METHOD FOR INSPECTING HOLLOW GLASS PRODUCTS OF GLASS PRODUCT MATERIAL

Abstract

Method and system for inspecting hollow glass products of glass product material, wherein the glass products are manufactured by: a. heating the glass product material; b. forming the heated glass product material into at least one glass product; c. cooling the formed glass product; wherein inspecting the glass products comprises the following steps: d. transporting the glass products formed in step b. successively along a predetermined path along at least one infrared light sensitive sensor, wherein with the at least one sensor, of a plurality of the glass products that are transported successively along the at least one sensor, with the at least one sensor per glass product an image is made, wherein step d. is carried out between steps b. and c.; e. processing the images made in step d. for obtaining information about a wall thickness of the glass products.

Claims

1. A method for inspecting hollow glass products of glass product material, wherein said glass products are manufactured by: a. heating the glass product material; b. forming the heated glass product material into at least one glass product in a production flow; c. cooling the formed glass product; wherein inspecting the glass products comprises the following steps: d. transporting the glass products formed in step b. successively along a predetermined path along at least one infrared light sensitive sensor, wherein with the at least one sensor, of a plurality of the glass products that are transported successively along the at least one sensor, with the at least one sensor per glass product an image is made, wherein step d. is carried out between steps b. and c.; e. processing the images made in step d. for obtaining information about a wall thickness of the glass products, wherein the sensor is sensitive to infrared light having at least one frequency where a glass product of the plurality of glass products is transparent to the infrared light so that an image of the plurality of images both shows a side of the glass product that faces the sensor with which the image has been made and shows a side of the glass product, located opposite the side, that faces away from the sensor with which the image has been made, wherein in step d. of each glass product of the plurality of glass products a rotational position of the glass product around an axial axis of the glass product relative to the at least one sensor is determined, wherein the images and associated rotational positions of the plurality of products are processed in combination for obtaining information about a lateral wall thickness distribution around an axial axis of a virtual glass product that represents the plurality of glass products.

2. The method of claim 1, wherein the plurality of images with their associated determined orientation are processed in combination according to the principle of tomography for obtaining the lateral glass thickness distribution of the virtual glass product.

3. The method of claim 1, wherein a glass thickness distribution indicates relative variations in glass thickness.

4. The method of claim 1, wherein a glass thickness distribution comprises absolute values of the glass thickness distribution.

5. The method of claim 1, wherein a calibration measurement on a glass product having a known glass thickness is performed, on the basis of which thereupon step e. is carried out.

6. The method of claim 1, wherein each image of the plurality of images both shows a side of the glass product that faces the sensor with which the image has been made and shows a side of the glass product, located opposite the side, that faces away from the sensor with which the image has been made.

7. The method of claim 1, wherein in step e.'s processing in combination of the plurality of images according to the principle of tomography for obtaining the lateral glass thickness distribution of the virtual glass product, of the sensor, solely infrared light is used that relative to the sensor comes from a direction of an axial axis of the respective associated glass product.

8. The method of claim 2, wherein the processing in combination according to the principle of tomography comprises a computation technique according to (Filtered) Back Projection, algebraic reconstruction technique (A.R.T) or simultaneous algebraic reconstruction technique (S.A.R.T).

9. The method of claim 1, wherein in the steps d. and e. the lateral glass thickness distribution is determined in an area of the virtual glass product that extends around the axial axis of the virtual glass product.

10. The method of claim 9, wherein the steps d. and e. are carried out repeatedly for obtaining a lateral glass thickness distribution in a second area of the virtual glass product that extends around the axial axis of the virtual glass product, wherein a first area and a second area are staggered with respect to each other in the axial direction.

11. The method of claim 10, wherein the steps d. and e. are respectively carried out repeatedly at least three times for respectively obtaining lateral glass thickness distributions in respectively at least three mutually different areas which each extend around the axial axis of the virtual glass product and are staggered with respect to each other in axial direction and which in combination cover at least substantially the whole virtual glass product.

12. The method of claim 10, wherein the axial axis is at least substantially vertically directed.

13. The method of claim 1, wherein the glass product between steps b. and c. is transported along the path on a conveyor.

14. The method of claim 13, wherein that the glass product between steps b. and c. is transported on the conveyor from a product forming mold in which the glass product has been formed in step b. to a cooling apparatus in which the product is cooled in step c.

15. The method of claim 13, wherein the rotational position of each of the glass products of the plurality of glass products around its axial axis on the conveyor is determined.

16. The method of claim 15, wherein the rotational position of a glass product of the plurality of glass products is determined with aid of one of the sensors with which an image of the respective glass product is determined by recognizing of a predetermined marking on or in the respective glass product.

17. The method of claim 16, wherein the marking is a seam and/or a dot.

18. The method of claim 1, wherein inspecting also comprises a controlling whereby at least one step of the steps a., b. and c. is adjusted on the basis of at least one determined glass thickness distribution of the virtual glass product and possibly an associated virtual rotational position of the virtual glass product relative to the path.

19. The method of claim 1, wherein with the sensor an image is made of a glass product when an axial axis of the respective glass product is at least substantially intersected by an optical axis of the respective sensor.

