Note: Descriptions are shown in the official language in which they were submitted.
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1 Background of the Invention
2 This invention relates to the field of electrical outlet
3 boxes having self-contained clamping means to mount and secure
4 the boxes in corresponding apertures provided in a wall panel of
a structure (such as a house or mobile home) in preparation for
6 wiring for electrical service.
7 For many years, outlet boxes were secured to studs and other
8 portions of a building wall by nails or screws, and many are
9 still secured by this method. In certain types of building con-
struction such as pre-fabricated housing, manufacture of mobile
11 homes and the like, assembly line techniques are employed which
12 lend themselves to time and labor saving techniques. Thus,
13 various self-contained clamping devices have been incorporated
14 into electrical outlet boxes to enable securing the box in place
in an aperture in a wall panel without the need for using screws
16 or nails driven into the studding framework. Among such self-
17 contained clamping devices are winglike members mounted on a-
18 frontal access screw to rotate upon rotation of the screw from a
19 folded position along a side of the box after the box has been
inserted in a receiving aperture in a wall panel to an extended
21 position wherein the winglike member extends outwardly from the
22 side of the box to sandwich an edge of the wall panel between
23 such member and a frontal flange of the box. Such clamping
24 devices rotate on an axis which is normal to the open front wall
25; f the outlet box and normal to the wall panel in which the
26 outlet box is being secured. The bearing surface of such devices
27 which faces the front of the box remains the same both in the
28 folded position against the side of the box and in the extended
230 position when rotated outwardly to bear against the rear surface
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1 of the wall panel after the box has been inserted in the aperture
2 in the wall panel. If this front facing bearing surface is made
3 relatively broad for good clamping contact when in the extended
4 position, the device will not clear when the box is inserted into
the receiving aperture. If the front facing bearing surface is
6 made narrow enough to clear when inserting the box in the
7 receiving aperture in the wall panel opening, it provides only
8 minimal clamping contact when rotated outwardly from the side of
9 the box to its extended position. Accordingly, when using this
type of device it is customary to provide one such device in each
11 corner of a rectangular outlet box in order to provide some degree
12 of stability to the box when installed.
13 Other attempts to provide self-contained clamping devices
14 for electrical outlet boxes have included forming integral ears
or clamping surfaces as outward projections from wall portions
16 of the outlet box, with a cam surface positioned to contact a
17 corresponding wall panel edge bounding the aperture in the wall
18 panel as the box is pushed into such aperture to flex the integral
19 ears or clamping surfaces inwardly until they are pushed beyond
the rear surface of the aperture of the wall panel whereupon they
21 are supposed to spring back to bear against such rear surface
22 and clamp the box in place with the wall edges held between such
23 ¦clamping surfaces and frontal flanges of the box. This type of
24 self contained device requires the use of materials capable of
25; flexing the clamping surfaces inwardly when the box is being
26 inserted and springing back when fully inserted. When used with
27 metal boxes, the cammed ears must be relatively thin to enable
28 them to flex inwardly when the box is pushedin the aperture in
29 the wall panel, thus limiting the area of bearing surface availabl~
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to clamp against the rear surface of the wall panel. ~hen this
type of device is used with various types of plastic outlet boxes,
the cammed ears do not always return to the fully extended
position and hence do not provide a satisfactory clamping surface.
The present invention overcomes the problems associated
with such prior art self-contained clamping devices. The L-shaped
clamp members described herein pivot between retracted and
clamping position on an axis which is parallel to the open front
wall of the box and to the surface of the wall panel in which the
box is mounted. This enables the use of a clamp which has a
relatively broader bearing surface than devices which rotate on
an axis normal to the surface of the wall in which the box is
mounted. A more secure clamp of the box to the wall panel can
thus be achieved, and with fewer clamp devices thus reducing cost.
According to one aspect of the present invention,
there is provided a clamp for use with an electrical outlet
box, said clamp receivably located in an elongated slot in a
wall of said outlet box, said clamp comprises a first leg
outside of said outlet box and a second leg inside of said
outlet box, said second leg consisting of a pair of spaced
apart projections, said first and second legs being connected
at a juncture and forming an initial predetermined angle slightly
greater than 90 degrees, said clamp being in a first position
before said outlet box is installed in a predetermined opening
in a house wall, said first leg being substantially parallel
and adjacent to said outlet box wall and extending toward said
rear wall of said outlet box, said second leg extending into
said outlet box,
a central appendage connected to said first leg of
said clamp near said juncture, said central appendage having
a step- dcwn end portion with a central apertureJ
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a pair of snap buttons located on the end of said
second leg opposite said juncture of said first and second
legs, a snap button being located on each of said pair of
spaced apart projections, for mating with a pair of apertures
in said outlet box wall,
such that after said outlet box is positioned in the
predetermined opening in the house wall, said clamp is manually
moved to a sesond position by pivoting said first and second
legs about said juncture in said elongated slot until said
snap buttons on said second leg are located in said corres-
ponding apertures in said outlet box wall, said first leg
effectively sandwiching the house wall between said second
leg and a frontal flange, extending laterally away from a front
edge of said outlet box wall, thereby securing said outlet box
in the house wall, and
an internally threaded bore in a center post extending
inwardly from said front edge of said outlet box wall and a
mounting screw, such that when said clamp is in said second
position, said central aperture and said threaded bore are in
registration, and when said mounting screw is inserted in said
threaded bore, said mounting screw extends through said central
aperture of said step-down portion of said central appendage thereby
substantially retaining said clamp in said second position.
