Tools – Wire stripper – Bench tools
Reexamination Certificate
2000-08-16
2003-07-08
Meislin, D. S. (Department: 3723)
Tools
Wire stripper
Bench tools
Reexamination Certificate
active
06588302
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus for severing multiple layers of coating or covering materials from a central core such as a conductor of a coaxial cable or an optical fiber. More specifically, the invention relates to improvements in automated machinery for sequentially severing and removing multiple layers of material from a wire or other filamentary member utilizing a cutting blade with a circular cutting edge which orbits the material being cut. The prior art includes many types of apparatus for severing and removing a covering layer from a central, filamentary member, as in the removal of insulation and sheathing from an electrical wire or coaxial cable. Such apparatus typically includes one or more cutter blades which are moved from a position spaced radially outwardly from the position at which the cut is to be made inwardly toward the wire, at least partially through the covering layer. The blade(s) may be moved only in linear, reciprocating motion, as in the apparatus of U.S. Pat. No. 5,445,051, or may be rotated about the axis of the wire as they are moved toward and away from the wire, as in the case of U.S. Pat. Nos. 4,745,828 and 4,993,287, or may be moved in a path which orbits the axis of the wire, as disclosed in U.S. Pat. No. 4,619,164. Typically, after the covering layer is severed, the severed section or slug is stripped from the wire. While some forms of apparatus are designed to cut and strip only a single layer of material from the central core, making only one cut at the same axial length from the end of the workpiece and at the same radial depth in each workpiece, others are programmable to make a series of cuts, each through a distinct layer of covering material, at different axial positions and different radial depths, as in the case of coaxial cable where several, superposed layers of covering material are required to be cut and stripped from a central conductor. It is with this latter type of apparatus, particularly that of aforementioned U.S. Pat. No. 4,6119,164 (hereinafter “the '164 patent”), that the present invention is concerned.
Orbital motion is imparted to one or the other of the cutting and the wire positioning members in the '164 patent by a rod which rotates about the axis of a motor output shaft but which is arranged with its own axis at an acute angle to the motor shaft axis. The rod passes through a bearing mounted in a housing for axial adjustment along the rod to selectively change the radius of the circular, orbiting motion of the blade. The bearing housing is affixed directly to the movable (cutting or wire positioning) member, thereby translating the nutational motion of the rod to orbiting motion of the movable member. Although effective for the intended purpose, the design subjects a number of parts to excessive wear, is not particularly compact, and has a good deal of inherent play and inaccuracy. One of the objects of the present invention is to provide novel and improved means for imparting orbital motion to a movable member in apparatus for cutting a coating layer on a wire, fiber, or the like.
The cutting edge is, of course, circular in orbiting cutter apparatus and thus, at any given time, engages the cut layer over a limited portion of its periphery, i.e., on only one side. Also, for relatively thin layers, the blade engages the cut layer for only a small depth. Stripping of a severed slug is normally accomplished by holding the workpiece axially stationary and moving the blade in a direction removing the slug, or by holding the cutter blade stationary and moving the workpiece axially. Obviously, if the blade engages the slug over a small peripheral portion at a small depth, stripping ability is impaired as compared to apparatus using two blades which engage the slug on both sides. Thus, the use of a single, orbiting cutting edge, as in the '164 patent, has the disadvantage of impaired stripping capability in at least some applications. Another object of the invention is to provide apparatus which improves the stripping function in cutting/stripping apparatus having an orbiting cutting blade.
The prior art apparatus, in respect of features usually associated with both orbiting blade and rotating blade cutting/stripping devices, is improved upon by the present invention in a number of other ways. These include ease of blade replacement, adjustability of the position of the axis of the wire guide, reduction of wire end “whip” during orbital blade movement, better gravity disposal of debris from stripping operation, improved bearing and bushing design in several mechanical areas, an improved centering technique for calibration of movable gripping members, and both mechanical and operational improvements in clamping assemblies.
A preferred embodiment of apparatus fulfilling and embodying the foregoing and other objects and advantages will be summarized, as well as disclosed in detail, in the following sections.
SUMMARY OF THE INVENTION
At what is considered the front end of the apparatus, a pair of clamping jaws are mounted for movement toward and away from one another to fix the axial position of the workpiece during the cutting and stripping operations. Each jaw incorporates a toothed rack engaged with a single pinion gear on the output shaft of a DC motor. The jaws are driven linearly by the. motor along a common central axis, providing a simple and reliable mechanical arrangement with a minimum of parts. The motor is controlled by drive electronics which digitally control current through the motor (motor torque) and hence the clamping force. A unique software feature increases the clamping force during the stripping operation, when axial movement of the workpiece is most likely to occur, and returns to the lower value for other functions. The higher and lower clamping forces are user programmable, permitting use of the clamping mechanism with appropriate clamping force over a wide range of cable sizes and other conditions. The mechanism also incorporates novel and improved means for adjusting the horizontal centering position of the jaws.
The workpiece may be, for example, a coaxial cable comprising a central conductor with a plurality of coating or covering layers and, for purposes of the present discussion, will be considered such. The cable is positioned for processing by axial advancement between the clamping jaws and through an opening in a guide bushing with the cutting blade acting as a stop for the end of the cable. Although such guide bushings have been used in prior art cutting/stripping apparatus, such as that of previously mentioned U.S. Pat. No. 4,993,287, the bushing is rotated together with the cutting blades about the axis of the stationary wire or cable. In order to avoid excessive generation of heat from friction between guide and workpiece and resulting expansion of the workpiece, it was necessary to provide an appreciable clearance with consequent degradation of centering accuracy. The apparatus of the present invention comprises a guide bushing which is stationary during severing of the covering layer(s), permitting very close clearance between cable and bushing, thereby improving positional accuracy of the cable axis. Furthermore, the apparatus incorporates a unique mechanical arrangement permitting both horizontal and vertical positioning of the structure holding the guide bushing for extremely accurate alignment of the central axes of the bushing and the circular cutting edge. Also, the entire bushing holding and positioning mechanism is movable to expose the cutting blade fully and permit easy and quick replacement thereof. After blade replacement, the bushing and its support structure may be quickly and easily returned to its prior, preset position.
The mounting and motion assembly for the cutting blade includes three plates, namely, a rear plate rigidly connected to the support upon which the blade is mounted, a stationary, center plate, and a front plate. The front plate is connected through horizontally disposed, linear, roller bearings to
Hancock & Estabrook, LLP
McGuire George R.
Meislin D. S.
Orbital Technologies, Inc.
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