U.S. patent application number 13/672164 was filed with the patent office on 2013-05-16 for tubular heater with external thermocouple.
This patent application is currently assigned to Shanklin Corporation. The applicant listed for this patent is Shanklin Corporation. Invention is credited to Todd Brown, Russell Christman, Edward Hunt, Michael Kalinowski, James Michaelian, Thomas Orsini.
Application Number | 20130118690 13/672164 |
Document ID | / |
Family ID | 48279495 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130118690 |
Kind Code |
A1 |
Orsini; Thomas ; et
al. |
May 16, 2013 |
Tubular Heater With External Thermocouple
Abstract
The problems associated with the prior art have been overcome by
the present invention, which describes a tubular heating element
having a more reliable and accurate temperature monitoring system.
The tubular heating element has a thermocouple attached to its
exterior surface, in close proximity to the cutting and sealing
portion of the tubular heating element. In addition to improving
the accuracy of the temperature measurement, this technique reduces
electromagnetic interference caused by the interaction between the
heating wire and the thermocouple.
Inventors: |
Orsini; Thomas; (Leominster,
MA) ; Brown; Todd; (Arlington, MA) ;
Kalinowski; Michael; (Merrimack, NH) ; Christman;
Russell; (Dunstable, MA) ; Hunt; Edward;
(Andover, MA) ; Michaelian; James; (Palmer,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shanklin Corporation; |
Ayer |
MA |
US |
|
|
Assignee: |
Shanklin Corporation
Ayer
MA
|
Family ID: |
48279495 |
Appl. No.: |
13/672164 |
Filed: |
November 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61558472 |
Nov 11, 2011 |
|
|
|
Current U.S.
Class: |
156/378 |
Current CPC
Class: |
B29C 66/816 20130101;
B65B 51/26 20130101; B29C 65/7439 20130101; B29C 66/1122 20130101;
B29C 65/18 20130101; B29C 66/8221 20130101; B29C 66/849 20130101;
B29C 66/8161 20130101; B29C 66/91651 20130101; B29C 66/91653
20130101; B29C 65/7873 20130101; B29C 66/91431 20130101; B29C
66/8167 20130101; B29C 66/8324 20130101; B29C 66/4312 20130101;
B29C 66/91655 20130101; B29C 66/8242 20130101; B29C 66/961
20130101; B29C 66/836 20130101; B65B 9/06 20130101; B29C 66/962
20130101; B29C 66/7373 20130101; B29C 66/91212 20130101; B29C
66/8244 20130101; B29C 66/91231 20130101; B29C 66/91421 20130101;
B29C 65/305 20130101; B29C 66/83221 20130101; B65B 51/10 20130101;
B29C 66/133 20130101; B29C 66/4322 20130101 |
Class at
Publication: |
156/378 |
International
Class: |
B65B 51/10 20060101
B65B051/10 |
Claims
1. A side sealing machine for sealing a film, comprising: a tubular
heating element, having an exterior, a hollow cavity within the
tube, a leading edge adapted to encounter said film first, and a
trailing edge adapted to encounter said film after said leading
edge; a heating element disposed within said hollow cavity of said
tubular heating element, to heat said tubular heating element; and
a thermocouple disposed outside of said tubular heating element to
monitor a temperature of said exterior of said tubular heating
element.
2. The side sealing machine of claim 1, wherein said thermocouple
is encased in a sheath, wherein said sheath contacts said exterior
of said tubular heating element.
3. The side sealing machine of claim 2, wherein said sheath
contacts said tubular heating element at a position where said
tubular heating element contacts said film.
4. The side sealing machine of claim 2, wherein said sheath is
thermally bonded to said tubular heating element.
5. The side sealing machine of claim 2, wherein said sheath is
mechanically coupled to said exterior of said tubular heating
element.
6. The side sealing machine of claim 2, wherein said sheath is
biased toward said exterior of said tubular heating element.
7. The side sealing machine of claim 1, wherein said thermocouple
contacts said tubular heating element at a position where said
tubular heating element contacts said film.
8. The side sealing machine of claim 1, wherein said thermocouple
is thermally bonded to said tubular heating element.
9. The side sealing machine of claim 1, wherein said thermocouple
is mechanically coupled to said exterior of said tubular heating
element.
10. The side sealing machine of claim 1, wherein said thermocouple
is biased toward said exterior of said tubular heating element.
