Patent Document

FIELD OF THE DISCLOSURE 
       [0001]    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. 
         [0002]    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 
       [0003]    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. 
         [0004]    The above method is performed by automatic machines which, to ensure a greatly reduced unit cost, must implement a very high hourly production rate. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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. 
         [0012]    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. 
         [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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/s 2 . 
         [0017]    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 
       [0018]    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. 
         [0019]    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. 
         [0020]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Further features and advantages of the present invention will be more clearly comprehensible from the description given below of some of its embodiments, made by way of a non-limiting example, with reference to the following drawings: 
           [0022]      FIGS. 1 to 4  schematically show a partial view from above of the functioning of a stretch-blowing machine comprising a handling system according to the invention, respectively in four different subsequent positions during a processing cycle of the machine; 
           [0023]      FIGS. 5 and 6  show a handling system in a perspective view together with a moulding unit of the stretch-moulding machine, respectively in a forward and in a retracted position; 
           [0024]      FIGS. 7 and 8  show a side view of a handling system together with a moulding unit of the stretch-moulding machine, respectively in a forward and in a retracted position; 
           [0025]      FIGS. 9 and 10  show a view from above of a handling system together with a moulding unit of the stretch-moulding machine, respectively in a forward and in a retracted position; 
           [0026]      FIG. 11  shows a view from above of a handling system together with a moulding unit of the stretch-moulding machine, in which the nipper is in a retracted position lying on a first circumference of the machine; 
           [0027]      FIGS. 12 and 13  respectively show a perspective and cross-section view with a plane orthogonal to the radial direction of the machine, in a second embodiment of the movement means; 
           [0028]      FIG. 14  schematically shows a view from above of equipment for making containers from preforms according to a particular aspect of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    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. 
         [0030]    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. 
         [0031]    With reference to the figures, reference numeral  100  globally indicates a system according to the invention, for handling objects  133 ,  133 ′ between a transferring star schematically indicated by reference numeral  130  and a rotary machine schematically indicate by reference numeral  1 . 
         [0032]    The rotary machine comprises, for example, a plurality of processing units  10 , and the transferring star  130  comprises along its perimeter  136  a plurality of seats  13 ,  13 ′ to house said objects  133 . 
         [0033]    Said processing units  10  are spaced apart at a first pitch  151  along a first circumference  155  and the seats  134 ,  134 ′ are spaced apart at a second pitch  131  along a second circumference  136 , wherein the second pitch  131  is different from the first pitch  151  ad wherein the circumferences  155  and  136  are not tangent. 
         [0034]    The aforesaid handling system  100  comprises a gripping unit  112  for each processing unit  10 , and the gripping unit  112  comprises a gripping nipper  103  able to grip the object  133 . 
         [0035]    Such system further comprises mean of moving  102 ,  202  the gripping nipper  103  suitable for alternately moving the nipper  103  between a first radial position, at the processing unit  10  and a second radial position at a seat  134 ,  134 ′ of the transferring star  130 . 
         [0036]    More specifically, the first radial position lies on the first circumference  155  and the second radial position lies on the second circumference  136 . 
         [0037]    According to one embodiment, the aforesaid objects  133 ,  133 ′ are preforms made of polymer material for making bottle or containers  141 , the aforesaid rotary machine  1  is a stretch-blowing machine for preforms  133  and the aforesaid processing units  10  are stretch-blowing moulding units. 
         [0038]    In a possible embodiment, for example the aforesaid moulding units  10  are 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. 
         [0039]    The aforesaid rotary machine  100  may 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. 
         [0040]    According to one embodiment said movement means of  102 ,  202  of the gripping nipper  103  are configured to make the nipper translate in a radial direction in relation to the rotation axis  2  of the rotary machine  1  alternately between an extended position lying on said second circumference  136  and a retracted position lying on said first circumference  155 . 
         [0041]    According to one embodiment said movement means  102 ,  202  of the gripping nipper  103  are configured to make the nipper  103  translate in a radial direction in relation to the rotation axis  2  of the rotary machine  1  alternately between an extended position lying on said second circumference  136  and a retracted uncoupled position lying on an uncoupling circumference  159  concentric with said first circumference  155  and having a radius R 3  less than the radius R 2  of said first circumference  155 . 
