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Патент USA US2115447

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April 26, 1938.
J. A. MCENTEE
NONTAMPERABLE FUSE
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2,115,447
2,115,447
Patented Apr. 26, 1938
UNITED STATES PATENT OFFICE
2,115,447
NONTAMPEBABLE FUSE
James A. McEntee, Newburyport, Mass., assigner
to The Chase-Shawmut Company, Newbury
port, Mass., a corporation of Massachusetts
Application March 5, 1936, Serial N0. 87,266
19 Claim.
(Cl. 20G-119)
5 in the copending application of Elmer H. Taylor,
ing an internal fusible element containing cham
ber closed at the bottom by a bottom wall inte
gral with the plug body and closed at the top by
a separate cap member, the fuse having a sepa
rate member carrying the non-tamperable ele
Serial No. 41,559, filed September 21, 1935, which
is assigned to the assignee of the present appli
ments, said member being held against the inte
gral wall of the chambered body by suitable
cation.
means as the screw-threaded terminal shell of
This invention relates to electric fuses and
particularly to non-tamperable plug fuses.
This invention in some respects is intended
as an improvement on the invention disclosed
'
A non-tamperable plug fuse is one that is so
10 arranged that the terminals of the socket or
receptacle that receives it cannot be bridged
readily by improper materials held in the recep
tacle by the blown receptacle plug- in an attempt
to restore electric service mterrupted by the
blowing of the plug.
The non-tamperable fuse usually comprises a
the fuse.
,
It is desirable- to provide a non-tamperable
construction such that the plug can be received
in a standard fuse receptacle that does not have
a non-tamperable member, or adapter, therein;
and such a construction constitutes another ob
ject of the invention.
,
15
A yet further object is the provision of a plug
plug that carries the fusible element and an `fuse and also an adapter therefor having a cir
adapter intended to be 'more or less permanently cuit controlling contact member of such small
retained in the plug receptacle, the plug and axial dimensions that the center contact mem
ber of the plug can engage it and also can en
adapter having cooperating elements that pro
vide the desirable feature of non-tamperability. gage the center contact of the receptacle when
the adapter is not in the receptacle, thereby to
It has been found desirable to have these coop
erating elements interflt or mesh so closely that adapt the plug for use in receptacles not hav
3
a bridging member of the order of tin-foil or a
ing an adapter.
thin wire cannot readily be lodged between them.
It is also desirable to form the plug body which
Another object is generally to improve the con
struction of fuses.
Fig. 1 is a sectional elevation through a fuse
embodying the present invention in the circuit
`
encloses the fusible element of some inorganic
material, or one which is inert and does not lib
erate gas when subjected to the arc formed upon
rupture of the fusible element upon heavy over
load. A body material such as porcelain, how
conducting relation of the parts.
ever, cannot be molded >economically tm the
close dimensions required for the intertltting of
the non-tamperable elements. An organic body
position and the movable contact member of the
adapter in open circuit position.
Fig. 3 is a perspective view of the fuse plug
35 such as an artiñcial resin and particularly a res
inous phenol condensation product can be molded
within the desired close limits but is not entirely
satisfactory as an enclosure for the fusible ele
ment because it liberates gas when subject to
40 the heat of a heavy circuit interrupting arc.
Hence an object of the present invention is the
provision of a non-tamperable plug fuse wherein
the plug body enclosing the fusible element or
link- comprises an inert material as porcelain and
45 wherein the non-tamperable elements comprise
Aa separate body formed of some material, as an
artificial resin, that is not necessarily inert when
subjected to an electric arc but which can be
molded to accurate dimensions, and means such
50 as the screw-threaded terminal shell of the fuse
to hold the two bodies together to form in effect
an integral structure.
A further object of’ the invention is the pro
vision of a non-tamperable plug fuse comprising
55 a plug body of inert material as porcelain hav
Fig. 2 is a fragmentary section similar to Fig.
