CA1136245A - Timed audible alarm system utilizing a piezoelectric transducer - Google Patents
Timed audible alarm system utilizing a piezoelectric transducerInfo
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- CA1136245A CA1136245A CA000325967A CA325967A CA1136245A CA 1136245 A CA1136245 A CA 1136245A CA 000325967 A CA000325967 A CA 000325967A CA 325967 A CA325967 A CA 325967A CA 1136245 A CA1136245 A CA 1136245A
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Abstract
A timed audible alarm system of the type including a piezoelectric component for providing an audible signal and circuitry for driving the piezoelectric component at substantially its resonant frequency provides circuitry for continuously producing the audible signal during the existence of a first condition, circuitry for intermittently producing the audible signal for a predetermined period during the existence of a second condition and in response to initiation of a third condition, the circuitry for intermittently providing including a heat activated bimetallic switch for controlling the predetermined period and for terminating the inter-mittently produced audible signal thereafter, the switch being coupled to begin heating in response to initiation of the third condition, and a visual signal device coupled to the bimetallic switch for visually signalling initiation of the third condition for the predetermined period and independent of the existence of the second condition, wherein the improvement enables an alarm system to provide recognizably different modes of operation to indicate the existence of different conditions.
Description
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BACKGROU~l3 OF TIIE ~IVE~TIO~
1. Field of the Inven-tion.
The present invention relates to audible alarm systems which utilize a piezoelectric component to provide an audible signa1 in response to the existence of at least one condition. More particularly, the audible alarm systems include circuitry for driving the piezoelectric component at substantially its resonant frequency where-in the circuitry usually includes a pulsator circuit for producin~ a pulsating audible signal and an amplifier circuit for excitin~ the piezoelectric component.
Generally speaking, the present invention includes a means operable independen-t of elimination of the condition for deactivating the audible alarm system after a predetermined interval of time whereby even if the condition continues to exist the pulsating audible signal is discontinued. Furthermore, a continuous audible signal is provided in response to the existence of one of at least two other conditions ; which is discontinued only if the other condition is eliminated.
BACKGROU~l3 OF TIIE ~IVE~TIO~
1. Field of the Inven-tion.
The present invention relates to audible alarm systems which utilize a piezoelectric component to provide an audible signa1 in response to the existence of at least one condition. More particularly, the audible alarm systems include circuitry for driving the piezoelectric component at substantially its resonant frequency where-in the circuitry usually includes a pulsator circuit for producin~ a pulsating audible signal and an amplifier circuit for excitin~ the piezoelectric component.
Generally speaking, the present invention includes a means operable independen-t of elimination of the condition for deactivating the audible alarm system after a predetermined interval of time whereby even if the condition continues to exist the pulsating audible signal is discontinued. Furthermore, a continuous audible signal is provided in response to the existence of one of at least two other conditions ; which is discontinued only if the other condition is eliminated.
2. Description of the Prior Art.
Embodiments of the present lnvention may be utilized in many applicatlons where an audlble alarm is required. The illustrated em-bod-iments of the present invention are adapted to provide a variety of audible alarm sounds ln response to electrical signals produced due to undesirable conditions within an automobile. For exarnple, one embodi-ment can provide one tone to indicate that seat belts are not fastenedi and another embodiment can provide one tone to indicate that seat belts are not fastened, another tone to remind the driver that his keys are in the ignition when he opens a door, and another tone to warn the driver that he has left his lights on when he leaves the automobile. The tones may be continuous or pulsing.
Audible alarm systems are well known in autonlobile applications to warn a driver oF a potential prob1em or alert him of a situation re-,;
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.
Embodiments of the present lnvention may be utilized in many applicatlons where an audlble alarm is required. The illustrated em-bod-iments of the present invention are adapted to provide a variety of audible alarm sounds ln response to electrical signals produced due to undesirable conditions within an automobile. For exarnple, one embodi-ment can provide one tone to indicate that seat belts are not fastenedi and another embodiment can provide one tone to indicate that seat belts are not fastened, another tone to remind the driver that his keys are in the ignition when he opens a door, and another tone to warn the driver that he has left his lights on when he leaves the automobile. The tones may be continuous or pulsing.
Audible alarm systems are well known in autonlobile applications to warn a driver oF a potential prob1em or alert him of a situation re-,;
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quiriny immediate attention. Many of these alarms are in -the form of electromagnetic buzzers, and one buzzer is normally re~uired for each warning signal required. In recent years, more and more ~arnings are being required in automobile applications.
One of the problems associated with previous audib1e alarm systems has been the ability to discontinuc the audible signal if the undesirable condition has not been corrected or eliminated. For example, if the driver of the automobile gets ;nto the automobile and inserts the key in ignition switch in preparation for starting the automob-ile with out also buckling his seat belt, an audible signal is produced which can only-be discontinued if the condition is eliminated, i.e. if the seat belt is buckled. Many individuals who drive automobiles do not desire to use seat belts and therefore unless the seat belt is buckled behind the driver in the seat the audible siynal will continue while the auto-mobile is~being driven. It is therefore desirable at least in some in-stances that the audible signal be discontinued even if the undesirable condition continues to exist. As disclosed by Little et al in U.S.
Patent #4,003,043 dated January ll, 1977 and entitled "Timed Buzzer" a timing mechanism has been incorporated into the prior art electromagnetic buzzer to accomplish the discontinuance of the audible signal after a predetermined interval of time for one undesirable condition, e.g. the buckling of a seat belt.
Another problem associated with electromagnetic buzzers is their inherently unpleasant sound. This buzzer noise is sometimes a dangerous distraction to a driver of an automobile. The present in-vention solves this problem by utilizing a piezoelectric transducer which .produces a pleasing audible tone.
Furthermore, locating several audible alarm systems in a car can be difficult. For a driver to recognize one signal from another, the systems are sometinles separated so that, for example, a head light ... , , , . , ~ ~ . , .
; ~L13~ ~5 warning signal comes from his left and a "fasten seat belt" s;gnal can be heard from his right. The present invention eliminates this location problem by providing one alarm system centrally located. The transducer signals, each indicating a different warning, are distinguishable because they differ in rate of pulsing. An audible alarm system which has recognized this problem and the inherently unpleasant sounds associated with buzzers and provided a solution therefor is disclosed by Birt et al in U. S. Patent ~3,922,672 dated November 25, 1975 and entitled "Audible Alarm Device." However, the Birt et al device lacks any means for con-trolling the length of time during which the audible signal will beproduced if one or more of the undesirable conditions exist.
It may also be desirable in a system such as that disclosed by Birt et al to have one audible signal timed and the other audible signals allowed to operate continuously until the undesired condition (or conditions) is corrected or eliminated.
