Process and device for shaping a gob

In a process for shaping a gob in order to obtain a hollow glass article by means of an electronically-regulated and hydraulically-propelled level, the process of shaping the gob into a rough or finished product is rationally effected in a predefinable and in particular precisely reproducible manner by the fact that an electro-hydraulic servo-drive is used as a means for driving the level, and that the latter, during at least the practically total performance of the movement, is adjusted in position by means of a closed position-regulating circuit. In a device suited for this purpose the drive device of the level consists of an electro-hydraulic servo-drive and an electronic position-adjusting device for the at least approximately total movement of the level. Preferably the movement of the level in the glass article is also effected at a regulated speed and, ideally, the shaping stage is completed by a pressure-regulated forward movement of the level.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The invention relates to an apparatus and a process for the shaping of a 
glass piece, especially in a closed-forming system, into a hollow glass 
article and namely, to a rough or final product, especially by means of 
producing machines working by the series principle, such as IS and RIS and 
other glass-working machines by means of a presettable plunger which can 
be driven into the glass piece. The plunger is movable from a loading 
position to a final pressing position, is speed regulated, and is also 
preferably pressure regulated. 
2. Background Art 
Machines for the production of hollow glass articles, such as the so-called 
IS and RIS machines working as series machines are known. In these known 
machines, the production process takes place at several production 
stations arranged one after the other. At each production station, the 
same production step takes place on one or on a plurality of pieces of 
glass. Therefore, the work cycles on the different pieces of glass are 
displaced in time. For the production of a hollow glass article, liquid 
drops of glass are pressed, or blown into a meal pre-mold to form a rough 
product, the so-called blank. After transferring this blank to the finish 
mold assigned to the pre-mold, the blank is formed in the finish mold into 
the finished product by blowing out or evacuating. 
The drop of glass falls from above into the glass pre-mold closed at the 
side to the lower opening of which is connected a mouth tool. The drop 
falls on a plunger which is positioned in a loading position and which is 
variable in its height position. A bottom of the mold then closes the 
upper part of the mold. By means of a piston in a piston-cylinder 
arrangement, the plunger can be moved vertically up and down. After the 
closing of the pre-mold with the bottom of the pre-mold, the plunger 
through an upward movement presses the glass against the forming contour 
of the pre-mold and also against the contour of the mouth tool and the 
bottom of the pre-mold to give the glass the desired inner and outer 
contour at the same time. The liquid glass is limited therefore, for a 
short period of time at its total inner and outer surface by contours 
defined by the mold, and completely fills the free volume of the mold. 
When the liquid glass drop falls into the pre-mold, the plunger is in its 
loading position at which is closes the mouth opening of the mold in part. 
Only for the molding of the liquid glass is the level struck into the 
glass, and as a rule produces at the same time the mouth of the hollow 
glass article. 
In this known glass-forming apparatus and process, the level, known in the 
art in the past and still today as a "plunger", is moved forward and 
backward pneumatically. Here, the loading position, as the lower outlet 
position for the present hollow glass article, can only be sufficiently 
positioned and changed with very great loss of time by means of distancing 
bushings or so-called "loading screws". Another disadvantage is the need 
of regulating the pneumatic pressure for each individual plunger. This 
pneumatic pressure must be so dimensioned that the mouth of the blank is 
completely formed. The pneumatic pressure may lie between about 0.4 and 
1.5 bar, and must be empirically determined from quality control of the 
finished hollow glass article for each individual plunger. Changes in 
property value of the liquid glass might also lead to changes in quality. 
This necessitates another change of the pneumatic pressure. 
However, with the known process and apparatus, the cycle of forming cannot 
be changed independently of other influencing factors. Instead, the 
pressure for advancing the plunger, the forming speed, and the static 
pressure on the glass and the mold system depend directly on the time axis 
and can only be changed slightly in part or not at all. 
