Roller Gear Drive

Hi Guys,

I´m trying to design a roller gear drive that is an indexing mechanism
-in this case a 8 index swatations-, but I do not have clearly how can
I do it, especially in how to model the complex tapered wedge rib that
this the core of the index cam, maybe someone of you have much
experience on this kind of designs than I, if someone don´t know what I
´m talking about, I can send the pictures of this mechanism.

Best regards

Pablo Ulloa

 

Hi Guys,

I´m trying to design a roller gear drive that is an indexing mechanism
-in this case a 8 index swatations-, but I do not have clearly how can
I do it, especially in how to model the complex tapered wedge rib that
this the core of the index cam, maybe someone of you have much
experience on this kind of designs than I, if someone don´t know what I
´m talking about, I can send the pictures of this mechanism.

Best regards

Pablo Ulloa

Sweep a cut around the outer edges of the cam at the required angle.

 

Look at this

http://www.profilesmagazine.com/p33/marsalek.html

 

Hi Guys,

I´m trying to design a roller gear drive that is an indexing mechanism
-in this case a 8 index swatations-, but I do not have clearly how can
I do it, especially in how to model the complex tapered wedge rib that
this the core of the index cam, maybe someone of you have much
experience on this kind of designs than I, if someone don´t know what I
´m talking about, I can send the pictures of this mechanism.

Best regards

Pablo Ulloa

Sweep a cut around the outer edges of the cam at the required angle.
Having looked at the gear, I now see that its a simple worm (though I haven't seen the worm gear it drives). What makes this worm a little special is that it has three leads so that it advances three teeth per revolution, with the force spread over these three teeth. From the picture, there is nothing special about the the teeth, probably a 20 degree pressure angle on the tooth geometry draft, each tooth advancing a third of the way around the gear. The result is that when the worm turns one rev, the worm gear advances three teeth. The teeth may be smaller, but the application of force smoother.

 

Hi Guys,

I´m trying to design a roller gear drive that is an indexing mechanism
-in this case a 8 index swatations-, but I do not have clearly how can
I do it, especially in how to model the complex tapered wedge rib that
this the core of the index cam, maybe someone of you have much
experience on this kind of designs than I, if someone don´t know what I
´m talking about, I can send the pictures of this mechanism.

Best regards

Pablo Ulloa

Sweep a cut around the outer edges of the cam at the required angle.
Looking at the picture of the gear, I now see that its a simple worm (though I haven't seen the worm gear it drives). What makes this worm a little special is that it has three leads so that it advances three teeth per revolution, with the force spread over these three teeth. From the picture, there is nothing special about the the teeth, probably a 20 degree pressure angle on the tooth geometry draft, each tooth advancing a third of the way around the gear. The result is that when the worm turns one rev, the worm gear advances three teeth. The teeth may be smaller, but the application of force smoother. The pitch is 1/3 of the thickness of the gear blank. Then the tooth is patterned around the axis to obtain the three leads.

David Janes

 

Hi Guys,

I´m trying to design a roller gear drive that is an indexing mechanism
-in this case a 8 index swatations-, but I do not have clearly how can
I do it, especially in how to model the complex tapered wedge rib that
this the core of the index cam, maybe someone of you have much
experience on this kind of designs than I, if someone don´t know what I
´m talking about, I can send the pictures of this mechanism.

Best regards

Pablo Ulloa

Sweep a cut around the outer edges of the cam at the required angle.
Looking at the picture of the gear, I now see that its a simple worm (though I haven't seen the worm gear it drives). What makes this worm a little special is that it has three leads so that it advances three teeth per revolution, with the force spread over these three teeth. From the picture, there is nothing special about the the teeth, probably a 20 degree pressure angle on the tooth geometry draft, each tooth advancing a third of the way around the gear. The result is that when the worm turns one rev, the worm gear advances three teeth. The teeth may be smaller, but the application of force smoother. The pitch is 1/3 of the thickness of the gear blank. Then the tooth is patterned around the axis to obtain the three leads.

David Janes


I need to correct one thing I said above: the pitch is actually 3 times the thickness of the blank (not one third) so that it goes around a third of the way from lead in to lead out. If I were doing it on a thread mill, I'd have to figure out the worm lead angle, but, in Pro/e, when creating the helical sweep, you should be able to just set the number 3t (where t is the blank thickness) when it asks for the pitch. Then do an axial pattern of that cut geometry at 120 degrees apart. BTW, when you're first creating your trajectory curve which will just be a straight line on the gear profile parallel to the axis, start and end it off the part.

David Janes

 

Hi Guys,

I´m trying to design a roller gear drive that is an indexing mechanism
-in this case a 8 index swatations-, but I do not have clearly how can
I do it, especially in how to model the complex tapered wedge rib that
this the core of the index cam, maybe someone of you have much
experience on this kind of designs than I, if someone don´t know what I
´m talking about, I can send the pictures of this mechanism.

Best regards

Pablo Ulloa

Sweep a cut around the outer edges of the cam at the required angle.
Looking at the picture of the gear, I now see that its a simple worm (though I haven't seen the worm gear it drives). What makes this worm a little special is that it has three leads so that it advances three teeth per revolution, with the force spread over these three teeth. From the picture, there is nothing special about the the teeth, probably a 20 degree pressure angle on the tooth geometry draft, each tooth advancing a third of the way around the gear. The result is that when the worm turns one rev, the worm gear advances three teeth. The teeth may be smaller, but the application of force smoother. The pitch is 1/3 of the thickness of the gear blank. Then the tooth is patterned around the axis to obtain the three leads.

David Janes


I need to correct one thing I said above: the pitch is actually 3 times the thickness of the blank (not one third) so that it goes around a third of the way from lead in to lead out. If I were doing it on a thread mill, I'd have to figure out the worm lead angle, but, in Pro/e, when creating the helical sweep, you should be able to just set the number 3t (where t is the blank thickness) when it asks for the pitch. Then do an axial pattern of that cut geometry at 120 degrees apart. BTW, when you're first creating your trajectory curve which will just be a straight line on the gear profile parallel to the axis, start and end it off the part.

David Janes


Once again, I correct myself (it's been a learning process, taught by an excellent, very patient teacher in Mr. Pablo Ulloa). My last lesson was an MPEG file that showed the gear in motion. Clarified everything, from the shape of the gear/cam to the trajectory to the type of follower and motion translation (rotational to counter rotational [ at 90 degrees to drive] and intermittent.) I've seen continuous indexing cams in the shape of a simple worm gear, but this indexes one cam follower per one revolution of the cam drive. It's pretty slick, I'd never seen this type of cam before and, even now, could barely desribe its geometry. I can send the MPEG, if anyone wants to take a gander (and take a crack at answering the OP's question).

David Janes, participant (former Slug, Kibbitzer, Know-it-all, Observer, Lurker), to/for/with my brothers and sisters