US2262408A

US2262408A - Carburetor choke control

Info

Publication number: US2262408A
Application number: US380784A
Authority: US
Inventors: Leland B Read
Original assignee: Carter Carburetor Corp
Current assignee: Carter Carburetor Corp
Priority date: 1941-02-27
Filing date: 1941-02-27
Publication date: 1941-11-11
Anticipated expiration: 1958-11-11

Description

Nov..11, 1941. 5 L, R D-+- 2,262,408

CARBURE' IOR CHOKE CONTROL Filed Feb. 27, 1941 INVENTOR.

LELAND B. READ .5 t UNITED: "STAT Patente'ci' Nov'. 1 1;

Es PATENT ori ice 6 Claims. This invention relates to carburetors for internal combustion engines and more particularly to automatic choke control devices therefor.

Many of the current automaticv choke constructions involve theuse of a spirally wound bi-metallic element which is either directly attached to the choke valve shaft ordisposed immediately adjacent thereto and subjectedto a controlled amount of heat conducted thereto from some part of the engine which becomes 'more quicklyheated after starting. The means employed for controlled heating usually comprises providing a housingfor the coil, a stove I or heating jacket attached to the exhaust manifold and a conduit for conducting the heated air from the stove to'the coil housing. 'The flow of warm airfrom the'stove to the coil housing being induced and. controlled by a calibrated and sometimes variable passageway connecting -the coil housing with a zone of high suction in the carburetor mixture conduit.

In downdraft carburetor constructions in which -the air inlet and choke valve areat'the'upper end of the carburetor, it will be seen that when the choke control coilis arranged in the above manner it will be located at a considerable distance from the engine and exhaust manifold. Also that when the engine is turned off the induction of hot air from the stove to the coil housing will be discontinued and the rate of cooling of the coil and housing structure will be much greater than the engine and exhaust'manifolds due to the-much greater mass of these latter elements and the remote disposition of the coil with respect thereto.

While the advantage of disposing the temperature' responsive coil element so as to minimize uncontrolled heatingthereof by the engine is apparent,-it has been found that under the follow-L ing-conditions; as when, a'motor vehicle which thereafter diminishes until such difference ceases to give rise to. the aforementioned diificulty.

I It is an object of the present invention to provide an automatic choking device of the above character, in which the aforementioned difflculty is overcome by the provision of a secondary temperature responsive controllingelement which is;

more directly effectedby the engine temperature.

It is a further object of the present invention. to provide an improved automatic choking device having a temperature responsive choke actuating element subjected to a controlled temperature during operation of the engine and a secondary temperature responsive element dilimiting the control merit.

rectly effected by the engine temperature for Other objects and advantages will appear upon reference to the following description and accompanying drawing. Referring to the drawing:

Fig. l is a side elevation of a downdraft 'carburetor equipped with a choke control mechahas been driven sufficiently to thoroughly-heat the engine and then parked, with the engine turned off, that after a certain interval econ-- dition exists wherein the temperature responsive coil has cooled and responded-to move the choke valve to a' position which "willresult in the clearly illustrate.

nism constructed in accordance with the present invention. Parts being broken away to more Fig. 2' is a fragmentary section taken on line 22ofFig.l.

Fig. 3' is a fragmentary se'ctiontaken on line 3--3 of Fig. 1.

a'rotatable choke shaft 4. The outlet at the lower end of the carburetor is controlled by a throttle valve 5 mounted on a rotatable throttle end a throttle lever I.

The carburetor ismoun-ted on an engine intake manifold 8 and is attached theretoby the bolts 9. An engine exhaust manifold isindi- "cated at H) below and parallel to intake mani--.

fold 8. The'near end of the choke shaft 4 cardeliverance of a starting mixturewhich is-too rich for the still comparatively warm engine if re-started atthis time.

perature within the eng'ine hood enclosure is lowered by drafts of cold air. Obviously, during This difliculty will be aggravated on cold windy days when the .tem-

l of coil l8 engages the projection ii on lever I. Coil I8'is constructed of a bi-metallic' strip and the cooling down period a critical point is 1 reached at which the difference in'the tempera.

tures of the coil and the engine is greatest and I'i'eS rigidly attached thereto a'lever in having a bent-up axially extending arm l2 and a second arm I! which carries pivotally attached thereto alinkl5. Attached to the air inlet is a therrnostatic. coil housing It having a square split mounting stud i1 rigid y attached thereto which receives and rigidly anchors the inner end of a 1 temperature responsive coil l8; The outer end so'wound as to tend to unwind with-decreasmg temperatures; Being thus wound and an- "chored at its inner en} theouterend will urge of the choke actuating ele- I Numeral i indicates a modern downdraft carburetor having an air inlet 2 at its upper end in l which is mounted a disk-type choke valve ,8 on.

lever II in a counterclockwise or valve closing direction with decreasing temperatures. A substantial portion of the inside of housing I 6 is lined with insulating material l6a.

