US2586722A - Pull switch for mine shaft signal systems - Google Patents

Description

Feb. 19, 1952 R. L. RUTHERFORD PULL SWITCH FOR MINE SHAFT SI NAL SYSTEMS Filed June 18, 1948 Patented Feb. 19, 1952 UNITED STATES PATENT OFFICE PULL SWITCH FOR MINE SHAFT SIGNAL SYSTEMS My invention is related to mine shaft signal systems as set forth in U. S. Letters Patent No. 2,248,825 granted to me July 8, 1941, in which signals are dispatched from an elevator cage, or skip, in a mine shaft by means of an oscillatory circuit, said signals being reproduced in a radio frequency receiver located at the mouth of the shaft. The radio frequency sending apparatus embodies the use of one or more thermionic vac-v uum tubes in a feed back circuit to which current supplied by a battery carried on the elevator cage and by reason of the space available for accommodation of the apparatus it is desirable to make it compact and operate it from a small battery. Inasmuch as the energizing of the circuit is only required at the time'when it is desired to transmit a signal I have found in practice that it is desired to transmit a signal I have found in practice that it is preferable to maintain it inoperative and thus extend the life of the thermionic tube or tubes and also maintain the voltage of the battery.

The object of my present invention is to incorporate in conjunction with the switch employed for interrupting the oscillatory circuit when radio signal waves are to be dispatched, means for first energizing said circuit so that by means of a single instrumentality in the hand of the operator these results may be accomplished seriatim without thought on his part.

Another object of my invention is to conserve the power of the battery used for energizing the oscillatory circuit to obviate the necessity of frequentlyrenewing it as is the case where said cir cult is maintained energized continuously by providing a switching means which is so arranged that the battery current is applied automatically when the operator grasps the signal handle preparatory to transmitting a radio signal, there being provided a delayed action between the energizing of the oscillatory circuit and the pulling of the signal cord which occurs independently of any action on the part of the operator.

To these and other ends my invention comprises further improvements and advantages as will be further described in the accompanying specification, the novel features thereof being set forth in the appended claims.

In the drawings:

Figure 1 is a view conventionally illustrating my invention, the parts thereof being a mine shaft and radio transmitting and receiving apparatus employed in conjunction with the elevator and its hoist. 5

Figure 2 is a diagrammatic illustration of the signal dispatching apparatus carried on the elevator.

Figure 3 is a similar view of the radio receiving circuit located at the mouth of the shaft which operates in conjunction with the circuit of Fig. 2.

Figure 4 is an enlarged view partly in section illustrating a pull switch embodying one form of shown in their normal inoperative position, and

Figure 5 is a similar view in detail showing the pull switch in its signal transmitting position.

Figure 6 is a view similar to Figure 4 showing the filaments which are located on the pull cord shaft and operated by means of a Bowden wire from the pull cord handle.

Similar reference numerals, in the several figures, indicate similar parts.

Figure 1 shows in cross section a vertical mine shaft [0 in which an elevator cage or skip H is lowered and raised by means of a cable l2 carried by the usual hoisting apparatus l3 at the mouth of the shaft.

Carried on the elevator is a radio frequency generator indicated generally by A in Fig. 1 and in the vicinity of the hoist operator's stand in a radio frequency receiver B, having a loud speaker I) for reproducing the signals transmitted from the elevator cage, as will be understood by reference to my prior Patent No. 2,248,825.

The oscillator circuit (see Fig. 2) may be of any preferred design and the one employed for illustrative purposes comprises a thermionic vacuum tube comprising the usual cathode l5, grid l6 and plate H, in circuit with other elements forming the input, output and feed back circuits fed with direct current from a main battery H3.

The input circuit of the tube comprises a fixed inductance l9, one terminal of which is in electrical connection with the elevator cage II, and thus with cable I2, and also is joined to the grid [6. The opposite end of inductance I9 is connected by wire 2| to one end of the secondary winding 22 of an iron core transformer 23 which is connected at its opposite extremity tothe-tubc plate [1. This winding is bridged by a bypass condenser 24.

Low voltage current for heating the cathode of the tube is supplied to one terminal of the cathode l5 from one pole of battery 18 via wire and extending from the other pole of the battery is a connection to the second terminal of the cathode which comprises wires 26 and 21 which lead through the signalling switch to a separate hand operated switch, generally designated by C in Fig. 4, to be later referred to more in detail.

The battery terminals are also connected to the ends of the coil forming the primary winding of transformer 23. In one of these leads indicated by 30 is an adjustable vibrator 3|, for controlling the tone of thesignal and in, the other, indicated by 32 is a switch D the contacts of which are position of the two switches, the signal switch being indicated by D and the cathode circuit switch by C. In this instance switch C is mounted rigidly on the inner end of the pull cord shaft H and its terminals are closed by a spring arm 10 the upper end of which projects over the open end of said shaft. A Bowden wire 12, extending through the latter and the pull cord, is attached at its upper end to spring 10 and at its lower end to a trigger l3 pivoted on the pull end handle 14 and normally held in an inoperative position by an expansible spring 15. In this arrangement of the parts it will be seen that when the operator grasps the handle 14 and closesthe trigger I3 normally open as are also the contacts of switch C.

