Patent Publication Number: US-4547673-A

Title: Smoke and flame detector

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to apparatus for detecting the presence of flame and/or smoke, or radiation absorbing vapors, utilizing a single radiation detection tube. 
     U.S. Pat. No. 3,952,196, issued Apr. 20, 1976 and owned by the assignee of the present invention, discloses a device for determining whether the optical surfaces through which radiation must travel from a hazardous area of radiation to the radiation detector are free from radiation-absorbing material or radiation-blocking material. The device disclosed in this patent includes an enclosure for commonly housing both an auxiliary light source and a radiation detector tube, while isolating the same from each other, preventing radiation transmission within the housing from the light source to the detector. The patent also discloses a radiation path from the light source outwardly from the housing to a reflective surface or surfaces external of the housing, which surfaces reflect at least some of the radiation back to the detector through the same optical surfaces that other external radiation passes. The patent contemplates external reflective surfaces which either form a part of the outside housing structure, or are remotely located therefrom. 
     U.S. patent application No. 289,813, filed Aug. 3, 1981, now U.S. Pat. No. 4,405,234 and owned by the assignee of the present invention, discloses a radiation detector tube enclosed in a housing having a light transparent window at one end thereof, with an auxiliary light source enclosed within the housing in optical isolation with respect to the radiation detection tube. The transparent window is constructed with a beveled edge surface and the auxiliary light source is positioned so as to radiate light through the beveled edge, a portion of which is reflected backwards from the interface surface of the front of the transparent window and back through the diametrically-opposite beveled edge of the transparent window. An internal mirrored surface is positioned to collect and reflect the light so received, and to direct the light radiation to the detection tube. The invention provides a self-checking feature for the radiation detection tube and the optical path to the radiation detection tube to the point of interface with the external environment, through a totally-enclosed construction. 
     SUMMARY OF THE INVENTION 
     The present invention provides a self-checking feature for the operation of a radiation detection tube, while at the same time providing, through an optical path external to the device, an apparatus for detecting smoke, and other optically-opaque or absorbing vapors. The radiation detection tube is enclosed within a housing which is optically sealed except for a window at one end thereof. A first internal radiation source emits light over an optical path through the window and is reflected by a surface outside the housing but adjacent the window, back to the radiation detection tube. A second radiation source is included within the housing, but emits light over an optical path external to the housing, which optical path extends from proximate the rear end of the housing to a region in front of the housing window. A reflective surface is positioned external to the housing and in front of the housing window so as to reflect light from the second radiation source back through the window and into the radiation detection tube. The radiation detection tube may also receive light from an externally-detected flame, and therefore serve as a flame detector, or it may receive reflected light from the second radiation source and therefore serve as a smoke monitor and detector, and may receive light from the first internal radiation source which may be used as a calibration base for the other sources of light as well as a self-checking feature for the operation of the apparatus. 
     It is a principal object of the present invention to provide a radiation detection device which functions both as a smoke detector and as an external radiation detector. 
     It is another object of the present invention to provide a radiation detection apparatus having a self-checking feature for monitoring the operation of the apparatus. 
     It is a further object of the present invention to provide a radiation and smoke detector having an internal light source for calibration and monitoring the apparatus, and a second light source for transmitting light over a predetermined external path for smoke or vapor detection. 
     These and other objects and advantages of the invention will become apparent from the following specification and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the invention in isometric view; and 
     FIG. 2 shows a front end view; and 
     FIG. 3 shows a partial cross section view taken along the lines 3--3 of FIG. 2; and 
     FIG. 4 shows a partial cross section view taken along the lines 4--4 of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, the invention is shown in isometric view. A radiation and smoke detector 10 has a tubular housing 12 which is threadably attached at one of its ends to an end cap 18. Threadably attached to the other end of tubular housing 12 is a lens cap 16. Lens cap 16 contains a transparent lens or window 14 which is securely held therein. A removable ring 24 is attached at the front of lens cap 16 in a manner which will be hereinafter described. A cover 22 is attached threadably into end cap 18, and a positioning bar 26 extends between the ring 24 and cover 22. An electrical cable 20 extends through an opening in the rear of end cap 18, and cable 20 contains all of the electrical wires necessary for the operation of the apparatus. 
     FIG. 2 shows a front end view of the apparatus, illustrating a number of concentrically-aligned components. A radiation detector 30 is axially aligned with tubular housing 12, and a number of additional components to be hereinafter described are concentrically arranged about radiation detector 30. Radiation detector 30 may be an ultraviolet detection tube having a relatively high degree of sensitivity for detecting radiation in the range of 1850 Angstroms (A) to 2450 Angstroms, or it may be any other similar device having radiation detection sensitivity. A tubular shield 32 is concentrically aligned about radiation detector 30 and is characterized principally by being constructed of optically-opaque material. Tubular shield 32 may be made from material so as to form an optical shield about radiation detector 30. An internal light source 34 is positioned adjacent the outside surface of tubular shield 32, and is directed generally toward window 14. Light source 34 may be contained within a lamp housing 35, or may be otherwise attached to tubular shield 32. Light source 34 is characterized in that it is capable of generating radiant energy in the 1850 A - 2450 A frequency range. Lens cap 16 contains lens or window 14, and positions window 14 in abutting relationship adjacent the end of tubular shield 32. 
