Patent Publication Number: US-2018037355-A1

Title: A forming apparatus for forming a base of a container

Description:
TECHNICAL FIELD 
     The present invention relates to a forming apparatus for forming a base of a container, such as for example a plastic bottle, filled with a pourable product and closed with a cap. 
     The present invention is advantageously but not exclusively applicable in the sector of plastic hot fill containers, which the following description will refer to, although this is in no way intended to limit the scope of protection as defined by the accompanying claims. 
     BACKGROUND ART 
     As known, the containers of the above mentioned type, after having been filled with hot—for example at about 85° C.—pourable products or liquids, are first subjected to a capping operation and then cooled so as to return to a room temperature. By effect of the capping operation, the heated air present in the top portion (“head space”) of the container expands causing a stress tending to produce a general swelling of the container at the side wall and at the base wall. 
     The following cooling to which the container is subjected, causes, vice versa, a reduction of the volume of air and minimally of the product contained in the container; a depression is therefore created, which tends to pull the side walls and the base wall of the container inwards. This may determine deformations in the walls of the container if these are not rigid enough to resist the action of the above disclosed stresses. 
     In order to compensate the depressive stresses generated during the cooling of the product within the containers without generating undesired deformations on the containers, they are typically provided, at their side walls, with a series of vertical panels, known as “vacuum panels”. These panels, in the presence of depressive stresses, are deformed inwardly of the relative container allowing it to resist to the hot fill process without generating undesired deformations in other areas of the container itself. 
     Likewise, the known containers intended to be subjected to a hot fill process can also have an optimised lower portion or base adapted to be deformed upwards under the action of the depressive stresses. 
     Even though the disclosed solutions allow to “relieve” the pressure stresses on specific parts of the containers, i.e. the vertical vacuum panels or the base, thus avoiding the occurrence of undesired deformations in other parts of the containers, they do not allow the cancellation of the above said stresses; in other words, the containers remain in any case subject to internal depressive stresses and must therefore be provided with a structure capable of resisting such stresses. 
     Patent application WO2006/068511 shows a container having a deformable base, which can have two different configurations: a first unstable configuration, in which this base has a central area projecting downwards with respect to the outermost annular area immediately adjacent thereto, and a second stable configuration, in which the central area is retracted inwardly of the container, i.e. it is arranged at a higher position with respect to the adjacent annular area. 
     Following the filling with the hot pourable product, the base of the container is deformed into the first unstable configuration and must be supported by a special cup element to which it is coupled. Thereby, the downward deformation of the base of the container can be maximised without compromising the stable support of the container, since such a support is provided by the cup element. Following the cooling, the base can be displaced by an external action, for example a vertical thrust upwards performed by a rod or plunger, in the second stable configuration with the subsequent possibility of removing the cup element. 
     The displacement of the base of the container from the first to the second configuration determines a considerable reduction of the containment volume of the container, much higher than that would be obtained in the known containers simply by the deformation of the base by the effect of the sole depressive stresses; the final effect is therefore substantially the cancellation of the depressive stresses acting on the inside of the container. 
     The applicant has observed that this kind of operation may become quite critical, in particular when the time necessary to perform the deformation of the base of each container has to be strongly limited or reduced, for instance due to production constraints; in such cases, the plastic material may return at least in part towards the original first configuration after release of the plunger; this normally occurs when the plastic material has a reaction time exceeding the time for performing the operation of deformation. 
     The non-correctly formed containers have therefore to be rejected at the end of the production line. 
     Another problem posed in connection with the described containers is the complexity of the plant layout for producing them. In particular, the disclosed containers must be subjected to the following operations to achieve their final shape:
         a filling operation with the hot pourable product on a filling machine;   a subsequent operation of capping on a capping machine;   a cooling operation in an appropriate station; and   a deforming operation on a forming machine, in which the bases of the containers are mechanically displaced from the first to the second configuration.       

