US 3872471 A
A pulsing bell of the type which sounds intermittently so as to provide an emergency alarm indication. The pulsing bell includes an actuator circuit which is incorporated within the bell structure and is extremely simple in design. The actuator circuit is adapted to operate efficiently on a conventional AC power supply.
Claims available in
Description (OCR text may contain errors)
United States Patent Bird et al.
1 Mar. 18, 1975 [S PULSING BELL HAVING RECTIFIER 3,618,079 11/1971 Denning 340/384 E CIRCUIT  Inventors: Nicholas W. F. Bird; Chang-Whan Fri-mar y Examiner-Harold l. Pitts g f of Owen Sound Omano Attorney, Agent, or FirmGeorge W. Killian; Milton am a E. Kleinman; John F. Ohlandt  Assignee: General Signal Corporation,
22 Pl d: M 2 l 7 I 1 ay 9 3 57 ABSTRACT  Appl. No.: 362,643
- A pulsing bellof the type which sounds intermittently  U5. Cl. 340/384 R, 340/384 R 50 as to p ide an em rgency alarm indication. The  Int. Cl. G08b 3/10 p ng ll n l n c or ir uit which is incor-  Field of Search 307/10 R, 106; 340/384 E, porated within the bell structure and is extremely sim- 340/384 R ple in design. The actuator circuit is adapted to operate efficiently on a conventional AC power supply.  References Cited UNITED STATES PATENTS 8 Claims, 2 Drawing Figures 3,460,136 8/1959 Jambazian 340/384 E I l 1 40 I 46 2f 55 66 l 62 701 g /Z0l/ I 42 50 52 1 54 50 //z i l .58 1 74 I l I 47 l A PULSING BELL HAVING RECTIFIER CIRCUIT BACKGROUND, OBJECTS AND SUMMARY OF THE INVENTION on an intermittent basis. This is because it has been found that an intermittent signal is more effective, particularly where there is a high background noise level in the ambient where the emergency alarm indication is to be given.
An example of a system that has been known'in the prior art for producing an intermittent signal is one described in U.S. Pat. No. 3,514,622 granted May 26, 1970. In this patent an actuator circuit is provided for a vehicle horn or the like and according to this arrangement, the power supplied to the horn or like device is interrupted at a prescribed beep frequency by means of the control on the SCR (silicon controlled rectifier) device in response to the output of a flip-flop arrangement. However, the circuit of the above noted patent is adapted to be used with a DC power supply. As a re-, sult of the fact that the supply to the horn or other audible signal indicating device is direct current, the horn must be provided with an interrupter contact. Otherwise, the primary horn tone would not be produced; moreover, without such interrupter contact the SCR control device would be continuously conductive once its gate electrode had been properly triggered.
However, as a consequence of the provision for the aforesaid interrupter contact, undesirable transient negative voltages are produced. It therefore becomes necessary to provide transient protection for both the born, or other actuator device, and also for the SCR device. Accordingly, in Patent 3,514,622, suitable diodes are connected across the horn and the SCR device for the above stated purposes.
It is therefore a primary object of the present invention to overcome the drawbacks thus present in the prior art and to provide a simplified, intermittently operated, device that can function efficiently upon connection to a conventional AC power supply, thereby avoiding the need for protection devices.
Another object is to provide a simple, economic and versatile structure for a pulsing alarm device that can be sold as a unit to the customer without requiring the addition of flasher circuits and the like.
Another object is to simplify the actuator circuit for the pulsing alarm device by providing that the driver stage of the actuator circuit comprises only a single transistor.
In fulfillment of the above recited objects, the present invention provides in essence a unitary, intermittently operated, alarm indicating device, such as a bell, born or similar device, which features a built-in control system or actuator circuit uniquely connected to an AC power supply for achieving the desired intermittent operation.
More specifically the control system includes a' (l) triggering circuit, which operates to trigger the gate of (2) a control device, preferably in the form of a silicon controlled rectifier; and (3) a bridge rectifier circuit,
which is specifically utilized in the instance where full wave rectification is desired. Moreover, in this instance the silicon controlled rectifier device is connected across two opposite corners of the bridge, the AC power supply being connected to the other two opposite corners.
