Patent GB-1010766-A (GB)
Title: Process and apparatus for the colorimetric sorting of ground and wall covering elements
IPC: G01J3/51
Filed: 1962-07-05
Abstract: 1,010,766. Colorimeters. SOC: FRANCAISE DE CERAMIQUE CENTRE NATIONAL D'ETUDES ET RECHERCHES CERAMIQUES. July 5, 1962 [July 7, 1961], No. 25762/62. Heading G2J. [Also in Division G1] A process for sorting objects such as ceramic tiles according to colour comprises illuminating each object with a diffused light, separating the reflected light rays into two beams, each directed beam through a different one of two filters of different colours, comparing the intensities of said beams as transmitted by said filters and classifying the object in accordance with this comparison. In the embodiment a sample ceramic tile E and a reference element T are illuminated by diffused white light from an Ulbricht sphere S. Reflected light from the tile E is received by lenses 23, 24, contained in a T-shaped mount M having in its horizontal arms a double total reflection prism 25 which separates the rays from the lenses 23, 24 into two opposite beams which are respectively directed through adjustable diaphragms 26, 27 to photo-electric cells C 1  and C 2  through exchangeable filters F 1 , F 2  carried in wheels 32, 33. Reflected light from the reference element T is similarly directed through lenses 44, 45 and an adjustable diaphragm 46 carried in a mount M 1 , through similar exchangeable F 3  mounted in a wheel 47, to a photo-electric cell C 3 . Initially, a tile E of the desired hue is placed beneath the opening 20 and filters F 1  and F 3  of identical colour are placed in front of the cells C 1  and C 3  by rotating the wheels 32 and 47 respectively to the appropriate position. The cells C 1 , C 3  are connected in opposition by a switch 105 (see Fig. 3), in a bridge circuit the out of balance current of which is connected through a reversing switch 110 to a mirror galvanometer G. Light from a projector P shines on the mirror which directs it to a graduated scale 60 or to a retractable mirror 65 where it is reflected to a photoresistive cell photo-electric C 4  connected in the grid circuit of a tetrode thyratron 116. The diaphragm 26 is adjusted until the light intensities received by the cells C 1  and C 3  are equal and the beam from the galvanometer mirror impinging on the scale 60 indicates balance. The procedure is repeated with cells C 2  and C 3  but using filters F 2  and F 3  on the wheels 33 and 47 identical to each other but having mean wavelengths of their transmission bands as remote as possible from those of the filters used when the cells C 1  and C 3  were used as described above. After balance of the bridge circuit is obtained with cells C 2  and C 3 , the cells C 1  and C 2  are connected in opposition a tile for test is placed beneath the opening 20 and the mirror 65 is moved into the light beam from the galvanometer mirror as shown in Fig. 3. If the tile E is not of the same hue as the initial sample then the bridge becomes unbalanced and the beam from the galvanometer is deflected on to the cell C 4  whose resistance drops and thus causes the coil 118 of a relay connected to the thyratron 116 to become de-energized. The contact arm 120 of the relay, then closes and energizes the coil 122 of an ejector mechanism J which then ejects the unsatisfactory tile E. If the tile E is of the correct hue and the bridge circuit is correspondingly balanced, the cell C 4  is not illuminated and the thyratron keeps the coil 118 energized thus preventing ejection of the tile. If desired the mirror 65 may be retracted and selection of the tiles may be then carried out manually by observation of the deflection of the light beam striking the scale 60.