Device for optically detecting a positioning or shape defect of a hollow body in a conveyor of a thermal treatment plant

Description

[0001] The invention relates to the automated control of the transport of hollow bodies by a conveyor.

[0002] More specifically, it concerns a device for detecting a positioning error of a hollow body traveling a rectilinear path defined by a hollow body conveyor.

[0003] These hollow bodies are, for example, preforms of plastic containers (e.g. PET). A preform typically comprises a cylindrical body which ends in a hemispherical base, a neck which has its final shape, and a flange separating the neck from the body.

[0004] In a container manufacturing facility from preforms, the raw injection preforms are usually stored in bulk in a container. The preforms are first removed from the container, oriented and ordered in line to be introduced into a thermal conditioning unit (more simply called an "oven") equipped with infrared emitters (typically in the form of tubular halogen lamps, or laser diode), where the bodies of the preforms are brought to a temperature above their glass transition temperature (which is approximately 80°C for PET). The hot preforms are then transferred to a forming unit equipped with a plurality of molds in which the preforms are formed to the container cavity by blow molding or stretch blow molding.

[0005] In the oven, the preforms are conveyed in line by means of a transport chain comprising a plurality of links, each a support called a "turntable", provided with a mandrel mounted in translation between an inactive position and an active position in which the mandrel fits into the neck of a preform.

[0006] During the translation of the chain, each turntable is driven in rotation by means of a rack which meshes with a pinion secured to the mandrel. In this way, the preform fitted on the head of the mandrel is driven both in translation and in rotation in the oven, so as to be fully exposed to the radiation of the infrared emitters.

[0007] The structure of such a conveyor chain is well described in European patent EP 0 935 572 (Sidel). This chain is usually mounted between two wheels, namely a drive wheel, which drives the chain, and a follower wheel. One of the wheels (e.g. the drive wheel) is placed upstream of the furnace, and the other (e.g. the follower wheel) downstream of it.

[0008] In certain configurations, the conveyor chain forms several parallel paths along which the hollow bodies are subdivided into several rows, see e.g. European patent EP 2 623 439 (Sidel).

[0009] The preforms from the container are loaded onto the upstream wheel by means of a rail or a toothed wheel, each preform coming directly above a turntable whose mandrel is in the inactive position. During the rotation of the upstream wheel, the mandrel is moved to its active position, the head fitting into the neck of the preform (an operation known as dressing), which is thus secured in rotation with the mandrel. As soon as the pinion meshes with the rack at the entrance of the oven, the preform is driven in rotation.

[0010] The production rate of such an installation is generally around 50,000 containers per hour, which corresponds to the rate of movement of the preforms in the oven where the speed of the preforms on the wheel is around 1 m / s.

[0011] At this speed, positioning problems can occur; in fact, it happens that a preform is not correctly centered in relation to the mandrel, which cannot therefore fit correctly into the neck.

[0012] Missing a preform on the production line does not pose a particular problem, but for safety reasons it is necessary to detect incorrectly positioned preforms, so as to allow their ejection from the oven. A preform is incorrectly positioned on the mandrel, for example when it is off-center with respect to the axis of the mandrel or fitted in an angularly deviated manner with respect to the axis of the mandrel, and can cause breakage of tubular halogen lamps or laser diodes placed nearby during its movement.

[0013] It is known in particular from European patent EP1781460 (Sidel) to eject a poorly positioned preform, by means of a mechanical device which detects a position of the mandrel intermediate between its active position and its inactive position, corresponding to a poor fitting of the mandrel head in the neck of the preform.

[0014] This device is satisfactory when (in the majority of cases) a preform is poorly positioned at the wheel, but it does not allow the detection of: Neither a preform which, while being correctly positioned at the upstream wheel, would then find itself incorrectly positioned, e.g. during the turning which occurs between the upstream wheel and the heating zone (where the path is straight), typically due to the centrifugal force accompanying the turning; Nor a preform which, while being correctly positioned, would have a shape defect (e.g. due to crushing).

[0015] CH424283 describes a device for testing glass objects, particularly hollow glassware, for cracks, glass distribution (wall thickness), and shape accuracy using light beams. The device is placed above the glassware transport path. Résumé de l'invention:

[0016] The invention aims to propose a solution making it possible to detect with increased reliability a shape or positioning defect of a hollow body (typically a preform) in a conveyor.

