Abstract: A barrier operator moves a movable barrier using a motive source having a movable member, a station, and first and second flexible members. The station includes a drive system operatively coupled to the movable member of the motive source. The drive system includes input and output members. The first and second flexible members each have first and second ends and a portion extending from the station. The first ends of each flexible members are operatively coupled to the movable barrier and the second ends of each of the flexible members are operatively coupled to the output drive system member of the station. Aspects include the first and second flexible members being cable or wire. Other aspects include the output drive system member of the station being a spool. The drive system further includes a gear box operatively coupled to the spool. Other aspects include the movable barrier being a gate or door.

Abstract: A barrier operator moves a movable barrier using a motive source having a movable member, a station, and first and second flexible members. The station includes a drive system operatively coupled to the movable member of the motive source. The drive system includes input and output members. The first and second flexible members each have first and second ends and a portion extending from the station. The first ends of each flexible members are operatively coupled to the movable barrier and the second ends of each of the flexible members are operatively coupled to the output drive system member of the station. Aspects include the first and second flexible members being cable or wire. Other aspects include the output drive system member of the station being a spool. The drive system further includes a gear box operatively coupled to the spool. Other aspects include the movable barrier being a gate or door.

Abstract: A system for controlling the speed, torque and power of three phase a.c. motor. A binary logic circuit generates a variable frequency three phase signal which controls three driver pairs in an inverter to selectively apply either the positive voltage or the negative voltage of a direct current power source to each of the three motor phases. The three phase binary driver control signal is pulse frequency modulated below 60 cycles per second to operate the motor in a constant torque mode without varying the rectifier output voltage. The logic control signal also includes a delay to protect the drivers by assuring that one driver of a pair is "off" prior to turning the other driver "on". In addition the system comprises high response voltage and current limiting circuits to protect the system and to reduce the overcapacity requirement of the components. An accelerator/decelerator circuit achieves a nearly linear characteristic through the use of switching transistors to permit substantial cost savings.

Abstract: A pulley drive system utilizes a driven pulley and a driving pulley and a belt connecting the pulleys. The driving pulley has spaced discs and there are means for varying the spacing between the discs to vary the speed of the belt driving the driven pulley. Speed sensing means are positioned adjacent the driven pulley to provide a signal representative of the speed of the driven pulley. The speed sensing signal is utilized in a regulating circuit to control the means for varying the spacing between the discs to thus control the speed of the belt.