Cutter system of a strand cutting machine

Abstract: A cutter assembly of a strand cutting machine comprises a fixed cutter member (1), over which the strand is to be drawn after being cooled and dewatered, and a rotary cutter member (2) coactive with said fixed cutter member (1) to cut a strand of resin into pellets. The rotary cutter member (2) includes i) a cylindrical rotary body having a forward side surface (3a) parallel to a supply-side end surface (1a) of the fixed cutter member (1), ii) a rotary shaft (4) extending perpendicularly to the supply-side end surface of the fixed cutter member and supporting thereon the rotary body, and iii) a plurality of blades (6) mounted on the rotary body (2) in a forward inclined posture in the direction of rotation. The rotary body (2) has a plurality of through-holes (5) arranged at regular distances along a circle concentric with the rotary body, each through-hole (5) extending between opposite surfaces. Each blade (6) is attached to an inside surface of the respective through-hole (5) and has at its end a cutting edge.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a cutter assembly of a strand cutting machine in which a strand of resin is cut by a fixed cutter member and a rotary cutter member as the strand is supplied to the fixed cutter member. This invention relates also to a resin material cutting assembly. 2. Description of the Related Art In a conventional strand cutting machine, a strand of cooled and dewatered resin is drawn over a fixed cutter member and is then cut into pellets as the fixed cutter member coacts with a rotary cutter member. As shown in FIG. 19 and 20 of the accompanying drawings, the rotary cutter member 2 is mounted on a rotary shaft 4a parallel to a supply-side end surface 1a of the fixed cutter member 1, and the rotary cutter member 2 has along its outer periphery a sawtoothed blade assembly with a plurality of cutting edges 2a each having an inner surface at an angle () of about 20 degrees. However, in such conventional technology, when a strand is cut by the rotary cutter member, the thus cut pellets can become jammed between the teeth of the sawtoothed blade assembly so that they get carried around, as the sawtoothed blade assembly makes a complete rotation, and hence are recut into smaller pellets which are not of standard size or they can be discharged from a portion other than a predetermined discharge position, thus making such portion dirty. Further, with this conventional technology, when the blade is worn out, the whole rotary cutter member must be removed and polished, which is laborious and time-consuming; if it is polished repeatedly, the rotary cutter member must be exchanged with a new one, which is expensive. Moreover, with this conventional technology, since a strand is cut by being smashed by the rotary cutter member, the cut ends of individual pellets have fine white splits, which gives them an unsightly appearance, so that the quality of pellets is lowered. Also, a considerably large sound is produced during cutting, thus causing noise pollution. Still further, a device, corresponding to the features of the preamble of claim 1 and disclosed in U.S.-A-4340342, comprises a conduit for supplying cooling water for cooling a warm resin, a pair of rollers for delivering the resin cooled by the water to a cutting device, and a cutting device for cutting the delivered resin. The cutting device comprises a rotary cutter member and a fixed cutter member. Similarly to the aforementioned prior art, the rotary cutter member has a rotary shaft extending in parallel to a supply-side end face of the fixed cutter, in other words, perpendicularly to a direction in which the resin is to be supplied. The construction of this device is substantially the same as that of the device shown in figure 19, therefore this device has the same problem as the device in figure 19. In addition, US-A-4251198 discloses a device which cuts resin just after the resin has been extruded from the extruder while the resin is still warm. The device comprises a rotary cutter member having a hub body and blades fixed to the hub body, and a shaft for the hub body. The shaft of the hub body is provided in parallel to the resin feeding direction. This is different from the aforementioned two references. As warm and soft is cut by the device, the cut cross section cannot be smooth. If this device is used for cutting resin which has been cooled and hardened, the pellets generated by cutting the cooled resin will scatter around radially and cannot be delivered to a desired or predetermined place. Although not directly relevant to the present invention. DE-U-8715410 and EP-A-0242313 also disclose a cutter, which, however, is for cutting edible root vegetables. SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a cutter system of a strand cutting machine for cutting a strand of resin into neat, good-quality pellets of standard size without making nearby areas dirty and with less noise and which enables a reduction in the cost of polishing the blade of a rotary cutter member, and which is for