Wire attachment
A swaged fitting can be fixed to a wire rope while simultaneously providing a desired shape and size, thereby avoiding the need for subsequent material removal. In one application, the swaged fitting is fixed to the wire rope by a forging operation such that the fitting is securely fixed provides a straight-sided construct once fixed to the wire rope. After the forging operation and without further material removal, the straight sides of the finished fitting are generally parallel to the longitudinal axis of the wire rope, while the end surfaces of the fitting are generally perpendicular to this longitudinal axis. This arrangement provides a strong and effective force-transfer interface for, e.g., end-effectors in medical devices.
1. An actuator assembly comprising:
a wire rope including a plurality of wire elements, the wire rope having a pair of opposing terminal ends; and
a fitting fixed along a length of the wire rope and spaced from each of the pair of opposing terminal ends, the fitting comprising:
a body with a straight-sided sidewall defining a longitudinal body axis;
an aperture formed through the straight-sided sidewall of the body, the aperture defining a longitudinal aperture axis substantially perpendicular to the body axis; and
a pair of end surfaces defining opposing longitudinal ends of the body, wherein the pair of end surfaces are each substantially planar across an entirety of the respective end surface.
2. The actuator assembly of claim 1 , wherein each of the pair of end surfaces is substantially parallel to the aperture axis.
3. The actuator assembly of claim 1 , wherein the body of the fitting is one of cylindrical, cuboid and prismatic.
4. The actuator assembly of claim 1 , wherein the straight-sided sidewall of the body defines a linear profile in the plane of the body axis.
5. The actuator assembly of claim 1 , wherein the aperture includes a deformed interior surface creating a multi-faceted interface with valleys and interstices between the plurality of wire elements of the wire rope.
6. The actuator assembly of claim 1 , wherein the wire rope has a diameter between 0.0015 in and 0.187 in.
7. The actuator assembly of claim 6 , wherein the wire rope is made from one of stainless steel, Co—Cr alloys, titanium alloys, shape memory alloys including NiTi, and tungsten.
8. The actuator assembly of claim 6 , wherein the fitting has an outer diameter between 0.020 in and 0.250 in.
9. The actuator assembly of claim 6 , wherein the fitting can withstand a pull force of at least 80% of a break-load strength of the wire rope without slipping relative to the wire rope.
10. The actuator assembly of claim 6 , wherein the fitting can withstand a rotational moment of at least 75 lbf relative to the wire rope.
11. The actuator assembly of claim 1 , wherein the body defines a maximum lateral extent extending laterally away from the longitudinal body axis, the substantially planar end surfaces extending across more than 95% of the maximum lateral extent.
12. The actuator assembly of claim 1 , wherein each of the pair of end surfaces occupies an area bounded by the straight-sided sidewall.
13. A precursor fitting system, comprising:
a wire rope including a plurality of wire elements; and
a straight-sided body defining a longitudinal body axis, the body comprising;
an aperture formed through the straight-sided body, the aperture defining a longitudinal aperture axis substantially perpendicular to the body axis and sized to receive the wire rope such that a void is formed between the wire rope and an interior surface of the aperture;
a pair of opposing ends of the straight-sided body; and
a pair of bosses sitting proud of the respective pair of opposing ends, the pair of bosses collectively defining a volume commensurate with a volume of the void.
14. The precursor fitting system of claim 13 , wherein each of the pair of bosses defines an angled surface meeting the adjacent one of the pair of end surfaces.
15. The precursor fitting system of claim 14 , wherein the angled surface forms a truncated conical shape.
16. The precursor fitting system of claim 14 , wherein the angled surface is one of a plurality of angled surfaces corresponding to sides of the straight-sided body.
17. The precursor fitting system of claim 13 , wherein the pair of bosses are sized and configured form a pair of opposing end surfaces that are substantially planar after the material flow into the aperture, the pair of opposing end surfaces being substantially planar and extending across an entirety of each of the pair of opposing ends.
18. A method of affixing a fitting to a wire rope, comprising:
passing the wire rope through an aperture formed in the fitting, the wire rope having a plurality of wire elements and the aperture defining an aperture axis;
impacting an end surface of the fitting to cause material to flow into the aperture and into contact with the wire rope; and
by the step of impacting, forming an end surface of the fitting that is substantially planar across an entirety of the end surface and is substantially parallel to the aperture axis.
19. The method of claim 18 , wherein the step of impacting comprises impacting a boss sitting proud of the end surface of the fitting.
20. The method of claim 19 , wherein the step of impacting the boss comprises causing a flow of material into the aperture having a volume that is substantially equal to a volume of the boss.
21. The method of claim 20 , wherein the step of impacting comprises causing material to flow into interstices between the plurality of wire elements of the wire rope.
22. The method of claim 18 , further comprising placing the fitting into a die before the step of impacting, whereby an exterior surface of the fitting conforms to the die after the step of impacting.
23. The method of claim 18 , wherein the fitting is placed along a length of the wire rope, spaced from each respective end of the wire rope.
24. The method of claim 18 , wherein the step of forming comprises forming the end surface of the fitting to occupy an area bounded by the straight-sided sidewall.