Abstract: An automatic aspirator-transfer valve is disclosed which controls the delivery of washing and rinsing fluid from a supply to a cleaning gun. The device includes a valving piston which moves between a first or rinsing position to open communications to the bypass conduits and a second or washing position to close the bypass conduit. The injector aspirates washing fluid from a reservoir through a non-return valve, a side inlet and conduit of the side inlet, the side inlet conduit being separated from a passage within the housing bore. By this novel aspect, a user may change from the washing mode to the rinsing mode without the aspiration of dangerously high concentrations of washing agent and without unnecessary waste of the washing agent during operation.

Abstract: In high-pressure cleaning units with heating stages, i.e. with a possibility for circulating a partial flow of the forwardly pumped water through a constricted, heat-generating nozzle (74) in a return conduit to the pump's inlet side, the problem occurs that the entire water flow circulates at high pump pressure upon temporary interruption of ejection, which causes an inexpediently high heating of the water. By the invention, apparatus is provided for sensing this situation and thus block the return conduit (70,72), so that the pressure tends to rise; in this way, however, the cleaning unit's ordinary bypass valve (12) will sense that delivery from the pump (P) is totally blocked, whereby it connects the pump in bypass state in the ordinary way through a non-constricted bypass connection (14). In this way, ejection can be interrupted temporarily without any substantial heat accumulation in the circulating water, and another advantage is that the ejection conduit itself is pressure relieved in the situation.

Abstract: In operating high-pressure cleaning units, the outflow of the water discharged from the associated pump (6,8) may be temporarily interrupted. As the pump normally operates continuously, care must be taken to ensure that the water can then be returned in a bypass to the pump's suction side. This can be achieved by a bypass valve sensing a rising pressure in the said closing situation, thus opening for the bypass. Correspondingly, the bypass valve (36,44,32) senses a declining pressure when the discharge or ejection is resumed, thus causing a block to the bypass (40). However, a corresponding, declining pressure occurs when the pump is stopped, for which reason the bypass valve will block the bypass also in this condition. Thus, the result is that during the stopping process determined by the pump's inertia a substantial and dangerous pressure may build up in the discharge conduit (26) from the pump.