Method and apparatus for adjustable cutting of a filamentary material

A cutting apparatus for continuous lengths of filaments bundles, film ribbons, filamentary-type or other material in strip like form is disclosed containing a tube that is readily adjustable in very small increments relative to rotating blades. A housing surrounds the exit end of the tube and rotating blades which is attached to a suction device. The device creates a high velocity flow of air through the tube which aligns the filamentary material for cutting. An insert may be placed in the tube which contains an upper surface or anvil at its outer end. The tube and/or the insert in the tube is adjustable in two dimensions relative to one or more blades rotating in a plane transverse to the axis of the tube. These adjustments which may be made during operation of the cutting process to facilitate a cleaner, uniform cutting of the filamentary material.

BACKGROUND OF THE INVENTION

A. Field of Invention

The dependable and accurate cutting of moving and continuous lengths of filament bundles, film ribbons, filamentary tapes or other materials in strip-like form is a challenging and difficult problem, particularly so when the ribbon thickness or the diameter of the filaments is only a few microns.

Such materials have no appreciable stiffness and must be conveyed and aligned by a moving stream of air, feed rolls or other mechanical means or by air jets, or a combination of these, to the cutting location, where it is cut into discrete lengths, the length being determined by dividing the material transport speed by the number of cuts/minute. Fixing these two parameters when cutting filaments, into staple or flock, or ribbons will result in the desirable, uniform length product.

In scrap recovery or disposal systems, where uniform cut length is of little concern, cutting speed is normally fixed but cut length will vary with the changing speed of the process and a random length product results.

B. Description of the Related Art

Various approaches to uniform cutting of such fibers or film have been described in the prior art. U.S. Pat. No. 3,119,294 issued Jan. 28, 1964 describes a cutting apparatus in which counter-rotating rolls feed a filamentary material into an air nozzle which terminates at a stationary bed knife. A mating blade mounted on a rapidly rotating shaft cuts the filamentary material as it exits the air nozzle. See column 2, lines 23-32 and FIG. 1. This patent describes an elaborate mechanism to maintain a uniform distance between rotating cutting blade and stationery bed knife. Satisfactory cutting of the feed filaments or ribbon requires that the distance between these two elements be only a fraction of the diameter of the filaments or of the ribbon to be cut. Maintenance of this distance insures a uniform length of the cut filamentary material and long life for the cutting blades (column 4, lines 17-21). That mechanism, however, is a very complex piece of machinery with expensive precision parts that are costly and requires substantial expertise to adjust.

U.S. Pat. No. 3,831,482 issued Aug. 27, 1974 discloses an apparatus for cutting fiber into staple fiber strands. It consists of a rotating two-part disc with discardable knife blades clamped between the disc halves. The stated advantage of this arrangement is that it “eliminates the need for a removal and replacement of knives for re-grinding” (Column 2, lines 33-36). There is no disclosure of means for adjusting the length of cut fibers or apparatus associated with the cutting blades to adjust the length of the cut fiber.

Another approach to cutting filamentary material is illustrated in commonly assigned U.S. Pat. Nos. 5,450,777 and 5,836,225. These patents describe apparatus for cutting lengthy continuous tows of fiber into short, chopped fiber. This goal is accomplished by feeding multiple tows into a venturi tube which pulls the tows by negative pressure toward a cutter at the outlet of the tube. The cutter mechanism has one or more blades mounted to a high-speed drive shaft which operate in a plane transverse to the direction of movement of the tow. As the blades rotate near a cutter plate at the exit of the venturi tube, the tow fibers are cut into uniform lengths as the blade passes across the cutter plate. The cross sectional area of the cutter plate opening is such that it is momentarily covered (blocked) by the cutting blade as it rotates across the plate (See FIG. 8 of '225 patent). This arrangement tends to create a lot of high frequency noise as the air stream exiting the venture tube is repeatedly interrupted.

