Abstract:
A blow-molded container includes an opening section that can be closed, a side wall, and a closed bottom. The material in the region of the side wall is shaped by blow forming an injection-molded preform. At least three recessed grips are arranged along an outer perimeter of the container. At least two longitudinal ribs oriented in a longitudinal direction of the container are arranged between each pair of recessed grips. The longitudinal ribs are separated from each other by a recess, which also extends in a longitudinal direction. At least one circumferential rib, which extends in a circumferential direction of the container, is arranged inside each of the recessed grips.

Description:
The present application is a 371 of International application PCT/DE2011/001537, filed Jul. 26, 2011, which claims priority of DE 10 2010 033 377.8, filed Jul. 29, 2010, the priority of these applications is hereby claimed and these applications are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention concerns a method for producing a blow-molded container with a closable mouth section, a side wall, and a closed base. 
     The invention also concerns a blow-molded container with a closable mouth section, a side wall, and a closed base. 
     In container molding by the action of blowing pressure, preforms made of a thermoplastic material, for example, preforms made of PET (polyethylene terephthalate), are fed to different processing stations within a blow-molding machine. A blow-molding machine of this type typically has a heating system and a blowing system, in which the preform, which has first been brought to a desired temperature, is expanded by biaxial orientation to form a container. The expansion is effected by means of compressed air, which is fed into the preform to be expanded. DE-OS 43 40 291 explains the process-engineering sequence in this type of expansion of the preform. The aforementioned introduction of the pressurized gas comprises both the introduction of compressed gas into the developing container bubble and the introduction of compressed gas into the preform at the beginning of the blowing process. 
     The basic structure of a blowing station for container molding is described in DE-OS 42 12 583. Possible means of bringing the preforms to the desired temperature are explained in DE-OS 23 52 926. 
     Various handling devices can be used to convey the preforms and the blow-molded containers within the blow-molding machine. The use of transport mandrels, onto which the preforms are slipped, has proven especially effective. However, the preforms can also be handled with other supporting devices. Other available designs are grippers for handling the preforms and expanding mandrels, which can be inserted in the mouth region of the preform to support the preform. 
     The handling of containers with the use of transfer wheels is described, for example, in DE-OS 199 06 438 with the transfer wheel arranged between a blowing wheel and a delivery line. 
     The above-explained handling of the preforms occurs, for one thing, in so-called two-step processes, in which the preforms are first produced by injection molding and temporarily stored and then later conditioned with respect to their temperature and blown into containers. For another, the preforms can be handled in so-called one-step processes, in which the preforms are first produced by injection molding and allowed to solidify sufficiently and are then immediately suitably conditioned with respect to their temperature and then blow molded. 
     With respect to the blowing stations that are used, various embodiments are known. In the case of blowing stations that are arranged on rotating transport wheels, book-like opening of the mold supports is often encountered. However, it is also possible to use mold supports that can be moved relative to each other or that are supported in a different way. In stationary blowing stations, which are suitable especially for accommodating several cavities for container molding, plates arranged parallel to one another are typically used as mold supports. 
     Before a heating operation is carried out, the preforms are typically slipped onto transport mandrels, which either convey the preforms through the entire blow-molding machine or merely revolve within the heating system. In the case of vertical heating of the preforms in such a way that the mouths of the preforms are oriented vertically downward, the preforms are usually placed on a sleeve-like mounting element of the transport mandrel. In the case of suspended heating of the preforms, in which the mouths of the preforms are oriented vertically upward, expanding mandrels are usually inserted into the mouths of the preforms to clamp them tightly. 
     Blow-molded containers of this type are used in a great variety of designs for the packaging of products. In particular, containers of this type are filled with carbonated and noncarbonated beverages. 
     An important cost factor in the manufacture of these containers is the weight of the material that is used. For one thing, the material is relatively expensive and, for another, it is necessary to heat the material before the blow molding is carried out, and this requires considerable energy input. Accordingly, there is an ongoing effort to reduce the amount of material used and to form the blow-molded containers with walls as thin as possible. 
