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Патент USA US2128883

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Aug. 30, 1938.
2,128,883
G. H. BURT
ELECTRICAL PLUG
Filed March 23, 41938
I
4
y
LZ
A TTORNEYS.
‘ Patented Aug. 30, 1938
' 2,128,883
NITED
2,128,883
EMECC
PLUG
Guy H. Burt; Providence, R. I.
‘Application
ch 23, 1938, Serial No. 197,557
2 (is. (oi. ire-e22)
This invention relates to an electrical con
nector or plug, and more particularly to an im
proved electrical cord connector plug of the type
commonly employed to attach a circuit cable or
5 extension cord to a heater such as an electric
iron, toaster orother electrical appliance.
An object of the invention is to provide an
improved electrical connector construction hav
ing means whereby the electrical contacts and
W the connector wires attached thereto within the
plug are relieved from extreme pulling strains
such as when the plug is withdrawn from the
socket of the appliance by seizure of the cable.
Another object of the invention is to provide
w an improved cord connector plug construction
having means for ?rmly gripping and anchoring
the extension cord or cable thereto whereby the
plug may be easily separated from the socket by
a straight axial pull on the cable without in?ict
20 ing detrimental strain on either the connector
wires or the contacts within the plug structure.
Another object of the invention is the pro
vision of an electrical cord connector of the
above character having anchoring means for the
25 extension cord as it emerges from the plug de
signed so as to relieve the contact and connector
wires within the structure from torsional strain
when the extension cord is subjectedto a torque
by being twisted.
30
,
A further object of the invention is to provide
an electrical plug and cord assembly in which
the grip on the cord will be sumcient to prevent
within certain tolerances a pull or torque ap
plied to the cord outside of the plug from being
35 so transmitted to the part of the cord within
the plug as to cause a movement of the cord
Fig. 5 is an enlarged sectional view of a frag,
mental portion of the showing of Fig; 4 with‘ the
wire and the recess therefor greatly enlarged;
Fig. 6 is a. longitudinal sectional view taken on
the line t—b of Fig. 1;
Fig. 7 is a plan view of the connector plug
shown in Fig. 1 but with the extension cord re
moved;
'
’
Fig. 8 is a perspective view of a fragmental
portion of the plug;
10
Figs. 9 and 10 are fragmental sectional views
showing various modi?cations of recesses in the
portion of the plug which grips the connector
‘ cord.
Fig. 11 is a view similar to Fig. 3 of a modi?ed 15
form of section of connector plug;
It is well-known practice in the use of ordi
nary electrical cord attachment plugs that such
devices are many times withdrawn from the
socket of the electrical ‘appliance by seizure and 20
sudden jerking oi the cable or extension cord,
thereby causing extreme strain to be imposed
on the connection wires of the cable with the
contacts of the plug and consequently resulting
in'a rapid destruction and deterioration of the 35
portion of the cable adjacent to the plug. Fur
ther, twisting of the cord often occurs causing
a di?'erent strain to be transmitted to and into
the plug. The strain placed on these extension
cords \under these conditions often is of such
force that many times the connector wires of
the cable where they are attached to the metal
contacts of the plug are broken and short cir
cuits result; and in order to obviate such dif
ilculties I have provided an electrical cord con- 35
nector plug construction having means dis
posed within the plug so constructed and ar
ranged as to prevent the connection between the
With these and other objects in view, the in
wires and the contacts within the plug from ‘be
vention consists of certain novel features of con
40 struction, as will be, more fully described, and ing materially strained by reason of excessive 40
particularly pointed out in the appended claims. tension or torque being transmitted thereto if
In the accompanying drawing:
the cable is pulled or twisted; and in order to
accomplish these advantageous results I have
Fig. 1 is a vertical elevational view of. an elec
trical cord connector plug formed of a pair of provided in each of the sections of the connector
plug adjacent the rear opening thereof through 45
45 sections in opposed face to face relation embody
which the extension cord extends into the con
ing my invention;
Fig. 2 is an elevational view of the connector nector block, anchoring means adapted to bite
plug structure in Fig. 1 but with the front section into exterior portions of the cable or extension
cord that is clampedvbetween the sections for
removed;
.
