U.S. patent number 3,846,641 [Application Number 05/396,125] was granted by the patent office on 1974-11-05 for control system for a plurality of loads.
This patent grant is currently assigned to Hochiki Kabushiki Kaisha. Invention is credited to Yoshihiro Eguchi.
United States Patent |
3,846,641 |
Eguchi |
November 5, 1974 |
CONTROL SYSTEM FOR A PLURALITY OF LOADS
Abstract
In a control system wherein a plurality of loads are
sequentially connected in parallel across supply conductors, each
load is connected across the supply conductors through a switching
circuit which is closed a predetermined interval after the
application of an operating voltage, the loads in the second and
succeeding stages are connected across the supply conductors
through transfer switches which are operated in response to the
operation of the loads in the preceding stages, a relay contact is
connected in parallel with each transfer switch, and relay means is
provided for each stage for opening the contact when the load and
the switching circuit in that stage are energized, and for closing
the contact after a predetermining interval. For the purpose of
performing a conduction test of the whole system, the supply
conductors are terminated with an impedance element, and a test
voltage lower than the operating voltage is connected to the supply
conductors at the time of the conduction test.
Inventors: |
Eguchi; Yoshihiro (Tokyo,
JA) |
Assignee: |
Hochiki Kabushiki Kaisha
(N/A)
|
Family
ID: |
14144734 |
Appl.
No.: |
05/396,125 |
Filed: |
September 10, 1973 |
Foreign Application Priority Data
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Sep 22, 1972 [JA] |
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47-95699 |
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Current U.S.
Class: |
307/41;
361/166 |
Current CPC
Class: |
H03K
17/292 (20130101); G05B 19/07 (20130101) |
Current International
Class: |
G05B
19/04 (20060101); H03K 17/292 (20060101); H03K
17/28 (20060101); G05B 19/07 (20060101); H02j
003/14 () |
Field of
Search: |
;307/41,38,39,40,141,141.4,141.8 ;317/123,136,139,141 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hohauser; Herman J.
Attorney, Agent or Firm: Waters, Roditi, Schwartz &
Nissen
Claims
What is claimed is:
1. A control system for sequentially operating a plurality of loads
connected in parallel across supply conductors, said control system
comprising a plurality of switching circuits for respective loads,
each one of said switching circuits being closed a predetermined
interval after the application of the operating voltage for
connecting the associated load to said supply conductors, a
plurality of transfer switches for connecting the loads to said
supply conductors in the second and succeeding stages, means
responsive to the operation of the load in the preceding stage for
operating the transfer switch of the succeeding stage to connect
the load of said succeeding stage across said supply conductors, a
plurality of relay contacts respectively connected in parallel with
said transfer switches, relay means connected in preceding stages
for opening said contacts when the loads and said switching
circuits in the preceding stages are energized, and for closing
said contacts after a predetermined interval, and a terminal
impedance element connected across the end terminals of said supply
conductors.
2. The control system according to claim 1, which further comprises
a first source for supplying a normal operating voltage for said
loads, a second source having a test voltage lower than said normal
operating voltage, a transfer switch for selectively connecting
said supply conductors across either one of said first and second
said sources, and a meter for measuring the current flowing through
said supply conductors when said second source is connected
thereto.
3. The control system according to claim 2 wherein, each one of
said respective switching circuits comprises a silicon controlled
rectifier connected in series with one load, a Zener diode
connected to supply a gate voltage to said silicon controlled
rectifier, a CR time constant circuit for applying a driving
voltage for said Zener diode a predetermined interval after
energization of the switching circuit, said Zener diode not
becoming conductive when supplied with said test voltage.
4. The control system according to claim 3 which, further comprises
a plurality of protective circuits, each connected parallel with
the serially connected with one load and one switching circuit and
comprising a relay coil for operating said contact, a transistor
connected in series with said relay coil, and a CR time constant
circuit and a Zener diode which are connected in series for
applying a control current to said transistor, said last-named
Zener diode becoming conductive when applied with said operating
voltage for rendering conductive said transistor within the delay
time of said switching circuit, said Zener diode becoming not
conductive when applied with said test voltage which is lower than
said operating voltage, and said last-named CR time constant
circuit having a time constant which is predetermined such that
said control current for said transistor is maintained for a
interval somewhat longer than the operating time of said load and
is then decreased to a value sufficient to interrupt said
transistor.
Description
BACKGROUND OF THE INVENTION
This invention relates to a control system, and more particularly
to a control system for sequentially operating a plurality of loads
connected in parallel to a source of supply, for example,
fire-preventing doors or shutters, unlocking means for emergency
doors, smoke exhaust fans, automatic water sprinklers, alarms,
etc., installed in buildings.
