Pipe clamp with improved fastener

A band clamp, comprising:

• a band including a circumferentially-extending body portion having a pair of opposed radially-extending flanges at opposite ends of said body portion, said flanges each having an aperture therethrough;
• and
• a fastener for drawing said opposed flanges of said band together such that said band can be tightened, said fastener including:
• a bolt extending through said apertures of said opposed flanges and including
• a head at a first end and a shank extending from said head and terminating in a second end, said shank including:
• a neck extending from said head toward said second end,
• a threaded body extending from said second end toward said first end, and
• a tapered transition between said neck and said body;
• and
• a nut threaded to said threaded body of said bolt, said nut having a shoulder that engages said tapered transition when said nut is tightened onto said bolt to thereby cause a sharp increase in torque required to further thread said nut onto said bolt.

A band clamp for connecting tubular members, comprising:

• a band including a circumferentially-extending body portion that fits at least partially around the tubular members, said band further including radially-extending opposed flanges at opposite ends of said body portion, said flanges each being formed by a unitary extension of said band that extends radially outwardly from said body portion to an outer free end of said flange where said unitary extension is folded back on itself to form inner and outer layers, wherein said inner and outer layers together have an aligned aperture and a curved profile in the radial direction that gives each flange a convex inner surface facing the other flange and an concave outer surface, said unitary extensions being secured to said body portion adjacent said flanges;
• and
• a tightening mechanism that includes a reaction member, spacer bar, and fastener for drawing said opposed flanges of said band together such that said band can be tightened about the tubular members;
• said reaction member having inner and outer ends separated from each other by a pair of oppositely facing concave surfaces that mate with the convex inner surfaces of said flanges;
• said spacer bar having a convex surface that mates with said concave surface of a first one of said flanges, wherein said reaction member and said spacer bar each having an aperture that is aligned with the apertures of said flanges;
• said fastener comprising a nut and bolt with said bolt extending through said apertures and including a head at a first end and a shank extending from said head and terminating in a second end, said head comprising a bar with a convex surface that mates with said concave surface of a second one of said flanges, said shank including a neck extending from said head toward said second end, a threaded body extending from said second end toward said first end, and a tapered transition located between said neck and said threaded body and extending only partially around said shank such that a portion of said neck has a common surface with said threaded body, said threaded body having a circular cross-section and said neck having an oval-shaped cross-section that includes a minor diameter equal in length to the diameter of said threaded body and a major diameter that is greater than said minor diameter;
• wherein said apertures of said flanges are at least partially defined by radially inward facing surfaces extending through said flanges, and wherein said neck meets said threaded body at a common surface defined by an interruption in said tapered transition such that, during tightening of said fastener, said radially inward facing surface of said first flange can engage said threaded body and slide from said threaded body along said common surface to said neck during further tightening without engaging said tapered transition.

A method of fastening a band clamp around tubular members, said method comprising the steps of:

• providing a band including a circumferentially-extending body portion having a pair of radially-extending opposed flanges located at opposite ends of said body portion;
• inserting a bolt through apertures in said opposed flanges, said bolt including a head at a first end and a shank extending from said head and terminating in a second end, said shank including a neck extending from said head toward said second end, a threaded body extending from said second end toward said first end, and a tapered transition between said neck and said body;
• assembling a nut to said threaded body of said bolt, said nut having a shoulder;
• monitoring torque applied to said nut;
• and
• tightening said nut to said bolt until said monitored torque increases due to engagement of said shoulder of said nut with said tapered transition of said shank of said bolt.