Abstract:
The present invention relates to a process and equipment for the fabrication of glass containers with internally threaded neck and such containers. The plunger ( 6 ) is from the glass leaving an imprint corresponding to the mouth (M) of a bottle, wherein the plunger has at least one helical groove ( 15 ) in its outside surface. During the extraction, the plunger is rotated around a longitudinal axis (X-X) performing a roto-translational motion to unscrew the plunger out of the partially solidified glass, leaving an internal thread in the mouth (M) of the bottle. The roto-translational motion for the extraction of the plunger is generated by: a linear actuator ( 30 ) acting on the plunger ( 6 ), thereby effecting a linear movement of the plunger ( 6 ) along said longitudinal axis (X-X), a guide body ( 14 ) wherein the plunger ( 6 ) is moved relative to the guide body ( 14 ) along said longitudinal axis (X-X), and a helical guide ( 16, 17 ) coaxial to the longitudinal axis (X-X) and being provided between said guide body ( 14 ) and said plunger ( 6 ) and transforming said linear movement effected by said linear actuator ( 30 ) on said plunger ( 6 ) into said roto-translational motion of said plunger ( 6 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a process and equipment for the fabrication of glass containers, particularly bottles, provided with an internally threaded neck and to such a glass container. In particular, the present invention relates to a process and equipment suitable for making wine or spirit bottles with a thread located on an internal surface of the neck of the container and suitable for reversible engaging/disengaging a compressible stopper by screwing/unscrewing. 
     BACKGROUND AND SUMMARY OF THE DISCLOSURE 
     It is known for many decades to plug wine and spirit bottles by means of a cylindrical cork stopper which is pressed in the neck of the bottle with a certain compression rate. Although this technique has been used exclusively for a very long time, in recent years the cork stopper was called into question again for various reasons linked mainly to the cost and the quality of the stored wine, in particular the development of the so-called “cork” taste. 
     Compressible stoppers made of synthetic material were developed as replacements for wine bottle cork stoppers and are being used more and more. These compressible synthetic stoppers are considered neutral relative to the bottled wine, and their cost is easier kept under control than that of cork stoppers. However, they have the disadvantage of having low or no recyclability and are not always being easy to extract. These synthetic stoppers also may evoke an image with consumers of industrial production and low quality. 
     It is also known that wine bottles can be plugged with screw caps. This plugging technique can be well controlled and the preservation performance is considered similar to that of cork or synthetic stoppers. Furthermore, screw caps are recyclable, at least in theory, after separating the internal liner from the cap. However, especially in Europe, this plugging technique may still be considered reserved for low range wines and wines from the so-called New World. 
     Bottles provided with internal thread have been known for a long time. Such type of bottle is described, for instance in documents U.S. Pat. No. 2,026,304, FR1170472, U.S. Pat. No. 516,726, U.S. Pat. No. 868,914, U.S. Pat. No. 173,089, U.S. Pat. No. 482,682, U.S. Pat. No. 52,269 and EP0027780. 
     EP1501738 describes a method for making a ceramic bottle provided with an internally threaded neck. The method consists of the following phases: mating a threaded tube with the lower extremity of a funnel shaped body; positioning the threaded tube and the funnel shaped body on the upper extremity of a two part model and injecting the ceramic material through the body in the model; discharging the excess material by turning the model upside down; separating the body from the model leaving the threaded tube in the neck of the bottle; reducing the threaded tube to ash in order to release the thread. 
     Automated processes are also known today for the production of glass containers. For instance, in the so-called “blow-and-blow” process, gobs of molten glass are fed in chambers of respective blank molds each provided, in a lower part, with a plunger, movable in vertical direction between a lowered and raised position. Just before the gob enters the mold, the plunger is raised and forms an imprint in the glass surrounding the plunger. The plunger is lowered leaving the imprint in the gob and subsequently, air is blown through the imprint to form the gob into a tubular body, closed at the upper extremity and known in the technical field as a “parison”. The parison is then transferred to a final blow mold in which it is suspended by the neck. Air is again blown in the parison, which inflates filling the whole cavity of the final blow mold, assuming the final form of the bottle. 
