Kärcher’s first portable pressure washer for private households was developed in 1984.
The heart of every machine is the pump/motor unit. The method of operation is described below:
The motor drives the shaft and causes the swashplate to rotate. Three pistons are attached to the swashplate at 120° intervals. The pistons travel forwards and backwards one after another on each revolution of the angled swashplate. Each piston has an intake valve and a delivery valve. All moving parts are lubricated with oil. The oil-filled side of the pump is separated from the water side of the pump by seals.
How does water flow through the unit? Each piston is pushed against the swashplate by a spring. When the piston moves in the direction of the motor, a vacuum is created – the intake valve opens. Water flows in through the garden hose and is filtered. The intake valve closes as soon as the swashplate moves the piston back in the direction of the pump head. The delivery valve opens at the same time and the intake water leaves the pump head outlet, which is connected to the high pressure hose. A pressure of about 20 to 150 bar (household units) is produced at the spray lance’s high pressure nozzle. The rapid movements of the three pistons practically eliminate pulsations in the line.
If required, detergent can be picked up in the low pressure mode via a valve. It is mixed with water at the injector before it leaves the pump head. Anyone who has used a pressure washer knows that it switches off automatically as soon as the trigger is released. This reduces the noise level, saves electricity and prolongs the machine’s useful life. The method of operation is simple: If water flow is blocked in the trigger gun and hose, pressure increases in the pump head. This causes the control piston to move and interrupt an electric contact in the pressure switch – the motor is switched off. When the trigger gun is operated again, water is expelled and the pressure drops. The spring of the control piston returns to its idle position, causing the electrical circuit to be closed and the motor to restart.