Stephenson valve gear

A backdrop is a method used in mechanical transmission element for transmitting force ( sliding guide ).

The scenes (of French coulisse ) were originally slides, in which the sliding walls, parts of the theater decoration have been moved.

The backdrop has a slot, ridge or groove, in / on the / which a sliding block is constrained on both sides to implement a movement of the scenery in a movement of the sliding block. The transfer function of the slide guide is exclusively determined by the shape of the slot, ridge or groove and is freely selectable within wide limits. The sliding guide is used in particular for the realization of complex transfer functions.

Function

On the axis shown in the drawing with A two eccentric E and E1 at a certain angle relative to each other mounted on the axle shaft. By means of two eccentric rods B and B1 are those connected to the upper or lower end of the curved gate KK, which are suspended at the lower end with two rods of the three-armed reversing lever U U1. In the interior of setting K is an arcuate slot in which a block is. This so-called sliding block KS shifts the push rod serving to move ST and thus actuates the control valve. By the hand lever H, which moves to the toothed grid sheet H1 back and forth, the setting can be raised and lowered in order to control a desired forward or reverse movement of the machine. To the direction of movement of the machine are changed, the scenery KK is lifted by the operation of the handle H in the highest position and the push rod ST changes the function of the control slide.

Application

Scenes are used in machines and allow to switch control the operation of the machine during operation from forward gear to reverse and vice versa. Application examples are locomotives, weapons, ship machinery or other machines which require a reversal of movement during operation. The most important control is the set for Robert Stephenson link motion. The link control was described by James Howe, who worked for Stephenson invented in 1842 and improved in the following years.

See also: control ( steam engine ), engine ( steam engine ), shift drum