50
Fig. 3 is a detail view, in elevation, of one of ?rmly gripping and holding the cord preferably 50
the sections showing the anchoring means for the at oppositely disposed points upon sections of the
plug in opposed face to face relation whereby
extension cord;
_
Fig. 4 is a sectional view taken on line 4-4 of any force applied to the cable will be borne by
Fig. 3 but showing both sections of the plug body such anchoring and gripping means of the plug
and will so relieve the cord within the‘ plug that
' in assembled position;
,
parts within the plug beyond certain limits.
2
2,128,883
these forces will not be imposed to a substan
tial degree or a degree to cause deterimental
movement upon the connector wires within the
plug; and the following is a more detailed de
scription of the present embodiment of this in
vention, illustrating the preferred means by which
15
able torsional movement or excessive outward
pulling and to prevent the transmission of strain
to the connector wires and contacts within the
plug, the inner surface of the opening 28 on the
?ange which projects inwardly from the sides
is of such size as to tightly grip the cord, and
these advantageous results may be accomplished:
With reference to the drawing, l0 designates
in order to assist this gripping, I have provided
generally the electrical cord connector or at
wall of the chamber 25 projections extending in
on the face of the opening 28 of the inner end
tachment plug and comprises a body member
wardly at oppositely disposed points toward the
generally oblong in cross-section formed of op~
axis of the plug and having portions adapted
to bite into the exterior surface of the cord, but
posedhalves or sections H and E2, of hard rub
ber or other suitable hard insulating material.
The sections H and i2 are of substantially iden
tical construction and they are held in face to
face contact with each other by means of suit
able screws M and nuts l5, as is the usual con
struction of such connector plugs. The opposed
faces of the sections H and I2 are formed with
20 spaced complementary longitudinal grooves or re
cesses of generally rectangular cross-section Ill
and i8 which cooperate to form parallel contact
housing channels or sockets extending inwardly
from the forward end of the connector plug when
25 the body pieces ii and i2 are clamped together.
The shape of these channels is not material so
long as they ?t the contacts of the plug.
In each of these sockets in the front of the in
sulating plug comprising sections H and I2 there
30 is mounted a pair of opposed resilient metal con
tacts 20 and 2! which are of the usual construc
tion employed for connector plugs of this type,
and are of substantially semi-tubular formation
from sheet stock. The contacts 20 and 2! each
35 present split terminal sockets for the reception,
of the contact prongs or blades carried by the
electrical appliance. As shown in Fig. 2, the in
ner ends of each pair of the contacts“ and 2|
are ?attened, as indicated at 22, and they are
40 ?xed to the plug consistingpf sections i I and I2
in any suitable and well-known manner. The
grooves l1 and H! in the sections II and I2 are
of a size sufficient to leave a slight clearance
between the contact strips 20 and 2| respectively,
in order to permit the same to expand laterally
when in tight gripping engagement with the in
serted terminal pins, blades or prongs of the usual
appliance.
As shown in Fig. 2, the back end of the plug
50 body is hollow and provided with a laterally dis
posed chamber 25 of generally V-shape formation
for accommodating the connector wires of the
extension cord C, the forward portion of the
chamber 25 communicating with the rear end
55 portions of the recesses l1 and 18 to permit at
tachment of the connector wires to the wiring
terminal ends of said contacts 20 and 2| . Formed
in the rear wall of the sections are a series of
axially disposed semi-cylindrical recesses 26 and
60 21 which are of stepped formation and which
10
of such structure as not to cut the threads there
of upon clamping of the cord between the sec
15
tions it and i2, respectively.
As shown in my preferred construction illus
trated in Figs. 3 and 7 of the drawing, a plurality
of laterally extending projections or pins 39 are
provided on the recessed face of the end wall de
~fining the part of the rear opening 28 of each 20
section H and i2, and these projections are in
the form of tapered blunt-ended pins of equal
length to allow for accommodation of the two
wire cord, which terminate close to the axis of
the rear opening of the plug when the clamping 25
blocks are assembled and clamped together in
opposed relation, in which instance, the pins act
tobite into but do not cut the outer envelope
‘of the extension cord from opposite sides, whereby
the cord is~tightly clamped and held anchored 30
in position.
As shown in Fig. 5, the middle pin 30a serves
as a positioning or separating pin, whereas the
pins 301) on either side thereof serve to press into I
each of the individual two wires and deform the
same su?iciently so as to provide a firm and se
cure grip thereon. . The asbestos covering be
neath the braid of the cord c ?lls in the spaces
between the pins 30 which maintains a ?rm bind
ing relation on the cord.
