Patent Grant
8925509
This application is a national stage entry of PCT/US2009/066709, which was filed on Dec. 4, 2009, said application is expressly incorporated herein in its entirety.
The present invention relates to a fuel delivery system. In particular, the present invention relates to fuel delivery systems for internal combustion engines which are used in hand-held power tools.
Hand-held power-tools such as, but not limited to, chain saws and line trimmers, are often powered by small two stroke internal combustion engines that are equipped with diaphragm carburettors.
Generally, a diaphragm carburettor has an air passage where fuel and air is mixed in a correct ratio. An outlet of the air passage leads to a crankcase of the engine. Typically, a throttle valve is provided in the air passage to control the amount of fuel and air mixture that enters the crankcase.
Usually, before starting an engine either a purging system or a priming system is actuated at least once to introduce fresh fuel into the carburettor. Typically, the purging system is used to remove residual air or fuel from the carburettor and fill desired fuel passages and chambers of the carburettor with the fresh fuel. On the other hand the priming system is used to inject a small quantity of fuel into the air passage, often in addition to performing the functions of a purging system. The fresh fuel supplied to the carburettor before starting the engine helps in an easy and quick starting of the engine. The purging system and the priming system are typically actuated by a purge bulb and a primer bulb respectively.
Further, the engines are also provided with a fuel enrichment system which is actuated in order to achieve a rich mixture of air and fuel (more fuel to air) during a cranking of the engine. The fuel enrichment system works by supplying extra fuel during the cranking of the engine, which facilitates a stable starting of the engine. One kind of a fuel enrichment system is the choke system. The choke system may include a butterfly or a slide valve located at the entrance of the carburettor (internal choke system). The valve can be moved between multiple positions via a lever, in order to control the air flow into the carburettor. The choke system may also be a separate system outside the carburettor (external choke system). The choke system is used to create an increased vacuum in the air passage, which draws extra fuel from fuel circuits of the carburettor. Another kind of fuel enrichment system includes a fuel enrichment circuit, which can be actuated by pressing a push button to introduce extra fuel into the air passage as soon as the engine cranking cycles are started. Sometimes both a choke system and a fuel enrichment circuit are used to enrich the fuel and air mixture.
To achieve an easy and quick starting of the engine followed by a stable cranking (typically by pulling a rope) may require actuation of multiple systems, for example a purging system or a priming system, and the choke valve and/or the fuel enrichment circuit. Therefore, the starting procedure for this kind of engines usually consists of three steps: 1) depressing a purge or primer bulb at least once, 2) actuating a fuel enrichment system and 3) pulling a rope to start the engine.
U.S. Pat. No. 7,334,551 issued on Feb. 26, 2008 to George M. Pattullo, titled “Combustion engine pull cord start system” describes a two-step starting system. In the two-step starting system taught by this patent, a pull-rope system of an internal combustion engine is linked to a throttle valve and a choke valve. The choke valve is actuated in different positions by a rope tension of the pull-cord system. However, the design is quite complex with many moving parts.
In light of the foregoing, there is a need for an improved two-step starting system, for an internal combustion engine, having a simple design with a lower number of moving parts.
In view of the above, it is an objective to solve or at least reduce the problems discussed above. In particular, the objective is to provide an improved fuel delivery system, for an internal combustion engine of a hand-held power tool, which has a simple design and a minimum number of moving parts and permits a two-step starting of the engine.
Some example embodiments may provide a fuel delivery system in which the fuel delivery system includes a diaphragm carburettor, a start preparation system and a fuel enrichment system. The fuel enrichment system is connected to the start preparation system such that the fuel enrichment system can be activated by an actuation of the start preparation system. Thus, the fuel enrichment system need not be activated in a separate step. The start preparation system is utilized to introduce fuel into the diaphragm carburettor before the engine is started. Further, the fuel enrichment system provides a rich air and fuel mixture that is necessary for a stable initial operation of the engine when the engine is cranked.
