GB652244A - Improvements in or relating to calenders - Google Patents

Abstract

652,244. Coating webs. FIRESTONE TYRE & RUBBER CO., Ltd., and COLLINS, J. B. June 17, 1947, No. 15977. [Class 140] A calender for forming an insulating coating, e.g. of rubber, and applying it to a backing material as it passes over one bowl of the calender, comprises an electric circuit controlled by said film such that a discontinuity therein energizes a relay to stop the calender. In a three bowl calender the rubber, taken up by the top roll 1 is applied to the backing in the nip of the lower and bottom rolls 2, 3. An electrically conducting rod 8 parallel to the middle bowl 2 carries a number of tubes 7 each having attached a U-member 6, bearing spring contacts 5 urged against the bowl or coating thereon by a weight 9 attached to the other arm of the U. The contacts and the bowl are in series in an electric circuit, Fig. 3, supplied at 15 volts from the secondary of a transformer 16 receiving its energy at 230 volts. In series with the contacts 5 and bowl 2 is the primary of a transformer 17, the secondary of which energizes at 110 volts a relay 18 which operates a circuit 18a for stopping the calender motor. A signal lamp 19 is also included in the relay circuit. A press button 20 is provided to de-energize the system. Discontinuity of the rubber coating film allows contact between the contacts 5 and the bowl 2 to close the circuit, causing the calender to stop and the lamp 19 to light. To restart the calender, the press button 20 must be held closed until the bowl is again covered with rubber. In order to put the device out of action a lifter bar 11 is provided carried by levers 12 pivoted at 13 in brackets 10 carried by the machine frame and which levers also carry a bar 15 to facilitate raising and lowering of the bar 11. In a modification, the electric circuit comprises a condenser, one plate of which is constituted by the bowl of the calender and the other by an arcuate plate parallel to a part of said surface, the coating material acting as the condenser dielectric discontinuity of which alters the capacity of the condenser to influence the circuit to which it is connected and thus stop the calender. According to the Provisional Specification, the electric circuit may operate to control the calender in any desired manner.