US2272972A - Safety switch - Google Patents

Description

3 Sheets-Sheet 1 INVENTOR ATTORNEYS Feb. l0, 1942. M. HERMAN SAFETY SWITCH Filed Feb.` 26, 1940 WITNESS. ff ff/ Feb. 10, 1942. M. HERMAN 2,272,972

SAFETY SWITCH' Filed Feb. 26, 1940 3 Sheets-Sheet 2 INVENTOR 'n ATTORNEYS M. HERMAN SAFETY SWITCH Feb. 10, 1942.

Filed Feb. 26, 1940 3 Sheets-Sheet 5 INVENTOR ATTORNEYS Patented Feb. 10, 1942 UNETED STATES PATENT OFFICE SAFETY SWITCH Martin Herman, Drumheller, Alberta, Canada Application February 26, 1940, Serial No. 320,949

(Cl. 20G- 50) 4 Claims.

This invention relates generally to electrical switches and especially is concerned with the novel switching device useful in connecting trailing cables to electrical devices or sources of current supply.

In the use of portable electrical equipment it is frequently desirable to use the equipment in a locality remote with respect to the source of current supply whereby it becomes necessary to' connect the device with the current supply by means of a ex'ible trailing cable. For instance in coal mines or the like the occasion frequently arises that a machine is to be used upon a track spur which is not electrified with the result that means must be provided for connecting the machine with the electrified portion of the track. In making this connection it is important to avoid tensioning of the cable to a degree such that the cable is pulled from connection with the power supply since, with devices now in use, arcs might be so produced as to cause detonation of combustible gaseous mixtures in the mine or otherwise to cause damage. A need has been feit therefore for means facilitating connection of a trailing cable with a power supply whereby possibility of arcing in the manner mentioned is prevented without so attaching the cable to the power supply as to preclude disengagement when the cable is tensioned.

It is an object of the present invention to satisfy this industrial want by providing a novel means for connecting a cable end plug with a power supply in a manner such that attempted disengagement of the plug causes interruption of the connection with the power supply in a man- Iva novel switching means for connecting a cable 'f' end plug with a power source which is in oper*- able condition solely when the cable and plug is received in a receptacle provided for the purpose but which can control connection and disconnection at will of the cable end to the power source while the plug is so positioned.

An advantage of the novel electrical switching device according to this invention over other devices now in use is that the contact elements of the switch are submersed in an essentially incombustible or at least not readily combustible luid material of high dielectric strength which quenches arcs likely to form between the contact terminals of the switch when the switch is operated whereby possibility of ignition of surrounding combustible gaseous materials during operation of the switch is substantially preeluded.

Another advantage of the novel safety switch according to this invention is that when the cable end plug is withdrawn from the receptacle provided for the same the switch functions automatically to interrupt passage of current from the supply to the receptacle and when so interrupted the switch is not movable into closed position in the proper manner except when the plug is returned to position within the receptacle.

A feature of the novel electric switch according to this invention is its simplicity and ruggedness of construction, the former serving to minimize cost of manufacture by suiting the device to the requirements of mass production and the latter assuring long useful life with minimum necessity for repair.

Other objects, advantages and features of the new and improved safety switch according to the present invention will be apparent to those skilled in this art during the course of the following description.

Regarded in certain of its broader aspects, the present invention comprises in combination with an electrical switch of the type comprising a casing within which is mounted a set of switch elements electrically connectable through a plug receptacle to a plug and a freely rotatable shaft carrying rigid switch arms which is, upon occasion, arcuately swingable whereby the arms make contact with the switch elements although the arms are normally spring-urged out of contacting position, of means functioning solely when the plug is in the receptacle for holding the switch arms in position making contact with the switch elements. f

In order to facilitate a fuller and more complete understanding of the present invention a specific embodiment thereof herein illustrated will be hereinafter described, it being clearly understood, however, that the illustrated embodiment, although present preferred, is provided solely by way of example of the practice of this invention and not by way of limitation thereof except insofar as the invention is recited in the subjoined claims.

