Metal deforming – With cutting – By shearing tool-couple
Reexamination Certificate
2001-02-21
2002-08-06
Crane, Daniel C. (Department: 3725)
Metal deforming
With cutting
By shearing tool-couple
C072S327000, C072S339000, C072S420000, C083S040000, C083S055000, C083S861000, C083S412000
Reexamination Certificate
active
06427512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and an apparatus for blanking elements of a belt for use in a continuously variable transmission.
2. Description of the Prior Art
Generally, each of elements of a belt for use in a continuously variable transmission (CVT) comprises a body having a V-shaped surface for contact with a pulley of the continuously variable transmission and a head joined to an upper edge of the body. The element also has a pair of recesses defined between the body and the head. A plurality of elements are stacked and bundled into an annular form as the belt by endless rings that are mounted respectively in the recesses. When the belt is completed, the bodies with the V-shaped surfaces are positioned radially inside of the annular form and the heads are positioned radially outside of the annular form.
The elements are blanked out of a metal sheet by a die and a punch. A process of blanking an element out of a metal sheet comprises the steps of blanking an element out of the metal sheet while keeping the element joined to the metal sheet by a connector and separating the element from the metal sheet by cutting off the connector. According to the blanking process, the connector is positioned at two locations, i.e., a central region or tip end of the head and a central region or lower edge of the body, which are not required to be highly accurate dimensionally in the shearing process that is performed in the blanking step. In the blanking step, the V-shaped surface that needs to be of the highest dimensional accuracy of the element is reliably sheared to a desired level of dimensional accuracy.
When the connector is cut off in the separating step, however, a so-called shear drop, which is a thin region whose surface is inclined to the blanking direction, is created in the central region of the head and the central region of the body. If such a shear drop is positioned on the tip end of each of the heads that are located radially outside of the annular form of the belt, then the annular stack of the elements tends to bend toward the heads out of the circumferential direction due to the contact between the shear drops, thus adversely affecting the accuracy with which the elements are stacked.
The body of each of the elements has, on one side thereof, a thin portion for smoothly guiding the stacked elements to bend in the circumferential direction. The thin portion has already been prepared by a pair of corners on the opposite edges of the metal sheet, and serves as a blanking position corresponding to a substantially lower half portion of the body. Since such thin portions are positioned on the respective opposite edges of the metal sheet, a pair of symmetrical elements is blanked out of the metal sheet at the respective positions corresponding to the thin portions. Specifically, a pair of punches is used to blank the respective elements out of the metal sheet such that the thin portions are located at respective predetermined positioned on the elements. In order to keep the blanking positions highly accurately in alignment with the respective thin portions of the metal sheet prior to the blanking step, it is necessary to center the metal sheet to align the center between the blanking positions, i.e., between the punches, with the transverse center of the metal sheet.
Heretofore, it has been customary to center the metal sheet with a pair of guide members such as guide plates or abutment pins on both sides of a feed path for delivering the metal sheet for contacting and positionally limiting the opposite edges of the metal sheet. The guide members are spaced from each other by a distance substantially equal to the width of the metal sheet.
However, if the clearance between the guide members and the opposite edges of the metal sheet is reduced to center the metal sheet highly accurately with the guide members, then the metal sheet as it is delivered is subject to increased resistance due to contact between the metal sheet and the guide members, resulting in a failure to deliver the metal sheet at a high speed.
With the metal sheet having the thin portions on the opposite edges thereof, the width of one of the thin portions may possibly be different from the width of the other thin portion. If the widths of the thin portions are different from each other, then even when the transverse center of the metal sheet is aligned with the center between the punches by the guide members, the thin portions are not located in the desired positions on the bodies, and hence the thin portions of the blanked elements may be positioned differently from each other.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of and an apparatus for highly accurately blanking elements of a belt for use in a continuously variable transmission.
To achieve the above object, there is provided in accordance with the present invention a method of blanking elements of a belt for use in a continuously variable transmission, each having a body having opposite side edges which jointly provide a V-shaped surface for contact with a pulley of the continuously variable transmission and a head joined to a first edge of the body, symmetrically out of a metal sheet having a pair of thin portions on respective marginal edges thereof which are joined to a remaining portion of the metal sheet via respective corners, the method comprising the steps of centering the metal sheet by positioning a center between the corners as a center of the metal sheet, blanking the elements out of the metal sheet, the elements remaining joined to the metal sheet by respective connectors which are formed in the respective thin portions of the metal sheet, the bodies having respective second edges remote from the first edge and formed in the respective thin portions of the metal sheet, and separating the elements from the metal sheet by cutting off the connectors along the second edges of the bodies.
In the above method, first, the metal sheet is centered. Since the metal sheet is centered by positioning the center between the corners as the center of the metal sheet, the metal sheet can be centered accurately without being affected by the widths of the thin portions, i.e., the distances from the corners to the opposite edges of the metal sheet.
Then, the elements are blanked out of the metal sheet while they remain joined to the metal sheet by the connectors. The connectors are disposed at the second edges, i.e., lower edges, of the bodies. The V-shaped surface provided by the opposite side edges of each of the bodies is thus reliably sheared off with a sufficient level of accuracy.
Thereafter, the elements are separated from the metal sheet by cutting off the connectors. Since the connectors are disposed between the opposite side edges of the bodies which provide the V-shaped surface, only the connectors are required to be severed between the opposite side edges of the bodies. Because the peripheral edges of the elements have already been sheared highly accurately by this time, no shear drop occurs on the heads as the connectors to be sheared off are not joined to the heads, so that the heads are kept flat as desired. When the elements are stacked, the heads are held in reliable contact with each other, and the stack of the elements does not tend to bend toward the heads out of the circumferential direction, thus increasing the accuracy with which the elements are stacked. Even if a shear drop occurs when the connectors joined to the bodies are cut off, since the bodies are positioned radially inside of the annular form when the elements are stacked into the annular form, the shear drop does not adversely affect the accuracy with which the elements are stacked, and hence the elements can be stacked well in the circumferential direction.
The step of blanking the elements comprises the step of blanking the elements out of the metal sheet so as to be displaced in a blanking direction by a distance equal to at least the thickness of th
Kobayashi Makoto
Suzuki Tetsuo
Tachibana Takumitsu
Birch & Stewart Kolasch & Birch, LLP
Crane Daniel C.
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