| 摘要 |
In an elongate truck trailer tongue assembly having hollow, inner and outer telescoping tongue members movable between shortened and extended tongue positions, a remotely controlled, pneumatically actuated friction shoe is mounted within the tongue to selectively lock the tongue members in either the shortened or extended position. The tongue members are tubular and have square-shaped cross sections, and the friction shoe is shaped and mounted so as to be supported by the inner tubular member and, when actuated, to bear against interior wall surfaces of the outer tubular member, frictionally locking the members against relative movement and rigidifying the tongue assembly so that it acts as a unitary structure between the trailer and towing tractor. Cooperating with the friction shoe is a pneumatically actuated, spring-biased safety pin assembly which is mounted on the inner tongue member and engages mating holes on the outer tongue member at the shortened and extended tongue positions, to provide a backup lock for the tongue assembly should there be a loss of air pressure to the pneumatically actuated friction shoe. The safety pin is normally held in a locked position by the spring bias and is withdrawn therefrom whenever the normally pressurized actuator of the friction shoe is vented to allow telescoping of the tongue members so as to adjust the tongue length. In an alternative embodiment, the friction shoe is actuated by a pair of hydraulic cylinders powered by a hydraulic fluid that is pressurized via an air-to-hydraulic pressure converter mounted inside the hollow tongue members.
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