Cutting device for metal foil

Metal foil base material placed on lower blade is first restricted under pressure by lower blade and pad and then cut by a shearing action based on an engagement of lower blade side cutting edge and upper blade side cutting edge. Resin face sheets are fixed to the top surface of lower blade and the pressing surface of pad, the face sheets having a larger friction coefficient than that of these surfaces. By frictional forces imparted by face sheets, metal foil base material is prevented from being dragged and moved by the pressing force of the upper blade prior to cutting. Consequently, the occurrence of “burr”, “roll-up”, and so forth is eliminated thereby ensuring a good cutting quality.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent Application No. 2013-202867, filed Sep. 30, 2013, incorporated herein in its entirety.

TECHNICAL FIELD

The present invention relates to a cutting device for metal foil as represented by aluminum foil, copper foil and the like.

BACKGROUND

As this kind of metal foil cutting device, an example as discussed in Japanese Patent Application Publication No. 2007-152436 has been proposed. A cutting device as discussed in Japanese Patent Application Publication No. 2007-152436 is provided for the purpose of cutting metal foil for use in a capacitor such as aluminum, tantalum, niobium, titanium and zirconium by a shearing action caused by an engagement between a first blade and a second blade, in which both of the blades are adapted to have a depth of engagement (or a lap margin) and a clearance therebetween within a specified numerical value range.

However, the cutting device discussed in Japanese Patent Application Publication No. 2007-152436 is provided based on a shearing action caused by an engagement between the first and second blades and therefore it cannot avoid the occurrence of a phenomenon where metal foil is pulled toward the side of an engaged portion of both of the blades. The trend becomes noticeable as the thickness dimension of a metal foil to be cut increases; this is because the depth of engagement and a clearance between the blades are inevitably increased according to the increase of the thickness dimension of metal foil. As a result, the metal foil is moved thereby possibly causing the deterioration of cutting quality and the occurrence of “burr” and “roll-up” on the cut surface.

SUMMARY

The present invention has been made in view of such problems, for the purpose of providing a cutting device able to restrain metal foil from being dragged and moved at the time of cutting while basically performing cutting under a shearing action caused by the engagement of both blades.

The present invention is adapted to cut metal foil placed on a lower blade by a shearing action based on an engagement of a lower blade and an upper blade, in which a holding device having a larger friction coefficient than that of the lower blade is provided on the lower blade in such a manner as to interpose between the lower blade and metal foil placed thereon.

According to the present invention, a holding device having a larger friction coefficient than that of the lower blade is provided to intervene between the lower blade and metal foil, with which it becomes possible to prevent the metal foil from being dragged and moved at the time of cutting and prevent the occurrence of “burr” and “roll-up” while improving cutting accuracy and cutting quality.

DESCRIPTION OF THE EMBODIMENTS

FIGS. 1 to 6are provided showing a first embodiment of a metal foil cutting device according to the present invention. In particular,FIGS. 1 to 3show a basic structure of a cutting device of a press type, and operations made under the structure.FIGS. 4 and 5specifically shows an essential part of the cutting device.

As shown inFIG. 1, a cutting device is composed of lower die1and upper die2vertically movably disposed opposite to lower die1.

Lower die1is provided including lower holder3, and lower blade4fixed onto lower holder3and formed of steel, a super hard metal or the like. Lower blade4has a corner part formed between its front-side vertical wall and top surface, the corner part serving as cutting edge4aof the lower blade4side. An object to be cut, i.e., a long lengths of metal foil base material (for example, a long lengths of multilayered metal foil base material W) is to be supplied and placed onto lower blade4.

On the other hand, upper die2is provided having upper holder5as a main body, with which upper blade6formed of steel, a super hard metal or the like and pad7serving as a pressing member formed of steel or the like are combined. Pad7is secured to pad holder8. Upper blade6has a corner part at its lower end portion and on the side closer to pad7, the corner part serving as cutting edge6a. Additionally, upper blade6is supported to be vertically movable with respect to upper holder5, while pad holder8is vertically movably and elastically supported by upper holder5through elastic member9such as urethane and compression coil spring. In the state where pad7is brought up to the uppermost position as shown inFIG. 1, the lower end portion of pad7is disposed lower than upper blade6.

In the thus constructed cutting device, when the long lengths of multilayered metal foil base material W is conveyed from the left ofFIG. 1at a given rate and then metal foil base material W having been conveyed to some extent is stopped and positioned on lower blade4, upper die2including upper holder5as the main body is moved down toward lower die1as a whole. According to the downward movement of upper die2, pad7is firstly brought into contact with metal foil base material W placed on lower blade4as shown inFIG. 2, and then compresses elastic member9, with which elastic force pad7begins to press metal foil base material W against lower blade4. With this, the vicinity of a section of metal foil base material W which is to serve as a cutting line (i.e., a section where cutting edge4aof the lower blade4side and cutting edge6aof the upper blade6side are engaged) is restricted under pressure by lower blade4and pad7.

