IMPROVEMENTS RELATING TO TIRE CURING PRESSES

Abstract: To obtain an expedite and automatic engagement and disengagement of the bladder (10), with respect to the relative operating mechanism, in particular in the presses used for curing pneumatic tires, the movable clamp (13), and the fixed clamp (14), respectively, which block the beads of the flexible, elastically deformable sleeve constituting the bladder, comprise annular grooves (136,145), coaxial with the axis of the bladder, which, in operation, contain the heads of a plurality of pegs (242,213), situated in the head (24), to be assembled to the movable clamp and in the body (21), of the support to be associated to the fixed clamp, said pegs being radially movable in both senses between two positions, i.e. a work position in operating condition and a rest position in which said pegs are completely collapsed into the body of said head and of said support so as to allow the axial insertion of said bladder on said mechanism and its removal therefrom.

Description: The present invention relates to the presses used for curing pneumatic tires and, more specifically, it concerns the bladder mounted on the press and the mechanism used for its operation. It is known that, to cure hollow articles of elastomeric or plastomeric material, having a relatively thin wall, curing moulds are used, which are formed by at least two hollow halves, mutually engageable and disengageable, able to allow the insertion and the subsequent removal of the article being cured, which, when the mould is closed, originate an outwardly closed cavity, defining the external shape of the article itself. Inside the mould a bladder is instead provided, constituted by a flexible envelope, generally made of cured elastomeric material, reinforced if desired with textile or metal cords, which is inflated by a fluid under pressure at a high temperature; by virtue of said inflation fluid, the bladder expands against the internal surface of the article being cured, thus pressing the wall of the latter against the inner surface of the mould till to the end of the curing cycle. When the curing cycle is over, the bladder is deflated or placed under vacuum to reduce at the most its overall size, so that the removal of the cured article from the mould, opened in the meantime, is facilitated. All the movements necessary to open or to close the mould and to operate the bladder are carried out by means of a machine of well known structure, known as curing press. For the sake of clearness and simplicity and in view of a better understanding, the invention will be described with specific reference to the presses used to cure pneumatic tires, although it is clearly evident from the previous introduction that the invention itself is not restricted to this machine and to obtain this specific product, but concerns all the range of machines which comply with the above indicated requirements. The conventional press used for curing pneumatic tires is well known: substantially, it is formed of a basement and of an upper frame, movable with respect to it. The basement carries a curing mould constituted of two opposite coaxial hollow elements, one fixed to the basement and the other connected to the frame, which, in position of mutual assembling (press and mould closed), define a cavity which reproduces the outer toroidal surface of the tire being cured. Sometimes, in the mould, the two hollow elements have the shape of two annular plates corresponding to the tire sidewalls and the mould comprises a plurality of sectors, arranged circumferentially and inserted between said plates, which are connected to the frame by an annular device with inclined plates, so as to be radially movable in both senses with respect to the two annular plates and axially movable in both senses with respect to at least one of said plates. Irrespective of the type of mould used, the presses concerned by the invention are provided with a bladder arranged coaxially inside the hollow elements or the annular plates and necessary for the admission of fluid under pressure inside the tire being cured, whose operation is controlled by an actuation mechanism permanently housed in said basement. Although the bladder is actually the only flexible envelope, in the present specification as set forth hereinafter and in the appended claims the expression "bladder", for simplicity's sake, will indicate the assembly formed by the flexible envelope and the two end clamps which block said envelope and guide its shaping during the press working cycle. The flexible envelope, by itself, will be indicated as "cylindrical sleeve", such being substantially its shape in rest condition. It is known that the bladder must be replaced with a certain frequency during the press working cycle, owing to its natural wear or for accidental reasons depending on the severe working conditions, or when the mould is to be changed, being different the size of the tire being cured. Also, it is known that all the operations effected on the presses to change their equipment are to be carried out manually and are consequently long and expensive, since it is necessary to await the press cooling before effecting the equipment