     As known, the filling machines, the capping machines and the forming machines are generally rotating machines, in which the containers are fed on respective carousels. In particular, each carousel is provided with a plurality of operative units for receiving and processing the containers, uniformly distributed about the rotation axis of the carousel; more precisely, each operative unit is commonly provided with an element for supporting the relative container which maintains it in a predetermined position for carrying out the specific operation/s. 
     As can be easily noted, the above-described process for the production of filled and closed containers is rather time-consuming and requires considerable room within the relative plants; in order to carry out the different operations indicated, it is necessary to provide a relatively high number of carousel-type machines and linear and starwheel conveyors adapted to transfer the containers from a machine to another. 
     DISCLOSURE OF INVENTION 
     It is therefore an object of the present invention to find a simple and cost-effective solution to solve at least one of the above described problems. 
     This object is achieved by a forming apparatus as claimed in claim  1 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment is hereinafter disclosed for a better understanding of the present invention, by mere way of non-limitative example and with reference to the accompanying drawings, in which: 
         FIG. 1  shows a side view of a forming apparatus according to the present invention, with parts removed for clarity; 
         FIG. 2  shows a top plan view of the forming apparatus of  FIG. 1 , with parts removed for clarity; 
         FIG. 3  shows a larger-scale section along line III-III in  FIG. 1 ; 
         FIG. 4  shows a larger-scale front view of a detail of  FIG. 3 , with parts removed for clarity; and 
         FIG. 5  shows a larger-scale section along line V-V in  FIG. 1 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     With reference to  FIGS. 1 and 2 , numeral  1  indicates as a whole a forming apparatus for forming containers, such as for example plastic bottles  2 , filled with a pourable product and closed with removable caps  3 . 
     As may be seen in detail in  FIGS. 3 and 5 , each bottle  2  has a longitudinal axis A, a base  4  and a neck  5  defining an opening (not visible) for pouring the product contained in the bottle  2  and closed with the cap  3 . 
     In the case shown, the base  4  of each bottle  2  has an annular area  6  having axis A, radially external and defining an annular resting surface of the bottle  2  itself, and a recessed central area  7 , surrounded by annular area  6  and arranged normally higher along axis A with respect to annular area  6  in a vertical position of the bottle  2 , i.e. with neck  5  placed above base  4 ; in other words, central area  7  is arranged at a distance from neck  5  along axis A smaller than the distance between neck  5  and annular area  6 . 
     The base  4  of each bottle  2  is deformable and can have two different configurations, shown in  FIGS. 3 and 5 . In the first configuration ( FIG. 3 ), central area  7  of base  4  is deformed and swollen downwards, i.e. it is arranged at a maximum distance from neck  5  along axis A so as to define a maximum internal volume of the relative bottle  2 ; in the second configuration ( FIG. 5 ), central area  7  is instead retracted inwardly of the relative bottle  2  with respect to the first configuration, i.e. central area  7  is arranged at a smaller distance along axis A from neck  5  with respect to the first configuration. It is apparent that each bottle  2  has, in the second configuration of its base  4 , a containing volume smaller than that in the first configuration. 
     In the case shown, bottles  2  are fed to forming apparatus  1  after having been filled with a hot—for example at about 85° C.—pourable product or liquid, closed with the respective caps  3  and subjected to a cooling operation so as to return to a room temperature. 
     Base  4  of each bottle  2  is therefore arranged in the first configuration, i.e. it is deformed and swollen downwards, and within the bottle  2  there are depressive stresses which tend to displace the relative base  4  towards the second configuration. 
     Each bottle  2  reaches forming apparatus  1  in a vertical position, i.e. with its base  4  arranged on the bottom with respect to its neck  5  and to its cap  3 . 
     Each bottle  2  is released from forming apparatus  1  in its vertical position and with its base  4  in the second configuration, which corresponds to the desired final configuration. 
