Safer trigger for pneumatics

[tromic]

What do you think about trigger like this. This should be safe, but difficult to produce and adjust. Trigger force on finger might be adjusted for each pressure by an external adjustment spring. In this case friction force on sear lever tooth is higher than the sliding force. Well this is just an idea.

 

[popgun pete]

The blue locking lever is very small and its pivot pin being mounted high up the internal curvature of the inner barrel will impose a restriction on clearances when considering the lateral dimension of this part, unless it operates in a barrel slot of its own, similar to the sear lever. If levers and pins are too small in section then their assembly becomes difficult and the parts may not be strong enough. It is asking a lot of a 3 mm diameter pin to provide this function when slotted at the top, which weakens it, for the pivoting link connection to the internal trigger or locking lever. A trigger mechanism needs to be durable and reliable, so the parts have to be strong enough to do the job required of them for a long period without the need to dismantle the gun. Hence manufacturers have opted for the simplest designs which rarely give problems, having been in use now for many years.

The current arrangement was used in the old Nemrod mid-handle spearguns with the spear in the front barrel and the rear tank just an empty pressure vessel. Conceptually remove and wrap the rear pressure tank around the front barrel and you have a "Sten", only Nemrod never thought about doing it, instead they later ran the inner barrel back inside the rear tank. Other manufacturers followed suit, but fortunately Mares decided a tank at the front was the way to go for their lightweight pneumatic guns. So the externally actuated, flattened, internal single-piece trigger mechanism has had fifty or more years of use.

 

[tromic]

That's all right Pete. This schematic is just to have something to start with, to see some possibilities, problems...


This is an more simple solution:

 

[popgun pete]

I can see what you are trying to do, but the problem with a locking lever is if it re-engages on the sear lever tail again straight after the shot then the mechanism is already locked up and the piston tail will not be able to push the sear tooth aside for the next loading cycle. What usually happens with locking lever trigger mechanisms is the levers are deliberately held out of position by the biasing springs after the shot until the sear lever is pushed back against their action by the spear or piston tail until a new position is reached where the levers then move to a lock condition. So in your new version the mechanism will immediately reset once the piston is released and to get it to open again the trigger will need to be pulled and held for the piston tail to be caught again by the sear tooth. This is assuming the locking lever has a biasing spring to rotate it clockwise as seen in this drawing.

 

[tromic]

I can see what you are trying to do, but the problem with a locking lever is if it re-engages on the sear lever tail again straight after the shot then the mechanism is already locked up and the piston tail will not be able to push the sear tooth aside for the next loading cycle. What usually happens with locking lever trigger mechanisms is the levers are deliberately held out of position by the biasing springs after the shot until the sear lever is pushed back against their action by the spear or piston tail until a new position is reached where the levers then move to a lock condition. So in your new version the mechanism will immediately reset once the piston is released and to get it to open again the trigger will need to be pulled and held for the piston tail to be caught again by the sear tooth. This is assuming the locking lever has a biasing spring to rotate it clockwise as seen in this drawing.

Yes, you are right! Neither I like it because of that. But there might be same kind of safety switch. You pull the trigger 2-3 mm and prevent it to go back. Than you can use a gun as normally, load, shoot, but without safety. Or you might release the switch after each loading and you will have additional safety. Not practical, but very simple and safe. This safety switch would block the sear lever, not the trigger as usual.

 

[popgun pete]

I just wrote this for another thread.

"Whenever I use a pneumatic gun I always engage the safety before I load the gun as that action pushes the trigger to the ready to shoot position and the line release lever as well. Unlike band guns the sear lever in a rear handle pneumatic is not influenced by the position of the safety, whereas in most band guns the trigger mechanism will not reset if you engage the safety first because during relatch the trigger moves back fractionally (being pushed by the reverse rotation of the sear lever) and it cannot do that with a safety blocking it."

Putting a safety on the sear lever could cause problems if you forget to remove it for relatching. The ideal safety mechanism would trap all levers, but as most pneumatic guns have a remote trigger that either pushes or pulls a rod, trigger only safeties don't influence what goes on inside the gun.

 

[tromic]

I just wrote this for another thread.

"Whenever I use a pneumatic gun I always engage the safety before I load the gun as that action pushes the trigger to the ready to shoot position and the line release lever as well. Unlike band guns the sear lever in a rear handle pneumatic is not influenced by the position of the safety, whereas in most band guns the trigger mechanism will not reset if you engage the safety first because during relatch the trigger moves back fractionally (being pushed by the reverse rotation of the sear lever) and it cannot do that with a safety blocking it."

