For the manufacture of glass articles, it is necessary to feed, through a series of orifices in a feeder, a continuous flow of molten glass, same which is shear afterwards, by a proper cut mechanism, into portions named drops, according to the required weight and size.
Nevertheless, the weight and size of the gobs are variable, for they depend upon the temperature of the glass infeeder, the height of the rotary tube, the cutting rhythm, and last but not least the diameter of the orifices themselves.
In view of the necessity of manufacturing smaller articles, certain improvements in the feeder were developed, same which introduced plates of three or four discharge orifices. As the number of orifices increased, the need for plungers in the interior of the tube grew too (one plunger per orifice), causing, there fore, problems of space within it, since the cited plungers must be all placed in the interior of such tube, but also keeping some distance between each.
Moreover, due to the space limitation within the tube, the inclusion of more than two plungers therein forces the same to be thinner than the ordinary ones, and, so, more liable to be broken by the normal vibrations of the feeding system, particularly when the speed is high. As the result of the breakage of any one of such plugs, the production would have to be stopped for exchanging the corresponding plunger or plungers.
Another problem found in the feeders, is that consisting of the adjustment of the plungers once the production is started, since, as it had been previously explained, there are some variations in glass that affect the size and weight of the gobs.
At present, there are several systems based on the feeding through three orifices, but the same have to be adjusted before the production is started. The U.S. Pat. No. 3,582,309 to R. S. Bracker discloses a triple gob glass feeder with adjustable plungers, featuring the respective discharge orifice-plate, so as to facilitate the discharge of three different flows of glass, which are cut afterwards into gobs of the size required. In this case, the central plunger is vertically adjustable, and the lateral ones are adjustable both, horizontally and vertically.
The U.S. Pat. No. 3,711,266, discloses a supporting mechanism which holds a plurality of plungers in one feeder in an individual manner, this is to say, in a way which permits the individual adjustment of each, thus allowing the plunger to keep aligned in respect of the discharge orifice-plate. In this case, the supporting mechanism lets each plunger be independently adjusted, both, vertically and horizontally.
The problem found in these systems consists in that, once the plungers are adjusted and placed in the feeder, they are not easily adjustable when the conditions of the system (the adjustment of the glass flow and/or of the weight of the gobs) vary. This circumstance, in turn, would force a stoppage of production to carry out the necessary corrections, situation from which a loss of production may derive. But if uniformizing the weight and shape of the gobs in a triple gob glass-feeder is hard, it is difficult in a four-gob glass feeder, just as the one featured and claimed in the U.S. Pat. No. 4,305,747 of Kirkman et al, which uses only one plunger for the simultaneous feeding of a number of orifices ranging from three to six. Said plunger is placed in the interior of a cylindrical tube which controls the supply of molten glass. The improvement in this system consists of a tubular structure coupled to the bottom of the feeder, as well as of an orifice-plate (fastened to that tubular structure) which may comprise from three to six orifices. The said structure is relatively tall, showing a circular shape in its upper part and an elongated slot passageway in the bottom thereof, where the orifice-plate is fastened to.
In systems of this kind and due to the variation of the temperature of glass or to the loss of heat of same, the problem is that the flow of glass in the external orifices tends to be slower than in the central ones, therefore resulting in the formation of lighter and cooler gobs coming out through the external orifices.
Another disadvantage of the gob-feeders known to date is that, as the number of plungers in the tube is increased, there is less homogenization and loss of heat of the molten glass within the tube, just as it happens with the systems featured by the Bracker and Daly patents.
The same problems occur in the system of the Kirkman Patent, for, with only one plunger and a special fixture in the bottom of the feeder, is intended to feed from three to six glass gobs bearing the same form and weight. However it is well known that with only one plunger, a maximum of two orifices can be controlled.
A further disadvantage of this system is that, due to the thickness of the plunger, a variable condition of glass prevails, since the space between the tube and the plunger is reduced, thus affecting the viscosity and temperature of glass.
Hence, aware of these problems, the author of this invention devised a system for the angular graduation of the position of two plungers, according to the position required in respect of the orifices of a glass feeder; in order to provide a uniform flow through each of them. Said system may be graduated even when the feeding system is at work, thus avoiding the stoppages of production.
Besides, this system which features the least possible number of plungers (two), may feed up to four orifices; offering the advantage that, when there might be any variations of weight between the internal and the external orifices--in a four-orifice system--or between the external and central orifices--in a triple-orifice system--the same may be angularly and symmetrically adjusted, until a achieving an identical form in the gobs. Furthermore, there is no need to change this system when a triple-individual sectional glass forming machine is substituted for a quadruple one or vice versa.
Thus, by means of these systems, the ideal centering of the plungers is attained through an angular variation of same, so allowing to perform any operation of adjustment of weight and shape of the gobs with the system at work; putting aside in this manner, the stoppages of production.
One more characteristic of this system is that, in using fewer plungers, it will permit that they be bigger, stronger and less liable to be broken; and, also, this system of variable centers could be adapted for the process of feeding through two, three or four orifices.