Title of Invention

AN ELECTRIC HORN HAVING AN OPTO-ELECTRONIC FEEDBACK SYSTEM

Abstract

An electric horn for vehicular and other uses is described and comprises an opto-electronic coupling between the diaphragm assembly and the energising coil thereof such that the cycle time of the energisation and de-energisation cycle of the coil is maintained substantially corresponding to the natural frequency of vibration of said diaphragm assembly thereof during operation Said coupling comprises an infra-red light emitting diode(IRLED) and a photoelectric cell, the beam there between being periodically cut by an interrupter attached to said diaphragm assembly and the pulsed current obtained from said coupling being of said natural frequency. The pulsed current is inverted, amplified and fed to said coil. Said IRLED and cell are mounted on the arms of a U--shaped member which is preferably made of ABS(Acrylo-Butadiene-Styrene).

Full Text

This invention relates to an electric horn for automobile, rail and other vehicles and more particularly to an electric horn comprising an opto-electronic coupling between the diaphragm movement and the electromagnet circuit thereof, thereby providing a substantially spark-free (arc free) operation thereof. Horns are sometimes referred to as signalling devices and warning devices. In this specification, however, the terms 'electric horn' and "horn' are used and are intended to cover within their scope said equivalent terms mentioned hereinabove and also other equivalent terms thereof used in the art. The scope of the invention covers horns for application in vehicles for road, rail, water and air and combinations thereof. Specifically, it covers vehicles such as cycles, motorcycles, automobiles(cars), mopeds, scooters, lorries and trucks, trailers, boats and earthmoving and construction vehicles and tracked vehicles. The scope also covers applications other than vehicular in which applications they are simply and easily adapted by persons of average skill in the art. Such applications are alarm, warning and annunciatory systems. However in the description and claims hereinbelow, reference is only made to the vehicular application thereof. This is in the interests of conciseness without affecting the scope of the invention. In an electric horn, an electromagnet circuit drives a vibratory diaphragm producing a low frequency sound of about 300-450 Hz. Said electromagnet comprises an electric coil with an iron core located therein and said diaphragm is attached to, or is, integral with an armature and tone disc which is sometimes referred to as a resonance disc or resonator. Said iron core is sometimes referred to as a pole piece and said armature as a plunger. During operation of the horn, said coil is alternately energised and de-energised. Upon said energisation said armature is drawn towards said core and impacts thereupon. The forward movement(towards said core) of said armature system comprising said armature, diaphragm and tone disc, causes flexing of said diaphragm which is held at the periphery thereof in the horn housing. Said flexing, in other words, the spring bias of the diaphragm, provides the restoring force which causes said armature system(diaphragm system) to move backwards when said coil is de-energised. Said periodic impacts(strikes) produced in the core-armature system generate and sustain, x'ibrations in said resonator in the frequency range of 2000-4000 Hz, The note produced by said diaphragm and the high frequency note generated by the resonator combine to create a composite sound which is quite penetrating without being harsh on the ear. In some horns, the armatures do not impact on their respective pole pieces. Such horns do not have said resonators and the horn sound produced is solely by the movement of the diaphragm. This sound is amplified by a trumpet-like construction located at the front of the horn. Said trumpets may be straight, spiral or of other configurations. In contrast, said resonator type horns do not have said trumpet-like constructions but may have grilles or projector pieces at the front of the horns to direct the generated sound towards the front. Thus we have two major types of electric horns: resonator type and non-resonator type, the former operating at about 350-400 Hz and the latter at 400-750 Hz. It may be noted that the novel opto-electronic coupling of this invention is easily adapted to both said types by persons of average skill in the art. The alternate energisation and de-energisation of said coil, that is, the electromagnet circuit is achieved by operation of a mechanical switch located in the circuit. The supply of power to said circuit is controlled by means of the horn button or other means provided in the vehicle for operation of the horn. Said mechanical switch is of NC(normally closed) configuration and comprises generally two longitudinal arm-like members(arms) provided with electrical contacts(elements) at the outer ends thereof. One said arm is generally stationary while the other is movable to and from the first, such as to establish butt contact between said elements in the closed position of said switch and break the same in the open position thereof. Said movable arm and sometimes also said stationary arm are made of spring steel or other material having adequate resiliency such that when said switch is opened and the restraint on said movable arm is removed, said movable arm returns at the desired speed to re-make said butt contact. Said resiliency further, provides the desired pressure of contact