[0017] For this purpose, there is proposed, firstly, a detection device according to claim 1.

[0018] When a hollow body has a shape or positioning defect, it is inserted into the optical path between the optical unit and the target and is struck by the laser beam, resulting in detection of the shape or positioning defect.

[0019] Various additional features may be provided, alone or in combination. For example: The optical unit is mounted on an adjustable support; The support comprises a bracket including an upright and a crosspiece fixed to the upright and on which the optical unit is mounted; The upright is mounted in translation, in a vertical direction, relative to a fixed bracket; The support comprises a wheel for adjusting the position of the upright relative to the bracket in the vertical direction; The support comprises a brake lever, the tightening of which is suitable for ensuring the locking in position of the upright relative to the bracket; The crosspiece is mounted in translation, relative to the upright, in a transverse direction; The crosspiece is mounted in translation, relative to the upright, in a longitudinal direction; The support comprises a slider mounted in translation, relative to the upright, in the transverse direction, and the crosspiece is mounted in translation, relative to the slider, in the longitudinal direction;The support comprises a wheel for adjusting the position of the crosspiece relative to the upright, in the transverse direction; The support comprises a brake lever, the tightening of which is suitable for ensuring the locking in position of the crosspiece in the transverse direction; The support comprises at least one indicator of the position of the optical unit; The target comprises a reflector lined with prisms; The target is mounted in an adjustable manner on a foot. ;

[0020] According to a particular embodiment, the device comprises, for the detection, on two rectilinear paths, of a shape or positioning defect of a hollow body traveling along at least one of these paths: A first optical unit incorporating an emitter producing an optical beam along a first optical path of which at least one segment is oriented parallel to a first path; A first target positioned at a distance from the first optical unit, this first target being provided with a photosensitive sensor or a reflector intercepting the first optical path; A second optical unit incorporating an emitter producing an optical beam along a second optical path of which at least one segment is oriented parallel to a second path; A second target positioned at a distance from the first optical unit, this first target being provided with a photosensitive sensor or a reflector intercepting the second optical path.

[0021] Other additional features may still be provided. For example: The optical block is positioned in the extension of the path; The target is positioned opposite the optical unit; The path being defined between an entry point and an exit point, the optical unit is positioned beyond the exit point or the entry point; The target is positioned opposite the optical unit beyond the entry point or, respectively, the exit point; The optical unit is laterally offset from the path, and the device comprises an optical angle deflection (such as a prism or a mirror) positioned to orient the segment of the optical path parallel to the path; The optical unit incorporates a bandpass optical filter having a bandwidth centered on a predetermined wavelength. The emitter produces a laser beam.

[0022] Secondly, a conveyor of a thermal conditioning unit for transporting hollow bodies (2) is proposed, equipped with a detection device (23) as presented above.

[0023] Other objects and advantages of the invention will appear in the light of the description of an embodiment, given below with reference to the appended drawings in which: [ Fig. 1 ] is a perspective view showing a thermal preform conditioning unit, equipped with a detection device according to the invention, with, in the top medallion, a larger-scale detail centered on the area where the optical block is positioned and, in the bottom medallion, a larger-scale detail centered on the area where the target is positioned; [ Fig. 2 ] is a detailed perspective view showing the detection device in operation, when the hollow bodies are normal in shape and positioning; [ Fig. 3 ] is a detailed perspective view of the device of the figure 2 , from another angle of view; [ Fig. 4 ] is a detailed perspective view, on a larger scale, of the optical block of the detection device as illustrated in the figure 2 ; [ Fig. 5 ] is a detailed perspective view of the optical block of the figure.4 , from another angle of view; [ Fig. 6 ] is a view similar to the figure 2 , showing the detection device in operation, when a hollow body has a shape or positioning defect; [ Fig. 7 ] is a schematic view taken along the axis of the optical unit, illustrating its operation.

[0024] On the figure 1 a conveyor is represented 1 configured to provide body transport 2 hollow. In the example shown, the bodies 2 hollow bodies are preforms, from which containers must be formed (by blowing or stretch blowing). Certainly, the bodies 2hollow bodies could be different: they could be parisons, or even containers. In what follows, however, it is assumed that the bodies 2 hollow are preforms, which are advantageously made of a plastic material (typically PET).

