[GDG 2337]

Need to start by explaining how we raised and lowered our arm for those of you who are unfamiliar. In the picture on slide 1, lever arm (right side) with the nylon block attached pushed/pulled the arm up and down (thanks Adam) like HOT in 07. We used a chain driven trolley to move the lever arm, essentially a vertical conveyor. Now to answer your question, friction brake is attached to the 3/8 “hex upper shaft of conveyor system. The two hockey puck brake pads attached to shaft are tensioned against gear by compression springs. In the screen prints, going up would be in the clockwise direction, with the gear trapped between the tensioned brake pads, teeth contact curved side of pawl and force it to walk up and over the teeth producing the familiar click, click, click ratcheting noise. When arm stops, torsion spring helps push pawl down in between the gear teeth locking it in position. With lifted arm stopped, gravity takes over (blame Newton), as you know tries to back drive lift system down, turning brake pads against stationary gear. Key is finding the right balance between having brake pads stick to gear holding arm in position and still be able to have them slip to drive arm back down. Compression springs allow fine tuning tension (think of a slipper clutch) instead of just cranking down on the lock nuts and act as a self adjuster mechanism to compensate for pad wear. This where the superior problem solving and design skills came into play, it was priceless watching son (who isn’t an engineering graduate) outshine his talented father. Hope is answers the question.