GB2096923A

GB2096923A - Impregnation of cellular sheet material

Info

Publication number: GB2096923A
Application number: GB8105140A
Authority: GB
Original assignee: BRITISH VITA CO Ltd
Current assignee: BRITISH VITA CO Ltd
Priority date: 1981-02-18
Filing date: 1981-02-18
Publication date: 1982-10-27

Abstract

Each side of cellular sheet material (22) is impregnated simultaneously with a different impregnant by passage through the nip of a pair of rollers (10, 12). Impregnant is delivered to the crown of each roller, upstream of the nip, from a tiltable reservoir (14) the lip (20) of which rests on the crown. <IMAGE>

Description

SPECIFICATION Impregnation of cellular material This invention relates to impregnation of cellular material and more particularly apparatus for impregnation of cellular material such as foamed plastics material.

Impregnation of foamed plastics material has been carried out in the past in a number of different ways. One simple method is by dipping form in a bath of impregnant. Such a method does not permit close control of the loading of the foam with impregnant.

Another method comprises passing sheet foam through the nip of a pair of rollers, there being a pond of impregnant in the generally triangular section space above the nip. This method does permit better control of the amount of impregnation by adjustment of the speed of travel of the foam and the pressure applied by the nip.

It is sometimes desirable to impregnate only one side of sheet material or to impregnate opposite surfaces of sheet material with two different impregnants. At present that cannot be effected using the above described methods.

According to the present invention there is provided for impregnating cellular material comprising a pair of rotatable rollers arranged to form a nip therebetween, a reservoir for impregnant arranged to deliver impregnant onto the surface of a roller at a distance from the nip whereby in use on rotation of the rollers, impregnant is conveyed on a roller surface from the reservoir to the side of sheet material passing through the nip in contact with the said roller surface.

The present invention enables, therefore, one side only of sheet material to be impregnated. The other side of the material can be impregnated with a different material by providing a second reservoir arranged to deliver the other impregnant material to the other roller. The loading of impregnant material depends, inter alia, on the speed of the rollers and on the quantity of impregnant delivered by a reservoir onto the associated roller surface.

The latter factor is important because it makes it possible with the present invention to apply impregnant to the rollers from the two reservoirs at different rates so that the loading with impregnant on one side of the cellular material is different to that on the other side.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows apparatus for impregnating sheet material diagrammatically in end elevation.

Referring to the drawing the impregnation apparatus comprises a pair of rollers, 10, 12 arranged to form a nip therebetween. Means (not shown) is provided for rotating the rollers in opposite directions about their axes as indicated by the arrows.

A reservoir 14 for impregnant is disposed adjacent roller 10. The reservoir is in the form of an elongate box that extends along the length of the roller. The box is arranged to pivot about an axis 17 parallel to the roller axis. The side 18 of the box adjacent the roller is open and the floor of the box is extended by a flexible lip 20 which rests on the roller surface. As can be seen in the drawing reservoir 14 is arranged to deliver impregnant material to an upwardly moving surface of the roller 10 shortly before such surface reaches its highest point. Reservoir 14 can be arranged so that the lip 20 rests on the crown of the roller 10 so that the impregnant only has to flow horizontally onto the roller avoiding the need for the impregnant to be carried on the roller surface against gravity in an upwardly moving surface of the roller 10.Similar provision is made in respect of reservoir 16 and it is, therefore, not necessary to describe that further.

In use sheet material 22 to be impregnated is led through the nip of the rotating rollers 10, 12.

Impregnant from reservoir 14 is carried on the surface of roller 10 into contact with one side of the sheet (the left side as viewed in the drawing).

At the same time impregnant from reservoir 1 6 is carried on the surface of roller 12 into contact with the other side of the sheet material.

The impregnant flows from each reservoir onto the associated roller and forms a layer of substantially uniform thickness around the upper surface of the layer. The thickness of the layer can be adjusted by pivotting the reservoir about axis 17. To maintain a constant delivery of impregnant onto the rollers it is necessary that the reservoirs themselves be continuously replenished from a supply (not shown) by means of taps 24 arranged at intervals along the reservoir. If the impregnant contains suspended solids it may be desirable to provide means for preventing such solids from settling out. Such means may comprise a recycling arrangement for transferring impregnant from the reservoir back to the supply.

The quantity of impregnant delivered to a roller need never exceed that which can be absorbed by the material 22. Nevertheless doctor blades 26 are provided for engagement on the roller between the nip and the point of application of impregnant so as to remove any traces of impregnant left on the roller surface after impregnation.

With the invention it has been found that precise and uniform levels of impregnation can be obtained. What is more the level solids in the impregnant can be relatively high so that less time and energy is required to dry the impregnated material.

The present invention can be used for impregnation of any material but it is particularly useful for impregnation of foamed plastics such as polyurethane foam which requires to be impregnated with appropriate flame retardant or other substance to make it suitable for use in upholstered furniture.

