Apparatus and method for producing a container by blow molding or stretch blow molding

Description

[0001] The field of the invention is that of the manufacture of containers by blow molding or stretch blow molding from a plastic blank.

[0002] The invention relates more particularly to the manufacture of containers by blowing or stretch-blow molding using a device comprising a mold comprising two half-molds, and pneumatic means for compensating a blowing pressure inside the mold.

[0003] It is known to manufacture containers, particularly bottles, by blow molding or stretch blow molding from a plastic blank. A blank corresponds to a preform or an intermediate shape between the preform and the final container.

[0004] To do this, blanks are brought to a thermal conditioning station at a glass transition temperature such that they can be deformed. The hot blanks are then transferred into a mold, comprising assembled half-molds, where they are "blown" or "stretched and blown." Blowing is carried out using a pressurized gaseous fluid, usually air.

[0005] The pressures involved during blowing frequently reach 40 bars. As a result, when manufacturing a container with a capacity of 1.5 l, which has a projected surface area of ​​approximately 250 cm2, a force of around 9,800 daN tends to separate the two assembled half-molds that constitute the blow mold.

[0006] A classic device includes: a mold comprising a first half-mold and a second half-mold which together define the imprint of the container to be formed; a support for each half-mold, each support carrying one of the half-molds.

[0007] Despite all the care taken in the production of the half-molds and their support, under the action of the force generated by the pressure of the blowing fluid, the two half-molds move away from each other and a shift of a few tenths of a millimeter may appear at the joint plane of the half-molds.

[0008] A joint plane with an offset of one tenth of a millimeter results in the formed container having poor visual quality.

[0009] In other words, although the structural strength of the container is intact, the shift induced by the blowing pressure at the joint plane degrades the appearance of the container.

[0010] It should be noted that the quality is then perceived as disappointing and may prevent the container from being marketed.

[0011] It is therefore important to avoid such play at the joint plane of the molds.

[0012] We know from the patent document published under number FR2659265 a compensation system integrated into the container manufacturing device.

[0013] More specifically, the device comprises a sealed chamber interposed between one of the half-molds, the first half-mold, and its support. The first half-mold is thus partially movable relative to its support.

[0014] Pressurized air injection means inject compressed air into the sealed chamber when the container is blown. Injecting compressed air into the sealed chamber allows the first movable half-mold to be pressed against the second half-mold to compensate for the blowing pressure inside the container.

[0015] Inherent in the locking system of such manufacturing devices, a mold unlocking and locking clearance always exists. The injection of air into the sealed chamber thus makes it possible to compensate for the mold unlocking and locking clearance to achieve the pressing of the first mold half against the second mold half.

[0016] The second half-mold is fixed firmly to its support, without the interposition of elastic means. This second half-mold serves as a reference point for centering the blank inside the mold and for making certain adjustments to the device.

[0017] This solution improves the visual appearance of the resulting container.

[0018] However, this solution does not provide complete satisfaction with the final result.

[0019] Indeed, it has been noted that visual defects at the joint plane, although less significant, can still be observed (presence of a step in particular) on containers produced with this type of device.

[0020] Furthermore, it has also been observed that the blowing pressure (which can reach 40 bars) can temporarily deform the material constituting the mold, and produce an undesirable ovalization of the container.

[0021] Finally, the pneumatically compensated half-mold has degraded cooling performance compared to the second half-mold secured to its support. Indeed, the sealed chamber between the first half-mold and its support induces the presence of an air gap preventing optimal transfer of temperature from the half-mold to its support. This difference in cooling performance between the two half-molds can produce a lack of symmetry between the two parts of the container pressed against each of the half-molds during blowing. Thus, even if the container would have an unwanted ovalization, it would also have a lack of symmetry between the two parts previously described.

[0022] A compensation system integrated into the container manufacturing device is known from the patent document published under number CH534044.

[0023] This compensation system allows for double compensation. In fact, each of the half-molds is coupled to its support by means of a compensation means in the form of two flexible plates hermetically coupled to each other on their edge. These two flexible plates define between them a sealed chamber capable of receiving a pressurized fluid. The chambers, located behind each half-mold, are connected to a pipe carrying a pressurized fluid. Before blowing a container into the mold, the two chambers are pressurized so as to press the half-molds against each other.

[0024] Such a technique, although allowing each of the half-molds to be compensated, produces containers with visual defects.

[0025] Other relevant prior art documents are EP 3 319 780 B1 and EP 2 803 469 B1.

