A corner cutter

Abstract: A movable blade provided with a circular edge (10) for cutting the corner (102) of the paper (1) and a straight edge (11) for cutting the corner edge (101) is inserted in a movable blade inserting hole provided in the stationary blade, and the corner (102) of the paper (1) inserted in a slit is cut between the stationary edge, and the circular edge (10) and the straight edge (11). Thereby, during the cutting of the corner (102) by the straight edge (11), both of the circular edge (10) and the straight edge (11) cut the corner (102), the corner (102) is cut in the state of being tensioned between the circular edge (10) and the straight edge (11), as if the corner edge (101) is held by the straight edge (11), thereby, the bite of the paper is disappeared to be handled easily and an uneven alignment of the cut corners is diminished.

Description: Background of the invention Field of the invention The present invention relates to a corner cutter to cut a corner of a sheet of paper in a rounded shape. Prior art Conventionally, in general, there is a case where the corners of sheets of papers such as "Loose Leaf" (a trade name) to be bound in a binder are to be cut in a rounded shape. In this case, since there has not been an appropriate corner cutter, it has been necessary to cut the corner circle with normal scissors. Further the corners of papers such as loose leaf papers found in a market are mostly rounded, which usually have been cut, as shown in Fig. 10, by pushing down a cutter 3 of a semi-circular shape and cutting the corner 4 of the stacked sheets of paper 1. In the above conventional manner, when cutting the corner of sheet of paper using a scissors, the rounded or circle arc of the cut corners are not set in order to show good appearance, and not efficient for making a plurality of corners all rounded at the same time. And, when using the semi-circular cutter 3 as shown in Fig. 10, although the circular shape cut in a rounded or circle arc is in order; when the user is not an adult, for instance a child, he is apt to be hurt, so that it is not an appropriate cutting device, in addition it becomes expensive when the cutter 3 is arranged to be pushed down mechanically. A prior art that is of interest is US-A-2 936 665 in which a device for forming rounded corners on sheets of material comprises a cutting blade in the form of an inner vertical cylindrical tube formed at its lower end with a cutting edge curving in a manner defining two downwardly extending prongs, said inner tube being slidable in an outer cylindrical housing. The two prongs are formed by cutting away portions of the inner tube so that the two prongs define between them a parabolic-like cutting edge extending in a vertical direction and defining, in plan view, approximately a quarter of a circle. The outer cylindrical housing has a slot permitting a corner of a sheet of material to be inserted therein for cutting by said cutting edge. Below the slot is a shearing element in the form of a solid cylindrical body of less diameter than the inner diameter of the outer cylindrical housing. The shearing element is rockable about a lower horizontal axis extending in a direction that is parallel with an imaginary straight line between the lowermost tips of said two prongs. A compression spring acts on the shearing element in a manner rocking its upper end away from the aforesaid slot. After the corner of a sheet of material has been inserted into said slot, the iner tube is lowered and its aforesaid cutting edge cuts the corner of the sheet of material to an arcuate shape. During the cutting operation the two prongs pass into a spacing between the cylindrical shearing element and said outer cylindrical housing and co-operate with said pivotable shearing element in a manner rocking it against its biassing spring towards said slot in the outer cylindrical housing, the result being that a slicing action on said sheet of material takes place along an arcuate line from opposite directions, commencing from two adjacent side edges of said material and meeting at the central point of said arcuate line. Summary of the invention The present invention relates to a corner cutter, which gives corners of paper a stable rounded shape and is very simple in operation as a business machine and cheap in cost. The present invention comprises, in order to solve the above problem, a corner cutter for cutting a corner of sheets of paper to form a rounded shape; said corner cutter comprising: a stationary blade and a movable blade; said stationary blade being provided with a slit for insertion therein of a corner edge of said papers to be cut, said stationary blade being further provided with a movable blade inserting hole which intersects said stationary blade perpendicularly to said slit; the stationary blade having a stationary edge which is formed at the intersection between the slit and said movable blade inserting hole; the movable blade being formed at its cutting end with: a first cutting edge that is circular when viewed in the direction of movement of the movable blade, for cutting a corner of sheets of paper to form said rounded shape; the radius of said circular cutting edge being larger than the radius of a circle which is tangential to the two edges of the sheets of paper where they are cut by said circular edge; and a second cutting edge spaced rearwardly from said first cutting edge, when viewed in the direction of movement of the movable blade, for cutting said papers additionally along: (a) a