20. The method of claim 9, wherein the sensor is displaced in the axial direction for obtaining recordings in different areas.

21. The method of claim 9, wherein the sensor comprises an IR camera.

22. The method of claim 1, wherein the sensor is sensitive to light having a bandwidth of 900 nm 3500 nm.

23. The method of claim 2, wherein in the processing in combination of the plurality of images according to the principle of tomography for obtaining a lateral glass thickness distribution of the glass that is in an area, ray tracing is applied.

24. The method of claim 1, wherein a sufficiently large number of recordings of products from a production flow are selected in order that these recordings in combination cover an associated virtual glass product completely around the axial axis of the virtual glass product.

25. The method of claim 1, wherein a plurality of the steps b. are carried out parallel to each other for producing parallel to each other a plurality of the products in a plurality of production flows which each comprise a step b., wherein each glass thickness distribution of a virtual glass product has been obtained on the basis of recordings of products that have been manufactured in a same production flow.

26. The method of claim 1, wherein in step d. the product is transported in a horizontally directed plane, wherein the axial axis of the product is vertically directed.

27. The method of claim 1, wherein a plurality of products that are transported in step d. comprise mutually different rotational positions and/or that the glass products that are transported along the path mutually have a more or less random rotational position.

28. Method for producing and inspecting hollow glass products of glass product material, the method comprising: a. heating the glass product material; b. forming the heated glass product material into a glass product in a production flow; c. cooling the formed glass product; wherein inspecting the glass products comprises the following steps: d. transporting the glass products formed in step b. successively along a predetermined path along at least one infrared light sensitive sensor, wherein with the at least one sensor, of a plurality of the glass products that are transported successively along the at least one sensor, with the at least one sensor per glass product an image is made, wherein step d. is carried out between steps b. and c.; e. processing the images made in step d. for obtaining information about a wall thickness of the glass products, wherein the method is further carried out according to the characterizing step of claim 1.

29. (canceled)

30. The method of claim 28, further comprising a plurality of the steps b. carried out parallel to each other for producing parallel to each other a plurality of the products in a plurality of production flows which each comprise a step b., wherein each glass thickness distribution of a virtual glass product has been obtained on the basis of recordings of products that have been manufactured from a same production flow, more particularly wherein on the basis of at least one determined glass thickness distribution of at least one virtual glass product that has been obtained from recordings of products that stem from a same production flow, that production flow is controlled.

31. A system for producing and inspecting glass products of glass product material according to claim 1, wherein the system comprises: a heating apparatus for carrying out step a.; a product forming mold for carrying out step b.; a cooling apparatus for carrying out step c.; at least one sensor for carrying out step d.; and a signal processing unit connected with the at least one sensor for processing signals coming from the at least one sensor, the signals each representing an image obtained with the at least one sensor, wherein the signal processing unit is configured for processing the plurality of images for obtaining information about a wall thickness of the glass products, wherein the at least one sensor is sensitive to infrared light having at least one frequency where each glass product of the plurality of glass products is transparent to the infrared light so that an image of the plurality of images both shows a side of the glass product that faces the at least one sensor with which the image has been made and shows a side of the glass product, located opposite the side, that faces away from the at least one sensor with which the image has been made, wherein the system is configured such that, in use, in step d. of each glass product of the plurality of glass products, the rotational position of the glass product around an axial axis of the glass product relative to the at least one sensor is determined, wherein the signal processing unit is configured such that, in use, the images and the associated rotational positions of the plurality of products are processed in combination for obtaining information about a lateral wall thickness distribution around an axial axis of a virtual glass product that represents the plurality of glass products.

32. (canceled)

33. The system of claim 31, further comprising a conveyor for transporting the glass products along a path.

34. The system of claim 31, wherein the system is configured such that, in use, a plurality of the steps b. are carried out parallel to each other for producing parallel to each other a plurality of the products in a plurality of production flows which each comprise a step b., wherein the signal processing unit is configured such that, in use, each glass thickness distribution of a virtual glass product is obtained on the basis of recordings of products that have been manufactured in a same production flow, more particularly wherein on the basis of at least one determined glass thickness distribution of at least one virtual glass product that has been obtained from recordings of products which that from a same production flow, in an automatic manner that production flow is controlled.

35. A system for inspecting glass products of glass product material, according to the method according to claim 1, wherein the system comprises: at least one sensor for carrying out step d.; and a signal processing unit connected with the at least one sensor for processing signals coming from the at least one sensor, the signals each representing an image obtained with the at least one sensor, wherein the signal processing unit is configured for processing the plurality of images for obtaining information about a wall thickness of the glass products, characterized in that the at least one sensor is sensitive to infrared light having at least one frequency where each glass product of the plurality of glass products is transparent to the infrared light so that an image of the plurality of images both shows a side of the glass product that faces the at least one sensor with which the image has been made and shows a side of the glass product, located opposite the side, that faces away from the at least one sensor with which the image has been made, wherein the system is configured such that, in use, in step d. of each glass product of the plurality of glass products a rotational position of the glass product around an axial axis of the glass product relative to the at least one sensor is determined, wherein the signal processing unit is configured such that, in use, the images and associated rotational positions of the plurality of products are processed in combination for obtaining information about a lateral wall thickness distribution around an axial axis of a virtual glass product that represents the plurality of glass products.

