HOLLOW HEATING UNIT FOR A PLASTIC CONTAINER MANUFACTURING MACHINE

Description

[0001] The field of the invention is that of the design and manufacture of machines for the manufacture of plastic containers.

[0002] More specifically, the invention relates to a heating unit for heating hollow plastic bodies to or above a glass transition temperature, prior to forming containers from said hollow bodies.

[0003] To manufacture plastic containers from hollow bodies, it is necessary to heat said hollow bodies until their constituent plastic material reaches or exceeds the glass transition temperature at which the material can be easily deformed, while limiting the risk of tearing of the plastic material.

[0004] In the case of containers in the form of bottles, the hollow bodies are heated and then introduced into a forming unit in which they will be blown, generally by injecting a pressurized fluid.

[0005] To heat the hollow bodies, they circulate in a parade to enter a heating unit and be heated by heating modules.

[0006] Heating units are traditionally made up of modules placed next to each other to form a wall emitting heating radiation intended to heat and soften the plastic material of hollow bodies.

[0007] The heating modules carry sub-modules, each having means of emission.

[0008] For example, the emission means may use laser technology or halogen technology.

[0009] Typically, heating modules comprise a frame on which several emission sub-modules are mounted, one on top of the other.

[0010] The transmission sub-modules each comprise a support on which the transmission means are mounted.

[0011] More particularly, the transmission means extend over a width less than the width of the support so that a technical zone is arranged on either side of the transmission means.

[0012] In other words, these technical zones are formed by a portion of the support which is devoid of means of emission.

[0013] These technical areas allow both cooling of the transmission means and the connection of the transmission means to an energy source.

[0014] The classically known modules thus present, depending on the direction of movement of the hollow bodies facing them, a succession of zones emitting thermal radiation, framed by a zone not emitting thermal radiation.

[0015] On the emission wall, columns are therefore observed that do not emit thermal radiation. Therefore, as they pass in front of the emission wall, the hollow bodies encounter zones that do not emit thermal radiation over their entire height.

[0016] These columns, which do not emit thermal radiation, therefore impact the homogeneity of the heating of hollow bodies.

[0017] To overcome this, the furnaces generally include two facing emission walls to form a corridor in which the hollow bodies pass.

[0018] The emitting walls may in particular be offset from each other so that an emitting zone of a first wall is opposite a non-emitting zone of the second wall.

[0019] Another technique is to rotate the hollow bodies on themselves along their path in the heating unit. This allows faces not initially exposed to radiation to be exposed to radiation in a second stage.

[0020] Although these techniques improve the heating of hollow bodies by homogenizing them, they nevertheless have drawbacks.

[0021] In fact, the use of two emitting walls increases the energy consumption of the heating unit.

[0022] Furthermore, the rotation of hollow bodies requires either a guiding mechanism, for example a mechanical one, for the rotation of hollow bodies, which can be controlled by a computer. Such guidance then requires a significant and costly design of the guiding means.

[0023] Furthermore, for preferential heating, i.e. heating during which a part of the hollow bodies is heated more or less than other parts of the same hollow body, the design and installation of the systems for guiding and / or rotating the hollow bodies are further complicated.

[0024] Finally, to achieve even heating, it may be useful to heat certain portions of the hollow body more intensely, such as the bottom and the part near the neck of the hollow body. Indeed, the central portion is the most heated portion of hollow bodies, particularly due to the thermal conduction of the plastic material.

[0025] Therefore, it may be useful to heat the upper and lower parts more intensely so that the hollow body leaving the heating unit has a constant temperature or almost the same temperature over its entire height.

[0026] Document DE 10 2017 120634 A1 describes a unit for heating a succession of hollow bodies, comprising at least two contiguous emission modules, each emission module comprising a superposition of zones emitting thermal radiation and zones not capable of emitting thermal radiation, in which said modules are arranged in such a way that, over the same height and along a trajectory of movement of the hollow bodies in the heating unit, a zone emitting thermal radiation of a first module is followed by a zone not capable of emitting thermal radiation of a second module.

[0027] The invention aims in particular to overcome the drawbacks of the prior art.

[0028] More specifically, the invention aims to propose a heating unit making it possible to obtain homogeneous heating of hollow bodies, or on the contrary preferential and precise heating of hollow bodies.