In modern large buildings, a large number of emergency apparatus of
the type described above and consuming a relatively large power are
installed. Accordingly, if such a large number of emergency
apparatus are operated simultaneously upon occurence of an
emergency such as a fire hazard a large electric power would be
consumed thereby causing overload of the source of supply and a
large voltage drop of the feeder. Accordingly, it has been proposed
to sequentially start such emergency apparatus one after one or
group after group.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an
improved control system for a plurality of loads connected in
parallel across common supply conductors, according to which it is
possible not only to sequentially start the plurality of loads,
thereby preventing the source from overloading, but also to perform
a conduction test of the whole system.
Briefly stated, according to this invention the loads are connected
to the supply conductors through respective switch circuits which
are closed a predetermined interval after the application of an
operating voltage under the control of suitable time delay means,
such as timers. Loads in the second and succeeding stages are
connected to the supply conductors through transfer switches which
are operated when the loads in the preceding stages are operated.
Relay contacts are closed when the operating voltage is impressed
upon the loads and the switching circuits in respectively preceding
stages, and are opened a predetermined interval thereafter. The
relay contacts are connected in parallel with the transfer
switches, and an impedance is connected across the ends of the
supply conductors.
On the supply ends of the supply conductors there are provided a
first source to supply the operating voltage, a second source for
supplying a test voltage which is lower than the operating voltage,
switch means for selectively connecting the supply conductors to
either one of the first and the second sources, and a meter for
measuring the current flowing through the supply conductors and the
terminal impedance when the second source is connected to the
supply conductors.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a connection diagram of a prior-art control system for
sequentially operating a plurality of loads, for example door
unlocking circuits;
FIG. 2 shows a sectional view of a door unlocking device utilized
in the circuit shown in FIG. 1;
FIG. 3 shows a connection diagram of the novel control system
embodying the present invention; and
FIG. 4 shows voltage and current waveforms of the various elements
utilized in the circuit shown in FIG. 3.
FIG. 1 of the accompanying drawing illustrates a typical connection
diagram of a prior-art control system in which the loads are shown
as a plurality of door unlocking devices DL.sub.1, DL.sub.2 .....
connected in parallel across supply conductors CL and L. Each of
the door unlocking device comprises an operating coil L for
unlocking a door, not shown, a time delay circuit T which are
connected in parallel across supply conductors CL and L, a relay A
including a contact a and connected in parallel with the time delay
circuit T, and a transfer switch MS connected in parallel with
contact a.
As shown in FIG. 2, the operating coil L comprises the coil of an
electromagnet for operating a door unlocking device. More
particularly, in the example shown in FIG. 2, a fire preventing
door DR is provided with an armature PT secured thereto, and a
permanent magnet M. The magnetic flux produced by the permanent
magnet M flows through a magnetic circuit including a yoke for the
permanent magnet M and the electromagnet and the armature as shown
by solid line arrows X whereby the armature PT is attracted by the
magnet assembly to lock the door in the closed position.
When a current flows through the coil L, the magnetic flux produced
thereby flows in a direction indicated by dotted line arrows Y thus
cancelling the flux produced by the permanent magnet M.
Consequently, the armature PT will be released and the door DR will
be biassed to the open position by the action of springs mounted on
the door hinges (not shown). As the door is opened in this manner,
a plunger PG is pushed outwardly to the position indicated by
dotted lines by the action of a spring SP so that the inner end of
the plunger PG actuates the transfer switch MS.
As can be readily noted from FIG. 1, when the transfer switch MS is
operated in this manner, that is transferred from the upper contact
to the lower contact, the door unlocking circuit DL.sub.1 is
deenergized and the next door unlocking circuit DL.sub.2 is
energized. In this manner, a plurality of door unlocking circuits
are energized sequentially.
In the second door unlocking circuit DL.sub.2, relay A is actuated
after a predetermined time determined by the delay circuit T
associated therewith thereby closing a contact a in parallel with
the transfer switch MS of the second door unlocking circuit
DL.sub.2. For this reason, even if the transfer switch M of the
preceding door unlocking circuit DL.sub.1 were not operated due to
a fault or the like cause, the second door would be positively
unlocked after a predetermined interval.
Although the control system described above is advantageous in that
a plurality of loads or door unlocking circuits are operated
sequentially and that succeeding door unlocking circuits are caused
to operate sequentially even when a preceding door unlocking
circuit fails to operate, since the door unlocking circuits are
opened prior to their operation, it is impossible to test their
conduction.
Even if a test contact is connected in parallel with the contact a
of relay A and the transfer switch MS, because of the low impedance
of coil L, it is impossible to determine the value of a terminal
resistor connected at the end of the supply conductors from their
supply ends. Thus, it is impossible to perform a conduction test of
the whole system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 3, there is shown a preferred embodiment of
the control system constructed according to the teaching of this
invention, which comprises a source E.sub.1 for driving the loads,
a source E.sub.2 for performing a conduction test, an ammeter (or
ohmmeter) M, and a transfer switch SW between sources E.sub.1 and
E.sub.2. Although in this example door unlocking circuits DL.sub.1
and DL.sub.2 are shown as the loads it should be understood that
various emergency apparatus of the type described above are used in
practical applications.