36. (canceled)

37. The system of claim 35, wherein the system is configured such that, in use, a plurality of the steps b. are carried out parallel to each other for producing parallel to each other a plurality of the products in a plurality of production flows which each comprise a step b., wherein the signal processing unit is configured such that, in use, each glass thickness distribution of a virtual glass product is obtained on the basis of recordings of products that have been manufactured in a same production flow.

Description

[0045] The invention will now be further explained on the basis of the drawing. In the drawing:

[0046] FIG. 1 shows a possible embodiment of a system according to the invention for carrying out a method according to the invention;

[0047] FIG. 2 shows the use of a part of the system of FIG. 1;

[0048] FIG. 3 shows a part of the use according to FIG. 2;

[0049] FIG. 4 shows a possible implementation of the glass product that is manufactured in the system of FIG. 1;

[0050] FIG. 5 shows schematically a 3D view of a glass product in which areas are hatched of which an LGD has been determined;

[0051] FIG. 6 shows schematically a top plan view of a possible embodiment of the product forming apparatus of FIG. 1.

[0052] In FIG. 1 there is indicated with reference numeral 1 a system according to the invention for carrying out a method according to the invention. The system comprises a schematically shown heating apparatus 2 for heating glass product material so that the glass product material enters a molten state. The molten material is transported to a product forming apparatus 3. In addition, other materials may be supplied to the product forming apparatus 3 if this is necessary, such as other materials and/or semimanufactures. In this embodiment, the product forming apparatus 3 successively manufactures in each case one hollow glass product 4.i (i=1, 2, 3, . . . ) in a production flow. The glass product 4.i is here manufactured after the glass product 4.i1. The product forming apparatus 3 in this example includes for this purpose one mould, known per se, 104 (shown schematically in FIG. 1) into which a portion of the heated glass product material is introduced, and at least one trough 102 (shown schematically in FIG. 1) to guide a glass gob to the mould (the glass gob slides via the inclined trough to the mould concerned). Also, the product forming apparatus 3 comprises blowing means (not shown) for blowing or pushing the glass product material into the mould for obtaining the final shape of the glass product. While in this example the product forming apparatus comprises one mould for manufacturing a glass product in one production flow, it is, of course, also possible that the product forming apparatus comprises a plurality of moulds for manufacturing parallel to each other a plurality of products in a plurality of parallel production flows. An example of this will, after the discussion of the variant with one mould, be discussed as well, with reference to a variant with six moulds.

[0053] The successively formed glass products 4.i are placed with the aid of a placing unit 5 on a conveyor 6. For different values of i, then, the corresponding products have been produced at different points of time because products are produced one at a time with one and the same mould in a single production flow.

[0054] The glass products 4.i produced as described above are transported with the aid of the conveyor 6 to a position P where inspection of a glass product can take place as will be set out hereinafter. Using the conveyor, the products are then transported further to a cooling apparatus 7 for cooling of the glass product. With the arrow 8, the direction of transport of the conveyor is indicated.

[0055] In this example, a sensor, in this example in the form of an infrared camera 10, is arranged for making a recording of a glass product 4.i when the respective glass product 4.i is at the position P. It holds in this example that with the sensor 10 an image is made of a glass product when an axial axis of the respective glass product is at least substantially intersected by an optical axis of the respective sensor. The infrared camera 10 is herein also referred to as (infrared) sensor 10.

[0056] Via line 12 which is connected with the infrared camera 10, a signal of the infrared camera is supplied to a signal processing unit 14. The signal processing unit 14 is connected via a line 16 with a display 18.

[0057] The working of the system according to the invention is as follows. In a step a., glass product material is heated with the heating unit 2. Then, in a step b., with a product forming apparatus the heated and molten liquid glass material (often having the shape of gob then) is formed into a glass product 4.i. In a step c. the glass product is cooled with a cooling apparatus 7.

[0058] The glass product 4.i formed in the product forming apparatus is placed with the aid of the placing unit 5 on the conveyor 6 for transport in the direction 8. Glass product 4.i, as has been mentioned, is produced after glass product 4.i1. The products, in this case, are bottles as shown in FIGS. 4 and 5. The product 4.i is provided with an axial axis A which in this example is vertically directed. If a product 4.i which has been formed arrives at the position P, a recording of the product is made with the camera 10.

[0059] Further, it holds in this example that with the aid of the signal processing unit 14, from the image that is made of the product 4.i with the camera 10, the rotational position R of the glass product on the conveyor around its axial axis relative to, in this example, the viewing direction/optical axis 20 of the camera is determined. This may for instance be carried out by detecting where a marking and/or a seam and/or a dot M of the glass product is. Because a recording thus already comprises information about the rotational position of the glass product that is visible on the recording, it is stated that the rotational position is determined in step d. Because the rotational position is recognized by the signal processing unit from a recording, it may also be said that the rotational position has been determined in step e. The rotational position R may then for instance be an angle R with respect to the viewing direction/optical axis 20 (see FIGS. 1 and 3). When the glass product is manufactured, it may beforehand be provided with a marking such as a dot or a seam. When the glass product is placed with the aid of the placing means 5 on a conveyor, knowledge about the rotational position of the product is lost because during placing the product can turn about its axial axis.

