Detergent supply control for automatic dishwasher

In combination:

• a motor-driven circulating pump for recirculating a liquid solution;
• a motor-driven supply pump for supplying a substance to said solution which changes the electrical conductivity thereof;
• first control means for operating said circulating pump for a first predetermined interval of time;
• and second control means for operating said supply pump during (within) said predetermined interval of time and comprising a timer and a conductivity sensor,
• said timer being operable to enable said conductivity sensor to effect operation of said timer and said supply pump in response to a low conductivity level, said timer being further operable to prevent said conductivity sensor from effecting operation of said timer and said supply pump in response to a low conductivity level after said timer has operated for a second predetermined interval of time which is less than said first predetermined interval of time.

Apparatus including:

• a motor-driven circulating pump operable for recirculating a liquid solution;
• electrically operated supply means operable for adding a substance to said solution which changes the electrical conductivity level thereof;
• and a control system, including control means for operating said circulating pump for a time cycle of predetermined length, and supply control means operable during said time cycle and responsive to the conductivity level of said solution for operating said supply means as required during said time cycle to supply a desired amount of said substance to said solution;
• said supply control means including a warning device, a conductivity sensor and an automatic timer operable for a time interval less than the time of said cycle, but long enough to ensure that a sufficient amount of said substance can normally be supplied during said time interval to last for said time cycle, said timer operating in response to a low conductivity level existing at the end of the said time interval to deactivate said supply means and to actuate said warning device.

Apparatus including:

• a motor-driven circulating pump operable for recirculating a liquid solution;
• a motor-driven supply pump operable for adding a substance to said solution which changes the electrical conductivity level thereof;
• and a control system, including circulating pump control means for operating said circulating pump for a time cycle of predetermined length, and supply pump control means responsive to the conductivity level of said solution for operating said supply pump as required during said time cycle to supply a desired amount of said substance to said solution;
• said supply pump control means including a warning device, a conductivity sensor means, and an automatic timer operable for a time interval less than the time of said cycle, but long enough to ensure that a sufficient amount of said substance can normally be supplied during said time interval to last for said time cycle, said timer operating in response to a low conductivity level existing at the end of said time interval to deactivate said supply pump and to actuate said warning device.

In a washing machine:

• a motor-driven circulating pump for recirculating a washing solution;
• a motor-driven supply pump for adding detergent to said solution which changes the electrical conductivity level thereof;
• and a control system, including wash control means for operating said circulating pump for a wash cycle of predetermined length, and supply pump control means responsive to the conductivity level of said solution for operating said supply pump as required during said wash cycle to maintain a desired amount of detergent in said solution;
• said supply pump control means including a warning device, a conductivity sensor, and an adjustable automatic timer operable for a time interval less than the time of said wash cycle, but long enough to ensure that a sufficient amount of detergent can normally be supplied during said time interval to last for said wash cycle, said timer operating in response to a low conductivity level existing at the end of the said time interval and indicative of a loss of detergent supply to turn off said supply pump and actuate said warning device.