Gob feeder chutes for glass molding machines

A feeder chute for glass molding machines has a cross section defined by an even number, preferably four of equal length sides. Each side may be either plane or curved convexly inwardly in a horizontal plane.

In modern high speed glass molding machinery for example, as disclosed in 
my prior U.S. Pat. No. 4,200,449, molten gobs of glass are sheared off in 
a gob feeder and allowed to fall by gravity through a system of chutes to 
the molds where they are shaped into a final product. While the 
aforementioned patent is directed to a so called paste mold machine, the 
present invention is applicable to glass molding machines generally 
wherever the molds are fed by a closed chute which extends between the gob 
feeder and the molds. Such chutes in machines in the prior art 
conventionally include a first inclined portion U-shaped in cross section 
which receives the severed gob and delivers it to a second inclined 
portion also U-shaped but with the open side of the U facing in the 
opposite direction. The second U-shaped portion delivers the gob to a 
third vertically arranged portion which in the machines of the prior art 
is usually round or also U-shaped and positioned to deliver the gob to the 
mold proper. Even if the chutes are stationary during passage of a gob 
therethrough, the gob inevitably makes contact with the walls of the 
vertical portion of the chutes and this leads to what is known in the 
trade as "brush marks" in the finished ware. The gob is falling through 
the vertical portion of the chute and particularly where such portion has 
a closed cross section, must push the air in the chute ahead of it. The 
net effect may be compared with a piston in a cylinder such as a shock 
absorber because pushing of the air through the closed chute slows the 
passage of the gob through the chute as compared to what the travel time 
would be in an unconfined space. Since the "name of the game" in glass 
molding machinery is maximum speed commensurate with quality of the 
product produced, anything which can be done to speed the travel of the 
molten gob between the gob feeder and the mold will result in an increase 
in operating speed of the machine. 
BRIEF SUMMARY OF THE INVENTION 
The applicant herein has discovered that the problems of brush marks in the 
finished ware and the slowing of the falling gob in the vertical portion 
of the chute can both be avoided by a simple alteration of the cross 
section of the vertical portion of the chutes. Specifically, it has been 
found that if the side walls of the vertical section chutes are of equal 
length, equal in number, preferably four, that the molten glass gobs 
inherently center themselves in the chutes and pass therethrough without 
significant contact with the walls. As a result of empirical testing, 
applicant has further discovered that the ideal situation is one in which 
the cross sectional area of the falling gob is substantially equal to, the 
cross sectional area of the interior of the chute minus the cross 
sectional area of the gob itself.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 of the drawing shows a pair of vertical closed wall feed chutes 10 
supported on a shaft 12 which permits them to be moved into and out of 
alignment with the neck rings 13 and molds in a blow molding machine. This 
drawing corresponds to FIG. 3 of my prior U.S. Pat. No. 4,200,449. The 
chutes 10 are fed from a gob feeder not shown, via a pair of channel 
shaped chutes 14 and 16 the open sides of which face in opposite 
directions. As shown in FIG. 2, the side walls 18 of the chutes 10 are 
inwardly curved but this is not essential to practice of the invention. 
Such curvature merely permits adaptation of a chute with straight side 
walls to the handling of smaller sized gobs of glass. The glass gobs are 
indicated by the dotted line circles in this Figure in substantially the 
position which it has been found they will automatically occupy with 
respect to the inner surface of the walls 18 as they pass through the 
chutes 10. As will be seen in this Figure, such position is one in which 
the gob in each instance is spaced substantially equidistantly from each 
of the four inner surfaces of the chute. 
Reverting for a moment to the situation of a gob falling through a chute of 
circular cross section, it can be clearly demonstrated that with a 
circular cross section chute the gob makes substantial contact with the 
inner surfaces of the chute and further that it pushes substantially all 
of the air in the chute ahead of it during its passage through the chute. 
By using a "lazy" gas flame at the bottom of a circular chute, it can be 
shown that this is the fact because the flame will be extinguished every 
time. 
Turning to the chute of substantially square cross section as shown in FIG. 
2, the exact reason for the automatic symmetrical positioning of the gob 
within the chute is not entirely understood. Again applying the lazy gas 
flame test at the bottom of the tube, it can be conclusively demonstrated 
that in the case of a tube of square cross section, whether the side walls 
are plane or inwardly curved as shown in FIG. 2, that the gas flame is 
blown but not extinguished. This then gives rise to two possible 
explanations which are offered here by way of theory and not by way of 
limitation. The first of these is simply that the gob in falling through a 
chute as shown in FIG. 2 no longer pushes all of the air ahead of it 
through the chute but only a portion and what is not pushed ahead of the 
gob either flows upwardly around the gob in each corner of the chute or it 
remains substantially stationary in the corners. It seams more plausible 
that there is an upward flow in the corners of the chutes which creates 
forces which are equal and opposite on opposite sides of the gob and 
therefore tends to center it as shown in this Figure. Another possible 
explanation is that a partial vacuum is created by the gob falling through 
the chute and the air not moved downwardly ahead of the gob is sucked 
upwardly due to this partial vacuum. Regardless of the technical reasons, 
it has been definitely established that little or no contact occurs when 
the chute has a cross section which is a substantially regular polygon 
having a even number of sides preferably equal to four. Referring again to 
the speed of travel of the gobs through the closed chute, as pointed out 
above, the fall of the gob through a square chute is measurably faster 
than the fall of the gob through a circular chute because of the lack of 
contact between the gob and the inner surfaces of the square chute. 
Further empirical testing has proven that the ideal situation is one in 
which the size of the gob is so related to the size of the chute that the 
cross sectional area of the gob is substantially equal to the cross 
sectional area of the space between the gob and the inner surfaces of the 
chute. Stated otherwise, the cross sectional area of the chute is 
preferably substantially twice the cross sectional area of the gob falling 
through the chute. This preferred situation results in maximum speed of 
travel of the gob through the chute combined with symmetrical positioning 
of the gob in spaced relation to the inner walls of the chute. 
While preferred embodiments of the present invention have been herein shown 
and described, applicant claims the benefit of a full range of equivalents 
within the scope of the appended claims.