U.S. patent application number 09/731768 was filed with the patent office on 2001-09-13 for apparatus for sensing fluid flow and associated load control circuit.
Invention is credited to Doner, Thomas O., McHugh, George J..
Application Number | 20010020901 09/731768 |
Document ID | / |
Family ID | 22844512 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010020901 |
Kind Code |
A1 |
McHugh, George J. ; et
al. |
September 13, 2001 |
Apparatus for sensing fluid flow and associated load control
circuit
Abstract
A circuit and apparatus for magnetically sensing fluid flow and
applying voltage to a load has a spring loaded check valve disposed
within a conduit and provided with a magnetic shield. A magnet is
located on one side of the magnetic shield while a sensor,
associated with the valve, is located on the opposite side of the
magnetic shield. The check valve, and hence the magnetic shield,
moves to permit fluid flow. When the magnetic shield moves due to
fluid flow, the magnet activates the sensor. A load control circuit
includes a supply terminal for receiving a supply voltage and a
detector which detects a condition requiring the operation of a
load. The detector causes a threshold voltage to be generated from
the supply voltage, and a time delay controller controls the time
required to generate the threshold voltage. A DIAC or equivalent
element conducts to generate a first trigger signal once the
threshold voltage is achieved, and a silicon-controlled rectifier
(SCR) generates a second trigger signal in response to the first
trigger signal. The circuit includes an opto-TRIAC and triac which
are rendered conductive by the second trigger signal to cause a
voltage to be provided to the load.
Inventors: |
McHugh, George J.;
(Broomall, PA) ; Doner, Thomas O.; (Cary,
IL) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
22844512 |
Appl. No.: |
09/731768 |
Filed: |
December 8, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09731768 |
Dec 8, 2000 |
|
|
|
09484168 |
Jan 18, 2000 |
|
|
|
6246331 |
|
|
|
|
09484168 |
Jan 18, 2000 |
|
|
|
09225344 |
Jan 5, 1999 |
|
|
|
6246333 |
|
|
|
|
Current U.S.
Class: |
340/686.1 ;
340/506; 340/551; 340/577; 340/584; 340/628; 340/686.3;
340/686.6 |
Current CPC
Class: |
A62C 35/605 20130101;
Y10T 137/8242 20150401; A62C 35/68 20130101; F16K 37/0041 20130101;
F16K 15/033 20130101; F16K 37/0033 20130101; F16K 15/066
20130101 |
Class at
Publication: |
340/686.1 ;
340/686.3; 340/686.6; 340/551; 340/577; 340/584; 340/628;
340/506 |
International
Class: |
G08B 021/00 |
Claims
What is cladmed is:
1. A spring loaded check valve comprising: an inlet; an outlet;
spring loaded valve member means which prevents passage of fluid
from the inlet to the outlet in a closed position, and which allows
passage of fluid from the inlet to the outlet in an open position;
and magnetic switch means associated with the spring loaded valve
member means for sensing a position of the spring loaded valve
member means.
2. The spring loaded check valve of claim 1, wherein said magnetic
switch means further comprises: magnetic shield means attached to
the spring loaded valve member means for movement therewith between
the open position and closed position; and circuit means to sense
the magnetic shield means, whereby the position of the spring
loaded valve member means may be determined.
3. The spring loaded check valve of claim 2, wherein the circuit
means includes a Hall Effect sensor located in close proximity to a
magnet.
4. The spring loaded check valve of claim 3, wherein the Hall
Effect sensor is activated by the magnet, and wherein the magnetic
shield means blocks the Hall Effect sensor from being activated
when the spring loaded valve member means is in the closed
position.
5. The spring loaded check valve of claim 1, further comprising a
valve seat and wherein the spring loaded valve member means
includes a member which is positioned against the valve seat when
said spring loaded valve member means is in said closed
position.
6. The spring loaded check valve of claim 2, wherein the circuit
means further comprises a reed switch located in close proximity to
a magnet.
7. The spring loaded check valve of claim 6, wherein the reed
switch is activated by the magnet, wherein the magnetic shield
means prevents the reed switch from being activated when the spring
loaded valve member means is in the closed position, and wherein
the magnetic shield means does not prevent the reed switch from
activating when the spring loaded check valve member means is in
the open position.
8. The spring loaded check valve of claim 3, wherein the Hall
Effect sensor is provided in a casing located within the spring
loaded check valve.
9. The spring loaded check valve of claim 8, wherein the casing is
provided with -threads to cooperate with a threaded hole in a wall
of the spring loaded check valve.
10. The spring loaded check valve of claim 4, further comprising
alarm means for sounding an alarm in response to current provided
by the Hall Effect sensor, when activated.
11. The spring loaded check valve of claim 4, wherein the circuit
means includes a time delay circuit for delaying the supply of
current to a load.
12. The spring loaded check valve of claim 6, wherein the reed
switch is provided in a casing located within the spring loaded
check valve.
13. The spring loaded check valve of claim 12, wherein the casing
is provided with threads to cooperate with a threaded hole in a
wall of the spring loaded check valve.
