Abstract:
An apparatus for manufacturing hollow, plastics articles having internal undercuts, comprising at least one compression-molding unit, composed of an upper male mold part comprising a plug and of a lower female mold part aligned, with the male mold part, an actuation for actuating the mold parts between a spaced position, at which a dose of plastics is deposited in the female mold part, and an adjacent, compression molding position, a slideable tube, having an end portion with angularly distributed seats with oscillating elements articulated along radial planes, provided externally with recesses, a stem accommodated coaxially inside the tube, that actuates during the mold closure, the oscillating elements to form, with the tube end portion, the molding plug, and, during the mold opening a position in which to allow the extractor to remove articles from the plug.

Description:
BACKGORUND OF THE INVENTION 
   The present invention relates to a carousel apparatus for manufacturing articles made of plastics by compression molding. 
   Compression molding apparatuses generally comprise a carousel that can rotate about a vertical axis and on which a plurality of angularly spaced molding units are installed. Each unit comprises an upper male element (plug) aligned with a lower female mold part (cavity). 
   In order to obtain the article, a dose of semifluid plastic material is deposited in the female mold part and pressed by means of a mutual relative movement of the two mold parts. 
   In the manufacture of caps for closing containers provided with internal undercuts (for example constituted by teeth for engaging a collar of the container to which the cap is to be applied), the molded cap, after opening the mold parts, remains attached to the plug and is removed by means of an ejector which, by utilizing the elasticity of the plastic material, which has not hardened yet, pulls the cap off the plug. This type of removal is applicable to cases in which the internal undercuts do not protrude substantially. In any case, it is necessary to foresee that in a significant percentage of articles, separating the formed caps from the plug by forcing causes damage to the undercuts, especially when the undercuts are particularly large or arranged at right angles with respect to the wall from which they protrude. 
   SUMMARY OF THE INVENTION 
   The aim of the present invention is to obviate the above cited drawbacks of known devices, by providing a carousel apparatus for forming hollow articles, particularly caps for closing containers, which have internal undercuts and protrusions, and for extracting them without compromising the integrity of the article removed from the molding plug. 
   Within this aim, an object of the present invention is to provide an apparatus in which the cap forming means assist in the extraction of the molded caps from the mold. 
   This aim and this object are both achieved by the present apparatus, whose characteristics are defined in the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a carousel apparatus for manufacturing caps provided with internal teeth by compression-molding plastic material, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
       FIG. 1  is a sectional view, taken along a vertical line, of a molding unit of the apparatus; 
       FIG. 2  is an enlarged-scale view of the lower part of  FIG. 1  related to the molding plug; 
       FIG. 3  is a sectional view, taken along the line III—III of  FIG. 1 ; 
       FIG. 4  is a view of the unit in the operating situation in which the cap is extracted; 
       FIG. 5  is an enlarged-scale view of the lower part of  FIG. 4 ; and finally 
       FIG. 6  is a view of a second embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 1 to 3 , the apparatus is constituted by a carousel which can rotate about a vertical axis Z and supports, on its peripheral region, multiple units S for molding caps that consist of closures A made of plastic material. 
   Hereinafter, it is assumed that the closures A are shaped like a cylindrical cup with a bottom B and a cylindrical wall C provided with internal protrusions. For the sake of greater clarity of presentation and merely by way of example, it is assumed hereinafter that the protrusions consist of four teeth D, constituted by four ribs which are arranged in a cross-like configuration and trace a helical path in order to allow to screw the closure on so as to close a container. 
   Each unit S is composed of an upper male mold part, generally designated by the reference numeral  1 , and by a lower female mold part, generally designated by the reference numeral  2 , which are mutually coaxial along an axis X, which is parallel to the axis Z. The female mold part  2  can be actuated against the male mold part  1  by means of a hydraulic jack, not shown. 
   The male mold part  1  comprises a vertical tubular stem  3 , composed of seven tubular elements  4 ,  5 ,  6 ,  7 ,  8 ,  9  and  10 , in which the elements  4 – 8  are connected to each other by screw coupling, while the element  9  is retained between the top of the element  7  and a shoulder  11  of the element  8 . The element  10  is external to the element  8  and is retained between an elastic retention ring  12 , inserted in an annular slot of the outer element  10 , and a shoulder  13  of the element  9 . 
   A narrow tube  14  lies inside the tubular stem  3  and forms two mutually coaxial interspaces, which are connected respectively to the delivery and the return of a liquid for cooling the plate  15  that closes the tubular stem  3  in a downward region. 
   The element  6  is provided with a flange  16 , by way of which it rests, by means of a spacer  17 , on a drum  18 , which constitutes the supporting structure of the molding units, which is turned about the axis Z by means of a motor drive, not shown. 
