U.S. patent application number 11/568518 was filed with the patent office on 2007-08-16 for process and machine for packaging products with stretchable thermoplastic film.
Invention is credited to Renato Rimondi.
Application Number | 20070186512 11/568518 |
Document ID | / |
Family ID | 34969610 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070186512 |
Kind Code |
A1 |
Rimondi; Renato |
August 16, 2007 |
Process and machine for packaging products with stretchable
thermoplastic film
Abstract
Means are provided to ensure that during the stage of formation
through the tube- forming and longitudinal welding means (1, 18)
the wrapping is subjected to longitudinal stretching which causes
it to adhere intimately in a direction transverse to the product
and this condition is ensured by means which bring about a
particular difference in velocity between the jaw (19, 119) which
supports the tubular wrapping and causes it to advance and the
means (15, 115, 17) which feed the film to the tube-forming means
(1) which also remain suitably active during the subsequent stage
in which the tubular wrapping is seized posteriorly by the
appropriate posterior closing jaw (119, 19), all in such a way that
the wrapping film runs over the said tube-forming means in an
almost continuous movement to prevent localised appearance defects
in the packaging and to assist operation of the longitudinal
welding means (18) which are then able to operate substantially
continuously.
Inventors: |
Rimondi; Renato; (Bazzano,
IT) |
Correspondence
Address: |
STITES & HARBISON PLLC
1199 NORTH FAIRFAX STREET
SUITE 900
ALEXANDRIA
VA
22314
US
|
Family ID: |
34969610 |
Appl. No.: |
11/568518 |
Filed: |
May 27, 2005 |
PCT Filed: |
May 27, 2005 |
PCT NO: |
PCT/EP05/52422 |
371 Date: |
October 31, 2006 |
Current U.S.
Class: |
53/441 ; 53/450;
53/550; 53/556 |
Current CPC
Class: |
B65B 53/00 20130101;
B65B 9/073 20130101 |
Class at
Publication: |
053/441 ;
053/556; 053/450; 053/550 |
International
Class: |
B65B 9/12 20060101
B65B009/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2004 |
IT |
BO2004A000349 |
Claims
1) Machine for the packaging of products with stretchable
thermoplastic film characterised in that it comprises: means (1)
for making the wrapping film unwind from a spool into a tube and
means (18) for longitudinally welding the overlapping edges of that
film so as to produce a continuous tubular wrapping, means (15,
115, 17) to feed the film unwound from the spool to the said
tube-forming means (1) in a controlled way, jaw means (19, 119)
located downstream from the film-tube-forming means (1) which
alternate in transverse gripping of the head and tail ends of the
tubular wrapping leaving the said tube-forming means, and into
which the product being packed is inserted at the appropriate
stage, these jaw means being designed to support and cause the said
wrapping to advance longitudinally and produce two transverse
parallel leaktight welds therein, a transverse cut between the two
welds and to hold the wrapping upstream and downstream from the two
welded areas separated by the cut, means for cyclically inserting a
product (P) through the said tube-forming means and for
accompanying it as it exits therefrom and inserting it into the
tubular wrapping being formed which is held anteriorly by one of
the said jaw means (19, 119), means to ensure that the wrapping in
the stage of being formed through the said tube-forming and
longitudinal welding means (1) is subjected to longitudinal
stretching in such a way as to adhere intimately to the product in
a transverse direction, this condition being ensured by means which
bring about a particular difference in speed between the jaw (19,
119) which supports the tubular wrapping and causes it to advance,
and the said means (15, 115, 17) which feed the film to the
tube-forming means (1), which also remain suitably active during
the subsequent stage during which the tubular wrapping is gripped
posteriorly by the appropriate posterior sealing jaw (119, 19), all
in such a way that the wrapping film moves with an almost
continuous movement over the said tube-forming means to prevent
local unsightliness in the packaging and to assist operation of the
longitudinal welding means (18) which are then able to operate
substantially continuously, means (23) for collecting and removing
the packs (Z) which are cyclically formed.
