Signal annunciators

#This invention relates to audio indicating devices and specifically to automobile turn signal and emergency light flasher operation audio indicators.

#The present invention, as have many before, addresses the problem of alerting a driver to the operation of his turn signals and emergency flasher lights. And, more specifically, to doing so in a pleasant manner. A more complete discussion of the prior art can be found in applicant's previous U.S. Pat. No. 4,980,669, ANNUNCIATOR FOR AUTOMOTIVE SIGNAL LIGHT FLASHERS to Knowles(1990). This previous invention operated by allowing a capacitor to charge through one path while the flasher was open (lights `off`) and discharge through another path when the flasher closed (lights `on`). To create sound, an oscillator and transducer were placed in the discharge path. Because the capacitor discharge current decayed exponentially, so did the volume of the sound produced by the oscillator and transducer, creating a natural sounding note, like a dampened piano key being struck. The present invention is an improvement over this prior invention.

#The prior device was intended for aftermarket installation at the turn signal flasher and for that reason was designed to function with the connections available there. This leads to three operational shortcomings--First, because some flashers start in their closed position, the lights are turned `on` immediately when the turn signal lever is operated. With no preceding `off` period in which to charge, the earlier annunciator does not function the first time the lights turn on. Second, with these flashers, this prior device will perform an extra beep if the signal lights are turned off during the `off` portion of the flasher cycle because this type of flasher comes to rest in its `on` position whether or not the circuit is completed through the turn signal light switch to the lights and ground. Third, this prior device did not respond to the emergency light flasher unless a second, identical device was purchased and installed on the emergency lights flasher.

#FIG. 1 is a generalized schematic diagram of the invention.

#FIG. 2 is a schematic diagram of a preferred embodiment of Species 1, including the pertinent parts of a vehicular turn light signaling system.

#FIG. 3 is a schematic diagram of a preferred embodiment of Species 2.

#Referring to FIG. 1, a generalized schematic of the invention is presented. Input conductor 1 is connected between the input signal and the input of amplifier 2. Capacitor 3, placed in series with the input conductor serves to limit input current as will be described below. Disc 4 is a piezoelectric disc comprising a metal diaphragm, a piezoelectric material and three metal electrodes of the configuration proposed in Sweany. Two of the electrodes are main electrodes, commonly called drive and common. The disc deforms when a voltage is placed across these electrodes, and oscillates when a pulsed voltage is applied, emitting sound. The third, feedback electrode outputs a brief voltage spike as the disc deforms. Its polarity depends on a poling voltage used during manufacture of the disc and the direction of deformation, which in turn depends on the polarity of the voltage across the drive and common electrodes. Load conductor connections to amplifier 2 at its ground and output terminals and are made to the ground voltage source and to one of three possible positive voltage sources dependent upon species type as indicated by the dashed lines and described below. Load resistor 5 is in series with the load conductor between the output of amplifier 2 and the positive voltage source. The output of amplifier 2 is also connected to one main electrode of disc 4, and the feedback electrode from disc 4 is connected to the amplifier input providing an AC signal to be amplified and fed back. The other main electrode of disc 4 is shown connected to ground. The required DC component of the input signal is provided by input conductor 1 through bias resistance 6.

#As with other amplifying circuits, other possible connections between amplifier 2, load resistor 5 and disc 4 exist. Load resistor 5 can be anywhere in the circuit in series with the load connections of amplifier 2. The main electrodes of disc 4 can be across either the amplifier or the load resistor. As taught in Sweany, the polarity of the main electrode connections (drive and common) is chosen so that the feedback signal from the disc creates amplifier output that is in phase with the disc oscillations. The choice is affected by the type of amplifier (inverting or non-inverting, positive input or negative input) and the polarity of the poling voltage used in the manufacture of the particular disc.

#The species of the invention is determined by the positive voltage source to which amplifier 2 is connected. S.1 indicates the connection used in Species 1; S.2 is for Species 2; S.3 is the connection used in Species 3. In Species 1, capacitor 3 provides all the circuit current because the load conductor connected to the output of amplifier 2 connects to the signal conductor `after` the capacitor. In Species 2, only the bias input current to amplifier 2 is provided by capacitor 3, however, all of the circuit current is still provided by the signal. In Species 3, capacitor 3 again provides only the bias input current but because the current source for amplifier 2 is now a permanent positive voltage source, only the input bias current is supplied by the signal.