Internal-combustion engines – Cooling – Air-cooled
Reexamination Certificate
2000-03-13
2001-10-02
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
Air-cooled
C123S19800E, 43, 43
Reexamination Certificate
active
06295953
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a portable power working machine, such as a chain saw, a brush cutter, a hedge trimmer, and the like, in which the working components are driven by an internal combustion engine. In particular, the present invention relates to a portable power working machine that is constructed to prevent as much as possible an air cleaner attached to an air intake system of the internal combustion engine from becoming clogged with dust.
A conventional portable power working machine, such as a chain saw, generally has a small air-cooled internal combustion engine for driving the working components, such as a saw chain. The engine is mounted in a main housing. A cooling fan driven by the internal combustion engine is disposed on one side of the main housing. A carburetor chamber containing an air cleaner and a carburetor is mounted on an upper rear side of the internal combustion engine.
In the operation of a portable power working machine of the type described above, dust that includes sawdust of relatively large size, powder of cut material and sand-like dust are inevitably generated. When dust of those kinds is allowed to enter together with air into the air intake system of the internal combustion engine and to collect on the filter element of the air cleaner, clogging of the filter results. Clogging causes irregularities in the operation of the engine as well as a deterioration in the performance of the engine due to an insufficiency in the flow rate of intake air. Accordingly, it is required in the operation of the portable power working machine to frequently clean the air cleaner, which is a task that is quite troublesome for the operator.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to solve the aforementioned problems. In particular, it is an object of the present invention to provide a portable power working machine which is capable of preventing as much as possible the air cleaner of the air intake system of a small air-cooled internal combustion engine acting as a driving power source for working components from becoming clogged with dust, thereby relieving an operator from the task of frequently cleaning the air cleaner.
With a view to attaining the aforementioned object, there is provided, in accordance with the present invention, a portable power working machine having a small air-cooled internal combustion engine received in a main housing. A cooling fan which is driven by the internal combustion engine is located on one side of the main housing. A carburetor chamber containing an air cleaner for the internal combustion engine and a carburetor is mounted on the engine. A dust-separating air duct is interposed between a region close to the cooling fan and the carburetor chamber housing. The dust-separating air duct is configured to separate dust contained in the intake air from air by taking advantage of an air flow, thereby allowing clean air separated from the dust to be delivered to the carburetor chamber housing and allowing the dust separated from the intake air to be sucked by the cooling fan.
In a preferred embodiment, the dust-separating air duct includes a downwardly inclined L-shaped rectangular pipe and a partitioning wall member disposed inside the L-shaped rectangular pipe and extending along the longitudinal direction of the L-shaped rectangular pipe toward the carburetor chamber housing. The partitioning wall member partitions the pipe into a dust-separating passageway and a dust-exhaust passageway extending parallel with and below the dust-separating passageway. The dust-separating passageway includes an air inlet port for admitting air, which is open in a direction opposite to that facing an impeller of the cooling fan. The dust-separating passageway further includes an air-feeding port for delivering the air to the carburetor chamber housing, which is formed below a top wall disposed close to the air cleaner of the carburetor chamber housing. The dust-exhaust passageway communicates with the dust-separating passageway through an opening in the partitioning wall member, which is formed close to the top wall and has an outlet port opening close to the impeller. That arrangement allows the dust collected at an inner corner portion of the top wall to be carried by an air flow and then to be discharged from the outlet port by the suction of the cooling fan.
A typical example of a portable power working machine in which the present invention is especially advantageous is a chain saw. The chain saw includes a saw chain set that is located on the side of the main housing opposite from the cooling fan and the carburetor chamber housing and includes a saw chain and a guide bar. Chain saws produce large quantities of dust, which includes relatively large particles. Reducing the rate of accumulation of dust on the air cleaner offers important improvements in the chain saw.
In the aforementioned preferred embodiment of the portable power working machine, a juxtaposed structure consisting of the overlying dust-separating passageway and the underlying dust-exhaust passageway formed by the partitioning wall member is mounted, as a dust-separating air duct structure, on one side (the cooling fan side) of the main housing. Accordingly, when the power working machine is operated, the cooling air that has been introduced from one side of the main housing by the suction of the cooling fan and hence accelerated and pressurized is transmitted so as to cool the internal combustion engine. The air is then discharged through a discharge port formed in the main housing to the external atmosphere. The air introduced into the carburetor chamber housing is drawn in through the air cleaner so as to be mixed with a fuel to form an air-fuel mixture. The air-fuel mixture is introduced into the intake port of the internal combustion engine.
Since the pressure of air in the carburetor chamber housing is lower than the air pressure in the vicinity of the cooling fan, external air containing dust, such as sawdust of relatively large size, is drawn into the dust-separating passageway of the dust-separating air duct structure from the air inlet port during the intake stroke of the engine. Because the dust-separating passageway is of a downwardly inclined L-shape and is partitioned by the partitioning wall member, the dust, such as sawdust, entrained in the external air is separated from the air. In at regard, the dust is caused to move straight ahead by its inertia and flows along the partitioning wall member and reaches the region in the vicinity of the top wall. Air largely free of dust is discharged into the carburetor chamber housing through a side opening formed below a top wall, which is disposed close to the air cleaner.
The dust that reaches a region in the vicinity of the top wall is then picked up by an air flow generated by the suction of the cooling fan, so that the dust is caused to enter through the opening formed in the vicinity of the top wall into the dust-exhaust passageway formed underneath the dust-separating passageway by the partitioning wall member. Further, due to the suction force of the cooling fan, the dust introduced into the dust-exhaust passageway in this manner is then allowed to pass through the outlet port formed close to the impeller and discharged together with the engine cooling air from the discharge port of the main housing into the external atmosphere.
As mentioned above, since the portable power working machine according to the present invention is featured in that a dust-separating air duct is interposed between a region close to the cooling fan and the carburetor chamber housing so as to separate dust included in an intake air from air by taking advantage of an air flow, clean air separated from the dust is supplied to the carburetor chamber housing. Dust separated from the intake air is sucked by the cooling fan. Thus, clogging of the air cleaner is minimized, and frequent cleaning of the air cleaner is unnecessary, which improves the efficiency of the work performed with the
Ohsawa Hisato
Yamami Hirofumi
Kamen Noah P.
Kioritz & Corporation
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