Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1982-11-19
1984-08-28
Massie, Jerome W.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
144347, 144352, 144354, 156264, 156293, 156295, 1563042, 156497, B27G 1100, B32B 3120
Patent
active
044682735
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL SCOPE
The invention relates to a method for manufacturing wood poles consisting of a number of sections which are glued together along abutting side surfaces so that a tubular pole with central cavity is formed. Poles of this type can be used primarily as power line poles but also as masts of various types, columns for buildings, bridges etc.
BACKGROUND OF THE INVENTION
For many years power lines have been constructed using natural poles made from pressure-impregnated pine. Because of developments in modern forestry however there has been a drastic reduction in the availability of full-grown timber and hence also of natural poles having the requisite dimensions. Because of this poles of glued timer have been developed which are designed to replace natural poles. Examples of such designs are shown in DE No. 665 210, GB No. 745 540, FR No. 2 348 345 and WO No. 80/02709.
In spite of the urgent demand for glued poles and in spite of the fact that a plurality of glued pole designs have been produced in past years, the tubular glued timber pole has not as yet however been widely employed for power lines and similar demanding applications. One reason for this is that from the production viewpoint these poles give rise to a number of problems which have not been satisfactorily solved using available techniques. These problems concern both the jointing and the gluing of the individual sections, also the requisite impregnation of the glued construction.
DESCRIPTION OF THE INVENTION
The aim of the invention is to solve the above-mentioned problem in providing initially a method for facilitating the jointing and gluing of the sections. Hence in accordance with the present invention it is proposed that glue be applied to the side faces which are to be joined together, that the side faces provided with glue be brought into intimate contact with each other so that a tube is obtained, that sealing covers or the like are applied at both ends of the tube so that this is sealed (instead of covers it is naturally possible to envisage plugs of various types), that air is pumped out of the central cavity through one or both of the said covers or the like, thus giving a vacuum in the cavity in relation to the external pressure, whereby the contact pressure between the abutting side faces increases, and that the vacuum is maintained until these glued joints have become fixed. Possibly the outside of the tube is also subjected to an overpressure in comparison with the surrounding pressure, whereby the contact pressure between the abutting side edges is further increased.
Because in accordance with the invention the air is pumped out so that the pressure drops in the pole, the boiling point of the glue also drops if the glued joint is in communication with the cavity. To prevent this a barrier is applied appropriately between the cavity and the glued joint. This barrier can for example consist of a thin extended sealing strip or a metal wire between the two abutting side faces near the inside of the tube. Preferably however, in accordance with one embodiment of the invention, the barrier is obtained by providing at least one of the two side faces with a slight projection--a mini-tongue--which extends along one side face immediately inside the inner face of the tube. During assembly the mini-tongue is partially pressed into the abutting side surface so that a complete seal is obtained. By this means the risk of boiling because of pressure reduction can be eliminated even if the pole is heated, which as such as favourable in order to accelerate the curing of the glue.
The individual sections are preferably given a trapezoidal shape, which as such is known. To facilitate jointing in accordance with the invention the side faces are preferably provided with round tongues and grooves which both from the viewpoint of production technique and for jointing the sections together is considerably more favourable than previously proposed tongue and groove shapes. To facilitate effect impregnation and to adapt the construction t
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patent: 3916502 (1975-11-01), Bagnulo
patent: 4111247 (1978-09-01), Hasenwinkle
patent: 4394409 (1983-07-01), Hertel
Eklund Tore
Schmidt Torbjorn
Massie Jerome W.
NYA Varmlands Limtra Aktiebolag
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