IL27293A - Particle detector - Google Patents

Description

PATENTS AND DESIGNS ORDINANCE SPECIFICATION A Particle Detector I/We PYROTECTOR, INCORPORATED, a corporation of Massachusetts, of 349 Lincoln Street, Hingham, Massachusetts, U.S.A. do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement :- 1 This invention rel ates general 1 y to a device for 2 detecting particles in a fluid suspending medium and to a 3 circuit controlling system adapted for use therewith, and has particular reference to a smoke detector of the dif- 5 fusion type. 6 Particle detectors of this type utilize a dark chamber 7 with means projecting a light beam across the chamber, and 8 a photo-cell viewing the medial portion of the light beam 9 and shielded from direct radiation from the light source.

When a fluid medium carrying suspended particles enters the 11 housing through suitable openings and passes through the 12 light beam, the particles carried by the fluid medium cause 13 radiation from the light source to be reflected or diffused ] onto the photo cell. The resulting change in resistance of the cell is utilized to actuate an external alarm system. 16 _. Since such devices must operate for long periods of 17 time with a minimum amount of attention and ma ntenance, it 18 is desirable to incorporate, into the alarm control circuit 19 a so-called fail safe provision, by which the alarm will be 0 actuated by the failure of the light source or the power 1 source, in addition to being actuated by the presence of 2 smoke particles in the chamber. 3 The object of the invention is to provide a smoke k detector of the diffusion type, which has control means 5 energized by the energization of the light source to main- 6 tain a normally on alarm swi ch in the off position, and 7 means responsive to the presence of smoke particles in the 3 detector to de-energize said control means. 9 A further object of the invention is to provide a smoke 0 detector of the diffusion type in which a direct current 1 relay's normally closed contacts are connected to an alarm 2 actuating circuit, said relay is energized to the open 3 position by the energization of the light source, and means h is provided responsive to the exi stance of smoke particles in the detector to de-energize the relay. 6 A further object of the invention is to provide a 7 circuit controlling system having switching means respon- 8 sive to direct current to maintain a circuit in a first 9 condition and responsive to alternating current to main-' 0 tain the circuit in a second condition. 1 Other objects of the invention will be apparent to 2 one skilled in the art from the following detailed descrip-3 tion of a specific embodiment thereof. 4 In the drawing: PIG. 1 is a top plan view of a particle detector 6 labyrinth embodying the features of the invention, partly 7 broken away to show the interior arrangement; 8 FIG. 2 is a view in section taken on line 2 -2 of 9 FIG. 1; 0 FIG. 3 is a schematic diagram of the electrical 1 circuit of a particle detector embodying the features of 2 the invention. 3 Referring to the drawing, there is illustrated a k particle detector 10, which comprises generally a housing 5 12, a light source ] k disposed outside the housing, and a 6 detector element 16 disposed in the housing in operative 7 relation to appear hereinafter. 8 The detector 10, in the illustrated embodime t, is 9 particularl adapted for use as the detector unit of a 0 smoke alarm and for this purpose the housing 12 comprises 1 a peripheral wall 18 having a pair of end caps 20 and 22 2 forming an internal dark chamber 2h . The end caps extend 3 beyond the periphery of the wal 1 IS and have inwardly k turned flanges 26 and 28 which are spaced outwardly from the wall. Each end of the wall is provided with a series 6 of outwardly inclined spacing lugs 30, which are adapted to 7 engage frictionally the inner surface of the flanges to 8 retain the caps in assembly. The flanges 26 and 28 , in 9 conjunction with the spacing lugs 30 , form a peripheral 1 0 passageway at each end of the wall to permit smoke to enter 1 1 the chamber from the surrounding atmosphere. 12 To direct and control the beam from the light source 13 ] k , a focusing tube 32 extends through the housing wall on I h one side thereof, and a light trap tube 3^ s disposed in the housing via] ] on the opposite side in alingment with 16 the focusing tube 32 . A lens 36 of the converging type is 1 7 disposed in the focusing tube 32 , with a focal length such 1 8 that light from the source l^ is focused in a converging 19 beam onto the bottom of the light trap tube 3^ , so that the 0 beam from the light has a minimum size at the bottom of 1 said trap, and a minimum amount of the light from the 2 source falls on any other portion of the interior surface 3 of the housing. h A detector tube 33 extends through the housing wall 5 between the light trap tube and the focusing tube, and is 6 disposed generally perpendicular to the axes thereof. The 7 detector element 16 is disposed in the detector tube, and. 3 to restrict the field of view of the detector, a lens hO of 9 the converging type is disposed in the detector tube 0 between the detector element and the chamber. The lens ho has a focal length such that the image of the detector element is focused onto a minimum area on the opposite surface of the housing v;a 11 and the cone of focus of -the detector element is directed across the cone of focus of the light beam, so that the detector element views only the medial portion of the light beam and the field of view of the cell at the opposite wall portion is confined to the medial portion of the wall, so that the cell does not view the peripheral apertures at the top and bottom of the wall. Hence substantially no light reaches the detector element except light appearing in the focus cone of the lens ^O. To further insure that a minimum amount of the internal stray light reaches the detector element, the end k2 of the detector tube on the side adjacent the light tube extends forwardly to the cone of focus of the light beam to provide a shield against stray light from the inside surface of the focus tube. The end of the detector tube from this foremost point is inclined rear-wardly at an ancle such that the inside surface of the detector tube cannot view the inside surface of the focus tube. To prevent stray reflected light from the inside of the light trap tube from reaching the detector lens ^O, the side of the end of the detector tube adjacent the light trap tube is provided with an inclined shield kk.

