US3180576A - Means for mounting a thermostatic element - Google Patents

Description

A ril 27, 1965 R. E. HERMAN 'MEANS FOR MOUNTING A THERMOSTATIC ELEMENT 2 Sheets-Sheet '1 Filed May 8, 1962 April 27, "1.965 R. E. HERMAN 3,180,576

MEKNS FOR MOUNTING A THEBMOSTATIC ELEMENT Fi'lsed May 8, 1962 2 Sheets-Sheet 2 INVENTOR. RON/11 D t. ME/PMAA .Zbwi

ATTORNEY United States Patent O 3,180,576 MEANS FOR MGUNTING A THERMOSTATIC ELEMENT Ronald E. Herman, Warren, Mich, assignor to Holley Carburetor Company, Warren, Mich, a corporation of Michigan Filed May 8, 1962, Ser. No. 193,252 Claims. (Cl. 236101) This invention relates generally to internal combus- -tion engine carburetors having thermostatically controlled automatic choke systems, and more particularly to novel means for relieving stress that may otherwise build up in the thermostatic element at higher engine temperatures when the choke is open.

Most carburetor automatic choke systems comprise a choke plate mounted on a shaft in such a way that the flow of air to the engine tends to open the choke plate, and the openingof the choke valve is resisted when the engine is cold by the free end of a thermostatic coil spring having its inner end anchored to the choke housing. In the usual case, the coil is unwound when cold and winds up when heated; thus, the resistance of the thermostatic coil spring to choke opening decreases as the engine temperature increases.

The above described arrangement is generally acceptable. 'However, in some carburetor designs, it is essential that the choke housing comprise a compact shape, which in some instances is other than circular. In such a housing, it is conceivable that the tang or free end of the thermostatic bimetal spring, after a certain amount of travel, would abut against a side of the choke housing, and thus not be free to further wind about its center as the temperature in the housing continued to rise.

Accordingly, a general object of the invention is to provide a means for stress relieving the thermostatic bimetal spring after it comes into contact with the choke housing wall.

A more specific object of the invention is to provide a movable anchor which would permit the inner end of the bimetallic coil spring to rotate about its axis in a direction opposite to the rotation of the external tang, and

- thus relieve the stress that would otherwise be present in the bimetallic spring.

A further object of the invention is to provide for smaller choke housings, or for housings which depart from 'a circular shape, thus permitting a more compact configuration of thecarburetor and air-cleaner combination.

vention willbecome apparent when reference is made to' the following description and the accompanying illustrations wherein:

FIGURE 1 is a front elevational view, with portions thereof cut away and in cross section, illustrating generally a carburetor embodying the invention, the carburetor being mounted on the intake manifold of an engine;

FIGURE 2 is a side elevational fragmentary view of the carburetor shown by FIGURE 1;

FIGURE 3 is a cross-sectional view, taken on the plane of line 3''-3 of FIGURE 1 and looking in the directions "of the arrows; i

FIGURE 4 is an enlarged, cross-sectional view of the automatic choke assembly, taken on the plane of line 4-4 of FIGURE and looking in the direction of the $18,576 Patented Apr. 27, 1965 FIGURE 5 is a cross-sectional view, taken on the plane of line 55 of FIGURE 4 and looking in the direction of the arrows;

FIGURE 6 is an enlarged cross-sectional view, taken on the plane of line 66 of FIGURE 4 and looking in the direction of the arrows;

Referring to the drawings in greater detail, FIGURE 1 illustrates generally a carburetor assembly 10 mounted on the engine intake manifold 12. The carburetor 10 includes the usual carburetor body 14 with an air inlet passage 16 therethrough. The air inlet passage 16 includes the usual choke valve 18, venturi 20 and throttle valve 22. The choke valve 18 is operatively connected to a bimetallic thermostat spring 24, positioned in the automatic choke housing 26, by means of the choke shaft 28 and the choke lever 30. The choke housing 26 is warmed by air which enters the system through the air inlet passage 16 and then passes through a cold air intake 32 and cold air tube 34 to the exhaust manifold 36 to become heated by a stove 38 located therein; the heated air then passes through the hot air tube 49 and into the choke housing inlet 42.

FIGURE 2 illustrates the fast idle cam 44 pivotally fastened to the carburetor body 14 by a fast idle cam -nected to a throttle lever 52 which is responsive in the well-known manner through appropriate linkage to manual movement of the foot pedal (not shown). A throttle shaft 50 is fixedly attached to the throttle lever 52 for ro tation therewith in order to actuate the throttle valve 22.

Maximum movement of the throttle lever 52 is controlled by the usual throttle stop screw 54 which abuts against a lug cast on the side of the carburetor body 14. Manual adjustment of the fast idle screw 48 and the throttle stop screw 54 are maintained'by the compressed springs 58. The cam 44 is operatively connected to the choke shaft 28 by means of a fast idle link 60, a linking element 61 and a set screw 62.

