US2735992A

US2735992A - bailey

Info

Publication number: US2735992A
Authority: US
Publication date: 1956-02-21
Anticipated expiration: 1973-02-21

Description

Feb. 21, 1956 N. l. BAILEY SWIVEL COUPLINGS WITH MAGNET CONTROLLED LOCK Filed May 12, 1951 2 Sheets-Sheet l FIG. I.

"X(/ 64\1X,' 5756 4/ 5,2550 2 37 INVENTORV:

\ /4 NORMAN l. BAILEY flaw/4 Zimm- ATTORNEY Feb. 21, 1956 1, BAlLEY 2,735,992

SWIVEL COUPLINGS WITH MAGNET CONTROLLED LOCK Filed May 12, 1951 2 Sheets-Sheet 2 FIG. 7.

7 7% V as FIG 9 FIG 8. //5 66 av ,//0 //0/ (9 m0 /00 I /0 J2 M mm! mm mm llHlv INVENTORZ NORMAN l. BAILEY ATTORNEY United States Patent SWIVEL COUPLINGS WITH MAGNET CONTROLLED LOCK Norman I. Bailey, Kirkwood, Mo., assignor to :loy Manufacturing Company, Pittsburgh, =Pa., a corporation of Pennsylvania Application May 12, 1951, SerialNo..226,05.5 8 Claims. ((1339-91) This invention relates to electrical cable connectors and particularly to connectors of the so-called swivel coupling type.

Swivel couplings, in a well-known form, include molded rubber connectors provided with pin and socket elements adapted to be engaged with each other to establish circuitsone or more, dependent on the number of pin and socket elements, and they are equipped with threaded metal collars, sleeves or couplings which 'prevent accidental disconnection and which, through relative rotation, effect relative longitudinal movement between the pin and socket elements. The pin and'socket elements may be variously arranged on the cooperating connectors, and so from time to time herein the term plug-socket will be used as a generic designation of a connector element having only pin elements, one having only socket elements, and one having both types of ele ments thereon. It may also be noted that plug-socket contacts may be either of power, ground, or pilot type depending upon the circuits of which they form parts. The metal collars, sleeves or'couplings are supported for relative rotation, and either or both of a cooperating pair may be rotatably mounted on its connector; and these sleeves are often supported by ball bearings arranged on metal collars at the periphery of oneor both of the molded rubber couplings; and the sleeves respectively carry external and internal threads which may be readily engaged and disengaged by relative rotation.

The current flowing in the power circuit or circuits established by such connectors is frequently substantial, and it is unsafe to have such circuits broken by the separation of the pin and socket elementsfrom each other while there is current flowing in the conductors which are connected by such elements.

It has been proposed to provide such couplings with magnetically releasable locks, and to provideforemen, or other especially reliable supervisory personnel, with appropriate magnets, and by requiring these men .to turn ofl. all current in the circuits in which the couplings are included before releasing the locks by the use of their magnets, to insure against accidents at the couplings. Such magnetically controlled, latch equipped couplings are disclosed in one form in an application of Reimer G. Gehlsen, Serial No. 125,758, filed November 5, 1949, for Magnet Controlled Connectors, now abandoned, and replaced by continuation application, Serial No. 339,125, filed February 26, 1953. In another form they are disclosed in an application of James H. Sirnpson, Serial No. 126,389, filed November 9, 1949, for Connector with Magnetically Controlled Lock, now abandoned, and replaced by continuation-impart application, Serial No. 367,283, filed July 10, 1953, now matured into Patent No. 2,688,736, dated September 7, 1954.

Objects of the present invention are to provide an improved releasable connector-locking means. Another object is to provide an improved locking means of the character mentioned in which the latch-shallprornptly become 2 effective, in most degrees of overlap of the couplings, on removal of the magnet. A further object'is to provide an improved magnetically controlled lock which shall, through its arrangement, provide an improved ratio of strength to sleeve rotating force. Still another object of Y the invention is to provide an improved enclosed magnetically controlled latch having improved positioning means for the magnet which shall not only facilitate proper location (or application) of the magnet, but aid 'in its maintenance in latch releasing position. Yet a further object is to provide an improved magnetically releasable connector-locking means constructed and arranged 'to hold the control magnet securely in position when in use and with minimum projection of the magnet when so positioned. Still another object is to provide an improved magnetically controlled swivel coupling.

