GB2228754A

GB2228754A - A "nailable" plastics member and method of manufacture

Info

Publication number: GB2228754A
Application number: GB9004265A
Authority: GB
Inventors: Alf Ekstroem
Original assignee: KABE HUSVAGNAR AB
Current assignee: KABE HUSVAGNAR AB
Priority date: 1989-03-01
Filing date: 1990-02-26
Publication date: 1990-09-05
Anticipated expiration: 2010-02-26
Also published as: SE463371B; SE8900703L; GB9004265D0; SE8900703D0; DE4006092A1; FI901021A0; GB2228754B

Description

A PLASTICS MATERIAL PROFILE MEMBER ANTD METHOD OF MANUFACTURE one of our

oldest building materials is wood, Wood is easy to machine and to some extent it can be moulded, as well. Unfortunately, wood has the disadvantage of being moisture-sensitive and susceptible to decay and f ungi. Another disadvantage is that wood changes in volume differently in different directions when exposed to moisture.

This is a well-known phenomenon which the specialist in the field has been trying to overcome for thousands of years. It would be of great benef it if certain of the disadvantages of wood could be eliminated.

It is an object of the invention to at least minimise the disadvantages referred to above. The present invention provides a new type of batten or profiled batten which is eminently suitable for building purposes, and also provides a new method of manufacturing such batten.

Profile sections formed of plastics material and with very good properties have been produced f or window sills and frames. They are unaffected by damp. They do not go mouldy and are not attacked by rot. They can be coloured. Moreover, their structure is such that low thermal conductivity is built-in. However, nailed joints and screwed joints cannot be made in these secions, which are usually made of polyvinyl chloride (PVC).

Insulating building materials formed of plastics material have existed for a long time also. These have 1 the disadvantage of low strength and, in many cases, of being hygroscopic.

According to the present invention there is provided a plastics material profile member having the same characteristics as a wooden batten which member is extruded from thermoplastics material into profile sections containing air-filled cavities, whose external form is calibrated after extrusion, characterised by an expanding agent being added to the thermoplastics material with the result that the finished profile contains small bubbles, i.e. is an expanded thermoplastics material and by projecting external parts of the profile surrounding cavities containing one or more inwardly extending projections, extensions or pins which, after expansion of the plastics material, partially fill the cavities and can form supports for nails or screws.

Also according to the present invention there is provided a method of manufacturing a plastics material profile member formed,of thermoplastics material according to the invention characterised by the profile tool also providing space for a central projection extension or pin when forming surrounding narrow cavities, and the projection extension or pin having, on its side facing the cavity, one or more narrow grooves where expansion of the thermoplastics material can be initiated, and also characterised by surrounding parts of the profile cooling so that welding together of expanded plastics material in the projection extension or pin and surrounding profile does not take place.

"I ai 1 1 A characteristic feature of the plastics material profile member of the invention is that it provides an excellent nailed or screwed joint. Modern self-tapping screws can be used. Another characteristic is that the profile or batten has low thermal conductivity, achieved in two ways; the batten is hollow and the load-bearing parts are formed of expanded plastics material.

It follows that, with these properties, the profile or batten does not absorb moisture and is not susceptible to rot or fungal attack.

A characteristic of the method of manufacturing the profile section is that a projection, extension or pin is formed between two walls of a profile, and that this pin has longitudinal grooves which expand when the extruded plastics material leaves the forming die.

The present invention will be further illustrated, by way, of example, with reference to the accompanying drawings, in which:

Fig. 1 is a cross-section through an ordinary milled batten. The shape shown is not typical of the invention, but is an example.

Fig. 2 is an ordinary profile section utilipable by window manufacturers.

Fig. 3 is a cross-section of a profile made from solid PVC. Such figure also shows the cavity in the f -i forming die of an extruder which should be capable of producing a batten in accordance with the invention.

Fig.4 is an example of an invented hollow batten in accordance with the invention.

Fig. 5 and 6 show details of a mould and the slender profile obtained from it.

Fig. 7 and 8 show an example of a similar invention but with a thick profile.

In many of the f ields of application for wood, the shape of the batten shown in Fig. 1 is required. A characteristic of such a batten is that it has a thick part 1 and a thin part, the f lange 2. If this shape of batten is manufactured in wood, it must be ensured that the wood is knot- free and that the batten is straight after a long drying period.

A plastics material profile can be simply produced by extruding PVC into a profile as shown in Fig. 2. The same external boundary lines are obtained. By means of calibration (finish-sizing) in manufacture, a smooth surface and straight profiles are obtained, as every tradesman knows. The profile in the figure has not been hatched, because it also represents the shape of the hollow space in the forming die from which the profile is t 0 1 extruded. If the profile is made of PVC, high flexural strength-values are obtained. The prof ile will not be susceptible to attack by moisture or rot; but unfortunately, nailed joints cannot be arranged in the profile, and the tradesman would like to have this.

A requirement for nailed joints is that the nail must be able to penetrate the material without the material cracking or splitting. In addition, the material in which the nail is to be fixed must present a sufficient length for contact with the nail.

The characteristic of the invention with a long nailing length can be seen in Fig. 3, in which a pin 3 is drawn in the f lange 2. Compared with Fig. 2, a 50% increase of the nailing is achieved in Fig. 3 if the nail is driven through the pin 3.

The pin 3 is the special novel f eature of the invention. It can be varied in length so that adequate strength is obtained, whilst at the same time the necessity for correct positioning of the nail is reduced. If the profile is made of solid pure PVC, however, there is still risk of the pin being broken off when a nail is driven through the flange 2 and pin 3.

