OF POLYMER MATERIAL

Description

The present invention relates to a blowing or stretch-blowing machine for preforms made of polymer material adapted to transform said preforms into bottles or containers, and in particular to the closing mechanism of the forming half-molds.

Obtaining bottles or containers by blowing suitable appropriately heated preforms in a mold of the desired shape is a widely known technique in the packaging sector, in particular for making bottles or containers .

There are substantially two different techniques, simple blowing and stretch-blowing, which include pneumatic blowing and the concurrent mechanical stretching of the preform in the mold. In both cases, the preforms must reach the blowing or stretch-blowing machine in a thermal condition which corresponds to the softening point of the material, so as to be able to be plastically deformed inside the molds.

Blowing or stretch-blowing machines for preforms are known and comprise a plurality of openable molds comprising two half-molds hinged at an end and actuated by means of appropriately arranged leverages sized to allow the opening and closing thereof in synchronized manner with predetermined steps of loading of the preforms and of unloading of the formed bottle. Such leverages are generally operated by means of a shaped cam coupling, such a coupling being adapted to provide an alternating motion with pattern defined by the shape of the cam itself.

In rotary machines, a plurality of molds is arranged radially about a central rotation axis and means for opening and closing the molds are synchronized with the movement of other devices which cooperate in the operation of the machine, e.g. a movement device for the entering preforms and the exiting bottles, or a blowing and movement device of different components of the molds.

The conventional mold movement and opening/closing systems are complex and, above all, not very versatile. Indeed, in order to modify the opening/closing pattern it is necessary to replace the cam system with a different one in which the profile of the cam corresponds to the new movement. Furthermore, by implying the use of complex mechanical movement transmission systems, the conventional machines are subject to high wear and thus to frequent and careful maintenance.

The problem addressed by the present invention is to make available a blowing or stretch-blowing machine for bottles made of plastic material which allows to overcome the disadvantages illustrated above and which is thus simpler to construct, requiring less maintenance and having greater flexibility .

Such a problem is solved by a machine as outlined in the accompanying claims, the definitions of which form an integral part of the present description .

Further features and advantages of the present invention will be apparent from the description of some exemplary embodiments, given here by way of non- limiting example with reference to the following figures :

Figures 1A and IB show perspective views of a first embodiment of a mold for containers made of plastic material according to the invention, in two different operating conditions;

Figures 2A and 2B show views from the bottom of the mold in figures 1A and IB, in the respective operating conditions; Figures 3A and 3B show section side views of the mold in figures 1A and IB, in the respective operating conditions;

Figures 4A and 4B show section side views of a second embodiment of a mold for containers made of plastic material according to the invention, in two different operating conditions;

Figure 5 shows a perspective view of a third embodiment of a mold for containers made of plastic material according to the invention in open mold operating condition;

Figures 6A and 6B show section side views of the mold in figure 5, in two different operating conditions ;

Figure 7 shows a section side view of the mold in figure 6A, on which a shaped profile is mounted;

Figure 8 shows a partial side view of a different embodiment of a mold for containers made of plastic material according to the invention;

Figures 9A and 9B show section side views of the mold in figure 8, in two different operating conditions .

With reference to the figures, reference numeral 1 indicates as a whole an injection forming mold of a container in blowing or stretch-blowing machines. Typically, a blowing or stretch-blowing machine according to the invention is of the rotary type and comprises a plurality of molds 1 arranged radially with respect to a substantially vertical rotation axis of the machine.

By turning about the rotation axis of the machine, each mold 1 is cyclically carried to a loading station of a preform and/or an unloading station of a bottle obtained from the preform. The blowing or stretch-blowing is performed between the loading of the preform and the unloading of the bottle .

Each mold 1 comprises a first half-mold 2a and a second half-mold 2b hinged about a hinge axis 3, normally parallel to the rotation axis of the machine. The hinge axis 3 is arranged at an end of the half-molds 2a, 2b facing towards the axis of the machine, while the half-molds 2a, 2b on the opposite end comprise edges 9a, 9b intended to face each other when the mold 1 is closed.

