Abstract:
A mold for a machine which is used for the blow molding of containers from performs. The inventive mold includes a wall defining a cavity that is intended to receive a preform. In addition, the mold includes at least one mold insert which is equipped with a lug and which is mounted such that it can move in relation to the wall by means of a cam system, between: an out position in which the lug projects out at least partially from the wall into the cavity, and a retracted position in which the lug is retracted into the wall. The invention also relates to a method of producing a container by means of blow molding using one such mold.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to blow molding containers from preforms, generally made of thermoplastic material.  
       BACKGROUND OF THE INVENTION  
       [0002]     It will be recalled that the blow molding of a container takes place in a mold of which the wall defines a cavity into which the preform is introduced, said preform, during blow molding, conforming in shape with the wall under the action of the increased gas pressure which prevails in the preform, which is previously heated so as to allow the plastic deformation thereof.  
         [0003]     A need has been expressed for certain applications for providing the containers with a handle which defines, with the body of the container, an aperture allowing the free passage of the hand.  
         [0004]     Currently, the manufacture of this type of container may be carried out according to two specific techniques.  
         [0005]     The first consists in injection-molding the container, the handle being formed from a block with the body of the container to which it is attached. However, as already indicated, the present application relates to the technique of blow molding. In addition, the injection-molding technique is, in this case, outside the subject of the invention.  
         [0006]     The second technique consists in producing the body of the container by blow molding around a detachable handle, introduced into the mold prior to the blow molding.  
         [0007]     This technique, disclosed in the European patent issued under the number EP-1 204 524 and originating from the applicant, has shown that it is possible to produce a container with a handle by blow molding. However, it requires complex and costly kinematics for the positioning of the handle, the synchronization of all the operations proving to be particularly difficult to master and generating, in spite of the forces produced, a reduction in the speed of the operation.  
         [0008]     It has recently been proposed to form directly in the container, during blow molding, hollow impressions able subsequently to receive a handle by a snap connection.  
         [0009]     According to this technique, disclosed in the American patent U.S. Pat. No. 5,649,612, retractable protuberances are formed in the mold cavity and about which the container is formed. During the blow molding, these protuberances are displaced further to the front in the cavity to form completely the aforementioned impressions.  
         [0010]     If, in theory, this technique allows impressions to be made on the container allowing the mounting of the handle, in reality there is a risk of perforating the wall of the container by means of the protuberances during the blow molding.  
         [0011]     Moreover, from a structural point of view, the protuberances are formed at the ends of mobile arms mounted on rams which ensure their displacement. Here again, this technique, which is attractive in theory, is not able to be easily put into practice. More specifically, the arms have the tendency, due to their significant overhang, to be braced and to jam during their displacement. In fact, at their end shaped as a protuberance a force is exerted, under the pressure prevailing in the container during the blow molding, which opposes the thrust force of the ram which is exerted at the opposing end, the resultant of these forces being a torque which tends to make the arm pivot about an axis perpendicular to the direction of displacement thereof.  
         [0012]     A further technique, disclosed in the American patent application published under the number US 2002/0195749 proposes a method for molding an article according to which a sleeve is initially introduced into the mold cavity which extends around a rod which is fixed relative to the mold and of which the external diameter corresponds to the internal diameter of an impression to be formed in the wall of the article, then, after molding, to allow the article to rest for a given duration, before retracting the sleeve so that the wall of the article conforms to the shape of the rod.  
         [0013]     An unmolding problem occurs with this technique, as the rod remains fixed relative to the mold. In these conditions, specific gripping means have to be provided to separate the article from the mold at the end of the blow molding, which increases both the costs of the mold and the duration of the cycle.  
         [0014]     The inventors have endeavored, whilst remaining within the technique of blow molding, to propose an alternative solution to the known techniques, which makes it possible in particular to resolve the aforementioned problems.  
         [0015]     To this end, the inventors propose, in the first instance, a mold for a machine for blow molding containers from preforms, this mold comprising a wall defining a cavity intended to receive a preform and comprising at least one mold insert which, provided with a lug, is displaceably mounted relative to the wall, between:  
         [0016]     an extended position in which the lug projects at least partially relative to the wall, into the cavity, and  
         [0017]     a retracted position in which the lug is retracted into the wall,  
         [0018]     said mold being characterized in that the insert is in the form of a cam follower, the mold comprising an actuating mechanism, which comprises a cam which is mounted mobile relative to the wall, between:  
         [0019]     an inactive position in which it allows the insert to adopt its retracted position, and  
         [0020]     an active position in which it displaces the insert toward its extended position.  
         [0021]     During blow molding, the material of the preform conforms to the shape of the projecting lug which thus forms in the body of the container a hollow impression with which ultimately a detachable grip handle of the container cooperates. It is noteworthy that the cam/cam follower mechanism allows a more reliable functioning of the mold to be obtained.  