2) Machine according to claim 1), in which the film (5) is unwound
from the spool (105) by means which are expressly dedicated to that
function and which are capable of constantly providing the
necessary suitably stretched quantity of film to the subsequent
means (15, 115, 17) for controlled delivery of that film to the
tube-forming means (1), motor-driven means (6, 7) being provided
for rotation of the spool (105) and subsequent swinging arm means
(8, 108, 10) for buffer storage of the cyclically unwound film, and
means (12) which detect the angular position of the swinging arm
and consequently the quantity of buffer film to produce a signal
which is useful for control of the said means (6, 7) for unwinding
film from the spool.
3) Machine according to claim 1), in which the said means for the
controlled feed of film to the tube-forming means (1) comprise at
least one roller (15) with a high coefficient of friction in
relation to the film, for example a rubber-coated roller, on which
the film is held and delivered with an extensive contact surface
area by at least one parallel opposing roller (115), which idles
and can be removed when necessary, the said rubber-coated roller
(15) being connected to controlled rotation means which comprise a
motor (17) under electronic control of speed and phase, such as for
example a stepping motor, governed by a main processor (13) of the
machine which operates it in proper phase with the lateral and
closure movements of the jaws (19, 119), which are themselves also
controlled by the said processor.
4) Machine according to claim 3), in which the processor (13)
detects the dimensions of the product being packed through suitably
dedicated means (30, 2) and suitably automatically adjusts the
function of the said film feed means (15, 115, 17) and the
operation of the jaws (19, 119) drawing, supporting, welding and
transversely cutting the wrappings to those dimensions.
5) Process for the packaging of products with stretchable
thermoplastic film, characterised by the following sequence of
stages: formation of a tube of stretchable thermoplastic film
unwound from a corresponding feed spool, with welding along its
longitudinal edges in such a way as to form a continuous tube which
is positioned almost horizontally and has a transverse
cross-section of sufficient size for the product which is being
packed to be inserted therein, closure of the head end of the said
tube of film leaving the tube-forming and longitudinal welding
stage with at least one transverse weld and support of the closed
head in such a way that the tube which is also supported by the
tube-forming means remains in a substantially horizontal position,
insertion of the product (P), which is usually placed in a tray,
within the length of tubular wrapping which is sealed and supported
anteriorly in such a way as to be close to that anterior end of the
tubular wrapping, longitudinal stretching of the tubular wrapping
while this is being created through the tube-forming and
longitudinal welding means, as it leaves these means and while the
product being packed is being inserted into the said wrapping, all
in such a way that through the effect of the stretching and as a
result also of the properties of the film used the tubular wrapping
shrinks transversely onto the product and wraps it intimately,
closure of the posterior extremity of the longitudinally stretched
tubular wrapping downstream from the product packed therein by at
least one transverse weld, sealing of the end of the tubular
wrapping following the packaging formed with at least one other
transverse weld, transverse cutting of the tubular wrapping in the
area between the said two transverse welds, while the head end of
the next tubular wrapping is held while the tail end of the
packaging formed is also held, while such packaging is supported
horizontally and while at the appropriate time the head end of the
same packaging is released in such a way that the film forming it
can react longitudinally to adhere intimately to the packed product
in that direction too, release of the posterior extremity of the
packaging formed from the clamp and removal of the same from the
packaging area.
6) Process according to claim 5, in which the film unwound from the
spool (105) by the dedicated means (6, 7, 8, 108, 10) is fed
positively and in a controlled way from the appropriate means (15,
115, 17) to the subsequent tube-forming and longitudinal welding
means (1, 18) both during the stage of formation and longitudinal
stretching of the tubular wrapping by the jaw means (119, 19)
operating on the head end of the packaging being formed, and during
the stage of sealing by the jaw means (19, 119) which takes place
on the tail end of the said packaging during the completion stage,
stretching of the film being ensured by a suitable difference in
speed between the said feed means (15, 115, 17) and the successive
jaw means (19, 119) which operate upstream and downstream of the
said means (1, 18) respectively.
