| 摘要 |
1488426 Change-speed control CATERPILLAR TRACTOR CO 12 Nov 1975 [17 April 1975] 46750/75 Heading F2D In a large vehicle such as an earth mover, provided with a park brake (10, Fig. 1, not shown), applied automatically as by a spring (20), and released by fluid pressure 36 applied to a piston (16) to overcome the spring (20), failure of the brake-release pressure 36 is indicated to the operator by imposing a resistance to movement from neutral of a member 42 in the vehicle transmission control linkage. Failure of such brake-release pressure 36 permits a spring 68 to maintain a cam plunger 64 in the position shown, in which its cam surface 66, through a ball 88 and spring 90, maintains a detent ball 84 in a groove 48 in a sleeve 46, slidably mounted on the transmission control member 42 and maintained in a central position, shown, by springs 58, 60 which resist movement of the control member 42 from neutral. Presence of brake-release pressure 36 shifts the cam plunger 64 to the right, removing pressure from the detent ball 84 to permit normal shift movement. For an emergency move, the operator can override the springs 58, 60.
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