Abstract:
An apparatus for manufacturing threaded caps comprises a plurality of compression molding assemblies which are arranged on a rotating carousel and comprise an upper male mold half and a lower female mold half. The male mold half comprises a tubular element, a sleeve guided coaxially to said tubular element, and a punch guided in the tubular element and having a helical slot for forming the thread of the cap. The punch enters the female mold half and produces, together with it, the cap through compression of a dose of plastic material deposited in the female mold half. After the spacing of the punch from the female mold half, the removal of the cap from the punch occurs by way of a removal device, which comprises a ring gear associated with the sleeve and provided with a collar in sliding contact on the punch, a rod which can slide axially in a seat of the carousel and supports a gear meshing with the ring gear and connected to a motor drive mechanism. The rod is axially connected to the sleeve and is controlled by a stationary actuation cam which is suitable to impart axial movements to the rod. The cam and the motor drive mechanism are synchronized so as to move axially and rotate the collar so as to produce the unscrewing of the cap from the punch.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a carousel-type apparatus for manufacturing threaded plastics caps by compression molding. 
     Such apparatuses are already known, for example from publication PCT/EP95/03644 in the name of the Applicant, from German publication no. 2,007,777, from European publications no. 91,653 and 162,456, and from U.S. Pat. Nos. 2,155,316, 2,891,281, 4,343,754, 4,497,765, 4,640,673, 5,451,360, 5,554,327. 
     Compression molding apparatuses generally comprise a carousel which can rotate about a vertical axis and on which a plurality of molding assemblies are installed so as to be spaced one another by an equal angle. Each assembly comprises an upper male mold half (punch) which is aligned with a lower female mold half. 
     A dose of semifluid plastic material is introduced in the female mold half and compressed by means of a relative motion of the two mold halves in order to obtain the item. 
     In the manufacture of caps for closing containers, the molded cap, which remains attached to the punch after the opening of the mold halves, is removed by means of an ejector. 
     In the case of caps provided with an internal thread, removal occurs by utilizing the elasticity of the material, which allows to force the cap on its threads. 
     In order to prevent the caps from being damaged due to the forcing with which they are removed, solutions have been proposed which entail unscrewing the punch while the cap is rotationally locked or unscrewing the cap from the punch by means of an external element. Solutions for removing the caps from the molds are known from Japanese publications no. 62-264923 and 4-113820 and from U.S. Pat. Nos. 2,363,308, 2,799,049, 3,712,786, 3,856,255, 4,496,302, 5,383,780. 
     However, conventional solutions are applied exclusively to injection molding machines and are constructively too complicated and heavy to be used in carousel-type apparatuses, in which the opening of the mold and the expulsion of the caps must be actuated in very specific angular positions and in which it is important to reduce the rotating mass. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is therefore to devise a carousel-type apparatus in which said caps are rotated with respect to the male mold half in order to remove them. 
     Within the scope of this aim, an object of the present invention is to provide a carousel-type apparatus in which the molds are structurally simple, reliable in operation and easily adaptable to the characteristics of the caps to be manufactured. 
     This and other objects are achieved with an apparatus whose characteristics are defined in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the present invention will become better apparent from the following description of two preferred embodiments, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a sectional elevation view, taken along a vertical plane, of a first embodiment of a compression molding assembly, shown with the mold open, for forming a frustum-shaped screw cap; 
     FIG. 2 is an enlarged-scale view of the assembly of FIG. 1, with the mold closed; 
     FIGS. 3 and 4 are enlarged-scale views of the upper half and, respectively, of the lower half of the assembly of FIG. 2, with the mold closed; 
     FIGS. 5,  6  and  7  are views of the assembly in various successive operating conditions; 
     FIG. 8 is an elevation view of a second embodiment of a compression molding assembly; 
     FIG. 9 is a sectional view of a third embodiment of the present invention; and 
     FIG. 10 is a schematic plan view of the embodiment of FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1 to  4 , the apparatus is constituted by a carousel which can rotate about a vertical central axis Z and supports, on its peripheral region, a plurality of assemblies for molding frustum-shaped plastic caps (closures) (see FIGS.  5 - 7 ). 
     Hereinafter, it is assumed that said caps A are composed of a frustum-shaped cup B which is provided with an internal thread C. Each assembly is composed of an upper male mold half,generally designated by the reference numeral  1 , and by a lower female mold half, 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 half  3  can be actuated against the male mold half  1  by means of a hydraulic jack, not shown. 