If, on the other hand, an expanded plastics material is chosen - and this is specified by the pre.sent invention - a nail can penetrate into the pin without the pin splitting or being deformed in some other way. By selecting a width for the pin relative to the surrounding free space such that the free space is partially filled with expanded plastics material a support is obtained for the plastic pin, and also longer nail contact.

The invented batten therefore has a cavity in the flange 2, for example, containing a pin 3 which, owing to expansion after leaving the forming die, has varying density and in the favourable case fills the cavity with a denser part surrounded on one or both sides by an expanded plastics material which has bubbled out of the pin. This is shown with the irregular bulges 4 on the pin in Fig. 4.

A beneficial characteristic of this is that the swollen parts 4 of the pin 3 touch the walls of the profile; consequently the pin is not bent so easily when a nail has to penetrate the pin. Since cooling of the profile is different between the pin and the external walls of the profile, usually no welding together of external walls and expanded plastics material from the pin takes place.

Although the method of extruding plastics material originated with PVC, other materials can be included within the scope of the present invention. HQwever, expanded PVC will probably have considerable advantages and has yielded excellent results. The profile shape shown is not characteristic of the invented batten, and other versions can be produced by the specialist, within the scope of the present invention. Another version of the pin 3 is shown in Fig. 8.

A characteristic of the invented method is that the pin 3 - which has a cavity in the f orming die as its counterpart - does not have a smooth surface. Instead, the pin has grooves in it on the sides facing the external profile walls. Any specialist can make this form.

:1 A The specialist knows that if the hot soft profile from the former comes into contact with a cool calibrating device, the extruded expanding profile acquires a skin. The thickness of this skin can be varied by varying the cooling of the surface of the profile.

Inside the profile, where the pin 3 is situated, cooling cannot be achieved. Little skin is formed; instead, the plastic expands and shows a tendency to fill up the space between the external walls of the profile. This filling will be of low density. Contact the external walls is achieved also in the invented profile; but since the external calibrating former is cool, no welding together takes place between expanded plastics material from the pin and plastics material already set from the external walls.

In Fig. 5 an example is shown of the cavity 5 in a part of a forming die 6. In the centre is the cavity for a pin 7. Unlike the pin 3 in Fig. 3, this exhibits widening of the cavity in two places 8 and 9. With sole plastics material these widenings would have as their counterpart essentially a pin with raised portions on it. Since the invented method states explicitly that expanded plastics material is to be used, these prominences give indication of fracture in the skin around the pin. Plastics material bubbles out and can occupy after the former in the extruder, the cavity of the profile with a denser core 10 in the pin 3, surrounded by plastics material of a lower density 11 on each side of the pin in Fig. 6. The contact between expanded plastics material in the pin and the surrounding wall provides a support for the pin when a nail is to be driven through the prof ile wall and pin, but not penetrate through the other profile wall.

The method can be used also with a larger cavity. An example is given in Fig. 7 with the cavity in the f orming die and the resultant profile in Fig. 8. A IRT91 01 12, has formed in the middle of the profile. Distinct indications of fracture for the plastic skin are given with the tips 13. Around these tips, the plastics material expands and bursts the skin, f orming suitable supports for nails inside the profile.

The cavity shapes shown, see Figs.5 and 6, have provided good nail support from expanded plastics material resting against the external walls of the profile, usually without welding same together. Other types of indication of fracture for skin can be chosen by the specialist, as well. The choice usually depends upon the machine and upon the techniques of cooling and calibration, which are well known methods..

Expanded thermoplastics material has the advantage of being formable in heat, implying the further advantage that the profile produced can be heated and bent.

With the present invention, a method is obtained of producing a profile with the same characteristics as wood with regard to nailed and screwed joints. Compared with wood, formability, insusceptibility to moisture and low thermal conductivity are obtained, giving in every respect a simple product with many applications.

4 1 f k.

Claims

1. A plastics material profile member having the same characteristics as a wooden batten which member is extruded from thermoplastics material into profile sections containing air-filled cavities, whose ekternal form is calibrated after extrusion, characterised by an expanding agent being added to the thermoplastics material with the result that the finished profile contains small bubbles, i.e. is an expanded thermoplastics material and by projecting external parts of the profile surrounding cavities containing one or more inwardly extending projections, extensions or pins which, after expansion of the plastics material, partially fill the cavities and can form supports for nails or screws.

2. A plastics material profile member as claimed in claim 1, characterised by the expanded plastics material from the projections, extensions or pins being anchored at the projections extension or pin but not welded together with a surrounding external wall or walls.

3. A plastics material profile member as claimed in claim 1 or 2, characterised by the thermoplastics material consisting of PVC.

4. A plastics material profile member substantially as hereinbefore described with referenced to the accompanying drawings.

5. A method of manufacturing a plastics material profile member formed of thermoplastics material according A.I - to any preceding claim characterised by the profile tool also providing space for a central projection extension on pin when forming surrounding narrow cavities, and the projection extension or pin having, on its side facing the cavity, one or more narrow grooves where expansion of the thermoplastics material can be initiated, and also characterised by surrounding parts of the profile cooling so that welding together of expanded plastics material in the projection extension or pin and surrounding profile does not take place.

6. A method as claimed in claim 5 characterised by the grooves being formed by widenings of the projection, extension or pin in the cavity of the former for the projection, extension or the pin.

7. A method as claimed in claim 5 or 6, characterised by the expanding thermoplastics material consisting of PVC.

8. A method of manufacturing a plastics material profile member as claimed in claim 5, 6 or 7, substantially as hereinbefore described and illustrated.

Published 1990 atThe Patent Office, State House. 66 71 lijlbnrn. London WC1R 4TP. Further copies maybe obtainedfrom The Patent Ofrice. Sales Branch, St Mary ^,ray. Orpington, Kent BR5 3RD. Prir ted by Multiplex techniques ltd. St Mary Cray. Kent. Con- V87