14. A fluid flow alarm system, comprising: a spring loaded check
valve comprising an inlet and an outlet, spring loaded valve member
means which prevents passage of fluid from the inlet to the outlet
of the spring loaded check valve in a closed position, and which
allows passage of fluid from the inlet to the outlet of the spring
loaded check valve in an open position, magnetic switch means
associated with the spring loaded valve member means for sensing
the position of the spring loaded valve member means, said magnetic
switch means further comprising: magnetic shield means attached to
the spring loaded valve member means for movement therewith between
the open position and closed position; and circuit means to sense
the position of the magnetic shield means, whereby the position of
the spring loaded valve member means may be determined, the circuit
means further including: first voltage supply means; first trigger
means that detects activation of a sensor when the spring loaded
valve member means is in an open position and generates a first
trigger signal; time controller means for adjustably controlling
the time required to generate the first trigger signal; second
trigger means that generates a second trigger signal in response to
said first trigger signal; and switch means for providing a load
voltage to an alarm in response to said second trigger signal.
15. The system of claim 14, wherein said spring loaded check valve
member means can be manually placed into the closed position and
wherein the spring loaded check valve member means is situated
against a valve seat when the spring loaded check valve member is
in the closed position.
16. The fluid flow alarm system of claim 14, wherein said time
controller means comprises a dip switch.
17. The fluid flow alarm system of claim 16, wherein the time
required to generate the first trigger signal is adjustable from 0
to 90 seconds.
18. The fluid flow alarm system of claim 14, wherein the circuit
means comprises an A.C. power source and back-up battery.
19. The fluid flow alarm system of claim 14, wherein the circuit
means comprises a battery.
Description
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/225,344 (Attorney Docket No. 017100-072)
filed Jan. 5, 1999.
FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus for sensing
fluid flow through a conduit and controlling a load based upon the
sensing of the fluid flow. More specifically, the present invention
is directed toward a fluid flow sensor and a load control circuit
employing a variable time delay to control activation of an alarm
circuit in a fire protection system.
BACKGROUND OF THE INVENTION
[0003] Numerous control circuits have been designed to apply a
voltage or current to an electrical load after a time delay.
Examples of such circuits are disclosed in U.S. Pat. No. 3,745,382
to Hoge et al., U.S. Pat. No. 3,597,632 to Vandemore, and U.S. Pat.
No. 3,764,832 to Stettner. However, these and other known control
circuits are relatively complicated and have numerous components,
thus increasing manufacturing difficulty and costs. Further, these
and other known control circuits typically provide relatively
lengthy time delays, on the order of five minutes, and are
unreliable when needed to be reduced to a lesser amount of
time.
[0004] Control circuits are used in a variety of applications
including, for example, to activate an alarm circuit in a fire
protection system. Conventional fire protection systems typically
include a source of water or other fire-extinguishing fluid, a
detector for detecting the flow of the fire extinguishing fluid
through a pipe or conduit, and an alarm circuit or other load that
is activated when a sufficient flow is detected.
[0005] In such systems, the alarm is preferably not activated
immediately upon detection of fluid flow in the conduit, because
flow may occur due to a "water hammer" or fluid backwash within the
system. If the alarm were activated immediately upon detection of a
water flow, a large number of false alarms would result.
[0006] In order to reduce or eliminate such false alarms, a control
circuit can delay the activation of the alarm for a predetermined
time following detection of an alarm condition. Early detection and
control circuits included simple mechanical devices, such as
dashpots in which air was forced into and out of a chamber. The
alarm would not sound until the air was completely out of the
chamber, at which time a switch would close to activate the
alarm.
[0007] These and other conventional detection mechanisms were
designed to provide a delay in the range of 30 seconds to 90
seconds. However, these devices were unreliable and inaccurate, and
were thus unsuccessful in eliminating false alarms. Accordingly,
solid state electrical load control circuits were developed for
fire protection systems such as the time delay circuit known as
ICM/HMKS-W1104. These electrical load control circuits delay
activation of the alarm until an electrical sensor or switch is
rendered conductive.
[0008] It would be desirable to provide a relatively simple,
reliable, and easy-to-install sensor circuit with minimal current
draw, in order to detect a condition (such as fluid flow) which
requires activation of a load such as an alarm. While certain flow
sensing devices are known, such as those described in U.S. Pat. No.
3,749,864 to Tice, U.S. Pat. No. 4,791,254 to Polverari and U.S.
Pat. Nos. 5,086,273 and 5,140,263 to Leon, these and other similar
devices include relatively complex arrangements of moving parts. In
addition, it would also be desirable to provide an accurate load
control circuit which delays activation of a load by using an
integrated circuit.
SUMMARY OF THE INVENTION
[0009] The present invention solves the foregoing problems, and
provides additional advantages, by providing an apparatus for
sensing fluid flow through a fluid-carrying conduit. According to
exemplary embodiments of the present invention, a valve such as a
spring loaded check valve disposed within the conduit has a spring
loaded check valve member which is provided with a magnetic shield.
