Patent GB-469458-A (GB)
Title: Improvements in apparatus for detecting the presence of foreign bodies in or on transparent vessels
IPC: G01N33/00
Filed: 1936-01-25
Abstract: 469,458. Photo-electric apparatus for examining milk bottles etc.; valve relay circuits. STOATE, N. P., and ROBINSON, W. A. Jan. 25, 1936, No. 2411. [Classes 40 (iii) and 40 (v)] Relates to apparatus of the kind described in Specification 425,602, for examining transparent vessels, such as milk bottles, for detecting the presence of foreign bodies on the bottoms of such vessels. According to the invention, each vessel is rotated about its longitudinal axis when on a support having a narrow slit beneath which a light-sensitive device is disposed, light being so directed as to pass through the bottom of the vessel on to the slit, so that a signal or indication is given by means under the control of the lightsensitive device when the light is intercepted by a foreign body. The indication may be given by the automatic separation of a defective bottle from the others, but instead of or in addition to this operation, a visible or audible signal may be given. The machine shown comprises a motor-driven casing 4 having a head 5 with platforms 6, each adapted to receive a milk bottle fed thereto by a conveyer band 7. The head 5 is divided into chambers, each containing a lamp 10 from which light passes through an aperture 11, the bottle B and a slit 12 in the platform on which the bottle is supported. Below each platform 6 is a chamber containing a photo-electric cell 14 and a mirror 13, the casing 4 having compartments each containing an amplifier 17 to which the appropriate photo-cell is connected. The bottles are rotated about their own axes by contact with a fixed rail 23, as they are carried round by the head 5, and as each slit is located so that it is substantially radial to the bottle placed over it, (or preferably displaced slightly to one side of a radius) the whole of the bottom of the vessel is scanned by the light-beam. If an opaque particle on the glass bottom intercepts the beam, the consequent effect on the cell increases the current through the amplifier. This causes a relay to give a signal, or to operate means which diverts the bottle from the conveyer band 7 after it has been passed back thereto from the rotating head 5. Each bottle after being carried round by the head 5 is pushed on to the band 7 by a rotating finger piece 29, mounted on a shaft 30 which is driven by gearing from the casing 4. To divert each bottle in which a particle has been detected, a guide 36 is provided on a shaft 37 which is normally latched in an inoperative position, but which is pulled by a spring into position to intercept a bottle on the band 7, and to guide it on to a receiving platform, when a magnet (not shown) is energized. This occurs when contacts 35 are closed by a contact 28 on a trip rod 27, one such rod being associated with each photo-electric cell, and being normally held up by a magnet 25. When the energization of one of these magnets is effected by a relay through the action of the associated cell, as described above, the rod 27 drops and rests on a ring 34 on which it is supported until it has closed the contacts 35. A ramp 39 resets the trip rod. Means are provided for preventing the ejecting device 36 from being set in the operative position as the result of the effect on the light-beam of the walls of a bottle as it passes off a platform 6. A common form of amplifier circuit for use with battery supply is given. Fig. 7 shows a preferred circuit for use with A.C. supplied from the mains. The centre-tapped secondary winding 61, 62 of a mains transformer has potentiometers 66, 67 across it, the slider of 66 being connected through a resistance 68 to the anode of an amplifying valve 70, and that of 67 being connected to the anode 72 of a photo-electric cell. The anode of the valve 70 is connected to the grid 73 of a gas-filled relay 65, in the anode circuit of which is the switching magnet 25. With correct settings of the potentiometers for a given light intensity on the cell, no current flows through the magnet 25, but on reduction of the light below a predetermined value, the magnet 25 becomes energized.