         [0042]    In one embodiment said movement means  102 ,  202  of the gripping nipper  103  act contemporarily with the rotation of the rotary machine  1 , conducting the gripping nipper  103  along a curved section  161  of trajectory tangent to said first circumference  155  in a first point of tangency  162  and tangent to said second circumference  136  in a second point of tangency  163 . 
         [0043]    In one embodiment said movement means  102 ,  202  of the gripping nipper  103  act contemporarily with the rotation of the rotary machine, conducting the gripping nipper  103  along a curved section  161  of trajectory having its centre of curvature on the rotation axis  2  of the rotary machine and having a radius varying from a first value corresponding to the radius of the first circumference  155  and a second value corresponding to the radius of the second circumference  136 . 
         [0044]    According to one embodiment said variable radius varies in a linear manner in relation to time. 
         [0045]    According to one embodiment the trajectory of the nipper  103  between the second point  163  and the first point  162  is such that the tangential acceleration of the nipper  103  is negligible. 
         [0046]    According to one embodiment said movement means  102 ,  202  of the gripping nipper  103  act contemporarily with the rotation of the rotary machine, conducting the nipper  103  along a predefined trajectory  161  between a point  163  lying on said second circumference  136  and a point  162  lying on said first circumference  155 , wherein at least in said points on said first and second circumference  155 ,  136 , the tangential acceleration of the nipper  103  is negligible. 
         [0047]    In other words, the combination of the rotation movement of the nipper  103  around the rotation axis  2  of the machine  1  and the translation movement of the nipper  103  in a radial direction in relation to the rotation axis  2  of the machine, produces a resulting movement of the nipper  103  between the second circumference  136  of the transferring star and the first circumference  155  of the machine, wherein such movement is homokinetic. 
         [0048]    This produces the advantage that the preform has reduced values of accelerations along its path between the transferring star  130  and the rotary machine  1 , 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. 
         [0049]    In one embodiment, said movement means  102  comprise a gear transmission configured to transmit a first alternate shift in a radial direction of a motor input element  106  into a second alternate shift in a radial direction of an output element  111  to which the gripping nipper  103  is attached, wherein the second relative shift is greater than the first relative shift. 
         [0050]    According to one embodiment the gear transmission comprises:
       a ratchet having a rotation axis  101 , a first wheel  107  and a second wheel  108  of greater diameter, said first wheel  107  and said second wheel  108  being coaxial and integral with each other and with the ratchet  101 , said ratchet ending with said motor input element  106 ;   a first rack  109  fixed in relation to the machine, said first wheel  107  meshing with said fixed rack  109  so that a radial translation of the input element  106  corresponds to a rotation of the ratchet;   a second rack  110  sliding in a radial direction in relation to the machine, said second wheel  108  meshing with said sliding rack  110 , so that a rotation of the second wheel  108  corresponds to a translation of said second rack  110 ; said second rack being rigidly connected to the output element  111 .       
 
         [0054]    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. 
         [0055]    According to one embodiment the first wheel  107  and the second wheel  108  are wheels externally toothed, and said first rack  109  and said second rack  110  are toothed racks with a linear extension. 
         [0056]    According to one embodiment the first rack  109  and the second rack  110  are positioned substantially parallel on opposite sides of the axis  101  of the ratchet and in a radial direction in relation the machine. 
         [0057]    According to one embodiment the first wheel  107  and the second wheel  108  are positioned at different heights along the axis  101  of the ratchet. 
         [0058]    According to one embodiment, the output element  111  has a first end rigidly connected to said second rack  110  and a second end rigidly connected to said gripping nipper  103 , said output element being configured to keep the gripping nipper  103  substantially parallel to the second rack  110 , in particular at a lesser height than the height of the second rack  110 . 
         [0059]    According to one embodiment the output element  111  comprises at least one plate positioned along a substantially vertical plane. 
         [0060]    According to one embodiment the input element  106  is 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 profile  12  of said cam. 
         [0061]    According to a second embodiment of the present invention, shown in  FIGS. 12 and 13 , the movement means  202  comprise a motor transmission configured to transmit a first alternate angular shift  223  of a lever element  221  connected to a motor input element  206  into second alternate linear shift  224  in a radial direction of an output element  111  to which the gripping nipper  103  is rigidly connected. 
