AU2014215319A1 - Scissors - Google Patents

Abstract

Scissors (H) comprise scissor bodies (11, 12) that form a pair and are each provided with a handle (21, 22) and a blade piece (31, 32) having a blade edge (31c, 32c), and the scissors have a pin (4) that rotatably attaches the pair of scissor bodies (11, 12), wherein the following are set: blade base-side regions (31c1, 32c1) that are curved and in which an intersection angle formed by both blade edges (31c, 32c) becomes gradually smaller as a cutting position, in conjunction with a cutting operation, moves farther away from the pin (4); and blade tip-side regions (31c2, 32c2) in which the intersection angle does not substantially change or the intersection angle becomes larger as the cutting position moves farther away from the pin (4).

Description

SPECIFICATION TITLE OF THE INVENTION: SCISSORS TECHNICAL FIELD [0001] The present invention relates to a pair of scissors preferably used in offices, at 5 home, or the like. BACKGROUND ART [0002] Conventionally, edge lines of blades of many scissors used in offices or at home are formed into approximately straight lines. However, it has become clear in recent years that the scissors with the edge lines having such shapes causes the following 10 problem. That is, there is need to cut corrugated cardboards, plastic sheets, plastic packing bands, and so on in offices or at home, with respect to the scissors with the edge lines having such shapes, as indicated by broken lines b on a graph in FIG. 5, a crossing angle at which both of the edge lines cross each other gradually decreases as a cutting point goes away from a pivot through cutting operation, the crossing angle becomes small 15 in a neighborhood of the tips of the blades. Hence, as shown in FIG. 5, a load required for cutting with the neighborhood of the tips of the blades is enlarged, it is therefore difficult to satisfy the above need. [0003] On the other hand, a pair of scissors containing a blade with an edge line formed into an arc shape that is smaller in radius of curvature over the whole thereof than the edge 20 lines of the conventional scissors has been designed, so that a crossing angle at which both of the edge lines cross each other is large in comparison with the conventional scissors when a cutting point arrives at a neighborhood of the tips of the blades through cutting operation, and besides the crossing angle is set to be approximately constant over the whole of the edge lines (See Patent document 1, for example). As indicated by two-dot 25 chain lines c on the graph in FIG. 5, the crossing angle at which both of the edge lines cross 1 each other in the scissors of this kind is set to be approximately constant within a range of about 18 to 30 degrees independently of the cutting point. [0004] By the way, regarding the conventional scissors with the edge lines formed into approximately straight lines, as shown in FIG. 5, the crossing angle is a large angle nearly 5 equal to 90 degrees when the cutting point is in a neighborhood of ends of the edge lines closer to the pivot, a load required for cutting with the neighborhood of the bases of the blades can be reduced. In contrast, regarding the scissors with the edge line having such shape as mentioned in the preceding paragraph, the crossing angle is approximately constant in the range of 18 to 30 degrees independently of the cutting point, another 10 problem may consequently occur that it is not enough appropriate to, for example, usage to cut plastic sheets, plastic packing bands, and so on with base sides of the blades. RELATED ART DOCUMENTS PATENT DOCUMENTS [0005] 15 Patent document 1: Japanese Unexamined Utility Model Application Publication No. S48-86482. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0006] The present invention has paid attention to the above defects, it is an object of the 20 present invention to meet a demand for easily cutting corrugated cardboards, plastic sheets, plastic packing bands, and so on without enlarging necessary load to cut in a neighborhood of tips of blades as well as maintain the conventional characteristic of scissors that a crossing angle on base sides of the blades becomes large similarly to the conventional scissors. 25 MEANS OF SOLVING THE PROBLEMS 2 [0007] In order to achieve the above object, the present invention has prepared the following means. That is, scissors according to the present invention include a pair of scissor bodies that each have a handle and a blade piece with an edge line, and a pivot that links the scissor bodies with each other in a rotatable manner, wherein a base side area and 5 a tip side area are provided, the base side area being curved and such that a crossing angle at which both of the edge lines cross each other gradually decreases as a cutting point goes away from the pivot through cutting operation, the tip side area being adjacent to a tip side of the base side area and such that the crossing angle remains approximately constant or increases as the cutting point goes away from the pivot through the cutting operation. 10 [0008] In respect to such scissors, the crossing angle in the base side area is large similarly to the conventional scissors, and the crossing angle in the tip side area remains approximately constant or increases as the cutting point goes away from the pivot. Hence, it is easy to provide a characteristic that a load required for cutting does not become extremely large even in the tip side area. 15 [0009] As a configuration of the scissors to more reduce the load required for cutting with a neighborhood of the tips of the blades, it can be cited that the tip side area has a crossing-angle-rapidly-changing part near a border between the base side area and the tip side area, the crossing-angle-rapidly-changing part being such that the crossing angle rapidly increases as the cutting point goes away from the pivot. 20 [0010] As an example of specific configurations of the scissors to obtain the effect as described above, it can be cited that the handle has a finger-hooking portion for a user's finger to be hooked in a prescribed finger-hooking area, the base side area and the tip side area are provided in at least one of the edge lines, the crossing angle is larger over the whole of the tip side area than the crossing angle at the border between the base side area 25 and the tip side area. 3 [0011] As a specific configuration to make the load required for cutting in the tip side area approximately constant regardless of the cutting point, it can be cited that the tip side area has a plurality of small-radius curved parts that are different in radius of curvature from each other. 