[0026] The invention aims in particular to overcome the drawbacks of the prior art.

[0027] More specifically, the invention aims to propose a device for manufacturing a container by blow molding or stretch blow molding which makes it possible to obtain a container having a visual quality greater than that of the containers which can be obtained by means of the devices according to the prior art.

[0028] The invention also aims to provide such a device which has a better joint plane than those of the devices according to the prior art which include pneumatic compensation.

[0029] These objectives, as well as others which will appear subsequently, are achieved thanks to the invention which relates to a device for the manufacture of a container by blowing or stretch-blow molding from a plastic blank, the device comprising: a mold comprising two half-molds together defining an imprint of the container to be formed; a support for each of the half-molds, each half-mold having a clearance relative to its support; means for compensating for a blowing pressure inside the mold; the compensation means comprising: at least one sealed chamber interposed between each half-mold and its support; means for injecting a pressurized fluid into the sealed chambers; characterized in that it comprises a mechanism for referential positioning of one of the half-molds, called the reference half-mold, against at least one reference stop carried by the support of the reference half-mold, the reference stop(s) tending to limit the movement of the reference half-mold towards its support, and means for holding the reference half-mold in support against the reference stop(s) while the other of the half-molds, called the second half-mold, is movable under the action of the pressurized fluid.

[0030] Thanks to the device according to the invention, double compensation is achieved during the blowing or stretch-blow molding of the plastic blank.

[0031] Double compensation allows for a better mold parting plane.

[0032] The best joint plane is obtained thanks to the two half-molds which are both pressed against each other, each by means of its own sealed chamber during blowing. Thus, when the container is blown, the pressure exerted on each of the half-molds is compensated on both sides of the mold, and the forces are distributed evenly, whether on the side of the reference half-mold or on the side of the other half-mold.

[0033] Thanks to the reference half-mold and the moving reference stop(s), it is avoided that, although there is double compensation, the two half-molds are both "floating", and that there is no fixed spatial reference for the positioning of a blank in the mold during blowing.

[0034] Indeed, for good centering of the blanks in the mold before and during blowing, it is necessary that the neck of these blanks is well maintained. Consequently, thanks to the reference half-mold which is in abutment, and thus fixed, during blowing and compensation, the neck of the blanks does not tend to move.

[0035] The device settings are also simplified thanks to this reference positioning mechanism which maintains a reference point despite the double compensation carried out.

[0036] Thanks to the double compensation, the device can also be designed to avoid or mitigate the phenomenon of container ovalization.

[0037] In addition, the deformation of the half-molds under the effect of pressure and thus the deformation of the container, although inevitable, can then be anticipated.

[0038] Thanks to this anticipation of deformations, the design of the device can be planned to predetermine the phenomenon of ovalization of the container in order to minimize it.

[0039] More precisely, thanks to the double compensation, the two half-molds will touch each other but will not themselves maintain their shape. For example, if they both define a round cross-section shape (each half-mold having a semi-circular shape), then, under the effect of pressure, this round shape tends to become oval due to the deformation of the metal and the opening of the half-molds under the effect of pressure.

[0040] In the case where only one of the half-molds is compensated, this ovalization is not the same on the side of the first half-mold compared to that occurring on the side of the second half-mold.

[0041] Double compensation thus allows for symmetrical deformation, or at least the most symmetrical possible.

[0042] Furthermore, by incorporating compensation means in the form of a sealed chamber between each of the half-molds and their support, the cooling of the half-molds tends to be as uniform as possible on either side of the mold.

[0043] So, rather than having a mold having a second half-mold cooling faster than its first half-mold (because the first half-mold is separated from its support by an air gap which prevents or limits good temperature transmission from the half-mold to the support), then this characteristic (the air gap) is found on each of the half-molds and the temperature transfer is achieved homogeneously.

[0044] According to a particular embodiment of the device: the reference half-mold has a compensation surface S1 defined by the sealed chamber inserted between the reference half-mold and its support; the second half-mold has a compensation surface S2 defined by the sealed chamber inserted between the second half-mold and its support; with S2 > S1.

[0045] Thanks to this embodiment, the difference in compensation surface of the sealed chambers contributes to forming the means for holding the reference half-mold in support against the reference stop(s).

[0046] In fact, due to the difference in surface area, the injection of a fluid into the sealed chambers at an identical pressure, or failing that at a higher pressure in the sealed chamber of the second half-mold, makes it possible to place and maintain the reference half-mold in support against the reference stop(s).

