GB1577580A

GB1577580A - Treatment of foamed synthetic plastics materials

Info

Publication number: GB1577580A
Application number: GB2039177A
Authority: GB
Original assignee: RANWAL Ltd
Current assignee: RANWAL Ltd
Priority date: 1978-05-15
Filing date: 1978-05-15
Publication date: 1980-10-29

Description

(54) IMPROVEMENTS 1N OR RELATING TO THE TREATMENT OF FOAMED SYNTHET1C PLASTICS MATERIALS (71) We, RANWAL LIMITED, of Chaul End Lane, Luton, Bedfordshire, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the treatment of articles of foamed synthetic plastics materials and, in particules, relates to methods and apparatus for creating voids extending inwardly from surface regions of the body portions of such articles.

In accordance with one aspect of the invention there is provided a method of creating voids in a body portion of an article, the body portion being of foamed synthetic plastics material and each void extending from a surface region of and inwardly into the body portion, the method comprising applying heated surface elements to said surface region of the body portion of the article and relatively moving the heated surface elements and the body portion so that the heated surface elements pass into the body portion to create said voids, the heated surface elements having a temperature sufficient to cause destruction of the plastics material in contact wfth the heated surface elements.

In accordance with another aspect of the invention there is provided apparatus for creating voids in a body portion of an article, the body portion being of foamed synthetic plastics material and each void extending from a surface region of and inwardly into the body portion, the apparatus comprising a plurality of heatable surface elements, means for heating the surface elements to a temperature to effect destruction of the plastics material, and means for applying the heatable surface elements and said surface region of the body portion of the article against each other so that the heated surface elements can pass into the body portion of the article to a required depth to create said voids.

The invention also extends to articles manufactured in accordance with methods or on apparatus embodying the invention and particularly to such articles which are paint rollers.

The particular shape of an article to be treated and the material of which the article is comprised will determine particular characteristics of the inventive method or the inventive apparatus which are used. In a particular form of the method of the invention for use with articles of cylindrical form in which the voids are to be created in the peripheral surface of the article, the article is rolled over the heated surface elements, the heated surface elements penetrating into the body of the article to a predetermined depth. In accordance with the invention apparatus for treating such an article comprises heated surface elements and means for heating the surface elements to a required temperature and means for rolling the article across the surface elements together with means for limiting the degree of penetration of the surface elements into the body of the article.

These and other more detailed aspects of the invention will be described more completely in connection with apparatus embodying the invention for making paint rollers which is illustrated in the accompanying drawings, in which: Figure 1 is a schematic plan view of, and Figure 2 is a schematic view on line II--II of Figure 1, of the principal elements of the apparatus.

The embodiment of the invention now to be described is a machine for the treatment of cylindrical articles of a predetermined length and diameter which are to be used as rollers in the application of paint to generally flat surfaces. However, many of the principles described with respect to these articles will be applicable to other articles of different configurations.

The machine 1 comprises a main framework (not shown) on which is mounted a horizontal bed plate 2. Angle members 3 and 4 of equal length are located on the upper surface of the bed plate and extend parallel to each other longitudinally of the bed plate.

The angle members are spaced apart at a distance approximately equal to the length of the roller to be treated and the vertical surfaces thereof define therebetween and in cooperation with the bed plate a guide for a roller. The bed plate is covered with friction enhancing material.

Two apertures 5, 6 are formed in the bed plate 1 at opposite sides of the bed plate with respect to each other and at spaced apart points along the length of the bed plate. The apertures 5, 6 are of generally rectangular form and have transverse overlap, that is, they each extend from one edge to beyond the middle line of the bed plate.

Extending upwardly through each of the apertures are raised portions 7 of heatable platens 8. Each platen 8 is substantially coextensive with its corresponding aperture 5 or 6 and comprises a substantial metal main plate 9 from whose upper surface extend the integral raised portions 7 which, in the present embodiment, are formed as three ridges extending parallel to each other and parallel to the longitudinal direction of the bed plate. The upper surfaces of the ridges lie above the bed plate a required amount and constitute the heated surface elements which are to be applied to the surface region of the roller. The upper surface of the main plate is spaced a sufficient distance below the surface of the bed plate to provide a substantial air gap between the surface of the plate of the platen and an article rolling along the bed plate. A heat source (not shown) is located within the platen and comprises electric resistance elements. The platens in the respective apertures are of the same general form.

A sub-frame (not shown) is hingedly mounted on the main frame on an axis extending parallel to the angle members 3, 4 and is pivotable from a position in which it extends substantially parallel and coextensively with the bed plate 1 and spaced thereabove into a position displaced from the first position so as to provide access to the bed plate. Drive shafts 10 and 11 extend respectively across one end and the middle of the sub-frame and idle shafts 12 and 13 extend respectively across the middle and the other end of the sub-frame. A plurality of individual flat belts 14 extend around and between associated ones of the drive and idle shafts and the lower runs of these define a plane spaced above the bed plate, in the first position of the sub-frame, a distance which is slightly less than the diameter of the cylindrical article to be passed through the machine. A drive motor and reduction gearing 15 are also mounted on the main frame and are suitably connected to the drive shafts for driving the flat belts.