     Lens cap 16 has a circular groove 17 cut into its front face. Reflector ring 24 has a pair of ring clips 28, 29 attached thereto and projecting radially inwardly toward lens 14. Ring clips 28, 29 each have an ear 28a, 29a, adapted for a clamping fit against groove 17. Ring clips 28, 29 are aligned along an axis 3--3 which preferably is orthogonal to the axis of alignment 4--4 of cover 22. Ear 28a projects slightly over the edge of window 14, and is aligned with internal light source 34 as will be hereinafter described. 
     Referring next to FIG. 3, there is shown in partial cross section a view taken along the lines 3--3 of FIG. 2. Lens cap 16 is formed of two tubular sections 16a and 16b. Section 16a is threadably atttached to housing 12, and an O-ring 36 provides a seal therebetween. Section 16b is threadably attached to section 16a to compress a number of components tightly against the forward edge of housing 12. A ring 38 is tightly compressed immediately adjacent the front edge of housing 12. A pair of O-rings 39, 40 are compressed between ring 38 and window 14. O-rings 39, 40 may be replaced by a suitable gasket member having the necessary sealing and compression characteristics. The front surface of section 16b compresses window 14 inwardly toward housing 12, and is preferably threadably tightened to provide a secure seal between window 14 and the respective interior components. Window 14 is also compressed snugly against the forward edge of tubular shield 32 to provide an optical seal, and to thereby ensure that all radiation impinging upon radiation detector 30 must pass through window 14. 
     Ring clips 28 and 29 are attached to ring 24 by a suitable attachment mechanism. Ring clips 28 and 29 and ring 24 are preferably constructed of plastic material, and may therefore be molded as a single unit, or they may be molded into separate parts which are snapped together through appropriate locking grooves and tabs. Ring clips 28 and 29 each have an ear 28a, 29a projecting radially inwardly over at least a portion of window 14. Ear 28a has a curved inner surface 28b which is cut at an angle so as to reflect light from light source 34 to radiation detector 30. Surface 28b is preferably plated with a highly reflective plating material so as to form a mirrored surface. Ear 29a may have a similar surface. It should be noted that light source 34a passes outwardly through window 14, reflects against mirrored surface 28b back toward window 14, and passes through window 14 into the inner volume of tubular shield 32 to impinge upon radiation detector 30. 
     FIG. 4 shows a view taken along the lines 4--4 of FIG. 2, partially in cross section. Ring 24 is indexed by means of a suitable notch and groove 42, forming a connection between ring 24 and positioning bar 26. Positioning bar 26 is located about cover 22, each of which having mating flat surfaces 31, 33 to provide an indexing seat. Cover 22 has a forwardly-facing opening 23 to it&#39;s interior. A light source 21 is positioned inside cover 22, immediately adjacent opening 23 so as to permit light to escape therefrom. Ring 24 has an internal beveled surface 25 which surrounds window 14, and which is preferably plated with a metallic material so as to create a mirrored surface. Mirrored surface 25 receives light from light source 21 and reflects as least a portion of said light to window 14. Window 14 passes at least a portion of this light into the interior of tubular shield 32, to be received by radiation detector 30. The light transmission path from light source 21 to mirrored surface 25 passes through open air proximate the length of detector 10, and is thus affected by atmospheric conditions around detector 10. In the event smoke accumulates in the air around detector 10, the smoke will severely inhibit the light transmission path from light source 21 to radiation detector 30, resulting in a degradation of the electrical signal generated by detector 10 in response thereto. 
     In operation, detector 10 is typically placed in a hazardous environment having a high probability of generating flame or smoke. Detector 10 is usually positioned with window 14 facing the likely source of flame, and is connected to suitable electronic equipment capable of generating and receiving signals for operating detector 10. For example, radiation detector 30 is coupled through wires to amplifier circuits for amplifying and detecting electrical signals which are generated in response to the receipt of radiation by radiation detector 30. Internal light source 34 is coupled to siqnal generators for periodically illuminating light source 34, usually as a means for testing the optical path through window 14 as well as the radiation-receiving characteristics of radiation detector 30. Similarly, light source 21 is connected to suitable signal generation means for periodically generating light to be reflected by mirrored surface 25 back through window 14 for receipt by radiation detector 30. Circuits may be devised for comparing the respective signals received by radiation detector 30 from light transmitted from light source 34 by way of comparison with light transmitted from light source 21. In this manner, light source 34 may be used more or less as a base signal, as a point of comparison for measuring the relative degradation of the light signals received from light source 21, which degradation would principally be caused by smoke obscuring the light transmission path from light source 21. All of these signals are transmitted over wires contained within cable 20. 
     Respective light sources and light transmission paths may also be used to monitor the quality of maintenance of detector 10. For example, in the event the outer surface of window 14 becomes contaminated with dirt, vapors, or other opaque materials, radiation detector 10 will cease to function effectively. This contamination also affects the relative efficiency of transmission of light from both light sources 21 and 34, and may be detected by noting a reduction in signal strength received by radiation detector 30 from these sources. Similarly, if any of the mirrored surfaces described herein become contaminated by dirt, dust or other materials, this contamination may be monitored by means of monitoring the signal strength received from radiation detector 30. A significant reduction in any or all of the signals received by radiation detector 30 may be utilized as a maintenance warning to be generated by the electrical circuits connected thereto. 
     A further operational function is served by positioning bar 26 beyond that hereinbefore noted. In addition to serving as an indexing mechanism to provide the proper positioning for ring 24, positioning bar 26 also forms a protective arm to prevent the mounting of radiation detector 10 at a position so as to obscure the light transmission path between light source 21 and mirrored surface 25. Further, positioning bar 26 may be disconnected from contact with ring 24 to serve as a wrench for loosening cover 22 in the event light source 21 must be replaced. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.