System for handling objects in rotary machines

A system for handling objects in rotary machines, and, more particularly, a system for handling preforms in blowing machines. The system picks up a pre-heated preform from a transferring star of the preform and takes it to a mold of a stretch-blowing machine by using movements entailing reduced acceleration values, in particular of the tangential acceleration component, so as to prevent uncontrolled oscillatory movements of the softened preform. In the blowing machine, the preform is blown to obtain a bottle, and the bottle thus obtained is picked up from the stretch-blow molding position and transferred to an unloading position.

FIELD OF THE DISCLOSURE

The present invention relates to a system for handling objects in rotary machines, in particular it relates to a system for handling preforms in blowing machines, able to pick up a pre-heated preform from a pick-up position of the preform, take it to a stretch-blow moulding position in the blowing machine, in which the preform is blown to obtain a bottle, picking up the bottle thus obtained from the stretch-blow moulding position and transferring it to an unloading position of the bottle.

The invention also relates to a stretch-blow moulding machine having at least one such automatic handling system. The invention relates, in addition, to a stretch blow moulding system comprising at least one stretch-blow moulding machine having at least one such automatic handling system.

BACKGROUND

In the production of bottles in polymer material a method is known for making plastic bottles starting from a preform in plastic or polymer material comprising a pre-heating step of the preform at a predefined process temperature, a transfer step of the preheated preform to a mould and insertion therein, and a blowing step inside the preform positioned in the mould in a closed position, of air at a predetermined pressure so that the preform is inflated inside a cavity made in the mould, shaped like the bottle to be obtained, until the preform, inflated by said pressurised air, adheres to the walls of the cavity, cooling upon contact and stiffening, thereby acquiring the definitive shape of the bottle to be obtained. As well as the blowing step described, there may also be a step of stretching the preform when softened, suitable for elongating or mechanically extending the preform being prepared and simultaneously with the blowing. Such combined method is called stretch-blowing.

The above method is performed by automatic machines which, to ensure a greatly reduced unit cost, must implement a very high hourly production rate.

To maximise efficiency, the preforms need to be moved at high speed along a circuit between the output of a preheating furnace and the mould, passing through one or more movement devices comprising the aforesaid feed device suitable for positioning one preform at a time in the mould.

Such circuit is generally formed of straight and curved sections having different curvatures and therefore speed variations of modulus and direction at the point of changes in direction, thereby causing damaging accelerations for the preheated preform.

The problem of acceleration is particularly felt in the passage of the preform from the feed device to the mould on account of the oscillatory movements which are triggered on the preheated, therefore softened preform, as a result of the aforesaid acceleration.

To better describe the aforesaid drawback of the prior art the preform and its behaviour along the aforesaid circuit must be described in more detail.

The preform has generally an elongated tubular shape having a first open end having a mouth and a second opposite closed end. The preform is transported hanging vertically, gripped at the mouth.

In the pre-heating furnace the preform is brought to the softening point, so as to be subsequently inflated inside the cavity in the mould.

It is evident that the preform, in the above conditions, being softened, reacts to the accelerations it is subjected to by gently swinging like a pendulum and deforming in relation to its mouth. The oscillation caused by an acceleration can be summed to a previous acceleration not yet damped producing an uncontrolled oscillation movement of the preheated preform. Such uncontrolled movement of the preform may persist even when the preform is inserted in the mould, with the risk of brushing against the mould in some points before the stretch-blowing step cooling and solidifying irregularly in that point and thereby giving rise to a bottle or container with moulding defects.

Returning to the known stretch-blowing systems, a widely used method is to use a stretch-blowing machine of the type rotating around to a vertical axis. Such machine generally comprises a plurality of moulds positioned radially in relation to the axis of the machine and provided with opening/closing means of the moulds, operable in a manner synchronised with the corresponding movement devices of the preform.

Sometimes such movement devices comprise a transferring star. A transferring star is taken to mean for example a support having a plurality of seats for receiving a preform positioned spaced tangentially around a rotation axis, in particular along a circumference with its centre in the rotation axis. Such transferring star is suitable for sequentially supplying the preforms to the mould of the blowing machine.

