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Патент USA US3066281

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NOV- 27, 1952
E. R. CARLSON
3,066,271
MEANS FOR CAPTIVATING A SCREW 1N AN INTERNALLY
THREÁDED SUPPORTINGl MEMBER
Filed July e, 1959
ATTOR E
United States Patent Olitice
3,066,271
Patented Nov. 27, 1962
2
1
forming the free end of the screw shank so as to pro
vide a radially extending portion thereat of larger external
3,066,271
MEANS FOR CAPTIVATÍNG A SCREW IN AN IN
TERNALLY THREADEEB SUPPGR'HNG MEMBER
diameter than the internal diameter of the threaded por
tion of the passageway. The object of the invention in
Ernest R. Carlson, Fairfield, Conn., assigner to Harvey
a particular sense is accomplished by preliminarily em
Hubbell, Incorporated, Bridgeport, Conn., a corpora
bedding
the supporting member referred to in the pre
tion of Connecticut
ceding sentence in the body of an electrical connecting
Filed July 6, 1959, Ser. No. 824,969
device prior to the insertion of the screw in the passage
«
2 Claims. (Cl. 339-44)
way of said member.
The above and other objects and further details of
This invention relates generally to means for captivat l0
that which I believe to be novel and my invention Will be
ing a screw in an internally threaded supporting member
clear from the following description and claims taken
and particularly in structural settings wherein it is not
with the accompanying drawing, wherein:
reasonably possible to have access to the free end of
FIG. l is a rear plan view of a grounding electrical
the screw shank, i.e. the end which is disposed within
adapter plug which incorporates the invention;
the internally threaded supporting member, to capti
FIG. 2 is a sectional View taken substantially on line
vate it.
2-~2 of FIG. l;
FIG. 3 is a front plan view thereof;
It frequently occurs in manufacturing various products
having screws that it is desirable to mount a screw in
FIG. 4 is a sectional view taken substantially on line
an internally threaded supporting member in such a
manner that after being initially mounted, it is capti~ 20 4-4 of FIG. l;_
FIG. 5 is an enlarged perspective view of one of the
vated; that is, not capable of being removed by unscrew
ing in normal use of the product.
A particularly important product area in which this oc
parts;
curs is that including electrical connecting devices, and
its supporting member showing the screw in different
particularly grounding electrical connecting devices. A11
FlG. 6 is an enlarged sectional view of a screw and
25
positions which it occupies during initial assembly and
use in solid, dotted, and dot-dash lines, and
example of such a device a grounding electrical plug,
FIG. 7 is an enlarged perspective view of a modilied
and such plugs usually include a grounding contact hav
form of the part shown in FIG. 5.
ing a terminal that has a binding screw which is used
Referring to the drawing, and particularly to FIGS.
to attach a grounding electrical wire to the plug. In
View of the fact that the binding screw is an important 30 1_4, there is illustrated a grounding electrical adapter
part of the grounding system, safety requirements dictate
that it be captivated, and thereby preclude inadvertent
plug which incorporates the instant invention. The illus
trated plug generally comprises a body lll, a pair of
removal, loss and subsequent use of the plug in an un
polarized male electrical contact blades l2, and a male
tivation are normally such as to require access to the
one practical application of the invention in an electrical
grounding contact blade i4. The illustrated plug, it
grounded manner. The general concept of captivating
screws is known; however, the methods fo-r effecting cap 35 should be clearly understood, is merely exemplary of
free end of the threaded screw shank. When dealing
with electrical connecting devices, the free end of the
threaded screw shank is normally not accessible, and
therefore conventional screw captivating means and meth
ods are not feasible. This is true because these elec
connecting device. The illustrated plug is designed to
be received in an appropriate grounded electrical con
necting device, such as a receptacle, having female con
40 tact means for receiving the male contact blades of the
plug.
The illustrated plug is adapted to have a three
trical connecting devices usually comprise a body of
wire electrical cord, one of the wires of which is a
electrical insulating material in which is embedded one
grounding wire, connected to electrical terminal means
or more screw supporting members in the form of in
of the plug. In addition, the illustrated plug includes
serts having elongated, internally threaded passageways
female contact means for receiving a three-contact bladed
to receive the threaded screw shank.
grounding plug. Therefore, the illustrated plug is de
Once an insert
signed to effect two separate grounded connections to
is embedded in the body and a screw is inserted in the
a grounded electrical connecting device having means for
insert, it is not possible to have access to the inner end
receiving only a single grounded three-contact bladed
of the insert passageway, where the free end of the
50 electrical plug.
screw is disposed, in order to captivate the screw.