1. Apparatus for impregnating cellular material comprising a pair of rotatable rollers arranged to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Impregnation of cellular material This invention relates to impregnation of cellular material and more particularly apparatus for impregnation of cellular material such as foamed plastics material. Impregnation of foamed plastics material has been carried out in the past in a number of different ways. One simple method is by dipping form in a bath of impregnant. Such a method does not permit close control of the loading of the foam with impregnant. Another method comprises passing sheet foam through the nip of a pair of rollers, there being a pond of impregnant in the generally triangular section space above the nip. This method does permit better control of the amount of impregnation by adjustment of the speed of travel of the foam and the pressure applied by the nip. It is sometimes desirable to impregnate only one side of sheet material or to impregnate opposite surfaces of sheet material with two different impregnants. At present that cannot be effected using the above described methods. According to the present invention there is provided for impregnating cellular material comprising a pair of rotatable rollers arranged to form a nip therebetween, a reservoir for impregnant arranged to deliver impregnant onto the surface of a roller at a distance from the nip whereby in use on rotation of the rollers, impregnant is conveyed on a roller surface from the reservoir to the side of sheet material passing through the nip in contact with the said roller surface. The present invention enables, therefore, one side only of sheet material to be impregnated. The other side of the material can be impregnated with a different material by providing a second reservoir arranged to deliver the other impregnant material to the other roller. The loading of impregnant material depends, inter alia, on the speed of the rollers and on the quantity of impregnant delivered by a reservoir onto the associated roller surface. The latter factor is important because it makes it possible with the present invention to apply impregnant to the rollers from the two reservoirs at different rates so that the loading with impregnant on one side of the cellular material is different to that on the other side. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows apparatus for impregnating sheet material diagrammatically in end elevation. Referring to the drawing the impregnation apparatus comprises a pair of rollers, 10, 12 arranged to form a nip therebetween. Means (not shown) is provided for rotating the rollers in opposite directions about their axes as indicated by the arrows. A reservoir 14 for impregnant is disposed adjacent roller 10. The reservoir is in the form of an elongate box that extends along the length of the roller. The box is arranged to pivot about an axis 17 parallel to the roller axis. The side 18 of the box adjacent the roller is open and the floor of the box is extended by a flexible lip 20 which rests on the roller surface. As can be seen in the drawing reservoir 14 is arranged to deliver impregnant material to an upwardly moving surface of the roller 10 shortly before such surface reaches its highest point. Reservoir 14 can be arranged so that the lip 20 rests on the crown of the roller 10 so that the impregnant only has to flow horizontally onto the roller avoiding the need for the impregnant to be carried on the roller surface against gravity in an upwardly moving surface of the roller 10.Similar provision is made in respect of reservoir 16 and it is, therefore, not necessary to describe that further. In use sheet material 22 to be impregnated is led through the nip of the rotating rollers 10, 12. Impregnant from reservoir 14 is carried on the surface of roller 10 into contact with one side of the sheet (the left side as viewed in the drawing). At the same time impregnant from reservoir 1 6 is carried on the surface of roller 12 into contact with the other side of the sheet material. The impregnant flows from each reservoir onto the associated roller and forms a layer of substantially uniform thickness around the upper surface of the layer. The thickness of the layer can be adjusted by pivotting the reservoir about axis 17. To maintain a constant delivery of impregnant onto the rollers it is necessary that the reservoirs themselves be continuously replenished from a supply (not shown) by means of taps 24 arranged at intervals along the reservoir. If the impregnant contains suspended solids it may be desirable to provide means for preventing such solids from settling out. Such means may comprise a recycling arrangement for transferring impregnant from the reservoir back to the supply. The quantity of impregnant delivered to a roller need never exceed that which can be absorbed by the material 22. Nevertheless doctor blades 26 are provided for engagement on the roller between the nip and the point of application of impregnant so as to remove any traces of impregnant left on the roller surface after impregnation. With the invention it has been found that precise and uniform levels of impregnation can be obtained. What is more the level solids in the impregnant can be relatively high so that less time and energy is required to dry the impregnated material. The present invention can be used for impregnation of any material but it is particularly useful for impregnation of foamed plastics such as polyurethane foam which requires to be impregnated with appropriate flame retardant or other substance to make it suitable for use in upholstered furniture. CLAIMS

1. Apparatus for impregnating cellular material comprising a pair of rotatable rollers arranged to form a nip therebetween, a reservoir for impregnant arranged to deliver impregnant onto the surface of a roller of said pair at a distance from the nip whereby in use on rotation of the rollers impregnant is conveyed on a roller surface from the reservoir to the side of cellular sheet material passing through the nip in contact with the roller surface.

2. Apparatus as claimed in Claim 1, wherein a second reservoir is provided for impregnant, said second reservoir being arranged to deliver impregnant onto the surface of the other roller of said pair at a distance from the nip whereby in use on rotation of the rollers impregnant is conveyed on the other roller surface from the reservoir to the other side of sheet material passing through the nip in contact with the other roller surface.

3. Apparatus as claimed in Claim 1 or Claim 2, wherein means are provided for rotating the rollers in opposite directions.

4. Apparatus as claimed in any preceding claim wherein the rollers are arranged for rotation about substantially horizontal axes.

5. Apparatus as claimed in Claim 4, wherein one or both reservoirs are arranged to deliver impregnant to a roller at or adjacent to the highest point of travel of said roller surface.

6. Apparatus as claimed in any preceding claim, wherein means are provided for removing impregnant from a roller downstream of said nip and upstream of the point at which impregnant is applied to the roller from a reservoir.

7. Apparatus for impregnating cellular material substantially as described with reference to the accompanying drawing.