11. The side sealing machine of claim 1, further comprising a
biasing member attached to said trailing edge, which in one
position, urges said trailing edge downward toward a plane of said
film; and wherein said tubular heating element is rotatably
attached to a pivot point on said machine.
12. The side sealing machine of claim 1, further comprising a
controller in communication with said thermocouple and said heating
element so as to control a temperature of said tubular heating
element in response to said thermocouple.
13. A tubular heating element for use with a side sealing machine,
comprising: a hollow cavity within the tube; a heating element
disposed within said hollow cavity of said tubular heating element,
to heat said tubular heating element; and a thermocouple disposed
outside of said tubular heating element to monitor a temperature of
said exterior of said tubular heating element.
14. The tubular heating element of claim 13, further comprising a
sheath that contacts said exterior of said tubular heating element,
wherein said thermocouple is encased in said sheath to monitor a
temperature of said exterior of said tubular heating element.
15. The side sealing machine of claim 14, wherein said sheath
contacts said tubular heating element at a position where said
tubular heating element contacts said film.
16. The side sealing machine of claim 14, wherein said sheath is
thermally bonded to said exterior of said tubular heating
element.
17. The side sealing machine of claim 14, wherein said sheath is
attached to said exterior of said tubular heating element using a
mechanical coupler.
18. The side sealing machine of claim 14, wherein said sheath is
biased toward said exterior of said tubular heating element.
19. The side sealing machine of claim 13, wherein said thermocouple
contacts said tubular heating element at a position where said
tubular heating element contacts said film.
20. The side sealing machine of claim 13, wherein said thermocouple
is thermally bonded to said exterior of said tubular heating
element.
21. The side sealing machine of claim 13, wherein said thermocouple
is attached to said exterior of said tubular heating element using
a mechanical coupler.
22. The side sealing machine of claim 13, wherein said thermocouple
is biased toward said exterior of said tubular heating element.
Description
[0001] This application claims priority of U.S. Provisional Patent
Application Ser. No. 61/558,472, filed Nov. 11, 2011, the
disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] Machines used to wrap and seal articles and packages in
thermoplastic film are well known in the art. Two types of machines
are commonly referred to as side-sealing and lap-sealing machines.
In the typical side-sealing configuration, an article or set of
articles travels, typically via a conveyor belt, toward the
machine. A sheet of center-folded plastic film, having two layers,
is fed from a direction, which is preferably perpendicular to the
direction of the conveyor. The two layers of the film are then
separated such that the article is placed between the lower layer
and the upper layer. On one side of the article is the center-fold,
while on the other side, there is an open edge where the two layers
are not attached. The machine has several sets of belts to hold and
guide the film, and a side sealing mechanism, which typically
comprises a heating/sealing element that fuses or welds the two
layers together and a cutting element that removes the excess
material. In some embodiments, the heating element serves to cut
the film as well. These elements, whether a unitary element or
separate components, are referred to as the heating/sealing/cutting
element throughout this disclosure. Thus, as the article passes by
the side sealing mechanism, this open edge is sealed by welding the
two layers together, the plastic is cut and the waste is removed
and discarded. At this point, the plastic film resembles a tube,
with openings at both the leading and trailing ends of the article,
but sealed along both sides. As the article continues to advance,
an end sealing mechanism is then employed to seal the film at the
leading end of the article. The article is then advanced and the
end sealing mechanism then seals the film at the trailing end of
the article.
[0003] Incomplete, inconsistent or sloppy welds can be problematic
with these types of machines. The choice of heating/sealing/cutting
element, film thickness and film speed are all factors in
determining the quality of the seal. It is possible that different
types of side sealing mechanisms may optimize seals for certain
configurations. For example, tubular heating elements may optimize
seals for high speed and/or thick films, while heated cutting
blades may optimize seals for lower speed and/or thinner films.
[0004] One potential issue associated with any side sealing
mechanism is the ability to accurately control the temperature of
the heating element. For some devices, such as hot wire heaters,
the temperature is measured indirectly by monitoring a change in
the length of the wire. For other heating elements, the temperature
may be monitored directly, typically at a location away from the
cutting surface to minimize the chance of damaging the
thermocouple. This approach may work well where the heating element
has a high thermal capacity, such as a cutting blade having a
substantial mass. However, tubular heating elements have much less
mass, and therefore more instantaneous temperature change and
localized temperature variation.
