Method for regulating the throughput of preforms in a preform distribution device

Abstract

The invention relates to a method for regulating the throughput of preforms (18) in a distribution device (10) for distributing preforms (18) supplied by a supply device (12) for supplying loose preforms (18) that delivers the preforms (18) at an inlet throughput (Qin), the distribution device (10) comprising: - a device (14) for aligning the preforms (18) in a row and uprighting them, which comprises a centrifuge bowl (32); - an outlet conveyor (16) that receives the preforms thus aligned and uprighted at an outlet throughput (Qout), and that distributes the preforms one by one to the manufacturing facility at a given rate; characterised in that the number (N) of preforms (18) simultaneously contained in the distribution device (10) is controlled using the difference between the inlet throughput (Qin) and the outlet throughput (Qout).

Description

METHOD FOR REGULATING THE FLOW OF PREFORMS IN A PREFORM DISTRIBUTION DEVICE TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a method for regulating the flow of preforms in a preform distribution device arranged at the inlet of a container manufacturing installation for the mass production of stretch-blowing said preforms, the distribution device being fed by a bulk preform feeding device which delivers the preforms with an inlet flow rate, the distribution device comprising:

[0002] - a single-line alignment and preform straightening device comprising a centrifuge bowl having a horizontal circular plate rotating around a vertical axis, the upper face of which is intended to receive bulk preforms via the feeding device, the preforms being projected and aligned by centrifugation against a fixed peripheral railing during the rotation of the plate, the preforms thus aligned straightening in a peripheral gap which extends along an angular sector between the plate and the railing;

[0003] - an output conveyor which receives the preforms thus aligned and straightened with an output flow rate, and which distributes the preforms one by one to the manufacturing installation at a determined rate. TECHNICAL BACKGROUND OF THE INVENTION

[0004] Such a preform distribution system is designed for use in a manufacturing plant for thermoplastic containers, particularly those made of polyethylene terephthalate (PET), through the forming of preforms, notably by blow molding or stretch blow molding. This type of plant enables the production of containers in very large quantities at very high rates, for example, exceeding 85,000 bottles per hour.

[0005] According to a well-established technique, such containers are produced in two main stages. The first stage involves injection or injection-compression molding of a PET preform. This preform has a roughly tubular body that is closed at one of its axial ends, while the opposite end is open via a neck. The neck, from this injection molding operation onward, has the final shape of the container's neck. Generally, the container neck has a thread or a groove.

[0006] The preform generally includes an annular support face that projects radially outwards from the rest of the body and is oriented axially towards the closed end of the body. Such a support face is, for example, carried by an annular support collar that extends radially outwards from the rest of the preform and is arranged at the base of the neck.

[0007] There are facilities in which the preforms, once injected, are directly transmitted to a forming unit, each preform being transported individually.

[0008] However, in many cases, preforms are first manufactured by injection molding and then blow-molded into the final container shape at a second location on a dedicated manufacturing line. This technology allows the blow-molding operation to be carried out as close as possible to the bottling site, while the injection molding operation can be performed anywhere. Indeed, transporting small preforms is relatively easy and inexpensive, whereas transporting blow-molded containers is economically unviable due to their large size.

[0009] In cases where the injection molding station and the forming plant are two completely independent machines, the preforms are generally delivered in bulk. The forming plant therefore has a preform distribution device equipped with a single-line alignment and preform straightening device. The present invention relates to such a device.

[0010] A straightening and alignment device incorporating a centrifuge bowl is already known. The preforms are thrown loosely onto a rotating platform forming the bottom of the bowl. The preforms are then propelled by centrifugal force against a peripheral railing. A radial gap between the railing and the rotating platform allows the body of the preforms to pass through while retaining them by their collars. The preforms are thus aligned at the periphery of the bowl, their principal axis having a nearly vertical orientation under the effect of gravity.

[0011] Such preforms, aligned and straightened in a line, will subsequently be called "correctly positioned preforms".

[0012] The correctly positioned preforms are then conveyed to a tangential outlet of the bowl by the rotation of the turntable. Typically, after exiting the centrifuge bowl, the preforms are accumulated in a queue on an outfeed conveyor to ensure a continuous feed to the manufacturing system. At the outfeed conveyor, the preforms are distributed one by one to the manufacturing system at the system's operating rate. For example, the downstream end of the outfeed conveyor may have a retractable finger that allows the preforms to pass through one by one at the required rate.

[0013] Ideally, the output flow rate of preforms leaving the device should be equal at all times to the input flow rate of preforms entering the device. The output flow rate is equal to the operating rate of the manufacturing plant.

[0014] However, in practice, a variable quantity of preforms injected into the straightening and alignment device do not emerge immediately, for example, because they have not properly aligned or straightened in the centrifuge bowl. These preforms therefore wander on the tray for some time before finally being correctly aligned and straightened. These preforms that are not immediately straightened and aligned are subsequently referred to as "recycled preforms."

