U.S. patent number RE28,489 [Application Number 05/382,083] was granted by the patent office on 1975-07-22 for molded electrical junction box.
This patent grant is currently assigned to Nelco Corporation. Invention is credited to John C. McEachron, Edgar C. Schindler.
United States Patent |
RE28,489 |
Schindler , et al. |
July 22, 1975 |
Molded electrical junction box
Abstract
An electrical junction box characterized by the provision of
knockouts provided in the walls of the outlet box which are
accessible from the interior of the box for easy removal. The
junction box, which is constructed of an injection moldable
resinous material having insulating properties, is provided with
tapered ribs on the exterior surface of the side walls to properly
orient the box with respect to the wall yet provide sufficient
draft angle to enable injection molding. Additional volume on the
interior of the electrical outlet box is provided by a lateral
extension of the box constructed and arranged to fit within the
wall structure. Grounding means for use with the boxes is provided
wherever necessary.
Inventors: |
Schindler; Edgar C. (Puyallup,
WA), McEachron; John C. (Tacoma, WA) |
Assignee: |
Nelco Corporation (Orting,
WA)
|
Family
ID: |
26951136 |
Appl.
No.: |
05/382,083 |
Filed: |
July 23, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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69266 |
Sep 3, 1970 |
3701451 |
|
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Reissue of: |
265342 |
Jun 22, 1972 |
03740451 |
Jun 19, 1973 |
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Current U.S.
Class: |
174/58; 220/3.2;
220/3.9; 264/334 |
Current CPC
Class: |
H02G
3/085 (20130101) |
Current International
Class: |
H02G
3/08 (20060101); H02G 003/12 () |
Field of
Search: |
;174/53-58
;220/3.2-3.6,3.9 ;264/334 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truhe; J. V.
Assistant Examiner: Tone; D. A.
Attorney, Agent or Firm: Rathbun; Harold J. Kettelson;
Ernest S.
Parent Case Text
This application is a division of application Ser. No. 69,266 filed
Sept. 3, 1970, now U.S. Pat. No. 3,701,451.
Claims
What is claimed is: .[.1. An electrical junction box having a wall
structure defining a plurality of front-to-rear walls which
terminate in a common frontal plane of the box and are
interconnected with one another to define a chamber within the box
that opens to the ambient surroundings of the box through the
frontal plane thereof, a pair of which front-to-rear walls are
oppositely disposed to one another and taper relatively toward one
another in the direction relatively rearwardly away from the
frontal plane of the box, and have corresponding laterally
outstanding ribs thereon which extend in the front-to-rear
direction of the box and define a pair of flat surfaces thereon
that are disposed in spaced parallel planes extending perpendicular
to the frontal plane of the box..]. .[.2. An electrical junction
box according to claim 1 wherein there is a pair of spaced ribs on
each of the oppositely disposed front-to-rear walls of the
structure..]. .Iadd. 3. A molded plastic electrical junction box
having a wall structure defining a plurality of front-to-rear walls
which terminate in a common frontal plane of the box and are
interconnected with one another to define a chamber within the box
that opens to the ambient surroundings of the box through the
frontal plane thereof, a pair of which front-to-rear walls are
oppositely disposed to one another and taper relatively toward one
another in the direction relatively rearwardly away from the
frontal plane of the box, and have corresponding laterally
outstanding ribs thereon which extend in the front-to-rear
direction of the box and define a pair of flat surfaces thereon
that are disposed in spaced parallel planes extending perpendicular
to the frontal plane of the box, said ribs providing blunt bearing
surfaces having at least as much bearing area at their rearward
portions as there is at their forward portions and formed to
resistingly bear against the surface of a mounting stud throughout
at least their rearward portions so that the frontal plane of a
mounted box is generally perpendicular to the surface of the
mounting stud, and means on the said box for anchoring said box to
a mounting stud, such that the anchor point between the box and a
mounting stud is spaced from both the body of the rib and the
rearward portion of said rib by an amount sufficient to insure that
the rearward portion of said rib is not loaded by mounting forces
to an extent that said rearward portion substantially deforms said
stud whereby, when the box is mounted on a stud, the box is
oriented so that the frontal plane of the box is substantially
perpendicular to the surface of the stud to which the box is
attached. .Iaddend..Iadd. 4. A molded plastic electrical junction
box according to claim 3 wherein there is a pair of said spaced
ribs on each of the oppositely disposed front-to-rear walls of the
structure. .Iaddend..Iadd. 5. A molded plastic electrical junction
box having a wall structure defining a plurality of front-to-rear
walls which terminate in a common frontal plane of the box and are
interconnected with one another to define a chamber within the box
that opens to the ambient surroundings of the box through the
frontal plane thereof, a pair of which front to rear walls are
