Abstract:
An apparatus for manufacturing plastics items provided with external undercuts, comprising at least one compression molding unit, which is composed of an upper male mold part comprising a plug and of a lower female mold part aligned, along a vertical axis, with the male mold part, means for actuating the mold parts between a spaced position, at which a dose of plastics sufficient to form an item is deposited in the female mold part, and a mating position for producing the compression molding of an item, the male mold part comprising a plug and an ejector that is associated with the plug in order to remove the molded item when the mold parts are in the spaced position, further comprising a bushing that is arranged externally and coaxially to the plug, a plurality of sectors for forming raised portions and undercuts on the outer surface of the item, the sectors being coupled axially to the bushing and being able to expand with respect to the plug, means for actuating the sectors between a position that produces mating with the plug in order to allow the compression molding of the item and the molding of the raised portions and undercuts, and a spaced position in order to allow to remove the molded item from the plug.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a carrousel apparatus for manufacturing, by compression molding, plastics items. 
     Compression molding apparatuses generally comprise a carrousel, which 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 item, a dose of semifluid plastics is introduced in the female mold part and is pressed by means of a relative movement of the two mold parts in order to obtain the item. 
     In the manufacture of caps for closing containers provided with internal undercuts (for example screw caps), the molded cap, after the mold parts have been opened, remains attached to the plug and is removed by means of an ejector, utilizing the elasticity of the plastics that has not yet hardened. 
     In the case of caps having external undercuts, it is not possible to perform removal by simply pushing downward the ejector, since the cap cannot retract inward. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to obviate the above cited drawbacks of known devices, i.e., to provide a carrousel apparatus provided with means that allow to form items, particularly hollow items, such as caps provided with raised portions and undercuts on their outer surface. 
     Within this aim, an object of the present invention is to provide an apparatus in which the cap forming means assist the extraction of the molded caps from the mold. 
     This aim and this object are achieved by the present apparatus, whose characteristics are defined in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages will become better apparent from the detailed description of a preferred but not exclusive embodiment of a carrousel apparatus for manufacturing screw caps by compression molding of plastics, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a sectional view, taken along a vertical plane, of a molding unit of the apparatus; 
     FIG. 2 is an enlarged-scale view of the upper part of the unit of FIG. 1; 
     FIG. 3 is an enlarged-scale view of the lower part of the unit of FIG. 1; 
     FIG. 4 is a sectional view of a detail of the unit of FIG. 1; 
     FIG. 5 is a sectional view, taken along the line V—V of FIG. 4; 
     FIGS. 6,  7  and  8  are views of the lower part of the unit in three successive operating conditions; 
     FIGS. 9 and 10 are two sectional views, taken along a vertical plane, of the lower part of a second embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1 to  5 , the apparatus is constituted by a carrousel, which rotates about a vertical axis Z and supports peripherally a plurality of units S for the molding of caps that consist of screw caps A made of plastics. One of said caps is illustrated more clearly in FIG.  8 . 
     Hereinafter, it is assumed that said caps A are composed of a cup B provided with an internal thread C and of a tamper-evident band D provided with inner teeth E and with an outer annular ridge F. The band D forms, together with the rim of the cup, an outer step G. 
     Each unit S is composed of an upper male mold part, generally designated by the reference numeral  1 , and of a lower female mold part, generally designated by the reference numeral  2 , which are mutually coaxial along an axis X that 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, which is not shown. 
     The male mold part  1  comprises a plate  3  (see FIG.  3 ), which is screwed, by means of a tubular tang  4 , into a sleeve  5   b , which is in turn screwed to the lower end of a sleeve  5   a  so as to form a single hollow stem  6  (FIG.  1 ). 
     A hollow tube  7  is inserted hermetically in the tubular tang  4  and is composed of two portions  7   a  and  7   b  which are screwed together; said hollow tube forms, together with the hollow stem  6  (i.e., with the sleeves  5  and  5   a ), a tubular interspace  8 . The sleeve  5   b  has, at its lower end, a wider portion  9  in which the plate  3  is centered hermetically. The wider portion  9  with the tubular tang  4  forms a chamber  10  that is connected to the interspace  8  through openings  11  of the tang  4 . Furthermore, the chamber  10  is connected to the inside of the hollow tube  7  through openings  12  formed in the region of the tang  4  directly above the plate  3 . 
