Self-service freezer chest with inventory monitoring means

Apparatus for remotely monitoring the inventory of stackable products contained within the holding compartment of a customer accessible, open bin storage chest comprising, n combination:

• a modular storage bin dimensioned for insertion into and withdrawal from the holding compartment of the storage chest, the storage bin including a base panel and sidewall panels forming boundaries of a product load space that is open at the top allowing customer access to products stacked therein;
• a coil spring disposed on the base panel, the coil spring having a total deflection length L as measured from an uncompressed (empty bin) no-load position to a compression limit position and being yieldably deflectable relative to the base panel within the product load space;
• a stack plate mounted on the coil spring, the stack plate providing a platform for supporting a stack of products and being movable through the product load space in response to extension and retraction of the coil spring;
• position sensors disposed at vertically spaced locations along one sidewall panel of the storage bin, the position sensors extending along at least the upper half of the storage bin from the no-load (empty bin) position to a loaded position corresponding with a deflection distance of from about one-half L to about two-thirds L, each sensor providing an output signal in true and complement logic states in response to being coupled with and decoupled from a magnetic flux field, respectively;
• a permanent magnet attached to the stack plate, the permanent magnet producing a magnetic flux field that magnetically links with individual position sensors as the stack plate moves vertically through the product load space;
• an analog-to-digital converter coupled to the sensors for generating a digital data word corresponding with the operating logic state conditions of the position sensors;
• a controller including a random access memory unit coupled to the analog-to-digital converter for storing in the random access memory digital data words generated by the position sensors;
• and,
• a communication interface circuit coupled to the controller for transmitting information stored in the memory unit to a remote monitoring station.