     Of course, reduction of wall thickness also leads to reduced stability of the containers. Therefore, the side walls of the container are provided with special ribbing. Efforts are also made to reduce the wall thickness in the area of the base of the container. 
     It is typically necessary to satisfy a number of requirements in the area of the side walls. On the one hand, the container needs sufficient stability in the longitudinal direction to enable it to absorb force loads during filling. On the other hand, consumers demand recessed grips to allow more secure gripping and handling of the bottle. However, these recessed grips reduce stability. 
     SUMMARY OF THE INVENTION 
     Therefore, the objective of the present invention is to improve a method of the aforementioned type in such a way that the stability of the side walls of the containers is improved. 
     In accordance with the invention, this objective is achieved by subjecting an injection-molded preform to a heat treatment and molding it into a container by a blowing process in such a way that the material in the area of the side wall is molded by the blow-molding process in such a way that at least three recessed grips are arranged along the outer periphery of the container, between each pair of which are arranged at least two longitudinal ribs oriented in the longitudinal direction of the container, which are separated from each other by a recess that also extends in the longitudinal direction, and that at least one peripheral rib, which extends in the peripheral direction of the container, is located within each of the recessed grips. 
     A further objective of the present invention is to design a container of the aforementioned type in such a way that improved stability properties are obtained. 
     In accordance with the invention, this objective is achieved by virtue of the fact that the material in the area of the side wall is molded in such a way by blow molding an injection-molded preform that at least three recessed grips are arranged along the outer periphery of the container, between each pair of which are arranged at least two longitudinal ribs oriented in the longitudinal direction of the container, which are separated from each other by a recess that also extends in the longitudinal direction, and that at least one peripheral rib, which extends in the peripheral direction of the container, is located within each of the recessed grips. 
     The arrangement of at least three recessed grips along the outer periphery of the container helps with reliable manual grasping of the container in any position of the container relative to a user. The arrangement of the longitudinal ribs between the recessed grips stabilizes the container in the longitudinal direction. The distribution to at least two longitudinal ribs separated by a recess further improves the stability of the container. The arrangement of the longitudinal ribs inside the recessed grips stabilizes the container with respect to manual deformation when grasped by a user. Furthermore, contour stability in storage is promoted. 
     Increased stability when the container is grasped is achieved if at least three peripheral ribs extend peripherally within the recessed grip, at least one of which is arranged at a different level in the radial direction of the container than at least one of the other peripheral ribs. 
     Increased stability when the container is grasped is achieved if three peripheral ribs are arranged one above the other in the area of a radially inner base of the recessed grip. 
     A further increase in the stability of the container under mechanical load can be achieved if, in the longitudinal direction of the container, the base of the recessed grip makes a transition into the area of the side wall of the container both vertically upward and vertically downward by means of at least two stepped peripheral ribs. 
     A good compromise between moldability by blow-molding technology and high stability is achieved if the recess separating the longitudinal ribs from each other is provided with a depth in the radial direction of the container which is at most 50% of the height of the longitudinal ribs in the radial direction of the container. 
     A good functional design is obtained if the vertical cross-sectional area of the recessed grip has a trapezoidal contour. 
     High stability to forces acting from the outside is achieved if, in a vertical cross-sectional area, at least one of the peripheral ribs is defined, at least sectionally, by a circular segment and curves radially outward. 
     Mutual support of the peripheral ribs is achieved if at least two adjacent peripheral ribs are molded with an angular transition relative to each other. 
     Specific embodiments of the invention are schematically illustrated in the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a schematic drawing of a blow-molded container with recessed grips. 
         FIG. 2  is a perspective view of the container of  FIG. 1 . 
         FIG. 3  is a cross section along sectional line III-III in  FIG. 1 . 
         FIG. 4  is a cross section along sectional line IV-IV in  FIG. 1 . 
         FIG. 5  is a cross section corresponding to  FIG. 4  with additional dimensioning examples incorporated. 