5 [0012] As a configuration to support usage to cut corrugated cardboards or the like with the neighborhood of the tips of the blades without rapidly changing the crossing angle as the cutting point goes away from the pivot in the neighborhood of the tips, it can be cited that the small-radius curved part closest to the base side area is smaller in radius of curvature than the other small-radius curved part and is the 10 crossing-angle-rapidly-changing part in that the crossing angle rapidly increases as the cutting point goes away from the pivot. Also, it can be cited that the tip side area has three or more small-radius curved parts, the small-radius curved part second closest to the base side area is smaller in radius of curvature than the other small-radius curved parts and is the crossing-angle-rapidly-changing part in that the crossing angle rapidly increases 15 as the cutting point goes away from the pivot. [0013] It is desirable that the base side area and the tip side area be provided in each of the edge lines so as to obtain the above effect more favorably. [0014] As a specific configuration to obtain the same feeling of use as the conventional scissors in the base side area, it can be cited that the maximum value of the crossing angle 20 is 90 degrees or more. [0015] As a specific configuration to make the load required for cutting approximately constant regardless of the cutting point in the tip side area without enlarging the load extremely, it can be cited that the crossing angle at the border between the base side area and the tip side area is 18 degrees or more. 25 [0016] As a preferable configuration for the crossing angle to increase as the cutting point 4 goes away from the pivot, it can be cited that the radius of curvature of one of the small-radius curved parts is smaller than the total length of the edge line containing the small-radius curved parts. [0017] Regarding the present invention, the term "curved" is not limited to a single arc or 5 a joining of a plurality of arcs, and refers to curves in general, for example, quadratic curves, cubic curves, and curves having different forms from those. In addition, the term "radius of curvature" refers to a radius of an arc part or a radius of an approximation arc to a curved part having a non-arc shape. EFFECTS OF THE INVENTION 10 [0018] The present invention is able to meet a demand for easily cutting corrugated cardboards, plastic sheets, plastic packing bands, and so on without enlarging necessary load to cut in a neighborhood of tips of blades as well as maintain the conventional characteristic of scissors that a crossing angle on base sides of the blades becomes large similarly to the conventional scissors. 15 BRIEF DESCRIPTION OF THE DRAWINGS [0019] FIG. 1 is a perspective view of scissors according to a first embodiment of the present invention. FIG. 2 is a planar view of the scissors according to the embodiment. 20 FIG. 3 is a planar view of a movable blade of the scissors according to the embodiment. FIG. 4 is a planar view of a stationary blade of the scissors according to the embodiment. FIG. 5 is a diagram of relation between a crossing angle at which both of edge 5 lines cross each other and cutting load of the scissors according to the embodiment. FIG. 6 is a perspective view of scissors according to a second embodiment of the present invention. FIG. 7 is a planar view of the scissors according to the embodiment. 5 FIG. 8 is a planar view of a movable blade of the scissors according to the embodiment. FIG. 9 is a planar view of a stationary blade of the scissors according to the embodiment. FIG. 10 is a diagram of relation between a crossing angle at which both of edge 10 lines cross each other and cutting load of the scissors according to the embodiment. FIG. 11 is a planar view of movable blades of scissors according to another embodiment of the present invention. FIG. 12 is a planar view of a movable blade of scissors according to another embodiment of the present invention. 15 FIG. 13 is a cross section taken along the line A-A in FIG. 12. FIG. 14 is a planar view of a movable blade of scissors according to another embodiment of the present invention. FIG. 15 is a cross section taken along the line B-B in FIG. 14. FIG. 16 is a planar view of movable blades of scissors according to another 20 embodiment of the present invention. FIG. 17 is a transverse cross section of a blade of scissors according to another embodiment of the present invention. FIG. 18 is a transverse cross section of a blade of scissors according to another embodiment of the present invention. 25 FIG. 19 is a perspective view of scissors according to another embodiment of the 6 present invention. FIG. 20 is a perspective view of scissors according to another embodiment of the present invention. FIG. 21 is a perspective view of scissors according to another embodiment of the 5 present invention. MODE FOR CARRYING OUT THE INVENTION [0020] Described below is a first embodiment of the present invention with reference to FIGs. 1 to 5. [0021] As shown in FIGs. 1 and 2, a pair of scissors H according to the embodiment is 10 configured such that a first scissor body 11 and a second scissor body 12 are linked with each other in a rotatable manner about a pivot 4, the first scissor body 11 having a movable blade 31 as a first blade piece, the second scissor body 12 having a stationary blade 32 as a second blade piece paired with the movable blade 31. [0022] As shown in FIGs. 1 and 2, the first scissor body 11 is made up of a first handle 21 15 and the movable blade 31 with a base end side to be fit into a front end side of the first handle 21. [0023] The first handle 21 has a finger-hooking portion 21a for a user's thumb to be inserted in a first finger ring 21b as a prescribed finger-hooking area. As described above, the base end side of the movable blade 31 is inserted and fixed in the front end side of the 20 first handle 21. [0024] The movable blade 31 is to be put under paper or the like when cutting the paper or the like with the scissors H. The movable blade 31 is formed into a plate shape with a metal sheet made of stainless steel as a material by integrally pressing the whole body. Thickness of the metal sheet can be set arbitrarily, and is set to 1.8 mm in the embodiment. 