[DESCRIPTION]

[Invention Title]

MILLING CUTTER

[Technical Field]

The present invention relates to a milling cutter comprising a ring-shaped first body adapted to mount a cutting insert and a second body engaged to a spindle. More specifically, the present invention relates to a milling cutter wherein the first and second bodies are made of different materials to reduce weight of the milling cutter while ensuring firm engagement between the two bodies.

[Background Art]

A milling cutter is generally made of steel having a high strength so as to endure a heavy load applied to a cutting insert during a cutting process. However, when the milling cutter is made of steel, the milling cutter is so heavy that it is difficult for an operator to take the milling cutter out of the spindle for exchange or repair.

Further, because the weight of the milling cutter is so heavy, it may threaten the safety of the operator working with the milling cutter. Also, the body may be hung down due to the heavy weight. This deteriorates accuracy of the cutting process and imposes a heavy load upon the spindle, thereby shortening the lifespan of the spindle.

In order to solve the above problems, a lightweight milling cutter was suggested as shown in Fig. 1. The milling cutter (1) comprises a cutting ring (2) in an annular shape. The cutting ring (2) is provided with a plurality of recesses (3) to be engaged with a plurality of cutting inserts. A body (4) has an outer circumferential surface (5) to be engaged with the cutting ring (2) via a screw. Further, the body (4) has a plurality of surfaces (6) and holes (7) to be engaged with a spindle (not shown). The body (4) is made of a light non-ferrous metal such as aluminum alloy, which is light and excellent in terms of absorbing vibrations.

However, the conventional milling cutter (1) poses a problem since the cutting ring located outside of the milling cutter expands due to the centrifugal force during a high-speed rotation. Thus, the cutting edge of the cutting insert moves to the outside of the rotational axis, which deteriorates the accuracy of cutting performance.

[Disclosure] [Technical Problem]

To solve the above problems of the prior art, the present invention provides a milling cutter comprising a first body and a second body made of different materials. When the cutting insert of the present invention has been mounted to the tool holder, the ring-shaped first body engaged with the cutting insert is prevented from expanding outwardly due to the centrifugal force during a high-speed rotation.

[Technical Solution]

In order to achieve the above objective, the milling cutter provided to be rotatable around a rotational axis (A) is configured to be in an annular ring. Such a milling cutter comprises a first body (10) and a second body (20). The first body comprises recesses for engagement with a plurality of cutting inserts and a first threaded portion formed inside the ring shape. The second body comprises a second threaded portion engaged with the first threaded portion of the first body via a screw and a support portion, which comes into contact with the first body for mutual support in the rotational axis (A) direction. The first body is made of a material with a greater strength than that of the second body. The support portion of the second body comprises an inclined surface inclined by the angle "a" from the planar surface, which is vertical to the rotational axis (A) as it proceeds away therefrom toward the outside.

The support portion of the second body may be in a step-like shape by being formed to go up as the support portion goes away from the rotational axis (A) toward the outside.

[Advantageous Effects]

The present invention provides advantages such as easy handling of the cutting tool due to the reduced weight of the body of the milling cutter and minimizing movement of the body of the milling cutter due to the centrifugal force during the high-speed rotation. Accordingly, the present invention ensures a cutting process with high accuracy even during the cutting process with a high-speed rotation. In addition, the milling cutter with the dual-body system can be stably secured by using an elastic bush-member.

[Description of Drawings]

Fig. 1 illustrates a milling cutter according to the prior art. Fig. 2 is a perspective view of a milling cutter comprising a first body and a second body according to the present invention.

Fig. 3 is a perspective view of the first body according to the present invention. Fig. 4 is a perspective view of the second body according to the present invention.

Fig. 5 is a cross-sectional view showing the first and second bodies engaged with each other.

Figs. 6 and 7 illustrate the first body being expanded due to the centrifugal force during a high-speed rotation when the inclination angles "a" formed between the support portion of the second body and the planar surface vertical to the rotational axis (A) are 0° and 5°.

Fig. 8 is a cross-sectional view showing the first body and the second body engaged with each other according to Embodiment 2 of the present invention.

Fig. 9 is a partial cross-sectional view of the first body and the second body engaged with each other.

Fig. 10 is a perspective view of the first body, the second body and the bush-member engaged with one another.

Fig. 11 is an enlarged view of portion A in Fig. 9.

Fig. 12 is a perspective view of the bush-member according to the present invention.

Fig. 13 is a cross-sectional view of the bush-member according to the present invention.

[Best Mode]

The present invention is described below with reference to the accompanying drawings.

