Double Eccentric Reversing Gear.—A well known form of gear is shown in [Fig. 61], in which the engine shaft A has two eccentrics B, C, the upper eccentric B being connected with the upper end of a slotted segment D by means of a stem E, and the other eccentric C is connected with the lower end of the segment by the stem F. The eccentrics B, C, are mounted on the shaft so they project in opposite directions.
The slotted segment carries therewith the pin G of a valve rod H, and the upper end of the segment has an eye I, to which eye is a rod J operated by a lever.
By this arrangement the link may be raised or lowered, and as the valve rod pin has no vertical movement, either the connecting link E or F may be brought into direct line with the valve rod H.
[Fig. 61] shows the first position, in which the valve rod H is in direct line with the upper connecting rod E, actuated by the cam B.
[Fig. 62] shows the neutral position. Here the pin G serves as a fulcrum for the rocking movement of the segment; whereas in [Fig. 63] the valve rod H is in line with the lower connecting rod F, so that the valve is pushed to and fro by the eccentric C.
