Technical Field

The present invention relates to an apparatus for control of an article, preferably a wooden article, said appa- ratus comprising a conveyor with measuring and control devices for control measuring of the article and a grad¬ ing device adapted to remove discarded articles.

Background Art

When manufacturing wooden articles, such as ice lollies and chopsticks it is essential to remove defective articles no matter whether the defect is due to the stick being loopsided, having knots, having the wrong dimensions or being discoloured.

The object of the present invention is to provide an appa- ratus which at a great speed, corresponding to the speed of manufacture of the article in question can perform an effective control so that the approved manufactured goods are usable and appear uniform and preferably appetizing.

According to the invention the apparatus of the above stated type is characterised by the control devices com¬ prising at least one first set of optical fibres situated opposite to each other on each side of the conveyor and at a predetermined height whereby the optical fibres on one side are adapted to emit a light ray along and parallel with the surface of the article, and whereby the optical fibres on the other side are adapted to receive the emitted light ray the latter fibres being connected to a light sensitive detector adapted to provide a signal to a micro¬ processor, at least one second set of optical fibres placed at mutually different heights close to the upper edge of a reflective plate member being elevationally slidable in

response to the thickness (height) of the article, said optical fibres being adapted to emit and recieve an op¬ tionally reflected light ray, whereby the mutual, eleva¬ tional location of said optical fibres is arranged so that an article being too high causes a reflection of more than a predetermined number of the second set of optical fibres, and an article being too low causes a reflection of less than a predetermined number of the light-rays emitted from the second set of optical fibres and whereby the optical fibres of the second set of optical fibres are connected to light sensitive detectors adapted to receive the reflected light rays and depending thereon to provide signals to the microprocessor, one or more screen scanning camera(s) mounted so that the conveyor and a number of articles thereon can be scanned from above and/or from below, and devices for activating the screen scanning camera in response to the speed of the conveyor and preferably each time an article passes, said screen scanning camera being adapted to provide electric signals, representing one or more pictures of the scanned area, said picture signals being transferred to the micropro¬ cessor which is adapted to process and evaluate the picture signals in order to determine width, curvature in the horizontal plane and length of each article and to com- pare these quantities with predetermined values and based on this comparison to decide whether or not the article is to be discarded and to provide corresponding impulses to the grading device.

In this way an unusually fast and effective grading of the articles is achieved. The first set of optical fibres grades articles curving in the perpendicular plane as such curvatures cause the article to block a light ray which can only pass if the article is linear and not too thick. The second set of optical fibres grades articles which are to high or too low, and such a second set of optical fibres is preferably placed on each side of the

conveyor so that both ends of the article are measured. By means of the camera and the associated microprocessor all dimensions in the horizontal plane can be controlled. By means of the suggested apparatus a very fast control in all three dimensions of a spatial article is achieved. The apparatus is particularly suitable for flat, oblong ar¬ ticles, such as ice lollies and chopsticks.

The width is preferably determined locally at intervals along the article and the article is preferably divided into a number of transverse sections and an average width for each section can be determined. The curvature is pre¬ ferably measured in the horizontal plane as an aberration from a predetermined straight line. By the described appa¬ ratus it is possible to control the colour of the article. According to the invention, the microprocessor is adapted to determine the total colour level of the article by summing up the light intensity over the entire article.

Local colour variations can advantageously be determined by summing up the light intensity in a number of limited areas and determining optional variations.

Small local areas having a particularly low light intensity are preferably registered. In this way it is possible to ascertain whether or not the article is knotty. According to the invention predetermined acceptable values can be recorded in the microprocessor in order to compare these with the data achieved by control of the articles. Such data are preferably recorded in the microprocessor during a learning phase by sending a number of first-grading- articles through the apparatus which then measures and registers the characteristics of the articles. Such learn¬ ing-articles are to be selected so that they only just fulfil the wanted margins as these articles define these margins to the microprocessor. Preferably the apparatus is adapted to receive an alternative set of margin-values

corresponding to a second-grading of the articles. Brief Description of the Drawing

The invention is explained in the following with reference to the accompanying drawing, in which

Fig. 1 shows an example of an embodiment of an inventive apparatus ,

Fig. 2 is a block diagram corresponding to the apparatus of Fig. 1,

Fig. 3 is a section of the apparatus of Fig. 1 on a larger scale and without shielding,

Fig. 4 is a first screen picture,

Fig. 5 is a second screen picture,

Fig. 6 is an example of measurement of local width,

Fig. 7 is an example of measurement of an average width,

Fig. 8 is an example of measurement of curvature,

Fig. 9 is an example of measurement of length,

Figs. 10, 11 and 12 are examples of different shades of the article.

