Automatic sliding door system for refrigerator unit

Abstract

An automatic sliding door system especially well suited for use in walk-in freezer or refrigerator units includes an exterior sensor unit for detecting opening conditions on the exterior of a freezer or refrigerator unit, and an interior sensor unit for detecting opening conditions in the interior of the freezer or refrigerator unit. Each sensor unit comprises both a motion sensor and a presence detector. The motion sensor detects motion towards the sliding doors, and opens the doors as they are approached. Once motion is detected, the motion sensor tracks the motion no matter whether towards or away from the door, and keep the doors open so long as the motion is present. The presence detector of each sensor unit detects a change in the ambient conditions directly underneath the doorway, and keeps the door open when the ambient conditions change. The right and left side doors that are opened and closed simultaneously and in synchronism using a pulley mechanism connected to both the right and left side doors. A brushless DC servo motor is preferably employed to move the pulley and thereby open and close the doors. Optical sensors are deployed above one or both doors at selected locations so as to indicate deceleration and stopping points for the doors. Safety and security features include a manual push plate or pushbutton, a key lock on the exterior of the unit, and a multi-tier alarm system.