25 As shown in FIGs. 1 to 3, an edge line 31c is put between a flat blade rear face 31a capable 7 of sliding on the stationary blade 32 and an outer face, namely, a blade surface 31b that is a face opposite to the blade rear face 31a in the movable blade 31 according to the embodiment. Total length of the edge line 31c is set to 70 mm in the embodiment. The included angle 6 at the edge line 31c between the blade rear face 31a and the blade surface 5 31b is set to 40 degrees in the embodiment. The movable blade 31 further contains a blade back 31d formed on a side end edge opposite to the edge line 31c, a blade tip 31e positioned at a top end part thereof, and a blade base 31f positioned in a base end part thereof, namely, a neighborhood of the pivot 4. As described above, the stationary blade 32 that is a component of the second scissor body 12 is joined to the movable blade 31 via 10 the pivot 4. [0025] On the other hand, as shown in FIGs. 1 and 2, the second scissor body 12 is made up of a second handle 22 and the stationary blade 32 with a base end side to be fit into a front end side of the second handle 22. [0026] The second handle 22 has a finger-hooking portion 22a for the user's index finger, 15 middle finger and ring finger to be inserted in a first finger ring 22b as a prescribed finger-hooking area. As described above, the base end side of the stationary blade 32 is inserted and fixed in the front end side of the second handle 22. [0027] The stationary blade 32, which is paired with the movable blade 31, is to be put over the paper or the like when cutting the paper or the like with the scissors H. Similarly 20 to the movable blade 31, the stationary blade 32 is formed into a plate shape with a metal sheet made of stainless steel as a material by integrally pressing the whole body. As shown in FIGs. 1, 2 and 4, an edge line 32c is put between a flat blade rear face 32a capable of sliding on the movable blade 31 and an outer face, namely, a blade surface 32b that is a face opposite to the blade rear face 32a in the stationary blade 32 according to the 25 embodiment. Total length of the edge line 32c is also set to 70 mm in the embodiment. 8 The included angle 6 at the edge line 32c between the blade rear face 32a and the blade surface 32b is set to 50 degrees in the embodiment. The stationary blade 32 further contains a blade back 32d formed on a side end edge opposite to the edge line 32c, a blade tip 32e positioned at a top end part thereof, and a blade base 32f positioned in a base end 5 part thereof, namely, a neighborhood of the pivot 4. The included angle 6 can be set in a range of 40 to 50 degrees. Setting the included angle 6 smaller than 40 degrees is prone to cause a phenomenon what is called edge damage. [0028] On top of that, according to the embodiment, base side areas 31c1 and 32c1 and tip side areas 31c2 and 32c2 are each provided on the movable blade 31 and the stationary 10 blade 32. The base side areas 31c1 and 32c1 are curved, and such that a crossing angle at which the edge line 31c and the edge line 32c cross each other gradually decreases as a cutting point goes away from the pivot through cutting operation. The tip side areas 31c2 and 32c2 are respectively adjacent to a tip side of the base side area 31c1 and a tip side of the base side area 32c1, and such that the crossing angle remains approximately constant 15 or increases as the cutting point goes away from the pivot through the cutting operation. In other words, the curved base side areas 31c1 and 32c1 such that the crossing angle at which the edge lines 31c and 32c cross each other gradually decreases as the cutting point goes away from the pivot 4 through the cutting operation, and the tip side areas 31c2 and 32c2 adjacent to the sides close to the blade tips 31e and 32e of the base side areas 31c1 and 20 32c1 such that the crossing angle is larger over the whole of the tip side areas 31c2 and 32c2 than the crossing angle at the border between the base side areas 31c1, 32c1 and the tip side areas 31c2, 32c2 are formed in the edge lines 31c and 32c on both of the movable blade 31 and the stationary blade 32. Only the edge line 31c of the movable blade 31 will be explained below because the edge line 32c of the stationary blade 32 has the entirely same 25 shape as the edge line 31c of the movable blade 31. 9 [0029] The radius of curvature of the base side area 31c1 is 4366 mm in the embodiment. The tip side area 31c2 is adjacent to the side close to the blade tip 31e of the base side area 31c1. [0030] The tip side area 31c2 has a plurality of small-radius curved parts that are different 5 in radius of curvature from each other, namely, a first small-radius curved part 31ca, a second small-radius curved part 31cb, a third small-radius curved part 31ca, a fourth small-radius curved part 31cd, and a fifth small-radius curved part 31ce in order from the base side area 31c1. The radii of curvature of the first to fifth small-radius curved parts 31ca to 31ce are smaller than the radius of curvature of the base side area 31c1. In detail, 10 the radius of curvature of the first small-radius curved part 31ca is 170 mm, the radius of curvature of the second small-radius curved part 31cb is 40 mm. The radius of curvature of the third small-radius curved part 31cc, the one of the fourth small-radius curved part 31cd, and the one of the fifth small-radius curved part 31ce are 114 mm, 282 mm, and 2000 mm, respectively. According to the embodiment, the second small-radius curved part 15 31cb is smaller in radius of curvature than the other small-radius curved parts, i.e., the first and third to fifth small-radius curved parts 31ca and 31cc to 31ce, and besides the radius of curvature of the second small-radius curved part 31cb is shorter than the total length of the edge line 31c. In the following description, elements of the stationary blade 32 are given the same names and reference signs as the