Method and apparatus for bending glass plates in a horizontal position

In a method for bending glass plates, the glass plates are heated in a horizontal position in a continuous furnace (1) to the bending temperature and in a following bending chamber (5) are pressed by an upwardly flowing hot gas stream against a convex bending mold (7) positioned above the conveying plane. The bent glass plates (3') are placed on a displaceable shaping ring (13) and transferred with the latter into a following cooling station (16). The glass plates (3) are raised from the conveying roller train (2) of the continuous furnace (1) by a suction plate (3) are positioned relative to the transfer ring (28) on the latter. With the aid of the transfer ring (28) the glass plates (3) are transferred into the bending chamber, where in the end position of the transfer ring (28) they assume the desired end position relative to the bending mold (7).

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a method and an apparatus for bending glass 
plates, in which the glass plates are heated to the bending temperature in 
a horizontal position in a furnace including a conveyor and transferred 
into a bending chamber in which they are raised by a differential gas 
pressure against a convex bending mold positioned above the conveying 
plane of the glass plates, are bent into their final shape and with the 
aid of a shaping ring corresponding to the final glass plate shape and are 
transferred from the bending chamber into a following cooling station. 
2. Description of the Related Art 
A method of the aforementioned type is known from U.S. Pat. No. 4,682,997. 
In this known method the glass plates are transferred from the roller-type 
continuous furnace into the following bending chamber on driven conveying 
rollers. The glass plates are raised from the conveying rollers in the 
bending chamber by means of an upwardly flowing, hot gas stream and 
pressed against the upper bending mold. 
Another method of the aforementioned type is described in U.S. Pat. No. 
3,778,244. In this known method the conveying roller train also extends 
from the roller-type continuous furnace into the bending chamber. In this 
case the glass plates are raised from the conveying rollers by suction. 
The vacuum required for the suction process is applied along the 
circumferential edge of the bending mold. 
In order to achieve good quality, the glass plates heated to the bending 
temperature within the bending chamber must initially be very accurately 
positioned on the conveyor, which is generally of the roller-type, i.e., 
brought into the correct position with respect to the bending mold before 
being raised from the conveying rollers by the hot gas stream or by 
suction, followed by pressing against the upper bending mold. This 
positioning process is time consuming and lengthens a bending cycle time. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to further develop the bending 
method defined hereinbefore so that the bending cycle time is reduced and 
consequently the economics of the method are further improved. 
According to the invention this problem is solved in that, within the 
furnace, the glass plates are raised from a conveyor with the aid of a 
suction plate, placed on a transfer ring displaceable within the bending 
chamber and, with the aid of the transfer ring, are transferred into 
position with respect to the bending mold at the end position of the 
transfer ring in the bending chamber. 
In the method according to the invention, the process of positioning the 
glass plates with respect to the upper bending mold is performed in two 
steps, namely a first step during which the glass plates are brought into 
a precise position with respect to a mechanically guided intermediate 
member, i.e., the transfer ring, and a second step in which the transfer 
ring is brought into its clearly defined end position below the bending 
mold. The second positioning step, namely the transfer of the transfer 
ring into the bending chamber, can be carried out accurately and 
relatively rapidly. However, the first positioning step, which takes up 
much more time, can be performed during the bending in the bending chamber 
of the preceding glass plate or when the bending chamber is still occupied 
by the preceding glass plate, i.e., the bent glass has still not been 
removed from the bending chamber. As a result of the subdivision of steps 
of the process and upstream displacement of the positioning step in 
accordance with the invention, it is possible to significantly reduce the 
bending cycle time and therefore improve the economics of the method 
according to the invention. 
The method according to the invention can be performed with any process 
according to which the glass plate is raised from its conveying plane and 
pressed against the upper mold by means of a differential gas pressure, 
for example an upwardly flowing hot gaseous current or suction through the 
upper mold or at its periphery. 
The invention relates also to a bending apparatus with a furnace, a bending 
chamber with an upper bending mold positioned in a raisible and lowerable 
manner above the conveying plane of the glass plate and means for 
producing a differential gas pressure for raising the glass plates from 
the conveying plane against the bending mold, a cooling station following 
the bending chamber and means for the transfer of the bent glass plates 
into the cooling station. According to the invention, the apparatus also 
comprises an intermediate station located between the conveyor ending 
upstream of the bending chamber and the latter, a suction plate movably 
arranged above the end portion of the conveyor, a transfer ring 
displaceable between an end position below the suction plate and an end 
position below the bending mold and means for positioning the glass plate 
relative to the transfer ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The installation shown in FIG. 1 includes a roller-type continuous furnace 
1 with a conveying train formed from driven conveying rollers 2, on which 
the planar glass plates 3 are heated to their bending temperature during 
their continuous preheating movement. It also includes a bending chamber 
5, which is located within a vertically positioned flow channel 6, in 
which vertically rising hot air streams with a given volume flow during 
the bending process. This hot gas stream presses the glass plate 3 in the 
bending chamber against the upper bending mold 7 which is in the form of a 
full-surface, convex mold. The bending mold 7 is provided on its bending 
surface with openings which are connected to a cavity and which, by means 
of a fan 8, can be placed under a vacuum. The bending mold 7 is fixed by 
means of struts 9 to a frame 10, which can be moved up and down by means 
of rods 11 and a lifting mechanism 12. 