In the conventional machines, in the passage from the transferring star to the mould of the rotary machine, the preform may be subject to brusque speed variations back and forth, and thus an acceleration, with the drawbacks mentioned above.

The acceleration to which the preform is subjected is formed by a tangential component along the direction of advancement and a radial component orthogonal thereto.

While the known systems are generally able to keep the radial component of the acceleration at a low value, the value of the tangential component has often an high value, to the order of hundreds of m/s2.

The need is therefore felt to provide a handling system of a preform able to pick it up from a feed device and rapidly transfer it to a stretch-blow moulding position by movements entailing reduced acceleration values, in particular of the tangential acceleration component, so as to prevent uncontrolled oscillatory movements of the softened preform from being triggered.

SUMMARY OF THE INVENTION

The problem addressed by the present invention is to provide a system for handling objects between a transferring star and a rotary machine comprising a plurality of processing units which overcomes the drawbacks described above.

A further purpose of the present invention is to make available a handling system of preforms in blowing or stretch-blowing machines able to pick up a preheated preform from a transferring star of the preform and take it to a mould of a stretch-blowing machine, which makes it possible to overcome the drawbacks described above.

Such problem is solved by a handling system in rotary machines as delineated in the appended claims, the definitions of which form an integral part of this description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “blow-moulding machine” or “blowing machine” is understood to mean any type of machine having at least one mould which can be opened defining a cavity therein, in which a preform is made to expand by blowing air at a predetermined pressure inside it.

The term “stretch blow-moulding machine” or “stretching-blowing machine” is understood to mean a blowing machine further comprising stretching means, comprising for example an element which penetrates inside the preform through the mouth and pushes the end of the preform opposite the mouth from the inside elongating the preform so as to prepare it for blowing or simultaneously.

With reference to the figures, reference numeral100globally indicates a system according to the invention, for handling objects133,133′ between a transferring star schematically indicated by reference numeral130and a rotary machine schematically indicate by reference numeral1.

The rotary machine comprises, for example, a plurality of processing units10, and the transferring star130comprises along its perimeter136a plurality of seats13,13′ to house said objects133.

Said processing units10are spaced apart at a first pitch151along a first circumference155and the seats134,134′ are spaced apart at a second pitch131along a second circumference136, wherein the second pitch131is different from the first pitch151and wherein the circumferences155and136are not tangent.

The aforesaid handling system100comprises a gripping unit112for each processing unit10, and the gripping unit112comprises a gripping nipper103able to grip the object133.

Such system further comprises mean of moving102,202the gripping nipper103suitable for alternately moving the nipper103between a first radial position, at the processing unit10and a second radial position at a seat134,134′ of the transferring star130.

More specifically, the first radial position lies on the first circumference155and the second radial position lies on the second circumference136.

According to one embodiment, the aforesaid objects133,133′ are preforms made of polymer material for making bottle or containers141, the aforesaid rotary machine1is a stretch-blowing machine for preforms133and the aforesaid processing units10are stretch-blowing moulding units.

In a possible embodiment, for example the aforesaid moulding units10are of the type shown in the Italian patent application no. MI2011A002033, in the name of the same Applicant. However, other embodiments of the moulding unit for stretch-blowing machines may also be used.

The aforesaid rotary machine100may alternatively, be a blowing machine for preforms in the cases in which the moulding does not provide for the preventive or simultaneous stretching of the preform with the blowing.

According to one embodiment said movement means of102,202of the gripping nipper103are configured to make the nipper translate in a radial direction in relation to the rotation axis2of the rotary machine1alternately between an extended position lying on said second circumference136and a retracted position lying on said first circumference155.

According to one embodiment said movement means102,202of the gripping nipper103are configured to make the nipper103translate in a radial direction in relation to the rotation axis2of the rotary machine1alternately between an extended position lying on said second circumference136and a retracted uncoupled position lying on an uncoupling circumference159concentric with said first circumference155and having a radius R3less than the radius R2of said first circumference155.

In one embodiment said movement means102,202of the gripping nipper103act contemporarily with the rotation of the rotary machine1, conducting the gripping nipper103along a curved section161of trajectory tangent to said first circumference155in a first point of tangency162and tangent to said second circumference136in a second point of tangency163.

