ROTARY CUTTER FOR CUTTING A CONTINUOUS CORRUGATED STRIP

Abstract: A high speed rotary cutter (30) includes a toothed counterwheel (72) which has a plurality of radial slots (721) extending across the wheel. First cutting blades (88) are slidably received in the radial slots each of which has a first cutting edge (68) on its outer end. The first cutting edge (68) is inclined to the line which is perpendicular to the advancing direction of a continuous corrgated strip (90). The movement of the first cutting blade between protruding and a retracted positions is controlled by a fixed cam (78) which is located inside the toothed counterwheel. The rotary cutter also includes a second cutting blade (42) which has a second cutting edge (422) and is aligned relative to the first cutting blade (88) so that the continuous corrugated strip is sheared gradually across its width. The first and the second cutting blades (88,42) are biased to engage each other to cut the corrugated strip.

Description: The present invention relates to a rotary cutter for cutting a continuous corrugated strip into strip sections having variable lengths. More particularly, this invention is applicable to a rotary cutter for shearing a metallic corrugated strip into sections which are used as corrugated fins in the manufacture of automobile radiators. Certain types of automotive radiator cores include corrugated fins welded or soldered to water tubes. Corrugated fins are obtained by passing a continuous metallic strip between a pair of toothed forming rollers or wheels to form a continuous corrugated strip, which is then sheared by a cutting machine into sections having a desired length. For the manufacture of radiators on a mass production basis, it is desirable for a cutting machine to operate at as high a speed as possible to shear a corrugated strip discharged continuously and at a high speed from the forming rollers. Another requirement for cutting machine is the capability of shearing the corrugated strip into a desired length, which may vary depending upon the size of the radiator cores to be manufactured. A further requirement is to cut the corrugated strip precisely at a desired shearing point in order to obtain a series of strip sections having a uniform length. U.S. Pat. No. 4,685,318 issued to Ueda et al. illustrates an example of a conventional cutting apparatus. This type of apparatus called rotary cutter and has a toothed wheel and a rotary drum that are rotated in synchronization with each other. A fixed cutter blade is disposed in the toothed wheel and a movable cutter blade is disposed in the rotary drum. The continuous corrugated fin passes through between the toothed wheel and rotary drum and is sheared to a predetermined length by pushing the movable cutter blade towards the fixed cutter blade wich a guillotine movement. In this conventional apparatus, it is required that both cutter blades are shaped and assembled accurately because both cutter blades are engaged at one point at which the outer circles of the toothed wheel and the rotary drum contact each other. Therefore, the conventional apparatus has a high production cost. The other problem is that the edges of the cutter blades wear away in a short period because each edge of the cutter blades engages with the other at a high speed. The worn edge causes the cutting condition of the cutters to worsen. A further problem is that the guillotine type cutter is capable of cutting corrugated fins made of low-ductility materials such as aluminum but is not capable of cutting fins made of high-ductility materials such as copper, thin corrugated fins, or wide corrugated fins. According to the present invention, there is provided a rotary cutter for cutting a continuous corrugated strip comprising: a frame; a toothed counterwheel rotatably supported on the frame and having at least one radial slot extending in the axial direction of the wheel; a first cutting blade having a first cutting edge, the first cutting blade being received in the respective radial slot; a second cutting blade having a second cutting edge for contacting the first cutting edge; and first biasing means for biasing the second cutting blade towards a cutting position at which the first cutting edge may shear the continuous corrugated strip in cooperation with the second cutting edge; characterized in that: the first cutting blade is slidably received in the respective radial slot in such a manner that the first cutting blade is movable between a retracted position at which the first cutting edge is substantially retracted into the radial slot and a protruding position at which the first cutting edge projects radially outwards from the radial slot; the rotary cutter further comprises second biasing means for biasing the first cutting edge towards the retracted position and the protruding position; the first and second cutting edges are arranged to shear the continuous corrugated strip when the first cutting edge is in its protruding position and the second cutting edge is in its cutting position; and at least one of the first cutting edge and the second cutting edge is inclined relative to a line which is perpendicular to the direction of movement of the continuous corrugated strip at the cutting location so that a contact