Timed switching circuit

• US 3,988,727 A
• Filed: 06/24/1974
• Issued: 10/26/1976
• Est. Priority Date: 06/24/1974
• Status: Expired due to Term

• Current Assignee: Emerson Electric Company
• Original Assignee: P R Mallory & Company Incorporated (Tupperware Brands Corporation)
• Inventors: Scott, Charles E.
• Primary Examiner(s): Pitts, Harold I.
• Application Number:
  US05/482,650
• Time in Patent Office: 855 Days
• Field of Search: 307/141, 307/141.4, 307/252 F, 307/293, 340/309.1
• US Class Current: 340/309.8
• CPC Class Codes: H03K 17/292 in thyristor, unijunction transistor or programmable unijunction transistor switches
• CPC Class Codes: H05B 6/666 Safety circuits emergency protective circuits in general H02H

Abstract

A timed switching circuit includes timer means for timing an event, timer means for timing the length of an alarm signal, and timer means for timing delays prior to and immediately after an event is timed. The circuit also includes an appliance control/indicator means for controlling an appliance in response to a timed event and indicating the operational state thereof.

Claims

1. A timed switching circuit for controlling the operation of an appliance comprising in combination:

a. means connecting said timed switching circuit to an alternating current power supply;

b. an alarm timer means providing an audible alarm at predetermined time intervals;

c. a function timer means connected to said alarm timer means for providing an operational sequence at predetermined time intervals;

d. a power supply means connected between first and second sides of said timed switching circuit;

e. an on-delay timing means connected to said power supply means for producing a predetermined time delay before power is applied to said appliance from said alternating current power supply;

f. power-turn on means connected to said on-delay timing means for turning power on from said power supply means;

g. an off-delay timing means connected to said function timer means producing a time delay after power is disconnected through said power turn-on means;

h. a power turn-off means connected to said off-delay timing means for maintaining power during said time delay and subsequently turning off power from said power supply means;

e. snubber means connected to said power turn-on means to prevent same from turning on momentarily at the beginning of a timing cycle; and

j. an appliance control/indicator means connected to said appliance for controlling a function and indicating a state of operation of same.

2. The combination as recited in claim 1, wherein said alarm timer means includes:

a. an audible alarm;

b. a first timing means connected to said audible alarm;

c. alarm turn-on means connected to said timing means; and

d. a relay/alarm switching means for switching power to said audible alarm and to said first timing means.

3. The combination as recited in claim 2 wherein said audible alarm comprises an electromechanical buzzer, said alarm turn-on means comprises a silicon-controlled rectifier, said relay/alarm switching means comprises a multi-pole push button switch, and said first timing means comprises:

a. one side of a first capacitor connected to a first side of said timed switching circuit;

b. a first resistor connected between another side of said first capacitor and a cathode of a first diode;

c. a second resistor connected between the junction of said first resistor and said first capacitor and a gate of said silicon-controlled rectifier; and

d. a third resistor connected between said gate and said first side of said timed switching circuit.

4. The combination as recited in claim 1 wherein said function timer includes:

a. an electrical switching means;

b. a low-current power supply connected to said electrical switching means;

c. a switch reset means for periodically resetting said electrical switching means; and

d. a second timing means connected between said electrical switching means and said switch reset means.

5. The combination is recited in claim 4 wherein:

a. said electrical switching means includes a gang of single-pole double-throw switches in combination with a chain of resistors, said resistors capable of being connected via patch cords to said gang of single-pole double-throw switches;

b. said low current power supply comprises a series combination of a fourth resistor, a second diode, and a second capacitor;

c. said switch reset means includes a solenoid connected between an anode of a second silicon-controlled rectifier and a first side of said timed switching circuit, said anode also being connected to said low current power supply, and a cathode of said silicon-controlled rectifier connected to said second timing means; and

d. said second timing means comprises;

i. a programmable unijunction transistor, a gate of which is connected to a variable resistor, an anode of which is connected through a fifth resistor to a junction between a sixth resistor and a third capacitor, and a cathode of which is connected to a gate of said second silicon-controlled rectifier and also through a seventh resistor to said third capacitor.

ii. another side of said sixth resistor connected to said electrical switching means;

iii. a third diode, an anode of which is connected to said low current power supply, and a cathode of which is connected through an eighth resistor to said variable resistor; and

iv. a ninth resistor connected between said variable resistor and said third capacitor.

6. The combination as recited in claim 1 wherein:

a. said power supply means includes a series combination of a fourth diode, a tenth resistor and a fourth capacitor, an anode of said diode connected to a first side of said circuit and said capacitor connected to said on-delay timing means;

b. said on-delay timing means includes;

i. a second programmable unijunction transistor, an anode of which is connected through an eleventh resistor to said power supply means, a gate of which is connected through a twelfth resistor and a fifth capacitor to said power supply means, and a cathode of which is connected through a thirteenth resistor to a second side of said timed switching circuit,

ii. a fourteenth resistor connected between said anode of said second programmable unijunction transistor and said second side of said timed switching circuit, and

iii. a fifteenth resistor connected between the junction of said twelfth resistor and said fifth capacitor and said second side of said timed switching circuit.

c. said power turn-on means includes;

a triac, a first anode of which is connected to said second side of said timed switching circuit, a second anode of which is connected to said appliance control/indicating means, and a gate of which is connected through a fifth diode to said on-delay timing means;

d. said off-delay timing means includes;

i. a third programmable unijunction transistor, an anode of which is connected to a junction of sixteenth and seventeenth resistors, a gate of which is connected through an eighteenth resistor to a junction between a sixth capacitor and a nineteenth resistor, and a cathode of which is connected through a twentieth resistor to said power turn-off means,

ii. said sixteenth resistor and said sixth capacitor connected to said function timer means, and

iii. said seventeenth and nineteenth resistors connected to said second side of said timed switching circuit; and

e. said power turn-off means includes;

i. a triac, a first anode of which is connected to a second side of said timed switching circuit, a second anode of which is connected to said appliance control/indicator means, and a gate of which is connected to a cathode of a sixth diode and a twenty-first resistor,

ii. said twenty-first resistor connected to said second side of said timed switching circuit,

iii. an anode of said sixth diode connected through a twenty-second resistor to said power supply means, and

iv. a transistor, a collector of which is connected through a seventh diode to said twenty-second resistor, an emitter of which is connected to said second side of said timer switching circuit, and a base of which is connected to said twentieth resistor.

7. The combination as recited in claim 1 wherein said snubber means comprises a series combination of a twenty-third resistor and a seventh capacitor connected between said power turn-on means and to a second side of said timed switching circuit.

8. The combination as recited in claim 1 wherein said appliance control/indicator means includes:

a. a power switch connected to said alternating current power supply, for switching power to an appliance;

b. a power relay connected to said alternating current power supply for activating said power switch;

c. a ready indicator connected to said power switch for visually indicating that power is applied to said timed switching circuit;

d. an operation relay connected to said alarm timer means;

e. an operation indicator for visually indicating power being applied to said function timer means; and

f. a safety switch connected between said delay timer means and said function timer means for shutting off power to said function timer means.