         [0022]     According to one embodiment, as the cavity extends along a principal axis, the lug extends, in the extended position, substantially parallel to this axis, by being for example mounted mobile in translation relative to the wall of the mold.  
         [0023]     According to one embodiment, the wall of the mold has a protuberance toward the inside of the cavity, a protuberance in which the insert is received.  
         [0024]     The insert is, for example, displaceable in translation in a direction parallel to a principal axis of the mold cavity, the cam being, in turn, displaceable in translation in a direction perpendicular to this principal axis.  
         [0025]     According to one embodiment, the cam has a cam surface which is oblique relative to the direction of displacement of the cam which cooperates with a bearing surface made on the cam follower and which is oblique relative to the direction of displacement of the cam follower.  
         [0026]     The cam follower is, for example, provided with at least one pin which projects perpendicularly to the direction of displacement of the cam follower, this pin cooperating with a groove made in the cam parallel to the cam surface.  
         [0027]     The actuating mechanism may comprise a return spring which urges the cam toward its inactive position, in addition to, for example, a ram provided with a rod, at one end of which the cam is mounted.  
         [0028]     The mold may also comprise a return spring which urges the insert toward its retracted position.  
         [0029]     According to one embodiment, the mold comprises, in practice, two inserts each provided with a lug and jointly displaceable relative to the wall, between:  
         [0030]     an extended position in which the lugs project both at least partially relative to the wall into the cavity, and  
         [0031]     a retracted position in which the lugs are both retracted into the wall.  
         [0032]     The inventors also propose, in the second instance, a method for producing a container by blow molding from a preform made of thermoplastic material, said method using a mold comprising a wall defining a cavity intended to receive a preform, in addition to at least one mold insert which, provided with a lug, is displaceably mounted relative to the wall, between:  
         [0033]     an extended position in which the lug projects at least partially relative to the wall, into the cavity, and  
         [0034]     a retracted position in which the lug is retracted into the wall,  
         [0035]     this method comprising the steps consisting of:  
         [0036]     introducing the preform into the cavity;  
         [0037]     placing the mold insert in its extended position;  
         [0038]     forming the container by blow molding or stretch blow molding of the preform in the cavity so as to allow a complementary impression of said insert on the formed container;  
         [0039]     once the container is formed, placing the insert mold in its retracted position;  
         [0040]     removing the container thus formed from the mold.  
         [0041]     According to one embodiment, the step for positioning the insert is carried out during the blow molding step before the material of the preform reaches the lugs.  
         [0042]     The method finally comprises, for the finishing of the product, a step consisting, after the formation of the container, in mounting thereon a detachable handle provided with at least one claw capable of cooperating in a removable manner with a hollow impression formed, in the wall of the container, by the lug of the insert during the step of forming the container. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     Further objects and advantages of the invention will emerge from viewing the description made below, by referring to the accompanying drawings, in which:  
         [0044]      FIG. 1  is a partial perspective view showing a mold according to the invention, in the retracted position of the inserts;  
         [0045]      FIG. 2  is a perspective view of the mold of  FIG. 1  in the same position, according to a further viewing angle;  
         [0046]      FIG. 3  is a sectional view of a mold according to the invention, in the retracted position of the mold inserts;  
         [0047]      FIG. 4  is a sectional view according to the plane IV-IV of  FIG. 3 ;  
         [0048]      FIG. 5  is a view similar to  FIG. 3  in the extended position of the mold inserts;  
         [0049]      FIG. 6  is a sectional view according to the plane VI-VI of  FIG. 5 ;  
         [0050]      FIGS. 7 and 8  are perspective views showing the mold inserts of the mold of the preceding figures, associated with their actuating mechanism; and  
         [0051]      FIGS. 9 and 10  illustrate the step of mounting a detachable handle on a container formed by means of a mold as shown in the preceding figures.  
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0052]     It is desirable to produce by blow molding or by stretch blow molding from a preform  1  made of thermoplastic material (said preform, as shown in dotted lines in  FIG. 3 , is in this case a preform previously produced by injection molding), a container  2  having a body  3  onto which a detachable handle  4  is then hooked, mounted by a snap connection, as shown in  FIGS. 9 and 10 .  
         [0053]     In order to allow the hooking of the handle  4  onto the body  3  of the container  2 , it is desirable to form in the body  3  at least one hollow impression  5 ,  6  with which a claw  7 ,  8  of the handle  4  cooperates.  
         [0054]     More specifically, according to one embodiment illustrated in  FIGS. 9 and 10 , it is desirable to form in the body  3  of the container  2  two opposing impressions  5 ,  6  i.e. of which the respective concavities are opposing, intended to receive two claws  7 ,  8  of the handle  4 , with which they are complementary.  
