GB2094218A - Method of manufacturing corrugated sheets - Google Patents

Abstract

Method and apparatus for continuous manufacturing of corrugated sheets P of thermoplastic synthetic resin, the apparatus including an extruder 11 to produce sheeting, a polishing station 12, a corrugating station 13, a trimming station 14, a takeup station 15 and a cutting station 17, the corrugating station 13 including a number of sets of upper and lower corrugating rolls, having different corrugating pattern in each set, the method comprising bringing one set close to each other at the plane of the sheeting while all other rolls are kept separated from each other. <IMAGE>

Description

SPECIFICATION Method of manufacturing corrugated sheets This invention relates to a method of manufacturing corrugated synthetic resin sheets continuously.

More particularly, it is concerned with a method which can continuously manufacture corrugated sheets having different corrugated patterns without interrupting the moulding operation.

It is known to manufacture a large number of corrugated synthetic resin sheets having a single corrugated pattern applied continuously by employing a large moulding line handling the entire moulding process, including extrusion moulding of synthetic resin sheeting, polishing, corrugating trimming, cutting, and delivery at stations arranged in line.

In the event that it is desired to apply a different corrugated pattern to corrugated sheet, however, it is necessary to change a series of equipment beginning with the corrugating station to another series of equipment suited for the manufacture of differently corrugated sheets. This series of equipment is usually carried on a bogie, but its change requires a long time of at least four hours before the operation can be resumed. Such change of equipment amounts to a heavy loss of time and labour.

The change of equipment for the manufacture of differently corrugated sheets has necessarily required extensive work, and presented a lot of problems. The interruption of the moulding operation in a manufacturing line including a serial combination of the extruder and the corrugated station has led to a number of disadvantages for example: 1) Polyvinyl choride (PVC), which is a thermoplastic synthetic resin which is most often used for the manufacture of corrugated synthetic resin sheets, is very liable to decomposition under heat in the extruder or die. If the extruding operation is interrupted, the PVC remaining in the extruder and the die is decomposed and corrodes the extruder and the die. A long time of, say, at least 20 hours is required for dismantling grinding the corroded surfaces, and reassembling the equipment.

2) If the change of equipment beginning with the corrugating station is carried out with the extruder kept in operation in order to avoid the loss of time referred to in (1 ) above, there results a loss of synthetic resin, though the extruder can be maintained in order. This loss amounts to at least 680 Kg, if the extruder is operating for extrusion at a rate of 170 kg per hour.

3) In order to avoid the loss of the synthetic resin as referred to in (2) above, it is possible to cool and crush into pellets for reuse any synthetic resin sheeting extruded from the extruder during the period of change of equipment. This method, however, requires a considerable amount of labour, and a separate apparatus for the purpose.

4) A large space is required for the preparation and storage of the corrugating apparatus for the manufacture of differently corrugated sheets, and all the other apparatus associated therewith, and for the work of any such change.

5) The series of equipment beginning with the corrugating station is usually carried integrally on a frame, and forms a unit which is extensive in size, and is not easy to move.

It has been usual to manufacture a few kinds of differently corrugated synthetic resin sheets in large quantities in order to maintain the cost of the products at a low level. The various problems as hereinabove pointed out in connection with the change of equipment still remain to be solved, and hinder the realization on an industrial basis of the manufacture of many kinds of differently corrugated sheet products each in a small quantity.

An object of this invention is to provide a method of manufacturing differently corrugated thermoplastic synthetic resin sheets continuously without interrupting the extruding operation, which eliminates the various drawbacks of the prior art.

It is also an object of this invention to provide apparatus for carrying out the method which can easily continue to manufacture differently corrugated thermoplastic synthetic resin sheets without interrupting the extrusion moulding operation.

