CONTROLLED TENSION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application 63/381,815 filed November 1, 2023, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Exemplary embodiments pertain to the art of feeding thin wires.

[0003] Thin wires are utilized in many technological applications, such as manufacturing applications (e.g., welding, coating, and 3D printing, etc.), and medical procedures (e.g. minimally invasive surgeries, stent placement and deep brain stimulation, etc.), to name a few. In such applications, there is a need to feed one end of a thin wire through a tube to a specific spatial location at a specific speed and/or angle. However, as the diameter of the wire to be fed gets thinner and eventually becomes arbitrarily close to zero, the following distinctive properties inevitably arise regardless of the constituent materials.

[0004] An arbitrarily thin wire has reduced visibility and may even become practically invisible to human eyes. The visibility of a thin wire can be approximately gauged by how close its diameter is to the Abbe diffraction limit of visible light, which is on the order of 100 nm. There exists a fundamental limit of the wire diameter below which human eyes can no longer distinguish the wire from its surroundings.

[0005] An arbitrarily thin wire has negligibly small bending stiffness that scales with - , where E is the Youngs Modulus of the wire, f the area moment of inertia of the wire assuming circular cross section with a diameter of , and £ the total length of the wire. With the effect of wire diameter on the bending stiffness raised to the 4 ^th power, an initially straight arbitrarily thin wire without support or constraints may bend under any minute external disturbances including its own weight to an unacceptably large degree.

[0006] An initially bent arbitrarily thin wire is harder to be straightened using plastic deformation due to its reduced minimum bending radius that scales with where a is the yield strength of the wire. Any residual stress induced initial bending with a radius of curvature that is larger than the minimum bending radius is not able to be straightened by plastic deformation. And as the diameter of the wire approaches zero, this non-straighten-able minimum bending radius approaches zero as well.

[0007] An arbitrarily thin wire can buckle under negligibly small compression forces. Estimated by Euler’s critical load for buckling which scales with the compression load required to buckle an arbitrarily thin wire quickly drops to negligibly small magnitudes as the diameter of the wire approaches zero.

[0008] These distinctive properties of an arbitrarily thin wire give rise challenges that are generally considered not possible to overcome simultaneously to enable its feeding through a thin tube.

[0009] First, the reduced visibility, negligibly small bending stiffness, and the non- straighten-able minimum bending radius of an arbitrarily thin wire makes the initiation of the feeding process challenging due to the lack of a reliable and convenient method to align the feeding end of an arbitrarily thin wire with the tube inlet before insertion.

[0010] Second, even if an arbitrarily thin wire is successfully inserted into the tube, stiction between the wire and the inner wall of the tube would occur due to the attractive van der Waals force resulting in a finite static friction force that needs to be overcome to further advance the arbitrarily thin wire toward the tube outlet. However, since an arbitrarily thin wire can buckle under negligibly small compression forces which scales with the 4 ^th power of the wire diameter, it would buckle before the compression load on the wire becoming large enough to overcome the static friction which only scales with the 2 ^nd power of the wire diameter.

[0011] Additionally, due to the negligibly small bending stiffness, the non-straighten- able minimum bending radius, and the negligibly small critical buckling load of an arbitrarily thin wire, the only way to keep it straight during feeding is to maintain sufficient tension along the wire, which contradicts the purpose of feeding through a thin tube, where the feeding end of the arbitrarily thin wire needs to be free from any mechanical support. In other words, sufficient tension must be maintained on the wire without supporting the feeding end. [0012] While a sufficiently thin wire may be faced with one or more of the three challenges when being fed through a thin tube, the successful feeding of an arbitrarily thin wire requires a method capable of overcoming all three challenges simultaneously.

BRIEF DESCRIPTION

[0013] In one embodiment, a method of aligning a wire with a pathway inlet includes directing a feeding end of a wire toward a pathway inlet of a feed pathway, creating a pressure differential between the pathway inlet and a pathway outlet of the feed pathway thus creating a pressure-driven gas flow around the wire and into the pathway inlet. The wire is urged along the feed pathway toward the pathway outlet via the shear force of the gas flow created by the pressure differential.

[0014] Additionally or alternatively, in this or other embodiments one of a flutter or vibration is induced in the wire at the feeding end of the wire.

