Patent GB-1262853-A (GB)
Title: Fibrillators
Inventor: SLACK PHILIP TREVOR
IPC: D01D5/42
Filed: 1968-02-14
Abstract: 1,262,853. Film fibrillator; slitting web material. PLASTICISERS Ltd. 4 Feb., 1969 [14 Feb., 1968], No. 7207/68. Addition to 1,073,741. Headings B4B and B5B. In a fibrillator suitable for use in the process of the parent Specification which involves the slitting of synthetic resinous film material, and which comprises a cylindrical drum rotatable about its axis, each row of cutting elements comprises a plurality of needles 16 secured to a metal strip to form a comb with the needles equally spaced apart along the length of the strip, and the drum 10 is cut away to form axially parallel slots 14 to receive the metal strip portions of the combs, the combs being secured in the slots, by cover-plates 24 so that the needles protrude beyond the surface of the drum. As shown, the slots are inclined to the surface of the drum so that the needles protrude therebeyond at an angle # to the drum surface. Spacer means (26) (Fig. 2, not shown) may be provided between the ends of the slots 14 and the ends of the combs so that the needles in adjacent combs are staggered in a direction parallel to the axis of the drum. Alternatively, as in Fig. 3, each row of cutting elements may comprise a plurality of tapered pins 34 and the drum 32 is formed with a corresponding number of apertures 36 arranged in axially parallel rows, the cross-section of the apertures tapering towards the drum surface to receive the tapered pins so that the pointed ends of the latter protrude beyond the surface of the drum, the apertures in adjacent rows being staggered to obtain the desired lateral spacing between the pins in adjacent rows. Alternatively, as in Figs. 4A and 4B, the'surface of the drum 40 may be cut away to define a helical thread and cutting elements formed by removing axially parallel sections of the thread at regular intervals around the drum. Thus, in Fig. 4A, a cylindrical drum 40 has a multi-start helical thread profile formed in its outer surface. Axially parallel slots 42 are formed in the surface of the drum 40 at regular intervals around the drum. The slots 42 cut right through the thread profile 44 and result in a line of cutting edges along each side of each slot 42 defined by the peaks of the thread profile. Since the thread follows a helical path the cutting edge defined by the peak of each thread profile and one slot 42 will be displaced axially from the corresponding cutting elements formed by the same thread profile peaks and the adjacent slots 42. In Fig. 4B, the bases of the slots 42<SP>1</SP> are inclined to the surface of the drum. In the embodiment shown, the bases of the slots extend between the peaks of one line of cutting edges to the bases of an adjacent line of cutting edges. Another form of fibrillator comprises, as in Fig. 5, a plurality of circular discs 50 arranged in axial alignment and stacked side-by-side to form a hollow drum, radial protrusions 52 at regular intervals around the periphery of each disc, each sharpened to form a cutting edge, each radial protrusion being cut away more on one side than the other, so that the cutting edge is displaced towards one side of the disc, and the protrusions being cut away alternately on opposite sides around each disc. (Figs. 6A and 6B, not reproduced.) In such a fibrillator the cutting edge of each protrusion may be displaced from one face of the disc by a distance equal to one quarter of the thickness of the disc and cutting edges of adjacent protrusions may be displaced from the other face of the disc by the same distance. By stacking a number of discs 50, with the radial protrusions 52 in axial alignment, a fibrillator can be formed. Holes 54 are preferably formed in the discs 50 so that when assembled, the discs can be held together, e.g. by bolts, or wads passed through the aligned holes 54 and secured at each end. In any of the above embodiments, more than one set of cutting elements may be arranged around the periphery of the fibrillator drum, so that the fibrillator can be rotated at lower speeds.