     The male mold half  1  comprises a plate  3  which is screwed into a sleeve  5  by means of a tubular shank  4 ; said sleeve  5  is in turn screwed into the lower end of a hollow tube  5 a so as to form a single tubular stem  6  (FIG.  1 ). 
     A pipe is inserted hermetically in the tubular shank  4  and defines a tubular interspace  8  together with the tubular stem  6  (i.e., with the sleeve  5  and the tube  5   a ). The sleeve  5  has, at its lower end, a portion  9  which tapers downward and is externally threaded; the plate  3  is centered hermetically in said portion and forms, together with the tubular shank  4 , a chamber  10  which is connected to the interspace  8  through openings  11  of the tubular portion  4 . Moreover, the chamber  10 , through openings  12  provided in the region of the shank  4  directly above the plate  3 , is connected to the inside of the pipe  7 . 
     The portion  9  of the sleeve  5  and the plate  3  form the molding punch  13 , which produces the worm of the thread C inside the cap A. 
     The upper end of the pipe  7  is connected hermetically in a seat  16  of a cylindrical body which is in turn screwed hermetically, by means of a threaded portion thereof, in a seat  15  formed at the upper end of the hollow tube  5   a.    
     A narrow tube  17  lies coaxially inside the pipe  7 , protrudes out of the top of the pipe  7  and is inserted hermetically in a hole  18  of the body  14 . The narrow tube  17 , together with the pipe  7 , internally delimits a tubular channel  19  which is connected to the seat  16 . 
     The lower end of the narrow tube  17  is inserted hermetically in a bush  20  (FIG. 3) which is in turn hermetically inserted in the bottom of the shank is  4 . The narrow tube  17 , through the axial hole  21  of the bush  20 , is connected to a plurality of holes  22  which are formed radially on the outside of the punch  13  through ports  23  constituted by openings provided in the centering region of the bell-shaped portion  9  between the edge of said portion and the plate  3 . 
     The upper end of the narrow tube  17  is connected, through a hole  24  arranged diametrically to the hole  18 , to a supply of compressed air, which accordingly, after flowing through the narrow tube  17 , can exit through the radial holes  22  and the openings  23 . 
     Two axial holes  25 ,  26  are formed in the body  14 , eccentrically with respect to the hole  18 , and are connected by means of couplings  27 ,  28  to the delivery and the return of a coolant fluid. The hole  26  is connected to the interspace  8 , while the hole  25  is connected to the tubular channel  19  through a radial opening  29 . This provides a connection between the couplings  27  and  28  which allows recirculation of the coolant fluid. 
     The upper portion  30  of the sleeve  5 , screwed onto the hollow tube  5   a , has a smaller diameter than the remaining portion, so as to form an external annular shoulder  31 . An axial slot  32  is formed in the portion  30  and is slidingly engaged by a key  33  which is rigidly coupled inside a tubular element  34  in which the stem  6  is slidingly guided with the portion  30  and the hollow tube  5   a.    
     The tubular element  34  is provided with a flange  35  which is centered in a cylindrical case  37  by means of a lower annular lip  36 . 
     The cylindrical case  37  is inserted in a cylindrical seat  38   a  of a rotating body which belongs to the structure of the carousel. Said body is constituted by a sort of rotating drum  38  which is mounted on a vertical shaft (not shown) whose axis is the rotation axis Z of the carousel. The case  37  rests on the drum  38  with a shoulder  39 , so as to allow the mutual coaxial locking of the tubular element  34  and of the cylindrical case  37  by means of blocks  40  which are fastened onto the drum  38  by screws  41 . 
     A compartment  42  is formed between the case  37  and-the tubular element  34  and accommodates a bush  43  which has an internal lip  44  at its lower end. A center bearing  45  is arranged at the top of the bush  43  and is guided between the wider portion of the case  37  and the tubular element  34 . 
     A ring  46  of elastic material is placed between the flange  35  and the center bearing  45 , and a cylindrical spring  47  is interposed between the center bearing  45  and the lip  44  of the bush  43 . 
     The stem  6  can move between a raised position and a lowered position. The raised position is determined by the abutment of the shoulder  31  against the lower end of the tubular element  34  by means of the lifting action applied to the stem  6  by an additional cylindrical spring  48  which rests on the flange  35  in a downward region and on a ring  49  in an upward region, said ring abutting against circular segments  50  which are recessed in a perimetric slot of the body  14 . 