7) Process according to claim 6) in which activation of the said
means (15, 115, 17) feeding film to the subsequent tube-forming and
longitudinal welding means is automatically correlated with the
size of the product being packed.
8) Process according to claim 5), in which the operation of
longitudinal welding of the tubular wrapping of film as it passes
over the tube-forming mandrel (1) is continuous because the
wrapping film runs over the said mandrel continuously during both
every cycle of product packaging and the transition from one cycle
to the next, provided that continuity in the cyclical feed of
products to be packed is ensured upstream of the said mandrel.
9) Process according to claim 5), in which the lateral movement (A)
of the jaw (19) supporting the head end of the packaging being
formed can begin at the same time as the movement (B) of the unit
(15, 115, 17) feeding the film and the difference in speed between
the two movements controls the percentage stretching of the film,
and the said first movement (A) can cease in phase with the said
second movement (B) which is reactivated at the appropriate stage
with the closing movement (C) of the jaw (119) acting on the tail
end of the packaging being formed.
10) Process according to claim 5) in which the movement (B) of the
film feed means (15, 115, 17) begins after lateral movement (A) of
the upstream jaw and ends before that movement (A) so that the film
wrapping is stretched to a greater extent and adheres to the
product (P) and that the film is under greater tension at the
beginning of the next packaging cycle when the film is unwound for
the next pack.
11) Process according to claim 9), in which the movement (B) of the
film feed means (15, 115, 17) can be stopped with a delay in
relation to the stopping of closing movement (C) of the jaw acting
on the tail end of the packaging at the completion stage and/or can
begin in advance of the horizontal and/or vertical movements (A
and/or C) of the jaws (19, 119).
12) Process according to claims 10), in which the movement (B) of
the film feed means (15, 115, 17) can be stopped with a delay in
relation to the stopping of closing movement (C) of the jaw acting
on the tail end of the packaging at the completion stage and/or can
begin in advance of the horizontal and/or vertical movements (A
and/or C) of the jaws (19, 119).
13) Process according to claim 5), in which the speed of movement
(B) of the film feeding means (15, 115, 17) can be progressively
increased towards the end of the wrapping cycle in such a way that
the tube of film wrapping the product is firmly tensioned at the
start and then progressively becomes slower or more relaxed, with
beneficial effects on the risk of film breakage at high packaging
speeds, particularly during the stage of the start of stretching by
the jaw acting on the head end of the wrapping.
Description
[0001] The invention relates to structural and functional
improvements to the process and machine described in document WO
03/051715 A1 of the same applicant, to which the most extensive
reference is made. For a better understanding of the aims of the
invention it must be remembered that the process described in the
above cited document provides for unwinding the stretchable film
from a feed spool, inserting that film in a horizontal mandrel to
form a welded leaktight wrapping tube with overlapping longitudinal
edges, holding and sealing the forward end of the said tube with
jaw means by making two welds and cutting in-between, inserting the
product which is to be packed into the inlet opening of the said
film-tube-forming mandrel and positioning it at the anterior closed
extremity of that tubular packaging which is caused to advance
horizontally as an extension of the said forming mandrel by the
said anterior jaw and supporting means. When a sufficient length of
the tubular wrapping with the product within it, which is in
proportion to the dimensions of that product, has left the forming
mandrel, the tube wrapping is stopped and decelerated transversely
by opposing clamps which clamp it for example at the discharge
outlet from the forming mandrel complex, while the said anterior
jaw means continue to advance the length of the progressively
elongating tubular wrapping so as to stretch it longitudinally by a
certain amount, this then shrinking by reaction transversely and
adhering closely to the product located within it. When the product
has completely exited from the tube-forming mandrel complex and is
sufficiently distant therefrom, the posterior extremity of the
stretched packaging is gripped transversely by a second clamping
device which forms two transverse welds and a cut between them to
seal and hold the rear end of the packaging with the product, while
the anterior clamping, welding and cutting device opens, reverses
the horizontal movement to return to the cycle start position and
leaves the packed product supported on comb means associated with
the lower component of the active jaw, welding and cutting device,
which holds the end of the new length of tube of film at the outlet
from the forming mandrel to repeat a new working cycle as
described. At the appropriate time the said clamps which
immobilised the film at the discharge opening of the forming
mandrel complex draw back to allow the new tubular packaging film
to advance, while the pack formed in the previous cycle is moved
away from the active transverse jaw, welding and cutting device,
and while that device is at its opening stage the pack is set down
on a comb conveyor which carries it away.
