Abstract: A pressure relief and drain valve includes a poppet valve on a valve body movable in a primary valve chamber between closed and open positions and spring biased to the closed position. A secondary valve slidable on the poppet valve cooperates therewith and with the valve body in defining a variable volume secondary chamber within the primary chamber. Passages in the poppet valve connect the fluid circuit upstream of the poppet valve with the secondary chamber and drain orifices in the poppet valve connect the secondary chamber with a sump. When the net fluid pressure force on the poppet valve in the opening direction exceeds the spring force, the poppet valve opens for pressure relief. The fluid flows over a suction surface on the poppet valve when the latter is open and the pressure drop at the suction surface proportional to the flow velocity is communicated by the passages to the secondary chamber so that the valve opens further and the pressure drop across the valve is substantially constant.

Abstract: A power transmission has a variable belt drive, a two-speed planetary gear arrangement and a countershaft type gear arrangement disposed in combination to provide a continuously variable synchronously shifting transmission. The planetary gear arrangement and the variable belt drive are disposed in parallel drive relationship thereby reducing the belt load. The planetary gear arrangement has two output members selectively connectible via clutches with respective countershafts in the countershaft type gear arrangement. The countershafts support selectively engageable ratio gears which mesh with respective drive gears on the transmission output shaft in a manner to provide pairs of identical gear ratios between the shafts such that ratios on each countershaft may be simultaneously engaged and the output clutches of the planetary gear set can be interchanged at a synchronous speed point to permit a ratio change. Speed change within any given gear ratio is provided by controlling the ratio of the belt drive.

Abstract: A transmission having hydraulic components including a hydrostatic unit with a variable displacement component having a hydraulic displacement control with a lubrication circuit for the components and a charge circuit for supplying fluid under pressure. First and second pumps are connected in series, with the first pump having a larger volume than the second pump to provide fluid to the second pump and to a lubricating circuit. A fluid line connects between the charge circuit and the lubrication circuit and has a lubrication priority valve therein which operates to provide fluid flow from the charge circuit to the lubrication circuit when required to maintain pressure in the lubrication circuit. Additionally, the charge circuit has a pair of branch lines, with one branch line having a charge priority valve therein which functions to control the flow through the one branch line leading to the hydraulic displacement control for the hydrostatic unit and to thus provide pressure control in the other branch line.