Machine for producing containers from extruded and blow-molded plastic material

Apparatus for forming containers by blow molding a closed end parison, comprising a chain conveyor for moving closed-end parisons on blow pins vertically dispased and extending above the conveyor. The invention includes electrically heated reciprocal cylinders which are sequentially lowered about the parisons for tempering same before the parisons are introduced into the blow molds on the blow pins.

The production of containers in plastic material, such as for example 
bottles, requires a highly automated installation, which carries out, 
without people intervening, the different phases of the method. It is in 
particular known as advantageous to use as a basis, preforms obtained by 
extrusion and blow-molding, or by any other means. Said preforms, which 
are sorts of cylindrical blanks, closed at one of their ends, are heated 
up to a suitable temperature, and more specifically to temperatures 
varying along the preform. They are then extruded and blow-molded in molds 
of suitable shape. After this operation, the finished container has to be 
adequately cooled before it is handled for storing purposes, or to be 
taken to a filling station. 
To enable an accurate shaping of the container, the temperature of the 
preform should be as homogenous as possible when it is introduced into the 
mold. To be more precise, the temperature of the preform should be around 
118.degree., not only on the inner and outer surfaces of its wall which 
will be subjected to the extruding and blowing operations 
("double-orientation") but also and especially through the thickness of 
said wall. 
In most of the known techniques, and in particular in French Pat. Nos. 1 
307 954, 88 224, 1 430 899 and 2 419 810, as well as in U.S. Pat. Nos. 
3,283,046 and 4,141,680, the preform which at first is at room 
temperature, is heated up in an oven to a suitable temperature before 
being introduced into the shaping mold. This prior technique however does 
not permit to easily obtain a homogeneous temperature through the entire 
thickness of the wall, and the time needed to produce one container is 
relatively long. 
It is a first object of the present invention to propose a method for 
producing plastic containers from suitably heated preforms and in 
particular for obtaining rapidly a homogeneous temperature of the wall of 
the preforms before these are introduced in the container-shaping molds. 
According to the invention, each preform, of which the outer surface of the 
wall has been heated beforehand to a temperature at least equal to 
140.degree. C., is first cooled by the ambient atmosphere, then by a 
controlled cooling designed to bring the temperature through the entire 
wall thickness to a value approaching 118.degree. C. To this effect, the 
preform is caused to pass through a plurality of enclosures closed at 
their upper end, in which enclosures heat is supplied on the outer surface 
of the preform wall. Said heat supply is defined both in relation to the 
row of the enclosure and to the estimated temperature gradient through the 
thickness of the preform wall, for any horizontal section thereof, in 
order to obtain at the exit from the last enclosure, as uniform a 
temperature as possible, approaching 118.degree. through the wall 
thickness of the preform. 
The number of enclosures is of course related to the dwelling time of one 
preform in each one, and that time can be very short, such as 5 seconds or 
even less. It is in fact determined by the time needed to shape a 
container, this in turn depending on the working characteristics of the 
container-shaping mold and on the efficiency of its cooling device. 
Advantageously, the controlled cooling of the preform will be immediately 
preceded by the shaping of said preform in a mold of which the cooling 
means enable to lower the temperature of the outer surface of the preform 
wall to a temperature at least equal to 140.degree. C. Preferably also, 
the shaping of said preform will be immediately preceded by the extrusion 
of a vertical tubular parison at a temperature at least equal to 
180.degree. C., said parison being shaped at its upper end. 
Owing to these dispositions, the production of plastic containers can 
easily be mechanized from the extrusion of the tubular parison to the 
receipt of the finished containers, and the rate of production of the 
containers can be very high. 
A further object of the invention is a machine for carrying out the method 
defined hereinabove, which machine enables to benefit from all the 
advantages presented by said method and to keep up a high rate of 
production. 
To this effect, it is known that most of the currently existing machines 
are not mechanized to perform all the operations required by the 
production of plastic containers. A plurality of successive machines are 
often necessary, with intermediate help from people, which could entail 
risks of pollution especially in the case of containers designed to 
receive food products. 
The invention therefore relates also to a machine which is entirely 
self-operating from the extrusion of the parison and its blow-molding into 
a preform, to the discharge of the finished container towards a storage or 
utilizing station. The preforms are thus brought automatically to the 
different stations of the machine; this contributing to further increasing 
the rate of production and the quality. 
