Garage door opener limit switches electrically limit the door travel as it opens and closes. These switches “tell” the opener or operator when to stop.
The most common limit switch comes in most of the Sears, Chamberlain and Liftmaster openers made since the early nineties.
Another common type of limit switch found on commercial and industrial operators use a limit shaft with two plastic nuts, as shown on this LiftMaster operator.
PowerMaster operators use plastic nuts with a design similar to the LiftMaster limit assemblies.
The older Edko operators used wooden nuts that slid between the open and closed switches.
Link operators used plastic nuts sliding along the limit shaft.
McKeon operators use a similar system with round plastic nuts. A steel plate prevents the nuts from turning on the shaft as the shaft turns.
The older Crane operators used limit assemblies with two nuts.
Allister, Allstar, and MVP openers normally used chain dogs to stop the door as it opens and closes.
Below you can see where the limit dog has moved an arm. The arm then activated the switch to stop the door travel. The limit dog can be moved along the chain by loosening the screw that secures the dog to the chain.
Over the decades, Genie has used switches mounted to the track.
The older Scientific operators also used track-mounted switches to stop the door when it opens and closes.
The older Vemco operators used a small tube that ran the full length of the operator rail.
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YES, WE'RE OPEN FOR BUSINESS! DDM is considered a life-sustaining company because we are an internet retail company that provides essential products. Due to the recent outbreak of Coronavirus, however, we are changing our local order pickup policy at our West Chicago location. To pick up an order you will need to order first. The quickest way is to order in advance through our online shopping cart. There you can select the local pickup option. Or, you can call 630-293-1337 for assistance, to confirm availability of parts, and to place your order. Once ordered, your parts will be available for pickup in the lobby of our north side front entrance. Longer items will be picked up on the south side loading dock. Please honor the six foot social distancing rule. Thank you for your patience and understanding as we all navigate this challenge together. More information is available on our blog titled DDM Adjusts to the COVID-19 Coronavirus. In the same article you will also find documentation and an answer to the question: "Is a garage door repair company a life sustaining business?"
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