[0015] Taking this reality into account, it is important to ensure that the number of preforms contained simultaneously in the centrifuge bowl is sufficient to ensure an output flow rate adapted to the operating rate of the manufacturing installation.

[0016] However, care must be taken to ensure that the number of preforms contained simultaneously in the centrifuge bowl is not too high. Indeed, if there is an excessive excess of preforms, the straightening and alignment device may jam.

[0017] Until now, this problem was solved by placing numerous preform presence sensors around the periphery of the centrifuge bowl. The accumulation line of the outfeed conveyor is designed to extend into the centrifuge bowl.

[0018] These sensors detect the length of the queue of straightened and aligned preforms ready to exit the bowl. When the queue is too long, the feed rate of preforms injected into the bowl is reduced, while when the queue is too short, the feed rate of preforms injected into the bowl is increased.

[0019] Such sensors are very expensive and can be prone to malfunctions.

[0020] Furthermore, the accumulation queue in the centrifuge bowl may be discontinuous. In this case, the sensors may detect the presence of preforms corresponding to a large accumulation queue length, even though the actual number of preforms in the queue is much lower than expected.

[0021] Similarly, it can happen that many preforms are lying on the centrifuge tray and being aligned while the accumulation queue is very short. Following only the sensor readings, the centrifuge bowl is then fed with many preforms when it is already close to saturation.

[0022] Therefore, there is a need to regulate the number of preforms present simultaneously in the centrifuge bowl in a way that is less expensive and more reliable. BRIEF SUMMARY OF THE INVENTION

[0023] The invention proposes a method for regulating the flow of preforms in a preform distribution device arranged at the inlet of a container manufacturing installation for the mass production of stretch-blowing said preforms, the distribution device being fed by a bulk preform feeding device which delivers the preforms with an inlet flow rate, the distribution device comprising:

[0024] - a single-line alignment and preform straightening device comprising a centrifuge bowl having a horizontal circular plate rotating around a vertical axis, the upper face of which is intended to receive bulk preforms via the feeding device, the preforms being projected and aligned by centrifugation against a fixed peripheral railing during the rotation of the plate, the preforms thus aligned straightening in a peripheral gap which extends along an angular sector between the plate and the railing;

[0025] - an output conveyor which receives the preforms thus aligned and straightened with an output flow rate, and which distributes the preforms one by one to the manufacturing installation at a determined rate;

[0026] characterized in that the number of preforms contained simultaneously in the distribution device is controlled by using the difference between the inlet flow rate and the outlet flow rate.

[0027] According to another feature of the invention, the input flow rate is controlled by a setpoint value for the number of preforms contained simultaneously in the distribution device.

[0028] According to another feature of the invention, the setpoint value of the number of preforms contained simultaneously in the distribution device is at least equal to a number of preforms 18 received in an accumulation queue of optimal length determined experimentally.

[0029] According to another feature of the invention, the setpoint value of the number of preforms contained simultaneously in the distribution device is greater than the number of preforms 18 received in an accumulation queue of optimal length.

[0030] According to another feature of the invention, a default setpoint value for the number of preforms contained simultaneously in the distribution device is equal to the sum of the number of preforms 18 received in an accumulation queue of optimal length and an average number of recycled preforms that are not immediately aligned and straightened by the alignment and straightening device.

[0031] According to another feature of the invention, the average number of recycled preforms is determined experimentally, in particular as a function of the geometry of the preforms and the output flow rate.

[0032] According to another feature of the invention, the inlet flow rate is controlled so that the number of preforms contained in the centrifuge bowl is less than a saturation threshold of the straightening and alignment device beyond which the entire peripheral length of the centrifuge bowl is occupied by preforms.

[0033] According to another feature of the invention, the setpoint value is capable of being manually modified from the default setpoint value, the setpoint value being selectable between the number of preforms 18 received in an accumulation queue of optimal length and the saturation threshold.

[0034] According to another feature of the invention, the output flow rate is equal to the operating rate of the installation.

[0035] According to another feature of the invention, the feeding device is equipped with means for counting preforms, the input flow rate being calculated as a function of the quantity of preforms counted per unit of time. BRIEF DESCRIPTION OF THE FIGURES

[0036] Other features and advantages of the invention will become apparent during the reading of the detailed description which follows, for the understanding of which reference should be made to the attached drawings briefly described below.

[0037] This is a perspective view which represents a preform distribution device and an associated feeding device for the implementation of the process according to the teachings of the invention.

[0038] Laest is a front view which represents a preform adapted for use with the device of the, the axis of the preform being here oriented vertically.

[0039] This is a schematic side view representing a conveyor belt of an infeed conveyor of the feeding device which is equipped with preform counting means.

[0040] This is a perspective view that schematically represents a distribution system for the set shown in the image.

