JPH0534926B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a mower blade attachment device for a brush cutter, and more particularly to a device for reliably and safely attaching a mower blade to an output shaft of a gear case included in a brush cutter.

[Conventional technology]

In most of the conventionally known brush cutters, a small engine is attached to one end of the main operating rod as a power source, and the output of this engine is transmitted through a transmission shaft that passes through the inside of the main operating rod. is input to the gear case provided at the other end of the main operating rod.
The cutting blade is configured to be fastened and fixed by a cutting blade retainer attached to the output shaft of the gear case and a fastening washer for the cutting blade. More specifically, a disk-shaped cutting blade holder is integrally fixed to the output shaft, and the cutting blade that comes into close contact with the cutting blade holder is fitted into the output shaft, and a male threaded portion formed on the output shaft is formed. The cutting blade is tightened to the output shaft by screwing in a fixing nut to the output shaft.

[Problem to be solved by the invention]

By the way, mower blades can rotate at high speeds of several thousand revolutions per minute, so if the mower blades fall off while rotating at high speeds, the mower blades may fly around while rotating and cause an unexpected accident. will occur. Therefore, the cutting blade is often fastened to the output shaft with a double nut. Therefore, when installing or replacing the cutting blade, it is necessary to tighten and loosen the double nuts, which is very troublesome, and women and girls with little knowledge of machines may not be able to replace the cutting blade. Since the output shaft is rotated to the left, it is fastened with a left-hand thread, so if an inexperienced operator replaces the cutting blade, the fastening may not be done reliably, which is extremely dangerous. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a mounting device that allows a cutting blade to be attached and removed with a relatively simple operation, and that can tighten and fix the cutting blade more tightly as the rotation speed of the cutting blade increases. It is something.

[Means to solve the problem]

In order to achieve the above-mentioned objects, the present invention has an engine at one end of the main operating rod, a gear case at the other end, a cutting blade retainer attached to the output shaft of the gear case, and an output shaft. A mower blade attachment device for a brush cutter, which includes a mower blade clamping base attached to a shaft and attaching the mower blade between the mower blade retainer, the clamping base having an attachment portion for the output shaft;
The movable element is housed in a storage space formed inside and moves by centrifugal force, and a friction plate is pressed against the cutting blade holder by the movement of the moving element, and the friction plate and the cutting blade holder are connected to each other. The cutting blade is configured to be frictionally fixed between the blades at a predetermined rotation speed or higher.

[Effect]

In the mower blade mounting device of the present invention, the movable element housed in the internal space of the fastening base moves in the radial direction due to centrifugal force generated by high-speed rotation of the output shaft, and the friction plate rises due to this movement. When the cutting blade is strongly tightened against the cutting blade retainer and the rotation of the output shaft decreases, the tightening force also decreases as the centrifugal force decreases, and the relationship between the output shaft and the cutting blade becomes Become free.