1 but showing the plug partly out of operative
body of Fig. 1.
35
Fig. 4 is a perspective view of the non-tamper
able member of the fuse plug of Fig. 1.
Fig. 5 is a perspective view of the adapter of
Fig. 1.
Fig. 6 is a plan view of the movable contact
member of the adapter.
_
Fig. 7 is a sectional detail illustrating a modi
ñed manner of accurately-registering the plug
body and tamper-preventing section co-axially.
The fuse embodying the present invention is
adapted to be located in a socket or receptacle
comprising an insulating base I0 having, usually,
a circular upstanding insulating flange I2 within
the well of which an internally screw-threaded
shell I4 is located, which shell is connected to a
conductor terminal It of the base by a conduct
ing strap il. The receptacle has a center con
tact member Il located in the bottom of the well
and co-axially therewith and is connected by a
2
2,115,447
strap 22 with a second conductor terminal 24
of the base.
The receptacle as thus constructed is arranged
to receive a so-called standard plug fuse having an
outer screw-threaded shell adapted to be screw
face of said cover plate and tend to urge the upper
part of the contact member against the bottom
wall of the recess 48, which is the normal open
circuit position of the contact member. In this
threaded in the terminal shell I4 and a center con
tact member adapted to engage the center con
within the upper end of the passage~l52~ 'I'he
boss 32 is provided with a small diameter axial
passage 53 adapted to permit access of the center
tact member 28. With such a plug the contact
terminals- of the receptacle can be bridged readily
position the cup shaped member preferably is
contact member of the associated plug to said
10 by inserting metal foil, wire and the like within
contact member 48.
the receptacle and holding the bridging material
in place under a blown standard plug.
For the purpose of rendering it diiìicult to
bridge the terminals of, or tamper with, the fuse
15 and the receptacle, an adapter 26 is inserted in
the receptacle, in the bottom of the shell I4 and
YThe plug associated with the adapter comprises
a cylindrical body 54 composed of a molded in
organic material that is inert or does not give oil.'
gas and is not otherwise harmfully affected by the
heat of the circuit interrupting arc. At present 15
porcelain is the best material known to me.
Said cylindrical body is provided with a fuse link
over and, for many receptacles, upon the center
contact member 20. The body of said adapter is
composed of insulating material, preferably a
20 molded artificial resin, that can be molded _ac
curately to dimensions. The adapter is formed
with a lower cylindrical body or flange 28 which
is
externally screw-threaded and is
screw
»
chamber or recess 56 which is closed at the bot
tom by a flat porcelain wall 58 that is integral
with the cylindrical side wall. The chamber is
open at its upper end and is closed by a trans
parent window preferably by mica 60 which is
heldin place on the end of the cylindrical body by
threaded in the internal threads of the receptacle ` a centrally apertured metal cap 62 having a side
25 shell I4. Means such as one or more projecting wall the end 64 of which is reflexed about the
lower edge of the outstanding notched flange 66
resilient locking members 36 are, or can be, car
rled by the adapter to dig into the receptacle shell
of the plug body.
when it is attempted to screw the adapter out of
the shell, for the purpose of irremovably lock
' The plug body is provided with external screw
threads 68 on which is located an interiorly and
-30 ing the adapter in place.
‘
The adapter also is formed with an upstanding
cylindrical boss or projection 32 which is co-axial
with the threaded flange 28. Said boss is sur
rounded by a circular rib 34 which is co-axial with
the boss and preferably is level therewith and is
circularly spaced therefrom to provide an annular
recess 36 which preferably is deeper than the
height of said rib. 'I'he top of said rib is formed
or provided with a series of angularly spaced
40 sharp-edged notches 38 in which bridging ma
terial such as a fuse wire is adapted to be caught
and sheared off by the rotation of the cooperating
plug presently to be described.
