ELECTRIC KETTLE

BOUILLOIRE ELECTRIQUE

English Abstract

ABSTRACT
An electric kettle consists of a unitary polypropylene
upper portion to which a soft copper metal bottom is attached
by a leak-proof joint. The joint is formed by forming the copper
bottom around a downwardly extending cylindrical lip of the
upper portion, the bottom having inward of the lip a peripheral
channel which permits deformation of the bottom without spoiling
the seal at the joint.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electric appliance comprising; a polypropylene
container body having a bottom rim defining a circular aperture
of predetermined radius, an electrical heating means including
a heating element adapted to fit within the container, terminals
and an external electrical power source, a circular metal plate
having a circumference of a radius greater than the radius of
the aperture, said plate having a groove around its circumference
adapted to receive the rim in a snug press fit connection to
seal the aperture, said plate supporting the element within
the container and permitting the terminals to extend through
the plate to make electrical connection with the external power
source, in which said plate is made of a soft copper material
having a rampart portion bending away from said groove at an
angle and extending a short distance towards a central portion
of the plate, said rampart portion being adapted to permit deflection,
expansion and contraction of the plate during heating and cool mg
while maintaining the snug connection between the rim and the
groove.
2. The invention defined by Claim 1 wherein the copper
material is substantially pure copper.
3. The invention defined by Claim 1 wherein the copper
material is brass having a mixture in the range of 70% or more
copper with 30% or less zinc, respectively.
4. The invention defined by Claim 1 in which the copper
material is brass having a mixture in the range of 80% or more
copper with 20% or less zinc respectively.

5. The invention of Claims 2, 3 or 4 in which the copper
material is dead soft.
6. The invention defined by Claim 1 in which the copper
material is brass being about 85% copper and 15% zinc.
7. The invention of Claim 6 in which the brass is dead
soft.
8. The invention defined in Claims 1, 2 or 3 where the
electrical heating means has a power output of greater than
500 watts.
9. The invention defined in Claims 1, 2 or 3 in which
the power output of the electrical heating means is greater
than 1000 watts.
10. The invention defined in Claims 1, 2 or 3 where the
power output of the electrical heating means is about 1500 watts.
11, The invention defined in Claim 1 having a shoulder
about the outside of the rim to provide increased strength against
radial deflection.
12. The invention defined by Claim 11 in which the groove
of the metal plate has an outside peripheral flange adapted
to fit under said shoulder.
13. The invention defined by Claims 11 and 2.

14. The invention defined by Claims 11 and 3.
15. The invention defined by Claims 11 and 4.
16. An electrical appliance comprising, a polypropylene
container body having a bottom rim defining a circular aperture
of predetermined radius and having an integral shoulder slightly
above the aperture outside the rim, an electrical heating means
including a heating element adapted to fit within the container,
terminals and an external electrical power source, said heating
means having a power greater than 1000 watts, a circular metal
plate of a soft copper material having a circumference of a
radius greater than the radius of the aperture, said plate
having a flange around its circumference adapted to fit under
said shoulder, having, next within a groove adapted to fit
about the rim in a snug press fit connection and having, next
within, a rampart portion bending away from the groove inside
the rim at an angle between 20° and 70° from a horizontal
plane towards a central portion of the plate for a short
distance to permit expansion and contraction of the plate
during heating and cooling while maintaining the snug
connection between the rim and the groove, said central
portion of the plate supporting the element within the
container and permitting the terminals to extend through
to make electrical connection with the external power source.
17. The invention of Claim 16 in which the copper
material is substantially pure copper.

