Granted Patent B2

US 9,136,694 · App. 13/840,530 · Granted Sep 15, 2015

Abstract

Claims (49)

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.

2. The method of claim 1 ,

wherein said step of setting comprises:

procuring a time-versus-current function expressing the maximum time values of excessive current that may be safely drawn by said motor; and,

wherein said step of interrupting comprises:

switching off said motor when a maximum time of flow for a measured current exceeds a corresponding maximum time value given by said function.

3. The method of claim 1 , which further comprises:

comparing said amperage to a preset maximum current limit; and

switching off said motor when said limit is exceeded.

4. The method of claim 1 , wherein said measuring occurs continuously.

5. The method of claim 1 , which further comprises:

subsequently detecting that said measured current exceeds said next larger one of said threshold amperages; and,

interrupting said supply when said limit for said next larger one of said threshold amperages reached without resetting said accumulated time.

6. The method of claim 1 , which further comprises programming a microprocessor for performing said measuring, setting, accumulating and interrupting.

7. The method of claim 6 , wherein said programming further comprises:

assigning at least three of said plurality of threshold amperages from a continuous range of selectable amperages falling between a minimum current for possible cutoff and a maximum allowable current.

8. The method of claim 1 , wherein said motor is used to translate a canopy over a cargo compartment.

9. The method of claim 8 , which further comprises:

said motor being a first non-freewheeling motor driving a spool winding up a strap secured to the leading edge of the canopy;

a second non-freewheeling motor driving a canopy take-up roller; and

coupling said first motor to said spool via a first ratcheting gear.

10. The method of claim 9 , which further comprises coupling said second motor to said roller via a second ratcheting gear.

11. The method of claim 9 , which further comprises performing a braking action upon the spool.

12. The method of claim 1 , which further comprises running the first motor is run in reverse rotation during retraction of the canopy.

13. The method of claim 12 , which further comprises said first ratchet gear intermittently disengaging the spool from the first motor during reverse rotation as the canopy is being retracted.

14. The method of claim 13 , which further comprises running the second motor is run in reverse rotation during deployment of the canopy.

15. The method of claim 14 , which further comprises said second ratchet gear intermittently disengaging the second motor during reverse rotation as the canopy is being deployed.

16. The method of claim 9 , wherein the roller is connected to a median portion of the canopy and is rotated to take up and wind together both straddling sections of the canopy; and said mechanism further comprises:

a track spanning one end of the cargo area, said track supporting the second motor; and

a motor-stabilizing torque arm riding on said track.

17. The method of claim 9 , which further comprises:

said strap being a first strap which comprises:

a first distal portion connected to said leading edge; and

a first proximal portion wound-up on said spool; and,

a second strap which comprises:

a second distal portion connected to said leading edge; and

a second proximal portion wound-up on said spool.

18. The method of claim 17 , which further comprises winding each of said first and second straps upon separate cooperating reels of said spool.

19. 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.

Assignments (8)