Patent GB-190609068-A (GB)
Title: Improvements in Selective Signalling Mechanism.
Inventor: FAIRWEATHER WALLACE
Filed: 1906-04-17
Granted: 1907-04-11
Abstract: 9068. Fairweather, W., [International Telegraphic Call Co.]. April 17. Signals, electric, pneumatic, and indicator or visible.-Relates to selective signalling-apparatus controlled _by combinations of short and long impulses, applicable to telegraph and telephone calls, signals, wireless signalling, &c. An electrically-operated form of apparatus is described, but modifications may be operated manually, pneumatically, or otherwise. In the telegraph. call apparatus shown, the selecting ratchet-wheel 10 is rotated by a wire frame 15, Figs. 2 and 4, carried by the operating-lever 16, which is connected by the rod 25 to a bowed spring 22 &c. mounted so as to be straightened by the movement of the armature 20 of the magnet 19. The selecting-arm 14 engages the lever 9 at the desired station so as to raise the hooked lever 7 and'release the shutter 4 and thereby to open the contact 6 and effect a call of any desired nature. The wheel 10 has two types of teeth in a prearranged order. The " upper-contact" tooth, shown in Fig. 6 and at a, Fig. 4, has its lower part 37 cut away slantingly, the upper part 38 being left square. The " lower- " contact" tooth, shown in Fig. 5 and at d, Fig. 4, is cut away at its upper part 39 and left square at 40. A retaining-pawl 28 is provided on the side of the lever 29. fixed on the inclined shaft 30, Fig. 3. This pawl can take up two positions, namely : a lower one as shown in Fig. 4 in which it engages the "lower-contact" teeth d, but can be-moved laterally by the bevelled parts of the "upper- " contact" teeth a, and an upper position in which the shelf 34 engages the notch in the arm 35 and in which the teeth a are held but the teeth d can move the pawl laterally. Since " upper-contact " and "lower-contact" teeth follow each other in a certain order, complete revolutions of the wheel can be accomplished only by supporting, the pawl (as by the hook 35) when opposite each upper- " contact " tooth and dropping the pawl when opposite each " lower-contact " tooth. To drop the pawl selectively at proper intervals, a retarded freeing means is used, whereby when the circuit is closed for a long interval a rolling wheel rocks the shaft 36 on which the hook 35 is mounted so as to let the pawl 28 drop into engagement with the " lower-contact " teeth. The retarding means, is shown in Figs. 3 and 8, and consists of two disks 45 joined by a shaft 46 rolling on the inclined wire 47. The disks 45 are mounted in a frame 44, Fig. 3, swinging on the shaft 43, which is connected by the arm 42 to the shaft 41. When the operating-pawl 15 is raised, the returning arm 50 on the shaft 17 holds the frame 44 forward, but when the pawl 15 drops the arm 50 swings backward and the wheel is free to roll down the track 47. This movement is slow, owing to rotative inertia. If the magnet 19 is energized for a short time, the arm 50 pushes the frame 44 back quickly, but if the magnet is energized for a long interval the wheel rolls on the rack 47 and brings the frame 44 against the frame 51 on the shaft 36 so as to rock this shaft and release the pawl 28. If the sequence of short and long impulses differs from that required for a particular ratchet-wheel, the latter cannot be operated, since, if the pawl 28 is raised opposite a " lower-contact " tooth or lowered opposite an "upper-contact" tooth, it will strike the bevelled part of the tooth, which will move the pawl laterally to free the wheel, which is then returned to its zero position by a spring. When the call signal has been given by dropping the shutter 4, the return of the ratchet-wheel is ensured by providing a tooth bevelled from top to bottom, so that it disengages the pawl 28 whether this is in its upper or lower position. During the return to zero, the pin 33 on the wheel 10 strikes the inclined part of the lever 29 and raises the pawl 28 so as to re-engage the teeth of the ratchet-wheel, this return being effected by the weight of the inclined shaft 30. The invention contemplates the use of two automatic freeing devices for the ratchet-wheel broadly, one of which (as the " lower-contact " tooth) is operated by the movement of the wheel alone, while the other (as the retarded frame 44 and " upper-contact" " tooth) is operated by the main impelling means (the shaft 17). By arranging these so that the retarded means may be used at will to prevent operation of the unretarded means, it is possible to employ any combination of teeth operated by short and long impulses. Specification No. 15,013, A.D. 1896, is referred to.