Patent Application
20160236371
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1. Field of the Invention
The present invention relates to an external apparatus that attaches to, or is mounted adjacent to, a woodturning lathe in order to hold and control the motion of cutting tools used for shaping and hollowing vessels and bowls mounted on the lathe. Wood lathes have existed for over two thousand years and most frequently have relied upon handheld tools to accomplish the shaping and hollowing of wood. This approach is adequate for smaller projects involving relatively uniform woods. However, for larger projects utilizing more interesting woods (burls, crotches, roots and stumps) that may include knots, voids, inclusions, debris, metal objects, and complex gram structures, a more robust method for holding and controlling the cutting tools is required. The present apparatus is also useful for wood turners who may be experiencing certain physical limitations.
2. Description of the Prior Art
Previous hollowing systems may be broadly characterized as either “articulating arm” or “capture” types. Systems that have been patented are noted below.
U.S. Pat. No. 8,042,435 by Ray P. Thompson, et al. describes a “Special Articulating Tool Holder” comprising multiple articulating arms, a vertical mounting post and method for holding a variety of cutting tools. This system can experience significant vibration for deep aggressive cuts, and in certain orientations experience a tendency to have the articulating arms lock.
U.S. Pat. No. 7,191,689 B2 by Keith Clark describes a “Hollowing System” that controls the cutting tool movements along certain axes while allowing full movement along other axes. While the figures show the stabilization assembly mounted on the lathe, the Claims are for a stabilization assembly mounted adjacent to the lathe.
For both of these hollowing systems there comes a point where the hollowing system becomes physically decoupled from the lathe. For the “Special Articulating Tool Holder” the decoupling occurs at the tool rest, while for the “Hollowing System” the decoupling occurs at the tool rest and because the stabilization assembly is mounted adjacent to the lathe. In both instances, this decoupling can lead to hollowing system vibrations and resonances induced by cutting tool chatter and catches, making it more difficult to make accurate and repeatable hollowing cuts. The present invention mitigates the possibility of tool chatter and catches with multiple techniques that include friction control, vibration damping, close and adjustable tolerances, and robust system mass.
The present invention provides a method and apparatus for the longitudinal, lateral, vertical and rotational control of a toolbar that can hold a variety of cutting tools. The assemblies that comprise the complete system are interconnected in such a way that the friction and rigidity between the toolbar and the various assemblies can be controlled and varied easily. Moreover, the materials of construction for certain of the assemblies provide friction control and vibration damping.
It is therefore a primary object of the present invention to provide a method and apparatus that will enable a wood turner to concentrate on the form of a vessel being turned on a wood lathe without being overly concerned with countering the various forces that are experienced as the hollowing and shaping of the vessel progresses.
It is another object of the present invention, to provide an adjustable method to control the longitudinal (along the long axis of the lathe) force on the tool bar caused by the tendency of a cutter to self-feed as the vessel rotates.
It is a further object of the present invention to provide an adjustable method to control the lateral (at right angle to longitudinal axis of the lathe) force on the toolbar caused by the tendency of the cutter to self-feed as the vessel rotates.
It is still another object of the present invention to provide an adjustable method to control the torsion force (the force that twists the toolbar about its longitudinal axis) caused by a cutter that is not aligned with the toolbar axis of rotation.
It is still a further object of the present invention to provide a method to control the vertical force (the force that tends to raise the end of the toolbar vertically) caused by the moment induced by the overhang of the toolbar from its last vertical support.
These and other objects of the present invention will become apparent to those skilled in this art upon reading the accompanying description, drawings, and claims set forth herein.
The accompanying drawings illustrate a preferred and an alternative embodiment for the Hollowing System for a Wood Lathe. The drawings together with the summary description given above and the detailed description given, below serve to explain the principles of the Hollowing System for a Wood Lathe. However, it is understood that the device is not limited to the precise arrangements shown herein.
The toolbar support assembly 8 is secured on the ways 4 by locking bolt 8a and is easily adjusted to any orientation by rotating it around a vertical axis and sliding it laterally and longitudinally through slot 8b.
Similarly, the swivel assembly 10, which is mounted in the lathe banjo 6, is easily adjusted to any location and orientation by using the banjo locking lever 6a.
The first step in using the invention is to prepare the external shape of the wood blank to be hollowed. In general the starting wood blank, e.g., a burl, would be mounted between lathe centers, and traditional wood turning tools and techniques would be used to obtain the desired final shape. As a last step a tenon would be cut on what is to be the bottom of the vessel. The burl is then turned around and mounted in a chuck that has been placed on lathe spindle 3. Frequently a drill bit would then be used to remove the center of the burl and establish the depth to be hollowed. At this point the Hollowing System for a Wood Lathe would be mounted on the lathe ways as shown in
Depending upon the desired shape of the finished vessel, a variety of different tool cutters would be mounted in the Hollowing System for a Wood Lathe cutter adapter 11 and used in the hollowing process. Cutter adapter 11a would be used for lateral and longitudinal roughing cuts where the uniformity of the cut is not important. Similarly cutter adapter 11b would be used for longitudinal plunge cuts. Cutter adapter 11c would be used for more controlled cuts as the final wall thickness is approached. Cutter adapter 11d would be used for final smoothing cuts. In general, the hollowing process would proceed from the center and top of the vessel until the desired wall and bottom thicknesses were obtained. These thicknesses could be determined visually, by feel, with calipers, or by one of several commercially available laser or camera-based systems. The final step in the hollowing procedure would consist of sanding to the desired level of smoothness and the application of an appropriate finish.