SUMMARY OF THE INVENTION
In accordance with the present invention in its broadest concept, there is provided an audible alarm system of the type including a piezo-electric component for providing an audible signal and circuitry for ? driving the piezoelectric component at substantially its resonant frequency wherein the improvement comprises: means for continuously providing the audible signal during the existence of a first condition, means for intermittently providing the audible signal for a predetermined period during the existence of a second condition and in response to initiation of a third condition, the means for intermittently providing including a heat activated bimetallic switch means for controlling the predetermined period and for terminating the intermittently provided audible signal thereafter, the switch means being coupled to begln heating in response to initiation of the third condition; and visual slgnal means coupled to the himetallic switch means for visually slgnalling ~ 3 .
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initiation of the third condition for the predeterm;ned period and independent of the existence of the second condition, wherein the improvement enables an alarm system to provide recognizably different modes of operation to indicate the existence of different conditions.
Accordingly, it is a feature of the present invention to provide a timed audible alarm system as described hereinabove wherein the audible signal ;s discontinued at the end of the predetermined interval time even if the condition continues to exist.
It is another feature of the present invention to prov;de a t;med audible alarm system wherein the system is capable of ;ndependently providing a pulsating audible signal for a predetermined interval of -3a-. ., ~ : , , .' , ~ ;
-' ~13t~Z45 time and a continuous audible siynal in response to the existence o-f one of at least two other conditions which is discontinued only iF the other condition is eliminated whereby the individual beiny warned can distinguish the conditions which exist by the type and len~th o-f the audible signal produced.
Other features and advantages of the present invention will be apparent from the following detailed description of embodiments thereof, which description should be considered in conjunction ~ith the accompanying drawings.
BRIEF DESCRIPTION OF TIIE DRA~ IGS
FIGURE l is a schematic illustration of a first embodiment of the timed audible alarm system of the present invention.
FIGURE 2 is a schematic illustration of a second embodiment of the.timed audible alarm system of the present invention.
DESCRIPTIO~I OF THE PREFERRED EMBODIMCNT
. Referring to the above-described figures and more particularly to FIGURE 1, a timed audible alarm system 10 includes a tone generator circuit 12 which utilizes.a piezoelectric transducer 14 to produce an audible signal, a pulsator circuit 16 electrically coupled to tone generator circuit 12 for providing pulsations in the audible signal, a system protection means l8 electrically coupled to tone generator circuit 12, an input-output terminal means 20 electrically coupled to system pro-tection means 18, and means 22 for deactivating the audible alarm system after a predetermined interval of time.
System protection means 18 includes a plurality oF protective circuit components electrically coupled so as to provide protection to the audible alarrn system 10. Included within system protection means 18 is a resistor 36 for providing transient voltage protection having a first side electrically coupled to the positive voltage terminal 62 of the integrated circuit package 94 and a second side electrically coupled to ,:
", 1~ 5 termination 26 and deactivating means 22; a resistor 3~ for preventing operation of the system due to external current leakages passing through input-output terminal means 20 having a first side electrically coupled to termination 24 and a second side electrically coupled to the second side of resistor 36, to deàctivating rneans 22, and termination 26; and a diode 40 for providing reverse polarity protection having its anode electrically coupled to the negative voltage terminal 64 of integrated circuit package 94 and electrode 90 of transducer 14 and its cathode electrically coupled to the first side of resistor 3~3 and to termination 24. System protection means l8 is electrically coupled between various other portions of the system lO and the input-output terminal means 20.
In-put-output terminal means 20 for providiny electrical terminations to the system lO includes terminations 24, 26, 28, and 30., Terminations 24 and 26 are electrically coupled to system protection means l~ and to deac-tivating means 22. Terminations 2~ and 30 are each electrically coupled to deact'ivating means 22.
Pulsator circuit l6 for prod~cing pulsations in an audible signal incorporates two two-input NAND gates 46 and 54 of a Quad two-input NAND
gate integrated circuit package 94. Inputs 42 and 44 of gate 46 are commonly electrically coupled to a first side of a resistor 50 and a capacitor 52. Inputs 56 and 58 of gate 54 are commonly electrically coupled to a second side of a resistance means 50 and to an output 48 of gate 46. An output 60 of gate 54 is electrically coupled to tone generator circuit 12 and to a second side of a capacitor 52.
Tone generator circuit l2 for producing an audible signal in-corporates two two-input NAND gates 66 and 74 of the Quad t~Jo-inpu-t NAND
gate integrated circuit package 40 mentioned hereinabove. Piezoelectric transducer l4 includes electrodes 86, 88 and 90. Electrode 90 is elec-trically coupled to system protection means l8. An input 70 of NAND
gate 66 and an input 78 of NAND gate 74 are each electrically coupled to ~,, .
~ . .. :, : , , , s pulsator circuit 16. An input 68 of ~IA~ID gate 66 and an input 7& of ~AN~
gate 74 are comInonly electrically coupled to a first side o-f a resistor 82 and to electrode 88 of piezoelectric transducer 14, An output 72 of NAND gate 66 and an output 80 of NAND gate 74 are commonly electrically coupled to a second side of resistor 82 and through a resistor 84 to electrode 86 of transducer 14. In combination, the coupling of ~lAND
gates 66 and 74 in the manner described hereinabove forms a means 92 for amplifying the electrical signal provided by electrode 88 of transducer 14 such that transducer 14 is driven substantially at its resonant frequency.
As shown, the negative voltage terminal 64 of integrated circuit package 94-is also electrically coupled to electrode 90 of piezoelectric transducer 14.
Continuing to refer to FIGURE l, means 22 for deactivating the audible alarm system lO after a predetermined interval of time is a temperature actuated switching device which in the absence of an electri-cal signal being applied thereto is no~mally closed. Deactivating means 22 includes a heated bi-metallic member 32 and an unheated bi-metallic member 34 which, in the absence of and for a short time after the appli-~cation of an electrical signal, contact each other thereby providing an electrical transmission path therebetween. As illustrated, the heated bi-metallic member 32 is electrically coupled to termination 30, elec-trically coupled to termination 28, and electrically coupled to the unheated bi-metallic member 34 as long as an electrical signal is not supplied to the heated bi-metallic member 32. ~Ihen an electrical signal is applied to deactivating means 22 the temperature of the heated bi-metallic member 32 will yradually increase thereby causing the heated bi-metallic merIlber 32 to gradually bend a~Jay from the unheated bi-metallic menlber 34 and interrupt the electrical coupling therebetween.
A typical application for timed audible alarm system lO is in 3~ 5 an automobile to produce a pulsatiny audible siynal to alert a driver to a situation requiring his attention. FIGU~E 1 illustrates a portion o~
a typical automobile electrical circuit 100 electrically coupled to audible alarm system 10. A DC power supply 102, which may comprise an automotive battery is electrically coupled positive ter~ninal 104 to termination 28 of system 10 through a switch 108 which is typically the ignition switch of the automobile such that when the ignition switch is closed an electrical signal is supplied to system 10. A lamp or liyht source 110 is electrically coupled between the negative side 106 of DC
power supply 102 and termination 26. Further, a switching device 112 is electricaliy coupled between the negative side 106 of DC power supply 102 and termination 24. The neyative side 106 of DC po~er supply 102 is also shown to be electrically coupled to terMination 30.
