Fail-safe timing circuit

Claim 2

Means responsive to a predetermined input condition for obtaining a delayed output signal only when said input condition persists of over the entire first delay period comprising: a source of electrical energy; energy storage means; output means having first quiescent and second active operating states; amplifier means; transfer means coupling said amplifier means to said output means; charging means normally coupling said energy storage means to said energy source and responsive to said input condition to decouple said energy storage means from said energy source; discharge control means responsive to said input condition for coupling said energy storage means to said amplifying means in a repetitive alternating fashion; said transfer means comprising means for coupling only said alternating components of the output of said amplifier means to said output means; said output means being operated in its active state upon occurrence of said input condition and being moved to its quiescent state only if said input condition persists after said energy storage means is fully discharged.

Claim 3

The device of claim 1 wherein said energy storage means is a capacitor.

Claim 4

The device of claim 2 wherein said discharge control means comprises a vibratory relay for coupling said capacitor to said amplifier means in pulsating fashion.

Claim 5

The device of claim 3 further comprising adjustable current limiting means coupled to said relay for adjustably controlling the discharge rate of said capacitor.

Claim 6

The device of claim 1 wherein said transfer means comprises a transformer having input and output windings respectively coupled to said amplifying means and said output means.

Claim 7

The device of claim 1 wherein said output means comprises a relay.

Claim 8

The device of claim 3 wherein said charging means comprises first switch means for coupling said energy source to said capacitor only during the absence of said input condition and second switch means for coupling said energy source to said vibratory relay only during the presence of said input condition.

Claim 9

The device of claim 1 wherein said charging means comprises a first transistor for coupling said energy storage means only when said input condition is absent.

Claim 10

The device of claim 1 wherein said discharge control means comprises a transistor coupled to said energy storage means and means coupled to the input of said transistor for operating said transistor in a pulsating fashion between its conductive and non-conductive state to thereby cause the energy stored therein to be discharged into said amplifying means in a pulsating fashion.

Claim 11

The device of claim 1 wherein said amplifying means has a high input impedance to cause the energy stored in said energy storage means to be discharged at a low rate.

Claim 12

The device of claim 1 further comprising filter means coupled between said transfer means and said output means.

Claim 13

Means responsive to a predetermined input condition for obtaining a delayed output signal only when said input condition persists of over the entire first delay period comprising: a source of electrical energy; energy storage means; output means having first quiescent and second active operating states; transfer means coupling said energy storage means to said output means; charging means normally coupling said energy storage means to said energy source and responsive to said input condition to decouple said energy storage means from said energy source; discharge control means responsive to said input condition for coupling said energy storage means to said transfer means in an alternating fashion; said transfer means comprising means for coupling said alternating components of the output of said amplifier means to said output means; said output means being operated in its active state upon occurrence of said input condition and being moved to its high input impedance to cause the energy stored in said energy storage means to be discharged at a low rate.

Claim 14

Means responsive to a predetermined input condition for obtaining a delayed output signal only when said input condition persists of over the entire first delay period comprising: a source of electrical energy; energy storage means; output means having first quiescent and second active operating states; transfer means coupling said energy storage means to said output means; charging means normally coupling said energy storage means to said energy source and responsive to said input condition to decouple said energy storage means from said energy source; discharge control means responsive to said input condition for coupling said energy storage means to said transfer means in an alternating fashion; said transfer means comprising means for coupling said alternating components of the output of said amplifier means to said output means; said output means being operated in its active state upon occurrence of said input condition and being moved to its high input impedance to cause the energy stored in said energy storage means to be discharged at a low rate.

Claim 15

An electronic timing device which, in response to an input signal, supplies with failureproof reliability a delayed output signal, utilizable, for example, for interventions of protection, characterized by the fact that it comprises: at least one source of energy; an energy storage device (for example, a capacitor 8 in FIG. 2, 6 in FIG. 4); means Coupled to said source for charging a maximum quantity of energy in said storage device prior to initiation of the time count; means responsive to the input signal for controlling the discharge rate, during the time count, of the energy stored in said storage devices; means for modulating said discharge control means; means for amplifying the power discharged by the energy storage device during the time count; means for filtering the output of said amplifying means; means coupling said amplifying means to said filtering means whereby only the alternate components produced by the modulation are coupled to said filtering means; output means coupled to said filtering means and which, in its rest condition, that is without any external energy supplied thereto, securely assumes a stable state unequivocally recognizable as ''''end time'''' signal, and which utilizes said filtered power made available during the time count to maintain said output means in a state opposite said rest state indicating that the end time signal has not yet occurred.

Claim 16

An electronic timing device which, in response to an input signal, supplies with failureproof reliability a delayed output signal, utilizable, for example, for interventions of protection, characterized by the fact that it comprises: at least one source of energy; an energy storage device (for example, a capacitor 8 in FIG. 2, 6 in FIG. 4); means Coupled to said source for charging a maximum quantity of energy in said storage device prior to initiation of the time count; means responsive to the input signal for controlling the discharge rate, during the time count, of the energy stored in said storage devices; means for modulating said discharge control means; means for amplifying the power discharged by the energy storage device during the time count; means for filtering the output of said amplifying means; means coupling said amplifying means to said filtering means whereby only the alternate components produced by the modulation are coupled to said filtering means; output means coupled to said filtering means and which, in its rest condition, that is without any external energy supplied thereto, securely assumes a stable state unequivocally recognizable as ''''end time'''' signal, and which utilizes said filtered power made available during the time count to maintain said output means in a state opposite said rest state indicating that the end time signal has not yet occurred.

Claim 17

The device of claim 1 wherein the time count may be adjusted by varying at least one parameter which characterizes the modulation of power associated to the discharge of the stored energy.

Claim 18

The device of claim 1 further comprising second energy storage means coupled across said output means for storing energy transferred thereto by said transfer means to maintain said output means in the active state for a second time period greater than said first delay period whereby said output means will be returned to its quiescent state when said predetermined input condition persists for a time interval greater than said second time period thereby providing a device which generates an output in cases where a cyclically variable input signal deviates from its normal waveslope.