     The lowered position of the stem  6  is determined by a stationary cam  51  which, as will become apparent hereinafter from the description of the operation of the apparatus, acts on a free roller  52  which protrudes from a plate  53  which is applied to the body  14  which rests on the segments  50 . The plate  53  is provided with an arm  54  which, by means of a bearing  55 , can slide on a post  56  which rises vertically from the screw  41  on which it is screwed with the lower nut-shaped end  56   a.    
     A sleeve  57  is accommodated in the portion of the seat  38   a  arranged below the bush  43 , and its upper end is in contact with the lip  44  of the bush  43 . 
     The sleeve  57  is supported so that it can rotate and slide axially in the seat  38   a  by means of a bearing  58  and rotationally and axially supports the sleeve  5  by means of an additional bearing  59 . 
     The sleeve  57  comprises a portion  57   a  which protrudes below the drum  38  and ends with a collar  60  which is in sliding contact on the sleeve  5  and has, along its lower edge, teeth  61  for engagement on the edge of the cap A which is to be removed once molding has been completed. 
     A bearing  63  is fixed above the collar  60  by means of a ring  62 , and a ring gear  64  is formed above said bearing. 
     The ring gear  64  meshes with a gear  65  which can rotate, by means of a bearing  66 , on a pipe  67  which is inserted in a recess  68  of a rod  69  which passes through the drum  38 . 
     A bolt  69   a  is inserted in the pipe  67  and is screwed into the bottom of the recess  68 , on which the pipe  67  is fixed by a nut  70 . 
     The rod  69  is mechanically connected to the sleeve  57  by a plate  71  which is fixed by the nut  70  against a collar  67   a  of the pipe  67  and has a seat in which the outer ring of the bearing  63  is fixed by means of a ring  72 . Accordingly, the axial movement of the rod  69  actuates the simultaneous axial movement of the sleeve  57 , while the ring gear  64  and the gear  65  remain mutually in mesh. 
     The rod  69  can slide vertically, by means of a bearing  73 , in a jacket  74  which is inserted in a seat  75  of the drum  38 . 
     The rod  69  protrudes upward with a shank  76 , screwed into a threaded hole of the rod  69 , and supports a cuff  78  arranged so as to be slideable on interposed bearings  77 . 
     The cuff  78  has a shoulder  79  and is surmounted by a plate  80  which is centered on the edge of the cuff  78  with a peripheral lip  81 . A precompressed spring  82  rests on the plate  80 , and its top rests on a collar  83  of a bush  84  which is guided on a threaded end portion  76   a  of the shank  76 . The collar  83  is pushed by the precompressed spring  82  against a bolt  85  which is screwed into the threaded end portion  76   a  of the shank  76  so as to be able to adjust the precompression of the spring  82 . 
     A ring  86  is screwed onto the cuff  78  until it abuts against the shoulder  79 , and a stem  87  protrudes from said ring and supports two rollers  88  and  89 . The roller  89  is engaged in a cam  90  which is rigidly coupled to the fixed structure of the apparatus and is therefore stationary with respect to the drum  38 . The roller  88  is guided in a vertical slot of a bracket (not shown in the drawing) which is fixed to the drum  38  and is designed to prevent the rotation of the shank  76  and of the rod  69 . 
     The cam  90  has a circular path which is concentric to the rotation axis Z of the carousel, so as to apply axial movements to the rod  69  and, by means of the connection provided by the plate  71 , to the sleeve  57 . 
     The gear  65  meshes constantly with an idler gear  91  which is rotatably supported on a pivot  92  which protrudes downward from the drum  38  and is parallel to the rod  69 . 
     The gear  91 , which as shown by the drawing is arranged on a rearward plane with respect to the plane of the gear  65 , has longer teeth than the gear  65 , so as to always remain in mesh with it even when the gear  65  moves away from the drum  38  in order to follow the movements of the rod  69 . 
     A third gear  93  meshes with the gear  91  and is keyed, together with two friction wheels  94 , on a shaft  95  which is supported so that it can rotate below the drum  38 . FIG. 3 illustrates only the upper part of the shaft  95  with the corresponding supporting bearing  96 , which is accommodated in a seat of the drum  38 . 
     The friction wheels  94  are made of rubber-like material and are adapted to make contact with a track  97  which covers a certain angular portion outside the drum  38  and concentrically to the axis Z. The track  97  is fixed, by means of bolts  98  and nuts  99 , to fixed parts  100  of the apparatus, so as to produce a radial thrust on the friction wheels  94  which is sufficient to turn them and, with them, the sleeve  57  by means of the gear train  93 ,  91  and  65 . 
