Fastening device

A fastening device for fastening a first member and a second member, the device comprising:

• a bolt having a male screw thread portion located at a front end of a cylindrical shaft portion thereof and a head at a rear end thereof, the male screw thread portion having a triangular cross-sectional shape;
• a spacer comprising a first, female screw thread portion engageable with the male screw thread portion of the bolt, and a second, male screw thread;
• torque transmitting means between the bolt and the spacer, the torque transmitting means providing a frictional resistance between the male screw thread portion of the bolt and the first screw thread portion of the spacer, and for transmitting a rotation force of the bolt to the spacer such that the bolt and spacer are rotated integrally;
• a first member comprising first and second sides and having a first throughhole extending between the first and second sides;
• a sleeve comprising a female screw thread aligned with the first throughhole of the first member, the second screw thread of the spacer engageable with female screw thread of the sleeve;
• a clip removably fixing the sleeve to the first side of the first member;
• a nut fixed to the second side of the first member, the nut comprising a female screw thread aligned with the first throughhole of the first member;
• and
• a second member comprising first and second sides and a second throughhole extending between the first and second sides, the cylindrical shaft portion of the bolt extending through the second throughhole;
• wherein the second screw thread of the spacer is screw-fastened with the female screw thread of the sleeve such that when the spacer receives a rotation torque from the bolt through the torque transmitting means, the spacer rotates, thereby moving the spacer to a position apart from the first side of the first member into contact with the second side of the second member, so that when the spacer moves to a position in which the spacer contacts the second member, and when the bolt continues receiving torque, the bolt overcomes the torque-transmitting means and moves relative to the spacer, and the male screw thread portion of the bolt is released from the first, female screw thread portion of the spacer;
• wherein, after the male screw thread portion of the bolt is released from the first, female screw thread portion of the spacer, the bolt is movable through the spacer and the sleeve towards the female screw thread of the nut, such that when the male screw thread portion of the bolt engages the female screw thread of the nut, and torque is applied to the bolt, the male screw thread portion of the bolt screw-fastens to the female screw thread of the nut, and the head of the bolt engages the first side of the second member, thereby fixing the first member relative to the second member;
• wherein the first female screw thread portion of the spacer has a trapezoidal cross-sectional shape, thereby enlarging the inner diameter of the spacer, the root diameter of the male screw thread portion of the bolt is smaller than the diameter of the cylindrical shaft portion in the region in which the bolt passes through the spacer, the inside diameter of the first, female screw thread portion of the spacer is larger than the diameter of the cylindrical shaft portion of the bolt, and the male screw thread portion of the bolt has an axial length that is shorter than the axial length of the spacer.