Other objects and advantages of the invention will hereinafter more fully appear.

In the accompanying drawings, in which for purposes of illustration one embodiment of the invention is shown:

Fig. 1 is a view partially in longitudinal axial section and with certain parts shown in elevation and others broken away, the section beingtaken on the plane of the line 1-1 of Fig. 2.

Fig. 2 is a transverse section on the plane of the line 22 of Fig. 1.

Fig. 3 is a detail longitudinal section on the plane of the section line 3-3 of'Fig. 1.

Fig. 4 is a fragmentary sectional view of parts shown in Fig. 1, showing the lock in releasedposition.

Fig. 5 is a fragmentary peripheral viewof a portion of the internal coupling sleeve and adjacent parts, showing one groove with which a locking tongue cooperates in the locking of the parts together.

Fig. 6 is a fragmentary peripheral view of a portion of the latch or lock-carrying connector sleeve showing a magnet positioning or locating device.

Fig. 7 is a view, partially in longitudinal section, on the planes of the section line 77 of Fig. '8, showing another embodiment of the invention.

Fig. 8 is a transverse sectional view on the plane of the section line 8-8 of Fig. 7.

Fig. 9is a fragmentary peripheral view of a portion of the external coupling sleeve showing the magnet mounted on it in lock releasing position.

Fig. 10 is a transverse sectional view, on a reduced scale, on the plane of the line 10-10 of Fig. 7.

Fig. 11 is a transverse sectional view, on the same scale as Fig. 10, taken on the plane of the section line 11- 11 of Fig. 7.

Fig. 12 is a perspective view of a magnet for use with connectors constructed as shown in Figs. 7 to 11.

Referring now to the drawings, and initially particularly to Fig. 1, it will be observed that there is shown in this figure a pair of connector plug members 1 and 2, each formed of a suitable dielectric material such as molded rubber, and provided with mutually

opposite faces

3 and 4, having annular ridge

type water seals

5, 5.

Each of the plug members land 2 is provided, in the structure shown, with at least one connector pin element 7, the pin element shown on the plug member 1 being designated 71, and the plug member 2 being shown as having two pin elements '72, 72. Each of theplug members 1 and 2 alsohas at least onesocket element 8 adapted to receive a pin element, there being, as shown, two

socket elements

81, 81 on the plug member 1, and one, 82, on the plug member 2. Projecting sleeve portions 9 surround each of the pin elements, and recesses 10 are formed to receive these sleeve portions. These provide an additional sealin and also assist'in centering the plugmembers 1,.2. Each of the plug members 1, 2 is provided with an annular ball seat providing member 12, each of the members 12 providing a circumferential groove 13 in which a series of bearing balls 14 is received and guided. The ball seat-providing members are desirably metallic, and they may, if desired, be molded in position on the plugs. Suitable conductors are connected to the plug and socket elements, two of these being shown at 15. The plugs l and 2 are carried at the adjacent ends of cable sections, not illustrated, being vulcanized, desirably, to the latter.

Each of the plug member 1 and 2 is surrounded by a coupling sleeve, the one associated with the plug member 1 being designated 21 and the one connected with the plug member 2 being designated 22. These sleeves or collars are desirably of bronze, brass or other non-magnetic material. These have internal circular grooves 23 formed in them, these grooves being wider than the grooves 13 and cooperating with the series of balls 14 and providing for a limited degree of free relative longitudinal movement of the

sleeves

21 and 22 with respect to their associated plug members i and 2. A suitable flexible rubber or the like annular shield 25 is adapted to extend over the joint between the

sleeves

21 and 22 and is mounted in suitable longitudinal relation to the coupling sleeve 21 by means of an internal groove 26 and a projecting annular portion 27 formed on the coupling sleeve 21. An annular portion 2?; of reduced thickness is so arranged on the sleeve 21 as to provide an annular recess 29 in which the coupling portion of the coupling sleeve member 22 is receivable. A

groove and lug connection 30 connects the shield 25 in non-rotative relation to the sleeve 21. The adjacent ends of the

sleeve members

21 and 22 are each threaded. The adjacent end of the sleeve 21, designated for easy identification 31, is externally threaded as at 32 for a substantial length from its free end. The member 25 protects the threads 32, it may be noted, when the connector is disassembled. The outer end portion 33 of the coupling sleeves 22 is internally threaded as at 34, and the two sets of threads are adapted to draw the parts together and secure them in connected relation, and the threads may be readily connected and released because the coupling sleeves are freely rotatable on the connector plugs and have, to aid in turning them, indentations 36 and 37-the former a part of the connection 36 above mentionedformed around their peripheries so that they may be easily grasped either manually or by wrench. The threaded connection is shown as of the fire hydrant type.

