FAIL-SAFE DETECTOR

• US 3,743,056 A
• Filed: 05/19/1971
• Issued: 07/03/1973
• Est. Priority Date: 05/19/1971
• Status: Expired due to Term

• Current Assignee: Charles L. Winkler, William E. Zitelli
• Original Assignee: Charles L. Winkler, William E. Zitelli
• Inventors: Zitelli, William E., Winkler, Charles L.
• Primary Examiner(s): Gilheany, Bernard A.
• Assistant Examiner(s): Duncanson, Jr., W. E.
• Application Number:
  US05/144,726
• Time in Patent Office: 776 Days
• Field of Search: 187/29 318/480 307/117
• US Class Current: 187/394
• CPC Class Codes: B66B 1/50 with operating or control mechanisms mounted in the car or cage or in the lift well or hoistway

Abstract

A fail-safe position detector in which a pulsed light source induces corresponding electrical pulses in a light responsive receiver circuit when the components are in a desired relative position. The pulses generated in the receiver circuit are effective to operate a translating device through an isolation transformer. Threshold devices at critical junctures in the circuit eliminate marginal operation. The components are selected so that failure of one component or a combination of components will not cause false triggering of the translating device.

Claims

1. A fail-safe position detector for determining when two objects are in a desired relative position with respect to each other comprising:

electrical energy means, a transmitter connected to said electrical energy means, said transmitter being operative to generate a beam of pulses of electromagnetic radiation, a receiver connected to said electrical energy means, said receiver being responsive to electromagnetic radiation of the wavelength generated by the transmitter and operative to generate corresponding pulses of electrical energy when the two objects are in a relative position such that the beam of pulses generated by the transmitter impinges upon the receiver;

translating means operative from a first to a second condition when energized; and

coupling means connected between the receiver and the translating means for energizing thE translating means only with the pulses of electrical energy generated by the receiver, said coupling means completely isolating said translating means from said electrical energy means, preventing operation of said translating means from said electrical energy means due to component failure.

2. The detector of claim 1 including a threshold device comprising:

a comparator having two inputs and an output; and

a reference signal source for generating a reference signal having a predetermined value;

said receiver being connected to one input of the comparator, the reference signal source being connected to the other input and the coupling means being connected to the output, said comparator being operative to deliver the pulses generated by the receiver to the coupling means only when they reach a predetermined value with respect to the reference signal.

3. The detector of claim 2 wherein said transmitter includes a function generator operative to generate a repetitive electrical signal having a frequency in the kilohertz range and a light emitting diode energized by said function generator and operative to emit pulses of light at the frequency of said repetitive electrical signal, wherein said receiver includes a photoresponsive device responsive to the pulses of light emitted by the light emitting diode and operative to generate pulses of electrical energy of a corresponding frequency, and wherein the coupling means is an isolation transformer having a primary connected to the output of said comparator and a secondary connected to said translating device and operative to couple only signals in the kilohertz range between the primary and the secondary.

4. A fail-safe position detector for determining when two objects are in a desired relative position with respect to each other comprising:

a transmitter operative to generate a beam of pulses of electromagnetic radiation having a wavelength between approximately 2,000 and 10,000A, said transmitter including a function generator operative to generate a repetitive electrical signal having a frequency in the kilohertz range and a light emitting diode energized by said function generator and operative to emit pulses of light at the frequency of said repetitive electrical signal, a receiver responsive to electromagnetic radiation of the wavelength generated by the transmitter and operative to generate corresponding pulses of electrical energy when the two objects are in a relative position such that the beam of pulses generated by the transmitter impinges upon the receiver, said receiver including a photoresponsive device responsive to the pulses of light emitted by the light emitting diode and operative to generate pulses of electrical energy of a corresponding frequency, a translating device operative from a first to a second condition when energized, an A.C. coupling device connected between the receiver and the translating device for energizing the translating device with the pulses of electrical energy generated by the receiver, said A.C. coupling device being an isolation transformer having a primary connected to the output of said comparator and a secondary connected to said translating device and operative to couple only signals in the kilohertz range between the primary and the secondary, and a threshold device including a comparator having two inputs and an output and a reference signal source for generating a reference signal having a predetermined value, said receiver being connected to one input of the comparator, the reference signal source being connected to the other input and the A.C. coupling device being connected to the output, said comparator being operative to deliver the pulses generated by the receiver to the A.C. coupling device only when they reach a predetermined value with respect to the reference signal, said comparator including an operational amplifier having two inputs and one output with said receivEr connected to one input and said reference signal source connected to the other, and a Zener diode having a breakdown voltage of a predetermined threshold value and an impedance device connected in series to the output of said operational amplifier, whereby the comparator will generate an output only when the pulses generated by the receiver have a value with respect to the reference signal which is determined by the breakdown voltage of the Zener diode and the transfer function of the operational amplifier.