substitution and then to bring again the press to the pre-established temperature before re-starting the curing operation. Therefore, it can be easily understood how deep is the interest of the technicians in respect of machines and apparatuses which allow an automatic replacement of the equipment and are consequently able to operate immediately after the end of a curing cycle, namely on the press still at a high temperature. In fact, studies were already made with reference to the moulds substitution; however, the problem was not completely solved since the automatic replacement of the bladder did not yet find a convenient solution. The Applicant has now devised a new type of bladder, together with its relative operation mechanism, by means of which this problem can be considered as completely overcome, since the replacement of the bladder takes place quite automatically in a very short time interval, on the machine still hot, so that the cooling suffered by the press and the mould during said replacement is of moderate entity and does not require idle times to reach again the curing temperature. The present invention is set forth in the claims and aims at providing a bladder and the corresponding mechanism for its operation, which are able to permit an expedite engagement and disengagement of said bladder with respect to said mechanism. Accordingly, a first object of the present invention is represented by a bladder comprising a substantially cylindrical, flexible and elastically deformable sleeve provided with beads on each end, a movable clamp to block one end of the sleeve and a fixed clamp to block the other end of the sleeve, the movable clamp comprising a disc provided with a coaxial hub and a first fastening ring secured to said disc, the disc and the ring having a peripheral portion of their surface which can be associated to a first bead of the sleeve, and connecting means to block said first bead between said disc and said ring, the fixed clamp comprising a pair of distinct coaxial elements to be firmly secured together, each element having an annular portion of its surface which can be associated to the second bead of the sleeve, and connecting means to block said second bead on the fixed clamp, the bladder being characterized in that it comprises devices for the automatic engagement and disengagement of the movable and fixed clamps with respect to a corresponding supporting and operating mechanism. The second object of the invention, in any case inseparable from the above cited first object of the same, is represented by a supporting and operating mechanism for said bladder, the mechanism comprising a support to be associated to the fixed clamp of said bladder and a stem, coaxil with said support, axially slidable into it, to be associated to the movable clamp of the bladder, and means to carry out the axial displacement of the stem with respect to the support, the mechanism being characterized in that the support and the stem are provided with devices for the automatic engagement and the disengagement of the movable and fixed clamps. According to an appropriate embodiment of the invention, said devices comprise an annular groove obtained on the radially inner surface of the movable clamp and another annular groove obtained on the radially outer surface of a flanged tube which represents one of the two elements constituting the fixed clamp, the other element being constituted by a ring fastening the bead, which can be integrally associated to the flanged tube. Correspondingly, the devices provided on the mechanism actuating the bladder according to the invention comprise a plurality of pegs, housed into corresponding holes, obtained both on a head fast with the end of the stem which is to be associated to the movable clamp, and on the support which is to be associated to the fixed clamp, said pegs being radially movable in both senses, in a plane perpendicular to the axis of the mechanism, between two positions, namely an expanded or work position and a collapsed or rest position, respectively, means being provided to move the pegs from the collapsed to the expanded position, the pegs in expanded position being at least partially protruding from the lateral surfaces of the head and of the support which face the corresponding surfaces of the hub and of the flanged tube and being housed in the corresponding annular grooves obtained on the hub and on the flanged tube. In the preferred embodiment, the head fast with the stem and associable to the movable clamp is cup-shaped; its lateral wall is provided with radial holes, whose axis lies in a plane perpendicular to the axis of said stem, to house corresponding pegs alternatively movable radially between said expanded position and said collapsed position, the pegs being provided, on their end directed towards the cup inside, with two axially opposite wings, the motion of the pegs between said two positions comprising a rotation around one of said wings, the cup containing an axial small piston, shaped as an overturned goblet and axially slidable inside the cup, contrast means being provided to prevent the small piston from outcoming from the cup and elastically deformable means being provided