Patent Application
20130000782
1. Field of the Invention
The instant invention relates to an accessory for a bandsaw wherein the bandsaw coupled with the accessory is capable of functioning as a wood, lathe, the lathe accessory being a small, portable device that can be attached to the table of the bandsaw.
2. Description of the Related Art
As is known in the art a lathe is a machine tool, which, by rotating a workpiece on its axis, can perform various operations. By cutting, sanding, knurling, or drilling, these tools are applied to the workpiece to create an object which has symmetry about an axis of rotation. Used in woodturning, metalworking, metal spinning, and glass-working, lathes can be used to shape a variety of articles such as chess pieces, furniture legs, and ornamental objects such as candlesticks and bowls.
Furthermore, multi-purpose tools having a lathe function can be adapted to produce variably-shaped works of metal or wood as is are known in the art. For example, U.S. Pat. No. 6,293,320 to McGregor, II is a multi-purpose machining apparatus which includes a motor, a grip means, and a guide. U.S. Patent Pub. 2007/0089804 to Vincent is a lathe apparatus. U.S. Pat. No. 4,899,795 to Hackett reveals a guide (bed plate) which engages a saw table and is slidable thereon in a fore-and-aft direction relative to the saw blade.
Most lathes, especially modern lathes, are complex and expensive, not efficiently usable by the hobbyist. The blade mechanisms present on these devices further add to the complexity and cost. There is a need then for a lathe accessory which is a small and portable and that can be easily attached to the table of a bandsaw, thereby giving the bandsaw the ability to function as a wood lathe in a cost-effective, user-friendly manner.
The instant lathe accessory (“device”) is a small, portable device that can be attached to the table of a bandsaw, thereby giving the bandsaw the ability to function as a wood lathe. The action (power) required to remove material from the workplace is provided entirely by the bandsaw itself, thus allowing wood to be removed in a more controlled manner than with a conventional wood lathe. The device acts as a means for precisely holding and moving the workpiece relative to the bandsaw blade.
A workpiece is turned within a workspace defined by a carriage and frame. Turning involves rotating the workpiece on its axis, and as the carriage moves both left/right and forward/backward the bandsaw removes material, thus giving the workpiece axial (rotational) symmetry. The axis of rotation is oriented in the horizontal (left/right) direction, for example about 4″ above the bandsaw table. The device uses a pattern (“template”) that can be made by the operator, or otherwise made available, beforehand. Templates range from uniform, e.g., for turning dowel rod; to tapered, e.g., for turning pegs; to detailed, e.g., for turning chess pieces, decorative posts, etc. The operator moves the carriage and therefore the workpiece as guided by the template, thus transferring the profile of the template to the workpiece.
More specifically, the invention comprehends a lathe accessory for a band saw, comprising a foundation assembly adapted to attach to a table for the band saw, the foundation assembly having a pair of long edges with one of the long edges configured to overhang the table, and further comprising a pair of foundation rails inward from the long edges and traveling a length of the foundation assembly. A stylus base is disposed on the bottom surface, and a stylus is attached to the stylus base upstanding therefrom. A ridge on the bottom surface extends downward therefrom, the ridge configured to fit into a tool guide groove of the band saw table. Next, a translating layer assembly engages the foundation assembly, the translating layer assembly having a top, an underside, a left half, and a right half, and further comprising a pair of grooves defined within the underside, each groove shaped to mate with a respective one of the foundation rails. Further included on the translating layer is a pair of translating rails on the top and a slot defined within the left half permitting movement of the translating layer without interference with the stylus. Then a carriage assembly is disposed on the translating layer, the carriage assembly further comprising a frame subassembly and a bulkhead subassembly, the frame subassembly further comprising an endwall adapted to support a left end of a workpiece. A template platform extends from the endwall, and a front frame rail extends from the endwall spaced from the template platform defined over the slot. A back frame rail extends from the endwall opposite both the template platform and the front frame rail, and a frame leg perpendicular to the back frame rail opposite the endwall connects the front frame rail and the back frame rail and is slidably disposed over one of the translating rails, wherein the front frame rail and the back frame rail are both connected to the frame leg to thereby slidably connect the frame subassembly to the translating layer.
The bulkhead subassembly has a bulkhead bottom conforming to the frame leg, a housing, an outside bulkhead wall, and an inside bulkhead wall, thereby defining a workspace between the endwall and the bulkhead subassembly. Internal components within the interior of the bulkhead motorize the bulkhead and also a fixturing assembly, so in this manner the workpiece can be turned within the workspace while providing a means for further manipulating the workpiece in two dimensions (left/right and forward/backward) as the bandsaw blade cuts the rotating workpiece.
