Automatic clamping unit for receiving and holding a tool holder

An clamping unit for holding a tubular tool holder shank, comprising:

• (a) a tool support member having a forwardly facing surface and a bore intersecting the forwardly facing surface and extending rearwardly therefrom for receiving the tool holder shank;
• (b) a stub disposed in the bore and having a passageway formed therein, the stub being adapted to be received within the tubular tool holder shank;
• (c) a locking rod movably mounted within the passageway of the stub and having a stroke wherein the same moves between unlocked and locked positions;
• (d) first and second circumferentially spaced apertures formed in the stub and radially extending away from the wall of the bore and intersecting the passageway;
• (e) a pair of locking balls contained within the apertures and engaged with the locking rod;
• (f) means for moving the locking rod from the unlocked position to the locked position;
• (g) depression means formed in the locking rod for receiving the locking balls when the locking rod is in the unlocked position;
• (h) means associated with the locking rod for engaging the locking balls and moving the same from an unlocked position to a locked position and varying the mechanical advantage applied to the locking balls in the process wherein in the locked position the locking balls are forced against the hollow tool holder shank and holds the tool holder shank within the bore of the tool support member;
• (i) the means for engaging the locking balls and moving the same from the unlocked to the locked position and varying the applied mechanical advantage including a variable sloped locking ramp that extends from the depression means along a side portion of the locking rod and serves to engage and urge the locking balls outwardly towards their locked position in response to the locking rod being moved from its unlocked position towards it locked position;
• and
• (j) wherein the variable sloped locking ramp is configured so as to vary the mechanical advantage applied to the looking balls throughout a substantial portion of the locking rod's stroke such that the radial locking load exerted by the ball is relatively constant for a selected portion of the lacking rod's stroke.

A method of securing a clamping unit to the tubular shank of a tool holder comprising:

• (a) inserting a tubular tool holder shank into a bore of a clamping unit;
• (b) engaging at least one locking element of the clamping unit with a locking ramp forming a part of a locking rod;
• (c) moving the locking rod from an unlocked position to a locked position and urging the locking element outwardly towards engagement with the shank of the tool holder;
• and
• (d) varying the mechanical advantage applied to the locking element by varying the angle of the locking ramp along its run such that the radial locking load exerted by the locking element is relatively constant for a selected portion of the locking rod's stroke.

An clamping unit for holding a tool holder shank having a locking surface, comprising:

• (a) a clamping unit having a bore formed therein for receiving the shank of the tool holder;
• (b) a lock rod movably mounted within the clamping unit and moveable back and forth between a locked and unlocked position;
• (c) means engaged with the lock rod for applying a range of loading forces on the locking rod as the same moves between the unlocked and locked positions;
• (d) at least one locking element disposed within the clamping unit and engageable with the lock rod and moveable from an unlocked position to a locked position where the locking element engages the locking surface of a tool holder shank, resulting in the tool holder being secured within the clamping unit;
• and
• (e) variable slope ramp means associated with the locking rod for engaging the locking element and varying the mechanical advantage applied to the locking element as the locking element moves from its unlocked position to its locked position so as to maintain a relatively constant radial locking load on the locking element for a selected portion of the locking rod's stroke.