TRIPPER ASSEMBLY FOR CLAMSHELL TYPE MACHINING LATHE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This claims the benefit of U.S. Provisional Patent Application No. 60/863,070 filed October 26, 2006.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH [0002] Not applicable.

FIELD OF THE INVENTION

[0003] This invention relates generally to a machining lathe, and more specifically to an improved tripper assembly for a split frame clamshell type portable machining lathe.

BACKGROUND OF THE INVENTION

[0004] The general concept of a split frame clamshell type portable machining lathe is known in the art. One such lathe is shown in U.S. Patent No. 4,739,685, granted to Donato Ricci, and titled "Split Frame Portable Machining Lathe". The clamshell-type machining lathe described in the '685 patent includes a rotatable ring, a stationary ring, and a starwheel or star gear for imparting rotation to a feed screw in a tool bit slide assembly or tool module which holds a tool bit. Both the starwheel and the tool bit slide assembly are mounted on the rotatable ring of the clamshell lathe and a pin is mounted on the stationary ring. As the starwheel orbits the workpiece, upon each revolution, the pin engages a tooth on the starwheel to rotate the starwheel, thereby imparting rotation to the feed screw on which the starwheel is mounted and moving the tool bit radially with respect to the workpiece. As described in the '685 patent, the pin can be manually moved in and out in a radial direction to move it from an engaged position with respect to the starwheel to a disengaged position. Room exists for improvement in this area of the tripper assembly.

SUMMARY OF THE INVENTION

[0005] A tripper assembly of the invention allows for a pin to be moved into or out of engagement with a starwheel without movement toward the moving assembly. Rather, the pin is moved in an arc roughly parallel to the assembly. In particular, the tripper assembly is adapted for use with a clamshell lathe of the type having a stationary ring adapted to be clamped to a

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generally cylindrical workpiece and a rotatable ring journaled for rotation on the stationary ring. The rotatable ring includes a tool module for holding a tool bit, and the tool module has a starwheel with a plurality of teeth coupled to a feed screw for moving the tool bit as the starwheel rotates. The tool bit is fed by the feed screw in a radial direction with respect to the rings. The tripper assembly includes a bracket affixed to the stationary ring of the lathe, a radially extending shaft mounted in the bracket, a pin holder mounted on the shaft, and a radially extending pin held by the pin holder. Rotation of the shaft moves the pin along an arc to move the pin between an engaged position and a disengaged position with respect to the starwheel. When the pin is at the engaged position, upon each revolution of the starwheel, the pin engages a tooth on the starwheel to rotate the starwheel and when the pin is at the disengaged position, the pin does not engage a tooth on the starwheel and the starwheel does not rotate. The tripper assembly is easy to use and easy to manufacture.

[0006] These and other advantages of the invention will be apparent from the detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Fig. 1 is a perspective view of a tripper assembly of the invention; [0008] Fig. 2 is an exploded view of the tripper assembly of Fig. 1;

[0009] Fig. 3 is a perspective view of the tripper assembly of Fig. 1 mounted to the stationary ring of a clamshell type lathe such that a pin is in an engaged position with respect to the starwheel;

[0010] Fig. 4 is an enlarged view of the tripper assembly with the pin in an engaged position with respect to the starwheel;

[0011] Fig. 5 is a view similar to that of Fig. 3 but wherein the pin is in a disengaged position with respect to the starwheel; and

[0012] Fig. 6 is an enlarged view of the tripper assembly with the pin in a disengaged position with respect to the starwheel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] Fig. 1 illustrates a tripper assembly 10 of the present invention. The tripper assembly 10 is suited for use in conjunction with a clamshell lathe 12, such as shown in Fig. 3. Those skilled in the art will recognize that the tripper assembly 10 also can be used advantageously with other automated lathe designs. Referring to Figs. 1 and 2, the tripper assembly 10 includes a bracket

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14, a shaft 16 coupled to the bracket 14 and having a handle 18 affixed to the shaft 16, a pin holder 20, and a pin 22 mounted to the pin holder 20. The illustrated pin holder 20 includes a shaft portion 24 having arms 26, and an outer support portion 28.

