Apparatuses for forming objects with undercut portions

Abstract

An apparatus for forming an object from a dose of plastics comprises a die arrangement provided with a cavity for receiving said dose and with at least two parts that are reciprocally movable for shaping an undercut portion of said object, at least one fluid for applying a clamping force so as to keep said at least two parts in contact; said at least one fluid is such as to increase discontinuously said clamping force from an initial force that is applicable when said dose is substantially contained in said cavity to a final force applicable when said at least two parts shape said undercut portion.

1 . Apparatus for compression-moulding an object from a dose of plastics, comprising a die arrangement provided with a cavity for receiving said dose and with at least two parts suitable for shaping an undercut portion of said object, wherein said at least two parts are movable with respect to one another along a substantially rectilinear trajectory. 
     
     
         2 . Apparatus according to  claim 1 , wherein said at least two parts comprise a first part and a second part. 
     
     
         3 . Apparatus according to  claim 2 , wherein said first part and said second part are mounted on a carriage movable parallel to a approach direction along which said die arrangement and a punch move together for shaping said dose. 
     
     
         4 . Apparatus according to  claim 3 , wherein said carriage is slidingly drivable along a guiding arrangement parallel to said approach direction through a driving bar. 
     
     
         5 . Apparatus according to  claim 2 , wherein said first part and said second part are fixed respectively to a first supporting element and to a second supporting element. 
     
     
         6 . Apparatus according to  claim 5 , wherein said first supporting element and said second supporting element comprise respectively a first sliding portion and a second sliding portion, that are movable with respect to one another parallel to said trajectory. 
     
     
         7 . Apparatus according to  claim 6 , wherein said first part and said second part are mounted on a carriage movable parallel to a approach direction along which said die arrangement and a punch move together for shaping said dose and wherein said first sliding portion and said second sliding portion are slidingly movable along a bar of said carriage, arranged transversely to said approach direction. 
     
     
         8 . Apparatus according to  claim 7 , wherein said first sliding portion and said second sliding portion is provided with respective rollers, rotatable around respective rotation axes arranged transversely to said bar and to said approach direction. 
     
     
         9 . Apparatus according to  claim 8 , wherein said rotation axes are substantially orthogonal to said bar and to said approach direction. 
     
     
         10 . Apparatus according to  claim 2 , and further comprising a cam profile for driving said first part and said second part along said trajectory. 
     
     
         11 . Apparatus according to  claim 10 , wherein said cam profile comprises a pair of tracks along which said rollers can run and which are arranged symmetrically with respect to a plane parallel to said approach direction. 
     
     
         12 . Apparatus according to  claim 2 , and further comprising a positioning arrangement for positioning said first part in a contact position wherein said undercut portion can be shaped. 
     
     
         13 . Apparatus according to  claim 12 , wherein said first part and said second part are mounted on a carriage movable parallel to a approach direction along which said die arrangement and a punch move together for shaping said dose and wherein said first sliding portion and said second sliding portion are slidingly movable along a bar of said carriage, arranged transversely to said approach direction and wherein said positioning arrangement comprises a projection that projects transversely from said bar so that said first sliding portion can abut against said projection in said contact position. 
     
     
         14 . Apparatus according to  claim 13 , wherein said projection projects from an intermediate portion of said bar substantially orthogonally to a longitudinal axis of said bar. 
     
     
         15 . Apparatus according to  claim 13 , wherein said positioning arrangement comprises an elastic element arranged for pushing said first sliding portion against said projection in said contact position. 
     
     
         16 . Apparatus according to  claim 15 , wherein said elastic element comprises a helical spring wound around a said bar. 
     
     
         17 . Apparatus according to  claim 12 , and further comprising a pressing element arranged for pushing said second part against said first part in said contact position. 
     
     
         18 . Apparatus according to  claim 17 , wherein said positioning arrangement comprises an elastic element arranged for pushing said first sliding portion against said projection in said contact position and wherein said pressing element comprises a further elastic element having stiffness less than said elastic element. 
     
     
         19 . Apparatus according to  claim 18 , wherein said further elastic element comprises a further helical spring wound around said bar. 
     