Putting a safety on the sear lever could cause problems if you forget to remove it for relatching. The ideal safety mechanism would trap all levers, but as most pneumatic guns have a remote trigger that either pushes or pulls a rod, trigger only safeties don't influence what goes on inside the gun.

Yes, that is potential problem with this approach. You can not latch the gun if you forget to switch off safety before loading the gun.

 

[popgun pete]

It would be better to create a "cam lock" trigger mechanism or something like the "Airbalete" where the discharged sear lever stays tipped over until the piston tail pushes it back the other way during the next loading of the gun. Your internal locking lever can help in keeping the sear lever tipped over and during reloading when the revolving sear lever tail pushes back on the locking lever it too is moved back and the two components then lock the mechanism again. The problem is the lack of space inside the inner barrel tube as the current guns are built to make use of the existing sear lever and have left little opportunity to re-engineer the mechanism.

The only free space is behind the sear lever inside the inner barrel. If a sprung loaded sliding element such as a cylinder fitting inside the inner barrel bore (which would be vented for air flow) was pushed forwards by a coil spring located directly behind it then the cylinder could push your locking lever further forwards. Internal air pressure will push the actuating pin down once you release the trigger. I am attaching a quick modification of your drawings to illustrate the idea, the shapes are not exact, the sliding cylinder partly envelops your locking lever at the sides to stop the cylinder rotating in the inner barrel, but I am sure you could draw a better version.

 

[tromic]

Now we are closer to better solution!

 

[tromic]

I would maybe try this design, because of lack of free space on the right of the trigger lever. This would be an easy to make at home version.

 

[popgun pete]

The sear lever needs a biasing spring as well, maybe you can use a similar one wrapped around the sear pivot pin as you have on the locking lever.

 

[tromic]

The sear lever needs a biasing spring as well, maybe you can use a similar one wrapped around the sear pivot pin as you have on the locking lever.

I would maybe try to make it without biasing spring, using angled tooth and pistons mushroom (angle greater than the "miracle angle").

 

[tromic]

Trigger activated by magnet?

 

[popgun pete]

You really need the biasing spring on the sear lever to stop a premature mechanism lock if the sear lever tail falls back and is caught by the locking lever without the piston already being engaged on the sear tooth. The Prodanovich balanced sear lever has no spring because the weight of the long forward projecting arm that holds the line release "rabbit ears" keeps the sear lever tipped forwards. If it did not have that arm then the Prodanovich sear lever would need a biasing spring. Usually forward located sear lever trigger mechanisms have a biasing spring that simultaneously pulls on both levers, so you only need one coil spring, but that is not possible inside the inner barrel of a pneumatic speargun. Spearguns like the JBL "Magnum" band gun have a coil spring pushing the trigger and a wire two leg spring on the sear lever wrapping around the sear lever pivot pin to anchor it in position.

A magnet loses its grip once a very slight gap opens, so a jerk on the sear lever could fire the gun as you release the effort on the loading bar. I think few people would want to trust a magnet in this application.

 

[tromic]

You really need the biasing spring on the sear lever to stop a premature mechanism lock if the sear lever tail falls back and is caught by the locking lever without the piston already being engaged on the sear tooth. The Prodanovich balanced sear lever has no spring because the weight of the long forward projecting arm that holds the line release "rabbit ears" keeps the sear lever tipped forwards. If it did not have that arm then the Prodanovich sear lever would need a biasing spring. Usually forward located sear lever trigger mechanisms have a biasing spring that simultaneously pulls on both levers, so you only need one coil spring, but that is not possible inside the inner barrel of a pneumatic speargun. Spearguns like the JBL "Magnum" band gun have a coil spring pushing the trigger and a wire two leg spring on the sear lever wrapping around the sear lever pivot pin to anchor it in position.

A magnet loses its grip once a very slight gap opens, so a jerk on the sear lever could fire the gun as you release the effort on the loading bar. I think few people would want to trust a magnet in this application.

At least a small biasing spring would be helpful, I agree, but maybe not necessary. Latching would not be possible before the tooth were in its place.

This magnets are extremely strong (neodymium rare earth magnet) and I supposed they might normally work with a gap of 2 mm and still having huge retracting force. Of course this should be examined and tested on a desk before mounting it in a gun.
I believe it might work but a design would be more demanding.