[0060] Thus, therefore, of each product 4.i arriving at the position P an image is made with the camera 10, the information of which is supplied via line 12 to the signal processing unit 14. The signal processing unit determines from the information about the image the rotational position R of the respective product 4.i. Of course, in step d. the rotational position may also be determined in a different way, for instance with a separate sensor whose signals that contain information about the rotational position are supplied to the signal processing unit.

[0061] In FIG. 1, with M.i (i=0.1, 2, 3, . . . ), respectively, the marking of the glass product 4.i (i=1, 2, 3,) is denoted. As can be seen from the markings M.i, the glass products have a random rotational position with respect to the centerline 6 of the conveyor 6 and hence a random rotational position R.i with respect to the viewing direction/optical axis 20. This in contrast to the product forming apparatus 3, in which all products 4.i, as soon as they have been formed, have a same direction of rotation with respect to the centerline 6. This rotational position, however, can change when a product 4.i is placed on the conveyor.

[0062] Due to the products 4.i having a random rotational position Ri on the conveyor 6, the successively made recordings of the products 4.i will show the products in each case from a different viewing direction relative to the marking M.i. If it is assumed that all products are the same, given a sufficient number of recordings, a complete recording in tangential direction of an outer side of the product is available. If the aperture angle of the camera 10 is large enough in vertical direction, the glass product is moreover completely visible in vertical direction. If not, the product is visible in a first area that extends around the product, this area being lower than the height of the product. If there is a fault or a faulty setting present in for instance the glass product forming apparatus, this will typically be present in all glass products 4.i at the same position relative to the marking M.i. By analysing sufficient images of the successively made products 4.i, a fault or deviation can be found in the whole first area (or, if the vertical aperture angle of the camera 10 is sufficiently large, in the whole product). Accordingly, a fully circular image of a virtual product 4 can be constructed from a sufficient number of images of the products 4.i.

[0063] This is further clarified in FIG. 2. In FIG. 2, with camera 10.8 the relative virtual position of the camera 10.8 is indicated with respect to the glass product 4.8 when at the position P an image of the glass product 4.8 is made. Here, in FIG. 2, the position and orientation of the glass product 4.8 has been chosen such that M.8 coincides with a randomly fixedly chosen position M (in this example fixedly chosen to be at twelve o'clock in the drawing). Also, with camera 10.12, the relative virtual position of the camera 10.12 with respect to the glass product 4.12 is indicated, when at the position P an image of the glass product 4.12 is made. Here, in FIG. 2, the relative position of the product 4.12 has again been chosen such that M.12 coincides with the randomly fixedly chosen position M. In FIG. 2, thus, the rotational position of the glass product 4.8 is imaged so as to be coincidental with the rotational position of the product 4.12, such that M.8 coincides with M.12. Looking at the real position of the camera 10 with respect to the glass product 4.12 when the glass product 4.12 is at the position P, the viewing direction/optical axis 20 of the camera 10 and the rotational position of the product 4.12, measured with respect to the marking M.12, include an angle R12 (see FIG. 1). The rotational position of the product 4.12 is indicated in FIG. 1 with the line L12. The line L12 is parallel to the line L12 and indicates the rotational position of the product 4.12 when it would be at the position P. In that position, the rotational position of the product 4.12 with respect to the viewing direction/optical axis 20 of the camera can be indicated with the angle R12. In FIG. 2 the same rotational position R12 is indicated. However, because in FIG. 2 the rotational position of the product 4.12 is imaged so as to be coincidental with the rotational position of the product 4.8 (since M.8 and M.12 coincide in FIG. 2), the virtual position of the camera 10.12 will not coincide with the virtual position of the camera 10.8. In FIG. 2, entirely analogously, for the products 4.7, 4.9, 4.10 and 4.11, the relative positions of the associated cameras 10.7, 10.9, 10.10 and 10.11 are indicated. The images of the virtual cameras 10-7-10-12 in FIG. 2 form in combination an image extending around a virtual product 4. To put it differently, the images of the virtual cameras 10.i are equivalent to images of real cameras which are set up at the positions of virtual cameras in FIG. 2 around a real product which is set up at the position of the virtual product in FIG. 2. It follows, therefore, that a measurement with the virtual sensor 10.i on the virtual product 4 in FIG. 2 is equivalent to a measurement with the real sensor 10 on product 4.i in FIG. 1.