     
         20 . Apparatus according to  claim 13 , wherein, in said contact position, between said second sliding portion and said projection a gap is defined. 
     
     
         21 . Apparatus according to  claim 1 , wherein said die arrangement is included in a forming device for compression-moulding a preform of a container from said dose. 
     
     
         22 . Apparatus according to  claim 21 , wherein said forming device comprises a plurality of moulds arranged peripherally on a carousel rotatable around a rotation axis. 
     
     
         23 . Apparatus according to  claim 22 , wherein said rotation axis is substantially vertical. 
     
     
         24 . Apparatus for forming an object, comprising a die arrangement having a reciprocally movable first part and second part so as to shape an undercut portion of said object in a contact position (P 1 ), wherein it comprises a positioning arrangement for positioning said first part in said contact position and a pressing element for pushing said second part against said first part in said contact position. 
     
     
         25 . Apparatus according to  claim 24 , wherein said first part and said second part are mounted on a carriage that is movable parallel to an approach direction along which said die arrangement and a punch approach mutually for forming said object. 
     
     
         26 . Apparatus according to  claim 25 , wherein said carriage is slidingly drivable along a guiding arrangement parallel to said approach direction through a driving bar. 
     
     
         27 . Apparatus according to  claim 24 , wherein said first part and said second part are fixed respectively to a first supporting element and to a second supporting element. 
     
     
         28 . Apparatus according to  claim 27 , wherein said first supporting element and said second supporting element comprise respectively a first sliding portion and a second sliding portion, that are movable with respect to one another to move said first part and said second part between said contact position and a distanced position. 
     
     
         29 . Apparatus according to  claim 28 , wherein said first part and said second part are mounted on a carriage that is movable parallel to an approach direction along which said die arrangement and a punch approach mutually for forming said object and wherein said first sliding portion and said second sliding portion are slidingly movable along a bar of said carriage, arranged transversely to said approach direction. 
     
     
         30 . Apparatus according to  claim 28 , wherein said positioning arrangement comprises a projection against which said first sliding portion can abut in said contact position. 
     
     
         31 . Apparatus according to  claim 30 , wherein said first part and said second part are mounted on a carriage that is movable parallel to an approach direction along which said die arrangement and a punch approach mutually for forming said object and wherein said first sliding portion and said second sliding portion are slidingly movable along a bar of said carriage, arranged transversely to said approach direction and wherein said projection projects transversely from said bar. 
     
     
         32 . Apparatus according to  claim 31 , wherein said projection projects from an intermediate portion of said bar substantially orthogonally to a longitudinal axis of said bar. 
     
     
         33 . Apparatus according to  claim 30 , wherein said positioning arrangement comprises an elastic element arranged for pushing said first sliding portion against said projection in said contact position. 
     
     
         34 . Apparatus according to  claim 33 , wherein said first part and said second part are mounted on a carriage that is movable parallel to an approach direction along which said die arrangement and a punch approach mutually for forming said object and wherein said first sliding portion and said second sliding portion are slidingly movable along a bar of said carriage, arranged transversely to said approach direction and wherein said elastic element comprises a helical spring wound around said bar. 
     
     
         35 . Apparatus according to  claim 24 , and further comprising a pressing element arranged for pushing said second part against said first part in said contact position. 
     
     
         36 . Apparatus according to  claim 35 , and further comprising a pressing element arranged for pushing said second part against said first part in said contact position and wherein said pressing element comprises a further elastic element having stiffness less than said elastic element. 
     
     
         37 . Apparatus according to  claim 30 , wherein, in said contact position, between said second sliding portion and said projection a gap is defined. 
     
     
         38 . Apparatus according to  claim 24 , wherein said die arrangement is included in a forming device for compression-moulding said object from a dose of plastics. 
     
     
         39 . Apparatus according to  claim 38 , wherein said forming device is shaped in such a way as to obtain a container preform from said dose. 
     
     
         40 . Apparatus according to  claim 38 , wherein said forming device comprises a plurality of moulds mounted on a carousel rotatable around a rotation axis. 
     
     
         41 . Apparatus according to  claim 40 , wherein said rotation axis is substantially vertical.