h a l f b a k e r yThe word "How?" springs to mind at this point.
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A ball screw is a useful type of linear actuator. It converts rotation to linear movement. A helical/threaded shaft rotates, causing a nut to travel up/down the shaft. The nut is prevented from rotating by a guide rail.
As the nut moves it pushes against the guide rail causes a twisting torque. This
is fine if there is a rigid frame to hold the guide rail.
However, there are many applications where it is inconvenient to have a rigid frame, particularly when there are size constraints.
I propose a ball screw that has two adjacent counter-rotating shafts. A nut travels on each shaft. One end of the shafts move in bearings. The bearings are rotable mounted in an end cap. The other end of the shafts have gears that keep the shafts moving in sync and counter-rotating.
The two nuts are mounted side-by-side in a housing. The torque from one nut is counteracted by the torque of the other nut via the housing, this obviating the need for the guide rail.
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Doesn't the "work" contact that the nut does hold it in position? How would it create any force if it wasn't in contact with the recipient of the joules? |
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What is the precise and specific mechanism which will convert from a rotational input shaft, to drive a pair of parallel counter-rotating shafts, without imparting a twisting torque to the assembly containing the counter-rotating shafts? |
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[minoradjustments] I've edited the sentence "The two nuts are rotatably mounted..." to remove the word 'rotatably'. Not sure if this addresses your point. |
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[pocmloc] I have (perhaps naively) assumed that the counter-rotating-ness of the shafts will cancel out the twisting torque. I acknowledge that this assumption could be completely wrong. |
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If there are two shafts the slide will of course maintain its orientation with that degree of freedom being eliminated by simply being captured at 2 points. |
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OK let me rephrase my question. Where does the twin counterrotating input come from? What kind of power source produces two parallel counterrotating torques? Apart from a siamese-twin mirrored-double-crankshaft reciprocating engine, obviously. |
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Two electric motors, bolted together...? |
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Yes of course. They would need to be synchronised though, preferably mechanically. |
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