The plug body 10 comprises a solid mass of electrical
It is an object of the invention generally to provide
insulating material having a plurality of slots, passage
improved means for‘ captivating screws in internally
ways and recesses formed therein, as will be subsequently
threaded supporting members, and particularly to pro
set forth. The plug body supports all of the other com
vide improved means for captivating screws in elec
trical connecting device bodies.
55
ponents of the plug, including the previously’mentioned
male contact blades 12 and 14. The plug body is some
what cylindrical and includes a generally flat front wall
16, a cylindrical side wall 18, and a flat, multiply recessed
rear wall 20. A cut-out portion 22 is formed in the plug
threaded screw shank of the screw, and means disposed 60 body in the vicinity of where a part of the front wall 16
intersects a part of the side wall 18. A circular opening
at the inner end of the passageway which cooperates
2.4 communicates with the cut-out portion 22, extends
with the free end of the threaded screw shank the first
completely through the plug body, and communicates with
l, time the screw is inserted into the passageway and fully
The object of the invention in a general sense is ac
complished by providing a screw supporting member hav
ing an elongated passageway with an internally threaded
portion of reduced diameter for threadedly receivingthe
1¿screw tightened therein to captivate the screw by de
a recess 21 in the
2t). Cut-out portion 22, open
3,066,271
3
4
ing 24 and rccess 21 permit the passage of an electrical
cord from the front of the plug through the latter to the
rear thereof, where the wires of the electrical cord may
be connected to the terminal means of the plug, which
is disposed at the rear of the plug body, as will become
headed binding screw 66, insert 44, contact spring leg 56
materials, preferably metallic materials, and for general
operating convenience the contact spring 50 is made of
apparent.
A pair of spaced elongated slots 26, one being larger
a springy metallic material.
rïhe illustrated plug includes a grounding' contact as
and male contact blade leg 60. All of the parts of the
contact assemblies are made of good electrical conducting
than the other to accommodate polarized male contact
sem ly which comprises the previously mentioned male
blades of an associated plug in a manner and for a pur
grounding contact blade 14 which has a generally U
shaped cross section and a bent mounting and terminal
wall 76 that is rigidly connected to a hat contact wall 72,
pose generally known in the electrical art, extend com
pletely through the plug body 18 from the front to the
rear thereof. The Íront ends of the Slots are bevelled at
28 to facilitate insertion of the male contact blades of an
associated plug, and the rear ends of the slots 26 com
municate with irregularly shaped, shallow recesses 30
(see FIGS. 1 and 4), which in turn communicate with an
enlarged recess 32 formed in the rear end of the plug body.
A noncircular opening 34 having a bevel 36 is formed in
the front wall 16 of the plug body 16 and communicates
with an enlarged passageway 38 which extends to the
rear completely through the plug body and communicates
as by the rivet 74 (see PEG. 2). The grounding contact
assembly also includes a female contact ’76 in the form of
a resilient U-shaped clip which is rigidly connected to the
contact wall 72, as by rivet '78. When the grounding
contact assembly is fully assembled on the plug, the
female contact 76 is disposed in the passageway 38, its
positioning therein being facilitated by >guide projections
88, and the contact wall 72 and mounting and terminal
wall 70 are disposed in the recess 40.
The grounding contact assembly is intimately .opera
with an irregularly shaped recess 40, which in turn com
tively assocated with an insert 82 which is Securely em
municates with the previously mentioned enlarged recess
bedded in the plug body 10. Insert 82 is unitary, gener
32 (see FIGS. 1 and 2). As can best be seen in PEG. 1,
ally cylindrical and is provided with radially extending
the recesses 30 and 40 are spaced from each other, andV 25 portions (not shown) to facilitate embedding and an elon
as can best be seen in FIG. 3, the slots 26 and opening 34
gated circular passageway 84. A portion 86 of the insert
are kspaced from each other at` the front of the plug.
The slots 26 have laterally extending portions 42 which
82 extends into the recess 4t) and is rigidly connected to
anV end portion 88 of the male contact blade mounting
extend toward each other and which are disposed so as
and terminal wall ’70 by extending through an opening 90
. to extend from the rear of the plug body 10 toward, but 30 which is formed in the end portion 88, and having its
short of, the front thereof (see FIG. 4). Adjacent, but
spaced from, each ofthe slots 26 at the rear ofthe plug
body there is disposed a generally cylindrical insert 44
free extremity ñanged over to rigidly connect the parts.
