These and other objects, features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments and best mode, appended claims, and accompanying drawings in which:
Referring in more detail to the drawings,
The main body 12 may be composed of any suitable material but is preferably composed of metal such as cast aluminum or the like. The main body 12 provides structural support for the aforementioned assemblies 14, 16, 18 and various other components and passages as will be described in further detail herein below. Externally, the main body 12 carries a fuel inlet fitting 20 for connection to a fuel tank and a fuel outlet fitting 22 for discharging purged fuel and any fuel vapor and air and preferably returning them to the tank.
Internally, and referring now to
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The auxiliary fuel and air supply apparatus 89 preferably includes a bore 90, and an auxiliary fuel and air mixing piston or valve 92 disposed therein. The valve 92 at least partially defines a valve actuation chamber 94 and a fuel and air mixing chamber 96 separated from the actuation chamber 94 by a seal 98. The seal 98 is preferably an elastomeric quad seal on one end of a body 100 of the valve 92, opposite a head 118 connected to the body 100 of the valve 92. The seal 98 tends to hold the valve 92 in place by friction between the outer diameter of the seal 98 and the inner diameter of the fuel and air mixing bore 90. The fuel and air mixing chamber 96 is in communication with the fuel and air mixing passage 24 at a location downstream of the throttle valve 32, via a transversely-oriented mixed fuel and air outlet passage 102 and passages 116 and 114 through the throttle shaft 34 and valve 92 as will be described herein below.
The auxiliary fuel and air supply apparatus 89 also preferably includes a number of other passages. An air passage 104 includes an upstream end in communication with the fuel and air mixing passage 24 at a location upstream of the throttle valve 32, preferably at the air inlet 26 of the main body 12. The air passage 104 further includes a downstream end in communication with the fuel and air mixing chamber 96. A fuel passage 106 has an upstream end in communication with the fuel metering chamber 62 and a downstream end in communication with the auxiliary fuel and air mixing chamber 96. A purge outlet passage 108 has an upstream end in communication with the purge outlet chamber 88 of the purge apparatus 18 and a downstream end in communication with the valve actuation chamber 94. A return fuel passage 110 has an upstream end in communication with the valve actuation chamber 94 and a downstream end in communication with the outlet fitting 22 which preferably communicates with the fuel tank (not shown). The auxiliary fuel and air supply apparatus may also include the fuel chamber 62, the fuel chamber purge apparatus 18, and the throttle shaft 34.
In operation, the fuel chamber purge apparatus 18 may be manually actuated to expel any air, fuel vapor, and/or stale fuel from the fuel pump assembly 14 and fuel metering chamber 62 before starting the engine. In general, the bulb 76 of the fuel chamber purge apparatus 18 is actuated to a depressed state, thereby causing liquid fuel and fuel vapor within the bulb 76 to be expelled from therein, and the bulb 76 is then allowed to return to a non-depressed state, thereby drawing liquid fuel and any fuel vapor from the metering chamber 62 and fuel pump assembly 14 into the bulb 76. This manual purging is generally repeated as necessary.
Moreover, upon actuation of the fuel chamber purge apparatus 18, pressurized fluid flows from within the bulb 76 through the valve 86 and chamber 88, through the purge outlet passage 108 into the valve actuation chamber 94. Accordingly, with the throttle valve 34 in its idle position, the pressurized fluid effectively pressurizes the valve actuation chamber and thereby moves the fuel and air mixing valve 92 from a rest or closed position to an open or engine start up or idle position as shown in
Accordingly, mixed air and fuel flow from the fuel and air mixing chamber 96, through a transverse passage 112 in the body 100 of the valve 92, through a longitudinal bore 114 in the head 118 of the valve 92, through a transverse passage 116 in the valve shaft 34, and through the mixed fuel and air outlet passage 102 in the main body 12 into the fuel and air mixing passage 24 downstream of the throttle valve 32. When the valve 92 is advanced in this way, and when the valve 32 and valve shaft 34 are in their idle position, the head 118 of the valve 92 fits into a notch 120 of the valve shaft 34. A plug 122 is preferably fit into the bore 90 to close it to force fluid flow through passage 102.
