Note: Descriptions are shown in the official language in which they were submitted.
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METHODS AND APPARATUS FOR WEB HANDLING AND
APPARATUS FOR HEATING SPACED AREAS OF A MOVING OBJECT
The present invention relates to methods and apparatus
for handling moving webs and in a second aspect relates to
apparatus for heating spaced areas of a moving object which
may be a web.
When lengths are cut from a moving web of material, they
are usually transported for further processing initially at
a speed which is the same as that at which the web moves. A
need has now arisen for lengths cut from a web to be
accelerated rapidly to a higher speed of movement for further
processing.
Accordingly, according to a first aspect the present
invention provides a method for sep~rating and accelerating
portions of a moving web comprising leading a moving web over
the surface of a rotating web support member, which member has
a surface speed higher than the speed of the moving web such
that the web slips on said member, periodically cutting
lengths of web material from said web on said support member,
capturing said cut lengths on said support member by
attraction of said cut lengths to the surface of said support
member and transporting said cut lengths thereon at the
surface speed of the support member.
The invention in its preferred embodiments is
particularly applicable to handling cut lengths of web
material which are insufficiently stiff or too small to be
handled by more conventional means such as pairs of opposed
rollers or conveyor belts. Thus the invention has particular
applicability to the handling of cut lengths of thin plastics
film, especially lengths of 10 cm or less, e.g. 3 cm or less
(measured on the web length direction).
In a first preferred practice according to the invention,
the end portion of the web is first cut off and then the
resulting cut length is accelerated to the speed of the web
support member.
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Preferably, the cut lengths are attracted to the support
member by negative pressure (suction) applied at the surface
of the support member beneath said cut lengths through one or
more cut length attracting openings in said surface. However,
alternative methods of attracting the cut lengths to the
support member may be employed such as electrostatic
attraction or the choice of materials for the surface of the
web support member and the moving web which naturally tend to
cling to one another.
The web is preferably attracted to the support member
upstream of a cutting station at which it is cut into lengths.
The attraction of the web to the support member may be of the
same nature as the attraction of the cut lengths to the
support member but is preferably less intense. Once again
therefore, the web may be attracted to the support member by
negative pressure applied at the surface of the support member
beneath said web through web attracting openings in said
surface.
Preferably, the attraction of the cut lengths to the
surface of said support member is commenced or is increased
in synchrony with the cutting of said cut lengths from the web
and this thereby made sufficiently strong as to prevent
slipping of the cut lengths on the surface. The support
member preferably comprises a roller having a radially outward
facing web support surface over which said web is led, which
surface has at least one cut length attracting opening therein
communicating with a source of negative pressure e.g.
communicating through means defining a gas-flow path with a
corresponding opening or openings on a second surface portion
of said roller which is rotated so as to bring said
corresponding opening or openings into constant or periodic
connection with the negative pressure source.
The corresponding opening or openings may be brought into
connection with the negative pressure source periodically in
synchrony with said at least one cut length attracting opening
passing through a cutting station at which said web is cut
.. . ,. .. . . .
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into said cut lengths, whereby the attraction of said cut
lengths to the surface of the suppo:rt member is commenced or
is increased in synchrony with the cutting of said cut lengths
from the web to capture each said cut length on said support
member. The cut length is preferably held in a non-slipping
manner on the support surface.
The corresponding opening or openings may be brought out
of connection with said negative pressure source to release
each said cut length before the at least one opening
attracting a cut length is brought round by rotation of the
support member once more to underlie the web.
Thus, the web may be advanced over the rotating roller
at a speed which is less than the surface speed of the roller
so that the roller slips beneath the web and vacuum openings
on the surface of the roller may be actuated as a cutting
means cuts across the web to separate cut lengths repeatedly
from the web. The cut lengths are then attracted by the
vacuum to the surface of the roller and rapidly (preferably
essentially instantaneously) accelerated to roller speed
whilst being held thereon. They may then be subjected to any
desired form of further processing.
Preferably, the web slipping on the roller is also
attracted to the roller, but not so intensively as to prevent
the desired slipping action.
Preferably therefore the support surface has, for
attracting said web, a succession of web attracting openings
circumferentially spaced, each communicating with a source of
negative pressure, e.g. communicating through a said means
defining a gas-flow path with a said corresponding opening or
openings on said second surface portion of said roller, each
said corresponding opening being in communication with said
negative pressure source at least when the respective web
attracting opening is beneath said web. Thus there may be
openings on said support surface which comprise both said
succession of web attracting openings and at least one cut
length attracting opening.
.