18. The invention of Claim 16 in which the copper material
is brass having a mixture range of 80% or more copper with
20% or less zinc.
19. The invention of Claim 16 in which the copper material
is brass having a mixture of about 85% copper and 15% zinc.
The invention of Claims 17, 18 or 19 in which the
copper material is dead soft.
21. The invention of Claims 17, 18 or 19 in which the
angle of the rampart portion is between 25° and 65° from a
horizontal plane.
22. The invention of Claims 17, 18 or 19 in which the
copper material is dead soft and the angle of the rampart
portion is between 25° and 65° from a horizontal plane.
23. An electrical kettle comprising, polypropylene
container body having a bottom rim defining a circular aperture
of a radius between 8 and 10 inches and having an integral,
peripheral shoulder slightly above the aperture outside the
rim, an electrical heating means including a heating element
adapted to fit within the container, terminals, a thermostat
and an external power source, said heating means having a power
greater than 1000 watts, a circular metal plate of a soft copper
material of a radius greater than the radius of the aperture
but within the shoulder, said plate having a flange around
its circumference adapted to fit under said shoulder, having

next a groove adapted to fit about the rim in a snug press
fit connection and having next a rampart portion bending
away from the groove inside the rim at an angle in the range
of 25° to 65° from the horizontal towards a central portion
of the plate for a distance in the range of 0.5 to 1 inches,
the central portion being flat thereafter to an upward cup-
shaped indentation adapted to contain the thermostat, said
plate supporting the element within the container and per-
mitting the terminals to protrude through the plate to con-
nect to the external power source and permitting the thermostat
to protrude through to the element.
24. The electric kettle of Claim 23 in which the rim
depends vertically downward from the bottom of the aperture,
curves under, out and upwards into an indentation above the
bottom of the rim and beneath the shoulder, and in which the
flange of the metal plate is adapted to fit under the
shoulder and the groove is adapted to fit in a snug press
fit connection into the said indentation, around the underside
of the rim and up inside the rim to a position near the top
of the shoulder, and in which the rampart portion slants
downward from the groove inside the rim at an angle from
the horizontal of between 25° and 50°.
25. The electric kettle of Claim 24 in which the copper
material is dead soft copper.
26. The electric kettle of Claim 24 in which the copper
material is dead soft brass.
11

27. The electric kettle of Claim 24 in which the copper
material is dead soft brass in the range of 80% copper or
more to 20% zinc or less.
28. The electric kettle of Claim 24 in which the copper
material is soft brass of about 85% copper and 15% zinc.
29. The electric kettle of Claim 24 in which the copper
material is dead soft brass of about 85% copper and 15% zinc.
30. An electrical kettle comprising, a polypropylene
container body having a bottom rim defining a circular
aperture of a diameter between 8 and 10 inches, said rim having
a first portion within the aperture, a second portion curving
from within the aperture to outside the aperture, a third
portion extending upwards and into a neck portion, and said
body having an integral, peripheral shoulder with a flat
underside encircling the body next above the neck, an elec-
trical heating means including a heating element adapted to
fit within the container, a thermostat, terminals and an
electrical power source, said electrical heating means having
a power greater than 1000 watts and being adapted to heat
water within the kettle, a circular soft metal plate of a
soft copper material of a radius greater than the radius of
the aperture but within the shoulder, said plate having an
integral flange about its circumference adapted to fit against
the underside of the shoulder, said metal plate having next
within said flange, an integral groove adapted to fit in snug
press fit connection about the neck, the third portion, the
second portion, the first portion of the rim and up within the
12

aperture to a position opposite the shoulder above the neck
portion, said metal plate having, next within said groove,
an integral rampart portion downwardly depending from the
groove inside the rim of the aperture at an angle in the
range of 25° - 50° from the horizontal over a horizontal
distance of between 0.5 to 1.0 inches, being adapted to help
secure the snug fit of the groove about the rim during heat-
ing and cooling, said metal plate having, next within said
rampart portion, a flat horizontal portion adapted to permit
location of the terminals for the element and the like, said
metal plate having, next within the flat horizontal portion,
an indentation adapted to receive a thermostat for control
of the power source, said metal plate being adapted to seal
the aperture about the rim and to provide a support for the
electrical heating means.
31. The electrical kettle of Claim 30 having a bowl
shaped based under the shoulder and the metal plate and
attached to said plate, said bowl being adapted to provide
a base for the kettle and to cover the metal plate, the
terminals and the thermostat.
32. The electrical kettle of Claim 30 wherein the soft
copper material is brass being about 85% copper and 15% zinc.
33. An electric kettle comprising a polypropylene body
that is closed at the bottom by a metal sheet, the body having
at the bottom a peripheral generally cylindrical lip and
spaced upwardly from the bottom edge of the lip, a peripheral
13

