MULTI-PURPOSE SENSOR ASSEMBLY FOR AUTOMATIC WASHER

• US 3,707,857 A
• Filed: 09/20/1971
• Issued: 01/02/1973
• Est. Priority Date: 09/20/1971
• Status: Expired due to Term

• Current Assignee: Robert T. Wigfall
• Original Assignee: Robert T. Wigfall
• Inventors: Wigfall, Robert T.
• Primary Examiner(s): Price, William I.
• Application Number:
  US05/181,891
• Time in Patent Office: 470 Days
• Field of Search: 68/12R,12F
• US Class Current: 68/12.27
• CPC Class Codes: D06F 2103/16 Washing liquid temperature
• CPC Class Codes: D06F 2103/44 Current or voltage
• CPC Class Codes: D06F 2105/10 Temperature of washing liquids; Heating means therefor
• CPC Class Codes: D06F 2105/28 Electric heating
• CPC Class Codes: D06F 34/24 Liquid temperature

Abstract

A sensing system for a laundry appliance includes a pair of temperature responsive devices, heating means, and a thermally conductive disk which places one of the temperature responsive devices in good heat-flow relationship with the heating means and the washing fluid. The sensing system includes associated switching and biasing circuitry which enables the system to be used to sense a variety of machine functions.

Claims

1. In an automatic washer having a clothes receiving chamber and indexable control means for sequencing the washer through a wash cycle, a sensing system comprising a first temperature responsive device, heating means, means placing said temperature responsive device and said heating means in good heat flow relationship with each other and with washing fluid in said washing chamber, a second temperature responsive device electrically connected in series with said first temperature responsive device, and switching means for selectively altering the energization of said heating means and the bias applied to said temperature responsive devices.

2. The sensing system of claim 1 further including circuit means for receiving the signal developed at the junction of said first and second temperature responsive devices and providing an indexing signal for said indexable control means in response to a predetermined received signal.

3. The sensing system of claim 2 wherein said circuit means comprises an amplifier circuit connected to said junction and a trigger circuit connected to said amplifier circuit for producing a step-like voltage change in response to a predetermined signal level at said junction.

4. The sensing system of claim 1 wherein said first and second temperature responsive devices are serially connected between first and second terminals of a power supply respectively, and wherein said switching means includes a first switch connecting said second temperature responsive device to said second power supply terminal, a second switch connected to the junction of said temperature responsive devices and operable to connect a resistance from said junction to said second power supply terminal, and a third switch connected in series with said heating means for controlling the power supplied thereto.

5. The sensing system of claim 4 wherein said heating means receives power from the 117 volt AC power line.

6. The sensing system of claim 5 wherein said heating means comprises a power resistor and said first and second temperature responsive devices comprise negative temperature coefficient thermistors.

7. The sensing system of claim 1 wherein said means for placing said temperature responsive device and said heating means in good heat flow relationship comprises a plate-like member, and said first temperature responsive device and said heating means are affixed to a first surface thereof.

8. The sensing system of claim 7 wherein said plate-like member comprises a ceramic disk located adjacent said clothes receiving chamber such that a second surface of said disk contacts washing fluid During selected portions of a wash cycle.