The present invention relates to a machine for the production of
plastic receptacles comprising a chassis and arranged along a guide path at least
one heating device and a blow-molding device, the receptacles being formed from
pre-forms disposed on conveyors moved in one direction of movement along the guide
path, the heating device comprising heating elements mounted facing at least one
row of pre-forms.
There are known such machines described for example in WO 97/13632.
The machine described in this latter document has a heating device with several
rows of parallel pre-forms. Heating tubes are disposed between two rows of pre-forms
to heat these latter. When it is desired to change the tubes or to adjust their
position, it is necessary to stop the heating device and to immobilize the machine
for a prolonged period until a temperature suitable for handling the heating elements
is reached. Then, the operations of maintenance and adjustment are difficult to
carry out because the heating elements are disposed at the center of the machine
and are therefore difficult of access. The known machine therefore requires prolonged
down periods and complicated and impractical handling and adjustment operations.
U.S. Patent 5,121,828 discloses a machine for the production of articles
from pre-forms comprising a chassis with a base which has rails on which an oven
for heating the pre-forms is mounted in a slidable manner. The assembly of the
oven can thus be moved slidingly on the rails relative to its base. However, when
a single heating tube is to be replaced or adjusted, it is necessary to withdraw
and remove the assembly from the oven. Moreover, if this tube to be replaced is
located in the middle of the oven, the access to this tube is far from being easy.
It is necessary to wait until the temperature of the heating elements has reached
a sufficiently low level to permit an operation of repair or adjustment. The down
time for operations and maintenance and adjustment therefore becomes long even
for this type of machine.
The present invention has for its object to overcome these drawbacks,
and the machine according to the present invention is characterized to this effect
by the fact that the heating device comprises, associated with the different rows
of pre-forms, sliding mechanisms arranged so as to permit withdrawing and reintroducing
individually the heating elements of a predetermined row relative to other heating
elements associated with other rows of pre-forms and relative to a fixed frame
of the heating device.
Thanks to these characteristics, it is possible to withdraw the heating
elements of the heating device by simple sliding in the manner of a drawer, which
assures easy access to the heating elements, and hence facilitated maintenance
and adjustment of these heating elements. The cooling of these latter outside the
heating device is moreover swifter, which significantly shortens the down time
of the machine during operations of maintenance and/or adjustment.
According to a preferred embodiment, the machine comprises pairs
of parallel rows of pre-forms at the level of the heating device and is characterized
by the fact that the heating elements are disposed between the pairs of parallel
rows and mounted on sliding mechanisms such that the heating elements associated
with a pair of parallel rows can be withdrawn from the heating device relative
to other heating elements associated with the other pairs of parallel rows by sliding
in said direction of movement.
These characteristics permit easy removal of the heating elements
for maintenance and adjustment.
Preferably, the sliding mechanism comprises two telescopic devices
fixed above the two rows of pre-forms to the frame of the heating device, the
heating elements being suspended from cross-pieces connecting the two telescopic
There is obtained by these characteristics a particularly simple
construction, a reliable operation and a reduced size.
Preferably, the heating elements are distributed in two heating bodies
arranged one behind the other on the sliding mechanism separated by a predetermined
The two heating separated heating bodies can thus be adjusted individually
rapidly and easily, which permits an adaptation of the heating device to the production
of receptacles and other hollow bodies, of different shapes and sizes and compositions.
In a preferred embodiment, each heating body comprises two parallel
series of heating tubes substantially superposed and mounted facing two rows of
pre-forms on vertical suspension bars connected to the sliding mechanism.
There is thus obtained a very efficacious and precise heating of the
pre-forms, whilst having a construction greatly facilitating maintenance and adjustment
of the heating elements.
The heating tubes are preferably mounted adjustably on suspension
bars such that the distance separating the pre-forms can be individually adjusted.
These characteristics permit obtaining and adjusting heating profiles
along the axis of the pre-forms assuring high quality of the produced products.
According to a preferred modification, the heating device comprises
a frame with feet whose length can be adjusted by a simple mechanism with pinions
and a chain such that the position of the assembly of heating elements relative
to the pre-forms can be adjusted vertically.
An adaptation of the heating device to pre-forms of different lengths
can thus be obtained in a rapid and precise manner.
Preferably, the heating device comprises at least three sliding mechanisms
disposed parallel to each other and whose heating elements are disposed in the
middle of three pairs of rows of pre-forms, each sliding mechanism being arranged
so as to permit withdrawing individually the heating elements located between two
adjacent rows of pre-forms.
There is thus obtained a rapid and easy maintenance and adjustment,
even in the environment of a heating device of large size having at least six parallel
rows of pre-forms.
