Many of the newer stock vending machines (see photo) have a "double-door lock" mechanism in their dispensary. Postboxes and book returns also employ this mechanism.

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The principle of the device is to keep the inside of the vending machine completely sealed and inaccessible at all times. Reaching into the machine through the frontal door (lock) automatically forces the more distal door shut, which (for example) prevents a piece of wire from being forced up inside the machine to pilfer the goodies.

Is there a recognized name for this type of double-door lock mechanism?

Web searches for "vending machine locks", "vending machine doors", "vending machine dispensing devices", etc. have proven fruitless due to the fact that "vending machine" refers to a remarkably broad range of devices, all of which have a variety of locks, doors, latches, and dispensary mechanisms.

  • Double door front locking newspaper vending machine:google.com/patents/US4784252
    – user66974
    Dec 12, 2014 at 21:16
  • @Josh61: So "double door front locking mechanism" is the best term we have for it? I was holding out hope for something like "Jensen door", etc.
    – COTO
    Dec 12, 2014 at 21:22

2 Answers 2


It may be a stretch to apply the term to a vending machine, but in forts and prisons, such double doors are called sally ports:

the first opened door to the sally port is closed locked and secured prior to unlocking and/or opening the second door

  • The two are actually close enough conceptually that the term could be repurposed. It suits my purposes well, too.
    – COTO
    Dec 12, 2014 at 23:11

This sounds to me like a type of interlock.

  • "Interlock" has too many other meanings and would be more confusing than enlightening.
    – Hot Licks
    Dec 12, 2014 at 22:55
  • @HotLicks - I disagree.
    – Erik Kowal
    Dec 13, 2014 at 1:32

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