[0005] In addition, some tubular heating elements dispose the
thermocouple within the tube adjacent to, or proximate the heating
element. This proximity of the heating element introduces a source
of error between the temperature being monitored and the actual
temperature at the cutting surface. In addition, the proximity of
the heating element to the thermocouple may also cause
electromagnetic interference which affects the reliability of the
data received from the thermocouple.
[0006] Therefore, a tubular heating element for which the
temperature of the cutting surface may be more accurately measured
would be beneficial.
SUMMARY OF THE INVENTION
[0007] The problems associated with the prior art have been
overcome by the present invention, which describes a tubular
heating element having a more reliable and accurate temperature
monitoring system. The tubular heating element has a thermocouple
attached to its exterior surface, in close proximity to the cutting
and sealing portion of the tubular heating element. In addition to
improving the accuracy of the temperature measurement, this
technique reduces electromagnetic interference caused by the
interaction between the heating element and the thermocouple.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a representative side-sealing machine of
the prior art;
[0009] FIG. 2 illustrates a view of the side-sealing mechanism in
accordance with the present invention;
[0010] FIG. 3 illustrates a top view of the side-sealing mechanism
shown in FIG. 2;
[0011] FIG. 4 illustrates the shape of a tubular heater and its
relationship to the film;
[0012] FIG. 5 illustrates a tubular heating element and
thermocouple assembly according to one embodiment;
[0013] FIG. 6 shows an isometric view of the tubular heating
element of FIG. 5 in the stowed position;
[0014] FIG. 7 shows a front view of the tubular heating element in
an operative position;
[0015] FIGS. 8A-8B illustrate the relationship of the tubular
heating element to the film when in various positions;
[0016] FIGS. 9A-9B illustrate how the tubular heating element
responds to a foreign material in its path;
[0017] FIG. 10 shows another embodiment of the tubular heating
element; and
[0018] FIG. 11 shows the placement of a thermocouple in a tubular
heating element according to the prior art.
DETAILED DESCRIPTION OF THE INVENTION
[0019] FIG. 1 illustrates a representative side-sealing machine
used to encapsulate or wrap an article in thermoplastic film, as
described in U.S. Pat. No. 6,526,728. The machine 10 utilizes a
conveyor belt 12 operating at a relatively constant speed to
deliver articles 8 that are to be encapsulated. The thermoplastic
film 1 is center-folded, such that the side with the fold is
closed, while the opposite side 6 is open. On this opposite side,
there are two layers of film 4,5, which will later be sealed. This
center-folded thermoplastic film 1 is fed from a reel (not shown)
that is preferably mounted such that the film is fed perpendicular
to the direction of travel of the conveyor belt 12. The film is
then inverted and separated by an inverter 13 such that the article
is enveloped between the two layers 4,5. At this point, the film 1
on one side of the article is closed, while the opposite side 6
remains open. Also, the film at both the leading and trailing ends
of the article are not sealed. Downstream from the inverter is the
side-sealing mechanism 20. After proper relative positioning of the
article between the layers of the film 4,5, the enveloped article
approaches the side-sealing mechanism 20.
[0020] The side-sealing mechanism 20 is located on the open side 6
of the enveloped article. The mechanism holds the two layers of
film 4,5 together, and guides the layers through the heating and
cutting means. It then welds the two layers together, and cuts off
the surplus material. The surplus material is pulled away so as not
to reattach to the film while it is still at an elevated
temperature.
[0021] As shown in FIG. 2, to perform these actions, the mechanism
20 preferably comprises two sets of cooperating pulleys, an upper
set 101 and a lower set 102. These sets work in unison to pull the
two layers of film 103 into the mechanism and hold the layers in
place. In the preferred embodiment, each of the pulleys has teeth
110 in its channel so as to accept one or more, preferably two,
timing belts 120. The presence of teeth 110 ensures that the timing
belt does not slip relative to the pulleys. However, V belts can
also be utilized with this invention, as well. The first set of
pulleys 101 is located above the layers of film, while the second
set 102 is located below the layers. Each set comprises a drive
pulley 101a , 102a and a tail pulley 101b, 102b. There may
optionally be one or more idler pulleys (not shown). Each of these
pulleys also may have one or more O-rings mounted in the channel
where the belts are located, so as to provide individual channels
for each of the timing belts.