In one embodiment said movement means102,202of the gripping nipper103act contemporarily with the rotation of the rotary machine, conducting the gripping nipper103along a curved section161of trajectory having its centre of curvature on the rotation axis2of the rotary machine and having a radius varying from a first value corresponding to the radius of the first circumference155and a second value corresponding to the radius of the second circumference136.

According to one embodiment said variable radius varies in a linear manner in relation to time.

According to one embodiment the trajectory of the nipper103between the second point163and the first point162is such that the tangential acceleration of the nipper103is negligible.

According to one embodiment said movement means102,202of the gripping nipper103act contemporarily with the rotation of the rotary machine, conducting the nipper103along a predefined trajectory161between a point163lying on said second circumference136and a point162lying on said first circumference155, wherein at least in said points on said first and second circumference155,136, the tangential acceleration of the nipper103is negligible.

In other words, the combination of the rotation movement of the nipper103around the rotation axis2of the machine1and the translation movement of the nipper103in a radial direction in relation to the rotation axis2of the machine, produces a resulting movement of the nipper103between the second circumference136of the transferring star and the first circumference155of the machine, wherein such movement is homokinetic.

This produces the advantage that the preform has reduced values of accelerations along its path between the transferring star130and the rotary machine1, thereby preventing the triggering of dangerous uncontrolled oscillatory movements of the preform which would risk making the heated preform come into contact with the inner walls of the cold mould before blowing, leading to a moulding defect.

In one embodiment, said movement means102comprise a gear transmission configured to transmit a first alternate shift in a radial direction of a motion input element106into a second alternate shift in a radial direction of an output element111to which the gripping nipper103is attached, wherein the second alternate relative shift is greater than the first alternate shift.

According to one embodiment the gear transmission comprises:a ratchet having a rotation axis101, a first wheel107and a second wheel108of greater diameter, said first wheel107and said second wheel108being coaxial and integral with each other and with the ratchet101, said ratchet ending with said meter motion input element106;a first rack109fixed in relation to the machine, said first wheel107meshing with said fixed rack109so that a radial translation of the input element106corresponds to a rotation of the ratchet;a second rack110sliding in a radial direction in relation to the machine, said second wheel108meshing with said sliding rack110, so that a rotation of the second wheel108corresponds to a translation of said second rack110; said second rack being rigidly connected to the output element111.

According to one embodiment of the invention, the second shift is a multiple of the first shift according to a transmission ratio of 1.5 to 3, for example substantially equal to 2.5.

According to one embodiment the first wheel107and the second wheel108are wheels externally toothed, and said first rack109and said second rack110are toothed racks with a linear extension.

According to one embodiment the first rack109and the second rack110are positioned substantially parallel on opposite sides of the axis101of the ratchet and in a radial direction in relation the machine.

According to one embodiment the first wheel107and the second wheel108are positioned at different heights along the axis101of the ratchet.

According to one embodiment, the output element111has a first end rigidly connected to said second rack110and a second end rigidly connected to said gripping nipper103, said output element being configured to keep the gripping nipper103substantially parallel to the second rack110, in particular at a lesser height than the height of the second rack110.

According to one embodiment the output element111comprises at least one plate positioned along a substantially vertical plane.

According to one embodiment the input element106is a cam follower for a shaped cam, suitable for being alternately translated in a radial direction to the rotation axis of the machine, following a sliding coupling along a shaped profile12of said cam.

According to a second embodiment of the present invention, shown inFIGS. 12 and 13, the movement means202comprise a motion transmission configured to transmit a first alternate angular shift223of a lever element221connected to a meter motion input element206into second alternate linear shift224in a radial direction of an output element111to which the gripping nipper103is rigidly connected.

According to such embodiment, the movement means202comprises a toothed wheel208carried in rotation by said lever element221around a rotation axis201, said wheel meshing with a second rack210, integral with the nipper103, so that a rotation of the lever element221corresponds to a translation of the rack210. The rack210is the same rack as that indicated by reference numeral110in the first embodiment shown inFIGS. 5 to 8.

The toothed wheel208may be fitted on a shaft233connected to a fixed support229so as to rotate.

The fixed support229may comprise a projecting shelf element227having at one end an abutment roller228suitable for constraining the rack210in a meshed condition with the toothed wheel208.

