Note: Descriptions are shown in the official language in which they were submitted.
CA 02398511 2002-08-15
-1-
MOTORIZED AIR RING
FIELD OF THE INVENTION
The present invention relates to air rings for the production of blown
polyolefin film.
The invention also relates to a process for preparing such film.
BACKGROUND OF THE INVENT10N
In the production of blown polyolefin film, a source of molten plastic is fed
to a
circular die. The emerging molten plastic foams a continuous cylindrical film
extending from
the die. As the film progresses away from the die it is cooled and solidifies.
After
solidification the cylindrical film is collapsed into a folded tube by a
collapsing frame and
drawn through nip rollers. The flat tube proceeds to a secondary process and
is then taken up
on spools.
While the film is forming, between the die and the nip rollers, it is referred
to as a
bubble. After leaving the die, the film material is still molten and it
expands as aresult of the
air pressure within the bubble. As the film progresses towards the nip
rollers, it cools down
and solidifies. The nip rollers are positioned so that the film is solidified
when itreaches them.
The point at which the film solidifies is called the frost line or material
freezing line. The frost
line represents a generally circumferential line around the cylinder of film,
or bubble,
somewhere between the die and the nip rollers. The location of the frost line
varies depending
on the prevailing conditions, for example, on how quickly or slowly the
material cools after
leaving the die.
The frost line represents the transition from a molten state of the polymer
(in which
the polymer may still be stretched, thus reducing thickness) to a solid state
(in which the
thickness of the film is effectively fixed). After the molten polymer material
leaves the die,
foaming the bubble, the bubble expands in diameter by viatue of the pressure
of the air inside
the bubble. As the diameter of the bubble increases, the polymer becomes
thinner until it
solidifies. Thus for a constant feed of material through the die, the lar ger
the bubble diameter,
the thinner the film; conversely, the narrower the bubble, the thicker the
film. Consistency of
ftlm thickness or gauge determines film quality for a given film material.
Thus cooling of the
emerging bubble is important in controlling the thickness or quality of the
film.
CA 02398511 2002-08-15
-2-
Although the blown film process is an effective continuous process for
preparing film,
quality control depends on being able to provide consistent control of the
cooling of the
bubble. Such consistent control is made difficult by the sensitivity of the
thin molten polymer
material to changes in conditions before it reaches the frost line. Various
conditions, such as
the ambient air temperature, pressure and relative humidity, can affect the
cooling of the
bubble. Thus consistent cooling systems are needed. The film quality or gauge
is also affected
by various process and apparatus parameters such as the speed of the nip
rollers, the extruder
output and the blower delivery rate (which determines volume of air flow
delivered to the air
ring).
It is now standard practice in systems for the production of blown plastic
film to
provide an air ring immediately adjacent to the outlet of the die from which
the extruded tube
of molten plastic emerges. The ring delivers an annular stream of cooling air
against the
outside surface of the tube.
This stream of cooling air is guided around the bubble by conical collars or
cones. In
one type of conventional air ring there are two such cones. A first cone
immediately adjacent
the die serves as a forming cone and a second cone, usually of greater
diameter and further
from the die, seines as a bubble cone. Air streams are then directed between
these cones and
the emerging bubble, to affect and control the cooling of the polymer. The
control of the air
streams provided by an air ring is generally effected by a number of movable
components. For
example, the cones themselves may be adjustable to vary the flow or direction
of the air
streams. The cones may have an adjustable lip. The quantity of air flowing may
be adjusted
and the proportions of air passing though one cone, in relation to the other
cone, may be
adj ustable. A cone, for example the bubble cone, may have adj ustable
apertures to allow more
air in. Any or all of such features contribute to the adj ustability and
control of the air streams
provided by an air ring. Thus the development of such features and such
adjustability has led
to the development of air ring design.
Although air ring adjustment is critical to the quality and yield of the blown
film
process, it has not been possible to automate it with satisfactory results.
Typically, therefore,
air ring adjustment is performed by skilled operators, and although attempts
have been made
to record component settings, currently, adjustment tends to be affected
according to the
experience of the operator in response to observation of the bubble shape.
Such a person
CA 02398511 2002-08-15
-3-
becomes familiar with the air ung and learns to make appropriate adjustments
to obtain the
required film thickness or gauge of acceptable quality. Since the film gauge
usually varies in
response to changes in the ambient conditions in the environment around the
bubble, such as
air temperature, pressure and humidity, and since such environmental
conditions may change
during the day, the operator must be constantly checking the process and
making appropriate
adjustments. Production results can therefore vary fi-om batch to batch.