counterparts of the above movable blade 31, but 20 the numeral of "31" is replaced with "32" in the reference signs. [0031] As described below and shown in FIG. 5, according the embodiment, the crossing angle between the edge line 31c and the edge line 32c, and a load required for cutting each change as the cutting point goes away from the pivot 4. [0032] As indicated by solid lines a on the graph in FIG. 5, the crossing angle between the 25 edge lines 31c and 32c is 90 degrees in a state where the edge line 31c and the edge line 32c 10 cross at ends close to the pivot 4, that is, the ends close to the blade bases 31f and 32f of the edge lines 31c and 32c. Subsequently, the cutting point goes away from the pivot 4 in the base side areas 31c1 and 32c1 through the cutting operation. The crossing angle formed by the edge lines 31c and 32c gradually decreases as the cutting point goes away from the 5 pivot 4, and takes a minimum value at the border to the tip side areas 31c2 and 32c2, specifically the minimum value is about 23 degrees. In addition, the load required for cutting is gradually enlarged as the cutting point goes away from the pivot 4. [0033] The cutting point then moves into the tip side areas 31c2 and 32c2. As indicated by the solid lines a on the graph in FIG. 5, while the cutting point exists in the first to third 10 small-radius curved parts 31ca to 31cc and 32ca to 32cc, the crossing angle formed by the edge lines gradually increases from the minimum value as the cutting point goes away from the pivot 4. In particular, while the cutting point is in the second small-radius curved parts 31cb and 32cb, the crossing angle formed by the edge lines rapidly increases as the cutting point goes away from the pivot. Therefore the second small-radius curved 15 parts 31cb and 32cb correspond to the crossing-angle-rapidly-changing parts in claims. The second small-radius curved parts (the crossing-angle-rapidly-changing parts) 31cb and 32cb are provided in a range of 41.4 to 44.8 mm from the base ends (the ends close to the blade bases) of the edge lines 31c and 32c or in a range of about 59 to 64 percent of the total length of the edge lines. More specifically, the crossing angle is about 24 degrees at a 20 border between the first small-radius curved parts 31ca, 32ca and the second small-radius curved parts 31cb, 32cb. In contrast, the crossing angle is about 32 degrees at a border between the second small-radius curved parts 31cb, 32cb and the third small-radius curved parts 31cc, 32cc. Furthermore, the crossing angle takes a maximum value when the cutting point arrives at a border between the third small-radius curved parts 31cc, 32cc 25 and the fourth small-radius curved parts 31cd, 32cd, specifically the maximum value is 11 about 35 degrees. After that, the crossing angle between the edge lines gradually decreases as the cutting point goes away from the pivot 4 while the crossing angle is kept larger than or equal to 30 degrees. On the other hand, as indicated by the solid lines a on the graph in FIG. 5, the load required for cutting is approximately constant independently 5 of the cutting point when the cutting point exists in the tip side areas 31c2 and 32c2. The load required for cutting is measured with a method as described below. That is, in a state where a corrugated cardboard which is an object to be cut is positioned such that the corrugated cardboard is the same distance from the movable blade 31 and the stationary blade 32, input terminals of a load measuring apparatus which is not illustrated are set into 10 the first and second finger-hooking portions 21a and 22a so that the pivot 4 and the input terminals are apexes of an isosceles triangle, then the object gets cut with moving of the input terminals to approach each other, in other words, the object gets cut while the triangle continues to be an isosceles triangle during the moving of each of the input terminals so as to measure the load required for cutting. 15 [0034] As described above, according to the embodiment, the crossing angle becomes larger over the whole of the tip side areas 31c2 and 32c2 than the crossing angle at the border to the base side areas 31c1 and 32c1 though the crossing angle in the base side areas 31c1 and 32c1 is large similarly to the conventional scissors, the load required for cutting is approximately constant independently of the cutting point. Hence, the load required for 20 cutting with any parts of the tip side areas 31c2 and 32c2 is approximately equal to the load for cutting with the border to the base side areas 31c1 and 32c1, therefore even the neighborhood of the blade tips 31e and 32e can be used for the purpose of cutting corrugated cardboards, plastic sheets, plastic packing bands, and so on. [0035] Since the tip side areas 31c2 and 32c2 have the first to fifth small-radius curved 25 parts 31ca to 31ce and 32ca to 32ce that are different in radius of curvature from each other, 12 the load for cutting with the tip side areas 31c2 and 32c2 remains approximately constant independently of the cutting point. [0036] Since the second small-radius curved parts 31cb and 32cb are the smallest in radius of curvature among the first to fifth small-radius curved parts 31ca to 31ce and 32ca 5 to 32ce, the configuration is able to be made preferably in which even the neighborhood of the blade tips 31e and 32e can be used for the purpose of cutting corrugated cardboards, plastic sheets, plastic packing bands, and so on without rapid change of the crossing angle between the edge lines in the neighborhood of the blade tips 31e and 32e as the cutting point goes away from the pivot 4 through the cutting operation, and without rapid change 10 of cutting efficiency. [0037] In addition, since the base side area 31c1 and the tip side area 31c2 are provided in the edge line 31c, and besides the base side area 32c1 and the tip side area 32c2 are provided in the edge line 32c, the above effect can be obtained without extremely reducing the radius of curvature of the tip side areas 31c2 and 32c2 in the edge lines, width of the 15 blade pieces, namely, the movable blade 31 and the stationary blade 32 is reducible. [0038] Furthermore, since the crossing angle at the border between the base side areas 31c1, 32c1 and the tip side areas 31c2, 32c2 is about 23 degrees, the load for cutting in the tip side areas 31c2 and 32c2 is sufficiently reduced, compared to that of the conventional scissors. 