The threaded portion 31 of the coupling sleeve 21 may be provided with one or more longitudinally extending peripheral recesses, one being shown, in the form of a parallel sided groove, at 41; and a diametrically opposite groove being shown at 42. If it should be desired to insure effective engagement of the lock with shorter arcs of rotation additional slots may be provided.

The coupling sleeve 22 has a recess 59 milled or otherwise suitably formed in it and adapted to receive a lock element or latch strip 51. The

sleeves

21 and 22 are, as above noted, of non-magnetic material. The latch member is desirably made of magnetic material so that it may be attracted and drawn outwardly by a magnet applied adjacent point X on the periphery of the coupling sleeve 22. A non-magnetic strip with an iron or steel armature attached could be used. The latch 51 is shown as held in position by a radially extending pin 52, desirably of brass or the like, and having an upper head 53 securing it in position and a lower head 54 supporting the latch element 51, an opening 55 in which receives the body of the pin. A smaller spacer sleeve 56 surrounds the pin 52 and serves as a spring support, and a non-magnetic spring, as for example a spring-bronze spring element 58, may also surround the pin and act on the latch element 51. The latch element is bent as at 59 so that its free portion may be moved between the inclined position shown in Fig. 1 in which it engages in the recess 41, and the position shown in Fig. 4, in which it lies against the radially outer wall of the recess St). A headed pin 60 is carried by the member 22, and extends through an opening 61 in the latch strip 51, and keeps the latter from moving too far inward when the coupling is disconnected.

The peripheral wall of the sleeve 22 is provided with a magnet guiding and positioning element 64, which in the construction shown overlies the pin 65 As best seen in Figs. 1, 4 and 6 this element is made in cross section with a downward taper, so that the poles of a horseshoe magnet may interlock with it when such a magnet of appropriate size is moved in a direction tangential to the sleeve 22 onto it. The element 64 is rounded at one end, as at 65, to guide, so to speak, the magnet onto it. Its other end has a cross portion 66 whose legs 67 serve as stops to position the magnet directly over the latch 51 when the side of the magnet is against the legs. A magnet of the horseshoe type is indicated a M, and its pole pieces at Mn and M5. Spaces beneath the ends of the element 64 may be avoided by making its concave on its lower side, by seating its bottom on a flat in the sleeve 22, or by filling in beneath its ends, if it be of flat strip and be not set down in a slot, with solder or the like. The magnet may desirably be made of an alloy like Alnico. If a wound magnet is used the magnet positioning element 64 may be omitted.

The mode of operation of this illustrative embodiment of the invention will be readily understood. Let it be imagined that the coupling is in connection-establishing use, and that it is desired to disconnect its parts from each other. This cannot be done by anyone not provided with a magnet of suitable strength. A trusted employee who may be relied on to do his job correctly and infallibly will open the circuit at such a point as to render the conductors, to which the pin and socket elements '7 and 8 are electrically connected, dead. He will then take a suitable magnet M and place it against the coupjng sleeve 22 in such relation to the latch 5'1 as to lift the latter. This will be done by moving the poles Mn and Ms along the element 64 and up against the shoulders 67, 67. This will raise the latch element 51 out of engagement with the side walls of the recess 41, and it will then be possible to unscrew the coupling sleeve 21 from the coupling sleeve 22 and thus to separate the pin and

socket elements

7, 8. During this separative movement it will be necessary that the magnet-held latch 51 be retracted. it would be practicable, were it desired, to make the sleeve 22 non-rotatable with respect to the plug 2, but the magnet strength is such that the sleeve 22 can be turned without causing the magnet to drop ofi, both because of the strength of its attraction and because of the interlock, so to speak, between the magnet and the element 6a.

