Patent GB-191505623-A (GB)
Title: Improvements in or relating to Electrical Alarm Systems.
IPC: G08B25/12
Filed: 1915-04-14
Abstract: 5623. Siemens & Halske Akt.-Ges. April 16, 1914, [Convention date]. Fire and like alarm systems and apparatus.- Relates to closed-circuit fire-alarm signalling systems in which means are provided for preventing interference when several alarms are set in action simultaneously, and in which an earth connexion is made at each alarm before its code signal is transmitted, and consists primarily in providing two earthing- switches at each transmitter, both controlled by the rotating codewbeel, one of which is closed only in the event of the non-response of the line magnet at the starting of the alarm. In one form, shown in Fig. 1, the transmitter comprises a code-wheel 6 rigidly connected to a gear-wheel 9 and to concentric disks 8, 10, 11, 12 2 having camsurfaces on their rims. A loose gear-wheel, similar and adjacent to the wheel 9 and capable of being connected thereto by a removable pinion 19, is driven by a weight motor 16 controlled by an escapement 17. The motor is normally locked by a pin 31 on an armature lever 21, but is released when the lever is raised or lowered. An alarm is given by pressing a button 27, which is retained in its depressed position. This allows the lever arm 21 to rise and the motor to start, the code-wheel being driven through the pinion 19 which is held in gear temporarily by a lever 33 and arm 34 engaging the rim of the disk 10. As the disk 11 rotates, a projection 11<1> allows a short-circuiting switch 37 to open, thus putting the magnet 20 and the code switch 7 in the loop circuit. The magnet 20 attracts its armature 21<x> and depresses the other arm of the lever 21 thus allowing a bent lever 25 carrying a pivoted extension 40 to be withdrawn by a spring 39 from the path of a cam 42. A bevel surface on the lever 21 also engages the lower end of the arm 18 carrying the pinion 19 and ensures the engagement of the pinion. As the code-wheel rotates, a series of recesses spaced by projections cause the switch 7 to open and close the circuit and to transmit the signal to the central station, At each opening of the circuit, the armature 21<x> is kept up to the magnet 20 by a lever 44 controlled by the switch 7. At a definite interval after the starting of the motor, an earthing-switch 47 is allowed to close by the receding of a cam-ledge 46, thus giving an earth return to the centre of the battery C at the central station. If there is a break D in the loop, the opening of the short-circuit switch 37 will not energize the magnet 20, and consequently the lever 25 will be tilted by the cam 42 and will close an earthing-switch 26. This allows one coil of the magnet 20 to be energized and the armature lever 21 is attracted and the code signal transmitted through an earth return circuit. If another transmitter, say M', is running off when the transmitter M<2> is released, the loop circuit is being alternately opened and closed. The motor 'starts up and drives the code-wheel until the shoulder 43 on the disk 10 reaches a catch 35 on the arm 34, whereupon the bar 18 carrying the coupling-pinion 19 is released. If at this moment the loop circuit is open, the armature lever 21 is in the position shown, and the bar 18 is free to move to the left, thereby disconnecting the motor from the codewheel which is retained in position by the catch 35 engaging the shoulder 43. If the loop circuit is closed at the particular moment, then the disconnection of the pinion 19 is not effected until the next opening of the circuit, the code-wheel being returned by a spring 50 and crank 49 to the position in which the shoulder 43 is retained by the catch 35. The code-wheel 6 thus oscillates but does not advance sufficiently to transmit any portion of its signal. At each de-energization of the magnet 20, the spring 30 raises the arm 21 so far as is allowed by a swell 48 on a disk 12, the stop 31 being placed in the path of the pin 32 so that only one revolution of the escapement wheel is allowed for each energization of the magnet, the motor thus being prevented from running idly. When the alarm M<1> has finished, the loop circuit is restored to normal condition, and the code signal is transmitted from the alarm M<2>. If two alarms M', M<2> situated on the same side of a break D are released simultaneously, both run until an earth connexion is made at each, the alarm M<1> nearer the central station then sending its signal and subsequently breaking its earth connexion, whereupon the other receives current and transmits its signal. In a modified form of the apparatus, shown in Fig. 5, the armature lever 21 is separate from, but is pivoted on the same pin 21<1> as, the locking-lever 61. The motor shaft 90 is geared positively to the shaft 5 on which are fixed the code-wheel 6, the cam-disks 8, 46', and the locking-disk 60. A disk 7 on the motor shaft carries a series of teeth 76 which co-operate with the upturned end 78 of the armature lever 21 at the beginning and end of the workir g of an alarm, the distance between the teeth 76 corresponding to one complete rotation of the code-wheel. The locking-lever 61 has a nosepiece 61<1> at one end overhanging a screw 59 on the armature lever. At the other end, the lever 61 has a cross-arm co-operating, at its lower part with a pin on the escapement-wheel 17, and at its upper part with the recesses 64, 61<1> in the locking-disk 60. The earthing-switch 25 is engaged by a blade spring 75 attached to the lever 61. The camdisk 46' has three steps 65, 66, 67 operating in turn, directly after the commencement of the rotation of the shaft 5, to lower gradually the bent lever 69 and so operate the switch arms 70 .. 74. The first step opens the short circuit at the contact 37, the second step closes the arms 72, 73 and so prepares the earth circuit through the switch 26, and the third step closes the normal earth circuit through the arms 73, 74. For ordinary working with a complete loop circuit, the motor starts when the button 27 is pushed, and as the short-circuit contact 37 is opened, the magnet 20 receives current and attracts its armature 21 thereby tilting the lever 61 and withdrawing its end from the recess 62 in the locking-disk 60, and also removing the lever 25 from the path of the cam 42. At the first interruption of the line current the armature 21 is allowed to drop on to a stop 79, provided that its lug 78 has cleared the tooth 76, and when thus fallen the armature cannot again attract it until a stronger current is switched in at the central station. This is effected automatically by a long closure of the circuit occurring at the end of the working of an alarm owing to the continuous surface 6<1> of that part of the code-wheels. When there is a fault in the line circuit, the magnet 20 is at first unenergized and therefore the lever 25 remains in the path of the cam 42. The earthing-switch 26 is thus closed, whereupon one (oil of the magnet 20 receives current and the alarm runs down as before. When an alarm is already in action, the magnet of the second alarm is alternately energized and de-energized, and the armature oscillates until its end 78 is free from the tooth 76. It then falls away, and the code-wheel is locked at the recess 64<1>. When the first alarm has nearly run down, the reinforced current lifts the armature 21 of the second alarm and allows it to transmit its signal. If an alarm is started between two alarms already working, its magnet does not receive current owing to the earth connexion on each side of it. Consequently the lever 25 is engaged by the cam 42 and the earth-switch 26 is closed. The code-wheel rotates until the stop 64<1> engages the lever 61 and the switch arms 72, 73 are closed to complete the earth circuit through the switch 26. At the conclusion of the other signals, the re-inforced current releases the locking-lever by attracting the armature 21, and the alarm runs down. If two alarms are actuated between a working alarm and the central station, the line magnets of these alarms will receive current intermittently a d no earth connexion will be made at the switch 26. Each alarm will run until the stop 64<1> reaches the locking-lever 61, and when the working alarm has nearly run down, a reinforced current will again relea-e each alarm and allow its earth contacts 73, 74 to be closed. The alarm farther from the central station is thus short-circuited and its magnet de-energized, causing its lever 61 to lock in the second recess 64. The alarm nearer the central station sends its signal and at its completion the armature 21 of the farther alarm is attracted and its code-wheel released.