Abstract:
A labeler for in-mold labeling of plastic bottles as well as to a labeling method for use of the labeler, including that a transfer star wheel and a transfer device of the labeler move the preforms and the labels in a transfer region towards one another in such a way that a respective label is only affixed to a circumferential subarea of a perform. In this manner, the label can be inserted in the blow mold in a particularly fast and reliable manner and excessive stretching of the label during blow molding can be avoided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of priority of German Application No. 102010001184.3, filed Jan. 25, 2010. The entire text of the priority application is incorporated herein by reference in its entirety. 
     FIELD OF THE DISCLOSURE 
     The disclosure relates to a labeler for in-mold labeling of plastic bottles as well as to a labeling method for use of the labeler. 
     BACKGROUND 
     As is generally known, plastic bottles can be already be labeled in the course of the production process through so-called in-mold labeling (IML) by introducing the labels in the blow mold before blow molding is executed. To this end, the label is positioned by means of grippers on the inner wall of the opened blow mold, as described in U.S. Pat. No. 6,649,119 B2, U.S. Pat. No. 5,266,149 A and WO 00 785 26 A1 for rotary blow molders. Transfer star wheels with grippers are, however, technically complicated. Non-rotating, clocked transfer systems do not achieve the manufacturing efficiency demanded. In addition, there is a need for a device that can easily be integrated in existing blow molder such that it takes up little space. 
     Hence, US 2002/0166833 A1 and DE 2135406 A suggest as an alternative that sleeve-shaped labels should be pushed onto or shrunk onto a preform, and DE 198 06 647 A1 additionally suggests that a flat label section should be applied to the preform by winding and transferred to a blow molding carousel via a transfer star wheel. In the case of these methods the label is, however, substantially stretched together with the preform and the suitability of these methods for lettered labels is therefore very limited. 
     Furthermore, EP 0098351 A2 and U.S. Pat. No. 4,708,630 A disclose blow molders in which flat labels are fixed, at the outlet of an extruder, to an unfinished bottle by pressing them onto the just extruded, still plastically deformable sleeve of the unfinished bottle. This method is, however, not suitable for use with preforms prefabricated by injection molding. 
     The introduction of self-gluing labels into the blow mold with the aid of a carrier strip conducted through or along the blow mold is known e.g. from CH 509864 A and DE 1479083 A; the labels can here be separated from the carrier strip by punching them out or by removing them at a peel-off edge. This solution, however, limits the design flexibility as regards mold construction and bottle design, it causes problems when the carrier strips are being exchanged, and it is inflexible and technically complicated, since separate supply units are required for the individual blow molds. 
     The labeling of bottles with the aid of print heads integrated in the blow molds is described e.g. in DE 1479322 A1, U.S. Pat. No. 2,601,700 A or U.S. Pat. No. 3,438,085 A. However, this solution is not suitable for all kinds of bottle designs either. It is also disadvantageous insofar as at least one print head is required for each blow mold, printing qualities and/or printing formats are restricted, and the dyes must be handled at the blow molder. 
     SUMMARY OF THE INVENTION 
     It is one aspect of the present disclosure to provide a device and a method for in-mold labeling of plastic bottles with high process reliability and a high throughput of bottles, without the above-mentioned drawbacks. 
     This aspect is achieved in that a transfer star wheel and a transfer device of the labeler move the preforms and the labels in a transfer region towards one another in such a way that a respective label is affixed to a circumferential subarea of a preform. 
     Due to the fact that both the transfer star wheel and the transfer device move the preforms and the labels towards one another, a complex movement can be carried out and a high throughput of bottles can be realized. The movement can be executed particularly fast and the transfer can be carried out with particular high reliability, since the label is only affixed to a circumferential subarea of the preform instead of being affixed to the whole circumference of the latter. In addition, excessive stretching of the label during blow molding is avoided in this way. 
     Preferably, the labeler additionally comprises a glue-application device for applying glue to a circumferential subarea of the preform and/or to a subarea of the label. It is thus possible to grade the adhesion effect in a particularly precise manner, so that the labels will be reliably introduced in the blow molds, where they can be correctly positioned or where they will migrate to the intended position on the bottle during blow molding. 