The insert 82 has an inwardly extending internally
threaded portion 92 disposed adjacent the portion 86.
which is rigidly secured to the plug body by being em
The internal diameter of the threaded portion 92 is less
bedded therein.-
Inserts 44 include radially outwardly 35 than the internal diameter of the remainder 94 of the
extending ribs 46 on the exterior thereof for facilitating
passageway 84, which is plain.
embedding of the >inserts >in the plug body. Each insert
Adjacent and closing the interior end 96 of the insert
44 includes an elongated circular passageway 48 that is
‘82 there is disposed a solid plug-like member 98, which
will hereinafter be referred to as an anvil, which'is shown
Y Each insert 44 is intimately operatively associated with 40 by itself in FIG. 5. The anvil 98 is generally cylindrical
a contact spring 50 and one of the previously mentioned
and comprises a cylindrical portion 100 that is disposed
male contact blades 12. As can be most clearly seen in
in and frictionally engages the inner surface of the insert
FIG. 4, each contact spring 5i) includes an acutely bent
end 96, a radial flange 102 which contacts the axial end
contact leg 52, an intermediate leg 54, and a perpendic
of the insert end 96, and the reduced diameter portion
internally threaded.
ularly bent mounting’leg 56. Each contact spring mount 45 184 which ‘is embedded in the plug body 10. The face of
ing leg 56 includes an opening 58 that is arranged to
the Vanvil 98 is disposed within the insert 82 and comprises
surround a portion of van associated insert 44 and be
a ñat annular wall 106 which is located in a planerthat is
adjacent one of the ribs 46. When the Contact springs are
Vperpendicular to the axis of the insert 82, and a central
mounted on the plug body 1t), the contact spring legs
conicalrecess 108 that is po-sitioned within the wall 106.
52 and 54 are positioned in the slots 26 and their enlarged 50 The anvil 98 comprises means for automatically captivat
portions 42 and the contact spring mounting legs 56 are
ing a binding screw in the insert 82 on its initially being
disposed in the recesses 30. Adjacent each of the contact
inserted into the insert and fully tightened therein, as
spring mounting legs 56 is disposed a bent mounting leg
will Vbecome apparent.
Y
60 of a male contact blade 12. Each of the mounting legs
A_ headed binding screw 110 is adjustably received in
60 includes an opening 62 which surrounds a portion of 55 the insert 82 so as to be capable of selective manual longi
its associated insert 44. When assembled, the mounting
tudinal adjustment therein. However, after its initial
legs 60 yare also disposed in the recesses 30. ` Each asso
mounting in the insert 82, the binding screw 110 is Capti
ciated pair of contact spring mounting legs 56 and male
V'ated, i.e. not capable of being removed therefrom there
contact blade mounting legs 68 is rigidly retained on its
after in normal use of the plug. When the parts of the
associated insert 44 by the flanged-over end 64 of the
plug are »fully assembled, as shown in FlG. 2, the binding
insert.
screw 110 has its head 112, which is illustrated as being
A headed binding screw 66 is threadedly mounted in
hexagonal and having a kerf 114 formed therein, 'acces
each Iof the (inserts 44. >Each associated male contact
sible for receiving an adjusting implement, such as a
blade 12, insert 44, binding screw 66 and Contact spring
screwdriver, to'selectively manually adjust the position of
50 comprises acontact assembly. Each contact assembly m Ul the screw V11€) in the insert 82. The screw 110 includes
is capable‘of (l) being electrically connected to a male
a shank 116 which is threaded over its entire axial extent.
electrical contact of an associated plug which is inserted
through a slot 26 and contacts the bent leg 52 of a contact
A conical recess 118 is formed inthe free end of the screw
shank” 116, i.e. the'end which is opposite the screw head
spring'SO, it being vnoted in this regard that beads 68 which
112.