FIGURE 2 further illustrates the choke housing cover assembly 64 which comprises a choke housing plate 66, a thermostat cap and baffle assembly 68, a thermostat cap clamp and a thermostat cap clamp screw 72.

FIGURE 3 illustrates the inner chamber 74 of the choke housing 26, with the choke housing cover assembly 64 removed. The choke lever 30 is shown rigidly attached to the choke shaft 28'so that it can control the opening and closing of the choke plate 18. The choke housing chamber 74 is subjected to vacuum from the intake manifold 12 through a vacuum passage 76 and an inlet 78.

FIGURE 4 is an enlarged view of the complete automatic choke assembly demonstrating the passageway 80 into the choke housing chamber 74 for the hot air which enters the choke housing 26 through the thermostat cap inlet 42. The choke housing plate 66 can be seen to include a gasket 82 that may be cemented to its outer face that many carburetor designs utilize a single cover instead of the housing plate 66 and the thermostat cap and baflie assembly 68; in that event, the support extension 86 for bimetallic thermostat spring 24 is attached to the support 3 extension 86. This View also demonstrates the cooperation of the thermostatspring tang 90 with the choke lever 39, and the subsequent contact by the tang 90 with the choke housing wall 92.

With respect to the support extension 86, it can be seen that it amounts to a cylindrical stem being first formed with a pair of diametric, right angle slots, the slots being as wide as the thickness of the spring 24 and at least as long the the. spring 24 is wide so as to provide tour 90 sections and then having a pair of oppositely disposed sections removed. The two remaining sections 87 and 89 adequately retain the inner end 91 of the coil spring 24, but permit a 90 rotation thereof between the sections 8'? and 89 from the solid line to the dotted line portion D.

Operation have pivoted the fast idle screw 48 (FIGURE 2) away.

from whichever step of the fast idle cam 44 it was contact ing from the previous operating of the vehicle. The cold bimetallic thermostat spring 24' in the chamber 74, thus freed, would have immediately loosened or'unwound itself with respect to the support extension. 86 so as to retate the choke lever in a counterclockwise direction to position A. The fast idle cam 44 would have been rotated by the fast idle link 6% leading from the choke shaft 28, which was also turnedby the cold bimetallic depression would then have allowed the fast idle screw 43 to return against the now rotated high step of the fast idle cam 44.

Referring again to FIGURE 6, as the warm air from the.

exhaust manifold 36 enters the chamber 74 through. the inlet-42 and the passageway St) shown in FIGURES 4 and 5, the bimetallic thermostat spring 24 becomes warmed and begins to tighten about the support extension Q 06, rotating in a clockwise direction, thus offering less and less resistance to the opening of the unbalanced or offthermostat spring 24. Release of the initial foot pedal 1 higher temperatures is, effectively reduced or eliminated.

As stated previously, some prior choke designs have the tang 9t) actually looped about the lever 3%. Here, again, the spring 24 would be stressed at temperatures above the choke open temperature because the lever 39 is prevented from further clockwise rotation due to an abutment which is necessary to prevent the choke plate from opening beyond the fully opened position.

Relieving stress in the thermostatic coil spring as d"- scribed above is important because the stress may exceed the elastic limit of the spring material so that a permanent set or deformation of a spring occurs. This set is in the direction such that it increases the resistance of the spring to choke opening when the engine is cold. Thus, the next cold start would be either impossible or excessively rich. In other words, the permanently deformed coil spring would thereafter keep the choke on too long and adversely efiect cold starting and operation.

Thus, it can be seen that the invention enables the use of compact and irregularly shaped choke housings or the use of looped connections between the thermostatic coil spring and the choke lever, at the same time relieving or eliminating harmful stresses that may otherwise exist on account of such constructions.

Although but one embodiment of the invention has been shown and described, it is conceivable that various modifications are possible, and no limitation not recited in the appended claims is intended.

What I claim as myinvention is:

1. In an internal combustion engine carburetor including an air inlet-passage, a'choke .valve in saidair inlet passage and means-tor automatically controlling the posi tion of said choke valve, said means'including' a spiral type thermostatic element having a free outer end operatively connected to said choke valve and an inner end, said .outer end being restrained from further movement when a predetermined temperature has been attained, means for mounting said inner end so as toprovide a limited degree. of stress relieving motion thereof and.

when said outer end is restrained, said latter means comprising a pin having oppositely disposed wedge portions set choke plate 18 by the fresh air entering through the air inlet passage 16 (FIGURE 1). The choke plate 18 is thus progressively opened as engine temperature in.

creases until the choke lever 30 forces the thermostat springtang 9t: to position B, at which time the choke valve 13 would be fully open. 7

