Pipe element coupler and coupling method thereof

A combination of a pipe element and a pipe element coupler for coupling two pipe elements each having a groove and a groove circumference at a bottom of the groove, wherein the pipe element coupler comprises:

• a plurality of coupling members, wherein each of said coupling members comprises two engaging keys at two coupling end portions thereof, wherein each of said engaging keys has an engaging surface having varying radiuses of curvature;
• a gasket disposed in said coupling members;
• and a fastening element mounted on said coupling members, wherein said pipe element coupler is adapted for being preassembled on the two pipe elements to align said engaging keys with the corresponding grooves, wherein when said fastening element is operated to fasten said coupling members together, each of said engaging surfaces is deformed to change said varying radiuses of curvature, so as to substantially match a radius of curvature of the groove circumference;
• said plurality of coupling members comprises two coupling members, wherein said pipe element coupler further comprises a pivotally connecting element pivotally connecting said two coupling members, wherein said pivotally connecting element and said fastening element are respectively assembled on two opposite sides of the two coupling members;
• each of the two pipe element further comprises an enlarged coupling end portion, wherein each of said engaging surfaces defines a logarithmic spiral curve having an equation of ρ=eθ, wherein θ has a range of 0-180°, wherein ρ denotes a radius of curvature of the engaging surface, and θ denotes a center angle between said distal end point and said proximate end point, wherein ρ1 denotes said radius curvature at said proximate end point, ρ2 denote a radius curvature at said distal end point, D1 denotes a diameter of the groove circumference, D2 denotes a diameter of the enlarged coupling end portion, wherein ρ1=D1/2, ρ2=D2/2+R, wherein R is an additional allowance for parameter ρ2 and has a value range of 0.3-1 mm;
• wherein said gasket comprises a plurality of protrusions which are spaced apart from each other, wherein said protrusions are adapted for being sandwiched between the two enlarged coupling end portions of the pipe elements.

A coupling method for coupling two pipe elements by a pipe element coupler, comprising the following steps:

• (A) sleeving a first coupling end portion of said pipe element coupler on an enlarged coupling end portion of a first pipe element of the two pipe elements, and inserting an enlarged coupling end portion of a second pipe element of the two pipe elements into a second coupling end portion of said pipe element coupler in such a manner that engaging keys of a plurality of coupling members are respectively aligned with the corresponding grooves of the first and second pipe elements, sandwiching a plurality of protrusions of a gasket between the two enlarged coupling end portions of the pipe elements, wherein said engaging surface of each of said engaging keys has varying radiuses of curvature, wherein a gap is defined between said engaging surface and a corresponding groove circumference at a bottom of the groove;
• and
• (B) reducing said gap between said engaging surface and the corresponding groove circumference by fastening two fastening end portions of said coupling members through said fastening element, so as to retain said engaging keys at the corresponding grooves;
• each of said engaging surfaces defines a logarithmic spiral curve having an equation of ρ=eθ, wherein ρ denotes a radius of curvature of the engaging surface, θ denotes a center angle between said distal end point and said proximate end point and Sp denotes a dimension of the pipe element;
• wherein when Sρ=60.3 mm, θ has a range of 0-169.88°;
• wherein when Sρ=73.0 mm, θ has a range of 0-170.67°;
• wherein when Sρ=76.1 mm, θ has a range of 0-171.23°;
• wherein when Sρ=88.9 mm, θ has a range of 0-172.46°;
• wherein when Sρ=108.0 mm, θ has a range of 0-173.53°;
• wherein when Sρ=114.3 mm, θ has a range of 0-173.92°;
• wherein when Sρ=133.0 mm, θ has a range of 0-174.84°;
• wherein when Sρ=139.7 mm, θ has a range of 0-175.02°;
• wherein when Sρ=141.3 mm, θ has a range of 0-175.05°;
• wherein when Sρ=159.0 mm, θ has a range of 0-175.57°;
• wherein when Sρ=165.1 mm, θ has a range of 0-175.68°;
• wherein when Sρ=168.3 mm, θ has a range of 0-175.76°;
• wherein when Sρ=216.3 mm, θ has a range of 0-175.42°;
• wherein when Sρ=219.1 mm, θ has a range of 0-175.47°.