Z~
--4--
The cut length attracting opening or openings may be
communicated periodically with a first said source of negative
pressure and the web attracting openings may be communicated
with a second source of negative pressure. The suction
applied through said at least one cut length attracting
opening may be more intense than the suction applied through
said web attracting openings. This may be achieved by
suitable choice of the intensity of action of the first and
second sources of negative pressure or a common source of
negative pressure may be employed for the cut length
attracting opening or openings and for the web attracting
openings and the required difference in intensity of action
can be obtained through a suitable choice for the size and
spacing of the openings or the flow paths by which they
communicate with the source of negative pressure.
An alternative preferred practice according to the
invention is to accelerate the end portion of the web
immediately before it is cut off.
One type of further handling for the cut lengths which
may be envisaged is the temporary or permanent application of
the cut lengths to spaced locations on a second moving web or
a stream of objects such as lengths cut from a second web.
For this purpose, a second moving web or lengths cut therefrom
may be led over a portion of the surface of the rotating web
support member, suitably at a speed substantially equal to
that of the surface of the web support member, said portion
being downstream from the cutting of said cut lengths, and
said cut lengths may be carried on said web support member to
lie between the web support member and said second web or web
lengths. The difference between the speed of the first moving
web and the higher speed of the second moving web or web
lengths will cause the cut lengths to be applied at spaced
locations on the second web or on respective lengths cut from
said second web.
Preferably, the attraction of the cut lengths to the
support member is reduced or ended whilst the cut lengths
h '~
--5--
are positioned between the support member and the second web
or lengths thereof overlying the support member.
The cut lengths may be adhered to the second web or
lengths thereof at said spaced locations. For this purpose,
the cut lengths or the web from which they are cut or said
spaced locations on said second web may be heated to a heat
sealing temperature before contacting said second web with
said cut lengths. To achieve this, the web from which said
cut lengths are cut or said second web or lengths thereof may
be passed adjacent to source of heat to raise at least
portions thereof to a heat sealing temperature.
Generally, it will be desirable that the areas which are
heated are spaced from other heated areas along the direction
of the moving first or second web material by areas which are
relatively unheated. In particular, if the first web (from
the which the lengths are to be cut) is heated, it will
generally be desirable to avoid heating zones in which cuts
are to be made as there will otherwise be a risk that the
heated web will stick to the cutter used. If the second web
material is to be heated, (i.e. the continuous web or cut
lengths thereof to which the cut lengths of the first web are
to be applied) it will be undesirable to heat areas other than
those which are to receive the cut lengths as this is likely
to have a permanent visible effect upon the web surface.
To this end, at least one shield member is preferably
interposed between said heat source and said web to be heated
so as to prevent portions of said web to be heated being
raised to heat sealing temperature.
Preferably, said at least one shield member is moved in
synchrony with and in the same direction with said web to be
heated so as to shield a respective area of the web from said
heat source whilst allowing areas bordering on said shielded
area in the direction of web extension to be heated. A
plurality of said shield members spaced from one another in
the direction of the extension of the web to be heated may be
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moved in synchrony with the web to be heated in said web
extension direction.
Preferably therefore said shield member or members are
moved along an endless path, at least a portion of which lies
between said heat source and said web to be heated. The
shield members may take the form of fingers protruding from
a flexible endless carrier.
The heat source may be a hot gas blower or a radiant
heater.
Means may be provided for cooling the support member,
e.g. by passing a coolant liquid through channels in it, by
passing cool air over it or by contacting it with a further
chilled roller upstream of its point of contact with the first
web. Suitably, the chilled roller is a pressure roller used
to press the second web against the support member.
Means may also be provided for cooling the cutting member
of the cutter used to separate the cut lengths from the web.
Such cooling may reduce any tendency for the heated web to
stick to the cutter member, even if the heat shield described
above is not used.
An alternative option to the use of heating to adhere the
cut lengths to the second web is to apply adhesive to said cut
lengths, the web from which they are cut or said spaced
locations of the second web. The adhesive may be a molten hot
melt adhesive. This may be applied at spaced locations on the
first web, for instance by a process of printing. Other
methods of applying hot melt adhesive may be used if they a.e
suitable for the required speed of operation. Once again, it
will be desirable to apply the adhesive at spaced locations
avoiding areas in which cuts are to be made.
The application of adhesive or the heating to a heat
sealing temperature described above is preferably carried out
on the first web rather than the second web because of the
lower speed of advancement of the first web. Particularly in
high speed operations, it may be impracticable to carry out
these operations on the faster moving second web.
.. .. . . . .
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The second web may be a web of carton forming material
such as paperboard or cardboard, ~ypically laminated with
other materials such as plastics films and/or metal foils.
Typically, such carton forming webs have a heat sealable
plastics layer on each surface, typically of polyethylene.