     With reference to  FIGS. 1 to 3 and 5 , forming apparatus  1  essentially comprises:
         a conveying device  8  for advancing in use a succession of bottles  2  in their vertical positions and along a path P orthogonal to the axes A of the bottles  2  themselves;   upper retaining means  9 , which are arranged in use above the bottles  2  moving along path P and cooperate in use with the caps  3 , i.e. with the top parts, of such bottles  2 ; and   a plurality of deformation devices  10 , which are arranged below path P, are advanced in use to follow respective bottles  2  moving along the path P itself and are configured to interact with such bottles  2  to deform their bases  4  from the first configuration to the second configuration.       

     In practice, deformation devices  10  extend on the opposite side of path P with respect to upper retaining means  9 . 
     As visible in  FIGS. 1, 2, 3 and 5 , bottles  2  are brought at desired spacings D between each other along conveying device  8  by a variable-pitch feed screw  11  of known type. 
     In particular, feed screw  11  has an axis B parallel to path P and is arranged on one side of the path P itself; more specifically, feed screw  11  is positioned at an inlet section of forming apparatus  1  and has in use a rotating motion about its axis B. 
     Feed screw  11  comprises a thread  12  having an increasing pitch along path P and, during its rotation about axis B, cooperates in use laterally with the bottles  2  advanced by the conveying device  8  to bring them at the desired spacings D. 
     As clearly shown in  FIGS. 3 and 5 , conveying device  8  advantageously comprises two substantially parallel and aligned linear conveyors  15  arranged side by side, defining a linear gap  16  therebetween and having respective horizontal linear transport branches  15   a  lying on a common horizontal plane Q and configured to support respective opposite side portions  17  of the annular area  6  of the base  4  of each bottle  2 . 
     In this way, while being transported by conveyors  15 , the base  4  of each bottle  2  has its central area  7  placed above gap  16  and facing the latter in order to interact with a respective deformation device  10 , as it will explained in detail later on (see in particular  FIGS. 3 and 5 ). 
     As a consequence of the structure of conveyors  15 , path P has a linear configuration. 
     More specifically, each conveyor  15  is of belt-type and comprises a driving pulley  18 , a driven pulley  19  and an endless belt  20  wound about respective pulleys  18 ,  19 . 
     In particular, pulleys  18 ,  19  have respective horizontal axes E, F orthogonal to path P and to the axes A of the bottles  2  transported by conveyors  15 . 
     Each belt  20  comprises:
         the relative transport branch  15   a;      a linear return branch  15   b , which is parallel to the transport branch  15   a  and is arranged below the latter; and   curved connection portions  15   c , which connect respective end portions of the transport branch  15   a  to corresponding end portions of the return branch  15   b.          

     According to a possible alternative not shown, conveyors  15  may be also of chain-type or of any suitable type including an endless, flat transport element wound about at least two pulleys. 
     With reference to  FIGS. 1, 3 and 5 , forming apparatus  1  also comprises a further linear conveyor  21 , distinct from conveyors  15 , placed below the conveyors  15  and configured to advance the deformation devices  10  along a path R, distinct from path P and having a linear operative portion R 1 , which is parallel to the path P itself and along which the deformation devices  10  extend within gap  16 . 
     In particular, conveyor  21  is of chain-type and comprises a driving pulley  22 , a driven pulley  23  and an endless chain  24  wound about respective pulleys  22 ,  23 . 
     Deformation devices  10  are connected to respective equally spaced portions of chain  24  so as to be moved by the latter along path R; more specifically, deformation devices  10  are placed along chain  24  at the same spacings D between each other as the bottles  2  on which such deformation devices  10  are destined to act. 
     Conveyor  21  is synchronized with conveyors  15  so that each deformation device  10  interact with one specific bottle  2  advanced along path P. 
     Pulleys  22 ,  23  have respective horizontal axes G, H parallel to axes E, F and orthogonal to path P. 
     Chain  24  comprises:
         an upper linear operative branch  24   a  parallel to transport branches  15   a  of conveyors  15  and defining linear portion R 1  of path R;   a linear return branch  24   b , which is parallel to the operative branch  24   a  and is arranged below the latter; and   curved connection portions  24   c , which connect respective end portions of the operative branch  24   a  to corresponding end portions of the return branch  24   b.          