[0022] Each of the timing belts preferably has a special gripping
outer surface, that is bonded to a truly endless steel or Kevlar
reinforced timing belt. Each corresponding set of belts has upper
and lower pressure plates that are preset to insure good contact
between the pair of belts.
[0023] In one embodiment, as shown in FIG. 3, one set of O-rings
200 is positioned such that the movement of the outermost belt 210
is made to be parallel to the direction of the film movement. The
outer wall of the pulley 240 and this first set of O-rings 200
provide the guides for the outermost belt 210. As shown in FIG. 3,
O-ring 200a and O-ring 200b are equidistant from the outer wall of
their respective pulleys. A second set of O-rings 201 is used to
guide the innermost belt 220 in a path that diverges away from the
direction of the film and the outermost belt. This can be
accomplished in a number of ways. For example, a combination of one
O-ring and the inner wall of the downstream pulley 250b can be used
to define the channel for the innermost belt 220, as shown in FIG.
3. Similarly, two O-rings may be inserted on the upstream pulley to
define a channel for the innermost belt. Alternatively, a single
O-ring 201a, as shown in FIG. 3, can be used to define the inner
wall of the channel for the innermost belt 220. Because of the
divergence angle, there are no forces pushing the innermost belt
220 toward the outermost belt 210, thus the second O-ring may be
eliminated. In other words, in the channel associated with the
upstream pulley 240a, the O-ring 201a provides the inner guide for
the belt 220. In the channel associated with the downstream pulley
240b, the O-ring 201b provides the outer guide for the belt 220. As
a result, the innermost belt 220 is closest to the outermost belt
210 at the upstream pulley, and farthest away from it at the
downstream pulley. The tubular heating element 230 is preferably
located between the upstream and downstream pulleys. Thus, as the
film passes the upstream pulley, it is still intact; however, it is
cut before it reaches the downstream pulley. By introducing this
divergence angle, the innermost belt 220 helps guide the unwanted
surplus away from the film after it is cut. In one preferred
embodiment, the innermost belt 220 is guided in the channel of the
downstream pulley a distance further away from the film than on the
upstream pulley sufficient to force the surplus plastic away from
the film. One such suitable distance is about 1/4 inch, although
other distances may be used. This ensures that the surplus material
does not reattach itself to the film while still at an elevated
temperature. This surplus material is then held under tension and
fed into a reel, which is later discarded. While the use of
multiple belts, with a divergence between them is preferred, the
use of a single belt, or multiple parallel belts is also within the
scope of the present invention.
[0024] The side-sealing mechanism 20 includes the tubular heating
element 230. As described above, this element is preferably located
between the upstream and downstream pulleys, so that it can seal
and cut the film before it is separated by the downstream pulley.
The tubular heating element 230 may be a tube, having a circular
cross-section. The tubular heating element 230 may be formed into
an open oval, such as is shown in FIG. 4. The leading edge 231 of
the tubular heating element may be semi-circular, and the first end
232 may contain the connections, such as electrical wires, which
supply current allowing the tubular heating element 230 to be
heated. The tubular heating element 230 may have an extended
straight portion 234, which terminates in a curvilinear trailing
end 235, which may be mounted or supported, such as by one or more
brackets. In some embodiments, the tubular heating element 230 may
be rigidly mounted to the machine 20, and positioned such that a
portion of the tubular heating element rests beneath the plane of
film 237. In other words, plane 237 is the horizontal level at
which the tubular heating element 230 passes through the film.
Thus, the leading edge 231 is responsible for initially heating and
cutting the film. Although not shown in FIG. 4, the tubular heating
element 230 may include an electrically actuated heater located
within a cavity in the tubular heating element 230.
[0025] One issue with this tubular heating element 230 is the
potential difference between the actual temperature of the leading
edge 231 and the measured temperature. To measure the temperature
of the tubular heating element 230, a thermocouple 300 may be
installed within a hollow cavity in the tube, as shown in FIG. 11.
In this embodiment, the tubular heating element 230 has a connector
305 at first end 232. This connector may have four connections; two
of which provide current and a return path to the heating element
310; while the other two are for use with the thermocouple 300. The
heating element 310 extends a significant amount of the way into a
hollow cavity in the tube 230. The thermocouple 300 is preferably
positioned near the cutting surface 231. As best shown in the
expanded view on FIG. 11, the heating element 310 and the
thermocouple 300 are in close proximity as they extend into a
hollow cavity within the tubular heating element 230. In some
embodiments, after the thermocouple 300 and heating element 310
have been added, a filler material (not shown) is used to fill the
cavity. This filler material may have a high thermal conductivity
such that the thermocouple 300 measures a temperature close to that
of the tubular heating element 230. The filler material serves to
fix the heating element 310 and thermocouple 300 in place.