between said elements. Said outer end of said movable arm is also referred to as the free end. During the course of said forward movement, said armature abuts said free end and pushes it down causing the breaking of said butt contact and opening of said switch. When the armature commences the backward movement thereof, it comes free of said free end. Said movable arm that is, said free end now moves and restores said butt contact thus causing the closing of said switch. The impulse for said restoring movement of the free end comes from said resiliency of the movable arm. In other words, said impulse is the restoring force generated during the deflection of said movable arm caused by said armature during the forward motion thereof. In the arrangement described hereinabove, the imparting of movement to said free end by said armature is by direct contact and abutment between the two during said forward movement. In some mechanical switches, a member is interposed between said armature and free end. Such an inteiposed member is either attached to, or is integral with said armature. References to directions such as forward, backward, up, and down and others are in relation to the horn configuration wherein the diaphragm axis and horn axis are coincident and vertically disposed with the diaphragm-armature assembly located generally vertically above said coil and core assembly. Said stationary arm is anchored at both ends but the end thereof whereat said element is located, there is provision of screw and spring means (adjusting means) for adjusting the parameters of said butt contact. The tightening of said adjusting means enhances the pressure of said butt contact. Simultaneously it increases the deflection of said moving arm and furthermore adjusts the point along the travel path of said armature where the abutment of said armature and moving arm occurs. The magnitude of said deflection governs the speed at which said moving arm returns to re-establish said butt contact. Said pressure, said deflection, said speed of return of said moving arm, length of said travel path, the location of said point of abutment, the speed of armature travel and the armature-pole piece gap (air gap) are the parameters that determine the tone, pitch and sound output of the horn. Said adjustment (tuning) is first carried out at the manufacturing stage following which periodical adjustments are made to take into account the wear and tear of said elements and the fall, if any, In the resiliency of said arms, in particular the moving arm. Said periodical adjustments restore the performance of the horn to substantially the optimum value thereof. The cycle time of energisation and de-energisation is the time between one said energisation and the next. The period of the armature system, that is, of the armature-diaphragm-tone disc combination is the time between one said impact and the next. It will be observed that in operation said period and cycle time will be equal because of the link or feedback provided between the armature system and the electromagnet system by said mechanical switch. If the total energy output (sound output) of a horn is evaluated at different said cycle times a maximum is observed at a particular value thereof. Said particular value is found to correspond to the natural frequency of said armature system (diaphragm system). In other words, the performance of a horn peaks when the period of the armature thereof is matched to the natural frequency (period of vibration) of the diaphragm system. It follows therefore that for maximum energy conversion efficiency a horn must be operated at a cycle time, which is continuously substantially equal to or close to the natural period of vibration of the armature system thereof Said natural frequency is also referred to as the resonance frequency of the diaphragm system. Horns incorporating said mechanical switches have therefore been extremely successful products whose basic design is only now beginning to change after decades of use in the industry. It will be observed that the central feature of said mechanical switches is the closed loop system it provides wherein feedback from the diaphragm motion is provided to the process of said energisation and de-energisation of the electromagnet system. Said success of horns having mechanical switches has been despite some severe drawbacks associated therewith. Most of these drawbacks are the consequences of the mechanical nature of said mechanical switches. More often that not, failure of a horn is caused by the failure of the mechanical switch thereof The most often observed causes of the failures of said switches are: i. drop in resiliency of said stationary and movable arms over a period of time; ii. wear and tear of said elements; iii. failure of the movable arm due to fatigue or otherwise; iv. wear and tear of other parts of the switch and of the anchoring of said arms; and V. sparking/arcing at said elements. This led to the development of electronic switching systems for horns. Such systems comprise oscillator systems, which provide pulsed currents (signals) such as of square wave type. Such pulsed currents provide the basic means for said alternate energisation and de-energisation, said signals being processed in one or more amplifiers and in a power amplifier to provide adequate current for the energisation of said coil. Said electronic systems offer far more reliability of operation than said mechanical systems and therefore failure rates thereof are far lower. In addition, said systems are compact and save on