Referring then to the drawings,

Figure l is substantially a vertical sectional view of the presently preferred embodiment of this invention showing the cable end in engaged position and the switch closed,

Fig. 2 is substantially a vertical sectional View of the presently preferred embodiment of this invention showing the cable end in position and the switch opened,

Fig. 3 is substantially a Vertical sectional view of the presently preferred embodiment of this invention showing the cable end in disengaged position and the switch opened,

Fig. 4 is substantially a front elevational view of the switch illustrated in Fig. 1 with the cable end removed,

Fig. 5 is substantially an oblique cross sectional view of the cable and receiving members,

Fig. 6 is substantially a top plan view of the cable end plug,

Fig. 'I is substantially a cross-sectional View of Fig. 3 taken along the line 1 1 thereof,

Fig. 8 is substantially a. cross-sectional View of Fig. 3 taken along the line 8 8 thereof,

Fig. 9 is substantially an end view of the blocks forming part of the plug receptacle,

Fig. 10 is substantiallya detail vertical sectional view of the oil chamber filling means and closure for same,

Fig. 11 is substantially a diagrammatic illustration of electrical circuits within the switch when connected to a direct current source and feeding a three wire cable,

Fig. 12 is substantially a diagrammatic illustration of electrical circuits within the switch when connected to an alternating current source and feeding a four wire cable,

Fig. 13 is substantially a cross-sectional view of Fig. 4 taken along the line |3-l3 thereof,

Fig. 14 is substantially a cross-sectional view of Fig. 2 taken along the line |4-I4 thereof, and

Fig. 15 is substantially a cross-sectional View of Fig. 2 taken along the line I5--l5 thereof.

The illustrated preferred embodiment of this invention generally designated by the reference character comprises, it will be noted, box-like casing member 2| operable upon brackets 22 fixed to the back face thereof having a removable front 23 connected thereto by appropriate fastening means such as the screws 24 received within openings formed in anged edge portions of the front and of the casing proper 2 I. The bottom part 25 of the casing attached to the top portion by bolts 25a is seamless or at least fluid tight in construction and serves as a sump for receiving a fluid dielectric 26, the level of which within the sump is viewed through an indicator glass generally designated by the reference character 21. As will be apparent from an inspection of Fig. 13, the indicator glass is held behind a vertically eX- tending opening 29 formed in the front of the sump 25 behind which is positioned a transparent slip of material 3U, preferably mica or the like, held in place by mounting means 3| attached to the sump side by bolts 32 essentially as is illustrated, The sump is interiorly subdivided by partitions 33 which, although fitting to a close degree of proximity against the walls of the sump, nevertheless are spaced therefrom to a degree such as to permit the flood of high dielectric strength to pass from one subdivision of the sumn interior to another whereby the level of liquid observable through the transparent slip is a level common throughout the sump. An upwardly extending elbow 34 communicates with the interior of the sump 25 and is provided for facilitating the filling of same with a fluid dielectric. The

distal end of the elbow 34 is tapped to receive a plug closure 35 for sealing the inlet.

A cross piece formed of electrically insulative material and extending transversely within the casing 2| superjacent the sump 25 is rigidly connected to the casing sides and carries a plurality of stationary downwardly extending switch elements 4| and 42 attached thereto by bolts 43 and 44 respectively. It is to be noted that the stationary arms 4| and 42 each comprise the arm proper and an auxiliary conductor member designated by the reference character 45 in Figs. 1, 2 and 3 wherein this detail is best illustrated, the conductor member serving to assure contact between the terminal member 46 carried on the end of the arm and the conductor terminal member 4T connected to the bolt by which the switch element is mounted on the cross piece.

Leads 48 and 49 connected to the stationary switch elements 4| and 42 respectively and a lead 50 are connected respectively to sockets 5|, 52 and 53 held between the split sections 54 and 55 of an insulative block, the block sections being fastened together by registry pins 56.

Referring particularly to Figs. l, 2, 3 and 5, it will be noticed that the socket 53 is provided with a shoulder 53a which facilitates holding the socket in position between the split block sections. In like manner the sockets 5| and 52 are provided with shoulders 5|a and 52a respectively. The block is formed of suitable electrically insulative material such as rubber, either soft or hard, molded phenolic resin or the like. A face plate 5l attached to the split block sections by screws 58 is provided with openings registerable with the open ends of the sockets 5|, 52 and 53 and this face plate too is formed of insulative material for the purpose of preventing accidental shorting of the sockets by a piece of material placed across the front of the blocks.

The assembly comprising the split sections 54 and 55 and the sockets 5I, 52 and 53 is received within a receptacle member 6|) rigidly attached to portions of the casing front 23 and slanting outwardly downwardly whereby the open ends of the sockets point in a downward direction substantially as shown. A guide trough 6I is provided beneath the outer bottom portion of the receptacle member to facilitate guiding a plug generally designated by the reference character 62 therein.

The plug generally designated by the reference character 62 is best illustrated in Fig. 6 and, it will be noted, comprises a pair of split sections 63 and 64 united by fastening means 65. The cable B6 is connected within the plug which is of course formed of electrically insulative material to outwardly extending prongs 61, 68 and 59, which prongs are registerable with and receivable within the sockets 52, 53 and 5| respectively hereinabove described, whereby electrical circuit is completed from the lines of the cable S6 to the stationary switch elements 4| and 42 and the grounded line 50. A cam 10 mounted upon the top of plug 62 by bolts 1| extending therethrough is curved upwardly and backwardly from the face of the plug and serves to operate portions of the switch mechanism in a manner now to be described. It should be noted that the bottom of the plug is attened and is received upon the receptacle guide member 6I in a manner such that the plug can not be inserted within the receptacle except when the cam member 10 is uppermost.

