Self-correcting drive and motor control for cargo canopy systems

A canopy deployment and retraction drive mechanism for cargo vehicles comprises:

• a flexible sheet canopy deployably and retractably wound upon a roller spanning an open topped cargo compartment;
• a spool winding up a strap secured to the leading edge of the canopy;
• a first non-free-wheeling motor;
• and,
• a first ratcheting gear coupling the first motor to the spool. 1. A method for disabling an electrical motor when the amount of energy consumed by the motor exceeds a preset limit, said method comprising the steps of:
• assigning a plurality of threshold amperages of an electric current drawn by the motor;
• setting a time duration limit for each of said plurality of threshold amperages;
• measuring the amperage of the current drawn by the motor to get a measured current;
• detecting that said measured current has exceeded a first one of said threshold amperages and not exceeded a next larger one of said threshold amperages;
• accumulating the time said measured current is drawn;
• and
• interrupting a supply of said current when said limit for said first one of said threshold amperages is reached.

In an installation controlling the operation of a motor driving a mechanism for deploying or retracting a protective canopy over the cargo compartment, an improvement for protecting the motor windings against excessive power use comprises:

• a digital ammeter substantially continuously measuring the level of electrical current drawn by said motor;
• means for determining when said current reaches a threshold level of operation;
• a timer accumulating the time period the current remains at said threshold level;
• and
• means for tripping a cutoff switch as soon as a given absolute safe period of operation is surpassed.