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! Due to the Coronavirus with the Delta and Omicron varations, we have changed our local order pickup policy at our West Chicago location. To pick up an order you will need to order first. The quickest way to do this is through our online shopping cart. There you can select the local pickup option. Or, you can call 630-293-1337 for assistance and to place your order. When ready, we will call you and your parts will be available for pickup in the front entrance on the north side of the building. Longer items will be picked up on the south side loading dock. Please do not arrive until you have been notified that your order is ready.
COVID / DELTA / OMICRON VARIANT UPDATE! NO MASK, NO SERVICE! When picking up parts please wear a mask. If you don't bring one we'll gladly provide one. Please honor the six foot social distancing rule to protect yourself and our employees. 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.
DELAYS AND INFLATION: COVID has interrupted global supply distribution chains resulting in unprecedented delays on incoming door and dock industry products. The result is limited availability of many products, two to three month delays on incoming shipments, and an inflationary rate of over 100% on most of our products, and 200-300% on many of our core products such as springs and cones.
SHIPPING CHANGES: Shipping times are currently not guaranteed, even on next day and second day shipments. Normal transit times do not apply. Shipping prices on items over 10 feet long have tripled in many cases.
SPRING WIRE AND CONE SHORTAGES: We currntly have a good inventory of 2" ID springs and cones. However, due to cone and wire shortages, we currently do not have cones for the residential 1 3/4" and 2 1/4" ID springs. For these sizes many customers are reusing their existing cones. If you need the larger inside diameter springs for commercial doors, there will be a one to two month delay on your order. If you are willing to wait two months for your springs, please note that in the comment section of your order. We deeply regret the hardships this will create for many of our customers.