outwardly extending ridge, with a peripheral indentation
in the outer surface of the lip below the ridge, the metal
sheet comprising a sheet of soft copper with a circular in-
verted peripheral channel one side of which fits snugly
against the inside of the lip and continues, in snug engage-
ment, with the lip, under the lip and then upwardly into
the peripheral indentation of the lip, the channel permitting
deflection, expansion and contraction of the central portion
of the sheet without relaxing the engagement of its periphery
with the lip whereby a water-tight seal is provided between
the body and the body and the sheet.
34. A kettle as claimed in Claim 33, including a metal
cup-shaped base having an upper peripheral edge engaging
the outwardly extending ridge, the base and said sheet being
fastened together at the central portion of the sheet.
14

Description

~ 2~ ~ ~
~ ~ _ ]
This invention relates to the attachment of a rnetal
bottom onto an otherwise plastic container.
The invention more specifically relates to the attachment
of a metal bottom plate onto a molded plastic upper portion
of an electric kettle. Formerly, such kettles were made largely
of metal, but due to the increasing costs of metals it was
considered advantageous to develop a kettle which incorporated
the largest possible proportion of a suitable plastic material.
A difficulty encountered in achieving this goal has been to
provide a suitable kettle bottom. A metal bottom is desirable
but a problem is created in securing a metal bottom to the
plastic portion of the kettle. Such an attachment requires
a joint which will be water-tight over the usual operating
`` temperature range, and which possesses the necessary strength
and flexibility to withstand normal day to day usage, including
the likelihood of accidents such as dropping the kettle from
countertop height to the floor.
In the prior art, t~he a-ttempts to connect a metal
plate to the bottom of a plastic container for use in making
electric appliances like kettles, coffee percolators and the
like have been unsuccessful in providing a product which could
maintain in a cost-efficient manner a water tight seal between
plastic and metal for e~tended periods of time under conditions
of heating and cooling, particularly, where the appliance was
intended for operation with a heating element having a power
greater than 1000 watts.
In a broad sense, the invention consists of a plastic
body having a bottom closure of soft metal, the body having
a peripheral, circular bead around which the closure is

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-- 2 --
.
crimped to provide a liquid seal, the closure having a peripheral
inverted channel ~lwardly of the bead whereby movement of the
central portion of the closure does not impair the seal.
More particularly, the present invention provides
an electric appliance comprising a polypropylene container
body having a bottom rim defining a circular aperture of predetermined
radius7 an electrical heating means including a heating element
adapted to fit within the container, terminals and an external
power source in combination with a circular metal plate having
a circumference of a radius greater than the radius of the
aperture and having a groove around its circumference adapted
to receive the rim in a snùg press fit connection to seal the
aperture, the plate also supporting the heating element within
the container and permitting the terminals to extend there
through to make electrical connection with the external power
source. The metal plate is made of soft copper material having
an inverted channel like a rampart bending at an angle away
from the groove just inside the rim and extending a short distarlce
towards a central portion of the plate. The rampart portion
is adapted to act like a spring between the joint :Eormed by
the groove and the rim to permit expansion and contraction
during heating and cooling while maintaining a snug connection
between the rim and the groove.
It is preferred that the metal plate be made of soft
copper or brass with a high content of copper. In this specification
"Copper material" is used to include both substantially pure
copper and brass. Brass having a copper content of less than
70% is not preferred for electric kettles as the 30%
- 30

- 3
zinc wlll leach out into water being boiled. Brass having
higher copper contents is preferred and 85% copper - 15% zinc
brass is quite satisfactory.
It is further preferred that the copper material
is "dead soft".
The present invention also discloses an electric
kettle comprising a polypropylene body that is closed at the
bottom by a metal sheet, the body having at the bottom a peripheral
13 generally cylindrical lip and, spaced upwardly from the bottom
edge of the lip, a peripheral outwardly extending ridge, with
a peripheral indentation in the outer surface of the lip below
the ridge, the metal sheet comprising a sheet of soft copper
with a circular inverted peripheral inden~ation of the lip)
the channel permitting deflection, expansion and contraction
of the central portion of the sheet without relaxing the engagement
of its periphery with the lip whereby a water~tight seal is
provided between the body and~the sheet.
It has been found that electric kettles constructed
in accordance with the directlons of this specification can
operate with a heating element of 15G0 watts in a kettle having
a diameter of less than 12 inches.
l In the preferred embodiment of this invention an
integral ridge or shoulder of polypropolene is provided about
the outside of the rim of the aperture to reinforce it against
breaking. Further, the metal plate is brought around the rim
and continued under the shoulder to provide extra stength and
to provide a better seal in the joint.
~,~

