Patent GB-586935-A (GB)
Title: Improvements in or relating to apparatus for detecting the presence of foreign bodies in transparent vessels
IPC: G01N33/00
Filed: 1944-09-19
Abstract: 586,935. Photo - electric apparatus for examining transparent vessels. UNITED DAIRIES, Ltd., and STOATE, N. P.. Sept. 19, 1944, No. 17880. [Class 40 (iii)] In apparatus for scanning the bottom of a transparent vessel to detect foreign bodies, e.g. dust, thereon by means of a light directed longitudinally through the mouth and bottom of the vessel onto a light-sensitive device and in which the vessel is rotated about its longitudinal axis relatively to a screen disposed between a source of light and the light-sensitive device the screen is formed with a number of apertures having an area small in relation to that of the bottom of the vessel and located at different radial distances from the centre of the bottom of the vessel when the latter is in scanning position and the apertures being spaced closer together radially in regions in which detection of smaller particles is required than in regions where larger particles are to be detected. When the bottom of the vessel has a concave inner surface the apertures are more closed spaced near the centre. The size of the apertures or the sensitivity of the associated ligh-sensitive device may be adjusted according to the light transmission value of the vessel bottom from its centre to its periphery due to its concave or convex shape. As shown, milk bottles are fed from a belt 7 on to platforms 6 formed in the head 5 of a casing 4 rotated by a motor 19. Each platform 6 has apertures 11 which are unequally spaced in a radial direction and forms the screen between a lamp 10 and the photo-electric cell 13 associated with the apertures 11. and secured to the wall of a compartment 12 formed in the casing 4. The bottles are rotated about their axes by engagement with a flexible inelastic band 24 anchored at 23a, 23b and having an inner layer 24a of rubber as described in Specification 586,938. Bottles. having no obstructing particles are removed from the rotatable head by a rotating arm 34 driven at a speed slightly greater than that of the platform. Each cell 13 is connected to an associated amplifier 27,mounted within a compartment of the casing and a decrease of the light on any cell 13 energizes a relay which releases a magnet 30 carrying a trip arm 31 having a disc 33 which bridges contacts 32 on a fixed ring 40 secured to standard 39 on the base plate 3. An electro-magnet connected to the contacts 32 releases an arm 41 which directs the faulty bottle off the belt 7. A guard plate 43 suitably located relative to the contacts 32 prevents the disc 33 from dropping if the magnet is released by diminution of the transmittted light as a bottle is moved from its platform. The disc 33 is restored to its upper position after passing contacts 32 by a ramp 44, and if the illumination through the apertures 11 is insufficient to prevent reoperation of the relay of the amplifier, a fixed lamp 95 is utilised to provide temporaryadditional illumination of the platforms and the associated cells as described in Specification 586,939. An arrangement to compensate for any sustained fluctuation in the voltage supply to the lamps 10 comprises a composite screen with light and dark sections 70, 71 which respectively transmit light to the cells corresponding to a vessel bottom without obstruction and to the obstruction of one of the apertures. A four-armed spider 77, Fig. 6, secured to the trip rod 31 by a sleeve 75 may engage fixed studs 85, 86 in its upper- and lower positions, the lower stud 85 lying between the screens 70, 71 and the upper stud being located beyond the darker screens. A Worm 78 splined to the sleeve 75 meshes with a wheel 79 secured to a spindle 80 carrying an arm 81 of a rheostat 82 controlling the voltage of the lamps '10. If the voltage is too low the magnet 30 is deenergized, the spider drops so that its arms engage the lower stud 85 and the sleeve is rotated to increase the voltage. When the voltage is too high, the magnet 30 and spider - are not released when light passes through the darker screen and the arms of the spider 'engage the upper stud 86 so that the worm gearing is rotated in a direction to effect a reduction of the voltage. An additional ramp 90 is provided to reset to its upper position any spider 77 which may have descended through detection of a particle before the platform reaches the lighter screen 70. In a modification, the lighter screen 70 and stud 80 may be omitted with the result that no automatic compensation is effected and over sensitivity will reject all bottles thereby indicating that the voltage requires adjustment. As shown in Fig. 8 the apertures 116 are not located on a radial line relatively to the bottom of the vessel and the more closely spaced outer apertures may merge into a single aperture 11d. Specification 586,936 also is referred to.