Fire and intruder detection and alarm apparatus

• US 4,052,716 A
• Filed: 03/29/1976
• Issued: 10/04/1977
• Est. Priority Date: 03/29/1976
• Status: Expired due to Term

• Current Assignee: Tage A. Mortensen
• Original Assignee: Tage A. Mortensen
• Inventors: Mortensen, Tage A.
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/671,267
• Time in Patent Office: 554 Days
• Field of Search: 340/233, 340/228 R
• US Class Current: 340/552
• CPC Class Codes: G08B 13/1895 using light change detection systems G08B13/194 takes precedence
• CPC Class Codes: G08B 13/19 using infrared-radiation detection systems G08B13/194 takes precedence
• CPC Class Codes: G08B 13/193 using focusing means
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
• CPC Class Codes: G08B 19/005 combined burglary and fire alarm systems
• CPC Class Codes: Y10S 250/01 Passive intrusion detectors

Abstract

Improved apparatus is provided for monitoring a space under surveillance, for detecting the existence of a fire, the presence of an intruder or the occurrence of other abnormal conditions, and for providing a warning signal for actuating an alarm or the like in response thereto. The apparatus employs a plurality of sensors which respond by changes in the electrical characteristics thereof to the level of infrared, light or other radiations from the monitored space respectively sensed thereby. The apparatus significantly provides means for rendering the individual sensors directionally responsive to radiations from respectively corresponding portions of the space being monitored, for employing such sensors as output-affecting elements in more than a single arm of an electrical bridge circuit, for employing such sensors when desired in a plurality of operationally related electrical bridge circuits, for employing capacitative coupling between the output of a sensor-controlled bridge circuit and a differential amplifier to "mask" very slow changes in the output of the bridge circuit due to normal ambient variations while retaining high sensitivity in responding to more rapid changes of such output typical of fire, intruder or other abnormal conditions requiring alarm actuation, for employing such differential amplifier for converting changes in capacitatively coupled output from a sensor-controlled bridge circuit into direct current signals of polarity dependent upon the direction of change in such bridge circuit output, and for employing bridge type rectification for converting signals of either polarity from such differential amplifier into control signals of a single polarity for actuating an alarm activating switching component.

Claims

1. For use in alarm systems or the like wherein at least a pair of adjacent portions of a single space are under surveillance, apparatus for detecting changes in the nature of free-space radiations emanating from said adjacent portions resulting from an occurrence associated with an alarm condition including:

at least one pair of radiation responsive sensing means each having a pair of electrical connection points and characterized by presenting between said points an electrical parameter of variable level which changes in response to changes in the level of radiations being sensed,

said one pair of said sensing means being operative to sense radiations emanating from said adjacent portions of said space;

means for rendering each of said one pair of said sensing means respectively operative to receive and sense radiations emanating from corresponding ones of said adjacent portions of said space;

electrical bridge circuit means having a pair of opposed reference terminals, a pair of opposed output terminals, and a plurality of electrically conductive bridge arms respectively extending to each of said output terminals respectively;

means electrically coupling said points of each of said one pair of said sensing means respectively in electrical series with the respective ones of one adjacent pair of said bridge arms; and

means for detecting changes occurring in an electrical parameter presented between said output terminals in excess of a prescribed rate of change of said parameter and indicative of an alarm condition, whereby changes including those due either to a fire or to the presence of an intruder in either of said adjacent portions of said space will be detected, while slow changes due to gradual alteration of radiation conditions such as the ambient temperature of said adjacent portions will be ignored.

2. The invention of claim 1, wherein:

there is provided a second pair of said radiation responsive sensing means,

said second pair of said sensing means being operative to sense radiations emanating from said adjacent portions of said space,

said rendering means further functioning to render each of said second pair of said sensing means respectively operative to receive and sense radiations emanating from corresponding ones of said adjacent portions of said space,

there being further provided means for electrically coupling said points of each of said second pair of said sensing means respectively in electrical series with the respective ones of the other adjacent pair of said bridge arms.

3. The invention of claim 2, wherein:

the sensing means coupled in one pair of opposing arms of said bridge circuit means are operative to sense radiations emanating from substantially overlapping areas within one of said adjacent portions and,

the sensing means coupled in the other pair of opposing arms of said bridge circuit means are operative to sense radiations emanating from substantially overlapping areas within the other of said adjacent portions.

4. The invention of claim 1, wherein:

said sensing means is provided with directionally discriminatory means for receiving radiations to be sensed thereby,

there being further provided radiation reflecting means,

said receiving means of said sensing means being disposed between said space and said reflecting means and oriented away from said space and toward said reflecting means for receiving substantially only radiations reflected from the latter.

5. The invention of claim 1, wherein:

said detecting means includes a differential amplifier having the inputs thereof capacitatively coupled with said output terminals of said bridge circuit means.

6. The invention of claim 4, wherein:

said reflecting means comprise a curved mirror, and

said receiving means are respectively disposed in differing angular orientations with respect to the focal characteristics of said mirror.

7. The invention of claim 1, wherein:

at least certain of said sensing means are primarily responsive to radiations in the infrared portion of the electromagnetic radiation spectrum.

