JPH09107764A - Mowing circular saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sharpness of a mowing circular saw by adopting a chip-embedded structure. SOLUTION: Plural dent parts 12 and protruding parts 11 are alternatively formed on the outer peripheral edge of a circular base board 10. A cemented carbide chip 14 of an embedded type is soldered at the tip of the front edge in a specified rotary direction of each of the protruding parts and a side cutting edge 15 is formed on the chip. In this circular saw, a front edge of a specified rotary direction of a protruding part of the base board existing at the inner side of a radius direction of the circular saw than the position of a side cutting edge formed at a chip is formed into a secondary side cutting edge 18. The side cutting edges have a side rake angle same as an ordinary side rake angle, and a secondary side rake face 17 having a larger angle than the side rake angle is formed on a chip leaving the side rake face 16 forming the side rake angle by a thread width in the order of a thread chamfer at the side of the side cutting edge. The chips are protruded by the thread width in the direction of the thickness of the base board so that the secondary rake faces of the side cutting edges and the side rake faces 19 of the secondary side cutting edges form continuous single planes. Further, the secondary side cutting edges are placed at the forward side than the side cutting edges in a specified rotation direction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mowing circular saw.

[0002]

2. Description of the Related Art An earlier conventional mowing circular saw had a saw-shaped tooth formed on the outer periphery of a disk made of tool steel. That is, the cutting edge portion continued to the substrate, and was made of the tool steel of the substrate. Thereafter, since durability is required, the cutting edge portion is formed of a cemented carbide tip, and various tip shapes and brazing structures have been proposed. An example is shown in FIG. In the figure, 1 and 2 are cemented carbide chips,
3 and 4 are tool steel substrates, 5 and 6 are brazing surfaces,
θ1 is a horizontal scooping angle and is usually about 5 to 8 °. FIG.
The mowing circular saw 7 shown in (a) and (b), and FIG.
With the mowing circular saw 8 shown in (d), while one circular saw 7 is a substantially L-shaped brazing surface 5 in the front shape,
The difference lies in that the other circular saw 8 is formed in a substantially U-shaped brazing surface 6, that is, an embedded shape in which the chip is embedded not only on one side but also on both sides. Such a mowing circular saw 8 is superior in that the brazing area of the chips can be larger than that of 7, so that the brazing strength is high and the chips are less likely to fall off. The arrow in the figure indicates the direction of rotation during use.

[0003] In general, when using a mowing circular saw, not only the grass always hits the blade but also a hard object such as a stone or a piece of metal. In such a case, a large impact force is applied to the tip. It is better that the chip is firmly fixed to the substrate. Therefore, there are many embed-type configurations, such as the mowing circular saw 8, which allow a large brazing area between the chip and the substrate. In this case, the length of the cutting edge is short. However, since the mowing circular saw is used at a high speed, the cutting amount per tooth is small, so it is considered that there is no problem.

[0004] However, the cutting edge formed by a cemented carbide tip is significantly improved in terms of durability as compared with the former cutting edge portion formed of a substrate (tool steel). However, there is a fact that it is inferior in sharpness. This is because if the lateral scooping angle θ1 is too large for the chip of the cemented carbide to be easily chipped, the durability is reduced.
The emphasis is on durability rather than a bit of poor sharpness.

[0005]

When the reason why it is said that the sharpness of a mowing circular saw using a cemented carbide tip is not always good is considered, the following can be considered. First of all, conventionally it was thought that the cutting rate per tooth was small because the mowing circular saw rotates at high speed, and the cutting edge may be short, but looking at the actual usage situation, the circular saw part is swung. However, the cut amount is not constant depending on the user or the use condition, and is not a substantially constant cutting state like a circular saw for woodwork, but rather irregular. Therefore, it is considered that the grass cut at a considerable rate in the mowing operation has entered the bottom side of the concave portion on the front side of the tooth beyond the position of the cutting edge. In such a state, the cutting is not effected by the cutting edge, and the grass is torn off while being caught on the portion of the tooth base without the cutting edge. While such a situation may occur depending on the use condition, the recent one having excellent durability has a configuration in which the brazing area is large as in the above-mentioned mowing circular saw 8, so that the length of the cutting edge is inevitably increased. It has an element that makes it shorter. For this reason, the grass that has entered inside the turning range of the cutting edge is not cut by the cutting edge, so that the sharpness is poor.