oppositely disposed to one another and taper relatively toward one
another in the direction relatively rearwardly away from the
frontal plane of the box, there being laterally outstanding ribs on
one of the pair of front to rear walls which extend in the front to
rear direction of the box and define a pair of surfaces thereon
that are disposed in a plane extending perpendicular to the frontal
plane of the box, said ribs providing rearwardly diverging bearing
means, said bearing means being formed to resistingly bear against
the surface of a mounting stud throughout at least the rearward
portion of said rib so that the frontal plane of a mounted box is
generally perpendicular to the surface of the mounting stud, and
means on the said box for anchoring said box to a mounting stud,
such that the anchor point between the box and a mounting stud is
spaced from both the body of the rib and the rearward portion of
said rib by an amount sufficient to insure that the rearward
portion of said rib is not loaded by mounting forces to an extent
that said rearward portion substantially deforms said stud whereby,
when the box is mounted on a stud, the box is oriented so that the
frontal plane of the box is substantially perpendicular to the
surface of the stud to which the box is attached. .Iaddend..Iadd.6.
A molded plastic electrical junction box according to claim 5
wherein the surfaces of the said ribs are flat. .Iaddend..Iadd. 7.
A molded plastic electrical junction box according to claim 5,
wherein said rearwardly diverging bearing means comprises the body
portion of said rib which diverges around the longitudinal axis of
said rib in the direction from front to rear to provide a greater
surface area of said ribs as they extend rearwardly.
.Iaddend..Iadd. 8. A molded plastic electrical junction box
according to claim 5, including angular junction lines forming a
vertex along each side of said ribs at the point of juncture with
said wall, said junction lines including first ends relatively
nearer the front edge of said front-to-rear wall and second ends
relatively nearer the rear edge of said front-to-rear wall, said
junction lines being spaced apart, said second ends of said
junction lines being spaced apart a distance at least as great as
the distance between said first ends of said junction lines.
.Iaddend..Iadd. 9. A molded plastic electrical junction box
according to claim 5 wherein said bearing means of said ribs formed
to resistingly abut the surface of a mounting stud include a broad
surface portion relatively nearer the rear edge of said
front-to-rear wall on which said ribs are held to bear against a
correspondingly broad region of said mounting stud to resistingly
restrain said rib from penetration into the surface of said stud.
.Iaddend. .Iadd. 10. A molded plastic electrical junction box
according to claim 5 wherein said bearing means of said ribs formed
to resistingly abut the surface of a mounting stud include a blunt
contact portion rearwardly thereof to bear against said mounting
stud to resistingly restrain said rib from penetration into the
surface of said stud. .Iaddend..Iadd. 11. A molded plastic
electrical junction box having a wall structure defining a
plurality of front-to-rear walls which terminate in a common
frontal plane of the box and which are interconnected with one
another to define a chamber within the box that opens to the
ambient surroundings of the box through the frontal plane thereof,
a pair of the front-to-rear walls being oppositely disposed to one
another and tapering relatively toward one another in the direction
rearwardly away from the frontal plane of the box, one wall of said
pair of front-to-rear walls having an outstanding rib thereon which
extends in the front-to-rear direction of the box and defines a
first abutment surface that is disposed in a plane extending
perpendicular to the frontal plane of the box, said abutment
surface being formed to resistingly bear against the surface of a
mounting stud to restrain said rib from penetration therein so that
the frontal plane of a mounted box will be generally perpendicular
to the surface of the mounting stud, and means on the said box for
anchoring said box to the mounting stud, such that the anchor point
between the box and the mounting stud is spaced from both the body
of the rib and the rearward portion of said rib by an amount
sufficient to insure that the rearward portion of said rib is not
loaded by mounting forces to an extent that said rearward portion
substantilly deforms said stud whereby, when the box is mounted on
the stud, the box is oriented so that the frontal plane of the box
is substantially perpendicular to the surface of the stud to which
the box is attached. .Iaddend..Iadd. 12. A molded plastic
electrical junction box according to claim 11, wherein said
abutment surface includes a broad surface portion relatively nearer
the rear edge of said front-to-rear wall on which said rib is
formed to bear against a correspondingly broad region of said
mounting stud to resistingly restrain said rib from penetration
into the surface of said stud. .Iaddend..Iadd. 13. A molded plastic
electrical junction box according to claim 11 wherein said abutment
surface includes a blunt contact portion extending rearwardly of
said rib to bear against said mounting stud to resistingly restrain
said rib from penetration into the surface of said stud.