     According to a particularly advantageous embodiment of the labeler, the transfer star wheel comprises gripping arms, which move the preform in a direction perpendicular to its main axis towards the label so as to affix the label to the preform. It is thus possible to affix the label to the preform in a particularly controlled manner. 
     Preferably, the transfer device is configured such that it moves the label at least partially in a direction parallel to the main axis of the preform towards said preform so as to orient the label relative to the circumferential subarea of the preform before the label is affixed. Due to the fact that the transfer device executes a motion component parallel to the main axis, sleeve-shaped labels can be affixed in a particularly fast and reliable manner. 
     In the case of one embodiment, the transfer device rotates together with the transfer star wheel about a common axis. An additional star wheel acting as a transfer device is here not necessary. 
     In addition, the transfer device can be configured such that it moves the label at least partially in a direction perpendicular to the main axis of the preform towards said preform so as to affix the label to the preform. This allows a simpler structural design of the gripping mechanism of the transfer star wheel. 
     Preferably, the transfer device comprises a label holder supported on a lifting unit and provided with a fixing cage for sleeve-shaped labels. It is thus possible to affix the labels in a particularly reliable and reproducible manner. 
     According to one embodiment, the transfer device is a stationary dispenser for sleeve-shaped labels and is configured such that it shoots the label towards the preform so that the label will encompass the circumferential subarea at least partially. This variant is particularly space-saving and can easily be integrated in existing machines. 
     According to another embodiment, the transfer device is a rotatable cylinder with vacuum grippers or mechanical grippers. Making use of this rotatable cylinder, also planar labels can be affixed to the preform. 
     Preferably, the labeler additionally comprises a contact-pressure device for enlarging the adhesion area between the label and the preform. It is thus possible to increase the reliability of the glued joint. 
     The underlying technical problem is furthermore solved by a method for labeling plastic bottles, in particular in a rotary blow molder, making use of the labeler according to the present disclosure and comprising the following steps: affixing a label to a circumferential subarea of a preform; transferring the preform, equipped with the label, into a blow mold; and blow molding the preform, whereby the label will be applied to the bottle. 
     The affixing can be carried out rapidly and with high reliability, since the label is only affixed to a circumferential subarea of the preform. In addition, excessive stretching of the label during blow molding will be avoided in this way. 
     Preferably, the label is affixed with the aid of glue applied to a certain area or to certain areas of the preform and/or of the label. The adhesion effect can thus be graded in a particularly precise manner, so that the labels will be reliably introduced in the blow molds, where they can be correctly positioned or where they will migrate to the intended position on the bottle during blow molding. 
     According to another advantageous embodiment, the label is affixed by adhesion which is effective directly between the preform and the label. An additional application of glue will then not be necessary. 
     Preferably, the circumferential subarea of the preform encloses an angle of 180° at the most. It is thus possible that the label temporarily detaches itself from the preform during blow molding, so that it will migrate in the blow mold to the intended position. 
     According to a particularly advantageous embodiment of the method according to the present disclosure, the label is sleeve-shaped, and in step a): the preform is oriented relative to the label such that the main axis of the preform lies within the label; in step b): the label is moved at least partially parallel to the main axis of the preform so that, in the direction of the main axis, it will overlap with the circumferential subarea for affixing the label; and in step c): the preform and the label are moved towards one another perpendicular to the main axis, so that the label will be brought into contact with the preform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments are shown in the drawing, in which: 
         FIG. 1  shows a schematic top view of a first embodiment of the labeler; 
         FIG. 2  shows a lifting device with a label holder according to the first embodiment; 
         FIG. 3   a  show a schematic side view of a lifting device with a label holder according to and  3   b  a second embodiment; 
         FIG. 4  shows a schematic representation of the functional principle of a third embodiment; 
         FIG. 5  shows a schematic fragmentary view of a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As can be seen from  FIG. 1 , the first embodiment of the labeler  1  comprises a blow wheel  2  with a plurality of blown molds  3  for producing labeled bottles  5  or other plastic containers from preforms  7 . The latter are heated in an oven  9  in the manner known, whereupon a circumferential subarea  7   a  of said preforms  7  has tangentially applied thereto a glue  12  by means of a gluing roller  11  and the preforms  7  are taken over by a transfer star wheel  13 , pitch adaptation star wheel. On the circumference of said transfer star wheel  13  there are provided rotatably supported gripping arms  15 , which are variable in length and which are equipped with grippers  15   a  for the preforms  7 , as well as a first control cam  17  for controlling the gripping arms  15 , in particular for adjusting the radial position and the track speed of the gripping arms  15 . 
