Design Clutch for pen-like object

[U Offor]

Hello all,

I am trying to make a pen-like product that moves out fluid from its tip for some special chores, but I am having issues about the motion of the clutch. The picture you see is a sectioned concept because my thought isn't fully fleshed out.

Legend: Black stripes - fluid, Yellow - Button, Orange - Body, Pink - Spring, Teal - Clutch, Green - Clutch ring, Blue - Plunger, Red - Cap, Grey - Cartridge

Goal: When I push the button once, the plunger pushes up the red cap, which pushes up the fluid in the cartridge. As more liquid is expended, the red cap moves up until it reaches the top, when there's no liquid. Each time the button is pushed, I want the plunger to move and stop in accordance to the level of fluid left in the cartridge. For example, if the liquid is halfway, the plunger will be more upward.

I have a clutch system where the clutch ring is press fitted inside and a clutch has a tight fit against the clutch ring, to force the clutch to hold on to the plunger as it moves upward. This way, the plunger can move up then stay still without any external force acted on it (the button being pressed).

Main problem for me: After a certain level of fluid is gone but fluid still remains, the button won't be able to touch the plunger no matter how much I press the button. I tried introducing a small connection between the button and the clutch, so the plunger can still move even if the button doesn't have contact with it, but that introduces more problems.

You may notice more problems but the bottom line question is: will this mechanism work? If so, how can I resolve this main issue and if not, what other mechanism(s) will work? I'm not looking for specific numbers, but just needed to be point in the right direction (mechanism choice) to use.

I appreciate any and all responses!

 

[EngineerTex]

Mechanical pencils?

Engineering is not the science behind building. It is the science behind not building.

 

[U Offor]

@EngineerTex

Not necessarily, haven't found any name for it. If there's something I can compare it to, it will be dental syringes, where you can remove a used up cartridge after the fluid is finished. However, it's not a medical device.

 

[3DDave]

Legend:
Body - Orange
Button - Yellow
Spring - Pink
Clutch - Teal
Clutch ring - Green
Plunger - Blue
Cap - Red
Fluid - Black stripes
Cartridge - Grey

Now that I have a clear list of the components untangled, I am left trying to untangle the question.

One place you say that it does not work, and then you ask if it will work, then you ask if something else will work. I don't see any time the button needs to touch the plunger, the clutch already does that.

Most applications would use ratchet teeth rather than a friction clutch. Using multiple ratchets to give different phases of contact allows arbitrarily small increments, subject to molding cost. There can be a separate ratchet on the button to actuate the plunger from one that keeps the plunger from reversing.

Most confusing is the requirement that the dispensed volume depends on how much is left. Normally that would be simply proportional to the distance the plunger is moved.

 

[zeusfaber]

As @EngineerTex suggested, take a mechanical pencil apart - then imagine if the lead, instead of being consumable, was replaced with your syringe plunger. What's the difference? The pencil drives forward through the clutch, so there's no requirement for the button to touch the plunger.

Can we do a quick language check on the bit about "move and stop in accordance to the level of fluid left in the cartridge". Dave's interpreted that to mean that the "move" bit needs to depend on the remaining fluid level - and you can certainly read it that way. Do you really mean that, or simply that the plunger needs to end up one step further along after each stroke (so it's the "stop" bit that depends on the remaining fluid)? One implies a dispensed volume that varies from stroke to stroke, while the other implies one that remains constant.

A.

 

[U Offor]

@zeusfaber

Oh I thought @EngineerTex meant whether my idea was a mechanical pencil haha. Yes, that's definitely something I can look into that can work.

When I mean "move and stop in accordance to the level of fluid left in the cartridge", @3DDave has the right idea. Essentially, each time the button is pressed, fluid is used and the plunger moves up, in respective increments, until all the fluid is gone. At this point, the plunger will be at it's "highest" point, when the cartridge is empty.

 

[U Offor]

@3DDave

I think you have the correct idea of what I'm trying to get done. The remaining fluid is dependent on the distance the plunger moved. I'm not familiar with how the ratchet works. What tool are they used in that I can see how they work? Seems very interesting.

Just trying to get as much ideas as I can.

 

[Compositepro]

It seems that you are reinventing the trigger action caulking gun or trigger action epoxy syringe dispenser except without the trigger lever. The trigger lever is important to give force multiplication on the plunger. Try using a caulking gun by just pressing on the plunger. Bad idea.