A HYDRAULIC OPERATING SYSTEM FOR TRACTORS

Abstract: A hydraulic operating system for tractors includes two separate hydraulic circuits (1, 2) with respective separate reservoirs (3, 7), of which the first includes a pump (4) for supplying the lubricating circuit of the gearbox (6) and the power take-off (5) of the tractor and the second includes two pumps (8, 9) in parallel, of which the first supplies the hydraulic steering system (10) and the lifting system (12) and the second supplies the auxiliary hydraulic devices (11) of the tractor. The second circuit further includes means (13, 14) for selectively boosting the supply from the two pumps (8, 9) to the auxiliary hydraulic devices (11) or the lifting system (12).

Description: The present invention provides a new hydraulic operating system for tractors of the type including a gearbox with a lubricating circuit, a hydraulic steering system, a power take _ off, a hydraulically-operated controlled lifting system, and auxiliary hydraulic devices. The hydraulic system according to the invention is characterised by the features of the characterizing part of claim 1. The hydraulic system according to the invention has the following advantages over conventional hydraulic systems with a single circuit currently installed in tractors: less power absorbed by the engine, less power dissipated, longer life/better reliability of the components (due to the possibility of better filtration of the hydraulic fluid resulting from the division of the circuit into two separate parts), greater flexibility in use, the lifting system and the auxiliary hydraulic devices being operable simultaneously at two power levels, low gearbox oil level. The invention will now be described in detail with reference to the appended drawing which shows diagrammatically a hydraulic operating system for tractors according to the invention. With reference to the drawing, the hydraulic operating system according to the invention includes two separate and distinct hydraulic circuits, indicated 1 and 2 respectively. The first circuit 1 includes an oil reservoir 3 (the casing of the tractor gearbox) and a hydraulic pump 4 which operates the power take-off 5 of the tractor, supplies the lubricating circuit 6 of the tractor gearbox, and operates any other locking and clutch devices. The second hydraulic circuit 2 includes a reservoir 7 and a pair of hydraulic pumps 8, 9 disposed in parallel, of which the first supplies the hydraulic steering system 10 and the controlled lifting system 12 of the tractor and the second supplies the distributors of the auxiliary hydraulic devices 11. The circuit 2 further includes a solenoid valve 13 for connecting the output of the hydraulic steering system 10 selectively to the input of the auxiliary distributors 11, and a piloted valve 14 which enables the output of the auxiliary distributors 11 to be connected selectively to the lifting system 12. In practice, the solenoid valve 13 and the piloted valve 14 enable the selective boosting of the supply from the pump 8 and the pump 9 respectively to the auxiliary distributors 11 or to the lifting system 12. The adoption of the two separate circuits 1 and 2 enables the power absorbed by the engine of the tractor and the power dissipated, as well as the level of the oil in the tractor gearbox, to be reduced and at the same time ensures that the various hydraulic components have a longer working life by virtue of the possibility of more effective filtration of the hydraulic fluid which is divided between the two separate circuits. The conformation of the circuit 2, particularly the adoption of the two pumps 8 and 9, the solenoid valve 13 and the piloted valve 14, ensures that the auxiliary devices 11 and the lifting system 12 operate simultaneously, as well as providing greater flexibility in use by virtue of the possibility of operation at selectively different power levels.

Claims: 1. A hydraulic operating system for tractors including a gearbox with a lubricating circuit, a hydraulic steering system, a power take-off, a hydraulically-operated controlled lifting system, and auxiliary hydraulic devices, characterised in that it includes two separate hydraulic circuits (1, 2) with respective separate reservoirs (3, 7), of which the first circuit (1) includes a pump (4) for supplying the lubricating circuit of the gearbox (6) and the power take-off (5) and the second circuit (2) includes two pumps (8, 9) in parallel, of which the first (8) simultaneously supplies the hydraulic steering system (10) and the lifting system (12) and the second (9) supplies the auxiliary hydraulic devices (11); the second circuit (2) further including means (13, 14) for selectively boosting the supply to the auxiliary hydraulic devices (11) or the lifting system (12) from the first pump (8) and the second pump (9) respectively.

Inventors: BISLERI, SECONDO
Applicants: SAME S.P.A.
Application year: 1988
Main classification: B60R16
IPC codes: B60R16, B62D5