Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INDUCTION FOIL CAP SEALER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an induction
sealing apparatus which seals a foil sheet or liner to
the opening of a container and, more particularly, to
an induction sealing apparatus which is air cooled and
which does not require the use of thermally conductive
material disposed within ferrite cores of the
apparatus to facilitate heat removal.
2. Related Art
Induction sealing units for sealing and
hermetically sealing or tamper-proof sealing
containers with foil liners are typically included in
conveyer systems for high volume applications.
Conventional systems comprise an induction head
which includes ferrite materials arranged to channel
and direct the electromagnetic field towards the foil
liner. An electric current is induced in the foil
liner which heats the foil to a temperature sufficient
to bond the foil to the rim of the container. As the
foil and rim cool, the foil is firmly joined to the
rim providing a securely sealed container.
Induction sealing systems generate a significant
amount of excess thermal energy and have to be cooled
in some way. Some systems use water cooling while
others circulate air across heat sinks to draw heat
away from the core.
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In air cooled systems, a thermally conductive
material is disposed within the ferrite core in order
to conduct the heat generated within the core to heat
sinks which are used to transfer the thermal energy to
the air used to cool the unit. This thermally
conductive material adds to the cost and weight of the
device and is subject to mechanical failure and
cracking. Heat sinks are usually made of metal and
are produced with a plurality of fin projections to
help dissipate the excess heat produced within the
ferrite core. Exposed fins are subject to breakage
which reduces the effectiveness of the heatsinks.
Also, the use of extensive heatsinks add to the
complexity and weight of the device.
Water cooled systems are necessarily more
complicated and more costly. Water cooled systems
require plumbing and a pumping system to circulate the
water throughout the induction sealing head.
SiTirIIKARY OF THE INVENTION
Accordingly, the present invention provides an
induction sealing unit which does not require
thermally conductive materials disposed within the
ferrite core and is thus less expensive to produce
than the prior art.
The present invention also provides an induction
sealing head which utilizes an air cooled slotted
ferrite core to minimize the use of complex heat sink
configurations.
The present invention also provides an induction
sealing head which is more energy efficient than
conventional induction sealers.
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The present invention also provides an induction
sealing unit that is easy to use, manufacture and
maintain.
The present invention attains these features by
providing a sealing unit having a horizontal mounting
plate, a ferrite core having openings formed
therethrough, disposed on the mounting plate and a
litz wire coil disposed proximate to the ferrite core
for producing an electromagnetic field. The ferrite
core and litz wire coil are adapted to direct an
electromagnetic field toward a foil used to seal an
opening of a container. The horizontal mounting plate
has openings coinciding with the openings within the
ferrite core to provide air flow through and around
the core and sealing head.
In one aspect, an induction sealing unit is
provided. The induction sealing unit comprises: a
ferrite core, which has individual ferrite elements
and has a plurality of core openings therethrough, and
is structured and arranged to allow a cooling gas to
flow through the ferrite core; a conductive coil which
is disposed proximate to the ferrite core and is
structured and arranged to direct an electromagnetic
field towards an object to be heated; a mounting plate
which has a plurality of plate openings therethrough,
which are aligned with the core openings of the
ferrite core openings to allow a cooling gas to
circulate through the unit; and the individual ferrite
elements are attached to the mounting plate.
In the induction sealing unit, the conductive
coil may be a litz wire coil.
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The induction sealing unit may further comprise a
housing, which substantially covers an upper portion
of the ferrite core.
The induction sealing unit may also comprise at
least one cooling fan which is disposed in the housing
and the at least one cooling fan is directed to
circulate a cooling gas through the plurality of core
openings within the ferrite core.
In the induction sealing unit, the cooling gas
may be air.
The induction sealing unit may further comprise a
heatsink which is operably coupled to the ferrite core
for drawing heat away from the ferrite core.
In the induction sealing unit, the at least one
cooling fan may also direct the cooling gas across the
heatsink.
The induction sealing unit may further comprise:
at least one intake fan which is disposed in the
housing; at least one outtake fan which is disposed in
the housing; and the at least one intake fan and the
at least one outtake fan are structured and arranged
within the housing to cooperatively circulate a
cooling gas through the plurality of core opening
within the ferrite core.
In the induction sealing unit, the individual
ferrite elements may include E-shaped ferrite elements
which are structured and arranged with an open end of
the E-shaped ferrite element facing another open end
of another E-shaped ferrite element, thereby forming
the plurality of core openings.
The induction sealing unit may further comprise a
cover which substantially covers a downwardly
projecting portion of the ferrite core.
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The induction sealing unit may further comprise
an energizing assembly which includes at least the
litz wire coil; a capacitor which is electrically
connected to the litz wire coil and a transformer; and
a power supply which is electrically coupled to the
transformer.
