Page:The Kinematics of Machinery.djvu/535

 SUPPLY AND DELIVERY GEAR. 513

In the steam-engine above mentioned the directing-gear is simply the familiar mechanism by which the slide-valve is opened and closed at the right instant ; in a planing machine driven by a rack the directing-gear determines the periodic reciprocation of the table ; in the self-acting spinning machine the gear is a train of no little complexity, comprehending, as Stamm first showed theoretically,* four different motions in succession, which he called Sortie, Torsion, Depointage and Eenvidage respectively.

Within the directing-gear there is often an arrangement made to provide for bringing fresh portions of the material which forms the work-piece regularly under the action of the machine. In the carding engine a band of cloth with two feed-rollers is used for this purpose ; in the cotton-preparing machine, combs or spiked rollers serve to supply the machine with raw cotton ; in the mill feed-rollers are sometimes used to convey the grain regularly to the stones ; in the needle-grinding machine a toothed-wheel gives the requisite feed to the needle-frame. In many machines, also, a similar arrange- ment exists for the purpose of bringing continually into action fresh portions of the driver. All these mechanisms we may include under the one head of feed or supply gear. The arrangements for moving the tool in planing-machines, lathes, drills, &c., as well as those for feeding boilers are examples of them.

For a purpose exactly opposite to that of the supply there is often another special arrangement added to the machine, an apparatus, namely, to remove the finished work-piece from the direct-actor. We may call this the delivery-gear; as examples of it we have the delivery tables in brick-making machines, the delivery drum (or in recent machines a more complicated arrangement) from which the prepared fleece is passed out of the carding-engine, the mechanism for shooting out the finished rivets from the die of the rivet-making machine, and so on. Supply and delivery form as it were the entrance and exit doors of the machine. Through the one the raw material enters the mechanism, through the other the finished manufacture leaves it. It is in connection with direct-actors chiefly that the construction of delivery-gear has been very fully developed.

Along with the director we find in very many complete machines a second mechanism, having special characteristics of its own,

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 * Stamm, Traite thtoretique, . , des Metiers & filer Automates, &c., Paris, 1861.