[0029] The invention also aims to provide such a heating unit which makes it possible to increase the service life of the transmission sub-modules.

[0030] The invention further aims to provide such a heating unit for which maintenance and / or replacement can be carried out easily.

[0031] These objectives, as well as others which will appear subsequently, are achieved thanks to the invention according to claim 1 which relates to a unit for heating a succession of hollow bodies comprising at least two contiguous emission modules, each emission module comprising a superposition of zones emitting thermal radiation and zones not emitting thermal radiation, characterized in that the modules are arranged in such a way that, over the same height and along a trajectory of movement of the hollow bodies in the heating unit, a zone emitting thermal radiation of a first module is followed by a zone not emitting thermal radiation of a second module. In addition, the emitting zones (11) of each module (3) extend over the entire width of said module (3).

[0032] The emission modules are adjacent to each other along the path of movement of the hollow bodies and the emitting and non-emitting zones are superimposed on each other in the height direction, i.e. in a direction transverse to the path of movement of the hollow bodies in the heating unit.

[0033] Thus, the pattern created by the emitting and non-emitting zones is a checkerboard according to the movement path of the hollow bodies in the heating unit.

[0034] Depending on the type of heating required, i.e. homogeneous heating or preferential heating, it is possible to have either a complete alternation of emitting zones and non-emitting zones, or at least a partial overlap of the emitting zones of two adjacent modules, along the trajectory of the hollow bodies.

[0035] Advantageously, each transmission module comprises a plurality of transmission sub-modules each including a support having a transmission face and transmission means mounted on the transmission face.

[0036] The emission face is then turned towards the hollow bodies which pass through the heating unit, so as to form an emission wall.

[0037] The emission means are thus mounted on the emission face, for example by simply being fixed on it or by being embedded in it.

[0038] Preferably, each support has a first height HS, and the emission means have a second height HE lower than the first height HS.

[0039] This height difference makes it possible to create non-emitting zones to cool the emission means along their entire length.

[0040] In fact, the emission means are spaced apart from each other so that they can be cooled both from the rear, but also from above and below. This extends the service life of the emission means.

[0041] According to one embodiment, the transmission means of each transmission sub-module comprise a single transmission member.

[0042] This allows for the creation of a checkerboard pattern but also for increased cooling capacity of the emission means.

[0043] The checkerboard pattern can also be created in a fine way to provide the best heating uniformity or, on the contrary, the precision sought to create more or less hot sectors on hollow bodies.

[0044] Preferably, the emitting member comprises a plurality of diodes arranged in the form of a bar.

[0045] This makes cooling the modules, and in particular the emission organ, easier, as does the creation of the checkerboard pattern.

[0046] Advantageously, for each emission sub-module, the emission means are centered on the emission face.

[0047] Cooling of the emission organ can therefore be ensured by the support which carries them, as well as by a lower sub-module and / or an upper sub-module.

[0048] Alternatively, for each emission sub-module, the emission means are located near a lower edge or an upper edge of the emission surface.

[0049] According to this variant, the cooling of the emission organ remains equivalent in relation to the centering of the emission means on the emission face, but the installation of the sub-modules allows, in an intuitive and easy way, to create the checkerboard pattern, on two adjacent modules.

[0050] In fact, on a first module, the sub-modules can be mounted in a first direction, while on the adjacent sub-module, the sub-modules are mounted in the opposite direction, for example by being rotated 180°.

[0051] According to a preferred embodiment, the emission face carries a coating reflecting thermal radiation.

[0052] This reflective coating redirects thermal radiation towards hollow bodies to promote their heating but also prevents the support from heating, in order to ensure the cooling of the emission means.

[0053] According to another aspect, the invention relates to a unit for heating a succession of hollow bodies comprising at least two contiguous emission modules, each emission module comprising a superposition of zones emitting thermal radiation and zones not capable of emitting thermal radiation, characterized in that the modules are arranged in such a way that, over the same height and along a trajectory of movement of the hollow bodies in the heating unit, a zone emitting thermal radiation of a first module is followed by a zone not capable of emitting thermal radiation of a second module.