[0047] According to another embodiment: the reference half-mold has a compensation surface S1 defined by the sealed chamber inserted between the reference half-mold and its support; the second half-mold has a compensation surface S2 defined by the sealed chamber inserted between the second half-mold and its support; with S2 = S1, and the compensation surface S1 of the reference half-mold is symmetrical to the compensation surface S2 of the second half-mold.

[0048] In this way, the distribution of the compensation force is symmetrical, and tends to produce homogeneous effects, for the reference half-mold or the second half-mold.

[0049] According to a first solution, the injection means are configured to: injecting a fluid at a first pressure P1 into the sealed chamber, called the first sealed chamber, inserted between the reference half-mold and its support; injecting a fluid at a second pressure P2 into the sealed chamber, called the second sealed chamber, inserted between the second half-mold and its support, with P2 > P1.

[0050] Thanks to this solution, the pressure difference makes it possible to simply keep the reference half-mold in contact with the reference stop(s).

[0051] According to a second, preferred solution, the injection means are configured to: injecting a fluid at a first pressure P1 into the sealed chamber, called the first sealed chamber, inserted between the reference half-mold and its support; injecting a fluid at a second pressure P2 into the sealed chamber, called the second sealed chamber, inserted between the second half-mold and its support, with P2 = P1.

[0052] With this solution, the same pressure is injected into both sealed chambers, namely the first sealed chamber and the second sealed chamber.

[0053] Since the first pressure and the second pressure are identical, the design of the injection means can then be simplified by using the same circuit which supplies all the sealed chambers of the compensation means.

[0054] Identical pressure also helps to contribute to uniform compensation of the forces resulting from the blowing of a container.

[0055] According to an advantageous characteristic, the holding means comprise at least one elastic return member, called the first return member, of the reference half-mold in a position pressed against its support.

[0056] Thanks to this characteristic, an element independent of the compensation means helps to maintain the reference half-mold in its position pressed against its support, in abutment against the reference stop(s) carried by said support.

[0057] This feature is particularly advantageous in the case where the compensation surfaces have symmetry with respect to a mold joint plane, and where the first pressure and the second pressure injected into the sealed chambers are identical.

[0058] Indeed, in this case, the compensation of the mold produces an identical compensation force on either side of the mold and then, only the elastic return member of the means, first return member, makes it possible to keep the reference half-mold pressed against its support, and in particular against the reference stop(s) carried by said support.

[0059] In this case, according to a particularly advantageous characteristic, the device comprises at least one elastic return member, called the second return member, of the second half-mold against its support, and in that: the first return member(s) exert a return force E1; the second return member(s) exert a return force E2, with E1 > E2.

[0060] In this configuration, each of the half-molds is subject to an elastic return against its support. This elastic return facilitates the opening and closing of the mold while helping to maintain the reference half-mold against the reference stop(s) when blowing a container.

[0061] Indeed, due to the difference between the return forces of the first return member and the second return member, then the total of the forces exerted on the half-mold tends, at the level of the return forces alone, to keep the reference half-mold pressed against its support and its reference stop(s).

[0062] The invention also relates to a method of manufacturing a container by blow molding or stretch blow molding of a plastic blank in a mold comprising two half-molds each carried by a support, for each half-mold at least one sealed chamber being interposed between said half-mold and its support, the method comprising a step of compensating for a blowing pressure inside the mold, in which the compensation step consists of injecting a pressurized fluid into the sealed chambers to exert a compensation force, characterized in that during the compensation step, one of the half-molds, called the reference half-mold, adopts a reference spatial position by bearing against at least one reference stop carried by the support of the reference half-mold, while the other half-mold, called the second half-mold, is pressed against the reference half-mold.

[0063] By means of such a method, compensation can be achieved for each of the half-molds of a mold of a device for manufacturing a container by blow molding or stretch blow molding from a plastic blank.

[0064] This double compensation makes it possible to tend to homogenize the deformation of the half-molds under the effect of blowing a container.

[0065] Indeed, unlike the devices and methods according to the prior art in which only one of the two half-molds is compensated, in particular pneumatically, then, according to the method according to the invention, even the second half-mold benefits from this compensation.

[0066] According to the method according to the invention, this double compensation is not carried out to the detriment of obtaining a fixed spatial reference allowing the adjustment of the related settings of the device allowing the container to be manufactured, and to the correct centering of the blank in the mold.

