| 摘要 |
A gate operator with an extensible actuating arm adapted for light to moderate gate passing traffic. The operator comprises a small drive unit, such as an electric motor drive, and a rotatable drive shaft, such as a worm shaft driven through operation of the motor. An extensible shaft or so-called ball race shaft, cooperates with the rotatable shaft and extends inwardly or outwardly in response to rotation of the rotatable shaft. A microprocessor operated control circuit is used with or forms part of the operator, and measures a number of counts generated by magnetic elements rotatable with the worm shaft, and which are equivalent to distance units of measurement. In this way, the distance on the opening and closing movement is measured and stored in the microprocessor, so that on subsequent movements, the gate can open and close to precisely the open and closed positions without stopping short of or banging into such end positions. The motor mechanism of the operator is pulsed during the complete first opening movement and the complete first closing movement due to the fact that the operator does not know the exact position of the gate when the operator is first started. In this way, in the event of any bottoming out of the extensible and retractable arm, such as the ball race shaft against the end of the worm shaft, damage to the operator will not result. |
