U.S. patent application number 10/872939 was filed with the patent office on 2004-11-25 for cover system for an electrical-energy meter, and process for manufacture thereof.
This patent application is currently assigned to ABB Inc.. Invention is credited to Lindqvist, Lars A., Loy, Garry M..
Application Number | 20040232593 10/872939 |
Document ID | / |
Family ID | 32041986 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040232593 |
Kind Code |
A1 |
Loy, Garry M. ; et
al. |
November 25, 2004 |
Cover system for an electrical-energy meter, and process for
manufacture thereof
Abstract
A preferred process comprises providing a pre-formed,
substantially transparent window for a cover of an
electrical-energy meter, and molding the cover from a molten resin
that, when solidified, is substantially opaque. Molding the cover
from a molten resin comprises causing a portion of the molten resin
to contact a periphery of the window and allowing the portion of
the molten resin to cool and thereby solidify so that the portion
of the molten resin, upon solidifying, is molded over the periphery
of the window and thereby seals and secures the window to the
cover.
Inventors: |
Loy, Garry M.; (Raleigh,
NC) ; Lindqvist, Lars A.; (Apex, NC) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
ONE LIBERTY PLACE, 46TH FLOOR
1650 MARKET STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
ABB Inc.
Elster Electricity, LLC
|
Family ID: |
32041986 |
Appl. No.: |
10/872939 |
Filed: |
June 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10872939 |
Jun 21, 2004 |
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10263401 |
Oct 2, 2002 |
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6773652 |
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Current U.S.
Class: |
264/271.1 |
Current CPC
Class: |
B29L 2031/778 20130101;
G01R 22/065 20130101 |
Class at
Publication: |
264/271.1 |
International
Class: |
B29B 013/00 |
Claims
1-19 Canceled
20. An electrical-energy meter, comprising: a base adapted to be
mounted on a supporting surface; a current sensor assembly
comprising a plurality of contact blades extending through the base
and adapted to electrically contact a conductor of electrical
energy, and a current transformer mechanically coupled to the base
and electrically coupled to the contact blades, the current
transformer being adapted to produce an electrical output
proportional to an electrical current in the conductor of
electrical energy; a circuit-board assembly comprising a main
circuit board electrically coupled to the current transformer and
the contact blades, the circuit-board assembly being adapted to
calculate a cumulative amount of electrical energy passing through
the conductor of electrical energy based on the electrical output
of the current transformer and a voltage of the conductor of
electrical energy; and a cover system mounted on the base and
comprising a substantially transparent window and a cover
mechanically coupled to the base, wherein a portion of the cover is
molded over a portion of the window.
21. The electrical-energy meter of claim 20, wherein the cover has
a cam surface formed thereon and the base has a complementary cam
surface formed thereon and adapted to securely engage the cam
surface on the cover.
22. The electrical-energy meter of claim 20, wherein the cover is
formed from a substantially opaque material.
23. The electrical-energy meter of claim 20, wherein the cover
comprises a side portion and a rim portion coupled to a first end
of the side portion.
24. The electrical-energy meter of claim 23, wherein the cover
further comprises a face portion coupled to a second end of the
side portion and at least partially molded over a portion of the
window.
25. The electrical-energy meter of claim 24, wherein the face
portion has an edge defining a cutout in the face portion, and the
edge is molded over the portion of the window.
26. The electrical-energy meter of claim 23, wherein the cover
further comprises a lip coupled to a second end of the side portion
and the lip is molded over the portion of the window.
27. The electrical-energy meter of claim 20, wherein the portion of
the window is a peripheral edge of the window.
28. The electrical-energy meter of claim 20, wherein the portion of
the window has a recess formed on a first side thereon and a ridge
formed on a second side thereof.
29. The electrical-energy meter of claim 20, wherein the portion of
the window is substantially curved.
30. The electrical-energy meter of claim 20, wherein the window and
the cover are formed from polycarbonate.
31. A cover system for an electrical-energy meter, comprising: a
window formed from a substantially transparent material; and a
substantially cup-shaped cover comprising a
circumferentially-extending side portion, a rim portion unitarily
formed with a first end of the side portion and adapted to mate
with a base of the electrical-power meter, and a lip extending from
a second end of the side portion, wherein at least a portion of the
lip is molded over a peripheral portion of the window.