[0067] Indeed, thanks to the method according to the invention, the reference half-mold is not floating during the compensation step. More precisely, during the compensation step, the reference half-mold is supported against at least one reference stop which is carried by the support of this reference half-mold. Consequently, this reference half-mold adopts a fixed position relative to its support, and it is in a predictable manner that the settings of the device can be indexed to the spatial position of the reference half-mold which is a reference spatial position.

[0068] According to a particularly advantageous characteristic, during the compensation step, an identical compensation force is exerted for each half-mold, and a return force of the reference half-mold in a position bearing against the reference stop(s) is exerted, the return force being distinct from said compensation forces.

[0069] Thanks to this characteristic, the compensation of each of the half-molds is identical, and only the restoring force exerts an action to keep the reference half-mold pressed against the reference stop(s) carried by the support of the reference half-mold.

[0070] This characteristic thus makes it possible to homogenize the compensation forces produced by the compensation means between the half-molds and to dedicate the maintenance of the reference half-mold in its reference position to an element which does not, in itself, participate in the compensation.

[0071] Advantageously, during the compensation stage: a compensation force F1 is exerted for the reference half-mold; a compensation force F2 is exerted for the second half-mold, with F2 >F1.

[0072] According to this advantageous characteristic, it is the compensation force exerted for each of the half-molds which makes it possible to press the reference half-mold against its support, and in particular against the reference stop(s).

[0073] According to a particular solution, during the compensation step: a fluid under a pressure P2 is injected into the sealed chamber inserted between the second half-mold and its support; a fluid under a pressure P1 is injected into the sealed chamber inserted between the reference half-mold and its support, with P2 > P1.

[0074] According to this solution, the pressure difference injected into the sealed chambers of each of the half-molds allows the reference half-mold to adopt its reference spatial position.

[0075] Other characteristics and advantages of the invention will appear more clearly on reading the following description of different preferred embodiments of the invention, given as illustrative and non-limiting examples, and the appended drawings among which: [ Fig. 1 ] there figure 1 is a longitudinal sectional representation of a device for manufacturing a container by blow molding or stretch blow molding, according to the invention, passing through the middle of an imprint defined by a mold of the device; [ Fig. 2 ] there figure 2 is a side view of a support of a half-mold of the device according to the invention; [ Fig. 3 ] there figure 3 is a schematic cross-sectional illustration of the device according to the invention in a mold-open position; [ Fig. 4 ] there figure 4 is a schematic representation of a detail centered on an elastic return member of means for holding the device according to the invention; [ Fig. 5 ] there figure 5 is a schematic cross-sectional representation of a device according to the invention, in which the mold is in a closed position and where no compensating force is made; [ Fig. 6 ] there figure 6 is a schematic cross-sectional representation of the mold of the device according to the invention in which the mold is compensated.

[0076] There figure 1 illustrates a device 1 according to the invention for manufacturing a plastic container by blow molding or stretch blow molding from a blank.

[0077] Device 1 includes: a mold 2; two supports 3.

[0078] Mold 2 comprises two half-molds, one half-mold of reference 21, and a second half-mold 22.

[0079] For blowing a container, the reference half-mold 21 and the second half-mold 22 are applied against each other and define between them a cavity with the imprint E of the container to be formed.

[0080] The reference half-mold 21 and the second half-mold 22 also define a parting plane P (illustrated on the figure 6 ) by bringing them into contact. More precisely, this joint plane P is defined at the level of the respective faces of the reference half-mold 21 and the second half-mold 22 which are in contact with each other during the blowing of the container.

[0081] The reference half-mold 21 more precisely comprises a first half-shell 211 and a first shell support 212.

[0082] Likewise, the second half-mold 22 comprises a second half-shell 221 and a second shell support 222.

[0083] This mold structure is notably described in the patent document published under number EP 0 821 641.

[0084] The two supports 3 more specifically comprise a first support 31 and a second support 32. This first support 31 and this second support 32 are conventionally referred to as a bracket.

[0085] The first support 31 and the second support 32 respectively carry the reference half-mold 21 and the second half-mold 22.

[0086] In other words, the first support 31 and the second support 32 encase the mold 2.

[0087] The first support 31 and the second support 32 are designed to take up and distribute the blowing forces exerted inside the mold 2 during blowing.