In the illustrated embodiment the housino 12 is adapted to be mounted onto a support panel k&, and the light source 1*+ is also mounted on the panel in alignment with the focusing tube 32, and connected to a suitable source of electric current. The external mounting of the light source provides a visual check on its condition and 1 The detector element 16 may be any type of device 2 which is .responsive to a change in light intensity, such 3 as a photo-electric or a photo-resistive cell. One type of cell which has been found satisfactory is cadmium sulfide, which responds to an increase in light intensity 6 by a decrease in resistance. Hence in the illustrated 7 embodiment a detector circuit may be connected to the 8 detector element and adjusted to the cell resistance under 9 normal conditions of no smoke so that a predetermined further decrease in cell resistance will actuate an 11 external alarm connected to the detector circuit. V.'hen r 12* smoke enters the housing and appears in the light beam, 13 light from the smoke particles in the portion of the light ] h beam viewed by the detector is reflected or diffused onto the detector cell, thereby lowering the resistance of the 16 cell and actuating the alarm circuit. 17 Referring to FIG. 3, there is illustrated an alarm and 18 control circuit for use with the labyrinth of FIGS. 1 & 2 . 13 The circui of FIG. 3, which may be energized from an alter - 0 nating current source E is intended to actuate means for 1 energizing an alarm A when the cell 16 views illuminated 2 particles in the labyrinth, and also to actuate a control 3 device D which may control the operation of a fire door or k the like, for example, fire doors are ordinar ly designed 5 to be biased by weights or springs to the closed condition, 6 and are held open by a retaining means which may include 7 .control wire having a portion responsive to excessive heat 8 to release the retaining wire and allow the door to close. 9 The retaining means may also include an electrically 0 operated latch, which is normally energized, and which on 1 de-energization releases the control wire to allow the door 2 to close. In the drawing the device D represents an 3 electrically operated latch which, when energized, retains k a fire door or analogous device (not shown) in the open condition, and when de-energized, releases the door to 6 allow it to close automatically. 7 In the llustrated embodiment the alarm A may be 8 energized by a separate source of power such as a battery 9 B, whereas the door control device may be energized by the 0 source E. 1 To provide a "fail safe" type of operation, it is nece 2 sary that the alarm be sounded and fire doors be closed if 3 any portion of the circuit for actuating the alarm and the door control devices becomes inoperative. For this purpose 5 the alarm is connected to its power source 3, through 6 normally closed contacts XI of a direct current relay l 7 said contacts being held open when the relay coil is 3 energized, and the door control device D is connected to 9 the power source E through normally open contacts X2 of sai 0 relay, the contacts X2 being held closed when said relay is 1 energized. During norma! operation of the device, v/hen no 2 smoke is present in the housing, the coil of relay Rl is 3 energized from the A.C. source E through a series connected k photocell PC2 and a diode recti ier 01. Also connected in 5 series with the relay coil across the A.C. source is a 6 third photocell PC3 and a diode 02 which is reversed in 7 polarity in relation to the diode 01 for a purpose to appea 3 hereinafter. 9 The cell PC2 is physically positioned in relation to 0 the light source bulb ] k so that when the bulb ] h is lit 1 the cell PC-2 receives radiation therefrom and its 2 resistance is therefore maintained at a value low enough 3 to permit sufficient half wave D.C. current to flow through k the diode Dl and the coil of relay to hold contacts XI open Hence in case of bulb failure or power failure, the relay 6 is de-energized, whereby the contacts XI close to energize 7 the alarm and contacts X2 open to de-energize the door 8 control device D. 9 To cause the presence of smoke particles in the 0 housing to actuate the alarm, the photocell 16 is connected 1 to the A.C. source E in series with a calibrating resistor 2 K 1 , with a neon bulb 50 being connected in parallel with 3 the resistor Kl, and in series wi h the photocell 1 6 . In 4 the absence of smoke in the housing the resistance of the 5 cell 1 6 is so high that the voltage appearing across the 6 resistor Kl and the neon bulb is not sufficient to 7 ignite the bulb. However, when smoke particles diffuse 8 into the housing 1 2 and enter the light beam, they are 9 "seen" by the cell 1 6 so that its resistance decreases. 0 When its resistance has dropped to a predetermined value, 1 the voltage across the neon bulb 50 and the resistor K 1 2 becomes sufficient to ignite said neon bulb. The cell PC3, 3 which is positioned to receive radiation from the bul 0 k is thereby illuminated and becomes conductive. Current 5 can thereby flow through the diode D2 and the cell PC3, 6 however only on the opposite half cycle from that on v/hich 7 current flows through the cell PC2 and the diode Dl. Full 3 wave A.C. voltage therefore appears across the coil of the 9 relay l and the capacitor F. The capacitor acts as a low 1 current through the coil of relay Rl to a val^'e such that 2 the relay is de-energ zed and the contacts XI close to 3 energize the alarm. k In the illustrated embodiment the alarm is automatical 1y shut off when the smoke conditions are eliminated, since 6 the resulting rise in resistance of cell 16 extinguishes th 7 neon bulb 50 , raising the resistance of cell P C 3 , so that 3 only D.C. power is now impressed across the relay coil and 9 the capacitor F. The relay co l is thereby energized again to open contacts XI and close contacts X2, so that the 1 1 door latch device is again energized. In some embodiments 1 2 it may be desirable to have the alarm contacts lock closed 13 when smoke is detected, which may be accomplished by a I k holding circuit to the relay co l as is well known in the 1 5 ar t . 1 6 ' Although in the illustrated embodiment the circuit 1 7 providing the direct current to the relay coil is completed 1 8 through a photocell, in some cases in place thereof a 19 relay can be provided having a coil in series with the light 14 , said relay having normally open contacts in the 1 0 1 circuit to the relay Rl, which contacts are maintained 2 closed when the l ght is energized. 3 The relay Rl, condenser F and the two circuit paths k thereto including the diodes 0 1 5- D2 form a circuit con- 5 trolling system which provides a method by which direct 6 current is provided to maintain a controlled circuit in a 7 first condition and alternating current is provided to 8 maintain the circuit in a second condition. The specific 9 embodiment illustrated also provides a system in which the 0 illumination of one hotocell maintains the circuit in the first cond tion, and the illumination of both photocells maintains the circuit in the second condition.