The first web is preferably of plastics film, preferably
being composed of or having a surface layer of compatible
heat-sealable plastics material. The film may be a laminated
film and in particular may have a first layer of relatively
tough heat-resistant material and a surface layer of readily
heat-sealable plastics material such as polyethylene, poly-
ethylene/vinyl acetate blends or microcrystalline wax. The
relatively tough layer may for instance be of polyester, nylon
or regenerated cellulose.
The method described above may therefore be employed to
apply spaced cut lengths of plastics film on to a web from
which carton blanks will be cut. The cut lengths of plastics
film may serve as sealing tapes over lines of weakness or
apertures in the carton forming material or as tabs to be
grasped by a user of finished carton. For this latter
purpose, the cut lengths may be adhered to the second web over
only part of their surface, leaving the remainder of the cut
length free.
According to a second aspect of the invention, there is
provided a method of heating areas of a moving object which
are spaced from one another in the direction of movement of
the object whilst intervening areas are not heated or are less
intensively heated, which method comprises applying heat to
said object from a heat source spaced from said object,
interposing between said object and heat source at least one
shield member, and moving said shield member in the direction
of movement of said objection in substantial synchrony
therewith. The application of such a method to the securing
of cut lengths of a first web to a second higher speed web at
spaced locations has been described above.
-8-
For use in a method in accordance with the first aspect
of the invention, there is provided apparatus for separating
and accelerating portions of a moving web comprising a
rotating support member, means for supplying a said web at a
web supply speed to lie over a por-tion of the surface of the
web support member, means for rotating said web support member
at a surface speed higher than the speed of the moving web
such that the web slips on said member, means for periodically
cutting lengths of web material from said web on said support
member, and means for capturing said cut lengths on said
support member by attraction of said cut lengths to the
surface of said support member and thereby accelerating said
cut lengths to the surface speed of the support member.
Said means for capturing said cut lengths may comprise
a source of negative pressure and means for applying said
negative pressure at the surface of the support member beneath
said cut lengths through one or more cut length attracting
openings in said surface. There may also be means for
attracting said web to said support member upstream of said
means for cutting said web into lengths and said means for
attracting said web to said support member may comprise a
source of negative pressure and means for applying said
negative pressure at the surface of the support member beneath
said web through web attracting openings in said surface.
The means for capturing said cut lengths by attraction
of said cut lengths to the surface of the said support member
may be adapted to commence its action or increase the
intensity of its action in synchrony with the cutting of said
cut lengths from the web and thereby to make the attraction
sufficiently strong as to prevent slipping of said cut lengths
on said surface.
The support member may comprise a roller having a
radially outward facing web support surface over which said
web is led, which surface has at least one cut length
attracting opening therein, a corresponding opening or
openings on a second surface portion of said roller, means
- 9 -
defining a gas-flow path communicat:ing between said at least
one cut length attracting opening and said corresponding
opening or openings, and means defining a flow path providing
a constant or periodic connection between said corresponding
opening or openings and a said negative pressure source.
Said means defining a flow path between said
corresponding opening or openings and said negative pressure
source may comprise at least one slide valve having a
respective gas-flow port connected to a respective said
negative pressure source sliding over a second surface portion
of said roller and making periodic connections with said
corresponding opening or with at least a respective set of
said corresponding openings.
A said corresponding opening or a set of corresponding
openings may be so positioned in said second surface portion
of said roller as to be rotated into connection with a said
gas-flow port periodically in synchrony with said at least one
cut length attracting opening passing said means for cutting
lengths of web material, whereby the attraction of said cut
lengths to the surface of the support member is commenced or
is increased in synchrony with the cutting of said cut lengths
from the web to capture each said cut length on said support
member.
The position of said corresponding opening or openings
on said second surface portion of said roller may be such that
said corresponding opening or openings is or are rotated out
of connection with gas-flow port to release each said cut
length before the cut length is brought round by the rotation
of the support member once more to underlie the web.
The support surface may have, for attracting said web,
a succession of web attracting openings circumferentially
spaced, each communicating through means defining a gas-flow
path with a said corresponding opening or openings on said
second surface portion of said roller, each said corresponding
opening being in communication with a negative pressure source
at least when the respective web attracting opening is beneath
2~
--10--
said web. Said openings on said support surface may comprise
both said succession of web attracting openings and at least
one cut length attracting opening.
The apparatus may comprise a first source of negative
pressure and a second source of negative pressure and the cut
length attracting opening or openings may be communicated
periodically with said first source of negative pressure and
the web attracting openings may be communicated with said
second source of negative pressure.