A magnet is located on one side of the magnetic shield while a
sensor, associated with the valve is located on the opposite side
of the magnetic shield. The spring loaded check valve member, and
hence the magnetic shield, moves to permit fluid flow. When the
magnetic shield is removed from between the magnet and sensor, the
magnet activates the sensor. Thus the sensor, which can be a Hall
effect sensor, generates a signal when the valve is opened to
permit fluid flow.
[0010] According to one aspect of the present invention, the sensor
and magnet can both be encased in a tube sealed with substantially
watertight material and inserted into the conduit (e.g., by
threading the encased sensor through a threaded pipe opening) near
the valve.
[0011] In another exemplary embodiment of the present invention, a
load control circuit includes a supply terminal for receiving a
supply voltage and a detector which detects a condition requiring
the operation of a load. The detector causes a threshold voltage to
be generated from the supply voltage, and a time delay controller
controls the time required to generate the threshold voltage. A
DIAC or equivalent element conducts to generate a first trigger
signal once the threshold voltage is achieved, and a
silicon-controlled rectifier (SCR) generates a second trigger
signal in response to the first trigger signal. The load control
circuit includes an opto-TRIAC and a TRIAC or similar switches
which are rendered conductive by the second trigger signal to cause
a voltage to be provided to the load. According to another
embodiment of the present invention, multiple electrically isolated
loads can also be controlled.
[0012] If the supply voltage is an AC (alternating current)
voltage, the load control circuit also includes a rectifying diode
or equivalent element for converting the AC voltage to a DC (direct
current) voltage. The time delay controller may include a
potentiometer (variable resistor) to vary the delay time required
to generate the threshold voltage. Additionally, the time delay
controller can be implemented via a digital implementation. When
digitally employed, a dip switch is used in combination with a
digital control to vary the amount of time delay from zero to
ninety seconds.
[0013] For implementation in a fire protection system in accordance
with the present invention, the detector may be a magnet operated
reed switch, or a Hall effect sensor, for detecting a threshold
fluid flow in a conduit and the load is an alarm for indicating the
threshold flow in the pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The features and advantages of the present invention will be
more fully understood upon reading the following Detailed
Description of the Preferred Embodiments in conjunction with the
accompanying drawings, in which like reference indicia indicate
like elements, and in which:
[0015] FIG. 1 illustrates a block diagram of the sensor circuit and
load control circuit in accordance with an exemplary embodiment of
the present invention;
[0016] FIG. 2 illustrates a schematic diagram showing an exemplary
implementation of a fluid flow sensor of the present invention;
[0017] FIGS. 3A and 3B illustrate schematic diagrams of the fluid
flow sensor and the magnetic shield in accordance with an exemplary
embodiment of the present invention;
[0018] FIG. 4 illustrates a schematic diagram of a reed switch in
accordance with an exemplary embodiment of the present
invention;
[0019] FIG. 5 illustrates a schematic diagram of a spring loaded
check valve and the magnetic shield in accordance with an exemplary
embodiment of the present invention;
[0020] FIG. 6 illustrates a circuit diagram illustrating the load
control circuit in accordance with an exemplary embodiment of the
present invention;
[0021] FIG. 7 illustrates a circuit diagram of the load control
circuit with multiple loads in accordance with an exemplary
embodiment of the present invention;
[0022] FIG. 8 illustrates a circuit diagram of the load control
circuit implementing a digital time delay implementation in
accordance with an exemplary embodiment of the present invention;
and
[0023] FIG. 9 illustrates a schematic diagram of a fire protection
system in which the circuit of the present invention may be
implemented.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Referring now to FIG. 1, an exemplary embodiment of an alarm
circuit according to the present invention is shown. A sensor
circuit 10 is implemented in a fire protection circuit. The fire
protection circuit also includes a load control circuit 14 which
further comprises a delay circuit for controlling the activation of
a load such as an alarm circuit in a fire protection system. In
such a system, the flow of water or other fire suppression fluid
through the pipes of a building sprinkler system (to prevent or
minimize fire damage) is detected, causing a switch to close and
apply an operating voltage to the alarm circuit after a time delay
to guard against false alarms.
[0025] According to the invention, sensor circuit 10 is connected
as shown between a neutral wire 12, an input of a load control
circuit 14, and a terminal 16 of a load L (e.g., an alarm, which
can be embodied by one or more lights, sirens, motors, solenoids,
or other loads) which is connected between a power input terminal
18 and the load control circuit 14. The power input terminal
receives an input voltage of, for example, 24-130 volts A.C. The
sensor circuit 10 senses fluid flow through a pipe, and when fluid
flow is sensed, the sensor circuit 10 generates an output signal
and supplies this signal to the load control circuit 14. The load
control circuit 14 then operates to apply the supply voltage across
the terminals 12 and 18, thereby applying the supply voltage to the
load 16 and activating the alarm. The sensor circuit 10 can be
implemented using a Hall effect sensor or other suitable sensor
such as a reed switch, as will be described in more detail with
respect to FIGS. 2-5 below. It will be appreciated that the time
delay circuit is useful for preventing false alarms.