On the basis of such a concept, sharpness can be improved by increasing the length of the cutting edge in the radial direction of the substrate. However, increasing the length of the cutting edge has a problem in that the brazing area of the tip 3 is reduced as in the above-described mowing circular saw 7. In addition, since the grass cutting circular saw is used at high speed rotation, it is certain that the cutting edge used for cutting grass is mainly the tip portion of the cutting edge far from the center of rotation. Therefore, it is necessary to improve the sharpness of the tip of the cutting edge.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a chip made of cemented carbide and to use a strong brazing structure for the chip, that is, an embedded structure as it is, and to improve the sharpness of a mowing circular saw.

[0008]

Means for Solving the Problems According to the means of the present invention, a plurality of recesses and projections are alternately formed on the outer edge of a disk-shaped substrate, and the projections are embedded in the tip of the front edge in a predetermined rotation direction. Shaped cemented carbide tip is brazed, and in a grass cutting circular saw in which a horizontal cutting edge is formed on the tip, a predetermined position of the convex portion at a position radially inside the circular saw than the position of the horizontal cutting edge formed by the tip The front edge portion in the rotational direction is formed on the second horizontal cutting edge.

In this means, the brazing strength is high because the cemented carbide tip is embedded, but the cutting edge is short, so that the grass is used on the bottom side of the recess inside the horizontal cutting edge during use. High probability of getting into. When it enters the bottom side, it is not cut by the horizontal cutting edge of the chip, but the second horizontal cutting edge acts. The second horizontal cutting edge is formed of the tool steel of the substrate, and therefore is a material that is more easily worn than the horizontal cutting edge of the cemented carbide chip, but basically the horizontal cutting edge of the chip mainly acts to cut. Therefore, the second cutting edge is an auxiliary tool, and since the frequency of cutting is low, a sharp cutting state can be maintained for a considerable period of time.

In the above-mentioned means, the horizontal cutting edge has a horizontal scooping angle which is the same as a normal horizontal scooping angle, and the horizontal scooping surface forming the horizontal scooping angle is on the side of the horizontal cutting edge. It is advisable to form a second horizontal scooping surface having an angle larger than the horizontal scooping angle, leaving only the surface width. This configuration has a small horizontal scooping angle where the horizontal scooping surface has a narrow width when it is new, but the horizontal cutting edge is less likely to cause chipping, and when the cross-sectional shape of the horizontal cutting edge becomes rounded when the wear progresses to some extent, Since the width of the scooping surface is small and the second scooping angle is large, the radius of the roundness is smaller than that of the conventional single horizontal scooping surface and the sharpness lasts longer. To do. The horizontal scooping angle is preferably in the range of 4 to 8 °, more preferably 5 to 6 °.
This is almost the same as the conventional horizontal scooping angle, and if the angle is large, the sharpness is good but chipping of the cutting edge is likely to occur, and if it is small, chipping is difficult to occur but the sharpness is reduced, so It is better to make a decision in relation to it, and it is better to make it small when the yarn surface width is small and to make it large when the yarn surface width is large. The yarn surface width is preferably in the range of 0.5 to 0.8 mm, more preferably 0.6 to 0.7 mm,
If it is too wide, the meaning of providing the second salvage surface will be less. The angle of the second scooping surface is 30 to 50 °, more preferably 40 to 45 °.

The chip is protruded in the thickness direction of the substrate by the width of the thread surface, and the second scooping surface of the horizontal cutting edge and the horizontal scooping surface of the second horizontal cutting edge are formed in the same plane. It is better to assume that With this configuration, the second scooping surface of the side cutting edge and the side scooping surface of the second side cutting edge can be simultaneously polished.