Description of the Preferred Embodiments of the Invention

A example of an embodiment of an apparatus according to the invention is shown in Figs. 1 and 2. On a chain con¬ veyor 15 a number of oblong articles 17 are advanced and in the present case each article consists of two chopsticks sticking together at their thick ends. In the first control

station 16, the articles are evaluated with respect to curvature and thickness (height) in the vertical direction.

In the first half 16a. of the control station, see Fig. 3, the article just passes below a light ray if it is rec- tilinear and not too high, said light ray being emitted from an optical fibre 18 and passing across the conveyor belt along the surface of the article to a receiving op¬ tical fibre 19 on the other side of the conveyor. If the article curves too much or is too high, this light ray is blocked. Such blocking is detected by an appropriate light sensitive circuit which may be of known art, and infor¬ mation on the approval or disapproval of the article is sent to a microprocessor 13.

The control station comprises preferably two such curvature controls 18, 18' , 19, 19' , of which one is adjusted to approve of first-grading articles whereas the second is adjusted to approve of second-grading articles.

In the last half of the control station 16 a thickness control 16b, is provided, which is also shown in greater detail in Fig. 3. By the chain conveyor the article is guided in between two pairs of rollers 20, 21 mounted on each side, and of which the lower rollers are fixed whereas the upper rollers are pressed upwards by the article to a level depending on the thickness of the article; for the sake of lucidity only one pair of rollers has been shown. The upper roller is mounted on a perpendicularly displac- able plate or wing 22 which is pulled downwards towards the article by a spring 35. The upper edge of the plate can be made covering a number of optical fibres 26 connected to optoreflectors which partly emit a light ray and partly register whether or not this light ray is reflected. If the article is much too thick, the plate is lifted so high that the shiny plate covers all optical fibres and thus reflects all the rays of light. The reflection is register-

ed by light sensitive detectors and information is trans¬ ferred to the microprocessor 13. Preferably four measuring points are used, i.e. preferable four optical fibres 26 are mounted, the fibre ends facing the reflective plate 5 face close to the upper edge of the plate, yet at sligthly different heights so that a first-grading article causes the reflective plate to cover two of the optical fibres and let the two other radiate freely whereas a second- grading article being a little too thick causes the re- lOJ.flective plate to cover three optical fibres and let one radiate freely, and a second- rading article being a little too thin causes the reflective plate to cover only one optical fibre and let the three others radiate freely. In the preferred embodiment, the perpendicular positions of

]_5 the optical fibres 26 are adjustable from above by means of adjusting screws 31.

When the article has passed the control station 16, the chain conveyor continues under a camera 11 scanning the chain conveyor and the articles thereon. Two lamps 12

20 illuminate the articles concurrently with the scanning. The camera 11 is a screen scanning camera and the picture information registered is transferred optionally to a not shown data screen and, particularly to a computer comparing and evaluating the picture information with predetermined

25 data and based on this comparison providing impulses to the grading devices 41, 42, of which 41 takes care of removing all articles to be totally discarded whereas the device 42 grades second-grading sticks so that only first- grading sticks continue on the conveyor for further proces-

30 sing.

The impulses to the grading device 41, 42 are provided by the microprocessor with such a time delay that the article having been measured by the control station, reaches the grading station together with its corresponding grading 35 impulse. Such a time delay can be provided e.g. in con-

nection with the dataprocessing in the microprocessor by storing the grading bits, 0 or 1 in a shift register with one location for each article-point on the conveyor from the first measuring point of the control station to the 5 grading station so that the location for the grading bit in question in the shift register is shifted simultaneously with the moving of the article on the conveyor and so that the microprocessor after a check calculation places the result on the correct location in the shift register 0 and so that the article in question has just reached the grading station at the same time as the corresponding grading bit reaches an output from the shift register.