Each half-mold 2a, 2b is C-shaped in cross section, comprising a front portion 37a, 37b, a side portion 38a, 38b and a rear portion 39a, 39b.

The first half-mold 2a and the second half-mold 2b can thus turn about the hinge axis 3 between a closed mold configuration (Fig. 1A, 2A, 3A, 4A, 6A and 9A) and an open mold configuration (Fig. IB, 2B, 3B, 4B, 5, 6B and 9B) . The half-molds 2a, 2b can thus be opened/closed like two shells of a bivalve shell.

Mold 1 comprises a bottom plate 4 adapted to cooperate with the half-mold 2a, 2b for closing the bottom of the mold 1 and bottom plate vertical/translational movement means, for cyclically forming a closed cavity adapted to receive a preheated preform and for allowing the expansion of the preform by blowing or stretch-blowing in the cavity to obtain a bottle or a container.

The bottom plate 4 slides vertically on a guide element 46, fixed to the support structure of the blowing or stretch-blowing machine or of the mold 1, by means of a slide 47.

The half-molds 2a, 2b comprise an outer face 5a, 5b and an inner face 6a, 6b, respectively. Respective shaped portions S (the bottom portion of shaped portion S is shown by way of example in figure 7 relatively to the embodiment in figure 5) are applied onto the inner faces 6a, 6b, which portions taken as a whole, with the mold closed, reproduce as a negative shape the outer shape of the bottle to be obtained from the preform and delimit the space in which the preform is expanded.

In some embodiments, such a shaped portion S can be separated from the half-molds 2a, 2b and is interchangeable, so as to allow the forming of bottles having different shapes and sizes. In such a manner, it is sufficient to replace the shaped portions S to start the production of different bottles .

The half-molds 2a, 2b comprise a bottom opening from which the lower part of the shaped portions S protrude, the shaped portions S having, in turn, a bottom opening at a bottom portion of the bottle to be obtained, said opening adapted to be closed with alternate motion by the aforesaid bottom plate 4.

As shown in figure 3, abutment profiles 10a, 10b are applied on the edges 9a, 9b of the respective half-molds 2a, 2b.

In preferred embodiments, the abutment profiles 10a, 10b are removable and may be changed in case of wear .

On one of the two half-molds 2a, 2b (on the right half-mold 2b, in the example in the figures) a closing element 19 of the mold 1 is rotationally mounted, the closing element 19 being adapted to keep the half-molds 2a, 2b joined during the blowing or stretch-blowing process.

The movement mechanism of the closing element 19 and the retaining system of the half-molds is described in patent application EP15164317.8 filed on 20 April 2015 by the same Applicant.

The blowing and stretch-blowing machine of containers according to the present invention is characterized in that it envisages an opening/closing system of the half-molds 2a, 2b and of the bottom plate 4 which envisages an independent motorization instead of the actuation cam. Thus, each mold 1 of the blowing and stretch-blowing machine comprises its own motorization which will open/close the half-molds 2a, 2b and bottom plate 4 and will be independent from the motorization of the machine which in turn transports the molds 1 along the working path.

The aforesaid motorization for the opening/closing the half-molds 2a, 2b and the bottom plate 4 is an actuator with either rotary or linear movement. Preferred examples of actuators are stepper motors, preferably either linear or rotating brushless motors.

Mold 1 according to the invention thus comprises an actuator which moves a single synchronized actuation opening/closing mechanism of the half-molds 2a, 2b and of the bottom plate 4.

This embodiment, as described in better detail below, further to allowing a greater control of the blowing or stretch-blowing process, it has the advantage of reducing vibrations, noise and wear of the machine by virtue of the fact that it is free of mechanical cams.

In the figures from 1A to 3B, it is shown a first embodiment of the mold 1 according to the invention in a close operating condition (figures 1A, 2A and 3A) and in an open operating condition (figure IB, 2B and 3B) .

