Locking wedge apparatus for printed circuit board

A locking wedge apparatus for locking a printed circuit board within an elongated slot in a rack, comprising:

• a center wedge having sloped surfaces at its opposite ends;
• first and second end wedges located at opposite ends of the center wedge and having surfaces that abut against the sloped surfaces of the center wedge;
• a screw interconnecting the first and second end wedges, wherein the remote end of the screw, opposite the screw's head, threadedly engages a threaded bore in the first end wedge and projects beyond the first end wedge, and wherein rotation of the screw in a first direction draws the two end wedges toward each other such that the end wedges and interconnecting screw are deflected transversely by the sloped surfaces of the center wedge, to lock the printed circuit board within the elongated slot in the rack;
• a friction nut threaded onto the portion of the remote end of the screw projecting beyond the first end wedge;
• and
• two flat, low-friction spacers encircling the remote end of the screw, between the friction nut and the first end wedge, wherein the facing surfaces of the spacers form low-friction abutting surfaces having a predetermined coefficient o friction between them that is sufficiently low that, when the screw is lossened, the frictional torque developed between the nut and the first end wedge is exceeded by the frictional torque developed between the nut and the screw, whereby an excessive unthreading of the screw from the first end wedge is prevented.

A locking wedge apparatus for locking a printed circuit board within an elongated slot in a rack, comprising:

• a center wedge having sloped surfaces at its opposite ends;
• first and second end wedges located at opposite ends of the center wedge ad having surfaces that abut against the sloped surfaces of the center wedge;
• a screw interconnecting the first and second end wedges, wherein the remote end of the screw, opposite the screw's head, threadedly engages a threaded bore in the first end wedge and projects beyond the first end wedge, wherein the screw head is adapted for engagement by means for rotatably driving the screw, and wherein rotation of the screw i a first direction draws the two end wedges toward each other such that the end wedges and interconnecting screw are deflected transversely by the sloped surfaces of the center wedge, to lock the printed circuit board within the elongated slot in the rack;
• and
• a friction nut threaded onto the portion of the remote end of the screw projecting beyond the first end wedge, the friction nut being spaced from the first end wedge when the two end wedges and the screw are defected transversely;
• wherein the apparatus is configured to include a pair of low-friction abutting surfaces between the friction nut and the first end wedge,
• and wherein the abutting surfaces have a predetermined coefficient of friction between them that is sufficiently low that, when the screw is loosened, the frictional torque developed between the nut and the first end wedge is exceeded by the frictional torque developed between the nut and the screw, whereby an excessive unthreading of the screw from the first end wedge is prevented.