Feed and vent valve?

[ibrooks]

OK - I'm trying to sort the pneumatic bead breaker on my Harvey Frost tyre changer so that it doesn't take three pairs of hands to use it. I'm looking for a valve that will supply air in a controlled fashion to extend the ram when you operate it and then allow air to vent freely from the cylinder when it's released. Ideally I'd like the valve to be foot operated.

Anybody any idea where I'd get such a beast? Or even what it would be called so I can search?

I did get a ball "L" valve but unfortunately between the positions all three ports are connected which means that as well as losing a load of air as you turn the handle you will have little or no control of the ram extending. I've an awful feeling that I'm going to be using two valves - one for supply and one for exhaust. I'm hoping for something with a single operation though if it's available.

 

[carbon]

I think you will be looking for a pneumatic spool valve and at least one flow control valve. The flow control valve will restrict flow in one direction and not in the other

Think it would need to be a five port valve. I have one fitted on my lorry that is electrically operated with spring return but there are a selection of control options

 

[carbon]

There are some cheap foot operated 5 port pneumatic valves on eBay that would need a flow control valve added to adjust the speed for the ram extending. This flow control valve restricts flow in one direction only https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/232403164266

possibly cheaper options available but it’s the first I found with the correct markings. I didn’t check if port sizes matched

 

[ibrooks]

Cheers - will have a look and see what I can come up with.

 

[bricol]

Assuming its operated by some form of valve at the moment, that allows the non-pressured side of the cylinder to vent to atmosphere, all you need is something like:

http://www.thoritedirect.co.uk/prod...ories/flow_regulators/thorite_flow_regulator/

on the exhaust. Control the air being exhausted rather than the air going in - more control and still allows full power to be exerted.

 

[ibrooks]

The cylinder has a single port. At the moment I shove the tyre inflator onto it and use it's trigger to control the flow of air. It's a smooth stub of pipe so you have to hold the end of the inflator on with one hand whilst pulling the trigger with the other. Your second pair of hands are holding the wheel in place and angling the cylinder so that the "blade" hits the tyre close to the rim. Once the thing has broken the bead you pull the inflator off to let it vent.

Yes it's just as much of a rigmarole as it sounds. Hence I want something better involving less hands (plus I've just upgraded the inflator and the new one needs the central pin in the valve or it doesn't let air out).

I'm thinking a 3/2 valve to switch between feed and vent to the cylinder and a trigger/foot operated valve to supply air to it in a controlled fashion. I know you get smoother operation and full power at slow speeds by controlling the exhaust rather than the feed but that would mean that I'm venting the compressor to atmosphere when I'm letting the cylinder back up so not practical without a fair amount of plumbing which isn't necessary for this application.