Patent GB-272975-A (GB)
Title: Electric means for providing selective remote indication
IPC: H02J13/00
Filed: 1926-02-02
Abstract: 272,975. British Thomson-Houston Co., Ltd., Petch, H. S., and Wheatcroft, E. L. E. Feb. 2, 1926, Tell-tale apparatus.-Comprises telemetering systems whereby a distant indicator is moved step-by-step into agreement with a master pointer at a transmitting station for the purpose of signalling such quantities as electric current, load, water-level, or temperature, or for telegraphing orders. So long as the master pointer closes one or other of two contacts carried by a follower, a repeating cycle of impulses passes between the two stations until agreement is restored. A number of transmitters mav be connected to a number of receivers over a single line through rotary distributors, and a system is described whereby anv one of a number of transmitters may be selected for co-operation with any one of a numbers of receivers. The Specification also describes means for establishing the contact between the master pointer 21 when displaced and the follower contacts 24, 25, in cases where the master-pointer is moved with high or with low torque. In the drawings the relays concerned with a pointer-movement to the right (raising movement) and to the left (lowering movement) are designated by the letters R and L respectively, while the transmitter and receiver (or indicator) relays are designated respectively by the letters T and I. Thus the relay ALT is the leftward ratchet relay at the transmitting station whiles ARI is the rightward ratchet relay at the indicating (receiving) station, the letter A being appropriated to the ratchet relays. System employing a cycle of four impulses passing reciprocally from transmitter to receiver and vice versa in alternation. In a modification of the main invention shown in Fig. 1<b> a positive impulse is sent from the transmitter T to the indicator I over the line 47 for a falling (leftward) indication or 46 for a rising (rightward) indication to move the receiver pointer through one step. A positive impulse is then sent back over the line 48 to move the follower 22 one step. A negative impulse over the line 47 or 46 as the case mav be next resets the indicator relays, and finally a negative impulse over the line 48 resets the transmitter relays. The cycle continues so long as the master pointer 21 touches contact 24 or 25 of the follower. Thus with a falling indication the relay FL is energized through the contacts 21, 24 and sends a positive current through its contacts FL3 over the line 47 to the indicator relay GL, which operates and so energizes the ratchet relay ALI. The latter moves the indicator receiver pointer 33 one step, and simultaneously sends a positive current through the contacts ALI2 over the line 48 to the relay H, which thereupon energizes the ratchet relay ALT over a circuit including contacts H2 and FL2. Relay ALT moves the follower 22 one step and sends a negative impulse through its contacts ALT3 over the line 47 to reset the relay GL. which breaks the circuit of the relay ALI. The latter then sends a negative current through its contacts ALI3 over the line 48 to reset the magnet H. The magnet ALT is not immediately reset since it has now an alternative (self-holding) path to positive through contacts ALT. but the resetting of H breaks at H2 the alternative circuit of the relay FL (whose original circuit is now broken by relay ALT), and de-energization of FL breaks at FL2 the circuit of ALT, which is consequently reset. During the cycle the contacts FL1 provide for the master current a path alternative to the original path through 21, 24, and inaction of the relay ARI is ensured by disconnection at ALI1. For a rising indication a similar cycle is carried out by relays FR, ART, GA, ARI, and H. Systems of using unpolarized relays effecting a reciprocal two-impulse cycle. The system according to the main feature of the invention (shown in Fig. 9<b>) operates similarly to that shown in Fig. 1<b>, but only two lines are needed in addition to the earth return, unpolarized relays are employed, and the relay H is controlled through additional contacts FL4, FR4 on the F relays. Resetting is therefore effected not by reversal of polarity but by breaking of circuits. For a falling indication an impulse is sent from transmitter relay FL to indicator relay GL over the line 47, and the consequent operation of the relay ALI sends a return impulse over the line 46 to operate the relay H controlling the ratchet relay ALT. The latter on operating breaks) the line 47 at ALT3 and so resets the relay AL1, which thereupon breaks the line 46 at AL1 and so resets, the relay H. For a rising indication the action is similar, but the roles of the lines 46, 47 are then reversed. In a modification, Fig. 10<b>, rotary distributors are employed for connecting several transmitter stations to corresponding indicator stations, a single line wire 42 performs the functions of the two lines 46, 47. If