Does someone have engineering drawings for a gas-spring lift-assist assembly (horizontal platform)?

I have a long-dormant project for a "powered" tricycle carrier for a car trailer-hitch. It occurred to me today that a piston "lift-assist" device could do the job. I wonder if anyone here has a technical design for a lift-assist assembly that I could use to understand the mechanism better. I need something that provides lift assistance both raising and lowering (maximum 10 lbs user force either way, for a ~50 lb load).

Comments

[frollard]

As burf says, a worm gear with a 12v motor geared down would lift anything you threw at it.

A pneumatic cylinder lift assist is just that - a valved-sealed cylinder that has a return spring that does the lifting, and letting air in or out allows it to move further.
http://en.wikipedia.org/wiki/Gas_spring

the design I can think of:

Lift platform has a vertical member connected to a vertical member of the trailer hitch with 2 parallel linkages - so it moves up and down while staying parallel.
Have the pneumatic spring attached in the same manner as the connecting members, but perpendicular to their orientation, so the spring compresses when the platform is down, and expands when the platform is up. Calibrate it so the springs make the platform 'nearly weightless' and tighten 'something' frictiontastic so that it stays wherever you put it - until the trike is on it.

[frollard]

See attached

[kelseymh]

Thanks, and thanks for the attached drawing! It looks like the platform "pulls out" as you lower and raise it; correct? I have found gas springs that apply force "either" on opening or on closing. For this application I think I need both (maybe one of each kind on either side?), so that my wife can both raise and lower the platform.

[frollard]

The platform does have an arc-movement, mostly vertical though. The gas spring provides enough lift to be 'neutrally buoyant' - exactly enough force to make the platform without the trike weightless, so you can push it down (takes some force) and it stays there. To lift you're still lifting the entire weight of the load unless you have something to help the 'up' portion. OR Have the platform with enough spring to lift platform plus trike. You'll need to stand on the empty platform to make it go down. Because once its down it locks in that position (because the spring pushes harder down) you can add the trike, then a very small lift to overcome the difference in force and it lifts up. yay!

[Burf]

I don't have a direct answer for your question, but looking at your drawings made me think that something along the lines of a worm gear assembly might do the trick. Think of a screw type, garage door opener mounted vertically. It seems that would be a lot less challenging to engineer than a a gas-spring lift.

[kelseymh]

Thanks! Yes, I have a different design where the scissor lift is replaced with an RV "tongue jack." But those things cost several hundred dollars, so I'm trying to come up with a less expensive (and preferably not powered) alternative. I think you're probably right about doing a worm gear by hand.

[seandogue]

I'm afraid don't have anything
But this link might help a bit (or not)