U.S. patent number 3,829,819 [Application Number 05/302,230] was granted by the patent office on 1974-08-13 for fused electrical plug.
This patent grant is currently assigned to Daniel Woodhead Inc.. Invention is credited to George R. Eckart.
United States Patent |
3,829,819 |
Eckart |
August 13, 1974 |
FUSED ELECTRICAL PLUG
Abstract
A dead front, back-wired electrical plug having a front
accessible fuse mounted in a fuse well in the front face, a
pivotable safety cover on the front face swingable into covering
and uncovering relationship with the well, and a hollow plug
housing with back-wired terminal posts for the respective contact
blades and ground pin which project from the front face.
Inventors: |
Eckart; George R. (Lake Zurich,
IL) |
Assignee: |
Daniel Woodhead Inc.
(Northbrook, IL)
|
Family
ID: |
23166865 |
Appl.
No.: |
05/302,230 |
Filed: |
October 30, 1972 |
Current U.S.
Class: |
439/142;
337/201 |
Current CPC
Class: |
H01R
13/68 (20130101); H01R 13/595 (20130101) |
Current International
Class: |
H01R
13/68 (20060101); H01R 13/595 (20060101); H01R
13/58 (20060101); H01r 013/58 (); H01r
013/68 () |
Field of
Search: |
;337/196,201
;339/39,44,147,206,103 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Moore; Richard E.
Attorney, Agent or Firm: Johnston, Keil, Thompson &
Shurtleff
Claims
The invention is hereby claimed as follows:
1. A dead front, back-wired electrical plug with a front-accessible
fuse comprising a hollow plug body of dielectric material, a
blade-mounting body of dielectric material mounted in one end of
said hollow plug body, the blade-mounting body having electrical
contact blades projecting from its front face, means on the rear of
said blade-mounting body for connecting said blades to current
wires of an electrical cord or cable, a well in an offset segment
of said front face, said offset segment and the well therein
extending longitudinally across one side of said face, fuse means
in the circuit of one blade, said fuse means including
fuse-mounting clips in said well, and a thin plate cover member of
dielectric material swingably mounted on said front face and
movable into and out of covering relationship with relation to said
well and lying flush with said front face when said plate is swung
to overlie said offset segment and the well therein.
2. An electrical plug as claimed in claim 1, said thin plate being
connected by pivot means in said offset segment to said front
face.
3. An electrical plug as claimed in claim 2, said a thin plate
having a projecting arm, and said pivot means being a pin pivotally
connecting said arm to said front face, and said arm lying flush
with said front face and said plate when said plate is swung to
overlie said offset segment and the well therein.
4. A dead front, back-wired electrical plug with a front-accessible
fuse comprising a hollow plug body of dielectric material, a
blade-mounting body of dielectric material mounted in one end of
said hollow plug body, the blade-mounting body having electrical
contact blades projecting from its front face, means on the rear of
said blade-mounting body for connecting said blades to current
wires of an electrical cord or cable, a well in and extending
longitudinally across one side of said front face, said fuse means
including fuse-mounting clips in said well, a slot extending
transversely across a side wall of said well, and one of said
blades being mounted in said slot and extending across said side
wall.
5. A dead front, back wired electrical plug with a front-accessible
fuse comprising a hollow plug body of dielectric material, a
blade-mounting body of dielectric material mounted in one end of
said hollow plug body, the blade-mounting body having electrical
contact blades projecting from its front face, means on the rear of
said blade-mounting body for connecting said blades to current
wires of an electrical cord or cable, a well in said front face,
fuse means in the circuit of one blade, said fuse means including
fuse-mounting clips in said well, said fuse mounting clips being a
pair of spaced, fuse-mounting clips mounted in said well, a
plurality of recesses in the rearward portion of said
blade-mounting body, means mounting one of said blades in one of
said recesses in electrical contact with one of said clips, a
terminal post with wire-clamping means mounted in one of said
recesses by means providing electrical contact with the other of
said clips, and the other of said blades extending through said
body and having a rearward terminal post positioned in another of
said recesses.
6. An electrical plug as claimed in claim 5, said well being
located along one side of said front face, a slot extending
transversely across a side wall of said well, and said one of said
blades being mounted in said slot and extending across said side
wall.
7. A dead front, back-wired electrical plug with a front-accessible
fuse comprising a hollow plug body of dielectric material, a
blade-mounting body of dielectric material mounted in one end of
said hollow plug body, the blade-mounting body having electrical
contact blades projecting from its front face, means on the rear of
said blade-mounting body for connecting said blades to current
wires of an electrical cord or cable, a well in said front face,
fuse means in the circuit of one blade, said fuse means including
fuse-mounting clips in said well, said one of said blades having a
laterally extending base portion seated in a recess in the rearward
portion of said body directly behind said well, an aperture through
said body connecting one end of said well and said recess, and a
metal fastener in said aperture and connecting and mounting one
fuse-mounting clip in said well and said base portion in said
recess.