However there may
be some predictability in the nature of the environmental changes. For
example, the air
temperature may rise predictably each day as the day progresses. 1t would
therefore be
advantageous to have a system which could accommodate such changes, with some
degree
of automation, without reliance on the skill of an operator. However, although
it would be
desirable to improve automation of the adjustment and reduce dependence on the
operator,
such automation has proved an elusive goal.
There have been various attempts to provide automation. For example, U. S.
Patent
No. 5,676,893 (issued Oct 14, 1997, inventor - Robeut Cree, assigned to Addex
Design, Inc.)
describes a design which includes a device for continuously measuring the
thickness of the
bubble all around the circumference of the film. These measurements we used to
make
continuous adjustment to a number of air baffles, each of which controls a
portion of the air
stream cooling the bubble at a particular corresponding portion of the
circumference of the
bubble. However, although the baffles are moved in response to the thickness
measurement,
their position is not recorded and there is no signal generated to indicate
their position. Such
a design is complex and expensive.
Until now, none of the various attempts to automate air ring adjustment have
been
entirely satisfactory. It would therefore be desirable to provide an air ring
capable of
consistent repeatable results, and which can provide automated air nng
adjustment to reduce
or eliminate dependence on an operator.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an air ring
for a
blown film process, the air ring comprising: at least one air outlet for
directing a stream of air
outside the film; at least one component movable through a r ange of positions
for controlling
the air stream, said component being moveable to a set position within the
range of positions
CA 02398511 2002-08-15
-4-
for achieving a film of preselected properties; adjustor means for moving the
component to
any one of the positions; and output generating means for generating a unique
output signal
for each of said positions in said range to produce a unique signal
representative of the set
position.
According to a further aspect of the present invention there is provided in an
air ring to
provide at least one air stream outside a bubble in a blown film process, the
air ring
comprising aplurality ofcomponents at least one component adjustable to modify
at least one
air stream, wherein the components include an upper lip and a lower lip, a
forming cone, and
a bubble cone; the improvement comprising providing an output generating means
to generate
an output signal to identify the position of said at least one adjustable
component.
According to another aspect of the present invention there is provided a
method of
preparing a blown plastic film which comprises: extruding melted plastic
through a circular
di e; continuously removing the melted plastic from the die in the form of a
cylindrical plastic
film; providing an air flow around the outside of the film by means of an air
ring adjusting
at least one component of the air ring to modify the air flow; recording, in a
processing unit,
a signal generated by an output generating means, which signal identifies a
unique position
of said at least one component.
According to a still further aspect of the present invention there is provided
a process
for the continuous production of a blown plastic film using an apparatus which
comprises an
air ring which provides an air flow to cool the plastic film, the air ring
having at least one
component movable to control the air flow, the component movable in response
to a set of
external conditions affecting the quality of the film, the method comprising:
making at least
one adjustment to said at least one movable component of the air ring to
obtain a pre-selected
film quality corresponding to a first set of said external conditions;
recording in a processing
unit a first output signal generated by an output generating means to identify
a first position
of said at least one movable component corresponding to said first set of
conditions; adj usting
said at least one movable component in response to a second set of said
external conditions
to obtain saidpre-selected film quality; recording in the processing unit a
second output signal
generated by the output generating means to identify a second position of said
at least one
movable component eom-esponding to said second set of conditions; calculating,
based on said
first and second output signals, an appropriate adjustment for said at least
one movable
CA 02398511 2002-08-15
-5-
component in response to a third set of said external conditions, making said
appropriate
adjustment to said at least one movable component.
According to another aspect of the present invention there is provided a
method of
preparing a blown film of a preselected quality comprising: observing a first
change in an
environmental condition affecting the film quality; adjusting a movable
component of an air
ring to change an air flow from the air ring to restore the preselected film
quality; recording
an output signal generated by an output generating means, the signal
identifying the position
of the component corresponding to the adjustment; repeating said adjusting and
recording in
response to subsequent changes in said environmental condition to obtain a
database of output
signal values corresponding to unique positions of the movable component.
The air ring has at least one movable component. Preferably the air ring has a
plurality
of movable components. These components are movable to affect the quality of
the finished
film. Generally the components are movable to affect and control the air
streams provided by
the air ring. The nature of the movable components will depend upon the type
or design of the
particular air ring used.