In one application, switches 10~ and 112 may have these relation ships to other automotive components: switch 108 is included in an ignition switch to be switched when the ignition switch is activated;
and switch 112 is included in the seat belt and ls responsive to fastening or unfastening of the seat belt.
In operation, termination 28 receives a positive electrical signal from power supply 102 upon the closing of switch 108 (ignition SWl tch). Termination Z4 becomes completed to ground upon closing of switch 112 (seat belt unbuckled). In the condition wherein switch 112 is closed, pie~oelectric transducer 14 provides a pulsating audible signal, the tone being produced by tone generator circuit 12 and the pulsations being produced by pulsator circuit 16. With the positive electrical signal applied to termination 2~ and terMination 30 electri-cally coupled to the negative side of DC power supply 102, voltage is applied to pulsator circuit 16, tone generator circuit 12 and warning lamp 110 throuyh deactivating means 22, AccordintJly, where switch 112 is closed (seat belt not fastened) the pulsatiny audible signal will be ., .....
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produced until the tempera-ture of the heated bi-rnetallic melnl)er 3Z of deactivating means 22 has increased sufficiently -to cause an interruption in the electrical signal. The time required for the ternperature to increase sufficiently is typically about 6 seconds. Therefore upon closing switch 108, if the seat belt is unfastened, the pulsatiny audible signal is produced for a predetermined interval of time at the conclusion of which the audible siynal is discontinued and the ~arning lamp 110 is turned off independent of whether the seat belt is in fact fastened. If upon closing switch 10~ the seat belt is fastened either before initiation of or during the predetermined interval of time, i.e. s~litch 112 is open, termination 24 will not be grounded and therefore no audible signal is produced; however, the warning lamp 110 will still be activated for the predetermined interval of time.
In pulsator circuit 16, first and second NAND gates 46 and 54 cooperate.with resistor 50 and capacitor 52 to cause the voltage at output 60 to alternately rise.and fall in essentially a square wave manner at a repetition rate controlled,by the values of resistor 50 and capacitor 52. When the output 60 of gate 54 is high the tone generator circuit 12 operates and when the output 60 of gate 54 is low the tone .
generator circuit 12 ceases to operate thereby producing the pulsations in the audible signal.
NAND gates 66 and 74 are electrically coupled in parallel and cooperate wlth piezoelectric transducer 14 in an oscillitory manner so that transducer 14 is excited into vibration near its resonant frequency ~ and an audlble signal is produced. Electrode 88 of transducer 14 pro-vides a feedback voltage of a magnitude and phase to permit sustained oscillations in the circuit. When the voltage supplied from output 60 of NAND gate 54 to inputs 70 and 78 of NAND gates 66 and 74 is near the supply voltage, oscillation will occur. in tone genera-tor circuit 12 When voltage from output 60 is down or near ground potential the oscillations . .
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cease.
Referring now to FIGURE 2 there is shown a second embodiment of a timed audible alarm system 210 which is capable of providing a variety of audible signals in response to the existence of a plurality of conditions wherein at least one of the audible siynals is discontinued after a predetermined interval of time even if the condit;on still exists. The timed audible alarm system 210 includes a tone generator clrcuit 212 which utilizes a piezoelectric transducer 214 to produce an audible signal; a pulsator circuit 216 electrically coupled to tone generator circuit 212 for providiny pulsations in the audible signal; a transient protection means 218 electrically coupled to pulsator circuit 216 and tone generator means 212; an input-output terrninal means 220 electrically coupled to transient protection means 218; a ground iso-lation means 222 electrically coupled to tone generator circuit 212, transient protection means 218, and input-output terminal means 220; and means 219 for deactivatiny the audible alarm system 210 after a predeter-mined interval of time even though a condition still exists.
Ground isolation rneans 222, for providing more than one ground path to system 210, is electrically coupled directly to transient pro tection means 218 and input-output terminal means 220 and is also elec-trically~coupled through a resistor 237 to transient protection means 218 deactivating means 219 and input-output terminal means 220.
~ Input-output terminal means 220 for providing electrical terminations to the system 210 includes terminat;ons 224, 225, 226, 227, 228, 229, and 230. Termination 224 is electrically coupled to ground isolation means 222 and a first side of resistor 237. Termination 229 is electrically coupled to voltage transient protection means 21~ and to a second side of resistor 237, Termination 225 is electrically coupled to voltage transient protection means 218 and to a first side of a resistor 238. Terlllination 226 is electrically coupled to volta~e . . ; , :~
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transient protection mearIs 218. A resistor 236 is electrically coupled between termination 225 and 226. Termination 227 is electrically coupled through a resistor 235 to the base of an NPN transistor 296.
The transistor 296 has its collector electrically coupled to a second side of resistor 23~ and its emitter electrical'ly coupled to termination 228. Termination 228 is in addition electrically coupled through de-activating means 219 to voltage transient protection means 218. Term-ination means 230 is also electrically coupled to deactivating means 219.
Pulsator means 216 for producing pulsations in an audible signal incorporates two two-input NAND gates 246 and 254 of a Quad t~o-input NAND gate integrated circuit package 294. An input 242 of gate 246 is electrically coupled to voltage transient protection ~eans 218 and another input 244 of gaté 246 is electrically coupled to a first side of a resistor 249. An input 256 of gate 254 is also electrically coupled to voltage transient protection means 218. Another input 258 of gate 2~4 ;s electrically coupled to a ~irst side of a resistor 250 and ''-to an output 248 of gate 246. An output 260 of gate 254 is electrically coupled to tone generator circuit 212 and to a first side of a capacitor 252. A second side of resistor 249 is electrically coupled to a second side of resistor Z50 and to a second side of capacitor 252.
Tone generator circuit 212 for produeing an audible signal in-corporates two t~o-input NAND gates 266 and 274 of the Quad t~o-input NAND gate integrated-circuit package 294. Piezoelectric transducer 214 includes electrodes 286 288 and 290. Electrode 290 is electrically ' coup'led to ground isolation means 222. An input 270 of NAND gate 266 - and an input 278 of NAND gate 274 are each e'lectrically coupled to pulsator circuit 216. An input 26g of NAND gate 266 and an ~nput 276 of NAND gate 274 are each comIllonly e'Iectrica'Ily coupled to a first side of a resistor 2~2 and to electrode 28~ of piezoelectric transducer 214. An , -~n-,, . , ; I
output 272 o f IlAND gate 266 and an output 2gO of NAND gate 274 are each commonly electrica11y coupled to a second side of resistor 2~2 and -through a resistor 284 to electrode 2~6 oF transducer 214. In combi-nation, the coupling of NA~ID yates 266 and 274 in the manner described hereinabove forms a means 292 for amplifying the electrical signal produced by electrode 2~8 of transducer 214.
