Patent GB-681524-A (GB)
Title: Apparatus for the treatment of calender rolls of a calender for sheeting plastic material into film
IPC: B29C59/00
Filed: 1951-01-03
Abstract: 681,524. Abrasive blasting. WINGFOOT CORPORATION. Jan. 3, 1951 [Sept. 2, 1950], No. 262/51. Class 60. [Also in Group V] Apparatus for blasting calender roll surfaces includes a hood having one side open and contoured to engage the roll and the other side slotted longitudinally, a blasting nozzle extending through the slot and directed toward the roll, a blasting material supply line connected to the nozzle, a vacuum line connected to the hood and means for reciprocating the nozzle in the slot. A calender for sheeting plastic material into film comprises a frame 2 supporting four calender rolls 3-6; rolls 3, 4 carry between them a bank of plastic 7 to which plastic in ribbon or other form is continuously fed; rolls 4, 5 have a secondary bank 8 of plastic formed between them; rolls 5, 6 impart the final gauge and surface texture to the sheet of plastic film 9. The apparatus for blasting the surfaces of the rolls comprises a hood 10 of the same length as the roll to be blasted and adapted to be mounted by brackets 11 on the calender frame 2 which has T-slots 12 for that purpose. The hood 10 has an open side 13 shaped to the contour of the roll, felt or other sealing means 14 being provided on the edge of the hood. The bottom of the hood 10 forms two funnels 15, 16 to collect blasting grit such as sand or shot. The bottoms of the funnels 15, 16 are connected by vacuum lines 18, 19 to a storage compartment 20 which collects the blasting grit and allows the air to escape. At the edge of the hood 10 opposite to the open side 13 is mounted a blasting nozzle 21 connected by conduit 22 to the compartment 20. The nozzle 21 extends through a longitudinal slot 24 in the side 23 of hood 10. The nozzle 21 is mounted, by means of a set screw 26, in a circular boss 25 carried on a plate 27 secured to a nut 28 threaded on a screw 29 journalled at its ends in pillows 30, 31 secured to the hood, the screw 29 being driven by a motor 32 through a flexible shaft 33; limit switches 34, 35 automatically reverse the motor 32 to cause the nozzle 21 to reciprocate back and forth along the roll. The cylindrical boss 25 is secured to a plate 36 slidably carried in gib plates 37, 38. To seal the groove 24 at each side of the nozzle 21, a channel 39 immediately behind the side 23 of the hood slidably receives a flexible belt 40 of rubber or leather; the nozzle 21 extends through a central hole in the belt 40, the belt being secured to the sliding plate 36, so that the belt moves with the nozzle and closes the slot 24 on each side of the nozzle. The roll surface produced by blasting with metal shot has a number of shallow craters 44, Fig. 11, surrounded by a splashed-up circular rib 46, the craters being separated, where not overlapped, by relatively flat portions 47. Rolls 5, 6 having been thus treated impart to both sides of the plastic film 9 a tooth which gives the film a more cloth-like feel. To form a design on the roll surface, the roll after a first blasting is completely covered with a stencil 50, Fig. 8, e.g. of thin resilient sheet rubber, having a design opening 51 therein; the roll is then subjected to a second blasting to produce a depressed design surface 52; alternatively, the stencil 53, Fig. 9, covers the roll in certain areas only, so that after the second blasting operation, a raised design surface is left; in either case, the metal shot or grit used for the second blasting operation is of different weight and size from that used in the first blasting operation, so that a different texture is imparted to the plastic film by the design surface than by the remainder of the roll surface.