JPH0518903Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cutter blade for a lawn mower, which reduces noise as much as possible during rotation.

PRIOR ART

Generally, a cutter blade used in a self-propelled lawn mower, etc., as shown in FIG. A raised part 21 is formed at the rear edge in the rotating direction for winding up the cut grass, and this part is pivoted below the engine of the lawn mower and cut. The lawn mower moves while rotating the tar blade to cut the grass.

[The problem that the idea attempts to solve]

Since the conventionally used cutter blade 20 has the above-described structure, as the cutter blade 20 rotates at high speed, the airflow flows over the back surface of the cutter blade 20 and the cutter blade, as shown in FIG. 3b. Air vortices and air separation occur on the back side of the rising portion 22 at the rear of the blade 20, and large eddy currents and air separation tend to occur particularly on the back side of the tip of the cutter blade 20, which causes noise during reaping work. The reality is that most of the noise generated by lawn mowers comes from the rotation of the cutter blade. This causes workers to feel extra fatigued and uncomfortable, resulting in a decrease in work efficiency, as well as causing inconveniences such as noise spreading to neighboring areas of the work area.

[Purpose of the invention and means for solving the problem]

The present invention was developed in view of the problems of the conventional technology, and its purpose is to prevent as much as possible the occurrence of air vortices and separation caused by the rotation of the cutter blade, thereby reducing the To provide a cutter blade that reduces the noise of the cutter blade as much as possible, does not cause extra fatigue or discomfort to workers, and does not interfere with the work efficiency of lawn mowers, etc. In a cutter blade in which a blade is formed at the front edge in the rotational direction on both sides in the longitudinal direction, the cross-sectional shape of both sides or the tip of the cutter blade is defined as the blade at both longitudinal ends. The blade is formed into an airfoil shape whose vertical shape is approximately symmetrical with respect to the center line connecting the front end and the rear end, and the blade portion is positioned rearward in the rotational direction from the horizontal portion including the central pivoting portion. It is raised toward the edge at a predetermined angle of attack.

[Effect]

The airflow that hits the cutter blade as it rotates flows along the streamlined curved surface of the airfoil shape and is rectified, causing air vortices and air separation behind the cutter blade. By having a predetermined angle of attack, the mown grass is smoothly discharged to the rear.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

In Fig. 1, 1 is a self-propelled lawn mower equipped with a cutter blade according to the present invention, and this lawn mower 1
The lawn mower 1 can be driven by using an engine 2 installed in front of the mower as a power source and operating a travel clutch lever 4 installed on a handle 3 side.

Reference numeral 5 denotes a cutter blade, which is pivotally attached to the lower part of the engine 2 via a clutch. This cutter blade 5 is rotatable by operating a clutch lever 6 provided on the handle side, and cuts the grass as the lawn mower 1 travels. A cutter housing 7 covers the cutter blade 5 provided below the engine 2.
In the figure, 8 is a glass box for storing cut grass, and 9 is a throttle lever of the engine 2.

Next, the structure of the cutter blade 5 according to the present invention will be explained based on FIG. 2.

Reference numeral 5a denotes a blade portion of the cutter blade 5, and the blade portion 5a is formed at the front edge in the rotational direction of the cutter blade 5, as indicated by the arrow in the figure, on both sides near the tip in the longitudinal direction of the cutter blade 5. ing.
In the present invention, as shown in the cross-sectional shape of both sides of the cutter blade 5 (FIG. 2b),
It is formed into the shape of an airfoil 5 whose upper and lower shapes are approximately symmetrical with respect to the center line connecting the front end and the rear end of the blade portions at both ends in the longitudinal direction, and the blade portion 5a portion is connected to the center pivot portion 5c. The angle of attack α is set between 4° and 10° from the horizontal portion 5d including the horizontal portion 5d toward the rear edge 5e in the rotational direction.

In the present invention configured as described above, as the cutter blade 5 rotates at high speed, the airflow flows along the shape of the airfoil 5b of the cutter blade 5 and is rectified. Therefore, the generation of air vortices and separation of air are suppressed at the back of the cutter blade 5, especially at both ends of the cutter blade 5, and the airflow flows smoothly behind the cutter blade 5 and the cutter blade Since there is no risk of large air vortices and air separation occurring on the back or rear surface of the cutter blade 5, the noise of the cutter blade 5 during rotation is reduced as much as possible. As shown in this embodiment, the angle of attack α of the shape of the airfoil 5b of the cutter blade 5 is 4° to
The angle of attack α must be between 10° and
It is effective in preventing the occurrence of air vortices and air separation within a range of 300 to 300 cm, and the mown grass is rolled up backwards without hindering the ability to discharge the grass.

In this embodiment, the blade portion 5 of the cutter blade 5
Although the cross-sectional shape of the entire portion where a is formed is formed into the shape of the airfoil 5b, the cross-sectional shape of both tips of the cutter blade 5 where air vortices and separation are particularly likely to occur is formed into the shape of the airfoil 5b. It may be formed into the shape of a mold.

[Effect of idea]

As described above, the present invention provides a cutter blade in which a cutting edge is formed at the front edge in the rotational direction on both sides in the longitudinal direction, and the cross-sectional shape of both sides or the tip of the cutter blade is shaped like an airfoil. At the same time, the blade part is made to rise at a predetermined angle of attack toward the trailing edge in the direction of rotation from the horizontal part including the central pivoting part, so that the airflow is directed to the top and bottom of the cutter blade. The air flows smoothly over the curved surface, effectively preventing air vortices and air separation, and reducing the noise caused by the rotation of the cutter blade.
This has the effect of providing a cutter blade with low noise.

This reduction in noise does not cause workers to feel unnecessarily fatigued or uncomfortable, and has excellent effects such as improving work efficiency and preventing noise from reaching neighboring areas.

Further, since the cross-sectional shape of the airfoil is formed with a predetermined angle of attack as described above, the cut grass is smoothly discharged behind the cutter blade, and the grass discharge ability of the cutter blade is not hindered in any way. It never happens.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a perspective view of a lawn mower equipped with a cutter blade according to the present invention, FIG. 2a is a perspective view of a cutter blade according to the present invention, and FIG. FIG. 3A is a perspective view of a conventional cutter blade, and FIG. 3B is an explanatory diagram showing the flow of air in a conventional cutter blade. . DESCRIPTION OF SYMBOLS 1...Lawn mower, 2...Engine, 3...Handle, 4...Travel clutch lever, 5...Cutter blade, 5a...Blade part, 5b...Airfoil, 5c...
... Pivoting part, 5d... Horizontal part, 5e... Trailing edge,
6...Clutch lever, 7...Cutter housing, 8...Glass box, 9...Throttle lever.

Claims (1)

[Scope of utility model registration request] In a cutter blade in which a cutting edge is formed at the front edge in the rotational direction on both sides in the longitudinal direction, the cross-sectional shape of both sides or the tip of the cutter blade is connected to the front end and the rear end of the cutting edge at both longitudinal ends. The blade portion is formed into an airfoil shape whose upper and lower sides are approximately symmetrical with respect to the center line, and the blade portion is tilted toward the trailing edge in the rotational direction from the horizontal portion including the center shaft attachment portion at a predetermined angle of attack. A cutter blade that stands up with a .