For the coupling to be reconnected, it is necessary that the magnet maintain the latch retracted within the socket 50, for otherwise it would drop into one or the other of the

slots

41, 42 before a connection was completely made.

it will be evident that by the use of t. e structure described, neither the connection nor the disconnection of the coupling will be possible without the holding of the latch retracted by a magnet as above described. By confining the possession of suitable magnets to duly responsible personnel a very safe system can be assured. It will be particularly noted that the abutment of the latch 51 with the side walls of the recess *1 or 42 is in a very efiective manner. Relative rotation of the sleeves is prevented by a locking action directly transverse to the direction of relative rotation. Thus even the use of wrenches on the sleeves is unlikely to cause difficulty. The locking action extends over a relatively great length. Locking occurs at substantially any degree of mutual overlap of the sleeves if the magnet is removed. Location of the magnet is not only facilitated, but need to rely wholly on its own strength to hold it in latch withdrawing position .is avoided. ,At thejsame time, additional equipment and expense and the additional complicationof pil'ot control safety switches maybe avoided. It will be evident that the construction is'strong,;fully protected from accidental injury, durable and effective.

Another embodiment of the invention is illustrated in Figs. 7 to 12. .In this embodiment, the two

connector elements

71 and 72 each have a body portion, the body portion'of the connector element 71 being designated 73 and that of the connector element 72 being designated 74. These bodies may be formed of any suitable insulatin material. Rubber is a suitable material, as is also neoprene; and the contacts forming parts of the connectors are molded in thematerial of the bodies in a well-known manner.

Each of the connector elements, as illustrated, carries three contact elements. Connector elements 71 carries one plug connector 75 and two socket connectors 76, while .connector element 72 carries two plug connectors 75 and one socket connector 76, all of said contacts connected to power conductors (not shown), but obviously this arrangement is but illustrative of many which may be employed. The power conductors associated with each connector element may be embodied in a single cable in a well-known manner. Fig. 8 shows the socket contact 76 upon the connector element 72, the two plug contacts 75 upon thatconnector element, and the plug contact 75 projectingfrom the connector element 71.

7 As in the first embodiment, an enclosure is provided for all of the contacts. This enclosure is provided by a pair of screw collars orsleeves Hand 82 of non-magnetic material,one on each of the

complementary connector elements

71 and 72. The collar 81 is arranged 'to be rotatable on the body 73 and is secured in place by a ball bearing comprising balls 83 arranged to run in a groove 84 in a metalcollar 85 providing a ball race for the bearing and molded into the connector body 73. The collar or sleeve 82 is herein similarly mounted on the connector body 74. Eachcollar or sleeve member has a relatively thicker portion 86 in which a groove 87 substantially wider than .the diameter of the balls 83 is formed, the grooves87 receiving the balls and, due to their width, permitting a certain amount of endwise movement of the collars or sleeves relative to the bodies with which they are respectively associated. The fit between the sleeves .and the collars is a close one and of substantial length, so. that a flame-proof relation is assured. The collar or. sleeve 82 has a generally cylindrical portion 92 of larger internal diameter than the portion 86, and has a counterbore 93, and, outwardly of the counterbore, an elongated threaded portion 94, the threads 95 upon which are adapted to cooperate with external threads 96 upon theouter portion of thecollar or sleeve 81.

It will be evident that the

connector elements

71 and 72 may be drawn together .to establish the relation of the parts shown in Fig. '7, vor may be separated, by relative rotation between the

collars

81 and 82. In view of the plug-socket connections,if rotation between both collars or sleeves and their supporting bodies is prevented, neither fullconnection of the sleeves or collars when they are .not fully-connected, :nor disconnection when they are connected, will be possible.

To prevent such relative rotation except when provision therefor is deliberately made, there is provided a looking or latchingfarr'angement between each collar or sleeve and the body on which it ismounted. This, as shown .for purposes of illustration, includes a circumferentially'elongated latch body L, shown as laminated but capable of being formed from a single piece of metal, if desired. In the illustrative construction a plurality of laminae 1 are stamped to shape and are held together by one or more rivetelements 97, therivet element 97 herein being shown as securing to the latch structure a flexible spring element 98 having down-bent ears 99 at either side of the bundle of laminae and having projecting resilient collapsible ,PQrtions, .100 normally resiliently forciingthedatch element L,ra diallyinwa rdly ofa recess 101 formed in the associated sleeve or collar. The latch element L at its side toward the axis of the associated .connectorelement is ,formed With