The apparatus described above takes the place against it that the cathode circuit will be first closed through switch C to render the oscillator circuit active before he transmits a radio freof the more primitive signalling means originally employed in mine shafts consisting of a bell located at the mouth of the shaft and a bell cord or wire suspended in the shaft which an elevator operator would pull to signal the hoist operator. It is because of the general lack of skill of such operators that it has been found in practice desirable to retain a semblance in the operation of '"this newerapparatusto the original-method of transmitting signals that I retain the form of a pull cord due to the fact that all operators are 'familiar therewith. and no special directions or instructions are required in order to teach them;

the modus operandi of the signal mechanism per" se. To this end, therefore, I provide a pull cord 40 suspended from a tubular shaft 41 guided for 'vertical movement in an aperture in the bot- 1 tom 'ofithe case A containing the oscillator circuit. The shaft is (held in anormal retracted position, :'.as shown in'Figs. 2, 4 and 5, by a coil spring 42,

enclosed in a casing 43 and operating against a '"collarM which engages the: outer face of the bottom 'of case A, The'upper, or inner end of j'shaftAl has an outwardly flaring rim 45 which iwhenthe shaft is pulled downwardly serves to atdeiiect a spring arm '50 associated with switch'D for moving the switch plunger 5| to close the oscillator'circuit, as. shown in Fig. 5.

At the lower end of the. pull cord,40 is an opcrating handle 55. Thisis hollow and contains -1 the switch C whichhas terminals for the cathode wires 26, 21 which are led through the top of the hollow shaft 4| and the tubular pull cord.

I deem it important that whatever means is employed for closing the cathode circuit. that the arrangement be such that when the operator 1 grasps: the handle 21that swtich C be immediately 1., closed and retained closed during the dispatching "I of signal impulses. This calls therefore for a special construction of they handle. andthe provision of a lag or delayed action in the closing of the signal circuit at switch D. The delayed action is ac- .;complished by, providing a short travel in. the movement of shaft 4 lbefore its flange 45 engages I switch spring 50.

ofconstruction .of handlefl-I have shown it pro- .tvided on one edge with a sinuous grip portion Bil As an example of one form for engagement by the operators fingers. Ex-

quency impulse by a downward movement of the ull cord to close the signal transmitting circuit through switch D.

In the structures described it will be observed that in a single instrumentality I have provided means for conserving the life of both the battery and the thermionic vacuum tube and assuring that an operator observe the necessary sequence in operation in rendering operativetwo difierent circuits with a delayed operation of one of them. Moreover, following the act of readying thetwo circuits the one which must be first closed is maintained closed while the second is opened and closed for signalling purposes and is finallyopened upon discontinuing the. signals. It .willbe further noted that the described sequence in operation of the two circuits is accomplished. automatically and without the exercise of skill on the part ofthe operator.

I claim:

1. In mine shaftisignalling,apparatus embodying a radio frequency oscillator comprisinga thermionic vacuum tube havinga cathodeprovided with a heating circuit, associated input and output circuits for generatin signal impulses and a source of battery current supply for said circuits, a longitudinally, movable spring biased member having an operating handle, a trigger thereon adapted to be operated when the handle is grasped, a switch in the cathode circuit controlled by movement ofthetrigger, and a switch controlling the other circuits for the dispatch of signals arranged to be actuated upon the, longitudinal movement of said, memberagainst said bias subsequent to the closure of. the first mentioned switch.

2. A signal device for mine shafts comprising a radio frequency oscillation generator including a vacuum tube having a cathode, associated input and output circuits forgenerating signal-impulses and a source of battery current supply for said circuits, a cathode heating circuit, afswitch connected in said cathode heating circuit, alongitudinally movable spring biased member having an operating handle, said operating-hand1e in eluding a Bowden Wire extending through said longitudinal member and adapted-to actuatesaid switch when the handle is grasped,- a second switch, said second switch being connectedin said output circuit, said longitudinalmember upon its longitudinal movement againstsaid; bias actuating said second switch into circuit closing postion.

3. A signal device for-mine shafts comprising a radio frequency oscillation generator including a vacuum tube having a cathode, associatedinput and output circuits for generating,JSl nalZ; im

pulses and a' source of'battery current supply for 5 6 said circuits, acathode heating circuit, a switch REFERENCES CITED connected in said cathode heating circuit,alongi- The following references are of record in the tudinally movable spring biased member having me of this patent: an operating handle, said operating handle havin said switch mounted thereon and a spring UNITED STATES PATENTS biased trigger adapted to actuate the switch when Number Name Date the handle is grasped, a second switch, said sec- 857,797 Euker June 25, 1907 and switch being connected in said output circuit, 2,073,701 Lazzarini Mar. 16, 1937 said longitudinal member upon its longitudinal FOREIGN PATENTS movement against said spring bias actuating said is second switch into circuit closing position. Number Country Date RICHMOND L. RUTHERFORD. 487,385 Germany Nov. 21, 1929

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