Once the choke plate 18 is fully opened, the movement of the choke lever3tl, of course, will be stopped. Thereafter, however, depending upon the thermal activity rate of the bimetallic thermostat spring 24 involved, the spring 24 may continue to wind up. In fact, a typical high rate spring 24 would continue to wind about the center support struction where the inner end 91 of the coil is rigidly anchored, the above restraint-of tang 9i? of wall 92 would cause undue stresswithin the thermostatic spring 24 as long as the higher temperatures exist. g

It will be seen from FIGURE 6 that the invention eliminates the above objections to present choke constructions, particularly in the smaller carburetor designs for the socalled compact vehicles. That is,'.the structure of the support 86 for mounting the coil spring 24 issuch thatthe inner end 91 of the spring'is free to rotate 90 in a man terclockwise direction to the dotted-line position when tang 90 is restrained by wall 92. Actually, the inner end 91 may begin to rotate in the counterclockwise direction I once the tang 9% leaves contact with the choke lever 30 '86 until its tang 9t) abuted against the choke housing wall I 92, as shown at C. In the usual automatic choke con between which said inner end is mounted and the opposite aligned surfaces of which provide'two limits of movement of said inner end.

2.iIn an automatic choke mechanism, athermostatic element having a free outer end and a .pivotable' inner end formed thereon, means for heating said thermostatic element, a pair of oppositely disposed wedge-shaped supports, means for pivota bly connecting said :inner end to said wedge-shaped supports, and means for at times restraining movement of said free. outer end in one direction; one side of each of said Wedge-shaped supports serving torestrain' movement ofsaid inner end-in said one direction while'said free outer end is moving in the same direction, the-other twosides of each. of said wedgeshaped supportsserving to restrain further movement of said inner. end in-the other direction after said inner end has moved a predetermined distance.

3. In an automatic choke mechanism including a choke shaft and a choke lever secured thereto, a spiral thermostatic'ele'ment having a 'free radially-extending outer end and a dian retrically-extending inner end formed thereon, said outer end at times being in contact withsaid choke lever, means for heatingsaid thermostatic element, a pair of oppositely disposed wedge-shaped supports, said inner end being positioned between said wedge-shaped supports, means forrestraining movement ofsaid outer end in one direction after said outer end hasleft contactwith said choke lever, said inner; endbeingtree'to rotate from a position adjacent one side offeach of said wedge-shaped supports toward the other sideoif each of said wedgeshaped supportssonce said outerend leaves contact with said choke lever.

4.- In an automatio'choke mechanism including a choke shaft and a choke lever securedthereto, a spiral thermostatic element having a radially-extending outer end and a diametrically-extending inner end formed thereon, said outer end being in contact with said choke lever, means for heating said thermostatic element, a pair of oppositely disposed wedge-shaped supports, said inner end being positioned between said wedge-shaped supports, means for restraining movement of said outer end in one direction, said inner end being free to rotate from a position adjacent one side of each of said wedge-shaped supports toward the other side of each of said wedge-shaped supports with increased temperature.

5. A temperature-controlled mechanism, comprising a membert to be positioned in accordance with temperature, a thermostatic spiral coil element having the outer free end thereof operatively connected to said member and an inner end, means restraining the further movement of said outer end as temperature increases, and rigid abutment means for mounting said inner end in a manner to allow said inner end to assume any position between two limits, said rigid abutment means including a mounting pin formed to provide a pair of oppositely disposed wedge sections, the inner coil of said spiral coil element surrounding said pin and said inner end being positioned between said wedge sections.

References Cited by the Examiner UNITED STATES PATENTS GEORGE D. MITCHELL, Primary Examiner.

HERBERT L. MARTIN, Examiner.

Claims (1)

1. IN AN INTERNAL COMBUSTION ENGINE CARBURETOR INCLUDING AN AIR INLET PASSAGE, A CHOKE VALVE IN SAID AIR INLET PASSAGE AND MEANS FOR AUTOMATICALLY CONTROLLING THE POSITION OF SAID CHOKE VALVE, SAID MEANS INCLUDING A SPIRAL TYPE THERMOSTATIC ELEMENT HAVING A FREE OUTER END OPERATIVELY CONNECTED TO SAID CHOKE VALVE AND AN INNER END, SAID OUTER END BEING RESTRAINED FROM FURTHER MOVEMENT WHEN A PREDETEMRINED TEMPERATURE HAS BEEN ATTAINED, MEANS FOR MOUNTING SAID INNER END SO AS TO PROVIDE A LIMITED DEGREE OF STRESS RELIEVING MOTION THEREOF AND WHEN SAID OUTER END IS RESTRAINED, SAID LATTER MEANS COMPRISING A PIN HAVING OPPOSITELY DISPOSED WEDGE PORTIONS BETWEEN WHICH SAID INNER END IS MOUNTED AND THE OPPOSITE ALIGNED SURFACES OF WHICH PROVIDE TWO LIMITS OF MOVEMENT OF SAID INNER END.

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