Note: Descriptions are shown in the official language in which they were submitted.
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POSITION INDICATOR WITH LIGHT EMITTER
AND TWO LIGHT SENSORS
CROSS-REFERENCE TO RELATED APPLICATION
This is a division of my application No. 537,350, filed
on May 19, 1987, entitled Switch Position Detector and
Indicator with Multicolour Light Emitter.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to electromagnetically
actuated switches and more specifically to a method and
apparatus for verifying correct positions of a contact in a
switch.
2. Description of the Prior Art
Commercially well known reed relay usually includes two
flat reed contacts enclosed in a sealed tube. The reed
contacts are made from soft magnetic material and serve as a
core for transferring magnetic flux. When a magnetic field
is produced by energizing a winding that surrounds the tube,
the reed contacts are mutually magnetically attracted into a
contact engagement. To achieve consistent contact
resistance, the reed contacts must be perfectly parallel and
precisely positioned. Incorrect contact position, due to
manufacturing imperfections or misuse, may adversely affect
performance and life span of the relay. A certain degree of
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operational integrity of a relay may be verified by
measuring resistance of its contacts when the relay is
energized. However, such tests do not reveal slightly
misaligned contacts, do not unveil marginal relays, and are
not always practical to perform in complex devices that
contain large numbers of relays.
A switching device in the form of a reed relay including
a pair of magnetically soft reed contacts and control
winding for effecting closure of the contacts is disclosed
in U. S. Patent No. 3,070,677 issued on December 25, 1962 to
Terrell N. Lowry.
A switching device capable of displaying different
positions of its contact by respectively different colours
is unknown.
A multicolour semiconductor lamp comprising a plurality
of light emitting diodes for emitting light of respectively
different colours is disclosed in U. S. Patent No.
3,875,456 issued on April 1, 1975 to Tsuyoshi Kano et al.
The light emitting diodes are closely adjacent and covered
by a layer of light scattering material to provide an
appearance of a single light source.
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S~MMARY OF THE INVENTION
The present invention endeavors to provide a method and
apparatus for verifying the correct positions, in open and
closed states, of a contact in a switching device.
It is the primary object of the invention to provide a
switching device that includes a multicolour light emitting
diode for indicating different positions of a movable
contact by respectively different colours.
In summary, the invention resides in the addition, to a
switching device, of a multicolour light source for
directing a light beam on a movable contact. The light beam
is reflected from the contact in accordance with its
position on one of two light sensors. The output of the
light sensor activated by the reflected light beam is used
to control the colour of the light beam to thereby indicate
the position of the contact.
Further objects of the invention will become obvious from
the accompanying drawings and their description.
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BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings in which are shown several possible
embodiments of the invention,
FIG. 1 is a cross-sectional view illustrating the
inventive concepts of a switching device of the present
invention.
FIG. 2 is a schematic diagram of a circuit for
verification of the contact position.
FIG. 3 is a cross-sectional view revealing internal
structure of a switching device of the invention.
Throughout the drawings, like characters indicate like
parts.
889
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now, more particularly, -to the drawings, in
FIG. 1 is shown, in very general configuration, a switching
device of the present invention in the form of a reed relay
accommodated in a sealed opaque enclosure 10 having internal
substantially non-reflecting surfaces 5. It would be obvious
to those skilled in the art that the principles of the
invention may be alternatively applied to other types of
relays and switching devices, such are reciprocating,
rotary, step-by-step, and armature types.
The switching device includes a pair of flat reed
contacts 13 and 14 extending through the enclosure and
having overlapping ends inside thereof adapted for contac-t
engagement. The reed contacts may be provided with
externally projecting terminals adapted for joining
conductors thereto (not shown). Stationary reed contact 13
is secured in one wall of the enclosure, and a movable reed
contact 14 having a flexible portion (not shown) and being
capable of moving between its first angular position 14a and
second angular position 14b is secured in the opposite wall.
