This document describes a patent for an improved electric plug and socket coupling device with a latching mechanism. Specifically, it details: 1) A pin projecting from one unit (typically the socket unit) that has a shoulder to engage behind a resilient latching member on the opposing unit (typically the plug unit). 2) The latching member can be deflected to disengage from the shoulder pin for uncoupling. 3) The tapered leading end of the pin acts as a pilot to move the latching member aside during coupling, allowing it to snap into place behind the shoulder once fully engaged.

1. * GB780077 (A)
Description: GB780077 (A) ? 1957-07-31
Improvements in or relating to electric plug and socket couplings
Description of GB780077 (A)
PATENT SPECIFICATION
780,077 Date of filing Complete Specification: Sept. 14, 1955.
Application Date: Sept. 17, 1954.
No. 26967/54.
Complete Specification Published: July 31, 1957.
Index at acceptance:-Class 38(1), E3A(4A: 4D; 6C: 11B), E3B6.
International Classification:-H02f.
COMPLETE SIPECIFICATION Improvements in or relating to Electric Plug
and' Socket Couplings I, WALTER STANLEY CATOR, a British Subject, of "
Brooklyn," Kettering Road, Moulton, Northamptonshire, do hereby
declare the invention, for which I pray that a patent may be granted
to me, and, the method by which it is to be performed, to be
particularly described in and by the following statement: -
This invention relates to electric couplings, and has reference
particularly to those of the multi-way plug-and-socket type.
A coupling of the type concerned comprises a plug unit in the form of
a body of insulating material furnished with-a plurality of
appropriately disposed conducting elements, and an opposing socket
unit consisting of a similar insulating body having fitted therein the
same number of correspondingly disposed conducting sockets. To couple
the two pieces or sets of electrical or electronic apparatus or the
like with which the plug and socket units are respectively associated,
the conducting elements protruding from the plug unit are simply
pushed into the complementary sockets housed within the socket unit
with a sliding action. In such a coupling, moreover, the conducting
elements fitted into the plug unit often consist of blades of flat
section, although they may be constituted by pins. In any event, the
inner ends both of these elements and of the complementary sockets are
provided with hook or equivalently shaped terminal portions to which
the appropriate conducting wires of the two pieces or sets of

2. apparatus or the like are soldered or otherwise secured. It is
sometimes the practice to house the plug unit in a case having therein
a bossed opening through which is passed one end of a multicored
cable., The socket unit, on the other hand, may be either located in a
casing or secured upon a panel.
Multi-way plug-and-socket couplings are of course, used for a variety
of different purposes of which may be mentioned, by way of example,
the coupling of microphones to appropriate equipment, and the
inter-connection of power supplies between a power unit and equipment
to be supplied with current, Now a disadvantage of an electric
coupling of the type referred to as heretofore usually constructed is
that the plug unit tends to become disconnected from the socket unit.
This may happen, for instance, as a consequence of vibration or as the
result of the plug unit being knocked out.. There is also a marked
tendency for the plug unit to be inadvertently pulled out when a heavy
cable is swinging therefrom.
The object of the present invention is to provide, in conjunction with
a multi-way plug and-socklet coupling, a particularly simple and
efficient form of readily releasible latching device designed to lock
the plug unit securely to the socket unit whenever these units are
interengaged.
According to this invention, a pin projects from one of the said two
inter-engageable units and is formed with a shoulder adapted to engage
behind a portion of an inherently resilient latching member provided
on the opposed unit, the said latching member being adapted to be
released from the shouldered pin by laterally deflecting the member
against the resilient action thereof to move it clear of the shoulder,
and the leading end of the said pin being of pointed or tapered form
and thereby constituting a pilot whereby, when the two units are being
engaged, the relevant portion.of the latching member is moved aside
against the resilient action until, as a result of continuing relative
longitudinal movement between the said member and the shouldered pin,
the deflected portion is freed to, react under the resilient action
and snap into position behind the shoulder.
The said leading end of the shouldered pin may advantageously be of
pointed or tapered form and thereby constitute a pilot by means of
which the latching element is moved aside ahead. of the shoulder and
loaded preparatory to being released for movement sharply into
operative latching position behind the shoulder..
It will accordingly be appreciated that the device, besides--being
self-engaging is shockproof in the sense that neither vibration nor a
blow can dislodge the plug unit from the socket unit. An incidental
advantage of the device of this invention is that the interengagement
of the latching member with the shouldered pin produces a clearly

