US3916209A

US3916209A - Vaned baffle for optical smoke detector

Info

Publication number: US3916209A
Application number: US458829A
Authority: US
Inventors: Donald F Steele; Robert B Enemark
Original assignee: Electro Signal Lab Inc
Current assignee: Electro Signal Lab Inc; Sentrol Inc
Priority date: 1973-07-24
Filing date: 1974-04-08
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28
Also published as: CA1022645A

Abstract

An optical smoke detector comprises split optical block mounting an exciter lamp and a smoke sensing photocell in two passages directed toward an intersection zone in a dark chamber formed by one side of the block, a base with a bottom and side wall and a cover, all secured together by one screw. A light pipe from the lamp extends outside the cover to indicate lamp operation. A second photocell is in a third passage communicating with the lamp passage, the third passage mounting diffuser and pin hole apertured disks for spreading a controlled light intensity over the second photocell. The optical block assembly includes an alarm circuit board operationally connected to the photocells and physically positioning the block on the base. Smoke enters the dark chamber through passages formed by curved, light obstructing vanes converging toward an opening to the chamber between the opening and a baffle.

Description

Steele et al.

[ VANED BAFFLE FOR OPTICAL SMOKE 3,430,220 2/1969 13611111 340/237 s DETECTOR 3,460,l24 8/1969 Smith et al 356/207 X [75] Inventors: Donald F. Steele, Cohasset; Robert B. Enemark, weymouth both of Przmary E.\ammerI:lYalter StolwgnG Ma Attorney, Agent, or 1rmJames rover [73] Assignee: Electro Signal Lab, Inc., Rockland, [57] ABSTRACT Mass. An optical smoke detector comprises split optical Flledi P 1974 block mounting an exciter lamp and a smoke sensing [21] AppL No: 458 829 photocell in two passages directed toward an intersection zone in a dark chamber formed by one side of the Related Appllcatlon Dam block, a base with a bottom and side wall and a cover, [63-] Continuation-impart of Ser. No. 382,058, Jul 24, all secured together by one screw. A light pipe from 1973, Pat. No. 3,863,076. the lamp extends outside the cover to indicate lamp operation. A second photocell is in a third passage [52] 5- Cl- 0/5 340/237 communicating with the lamp passage, the third pas- 250/239 sage mounting diffuser and pin hole apertured disks [51] Int. Cl. G01N 21/26 for spreading a controlled light intensity over the secl Field Search 0nd photocell. The optical block assembly includes an 356/207; 340/237 S alarm circuit board operationally connected to the photocells and physically positioning the block on the [56] References Cited base. Smoke enters the dark chamber through pas- UNITED STATES PATENTS sages formed by curved, light obstructing vanes con- 2,537,028 1/1951 Cahusac et al. 250/574 verging an opening to the chamber between 3,222,662 12/1965 Giuffrida 340 237 5 the OPemng and a baffle- 3,3l3,946 4/1967 Goodwin et al. 340/237 S X 3,409,885 11/1968 1-1311 340/233 x 14 Clams 11 Drawmg Flgures 68 9 82 l 1 l 1 l I. ii 111 W i 66 g. I l .5 1-1 ll 1- 1 1' o J a 64 09 Oct. 28, '1975 US. Patent -Oct.28, 1975 Sheet10f2 3,916,209

U.S. Patent Oct.28, 1975 Sheet20f 2 3,916,209

VANED BAFFLE FOR OPTICAL SMOKE DETECTOR RELATED APPLICATION This application is a continuation in part of our copending application for OPTICAL SMOKE DETEC- TOR, Ser. No. 382,058, filed July 24, 1973, now U.S. Pat. No. 3,863,076.

DRAWINGS FIG. 1 is an isometric view of a fully assembled and enclosed optical smoke detector;

FIG. 2 is an exploded isometric of the detector with its face panel removed;

FIG. 3 is an enlarged, exploded isometric view of the detector with its outer cover removed;

FIG. 4. is an isometric view with its inner cover removed, showing its optical block and an inner vaned baffle shown exploded;

FIG. 5 is an isometric view of the optical block assembled;

FIG. 6 is a further enlarged, exploded isometric view of the optical block;

FIG. 7 is an enlarged horizontal section of the assembled detector view from plane 77 of FIG. 3;

FIG. 8 is a fragmentary section view from plane 88 of FIG. 1;

FIG. 9 is a fragmentary vertical section viewed from plane 99 of FIG. 1;

FIG. 10 is bottom plan view from plane 1010 of FIG. 9 of the inner and outer covers and face plate assembled; and

FIG. 11 is a bottom plan view of the vaned baffle shown exploded in FIG. 3.

