Abstract: A pressure washer for use by an operator. A heat exchanger has a water input adapted to connect to a water source and has a water output providing discharge water. A water pump supples water to the heat. A temperature selector is responsive to operator. A burner in thermodynamic communication with the heat exchanger applies heat to the heat exchanger and the water in the heat exchanger. The burner has a fuel input connecting a fuel source to the burner. A fuel switch selectively allows fuel from the fuel source to be supplied to the combustion chamber via the fuel input. A duty cycle timer has a uniform duty cycle and is energized when water flows through the heat exchanger. The duty cycle timer is responsive to the temperature selection switch to vary its duty cycle as a function of the operator input provided to the temperature selector.

Abstract: A chemical injector valve connected to a source of water under pressure harnesses the venturi effect to entrain liquid chemicals into a water stream and employs a variable size pressure chamber to ensure that the flow rate and quantity of chemicals entrained remains constant even when the pressure of water entering the valve varies widely. An increase in incoming water pressure causes expansion of the variable size pressure chamber and a decrease in incoming water pressure causes contraction of the variable size pressure chamber. A slidably mounted piston is biased toward the variable size pressure chamber so that the size of the pressure chamber does not increase unless the accumulation of water in the chamber exceeds the bias acting on the piston. When the bias is exceeded, a shank of the piston moves toward a piston stop and the flow of water into the valve is throttled.