A shaping ring 13 cooperates with the upper bending mold 7 and its upper 
bending surface corresponds to the desired shape of the glass plate and to 
the upper bending mold 7. The shaping ring 13 is movable in the 
longitudinal direction of the furnace by means of wheels 14 on rails 15. 
With the aid of this movable shaping ring 13, following the bending 
process, the bent glass plate 3' is transferred into the cooling station 
16 following the bending chamber 5. The cooling station 16 contains 
suitable blowing plenums 17, 18, which direct the cooling air onto the 
bent glass plates 3' while they are resting-on the shaping ring 13. During 
this cooling process the door 20 closes the opening 21 through which the 
glass plates are discharged from the bending chamber 5. 
Within the roller-type continuous furnace 1 a horizontally displaceable, 
planar suction plate 23, which is provided with a suction fan 24, is 
located above the final conveying rollers 2. The suction plate 23 can move 
backwards and forwards on rails 25 between an end position above the 
conveying rollers 2 and an end position in an intermediate station 27 
located between the conveying rollers 2 and the bending chamber 5. 
Between the intermediate station 27 and the bending chamber 5 a transfer 
ring 28, which is mounted on wheels 29, can move backwards and forwards on 
the rails 15 between an end position in the intermediate station 27 and an 
end portion in the bending chamber 5. The transfer ring 28 can be a ring 
with a planar surface adapted to the glass plate contour. However, it is 
instead also possible to use a transfer ring with a slightly bent or 
curved surface, so that the glass plate undergoes a slight gravitational 
deformation prior to the following bending in the bending chamber 5. The 
drive mechanisms for the suction plate 23, the transfer ring 28 and the 
shaping ring 13, which are conventional constructions, have been omitted 
from the drawings for reasons of simplicity. 
The intermediate station 27 also contains suitable positioning means, e.g., 
plungers, which are shown in the form of arrows 30. With the aid of these 
plungers the glass plates placed on the transfer ring 28 are moved into 
precise position relative to the transfer ring 28. 
The sequence within a bending cycle is as follows. As soon as a glass plate 
3 heated to its bending temperature arrives at the end of the conveying 
train comprising the conveying rollers 2, it is raised from the conveying 
rollers by the suction plate 23 and secured by the latter. The suction 
plate 23 now travels with the glass plate 3 into the intermediate station 
27 and places said glass plate 3 on the transfer ring 28, which at this 
time assumes its end position in the intermediate station 27. The glass 
plate 3 is brought into the desired position with respect to the transfer 
ring 28 with the aid of the movable plungers 30. 
The means for positioning the glass plates with respect to the transfer 
ring, e.g., the plungers, may be mounted either on the latter or 
independently in the area below the suction plate or the transfer ring. 
During this transfer and positioning process the preceding glass plate 3' 
is still in the bending chamber 5. As a result of the upwardly flowing hot 
gas stream it is pressed against the convex surface of the bending mold 7. 
The shaping ring 13, which in the meantime has returned from the cooling 
station 16 into the bending station, is located in the precise bending 
position below the upper bending mold 7. The bending mold 7 is now lowered 
and presses the largely already prebent glass plate 3' against the shaping 
ring 13. At this instant a brief overpressure in the cavity within the 
bending mold 7 releases the glass plate 3' from the latter and the bending 
mold 7 returns to its upper end position. 
As soon as the bending mold 7 has freed the path for the movable shaping 
ring 13 and the transfer ring 28, the door 20 opens and the shaping ring 
13 travels together with the bent glass plate into the cooling station 16. 
Simultaneously the transfer ring 28 with the glass plate positioned 
thereon travels from the intermediate station 27 into the bending station 
5. When the transfer ring 28 reaches its fixed end position, the hot gas 
stream is switched on so that the glass plate is raised from the transfer 
ring 28 and pressed against the upper bending mold 7. The transfer ring 28 
now moves back into its starting position and again frees the bending 
chamber 5 for the shaping ring 13, which, after the preceding glass plate 
has cooled and been removed from the bending ring, again moves into the 
bending chamber 5 and assumes its end position below the bending mold. The 
described process then starts anew. 