     At a first glance, producing a glass container with internal threaded neck may appear to be simple. In practice, this is not the case, in particular when it comes to industrial production at controlled costs. In fact, it is difficult to produce such containers with threaded neck with a controlled, reproducible and robust process, which is easily transferred from one plant to another or from one production line to another. Furthermore, the production speed of existing machines should be maintained, while controlling the quality produced in the production lines to avoid any glass debris. 
     JP 62-003028 describes an apparatus for producing an inside screw bottle. A screw is formed on the inner surface of the bottom of the gob by the part of the plunger. The plunger is then lowered under rotation and the counter-blow operation is carried out. 
     U.S. Pat. No. 1,502,560 describes a machine for making bottles, or similar containers, which are provided within the mouth-portion with an internal screw thread. It uses a mandrel or plunger associated with each mold having a tip portion being provided with a thread which serves to form a thread within the mouth of the bottle. 
     Other manufacturing processes mainly proposed in the first half of the 19 th  century are described in GB 132,589, U.S. Pat. No. 2,215,984, DE 183525, U.S. Pat. No. 1,406,722, FR 697,986, U.S. Pat. No. 1,560,158, BE 488693. 
     However the equipment described therein uses complicated mechanisms to generate a rotational movement of a screwed tap which seem to be prone to failure and need a lot of space making it difficult to be used with today&#39;s manufacturing equipment. Furthermore, the parison forming operation as shown therein is time-consuming and may slow down the production speed. Moreover, those methods imprint a single thread with small pitch and several turns in the container, making the container unergonomic and cumbersome to open and to close for the user. 
     Therefore, it is an object of the present invention to provide a fast and efficient process for the fabrication of glass bottles with an internally threaded neck. 
     Another object of the present invention is to provide a structurally simple and reliable equipment for the fabrication of glass bottles with an internally threaded neck, which can be used within existing glass container manufacturing machines with minimum change of the existing equipment. 
     A further object of the invention is to provide a glass container which can be produced with the method and/or equipment of the present invention, specifically a bottle for holding wine and/or spirits, with an internally threaded neck which can be opened and closed quickly and ergonomically while still providing good sealing capabilities. 
     The objects of the invention are achieved by subject matter of the independent claims. Preferred embodiments are defined in the dependent claims. 
     According to a first aspect, the present invention relates to a process for the fabrication of glass containers, preferably bottles, provided with an internally threaded neck/mouth comprising the steps of: a) feeding a gob of molten glass inside the chamber of a first mold equipped with a tap or plunger having at least one helical rib or groove on its outside surface; b) extracting the plunger from the partially solidified glass by a roto-translational motion, wherein said plunger is rotated around a longitudinal axis coaxial to the outside surface with said at least one helical rib or groove while being longitudinally extracted, in order to unscrew the plunger from the partially solidified glass, leaving a threaded imprint in the glass portion corresponding to the mouth of the container to be produced; c) blowing air into the mouth until the container is formed. 
     The roto-translational motion for the extraction of the plunger in step b) is generated as follows: A linear actuator acts on the plunger, thereby effecting a linear movement of the plunger along said longitudinal axis and relative to a guide body which is fixed relative to the first mold and surrounding the plunger in said step b). A helical guide being coaxial to the longitudinal axis is provided between said guide body and said plunger and directly transforms said linear movement effected by said linear actuator on said plunger into said roto-translational motion of said plunger. In the production process the gobs are fed in sequence in the chamber of the first mold and the phases a), b) and c) are repeated for every gob. 
     Advantageously this type of drive mechanism is simple, reliable and well suited to be used with already existing glass production machines, e.g. existing I.S. machines and requires only minimum adaptations of the existing machines. In particular a pneumatic or hydraulic piston drive or a servo-electric drive, being coaxial to the plunger can still be used. Using a helical guide coaxial to the plunger to transform the linear movement effected by the piston or servo-electric drive drive can advantageously be provided within the restricted space of such a machine. 
     Advantageously, the process is well suited for internal threads in the neck with specifically desired thread geometries. For imprinting such an internal thread in the container neck the at least one helical rib or groove winds around said longitudinal axis over a predefined angle and the plunger is rotated over an angle of rotation equal to or greater than said predefined angle in said roto-translational motion in step b), wherein the angle of plunger rotation is preferably smaller than 360°, more preferably smaller than 200° and according to a preferred embodiment only 90°+/−30°, allowing to maintain a high production speed. 