In accordance with the invention there is provided a method of manufacturing corrugated thermoplastic synthetic resin sheets continuously by passing continuously extrusion moulded theremoplastic synthetic resin sheeting between a set of upper and lower corrugated rolls under heat in a corrugating station, said corrugating station including a plurality of sets of upper and lower corrugated rolls, each of said sets consisting of corrugated rolls having a corrugated pattern which is different from that of the corrugated rolls forming another set, said method comprising bringing the upper and lower corrugated rolls forming one of the said sets close to each other selectively in a plane in which said sheeting is fed, while keeping all the other rolls separated from each other.

According to a further aspect there is provided apparatus for manufacturing synthetic resin sheets continously comprising an extruder for continuously extrusion moulding thermoplastic synthetic resin sheeting a corrugating station at which the resin sheeting is passed between a set of upper and lower corrugated rolls under heat said corrugating station including a plurality of sets of upper and lower corrugated rolls, each of said sets consisting of corrugated rolls having a corruated pattern which is different from that of the corrugated rolls forming another set, and means for bringing the upper and lower corrugated rolls forming one of said sets close to each other selectively in a plane in which said sheeting is fed, while all the other rolls are kept separated from each other.

With this method and apparatus it is possible to manufacture differently corrugated sheets for example, having small corrugations with a pitch of, say, 30 to 70 mm, or large corrugations with a pitch of, say 70 to 130 mm, or square corrugations, continuously in a single manufacturing line.

The invention will now be described by way of example with reference to the drawings in which: Figure 1 is a diagrammatic view of a conventional apparatus for the manufacture of corrugated sheets of thermoplastic synthetic resin, Figures 2A and 2B are diagrammatic representations of sets of rolls in a corrugating station of apparatus constructed in accordance with the invention, Figure 3 is a perspective view of a corrugating unit constructed according to the invention, and Figure 4 is a diagrammatic view of apparatus constructed in accordance with the invention for the manufacture of corrugated sheets of thermoplastic synthetic resin.

Figures 1A and 5B are views showing alternative pairs of rolls for use in the apparatus.

In Figure 1 conventional apparatus is shown for producing corrugated sheets of a thermoplastic synthetic resin material. Sheeting of a thermoplastic synthetic resin, such as polyvinyl chloride, having a thickness of 0.6 to 1.0 mm, is extrusion moulded by an extruder 1 having a T-shaped or circular moulding die at its outlet. The sheeting thus moulded is polished by polishing rolls 2, and corrugated in a corrugating station 3 by a set of corrugated rolls of the kind shown, for example, in Figures 5A or 5B.

The sheeting thus corrugated is cold and solid when leaving the corrugating station. The corrugated sheeting is trimmed along its longitudinal edges by a trimming device 4, and cut into corrugated sheets of desired length by a cutter 7, while it is held by a vice 6 travelling synchronously with the sheeting. The corrugated sheets P thus obtained are separated from the moulding line by a discharge roll device 8, and delivered to a storage area.

Figure 4 illustrates similar apparatus but constructed according to the invention. It is an integrated corrugated sheet manufacturing line which is used for carrying outthe method of the invention. As in the Figure 1 construction sheeting of a thermoplastic synthetic resin, such as a polyvinyl chloride or polycarbonate resin, having a thickness of 0.6 to 1.0 mm is extruded through the die of an extruder 11 at a rate of 3 to 3.5 meters per minute. The sheeting is polished by polishing rolls 12, and preheated by a preheating unit to a temperature of 1200 to 1300C.

The preheated sheeting is fed into a corrugated roll unit 13.

