Hydraulic directional control valve combining pressure compensation and maximum pressure selection for controlling a feed pump, and multiple hydraulic control apparatus including a plurality of such valves

A pressure compensating hydraulic directional control valve comprising:

• a valve body;
• a slide received in the body to be capable of being displaced longitudinally therein for selectively transmitting a pressurized hydraulic fluid to working orifices provided in the body from an orifice for admitting pressurized hydraulic fluid;
• a passage in said body for connecting a distribution chamber to the working orifices, the distribution chamber being associated with the slide and being suitable for being connected selectively to the admission orifice by the displaced slide;
• a load sensing line channel combined with maximum pressure selecting means organized to establish in said channel the maximum pressure selected from the pressure existing in said channel and the pressure of the pressurized fluid of the valve;
• and
• pressure compensating means placed in said passage and responsive to the difference between the pressure of the fluid in the valve and the pressure existing in said channel in order to generate a substantially fixed pressure drop in the pressurized fluid flowing towards the working orifices;
• wherein, in the valve, the pressure compensating means are combined with the maximum pressure selecting means;
• and selective link means exist that are suitable for selectively establishing a link between the channel and the passage upstream from the pressure compensating means in such a manner that:
• if the pressure in the channel is greater than or equal to the pressure of the fluid in the passage upstream from the pressure compensating means, no communication exists between said passage and said channel, and the pressure in the channel retains its value;
• or else
• if the pressure in the channel is less than the pressure of the fluid in the passage upstream from the pressure compensating means, communication is established between said passage upstream from the pressure compensating means and said channel, and the pressure in the channel becomes the same as the pressure of the fluid present in the passage upstream from the pressure compensating means.