creep seed drive

By using creep speed drive, one can get 2 different speeds (typically lower speed is 10 % of normal speed) on same shaft. Creep speed drive unit includes 3 different parts assembled together viz. induction motor, helical gear box, electrically applied clutch.

Typical application of this creep speed drive would be horizontal long travel mechanism of crane. Imagine that total long travel span of a crane is 40 feet. And crane operator is required to drop (already lifted load) at distance of 37th feet.

In order to save time, crane operator will prefer moving load with higher speed till 35th feet. And then from 35th feet to 37th feet he will prefer moving load very slowly (say about 10 % of initial speed). Because of this reduced speed, he will be able to drop load at exact 37th feet. Creep speed drive is often used in this type of application.

Whenever lower speed is required, main electric motor is switched off and clutch is engaged. This clutch connects helical gearbox to driven shaft. Now creep speed motor is ready to move load.

Please note that helical gearbox is having speed ratio of about 10. i.e

Helical gear box output speed is 10 times slower than input speed. Therefore creep speed motor runs at synchronous speed and driven shaft rotates at 10th motor speed. Because of high speed ratio of helical gear box , creep speed drive is self locking. This feature is very important (say in a case of heavy load being lifted) for safety aspect.

AVAILABLE COMBINATIONS OF SPEED RATIO AND MAIN MOTOR POWER