     Therewith, a high production speed can be maintained. Furthermore, this allows the production of a neck with an internal thread of coarse pitch and small angular extension around said longitudinal axis (azimuth angle), which can be advantageous for certain applications, e.g. for wine or spirit bottles. 
     Preferably, said guide body is realized as a thimble which engages the neck ring and longitudinally guides the plunger and the helical guide is provided between the thimble and the plunger. In said steps a) and b) the thimble is fixed relative to the first mold by engaging the neck ring and after extracting the plunger the thimble is moved away down out of engagement with the neck ring. 
     According to a preferred embodiment of the invention, the fabrication process is a blow-and-blow process, wherein
         said first mold is a blank mold and in a step b1) after extracting the plunger the gob is blown to form a parison inside the chamber of said blank mold,   in a step b2) said parison is transferred from the blank mold in a chamber of a blow mold,   in step c) said parison is blown to form the container inside the chamber of the blow mold.       

     According to a second aspect, the present invention relates to equipment for the fabrication of glass containers provided with an internally threaded neck, comprising: a first mold delimiting an internal chamber; a plunger movable between a first position, in which it is located inside the chamber delimiting a volume, in negative, corresponding to the mouth of the container, and a second position, in which it is extracted from said chamber; a moving device operatively coupled to the plunger in order to move it from the first position to the second position. The plunger has at least one helical rib or groove on its outside surface and the movement between said first and second position is a roto-translational motion to unscrew the plunger from the glass portion corresponding to the mouth of the container to be produced. The roto-translational motion of the plunger when it is extracted from the imprint which corresponds to the mouth of the container to be produced allows to release the plunger off the mouth without damaging the internal thread formed in it. The roto-translational motion is generated with the following equipment:
         a linear actuator which acts on the plunger, thereby effecting a linear movement of the plunger along said longitudinal axis between said first and second position;   a guide body being fixed relative to the first mold and surrounding the plunger, wherein the plunger is movable relative to the guide body along said longitudinal axis; and   a helical guide coaxial to the longitudinal axis and being provided between said guide body and said plunger wherein said helical guide directly transforms said linear movement effected by said linear actuator on said plunger into said roto-translational motion of said plunger between said first and second position. Again, this allows to maintain the production speed and to use the equipment in existing machines with minimum changes.       

     According to a preferred embodiment of the invention, the plunger has a work portion in the form of a mandrel extending in the neck ring of the first mold in step a) and a base located below the neck ring. Said at least one helical rib or groove forming said internal thread in the container neck is provided on the circumferential outside surface of the mandrel. 
     Preferably, the linear actuator comprises a pneumatic or hydraulic piston drive or a servo-electric drive and a driving rod, all being arranged coaxially with the plunger and the first mold. The driving rod is movable coaxially with said longitudinal axis and has a terminating head portion being longitudinally fixedly connected to the base of the plunger. 
     Preferably, the terminating head portion of the driving rod has an upper flange and the base of the plunger has a lower flange. The flanges of the terminating head portion and the base are engaged by a clamp, e.g. a split ring to connect the terminating head portion of the driving rod and the plunger base. 
     The flanges of the terminating head portion of the driving rod and the plunger base are slidingly engaged with each other to allow for relative rotation between the driving rod and the plunger base. Thus, the plunger may carry out the roto-translational motion, while the driving rod is purely linearly moving without rotational motion component. Therewith, the equipment can be simply retrofitted in existing machine constructions. 
     Preferably, said at least one helical rib or groove winds around said longitudinal axis over a predefined angle γ 1  (azimuth angle), which is preferably smaller than 360°, more preferably smaller than 200° and according to a preferred embodiment γ 1 =90°+/−30°. The plunger is rotated over an angle of rotation equal to or greater than the predefined angle γ 1 , but preferably not more than 360°. 
     This geometry allows for rapid disengagement of the plunger from the threaded mouth. 
     Preferably m helical ribs or grooves are provided on the plunger, wherein m is greater than or equal to two, thus forming a multi-turn thread with m independent thread turns. According to a preferred embodiment m is chosen between three and five, preferably is equal to four. The m ribs or grooves are preferably angularly staggered by an angle equal to 360° divided by m. 
     Furthermore, the helical guide has the same pitch angle as the at least one helical rib or groove on the outside of the plunger which imprints the internal thread in the glass portion corresponding to the mouth of the container to be produced. 