[0054] Advantageously, the emission modules are contiguous to one another along the path of movement of the hollow bodies and the emitting and non-emitting zones are superimposed on one another in the height direction, that is to say in a direction transverse to the path of movement of the hollow bodies in the heating unit.

[0055] Thus, the pattern created by the emitting zones and the zones not capable of emitting thermal radiation is a checkerboard according to the trajectory of movement of the hollow bodies in the heating unit.

[0056] Depending on the type of heating required, i.e. homogeneous heating or preferential heating, it is possible to have either a complete alternation of emitting zones and zones not capable of emitting thermal radiation, or at least a partial overlap of the emitting zones of two adjacent modules, along the trajectory of the hollow bodies.

[0057] Advantageously, each transmission module comprises a plurality of transmission sub-modules each including a support having a transmission face and transmission means mounted on the transmission face.

[0058] The emission face is then turned towards the hollow bodies which pass through the heating unit, so as to form an emission wall.

[0059] The emission means are thus mounted on the emission face, for example by simply being fixed on it or by being embedded in it.

[0060] Preferably, each support has a first height HS, and the emission means have a second height HE lower than the first height HS.

[0061] This difference in height makes it possible to create areas that are unable to emit thermal radiation, allowing the emission means to be cooled along their entire length.

[0062] In fact, the emission means are spaced apart from each other so that they can be cooled both from the rear, but also from above and below. This extends the service life of the emission means.

[0063] According to one embodiment, the transmission means of each transmission sub-module comprise a single transmission member.

[0064] This allows for the creation of a checkerboard pattern but also for increased cooling capacity of the emission means.

[0065] The checkerboard pattern can also be created in a fine way to provide the best heating uniformity or, on the contrary, the precision sought to create more or less hot sectors on hollow bodies.

[0066] Preferably, the emitting member comprises a plurality of diodes arranged in the form of a bar.

[0067] This makes cooling the modules, and in particular the emission organ, easier, as does the creation of the checkerboard pattern.

[0068] Advantageously, for each emission sub-module, the emission means are centered on the emission face.

[0069] Cooling of the emission organ can therefore be ensured by the support which carries them, as well as by a lower sub-module and / or an upper sub-module.

[0070] Alternatively, for each emission sub-module, the emission means are located near a lower edge or an upper edge of the emission surface.

[0071] According to this variant, the cooling of the emission organ remains equivalent in relation to the centering of the emission means on the emission face, but the installation of the sub-modules allows, in an intuitive and easy way, to create the checkerboard pattern, on two adjacent modules.

[0072] In fact, on a first module, the sub-modules can be mounted in a first direction, while on the adjacent sub-module, the sub-modules are mounted in the opposite direction, for example by being rotated 180°.

[0073] According to a preferred embodiment, the emission face carries a coating reflecting thermal radiation.

[0074] This reflective coating allows the thermal radiation to be redirected towards the hollow bodies to promote their heating but also to prevent the support from heating, in order to ensure the cooling of the emission means.

[0075] Other characteristics and advantages of the invention will appear more clearly on reading the following description of preferred embodiments of the invention, given by way of illustrative and non-limiting example, and the appended drawings among which: [ Fig. 1 ] is a schematic perspective view from above of a heating unit according to the invention; [ Fig. 2 ] is a schematic perspective view showing a module of the heating unit according to the invention; [ Fig. 3 ] is a schematic rear perspective view of a transmission subsystem of a module according to the invention; [ Fig. 4 ] is a schematic sectional view of a transmission subsystem of a module according to the invention, according to a first embodiment; [ Fig. 5 ] is a schematic sectional view of a transmission subsystem of a module according to the invention, according to a second embodiment; [ Fig. 6 ] is a schematic sectional view of a transmission subsystem of a module according to the invention, according to a third embodiment; [ Fig. 7 ] is a partial schematic front view of a heating wall of a heating unit according to the invention. [ Fig. 8 ] is a schematic view illustrating a variant of the heating wall of the figure 7 . There figure 8 is not part of the invention.

[0076] There figure 1 illustrates a heating unit 1 according to the invention, for heating hollow bodies 2, made of plastic material, to or above a glass transition temperature of the plastic material of the hollow bodies 2.

[0077] The path of the hollow bodies 2 around and in the heating unit 1 is as follows. Upstream and downstream of the heating unit 1, the hollow bodies 2 pass in a linear manner, i.e. one behind the other. During their passage through the heating unit 1, the hollow bodies 2 can be arranged in a staggered pattern. The flow of hollow bodies 2 upstream of the heating unit 1 is thus split into two at the inlet of the heating unit 1, then grouped together at the outlet of the heating unit 1.

[0078] The heating unit 1 is composed of modules 3 joined together to form a wall for emitting heating radiation.

[0079] More specifically, as illustrated in the figure 1 , the heating unit 1 has a corridor 4 formed by two walls emitting heating radiation, this corridor 4 being intended to be crossed by the hollow bodies 2 made of plastic material, during their movement.

[0080] In reference to the figure 2 , a module 3 of the heating unit 1 is illustrated.

[0081] This module 3 comprises a frame 5 on which several transmission sub-modules 6 are mounted next to each other.

[0082] The emission sub-modules 6 are more precisely superimposed on each other. As illustrated in the figure 3 , a transmission sub-module 6 comprises: a support 7; transmission means 8; electrical connection means 9 of the transmission sub-module 6 to an electrical energy source.

[0083] The electrical connection means 9 are for example in the form of single electrical cables joining the support 7 via the rear of the transmission sub-module 6 and allowing connection to the electrical energy source.

[0084] The support 7 has a rear face 71 intended to bear against the frame 5 of the module, and an emission face 72, opposite the rear face 71, and intended to receive the emission means 8.

[0085] The support 7 also has an upper face 73 and a lower face 74 opposite each other, the upper face 73 of a first support 7 being able to receive the lower face 74 of a second support 7 when several transmission sub-modules 6 are superimposed on each other, as illustrated in the figure 2 .

[0086] In addition, the support 7 has an internal network of channels for circulating a cooling fluid, for example distilled water.

[0087] The emission means 8 are composed of a single emission member and are, for example, in the form of an emission bar. More particularly, the emission means 8 are in the form of a bar of laser diodes.

[0088] Even more precisely, the emission means 8 comprise a plurality of light-emitting semiconductor components, such as VCSELs (acronym for Vertical-Cavity Surface-Emitting Laser), placed next to each other to form said emitting bar.

[0089] As seen on the figure 2 and on the figure 3 , the emission means 8 extend over the entire width of the support 7.

[0090] More particularly, the support has a first width L1, and the emission means 8 have a second width L2 substantially equal to the first width L1 of the support 7.

[0091] Likewise, the support 7 has a height HS and the emission means 8 have a height HE.

[0092] Advantageously, the height HE of the emission means 8 is less than the height HS of the support 7. For example, the height HE of the emission means 8 is twice less than the height HS of the support 7.

[0093] THE figures 4 , 5 And 6 illustrate three embodiments of an emission subsystem 6 of the heating unit 1 according to the invention.

[0094] According to a first embodiment illustrated on the figure 4 , the support 7 has a groove 75 intended to receive the emission means 8.

[0095] More precisely, the groove 75 is made on the emission face 72 of the support 7 in the direction of the rear face 71.

[0096] As seen on the figure 4 , when the emission means 8 are coupled to the support 7, they are integrated into the groove 75, flush with the emission face 72 of the support 7.

[0097] The groove 75 is advantageously positioned in the center of the emission face 72 of the support 7. Thus, the emission means 8 are housed in the support 7 which has an upper part 76 and a lower part 77 respectively above and below the emission means 8.

[0098] According to this embodiment, the support 7, thanks to the upper part 76 and the lower part 77, can dissipate the calories produced by the emission means 8 outside the module 3 or towards the frame 5 of the module 3. This transmission of calories is done in particular by thermal conductivity inside the support 7 and extraction of the calories by the cooling fluids.

[0099] According to a second embodiment illustrated in the figure 5 and a third embodiment illustrated in the figure 6 , the emission means 8 are mounted directly on the emission face 72 of the support 7, the support 7 then being devoid of the groove 75.

[0100] The emission means 8 are therefore supported by the support 7 only by the emission face 72 of the latter.

[0101] Thus, when the emission means 8 emit heating radiation, the calories dissipated by the emission means 8 can be evacuated through the emission face 72, all the more easily since the dissipation can take place in a volume whose height is greater than the height of the emission means 8 alone.

[0102] According to the second embodiment, the emission means 8 are located in the middle of the emission face 72 of the support 7.

[0103] More precisely, the emission means 8 are located at a height h1 and h2 of the upper face 73 and the lower face 74 of the support 7 respectively.

[0104] In other words, the heights h1 and h2 are equal to each other.

[0105] According to the third embodiment illustrated in the figure 6 , the emission means 8 are located near a lower edge or an upper edge of the emission surface 72.

[0106] In other words, the emission means 8 are located in the vicinity of the upper face 73 or the lower face 74 of the support 7.

[0107] More specifically, as illustrated in the figure 6 , the emission means 8 are located close to the lower face 74 of the support 7 and are spaced from the upper face 73 by a height h3 equal to or almost two-thirds of the height HS of the support 7.

[0108] Thus, when the emission means 8 are active, that is to say when they emit thermal radiation, the calories produced by the emission means 8 are advantageously evacuated towards the upper face 73 of the support 7 by thermal conduction between the support 7 and the emission means 8.

[0109] In reference to the figure 7 , an emission wall is partially represented. This emission wall is composed or formed by the abutment of several modules 3 side by side.

[0110] As seen on the figures 2 And 7 , between two emission means 8 superimposed on each other, a spacing height 10 is created.

[0111] This spacing height 10 allows the dissipation of the calories emitted by the emission means 8.

[0112] Advantageously, the spacing height 10 is equal to the height of the emission means 8.

[0113] As seen on the figures 2 ,7 and / or 8, a module 3 then has a vertical pattern formed by an alternation of emitting zones 11, that is to say zones formed by the emission means 8, and non-emitting zones 12, that is to say zones formed by the spacing heights 10. In other words, the expression “non-emitting zones 12” means a zone which is not capable of emitting thermal radiation.

[0114] In reference to the figure 7 , the emission modules 3 are arranged to form a checkerboard.

[0115] More precisely, the spacing heights 10 of a first module 3 are followed, according to a trajectory T of movement of the hollow bodies 2 in the heating unit 1, by an emitting zone 11 of a second contiguous module 3.

[0116] This checkerboard pattern is advantageously repeated over the entire wall of the heating unit 1, or on each wall of the heating unit 1.

[0117] Such a checkerboard pattern makes it possible to avoid vertical zones that are not capable of emitting thermal radiation, i.e. zones 12 that are not capable of emitting thermal radiation over the entire height of the module 3, along the trajectory T of the hollow bodies 2 in the heating unit 1.

[0118] Indeed, the zones 12 not capable of emitting thermal radiation, that is to say the spacing heights 10, extend parallel to the trajectory T of the hollow bodies 2 and have a height low enough for the thermal conduction in the material to generate substantially uniform heating over the entire periphery of the hollow body 2. Furthermore, to obtain perfectly uniform heating, it may be possible to combine the checkerboard pattern with a rotation of the hollow bodies 2 during their passage through the heating unit 1.

[0119] Advantageously, the width of a module 3 is equal to the peripheral development of the hollow bodies 2. However, it is possible to modulate this value according to the speed of rotation of the hollow bodies 2, it being understood that, depending on its displacement, the entire periphery of the hollow body 2 is subjected to the radiation of the same module.

[0120] In other words, for the same module 3, a hollow body 2 is exposed to an equal emission time at each point of its periphery.

[0121] Similarly, the number of modules 3 for each wall is advantageously an even number. Considering a wall for emitting heating radiation, the rotation speed of the hollow bodies 2 (for example five revolutions per second) as a function of the width of the modules 3 on each wall of the heating unit 1 makes it possible to achieve completely homogeneous heating of the hollow bodies 2 in that each point of the hollow bodies 2, on the periphery of the hollow bodies 2, receives identical exposure to the radiation from the emission means 8.

[0122] In other words, the heating of hollow bodies 2, according to the figure 7 , is homogeneous from the point of view of the heating unit 1.

[0123] On the other hand, considering the hollow bodies 2, the homogeneity of the heating can be obtained thanks to a preferential heating of the hollow bodies 2.