[0041] This is a top view of the distribution device.

[0042] Laest is a block diagram that represents a process for controlling the number of preforms present in the distribution device.

[0043] This is a block diagram that represents a method of controlling the input flow rate of preforms as a function of the number of preforms counted by the control method.

[0044] This is a top view that represents the centrifuge bowl of the.

[0045] This is a radial cross-sectional view of a centrifuge bowl alignment sector, which represents a peripheral railing and the bottom of the centrifuge bowl as well as an aligned preform.

[0046] This is a top view that represents part of the alignment sector of the centrifuge bowl, as well as the different stages of the path of a preform poured into the centrifuge bowl.

[0047] This is a radial cross-sectional view of a straightening sector of the centrifuge bowl, which represents the peripheral railing and rotating plate of the centrifuge bowl as well as an aligned and straightened preform.

[0048] This is a schematic view along a radial direction which represents a preform aligned along the railing in the alignment sector of the centrifuge bowl in the figure.

[0049] This is a top view of the.

[0050] This is a view similar to that of the one that represents the preform of the one undergoing rectification at the beginning of the rectification sector of the centrifuge bowl.

[0051] This is a top view of the.

[0052] This is a view similar to that of the one that represents the preform of the straightened one in the straightening sector of the centrifuge bowl.

[0053] This is a top view of the.

[0054] This is a top view which represents an area of ​​the centrifuge bowl located straddling the rectifier sector and an outlet sector and which includes a detangling wheel. DETAILED DESCRIPTION OF THE FIGURES

[0055] In the following description, elements with an identical structure or analogous functions will be designated by the same references.

[0056] In the remainder of this description, the following guidelines will be adopted, without limitation:

[0057] - radial "R" directed from the inside out from the axis "B" of rotation of the central plate 28;

[0058] - tangential "T" which is orthogonal to the radial direction "R" and which extends parallel to the plane of the central plateau 28, directed from upstream to downstream in the positive direction of rotation of the central plateau 28;

[0059] - vertical "V" directed parallel to the axis "B" of rotation of the central plate 28, from bottom to top in the opposite direction of Earth's gravity.

[0060] A schematic representation of a distribution device 10 is shown, which includes:

[0061] - a device 14 for straightening and aligning preforms;

[0062] - an output conveyor 16 which receives preforms aligned in a line and straightened by the straightening and alignment device 14.

[0063] The straightening and alignment device 14 of the distribution device 10 is supplied with preforms by a bulk preform supply device 12.

[0064] An example of a preform 18 intended for use with the straightening and alignment device 14 is illustrated in Figure 1. Such a preform 18 is made of thermoplastic material, here polyethylene terephthalate (PET). It is conventionally obtained by injection molding. It has a substantially axisymmetric shape around a principal axis "A" shown vertically in Figure 1.

[0065] It comprises a body 20 in the shape of an elongated tube along the main axis "A" having a closed axial end and which has at its opposite end, shown at the top, an axially open neck 22.

[0066] The preform 18 also includes an annular support face 24 which is oriented axially towards the closed end of the preform 18, which protrudes radially from the rest of the body 20. The support face 24 is arranged above a center "G" of gravity of the preform 18. The support face 24 goes around the preform 18 either continuously, as illustrated in the figure, or discontinuously (not shown).

[0067] When the support face 24 is discontinuous, the annular face is for example formed of disjoint segments which go around the preform 18 and which are nevertheless close enough so that the preform 18 can be supported between two diametrically opposed supports regardless of the position of the preform 18 around its main axis.

[0068] In the example shown in the figure, the base of the neck 22, at the junction with the body 20, has a collar which extends radially in projection relative to the rest of the preform 18. The lower face of the collar thus forms said support face 24.

[0069] As an alternative not shown, the collar can be arranged elsewhere than at the base of the neck, for example at the level of the mouth.

[0070] According to another variant not shown, the support face 24 is for example formed by a lower face of a thread of the neck.

[0071] According to yet another variant not shown, the support face 24 is attached to the preform 18, for example by means of a plug.

[0072] An outer diameter "D1" of the support face 24, in this case the collar, is thus greater than the maximum outer diameter "D2" of the body 20, located here directly below the collar. In the example shown in the figure, the closed end section of the body 20 has a minimum outer diameter "D3".

[0073] Neck 22 has its final shape, while body 20 is intended to be stretched in a subsequent forming operation to form the body of the finished container.

[0074] The example shown is not limiting. It will be understood that the distribution device 10 is intended to support any type of preform 18 having a support face 24 that protrudes radially from the rest of the body 20, and having a center of gravity that is axially offset towards the body 20 with respect to said support face 24.

[0075] As will be explained later, the distribution device 10 is capable of processing identical batches of preforms 18, although the format of the preforms 18 may vary from batch to batch. Therefore, different adjustments may be required on the various components of the distribution device 10 when the format of the preform 18 changes.