use in combination with an extruder. According to the invention, there is provided a cutter system as claimed in claim 1. Preferably, both forward and rear inside surfaces, as viewed in the direction of rotation, of each through-hole are inclined at an angle (α) of 35 to 60 degrees with respect to the front surface of the rotary body. Further, each blade may have on a side toward the cutting edge a V-shaped end assuming an angle (β) of 30 to 50 degrees and projecting beyond the front surface of the rotary body. Each blade may be adjustably mounted on the rotary body so as to be adjusted towards and away from the front surface of the rotary body. With the cutter system of the invention, a strand of cooled and dewatered resin is supplied over the fixed cutter member whereupon the rotary cutter member is rotated on the rotary shaft with the side surface of the rotary cutter member being parallel to the supply-side end surface of the fixed cutter member. As a result, by the forwardly inclined blade of the rotary cutter member, the strand is cut into pellets smoothly so as to have a cut surface parallel to the plane of rotation of the rotary cutter member. Therefore, it is possible to cut a strand of even soft resin into pellets effectively and accurately so that the pellets can flow through a hole smoothly and can hence be discharged to a predetermined discharge position precisely and orderly. In the case where the individual blades are detachably mounted, when a part of the blades is worn out, it is only necessary to exchange the worn blade with a new one. Also when any blade is damaged such as by a piece of metal accidentally entering between the cutter members during cutting, only the worn blade needs to be exchanged with a new one. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary cross-sectional view showing a cutter assembly of a strand cutting machine according to a first embodiment of this invention; FIG. 2 is a side view showing a part of a pellet manufacturing apparatus according to the first embodiment; FIG. 3 is a front view showing a rotary cutter member according to the first embodiment: FIG. 4 is a cross-sectional view of a part of the rotary cutter member of FIG. 3; FIG. 5 is a plan view showing a blade according to the first embodiment; FIG. 6 is a side view of the blade of FIG. 5; FIG. 7 is a front view of a rotary cutter member according to a second embodiment; FIG. 8 is a cross-sectional view of the rotary cutter member of FIG. 7; FIG. 9 is a cross-sectional view showing a rotary cutter member according to a third embodiment; FIG. 10 is a front view showing a rotary cutter member according to a fourth embodiment; FIG. 11 is a rear view of the rotary cutter member of FIG. 10; FIG. 12 is a cross-sectional view of the rotary cutter member of FIG. 10 ; FIG. 13 is a front view showing a rotary cutter member according to a fifth embodiment; FIG. 14 is a cross-sectional view of the rotary cutter member of FIG. 13; FIG. 15 is a side view showing a blade according to a sixth embodiment; FIG. 16 is a side view showing a blade according to an seventh embodiment; FIG. 17 is a fragmentary cross-sectional view showing a cutter assembly of a strand cutting machine according to a eighth embodiment; and FIG. 18 is a side view showing a conventional rotary cutter member. FIG. 19 is a side elevation view of a conventional rotary cutter member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of this invention will now be described with reference to the accompanying drawings. FIGS. 1 through 6 show a cutter assembly of a strand cutting machine for a pellet manufacturing apparatus, according to a first embodiment. As shown in FIG. 2, the pellet manufacturing apparatus includes an extruder having a screw 12 received in a cylinder 10 and adapted to be driven by a motor 11. The cylinder 10 has a feed hole 7 into which a starting material is to be introduced, a vent hole 8, a heater 9, etc. The pellet manufacturing apparatus causes a strand A of resin in a melted form to flow from a die head 13 at the distal end of the extruder into a water tank 14 in order to cool the strand A whereupon the strand A drawn out from the water tank 14 is dewatered by a suction-type dewatering unit 15 and is then drawn over the upper surface of a fixed cutter member 1 (described below) by a pair of feed rollers 16. The cutter assembly comprises the fixed cutter member 1 and a rotary cutter member 2 disposed in confronting relation thereto; the strand A of resin is taken from the upstream source over the fixed cutter member 1 and is then cut at a position downstream of the fixed cutter member 1 by the rotary cutter member 2 which is rotated about a rotary shaft 4. The fixed cutter member 1 can be horizontally adjusted toward and away from the rotary cutter member 2 by an adjuster. The rotary shaft 4 is inserted perpendicularly to and centrally through the rotary cutter member 2 and is secured thereto, extending in the direction of travel of the strand A and being supported by a metal plate 18. Further, the rotary shaft 4 is operatively connected to a motor 19 