| 摘要 |
An improved thread-tensioning mechanism for the stop motion means of a multi-needle machine of a well known type wherein each needle thread, in extending from its supply spool to its needle, normally travels through a thread-tensioning section at a speed and tension which varies in proportion to its rate of variable usage within a given operating or usage range. Its tension variations are sensed by a sag sensor that shuts down the machine when the tension falls below said given range. In our improved thread-tensioning mechanism, a group of independently rotatable idler wheels is provided, one for each needle thread of a corresponding group of individual threads. The periphery of each idler wheel gravitationally engages and presses its needle thread against the periphery of a rotating shaft common to all wheels. Through this engagement, each wheel is rotated by and at the varying speed of its thread. The common shaft is driven at a constant peripheral speed somewhat below the slowest lineal speed of a given operative range over which the thread and wheel speeds vary. In other words, the slowest thread and wheel speed encountered during normal operation should be slightly above the constant speed of the common shaft. So long as the lineal speed of each given thread is higher than the peripheral speed of the common shaft, the slippage therebetween causes the common shaft to operate as a frictional brake, which tensions each thread in accordance with the corresponding speed differential. When the rate of speed of one thread or another falls below the lowest speed of a given speed range for all threads, the common shaft then takes over the operation of driving said slowest thread and continues to do so until the sensed tension of that thread decreases to the point where the sag sensor shuts down the machine.
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