[0025] Each preform 2 (see in particular the figure 2 ) includes a body 3 cylindrical, extending along an axis X main, a pass 4 open extending from a first end of the body 3, and a hemispherical bottom 5 which extends to the other end of the body 3. In the example shown, the preform 2 includes a collar 6 which separates the body 3 from the neck 4. We note R half the width of a preform 2, measured between the axis X main and periphery of the body 3. When, as in the example illustrated, the body 3is cylindrical of revolution, the half-width R denotes the radius of the body 3.

[0026] The conveyor 1 is planned here to transport the preforms to the parade 2 in a unit 7 thermal conditioning, also called an oven, which includes one or more walls 8 radiant (two in the example shown) each equipped with one or more rows of infrared radiation sources, here in the form of tubular (e.g. halogen) lamps.

[0027] In the oven 7, the bodies of the preforms 2 are exposed to radiation from the walls 8 to be heated to a temperature above their glass transition temperature (approximately 80°C in the case of PET), with a view to then being shaped into containers within a forming unit (not shown) equipped with a plurality of molds with the imprint of a given container model.

[0028] The conveyor 1 includes, firstly, a frame 9 fixed. In the example shown, the frame 9 includes a pair of legs 10 and one or more beams 11 connecting the legs.

[0029] The conveyor 1 includes, secondly, a chain 12 transport that defines a predefined route along which the preforms 2 are moved. This path extends in a closed loop. In the example shown, the path includes two paths TR straight lines connected by paths TC curvilinear (in this case circular). In a variant not illustrated, the route comprises a single path TR straight. In another variant not shown, the route includes two paths TR rectilinear neighbors close together, on which the preforms 2are moved in two parallel rows, as in the configuration described in patent EP 2 623 439 (Sidel).

[0030] Returning to the illustrated example, the chain 12, of which only a part is shown in the drawings, comprises two straight strands 13 which each define a journey TR straight, and two strands 14 in an arc that defines the paths TC curvilinear. In its strands 14 curvilinear, the chain 12 moves on wheels 15 at least one of which is motorized. Each journey TR rectilinear defines a longitudinal direction of movement and extends between a point E entry and a point S exit.

[0031] The chain 12 comprises a plurality of links 16 articulated with respect to each other by means of couplings 17.

[0032] Each link16 wears at least one scabbard 18 and a support 19 for a preform 2. This support 19, hereinafter called a spinner because of its rotating nature, is provided with: From a chuck 20 mounted on a sliding pivot relative to the sheath 18 and one end of which forms a nose suitable for being fitted into the neck 4 of a preform, of a pinion 21 rotationally fixed to the mandrel 20, which engages a fixed rack (not visible on the figure 1 because hidden by the chain 12 ).

[0033] Each link 16 also carries an ejector 22 attached to the sheath 18.

[0034] When a preform 2 is mounted on a spinner 19, the preform 2 is rotated by it, so that the entire surface of its body 3is exposed to the radiation of the (or each) wall 8.

[0035] Each spin 19 is mounted in translation relative to the sheath 18 between an extended position, in which the chuck 20 protrudes from the ejector 22 to fit into the collar 4 of a preform 2 (so-called dressing operation), and a retracted position in which the mandrel 20 is housed in the ejector 20 to get out of the pass 4 which comes up against the ejector 22 (operation known as undressing).

[0036] Dressing and undressing are carried out along a route TC curvilinear, on the periphery of one of the wheels 15 (the one on the left on the figure 1 ). During these operations, the preforms 2 are neck-oriented 4 at the top. After dressing, the preforms 2undergo a reversal to be oriented towards the neck 4 at the bottom before being introduced into the oven 7. Out of the oven 7 (and therefore at the end of thermal conditioning), the preforms 2 are returned again to be evacuated from the conveyor 1 and transferred to the forming unit.

[0037] In the journeys TR straight lines of the route, the axes X main preforms 2 positioned nominally (i.e. vertically, in the absence of any defect in form or positioning) sweep across a plane M median that extends both vertically and longitudinally.

[0038] In the illustrated example, the point E entry and point S exit points are the end points of the path TR rectilinear where the axes X main preforms 2 deviate from the plan Mmedian (or join it), either when the preforms enter a path TC curvilinear (or come out of it), or when they are turned over.

