Abstract:
Blow mold for producing plastic containers, having a base body in the interior of which a body of the container to be produced can be accommodated and the inside wall of which completely surrounds the container that is to be produced, such that the blow mold has a ring for supporting a neck of the container with respect to the blow mold, along with a spacer device protruding inward with respect to the circumferential edge of the ring, for preventing the body of the container from coming in contact with the inside wall of the blow mold in the event of tilting of the container with respect to the blow mold.

Description:
The present application claims the benefit of priority of German Patent Application No. 20 2007 002 873.3, filed on Feb. 27, 2007. The entire text of the priority application is incorporated herein by reference in its entirety. 
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to a blow mold for the production of plastic containers, such as used in beverage bottling operations. 
     BACKGROUND 
     In the area of the beverage industry in particular, plastic bottles have for a long time been used in addition to glass bottles for bottled beverages. In the production of these plastic bottles, a plastic blank, also called a parison or preform, may be heated, placed in a blow mold and then blow molded to its final size. This is usually done by using blow molds, which are closed around the outside of the blank to be blow molded, and then compressed air is injected through the opening in the mold. 
     The mouthpiece of the future bottle is already completed on the parison and is not processed further. For the actual blowing operation, a circumferential edge or collar of the parison rests on a circumferential edge of the blow mold, thus preventing the parison from collapsing into the interior of the blow mold. 
     In other words, as soon as the blow mold is closed, the parison, i.e., the so-called perform, lies directly on a plane of the blow mold and/or a ring, which is also referred to as the neck plate, before the stretch blow molding operation. 
     A spring-loaded grip is generally used for feeding the parison into the blow mold. Following this, the mold is closed and then the spring-loaded grip is tightened. In this stage of production, the preform may become tilted slightly in the blow mold because a mold gap must be maintained between the preform and the blow mold at this point. This mold gap is necessary to ensure clean closing of the blow mold. The size of this gap between the preform and the blow mold is usually between 0.25 mm and 0.4 mm. 
     When there are large mold gaps in particular, it may happen that a one-sided contact with the inside wall of the blow mold occurs with the above-mentioned slight tilting of the preform when the grip is removed. At this contact point, the hot preform cools slightly, but after the blow molding operation, this contact may result in the bottle having a one-sided accumulation of material, which is also known as a quenching lens, beneath the supporting ring. 
     Therefore, the object of the present disclosure is to rule out or at least reduce the risk of development of such a quenching lens. The inventive blow mold for producing plastic containers has a base body, which is preferably closable; the body of the container to be produced can be held in the interior of this base body; the inside wall of this base body, in particular in the closed state, completely surrounds the body of the container to be held. The blow mold here has a circumferential edge for supporting the neck of the container with respect to the blow mold. 
     According to the present disclosure, a spacer device that protrudes toward the inside with respect to the blow mold and/or the circumferential edge is provided on the circumferential edge, preventing the body of the container from coming in contact with the inside wall of the blow mold in the event the container becomes tilted with respect to the blow mold. 
     The circumferential edge of the blow mold may be designed in one piece with the blow mold but the circumferential edge is preferably part of a ring on which the bottle, i.e., the preform, rests during the blowing operation. More precisely, the collar or a circumferential edge of the bottle rests on this circumferential edge. Support of the container with respect to the blow mold is understood in particular to refer to the fact that before the blowing operation, the container and the blow mold are in contact only at said collar of the container and preferably there are no other points of contact between the container and the inside wall of the blow mold. 
     The spacer device is preferably designed in one piece with the ring and protrudes inward with respect to an opening formed by the ring. 
     The spacer device is preferably designed in the form of a ring, such that it completely surrounds a section of the container. This ring-shaped spacer device is designed especially preferably in one piece with the ring. In addition, however, it would also be conceivable for the spacer device to have a plurality of protrusions extending radially inward with respect to the blow mold and/or the ring and extending in the direction of the longitudinal axis of the container. The diameter of the opening formed by the ring is thus reduced by the spacer device. 
     The spacer device is preferably flush with the circumferential edge upwardly. This means that the spacer device protrudes up out of the circumferential edge and/or the ring and thus the collar of the container with its underside do not come in contact with this spacer device at all or do not come in contact with it exclusively. In addition, the spacer device in this embodiment is connected directly to the circumferential edge toward the bottom. This will be explained in greater detail below with reference to the figures. 
     In another embodiment, the spacer device has a rectangular cross section in its circumferential direction. Although, as mentioned above, the spacer device is designed as a ring, this ring in turn has said rectangular cross-section in its circumferential direction. In particular, the transition between the spacer device and the centering ring and/or the blow mold is selected to be sharp-edged and without a burr. 