The adapter is provided with a movable con
45 tact member 48 adapted to be engaged by the
center contact member of the plug and moved
thereby into engagement with the center contact
exteriorly screw-threaded metalshell 10 which 30
constitutes a terminal of the plug body. Said
shell is adapted to be screwed into and elec
trically engage the vshell I4 of the receptacle.
The plug body is provided with a center con
tact member 12 in the form of a relatively long,
small diameter cylindrical metal rod located
coaxially with the plug body and secured in the
bottom wall 58 and projecting downwardly there
from and also into the link chamber 56. A fusible
element or fuse link 14 has one end connected
with the upper end of the contact member 12.
The other end of the link is located in a channel
16 of the plug body and is connected to the
terminal shell 10 by a mass of solder 18. Said
solder mass also serves as a key to hold the
terminal shell against rotation on the plug body.
'I‘he plug is provided with non-tamperable
member 20 of the receptacle but is normally biased _ means cooperating with the boss 32, rib 34 and
for, movement out of engagement with said re
Said contact member
40 is of small axial length so that the plug which
cooperates with the adapter can also be inserted
in and make operative engagement with the center
contact member of a similar receptacle not hav
50 ceptacle contact member.
55 ing the adapter.
Said contact member 48 comprises a cup-shaped
member having a thin bottom wall 44 which is
adapted to engage the receptacle contact mem
ber 28. The cup shaped member is carried by or,
60 as here shown, ls integral with resilient means
which act to urge the cup-shaped member up
wardly. Said resilient means comprise a plurality
~of outwardly extended resilient arms 46. Said
contact member 48 is located in a circular recess
65 48 formed in the lower face of the adapter. The
bottom end of -said recess is closed by an insulat
ing plate 58 which is pressed into an enlargement
of said recess. Said cover plate is provided with
a circular passage 52 therethrough which is co
70 axial with the adapter. The cup member 42 of
the contact member is movable axially in said
passage into and out of engagement with the
center contact member of the receptacle. The
spring arms 46 are reilexed downwardly and the
75 ends thereof constantly bear against the inner
channel 36 of the adapter, said means, however,
being a part of a member 88 that is separate from
the plug body. Said member 88 comprises a flat
upper circular wall 82 from the periphery of
' which depends an outer annular rib 84 and, inter
nally spaced therefrom, an inner annular rib 86.
providing an annular channel 88 between the ribs
and a cylindrical passage 88 within the inner rib.
The inner rib 86 is adapted to fit snugly into
the annular recess 36 of the adapter and the
outer rib 34 of the adapter is adapted to fit
snugly in the annular recess 88 of said member 80.
The outer rib 84 surrounds the adapter rib 34
and the inner rib 86 surrounds the adapter boss
32. The inner rib 86 preferably depends sub
stantially below the outer rib 84. The bottom
face of the inner rib is provided with a series
of angularly spaced sharp-edged notches 92
which cooperate with the notches 38 of the
adapter in catching and shearing oif bridging
material.
'
, The radial clearance between the intermeshing 70
ribs is intended to be as small as practical so
that bridging material cannot occupy the space
between the confronting faces of the intermeshed
ribs. For this purpose the member 80 is molded
in the above described shape and is composed
3
2,115,447
‘ of some moldable material as an artificial resin ì
that can be molded accurately to dimension.
The terminal shellllof the plug body surrounds
and engages the periphery 'of said member Il
and has its inwardly extended lower end flange
94 seated upon the bottom face of the rib Il,
whereby to hold the flat wall l2 of said member
80 seated upon the bottom face of the wall 5l
of the plug body.
The terminal shell 1I serves to locate the mem
10
ber 80 co-axial with the center'contact. member
12. The wall 82 of said member is provided with
a pair of upstanding projections 90 which are
snugly received in correspondingly shaped re
cesses 9B in the end wall 5I additionally to locate
the member 80 co-axially with the plug body
and also to keep the two together for conjoint
rotation.
ber, a member on the end of said body composed
of an artiñcial resin having tamper-preventing
means exposed at the end of the plug, fuse ter«
minals, means irremovably securing said body
and member together, and means isolating said
member from the action of the arc formed by
the rupture of said link.