The mold 1 comprises an actuator 30. In the example shown, the actuator 30 is either a stepper or a brushless motor of the rotary type coupled to a ratio motor.

The actuator 30 is placed vertically with the shaft facing downwards and acts on an eccentric member 31, in turn hinged to an end of a crank 32. The opposite end of the crank 32 is instead hinged to a sliding member 33, which slides horizontally along a direction defined by a straight line which lies on the vertical plane that divides the half-molds 2a, 2b. The sliding member 33 comprises a slide 34 slidingly mounted on guide means 35, which may comprise a rail or a single rail. The guide means 35 are fixed and are mounted on the support structure of the blowing or stretch-blowing machine or of the mold 1. The sliding member 33 may thus slide between an advanced (or closed) position and a retreated (or open) position.

The sliding member 33 is connected to the two half-molds 2a, 2b by means of respective connecting rods 36a, 36b.

The first ends of the two connecting rods 36a, 36b are coaxially hinged onto the sliding member 33, while the opposite ends are hinged at the joint point between the side portions 38a, 38b and the rear portions 39a, 39b of the half-molds 2a, 2b, respectively. In this manner, as shown in particular in figures 2A and 2B, when the sliding member 33 is in advanced position, the half-molds 2a, 2b are found facing along the edges 9a, 9b and the mold 1 is closed; conversely, when the sliding member 33 is in the retreated position (figure 2B) , the connecting rods 36a, 36b act on the hinging points with the half-molds 2a, 2b, taking them to the open position. It is apparent that all intermediate positions of the sliding member 33 along the guide means 35 correspond to a different degree of opening of the half-molds 2a, 2b. As will be explained better below, the possibility of defining a different degree of opening of the half-molds 2a, 2b as a function of the size of the container to be formed allows to optimize the processing times: indeed, for small size containers it will not be necessary to open the molds completely to load the preform and unload the formed container, thus reducing the overall time for each working step and allowing to speed up the production cycle. This is also the case of larger containers, because it will still be possible to open the half- molds 2a, 2b only partially to load the preforms, which are small.

Another advantage connected to an only partial opening of the half-molds 2a, 2b resides in the decrease of the forces in hand and of the vibrations of the machine.

The sliding member 33 is also operatively connected to an opening-closing mechanism of the bottom plate 4.

As shown in the figures, such a mechanism is a pantograph mechanism. A system of articulated arms 40 is associated with the lower side of the sliding member 33, the system comprising:

- a first arm 41 having a proximal end and a distal end, wherein the proximal end is fixed on the lower part to the sliding member 33;

- a second arm 42, having a proximal end and a distal end, wherein the proximal end is hinged at the distal end of the first arm 41;

- a pair of connecting rod-like arms 43, 44, each having a proximal end and a distal end, wherein the respective proximal ends are coaxially hinged to the distal end of the second arm 42,

and wherein:

- the distal end of a first connecting rod-like arm 43 is hinged on the lower surface of the bottom plate 4, and

- the distal end of the second connecting rod ^¬ like arm 44 is hinged to a fixed element 45.

The fixed element 45 is supported by the support structure of the blowing or stretch-blowing machine or of the mold 1.

As shown in figures 2A and 2B, in some embodiments both the first 43 and the second 44 connecting rod-like arms consist of a pair of parallel arms. As shown in particular in figures 3A and 3B, when the sliding member 33 is in an advanced position

(figure 3A) , the connecting rod-like arms 43, 44 are positioned aligned perpendicularly with respect to the second arm 42, and the bottom plate 4 is in a raised position (or closed position) ; conversely, when the sliding member 33 is in a retreated position

(figure 3B) , the connecting rod-like arms 43, 44 assume a V-position and the bottom plate is in a lowered position (or open position) .