[0076] As shown in the figure, the feeding device 12 includes at least one infeed conveyor 26A, 26B which carries the bulk preforms 18 to the straightening and alignment device 14.

[0077] By way of non-limiting example, a first infeed conveyor 26A includes a cleated conveyor belt that receives preforms 18 from a hopper 28 in which the preforms 18 are in bulk. The cleated conveyor belt of the first infeed conveyor 26A is inclined and includes cleats that allow the preforms 18 to rise above the straightening and alignment device 14 without slipping.

[0078] The feeding device 12 includes here, in addition to the first infeed conveyor 26A, a second infeed conveyor 26B formed by a horizontal conveying belt 29, illustrated here in the figure, which allows the preforms 18 to be conveyed in bulk from the upper end of the first infeed conveyor 26A to a feeder weir 30 of the straightening and alignment device 14, as will be explained in more detail later.

[0079] The straightening and alignment device 14 is designed to straighten the preforms 18 fed by the feeding device 12 so that their axis "A" is vertical and to align them in a line. As schematically shown in Figures 4 and 5, this straightening and alignment device 14 comprises a centrifuge bowl 32 with a rotating plate 34 about a vertical axis "B" on which the preforms 18 slide freely. As it rotates, the rotating plate 34 presses the preforms 18 against a peripheral rail 36 to align them. The aligned preforms 18 are then straightened by means of a gap 38 radially positioned between a portion of the rail 36 and a portion of the periphery of the rotating plate 34.The body 20 of the preforms 18 tilts into the gap 38 while the preform 18 is held by its support face 24 between a support rail 40 of the guardrail 36 and the edge 42 of the rotating platform 34. The preforms 18, which have been correctly straightened and aligned in a row, are conveyed to an exit passage 44 of the centrifuge bowl 32 towards the exit conveyor 16.

[0080] The output conveyor 16 is intended to convey the preforms 18 thus aligned and straightened from the output passage 44 of the straightening and alignment device 14 to an inlet of the manufacturing installation to distribute them one by one to means for individual handling of each preform 18 of a subsequent processing unit (not shown) of the manufacturing installation, for example a preform 18 thermal conditioning unit.

[0081] To ensure that the manufacturing plant is constantly supplied with preforms 18, the output conveyor 16 is designed to accumulate the preforms 18 in a preform accumulation line 50 to guarantee a regular supply to the manufacturing plant. The accumulation line 50 preferably extends into the centrifuge bowl.

[0082] Such an outfeed conveyor 16 primarily comprises a sliding track delimited by two guide rails 46 against which the preform 18 rests by its support face 24, the body 20 of the preform 18 hanging between the rails. Mechanisms are also provided to drive all the preforms 18 along the entire length of the outfeed conveyor 16. Indeed, without such drive mechanisms, the preforms 18, passively pushed by the pressure of preforms 18 upstream in the line, risk becoming jammed between the guide rails 46, thus causing a blockage.

[0083] This is, for example, a so-called "brush" outfeed conveyor 16, which has endless belts 48 equipped with friction elements, in this case brushes, arranged on either side of the rails. The friction elements, here the brush bristles, rub against the body 20 of the preforms 18 to push them towards a downstream end of the guide rails 46. A preform 18 is thus rapidly pushed towards the downstream end by the brushes until it reaches the accumulation line 50. Once it reaches the accumulation line 50, the preform 18 then advances more slowly at the rate of the manufacturing installation towards a downstream end of the accumulation line 50, still under the effect of friction with the brush bristles.

[0084] Alternatively, it is an air conveyor which pushes the preforms 18 downstream by means of air jets.

[0085] We subsequently define a flow rate "Qin" of the input of preforms 18 into the distribution device 10 which is equal to the number of preforms 18 conveyed by the feeding device 12 per unit of time.

[0086] We also define a flow rate "Qout" of the preforms exiting the distribution device 10, which is equal to the number of preforms 18 exiting the output conveyor 16 to the manufacturing plant per unit of time. The output flow rate "Qout" is equal to the operating rate of the manufacturing plant.

[0087] In a stationary operating regime of the distribution device 10, which occurs when the installation is in operation, the output flow rate "Qout" of the preforms 18 exiting the output conveyor 16 must be equal to the input flow rate "Qin" of the preforms 18 entering the straightening and alignment device 14 through the weir 30.

[0088] However, the distribution device 10 must contain sufficient preforms 18 in the accumulation queue 50 to ensure proper operation of the installation. To this end, during a transient start-up regime, which generally occurs when the installation is brought online, the incoming flow rate "Qin" of preforms 18 must be greater than the outgoing flow rate "Qout". The ideal number "N1" of preforms 18 present in the accumulation queue 50 is predetermined based on the size of the preforms 18, particularly their diameter, and the optimal length of the accumulation queue 50.

