Abstract: The cylinder of a reciprocating compressor is provided with a flanged collar defining an annular recess adjacent the side walls of the cylinder bore disposed for entry of the piston skirt during the downstroke into the recess, compressing gas therein. Communication is provided between the recess and the space above the piston and cylinder head, increasing the initial pressure above the piston and causing greater pressure to be developed during the compression stroke. The result is an increase in the volumetric efficiency of the compressor.

Abstract: A solar heating unit for disposition exteriorly of a building window for heating the air within the space interiorly of the window embodying a casing with a transverse divider for creating a rear passage and a front passage which are in communication in their lower portions. The upper end of the rear passage connects with the forward end of a rearwardly extending lower duct having a cool air inlet at the rearward end thereof. The upper end of the front passage connects with the forward end of an upper duct progressing rearwardly above the lower duct and with there being a warm air outlet at the rearward extremity thereof. A heat exchanger is disposed within the front passage for impingement thereon of solar radiation passing through a transparent panel defining the front of said casing. A thermal responsive closure is provided at the upper end of said front passage for closing same when the temperature within the front passage has descended to a predetermined level.