     In addition, there are provided at least one label dispenser  19 , such as a sleeving unit for wrap-around labels  21  or label sleeves  21 , and a preferably star-shaped transfer device  23  with label holders  25 , which are fixed to lifting units  24  and used for attaching the labels  21  to the preforms  7  in a transfer region  27 . The vertical position of the label holders  25  is determined by a second control cam  29 . 
     The lifting units  24  are secured in position on the transfer device  23 , e.g. via a clamping and guide unit  30  outlined in  FIG. 2 . The lifting movement is linear, i.e. the radial position (identified by arrow R in  FIG. 3 ) of the label holders  25  on the transfer device  23  remains substantially unchanged. The control cam  29  lowers the label holder  25  with the guide roller  26  before or below the label dispenser  19  and raises it below the gripping arm  15 . 
     The label holder  25  comprises an inner fixing cage  31  used for horizontally orienting the label  21  and consisting e.g. of pins that are axially adjustable on said holder  25  in elongated holes  33 ; in addition, the supporting surface  35  of the holder is preferably adapted to be vertically adjusted relative to the second control cam  29  and the guide roller  26 , e.g. by means of a pin  39  that can be fixed in position. This allows an adaptation of the label holder  25  to different label sizes. 
     The mode of operation of the labeler  1  when the label  21  is being attached to the preform  7  and when both said components are being transferred to the blow mold  3  in common, is exemplarily shown in  FIG. 1  on the basis of positions A to H of the gripping arms  15 : 
     At position A, the gripper  15   a  takes hold of a preform  7 , which has glue applied thereto on the circumferential subarea  7   a , at a section which is free of glue, e.g. at the mouth of the preform  7  above the glue  12 . 
     At positions B and C, the preform  7  is conducted to the transfer device  23 , so that, as indicated at position D, the preform  7  will be positioned above a label  21  which has been lowered following the control cam  29 . The rotary position of the preform  7  could here be additionally corrected so as to orient the glue-coated subarea  7   a  of the preform  7  relative to the label  21  and the gripping arm  15 , respectively. In the example shown this is, however, not necessary, since the glue-coated preform  7  has already been correctly oriented with respect to its rotary position in the gripper  15   a , viz. such that the glue-coated area  7   a  is directed towards the gripping arm  15  and the transfer star wheel  13 , respectively. 
     At position D, i.e. in the transfer region  27 , the grippers  15   a  substantially follow the track of the label holders  25  while the label holder  25  rises until the label  21  has been pushed over the preform  7  and the glue-coated area  7   a  is positioned fully within the label  21 . Simultaneously, and/or subsequently, the gripping arm  15  is pivoted and/or drawn back such that it presses the glue-coated area  7   a  against the label  21 , and thus attaches the label  21  to the preform  7 . In the example shown, the glue-coated area  7   a  faces the gripping arm  15  and the transfer star wheel  13 , respectively, so that the preform  7  is pressed against the label  21  primarily by drawing back the gripper  15   a . The pressing of the preform  7  against the label  21  can be supported by a stop, by temporarily pinching the label  21  between the stop and the preform  7 , said stop being is provided on the transfer star wheel  13  and being not shown in  FIG. 1  for the sake of clarity. 