     The spacer device  10  preferably has a length of between 0.5 mm and 8 mm, preferably between 1 mm and 4 mm and more preferably between 1.5 mm and 3 mm in the longitudinal direction of the container  4 . A length in the range of 2 mm has proven to be especially advantageous to prevent tilting of the container and thus the quenching lenses mentioned above, while on the other hand not having an excessively negative effect on the container production process. In other words, by narrowing this area beneath the collar of the container, the tilt angle is reduced. In addition, this also achieves the result that the mold contact occurs in the (immediate) vicinity of the supporting ring and/or the area in which the collar of the container is supported. This is not problematical because the plastic material is still cold in these areas and thus not participate in the stretch blow molding operation. 
     The disclosure narrowing of the area beneath the collar and/or the spacer device is advantageous in particular with such blow molds that produce a steep bottleneck such as that on a contoured bottle, for example. 
     Both the circumferential edge and the spacer device on the ring mentioned above are thus advantageously arranged there. 
     The present disclosure is also directed at a ring for a blow mold of the type described above such that this ring has a planar circumferential edge on which may be supported a collar of a container that is to be processed and in particular is to be blow molded. 
     In addition, a cylindrical section is provided, extending essentially perpendicular to the plane of the circumferential edge. A spacer device extending radially inward with regard to this cylindrical section is provided on this cylindrical section according to this disclosure. This spacer device preferably has a circular cross section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other advantages and embodiments are derived from the accompanying drawings, in which: 
         FIGS. 1   a - 1   c  show three diagrams to illustrate the disclosed idea; 
         FIG. 2   a  shows a first view of a container to be produced; 
         FIG. 2   b  shows a top view of the container from  FIG. 2   a  along lines A-A from  FIG. 2   a;    
         FIG. 2   c  shows a top view of an upper area of the container from  FIG. 2   a;    
         FIG. 2   d  shows a detailed view of the detail C from  FIG. 2   a;    
         FIG. 3   a  shows a top view of an disclosed ring half; 
         FIG. 3   b  shows an inclined view of the ring half from  FIG. 3   a;    
         FIG. 3   c  shows a side view of the ring half from  FIG. 3   a ; and 
         FIG. 3   d  shows a detailed view of the detail A from  FIG. 3   c.    
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1   a  shows a part of a container  4  in a blow mold  1  according to the state of the art. Of the container, only a collar  7  and a short section of the bottleneck and/or neck area  12  of the container  4  are shown here. Above the collar  7  there is a bottle thread (not shown) and beneath the neck area  12  is the belly (not shown) of the bottle. Likewise, only a portion of the blow mold  1  according to the state of the art is shown here. As shown in  FIG. 1   a , there is a relatively great play between the container  4  and/or the neck area  12  of the container  4  and the neck  1   a  of the blow mold  1 . If the tilting of the container  4  with respect to the blow mold  1  as shown in  FIG. 1   a  occurs now, one-sided contact may occur between the container  4  and the blow mold  1 , or more precisely, between the neck area  1   a  of the blow mold  1  and the neck area  12  of the container  4 . This is illustrated by reference numeral I. 
     Since the blow mold  1  and/or its inside wall  5  is cooler in comparison with the container  4 , the container  4  cools in the area labeled as  1 . As a result, the container  4  has a one-sided accumulation of material (quenching lens) beneath the collar  7  after the stretch blow molding operation. 
       FIG. 1   b  shows schematically a disclosed blow mold  1 . This disclosed blow mold  1  additionally has a spacer device  10 . This spacer device  10  reduces the mold gap between the container  4  and the blow mold  1  and/or the neck area  12  of the container  4  and the neck area  1   a  of the blow mold  1 . In the case of tilting of the container  4  with respect to the blow mold  1 , the spacer device  10  prevents the container  4  from coming in contact with the blow mold  1 , as shown in  FIG. 1   c . In this case, there is contact between the spacer device  10  and the area of the container  4  directly beneath the collar  7 , as illustrated by the two circles K 1  and K 2 . However, this contact is not problematical because the plastic material is relatively cold in this area and participates very little or not at all in the stretch blow molding operation. It should be noted here that the heating of the container  4  is ideally limited to the area beneath the collar  7  and the preform already has its final shape in the area above the collar  7  even before the stretch blow molding operation. Thus, on the whole, a narrowing beneath the collar  7  and/or the ring of the blow mold  1 , which is not shown in detail in  FIG. 1   c , is proposed. The development of the quenching lens described above can thus be prevented through the narrowing according to the present disclosure. The spacer device  10  preferably has a length of between 0.5 mm and 8 mm, preferably between 1 mm and 4 mm and more preferably between 1.5 mm and 3 mm in the longitudinal direction of the container  4 . 