The arrangement may be such that the suction applied
through said at least one cut length attracting opening is
more intense than the suction applied through said web
attracting openings.
Means may be provided for leading a second moving web
over a portion of the surface of the rotating web support
member at a speed substantially equal to that of the surface
of the web support member, said portion being downstream from
the means for cutting said cut lengths, and said cut lengths
being carried on said web support member to l.ie between said
web support member and said second web.
The apparatus may further comprise means for heating said
cut lengths or the web from which they are cut or said spaced
locations of the second web to a heat sealing temperature
before contacting said second web with said cut lengths.
Said means for heating may comprise a source of heat
disposed adjacent said web from which said lengths are cut
or said second web and operating so as to raise at least
portions thereof to a heat sealing temperature.
The apparatus may further comprise at least one shield
member interposed between said heat source and said web to be
heated so as prevent portions of said web to be heated being
raised to a heat sealing temperature.
Said at least one shield member may be mounted to be
movable and means may be provided for moving said shield
member in synchrony with and in the same direction with said
web to be heated so as to shield a respective area of said web
.
-11- 2 ~ k~,
from said heat source whilst allowing areas bordering upon
shielded area in the direction of web extension to be heated.
The apparatus may comprise a plurality of said shield
members spaced from one another in the direction of extension
of the web to be heated, which shield members are mounted for
movement, and said means for moving said shield members may
operate to move said plurality of shield members in synchrony
with the web to be heated in said web extension direction,
suitably about an endless path, at least a portion of which
lies between said heat source and said web to be heated.
Alternatively or additionally, means may be provided for
applying an adhesive to said cut lengths, the web from which
they are cut or said spaced locations of the second web, e.g.
a hot melt adhesive.
According to the second aspect of the invention there is
further provided apparatus for heating areas of a moving
object which are spaced from one another in a direction of
movement of the object whilst intervening areas are not heated
or are less intensively heated, which apparatus comprises a
heat source spaced from said object for applying heat to said
object, at least one shield member interposed between said
ob~ect and said heat source, and means for moving said at
least one shield member in the direction of movement of said
object in substantial synchrony therewith.
Such apparatus may further comprise means for cutting
said object arranged to act after said heating to make cuts
in said intervening areas.
The apparatus may further comprise means for moving the
said object over a path in spaced relation to said heat source
and in substantial synchrony with said at least one shield
member.
The invention will be illustrated and further described
with reference to the preferred embodiments illustrated in the
accompanying drawings in which:-
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Figure 1 is a perspective view of a first embodiment of
apparatus according to the first and second aspects of
invention;
Figure 2 is a schematic side view of a second embodiment
of apparatus according to the first aspect of the invention;
Figure 3 is an elevation of a further apparatus according
to the invention;
Figure 4 is a plan view of the apparatus of Figure 3;
Figure 5 is a longitudinal cross-section on the line A-A
of Figure 6 of the knife assembly of the apparatus of Figure
3;
Figure 6 is a transverse cross-section of the line B-B
of Figure 5.
Figure 7 is a perspective view of an alternative form of
cutting station from that used in the apparatus of Figures 2
to 6;
Figure 8 is an elevation view of the face of the knife
of Figure 7 with part of the web support member shown in
section; and
Figure 9 is an enlarged sectional view of the line IX-IX
of Figure 8.
Figure 1 illustrates apparatus for separating tabs of
plastics film from a continuous web, accelerating the tabs to
the speed of advancement of a faster moving second web of
carton forming material and securing the tabs on the carton
forming material by heat sealing.
A first web 10 of tab forming plastics film is supplied
from a reel 12 and passes over and between a pair of driven
metering rolls 14, 16 and hence over the surface of a rotating
web support member constituted by a vacuum roller 18.- A
second web 20 of carton forming paperboard is mounted on a
supply (not shown) and led between roller 20 and a co-
operating pressure roller 22, which may be cooled by means
(not shown) such as means for circulating a cooling fluid
therethrough.
.
-13- 2~
The speed of rotation of vacuum roller 18 substantially
exceeds the rate at which the plastics film of the first web
is supplied by the metering rollers 14, 16.
Between the metering rollers 14, 16 and the surface of
the vacuum roller 18, the first web passes beneath a hot air
heater 24 which co-operates with a movable heat shield
assembly 26. Vacuum roller 18 is provided with a first set
of surface openings constituting cut length attracting
openings 28 which are grouped in three small approximately
square areas (only one shown) equi-spaced circumferentially
on the web supporting surface of the vacuum roller 18 and
which communicate via bores in said roller with a set of
corresponding openings 30 on a second surface portion of the
roller provided on the side face of the roller.
