Pulse Generating Apparatus Having a Chattering Pulse Elimination Circuit

1. Field of the Invention

The present invention relates to a generating apparatus of such pulse signal as corresponding to the building up phase of the rectangular wave signal generated by opening and closing of a mechanical contact, particularly to a pulse generating apparatus having a prevention circuit for erroneous function by chattering, improper contact, etc., at the time of opening and closing of a contact.

2. Description of the Prior Art

An apparatus to generate such pulse signal as corresponding to a rotating speed of a rotating machine by opening and closing a mechanical contact with rotation of the machine to put the current ON or OFF, and to control the rotation of other rotating machines to secure synchronism is generally used as, for example, a synchronizing equipment between a magnetic reproducing machine and a cine-projector, and between a magnetic sound recording equipment and a cine-camera, etc. In such apparatus employing the opening and closing of a mechanical contact, unnecessary pulse may be generated by chattering, improper contact, etc. which take place in opening and closing the contact, and erroneous functioning may be caused thereby, which need to be prevented. That is, when the rectangular wave output generated by opening and closing of a contact is differentiated by a differentiation circuit to make it pulse signal, as it becomes rectangular wave signal accompanying short pulse at the time of opening and closing by chattering, etc. of the contact, if it is simply differentiated to take out such pulse signal as corresponding to the building up phase, false pulse is mixed into normal driving pulse, thereby causing erroneous action in control of the equipment being controlled.

The object of the present invention is to provide a pulse generating apparatus with very simple arrangement, in which the above mentioned short-comings of conventional apparatus are eliminated and such false pulse as causing erroneous functioning will not be mixed in the pulse control signal generated by opening and closing a mechanical contact.

Another object of the present invention is to provide a pulse generating apparatus having a differentiation pulse to differentiate the rectangular wave signal generated by opening and closing of mechanical contact and to generate such pulse signal as corresponding to its building up phase, wherein said rectangular wave signal is impressed to high resistance through a diode connected in series in a normal direction, and the terminal voltage of said high resistance is impressed to the above mentioned differentiation circuit.

Further other objects of the present invention will become clear by the detailed explanation of the invention made below together with explanation of the drawings.

FIG. 1 is a circuit connection diagram showing an example of a conventional pulse generation apparatus.

FIG. 2 are wave form drawings of each part of the apparatus in FIG. 1.

FIG. 3 is a circuit connection diagram to show an example of the pulse generation apparatus according to the present invention.

FIG. 4 shows wave forms of each part of the apparatus of FIG. 3.

FIG. 5 is a circuit connection diagram to show other example of the pulse generation apparatus according to the present invention.

FIG. 1 is a circuit connection diagram to show an example of a conventional pulse generation apparatus.

In the drawing, E is a power source, S.sub.1 is an opening and closing switch by a mechanical contact, for example a drum switch installed to a rotating axle, etc. of the apparatus. R.sub.1 and R.sub.2 are series resistances employing rectangular wave signal generated at the terminal of the resistance R.sub.2. C.sub.1 and R.sub.3 are a condensor and a resistance composing a differentiation circuit, generating pulse signal between the output terminals O.sub.1, O.sub.2 utilizing commonly known CR time constant factor.

FIG. 2 are waveform drawing for each part of the apparatus shown in FIG. 1. In this drawing the axis of abscissas shows time while the axis of ordinates shows amplitude. The function of the apparatus in FIG. 1 is such that when the switch S.sub.1 is mechanically opened and closed causing chattering, the current being made ON or OFF by the S.sub.1 and flows from the power source E to the resistances R.sub.1, R.sub.2 becomes such rectangular wave as shown in FIG. 2(A). That is, such pulse with small width as shown in the drawing as (a) is accompanied at the time of rising and coming down of the rectangular wave.

When the rectangular wave signal of FIG. 2 (A) is differentiated by such differentiation circuit as shown in FIG. 1, the pulse as shown in FIG. 2 (B) can be obtained. When it is sliced with an appropriate circuit (not shown in the drawing), such pulse in normal direction as shown in FIG. 2 (C) can be obtained. In the drawing a.sub.1 and a.sub.2 are normal driving pulses, but b.sub.1 through b.sub.5 are unnecessary pulses, by which the devices controlled are caused to make erroneous function.

Next, FIG. 3 is a circuit connection diagram to show an example of a pulse generating apparatus according to the present invention. Some parts in this drawing as in FIG. 1 are shown with same identification number or code. D.sub.1 in the drawing is an element having one way conducting characteristics for example a diode, and R.sub.4 is a high resistance, and these parts are different from the apparatus shown in FIG. 1. In the apparatus of this drawing the fact that the reverse direction impedance of the diode D.sub.1 has high value is used and by using the same and the high resistance R.sub.4 the input end of the differentiation circuit is made to have high impedance, thereby the discharge time constant factor of C.sub.1 is made long. FIG. 4 shows wave form of each part of the apparatus shown in FIG. 3. When chattering takes place at the time of opening and closing the mechanical contact S.sub.1, the current flowing from the power source E to R.sub.1, R.sub.2 will become as shown in FIG. 4 (A). When the rectangular wave signal of FIG. 4 (A) is impressed to the high resistance R.sub.4 through the diode D.sub.1, its output waveform will become as shown in FIG. 4 (B). This is because the discharge time constant factor of C.sub.1 becomes long by the diode D.sub.1 and the high resistance R.sub.4, and as it is differentiated by a differentiation circuit consisting of C.sub.1, R.sub.3, such pulse as shown in FIG. 4 (C) can be obtained. In the waveform of FIG. 4 (C), the pulses a.sub.1, a.sub.2 which are in synchronism with the opening and the closing of the switch S.sub.1 have distinctly different amplitudes and directions from those in other pulses, therefore by slicing the same such normal pulses a.sub.1, a.sub.2 only as in FIG. 4 (D) can be obtained. By controlling the equipment to be controlled with the pulse of said waveform, normal synchronized driving can be secured and erroneous function can be prevented.

FIG. 5 is a circuit connection diagram to show another example of the pulse generating apparatus according to the present invention, wherein the high resistance R.sub.4 shown in FIG. 3 is connected in parallel with the diode D.sub.1. In this case as the electric charge of the condensor C.sub.1 is discharged through the high resistance R.sub.4, the resistance R.sub.2, false pulse caused by chattering, etc. will be eliminated same as in the example shown in FIG. 3.

According to the pulse generating apparatus of the present invention the generation of false pulse caused by the chattering, etc. by opening and closing of a mechanical contact can be prevented by simple circuit as mentioned above, therefore it has great effect as applied to various equipment and is usefully industrially.