The switching device also includes a multicolour LED (Light
Emitting Diode) 12 disposed within the enclosure and adapted
for directing a light beam of a predetermined colour on a
reflecting surface 7 of -the movable reed contact 14. Two
LADs (Light Activated Devices) lla and llb are also
disposed within the enclosure and oriented to respectively
intercept reflected light beams la and lb. When the movable
contact is in its normally open position 14a, light beam 1
emitted by the LED 12 reflects from a reflecting surface 7,
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and reflected light beam la is directed on the active area
of the LAD lla. When the movable contact is in its closed
position 14b, reflected light beam lb is directed on the
LAD llb. The output of the LAD activated by the light beam
is used to control the colour of the light beam emitted by
the LED, as will be more fully revealed subsequently, to
thereby indicate the position of the movable contact.
The term 'light activated device' as used throughout
the description of the invention is intended to be
interpreted in a broad sense and may include
phototransistors, photodiodes, photodarlingtons,
phototriacs, photo sensitive silicon controlled rectifiers,
photodetectors, photoresistors, photoconductive cells, and
the like.
A device for verification of the contact position in the
switching device of the present invention is illustrated in
a schematic diagram form in FIG. 2. The device employs
commercially well known phototransistors 16a and 16b, which
exhibit very high resistance, typically hundreds of
Megaohms, when maintained in dark and very low resistance,
typically tens of Ohms, when illuminated, and a multicolour
light source utilizing a red light emitting diode 12a and
green light emitting diode 12b. When a positive voltage
+VCC of a suitable value is applied to the circuit, current
flows from +VCC, via resistor 18a and LED 12a to ground and,
in parallel, via resistor 18b and LED 12b to ground. The
resistors 18a and 18b are selected to have relatively large
values. By way of an example, when voltage +VCC is +5 Volts
and each resistor 18a, 18b is approximately 10 kOhms, the
current in each LED branch is approximately 0.5 mA. As a
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consequence, both LEDs faintly illuminate, and relatively
faint light beam 1 of substantially yellow colour is
produced by blending emissions of the red and green primary
colours and is directed to the movable contact. When the
contact is in its position 14a, reflected light beam la is
directed on the phototransistor 16a, thereby causing it to
exhibit decreased resistance. Additional current now flows
from +VCC, via lower resistance of the phototransistor 16a,
current limiting resistor 17a of relatively small value and
red LED 12a to ground. By virtue of a positive optical
feedback between the LED 12a and phototransistor 16a,
whereby the increase in luminance of the LED causes the
decrease in resistance of the phototransistor which in turn
has an effect of further increase in the luminance and
further decrease in the resistance, the current in the
phototransistor branch, from +VCC, via phototransistor 16a,
resistor 17a, and LED 12a, sharply rises to a value
sufficient to maintain the LED brightly illuminated. If we
consider an exemplary value of the resistor 17a to be
approximately 1 kOhm, current in the phototransistor 16a
branch reaches approximately 5 mA. Thus the combined
current through the red LED 12a is approximately 5.5 mA,
while current through the green LED 12b remains to be
approximately 0.5 mA~ The red LED is brightly illuminated~
and the green LED is faintly illuminated. The colour of
composite light beam 1 is therefore predominantly red. It
is readily apparent that this state exists as long as the
contact is in its position 14a.
When the contact is in its other position 14b, reflected
light beam lb is directed on the phototransistor 16b,
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thereby causing it to exhibit decreased resistance.
Additional current now flows from ~VCC, via low resistance
of the phototransistor 16b, resistor 17b and green LED 12b
to ground. Considering again the resistor 17b to be
approximately 1 kOhm, current in the branch of the
phototransistor 16b reaches approximately 5 mA. Thus the
combined current through the green LED 12b is approximately
5.5 mA, while current through the red LED 12a remains to be
approximately 0.5 mA. The colour of composite light beam 1
is therefore predominantly green. This state exists as long
as the contact is in its position 14b.
When the contact is in an incorrect position different
from the position l~a or l~b, e. g., because it is
misaligned, bent, or broken, the reflected light beam falls
either in an incorrect direction or there is no reflected
light beam at all. There is no optical feedback, and both
phototransistors 16a 16b exhibit very high resistances.