Between the lever element221and the toothed wheel208an angular speed multiplier222may be positioned, having an input rigidly connected to the lever element221and an output232rigidly connected to the toothed wheel208, for example by means of a shaft233.

According to one embodiment the angular speed multiplier222is of the planetary gear type. According to one embodiment the movement means202are supported by a fixed, L-shaped support bracket240comprising an element substantially parallel to the rotation axis201and an element substantially orthogonal to such rotation axis201.

According to one embodiment said nipper103comprises a coupling portion104comprising two pincers105projecting from a free end of the nipper103, said coupling pincers105being positioned substantially parallel to each other and defining between them a retention seat113suitable for receiving and snap engaging the mouth of a preform.

According to one embodiment said retention seat113has at least partially circular shape so as to embrace the mouth and present a front aperture to permit the coupling of the mouth in the seat133by means of a relative drawing together of the nipper13and the preform and the release of the mouth by means of the relative translation away from each other of the nipper and the preform.

According to one embodiment the pincers105of the nipper present at the front guide profiles inclined towards the inside of the retention seat113, suitable for facilitating the entrance of the mouth of the preform in the seat113.

According to one embodiment the coupling portion104is made of an elastic material, for example but not necessarily in harmonic steel.

According to one embodiment the coupling portion104is formed of a U-shaped plate having an aperture positioned in a radial direction outwards in relation to a rotation axis2of the stretch-blowing machine1.

According to one embodiment said coupling portion104extends substantially according to a horizontal plane.

According to one embodiment said nipper103comprises an elongated connection portion114positioned between said movement means102of the gripping nipper112and the coupling portion104, said elongated body extending, for example but not necessarily, in a radial direction opposite the rotation axis2of the rotary machine1.

According to one embodiment said elongated connection body114is a flat shape and extends substantially along a horizontal plane.

According to one embodiment said coupling portion104and said elongated connection body114extend along the same plane.

According to one embodiment each moulding unit10comprises a mould20which can be opened having an inner cavity24suitable for receiving the preheated preform and permitting within it the expansion thereof by blowing inside the preform. Such cavity24may comprises a moulding surface25having a complementary shape to that of the bottle to be obtained.

In one embodiment, the mould20comprises a universal seat26for removably housing a mould element27shaped so as to comprise said moulding surface25.

In one embodiment, each said mould20comprises a first half-shell21and a second half-shell22hinged around a hinge axis23so that they can be opened and closed by means of a rotation opening and closing the same around the hinge axis. When closed, the aforementioned half-shells21and22form between them a through seat156which places the cavity24in communication with the outside suitable for housing the mouth of the preform so that such mouth remains facing outwards while the remaining portion of the preform remains inside the cavity244, to allow the introduction of pressurised air inside the preform through the mouth, to expand the preform134in the inner cavity24until it adheres to the moulding surface25, and impress upon the preform a shape complementary to that of the moulding surface25, complementary to that of the bottle to be obtained.

In one embodiment, the moulding units comprise means of opening and closing the moulds20, wherein such means are synchronised with the movement means102of the nipper103so that during at least a part of the translation movement of the nipper103, the half-shells are opened so as to permit the introduction of the preform in the moulds and the extraction of the bottle moulded by the moulds.

According to one embodiment the opening/closing means of the moulding unit10comprise a self-locking system suitable for keeping the half-shells pressed together in a closed position during the blowing operation.

In the example of the blowing or stretch blowing machine1shown in the figures, the moulding units10are attached to a rotating platform153which rotates around the rotation axis2of the machine.

The blowing or stretch-blowing machine may be coupled to a second rotating star140unloading the moulded bottles141, having a plurality of seats for said bottles.

After the moulding operation, and after a rotation of the machine by a predetermined angle, the nipper103translates outwards to transfer the moulded bottle141, from the inside of the mould towards the bottle seat of the aforesaid second rotating star140.

According to one possible embodiment, the moulding units10of the machine1are angularly equidistant from one another.

According to one embodiment the seats134of the transferring star130are angularly equidistant from one another.

According to one embodiment the seats for the bottles141of the second rotating star140are angularly equidistant from one another.