Ground isolation means 222 includes diodes 223 and 221. The anodes of diodes 223 and 221 are electrically coupled together and to the tone generator circuit 212 and to a negative voltage terminal 264 of integrated circuit package 294. A cathode of diode 223 is electrically coupled to termination 224 of input-output terminal means 220 and through resistor 237 to termination 229. A cathode of second diode 221 is electrically coupled to ternlination 225 and to transient protection means 218.
Transient protection means 218 for protecting system 210 against electrical transient voltages includes four resistors 211, 213, 215 and 217. Resistor 215 is electrically coupled to termination 228 through deactivating Ineans 219 and to input 242 of first NAND gate 246.
Resjstor 213 is electricalIy coupled between termination 226 and a positive voltage terminal 262 of integrated circuit package 294. Re-sistor 211 is electrically coupled between termination 225 and input 256 of second NAND gate 254. Further, resistor 217 is electrically coupled across the inputs 242 and 256 of gates 246 and 254 respectively.
A negative voltage terminal 264 of integrated circuit package 294 is electrically coupled to electrode 290 of piezoelectric transducer 214 and to ground isolation means 222.
Continuing to refer to FIGURE 2, means 219 for deactivating the audible alarm s~stem 210 after a predetermined interval oF tinle is a temperature actuated switchiny device which in the absence oF an elec-trical signal being applied thereto is normally closed. Deactivating , 1 'I
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means 219 includes a heated bi-metallic nlember 232 and an unheated bi-metallic melllber 234 which, in the absence of and for a short time after the application of an electrical signal, contact each other thereby providing an electrical transmission path therebe-t~een. As illustrated, the heated bi-metallic melllber 232 is electrically couple.d to -termination 230, electrically coupled to termination 22~, and electrically coupled to the unheated bi-metallic melllber 234 as long as an electrical siynal is not supplied to the heated bi-metallic mell1ber 232. When an electrical signal is applied to deactivating means 219~ the temperature of the heated bi-metallic melllber 232 will gradually increase thereby causing the heated bi-metallic melllber 232 to gradually bend away from the un-heated bi-metallic member 234 and interrupting the electrical trans-mission path therebetween.
A typical application for timed audible alarm system 210 is again in an automobile to produce a plurality of audible signals one of which is timed to alert a driver to various different situations requiring his attention. FIGURE 2 illustrates a,portion of a typical automobile electrical circuit 300 electrically coupled to audible alarm system 210.
A DC power supply 302, which may comprise an automotive battery is electrically coupled positive term;nal 304 to termination 228 of system 210 through a switch 308 which is typically the ignition switch of the automobile such that when the ignition switch is closed an electrical signal is applied to system 210 through termination 228. The positive - terminal 304 is further electrically coupled, before the switch 308, through a circuit breaker device 324 to termination 226 and through the series combination of a switch 32Z, potentiol-neter 320, and another circuit breaker device 326 to termination 227 and in parallel thereto to at least one instrument lamp, as for example lamps 313 and 319. Another lamp 310 is electrically coupled be~ween the ne~Jative side 306 oF DC
power supply 302 and termination 22~. Two switches 314 and 316 are -1?-., ,..", , ~ . , .~,, .,, , . i~
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electrically coupled in series be~ween the neyative side 306 of DC po~er supply 302 and termina-tion 225. Fur-ther, a switch 31Z is electricall~
coupled between the negative side 306 oF DC power supply 302 and termi-nation 224. The negative side 306 of DC power supply 30Z is also sho~ln to be electrically coupled to termination 230.
In one application of timed audible alarm system 210, s~"itches 308, 312, 314, 316 and 322 may have these relationships to other auto-motive components: swi~ch 308 is included in an iynition s~litch to be switched when the ignition switch is activated; switch 312 is included in the seat belt and is responsive to fastening or unfastening of the seat belt; switch 314 is incorporated in an ignition lock (separate from switch 308) to be switched upon insertion or withdrawal of ignition key;
switch 316 is located in a passage doorway in such a manner as to be switched upon opening and closing of the door; and switch 322 is incor-porated in a head light control system to be switched on when the head lights o~ the automobile are switched on.
: In operation, termination 226 receives a positive voltage from DC power supply 302. Termination 228 also receives a positive voltage from power supply 302, but only upon the clo~ing of switch 308. Term-ination 224 becomes completed to ground upon closing of s~litch 312. In :
the condition wherein switches 30& and 312 are clos~d, piezoelectric transducer 214 ernits a pulsating tone, the tone being produced by tone generator circuit 212 and the pulsations being produced by pulsatorcircuit 216. Wlth the positive electrical signal applied to termination 228 and terminatlon 230 electrically coupled to the negative side 306 of DC power supply 302 voltage is applied to pulsator circuit 216, tone .generator circuit 212 and warniny lamp 310 throuyh deactivating means 219. Accordingly, where switch 312 is closed (seat belt not fastened) a pulsating audible siynal will be produced and lamp 310 will be lit until . the temperature oP the heated bi-metallic menlber 232 of de~ctivating .. -13-: - . " ,., .. . ..
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means 219 has increased sufficiently to cause an in-terruption in the electrical transmission path. Therefore upon closing switch 30g, if the seat belt is unfastened, the pu1satiny audible signal is produced for a predetermined interval of time at the conclusion of which the audible signal is discontinued and the warniny lamp 310 is turned off independent of whether the seat belt is in fact fastened. If upon closiny switch 308, the seat belt is fastened either before initiation of or during the predetermined interval of time, i.e. switch 312 is open, termina-tion 224 will not be grounded and therefore no audible signal is produced; how-ever, the warniny lamp 310 will still be activated for the predetermined interval of time.
Pulsator circuit 216 and tone generator circuit 212 operate in the same manner as previously described. Accordingly, when the output 260 of gate 25~ is high the tone generator circuit 212 operates and when the output 260 of gate 254 is low the tone generator circuit 212 does not operate. By alternately chanying the output 260 of gate 25~ from a high to a low state, tone generator circuit 212 is made to produce a pulsating audible siynal.
In the condition where switch 308 is open (ignition switch turned off) and the head lights are on, i.e. switch 322 is closed, NPN
transistor 296 is activated through termination 227 and resistor 235.
The emitter of transistor 296 is grounded through deactivating means 219, which has no electrical signal applied thereto, and either termination ;
229 or termination 230. Input 256 is caused to bé low and therefore gate 254 has an output 260 which is constantly high whereby tone generator circuit 212 produces a continuous audible siynal, Since the electrical signal supplied to the system 210 does not pass through deactivating means 219, the continuous audible signal ,is continuously produced until switch 322 is opened (head lights turned of-f) thereby allowing the base of tran-sistor 296 to be grounded through lamps 31~ and 319 which have also been ;, . . . . , . , .. ;; . .
