This invention relates to chucks for releasably holding tools (e.g., drill bits), and more particularly to such chucks which can be easily and simply operated to very securely hold a tool without the need for a key to tighten the chuck on the tool.
Chucks with keys for imparting final tightening torque to the chuck to securely hold a tool are well known. While such chucks have been highly successful, they may have certain disadvantages. For example, the key must be removed from the chuck before the chuck is rotated at high speed (e.g., in a drilling operation). Failure to remove the key may unbalance the chuck when rotated at high speed, or cause the key to be thrown out from the chuck in a radial direction in a possibly unsafe manner. Although the key must thus be frequently removed from the chuck, the key must somehow be kept with the chuck or it may become lost.
Because of these disadvantages of keyed chucks, there has been increasing interest in recent years in chucks which can be operated by hand without the need for keys (see, for example, Huff et al. U.S. Pat. No. 5,125,673 and Jordan et al. U.S. Pat. No. 5,215,317). Some of these keyless chucks have been highly successful, but there is always room for further improvement.
To be acceptable a chuck must be able to hold a tool very securely. Chuck jaws with relatively fine threads serve this objective because fine threads give increased mechanical advantage. However, fine threads make a chuck relatively slow to operate, thereby making the chuck objectionable or even unacceptable to some users. A chuck should also be as simple and easy to operate as possible. For example, it is preferable for the operator to be able to use a single, simple type of motion to tighten or loosen the chuck. The chuck should also reset reliably and automatically after each use so that no additional resetting operation is required from the operator.
In view of the foregoing, it is an object of this invention to provide improved chucks.
It is another object of this invention to provide manually operable, keyless chucks which do not require especially fine jaw threads to hold a tool very securely, indeed more securely than conventional keyless chucks with fine threads.
It is still another object of this invention to provide manually operable, keyless chucks which require the operator to perform only a single, straightforward motion to tighten or loosen the chuck, and which automatically reset after each use in a highgly reliable manner.