According to one embodiment the rotation axis135of the transferring star130is placed at a distance from the rotation axis2of the machine, having a value greater than the sum of the radius R1of the second circumference and of the radius R2of the first circumference155, leaving a distance D between the first circumference155and the second circumference136the value of which is chosen so as to be able to obtain a transfer movement of the nipper103which is homokinetic at the pick-up point of the preform.

According to one embodiment the handling system comprises transfer means of the preheated preforms from the preheating furnace300to the aforesaid transferring star130(FIG. 14)

The functioning of the handling system of objects between a transferring star130and a rotary machine1comprising a plurality of processing units10, is as follows.

Each preheated preform133coming out of a preheating furnace300is taken to a seat for preforms of the transferring star130, which rotates around its axis135, for example in a clockwise direction in the direction of the arrow132.

After a rotation of the transferring star according to a predetermined angle of rotation, the preform finds itself in a point of the second circumference136in which the nipper simultaneously advances homokinetically coupling the preform. In such point, the half-shells are open to allow the subsequent introduction of the preform in the cavity between the half-shells (FIG. 1).

Starting from such point the nipper103begins its radial translation according to a rearward movement towards the machine axis1, simultaneously with the rotation of said machine. The section of curved trajectory161performed by the nipper103from the pick-up point163of the transferring star on the second circumference136, as far as the first circumference155(FIG. 2) derives from the combination of such radial translation and the rotation movement of the machine.

The passage of the preform, coupled to the nipper103, from the star to the stretch-blowing machine takes place homokinetically.

When the preform is transferred by the nipper103inside the corresponding moulding unit10and the half-shells21and22are then closed, the preform begins its path along the first circumference155of the machine during which blowing is performed, as far as a predetermined angular position on the opposite side, wherein the half shells21and22open to allow the unloading of the moulded bottle141. Unloading takes place by means of a radial translation of the nipper103towards the outside of the machine as far as encountering a corresponding seat144for bottles made on the second rotating star140, which rotating transfers the bottle obtained141towards a collection zone, or towards a subsequent bottling station for example of liquids.

A further purpose of the invention relates to equipment for blowing or stretch-blowing bottles in plastic material, comprising a furnace300for heating and dealing with the heat profile of the preforms133, a blowing or stretch-blowing machine100, comprising a plurality of processing units10as defined above, and movement means130,140of the preforms going into and coming out of said furnace300, wherein said furnace300comprises means of transport308for the preforms and means of heating309the preforms, and wherein said movement means130for the preforms coming out of the furnace300, comprise a plurality of gripping means134for the preforms spaced apart at a fixed pitch, characterised in that said furnace300comprises movement and distancing means344bof the heated preforms133, from a minimum pitch to a pitch substantially corresponding to the pitch of the gripping means134of the movement means130for the preforms coming out of the furnace300.

A furnace having the aforementioned features is described in the Italian patent application MI2011A001762 filed on 30 Sep. 2011 in the name of the same Applicant, and the description of which is incorporated hereto for reference.

This way a homokinetic transmission system of the preforms133is realised, from the furnace300to the single processing units10of the blowing or stretch blowing machine, minimising or substantially eliminating the accelerations to which said preforms are subject in the traditional machines.

In one embodiment, said movement and distancing means344bof the heated preforms133consist of an Archimedean screw or auger comprising a variable pitch helical groove, wherein the greatest pitch is at the release end of the preforms to the movement means130.

The advantages of this solution are various.

First of all, the handling system described makes it possible to transfer the preheated preform from the transferring star as far as inside the mould, homokinetically.

In other words, the system makes it possible to transfer the preheated preform from the transferring star as far as inside the mould, avoiding subjecting the preform to jolting and brusque variations of speed upon passing from its circular trajectory along the second circumference of the transferring star to its different circular trajectory along the first circumference of the blowing machine.

The system makes it possible to transfer the preheated preform from a first circumference having a first pitch to a second circumference having a second pitch, in which the second pitch is different from the first pitch and wherein said circumferences are not tangent, such that the aforesaid transfer takes place at reduced tangential acceleration.

Clearly only some particular embodiments of the present invention have been described, to which a person skilled in the art may make all the modifications needed for its adaptation to specific applications while remaining within the scope of protection of the present invention.