In an air ring with both a forming cone and a bubble cone, examples of such
movable
components include: a component to operate a valve to control air flow to the
forming cone;
an upper lip component movable vertically (up or down) when the air ring is
oriented to form
the bubble upwardly away from the die, so that movement of the upper lip
affects the flow of
air in a sh~eam flowing towards the center of the air ring and then also
affects the air stream
flowing between the bubble cone and the foaming cone; the bubble cone
component itself,
which may be mounted on the upper lip and movable (for example, vertically)
independently
and in relation to the upper lip so that the quantity of air in the air stream
between the bubble
cone and the foaming cone, and the shape or direction of that air stream can
be controlled; a
movable component to open and close a plurality of apertures in the bubble
cone (since the
bubble cone in such air rings extends above the general plane of the air ring,
such apertures
allow ambient air to be drawn into the air stream exiting from the air ring
and thus increase
the flow). The movement of such components may affect the quantity or volume
of air in the
air stream and the velocity of the air stream or it may affect the shape or
direction of the
stream. 1t may also affect whether there is turbulence in the air stream. The
greater and more
varied the control of the air stream, the more options are available to
control the cooling of
CA 02398511 2002-08-15
-6-
the film emerging from the die and thus the quality of the finished film.
The movable components are movable through a range of positions. The range of
positions may be continuous to form a continuum of positions or each position
may be one
of a series of discrete steps. In some cases the range of positions may vary
from a maximum
position at one end of the range to a minimum position at the other end of the
range. However,
the range may also be circular so that the component moves from a starting
position through
the range to return to the starting position. The components may move in a
variety of ways,
but regardless of how they move, each position in the range represents a set
position, or a
setting of that component. The components are movable by adj ustor means or
actuators which
may be, for example, an electric motor such as a stepper motor or the adjustor
means may be
fluidic, hydraulic, electronic, mechanical or any other means to generate or
create the desired
movement of the component.
Associated with at least one of the movable components there is an output
generating
means to generate an output signal. Preferably there is at least one output
generating means
associated with each movable component. 'Che propose of the output signal is
to identify the
position of the component with which the signal is associated. It is not
necessary to know the
absolute position of the component. It is only necessary to be able to
identify its position, so
that the component may be returned to the same position on another occasion.
For example,
if the component is moved vertically by rotating a threaded bolt, it would not
be necessary to
know the distance moved by the component, it would only be necessary to know
the number
of turns of the threaded bolt from some reference position in order to
identify the position of
the component. Thus the position of the component may be identified either
directly or
indirectly.
The output generating means may include ameans to detect the position of the
movable
component either directly or indirectly, such as a sensor. The corresponding
signal, which
identifies a unique position of the component, may then be generated.
If the component is moved by an actuator, the output generating means could be
in the
actuator itself (built-in) or outside the actuator (external) mounted in any
place where a
relative movement reading can be made.
The output generating means may be combined with the adjustor means in a
single unit.
For example, it is now possible to obtain actuators (which may be motorized)
with built-in
CA 02398511 2002-08-15
_7_
encoders or potentiometers. The encoders, which may be linear or rotary, can
show a unique
value in a range of 1 to 100 (for example) for each position of the associated
actuator, thus
identifying its position. Encoders generally use TTL 5 volt signal pulses to
identify the value
in the range. Encoders generate digital signals. Potentiometers, on the other
hand, generate
analog signals according to an increase or decrease in the value of an
electrical parameter such
as current or voltage. The output generating means can thus include a counter
of some kind,
for example to count the number of steps made by a stepper motor, which then
generates a
signal indicating the count made. It can also include a recording device which
can read a
position such as a laser position sensor or optical sensor.
The type of output generating means will be governed in part by the type of
signal to
be generated. Thus an electrical signal can be generated, for example, by a
linear or rotary
potentiometer. Other suitable output generating means include encoders (linear
or rotary),
optical devices, slides and numbered rules. The position of the component
might also be
uniquely indicated by a combination ofmore than one signal, for example from
more than one
output generating device.
In order to achieve reproducibility, the signal should be unique for any
particular
position of the component. Thus each position in the range should be
identifiable by a unique
signal. Any kind of signal which can uniquely indicate the position of the
component may be
used. The signal is a means to transfer information. Suitable signals include
visual, optical,
electrical and magnetic signals. Signals may also be analog or digital. A
preferred signal is
an electronic signal or a signal which can be directly processed by a
processor such as a
computer. Suitable processors include laptop, desktop and industrial
computers.
