostatic spring having an end portion for engaging said arm when the temperature is low, to urge said choke valve -closed,.and a .prestressed spring positioned to be engaged by said end portion of said thermostatic spring during its action to effect the last part of the closing movement of-said choke valve for ophigh temperatures.

2. In a carburetor, a mixture conduit having a butterfly choke valve therein, an arm rigid with the choke shaft outside said conduit, a thermostatic coil spring mounted adjacent said arm and having a hooked outer'extremity forming a oneway operative connection therewith for urgin said choke valve closed when the temperature is low, and an additional coiled spring mounted adjacent said thermostat and having a turned over end for engagement by the hooked end of said thermostat during the portion of the thermostat action which effects the last part only of the choke closing movement for opposing said part of the thermostat action.

3. A-carburetor as described in claim 2 in which the center of said second coiled spring is permanently mounted and further including a stop element for cooperating with the turned-over outer end of said second spring to maintain the same in prestressed condition so as to be picked up by said thermostat hooked end during the choke closing action thereof.

4. In an automatic choke control for a carburetor, a casing having a pintle projecting from a Wall thereof, a thermostatic coil centrally secured to said pintle, and a bumper spring also secured to said pintle with a portion disposed in the path of movement of the choke operative outer portion of said thermostat so as to resist a portion of the thermostat action.

LEONARD D. BOYCE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,162,296 Chappell June 13, 1939 2,237,732 Giesler Apr. 8, 1941 2,361,132 Smith Oct. 24, 1944 2,402,361 Bickwell June 18, 1946 2,410,758 Thompson Nov. 5, 1946