     According to a possible alternative not shown, conveyor  21  may be also of belt-type or of any suitable type including an endless, flat transport element wound about at least two pulleys. 
     With reference to  FIGS. 1 and 3 to 5 , each deformation device  10  comprises a carriage  25  secured to a relative portion of chain  24  and coupled in a sliding manner with an endless fixed guide  26  extending parallel to chain  24 . 
     In particular, guide  26  is formed as an endless rib protruding towards conveyor  21  from a fixed wall  27  arranged on one side of conveyor  21  and extending orthogonally to axes G, H of pulleys  22 ,  23 . 
     Each carriage  25  is provided with four wheels  28  sliding in pairs on opposite sides of guide  26 ; in this way, each carriage  25  is supported by the guide  26  during its motion imparted by chain  24 . 
     Each deformation device  10  further comprises a plunger element  30  adapted to interact with a relative bottle  2  to produce deformation of the base  4  thereof and carried by the relative carriage  25  in a sliding manner along an axis L orthogonal to the portion of chain  24  to which the carriage  25  itself is connected. 
     In particular, when each deformation device  10  runs along the portion R 1  of path R, axis L of the relative plunger element  30  is orthogonal to such portion R 1  and is coaxial to the axis A of the bottle  2  on which such deformation device  10  is destined to act. 
     In greater details, each plunger element  30  has a longitudinal bar  31  coupled in a sliding manner with two pairs of wheels  32  of the relative carriage  25  in such a way that the plunger element  30  is displaceable along the relative axis L with respect to the carriage  25  itself. In this way, during its displacements along the relative axis L, each plunger element  30  is guided by the wheels  32  of the relative carriage  25 . 
     More specifically, each plunger element  30  moves axially between a first rest position (not shown), wherein it is arranged at a minimum distance from the portion of chain  24  to which the relative carriage  25  is secured, and a second operative position ( FIG. 5 ), reached along operative portion R 1  of path R, wherein it is arranged at a maximum distance from said portion of the chain  24 , crosses the entire gap  16  between conveyors  15  and has completed deformation of the base  4  of the relative bottle  2  into the second configuration. 
     In practice, in its first rest position, each plunger element  30  is detached from the base  4  of the relative bottle  2  advancing along path P. 
     Each plunger element  30  has a shaped end  35  adapted to cooperate in use with the recessed annular area  7  of the base  4  of the relative bottle  2 ; in particular, shaped ends of plunger elements  30  have respective profiles complementary to the desired final profiles of the annular areas  7  of the bases  4  of the bottles  2  in their second configurations. 
     Each plunger element  30  has a cam follower roller  36  coupled in a sliding manner with an endless cam  37  formed on a fixed wall  38  arranged parallel to wall  27  and on the opposite side of conveyor  21  with respect to the wall  27  itself. 
     In particular, cam  37  is formed as an endless groove of wall  38 , extending around chain  24 . 
     More specifically, cam  37  has:
         a linear operative portion  37   a , which is parallel and adjacent to path P and along which plunger elements  30  are maintained in their second operative positions;   a return portion  37   b , along which plunger elements  30  are maintained in their first rest positions;   a first ramp-shaped portion  37   c  connecting one end of operative portion  37   a  to an adjacent end of return portion  37   b  and along which plunger elements  30  are moved from the first rest position to the second operative position; and   a second ramp-shaped portion  37   d  connecting the other end of operative portion  37   a  to the other end of return portion  37   b  and along which plunger elements  30  are moved from the second operative position to the first rest position.       

     According to another possible alternative not shown, each plunger element  30  may be moved along its axis L by a fluidic actuator carried by the relative carriage  25 . 
     According to a further possible alternative not shown, each plunger element  30  may be driven by an electric motor carried by the relative carriage  25  and coupled with a worm screw in turn connected to the plunger element  30  itself. 