power. They eliminate arcing/sparking at said elements, which is one of the main causes of wear and tear and failure of said elements. They also eliminate the periodical adjustments required in a horn to counteract the effect of wear and tear of contacts, loss of resiliency of said arms and other factors. Said electronic systems do however need periodical adjustments so as to take into account the drop in the natural frequency of said diaphragm assembly. As is known, all diaphragms deteriorate over time due to wear and tear thereof and particularly due to the loss of resiliency of the material thereof Means are therefore provided in electronic horns for said periodical adjustments. However, electronic horns of the art are unable to take care of the mismatch of said cycle time and period that arises in the period between said adjustments. It will be noted that said mismatch involves loss of power in the hom, as the hom does not function at the peak energy efficiency thereof It may also be noted that the cause of said mismatch is the absence of said feedback in the electronic horns of the prior art. This invention is the first to conceive and develop a said feedback system for electronic horns. Said problem of mismatch or a solution thereto, has thus far not been considered or proposed in prior art. This invention is the first to consider and develop a novel solution to said problem, the solution consisting of providing a closed loop arrangement (feedback system) for electronic horns wherein a sensor monitors the position of said armature system along the travel path thereof and feeds information on said position to an electronic switching system (signal processing system) that provides said pulsed power supply to said coil for alternate energisation and de-energisation thereof Said sensor in effect, determines said period of the diaphragm system and inputs the information into said electronic switching system such as to regulate said cycle time. The device of the invention therefore provides continuous correspondence between said period and cycle time ensuring that the horn of the invention maintains substantially the peak sound output thereof substantially all of the time. The sensor of the invention comprises a light emitter, that is, a source of light, visible or non-visible and a photoelectric device (cell). The beam of light from said emitter is adjusted to fall on said cell and the principle of operation of the sensor of the invention is that movement of said armature interrupts/cuts out said beam at a certain point in the travel path thereof Al a pre-determined point in said travel path, an arm-like member, attached to or integral with said armature cuts the path of said beam and interrupts said photoelectric current. With further movement of said armature, said arm-like member moves away from the line of the beam causing the reappearance of said photoelectric current. The sensor of the invention, therefore constitutes a pulsing device which receives said feedback of information on the position of said armature and provides a pulsed current output having a cycle time corresponding to said period of the diaphragm assembly. Said arm-like member is referred to further hereinbelow as the interrupter. The digital signal output of the photoelectric detector (photoelectric cell)) is fed into a preamplifier. Further amplification is provided by means of a MOSFET power amplification system from which a pulse current signal having power output sufficient to energise said coil is obtained. Provisions are made in the circuits to take care of EMI (electromagnetic interference) and RFI (radio frequency interference) spikes that may arise. Said EMI and RFI spikes arise because of the highly inductive nature of said coil and the fact of high current pulses flowing through said coil in a stop-start fashion. According to the invention, therefore, there is provided an electric horn for vehicular and other uses, comprising: i. an electromagnet coil with a pole piece thereof; ii. a diaphragm assembly comprising a vibratory diaphragm attached to, or integral with an armature and further with a resonance disc if required; and iii. a feedback system that provides correspondence between said cycle time and said period of vibration of said diaphragm assembly and comprises an opto-electronic coupling and a signal processing system, said coupling comprising a light emitter and a photoelectric cell for monitoring said motion of said diaphragm assembly and generating a pulsed signal which is processed in said signal processing system and applied to said electromagnet coil thereafter, said signal processing system comprising one or more amplifiers. The housing of the horn of the invention is of generally cylindrical shape and generally of pressed steel sheet but within the scope of the invention other shapes, materials and processing methods of manufacture are feasible. An electromagnet coil is housed in said housing. Passing axially through said coil is a pole piece of ferromagnetic material. Said coil, which is generally of hollow cylindrical configuration, is wound on a plastic support member, which is attached to said housing. Within the scope of the invention, other coil configurations, methods of attachments of the various and materials of construction thereof are feasible. The diaphragm of the horn comprises a substantially flat disc of spring steel or other material to which is attached by threading or other means an armature and if required, a tone disc which is normally of cold rolled carbon steel sheet or aluminium