Pressurized fluid supply circuit comprising a variable displacement pump

A pressurized fluid supply circuit of the type supplying at least one consuming part, comprising:

• (a) at least one consuming part;
• (b) at least one variable displacement pump, each said variable displacement pump being equipped with a delivery pipe and being coupled to a driving shaft;
• (c) means for adjusting the volume of said variable displacement pump;
• (d) as many main distributors of pressurized fluid as there are said at least one consuming part, each of said main distributors being operationally coupled with a corresponding said consuming part and interposed between said consuming part and said delivery pipe with which said variable displacement pump is equipped;
• (e) as many hydraulic manipulators as there are said main distributors, said hydraulic manipulators being manually actuated and of a potentiometric type, each said manipulator being operationally coupled with one of said main distributors and being interposed between said one of said main distributors and said source of control fluid;
• and
• (f) tachometric device means for delivering a control pressure whose valve is a function of the speed driving said at least one variable displacement pump, said tachometric device means including a source of control fluid to control each said main distributor comprising a tachometric pump having a delivery circuit, said tachometric pump being coupled to said same driving shaft as said at least one variable displacement pump and being equipped with a delivery pipe on which is mounted a calibrated discharge valve, at least two pressure-using circuits corresponding to said main distributors, a restriction situated on said delivery circuit of said tachometric pump between said tachometric pump and said calibrated discharge valve, and a pressure modulation distributor having first and second positions connected via a supply pipe to the part of said delivery pipe of said tachometric pump which is situated between said restriction and said calibrated discharge valve via said control pipe connected to each said manipulator and via a discharge pipe to a pressure-free exhaust, each said manipulator being connected in parallel to said control pipe, said pressure modulation distributor being coupled to two fluid jacks of mutually antagonistic effect, connected to those parts of said delivery pipe of said tachometric pump which are situated, for one of said jacks, between said pump and said restriction, and for the other of said jacks, between said restriction and said calibrated discharge valve, said first position of said pressure modulation distributor corresponding to creating a communication between said supply and control pipes, and said second position of said pressure modulating distributor corresponding to creating a communication between said control and discharge pipes, the active portions of said two jacks and said restriction having selected values, such that said pressure modulation distributor is placed in said first position when the driving speed of said tachometric pump is equal to a preset nominal speed, and in said second position, when the driving speed of said tachometric pump is below the nominal speed.