Metal deforming – By use of tool acting during relative rotation between tool... – With modification or control of temperature of work – tool or...
Reexamination Certificate
1999-04-21
2001-04-10
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of tool acting during relative rotation between tool...
With modification or control of temperature of work, tool or...
C072S084000
Reexamination Certificate
active
06212926
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to forming techniques. More particularly, the present invention relates to spin forming techniques for shaping metallic tubes.
BACKGROUND OF THE INVENTION
Spin forming techniques are used to manufacture tanks, drums and other vessels. For example, spin forming techniques are used to manufacture vessels ranging in size from fire extinguishers to heads for concrete truck drums. Spin forming techniques commonly include rotating a cylindrical tube about its longitudinal axis, while concurrently heating an end portion of the tube. The tube is formed by applying pressure to the heated end portion to either constrict or expand the end portion of the tube. In this regard, U.S. Pat. No. 2,408,596 (Bednar et al.) discloses a method for forming cylindrical ends by torch heating, rotating, and applying pressure to a cylindrical work piece. Pressure is applied by a tool moving in arcuate paths that curve toward a desired contour of the work piece. Similarly, U.S. Pat. No. 5,235,837 (Werner) discloses an apparatus for producing thin-walled cylindrical pressure vessels or tanks through metal spinning operations. A cylindrical work tube is rotated about its longitudinal axis, and the end of the work tube is heated by heating torches. Forming rollers are moved along a plurality of arcuate stroking paths to shape the end of the work tube. The arcuate stroking paths curve toward a desired final shape of the work tube.
U.S. Pat. No. 5,598,729 (Hoffmann et al.) discloses another method for spin forming a metallic tube. The metallic tube is rotated about its longitudinal axis, and inductive heating elements are used to heat an end portion of the tube. Forming rollers are used to form the heated end portion of the tube. The forming rollers are moved along a succession of angularly spaced apart, substantially straight forming passes.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a method for forming an end portion of a tube. The method includes rotating the tube about a longitudinal axis, heating the end portion of the tube, and forming the end portion of the tube by reciprocating a forming member along a succession of curved forming passes. Each curved forming path is tangent to a corresponding one of a succession of angularly spaced apart, substantially straight reference lines. A forming reduction is provided between each curved forming path and its corresponding one of the reference lines.
Another aspect of the present invention relates to a method for constricting an end portion of a tube. The method includes rotating the tube about a longitudinal axis, heating the end portion of the tube and constricting the end portion of the tube by reciprocating a forming member along a succession of curved forming passes. Preferably, at least some of the curved forming paths curve away from the longitudinal axis of the tube.
A further aspect of the present invention relates to a method for forming an end portion of a tube from an initial shape to a desired final shape. The method includes rotating tube about a longitudinal axis, heating the end portion of the tube, and forming the end portion of the tube by reciprocating a forming member along a succession of curved forming paths. Preferably, at least some of the curved forming paths curve away from the desired final shape.
A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
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Larson Lowell A.
Merchant & Gould P.C.
Tandem Systems, Inc.
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