point between the first cutting edge and the second cutting edge moves along the cutting edges and hence across the continuous corrugated strip. The continuous corrugated fin is not sheared across its full width simultaneously by hitting the first cutting blade against the second cutting blade, but is sheared gradually from one side to the other side of the fin. Therefore, the high accuracy of assembling the first cutting blade and the second blade is not required and the manufacturing cost of the apparatus is less than that of the conventional apparatus. The continuous corrugated fin is sheared easily even if it is thin or wide or is made of high-ductility material. The wearing of the edges of the cutting blades of the present invention is kept low compared with the conventional guillotine type cutter because there is no hitting of the first edge against the second edge. The invention will now be described by way of non-limiting embodiments with reference to the accompanying drawings, in which: Fig. 1 is a schematic perspective view illustrating the essential parts of a corrugated fin manufacturing apparatus incorporating the rotary cutter according to the present invention as combined with a corrugation forming station; Fig. 2 is a front elevation view of the apparatus shown in Fig. 1; Fig. 3 is a sectional view along with III-III line of Fig. 2; Fig. 4 is a front elevation view illustrating the essential parts of the apparatus shown in Figs. 1 - 3; Fig. 5 is an enlarged perspective view of the first cutting blade and the second cutting blade; Fig. 6 is an enlarged perspective view illustrating the corrugated fin in a shearing condition; Fig. 7 is a plane view of the first cutting blade; Fig. 8 is a sectional view showing the other embodiment of the invention; and Fig. 9 is an enlarged perspective view illustrating the pin wheel shown in Fig. 8. Fig. 1 is schematic perspective view showing the essential parts of the corrugated fin manufacturing apparatus including the rotary cutter and Fig. 2 is a front view of the apparatus shown in Fig. 1. A thin flat strip 20 made of cupper alloy advances from a source of supply (not shown) through between a pair of toothed forming wheels 10 and 12. A plurality of teeth are formed on the outer surface of the forming wheels 10 and 12. The drive force is given to the forming wheel 10 and transmitted to the forming wheel 12 through a gear wheel mechanism (not shown). The forming wheel 10 and the forming wheel 12 rotate synchronously in engagement with each other. The thin strip 20 advances into the engaging point of the wheels 10 and 12 so that the strip 20 is formed into the corrugated shape. The corrugated strip ( the corrugated fin) is conveyed to a cutting apparatus 30 by the feed wheel 24. The feed wheel 24 has teeth on the outer surface thereof and rotates synchronously with the forming wheels 10 and 12 by receiving the drive force from AC motor 16 via a gear mechanism. A guide plate 22 for guiding a corrugated fin 90 from the forming wheels 10 and 12 to the feed wheel 24 is disposed between the forming wheels 10 and 12 and the feed wheel 24, and a guide plate 26 for guiding the corrugated fin 90 towards the cutting apparatus 30 is disposed below the feed wheel 24 in order to maintain the engagement of the corrugated fin 90 with the feed wheel 24. The cutting apparatus 30 is described in detail hereinbelow. Fig. 3 is a sectional view taken along III-III line of Fig. 2, Fig. 4 is a front view illustrating the essential parts of the cutting apparatus 30. A toothed counterwheel 72 has a plurality of (twenty five) tooth portions 72a on its outersurface and engages with the feed wheel 24. The toothed counterwheel 72 is supported by a bearing 150 on a frame 40 of the cutting apparatus 30, and receives a driving force from the AC motor 16 through a gear mechanism (not shown). A rotary-encoder 74 is connected with a shaft 76 of the toothed counterwheel 72 for generating pulse signals in accordance with the rotation of the toothed counterwheel 72. The toothed counterwheel 72 is like a doughnut shape having an inner space therein, and five slits are formed in the counterwheel in such a manner that they open onto the summit of every fifth tooth portion 72a. Plate shaped first cutting blades 88 reciprocate in the slits. Two guide slits 724 having a certain depth for receiving a guide member 96 are formed on the outer surface of the toothed counterwheel 72. The first cutting blades 88 have a first cutting edge 68 at the outer edge portion. Fig. 7 is a plan view of the first cutting blade 88 looking from the first edge 68 side. Fig. 5 is a perspective view of the first cutting blade 88 and a second cutting blade 42 (described later). As shown from these figures, the first cutting edge 68 is not at right angles to the advancing direction of the corrugated fin 90, and the same makes a certain angle (2° in this embodiment) relative to the perpendicular to the advancing direction. Non-cutter portions 64 are formed on the both side of the first cutting edge. The inner side portion of the first cutting blade 88 is shaped like a letter "U" so that an inner space in which a cylindrical roller 84 is provided is formed. The roller 84 is supported and a cylindrical roller 86 is supported at the outside of the first