【Example】

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, FIG. 1 is a partial cross-sectional view showing a cutting blade of a mowing machine and the output shaft portion of a gear case to which the cutting blade is attached. Reference numeral 1 indicates a gear case that includes, for example, a reduction mechanism. , a stepped output shaft 2 is protruded, and the output shaft 2 has a large diameter portion 2A near the gear case 1, and a small diameter portion 2B near the lower end, and the large diameter portion 2A,
Both of the small diameter portions 2B are formed with left-handed male threads. Further, on the lower surface of the gear case 1, a disc-shaped cutting blade retainer 3 is screwed into the male threaded portion of the large diameter portion 2A and placed in a closed state.
has a stepped portion 3 at the center of the flange portion 3A on its periphery.
It connects to the boss portion 3C via B. The diameter of this boss portion 3C is determined to fit into the center hole _X1 of the cutting blade X. A fastening table 4 is provided on the small diameter portion 2B of the output shaft 2.
The female threaded hole 4A serving as a mounting portion provided at the center is screwed into the threaded hole 4A. This fastening base 4
has a container shape with a gently curved lower surface 41, and the boss portion 3 is located above the center.
A donut-shaped boss portion 4 having an inner diameter that can accommodate C.
2 is formed, and the outer diameter of the boss portion 42 is slightly smaller than the outer diameter of the flange portion 3A of the cutting blade retainer 3. Furthermore, a donut-shaped space is formed on the outer periphery of the boss portion 42, and the bottom surface becomes gradually shallower toward the outer periphery to form a tapered surface 43, which serves as a mover housing space 44 for accommodating a ball as a mover. The outer periphery of the slider housing space 44 is a rim 45, and the rim 45 has an unevenness 4 on the outer periphery that serves as a finger rest for screwing and loosening the fastening base 4 onto the output shaft 2.
5A is provided. A donut-shaped leaf spring 5 as a friction plate is placed over the open surface of the slider housing space 44, and the inner circumferential edge 5A of this plate spring 5 is engaged with the inner peripheral wall of the slider housing space 44 by means such as press fitting. It is in a stationary state and integrated, and its outer periphery is in a free state and constantly tries to return to its flat state due to elasticity (Fig. 3). In addition, a plurality of balls 6, rolls, wedges, etc. (not shown) as movers are accommodated in the mover accommodation space 44, and the diameter of the balls 6 is the center of the mover accommodation space 44. In the nearer portion, when it moves in the outer circumferential direction along the tapered surface 43 without contacting the leaf spring 5, it is set to a dimension that hits the leaf spring 5, so that a wedge effect can be expected. They can be arranged in a line along the outer periphery of the section 42. When the cutting blade X is attached to the output shaft ₂ , the center hole
C, screw the female screw hole 4A of the fastening base 4 onto the small diameter portion 2B of the output shaft 2, and then tighten the plate between the upper edge of the boss portion 42 and the flange portion 3A of the cutting blade retainer 3. The spring 5 is tightened. Since the rotational speed of the engine is not very high when the engine is started, even when the output shaft 2 rotates, no large centrifugal force is applied to the ball 6. It is in a floating state in proportion to the magnitude of the force. In this state, the output shaft 2 and the fastening base 4
Even if it is rotated, the cutting blade Until sufficient frictional force is generated between the friction plate and the cutting blade to cause the cutting blade to move, it functions as a clutch, and the cutting blade X itself is in a rotational state where it is only gently rotated. . As the engine speed increases, the output shaft 2 also rotates at high speed, and the centrifugal force acting on the ball 6 increases, causing the ball 6 to move along the tapered surface 43 to the outer periphery of the slider housing space 44. Moving. The ball 6 is located between the tapered surface 43 and the leaf spring 5 and moves toward the outer periphery in proportion to the magnitude of the centrifugal force, so when a centrifugal force that exceeds the elasticity of the leaf spring 5 acts, in other words, the ball 6 moves at high speed. When the leaf spring 5 is in a rotating state, it is pushed up by the ball 6 against its own elasticity, and a strong frictional force is generated between the leaf spring 5 and the cutting blade X. This frictional force causes the output shaft 2 and the cutting blade The cutting blade X is rotated integrally with the blade retainer 3 and the clamping base 4. In the low rotational range of the engine, there is no centrifugal force acting on the ball 6 that strongly presses the leaf spring 5 against the cutting blade X, so there is a kind of centrifugal clutch between the cutting blade X and the output shaft 2. Due to the presence of the mechanism, the mower blade X does not rotate, and conversely, when the mower blade X bites into the tree and becomes locked, the friction between the mower blade This allows the sudden increase in load to be absorbed. In the above embodiment, the inner peripheral edge of the leaf spring 5 is locked inside the boss portion 42, but as shown in FIGS. 4 and 5, the inner peripheral edge of the leaf spring 5 is Alternatively, the unevenness 5B of the leaf spring 5 may be fitted into the uneven slit 42A, rotated by the pitch of the unevenness, and fixed with screws 7. In this case, the upper edge of the boss portion 42 is located in a plane slightly higher than the upper edge of the rim 45, and the center hole _X1 of the cutting blade X is fitted into the boss portion 42. Note that 5C is a screw hole into which the screw 7 is inserted. In particular, in the embodiments of the present invention, an example is given in which the clamping base 4 is attached to the output shaft 2 using screws, but it is of course possible to adopt attachment methods other than screws, and it is possible to securely attach the cutting blade X. The format does not matter as long as it can be obtained.

【Effect of the invention】

As is clear from the above description, the mowing blade attachment device for a brush cutter of the present invention has a fastening base that is attached to the output shaft and fastens the mowing blade to the mower blade holder, and the mowing blade is spread outward by the action of centrifugal force. A movable element is provided, and the movable element is moved by centrifugal force, and the friction plate provided on the clamping base is pressed against the cutting blade, resulting in a frictional force that can be integrated with the output shaft and the clamping base. From this, the following effects can be obtained. (a) Since the frictional force for fixing the cutting blade increases in proportion to the increase in engine output, the cutting blade can be fixed securely. (b) When the engine output is low, for example when idling, direct power transmission is cut off between the cutting blade and the output shaft, so the cutting blade rotates only a small amount, and when the engine starts, the cutting blade rotates as the engine rotates. It is safe as it does not rotate. (c) The centrifugal clutch provided on the engine crankshaft can be omitted and the output shaft and engine can be connected in series, simplifying the mechanism.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention, in which FIG. 1 is a side sectional view of the main part, FIG. 2 is a diagram showing the plane and bottom surface of the fastening base, and FIG. 3 is an enlarged sectional view of the part shown in FIG. 1. Fourth
The figure is an enlarged sectional view corresponding to FIG. 3 according to another embodiment, and FIG. 5 is a plan view showing the state shown in FIG. 4 before installation. 1...Gear case, 2...Output shaft, 2A...Large diameter section, 2B...Small diameter section, 3...Mower blade retainer, 3A...
...Flange part, 3B...Step part, 3C...Boss part,
4...Tightening base, 4A...Female screw hole, 41...Bottom surface, 42...Boss part, 42A...Irregular slit,
43... Tapered surface, 44... Mover housing space, 4
5... Rim, 45A... Unevenness, 5... Leaf spring, 6
...ball, 7...screw.

Claims (1)

[Claims] 1 The main operating rod has an engine at one end and a gear case at the other end, and the cutting blade holder attached to the output shaft of this gear case is connected to the cutting blade holder attached to the output shaft. A mower blade attachment device for a brush cutter comprising a mower blade clamping base for attaching a blade, the clamping base having a mounting portion for the output shaft;
The movable element is housed in a storage space formed inside and moves by centrifugal force, and a friction plate is pressed against the cutting blade holder by the movement of the moving element, and the friction plate is in contact with the cutting blade holder. A mower blade attachment device for a brush cutter, characterized in that the mower blade is frictionally fixed between the mowers at a predetermined rotation speed or higher.