Patent ID: 7284807

Claim:
A method for detecting a quantity of waste liquid which is not used in a predetermined operation when a predetermined type of liquid is supplied from a liquid container to an operation unit performing the predetermined operation and is consumed, the method comprising the steps of: accumulating liquid consumption for a period from the start of using the liquid container up to the present to obtain total consumption (T), wherein the total consumption (T) of the liquid is calculated according to the formula T=V ( N+ 1)− R where V is the capacity of the liquid container, N is the number of times of refilling or replacing the liquid container, and R is the quantity of the liquid remaining in the current liquid container, the quantity being detected by a liquid remaining-quantity detector provided in the liquid container; accumulating liquid quantity used for the operation by the operation unit for the period to obtain total use (P); subtracting the total use (P) from the total consumption (T); and obtaining quantity (D) of the waste liquid by regarding the subtraction result (T-P) as the quantity (D) of the waste liquid.