[0026] Fluid flow can be sensed by the use of a sensor, (e.g. Hall
effect sensor), a magnetic shield, and a magnet used in
combination. The particular Hall effect sensor discussed above is
approximately {fraction (3/16)}".times.{fraction
(3/16)}".times.{fraction (1/16)}", and the magnet can have a 1/4"
diameter and a thickness of 1/8". Due to the relatively small size
of both the Hall Effect sensor and the magnet, each element can be
inserted into a threaded tube (made of, e.g., plastic), and the
tubes can be covered with epoxy or some other suitable material to
provide a substantially watertight seal for the contents of the
tubes. Each of the threaded tubes can then be rotated into the
fluid-carrying conduit through a threaded orifice in the conduit
such that the end of each tube, one containing the sensor and one
containing the magnet are located in close (e.g., within
approximately 1/8") proximity to each other. Alternatively, the
tubes need not be threaded. The tubes containing the sensing device
and magnet can be lowered down through holes to ensure that they
are correctly positioned, and tightened through the use of a nut or
rubber gasket.
[0027] FIG. 2 illustrates a (not to scale) view of a tube 47
inserted into a pipe defined by pipe wall 40, and having a check
valve with a hinged clapper 42. The pipe contains a fluid flowing
in the direction indicated by the flow arrow. Threaded tubes 46 and
47 (shown in FIG. 3A) are inserted into similarly-threaded holes in
pipe wall 40 and this connection is sealed by a suitable seal 49.
The tube 47 includes a Hall Effect sensor 44 and is encased in a
suitable substantially water-tight material. Tube 46 (not shown in
FIG. 2) includes the magnet 45 which is encased in a suitable
substantially water-tight material. Hinged clapper 42 is provided
with sealing portions 48a which cooperate with corresponding
portions 48b of the pipe 40 when the clapper is in a closed
position. Magnetic shield 50 is attached to the hinged clapper 42
so that the magnet is prevented from actuating the Hall Effect
sensor 44 when there is no flow of water through a valve. As shown
in FIGS. 2 and 3A, the magnetic shield 50 is located between the
encased magnet 45 and Hall Effect sensor 44. While the magnetic
shield 50 can be made of any material that is able to shield the
magnetic field of the magnet from the sensor, it is advantageous
for the material to be composed of approximately 3 percent Nickel
Iron to prevent oxidation of the shield.
[0028] As illustrated in FIG. 3B, when there is substantially no
fluid flow in the pipe, hinged clapper valve 42 is in a closed
position and its associated magnetic shield 50 is positioned
between the encased Hall Effect 44 sensor and the magnet 45 to
substantially neutralize the magnet 45. When there is fluid flow
within the pipe, the flapper valve 42 is moved in the direction of
the flow arrow shown in FIG. 2, and the magnetic shield 50 is moved
away from the Hall Effect sensor 44 and magnet 45, thereby freeing
the magnet to bias the sensor such that the sensor conducts to
enable the operation of the sensor circuit 10 and load control
circuit 14. The remainder of the sensor circuit 10 can consist of
three additional components (such as a zener diode, a capacitor and
resistor) which act as a power supply to the Hall Effect sensor.
These elements are described in detail in commonly assigned
application Ser. No. 09/001,216, incorporated herein by reference.
Additionally, the sensor circuit 10 can also include an indicator
circuit described in detail in the above-mentioned commonly
assigned application.
[0029] It should be appreciated that the sensor of the sensor
circuit 10 illustrated in FIG. 1 can alternatively be embodied by a
reed switch associated with a magnet such that motion of the valve
or other indication of fluid flow causes the reed switch to close,
thereby supplying an input to the time delay circuit 14. The reed
switch is set up within the valve in the same manner as described
above with respect to the Hall Effect sensor. However, the manner
in which the switch is activated differs slightly. As illustrated
in FIG. 4, a reed switch 60 encased in tube 47, in this embodiment,
can be biased in an "on" (conductive) state by its associated
magnet 45 encased in tube 46. The reed switch 60, as is known
within the art, consists of two electrodes maintained within a
glass tube. When a magnet is close to the reed switch 60, the
magnet attracts the reed switch electrodes to contact and thus
provide a closed circuit. As illustrated in FIG. 4, the reed switch
magnet 45 is substantially neutralized by the use of the magnetic
shield 50 when the valve is in a closed (no fluid flow) state. When
the magnetic shield 50 is removed from the reed switch, the magnet
45 causes the reed switch 60 to close thereby providing power to
the sensor circuit 10 and load circuit 14. This alternative has the
advantage of lower cost and a reduced number of parts when compared
to employing the Hall Effect sensor.