     Preferably, said at least one helical rib or groove has a pitch angle β 1  (angle between the at least one rib or groove and a plane perpendicular to the longitudinal axis) of between 30° and 50°. It has turned out that a particularly preferred pitch angle is β 1 =37°+/−5°, allowing for a smooth transformation of the linear movement to the roto-translational motion on the one hand side. On the other hand side, these geometric characteristics result in a thread that guarantees secure engagement and tight holding of a cork stopper and, at the same time, easy and fast extraction of the plunger during the mass production phase of the containers. 
     As already indicated, the plunger has preferably a work portion or mandrel on which the at least one helical rib or groove forming said internal thread in the container neck is provided and a base for connecting with the plunger rod. According to a preferred embodiment of the container to be produced the mandrel has a thread-free ring below the ribs or grooves on its outside surface to form a thread-free portion of the container mouth adjacent to the finish of the container. This can be advantageous in view of the sealing properties of the container when being closed with a cork stopper. 
     Preferably, the helical guide comprises at least one helical slot made in the outside surface of the base of the plunger or in an internal surface of the guide body and at least one pin solidly connected to the guide body or to the base of the plunger. Said pin is engaged and slides in said helical slot to transform the linear movement effected by the linear actuator into said roto-translational motion of the plunger. 
     This type of construction is relatively simple and therefore reliable. With this type of construction it is facilitated to apply the invention with already used equipment without necessitating a replacement of the blank mold or the addition of exceedingly other components to the production line. 
     Preferably, said at least one helical slot winds around said longitudinal axis over an azimuth angle γ 2  equal to or greater than said predefined azimuth angle γ 1  of the at least one helical rib or groove. 
     Preferably, said at least one helical slot winds around said longitudinal axis over an azimuth angle γ 2  smaller than 360°, more preferably smaller than 200° and according to a preferred embodiment over an azimuth angle of γ 2 =90°+/−30°. 
     Further preferably, the helical guide comprises n independently starting helical slots, with n greater than or equal to two, and the n helical slots are staggered angularly by an angle equal to 360° divided by n. 
     In accordance with the preferred pitch angle β 1  of the helical ribs or grooves in the plunger mandrel, the at least one helical slot has a constant pitch angle β 2  between 30° and 50°, preferably a constant pitch angle of β 2 =37°+/−5°. 
     With the afore-mentioned method and equipment a glass container, specifically a bottle, is producible which is provided with a neck with approximately cylindrical form suitable for plugging the container with a stopper inserted in said neck. Said neck has an internal thread for reversible plugging and unplugging of the container by unscrewing and screwing of said compressible stopper, respectively. With the method and equipment of the present invention in particular a wine or spirit bottle can be produced which has a neck with an internal thread comprising two or more independent thread turns imprinted by the ribs or grooves on the outside surface of the mandrel and having a constant pitch angle β of between 30° and 50°, while the method and fabrication equipment is not necessarily limited hereto. 
     Preferably, the thread turns in the container neck wind around the longitudinal axis over an angle of rotation (azimuth angle) γ of less than 360°, more preferably between 45° and 200°, and more preferably of γ=90°±30°. 
     According to a preferred embodiment the ribs or grooves in the plunger mandrel and therewith the thread turns in the container neck extend over a height h 3  of between 5 mm and 20 mm along the longitudinal axis. 
     Preferably the internal thread of the container neck comprises between 3 and 5 independent thread turns. 
     Further preferably the neck comprises an internal thread-free sealing ring extending from the finish of the container to the beginning of the thread turns made by the thread-free ring below the ribs or grooves on the outside surface of the mandrel. In other words, the thread turns inside the container neck do preferably not extend to the container finish, but have an upper end at a distance of about 2 mm to 5 mm to the container finish. 
     In accordance with the ribs or grooves on the outside surface of the mandrel, the independent thread turns of the internal thread of the neck are identical and distributed at regular angular intervals over the internal wall of the neck. The independent thread turns of the internal thread have a preferred radial thickness of between 1 and 3 mm. 