[0089] Furthermore, a certain number of preforms 18 are not immediately aligned and straightened in the straightening and alignment device 14. These preforms 18, referred to as recycled preforms 18, complete at least a second rotation of the rotating plate 34 before finding their place in the line of correctly aligned and straightened preforms 18. The number of recycled preforms 18 present in the centrifuge bowl 32 is random. It depends on numerous parameters such as the rotational speed of the rotating plate 34, the size and geometry of the preforms 18, etc.

[0090] To be able to guarantee a regular output flow despite the presence of a random quantity of recycled preforms 18, it is therefore necessary to provide a number "N" of preforms which is equal to the sum of the number "N1" of preforms 18 provided for the accumulation queue and a number "N2" of additional preforms corresponding to the average quantity of recycled preforms 18.

[0091] The number "N2" of additional preforms 18 can be determined experimentally, for example as a function of the geometry and weight of the preforms 18. In addition, as will be explained later, this number "N2" of additional preforms 18 can be adjusted during operation when it is observed that the straightening and alignment device 14 has too many preforms 18 or, on the contrary, too few preforms.

[0092] In particular, the proportion of recycled preforms 18 can be tested in the laboratory as a function of the rotation speed of the rotating plate 34. From this data, it is easy to establish a correspondence between the number "N" of preforms 18 that the distribution device 10 must contain simultaneously and the operating rate, i.e., the output flow rate "Qout".

[0093] This determines a default value for the number "N" of preforms 10 contained simultaneously in the distribution device 10.

[0094] The invention provides a method for regulating the flow of preforms 18 in the preform distribution device 10, in which the number "N" of preforms 18 simultaneously contained in the distribution device 10 is controlled by calculating the difference between the inlet flow rate "Qin" and the outlet flow rate "Qout". Thus, it is possible to continuously know the quantity of preforms 18 present in the centrifuge bowl 32 and in the outlet conveyor 16.

[0095] To determine the input flow rate "Qin" of preforms 18, the feeding device 12 is equipped with means for counting the preforms 18. Conventionally, the input flow rate "Qin" is calculated based on the quantity of preforms 18 counted per unit of time.

[0096] As shown in Figure 1, this is, for example, an image-capturing device 52, such as a camera, arranged to capture images of successive portions of the conveyor belt 29 of one of the inlet conveyors 26A, 26B, here the second inlet conveyor 26B, as they pass through an image-capture zone 54. The frequency at which the images are captured is configured so that the portions of the conveyor belt 29 captured in successive images are directly adjacent, to avoid missing any preforms 18, and without overlapping, to prevent the same preforms 18 from appearing in two images. Thus, the image-capture frequency depends on the speed of the conveyor belt 29 of the inlet conveyor 26B.

[0097] These images are then sent to an electronic control unit 56 which is capable of recognizing the preforms 18, for example by means of pattern recognition software, and of automatically counting the quantity of preforms 18 recognized on each image.

[0098] Then, the electronic control unit 56 automatically calculates the instantaneous flow rate of preforms 18 at the image capture zone 54 based on the speed of the conveyor belt 29 of the infeed conveyor 26B, the quantity of preforms 18 counted in the image, and the length of the visible section in the image. This instantaneous flow rate constitutes the infeed flow rate "Qin" of preforms 18.

[0099] The output flow rate "Qout" of the centrifuge bowl 32 is equal to the operating rate of the installation.

[0100] The number "N" of preforms 18 contained simultaneously in the dispensing device 10 is automatically calculated by the electronic control unit 56 by subtracting the preforms 18 output flow rate "Qout" from the inlet flow rate "Qin". This difference is calculated over a predetermined time step. This process is repeated at a frequency corresponding to said time step.

[0101] An example of how this process can be implemented is illustrated in the following.

[0102] In the first step "E1", to obtain the number "N" of preforms 18 contained simultaneously in the dispensing device 10, this difference is multiplied by the determined time step. Then, in a second step "E2", this number is added to the number "N" of preforms recorded in the previous iteration of the process. The time step is, for example, on the order of a second. This number "N" is stored by the electronic unit 56 at the end of the current iteration so that it can be reused in the next iteration.

[0103] Simply checking the number "N" of preforms 18 contained simultaneously in the distribution device 10 provides a valuable indication of the operating status of the distribution device 10. This is because all preforms 18 that enter the alignment and straightening device 14 necessarily exit via the output conveyor 16 without being ejected from the flow, even when these preforms 18 are recycled.

[0104] According to a second embodiment of the invention shown in Figure 1, the input flow rate "Qin" of preforms 18 is automatically controlled by the electronic control unit 56 according to a setpoint value for said number "N" of preforms 18

[0105] In normal operation, the setpoint value is the default value that has been experimentally predetermined for each preform model based on the operating rate of the manufacturing facility.