32. The cover system of claim 31, wherein the cover is
substantially opaque.
33. The cover system of claim 31, wherein the peripheral portion of
the window is substantially curved to facilitate mechanical
interlocking with the lip.
34. The cover system of claim 31, wherein the window and the cover
are formed from polycarbonate.
35. The cover system of claim 31, wherein the window has a mold
shutoff section formed thereon.
36. The cover system of claim 35, wherein the mold shutoff section
comprises a first substantially smooth surface portion located on a
first surface of the window immediately inward of the peripheral
portion of the window, and a second substantially smooth surface
portion located on a second surface of the window immediately
inward of the peripheral portion of the window.
37. The cover system of claim 31, wherein the window has a
pin-shaped projection formed thereon.
38. A cover system for an electrical-energy meter, comprising: a
substantially transparent window; and a substantially cup-shaped
cover comprising a circumferentially-extending side portion, a rim
portion unitarily formed with a first end of the side portion and
adapted to mate with a base of the electrical-power meter, and a
face portion adjoining a second end of the side portion, wherein
the face portion has a cutout formed therein and adapted to receive
the window, and at least a portion of the lip is molded over a
peripheral portion of the window.
39. The cover system of claim 38, wherein the window is
substantially flat.
40. The cover system of claim 38, wherein the window has a first
and a second pin formed thereon.
41. The cover system of claim 38, wherein the cover is
substantially opaque.
42. The cover system of claim 38, wherein the peripheral portion of
the window has a ridge formed thereon and a trough formed therein
to facilitate mechanical interlocking with the lip.
43. The cover system of claim 38, wherein the window has a mold
shutoff section formed thereon.
44. The cover system of claim 43, wherein the mold shutoff section
comprises a first substantially smooth surface portion located on a
first surface of the window immediately inward of the peripheral
portion of the window, and a second substantially smooth surface
portion located on a second surface of the window immediately
inward of the peripheral portion of the window.
45. The cover system of claim 38, wherein the window and the cover
are formed from polycarbonate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates electrical-energy meters, also
referred to as "watt-hour meters" or "power meters," for measuring
consumption of electrical power. More particularly, the invention
relates to a cover system for an electrical-energy meter, and to a
process for manufacturing the cover system.
BACKGROUND OF THE INVENTION
[0002] Electrical-energy meters are often installed in outside
locations, and are thus equipped with covers to protect the various
internal components of the meter from physical impacts, tampering,
exposure to contaminates and adverse weather conditions, etc.
[0003] Exposure to direct sunlight can substantially raise the
operating temperature of an electrical-energy meter.
Electrical-energy meters of the solid-state type are particularly
susceptible to elevated operating temperatures. In particular,
relatively high operating temperatures are believed to decrease the
reliability and the useful life of the electronic components of
solid-state meters.
[0004] Electrical-energy meters of the electro-mechanical type are
generally less susceptible to the effects of direct sunlight than
solid-state meters. Electro-mechanical meters are usually equipped
with a substantially transparent cover formed from glass. The use
of a transparent cover facilitates visual access to the internal
components of the meter. This feature is necessary to permit
utility-company personnel to periodically read the meter, i.e., to
view the nameplate and the display (readout) of the meter and
thereby ascertain the amount of power consumed by the user
subsequent to the prior meter reading.
[0005] Electrical-energy meters of the solid-state type are usually
equipped with one or more features that protect the meter from the
potentially harmful effects of direct sunlight. For example, the
outer casing of solid-state meters is sometimes lined with a
reflective or light-colored film that reflects or inhibits the
transmission of sunlight. The film usually has a cut-out formed
therein to facilitate visual access to the meter's nameplate and
display. Lining the outer cover with a reflective or light-colored
film can substantially increase the overall cost of the meter.
Moreover, reflective or light-colored films do not always provide
adequate protection against elevated operating temperatures caused
by exposure to sunlight (this phenomenon is typically referred to
as "solar heat gain").
[0006] Alternatively, the outer cover may be formed from an opaque
material that substantially blocks the passage of all sunlight
through the cover. This approach generally provides greater
protection from solar heat gain than the use of reflective or
light-colored films.
[0007] Covers formed from opaque materials are usually equipped
with a transparent window to facilitate visual access to the
nameplate and readout of the corresponding electrical-power meter.