contacts 21, 24 be closed so as to energize relay FL, then when the wipers 31, 39 reach their contacts 7 or 7<1> positive is connected through FR3, FL3, ALT2, and the distributors to the relay GL, which operates and energizes the ratchet relay ALI. The wipers 31, 39, having now reached contacts 1 or 1<1>, a return impulse passes through contacts ALI2, relay GR, the distributors, contacts FL4, and relay H. Relay GR on operating resets relay ALI, so that the station I is in statu quo, and relay H energizes the slow-release relay N, which acts to energize the ratchet magnet ALT even after the distributor contact &c. has been broken. The resetting of relay N while ALT is energized cuts off the positive from FL, which resets and so deenergizes ALT, restoring the status quo. This cycle of operations then repeats itself until contact is broken at 21, 24. In the embodiment the magnet J, effecting the intermittent contact at 21, 24, is controlled by cam-operated contacts 76. Apparatus for selecting station and instrument. The apparatus shown in each rectangle 77, Fig. 11<b>, is similar to the transmitter T, Fig. 9<b>, while the apparatus in each rectangle 77<1>, Fig. 11<b1>, is similar to the indicator I, Fig. 9<b>; several groups of instruments, each forming a station, are provided, and the common lines 46, 47 can be appropriated to any transmitter and any indicator by means of the apparatus shown. All irstruments when put out of action notch back to zero, but any instrument at a transmitting station can be made to give a reading by inserting a test key. The transmitter shown in Fig. 11<b> is selected by setting the station switch 81 to the contact 81<a>. The arm of this switch is connected to positive through relay 0, which operates to appropiate the lines 46, 47, to the station; while the contact 81<a> is connected to negative through relay PT, which operates to prepare the circuits of the relays FL, FR, ALT, ART, H, cuts out the zeroizing relay UT at PT5, and holds on through its contact PT1. Similarly at the indicating station, Fig. 11<b1>, the instrument shown is selected by setting switch arm 80 to contact 80a. The arm 80 is connected to positive through the hold-on relay S, which operates to light the pilot lamp 84; and contact 80a is connected to negative through the relay PI which appropriates the lines 46, 47, and relays GL, GR, to the instrument shown in detail, cuts out the zeroizing relay UI at PI4, and holds on through its contacts PI1. Telemetering thus takes place as described with reference to Fig. 9<b>. To disconnect the transmitter, Fig. 11<b>, switch 86 must be closed so as to energize relay QT, which cuts out relays 0, PT, these reset and relays UT, ALT, zeroize the instrument. Similarly to disconnect the indicator, Fig. 11<b1>, relay QI must be energized by closure of switch 85, whereupon it causes relay S and PI to reset. Zeroizing is then affected at the indicator as follows : contact UI1 cuts in the ratchet relay ALI, which lowers the indicator reading by one notch and at ALI1 cuts out relay UI, which on resetting causes ALI to reset. Relay UI then operates again, and the cycle of operations repeats itself until the instrument, on reaching zero, opens contact 88 and so ends the repetition. The action of relays UT and ALT is similar, the contact 87 being open when the instrument reads zero. If a disengaged instrument at the transmitting station is to be read locally a key is withdrawn from a lock so as to open the station contacts 82, 83, thereby disconnecting relay O from outside interference and to close the contact 89. The key is then inserted in the selected instrument so as to close its contacts 90 and the relay PT. If there is any reading to be indicated, the points 21 will be in contact with -pointer 25, and relay FR will be energized through contacts ART2 : thereupon relay H is energized through FR3 89, FR4 and PT4. Relay ART is energized through H2 and PT3, breaking the FR circuit; the relays FR, H, ART, therefore reset in succession and the cycle repeats itself until the pointer 21 is free of the follower contact 25. Intermittent actuation of pointer contact. A hunting switch is shown in Figs. 2, 4, such that when the pointer 21 is displaced relative to the follower 22, contact is made intermittently in order to avoid continuous mechanical constraint. In the system shown in Fig. 9<b> the switch is controlled by a magnet J which, when the follower and pointer are in agreement, is intermittently energized through its co-operation with the longlag slow-acting relay K (whose circuit it controls at J1) and the short-lag slow-acting relay M, whose circuit is controlled by the relay K. The magnet M in turn controls the quick-acting relay J, so that normally a continuously repeating chain of operations is maintained by the three relays, and the pointer contact is actuated by the magnet J at regular intervals. When, however, a signal is being sent, the frequency of energization of J is increased to the frequency of the signal