[0002] Transverse clamping of the tubular film above and below the
discharge opening from the tube-forming mandrel, through the action
of the corresponding upper and lower transverse clamps, leaves the
side portions of the tubular film free and these transmit
imbalanced tensions to the film both upstream and downstream, with
the danger that the proper position of the film on the said mandrel
and also the spatial relationship with the longitudinal welding
means is altered. In order to overcome these disadvantages, the
clamps in front of the same have been removed and it is provided
that the advance of the packaging film is stopped temporarily,
stopping the return rollers located upstream of the tube-forming
mandrel which act on the film transversely when the latter is still
stretched, before it reaches the inlet opening of the said mandrel.
One of these rollers is a rubber-coated roller and means which can
stop it under control, for example drive means with a brake or an
electromagnetic brake, are associated with it, and when this roller
is stopped it forms an effective clamp which engages the film
transversely and uniformly over its entire length. The longitudinal
stretching to which the length of film which has left the forming
mandrel is cyclically subjected and within which the tray with the
product is positioned uniformly discharges its own energy over the
entire length of film between the stretching clamps and the said
rubber-coated roller, so that the film itself is not subjected to
any appreciable longitudinal displacements which would have an
adverse effect on the longitudinal welding means.
[0003] Through this arrangement it has been found that use of the
said film-braking means upstream of the tube-forming mandrel often
does not make it possible to deliver all the quantity of film which
is effectively required by the sealing and stretching movements of
the stretching and sealing jaws and transverse cutting of the
packaging. The film tended to remain on the tube-forming mandrel,
required difficult intermittent operation of the longitudinal
welder and created friction when the film was first detached from
the mandrel which substantially adversely affected the stretching
and deformation gradient of the film and which could result in
local laceration of the film and/or unsightliness in the
packaging.
[0004] In order to overcome these disadvantages it has been found
suitable to control the said rubber-coated roller through a motor
with electronic speed and phase control and to operate that motor
in a close relationship with the pull exerted by the pulling jaw,
which is cyclically activated. The characteristics of this
arrangement and the advantages deriving therefrom will be apparent
from the following description of a preferred embodiment of the
same, which is illustrated purely by way of a non-restrictive
example in the figures of the appended sheets of drawings, in
which:
[0005] FIG. 1 is a diagrammatical view in lateral elevation of the
machine in question incorporating the improvements according to the
invention,
[0006] FIGS. 2, 3, 4, 5 and 6 show diagrams illustrating the
different modes of operation of the said film feed motor in
relation to the horizontal translational and sealing movement of
the one of the two drawing jaws which is cyclically activated.
[0007] In FIG. 1 it will be seen that the machine comprises a
forming mandrel 1, of the so-called sling type, which is fixed or
possibly adjustable, located in an almost horizontal position,
formed by angled parts supported on supports 101 and through which
there passes longitudinally a tubular guide 1' supported by
external parts 14 which has for example a rectangular cross-section
and is such that product P being packed, which is normally intended
to be placed in a tray, can pass through it with sufficient play,
this being delivered in indian file by a subjacent feed line 2 of
which at least the terminal part is in the form of a comb and acts
together with a lifter 3 of matching shape which on command raises
the product in line with the end wall of guide 1', whereupon a
thruster 4 which discharges the product from the lifter and inserts
it into guide 1'operates at the appropriate time, using the working
logic described above. 30 indicates known means which determine the
dimensions of the product and transmit this information to machine
processor 13, which also detects the rate of advance of conveyor 2,
all so that the processor can automatically adjust the various
working stages of the machine to the different dimensions of the
products being packed.