via a continuous belt 20. Under the rotary cutter member 2, a pellet fall passageway 21 is provided. Under the pellet fall passageway 21, a bellows 22 and an air blower 23 are provided. As shown in FIG. 3, the rotary cutter member 2 includes a multiplicity of blades 6 attached on a cylindrical rotary body 3. The cylindrical rotary body 3 has a center portion 31, a ring portion 32 formed in a ring configuration around the center portion 31 and a plurality of blade support portions 33 (fig. 3). The center portion 31 is mounted on the rotary shaft 4 in such a manner that a front side surface 3a of the rotary body 3 is parallel to the supply-side end surface 1a of the fixed cutter member 1. The blade support portions 33 link the center portion 31 and the ring portion 32 in such a manner that a a plurality of through-holes 5 may be formed between the center portion 31 and the ring portion 32. The rotary body 3 has a plurality of through-holes 5 at regular distances along a concentric circle, each through-hole 5 extending through the rotary body 3 between front and rear side surfaces 3a, 3b thereof. As shown in FIG. 4, forward and rear (in the direction of rotation) inside surfaces 5b, 5a of each through-hole 5 are forwardly inclined by an angle α of 35 to 60 degrees with respect to the front side surface 3a of the rotary body 3. The rotary body 3 also has four threaded holes 24 per blade 6 each extending from the forward inside surface 5a to the rear inside surface 5b. Each blade 6 extends radially from the center of the rotary body 3 and is forwardly inclined with respect to the forward inside surface 5a, thus slanting from the upstream side toward the downstream side in the direction of rotation. Each blade 6 has an end, i.e., a cutting edge 6a at a forward (in the direction of rotation) position toward the fixed cutter member 1. The angle β of a V-shaped end 6b on the side of the cutting edge 6a is 30 to 50 degrees, as shown in FIG. 6. As shown in FIG. 5, each blade 6 has four slots 26 through which a screw 25 is to be inserted. The blade 6 is adjustably attached to the forward inside surface 5a of the rotary body 3 in such a manner that its end 6b projects beyond the front side surface 3a of the rotary body 3 and is adjustable with respect to the front side surface 3a. The operation of the strand cutting machine will now be described. In FIG. 1, while the rotary cutter member 2 is rotating in the direction of arrow a (FIG. 3), a strand A of resin or even soft resin cooled and dewatered is drawn in the direction of arrow b over the fixed cutter member 1 by the coacting feed rollers 16, 16. The rotary cutter member 2 is rotated about the rotary shaft 4 with the side surface 3a of the rotary body 3 in parallel to the supply-side end surface 1a of the fixed cutter member 1. The strand A is cut into pellets smoothly, by the end 6b of the forwardly inclined individual blade 6 of the rotary body 3, and in such a manner that the cut surface is parallel to the plane of rotation. Therefore it is possible to cut a strand of even soft resin into pellets effectively and accurately so that the pellets can flow through the forwardly inclined through-hole 5 smoothly and hence can be discharged to a predetermined discharge position, i.e., the pellet fall passageway 21 underneath precisely and orderly. Further, the lower limit of projection of the end 6b of the blade 6 can be adjusted by loosing the individual screws 25 and then moving the blade 6 forwards or backwards. If a part of the cutting edge is worn out, or if a part of the cutting edge 6a is broken by a metal piece accidentally entering between the two cutter members 1. 2. it is only necessary for the worn blade to be exchanged with a new one, thus saving labor and production costs. FIGS. 7 and 8 show a modified rotary cutter member 30 according to a second embodiment. Like reference numerals designate parts or elements similar to those of the first embodiment; any repetition of description is omitted here for clarity. As shown in FIG. 7, the rotary cutter member 30 includes a central portion 31, a ring portion 32, a plurality of support portions 33, and a plurality of blades 34. The central portion 31 is made up of a disk fixed perpendicularly to a rotary shaft 4 of the rotary cutter member 30 at a central hole 31a. The ring portion 32 is concentric with the central portion 31 and is spaced radially therefrom. Each blade 34 is integral with the central portion 31, extending radially from the central portion 31 to the ring portion 32. Each blade 34 is fastened to the ring portion 32 by two screws 35b, connecting the ring portion 32 with the central portion 31. As shown in FIG. 8, each blade 34 is placed over and secured to the respective support portion 33 by four screws 35a extending through four slots 34a. Each support portion 33 and the respective blade 34 defines therebetween a through-hole 34a on the forward side in the direction of rotation as indicated by arrow c and is located between the central portion 31 and the ring portion 32. Each blade 34 slants from its rear surface to its front surface