Abstract: A method of assembling a heat exchanger unit (12) that involves an expansion technique for securing a heat exchanger tube (18) to a number of fins (24) without physical intrusion into the tube passage. The method includes forming the tube (18) to have substantially parallel tube portions (26). Pairs of tubes portions (26) may be connected by a bend or an elbow (28) to yield a serpentine tube configuration. Each of the fins (24) is formed to include one or more apertures that are sized to receive the tube portions (26). The fins (24) are then arranged to form a fin pack (22), so that their apertures are aligned to form an aggregate passage through the fin pack (22). The tube portions (26) are then inserted into the aggregate passage, such that the elbow (28) (if present) and/or the ends of the tube (18) remain outside the fin pack (22).

Abstract: An improved method is provided for assembling a heat exchanger by mechanically joining one or more pairs of tubes with fins arranged in a fin pack. The method involves a novel external expansion technique that is performed between pairs of tubes and internally of the fin pack, in a manner that enhances the mechanical joint strength and metal-to-metal contact between the tubes and fins of the heat exchanger, while enabling the assembly process to be reduced to a single operation. Consequently, the method of this invention avoids the shortcomings of internal expansion techniques, and provides a significant improvement over prior art external expansion techniques. The method of this invention also yields a novel heat exchanger configuration, in which only facing surfaces of the tube within the fin pack are deformed in order to expand and mechanically join the tube to the fins. Finally, the present invention also encompasses a unique expansion tool for externally expanding the tube portions within the fin pack.

Abstract: A valve assembly is disclosed. The valve assembly includes a valve body having inlet and outlet openings. A central cavity is defined by the valve body. A movable poppet is positioned within the cavity. A plug closes the cavity and a spring extends between the rear end of the poppet and the plug. The rear end of the poppet defines a cylindrical recess and the valve body defines a drain opening adjacent the outlet. The cylindrical recess provides a fluid passage to the drain opening. The poppet is opened when the fluid pressure on the inlet side overcomes the force of the spring and is closed when the force of the spring is greater than the fluid pressure force on the front of the poppet.