GB2096753A - Drying adhesive - Google Patents

Abstract

An apparatus for drying the adhesive between the adjacent plies of corrugated board during manufacture comprises an array of hotplates (1) and an endless belt (3) having a portion extending across and closely adjacent the hotplates. A web (2) of board to be dried is sandwiched between the belt and the hotplates and is drawn across the latter at the same speed and in the same direction as the belt. The web is pressed into close contact with the hotplates by supplying air under pressure to air plenum chambers (1) arranged on the opposite side of the belt to the web and having one side open to the belt. This arrangement of chambers supplied with air under pressure replaces the conventional method of loading the belt which uses intermittently spaced steel rollers, and thus avoids the disadvantages associated with the latter such as inefficient heat transfer due to intermittent narrow point loading, maintainence of the roller bearings, wear on the belt by the rollers, and the need to manually raise and lower the rollers in order to change the loading for different grades of board. <IMAGE>

Description

SPECIFICATION improvements in or relating to cokrugating machines This invention relates to corrugating machines, and in particularto the section thereof for drying the adhesive between adjacent plies of corrugated board produced by the machine.

Traditionally, the board in the form of a web is carried through the drying section by an endless belt which presses down on the moving web of board, forcing it into contact with hotplates in the form of steam-heated chests which impart the necessary heat to the board to dry the adhesive between the plies. At the end, beyond the hotplates, there is a section where there are two belts, one above and one below the web, which supply the main traction to the web. In order to keep the upper belt flat and pressed down onto the web, the upper belt is loaded with steel rollers arranged at intervals along its length.

There are several disadvantages with this known drying apparatus. Firstly, up to half the heat input to the hotplates is lost, and thus ineffective, as the heat transfer to the board is very inefficient.

Even though the rollers mentioned above are typically spaced every twelve inches along the belt they only exert a narrow point loading. The heat transfer would be more efficient if the loading could be made more uniform over the web in the region of the hotplates.

Secondly, the rollers require maintainance and this is quite expensive when one considers that there are typically 60 rollers and 120 sets of bearings for each drying section. Furthermore, the rollers cause damage to the belt which therefore needs occasional replacement.

Thirdly, the rollers must be lifted and lowered manually, depending on the weight desired by the operator for various grades of board, which can take 5 to 10 minutes before the machine is brought up to full speed.

Fourthly, there is a tendency for the board to be crushed by its passage through so many heavy rollers in succession. This leads to higher waste levels and customer rejects.

It is therefore an object of the present invention to provide a novel construction of drying apparatus for corrugated board which eliminates or reduces these disadvantages.

Accordingly, the present invention provides an apparatus for drying the adhesive between adjacent plies of corrugated board during manufacture thereof, the apparatus comprising an array of hotplates, and endless belt having a portion extending across and closely adjacent the hotplates, means for driving the endless belt, means for transporting a web of corrugated board across the hotplates in the same direction and at the same speed as the belt, the web being between the belt and hotplates, at least one air plenum chamber on the opposite side of the belt to the hotplates, one side of the chamber being open to the belt, and means for supplying air under pressure to the chamber, whereby the pressure of air in the chamber acting on the said opposite side of the belt is effective to press a moving web of board into close contact with the hotplates.

The advantages of the invention are that by replacing the steel rollers by air pressure inside one or more chambers a more uniform-loading of the web can be achieved, leading to a higher heating efficiency, and since the loading is achieved by pressurised air there are no moving parts to be maintained and wear on the belt is reduced. Furthermore, a change of loading pressure at present performed manually, can be effected by remote control, instantaneously, and can be changed during a run if desired. Finally, with a more uniform loading on the web the tendency for crushing the board may be reduced.

Preferably, the means for transporting the web of board across the hotplates comprises a further portion of the endless belt beyond the hotplates, a second endless belt having a portion extending closely adjacent and in the same direction as the further portion of the first mentioned belt, the arrangement being such that the web is sandwiched between the two belts in use, and means for pressing the adjacent portions of the two belts together.

The means for pressing the adjacent portions of the two belts together may comprise at least one further air plenum chamber on the opposite side of the further portion of the first mentioned belt to the second belt.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through the drying apparatus of a prior art corrugating machine, and Figure 2 is a similar cross-section through a drying apparatus according to the present invention.

