Device for controlling the lye pumping-off operation in washing machines

The feed capacity of the lye pump must correspond to the quantity of waste water occurring during spinning. In appliances which are on the market, the lye pump is activated at intervals via a program-switching unit. The "on" and "off" times of the pump do not run in synchronism with the quantity of waste water thrown out, so that the pump running empty sucks in air or does not discharge the lye immediately. In the device according to the invention, the lye-pump feed capacity is matched exactly to the quantity of waste water which occurs. A pressure regulator (8) activating the lye pump (5) is arranged at the lowest point of a tub (1) via a branch line (7). The pressure regulator (8) ensures that a minimum head of water (h) is always present above the lye pump (5). When this is exceeded, the pressure regulator (8) switches on the lye pump (5) and, when it is reached or below it, switches it off again. By means of the program-switching unit, the activation of the lye pump takes place only during the spin mode. The device is suitable for installation in domestic washing machines.