The camera 11 scans the conveyor with articles, c.f. Fig. 4. The microprocessor 13 evaluates the pictures one by 5 one and if a data screen 14 is connected, the control may be followed on a screen picture as shown in Fig. 4. In said Fig. , the article to be controlled is framed in a frame 44. On basis of the picture the geometric measure¬ ments shown in Figs. 6 - 9 are performed. Each measurment o is compared to predetermined, desired previously stored data and if it turns out that the article does not ful¬ fill the allowable tolerances, an impulse is provided to the subsequent grading device preferably the latter grading device comprising a blow nozzle. In the apparatus of Fig. 5 1 said nozzle being arranged to blow the discarded article away from the conveyor. As appears from Fig. 4 the appara¬ tus is adapted to be able to control sticks oriented in both directions.

Preferably the microprocessor is adapted to initially 0 control whether or not the articles fulfil a set of second- grading tolerance values which are manually adjustable by means of thumb wheels 51 of Fig. 1 and if they do not, to store and later to give an impulse to a first blow nozzle mounted at the first grading station 41 grading discarded 5 articles. If the article falls within said tolerance zone,

the microprocessor evaluates whether the articles fulfils the tolerances given by the first-grading articles, and if this is not the case, an impulse is stored and given to a second blow nozzle 42 in a subsequent grading station thus removing second-grading articles from the conveyor.

As shown in Fig. 4, the camera has been turned a few de¬ grees, e.g. 5*, in relation to the articles so that the scanning lines of the camera do not merge with the longi¬ tudinal limits of the article.

As appears from Figs. 6 - 9, the microprocessor performs a number of calculations on the geometry of the article. In accordance with specified tolerances demands are made on correct width, which is measured at intervals of about 3 mm, and correct average width, whereby the calculations are performed by dividing the article into a number of transverse sections, preferably six, and whereby each section must show a correct average width. Furthermore the curvature of the article is determined as the article is supposed to be limited by straight lines. Also the ength is determined, preferably by measurements on each side of the separation line for separating the article into two chopsticks.

Apart from the geometry it is also desirable that the article presents itself with a uniform colour effect so that discoloured sticks and sticks with knots are discard¬ ed. This is achieved by measuring and summing up the light intensity over the entire picture of the stick and compar¬ ing the result with a prede ermined value. Local colour variations which may be due to local discolourings can be determined by measuring changes in the light intensity in small limited areas. The circuits can advantageously be adapted to divide the article into small sections and summing up the light intensity for the individual sections and then making a comparison.

Finally knots can be registered by examining whether small areas having a particularly low light intensity exist as knots are normally dark and therefore reflect less light.

The predetermined values - which constitute the standard of comparison when the microprocessor is to evaluate whet¬ her or not the registered measurings are to be approved of - are provided preferably in the form of a learning phase comprising that the apparatus and thus the micro¬ processor is set to a learning condition whereafter a number of first grading articles, of varying quality, some of which are almost second grading, are conveyed through the apparatus and measured and scanned as explained above. The articles chosen for the learning define the limits between first and second grading and the articles chosen for the learning should therefore comprise all variants allowable among the first-grading articles. During learn¬ ing, the apparatus measures and registers all the above parameters for width, length, curvature in the horizontal plane and total colour and colour variations.

The set of tolerances for second-grading articles set by means of the thumb wheels 51 comprises preferably the fol¬ lowing: a) the point by point measurements of the average width, b) the curvature in the horizontal plane, c) the length, and d) colour level, colour variation and knots.

In a preferred embodiment the microprocessor is adapted to show how many articles have been discarded and why after the control of a production series and this may e.g. be done by means of a screen picture as shown in Fig. 5.

Preferably the microprocessor is adapted to determine an " idling" -colour level and a light intensity in between the articles, ie. adapted to measure in the gaps between the

articles. Such a measuring is used to correct for varia¬ tions in the luminous intensity of the lamps, e.g. because of the ageing of the bulbs, and a control circuit is pro¬ vided which indicates when a bulb is to be replaced by lighting a warning lamp.

The apparatus described allows a very fast grading of articles on basis of a large number of complex measurings and thus ensures a suitable quality of the approved ar¬ ticles .

The programming of the microprocessor is not be described more closely as it may be done by a person skilled in the art in numerous ways .