The coil movement of the bell or other actuator device is series-connected with the AC power supply, the SCR control device also being connected in series with the coil movement. Accordingly, the coil movement produced by the AC power supply, which results in the primary belltone, is interrupted precisely in accordance with the triggering signal supplied to the control device so as to produce a beep or intermittent effect.
Further objects, features and advantages of the present invention will be apparent from the description which follows in the specification, taken in conjunction I with the drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of the actuator circuit for the system of the present invention.
FIG. 2 is a view of the bell or actuator device of the present invention and illustrating the incorporation of the actuator circuit within the bell structure.
DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawing, the pulsing bell 10 of the present invention is provided with a coil 10A and a conventional gong which sounds at a predetermined primary frequency when the AC voltage, typically volt, 60 Hz, as schematically indicated in FIG. I, is applied to the bell. The bell I0 is unitarily constructed; that is to say, an actuator circuit 20 is enclosed within the housing 108 of the bell. Consequently, the user need only connect the leads 12 and 14 of the unit to a suitable source such as the I20 volt AC supply normally found in most facilities for the desired intermittent operation. The actuator circuit 20 is mounted on a printed circuit board and is selectively connected to the coil movement of the bell 10 by a manually operable switch if desired, such switch not being shown. The actuator circuit 20 is connected by means of leads l2 and 14 to the 120 volt AC supply and this circuit includes a control device 22,'preferably in the form of a silicon controlled rectifier device, which is seriesconnected with the coil movement of the bell l0and with the power supply.
The control device 22 is part of a bridge rectifier circuit 24 and is shown connected to the upper and lower corners of the bridge. The circuit 24 is operable in conventional fashion to provide for current flow on successive half cycles of the AC power supply. Thus on the positive half wave, the diodes 30 and 32 in opposite legs of the bridge will be conductive so as to permit current flow in the downward direction through the control device 22. On this positive half cycle, of course. the diodes 34 and 36 in'the other two opposed legs of the bridge will be non-conductive. Correspondingly, on the negative half cycle of the AC power wave, the diodes 34 and 36 will be conductive so as to enable the same direction of current flow through device 22 as was the case previously. During the negative half cycle the di-' odes 30 and 32 will be non-conductive.
Control of current flow through the bell 10 is effectuated by the connection of the output of a triggerig circuit 26 to the gate electrode of the control device 22.
This control can be varied in accordance with the parameters selected for the triggering circuit. In other words, the partielar component values selected will determine the repetition rate and duty cycle for the pulse wave produced. As an example, the control on the 60 cycle tone produced by the bell 10 is V2 second on and second off which'results from the frequency and shape of the triggering pulses 28 supplied to the gate electrode of control device 22. The triggering circuit 26 is also connected to the power supply by way of a voltage divider, comprising the resistors 40 and 42, and a diode 46. This diode 46 operates as a rectifier to convert the AC power supply to half wave rectified DC voltage. The voltage divider operates to lower the voltage to the trigger circuit.26 so that smaller and less expensive components can be used therein. A reference line 47 for the several components in the circuit 26 is seen connected to the lower corner of the bridge rectifier 24.
It will be noted that a further diode 48 is connected to the junction between the diode 46 and the resistor 42. This diode functions to prevent unwanted discharge of the capacitors to be discussed; that is to say, such diode is so connected that during the negative half cycle of the power supply it operates as a high impedence so as to prevent establishment of a discharge path. It also functions, along with the capacitors 50, 52 and 54, to produce a sufficiently stable voltage for the requisite power supply to the astable multivibrator 56, which produces the aforesaid pulse output to the gate electrode of control device 22.
The astable multivibrator 56 includes a pair of cross coupled transistors 58 and 60, such transistors having their respective collectors connected to the power supply by way of resistors 62 and 64 and their respective bases connected to the power supply by the resistors 66 and'68. The requisite cross coupling is provided by the capacitors 70 and 72 between the collector of a respective transistor and the base of the opposite transistor.
It will be noted that diodes 74 and 76 are connected in the emitter legs of the respective transistors 58 and 60. These diodes are placed in the circuit because the capacitors 70 and 72 have been found to experience reverse voltages which are likely to exceed their normal breakdown voltages. Hence these diodes are utilized to operate as protecttive devices for the capacitors.