[0014] Shaft 16 is journaled by suitable bearings at opposite ends in endwalls 17, 19 of the bracket 14. A bore 30 in the shaft portion is configured to match the shape of the center part of the shaft 16, which in the illustrated embodiment is hexagonally shaped. The position of the pin holder 20 along the shaft 16 is adjustable since the pin holder 20 is slidable on the shaft 16. The position can be locked by tightening a set screw 34 extending through a bore 32 in the shaft portion 24 to bear against the shaft 16. The distance D (Fig. 1) between the pin 22 and the shaft 16 is also adjustable by removing screws 27 and moving the support portion 28 along the arms 26 of the shaft portion 24, and resecuring the support portion to the shaft portion at a selected position using a different one of the three sets of screw holes illustrated. Appropriate adjustments of the pin location can thus be made to match different applications. [0015] Referring to Figs. 3-6, clamshell lathe 12 includes a stationary ring 38 which is adapted to be centered about and affixed to a cylindrical workpiece (not shown) such as a large diameter pipe or shaft. Lathe 12 also includes a rotatable ring 40 that is journaled for rotation on the stationary ring 38 and which is driven by a drive motor (not shown) in a conventional manner so that the rotatable ring 40 can be made to rotate about an axis 42 and about the workpiece. Further details regarding the construction and operation of such a clamshell lathe are well known, for example, from U.S. Pat. No. 4,739,685.

[0016] A tool module 44 is affixed to an outer surface of the rotatable ring 40 and therefore orbits the workpiece when the motor drives the rotatable ring 40. The bracket 14 of the tripper assembly 10 is affixed to the outer surface of the stationary ring 38 as shown by fasteners extending through one or more of the holes 13 and threaded into ring 38. The position along the shaft and the height of the pin 22 can be adjusted so that the pin 22 is appropriately positioned with respect to a starwheel 46 of the tool module 44. The pin 22 extends radially, i.e., in a radial direction relative to the rings 38, 40.

[0017] The tool module 44 includes a tool block slide 48 affixed to the rotatable ring 40 and a tool block 50 having an opening 53 to receive and securely hold a tool bit (not shown), as is conventional and also described for example in U.S. Pat. No. 4,739,685. Further, a threaded

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shaft 57 is secured within the tool block 48. As the ring 40 is made to rotate, the tool module 44 is carried with the ring 40.

[0018] When the pin 22 is in an engaged position, such as shown in Figs. 3 and 4, upon each complete revolution of the tool module 44, the pin 22 engages a tooth on the starwheel 46 to rotate the starwheel a fraction of a turn, thereby causing rotation of the shaft 57. Shaft 57 is in threaded engagement with the slide 50 so that rotation of the shaft 57 causes a radial movement of the tool block slide 50. The movement of the tool block slide 50 to move the tool radially deeper into the workpiece about which the tool is orbiting.

[0019] As the handle 18 of the tool assembly is turned approximately 90°, the shaft 16 is rotated, and the pin 22 is rotated between an engaged position with respect to the starwheel 46 such as shown in Figs. 3 and 4 and a disengaged position with respect to the starwheel 46 such as shown in Figs. 5 and 6. In the disengaged position, the pin and starwheel are not coupled together. In the engaged position, the shaft 16 cannot be turned any further counterclockwise (as viewed from the left side of handle 18 in Fig. 1). Wall 29 of bracket 14 interferes with further counterclockwise motion of the pin holder 20. Counterclockwise is the direction that the starwheel 46 tends to turn shaft 16 each time the starwheel 46 hits the pin 22 on each revolution of the assembly 44. When disengaged, wall 31 stops further clockwise rotation of the pin 22. [0020] It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.

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