[0088] In reference to the figures 1 , 3 , 5 And 6, the first support 31 and the second support 32 are movable, by means of a hinge 33 between an open position ( figure 3 ) and a closed position, illustrated by the figures 1 , 5 And 6 , positions in which mold 2 is also closed.

[0089] In reference to the figure 2 which illustrates a second support 32, as well as the figure 5 , the device 1 comprises means for locking the first support 31 and the second support 32 in the container blowing position.

[0090] The locking means are known and are in particular of the type comprising: legs 34 presented by the first support 31 and the second support 32, pierced with concentric bores, the legs 34 fitting into each other in the container blowing position, and being distributed over the entire height of the supports 31, 32; fingers 35, controlled by a common shaft, locking two successive legs 34 and inserting into the bores.

[0091] The device 1 has a locking and unlocking clearance between the reference half-mold 21 and the second half-mold 22 allowing the locking means to move from an unlocked state to a locked state, and vice versa.

[0092] In reference to the figures 1 , 3 , 5 And 6 , according to the principle of the invention, the device 1 also comprises means for compensating for a blowing pressure inside the mold 2.

[0093] For this purpose, the compensation means use a fluid to compensate for the blowing pressure inside the mold 2.

[0094] As detailed below, the compensation means make it possible to exert a compensation force F1 on the reference half-mold 21, and a compensation force F2 on the second half-mold 22.

[0095] These means of compensation are notably pneumatic, and the fluid is pressurized air.

[0096] These means of compensation include: a first sealed chamber 41 interposed between the reference half-mold 21 and the first support 31; a second sealed chamber 42 interposed between the second half-mold 22 and the second support 32; means 43 for injecting a pressurized fluid coupled to the first sealed chamber 41 and to the second sealed chamber 42 (shown in the figure 6 ).

[0097] The reference half-mold 21 is movable relative to the first support 31. The reference half-mold 21 in particular has a clearance relative to the first support 31.

[0098] Similarly, the second half-mold 22 is movable relative to the second support 32, the second half-mold 22 thus having a clearance relative to the second support 32.

[0099] As illustrated more specifically on the figure 5 , the reference half-mold 21 has a compensation surface S1 which is defined by the first sealed chamber 41 interposed between the reference half-mold 21 and the first support 31.

[0100] As for it, the second half-mold 22 has a compensation surface S2 defined by the second sealed chamber 42 interposed between the second half-mold 22 and the second support 32.

[0101] The compensation surface S2 of the second half-mold 22 is greater than or equal to the compensation surface S1 of the reference half-mold 21, i.e. S2 ≥ S1.

[0102] According to the present embodiment and as illustrated by the figure 5 , the compensation surface S2 is strictly greater than the compensation surface S1, i.e. S2 > S1.

[0103] However, according to another more advantageous embodiment, the compensation surface S1 of the reference half-mold 21 is equal to the compensation surface S2 of the second half-mold 22, i.e. S1 = S2.

[0104] In this case, the compensation surface S1 is advantageously symmetrical to the compensation surface S2. This is in particular a planar symmetry according to the joint plane P illustrated in the figure 6 .

[0105] The device 1 also comprises a first elastically deformable peripheral seal 51 as well as a second elastically deformable peripheral seal 52.

[0106] The first peripheral seal 51 delimits the first sealed chamber 41 between the first support 31 and the reference half-mold 21.

[0107] Similarly, the second peripheral seal 52 delimits the second sealed chamber 42 between the second support 32 and the second half-mold 22.

[0108] During blowing, pressurized air is injected into the sealed chambers 41, 42, which causes an increase in the pressure therein. This pressure is capable of moving the half-molds 21, 22 away from each other and their supports 31, 32. The elastically deformable peripheral seals 51, 52 provide a sealed connection between each of the half-molds 21, 22 and their respective support 31, 32.

[0109] The first peripheral seal 51 and the second peripheral seal 52 are advantageously lip seals which have a substantially U-shaped section.

[0110] In reference to the figure 1 , each peripheral seal 51, 52 is housed in a groove 510, 520 presented respectively by the reference half-mold 21 and by the second half-mold 22.

[0111] The device 1 also comprises a mechanism for referential positioning of one of the half-molds, then designated by the expression reference half-mold 21, against at least one referential stop 61 carried by the support of the reference half-mold 21 while the second half-mold 22 is itself movable under the action of the pressurized fluid.

[0112] The reference positioning mechanism prevents, during compensation, the pressurized fluid injected into the first sealed chamber 41 from moving the reference half-mold away from the reference stop(s) 61.