     With such an internal thread, the container has the advantage that it can be plugged and unplugged by simple screwing and unscrewing of a compressible stopper, e.g. a cork stopper, provided with a head suitable to be grabbed by hand and a body suitable for insertion in the threaded neck and conforming during the insertion. This kind of plugging solution seals the container tightly, while providing great ease and practicality of use for the user, who can indefinitely plug and unplug the container by the simple manual operation of screwing and unscrewing the stopper in the neck of the container without to much effort. Furthermore, this kind of plugging solution preserves the high range image of the product held in the container by retaining, for instance, a natural cork stopper with the advantages of a metallic or plastic screw cap. 
     Other characteristics and advantages of the present invention will become apparent from the exemplary and non-limiting description of a preferred, but not exclusive example of a process and equipment for the fabrication of glass containers provided with internally threaded neck and such glass container, as illustrated in the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 4  show in schematic section a part of the equipment for forming the parison from a gob of molten glass in successive phases of the process according to the present invention; 
         FIG. 5  schematically illustrates the transfer of the parison from the blank mold as shown in  FIGS. 1 to 4  to the blow mold; 
         FIG. 6  schematically illustrates blowing of the parison to the final container in the blow mold; 
         FIGS. 7 a  to 7 c    show enlarged views of the equipment in successive phases of the plunger extraction from the blank mold, wherein the plunger having a different helical geometry than the plunger as shown in  FIGS. 1 to 4 ; 
         FIG. 8  shows a plan view of the external surface of the unrolled surface of the work portion of the plunger as shown in  FIGS. 7 a    to  7   c;    
         FIG. 9  shows a sectional view of the container produced with the plunger as shown in  FIGS. 7 a    to  7   c.    
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the attached drawings, reference number  1  indicates equipment for mass production of glass bottles provided with an internally threaded neck, for instance equipment of an I.S. machine. An I.S. machine has a plurality of individual sections. Each section may be of single or multiple gob type (typically one, two, three or four gobs per section), wherein the equipment of the shown embodiment will be provided together with each blank mold of the I.S. machine. The illustrated equipment is a “blow-and-blow” type of equipment. 
     Referring to  FIGS. 1 to 4 , gobs of molten glass  2  are supplied from a furnace (not shown) by gravity one at the time, through channels  3  to a blank mold  4  or to a battery of blank molds, where each gob is transformed in a preform or parison ( FIG. 4 ). For this purpose, the inside of the blank mold  4  delimits an elongated cylindrical chamber  5  or cavity, which extends along a longitudinal axis X-X and has an upper opening  5   a , through which the gob  2  enters, and a lower opening  5   b  in which a plunger  6  is positioned when the gob is inserted in the chamber. 
     The equipment  1  further comprises for each blank mold  4 , a funnel  7  movable between a first position, in which it is at a distance from the blank mold  4 , and a second position, in which it is located on the upper opening  5   a . When positioned on the upper opening  5   a , the funnel  7  delimits a substantially tapered passage  7   a  diverging upward. Equipment  1  comprises, for each blank mold  4 , a closing body (so-called baffle)  8  provided with internal channels  9 , in fluid communication with a not shown compressed air source, leading to an outside surface of baffle  8 . 
     The baffle  8  is movable between a first position, in which it is in contact with funnel  7  when the funnel is located on the upper opening  5   a  and its internal channels  9  are facing the inside of the substantially tapered passage  7   a , a second position, in which it is at a distance from the blank mold  4  and funnel  7 , and a third position, in which it is in direct contact with the blank mold  4  and closing the upper opening  5   a  while its internal channels  9  are closed by the blank mold  4 . 
     The blank mold  4  is mounted on a neck ring  10  which has a central passage opening  11  and forms the outside surface of the bottle neck. When the blank mold  4  is mounted on the neck ring  10 , the passage opening  11  extends continuously from the lower opening  5   b  of the elongated cylindrical chamber  5  to the plunger  6 . 
     The plunger  6  is arranged inside the passage opening  11  of neck ring  10  ( FIGS. 1 and 2 ) and is movable along the longitudinal axis X-X. 