[0030] It should also be noted that the check valve need not be
embodied only through the use of a hinged clapper. For example, as
illustrated in FIG. 5, a spring loaded check valve 500 is shown in
a closed position. Valve member 510 fits integrally into the check
valve housing 505 located between coupling flange 515 and coupling
flange 520. Valve member 510, located within the check valve 500,
is spring loaded with a spring 523. In accordance with the typical
operation of a spring-loaded check valve, the valve member 510 is
spring-biased into a normally closed position. The valve member 510
can be moved to an open position when water present in the inlet
530 is sufficient to overcome the spring bias and thereby to permit
a flow of water downstream from inlet 530 to an outlet 540.
[0031] The outlet 540 can additionally include a hydraulically
actuated relief valve 545 which is normally maintained in a closed
configuration by a line 550 which can be in fluid communication
with a main conduit upstream, for example. In the event pressure
within the main conduit upstream drops below the pressure in the
outlet detected via line 535, the relief valve 545 will open to
drain the passageway through port 555. Port 555 is provided above
an air gap fitting 560 which drains into a pipe 565.
[0032] The check valve housing 505 also includes an outlet 570
which is adapted to. receive an air/vacuum valve 575. The
air/vacuum 575 valve is normally closed when a passageway provided
by the plumbing fitting 578 is pressurized. However, when the
passageway is not pressurized, the air/vacuum valve 575 provides
communication between the atmosphere and the passageway to prevent
siphoning in the main conduit through the check valve 500.
[0033] The spring loaded check valve 500 can also be manually
closed through the proper rotation of a handle 580. As the handle
580 is rotated, a shaft 581 is urged against the valve member 510
to maintain the valve member 510 in a sealing abutment with the
valve seat 595. Once the shaft 581 is moved against the valve
member 510, the valve is maintained in the closed position.
[0034] As discussed previously with respect to the hinged clapper
member shown in FIG. 2, a magnetic shield 50 can be placed onto the
valve member 510 for the purpose of sensing fluid flow. The
magnetic shield 50 can be placed between threaded tubes 585 and 590
containing a Hall Effect sensor (or reed switch) and a magnet as
described with respect to FIGS. 3A and 4 and indicate to a control
circuit that (the valve is open and therefore) fluid has started to
flow through the valve. Note that threaded tube 590 is shown using
phantom markings as it is located behind the magnetic shield 50 as
shown in FIG. 5.
[0035] When there is substantially no fluid flow in the pipe, valve
member 510 is in a closed position as its associated magnetic
shield 50 is positioned between the encased Hall Effect 585 sensor
and the magnet 590 to substantially neutralize the magnet 590. When
there is fluid flow within the pipe, the valve member 510 is moved
in the direction of the flow arrow shown in FIG. 5, and the
magnetic shield 50 is moved away from the Hall Effect sensor 585
and magnet 590, thereby freeing the magnet to bias the sensor.
[0036] It should also be appreciated that the sensor circuit 10 of
the present invention can also be implemented using a push-button
or pressure switch, such as is commonly used to provide interior
lighting control of, for example, a refrigerator or automobile
door. In such an embodiment, the closed clapper of the valve exerts
pressure on the pressure-sensitive switch to indicate an open
condition (that is, would provide no output to the delay circuit).
When the valve is opened, indicating fluid flow through the pipe,
the pressure exerted by the clapper on the pressure switch is
reduced or eliminated and would indicate a closed condition (that
is, would provide an indicator signal to the delay circuits). It
should also be appreciated that alternative conventions of the reed
switch can be used (i.e., the sensor switch can be a normally open
or normally closed).
[0037] Referring to FIG. 6, according to another embodiment of the
present invention sensor circuit 10 and load control circuit 14 are
shown in detail. The load control circuit includes a neutral
terminal 12 connected to ground and a supply terminal 18 connected
to a power supply 620 which can comprise any standard A.C. power
source of between 30 and 120 volts at 60 Hz. The power supply 620
can also include a back-up battery that can be used to supply
necessary power in the event the A.C. power source has failed for
any reason. The back-up battery could also include a detector for
detecting a lack of A.C. power in the system. When the detector
determines that no A.C. power is available, the battery supplies
necessary current to the load control circuit 14. Furthermore, the
battery could be a rechargeable type battery that is charged when
the A.C. power source is in use. Alternatively, a battery can be
used as the main power source for the circuit in order avoid having
a constant supply of A.C. power.
[0038] A load 70 is connected to the supply terminal 18 to receive
the supply voltage. The load control circuit 14 is connected
between the load 70 and the neutral terminal 12 to selectively
connect the load between the supply terminal 18 and the neutral
terminal 12. In this embodiment, it is assumed that the load 70
draws a maximum of 6 amps; it will be readily appreciated that the
circuit may be readily modified to accommodate loads having a
current draw greater than 6 amps. As discussed above, the sensor
circuit 10 includes a switch 75, a diode 80, and a first capacitor
85 connected in series between the load 70 and the neutral terminal
12. In a preferred embodiment, the diode 80 is a 1N4005 diode, and
the first capacitor 85 is a 33 micro farad (MFD) capacitor rated at
160 volts D.C. (VDC). It will be appreciated that other suitable
diodes and other suitable charge storing elements may be used for
diode 80 and first capacitor 85, respectively.
