Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGRO~D OF THE rNVENTION
17 Smoke detectors of the photo-electric type utilize a focused light beam
18 passing through a volume which receives smoke from the ambient atmosphere, with ¦
l9 a photo-responsive device viewing the light beam at an angle to the axis
thereof, so that smoke particles illuminated by the beam are seen by the
21 photo-responsive device.
22 Such detectors are calibrated to provide an alarm when the concentration
23 of smoke in the light beam reaches a predetermined level. Cer-tain organizations
24 that test and approve smoke detectors require that means be provided whereby
the user of the detector can test the operability thereof, by simulating the
26 s~ount smoke to whioh the detector is req~ired to respond.
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1 Various methods have been proposed to providc such tegt means. However,
2 it has been fol~d difficult to provide a method which will ~ive consistent
3 results in a smoke detector manufactured in great quantity because of the
difficulty of holding accurate tolerances in the mechanical componcnts.
Methods nsed heretofore depend on light reflected or scattered from an object,
6 such as a wire~ inserted into the light bea~. However~ the amount of light
7 scattered onto the cell depends on the size of the wire~ the surf~ce finish
8 thereof~ and its position in the light beam. The diameter of the wire required
9 to provide the small amount of light re~uired is very small, and is therefore
susceptible to damage in handling during manufacture or damage in use by the
11 user .
SUMMA~Y OF T~E INVENTION
12 This invention provides a smoke detector with a test member and means for
13 positioning the test member in the light beam 80 that one side thereof is
14 illnminated by the light source and the other side thereof is in the view of
the photo-responsive device. In one embodiment of the inventiwl a portion of
16 the test member at or near the front edge thereof is sufficiently thin to be
17 translucentl said translucent portion being small in area in relation to the
18 cross-sectional area of the portion of the light beam into which it is inserted.
19 In another embodiment of the invention~ a small hole is provided in the
20 test member so that a predetermined amount of light passes through the test
21 member when the test member is moved into the light beam.
22 In one embodiment of the invention, the test member is in the form of a
23 plate positioned in a slot in the housing contsining the light source and photo-
24 cell~ and an external lever is provided to move the test plate out of the slot
90 that the leading edge of the test member enters the light beam. The light-
26 transmitting portion is so disposed on the test member so as to be centrally
27 disposed both in the light beam and in the field of view of the photo-cell when
28 moved into the test position.
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Hence, when the test member is projected forwardly
into the light beam, the amount of illumination passing
through the test member and seen by the photocell will be
consistent from one detector to another so long as the
light-transmitting portion of the test member is positioned
within about the center one quarter of the light beam. The
dimensional tolerances of the mechanical components necessary
to position the test member in the test position are there-
fore not restrictive.
In accordance with a particular embodiment of the
invention there is provided, in a smoke detector of the
photo-electric type which includes a light source providing
a light beam and photo-responsive means viewing transversely
a portion of the light beam, the improvement comprising test
means for simulating a predetermined smoke concentration, said
means comprising a substantially opaque plate and means for
temporarily positioning the plate in the light beam between
the light source and the photo-responsive device so that the
plate is illuminated on one side by the light beam and the
other side is viewed by the photo-responsive device, said
plate having a light-transmitting portion, said light trans-
mitting portion allowing a predetermined amount of light to
pass therethrough when the plate i9 SO positioned in the
light beam.
BRIEF DESCRIPTIO~ OF THE DRAWI~GS
Fig. 1 is a top plan view, partly broken away,
showing a housing for the optical components of a smoke
detector with the cover removed~
Fig. 2 is a view of the housing of Fig. 1 as seen
from the front, with the cover in place.
Fig. 3 is a view in section taken on line 3-3
- of Fig. 2, with the test member in the normal retracted
~ position.
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Fig. 4 is a view similar to Fig. 3 in which the
test member is in the forward or test position.
Fig. 5 is a top plan view of Fig. 4.
Fig. 6 is an enlarged view of the test member as
seen in Fig. 4.
