| 摘要 |
A multi position actuator includes a plurality of pistons which are disposed within a cylinder and adapted to be moved predetermined distances in steps in response to predetermined pressures applied thereto. One or more of a plurality of devices are selectively actuated to cause fluid pressure to be applied to move one or more of the pistons, dependent upon which ones of the devices are actuated. An output element is driven in accordance with the pistons actuated. In some applications, it is desirable to have an air or hydraulic cylinder extend in steps to specific positions in response to specific pressures. Many pressure position actuators presently in operation use a delicate counterbalance to assure that they are maintained in set positions after they have been moved to the desired positions. Such counterbalance devices are often subject to variations in forces which cause their positions to vary. One field in which it is desirable to maintain specific positions of a driven member is in connection with manual throttle operations used to control the speeds of vehicles, such as railway cars. It is generally desirable to maintain certain selected throttle positions and speeds after the vehicle has started to move. |
