A method of manufacturing a trailer hitch receiver tube with an integral reinforcing collar is described. A two piece die having an interior shape and dimensions conforming to the shape and dimensions of a selected trailer hitch receiver tube is provided, the two pieces of the die being a right half and a left half. Each of the right and left halves of the die are provided with means to forcefully move the die from an open position to a closed position around a workpiece. The die, around an upper edge thereof is provided with a relief cavity around its perimeter having the shape of a reinforcement collar. A base mandrel is provided between the right and left halves of the die, the base mandrel having a size and shape conforming to the size and shape of the interior of a trailer hitch receiver tube, and the base mandrel having a height less than the die. A steel receiver tube is positioned on the base mandrel, the tube having a height greater than the die halves. The die halves are then closed forcefully against the receiver tube. A forming mandrel is provided above the receiver tube. The forming mandrel has a longitudinal portion that conforms in shape to the interior of the receiver tube, and a lateral, forming portion for bearing against the upper edge of the receiver tube to form the upper portion of a receiver tube into a reinforcing collar by deforming the upper end of said tube into the relief cavity. An upper edge of the receiver tube is then forcefully struck with the forming portion of the forming mandrel, to form the collar, wherein the longitudinal portion of the forming mandrel closely approaches an upper surface of the base mandrel after the collar is formed.

A method of manufacturing a trailer hitch receiver tube with an integral reinforcing collar is described. A two piece die having an interior shape and dimensions conforming to the shape and dimensions of a selected trailer hitch receiver tube is provided, the two pieces of the die being a right half and a left half. Each of the right and left halves of the die are provided with means to forcefully move the die from an open position to a closed position around a workpiece. The die, around an upper edge thereof is provided with a relief cavity around its perimeter having the shape of a reinforcement collar. A base mandrel is provided between the right and left halves of the die, the base mandrel having a size and shape conforming to the size and shape of the interior of a trailer hitch receiver tube, and the base mandrel having a height less than the die. A steel receiver tube is positioned on the base mandrel, the tube having a height greater than the die halves. The die halves are then closed forcefully against the receiver tube. A forming mandrel is provided above the receiver tube. The forming mandrel has a longitudinal portion that conforms in shape to the interior of the receiver tube, and a lateral, forming portion for bearing against the upper edge of the receiver tube to form the upper portion of a receiver tube into a reinforcing collar by deforming the upper end of said tube into the relief cavity. An upper edge of the receiver tube is then forcefully struck with the forming portion of the forming mandrel, to form the collar, wherein the longitudinal portion of the forming mandrel closely approaches an upper surface of the base mandrel after the collar is formed.

A method for forming a semi-finished product is disclosed, wherein the semi-finished product is provided in a provision step and, in a solid-stock forming step, a forming region of the semi-finished product is formed such that a thickness of the deformed forming region increases continuously toward one margin of the semi-finished product.

A method for forming a semi-finished product is disclosed, wherein the semi-finished product is provided in a provision step and, in a solid-stock forming step, a forming region of the semi-finished product is formed such that a thickness of the deformed forming region increases continuously toward one margin of the semi-finished product.

After an annular plate is blanked from a metal flat plate in a blanking step, an inner peripheral portion of the annular plate is deformed upward in a burring step. As a result, a hat-shaped intermediate product having an upstanding tubular portion and an annular plate portion is formed. After that, an outer peripheral portion of the annular plate portion is folded step by step toward an inner peripheral side of the annular plate portion. As a result, a folded portion composed of a first folded portion and a second folded portion is formed, whereby a connection portion having a second flange portion is formed.

This manufacturing method of a structural member includes an intermediate step and a bending step. A height difference is provided on a bottom wall of a groove part between an intermediate position and both end positions sandwiching the intermediate position therebetween in a longitudinal sectional view in an extending direction of the groove part by the pressing in the intermediate step, and thereby at least one of a first curved part which has a concave curved shape in a plan view and a convex curved shape in the longitudinal sectional view and a second curved part which has a convex curved shape in the plan view and a concave curved shape in the longitudinal sectional view is formed on the bottom wall.

A pipe cross-section processing device that reduces friction during processing and improves the degree of freedom regarding the rotation angle of the pipe cross section is provided. The pipe cross-section processing device may include a rotation drive source configured to rotate the base, a shaft secured to a front end portion of the base, a slide base capable of a sliding movement along the axis of the shaft, a roller guide member secured to the slide base, a slide-base drive member configured to convert the rotational motion of the base into a linear motion so as to drive the slide base together with the roller guide member in a sliding movement, and a roller configured to be adhered to an inner surface of a pipe cross section to rotationally process a cross section of the pipe outwardly in a radial direction of the pipe.

After an annular plate is blanked from a metal flat plate in a blanking step, an inner peripheral portion of the annular plate is deformed upward in a burring step. As a result, a hat-shaped intermediate product having an upstanding tubular portion and an annular plate portion is formed. After that, an outer peripheral portion of the annular plate portion is folded step by step toward an inner peripheral side of the annular plate portion. As a result, a folded portion composed of a first folded portion and a second folded portion is formed, whereby a connection portion having a second flange portion is formed.

A pipe cross-section processing device that reduces friction during processing and improves the degree of freedom regarding the rotation angle of the pipe cross section is provided. The pipe cross-section processing device may include a rotation drive source configured to rotate the base, a shaft secured to a front end portion of the base, a slide base capable of a sliding movement along the axis of the shaft, a roller guide member secured to the slide base, a slide-base drive member configured to convert the rotational motion of the base into a linear motion so as to drive the slide base together with the roller guide member in a sliding movement, and a roller configured to be adhered to an inner surface of a pipe cross section to rotationally process a cross section of the pipe outwardly in a radial direction of the pipe.

A method of manufacturing a trailer hitch receiver tube with an integral reinforcing collar is described. A two piece die having an interior shape and dimensions conforming to the shape and dimensions of a selected trailer hitch receiver tube is provided, the two pieces of the die being a right half and a left half. Each of the right and left halves of the die are provided with means to forcefully move the die from an open position to a closed position around a workpiece. The die, around an upper edge thereof is provided with a relief cavity around its perimeter having the shape of a reinforcement collar. A base mandrel is provided between the right and left halves of the die, the base mandrel having a size and shape conforming to the size and shape of the interior of a trailer hitch receiver tube, and the base mandrel having a height less than the die. A steel receiver tube is positioned on the base mandrel, the tube having a height greater than the die halves. The die halves are then closed forcefully against the receiver tube. A forming mandrel is provided above the receiver tube. The forming mandrel has a longitudinal portion that conforms in shape to the interior of the receiver tube, and a lateral, forming portion for bearing against the upper edge of the receiver tube to form the upper portion of a receiver tube into a reinforcing collar by deforming the upper end of said tube into the relief cavity. An upper edge of the receiver tube is then forcefully struck with the forming portion of the forming mandrel, to form the collar, wherein the longitudinal portion of the forming mandrel closely approaches an upper surface of the base mandrel after the collar is formed.