5. A non-tamperable plug fuse comprising an
externally screw-threaded plug body having a
fuse link chamber therein and a bottom wall in 10
.
With the above arrangement the accurate di
20 mensioning property of the member 8l can be
utilized and yet the member is entirely excluded
from the arc formed upon the fusing of the fusi
ble element or link 'Il under excessive current,
while the arc takes place in an enclosure the
walls of which do not liberate gas into the fuse
chamber when subject to the arc.
'
The small axifl length of the adapter contact
member 4|) and the long center contact member
"I2 of the plug, which contact member projects
beyond any insulating part of the plug, adapts
the plug for service both in a fuse receptacle
having an adapter therein and also in a recepta
cle having no adapter therein.
In the modification illustrated in Rg. 7 a dif
ferent manner of locating the tamper-prevent
ing member 80 co-axially with the center con
>tact member 12 of the fuse is shown. In this
modification the central passage 90 is provided
with a transverse top wall Illl that has a central
passage |02 therein in which the center contact
member 12'is adapted to fit snugly. The passage
|02 can be accurately located co-axially with
the ribs B4 and 86 and thus the ribs can be ac
curately located co-axially with the center con
tact member and hence with the ribs of the
adapter.
I claim:
l. A non-tamperable plug fuse comprising the
combination of a plug body having means pro
viding a chamber, a fusible member in said cham
ber, a member on the end of said body having
tampa-preventing means exposed at the bottom
end of the member, means irremovably securing
said body and member together, and fuse termi
nals connected with said fusible member.
2. A non-tamperable plug fuse comprising a
body having a fuse link chamber therein, a bot
tom wall for said chamber integral with said
body, a separate closure for the top of said
chamber, a member on the bottom face of said
wall having -tamper-preventing means,- means
irremovably securing said body and member to
gether, a fusible link in said chamber, and ter
minals connected with said link.
3. A non-tamperable plug fuse comprising a
porcelain body having a fuse link chamber there
„ in and a bottom wall for said chamber that is
tegral with said body and _closing said chamber
at the bottom, a closure for the top of said cham
ber, a center contact member .carried by said
bottom wall and projecting downwardly there
below, a screw-threaded terminal shell on the
screw-threads of said body, a fusible link within
said chamber and connected between said con
tact member and shell, a member separate from
said body on said bottom wall and having an an
nular tamper-preventing recess in its ,end face, 20
said screw shell having means clamping said mem
ber on said bottom wall, and means securing said
member and plug body irremovably in the afore
said relation.
n
6. A non-tamperable plug fuse comprising a
screw-threaded plug body having a fuse link
chamber therein and a bottom wall integral with
said body and closing said chamber at the bot
tom, a closure for the top of said chamber, a
center contact member carried by said bottom
wall and projecting downwardly therebelow, a
screw-threaded terminal shell on the screw
threads of said body, a fusible link within said
chamber and connected between said contact
member and shell, a member separate from said
body on said bottom wall and having an annular
tamper-preventing recess in its end face, said
screw shell having means clamping said member
on said bottom wall, and means securing said
member and plug body in the aforesaid relation, 40
said center contact member projecting through
and beyond said member.
7. A non-tamperable plug fuse comprising a
screw-threaded plug body having a fuse link
chamber therein and a bottom wall integral with 45
said body and closing said chamber at the bot
tom, a closure for the top of said chamber, a
center contact member carried by said bottom
wall and projecting downwardly therebelow, a
screw-threaded terminal shell on the screw
threads of said body, a fusible link within said
chamber and connected between said lcontact
member and shell, a member separate from said
body on said bottom wall and having an annular
tamper-preventing recess in its end face, said
screw shell having means clamping said member
on said bottom wall, means securing said member
and plug body in the aforesaid relation, said
member composed of an arc-reactive mate
rial capable of being molded to accurate dimen ne
sions, and said plug.body composed of an arc
inert moldable material.