The window is typically accommodated in a cutout formed in the
cover. The window is usually fixed to the cover by conventional
bonding techniques such as adhesive or ultrasonic welding. The need
to fix the window to the cover in a separate production step adds
to the overall time and cost of producing the electrical-power
meter. The specialized equipment needed to perform these production
steps also adds to the overall production cost.
[0008] Covers for electrical-power meters are often required to
meet one or more standards for physical-impact resistance, e.g.,
Underwrites Laboratories standard UL 916. Meeting these
requirements generally requires a strong bond between the window
and the cover. The required degree of bond strength can be
difficult to achieve using conventional bonding techniques.
Moreover, a hermetic (leak-proof) seal is typically required
between the window and the cover to protect the internal components
of the meter from water and other contaminates. Hermetic sealing
between the cover and the window can be difficult to achieve on a
consistent basis using conventional bonding techniques.
[0009] Conventional bonding techniques such a ultrasonic welding
are usually compatible with substantially flat windows only. Hence,
design features that require the use of, for example, a curved
window, cannot be readily incorporated into electrical-energy
meters having covers formed using ultrasonic welding.
[0010] Consequently, a need exists for a cover system for an
electrical-energy meter that substantially protects the meter from
solar heat gain without adding substantially to the production time
and cost of the meter, and without detracting substantially from
the resistance of the cover to physical impacts or contaminates. A
cover system that can accommodate windows other than substantially
flat windows is also desirable.
SUMMARY OF THE INVENTION
[0011] A preferred process comprises providing a pre-formed,
substantially transparent window for a cover of an
electrical-energy meter, and molding the cover from a molten resin
that, when solidified, is substantially opaque. Molding the cover
from a molten resin comprises causing a portion of the molten resin
to contact a periphery of the window and allowing the portion of
the molten resin to cool and thereby solidify so that the portion
of the molten resin, upon solidifying, is molded over the periphery
of the window and thereby seals and secures the window to the
cover.
[0012] Another preferred process comprises placing a pre-formed,
substantially transparent window for a cover of an
electrical-energy meter in a mold, and clamping a portion of the
window between a first and a second surface of the mold so that a
periphery of the window is positioned within a cavity defined at
least in part by the mold and the periphery of the window. The
presently-preferred process also comprises introducing molten resin
into the cavity so that the periphery of the mold is substantially
immersed in the molten resin, and permitting the molten resin to
cool and solidify so that a portion of the molten resin, upon
solidifying, is molded around the periphery of the window and
thereby seals and secures the window to the cover.
[0013] Another preferred process comprises clamping a window for a
cover of an electrical-energy meter in a mold so that the window
and the mold form a cavity and a portion of the window is
positioned within the cavity, and molding a portion of the cover
over the portion of the window positioned within the cavity.
[0014] A preferred embodiment of an electrical-energy meter
comprises a base adapted to be mounted on a supporting surface. The
electrical-energy meter also comprises a current sensor assembly
comprising a plurality of contact blades extending through the base
and adapted to electrically contact a conductor of electrical
energy, and a current transformer mechanically coupled to the base
and electrically coupled to the contact blades. The current
transformer is adapted to produce an electrical output proportional
to an electrical current in the conductor of electrical energy.
[0015] The electrical-energy meter further comprises a
circuit-board assembly comprising a main circuit board electrically
coupled to the current transformer and the contact blades. The
circuit-board assembly is adapted to calculate a cumulative amount
of electrical energy passing through the conductor of electrical
energy based on the electrical output of the current transformer
and a voltage of the conductor of electrical energy. The
electrical-energy meter also comprises a cover system mounted on
the base and comprising a substantially transparent window and a
cover mechanically coupled to the base. A portion of the cover is
molded over a portion of the window.
[0016] A preferred embodiment of a cover system for an
electrical-energy meter comprises a window formed from a
substantially transparent material. The cover system also comprises
a substantially cup-shaped cover comprising a
circumferentially-extending side portion, a rim portion unitarily
formed with a first end of the side portion and adapted to mate
with a base of the electrical-power meter, and a lip extending from
a second end of the side portion. At least a portion of the lip is
molded over a peripheral portion of the window.