     With reference to  FIGS. 1, 3 and 5 , upper retaining means  9  comprise a linear conveyor  40 , distinct from conveyors  15 ,  21  and placed above horizontal plane Q on which transport branches  15   a  of conveyors the  15  themselves lie. 
     Conveyor  40  is preferably of belt type and includes a driving pulley  41 , a driven pulley  42 , both having respective axes M, N parallel to axes E, F, G, H, and an endless chain  43  wound about respective pulleys  41 ,  42  and having a linear operative branch  43   a  configured to cooperate in use with the caps  3 , i.e. the top parts, of the bottles  2  advanced along path. 
     In particular, belt  43  comprises:
         the linear operative branch  43   a  which extends parallel to path P and to horizontal plane Q of transport branches  15   a  of conveyors  15 ;   a return branch  43   b , which is arranged above operative branch  43   a ; and   curved connection portions  43   c , which connect respective end portions of the operative branch  43   a  to corresponding end portions of the return branch  43   b.          

     Operative branch  43   a  of belt  43  has the function to counteract from the top the force applied on bottles  3  from below to deform their bases  4  from the first configuration to the second configuration. 
     With reference to  FIGS. 2, 3 and 5 , forming apparatus  1  further comprises lateral retaining means  45  cooperating in use with the bottles  2  exiting from feed screw  11  to maintain them, along path P, at the spacings D imposed by the feed screw  11  itself. 
     Lateral retaining means  45  comprise a linear conveyor  46 , distinct from conveyors  15 ,  21 ,  40 , placed on one side of conveyor device  8  and provided with a plurality of retainers  47  moved by conveyor  46  along an endless path S having a linear operative portion S 1 , which is parallel and adjacent to path P and at which the retainers  47  cooperate laterally with respective bottles  2  to accompany them during the movement along path P imparted by the conveyor device  8  itself. 
     In particular, conveyor  46  is very similar to conveyor  21  and, like the latter, is of chain-type. It comprises a driving pulley  48 , a driven pulley  49 , both having respective vertical axes V, W orthogonal to axes E, F, G, H, L, M and to horizontal plane Q, and an endless chain  50  wound about respective pulleys  48 ,  49 . 
     Retainers  47  are connected to respective equally spaced portions of chain  50  so as to be moved by the latter along path S; more specifically, retainers  47  are placed along chain  50  at the same spacings D between each other as the bottles  2  on which such retainers  47  are destined to act. 
     Conveyor  46  is synchronized with conveyors  15  and  21  so that each retainer  47  interact with one specific bottle  2  advanced along path P. 
     Chain  50  comprises:
         a linear operative branch  50   a  parallel and laterally adjacent to path P and defining linear operative portion S 1  of path S;   a linear return branch  50   b , which is parallel to the operative branch  50   a  and is arranged on the opposite side of the operative branch  50  with respect to conveyor device  8 ; and   curved connection portions  50   c , which connect respective end portions of the operative branch  50   a  to corresponding end portions of the return branch  50   b.          

     According to a possible alternative not shown, conveyor  21  may be also of belt-type or of any suitable type including an endless, flat transport element wound about at least two pulleys. 
     With reference to  FIGS. 2, 3 and 5 , each retainer  47  comprises a carriage  51  secured to a relative portion of chain  50  and coupled in a sliding manner with an endless fixed guide  52  extending parallel to chain  50 . 
     In particular, guide  52  is formed as an endless rib protruding towards conveyor  46  from a fixed wall  53  arranged on one side of conveyor  46  and extending orthogonally to axes V, W of pulleys  48 ,  49  and parallel to transport branches  15   a  of conveyors  15 . In the example shown in  FIGS. 3 and 5 , wall  53  is coplanar with transport branches  15   a  of conveyors  15 . 
     In a completely analogous manner to carriages  25 , each carriage  51  is provided with four wheels  55  sliding in pairs on opposite sides of guide  52 ; in this way, each carriage  51  is supported by the guide  52  during its motion imparted by chain  50 . 