~3~415 deactivated by opening switch 322.
By grounding termination Z25 through switches 314 (key switch) and 316 (door'switch) a low again appears at input 256 of gate 260 thereby causing its output 260 to be high which resul-ts in a non-pulsat-ing or continuous audib'le signal produced by tone generator circuit 212.
Accordingly, if the keys remain in -the ignition switch (closing switch 314) and the driver opens the door thereby c'losiny switch 316 a continuous audible signal is continuously produced until either the key is removed or the door is closed. Resistor 236 serves to maintain input 256 high except when grounded through transistor 296 or termination 225, In view of the above description of the embodimen-ts of the present invention it will be seen that the several objects of the in-vention are achieved and other advantageous results attained and that further modifications can be made without departing from the spirit and scope of the invention as defined in the appended claims.
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quiriny immediate attention. Many of these alarms are in -the form of electromagnetic buzzers, and one buzzer is normally re~uired for each warning signal required. In recent years, more and more ~arnings are being required in automobile applications.
One of the problems associated with previous audib1e alarm systems has been the ability to discontinuc the audible signal if the undesirable condition has not been corrected or eliminated. For example, if the driver of the automobile gets ;nto the automobile and inserts the key in ignition switch in preparation for starting the automob-ile with out also buckling his seat belt, an audible signal is produced which can only-be discontinued if the condition is eliminated, i.e. if the seat belt is buckled. Many individuals who drive automobiles do not desire to use seat belts and therefore unless the seat belt is buckled behind the driver in the seat the audible siynal will continue while the auto-mobile is~being driven. It is therefore desirable at least in some in-stances that the audible signal be discontinued even if the undesirable condition continues to exist. As disclosed by Little et al in U.S.
Patent #4,003,043 dated January ll, 1977 and entitled "Timed Buzzer" a timing mechanism has been incorporated into the prior art electromagnetic buzzer to accomplish the discontinuance of the audible signal after a predetermined interval of time for one undesirable condition, e.g. the buckling of a seat belt.
Another problem associated with electromagnetic buzzers is their inherently unpleasant sound. This buzzer noise is sometimes a dangerous distraction to a driver of an automobile. The present in-vention solves this problem by utilizing a piezoelectric transducer which .produces a pleasing audible tone.
Furthermore, locating several audible alarm systems in a car can be difficult. For a driver to recognize one signal from another, the systems are sometinles separated so that, for example, a head light ... , , , . , ~ ~ . , .
; ~L13~ ~5 warning signal comes from his left and a "fasten seat belt" s;gnal can be heard from his right. The present invention eliminates this location problem by providing one alarm system centrally located. The transducer signals, each indicating a different warning, are distinguishable because they differ in rate of pulsing. An audible alarm system which has recognized this problem and the inherently unpleasant sounds associated with buzzers and provided a solution therefor is disclosed by Birt et al in U. S. Patent ~3,922,672 dated November 25, 1975 and entitled "Audible Alarm Device." However, the Birt et al device lacks any means for con-trolling the length of time during which the audible signal will beproduced if one or more of the undesirable conditions exist.
It may also be desirable in a system such as that disclosed by Birt et al to have one audible signal timed and the other audible signals allowed to operate continuously until the undesired condition (or conditions) is corrected or eliminated.
SUMMARY OF THE INVENTION
In accordance with the present invention in its broadest concept, there is provided an audible alarm system of the type including a piezo-electric component for providing an audible signal and circuitry for ? driving the piezoelectric component at substantially its resonant frequency wherein the improvement comprises: means for continuously providing the audible signal during the existence of a first condition, means for intermittently providing the audible signal for a predetermined period during the existence of a second condition and in response to initiation of a third condition, the means for intermittently providing including a heat activated bimetallic switch means for controlling the predetermined period and for terminating the intermittently provided audible signal thereafter, the switch means being coupled to begln heating in response to initiation of the third condition; and visual slgnal means coupled to the himetallic switch means for visually slgnalling ~ 3 .
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z~
initiation of the third condition for the predeterm;ned period and independent of the existence of the second condition, wherein the improvement enables an alarm system to provide recognizably different modes of operation to indicate the existence of different conditions.
Accordingly, it is a feature of the present invention to provide a timed audible alarm system as described hereinabove wherein the audible signal ;s discontinued at the end of the predetermined interval time even if the condition continues to exist.
It is another feature of the present invention to prov;de a t;med audible alarm system wherein the system is capable of ;ndependently providing a pulsating audible signal for a predetermined interval of -3a-. ., ~ : , , .' , ~ ;
-' ~13t~Z45 time and a continuous audible siynal in response to the existence o-f one of at least two other conditions which is discontinued only iF the other condition is eliminated whereby the individual beiny warned can distinguish the conditions which exist by the type and len~th o-f the audible signal produced.
Other features and advantages of the present invention will be apparent from the following detailed description of embodiments thereof, which description should be considered in conjunction ~ith the accompanying drawings.
BRIEF DESCRIPTION OF TIIE DRA~ IGS
FIGURE l is a schematic illustration of a first embodiment of the timed audible alarm system of the present invention.
FIGURE 2 is a schematic illustration of a second embodiment of the.timed audible alarm system of the present invention.
DESCRIPTIO~I OF THE PREFERRED EMBODIMCNT
. Referring to the above-described figures and more particularly to FIGURE 1, a timed audible alarm system 10 includes a tone generator circuit 12 which utilizes.a piezoelectric transducer 14 to produce an audible signal, a pulsator circuit 16 electrically coupled to tone generator circuit 12 for providing pulsations in the audible signal, a system protection means l8 electrically coupled to tone generator circuit 12, an input-output terminal means 20 electrically coupled to system pro-tection means 18, and means 22 for deactivating the audible alarm system after a predetermined interval of time.
System protection means 18 includes a plurality oF protective circuit components electrically coupled so as to provide protection to the audible alarrn system 10. Included within system protection means 18 is a resistor 36 for providing transient voltage protection having a first side electrically coupled to the positive voltage terminal 62 of the integrated circuit package 94 and a second side electrically coupled to ,:
", 1~ 5 termination 26 and deactivating means 22; a resistor 3~ for preventing operation of the system due to external current leakages passing through input-output terminal means 20 having a first side electrically coupled to termination 24 and a second side electrically coupled to the second side of resistor 36, to deàctivating rneans 22, and termination 26; and a diode 40 for providing reverse polarity protection having its anode electrically coupled to the negative voltage terminal 64 of integrated circuit package 94 and electrode 90 of transducer 14 and its cathode electrically coupled to the first side of resistor 3~3 and to termination 24. System protection means l8 is electrically coupled between various other portions of the system lO and the input-output terminal means 20.