cutting blade 88 by the pin 82. A fixed cam 70 is provided in the inner space 722 of the toothed counterwheel 72. The fixed cam 70reciprocates the first cutting blade 88 between a projecting position when the first cutting edge 68 protrudes from the slit 721 and a returning position when the first cutting edge 68 is sunk into the slit 721. A shaft 78 on which the fixed cam 70 is provided is supported by a bearing 152 which is mounted on the inner surface of the toothed counterwheel 72. The fixed cam 70 and the toothed counterwheel 72 are able to rotate relative to each other. The fixed cam 72 has an outer profile 70a and an inner profile 70b. The inner roller 84 engages with the outer profile 70a for moving the first cutting blade 88 to the projecting position at the predetermined rotating position of the toothed counter wheel 72. The outside roller 86 engages with the inner profile 70b for moving the first cutting blade 88 to the returning position. The predetermined rotating position of the toothed counterwheel 72 for the projecting position of the first cutting blade 88 is varied in accordance with the desired cutting length of the corrugated fin. The second cutting blade 42 is disposed at the outer side of the toothed counter wheel 72 in such a manner that the second cutting blade 42 shears the corrugated fin 90 with the first cutting blade 88 when the first cutting blade 88 comes to the projecting position. The cylindrical second cutting blade 42 has a flat portion on the outersurface thereof as shown in Fig. 5 and the edge of the flat portion forms a second cutting edge 422. The second cutting edge 422 is at right angles to the advancing direction of the corrugated fin 90 and the same forms certain angles with the first cutting edge 68. The second cutting blade 42 is supported by a pin 44 which is held between two confronting legs 481 of a cutter holder 48 confronting with each other. Two projecting walls 482 confronting with each other are formed on the upper surface of the cutter holder 48. The roller 52 is rotatably supported by a pin 50 which is held between two projecting walls 482. The second cutting blade 42 has a holding hole 424 on the upper surface thereof and the cutter holder 48 has a holding hole 484 coaxially with the hole 424. A square pin 46 prevents rotation of the second cutting blade 42. A rotational cam 54 having a cam-nose 62 is engaged with the roller 52. A shaft 56 of the rotational cam 54 is rotatably supported by bearings 154, 156, 157 which is mounted on the stay 32, and the shaft 56 is connected with a A.C. servo-motor 58. The rotational cam 54 rotates by receiving the driving force from the A.C. servo-motor 58. The second cutting edge 42 supported on the cutter holder 48 is forced toward the first cutting edge when the cam-nose 62 is engaged with the roller 52. The projecting amount of the cam-nose 62 is so designed that the first cutting edge 68 can confront with the second cutting edge 422 with no substantial clearance therebetween. The first cutting blade 88 and the second cutting blade 42 are assembled to slightly overlap each other, absorbing structural deformation of the cutting apparatus 30 while the apparatus 30 is cutting the corrugated fin 90. If the amount of overlapping is not enough, the first cutting edge 68 and the second cutting edge 422 would hit each other and abrasion both cutting edges 68 and 422 would be caused. Since the non-cutter portions 64 formed at the both sides of the first cutting edge 68 contact with cylindrical portions of the second cutting blade 42 formed at the both sides of the second cutting edge 422 initially in the cutting operation, both cutting edge 68 and 64 are prevented from hitting each other. The arch shaped stay 32 is supported on a frame 40 as shown in Figs. 1, 2 and 3. The rotational cam 54, the roller 52 and other parts are arranged in the stay 32. Two shafts 34 and 34 are held in the stay 32 in such a manner that the shafts reciprocate vertically. One end of each shaft 34 is connected with the cutter holder 48, and the other end of each shaft 34 is connected with a spring holder 38. The second cutting blade fixed on the cutter holder 48 is biassed to move apart from the first cutting blade 88 by a spring 36 which is disposed between the spring holder 38 and the upper surface of the stay 32. Guide members 28 and 92 for guiding the corrugated fin 90 to engage with the teeth 72a of the toothed counter wheel 72 are disposed at the outer periphery of the toothed counter wheel 72 and at both sides of the second cutting blade 42. The corrugated fins 90 sheared to a predetermined length by the cutting apparatus 30 are conveyed towards a chute 104 by a feed wheel 94 and a pair of feed wheels 100 and 102. The shape of the feed wheel 94 is same as that of the feed wheel 24. The feed wheels 100 and 102 rotate synchronously to feed the corrugated fin 90. The corrugated fin 90 which has been slightly deformed by previous stages is also reshaped as the corrugated fin 90 passes through the wheels 100 and 102. The chute 104 has a U-shaped groove through which the corrugated fin 90 is conveyed to an assembling stage of a radiator (not shown). The operation of the manufacturing apparatus is described hereinafter. The strip 20 fed from the source of supply is