linear line; or (b) an arcuate line having a radius greater than the radius of said first cutting edge; the arrangement being such that while cutting of said papers is being effected simultaneously by said first and second cutting edges the second cutting edge also serves to hold the corner edge of the papers from slipping away so that the corner of the paper is cut in a tensioned state. The aforesaid first cutting edge and second cutting edge of the movable blade may be configured concave to said stationary edge of the stationary blade. On both sides of said concave configuration of the first cutting edge and the second cutting edge there may be guide portions provided for strength. The length of said guide portions may be such that they cross said stationary edge even when the movable blade is lifted to its uppermost setting after completing a cutting stroke. Brief description of the drawings Fig. 1 is a front view of the main part of the movable blade in the embodiment of the present invention. Fig. 2 is a bottom view of Fig. 1. Fig. 3 is a sectional view of the main portion along the line A - A of Fig. 1. Fig. 4 is a plan view of the holding portion provided on the stationary blade. Fig. 5 is a perspective view of a broken corner cutter. Fig. 6 is a vertical sectional view of the corner cutter assembled. Fig. 7 is a vertical sectional view along the line B - B of Fig. 6. Fig. 8 shows the case where a punching out blade is provided in addition to the corner cutter. Fig. 9 is a bottom view of the bottom plate of Fig. 5. Fig. 10 is a perspective view of a conventional art. Fig. 11 is for general explanation for a corner cutting. Fig. 12 is for general explanation for a corner cutting. Preferred Embodiment Hereinafter, an embodiment of the present invention will be explained. First, based on Fig. 5, a corner cutter is explained as a whole. A movable blade 7 is fastened to a member which is in a unit with a spring receiver 16 for accepting the upper end of a spring 17 and a holding portion 15 for operating the movable blade 7 in the pushing down direction. Above the upper surface of the stationary blade 5 is a spring holding portion 22 for holding the lower end of the spring 17; and a movable blade inserting hole 8 passes through a slit 6 in the stationary blade in such a manner that it intersects perpendicular to the slit 6. The cutter has a cap 13 at its upper end that is formed with a hole 14. The spring 17 is inserted between the stationary blade 5 and the spring receiver 16 on the holding portion 15. The holding portion 15 projects into the hole 14 in the cap 13 and the spring receiver 16 is biassed against the cap 13 by the spring 17. When the holding portion 15 is pushed downwardly the movable blade 7 is pushed down but is adapted to be lifted up again by the spring 17. On the bottom plate 18, guide portions 19 for guiding the corner 102 of the paper 1 to be cut are provided, and on inserting the corner 102 of the paper 1 into the slit 6 it is guided along the guide portions 19 so that the corner edge 101 is positioned at an appropriate position with respect to the stationary edge 9 (Fig. 1) of the stationary blade 5. 20 is a hole for disposing the cut wastes. The cut wastes are adapted to be disposed from this hole. 21 is a cover which protects the user's hand from touching the edge of the blade when pushing down the movable blade 7. The bottom plate 18 is mounted removably on the back surface of the stationary blade 5. Figs. 6 and 7 show the assembled corner cutter in vertical section. As shown in Figs. 6 and 7, when the cap 13 is secured on the upper surface 181 (Fig. 5) of the bottom plate 18 a gap 191 (Figs. 6 and 7) is formed due to a step of the guide portions 19. This gap 191 is in line with the slit 6 provided in the stationary blade 5, so that the paper 1 can be inserted by being guided in the guide portions 19 into the slit 6. Figs. 1 and 2 show details of the main portion of the movable blade 7 of Fig. 5. Fig. 2 shows that at the bottom end of the movable blade 7 there is a circular edge 10 for cutting the corner of the paper 1 in a rounded shape and a straight edge 11 for cutting the corner edge 101 of the paper 1 in a straight manner. There is a width T between the center of the circular edge 10 and the straight edge 11. Guide portions 19 provided on the bottom plate 18 ensure that a corner edge 101 of the paper 1 projects beyond the straight edge 11 when a sheet of paper is inserted in the slit 6. Further, the radius of curvature R of the circular edge 10 of the movable blade 7 is, as shown in Fig. 2, and as measured from the point O1, set larger than the radius R1 (see Fig.11) of a circle which is tangential to the corner 102 of the paper 1 and has its center at O1. The straight edge 11 is formed linear in this embodiment. By setting R > R1, the circular edge 10 and the corner 102 of the paper intersect at the points P1, and as seen in Fig. 1, showing a front view of the movable blade 7, by making the configuration of the circular edge 10 and the straight edge 11 to be concave with respect to the stationary edge 9, the paper 1, as shown in Fig. 12, is cut starting from the two intersections P1 (hereinafter referred to "P1") formed between the circular edge 10 and the corner 102, the two cuts moving toward each other as shown by the arrows. This cutting is carried out like a scissors which cuts a paper. Thus, by cutting the paper 1 from the intersections P1 towards each other as shown by the arrows, a stuffing up of the paper corner 102 between the