The bed plate 1 and the sub-frame are enclosed in a housing (not shown) to which is connected an extraction duct for extracting gases from within the housing. In addition the machine is provided with a hopper and a pneumatic feed system arranged to feed cylindrical rollers of foamed plastics material one at a time between the flat belts and the bed plate in operation of the machine.

Means are also provided for varying the speed of the flat belts and for maintaining the temperature of the ridges in the platens 8 at required levels.

In operation of the machine the electrical heating means are switched on to raise the temperature of the ridges 7 in the platens 8 to predetermined levels and the sub-frame is lowered to its position in which the flat belts 14 define a plane parallel to and spaced above the bed plate 1 and the drive motor 15 for the flat belts is actuated. The suction device for drawing gases from within the housing is also operated.

The pneumatic feed system is now operated to feed cylindrical rollers one at a time onto the bed plate 1 between the angle members 3, 4. The flat belts then cause the rollers to roll along the bed plate and over the platens, the rollers being guided between the two angle members defining the lateral edges of the path of movement of the rollers.

The presence of the friction enhancing material on the bed plate ensures that the rollers roll along the bed plate rather than slide.

During their passage along the length of the bed plate the rollers pass over the heated platens. Since the ridges extend above the upper surface of the bed plate the surfaces of the ridges are caused to contact the circumferential surface region of the roller and to press into the body portion of the roller. The temperature ob the heated surface is chosen such that the foamed plastics material contacting the heated surface is destroyed, e.g. by being vaporised or combusted, with the result that voids are created which extend into the roller from the circumferential surface of the roller in accordance with the shape and location of the ridges on the platens.

Since the upper surface of the main plate of the platen is spaced below the upper surface of the bed plate there exists an air gap between the heated main plate and the roller which serves to insulate the surface of the roller which is not to be treated from the effects of heat rising from the main platen. In addition air is drawn from outside the housing over the heated platen and between the roller and the main plate of the platen to improve this insulation effect.

By dividing the platen longitudinally and transversely into two longitudinally and transversely spaced apart parts a firm support for the roller during its entire passage along the bed plate is assured. Thus about one half of the roller is firmly supported on the bed plate at all times.

The suction device extracts from the housing noxious gases which derive from the process of destruction of part of the heat degradable foamed plastics material of the roller.

Modifications and alternative methods of construction are possible within the terms of the present invention. For example, the platens may be combined into one single element which extends across the width of the bed plate and a suitable supporting surface is provided between the ridges of the platen. Such a supporting surface must be adequate to protect the surface of the roller which is not to be treated from the effects of heat. This modification may therefore provide for the ridges in the platen to extend through apertures in a plate or sheet of low heat conductive material whose lower surface is preferably spaced above the main plate of the platen so as to reduce the heat which passes inevitably into the sheet or low heat conductive material.

Although this invention has been particularly described with reference to the treatment of cylindrical rollers of foamed synthetics material, it will be apparent that the invention is equally applicable in the treatment of articles of foamed synthetic plastics material of different configurations. For example, the article may have a plane surface which it is desired to treat in accordance with this invention. The means for applying the heated surface against the surface of the article to be treated may then comprise a suitable mechanical means for relatively moving the platen and the article towards each other to impress the surface of the ridges of the platen onto the surface of the article to be treated and into the body of the article. Suitable means can be provided to ensure that the heated surfaces on the platen penetrate to a predetermined depth into the body of the article. The form of the voids formed in the surface of an article to be treated will depend upon the particular shape of platen and associated ridges adopted in a particular case and on the nature of the relative movements of the platen and the article during the method of the invention.

As an example of a material suitable for treatment by the methods and apparatus of the invention reference is made to a 45 ounce ester foam marketed by Harrison & Jones Ltd. under the name RA 16. The heated surfaces are maintained at a temperature approximately in the range 290"C to 300 C.

WHAT WE CLAIM IS: 1. A method of creating voids in a body portion of an article, the body portion being of foamed synthetic plastics material and each void extending from a surface region of and inwardly into the body portion, the method comprising applying heated surface elements to said surface region of the body portion of the article and relatively moving the heated surface elements and the body portion so that the heated surface elements pass into the body portion to create said voids, the heated surface elements having a temperature sufficient to cause destruction of the plastics material in contact with the heated surface elements.

2. A method according to claim 1 in which destruction of the plastics material is caused by vaporisation of the plastics material or by combustion of the plastics material.

3. A method according to claim 1 or claim 2 wherein the body portion of the article is formed with a surface of revolution and the method includes rolling the surface of revolution relative to the heated surface elements 4. A method according to claim 3 including applying the heated surface elements first to one axial portion of the surface of revolution and then to the other axial portion while providing support for the axial portion not applied to the heated surface elements.

