Push - Retract - Hold Without Linear Actuator - HELP

Do it manually....? We'll probably need more details...if you can't use an electric motor or hydraulic or pneumatic control, that leaves mechanical, like a wind-up spring mechanism...

We can't do it manually because we want to connect it to an App to let people make small adjustments.

Yes, the wind up engine would be a good idea but we want it to be mechanical without using a electric motor.

I was thinking maybe an electromagnet but I don't know of you can control the "Strongness" of the Magnet by voltage.

You say that all the good methods for doing this have been patented...

A push-pull solenoid will move its core in response to varying drive voltage. Perhaps the one shown below or a similar one will work. The magnetic force is opposed by the spring.

https://www.adafruit.com/product/413

If you need precision positioning, you might attach an LVDT sensor to feedback the position to a control loop.

https://en.wikipedia.org/wiki/Linear_variable_differential_transformer

"... we want to connect it to an App to let people make..."

When you say App, I think I know what that means, but it doesn't really seem to fit here. Can you expand on this a little bit?

It appears you are amending an existing design to circumvent the patent for the design.

We want to connect the device we use for the motion to the internet so it can connect to an app on your phone. I know it doesn't fit here but I wanted to explain the whole situation. I need to know if any solenoid exists that can do the Forward/Backward and hold(in the middle or somewhere else between the IN/OUT parameters) motion on command so we can connect that to the Internet.

Why an app? Does it have to be controlled remotely?
A simple lever or gearing may do the job just fine.... insisting everything is controlled via an "app" is just bonkers, complexity for the sake of it and a problem creation exercise.
Simplicity is best.
What most people actually want is reliability (although most of 'em don't realise it).
Del

Even though you said a linear motor doesnt work, I've used LinMot for positioning. Its similar to a stepper motor.

We can't use a electric motor, actuator,.. because of patent infringement. :/

The platform on which this tiny alum plate slides around, can it be tilted? Let gravity do the work.

How about puffs of air?

It just has to be a simple Go forward and come back motion. We also want it to be set at different stands so the user can adjust it to their likings.

You could make a larger version of this wind-up reversing motor...and a simple braking apparatus....you can purchase spring steel and make your own...

http://www.ebay.co.uk/bhp/clockwork-motor

I just did some research on the item but I don't think it is what I need. We want to connect the device we use for the motion to the internet so it can connect to an app on your phone. I know it doesn't fit here but I wanted to explain the whole situation. I need to know if any solenoid(or other device except from Actuators/Electric motors) exists that can do the Forward/Backward and hold(in the middle or somewhere else between the IN/OUT parameters) motion on command so we can connect that to a chip and connect that chip to the Internet.

You can use a solenoid to wind the mechanism and electronic components to control everything....everytime the spring winds down it hits a contact that triggers the solenoid, it's automatic winding...this strategy was used in early automobile clocks...

Thank you! I will do some research after it.

Is this a person or a robot ?

Why is the first sentence in #10 in reply to #9, the same as in the second sentence in #12 in reply to #7 .

If you haven't already consulted one, I think you may need a patent lawyer to know exactly what is and what isn't patented. In "lawyerese", tiny changes in wording can make big differences. [I'm definitely NOT one, so take all of this with a grain of salt...]

For example, a standard solenoid IS a linear actuator, and they have been used as such in common devices (eg. pinball machines) for 60 years in my personal experience, and (without doing any research), I suspect much longer. Come to think of it, solenoids were used as actuators in the original telegraphs, almost 200 years ago.

Likewise, any device that can "Push - Retract - Hold" IS by definition a linear actuator.

I can't imagine that any common electric mode of powering that actuator is patentable in this century!

Similarly, I remember observing linear actuators in my first technical job (1960 or '61), so any device that has a currently valid patent on a linear actuator must have some very specific details. Change some of those details, and that patent does not apply...

Good Luck!

Nitinol muscles.

Wow, I have been looking into this. This is serious business. The problem is we would still need a device that resets the spring to the "Long/Deformed" shape. We would heat it to become smaller. Thanks for this post!

A threaded rod with a nut and an electric motor comes to my mind. You'll have to locate a suitable motor driver and other motion control functions.

OP states (post #3 I think): "We can't use a electric motor, actuator,.. because of patent infringement."