     Referring to  FIGS. 7 a  and 7 b   , the plunger  6  has a base  12  and a work portion  13  forming a mandrel. The work portion  13  has the shape of a tap with an external surface “Se” complementary to the internal surface “Si” of the mouth “M” of the bottle to be produced. The work portion  13  extends from the base  12  into the neck ring  10  and delimits the passage opening  11  of the neck ring  10 , when the plunger  6  is in the upper first position. The plunger  6  is inserted in a tubular shaped thimble  14  forming a guide body which is coaxially engaged with the neck ring  10  when the gob is inserted ( FIG. 7 a   ) and when the parison is formed ( FIG. 7 b   ). For this, the thimble  14  has an upper head portion  14   a  with smaller diameter engaging a corresponding enlarged annular receptacle  10   b  of the neck ring  10 . In this exemplary embodiment, the neck ring  10  includes a one-piece annular guide ring  10   c  forming the finish of the container to be produced, wherein the upper head portion  14   a  of the thimble  14  engages the one-piece annular guide ring  10   c . The neck ring  10 —with its one-piece annular guide ring  10   c —further coaxially guides the upper part of the plunger base  12 , when the plunger  6  is in the first position. The plunger  6  slides and is longitudinally guided in the annular thimble  14  by an enlarged guide portion  12   b  of the base  12 . A linear actuator  30  comprising a pneumatic piston (not shown) and a driving rod or piston rod  31  coaxially arranged with the plunger  6  effect a linear movement of the plunger  6  (from the linear actuator  30  only the upper portion of the piston rod  31  is shown). The piston rod  31  acts upon a base flange  35  of base  12  to displace the plunger  6  along the longitudinal axis X-X between the upper first position and the lower second position. 
     The piston rod  31  terminates in an upper piston head  32  with head flange  33 . The head flange  33  is connected by a clamp  34  with the base flange  35  of base  12 . The thimble  14  is mounted on the upper end of a plunger sleeve  36  by a sleeve clamp  37 . The clamp  34  is in the form of a split ring and the plunger sleeve  36  together with the thimble  14  form a cylindrical tubing  38  in which the split ring  34  is longitudinally slidingly guided and being held together by the plunger sleeve  36  and the thimble  14 . 
     In the upper first position, illustrated in  FIGS. 1, 2, 7   a , the work portion  13  is completely inserted in the passage opening  11  and also partially in the lower opening  5   b  and closes the lower mouth of said passage opening  11 , in order to delimit a substantially tubular volume, in negative, corresponding to the mouth and the neck of the bottle to be produced. 
     In the second position, illustrated in  FIGS. 3, 4 and 7   b , the work portion  13  is in lowered position relative to the upper first position and is outside the passage opening  11 . The lower mouth of the passage opening  11  is no longer closed by the work portion  13  and is in fluid communication with a source of compressed air (not shown) to blow the gob  2  to a parison  18  in the so-called counter blow step. 
       FIG. 8  shows the unrolled outside surface of the work portion  13 , which comprises “m” helical grooves  15 , which extend to the upper end  13   a  of the work portion  13 . In the illustrated exemplary embodiment there are four helical grooves  15 . Each of the grooves  15  winds only partially around the longitudinal axis X-X over a predefined azimuth angle γ 1  of approximately 90°, measured in a plane perpendicular to the longitudinal axis X-X. Each helical groove  15  is also staggered angularly relative to the preceding and the successive groove  15  by an angle of approximately 90°. In this example the illustrated helical grooves  15  wind around the work portion  13  in clockwise direction. It will be appreciated that they could alternatively wind in counterclockwise direction, if desired. The pitch angle β 1  of each groove  15  measured relative to a plane perpendicular to the longitudinal axis X-X is approximately 37°. Each helical groove  15  has a maximum radial depth of approximately 1 mm and a width of approximately 2 mm. 
     The outside surface of the base  12  comprises n helical slots  16 . In the illustrated exemplary embodiment there are two helical slots  16 . Each slot  16  winds only partially around the longitudinal axis X-X over an azimuth angle γ 2  of approximately 180°, measured in a plane perpendicular to the longitudinal axis X-X. Each helical slot  16  is also staggered angularly relative to the other by an angle of 180°, in other words the two slots  16  are opposite to each other. The illustrated helical slots  16  are winding around the base  12  in clockwise direction. The pitch angle β 2  of each slot  16  is equal to the pitch angle β 1  of the grooves  15 , or approximately 37°. Each helical slot  16  has a radial depth of approximately 2 mm and width of approximately 3 mm. 
