limit the stroke of a cylinder with pneumatic valve

[Kaji]

I had to set a rectilinear movement of 78.5 mm repetitive once every 2 minutes (as order of magnitude) using a commercial pneumatic cylinder alesaggio 32 and race 80, to prevent during the last stretch the push impntasses the stem I was imposed a system of wreath and spring so that in the end the cylinder could make its 80 mm compressing the spring that through its slipper 1.5 mm.
predicted that I would simply tilt the axis of the cylinder compared to the axis of the motorcycle finding 78.5 with the trigonometry and inserting a simple snode, so the forces in place are so mechanically resible that I do not think it would inflate the flow of the structure, I wondered but from the pneumatic point of view are not simply available elementary and cheap valves that once the cylinder arrives to the "capolinea" feeling

 

[Vittorio]

Bye.
you have 3 possibilities
1) insert electric/magnetic ends that limit the standard cylinder stroke (but are not accurate to mm)
2) insert a thickness inside your cylinder (as attached image)
3) place the back cylinder of 1.5mm so that the maximum extension, of its standard stroke, arrives only at the desired point

sensors that detect the increase in pressure, personally I do not know them and however could only work on hydraulic cylinders.
on the pneumatic cylinders there is the softening effect because the air is compressible

 

[Vittorio]

I add that a ø32 cylinder has a stem from ø16 and considering the push pressure to 8bar
you have a boost of about 60kg
Now. If your ø16 stem is not longer than 10fold its diameter.. I doubt that it is unclean

 

[Kaji]

yes I often used internal race limiters, but they were usually "tubes" that embraced stem and had two or that tightened on stem and prevented it from dancing during movements.
here in theory when moving the yellow thickness is free to go back and forth and then I do not know if there is the contraindication that disassembling and reassembling a cheap commercial cylinder you can somehow compromise the scraper on the stem that is usually weak point.
But the fact remains that instead of a solution so "simple" and used has been imposed a decidedly more complicated

 

[ian3d]

more or less the same function is made with commercial components such as cylinder shock absorbers. are practically pistons that serve to limit shocks at the end of the race. the main manufacturers of pneumatic cylinders have to catalog these accessories.

 

[bip]

If your purpose is only to limit the stroke of a pneumatic cylinder, in addition to an internal spacer, you can apply an external mechanical line, perhaps using a chain with a screw rod (for precision adjustments), surely easier to apply and adjust

 

[wert]

Bye.
you have 3 possibilities
1) insert electric/magnetic ends that limit the standard cylinder stroke (but are not accurate to mm)
2) insert a thickness inside your cylinder (as attached image)
3) place the back cylinder of 1.5mm so that the maximum extension, of its standard stroke, arrives only at the desired point

sensors that detect the increase in pressure, personally I do not know them and however could only work on hydraulic cylinders.
on the pneumatic cylinders there is the softening effect because the air is compressibleView attachment 63719

you could try to put a pressure switch between the discharge and the flow regulator that regulates the output speed stem. reached your line, feeling that the pressure goes to zero, sends a signal to the valve that could go to the position "closed centers" and keep the cylinder steady.

 

[bip]

tire cylinders must work in mechanical lines, if you want to have a precise positioning.
that is the air always pushes, but the movement is blocked by another physical system. all the rest has a pretty aleatory positioning

 

[wert]

tire cylinders must work in mechanical lines, if you want to have a precise positioning.
that is the air always pushes, but the movement is blocked by another physical system. all the rest has a pretty aleatory positioning

My solution provides that the stem arrives at a bar but that the pressure does not remain. then it is clear that not all applications can accept that type of operation.

 

[stefanobruno]

tire cylinders must work in mechanical lines, if you want to have a precise positioning.
that is the air always pushes, but the movement is blocked by another physical system. all the rest has a pretty aleatory positioning

Exactly, never use the whole cylinder run.
stopping them with a valve doesn't make any sense, it's only used when the customer doesn't understand a patch.

 

[PIETRO2002]

Exactly, because complicating things, I've always seen adjustable mechanical stops, if you just want to reduce the final impact, you put a hydraulic shock, but the position is given by the mechanical line.

 

[meccanicamg]

if it were possible you could use a cylinder with passing stem from both ends. On the one hand I put the load and on the other I put a nut that beats on an adjustable match. if the spaces allow it is a good solution without uncomfortable soft or too technological things.

 

[stefanobruno]

"If it were possible you could use a cylinder with passing stem"

in this way also increases the stiffness of the stem.

 

[Kaji]

tire cylinders must work in mechanical lines, if you want to have a precise positioning.
that is the air always pushes, but the movement is blocked by another physical system. all the rest has a pretty aleatory positioning

yes in fact the request and the imposition surprised me too; up to 4 years I had always worked in hydraulic drills is there are all cylinders that arrive "at the end of the race" even in the case of the grippers we were forced to take the grip with a few mm of running left just to be sure that the clamp tightened on the rod.
Among other things in the present case are in the presence of pneumatic cylinders with circuits at 6 bar, therefore low forces than those always faced in hydraulic drills with circuits at 250 bar.