     Each retainer  47  further comprises an operative arm  56 , which is adapted to cooperate in use with a relative bottle  2  advanced along path P and is carried by the relative carriage  51  in a sliding manner along an axis Z orthogonal to the portion of chain  50  to which the carriage  51  itself is connected. 
     In particular, when each retainer  47  runs along the portion S 1  of path S, axis Z of the relative operative arm  56  extends horizontally and is orthogonal to such portion S 1  and to the axis A of the bottle  2  on which such retainer  47  is destined to act. 
     In greater details, each operative arm  56  has a longitudinal bar  57  coupled in a sliding manner with two pairs of wheels  58  of the relative carriage  51  in such a way that the operative arm  56  is displaceable along the relative axis Z with respect to the carriage  51  itself. In this way, during its displacements along the relative axis Z, each operative arm  56  is guided by the wheels  58  of the relative carriage  51 . 
     More specifically, each operative arm  56  moves axially between a first rest position ( FIG. 3 ), wherein it is arranged at a minimum distance from the portion of chain  50  to which the relative retainer  47  is secured, and a second operative position ( FIG. 5 ), reached along operative portion S 1  of path S, wherein it is arranged at a maximum distance from said portion of the chain  50  and cooperates laterally with the relative bottle  2  advanced along path P. 
     Each operative arm  56  terminates with a U- or C-shaped retaining end  59 , adapted to receive in use a relative bottle  2  advanced along path P. In practice, the retaining end  59  of each operative arm  56  partially encircles in use a relative bottle  2  to maintain it at a specific position on transport branches  15   a  of conveyors  15 . 
     As visible in  FIG. 2 , retaining ends  59  of operative arms  56  have respective profiles complementary to the hemi-cylindrical lateral profiles of the bottles  2  with which they cooperate. 
     Each operative arm  56  has a cam follower roller  60  coupled in a sliding manner with an endless cam  61  formed on a fixed wall  62  arranged parallel to wall  53  and on the opposite side of conveyor  46  with respect to the wall  53  itself. 
     In particular, cam  61  is formed as an endless groove of wall  62 , extending around chain  50 . 
     More specifically, cam  61  has:
         a linear operative portion  61   a , which is parallel and adjacent to path P and along which operative arms  56  are maintained in their second operative positions;   a return portion  61   b , along which operative arms  56  are maintained in their first rest positions;   a first ramp-shaped portion  61   c  connecting one end of operative portion  61   a  to an adjacent end of return portion  61   b  and along which operative arms  56  are moved from the first rest position to the second operative position; and   a second ramp-shaped portion  61   d  connecting the other end of operative portion  61   a  to the other end of return portion  61   b  and along which operative arms  56  are moved from the second operative position to the first rest position.       

     According to another possible alternative not shown, each operative arms  56  may be moved along its axis Z by a fluidic actuator carried by the relative carriage  51 . 
     According to a further possible alternative not shown, each operative arm  56  may be driven by an electric motor carried by the relative carriage  51  and coupled with a worm screw in turn connected to the operative arm  56  itself. 
     It is pointed out that the positions of conveyors  21  and  40  can be adjusted in a known manner with respect to conveyor device  8 ; in particular, conveyors  21  and  40  can be brought closer to, or moved away from, conveyor device  8  in order to adapt forming apparatus  1  to process different sizes of bottles  2 . A similar adjustment can be done in a known manner on conveyor  46 , which can be brought closer to, or moved away from, conveyor device  8 . 
     In use, bottles  2  are fed to conveyor device  8  after being filled with the above-mentioned hot pourable product, closed with respective caps  3  and cooled to take the pourable product to the desired temperature. 
     As known, by the effect of the capping operation, heated air present in the top portion of each bottle  2 , between the product and relative cap  3 , expands causing a stress that tends to produce a general swelling of the bottle  2  itself. During the subsequent cooling, depressive stresses are generated within bottles  2  and tend to shrink them. 
     At the end of this operations (filing, capping and cooling), bases  4  of bottles  2  are deformed assuming the first configuration shown in  FIG. 3 . 
