| 摘要 |
943,008. Change-speed control. DAVID BROWN INDUSTRIES Ltd. May 16, 1961 [April 28, 1960], No. 14856/60. Heading F2D. An auxiliary variable-speed hydrostatic gear is provided to facilitate changing speed in a main change-speed gear. As shown, a main change-speed gear of the constant mesh type comprises an input shaft 10, and a lay shaft 11 and an output shaft 12 which drive primary and secondary pumps 25, 26 forming the hydrostatic variable-speed gear. Double dog clutch members 21, 22 are shiftable by shift rails 23, 24 to connect gears 13 and 16, 18, 20 to the output shaft 12 for direct and reduced drives, movement of a shift rail in the direction for engaging a gear being first limited by a balk member 73 or 74 abutting the end of a groove 71 or 72 in the rail 23 or 24, in which position the dog clutch member is disengaged, but a valve groove 55 or 56 in the rail opens a selected pair of ports in a control cylinder 30 to exhaust. The pumps are of the swash-plate type, pump 25 having a variable inclination swash - plate controlled by a piston 29 in the cylinder 30 and pump 26 being of the fixed displacement type although it may also be of the variable displacement type if desired. The opening of the selected pair of ports of cylinder 30 to exhaust enables the variable inclination swashplate to readjust itself until the piston 29 is positioned between the pair of ports, differential pressure in the main hydraulic transmission lines 27, 28 displacing a valve 34 so that a make-up pump 38 supplies liquid to the appropriate end of the cylinder 30 through a line 32 or 33 to aid movement of the swash-plate. When the shafts 11, 12 are rotating in the desired ratio the differential pressure in the lines 27, 28 ceases and a valve 76 resumes its central position in which it ceases to lock the balk members 73, 74 and allows the shift rail to retract the associated balk member and engage the desired gear. In a modification, the constant-mesh gear is replaced by a gear having wheels on the output shaft axially slidable into mesh with wheels on the layshaft.
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