.Iaddend..Iadd. 14. A molded plastic electrical junction box
according to claim 11 wherein the other wall of said pair of
front-to-rear walls has an outstanding rib thereon which extends in
the front-to-rear direction of the box and defines a second
abutment surface that is disposed in a plane extending
perpendicular to the frontal plane of the box, said second abutment
surface being formed to resistingly bear against the surface of a
mounting stud to restrain said rib from penetration therein.
.Iaddend..Iadd. 15. A molded plastic electrical junction box
according to claim 11 wherein said rib includes rearwardly
diverging bearing means. .Iaddend..Iadd. 16. A molded plastic
electrical junction box according to claim 15 wherein said
rearwardly diverging bearing means comprises the body portion of
said rib which diverges around the longitudinal axis of said rib in
the direction from front to rear to provide a greater surface area
of said ribs as they extend rearwardly. .Iaddend..Iadd. 17. A
molded plastic electrical junction box having a wall structure
defining a plurality of front-to-rear walls which terminate in a
common frontal plane of the box and which are interconnected with
one another to define a chamber within the box that opens to the
ambient surroundings of the box through the frontal plane thereof,
a pair of front-to-rear walls being oppositely disposed to one
another and tapering toward one another in the direction relatively
rearwardly away from the frontal plane of the box, one wall of said
pair of front-to-rear walls having a pair of outstanding ribs
thereon which extend from the front-to-rear direction of the box
and define a pair of spaced apart exposed abutment surfaces that
are disposed in a common plane extending perpendicular to the
frontal plane of the box, said ribs providing a body portion which
diverges around the longitudinal axis of said rib in the direction
from front to rear, said diverging body portion providing a bearing
surface to resistingly bear against the surface of a mounting stud
throughout at least the rearward portion of said ribs so that the
frontal plane of a mounted box is generally perpendicular to the
surface of the mounting stud, and means on the said box for
anchoring said box to a mounting stud, such that the anchor point
between the box and a mounting stud is spaced from both the body of
the rib and the rearward portion of said rib by an amount
sufficient to insure that the rearward portion of said rib is not
loaded by mounting forces to an extent that said rearward portion
substantially deforms said stud whereby, when the box is mounted on
a stud, the box is oriented so that the frontal plane of the box is
substantially perpendicular to the surface of the stud to which the
box is attached. .Iaddend..Iadd. 18. A molded plastic electrical
junction box according to claim 17 wherein the other wall of said
pair of front-to-rear walls has a pair of said outstanding ribs
thereon which extend in the front-to-rear direction of the box and
define a pair of spaced apart exposed abutment surfaces that are
disposed in a common plane extending perpeneidulcar to the frontal
plane of the box. .Iaddend..Iadd.19. A molded plastic electrical
junction box in accordance with claim 17 wherein the body portion
of said ribs adjacent said wall is relatively narrow in
cross-section throughout its extent from front-to-rear, said ribs
being respectively positioned adjacent lateral edges of their
associated front-to-rear walls. .Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to junction boxes and electrical outlet
boxes constructed of a material having insulating properties, and
to grounding means for use with such boxes.
This invention further relates to molded electrical junction boxes
made of an insulating material which have a plurality of knockouts
designed to be readily removable from the interior of the box.
