1. Field of the Invention
This invention relates generally to tool holders and more specifically to apparatus for holding tools in a predetermined orientation with respect to the machine in which they are to be utilized as well as with respect to the work piece.
2. Description of the Prior Art
Various types of devices have been designed and utilized for securing a tool in a proper orientation with respect to the machine, with its power imparting mechanisms, in which the tool is to be employed. When such power imparting mechanisms are in an automatic milling, drilling, grinding or other similar machine, it is also desired to maintain the tool in proper orientation with respect to the work piece being acted upon. This is because in many modern machines of this type the movement of the work piece is programmed for predetermined motion relative to the machine, its power imparting mechanisms, the tool holder and the tool.
When, for example, the machine and tool constitute an end mill, as is the case with the preferred form or embodiment of the present invention, the tool is rotatable about its axis and that axis is the same as the axis of rotation of the holder supporting the tool. Only when in such orientation can the machine and tool function properly for accurate cuts of the work piece. Unfortunately, however, it often happens that the tool becomes moved from its preferred axial alignment and does not rotate in its proper and desired path of rotation. When this occurs, the action of the tool on the work piece cannot be effective to achieve the removal of material from the work piece with the necessary degree of precision which might be required. Further, if the tool is not held properly and securely within the holding apparatus, the proper action of the tool edge against the work piece may deflect the tool to an out of concentric orientation leading to the same undesirable result as if the tool were to be initially inserted improperly. Furthermore, the depth of the tool into the tool holder must also be done with great precision, particularly in those instances where the cutting by the tool is done by the end of the tool as in an end mill and excess axial forces exerted on a tool could disturb the original axial, and even radial, setting.
A wide variety of devices have been developed and utilized in the past in an effort to maintain tools such as end mills in proper orientation. In U.S. Pat. No. 4,229,130 to Franklin, for example, there is disclosed a collet for an externally threaded tool which seats a bit-engaging nut at its inboard end. When the tool is clamped within the collet and the collet is clamped within a tool holder, there are negligible undesirable radial forces on the tool. This improves the ability of the collet to generally retain the tool in its proper orientation. However, the length of the collet acting upon the tool is reduced along with its holding action due to the presence of the nut.
The German Published application Ser. No. 1,929,696 describes the relationship of a large number of specially machined elements including a tool and tool holder which retain the tool from incidental axial removal and also provide for axial adjustments.
U.S. Pat. No. 3,913,935 to Flannery et al. discloses a cutting tool adjustment mechanism wherein the adjustment sleeve is attached to a cutting tool by a lock screw. A set screw locks the entire assembly in position. Radial set screws are also known to lock an axially adjustable screw thread member in a cutting tool holder as described in U.S. Pat. No. 4,152,091 to Kucera. Radial set screws have also been used in holding tools into tool holders at various locations as illustrated by U.S. Pat. Nos. 4,226,562 to Schmid et al; 3,557,419 to Flannery; and 3,159,081 to Erikson. The use of set screws on the tool usually exerts undesirable radial forces on the tool thereby to eliminate the concentricity of the tool during rotation and cutting. Accuracy in cutting is thus impaired. Lastly, tool holding mechanisms of various other types are disclosed in U.S. Pat. Nos. 3,052,999 to Sedgwick et al. and 3,680,435 to Deplante.
As illustrated by the great number of prior art patents, efforts are continuously being made in an attempt to solve the problem of maintaining concentricity of rotating tools. None of these patents discloses or suggests the present inventive combination of elements for securing a tool to a holder to maintain concentricity and axial shifting during operation and use. These patents consistently apply forces to the tool which induce an improper orientation. Alternately, they do not apply forces to maintain such proper orientation. The present invention achieves its purposes, objectives, and advantages over the prior art through new, useful and unobvious tool holding elements which maintain both axial and radial tool orientation throughout operation and use with a minimum number of functioning parts, with a minimum of cost and through the utilization of only readily available materials and conventional components.
These objects and advantages should be construed as merely illustrative of some of the more prominent features and applications of the present invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and advantages as well as a fuller understanding of the invention may be had by referring to the summary of the invention and detailed description describing the preferred embodiment of the invention in addition to the scope of the invention as defined by the claims taken in conjunction with the accompanying drawings.