Attached to the exhaust manifold I is a stove l9 and a conduit connects the stove 19 with the inside of housing IS. A cylinder 2| is formed in the lower right hand side of housing l6 and has fitted therein a piston 22 which is pivotally connected to the link IS. A passageway 23 connecting the lower end of cylinder 2| with the carburetor mixing conduit at a point below the throttle valve is provided. A slot 24 in the wall of the cylinder 2| allows a predetermined amount of by-passing of the piston. The piston 22 responding to suction tends to move the choke valve open against the resistance of the coil element [8. The combination of coil l8 and suction actuated piston 22 provides the well known thermo-suction control and its operation is Well understood.

Attached to the choke valve shaft 4 at a point between the housing l6 and the air inlet 2 is a lever 25 having a link 25a. pivotally attached to its outer end at 26. Mounted on a pivot 21 toward the lower end of the carburetor is a rotatable throttle blocking element 28 usually called the fast idle cam. The portion of element 28 which extends to the left of pivot 21 carries a pivot pin 29 which engages the slot 30 in the lower end of link 25a. The portion of element 28 extending to the right of pivot 21 is provided with an abutting surface 3|. -Attached to the lower flange portion of the carburetor by means of a screw 32 is a U-formed strip of temperature responsive bi-metal 33 positioned so that at certain temperatures the end of free left leg 34 will block the clockwise rotation of element 28. The

arrangement of the mechanism, as shown, is such that the choke valve will be held in a substantially open position when element 33 is in a position to block the clockwise rotation of element 28. The temperatureresponsive bi-metallic element 33 is formed with the metal having the greater expansion on the inside so that with increasing temperatures the free leg 34 will move to the left into a blocking, position and to the right out of blocking position (as shown by dotted lines) with decreasing temperatures.

The operation is as follows:

When, after operation, the engine is stopped the flow of warm air from the exhaust manifold to the coil housing l6 will stop and the rate of cooling of the coil 18 will be greater than that of the engine and the blocking element 33 which is positioned closer thereto than coil l8. As the coil [8 continues to cool it will uncoil and move the choke valve toward a closed position. If the rate of cooling of coil l8 has been appreciably greater than that of element 33, the movement of the choke valve toward a closed position will be blocked by element 33 as it reaches the position shown. However, as soon as the engine temperature has dropped sufficiently for the adjacent element 33 to re-act and move out of blocking position the choke valve will again be under full control of element l8. It will be understood that the invention is susceptible to modification, and therefore I do not wish to be limited in my protection except as set forth in the accompanying claims.

I claim:

1. In an internal combustion engine, a carburetor having a choke valve, a temperature responsive element constructed and arranged to gradually move said choke valve toward a closed position with decreasing temperatures, and a second temperature responsive element constructed and arranged to prevent the closing of said choke valve until the temperature has fallen below a predetermined point, said first mentioned element being positioned at a greater distance from said engine than said last mentioned element.

2. ,In an internal combustion engine having an exhaust manifold, a carburetor having a choke valve, a temperature responsive element for controlling said choke valve, and a second temperature responsive element constructed and arranged to prevent the closing of said choke valve until the temperature has fallen below a predetermined point, said first mentioned element being positioned at a greater distance from the engine manifold than said last mentioned element.

3. In a carburetor, a choke valve, a temperature responsive element constructed and arranged to gradually close said choke valve with decreasing temperatures, a second temperature responsive element constructed and arranged to block the closing of said choke valve until the temperature has fallen below a predetermined point, said last mentioned element being subjected, under certain conditions, to higher temperature than said first mentioned element.

4. In an internal combustion engine, a carburetor having a choke valve, a temperature responsive element for controlling said choke valve, an insulated housing for said choke valve, means dependent upon the operation of the engine for supplying heated air to said housing, and a second temperature responsive element constructed and arranged to block the closing of said choke valve until the temperature has fallen below a predetermined point, said last mentioned element being positioned so as to receive heat from the engine by conduction and radiation more directly than said first mentioned element.

5. In an internal combustion engine having a downdraft carburetor mounted above the engine, an air inlet to said carburetor at the upper end thereof and a flanged outlet portion at the lower end thereof attached to saidengine, a choke valve in said air inlet, a temperature responsive element for controlling said choke valve positioned adjacent said choke valve, and mechanism including a second temperature element for blocking the closing movement of said choke valve under certain conditions, said second temperature responsive element being positioned adjacent said lower flanged outlet portion.

6. In an internal combustion engine having intake and exhaust manifolds, a downdraft car buretor mounted above said manifold, said carburetor having an air inlet at its upper end and a flanged outlet portion at its lower end adjacent said manifold, a choke valve in said air intake, a temperature responsive element for controlling said choke valve positioned adjacent said air inlet, an insulated housing for said choke valve, means including intake manifold suction whereby air heated by the exhaust manifold is induced to flow through said housing, and mechanism including a second temperature responsive element for limiting the control of said first mentioned temperature responsive element, said second element being positioned adjacent said lower flanged portion.

LELAND B. READ.