Even if upper die2is further lowered, pad7is kept being pressed against metal foil base material W and therefore only upper holder5and upper blade6are moved downward, so that cutting edge4aof the lower blade4side and cutting edge6aof the upper blade6side comes to engage with each other. By receiving a shearing action based on the engagement between cutting edge4aof the lower blade4side and cutting edge6aof the upper blade6side, metal foil piece P having a certain size is to be cut out of metal foil base material W as shown inFIG. 3.

When upper die2is moved upward after cutting, firstly upper blade6moves upward and then pad7moves upward to go away from metal foil base material W. Thus the whole of upper die2including upper blade6and pad7is reset to the initial state as shown inFIG. 1thereby completing one cycle. From then on, the above-mentioned operations are repeated.

FIG. 4(A)andFIG. 4(B)specifically illustrate an essential part of the cutting device as shown inFIGS. 1 to 3. In order to prevent metal foil base material W from being dragged and moved at the time of cutting as soon as possible, face sheets10and11having a prescribed thickness are fixedly attached as holding devices to sections of lower blade4and pad7directly brought into contact with metal foil base material W (which sections are also referred to as the top surface of lower blade4and a pressing surface or bottom surface of pad7), respectively, with an acrylic adhesive or the like.

With the above arrangement, when restraining lower blade4and metal foil base material W under pressure as shown inFIG. 4(A), face sheets10,11are adapted to intervene between the top surface of lower blade4and metal foil base material W and between the pressing surface of pad7and metal foil base material W, respectively. It is apparent from this that face sheets10,11disposed respectively on the lower blade4side and the pad7side are omitted fromFIGS. 1 to 3and that these figures illustrate only the basic structure of the cutting device and its basic operations.

Face sheets10,11are conditioned to have a friction coefficient larger than that of metal that forms lower blade4and pad7. In the present embodiment, a resin sheet having a larger friction coefficient than that of metal and formed of polypropylene (PP) or polyethylene (PE) is adopted as face sheets10,11. For example, in the case of regarding face sheet10of the lower blade4side, it has a width dimension Wa of about 2 mm as shown inFIG. 5, and fixedly attached at a location having a certain distance α (for example, about 0.5 mm) from cutting edge4ain order to prevent itself from getting caught up toward the cutting edge4aside. Such a relationship is also applied to face sheet11of the pad7side, and more specifically, face sheet11of the pad7side is fixedly attached at a location having a certain distance α (for example, 0.5 mm or more) from cutting edge6aof the upper blade6side as shown inFIG. 4(A).

Additionally, as apparent fromFIG. 4(B)further enlarging the part “a” ofFIG. 4(A), metal foil base material W before cutting is in direct contact with face sheet10of the lower blade4side having a certain thickness β so to be supported thereby, regardless of whether it is restrained under pressure by pad7; therefore, metal foil base material W droops toward cutting edge4adisposed lower than face sheet10while lying over face sheet10and cutting edge4athereby taking the form of the so-called “droop”. As a result, there is defined a certain extent of gap G (or a region enclosed with the top surface of lower blade4, face sheet10and metal foil base material W) at a location immediately close to cutting edge4aof the lower blade4side.

Hence, when metal foil base material W is cut under a searing action based on the engagement between cutting edge4aof the lower blade4side and cutting edge6aof the upper blade6side in the state where metal foil base material W is restricted under pressure by face sheet10of the lower blade4side and face sheet11of the pad7side, a section of metal foil base material W overhanging from the upper blade4side toward the upper blade6side is to be depressed by upper blade6. Due to the depressing force of upper blade6, even a section restricted under pressure between upper and lower face sheets10,11tends to be dragged and moved in advance of cutting.

However, the upper and lower face sheets10,11have so large friction coefficient as to generate a great frictional force against metal foil base material W, thereby resisting the action of metal foil base material W inclinable to be dragged by the above-mentioned depressing force of upper blade6. With this, it becomes possible to ease the action of metal foil base material W inclinable to be dragged in the depression direction by upper blade6. As a result, metal foil base material W and metal foil piece P cut out thereof can obtain a good cutting quality at their cut surfaces and the cut surfaces are prevented from the occurrence of “burr” and “roll-up”, thereby contributing to the improvement of the cutting quality.

Since lower blade4and pad7are provided with face sheets10,11at positions opposite to each other, metal foil base material W before cutting can surely be restricted under pressure while absorbing unevenness on the top surface of lower blade4and the pressing surface of pad7, defective parallelism between these surfaces etc, so that the action of metal foil base material W inclinable to be dragged in the depression direction by upper blade6can more excellently be suppressed.

