Turning – Portable lathe for pipe turning
Reexamination Certificate
1999-05-18
2001-08-28
Tsai, Henry (Department: 3722)
Turning
Portable lathe for pipe turning
16
Reexamination Certificate
active
06279437
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to pipe tools and more particularly to a pipe beveling machine with improved operation and structure.
In pipe beveling, a beveling machine is typically mounted within the pipe to be beveled, by means of a mandrel device that secures the machine in relation to the pipe by engaging the inner walls of the pipe. A draw bolt is provided and tightening of a draw nut causes portions of the mandrel to expand and engage the pipe. Heretofore, if the draw bolt was to break, components of the mandrel would fall off, into the pipe. Such an accident can be annoying and difficult to remedy, as the component might end up at rest in a bend in the pipe a great distance from the beveling site. The particular resting site would have to be located, and the pipe cut open to retrieve the components. To address this issue, some mandrels employ a spring that allows expansion of components for engaging the pipe walls, but still holds the components to the mandrel. However, this is not always satisfactory, as the spring can break (and fall off), and if the draw bolt does break, often the surrounding mechanisms that hold the spring also fall off, into the pipe.
In beveling and facing devices, it is desirable to have a backlash free engagement between the driving and driven portions of the devices. There are numerous designs of mechanical keys that fit into correspondingly shaped grooves or “keyways” of mechanical members to lock the mechanical members from moving relative to each other in one or more axes. The Woodruff, Saddle, and Gib-head keys are some of the more common designs. Most of the mechanical industry's keys are of a single piece design and are not adjustable. This means that they must be designed with somewhat relaxed tolerances that allow for friction fit and installation. In high torque situations this “loose” fit is undesirable as it leads to accelerated wear resulting in “backlash” (movement of one element relative to the other) and a greater potential for key failure due to the higher shear forces encountered with “backlash”. Conventional mechanical keys do not address this problem. If backlash is present, given the high torque situations, “chatter” can result, giving a rough or poor cut or faced portion.
A particular application for these keys is seen in such high torque applications as beveling tools for pipes or facing tools. A mandrel clamps to a pipe and a non-rotatable power unit is slideably mounted on the mandrel. The power unit has a rotatable portion that holds and rotates a cutting tool to “face” the pipe. The power unit itself does not rotate and is held from doing so by locking keys that are interposed between the axial mandrel grooves, and keyways cut into the non-rotatable power unit. These locking keys also mount the power unit onto the mandrel. The power unit slides axially along the mandrel to feed the cutting tool into the pipe. When in operation, these locking keys experience high torque loads in maintaining the stationary position of the non-rotatable power unit in response to the reactionary force experienced as its rotatable portion faces the pipe. These keys are subject to extreme shear forces and wear quickly. As they wear there is more “backlash” movement developed between the non-rotatable power unit and the mandrel, thereby increasing the shear forces and accelerating wear. Most of the locking keys in the industry do not accommodate for wear and are not adjustable, requiring frequent replacement.
SUMMARY OF THE INVENTION
In accordance with the invention, a pipe beveling machine includes a mandrel portion with ramps that move outwardly to engage a pipe's inner surface. A draw bolt attaches to an actuator having ramp receiving portions thereon, and as the draw nut is tightened, the actuator is pulled back by the draw bolt, causing the ramp portions to extend.
Accordingly, it is an object of the present invention to provide an improved mandrel system that prevents pieces from falling off should the draw bolt break.
It is a further object of the present invention to provide an improved mandrel system that is able to fit in smaller diameter pipes.
A further object of the invention is to provide an improved backlash free wedge key engagement between a mandrel and the rest of the device.
It is yet another object of the present invention to provide an improved pipe beveling machine that reduces backlash.
A further object of the invention is to provide an improved backlash prevention system that accommodates wear.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.
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Climax Portable Machine Tools, Inc.
Dellett and Walters
Tsai Henry
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