Filling machine for thermoplastic cups

A filling machine for thermoplastic cups, with a cyclically operating conveying section which takes over a cup sheet web with thermoformed cups from a thermoforming station, there being provided, for the simultaneous filling of a batch of cups, for each cup of the batch, a filling unit with a filling cylinder and a filling pipe for a pasty filling product, the filling cylinder containing a filling piston on the product side. The technical problem is to provide a filling machine which is easily adjustable in terms of volume, works without a sucking action, and is easy to clean and sterilize. An air piston (31) is connected, on the drive side, to the filling piston (24) by a piston rod (40) and the filling cylinder (23) is closed off above the air piston (31) by a cylinder head (32) which is connected to a pressure compensation reservoir via a compensation pipe (35).

BACKGROUND OF THE INVENTION 
1. Technical Field of the Invention 
The present invention relates to a filling machine for thermoplastic cups, 
having a cyclically operating conveying section, for processing a cup 
sheet with thermoformed cups from a thermoforming station for a 
simultaneous filling of a batch of cups. 
The field of the invention is the online filling of thermoplastic cups with 
a pasty filling product. A pasty filling product is also taken to mean a 
liquid filling product such as a beverage preparation. Possible filling 
products are food preparations such as cottage cheese or other milk 
products, pudding, jam, beverages or the like. 
2. Prior Art 
A filling machine for thermoplastic cups is disclosed in Federal Republic 
of Germany patent application No. 40 25 714 A1. 
SUMMARY OF THE INVENTION 
The object of the invention is to provide a filling machine which is easily 
adjustable in terms of volume, works without a sucking action, and is easy 
to clean and sterilize. 
The foregoing and related objects are achieved by the presently claimed 
invention for a filling machine for thermoplastic cups, which includes a 
cyclically operating conveying section for processing a cup sheet web with 
thermoformed cups from a thermoforming station for the simultaneous filing 
of a batch of cups. For each cup of the batch, a filling unit with a 
filling cylinder is provided, along with a filling pipe for a pasty 
filling product. The filling cylinder contains a filling piston on a 
product side, in which an air piston is connected, on a drive side, to the 
filling piston by a piston rod and in which the filling cylinder is closed 
off above the air piston by a cylinder head, which is connected to a 
pressure compensation reservoir via a compensation pipe. 
The invention differs from the prior art in that the filling product is 
pressed into the filling cylinder and, as a result of the pressure in the 
pressure compensation reservoir, is forced out of the filling cylinder, 
the pressure in the pressure compensation reservoir being increased only 
slightly as the filling product is pressed in. The pressure depends on the 
viscosity of the filling product. A special drive for the filling piston 
is not necessary. Nor is a low-pressure action required to fill the 
filling cylinder with filling product. The air piston, which is separated 
from the filling piston, prevents the filling product from penetrating 
into the compensation space, so that the same is easy to sterilize and 
keep clean. The number of filling pistons can be adapted to the particular 
cup batch to be filled. 
The cleaning operation is facilitated by virtue of the fact that the 
filling cylinder is designed as a stepped cylinder with a filling-side 
portion having the smaller diameter for the filling piston and a 
drive-side portion having a larger diameter for the air piston. 
The unhindered flow of the cleaning agent is facilitated by virtue of the 
fact that a further portion, having the largest diameter, adjoins the 
portion of the filling cylinder and this further portion receives the air 
piston during the cleaning phase. For cleaning, the filling piston is 
displaced as far as it will go, to allow the cleaning agent to flow 
unhindered. 
The adjustment of the filling volume is made possible by virtue of the fact 
that, on the drive side, a spindle is arranged on the axis of the filling 
cylinder, a stop ring for the piston rod being displaceable on said 
spindle for the purpose of adjusting the filling volume. Each filling 
piston can thus be continuously adjusted from a volume of 0 up to the 
maximum value. The maximum value, or maximum limitation, of the filling 
piston is defined by a stop ring abutting against a plate, as further 
explained and illustrated in the accompanying drawing figures. A zero 
volume for the filling piston exists, and is so defined, as when this 
piston is not being used. This is also important for premetering or other 
additional metering. 
Guidance of the spindle at the end is achieved by virtue of the fact that 
the piston rod is of hollow design and can slide over the spindle. 
The filling product is treated better by virtue of the fact that the 
filling piston bears with a sealing lip against the cylinder wall. The 
filling piston is safe to run dry. The filling product is prevented from 
accumulating on the piston. 
The filling is controlled by virtue of the fact that a product conduit 
leading into a product chamber of filling cylinder can be shut off by a 
closing piston. 
The filling of the thermoplastic cups takes place by virtue of the fact 
that a filling valve leading to the filling pipe is provided at an outlet 
of product chamber. 
Any number of filling cylinders can be connected to a group conduit. The 
filling product is supplied under pressure in the group conduit. The 
pressure in the pressure compensation reservoir is about 0.5 bar. This 
pressure is adapted to the viscosity of the filling product. By pressing 
the filling product into the filling cylinder, the pressure in the 
pressure compensation reservoir changes only slightly, by about 0.05 bar. 
During operation, only negligible leakage losses occur, so that the 
compressed-air requirement is likewise negligible. The filling cylinder 
can be employed for premetering and for main metering.