8. An electrical plug as claimed in claim 7, a terminal post
mounted in a further recess in the rearward portion of said body in
spaced relation to said one of said blades and its base portion, a
second aperture through said body connecting the other end of said
well and said last-mentioned recess, and a second metal fastener in
said second aperture and connecting and mounting another
fuse-mounting clip in said well and said terminal post in said
last-mentioned recess.
Description
The invention herein concerns improvements in fused electrical
plugs, particularly those having a dead front and back-wiring of
the terminal posts of the blades and ground pin, having a well for
a fuse in the front face of the plug, the well having a safety
cover movable into and out of covering relationship with the well.
The fuse is connected in the plug's circuit between a terminal post
and its contact blade. Other improvements of the invention reside
in the configuration of the contact blade-mounting block to provide
a compact assembly of the fuse contacts, the contact blades, the
ground pin and the terminal post therefor.
A fused plug will protect motors, test instruments, data processing
equipment, and other similar machines or equipment against damage
caused by "brown-outs," unexpected voltage drops or other
electrical malfunctions. The amperage reading for the fuses may be
tailored to the safety needs for each particular motor, instrument,
piece of equipment, or machine, e.g., over a fuse range of 0.25 -
15 amps.
The location of the fuse well in the dead front of the plug and the
provision of a fuse well cover on the dead front has several
advantages. For added safety, the fuse can be removed only after
the plug has been removed from the receptacle. When removed, the
cover plate is readily moved into and out of covering relationship
relative to the fuse well whereby fuses may be quickly checked or
replaced.
One previously known type of fuse plug is a front-wired plug in
which the terminal posts for one contact blade and the ground pin
are recessed in forwardly opening wells immediately behind the
front face of the plug. The terminal post for the other contact
blade is positioned in a fuse well located next to the aforesaid
wells. One of the fuse clips is electrically connected with the
latter terminal post, while the other fuse clip is electrically
connected with the latter blade.
The front face of said known plug is a removable dielectric cover
plate with openings for the contact blades and ground pin. A body
with a cylindrical passage is integrally molded on the back face of
the dielectric cover plate. This body holds the midportion of a
cylindrical fuse and slips between the fuse-mounting clips in the
well when the cover plate is slid over the blades and ground pin
and mounted on the plug body. The contact ends of the fuse are
pressed into their respective contact clips as the cover is pressed
into its seated position on the plug body.
THE INVENTION HEREIN
This invention provides improvements over the known fused
electrical plug described above and other fusing arrangements for
electrical plugs by providing a dead front, back-wired electrical
plug with a front-accessible fuse. The plug of the invention
comprises a hollow plug body of dielectric material with a
blade-mounting body of dielectric material mounted in one end of
the hollow plug body. The blade-mounting body has electrical
contact blades, and optionally a ground pin, projecting from its
front face, which also serves as the front face of the plug. The
plug has circuit means for connecting its blades to the current
wires of an electrical cord or cable and, where provided, for
connecting the ground pin to the ground wire of such cord or
cable.
The circuit means includes a fuse in the circuit for the blade
connected to the hot wire. This fuse is located in a well in the
front face of the plug. Two fuse-mounting clips are seated in the
well. A cover member of dielectric material is mounted on the front
face of the plug and is movable into and out of covering
relationship with relation to the well.
Preferably, the cover member is a thin plate of dielectric material
connected by pivot means to the front face providing for the
swinging of the cover member into and out of covering relationship
with the well. The pivot means advantageously is provided with an
arm projecting from the side of the thin plate, the base of the arm
being pivotally connected to the front face.
The terminal posts for the respective blades and ground pin are
located on the rearward side of the blade-mounting body. These
terminal posts are seated in wells or recesses in the rear face of
the blade-mounting body. A separable cap covers the rear face and
the wells or recesses therein to keep the bare ends of the wires
well separated and isolated where they are attached to the
respective terminal posts. The cap has passages or apertures
through which the wires can pass into the respective wells or
recesses.
The rearward end of the plug has a clamp for securely clamping the
sheathed portion of the electrical cord or cable for the plug. Such
clamp preferably has one section integrally molded with the rear
portion of the hollow body of the plug and a removable section
attached by bolts to the first-mentioned section. The cord is
clamped between the sections by a bevelled, arcuate wall provided
in the clamping face of the first-mentioned section and a pair of
arcuate walls provided in the clamping face of the removable
section. These arcuate walls accommodate cords or cables of various
sizes and securely clamp such cords or cables by a biting action of
the respective arcuate walls into the outer, insulated sheath of
such cords or cables.