[0012] It is preferable that the second horizontal cutting edge is provided at a position in front of the horizontal cutting edge in the predetermined rotation direction. According to this configuration, the thickness of the embedded portion in the front-rear direction in the rotational direction may be reduced depending on the brazing structure of the chip. Can be large. The second cutting edge is provided at the protruding portion in order to increase its size, and there is no reduction in brazing strength.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. The figure shows one of a number of teeth provided along the outer circumference of a mowing circular saw. A disk-shaped substrate 10 has a convex portion 11 and a concave portion 12 formed therein. The cemented carbide tip 14 with the U-shaped brazing surface 13
Have been brazed. In the drawing, α is a tilt angle of the chip with respect to a straight line C passing through the center of rotation of the substrate. The tip 14 has a horizontal cutting edge 15, and the horizontal cutting edge 15 has a horizontal scooping surface 16 having a horizontal scooping angle θ1 and a second horizontal scooping surface 17 having a horizontal scooping angle θ2. Have. The horizontal scoop angle θ1 is an angle (4 to 8 °) at which chipping is unlikely to occur as in a normal mowing saw blade, and the horizontal scoop angle θ
2 is substantially larger (30 to 50 degrees) than θ1. 1B, the thickness T of the chip 14 is slightly larger than the thickness t of the substrate 10, and at least the small dimension T1 (0.5
〜0.8 mm). The scooping surface 16 is formed with a width corresponding to the small dimension T1.

At the time of use of the convex portion 11 of the substrate 10 in the rotation direction front edge, a second horizontal cutting edge 18 having an angle θ2 is attached to the horizontal cutting edge 1.
5 is provided so as to be substantially continuous. This second horizontal cutting edge 1
8 is a horizontal scooping surface 19 which is an extension of the second horizontal scooping surface 17
Is formed.

A second embodiment of the present invention will be described with reference to FIG. This second embodiment also shows one of a large number of teeth provided along the outer circumference of the mowing circular saw, and the disk-shaped substrate 20
Are formed with a convex portion 21 and a concave portion 22, and a cemented carbide chip 24 is brazed to the convex portion 21 with a brazing surface 23 similar to a conventional special embedded type. The first embodiment differs from the first embodiment in that a brazing structure for the tip 24 and a second lateral cutting edge 28 are provided.
Is mainly located slightly in front of the horizontal cutting edge 25 in the rotation direction, and the other points are almost the same, so that the description is omitted. 26 is the horizontal scooping surface of the chip, 27 is the second horizontal scooping surface, 28 is the second horizontal cutting edge, 29 is the horizontal scooping surface of the second horizontal cutting edge, θ1 is the same horizontal scooping angle as in the first embodiment, and θ2 is also the same. The angle is the same as in the first embodiment, and the horizontal scooping surfaces 27 and 29 are not continuous.

A third embodiment of the present invention will be described with reference to FIG. The third embodiment also shows one of a large number of teeth provided along the outer circumference of the mowing circular saw, and the disk-shaped substrate 30
Are formed with a convex portion 31 and a concave portion 32, and the convex portion 31 has a similar embedding type brazing surface 33, which is different from that of the first embodiment in the mounting angle of the chip and the way of providing the horizontal cutting edge to the chip. Is used to braze the cemented carbide tip 34. The second embodiment is different from the first embodiment mainly in that the position of the second lateral cutting edge 38 of the tip 34 is located slightly ahead of the lateral cutting edge 35 in the rotation direction, and the other parts are almost the same, so that the description is omitted. . 36 is the horizontal scooping surface of the chips,
37 is the second horizontal scooping surface, 38 is the second horizontal cutting edge, 39 is the second
The horizontal scooping surfaces of the horizontal cutting edge, θ1 and θ2, have the same angles as in the first embodiment, and the horizontal scooping surfaces 37 and 39 are not continuous.

In the above-mentioned first, second and third embodiments, the mowing circular saw mainly uses the chips 14, 24, 3
The cutting edges 15, 25 and 35 of No. 4 perform the cutting action, and the grass that has entered the center side beyond the horizontal cutting edges 15, 25 and 35 for some reason is cut by the second horizontal cutting edges 18, 28 and 38. The horizontal cutting edges 15, 25, and 35 of the chips have a horizontal scooping angle θ1 at which the normal chipping is unlikely to occur, and as the wear progresses, the cutting edge cross-sectional shape becomes rounded. It is smaller than the conventional one in which the surface 17 is not provided, and the cutting action is less reduced. Therefore, the chips 14, 24, 34 have a strong brazing structure, and the sharpness of the chips is less deteriorated even as the wear progresses, and the lateral cutting edges 18, 28, 38 are formed so that the lateral cutting edges are substantially Since it is formed to extend inward in the radial direction, there is little grass wrapping or cutting residue, and it has good durability. In the first embodiment, the horizontal scooping surfaces 16 and 18 are used.
Are continuous, so that they can be polished at the same time, and there is an advantage that manufacture is easy.