[0064] In FIG. 2 the position of the virtual camera 10.12 has therefore been chosen such that it has the rotational position R.12 with the virtual product 4 with marking M. To put it differently: in FIG. 2 the product 4.12 and the camera 10 have been rotated around the axial axis of the product 4.12 at the position P such that the marking M.12 of the product 4.12 coincides with the marking M.8 of the product 4.8 (which already coincided with M by the above-mentioned rotation of the camera 10 to the virtual camera 10.8), wherein after rotation the position of the camera 10 for product 4.12 is indicated with 10.12 and wherein after rotation the position of the camera 10 for product 4.8 is indicated with 10.8. This has been done in FIG. 2 entirely analogously for the products 4.7, 4.9, 4.10 and 4.11. For instance, entirely analogously, in FIG. 1, the rotational position of the product 4.11 is indicated with the line L11. The line L11 is parallel to the line L11 and indicates the rotational position R.11=0 of the product 4.11 when it would be at the position P. In that position, the rotational position of the product 4.11 with respect to the viewing direction/optical axis 20 of the camera 10 can be indicated with the angle R11. In FIG. 3 the rotational position R.i for the random product 4.i is indicated.

[0065] In this example, it holds that when in each case six images are combined, the virtual product is visible from all sides in the set of images. Of course, it may also be chosen to combine eight images in each case. A first set of eight images that are combined may or may not overlap with a next set of images that are combined. Also, it is conceivable that in each case a variable sufficient number of images are combined that show the virtual product that can be formed from these images as being visible from all sides (that is, the images in combination cover the virtual product completely in circular tangential direction).

[0066] In this example, the camera has an aperture angle in a horizontal plane so that an image that is made with a camera covers the whole product in horizontal direction. This is not requisite, however. In FIG. 3 the aperture angle concerned is indicated with a. However, the aperture angle may also be larger than or smaller than indicated. Viewed in vertical direction, the aperture angle (contained in a vertical plane) of the camera is such that likewise the whole product 4.i is covered (see FIG. 4). However, the angle may also be smaller than or larger than indicated.

[0067] It will be clear that the making of the plurality of images in step d. is carried out between the steps b. and c.

[0068] Each image that is made with an infrared camera 10 is respectively supplied via line 12 to the signal processing unit 14. These signals are processed in combination in a step e., for obtaining at least one parameter that depends on a wall thickness of the glass product.

[0069] As mentioned, the infrared camera applied in step d. is sensitive to infrared light. In particular, the camera 10 is sensitive to infrared light having at least one frequency where the glass product is transparent to the infrared light. Transparent is here understood to mean sufficiently transparent so that an image of the plurality of images both shows a side of the glass product that faces the sensor with which the image has been made and shows a side of the glass product, located opposite the side, that faces away from the sensor with which the image has been made. The camera can thus see through the product, but does see the inner and outer surfaces of the product. This has as a result that in an image that is made with a camera 10, both a side 22 of the glass product that faces the sensor (see FIG. 3) is visible and the side 24, located opposite the side 22, that faces away from the infrared camera 10. For the side 24 is visible to the camera 10 in FIG. 3 because the camera 10 can also see through the side 22. Having regard to the aperture angle , the image obtained with the aid of the camera 10 covers the whole product in the direction Phi (see FIG. 4), but it also holds, of course, that the plurality of images in combination covers a first area of the virtual glass product 4 that extends in tangential direction around an axial axis of the product. This first area, in this example, also covers the whole product seen in vertical direction. The images thus overlap each other in tangential direction T (see FIG. 4) of the product so that different images show a same part of the glass product. In this case, the camera 10 covers the complete product 4.i, both in the axial direction (vertical direction) and in the width direction b (horizontal direction) of the product. In this example, the set of six images are processed in combination for obtaining an image of the virtual product 4. It holds then, accordingly, that in step d. of each glass product of the plurality of glass products the rotational position of the glass product around an axial axis of the glass product relative to the at least one sensor is determined, wherein the images and the associated rotational positions of the plurality of products are processed in combination by the signal processor 14 for obtaining information about a lateral wall thickness distribution around an axial axis of a virtual glass product that represents the plurality of glass products. For, since in the images the product can be seen through, an impression can be obtained about the lateral glass thickness distribution. For instance, an image of the virtual product can be made in transparent view by combining the plurality of images into one image of the product in which a view of the product in transparent view is visible.

[0070] In particular, by the signal processor 14 the signals of the infrared camera 10, that is, the plurality of (in this example, six) successive images that have been made of the products 4.7-4.12 respectively, are processed in combination according to the principle of tomography, for obtaining a lateral glass thickness distribution of the virtual product 4. To this end, the signal processing unit determines the rotational position of the products 4.7-4.12 from the images on the basis of the position of the markings M.i of the products 4.i. Thus, a virtual situation as represented in FIG. 2 can be constructed by the signal processor 14. Because the camera 10 at the virtual positions indicated by cameras 10.7-10.12 makes recordings of the product 4 whereby through choice of the frequency sensitivity of the camera 10 the product is seen through, this allows the principle of tomography to be applied in a manner known per se to reconstruct a 3D image of the virtual product 4. This enables determining of the lateral glass thickness distribution of the product. The lateral glass thickness distribution can be expressed in numbers (for instance, a glass thickness at a particular position of the glass product) or by means of an image (for instance, an image of a view of the virtual glass product in transparent view where the glass thickness is also visible).

