Alarm apparatus for a freezer

• US 4,855,721 A
• Filed: 11/24/1987
• Issued: 08/08/1989
• Est. Priority Date: 11/24/1987
• Status: Expired due to Fees

• Current Assignee: Edward Ketelaar Jr, Robert Hallett
• Original Assignee: Edward Ketelaar Jr, Robert Hallett
• Inventors: Hallett, Robert, Ketelaar, Edward Jr.
• Primary Examiner(s): Swann III, Glen R.
• Application Number:
  US07/124,641
• Time in Patent Office: 623 Days
• Field of Search: 340/585, 340/693, 340/661, 340/384 E
• US Class Current: 340/585
• CPC Class Codes: F25D 2700/122 of freezer compartments
• CPC Class Codes: F25D 29/008 Alarm devices

Abstract

An alarm apparatus is provided for a freezer having a body and a closure member. The alarm apparatus has an electrical control unit having a power supply input. An alarm device and a temperature sensor are connected to the control unit. The temperature sensor is adapted for mounting in the freezer, for detecting temperatures exceeding a pre-set temperature. A flexible lead is provided for connecting at least two of the control unit, the alarm device and the temperature sensor together. The lead has a cross-section enabling it to extend between the lid and the body of a freezer, while permitting closure thereof. The alarm apparatus can include a second lead connecting the alarm device to the control unit, to enable the alarm device to be placed at a location remote from the freezer.

Claims

1. An alarm apparatus, for a freezer having a body and a closure member, the alarm apparatus comprising:

(a) an electrical control unit having a housing and located outside the freezer and including a power supply input;

(b) an alarm device remote from and connected to the control unit by a first flexible lead;

(c) a temperature sensor connected to the control unit, which temperature sensor is adapted for mounting in the freezer, for detecting temperatures exceeding a pre-set temperature; and

(d) a second flexible lead connecting the control unit to the temperature sensor, the second lead having a cross-section enabling the lead to extend between the body and the closure member of the freezer whilst permitting closure thereof; and

wherein said control unit includes;

(i) positive and negative lines connected to the power supply input, an operational amplifier connected between the positive and negative lines, which operational amplifier includes a sensor input connected to the temperature sensor, a reference input connected to a reference voltage source, and an output; and

wherein the control unit includes a first resistor and a light emitting diode connected in series between the positive and negative lines, to provide an indication that the control unit is operative;

(ii) a second resistor and a detector input for the temperature sensor, connected in series between the positive and negative lines, with the sensor input of the operational amplifier connected to a junction between the first resistor and the detector input;

(iii) a third resistor, a variable resistor and a fourth resistor connected in series between the positive and negative lines, a zener diode, which is connected between the third resistor and the negative line parallel to the variable resistor and the fourth resistor, with the reference voltage input of the operational amplifier being connected to the variable resistor; and

(iv) fifth and sixth resistors connected in series between an output of the operational amplifier and the negative line, a base of an output transistor being connected to a junction between the fifth and sixth resistors, the emitter of the output transistor being connected to the negative line, and a control unit output being connected between the positive line and the collector of the transistor, for connection to the alarm device; and

(v) an integrated circuit timer connected to the positive line and the collector of the transistor, and wherein the control unit output includes a common terminal connected to the collector of the transistor, a continuous output terminal connected to the positive line and an intermittent output terminal connected to the integrated circuit timer.

2. An alarm apparatus as claimed in claim 1 wherein the control unit includes a light emitting diode and a seventh resistor connected in series across the control unit output, with the light emitting diode being mounted in an aperture of the housing to provide a visual alarm.

3. An alarm apparatus as claimed in claim 1 wherein the control unit includes a first light emitting diode and a corresponding resistor connected in series between the positive and negative lines, and a second light emitting diode and a corresponding resistor connected in series across the control unit output, with the first and second light emitting diodes being mounted in apertures in the housing.