Cutters – for shaping – Comprising tool of specific chemical composition
Reexamination Certificate
2000-07-11
2002-10-29
Tsai, Henry (Department: 3722)
Cutters, for shaping
Comprising tool of specific chemical composition
12
Reexamination Certificate
active
06471449
ABSTRACT:
This application is based on application Nos. 11-307621, 11-307622 and 11-307623 filed in Japan, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a throw-away tip for use in a cutting process.
2. Description of Related Art
Throw-away tips are known which are adapted to be attached to a holder or the like to function as a cutting tool. Such a throw-away tip is a disposable tip which is changed, rather than polished for reuse, when its cutting edge is worn out. The throw-away tip has cutting ridges provided on respective corners of a generally planar rectangular or triangular base. When one of the corner cutting ridges is worn out, another of the corner cutting ridges is used. Then, the throw-away tip is changed when all the corner cutting ridges are worn out.
However, it is not easy to check how far the cutting ridges of the throw-away tip have been worn. In view of an operating environment, it is particularly difficult to detect the abrasion degree of a cutting ridge currently used for cutting without interrupting the cutting process.
Conventional methods for detecting the abrasion degree of the cutting ridge are as follows:
(1) The cutting process is interrupted, and the throw-away tip is removed from the holder to be observed the cutting ridge by means of a tool microscope or the like.
(2) The abrasion degree of the cutting ridge is estimated by detecting a phenomenon incidental to the abrasion of the cutting ridge. For example, a reduction in cutting ability, an increase in vibration, occurrence of a noise, or the like is detected by a sensor disposed adjacent a working portion on a machine tool, and the A-estimation of the abrasion degree is based on a detection signal from the sensor.
In the method (1), however, the cutting process is interrupted, and the abrasion degree of the cutting ridge cannot quantitatively be determined, so that the abrasion detection cannot accurately be performed.
The method (2) requires a complicated detector, and is less reliable with a poor sensitivity for the detection of the abrasion degree.
One approach to these problems is described in Japanese Unexamined Utility Model Publication No. 3-120323 (1991). This publication discloses a throw-away tip having a sensor line of a conductive film provided along a cutting ridge on a flank thereof. It is also disclosed that the sensor line has a width conforming to an allowable abrasion width. In accordance with the throw-away tip disclosed in the publication, the sensor line is worn as the cutting ridge is worn, so that expiration of the life of the cutting ridge can be detected when the sensor line is cut off.
Further, Japanese Unexamined Patent Publication No. 9-38846 (1997) proposes an ordinary cutting tool (not a throw-away tip) which has a thin film circuit on a flank thereof, wherein expiration of the life of the cutting tool is automatically detected by sensing a change in electrical resistance which occurs due to abrasion of the thin film circuit as the flank is worn.
The provision of the sensor line of the conductive film along the cutting ridge on the flank for the detection of the change in the line resistance is preferable for the detection of the abrasion of the cutting ridge.
Where this approach is applied to the throw-away tip, however, it is difficult in practice to connect the sensor line provided along the cutting ridge to an external detection circuit and the like.
More specifically, the throw-away tip is a disposable tip as described above, and is very small with a size of less than 1 cm
3
. During the cutting process, the tip in operation is exposed to a cutting fluid (water or oil) and shavings. However, no technique has been established for connecting the sensor line formed on the small throw-away tip to the external detection circuit and the like without any trouble in such a machining environment.
SUMMARY OF THE INVENTION
The present invention is to provide a throw-away tip having an abrasion sensor which serves for practical implementation to solve the aforesaid problems.
It is a principal object of the present invention to provide a throw-away tip having an abrasion sensor which, when attached to a holder or the like, ensures electrical connection between a sensor line provided thereon and an external circuit without any trouble in a cutting process.
It is another object of the invention to provide a throw-away tip which features protection of a connection portion between a sensor line provided thereon and an external circuit.
In accordance with the present invention, there is provided a throw-away tip with an abrasion sensor, which includes: a generally planar base having a rake face defined by one of opposite surfaces thereof, a seat face defined by the other surface thereof opposite from the rake face, and a flank defined by a side face thereof intersecting the rake face and the seat face; and a cutting ridge defined by an intersection between the rake face and the flank, the throw-away tip comprising: a sensor line of a conductive film provided along the cutting ridge on the flank in an electrically insulative relation with respect to the base; a pair of contact regions provided on the seat face in an electrically insulative relation with respect to the base, the contact regions being electrically connectable to a predetermined circuit; and a pair of connection lines provided on the base in an electrically insulative relation with respect to the base and respectively connecting the pair of contact regions to opposite ends of the sensor line, one of the pair of connection lines including a return line spaced a predetermined distance from the sensor line in a parallel relation to the sensor line.
With this arrangement, the provision of the return line extending parallel to the sensor line reduces the area of a region surrounded by an electrical conduction path including the pair of contact regions, the pair of connection lines and the sensor line. Therefore, even if the base has a small surface area, particularly with a small side face or a small flank, the electrical conduction path can properly be provided.
Particularly, where the throw-away tip has a plurality of cutting corner portions and sensor lines provided for the respective corner portions, connection lines for connection to the sensor lines can be arranged in a smaller space.
The connection lines may each have a greater width than the sensor line.
The connection lines which have a greater width than the sensor line have a lower electrical resistance than the sensor line. At detection of a change in the resistance of the sensor line, the resistance of the connection line is relatively low and, therefore, hardly influences the change in the sensor line resistance. As a result, the change in the sensor line resistance can accurately be detected.
It is preferable that the base has a plurality of side faces, which respectively define flanks, and a cutting corner portion is defined by an intersection between the rake face and each adjacent pair of flanks. Preferably, the sensor line extends along the cutting ridge as surrounding the corner portion and the return line extends parallel to the sensor line as surrounding the corner portion.
The return line surrounds the corner portion in a parallel relation to the sensor line which also surrounds the corner portion. Therefore, one end of the sensor line and an end of the return line extending from the other end of the sensor line toward the one end of the sensor line can be located on one of the adjacent pair of flanks. Thus, the pair of connection lines respectively connected to the sensor line and the return line can be provided in a spaced and parallel relation on the same flank. Further, the provision of the connection lines requires a smaller space, so that connection lines for the plurality of sensor lines can be provided on the single flank.
The pair of connection lines except the return line preferably extend parallel to each other at a predetermined inclination angl
Hogan & Hartson L.L.P.
Kyocera Corporation
Tsai Henry
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