     Depending on the position of the location of adhesion between the preform  7  and the label  21 , the gripping arm  15  may, however, also be moved in the opposite direction, i.e. away from the transfer star wheel  13  or substantially tangentially to the track of the label holders  25 , in that the gripper  15   a  follows the label holder  25 , at least in certain areas, with a higher or lower track speed until sufficient contact has been established between the preform  7  and the label  21 . 
     It follows that the gripping arm  15  executes in the transfer region  27  predominantly a movement in a direction perpendicular to the main axis  7   b  of the preform  7  shown in  FIG. 4 , whereas the transfer device  23  primarily has the function of moving the label  21  in a direction parallel to the main axis  7   b  towards the preform  7  so as to vertically orient the label  21  before it is affixed. The motion components to be executed can arbitrarily be distributed to the gripping arms  15  and the transfer device  23 , but in the interest of easy control it will be of advantage when the first control cam  17  controls the radial position and the track speed of the preforms  7  with the vertical position remaining constant and when the second control cam  29  controls the vertical position of the labels  21  with the track speed and the radial position remaining constant. 
     When the label  21  has been affixed to the preform  7 , the gripper  15   a  follows the circular track of the label holder  25  while the latter is lowered again, at least until the fixing cage  31  is positioned fully below the label  21 . As shown at position E, the gripping arm  15  can then be pivoted away from the track of the label holder  25 . 
     At positions F to H, the preform  7  and the label  21  are fed, in common, to an opened blow mold  3 , where the preform  7  is blow molded, possibly after having been stretched. 
     Positions I to K additionally indicate the blow molding of the bottle  5 ; during the blow molding process, the label  21  will migrate to the bottle location to be labeled due to stretching. The label  21  will preferably be configured such that its diameter is slightly smaller than that of the fully blown bottle  5 , so that the label  21  will closely fit to the bottle also at the location with the smallest bottle diameter or will be slightly stretched in diameter. It follows that it is primarily the elongation that holds the label  21  on the fully blown bottle  5 . 
     Depending on the speed with which the process take place, the deceleration of the label holder  25  during braking at the upper position of the lifting unit  24  may be so high that additional vertical fixing of the label  21  on the label holder  25  will be of advantage so as to prevent the label  21  e.g. from deforming or from becoming detached from the label holder  25  and being shot against the gripping arm  15 . Suitable means for such vertical fixing would e.g. be a hinged cover (not shown), which is swiveled in position only during lifting and deceleration, and which is provided with suitable openings for the preform  7  and the gripping arm  15 . 
     The glue  12  may e.g. be a temperature-sensitive or pressure-sensitive glue and it may be applied before, within or after the oven  9 . The glue is preferably applied directly at the discharge wheel  9   a  of the oven  9  by means of a special gluing roller  11  tangentially to the surface of the preform  7 , e.g. similar to the application of glue from the glue pallets of a conventional cold-glue unit, or in a contact-free manner by spraying on the glue in a clocked mode of operation. The amount of glue applied and the size of the glue-coated area  7   a  depend on the intended fit and on the nature of the label  21  used as well as on the preform  7 . 
     The glue-coated area comprises preferably a circumferential subarea  7   a  of the preform  7  of e.g. 180° at the most, in particular of 90° at the most, or, depending on the respective case of use, of only 45°, so that only a subarea  21   a  (cf.  FIG. 5 ) of the affixed label  21  will be in contact with the preform  7 . This has the effect that material will be saved and that the fit of the label  21  on the fully blown bottle  5  will be optimized. Depending on the nature of the label  21 , a deviating circumferential subarea  7   a  may, however, be of advantage as well. Alternatively, the label  21  may also be affixed to the preform  7  without making use of the glue  12 , e.g. by direct adhesion of the label  21  on the heated preform  7 . Label materials that are suitable for this purpose are e.g. PET and pre-stretched PP. 
     In the following, further embodiments of the present disclosure will be described; in so doing, features which the respective embodiments have in common and which have already been described hereinbefore will not be described once more. Likewise, individual features of the embodiments may be combined with one another. 