In another aspect, an induction sealing unit is
provided. The induction sealing unit comprises: a
mounting plate which has a plurality of plate openings
therethrough; a ferrite core which has a plurality of
core openings therethrough, and is mounted to the
mounting plate such that the plurality of plate
openings and the core openings coincide with each
other to allow a cooling gas to flow through the
ferrite core; and a litz wire coil, which is disposed
proximate to the ferrite core and is structured and
arranged to direct an electromagnetic field towards an
object to be heated.
In another aspect, an induction sealing unit is
provided. The induction sealing unit comprises: a
housing; a mounting plate which has a plurality of
plate openings therethrough and is attached to the
housing; a ferrite core which has a plurality of core
openings therethrough and is mounted to the mounting
plate such that the plurality of plate openings and
the core openings coincide with each other to allow a
cooling gas to flow through the ferrite core; a litz
wire coil, which is disposed proximate to the ferrite
core and is structured and arranged to direct an
electromagnetic field towards an object to be heated;
at least one cooling fan which is disposed in the
housing; and the at least one cooling fan is directed
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to circulate a cooling gas through the plurality of
core openings within the ferrite core.
Other features and advantages of the present
= invention will become apparent from the following
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description of the invention which refer to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For the purpose of illustrating the invention,
there are shown in the drawings an embodiment which is
presently preferred, it being understood, however,
that the invention is not limited to the precise
arrangement and instrumentality shown.
Fig. 1 shows a front view of an induction sealing
conveyor system employing an air cooled sealing head
which is constructed in accordance with the principles
of the present invention.
Fig. 2 is a top view showing slots in a metallic
plate used in the sealing head of the present
invention.
Fig. 3 is a bottom view of the sealing head used
in present invention showing the litz wires and the
slots.
Fig. 4 is a side view of the sealing head of the
present invention.
Fig. 5 is a sectional view along section lines 5-5
of Fig. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings wherein like
numerals indicate like elements, there is shown in
Fig. 1 an induction sealing unit designated generally
as 100. Sealing unit 100 comprises housing 102 and
sealing head 103. The components within housing 102
include capacitor 106, intake fan 110, outtake fan
114, transformer 118 electrically connected to the
capacitor 106 and a power supply 152 electrically
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connected to transformer 118. Sealing head 103
comprises a horizontal mounting plate 126, two
vertical mounting plates 170 (only one of which can be
seen in Fig. 1), a ferrite core 120 and a litz wire
5 coil 108 electrically connected to transformer 118.
Referring to Figs. 4 and 5, ferrite core 120 is
constructed from both "E"-shaped and "I"-shaped
ferrites (120e and 120i respectively) to form a
channel shape which includes bottom tab sections 122
and a center spine 124. Center spine 124 is
constructed of the "I"-shaped ferrites 120i bonded
together and centrally aligned along the longitudinal
axis (i.e. the axis extending from the left to the
right sides of ferrite core 120 as shown in Fig. 1) of
ferrite core 120.
Referring now to Fig. 1, a plurality of the
"E"-shaped ferrites 120e are joined open end to open
end to form slots 116v which are aligned perpendicular
to the longitudinal axis of ferrite core 120. Slots
116v are vertically oriented along the two outer
portions of ferrite core 120.
Now referring to Figs. 1 and 2, another plurality
of the "E"-shaped ferrites 120e are also arranged open
side to open side to form horizontal slots 116h.
Slots 116h are horizontally oriented and are aligned
perpendicular to the longitudinal axis. Slots 116h
provide air channels within ferrite core 120 and
increase the surface area exposed to cooling air 200,
thereby allowing ferrite core 120 to be air cooled
without the use of thermally conductive materials
encasing ferrite core 120.
In order to direct the electromagnetic field
within core 120, a conductor needs to be in intimate
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contact with the core, but the conductor must be
electrically insulated from core 120. Induction
sealing unit 100 utilizes high frequency current which
tends to flow near the surface of a conductor (known
as "the skin effect"). Therefore, the conductor needs
to be one suited for use with high frequencies. It is
for this reason that the litz wire coil 108 is used as
the conductor.
Preferably, litz wire coil 108 includes thousands
of individually insulated electrical conductors
surrounded by an insulating sheath, made from
polyethylene, polypropylene, Teflon (trade-mark), or
the like, which also electrically insulates litz wire
coil 108 from the surrounding structures, including
ferrite core 120.
Litz wire coil 108 has a very low resistance to
the flow of current as compared to the wire typically
used in conventional induction sealers. This lower
resistance allows the current to flow more efficiently
and requires less power to operate. Litz wire coil 108
also generates less heat than the wire typically used,
thereby making it easier to cool.
Litz wire coil 108 is sized such that the
effective resistance per unit length is only about 0.1
to 0.01 of the resistance per unit length of the wire
typically used in conventional induction sealers.
