| 摘要 |
A counter for counting objects (like parcels) passing over a conveyor belt. A plurality of belt-type conveyors is used to spread the parcels and to deliver them to a sampling line which includes a plurality of photoelectric cells over which the parcels are moved by a conveyor belt. As the parcels pass over the cells, light directed at the cells is blocked by the parcels to provide a sampling pattern of blocked and unblocked cells. Logic circuits successively compare each periodic sampling pattern with prior sampling pattern according to a predetermined set of logic equations so as to detect the "lead edges" of the parcels and their "trail edges" as they pass over the sampling line. Each periodic sampling pattern is loaded into a Present Shift Register, from which it is transferred to a Past Shift Register to become the "prior sampling pattern", which is compared with the "current" sampling pattern present in the Present Shift Register. Counters are used to count the "Lead Edge Events" and the "Trail Edge Events" defined by the logic equations, and the larger of the two counts (if the counts are not equal) is selected as the more accurate count of the parcels on the conveyor. A parcel may cross the sampling line at any position thereon to be counted, and parcels in contacting juxtaposition may also be counted.
|