     The wider portion  9  forms, together with the sleeve  5   b  of the hollow stem  6 , a step  9   a  for resting thereon the shoulder  13   b  of a tubular element  13  provided with a lower portion  13   a  that is shaped so as to have a helical outer slot  14  and recesses  13   c  which are distributed peripherally (see FIG.  8 ). As shown more clearly hereinafter, the hollow stem  6  is controlled by actuation elements which, starting from a position in which the step  9   a  abuts against the shoulder  13   b , impart thereto a downward stroke, which allows the plate  3  and the wider portion  9  to descend below the portion  13   a . In this manner, the step  9   a  abuts against the shoulder  13   b . The portion  13   a  and the plate  3 , together with the edge of the cylindrical wider portion  9  in which it is centered, form the forming plug  15  (see FIG. 6) that determines the internal profile of the cap A, i.e., the thread C, the bottom H of the cup B, and the internal protrusions of the tamper-evident band D for retaining the cap on the container to which it is applied. In the illustrated example, said protrusions, in order to match the recesses  13   c , consist of teeth E (see FIG.  8 ), but they can have any shape and in particular they can be constituted by an annular lip. 
     When the hollow stem  6  is actuated so as to descend, the plate  3  and the cylindrical wider portion  9  protrude from the tubular portion  13   a  and, by acting on the bottom H of the cap A, act as an ejector for said cap, hereinafter designated by the reference numerals  3  and  9 . 
     The upper end of the portion  7   a  of the hollow tube  7  is connected hermetically in a seat  16  (see FIG. 2) of the top of the stem  6 , which is in turn inserted hermetically in a seat  17  of a body  18  and is retained by a screw  19 . A connector  20  is arranged on the body  18 , and two holes  21 ,  22  are formed therein; said holes are connected to the delivery and to the return of a cooling liquid. The holes  21 ,  22  are connected to the hollow tube  7  and the tubular interspace  8  by means of passages  23 ,  24  of the body  18  and of the stem  6 , so as to convey the cooling liquid into the chamber  10  and ensure the cooling of the plug  15  and the setting of the plastics of which the cap A is made. 
     The hollow stem  6 , with its portion  5   a , is guided slidingly in a tubular element or sleeve  25 , which is accommodated coaxially in a cylindrical seat  26  of a supporting body that is part of the structure of the carrousel. In practice, said body is constituted by a sort of rotary drum  27 , which is mounted on a vertical shaft whose axis Z is the rotation axis of the carrousel. The sleeve  25  is suitable, with its lower end, to act as an abutment for the tubular element  13  during the molding of the cap A. 
     A bush  28  is inserted in the seat  26  and abuts, with an upper annular lip  29 , on the edge of the seat  26 . An external flange  32  of the sleeve  25  rests on the annular lip  29 , with the interposition of a ring of elastic material  30  and of a spacer ring  31 . Retention elements  33  engage on the flange  32  and, by means of screws (not shown in the drawing), lock on the upper face of the drum  27  the sleeve  25  and the bush  28  coaxially to each other and to the seat  26 . 
     The bush  28  forms, together with the tubular element  23  and the sleeve  25 , a compartment  34  in which there is a tube  35 , which can slide on the tubular element  13 , and there is a bushing  36 , which can slide on the tube  35 . The lower end  35   a  of the tube  35  is chamfered externally in a conical fashion. 
     Axial sliding bearings  37 ,  38  are interposed between the tube  35  and the bushing  36  and between said bushing and the bush  28 . 
     In the compartment  34 , above the bushing  36 , there is a cylindrical case  39 , which rests, with a lower inner lip  40 , on the top of the bushing  36 . A center bearing  41  is centered on the case  39 , and a ring  42  of elastic rubber-like material is interposed between said center bearing and the flange  32  of the sleeve  25 . 