arcuateportions

103 and 104 between which there is an inwardly projecting portion 105 which isreceivable, in one or anotherofa series of elongated parallel-walled recesses or notches 106 formed in theperiphery of the associated sleeve or collar. The recesses 106 have side walls 108 adapted relatively closely to fit the side walls 109 of the latch portion 105 when the latch is in radially inner position, thus to prevent material relative rotation, in the inner position of the latch, ,ofthe associated collar or sleeve relative to its supporting collar Y and the connector'element which it surrounds. The recesses106 are somewhat elongated in view of the range of free longitudinal movement ,of the collars or

sleeves

81 and 82, relative to the

connector element

71 and 72, provided by the widening of the ball receiving groove 87. r A suitable magnet M, shown as a permanent horseshoe magnet, is adapted to haveits opposite poles P 1 and PS applied to the periphery of the collar or sleeve 81 or to the periphery of the collar or sleeve 82, and, in order to insure the proper positioning of the Magnet M relative to the ,latch which is to be released so that the latter, which is of suitable material for attraction by the magnet, shall bedrawn outwardly by the magnet, magnet guide slots 110' and 110" are formed in the bosses or lugs..8 6 formed on the exterior of the collars or

sleeves

81 and 82 in a position and of such depth as to cause the magnet poles, which are secured in said guideslots, to overlie recess 101. It will be clear that if a magnet M of appropriate strength has its poles Pu and PS brought into the relation to the sleeve or collar 82 indicated in Figs. 7, 9 and II, the latchor lock will be drawn to releasing position, and then the collar or sleeve 82 may be rotated and the connector parts drawn together or separated as maybe-determined'by theirinitial relative position and;the direction of rotation of the sleeve or collar 82. The magnet will be made of suitable strength and will befirmlv .held, with minimum radial projection, with respect to the projection or boss 86 with which it is interfitted, wherefore it need not be manually held in position during coupling or uncouplingof the connector. The magnet M hasits poles Pm and Psarranged parallel to each other, and they are wider at one of the opposite faces of the magnet thangat the other, so that in ,efiect they may be said to dovetail with the correspondingly formed recesses, sockets or

slots

110 and 110", which are narrower at their outer sides than at their innermost portions. Moreover the longitudinal proportions of the magnet M are such that when the cross'poitionof the magnet approaches the end surface of the lugs or bosses '86, theends of the poles Willbe in most effective relation toth'elatch which they are to move outwardly. The magnet, when in use will, in distinction from the arrangement of the first embodiment described, lie flat against the-side of one of the sleeves or collars, and will not materially interfere with the application of turning forces to the sleeve orcollar which supports is. The collars or s1eeves'81 and 82 may be rotated relative to each other when eitherhas ,its associated latch liftedby the magnet, so a very convenient arrangement is provided.

As the described embodiments have many advantages in common, there is no occasion to recite the advantages implicit in both forms as a summary with respect to this second embodiment.

This application is a continuation-in-part of my application, Serial No. 126,402, filed November 9, 1949, and now abandoned.

While there are in this application specifically described two forms which the invention may assume in practice, it will be understood that these forms of the same are shown for purposes of illustration,,and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What is claimed is:

1. In a plug-socket connector, in combination, a pair of insulating bodies each carrying one or more power plug-socket contacts connectable with a power plugsocket contact on the other body, housing means for at least the mutually adjacent ends of said bodies comprising screw collars one on each of said bodies, said screw collars when screwed together and when unscrewed re spectively efiecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and means precluding inadvertent rotative movement between said screw collars including a magnetically releasable latch housed within one of said collars, and positioned for movement by a horseshoe type magnet applied to the exterior of said collar, said collar having upon its outer portion a magnet-positioning means for supporting the horseshoe magnet with one, of the side surfaces thereof parallel to the axes of said collars and preventing movement of said magnet away from said collar in a direction perpendicular to said side surface.

2. in a plug-socket connector, in combination, a pair of insulating bodies each carrying one or more power plug-socket contacts connectable with a power plugsocket contact on the other body, housing means for at least the mutually adjacent ends of said bodies comprising screw collars one on each of said bodies, said screw collars when screwed together and when unscrewed respectively effecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and means precluding inadvertent rotative movement between said screw collars including a magnetically releasable latch housed within one of said collars, and positioned for movement by a magnet applied to the exterior of said collar, said collar having a boss thereon having formed therein parallel sockets for receiving the poles of a magnet and holding the latter against movement out of said sockets in any direction except longitudinal of the latter.