[0106] Alternatively, an operator may manually adjust the setpoint for the number "N" of preforms that the dispensing device 10 must contain simultaneously to adapt the operation of the dispensing device 10 based on the operator's observations. For example, the operator may decide to increase or decrease the number "N" of preforms when they determine that the operation of the alignment and straightening device 14 is not optimal with the default value.

[0107] However, care must also be taken to ensure that the setpoint value of said number "N" of preforms 18 is less than a saturation threshold of the straightening and alignment device 14 beyond which the entire peripheral length of the straightening and alignment device 14 is occupied by preforms 18.

[0108] Preferably, the inlet flow rate "Qin" is controlled according to said number "N" of preforms 18 thus determined so that the number "N" of preforms 18 contained simultaneously in the centrifuge bowl 32 is less than this saturation threshold.

[0109] The saturation threshold depends in particular on the geometry and size of the preforms 18. Thus, the electronic control unit limits the possibility of changing the setpoint value so that it remains below the saturation threshold.

[0110] To determine the number "N" of preforms 18, steps "E1" and "E2" of the process are applied.

[0111] During the implementation of the process, in transient mode, the manufacturing plant is still stopped; only the distribution device 10 is active. In this case, the operating rate of the plant, and therefore the output flow rate "Qout", is zero. With each iteration of the process, the value of the number "N" of preforms 18 thus increases proportionally to the input flow rate "Qin".

[0112] In a third step "E3", the current value of the number "N" of preforms 18 calculated in the second step "E2" is compared to the setpoint value.

[0113] When the setpoint, for example the default value, is reached, the system starts up. The distribution device 10 then operates in steady state. The system's operating rate is equal to the output flow rate "Qout". The electronic control unit 56 therefore sets the input flow rate "Qin" to equal the output flow rate "Qout".

[0114] When, during production, the operating rate of the manufacturing installation is modified, the electronic control unit reflects this modification on the setpoint value of the number "N" of preforms and / or on the input flow rate "Qin" to adapt to this new output flow rate "Qout" before returning to steady state.

[0115] Similarly, if during production the operator determines that the setpoint for the number "N" of preforms 18 is not optimal, they modify it. The electronic control unit 56 automatically reflects this modification to the input flow rate "Qin" to adjust the number "N" of preforms 18 before returning to steady state.

[0116] The invention thus makes it possible to regulate the preform flow without the need to equip the centrifuge bowl with numerous preform sensors. This reduces the cost of the distribution device. Furthermore, it increases the operational reliability of the distribution device 10. Thus, unlike the prior art, which attempted to control the inlet flow rate based on the length of the accumulation queue, the invention proposes controlling the inlet flow rate solely based on the number of preforms present in the distribution device 10. The proper formation of the accumulation queue 50 is a direct consequence of the number "N" of preforms simultaneously contained in the distribution device 10.

[0117] By way of non-limiting example, Figures 8 to 17 show in more detail the device 14 for aligning in a single line and straightening preforms 18 which is part of a device 10 for distributing preforms 18. The device 10 for distributing preforms 18 is arranged at the entrance of an installation (not shown) for manufacturing containers from thermoplastic material by forming, in particular by blow molding or by stretch blow molding, the preforms 18.

[0118] The straightening and alignment device 14 mainly comprises the centrifuge bowl 32. The centrifuge bowl 32 includes a horizontal circular plate 34 rotating about a central vertical axis "B". The rotating plate 34 thus has a circular outer edge 42 shown in the figure. The upper face of the rotating plate 24 vertically delimits the interior of the centrifuge bowl 32 downwards. Thus, the plate 24 forms the bottom of the centrifuge bowl 32. The rotating plate 34 has an external diameter much larger than the dimensions of the preforms 18.

[0119] The rotating plate 34 is driven in rotation, here clockwise in top view, for example by a motor (not shown) which is arranged under the rotating plate 34. The rotational speed is controlled, for example, so that the outer edge 42 of the rotating plate 34 moves between 2 and 3 m / s.

[0120] The rotating platform 34 is here supported by a support table (not shown) fixed relative to the ground.

[0121] The centrifuge bowl 32 is radially delimited outwards by the fixed peripheral railing 36 which is here fixed to the support table.

[0122] The preforms 18 are intended to be discharged in bulk onto the rotating platform 34 via the fixed weir 30, which is fed by the feeding device 12. The weir 30 is positioned in the center of the rotating platform 34, as shown in the figure. The weir 30 is designed to discharge the preforms 18 in bulk, radially towards a first receiving section of the railing 36. The weir 30 is presented here in the form of a chute fed with preforms 18 from above.

[0123] As illustrated in the figure, for the purposes of the description, the centrifuge bowl 32 will be divided into three fixed zones relative to the table 26, each formed by an angular sector extending around the axis "B" of the rotating plate 34.

[0124] A first angular sector 32A, called the preform alignment sector 18, extends opposite the outlet of the spillway 30. This angular alignment sector 32A includes the receiving portion of the railing 36.

