Turning – Portable lathe for pipe turning
Reexamination Certificate
1999-06-25
2001-02-13
Tsai, Henry (Department: 3722)
Turning
Portable lathe for pipe turning
C082S128000, C082S130000, C082S131000
Reexamination Certificate
active
06186037
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates generally to power tools used for metal working, and more particularly to a machine for preparing industrial tubing by squaring the end thereof prior to joining same to another tube or fitting in a welding operation and/or for trimming such a tube to a precise length in plumbing a fluid flow system.
II. Discussion of the Prior Art
The E.H. Wachs Company of Welling, Ill., produces and sells a tube squaring tool that conforms to the teachings of the Pierce U.S. Pat. No. 5,619,893. It comprises a hand-held, electrically-powered drive motor similar in construction to a conventional ½″ power drill with a pistol grip, but instead of supporting a drill bit in a chuck, the motor shaft is coupled to a coaxially aligned shaft of the tube squaring tool which has a cutting tool retainer formed at the free end thereof. Surrounding the squaring tool shaft is a housing that is fixedly clamped to the drive motor housing at one end thereof, with the opposite end including a collet retainer for holding a collet used to clamp a tubular workpiece to be squared. Coaxially disposed about the housing is a feed nut having internal threads that mesh with external threads on a feed ring. When the feed nut is rotated in a clockwise direction, the shaft is displaced axially toward the end of the tube workpiece to be squared. In this manner, the rotatable cutting tool may be brought into contact with the end of a tube to thereby shave material from it.
Unfortunately, tube squaring machines conforming to the Pierce patent have a serious design flaw that adversely impacts the quality of the machining operation being performed. The shaft is journaled for rotation at two relatively closely spaced locations proximate the midpoint of the shaft such that a substantial portion of the tool's shaft and the weight of the tool holder portion thereof is cantilevered relative to the journal bearings. The cantilevered shaft length increases as the feed nut is rotated to advance the cutting tool toward the stationary workpiece. It is found that after a relatively short period of use, the cutting tool not only rotates but wobbles in a plane perpendicular to the normal axis of the shaft resulting in “chattering”. This chattering leads to irregularities in the end of the tube being machined. In addition, the bearings themselves are subject to relatively rapid wear that requires that the tool be taken out of service for refurbishment.
SUMMARY OF THE INVENTION
The present invention obviates the foregoing difficulties by providing a tool for squaring the ends of tubular workpieces having a shaft member with first and second ends, the first end including a clamping device for holding a cutting tool bit therein and the second end adapted to be coupled to a shaft of a drive motor. A tubular torque housing surrounds the shaft and the torque housing has axially extending keyways formed in a peripheral surface thereof. The shaft is journaled for rotation within a central bore of the torque housing by bearings that are located proximate opposite ends of the shaft so that only a relatively small portion of the shaft is cantilevered beyond the end of the frontmost bearing. The shaft is constrained from axial displacement within the torque housing.
A generally cylindrical axial feed housing having first and second ends and a central bore extending therethrough receives the torque housing and cutting tool shaft therein and it, too, has axially extending keyways projecting radially outward of its central bore. Key members share the keyways of both the torque housing and the axial feed housing, preventing rotation of the axial feed housing about the torque housing. The first end of the axial feed housing has external threads formed thereon and its second end includes a circular flange. A workpiece holding collet clamping assembly is affixed to this circular flange. A feed ring fits over the axial feed housing and the feed ring has internal threads that engage the external threads on the axial feed housing. Now, when the feed ring is manually rotated, it will axially displace the axial feed housing with its attached workpiece holding collet in an axial direction toward or away from the cutting tool secured to the outer end of the rotatable shaft, depending upon the discretion of rotation of the feed ring.
Because the shaft is immovable in the axial direction and is well supported by journal bearings proximate opposed ends thereof, with only a short length of the shaft being cantilevered, there is no tendency for chattering to occur as in the prior art E.H. Wachs Co. tube squaring tool.
REFERENCES:
patent: 5619893 (1997-04-01), Pierce
patent: 5671646 (1997-09-01), Sandford et al.
patent: 5711197 (1998-01-01), Ohmi et al.
patent: 5836727 (1998-11-01), Scheer
patent: 5941145 (1999-08-01), Marshall et al.
patent: 5960686 (1999-10-01), Bonow
Place Brent
Ricci Donato L.
Nikolai Mersereau & Dietz, P.A.
Ricci Donato L.
Tsai Henry
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