A similar approach to cutting filamentary material is described in U.S. Pat. No. 4,188,845 issued Feb. 19, 1980. In this arrangement, the material to be cut includes foils, plastic webs, etc., (See column 1, lines 7-9) and textile strips (See column 2, line 61). This material enters a funnel mounted atop a stationary cutting plate at the narrow end of the funnel. It proceeds through the funnel by gravity without assistance of the venturi effect described above. Rotating beneath the stationary cutting plate are multiple knife edges mounted vertically (in the plane of the foil or fiber flow) on a disc rotating below the stationary cutting plate. The knife edges are preferably adjustable to insure sliding engagement of the knife edges over the cutting plate, which is also adjustable.

Yet another approach to cutting fiber into fixed lengths for use as reinforcement in, for example, roofing shingles, is illustrated and described in U.S. Pat. No. 6,182,332 B1 issued Feb. 6, 2001. In this patent, several rotating discs with sharp edges are moved in orbit relative to a second member such as a ring with an internal track. The fiber to be cut passes between the sharp edges of the disc and internal track where it is cut. The length of the fiber to be cut is determined by adjusting the rate at which the continuous fibers are fed to the cutters and the speed at which the cutting discs are moved in orbit within the internal track (column 5, lines 23-35).

SUMMARY OF THE INVENTION

The current invention provides a simplified means for directing continuous lengths of film and/or fiber through a transport tube into a rotating cutter and, uniquely, of adjusting the clearance between the stationary cutting surface and the moving knife or knives to provide optimum cutting conditions while the cutting machine is in the operating mode. The stationary cutting surface, because of the versatility inherent in the design, can range from a transport tube to a cutting surface fixed at some chord within the transport tube. The design avoids the need for the heavy and expensive apparatus of U.S. Pat. No. 3,119,294, while functionally achieving improved operating flexibility and equivalent cutting capability at much lower cost. Air is drawn through the transport tube by a suitable suction device to align the continuous lengths of fiber or film within the transport tube to the point of cutting where one or more rotating blades traverse the exit end of the tube at high speed to cut the exiting filament, tape or film into suitable lengths, and to convey the cut material to some collection point.

This invention provides simplified means for adjusting the distance and orientation of the rotating blades and surfaces on or in the tube that interact to cut the material. In one embodiment, the cutting edge of the rotating blades clears a slightly tapered upper portion of the tube end which transitions into a vertical outer surface where cutting occurs. In another embodiment, an insert with a sloped inner face, such as a tapered section of a right cylinder, which terminates in a suitable cutting surface, is placed at one end of the tube to improve guidance of the film or fiber as it approaches the cutting blades at the exit end of the tube. The insert reduces the tube's exit area which increases air velocity. That increased velocity improves the alignment of the filament, film or tape as they approach the cutting blades.

The upper surface of the insert acts as an anvil against which the rotating cutting blades pass as they cut the fibers or film exiting the tube. Cutting blades are mounted on a rotating shaft, the axis of which is parallel to the tube. The cutting assembly is counter balanced by judicious placement of the blades, when two or more are used or by a counter weight when a single blade is used.

The insert in the tube, or the tube itself, may be oriented about the axis of the tube so that the anvil portion of the insert at the tube exit may be angularly adjusted relative to the leading edge of the blade passing over the anvil. It has been found that having an approach angle between the upper surface of the anvil in the tube insert or of the non-tapered portion of the transport tube, and the leading edge of the cutter blades improves cutting. This angling of the stationary cutting surface to the moving cutter blades reduces the amount of filament, tape or film being cut at any one time, thereby achieving both a reduced cutting load and a significantly lower cutting noise.