3. audible sharp sound or "click" so enabling an electrical engineer or
fitter safely to push home the plug unit into the socket unit without
the aid of vision. This is important where a coupling has to be made
round a corner or behind an obstruction blocking a sight of the
coupling.
In a convenient embodiment of the invention, the shouldered pin is
grooved or notched suchwise as to provide the required shoulder.
The latching member, on the other hand, may advantageously consist of
a single piece of relatively thin metal of spring temper which is bent
to approximately U-formation to provide a pair of spaced limbs one of
which is intended to lie flat against the appropriate unit of the
coupling whilst the other, which is inherently springy and capable of
being pressed aside and deflected, is spaced from the side of said
unit and apertured or equivalently formed in such a manner as to
present an edge behind which the aforesaid shoulder can engage.
In the preferred form of the invention, the shouldered pin extends
forwvardly from the socket unit whilst the inherently resilient
latching member is secured or held in position upon a side of the plug
unit. These relative dispositions of the co-operable parts of the
latching device, may, however, in certain circumstances be reversed.
In any event, although it is within the scope of the invention to
provide a multiway plug-and-socket coupling with but a single latching
device of the hereinbefore described form, it will usually be
preferred to provide at least two such devices to each coupling. Thus,
according to one arrangement, a plug unit is fitted at its opposite
sides with a pair of resilient latching members adapted for
co-operation with a corresponding pair of suitably spaced and parallel
shouldered pins extending forwards from the opposed socket unit.
Where, as may be in the interests of standardisation, the insulating
bodies of the plug and socket units are of precisely the same form and
are provided with lugs or ears to permit of the socket unit being
readily secured by means of screws, within a casing or on a panel,
then the said lugs or ears, or associated lugs on the plug unit may
conveniently be taken advantage of to clamp the latching members in
position upon the sides of a case serving to accommodate the last
mentioned unit.
In order that the invention may be more clearly understood and readily
carried into practical effect, a specific constructional example
thereof will now be described with reference to the accompanying
drawing, wherein.
Figure 1 is an exploded perspective view illustrating the various
components, including the latching members, of the plug unit of an 70
electric coupling constructed in accordance with said invention,
Figure 2 is a front face view of the socket unit of the coupling

4. secured on a panel. and shows the shouldered pins for co-operation 75
with the latching members, Figure 3 is a plan view of the assembled
plug unit, Figure 4 is a part-sectional plan view of the socket unit
taken on the line IV-IV of 80 Figure 2, and Figure 5 is a
part-sectional plan view of the complete electric coupling, depicting
the latching members interengaged with the shouldered pins. 85 Like
parts are designated by similar reference characters throughout the
drawing.
In, the drawing, the plug unit of the improved coupling is indicated
generally by the reference letter P. whilst the complementary socket
unit is similarly indicated by the letter S. The conducting blades of
the plug unit, indicated at 1, are provided with hookshaped terminal
portions 2. whilst the conducting sockets 3 of the unit S are provided
95 with similarly shaped terminal portions 4, The insulating body 5 of
each of the two opposed units P and S consists of a twopart block of
insulating material which is appropriately aperturel and interiorly
recessed to receive the conducting blades 1, or the conducting sockets
3. as the case may be. The frontal part 5a of each block 5 is formed,
at its opposite vertical sides with a pair of outwardly directed
apertured lugs or ears 6 105 whereas the comp.'ementing rear part 5b
of the block is provided at corresponding locations with somewvha,
less protuberant lugs 7, lengths of suitably bent wire 8, being passed
around the pairs of lugs 6, 7 to assist in holding together the said
two parts of the block.
The socket unit S in this example is secured upon the back of a
relatively thin vertically disposed panel 9 of suitable material in
which an opening 10 is made to reveal the whole 115 of the vertical
front face of the body 5 of said unit 'see Figures 2, 4 and 5). The
unit S is secured in position by means of the screw-threaded tail ends
1 la of horizontal pin 11 (Figures 4 and 5) passed rearwardly right
120 through holes 12 in the panel and aligned holes 13 in the lugs or
ears 6, and securing nuts 14 which are screwed onto the pins. The
remaining portions 1 lb of these pins extend horizontally forward from
the face of the 125 panel 9. If desired, and as shown in Figure 2, a
hexagonal-shaped flange 15 formed on each pin 11 between its
scre-x-threaded and plain portions lla and llb may bear on the face of
the panel. The leading end of each 130 780,077 ever, the plug unit P
is interengaged with the socket unit S and pushed home, as shown in
Figure 5, the pointed noses 1lc of the pilot pins 11 will first act on
the bowed edge portions l'9e of the resilient outer limbs 19a and 70
press the latter inwardly into the recesses 7a in the lugs 7 until the
noses have passed by these portions whereupon the loading outer limbs
will be released and snap back into latching position behind the
shoulders lie. 75 To release the plug unit P all that is necessary is

5. to take it between the thumb and first finger and squeeze it as a
result of which the outer limbs 19a of the two latching members 19
will be simultaneously pressed inwards, 80 thereby deflecting the
inwardly bowed front edge portions 19'e thereof clear of the pointed
noses 11c of the pilot pins 11 and enabling the plug unit to be
disconnected by a rearward pull. 85 When, during initial assembly of
the plug unit P, the latching members 19 have been engaged with the
backs of the recesses 18 in the case 16, and the body 5. of 'the said
unit has been subsequently positioned within this 90 case, the body is
secured within the case and the lugs or ears 6 are clamped upon the
latching members by means of a. U-shaped wire clip 20 (Figure 1) the
spaced limbs, 20a of which are inserted through' pairs of aligned 95
tubular formations 21 provided on the front of the case.
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* 5.8.23.4; 93p