Hydraulic actuating system for a pair of concurrently operating clutches or brakes

In a fluid-operated load-control system, in combination:

• first, second and third fluid-actuatable drive-establishing means for controlling the torque ratio of a vehicular transmission;
• a supply line;
• first valve means for connecting said supply line to a source of high-pressure fluid in a basic position and to a drain in an alternate position;
• further valve means in tandem with said first valve means controlling the admission of fluid from said supply line to said first drive-establishing means;
• second valve means in tandem with said first valve means controlling, jointly with said further valve means, the admission of fluid from said supply line to said second drive-establishing means, said further valve means being effective in a normal position to admit fluid at a relatively high rate from said supply line to said first and second drive-establishing means, said further valve means being effective in an off-normal position to throttle the fluid flow from said supply line to said first and second drive-establishing means, said second valve means having a downshifting position for cutting off the fluid flow to said third drive-establishing means and an upshifting position for cutting off the fluid flow to said second drive-establishing means;
• fluid-feedback means extending from said first drive-establishing means to said further valve means for displacing same from said normal to said off-normal position upon incipient pressure buildup in said first drive-establishing means;
• biasing means opposing displacement of said further valve means by said fluid-feedback means;
• throttled conduit means extending from said first drive-establishing means to said biasing means for exerting thereon a force-increasing action re-establishing said normal position upon a predetermined rise in the pressure of the fluid admitted to said first drive-establishing means;
• and
• drain means for said second drive-establishing means effective in said upshifting position of said second valve means independently of the position of said further valve means for preventing concurrent pressurization of all said drive-establishing means.