| 摘要 |
A protective device for movable mechanical shelves, such as paternoster shelves, discontinues movement of the shelves when obstructions are located in their path. The protective device includes light barriers positioned at the boundaries of an opening at which the shelves can be selectively positioned. Electric circuitry connects the light barriers and the motor for driving or moving the shelves. The electric circuitry permits the testing of the operational readiness of the overall protective device during the movement of the shelves. |