In addition to the auxiliary fuel and air supply apparatus 89, those of ordinary skill in the art will recognize that liquid fuel may also be supplied to a series of low speed fuel ports (not shown) which may open into the mixing passage 24 both upstream and downstream of the throttle valve 32 when in its idle or closed position. The low speed fuel may be supplied via a branch passage (not shown) in communication with passage 132, preferably an adjustable low speed fuel regulating needle valve (not shown), and a feeder passage (not shown) downstream of the low speed valve. Moreover, when the auxiliary fuel and air supply apparatus 89 is not used to supply fuel, such as when the throttle valve 32 is opened, liquid fuel may be supplied from the fuel metering chamber 62 through a primary fuel supply apparatus. The primary fuel supply apparatus can include a high speed fuel nozzle 124 opening into the mixing passage 24, a check valve 126, a passage 128, an adjustable fuel regulating needle valve 130, a passage 132, and a check valve 134.
A user may crank the engine associated with the carburetor 10, such as by pulling on a manual pull-starter cord (not shown) or activating an electric start apparatus (not shown). As the engine is cranked, movement of the engine piston(s) within the engine cylinder(s) creates a sub-atmospheric condition downstream of the throttle valve 32, and limited upstream air flow through the mixing passage 24. In turn, this causes liquid fuel and air to flow through the auxiliary fuel and air supply apparatus 89 into the mixing passage 24 downstream of the throttle valve 32 (in its idle position) and into the engine under startup idle and near idle operating conditions. The fuel and air supply via the auxiliary fuel and air supply apparatus 89 is provided to improve starting characteristics of the engine, particularly at low temperatures or for a “cold” engine. A pressure differential acts on the diaphragm 58 to open and close the metering valve 56 and thereby maintain a predetermined quantity of fuel in the metering chamber 62 and at a substantially constant pressure when the engine is operating. Accordingly, liquid fuel is supplied to the auxiliary fuel and air supply apparatus 89 and the high speed nozzle 124. Liquid fuel is also supplied to any low speed idle circuit (when the throttle valve is in its idle position).
After the engine is running, the engine may be accelerated by actuating or rotating the throttle valve 32 and its shaft 34. Rotation of the throttle valve 32 and shaft 34 causes cam slot 114 to move the fuel and air mixing valve 92 back to its rest position as shown in
Thus, to start the engine, a user moves the throttle valve 32 to its idle position, and then depresses the bulb 76 of the purge valve apparatus 18 to purge the fuel pump 14 and fuel chamber 62 of any fuel vapor and air and stale fuel. Upon depressing the bulb 76, fluid under pressure flows through the purge outlet passage 108 and into the valve actuation chamber 94 to move the valve 92 to its open position. Accordingly, the valve 92 is automatically displaced from its rest position of
Thereafter, once the engine is running, the operator actuates the throttle valve 32, which actuation automatically moves the valve 92 to its closed or rest position of
Therefore, when starting the engine, the operator need not manually actuate a manual control valve to open the conduit of the auxiliary fuel and air supply apparatus. And, when operating the running engine, the operator need not manually actuate a manual control valve to close the auxiliary fuel and air conduit. Rather, the auxiliary fuel and air supply conduit is opened and closed automatically, when the operator performs some other operation such as depressing a purge bulb or actuating a throttle. Accordingly, engine starting and operating is relatively simplified and requires relatively fewer components.
As used in this specification and claims, the terms “for example,” “for instance,” and “such as,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components, elements, or items. Moreover, directional words such as top, bottom, upper, lower, radial, circumferential, axial, lateral, longitudinal, vertical, horizontal, and the like are employed by way of description and not limitation. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. When introducing elements of the present invention or the embodiments thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements.
While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.