[0039] The first capacitor 85 is connected in parallel to a
resistor 87. A second capacitor 105 and a time delay setting
circuit 90 are connected in series, in a circuit path that is in
parallel with resistor 87 and in parallel with first capacitor 85.
Resistor 87 functions to discharge capacitor 85 when operation of
the load control circuit is completed. Resistor 87 can be a fixed
10 kilo ohm (k.OMEGA.) resistor rated for 2 watt (W) or other
suitable resistor. The second capacitor 105 may be a 47 MFD
capacitor rated at 50 VDC or other suitable charge storing
element.
[0040] Time delay circuit 90 includes two paths. The first path
includes diode 97 while the second path includes a potentiometer
95. The potentiometer 95 functions to adjustably control the
charging rate of capacitor 105 to delay activation of the load
70.
[0041] The time delay circuit 90 further includes a DIAC 110. The
DIAC 110 is preferably an MBS 4991 DIAC having a trigger voltage of
10 volts, though any suitable triggering element may be used. As
will be appreciated by those skilled in the art, a DIAC (DIode AC
switch) is a bidirectional diode which may be rendered conductive
when a "breakover" or "trigger" voltage is exceeded in either
direction by an applied voltage or trigger spike. Suitable DIACs
are available from numerous suppliers, including Motorola
Corporation.
[0042] The DIAC 110 is connected to a gate 120a of a silicon
controlled rectifier (SCR) 120 through a resistor 115. The resistor
115 may be a fixed 690 .OMEGA. resistor rated for 0.5 watts or
other suitable resistor element. SCR 120 is preferably an EC103B
SCR, available from numerous manufacturers, including the Teccor
Corporation of Dallas, Tex. The anode 120b of the SCR 120 is
connected to the cathode of the second capacitor 105, resistor 87,
and between the cathode of first capacitor 85 and the cathode of
the diode 80. The cathode 120c of the SCR 120 is connected to pin 2
of an MOC3020 opto-TRIAC 125. As a result, light emitting diode 127
connected between pins 1 and 2 of opto-TRIAC 125 is caused to emit
light thereby exciting optical triac 129 connected between pins 4
and 6 of opto-TRIAC 125. Pin 1 of the light emitting diode is
connected via resistor 140 to neutral line 12. Once optical triac
129 is excited, a trigger pulse is provided to the gate of triac
130. The pulse is supplied via the load 70 in series with resistor
135. Triac 130 then turns on the load 70. Resistor 135 can be a
fixed 100 ohm resistor or other suitable resistor element.
[0043] As will be appreciated by those skilled in the art, a
silicon controlled rectifier (SCR) is rendered conductive when a
proper signal is applied to its gate. The SCR remains conductive
when the gate signal is removed, and is turned off by removing the
anode voltage, reducing the anode voltage below the cathode
voltage, or making the anode voltage negative, as on the alternate
half-cycles of an A.C. power source. A TRIAC (TRIode AC switch) is
a gate-controlled bidirectional thyristor or SCR which is rendered
conductive in both directions when a proper signal is applied to
its gate. TRIAC 130 is preferably a Q4006L4 TRIAC available from
numerous suppliers including Teccor Corporation.
[0044] The load control circuit of FIG. 6 may be used, for example,
in a fire suppression system. In such an arrangement, the switch 75
may be a Hall Effect transistor in combination with a power supply
circuit as described above or a magnet operated reed switch on a
vane type water flow detector as discussed above with respect to
FIG. 4, and the load 70 may be an alarm circuit which causes bells,
horns, lights, etc., to be activated in response to a threshold
fluid flow in a conduit with a reed switch. It will be appreciated
that the circuit of the present invention may be used in connection
with other types of switches or detectors and/or with other types
of loads. Suitable reed switches are available from numerous
suppliers, including the C. P. Clare Corporation of Chicago, Ill.
and the Hammlin Corporation of Lake Mills, Wis.
[0045] Using the example of a fire suppression system, the
operation of the load control circuit 14 of the present invention
will now be described. When water or fire extinguishing fluid
starts to flow through the pipes of a sprinkler system in a
building to prevent fire damage, a small permanent magnet as
described above is enabled to activate switch 75 to cause
closure.
[0046] The closing of the switch 75 contacts applies the supply
voltage potential to the rectifying diode 80. In the embodiment of
FIG. 1, the supply voltage is between 24 and 120 volts A.C.
(alternating current).
[0047] The diode 80 rectifies the alternating current to provide a
half wave rectified current equivalent to a D.C. (direct current)
voltage which rapidly charges capacitor 85 to a voltage of about
160 volts D.C. (based on an input voltage of 120 volts A.C.). Diode
80 and capacitor 85 thus have the effect of converting the A.C.
voltage source into a D.C. power source. It will be appreciated
that if a D.C. power source with correct polarity is used, a
rectifying function does not need to be performed, and the diode 80
is therefore unnecessary. In this case, the closing of the switch
causes capacitor 85 to be rapidly charged directly by the power
source.