20 [0039] The maximum value of the crossing angle is 90 degrees, the same feeling of use as the conventional scissors can be obtained in the base side areas 31c1 and 32c1. [0040] Next, described below is a second embodiment of the present invention with reference to FIGs. 6 to 10. The elements that are equivalent to the ones described in the above embodiment are given the same names and reference signs thereas. 25 [0041] As shown in FIGs. 6 and 7, a pair of scissors H2 according to the embodiment is 13 configured such that a first scissor body 11 and a second scissor body 12 are linked with each other in a rotatable manner about a pivot 4, the first scissor body 11 having a movable blade 31 as a first blade piece, the second scissor body 12 having a stationary blade 32 as a second blade piece paired with the movable blade 31. Differences from the scissors H 5 according to the first embodiment will be described, however, the scissors H2 according to this embodiment has the same configuration as the above scissors H according to the first embodiment except the differences described below. [0042] As shown in FIGs. 8 and 9, according to the embodiment, base side areas 31c1 and 32c1 and tip side areas 31c2 and 32c2 are each provided in an edge lines 31c of the movable 10 blade 31 and an edge line 32c of the stationary blade 32. The base side areas 31c1 and 32c1 are curved, and such that a crossing angle at which the edge line 31c and the edge line 32c cross each other gradually decreases as a cutting point goes away from the pivot 4 through cutting operation. The tip side areas 31c2 and 32c2 are respectively adjacent to a side close to a blade tip 31e of the base side area 31c1 and a side close to a blade tip 32e of 15 the base side area 32c1, and such that the crossing angle is larger over the whole of the tip side areas 31c2 and 32c2 than the crossing angle at the border between the base side areas 31c1, 32c1 and the tip side areas 31c2, 32c2. Only the edge line 31c of the movable blade 31 will be explained below because the edge line 32c of the stationary blade 32 has the entirely same shape as the edge line 31c of the movable blade 31. 20 [0043] The radius of curvature of the base side area 31c1 is 1372.5 mm in the embodiment. As shown in FIG. 8, the tip side area 31c2 is adjacent to the side close to the blade tip 31e of the base side area 31c1. [0044] As shown in FIG. 8, the tip side area 31c2 has a plurality of small-radius curved parts that are different in radius of curvature from each other, namely, a first small-radius 25 curved part 31cx, and a second small-radius curved part 31cy in order from the base side 14 area 31c1. The radii of curvature of the first and second small-radius curved parts 31cx and 31cy are smaller than the radius of curvature of the base side area 31c1. In detail, the radius of curvature of the first small-radius curved part 31cx is 50 mm, the radius of curvature of the second small-radius curved part 31cy is 100 mm. In the following 5 description, elements of the stationary blade 32 are given the same names and reference signs as the counterparts of the above movable blade 31, but the numeral of "31" is replaced with "32" in the reference signs. [0045] As described below and shown in FIG. 10, according the embodiment, the crossing angle between the edge line 31c and the edge line 32c changes as the cutting point 10 goes away from the pivot 4. [0046] As indicated by solid lines a2 on the graph in FIG. 10, the crossing angle between the edge lines 31c and 32c is 90 degrees in a state where the edge line 31c and the edge line 32c cross at ends close to the pivot 4, that is, the ends close to the blade bases 31f and 32f of the edge lines 31c and 32c. Subsequently, the cutting point goes away from the pivot 4 in 15 the base side areas 31c1 and 32c1 through the cutting operation. The crossing angle formed by the edge lines 31c and 32c gradually decreases as the cutting point goes away from the pivot 4, and takes a minimum value at the border to the tip side areas 31c2 and 32c2, specifically the minimum value is about 18 degrees. [0047] The cutting point then moves into the tip side areas 31c2 and 32c2. As indicated 20 by the solid lines a2 on the graph in FIG. 10, the crossing angle formed by the edge lines gradually increases from the minimum value as the cutting point goes away from the pivot 4. In particular, while the cutting point is in the first small-radius curved parts 31cx and 32cx, the crossing angle formed by the edge lines rapidly increases as the cutting point goes away from the pivot. Therefore the first small-radius curved parts 31cx and 32cx 25 correspond to the crossing-angle-rapidly-changing parts in claims. The first small-radius 15 curved parts (the crossing-angle-rapidly-changing parts) 31cx and 32cx are provided in a range of 41.4 to 44.6 mm from the base ends (the ends close to the blade bases) of the edge lines 31c and 32c or in a range of about 59 to 64 percent of the total length of the edge lines. More specifically, the crossing angle is about 18 degrees at a border between the base side 5 areas 31c1, 32c1 and the tip side areas 31c2, 32c2, that is, at the border between the base side areas 31c1, 32c1 and he first small-radius curved parts 31cx, 32cx. In contrast, the crossing angle is about 25 degrees at a border between the first small-radius curved parts 31cx, 32cx and the second small-radius curved parts 31cy, 32cy. Also, while the cutting point exists in the second small-radius curved parts 31cy and 32cy, the crossing angle 10 formed by the edge lines 31c and 32c gradually increases as the cutting point goes away from the pivot 4. [0048] As described above, according to the embodiment, the crossing angle in the tip side areas 31c2 and 32c2 increases as the cutting point goes away from the pivot 4 though the crossing angle in the base side areas 31c1 and 32c1 is large similarly to the conventional 15 scissors. In other words, the crossing angle becomes larger over the whole of the tip side areas 31c2 and 32c2 than the crossing angle at the border to the base side areas 31c1 and 32c1. Hence, the load required for cutting with the tip side