A "bar-code" is a graphical code that consists of a number of black bars with variable widths, and of spaces in between the bars with also variable widths (FIG. 1). The widths of the bars, as well as the widths of the spaces in between the bars determine what specific code has been printed. The advantage of such a code is that it is easily readable by an optical scanning system. However, to make this scanning easy (e.g. that no complicated reading equipment is necessary) and reliable the printed bar-code must meet high standards as to edge sharpness, even density of the bars, etc.
Bar-code scanners, hand-held or otherwise, are employed in the check-outs of supermarkets to identify in rapid succession the products being bought by the customer. Each identification thus made must be unambiguous regarding the type and quantity (size) of the product. Products, which are identical in type and quantity may carry the same identification code (such as all 1-kg bags of white refined sugar from the XYZ Sugar Company). Since such products are usually manufactured in large series, it is most economical to affix the identification code to the product while manufacturing and packing it; this takes place invariably at a location away from the supermarket ("source coding"). The code of such products usually defines the country of origin, the manufacturer and the type of product including the invariable quantity or size.
When the product with its bar-code is scanned at the check-out, this identification is used to call the appropriate selling price of the product from computer memory, to register the sale of the product on a customer receipt, to add the price of the product to the customer bill, and to record the sale of one unit of the product for stock keeping and accounting purposes.
The majority of food products sold by a supermarket can be source marked by a bar-code as described above, because quantities have predetermined and fixed values. However, there are some types of commodities where the quantity sold varies from item to item; in particular this is the case for fruit and vegetables, delicatessen, bread and sweets, cheese and meat products of a large variety. Such products are usually sold "fresh", i.e. they are not portioned and packed until the customer expresses his intent directly to buy the product, with an indication of the approximate quantity he desires. Since at this time exact portioning to standard quantities is most often not possible, the quantity will vary from portion to portion; and so with the price which has to be paid. Identifying such products with codes containing only the origin and nature is therefore not sufficient. The commonly accepted notion is that in these cases the code must also contain information regarding the quantity or size, and/or its related price. The code for such variable weight products should consequently be printed after the quantity or price has been established, i.e. after the portioning according to the customers wish has taken place, and after the quantity of the order has been determined (i.e. by weighing).
Since this situation occurs at service counters of supermarkets, the notion would lead to the necessity of placing a bar-code printer for variable codes on or in the immediate vicinity of such service counters.
However since, as already stated above, a bar-code label has to meet high standards as to printing quality, the printers are usually complex, and therefore relatively large machines, so that they require a lot of space at a service counter. Since they are complex mechanisms they will also usually be sensitive to dirt, so that a supermarket service counter is not the right place to put them.
The problem to be solved by the invention therefore is to be able to code articles with variable qualities, with a bar-code, without having to place a large and sensitive bar-code printer on the service counters.
The present way of reaching this aim has been to make smaller printers. The quality of these printers however has not yet met the standards that are required for an easy and reliable scanning of the printed code.