How do vending machines prevent people from stealing goods?

Question

I never understood mechanically how a vending machine prevents people from accessing goods through the dispensing panel. From what I understand it's not a locked door that unlocks only upon payment, dispenses goods and then re-locks. In my experience it seems to be a non-automated mechanical system powered by the weight of the dispensed goods when they fall into it.

I remember as a young child I would out of curiosity try to stick my hand into the panel and see if I can reach up but was unable to do so as my hand would be blocked by what felt like a literal wall. So I know there is some mechanism in place to ensure goods can only flow out and nothing can come in, but I don't understood mechanically how such a thing works.

Answer 1

The vending machines have different product delivery box implementations.

One of the most common ones -I've encountered- is the following:

Basically you have a box which has an opening, as shown in the picture. The opening is big enough for the products to fall in.

When the box pivots, then the closed section of the curved face "closes" the access from the product storage area.

In most cases, there is physically no way to access the products inside the storage area.

Figure: Closed position the product can pass

Figure: Open position the product can be picked.

Answer 2

I think the locking mechanism is more or less like this:

Note, the actual setup could be different but the concept of locking through a barrier that prevents the slide plate been pushed up remains the same.

Answer 3

As others have mentioned, the door or flap can't prevent theft if someone is willing to put in the effort to steal. Same goes for some automated teller machines. As things stand the vending machine primary purpose is to process payment for the correct good that the buyer removes.

The most effective method to theft prevention I've seen is the security camera. While it does not prevent theft, it deters it and can help to easily file with law enforcement (some security companies do just that!). Usually someone brazen enough to steal in front of or vandalize a camera have other offences, and just goes to add charges when the person does something that gets them apprehended.

It is no wonder that some newer tech vending machines simply want a credit card authorization to open a cabinet and charge for anything removed- as detected via some other means than controlling a dispensing screw/clip.