The present invention relates to a blade for stripping insulation from electrical conductors in a wire stripping operation; and, more particularly, to a blade comprising arcuate cutting edges for minimizing the total area of uncut insulation around the conductors.

Prior art Figures 1, 3, and 4 show a known stripping blade 10, Figure 3 being an enlarged view of a portion of the blade shown in Figure 1. Blade 10 includes: a body of tool quality steel 11; a cutting opening 12 comprising a sharpened blade section; and a tooling attachment section 18 for connecting blade 10 to a stripping machine. Cutting opening 12 includes: first and second cutting edges 14,15 formed along a compound angle 13. Compound angle 13 extends across the thickness of body 11. As is best shown in Figures 3 and 4, second cutting edges 15 converge to a vertex 16. Cutting edges 14 and 15 include a respective angle of convergence A,B with angle A being less than angle B, as is shown in

Figure 3. When two blades 10 are brought together in a conventional wire stripping operation, as shown in Figure 4, a conductor 19 is disposed in the cutting openings for the purpose of stripping the conductor, preferably, without nicking the conductor during the stripping operation. Conductor 19 includes insulation 19a therearound, but, as the blades 10 are brought together, four areas of insulation 19b,19c remain uncut by blades 10. Such uncut areas 19b,19c are undesirable because, as the stripping blades move the slug of insulation away from the insulation which is to remain, slivers of insulation may extend along the sides of conductor 19. These slivers of insulation create manufacturing problems as they are likely to become lodged in a crimp barrel of a terminal during a crimping process, thereby compromising the quality of the crimp. Moreover, if the conductor is to be soldered rather than

crimped, the slivers of insulation will negatively effect the quality of the solder joint. Further, because the total area of insulation to be cut increases with increasing wire size, the likelihood of the appearance of uncut insulation slivers increases proportionately with increasing wire size.

Prior art Figures 2 and 5 show a V-type blade 20 for stripping wires. Blade 20 includes: a body of tool quality steel 21; a cutting opening 22 comprising a sharpened blade section; and a tooling attachment section 28 for connecting blade 20 to a stripping machine. Cutting edges 24 extend along a compound angle 23, and converge to a vertex 26. When two blades 29 are brought together in a conventional stripping operation to strip a conductor 29 having insulation 29a, four areas of uncut insulation 29b,29c remain around conductor 29. Such uncut areas of insulation are likewise disadvantageous for the reasons given above in respect of stripping blade 10. To overcome the foregoing problems, the present invention provides a universal wire stripping blade for stripping a range of wire sizes. The universal stripping blade of the present invention reduces the total area of uncut insulation and substantially eliminates two areas of uncut insulation when stripping relatively large size wires, and otherwise reduces the overall area of uncut insulation during the stripping of relatively smaller gauge wires.

The invention will now be described by way of example with reference to the accompanying drawings in which:

Figures 1 shows a wire stripping blade according to a first prior art device.

Figure 2 shows a wire stripping blade according to a second prior art device.

Figure 3 shows a close up view of the blade of Figure 1.

Figure 4 shows a pair of blades according to the device of Figures 1 and 3 when cutting the insulation of a conductor.

Figure 5 shows a pair of blades according to the device of Figure 2 when cutting the insulation of a conductor.

Figure 6 shows a wire stripping blade 50 according to the present invention having: an axis of symmetry X; a body 51 formed of tool quality steel; a cutting opening 52; and a tool attachment section 58. Cutting opening 52 comprises: a first set of cutting edges 54; a second set of cutting edges 55; a third set of cutting edges 56; and a vertex 57. Edges 54,55, 6 are generally symmetrically disposed in opening 52 relative to axis X. A compound angle 53, as best shown in Figure 6, extends across a thickness of body 51 and acts as a lead-in to guide wires toward cutting edges 54,55,56. A lead-in taper 60 is formed adjacent opening 52, as best shown in Figure 3. Taper 60 prevents stubbing of a set of blades 50 as they are being moved towards each other in a cutting stroke of a conventional stripping operation, as shown in Figures 8-9.

During the cutting stroke, blades 50 contact insulation 59a of a conductor 59, as follows: cutting edges 54 are lead-in edges and cut the insulation first, followed secondly by cutting edges 55, thirdly by cutting edges 56, and finally by vertices 57. Conductor 59, for example, is a relatively large size wire, e.g. 10 AWG. The fully advanced cutting stroke position is shown in Figure 9.

Referring to a preferred embodiment of the invention which is depicted in Figure 10, a pair of substantially identical blades 50 will be described in further detail. To avoid confusion, one side of cutting opening 52 will be described with the understanding, with reference to Figure 10, that each blade 50 includes

two such sides generally symmetrically disposed about axis X.

Cutting edges 54,55,56 define a series of distinct, sharp edges in opening 52. The edges are delimited by a series of transition points P ₁ -P ₄ , such that: first cutting edge 54 is between points Pι,P ₂ . second cutting edge 55 is between points P ,P ₃ ; and third cutting edge 56 is between points P ₃ .P ₄ . Edge 56 blends in with vertex 57 at transition point P ₄ . Each edge 54,55,56 is preferably shaped to define an arcuate profile, for example, a semi-circular profile having a radius with constant curvature about a respective radius point ^R ₅₄ ' ^R ₅₅ / ^R ₅₆ - Radius points R ₅₄ ,R ₅₅ ,R ₅₆ are advantageously placed in predetermined locations relative to axis X, for the purpose of forming the arcuate profiles, as follows: radius point R ₅₄ is located on the same side of axis X as edge 54; radius point R ₅₅ is generally centered on axis X; and radius point Rςg is located on an opposing side of axis X relative to edge 56. Respective edges 54 of a blade 50 thereby define lead-in cutting edges, and edges 55 and 56 define cutting edges which cut close to the conductor and yet conform to the circumference of the conductor 59 without nicking the same. Moreover, cutting edges 55,56 advantageously eliminate areas of insulation which were left uncut in prior cutting blades.

In an example of the present invention, the respective radius dimensions of edges 54,55,56, in inches, were formed as follows: Rj at about 0.6; R ₂ at about 0.07; and R ₃ at about 0.19. However, although the preferred embodiment of the present invention provides for semi-circular edges 54,55,56, it is contemplated that non-semicircular arcuate profiles, i.e. having a non-constant curvature about a point, can be used to define the three cutting edges as well. For example, profiles comprising a parabolic, elliptical, or other non-semi-circular arc can be used in accordance with the

scope of the present invention. Use of linear edges in combination with arcuate profiles is also contemplated.

Figure 11 is a partial cross sectional view of the blades 50 and conductor 59 as shown in Figure 9. In an important advantage of the invention, the arcuate profiles of edges 54,55,56 have cut all but two sections 59b of insulation 59a. This is advantageous because the total uncut insulation area of relatively large conductor 59 has been minimized. Moreover, edges 54,55,56 render blades 50 operative as universal cutting blades suitable for functioning in an apparatus, such as a wire cutting and stripping tool or a wire lead making machine, for stripping a range of sizes of conductors 59, for example, AWG sizes 10-26. Thus, while a preferred embodiment of the present invention has been disclosed, it is to be understood that the invention is not to be strictly limited to such embodiment but may be otherwise variously embodied and practiced within the scope of the appended claims.