Patent GB-750982-A (GB)
Title: Apparatus for cutting tire treads
IPC: B29D30/68
Filed: 1954-07-08
Abstract: 750,982. Pneumatic tyres. GOODYEAR TIRE & RUBBER CO. July 8, 1954 [Jan. 22, 1954], No. 20022/54. Class 144 (1). [Also in Group VIII] In apparatus for slitting the treads of rubber tyres to improve their resistance to skidding a tyre is mounted for free rotation on a fixed axis and its tread is engaged by a rotatable cutter so arranged that in its operation it advances the tyre tread circumferentially a distance euqal to the spacing between successive cuts, means being provided for driving the cutter. In the example a tyre 5, Fig. 1, is mounted on a wheel 4 rotatably mounted on a horizontal stub shaft 2 supported on a frame 1, adjacent to a pedestal supporting a slidable frame 13 carrying an electric motor 11 which, through a reduction gearing 12, drives a horizontal shaft 10 supporting a mount 9 for a cutter 16. As shown in Fig. 5 the cutter 16 extends continuously in a substantially spiral form through an angle of more than 360 degrees, and has a minimum diameter greater than the width of the tread. The cutter is secured by screws 18 to a shoulder 17 which is integral with or secured to the mount 9, and decreases in width throughout its circumference to provide a substantially spiral surface to which the cutter 16 is secured at right angles to the plane of the mount. A spacer 19 of uniform width throughout its length is secured between the overlapping portions 16a, 16c of the cutter. Preferably the height of the cutter increases gradually throughout the length of the cutting portion 16a so that it attains a height above the shoulder 17 equal to the depth of the groove to be cut. For the operation the tyre is inflated, the cutter is rotated by starting the motor 11 and, by operation of the hand-wheel 14, is brought into engagement with the tread of the tyre, so that the leading edge 16a of the cutter enters and slits the tread. The intermediate portion 16b of the cutter follows through the slit for approximately 270 degrees of arc, at which time the slit is displaced a distance equal to the width of spacer 19, as shown in Fig. 3. Various configurations of slits may be imparted to tyre treads by using cutters of different diameters. In a modification, Fig. 12 (not shown), three separate arcuate cutters are secured upon a rotary mount having a diameter much greater than the width of a tyre tread, the leading edge of each cutter being arranged to overlap the trailing edge of an adjacent cutter, and the distance between the centre of the mount and each trailing edge being less than the distance between the centre and each leading edge. During the passage of the cutter through the tyre the carcass and tread tend to stretch in the direction of movement of the cutter, thereby causing the centres of the arcuate slits to be displaced from the centre of the tread. To counteract this, means are provided for adjusting the tyre-carrying wheel 4 laterally relative to its shaft 2, in a direction opposite to the movement of the cutter through the tread, a reference pointer 25 being provided for indicating the position of the vertical diameter of the cutter mount 9.