   The spacer  17  is centered on the outer lip  19  of a cylindrical jacket  20 , which covers a cylindrical seat  21  that passes vertically through the drum  18 . The flange  16 , the spacer  17  and the lip  19  are locked in a packed configuration on the drum by means of a clamp  22 , which is fixed by screws. 
   The jacket  20  has an inner annular shoulder  23 , which is suitable to support a bush  24  that can slide in the part of the jacket that lies above the shoulder  23 . 
   An annular chamber  25  is formed between the tubular element  6  and the spacer  17  and accommodates a cylindrical spring  26 . The spring  26  is pre-compressed between the flange  16  and the top of the bush  24 , so as to push the bush toward the shoulder  23 . 
   The bush  24  has, at its lower end, an annular lip  27 , which protrudes inwardly and acts as a support for a second spring  28 , which is less rigid than the spring  25 . 
   The spring  28  abuts, with its end, against the outer annular lip  29  of a tube  30 , which is coaxial to the tubular stem  3 , actuating said tube upwardly so as to abut against a shoulder  31  formed at the lower end of the element  6 . 
   The tube  30  comprises, in a downward region, a tubular portion  32 , which extends below the drum  18  and can slide on the element  4  of the tubular stem  3 . 
   The tube  30 , by means of an axial bearing  33 , is guided slidingly in a sleeve  34 , which in turn is guided slidingly in the tubular jacket  20  by means of an additional axial bearing  35 . 
   The sleeve  34  comprises an upper edge, which is suitable to abut against the lip  27  of the bush  24 , and a lower tubular portion  36 , which can slide on the tubular portion  32  of the tube  30 . Such portion  36  is referenced hereinafter as extractor, owing to its function of removing the molded closure A from the plug. 
   The tube  30  and the extractor  36  can move axially with respect to each other but are rotationally rigidly coupled by means of a roller  37 , which protrudes into the extractor  36  in order to engage an axial slot  38  of the portion- 32  of the tube  30 . 
   As shown more clearly by  FIGS. 3 and 5 , the portion  32  encloses a channel  39  for the sliding of the tubular element  4 . The channel  39  tapers downward, forming an opening  40  whose diameter is such as to receive the plate  15  with a sliding coupling. 
   The portion  32  comprises an end part whose outer shape is complementary to the inner shape of the closure A and constitutes, together with the plate  15 , the plug for molding the closure A. 
   In order to allow the formation of the internal teeth D of the cap during molding and the removal of the cap once molding is complete, the sectors of the end part of the portion  32  that are designed to form the teeth D are constituted by oscillating elements or plate-like pawls  41  which, after the closure has been molded, are moved away from the inner wall in order to release the molded teeth. 
   For this purpose, in the end part of the portion  32  there are four radial notches  42  (see  FIG. 3 ), which are arranged in a cross-like configuration; each notch is formed by two parallel walls, which delimit the segments or sectors  43  interposed between the pawls  41 . 
   The respective pawls  41  are pivoted in the notches  42 , by means of pivots  44 , so as to oscillate on planes that are radial with respect to the axis X. The pawls  41  have an outer face which duplicates the outer profile of the end part of the portion  30  and is provided with a recess  45  which, together with the side walls of the notches and when the outer faces of the pawls  41  and of the sectors  43  lie on the same cylindrical plane, forms the receptacle for molding the teeth D. 
   The pawls  41  have an inner edge provided with ramps  46  which are in functional contact with the edge of the plate  15 , so that when the tube  30  reaches, with the opening  40 , the level of the plate  15 , the pawls  41  are pushed outward into the position for completing the plug, while when the tube  30  moves into the position in which the opening  40  lies below the plate  15 , the pawls  41  can oscillate toward the inside of the tube  30 . In order to ensure that the pawls  41  stop in the plug completion position, the pawls  41  have an extension  47  that is suitable to abut against the surface  48  that joins the walls that delimit the notch  42 . 
   In the portion  32  of the tube  30 , on the planes of the pawls  41 , there are axial holes  49 , which are parallel to the axis X and lead onto the surface  48  of the notches  42 . 
   The holes  49  slidingly accommodate respective rods  50 , which protrude with their lower end into the notches  42  through the surface  48 . 
   The rods  50  are actuated by springs  51 , which keep them in contact with the extensions  47 . The axis of the rods passes outside the axis of the pivots  44 , so that the pawls  41  are pushed inward until the ramps  46  abut against the end of the stem  3 . 
   The extractor  36  is provided externally with two collars  52  and  53 , between which an arm  54  is engaged; arm  54  is radially-rigidly coupled to a column  55 , which is guided slidingly, by means of bearings  56 , in a cylindrical seat  57  of the drum, which is parallel to the axis X. 
   The column  55  extends above the drum  18  with a part on which rollers  58 ,  59  are mounted so as to cantilever out. The roller  58  slides in a vertical slot of a bracket, not shown, which is fixed on the drum  18  and is designed to prevent the rotation of the column  55  while allowing its axial sliding. The roller  58  instead engages the channel of a stationary cam  60 , which protrudes concentrically to the axis Z and actuates the axial movements of the column  55  during the rotation of the drum. 