A preferred embodiment of the invention is characterized by the fact
that the heating device comprises at least four successive zones arranged along
the direction of movement, and ventilation means adapted to send an air flow along
the surface of the pre-forms, a first zone comprising heating elements adapted
to produce heating of the pre-forms, a second zone permitting balancing the thermal
conditions of the wall of the pre-forms by cooling their external surface, a third
zone comprising heating elements adapted to produce a second heating of the pre-forms
and a fourth zone permitting a final balancing of the thermal conditions of the
pre-forms before their transfer to the blow-molding device, the heating device
having ventilation means in the heating zones and in the balancing zones, these
ventilation means being arranged so as to send an air flow oriented perpendicularly
to the surfaces of the pre-forms in the balancing zone and in the two heating zones,
these latter having positions in which the pre-forms are simultaneously subjected
to heating radiation and to said air flow.
Thanks to these characteristics, it is possible to obtain an optimum
differential heating of the wall of the pre-forms, namely a given thermal profile
through the wall of the pre-forms. There can thus be obtained an external surface
at a lower temperature than the internal surface of the pre-form. The invention
therefore permits obtaining an optimized thermal distribution for pre-forms ensuring
a very regular expansion during the subsequent drawing-blowing operation.
Preferably, each of the four zones comprises a predetermined number
of stop positions in which the pre-forms are stopped during predetermined time
intervals, the ventilation means being arranged so as to direct in the stop positions
a substantially vertical flow of air in the direction of the pre-forms, which are
rotated about their longitudinal axes by means of at least one drive device.
The combined and successive heating-cooling actions and cooling alone,
in the precisely determined stop positions of the pre-forms, ensure a particularly
precise thermal distribution for the pre-forms, hence a very regular moving of
Preferably, the machine is characterized by the fact that the heating
device is arranged so as to carry out in the first zone a heating and a ventilation
such that the external surface of the pre-forms is at a temperature higher than
that of the internal surface, to carry out in the second zone a balancing by ventilation
such that the temperature of the external surface becomes lower than that of the
internal surface, to carry out in the third zone a ventilation and general heating
of the pre-form less pronounced than in the first zone, and to carry out in the
fourth zone balancing conditions by ventilation such that the temperature of the
external surface is lower than the internal temperature of the pre-forms at the
outlet of the heating device.
Thanks to these characteristics, the temperature of the internal and
external surfaces of the pre-forms can be adjusted in a precise manner whilst
obtaining a predetermined temperature profile through the walls of the pre-forms,
which ensures a particularly regular drawing-blowing operation and receptacles
of very high quality.
Other advantages will become apparent from the characteristics set
forth in the dependent claims and from the description given hereafter of the
invention in greater detail with the help of drawings which show schematically
and by way of example one embodiment.
Figure 1 is a perspective view of this embodiment of the machine.
Figure 2 is a fragmentary schematic plan view of this embodiment.
Figure 3 is a front view of the heating device integrated into this
Figure 4 shows this heating device in a side view.
With reference to Figures 1 and 2, the machine for the production
of receptacles of plastic material comprises a chassis 1 on which the different
devices and members of the machine are mounted in modular fashion. The pre-forms
2 for receptacles to be produced are supplied by means of a double rail 3 (Figure
1) forming an incline plane to arrive in an inverting loading device 5, in which
the pre-forms are inverted and disposed neck-down on supports 7 carried by conveyors
8, each conveyor having two supports 7.
The pre-forms 2 are then heated in a heating device 10 and moved
toward a drawing-blowing device 12. After their formation, the receptacles are
moved from the supports 7 in an inverting unloading device 14, from which they
can be packaged for their future use or sent to stations for sterilization, filling,
labelling, packaging, etc.
The empty supports 7 carried by the conveyors 8 are then sent to
the loading device 5 for the pre-forms.
The conveyors 8 are constituted by plates 16 of elongated rectangular
shape with rounded ends comprising two recesses 17 in which the supports 7 are
carried. The plates 16 rest laterally on a guide track 20 comprising two lateral
rails 18, 19 and touch each other. This guide path comprises two separate portions
21, 22 (Figure 2).
In a first portion 21, the plates 16 touch at their rounded ends and
are aligned one behind the other forming a single row of supports 7 and pre-forms
On the contrary, in a second portion 22 of the guide path 20, located
at the level of the heating device 10, the plates 16 touch by their long sides
and form three rows of parallel plates, hence six parallel rows of supports 7,
the two supports 7 of each conveyor 8 being aligned in a direction perpendicular
to the direction of movement of the conveyors.
Of course the number of parallel rows of conveyors 8 at the level
of the heating device could be less than or greater than three, according to the
uses and the size of the machine. This portion 22 will nevertheless comprise at
least two parallel rows of supports 7 aligned in the direction of movement and
encompassing the extent of the guide path in the heating device 10, as well as
its inlet 24 and its outlet 25.