In a prefen-ed embodiment, the signal is sent to a processor where it can be
stored. In
this way, signal readings can be taken con-esponding to environmental factors
such as the air
temperature andhumidity. Then, on another occasion when the environmental
factors are the
same or similar, the components can be moved to the positions they were in on
the previous
occasion. Similarly, signal readings can be taken co~-~-esponding to
particular process and
apparatus parameters or combinations of environmental conditions andprocess
and apparatus
parameters. Thus by providing signals to identify the positions of the
components, it becomes
possible to reproduce a successful combination of component settings
automatically. Also,
ifthe environmental factors are recorded, togetherwith the component settings,
a database can
CA 02398511 2002-08-15
_8_
be compiled. The processor can then be programmed to predict a suitable
combination of
component settings for a variety of different environmental and process
conditions.
In this type of embodiment, it woul d also be preferred that the movement or
adj ustment
of the components can be effected by the processor. For example, if the
adjustor means is
motorized, the processor can instruct the motor to move the component to a
selected position
or setting. In this way, adjustment can be automated.
Thus theprovision of an output generating means which can produce a signal to
identify
the position of the component, enables reproducibility of the component
settings and
automation of adjustment.
BRIEF DESCRIPTION OF THE DRAVVINGS
Embodiments of the present invention will now be described, by way of example,
with
reference to the attached Figures, in which:
Figure I is a cross-sectional view of an embodiment of an air ring according
to the
present invention;
Figure 2 is an orthogonal view of a cross-sectioned air ring according to an
embodiment
of the present invention; and,
Figures 3A and 3B show schematic representations oftwo kinds of actuator
suitable for
use with an air ring of the invention;
Figure 4 is a plan view of an air ring of the invention, showing various
actuators.
DETAILED DESCRIPTION
A motorized air ring system for producing consistent high quality blown film
is
disclosed. More specifically, the individual adjustable component pants of an
air ring, which
are normally adjusted manually are motorized. The controls will include an
electrical/mechanical device designed to feedback and display, for the benefit
of the operator,
the location of the components at any given time relative to a set of
standards or reference
points. The motorization of the individual adjustable component pants of the
air ring yields
consistent repeatable results for pr oducing consistent high quality blown
film with minimum
training for the machine operator. As a result, the producer attains improved
manufacturing
costs.
CA 02398511 2002-08-15
-9-
As shown schematically in Fig. 1 a prefen-ed air ring assembly comprises a
foaming
cone I, a bubble cone 2, an upper lip 3, a bottom lip 4 and an air chamber 5.
As the molten plastic emerges from the circular die (not shown) it foams a
cylindrical
film refewed to as the bubble. The foaming cone 1, upper lip 3 and bubble cone
2 guide air
streams around the outside of the bubble as it leaves the die.
Air is provided to the air ring from a distribution manifold (not shown) by
way of a
series of flexible hoses. Such hoses are suitably about four inches in
diameter. The hoses are
attached to the air ring assembly at air entry pons shown as port 6. The
direction of the air
flow is shown by arrow A. Poet 6 is connected to a plenum or chamber 5. The
number of
entries and their shape will vary in size relative to the size of the machine
itself. Chamber 5
provides a mixing and blending area which reunites the air from the multiple
hose supply into
a single chamber. The chamber 5 itself is a cylindrical shape which accepts
the tangential
entry of the air stream, and acts as a reservoir to reduce pulsation within
the hoses. Seals 7
allow the chamber 5 to move independently from the rest of the air ring. In
many air rings the
chamber 5 with hoses attached foams a sub-assembly which remains stationary
while the rest
of the air ring assembly is able to rotate. A fixed upper lip 8 has a series
of holes 9 engineered
to rectify the air flow by changing the tangential airflow into a flow pattern
directed straight
toward the centre of the assembly where it will exit. The fixed upper lip 8 is
attached to fixed
lower lip 10, which provides a foundation or primacy support for the assembly.