A second set of openings 32 is provided on the support
surface of the roller for attracting the web 10. These
openings 32 are arranged in a pair of parallel
circumferentially extending lines running around the whole
periphery of the vacuum roller 18 and pairs of said openings
32 are connected through a common bore in the vacuum roller
18 to a respective corresponding opening 34 on said second
surface portion of the roller. The corresponding openings 34
extend in a circle on the side face of the roller concentric
with the circle over which the corresponding openings 30
rotate, but of lesser radius.
A first source of negative pressure (not shown) is
connected via a high vacuum line 36 to a slide valve manifcld
38 positioned against the side face of the vacuum roller 18.
A second source of negative pressure (not shown) is connected
via a low vacuum line 40 to a second manifold 42 of the same
slide valve assembly. The first manifold 38 has a port which
lies on the circle of rotation of the corresponding openings
30 for the cut length attracting openings 28 whilst the second
manifold 42 has a port which lies on the circle of rotation
of the corresponding openings 34 of the web attracting
openings 32.
--14--
A cutter for cutting the web 10 periodically is
schematically shown at 44.
The movable heat shield assembly 26 comprises in more
detail an endless belt 46 mounted to run on an endless path
over a driving roller 48 and an idler roller 50 and carrying
a spaced succession of heat shielding fingers 52 which project
from one edge of the endless belt 46. The projecting portions
of the fingers 52 pass in succession beneath the hot air
heater 24. Hot heater 24 comprises an inlet duct 54 for hot
air from a supply (not shown) and an elongate outlet nozzle
directed downwardly towards the web 10 but spaced from the web
10 by an amount sufficient to accommodate the moving fingers
of the heat shield assembly 26.
In use, the second web of carton forming material is
advanced through the apparatus by rotation of the vacuum
roller 18 and the pressure roller 22 at a rate suitable for
use in carton making machinery. For instance at a rate
sufficient to produce about 800 blank lengths per minute. The
first web of plastics film is drawn from the reel 12 by the
metering rolls 14, 16 at a speed which may be in the region
of 1/lOth of that of the second web and hence of the surface
speed of the vacuum roller 18. Low intensity suction is
applied through the low vacuum line 40 and hence through the
succession of openings 32 in the surface of the vacuum roller
18 and the web 10 is attracted to the surface of the roller
but permitted to slip thereover. Hot air supplied through the
heater 24 raises spaced areas of the web 10 to a heat sealing
temperature. The fingers 52 of the heat shield assembly 26
are driven at the same speed as the web 10 beneath the heater
24 so as to protect areas intervening between the spaced
heated portions from the action of the hot air heater. The
heater also acts only upon part of the width of the web 10.
The cutter 44 is actuated to cut the web 10 in those
areas kept cool by the shielding action of the shield assembly
26, one cut being made for each carton blank length fed
through the apparatus. Generally, this will involve making
-15~
a small number (e.g. 3) of cuts per revolution of the vacuum
roller 18. The cutter 44 should be designed to avoid a speed
differential between its cutting blade and the vacuum roller
18.
As the cutter 44 is to be actuated, the cut length
attracting openings 28 on the vacuum roller 18 pass beneath
the cutting station at which the cutter is located. The
corresponding openings 30 for the cut length attracting
openings 28 pass into communication with the suction port of
the manifold 38 connected to the high vacuum line 36 and a
more intense suction is applied to the cut length than through
the web attracting openings 32. The cut length is thereby
seized by the surface of the vacuum roller 18 and essentially
instantaneously accelerated to the surface speed of the vacuum
roller 18 and is then applied to the second web in the nip
between the vacuum roller 18 and the pressure roller 22 to
effect the required heat seal. The heat sealed area is shown
shaded on a cut length 58 applied as a tab on the second web
illustrated in Figure 1, the unshaded area of the tab 58 being
free and not adhered to the second web.
The heater 24 and the heat shield assembly 26 together
constitute apparatus according to the second aspect of the
.invention.
A second embodiment of apparatus according to the first
aspect of the invention is illustrated in Figure 2. In this
variant of the apparatus previously described, the heater 24
and the heat shield assembly 26 are replaced by a hot melt
adhesive applicator system. The web 10 is fed through the nip
between metering rollers 14', 16' and hot melt adhesive is
printed on to the web 10 at spaced locations along the web by
the roller 16'. Suitable methods of printing hot melt
adhesives are well known to those skilled in the art and need
not be described here in detail.
The remaining operation of the apparatus is as described
with reference to Figure 1.