movable blade 7 and the stationary blade 5 may be prevented by the securing effect created by the cutting of the paper from the two intersections P1. Further, as shown in Fig. 2, by projecting the corner edge 101 of the paper beyond the straight edge 11, during cutting the corner 102 of the paper 1 by the circular edge 10 from the points P1 to the intersections P2' (hereinafter referred to "P2'"), the straight edge 11 has not yet started to cut the corner 102, thereby the cutting load during that time is lighter. And when the cutting of the circular edge 10 has progressed to the points P2', the straight edge 11 starts to cut the corner 102 from the two intersections P2 (hereinafter referred to "P2") formed between the straight edge 11 and the corner 102. Thereafter, the cutting of the circular edge 10 and the straight edge 11 is carried out simultaneously. That is, during the cutting of the space between the two points P2' by the circular edge 10, the straight edge 11 simultaneously cuts the space between the two points P2, which causes the straight edge 11 to hold the corner edge 101 of the paper 1 so that the circular edge 10 can cut the space between the two points P2' securely. Further, in the present embodiment the circular cutting edge 10 of radius R, and the straight cutting edge 11, are each formed with guide portions 12 (described hereinafter) that contribute a strength control permitting the dimension of T, Fig. 2, to be set as small as possible. Thereby, the two points P2 can be close to the two points P1 so that the starting of a holding action (actually the start of simultaneous cutting) on the corner edge 101 begins as soon as possible after the commencement of cutting by the cutting edge 10 and so the corner edge 101 is prevented from slipping away, thus permitting the circular edge 10 to be cut more securely. In addition, if the dimension T is made as small as possible by using a circular cutting edge 10 having a radius R' with its center at O, as shown in Fig.2, this causes the two points P1 to approach the two points P2 and this ensures a more secure cutting action at the radius R' by the circular edge 10. Alternatively, the straight edge 11 may be replaced by an edge having a large radius of R'', the center of which is shifted from the center O 1 to the center O 2 . In that case, the two points P2 will be spaced further apart and so ensure an earlier start of the cutting of the paper by the cutting edge 11. Thus, by using both the circular edge 10 and the straight or arcuate edge 11 the corner 102 of the paper 1 is cut, so that the escape of the corner edge 101 from being cut is prevented, and the corner 102 is cut in a tensioned state. Thereby, comparing this with a case in which the paper is cut only between the circular edge 10 and the stationary blade 9, the allowance of the clearance precision between the present stationary blade 9 with respect to the circular edge 10 and the straight or arcuate edge 11 can be loosened by 1/2 of the conventional one. Accordingly, the workability of the circular edge 10, the straight or arcuate edge 11 and the stationary blade 9 becomes improved. On both sides of the concave edge of the circular cutting edge 10 and the straight or arcuate edge 11, there are provided the aforesaid guide portions 12, and the length of the guide portions 12 is adapted to remain in crossing relationship with the stationary blade edge 9 even when the movable blade 7 is lifted to its upper most setting due to the elastic force of the spring 17. Thereby, the circular edge 10 and the straight or arcuate edge 11 can cross the slit 6 smoothly, and the clearance precision with respect to the stationary edge 9 can be increased, and as shown in Fig. 9, since the corner 102 of the paper 1 inserted in the slit 6 is guided by the guide portions 19 provided on the bottom plate 18, the positioning precision of the paper 1 to the circular edge 10 is thereby increased. Thereby, an uneven cut of the corner 102 of the paper 1 that is not in agreement with the roundness of radius R is avoided. Fig. 4 shows a plan view of the spring holding portion 22 of the stationary blade 5, and the configuration of the movable blade inserting hole 8 is similar to the cross-section of the movable blade 7. Fig. 8 shows the case where a punch 23 is provided together with the movable blade 7, in which, for instance as shown in Fig. 12, the cutting of the corner 102 in a rounded shape is carried out simultaneously with the punching of a pattern 103. In the case where this punch 23 is provided, a hole which is similar to the pattern and crosses through the slit 6 perpendicularly is provided in the stationary blade 5 separately from the movable blade inserting hole 8. The function of the present invention thus constituted will be explained next. As shown in Figs. 3 to 5 the corner 102 of the paper 1 when inserted in the slit 6 is adapted to be cut between the stationary blade 5, and the circular edge 10 for cutting a rounded corner of the paper 1 and also by the straight or arcuate edge 11 for additionally cutting the corner edge 101 of the paper 1, said edges being provided on the bottom end of the movable blade 7 that is slidable through the hole 8. Thus, during a simultaneous period both the circular edge 10 and the straight or arcuate edge 11 can cut the corner 102, so that the corner 102 is being cut in a state wherein it is tensioned between the circular edge 10 and the straight or arcuate edge 11, that is to say whilst the corner edge 101 is held by the straight or arcuate