[0026] One issue associated with this approach is that the current
passing through the heating element 310 may affect the thermocouple
300, or the transmission of data from the thermocouple 300 back to
connector 305. For example, the proximity of the heating element
310 to the thermocouple 300 may affect the temperature observed by
the thermocouple, such as providing a reading higher than the
actual temperature of the exterior of the tubular heating element
230. Another issue is that the passage of current through the
heating element 310, which may be a coil having an inductance, may
cause interference with the reading being transmitted by the
thermocouple 300, as these wires are positioned near to each other
within the tube 230.
[0027] To overcome these problems and provide an improved method of
measuring the actual temperature of a tubular heating element 230,
FIG. 5 shows a view of a tubular heating element 230 that uses an
external thermocouple assembly 330. One end of the thermocouple
assembly 330 is a sheath 335 that attaches to, or is in contact
with, the exterior of the tubular heating element 230 at a
connection point 340. This attachment at connection point 340 may
be a physical connection, such as one caused by the heating of a
material to thermally bond the sheath 335 to the tubular heating
element 230. Examples of this type of thermal bonding include
welding, braising or soldering. In other embodiments, a mechanical
coupling device, such as strapping, is used to hold the sheath 335
to the tubular heating element 230. In other embodiments, the
sheath 335 contacts the tubular heating element 230 without being
attached or coupled thereto. For example the sheath 335 may be
biased toward the tubular heating element 230, such that a bias
force serves to hold the sheath 335 in close proximity to the
tubular heating element 230. As demonstrated above, any method can
be used to position the sheath 335 close to the tubular heating
element 230 at the connection point 340. While a permanent
connection (such as a mechanical coupling or a heat related bond)
may be preferable, other methods which hold the sheath in close
proximity or in contact with the tubular heating element 230 may be
used as well, such as bias force.
[0028] A thermocouple (not shown) is positioned within the sheath
335, preferably at the connection point 340. If the thermocouple is
positioned away from the connection point 340, the sheath 335 may
be filled with a thermally conductive material such that the
thermocouple receives a temperature nearly identical to that of the
exterior of the tubular heating element 230.
[0029] In another embodiment, the thermocouple is not enclosed in a
sheath 335. In this embodiment, the thermocouple itself may be
soldered, welded, braised or mechanically coupled to the tubular
heating element 230 at a connection point 340, as described above.
In addition, the thermocouple may be biased to remain in close
proximity to the exterior of the tubular heating element 230. Thus,
while the use of a sheath 335 is disclosed, it is not required to
be present in the present invention.
[0030] The connection point 340 may be located anywhere on the
tubular heating element 230. However, in some embodiments, the
connection point 340 is the location where the tubular heating
element meets the plane of the film 237 (see FIGS. 8B, 9A and 10).
This location may give the truest indication of the tubular heating
element at the point where it is actually contacting the film.
[0031] In the embodiment shown in FIG. 5, a junction box 331 may be
used to change the thickness and type of wires that are used. In
some embodiments, the thermocouple uses a simple two wire
connection. In some embodiments, it may be advantageous to use
braided wires that are routed toward the side sealing machine. The
conversion from simple wires to braided wires may be performed in
junction box 331. In other embodiments, the junction box 331 may be
completely unnecessary and may be eliminated. These braided wires
may be placed in a conduit 337, and are in communication with a
controller, which is responsible for monitoring and adjusting the
temperature of the tubular heating element 230. While the present
invention utilizes braided wires, the conduit 337 may include one
or more wires, which may be optionally bundled and encased in a
tube, such as a plastic or metal liner. It should be noted that the
position of the junction box 331 relative to the sheath 335 and
conduit 337 is for illustrative purposes only. The exact position
of the junction box 331 may be changed as desired. In other
embodiments, the junction box 331 may not be present.
