| 摘要 |
A fail-safe thermostatically controlled circuit is disclosed for use in high-throughput thermoplastic material melting and dispensing apparatus including a hopper into which solid thermoplastic material is deposited for feeding the thermoplastic material to a grid melter which melts the thermoplastic material whereupon the molten thermoplastic material flows from the grid melter to a reservoir from which the molten thermoplastic material is pumped to an applicator or dispenser. Both the grid melter and the reservoir are preferably heated by electrical resistance heaters energized by separate fail-safe thermostatically controlled circuits. Each fail-safe thermostatically controlled circuit includes a manually adjustable thermostat for sensing the temperature of the molten thermoplastic material in order to connect a high voltage and current power source through a fusible element included in fail-safe circuitry to the electrical resistance heaters for energizing the electrical resistance heaters when the temperature of the molten thermoplastic material is below a preselected thermostat temperature setting. The fail-safe circuitry also includes a shut-off temperature detector for sensing the temperature of the molten thermoplastic material in order to energize a heat generating element for melting the fusible element if the temperature of the molten thermoplastic material reaches a predetermined shut-off temperature which is above the preselected thermostat temperature setting, thereby disconnecting the power source from the electrical resistance heaters.
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