It is often desirable to print markings on elongated material, such as insulated wires to be stranded into a cable, for identification purposes. This has heretofore been done with apparatuses of a type such as that illustrated in U.S. Pat. No. 2,865,323, which is assigned to the assignee of the present invention. This type of apparatus includes a rotatable disc-shaped device which has a set of peripheral orifices from which individual streams of a liquid printing medium such as ink may be radially emitted. By passing an insulated wire beside the rotating device along a route paralleling that of the axis of device rotation, individually spaced marks may be printed on the side of the wire facing the rotating device. By passing the wire between two of such devices, a series of annular bands may be printed.
FIGS. 1-3 of the drawing illustrate in further detail an example of apparatus of the prior art for printing encoded markings on elongated material. Here a pair of disc-shaped devices 10 and 12 are seen to be rotatably driven by motors M about mutually parallel axes within an enclosure 14. The apparatus includes a system for recirculating a liquid marking medium such as ink comprised of a pump P located within a sump portion of the enclosure, and a series of conduits 15, 16 and 17 through which the marking medium may be pumped from the sump into the two disc-shaped devices. By passing a wire 20 between the two rotating devices along an axis paralleling those of the two rotating devices through enclosure ports 13, a series of annular bands 21 may be printed on the wire as shown in FIG. 2.
In FIG. 3 each of the disc-shaped devices is seen to include a centrally apertured, cup shaped member 24 having an annularly arranged series of grooves 25, a flanged collar 27, a band screen 28 sized to be seated within a rim 29 of the flanged collar 27, a ring 30, and another centrally apertured cup shaped member 32 having a series of orifices 33 formed in its annular rim 34. The device also includes a hollow bolt 36 having a threaded end 37 which extends through each of the just described elements and threadedly into a drive shaft in fastening the members together into a motor driven assembly. So assembled, rotary drive may be applied to bolt 36 and liquid ink pumped into the assembly through the hollow bolts 36 and then radially outward from the rotating assembly through the orifices 33. The orifices of each of the two disc-shaped devices 10 and 12 are aligned so as to direct streams of liquid ink onto the wire 20 driven therebetween through the enclosure to form the annular bands 21 shown in FIG. 2.
Unfortunately, notwithstanding the inclusion of a screening or filtering element, printing apparatuses of the type just described have tended to become readily clogged. This may be attributable to the fact that the orifices 33 have had to be of relatively small size in order to provide well defined yet continuous ink streams to be sprayed onto elongated material being moved rapidly thereby for only brief periods of time and thereby print bands of relatively narrow widths. This predicated smallness of orifice size has enabled pigments to accumulate in the orifices and create clogging. Furthermore, it sometimes occurs that solid or semi-solid lumps or globules are to be found in the marking medium which also tend to clog the devices. Where either paints or inks are used globules may be formed by drying as from exposure to air.
Another problem with these prior art type printing apparatuses has been that associated with making changes in code markings. In order to distinguish specific wires within a bundle of wires it is often necessary to place differently encoded or identifying marks on each of the wires. Typically, this is either done by the use of marking medium of different colors, the use of different spacings between the marks, the use of different mark widths, or a combination of these. Where one specific device is to be used to print marks of different sizes or spacings it has been necessary to change that member having the peripheral orifices in order to change the orifice sizes to make wider or narrow bands or to change the angular spacing between the orifices in order to alter the spacing between the marks. This is attributable to the fact that it is rarely feasible to effect such changes in the marks by varying the speed of either the wire or the printing apparatus. In order to change the size orifice or the arrangement of the orifices, it is necessary to disassemble the rotary device and substitute one of its components with another. This is a time consuming and messy task.
Accordingly, it is to these problems to which the present invention is primarily directed.