[0071] It holds, therefore, that by the signal processing unit the plurality of images with their associated determined orientations are processed in combination according to the principle of tomography for obtaining information about the lateral glass thickness distribution of the virtual glass product. In particular, it holds that the glass thickness distribution indicates relative variations in glass thickness. Also, it is possible that the glass thickness distribution comprises absolute values of the glass thickness distribution. Further, it is possible that the lateral glass thickness distribution is imaged on the display 18 in a 3D picture of the product 4. Also, it is possible that a calibration measurement on a glass product having a known glass thickness is performed, on the basis of which thereupon step e. is carried out. For if the glass thickness is known upon the calibration measurement, the signal processing unit 14 can correct the lateral glass thickness distribution of the product 4. Preferably, it holds that each image of the plurality of images both shows a side of the glass product that faces the sensor with which the image has been made and shows a side of the glass product, located opposite the side, that faces away from the sensor with which the image has been made.

[0072] Also, it holds preferably that in step e.'s processing in combination of the plurality of images according to the principle of tomography for obtaining the lateral glass thickness distribution of the glass of the virtual glass product, of the sensor, solely infrared light is used that relative to the sensor comes from the direction of an axial axis of the respective associated glass product.

[0073] Processing the images in combination according to the principle of tomography may be carried out according to a computation technique which is known by the name of filter back projection, A.R.T. or S.A.R.T. In this way, the lateral glass distribution LGD of the virtual product has been determined as a function of h and phi. The glass distribution LGD (h,phi) can via a line 16 be shown on the display 18, for instance by means of numbers, a graph or an image. LGD is then for instance a number indicating the absolute wall thickness at the position (h,phi). It is also possible, however, that LGD indicates a relative wall thickness with respect to a reference wall thickness at the position (h, phi). Also, the lateral wall thickness may be depicted on the display in a 3D picture of the glass product. This picture then shows, for instance, a view of the glass product in transparent view. In this way, an operator can keep an eye on the glass thickness distribution of the successively produced products 4.i. When the glass thickness distribution starts to deviate, for instance because the wall thickness of the product becomes too large or too small at certain points, an intervention can be made in the production process, that is, an intervention can be made in the method step b. Such an intervention can be performed manually. However, it is also possible for such an intervention to be performed automatically with the aid of the signal processing unit, in this case via a feedback control line 30. It is possible, in case of a deviation of a glass thickness distribution, to correct manually or automatically in the production process of the products. It is also possible, in the case of a change per unit time in glass thickness distributions successively obtained spread in time and the change exceeding a predetermined value, to correct or control manually or automatically under control of the signal processing unit via line 30. Correcting or controlling may for instance be understood to mean adjusting a position and/or orientation of a trough and/or mould, providing a trough with a lubricant and/or replacing a mould. All this is schematically indicated in FIG. 1.

[0074] It is noted that the aperture angle of the camera 10 may also be smaller so that it has a value of for instance (see FIG. 4). In that case, with the camera 10 a first area 26.1 is covered, the LGD of which is determined with the signal processing unit. In that case, using a second camera 10 which is also provided with an aperture angle and which is at a greater height h than the camera 10 and whose output signals are also supplied to the signal processing unit (not shown in the drawing), a lateral glass thickness distribution of the second area 26.2 that extends around the product 4 can be determined with the signal processing unit (see FIG. 4). The second area 26.2 is staggered in axial direction with respect to the area 26.1. Also, entirely analogously, it is possible that using a third camera (not shown) the lateral glass thickness distribution of an area 26.3 is determined. The areas 26.1, 26.2 and 26.3 then, for instance, adjoin each other. Accordingly, it holds for the areas 26.1 and 26.2 that steps d. and e. are carried out repeatedly for obtaining a lateral glass distribution LGD in a second area of the glass product that extends around an axial axis of the product, with the first and second area being staggered relative to each other in the axial direction.

[0075] In particular, it holds for the areas 26.1 to 26.3 that the steps d. and e., respectively, are carried out repeatedly at least three times for respectively obtaining lateral glass thickness distributions in respectively at least three mutually different areas which each extend around the axial axis and are staggered with respect to each other in axial direction and which preferably in combination cover, at least substantially, the whole glass product 4.

[0076] Preferably, however, it holds that the aperture angle in vertical direction is so large that the respective area in which the glass thickness distribution is determined extends throughout the height of the product 4.i in the direction h. Further, it holds in this example that the aperture angle of the camera 10 is such that each image shows the product, seen in its horizontal direction b, completely. However, the aperture angle may also be smaller or larger than shown. The images according to FIG. 2 will, seen in horizontal direction, overlap each other partly so that different images show a same part of the product 4. This is a minimal condition to be able to make use of the principle of tomography.

[0077] In this example, it holds that the infrared cameras are sensitive to light in the spectrum for which the glass is transparent, more particularly that each camera is sensitive to light having a bandwidth of 900 nm-3500 nm, still more particularly that the sensor is sensitive to light having a bandwidth of 900 nm-1900 nm.

[0078] If a trend in a deviation of successively determined lateral glass thickness distributions is determined, it may for instance be inferred that a particular part, such as a mould, is wearing.