       FIG. 2   a  shows an example of a plastic container  4  that is to be blow molded. This plastic container  4  has the collar  7 , which was already shown in  FIGS. 1   a  and  1   c  and is supported with respect to the blow mold  1 . Directly beneath the collar  7 , the neck area  12  is provided, opening into a body  11  of the container  4  via an inclined area. Reference numeral  13  refers to the bottom of the container  4  and reference numeral  8  refers to the thread.  FIG. 2   b  shows a top view of the conditions from  FIG. 2   a  along line A-A from  FIG. 2   a . It can be seen here that in this case, the container  4  has a rectangular shape with rounded corners, but the present disclosure is not limited to this cross section. Reference notation L denotes the longitudinal direction of the container. 
       FIG. 2   c  shows a partial view of a finished container  4 , which was produced using a blow mold  1  according to the present disclosure. 
       FIG. 2   d  shows a detailed diagram of the area C from  FIG. 2   a . It can be seen here that a radially constricted area  12   a  of the neck area  12  is formed by the spacer device  10 . In addition, there is an area  12   b  that is unchanged radially. The radial distance R between the areas  12   a  and  12   b  results from the radial width of the spacer device  10 , as will be shown below. 
       FIG. 3   a  shows one half of a disclosed ring  3  which is arranged on the upper end of the blow mold  1 , which is shown only schematically in  FIGS. 1   a  through  1   c . This ring  3  may be screwed onto the blow mold  1 . To this end the ring  3  has boreholes  16 . The ring  3  may therefore be separated from the respective blow mold and replaced by another ring  3  having different diameters, for example. 
     The reference numeral  18  refers to a circumferential edge of the ring  3 , on which the collar  7  of the container  4  is supported (see  FIGS. 2   a - 2   c ). Reference numeral  10  denotes the spacer device. Reference numeral  14  refers to an area that is elevated with respect the plane E of the ring  3 . The elevated area  14  serves to create a cylindrical section  15 , which is shown in  FIG. 3   b  and is connected directly to the spacer device  10 . 
     The ring  3  may be manufactured as a one-piece part. With the rings  3  known from the state of the art, only the cylindrical section  15 , which is arranged at a right angle to the plane E, as mentioned above, is connected to the circumferential edge  18 . The disclosed spacer device  10  is arranged in the upper area, i.e., in the area of the cylindrical section  15  facing the collar  7  of the container  4 . This spacer device  10  does not prevent the blow mold  1  from closing. 
       FIG. 3   c  shows a side view of a disclosed ring  3 . Here again, the elevated area  14  which is supported opposite the plane E and/or the base of the ring  3  can be seen. Likewise, the cylindrical section  15  in which the area  12  of the container is located during the stretch blow molding operation can also be seen. It can be seen here that the height h 1  of the spacer device is less than the height h 2  of the cylindrical section below it. The height h 1  is in the range between 1 mm and 3 mm and preferably between 1.5 mm and 2.5 mm. 
       FIG. 3   d  shows a detailed diagram of area A from  FIG. 3   c . Reference notation D refers to the distance from the wall  10   a  of the spacer device  10  to the wall  15   a  of the cylindrical section. The distance D is in a range between 0.2 mm and 1.2 mm, preferably between 0.4 mm and 1 mm and especially preferably in the range of 0.8 mm. 
     As stated above, this distance D leads to the radial distance R in  FIG. 2 . This choice of the area has proven to be especially favorable for preventing the development of the aforementioned quenching lenses on the one hand, while on the other hand not excessively interfering with the production of the container  4 . As shown in  FIG. 3   d  in particular, the transition between the spacer device  10  and the cylindrical section  15  is sharp-edged and is preferably also free of burrs. Due to this sharp-edged transition, the onset of the aforementioned tilting of the container  4  with respect to the blow mold  1  can be prevented in an especially advantageous manner. 
     The radius of curvature Kr is in the range between 0.2 mm and 0.4 mm and preferably in a range between 0.25 mm and 0.35 mm. It should be pointed out that the precise dimensions of the spacer device  10  and/or of the cylindrical section  15  have been determined as a result of extensive experiments and tests, and additional process parameters such as the temperature of the container  4  in particular had to be taken into account. 
     All the features disclosed in the patent application documents are herewith claimed as essential to the disclosure if they are novel in comparison with the prior art when used individually or in combination.