The figures described herein and shown relate to one embodiment which is used with a DELTA® 10″ band saw, which has a height clearance of 6.75″ across its entire 10-inch throat depth. Deducting one inch for the endwall thickness (at left end of device), and doubling the result, yields a maximum workpiece length of 18″ that can be accommodated by the device, in this the preferred embodiment only. The device shown can accommodate a maximum workpiece diameter of 3.5″. Use with other band saw makes and models is possible, as well as with drill presses in conjunction with a rasp bit. (An adapter plate would be needed for use with a drill press.) “Band saw” as herein defined, refers to either a band saw or a drill press. Devices that can accommodate workpiece diameters up to 6″ are also possible. By interposing itself between the operator and the band saw (or drill press), the device provides an additional safety buffer for the operator. Accordingly, described herein is but one, preferred, embodiment, as follows.
The device consists of primarily three separate layers, or assemblies, namely the foundation assembly 10, translating layer assembly 20, and carriage assembly 30. Generally, the carriage assembly 30 holds the workpiece 50 in a fixture and allows it to rotate about an axis as needed within a workspace 314. The foundation assembly 10 supports the carriage while being attached to the band saw table 12, with an intermediary translating layer assembly 20 allowing the carriage to move about the foundation 10. This system constrains the axis of rotation to remain parallel to the front of the band saw table 12, while allowing the operator to move the workpiece 50 left, right, forward, and backward, as needed.
Therefore, with reference to
A stylus 15 is attached to the top surface 22 of the foundation 10 and is used to follow the contour of a template, which is held in the carriage, thus guiding the blade 14a to remove material from the workpiece 50 as further described. When assembled, the stylus 15 protrudes through a slot 25 in the translating layer and can make contact with the template in the carriage. More particularly, a stylus base 13 is disposed on the bottom surface 18, and a stylus 15 attached to the stylus base 13 upstands therefrom. In the preferred embodiment the stylus 15 is a thin metal beam (⅛″*½″) that is deep in the forward/backward direction to minimize deflection while allowing it to follow deep contours in the template. The front edge of the stylus 15. i.e., the edge that makes contact with the template, has a sufficiently small radius to permit detailed duplication of the pattern on the template. Although not critical, the radius of the front edge of the stylus 15 should not be smaller than about 0.01″ to avoid damaging the template. (There is little benefit of making the radius of the front edge of the stylus 15 smaller than 0.01″ since the band saw blade 14a is about 1/32″ thick, which limits the level of detail that can be duplicated.)
With reference to
The carnage assembly 30 shown in
As will be further described, using a motor 318 to turn the sprockets 40 thus causes the bulkhead subassembly 34 to move left and right to allow quick fixturing and release of the workpiece 50 (
Referencing
As above, the motor 318 is mounted on the outside bulkhead wall 310 for turning the sprockets 40, the motor 318 including a motor pinion 44 housed within the housing 300. Inside the bulkhead, the motor 318 pinion 44 engages the bull gear 46 (part of the selector assembly 60 (
In the preferred embodiment, the motor 318 and gearing rotate at 400 rpm, corresponding to a downward tangential velocity of about 5 ft/sec at a workpiece 50 radius of 3″. This is about 10% of the downward velocity of the saw blade 14a. This rate of rotation is great enough to expose the entire circumference of the workpiece 50 to the band saw blade 14a in a seemingly continuous manner to the operator, while maintaining a sufficiently high relative cutting speed on the workpiece 50. This supports allowing the operator to (slowly) move the translating layer horizontally while at a fixed (shallow) depth of cut, so as to reduce the turned diameter one thin layer at a time. The power source for the device shown is an external (12 VDC) battery, although alternatively the device could be powered by an onboard battery pack.
Referencing
Referencing now
A spring-loaded detent plate 66 locks the selector assembly 60 into one of the above three positions. A button in the center of the handle 61 passes through a hole 41 and pushes the detent plate 66 away from the selector arm 67, allowing it to turn. Whenever the selector assembly 60 is in the DRIVE or TURN position, the corresponding electric contact 45 beneath it is closed. Each electric contact 45 plate consists of a spring-loaded lever that, when pushed by the square lug 64 closes an electrical switch. When the selector assembly 60 is in the DRIVE or TURN positions, the lug presses down on the end of the corresponding lever, which then presses down and closes the corresponding electrical contact 45. Therefore, the selector assembly 60 further comprises a bull gear 46 and the selector pinion 43 mounted between two selector arms 67. The square lug 64 is mounted on one of the selector arms 67. The detent plate 66 is held in a fixed orientation when assembled into the housing 300 of the bulkhead subassembly 34 by means of an immobilization pin (not shown) which passes through the immobilization pin hole 65 in the detent plate and corresponding small holes in the outside bulkhead wall 310 and the inside bulkhead wall 312. A spring-loaded rod 68 located within a hole 41 in the selector shaft allows the detent plate 66 to be pushed away from the square lug 64. The shaft 48 of the selector assembly 60 passes through and is supported by a hole in the outside of the bulkhead wall 310 and the inside bulkhead wall 312. It also serves as the axis for the bull gear 46. The selector pinion 43 is attached to the far end of the selector arm 67 and is continually engaged with the bull gear 46. The position of the selector assembly 60 thus determines where the power is transferred.