A further shortening of the cycle times of such a bending furnace can be 
achieved with an apparatus like that shown in FIG. 2. In this case the 
transfer of the glass plates 3, heated to the bending temperature, into 
the bending chamber 5 and the transfer of the bent glass plates 3' from 
the bending chamber 5 into the cooling station take place completely 
independently of one another in two different planes. In this way it is 
possible to provide on each side of the bending chamber a cooling station 
into which the bent glass plates are alternately transferred. 
The installation also comprises a continuous furnace 1, an intermediate 
station 27 and a bending chamber 5, which are successively arranged in the 
longitudinal axis of the furnace. The suction plate 23 movable on the 
rails 25 once again transfers the glass plates 3 heated to the bending 
temperature from the conveying rollers 2 in the intermediate station 27 to 
the transfer ring 28, which is movable on the rails 37 into a clearly 
defined position below the bending mold 7. 
In the bending station 5, and below and transverse to the rails 37, are 
provided rails 40, on which are displaceable two trolleys 41 (only one is 
shown), each of which carries a shaping ring 42. On each of the two side 
walls 43 the bending chamber 5 is provided an opening 44 (only one is 
shown) leading to a cooling station. The rails 37 extend into the cooling 
stations on either side of the bending chamber. The two successively 
arranged trolleys 41 are firmly coupled together, or there are two bending 
rings 42 on a common trolley 41. The bending rings have a spacing 
corresponding to that between a bending station and the cooling station. 
Thus, in the working position, one of the two shaping rings 42 assumes a 
clearly defined position below the bending mold 7, while the other shaping 
ring simultaneously assumes its end position in the associated cooling 
station, in which the glass plate is cooled and subsequently removed from 
the bending ring. 
The operation of this apparatus fundamentally corresponds to the procedure 
described above, i.e. the transfer of the glass plate 3 from the conveying 
rollers 2 to the transfer ring 28, as well as the positioning of the glass 
plate on the transfer ring 28, take place while the frame 10 with the 
bending mold 7 is lowered in the bending chamber and the preceding glass 
plate is pressed into its final shape and placed on the shaping ring 42. 
As soon as the frame 10 with the bending mold 7, after having placed the 
bent glass plate on the shaping ring 42, has again been brought into the 
upper starting position, the path for the transfer ring 28 into the 
bending chamber is freed and the transfer ring 28 with the next glass 
plate moves into the bending chamber 5. Simultaneously, the shaping ring 
42 with the bent glass plate is transferred into the cooling station 
associated therewith, while from the other cooling station the shaping 
ring from which the glass plate has been removed is simultaneously moved 
into its end position below the bending mold 7. 
In the apparatus shown in FIG. 3, and contrary to what has been described 
in the previously described embodiments, the suction plate 23 is not 
horizontally movable and is instead mounted so as to be vertically 
raisible and lowerable. For this purpose it is fixed to rods 51 which can 
be transferred into different height positions by lifting mechanisms 50 
positioned above the furnace roof. The suction plate 23 can in this way, 
after it has taken the glass plate 3 from the conveying rollers 2, be 
raised to such an extent that the transfer ring 28 on the rails 52 can 
move into its end position below the suction plate 23. When the glass 
plate 3 has been placed on the transfer ring 28, a suitable mechanical 
means, such as, e.g., the schematically indicated plungers 30, carries out 
the precise positioning of the glass plate 3 with respect to the transfer 
ring 28. 
When, following a bending process in the bending chamber 5, the bending 
mold 7 has been returned to its upper position and the bent glass plate 31 
has been transferred into the following cooling station with the aid of 
the shaping ring 13 movable on the rails 53, the transfer ring 28 with the 
glass plate 3 positioned thereon moves from the end position below the 
suction plate 23 into the other end position in the bending chamber 5. 
Immediately after reaching the end position of the transfer ring 28 in the 
bending chamber, the glass plate 3 is raised from the transfer ring 28 by 
the hot gas stream and pressed against the bending mold 7. The transfer 
ring 28 then moves back to its waiting position in the intermediate 
station 27 and consequently frees the bending chamber 5 for performing the 
bending process. The transfer ring 28 waits in the intermediate station 27 
until the suction plate 23 has raised the next glass plate 3 from the 
conveying rollers 2 and has assumed its raised position. The transfer ring 
28 then moves into its end position below the suction plate 23 and the 
described process starts anew. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.