[0018]

EXAMPLE In the first embodiment, θ1 is 5 °, θ2 is 45 °, t is 1.2 mm, T is 2.0 mm, and T1 is 0.
5 mm.

[0019]

According to the first aspect of the present invention, the embedded type structure having a large brazing strength of the conventional tip is left as it is, and the cutting effect of the second cutting edge is improved. Play. According to the second aspect of the invention, the sharpness of the lateral cutting edge of the chip lasts for a long time, so that the overall sharpness also lasts longer. In the invention according to claim 3, the second scooping surface of the horizontal cutting edge and the horizontal scooping surface of the second horizontal cutting edge are formed in the same plane, which is continuous, so that the polishing can be performed at the same time, which facilitates production. Play. According to the invention described in claim 4, the front-side dimension of the substrate on the front side of the embedded portion of the chip can be made sufficiently large and the mounting strength of the chip can be secured, so that the durability is improved.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of the present invention, wherein (a) is an enlarged front view of one tooth and (b) is a plan view of (a).

2A and 2B show a second embodiment of the present invention, wherein FIG. 2A is an enlarged front view of one tooth, FIG. 2B is a view as viewed from the arrow B of FIG. 2A, and FIG. 2C is AA of FIG. It is sectional drawing.

3A and 3B show a third embodiment of the present invention, wherein FIG. 3A is an enlarged front view of one tooth, FIG. 3B is a view as viewed from an arrow E in FIG. 3A, and FIG. 3C is DD in FIG. It is sectional drawing.

4A and 4B show two examples of a conventional mowing circular saw, wherein FIG. 4A is an enlarged front view of one tooth of the first example, FIG. 4B is a plan view of FIG. 4A, and FIG. An enlarged front view of one tooth of an example of
(D) is a top view of (c).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 Convex part 12 Concavity 13 Brazing surface 14 Chip 15 Horizontal cutting edge 16 Horizontal scooping surface 17 No. 2 horizontal scooping surface 18 Second horizontal cutting edge 19 Second horizontal scooping surface 20 Substrate 21 Convex portion 22 Depressed portion 23 Brazing surface 24 Chip 25 Horizontal cutting edge 26 Horizontal scooping surface 27 No. 2 horizontal scooping surface 28 Second horizontal cutting edge 29 Second horizontal scooping surface 30 Substrate 31 Convex part 32 Concave 33 Brazing surface 34 Chip 35 Horizontal cutting edge 36 Horizontal scooping surface 37 No. 2 horizontal scooping surface 38 2nd horizontal cutting edge 39 2nd horizontal scooping surface

Claims (4)

[Claims] 1. A plurality of recesses and protrusions are alternately formed on the outer edge of a disk-shaped substrate, and an embedded cemented carbide chip is brazed to the tip of the front edge of each protrusion in the predetermined rotation direction. Then, in a mowing circular saw in which a horizontal cutting edge is formed on the tip, a second horizontal cutting edge is provided on a front edge portion in a predetermined rotation direction of the convex portion at a position radially inside the circular saw with respect to a position of the horizontal cutting edge formed by the tip. A circular saw for cutting grass characterized by being formed into a. 2. The mowing circular saw according to claim 1, wherein
The horizontal cutting edge has a horizontal scooping angle that is the same as a normal horizontal scooping angle, and the horizontal scooping surface forming the horizontal scooping angle is left on the side of the horizontal cutting edge by a thread surface width of a thread chamfering width. A circular saw for cutting grass, which is characterized by forming a second horizontal scooping surface having an angle larger than the scooping angle. 3. The circular saw according to claim 2, wherein:
The chip is projected in the thickness direction of the substrate by the width of the thread surface, and the second scooping surface of the horizontal cutting edge and the second horizontal cutting edge of the second horizontal cutting edge are provided.
A circular saw for mowing, characterized in that the horizontal scooping surface is formed in the same plane. 4. The mowing circular saw according to claim 2,
The grass cutting circular saw, wherein the second horizontal cutting edge is provided at a front side position in the predetermined rotation direction with respect to the horizontal cutting edge.