areas 31c2 and 32c2 is approximately constant independently of the cutting point, therefore even the neighborhood of the blade tips 31e and 32e can be used for the purpose of cutting 20 corrugated cardboards, plastic sheets, plastic packing bands, and so on. [0049] Since the first small-radius curved parts 31cx and 32cx are smaller in radius of curvature than the second small-radius curved parts 31cy and 32cy, the configuration is able to be made preferably in which even the neighborhood of the blade tips 31e and 32e can be used for the purpose of cutting corrugated cardboards, plastic sheets, plastic 25 packing bands, and so on without rapid change of the crossing angle between the edge 16 lines in the neighborhood of the blade tips 31e and 32e, that is, in the second small-radius curved parts 31cy and 32cy as the cutting point goes away from the pivot 4 through the cutting operation. [0050] In addition, since the base side area 31c1 and the tip side area 31c2 are provided in 5 the edge line 31c, and besides the base side area 32c1 and the tip side area 32c2 are provided in the edge line 32c, the above effect can be obtained without extremely reducing the radius of curvature of the tip side areas 31c2 and 32c2 in the edge lines, width of the blade pieces, namely, the movable blade 31 and the stationary blade 32 is reducible. [0051] Furthermore, since the crossing angle at the border between the base side areas 10 31c1, 32c1 and the tip side areas 31c2, 32c2 is about 18 degrees, the load for cutting in the tip side areas 31c2 and 32c2 is sufficiently reduced, compared to that of the conventional scissors. [0052] The maximum value of the crossing angle is 90 degrees, the same feeling of use as the conventional scissors can be obtained in the base side areas 31c1 and 32c1. 15 [0053] The present invention is not limited to the above-described embodiment. [0054] Though the tip side areas 31c2 and 32c2 according to the above first embodiment have the first to fifth small-radius curved parts 31ca to 31ce and 32ca to 32ce that are different in radius of curvature from each other, and the tip side areas 31c2 and 32c2 according to the above second embodiment have the first and second small-radius curved 20 parts 31cx, 31cy 32cx and 3 2 y that are different in radius of curvature from each other, for example, it is possible to set the number and layout of small-radius curved parts arbitrarily, it is also possible to set the radii of curvature of small-radius curved parts arbitrarily as long as those are smaller than the radii of curvature of base side areas. Further, of course, the edge line of a blade may have a non-arc shape like a quadratic 25 curve, a cubic curve, and so on, the edge line may also be a joining of such curves or an arc 17 and a non-arc curve. In other words, of course, the edge line may be formed so that the radii of curvature of several parts of the tip side area continuously change. However, it is more desirable that the small-radius curved part closest to the base side area be smaller in radius of curvature than the other small-radius curved part, in other words, the 5 small-radius curved part closest to the base side area be a crossing-angle-rapidly-changing part, or it is also more desirable that the tip side area have three or more small-radius curved parts and the small-radius curved part second closest to the base side area be smaller in radius of curvature than the other small-radius curved parts, in other words, the small-radius curved part second closest to the base side area be a 10 crossing-angle-rapidly-changing part, because usage to cut corrugated cardboards, plastic sheets, plastic packing bands, and so on with a neighborhood of the tips of the blades without rapidly changing the crossing angle as a cutting point goes away from the pivot in the neighborhood of the tips can be supported if so. In addition, though the crossing-angle-rapidly-changing parts according to the above first and second 15 embodiments are provided in the range of about 59 to 64 percent of the total length of the edge lines, a crossing-angle-rapidly-changing part provided in a range of about 55 to 70 percent of the total length of the edge line makes it possible to achieve the effect that the crossing angle becomes large enough in areas closer to the tips than the crossing-angle-rapidly-changing part. In particular, the crossing angle in a neighborhood 20 of the blade tips can remain larger when the crossing-angle-rapidly-changing part is provided near the blade tip. [0055] Though the base side areas and the tip side areas are provided on both of the edge lines according to the above first and second embodiments, of course, the base side area and the tip side area may be provided on one of the edge lines. 25 [0056] In addition, though the crossing angle at the border between the base side areas 18 and the tip side areas is set to about 23 degrees in the first embodiment, and is set to about 18 degrees in the second embodiment, the effect according to the above embodiments can be achieved if the crossing angle at the border between the base side area and the tip side area is 18 degrees or more. 5 [0057] Though the maximum value of the crossing angle between the edge lines is 90 degrees in each of the first and second embodiments, the effect according to the above first and second embodiments can be achieved if the maximum value of the crossing angle between the edge lines is larger than 90 degrees. On the other hand, even if the maximum value of the crossing angle between the edge lines is smaller than 90 degrees, 10 the crossing angle formed by the edge lines can be large in the base side area similarly to the conventional scissors and remain rather large in the tip side area so that a load required for cutting is approximately constant independently of the cutting point when the crossing angle gradually decreases in the base side area as a cutting point goes away from the pivot through cutting operation and takes a minimum value at the border between the base side 15 area and the tip side area. [0058] Moreover, though the blade rear faces according to the above first and second embodiments are flat, a recessed portion or a step portion may be provided on a blade rear face so as to prevent occurrence of the problem that an adhesive