are formed on bent legs 52`enhance such contact; (2) be- ~
recess 118 is signiñcantly larger in diameter than „the con-»
ical recess y108 formed in the anvil 98. The free end of
the screw shank >116 has a radially outwardly extending
ing electrically’connected to a female contact of an elec
trical connector, such as a receptacle, to which the plug is
connected by having its male contact blade 12 inserted
therein, and (3) having an electrical wire (not shown)
lt should be vparticularly noted that’theconical _
annular portion 120 that has an outer diameter in excess ' "
of the inner diameter of the threaded portion 92 of the» o
electrically connected `to the terminal 'formed-byV the 75 insertv v82. Therefore; the bindingscrew «110, lëtfítervît *i.Sj
3,066,271
G
screw with the axially facing shoulder 122 of the> insert
threaded portion 92, as is shown in dot-dash lines in
fully` assembled in the insert 82, as illustrated in FIG. 2,
is capable of being selectively adjusted manually so as to
withdraw much of its shank 116 outside of the insert.
However, it is captivated in the insert 82 because it is not
FIG. 6.
In FIG. 7 there is illustrated a modified form of anvil
capable of being fully withdrawn therefrom during nor
126 which may be substituted for the anvil 98 illustrated
mal use of the plug due to the interference engagement
in FIGS. 1-6. The major difference between the anvils
of the screw’s radially extending portion 120 and the axi- is that in the FIG. 7 modification, the face 128 of the
ally facing annular shoulder 122 formed by the axial
anvil, which opposes the free end of the screw shank when
inner end of the innermost thread of the insert’s threaded
>these parts are operatively associated, includes a raised,
portion 92. It will, therefore, be apparent that when fully 10 axially extending projection 130, instead of a recess as in
the case of anvil 98. When the anvil 128 is utilized 1n
assembled, the binding screw 110 is captivated in the in
sert 82. Captivated screws are highly desirable in many
place of the anvil 98, captivation of a binding screw which
practical applications. It is particularly desirable in a
corresponds to screw 110 occurs on its initially being in
grounding electrical plug, such as the illustrated plug
serted and fully tightened as a result of its recessed shank
adapter, wherein the binding screw 110 and the associ 15 end being upset and deformed by the projection 130 into
ated parts of the grounding contact assembly comprise
vital elements in the grounding system for the plug, that
a radially extending portion which corresponds to portion
120 of binding screw 110 in FIGS. 1-6. Both forms of
the screw 110 be captivated. Prudence and safety re
quirements dictate that the binding screw 110 be irre
anvils have proved to be successful in practice; however,
the FIG. 5 form is preferred. Regardless of the form of
movably mounted in order that it might not be inad 20 anvil used, after the binding screw is initially mounted
vertently withdrawn from the insert 82, which is possible
and captivated, it is thereafter incapable of being removedv
in normal usage. This is useful in many practical appli
if it were not captivated therein, lost, and thereafter the
cations, and particularly in grounded electrical connecting
My invention provides means for automatically capti
devices, wherein it is desirable that the grounding binding
vating the binding screw 110 in the insert 82 by forming 25 screw not be removable, as pointed out above.
the radially extending portion 120 at the free end of the
In view of the foregoing it should be apparent that
plug used in an ungrounded manner.
improved means for captivating screws in internally
threaded supporting members have been generally pro
vided and that they are of general utility, and that an im
binding screw shank 116 on the occurrence of the initial
insertion of the screw 110 into the insert 82 and the
tightening of the screw therein. Reference to FIG. 6 will
facilitate an understanding of the manner in which this 30 proved grounding electrical connecting device having a
occurs. In FIG. 6 the insert 82, anvil 98, and binding
captivated terminal binding screw which is part of the
screw 110 are illustrated in solid lines in the positions
grounding system of the device has been provided which
and configurations which they are in at the time of initial
satisfies a particular need in grounded electrical connect
insertion and assembly of the screw 110 into the insert
ing devices.
As will be evident from the foregoing description, cer
82. At this time, it should be carefully noted, the ex 35
terior surface of the screw shank 116 is threaded, but
tain aspects of my invention are not limited to the particu
generally cylindrical throughout its entire length, the radi
ally extending portion 120 not yet having been formed,
and therefore, it is capable of clearing and being threaded
ly inserted into the insert 82 through the threaded portion
lar details of construction of the examples illustrated,
and I contemplate that various and other .modifications
and applications will occur to those skilled in the art. It
40
is, therefore, my intension that the appended claims shall
92 of the latter. At this time in assembly, the screw
cover such modifications and applications as do not de.
shank 116 has a flat, radially extending annular wall por
part from the true spirit and scope of my invention.