to control the axial motion of the small piston with respect to the cup. Further, the means causing the motion of the pegs from the collapsed to the expanded position are conveniently represented by cam profiles obtained on elements coaxial with the axis of the mechanism and revolving about their own axis, as for instance a cam encased inside a cup-shaped head, integral with the stem end, associated to the movable clamp, and a ring nut revolving about an annular flange fast with the support, the latter being provided with a coaxial bush comprising said pegs, radially displaceable to be associated to the fixed clamp. Vice versa, in the head to be connected to the movable clamp, carried out according to the preferred embodiment, the displacement of the pegs from the collapsed to the expanded position is driven by the relative axial movement of the small piston. At last, the bladder according to the invention comprises devices, as for instance further annular grooves obtained on the radially outer surfaces of the movable and fixed clamps, in order to be picked up, transported and released, in a completely automatic manner, by appropriate pliers having gripping arms at least radially movable in both senses but, preferably, also axially movable in both senses with respect to the axis of the pliers. The present invention will be better understood with reference to the following description and to the attached drawings, given only by way of non-limiting example, in which: FIGURE 1, 2 and 3 - illustrate the state of the art prior to the invention, the general features and the operating system of the apparatus according to the invention; FIGURE 4 - illustrates in cross-section the particulars of the bladder according to the invention; FIGURE 5 - illustrates in cross-section the mechanism for operating the bladder shown in figure 4; FIGURE 6 - illustrates in cross-section a preferred embodiment of the head of the mechanism shown in figure 5; FIGURE 7 - illustrates the head of figure 5 in a section perpendicular to its axis; FIGURE 8 - illustrates, in a section perpendicular to its axis, a second portion of the mechanism shown in figure 5; and FIGURE 9 - illustrates the expedite automatic engagement of the bladder according to the invention on the corresponding operating mechanism. The first three figures illustrate the state of the art, on which the present invention is grounded, with reference to a peculiar type of press, equipped with a mould of the so-called "centripetal" kind, namely one comprising two axially opposite halves and a crown of radial sectors interposed between the halves, in any case of conventional construction. The basement B of the press, coaxial with the mould (figure 1), carries, encased into it, the bladder 1 which comprises a flexible cylindrical sleeve 10 provided with end beads 11 and 12 and retained between two clamps, herein indicated as movable clamp 13 and fixed clamp 14, respectively, since the latter, on certain presses, is integral with the basement. The movement of said clamps is controlled by an operating mechanism 2, permanently secured to the press and contained in the basement, which is coaxial with the mould and the bladder and comprises a support 21, axially movable with respect to the basement, on which is fastened clamp 14, and a stem 22, coaxially slidable within support 21 and having one end secured to the movable clamp 13. Obviously, the other ends of stem 22 and of support 21 are linked to the devices carrying out their movements, which are not illustrated. The figures, which have the only task of defining in its general structure the bladder and the relative operating mechanism, illustrate the loading of an uncured tire into the curing mould in three different phases, more precisely: the insertion of the uncured tire P in the mould opened (figure 1), the arrangement of the bladder, and in particular of the sleeve, into said uncured tire by partial inflation of the bladder itself (figure 2) and the mould closure (figure 3). The invention concerns therefore the bladder and its operating mechanism, since these elements are provided with means which allow a quick substitution of the former on the latter. The bladder is represented in detail in figure 4, from which it is possible to see the cylindrical sleeve 10 with its end beads 11 and 12 blocked between the two clamps 13 and 14. The movable clamp 13 comprises a disc 131 having a coaxial hollow hub 132, axially extending on both parts of the disc and opened outwardly from both sides, namely axially holed. A portion of the disc peripheral surface is shaped in such a way as to be associated to bead 11 without damaging said bead or the immediately adjacent sleeve portion on account of the deformations suffered by the sleeve in use and during the bladder substitution. A first fastening ring 133 is integrally secured on the disc edge by conventional means 134, for instance bolts; also a portion of the ring surface can be associated to bead 11 in the same manner foreseen for the disc. Moreover, the assembling of ring 133 on disc 131 originates the block of bead 11 on clamp 13. The radially outer surface of the hub which is directed towards the axially outer surface