The bottom
lip 4, attaches on the lower side to the fixed lower lip I 0. Thus a primary
air flow (shown by
am-ows B) is created between the bottom of upper lip 3 and the top of lower
lip 4. A motor unit
1 I having member 30 controls a secondary air flow through the bottom lip 4 by
means of a
cable 12 and an air control valve 13. The secondary air flow then passes
between the inside
face of foaming cone I and the emerging bubble, as shown by an-ows C. Thus the
motor unit
I 1 provides a means to control the secondary air flow. In the embodiment
shown, the forming
cone 1 is fixed to bottom lip 4. However, in other embodiments, foaming cone 1
may be
removable or adjustable. A number of holes may be positioned around the
diameter of the
larger wea of the foaming cone to permit air to pass through to the exit. In
the embodiment
shown, the secondary air flow is controlled by valve 13 which in turn is
controlled by motor
unit 1 1 via cable I 2, but any other suitable means may be used to control
the secondary air
flow. In the embodiment shown, motor unit I I has a built-in output generating
means (not
CA 02398511 2002-08-15
-1p-
shown) to provide an output signal to uniquely identify the position of valve
I 3. Thus motor
unit 11 seines as both the adjustor means, or actuator, to move valve 13 and
also an output
generating means to generate a suitable output signal. An adjusting nut 14 is
mounted on the
upper lip 3 and connects upper lip 3 to fixed upper lip 8. Adjusting nut l4
allows upper lip
3 to move vertically relative to a horizontal plane with the adjusting nut 14
being the fixed
mechanism to locate pants 3, and 2, and keep them concentric. The upper lip 3,
is allowed to
move either up or down in relation to fixed upper lip 8 and therefore develop
changes to
aerodynamic effect which may be used for gauging of the blown film. The bubble
cone 2
provides a collar to guide the air flow around the expanding bubble and thus
help to increase
control of the film. Bubble cone 2 is adjustable up and down. A gate I S is
mounted on the
bubble cone 2. Both the gate 15 and the bubble cone 2 have a series of holes
16, 17 that match
each other. By rotating the gate 15 the holes 16, 17 can be shut off
completely, or
proportionally opened. In this way, additional outside air (shown by arrows D)
can be allowed
to join the main airflow around the bubble since when holes 16, 17 are opened,
the reduced
pressure caused by the primary air flow will draw in additional air. The
location of the bubble
cone 2 moving up or down in relation to upper lip 3 can be used to develop a
venturi effect
as an additional adjustment of the airstream and thus a further control of the
gauge and quality
of the film. Thus the movable components shown in figure 1 are the valve 13,
upper lip 3,
bubble cone 2 and gate 15.
Preferably the air ring of the invention is motorized. That is, for those
pants which are
adjustable to control the air flow they are movedby way of a motor so that
manual adjustment
is not required and so that movement of the parts can be automated. Figure 2
shows one
embodiment of a motorized upper lip 3. The motorized air ring of Figure 2
includes a cam
unit 20 coupled to a ramp 21 adapted to communicate with the cam unit 20, and
an upper lip
actuator 22. The actuator 22 is mounted at one end 23 of aum 24 to the fixed
upper lip 8, and
at the other end 25 of ann 26 to upper lip 3. Thus extension or retraction of
arms 24 and 25
causes rotation of upper lip 3 which rotation is given a vertical component by
the movement
of cam unit 20 in the diagonal slot 27 in ramp 21. Valve 13 is operated by
motor unit 11 by
way of cable 12 which is held in position by member 30 and extended or
retracted by arm 31.
Bubble cone gate 15 has a pattern of holes 16 matching the holes 17 in bubble
cone 2. A
second actuator (not shown), similar to actuator 22, is positioned to move the
bubble cone
CA 02398511 2002-08-15
-11-
gate 15 so that the holes 16 can be completely in line with the holes 17 so
that air can flow
from outside the bubble cone into the air stream around the bubble from the
air ring or the
holes 16 can be moved so that no air can pass through. The bubble cone 2 can
also be adj usted
up and down in relation to the upper lip :3 by means of another actuator (not
shown) in
combination with the cam unit 28 movable in ramp 29 in the same manner that
actuator 22
moves upper lip 3 up and down by means of the movement of cam unit 20 in ramp
21. It
should be clear to a person skilled in the art that other possibilities may be
substituted for the
actuator, cams and ramps shown in order to move the components in the desired
fashion. In
the embodiment shown the output generating means would be built-in to the
actuators, for
example actuator 22, to generate the output signal to identify the position of
the movable
components. However, it will be readily apparent that the output generating
means could be
in the cam units or ramps, for example care unit 20 or ramp 21.