tion 124 formed around the recess 118 which faces the
What I claim as new and desire to secure by Letters
anvil 98. It should be particularly noted in FIG. 6, that
Patent of the United States is:
the screw recess 118 is of larger diameter than the anvil 45
1. A grounding electrical connecting device compris
recess 108 and that the flat annular wall 124 of the screw
ing: a body of electrical insulation material; a pair of
shank is narrower than and disposed to make planar con
load-carrying contacts carried by said body; a grounding
tact with the flat annular wall 106 of the anvil.
contact in addition to said pair of load-carrying contacts; a
In FIG. 6, the free end of the screw shank is shown in
terminal including a binding screw operatively associated
dotted lines in the condition that it assumes at the time 50 with said grounding contact and arranged to have a
of the initial insertion and full tightening of the screw 110
grounding wire attached thereto from the exterior of said
body; said grounding contact and said terminal being elec
in the insert 82. Planar contact of the flat, annular, radi
ally extending walls 124 and 106 results in the upsetting
and deformation of the first thread of the screw at the
trically connected to each other and supported by said
body; and means for irrernovably mounting said binding
free end thereof into the radially extending annular por 55 screw on said body whereby it may not be removed there
tion 120. This occurs because the relatively thin, flat an
from in normal use; said means comprising a unitary sup~
nular wall 124 of the screw shank yields to the relatively
porting member for said binding screw that is permanently
embedded in said body and a screw-deforming anvil also
wide, flat annular wall 106 of the anvil on the occurrence
of forced movement of the screw against the anvil. The
embedded in said body adjacent to said supporting mem
anvil recess 108 provides a clearance for the central por 60 ber; said anvil having a portion arranged for contacting
tion of the adjacent end of screw shank 116 during forma
and deforming the first screw thread on said binding screw
tion of the radially extending annular portion 120. As
the first time it is screwed fully into said supporting mern
illustrated in FIG. 6, this clearance does not appear neces
ber; said supporting member having an elongated passage
way formed therein which includes an internally threaded
sary; however, it sometimes is, as when a screw without
a recess 118 is inadvertently used, and therefore, the 65 cylindrical portion; said binding screw comprising a cylin
recess 108 is provided. After the radially extending por
drical threaded shank adapted to be threadedly received
tion is formed on the screw shank 116, the binding screw
in said cylindrical portion, a head at one end of the shank
110 is captivated in the insert 82.
and a radially outwardly extending annular portion at the
As pointed out above, the screw 110 is capable of being
other end of the shank; said supporting member housing
selectively manually adjusted longitudinally of the insert 70 said radially outwardly extending portion and a variable
82. However, in the event of a sufficient amount of ad
amount of said shank, depending upon the relative posi
justment of the screw 110 in the direction to withdraw
the screw out of the insert 82, complete withdrawal of the
screw out of the insert is prevented by the interference en
tions of said supporting member and said binding screw;
the internal diameter of said cylindrical portion being
less than the external diameter of said radially outwardly
of the radially extending PGì‘ÚOIl 12” Uf the 75 extending portion whereby on withdrawal Amovement of
`
‘t
3,066,271
7
V8
said- binding screw 1 from -saidç supportingV Amember said
radially extending portion «engages said cylindrical portion
projection »that extends towardlan'd opposes the» said other
end of’sa‘id shank and is arranged to be engaged thereby to
and thereby prevents further withdrawal movement of said
binding» screw; said~binding- screw prior to being initially
disposed in said supporting member being devoid of said
contact and ~upset said other end‘the` first time'said bind
ing screw is screwed into the supporting member.
radially outwardly extending >annular portion; and said
anvil Vhaving- a portion disposed lWithinsaid supporting
References Cited in the' ñle of thisrpatent
member in» position-to `Contact and upset said other end
of said shank'the first time said other end of said shank
is screwed-into said supporting member to thereby form
UNITED STATES PATENTS
1,257,730
Moulthrop ___________ __ Feb. 26, 1918
saidV radially `outwardly extending annularA portion.
1,482,765
Sanborn ______________ __ Feb. 5, 1924
1,801,937
‘Rathbun ______ __ _____ __ Apr. 12, 1931
2. A vdevice as defined in claim 1 wherein said -binding
screw initially has a circular recess formed in the >said
FOREIGN ' PATENTS
other end‘of its shank andthe ‘portionof said anvil that is
disposed within said supporting member includes a raised 15
137,972
~-Australia ____________ __ Mar.`25, 1948
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