PRIOR ART
Junction boxes of the general type with which the invention herein
is concerned are usually rugged die-cast aluminum housings having a
number of wall segments which may be removed by impact or
manipulation with tools from the outside of the box. It is usually
very difficult to remove these knockouts from the interior of the
box since no means is provided for ready manipulation and access
from the interior. Other types of outlet boxes are known to the
prior art in which plastic materials are molded into an open topped
receptacle; however, the knockout segments provided in these
devices suffer similarly from the problem of inaccessibility from
the interior of the box. Thus, whenever the outlet or junction box
is installed in a wall, it is very difficult to open one of the
knockout segments to provide access to the interior of the box
without either doing a great deal of damage to the adjacent wall
materials or completely removing the outlet box from the wall. The
junction boxes with which this invention is concerned are intended
to enable the mounting of a variety of electrical applicances, such
as switches, electrical receptacles and convenience outlets.
Mounting the devices of the prior art to structural members in the
wall has presented several problems. The first problem encountered
involves the manufacture and construction of the electrical
junction box. The mounting apparatus has presented some problems
with regard to the injection molding techniques necessary to form
the mounting apparatus as a part of the injection molded electrical
outlet box. The prior art devices, while providing for the
attachment of the device to the structural member, have resulted in
fabrication difficulties due to mold release problems. One
alternative has been to provide a separate mounting bracket to be
nailed to the structural member and to which the box is then
attached by screws or bolts.
OBJECTS OF THE INVENTION
It is an object of this invention to provide a molded electrical
outlet box constructed of a lightweight and inexpensive material
which is easy to manufacture. A releated object of this invention
is to provide an open-topped molded insulation wiring box which may
be constructed utilizing injection molding techniques.
One primary object of the present invention is to provide an
electrical outlet box having insulating properties which has a
fastening bracket molded as an integral part thereof and with which
standard nails may be used for fastening the outlet box to
structural members.
A further object of this invention is to provide an electrical
outlet box having knockouts accessible from the interior of the box
so that the knockouts may be readily removed from the interior of
the box using tools normally available to the electrician. A
related object of this invention is to provide a knockout structure
which presents a smooth-edged opening to any conductors placed
therein after the knockout blank has been removed.
A still further object of this invention is to provide an
electrical outlet box having means to ground appliances placed
therein such that the outlet box itself may be used for either
grounded or non-grounded electrical apparatus.
One specific object of this invention is to provide an electrical
outlet box for thin-wall constructionn having a sufficient volume
to meet the standards set up by governmental codes, yet which has a
standard-sized opening.
Accordingly, this invention provides an electrical outlet or
junction box which may be constructed of a plastic or other
suitable insulating material which can be molded into the desired
shape. Opposing side walls carry a pair of fastener ears through
which standard nails may be placed to secure the outlet boxes to a
structural member in a wall. Tapered ribs are provided adjacent the
dihedral corners of the box to compensate for the draft angle of
the box side walls. The draft angle is provided in the design of
the injection molded box to facilitate molding. The ribs are
positioned on the side walls of the box to engage the structural
members of the wall and cause the front face of the box to be
positioned in the plane of the wall into which the box is
installed.
Knockouts are positioned in the side walls of the box. The
knockouts are constructed so that they may be removed and
conductors inserted into the box after the box has been installed
in a wall. The knockouts are molded into the side of the junction
box in such a manner that they may be removed from the inside of
the box by insertion of the blade of a screwdriver or similar tool
into an exposed slot on the interior of the box and twisting the
screwdriver to break the portion of the knockout which covers the
aperture. The knockout is molded in a thin section so that it will
fracture readily, yet maintain adequate strength to close the
aperture in those instances in which the knockout is not
removed.
The outlet box of this invention can be provided with an offset
extension for use with a shallow depth or thin-wall type
construction so that while a single modular opening can be
utilized, the interior volume of the box may equal the electrical
code requirements. This is accomplished by providing a protrusion
from the side of the box extending into the interior of the wall
structure.
A grounding mechanism is provided with the injection molded
junction boxes which may be inserted into the box to ground any
appliance to be used with the box. The removable grounding
mechanism permits the use of the junction box described herein
interchangeably in appllications in which grounding of the
appliance is necessary and applications in which no grounding
device is required.
These and other objects and advantages of this invention will
become more readily apparent by an evaluation of the description of
several preferred embodiments of this invention as set out below
with particular reference to the attached drawings.