It is to be understood that the actual manufacture of the corrugated board, up to the point where the adhesive between the plies needs to be dried, and after the drying has been accomplished, may be entirely conventional. For this reason only the drying apparatus of the corrugating machine has been shown in each case.

Figure 1 shows the form of drying apparatus used in prior art corrugating machines and described briefly above. The apparatus comprises an array of substantially coplanar hotplates 1 disposed side by side along the direction of motion of the web of corrugated board 2 which enters the apparatus on the left and leaves on the right. Each hotplate 1 comprises a respective steam-heated chest of conventional design which extends at least across the full width of the web 2. During its motion across the hotplates 1 the web 2 is pressed downwardly by an endless belt 3 at least as wide as the web 2 and which is loaded by steel rollers 4.

After passing across the hotplate section on the left of figure 1, the web 2 enters the cooling section on the right which also provides the main traction to the web. In the cooling section the web 2 is sandwiched between the belt 3 and a further belt 10 of similar width, the belts 3 and 10 being driven at one end by drive rollers 11,12 respectively in the direction of the arrows at the same speed and passing at their other ends around freely rotating rollers 13, 14. Any tendency to slackness in the much longer upper belt 3 is taken up by tensioning rollers 1 5, 1 6. Further steel rollers 5 are used to press the upper belt 3 down towards the lower belt 10 O so that the web 2 does not slip.The load on the belts 3 and 10 exterted by the rollers 5 in the cooling section is supported by further rollers 6 beneath the belt 1 0. After cooling, the web passes on for cutting in conventional manner.

The conventional drying apparatus shown in figure 1 is modified, according to the present embodiment of the invention, by the substitution of a plurality of plenum chambers containing air under pressure for each set of rollers 4 and 5 of figure 1. This is shown in figure 2, where the same reference numerals have been used as in figure 1 for similar parts of the apparatus.

Each plenum chamber 7 is arranged closely adjacent the belt 3 and comprises a shallow housing 8 whose lower large area side is open to the upper surface of the belt 3 and which extends across substantially the full width of the belt 3. Air may be supplied under presure to each chamber 7 via a respective duct 9 by a respective variable high power electric fan of which one only is shown symbolically at 1 7. In the hotplate section each chamber 7 embraces a number of hotplates and within the area covered by each such chamber the loading on the web 2 is substantially more uniform than in the case of the rollers 4 of the prior art. Preferably the power of each fan 1 7 is independently variable so as to independently vary the pressure in each chamber 7. This permits changing not only the overall loading on the web 2 but, where a plurality of plenum chambers 7 are disposed immediately adjacent one another along the length of the drying section as shown in the preferred embodiment, also a differential loading as between one chamber and the next if required.

Claims (7)

1. In a machine for the manufacture of corrugated board, an apparatus for drying the adhesive between adjacent plies of the board comprising an array of hotplates, an endless belt having a portion extending across and closely adjacent the hotplates, means for driving the endless belt, means for transporting a web of corrugated board across the hotplates in the same direction and at the same speed as the belt, the web being between the belt and the hotplates, at least one air plenum chamber on the opposite side of the belt to the hotplates, one side of the chamber being open to the belt, and means for supplying air under pressure to the chamber, whereby the pressure of air in the chamber acting on the said opposite side of the belt is effective to press a moving web of board into close contact with the hotplates.

2. An apparatus according to claim 1, wherein the means for supplying air under pressure to the chamber comprises a variable high power fan.

3. An apparatus according to claim 1, including a plurality of air plenum chambers disposed immediately adjacent one another along the said portion of the belt, and means for supplying air under pressure to each chamber.

4. An apparatus according to claim 3, wherein the means for supplying air under pressure to each chamber comprises a respective independently variable high power fan.

5. An apparatus according to claim 1, 2, 3 or 4, wherein the means for transporting the web of board across the hotplates comprises a further portion of the endless belt beyond the hotplates, a second endless belt having a portion extending closely adjacent and in the same direction as the further portion of the first-mentioned belt, the arrangement being such that the web is sandwiched between the two belts in use, and means for pressing the adjacent portions of the two belts together.

6. An apparatus according to claim 5, wherein the means for pressing the adjacent portions of the two belts together comprises at least one further air plenum chamber on the opposite side of the further portion of the first-mentioned belt, and means for supplying air under pressure to the further chamber.

7. An apparatus as claimed in claim 1 substantially as herein described.