The sheeting is corrugated when passing between a set of upper and lower corrugated rolls a having a corrugated pattern as shown, for example, in Figure 5A. As the roll temperature is controlled to decrease from the entrance to the exit of the roll unit 13, the corrugated sheeting leaving the roll unit is cold and solid, and ready for trimming. The solidified corrugated sheeting is trimmed along its longitudinal edges in a trimming unit 14, and has a predeter mined width. The sheeting is, then, received by a takeup roll assembly 15 at a speed corresponding to that of extrusion moulding, and delivered to a vice 16 and cutter unit 17. The corrugated sheeting travels along a path through the vice 16 and cutter 17 and a delivery roll unit 18.The vice 16 closes to hold the corrugated sheeting P against movement as soon as its leading edge has contacted a limit switch 20. Simultaneously with the closure of the vice 16, the vice 16 and cutter unit 17 advance in the direction of travel of the sheeting at a speed which is equal to that of the sheeting, and afterthe advance of the vice 16 and cutter unit 17 over a predetermined distance, a cutter of the unit 17 cuts the sheeting. Immedately thereafter, the vice 16 opens, and the vice 16 and cutter unit 17 return to their original position. The corrugated sheets P thus obtained are quickly delivered by the delivery roll unit 18 to a stackerfor storage purposes.

Referring to Figure 2, there is show diagrammatically a plurality of sets of upper and lower corrugated rolls in the corrugating station 13. Thermoplastic synthetic resin sheeting P leaving the extruder 11 and polishing rolls 12 is fed into the corrugating station which has a plurality of sets of upper and lower corrugated rolls as shown, for example, in Figure 2A. In Figure 2A, there are shown a first set of upper and lower rolls a and a second set of upper and lower rolls b having a different corrugated pattern from that of the rolls a. Each set consists of five pairs of upper and lower rolls as designated at 1 to V. In Figure 2A, the first set of rolls a are in their corrugating positions relative to the sheeting P, while the second set of rolls b are kept vertically separated from the sheeting.The rolls of each set can be brought together or separated from opposite side of a plane coinciding with the plane of travel of the sheeting. Appropriate means (not shown) is provided to enable the rolls to be moved in this manner. The number of pairs of the rolls in each set can be varied as desired to suit the kind of the thermoplastic synthetic resin to be treated, the various conditions dictated by the sheeting, and the moulding conditions.

The alternative arrangement in Figure 2B has three sets of upper and lower a, b and c, each of which consists of four pairs of rolls as indicated at 1 to 1V.

The rolls a to care corrugated differently from one another. In Figure 2B, the rolls a are in their corrugating position relative to the thermoplastic synthetic resin sheeting P, while the other rolls b and care kept vertically separated from the sheeting P.

Referring now to Figure 3, there is shown a corrugated roll unit which is used for carrying out the method. The roll unit of Figure 3 embodies the roll arrangement shown in Figure 2A, and includes a frame 31. A plurality of takeup units 36 are provided on both sides of the frame 31 for supporting a plurality of pairs of upper and lower corrugated rolls a and a plurality of different pairs of upper and lower corrugated rolls b independently of one another. The rolls a are in their corrugating position, while the rolls b positioned alternately with the rolls a are dept vertically separated from their corrugating positions.

Pipes 34, 34', 35 and 35' are connected to the corrugated rolls by rotary joints to supply the rolls with a heating medium, such as hot water, delivered through a main pipeline 32 and manifolds 33 and 33' to control the roll temperature.

The process and apparatus described are suitable for the manufacture of corrugated sheet products having a corrugated pattern a. If it is desired to manufacture corrugated sheets having a different corrugated pattern b without interrupting the extru sion moulding operation the rolls b are used. In the corrugated roll unit 13, the corrugated rolls b provided in five pairs, and having a corrugated pattern as shown, for example, in Figure 5B are preheated to a predetermined temperature by hot water.

The rolls a are moved vertically away from the sheeting, and then, the other upper and lower rolls b, which have been in their inoperative positions, are moved vertically toward each other, and brought into contact with the sheeting which is being continuously extruded from the extruder, without being cut. Simultaneously with the change of the rolls in the corrugated roll unit 13, the corrugated pattern of the takeup roll assembly 15 is also changed from type a and b, so that the corrugated rolls b may immediately start the corrugating operation. The line is now ready for manufacturing corrugated sheet products having the corrugated pattern b continuously in the same way as the corrugated sheets having the corrugated pattern.

