Transmission problem involving oscillating arm

[sebufour]

Hi everyone,

I'm working on a mechanical system and would like your input on a kinematic question.

Here’s the setup:

I have a fixed bar, and at its end there's a gear (Gear A) that rotates at a constant speed.

At that same point, I’ve attached a second bar that acts like a lever or arm. This bar can oscillate, but not at a constant rate (its angular speed varies over time).

At the end of this oscillating bar, I’ve mounted another gear (Gear B).

Gears A and B are connected (either directly or via a chain).

My question:
Will Gear B rotate at a constant speed, or will its rotation be affected by the oscillating motion of the bar?

Thanks in advance for your help!

 

[sebufour]

 

[Baluncore]

Will Gear B rotate at a constant speed, or will its rotation be affected by the oscillating motion of the bar?

If the gears A and B had identical tooth counts, and were linked by a parallel chain, or an odd number of idler gears in a train, then the orientation of B would follow A, independent of the arm direction.

If the gear ratio was not unity, the chain was crossed, or there were an even number of intermediate idler gears, then rotation of B would be a function of arm direction.

You will need to be more specific if you want a yes/no answer.

 

[sebufour]

it is perfect thank you

 

[Lnewqban]

My question:
Will Gear B rotate at a constant speed, or will its rotation be affected by the oscillating motion of the bar?

The rotational velocity of gear B will be affected by the oscillating motion of the bar.

Instantaneous angular velocity of gear B = Instantaneous angular velocity of gear A + Instantaneous angular velocity of the bar.

If gear A and the bar rotate in the same direction, then:
Angular velocity of gear B > Angular velocity of gear A

If gear A and the bar rotate in opposite directions, then:
Angular velocity of gear B < Angular velocity of gear A

 

[sebufour]

Thanks a lot for your feedback. But how could gear B and A besoin connected with a belt if they rotate at different speed ?

 

[sebufour]

If we take make an excentric hole at the same place on both gears. The plan from their center to the respective hole should always ne parallel no ?

 

[Baluncore]

The plan from their center to the respective hole should always ne parallel no ?

No, yes. The orientation will only track if the gears have identical tooth counts.

There is an equivalent linkage in a drafting machine.

 

[sebufour]

Perfect thank you !

 

[jrmichler]

Here is a practical application of a similar linkage and gear train. It's from US Patent 9,604,381. Rotating bar 172 is mounted on a motor/controller 196, with axis of rotation 178. The two arms 200 sweep out a circular path while maintaining horizontal position. The arm orientation is controlled by sprockets 180 and 182, along with a toothed belt (not shown). The patent has a more detailed explanation.

This was designed as a high speed cutoff for cutting plastic film in a napkin wrapping machine. The arms 200 support hot wires 171 that do the actual cutting. Watching it cut quietly and cleanly at over double the speed of the previous fastest cutoff was an interesting experience.

 

[sebufour]

Interesting thank you !