For preparing the template 73, the template 73 is a pattern made from a thin, durable, precision-machinable material, that serves to guide the location of the carriage relative to the band saw blade 14a, by means of its interaction with the stylus 15. Templates can be made of hard wood or plastic (⅛″ thick), or metal (typically 1/32″ to 1/16″ thick). Templates may be provided already made, or custom made by the operator from template blanks. Examples of ready-made templates might include: uniform-width templates of various widths, for making dowel rods; tapered templates, for making pegs; templates for turning and/or indexing decorative posts; etc.
To custom make a template, the operator begins with a suitable blank, such as a ⅛″-thick piece of hardwood, and uses a saw and/or file to cut out the desired pattern. The portion of the template closest to the back of the template holder needs to include a fixed allowance (typically ½″) for the portion that lies on top of the template platform 38 and to provide rigidity to those portions where the workpiece 50 is turned to a narrow diameter. For templates that include pieces that will be separated from one another, the template should include physical markings (notches, steps, etc.) to indicate where the pieces, are to be separated after removal of the workpiece 50 from the device. A single template can include multiple patterns of the same or different items, if desired.
Now with reference to
As above, band saw blade guides 83, 85 are positioned above and below the elevation of the axis of rotation of the workpiece 50, to stabilize the band saw blade 14a while making precise cuts into the workpiece 50. Each band saw blade guide 83, 85 consists of a material having a low coefficient of friction (against the steel band saw blade 14a) and resistance to elevated temperature, such as brass. Each guide contains a thin, vertical blade slot 87 to accommodate the back of the band saw blade 14a, i.e., the portion of the band saw blade 14a without the teeth. Since they will eventually wear out, the guides 83, 85 are replaceable. The life of each guide 83, 85 can be doubled by making it reversible, as shown.
The guide tower subassembly 84 further includes a lower half 89 engaged with the ridge 17 and an upper half 89a connected to the lower half 89 and to the proximal end 86b of the main guide bar 86. Included is a means for rotating the upper half 89a about the lower half 89 wherein the blade guide subassembly 82 can be maneuvered. The guide tower subassembly 84 is a large cylindrical post which is mounted to the end of the foundation ridge 17 extension. The top half of the tower can be lifted and turned, to swing the blade guides 83, 85 away from the blade 14a for easy removal of the device from the band saw table 12. Pegs and holes 804 within the tower ensure that the guide consistently returns to the same position. A hollow axle helps maintain alignment during this process, and a spring within the axle holds the two halves firmly together.
A slot in the top of the upper half 89a of the tower accommodates the main guide bar 86, which preferably is a ½″ hollow square tube, held in place by means of an alien screw 800 and split washer 801. A slot in the main guide bar 86 allows horizontal alignment of the band saw blade guides 83, 85 with the band saw blade 14a. A square or rectangular hole in the distal end 86a of the main guide bar 86 accommodates the secondary guide bar 88, which preferably is a ¼″ square bar, also held in place with an alien screw for forward/backward adjustment, in the preferred embodiment the vertical guide bar 81 is a 3/16″ square bar that has received a ¼″-20 external thread and is brazed to the end of the secondary guide bar 88. The guides 83, 85 include 3/16″ square holes (to prevent rotation) and are held in place with nuts and washers.
With reference to
In indexing, the workpiece 50 is machined in a similar mariner as in turning, except that it is held at a fixed angle about its axis of rotation by means of an indexing wheel 90 and pin. Once the workpiece 50 has been machined along one face, the workpiece 50 is indexed at another angle and the process is repeated. This method produces non-circular cross sections that are either uniform along the axial direction (e.g., triangular or octagonal prisms), or that vary along the axis (such as a shaped chair leg square in cross section). Pieces having cross sections that are not rotationally symmetric can be produced by using multiple templates, each for use with a specific index angle. For example, one template for the front and back views (0° and 180°) and one template for the side views (90° and 270°) can be used to produce the starting point for carving wooden figures, such as knights for a chess set. Using templates for more than 4 index angles can be used to produce higher three-dimensional detail, such as a bust of a famous composer. The external pinion 92 also has an index wheel 90 with thirty (30) evenly-spaced holes. An index pin can be inserted through the bulkhead (i.e., from the right-hand side of the bulkhead) and into one of these index holes. (The index pin is stowed in a clip on the right side of the bulkhead when not in use.) For convenience, the holes are numbered as follows: A0, B0, C0, A1, B1, C1, A9, B9, C9. The following table 1 can be used to rotate the workpiece 50 in N even increments. When using this table, it is important that the index wheel 90 is always turned in the direction of increasing hole number:
Using a removable gear 53 between the external pinion 92 and the fixturing grip 52a enables the workpiece 50 to be reversed end-to-end within the carriage, without detaching the grips from the workpiece 50.
With reference to
The instant application claims benefit of provisional application Ser. No. 61/501,915 filed Jun. 28, 2011, the contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61501915 | Jun 2011 | US |