[0039] While traveling the route TR rectilinear, the bodies 3 preforms 2 sweep a volume VB (hatched on the figure 7 ), symmetrical with respect to the plane M median and whose half-width, measured transversely (i.e. perpendicular to the plane M media) is equal to half-width R preforms.

[0040] However, it may happen that a preform 2 presents: A positioning defect, typically when the fitting has not been carried out correctly, or A shape defect (as illustrated in the figure 6 and dotted on the figure 7 ), e.g. when the preform 2has suffered deformation due in particular to poor injection, shock or even crushing.

[0041] In this case, it is necessary to detect it in order to eject it.

[0042] For this purpose, the conveyor 1 is equipped with a device 23 detection, configured to detect optically, on one and / or the other of the paths TR rectilinear, a defect in the shape or positioning of a preform 2 traveling this(these) route(s) TR.

[0043] The device 23 detection includes, firstly, a block 24 optical.

[0044] This block 24 integrates a transmitter which produces a beam 25 optics (advantageously collimated) following an optical path of which at least one segment (or portion) is oriented parallel to the path TR rectilinear, so that this segment (and therefore, at least locally, the beam 25) is offset laterally, relative to the plane M median, of a distance D greater than half width R preforms 2 (i.e. half the width of the volume VB swept away by the preforms 2 whose shape and positioning are nominal) and less than twice the width R of the preforms which normally corresponds to the position of the radiating wall. In other words, the optical beam 25 can advantageously be positioned between the wall of the preform and the radiating wall. In the case where the optical beam 25 is positioned on the wall of the hollow body or on the radiating wall then no defect detection is possible.

[0045] In other words, the distance from the beam to the median plane scanned along the straight path by the axes ( X) of the preforms is advantageously strictly greater than the maximum half width of the hollow body and / or strictly located inside a space extending between the lateral radiating wall and the wall of the preform.

[0046] In a first embodiment, the beam 25 optical is preferably a laser, i.e. an intense collimated optical beam with a narrow optical bandwidth. However, in a second embodiment, it could be an optical beam with a wider optical bandwidth. In this second embodiment, the optical block would integrate an optical bandpass filter having a bandwidth centered on a predetermined wavelength. Whatever the embodiment chosen, it is appropriate to choose the wavelength or, respectively, the bandwidth, so that the wavelengths of the radiation emitted by the preforms 2do not generate interference with the beam, to avoid any detection error.

[0047] In the following, we consider the first embodiment, and we therefore assume that the beam 25 optics is a laser, without this assumption excluding the other embodiment.

[0048] As illustrated in the detail medallion of the figure 1 , the optical path shift is performed towards the outside of the path TR, that is to say on the side opposite to the trajectory(ies) TC curvilinear(s), in order to prevent the preforms 2 which circulate nominally on the curvilinear path(s) do not intersect the beam 25.

[0049] The device 23 detection includes, secondly, a target 26 positioned at a distance from the block 24 optical.

[0050] The target 26 is provided with: Let (first case) be a photosensitive sensor intercepting the optical path of the beam 25 and suitable for detecting its impact, Either (second case, illustrated) of a reflector 27 intercepting the optical path of the beam 25 and capable of reflecting it towards an optical receiver integrated into the block 24 optical.

[0051] In the first case, the device 23 detection can operate in all or nothing mode, that is to say that: As long as the photosensitive sensor equipping the target 26 is excited, which indicates that the beam 25 reaches it without hindrance, it produces a first signal characteristic of nominal operation of the conveyor 1, where the preforms 2 are all compliant; However, the photosensitive sensor equipping the target 26is no longer excited, which indicates that an obstacle is interposed on the optical path between it and the transmitter, it produces a second signal characteristic of degraded operation where at least one of the preforms 2 has a defect in shape or positioning.

[0052] This first case is effective for detecting a shape or positioning defect in a preform 2, but it does not allow it to be located in order to be able to eject it without stopping the conveyor 1. To allow (manual) removal of the preform 2 concerned, it is therefore appropriate to stop the conveyor 1.