advanced through a pair of the toothed counter wheel 10 and 12 so that the shape of waves are formed in strip 20. The waved strip 20, that is the corrugated fin 90, is advanced by engaging with the under teeth of the feed wheel 24 and the toothed counter wheel 72 of the cutting apparatus 30. The toothed counter wheel 72 is rotated by receiving the rotary power from the A.C. motor 16 synchronized with the other wheels. The first cutting blade 88 disposed in the slit 721 is urged to project from the slit 721 by the outer profile 70a of the fixed cam 70 when the toothed counter wheel 72 rotates, and the first cutting blade 88 is urged to retract into the slit 721 by the inner profile of the fixed cam 70 as the toothed counter wheel 72 rotates. The rotation of the toothed counter wheel 72 is detected by the rotary encoder 74, and the rotational cam 54 is rotated in synchronized relationship with the toothed counter wheel 72 by an A.C. servo-motor 58 which is controlled by the detected signal of the rotary encoder 74. When the corrugated fin 90 is not required to be sheared, the cam-nose 62 does not contact with the outerface of the roller 52 so that the second cutting blade 42 is prevented from engaging with the first cutting blade 88. When the corrugated fin 90 is to be sheared, the speed of the rotation of the rotational cam 54 is accelerated or decelerated in order for the cam-nose 62 to engage with the outer surface of the roller 52, so that the second cutting blade 42 is moved downwardly towards the first cutting blade 88 to be in contact with that blade. The first cutting edge 68 contacts with the second cutting edge 42 to produce substantially no clearance therebetween when the corrugated fin 90 is located at the contact point. Since the first cutting blade 88 is rotated with the toothed counter wheel 72, the contact point of the first cutting edge 68 and the second cutting edge 422 moves from one side of the cutting edges to the other side and therefore the shearing point also moves from the one side of the corrugated fin 90 to the other side of the same. As a result, the shearing of the whole corrugated fin 90 is completed. The second cutting blade 42 is kept in its downward position at least while the contact point of the cutting edges moves from the one side to the other side thereof. Fig. 6 shows how the corrugated fin 90 is sheared on the first cutting blade 80. It is recognized that the shearing point moves from the one side 90a of the corrugated fin 90 to the other side 90b of the same. The sheared corrugated fin as described above is conveyed to the next stage by the feed wheel 94, the feed wheels 100 and 102 and the chute 104. The guide member 96 inserted into the guide slit 724 of the toothed counter wheel 72 guides the corrugated fin 90 for transmitting the same from the toothed counter wheel 72 to the feed wheel 94. The guide member 96 prevents the sheared corrugated fin 90 from failing to be transmitted and also from being engaged with the under teeth of the toothed counter wheel 72. Even though the guide member 96 is inserted into the guide slit 724 of the toothed counter wheel 72, the guide member 96 and the first cutting blade 88 do not interfere with each other because the first cutting blade 88 is restored into the slit 721 except during shearing of the corrugated fin 90. The second embodiment is described herein below. In the second embodiment of Fig. 8, the rotary cutter further includes a pin wheel 112 which has plural holding pins for preventing the sheared edge of the corrugated fin from lifting off from the teeth 72a of the toothed counter wheel. As shown in Fig. 9, the pin wheel 112 comprises a disk plate 112a and plural holding pins 112b which extend from the surface of the disk plate 112a, and the wheel 112 is rotatably supported at both sides of the cutter holder 48 by a pin 114 in such a manner that the holding pins 112b hold the corrugated fin 90 prior to shearing. A small gear 122 on the side surface of the disk plate 112a is engaged with a large gear 124 fixed on the side surface of the toothed counter wheel 72. The rotating force of the toothed counter wheel 72 is transmitted to the pin wheel 112 through the large gear 124 and the small gear 122, so that the toothed counter wheel 72 and the pin wheel 112 rotate together. The sheared edge 901 of the corrugated fin 90 is held on the tooth 72a of the toothed counter wheel 72 from just before the corrugated fin 90 is sheared to just after the same is sheared. Therefore, the sheared edge 901 of the corrugated fin 90 is prevented from lifting off from the toothed counter wheel 72, and the corrugated fin 90 is well transmitted to the next stage without fail. The second cutting blade 42 of the second embodiment is a cylinder which has smaller diameter than that of the first embodiment, and the same is fixed on the cutter holder 48 by a key pin 44. The remaining construction and operation of the second embodiment is as for the first embodiment. While the present invention has been described with reference to a specific embodiment thereof, it should be understood that the invention is not limited to only the rotary cutter of corrugated fin used for an automobile but also the rotary cutter of a continuous corrugated strip used for other heat exchangers.

