Method and apparatus for instrument propulsion
Embodiments generally relate to propulsion tube units and propulsion devices for progressing instruments along passages, and associated methods of use. For example, the instruments may include, tools, sensors, probes and/or monitoring equipment for medical use (such as endoscopy) or industrial use (such as mining). In some embodiments, the propulsion device may comprise an elongate tube defining a channel configured to accommodate a liquid and a pressure actuator in communication with the channel. The pressure actuator may be configured to selectively adjust a pressure of the liquid in the channel to alternatingly: reduce the pressure to induce cavitation and form gas bubbles in the liquid; and increase the pressure to collapse some or all of the gas bubbles back into the liquid, thereby accelerating at least part of the liquid towards the first end of the tube and transferring momentum to the tube to progress the tube along the passage.
1 . A propulsion device for progressing an instrument along a passage, the propulsion device comprising:
an elongate tube comprising a first end and a second end opposite the first end, the tube defining a channel configured to accommodate a liquid, a first end of the channel being closed at or near the first end of the tube and a second end of the channel being defined by the second end of the tube; and
a pressure actuator in communication with the second end of the channel and configured to selectively adjust a pressure of the liquid in the channel to alternatingly:
reduce the pressure to induce cavitation and form gas bubbles in the liquid; and
increase the pressure to collapse some or all of the gas bubbles back into the liquid, thereby accelerating at least part of the liquid towards the first end of the tube and transferring momentum to the tube to progress the tube along the passage.
2 . The propulsion device of claim 1 , further comprising one or more mechanisms configured to promote cavitation in one or more regions of the channel when the pressure is reduced, wherein the one or more regions extend along at least part of a length of the channel.
3 . The propulsion device of claim 2 , wherein the one or more mechanisms are configured to promote cavitation in a plurality of regions spaced along at least part of the length of the channel.
4 . The propulsion device of claim 2 , wherein the one or more mechanisms comprise a surface variation on an internal surface of the channel.
5 . The propulsion device of claim 4 , wherein the surface variation comprises a coating.
6 . The propulsion device of claim 5 , wherein the coating comprises a hydrophobic material.
7 . The propulsion device of claim 4 , wherein the surface variation comprises a topographical variation.
8 . The propulsion device of claim 7 , wherein the topographical variation comprises a scratched or pitted surface.
9 . The propulsion device of claim 7 , wherein the topographical variation defines a plurality of V-shaped channels.
10 . The propulsion device of claim 7 , wherein the topographical variation defines a porous surface.
11 . The propulsion device of claim 2 , wherein the one or more mechanisms comprise a variation in a thermal conductivity of a wall of the tube along the length of the channel.
12 . The propulsion device of claim 2 , wherein the one or more mechanisms comprise one or more acoustic transducers.
13 . The propulsion device of claim 1 , wherein the device is configured for progressing a medical instrument along a lumen within a patient.
14 . The propulsion device of claim 1 , wherein the tube is reinforced against expansion or contraction due to internal pressure changes.
15 . The propulsion device of claim 1 , further comprising a plurality of the tubes of claim 1 extending side by side.
16 . The propulsion device of claim 1 , wherein the pressure actuator comprises:
a piston assembly including a moveable piston disposed within a bore of the piston assembly; and
a driving mechanism configured to drive the piston of the piston assembly to selectively adjust the pressure of the liquid in the channel.
17 . The propulsion device of claim 16 , wherein the piston assembly is connected to the tube to form a sealed tube unit containing the liquid, and
wherein the piston assembly is removably coupleable to the driving mechanism.
18 . A propulsion tube unit comprising:
one or more of the tubes according to claim 1 ; and
a piston assembly connected to the second end of the tube, the piston assembly comprising:
a body defining a bore in fluid communication with the channel of each of the one or more tubes; and
a movable piston disposed within the bore and configured to seal against an internal surface of the bore.
19 . The propulsion tube unit of claim 18 , wherein the piston assembly and the one or more tubes cooperate to define a sealed vessel containing a selected mass of liquid and a selected mass of gas.
20 . A method of progressing an instrument along a passage, the method comprising selectively adjusting a pressure of a liquid within a tube connected to the instrument to successively induce cavitation of gas bubbles in the liquid and subsequently collapse the gas bubbles back into the liquid to accelerate the liquid within the tube, transfer momentum from the liquid to the tube, and progress the tube along the passageway.