[0113] The reference positioning mechanism thus more specifically comprises at least one reference stop 61 carried by the first support 31.

[0114] According to the present embodiment, the device 1 comprises three reference stops 61 carried by the first support 31.

[0115] These reference stops 61 tend to limit the movement of the reference half-mold 21 towards its support.

[0116] Still according to the present embodiment, and as illustrated by the figures 1 à 3 , 5 And 6 , the device 1 also comprises additional stops 62 which limit the movement of the second half-mold 22 relative to the second support 32.

[0117] The reference stops 61 and the additional stops 62 are more specifically screw stops which can be adjusted to modify the movement of the reference half-mold 21 and the second half-mold 22.

[0118] As mentioned previously, the device 1 comprises means 43 for injecting a pressurized fluid into the sealed chambers 41, 42.

[0119] More specifically, these injection means 43 are configured to inject: a fluid under a first pressure P1 in the sealed chamber interposed between the reference half-mold 21 and its support 31, or in other words in the first sealed chamber 41; a fluid under a second pressure P2 in the sealed chamber interposed between the second half-mold 22 and its support, or in other words in the second sealed chamber 42.

[0120] According to a first solution, the pressure P2 is strictly greater than the pressure P1.

[0121] According to another, more advantageous solution, the pressure P2 is equal to the pressure P1.

[0122] According to the present embodiment, the holding means also comprise elastic return members, called first return members 71, of the reference half-mold 21 in a position pressed against its support.

[0123] As illustrated by the figure 4 , the first return members 71 comprise springs 710.

[0124] The first return members 71 are calibrated so as to exert a return force E1. This return force E1 can for example be adjusted by the choice of a spring 710 with a suitable elastic return force.

[0125] Likewise and with reference to the figures 2 , 3 , 5 And 6 , the device 1 comprises second return members 72 of the second half-mold 22 against its support 32.

[0126] These second return members 72 are configured to exert a return force E2.

[0127] As illustrated more specifically on the figure 2 , three additional stops 62 and four second return members 72 can be observed on the second support 32. The first support 31, not shown, has a similar design and an identical number of reference stops 61 and first return members 71.

[0128] According to an embodiment in which the compensation forces F1, F2 of each of the half-molds are equal on either side of the mold 2, then the return force E1 is greater than the return force E2.

[0129] In this case, the first return members 71 tend to always keep the reference half-mold 21 pressing against the reference stops 61, and thus in a position pressed against its support 31.

[0130] The device 1 according to the invention previously described allows the implementation of a method for manufacturing a container by blowing or stretch-blow molding from a plastic blank.

[0131] This manufacturing process includes a step of compensating for a blowing pressure inside the mold.

[0132] During the compensation stage, a pressurized fluid, particularly air, is injected into the sealed chambers to exert a compensation force.

[0133] In particular, a fluid is injected under a pressure P1 into the first sealed chamber 41, as well as a fluid under a pressure P2 into the sealed chamber 42.

[0134] These pressurized fluids fill the sealed chambers 41, 42 and exert a compensation force F1, F2 on the compensation surface S1, S2 of these sealed chambers 41, 42.

[0135] According to the principle of the invention, during the compensation step, the reference half-mold 21 adopts a reference spatial position by resting against the reference stops 61 carried by the support of the reference half-mold 21 (the first support 31), while the second half-mold 22 is pressed against the reference half-mold 21.

[0136] In reference to the figure 6 which illustrates the compensation step, it can be observed that the two half-molds are in contact with each other.

[0137] During this step, the first sealed chamber 41 and the second sealed chamber 42 are pressurized using the injection means 43.

[0138] Thanks to the holding means, during this compensation step, the reference half-mold 21 adopts its reference spatial position by resting against the reference stops 61.

[0139] As seen on the figure 6 , the second half-mold 22 is detached from the additional stops 62 under the effect of the compensation, and pressed against the reference half-mold 21.

[0140] The adoption of the reference spatial position by the reference half-mold 21 during the compensation step can be obtained in different ways.

[0141] During the compensation stage, different forces are exerted on each of the half-molds, including in particular: a compensation force F1, F2 for each half-mold 21, 22, exerted by the compensation means; a return force E1, E2, exerted by the first return members 71 and by the second return members 72.

[0142] To achieve the objective of the invention, the sum of the forces exerted on the reference half-mold 21 and the sum of the forces exerted on the second half-mold 22 have a difference such that the reference half-mold 21 is held in abutment against the reference stops 61.