From EPO 165 012 A1 are known a process and an apparatus of the kind 
mentioned. Here the plunger is moved hydraulically according to a set time 
frame, whereby at given times, the speed course for the plunger can be 
preset. For the purpose, the computer is continually fed with external 
time pulses. A Hall sensor with a piston rod designed in screw form on its 
outer surface is used as a position sensor, and a pressure sensor is used 
to indicate the fluid pressure existing against the plunger. Through a 
computer arranged after these two sensors, the amounts of pressure and the 
supply of the hydraulic fluid moving the plunger can be varied according 
to the ratio between actual and desired values. This process has the 
disadvantage in that only a time frame for the individual flow phases is 
taken into consideration, whereas the continued position pattern of the 
plunger will not be taken into consideration so that the speed errors lead 
to unpredictable final positions of the plunger. It has been recognized 
that in this way, a sag in uniformity of product quality can result. It 
was further learned that in this known process, the plunger provided only 
speed measurements. The pressure was taken into consideration in this 
process, however, regulation of the pressure level in relation to time set 
in when the highest pressure position of the plunger is reached, that is, 
when the pressure between the plunger and the piece of glass stops 
movement of the plunger. It has been found especially harmful to the 
quality of the glass when the pressure against the plunger, as proposed 
there, is increased still more after reaching the stopped position of the 
plunger. The pressure regulation dependent on time is also a disadvantage, 
however, if it has been carried out during the forming step. Namely, it 
has been found that only when taking into account of the particular 
position of the plunger does a pressure change lead to the desired quality 
improvement or improvement of the uniformity of the quality of the glass 
article, while a pressure variation dependent on time very easily leads 
even to a worsening of quality or at least to a higher rate of rejects. 
SUMMARY OF THE INVENTION 
With this premise, the invention provides an apparatus and a process for 
the forming of a piece of glass. The invention does not have the 
above-mentioned disadvantages and should give entirely new possibilities 
for the forming of glass. In particular, it should be possible in the 
forming of a piece of glass to prescribe accurately the forming cycle for 
the rough product and the finished product, and in particular, to 
reproduce exactly. In particular, in the forming of a glass piece to a 
rough or finished product, the forming cycle should be carried out, 
according to the quality requirements and the values of the operating 
parameters of the glass piece itself as well as the mold, with the least 
reject waste at higher stroke speeds. 
This problem is solved in the apparatus and process according to the 
invention recited in the claims of the present application. In one 
embodiment of the present invention, an electro-hydraulic servo drive is 
used for driving the plunger. The servo-drive includes special hydraulic 
cylinders which act as regulating and drive elements for the vertical up 
and down motion of the plunger. The servo-drive further includes an 
electronic position-regulating device. 
Through the invention, among other things the quality of the product is 
uniform and improved. In particular, waste is diminished and the set-up 
time for the individual plungers is noticeably shortened. The subject of 
the invention may be applied in various common glass forming processes, 
such as the blow-blow process, the press-blow process ,the 
press-blow-narrow neck, and the solid-blank process. The plunger mechanism 
may be installed directly at production stations already present, that is, 
existing machines may be re-equipped. 
An "electro-hydraulic power drive", according to the invention, is 
understood as the following. A piston-cylinder arrangement is used for 
moving the plunger forward and backward. The piston can be moved forward 
and backward, as well as held in place, by hydraulic fluid. To obtain an 
exact prescribed movement forward and backward of the piston, a valve is 
used to supply and take away hydraulic fluid in prescribed amounts and 
speeds at the two ends of the piston. The valve is actuated electrically. 
Between the zero position of the valve and the maximum open position, all 
intermediate positions for the advance and retraction of the plunger are 
possible. Normally, the valve is characterized with very fine oscillation 
movements to assure the best possible accuracy of regulation. In this way, 
the hydraulically driven piston can be moved and positioned with great 
precision. 
An "electronic position-regulating device", according to the invention, is 
understood as follows. The distance covered by the plunger during one 
forming cycle is divided into partial steps which are determined by very 
definite, preferably preset positions of the plunger in relation to the 
cylinder. For example, the preset positions include not only loading 
position, end position, and pull-back position, but also intermediate 
positions in which the advance characteristic of the plunger is changed. 
These positions are taken and held by the plunger, or released again, 
through a closed regulating circuit. For this, the position of the plunger 
through its whole cycle of movement is taken constantly by measurement and 
is preferably provided as an electrical signal fed to an evaluating unit 
such as a microprocessor. The actual position is compared with the desired 
position, and is forwarded on command to the electro-hydraulic power 
drive. 
According to the invention, the plunger, at least from the loading position 
of the glass piece to the end position of the plunger or to a 
predetermined position before the final pressing position of the plunger, 
may be run at a regulated speed which may be predetermined. This 
speed-regulated movement step of the plunger is overlaid by the position 
regulation, that is, the speeds which can be preset between the positions 
of the plunger which can be preset can be kept adjustable. This is 
possible with the use of the above-mentioned actual position measurement 
with the use of a suitable microprocessor which is programmed with desired 
speed data, and which also contains the regulation of position. Through 
the linking of the speed regulation circuit with the closed position 
regulating circuit, the speed regulating circuit is also a closed 
regulating circuit. 