   The operation of the described apparatus is as follows. During the rotation of the carousel, a dose of pasty plastic material is deposited in the cavity  61  of the female mold part  2 . During this step, the female mold part  2  is lowered with respect to the male mold part  1 . 
   In this lowered position of the female mold part  2 , the plate  15  of the stem  3  closes the opening  40  of the portion  32 , so that the pawls  41  complete the shape of the molding plug. 
   By way of the hydraulic lifting of the female mold part  2 , the lower edge  62  of the extractor  36  first abuts against the shoulder  63  of the mold part  2  (see  FIG. 1 ), thus delimiting the molding chamber of the closure A. 
   As the lifting of the female mold part  2  continues, the plastic material is compressed and is distributed in the molding chamber, filling it and causing, by way of its incompressibility, the stopping of the female mold part in the final position in which the closure A has assumed its final shape. 
   It should be noted that during this step the tube  30  remains motionless, while the sleeve  34  moves upward, acting on the bush  24  and compressing the springs  28  and  26 . 
   Once the molding of the closure A has been completed and the female mold part  2  has been moved away, the descent of the column  55  is started by way of the actuation imparted by the stationary cam  60  to the roller  59 ; the column draws the sleeve  34  with it by means of the arm  54 . 
   In this manner, the extractor  36  acts, with its edge  62 , on the edge of the closure A, which by being engaged by the teeth D with the pawls  41 , draws the tube  30  with it. The descent of the tube  30  is contrasted by the spring  28 , which however, being very weak with respect to the traction force applied by the extractor  36 , is unable to allow the forced disengagement of the teeth D from the recesses of the pawls  41 . 
   With the descent of the tube  30 , the plate  15  frees the opening  40 , allowing the pawls  41  to oscillate inward as the plate  15  moves away. The inward oscillation of the pawls  41  is partly due to the shape of the teeth D (which resolves the thrust applied axially to the closure A by the extractor  36  into a component that is directed toward the axis X) and partly due to the thrust applied by the rods  50  on the extensions  47  of the pawls. 
   After the pawls  41  have turned through an angle that is sufficient for the teeth D to disengage from the recesses  45  (the position shown in  FIGS. 4 and 5 ), the thrust applied by the extractor  36  to the closure A allows the closure to slide on the outer surface of the sectors  43 , disengaging from the plug, and allows to remove said closure in manners that can vary according to requirements. 
   As soon as the closure A has abandoned the plug, the actuation cam  60  imparts to the column  55  an upward stroke, which raises the extractor  36  and returns the sleeve  34  into abutment with the lip  27  of the bush  24 , while the previously compressed spring  28  lifts the tube  30  again into abutment with the shoulder  31  of the tubular element  6 . Due to the relative motion between the tube  30  and the tubular stem  3 , the pawls  41  are pushed outward again by the engagement of the plate  15  on the ramps  46 , so as to reestablish the final shape of the plug, in which the pawls complete the outer cylindrical wall and the plate  15  closes the opening  40 . 
   The described apparatus is susceptible of numerous modifications and variations, all of which are within the scope of the same inventive concept. For example, it is possible to close the opening  40 , giving the stem  3  solely the function of actuating the pawls  41 . 
   Furthermore, by varying the shape of the outer edge of the pawls and their number it is possible to obtain a plug that is capable of molding caps provided with internal undercuts of any shape and angular extension. 
     FIG. 6  is a view of a second embodiment of the apparatus, in which the pawls  41  are actuated positively by the stem  3  both inward, in order to disengage from the molded closure, and outward, when it is necessary to form the molding chamber. 
   For this purpose, the pawls  41  have, on their inner edge, a tooth  63 , which is suitable to mesh with play with a corresponding complementary tooth  64  formed outside the tubular element  4  proximate to the plate  15 . In order to allow the inward oscillation of the pawls, below the tooth  63  there is a hollow  65 , which forms a ramp  66  that corresponds to the ramp  46  of the preceding example. Accordingly, when the tube  30  is drawn downward by the extractor  36 , the teeth  63  strike the teeth  64 , causing the inward rotation of the pawls  41  without the thrust applied by the internal protrusions of the closure contributing to the movement of the pawls. Risk of damage to the closures is thus avoided. The repositioning of the pawls is achieved during the upward movement of the extractor by way of the abutment of the complementary teeth  64  on the ramps  66 . 
   In another variation, the upper mold part  1  and the lower mold part  2  are provided with connections to a source of compressed air which, injected into the mold parts, separates the molded article from the walls of the molding cavity and assists the mechanical expulsive action applied by the ejector  32 . 
   The disclosures in Italian Patent Application No. BO2001A000228 from which this application claims priority are incorporated herein by reference.