Mutilated Worm Drive for Intermittent Cam 5

[vne147]

Hello everyone. Mods, if you think there is a more appropriate forum for this question, please let me know. And thank you in advance to anyone who can provide some advice.

I’m working on developing a machine. This machine will have an output gear that will turn while the machine is in operation, and it will make one complete revolution per actuation of the machine. At about the 330° point in its rotation I need this output gear to turn a cam one complete revolution. The cam needs to be intermittent though. I can’t have it turning continuously along with the output gear. The cam needs to do nothing for almost the entire time until the output gear gets to about 330°. Then it will turn once, and just sit there again until the next cycle. Also, once the output gear gets to the point where it's time to turn the cam, I need that cam to turn as fast as practically possible.

So, the solution I came up with was to use a worm drive. The worm gear is mutilated with only a single tooth remaining, and the worm is offset so the single tooth on the worm gear will only mesh with a single turn on the worm. I attached a short animation with several angles to show what I’m talking about.

There are tons of mutilated gear examples I’ve seen, but very few with a worm drive, and none that I’ve seen with only a single tooth. So, this leads me to believe that maybe this isn’t the best solution, or it won’t work for some reason. Can you share your thoughts? How would you solve this problem? I’m not a mechanical engineer. Maybe there is a simpler solution. I just don’t know.

Thanks again.


View attachment WormGearExample.mp4

 

[vne147]

I'm trying to stay away from the spur gear solution to keep the part count down and also to avoid having a partial gear in the output stage, which I think I would need.

What does everyone think about this idea? What was the single tooth worm gear in my first design is now a wheel with a single 5mm OD ball bearing. That meshes with what I'm loosely calling a 4 tooth helical gear. The helical gear rotates 1/4 turn per cycle of the machine. It's not shown in the animation, but output shaft of the helical gear will drive a 4:1 spur gear combination so that the output cam at the bottom will rotate one complete turn per cycle of the machine. I ran some numbers and ignoring friction the output torque of the helical gear will be about 25% that of the wheel with the ball bearing on it. That's more than enough for what I'm doing. The output wheel is 95mm in diameter and the helical gear is 25mm. The cutting action that the cam drives will take place in about 4.3° of rotation of the wheel with the ball bearing, which is good enough.


View attachment NewWorm.mp4

 

[mfgenggear]

that is small , what is the tooth thickness of the helical gear., what will the maximum cycles , sn curves, what is the contact stress. will that be an issue. what is the bending strength of the teeth. what is the torque, and rpm required.

 

[vne147]

that is small , what is the tooth thickness of the helical gear., what will the maximum cycles , sn curves, what is the contact stress. will that be an issue. what is the bending strength of the teeth. what is the torque, and rpm required.

Great questions. I'm only prepared to answer a few of them right now.

The tooth thickness is about 2.5mm and the average RPM during the 1/4 rotation of the bevel gear per cycle of the machine will be about 2000 RPM at the most. That part is based on how fast a person pulls down on a manually operated lever at the input of the machine. So, it'll be a wide range, but that 2000 should be a conservative maximum value.

I should be able to figure out a ballpark value on the torque at this point. I'll work on that next.