Fluid handling – Systems – Supply and exhaust
Patent
1999-03-12
2000-08-22
Michalsky, Gerald A.
Fluid handling
Systems
Supply and exhaust
91452, F15B 1304
Patent
active
061056138
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a distributor for a hydraulic hoist which is controllable with regard to position and applied force, for tractors and agricultural machines. In particular, this distributor is to be used to regulate and control the movement of a three-point coupling which is mounted on the tractor or agricultural machine and to which an implement for working or preparing the ground is connected.
Various types of hoist for three-point couplings and various types of distributor which are to control the movement thereof are known. One of those known distributors is described, for example, in Italian patent application MO91A000137 belonging to the same applicant. Basically, distributor of the known type comprises a substantially cylindrical and compact body in which various valve elements are arranged, the most important of which is a slide valve of which the slider is operated by the hoist levers and which permits modulation of a specific rate of flow of pressurised fluid to an actuator cylinder or, alternatively, discharge from that actuator cylinder of a specific amount of fluid. Hoists are normally connected to the pressurised oil distribution system which is already arranged on the agricultural machine for other equipment.
Oil distribution systems normally comprise positive-displacement pumps which, in most tractors, are of the fixed displacement type because they are far less expensive than the variable displacement type. It often happens that the oil flow necessary for the ancillary equipment of the tractor is very high; in that case, above all in the presence of fixed displacement positive-displacement pumps and of medium-low displacements of the hoist cylinders, distributors of the known type may exhibit an oscillatory behaviour owing to an instability caused by the system's excessive rate of response. In addition, the distributor is subject to pressure peaks which may prove to be detrimental both to the strength and to the precision of the system.
In order to solve the above problems the known solutions necessarily involve a substantial increase in the dimensions of the distributor or a complication of the system with the addition of separate valves in positions to which access is difficult.
SUMMARY OF THE INVENTION
The aim of the present invention is to overcome the disadvantages mentioned above by means of an improved distributor which is simple and economical to produce, is simple to install and has a compact configuration and which permits very accurate regulation of the applied force and position. In fact, with the present invention it is possible to obtain, in controlled position operation, more than 150 different positions of the hoist arms.
In order to achieve the aims indicated above, the invention discloses a new and improved distributor for a hydraulic hoist which is controllable with regard to position and applied force, for tractors and agricultural machines, comprising a compact body having at least one inlet duct for a pressurised fluid, at least one discharge duct and at least one duct for connection to a hydraulic cylinder for lifting hoist arms, there being arranged in the body valve means for modulating the flow of pressurised fluid, a slider being movable inside the body in two opposite directions with respect to a neutral position and a valve unit for discharging the fluid coming from the hydraulic cylinder, wherein the slider controls the modulating valve means hydraulically with interposition of consent valve means.
The distributor produced in accordance with the present invention is readily installed in the hoist owing to its small space requirement. In addition, the distributor comprises a complete hydraulic circuit for controlling both the flow and the pressure conveyed to an actuator cylinder.
A further advantage of the invention resides in the fact that the distributor controls the movement of the hoist arms and consequently of the three-point coupling, and thus of the agricultural implement connected thereto, in order to ens
REFERENCES:
patent: 4176685 (1979-12-01), Hoefer et al.
patent: 4246832 (1981-01-01), Hofer et al.
Michalsky Gerald A.
Mita Oleodinamica S.p.A.
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