[0053] In the second case, the device 23 detection unit allows distance measurement to be carried out. The block 24optical system, which is equipped with both a transmitter and a receiver, is configured to measure by triangulation the length of the optical path actually traveled by the beam 25 laser: As long as the measured optical path length is equal to a predetermined standard value (roughly corresponding to twice the distance separating the block 24 reflector optics 27 ), the block 24 produces a first signal characteristic of nominal operation where the preforms 2 are all compliant; However, if the measured length of the optical path is less than the standard value, this indicates the presence of a preform 2 which, having a defect in shape or positioning, cuts the beam 25, the block 24 optical produces a second signal characteristic of degraded operation where at least one of the preforms 2has a shape or positioning defect. As the distance (along the optical path) of the block 24 optics to the preform 2 concerned can be measured, a calculator can precisely locate the preform 2 and, taking into account its (known) speed of movement, order its ejection when it reaches an area of ​​the conveyor 1 where an ejection system is installed.

[0054] The block 24 optics is for example of the type (with transmitter and receiver) marketed by the company Sick under the reference Dx50. According to a preferred embodiment, the reflector 27 is lined with prisms, which improves the quality of the optical signal captured by the receiver equipping the block 24 optical. Thus, the reflector is, for example, of the type marketed by the company SICK under the reference PL100.

[0055] In the illustrated configuration, where the optical path is straight, the (or each) block 24 is positioned in the extension of the journey TR straight beyond the point S exit (or, alternatively, beyond the entry point E). In this same configuration, the (or each) target 26 is positioned in the extension of the journey TR straight beyond the point E entry (or, respectively, beyond the point S output when the block 24 optic is positioned beyond the point E input). In this configuration, the (or each) target 26 is positioned opposite the block 24 corresponding optics.

[0056] Alternatively, the (or each) block 24 optics can be offset laterally from the path TR preforms. In this case, the device 23includes an optical angle deflector (such as a prism or mirror) positioned to orient the optical path segment parallel to the path TR.

[0057] When the preforms route 2 includes two journeys TR rectilinear, the device 23 includes, for the detection on these two paths, of a shape or positioning defect of a preform 2 traveling at least one of these routes: A first block 24 optics integrating an emitter producing a beam 25 following a first optical path of which at least one segment is oriented parallel to a first path TR ; A first target 26 positioned at a distance from the first block 24 optical, this first target 26 being provided with a photosensitive sensor or a reflector 27 intercepting the first optical path; A second block 24optics integrating an emitter producing a beam 25 following a second optical path of which at least one segment is oriented parallel to a second path TR ; A second target 26 positioned at a distance from the first block 24 optical, this first target 26 being provided with a photosensitive sensor or a reflector 27 intercepting the second optical path.

[0058] Whatever the chosen method of implementation, the (or each) block 24 otic is advantageously mounted on the frame 9 of the conveyor 1. More precisely, and as illustrated in the drawings, the block 24 optic is mounted on a pole 28 attached to a base 10.

[0059] As the size (especially the half-width R, but also possibly the height) of the preforms 2may vary from one range to another depending on the model of container to be manufactured, it is preferable to be able to adjust at least the position of the block accordingly 24 optics (and, where appropriate, the position of the target 26 ).

[0060] This is why, in the illustrated example, the block 24 optics is mounted on a support 29 adjustable. As seen in particular on the figure 4 , this support 29 is in turn fixed to the post 28.

[0061] According to one embodiment, the support 29 includes a gallows 30. The gallows 30 includes an amount 31 and a crosspiece 32. The crossing 32 is fixed on the amount 30. The block 24 optics are mounted on the crossbar 32.

[0062] The amount 31 extends vertically; the crosspiece 32 extends longitudinally. The block24 optic is mounted at one end of the crossbar 32, e.g. by screwing.

[0063] In the example illustrated in particular on the figure 4 , the support 29 includes a wall light 33 through which the amount 31 is attached to the post 28. The amount 31 is here mounted in translation, following a vertical direction (represented by the arrow V on the figure 4 ) compared to the wall light 33. The wall light is fixed; however it can be fixed to the pole 28 at different predetermined heights. For this purpose, and as illustrated in the figure 2 , a turntable 34 graduated can be interposed between the wall light 33 and the pole 28.

[0064] Fixing the wall light 33 on the turntable 34 (or on the pole 28 through the turntable 34) can be achieved by means of a nut 35 (e.g. a star nut), while an index finger 36 (here in the form of a line engraved in an edge of the applique 33 ) indicates the fixing height of the wall light by cooperation with the graduation of the plate 34.