An arm '15 freely swingingly mounted upon a transversely extending pivot member 16 is provided with a relatively elongate end portion 15a projecting outwardly through an opening in the casing front 23 terminates in a freely rotating cam rider 11 engageable with the. cam 10 carried upon the plug 62 when the last mentioned is inserted within the receptacle as hereinabove described. The cam rider is urged into engagement with the cam by spring tensioning means 18 which connect a cross piece 19 Within the casing and an extension 15b of the member 15. A series of freely sliding strips 8B held within a sheath 8| attached to the casing front 23 serve to embrace the extension 15a of the member 15 whereby a substantially tight fitting is assured although free movement. of the member is permitted.

A transversely extending bar 85 formed of electrically insulative material is freely rotatably mounted upon trunnion pins 8E and 85a. carried in standards 81 within the casing substantially as shown. The trunnion 86a is extended outwardly through the casing 2| and is keyed both to the insulative bar 85 and to a handle 83, the motion of which is limited by the stop 30 whereby the bar can be swung through a limited arc for purposes hereinafter to be described. Downwardly extending switch arms 92 and 33 are mounted upon the swingable bar 85 in a manner such that contact elements 94 and 35 carried on the ends thereof register with and make electrical contact with corresponding portions of the switch elements 4| and 42 hereinabove described. The switch arms 32 and 93 are connected by cables 95 and 91 respectively passing through a gas tight outlet generally designated by the reference character 93 with the current supply. As will be apparent from the foregoing, oscillation of the bar 85 by means of the handle 89 can cause the making and breaking of contact between the switch arms and the switch elements whereby circuit is completed and interrupted between the power supply and the sockets wherein the plug prongs are received.

The switch arms normally are urged from contact with the switch elements by spring tensioning means |33 connecting brackets llil mounted upon the bar 35 with connector links |02 attached to the pivot member 16.

An inverted V-shaped finger |35 upwardly extending from and rigidly mounted upon a bar 85 engages with an extension arm |06 integrally formed of a portion of the member 15 and having a lock portion |51 engaging with the cross member i438 of the finger substantially as shown in Figs. l to 3 inclusive of the drawings. As will be evident to those skilled in this art, counter clockwise movement of the bar B whereby the cross piece |23 of the nger |55 moves along the top part of the extension arm |26 and lock |01 will cause the cross piece to be received behind the lock portion and due to action of the spring tensioning means 13 will cause inhibition of clockwise motion of the bar B5 except when the plug 62 is in position within the receptacle raising the rider carrying extension 15a by means of the cam 1U.

A swinging latch element lill mounted upon the portion 15b of the member 15 is swingable by means of an arm |i| pivoted on the transversely extending shaft la connected with the latch by Tf the link l2, the arm being operable by means of a plunger ||3 received in a bushing lill mounted in the top portion 2|a of the casing 2|. It is to be noted that the plunger H3 terminates in a handle ||3a for facilitating operation thereof.

The arm normally is urged in a clockwise direction by spring tensioning means ||5 whereby the latch element |||l is pressed downwardly in a manner such that when the extension 15a of the member 15 is raised by engagement of the cam 10' with the rider 11 and the bar 35 is rotated in a clockwise direction by means of the handle 89, the latch element ||0 will dispose itself in obstructing position before the cross piece |33 of the V-shaped finger |05 substantially as shown in Fig. l. When the parts are so positioned it will be noticed that circuit is completed between the lines connected to the power supply and the cable 66 connected to the plug |52. If it is desirable to cause disengag-ement of the latch and finger cross piece whereby the switch arms are moved iout of contact with the switch elements, the plunger ||3 is depressed in the manner illustrated in Fig. 2 whereby the latch element lil is raised and the finger cross piece |53 is permitted to move in a counter-clockwise direction under action of the spring tensioning means When the plug 6,2 is withdrawn for the receptacle 3i the cam rider 11 travelling down the face of the cam 10 permits swinging of the member 15 by action of the spring tensioning means 'lil whereby the latch element ||ll is raised and the finger cross piece |58 moved by action of the spring tensioning means |00 disposes itself in engaged position behind the lock |01 carriedv on the inember 15. As will be apparent from the foregoing the switch can be manually operated in the intended manner only when the plug is in the receptacle.