The machine according to the invention comprises in known manner, a 
continuous transfer chain, some links of which support vertical pins which 
constitute the preform-receiving members, which transfer chain moves 
horizontally under the action of a stepwise drive mechanism. The pins are 
thus brought successively, first into a cooling device which is controlled 
by heating members, then into a shaping device, and finally into a device 
receiving the finished containers, all said devices being distributed in 
that order along the closed course followed by the continuous transfer 
chain. 
The preforms are positioned on the receiving pins by gravity, the open part 
of the preform being directed downwards when it is lowered on the pin over 
which it is brought. Conceivably, the preforms can be dropped onto the 
pins at their exit from an extruding and blow-molding machine of which the 
mold delivers preforms whose aperture faces downwards. 
According to an important characteristic of the invention, the controlled 
cooling device is constituted by a plurality of heating bell-shaped 
enclosures, substantially cylindrical and vertical, closed at their upper 
end and mounted on a support sliding vertically according to a reciprocal 
movement over a range at least equal to the height of the receiving pins 
above the continuous transfer chain.

Referring to the drawings, the machine according to the invention comprises 
a frame 1 presenting a guiding path 2 for a conveyor chain 3 following a 
continuous course, in the direction of arrow F, under the action of a 
stepwise mechanism 4 (FIG. 4). 
After a first station receiving the preforms and generally designated as 5, 
there follows a controlled cooling device 6, a shaping device 7 and the 
device 8 receiving the finished containers. 
On some links of the conveyor chain 3, and preferably in the middle of 
these links, are fitted supports 9 for sliding pins 21, one part at least 
of which extends vertically above the plane of the conveyor chain. 
The controlled cooling device 6 is essentially composed of a plurality of 
substantially cylindrical and vertical bell-shaped heating elements 10. 
The upper end of said elements is closed whereas their lower end is open. 
Said heating bells are secured on a support 11 mounted for vertical 
sliding with respect to the frame 1. A hydraulic or pneumatic jack 12 is, 
on the one hand, secured to the frame 1, and on the other hand coupled to 
one of the elements of the support 11. Said jack enables, in conditions to 
be specified hereinafter, a reciprocal vertical movement of the support 
11. 
Said heating bells 10 are equipped on the inside with electrical element 
permitting to obtain any required temperature. It should however be 
pointed out that it is advantageous to be able to regulate the temperature 
in one bell independently of the temperature regulated in the next bell. 
Moreover, it will be further advantageous to distribute sensibly the 
heating zones and, as a result, the temperature zones, in relation to the 
position with respect to one of the ends of the bell. It is indeed known 
that some containers, and in particular certain areas of those containers, 
need to be subjected to a double orientation when they are being shaped, 
this necessitating a very accurate distribution of the temperatures along 
the preform. The precise role of the heating bells in controlling the 
cooling of the preforms will be explained hereinafter. 
Preferably, the assembly of heating bells 10 moves inside an insulated 
casing 13, which insulates them from heat at least when they are in the 
lowered position. 
Adjacent the outlet of the controlled device 6, is situated the shaping 
device 7. This essentially comprises a mold 14, in three parts, as can be 
seen in FIG. 4. The two lower parts of the mold are shaped to correspond 
to the shapes of the container walls and of its orifice; said lower parts 
are coupled to a conventional toggle mechanism, not shown. 
The shaping device 7 is coupled to an extruding and blow-molding device 
designated by the general reference 18. It is essentially composed of a 
head 19 adapted to receive the correspondingly-shaped endpiece 20 of the 
lower end of a hollow pin 21 mounted for sliding on its support 9. In said 
head 19 is provided a conduit 22 adapted to be connected with a source of 
compressed air via pipe 23. When said head 19 is resting on the endpiece 
20, the conduit 22 communicates tightly with the inside of the hollow pin 
21 the upper end of which is rounded and provided with at least one 
orifice issuing outside the pin. 
The head 19 is mounted at the upper end of the movable element 24 of a jack 
25 fitted on the frame, co-axially to the mold 14 in its closing position. 
