Rotary cutter

Abstract: According to the invention, a rotary cutter is provided, which includes a fixed blade (40) having a straight cutting edge (42) and a rotary blade (52) having a spiral cutting edge (58). The rotary blade is installed for rotation about an axis extending parallel to the cutting edge of the fixed blade, the spiral cutting edge of the rotary blade moving along a path which extends tangentially to said cutting edge of the fixed blade. At least one of the fixed blade and the rotary blade is shorter than the width of a paper strip (30). Accordingly, the rotary blade and the fixed blade cooperate with each other to partially cut the paper strip widthwise while leaving the opposite end portions uncut. The fixed blade has opposite surfaces (64,66) extending toward the cutting edge thereof, one (64) of which comprises an inclined surface formed on the paper inlet side of the fixed blade and disposed at an angle less than 60° with respect to the paper strip. Accordingly, the cut strip can get over the fixed blade without being caught thereon immediately after cutting.

Description: The invention relates to a rotary cutter for partially cutting a paper strip widthwise while leaving opposite side portions uncut. PRIOR ART When producing a number of labels, a pattern is printed on each of successive lengths of a paper strip. The paper strip is then cut widthwise into the lengths to obtain the labels each having a pattern. In such the case, a shearing-type rotary cutter is commonly used to cut the paper strip widthwise. As shown in Fig. 6, the rotary cutter includes a fixed blade 22 having a straight cutting edge 24 and a rotary blade 26 installed for rotation about an axis extending parallel to the cutting edge 24 of the fixed blade 22. The rotary blade 26 includes a spiral cutting edge 28 moving along a path which extends tangentially to the cutting edge 24 of the fixed blade 22. Accordingly, the rotary blade 26 and the fixed blade 22 cooperate with each other so that the paper strip 30 is cut widthwise from one end of the cut to the other end in the shearing mode by the spiral cutting edge 28 of the rotary blade 26 when the paper strip 30 is fed continuousely between the fixed blade 22 and the rotary blade 26. The paper strip 30 can be fed continuousely into the printing station without interruption. It is also known in the shearing-type rotary cutter to provide that at least one of the fixed blade 22 and the rotary blade 26 is shorter than the width of the paper strip 30 to partially cut the paper strip 30 widthwise while leaving uncut opposite side portions of the strip i.e. leaving uncut portions of the strip at the ends of the cut. In this case, the paper strip 30 remains continuous to prevent the labels from dispersion. The labels can be easily separated one by one on occasion. As to the rotary cutter in the prior art, the fixed blade 22 has opposite surfaces 32 and 34 extending toward the cutting edge 24 thereof. One surface 32 comprises a vertical surface formed on the paper inlet side of the fixed blade 22 and disposed perpendicularly to the paper strip 30. The other surface 34 comprises an inclined surface formed on the paper outlet side of the fixed blade 22 and disposed at an angle less than 90° with respect to the paper strip 30. The rotary blade 26 also has opposite surfaces 36 and 38 extending toward the cutting edge 28 thereof. One surface 36 comprises a vertical surface formed on the rotary leading side of the rotary blade 26 and disposed perpendicularly to the paper strip 30. The other surface 38 comprises an inclined surface formed on the rotary trailing side of the rotary blade 26 and disposed at an angle less than 90° with respect to the paper strip 30. However, when partially cutting the paper strip 30 widthwise while leaving the opposite side portions uncut in such rotary cutter, the cut strip 30 is caught on the vertical surface 32 of the fixed blade 22 on the paper inlet side thereof immediately after cutting. The cut strip 30 is also caught and then pulled by the vertical surface 36 of the rotary blade 26 on he rotary leading side thereof, thus forming tears (b) at the ends of the cut (c) as shown in Fig. 7. Accordingly, when separating the labels, the tears (b) lengthen, ruining the labels. GB-A-1 518 844 discloses a rotary cutter for cutting a paper web into smaller pieces, the rotary cutter including a fixed blade having a straight cutting edge, and a rotary blade installed for rotation about an axis extending parallel to the cutting edge of the fixed blade, the rotary blade including a helical cutting edge moving along a path which extends tangentially to said cutting edge of the fixed blade, the fixed blade having opposite surfaces extending toward said cutting edge thereof, one of which surfaces is on the paper inlet side of the fixed blade and is inclined at an angle (approximately 65°) with respect to the paper web. GB-A-867 071 discloses a rotary cutter for cutting perforations across a paper web, the rotary cutter comprising a rotary blade which has opposite surfaces extending toward a cutting edge thereof, one of which surfaces is formed on the rotary leading side of said rotary blade and is inclined at an angle less than 90° with respect to the paper web. SUMMARY OF THE INVENTION An