The driver stage of the triggering circuit 26 consists of a single transistor 80 which, as can be seen, is connected to the collector of transistor 60 by means of the diode 82. This diode 82 functions as a compensating means for the fact that voltage level changes are brought about by the use of the diodes 74 and 76 in the multivibrator circuit.
It will be understood that the driver stage consisting of the transistor 80 is a high impedence stage, being basically an emitter follower stage. The emitter of transistor 80 is connected to a voltage divider consisting of the resistors 84 and 86, the output being taken at the junction of these two resistors. Output is shown by the aforenoted pulse wave 28.
It should be noted that, although exact synchronism does not obtain between the pulse output 28 and the AC power supply wave, as that power is being applied to the bell l0, nevertheless automatic synchronism results from the fact that the termination of a given positive pulse in'the wave 28 results in removing bias from the gate electrode of control device 22. Accordingly, as
the particular cycle of AC power through the coil A reaches its zero crossing (in the case of full wave), the
SCR device 22.at that point in time goes into its high impedence state so as to prevent further current flow 5 through the bell 10 until the next occurrence of a positive pulse in wave 28. Thus it will be appreciated that turn off of the SCR device 22 is always effected substantially at the moment that the AC power has reached the zero level. Hence there is no problem with transient effects.
It will be appreciated that the trigger pulse 28 as applied to the gate of SCR device 22 is a relatively long continuous pulse. As noted previously it is on the order of /2 second which is equivalent to cycles for the 60 cycle power supply.
In order that the man skilled in the art may have a detailed set of specifications that were used in one practical embodiment of the present invention, the following table of components for the actuator circuit is pro- 20 vided:
COMPONENTS TYPE/VALUE AND RATING Diodes 30,32, 34, 36, 46,
3.900 ohms. SW 220 ohms. V4 W 10,000 ohms. A W 150,000 ohms. V4 W L000 ohms, V4 W 1,800 ohms. /4 W Resistor 40 Resistor 42 Resistors 62 & 64 Resistors 66 & 68 Resistor 86 Resistor 88 While there has been shown and described what is considered at present to be the preferred embodiment of the invention, it will be appreciated that other embodiments can be devised. For example, although a full wave bridge rectifier circuit 24 has been illustrated in FIG. 1, a half wave rectifier circuit can similarly be employed to operate the bell 10 or other load.
Other modifications will readily occur to those skilled in the related arts. It is desired, therefore, that the invention not be limited to the embodiment shown and described, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
What is claimed is:
l. A unitary alarm indicating device adapted to be intermittently operated from an AC power supply, comprising:
a. an actuator device including a housing therefore.
b. an actuator circuit enclosed within said actuator housing, said actuator circuit including, l. a control device having an anode, cathode and gate,
2. an electronic triggering circuit for producing a series of square wave pulses for effectuating intermittent operation of said actuator, said triggering circuit having its output connected to the gate of said control device, and 3. a rectifier circuit connecting said AC power supply to the anode and cathode of said control device. 2. A device as defined in claim 1, in which said control device is a silicon controlled rectifier.
3. An alarm device as defined in claim 2 in which said rectifier is a full wave bridge rectifier, said silicon controlled rectifier being connected between two opposed corners of said bridge, the power supply being connected to the remaining opposed corners of said bridge.
4. An alarm device or system as defined in claim 2 in which said triggering circuit includes an astable multivibrator and a driver stage connected to the output of the multivibrator, said driver stage consisting of a single transistor; a first voltage divider connected to the output of said transistor, the gate electrode of said silicon controlled rectifier being connected to the junction of the pair of resistors defining said voltage divider.
5. A device as defined in claim 2 in which said triggering circuit has its output connected to the gate electrode of said silicon controlled rectifier device, and including a reference line for said triggering circuit connected to the cathode of said SCR device.
6. A device as dcfincd in claim I, further including a second rectifier device connected to the AC power supply so as to furnish DC power to said triggering circuit.
7. A device as defined in claim 4, further comprising a second voltage divider, a second rectifier device, and
for said triggering circuit.