In-put-output terminal means 20 for providiny electrical terminations to the system lO includes terminations 24, 26, 28, and 30., Terminations 24 and 26 are electrically coupled to system protection means l~ and to deac-tivating means 22. Terminations 2~ and 30 are each electrically coupled to deact'ivating means 22.
Pulsator circuit l6 for prod~cing pulsations in an audible signal incorporates two two-input NAND gates 46 and 54 of a Quad two-input NAND
gate integrated circuit package 94. Inputs 42 and 44 of gate 46 are commonly electrically coupled to a first side of a resistor 50 and a capacitor 52. Inputs 56 and 58 of gate 54 are commonly electrically coupled to a second side of a resistance means 50 and to an output 48 of gate 46. An output 60 of gate 54 is electrically coupled to tone generator circuit 12 and to a second side of a capacitor 52.
Tone generator circuit l2 for producing an audible signal in-corporates two two-input NAND gates 66 and 74 of the Quad t~Jo-inpu-t NAND
gate integrated circuit package 40 mentioned hereinabove. Piezoelectric transducer l4 includes electrodes 86, 88 and 90. Electrode 90 is elec-trically coupled to system protection means l8. An input 70 of NAND
gate 66 and an input 78 of NAND gate 74 are each electrically coupled to ~,, .
~ . .. :, : , , , s pulsator circuit 16. An input 68 of ~IA~ID gate 66 and an input 7& of ~AN~
gate 74 are comInonly electrically coupled to a first side o-f a resistor 82 and to electrode 88 of piezoelectric transducer 14, An output 72 of NAND gate 66 and an output 80 of NAND gate 74 are commonly electrically coupled to a second side of resistor 82 and through a resistor 84 to electrode 86 of transducer 14. In combination, the coupling of ~lAND
gates 66 and 74 in the manner described hereinabove forms a means 92 for amplifying the electrical signal provided by electrode 88 of transducer 14 such that transducer 14 is driven substantially at its resonant frequency.
As shown, the negative voltage terminal 64 of integrated circuit package 94-is also electrically coupled to electrode 90 of piezoelectric transducer 14.
Continuing to refer to FIGURE l, means 22 for deactivating the audible alarm system lO after a predetermined interval of time is a temperature actuated switching device which in the absence of an electri-cal signal being applied thereto is no~mally closed. Deactivating means 22 includes a heated bi-metallic member 32 and an unheated bi-metallic member 34 which, in the absence of and for a short time after the appli-~cation of an electrical signal, contact each other thereby providing an electrical transmission path therebetween. As illustrated, the heated bi-metallic member 32 is electrically coupled to termination 30, elec-trically coupled to termination 28, and electrically coupled to the unheated bi-metallic member 34 as long as an electrical signal is not supplied to the heated bi-metallic member 32. ~Ihen an electrical signal is applied to deactivating means 22 the temperature of the heated bi-metallic member 32 will yradually increase thereby causing the heated bi-metallic merIlber 32 to gradually bend a~Jay from the unheated bi-metallic menlber 34 and interrupt the electrical coupling therebetween.
A typical application for timed audible alarm system lO is in 3~ 5 an automobile to produce a pulsatiny audible siynal to alert a driver to a situation requiring his attention. FIGU~E 1 illustrates a portion o~
a typical automobile electrical circuit 100 electrically coupled to audible alarm system 10. A DC power supply 102, which may comprise an automotive battery is electrically coupled positive ter~ninal 104 to termination 28 of system 10 through a switch 108 which is typically the ignition switch of the automobile such that when the ignition switch is closed an electrical signal is supplied to system 10. A lamp or liyht source 110 is electrically coupled between the negative side 106 of DC
power supply 102 and termination 26. Further, a switching device 112 is electricaliy coupled between the negative side 106 of DC power supply 102 and termination 24. The neyative side 106 of DC po~er supply 102 is also shown to be electrically coupled to terMination 30.
In one application, switches 10~ and 112 may have these relation ships to other automotive components: switch 108 is included in an ignition switch to be switched when the ignition switch is activated;
and switch 112 is included in the seat belt and ls responsive to fastening or unfastening of the seat belt.
In operation, termination 28 receives a positive electrical signal from power supply 102 upon the closing of switch 108 (ignition SWl tch). Termination Z4 becomes completed to ground upon closing of switch 112 (seat belt unbuckled). In the condition wherein switch 112 is closed, pie~oelectric transducer 14 provides a pulsating audible signal, the tone being produced by tone generator circuit 12 and the pulsations being produced by pulsator circuit 16. With the positive electrical signal applied to termination 2~ and terMination 30 electri-cally coupled to the negative side of DC power supply 102, voltage is applied to pulsator circuit 16, tone generator circuit 12 and warning lamp 110 throuyh deactivating means 22, AccordintJly, where switch 112 is closed (seat belt not fastened) the pulsatiny audible signal will be ., .....
~ -7 . ..... . . . .
,, , ~ ' ! .. ~
.,.~ r~.
produced until the tempera-ture of the heated bi-rnetallic melnl)er 3Z of deactivating means 22 has increased sufficiently -to cause an interruption in the electrical signal. The time required for the ternperature to increase sufficiently is typically about 6 seconds. Therefore upon closing switch 108, if the seat belt is unfastened, the pulsatiny audible signal is produced for a predetermined interval of time at the conclusion of which the audible siynal is discontinued and the ~arning lamp 110 is turned off independent of whether the seat belt is in fact fastened. If upon closing switch 10~ the seat belt is fastened either before initiation of or during the predetermined interval of time, i.e. s~litch 112 is open, termination 24 will not be grounded and therefore no audible signal is produced; however, the warning lamp 110 will still be activated for the predetermined interval of time.
In pulsator circuit 16, first and second NAND gates 46 and 54 cooperate.with resistor 50 and capacitor 52 to cause the voltage at output 60 to alternately rise.and fall in essentially a square wave manner at a repetition rate controlled,by the values of resistor 50 and capacitor 52. When the output 60 of gate 54 is high the tone generator circuit 12 operates and when the output 60 of gate 54 is low the tone .
generator circuit 12 ceases to operate thereby producing the pulsations in the audible signal.
NAND gates 66 and 74 are electrically coupled in parallel and cooperate wlth piezoelectric transducer 14 in an oscillitory manner so that transducer 14 is excited into vibration near its resonant frequency ~ and an audlble signal is produced. Electrode 88 of transducer 14 pro-vides a feedback voltage of a magnitude and phase to permit sustained oscillations in the circuit. When the voltage supplied from output 60 of NAND gate 54 to inputs 70 and 78 of NAND gates 66 and 74 is near the supply voltage, oscillation will occur. in tone genera-tor circuit 12 When voltage from output 60 is down or near ground potential the oscillations . .
.
...
~. ' ~' ~-~3$JJZ~S
cease.