IN THE DRAWINGS
FIG. 1 shows an exploded perspective view of one embodiment of this
invention which is a drop-wall style outlet or junction box
suitable for standard building applications;
FIG. 2 shows a bottom perspective view of the device shown in FIG.
1;
FIG. 3 shows an upper perspective view of one embodiment of this
invention which is suitable deep-wall use in thin-wall construction
such as mobile homes and the like;
FIG. 4 is a front view of the device shown in FIG. 3;
FIG. 5 is a side view of the device shown in FIG. 3;
FIG. 6 is an end view of the device shown in FIG. 3;
FIG. 7 is a partial plan view of the knockouts utilized in the
device shown in FIG. 3;
FIG. 8 is a partial cross section of the knockout area shown in
FIG. 7 taken along lines 8--8;
FIG. 9 is a partial cross section of the knockout area shown in
FIG. 7 taken along lines 9--9 of FIG. 7;
FIG. 10 is a partial plan view of one of the knockouts used in the
device shown in FIG. 1;
FIG. 11 is a partial cross-sectional view of the knockout area
shown in FIG. 10 taken along lines 11--11 of FIG. 10;
FIG. 12 is a partial cross-sectional view of the knockout area
shown in FIG. 10 taken along lines 12--12 of FIG. 10;
FIG. 13 is a cross-sectional view of a second embodiment of the
knockout shown in FIGS. 10-12;
FIG. 14 shows one type of grounding mechanism suitable for use with
the various embodiments of this invention;
FIG. 15 is a perspective view of the apparatus shown in FIG. 14 in
assembled position;
FIG. 16 is a partial cross-sectional view of the apparatus shown in
FIG. 15 taken along lines 16--16 in FIG. 15;
FIG. 17 shows a second embodiment of the grounding means utilized
in this invention; and,
FIG. 18 shows a third embodiment of the grounding means utilized in
this invention.
Referring more particularly to the drawings, wherein like numerals
indicate like parts, there is seen in FIG. 1 an outlet box
indicated generally at 20 which is of the deep-wall style having a
standard size aperture defined by front face 35 into which an
appliance such as the convenience outlet 28 may be inserted. The
deep-wall molded junction box 20 has side walls 21, end walls 22
and a plurality of knockout elements 26 placed in the end walls 22.
A pair of fastener ears 23 are molded as an integral part of each
end wall 22 and provide means for attaching the box to a structural
member by use of nails 25. The fastener ears 23 are set at an angle
.alpha. with respect to the rear wall of the junction box 20 to
permit easier access in nails 25 for nailing the box to the
structural member. A threaded lug member 30 is molded into each end
wall 22 and the ridge formed thereby extends completely through to
the back wall 39. A slot 31 extends partially along the exterior of
side wall 22 and serves to decrease the amount of plastic necessary
to form the box while permitting the box to be formed by injection
molding techniques. The threaded lug member 30 must extend
completely to the back wall 39 of the box 20 to permit release of
the box from the mold. A depth guide 27 is provided on each end
wall to insure that the front face 35 of the box is flush with the
outer surface of the wall board or panelling used on the wall.
An important feature of this invention is to provision of the
tapered ribs 24 along the outer portion of the side walls 21 of the
deep-wall molded junction box. Ribs 24 are provided to properly
orient the side wall of the box so that the front wall 35 will be
precisely perpendicular to the structural member to which the box
is attached. It is necessary to provide the tapered ribs 24 so that
the injection molding techniques well known in the art may be
utilized to form the box. A draft angle equivalent to the angle
.gamma. must be imparted to the side walls in order to insure
release of the box from the mold. The tapered ribs 24 thus are
formed in the side walls 21 of the boxes 20 so that adjacent the
front wall 35 the ridge is flush with the surface of side wall 21.
Extending toward the rearward portion of the box the width of the
rib 24 increases so that the upper surface of rib 24 remains
perpendicular to the front face 35, and thus extends at the angle
.gamma. with respect to side wall 21. The tapered ribs 24 are
particularly useful in the deep-wall molded junction box 20 as
shown in FIGS. 1 and 2. However it may be used in all embodiments
of this invention, if desired.