DESCRIPTION Generally As shown in FIGS. 1 to 4 and 7 an optical smoke detector generally comprises a molded plastic base I having a bottom wall 2 and a semicircularside wall 3, a molded plastic optical block assembly 4 including an optical block 6 and a printed circuit board 7. Over the optical block and base is a two part dark chamber cover of molded plastic including an inner cover 8 and an outer cover 9. Outside these operative parts of the detector are a molded plastic enclosing ring 11 and face plate 12.

As shown particularly in FIGS. 4 and 7 the electronic components of the detector comprise an exciter lamp 13, a smoke sensing photocell 14, a compensating photocell 16, a transformer T with alternating current input leads A, C and an alarm horn H, all connected to the printed circuit board 7.

Optical Block Assembly 4 As shown particularly in FIGS. 5, 6 and 7 the optical block is approximately symmetrically split into two

mating portions

6a and 6b. Respective block portions include a bracket halves 21 receiving and holding the spring clip 22 of a holder 23 for the lamp 13. Between the lamp 13 and the inner side 24 of the block a light passage along axis A] (FIG. 7) including an annular recess for a lens 26 directing a divergent light beam along the axis Al to an opening 27 at the inner side of the block. The passage is annularlyv ribbed to minimize light scatter outside the beam.

The smoke sensing photocell is positioned in an annular recess 28 (semiannular in each block half) receiving the smoke sensing cell 14. From the recess 28 a second light passage 29 extends through a lens 31 along an axis A2 to a zone Z of intersection with the light beam axis A1. The smoke sensing cell views along the axis A2 through an opening 32 on the inner side of the block slightly spaced from the light beam opening 27. The two

passages

27 and 29 on the respective axes Al and A2 are preferably at a included angle.

The second, compensating photocell 16 is similarly located in an annular recess 33 at the outer end .of a passage 34 extending toward a wall 36 which blocks the compensating cell from viewing outside the block. Instead the compensating cell 16 views and receives light from the lamp lens 26 passing through two diffusing disks 37 and two centrally pin-hole apertured disks 38 reducing the light reaching the compensating cell 16 to approximately the intensity of light scattered to the sensing cell 14 by smoke of density at the zone Z which will in one foot attenuate light about 2% to 10%.

In assembly the optical components (lamp, cells, lenses, diffusers and pin-hole disks) are placed in the annular recesses of one half of the block and the other half is mated with the first half, correct positioning being assured by two register pins 39 on half block 6b fitting in holes 41 on half block 6a. Themated half blocks may be clamped or taped together temporarily prior to being mounted as will be explained in connection with the base 1 and

cover

8, 9. After mating .the halves a flexible strip 42' of blackened paper is inserted in a track formed by two opposed grooves 43 above and below the inner side 24 of the block. The strip masks the photocells from ambient light allowing them to acquire operating characteristics by a period in the dark.

The mated optical block is physically joined with the printed circuit board by two screws 43 through the board into the inner side 24 of the block (FIG. 4) to complete the optical block assembly.

The circuit board carries an alarm circuit such as is shown in application Ser. No. 234,775, now US. Pat. No. 3,744,186. The-lamp 13, the

photocells

14 and 16, a transformer T, a hornH and suitable alternating current leads are electrically connected in the alarm circuit. The optical and electric components of the detector are then electrically operational when the masking strip 42 is withdrawn from the track 43, except that a pair of spaced terminals'45 on the circuit board must be interconnected by a temporary jumper for testing the alarm circuit, or by a spring connector described with respect to Enclosing Ring 11 and Face Plate 12.

Base 1 and Two

Part Cover

8, 9

The smoke detector base 1 on which the above described optical block assembly is mounted comprises a bottom wall 2 and a circular side wall 3 extending part way around the edge of the base, specifically between two

smoke ports

44 and 46. These ports are closed with panels 47 of a porous sponge-like material which, as fully described in US. Pat. No. 3,497,303, passes air borne smoke particles but excludes light. The side wall 3 is opposed by the optical block assembly which with the base 1 defines the bottom and sides of a dark chamber 5 around the smoke sensing zone Z.

The circuit board portion 7 of the optical block assembly comprises a planar, rectangular phenolic board 7 whose parallel end edges 47 slide into two vertical slots in guides 48 upstanding from the base. So inserted in the base the inner side 24 of the optical block and one end 49 of the circuit board 7 close one side of the dark chamber between the

ports

44 and 46. The board end 49 and a baffle 51 form a funnel converging toward the dark chamber and smoke sensing zone Z, tending to direct inflowing smoke toward the zone. Such directed smoke flow is aided by thermal convection through the funnel caused by the heating of one or more ohmic components 52 on the end 49 of the circuit board. This baffle 51 and

other baffles

53, 54 and 56 reduce entry of ambient light into the dark chamber and scattering from the lamp beam and dark chamber walls toward the smoke cell 14.