Fig. 7 is a view in section taken on line 7-7 of
Fig. 6.
Fig. 8 is a view similar to Fig. 6, illustrating
a modified form of test member.
Fig. 9 is a view taken on line 9-9 of Fig. 8.
Fig. 10 is a view similar to Fig. 6 illustrating
another modified form of test member.
Fig. 11 is a vi~w taken on line 11-11 of Fig. 10.
D - 3a -
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DESCRIPTION OF T~E ILI,USTRATEV E~OD~1EN~
1 Referring to the drawing, thcre is illllstrated a llousing 10 for use in a
2 smoke dciector of t}~lC photo-electric type. The llollsillg is preferably formed of
3 injection molAed plastic and comprises a body 12 comprising a ba9e 1IL, a back
4 wall 16, end walls 18, front wall portions 20 and a pair of up~t~ding members
22 medially disposed between the ends of the front wall portions, forming
~ openings 24 and 26. The upstanding members 22 are spaced apart fo~ng a
7 slot 28.
8 Other upwardly extending members are provided in the housing to form
9 suitably shaped cavities 30 and 32 to receive a light source 34 and a photo-
responsive device 36, with associated focusing lenses 38 and 40.
11 The cavitieg 30 and 32 are shaped and dimensioned to retain the light
12 source and photo-responsive device in a position and orientation such t~at the
13 light beam from the source projects out of the opening 26 at an angle of about
14 22~- from the longitudinal axis of the housing and the viewing axis of the
photo-responsive device extends out of the opening 24 also at an angle of
16 about 222 to the axis of the housing, so that thc vicwing axis of tbe photo-
17 responsive device intersects the axis of the light beam in front of the medial
18 portion of the housing at a point A ~ig. 5) at an angle of about 135 to take
19 advantage of the well-known "forward scatter" effect. The intersection of the
viewing cone of the photo-cell and the cone of the light beam is illustrated
21 by the shaded area V.
22 The light source and photo-responsive device may be connected into suitable
23 circuitry (not shown), by which the light source is energi~ed in a desired
24 manner, and light reflected onto the photo-responsive device irom smoke
particles in the light beam cause a response of said photo-responsive device
26 that actuates an alarm.
27 Examples of such circuitry may be found in U.S. patents 3,946,241 issued
28 March 23, 1976~ 3,917,956 issued November 4? 1975, and patent 4,125~779 issued
29 November 14, 1978.
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1 The viewing area of the photo-cell may be surrounded by a suitable
2 enclosure 41 having internal light absorbing baffles 43, said enclosure having
3 suitable apertures (not shown) to freely admit ambient atmosphere.
~ A cover plate 42 is provided for the housing~ said plate being providedwith an aperture 44 in the medial portion of the front edge and a pair of
6 support arms 46 extending upwardly on opposite sides of the aperture, each
7 leg having an inwardly extending pin ~8 near the upper end thereof.
8 Assembled with the cover is a test lever 50, comprising a medial portion
9 having a pair of recesses 52 on opposite sides thereof receiving the pins 48so that the lever is movable on said pins as an axis. Depending from the
11 medial portion is a test plate 54 which is disposed in the slot 28 of the
12 housing, and extending upwardly and rearwardly therefrom is an operating member
13 56. Extending rearwardly from the lever 50 is an integral plastic leaf spIing
14 58, which, when the lever and cover are assembled with the housing, rests on a
spring support 60 on the rear of the housing, so that the lever is biased
16 clockwise (as seen in Fig. 3) retaining the test plate 54 retracted into the17 slot 28.
18 The test plate 54 is moved to the test position by depressing the operating
19 member 56~ thereby pivoting the lever 50 counter-clockwise (Fig. 1~) and
flexing the spring 58.
21 To limit the pivotine movement of the lever~ so that when the operating22 member is depressed a predetermined portion of the test plate stops substantiall
23 at the center of the light beam~ stop member 61 is provided on the cover,
24 positioned to contact the operating member 56 and limit the downward movement
thereof.