8. The invention of claim 1, wherein:

at least certain of said sensing means are primarily responsive to radiations in the visible light portion of the electromagnetic radiation spectrum.

9. The invention of claim 1, wherein:

a direct current potential is applied across said reference terminals,

the electrical parameter presented between said output terminals is a direct current potential of variable level, and the changes thereof to be detected may be of either electrical polarity,

there is an alarm controlling switching means having a control terminal which responds for operating said switching means to electrical potentials of predetermined level but of one electrical polarity only, and

there is provided means electrically coupled between said detecting means and said control terminal of said switching means for rectifying changes in said variable level potential to present a control signal of said one electrical polarity.

10. For use in alarm systems or the like wherein at least one portion of a single space is under surveilance, apparatus for detecting changes in the nature of freespace radiations emanating from said portion resulting from an occurrence associated with an alarm condition including:

a first plurality of radiation responsive sensing means each having a pair of electrical connection points and characterized by presenting between said points an electrical parameter of variable level which changes in response to changes in the level of radiations being sensed,

at least one of the sensing means included in said first plurality thereof being operative to sense radiations emanating from said one portion of said space;

means for rendering each of the remaining of said first plurality of sensing means respectively operative to receive and sense radiations emanating from some corresponding portion of said space;

a second plurality of radiation responsive sensing means each having a pair of electrical connection points and characterized by presenting between said points an electrical parameter of variable level which changes in response to changes in the level of radiations being sensed,

at least one of the sensing means included in said second plurality thereof being operative to sense radiations emanating from said one portion of said space;

means for rendering each of the remaining of said second plurality of sensing means respectively operative to receive and sense radiations emanating from some corresponding portion of said space;

first electrical bridge circuit means having a pair of opposed reference terminals, a pair of opposed output terminals, and a plurality of electrically conductive bridge arms respectively extending from each of said reference terminals respectively to each of said output terminals respectively;

means electrically coupling said points of each of said first plurality of sensing means respectively in electrical series with a different one of said bridge arms of said first bridge circuit means;

second electrical bridge circuit means having a pair of opposed reference terminals, a pair of opposed output terminals, and a plurality of electrically conductive bridge arms respectively extending from each of said reference terminals respectively to each of said output terminals respectively;

means electrically coupling said points of each of said second plurality of sensing means respectively in electrical series with a different one of said bridge arms of said second bridge circuit means;

detecting and control means electrically coupled with said output terminals of said first and second control bridge circuit means for activating an alarm or the like in response to changes occurring in an electrical parameter presented between said output terminals of either of said first and second bridge circuit means.

11. The invention of claim 10, wherein:

at least certain of said first sensing means are primarily responsive to radiations in the infrared portion of the electromagnetic radiation spectrum, and

at least certain of said second sensing means are primarily responsive to radiations in the visible light portion of the electromagnetic radiation spectrum.

12. The invention of claim 10, wherein each of said rendering means includes:

radiation focusing means for a focusing radiations from said portions of said space including said one portion thereof for reception by corresponding ones of said sensing means.

13. The invention of claim 10, wherein:

said detecting and control means includes a differential amplifier having the inputs thereof capacitatively coupled with said output terminals of said first and second bridge circuit means, and

said detecting and control means is operative to detect only those changes occurring in said electrical parameter in excess of a prescribed rate of change of said parameter and indicative of an alarm condition, whereby changes such as those due to a fire or the presence of an intruder in said portions of said space will be detected, while slow changes due to gradual alteration of radiation conditions such as the ambient temperature in said portions of said space will be ignored.

14. For use in alarm systems or the like wherein at least one portion of a single space is under surveillance, apparatus for detecting changes in the nature of free-space radiations emanating from said portion resulting from an occurrence associated with an alarm condition including:

at least one pair of radiation responsive sensing means each having a pair of electrical connection points and characterized by presenting between said points an electrical parameter of variable level which changes in response to changes in the level of radiations being sensed,

each of said sensing means being respectively operative to sense radiations emanating from substantially overlapping areas in said one portion of said space;

electrical bridge circuit means having a pair of opposed reference terminals, a pair of opposed output terminals, and a plurality of electrically conductive bridge arms respectively extending from each of said reference terminals respectively to each of said output terminals respectively;

means electrically coupling said points of each of said one pair of said sensing means respectively in electrical series with the respective ones of one opposing pair of said bridge arms; and

means for detecting changes occurring in an electrical parameter presented between output terminals.

15. The invention of claim 14, wherein there is further provided:

a second pair of said radiation responsive sensing means respectively operative to sense radiations emanating from another portion of said space; and

means for electrically coupling said points of each of said second pair of said sensing means respectively in electrical series with the respective ones of the other opposing pair of said bridge arms.

16. The invention of claim 14, wherein:

said detecting means includes a differential amplifier having the inputs thereof capacitatively coupled with said output terminals of said bridge circuit means,

said detecting means functioning to detect only those changes occurring in said electrical parameter in excess of a prescribed rate of change of said parameter and indicative of an alarm condition, whereby changes such as those due to a fire in said one portion of said space will be detected, while slow changes due to gradual alteration of radiation conditions such as the ambient temperature in said one portion of said space will be ignored.