Enclosure of the dark chamber is completed by the two part cover comprising inner cover 8 and outer cover 9. The inner cover 8 has small depending lips 57 which telescope over the side wall 3 and other upstanding portions of the base and positively position the inner cover on the base (FIG. 4). A single screw 58 whose head 59 is countersunk in a boss 61 on the inner cover 8 is selfthreaded through a hole 62 in the two

halves

6a, 6b of the optical block 4 into an apertured boss 63 upstanding from the base 1 (FIG. 9). This single screw secures the inner cover, optical block and base physically in assembled condition and optically and electronically operational, except that the circuit board terminals 45 must be jumped and that an opening 64 will admit light to the dark chamber 5 and intersection zone Z. The inner cover opening may be used to admit a calibrated intensity of light to the dark chamber for testing detector operation.

The outer dark chamber cover 9, shown most clearly in FIG. 3, has a pair of register pins 66 fitting in corresponding holes 67 in the inner cover. A whorled array of curved vanes 68 blocks light from entering laterally under the outer cover to the opening 64 through the inner cover, and imparts an eddying current to smoke entering the dark chamber. Like the other register pins of the detector the pins 66 fit the holes 67 sufficiently snugly to hold the outer cover in place, with the vanes bearing on the inner cover 8 except at clearances 70, until positively secured by the face plate 12.

As shown in FIG. 11 the outer cover 9 comprises a baffle 69 with which the vanes 68 are integrally molded. The baffle 69 is spaced outwardly from the chamber opening 64, which opening is adjacent to the light scattering, intersection zone Z (FIGS. 7 and 11). The vanes extend laterally of the opening to the baffle above the lip of the encircling ring 11 and are curved convergently from their outer entrances 68a to their inner exits 68b at the opening 64. The vanes form curved passages converging toward the opening which by reason of their narrowing toward the exits 68b accelerate the air and smoke particles at the exits. The curvature of the vanes not only obstructs direct light rays from entering to the chamber opening 64 but also imparts an eddying motion to the air and particles so that after entering the opening 64 into the dark chamber they will have a swirling motion substantially greater than that of normal thermal convection flow, and rapid movement of the particles into the light scattering zone Z is promoted. This speed of smoke entry, or entry coefficient, assured by the vanes has been shown to be substantially improved over that of comparable prior smoke detectors tested simultaneously with the present detector. Preferably the vanes are gradually curved and smooth surfaced (with light absorbing black) to minimize air friction and turbulence in the passages. The vanes radiate with their entrances 68a extending through at least 180 or greater, preferably 360 or near, around the opening 64. As shown the vanes form overlapping groups of three or trios, the outer two vanes 68 of each trio being joined at the opening, and the intermediate vane 68c terminating short of the junction 68d so that the junction tends to deflect air downward through the opening 64 while allowing an air passage around the intermediate vane 68c termination for eddying.

Enclosing Ring 11 and Face Plate 12 The face plate 12, shown particularly in FIGS. 2 and 10, is disk shaped and with the enclosing ring 11 forms the outer decorative housing of the present smoke detector. Depending from the center of the face plate are a pair of integrally molded plastic spring detents 71 each of whose tapered free ends diverge to a shoulder 72 (FIG. 9). As shown in FIG. 10, the free ends are of different lateral width and can fit only one way through a first keyhole 73 in the outer cover 9 and a second, aligned keyhole 75 in the inner cover 8, the detent shoulders 72 then springing apart to latch inside the inner cover and positively secure the face plate 12, and outer cover 9 to the detector.

Also on the face plate is a bifurcated, conductive spring jumper connector 74 having two shouldered prongs adapted to be compressed between the two open circuit terminals 45 on the terminal board 7. These terminals may be in one of the alternating current supply leads to the alarm circuit, that is forming an interruption in that lead closed by the jumper 74. If the open circuit terminals carry high voltage they should be recessed in an insulating shroud 76 beyond manual contact.

The face plate has a circular opening 77 for receiving the outer end of a tinted translucent light pipe 78 flush with the outside of the face plate. The light pipe is held frictionally in a socket 78 in one optical half block 6a (FIG. 6), which socket opens inwardly to the lamp 13. The pipe 77 extends from the optical block through

snug holes

81 and 82 in the inner and outer covers respectively and indicates burning of the lamp 13.