26 In the embodiment of Figs. 6 and 7~ the leading portion of the test plate
27 has an area 62 which is thin in relation to rest of the mcmbcr, said arca bcing
28 substantially smaller than that of the light beam at the intersection of the29 light beam and the field of view of the photo-cell. When the test plate is
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1 moved forwardly into t~e light beam, one side thereof is i~ minatPd by the
2 light beam, and the other side is viewed by the photo-responsive dcvicc. In
3 a preferred cmbodiment of the invention the housing lO and the lever 50 are
Il formed of black plastic, to absorb stray radiation and to mini~i~e the
transmission of light through the test plate 54.
6 ~owever, it has been fol~d that if the area 62 of the test plate is made
7 thin enough, sufficient light is transmitted therethrough and seen by the
8 photo-responsive device to simulate the reqllired ~lolmt of smoke and actuate
9 the alarm.
The amount of light passing through the thin area 62 of the test plate for
11 a given plastic composition, is a function of the thickness of said thin area
12 and the area thereof. For a detector housing of given size and composition,
13 and with a known amount of smoke to be simulated, the area and thickness that
14 will simulate a required amount of smoke can easily be dete~ined by experiment.
In the accompanying drawing, the thickness of the portion 62 as shown in
16 Fig. 7 is not intended to be a representation of the actual thickness necessary
17 for the desired result. ~
18 Although in the embodiment of Figs. 6 and 7 the translucent portion is
19 provided near the leading edge of the test plate, it will be understood that the
thin translucent portion could be in a central portion of the test plate, and
21 means provided ~or projecting the test plate further into or completely across
22 the light beam so that the thin translucent portion is centered in the light
23 beam.
24 Referring to Figs. 8 and 9, there is illustrated a modified form of test
plate 54a which is similar to test plate 54, with the e~ception that the
26 portion 62a need not be so thin as to be translucent~ and a small aperture 6l~
27 is provided in the portion 62a to allow a predetermined amount of light to pass
28 therethrough, The aperture 6~ may be 80 positioned in thé portion 62a as to be
29 substantially centrally located in the light beam when the test plate is in the
3o test position.
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1 Although in the embodiment o~ Figs. 8 and 9, the aperture 6!l is positioned ¦
2 in a thin portion 62a, it will be undcrstood that if desired the plate may be
3 of uniform thickness with the aperture suitably positioned in the plate.
4 ~owever~ the providing of such a small hole in a plate o~ any appreciable
thickness may be a more difficult molding process~ and therefore it is preferred
6 to provide a plate of sufficient thickness to impart the necessary strength for
7 handling in bulk after molding and individually after molding, and provide a
8 thin portion in which the aperture is molded, said thin portion being spaced
9 inwardly from the edges of the plate, ~o that it is protected from damage by
the surrounding thicker portion of the plate.
11 Referring now to Figs. 10 and 11~ there is illustrated another modified
12 form of test plate 54b, which may be of uniform thickness except for the front
13 edge which is beveled, forming surface~ 66 and 68 disposed at a predetermined
14 acute angle to each other~ forming an extreme forward edge portion 70. When
the plate 54b is moved forwardly so that the edge 70 approximately bisectY the
16 light beam, sufficient light is transmitted through the thin extreme forward
17 edge 70 and seen by the photo-responsive device to simulate the required
18 amount of smoke and actuate the alarm.
19 The amount of light passing through the forward edge of the beveled portion
of the test plate for a given plastic composition, is a function of the
21 included angle between the two surfaces and the length thereof e~posed to the
22 light~ witb a greater ligllt transmission resulting with smaller angles. For
23 a detector housing of given size and composition, the angle between the surfaces
24 that will simulate a required amount of smoke can easily be determined by
experiment.
26 Since changes apparent to one skilled in the art may be made in the
27 illustrated embodiment of the invention without departing from the scope of
28 the invention, it is intended that all matter contained hercin be interpreted
29 ~in an i trative and not n limitin~ sen~e.
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