Metal deforming – By deflecting successively-presented portions of work during... – By use of deflector arranged to bend work transversely of...
Reexamination Certificate
2001-09-04
2003-07-15
Crane, Daniel C. (Department: 3725)
Metal deforming
By deflecting successively-presented portions of work during...
By use of deflector arranged to bend work transversely of...
C072S377000
Reexamination Certificate
active
06591653
ABSTRACT:
TECHNICAL FIELD
Multi-gauge strips are mainly used as materials for terminals of lead frames, relays, connectors, etc. of power trasistors. The present invention relates to a method of producing a multi-gauge strips by means of forming copper, a copper alloy, or a metal strip which can undergo plastic work in such a manner that its two sides in the widthwise direction are thinner than the center portion.
BACKGROUND ART
As for the conventional methods of producing a multi-gauge strips, the following methods are generally known: a scalping method of thinly cutting the surfaces of the two sides of a strip to reduce the thickness thereof while leaving its center portion intact by means of using a cutting tool; a welding method of joining thin materials to the two sides from the center of a strip; a seesaw method (hereinafter SS) of rolling at a right angle to the direction of progression of a material in feed; and a rectilinear rolling method (hereinafter RL) of rolling in the direction of progression of a material in feed. The items of specification requirements for a multi-gauge strips are as follows: shape, thickness, precision, surface roughness, straightness, hardness, etc. In this regard, with the scalping method, among other methods aforementioned, the quality of the material at the thick portion and that of the thin portion are the same as a result of scalping the surfaces of the two sides of the same material, and thus the method is able to satisfy the hardness requirement among others, but it nonetheless leads to difficulties in satisfying other specification requirements. Moreover, in conjunction with the losses associated with the cut portions, the size of the material is set to be larger than that of the finished product, and these factors lead to a disadvantage of lowering the utility ratio of a material.
With respect to the welding method, as well, even if the welding can be achieved in an instant, a source of heat of high temperature is required for such welding. To void interposition of oxides at the welding area on account of such welding, it needs a non-oxide atmosphere in a nearly vacuum condition, and to maintain such a non-oxide atmosphere, it necessarily incurs high installment and operation costs, which in turn leads to a high production cost. Moreover, with respect to the welding area, the quality reliability is lowered, which in than tends to limit the utility of a strip.
As for another method in addition to those aforementioned, there is a seesaw method (SS) or a V-MILL method, wherein pressure is put onto a strip material (M) which in turn is placed on a metal mold (TL), as shown in
FIG. 1
, with a direction of rolling in a back-and-forth motion, or by a method of working from left to right, much like a seesaw, at a right angle (RA) to the material (M). In this manner, the center portion of the strip material (M) is indented by the lower surface (S) of the mold, and the two sides thereof in the width direction are stretched out to the respective space (S) at either side, thereby forming a thick portion (TK) and a thin portion (TN) therein. In this method, pressure is effectuated vertically on the material, which in turn is placed on the flat metal mold. As such, the stretching work on the material is made difficult due to a sticking caused by friction between the mold and the material. As compare to drawing works, it requires pressure of several tens of times, which in turn necessitates equipment of large capacity in addition to the high-strength metal molds. Moreover, since the operation of a rolling roll or a metal mold must be carried out in the direction which is left and right to the direction of progression of the material, there is an ensuing problem of requiring high-priced special-purpose equipment of large capacity, instead of ordinary general-purpose equipment. Further, since the ends of the two sides of a material in the width direction must be maintained at a slant while stretching the same for continuous formation, it limits the feed speed to the level of 1~2 m/minute, which in turn dramatically lowers productivity.
Further, as another method in addition to those aforementioned, the rectilinear rolling method (RL) involves passing the material (M) between the two rolling rolls (R), one on the top and the other on the bottom, each having a rectilinear indentation and a protrusion. In this manner, by folding the two sides of the material in the widthwise direction (WO), the primary rolling (RL
1
) is carried out into the shape having a protrusion at the center portion (V
1
) thereof Then, in the secondary rolling (RL
2
), by compressing the upper end of the center portion (V
1
), the widths (L
1
, V
1
, W
1
) and the thickness (T
1
, t
1
) formed during the primary rolling (RL
1
) are formed into the following widths (L
2
, V
2
, W
2
) and thicknesses (T
2
, t
2
). Receiving the material therefrom, the tertiary rolling (RL
3
) using the same method of the primary rolling (RL
1
) carries out the process of rolling it into the shape with the following widths (L
3
, V
3
, W
3
) and the thicknesses (T
3
, t
3
). By repetitively carrying out the aforementioned process, the material is formed into the following specifications of widths (L, V, W) and thicknesses (T, t).
Here, the width of the center portion is reduced from V
1
to V
2
and then to V
3
, and the width of the either side is widened from L
1
to L
2
and then to L
3
. The total width thereof is enlarged from W
1
to W
2
and then to W
3
, and the thickness at the center is reduced from T
1
to T
1
and then to T
3
. The thickness of the either side from the center portion (V
1
) is also reduced from t
1
, to t
2
and then to t
3
. In this manner, a multi-gauge strips is formed thereby, the art of which is generally known in the field.
However, in the aforementioned rectilinear rolling method, due to the peculiarity of the rolling work, the direction of staining (stretching) of the material is such that the staining of the material is achieved only in the lengthwise direction of the material, which is the direction of progression of rolling. The straining of the material in the width direction, which is perpendicular to the direction of progression of the material, or the elongation as a result of stretching, is insignificant as compared to that in the direction of progression of the material. As such, by compressing the lower side of said center portion (V
1
) in the width direction, the ends of the two sides are widened while the thickness (t
1
) of the either side is reduced to the thickness (t
2
) by means of rolling work. As such, 8 to 10 units of rolling mills must be arranged continuously therein since the above process of widening by stretching the two sides (L
2
) in the widthwise direction must be carried out repetitively for about ten times or so. Hence, in terms of facility investment, there is indeed a problem of economical efficiency.
Moreover, as for the tandem rolling method having a continuous placement of rolling rolls in a serial manner, the continuous rolling is carried out in such a manner that a strip with a given length after undergone the rolling process in the preceding roll (R) is received by the subsequent roll (R), which in turn is received by the next subsequent roll (R).
With respect to the length of the material, stretched at that time, the length of the strip is elongated in the order of primary, secondary and tertiary rollings. As such, with the same rotation speed with resect to the primary, secondary and tertiary rolling rolls, the continuous work cannot possibly be carried out therein. To solve this problem, equipment with a special function to control the rotation speed of the rolls (R) is required, which is rather problematic in itself.
Moreover, the rolls (R), which are used in the rolling process are tools with specifications of multi-gauge strips materials (P), and the rolls (R) of various specifications in small lots must be provided beforehand, which leads to a problem of rising cost with the inconvenience of operational management in disass
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