of the disc is provided with an annular groove 135 whose function will be explained herebelow. Also the radially inner surface of the hub is provided with an annular groove 136, preferably without sharp edges, which in the drawing is shown as corresponding to the outer annular groove. Also the function of this groove will be indicated hereinafter; however, it is by now pointed out that groove 136 can be located in any point of the hub body, along the axial development of the latter, and more precisely it can be situated in the hub portion, both on its radially outer and on its radially inner surface, which is directed towards the axially inner surface of the disc. At last, a spacer 137 can be mounted on the inner surface of the disc in order to obtain the minimum desidered distance between the clamps during the various operations. The fixed clamp 14 comprises a tube 141 flanged at one end, and a second fastening ring 142, which can be made integral with flange 143 of the tube by virtue of conventional connecting means 144, for example bolts. Like in clamp 13, also the tube flange and the relative fastening ring have a portion of their peripheral surface which is so shaped as to be associated without any prejudice to the bead 12 of the sleeve, locking moreover said bead on clamp 14. The sleeve body is provided with an annular groove 145, described in detail hereinafter, which is here represented on the radially outer surface of the tube, but which could be obtained on its radially inner surface. At last, the fastening ring 142 has an annular groove 146 on its axially outer surface; the function of said groove will be considered herebelow. As it will be clearly apparent, the bladder according to the invention permits an expedite engagement and disengagement of the relative operating mechanism, provided that the latter comprises corresponding means exploiting the bladder features. Figure 5 illustrates the mechanism according to the invention, which is associated to said bladder. Mechanism 2 comprises substantially an axially holed annular support 21, which can be movable or fixed with respect to the basement of the press on which it is associated, a coaxial stem 22, axially slidable in said support, and an annular ring nut 23, coaxially rotating around support 21. As already said, support 21 is associated to the fixed clamp, whilst the end of stem 22 is associated to the movable clamp, so that the movement of the stem, of the support, and of the former with respect to the latter, originate the operation of the bladder as required for the various steps of the curing process. To assemble the movable clamp on the end of stem 22, a head 24 is appropriately provided; it is made fast with said stem 22 for instance by screwing in the stem body, according to conventional systems already known. Head 24 is cup-shaped and its wall 241 is provided with at least one - but preferably three - holes circumferentially arranged at 120°, the axes of which lie in a plane (VII-VII) perpendicular to the axis of stem 22. A peg 242 is freely axially slidable inside each hole. The end (head) of peg 242 which protrudes radially outwardly is conveniently rounded in the form of a spherical cap and its end (tail) which protrudes radially inwardly comprises an annular ridge which prevents the peg from outcoming from its seat. The peg length is such that, when the annular ridge abuts against the radially inner surface of the cup, its head protrudes outwardly from the cup wall. The head contains a cam 243 (figures 5 and 7) secured into it and fast with a nut 244, having sharp edges, which is coaxial with the cup and can freely rotate about its own axis. The circumferential profile of the cam comprises a plurality of arcs arranged to have a variable distance with respect to the cup axis and radiused to one another by radial rectilinear sections. The number of arcs corresponds to the number of pegs and the cam profile is such that, at the position of maximum distance between the arc and the cup axis, the corresponding peg is abutting against the cup wall, whilst, at the position of minimum distance from the axis, a sufficient clearance exists between the cam profile and the peg tail to allow the peg to slide towards the cup axis, with the consequent collapse of its head into said cup wall. It can be easily understood that, when cam 243 is rotated by acting on a nut 244 previously grasped with a correspondingly shaped tool, the pegs can be blocked in a so-called "expanded" position, in which their head extend from the cup wall, or vice versa they can be left free to take a second position, called "collapsed", in which their heads are completely contained into the cup wall. At last, the cup opening can be suitably covered with a lid 245, pierced at its center, to give access to a nut 244; further, the outer lateral surface of the cup is conveniently provided with circumferential grooves containing conventional fluid-tight means 246 (O-ring) to prevent any percolation of the inflation fluid from the bladder. Figure 6 illustrates a second preferred embodiment of the head assembled to the movable clamp. According to said embodiment, the head 25, which can be screwed on stem 22 like head 