     The tube  35  has, at the top, an outer lip  43  for abutment on the inner lip  40  of the case  39 , which supports a center bearing  44  for the resting of a cylindrical spring  45 . The spring  45  is accommodated in an annular chamber  45   a  comprised between the sleeve  25  and the case  39  and abuts against the center bearing  41 . The compression strokes of the spring  45 , i.e., the upward strokes of the tube  35 , are limited by the abutment of the center bearing  44  against a shoulder  46  of the sleeve  25 . 
     The tube  35  has, at its lower end, a circular hollow  47  (see FIG. 3) for the vertical retention of four sectors  48 , which are arranged so as to constitute a forming ring for a region of the tamper-evident band D of the plug A and at the same time act as an aid for the ejection of the cap A performed by the plug  15  after molding the plastics and opening the mold. 
     The sectors  48  cover a 90° angle about the axis X and are provided with collars  49 , which engage in the hollow  47 . 
     Furthermore, the sectors  48  protrude downward, beyond the lower end of the sleeve  35 , with a conical segment  50 , which ends with an edge  51  that is concentric to the axis B and is provided with a slot  51   a , which faces the portion  13   a  of the tubular element  13 . The edge  51  therefore allows to form, on the outside of the cap A, the step G and the collar F, i.e., undercuts which, in conventional molds, contrast the extraction of the molded item. 
     The ring constituted by the sectors  48  is substantially frustum-shaped, and on the outer surface of each sector there is a dovetail slot  52 , which lies on a radial plane that passes through the axis X. The slots  52  constitute sliding guides for keys  53 , which are fixed in seats  54  of a conical ring  55  that is centered and fixed by means of screws  56  coaxially to the axis X under a plate  57 , which is slidingly guided on the bushing  36 . 
     The keys  53  diverge downward with the same angle as the slots  52 , so that when the bushing  36  is actuated so as to descend, the sectors  48  move mutually apart in a radial and circumferential direction and remain engaged axially with the hollows  47  by means of the collars  49 . 
     The plate  57  is rigidly coupled to the rotary drum  27  by means of a pin  58  (see FIGS.  1  and  4 ), which is fixed with one end under said drum and is provided, at its opposite end, with a mushroom-like part  59 . The pin  58  can slide in a hole  60  formed in a wing  61  of the plate  57 , and on the portion of the pin  58  that lies between the wing  60  and the drum  27  there is a spring  62  which, by means of its opposite ends, rests on the wing  61  and on the drum  27 , with bushings  63  and  64  interposed. 
     The spring  62  keeps the plate  57  rested on the sectors  48 , which accordingly, during the descent of the bushing  36 , remain closed in a ring-like arrangement until the wing  61  abuts against the mushroom-like part  59  of the pin  58 . 
     When the wing  61 , after performing a stroke “h” from a preset raised position, abuts against the mushroom-like part  59 , by means of the additional stroke of the bushing  36  the sectors  48  are forced, by the engagement of the keys  53  in the slots  52 , to follow a path that diverges downward and causes the edges  51  to be spaced from the lower threaded portion  13   a  of the tubular element  13 . In order to actuate the bushing  36  there is a column  65  (see FIG.  2 ), which can slide, by means of bearings  66  and  67 , in a seat  68  of the drum  27  that is parallel to the seat  26  and whose axis is radially internal with respect to the axis X of the unit S. 
     An arm  69  (see FIGS. 1 and 3) is fixed to the lower end of the column  65  by means of a screw  68  and is provided with an opening  70 , through which the bushing  36  is guided. The opening  70  is shaped so that its edge remains gripped between two collars  71 ,  72  of the bushing  36 , so as to provide an axial connection thereof with the column  65 . The sleeve  36  can be positioned at an angle to the arm  69  by means of a pin  73 , which is guided in a radial hole  73   a  of the arm  69  and is provided with a knob  74 ; by acting on said knob in contrast with a return spring  75 , it is possible to cause the engagement of the pin  73  in any one of a plurality of holes formed in the sleeve  36  between the collars  71  and  72 . 
     The column  65  protrudes above the drum  27  with a tang  76  (see FIG.  2 ), which slidingly supports, with the aid of bearings  77  and  78 , a sleeve  79 . The sleeve  79  has a collar, which acts as a shoulder  80 , and is surmounted by a washer  81  that rests on the upper edge of the sleeve  79 . A precompressed spring  82  rests on the washer, and its top end rests against a bushing  83 , which is fixed to the upper end of the tang  76  in an adjustable manner in order to be able to adjust the precompression of said spring  82 . 
