GB517229A - Improvements in or relating to apparatus for detecting the presence of foreign bodies on the bottoms of transparent vessels - Google Patents

Abstract

517,229. Photo-electric examination of transparent vessels. STOATE, N. P. July 22, 1938. No. 21808. [Class 40 (iii)] An apparatus for detecting the presence of a foreign body on the bottom of a transparent vessel comprises in combination means for scanning the bottom of the vessel by means of light passing longitudinally through the mouth of the vessel and through the bottom thereof on to a light-sensitive device in such a way that the light does not pass through the walls of the vessel, and means for giving an indication when the light falling on the light-sensitive device is reduced below a predetermined value. The light source may be at either end of the vessel and the light-sensitive device at the other end ; and this scanning device may be adjacent the light source or the light-sensitive device. Reference is made to Specifications 425,602. and 469,458, for other forms of photo-electric apparatus for the examination of transparent vessels. In the apparatus shown, bottles are fed by a conveyer to a slot in the circumference of a dial plate 2 rotated in steps of a quarter of a revolution by a shaft 40 driven by a Maltese cross mechanism 44, 47, 51 from a counter shaft 48 driven continuously by a sprocket wheel 52 connected by a chain to a suitable power source. The first step of the rotation of the dial plate 2 brings the bottle B1, Fig. 1, over an aperture 3 in a top plate 4. There, the scanning operation takes place. The second step takes the bottle to the discharge conveyer 39, Fig. 5. Scanning.-The scanning of the base of the bottle is performed by means of a light-sensitive cell C1 situated above the mouth of the bottle and a lamp 31 situated below the bottom of the bottle in a casing 34 having an aperture 35 in the vertical axis of the casing, which is so moved that the aperture 35 follows a spiral path scanning the whole base of the bottle. The casing 34 is rotatably supported by a pivot 29 on a block 28 on a radial slide 26 connected by a link 25 to an eccentric 23 on a shaft 22 geared by worms 21, 20 to a radial spindle 19. All these parts supporting the lamp casing 34 are carried by a drum 7 rotatable about a fixed shaft 8 carrying a bevel pinion 17 in mesh with a bevel pinion 18 on the spindle 19, so that as the drum 7 rotates the eccentric 23 gradually moves the casing 34 out of centre and then gradually back to central position. The aperture 35 therefore moves in a spiral and scans the whole of the base of the bottle. To ensure thorough scanning of the outer periphery, the slide 26 is connected to the link 25 by a slot which provides lost motion so that the aperture 35 remains in its outermost position for at least one revolution of the casing 7. The drum 7 is rotated by gearing 10, 11, 13, 16, 15 from a motor M. A similar scanning down device 7a is provided for a clean bottle B2 in a stationary position beneath a light-sensitive device C2. The two light-sensitive devices C1, C2 are mounted in a casing 5 supported by pillars 6, and are connected as a Wheatstone bridge as shown in Fig. 5, this arrangement giving indications independent of fluctuations of voltage supply. If the bottle B1 is clean, the Wheatstone bridge remains in balance ; but any foreign body in the bottle B1 upsets the balance and causes a current to be sent from terminals 36 to an amplifier 38. Alternatively, the scanning device may be of the kind described in Specification 469,458. Bottle ejecting apparatus.-If the bottle B1 is detected as containing a foreign body by the devices described above, it is deflected out of the outlet conveyer 39 by the following means. The amplifier 38 sends a current to a relay 67 which closes contacts 68 energizing relay 69. This relay closes a holding-on circuit at contacts 72 to remain energized and pulls a pawl 60 from a disc 62 on a shaft 54 which can then be rotated one complete revolution through clutch 57, 58 and gearing 56, 55 from shaft 40 when the dial plate 2 makes its next quarter revolution. The clutch slips when the disc 62 is locked. During the revolution of the shaft 54, a cam 78 thereon first opens a switch 76 and subsequently closes a switch 79. The opening of switch 76 breaks the holding-on circuit of relay 69 whereupon pawl 60 is released in readiness to stop the disc 62 at the end of its revolution. The closing of the switch 79 energizes a solenoid 84 which moves a wedge 88 across the outlet conveyer 39 to deflect the defective bottle out of the conveyer. The solenoid also closes a circuit at contacts 92 to hold itself on until the beginning of the next quarter revolution of the dial-plate 2 when a cam 89 on the shaft 40 temporarily breaks the circuit at a switch 82.