METHOD FOR PRODUCING PIPE SLEEVES FROM MINERAL WOOL

Abstract: A method for producing pipe sleeves of mineral wool is explained according to which cut strips of impregnated non-cured mineral wool on a belt are allowed to pass into a forming unit in order to be cured by having hot air blown through. When the sleeve has been discharged the belt being endless returns via a drive station to the initial position. The sleeve thus produced is cut to the required length.

Description: Method for producing pipe sleeves from mineral wool The material mineral wool possesses in addition to good insulating characteristics also other advantageous properties such as good temperature resistance. As a rule use is made of products in the form of parallelepipeds but in certain cases cylindrical tuhular products are required for insulating tubes for conveying heat or cooling media. Such products are known as pipe sleeves. They are used in industrial applications as well as in ordinary housing construction. They are also of interest as insulating materials for district heating lines. The conventional method for producing pipe sleeves of mineral wool is characterised in that using a winding machine one winds thin gauze about a core so as to form a pipe sleeve. The mineral wool is impregnate with a resin, e.g. phenolic resin in non-cured condition. The winding process entails winding one pipe sleeve at a time. Later on it must be cured by blowing through hot air. Thereafter it is often necessary to trim the outer diameter before cutting off the outer ends so as to achiev a pipe sleeve of the right length. This is done in a sawing machine. In another sawing machine the slot extending in the longitudinal direction of the sleeve is made, which enables the sleeve to be fitted to the pipe which is to be insulated. As can be deduced from the above such a production method is time-consuming since all the above operations must be carried out on a single pipe sleeve the length of which is normally < 1 metre. If one then wishes to automate the process very complicated machines are required. After all, if the internal diameter is to be changed when using such an automatic machine it is necessary to replace all the cores. It should also be clear that the costs of such a machine are high and that it requires much space. A sophisticated timer has to be provided but even if this is available problems arise since the raw material used entails variations within the process. This principle of automated winding thus results in a sensitive machine involving much downtime and poor quality yield. How the present invention relates to a method of producing pipe sleeves. This method can be described as a kind of continuous compression moulding. A web of non-cured mineral wool on a belt conveyor is made to form a pipe-.sleeve by the belt with the material on top of it being bent to a pipe sleeve between two pipes: AXL inner one known as the core and an outer one known as the moulding pipe. The belt consists advantageously of a readily flexible material. At the same time it should be of mesh- ype, on the one hand to give a better grip and on the other hand to enable hot air to pass through at the curing stage. Curing can be achieved by quite simply heating the entire machine and relies on heat conduction. This is an inefficient method. It is considerably more efficient to allow hot air to pass through the material. This can be achieved by e.g. conducting hot air through the inside of the core, which through holes drilled through the core can be made to pass along the material. If now the belt and the moulding pipe are also perforated the gases can be evacuated by connecting an enclosure surrounding the entire unit to the suction side of a fan. The hot air can be generated in several different ways. Even hot exhaust gases can be used. Ξlectric heating toe is feasible. A figure is enclosed with a view to describing the method in greater detail. It shows a section of the forming unit not containing any material. The core (l) is a pipe(faulty section in figure). The most suitable material is a steel pipe. The core is located in such a position as to be resting on the web of mineral wool directly within the inlet of the forming unit. An upward-bent outer part enables connection to be made for hot air. The outer part of the forming unit is the outer moulding pipe (2), which in the same way as the core advantageously consists of steel. The inlet end of this pipe may be funnel-shaped. The funnel in its turn may be secured by means of stays to a stand, which holds the entire unit together. The inner shell of this pipe must be subjected to extremely fine surface treatment since at this point the friction between the belt and the pipe must be kept as low as possible in order to expose the belt during its operation to as little tensile force as possible. This pipe too should be perforated so as to allow hot air to be blown through in either direction. The pipe is also slotted. This slot is described in greater detail below. To hold the core against the pipe, which as stated above is