THE DRAWINGS
A preferred embodiment of the invention is illustrated in the
drawings, wherein:
FIG. 1 is a rear perspective view of the embodiment with the
removable, electric cord or cable-clamping member also shown in
phantom in exploded position;
FIG. 2 is a front perspective view of the embodiment with the cover
plate for the fuse well in closed position;
FIG. 3 is a view similar to FIG. 2 with the cover plate in open
position and the fuse in exploded, perspective view;
FIG. 4 is an exploded, front, perspective view of the three major
components of the electrical plug, i.e., the hollow plug body, the
contact blade-mounting block, and the removable electrical cable or
cord clamp member;
FIG. 5 is an exploded, rear perspective view of the blade-mounting
block, and its rear cap with one contact blade and the ground pin
in exploded view and the other contact blade mounted in the
block;
FIG. 6 is an exploded, front perspective view of the contact
blade-mounting block with the other contact blade, its terminal
post assembly, and the fuse-mounting clips in exploded view;
FIG. 7 is a side plan view of the blade-mounting block as viewed
from plane 7--7 of FIG. 2; and
FIG. 8 is a schematic diagram of the wiring of the electrical
components of the plug.
THE ILLUSTRATED EMBODIMENT
The electrical plug 10 has as its main components a dielectric
hollow plug body 11 made of an opaque, translucent or transparent
thermoplastic or thermosetting synthetic polymer and a dielectric,
contact blade-mounting block 12 molded from like or different
thermoplastic or thermosetting synthetic polymer, e.g., Lexan
(trademark), a polycarbonate polymer or resin. The block 12 has a
dead front face 13. The so-called dead face results from
back-wiring of the rearwardly located terminal posts 16 and 17 for
the contact blades 14 and 15 which project from the dead front
face. The ground pin 18 also projects from the front face with its
terminal post 19 also being back-wired.
The block 12 fits into the end 20 of the plug body 11 with its
groove 21 mating with the internal rib 22 in the body 11. The block
has a blade-accommodating passage 23, a ground pin-accommodating
passage 24, and a blade-accommodating slot 25. The latter extends
transversely across the inner side wall 94 of a fuse-receiving well
95 extending longitudinally along one side of the front face.
The blade 14 lies in slot 25. Its base has a diagonal leg 26 and an
apertured ear 27. The latter is conductively connected by rivet 28
to the apertured spring metal fuse-mounting clip 29. The diagonal
leg 26 lies on the diagonal surface 30 on the rear face of the
block 12. The rivet extends through hole 31 extending from the rear
face to the bottom wall of well 95.
The other fuse-mounting clip 32 is also made of spring metal and is
seated at the opposite end of the well 95. It is connected
conductively with the terminal post 16 by a rivet 33 which extends
through the apertured ear 34 of the terminal bracket 35, the latter
having mounted thereon a bolt 36 with a wire-holding nut 37. An
insulating gasket 38 with an apertured ear 39 lies on the bottom
wall of the recess 40 which extends diagonally into the rear face
from the side 41 of the block 12. The terminal post 16 is thus
conductively connected with the blade 14 via the fuse 42 and its
fuse-mounting contacts 29 and 32. The gasket 38 lies between the
terminal post 16 and the contact blade 14 and its diagonal leg 26.
It shields the latter against accidental contact by the wire
attached to terminal post 16 and also prevents conductive foreign
material from accidentally bridging the gap therebetween.
The other blade 15 projects through passage 23, the rearward end of
which intersects a recess 43 which opens into the rear face edge
portion 44 and the rear portion of the side wall 45 of the block
12. The wall 46 of recess 43 is slotted for the purpose of
receiving one edge of the base 47 of the blade 15. The bolt 49 and
nut 48 serve the purpose of clamping a wire to the terminal post
17. The arched portion 50 of the third wall of the recess 43
accommodates the projecting end of the bolt, the slotted head of
which is accessible through the slotted opening in the side wall
45.
The terminal post 19 of the ground pin 18 is seated in the same
manner in a recess 51 of like configuration to the recess 43 with
an edge of the base 52 seated in the slot 53. The wire clamping nut
54 is threaded on the bolt 55, the projecting end of which is
accommodated by the arched portion 56.
The block 12 has a rear cap 57 composed of a rear, cover plate 58
and side walls 59 and 60 dimensioned to enclose the two open sides
of the rear corner notch 61 of the block 12.