In operation, air enters port 6 (as shown by avow A) and then chamber 5. It
then passes
through the rectifying holes 9 into the passageway foamed between upper lip 3
and bottom
lip 4 (shown by avows B). The flow of air in this passageway is generally
toward the centre
of the air ring. When the air flow has almost reached the end of the bottom
lip 4 it is split into
two paths. One path flows through valve 13 towards the die (not shown) located
around the
central axis of the air ring. This air path then flows upwards in the passage
foamed by the
inside surface of forming cone 1 and the outside surface of the bubble exiting
from the die(as
shown by arrows C). The other air path continues past the end of upper lip 3
and flows
upwards in the passage formed firstly by the outside surface of foaming cone l
and the upward
curved surface of upper lip 3 (as shown by arrows E). Then this passage
becomes the passage
formed between the inside surface of the bubble cone 2 and the outside surface
of the exiting
bubble. Since gate 15 has openings 16 which match openings 17 in bubble cone
2, movement
of gate 15 can cause the openings 16 and 17 to have various degrees of
alignment from a
position in which none of the holes are in line to a position in which all the
holes are in line
and air from the outside of the air ring may pass through the holes 16 and 17
(shown by
arrows D) and increase the air flow in this air passage between the bubble
cone 2 and the
exiting bubble. Thus it can be seen that the air flow is affected by movement
of any of the
movable components; bubble cone 2; upper lip 3; valve 13; and gate 15.
In the air ring of the invention an output generating means is provided for at
least one
CA 02398511 2002-08-15
-12-
of the movable components which affects the film quality. Preferably an output
generating
means is provided for all the adjustable components. The components which are
movable or
adjustable are movable through a range of unique positions. The output
generating means
generates an output signal which identifies a unique position of the
adjustable component so
that the component can be automatically returned to that position.
It is also possible to have more than one output generating means for each
component.
Since it is an object of the invention to provide reproducibility, it is
preferred that the
movable components are motorized or provided with some other equivalent means
which is
capable of remote and automatic movement. In this way the output signal
generated by any
output generating means can be recorded and an automated control can move the
component
to a previous or similar position as desired.
Figures 3A and 3B show two kinds of actuator suitable for use with air rings
of the
invention. In figure 3A an actuator or adjustor means is generally indicated
as 40. The
actuator is operated by a motor 41 mounted on a cylinder 42 from which
protrude arms 43 and
44 which have ends 45 and 46 which may be secured to components of the air
ring. An end
st1-oke limit switch 47 may be used to control the range of extension of aims
43 and 44 by
cutting off the power at a pre-selected point. Wiring 48 and 49 is used to
supply power to the
switch 47 and motor 41 respectively. The output generating means (not shown)
is built into
the actuator 40. The output signal generated by the output generating means,
may be
transmitted through wiring 50. A suitable output generating means in such an
actuator would
be a potentiometer, for example. Such actuators, with built-in output
generating means, are
readily available commercially.
Figure 3B shows a smaller version of a suitable adjustor means or actuator'
generally
indicated as 55. Bolt holes 56 accommodate the mounting of the actuator 55 on
a component
of the air ring. A movable arm 57 transmits movement (rotary or extension)
from a motor (not
shown) inside the actuator 55. Again, the output generating means in such an
actuator can be
built-in and might suitably be apotentiometer. The output signal can be
t~~ansmitted by wiring
58.
Figure 4 is a schematic plan view of an air ring (generally indicated as 65)
according
to the invention with the cover removed to reveal one possible arrangement of
actuators. The
figure is only intended to illustrate apossible arrangement and so some
components havebeen
CA 02398511 2002-08-15
-13-
omitted for simplicity. Thus various components needed to connect the
actuators to the
components which they control a1-e not shown. The precise nature of such
components should
be readily apparent to a person skilled in the ant. A first actuator 66
controls movement of
valve 13 (not shown) by means of a shield cable connection symbolically
represented by 66a
and 66b. Thus actuator 66 controls a secondary air' flow to the forming cone
1. A second
actuator 67 controls movement of the upper lip 3 (not shown). Actuator 67 is
mounted so that
end 67b is connected to fixed upper lip 8 (not shown) and the other end 67a is
connected to
movable upper lip 3 (not shown). Thus extension and retraction of ends 67a or
67b will effect
a movement of the upper lip 3 in relation to the position of fixed upper lip
8. A third actuator
68 is connected to the bubble cone 2 through end 68b and to the upper lip 3
(not shown)
through end 68a. In such an embodiment, actuator 68 is mounted on upper lip 3
and thus
moves with it. This facilitates controlling the bubble cone 2 to move either
simultaneously
with movement of upper lip 3 or independently of upper lip 3. A fourth
actuator 69 controls
movement of the bubble gate 15 (not shown). In one embodiment, actuator 69 is
mounted on
the bubble cone 2 with an actuatable connection to bubble gate 15 so that gate
15 can be
moved independently of bubble cone 2. Each of these actuators or adjustor
means would
suitably have a built-in output generating means to provide output signals
which uniquely
identify the location of the movable components with which they are
associated.