In the embodiment shown in figures from 1A to 3B, the eccentric 31 - crank 32 system for moving the sliding member 33 allows to operate the mold 1 between the closed position (figures 1A, 2A and 3A) and a total opened condition (figures IB, 2B and 3B) by means of the rotation of the shaft of the rotary actuator 30 to only one direction. This allows to avoid the steps of stopping and restarting which can cause vibrations to the machine. Conversely, a movement in alternating directions must be envisaged if it is desired to open the mold 1 only partially

(as mentioned above in the case of small size containers) .

Figures 4A, 4B and figures 5, 6A and 6B show two alternative embodiments of the mold 1 of the invention, respectively. In such embodiments, the operating connection between sliding member 33 and half-molds 2a, 2b and bottom plate 4 is the same and consequently will not be described again. Conversely, such embodiments envisage different types of movement of the sliding member 33 by means of an actuator 30.

With reference to figures 4A and 4B, the rotary actuator 30 is connected, by means of a ratio motor 50 or a suitable ball bearing, to an Archimedes' screw 51, in particular to a recirculating ball and nut .

The Archimedes' screw 51 is operatively connected to a movable member 52. The movable member 52 comprises a tubular portion having inner bosses which mate with the grooves of the Archimedes' screw 51. In such a manner, when Archimedes' screw 51 rotates, the movable member 52 moves upwards or downwards according to the rotation direction of the Archimedes' screw 51.

The movable member 52 comprises an outer support portion 53 comprising a slide 54 arranged parallel to the Archimedes' screw 51. The slide 54 slides on a guide element 55 fixed onto the support structure of the blowing or stretch-blowing machine or of the mold 1. A greater stability of the movable member with respect to possible oscillations about the vertical axis is obtained in this manner.

A pantograph mechanism 56 for horizontal movement of the sliding member 33 is inferiorly hinged onto the outer support portion 53 of the movable member 52.

The pantograph mechanism 56 comprises an articulated arm 57 having a proximal end hinged on the outer support portion 53 of the movable member 52 and a distal end. A first 58 and a second connecting rod-like arm 59 comprising respective proximal and distal ends are coaxially hinged on the distal end of the articulated arm 57 by means of said proximal ends. Conversely, the distal end of the first connecting rod-like arm 58 is hinged onto a fixed element 60 associated with the support structure of the blowing or stretch-blowing machine or of the mold 1, while the distal end of the second connecting rod ^¬ like arm 59 is hinged on the sliding element 33.

In this manner, when the movable member 52 slides downwards, following the rotation in one direction of the Archimedes' screw 51, the two connecting rod-like arms 58, 59 move to the aligned or nearly aligned position so as to reach the maximum spatial distance between the respective distal ends (figure 4A) . The sliding member 33 is thus in its advanced position and the mold 1 is closed.

Conversely, when the Archimedes' screw 51 turns in the opposite direction and thus the movable member 52 slides upwards, the two connecting rod-like arms 58, 59 assume an upside-down V position, which corresponds to a smaller distance between the respective distal ends. Consequently, the sliding member 33 is found in the retreated position and the mold 1 is open (figure 4B) .

With reference to figures 5, 6A and 6B, the sliding of the sliding member 33 between the retreated position (figure 6B) and the advanced position (figure 6A) is operated by means of an Archimedes' screw 60 which directly acts on the sliding member 33. For this purpose, the sliding member 33 comprises a tubular cavity 61, arranged along an horizontal straight line lying in the vertical plane which divides the two half-molds 2a, 2b, inside which cavity 61 the Archimedes' screw 60 is inserted. Suitable bosses present on the inner surface of the tubular cavity 61 cooperate with the grooves of the Archimedes' screw 60 so that the sliding member 33 either advances or retreats according to the rotation direction of the Archimedes' screw 60 when the latter rotates.

The Archimedes' screw 60 is connected to the rotary actuator 30 by means of a belt or chain transmission system 62. The actuator 30 is horizontally arranged above the sliding member 33, with its body protruding towards the mold 1, so as to minimize dimensions. The transmission system 62 comprises a first pinion 63, directly associated with the actuator 30 shaft, a second pinion 64, either directly or indirectly associated with the Archimedes' screw 60, and a belt or chain 65.