object of the invention is to provide a shearing-type rotary cutter in which the paper strip can be partially cut widthwise without forming tears at the ends of the cut. According to the present invention, there is provided a rotary cutter including a fixed blade having a straight cutting edge, and a rotary blade installed for rotation about an axis extending parallel to said cutting edge of the fixed blade, said rotary blade including a helical cutting edge moving along a path which extends tangentially to said cutting edge of the fixed blade, said fixed blade having opposite surfaces extending toward said cutting edge thereof, one of which comprises an inclined surface formed on the paper inlet side of said fixed blade and disposed at an angle with respect to said paper strip, said rotary cutter being characterized in that: at least one of said fixed blade and said rotary blade is shorter than the width of a paper strip so that said rotary blade and said fixed blade cooperate with each other to partially cut the paper strip widthwise while leaving the side portions of the strip uncut; said angle between said inclined surface of the fixed blade and said paper strip is less than 60° whereby the cut strip can pass over said fixed blade without being caught thereon immediately after cutting; said path extends tangentially to said paper strip; and said rotary blade has opposite surfaces extending toward said cutting edge thereof, one of which surfaces, formed on the rotary leading side of said rotary blade, is inclined at an angle less than 90° with respect to said paper strip whereby said rotary blade can slip over the cut strip without catching it immediately after cutting. The invention enables the cut strip to pass over the fixed blade without being caught thereon immediately after cutting. and enables the rotary blade to slip over the cut strip without catching it immediately after cutting. Accordingly tears are therefore hardly ever formed at the ends of the cut even if the cut strip is pulled by the rotary blade. The angle between the inclined surface of the fixed blade and the paper strip may preferably be 45° . The angle between the inclined surface of the rotary blade and the paper strip may preferably be 30 ° . The fixed blade and the rotary blade are preferably disposed to be slightly inclined at an angle with respect to a transverse line normal to the feed direction of the paper strip. The angle between the fixed and rotary blades and the transverse line substantially corresponds to the angle of twist of the helical cutting edge of the rotary blade. Accordingly, the paper strip is cut along the transverse line normal to the feed direction thereof. A rotary cutter embodying the invention is hereinafter described, by way of example, with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a elevational view of a preferred embodiment of the invention. Fig. 2 is a plan view of Fig. 1 embodiment. Fig. 3 is a sectional view of Fig. 1 embodiment. Fig. 4 is a sectional view, on an enlarged scale, of a fixed blade and a rotary blade in Fig. 3. Fig. 5 is a sectional view, on an enlarged scale, showing the fixed blade and the rotary blade in Fig. 3 and a paper strip immediately after cutting. Fig. 6 is a sectional view, on an enlarged scale, of a rotary cutter in the prior art and a paper strip immediately after cut in comparison with those in Fig. 5. Fig. 7 is a plan view of a paper strip cut widthwise by the rotary cutter in the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, a shearing-type rotary cutter according to the invention is shown. The rotary cutter includes a fixed blade 40 having a straight cutting edge 42 as shown in Fig. 3, the fixed blade 40 being received in a recess 44 formed in a block 46. A holder 48 is pressed against the fixed blade 40 by bolts 50 so that the fixed blade 40 is fixedly mounted on the block 46. The rotary cutter also includes a rotary blade 52. The rotary blade 52 is formed helically on the drum 54 which is mounted on a pair of brackets 56 for rotation about an axis extending parallel to the cutting edge 42 of the fixed blade 40. The drum 54 is operatively connected to a drive motor by means of gears or belts not shown. The rotary blade 52 has a helical cutting edge 58 moving along a path 60 which extends tangentially to the cutting edge 42 of the fixed blade 40. In this rotary cutter, a paper strip 30 is fed continuously to the left in Fig. 3 and between the fixed blade 40 and the rotary blade 52. The drum 54 is driven by the moter so that the rotary blade 52 rotates clockwise at a circumferential rate corresponding to or slightly higher than the feed rate of the paper strip 30. Accordingly, the rotary blade 52 and the fixed blade 40 cooperate with each other so that the paper strip 30 is cut widthwise from one end of the cut to the other end in the shearing mode by the spiral cutting edge 58 of the rotary blade 52. This permits the paper strip 30 to be cut into lengths without interruption of feeding of the paper strip 30. In plan view, the fixed blade 40 and the rotary blade 52 are disposed to be slightly inclined at an angle (α) with respect to a transverse line 62 normal to the feed direction of the paper strip 30. The angle (α) between the fixed and rotary blades 40 and 52 and the