Next to the shaping device 7 and still on the path followed by the conveyor 
chain 3 along arrow F, is situated the device receiving the finished 
containers. 
Said device essentially comprises a mechanism for removing the containers 
constituted in the illustrated example by a clamp 26 situated above the 
conveyor chain in the area where, as will become obvious hereinafter, is 
situated the orifice of the finished container to be removed from the pin 
21 supporting it. 
The support 27 of the clamp 26 is mounted for sliding vertically with 
respect to the frame of the machine over a range at least equal to the 
height of a finished container. A drive mechanism ensures the reciprocal 
movement of said support 27. 
But, preferably, and as shown in the drawings, the support 27 of the clamp 
26 is integral with the support 11 of the heating bells. The jack 12 
therefore ensures its reciprocal movement in conditions to be specified 
hereinafter. 
Vertically to the gripping zone of the clamp 26, there is provided a gullet 
28 of which the inlet faces downwards. Said gullet, in which the finished 
containers are introduced, is equipped with a braking device preventing 
the containers from falling under their own weight. The gullet in the 
illustrated example is constituted, to this effect, by a plurality of 
flexible strips 29 defining a passage of diameter smaller than the 
external diameter of a container. Preferably, an elastic ring 30 
cooperates with the flexible strips to keep a narrow passage at the inlet 
to the gullet 28. This latter is on the other hand extended upwards by a 
tube 31 of inner diameter substantially greater than the external diameter 
of the finished containers. The path of the tube 31 thereafter presents 
adequate sinuosities to bring the containers that it conveys, towards a 
storage or filling station. 
The machine according to the invention operates as follows: 
The conveyor chain 3 being driven stepwise by its mechanism 4, a preform A 
is placed over each pin 21. As indicated hereinabove, the preform can be 
placed by hand on a pin of the preform receiving zone 5, or on the 
contrary, fall by gravity from a preform producing apparatus, of the 
extrusion and blow-molding type. It is however essential that this 
apparatus delivers preforms of which the lower end is open, their upper 
end being closed. When it is placed or falls on the pin 21, the 
temperature of the preform on the external surface of its wall is at least 
equal to 140.degree. C. Such a temperature can be due in particular to the 
existence of a cooling device inside the preform mold shaping the preforms 
by extrusion and blow-molding. The temperature of the tubular parison 
supplying this mold is generally about 180.degree. C. 
The preform A is then taken by the pin 21 over which it is fitted, into the 
controlled cooling device 6. During the movement of the conveyor chain 3, 
the support 11 of the heating bells 10 is held in a high position by its 
jack 12. As soon as the preform A has reached a vertical position with 
respect to the first bell 10, the jack 12 lowers down the support 11 and 
the first bell in turn comes over the preform A. After a suitable interval 
of time, a few seconds for example, the jack 12 lifts back all the heating 
bells. The path is then cleared for the preforms and the conveyor chain 3 
can bring preform A under the second bell 10. The cycle continues until 
the preform A has reached the last bell. 
Before entering the container-shaping phase, the role played by the heating 
bells 10 should be specified, said bells in effect constituting a preform 
controlled-cooling means. Reference will be made particularly, to this 
effect, to FIG. 5; it is assumed in the diagrammatical representation, 
that the passage from a position n to a position n+1 will be instantaneous 
when the preform has reached its lowest temperature at the position n. 
As indicated hereinabove, the skin (temperature or temperature of the outer 
surface of the wall) of a preform is at least equal to 140.degree. C. when 
said preform reaches a pin 21 (position c). In the case of the machine 
described herein, said temperature is that obtained when cooling the 
preform-shaping mold 5. 
However, the temperature on the inner surface of the wall is then greater 
than 140.degree. C. and in the center of said wall the temperature has 
remained around the extrusion temperature, namely around 180.degree. C. 
There is therefore an heterogeneousness of the temperatures through the 
thickness of the wall which it is necessary to reduce if not altogether 
eliminate, before reaching the container-shaping phase, which should take 
place at around 118.degree. C. 
In a first stage, up to position c, the preform is transported in the open, 
and its skin temperature is reduced to about 125.degree. C. However, the 
temperature gradient through the thickness remains high. 
From position d to position m inclusive, the preform enters the 
controlled-cooling device 6 in which it is successively covered over by 
each one of the eight bells 10 described hereinabove (positions d to k). 