[0125] A second angular sector 32B for straightening the aligned preforms 18 is arranged directly downstream of the first angular alignment sector 32A. Without limitation, it extends here approximately to 180°.

[0126] A third angular sorting sector 32C for incorrectly aligned preforms 18 is arranged directly downstream of the second angular straightening sector 32B and directly upstream of the first angular alignment sector 32A. At the downstream end of this sorting sector 32C, the preform 18 exit passage 44 is opened in the railing 36 to guide the correctly aligned and straightened preforms 18 towards the exit conveyor 16. The exit conveyor 16 passes behind the receiving portion of the railing 36.

[0127] It will be understood later that preforms 18 not aligned at the level of the first sector 32A of alignment can nevertheless be aligned and straightened at the level of the second angular sector 32B depending on the circumstances.

[0128] Around the entire periphery of the first angular alignment sector 32A, a clearance is maintained between the guardrail 36 and the rotating plate 34. As shown in the figure, the guardrail 36 extends vertically above the rotating plate 34, such that the outer edge 42 of the rotating plate 34 is positioned outside the centrifuge bowl 32. This clearance allows the rotating plate 34 to rotate, but it is nevertheless small enough to allow the guardrail 36 to retain the entire preform 18 inside the centrifuge bowl 32. This clearance is thus less than the minimum diameter "D3" of the body 20 of the preform 18.

[0129] During the operation of the straightening and alignment device 14, as shown in the figure, the preforms 18 are initially discharged in bulk from the weir 30. They are projected radially against the receiving portion of the railing 36 by the combined effect of their radial sliding velocity at the outlet of the weir 30 and the centrifugal force produced by the rotation of the rotating plate 34. At the same time, the rotating plate 34 also begins to carry the preforms 18 tangentially downstream in its rotation.

[0130] The preforms 18 are held inside the centrifuge bowl 32 by the railing 36. After one or more rebounds against the railing 36, the preforms 18 gradually lose speed in the radial direction. They are then constantly held radially against the railing 36 by centrifugal force. The path followed by a single preform 18 from its arrival via the weir 30 to its stable position against the railing 36 is shown. The preforms 18 are then driven in a purely tangential, clockwise direction by the rotating plate 34 along the railing 36.

[0131] In this configuration, the preforms 18 naturally occupy the most stable position in which their main axis "A" is oriented in a tangent direction relative to the rotating plate 34.

[0132] Most of the preforms 18 present in the angular alignment sector 32A of the centrifuge bowl 32 are thus aligned tangentially against the railing 36, their principal axis "A" being oriented substantially tangentially to their direction of travel. The tangential distance between two successive aligned preforms 18 is random because the rotating platform 34 is perfectly flat and has no indexing notches for the preforms 18. The preforms 18 can therefore be in contact at their ends under the effect of the centrifugal force, which forces the preforms 18 to slide relative to each other. The preforms 18 thus optimally occupy the entire peripheral length of the centrifuge bowl 32.

[0133] The preforms 18, thus aligned, continue their peripheral movement in the straightening sector 32B. The fact that the preforms 18 are held on the rotating platform 34 allows them to be held radially against the railing 36. Thus, the preforms 18 are stably guided by the railing 36 during their movement around the centrifuge bowl 32.

[0134] As shown in Figure 1, on the second angular sector 32B of the centrifuge bowl 32, the centrifuge bowl 32 has a peripheral gap 38 formed by the radial separation of the rail 36 from the outer edge 42 of the rotating plate 34. The radial width of the gap 38 is between the maximum diameter "D2" of the body 20 and the diameter "D1" of the support face 24, in this case the flange. This gap 38 extends circumferentially to the preform outlet 44.

[0135] At least along the entire length of the second rectification sector 32B, the railing 36 has a support rail 40 for the support face 24. The support rail 40 projects radially inwards at the same level as the upper face of the rotating plate 34 to define the gap 38 outwards. The support rail 40 extends here to the exit passage 44.

[0136] Thus, the preforms 18 are likely to be supported by their support face 24, in the present case by their collar, which rests at two diametrically opposite points on the upper horizontal face of the rotating plate 34, on the one hand, and on an upper horizontal face of the support rail 40, on the other hand, the body 20 of the preforms 18 hanging below the level of the rotating plate 34 through said gap 38.

[0137] Thus, during a third straightening stage, as shown in Figures 12 and 13, the preforms 18 aligned during the second stage arrive from the first alignment sector 32A, aligned in a single file along the railing 36, their main axis "A" oriented tangentially. The aligned preforms 18 are randomly arranged with column 22 upstream or column 22 downstream, without this affecting their straightening.