According to a preferred embodiment of the invention, the plunger is run 
pressure regulated toward the end of the forming step carried out between 
the loading position and the end pressing position. This 
pressure-regulated work step may either be connected seamlessly to the 
position-regulated step and the speed-regulated step, or overlaid by the 
combined position-regulated and speed-regulated step, wholly or in part. 
The plunger positions at which the pressure regulation begins and, if 
desired, the other positions up to which the pressure regulation is 
overlaid by the speed-regulation and position regulation, may be preset 
through the position regulating circuit. In any case, it should be 
position-regulated up into the final pressing position. The pressure 
regulation circuit requires at least one pressure sensor which forwards 
the actual pressure value, for example, to the microprocessor where it is 
compared with the desired pressure value. Consequently, the microprocessor 
causes the valve used for this purpose to supply the hydraulic fluid for 
the desired pressure. Preferably, a pressure and amount-regulating valve 
which is a basic part of the power drive mentioned above is used. 
Suitable developments of the subject of the invention which assure in 
particular, in advantageous cycle of movement, a simple handling of the 
plunger mechanism, and an improved quality of product, are contained in 
the further claims. 
The parts or process steps to be used according to the invention are not 
subject, in their size, shape, choice of material and technical concept or 
their processing conditions, to any special exceptional conditions. This 
is so that the criteria of choice in the particular field of use may be 
used without limitation.

DESCRIPTION OF A PREFERRED EMBODIMENT 
According to FIGS. 1, 6 and 7, a plunger 1 hollow inside and having cooling 
or compressed air passages is fastened, e.g., screwed at the end 11 to a 
piston rod 10 through which air can pass. The piston rod 10 bears a piston 
2 which can be pushed along axially with ease in a cylinder housing 13, 
and which is connected fluid-tight through an end wall 14 of the cylinder 
13. Through bores 16 and 17, hydraulic fluid can flow into and out of the 
chambers 21 and 22 for the advance and retraction of the piston 2. 
The plunger 1 is protected over a large part of its total stroke of about 
180 mm by a housing 12 extending in continuation of the cylinder housing 
13 having an open end for the passage of the plunger 1. 
At the lower end position (Pos. 1) of the plunger 1 or the piston 2, the 
piston lies against a lower mechanical stop 13a of the cylinder housing 
13. At the beginning of a work cycle, a microprocessor 20 (FIG. 7) 
provides to an electro-hydraulic power valve 18, known per se, an outer 
starting signal by which a movement of the plunger 1 into a load or 
charging position (Pos. 2) begins at a speed which can be controlled or 
regulated, especially a maximum speed. This charging position may be 
adjusted continuously in both directions (directions "a" and "b" in FIG. 
1). In the distance-time diagram of FIG. 1, this cycle movements is 
represented on a larger scale as linear. But actually, the acceleration 
and braking process leads, for example, to a sinus or exponential course 
which may be preset of the distance-time curve. During this movement 
cycle, the actual position of the plunger 1 is continuously monitored and 
reported back to the microprocessor 20 by a position sensor 7 known per 
se, especially one arranged with in an air feed pipe to the plunger 1. 
Based on a desired-actual comparator, the microprocessor gives the power 
valve 18 a suitable signal through which the movement of the plunger 1, 
position-regulated and preferably also speed-regulated, into the charging 
position (Pos. 2) is made possible. In this way, an exactly reproducible 
finding of the charging position is allowed. In principle, the work cycle 
may also be started or stopped in any other position such as an 
intermediate or the charging position. 
In the charging position (Pos. 2), the plunger 1 closes the pre-mold 
consisting of the side parts of the mold 3, a neck forming tool 4, and the 
bottom 6 of the mold, only in part, and forms in the neck zone of the 
pre-mold a ring gap. A glass piece, consisting of a dropping of glass 5', 
introduced by falling into the mold per work cycle, is pre-molded by the 
further movement of the plunger 1. Just before this, or at the same time, 
the pre-mold is the mold and is closed by the mold bottom 6. 
The forming step is introduced again by a suitable external start signal 
from the microprocessor 20 to the power valve 18. The desired speeds of 
movement of the plunger 1 in the forming step are fed into the 
microprocessor 20. In particular, any desired distance-time profile may be 
programmed, for example, sinus form or exponential. This regulated 
penetration speed may also be linear. Preferably, it changes toward the 
end of the forming step, toward lower speeds, and amounts to zero when the 
so-called final pressing position (Pos. 3) is reached, that is, when the 
glass piece 5 has been finished. The exact maintenance of the prescribed 
speeds will be assured by a combined position and speed regulation circuit 
of the microprocessor 20. 