     A ring  84  is screwed onto the sleeve  79  until it abuts against the shoulder  80 , and a stem  85  protrudes from said ring  84  and supports two rollers  86 ,  87 . The roller  87  is engaged in a cam  88 , which is rigidly coupled to the fixed structure of the apparatus and is therefore stationary with respect to the drum  27 . The roller  86  is guided in a vertical slot of a bracket (not shown in the drawing), which is fixed on the drum  27  and is meant to prevent the rotation of the sleeve  79  with respect to the tang  76 . 
     The cam  88  has a circular extension that is concentric with respect to the axis Z of the carrousel, so as to produce axial movements of the column  65 , and, by way of the connection provided by the arm  69 , of the bushing  36 . 
     The axial movement of the bushing  36  is combined with the movement of the ejector  3 ,  9 . For this last movement, there is a roller  89 , which is mounted on the cylindrical body  18  at the top end of the stem  6  and is capable of following an axial cam  90 , which is also stationary and concentric with respect to the cam  88 . 
     The roller  89  is retained on the profile of the cam  90  by a spring  91 , which rests on the flange  32  in a downward region and on a shoulder  92  of the body  18 , with a cup-shaped washer  93  interposed, in an upper region. 
     In order to prevent the rotation of the stem  6  and of the body  18  about their own axis, there is a bridge  94 , which is fixed to the top of two columns  95 ,  96  and has an opening  97  through which the cylindrical body  18  is slidingly guided. 
     An axial slot  98  is formed in the outer surface of the cylindrical body  18 , and a key  99  slidingly engages therein; said key is fixed to the bridge  94  and protrudes into the opening  97 , allowing the body  18  to slide, but not rotate, in the opening  97 . 
     The operation of the described apparatus is as follows. During the rotation of the carrousel, a dose of plastics having a pasty consistency is deposited in the cavity of the female mold part  2 . In this step, the female mold part  2  is lowered with respect to the male mold part  1 , while the plug  15 , by means of the spring  91 , is actuated into the upward stop position determined by the abutment of the step  9   a  of the portion  9  against the shoulder  13   b  of the tubular element  13  and of the top end thereof against the lower end of the sleeve  25 . 
     In this stop position, the lower end  35   a  of the tube  35  lies above the edges  51  of the sectors  48 , in front of the recesses  13   c  of the portion  13   a.    
     When the female mold part  2  is lifted hydraulically, the edges  51  of the sectors  48  initially abut against the shoulder  100  of the mold part  2  (see FIG. 1) and then against the lower end  35   a  of the tube  35 , thus delimiting the cap forming chamber. As the upward motion of the female mold part  2  continues, the plastics is distributed into the forming chamber, filling it and causing, owing to its own incompressibility, the female mold part to stop in the final position, in which the cap A has assumed its final shape. 
     It should be noted that the spring  45 , by acting on the tube  35  and, by means of the lip  44  of the case  39 , on the bushing  36 , keeps the edges  51  rested on the shoulder  100  and allows to vary the volume of the forming chamber according to the quantitative variations of the dose of plastics that is deposited in the cavity of the female mold part. 
     When the plastics has reached a suitable setting point, determined by feeding cooling liquid into the chamber  10  and into the similar chamber of the female mold part, so that plastic deformations of the cap are no longer a concern, the descent of the female mold part  2  is actuated. However, the cap A is retained on the plug  15  by the engagement of the thread C in the slot  14  of the portion  13   a  and by the retention of the tamper-evident band D between the outer surface composed of the edges  51  of the sectors  48  and the conical end  35   a  of the tube  35  and the inner surface, composed of the region of the portion  13   a  that is provided with the recesses  13   c.    
     When the female mold part  2  is spaced sufficiently from the plug  15 , the downward movement of the column  65  and of the hollow stem  6  is actuated by means of the cams  88  and  90 . 
