| 摘要 |
A diffusion pump includes a flat metal boiler plate having an upper face defining a floor for a pool of a vaporizable diffusion pump fluid or oil and a lower face against which the metallic sheath of a tubular electric heater is pressed by a coextensive massive clamping plate. The heater has a tendency to be overheated if only air is its thermal load. To prevent overheating of the heater because of variations in the geometry of the heater sheath which tend to cause air spaces between the sheath and the face of the boiler plate, a thin flexible metal crush plate is disposed between the clamping plate and the heater. The crush plate has a plurality of spaced, raised dimples adapted to contact many portions of the heater sheath throughout the length of the sheath. As the clamping plate, the flexible plate and the heater are urged toward the boiler plate by nut and bolt assemblies securing the clamping plate to the boiler plate, the dimples are deformed whenever they are in contact with the heater sheath. The deformed dimples urge virtually the entire length of the sheath into contact with the face of the boiler plate and insure that pressure is applied to the heater sheath at the points of contact. Since there are many points of contact, the occurrence of local overheating, i.e., hot spots, is virtually eliminated.
|