[0017] Another preferred embodiment of a cover system for an
electrical-energy meter comprises a substantially transparent
window. The cover system also comprises a substantially cup-shaped
cover comprising a circumferentially-extending side portion, a rim
portion unitarily formed with a first end of the side portion and
adapted to mate with a base of the electrical-power meter, and a
face portion adjoining a second end of the side portion. The face
portion has a cutout formed therein and adapted to receive the
window, and at least a portion of the lip is molded over a
peripheral portion of the window.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing summary, as well as the following detailed
description of a presently-preferred embodiment, is better
understood when read in conjunction with the appended drawings. For
the purpose of illustrating the invention, the drawings show an
embodiment that is presently preferred. The invention is not
limited, however, to the specific instrumentalities disclosed in
the drawings. In the drawings:
[0019] FIG. 1 is an exploded view of an electrical-energy meter,
including a preferred embodiment of a cover system for the
electrical-energy meter;
[0020] FIG. 2 is a perspective view of the cover system depicted in
FIG. 1;
[0021] FIG. 3 is a partial cross-sectional view taken through the
line "A-A" of FIG. 2;
[0022] FIG. 4 is a magnified view of the area designated "B" in
FIG. 3;
[0023] FIG. 5 is a cross-sectional side view of a mold capable of
manufacturing the cover system depicted in FIGS. 1-4, showing a
portion of a window of the cover system installed in the mold;
[0024] FIG. 6 is a side perspective view of an alternative
embodiment of the cover system depicted in FIGS. 1-4;
[0025] FIG. 7 is a side perspective view of a window of the cover
system depicted in FIG. 6;
[0026] FIG. 8 is a partial cross-sectional view taken through the
line "C-C" of FIG. 6; and
[0027] FIG. 9 is a magnified view of the area designated "D" in
FIG. 8.
DESCRIPTION OF PRESENTLY-PREFERRED EMBODIMENTS
[0028] A presently-preferred embodiment of a cover system 10 for a
solid-state electrical-energy meter 11 is depicted in FIGS. 1-4. It
should be noted that the cover system 10 is described in connection
with the electrical-energy meter 11 for exemplary purposes only.
The cover system 10 can be used in conjunction with virtually any
type of electrical-energy meter, including electrical-energy meters
of the electro-mechanical type.
[0029] The electrical-energy meter 11 is depicted in FIG. 1, and
comprises a base 50, a current sensor assembly 52, and a power
transformer 54. The current sensor assembly 52 and the power
transformer 54 are mounted on the base 50 by way of a retainer 56.
The electrical-energy meter 11 also includes a circuit-board
assembly 58, a radio-communications antenna 60 mounted on the
circuit-board assembly 58, a name plate 62, and a digital display
63 mounted on the name plate 62. The circuit-board assembly 58,
radio communications antenna 60, and name plate 62 are mounted on
snap posts 64 formed in the base 50.
[0030] The current sensor assembly 52 comprises an annular current
sensor 66, current conductors 68 that conduct electrical current to
the current sensor 66, and meter blades 69 connected to opposite
ends of each current conductor 68. The meter blades 69 are retained
in the base 50 by way of keyhole slots 70 formed in the base 50.
The meter blades 69 are each adapted to slidably and securely
engage a corresponding receptacle (not shown) mounted on the
residential or commercial establishment in which the
electrical-energy meter 11 is used. The engagement of the blades 69
and the corresponding sockets electrically couples the
electrical-power meter 11 to the conductor that supplies electrical
power to the residential or commercial establishment.
[0031] The current sensor 66 is electrically coupled to the
circuit-board assembly 58, and is adapted to measure the electrical
current flowing through the electrical-power meter 11 by way of the
current conductors 68 and the meter blades 69. The meter blades 69
are electrically coupled to the circuit-board assembly 58 through
the output of the current sensor (66). The circuit-board assembly
58 thus receives a voltage input that is proportional to the
voltage of the conductor that supplies electrical power to the
residential or commercial establishment. The circuit-board assembly
58 is adapted to calculate the total (cumulative) watt-hours of
power that have passed through the electrical-energy meter 11 over
time based on the measured current and the voltage input, using
conventional techniques known to those skilled in the field of
electrical-energy meter design. The circuit-board assembly 58
continually updates the cumulative watt-hours, and displays the
updated value on the digital display 63.