The gap between the face of the tube and the leading edge of the cutting blade is adjustable in very small increments through the use of a unique adjustment means associated with the tube through which the filamentary material is fed. This is accomplished with a differential screw arrangement consisting of an adjustment ring with (1) internal screw threads of one hand and pitch mating with external threads on the tube containing the insert and (2) with internal threads of the opposite hand and a different pitch mating with external threads on a stationary upstream feed conduit. As the adjustment ring is rotated in one direction, the tube moves toward the cutting blades a distance equal to the difference in the pitch of the two external threads, times the degrees of rotation divided by 360 degrees. For example, a 10° rotation of the adjustment ring with external thread pitches of 20 and 22 will advance the tube only one ten thousands of an inch (“0.0001”) toward the cutting blades. Conversely, rotation of the adjustment ring in the other direction will move the tube away from the cutting blades.

This simple, but effective, fine adjustment arrangement facilitates ready operation of the disclosed cutting system by relatively unskilled operators. The operator need only rotate the adjustment ring a small amount to accommodate erosion of the cutting surface on or in the tube. This easy adjustment facilitates an empirical evaluation of the cutting as it takes place, i.e., the adjustment ring can be rotated thereby advancing the tube in a direction toward the blades until a suitable cut fiber or film exits the tube. In addition, the tube, with or without an insert, can be incrementally advanced toward the rotating blades to shave microscopically thin slices of material from the edge of the insert or of the tube, thereby removing the eroded or worn surfaces of that edge. This re-establishes a sharp cutting edge and the close cutting clearance deemed best for effective cutting of the material.

The area surrounding the cutting is easily isolated in this system for safety and noise reasons. Because the alignment of the axes of the cutting blade drive shaft and tube is parallel, it is easy to mount a protective hood over the rotating blade and the area where the film or fiber exits the tube. A suction device attached to the protective hood draws the fiber, tape or other filamentary material to, and through, the cutting apparatus. The suction device preferably generates air velocity in the tube sufficient to both keep the film or filaments relatively straight at the cutting point and to effectively and efficiently convey the cut material to the collection point. Conveying velocities for transporting lightweight material in this fashion typically range between 3500-5000 feet per minute (approx. 40-60 miles per hour). High velocities in the tube tend to pull the material through the center of the tube and stiffen the otherwise flexible material being cut. This straight alignment of material presents the material in a preferred orientation for cutting by the rotating blades passing in front of the tube exit. When the insert is used in the tube, the exit velocity of air through the tube is increased because of the smaller tube outlet area. This further enhances the stiffness and alignment of the material relative to the rotating blades. The materials of the tube, of the upper surface of the insert and of the moving knives, are selected to be compatible with each other and with the materials to be cut. The moving knives are always the hardest.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some elements of one presently preferred embodiment of the apparatus10of this invention are illustrated inFIGS. 1-3. More particularly, a base12forms a foundation for mounting an adjustable tube14thereon. A clamp16affixed to the outer surface of tube14contains a guide pin18extending from one or more portions of the clamp16to prevent rotation of tube14. The guide pin18is free to move longitudinally in slot20in a U-shaped guide22mounted on base12. Thus, while guide pin18prevents rotation of tube14, that pin does allow travel of the tube14along the longitudinal axis of the tube as it slides in the slot20in U-shaped guide22.

A mounting bracket24holds tube14in position relative to base12and the adjacent shaft52of cutting apparatus described more fully below. A small clearance between the outside circumference of tube14and the inside of a bore in bracket24permits longitudinal movement of tube14with minimum vibration or chatter as the cutting takes place.

The outer circumference of tube14furthest from the cutting contains threads26. This threaded end26of tube14is coupled to a feed conduit28via an adjusting ring30. This feed conduit28is fixed to base12with clamp32. This clamp32holds feed conduit28in alignment with tube14and prevents movement, either rotationally or longitudinally, of feed conduit28.

Fine adjustment of tube14in a direction along the longitudinal axis is possible by a slight rotation of adjusting ring30. As shown inFIG. 4, tube14has external threads26, which mate with like internal threads34in adjusting ring30. Internal threads36on adjusting ring30likewise mate with external threads38on feed conduit28. A very fine adjustment of tube14, for example 0.0001 inches, in a longitudinal direction is possible by very little (10°) rotation of adjustment ring30. More specifically, if external threads26on tube14have a pitch of 20 threads per inch and the external threads38on feed conduit28have a pitch of 22 threads per inch, a 10° rotation of adjusting ring30will move the end of tube14about one-ten thousands of an inch (0.0001″).