         FIG. 6  is a side view of two recessed grips. 
         FIG. 7  is a partial view of an enlarged longitudinal section. 
         FIG. 8  is a view similar to  FIG. 6  but from a different viewing direction. 
         FIG. 9  is a cross section along sectional line IX-IX in  FIG. 8 . 
         FIG. 10  is a view similar to  FIG. 8  but with dimensional specifications. 
         FIG. 11  is a schematic representation illustrating the geometry of a recessed grip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a blow-molded container  1  with a mouth section  2 , side walls  3 , and a base  4 . The mouth section  2  has an external thread  5  and is separated from the side walls  3  by a support ring  6 . 
     The base  4  is provided with several base supports  7  separated by spaces  8 . The container  1  extends along a longitudinal axis  9 . 
     Several recessed grips  10  are arranged along the outer circumference of the container  1 . In particular, the use of at least three recessed grips  10  is proposed. The specific embodiment in  FIG. 1  shows the use of five recessed grips  10 . In the embodiment illustrated in  FIG. 1 , the recessed grips  10  are arranged in a middle section of the container  1  with respect to the direction of the longitudinal axis  9 . The region of the container  1  located vertically above the recessed grips  10  is provided with peripheral ribs  11 . The region of the container  1  located vertically below the recessed grips  10  is likewise provided with peripheral ribs  12 . The ribs  11 ,  12  are typically realized as groove-like depressions extending in the direction of the interior of the container  1 . However, they can also take the form of ring-shaped outward projections. Moreover, it is possible to use not only peripheral ribs  11 ,  12  that extend completely around the container  1  but also peripheral ribs  11 ,  12  that are segmented. 
     Longitudinal ribs  13  are arranged between the recessed grips  10 . In the specific embodiment in  FIG. 1 , two longitudinal ribs  13  are arranged side by side between each pair of recessed grips  10 . These two longitudinal ribs  13  are separated by a recess  14 . At least one peripheral rib  15  is arranged inside each recessed grip  10 .  FIG. 1  shows the use of five peripheral ribs  15  in each of the recessed grips  10 . The perspective view in  FIG. 2  again illustrates the design of the container  1  according to  FIG. 1 . This view clearly shows the arrangement of the peripheral ribs  15  inside the recessed grips  10  and the comparatively flat design of the outside surface of the longitudinal ribs  13 . The horizontal cross section in  FIG. 3  illustrates the depth of the ribs  12 . In particular, the drawing shows that small-dimensioned outward projections  16  are present within the ribs  12 . These outward projections  16  increase the stability of the container  1  and to a viewer have the appearance of drops. The horizontal cross section in  FIG. 4  shows especially the depth of the recessed grips  10 . 
     For a volume of the container  1  of, for example, about 1.5 liters, its weight is about 18 grams. For a container  1  of about this size, a diameter  17  in  FIG. 3  is about 82.8 millimeters, and a diameter  18  in  FIG. 4  is about 76.3 millimeters. 
     In regard to the container  1  in  FIG. 1 , which is designed as a bottle, its length in the direction of the longitudinal axis  9  is about 309 millimeters. The upper ribs  11  extend over a length of about 60 millimeters.  FIG. 1  shows the use of five ribs  11 . The lower ribs  12  extend over a length of about 80 millimeters. The embodiment in  FIG. 1  illustrates the use of six ribs  12 . 
       FIG. 5  illustrates a horizontal section corresponding to  FIG. 4  with additional dimensioning drawn in. The diameter  18  is about 85% of the outside diameter  19 . The diameter  18  is typically about 75% to 95% of the outside diameter  19 . 
     The combination of the longitudinal ribs  13  and the recess  14  extends about 20 millimeters in the peripheral direction of the container  1 . The width  20  of the combination is typically about 15-25 millimeters. In a direction that runs parallel to the radial direction of the container  1 , a maximum extent of the longitudinal ribs  13  is about one fourth of the difference between the diameters  17  and  18 . The values are in the range of 0.05 to 0.5 multiplied by the difference between the diameters  17  and  18 . 