secured by means of the funnel holder, a blade flange is provided, which extends along the entire length of the core. It is welded (if use is made of a steel pipe) to the core. The height of this blade flange is such that the upper part of the blade fits into the above mentioned slot in the moulding pipe. In this way a slot is produced in the pipe sleeve, when the belt carries mi eral wool, which is cured as it passes through the forming unit. An outer shell (4) is provided with a view to creating a space capable of being evacuated for the gases passing and generated in connection with the curing process. The belt in the machine is pulled with the aid of a geared motor driving a shaft about which the belt is laid. In order to avoid slippage a counter-roller is provided, which as practical experience shows should if at all possible be rubberised so as tc ensure a better grip. The drive package is positioned in such a way -. ".. achieve a pull through the forming unit. On the opposite siue _ :÷_ " l _ * ion roller of preferably highly cambered design should be crcviαe:. r :r this in connection with the belt drive causes stabilisation. When changing the product, i.e. altering the __re • -___!, or moulding pipe diameter the belt is removed and the forming uni i.- t •..- ■ .en out of the outer shell which can be dismantled _.icr_g • _ gener-_.t i . .-_ new forming unit is inserted with the aid of the rciders and new furine1- shaped units are mounted in position once the belt has again been taken through the forming unit. There are of course many possibilities for different embodiments. To secure the blade flange to the core it is for instance also possible to weld a short blade flange to the opposite side. This then produces a groove on the side opposite to the slot in the pipe sleeve, which at a later stage facilitates application of the sleeve to the pipe which is to be insulated. The choice of material is important. In the first place a belt material must be found, which is capable of bearing the relatively high tensile forces encountered. In addition, the material must resist BAB Q RIQIN^W -_U this force at elevated temperatures resulting from the curing process. Temperatures of more than 200°C are possible. Now it has been shown that use can be made of a mesh of aramide fibres (e.g. with the trade mark Kevlar) . With a view to preventing excessively strong adhesion between the mineral wool and the mesh (belt) it is advisable to enclose this belt mesh by means of a PTFE-type material (e.g. Teflon). As stated above, the core and the moulding pipe are best made of steel. In this connection it is important to ensure by polishing that there is low friction between the mineral wool/belt and the moulding pipe on the one side and between the mineral wool and the core on the other side. The holes provided in the core and in the moulding pipe to enable air to be blown through for curing should if possible be countersunk or may be drilled with an angled drill. The angle should be- such that clearance is ensured, i.e. the axes of the holes should be so positioned that an acute angle is formed between them and the The material in the outer shell may be aluminium. It should in addition be insulated on the inside in order to prevent operating personnel from being burnt, use may advantageously be made of mineral wool. The diameter range to which pipe sleeves can be produced according to this method may be quite varied. Only the frictional forces constitute a restriction. I.e. the tensile strength limitationsof the belt are decisive. After all, the friction increases with the circumference.

Claims: Patent Claims 1. A method for producing pipe sleeves of mineral wool characterised in that one leaves strips of mineral wool with a width equal to the cuter diameter of the sleeves which are to be produced. The strips are introduced into a forming unit. The latter consists of a core (l) with welded flange blade (2) extending along the entire length of the core'. The outermoulding pipe is slotted, so that the ether longitudinal side of the flange blade fits into the slot. The strips are introduced into the forming unit on a flexible, perforated belt. The belt is made to lie against the inner surface of the moulding pipe. The belt is pulled through the forming unit and if heat at a certain temperature is introduced into the unit so that the non-cured resin contained in the mineral wool is cured, a pipe sleeve is thus formed, which having left the forming unit can be cut to the required lengths. 2. A forming unit for pipe sleeves in accordance with claim 1 characterised in that the core and theirculding pipe are perforated so that hot air for curing can be conducted from or to the core through the mineral wool and the forming pipe. The evacuation of air is then brought about either from the core or from the space surrounding the moulding pipe.This space is produced with the aid of an cuter shell (4).

Inventors: AOBERG ULF, AOBERG, ULF
Applicants: AOBERG ULF, AOBERG, ULF
Application year: 1985
Main classification: F16L59
IPC codes: B29C53, B29C67