The first eight bells, for example those in position, d, e and f, will 
limit the cooling down of the outer skin temperature, whilst adequately 
cooling down, mainly by convection, the inner temperature of the wall. The 
temperature difference between the two, outer and inner, surfaces of the 
wall tends to reduce, if not disappearing completely, whereas the 
temperature of these surfaces remains substantially under the final 
temperature. 
Nevertheless, the temperature in the middle of the thickness of the wall is 
still too high and it should be adequately reduced before shaping the 
container. 
This will be done by the next set of bells, for example by those occupying 
the positions g, h, i, j and k. 
The bell shaped heating devices in the positions g, h, i and j account for 
the outline of the next container and ensure a supply of heat by 
convection and radiation. The temperature is thus further lowered, but 
what is more, the desired reduction of the temperature gradient between 
the skin (inner or outer) and the middle of the wall thickness, is 
obtained. 
Finally, the last bell (position k) and the transfer to positions l and m, 
situated in the insulated casing 13 enable to ensure a "smoothing out" of 
the temperatures which are then around 118.degree. C. 
The cooling operated in the device 6 is therefore relatively long and many 
parameters are available to obtain the desired result, especially in 
relation to the plastic material used and to the shape of the final 
container. This does not prevent the production rate from being high, for 
example 750 containers per hour, said production rate being solely 
dependent on the time (which is about a few seconds) during which a 
preform stays in a specific position. 
On coming out of the insulated casing 13, the preform goes directly into 
the shaping mold 14. Said latter is of course open whilst the conveyor 
chain is moving, but it closes as soon as said chain stops. 
When the pin 21 which carries the preform A has arrived within the vertical 
axis of the mold 14, its lower endpiece 20 engages by translation, the 
head 19 of the blow-molding device. The pin 21 is therefore fast, in 
vertical translation, with the movable element 24 of the jack 25. 
As soon as the mold 14 closes, the jack 25 raises the pin 21 which slides 
inside its support 9, whereas its rounded upper end pulls the upper end of 
the preform to any suitable heights, to rest for example on the upper wall 
of the mold. Said axial drawing is possible since, when the mold closes, 
it grips firmly the lower end of the preform on the support 9, 
immobilizing it vertically. 
At the same time as the preform is drawn axially, the pipe 23 supplies 
compressed air to the orifice at the upper end of the pin 21 via conduit 
22 connected in sealed manner with the space inside the pin 21. The 
preform is then blow-molded and pushed back against the walls of the mold 
where it is simultaneously shaped and cooled. 
The shaping operations being over, the mold 14 opens, clearing a passage 
for the pin 21 carrying a finished container B. Simultaneously, the jack 
25 starts descending, releasing the endpiece 20 from the head 19 and 
allowing said endpiece to come out from said head as soon as the conveyor 
chain 3 moves. 
The pin 21 is then brought in stepwise manner, to the finished containers 
receiving device. The container continues to cool during the transfer. 
When the pin 21 arrives with its container B to a position vertically to 
the gullet 28, the clamp 26 and its support 27 are in a high position, the 
jaws of the clamp being open. As soon as the conveyor chain stops, the 
jack 12 lowers the support 27 and its clamp 26, the jaws of which close 
over the lower end of the container B, around the orifice thereof. 
When the support 27 goes up again, the clamp 26 carries away the container 
B by removing it from the pin 21. The bottom of the container B then 
arrives at the inlet to the gullet 28 and pushes back the orifice of the 
container previously set in and immobilized by the braking device of the 
gullet. At the end of the upwards movement of the support 27, the 
container B has taken over the place of the preceding one and is in turn 
immobilized under the pressure of the flexible strips 29 and of the ring 
30. The jaws of the clamp 26 finally open and the container-removing 
device is then ready to pick up the next finished container. Thus, the 
train of finished containers move in stepwise manner in the tube 31 as far 
as the utilizing station without any risk of pollution. 
The pin 21, clear of its container, returns in stepwise manner to the 
preform receiving station. On its course, the endpiece 20 meets up with a 
guide member secured to the frame guiding the lowering of the pin 21 
completely down in its support 9, so that said pin is ready to receive 
another preform.