     The descent of the hollow stem  6  causes (see FIG. 6) the lowering of the plug  15  to the stroke limit level, at which the tamper-evident band D lies below the conical end  35   a  of the tube  35 . At the same time, the descent of the column  65 , by means of the arm  69 , determines the descent of the bushing  36  and the downward actuation of the sectors  48 . 
     The descent stroke of the column  65  comprises a first portion, which is equal to the stroke of the plug  15 , during which the conical ring  55 , by way of the spring  62  that acts on the wing  61  of the plate  57 , remains engaged on the sectors  48  and prevents their opening. During said first portion, the descent of the sectors  48  is accompanied by the descent of the plug  15  and the edges  51  therefore remain in resting contact on the step G of the molded cap A. 
     At the end of the first portion of the stroke, the wing  61  abuts against the mushroom-like part  59  of the pin  58 , which stops the descent of the plate  57  and of the ring  55 , while the tubular element  13 , by way of the presence of a top collar  13   d  (see FIG. 2) that abuts on a shoulder  35   b  of the tube  35 , stops with respect to the stem  6 . 
     In particular, it should be noted that the descent of the tube  35  is prevented by the abutment of the outer lip  43  against the inner lip  40  of the case  39 , which in the meantime, by means of the spring  45 , has moved so as to rest against the internal shoulder  28   a  of the bush  28 . 
     The halting of the tube  35  allows the formation, above the edges  51 , of an annular opening  101  (see FIG.  6 ), into which the tamper-evident band D can expand in order to allow the teeth E to protrude from the respective recesses  13   c  of the portion  13   a.    
     With the second portion of the descent stroke of the column  65  and of the hollow stem  6  (see FIG.  7 ), the thrust applied to the sleeve  36  and to the stem  6  actuates downward the sectors  48  and the ejector  3 ,  9 , which by acting respectively on the step G and on the bottom H of the cap A cause the disengagement of the thread C from the slot  14  and of the teeth E from the respective recesses  13   c  of the portion  13   a , allowed by the elasticity of the plastics, which allows the cup B to expand radially and allows the tamper-evident band D to open out into the opening  101 . 
     As they continue their descent, the sectors  48  are forced, by the oblique orientation of the guides  52  and  53 , to move further away from the peripheral region of the cap until they leave the step G. At this point, the complete extraction of the cap A is entrusted solely to the ejector  3 ,  9 , whose thrust continues until the teeth E have descended below the lower edge of the portion  13   a , beyond which the cap A can fall freely into a collection area. 
     It is evident that the fundamental prerogative of the present invention is that the sectors  48  allow to act both as elements for forming undercuts that lie externally with respect to the cap and as elements that assist cap extraction. The thrust applied axially to the cylindrical wall of the cap by the sectors  48  in fact facilitates the widening of the cap that is required in order to allow the ejector  3 ,  9  to force the exit of the thread C from the helical slot  14  without causing the material of the cap to yield. 
     By contrast, it should be noted that in conventional molding units, in which cap extraction is entrusted solely to the ejector, the thrust applied by said ejector to the bottom of the cap causes the cylindrical wall of the cup B to clamp more tightly onto the tubular portion  13   a . This fact obviously requires more force to remove the thread C from the slot, with severe consequences for the integrity of the cap. 
     The described apparatus is susceptible of numerous variations in order to deal with the different types of product. 
     FIGS. 9 and 10 are sectional views of the lower part of a unit for the compression molding of the lower part L of a container made of plastics, which is composed of a frustum-shaped plate M and an externally threaded neck N. 
     In FIGS. 9 and 10, the elements constituting the unit that are identical or equivalent to those of the unit shown in FIGS. 1 to  8  are designated by the same reference numerals. 
     As clearly shown, the unit of FIGS. 9 and 10 is constructively simpler, owing to the fact that the part L to be molded is not provided with inner undercuts which, in order to be able to disengage from the respective molding recesses of the plug  15  during part extraction, would have to be able to expand outward, as allowed for example by the end  35   a  of the tube  35  of the molding unit described earlier. The absence of the inner undercuts therefore allows to remove the part simply by opening the conical segments  51 . 
     The disclosures in Italian Patent Application No. B02000A000704 from which this application claims priority are incorporated herein by reference.