JPH04106924U - lawn mower blade - Google Patents

Abstract

(57) [Summary] [Purpose] To easily and accurately suppress noise generated by air vortices on the back side of a blade twisting part using an inexpensive means. [Structure] A bar blade that is rotatably held in a horizontal plane and is provided with a cutter portion 14a at the front edge in the rotational direction of both radial end regions, and a twisted portion 14b that slopes upward from there toward the rear edge. In step 14, a large number of dimples 18 are formed on both the front and back surfaces of both radial end regions r occupied by the cutter portion 14a.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a lawn mower blade.

0002

[Conventional technology]

When a typical conventional power lawn mower is shown in a perspective view in FIG. It is equipped with wheels 12 at the front and rear of the vehicle, an engine 13 is placed in the center of the vehicle body, and a barb is installed below the engine 13. The radar 14 is rotatably held in a horizontal plane, and the operating hand is moved rearward from the vehicle body 11. A lawn storage box 16 is provided at the rear of the vehicle body 11.

0003 As shown in the perspective view of FIG. 4, the rectangular plate-shaped bar blade 14 is That is, the cutter portion 14a is provided at the front edge in the rotational direction of both end regions in the radial direction, and this cutter It has a twisted portion 14b that slopes upward from the portion 14a toward the rear edge. Therefore, The bar blade 14, which is rotated in the direction of the arrow by the engine 13, The grass is cut at part 14a, and the cut grass is moved upward at the subsequent twisting part 14b. At the same time, flip it up and place it on the wind generated by this twisting part 14b, and place it in the grass storage box next to it. Move to Cus 16 and save.

0004 However, such a bar blade 14, as shown in the cross-sectional view of FIG. By rotating at high speed, an air vortex 17 is generated on the back surface 14c of the twisted part, and the At the radial end edge 14d of the curved portion 14b, the influence of centrifugal force becomes significant and Air vortices are violently released from the radial end edge 14d and the back surface 14c of the twisted part, causing a large generates a lot of noise. With the spread of power lawn mowers in recent years, such noisy Low-noise lawn mowers are strongly desired.

[0005]

[Problem that the idea aims to solve]

This invention was proposed in view of these circumstances, and the twist part of the blade is Noise generated by surface air vortices can be suppressed easily and accurately using inexpensive means. The purpose is to provide lawn mower blades.

[0006]

[Means to solve the problem]

For this purpose, the present invention is rotatably held in a horizontal plane, and the rotation direction of both radial end regions is A cutter part is provided on the front edge and slopes upward from there towards the rear edge. In a lawn mower blade equipped with a twisted part, the cutter part occupies It is characterized in that a large number of concave and convex portions are formed on both the front and back surfaces of both radial end regions.

[0007]

[Effect]

The lawn mower blade of this invention has many uneven parts on the front and back surfaces of the blade. , suppresses the development of the boundary layer generation area that occurs when the blade rotates, and reduces the wake flow from the trailing edge of the blade. By making the width thinner, it is possible to suppress the noise caused by the air vortex emitted from the back of the twist part.

[0008]

【Example】

One embodiment of the lawn mower blade of the present invention will be explained with reference to the drawings. FIG. 1 is a perspective view. , FIG. 2 is a cross-sectional view. In the above figure, the cutter portion 14a of the bar blade 14 Let r be the radial length corresponding to A large number of dimples 18 of appropriate shapes and dimensions are formed. Furthermore, dimple 1 8 may be replaced by a protrusion of similar size.

Generally, in this type of lawn mower, the bar blade 14 is made of a metal plate, and has a hardness of H _RC 46 to 55 for safety reasons so that it will not break even if it collides with a pebble or the like during rotation. The dimples 18 can be easily formed on the front and back surfaces of the bar blade 14 by press molding or the like.

0010 In the bar blade 14 in which dimples 18 are formed in this way, as shown in FIG. As shown, the boundary layer generation area l due to the air vortex 17 generated in the twisted portion 14b during rotation. is thinner than when there is no dimple 18, so that the back surface 14c of the twisted portion Also, air vortex shedding noise generated from the radial end edge 14d is reduced. In other words, by experiment Then, a bar blade with blade circumferential speed v = 170 m/s and twist angle θ = 40° is directly When circular dimples with a diameter of 4 mm and a depth of 1 mm are provided at a pitch of 6 mm, the noise generated is approximately 2. dB(A) reduced.

[0011] Thus, according to this embodiment, the length corresponding to the cutter portion 14a of the bar blade 14 is By forming dimples 18 on both the front and back sides of the blade, the boundaries that occur when the blade rotates are eliminated. By suppressing the development of the interfacial layer generation area and reducing the wake width from the trailing edge of the blade, Noise caused by air vortex shedding sound from the radial end edge 14c and the radial end edge 14d can be suppressed. Also Since the dimple 18 can be easily formed by pressing etc., excessive cost is incurred. Generated noise can be suppressed without any noise.

0012

[Effect of the idea]

In short, according to the present invention, it is rotatably held in a horizontal plane, and the A cutter part is provided at the leading edge in the direction of rotation, and from there upward towards the trailing edge. In a lawnmower blade with an inclined twist part, the cutter part is By forming a large number of concave and convex portions on both the front and back surfaces of both radial end regions of the Easily and accurately suppresses the noise generated by the air vortex behind the twisted part of the card using inexpensive means. This invention is extremely useful industrially because it provides a lawn mower blade that can It is.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the lawn mower blade of the present invention.

FIG. 2 is a cross-sectional view of the same as above.

FIG. 3 is a perspective view of a known power lawn mower.

FIG. 4 is a perspective view of a conventional lawn mower blade.

FIG. 5 is a cross-sectional view of the same as above.

[Explanation of symbols]

14 bar blade 14a Cutter section 14b Twisted part 14c Back side of twist part 14d Radial edge 17 Air Vortex 18 dimples

Claims (1)

[Scope of utility model registration request] Claim 1: A lawn mower that is rotatably held in a horizontal plane and is provided with a cutter portion at the front edge in the rotational direction of both radial end regions, and a twist portion that slopes upward from there toward the rear edge. A lawn mower blade, characterized in that a large number of concave and convex portions are formed on both the front and back surfaces of both radial end regions occupied by the cutter portion.