edge 11, whilst the corner 102 is being cut in the given radius by the circular edge 10. Fig. 12 shows how the paper should be cut along an arc having its center of radius at a distance from the two sides of the paper that is less than the radius of said arc to ensure a cutting action on the paper at P1,P1 that is not tangential to the sides of the paper. The cutting action should not be as in Fig. 11 where the cutting arc is tangential to the sides of the paper. Further, the movable blade inserting hole 8 crosses laterally perpendicular to the slit 6 provided in the stationary blade 5, so that at the intersection where the slit 6 and the movable blade inserting hole 8 cross the stationary edge 9 is formed, and the corners 102 of the stacked paper 1 when inserted in the slit 6 all have their corners cut in the same radius. And, since the configuration of the circular edge 10 and the straight or arcuate edge 11 of the movable blade 7 are concave to the stationary edge 9, when the movable blade 7 is pushed down, as shown in a phantom line of Fig. 1, the corner of the paper 1 is cut between the intersections of P1' and P1'; and also of P1'' and P1'' as shown in Fig. 1 between the sides of the paper 1; and the circular edge 10 and the straight or arcuate edge 11 respectively, which is carried out lightly like a scissors, and that, as shown in Fig. 12, the corner 102 is cut from both sides in opposing arrow direction, so that the position of the paper 1 is not displaced at the time of cutting. Since, on both sides of the concave edge of the circular edge 10 and the straight or arcuate edge 11, the guide portions 12 are provided, as shown in Fig. 1, the corner edges 102 of the paper can be correctly positioned with respect to the circular edge 10. Further, as shown in Fig. 6, even when the movable blade 7 is lifted to its upper setting due to the resilient force of the spring 17, the length of the guide portions 12 are such that their lower ends remain in the stationary edge 9, whereby the clearance between the stationary edge 9, and the circular edge and the straight or arcuate edge 11 can be maintained precisely, to cut well. As mentioned above, according to the present invention the movable blade, having at its bottom end the circular edge for cutting the corner of the paper to form a rounded shape and the straight or arcuate edge for additionally cutting the corner edge of the paper, is inserted in the movable blade inserting hole to cut the corner of the paper inserted in the slit between the stationary edge and the circular edge, as well as by the straight edge or arcuate edge. And during the cutting of the corner by the straight edge or arcuate edge, both the circular edge and the straight or arcuate edge cut the corner jointly so that the corner is in a tensioned state between the circular edge and the straight or arcuate edge since the straight or arcuate cutting edge holds the corner edge. Thereby, there is no bite of the paper, easy handling is secured and an uneven alignment of the cut corners is avoided.

Claims: A corner cutter, for cutting a corner (102) of sheets of paper (1) to form a rounded shape comprising: a stationary blade (5); and a movable blade (7); said stationary blade (5) being provided with a slit (6) for insertion therein of a corner edge (101) of said papers to be cut said stationary blade (5) being further provided with a movable blade inserting hole (8) which intersects said stationary blade (5) perpendicularly to said slit (6); the stationary blade (5) having a stationary edge (9) which is formed at the intersection between the slit (6) and said movable blade inserting hole (8); the movable blade (7) being formed at its cutting end with: a first cutting edge (10) that is circular, when viewed in the direction of movement of the movable blade (7), for cutting a corner (102) of sheets of paper (1) to form said rounded shape; the radius (R) of said circular cutting edge (10) being larger than the radius (R1) of a circle which is tangential to the two edges of the sheets of paper (1) where they are cut by said circular edge (10); and a second cutting edge (11) spaced rearwardly from said first cutting edge (10), when viewed in the direction of movement of the movable blade, for cutting said papers additionally along: (a) a linear line; or (b) an arcuate line having a radius (R'') greater than the radius (R) of said first cutting edge (10); the arrangement being such that while cutting of said papers is being effected simultaneously by said first and second cutting edges (10, 11) the second cutting edge (11) also serves to hold the corner edge (101) of the papers (1) from slipping away so that the corner (102) of the paper is cut in a tensioned state. A corner cutter according to the Claim 1, wherein the first cutting edge (10) and the second cutting edge (11), of the movable blade (7) are configured concave to said stationary edge (9) of the stationary blade (5). A corner cutter according to the Claim 2, wherein on both sides of the concave edge of the first cutting edge (10) and the second cutting edge (11) guide portions (12) are provided for strength. A corner cutter according to Claim 3 wherein the length of said guide portions (12) is such that they cross said stationary edge (9) even when the movable blade (7) is lifted to its uppermost setting after completing a cutting stroke.

Inventors: MORI CHUZO, MORI, CHUZO
Applicants: CARL MFG CO, CARL MANUFACTURING CO., LTD.
Application year: 1996
Main classification: B26D3
IPC codes: B26D1, B26D3