[0079] The invention is not in any way limited to the embodiments outlined above. For instance, it is also possible that the camera 10 has an aperture angle while the camera 10, after making an image for obtaining a glass thickness distribution in the area 26.1, is moved up in axial direction for obtaining an image in order to obtain a glass thickness distribution in the area 26.2. After this, the camera may further be moved down for making an image of the area 26.3, etc. Further, it is clear that the camera 10 and the signal processing unit 14 can also be used in other production processes for forming glass products than described here. In fact, the camera in combination with the signal processing unit 14 constitutes an essential part of the invention. According to the invention, also, the cooling apparatus 7 could be omitted, since also without the cooling apparatus 7 the products will eventually cool down by themselves so that step c. may also be carried out without extra aids. Also, the cooling apparatus may, whether manually or automatically, be controlled (for example, the temperature of the cooling apparatus) on the basis of the determined LGD.

[0080] In particular, it holds that the infrared camera is a so-called high-speed infrared camera. However, other infrared cameras are also possible. In this example, a virtual product 4 has been constructed from recordings of the products 4.7-4.12. After this, for instance on the basis of the products 4.13-4.18 a next virtual product 4 may be constructed whose glass thickness distribution is determined entirely analogously to what has been discussed hereinabove for the products 4.7-4.12. More generally, from m recordings of the products 4.1+k with k=0, 1, 2, 3, . . . m1, the glass thickness distribution of a virtual product can be obtained. Next, from m recordings of the products 4.1+m+k with k=0, 1, 2, 3, . . . m1 a glass thickness distribution of a virtual product can be obtained. After this, from m recordings of the products 4.1+2m+k with k=0, 1, 2, 3, . . . m1 a glass thickness distribution of a virtual product can be obtained and then from m recordings of the products 4.1+3m+k with k=0, 1, 2, 3, . . . m1 a glass thickness distribution of a virtual product can be obtained. This can be continued so that after each m recordings a glass thickness distribution of a virtual product is determined. This brings with it that changes of the glass thickness distribution in time can be observed. This makes it possible to detect changes in the glass thickness distribution of successively determined virtual products as a result of for instance wear in troughs and the mould or changes in the glass thickness distribution of successive virtual products as a result of drifting settings of the trough and/or mould. When such a change exceeds a limiting value, automatically or manually the production flow may be controlled (as by setting a position and/or orientation of a trough and/or mould, supplying a lubricant to a trough, replacing a mould, etc.).

[0081] It is also possible that m is variable. In that case, the signal processing unit is configured to select a sufficient number of successive recordings in order that the virtual cameras associated with these recordings cover the associated virtual product completely around the axial axis of the virtual product. The signal processing unit then decides automatically which and how many recordings in each case are processed in combination for computing a glass thickness distribution of a virtual product.

[0082] In an alternative embodiment, it is for instance possible that six products are formed parallel to each other in six parallel production flows. To this end, the system, in this example the product forming apparatus 3, includes six production flow paths 106.j which, for instance, each comprise at least one trough and a mould. This is shown in FIG. 6 in which a glass gob formed in the heating apparatus 2 is guided via a switch 100 to a production flow path 106.j (j=1, 2, 3, . . . 6) selected with the switch, each production flow path 106.j comprising at least one trough 102.j and a mould 104.j. The glass gobs that are successively transported along the production flow path 106.j together form a production flow 107.j. By rotation of the switch in the direction of arrows 110 around an axis (pivot) 108, other production flow paths 106.j can be selected with the switch. The glass gob flows, in this example, via the selected at least one trough 102.j to the mould 104.j. In this example, for j, successively the value 1, 2, 3, 4, 5, 6 is selected by the switch 100. In this example, then, there are six parallel production flows.

[0083] Because there are six production flows, in succession six products 4.1, 4.2, 4.3, . . . 4.6 are formed which are placed in a row of six products on the conveyor. Here, product 4.1 has been formed from a glass gob which has been transported via production flow path 106.1 in production flow 107.1, product 4.2 has been formed from a glass gob which has been transported via production flow path 106.2 in production flow 107.2, product 4.3 has been formed from a glass gob which has been transported via production flow path 106.3 in production flow 107.3, etc. More generally, product 4.j has been formed from a glass gob which has been transported via production flow path 106.j in production flow 107.j, for j=1, 2, 3, 4, 5, 6. When thus six products have been produced, this process repeats itself.

[0084] Here, product 4.7 is formed from a glass gob which has been transported via production flow path 106.1 in production flow 107.1, product 4.8 is formed from a glass gob which has been transported via production flow path 106.2 in production flow 107.2, product 4.9 is formed from a glass gob which has been transported via production flow path 106.3 in production flow 107.3, etc. More generally, product 4.j+6 has been formed from a glass gob which has been transported via production flow path 106.j in production flow 107.j, for j=1, 2, 3, 4, 5, 6. When thus six products have been produced, this process repeats itself. Generally, therefore, it holds that product 4.j+n.6 with n=0, 1, 2, 3, . . . has been formed from a glass gob which has been transported via production flow path 106.j in production flow 107.j for j=1, 2, 3, 4, 5, 6.

