Abstract: According to a preferred embodiment, an improved method and apparatus for manufacturing tube and fin heat exchangers that includes a step for reducing the outer diameter of stock tubing to a value well below nominal prior to bending the tubing into hairpins. The reduced diameter increases the stiffness of the resultant hairpins and allows for efficient lacing of the heat exchanger fins and end plates. The method uses pre-size rollers that are adjustable for reducing the diameter of the tubing.

Abstract: An improved hairpin expander machine equipped with a closed-loop-controlled hydraulically positioned bolster plate and a heat exchanger-holding fixture characterized by a full-length, continuous front plate, back plate, and side rails. The hairpin expander includes a novel heat exchanger bottom end plate clamping mechanism as part of the fixture. These features enable the hairpin expander to provide larger expansion ratios and exert greater forces with tighter control, which is required for producing heat exchangers with reduced diameter hairpin tubes according to a preferred embodiment of the invention.

Abstract: According to a preferred embodiment, an improved method and apparatus for manufacturing tube and fin heat exchangers that includes a step for reducing the outer diameter of stock tubing to a value well below nominal prior to bending the tubing into hairpins. The reduced diameter increases the stiffness of the resultant hairpins and allows for efficient lacing of the heat exchanger fins and end plates. The method uses pre-size rollers that are adjustable for reducing the diameter of the tubing. The invention also includes a hairpin and heat exchanger manufactured according to the method.

Abstract: An improved hairpin expander machine equipped with a closed-loop-controlled hydraulically positioned bolster plate and a heat exchanger-holding fixture characterized by a full-length, continuous front plate, back plate, and side rails. The hairpin expander includes a novel heat exchanger bottom end plate clamping mechanism as part of the fixture. These features enable the hairpin expander to provide larger expansion ratios and exert greater forces with tighter control, which is required for producing heat exchangers with reduced diameter hairpin tubes according to a preferred embodiment of the invention.

Abstract: According to a preferred embodiment, an improved method and apparatus for manufacturing tube and fin heat exchangers that includes a step for reducing the outer diameter of stock tubing to a value well below nominal prior to bending the tubing into hairpins. The reduced diameter increases the stiffness of the resultant hairpins and allows for efficient lacing of the heat exchanger fins and end plates. The method uses pre-size rollers that are adjustable for reducing the diameter of the tubing. The invention also includes a hairpin and heat exchanger manufactured according to the method.

Abstract: A tool for mating two pipes, having two pairs of arcuate clamping jaws of adjustable locked diameter moved towards each other by a pair of linking means mounted to opposite sides of each pair of jaws so as to lie and move in a simple plane. Inserts are provided to further reduce the jaws locked diameter.