GB1396778A - Fluid supply systems - Google Patents

Abstract

1396778 Hydraulic circuits A F HYDRAULICS Ltd 28 March 1973 [28 March 1972] 14583/72 Heading F1P In a hydraulic circuit e.g. for a road drill, a quick warm-up of the hydraulic fluid is ensured by a pressure relief valve 19, Fig.1, which, when the fluid is cold and viscous and therefore under higher than normal pressure, by-passes fluid to a small chamber 14 within the main reservoir 15. Thus, only a small volume of fluid is initially warmed up. At the desired operating temperature a thermostatically controlled by-pass valve 23 in a return line 13 closes, so that fluid is diverted through a cooler 21 adjacent a thermostatically controlled fan 22. From the cooler fluid returns to the larger reservoir. Fig.2 (not shown), illustrates a similar circuit in which a thermostatic element in the small reservoir 14 controls the valve 23. In Fig.3, a restrictor 27 controlled by a thermostatic element 26 restricts fluid-flow increasingly as the temperature decreases. Fig.4, shows an arrangement in which a spring-loaded shuttle-valve 28 with two loads controls both by-pass circuits according to the viscosity of the fluid.