or other suitable material. Said diaphragm assembly comprising the diaphragm, the armature and the tone disc, if included, is attached at the periphery thereof (of the diaphragm) to the flanged end of said cylindrical housing. In the assembled state the axes of housing, said coil and said diaphragm assembly are substantially collinear. Within the scope of the invention, several simple variations and variants are feasible in said materials of construction, methods of manufacture, method of fastening, mounting and shape and configuration of said diaphragm assembly and housing. Said opto-electronic coupling (opto-coupler) comprises an LED (light emitting diode) which emits an infrared beam of light, which falls on a photoelectric detector (cell). Said armature is provided with an arm like member referred to hereinabove as the interrupter which cuts said beam substantially at the end of said forward motion of the armature assembly. As this cutting of the beam occurs once in every cycle of motion of said armature assembly the output realised from said cell is a pulsed current which corresponds to said period of said diaphragm assembly. Said opto-coupler comprises a U-shaped member made of plastics such as ABS, Nylon, Polycarbonate and others. The material of construction of said U-shaped member is preferably ABS or Nylon 6.6 and more preferably ABS. Said light emitter, LED is embedded in one arm thereof and said cell in the other. The travel path of said interrupter takes it between the arms of said U-shaped member where substantially at the end of the forward travel thereof it cuts said beam. In the embodiment described, said arms are oriented in a vertical plane but within the scope of the invention can be easily adapted to have other orientations and locations. The width of saixi interrupter, which determines the time during which said beam remains cut in a cycle, is carefully calibrated. There are several variations in orientations, arrangements, materials of construction and other factors relating to various parts of the opto-electronic coupler which would occur to persons of ordinary skill in the art and would therefore be within the scope of the invention. Said signal processing system comprises a solid stage inverting pre-amplifier, which amplifies said pulsed signal from said cell. The pre-amplified signal is then fed to a MOSFET power amplifier, which provides said pulsed signal of adequate strength to energise said coil. Adjustment means are provided to adjust said point of interruption of beam and duration thereof such that one can provide for: i. said armature pole piece impacts if desired; ii. desired intensity of said impacts. Said impacts are resorted to only in resonator type horns where the impacting is required to set up and sustain vibrations in said resonators. In non-resonator type horns said armature does not impact on said pole piece. In order to provide a clearer understanding of the invention and without limitation to the scope of the invention an embodiment thereof will now be described with reference to the accompanying drawings wherein like numerals refer to like parts. Said drawings are: Fig. 1: Sectional view of the horn of the invention looking from one side; Fig. 2: View from top of the horn of the invention with the diaphragm assembly removed; Fig. 3: Sectional view of the horn of the invention looking from one side and with the diaphragm assembly removed; Fig. 4: View from side showing the opto-electronic coupler of the invention; Fig. 5: View from top showing the opto-electronic coupler of the invention; Fig. 6: Details of the diaphragm assembly of the invention; and Fig. 7: Circuit diagram of the signal processing system of the invention. Reference numeral 1 denotes the horn housing which is of a generally cylindrical shape and comprises the bottom part 2 of the housing, the sides 3 and mouth 4 having flange 5 whereupon is fastened diaphragm assembly 6 comprising diaphragm 7, armature 8 and resonator 9 by fastening means 10. Front grille 11 of the horn is also fastened to flange 5. Necessary gaskets are provided where said diaphragm 7 and grill 11 are fastened to flange 5. Reference numeral 13 denotes the electromagnet coil at the centre whereof is located the pole piece 14, that is the stack of E-shaped laminations of ferromagnetic material that forms the electromagnetic core. Opto-electronic coupling 15 comprises a U-shaped member 12 made of ABS polymer. In one ann 16 of U-shaped member 12 is embedded light emitter, IRLED, 18 and in the second arm 17 a photoelectric cell(detector) 19. Light emitter 18 gives a beam of infra-red light which is periodically interrupted/cut by interrupter 20 which follows the motion of said armature 9 being attached to or integral therewith. The reciprocating travel path of interrupter 20 takes it between said arms 16,17 where it periodically interrupts said infrared beam. Said interruptions are in correspondence with the natural period of vibration of said diaphragm assembly 6 and consequently the pulsed current produced by said photo electric detector 19 has the same period as that of the diaphragm assembly 6. Said pulsed current is fed to the signal processing circuit 21 which comprises two parts 22,23 of which part 22 is a pre-amplifier circuit and part 23 is a MOSFET power amplifier circuit. The signal received from detector 19 of the opto-electronic coupler 15 is inverted and pre-amplified and fed to the MOSFET power amplifier 23, for further amplification. The power output of MOSFET power amplifier circuit 23 is applied to