According to some example embodiments, the start preparation system is provided with at least one first activation means and the fuel enichment system is provided with at least one second activation means. The first activation means and the second activation means are connected to each other in such a way that the fuel enrichment system can be activated via the first activation means. This configuration permits a simple design of the fuel delivery system, thereby reducing a cost associated with manufacturing and maintenance.
According to some example embodiments, the first activation means may be a purge bulb or a primer bulb and the second activation means is a choke lever. According to an example embodiment, the first activation means, e.g. the purge bulb or the primer bulb, is configured in such a manner that the start preparation system can be activated at least once before a start of the engine. According to some examples, the start preparation system is a purging system including the purge bulb. The purge bulb is depressed at least once to actuate the purging system. The purging system removes residual air and/or fuel and introduces fresh fuel in the diaphragm carburettor. According to some examples, the start preparation system is a priming system including the primer bulb. The primer bulb is depressed at least once to actuate the priming system. The priming system injects a fresh amount of fuel in a venturi of the diaphragm carburettor, via an auxiliary circuit, often in addition to performing the functions of a purging system. According to an example embodiment, the fuel enrichment system is actuated by the depression of the purge bulb or the primer bulb.
According to an example embodiment, the diaphragm carburettor also includes a throttle valve. The throttle valve is a butterfly throttle valve.
According to some examples, the fuel enrichment system includes a choke system. The choke system is ultilized to reduce an amount of air entering the diaphragm carburettor. The reduction in the amount of air results in a rich fuel and air mixture. The choke system can be actuated by the choke lever and the choke lever is connected to the start preparation system.
According to some examples, the fuel enrichment system includes an enrichment circuit. The enrichment circuit injects a fresh amount of fuel in the venturi of the diaphragm carburettor when the engine is being cranked. The enrichment circuit is activated by means of a push button. The push button is connected to the start preparation system.
According to some example embodiments, the fuel enrichment system includes an enrichment circuit as well as a choke system. The presence of both the enrichment circuit and the choke system results in a richer fuel and air mixture. The enrichment circuit and the choke system are connected to each other such that the enrichment circuit is actuated when the choke system is activated. Further, the choke system is linked to the start preparation system.
According to some example embodiments, the fuel enrichment system includes an enrichment circuit as well as a choke system. The enrichment circuit and the choke system are connected to each other such that the choke system is actuated when the enrichment circuit is activated. Further, the enrichment circuit is linked to the start preparation system.
According to an example embodiment, the throttle valve of the carburettor is a rotating throttle valve.
According to an example embodiment, the fuel enrichment system includes an enrichment circuit. The enrichment circuit is activated by means of a push button. The push button is connected to the start preparation system.
According to an example embodiment, the fuel delivery system includes a choke system which is external to the diaphragm carburettor. The choke system is actuated by means of a choke lever. The choke lever is connected to the start preparation system.
The invention will in the following be described in more detail with reference to the enclosed drawings, wherein:
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the invention incorporating one or more aspects of the present invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. For example, one or more aspects of the present invention can be utilized in other embodiments and even other types of devices. In the drawings, like numbers refer to like elements.
The diaphragm carburettor 102 may supply a fuel and air mixture to the engine. In an embodiment of the present invention, the diaphragm carburettor 102 may include a fuel and air mixing passage 108, a fuel pump system (not shown in
As shown in
In an embodiment of the present invention, a choke valve 116 may be provided upstream of the fuel and air mixing passage 108. In an embodiment of the present invention, the choke valve 116 may be an integral part of the diaphragm carburettor 102. In another embodiment of the present invention, the choke valve 116 may be an external choke which may be separate from the diaphragm carburettor 102. Further, the choke valve 116 may be oriented at multiple positions to regulate an amount of air that enters the fuel and air mixing passage 108. The multiple positions of the choke valve 116 may include, but not limiting to, a closed choke position, a half choke position and an open choke position. The choke valve 116 may be a part of the choke system (not shown in
The fuel delivery system 100, as described above, may be used for the internal combustion engine in various hand-held power tools. However, in a non-operational state of the engine, various components of the diaphragm carburettor 102 may contain a residual air and/or fuel. The start preparation system 104 may remove a residual air and/or fuel from the various components of the diaphragm carburettor 102 and/or introduce a fresh fuel before a start of the engine. The start preparation system 104 may include a first activation means to activate the start preparation system 104.
