Single insertion locking U-shaped padlock structure

A padlock comprising:

• a U-shaped shackle including a pair of .OMEGA.-shaped pintle interlock holes on each end thereof;
• a tubular padlock enclosure,
• a front protective sleeve received within the tubular padlock enclosure at a front end thereof,
• a rear protective sleeve received within the tubular padlock enclosure at the rear end thereof,
• a concentric tensile spring disposed within the tubular padlock enclosure adjacent the front protective sleeve,
• a stepped tumbler disposed within the tubular padlock enclosure adjacent and in cooperation with the spring, said stepped tumbler including a rotation limit notch disposed along a circumference thereof,
• a fan-shaped eccentric insertion hole extending through the front protective sleeve, the stepped tumbler and a portion of the rear protective sleeve,
• an eccentric pintle rod disposed within the tubular padlock enclosure in the eccentric insertion hole and movable between an unlocked position and a locked position, the eccentric insertion hole limiting the rotation of the pintle rod between the locked and unlocked position,
• the concentric tensile spring including an oval ring at the center thereof adapted to fit in surrounding relationship to the pintle rod, said spring urging the pintle rod in the locked position,
• wherein when the shackle is inserted into the tubular padlock enclosure, the pintle rod is first guided by the pintle interlock holes into the unlocked position, and upon further insertion of the shackle into the tubular padlock enclosure, the spring urges the pintle rod into the locked position, thereby causing the shackle to be locked within the tubular padlock enclosure.