in the direction of rotation, having a cutting edge 34b on the forward position (in the direction or rotation) toward the fixed cutter member 1. FIG. 9 shows a third embodiment in which the individual blade 34 is attached in a different way. Like reference numerals designate parts or elements similar to those of the second embodiment; any repetition of description is omitted here for clarity. As shown in FIG. 9, each cutting edge 34b of the rotary cutter member 30a is fixed to the respective blade 34 by welding. Each cutting edge 34b is made of an ultrahard alloy. FIGS. 10 through 12 show still another modified rotary cutter member 50 according to a fourth embodiment. Like reference numerals designate parts or elements similar to those of the first embodiment; any repetition of description is omitted here for clarity. As shown in FIGS. 10 through 12, the rotary cutter member 50 includes a central portion 51, a ring portion 52, a plurality of support portions 53 and a plurality of blades 54. The central portion 51 is fixed perpendicularly to a rotary shaft 4 of the rotary cutter member 50, the rotary shaft 4 being inserted through a central hole 51a of the central portion 51. The ring portion 52 is concentric with the central portion 51 and is spaced radially therefrom. Each support portion 53 is integral with both the central portion 51 and the ring portion 52 and extends radially therebetween, connecting the central portion 51 with the ring portion 52. The outer surface of the central portion 51 and the inner surface of the ring portion 52 have at their confronting positions a plurality of grooves 55a, 55b slanting from the downstream side to the upstream side in the direction of rotation. Each blade 54 is at either end 54a fitted in to the corresponding grooves 55a, 55b of the central portion 51 and the ring portion 52, respectively. FIGS. 13 and 14 show a further modified rotary cutter member 60 according to a fifth embodiment. Like reference numerals designate parts or elements similar to those of the first embodiment; any repetition of description is omitted here for clarity. As shown in FIG. 13, the rotary cutter member 60 is a monoblock casting with opposite surfaces in symmetry. Each blade 61 has a pair of cutting edges 61a one on each side of the blade 61 so that when the rotary cutter member 60 is mounted on the rotary shaft 4 in an inverted posture, one of the cutting edges 61a is located at the forward position toward the fixed cutter member 1 in the direction of rotation. FIG. 15 shows a modified blade 71 according to a sixth embodiment. Like reference numerals designate parts or elements similar to those of the first embodiment; any repetition of description is omitted here for clarity. As shown in FIG. 15 the blade 71 has a groove 72 in a cutting edge 71a. The groove 72 has an arcuate surface and extends parallel to the cutting portion 71b, serving to assist in removing cut material from the blade 71. FIG. 16 shows another modified blade 81 according to an seventh embodiment. Like reference numerals designate parts or elements similar to those of the first embodiment; any repetition of description is omitted here for clarity. As shown in FIG. 18, the blade 81 has in a cutting edge 81a a groove 82 of V-shaped cross section. FIGS. 17 and 18 show a resin material supply unit according to a eighth embodiment. Like reference numerals designate parts or elements similar to those of the first embodiment; any repetition of description is omitted here for clarity. As shown in FIG. 17 upstream of the coacting feed rollers 16, 16 and at a midpoint in the supply of resin material B to the fixed cutter member 1, a feed block 91 is located. As shown in FIG. 18, the feed block 91 has on its upper surface a plurality of cutting portions 92. The cutting portions 92 are arranged spaced apart and have ripping edges 92a on and along the upstream side in the direction of the supply of resin material B. This embodiment is suitable for cutting resin material B such as a continuous length of scrap sheet of polyvinyl chloride. As shown in FIG. 18, when it is fed on the feed block 91 to the downstream side, the resin material B is shredded in the feed direction by the cutting portions 92, whereupon the individually ripped strips of resin material B are further cut by the fixed cutter member 1 and the rotary cutter member 2. In each of the foregoing embodiments, the number of blades of the rotary cutter member should by no means be limited to the illustrated examples and may be any other number which is more than one. With the cutter assembly and the resin material cutting assembly according to this invention, since the resin material is cut smoothly so as to have a cut surface parallel to the plane of rotation, the resin material can be cut into good-quality neat pellets of standard size without making nearby areas dirty and with less noise. In the case that the individual blades are adjustably attached, it is possible to displace the cutting portion from the wearing position, thus reducing the cost of polishing the blades of the rotary cutter member.

