The end of a carrier is represented at T. As the carrier settles down to the bottom of the receiving tube, it comes in contact with the ends of the needles and presses them down, they being supported by two springs U and V. As the needle R is moved down, it makes contact with the spring clip W, located just below it, and closes an electric circuit that includes the electro-magnet X, Figs. 38 and 39, on the valve of the rotating cylinder O. When this electro-magnet is excited it attracts its armature and moves the piston slide-valve Y, that admits air to the top of the piston in the cylinder O, and allows the air under the piston to escape to the atmosphere. The piston moves downward and revolves the wheel by means of a connecting rod.
Upon the end of the carrier T is placed a thin circular metal disk, f, which may be copper, brass, tin-plate or any metal that is not easily oxidized. The diameter of this disk of metal determines the station at which the carrier will be discharged from the tube. Disks of various diameters, that may be attached to the carrier, are represented by dashed lines, g, in Fig. 40. When the carrier comes in contact with the two needles R and S, if the circular metal disk on the front end of the carrier has a diameter sufficient to span the space between the two needles, in the position in which it is held, then an electric circuit, made by the wires a and b, will be closed through the needles and the metal disk on the carrier. The metal disk makes a short-circuit from one needle to the other. If the metal disk is not large enough to span the distance between the two needles, then the electric circuit remains broken.
Returning again to Fig. 39, we have the opening J, where the carriers are discharged, closed by a sluice-gate. This gate is opened and closed by a piston moving in a cylinder, h, shown in Fig. 38. A piston slide-valve, i, similar in all respects to the valve on the cylinder O, controls the movement of the piston in this cylinder and the sluice-gate to which it is attached. The slide-valve is moved in one direction, that opens the sluice-gate, by an electro-magnet in the circuit of the wires a and b, Fig. 40.
When the electric circuit made by these wires is closed by a disk on the front end of a carrier, short-circuiting the two needles, the valve is moved by the electro-magnet in the circuit, and the sluice-gate is opened. As the wheel, including the receiving tube and carrier, revolves, a lug, j, Fig. 38, on the outside of the wheel comes in contact with the open sluice-gate and the wheel can rotate no farther. A blast of air through the valve L, Fig. 39, assisted by gravity, pushes the carrier out of the receiving tube, through the opening J and down the chute Q, on to the receiving table.
Had the disk on the front end of the carrier been too small to span the distance between the two needles, the circuit would not have been closed, the sluice-gate would not have been opened, no obstruction would have been placed in the path of the lug j, on the wheel, and the wheel would have continued its rotation through ninety degrees until the receiving tube F came in line with the tube D. During the latter part of the rotation, a pin on the wheel engages a lever, k, Fig. 38, and turns a valve, l, Fig. 39, stopping the flow of air through the passage C, compelling it to take another route through the passage m, and the receiving tube F, taking with it the carrier into the tube D. When the carrier leaves the receiving tube and passes through either of the openings J or K, it engages one of the fingers, n or o, that lie in its path. These fingers are connected by rods and levers to the valves on the rotating and sluice-gate cylinders. The ejected carrier pushes these fingers to one side, and after it has passed the fingers return, by the force of a spring, to their former position and move the valves, causing the sluice-gate to close and the wheel to rotate backward into its normal position ready to receive the next carrier. The connection between the fingers and the valves is similar to the mechanism on the open and closed receivers, so need not be described in detail here.
The speed with which the carriers are ejected from the receiving tube through the opening J and down the chute Q is regulated by the valve L, which can be opened or closed by a hand-wheel, p. Before the wheel and receiving tube can be rotated, the needles must be withdrawn from the receiving tube, and this is accomplished by a small cylinder and piston, q, shown in Fig. 40. The needles and their encasement are attached to a cross-head, r, on the end of a hollow piston-rod, s. When air is admitted to the top of the piston in the rotating cylinder O, Fig. 39, it is also admitted through the pipe t, Fig. 38, to the cylinder and upper side of the piston q, Fig. 40. This moves the piston q down against the force of a spring, u, and withdraws the needles from the receiving tube. This takes place after the needles have served their purpose and before the wheel is rotated. The piston q has much less inertia than the wheel, therefore it moves much quicker. When the wheel begins to rotate it closes a valve, v, in the pipe t, Fig. 38, confining the air in the cylinder q, and preventing the needles from being raised by the spring u before the wheel returns to its normal position. If by any accident the needles should be raised, no serious harm would result, for their ends would simply bear against the face of the wheel. If this took place constantly, grooves might be worn in the face of the wheel; for this reason the valve v is provided.
In order to facilitate the inspection of the needles and electric contact springs W, they are contained in a cylindrical brass case, w, that is held in place beneath the receiving tube by two bolts. By removing the nuts from these bolts the entire mechanism can be removed, examined, and cleaned. It also gives easy access to the receiving tube. The receiving tube is long enough to receive two carriers, if it should ever happen that two arrive at the same time.
Fig. 41.
DIAGRAM OF CONTACT-DISKS AND NEEDLES.
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