Yeah I saw that. I held back my complaint on that statement, until now.

To avoid a "patent infringement" worry there are only two clear avenues. One is to use a technology so old and obvious that it is considered to be in the public domain. Archimedes screw and an electric motor I believe fit that bill. The other option is to create a completely new technology worthy of a patent. I'll be damned to give away for free on a public blog anything that might be worthy of a new patent, thank you very much.

GA from me!! Sounds a little too nefarious for my liking...

On a beautiful Sunday afternoon in the midst of the French Revolution the revolting citizens led a priest, a drunkard and an engineer to the guillotine. They ask the priest if he wants to face up or down when he meets his fate. The priest says he would like to face up so he will be looking towards heaven when he dies. They raise the blade of the guillotine and release it. It comes speeding down and suddenly stops just inches from his neck. The authorities take this as divine intervention and release the priest.

The drunkard comes to the guillotine next. He also decides to die face up, hoping that he will be as fortunate as the priest. They raise the blade of the guillotine and release it. It comes speeding down and suddenly stops just inches from his neck. Again, the authorities take this as a sign of divine intervention, and they release the drunkard as well.

Next is the engineer. He, too, decides to die facing up. As they slowly raise the blade of the guillotine, the engineer suddenly says, "Hey, I see what your problem is ..."

I can't believe that the same people that raise a stink if THEIR patent was violated, would assist someone else commit the same crime...

That must be one hell of a patent write up...

they say that writing a patent, you can't encompass the patent with too much detail, that a minor change, that patent is worthless

And not enough detail, its just as bad.

And the only winners are the attorneys battling it out in the court system.

Such movement is normally done with an RC servo - look into airplane flaps. THese are pretty reliable have a high resolution are cheap - have limit stops and work also via Apps. They are the simplest and less patent claim affected thing. RC servos were invented in the 1940th or earlier the protocol used comes from the war time... You can get them very small with 3grm weight to big ones able to move heavy flaps of model air planes. THere are even linea moving ones for Cars smaller than H0 train format, see here:

https://www.conrad.de/de/spektrum-micro-servo-linear-servo-getriebe-material-kunststoff-stecksystem-jst-418428.html

Enlarge the picture and you can see the little plastic part with a hole which is coupled with a spindle, THis moves around 2 cm There are even end stops provided. Price around 13€.

Another source of such a linear movement can be THe Laser head drives from CD Players - look into Instructables - there are also solutins with stepper motors which would be better as you can calculate the number of steps and the movement distance.

But a solenoid used for positioning (as in your application) is by definition a linear actuator!

How about a small stepping motor with a ball screw? You can program the number of pulses that will translate into the linear movement. This system will be an open loop solution. If you want a signal back letting you know that the command was executed, than a linear sensor should be added to the construction, which would make the whole system closed loop. But that addition will make it more expensive.

That's known as a linear actuator.

see #2

I did an installation one time using two solenoids, a gear attached to a screw shaft and pickfeed pawls. Solenoid one operates one pickfeed and indexes the screw one step. The other solenoid operates the second pickfeed and indexes the screw the opposite direction. It was in a 1985 patent for an automatic grinding machine, so it's public domain now.

This ratchet mechanism is a simple solution theoretically, but practically the ball screw and stepping motor is simpler, reliable and more cost effective.

Make it a rotary action. or a linear action driven from a rotary motor with an encoder on it.
Del

Solenoid will not do a movement to your desire. they act in digital mode, position A or B. try a motor cam or rack and pinion or lead screw or ball screw etc, depend on application (type of motor depend on the level of precision you want)

So many responses! I may have missed it, but an old technology that may have been overlooked is a voice coil. That is your "linear" solenoid. Perhaps some sort of cam operated technology has been overlooked?

I've read all the comments and OP responses so far and it occurred to me NielsN that your infringement issue may not be related to the linear actuator in your device, unless that specific actuator is a key element of the competing patent. Anything that does work in a straight line is by definition a linear actuator and just the term "Linear actuator" could be hard to hang a patent on. A patent lawyer should be consulted on that.

That being said, if your loads are light enough you could look into shape memory metal wire. These elements move between 2 shape states based on heat, which can be created with current through the wire. I'm not sure of this but varying the temperature (power to the wire) may vary the amount of transition to give position control. Using multiple wires would multiply the applied force.