What component is fastened to the platen plate in the bolster assembly?

The plunger is the component that is fastened to the platen plate in the bolster assembly. In hydraulic elevators, the bolster assembly plays a crucial role in supporting the jack cylinder while allowing vertical movement. The plunger, which extends from the jack cylinder, connects to the platen plate, serving to transmit hydraulic pressure and subsequently produce the lifting motion of the elevator. This connection is vital for the operational efficiency of hydraulic systems, as it enables the conversion of hydraulic pressure into mechanical movement.

The other options represent different components within elevator systems that, while essential, do not directly attach to the platen plate in the bolster assembly. The jack cylinder is the main hydraulic component that generates lift, while the guide rail provides a path for the elevator car’s vertical movement. The piston rod connects the plunger to the jack mechanism but is not what directly interfaces with the platen plate in this assembly. Understanding these roles helps clarify the relationship and functions of each component within the hydraulic elevator system.