         [0062]    According to such embodiment, the movement means  202  comprises a toothed wheel  208  carried in rotation by said lever element  221  around a rotation axis  201 , said wheel meshing with a second rack  210 , integral with the nipper  103 , so that a rotation of the lever element  221  corresponds to a translation of the rack  210 . The rack  210  is the same rack as that indicated by reference numeral  110  in the first embodiment shown in  FIGS. 5 to 8 . 
         [0063]    The toothed wheel  208  may be fitted on a shaft  233  connected to a fixed support  229  so as to rotate. 
         [0064]    The fixed support  229  may comprise a projecting shelf element  227  having at one end an abutment roller  228  suitable for constraining the rack  210  in a meshed condition with the toothed wheel  208 . 
         [0065]    Between the lever element  221  and the toothed wheel  208  an angular speed multiplier  222  may be positioned, having an input rigidly connected to the lever element  221  and an output  232  rigidly connected to the toothed wheel  208 , for example by means of a shaft  233 . 
         [0000]    According to one embodiment the angular speed multiplier  222  is of the planetary gear type. According to one embodiment the movement means  202  are supported by a fixed, L-shaped support bracket  240  comprising an element substantially parallel to the rotation axis  201  and an element substantially orthogonal to such rotation axis  201 . 
         [0066]    According to one embodiment said nipper  103  comprises a coupling portion  104  comprising two pincers  105  projecting from a free end of the nipper  103 , said coupling pincers  105  being positioned substantially parallel to each other and defining between them a retention seat  113  suitable for receiving and snap engaging the mouth of a preform. 
         [0067]    According to one embodiment said retention seat  113  has 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 seat  133  by means of a relative drawing together of the nipper  13  and the preform and the release of the mouth by means of the relative translation away from each other of the nipper and the preform. 
         [0068]    According to one embodiment the pincers  105  of the nipper present at the front guide profiles inclined towards the inside of the retention seat  113 , suitable for facilitating the entrance of the mouth of the preform in the seat  113 . 
         [0069]    According to one embodiment the coupling portion  104  is made of an elastic material, for example but not necessarily in harmonic steel. 
         [0070]    According to one embodiment the coupling portion  104  is formed of a U-shaped plate having an aperture positioned in a radial direction outwards in relation to a rotation axis  2  of the stretch-blowing machine  1 . 
         [0071]    According to one embodiment said coupling portion  104  extends substantially according to a horizontal plane. 
         [0072]    According to one embodiment said nipper  103  comprises an elongated connection portion  114  positioned between said movement means  102  of the gripping nipper  112  and the coupling portion  104 , said elongated body extending, for example but not necessarily, in a radial direction opposite the rotation axis  2  of the rotary machine  1 . 
         [0073]    According to one embodiment said elongated connection body  114  is a flat shape and extends substantially along a horizontal plane. 
         [0074]    According to one embodiment said coupling portion  104  and said elongated connection body  114  extend along the same plane. 
         [0075]    According to one embodiment each moulding unit  10  comprises a mould  20  which can be opened having an inner cavity  24  suitable for receiving the preheated preform and permitting within it the expansion thereof by blowing inside the preform. Such cavity  24  may comprises a moulding surface  25  having a complementary shape to that of the bottle to be obtained. 
         [0076]    In one embodiment, the mould  20  comprises a universal seat  26  for removably housing a mould element  27  shaped so as to comprise said moulding surface  25 . 
         [0077]    In one embodiment, each said mould  20  comprises a first half-shell  21  and a second half-shell  22  hinged around a hinge axis  23  so 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-shells  21  and  22  form between them a through seat  156  which places the cavity  24  in 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 cavity  244 , to allow the introduction of pressurised air inside the preform through the mouth, to expand the preform  134  in the inner cavity  24  until it adheres to the moulding surface  25 , and impress upon the preform a shape complementary to that of the moulding surface  25 , complementary to that of the bottle to be obtained. 
         [0078]    In one embodiment, the moulding units comprise means of opening and closing the moulds  20 , wherein such means are synchronised with the movement means  102  of the nipper  103  so that during at least a part of the translation movement of the nipper  103 , 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. 
         [0079]    According to one embodiment the opening/closing means of the moulding unit  10  comprise a self-locking system suitable for keeping the half-shells pressed together in a closed position during the blowing operation. 
         [0080]    In the example of the blowing or stretch blowing machine  1  shown in the figures, the moulding units  10  are attached to a rotating platform  153  which rotates around the rotation axis  2  of the machine. 
