Abstract: An improved heat transfer fin structure of the type normally fabricated from sheet metal and wrapped about a conduit to provide enhanced heat transfer efficiency between the conduit and a fluid in contact with the conduit, has a plurality of elongated leg portions spaced apart from each other and openings defined in the space between the leg portions. The structure provides the advantage of high efficiency combined with high peripheral stability.

Abstract: An improved solar energy collector has a twisted expanded metal/bristle fin combination structure which provides improved energy absorbing efficiency, good peripheral stability, and efficient heat transfer capabilities. The structure is normally formed by wrapping and thereby expanding, a lanced sheet metal about a conduit in a spiral fashion. In the preferred embodiment, the outer peripheral structure presents a series of protrusions wherein every other protrusion is twisted at an angle with respect to the spiraling structure.

Abstract: The flapper valve is to be utilized in a compressor of the type having a valve chamber adjacent a discharge or outlet port. The valve comprises a flexible valve member in the valve chamber which has a port closure at the front end thereof to seal the discharge port of the compressor. A backer plate is similarly received in the valve chamber and has one end in engagement with the rear end of the valve member to normally bias the port closure to a position wherein the discharge port of the compressor is closed. The valve member is provided with forwardly extending arms which cooperate with upturned ears on the backer plate to prevent longitudinal and lateral movement of the valve member. Accordingly, the valve member and backer plate need not be connected together prior to placement into the valve chamber. Alternatively, if the member and plate are connected together, their relative positions will be maintained even if the connection breaks.