[0143] According to a first embodiment, particularly advantageous, during the compensation step, an identical compensation force F1, F2 is exerted for each half-mold 21, 22, and the return force E1 of the reference half-mold 21 in a position bearing against the reference stops 61 is exerted, this return force being distinct from the compensation forces. The return force E1 exerted by the first return members 71 is greater than the return force E2 exerted by the second return members 72.

[0144] However, care is taken to ensure that the restoring force E1 tends to have as little difference as possible with the restoring force E2.

[0145] According to a second embodiment, the compensation force F2 is strictly greater than the compensation force F1. The compensation forces F1, F2 then make it possible to maintain the reference half-mold 21 against the reference stops 61, while the second half-mold 22 is driven and pressed against the reference half-mold 21.

[0146] This difference in compensation forces can in particular be obtained by means of the injection of a fluid, into the second sealed chamber 42, at a pressure P2 which is strictly greater than a pressure P1 of the fluid injected into the first sealed chamber 41.

[0147] This difference in compensation force can also be obtained by injecting a fluid into the sealed chambers 41, 42 at an identical pressure P1, P2, with sealed chambers 41, 42 of different shape, and in particular with a compensation surface S2 of the second half-mold 22 greater than a compensation surface S1 of the reference half-mold 21.

[0148] In addition to these variants, it is particularly interesting that the sum of the forces (compensation force F2 - return force E2) exerted on the second half-mold 22 during the compensation step is greater than that of the forces (compensation force F1 - return force E1) exerted on the reference half-mold 21 with a maximum difference of the order of 5%.

[0149] For each of these possible variants, and other variants not mentioned, care is advantageously taken to ensure that the reference half-mold 21 never shifts from its reference stops 61 during blowing and compensation of the mold.

[0150] This objective is achieved by anticipating the injection of a fluid into the second sealed chamber 42 relative to the injection of the pressurized fluid into the first sealed chamber 41.

[0151] This objective is also achieved with a restoring force E1 strictly greater than the restoring force E2.

[0152] In reference to the figures 3 , 5 And 6 , the operation of the device 1 according to the invention is described below.

[0153] To form a container, mold 2 is opened and receives a blank.

[0154] The closing of the mold 2 is carried out by the passage of the first support 31 and the second support 32 from their open position to their closed position.

[0155] The locking means ensure that the mold 2 does not open during blowing. This closing of the mold is facilitated by the first return members 71 and the second return members 72 which keep the half-molds pressed respectively against the reference stops 61 and the annex stops 62 of their respective support 31, 32.

[0156] During the blowing phase, air is injected into the preform at the same time as the pressurized fluid injection means 43 are activated.

[0157] The injection means 43 are controlled so as to coordinate the pressure increase of the container in the mold 2 with that of the sealed chambers 41, 42. Compensation is then carried out symmetrically at the level of the two half-molds 21, 22.

[0158] Advantageously, the blowing pressure inside the mold 2 is equal to the injection pressure of a pressurized fluid inside the first sealed chamber 41 and inside the second sealed chamber 42.

[0159] The injection of air into the second sealed chamber 42 makes it possible to move the second half-mold 22 away from the second support 32, and thus to press the second half-mold 22 against the reference half-mold 21.

[0160] According to the principle of the invention, the first sealed chamber 41 is not far from its support 31.

[0161] Indeed, during blowing and, concomitantly during the compensation step, the reference half-mold 21 remains in its reference spatial position, bearing against the reference stops 61 carried by the first support 31.

[0162] This maintenance is ensured by the first return organs 71 which exert a sufficient return force E1.

[0163] At the end of the blowing of the container, the pressure is released in the mold 2, and the air from the sealed chambers 41, 42 is evacuated.

[0164] The first support 31 and the second support 32 then move from their closed position of the container to their open position to open the mold 2, and allow the extraction of the formed container, the start of a new cycle of forming a container.