8. A plug fuse comprising a body having a
chamber therein and a bottom wall integral with
said body forming a bottom closure for said cham
ber, a closure for the top of said chamber, an
insulating tamper-preventing member separate
integral with said body, a closure for the open
from said body and disposed on the end thereof
top of said chamber, a member` on the bottom
curing said body and member in the aforesaid 70
relation, terminals carried by said body, and a
fusible member in said chamber connected with
70 face of said wall having tamper-preventing
means and composed of a molded artificial resin,
>means irremovably securing s_aid body and mem
ber together, and a fusible link in said chamber.
4. A non-tamperable plug fuse having a cham
bered ceramic body, a fusible link in the cham
and on said bottom wall, means permanently se
said terminals.
~
9. A `non-tamperable plug fuse comprising a
plug body having a fuse link chamber therein and
4
2,115,447
‘a bottom wall integral with said body and clos
ing said chamber at the bottom, a closure for the
top of said chamber, a center contact member
carried by said bottom wall and projecting down
wardly therebelow, a screw-threaded terminal
shell on said body, a fusible link within said cham
ber and connected between said contact member
and shell, a member separate from said body on
said bottom wall and having outer and inner ra
dially spaced' annular tamper-preventing ribs
projecting endwise of said plug, said inner ribssurrounding and spaced from said center con
tact member, means positioning said ribs and con
tact member co-axially, and means irremovably
securing said member to said plug body.
10. A non-tamperable plug fuse comprising a
plug body having a fuse link chamber therein and
a bottom wall integral with said body and closing
said chamber at the bottom, a closure for the top
of said chamber, a center contact member carried
by said bottom wall andprojecting downwardly
therebelow, a screw-threaded terminal shell on
said body, a fusible link within said chamber and
connected between said contact member and shell,
a member separate from said body on said bot
tom wall and having outer and inner radially
spaced annular tamper-preventing ribs project
ing endwise of said plug, said inner ribs sur
rounding and spaced from said center contact
member, means positioning said ribs and contact
member co-axially including interiitting pro
jections and indentations of said member and end
wall, and means securing said member irremov
ably on said plug body.
_
11. A non-tamperable plug fuse comprising a
plug body having a fuse link chamber therein and
a bottom wall integral withsaid body and closing
said chamber at the bottom, a closure for the top
of said chamber, a center -contact member car
ried by said bottom wall and projecting down
wardly therebelow, a screw-threaded terminal
shell on said body, a fusible link within said cham
_ber and connected between said contact member
and shell, a member separate from said body on
45 said bottom wall and having outer and inner ra
dially spaced annular tamper-preventing ribs
projecting endwise of said plug, said inner ribs
surrounding and spaced from said center ccn
tact member, means positioning said ribs and
contact member co-axially, said member being
located within said shell, and said shell having
an inwardly directed end flange seated upon the
end face of said outer rib which clamps said mem
ber upon said plug body, and means permanently
anchoring said shell to said plug body.
12. The combination of a plug fuse and an
adapter having cooperating conductor dislodging
and rupturing means, said fuse having a terminal
shell and' a center contact member that projects
a substantial distance beyond the end of the
fuse, and said adapter comprising an insulating
body adapted to be located in a fuse receptacle
chamber therein, a bottom wall integral with said
body and constituting a closure for the bottom of
said chamber. a closure for the top of said cham
ber separate from said body, a terminal shell on
said body, a center contact member carried by and
extended below said bottom wall, a fusible element
in said chamber and connected with said shell and
contact member, and a tamper-preventing mem
ber separate from said body on said bottom wall
having outer and inner spaced projecting annular
ribs surrounding said contact member, means
irremovably securing said member and plug body
together, said adapter comprising a member hav
ing means providing screw threads, an outer up
standing annular rib adapted to enter the space 15
between the ribs of said fuse, a center upstanding
boss having a fuse contact passage therein and
adapted to enter the space within the inner rib
of said fuse, and a movable contact member un
der the passage of said boss.