-16- 7 ~
Apparatus in accordance with the illustrated embodiments
of invention discussed so far may be employed to attach tabs
of plastics film at spaced intervals on the surface of a web
of carton forming material. It may be employed with little
modification to apply longer strips of plastics film, for
instance to cover lines of weakness or openings in the carton
forming material which may be desired to provide an opening
mechanism for a subse~uently formed carton. However, the
methods and apparatus described herein may be employed in
fields other than carton manufacture.
A further apparatus according to the invention, in which
the end of the web of film is accelerated before being cut off
is shown in Figures 3 to 6.
As shown in Figure 3 a web of plastics film 118 is drawn
from a supply by a pair of feed rollers 120, 120' and passed
to a web cutting station 122 described in detail hereafter
which is located adjacent the web support member 114. Short
lengths are cut from the end of the web 118 of plastics film
at the cutting station 122 and are carried on the web support
member through the zone of operation of a hot air heater 126
and are eventually brought into contact with the paper board
web (not shown) at spaced intervals therealong and heat sealed
thereto.
Referring to Figure 3, the cutting station 122 comprises
a knife assembly 128 carried on a pair of beam members 130.
The knife assembly will be described in detail with referer.ce
to Figures 5 and 6 below. However, in brief the knife
assembly includes an elongate blade mounted to a support and
as can be seen in Figure 4, the support extends between and
runs transversely with respect to the beam members 130. Each
beam member 130 has a pattern of cut-out holes and slots such
that the beam member can operate as a stiff spring allowing
a degree of deflection along the plane of the blade of the
knife.
Z,,r~
Each beam member 130 is mounted in a similar manner. In
each case at each end of the beam member 130 there is provided
a pulley 132 rotatable on a shaft which also carries a
rotatable member 136 to be driven by the pulley about the same
axis. The beam member 130 is pivotally mounted to the
rotatable member 136 about an axis 134 spaced from the axis
of rotation of the pulley. The rotatable member 136 is
mushroom shaped and the "head" of the mushroom shape provides
a counterweight for the motion of the beam member and its
attached knife assembly, the beam member 130 being pivotally
mounted to the mushroom shaped rotatable member 136 at the end
of the "stalk" of the mushroom.
Each of the pulleys 132 is driven for rotation by a belt
138 driven by a motor 140.
The motion executed by the beam member can therefore be
seen to be a parallel motion, each point on the beam executing
a synchronised circular motion.
The plastics film web is fed via the pair of feed rollers
120, 120' one of which is driven by a belt 142 and passes from
the rollers 120, 120' to a further roller 144 constituting a
movable web carrier member is provided at the end of a bell
crank 146 which is pivotally mounted about a pivot axis 148
and which has a first arm 150 and a second arm 152 extending
initially at right angles to one another. The arm 150 is
towards its free end curved away from the arm 152 and carries
the roller 144 at its end. A curved plate 154 is carried on
the arm 150 in such a manner as to provide a guidance slot for
the plastics film web between the curved plate 154 and the
adjacent part of the arm 150. The roller 144 runs against the
curved plate 154 and is driven by belts 156 and 158. The bell
crank 146 is biassed towards the position shown in the figure
by a coil spring 160 attached to the second arm 152. The end
of the second arm 152 also carries a cam follower roller 162
which is positioned to interact with a cam 164 provided to
rotate with the pulley 132 at the right hand end of the beam
member 130.
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-18-
A cylindrical stop member 166 is provided which limits
pivoting movement of the bell crank in a clockwise sense.
The knife assembly 128 as shown in Figures 5 and 6
comprises an elongate blade carrier 168 carried towards each
end by beam members 130. An elongate blade 170 is adjustably
positioned on the blade carrier 168 by a plurality of bolts
172. Cylindrical end portions of the blade carrier 168
outboard of the attachment to the beam members 130 each carry
a rotatable buffer member 174 having a hard cylindrical outer
surface and supported for rotation on the knife carrier 168
by axially preloaded roller bearings 176 so as to eliminate
radial play between the buffer member 174 and the blade
carrier 168. The two cylindrical rotatable buffer members 174
define between them a surface of rotation and the blade member
170 is adjusted to lie just within that surface of rotation.
In cross-section as shown in Figure 6, the blade carrier
168 incorporates and L-shaped bracket extension 178, an arm
of which extends down parallel to the line of the blade 170.
To the free end area of the bracket 178 is mounted a member
for periodically preventing slippage between the plastics film
web and the rotatable support member 114. This takes the form
of a plate-like member 180 having an end portion which curves
round towards the point of application of the blade to form
a web pressing member. The web pressing member 180 is mounted
adjacent the blade on a pair of leaf springs 182 and its
motion upwards parallel to the blade is limited by an
elastomeric pad 184.