The rotation of the shaft of the actuator 30 either in one direction or in the opposite direction thus causes a corresponding rotation of the Archimedes' screw 60 which, as mentioned, makes the sliding member 33 either advance or retreat, thus obtaining the closing or the opening of the mold 1, respectively .

In some embodiments (not shown) the actuator 30 may be connected directly to the Archimedes' screw 60, without the interposition of the transmission system 62. This solution increases the dimensions but reduces the problems connected to the response delay of the Archimedes' screw 60 caused by the elasticity or by the clearances of the transmission system 62.

Figure 8, 9A and 9B show a further embodiment of the mold 1 of the invention. In such embodiments, the operating connection between sliding member 33 and half-molds 2a, 2b and bottom plate 4 is the same and consequently will not be described again. Conversely, such an embodiment envisages a different type of movement of the sliding member 33 by means of an actuator 30.

The rotary actuator 30 is connected, by means of a ratio motor 50 or a suitable ball bearing, to an Archimedes' screw 51, in particular to a recirculation ball and nut.

The Archimedes' screw 51 (or recirculation ball and nut) is operatively connected to a movable member 72. The movable member 72 comprises a tubular portion having inner bosses which mate with the grooves of the Archimedes' screw 51. In such a manner, when Archimedes' screw 51 rotates, the movable member 72 moves upwards or downwards according to the rotation direction of the Archimedes' screw 51.

The movable member 72 comprises an outer support portion 73 comprising a first slide 74 arranged parallel to the Archimedes' screw 51. The slide 74 slides on a guide element 75 fixed onto the support structure of the blowing or stretch-blowing machine or of the mold 1. A greater stability of the movable member with respect to possible oscillations about the vertical axis is obtained in this manner.

The outer support portion 73 comprises an inclined lower surface 76 with pattern from the top downwards away from the hinge axis 3. A second slide

77 is fixed on such a lower surface 76.

The sliding member 33 comprises, in turn, an inclined upper surface 78 with pattern from the top downwards away from the hinge axis 3, so as to mate with the lower surface 76 of the outer support portion 73. For this purpose, the upper surface 78 of the sliding member 33 comprises a rail 79 which slidingly mates with the slide 77.

In this manner, when the movable member 72, following the rotation in one direction of the Archimedes' screw 51, slides downwards integrally with the outer support portion 73, the latter imparts a force from the top downwards on the upper surface

78 of the sliding member 33. By virtue of the horizontal component of such a force and the fact that the lower surface 76 of the outer support portion 73 and the upper surface 78 of the sliding member 33 are inclined and slidingly mated, a wedge effect is obtained which causes the forward displacement of the sliding member 33, as shown in the operative sequence in figures 9A and 9B . The sliding member 33 is thus placed in its advanced position and the mold 1 is closed.

Conversely, when the Archimedes' screw 51 rotates in the opposite direction and thus the movable member 72 slides upwards integrally with the outer support portion 73, the latter feeds the sliding member 33 away from the hinge axis 3. Consequently, the sliding member 33 goes back to the retreated position and the mold 1 is open (figure 9A) .

In preferred embodiments, the blowing and stretch-blowing machine or the mold 1 comprise a command and control unit which governs the motion law for opening/closing the individual molds 1 thus allowing to provide predefined opening/closing cycles for every type of container to be formed. For example, an incomplete opening of the molds may be provided if the container to be formed is small in size, thus obtaining an increase of productivity, as mentioned above. This is a considerable advantage with respect to the conventional machines because no replacement of mechanical parts (cam profiles) is required.

In some embodiments, the command and control unit governs the entire operation of the machine, such as :

- the pressure sensors inside the molds

- the processing times

- the blowing process parameters

- the warning signals

- the preform heating

- the operating speed of the machine.

It is apparent that only some particular embodiments of the present invention have been described, to which a person skilled in the art will be able to make all the changes necessary to its adaptation and particular applications, without because of this departing from the scope of protection of the present invention.