5. The detector of claim 4 wherein the operational amplifier is an uncompensated microcircuit operational amplifier having a natural frequency in the megahertz range, whereby the oscillations due to failure of the operational amplifier cannot be passed through the isolation transformer to energize the translating device.

6. The detector of claim 1 including said mounting means for mounting both the transmitter and the receiver on a first one of the objects and guiding means for guiding the relative movement of the two objects such that the second object intersects the beam of pulses of the electromagnetic radiation between the transmitter and receiver when the two objects are in the desired position.

7. The detector of claim 1 including the mounting means includes means for mounting both the transmitter and the receiver on a first one of the objects and a control device mounted on the other object for controlling the flow of said pulses of electromagnetic radiation between the transmitter and the receiver.

8. The detector of claim 7 wherein the control device incorporates a reflective surface effective to reflect the pulses of electromagnetic radiation generated by the transmitter, wherein said transmitter includes focusing means to direct said pulses into a beam along a line of sight, and wherein said receiver includes focusing means making the receiver responsive only to pulses striking it along a predetermined line of sight, said focusing means being oriented such that the beam of pulses from the transmitter is reflected by the control device along the predetermined line of sight of the receiver only when the two objects are in the desired relative position with respect to each other.

9. A fail-safe position detector for determining when two objects are in a desired relative position with respect to each other comprising:

a transmitter operative to generate a beam of pulses of electromagnetic radiation having a wavelength between approximately 2,000 and 10,000A, said transmitter including focusing means to direct said pulses into a beam along a line of sight, a receiver responsive to electromagnetic radiation of the wavelength generated by the transmitter and operative to generate corresponding pulses of electrical energy when the two objects are in a relative position such that the beam of pulses generated by the transmitter impinges upon the receiver, said receiver including focusing means making the receiver responsive only to pulses striking it along a predetermined light of sight, a translating device operative from a first to a second condition when energized, an A.C. coupling device connected between the receiver and the translating device for energizing the translating device with the pulses of electrical energy generated by the receiver, mounting means for mounting both the transmitter and the receiver on a first one of the objects, a control device mounted on the other object for controlling the flow of said pulses of electromagnetic radiation between the transmitter and the receiver, said control device incorporating a reflective surface effective to reflect the pulses of electromagnetic radiation generated by the transmitter, said control device being a vane projecting perpendicular to the direction of relative movement of the two objects with the plane of the reflective surface oriented parallel to said direction of relative movement, and wherein the mOunting means includes means to mount the transmitter and receiver on said first object such that their lines of sight intersect at a point in the plane of said reflective surface, said focusing means of the transmitter and receiver being oriented such that the beam of pulses from the transmitter is reflected by the control device along the predetermined line of sight of the receiver only when the two objects are in the desired relative position with respect to each other.

10. The detector of claim 9 including a non-reflective shield mounted on said first object blocking the line of sight of said receiver at a point beyond the point at which the reflective surface of said vane intersects said line of sight when said objects are in the desired position, whereby the receiver is protected from stray radiation.

11. In a transportation system including a structure having a plurality of landings and a vehicle mounted for movement relative to the structure to serve the landings, a detector system for detecting the position of the vehicle relative to a selected landing and including:

a transmitter including a light emitting diode and a pulse generator operative to pulse said light emitting diode at a predetermined frequency, a receiver including photosensitive means responsive to the pulses of light generated by the transmitter and operative to generate electrical pulses at a corresponding frequency in response thereto, mounting means for mounting the transmitter and receiver such that the pulses of light generated by the transmitter impinge upon the receiver when the vehicle is in a desired position relative to the selected landing, translating means operative from a first to a second condition when energized, and an isolation transformer connected between the receiver and the translating means and operative to energize the translating means only in response to electrical pulses from the receiver.

12. In a transportation system including a structure having a plurality of landings and a vehicle mounted for movement relative to the structure to serve the landings, a detector system for detecting the position of the vehicle relative to a selected landing and including:

a transmitter including an infrared light emitting diode and a pulse generator operative to pulse said infrared light emitting diode at a frequency in the kilohertz range, a receiver including a phototransistor responsive to the pulses of infrared light generated by the transmitter and operative to generate electrical pulses at a corresponding frequency in response thereto, mounting means for mounting the transmitter and receiver such that the pulses of infrared light generated by the transmitter impinge upon the receiver when the vehicle is in a desired position relative to the selected landing, a translating device operative from a first to a second condition when energized, and an isolation transformer connected between the receiver and the translating device and operative to energize the translating device only in response to electrical pulses from the receiver having a frequency in the kilohertz range, and a vane having a metallic surface effective to reflect infrared light, said mounting means including means for mounting said vane to said structure adjacent the selected landing and means for mounting the transmitter and receiver on said vehicle such that the beam of pulses of infrared light transmitted by the receiver is reflected by the metallic surface of said vane to impinge upon said receiver only when said vehicle is in the desired position relative to the selected landing.