In an embodiment of the present invention, the start preparation system 104 may include a bulb assembly 118, a bulb inlet line 120 and a bulb outlet line 122. The bulb assembly 118 may include a resilient domed bulb 124 to define a bulb chamber 126. The bulb 124 may act as the first activation means to actuate the start preparation system 104 by a depression of the bulb 124. In an embodiment of the present invention, the start preparation system 104 may be a purging system and the bulb assembly 118 may be a purge bulb assembly. In this case, the bulb 124 may be a purge bulb which may be depressed to actuate the purging system. Before a start of the engine, a depression of the bulb 124 may cause a decrease in a volume of the bulb chamber 126 and a consequent increase in pressure inside the bulb chamber 126. The increase in pressure may force a fluid inside the bulb chamber 126 to be expelled through the bulb outlet line 122 to the fuel supply tank 110. The fluid inside the bulb chamber 126 may be air or a mixture of fuel and air. As the bulb 124 is released, it may return to its original shape, thereby decreasing the pressure inside the bulb chamber 126. This may result in a flow of a residual fuel and/or air from one or more components of the diaphragm carburettor 102, for example the fuel metering system, to the bulb chamber 126 via the bulb inlet line 120. In an embodiment of the present invention, repeated depressions of the bulb 124 may draw a fresh fuel from the fuel supply tank 110. Thus, the start preparation system 104 working as the purging system may fill one or more components of the diaphragm carburettor 102 with fresh fuel from the fuel supply tank 110.
In another embodiment of the present invention, the start preparation system 104 may be a priming system and the bulb assembly 118 may be a primer bulb assembly. In this case, the bulb 124 may be a primer bulb which may be depressed to actuate the priming system. The priming system may include an auxiliary circuit (not shown in
After the removal of a residual air and/or fuel by the start preparation system 104, the fuel enrichment system 106 may be used to provide an enriched fuel and air mixture to the engine when the engine is cranked. The fuel enrichment system 106 may be provided with a second activation means to activate the fuel enrichment system 106. In an embodiment of the present invention, the fuel enrichment system 106 may include an enrichment circuit 128. The enrichment circuit 128 may be used to supply an additional amount of fuel to the fuel and air mixing passage 108 during a cranking of the engine. In an embodiment of the present invention, the enrichment circuit 128 may include an enrichment chamber 130 and an enrichment line 132. The enrichment chamber 130 may be connected to the bulb inlet line 120 such that it permits a flow of the fuel from the bulb inlet line 120 into the enrichment chamber 130. Further, the enrichment line 132 may be provided between the diaphragm carburettor 102 and the enrichment chamber 130 and may have one or more openings (not shown in
In another embodiment of the present invention, fuel enrichment system 106 may include only the choke system and the choke lever may act as the second activation means. As described above, the choke system may be used to create an enriched fuel and air mixture by decreasing an amount of air entering the fuel and air mixing passage 108.
In another embodiment of the present invention, the fuel enrichment system 106 may include both the choke system and the enrichment circuit 128. In various embodiments of the present invention, the second activation means may include, for example but not limiting to, the choke lever and/or the push button 134 associated with the choke system and/or the enrichment circuit 128 respectively.
In another embodiment of the present invention, the fuel enrichment system 106 and the start preparation system 104 may be connected in such a way that the fuel enrichment system 106 may be activated by an activation of the start preparation system 104. The first activation means of the start preparation system 104 and the second activation means of the fuel enrichment system 106 may be connected to each other in such a way that the fuel enrichment system 106 may be activated by the first activation means. In an embodiment of the present invention, the bulb 124 of the start preparation system 104 may be connected to the choke lever or the push button 134 in such a way that the fuel enrichment system 106 may be activated by depressing the bulb 124.