Only a very short time of, say, 0.5 minutes is required for changing the rolls a to the rolls b in the corrugated roll unit 13. During this change, only a sheeting length of say, 2 m is lost without being corrugated.

The takeup roll assembly 15 comprises an upper pressing roll a orb having a corrugated pattern corresponding to the corrugated rolls a orn in the roll unit 13, and a lower larger diameter rubber roll C adapted to support the corrugated sheeting. The upper rolls a and b are rotatable about a counter 15' to suit the corrugated sheets to be manufactured.

The various units 12, 13, 14, 16 and 18 handling the various steps of the corrugated sheet manufacturing process may be carried on a pair of rails 10 to ensure that the sheeting advances in a fixed direction.

Alternatively, the wheels provided only on one side of the various units may be engaged with a rail to ensure that all the units be kept aligned with one another, while the wheels on the other side of the units are free to travel on a flat surface so that the movement and positioning of the entire equipment may be facilitated.

More than two sets of differently corrugated rolls may be provided as shown at a, b and c in Figure 2B.

It is thus possible to manufacture various kinds of differently corrugated sheets easily and quickly in a single corrugated roll unit. Each of the corrugated rolls may be composed of a plurality of unit members u as shown by broken lines in Figure 5A. These corrugated rolls can be easily adapted to different widths of the corrugated sheets to be manufactured, are light in weight and easy to handle, and provide a very high working efficiency in the change of corrugated rolls from one set to another, or the change of the rolls in their inoperative position to a different set of rolls.

It is therefore possible to manufacture differently corrugated sheets continuously without interrupting the extruder operation, since the corrugated rolls can be changed with the sheeting being continuously moulded, as has been described in detail. Accordingly, there is virtually on loss of the synthetic resin.

The change of the rolls is easier, and requires only a small amount of labour as compared with the prior art. It is possible to resume the corrugating operation almost simultaneously with the change the change of the corrugated rolls. Since the corrugated rolls in their inoperative position can be changed to different set of rolls during the corrugating operation, it is possible to manufacture many kinds of differently corrugated sheets continuously.

Claims (6)

1. A method of manufacturing corrugated thermoplastic synthetic resin sheets continuously by passing continuously extrusion moulded thermoplastic synthetic resin sheeting between a set of upper and lower corrugated rolls under heat in a corrugating station, said corrugating station including a plurality of sets of upper and lower corrugated rolls, each of said sets consisting of corrugated rolls having a corrugated pattern which is different from that of the corrugated rolls forming another set, said method comprising bringing the upper and lower corrugated rolls forming one of said set close to each other selectively in a plane in which said sheeting is fed, while keeping all the other rolls separated from each other.

2. A method as claimed in claim 1 wherein the rolls of each set are movable towards and way from one another from opposite sides of said plane.

3. Apparatus for manufacturing corrugated thermoplastic synthetic resin sheets continuously comprising an extruder for continuously extrusion moulding thermoplastic synthetic resin sheeting, a corrugating station at which the resin sheeting is passed between a set of upper and lower corrugated rolls under head said corrugating station including a plurality of sets of upper and lower corrugated rolls, each of said sets consisting of corrugated rolls having a corrugated pattern which is different from that of the corrugated rolls forming another set, and means for bringing the upper and lower corrugated rolls forming one of said sets close to each other selectively in a plane in which said sheeting is fed, while all the other rolls are kept separated from each other.

4. Apparatus as claimed in claim 3 including means for moving the rolls of each set towards and away from one another from opposite side of said plane.

5. A method of manufacturing corrugated thermoplastic synthetic resin sheets continuously substantially as hereinbefore described with reference to and as shown in Figures 2 to 5 of the accompanying drawings.

6. Apparatus for manufacturing corrugated theremoplastic synthetic resin sheets continuously substantially as hereinbefore described with reference to and as shown in Figures 2 to 5 of the accompanying drawings.