24, is still cup-shaped and is conveniently closed by an axially holed lid 251; the cup contains a small piston 252, having the form of an overturned goblet, which is axially slidable in head 25, but is kept pressed against lid 251 by a helical spring 253 housed in the cavity of the small piston and working under compression. The cup wall is provided with at least one, but preferably three, holes, circumferentially arranged at 120°, whose axis lies on the same plane, orthogonal to the cup axis. Each of said holes contains a peg 254 composed of a central body arranged inside the hole, in which the end facing the cup outer surface has a rounded form, preferably the form of a spherical cap, and two wings 255 and 256, diametrically opposite with respect to said central body, which have an axial orientation parallel to the cup axis. Said wings lean on the inner part of the cup and the end of each wing can act as a center of rotation for the peg, under the action of forces applied on the peg head, and at the same time as a mechanical stop against the outcoming of the peg from its seat. It is evident that the rotation of the peg around any of said wings originates its collapse into the cup wall, i.e. causes its movement between two positions, respectively defined as expanded and collapsed, with the same meaning as indicated above. Actually, in the illustrated embodiment, the peg can rotate only about wing 255 and only when the small piston 252 is in contact with the cup base; in this case, as hereinafter explained, wing 256 corresponds to stem 257 of the small piston (figure 9), which has a diameter smaller than that of the piston body, and consequently can freely move towards the cup inside. The engagement device for the fixed clamp will now be considered. As already said, it comprises an annular support 21, substantially composed of a cylindrical body, having an outer diameter slightly smaller than the inner diameter of tube 141 of clamp 41, which is provided with a flanged portion 211. The surface of said flanged portion directed towards the cylindrical body carries, fixed into it, a coaxial bush 212 whose body contains at least one, but preferably at least three, holes, circumferentially arranged at 120°, the axes of which lie in a plane (VIII-VIII) perpendicular to the axis of the annular support 21. Each of said holes contains a peg 213, freely slidable into it, whose size (along the hole axis) is greater than the thickness of the bush wall, so that the peg protrudes from the radially inner surface of said bush or protrudes from the radially outer surface of the latter, being it able, anyhow, to protrude simultaneously from both of said surfaces. For the sake of simplicity, the expression "rest position" means the position in which the pegs 213 do not extend from the radially inner surface of the bush (figure 9), and the expression "work position" means the diametrically opposite position, in which the pegs extend from the radially inner surface of the bush. The movement of pegs 213 from the rest to the work position is generated by the rotation of a ring nut 23, coaxial with the annular support 21, and rotatably mounted about the flanged portion 211. The rotation of the ring nut is driven in a conventional manner by known means, by acting for example on a suitable pin 231 integrally connected to the ring nut. The radially inner surface of the ring nut, in the position corresponding to the pegs, is in fact shaped (figure 8) as a broken line formed by circumferential sections radiused to one another by radial sections 233, each circumferential section 232 having one end substantially in contact with the bush body and the other end at a distance from the bush body allowing the peg 213 to collapse completely with respect to the radially inner surface of the bush, protruding obviously from the radially outer surface of the same. At last, it is pointed out that the bush rotation can be facilitated by the use of known means 214 (roller bearings or ball bearings) situated between the mutually displaceable facing surfaces; further, the body of the annular support 21 contains a duct 215 for the supply and the release of the curing fluid used to inflate the bladder, whilst the surfaces of the cylindrical portions of the annular support are conveniently provided with the already cited fluid-tight means (grooves and relative O-rings 216). After having described the construction details of the apparatus, its operation will now be taken into consideration. Figure 9 illustrates the insertion of the bladder according to the invention on its operating mechanism, carried out by means of an appropriate equipment, although, evidently, said operation of engagement and disengagement can be effected in any other way, even by hand. The bladder is taken up from the store area where it has been previously prepared by assembling the flexible sleeve to its clamps after having blocked the beads with the already cited fastening rings. This operation is effected by means of an equipment 26, slidable on suitable guides (not illustrated), which allow it to be positioned over the press, now opened, in coaxial arrangement with the press axis. Equipment 26 is provided with arms 261 and 