         [0081]    The blowing or stretch-blowing machine may be coupled to a second rotating star  140  unloading the moulded bottles  141 , having a plurality of seats for said bottles. 
         [0082]    After the moulding operation, and after a rotation of the machine by a predetermined angle, the nipper  103  translates outwards to transfer the moulded bottle  141 , from the inside of the mould towards the bottle seat of the aforesaid second rotating star  140 . 
         [0083]    According to one possible embodiment, the moulding units  10  of the machine  1  are angularly equidistant from one another. 
         [0084]    According to one embodiment the seats  134  of the transferring star  130  are angularly equidistant from one another. 
         [0085]    According to one embodiment the seats for the bottles  141  of the second rotating star  140  are angularly equidistant from one another. 
         [0086]    According to one embodiment the rotation axis  135  of the transferring star  130  is placed at a distance from the rotation axis  2  of the machine, having a value greater than the sum of the radius R 1  of the second circumference and of the radius R 2  of the first circumference  155 , leaving a distance D between the first circumference  155  and the second circumference  136  the value of which is chosen so as to be able to obtain a transfer movement of the nipper  103  which is homokinetic at the pick-up point of the preform. 
         [0087]    According to one embodiment the handling system comprises transfer means of the preheated preforms from the preheating furnace  300  to the aforesaid transferring star  130  ( FIG. 14 ) 
         [0088]    The functioning of the handling system of objects between a transferring star  130  and a rotary machine  1  comprising a plurality of processing units  10 , is as follows. 
         [0089]    Each preheated preform  133  coming out of a preheating furnace  300  is taken to a seat for preforms of the transferring star  130 , which rotates around its axis  135 , for example in a clockwise direction in the direction of the arrow  132 . 
         [0090]    After a rotation of the transferring star according to a predetermined angle of rotation, the preform finds itself in a point of the second circumference  136  in 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 ). 
         [0091]    Starting from such point the nipper  103  begins its radial translation according to a rearward movement towards the machine axis  1 , simultaneously with the rotation of said machine. The section of curved trajectory  161  performed by the nipper  103  from the pick-up point  163  of the transferring star on the second circumference  136 , as far as the first circumference  155  ( FIG. 2 ) derives from the combination of such radial translation and the rotation movement of the machine. 
         [0092]    The passage of the preform, coupled to the nipper  103 , from the star to the stretch-blowing machine takes place homokinetically. 
         [0093]    When the preform is transferred by the nipper  103  inside the corresponding moulding unit  10  and the half-shells  21  and  22  are then closed, the preform begins its path along the first circumference  155  of the machine during which blowing is performed, as far as a predetermined angular position on the opposite side, wherein the half shells  21  and  22  open to allow the unloading of the moulded bottle  141 . Unloading takes place by means of a radial translation of the nipper  103  towards the outside of the machine as far as encountering a corresponding seat  144  for bottles made on the second rotating star  140 , which rotating transfers the bottle obtained  141  towards a collection zone, or towards a subsequent bottling station for example of liquids. 
         [0094]    A further purpose of the invention relates to equipment for blowing or stretch-blowing bottles in plastic material, comprising a furnace  300  for heating and dealing with the heat profile of the preforms  133 , a blowing or stretch-blowing machine  100 , comprising a plurality of processing units  10  as defined above, and movement means  130 ,  140  of the preforms going into and coming out of said furnace  300 , wherein said furnace  300  comprises means of transport  308  for the preforms and means of heating  309  the preforms, and wherein said movement means  130  for the preforms coming out of the furnace  300 , comprise a plurality of gripping means  134  for the preforms spaced apart at a fixed pitch, characterised in that said furnace  300  comprises movement and distancing means  344   b  of the heated preforms  133 , from a minimum pitch to a pitch substantially corresponding to the pitch of the gripping means  134  of the movement means  130  for the preforms coming out of the furnace  300 . 
         [0095]    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. 
         [0096]    This way a homokinetic transmission system of the preforms  133  is realised, from the furnace  300  to the single processing units  10  of the blowing or stretch blowing machine, minimising or substantially eliminating the accelerations to which said preforms are subject in the traditional machines. 
         [0097]    In one embodiment, said movement and distancing means  344   b  of the heated preforms  133  consist 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 means  130 . 
         [0098]    The advantages of this solution are various. 
         [0099]    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. 
         [0100]    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. 
         [0101]    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. 
         [0102]    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.

Technology Category: 7