The wall mounting clamp provided for the electrical
outlet box of this invention is disposed in a slot which is
parallel to the front wall of the outlet box. The clamp is
pivotable from a retracted position to a clamping position
through the slot. In the retracted position, an over-center snap
lock with a stop is provided to insure that the clamp does not move
away and become detached from the outlet box during the process of
shipping and installation. The clamp has two legs which are disposed
obtuse angle, and in the clamping position the legs are resolved to
a substantially 90 relationship whereby the bending forces
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1 applied to a first leg of the clamp as it is pushed up against
2 the mounting wall are translated into shear forces at the point
3 of contact between the clamp and the slot. In the clamping
4 position, snap plugs on the other leg of the clamp hold a second
leg to an inner wall of the outlet box. A secondary locking means
6 is provided by a screw which connects the receptacle to the out-
let box. The screw also extends through the leg which abuts the
8 wall panel,and,in the event that the leg connected to the wall
of the leg
~ panel of the outlet box becomesdetached,rotation/would be re-
stricted over a limited distance, and the box would not become
11 detached from the wall panel.
12 These and other objects, features and advantages of this
13 invention will become apparent from the following description
14 and drawings.
Brief Description of the Drawings
16 Fig. 1 is a front elevation of an electrical outlet box in
17 accordance with this invention in partial cross section with a
18 receptacle in phantom having wall mounting clamps pivotally mounted
19 in the top and bottom walls shown in their clamping position;
Fig. 2a is a perspective view of the mounting clamp;
21 Fig. 2b is a side view of the mounting clamp;
22 Fig. 3 is a front elevation of an electrical outlet box in
23 accordance with this invention in partial cross section having
24 wall mounting clamps pivotally mounted in the top and bottom
25 ; walls shown in their retracted position;
26 Fig. 4 is a section view taken along lines 4-4 of Fig. 3;
27 Fig. 5 is a section view taken along lines 5-5 of Fig. 3;
28 ¦ Fig. 6 is a section view taken along line 6-6 of Fig. l;
29 ¦ Fig. 7 is an inverted section view taken along lines 7-7 of
3 ~ig. 6;
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Fig. 8 is a section view taken alon~ lines 8-8 of Fig. l;
and
Fig. 9 is a section view taken alon~ lines 9-9 of Fig. 1.
Detailed Description of the Invention
Referring to the drawings, an electrical outlet box 1 includes
a top wall 2 and a bottom wall 3 in which a pair of wall mounting
- clamps 4 and 4 ! are mounted respectively through elongated slots
5 extending transyersely through each of the walls 2 and 3.
A$ best seen in Figs. 2a and 2b, the wall mounting clamps
4 and 4' are L~shaped members. They are identical, as are the
walls 2 and 3~ so only one clamp and wall will be described in
detail,
me clamp 4 includes a clamping wall 6 as a first leg 7 of
the L-shaped member, and a pair of spaced apart projections 8
and 8 ! comprise a second leg 9 of the L. The first leg 7 is at
a slightly greater than 90 an~le, preferably 101, to the second
leg 9! whichr as best seen in Figs. 8 and 9, stresses the
clamping wall 6 against the inner surface of a receiving wall
panel lOa when the outlet box 1 is inserted therein and the
clamp members 4 and 4' are moved to their clamping position.
As best seen in Figs. 8 and 9, the legs are resolved to a sub-
stantially 9Q relationship to each other in the clamped position.
As shown in Fig. 2a, a clearance gap 10 is provided between
the spaced apart projections 8 and 8' of the second leg 9. A
center post 11 of the top wall 2 and the center post of the bot-
tom wall 3 (not shown) lie in the gap 10 between projections 8
and 8~ when the clamp member 4 is moved to its clamping position.
Each projection 8 and 8 ! has a primary locking means which
includes near the free ends thereof a snap button comprising
a short lug 12 having an enlarged head 13.
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1 When the clamp member 4 is moved to its clamping position, the
2 enlarged head 13 of each lug 12 is received in a corresponding
3 locking aperture 14 positioned in the top wall 2 for registration
4 with lugs 12 when said clamp is moved to said clamping position.