[0065] As we see in particular on the figure 4 , the support 29 advantageously includes a wheel 37 adjustment of the position of the amount 31 (and therefore of the gallows 30 ) compared to the wall light 33 (and therefore in relation to the post 28 ) following the direction V vertical. An indicator 38 electronics with a screen can be coupled to the wheel 37 to display the vertical position of the block 24 optical.

[0066] The support 29 preferably includes a brake lever 39whose tightening is suitable for ensuring the upright is locked in position 31 compared to the wall light 33. As illustrated in the figure 4 , the brake lever 39 is screwed into the wall light 33 ; it includes a lug which, in the tight position, comes to exert pressure against the upright 31 a localized frictional effort to lock it in position.

[0067] Vertical movement (by unscrewing then screwing the nut back in 35 ) of the wall light 33 compared to the turntable 34 allows for rough adjustment of the vertical position of the block 24 optical. The operation of the wheel 37 then allows fine adjustment of the vertical position of the block 24 optical.

[0068] According to a preferred embodiment, the crosspiece 32 is mounted in translation, relative to the amount 31,along a transverse direction (this direction, perpendicular to the plane M median, is materialized on the figure 4 by the arrow T ).

[0069] For this purpose, in the example illustrated on the figure 4 , the support includes a slider 40 mounted in translation relative to the amount 31 following the direction T transverse and on which the crosspiece 32 is fixed.

[0070] As seen on the figure 5 , the support is advantageously provided with a wheel 41 slide position adjustment 40 (and therefore of the crossing 32 ) compared to the amount 31, following the direction T transversal. An indicator 42 electronics with a screen can be coupled to the wheel 41 to display the transverse position of the block 24 optical.

[0071] The support29 preferably includes a brake lever 43 whose tightening is suitable for ensuring the slide is locked in position 39 (and therefore of the crossing 32 ) following the direction T transverse.

[0072] According to a preferred embodiment, the crosspiece 32 is also mounted in translation, relative to the slide 40, following the longitudinal direction (materialized on the figure 4 by the arrow L ). In the example shown, the crosspiece 32 is attached to a bracket 44 mounted, with one degree of freedom in longitudinal translation, on the slide 40. One or more wheel(s) 45 allow you to adjust the longitudinal position of the bracket 44 (and therefore of the crossing 32 ) relative to the slide 40 (and therefore in relation to the amount 31, to the wall light 33 and to the post 28 ).

[0073] The target 26 is advantageously chosen to be of sufficient dimensions to be able to always be struck by the beam 25 laser (except for preform cases) 2 poorly positioned or deformed); however, it may be preferable to be able to adjust it to ensure that it is correctly positioned in relation to the block 24 optical.

[0074] So, in the example shown, the target 26 is mounted in an adjustable manner on a foot 46 itself in solidarity with the building 9 (and more precisely, in the example illustrated, fixed on a beam 11 ).

[0075] As we can clearly see on the figure 2 , the foot 46 is preferably twisted, so as not to hinder the turning of the preforms 2 (by rotation of the links 16 ).

[0076] The device 23detection system just described provides the following advantages.

[0077] First, it allows to detect a preform 2 having a positioning defect in the path TR rectilinear (even when this preform 2 did not present such a defect in the journey TC curvilinear, at the wheel level 15 ).

[0078] Second, it allows to detect a preform 2 which, even if it does not present a positioning defect, nevertheless presents a form defect.

[0079] Third, it allows such detections to be carried out without contact.

[0080] This results in increased reliability of the device 23 detection, particularly compared to known mechanical detection devices.