Longitudinal adjustment of tube14is important for all of the reasons explained in U.S. Pat. No. 3,119,294, namely, wear on the stationary part of the cutting apparatus which changes the gap between cutting blades and that stationary part. Variation in that gap can affect the cutting capability of the cutting apparatus. In one embodiment of this invention, the stationary part of the cutting apparatus has an edge or anvil40as part of a sloped insert42in tube14(SeeFIG. 1). This edge40may extend a small distance, typically ⅛″ to ¼′, beyond the front face15of tube14as shown inFIG. 1.

Insert42has a sloped surface43within tube14which directs the fiber or film44being cut to a position just above anvil40at the time it is cut. (SeeFIG. 6). The sloped surface43of insert42also accomplishes an accelerated flow of air though tube14which improves the handleability of filamentary material44, especially very thin, filamentary material. Alternatively, an upper portion15aof the front face15of tube14may be slightly tapered as shown inFIGS. 5 and 7to direct the cutting blade to pass immediately adjacent the front face of tube14.

Cutting blades50are mounted on a shaft52driven by motor54(FIG. 3). As shaft52is turned, the leading edge56of blade50passes across the front face15of tube14and cuts material44exiting tube14. As mentioned above, tube14is adjustable in its longitudinal direction so that the leading edge56of blade50is always at the proper distance from the vertical portion of face15or from the edge40of insert42of tube14to insure a clean cut.

The ability of this apparatus10to cut filamentary material is also enhanced by the ability to adjust the angle at which the leading edge56of blades50approaches the material44in tube14. When insert42with edge40is used, it can be angled relative to the leading edge56of blade50. That angle is illustrated inFIG. 2as “A” and is the angle between a line drawn through the center line of shaft52to the outside edge of blade50and a line extending along the top surface of anvil40. This angle of approach of leading edge56of blade50to the upper surface of anvil40can be adjusted by rotating insert42within tube14and then fixing it in place after the optimum angle “A” is determined by empirical analysis or other means. SeeFIG. 6for another orientation of insert42relative to leading edge56of blade50. Where insert42is not used, tube14can also be oriented relative to the leading edge56of blade50by rotation of tube14in clamp16as shown inFIG. 7.

Blades50are preferably held in place by hub58mounted on shaft52. As illustrated inFIG. 7, the blades50have shanks51which are held in hub58. If the shanks51are circular in cross-section, the blades50can be rotated in the hub58so that the angle of approach to material exiting tube14can be adjusted through a wide range. The number of blades50is preferably an even number, for example 2 or 4, so that these counterbalance each other as shown inFIG. 7. However, a single blade may be used with a suitable counterweight62as shown inFIG. 2. Where multiple blades are used, it is important that they are all aligned in the same plane. To make such alignment, a reference plate74can be mounted in housing70. Each blade50can then be pressed against plate74and set screws60tightened to assure uniform alignment of the blades.

In operation fiber, tape or film44is introduced into feed conduit28and pulled through tube14by high speed air. Air movement through tube14is created by a suction device (not shown) attached to a housing70surrounding the outlet end of tube14(SeeFIGS. 8 and 9). The inlet side of the suction device is connected to a duct72extending from housing70. The housing70sealingly surrounds tube14and the blade assembly58so that all air drawn by the suction device passes through tubes14and28, thereby creating the aforementioned brisk air flow that presents the material in the proper position and condition for cutting by blades50. The air flow also helps to keep the fiber or film44from dragging on the bottom of feed conduit28and/or tube14.

The multiple adjustments in apparatus10, for example, angle “A”, fine adjustment of tube14with adjusting ring30are parameters that address cutting consistency and effectiveness whereas speed of motor54, number of blades50, and speed with which the fiber or film44is passed through apparatus10, address the cut length of the product.