[0085] The products 4.j, 4.j+6, 4.j+12, . . . 4.j+n.6 have then been made in a same production flow j, where j=1, 2, 3, 4, 5, 6 and n=0, 1, 2, 3, 4, According to this variant, a number of successive recordings of products 4.j+n.6 for different values of n and a same value of j (and which thus belong to a same production flow j) are processed in combination with the signal processing unit for obtaining a glass thickness distribution of a virtual glass product. This number may for instance be eight. Thus, for a value of j, recordings of the products for n=0, 1, 2, . . . 7 can be combined for obtaining a glass thickness distribution of a virtual product 4. Next, for the same value of j, recordings of the products for n=8, 9, 10, . . . 15 can be processed in combination with the signal processing unit for obtaining a glass thickness distribution of another virtual product 4, etc. These recordings are obtained spread in time, and have been obtained of products that have been produced with the aid of the production flow path 106.j in the production flow 107.j. This makes it possible to detect changes in the glass thickness distribution of successive virtual products as a result of for instance wear in the at least one trough and/or mould of production flow path 106.j or changes in the glass thickness distribution of successive virtual products as a result of drifting settings in production flow path 106.j. When such a change exceeds a limiting value, automatically or manually settings of production flow path 106.j can be changed (such as a position and/or orientation of a trough and/or mould of the respective production flow path), a trough of production flow path 106.j can be lubricated, a mould of production flow path 106.j can be replaced, etc. It is thus possible, in case of a change in glass thickness distributions successively obtained spread in time and the change exceeding a predetermined value, to correct manually or automatically under control of the signal processing unit via line 30. It is also possible, in case of a deviation in a single glass thickness distribution and the deviation exceeding a predetermined value, to correct manually or automatically under control of the signal processing unit via line 30. Correcting may for instance be understood to mean adjusting a position and/or orientation of a trough and/or mould, providing a trough with a lubricant and/or replacing a mould.

[0086] All this can also be carried out for all other possible values of j so that glass thickness distributions are obtained for different virtual glass products relating to different production flow paths 106.j and hence to different production flows 107.j. If there is a deviation in a glass thickness distribution of a virtual product 4 that has been obtained from a production flow j, for instance the position of a trough and a mould belonging to the production flow path j may be corrected with respect to each other, or a trough belonging to the production flow path j may be provided with a lubricant. Also, a mould of the production flow path j. may be replaced. All of this may be carried out manually or automatically via line 30 under control of the signal processing unit. Also, changes in glass thickness distributions of virtual products that have successively been obtained with the aid of a same production flow path 106.j can be detected by the signal processing unit. If these changes exceed a predetermined value, again, as discussed above, settings of the respective production flow path 106.j may be adjusted, a trough of the respective production flow path 106.j may be lubricated and/or a mould of the respective production flow path may be replaced, manually or automatically.

[0087] In this example, in each case, eight images of products which have been obtained from a same production flow j were processed in combination for obtaining information about the glass thickness distribution of a virtual product. Instead of using in each case a=8 images, the signal processing unit may also be configured to choose a to be variable, for instance such that a sufficient number of successive recordings are selected in order for the virtual cameras associated with these recordings to cover the associated virtual product completely around the axial axis of the virtual product. The signal processing unit then decides automatically which and how many recordings in each case are processed in combination for computing a glass thickness distribution of a virtual product associated with a particular production flow path j. Accordingly, it holds in particular that a plurality of the steps b. are carried out parallel to each other for producing parallel to each other a plurality of the products in a plurality of production flows which each comprise a step b., wherein each glass thickness distribution of a virtual product has been obtained on the basis of recordings of products that have been manufactured in a same production flow, more particularly wherein on the basis of at least one determined glass thickness distribution of a virtual product that has been obtained from recordings of products that stem from a same production flow, in an automatic manner the production flow is controlled, as by adjusting settings of that production flow.

[0088] Further, it holds thus, in particular, that the system is configured such that, in use, a plurality of the steps b. are carried out parallel to each other for producing parallel to each other a plurality of the products in a plurality of production flows which each comprise a step b., wherein the signal processing unit is configured such that, in use, each glass thickness distribution of a virtual product is obtained on the basis of recordings of products that have been manufactured in a same production flow, more particularly wherein on the basis of at least one determined glass thickness distribution of at least one virtual product that has been obtained from recordings of products that stem from a same production flow, in an automatic manner the production flow is controlled, as by adjusting settings of that production flow.

[0089] Finally, it is noted that automatic control loops via line 30 can comprise the adjusting, on the basis of a determined glass thickness distribution, of: [0090] Feeder temperature and temperature distribution [0091] Gob temperature distribution [0092] Gob forming process [0093] Gob loading process [0094] Mould cooling and residence time in the mould [0095] Design of the parison and the preform moulds [0096] Blowout process (B&B process) [0097] Plunger press process (NNPB, PB process) [0098] Plunger cooling process [0099] Blowout process at the front [0100] Shape and design of the blowing pipe [0101] Optimal lubricating method and lubricant moulds [0102] Optimal standing time determination of the moulds [0103] Optimal timing setting of the I.S. machine (glass forming machine) [0104] Optimal temperature settings of moulds and automatic control thereof [0105] Optimal air pressure control of product blowout [0106] Optimal air pressure control for making the parison [0107] Active reheating for an optimal temperature distribution of the glass gobs for an optimal LGD

[0108] Such variants each fall within the scope of the invention.