Guide path short detector

• US 4,975,685 A
• Filed: 05/08/1989
• Issued: 12/04/1990
• Est. Priority Date: 05/08/1989
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Rahhal, Rodger G.
• Primary Examiner(s): Goldstein, Herbert
• Assistant Examiner(s): Jackson, Jill
• Application Number:
  US07/348,750
• Time in Patent Office: 575 Days
• Field of Search: 340/651, 340/652, 364/424.01, 364/424.02, 364/478, 180/167-169, 246/28 F, 246/28 C, 246/28 E, 246/28 H, 246/28 K, 246/34 C, 246/34 CT, 246/41, 246/50, 246/58, 246/28 R, 324/508, 324/522, 324/525, 324/539, 324/541, 324/542, 324/555, 324/556
• US Class Current: 340/651
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

To detect a short circuit condition between guide paths embedded in the floor for automatic guided vehicles, a detection relay has a pair of current transformers having primary windings connected into a guide path circuit at points on the source and the return side of the circuit, the transformer secondary windings being connected in opposition to yield a null signal when there is no short and a finite signal when primary current inequalities are present. Amplifier circuitry discriminates between null and finite signals and controls a relay which activates an annunciator.

Claims

1. In a guide path system having adjacent guide paths, apparatus for detecting a short condition of the guide paths comprising:

means for generating different energizing currents in each of the guide paths,

means for sensing currents at spaced locations along one of the guide paths and generating signals proportional thereto, and

means coupled to the current sensing means for comparing the signals and producing an output when a difference exists between the signals, the existence of the output indicating the short condition of the guide paths between the spaced locations.

2. The short detection apparatus of claim 1 in which the different energizing currents differe in frequency.

3. In a guide path system having adjacent guide paths provided with different energizing currents, apparatus for detecting a short condition of the guide paths comprising:

two current transformers with primary and secondary windings having their respective primary windings connected at opposite ends of one of the guide paths for energization by guide paths currents at the respective ends of the one of the guide paths to produce secondary signals which are equal when the guide path currents are equal and are different when the guide path currents are unequal,

means for coupling the transformer secondary signals in counter phase to produce a null when the secondary signals are equal and a finite voltage when the secondary signals are not equal, and

amplifier means connected to the coupling means for detecting the finite voltage and producing an output when the finite voltage exceeds a threshold, and

relay means coupled to the amplifier for responding to he output thereof to indicate the short condition of the guide paths.

4. The invention as defined in claim 3 wherein the finite voltage is an alternating voltage and wherein the amplifier means includes a zero crossing detector for issuing an oscillating signal when the finite voltage is detected, and

a diode for rectifying the oscillating signal and coupling the rectified signal the relay means for effecting the response thereof when the oscillating signal is detected.

5. The invention as defined in claim 3 wherein the finite voltage is an alternating voltage and wherein the amplifier means includes a zero crossing detector for issuing an oscillating signal when the finite voltage is detected and a DC signal when the finite voltage is note detected,

a diode for rectifying the oscillating signal and coupling the rectified signal to the relay means for effecting the response thereof when the oscillating signal is detected, and

a resistor in parallel with the diode for passing the DC signal to the relay means, the DC signal having a polarity effective to prevent the response of the relay means in the absence of the oscillating signal.