The web support member 114 has six equi-radially spaced
anvil areas 186 at each of which a line of bores 188 extend
from the interior of the web support member 114 to its surface
as a line of vacuum ports. Interiorly, they are connected to
a manifold which is in turn connected to a source of vacuum
(not shown).
The operation of the apparatus as described above is as
follows:-
--19--
Plastics film is withdrawn from its web supply by feedrollers 120, 120' and is fed toward the roller 144 from where
it is fed on by the rotation of the roller 144 so as to pass
on to the surface of the web support member 114 immediately
up-stream of the location of the knife blade 170. At this
stage the bell crank 146 is held away from the knife blade 170
by the spring 160.
The web support member 114 is continuously rotated, anvil
portions 186 thereof passing in succession through the cutting
station 122.
In the cutting station 122, rotation of the pulleys 132
carries the knife assembly through a circular motion
essentially tangential to the web support member 114. This
is synchronised to the motion of the web support member 114
such that the knife blade 170 makes it closest approach to the
web support member as an anvil portion 186 thereof passes
through the cutting station.
As the knife assembly in its circular motion approaches
the web support member 114 a short length of the web of
plastics film 118 will have been fed over the surface of the
web support member and through the cutting station. It should
be appreciated that the rotational speed of the surface of the
web support member is substantially greater than the rate of
feed of the plastics web 118. As the knife assembly
approaches the web support member, the web pressing member 180
contacts the web 118 and presses it against the surface of the
web support member. Up to this point, the web support member
has been slipping underneath the web 118 but pressure of the
web pressing member holding the web against the web support
member 114 prevents the continuation of this slippage and the
web 118 at this point now seeks to advance at the rate of
motion of the web support member 114. It is temporarily able
to do this by drawing the roller 144 at the free end of the
bell crank 146 in toward the cutting station 122 against the
force of the spring 160 and until the first arm 150 of the
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bell crank 146 reaches the stop 166. Immediately prior to
this occurring, the knife blade 170 is brought into contact
with the web through the rotary motion of the knife assembly
on its beam 130 and makes a partia:L thickness cut through the
web. The buffer-members 174 are brought into contact with the
web support member 114 at this point in the operation. They
of course come down on to the web support member 114 on either
side of the width of the web 118 and do not contact the web
itself. The point of the knife blade 170 lies within the
circle of rotation defined by the buffer members 174 so that
the blade remains spaced by a predetermined extent from the
anvil surface 186 of the web support member 114 and therefore
cuts partially only through the thickness of the web 118.
Generally, the web 118 will be a multilayer plastics film in
which there is a relatively strong layer provided to give
mechanical strength to the film and at least one heat sealable
plastics layer which will be mechanically weak in comparison
and which is positioned at the bottom of the web immediately
on the surface of the web support member. There may well be
further layers. It is arranged that the knife cuts through
all or substantially all of the mechanically strong layers but
none or only a partial amount of the weaker heat sealing
layer. The cut is completed immediately before the arm 150
reaches the stop 166 at which point continued rapid rotation
of the web support member 114 snatches the portion of the web
118 held by the web pressing member 180 off the end of the web
118 along the cut line, tearing through the thin remainder of
the mechanically weak heat sealing layer not cut by the blade
170.
The blade assembly is driven such that the tip of the
blade 170 moves at substantially the same circumferential
speed as the surface of the web support member so that there
is no slippage between them as the cut is made.
Whilst desirably the buffer members 174 just touch the
surface of the web support member, any failure in adjustment
of those which protrudes them too far in the direction of the
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-21-
web support member surface is of no substantial consequence
as the beam 130 carrying the misaligned buffer 174 can deflect
to allow both buffer members 174 to come down on to the web
support surface. The knife blade 170 is held safely away from
the web support surface by its fixed disposition relative to
the buffer members 174, so avoiding blunting of the blade by
direct contact with the anvil area 186.
The separated end portions of the web 124 are held on the
web support surface by the application of vacuum through the
bores 188 and are carried under the zone of operation of the
heater 126.
A modification of the cutting station shown in the
preceding Figures 2 to 6 is illustrated in Figures 7 to 9.
In this modified form of cutting station, the plastics film
web is cut by a shearing action rather than by pressure of a
knife blade against a smoothly curved support surface.
Apart from the matters described below, the apparatus as
a whole is as described with reference to the earlier figures.
The apparatus of Figure 7 includes a web support member
118 having a generally cylindrical surface divided into a
broad central strip flanked on either side by portions which
are shaped as described below. The portions flanking the
central strip are symmetrical. That nearer to the viewer in
Figure 7 can be seen to comprise a series of recesses 213 all
of similar nature. Each recess 213 has a floor 215 concentric
with the outer surface of the web support member but recessed
radially inwards. An abutment face 217 connects the floor ~15
to the outer surface of the web support member. Starting from
the web support member and as best seen in Figure 9, the
abutment surface 217 is divided into a first portion 218 which
slopes downwardly from the web support surface against the
direction of rotation of the web support surface and connects
to a second portion 219 which forms an undercut by sloping
downwardly in the direction of rotation.