     It may be noted that, also in the first configuration, central area  6  of base  4  of each bottle  2  does not project downwards beyond adjacent annular area  7 ; thereby, annular area  7  always ensures a stable support for the relative bottle  2 . 
     At the entry of forming apparatus  1 , bottles  2  are fed in succession onto horizontal transport branches  15   a  of conveyors  15  in their vertical positions; in practice, each bottle  2  has the side portions  17  of its base  4  resting on the respective transport branches  15   a  and its central area  7  facing linear gap  16 . 
     During this step, bottles  2  interact with variable-pitch feed screw  11 , which, by rotating about its axis B, brings the bottles  2  themselves at the desired spacings D between each other. 
     Prior to leaving feed screw  11 , bottles  2  starts to cooperate with operative branch  43   a  of belt  43  of conveyor  40 ; in practice, caps  3  contact operative branch  43   a  of belt  43 , which moves at the same speed as belts  20  of conveyors  15 . 
     The action of operative branch  43   a  of belt  43  on caps of the bottles  2  is maintained up to the end of the deformation operations carried out on the bottles  2  themselves by deformation devices  10 , as it will be explained in greater details later on. 
     At the exit of feed screw  11 , each bottle  2  is taken by a relative retainer  47  and maintained at the spacings D from the adjacent bottles  2  along the path P. 
     In particular, retainers  47  are moved by conveyor  46  at the same speed as the bottles  2  advanced along path P by conveyors  15 . 
     More specifically, at the exit of feed screw  11 , the operative arm  56  of each retainer  47  is moved by ramp-shaped portion  61   c  of cam  61  from the first rest position to the second operative position, in which embraces, with its retaining end  59 , a relative bottle  2  ( FIG. 2 ). 
     During the subsequent movement of bottles  2  along path P, operative arms  56  of retainers  47  are maintained in their second operative positions by interaction of their cam follower rollers  60  with operative portion  61   a  of cam  61  ( FIG. 2 ). 
     Before each bottle  2  leaves feed screw  11 , the plunger element  30  of the relative deformation device  10  approaching conveyors  15   a  starts to move along its axis L from the first rest position to the second operative position; this movement is produced by interaction of the cam follower roller  36  of such plunger element  30  with ramp-shaped portion  37   c  of cam  37  and ends when the relative bottle  2  has left feed screw  11 . 
     During the movement of each plunger element  30  from the first rest position to the second operative position, the base  4  of the relative bottle  2  is deformed from the first to the second configuration, thus cancelling the depressive stresses acting within the bottle  2  itself. 
     Each plunger element  30  is then maintained into its second operative position along the entire operative portion R 1  of path R so as to minimize the risks that, after deformation, the plastic material of the deformed base  4  of the relative bottle  2  may return to its initial condition. 
     At the end of operative portion R 1  of path R, each plunger element  30  is moved along the relative axis L from the second operative position to the first rest position by interaction of its cam follower roller  36  with ramp-shaped portion  37   d  of cam  37 ; in this way, each plunger element  30  releases the relative bottle  2 . 
     The same occurs for each retainer  47 , which releases the relative bottle  2  by moving from the second operative position to the first rest position by interaction of its cam follower roller  60  with ramp-shaped portion  61   d  of cam  61 . 
     The advantages of forming apparatus  1  according to the present invention will be clear from the foregoing description. 
     In particular, forming apparatus  1  may be used to replace any linear conveyor within a normal processing plant of bottles  2 ; this may translate into a significant reduction of the overall space occupied by the processing plant with respect to the known plants using carousel-type deformation machines. 
     In addition, forming apparatus  1  may be located immediately downstream of the cooling station so as to limit the extension of the zones of the processing plant in which it is necessary to convey bottles  2  having non-perfectly defined geometry caused by internal depressive stresses. This also produces an improvement in line efficiency and line filling with respect to known solutions. 
     Clearly, changes may be made to forming apparatus  1  as described herein without, however, departing from the scope of protection as defined in the accompanying claims.