The face plate may be snap fitted on the detector either before or after the decorative enclosing ring is secured by the bayonet attachment of studs 83 on the base 1 in grooves 84 inside the ring.

With the detector fully assembled smoke has access to the dark chamber 5 through the

ports

44 and 46 and the inner cover opening 64. These ports enter the dark chamber at three widely divergent solid angles, that is not only laterally from opposite sides of the smoke detector but also through the inner cover opening at right angles to the plane of the lateral angles. This wide solid angle approach, the thermal convection and the whorled vanes of the outer cover greatly aid the flow of smoke in at least one path through the three openings regardless of the orientation of the detector on a wall or a ceiling, or the external flow of smoke.

It should be understood that the present disclosure is for the purpose of illustration only and that this inven tion includes all modifications and-equivalents which fall within the scope of the appended claims.

We claim:

I. A smoke detector for ceiling mounting comprising:

walls forming a dark chamber, one wall having an opening having a vertical axis,

a light source directed into the chamber,

a photoelectric cell detecting light scattered from particles in a zone of the light,

a horizontal light baffle spaced outside and lightshielding said opening and defining a horizontal space allowing unimpeded horizontal smoke flow into the space, and

a plurality of vanes between the baffle and said one wall leading horizontally toward the space between the baffle and opening, at least two of the vanes being curved convergently toward the opening to form at least one horizontal passage increasingly converging toward said opening, the increasing convergence of the passage accelerating the smoke, and the curvature imparting horizontal eddying motion to the smoke as it turns from horizontal flow between the vanes and enters the dark chamber vertically through the opening, thereby to promote movement of the smoke into the light zone.

2. A detector according to claim 1 wherein the curvature of the vanes obstructs direct light rays from the opening.

3. A detector according to claim 1 wherein the vanes are gradually curved to minimize air friction or turbulence in the passage.

4. A detector according to claim 1 wherein the vanes form entrances to a plurality of passages throughout more than 180 of angle.

5. A detector according to claim 4 wherein the vane entrances extend throughout substantially 360 of angle.

6. A detector according to claim 1 wherein the vanes form an entrance toand an exit from the passage, the exit being disposed at the chamber opening and communicating therewith.

7. A detector according to claim 1 wherein the chamber opening is adjacent to the light scattering zone and the vanes converge toward the opening.

8. A detector according to claim 7 wherein the vanes extend laterally of the opening.

9. A detector according to claim 7 wherein the vanes are disposed in tries, the outer two vanes of the trio having a junction at the opening, and the intermediate vane terminating short of the junction to form an air passage between the termination and junction.

10. A detector according to claim 1 wherein the chamber walls form a second opening to the chamber.

11. A detector according to claim I wherein the light baffle and vanes form a unitary structure detachable from-the chamber.

12. A detector according to claim 1 wherein a ring has a lip encircling the opening to the chamber, and the vanes extend from the opening beyond the lip so as to provide access to the passage unobstructed by the lip.

13. A detector according to claim 4 wherein at least two vanes converge to a junction deflecting air through the opening into the dark chamber.

14. A detector according to claim 13 wherein said junction extends across the convergent end of another passage thereby to obstruct air flow past the chamber opening and out an opposed passage.

Claims

1. A smoke detector for ceiling mounting comprising: walls forming a dark chamber, one wall having an opening having a vertical axis, a light source directed into the chamber, a photoelectric cell detecting light scattered from particles in a zone of the light, a horizontal light baffle spaced outside and light-shielding said opening and defining a horizontal space allowing unimpeded horizontal smoke flow into the space, and a plurality of vanes between the baffle and said one wall leading horizontally toward the space between the baffle and opening, at least two of the vanes being curved convergently toward the opening to form at least one horizontal passage increasingly converging toward said opening, the increasing convergence of the passage accelerating the smoke, and the curvature imparting horizontal eddying motion to the smoke as it turns from horizontal flow between the vanes and enters the dark chamber vertically through the opening, thereby to promote movement of the smoke into the light zone.

4. A detector according to claim 1 wherein the vanes form entrances to a plurality of passages throughout more than 180* of angle.

5. A detector according to claim 4 wherein the vane entrances extend throughout substantially 360* of angle.

6. A detector according to claim 1 wherein the vanes form an entrance to and an exit from the passage, the exit being disposed at the chamber opening and communicating therewith.

9. A detector according to claim 7 wherein the vanes are disposed in trios, the outer two vanes of the trio having a junction at the opening, and the intermediate vane terminating short of the junction to form an air passage between the termination and junction.

11. A detector according to claim 1 wherein the light baffle and vanes form a unitary structure detachable from the chamber.