DETAILED DESCRIPTION OF THE DRAWING AND PREFERRED EMBODIMENTS 
The latter comprises the following essential processing stations: 
an alternating unwinder 1 with two unwinding receptacles 2, 3 for in each 
case one reel 4 of a thermoplastic sheet 5, the reels 4 being alternately 
unwound; 
a continuous conveying section with conveying rolls, holders and grippers, 
which are not shown or explained in more detail. The conveying section is 
set for a cyclical movement, so that in each case one batch of 
thermoplastic cups is moved into a working station; 
a heating station 6 for heating the thermoplastic sheet 5 to the 
thermoforming temperature; 
a thermoforming station 7 for forming a batch of thermoplastic cups 8; 
a filling machine 9 for filling the thermoplastic cups 8 with a pasty 
filling product. The filling machine 9 is equipped with filling units 21, 
arranged in groups and each having a filling pipe 22, for filling a batch 
of thermoplastic cups; 
a sealing station 10 which is supplied with a lid foil web 11 from an 
alternating unwinder 12 via a heating station 13. The sealing station 
serves for heat sealing the lid foil onto the filled thermoplastic cups 
15; 
a punching station 14 for separating and singularizing the sealed 
thermoplastic cups 15 with a discharge gripper 16 which picks up the 
separated thermoplastic cups 20 batchwise and conveys them into 
a packing station 17, where the thermoplastic cups 20 are put into trays, 
cartons, pallets or other transport containers. The stations for final 
packaging are not shown. 
FIG. 2 shows a filling unit 21 with a filling cylinder 23 which receives a 
filling piston 24, the stroke of which is adjustable for the purpose of 
metering the filling product. The filling piston is bears with a sealing 
lip 45 against the internal wall of the cylinder, so that it works in such 
a manner as to be safe to run dry. Fouling of the filling piston by the 
filling product is thereby largely precluded. The filling cylinder 23 is 
connected, via a valve 25 with a closing piston 26, to a group conduit 27 
which supplies a group of filling units. 
The filling cylinder 23 is a stepped cylinder with a narrower portion 28 
for the filling piston 24, a widened portion 29, offset via an outer step, 
for an air piston 31, and a portion 30 again offset via an outer step. The 
filling cylinder 23 is closed off by a cylinder head 32 which receives two 
air conduits 34 connected via a compensation pipe 35 to a pressure 
compensation reservoir (not shown) or a pressure compensation pipe. 
Situated on the axis of the inner pipe 33 is a spindle 36 which is 
positioned in the axial direction in a plate 37 and has a head-side drive 
flange 38 for adjustment by hand, by means of a tool or by an actuating 
drive. The thread of the spindle 36 engages in the thread of a stop ring 
39 which is guided between the air conduits 34 in such a manner as to be 
secure against rotation. The stop ring 39 serves as a stop for a piston 
rod 40 or an end sleeve 33 of the piston rod 40, which carries the filling 
piston 24 and the air piston 31. The piston rod 40 is hollow at least in 
the head region to allow the spindle 36 to penetrate into the piston rod 
40. 
A product conduit 41 leads from the group conduit via the closing piston 26 
into a product chamber 42 of the filling cylinder 23. The product chamber 
42 is, on the other hand, connected to a filling pipe 22 via a filling 
valve 43 and a filling conduit 44. 
The mode of operation of the filling unit is as follows: in the pressure 
compensation reservoir there is normally a pressure of about 0.5 bar, 
which is adjusted in accordance with the viscosity of the filling product. 
To fill the filling cylinder 23, the closing piston 26 is opened, so that 
the filling product under pressure in the group conduit 27 enters the 
product chamber 42. The filling piston 24 is forced back. In the process, 
the pressure is increased slightly, by about 0.05 bar, to 0.55 bar as a 
result of the air in the pressure compensation reservoir being compressed. 
As soon as the set filling volume is reached, the end sleeve 33 of the 
piston rod 40 is abutting against the stop ring 39 and excites a sensor 
(not shown). The sensor signal results in the closure of the closing 
piston 26. 
Once the batch of thermoplastic cups is positioned in the filling station, 
a signal is generated to open the filling valve 43. The filling product is 
filled into the thermoplastic cups in each case via the filling pipe 22 as 
a result of the pressure in the pressure compensation reservoir. 
To clean the filling unit, the stop ring 39 of the spindle 36 is moved 
until it bears against the plate 37, thereby allowing the piston rod 40 to 
be pushed back a corresponding distance. This movement of the piston rod 
40 takes place under the pressure of the cleaning agent on the filling 
piston 24. When the piston rod 40 abuts against the stop ring 39 bearing 
against the plate 37, the filling piston 24 is situated in the portion 23 
and the air piston 31 in the portion 30, so that between the piston body 
and the internal wall of the cylinder in each case a gap remains free 
through which the cleaning agent can flow. The pressure compensation pipes 
serve as conduits for the cleaning agent. When the cleaning is finished, 
the stop ring 39 of the spindle 36 is in each case reset to the desired 
filling volume.