[0032] Further details relating to the electrical-energy meter 11
(other than the cover system 10) are not necessary to an
understanding of the invention, and therefore are not presented
herein.
[0033] Details relating to the cover system 10 are as follows. The
cover system 10 forms an enclosure shields the other components of
the electrical-energy meter 11 from the environment, inhibits
tampering with the electrical-energy meter 11, protects the
electrical-energy meter 11 from contamination or damage due to
contact with foreign objects, etc.
[0034] The cover system 10 comprises a cover 12 and a window 14
(see FIG. 24). The cover 12 is preferably formed from a
substantially opaque material, i.e., the cover 12 substantially
blocks the passage of radiant energy, and especially light. The
cover 12 has an outer surface 13 and an inner surface 15. The cover
12 comprises a circumferentially-extending side portion 18, a rim
portion 20, and a face portion 22. The rim portion 20 adjoins a
first end of the side portion 18, and the face portion 22 adjoins a
second end of the side portion 18.
[0035] The rim portion 20 is adapted to engage the base 50 of the
electrical-energy meter 11. More particularly, the rim portion 20
has a cam structure 23 is positioned around a circumference thereof
(see FIG. 1). The cam structure 23 is adapted to securely engage a
complementary cam structure 51 on the base 50 to secure the cover
12 to the base 50. A gasket 55 is preferably installed between the
rim portion 20 and the base 50 to inhibit water or other
contaminates from entering the electrical-energy meter 11 through
the interface between the rim portion 20 and the base 50. (It
should be noted that the cover 12 can be secured to the base 50 by
alternative means such as fasteners.)
[0036] The side portion 18 is substantially cylindrical, although
the side portion 18 can alternatively be formed in other types of
geometric configurations, e.g., frustoconcical.
[0037] A cutout 19 is formed in the face portion 22. The cutout 22
is defined by an edge portion 28 in the face portion 22. The cutout
19 accommodates the window 14. More particularly, the window 14 is
disposed within the cutout 19, and the edge portion 28 is molded
over an edge portion 32 of the window 14. Further details relating
to this feature are presented below. (It should be noted that the
term "cutout" is used for illustrative purposes only; the cutout
22, as explained in detail below, is formed by molding process that
produces the cover 14.)
[0038] The window 14 is preferably formed from a substantially
transparent material, i.e., from a material that substantially
transmits light without appreciable scattering so that bodies lying
beyond can be seen clearly. The window 14 thus facilitates visual
access to the interior of the electrical-power meter 10. More
particularly, the window 14 permits the information displayed on
the nameplate 62 and the digital display 63 to be read by, for
example, a utility company employee while the cover system 10 is
installed on the electric-energy meter 11.
[0039] The edge portion 32 forms an outer periphery of the window
14. The window 14 has a first, outward-facing side 30a and a
second, inward-facing side 30b. The window 14 includes a mold
shutoff section 33 adjacent the edge portion 32 (see FIG. 4). The
mold shutoff section 33 is formed by a first substantially smooth
surface 33a located on the first side 30a of the window 14, and a
second substantially smooth surface 33b located on the second side
30b of the window. The surfaces 33a, 33b preferably extend along a
substantial entirety of the inner circumference of the edge portion
32. Hence, the surfaces 33a, 33b are substantially aligned, i.e.,
the surfaces 33a, 33b are located in substantially identical
positions on opposing sides 30a, 30b of the window 14. The purpose
of the mold shutoff section 33 is discussed below.
[0040] The edge portion 32 preferably has a recess 34 and a ridge
35 formed thereon. The recess 34 is defined by an inwardly-curved
surface portion on the first side 30a of the window 14, and the
ridge 35 is formed by an outwardly-curved portion on second side
30b of the window. The recess 34 and the ridge 35 are substantially
aligned, i.e., the recess 34 and the ridge 35 are located in
substantially identical positions on opposing sides 30a, 30b of the
window 14. The function of the recess 34 and the ridge 35 is
explained below.
[0041] The window 14 includes a first and a second pin 36 that
project from the edge portion 32, on the second side 30b of the
window 14. The purpose of the pins 36 is addressed below.
[0042] The cover 12 and the window 14 are each preferably formed
from polycarbonate material. Other materials can be used in lieu of
polycarbonate, although the cover 12 and the window 14 should be
formed from respective materials that are capable of bonding with
each other through a molding process.