3. In a plug-socket connector, in combination, a pair of insulating bodies each carrying one or more power plug-socket contacts connectable with a power plug socket contact on the other body, housing means for at least the mutually adjacent ends of said bodies comprising screw collars one on each of said bodies, said screw collars when screwed together and when unscrewed respectively eifecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and means precluding inadvertent rotative movement between said screw collars including a magnetically releasable latch housed within one of said collars, and positioned for movement by a magnet applied to the exterior of said collar, said collar having formed thereon means for holding a magnet thereto, independent of the magnetic force exerted by said magnet, in a position in which a surface of said magnet extending longitudinally of the latter is at least substantially parallel to the axes of said collars.

4. In a plug-socket connector, in combination, a pair of insulating bodies each carrying one or more power plug-socket contacts connectable with a power plugsocket contact on the other body, screw collars mounted one on each of said bodies, each of which is freely rotatable relative to the body on which it is mounted, said screw collars when screwed together and when unscrewed respectively effecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and a magnetically releasable latch housed within a collar which is rotatable relative to its associated body for holding it against rotation relative to the latter, said last mentioned collar having means for mechanically securing a magnet thereto in latch releasing position, said last mentioned means including surfaces at least partially overlying the magnet whereby movement of the magnet radially outward of the collar is prevented.

5. In a plug-socket connector, in combination, a pair of insulating bodies each carrying one or more power plug-socket contacts connectable with a power plugsocket contact on the other body, screw collars mounted one on each of said bodies, each of which is freely rotatable relative to the body on which it is mounted, said screw collars when screwed together and when unscrewed respectively effecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and a magnetically releasable latch housed within a collar which is rotatable relative to its associated body for holding it against rotation relative to the latter, said last mentioned collar having means for interlockingly securing to it a magnet in latch releasing position, said last mentioned means and said magnet having surfaces coacting when said magnet is in latch releasing position to preclude movement of the magnet radially away from said collar.

6. In a plug-socket connector, in combination, a pair of insulating bodies each carrying one or more power plug-socket contacts connectable with a power plugsocket contact on the other body, screw collars mounted one on each of said bodies, each of which is rotatable relative to the body on which it is mounted, said screw collars when screwed together and when unscrewed respectively efiecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and a magnetically releasable latch housed within a collar which is rotatable relative to its associated body for holding it against rotation relative to the latter, said last mentioned collar having means for securing a magnet to it wholly by mechanical engagement therewith with the magnet having a line which is midway between its sides and which is parallel to the lower surface of said magnet when the latter is horizontal, extending parallel to the axis of the collar.

7. In a plug-socket connector, in combination, a pair of insulating bodies each carrying at least one power plugsocket contact formed and positioned for connection with a power plug-socket contact on the other body, housing means for at least the mutually adjacent ends of said bodies comprising screw collars one on each of said bodies and freely rotatable relative thereto, said screw collars so formed and so mounted on said bodies that relative rotation between them, when they are in threaded engagement with each other, may effect relative longitudinal movement between said power plug-socket contacts and between said bodies, one of said collars externally grooved and the other having an elongated recess opening through its inner wall, and means precluding substantial inadvertent relative rotation between said screw collars including a pivoted latch swingable in the recess in one of said screw collars and engageable with an external groove in the other, and having at least a portion thereof magnetically permeable, said recess closed at its radially outer side and having positioned outwardly thereof a magnet-positioning abutment for facilitating the location of a magnet in a position to attract said latch.

8. In a plug socket connector, in combination, a pair of insulating bodies each carrying one or more plugsocket contacts connectable with a plug-socket contact on the other body, screw collars mounted one on each of said bodies, each of which is freely rotatable relative to the body on which it is mounted, said screw collars when screwed together and when unscrewed respectively effecting engaging and disengaging movement between the power plug-socket contacts on said bodies, and a magnetically releasable latch housed within a collar which is rotatable relative to its associated body and operative when moved to released position to permit relative rotation between said collars, said collar in which said latch is housed having means thereon for engaging the poles of a horseshoe magnet for mechanically holding, against separat ive movement therefrom in a direction radial of said collar, a magnet in 1atch-re1easing position on said collar.

References Cited in the file of this patent 5 UNITED STATES PATENTS 10 Ruth Apr. 6, 1937 Baash Apr. 12, 1938 McLoughlin Sept. 18, 1945 Simpson et a1. Nov. 4, 1952 FOREIGN PATENTS Great Britain of 1899 Germany June 14, 1899 Germany June 26, 1916 Germany Nov. 10, 1922