Abstract: Means for hinging or removably attaching a cover to a chassis comprising a retainer device including a pair of arms spring-urged away from one another. The retainer device is fixed to the chassis with the ends of the arms extending outward into openings in the cover. The arms can be manually pinched to disengage them from the cover openings to thereby permit the cover to be removed from the chassis. Utilization of a pair of retainer devices on the chassis enables one of the devices to be disengaged while the other remains engaged to thus hinge the cover relative to the chassis.

Abstract: Disclosed is a unitary heat sink apparatus in the form of a U-shaped body of thermally conductive material adapted for use in connection with semiconductor device packages having a thermally conductive transfer plate adjacent one major face of the device package. Typical of such device packages is the TO-220 plastic power package. One leg of the U-shaped clip urges the thermal transfer plate into intimate contact with a flat portion of the opposite leg by the spring action provided by the base of the U. An aperture in the base of the U allows the leads to extend from the heat sink. Fins are included on one leg of the heat sink and means for attaching the heat sink apparatus to printed circuit boards are also disclosed.

Abstract: An infrared telescope that has a detector therein that must be cooled to r 20.degree.K in order to function properly is cooled by freezing a pool of liquid cryogen through rapid venting of a chamber containing the cryogen to a low pressure to cause the cryogen to freeze by the pressure of the liquid cryogen being dropped below the fluid triple point pressure. In this way, the frozen pool of liquid cryogen which is in contact with the detector maintains the detector in a cooled and operating range.

Abstract: A detector of an infrared telescope that must be cooled to near 20.degree4.degree. K in order to function properly is cooled by spraying a liquid cryogenic fluid through a small nozzle into a vented chamber of subatmospheric pressure to cause the pressure of the cryogenic fluid to be dropped below its fluid triple point pressure and thereby freeze to deposit frozen crystals on the detector and thereby cool the detector to the required temperature for proper functioning of the detector. The frozen crystals deposited on the detector will be sublimed therefrom by the heat leaked and generated in the detector.