[0008] Stretchable thermoplastic film 5 for wrapping the product
reaches and is returned from the same extremity of mandrel 1 at
which the product enters, being delivered from a spool 105 which is
in a sufficiently convenient location for replacement when it is
empty, for example above the packaging track, supported on a pair
of parallel rollers 6, one of which idles while the other is driven
by a drive unit 7 which unwinds the film from that spool. The film
unwound from the spool is delivered to a buffer device which
includes a set of rollers 108 which are mounted so as to idle on an
appendage of supporting structure 9 which also supports said
rollers 6 and comprises a set of rollers 8 mounted on a swinging
arm 10 pivoted on said structure 9 at 11 and which has a transducer
12 on the pivot which detects the angular position of the swinging
arm and converts it into an electrical signal which is used by
process unit 13 to control motor 7 so that there is always a
sufficient quantity of film in the buffer device to render the film
wrapping stage independent of spool 105 from which the film is fed
to tube-forming mandrel 1 through the action of a pair of rollers
15, 115 rotatably mounted on an appendage 109 of said structure 9
located above mandrel 1, at an appropriate distance therefrom and
for example approximately on the vertical of the discharge opening
from that mandrel. First roller 115 idles and is pressed by
resilient means 16 towards the other roller 15 which is preferably
rubber coated and positioned in relation to the upstream roller and
mandrel 1 in such a way that it comes into contact with a suitable
contact surface area of film, this roller being positively
connected to a motor 17 under electronic speed and phase control,
for example a stepping, brushless or other suitable type of motor
controlled by processor 13. Suitable means, which are not
illustrated, are provided so that roller 115 can be temporarily
moved away from roller 15 so that the film can be inserted between
them at the start of work.
[0009] Film 5 runs along mandrel 1 longitudinally in the same
direction of advance as product P and through that mandrel is
shaped in such a way as to form a tube which envelops tube guide
1', while the edges of the film overlap, for example at the bottom
of mandrel 1, where a device 18 of any type, for example a jet of
hot air, which welds the said edges together longitudinally with at
least one longitudinal weld which is preferably continuous and
leak-tight, is in operation.
[0010] The anterior extremity of tube of film 5 leaving mandrel 1
is welded transversely and is held alternately by jaws 19, 119
which clamp it, form two welds and cut between them, comprising two
matching and mutually overlapping parts connected to means
diagrammatically indicated by arrows 20, 120 and 21, 121 controlled
by processor 13, which on command moves them closer together and
further apart with a self-centering movement which causes them to
move horizontally away from and towards mandrel 1. The lower
components of jaws 19, 119 have attached to them on the side
opposite that facing mandrel 1 a corresponding projecting plane 22,
122 in the form of a comb. A motor-driven conveyor 23, formed by
parallel and horizontal belts, at least in its initial part,
through which the tines of planes 22, 122 of jaws 19, 119 can be
inserted without interference, are provided at a suitable distance
in line with and downstream from mandrel 1.
[0011] Bars 24, 124 which deliver hot air at the appropriate
temperature to the wrapping film leaving the mandrel are located
immediately downstream from mandrel 1. These components, which have
already been described in the patent cited in the foreword,
together with welding device 18 and other components which subject
the film or packaging to heat treatment, are also controlled by
processor 13.
