CONNECTION TO A PRESSURE VESSEL OF COMPOSITE MATERIAL

Abstract: A connection to a pressure vessel of composite material wound about a body part (1) a so-called liner of thermoplast with an end part (3) provided with an axial internal bore (5). The connection is characterized particularly in that the liner (1) extends somewhat into the bore (5) and ends with a first seat (8) across the bore (5) and in that a connection tube (9) provided with a second seat (11) is fixed relative to the end part (3) so that said seats (8, 11) seal towards each other, preferably with a packing between them (13).

Description: CONNECTION TO A PRESSURE VESSEL OF COMPOSITE MATERIAL The present invention relates to a connection to a pressure vessel of composite material, built of fibre material wound around a body part of thermoplast, a so-called liner, comprising an end part about which the fibre material is so provided, that the end part is embedded in and fixed by fibre material, the end part being provided with a substantially rotary-symmetrical axial internal bore. The composite material can have many different compositions. The most common is a matrix of epoxy plastic reinforced with glass fibres, but other plastics are also used, such as unsatu- rated polyester plastics. The fibres can be of various kinds, such as carbon fibres or aramide fibres. The thermoplast in the liner can be polyethylene, polypropylene or other appropriate plastic. It is chosen with regard to special requirements on e.g. chemical resistibility. Pressure vessels of composite material are becoming increasingly useful in various fields, particularly for heavier vehicles of various kinds. Originally such pressure vessels were manufactured by winding fibre material around a body part of aluminium, which thus formed the internal part, i.e. the liner, of the finished pressure vessel. Such a liner can be manufactured with a connect¬ ing part formed as a part of the liner with relatively thick material, which thereby admits an arrangement of a gas tight connection, e.g. by screwing on a connection tube. Aluminium has however certain drawbacks, e.g. in that it is unnecessary heavy and expensive. In addition, its resistance to fatigue is limited, which means that flaws can appear in a liner of the afore¬ mentioned kind due to the strain on the liner. Thermoplast has therefore come to be used as material in liners for pressure vessels of composite material. Here, it has proved to be a diffi¬ cult problem how to achieve a gas tight passage between the liner and the connection to the pressure vessel. The object of the present invention is to provide a connection of the kind mentioned in the introduction that is simple and reliable. According to the invention such a connection is characterized primarily in that the liner extends axially into said bore, connecting onto its surface, the liner ending with a rotatary- symmetrical first seat across the axial extension of the bore, the end part being provided with means to fix axially a connec¬ tion tube provided with a rotary-symmetrical second seat across its axial extension relative to the end parts, so that said seats, preferably with a relatively elastic packing between them, seal toward each other. In a preferred embodiment of the invention said fixing means con¬ sist of interacting threads arranged partly in said bore and partly on the exterior surface of the connection tube. The seats can have different shapes. The first seat can e.g. be plane, while the other seat is provided with a recessed groove, in which an elastic O-ring is placed. The invention is illustrated by the accompanying figure, which shows a longitudinal section through a portion of a pressure vessel of composite material with a liner of thermoplast and a connection according to the invention. A liner of polypropylene is designated by 1, and the composite material wound on it, i.e. glass fibre in a matrix of epoxy plastic, is designated by 2. An end part 3 externally provided with projecting parts in the form of both right-handed and left-handed threads 4 is embedded in the composite material. The end part 3 is formed with an internal axial bore 5, which is threaded with threads 6. The liner 1 extends with one part 7 somewhat into the bore 5, connecting with the threads of the end part 6 in its bore 5. The liner ends with a plane surface 8 which constitutes a first seat. A connection tube 9 provided with an external thread 10 is screwed on to the bore 5, the threads 6 interacting with the threads 10. The con¬ nection tube ends with a second seat 11 across its axial ex¬ tension. This seat 11 is formed with a recessed groove 12, in which a relatively elastic O-ring 13 is placed. The connection tube 9 is screwed on so much as to provide a secure seal between said seats 8 and 11. A manufacturing-technical advantage with the connection according to the invention is that the first seat can easily be adjusted to a plane form, or other desired form, across the bore 5 after the fibre material has been wound on the body part.

Claims: Claims 1. A connection to a pressure vessel of composite material, built of fibre material (2) wound around a body part (1) of thermo¬ plast, comprising an end part (3) about which the fibre material (2) is so provided, that the end part (3) is embedded in and fixed by the fibre material, the end part being provided with a substantially rotary-symmetrical axial internal bore (5), c h a r a c t e r i z e d in that the liner (1) extends axially into said bore (5), connecting onto its surface, the liner ending with a rotary-symmetrical first seat (8) across the axial extension of the bore, the end part (3) being provided with means (6, 8) to axially fix a connection tube (9), provided with a rotary-symmetrical second seat (11) across its axial extension relative to the end part, so that said seats, preferably with a relatively elastic packing between them, seal toward each other. 2. A connection according to claim 1, c h a r a c t e r i z e d in that said means for axial fixing consists of interacting threads (6, 8), provided partly in said bore (5) and partly on the external surface of the connection tube (9).

Inventors: KROGAGER MAX, LUNDIN ANDERS JAN ALLAN, SKOGLUND BO, KROGAGER, MAX, LUNDIN, ANDERS, JAN, ALLAN, SKOGLUND, BO
Applicants: SAAB COMPOSITE AB, SAAB COMPOSITE AKTIEBOLAG
Application year: 1989
Main classification: F16J12
IPC codes: F16L41, F16L58