Referring now to FIGURE 2 there is shown a second embodiment of a timed audible alarm system 210 which is capable of providing a variety of audible signals in response to the existence of a plurality of conditions wherein at least one of the audible siynals is discontinued after a predetermined interval of time even if the condit;on still exists. The timed audible alarm system 210 includes a tone generator clrcuit 212 which utilizes a piezoelectric transducer 214 to produce an audible signal; a pulsator circuit 216 electrically coupled to tone generator circuit 212 for providiny pulsations in the audible signal; a transient protection means 218 electrically coupled to pulsator circuit 216 and tone generator means 212; an input-output terrninal means 220 electrically coupled to transient protection means 218; a ground iso-lation means 222 electrically coupled to tone generator circuit 212, transient protection means 218, and input-output terminal means 220; and means 219 for deactivatiny the audible alarm system 210 after a predeter-mined interval of time even though a condition still exists.
Ground isolation rneans 222, for providing more than one ground path to system 210, is electrically coupled directly to transient pro tection means 218 and input-output terminal means 220 and is also elec-trically~coupled through a resistor 237 to transient protection means 218 deactivating means 219 and input-output terminal means 220.
~ Input-output terminal means 220 for providing electrical terminations to the system 210 includes terminat;ons 224, 225, 226, 227, 228, 229, and 230. Termination 224 is electrically coupled to ground isolation means 222 and a first side of resistor 237. Termination 229 is electrically coupled to voltage transient protection means 21~ and to a second side of resistor 237, Termination 225 is electrically coupled to voltage transient protection means 218 and to a first side of a resistor 238. Terlllination 226 is electrically coupled to volta~e . . ; , :~
13~ S
transient protection mearIs 218. A resistor 236 is electrically coupled between termination 225 and 226. Termination 227 is electrically coupled through a resistor 235 to the base of an NPN transistor 296.
The transistor 296 has its collector electrically coupled to a second side of resistor 23~ and its emitter electrical'ly coupled to termination 228. Termination 228 is in addition electrically coupled through de-activating means 219 to voltage transient protection means 218. Term-ination means 230 is also electrically coupled to deactivating means 219.
Pulsator means 216 for producing pulsations in an audible signal incorporates two two-input NAND gates 246 and 254 of a Quad t~o-input NAND gate integrated circuit package 294. An input 242 of gate 246 is electrically coupled to voltage transient protection ~eans 218 and another input 244 of gaté 246 is electrically coupled to a first side of a resistor 249. An input 256 of gate 254 is also electrically coupled to voltage transient protection means 218. Another input 258 of gate 2~4 ;s electrically coupled to a ~irst side of a resistor 250 and ''-to an output 248 of gate 246. An output 260 of gate 254 is electrically coupled to tone generator circuit 212 and to a first side of a capacitor 252. A second side of resistor 249 is electrically coupled to a second side of resistor Z50 and to a second side of capacitor 252.
Tone generator circuit 212 for produeing an audible signal in-corporates two t~o-input NAND gates 266 and 274 of the Quad t~o-input NAND gate integrated-circuit package 294. Piezoelectric transducer 214 includes electrodes 286 288 and 290. Electrode 290 is electrically ' coup'led to ground isolation means 222. An input 270 of NAND gate 266 - and an input 278 of NAND gate 274 are each e'lectrically coupled to pulsator circuit 216. An input 26g of NAND gate 266 and an ~nput 276 of NAND gate 274 are each comIllonly e'Iectrica'Ily coupled to a first side of a resistor 2~2 and to electrode 28~ of piezoelectric transducer 214. An , -~n-,, . , ; I
output 272 o f IlAND gate 266 and an output 2gO of NAND gate 274 are each commonly electrica11y coupled to a second side of resistor 2~2 and -through a resistor 284 to electrode 2~6 oF transducer 214. In combi-nation, the coupling of NA~ID yates 266 and 274 in the manner described hereinabove forms a means 292 for amplifying the electrical signal produced by electrode 2~8 of transducer 214.
Ground isolation means 222 includes diodes 223 and 221. The anodes of diodes 223 and 221 are electrically coupled together and to the tone generator circuit 212 and to a negative voltage terminal 264 of integrated circuit package 294. A cathode of diode 223 is electrically coupled to termination 224 of input-output terminal means 220 and through resistor 237 to termination 229. A cathode of second diode 221 is electrically coupled to ternlination 225 and to transient protection means 218.
Transient protection means 218 for protecting system 210 against electrical transient voltages includes four resistors 211, 213, 215 and 217. Resistor 215 is electrically coupled to termination 228 through deactivating Ineans 219 and to input 242 of first NAND gate 246.
Resjstor 213 is electricalIy coupled between termination 226 and a positive voltage terminal 262 of integrated circuit package 294. Re-sistor 211 is electrically coupled between termination 225 and input 256 of second NAND gate 254. Further, resistor 217 is electrically coupled across the inputs 242 and 256 of gates 246 and 254 respectively.
A negative voltage terminal 264 of integrated circuit package 294 is electrically coupled to electrode 290 of piezoelectric transducer 214 and to ground isolation means 222.
Continuing to refer to FIGURE 2, means 219 for deactivating the audible alarm s~stem 210 after a predetermined interval oF tinle is a temperature actuated switchiny device which in the absence oF an elec-trical signal being applied thereto is normally closed. Deactivating , 1 'I
, . -:.: . ~ , ' `. . .
, ,.:; . , . .
3fi~5 .
means 219 includes a heated bi-metallic nlember 232 and an unheated bi-metallic melllber 234 which, in the absence of and for a short time after the application of an electrical signal, contact each other thereby providing an electrical transmission path therebe-t~een. As illustrated, the heated bi-metallic melllber 232 is electrically couple.d to -termination 230, electrically coupled to termination 22~, and electrically coupled to the unheated bi-metallic melllber 234 as long as an electrical siynal is not supplied to the heated bi-metallic mell1ber 232. When an electrical signal is applied to deactivating means 219~ the temperature of the heated bi-metallic melllber 232 will gradually increase thereby causing the heated bi-metallic melllber 232 to gradually bend away from the un-heated bi-metallic member 234 and interrupting the electrical trans-mission path therebetween.
A typical application for timed audible alarm system 210 is again in an automobile to produce a plurality of audible signals one of which is timed to alert a driver to various different situations requiring his attention. FIGURE 2 illustrates a,portion of a typical automobile electrical circuit 300 electrically coupled to audible alarm system 210.