[0138] When the body 20 of each preform 18 rises above the gap 38, the body 20 falls, as shown in Figures 14 and 15, thus tilting the preform 18 around a radial axis passing through the support points of the support face 24, in this case the collar, of the preform 18. The tilting continues until the main axis "A" of the preform 18 is vertical, possibly after some rocking around the radial axis. The preform 18 is then supported by its support face 24 resting jointly on the support rail 40 and on the rotating plate 34, as shown in Figures 11, 16, and 17. The preform 18 is thus upright, with the collar 22 at the top. A preform 18 thus straightened is guided externally by the rail 40 supporting the railing 36, and it is guided internally by the peripheral edge 42 of the rotating plate 34.

[0139] The correctly positioned preforms 18, that is, aligned and straightened in this way, are rotated around their main axis by friction against the outer edge 42 of the rotating plate 34. The correctly positioned preforms 18 are thus moved around the centrifuge bowl 32 in the direction of rotation of the rotating plate 34 by rolling against the peripheral railing 36.

[0140] As illustrated in Figure 1, the correctly positioned preforms 18 are thus conveyed to the third exit sector 32C. The third exit sector 32C has a peripheral zone protected by a fixed deflector 62 arranged above the rotating plate 34 at a vertical distance less than the minimum diameter "D3" of the body 20 of the preforms 18 to prevent incorrectly positioned preforms 18 from coming into contact with the line of correctly positioned preforms 18 in the gap 38. An outer end of the deflector 62 is radially offset from the railing 36 to provide sufficient clearance for the correctly positioned preforms 18 to pass through.

[0141] The deflector 62 thus ensures that in the protected area located between the downstream face of the deflector 62 and the railing 36, no incorrectly positioned preform 18 is lying on the rotating plate 34.

[0142] It is also possible to equip the centrifuge bowl 32 with other means of sorting incorrectly positioned preforms 18 such as primary and / or secondary unscrambling wheels 64 described in application FR 3.035.090 A1.

Claims

A method for regulating the flow of preforms (18) in a preform distribution device (10) arranged at the inlet of a stretch-blowing container manufacturing installation, the distribution device (10) being fed by a bulk preform feeding device (12) which delivers the preforms (18) with an inlet flow rate (Qin), the distribution device (10) comprising: - a preform alignment and straightening device (14) comprising a centrifuge bowl (32) having a horizontal circular tray (34) rotating about a vertical axis (B), the upper face of which is intended to receive bulk preforms (18) via the feeding device (12), the preforms (18) being projected and aligned by centrifugation against a fixed peripheral railing (36) during the rotation of the tray (34),the preforms (18) thus aligned straightening in a peripheral gap (38) extending along an angular sector (32B, 32C) between the platform (34) and the railing (36); - an output conveyor (16) which receives the preforms thus aligned and straightened with an output flow rate (Qout), and which distributes the preforms one by one to the manufacturing installation at a determined rate; characterized in that the number (N) of preforms (18) simultaneously contained in the distribution device (10) is controlled using the difference between the input flow rate (Qin) and the output flow rate (Qout). Method according to the preceding claim, characterized in that the inlet flow rate (Qin) is controlled to a setpoint value for the number (N) of preforms (18) contained simultaneously in the distribution device (10). A method according to the preceding claim, characterized in that the setpoint value of the number (N) of preforms (18) contained simultaneously in the distribution device (10) is at least equal to a number (N1) of preforms 18 received in an accumulation queue (50) of optimal length determined experimentally. A method according to the preceding claim, characterized in that the setpoint value of the number (N) of preforms (18) contained simultaneously in the distribution device (10) is greater than the number (N1) of preforms 18 received in an accumulation queue (50) of optimal length. Method according to the preceding claim, characterized in that a default setpoint value of the number (N) of preforms (18) contained simultaneously in the distribution device (10) is equal to the sum of the number (N1) of preforms 18 received in an optimal length accumulation queue (50) and an average number (N2) of recycled preforms (18) which are not immediately aligned and straightened by the alignment and straightening device (14). Method according to the preceding claim, characterized in that the average number (N2) of recycled preforms (18) is determined experimentally, in particular as a function of the geometry of the preforms and the output flow rate (Qout). Method according to the preceding claim, characterized in that the inlet flow rate (Qin) is controlled so that the number (N) of preforms contained in the centrifuge bowl (32) is less than a saturation threshold of the straightening and alignment device (14) beyond which the entire peripheral length of the centrifuge bowl (32) is occupied by preforms (18). Method according to any one of claims 5 and 6, characterized in that the setpoint value is capable of being manually modified from the default setpoint value, the setpoint value being selectable between the number (N1) of preforms 18 received in an optimal length accumulation queue (50) and the saturation threshold. A method according to any one of the preceding claims, characterized in that the output flow rate (Qout) is equal to the operating rate of the installation. A method according to any one of the preceding claims, characterized in that the feeding device (12) is equipped with means for counting the preforms (18), the input flow rate being calculated as a function of the quantity of preforms (18) counted per unit of time.

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