Consequently, the light beam 1 remains to be faint and of
substantially yellow colour, thereby indicating that the
contact is out of position.
An important consideration has been given to physical
arrangement of the light sources and sensors in the
switching device of the invention, as illustrated in FIG. 3.
The contact position sensing assembly is generally
designated 20 and includes a chamber 21c having a cavity 22c
formed therein for light emitting diodes 12a and 12b,
chamber 21a having cavity 22a formed therein for
phototransistor 16a, and chamber 21b having cavity 22b
formed therein for phototransistor 16b. The dimensions of
the chambers should be considered as merely illustrative and
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may be modified. The light signals emitted by light
emitting diodes 12a and 12b are blended by passing through
light scattering material 23 and emerge at its top surface
as a composite light signal having colour in accordance with
the conditions of respective light emitting diodes. Larger
portion of the composite light signal is reflected from an
inclined reflecting surface 27d and directed by a director
25d through transparent member 31 out of the enclosure as a
beam ld to allow external visual observation of the contact
position. Complete hermetic seal between the internal wall
of the enclosure and the director 25d may be achieved by
disposing a sealant adhesive therein so as to secure the
interior of the enclosure from the presence of ambient
light.
The remaining portion of the composite light signal is
directed via relatively narrow aperture 26c in the light
director 25c, reflected by the inclined reflecting surface
27c, and emerges from the end of the director as relatively
narrow light beam 1 at an angle about 45 degrees from the
longitudinal axis of the enclosure 10. The light beam
reflects from the reflecting portion 7 of the movable
contact 14 in accordance with its angular position. The
reflecting portion of the contact may have the form of
highly polished metallic surface or, alternatively, a
miniature mirror secured to the contact surface. When the
contact is in its open position 14a, reflected light beam la
is directed into aperture 26a in the light director 25a,
reflected by the inclined reflecting surface 27a to an
active surface of the phototransistor 16a. When the
contact is in its closed position 14b, reflected light beam
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lb is directed into aperture 26b in the light director 25b,
reflected by the inclined reflecting surface 27b to an
active surface of the phototransistor 16b. The apertures
26a and 26b are slightly larger than the width of the
expected light beam to allow for small deviations in the
contact positions.
It would be obvious to those skilled in the art that,
alternatively, light channeling devices such are mirrors,
prismatic devices, lenses, optical fibers, filters, and the
like, may be used.
The invention may be now briefly summarized. The method
was disclosed of indicating position of a movable contact
element in a switching device by directing a multicolour
light beam on the reflecting surface of the contact element,
obtaining therefrom a reflected light beam having a
direction in accordance with the position of the contact
element, and controlling the colour of the multicolour
light beam in accordance with the direction of the reflected
light beam to thereby indicate the position of the contact.
A novel switching device capable of verifying correct
positions of its contact was disclosed. The swi-tching
device is accommodated in a sealed opaque enclosure having
internal substantially non-reflecting surfaces. A pair of
contact elements extends through the enclosure and has
contact ends inside of the enclosure adapted for engagement.
At least one of the contact elements is movable between its
first position, in which it closes an electrical path with
the other contact element, and its second position, in which
it opens the path. The movable contact element has a
reflecting surface. A multicolour light source is disposed
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within the enclosure and adapted for directing a light beam
on the reflecting surface of the movable contact element
whereby a reflected light beam is obtained having a
direction in accordance with the position of the movable
contact element. Light sensors are provided for
intercepting the reflected light beam to determine its
direction. The colour of the light beam is controlled in
accordance with the direction of the reflected light beam to
thereby indicate the position of the movable contact
element. A portion of the light beam is directed out of the
enclosure to provide an external visual indication of the
contact position.
All matter herein described and illustrated in
the accompanying drawings should be interpre-ted as
illustrative and not in a limiting sense. It would be
obvious that numerous modifications can be made in the
construction of the preferred embodiments shown herein,
without departing from the spirit of the invention as
defined in the appended claims.