5. A method according to either claim 3 or claim 4 wherein the body portion of the article has a cylindrical surface of revolution.

6. Apparatus for creating voids in a body portion of an article, the body portion being of foamed synthetic plastics material and each void extending from a surface region of and inwardly into the body portion, the apparatus comprising a plurality of heatable surface elements, means for heating the surface elements to a tempera ture to effect destruction of the plastics material, and means for applying the heatable surface elements and said surface region of the body portion of the article against each other so that the heated surface elements can pass into the body portion of the article to a required depth to create said voids.

7. Apparatus according to claim 6 wherein said applying means includes means for rolling the body portion surface region across the heatable surface elements.

8. Apparatus according to claim 6 or claim 7 including a means defining a planar support surface and means for rolling the body portion along the support surface, the heatable surface elements protruding with respect to said support surface towards said means for rolling.

9. Apparatus according to any one of claims 6 to 8 wherein the heatable surface elements are defined by the outer surface

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. along the bed plate is assured. Thus about one half of the roller is firmly supported on the bed plate at all times. The suction device extracts from the housing noxious gases which derive from the process of destruction of part of the heat degradable foamed plastics material of the roller. Modifications and alternative methods of construction are possible within the terms of the present invention. For example, the platens may be combined into one single element which extends across the width of the bed plate and a suitable supporting surface is provided between the ridges of the platen. Such a supporting surface must be adequate to protect the surface of the roller which is not to be treated from the effects of heat. This modification may therefore provide for the ridges in the platen to extend through apertures in a plate or sheet of low heat conductive material whose lower surface is preferably spaced above the main plate of the platen so as to reduce the heat which passes inevitably into the sheet or low heat conductive material. Although this invention has been particularly described with reference to the treatment of cylindrical rollers of foamed synthetics material, it will be apparent that the invention is equally applicable in the treatment of articles of foamed synthetic plastics material of different configurations. For example, the article may have a plane surface which it is desired to treat in accordance with this invention. The means for applying the heated surface against the surface of the article to be treated may then comprise a suitable mechanical means for relatively moving the platen and the article towards each other to impress the surface of the ridges of the platen onto the surface of the article to be treated and into the body of the article. Suitable means can be provided to ensure that the heated surfaces on the platen penetrate to a predetermined depth into the body of the article. The form of the voids formed in the surface of an article to be treated will depend upon the particular shape of platen and associated ridges adopted in a particular case and on the nature of the relative movements of the platen and the article during the method of the invention. As an example of a material suitable for treatment by the methods and apparatus of the invention reference is made to a 45 ounce ester foam marketed by Harrison & Jones Ltd. under the name RA 16. The heated surfaces are maintained at a temperature approximately in the range 290"C to 300 C. WHAT WE CLAIM IS:

1. A method of creating voids in a body portion of an article, the body portion being of foamed synthetic plastics material and each void extending from a surface region of and inwardly into the body portion, the method comprising applying heated surface elements to said surface region of the body portion of the article and relatively moving the heated surface elements and the body portion so that the heated surface elements pass into the body portion to create said voids, the heated surface elements having a temperature sufficient to cause destruction of the plastics material in contact with the heated surface elements.

3. A method according to claim 1 or claim 2 wherein the body portion of the article is formed with a surface of revolution and the method includes rolling the surface of revolution relative to the heated surface elements

4. A method according to claim 3 including applying the heated surface elements first to one axial portion of the surface of revolution and then to the other axial portion while providing support for the axial portion not applied to the heated surface elements.

portions of elements upstanding from a main plate of- a heatable platen.

10. Apparatus according to claim 9 when dependent on claim 8 wherein the surface of the main plate from which the elements extend is spaced away from said support surface.

11. Apparatus according to any one of claims 8 to 10 wherein said heatable surface elements are effective in one transverse portion only of the path of movement of the body portion of the article over a length of said path, said support surface being effective in the other transverse portion of said path over said length of said path.

12. Apparatus according to claim 11 wherein said length of said path is substantially equal to the circumference of said body portion.

13. Apparatus according to claim 11 or claim 12 wherein in another length of said path the heatable surface elements are effective in another transverse portion of the path.

14. Apparatus according to any one of claims 8 to 13 wherein belt drive means are provided so as to extend parallel to the support surface for causing the body portion of an article to roll over the support surface.

15. Apparatus according to any one of the preceding claims 6 to 14 wherein the apparatus includes a housing enclosing at least the said applying means and heatable surface elements and fume extraction means connected to the housing.

16. Apparatus according to claim 15, when dependent on claim 9, wherein air can be drawn from outside said housing over said main plate between said elements.

17. A method of creating voids in a body portion of an article in accordance with claim 1 and substantially as hereinbefore described.

18. Apparatus for creating voids in a body portion of an article in accordance with claim 6 and substantially as hereinbefore described.

19. An article when made by a method or on an apparatus according to any one of the preceding claims.

20. The article of claim 19 which is a paint roller having voids extending inwardly from its cylindrical surface.