     The thimble  14  comprises a pair of pins  17  solidly attached to the thimble  14 . The pins  17  radially project from an inside surface of thimble  14  and are each slidingly engaged in one of the two helical slots  16  of base  12  to form, for the plunger motion, a helical guide coaxial to the longitudinal axis X-X. The coupling between slots  16  and pins  17  forces a rotation of the plunger  6  inside thimble  14  around the longitudinal axis X-X when the plunger is moved longitudinally between the first and second position. In particular, when the plunger is pushed from the second position to the first position inside the blank mold  4 , the plunger rotates in clockwise direction. Vice versa, when the plunger  6  is extracted from the blank mold  4  and moves from the first to the second position, it rotates in counterclockwise direction. Therewith, the plunger  6  carries out a roto-translational motion between the two positions, wherein the angle of rotation of the plunger  6  is equal to or greater than the azimuthal winding angle γ 1  of each of the helical grooves  15  on the work portion  13 . 
     Referring to  FIG. 7 c    the thimble  14  surrounding the plunger  6  is moved down out of engagement with the neck ring  10 . 
     Referring back to  FIGS. 1 to 4 , when in use, with the funnel  7  located on the upper opening  5   a  of the blank mold  4  and the baffle  8  separated from the blank mold  4 , the plunger  6  is brought to the first position inside the passage opening  11  ( FIG. 1 ). A gob of molten glass  2  falls in the blank mold  4  through the funnel  7  and fills partially the elongated cylindrical chamber  5 . 
     The closing body  8  engages the funnel  7  in the mentioned first position and air is blown through internal channels  9  in the so-called settle blow step. The air pushes the glass downward and fills completely the substantially tubular volume delimited around the work portion  13  and fills also the helical grooves  15  ( FIG. 2 ). 
     The glass of the mouth and part of the neck of the bottle begin to solidify. At this moment, the plunger  6  is extracted from the mouth bringing it with a roto-translational motion from the first to the second position and leaving on the internal surface of the mouth of the parison helical ribs which form thread turns corresponding to the helical grooves  15  ( FIG. 3 ). 
     After extraction of the plunger  6 , the funnel  7  is removed and the baffle  8  is located directly on the blank mold  4  closing and sealing the upper opening  5   a  of chamber  5 . In the counter blow step, compressed air is introduced in the imprint left by the extracted plunger  6 , corresponding to the mouth of the bottle to be formed, provoking the deformation of the glass which fills completely the chamber  5  and forms the preform or parison  18 , which is a tubular body closed at the upper extremity ( FIG. 4 ). 
     Referring to  FIG. 5 , equipment  1  comprises also devices  19  for transferring the parison to a second mold  20 . In the illustrated exemplary embodiment, such devices  19  comprise an invert arm  21  with an extremity which is connected to the neck ring  10  and an opposite extremity hinged around a horizontal axis  22 . The second mold  20 , or blow mold, delimits internally a finishing chamber  23  representing in negative the final dimensions and contour of the bottle to be produced. 
     The parison  18  is released from the blank mold  4  and turned upside down by means of a 180° rotation of the arm  21  around the horizontal axis  22 , and remains suspended by the neck. The blow mold  20  is closed around the parison  18 . Through the effect of its own weight, parison  18  is elongated downward inside the finishing chamber  23 . 
     Referring to  FIG. 6 , at the end of the elongation, a blow head  24  is positioned above the blow mold  20  and begins to blow air in the parison  18 , inflating it until it fills the whole finishing chamber  23  (final blow step). The final blow mold opens and pincers, not shown, remove the bottle and transfer it to cooling devices. 
     Referring to  FIG. 9 , the bottle, such as a wine bottle which is produced with the afore-mentioned equipment shown in  FIGS. 7 a  to 7 c    is described in more detail, in which only the neck of the bottle is shown. 
     The formed bottle has on its internal surface “Si” of the mouth “M” four helical ribs, which form thread turns  25 , corresponding to the grooves  15  of plunger  6 . The thread turns  25  extend only partially on the internal surface of the neck of the container. 
     The neck  50  has a cylindrical throat  51  ending in a head  52 , also cylindrical, of slightly larger diameter than the neck, forming a retention shoulder  53  for a metallic or plastic cover for dressing the neck  50  after plugging. Throat  52  and head  53  of neck  50  are coaxial and cylindrical around the longitudinal axis of revolution X′-X′ of the container and form an internal tubing  54  of approximately constant diameter over the whole length of neck  50  except in the threaded zones. 