262 circumferentially situated around a common axis, represented by a stem 263, axially movable in both senses with respect to the equipment shell. Said arms are radially movable in both senses with respect to the common axis and, preferably, are also axially slidable with respect to the shell. The bladder is grasped by a centripetal movement of the arms, which brings their free ends, appropriately L-shaped, to be encased into the annular grooves 135 and 145 of clamp 13 and of clamp 14, respectively. Subsequently, equipment 26 takes a position coaxial to the press and begins inserting the bladder on the mechanism (figure 9). The mechanism has been prepared by lifting stem 22 to allow the insertion of both clamps on the respective supports with the cylindrical sleeve in stretched position; moreover, ring nut 23 has been rotated in the position corresponding to the rest position of the pegs. The operation is described with reference to the case in which stem 22 is equipped with a head 25; however, the different behaviour of the same stem, equipped with a head 24, will be brought into evidence hereinafter. As soon as the coaxial arrangement of the equipment, the bladder and the mechanism has been carried out, stem 263 of the equipment is pushed against head 25, enters said head and presses the small piston 257, overcoming the action of the helical spring 253, into the cup base, so that pegs 254 are allowed to rotate freely about wing 255 and therefore to be embedded in the thickness of the head wall. Now the bladder is lowered towards the mechanism; it is evident, after the above description and with reference to figure 9, that the radially inner surface of hub 132 interferes with the pegs, causing them to collapse into the head; the movement is continued until the axially outer portion of the hub abuts against the axially outer surface of head 25 and stops. In this position the annular groove 136 on the hub is situated corresponding to the pegs heads 254. As regards clamp 14, the situation is identical: tube 141, in its downward movement towards support 21, interferes with the heads of pegs 213, which might protrude from the radially inner surface of the bush, originating their collapse into the bush wall. The movement stops when the lower end of the tube abuts against the flanges wall 211 of the annular support; in this position the annular groove 145 obtained on the tube body is positioned corresponding to the heads of pegs 213. At this time, ring nut 23 is rotated to be brought to the work position illustrated in figure 8; on account of said rotation, not only pegs 213 outcome from their holes, encasing their heads into the annular groove 145, but also remain blocked in that position. At the same time, the pressure acting on stem 263 of the equipment is released. Owing to the release of spring 235, the small piston 252 rises again towards the upper end of head 25, pushing stem 263, now freely slidable, and consequently pushing radially outward, with respect to the cup, pegs 254, whose heads are encased in groove 136 of the hub, so that they remain blocked in said position (figure 6). Now arms 261 and 262 are radially moved, disengaging them from clamps 13 and 14, so that equipment 26 can move away from the press, leaving the latter provided with the new bladder and ready for the re-starting of the curing operations. The bladder disengagement takes place in a clearly understandable manner, by effecting all the above described operations in inverted sequence and in particular by allowing pegs 254 and 213 to move freely into their seats by virtue of the thrust exerted by the two clamps, as already seen, namely with the aid of stem 263 and by rotating ring nut 23 in opposite sense. Obviously, during the disengagement of the movable clamp 13, pegs 254 rotate about wing 255. At this moment, the differences in the operating process, necessary when stem 22 is equipped with head 24, will be clearly apparent. In that case the end of stem 263 must have a shape able to fit with the prismatic head of nut 244, so as to cause the latter, together with cam 243, to rotate axially in order to release and to block pegs 242 alternatively, analogously to what happens in respect of pegs 213. However, it was pointed out that preference is given to the system using head 25. To understand the reason of this preference it is to be taken into account that the above described expedite engagement and disengagement of the bladder must give the operator the assurance that, in particular, the engagement step has been properly effected, namely that the heads of the various pegs are firmly blocked into the corresponding annular grooves provided in the two clamps; in fact, in the contrary case, the admission of fluid under pressure and at a high temperature into the bladder might originate the disengagement of the clamps from the relative supports, with serious consequences for the safety of the operators working in proximity of the press and for the machine itself. As regards the fixed clamp, no problems are involved: the complete rotation of the ring nut between the two positions (rest and work) of pegs 213 can be easily checked since said positions are, or can be, rendered