It is also possible to convent a conventional air ring to an air ring
according to the
invention by providing output generating means and preferably motorizing the
movable
components. In some air rings, such a conversion would not require a redesign
but only a
retro-fitting.
For example, some conventional air rings have a thread between the adjusting
nut 14
and the fixed upper lip 8 which enables movement of the upper lip 3. A
preferred adaptation
of such an aurangement would be to replace the thread by a smooth machined
surface. As
shown in Figure 2, the upper lip 3 would preferably be provided with an
actuator 22 (also
attached to fixed upper lip 8) and a cam unit 20. A ramp 21 would be provided
on fixed upper
lip 8 to cooperate with cam unit 20. Thus a change in length of actuator 22,
as shown in
Figure 2, would result in a rotation of fixed upper lip 3. By virtue of the
angle of the slot in
ramp 21 cooperating with the cam unit 20, any rotation of fixed upper lip 3
will result in a
change of height in relation to the fixed lower lip 10.
CA 02398511 2002-08-15
-14-
A similar arrangement can be used for other movable components. For example,
adj ustment of the valve 13 can be motorized by providing a direct moving
mechanism to pull
or push the cable 12 to change the air flow to the forming cone 1 by adjusting
the valve 13.
The bubble cone gate 15, which moves holes 16 into and out of alignment with
holes
17 in bubble cone 2, can also be motorized. An actuator (not shown) may be
mountedto move
bubble cone gate 15 in slidable relation to bubble cone 2 to modify air flow
between the
bubble cone 2 and the bubble.
The angle of ramps 29 and 21 can be selected based on the degree of
sensitivity of
adjustment that is desired. All the actuators, ramps and cams for adjusting
the air ring
components are part of the air ring positioning means for altering the flow of
air through the
air ring as the components are shifted in position relative to each other.
In a prefen-ed embodiment of the present invention, all actuators will feed a
signal to
the control box indicating the pan position. Therefore the settings become
repeatable and all
the moving parts are adjusted relative to a desired physical point. Those of
skill in the art will
understand, for example, that the position of cam unit 20 and ramp 21 can be
exchanged
without affecting the operation of the invention.
1n operation, when the upper lip 3 is rotated with respect to the fixed upper
lip 8, a
change in height will develop between them because the cam 20 moves either up
or down the
ramp 21. A change in height will also develop between bubble cone 2 and bubble
cone gate
15 when its actuator (not shown) rotates cone 2 with respect to gate 15.
Although actuators such as upper lip actuator 22 is used to rotate the upper
lip 3 relative
to fixed upper lip 8, any means for moving the upper lip 3 relative to fixed
upper lip 8 can be
used. For example, cam unit 20 can be a motor driving a toothed wheel, and the
ramp 21 can
have complementary teeth in engagementwith the toothed wheel. Additionally,
the motorized
air ring can be part of a system in which it is possible for the operator to
recall specific
adjustment settings for the air ring used in previous production, to enable
duplication of
finished product end results. Furthermore, all the actuators can be
electronically controlled
as a system by a computer.
Therefore the motorized air ring according to the embodiments of the present
invention
can overcome difficulties in resetting the individual component pants relative
to a physical
position. It can deliver position repeatability, favourably affecting the
production process and
CA 02398511 2002-08-15
-15-
reducing uncertainty as-ound positioning of the individual parts thus aiding
the process of
producing consistent high quality blown film with a minimum of training for
the machine
operator.
The foregoing has constituted a description of specific embodiments showing
how the
invention may be applied and put into use. These embodiments are only
exemplary. The
invention in its broadest, and more specific aspects, is further described and
defined in the
claims which now follow.
These claims, and the language used therein, are to be understood in terms of
the
variants of the invention which have been described. They are not to be
restricted to such
variants, but are to be read as covering the full scope of the invention as is
implicit within the
invention and the disclosure that has been provided herein as follows:
