Preform heat treatment unit comprising series-connected heating elements
By connecting heating elements on both sides of the enclosure in series to a single current source, the heat treatment unit achieves uniform heating profiles and reduces energy consumption, addressing synchronization issues and enhancing production consistency.
Patent Information
- Application Number
- FR2023005384
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-05-31
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2043-05-31
AI Technical Summary
Existing heat treatment units face challenges in applying a uniform thermal profile to preforms due to synchronization issues between heating elements on opposite walls, leading to irregularities in container production, especially when preforms circulate in parallel rows.
The heating elements on both sides of the enclosure are electrically connected in series to the same current source, ensuring identical heating power and synchronized power variations, using a control device to manage current flow.
This approach ensures uniform heating profiles across preforms, reduces energy consumption by halving the number of current sources, and maintains consistent heating power across parallel rows, enhancing production consistency and efficiency.
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Abstract
Description
Title of the invention: Preform heat treatment unit comprising heating elements connected in series
[0001] The present invention relates to a preform heat treatment unit of a container manufacturing installation of the type comprising an enclosure delimited by a first wall and a second wall extending on either side of the enclosure within which the preforms pass along a predefined circulation path extending in a longitudinal direction, the first wall comprising at least one first heating element and the second wall comprising at least one second heating element, forming, with the first heating element, a pair of heating elements, the first heating element and the second heating element extending at least partly opposite each other on either side of the enclosure in a transverse direction, substantially perpendicular to the longitudinal direction, each heating element being supplied with electricity by a current source.
[0002] Such a heat treatment unit, or oven, is generally equipped with a plurality of heating elements arranged to emit heat towards preforms made of synthetic material passing through the heat treatment unit while rotating on themselves in order to apply a heating profile to these preforms and allow their subsequent deformation, for example by stretch blow molding, so as to produce containers from the preforms.
[0003] For example, it has been proposed to provide that the enclosure of the heat treatment unit is delimited by two walls extending along the path of the preforms and each comprising heating elements emitting heat into the enclosure. Such an arrangement makes it possible to improve the energy distribution in the enclosure and to improve the efficiency of a heat treatment unit. Document EP 2 782 741 describes, for example, such a heat treatment unit.
[0004] However, it becomes difficult to apply a uniform thermal profile to the different preforms circulating between the heating elements because, even if the heating elements are controlled in a synchronized manner, in particular to vary the heating power, there is in practice often a time lag between the application of a setpoint to the heating elements extending on one of the walls and the application of the same setpoint to the heating elements extending on the other wall. This can result in irregularity in the containers produced from the preforms whose heating profile is not uniformly applied from one preform to another. This problem is all the more significant when the heating unit comprises two rows of preforms circulating in parallel in the enclosure, as proposed in document EP 2 782 741. Indeed, in this case, the preforms of each row are more exposed to the heat coming from the wall to which they are closest and any heat difference between the heating elements arranged on either side of the enclosure causes a difference in the thermal profile applied to the preforms of each row, which results in the formation of containers having different characteristics depending on whether the containers are formed from preforms coming from one or the other row.
[0005] One of the aims of the invention is to overcome these drawbacks by proposing a heat treatment unit comprising heating elements extending on either side of an enclosure and delivering the same heating power.
[0006] To this end, the invention relates to a heat treatment unit of the aforementioned type, in which the first and second heating elements of said pair of heating elements are electrically connected in series to the same current source.
[0007] By connecting the heating elements of a pair of heating elements extending on either side of the enclosure in series with the same current source, it is ensured that the current flowing through the two heating elements is the same. Since the heating power is directly linked to the value of the current flowing in this series circuit, the heating powers delivered by the two heating elements are thus identical. Furthermore, during variations in setpoints, the modification of the current value is applied simultaneously to both heating elements, which makes it possible to obtain the same instantaneous power delivered by the two heating elements.
[0008] The heat treatment unit according to the invention may further comprise one or more of the following characteristics, taken individually or in any technically conceivable combination: - the heat treatment unit comprising a plurality of pairs of heating elements and a plurality of current sources, each pair of heating elements being electrically connected in series to a corresponding current source, - the first heating elements of said pairs are distributed at least in the longitudinal direction on the first wall and the second heating elements of said pairs are distributed in the longitudinal direction on the second wall, the first and second heating elements of a pair of heating elements extending at least partly opposite each other in the transverse direction,
[0009] - the first heating elements of said pairs are distributed at least according to a elevation direction, substantially perpendicular to the longitudinal and transverse, on the first wall and the second heating elements of said pairs are distributed according to the elevation direction on the second wall, the first and second heating elements of a pair of heating elements extending at least partly opposite each other in the transverse direction,
[0010] - the first and second heating elements each comprise a plurality of monochromatic or pseudomonochromatic electromagnetic radiation sources,
[0011] - the first and second heating elements each comprise at least one upper row and at least one lower row of electromagnetic radiation sources, said radiation sources being electrically connected in series with each other,
[0012] - the first heating element and the second heating element are offset relative to each other in the longitudinal direction,
[0013] - an electrical circuit connecting the first heating element, the second heating element and the current source in series comprises at least one device for measuring the voltage in said electrical circuit,
[0014] - the heat treatment unit comprises at least one device for controlling the current in the electrical circuit connecting the first heating element, the second heating element and the current source in series, said control device being arranged to vary the current in the electrical circuit in order to simultaneously vary the heating power delivered by the first heating element and by the second heating element,
[0015] - the heat treatment unit comprises a gripping and ungripping system placement of preforms according to the predefined circulation path in two staggered rows in the enclosure
[0016] Other aspects and advantages of the invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings in which:
[0017] [Fig-1] - [Fig.l] is a schematic cross-sectional representation of part of a heat treatment unit comprising a plurality of heating elements according to one embodiment of the invention,
[0018] [Fig.2] - [Fig.2] is a schematic representation of an electrical connection circuit of two heating elements of a pair of heating elements according to the invention, and
[0019] [Fig.3] - [Fig.3] is a schematic sectional representation of a portion of a heat treatment unit comprising a plurality of heating elements according to another embodiment of the invention.
[0020] With reference to [Fig.l], a heat treatment unit 1, or furnace, is described. of an installation for manufacturing containers from preforms 2, comprising a plurality of heating elements.
[0021] More particularly, the heat treatment unit 1 comprises a first wall 4, comprising at least one first heating element 6, and a second wall 8, comprising at least one second heating element 10. The first and second walls 4, 8 are opposite each other on either side of the heat treatment unit 1 and define between them an enclosure within which the preforms 2 circulate along a predefined circulation path T and defining a longitudinal direction. The first and second walls 4, 8 are spaced from each other in a transverse direction substantially perpendicular to the longitudinal direction so as to extend on either side of the circulation path T. In Figs. 1 and 3, the circulation path T has been shown as being rectilinear, but it is understood that it could be curved in certain areas depending on the configuration of the container manufacturing installation.The heat treatment unit comprises a system for gripping and moving the preforms 2 (not shown) along the circulation path T between the first and second walls 4, 8. The preforms 2 are more particularly held so that their respective axis extends along an elevation direction substantially perpendicular to the longitudinal direction and to the transverse direction. In other words, the elevation direction corresponds to the height of the preforms 2 and to the height of the first and second walls 4, 8. In a known manner, the gripping system can be arranged so that the preforms 2 rotate around their axis when they circulate along the circulation path T.
[0022] According to the embodiment of [Fig. 1], the preforms 2 are aligned one after the other in a row extending along the circulation path T. In the variant shown in [Fig. 3], the preforms 2 circulate in at least two parallel rows RI, R2 along the circulation path T, the preforms 2 being arranged in a staggered manner in the enclosure. By staggered manner, it is meant that the preforms 2 of one row RI are offset in the longitudinal direction relative to the preforms 2 of the other row R2. The spacing in the transverse direction between the rows RI, R2, and the spacing in the longitudinal direction between the preforms 2 can be adjusted depending in particular on the diameter of the preforms 2. The drive on two rows can be similar to that of the preforms 2 on a single row.
[0023] The first heating element 6 and the second heating element 10 are associated with each other, as will be described in more detail later, to form a pair of heating elements. As will be described in more detail later, the heat treatment unit 1 comprises, for example, several pairs of heating elements, each formed by a first heating element 6 extending on the first wall 4 and a second heating element 10 extending on the second wall 8. The first and second heating elements 6, 10 extend at least partly opposite each other on either side of the enclosure. By "extend at least partly opposite each other on either side of the enclosure", it is meant that the first and second heating elements 6, 10 extend substantially at the same height in the elevation direction and at least partly opposite each other in the transverse direction. According to one embodiment, the first and second heating elements 6, 10 of a pair of heating elements are however offset relative to each other in the longitudinal direction so that the second heating element 10 extends only partly opposite the first heating element 6.Such an embodiment is for example described in document EP 2 782 741 and those skilled in the art may refer to this document to obtain more details on such an embodiment, in particular in terms of dimensioning and positioning of the heating elements relative to each other.
[0024] The first heating element 6 and the second heating element 10 of a pair of heating elements are identical, as seen in [Fig. 2]. Thus, only the first heating element 6 will now be described in more detail.
[0025] The first heating element 6 comprises, for example, a plurality of monochromatic or pseudo-monochromatic electromagnetic radiation sources 12. More particularly, the first heating element 6 is, for example, a laser emitter and the radiation sources 12 are laser chips arranged to emit laser radiation in the infrared range in an emission direction E substantially parallel to the transverse direction. The radiation sources 12 are, for example, arranged next to each other on a support so as to form at least one row of radiation sources 12 extending in the longitudinal direction. According to one embodiment, the radiation sources 12 form at least one upper row 14 and at least one lower row 16 arranged one above the other in the elevation direction. According to the embodiment shown in [Fig.2], each heating element 6, 10 comprises two upper rows 14 and two lower rows 16 of radiation sources 12. The radiation sources 12 are electrically connected in series with each other between a positive connection terminal 18 and a negative connection terminal 20.
[0026] Such heating elements are for example described in document FR 3 124 030 and those skilled in the art may refer to this document to obtain more details, in particular with regard to the structure of each radiation source 12, the arrangement of the radiation sources 12 on a support, the connection of the radiation sources 12 to each other and the cooling of the heating elements. It is understood that the invention is not limited to heating elements formed by laser emitters and also applies to other types of heating element, such as halogen type incandescent tubular lamps.
[0027] When the heat treatment unit 1 comprises several pairs of heating elements, the heating elements are distributed to expose the entire enclosure, outside of a zone in which the neck of the preforms extend, to the heat emitted by the heating elements. Thus, the first heating elements 6 are for example distributed at least in the longitudinal direction on the first wall 4 and the second heating elements 10 are for example distributed at least in the longitudinal direction on the second wall 8, the first and second heating elements 6, 10 of a pair of heating elements extending at least partly opposite one another in the transverse direction.Alternatively or additionally, the first heating elements 6 are for example distributed at least along the elevation direction on the first wall 4 and the second heating elements 10 are for example distributed along the elevation direction on the second wall 8, the first and second heating elements 6, 10 of a pair of heating elements extending at least partly opposite each other along the transverse direction.
[0028] When the first and second heating elements 6, 10 of a pair of heating elements are offset relative to each other in the longitudinal direction, the first heating element 6 extends at least partly opposite a reflective section 22 of the second wall 8 and the second heating element 10 extends opposite a reflective section 22 of the first wall 4. The reflective sectors 22 extend for example between adjacent heating element columns so that the first and second walls 4, 8 are both heat-emitting and heat-reflecting. As indicated above, such an arrangement of a heat treatment unit 1 is already known per se and will not be described in more detail here. Those skilled in the art may refer to document EP 2 782 741.
[0029] The or each pair of heating elements is supplied with electricity by the same current source 24, as shown in [Fig. 2]. In other words, when the heat treatment unit comprises several pairs of heating elements, the heat treatment unit 1 comprises at least as many current sources 24 each supplying one of the pairs of heating elements. Since the electricity supply to the pairs of heating elements by means of current sources 24 is identical for each pair of heating elements, a single power supply circuit between the first and second heating elements 6, 10 and a current source 24 will now be described.
[0030] As shown in [Fig.2], the first and second heating elements 6, 10 of the pair of heating elements are electrically connected in series to the same current source 24. In other words, the electrical circuit connecting the first heating element 6, the second heating element 10 and the current source 24 in series comprises at least:
[0031] - a connection 26 going from a positive connection terminal 28 of the source of current 24 to the positive connection terminal 18 of the first heating element 6,
[0032] - a connection 30 going from the negative connection terminal 20 of the first element heating element 6 to the positive connection terminal of the second heating element 10, and
[0033] - a connection 32 going from the negative connection terminal 20 of the second element heating 10 to a negative connection terminal 34 of the current source 24.
[0034] By connecting the first heating element 6 and the second heating element 10 of a pair of heating elements in series with the same current source 24, it is ensured that the heating power, for example the laser power, delivered by the first heating element 6 is identical to the heating power delivered by the second heating element 10. Indeed, the heating power delivered by a heating element is directly linked to the current passing through this heating element so that by connecting the first heating element 6 and the second heating element 10 in series, it is ensured that the current passing through the first and second heating elements 6, 10 is the same and that the heating power delivered by these heating elements is also the same.Thus, the preforms 2 circulating in the enclosure are exposed to the same heating power coming from the first wall 4 and the second wall 8, which guarantees the uniform application of the desired heating profile. The invention is furthermore particularly advantageous when the preforms 2 circulate on two rows RI, R2 in the enclosure, as described above. Indeed, in this case, the preforms 2 of the row RI are closer to the first wall 4 while the preforms 2 of the row R2 are closer to the second wall 8. In order for the preforms 2 of the two rows RI, R2 to have the same heating profile applied to them, it is therefore crucial that the heating elements of the two walls deliver the same heating power, which is made possible by the series connection of the first and second heating elements 6, 10 of each pair of heating elements to a current source 24 assigned to each pair of heating elements.
[0035] Furthermore, the invention also makes it possible to reduce the number of current sources 24 of the thermal treatment unit compared to a treatment unit in which each heating element is powered by a dedicated current source. Indeed, since a current source powers two heating elements, the number of current sources is thus halved. This makes it possible to save energy and to reduce the size of the current sources.
[0036] Furthermore, when the heating profile applied to the preforms 2 must be modified, the invention makes it possible to ensure that the modification of the heating power is applied simultaneously to the first heating element 6 and to the second heating element 10 of a pair of heating elements. Indeed, by modifying the current value delivered by the current source 24, the current which passes through the first and second heating elements 6, 10 which then deliver the same instantaneous power is simultaneously modified. For this purpose, the heat treatment unit 1 comprises for example a device 36 for controlling the current in the electrical circuit connecting the first heating element, the second heating element and the current source in series.This control device is arranged to vary the current in the electrical circuit connecting the first heating element, the second heating element, by varying the value of the current delivered by the current source 24, in order to simultaneously vary the heating power of the first heating element 6 and the second heating element 10. Such a control device 36 is for example formed by a drive card. According to the embodiment shown in [Fig. 2], a control device 36 can form two current sources 24 with the corresponding connection terminals in order to simultaneously control two pairs of heating elements, for example pairs of heating elements arranged one above the other in the elevation direction.
[0037] According to the embodiment shown in [Fig. 2], the connection 30 going from the negative connection terminal 20 of the first heating element 6 to the positive connection terminal of the second heating element 10 further comprises a connection point 38 to a voltage measuring device (not shown) in the power supply circuit. Such a voltage measurement makes it possible to ensure the proper functioning of the heating elements by monitoring the voltage at the terminals of each heating element. The voltage measuring device is for example connected to the control device 36, as shown in [Fig. 2], in order to allow monitoring of the voltages of each heating element for the applied current. The measured voltage being linked to the operating conditions of the heating elements, conditions which can impact the heating power, the control device 36 can decide to modify the setpoint applied to the current source 24.If it is found that the voltage across one or more heating elements deviates from the nominal operating conditions of said heating elements, the control device 36 may also decide to cut off the current source 24 and / or to transmit a fault signal. For example, an alert signal may be emitted in the event of a drift of between 2.5% and 4% while the current source is cut off in the event of a drift greater than or equal to 4%.
Claims
Claims
1. Heat treatment unit (1) for preforms (2) of a container manufacturing facility, the heat treatment unit comprising an enclosure delimited by a first wall (4) and a second wall (8) extending on either side of the enclosure within which the preforms (2) pass along a predefined circulation path (T) extending in a longitudinal direction, the first wall (4) comprising at least one first heating element (6) and the second wall (8) comprising at least one second heating element (10), forming, with the first heating element (6), a pair of heating elements, the first heating element (6) and the second heating element (10) extending at least partly opposite each other on either side of the enclosure in a transverse direction, substantially perpendicular to the longitudinal direction, each heating element (6,10) being supplied with electricity by a current source (24), characterized in that the first and second heating elements (6, 10) of said pair of heating elements are electrically connected in series to the same current source (24).,
2. A heat treatment unit according to claim 1, comprising a plurality of pairs of heating elements and a plurality of current sources (24), each pair of heating elements being electrically connected in series to a corresponding current source (24).
3. Heat treatment unit according to claim 2, wherein the first heating elements (6) of said pairs are distributed at least in the longitudinal direction on the first wall (4) and the second heating elements (10) of said pairs are distributed in the longitudinal direction on the second wall (8), the first and second heating elements (6, 10) of a pair of heating elements extending at least partly opposite each other in the transverse direction.
4. Heat treatment unit according to claim 2 or 3, wherein the first heating elements (6) of said pairs are distributed at least in one direction of elevation, substantially perpendicular to the longitudinal and transverse directions, on the first wall (4) and the second heating elements (10) of said pairs are distributed in the direction of elevation on the second wall (8), the first and second heating elements (6, 10) of a pair of heating elements extending at least partly opposite each other in the transverse direction.
5. A heat treatment unit according to any one of claims 1 to 4, wherein the first and second heating elements (6, 10) each comprise a plurality of monochromatic or pseudomonochromatic electromagnetic radiation sources (12).
6. A heat treatment unit according to claim 5, wherein the first and second heating elements (6, 10) each comprise at least one upper row (14) and at least one lower row (16) of electromagnetic radiation sources (12), said radiation sources (12) being electrically connected in series with each other.
7. A heat treatment unit according to any one of claims 1 to 6, wherein the first heating element (6) and the second heating element (10) are offset relative to each other in the longitudinal direction.
8. A heat treatment unit according to any one of claims 1 to 7, wherein an electrical circuit (26, 30, 32) connecting the first heating element (6), the second heating element (10) and the current source (24) in series comprises at least one device for measuring the voltage in said electrical circuit.
9. Heat treatment unit according to any one of claims 1 to 8, comprising at least one control device (36) for the current in the electrical circuit (26, 30, 32) connecting the first heating element (6), the second heating element (10) and the current source (24) in series, said control device (36) being arranged to vary the current in the electrical circuit in order to simultaneously vary the heating power delivered by the first heating element (6) and by the second heating element (10).
10. Heat treatment unit according to any one of claims 1 to 9, comprising a system for gripping and moving the preforms (2) along the circulation path (T) predefined on two rows (RI, R2) staggered in the enclosure.