[0048] The charge stored by capacitor 85 slowly charges the second
capacitor 105 through potentiometer 95 and resistor 100. It will be
appreciated that an RC circuit is formed by second capacitor 105,
potentiometer 95, and fixed resistor 100, and that the RC time
constant and thus the charge time of capacitor 105 may be adjusted
by potentiometer 95. According to one embodiment of the present
invention, potentiometer 95 is a trim pot and allows the delay time
of time delay circuit 90 to be adjustable between about zero
seconds and approximately 90 seconds. A dial or other input device
(such as a screw head slot, not shown) connected to the
potentiometer 95 may be used to adjust the resistor and thus the
time delay. Diode 93 discharges capacitor 105 when power is
removed.
[0049] If not for the presence of DIAC 110, capacitor 105 would be
charged to approximately 170 volts (based on a 120 volt A.C. supply
voltage). However, when the charge stored in second capacitor 105
reaches 10 volts D:C., the break over voltage of DIAC 110 is
achieved, causing DIAC 110 to conduct and generate a first trigger
signal. The first trigger signal is supplied to gate 120a of SCR
120 through the resistor 115 which causes SCR 120 to conduct and
generate a second trigger signal.
[0050] The SCR 120 renders a negative pulse on pin 2 of opto-TRIAC
125. The current through LED 127 thereby renders optical triac 129
conductive. When optical triac 129 is conductive, AC voltage is
supplied to the TRIAC 130. The TRIAC 130 is rendered conductive in
response to A.C. voltage generated by the closure of the optical
triac 129. When the TRIAC 130 turns on, the A.C. voltage drop
across the load control circuit 14 is only about 6 volts. The
signal applied to the gate of TRIAC 130 is phase controlled such
that TRIAC 130 is about 95-98% conductive. If the TRIAC were 70%
conductive, the voltage drop across the TRIAC would be greater than
6 volts, and the power supplied to the load would be reduced. If
the voltage drop across the TRIAC is less than about 6 volts, the
TRIAC may oscillate between conductive and non-conductive states,
thus impairing operation of the load control circuit. It will be
appreciated that the actual voltage drop across the TRIAC is
approximately 6*(1/{square root}{square root over (2)}) which
equals approximately 4 volts RMS.
[0051] Because of the low voltage drop across the TRIAC, the load
70 receives a voltage substantially equal to the supply voltage
potential received at terminals 12 and 18. If the supply voltage is
120 volts A.C., the load receives approximately 114 volts A.C.,
which is more than sufficient to operate horns, lights, motors,
solenoids or any other component in the fire alarm circuit.
[0052] When the water or fire extinguishing fluid stops flowing,
the switch opens and the capacitors 85 and 105 are discharged to
ground. Capacitor 85 discharges through resistor 87 and neutral
terminal 12, and capacitor 105 discharges through diode 97 and
neutral terminal 12. It will be appreciated that other suitable
elements may instead be used to allow the capacitors 85 and 105 to
discharge. If capacitors 85 and 105 are not provided with an
effective discharge path, any remaining charge stored on the
capacitors will cause the delay time to be varied during a later
operation of the circuit. Once capacitors 85 and 105 are
discharged, the circuit is reset and ready for another load control
operation.
[0053] Referring now to FIG. 7, an alternate time delay circuit
according to the present invention is shown. In the embodiment of
FIG. 7, a voltage supply may be selectively applied after a time
delay to a second load. The circuit includes a first circuit having
substantially the same arrangement of components as in the
embodiment of FIG. 6 connected between a first input terminal 18
and a first neutral line 12, and also includes a second circuit 150
connected between second load 155 located on input terminal 154 and
second neutral line 152. Second circuit 150 includes opto-TRIAC
160, second TRIAC 165, and resistor 170, which is connected as
shown. Second load 155 is connected to receive a second voltage
supply via input terminal 154. In operation, once SCR 120 is
rendered conductive in the manner described above, the charge
stored by first capacitor 85 is discharged to provide a negative
pulse to pin 2 of opto-TRIAC 160. As a result of the discharge of
first capacitor 85, light-emitting diode (LED) 175, connected as
shown between pins 1 and 2 of opto-TRIAC 160, is caused to emit
light. The output of pin 1 of opto triac 160 is provided to pin 2
of opto TRIAC 125 as shown in FIG. 5. Thus light emitting diodes
127 and 175 are in series thereby causing each optical TRIAC 129
and 180 between pins pins 4 and 5 of opto-TRIACs 125 and 160, to
conduct. The conduction of optical TRIACs 129 and 180 causes
trigger pulses to be provided to the gates 130g and 165g of TRIACs
130 and 165, thereby rendering the TRIACs 130 and 165
simultaneously conductive and causing power to be applied to both
the first and second load 70 and 155. Resistor 170 is a
current-limiting resistor to limit the current applied to gate 165g
of second TRIAC 165.