stationary with respect to the press basement. Vice versa, as regards clamp 13, in the arrangement comprising head 24, equipment 26 must be provided with devices able not only to perform the coaxial positioning of stem 263 with respect to the press axis, but also the correct relationship with a certain angular orientation between stem 263 and nut 244, since only in stated mutual angular positions it is possible to connect the stem with the nut; further, equipment 26 must be provided with devices intended to measure the entity of the rotation effected by stem 263. All the above devices make equipment 26 more complicate and expensive. On the contrary, with head 25, stem 263 must effect only axial movements, easily obtained by means of a fluid-dynamic cylinder, whilst the position for blocking pegs 254 (small piston 252 in the top dead center) can be easily located by checking the axial displacement of stem 263, said check being made by means of transducers much simpler and cheaper than those indicating angular positions. In conclusion, by the adoption of head 25 the equipment is simpler, more reliable and less expensive and the engagement and disengagement operations are slightly quicker than those obtainable by using head 24. Reference is now made to the previous statement made in respect of the bladder, according to which the annular grooves on the hub of clamp 13 and on the tube of clamp 14 can be provided in any suitable position, and in particular even on the surfaces radially opposite to those illustrated. It is now clear that said grooves, being intended to receive the heads of the pegs which block the clamps on their corresponding elements of support of the mechanism, must be situated at said pegs, which can be located in positions completely different from those illustrated above. By way of example, a technician skilled in this field will have no difficulty in devising an annular support 21 inside which the pegs are housed in appropriate grooves obtained in the cylindrical portion of the support, with the consequent elimination of bush 212 and ring nut 23. Likewise, it will be easy to conceive a head, to be associated to the end of stem 22, which, instead of being inserted in the hub 132, is inserted on the hub or better on a corresponding pin; in that case it will be necessary to vary again the relative position of pegs 242, distributing them circumferentially at the radially outer surface of the hub, which latter will be therefore replaced with said pin. As to the pegs, they can be obviously obtained in any way which is technically equivalent to that described above; in other words, they can be small cylinders, prismatic stems or spheres, and can be connected to an appropriate operating mechanism also in respect of their movement from the work to the rest position. In other words, also the displacement which releases the pegs from their position of interference with the clamps can be obtained for instance by the rotation of ring nut 23 and of cam 243 or by the axial stroke of small piston 252. The bladder and the relative mechanism in accordance with the invention have achieved all the proposed aims and appear to be extremely advantageous; in fact they have a very simple structure, cheap and quite reliable. They permit to carry out automatically the bladder substitution, without any manual intervention on the press still hot, in a very short time interval. In the preferred embodiment they require only the axial centering between the bladder, the mechanism and the picking up equipment, with the exclusion of any angular orientation with respect to the press axis, improving therefore the remarkable advantages already obtained with the more general embodiment of the device according to the invention. At last, it is evident that the present invention has only an explanatory and not restricting purpose, so that it includes all the possible modifications and variations which, although not specifically described herein, are easily conceivable by a technician skilled in this field.

Claims: A bladder and supporting mechanism assembly in a press for curing hollow articles of elastomeric or plastomeric material wherein said bladder (1) comprises a substantially cylindrical flexible and elastically deformable sleeve (10) provided with beads (11, 12) on each end, a movable clamp (13) adapted to block one end of said sleeve, and a fixed clamp (14) adapted to block the other end of said sleeve, said movable clamp comprising a disc (131) provided with a coaxial hub (132) and a first fastening ring (133) secured to said disc, the disc and the ring having a peripheral portion of their surface that can be associated to a first bead (11) of the sleeve (10), and connecting means adapted to block said first bead (11) between said disc (131) and said ring (133), said fixed clamp (14) comprising a pair of distinct coaxial elements (142, 143) to be firmly secured together, each element having an annular portion of its surface which can be associated to the second bead (12) of the sleeve (10), and connecting means adapted to block said second bead (12) on the fixed clamp (14); and wherein said supporting mechanism (2) comprises a support body (21) to be associated to