. 40
In view of the above description, it will be ap
parent that when it is desired to withdraw 'the
plug from the appliance socket by pulling with
the ?ngers on the extension cord or cable, that
any pressure or straight axial pull of up to and
over fifty pounds and/or twisting movement or
torque of over three pounds will be carried direct‘;
ly by the projections 30 and will not be applied
to any material amount to the connector wires
where they are attached to the contacts within
the body of the plug.
Other variations of the gripping surface of
course will be readily apparent and I have shown
in Figs. 9 and 10 a recess on one section of the
plug and a projection on the other section tov 55
bind between the recess and the projection the
cord and hold it ?rmly locked in the connector
plug. In Figure 9 the recess 52 is shown as plain
with a series of spurs or projections 53 on the
other section to extend into this recess to lock 60
the material in position. In Fig. 10 the recess 54
is provided with notches 55 to accommodate the
municate with the chamber 25 in the plug by projection 56 and its detents 51 for locking the
means of an axially disposed opening 28 which is ‘ cord in position.
In Fig. 11 the same structure as provided in the 65
65 formed by opposed recesses in the inner end wall
of the chamber 25. The opening 21 is made of recess at 28 with its projections 30 is duplicated
larger diameter than the opening 26 and is in a smaller size by reason of a projection 60
adapted to receive and hold the usual ?anged with pins 6| extending therefrom for gripping the
sleeve, not shown, through which the extension individual wires 62 such as shown in Fig. 2 and
70
70 cord C extends into the interior of the connector locking them individually in position.
The foregoing description is directed solely to
plug, and in which the usual cord encircling
spring, not shown, is anchored, as the common wards the construction illustrated,>but I desire it
to be understood that I reserve the privilege of
construction of such cord connector plugs.
In order to tightly grip and anchor the cord resorting to all the mechanical changes to which
the device is susceptible, the invention being de- 75
75 secured to the plug connector against consider
provide in the assembly of the sections of the
plug cylindrical openings. These openings com
3
2,128,888
fined and limited only by the terms of ‘the ap
pended claims.
I claim:
1. ‘An electrical cord connector plug comprising
' a body of insulating material formed in two mem
bers each having an abutting face to contact the
other, said members providing complementary re
cesses at one end forming contact housing chan
nels when the body pieces are together, a plural
10 ity of metal contact members in said channels,
said body members being provided at the other
end with an opening at the rear end of the plug
body communicating with said channels provid
, ing an entrance for the connector wires of an
15 extension cord when the same are attached to
the wiring terminals of said contact members,
or slipping of‘ a cord relative to the body mem
bers.
,
i
2. An electrical cord connector plug comprising
a body of insulating material formed in two mem
bers each having an abutting face to contact the
other, said members providing complementary re
cesses at one end forming contact housing chan
nelswhen the body pieces are together, a plural-.
ity of metal contact members in said channels,
said body members being provided at the other 1O
end with an opening at the rear end of the plug
body communicating with said channels provid
ing an entrance for the connector wires of an
extension cord when the same are attached to
the wiring terminals of said contact members, 15
and a plurality of generally parallel prongs on
said members, each prong being molded integral
with one of said members and extending from the
wall of said rear end opening toward the wall of
and a plurality of generally parallel prongs on
said members, each prong being molded integral
with one of said members and extending from
the rear end opening of the other member, nor 20
20 the wall of said rear end opening toward the
wall of the rear end opening of the other mem » mal to the abutting surface of said member and
free from undercut or overhanging portions with
ber, normal to the abutting surface of said mem
respect to any surface remote from the abutting
ber and free from undercut or overhanging por
tions with respect to any surface remote from surface to permit a molding ‘die to be withdrawn
the abutting surface to permit a molding die to therefrom, the walls of said opening and prongs 25
being so constructed and arranged as to grip and
be withdrawn therefrom, the walls of said open
?atten out the cord engaged, said prongs being
ing and prongs being so constructed and ar
substantially spaced and so located as to engage
ranged as‘ to grip and ?atten out the cord en
on either side of the mid portion of the cord and
gaged, one of the prongs being so located as to
prevent substantial twisting of the cord in the 30
30 engage substantially the mid portion of the cord
and another of said prongs being substantially opening or slipping of the cord relative to‘the
'
spaced therefrom and at a location su?icient to body members.
engage a side portion of the cord and‘ prevent
GUY H. BURT.
substantial twisting of the cord in the opening
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