It is preferred that an indentation or neck be provided
about the outside of the rim under the shoulder to provide
better sealing characteristics~ The optimum angle o~ the rampart
portion adjacent the groove may be determined experimentally
for any particular copper material or plate diame~er. However,
it is expected that angles between 70~ and 20~ from the horizontal
will work satisfactorily. It is preferred that the angle be
between 25 to 65. About 30-45 has been successfully used
on electric kettles of about 10 inches in diameter.
It will be appreciated that the electrical heating
means is con~entional and may include a thermostat. The electrical
heating means is supported by the metal plate with m the container
body. The terminals project through the metal plate to connect
with the external power source. Where a thermostat is used,
a cup shaped indentation may be provided in the center of the
plate to receive the thermostat.
An electric kettle oE the appropriate design constructed
in accordance with the invention has been found to be a satisfactory
substitute for a conventional~all metal electric kettle.
A preferred embodiment of the invention is shown
in the accompanying drawings in which:
Figure l is a perspective view of a kettle; and
Figure 2 is an enlarged sectional view of the same
kettle.
The upper container portion l of the ke~tle has a
handle 2 and spout 3, and is formed as a unitary structure
of heat resistant polypropylene manufactured by injection molding.
Referring to Figure 2, the plastic upper container portion
of the kettle l has, arouna its bottom edge an ap~rture bounded
by a rim comprising a peripheral generally cylindrical lip 5,
't .,
- .~

- 5 -
around which a metal bottom 6 is snugly sealed. The metal bottom
is shaped with a central circular cup shaped indented area 7,
rampart portion or a peripheral circular inverted channel 8,
a groove 9 which fits against the inside of the lip, 5!,~ and
continues downwardly around the lower edge of the lip 5, in
snug engagement therewith, then upwardly and :into an indentation
10 in the lip 5, just below an outwardly protruding shoulder
or ridge ll of the upp~r container portion l and continues under
~0 ~he shouIder 11. Thus, the bottom is snugly crimped around
the lip or bead 5 to provide a water-tig~t seal Preferably,
the bottom 6 is made of .020 gauge dead soft copper. This material
re~ains its shape when bent, and once the metal-to-plastic joint
is made, the copper mainta,ins a snug engagement with the lip
5 of the polyproylene upper portion 1. The rampart portion
or inverted channel portion 8 in the bottom 6 permits expansion
and contraction of the metal bottom under ~arying temperature
; conditions without relaxing the engagement of the metal bottom
edge around lip 5.
Below the bottom 6 is a painted steel bowl-shaped
base 12 attached to the central portion of the bottom 6 by bolts
13. The upturned edge of the base 12 engages the underside
of the peripheral outwardly extending ridge ll. Forces applied
to the base 12 of the kettle are partly transmitted to the upper
portion 1 through the rib 11. Forces transmitted to the soft
copper bottom 6 through the bolts 13 may cause the bottom to
deflect, but the downwardly facing peripheral channel or rampart
portion 8 tends to isolate the groove 9 from such deflection
so that the channel side along the lip 5 is not affected. Supported
on !~he metal bottom 7 is a conventional heating element 14,

- 6 -
with leads 15 for attachment to a cord and plug (not sho~).
In construction the polypropylene container is injection
moulded as a piece. The metal plate bottom is stamped out and
fitted with the electrical heating element. The metal plate
is then fitted over the rim of the container and the edge or
groove of the plate is rolled about the rim to cold form it
in place. The connections to the electrical supply means can
then be made.
It will be appreciated by those skilled in the art
that the preferred embodiment may be modified without departing
from the principles of this invention.