[0054] It will be appreciated that the first and second circuits in
the time delay circuit of FIG. 7 are electrically isolated from one
another, and therefore enable the time delay circuit to reliably
control the operation of two loads. Because the first and second
circuits are electrically isolated, the voltage sources connected
to input terminals 18 and 154 may provide the same or different
supply voltages. Alternatively, first and second neutral lines 12
and 152 may be the same neutral line. Further, input terminals 18
and 154 may be connected to the same voltage source.
[0055] Preferably, the supply voltages provided on input terminals
18 and 154 are between approximately 24 and approximately 120 volts
A.C., and first and second loads 70 and 155 draw a current of no
more than approximately 6 amps. Opto-TRIAC 160 can be a 3047
opto-TRIAC available from numerous suppliers, and second TRIAC 165
can be a Q4006L4 TRIAC available from numerous suppliers. Resistor
170 can be implemented by a 100 .OMEGA. resistor. It will be
appreciated that other suitable components can be used.
[0056] Further, it will also be appreciated that the addition of
the second circuit 150 may require changes in the component values
of the first circuit. In the embodiment of the circuit of FIG. 7,
first capacitor 85 is a 33 microfarad capacitor rated for 160 volts
D.C. Further, in the embodiment of FIG. 7, resistor 87 is
preferably a 10 k.OMEGA. resistor rated for 2 watts. Additionally,
capacitor 105 would be changed to a 2200 MFD capacitor rated at 16
VDC. Other component values remain the same. It will be appreciated
that other suitable component values or components can be used for
the time delay circuit of FIG. 7. It will further be appreciated
that operation of more than two electrically isolated loads can be
controlled according to a circuit of the type shown in FIG. 2.
[0057] In yet another exemplary embodiment of the present
invention, the time delay circuit 90 employed within the load
control circuits illustrated in FIGS. 6 and 7 can be implemented
digitally. As illustrated in the FIG. 8 embodiment which shows a
load control circuit controlling two loads, when the switch 75 is
closed, AC voltage is applied to diode 80. The diode 80 changes the
alternating current to direct current and charges the capacitor 85.
The capacitor in combination with a 1N965A zener diode 205 and
resistor 210 form a power supply for a programmable digital IC
timer 215. The time delay can be adjusted by use of a dip switch
220. The dip switch 220 can comprise any multiple pole dip switch
which can be set so that a wanted time delay will elapse. Also,
resistor 225 and capacitor 230 on the output of the dip switch 220
and connected to the neutral node 12, form an oscillator circuit
used with IC timers. The dip switch 220 adjustably controls timing
the delay in the activation of load 70 in a range from 1 to 90
seconds. Upon timeout of the delay, a trigger signal is sent to SCR
120 via resistor 115 from digital IC timer 215. As described above,
the SCR 120 receives the trigger signal and provides a path for the
voltage stored in the capacitor 85 to the opto-TRIACs 125 and 160.
The opto-tiac conducts AC current in both directions providing
power to the load. When the valve closes, the timer 215 immediately
is reset and ready to initiate another time delay upon actuation of
the switch again. With the implementation of the digital control
the values of capacitor 85 would be changed to a 50 MF capacitor
rated at 160 VDC while the resistor would optimally be a 3 Kilo-ohm
resistor rated at 2 Watts or suitable resistor component.
Additionally capacitor 227 is a 0.1 Micro-Farad capacitor while
resistor 225 is optimally a 27 Kilo-ohm resistor or appropriate
resistor element. All remaining elements within the multiple load
control circuit remain the same values discussed with respect to
FIG. 7.
[0058] The digital timer, illustrated in FIG. 8 with multiple
loads, would also be able to be implemented in a load control
circuit containing a single load, illustrated with analog timing in
FIG. 5. Of course, the elements would need to be modified (to the
values described with respect to FIG. 5) in order to ensure proper
operation.
[0059] Referring now to FIG. 9, a fire suppression system including
a load control circuit 14 according to the present invention is
shown. When sufficient water flow through pipe 300 is detected by
switch 75, the switch closes the load control circuit 14 and causes
a load, e.g., an alarm or warning light, to be turned on after a
desired time delay. The time delay reduces false alarms by avoiding
registration of an alarm condition which might occur due to back
flow or other temporary movement of water in the pipe. The delay
period is selectable by the user or manufacturer as described above
to accommodate a given fire protection system. Of course, the time
delay control circuit according to the present invention may be
used in other applications using household or industrial current
and voltage levels. For instance, the switch 75 could detect any of
a number of conditions, such as gas flow, temperature (with a
thermal switch), the open or closed state of an enclosure or
movement of another physical object, to name but a few.
[0060] The foregoing description, while including many
specificities, is intended to be illustrative of the general nature
of the invention and not limiting. It will be appreciated that
those skilled in the art can, by applying current knowledge,
readily modify and/or adapt the specific embodiments described
above for various applications without departing from the spirit
and scope of the invention, as defined by the appended claims and
their legal equivalents.
* * * * *