Workholding clamping assembly

A failsafe workholding clamping assembly comprising:

• a base;
• a draw bar operatively connected to the base for movement along an axis relative to the base between open and closed positions;
• a structure operatively connected to the base for movement along the axis relative to the base between open and closed positions;
• a driver that operatively extends between the base and the structure and applies a continuous driving force to the structure that tends to bias the structure toward its closed position;
• a force amplifier operatively extending between the structure and the draw bar, the force :amplifier amplifying the driving force and applying a resulting amplified force to the draw bar to bias the draw bar toward its closed position, the force amplifier comprising a first surface that moves with the draw bar relative to the base along the axis, the first surface forming an acute angle B with the axis, a second surface that moves with the base relative to the draw bar, the second surface forming an acute angle (z with the axis, a third surface that moves with the structure and forms an acute, non-zero angle with the axis, and at least one circular roller disposed between and contacting the first, second, and third surfaces;
• and a collet opener supported by the base and constructed and arranged to apply a force to the structure that counteracts the driving force with an opening force, thereby preventing the driver from biasing the draw bar toward the closed position, wherein when the structure is in the open position an axial space utilized by the driver overlaps an axial space utilized by the third surface.

A workholding clamping assembly comprising:

• a base including a spindle;
• a draw bar operatively connected to the base for movement along an axis relative to the base between open and closed positions, the draw bar being rotatable relative to the base and spindle about the axis, the draw bar including a threaded portion that is constructed and arranged to threadingly engage a collet via rotation of the draw bar relative to the spindle, base, and collet;
• a driven gear operatively connected to the draw bar for rotation with the draw bar relative to the base and spindle;
• and
• a driving gear mounted to the base for rotation relative to the base, the driving gear meshing with the driven gear, the driving gear being selectively rotatable.

A failsafe workholding clamping assembly comprising:

• a base including a spindle having a bore therein that is concentric with an axis;
• a draw bar operatively connected to the base for movement along the axis relative to the base between open and closed positions, the draw bar having a threaded portion;
• a collet disposed in the bore, the collet and spindle including mating cam surfaces that form a non-zero angle with the axis, the collet having a threaded portion that is threadingly engaged with the threaded portion of the draw bar such that axial movement of the draw bar toward its closed position moves the collet toward its gripping position;
• a structure operatively connected to the base for movement along the axis relative to the base between open and closed positions;
• a driver that operatively extends between the base and the structure and applies a continuous driving force to the structure that tends to bias the structure toward its closed position;
• a force amplifier operatively extending between the structure and the draw bar, the force amplifier amplifying the driving force and applying a resulting amplified force to the draw bar to bias the draw bar toward its closed position, the force amplifier being formed in part by a surface of the draw bar;
• and
• a collet opener supported by the base and constructed and arranged to apply a force to the structure that counteracts the driving force with an opening force, thereby preventing the driver from biasing the draw bar toward the closed position,
• wherein the surface of the draw bar and the threaded portion of the draw bar are formed by a unitary piece of material.