Claims

1. Device (1) for manufacturing a container by blow moulding or stretch blow moulding from a plastics blank, the device comprising: - a mould (2) comprising two half-moulds (21, 22) which together define an impression (E) of the container to be formed; - a support (31, 32) for each of the half-moulds (21, 22), each half-mould (21, 22) having a degree of travel with respect to its support (31, 32); - means for compensating for a blowing pressure inside the mould (2); the compensation means comprising: - at least one sealed chamber (41, 42) interposed between each half-mould (21, 22) and its support (31, 32); - means (43) for injecting a pressurized fluid into the sealed chambers (41, 42); characterized in that it comprises a mechanism for the referential positioning of one of the half-moulds, referred to as reference half-mould (21), against at least one referential stop (61) borne by the support (31) of the reference half-mould (21), the referential stop or stops (61) tending to limit the movement of the reference half-mould (21) towards its support (31), and means for holding the reference half-mould (21) in abutment against the referential stop or stops (61) while the other of the half-moulds, referred to as second half-mould (22), is movable under the action of the pressurized fluid.

2. Device (1) according to the preceding claim, characterized in that: - the reference half-mould (21) has a compensation surface (S1) defined by the sealed chamber (41) interposed between the reference half-mould (21) and its support (31); - the second half-mould (22) has a compensation surface (S2) defined by the sealed chamber (42) interposed between the second half-mould (22) and its support (32); where S2 > S1.

3. Device (1) according to Claim 1, characterized in that: - the reference half-mould (21) has a compensation surface (S1) defined by the sealed chamber (41) interposed between the reference half-mould (21) and its support (31); - the second half-mould (22) has a compensation surface (S2) defined by the sealed chamber (42) interposed between the second half-mould (22) and its support (32); where S2 = S1, and in that the compensation surface (S1) of the reference half-mould (21) is symmetrical to the compensation surface (S2) of the second half-mould (22).

4. Device (1) according to any one of the preceding claims, characterized in that the injection means (43) are configured to: - inject a fluid at a first pressure (P1) into the sealed chamber, referred to as first sealed chamber (41), interposed between the reference half-mould (21) and its support (31); - inject a fluid at a second pressure (P2) into the sealed chamber, referred to as second sealed chamber (42), interposed between the second half-mould (22) and its support (32), where P2 > P1.

5. Device (1) according to any one of Claims 1 to 3, characterized in that the injection means (43) are configured to: - inject a fluid at a first pressure (P1) into the sealed chamber, referred to as first sealed chamber (41), interposed between the reference half-mould (21) and its support (31); - inject a fluid at a second pressure (P2) into the sealed chamber, referred to as second sealed chamber (42), interposed between the second half-mould (22) and its support (32), where P2 = P1.

6. Device (1) according to any one of the preceding claims, characterized in that the holding means comprise at least one elastic return member, referred to as first return member (71), for returning the reference half-mould (21) to a position pressed against its support (31).

7. Device (1) according to the preceding claim, characterized in that it comprises at least one elastic return member, referred to as second return member (72), for returning the second half-mould (22) against its support (32), and in that: - the first return member or members (71) exert a return force (E1); - the second return member or members (72) exert a return force (E2), where E1 > E2.

8. Method for manufacturing a container by blow-moulding or stretch-blow-moulding a plastics blank in a mould (2) comprising two half-moulds (21, 22) each borne by a support (31, 32), for each half-mould (21, 22) at least one sealed chamber (41, 42) being interposed between said half-mould (21, 22) and its support (31, 32), the method comprising a step of compensating for a blowing pressure inside the mould (2), wherein the compensation step consists in injecting a pressurized fluid into the sealed chambers (41, 42) in order to exert a compensation force, characterized in that, during the compensation step, one of the half-moulds, referred to as reference half-mould (21), adopts a reference spatial position, being in abutment against at least one referential stop (61) borne by the support (31) of the reference half-mould (21), while the other half-mould, referred to as second half-mould (22), is pressed against the reference half-mould (21).

9. Method according to the preceding claim, characterized in that, during the compensation step, an identical compensation force (F1, F2) is exerted for each half-mould (21, 22), and a return force (E1) for returning the reference half-mould (21) to a position in abutment against the referential stop or stops (61) is exerted, the return force (E1) being separate from said compensation forces (F1, F2).

10. Method according to Claim 8, characterized in that, during the compensation step: - a compensation force (F1) is exerted for the reference half-mould (21); - a compensation force (F2) is exerted for the second half-mould (22), where F2 > F1.

11. Method according to the preceding claim, characterized in that, during the compensation step: - a fluid under a pressure (P1) is injected into the sealed chamber, referred to as first sealed chamber (41), interposed between the reference half-mould (21) and its support (31); - a fluid under a pressure P2 is injected into the sealed chamber, referred to as second sealed chamber (42), interposed between the second half-mould (22) and its support (32); where P2 > P1.