Gas cylinders sold in Portugal are fitted with a detachable disc containing the said information However, these discs sometimes fall off during. transport and some cylinders are therefore sold not bearing the information required by law.

This invention solves the problem in an innovative way. It simultaneously ensures permanent provision of information, greater durability, 100% recycling and energy saving, which all contribute to greater economy and improved environmental protection.

STATE OF THE ART After conducting a market survey we concluded that the most efficient and long lasting method of attaching the information is the use of retractable polyurethane sleeves that almost totally cover the cylinder.

A number of methods exist for fitting these sleeves and they are used in various industries, for example for labelling soft drinks and for protecting products. But they have never been used on gas cylinders.

These systems employ heating by hot air or steam in tunnels to retract the sleeves.

A preliminary search showed the most important patent to be WO 9011223 of Bressendorf Ole for a film retracting method using heat and a tunnel. It also uncovered patent US 56116425 relating to a pasteurisation method and device for a continuous line of products.

As well as being rather expensive, since they use electrical energy and/or steam continuously, these methods also result in a major loss of energy, which invariably contributes to increased levels of pollution and heating of the planet.

On the other hand, experience shows that applying this continuous flow steam tunnel technique directly is ill advised for gas cylinders due to the physical and chemical behaviour of the various materials. And not just the product in the cylinders but also the materials making up the actual cylinders and fittings, in particular, the steel body and the brass, along with the plastic, rubber and soft steel making up the valve.

This mix of materials, with such a different coefficients of expansion, constitutes a safety risk not only during cylinder filling but in terms of component ageing, i. e., loss of elasticity due to large temperature changes from 15/20C to 100/120°C and the length of exposure inside the steam tunnel, reckoned at 21 seconds for retracting each sleeve.

For some of the components, such as the valve 0-rings, the temperatures reached are very close to the manufacturer's recommended yield point. This is a strong argument for not using a continuous flow steam tunnel The pressure of the gas in the cylinders, in a liquid state at pressures of between 2 bars for butane and 5 bars for propane, rises due to the sudden increase in temperature and consequently represents a safety risk at the filling station.

This invention, called a STEAM DRAGON, solves these problems, since it uses only non-polluting energy sources that are not a danger in highly explosive working areas: - compressed air - steam.

And the system works on a cylinder-by-cylinder basis that dramatically reduces the length of time each cylinder is exposed to the steam from 21 seconds to 0.7 seconds. This accounts for an energy saving of about 90% or more, and avoids injecting the steam directly into the cylinder's more sensitive parts, in particular the valve.

EQUIPMENT The Steam Dragon is basically comprised of two opposite twin units or subsystems (Fig. 1), working simultaneously. Each unit is made up of a hemisphere or steam chamber (7) and a perforated metal plate (8) on the inside, acting as a steam outlet. The units join together when a cylinder passes, surrounding it almost completely and forming a steam or pasteurising chamber while leaving the valve outside.

Each twin unit is fitted with a steam line consisting of an insulated cylinder and pipe with a hose to carry the steam to the consumption area, where it enters the equipment.

As the steam is produced discontinuously a condensation trap is incorporated in the steam line (Fig. 11).

Each unit consists of -base plate (1) - left guard (2) of hemisphere with slit for fitting of steam line - right guard (3) of hemisphere - chamber support (4) - steam chamber upper support (5) - steam chamber lower support (6) - steam chamber back end plate (7) - steam chamber perforated plate (8) - steam hose connector (9) - piston (21) - guiding shaft (15) Each unit is fitted with a guard (Fig. 8 & 9) that completely covers it and contains a slit at the side for the steam line.

The equipment also consists of an infrastructure made up of a line for conveying the cylinders through the steam area, that includes a compressed air admission sensor to control, upstream, the flow of cylinders in the sleeve attaching area and, downstream, the- admission into the steam area. The conveying line has a brake (Fig. 10), fitted with a pneumatic piston (22), to hold the cylinder when another is already in the steam area.

The attached figures show: FIG. 1-Perspective of a twin units set FIG. 2-Plan of operating installation-during steaming phase FIG. 3-Elevation of operating installation-during steaming phase FIG. 4-Plan of installation on standby FIG. 5-Elevation of installation on standby FIG. 6-Exploded diagram of a twin unit FIG. 7-Steam chamber hemisphere (side and front elevation, plan) FIG. 8-Plan of equipment guard cover FIG. 9-Elevation of equipment guard cover FIG. 10-Perspective of brake at beginning of cycle FIG. 11-Assembly diagram for steam line draining system FIG. 12-Diagram of steam circuit OPERATION As mentioned above, the cylinders are carried to the steam area by a conveyor and its various compressed air sensors control the flow of cylinders, first in the sleeve attaching area and then at the steam area entrance. These sensors are part of an automated system and are linked to the steam system. A timer controls the injection of steam into the chamber.

When information is received from a sensor that cylinder 1 has entered the steam area, a brake piston is operated by compressed air at the beginning of the cycle (Fig. 10), which restrains cylinder 2 on the conveyor so that another cylinder cannot force its way into the hemispheres. As the rod (45) driving the brake pushes back the stopper (46) and allows the cylinder to pass, two pistons (21) are automatically actuated which push the hemispheres against the cylinder with the sleeve already attached, totally surrounding it and gripping it. Steam, which meanwhile has been carried by the insulated pipe and the steam hose, is injected into the chamber formed by the junction of the two hemispheres through the holes in the perforated plate (8), causing it to stick to the outer walls of the cylinder. This process takes only 7/10* second. At the end of that time the pistons (21) pull the hemispheres (7) back, releasing cylinder 1. At the same time the brake (FIG. 11), which was restraining the cylinder, is removed, releasing the cylinder and restarting the cycle.

LEGEND Ref. Item 1 Base plate 2 Left chamber guard 3 Right chamber guard 4 Chamber support 5 Steam chamber upper support 6 Steam chamber lower support 7 Steam chamber back plate 8 Steam chamber perforated plate 9 Steam hose connector 10 Chamber guard fitting 11 Pneumatic support 12 Pneumatic support device 13Shaft bearing 14 Bush 15 Guiding shaft 16 Air compressed activators support 17 MIO hex head bolt 18 M10 hexagonal nut 19 M12 hexagonal nut 20 Guiding shaft fitting 21 Piston 22 50 x 80 double effect 23 Automatic blow-off float valve-3/4 FF 24 Male spherical valve 25 Air compressed angular valve with conical seat-3/4 FF-stainless steel 263/2-1/8-MEC/C 27 Closed timer 283/2-1/8-P/P 295/2-1/8-P/M 30 Open timer 31 Closed timer 323/2-1/8-P/M 33 Open timer 34 Closed timer 35 5/2-1/8-P/M 36 5/2-1/8-P/M 373/2-1/8-P/M 38 3/2-1/8-P/M 39 3/2-Button/M 40 3/2-ON-OFF switch 41"or"function 42 3/2-STOP interlock button 43"or"function 44 Counter/Meter 45 Brake driving rod 46 Rubber stopper