[0124] In reference to the figure 8 , which is not part of the invention, the homogeneity of the heating of the hollow bodies 2 results from overexposure and / or underexposure of a part of the hollow body 2 over its height.

[0125] Indeed, on a central portion of the hollow body 2, the heat is generally higher than at its ends (at the level of its neck and its bottom), even if the quantity of heating radiation received by the hollow body is identical at each point of the hollow body 2.

[0126] This is explained in particular by the fact that the temperature propagates by thermal convection in the plastic material of the hollow bodies 2.

[0127] Thus, the central portion receives the calories coming from the ends in addition to the calories from thermal radiation, the heat curve over the height of a hollow body 2 being able to take the form of a Gaussian (the ends being colder than the center of the preform over its height).

[0128] To overcome this, it may be possible to overheat the ends of the hollow bodies 2.

[0129] This overheating can be achieved by increasing the power of the thermal radiation emitted by the emission means 8 towards said end zones or by overlapping the emitting zones 11 of two contiguous modules 3, as illustrated in the figure 8 . which is not part of the invention.

[0130] In fact, the overlapping of two contiguous emitting zones causes an increase in the duration of exposure of the hollow body 2 to thermal radiation. The heating of the plastic material is then increased.

[0131] It is therefore possible to overheat the ends of the hollow body 2 by simply overlapping the emitting zones of two contiguous modules 3. Thermal convection in the hollow body 2 allows uniform heating to be maintained at the outlet of the heating unit 1.

[0132] According to a preferred embodiment, the emission face 72 of the support 7 is covered with a coating reflecting thermal radiation.

[0133] According to another embodiment, the zone 12 not capable of emitting thermal radiation can be covered with a coating reflecting thermal radiation.

[0134] As an indicative example, the reflective coating is a thin layer of gold.

[0135] This gold layer makes it possible in particular to reflect the laser radiation from the emission means 8 without the support 7 overheating.

[0136] The presence of the spacing height 10 below and / or above the emission means 8 makes it possible to offer a longer service life to the emission means 8, thanks to better cooling.

[0137] Indeed, the emission means 8 are cooled from above, below and behind, unlike the prior art where the emission means 8 are only cooled from the sides and from behind.

[0138] The exchange surface between the emission means 8 and the support 7 is then greater in the heating unit 1 according to the invention than according to the prior art.

[0139] According to an alternative embodiment not illustrated, the modules 3 are devoid of a frame 5 and then only comprise a superposition of transmission sub-modules 6.

[0140] In this case, a plate common to all the emission modules 3 is arranged in the heating unit 1 and forms a frame on which all the emission sub-modules 6 are fixed.

Claims

1. Unit (1) for heating a succession of hollow bodies, comprising at least two contiguous emission modules (3), each emission module (3) comprising a superposition of zones (11) that emit thermal radiation and zones (12) that are not able to emit thermal radiation, wherein said modules (3) are arranged such that, at one and the same height and along a trajectory (T) of movement of the hollow bodies (2) through the heating unit (1), a zone (11) that emits thermal radiation of a first module (3) is followed by zone (12) that is not able to emit thermal radiation of a second module (3), characterized in that the emitting zones of each module extend over the entire width of said module.

2. Heating unit (1) according to Claim 1, characterized in that each emission module (3) comprises a plurality of emission submodules (6) each including a support (7) having an emission face (72) and emission means (8) mounted on the emission face (72).

3. Heating unit (1) according to the preceding claim, characterized in that each support (7) has a first height (HS), and the emission means (8) have a second height (HE) less than the first height HS.

4. Heating unit (1) according to Claim 2 or Claim 3, characterized in that the emission means (8) of each emission submodule (6) comprise a single emission member.

5. Heating unit according to the preceding claim, characterized in that the emission member comprises a plurality of diodes arranged in the form of a bar.

6. Heating unit (1) according to any one of Claims 2 to 5, characterized in that, for each emission submodule (6), the emission means (8) are centred on the emission face (72).

7. Heating unit (1) according to any one of Claims 2 to 5, characterized in that, for each emission submodule (6), the emission means (8) are situated near a lower edge or an upper edge of the emission surface (72).

8. Heating unit (1) according to any one of Claims 2 to 7, characterized in that the emission face (72) bears a coating that reflects the thermal radiation.