[0015] Additionally or alternatively, in this or other embodiments the inducing the flutter prevents stiction of the wire to an interior wall of the feed pathway.

[0016] Additionally or alternatively, in this or other embodiments the pathway inlet has a larger cross-sectional area than the pathway outlet.

[0017] Additionally or alternatively, in this or other embodiments the wire is formed from a polymer material.

[0018] Additionally or alternatively, in this or other embodiments the wire has a wire diameter less than 100 pm.

[0019] Additionally or alternatively, in this or other embodiments the pressure-driven gas flow is directed from the pathway inlet along the pathway toward the pathway outlet.

[0020] In another embodiment, a method of preventing stiction of a wire with an inner wall of a thin pathway includes creating a pressure differential between a pathway inlet and a pathway outlet of the pathway thus creating a pressure-driven gas flow around a feeding end of the wire and into the pathway inlet of the pathway, and inducing one of a flutter or vibration in the wire at the feeding end of the wire. [0021] Additionally or alternatively, in this or other embodiments the wire is urged along the pathway toward the pathway outlet via the pressure-driven gas flow created by the pressure differential.

[0022] Additionally or alternatively, in this or other embodiments the pathway inlet has a larger cross-sectional area than the pathway outlet.

[0023] Additionally or alternatively, in this or other embodiments the wire is formed from a polymer material.

[0024] Additionally or alternatively, in this or other embodiments the wire has a wire diameter less than 100 pm.

[0025] Additionally or alternatively, in this or other embodiments the pressure-driven gas flow is directed from the pathway inlet along the pathway toward the pathway outlet.

[0026] In yet another embodiment, a method of controlling tension in a wire directed along a pathway includes positioning a feeding end of the wire inside the pathway and creating a pressure differential between a pathway inlet and a pathway outlet of the pathway thus creating a pressure-driven gas flow around the wire and into a pathway inlet of the pathway. The wire is urged along the pathway toward the pathway outlet via the shear force from the pressure-driven gas flow created by the pressure differential, and adjusting the pressure differential adjusts a tension of a segment of the wire between the pathway inlet and a releasing end of the wire opposite the feeding end.

[0027] Additionally or alternatively, in this or other embodiments one of a flutter or vibration is induced in the wire at the feeding end of the wire.

[0028] Additionally or alternatively, in this or other embodiments the inducing the flutter prevents stiction of the wire to an interior wall of the pathway.

[0029] Additionally or alternatively, in this or other embodiments the pathway inlet has a larger cross-sectional area than the pathway outlet.

[0030] Additionally or alternatively, in this or other embodiments the wire is formed from a polymer material. [0031] Additionally or alternatively, in this or other embodiments the wire has a wire diameter less than 100 |am.

[0032] Additionally or alternatively, in this or other embodiments the pressure-driven gas flow is directed from the pathway inlet along the pathway toward the pathway outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

[0034] FIG. 1 is a schematic illustration of feeding of a wire along a guide tube;

[0035] FIG. 2 is an illustration of an experimental apparatus to measure a wire tension;

[0036] FIG. 3 is an illustration of a wire entering a guide tube without a pressurized gas flow;

[0037] FIG. 4 is an illustration of a wire entering a guide tube with a pressurized gas flow;

[0038] FIG. 5 is an illustration of elimination of stiction of a wire to an interior wall of a guide tube;

[0039] FIG. 6 is an illustration of stiction of a wire to an interior wall of a guide tube;

[0040] FIG. 7 is an illustration of a sagging wire in a guide tube; and

[0041] FIG. 8 is an illustration of a tensioned wire in a guide tube.

DETAILED DESCRIPTION

[0042] A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

[0043] The present disclosure describes a method and apparatus to allow the use of a thin feeding pathway as a mechanical guide through which an arbitrarily thin wire is pulled and/or dragged from one end of the feeding pathway toward the other end of the feeding pathway predominantly, if not solely, by a shear force exerted on the wire by a pressure driven gas flow inside the feeding pathway, as shown in FIG. 1.