coil 13. In operation coil 13 is energised and de-energised by the pulsed current from amplifier 23, the period whereof is the same as that of the diaphragm assembly 6, By this means the cycle time of energisation is kept continuously in correspondence with, that is, substantially equal to said natural period of vibration of the diaphragm assembly 6. During operation said armature 8 strikes the pole piece 14 in each cycle. These impacts set up vibrations in resonator 9. Vibrations of the diaphragm 7 and of resonator 9 combine to produce the composite horn sound. The make-break ratio is adjusted by the altering the values of resistors R3, R4 and R5. The comparator(inverting amplifier) reference threshold is adjusted by R3 and R4. The positive feedback resistor R5 provides the hysterisis. Tuning means 24 provides adjustment of the position of said U-shaped member 12. By means of tuning means 24 the duration of interruption of the photoelectric current is controlled. The width of said interrupter 20 controls the duration of said beam interruption and is designed to provide the optimum operation of the horn from sound output point of view that is, at optimum energy efficiency. The width of said interrupter controls the duration of said beam interruption and is designed to provide the optimum operation of the horn from sound output point of view that is, at optimum energy efficiency. The hont of the invention can be easily adapted for operation on all vehicle batteries(accumulators) such as Of 6V, 12V, 18V and other ratings. Bracket 2S is provided for mounting the horn on a vehicle. Various embodiments and variations other than described above which axe whithin the art are within the scope and spirit of the invention. 1 claim: 1 - An electric horn for vehicular and other uses comprising: I. an electromagnet coil with a pole piece thereof; ii. a diaphragm assembly comprising a vibratory diaphragm attached to, or integral with an armature and further with a resonance disc, if required, and iii. a feedback system that provides correspondence between said cycle time and said period of vibration of said diaphragm assembly and comprises an opto-electronic coupling and a signal processing system, said coupling comprising a light emitter and a photoelectric cell for monitoring said motion of said diaphragm assembly and generating a pulsed signal which is processed in said signal processing system and applied to said electromagnet coil thereafter, said signal processing system comprising one or more amplifiers. 2. The electric horn as claimed in preceding claim 1 wherein said light emitter comprises an infrared light emitter. 3. The electric horn as claimed in preceding claim 2 wherein said light emitter and photoelectric cell are mounted on the arms of a U-shaped member and wherein said interrupter which is attached to, or integral with said armature assembly cuts the light beam between said emitter and said cell at generally the end of the forward motion of said armature assembly. 4. The electric horn as claimed in preceding claim 3 wherein said U-shaped member is of ABS(Acrylo-Butadiene-Styrene), 5. The electric horn as claimed in preceding claim 4 wherein said signal-processing system comprises a pre-amplifier and a Mosfet power amplification system. 6. An electric horn for vehicular and other uses substantially as hereindescribed with reference to and as illustrated in the accompanying drawings. 1 claim: 1 - An electric horn for vehicular and other uses comprising: I. an electromagnet coil with a pole piece thereof; ii. a diaphragm assembly comprising a vibratory diaphragm attached to, or integral with an armature and further with a resonance disc, if required, and iii. a feedback system that provides correspondence between said cycle time and said period of vibration of said diaphragm assembly and comprises an opto-electronic coupling and a signal processing system, said coupling comprising a light emitter and a photoelectric cell for monitoring said motion of said diaphragm assembly and generating a pulsed signal which is processed in said signal processing system and applied to said electromagnet coil thereafter, said signal processing system comprising one or more amplifiers. 2. The electric horn as claimed in preceding claim 1 wherein said light emitter comprises an infrared light emitter. 3. The electric horn as claimed in preceding claim 2 wherein said light emitter and photoelectric cell are mounted on the arms of a U-shaped member and wherein said interrupter which is attached to, or integral with said armature assembly cuts the light beam between said emitter and said cell at generally the end of the forward motion of said armature assembly. 4. The electric horn as claimed in preceding claim 3 wherein said U-shaped member is of ABS(Acrylo-Butadiene-Styrene), 5. The electric horn as claimed in preceding claim 4 wherein said signal-processing system comprises a pre-amplifier and a Mosfet power amplification system. 6. An electric horn for vehicular and other uses substantially as hereindescribed with reference to and as illustrated in the accompanying drawings.

Documents:

461-mas-2000-abstract.pdf

461-mas-2000-claims filed.pdf

461-mas-2000-claims granted.pdf

461-mas-2000-correspondnece-others.pdf

461-mas-2000-correspondnece-po.pdf

461-mas-2000-description(complete) filed.pdf

461-mas-2000-description(complete) granted.pdf

461-mas-2000-description(provisional).pdf

461-mas-2000-drawings.pdf

461-mas-2000-form 1.pdf

461-mas-2000-form 26.pdf

461-mas-2000-form 4.pdf

461-mas-2000-form 5.pdf