Claims

1. Device (23) for detecting a shape or positioning defect of a hollow body (2) for a unit (7) for thermal conditioning of the hollow body, also known as an oven, the unit (7) comprising one or more radiating walls (8) and a conveyor (1) of the hollow bodies (2) defining at least one rectilinear path (TR), the hollow bodies following the rectilinear path (TR) between an entry point (E) and an exit point (S) of the thermal conditioning unit (7) and each having a main axis (X), the device (23) comprising: - an optical block (24) incorporating an emitter producing an optical beam (25) positioned between the wall of the hollow body (2) and the radiating wall (8) along an optical pathway of which one segment is oriented parallel to the rectilinear path (TR) and offset laterally, with respect to a median plane (M) swept along by the main axes (X) of the nominally positioned hollow bodies (2), by a distance (D) greater than a half-width (R) of the hollow bodies (2) and less than twice the width (R) of the hollow bodies (2); - a target (26) positioned at a distance from the optical block (24), this target (26) being provided with a photosensitive sensor or a reflector (27) intercepting the optical pathway of the beam (25) and suitable, respectively, for detecting the impact thereof or for reflecting it towards an optical receiver incorporated in the optical block (24) such that, when a hollow body (2) has a shape or positioning defect, it is interposed on the optical pathway between the optical block (24) and the target (26) and is struck by the optical beam (25) between the wall of the hollow body (2) and the radiating wall (8), resulting in detection of the shape or positioning defect.

2. Device (23) according to Claim 1, characterized in that the optical block (24) is mounted on an adjustable support (29).

3. Device (23) according to Claim 2, characterized in that the support (29) comprises a bracket (30) including an upright (31) and a crossmember (32) fastened to the upright (31) and on which the optical block (24) is mounted.

4. Device (23) according to Claim 3, characterized in that the upright (31) is mounted for translational movement, in a vertical direction (V), with respect to a fixed fixture (33).

5. Device (23) according to Claim 4, characterized in that the support (29) comprises an adjustment wheel (37) for adjusting the position of the upright (31) with respect to the fixture (33) in the vertical direction (V).

6. Device (23) according to Claim 5, characterized in that the support (29) comprises a brake lever (39) of which the clamping is suitable for blocking the upright (31) in position with respect to the fixture (33) in the vertical direction (V).

7. Device (23) according to one of Claims 3 to 6, characterized in that the crossmember (32) is mounted for translational movement, with respect to the upright (31), in a transverse direction (T).

8. Device (23) according to one of Claims 3 to 7, characterized in that the crossmember (32) is mounted for translational movement, with respect to the upright (31), in a longitudinal direction (L).

9. Device (23) according to Claims 7 and 8, taken in combination, characterized in that the support (29) comprises a slider (40) mounted for translational movement, with respect to the upright (31), in the transverse direction (T), and in that the crossmember (32) is mounted for translational movement, with respect to the slider (40), in the longitudinal direction (L).

10. Device (23) according to Claim 7 or Claim 9, characterized in that the support (29) comprises an adjustment wheel (41) for adjusting the position of the crossmember (32) with respect to the upright (31), in the transverse direction (T); the support (29) preferably comprising a brake lever (43) of which the clamping is suitable for blocking the crossmember (32) in position in the transverse direction (T).

11. Device (23) according to one of Claims 2 to 10, characterized in that the support (29) comprises at least one indicator (38, 42) of the position of the optical block (24).

12. Device (23) according to one of the preceding claims, characterized in that the optical block (24) is positioned in the extension of the path (TR), the target (26) preferably being positioned facing the optical block (24).

13. Device (23) according to Claim 12, characterized in that the optical block (24) is positioned beyond the exit point (S) or the entry point (E); the target (26) preferably being positioned facing the optical block (24) beyond the entry point (E) or, respectively, the exit point (S).

14. Device (23) according to one of the preceding claims, characterized in that the target (26) comprises a reflector (27) covered with prisms; and / or the target (26) is mounted in an adjustable manner on a foot (46); and / or the device comprises, for the detection, on two rectilinear paths (TR), of a shape or positioning defect of a hollow body (2) following at least one of these paths (TR): - a second optical block (24) incorporating an emitter producing an optical beam (25) along a second optical pathway of which at least one segment is oriented parallel to a second path (TR); - a second target (26) positioned at a distance from the first optical block (24), this first target (26) being provided with a photosensitive sensor or a reflector (27) intercepting the second optical pathway; and / or the optical block (24) is laterally offset from the path (TR), and the device (23) comprises an optical angle deflector positioned to orient the optical pathway segment parallel to the path (TR); and / or the optical block (24) incorporates an optical bandpass filter having a bandwidth centred on a predetermined wavelength; and / or the emitter produces a laser beam (25).

15. Conveyor (1) of a thermal conditioning unit (7) for transporting hollow bodies (2), equipped with a detection device (23) according to one of the preceding claims.