The enlarged head 13 is compressed when it enters its respective
6 aperture 14 and when pushed through aperture 14 the enlarged
7 head 13 expands to its original dimension thus locking the clamp
8 member in the clamping position.
9 The first leg 7 of the clamp members 4 and 4' includes a
central appendage 15 having a step-down end portion 15a and a
11 central aperture 16 therethrough. The appendage 14 has a step-
12 down end portion 15a which is received in the rearward extension
13 15b of the slot 5, as shown in Figs. 4 and 6. The central
14 aperture 16 of each clamp is in registration with internally
threaded bore 17 through center post 11 when clamp 4 is moved to
16 its clamping position.
17 Mounting screws 18 which secure a wiring device in place,
18 such as duplex receptacle 19 as shown in Figs. 1 and 8, are
19 threaded through bore 17 and extend through the central apertures
16 of the clamp member 4 when it is in the clamping position.
21 The aperture 16 is not threaded and is slightly larger than the
22 diameter of the mounting screw 18. When the mounting screw 18
23 is extended through the aperture 16, it is received by a channel
24 l9a disposed in wall 2 and extending rearwardly from the
extension 15b. When the clamp member is positively locked in
26 place in the clamping position to securely mount the outlet box 1
27 in the receiving aperture of the wall panel lOa, the wall panel
28 lOa is sandwiched between the clamping wall 6 of clamp members 4
29 and frontal flange 22,which extends laterally from a front edge
31 23 of the t wall 2.
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1 In operation, the outlet boxes 1 are installed as follows.
2 Clamp 4 and top wall 2 are described below, but the operation for
3 clamp 4' and bottom wall 3 is identical.
4 The clamp 4 is connected through the elongated slot 5 in the
top wall 2 of the outlet box 1 and positioned in the retracted
6 position, preferably by the manufacturer before shipment.
7 The slot 5 is parallel to the open front wall 25 of the outle :
8 box 1. The slot 5 is selectively spaced inwardly from the front
~ edge 23 a distance which is equal to or slightly greater than the
width of the wall panel lOa in which the outlet box is to be
11 mounted. Dimensions of 1/4", 3/8" and 1/2" from the front wall
12 are used for wall panels having a thickness of 1/4" to 3/16", 5/16
13 to 3/8" and 7/16" to 1/2", respectively. A dimension of 1/4" is
14 shown in Fig. 5.
More specifically the connection between the clamp 4 and the
16 wall 2 is accomplished by inserting the first leg 7 through the
17 slot 5 from the bottom side until a pivot junction or junction
18 line 24, which joins the first leg 7 and second leg 9 of the L-
B 19 shaped clamp 4, reaches the slot 5. The bosses i~a extend laterally
from a forward side of the first leg portion 7 near the junction
21 line 24. The bosses ~ are selectively sized to allow the leg
22 portion 7 to be pushed through the slot 5 and then prevent the leg
23 portion 7 from moving back through the slot 5 in the event the
24 clamp 4 is jarred or shaken loose during shipment or installation.
When the junction line 24 of the clamp 4 is near the lower
26 edge of slot 5, the clamp 4 is then pivoted to the retracted
27 position so that the junction line 24 is above the top edge of
28 the slot 5 and leg 7 lies against an outer surface 26 of top
29 wall 2, as best seen in Figs. 4 and 5.
3o In the retracted position, as shown in Fig. 4, a free edge
31 27 of the step-down portion 15a of the central appendage 15 bears
32 against a corresponding edge 28 at point A of slot 5. The contact
33 ~f the free ge 27 against the corresponding edge 28 is slightly
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1 above a contact point B of the inner side of the second leg to the
2 inner side of the slot 5, as shown in Fig. 4, creating a over-
3 center switch action with the bearing at point A exerting a force
4 on the corresponding edge 28, thus providing a clockwise movement
about a fulcrum at point B, thus holding the clamp 4 in its re-
6 tracted position.
7 As best seen in Fig. 4, a boss 29a on the second leg also
8 acts as a stop means to prevent movement of the clamp outwardly
9 from the wall 2 when the clamp 4 is in the retracted position.
The respective corresponding edges 37 of central appendage 15
11 is preferably rounded slightly forming a cam surface to enable
12 free edge 27 of central appendage 15 to cam against corresponding
13 edge 28 of the slot ~ when the clamp 4 is pivoted from the re-
14 tracted position to the clamping position. When cammed against
the edge 28 the clamp may pivot to its clamping position. In
16 such clamping position, the clamping wall 6 of leg 7 extends
17 upright from the top wall 2. The projections 8 and 8' of the
18 second leg 9 of the L-shaped clamp member then lie against the
19 inner surface 29 of top wall 2 with the respective lugs 12 of
projections 8 and 8' being lockingly received in their corres-
21 ponding apertures 14. If the clamp 4 is moved to the clamping
22 position without a wall panel present, the clamping wall 6 will
23 be oblique to the rear surface of frontal flange 22.