         [0055]     It will ultimately be explained how the mounting of the handle  4  is carried out on the body  3  of the container  2 ; the means intended to form the impressions  5 ,  6  and their implementation now being detailed.  
         [0056]     In FIGS.  1  to  6  a mold  9  is shown which is intended to equip a blow molding machine (not shown) for forming containers  2 .  
         [0057]     This mold  9  is formed by assembling two half molds  10 ,  11  of which one  10  is shown alone in  FIGS. 1, 2 ,  3  and  5 .  
         [0058]     The mold  9  comprises a wall  12 , for example made in an aluminum alloy, and with pipes  13  cut through for the circulation of a coolant liquid for the heating or cooling of the mold  9 . This wall  12  defines a cavity  14  made by precision machining, intended to receive the preform  1 , as illustrated in  FIG. 3 , and of which the shape corresponds to that of the container  2  to be formed.  
         [0059]     As is visible in  FIG. 1 , the cavity  14  is generally distributed about a principal axis X which extends according to the greatest dimension of the cavity  14 , (i.e. of the container  2 ) with the exception of an area in which the wall  12  has a protuberance is which projects into the cavity  14 , this protuberance  15  being intended to form on the body  3  of the container  2 , during blow molding, a hollow protected area  16  of sufficient dimension to receive the hand of a user, a protected area  16  in which the handle  4  will be mounted.  
         [0060]     The protuberance  15  has a lateral face  17  which is substantially planar and parallel to the principal axis X of the cavity  14 , extended upward and downward, respectively through an upper face  18  and a lower face  19  which are also planar, but oblique relative to the principal axis X.  
         [0061]     The mold  9  comprises a specific device  20  for the formation of impressions  5 ,  6  mounted in the wall  12 , and which comprises two inserts  21 ,  22  known as mold inserts, namely an upper insert  21  and a lower insert  22 , received in the protuberance  15  and each provided with a respective lug  23 ,  24 , each of these inserts being mounted in the wall  12  by being displaceable relative to said wall, between:  
         [0062]     an extended position in which each lug  23 ,  24  projects at least partially relative to the wall  12  into the cavity  14 , substantially parallel to the principal axis X ( FIGS. 5 and 6 ) and  
         [0063]     a retracted position in which each lug  23 ,  24  is retracted into the wall  12  (FIGS.  1  to  4 ).  
         [0064]     In the extended position, the lug  23  of the upper insert  21  projects relative to the upper face  18  of the protuberance  15  whilst the lug  24  of the lower insert  22  projects relative to the lower face  19  of the protuberance  15 .  
         [0065]     More specifically, each insert  21 ,  22  is mounted mobile in translation relative to the wall  12 , substantially parallel to the principal axis X of the cavity  14 . The respective movements of the inserts  21 ,  22  are both synchronized and opposing. In other words, the inserts  21 ,  22  simultaneously occupy their extended position on the one hand, and their retracted position on the other hand, the passage from one to the other of these positions being carried out simultaneously for the two inserts  21 ,  22 .  
         [0066]     The guiding of each insert  21 ,  22  is ensured, on the one hand, by the lug  23 ,  24  which passes through a complementary aperture  25 ,  26  formed in the wall  12  and opening out into the cavity  14  and, on the other hand, by a finger  27 ,  28  received in a complementary groove  29 ,  30  formed in the wall  12  of the mold  9 . Return springs  31 ,  32  continually urge the inserts  21 ,  22  toward their retracted position.  
         [0067]     According to one embodiment illustrated in the figures, the inserts  21 ,  22  are cam followers, the device  20  comprising an actuating mechanism  33  provided with a cam  34  acting jointly on the two inserts  21 ,  22  and mounted in the wall  12  by being mobile relative to said wall between:  
         [0068]     an inactive position in which the cam  34  allows the inserts  21 ,  22  to occupy their retracted position, and  
         [0069]     an active position in which the cam  34  pushes back the inserts  21 ,  22  toward their extended position.  
         [0070]     According to an embodiment illustrated in the figures, and as this is more particularly visible in  FIGS. 4 and 6 , the cam  34  may be displaced in translation in a direction perpendicular to the principal axis X.  
         [0071]     As is shown in particular in  FIG. 6 , the cam  34  has a substantially trapezoidal profile and has two cam surfaces  35 ,  36  which are oblique relative to the direction of displacement of the cam  34 , each of these surfaces  35 ,  36  cooperating with a bearing surface  37 ,  38 , made on each insert  21 ,  22  opposite the lug  23 ,  24  and oblique relative to the direction of displacement of the insert  21 ,  22 .  
