1. Field of the Invention
This invention relates to an apparatus used to hold work pieces for machining and, more specifically, to a vise capable of holding two work pieces.
2. Description of the Prior Art
Numerical control equipment are devices which perform functions automatically upon computer-given instructions. A single tool is able to perform a function and to move automatically among several work pieces that are secured to the work table of the device. The only function that is performed manually is securing the raw stock to the work table and removing the pieces upon completion of the machine's operations.
The operation of machining materials using numerically controlled equipment is much more expedient and efficient if more than one work piece, either raw stock or a partially finished piece, is available to the numerically controlled equipment at one time. Various dual vises are available which are capable of holding two work pieces. Whether the two pieces are at the same stage of production or at different stages, the ability to hold two pieces with one vise reduces the time needed to set up before an operation is performed by the numerically controlled equipment.
A number of vises capable of holding two work pieces have been manufactured, with varying degrees of success. In U.S. Pat. No. 4,448,406, the moveable jaws are simultaneously driven in opposed reciprocation by a single shaft, the pressure exerted on both work pieces being the same.
In U.S. Pat. No. 4,341,375 a vise was designed for clamping a pair of snow skis. The vise uses a single shaft and is capable of clamping two skis of different widths. After the first ski is secured by the first vise assembly in a spring-tight position, continued rotation of the shaft causes pressure to be exerted on the second ski in the second vise assembly. After both skis are held spring-tight, further shaft rotation tightens each one equally. The operator is unable to apply varied pressures to the skis held in each vise assembly, and material of a delicate nature placed in the first vise assembly may be damaged by excessive force. A further problem with this design is that a ski held in the first vise assembly may slip from its original position while the second ski is being secured in the second vise assembly.
Other improvements have been made to dual vises. The dual vise in U.S. Pat. No. 4,529,183 is capable of holding delicate material in both vise assemblies while holding the shaft in tension. The pressure exerted on each work piece in the vise assembly is equal. The operator has no option to differ the amount of pressure exerted on each work piece.
While a work piece is being worked upon it needs to be securely held. However, the pressure should not be so excessive as to damage the finish of the work piece, or the work piece itself. A problem common to the prior art is an inability to hold two work pieces which may be at different stages of production without damaging the work piece at a more delicate stage, and yet to hold each work piece securely enough to avoid slippage.