[0032] In some embodiments, the controller receives data from the
thermocouple, such as via conduit 337. In response to this data,
the controller determines the power to be applied to the heating
element 310 within the tubular heating element 230. In some
embodiments, the controller may utilize a closed loop control
system to maintain the exterior of the tubular heating element 230
at a desired temperature. Various types of closed loop control
systems may be utilized, including proportional, derivative,
integral, or a combination thereof, such as a PID control loop.
[0033] The coupling between the sheath 335 and the tubular heating
element 230 (at connection point 340) is sufficiently strong so as
to tolerate the temperatures associated with sealing. The sheath
335 and connection point 340 are also rugged enough to tolerate the
possibility of melted plastic becoming attached thereto. In some
embodiments, the coupling at the connection point 340 is rigid such
that any movement of the tubular heating element 230 results in a
corresponding movement of the sheath 335.
[0034] In this configuration, the heating element 310 is still
within the hollow cavity within the tubular heating element 230 (as
illustrated in FIG. 11). As described above, this hollow cavity may
be filled with a filler material after the heating element has been
installed to insure the stability and placement of the heating
element 310. Thus, in the embodiment shown in FIG. 5, the heating
element 310 and the thermocouple have been physically separated
from each other, thereby alleviating the problems associated with
the configuration of FIG. 11 described above.
[0035] FIG. 6 shows a front view of a modular
heating/sealing/cutting assembly 600 using a tubular heating
element 230. This tubular heating assembly 600 may also be used
with a universal side mechanism, as disclosed in U.S. patent
application Ser. No. 13/195,132, the disclosure of which is
incorporated herein by reference in its entirety. The assembly 600
may have a round tubular heating element 230, which is made of a
metal, such as stainless steel. The tube 230 is heated through the
application of power to a heating element, such as a coiled wire,
located within a hollow cavity in the tube 230. The power applied
to the heating element may be a constant voltage and a variable
current. In other embodiments, this power is a variable voltage.
The power from the sealing machine 10 passes to the tube via a
power connector (not shown).
[0036] In some embodiments, the external thermocouple assembly is
held in place, or supported by thermocouple bracket 350. The
thermocouple bracket 350 adds rigidity and support to the
thermocouple assembly 330. In some embodiments, the tubular heating
element 230 is connected to an air cylinder 650, as disclosed in
U.S. patent application Ser. No. 13/195,117, the disclosure of
which is incorporated herein by reference in its entirety. In one
embodiment, the piston 660 (shown in FIG. 7) is attached to the
trailing edge 235 of the heating element 230. The air cylinder 650
allows the tube 230 to be pushed downward toward the film, or
pulled upward away from the film. The leading edge 231 of the tube
230 is pivotably attached to a point 651 on the tubular heating
assembly 600. This point serves as a hinge. In one mode, there is
no or little air in the air cylinder 650, and the tubular heating
element 230 is in a stowed position. FIG. 8A shows the tubular
heating element in the stowed position, where the tubular heating
element 230 is raised above the plane of the film 237.
[0037] Air can then be introduced to the air cylinder 650, so as to
force the piston 660 to extend downward from the air cylinder 650,
as shown in FIG. 8B. The air cylinder 650 causes the tubular
heating element 230 to pivot about the hinge 651. This causes at
least a portion of the extended straight portion 234 to extend
below the plane of the film 237. FIG. 8B shows one active position
for the tubular heating element 230 where the element extends
beneath the plane of the film 237. In this embodiment, the sheath
335 is rigidly attached to the tubular heating element 230, so that
it pivots as well, as shown in FIG. 8B.
[0038] In one embodiment, the air cylinder 650 is an adjustable
stroke air cylinder. In this embodiment, the amount of extension,
or stroke, allowed by the piston 660 is limited by an adjustable
mechanical stop. Thus, the portion of the tubular heating element
230 which is intended to contact the film can be changed by
adjusting the mechanical stop. In another embodiment, a cylinder
having multiple stop positions may be used, thereby allowing
different portions of the heating element 230 to contact the
film.
[0039] The thermocouple assembly 330 and the sheath 335 may be
configured to pivot with the tubular heating element 230. The
conduit 337 and/or wires may be designed to accommodate some amount
of rotation between the junction box 331 (if present), which
pivots, and its connection to the side sealing mechanism, which
does not pivot. In addition, referring to FIG. 5, the sheath 335
may be of any shape required. For example, as seen in FIG. 6, the
sheath 335 may pass between other components located on the side
sealing mechanism. In other embodiments, the sheath conduit 335 may
have a different shape, and therefore the shape or size of the
conduit is not limited by the embodiment shown in FIGS. 5 and
6.