Claims: 1. A rotary cutter (30) for cutting a continuous corrugated strip (90) comprising: a frame (40); a toothed counterwheel (72) rotatably supported on the frame (40) and having at least one radial slot (721) extending in the axial direction of the wheel; a first cutting blade (88) having a first cutting edge (68), the first cutting blade (88) being received in the respective radial slot (721); a second cutting blade (42) having a second cutting edge (422) for contacting the first cutting edge (68); and first biasing means (54) for biasing the second cutting blade (42) towards a cutting position at which the first cutting edge (68) may shear the continuous corrugated strip (90) in cooperation with the second cutting edge (422); characterized in that: the first cutting blade (88) is slidably received in the respective radial slot (721) in such a manner that the first cutting blade (88) is movable between a retracted position at which the first cutting edge (68) is substantially retracted into the radial slot (721) and a protruding position at which the first cutting edge (68) projects radially outwards from the radial slot (721); the rotary cutter (30) further comprises second biasing means (70) for biasing the first cutting edge (68) towards the retracted position and the protruding position; the first and second cutting edges (68, 422) are arranged to shear the continuous corrugated strip (90) when the first cutting edge (68) is in its protruding position and the second cutting edge (422) is in its cutting position; and at least one of the first cutting edge (68) and the second cutting edge (422) is inclined relative to a line which is perpendicular to the direction of movement of the continuous corrugated strip (90) at the cutting location so that a contact point between the first cutting edge (68) and the second cutting edge (422) moves along the cutting edges and hence across the continuous corrugated strip (90). 2. A rotary cutter (30) according to claim 1, further comprising holding pins (112b) for holding an end (901) of the continuous corrugated strip (90) sheared by the first cutting edge (68) and the second cutting edge (422) on teeth (72a) of the toothed counterwheel (72) in order to retain the sheared continous corrugated strip on the toothed counterwheel. 3. A rotary cutter (30) according to claim 1 or claim 2, wherein the second biasing means (70) comprises a fixed cam (70) which is engaged with an inner end (84) of the first cutting blade (88). 4. A rotary cutter (30) according to any one of claims 1 to 3, wherein the first biasing means (54) comprises a rotatable cam (54) which is engaged with an inner end (52) of the second cutting blade (42). 5. A rotary cutter (30) according to any one of claims 1 to 4, further comprising rotating means for rotating the toothed counterwheel (72). 6. A rotary cutter (30) according to claim 5, wherein the rotating means is an electric motor. 7. A rotary cutter (30) according to any one of claims 1 to 6, wherein the toothed counterwheel (72) has a circumferential guide slit (724), and the rotary cutter (30) further comprises a guide member (96) extending into the guide slit (724) for lifting the continuous corrugated strip (90) off the counterwheel (72) after shearing by the first and second cutting blades (88,42).

Inventors: HARA, YOSHIHIRO, IWASE, TAKATOSHI
Applicants: NIPPONDENSO CO., LTD.
Application year: 1989
Main classification: B21D13
IPC codes: B21D43, B21D13, B26D5, B26D1