In ythe event that heating of the dielectric liquid 26 necessitates free outlet for gaseous materials from the interior of the casing, a self quenching outlet generally designated by the reference character |23 is provided in the top portion of the casing substantially as shown.

The hereinabove described safety switching means can be used in a three line input circuit such as is conventionally used for carrying alternating current by providing three swinging switch arms |30, |3| and |32 connected tothe lines |33, |34 and |35 essentially as is shown in Fig. 12. Stationary switch elements |35, |31 and |38 mounted upon insulative posts |39, |40 and |4| serve to make Contact upon occasion with the switch arms and are connected with sockets |42, |43 and |44 by lines |45, |46 and |41 respectively. A fourth socket |50 is connected to the grounded casing |5| of the switch assembly by a line |52. The plug generally designated by the reference character |50 comprises four lines IGI, |62, |63 and |64 connected to prongs |55, |66, |51 and |68 respectively receivable within the sockets |42, |50, |43 and |44 in a manner analogous to that described in connection with the rst illustrated embodiment of this invention.

It is to be understood that this invention is capable of extended application and is not conlined to the precise illustrated forms nor described construction and, therefore, such changes and modifications may be made therein as do not affect the spirit of the invention nor exceed the scope of the appended claims.

Having thus described the present invention, What it is desired to secure by Letters Patent is:

l. In combination with an electrical switch of the type comprising a casing within which is mounted a set of switch elements electrically connectable through a plug receptacle to a plug, and a freely rotatable shaft carrying rigid switch arms which is, upon occasion, arcuately swingable whereby the arms may contact with the switch elements although the arms are normally spring urged out of contacting position; of the improved means, functioning solely when the plug is in the receptacle, for holding the switch arms in a position making contact with the switch elements, which comprise: a finger, rigidly mounted on the shaft; a cam on the plug; a freely swingably mounted member having an end portion adapted to overlie the plug when in the receptacle and engage with the cam whereby insertion of the plug in the receptacle causes swinging of the member; means on the member for engaging with and holding the finger when the plug is in the receptacle; and control means whereby the nger can be disengaged permitting the spring urged switch arms to move from contact with the switch elements.

2. In combination with an electrical switch of the type comprising a casing within which is mounted a set of switch elements electrically connectable through a plug receptacle to a plug, and a freely rotatable shaft carrying rigid switch arms which is, upon occasion, arcuately swingable whereby the arms make contact with the switch elements although the arms are normally spring-urged out of contacting position; of the improved means, functioning solely when the plug is in the receptacle, for holding the switch arms in a position making contact with the switch elements, which comprises: a finger, rigidly mounted on the shaft; a cam mounted on the plug; a freely swingably mounted member having an end portion adapted to overlie the plug when in the receptacle and engage with the cam whereby insertion of the plug in the receptacle causes swinging of the member; an oscillating latch carried on the member for engaging with and holding the finger when the plug is in the receptacle; and control means for oscillating the latch whereby the finger can be disengaged therefrom permitting the spring urged switch arms to move from contact with the switch elements.

3. In combination with an electrical switch of the type comprising a casing Within which is mounted a set of switch elements electrically connectable through a plug receptacle to a plug, and a freely rotatable shaft carrying rigid switch arms which is, upon occasion, arcuately swingable whereby the arms make contact with the switch elements although the arms are normally spring-urged out of contacting position; of the improved means, functioning solely when the plug is in the receptacle, for holding the switch arms in a position making contact with the switch elements, which comprises: a nger, rigidly mounted on the shaft; a cam mounted on the plug; a freely swingable mounted member having an end portion adapted to overlie the plug when in the receptacle and engage with the cam whereby insertion of the plug in the receptacle causes swinging of the member; an oscillating latch carried on the member for engaging with and holding the finger when the plug is in the receptacle; and control means for oscillating the latch whereby the finger can be disengaged therefrom permitting the spring urged switch arms to move from contact with the switch elements; the control means comprising an upwardly spring-urged reciprocable plunger; a lever connected to the plunger and oscillatable thereby, and a linkconnecting the lever and the latch whereby the latch can be raised from fingerengaging position irrespective of the position occupied by the swinging member.

4. In combination with an electrical switch of the type, comprising a casing, a switch element electrically connected through a plug in the casing, a socket for receiving a plug, a switch arm rigidly supported in the casing and having a contact point at its lower end, a fluid tank receiving said arm, a pivoted switch arm having a Contact submerged in the fluid of the tank, means for normally holding the contact points separated, means for moving the points in contact with each other, a latch for locking said means, an arm carried by the latch and extending through the casing and engaged by a plug inserted in a socket connecting the circuits of the switch arms, means carried by the arm for i releasing the latch, whereby the switch can be manually operated.

MARTIN HERMAN.

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