In an embodiment of the present invention, the enrichment circuit 128 and the choke system may be connected such that an activation of the choke system may result in an actuation of the enrichment circuit 128. In an embodiment of the present invention, the choke lever of the choke system and the push button 134 may be connected to each other in such a way that the enrichment circuit 128 may be activated by the choke lever. Further, the choke system may be connected to the start preparation system 104. In an embodiment of the invention of the present invention, the bulb 124 of the start preparation system 104 may be connected to the choke lever.
In an embodiment of the present invention, the enrichment circuit 128 and the choke system may be connected in such a way that an activation of the enrichment circuit 128 may result in an actuation of the choke system. In an embodiment of the present invention, the choke lever of the choke system and the push button 134 may be connected to each other in such a way that the choke system may be activated by the push button 134. Further, the enrichment circuit 128 may be connected to the start preparation system 104. In an embodiment of the invention of the present invention, the bulb 124 of the start preparation system 104 may be connected to the push button 134.
In an alternative embodiment of the present invention, the throttle valve 114 may be a butterfly throttle valve. In such a case, the fuel enrichment system 106 may include the choke system (not shown in
In an embodiment of the present invention, before a start of the engine, the choke valve 116 may be in an open choke position. The bulb assembly 118 together with at least the bulb inlet line 120 (not shown in
In an embodiment of the present invention, the fuel delivery system 100 may also include the enrichment circuit 128 in addition to the choke system 302. The enrichment circuit 128 may be activated when the choke rod 304 is rotated by a movement of the bulb assembly 118 in the direction C. Thus, the actuation of the choke system 302 may also result in the activation of the enrichment circuit 128. In an embodiment of the invention the choke rod 304 of the choke system may be connected to the push button 134 of the enrichment circuit 128.
In an embodiment of the present invention, before a start of the engine, the bulb assembly 118 is in a non-actuating position and the first engaging member 406 is in a first position. A corresponding orientation of the choke actuating lever 408 may be such that the choke valve 116 may be in an open choke position. In this case, the bulb assembly 118 may act as the start preparation system 104 and when the bulb 124 is depressed to activate a purging system or a priming system, the bulb assembly 118 may be displaced in the direction D from a non-actuating position to an actuating position. Consequently, the first engaging member 406 may be displaced from a first position to a second position along the slot 407. Thus, the choke actuating lever 408 may rotate to actuate the choke valve 116 in a closed choke position. The length of the slot 407 may be such that it may prevent further displacement of the bulb assembly 118 along the direction D even when the bulb 124 is depressed. Once the bulb assembly 118 is depressed to an actuating position, the bulb assembly 118 may be held in place by a locking system. In an embodiment of the present invention, the actuation of the throttle lever by manual or automatic means may automatically release the locking system and reset the bulb assembly 118 to a non-actuating position.
In an embodiment of the present invention, before a start of the engine, the external choke actuating lever 520 and the actuating pin 518 may be in a first position and a non-actuating position respectively. Consequently, the external choke valve 116 may be in an open choke position. In this case, the bulb assembly 118 together with at least the bulb inlet line 120 (not shown in
In an embodiment of the present invention, a locking lever 522 may be provided to actuate a trigger member 524 between an unlocking position and a locking position. A surface 526 of the external choke actuating lever 520 may engage with the locking lever 522, thereby resulting in a rotation of the locking lever 522 about a pivot 528. In an embodiment of the present invention, the locking lever 522 may include an angled surface 530 that may engage with the surface 526. Once the bulb assembly 118 is depressed to a second position, the bulb assembly 118 may be held in place by the locking lever 522 and the trigger member 524. In an embodiment of the present invention, the actuation of the throttle lever by manual or automatic means may release the trigger member 524 and reset the bulb assembly 118 to a first position.
In the drawings and specification, there have been disclosed preferred embodiments and examples of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation, the scope of the invention being set forth in the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2009/066709 | 12/4/2009 | WO | 00 | 8/7/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/068512 | 6/9/2011 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20120318249 A1 | Dec 2012 | US |