In accordance with this invention, a switching circuit SC is
connected in series with each door unlocking circuit. The switching
circuit SC comprises a silicon controlled rectifier SR connected in
series with the coil L, a control transistor Tr.sub.1 for the
silicon controlled transistor, resistors R.sub.1, R.sub.2 and
R.sub.3, capacitors C.sub.1 and C.sub.2, a diode D, and a Zener
diode ZD which are connected as shown.
Further, in accordance with this invention, a protective circuit PC
is connected in series with said serially connected coil L and
switching circuit SC. The protective circuit PC comprises a relay
A, a control transistor Tr.sub.2 connected in series therewith,
resistors R.sub.4, R.sub.5 and R.sub.6, a capacitor C.sub.3, and
Zener diodes ZD.sub.2 and ZD.sub.3 which are connected as shown. A
plurality of door unlocking circuits DL.sub.1, DL.sub.2...., each
having a construction as above described, are connected in parallel
across supply conductors CL and L.
Each of the second and succeeding door unlocking circuits DL.sub.2,
DL.sub.3.... is connected to the supply conductors CL and L through
the transfer switch MS shown in FIG. 1 or other suitable switch
which is switched when the preceding load is operated, and the
contact a of the relay A of the preceding load. The ends of the
supply conductors are terminated by a terminal impedance element RL
such as a resistor or a Zener diode.
The operation of the inventive control system shown in FIG. 3 will
now be described with reference to the wave forms shown in FIG. 4.
When the transfer switch SW of the source device S is thrown to the
upper side, source E.sub.1 having a voltage V.sub.1 will be
connected across the supply conductors CL and L. When impressed
with this voltage V.sub.1, Zener diodes ZD.sub.1, ZD.sub.2 and
ZD.sub.3 conduct, and transistor Tr.sub.2 becomes ON to operate
relay A after a short interval t.sub.o to open its contact a.
Consequently, the succeeding door unlocking circuits will not be
actuated because they are energized only a short interval.
For this reason, even if one of the relays A in the second and
following stages may be operated as shown by the contact a of the
door unlocking circuit DL.sub.2 shown in the lower portion of FIG.
4, due to the difference in the operating time of the relays of
these stages, such relay will be reset after an extremely short
time t.sub.3.
In the first door unlocking circuit DL.sub.1, the charging of
capacitor C.sub.1 is commenced and after a predetermined interval
t.sub.1 determined by the time constant C.sub.1 R.sub.1, the
terminal voltage across capacitor C.sub.1 reaches a predetermined
value thereby rendering conductive Zener diode ZD.sub.1 and hence
silicon controlled rectifier SR.
It is desirable that the interval t.sub.1 is longer than t.sub.o
for the purpose of preventing the control system from misoperating.
Capacitor C.sub.2 functions as a bypass capacitor to maintain a
sufficiently large gate voltage enough to render ON the silicon
controlled rectifier even when the voltage of source E.sub.1
fluctuates. When the silicon controlled rectifier SR is rendered
conductive, coil L is energized, thus unlocking the door shown in
FIG. 2.
When the door is opened, transfer switch MS will be thrown to the
lower contact thereby deenergizing the circuit DL.sub.1 in the
first stage and energizing the door unlocking circuit DL.sub.2. In
this manner, the loads or the door unlocking circuits are operated
sequentially.
Because the capacitor C.sub.3 is included in the control circuit
for transistor Tr.sub.2 of the protective circuit PC, after a
predetermined interval t.sub.2 determined by a time constant
C.sub.3 R.sub.5, the control current is decreased to turn OFF
transistor Tr.sub.2, thus deenergizing relay A. As a result,
contact a is reclosed. Under normal condition, since the transfer
switch MS is operated prior to the elapse of interval t.sub.o, the
reclosure of contact a does not cause any action, but when the
transfer switch MS fails to transfer, the reclosure of contact a
causes sequential operation of the succeeding door unlocking
circuits DL.sub.2, DL.sub.3... .
To perform a conduction test of the system, switch SW of source
device S is thrown to the lower contact to impress voltage V.sub.2
of source E.sub.2 across supply conductors CL and L. Since voltage
V.sub.2 is lower than the operating voltage V.sub.1, Zener diodes
ZD.sub.1, ZD.sub.2 and ZD.sub.3 are not turned ON. Accordingly, the
switching circuit SC is in its OFF condition to isolate coil L from
supply conductors CL and L. Thus, the protective circuit PC is also
in the inoperative condition which is important.
Accordingly, if there is no fault on supply conductors CL and L, it
may be considered that the supply conductors CL and L are
terminated with resistance RL. Accordingly, it is possible to
perform the conduction test over the entire length of conductors CL
and L by reading the current flowing through these conductors with
ammeter M. If either one of the conductors CL and L is interrupted,
the ammeter M will show a resistance value higher than RL.
As can be noted from the foregoing description, the invention
provides a new and improved control system capable of effecting not
only sequential operation of a plurality of loads such as emergency
machines and apparatus but also the conduction test of supply
conductors for the loads.
* * * * *