Speed Operated Safety System

The Pflow Speed Operated Safety (SOS) senses and responds to the failure of any component in a mechanical lifting drive mechanism (chain/cable breakage or failures of the gear reducer, brake equipped motor, drive shaft or sprockets). SOS employs a unique escapement device that senses the descent speed of the carriage. SOS actuates the lift Safety Cams if the descent speed exceeds a predetermined velocity. The SOS escapement device is fail-safe and requires no lubrication or maintenance.

How SOS Works

(View A):  The Speed Operated Safety (SOS) is equipped with a governor that is mounted at the top of the lift guide columns. As the lift carriage moves up and down, the SOS governor spins at a fixed rate that corresponds to the carriage travel speed. A weighted shaft on the SOS device slides down an enclosure tube when the rotational angle of the shaft reaches predetermined positions

(View B):  The SOS shaft rotates continuously whenever the vertical lift is in operation. A small chain connects the SOS governor to the lift Safety Cams.

(View C):  When a component of the lift drive mechanism fails, the carriage goes into a Free Fall mode. Carriage Free Fall causes the SOS governor to speed-up. As a result, the SOS shaft is held in its outer most position via centrifugal force. The SOS shaft then contacts a stop bar.

(View D):  Governor rotation ceases and the small chain pulls a trigger pin to activate the lift Safety Cams. The Safety Cams then rotate into a locked position and grip the guide columns to prevent Carriage Free Fall.