| 摘要 |
<p>The heating device is formed by two sheets of plastic or rubber, pref. black in colour and welded to form a storage vessel. This is enclosed by a transparent film together with an insulating, possibly metallised film which acts also as a support. Two valves are included for inflating the outer vessel and two fittings for filling and draining it. When empty to device folds up quite small.</p> |