Toward the end of the forming step, the position and speed regulating of 
the plunger 1 is preferably automatically converted into a pressure 
regulation with the use of a pressure measuring sensor 16' and 17'. 
Preferably, the pressure regulation overlays the position and speed 
regulation until it finally dominates. With this, the plunger moves 
farther into the piece of glass 5 until the counter-pressure on the 
plunger 1 through the forming of the piece of glass has reached the 
pressure fed in by the microprocessor 20. In this way, the position of the 
plunger 1 can be regulated exactly during its whole cycle of movement, and 
therefore very exactly known. In this way, for the first time, it is 
possible to take into account the property values of the piece of glass, 
the change of these property values during the forming process, and/or the 
changing of molds and tools because of wear, for example. 
When the equilibrium is established between the prescribed final pressing 
pressure of the plunger and the counter-pressure of the piece of glass, 
the ideal forming of the glass has taken place and the plunger 1 has 
reached the final pressing position (Pos. 3). With this, a further 
pressing forward of the plunger 1 is prevented, and the transmission of a 
higher static pressure from the plunger 1 to the glass and the mold system 
is prevented. 
After reaching the final pressing position (Pos. 3), the glass piece is 
finished. Its neck zone is, as a rule, already completely finished, that 
is, as provided for the hollow glass article. From this final pressing 
position, the plunger 1 is at first slightly retracted so that between the 
glass and the plunger a cooling air gap 8 results. In this cooling 
position (Pos. 4), the plunger is drawn back between 0.5 and 1.5 mm from 
the end pressing position (Pos. 3). A part of its cylindrical zone 1' is 
still in the zone of the neck forming tool 4 so that the neck zone of the 
glass is protected during the reheating process which is already beginning 
again. The conical zone 1" of the plunger 1 has then already loosened from 
the pre-pressed glass 5. The reheating of the part of the glass still to 
be formed can now begin. Damage to the inner surface of the glass, 
especially by the plunger, is reduced to a minimum. 
After reheating and reaching neck stability (Pos. 5), the plunger is 
retracted, through a corresponding signal, into the starting position. 
In empty run of a production station, that is, when the pre-mold is not 
loaded with a piece of glass, the plunger goes back into an upper end 
position (Pos. 6) of the piston 2 in which it stops at the distance 
position given to the microprocessor and from which it is retracted again 
into the starting position through a corresponding external signal. 
The piston rod 10 bearing the plunger 1 is provided with an axial passage 
bore 9 through which the cooling air is fed to the plunger 1. Preferably, 
the passage bore 9 also receives the position sensor 7 acting as an 
absolute distance measurement sensor arranged in an air feed tube. 
In the chamber or before the two chambers 21 and 22 formed by the cylinder 
housing 13 with the end walls 14 and 15, as well as the piston 2, are 
placed preferably in each case one or more hydro-electric analog pressure 
sensors 16' and 17', so that not only the hydraulic pressure, but also the 
actual force of the plunger 1 an be determined. 
The pressure increase or decrease desired for the actuation of the piston 2 
is obtained through the electro-hydraulic power valve 18. The power valve 
18 is arranged against the outer wall of the cylinder housing 13 or 
outside, especially in a control plate in common with the pressure sensors 
16' and 17', and is preferably designed so that the maximum pressure 
increase or decrease only takes place with a piston deflection of at least 
1.5%. The freely selectable loading position (Pos. 2) as well as the final 
pressing position (Pos. 3), also freely selectable, may be held with a 
greater accuracy, for example .+-.0.1 or better. Also, the adjustable end 
pressure desired value of the plunger which, according to experience, lies 
between 200 and 600 Newtons per square centimeter is held with a greater 
accuracy of .+-.5 Newtons per square centimeter, for example. All actual 
distance values of the plunger are taken by the position sensor 7 and 
reported back to the microprocessor 20. Through the end position reached 
at the end of the forming step, and through the pressured parameters of 
the plunger, a conclusion may be drawn, if the volume of the mold is 
known, about the exact dropping weight of the glass piece. 
It has been shown that a perfect distribution of the glass in the mold 
(even in the rather difficult press-blow process) and in the forming of 
the neck of the hollow glass article can be obtained by using a combined 
position, speed, and pressure regulation of the plunger in a closed 
regulating circuit. 
As can be seen, therefore, this new kind of use of an electro-hydraulic 
power drive in the forming of a piece of glass leads to unexpected great 
advantages. The same applies to the new use of an electronic data 
processing unit, especially a microprocessor, for the regulation of the 
cycle of movement of a hydraulic power drive with the use of a distance, 
flow and/or pressure-measuring sensor.