adheres to a neighborhood of the edge line of the blade in cutting sheets, like paper, to which the 20 adhesive is applied. As an example of such scissors, ones described below can be cited. In the following description, the elements that are equivalent to the ones described in the above first and second embodiments are given the same names and reference signs thereas. [0059] For example, as shown in FIG. 11 (a), a recessed portion 31x having a groove 25 shape with a bottom that extends along an edge line 31c may be provided on a blade rear 19 face 31a. As shown in FIG. 11 (b), a recessed portion 3 1y may be provided on nearly the entire region of a blade rear face 31a. Further, as shown in FIG. 11 (c), a recessed portion 31z may be open toward a blade back 31d and a blade tip 31e, in other words, a neighborhood of an edge line 31c may be formed to be closer to a stationary blade 32 than 5 the other parts. As shown in FIG. 11 (d), a plurality of recessed portions 31x having groove shapes may be provided. Of course, as shown in FIGs. 12 and 13, through holes 31h that go through a movable blade 31 may be provided in a neighborhood of an edge line 31e of the movable plate 31. Also, of course, as shown in FIGs. 14 and 15, many recessed portions 31k having a circular shape in a planar view may be provided on a blade 10 rear face 31a of a movable blade 31. FIGs. 11 to 15 show the movable blade 31 only, however, of course, a recessed portion or a through hole may be provided on a stationary blade 32. In the mode shown in FIGs. 11, the bottom faces of the recessed portions 31x and 3 1y may be parallel with the neighborhood of the edge line 31c in the blade rear face 31a. A center part in width of each of the movable blade 31 and the stationary blade 32 15 may be formed into a shape to be a recessed portion such that one of the movable blade 31 and the stationary blade 32 gets apart from the other in the thickness direction as closer to the center part in width. [0060] Furthermore, as scissors according to the present invention, ones described below can be cited. In the following description, the elements that are equivalent to the ones 20 described in the above first and second embodiments are given the same names and reference signs thereas. [0061] For example, as shown in FIG. 16 (a), a part of a tip side area 31c2 in an edge line 31c may be formed into a serrate shape. As shown in FIG. 16 (b), a part of a base side area 31c1 in an edge line 31c may be formed into a serrate shape. Of course, an edge line 32c 25 of a stationary blade 32 may be similarly configured, the mode such that serrate parts are 20 provided on both base side areas 31c1 and 32c1 and tip side areas 31c2 and 32c2, or the wholes of edge lines 31c and 32c are formed into serrate shapes can be employed. With respect to the scissors such that the part of the edge line 31c is formed into the serrate shape, the "crossing angle" in the part where the edge line 31c is formed into the serrate 5 shape means an angle formed by both of line segments, each of which joins points of the teeth of the serration. [0062] In addition, as shown in FIG. 17, the included angle at an edge line 32c between a blade rear face 32a and a blade surface 32b may be set to a first prescribed angle 61, for example, 50 degrees, and on top of that, a part that is at a second prescribed angle 62 10 smaller than the first prescribed angle 61 to blade rear face 32a may be provided on a side closer to the blade surface 32b. [0063] As shown in FIG. 18, the structure such that a neighborhood of an edge line 31c of a movable blade 31 and a neighborhood of an edge line 32c of a stationary blade 32 are opposed to each other, and besides the movable blade 31 and the stationary blade 32 get 15 apart from each other in the thickness direction as closer to blade backs 31d and 32d can be employed. [0064] Further, a first handle 21 and a second handle 22 may be configured as described below and shown in FIG. 19. That is, the configuration such that each of the first and second handles 21 and 22 includes a handle main body 211, 221 extending from a pivot 4 20 toward a direction opposite to a movable blade 31 or a stationary blade 32 with a finger-hooking portion in a part of an internal face thereof, a finger-hooking member 212, 222 capable of being in a subsiding state where the finger-hooking member 212, 222 is within the handle main body 211, 221 and a usage state where the finger-hooking member 212, 222 protrudes out of the handle main body 211, 221 constituting a finger ring together 25 with the finger-hooking portion, and an operation member 213, 223 connected to a free 21 end of the finger-hooking area 212, 222 and capable of moving between a subsidence position to put the finger-hooking area 212, 222 within the handle main body 211, 221 and a usage position to protrude the finger-hooking area 212, 222 out of the handle main body 211, 221 can be employed. 5 [0065] As shown in FIG. 20, the mode such that each of a first handle 21 and a second handle 22 is a half cut of a prism, a movable blade 31 and a stationary blade 32 overlying each other can be sheathed in a case 5, and besides a strap 210 is provided on the first handle 21 can be employed. Also, the scissors are configured such that a torsion coil spring 6 as an energizing means is connected with the movable blade 31 and the stationary 10 blade 32 so as to press the movable blade 31 and the stationary blade 32 unsheathed from the case toward a direction in which both of edge lines of the blades get apart from each other. [0066] In addition, though neighborhoods of the finger rings are made of soft resin softer than the other parts in the handles and the wholes of the handles are formed by two-color 15 molding according to the above first and second embodiments, the wholes of handles 21 and 22 may be made of a single material as shown in FIG. 21. [0067] Various other modifications are possible without departing from the scope and spirit of the present invention. DESCRIPTION OF THE REFERENCE NUMERAL 20 [0068] H scissors 11, 12 (first/second) scissor body 21, 22 (first/second) handle 21a, 22a finger-hooking portion 25 31 blade piece (movable blade) 22 32 blade piece (stationary blade) 31c, 32c edge line 31c1, 32c1 base side area 31c2, 32c2 tip side area 5 23

