US 3307836 A
Description (OCR text may contain errors)
March 7, 1967- D. N. ARNDT ETAL 3,307,836
MANUAL PRIMER MECHANI SM Filed Jan. 15, 1965 2 Sheets-Sheet l lNVENTORS DONALD N. ARNDT CHARLES H. TUCKEY BY J. D. TUCKEY ATTORNEYS D. N. ARNDT ETAL 3,307,836
MANUAL PRIMER MECHANISM March 7, 1967 2 Sheets-Sheet 2 Filed Jan. 15, 1965 FIG-2 FIG.3
INVEN TORS DONALD N. ARNDT CHARLES H. TUCKEY B) J. D. TUCKEY g M @imzz ATTORNEYS United States Patent O 3,307,836 7 MANUAL PRIMERMECHANISM Donald N. Arnd t, Charles H. Tuckey and .I. D. Tuckey, Cass City, Mich, assignors to Walbro Corporation, Cass City, Mich, a corporation of Michigan Filed Jan, 15, 1965, Ser. No. 425,715 1 Claim. (Cl. 261-34) This invention relates to a manual primer for carburetcm and is more specifically directed to a primer for carburetors for small engines, such as are used on power lawn mowers, chain saws, go-ca rts and the like.
Very frequently the starting of an engine is difficult particularly when the engine has been used to a conside'rable extent and the ignition system is apt to be weaker than it is intended to be. difficult when an engine has been sitting for some time Without being used and gasoline has evaporated from the passages of the carburetor so that it is not immediately available to the engine manifold.
It is an object of the present invention to provide a relatively simple manual primer which can introduce gasoline into the venturi throat of the carburetor Where it will become immediately available to the engine. Briefly, this is accomplished by a pressure device which can be utilized in combination with the normal vent of the carburetor to the fuel chamber to apply momentary pressure to the surface of the fuel in the fuel reservoir forcing fuel into the carburetor jet.
Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claim.
Drawings accompany the disclosure and the various views thereof may be briefly described as:
FIGURE 1 is a sectional view of the carburetor showing the manual primer in relation to the other parts.
FIGURE 2 is a top view of the carburetor.
FIGURE 3 is a horizontal section through the carburetor.
Referring to the drawings:
A carburetor housing H has a fuel inlet 20 controlled by a needle valve 22 actuated by a lift member 24 on a standard ring float 26 pivoted at 28 in a carburetor bowl 30, the bowl being suitably sealed at 32 to the housing. A spring-pressed drain pin 34 is provided at the bottom of the bowl and a brass nipple insert 36 screws into a depending portion 38 of the housing which serves as a mount post for the float chamber shell 30, there being suitable sealing washers 48 provided. In the threaded passage above the nipple 36 is a main fuel jet stem having a threaded portion 41 and an upward extending portion 42 extending into the horizontal venturi passage 44. In the nipple 36 is a threaded needle valve 46 to control the central passage 50 of the jet 42.
Fuel reaches the jet through a short passage 52 in portion 38 of housing H leading from the flat chamber to the space between the nipple 36 and the jet base 41. A suitable idling system can be provided through passage 54 shown in FIGURE 1 and a passage 56 shown in FIG- URE 3 terminating in idle ports 58 and 60, the port 60 being controlled by a suitable needle valve 62, these ports being located adjacent the throttle valve 64. In the inlet of the venturi passage 44 is a choke valve 66 of standard construction.
The primer mechanism is mounted on a tube 7 which projects down through the housing H and through the venturi passage 44 into the top of the float bowl chamber as shown in FIGURE 1. The end opening 72 of the tube 70 is positioned above the normal liquid level in the float bowl. Mounted on the tube 70 by a sleeve 74 is a small cup-like chamber 76 having a round de- The starting is also pending projection 77 which is firictionally engaged with the sleeve 74, the other end of the sleeve being frictionally engaged with the top of tube 70. The cup 76 has a flange 78 and is capped by a cover 80 which is preferably of such material as a resilient plastic so that it may have a snap-on connection.
Within the cup 76 is a plunger P formed of a disc 82 and a disc 84 which lie on either side of the center of a resilient sealing member 86, the sides of which extend beyond the disc 84 to contact, in a slidable sealing relation, the cylindrical walls of the cup 76. A small button 88 having an enlarged flange 90 at the bottom is captive within the cup and cover and is projected outwardly by (reason of the compression spring 92 seated on the bottom of the cup 76 and located on a small projection 94 on disc 82. This piston assembly can be made in various ways. One preferred embodiment comprises forming the button 88 as a unit and assembling the perforated sealing member 86 and perforated discs 82 and 84 over the projection 94 in frictional engagement. A small opening 96 in the wall of the cup normally vents the top of the float bowl chamber to atmosphere through the cup 76 and the tube 70.
In the operation of the manual primer, it will be seen that when the button 88 is pressed downwardly against the action of the spring 92, the atmospheric vent 96 will first be closed by the downward movement of the plunger P and then pressure will develop in the cup which is transmitted through tube 70 to the surface of the fuel in the float bowl. This will cause it to squirt into the passage 52 and up through the jet passage 50 into the Venturi, thus providing an immediate supply of fuel for engine starting. Repeated operation of the button will supplement this fuel injection and the engine being supplied may be readily started with an ample supply of fuel.
It will thus be seen that with a very simple mechanism to apply air pressure to the surface of the fuel in the float chamber, supplemental fuel may be supplied to the venturi passage of the carburetor.
In a carubertor for furnishing fuel to the intake manifold of an internal combustion engine and of the type having a fuel supply chamber connected to a venturi passage, an improvement for introducing supplemental fuel into said venturi passage comprising:
(a) a rigid tube mounted in said carburetor and projecting upwardly therefrom, said tube having a connection to the top of a fuel supply chamber above the normal fuel level in said chamber,
(b) a cup mounted on and supported by said tube having a depending hollow projection pneumatically associated with the interior of said tube, said cup having a lipped upper edge,
(0) an apertured cap for said cup having a peripheral flange to snap over the lipped edge of said cup, and
(d) a piston in said cup retained therein by said cap and having a button projection extending through said cap, said piston being biased outwardly wherein it may be reciprocated to create above atmospheric pressure in said tube.
References Cited by the Examiner UNITED STATES PATENTS 2,827,272 3/1958 Phillips 261-41 FOREIGN PATENTS 594,982 9/1925 France. 598,578 12/1925 France.
5,551 1/1916 Great Britain.
HARRY B. THORNTON, Primary Examiner.
T. R. MILES, Assistant Examiner.