An appliance such as the convenience outlet 28 may be readily
connected to wires extending into the interior of the box through
knockouts 26 and the appliance then pushed back into contact with
the threaded lug member 30 with screw 29 threadably engaging the
interior of threaded lug member 30. The ears 67 of convenience
outlet 28 are engaged by screw 29 to firmly hold the convenience
outlet 28 in its proper position within the box 20.
The knockout sections 26 are thin molded sections constructed of
the same material as makes up the rest of the box 20 and are formed
with an aperture 81 opening into the interior of the box. The
aperture 81 is formed so that the blade of a screwdriver may be
inserted into the aperture and the knockout 26 removed by twisting
the blade of the screwdriver to fracture the thin segment of
plastic material. A recess 32 extending along the sides of
knockouts 26 defines one wall of a very thin frangible member 34
which may be readily shattered by the twisting force of a
screwdriver blade in aperture 81. In FIGS. 10, 11 and 12 the
details of the knockouts 26 and the surrounding structure of box 20
is shown in detail. The straight entry port wall 33 presents a
smooth surface to any conductor entering the box to eliminate the
possibility of severing or otherwise injuring the insulation
thereon. The recesses 32 along the sides of the straight entry port
wall 33 insure that no jagged edges will be presented to the
conductor inserted through knockout 26 after removal of the
knockout blank.
The deep-wall molded junction box 20 is provided with end wall nail
guides 23 which are inclined at the angle .alpha. with respect to
the front face 35 to facilitate installation of the outlet box in a
standard wall construction. Angling the nail holders 23 with
respect to the front wall 35 gives easy access to the nails or
other fasteners being used to hold the outlet box 20 to the wall
studs. The fastener ears 23 are molded integrally with the junction
box and are designed to accept a standard nail or other fastener.
The fastener ears 23 are constructed by molding a forward facing
portion 52 and a rearward facing portion 53 by injection molding
techniques well-known in the art.
The deep-wall molded junction box 20 may be utilized in any
situation in which two-by-four timbers or similar structural
elements serve as the structural supports for the walls. Adequate
volume to meet the standards specified in the various applicable
building codes can readily be provided in the interior of the box
20 whenever there is adequate room for this style of box in the
wall structure. The box 20 can of course be made in double or
triple widths to accommodate gangs of switches or a plurality of
convenience outlets or other types of electrical apparatus,
switching gear and the like, which are to be mounted in the
interior of a wall.
Whenever the construction techniques utilized require a thin wall
type construction, adequate volume to meet the requirements of the
electrical codes frequently cannot be attained utilizing the shape
of outlet box shown in FIGS. 1 and 2. To meet this problem, a
second embodiment of this invention, as shown in FIGS. 3 through 6,
was devised to permit an adequate volume on the interior of the box
yet maintain the single standard width opening. In FIGS. 3 through
6, a shallow-wall molded junction box 40 is shown in various views.
This box 40 is made up of a pair of side walls 41, a pair of end
walls 42, a rear wall 44 and a covered or lanai section 48. The
lanai section 48 of the box is necessary to increase the interior
volume of the box to code standards while permitting installation
of the box in a thin-walled structure. The lanai section 48 has a
lanai cover 45 which may be molded as a separate piece and snapped
into place into the injection molded box 40 to cover the lanai
section 48 and reduce the size of the open area on the face of the
box to a standard opening. A pair of threaded lug members 50 are
disposed within the interior of the shallow-wall molded junction
box 40 and are molded as an integral part of the end walls 42. The
molding which forms the threaded lug member 50 extends through to
the back wall 44 of the box 40 but has a portion of the plastic
material removed from the outside to form slot 49 in the exterior
of the end walls 42. The threaded lug members are adapted to
receive appliances such as the convenience outlet 28 shown in FIG.
1.
On each end of the shallow wall molded junction box 40 a pair of
canted fastener ears 43 are attached to permit nailing of the
junction box to a support member. The canted fastener ears 43 are
positioned on the end walls of box 40 at an angle .delta. thereto
so as to facilitate the nailing of the box to a structural member
without danger of injury to the box from a hammer blow. The canted
fastener ears 43 are molded as a part of the end walls 42 and are
structured so that injection molding techniques may be utilized
with easy release of the formed box from the mold.