[0040] The above description relates to an air cylinder that is
configured to be in the stowed position in the absence of applied
air. However, other air cylinders may be used which are in the
operative position in the absence of air. In these embodiments, air
is introduced to move the heating element to the stowed position.
Air is then removed to move the heating element to contact the
film.
[0041] The above embodiment discloses a tubular heating element
having a pivotable leading edge, with a biasing member on the
trailing edge. However, in other embodiments, the leading edge may
be attached to the biasing element, while the trailing edge is
pivotable. In another embodiment, the pivot point may be located
between the leading edge and trailing edge.
[0042] The use of an air cylinder 650 has other benefits as well.
For example, the piston 660 is extended due to the force of the
compressed air within the cylinder 650. The force exerted by the
air on the piston is not infinite, and can be overcome by an
opposing force. For example, FIG. 9A shows the tubular heating
element 230 in the operative position. However, a foreign material
700 is positioned on the film in the path of the tubular heating
element 230. As described above, with rigidly mounted heating
elements, the foreign material may potentially damage the leading
edge 231 of the tubular heating element 230. However, in this
embodiment, the force exerted by the foreign material 700 on the
tubular heating element is sufficient to overcome the force of the
compressed air within the air cylinder 650. This then causes the
piston 660 to retract from its extended position, and allow the
tubular heating element 230 to be forced to its stowed position, as
shown in FIG. 9B.
[0043] Thus, the use of an air cylinder 650 attached near the
trailing edge, and a rotatable pivot 651 at or near the leading
edge of the tubular heating element 230 allows many benefits
currently not possible. This air cylinder 650 allows the use of at
least two different positions, an operational position (such as
FIG. 8B) and a stowed position (FIG. 8A). In addition, the air
cylinder 650 allows the possibility to adjust the angle of the
tubular heating element 230, and therefore, the portion of the
tubular heating element that contacts the film. Finally, the air
cylinder also allows the tubular heating element 230 to
automatically move out of the plane of the film, if confronted with
a foreign material, in the path of the heater.
[0044] Furthermore, the use of an air cylinder allows the movement
of the tubular heating element 230 to be controlled automatically.
For example, the side sealing machine 10 may include a controller.
The controller consists of a processing unit, such as a
microprocessor, PLC, embedded processor or other suitable device.
The controller also includes a memory element adapted to store the
instructions that are executed by the processing unit. In addition,
the memory element may contain volatile data as required. The
memory element may be a semiconductor memory device, such as RAM,
EEPROM, FLASH ROM, DRAM or other technologies. It may also include
magnetic or optical storage, such as disk drives, CDROMs, or DVDs.
In one embodiment, the controller can be programmed to introduce
air to the air cylinder prior to starting the pulleys, and
programmed to draw air from the air cylinder when sealing is
stopped or paused. Thus, the controller can control the position of
the tubular heating element relative to the plane of the film prior
to, during and after a sealing operation. In addition, in some
embodiments, the controller may control the position of the tubular
heater based on the type or thickness of the film being used.
[0045] While the air cylinder offers these many benefits, in
another embodiment, the only goal may be to create a mechanism that
allows the heating element to move out of the plane of the film
when confronted with a foreign material. In this case, as described
above, the air cylinder may be used. However, other embodiments are
also possible. For example, the air cylinder may be replaced with
an extendible piston 710, which is biased downward with a spring
711 or other biasing member, as shown in FIG. 10. In this
embodiment, the foreign material would push against the downward
force of the spring 711 or other biasing member and cause the
tubular heating element 230 to rotate so as to be above the plane
of the film 237. This allows the foreign material to pass under the
element 230, without causing any damage to that element. In
addition, any suitable biasing member may be used. For example, an
electronic solenoid may also be used.
[0046] While the present disclosure describes the use of air
cylinders and other biasing members with tubular heating elements,
the disclosure is not limited to this embodiment. For example,
other heating/cutting/sealing devices, such as heated blades or hot
wires may also benefit from the use of biasing members to allow
movement relative to the plane of the film.
[0047] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Further, although the present disclosure has been
described herein in the context of a particular implementation in a
particular environment for a particular purpose, those of ordinary
skill in the art will recognize that its usefulness is not limited
thereto and that the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes.
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