transverse line 62 substantially corresponds to the angle of twist of the helical cutting edge 58 of the rotary blade 52. Accordingly, the paper strip 30 can be cut along the transverse line 62 normal to the feed direction thereof in spite of the shearing mode. In addition, at least one of the fixed blade 40 and the rotary blade 52 is shorter than the width of the paper strip 30. In this embodiment, the fixed blade 40 is shorter than the width of the paper strip 30 while the rotary blade 52 is longer than the width of the paper strip 30. Accordingly, the paper strip 30 is partially cut widthwise while leaving opposite side portions uncut so that it remains continuous. In this rotary cutter, the fixed blade 40 has opposite surfaces 64 and 66 extending toward the cutting edge 42 thereof as shown in Fig. 4. One surface 64 comprises an inclined surface formed on the paper inlet side of the fixed blade 40 and disposed at an angle (β) less than 60 ° with respect to the paper strip 30. The angle (β) between the inclined surface 64 of the fixed blade 40 and the paper strip 30 is 45 ° . In this embodiment, the other surface 66 also comprises an inclined surface formed at the paper outlet side of the fixed blade 40 and disposed at an angle less than 90 ° with respect to the paper strip 30. The rotary blade 52 has opposite surfaces 68 and 70 extending toward the cutting edge 58 thereof. One surface 68 comprises an inclined surface formed on the rotary leading side of the rotary blade 52 and disposed at an angle (γ) less than 90 ° with respect to the paper strip 30. The angle (γ) between the inclined surface 68 of the rotary blade 52 and the paper strip 30 is 30° . The other surface 70 comprises a vertical surface formed on the rotary trailing side of the rotary blade 52 and disposed perpendicularly to the paper strip 30. Accordingly, when partially cutting the paper strip 30 widthwise while leaving opposite side portions uncut, the cut strip 30 moves along the inclined surface 64 of the fixed blade 40 to get over the fixed blade 40 without being caught thereon immediately after cutting as shown in Fig. 5. Unlike the paper strip 30 in the prior art shown in Fig. 7, the tears (b) are therefore hardly formed at the opposite ends of the cut (c). In addition, even if the rotary blade 52 rotates at a circumferential rate slightly higher than the feed rate of the paper strip 30, the cut strip 30 is pushed down by the inclined surface 68 of the rotary blade 52 so that the rotary blade 52 can slip over the cut strip 30 without catching it immediately after cutting. The cut strip 30 is not therefore pulled by the rotary blade 52. Accordingly, the tears (b) are not at all formed at the opposite ends of the cut (c).

Claims: A rotary cutter including a fixed blade (40) having a straight cutting edge (42), and a rotary blade (52) installed for rotation about an axis extending parallel to said cutting edge (42) of the fixed blade (40), said rotary blade (52) including helical cutting edge (58) moving along a path (60) which extends tangentially to said cutting edge (42) of the fixed blade (40), said fixed blade (40) having opposite surfaces (64, 66) extending toward said cutting edge (42) thereof, one of which comprises an inclined surface (64) formed on the paper inlet side of said fixed blade (40) and disposed at an angle (β) with respect to said paper strip (30), said rotary cutter being characterized in that: at least one of said fixed blade (40) and said rotary blade (52) is shorter than the width of a paper strip (30) so that said rotary blade (52) and said fixed blade (40) cooperate with each other to partially cut the paper strip (30) widthwise while leaving the side portions of the strip uncut; said angle (β) between said inclined surface (64) of the fixed blade (40) and said paper strip (30) is less than 60° whereby the cut strip (30) can pass over said fixed blade (40) without being caught thereon immediately after cutting; said path (60) extends tangentially to said paper strip (30); and said rotary blade (52) has opposite surfaces (68, 70) extending toward said cutting edge (58) thereof, one (68) of which, formed on the rotary leading side of said rotary blade (52), is inclined at an angle (τ) less than 90° with respect to said paper strip (30) whereby said rotary blade (52) can slip over the cut strip (30) without catching it immediately after cutting. A rotary cutter according to claim 1, wherein said angle (β) between said inclined surface (64) of the fixed blade (40) and said paper strip (30) is 45° and said angle (τ) between said inclined surface (68) of the rotary blade (52) and said paper strip (30) is 30°. A rotary cutter according to claim 2, wherein said fixed blade (40) and said rotary blade (52) are disposed to be slightly inclined at an angle (α) between said fixed and rotary blades (40, 52) and said transverse line (62) substantially corresponding to the angle of twist of the helical cutting edge (58) of said rotary blade (52) so that the paper strip (30) is cut along said transverse line (62) normal to the feed direction thereof.

Inventors: MYOGADANI SHIGEHARU, MYOGADANI, SHIGEHARU
Applicants: KANZAKI PAPER MFG CO LTD, KANZAKI PAPER MANUFACTURING CO., LTD.
Application year: 1989
Main classification: B26D1
IPC codes: B26D1, B26F1