Although the circuit is illustrated herein as being applied to a smoke detector, its use as shown in this application is exemplary only, since it is adapted for use in many other types of electrical devices.

Since certain other obvious changes may be made in the device without departing from the scope of the invention, i is intended that all matter contained herein be interpreted in an illustrative and not a lim ting sense. relay's normally closed contacts are connected to an alarm actuating circuit, said relay is energized to the open position by the energization of the light source, and means is 'provided responsive to the exi stance of smoke particles in the detector to de-energize the relay.

A further object of the invention is to provide a circuit controlling system having switching means responsive to direct current to maintain a circuit in a first condition and responsive to alternating current to main- _ tain, t e circuit in a second condition.

Other objects of the invention wi 11 b apparent to one skilled in the art from the following detailed description of a specific embodiment thereof.

I'p the draw ng: I FJG. 1 is a top plan view of a particle detector labyri th embodying the features of the invention, partly broke away to show the i nter ior . arrangement ; .

FJG. 2 is a view. ip section taken on line 2 -2 of FIG. 1 ; FIG. 3 is a schematic diagram of the electrical circuit of a particle detector embodying the features o the invention.

Referring to the drawing, there is illustrated a particle detector 10, which comprises generally a housing 12, a light source 1^ disposed outside the housing, and a detector element 16 disposed in the housing in operative relation to appear hereinafter.

The detecto .10, in the i 11 ustrated embodiment, . is particularly adapted for use as the detector unit of a

Claims (1)

1. insufficientOCRQuality