The cover plate 58 has a pair of apertures 62 and 63 for passage of
the two wires to be connected to the terminal posts 16 and 17. A
short tubular member 64 serves as a passage for the grounding wire
to be connected to the terminal post 19.
The block 12 and its rear cap 57 are held in the hollow housing 11
by bolts 64 and 65, the shanks of which extend through countersunk
passages 66 and 67 in the block 12 and apertures 68 and 69 in the
cover plate 58. The threads at the ends of the shanks are threaded
in integrally molded tubular columns 70 and 71 formed in two inner
corners of the rearward portion of the housing 11. The bolts 64 and
65 hold the cover plate 58 against an inner, peripheral lip 72
extending along the inner faces of the four sides of the rear
portion of the housing 11.
The hollow housing 11 has at its rearward end an electrical cable
or cord clamping unit 73. A half section 74 thereof is molded
integrally with the housing 11. This section has solid side
portions 75 and 76 with respective bolt-receiving passages 77 and
78. Its midportion has a bevelled, semi-circular opening 79 in its
clamping face 80. An electrical cable or cord passes through the
semi-circular opening 79 and is gripped on one side by the
relatively sharp, bevelled edge of the opening 79 when the
removable clamp section 81 is drawn against the cable by bolts 82
and 83.
The removable clamp section 81 is a molded plastic body having end
wells 84 and 85 for receiving said bolts. Its clamping face 86 has
planar end faces 87 and 88 with bolt passages 89 and 90 connecting
said faces and the respective wells 84 and 85. At the midportion of
the face 86 is a recess or well 91, the front and rear edges of
which have arcuate, cable or cord gripping walls 92 and 93
projecting outwardly therefrom. These walls oppose and coact with
the semi-circular passage 79 in the secure gripping of electrical
cables or cords of various diameters.
The fuse-mounting well 95 has a cover plate 96 which is movable
into and out of covering relationship with relation to the well.
The cover has a free end 97 which may overlie or cover, in the
well-covering position, the well and an offset shoulder 98' (FIG.
3) in the face of the front face 13. Its narrower neck 98 provides
a notched edge portion 99 in which the blade 14 is positioned with
the cover plate in well-covering position (FIG. 2). An arm 100
projects laterally from the base of the cover plate, the arm being
pivotally joined at its base by a plastic pin 101 having its end
deformed into a rivet-like head. The base of the arm lies in an
offset corner 102 in the front face 13 (FIG. 4) -- whereby the
front surfaces of the cover plate, its neck and its arm are
substantially flush with the plane of the front face 13.
As can be seen fron FIGS. 2 and 3, the swingable cover plate 96 and
the position of the fuse-mounting well 95 along one side of the
front face 13 gives ready, convenient access to the fuse 42 for its
inspection or replacement by simply swinging the cover plate 96 to
the position shown in FIG. 3. Removal of the fuse cannot be done
without removal of the plug from the receptacle. It is not
necessary, as is the case with previous known fused plugs, to
remove completely any part of the plug, e.g., a front cover plate
or its dielectric housing, to gain access to the fuse.
The back-wiring feature of the invention allows the plug to be
wired by removing the blade-mounting body 12 and its rear cap 57
from the hollow plug body 11, e.g., as shown in FIG. 4. The
respective bolts of the terminal posts are loosened. The wires of
the cable or cord are stripped of their insulating sheath to a
depth about equal to the depth of the respective wells or recesses
in which the respective terminal posts are mounted. The bare wire
ends are inserted through the respective apertures 62, 63 and 64 in
the rear cap 57 and pass between the respective nuts and the
terminal post portions 35, 47 and 52. The bolts are thereupon
turned by a screwdriver to securely clamp the wires on the
respective terminal posts.
The back-wiring feature provides complete isolation of the
respective ends of the wires from each other. Each bare wire end is
located in a well or recess with dielectric material separating the
wells or recesses. This arrangement provides one very safe wiring
arrangement which guards against accidental short-circuiting
between wires in the plug, voltage leakages across wires in the
plug and the like.
The configuration and orientation of contact blades 14 and 15 and
the optional ground pin 18 on the front face 13 is but one type of
many which may be used. Other configurations and orientations for
contact blade and ground pins of the non-locking or locking type
(such as those approved by the National Electrical Manufacturers
Association for various voltages and amperages) may be used instead
of that shown in the illustrated embodiment.
It is thought that the invention and its numerous attendant
advantages will be fully understood from the foregoing description,
and it is obvious that numerous changes may be made in the form,
construction and arrangement of the several parts without departing
from the spirit or scope of the invention, or sacrificing any of
its attendant advantages, the form herein disclosed being a
preferred embodiment for the purpose of illustrating the
invention.
* * * * *