Concentric with floor 215, there is a ledge 220 at a
higher level inboard from the floor 215. Ledge 220 therefore
.
~t 9.~
-22-
lies concentric with the surface of the support member but
spaced somewhat below it. The abutment 217 lies in each case
generally at the point of cut in the cutting operation but an
abutment face 223 at the end of ledge 220 defines a datum for
the positioning of the knife. The degree of alignment between
faces 217 and 223 depends on the extent if any to which the
rollers project in front of the knife blade. This may be by
a greater (as in Figure 7) or a lesser (as in Figure 9)
amount.
The central strip of the web support member has at each
cutting location a shearing edge 285 forming a step in the
surface connected to the next similar shearing edge 285 by a
gradually rising ramp portion of the web support surface. At
its outer ends, each shearing edge 285 connects with the
imaginary line along which the outer surface of the web
support member would meet the abutment face 219 if both were
projected to meet.
The knife assembly comprises a pair of support mounts
221, only one of which is shown the other being omitted for
clarity. Each support mount 221 is carried on a respective
beam member 130 which is mounted generally as shown in Figure
3. It is preferred that the beam members 130 for use in the
cutting station illustrated in Figure 7 are not cut away to
render them more springy but are relatively rigid.
A knife blade 270 is mounted in a blade carrier 268.
Blade carrier 268 has at each end a circular bore through
which passes a shaft 271 to which the blade carrier 268 is
made fast. Shaft 271 is received at each end in linear
bearings 273 through which it is slidable in the support mount
221 within limits imposed by a pair of stop members 275
positioned at each end of the support mount 221. The blade
carrier is biassed forwardly in the direction of rotation by
a coil spring 279 positioned around the shaft 271 in each
support mount 221.
The blade carrier 268 as best seen in Figure 8 has at
each end a downwardly projecting arm 281 which at its outer
~ q~
-23-
end carries a freely rotatable cam follower roller 274 and at
its inner end is formed with a shoulder 283 forming a step.
The spacing between the steps 283 at each end of the blade
carrier matches the spacing between the ledges 220 on opposite
ends of the web support member whilst the spacing between the
rollers 274 matches the spacings between the recesses 213 of
the web support member.
A sprung foot 280 is provided as in the arrangements
shown in the embodiment of Figure 2.
In use, the knife assembly including the knife carrier
and support mount is carried in a parallel circular motion on
the beams 130 in synchrony with the movement of the web
support member. The strip of plastics film web is fed over
the guide roller 244 as previously described and is trapped
upon the surface of the web support member by the sprung foot
280 as the blade assembly moves down towards the web support
member. The knife assembly rollers 274 come down on to the
surface of the web support member on the sloping faces of the
first portions 218 of the abutment face 217, the knife blade
being held off the shearing edge 285 on the web support member
and the blade and blade carrier 270, 268 being deflected back
against the action of the springs 271. As soon as the web
support member has rotated far enough to carry the shearing
edge 185 into the ideal position, the rollers 274 slip off the
slope face 118 of the abutment face 217 and pass on to the
undercut second portion 219 of the abutment face 217 allowing
the knife blade 270 to be pushed forward by the springs 271
against the shearing edge 285 to make a shearing cut of the
plastics web. To guide the knife blade into and through the
shearing action when the rollers 274 pass on to the second
portion 219 of the abutment face 217, the faces of shoulders
293 are pressed against the rearward facing (in the direction
of rotation) faces of the web support member at the ends of
the ledges 220. As a guard against blade misadjustment
causing the blade to contact the surface of the web support
member below and behind (in the direction of rotation) the
-
, ~ ~
~ 3~
-24-
shearing edge 285, the ledge 220 acts as a stop for the
shoulders 283 on the arms 281 of the blade carrier 268.
The severed strip of plastics film 124 is released by the
raising sprung foot 280 and carrieclaway on the surface of the
web support member 21~.
The knife blade 270 can have a self-sharpening action
with the shearing edge 285 of the web support member.
Many modifications and variations of the invention as
illustrated in the embodiments described in detail above are
possible within the scope of the invention.
For instance the invention could be used to apply tabs
or sealing strips to precut blanks rather than to a continuous
web.
The first web could optionally be extruded on-stream
instead of being drawn from a reel of pre-formed polymer tape.