     The operation of the described apparatus is as follows, During the rotation of the carousel, a dose P (see FIG. 1) of plastic material having a pasty consistency is deposited in the cavity of the female mold half  2 . During this step, the female mold half  2  is lowered with respect to the punch  13 , which by means of the spring  48  is actuated in the upward stop position determined by the abutment of the shoulder  31  of the stem  6  against the lower end of the tubular element  34 . 
     The stationary cam  90 , which actuates the stroke of the rod  69  and therefore of the sleeve  57 , is shaped so that in this step the threaded portion  9  of the punch  13  lies below the collar  60 . 
     By means of the hydraulic lifting of the female mold half  2 , the collar  60  abuts against an internal annular step of the female mold half  2 , the molding chamber is closed by the punch  13  and the stem  6  is lifted until the shoulder  31  abuts against the lower end of the tubular element  34 . 
     Therefore, the pressure applied to the female mold half  2  produces the gradual distribution of the plastic material in the molding chamber and the forming of the cap A (see FIG.  2 ). 
     It should be observed that the thrust applied by the female mold half  2  to the collar  60  causes a movement of the bush  43  which compresses the elastic ring  46 . 
     When the plastic material has reached an adequate hardening point, determined by feeding coolant liquid into the chamber  10  and into the chamber of the female mold half  2 , so that there is no further risk of plastic deformations, the descent of the female mold half  2  is actuated. However, when the female mold half  2  moves away, the cap A does not fall but remains attached to the punch  13  due to the thread. 
     When the female mold half  2  has moved away and the molding assembly has again reached the position of FIG. 1, the cam  90  actuates the descent of the rod  69 , which by means of the plate  71  draws downward with it the sleeve  57 . In this way, the collar  60  acts on the edge of the cap A which, by means of the thread, draws downward with it, with a stroke which is equal to the stroke of the rod  69 , the stem  6  (see FIG.  5 ), causing the compression of the spring  48 . At this point, in an appropriate angular position of the carousel, the friction wheels  94  engage the track  97  so as to start, by means of the gear train  93 ,  91 ,  65  and  64 , the rotation of the sleeve  57  in the direction for unscrewing the cap A from the portion  9 . The unscrewing of the cap is provided by the traction applied by the teeth  61  to the edge of the cap and by the simultaneous rise of the stem  6  caused by the return force applied by the spring  48  (see FIG.  7 ). 
     Since during this unscrewing step the material of the cap A has not yet solidified perfectly, in order to prevent the return force of the spring  48  from stripping the last turns of the thread, the cam  51  intervenes: by making contact with the roller  52 , said cam prevents a sudden upward movement of the stem  6 , allowing only its gradual rise as unscrewing of the cap advances (see FIG.  6 ). 
     Extraction of the cap from the punch  13  is conveniently facilitated by the injection of compressed air through the narrow tube  17 , the radial channels  22  and the openings  23  even before the cap unscrewing step begins. 
     The injection of compressed air is adjusted by valve means which intervene when the female mold half  2  has separated from the punch  13 . 
     The described apparatus is susceptible of numerous modifications and variations, all of which are within the scope of the same inventive concept. 
     One of these is shown in FIG. 8, in which the elements or parts that are identical or equivalent to those of the embodiment of FIGS. 1 to  4  are designated by the same reference numerals with the addition of an asterisk (*). 
     FIG. 8 shows the tubular stem  6 *, which supports, at its lower end, the shaped punch  13 * for forming cylindrical caps A*. The tubular stem  6 * can slide in a tubular element  34 * on which the sleeve  57 * is guided. By means of a bearing  58 *, the sleeve  57 * is guided in the provided seat of the drum  38 *. 
     With respect to the version of FIGS. 1 to  4 , a ring gear  64 * can rotate by means of a bearing  101  on the lower portion of the sleeve  57 *, and a collar  60 * protrudes downward from said ring gear in sliding contact on the outer surface of the punch  13 *. 
     The collar  60 * has, at the top, a circular plane  102  for contact with the lower edge of the sleeve  57 * and, in a downward region, a plurality of teeth  61 * for engagement on the edge of the cap A*. 
     The ring gear  64 * meshes with a gear  65 * which is keyed on a tubular column  103  which is supported so that it can rotate and slide axially, by means of bearings  104  and  105 , in a guiding seat  106  of the drum  38 * which is parallel to the stem  6 * and is radially internal thereto with respect to the rotation axis Z of the carousel. 
