Patent GB-163351-A (GB)
Title: Improvements in and connected with electric signalling telegraphs
IPC: G08B9/00
Filed: 1919-09-19
Abstract: 163,351. Grafton, W. F., and Jones, A. D. Sept. 19, 1919. Order apparatus of the ratchet type adapted for use on aircraft, as a ship's telegraph, or for mine signalling, comprises a self-centring two-way switch by which impulses may be sent for forward or reverse operation of the receiving-pointer, which is actuated by a double-ended pawl engaging one or other of two co-axial star-wheels according to the nature of the impulse sent. The initial movement of the switch closes a test circuit and energizes a magnet at the home station, releasing a detent which would otherwise prevent the switch from being fully operated. A reply apparatus identical with the signalling apparatus is preferably employed, the transmitter and receiver at each station being combined in one instrument. Fig. 1 is a section through such a combined instrument, Fig. 2 a side view with the casing removed, and Fig. 3 a diagram of electrical connections. The transmitter comprises a handle A fixed to a shaft B carrying a toothed locking wheel C engaged by a detent E, and a second toothed wheel W engaging a roller on the pivoted switch arm G. This arm carries three spring-pressed rollers X at its outer end co-operating with contacts 1 - - 10 on a curved track Y, these contacts being shown developed in the lower part of Fig. 2 and connected up as shown in Fig. 3. The track Y is eccentric relatively to the pivotal centre of the arm G, so that the springs tend to centralize this arm. For each advance of a tooth of the wheel W, the arm G is rocked and returns to central position. The receiver comprises two star wheels K<1>, K<2> fixed side by side to a sleeve carrying the indicator pointer N, the wheels having their teeth out of register so that the points of the driving pawl Z engage opposite faces of the teeth for driving in opposite directions. The pawl Z drives the wheel K<1> or K<2> half a tooth during the energization of the magnet H and the other half when the magnet is de-energized. For reverse driving, the pawl Z is slid out of the plane of the wheel K<1> into that of the wheel K<2> by a magnet M acting through a lever M<1>. When the handle A is operated to send an ahead signal, the switch arm G first engages a contact 5, thus connecting contacts 1, 5 at the home station and closing the battery circuit through the coil F. This withdraws the detent E and allows the handle A to go forward. The rollers X then move on to contacts 6, 7 thus connecting these contacts and energizing the magnet H at the distant station. The indicator N is thus advanced by the pawl Z and star wheel K<1>, its movement being completed as the switch arm G falls back to central position and de-energizes the magnet H. For astern signals, the handle A and switch arm G are moved in the opposite direction, making contact first between 1 and 4 which act similarly to the contacts 1, 5. A circuit is subsequently made between 9 and 10, thereby energizing the reversing-magnet M at the distant station and moving the pawl Z from wheel K<1> to wheel K<2>. Further movement of the switch arm G connects the contacts 8, 9, 10 thereby energizing the distant driving-magnet H and moving the pointer N in the reverse direction. At the distant station the switch arm G remains in central position connecting the upper set of contacts 1, 2, 3, Fig. 3. When reply signals are sent, as for verification of the original signals, the switch G corresponding to the lower set of contacts in Fig. 3 remains on the contacts 1, 2, 3 and the connections of the upper set of contacts are varied by the transmitter switch G.