Fig. 2 is a perspective view of a milling cutter constructed in accordance with the present invention. The milling cutter is configured to be rotatable around a rotational axis (A). The milling cutter comprises a first body (10) and a second body (20). The first body (10) has an annular ring-shape and comprises recesses configured to be engaged with a plurality of cutting inserts. The second body (20) is engaged with a spindle (not shown) of the milling cutter. The first body (10) is made of a material whose strength is greater than that of the second body (20). Generally, the first body (10) is made of steel and the second body (20) is made of a non-ferrous metal.

Preferably, the second body (20) is made of aluminum alloy, which is light and excellent in terms of absorbing vibrations.

Fig. 3 is a perspective view of the first body (10) according to the present invention. The first body (10) may be an annular ring. The first body (10) comprises recesses (12) and a first threaded portion (13). The recesses (12) may be engaged with a plurality of cutting inserts (11). The first threaded portion (13) is formed inside the ring shape.

Fig. 4 is a perspective view of the second body (20) according to the present invention. The second body (20) comprises a second threaded portion (22) and a support portion (21). The second threaded portion (22) is engaged with the first threaded portion (13) of the first body (10) via a screw. The support portion (21) comes into contact with the first body for mutual support in the direction of the rotational axis (A). Further, the second body (20) comprises parallel surfaces (23) with a predetermined length at an upper side of the second threaded portion (22).

Fig. 5 is a cross-sectional view showing the first and second bodies engaged with each other. As illustrated in Fig. 5, the support portion (21) is formed to be an inclined surface inclined by an angle "a" from the planar surface, which is vertical to the rotational axis (A). As illustrated in Fig. 5, the support portion (21) of the second body is formed to be an inclined surface inclined by "a" degree from the planar surface, which is vertical to the rotational axis (A) as it proceeds away therefrom toward the outside. The inclination angle "a" between the support portion (21) of the second body (20) and the planar surface vertical to the rotational axis (A) ranges from about 3° to 10°, preferably about 5°. If the inclination angle is smaller than 3°, then the first body (10) is rarely prevented from being expanded by the centrifugal force during the high-speed rotation. Further, if the angle exceeds 10°, then the first body fails to have sufficient strength.

Fig. 6 illustrates an expanded distance of the first body (10) due to the centrifugal force during the high-speed rotation when the inclination angle "a" between the support portion (21) of the second body (20) and the planar surface vertical to the rotational axis (A) is 0°. Fig. 7 illustrates an expanded distance of the first body (10) when the inclination angle "a" is 5°. As illustrated in Figs. 6 and 7, when the inclination angle is 0°, the first body (10) moves by maximum of 0.0523mm toward the outside of the rotational axis (A) by the centrifugal force. However, when the inclination angle is 5°, it moves only 0.03mm. As such, the expansion of the first body (10) during the high-speed rotation is remarkably minimized by forming the support portion (21), which comes into contact with the first body (10) and the second body (20), to be an inclined surface. Thus, the accuracy of cutting performance is ensured.

Fig. 8 is a cross-sectional view showing the first body and the second body engaged with each other according to Embodiment 2 of the present invention. When compared to Embodiment 1 illustrated in Figs. 2 to 7, Embodiment 2 is distinguishable in that the support portion, which makes contact with the first body (10) and the second body (20), is not an inclined surface but rather has a step-like shape (P). The step-like shape (P) is configured such that the support portion (21) of the second body (20) goes up as it proceeds away from the rotational axis (A) toward the outside.

Fig. 9 is a partial cross-sectional view of the first body and the second body engaged with each other. Fig. 10 shows a perspective view of the first body, second body and bush member (3) engaged with one another. As illustrated in Fig. 9, the bush member (30) is inserted into the inner center of the second body (20). Due to the elasticity of the bush member (30), the second body (20) is pressed toward the first body (10) in the direction along the arrow "a." Moreover, the first body (10) further comprises first parallel surfaces (14) in a predetermined length at the upper side of the first threaded portion (13). The second body further comprises second parallel surfaces (23), which come into contact with the first parallel surfaces (14). Thus, the pressuring force accruing from the elasticity of the bush member (30) ensures close contact between the first parallel surfaces (14) of the first body (10) and the second parallel surfaces (23) of the second body (20). It also guarantees stable securement between the first body (10) and the second body (20) during the high-speed rotation in the cutting process.

Fig. 11 is an enlarged view of portion A in Fig. 9. As illustrated in Fig. 11 , there is no gap between the bush member (30) and the second body (20), and also between the second body (20) and the first body (10).

Fig. 12 is a perspective view of the bush member (30) according to the present invention. Fig. 13 is a cross-sectional view of the bush member according to the present invention. As illustrated in Fig. 12, the bush member (30) has an annular strip shape with a hollow cavity (31) in the center.

Although the present invention has been described in detail for purposes of illustration, it is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the spirit and scope of the present invention, which is defined by the claims that follow.