20
14. The combination of a fuse receptacle hav
ing a terminal shell and a center contact mem
ber, a fuse having a center contact member and
a terminal shell engaged with said receptacle
shell, an adapter comprising an insulating body 25
within said shell over said receptacle contact
member and under said fuse, a movable contact
member carried by said insulating body adapted
to be clamped between the center contact mem
bers of said fuse and receptacle, and means act 30
ing on said body and contact member constantly
,biasing said movable contact member for move
ment away from said receptacle contact member,
said movable contact member being thin in the
axial direction of the receptacle to permit direct 35
engagement of the fuse contact member with the
receptacle contact member when the adapter is>
absent from the receptacle, said fuse and adapter
also having cooperating conductor dislodging and
rupturing means.
40
15. An adapter for fuses and fuse receptacles
comprising an insulating member having a pas
sage therethrough, a movable contact member
carried by said insulating member and located in
a part of said passage and including a thin con
tact plate that traverses said passage and has
oppositely facing contact faces, and resilient
means acting on said contact member and in
sulating body constantly biasing said contact
member for movement in a predetermined di
rection.
16. An adapter for fuses and fuse receptacles
50
comprising a member having a passage there
through, a movable contact member comprising a
cup-shaped member carried by said adapter 55
member and located in a. portion of said passage,
and resilient means acting between said contact
member and adapter member constantly biasing
said cup-shaped member for movement in a pre
determined direction, said cup-shaped member 60
w movable contact member being of such short
having a thin bottom wall providing internal and
external contact faces.
17. An adapter for fuses and fuse receptacles
comprising a supporting member having a pas
sage therethrough, a movable contact member l65
carried by said supporting member comprising a
cup-shaped member located in a portion of said
passage and guided by said passage for movement
axial length that the :f_use can also be opera
70 tively positioned in a receptacle lacking the
adapter and have its shell and center contact
member engaged with the shell and center con
tact of the receptacle.
lengthwise thereof, said cup-shaped member hav
ing a thin bottom wall providing both internal 70
and external contact faces, and spring means
acting on the peripheral portion of said cup
shaped member and on said supporting member
over the center contact thereof and a movable
contact member resiliently supported by said
65 body and adapted to be engaged by the fuse con
tact member and moved thereby into engage
ment with the receptacle center contact, said
13. 'I'he combination-of a plug fuse and an
adapter, said fuse comprising a body having a
and operative to bias it for movement in a pre
determined direction in said passage.
5
2,1 1 5,447
18. An adapter for fuses and fuse receptacles
comp ising a supporting member having an in
comprising a supporting member having a pas
sage therethrough, a movable contact member
terna recess and upper and lower passages lead
carried by said supporting member comprising a
cup-shaped member located in a portion of said
passage and guided by said passage for move
ment lengthwise thereof, and having a thin bot
tom wall providing both internal and external
' contact faces and resilient means extended out
10 wardly from the periphery of said cup-shaped
member and bearing on said adapter and opera
tive to constantly bias said cup-shaped member
i’or movement in a predetermined direction in
said passage.
15
ing in opposite directions from said recess to the
ends of said member, a movable contact member
in said recess comprising a cup-shaped member
interposed between said passages and movable
lengthwise of said lower passage, said cup-shaped
member having a. thin bottom wall providing both
internal and external contact faces and resilient
means extended peripherally therefrom seated 10
upon a face of said recess and operative to bias
said cup-shaped member constantly for move
ment toward said recess.
~
19. An adapter for fuses and -fuse receptacles
JAIWES A. MCENTEE.
15
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