| 摘要 |
An automatic filter has a roll of filter material that starts on a supply spool and passes over the filtering area to a receiving spool. The receiving spool is driven by a motor. Near the end of the roll of filter material there are excitation components in e.g. the form of a diagonal strip across the filter material width. An inductive or optical proximity detector is mounted on the frame of the filter, somewhere across its width. The proximity detector senses the excitation components and sends a signal to a controller that stops the motor driving the filter material roll. Used with automatic filters for gases, e.g. air. The proximity detector, control box and drive motor are all positioned close together and avoids running wires and other connections to the supply spool box. The same length of material is left on the spool no matter what length of filter area is. |