[0044] A wire 10 is fed into a feeding pathway, in the illustrated embodiment a feed tube 12, in a feed direction 14 at a tube inlet 16 at a first end of the feed tube 12 and urged toward a tube outlet 18 at a second end of the feed tube 12. In some embodiments the wire 10 is formed from a polymer, while in other embodiments the wire 10 is formed from a metallic material. The feed tube 12 acts as a mechanical guide to direct the wire 10 to a selected location at the tube outlet 18. The feed tube 12 includes a tube body 20 disposed between the tube inlet 16 and the tube outlet 18, which in some embodiments has a smaller inner diameter 22 less than a cross-sectional area or an inlet diameter 24 of the tube inlet 16. A pressure driven gas flow 26 is urged into the tube inlet 16 from a gas source 28 held at a pressure higher than the gas pressure at the tube outlet 18.

[0045] In one embodiment, illustrated in FIG. 2, this gas source 28 can be obtained by placing the tube inlet 16 and the wire 10 in a pressure chamber and the tube outlet 18 in the open atmosphere, while in other embodiments by leaving the tube inlet 16 and the wire 10 in the open atmosphere and the tube outlet 18 in a vacuum chamber 50. The pressure driven gas flow 26 acts on the wire 10 to guide, and push or pull the wire 10 into the tube inlet 16 and through the tube body 20 to the tube outlet 18, by shear forces of the pressure driven gas flow 26 acting on the wire 10.

[0046] While the speed of the wire 10 being released at a releasing end 38 of the wire 10 governs a target feeding speed of the wire 10 at a feeding end 30 or tip of the wire 10, the objective is to ensure that an actual wire speed of the wire 10 at the feeding end 30 precisely follows the target feeding speed set out at the releasing end 38 while maintaining/controlling the tension wire 10 at the releasing end 28. Generally, feeding a wire through a tube does not necessarily require the wire tension being controlled. However, in the case of an arbitrarily thin wire 10, a feeding method will fail without a mechanism to maintain sufficient wire tension due to the challenges discussed above. In some embodiments, the wire 10 has a thickness less than 100 pm, while in other embodiments the wire 10 has a thickness less than 10 pm. A key to achieving the target feeding speed while maintaining tension of the wire 10 is dynamic behavior of a thin wire interacting with the pressure driven gas flow 26 in the feed tube 12, which can be harnessed to overcome the aforementioned challenges to achieve the objective of feeding the wire 10 through the feed tube 12 with controlled tension, more specifically, via flow induced alignment, vibration, and tension.

[0047] The feeding process begins with inserting the feeding end 30 of the wire 10 with the tube inlet 16, which has an enlarged cross-sectional area relative to the tube body 20, as shown in FIG. 3. Referring to FIG. 4, the pressure driven gas flow 26 is turned on, and the pressure driven gas flow 26 aligns the feeding end 30 of the wire 10 with a body opening 32 of the tube body 20. More particularly, the pressure driven gas flow 26 is induced by the pressure difference between the tube inlet 16 and the tube outlet 18, where the gas pressure at the tube inlet 16 is held higher than that of the tube outlet 18 so that the gas flow 26 surrounding the tube inlet 16 flows into the tube toward the tube outlet 18. In some embodiments, the tube inlet 16 has a diameter in the range of 1 to 10 times the diameter of the wire 10. Further, while in some embodiments the tube inlet 16 is enlarged relative to the tube body 20, while in other embodiments the tube body 20 has a diameter equal to that of the tube inlet 16.

[0048] The enlarged tube inlet 16 relative to the tube body 20 gives rise to a converging flow pattern, as illustrated in FIG. 4, under proper conditions. When brought close to the tube inlet 16, the feeding end 30 of a sufficiently thin (hence light-weight and flexible) wire 10 is entrained toward the tube inlet 30 and self-align with the streamline of the converging gas flow 26 and automatically enter the feed tube 12 and the body opening 32 as more wire is being released from the releasing end 38. Depending on the amount of pressure difference applied to the gas flow 26, dimensions of the feed tube 12, and dimension and properties of the wire 10, the feeding end 30 of the wire 10 may or may not flutter under the gas flow 26 as it is being aligned and fed into the tube inlet 16. It is to be noted that how the feed wire 10 is being released or generated at the releasing end 38 should not be used to limit the scope of this disclosure.

