The oil filter and the the filter comprehensive hydraulic system for tractors.

摘要

In a high pressure oil filter having a replaceable element and a differential pressure relief valve which passes unfiltered oil directly from the inlet to the outlet of the filter when the element becomes blocked, damage can be caused to a precision mechanism consequently supplied with contaminated oil if the blocked element is not replaced promptly. To prevent damage and compel replacement of the element, the relief valve (16) is modified so that, when the element (12) becomes blocked, unfiltered oil passes to a secondary filter outlet (22) which bypasses the precision mechanism (35, 36) and thus renders it inoperative until the element (12) is replaced. When used in an agricultural tractor, oil normally supplied to the power lift mechanism (36) and thence for transmission lubrification (37) by-passes the power lift and passes directly to the transmission when the element (12) becomed blocked. Failure of the power lift (36) to operate obliges the driver to replace the element (12) before work can recommence.