# US 4,395,621 A · Timing control apparatus and circuit

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- Number: US 4,395,621 A
- Document ID: US4395621A
- Status: Granted
- Kind: A
- Application number: 06/127,334
- Filed: 1980-04-10
- Granted: 1983-07-26
- Earliest claimed: 1980-04-10
- Inventors: Randall W. Parker
- Web page: https://patentgrep.com/patent/US4395621A

## CPC

- G05D 23/1951: {with control of the working time of a temperature controlling device}
- A47J 37/0842: {with electronic timers}
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- A47J: KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES

## Abstract

A timing control apparatus and circuit for use in a toaster or other device, such as an oven, includes electronic solid-state circuitry including a thermistor operating in conjunction with a metal oxide semiconducter (CMOS) wherein when the predetermined voltage or heat buildup is attained, a condenser is charged to positive to activate the timing circuit, which, in turn, activates a SCR, shorting a full wave bridge to deactivate the heating elements and close a normally open solenoid, which unlocks a mechanical latch and permits the toast to be ejected. The device employs low operating current, expends no energy except at the moment of triggering the solenoid and is capable of being used as original equipment or to retrofit existing units.

## Claims

### Claim 1

An electric toaster comprising:
(A) a frame;
(B) at least one spring loaded rack for reception of bread to be toasted and being movable from an unloaded position to a loaded position against the force of a spring;
(C) a solid state control mounted on said frame and including
(1) means for mechanically engaging said rack and holding said rack in loaded position including a normally inert AC solenoid with a spring loaded plunger normally urged to an extended position and movable to a retracted position upon activation of said timing means,
(2) sensing and heat compensating means disposed on said frame,
(3) timing means connected to said sensing and heat compensating means and adapted to release said means for mechanically holding said rack in loaded position upon attainment of a predetermined heat build up, and
(4) trigger circuit means carried by said solid state control for recycling said timing means in response to failure of said means for holding said rack in loaded position.

### Claim 2 (depends on 1)

The toaster of claim 1 wherein said timing means includes an integrated circuit incorporating a metal oxide semiconductor element.

### Claim 3 (depends on 1)

The toaster of claim 1 wherein said sensing means is a thermistor.

### Claim 4 (depends on 1)

The toaster of claim 1 wherein said toaster includes heating elements, and switches disposed on said frame for activation of said heating elements upon movement of said rack from unloaded to loaded position and deactivation of said heating elements upon activation of said means for mechanically engaging said rack and movement of said rack from loaded to unloaded position.

### Claim 5 (depends on 1)

The toaster of claim 1 wherein a variable resistor is connected to said timing means for varying the predetermined heat build up.

### Claim 6 (depends on 1)

The toaster of claim 1 wherein said timing means include a single variable resistor and a single capacitor.