[0043] The cover system 10 is manufactured by molding a portion of
the cover 12 over a portion of the window 14. More particularly,
the cover 12 can be formed using a mold 50, a portion of which is
depicted in FIG. 5. It should be noted that the mold 50 is
described in detail for exemplary purposes only; the cover system
10 can be formed using other types of molds.
[0044] The mold 50 is adapted to receive the pre-formed window 14,
and to mold the edge 28 of the face portion 20 around the edge
portion 32 of the window 14.
[0045] The mold 50 comprises an outer mold portion 52 and an inner
mold portion 54. The outer mold portion 52 has an inner
circumferential surface 56 that includes a clamping portion 57. The
inner circumferential surface 56 has a shape that substantially
matches that of the outer surface 13 of the cover 12. The inner
mold portion 54 has an outer circumferential surface 58 that
includes a clamping portion 59. The outer circumferential surface
58 has a shape that substantially matches that of the inner surface
15 of the cover 12.
[0046] The inner mold portion 54 is adapted to move upwardly from
the position depicted in FIG. 5, i.e., in the direction denoted by
the arrow 55 in FIG. 5, so that the pre-formed window 14 can be
placed on the outer mold portion 52. More particularly, the widow
14 is positioned on the outer mold portion 52 so that the first
substantially smooth surface 33a of the mold shutoff section 33 is
positioned on the clamping portion 57 of the inner circumferential
surface 56.
[0047] The inner mold portion 54 is subsequently brought into
contact with the window 14. More specifically, the inner mold
portion 54 is lowered so that the clamping portion 59 of the outer
circumferential surface 58 is urged against the second
substantially smooth surface 33b of the mold shutoff section 33.
The inner mold portion 54 has bores formed therein (not shown) that
each receive a respective one of the pins 36 formed on the window
14. The engagement of the pins 36 and the inner mold portion 54
retains the window 14 in position in relation to the inner mold
portion 54.
[0048] The mold shutoff section 33 is thus clamped, or pinched,
between the inner mold portion 54 and the outer mold portion 52
when the inner mold portion 54 contacts the window 14, as depicted
in FIG. 5. Moreover, the inner circumferential surface 56, the
outer circumferential surface 58, and the edge portion 32 of the
window 14 define a cavity 60 when the mold 50 is configured as
shown in FIG. 5.
[0049] The cover 12 is formed by introducing molten resin into the
cavity 60, preferably by an injection process, i.e., by injecting
the molten resin into the cavity 60 under pressure. The molten
resin immerses the edge portion 32 as the molten resin fills the
cavity 60. The molten resin also contacts the outer circumferential
surface 58 of the inner mold portion 54, and the inner
circumferential surface 56 of the outer mold portion 52. The
clamping force exerted by the inner mold portion 54 and the outer
mold portion 52 on the mold shutoff section 33 substantially seals
the interface between the inner and outer mold portions 54, 56 and
the mold shutoff section 33. In other words, the clamping force
exerted by the inner mold portion 54 and the outer mold portion 52
on the mold shutoff section 33 prevents substantial leakage of the
molten resin out of the cavity 60.
[0050] The molten resin is allowed to cool after being injected
into the cavity 60. The molten resin hardens (solidifies) as it
cools, and thus forms the cover 12. The molten resin, upon being
injected into the cavity 60, immerses the edge portion 32 of the
window 14, as noted above. The molten resin thus hardens around the
edge portion 32 as the molten resin cools. More particularly, the
molten resin located around the edge portion 32 hardens into the
edge portion 28 of the cover 12. The edge portion 28 is thereby
molded around the edge portion 32 of the window 14.
[0051] The inner mold portion 54 is raised, i.e., moved in the
direction indicated by the arrow 55 in FIG. 5, as or after the
molten resin hardens, thereby permitting the cover 12 and the
window 14 to be removed from the mold 50.
[0052] The edge portion 28 of the face portion 22 retains the
window 14 on the cover 12. Furthermore, the molded interface
between the edge portion 28 of the face portion 22 and the edge
portion 32 of the window 14 seals the window 14. More particularly,
the molten resin that forms the edge portion 28 is believed to bond
molecularly with the material that forms the edge portion 32 of the
window 14 as the molten resin contacts the edge portion 32 and
subsequently cools.
