| 摘要 |
<p>A shutter consists of a plate (4) which pivots inside a surround (2). The plate is made from two identical halves (4a, 4b), fitted together face to face with overlapping edges, and its surround is made from two rectangular members, each having a thickness equivalent to half the plate and joined together to form stops for the plate edges. In a variant of the design the plate and surround can be circular in shape. The plate has spindles it diametrically-opposite edges which engage with matching holes in the surround and allow the shutter to turn about a central pivot for opening and closing. Seals can be included to make the shutter airtight.</p> |