A pair of knockouts 46 are also located in each end wall 42 and can
be removed from the interior of the box by inserting a screwdriver
tip into the aperture 81 and twisting the screwdriver as described
above for the embodiment of this invention shown in FIGS. 1 through
3. The structure of the knockouts used in this embodiment of the
invention may best be ascertained by reference to FIGS. 7 through 9
which show the knockout sections 46 and the surrounding plastic
material in detail. During removal of the knockout 46, the
frangible sections 51 are broken and the knockout itself is broken
close to the base of the box 40 to permit insertion of a conductor
into the box without presenting any rough or jagged edges which
might injure the insulation on the exterior of the conductor.
The shallow-wall molded junction box 40 is provided with a pair of
depth guides 47 attached to each end wall 42 of the box 40. These
depth guides 47 are so located that plasterboard, panelling or
other wall material may be situated around the face of the outlet
box to a depth which causes the front face 35 to be flush with the
outer surface of the panelling material. The depth guides 47 are so
located that the lanai cover 45 may be covered by the panelling
material leaving only the opening exposed for access to the
interior of the box. The lanai cover 45 has an offset of an
equivalent distance to that of the depth guides so that the
panelling material may be placed on top of the lanai cover 45.
For many applications of either the deep wall molded junction box
20 or the shallow wall molded junction box 40, a grounding means is
necessary to meet the standards of various electrical codes.
Furthermore, for safety purposes, it is advisable to have switches,
convenience outlets and other appliances grounded to prevent injury
to the user through electrical shock. FIGS. 14 through 18 show
various embodiments of grounding devices useful with this
invention. In FIG. 14 one preferred embodiment of the grounding
device is shown in which a lipped grounding clip 60 is utilized to
provide an earth or ground to the switch body 66. This grounding
mechanism, which is shown in conjunction with the deep-wall molded
junction box 20, comprises a piece of flat metalllic material which
encircles a grounding wire conductor 61 at crimp 68. The lipped
grounding clip 60 has a screw aperture 65 through which screw 62 is
passed to fasten the switch body to the outlet 20. A lip 64 extends
perpendicularly from the main body of the lipped grounding clip and
is inserted into slot 63 for assembly. An interference fit may be
provided between lip 64 and slot 63 to assist in assembling the
apparatus. In FIGS. 16 and 17 the grounding clip is shown in its
operative position with the switch body 66 engaging the grounding
mechanism at ear 67 to provide a secure ground contact between the
switch plate 69 and a remote ground. The grounding clip and switch
mechanism is assembled by first placing the lip 64 into the slot 63
and engaging the grounding clip 60 with ear 67. Screw 62 is then
passed through the apertures in both ear 67 and grounding clip 60
into the threaded lug member 30.
A second embodiment of the grounding clip is shown in FIG. 17. In
this embodiment a spring-type grounding clip 70 having a pair of
tongues 71 and 75 and a grounding tab is provided to engage the
grooves 72 and 73 cut into the sides of threaded lug member 30.
This embodiment of the grounding clip is readily assembled prior to
placing the appliance in the junction box and a contact for
grounding purposes is established between tab 71 and the ear 67 of
a convenience outlet or similar electrical appliance. A third
embodiment of the grounding apparatus is shown in FIG. 18 and
merely comprises a lug-type grounding clip 80 which is securely
attached to a grounding wire 61 at crimp 68. The appliance is held
in place by screw member 62 and a secure ground is established by
attaching the end of grounding wire 61 to the appliance in a manner
well known in the art.
The materials of construction which may be utilized in this
invention include any of the normally itilized injection moldable
plastics such as phenolic resins and the like. It is particularly
desirable to utilize a material which has good mold release
characteristics since the intricate shapes necessary to mold the
junction box of this invention may result in the adherence of the
mold to the material unless the proper material is used. However,
the design of this box results in several desirable design features
which enhance the mold release characteristics. For example, the
provision of the ridges adjacent the dihedral corners of the
junction box permit a larger draft angle to be molded into the box
than was previously thought to be desirable or possible. The
nailing means with which the box is attached to structural members
is also designed for simple mold release with adequate structural
strength to hold the box in its proper position.
While the present invention has been described with particular
reference to specific examples, it will be apparent to those
skilled in the art that various changes and modifications may be
made thereto.
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