[0053] The resulting interface between the edge portions 28, 30 is
believed to function as a relatively strong mechanical bond between
the cover 12 and the window 14. Moreover, the molecular bonding
between the cover 12 and the window 14 at the molded interface is
believed to make the interface substantially impervious to water
and other contaminates. In other words, the molded interface
substantially prevents water and other contaminates from passing
between the window 14 and the cover 12 and entering the interior of
the electrical-energy meter 11.
[0054] The mechanical bond between cover 12 and the window 14 is
believed to be strengthened by the recess 34 and the ridge 35
formed on the edge portion 32 of the window 14. More specifically,
molding the edge portion 28 of the cover 12 over the edge portion
32 of the window 14 causes the edge portion 28 to substantially
conform to the curved surfaces that define the recess 34 and the
ridge 35. The resulting contact between the surfaces that define
the recess 34 and the ridge 35 and the adjacent portion of the edge
portion 28 is believed to substantially increase the strength of
the mechanical bond between the cover 12 and the window 14. In
other words, the recess 34 and the ridge 35 are believed to
facilitate mechanical interlocking between the cover 12 and the
window 14. (The recess 34 and the ridge 35, as noted previously,
are an optional feature that may be omitted in alternative
embodiments of the cover system 10.)
[0055] The window 14 can thus be joined to the cover 12, and a
strong, watertight bond can be formed between the cover 12 and the
window 14, without the need for production techniques such as
ultrasonic welding or the application of adhesive. In other words,
Applicants have integrated the process by which the window 14 is
joined and sealed to the cover 12 with the molding process that
forms the cover 12. Hence, the process described herein can
eliminate the need for a separate production step (or steps) to
join and seal the window 14 to the cover 12, thus shortening the
production process and reducing the production cost of the cover
system 10. The described process can also eliminate the need for
the production equipment associated with the additional production
steps, e.g., ultrasonic welding machines, adhesive applicators,
etc.
[0056] Furthermore, it is believed that integrity in the seal
between the cover 12 and the window 14 can be achieved in more
consistent manner using the process described herein, in comparison
to conventional techniques. Also, molding the cover 12 around the
edge portion 32 of the window facilitates the use of features such
as the recess 34 and the ridge 35 that further strengthen the
mechanical bond between the cover 12 and the window 14.
Furthermore, although the window 14 is substantially flat, the mold
50 can readily be configured to accommodate windows having other
geometric configurations, e.g., curvilinear.
[0057] It is to be understood that even though numerous
characteristics and advantages of the present invention have been
set forth in the foregoing description, the disclosure is
illustrative only and changes may be made in detail within the
principles of the invention to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed.
[0058] For example, the FIGS. 6-9 depict an alternative cover
system 100 comprising a cover 102 and a substantially circular
window 104. The cover system 100 comprises a cover 102 and a window
104. The cover 102 comprises a circumferentially-extending side
portion 118, and a rim portion 120 that adjoins a first end of the
side portion 118. The cover 102 also comprises a substantially
annular lip 121 that adjoins a second end of the side portion 118.
The lip 121 is molded around an edge portion 128 of the window 104
(see FIG. 9). The window 104 thus extends around a substantial
entirety of the circumference of the side portion 118.
[0059] The edge portion 128 of the window 104 is curved inward as
depicted, for example, in FIG. 9. The lip 121, which is molded
around the edge portion 128, is thus curved inward in a likewise
manner. The curved interface between the lip 121 and the edge
portion 128 is believed to enhance the strength of the mechanical
bond between the cover 102 and the window 104.
[0060] The cover system 100 and the cover system 10 are formed in a
substantially identical manner. In other words, a mold shutoff
section 133 of the window 104 is clamped between portions of a mold
substantially similar to the mold 50 so that the mold and the edge
portion 128 of the window 104 form a cavity. Pins 129 formed on the
window 104 hold the window 104 in position in the mold.
[0061] Molten resin is injected into the cavity, and immerses the
edge portion 128. The molten resin eventually hardens (solidifies)
around the edge portion 128 to form the lip 121. The window 104 is
believed to be secured to the cover 102 by molecular bonding
between the materials that form the lip 121 and the edge portion
128, and by the mechanical interlocking resulting from the
curvilinear shape of the lip 121 and the edge portion 128.
* * * * *