     A depth  22  of the recess  14  measured from a maximum extent of the longitudinal ribs  13  is about 2.5 mm. A typical range is 0.5 to 5.0 millimeters. 
     The longitudinal ribs  13  have, at least sectionally, a cross sectional area similar to a segment of a circular surface. A diameter  23  of this circle is about 55% of the width  20 . A range of 40% to 70% of the width  20  is typical for the diameter  23 . 
       FIG. 6  illustrates examples of other possible dimensioning. The height  24  of the recessed grips  10  is about 24 millimeters. The value for the height  24  is typically in the range of 5 to 32 millimeters. 
     The width  25  of the recess  14  is about 2 millimeters. The value for the width  25  is typically in the range of 1 to 8 millimeters. 
     The distance  26  between the apex lines  27  of the longitudinal ribs  13  is about 8 millimeters. The value for this distance  26  is typically in the range of 6 to 12 millimeters. The apex lines  27  define the maximum radially outward extent of the longitudinal ribs  13 . 
     The outside height  28  of the recessed grips  10  is about 5.3 times the distance  21  shown in  FIG. 5 . 
       FIG. 7  is another schematic cross section that shows the rib-shaped contour of the recessed grips  10 . The vertical section shown in  FIG. 7  reveals the cross-sectional area of the recessed grips  10 . Peripheral ribs  15  arranged at the bottom of the recessed grips  10  have a height  29  of about 1 to 2 millimeters. A height  29  of about 1 millimeter is preferred. The radius of curvature  30  of these peripheral ribs  15  is about 4 millimeters. A typical value for the radius  30  is in the range of 3-5 millimeters. The specific embodiment shown in  FIG. 7  has three peripheral ribs  15  arranged side by side at the bottom of the recessed grip  10  with their vertices arranged in a common plane. 
     The drawing in  FIG. 8  shows essentially the same region of the container  1  as the drawing in  FIG. 6  but with the container  1  rotated about the longitudinal axis into a slightly different position. 
       FIG. 9  shows a horizontal section similar to  FIG. 4  but with additional dimensioning specifications. It shows a specific case of the general dimensions of  FIG. 5 . In this specific case, the diameter  18  is about 76.3 millimeters, the width  20  is about 19.8 millimeters, the dimension  21  is about 6.13 millimeters, the depth  22  is about 0.66 millimeters, and the diameter  23  is about 11 millimeters. 
       FIG. 10  is basically the same as  FIG. 6  with the following actual dimensioning specifications as examples. The height  24  is about 24.8 millimeters, the width  25  about 2.85 millimeters, the distance  26  about 8.0 millimeters, and the outside height  28  about 32.3 millimeters. Also indicated in the drawing with respect to the combination of two longitudinal ribs  13  and the recess  14  are an outside width  31  of about 19.4 millimeters and an inside width  32  of about 17.9 millimeters. 
       FIG. 11  is a highly schematic drawing showing the recessed grip  10  without any actual representation of the peripheral ribs  15  and longitudinal ribs  13 . In this drawing the recessed grip  10  has a trapezoidal cross-sectional area. 
       FIG. 11  again shows the diameters with reference numbers  18  and  19 . A transition radius  33  between the base of the recessed grip  10  and the oblique side walls of the recessed grip  10  is about 1-5 millimeters. A value of about 1 millimeter is preferred. A radius  34  in the transition zone between the oblique side walls of the recessed grip  10  and the vertical region of the wall of the container  1  is about 6 millimeters. A value in the range of 2-15 millimeters can be used for the radius  34 . 
     A base height  35  of the base of the recessed grip  10  is about 15 millimeters. A value in the range of 10-25 millimeters can be used for the base height  35 . An angle  36  between the vertical course of the side wall of the container  1  and the oblique side wall of the recessed grip  10  is about 35 degrees. A value in the range of 25-45 degrees can be used for the angle  36 .