     The tubular column  103  is driven through a plate  71 * which connects it to the sleeve  57 *. The plate  71 * has an opening for the passage of the sleeve  57 *; said opening is shaped so that its edge engages between two flanges  107 ,  108  of the sleeve  57 * and produces a side-fit (axial and rotary) coupling with the sleeve  57 *. The angular arrangement of the sleeve  57 * with respect to the plate  71 * is provided by means of a pin  109  which is guided in a radial hole  110  of the plate  71 * and can move by acting on an external knob  111  in contrast with the action of a return spring  112 . 
     The plate  71 * is rigidly coupled to the tubular column  103 , at the portion that lies between the gear  65 * and the lower face of the drum  38 *, by means of two thrust bearings  113  and  114  which allow the rotation of the tubular column  103  and the transfer of thrusts onto the plate  71 * and therefore onto the sleeve  57 *. 
     The upper end of the tubular column  103  lies above the drum  38 *, and a pinion  115  is formed thereon; said pinion is connected, by means of a gear train generally designated by the reference numeral  116 , to a source of motion. The pinion  115  has an axially extended set of teeth, so as to remain in mesh with the gears  116  during the axial movements of the tubular column  103 . 
     A cylindrical rod  120  (which corresponds to the parts  69 ,  76  of the version of FIGS. 1 to  4 ) is rotatably supported, by means of a lower bearing  117  and an upper bearing  118 , in the tubular column  103 , and rests on the column by means of a flange  119 . The top of the rod  120  protrudes from the tubular column  103 , and a stem  87 * is radially fixed thereon and supports a follower roller  89 * of an axial cam  90 *. 
     The cam  90 * is rigidly coupled to the fixed structure of the apparatus and is therefore stationary with respect to the drum  38 *, and its shape is circular and concentric with respect to the rotation axis Z of the carousel. In order to keep the roller  89 * engaged on the profile of the cam  90 *, a roller  88 * is arranged on the stem  87 *, on the outside of the cam  90 *, and is guided in a vertical slot of a bracket (not shown in the drawing) which is rigidly coupled to the drum  38 * and is meant to prevent the rotation of the rod  120 . 
     The cam  90 * positively actuates the downward movements of the sleeve  57 * only over an angle which is sufficient to remove the cap A* formed by the punch  13 *; over the remaining rotation angle, the sleeve  57 * can move upward in contrast with elastic abutment means. 
     Said means are constituted by a ring of elastic rubber-like material  46 * which is interposed between the flange  35 * of the tubular element  34 * and a center bearing  45 * which rests on a bush  43 * which is accommodated in the case  37 *. The bush  43 * has an internal lip  44 * on which a cylindrical spring  47 * rests, said spring being suitable to act against the center bearing  45 *. 
     The operation of the described apparatus is the same as the operation of the embodiment of FIGS. 1-4. 
     In particular, when the female mold half has moved away from the punch  13 * and the cap A* is still attached to said punch, the cam  90 * actuates the descent of the rod  120  and starts the rotation of the tubular column  103  by means of the gear train  116 , so that the collar  60 * performs a descent and rotation which cause the unscrewing of the cap A* from the punch  13 *. It should be observed that the axial thrust on the rod  120 , actuated by the cam  90 * and transmitted to the collar  60 * by means of the plate  71 * and the sleeve  57 *, acts on the cap A*, which is actuated downward, drawing with it the punch  13 * and the stem  6 * and compressing the return spring  48 *. 
     However, the simultaneous rotation of the collar  60 * causes the rotation of the cap A*, which by unscrewing from the punch  13 * allows it to rise due to the return force applied by the spring  48 *. 
     A further embodiment of the present invention, shown in FIGS. 9 and 10, has, instead of the track  97 , a toothed sector  121  which lies concentrically to the axis Z and is such as to mesh directly with the gear  93  only at the rotation angle of the carousel in which unscrewing of the cap is provided. 
     In order to allow meshing with the toothed sector  121 , the gear  93  supports a free roller  122  which is eccentric with respect to the rotation axis of the gear  93  and which, at the beginning of the toothed sector  121 , moves along an entry cam  123  which is shaped so as to turn the gear  93  so that its teeth can mesh with those of the toothed sector. Likewise, at the exit of the toothed sector  121  a further cam  124  orientates the gear  93  in the angular position that allows the roller  122  to mate with the cam  123 . 
     The kinematic connection of the toothed sector  121  with the gear  93  can be achieved, instead of directly as above-described, by means of an auxiliary gear which is keyed on the shaft  95  above the gear  93 . 
     The disclosures in Italian Patent Application No. BO2000A000256 from which this application claims priority are incorporated herein by reference.