Consequently, the heat produced within litz wire coil
108 (due to IZR losses) is reduced by a factor
somewhere between 10-100 times allowing induction
sealing unit 10 to be air cooled rather than liquid
cooled.
Referring to FIGS. 3 and 4, litz wire coil 108 is
attached so as to abut against the inner surface of
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ferrite core 120. Litz wire coil 108 may be attached
to ferrite core 120 with a heat resistant epoxy or by
using temperature resistant strapping materials.
Whatever method is used to attach litz wire coil 108,
it is important that litz wire coils 108 remain flush
against the inner surface of ferrite core 120.
Referring again to Figs. 1 and 2, horizontal.
mounting plate 126, which is formed from a metal with
good thermal conductivity such as aluminum, supports
ferrite core 120. Cooling slots 126h are aligned with
cooling slots 116h that are formed within ferrites
core 120. Slots 16h are aligned with respective slots
126h to provide cooling channels in ferrite core 120
through which cooling air 200 is circulated.
A first plurality of individual ferrites 120e are
horizontally positioned and epoxied to the lower
surface of horizontal mounting plate 126. Horizontal
mounting plate 126 is either unitarily formed with two
vertical mounting plates 170 or alternatively, the two
vertical mounting plates 170 can be attached to
horizontal mounting plate 126. Any method of
attachment is acceptable as long as the joint can
withstand thermal stress (i.e. welding, bolting,
gluing, etc.) Another plurality of individual
ferrites 120e are vertically mounted and epoxied along
the inner surface of mounting plates 170. The
vertical slots 116v formed in ferrite core 120
increase the surface area of the ferrite core 120
exposed to cooling air flow 200, but it is not
necessary for air to flow through the vertical slots
116v. However, it would be within the scope of this
disclosure to cut slots corresponding to vertical
slots 116v in the vertical mounting plates 170 to
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provide an airflow channel through the sides of
ferrite core 120 if additional cooling is desirable.
Referring to Figs. 1 and 4, heat is drawn from the
vertically mounted ferrites 120e using a heat sink 128
which is in intimate contact along the outer
longitudinal edges of mounting plates 126 and 170. A
plurality of fins 128a are inwardly exposed to cooling
air flow 200 to draw heat away from the sides of
ferrite core 120.
Cooling air 200 is directed to flow within ferrite
core 120 by an air circulation chamber 150 which is
defined within housing 102. Cooling air flow 200 is
drawn in through intake fan 110. A baffle 112 is
mounted at an angle within air circulation chamber 150
to direct cooling air 200 down through horizontally
mounted intake fan 110. Air is then pushed through
cooling slots (116h and 126h) thereby cooling core
120, and also cooling components such as capacitor 106
and transformer 118. Cooling air 200 also draws heat
away from heat sink 128. Cooling air is
simultaneously pulled with vertically mounted outtake
fan 114.
Protective boot 138 encloses the bottom of sealing
head 103 to protect litz wire coil 108 and ferrite
core 120. Protective boot 138 also directs air flow
200 to flow within ferrite core 120. Fans 110 and 114
are preferably capable of moving approximately 100
cubic feet of air per minute.
In operation, referring to Fig. 4, a container 130
having a foil liner 132 passes beneath sealing head
103. As the container 130 passes beneath sealing head
103, a circuit including the power supply 152, the
transformer 118, the capacitor 106 and the litz wire
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coil 108 cause a current to be induced in foil liner
132 heating and fusing it to the container 130. A cap
136 can be used to position and press foil liner 132
against the top of container 130.
Air is directed through slots (116h and 126h)
formed within the ferrite core 120 to advantageously
eliminate the need for thermally conductive materials
disposed therein. This lowers the cost of producing
the unit as well as reducing production time and
overall weight of the unit.
Because air is channeled within the core 120
itself, through slots 116h and 126h, operating
temperatures can be easily controlled, thereby
increasing the efficiency of the unit. Heat does not
build up within the core 120 and even in the event of
a power failure, air will naturally circulate through
the core 120, allowing some cooling to take place by
convection. Units using thermally conductive
materials disposed within the ferrite cores, store up
more heat when deprived of a cooling air flow within
the housing.
The mounting plates (126 and 170) and heat sink
128 can be made of any thermally conductive metal, but
aluminum is particularly well suited since it is
lightweight, easily machined, relatively inexpensive
and conducts heat quite effectively, i.e., has a
relatively high co-efficient of thermal conductivity.
The slots 126h in mounting plate 126 are shown as
oblong in shape, but any shaped opening can be
utilized as long as an air channel is formed allowing
the air to circulate within ferrite core 120.
The foregoing description of the preferred
embodiment of the invention has been presented for the
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purposes of illustration and description. It is not
intended to be exhaustive or to limit the invention to
the precise form disclosed. Many modifications and
variations are possible in light of the above
teaching.
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