The movement of conveyors 8 in the first and second portions 21,
22 of the guide path is obtained by pushing by means of jacks schematically indicated
at 27 and 28. Given that this guide path 20 constitutes a closed circuit, the linear
speed of movement is six times greater in the first portion 21 relative to the
second portion 22. This permits gradual and optimum heating of the pre-forms during
a prolonged period. As the heating phase of the pre-forms requires a longer duration
than the other phases and operations of this application, there is obtained a continuous
operation with a very high output, whilst reducing the length of the fabrication
path and hence the overall size of the machine.
The construction of the heating device 10 is explained in greater
detail with reference to Figures 3 and 4 and comprises a housing 40 with an upper
frame 41 mounted on a base 42 secured to the chassis 1 of the machine. The frame
41 comprises feet 43, of which only one is shown in Figure 3. These feet are provided
at their end with a screw-threaded rod 44 adapted to coact with the pinion 45 rotatably
mounted on the base 42 and comprising an internal screw-thread. A chain 46 surrounds
all the pinions 45 of the feet 43 of the frame 41 and can be driven by means of
a motor (not shown). This latter, the chain, the pinions and the screw-threaded
rods therefore constitute an adjustment mechanism 47 permitting raising or lowering
the frame 41 relative to the base 42.
The plates 16 of the conveyors 8 rest at the level of the heating
device 10 on a guide rail 50 (Figure 3). The pre-forms 2 are disposed neck-down
in the upper portion of the supports 7 which comprise a tubular body 51 with an
axial blowing channel. The two recesses 17 of the plates 16 form bearings thanks
to which the supports 7 can turn about their axes. These supports 7 are provided
at their lower end with a pinion 52 adapted to coact with chain drive members 53
provided at the level of the heating device 10. These members 53 comprise a motor
54 arranged so as to drive a chain 55 stretched between pinions 56. This chain
55 coacts with the pinions 52 of the supports 7 of a first row to rotate these
supports. A pinion 57 secured to the pinion 56 serves to drive a pinion 58 over
which is stretched a second chain 60 adapted to drive in rotation the supports
7 of the adjacent row of pre-forms. The connection between the pinion 57 and the
pinion 58 is thanks to a transverse chain (not shown) and a pinion 59 secured to
the pinion 58. In the illustrated embodiment, drive members 53 with a motor 54
are provided for each of the three pairs 65 of rows 66 of pre-forms. The drive
members 53 and the guide rails 50 are mounted on the base 42.
The upper frame 41 carries the assembly of the heating elements 70
and ventilating elements 71 for the pre-forms 2, which are distributed in three
parallel identical units 73. Each unit comprises ventilation elements in the form
of two lateral ventilating chambers 74, 75 disposed on the outer side of the pair
65 of rows of pre-forms. These chambers are provided with a certain number of
ventilating slots (not shown) arranged vertically so as to generate flat vertical
flows 72 (Figure 2) of cooling air directed against the pre-forms 2 which are
located in stop positions facing the slots. The ventilating chambers 74, 75 are
fixed rigidly to the frame 41 and supplied with cooling air that is dried or not,
by conduits 76 (Figure 4).
The ventilating elements moreover comprise one central ventilating
conduit 78 per parallel unit 73 disposed between the upper portions of the supports
7 of the two rows 66 and suspended from the frame 41 by means of vertical suspension
bars 79. Through suitable openings in the central ventilating conduit 78, cooling
air flows are directed in the direction of the supports 7 and the necks of the
pre-forms 2 to avoid prejudicial heating of these portions. Protective shields
80 are moreover mounted in a height-wise adjustable fashion on ventilating chambers
74, 75 and on the central ventilating conduits 78 and protect the supports 7 from
direct thermal radiation. These shields 80 are moreover cooled by a water cooling
The heating elements 70 comprise for each unit 73 two heating bodies
85 mounted at predetermined distances from each other. Each heating body 85 is
suspended from cross-members 86 and comprises two series 87, 88 of longitudinal
substantially superposed heating tubes 89. These heating tubes 89 are mounted on
vertical suspension bars 90 fixed on the cross-pieces 86 by means of levelling
members 91, two springs 92 and blockers 93.
All, or at least the three upper heating tubes and the two lower
ones, are mounted adjustably on the suspension bars 90 such that the distance separating
them from the pre-forms can be individually adjusted.
Each series 87, 88 moreover has a supplemental heating tube 94 whose
position can be adjusted in two perpendicular directions. Terminals 96 ensure the
electric supply of heating tubes 89.
The cross-pieces 86 are fixed on each side to telescopic tubes 95
permitting completely and individually withdrawing each of the heating elements
70 with its two heating bodies 85 in a longitudinal direction parallel to the heating
tubes of the heating device 10 and to the direction of movement x. It is thus
possible to withdraw the heating elements slidably in the manner of a drawer, from
the heating device. This construction thus permits easy maintenance and very rapid
adjustment of the heating bodies and their tubes because the access to the heating
tubes of a given unit 73 is in the immediate outlet position of the heating elements
70 (Figure 4).