       FIGS. 3   a  and  3   b  show a second embodiment in which the transfer device  40  with the lifting device  41 , the label holder  25  and the second control cam  29  are arranged on the transfer star wheel  13 , in particular below the gripping arms  15 . In view of the fact that the transfer device  40  and the transfer star wheel  13  are coupled and rotate about the common axis  13   a , the separate transfer star wheel of the transfer device  23  according to the first embodiment is not required. The lifting device  41  is configured as a parallel lever, which is shown in  FIG. 3   a  at a lowered position below the label dispenser  19  and in  FIG. 3   b  at a raised position below the gripping arm  15  while the label  21  is being applied to the preform  7  by means of contact pressure. When the label holder  25  is raised by means of the second control cam  29 , the label  21  will simultaneously move radially inwards (identified by arrow R). This has the effect that the label holder  25  presses the label  21  with the aid of a stop  33  against the glue-coated area of the preform  7 , said area facing here away from the transfer star wheel  13 . 
       FIG. 4  shows, at three successive moments in time T 1  to T 3 , a gripper  15   a  and a label dispenser  19  of a third embodiment, in which the transfer device  42  for the labels  21  is arranged in a stationary manner on the label dispenser  19  or integrated in a label dispenser  19 , e.g. in a sleeving unit. The transfer device  42  comprises e.g. a friction wheel drive for the labels  21 . Also in this case, the additional transfer star wheel of the transfer device  23  shown in  FIG. 1  can be dispensed with. Instead, the transfer device  42  is arranged below the track of the glue-coated preforms  7  held by the grippers  15   a . The transfer device  42  is configured such that it shoots the label  21  upwards at a moment in time T 1  at which the preform  7  is located above the label sleeve  21 . The moment in time T 1  and the speed of the label  21  are coordinated with the movement of the preform  7  (cf. the horizontal arrows) such that the label sleeve  21  will slip over the preform  7  (cf. T 2 ) and encompass the glue-coated label area at the moment in time T 3 . Due to the relative movement between the gripper  15   a  and the label dispenser  19  as well as due to the inertia of the label  21 , the latter is pressed against the glue  12  and affixed to the preform  7  in this way. If necessary, the strength and the area of the glued joint can be increased still further by subsequently blowing air onto the label or by applying brushes thereto (not shown). 
     This embodiment takes up particularly little space. The components required can, moreover, be easily retrofitted. 
       FIG. 5  shows a fourth embodiment in the case of which planar labels  21 , instead of label sleeves, are affixed to the preform  7  by means of the transfer device  44 . In contrast to the preceding embodiments, the label  21  is here preferably coated with the glue  12  in a certain area or in certain areas thereof. The label  21  is removed from a magazine (not shown) by means of a palette  45  of a conventional glue pallet carousel and transferred to a turning and transfer device  47 , e.g. to a conventional cylinder with vacuum grippers or mechanical grippers. The turning and transfer device  47  conducts the labels  21  tangentially along the transfer star wheel  13  and the gripping arms  15  (not shown) press a respective preform  7  against a glue-coated area  21   a  of the label  21 , thus affixing the labels  21  to the preforms  7 . If necessary, the strength and the area of the glued joint can be increased still further by means of a contact-pressure device  49 , e.g. by blowing air onto the label or by applying brushes thereto. 
     Alternatively, it is also possible to use self-gluing labels  21  stored on a wound carrier strip (not shown). Preferably, the self-gluing labels  21  have slue applied thereto only in a subarea  21   a . Instead of making use of a glue pallet carousel and of the turning device  47 , the labels  21  are pulled with the carrier strip across a peel-off edge in the manner known and are thus separated from the carrier strip; subsequently, the glue-coated subareas  21   a  are pressed against a respective preform  7 , which has the effect that the labels  21  will be affixed to the preform  7 . For improved fixing, also the self-gluing label  21  can then be pressed against the preform  7  over a larger area by blowing air onto the label or by applying brushes thereto. It is thus possible to introduce also planar labels  21  together with the preform  7  into the blow mold  3 .