[0049] After the feeding end 30 of the wire 10 enters the feed tube 12 under the pressure driven gas flow 26, the pressure difference between the tube inlet 16 and the tube outlet 18 may need to be adjusted so that the feeding end 30 of the wire 10 begins to or continues to flutter as it is being pulled further into the feed tube 12 by the shear force exerted by the gas flow 26 on the surface of the feed wire 10 as shown in FIG. 5. The vibration/fluttering of the feeding end 30 of the wire 10 prevents the wire 10 from adhering to an interior wall 36 of the feed tube 12, such as shown in FIG. 6, under any attractive intermolecular forces such as the Van der Waals forces.

[0050] While the feeding end 30 of the wire 10 is still inside the feed tube 12 and fluttering, the pressure difference between the tube inlet 16 and tube outlet 18 may still need to be adjusted so that the total shear force exerted by the pressure driven gas flow 26 on the surface of the wire 10 inside the feed tube 12 generates sufficient pulling/dragging force so that there is sufficient tension on the segment of the wire 10 outside of the feed tube 12 between the tube inlet 16 and the releasing end 28 to keep the wire 10 straight.

[0051] By using flow induced alignment, vibration, and tension, the wire 10 can be successfully fed through the feed tube 12 at a selected, controlled speed and tension with proper design of the feed tube 12 dimensions and operating pressures. In some embodiments, the pressure difference is less than about 15 psi.

[0052] Referring to FIG. 7, without the gas flow 26 turned on, the wire 10 may tend to sag because the wire tension is not maintained, but as illustrated in FIG. 8 with the gas flow 26 on, the tension of the wire 10 is maintained for proper feeding of the wire 10 through the guide tube 12.

[0053] Referring again to FIG. 2, illustrated is an experimental apparatus 52 to measure the tension of the wire 10 between the tube inlet 16 and the wire releasing end 38 during feeding of the wire 10 through the feed tube 12. A pressure difference between the tube inlet 16 and the tube outlet 18 is established using a vacuum system connected to the tube outlet 18 while the tube inlet 16 is exposed to open air at atmospheric pressure. The vacuum system consists of a vacuum pump 54 as the energy source, a variable throttle valve 56 that controls the flow rate and/or pressure of the gas, a flow meter 58 that measures the flow rate of the gas, and a pressure gage 60 that measures the gauge pressure of the gas at the tube outlet 18. Vacuum hoses 62 are used to hermetically connect all components of the vacuum system so that all the gas exiting the tube outlet 18 is evacuated by the vacuum pump 54 to the atmosphere without leakage. Note that an alternative way to create such a pressure difference is by connecting the tube inlet 16 to a pressure vessel while exposing the tube outlet 18 to open air at atmospheric pressure. Alternatively, such a pressure difference can also be created by connecting the tube inlet 16 to a pressure vessel while the tube outlet 18 is connected to a vacuum system at the same time. It should be further noted that it is the difference between the values of the pressure of the gas at the tube inlet 16 and the tube outlet 18 instead of the actual values of the gas pressures at the tube inlet 16 and the tube outlet 18 that matters.

[0054] A polymer wire 10 with diameter between 90 mm to 100 mm released from a payoff spool 64 is fed through several feed tubes 12 with different inner diameters, one at a time, while the tension of the wire segment between the tube outlet 18 of the feed tube 12 and the wire releasing end 38 is measured using an analytical balance 66.

[0055] The reading of the analytical balance 66 is first zeroed with a fixed roller placed 68 on it without the wire. The fixed roller 68 has a weight much larger than but a rotational friction much smaller than the magnitude of the flow induced tension to be measured. To measure the wire tension, two additional frictionless fixed rollers 70 are placed above the roller 68 on the analytical balance. The thin wire 10 is then wound over all three fixed rollers 68, 70 as shown as it is being fed through the feed tube 12. Care has been taken to make sure that the wire segments above the analytical balance 66 between the fixed rollers 68, 70 are vertical and that measurements are taken when the feeding/front end of the wire has just reached the tube outlet 18. The tension of the wire segment 72 between the tube outlet 18 and the releasing end 38 of the wires is thus measured as the half of the absolute value of the reading shown on the analytical balance 66. Table 1 illustrates the tabulated and plotted experimental tension data at different tube inner diameter, tube length, gas pressure, and flow rate. It is clearly seen from the data that the tension on the wire can be controlled by varying the pressure difference and tube dimensions.

Table 1. Experimental tension data during feeding

[0056] The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. [0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

[0058] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.