Each heating body 85 moreover comprises protective shields 97 mounted
above the two series 87, 88 of heating tubes.
With reference to Figures 2 and 4, the heating device 10 has for
each unit 73 four treatment zones arranged following each other in the direction
of movement, namely a first heating zone TH1 at the level of the first heating
body 85, a first balancing zone TE1, a second heating zone TH2 at the level of
the second heating body 85 and a second balancing zone TE2.
The pre-forms and their conveyors 8 are moved in an indexed manner
such that the pre-forms 2 are stopped in stop positions located facing the flat
cooling air flows 72 separated from each other by an interval corresponding to
the distance separating the middles of the two successive conveyors. The dwell
time of a pre-form in one zone depends on the length of the zone, hence on the
number of stop positions.
Thus, the first heating zone TH1 comprises between two and ten stop
positions. In this zone, the wall of the pre-form is intensely heated and the temperature
of the external surface increases more rapidly than that of the internal surface.
The following zone, which is the first balancing zone TE1, comprises
between four and 20 stop positions. This zone has no heating body. It permits a
balancing of the temperature through the wall of the pre-form considering that
the external surface is subjected to more marked cooling than the internal surface
of the wall of the pre-form. In the second half of this zone, the temperature is
even inverted because the external surface of the wall of the pre-form becomes
colder than the internal surface.
The following zone corresponds to the second heating zone TH2 and
has a heating body 85 similar to that of the zone TH1, of course given that the
adjustment of the heating tubes 89 can be different in the two zones. In this zone,
the heating permits obtaining a temperature profile along the pre-form, the temperature
of the external surface again becomes higher than that of the internal surface.
This zone comprises between two and ten stop positions. The heating in the first
zone TH1 is substantially more intense than that in the second zone TH2 which is
devoted above all to profiling the temperatures along the pre-forms.
This zone is followed by a second balancing zone TE2 without a heating
body. It can be partially free from ventilation and comprise between one and ten
stop positions. This zone permits supplemental adjustment between the external
and internal temperatures of the pre-form just before the latter will be introduced
into the drawing-blowing device 12. In fact, the external temperature again becomes
slightly lower than the temperature of the internal surface. It should be noted
that ventilation is provided in the four zones, hence also in the two heating zones.
Only the combination of ventilation and heating in the stop positions of the first
and third zones (TH1, TH2) permits very rapid and efficacious heating whilst avoiding
crystallization of the surface of the pre-forms.
The rotation of the pre-forms 2 and their supports 7 about their axis
can also be of an indexed nature. There could be provided one drive device 53
per zone TH1, TE1, TH2, TE2, which thus permits a different speed of rotation for
There could also be provided a different drive device for two or
three zones together. The longitudinal stepwise movement is also indexed such that
the pre-forms are completely stopped during predetermined durations in precise
positions with respect to the cooling flows 72.
The very precise blowing of air during the heating and balancing
phases ensures effective protection of the pre-form against any undesired crystallization.
The blowing of air onto the neck of the pre-form 2 and the upper portion of the
supports 7 permits avoiding deformations of the neck of the pre-form.
It is to be noted that at the outlet of the heating device 10, the
temperature of the external surface of the pre-forms is lower than that of the
internal surface, which is desirable for precise molding in the drawing-blowing
device, given that the internal surface moves a greater distance than the external
surface of the pre-form during molding.
The development of the temperatures of the external surface Tex and
of the internal surface Ten of the wall of the pre-forms plays an important role
in the quality of the produced products. The assembly is adjusted to obtain a
strong increase of temperatures in the first temperature zone TH1 with a greater
slope for the temperature of the external wall.
In the balancing zone TE1, the temperature of the external surface
falls substantially below that of the internal surface. The increase of the temperatures
is less strongly regulated in the profiling zone TH2 with a more pronounced slope
for the temperature of the external surface, which again becomes higher in temperature
than the internal surface. Finally, the temperatures of the external and internal
surfaces are again inverted in the second balancing zone TE2, so as to obtain an
optimum spread Tin-Tex for drawing-blow-molding.
Of course the embodiment described above is not limitative and can
be the subject of any desirable modifications within the scope defined by claim
1. In particular, the machine could have another number of pairs 65 of rows of
pre-forms. The number of stop positions in each zone could be different. The machine
could have more than four processing zones, for example six zones with two final
heating and balancing zones. The machine could also be adapted for the production
of other hollow bodies than receptacles in the strictest sense. The sliding mechanisms
could be different, for example in the form of drawers. The heating bodies 85 could
be differently arranged, they could for example be provided with a single series
of bidirectional heating tubes.