The present invention relates to a laundry machine control system and more particularly to a system for sensing the rotation of a laundry machine cylinder to generate a control voltage for a door locking unit.
In the past, many accidents have occurred by a user opening the door of a laundry machine while it is in operation. To prevent such accidents, special electrical door lock mechanisms have been devised, such as that shown in U.S. Pat. No. 3,243,977, to automatically maintain the laundry machine door locked during the operation until the entire washing cycle had been completed or a premature shutdown occurs.
Prior art systems for generating the necessary control voltage to operate such a door lock have been expensive and complicated. In one such system, a self-contained DC generator is mechanically connected to the rotating axis of the laundry cylinder to generate the necessary DC voltage by direct mechanical linkage with the axle. This approach requires a number of moving parts as well as considerable time and expense in connecting the necessary linkage to the rotating axle. Another system uses a plugging switch with a mechanical connection to the cylinder shaft which senses rotation and bends a contact by magnetic force to open or close a switch to actuate or deactuate a control circuit. Such a system is relatively expensive and complicated and is generally not sufficiently reliable and precise for continued long-term use.
USPTO Backgrounds
USPTO Backgrounds