Moreover, the upper and lower face sheets10,11are disposed at a location distant from cutting edge4aof the lower blade4side and from cutting edge6aof the upper blade6side, respectively, as shown inFIGS. 4 and 5, with which gap G is defined at a region enclosed with lower blade4, face sheet10and metal foil base material W. Consequently, face sheets10,11neither interfere with cutting edges4a,6anor involved in the engaged portion formed between both cutting edges4a,6aat the time of cutting.

FIG. 6shows variation in sheared plane ratio (%) or in an index of cutting quality, obtained by changing thickness β of face sheet10of the lower blade4side as shown inFIG. 4step by step. Incidentally, the sheared plane ratio (%) means a ratio obtained in such a manner as to repeat the cutting of metal foil piece P on a lot of sheets, observe a sheared incised surface of the sheets, and then divide the number of sheets the sheared incised surface of which were smooth sheared plane (or a burnished plane) having no occurrence of “burr” and “roll-up” by the total number of sheets. Furthermore, the case where the thickness β of face sheet10of the lower blade4side was 0 μm as shown inFIG. 6means a case where face sheet10of the lower blade4side was not used. As apparent fromFIG. 6, it can be confirmed that the sheared plane ratio is reduced when the thickness β of face sheet10of the lower blade4side was 0 μm, 150 μm and 200 μm. Additionally, if the desired sheared plane ratio was set to 90% or greater, it was attained when the thickness β of face sheet10of the lower blade4side attaining the target value was 50 μm and 100 μm.

In view of the above, when the thickness β of face sheet10is larger, metal foil base material W which droops from the face sheet10side toward the cutting edge4aside while lying over face sheet10and cutting edge4aas shown inFIG. 4(B)is made more vertical so as to get closer to a direction parallel with an engaged plane formed between both cutting edges4a,6a. It can be supposed this is why the sheared plane ratio (%) serving as an index of cutting quality reduced.

In other words, if angle θ formed between the top surface of lower blade4and metal foil base material W lying over face sheet10and cutting edge4aas shown inFIG. 4(B)becomes excessively large, the sheared plane ratio (%) serving as an index of cutting quality is to be reduced.

As has been explained onFIG. 5, face sheet10is fixed at a location about 0.5 mm (as a certain distance α) farther than the position of cutting edge4aof the lower blade4side in order to prevent face sheet10from being involved in the side of cutting edge4aof lower blade4and from interfering with cutting edge4a. Therefore, it was confirmed that, if angle θ formed between the top surface of lower blade4and metal foil base material W lying over face sheet10and cutting edge4aas shown inFIG. 4(B)exceeds 12°, the sheared plane ratio (%) serving as an index of cutting quality falls short of 90%.

On the precondition that face sheet10is fixed at a location about 0.5 mm (as a certain distance α) farther than the position of cutting edge4aof the lower blade4side, a 90% or greater sheared plane ratio (an index of cutting quality) should be ensured if the thickness β of face sheet10of the lower blade4side ranges from 50 to 100 μm and if angle θ is not larger than 12°. These conditions are considered to be also applicable to face sheet11of the pad7side.

FIG. 7illustrates a second embodiment of a cutting device according to the present invention, in which portions in common withFIG. 4(B)are given the same reference numerals. In the second embodiment face sheet20as a holding device on the lower blade4side is shaped to have an inclined plane20adescending toward cutting edge4aof the lower blade4side.

The second embodiment not only provides the same effect as the above-mentioned first embodiment provides but also brings the advantage of achieving a desired result even if angle θ formed between the top surface of lower blade4and metal foil base material W lying over face sheet10and cutting edge4ais relatively large.

Although the above embodiments have been described by reference to a case of cutting the multilayered metal foil base material W while keeping its multilayered state, the number of multilayered sheets are not particularly limited as far as the cutting quality is guaranteed. Moreover, a pattern where cutting is conducted on metal foil base material W having only one layer is also acceptable.

The primary function of face sheets10,11serving as holding devices in the above-mentioned embodiments is to generate a relatively great frictional force against metal foil base material W. So long as this requirement is satisfied, face sheets10,11are not necessarily limited to a resin product formed of polypropylene, polyethylene or the like. For example, face sheets10,11may be an elastic product such as rubber. In this case face sheets10,11formed of elastic material is positively subjected to elastic deformation due to the pressing force, thereby bringing the advantage of generating a greater frictional force.

Furthermore, it is also possible to employ an iron-based sheet or a nonferrous metal sheet as face sheets10,11, in which case the surfaces thereof may be formed to have a rough shape attaining a desired frictional force, such as a satin shape or an uneven shape. With such a rough shape, it becomes possible to generate a desired frictional force against metal foil base material W.