24 In the retracted position of clamp 4, as seen in Figs. 4 and
5' the first leg 7 lies against the outer surfaces 26 of the wall
26 2, and the projections 8 and 8' of the second leg 9 of the L-shape
27 clamp member 4 at such time extend inwardly into the cavity 30
28 of the outlet box 1.
29 The outlet boxes are preferably furnished to the job site
3o with the clamps 4 and 4' mounted therein in their retracted
31 position. The boxes may then be inserted in a pre-cut receiving
32 aperture 20 of a wall panel lOa from the front side 31 of said
33~wall panel. he first leg 7 D~ the clamp 4 lying flat against
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1 the top wall 2 of the outlet box 1 is able to clear the edges of
2 the aperture 20 as the box is pushed therein until the front side
3 31 of the wall panel lOa abuts against the fontral flanges 22 of
4 the outlet box 1. At such point, pressure is applied from the
front against the projections 8 and 8' of clamp member 4 which
6 in the retracted position are extending inwardly of the box
7 cavity 30, thus causing the clamp member 4 to pivot until it
8 reaches the clamping position. As the clamp is pivoted through
9 the slot the clamping wall 6 of the first leg 7 contacts the
inner side of the wall panel lOa commencing at a point near the
11 surface 26, and, as the rotation of the clamp is continued, the
12 area of surface contact increases between the clamping wall 6
13 and frontal flange 22 until the entire surface of wall 6 abuts
14 the flange 22, as best seen in Figs. 8 and 9. As the clamp
is rotated to the clamped position, the clamp is subjected to bend Lng
16 forces. However, when the locking is completed,the clamp is
17 resolved into substantially a 90 relationship between the legs
18 and the bending forces are at least partially translated into
19 shear forces which occur at the point of contact C between the
rear side of leg 7 and the rear edge of slot as shown in Fig. 9.
21 In the clamping position, additional manual pressure is appli~ d
22 agalnst the projections 8 and 8' of the second leg 9 until their
23 respective lugs 12 are lockingly seated in their respective
24 aperture 14.
The projections 8 and 8' of the second leg 9 are at such
26 time parallel with the respective wall of the outlet box in which
27 the clamp 4 is mounted, and the clamping wall 6 is in bearing
28 engagement against the inner surface 32 of the wall panel lOa.
11 S ce the clamping wall 6 of first leg 7 is at a slightly greater
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1 than 90 angle to the second leg 9, the clamping wall 6 becomes
2 stressed and flexes slightly when forced against the inner surface
3 32 of wall panel 21 when the clamp 4 is locked in its fully
4 clamped position. Such angle is perferably 101 as shown in
Fig. 2b.
To further secure the clamp 4 in place, the central aperture
7 16 of central appendage 15 of the first leg 7 is in registration
8 with the internally threaded bore 17 of center post 11 of the
9 outlet box when in the fully clamped position, to receive the
shank of mounting screw 18 therethrough when a wiring device is
11 secured to the outlet box 1. In the event the clamps are dis-
12 engaged from the clamping position,the apertures will rotate
13 about the pivotal axis and the screw 18 will permit
14 only a limited amount of rotation inasmuch as the screws will
become engaged with the wall of the channel l9a. This relation-
16 ship provides a secondary clamp and prevents the outlet box from
17 becoming detached from the wall panel lOa.
18 In like manner clamp 4' in bottom wall 3 is then moved from
19 its retracted position to the fully clamped position to clamp and
lock the opposite end of the outlet box 1 to the corresponding
21 edge of wall panel lOa.
22 The outlet box shown and described herein has the clamp 4
23 and 4' in the top wall 2 and bottom wall 3. It is understood
24 that the clamp members can be mounted at other positions of the
peripheral walls of the outlet box, such as in the side walls
26 of the box if desired. The application is not to be limited
27 to the particular locations illustrated and described herein.
28 The lugs 12 are press-fitted in corresponding apertures in
230 the projections 8 and 8' of the second leg 9 of the L-shaped
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1 clamp 4, in such a way that an end portion 33, as shown in Figs.
2 4 and 5, of the lug 12 extends through the projections 8 and 8'
3 to the opposite side as shown in Fig. 6. Such extending end
4 portion serves as a stop for a workman's thumb-nail, for example,
when pushing the L-clamp 4 from a retracted position to a clamping
6 position.
7 The outlet boxes and self-contained wall mounting clamps
8 in accordance with this invention may be either metallic or non-
~ metallic.
As shown by the description of the invention above, a novel
11 feature of the structure of the invention is that it allows the
12 electrical outlet box to be connected to a wall panel using
13 solely the manual efforts of a workman without resorting to tools
1 or other me anical d~vices ror assistance.
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