Thermostatic device for automatic choke control
AssigneeBriggs & Stratton Corporation
InventorsPaul R. Nau, James L. Bartlett, Heinz K. Gund
Life of this patent
Estimating the term…
Abstract
End portions of the choke valve shaft project outside the carburetor mixing passage duct. One end portion is connected with an actuator mechanism that is responsive to either engine speed or manifold pressure. The other projects into a cylindrical chamber on the carburetor body that houses a spirally coiled bimetal strip having its inner end connected with the shaft, its outer end engageable with circumferentially spaced abutments. The chamber is communicated with the crankcase breather and also with the mixing duct through a flapper valve, so that the bimetal is subjected to the temperature of vented crankcase vapors.
Claims10
An internal combustion engine that has a crankcase, a carburetor comprising a body in which there is a mixing passage and a choke that has a rotatable shaft which projects through a wall of the mixing passage, a crankcase breather that permits gases to flow substantially freely out of the crankcase but restricts entry of air thereinto, and duct means communicating the crankcase breather with said mixing passage, said engine being characterized by:
- A. a portion of said duct means comprising a chamber which is adjacent to the mixing passage and into which said shaft projects;
- and
- B. a spirally coiled bimetal element in said chamber
- 1. having its inner end portion connected with said shaft,
- 2. having its outer end portion adapted to react against a portion of the wall of the chamber so that the bimetal element tends to position the choke valve in accordance with the temperature that prevails in said chamber, and
- 3. which is so arranged in said chamber that gases pass thereacross in flowing from the crankcase to the mixing passage, so that the temperature in said chamber always closely reflects the operating temperature of the engine.
In a carburetor for an internal combustion engine that has a crankcase breather through which gases are expelled substantially freely from the engine crankcase and which restricts entry of air thereinto, said carburetor having a body in which there is a mixing passage, a choke valve in said mixing passage rotatable with a shaft that has end portions projecting through opposite wall portions of the mixing passage, and choke valve actuating means connected with one end portion of said shaft and which so responds to a function of engine speed as to tend to open the choke valve at high engine speeds and to close it when the engine is stopped, means for preventing excessive opening of the choke valve when the engine is cold and for preventing complete closure of the choke valve when the engine is hot, the last mentioned means comprising:
- A. means on the carburetor body defining a chamber
- 1. which is adjacent to said mixing passage and communicated therewith and
- 2. into which the other end portion of said shaft projects;
- B. means on the carburetor body for communicating said chamber with the crankcase breather, so that gases expelled from the crankcase flow through said chamber to the mixing passage to maintain a temperature in said chamber that corresponds to the temperature of the engine;
- and
- C. a spirally coiled bimetal element in said chamber
- 1. having an inner end portion connected with said other end portion of said shaft, and
- 2. having an outer end portion reacting against the carburetor body, so that the bimetal element tends to hold the choke valve open when high temperatures prevail in said chamber and to hold it closed when low temperatures prevail in said chamber.
An internal combustion engine carburetor of the type having a body in which there is a mixing passage and having a choke valve in said mixing passage that is movable between open and closed positions, and wherein movement of the choke valve is effected by automatic choke control means comprising a thermostatic element with which the choke valve is connected and which tends to establish the position of the choke valve in accordance with temperature at the thermostatic element, said carburetor being characterized by:
- A. the thermostatic element comprising a spirally coiled bimetal strip having a radially outwardly projecting outer end portion and a radially inwardly projecting inner end portion;
- B. the carburetor body having means thereon defining a chamber adjacent to said mixing passage, in which chamber the thermostatic element in housed;
- C. the choke valve having a shaft to which it is fixed and by which it is carried for rotational movement and one end portion of which projects into said chamber;
- D. said end portion of the shaft having a plurality of radially outwardly opening slots at circumferentially spaced intervals therearound, in each of which the inner end portion of the bimetal strip is receivable, the several slots providing for adjustment of the position in which the thermostatic element tends to hold the choke valve when the thermostatic element is at a predetermined temperature;
- E. the carburetor body having further means thereon defining opposite circumferentially facing abutments in said chamber, against each of which the outer end portion of the bimetal strip is engageable and which cooperate to limit rotation of the outermost convolution of the strip;
- and
- F. the carburetor body also having means thereon for communicating the interior of said chamber with a source of fluid that has a temperature which corresponds to the prevailing operating temperature of the engine.
Dependencies are inferred from the claim text.