[0012] The operation of the improved packaging machine differs, as
previously stated, from that described in the preceding patents in
the following way. While jaw 19, which is initially close to
forming mandrel 1 and has closed upon the end of the tubular
wrapping of the film produced by the said mandrel, begins to move
away therefrom and while thruster 4 inserts product P which has to
be packed within the said tubular wrapping of film leaving said
mandrel 1, motor 17 is also active and delivers film at a linear
rate which is suitably less than the rate of lateral movement of
the clamp, and this difference in speed determines the percentage
longitudinal stretching of the film which causes the tubular
wrapping to elongate and shrink transversely to adhere intimately
to product P through the particular elastic/plastic reaction
properties of the film used. Processor 13 adjusts the cycle
described to the dimensions of product P being packed, in
particular its length, which is detected through aforesaid means 30
and 2. In the diagram in FIG. 2, A indicates the lateral movement
of the anterior stretching jaw, B the rotational movement of
film-feeding unit 15, 115, 17 and C indicates the sealing movement
of the posterior jaw. These movements are inactive in the zero
position and are instead active in the top position indicated by 1
in the ordinates. In the situation in FIG. 2, lateral movement A of
the anterior jaw begins at the same time as activation of
film-feeding unit 15, 115 and the difference in speed between the
two movements determines the percentage stretching of the film,
which is usually over 100%. During this stage motor 17 acts as a
brake, or better applies changing friction, controlling the
stretching of the film but without causing the latter to stop on
forming mandrel 1, with the advantage that it assists the operation
of welding unit 18, which can now operate substantially
continuously and with the advantage that it prevents film stopping
on the mandrel, thus preventing friction on first detachment and
consequent local tensions in the film and unsightliness in the
packaging, as was on the contrary the case in the prior art. In the
example in FIG. 2, lateral movement A of the jaw ceases in phase
with the rotational movement B of rollers 15, 115, but is
reactivated in proper phase with sealing movement C of jaw 119 on
the tail end of forming packaging Z. In fact at the end of the
cycle, while the downstream welding jaw is closing, longitudinal
stretching of the film must be small to permit the film to move on
forming mandrel 1, in that the closing of this jaw will bring about
elongation of the film. During this stage rollers 15, 115 and motor
17 continue to feed a little film to the forming mandrel in a
controlled way to reduce longitudinal stretching during posterior
closure and welding of the said packaging formed, by posterior jaw
119. The quantity of material which is actively delivered during
this last stage depends in a directly proportional way on the
height of product P, and this is brought about through processor 13
which has determined the dimensions of the product which has to be
packed using aforesaid means 30 and 2.
[0013] The use of motor 17 with controlled speed and phase makes
possible easy control of both the position and speed of film feed
rollers 15, 115 to ensure that the advance of the film is in phase
with respect to the jaw movements through the position adjustment
control loop and the difference in linear feed between said feed
rollers 15, 115 and the movements of the said jaws through the
speed adjustment loop, all in such a way as to ensure good control
of film stretching.
[0014] The example in the diagram in FIG. 3 differs from the
preceding situation in FIG. 2 in that movement B of film feed
rollers 15, 115 begins after lateral movement A of the upstream jaw
and stops before the said movement A so that the film packaging is
stretched by a greater amount and adheres to product P. It is
obvious that at the start of the next packaging cycle, when the
film has to be unwound for the next pack, the film will be under
greater tension. In both the situations in FIGS. 2 and 3 the
stopping of movement B activating rollers 15, 115 can be delayed,
as illustrated for example in the diagram in FIG. 4, or its start
may be brought forward with respect to movements A and/or C of the
jaws, as illustrated in the diagram in FIG. 5. In particular if the
second part of movement B of rollers 15, 115, that which takes
place simultaneously with closing movement C of the downstream jaw,
is particularly long, for example as in FIG. 5, this has the effect
that the film is particularly relaxed at the start of the unwinding
cycle.
[0015] Similar effects can be achieved as illustrated in the
diagram in FIG. 6 by making use of control of the speed of feed
rollers 15, 115, in the sense that this speed can be progressively
increased towards the end of the unwinding cycle in such a way that
the tube of wrapping film for the product is well tensioned at the
start and then progressively becomes slower or more relaxed, with
beneficial effects on the risk of film breakage at high packaging
speeds, particularly during the initial stage of stretching by the
upstream jaw.
* * * * *