     The internal thread of the neck  50  is a multiple thread, in this example with four independent thread turns  25  on the internal wall  61  of neck  50  corresponding to the four helical grooves  15  on the work portion  13 , at the level of head  52  of neck  50 . 
     More particularly, the internal wall  61  of neck  50  forms from the upper end of the mouth M over a height h 1  of at least 30 mm a straight cylindrical section  71 , with internal diameter d 1  essentially constant over height h 1  and by preference equal to 19 mm to 20 mm. By preference, the tolerance applied to this diameter d 1  is ±0.5 mm. Within the straight cylindrical section  71  the angle of inclination between the internal wall  61  of neck  50  and the longitudinal axis X′-X′ is less than 3°. The diameter d 1  is made with such small tolerance by constraining, during the fabrication of the container, the outside diameter d 2  of the throat  51  of neck  50  to a value of 27.5 mm measured at height h 2  of 40 mm beneath the upper end of the mouth M. 
     The thread turns  25  of the internal threading of neck  50  are extending in the straight cylindrical section  71 , over a height h 3  of about 10 mm thereby forming the threaded section  73  of cylindrical form. 
     The straight cylindrical section  71  extends further from a lower end  25   a  of the thread turns  25  over a height h 4  of about 20 mm (at least 5 mm, and by preference at least 10 mm) and is extending also from the upper end of the mouth M to an upper end  25   b  of the thread turns  25  over a height h 5  of about 3 mm (at least 2 mm and preferably up to 5 mm). 
     Therewith, above and below the thread turns  25  there are two annular rings in the straight cylindrical section  71  which both have the same inside diameter d 1  (except for the tolerances of each of the rings). Therewith, the two annular rings provide two cylindrical thread-free sealing sections  74 ,  75 , where the stopper, when it is screwed in neck  50 , is perfectly circumferentially married against the plain internal wall  61  of neck  50  in these sections without disturbance of the thread turns  25 , on both sides (above and beneath) of the thread turns  25 . This improves preventing air and liquid from entering and/or exiting the container by passing along the thread turns  25  inside neck  50 . The upper thread-free sealing section  75  of height h 5  is formed by a thread-free portion  13   b  of the mandrel between the grooves  15  and the base  12 . 
     The thread turns  25  on the internal wall  61  of neck  50  consist of ribs protruding from the internal wall  61 . Advantageously, these thread turns  25  are identical and distributed at regular angular intervals over the internal surface  61  of neck  50 . 
     In other words the thread turns  25  are formed by protruding gadroons on the internal wall  61  of the straight cylindrical section  71  of the neck. In this embodiment, the useful passage diameter d 3  between the inner edges of the thread turns  7  is by preference between 18 mm and 19 mm, with a tolerance of ±0.5 mm. 
     The thread turns  25 , forming the internal thread  6  of neck  1 , have a pitch angle of β=37°, i.e. an angle of 37° relative to a horizontal section of the neck perpendicular to axis X′-X′. 
     Furthermore, the preferred embodiment shown in  FIG. 9  has four thread turns  25 , with one thread turn per angular sector of 90° of the internal cylindrical wall  61  of neck  50 . Each thread turn  25  extends around the longitudinal axis X′-X′ over an azimuth angle of about γ=90°, wherein generally an azimuth angle γ of between 45° and 180° is applicable. As shown in  FIG. 9  the thread turns  25  do not overlap along the direction of the longitudinal axis X′-X′ with the next thread turn  25 . The use of two or more independent ribs or thread turns  25 , and the use of a thread of coarse pitch as defined above, is advantageous for the container. The typical weight of a bottle to be produced by the described process is between 300 and 1000 g. 
     The manufacturing operation of the parison is fast and does not necessarily slow down the production process of existing equipment. Furthermore, the result is ergonomic for the user. First, it allows very quick screwing and unscrewing of the stopper, if applicable with a single hand movement. Second, the user can combine rotational and linear translational forces on the stopper by her/his hand when screwing in the stopper into the bottle neck, which is particularly ergonomically. When screwing in the stopper with the aid of the heel or palm of the hand, the user has more power compared to only use the fingers. 
     The invention is not limited to the described and shown examples because various modifications can be made without exceeding the scope of the claims. Every feature may individually define an essential feature of the invention, irrespective of whether disclosed in the description, the claims or the drawings, even if disclosed only together with other features.