Claims (10)

1. Scissors including a pair of scissor bodies that each have a handle and a blade piece with an edge line, and a pivot that links the scissor bodies with each other in a 5 rotatable manner, characterized in that: a base side area and a tip side area are provided, the base side area being curved and such that a crossing angle at which both of the edge lines cross each other gradually decreases as a cutting point goes away from the pivot through cutting operation, 10 the tip side area being adjacent to a tip side of the base side area and such that the crossing angle remains approximately constant or increases as the cutting point goes away from the pivot through the cutting operation.

2. The scissors according to claim 1, 15 wherein the tip side area has a crossing-angle-rapidly-changing part near a border between the base side area and the tip side area, the crossing-angle-rapidly-changing part being such that the crossing angle rapidly increases as the cutting point goes away from the pivot. 20

3. The scissors according to claim 1 or 2, wherein the handle has a finger-hooking portion for a user's finger to be hooked in a prescribed finger-hooking area, the base side area and the tip side area are provided in at least one of the edge lines, 25 the crossing angle is larger over the whole of the tip side area than the crossing 24 angle at the border between the base side area and the tip side area.

4. The scissors according to claim 1, 2, or 3, wherein the tip side area has a plurality of small-radius curved parts that are 5 different in radius of curvature from each other.

5. The scissors according to claim 4, wherein the small-radius curved part closest to the base side area is smaller in radius of curvature than the other small-radius curved part, and is the 10 crossing-angle-rapidly-changing part in that the crossing angle rapidly increases as the cutting point goes away from the pivot.

6. The scissors according to claim 4, wherein the tip side area has three or more small-radius curved parts, 15 the small-radius curved part second closest to the base side area is smaller in radius of curvature than the other small-radius curved parts, and is the crossing-angle-rapidly-changing part in that the crossing angle rapidly increases as the cutting point goes away from the pivot. 20

7. The scissors according to claim 1, 2, 3, 4, 5 or 6, wherein the base side area and the tip side area are provided in each of the edge lines.

8. The scissors according to claim 1, 2, 3, 4, 5, 6, or 7, 25 wherein the maximum value of the crossing angle is 90 degrees or more. 25

9. The scissors according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the crossing angle at the border between the base side area and the tip side area is 18 degrees or more. 5

10. The scissors according to claim 4, wherein the radius of curvature of one of the small-radius curved parts is smaller than the total length of the edge line containing the small-radius curved parts. 26