Claims: A cutter system of a strand cutting machine for cutting a strand of resin into pellets, which is for use in combination with an extruder, comprising : (a) a water tank (14), for cooling said strand extruded from said extruder ; (b) dewatering means (15) for dewatering a wet strand delivered from said water tank (14) ; (c) a cutter assembly comprising a fixed cutter member (1) over which the strand is to be drawn after being cooled and dewatered ; and a rotary cutter member (2) coacting with said fixed cutter member (1) ; (d) a pair of feed rollers (16), for introducing said strand, which has been cooled in the water tank (14) and dewatered in said dewatering means (15), into said cutter assembly ; characterized in that said rotary cutter member includes i) a cylindrical rotary body (3) having a front side surface (3a) parallel to a supply-side end surface (1a) of said fixed cutter member (1), a center portion (31), a ring portion (32) formed in a ring configuration and a plurality of blade support portions (33) linking the center portion (31) and the ring portion in a manner that a plurality of through-holes (5), arranged at regular distances around a circle concentric with said rotary body (3) and each extending between opposite surfaces (5a, 5b), may be formed between the center portion (31) and the ring portion (32), wherein both forward and rear surfaces (5a, 5b) of each of the support portions (33), as viewed in the direction of rotation and located radially between the center and the ring portions (31, 32), are inclined with respect to the front surface (3a) of the rotary body (3), ii) a rotary shaft (4) extending perpendicularly to the supply-side end surface (1a) of said fixed cutter member (1), mounted on the center portion (31) of said rotary body (3) and thus supporting it, said ring portion of said rotary body (3) being concentric with said shaft (4), and iii) a plurality of blades (6) supported respectively by said blade support portions (33) of said rotary body (3) and mounted thereon in a forward inclined posture in the direction of rotation, each blade (6) being attached to the forward surface (5a) of the respective through-hole (5) and having at its end a cutting edge (6a), protruding from the front surface (3a) of the rotary body (3). A cutter system according to claim 1, wherein both forward and rear inside surfaces (5a, 5b), as viewed in the direction of rotation, of each said through-hole (5) are inclined at an angle (α) of 35 to 60 degrees with respect to the front surface (3a) of said rotary body (2). A cutter system according to claim 1, wherein each said blade (6) has on a side (6b) toward said cutting edge (6a), a V-shaped end assuming an angle (β) of 30 to 50 degrees and projecting beyond the front surface (3a) of said rotary body (2). A cutter system according to claim 1, wherein each said blade (6) is adjustably mounted on said rotary body (2) so as to be adjusted towards and away from the front surface (3a) of said rotary body (2).

Inventors: HOSHI TADAICHI, HOSHI, TADAICHI
Applicants: HOSHI PLASTIC KK, KABUSHIKI KAISHA HOSHI PLASTIC
Application year: 1991
Main classification: B29B9
IPC codes: B29B9, B26D1, B26D9