Fig. 31. Type of Rise and Fall Machine.
In Fig. [30] the pulley A is supported on a shaft in the same position as the gear for the rack motion, and to the pulley a strip of belting B is attached, each end being fixed to the cross rail of the griffe at C. The belt motion is a simple arrangement, but the griffe must act freely and perfectly straight or the griffe will not descend low enough to allow the hooks to be pressed off by the cylinder.
THE RISE AND FALL OR CLOSE SHED MACHINE
The illustration, Fig. [31], shows a machine of this type. Its purpose is to have all the harnesses level at the center movement. The same working parts are used on this machine as are used on the single action, the distinctive difference being that cranked levers are attached to the usual lifting levers so that the grate through which the hooks pass can be raised and lowered, and so that the griffe is raised only half the usual distance.
After the cylinder has pressed off the hooks that are not to be lifted, the grate descends with these hooks, and at the same time the griffe raises the hooks that are to be lifted.
On some rise and fall machines, a batten cylinder motion is used, but is fixed in the opposite position from the usual batten motion; that is, the batten swings from the bottom instead of from the top of the machine, the set screws that hold it in position being placed in brackets fixed near the feet of the machine.
These machines cannot be run at a high speed, 130 being considered average, but faster speed is obtained when the pattern is equally balanced so that about the same number of ends are raised, as are falling. This style of machine is now extensively used for weaving table cloths, silk goods, etc.