the fixed clamp (14) of said bladder (1), a stem (22), coaxial with said support body (21) and axially sliding within it, to be associated to the movable clamp (13) of the bladder (1), and means for axially moving the stem (22) with respect to the support body (21); the assembly being characterized in that said bladder (1) comprises at least one coaxial annular groove (136) formed on the hub (132) of the movable clamp (13) and at least one coaxial annular groove (145) formed in one of the coaxial elements (143) of the fixed clamp (14); and in that said stem (22) of the supporting mechanism carries a head (24; 25) with first selectively radially protruding means (242; 245) for engaging said annular groove (136) formed on the hub (132) of the movable clamp (13), and that second selectively radially protruding means (213) are provided in said support body (21) for engaging the annular groove (145) in the fixed clamp (14); whereby said bladder (1) can easily and quickly engaged and disengaged with respect to said supporting mechanism (2). An assembly as in claim 1, characterized in that said first radially protruding means comprises at lest one peg (242; 254) housed in a hole formed in the head body (24; 25)), said peg (242; 254) being radially movable in both directions with respect to the stem axis, and means (244; 257) within said head (24; 25) for moving said peg (242; 254) into an expanded position in which the peg partially protrudes from the radial surface of the head (24; 25) facing the corresponding portion of the hub surface. An assembly as in claim 2, characterized in that said head (24) is cup-shaped and provided with radial holes in the cup lateral wall for housing said peg(s), and in that said moving means comprises a coaxial cam (244) rotatable about an axis coincident with the stem axis, the peripheral profile of said cam laying in a plane perpendicular to the stem axis and being continuously variable from a minimum radial extension to a maximum radial extension and then abruptly to the minimum radial extension, with said maximum radial extension corresponding to the expanded or protruding condition of said peg(s) (242). An assembly as in claim 2, characterized in that said head (25) is cup-shaped and provided with radial holes in the cup lateral wall, having their axes lying in a plane perpendicular to the stem axis and intended to house pegs (254), each peg being rotatable about one of a pair of axially opposite wings (255) provided thereon, and in that said moving means comprises a coaxial piston (257) shaped as an overturned goblet which is axially sliding inside the cup-shaped head (25) against the force of elastically deformable means (253), contrast means (251) being further provided for preventing the piston (257) from outcoming from the head (25). An assembly as in claims 1 to 4, characterized in that said support body (21) comprises a cylindrical body having a flanged portion (211) situated on its end opposed to the end to be associated with the fixed clamp (14) and carrying a coaxial bush (212) protruding from said flange towards the end to be associated with the fixed clamp (14), and in that said second selectively radially protruding means in said support body (21) comprises at least one peg (213) housed and slidably movable within a radial hole extending through said coaxial bush (212) for engaging the annular groove (145) in the fixed clamp (14). An assembly as in claim 5, characterized in that said support body (21) further comprises an annular ring nut (23) coaxial with and rotatable about said flange, and having a surface facing the radially outer surface of said bush (212), said ring nut (23) having, on its surface facing the bush (212) and the peg(s) (213), a repetitive profile, periodically varying from a maximum radial extension to a minimum radial extension. An assembly as in claim 1, characterized in that said annular groove (136) on the hub is formed in the radially inner surface thereof. An assembly as in claim 1, characterized in that said fixed clamp (14) comprises a tube (141) flanged at one end, and a second fastening ring (142) which can be integrally associated to the flange edge (143), said at least one coaxial annular groove (145) being formed in the tube body (141). An assembly as in claims 1 to 8, characterized in that an additional coaxial annular groove (135, 146) is formed on the outer surfaces of said movable clamp and fixed clamp, respectively, said additional coaxial grooves being adopted to be engaged by an external device for picking up, transporting and releasing said bladder (1). An assembly as in claim 9, characterized in that said additional annular groove (135) on the movable clamp is formed on the radially outer surface of the hub (132) on the portion which is radially external with respect to the bladder (1). An assembly as in claim 9, characterized in that said additional annular groove (146) on the fixed clamp is formed on the radially outer surface of the second fastening ring (142).

Inventors: PIZZORNO, AUGUSTO
Applicants: PIRELLI COORDINAMENTO PNEUMATICI SOCIETA PER AZIONI
Application year: 1987
Main classification: B29D30
IPC codes: B29D30, B29C33, B29K105, B29C35, B29L30, B29K21