         [0072]     In order to allow precise guiding of the inserts  21 ,  22 , each insert is provided with at least one pin  39 ,  40  which projects perpendicularly to the direction of displacement of the insert  21 ,  22 , this pin  39 ,  40  cooperating with a groove  41 ,  42  made in the cam  34  parallel to the cam surface  35 ,  36 . In practice, two pins  39 ,  40  are in fact provided on both sides of each insert  21 ,  22 , the cam  34  being, in turn, provided with four grooves  41 ,  42  symmetrical in pairs, each capable of receiving a pin  39 ,  40 .  
         [0073]     As is clearly visible in  FIGS. 4 and 6 , the actuating mechanism  33  comprises a pneumatic ram  43  provided with a rod  44  of which a first end  45  is formed in a piston mounted slidably in a cylinder  46  formed in the wall  12 , the cam  34  being mounted on a second end  47  of the rod  44 , opposite the first  45 .  
         [0074]     A washer  48  closes one end  49  of the cylinder  46 , located on the side of the cam  34 , an opposing end  50  of the cylinder  46  being closed by a plate  51  fixedly attached through the outside of the mold  9  onto the wall  12 . A return spring  52  mounted in the cylinder  46  and interposed between the first end  45  shaped as a piston of the rod  44  of the ram  43  and this washer  48 , continually urge the cam  34 , by means of the rod  44 , toward its inactive position, as illustrated in  FIG. 4 .  
         [0075]     The method for producing the container  2  is now disclosed, using the mold  9  which has been described above.  
         [0076]     This method firstly comprises a step of introducing the preform  1  into the cavity  14  whilst, as the cam  34  is in its inactive position, the inserts  21 ,  22  are in their retracted position ( FIG. 3 ).  
         [0077]     This conventional step of introduction is carried out in the known manner, the mold  9  being open (i.e. the two half molds  10 ,  11  are separated from one another), the preform  1 , which is hot, being moved transversely by means of an appropriate transfer device such as a transfer arm (not shown).  
         [0078]     Once the mold  9  is closed again, then the blow molding or the stretch blow molding of the preform is carried out in a manner known per se. The actuating mechanism  33  is controlled during the blow molding or the stretch blow molding of the preform  1  so as to remove the lugs  23 ,  24  before said lugs have been reached by the container during the course of forming.  
         [0079]     To this end, the cylinder  46  may be attached pneumatically, by means of a bypass to the feed circuit of the preform  1  (typically the feed circuit of the blow molding pipes in the machines is of the type of those of the applicant), the actuating of the ram  43  being thus carried out as soon as the pressurization of the preform  1  takes place.  
         [0080]     Taking account of its plasticity, the material of the container  2  comes into contact with the wall of the cavity  14  until around the lugs  23 ,  24 , with which it conforms in shape to form the impressions  5 ,  6  (thus the complementary impressions of the lugs  23  and  24 ) intended to receive ultimately the claws  7 ,  8  of the handle  4 .  
         [0081]     At the end of the blow molding or the stretch blow molding, the pressure in the container  2  is brought to atmospheric pressure, the inserts  21 ,  22  being thus brought to their retracted position by a combined action of the return springs  31 ,  32  and the reverse movement of the ram  43  to allow the unmolding of the container  2 .  
         [0082]     The mold  9  is then opened, from which the container  2  thus formed is removed, and on the body  3  of which the handle  4  is then fixed. Said handle comprises a body  53  in the form of an open ring, provided with a flexible tongue  54  carrying at one free end a tooth  55  which is clipped into a complementary housing  56  formed in one part of the body  53  opposite. Thus the handle  4  may adopt two configurations, namely:  
         [0083]     an open configuration, shown in  FIG. 9 , in which the tongue  54  is folded back inside the loop formed by the body  53 , and where the tooth  55  is located at a distance from its housing  56 ; in this configuration, under the action of the elasticity of the handle  4 , the distance separating the ends of the claws  7 ,  8  is less than the distance separating their respective impressions  5 ,  6 , so as to allow the introduction without force of the handle  4  in the protected area  16 , and  
         [0084]     a closed configuration shown in  FIG. 10 , in which, after having positioned the handle  4 , and pushed the tongue  54  until the tooth  55  is clipped into its housing  56 , the claws  7 ,  8  are received undetachably in their impressions  5 ,  6  except for when replacing the handle  4  in its open configuration by the action on the tongue  54 , for example to allow the same handle  4  to be reused on a plurality of successive containers as said containers are emptied of their contents.  
         [0085]     It is understood that it is thus possible to produce a container  2  with a detachable handle  4  easily by blow molding, said handle being mounted after the body  3  of the container  2  has been formed.  
         [0086]     On the one hand, this does not result in any arrangements which lead to any excessive complications in the production and structure of the mold. On the other hand, the method which has been disclosed above does not cause a reduction in the speed of the operation relative to conventional blow molding, the steps of extending and retracting the mold inserts being carried out in concurrent operation time during the usual steps of blow molding (stretching, degassing).