Method and expander for manufacturing a furnace heat exchanger and plate assembly

An expander for use in securing a tubular heat exchanger unit to a plate member wherein:

• said heat exchanger unit includes an opening into an interior chamber through a wall of said heat exchanger unit and said plate member includes an opening corresponding to said opening in said heat exchanger unit and defined by an perimeter flange projecting from a plane of said plate member and said plate member is assembled with said heat exchanger unit by inserting said flange through said opening in said heat exchanger unit, and said apparatus comprises:
• a plurality of at least eight flange engaging laminar jaw segments, each jaw segment defining an engaging surface for engaging a portion of the flange, a body member for supporting said flange engaging jaw segments for insertion through said openings in said plate member and said heat exchanger unit, means for moving said flange engaging jaw segments radially outward with respect to an axis and axially with respect to said axis to bend said flange into engagement with said heat exchanger unit about the perimeter of the opening and to compensate for variations of metal thickness of at least one of said flange and said wall to form a substantially rigid leakproof joint, and means for retracting said jaw segments, the number of flange engaging laminar jaw segments being at least five and being such that a single sequence of movement of said flange engaging jaw segments radially outward with respect to an axis and axially with respect to said axis to bend said flange into engagement with said heat exchanger unit is sufficient to form a substantially rigid leakproof joint.

A method for securing a tubular heat exchanger unit of a furnace to a plate member, comprising the steps of:

• providing said heat exchanger unit as a relatively thin walled sheet metal structure defining a chamber for the flow of fluid to be in heat exchange relationship with the walls of said heat exchanger unit, said heat exchanger unit having at least one opening into said chamber through a wall of said heat exchanger unit and defined by a peripheral rim;
• providing a plate member including an opening corresponding to said opening in said heat exchanger unit and defined by a perimeter flange projecting from the plane of said plate member;
• inserting said flange into said chamber through said opening in said heat exchanger unit;
• and
• bending said flange radially outwardly and axially into engagement with an inner wall surface of said heat exchanger unit at the periphery of said opening and substantially without displacement of said rim to form a substantially rigid leakproof joint between said heat exchanger unit and said plate member;
• the step of bending said flange being carried out using a tool including a plurality of at least eight radially expandable and contractable laminar jaw members, said method including the steps of inserting said tool through said opening in said plate member and into said chamber, actuating said jaw members to move radially outward into engagement with portions of said flange, moving said jaw members axially to bend said flange into engagement with said heat exchanger unit, contracting said jaw members radially inwardly, and removing said tool from said opening in said plate member, the number of flange engaging jaw segments being such that a single sequence of said flange engaging jaw segments radially outward with respect to an axis and axially with respect to said axis to bend said flange into engagement with said heat exchanger unit forms a substantially rigid leakproof joint.

An expander comprising:

• a body,
• an opening through the body,
• a mandrel movable axially through the opening,
• a plurality of at least eight laminar jaw segments extending axially within the opening and positioned circumferentially about the mandrel,
• the body having a crimping area on the body surrounding the opening, the jaw segments having complementary crimping areas,
• means on the mandrel for moving the jaws "radially outwardly and thereafter" axially upon movement of the mandrel in an axial direction to move the complementary jaw crimping areas toward the body crimping area for crimping two metal components together in a fluid-tight connection about an opening,
• the jaw segments being of sufficient number to minimize the space between adjacent jaw segments upon said radially outward movement of the jaw segments whereby a single operation of the expander produces a fluid-tight seal between the two metal components about the entire perimeter of the opening.