A DC power supply 302, which may comprise an automotive battery is electrically coupled positive term;nal 304 to termination 228 of system 210 through a switch 308 which is typically the ignition switch of the automobile such that when the ignition switch is closed an electrical signal is applied to system 210 through termination 228. The positive - terminal 304 is further electrically coupled, before the switch 308, through a circuit breaker device 324 to termination 226 and through the series combination of a switch 32Z, potentiol-neter 320, and another circuit breaker device 326 to termination 227 and in parallel thereto to at least one instrument lamp, as for example lamps 313 and 319. Another lamp 310 is electrically coupled be~ween the ne~Jative side 306 oF DC
power supply 302 and termination 22~. Two switches 314 and 316 are -1?-., ,..", , ~ . , .~,, .,, , . i~
3~
electrically coupled in series be~ween the neyative side 306 of DC po~er supply 302 and termina-tion 225. Fur-ther, a switch 31Z is electricall~
coupled between the negative side 306 oF DC power supply 302 and termi-nation 224. The negative side 306 of DC power supply 30Z is also sho~ln to be electrically coupled to termination 230.
In one application of timed audible alarm system 210, s~"itches 308, 312, 314, 316 and 322 may have these relationships to other auto-motive components: swi~ch 308 is included in an iynition s~litch to be switched when the ignition switch is activated; switch 312 is included in the seat belt and is responsive to fastening or unfastening of the seat belt; switch 314 is incorporated in an ignition lock (separate from switch 308) to be switched upon insertion or withdrawal of ignition key;
switch 316 is located in a passage doorway in such a manner as to be switched upon opening and closing of the door; and switch 322 is incor-porated in a head light control system to be switched on when the head lights o~ the automobile are switched on.
: In operation, termination 226 receives a positive voltage from DC power supply 302. Termination 228 also receives a positive voltage from power supply 302, but only upon the clo~ing of switch 308. Term-ination 224 becomes completed to ground upon closing of s~litch 312. In :
the condition wherein switches 30& and 312 are clos~d, piezoelectric transducer 214 ernits a pulsating tone, the tone being produced by tone generator circuit 212 and the pulsations being produced by pulsatorcircuit 216. Wlth the positive electrical signal applied to termination 228 and terminatlon 230 electrically coupled to the negative side 306 of DC power supply 302 voltage is applied to pulsator circuit 216, tone .generator circuit 212 and warniny lamp 310 throuyh deactivating means 219. Accordingly, where switch 312 is closed (seat belt not fastened) a pulsating audible siynal will be produced and lamp 310 will be lit until . the temperature oP the heated bi-metallic menlber 232 of de~ctivating .. -13-: - . " ,., .. . ..
~13~ S
means 219 has increased sufficiently to cause an in-terruption in the electrical transmission path. Therefore upon closing switch 30g, if the seat belt is unfastened, the pu1satiny audible signal is produced for a predetermined interval of time at the conclusion of which the audible signal is discontinued and the warniny lamp 310 is turned off independent of whether the seat belt is in fact fastened. If upon closiny switch 308, the seat belt is fastened either before initiation of or during the predetermined interval of time, i.e. switch 312 is open, termina-tion 224 will not be grounded and therefore no audible signal is produced; how-ever, the warniny lamp 310 will still be activated for the predetermined interval of time.
Pulsator circuit 216 and tone generator circuit 212 operate in the same manner as previously described. Accordingly, when the output 260 of gate 25~ is high the tone generator circuit 212 operates and when the output 260 of gate 254 is low the tone generator circuit 212 does not operate. By alternately chanying the output 260 of gate 25~ from a high to a low state, tone generator circuit 212 is made to produce a pulsating audible siynal.
In the condition where switch 308 is open (ignition switch turned off) and the head lights are on, i.e. switch 322 is closed, NPN
transistor 296 is activated through termination 227 and resistor 235.
The emitter of transistor 296 is grounded through deactivating means 219, which has no electrical signal applied thereto, and either termination ;
229 or termination 230. Input 256 is caused to bé low and therefore gate 254 has an output 260 which is constantly high whereby tone generator circuit 212 produces a continuous audible siynal, Since the electrical signal supplied to the system 210 does not pass through deactivating means 219, the continuous audible signal ,is continuously produced until switch 322 is opened (head lights turned of-f) thereby allowing the base of tran-sistor 296 to be grounded through lamps 31~ and 319 which have also been ;, . . . . , . , .. ;; . .
~3~415 deactivated by opening switch 322.
By grounding termination Z25 through switches 314 (key switch) and 316 (door'switch) a low again appears at input 256 of gate 260 thereby causing its output 260 to be high which resul-ts in a non-pulsat-ing or continuous audib'le signal produced by tone generator circuit 212.
Accordingly, if the keys remain in -the ignition switch (closing switch 314) and the driver opens the door thereby c'losiny switch 316 a continuous audible signal is continuously produced until either the key is removed or the door is closed. Resistor 236 serves to maintain input 256 high except when grounded through transistor 296 or termination 225, In view of the above description of the embodimen-ts of the present invention it will be seen that the several objects of the in-vention are achieved and other advantageous results attained and that further modifications can be made without departing from the spirit and scope of the invention as defined in the appended claims.
.
..
Claims
1. In an audible alarm system of the type including a piezo-electric component for providing an audible signal and circuitry for driving the piezoelectric component at substantially its resonant frequency wherein the improvement comprises:
means for continuously providing said audible signal during the existence of a first condition;
means for intermittently providing said audible signal for a pre-determined period during the existence of a second condition and in response to initiation of a third condition, said means for intermittently providing including a heat activated bimetallic switch means for controlling said predetermined period and for terminating said inter-mittently provided audible signal thereafter, said switch means being coupled to begin heating in response to initiation of said third condition;
and visual signal means coupled to said bimetallic switch means for visually signalling initiation of said third condition for said pre-determined period and independent of the existence of said second condition, wherein the improvement enables an alarm system to provide recognizably different modes of operation to indicate the existence of different conditions.
means for continuously providing said audible signal during the existence of a first condition;
means for intermittently providing said audible signal for a pre-determined period during the existence of a second condition and in response to initiation of a third condition, said means for intermittently providing including a heat activated bimetallic switch means for controlling said predetermined period and for terminating said inter-mittently provided audible signal thereafter, said switch means being coupled to begin heating in response to initiation of said third condition;
and visual signal means coupled to said bimetallic switch means for visually signalling initiation of said third condition for said pre-determined period and independent of the existence of said second condition, wherein the improvement enables an alarm system to provide recognizably different modes of operation to indicate the existence of different conditions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US90146178A | 1978-05-01 | 1978-05-01 | |
| US901,461 | 1978-05-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1136245A true CA1136245A (en) | 1982-11-23 |
Family
ID=25414231
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000325967A Expired CA1136245A (en) | 1978-05-01 | 1979-04-20 | Timed audible alarm system utilizing a piezoelectric transducer |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1136245A (en) |
| MX (1) | MX4432E (en) |
-
1979
- 1979-04-20 CA CA000325967A patent/CA1136245A/en not_active Expired
- 1979-04-30 MX MX10070979U patent/MX4432E/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| MX4432E (en) | 1982-04-29 |
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