This section provides a more comprehensive discussion of topics not (necessarily) fully described in other sections of this website.
It is assumed you have read and studied the information in the Air Circuit Components section.
0. There are Two Active Air Circuits.
It's significant to understand that, within the overall air circuit, there is a division of responsibilities... One of Power and one of Control. This insight reveals that there are actually two independent air circuits at work.
The Power Air Circuit provides pressurized air to cycle the cylinder (and thus move the ram). Pressurized air, entering the 4-way valve, is routed to either the front port or the rear port on the cylinder. When it's routed to the rear of the cylinder, the rod extends out of the cylinder. When air is routed to the front of the cylinder, the rod is retracted into the cylinder. Since the rod is attached to the ram, the ram cycles. When Butterfly Valve 1 is opened, pressurized air moves through the check valve into the center port of the 4-way valve, and then is routed to one of the ports on the other side of the valve.
The Control Air Circuit manages the pressurized air routing paths through the 4-way valve... and when they will be reconfigured. The 4-way valve has a shuttle (movable internal component) that, when moved between its normal (default) position and it's working (alternate) position, does the physical reconfiguration of the internal paths through the 4-way valve.
"Normal" and "Working" terms are used by Norgren in their technical documentation describing the functions of the shuttle.
The shuttle is held in its normal position by an internal spring. It's moved to its working position when pressurized air is presented at the Shuttle Port on the 4-way valve. When that pressurized air is released, the spring returns the shuttle to its normal position.
The Roller Valve is part of the Control circuit and manages when pressurized air is presented to (and released from) the 4-way valve shuttle port. When the roller (on the roller valve) is pressed in, pressurized air is allowed through the roller valve and moves on to the 4-way valve shuttle port (moving the shuttle to its working position). When the roller is let out (away from the roller valve), pressurized air is blocked from entering the roller valve and pressurized air that had been presented to the 4-way valve is released (allowing the shuttle to return to its normal position).
1. This dialog explains why the Ram moves to its upper-most position and stays there when the Cricket is turned on…. and why the Ram starts cycling when the Treadle is pressed down.
The Short Story
The Ram moves up when Butterfly Valve 1 is opened because pressurized air has entered the Air Circuit.
The Ram stays up because normal cycling has been disabled by the Air Gate.
The pressurized air needed to move the 4-Way Valve’s Spool (during normal cycling activity) has been blocked.
Normal cycling resumes when the Treadle is pressed down.
The Air Gate opens, allowing pressurized air to move forward toward the Roller Valve, resuming normal cycling.
The Long Story
Several things contribute to this feature.
Before Butterfly Valve 1 is opened….
The Treadle is in its fully-up position.
The Ram is down with the dies touching.
The lever on the Roller Valve is out because the roller is off the Dock.
The Ramp Dock Assembly is down because the Ram is down.
The air in the Air Circuit is not pressurized.
The 4-Way Valve’s Spool is in its “normal” position.
An internal spring is holding the spool in its normal position.
The Air Gate is closed.
When Butterfly Valve 1 is opened
Pressurized air enters the Air Circuit.
Pressurized air moves forward to the Air Gate
The pressurized air at the Air Gate is stopped because the Air Gate is closed.
Pressurized air moves into the 4-Way Valve (and through its air passages as configured by the its Spool).
Since the spool is in its normal position, air coming into the 4-Way Valve will be routed to the rear of the cylinder.
The Ram will rise.
As the Ram is rising, the Ramp Dock Assembly moves with it and interacts with the Roller Valve. The Roller Valve lever is pressed in as the Ramp moves by it (the roller moves onto the Dock).
During normal cycling, when the Ramp presses in the lever, the Roller Valve allows pressurized air (coming from the Air Gate) to move forward to the Spool Control Port (and causes the Spool to move to its working position).
Since the Air Gate is closed, the Roller Valve has no pressurized air to move forward… so the Spool in the 4-Way Valve remains in its normal position, allowing the Ram to continue its rise to its upper-most position.
As the Ramp-Dock rises, the Roller Valve lever remains in because its roller remains on the Dock.
The Ram rises to its upper-most position and stays there because the spool remains in its normal position (pressurized air continues to be directed to the rear of the cylinder).
Cycling is disabled because the 4-Way Valve’s spool does not change positions.
The air on the front side of the piston in the cylinder is allowed to exit because the path out is open and unencumbered.
The Ram will remain in its upper-most position until the Treadle is pressed down.
As the Treadle is pressed down, both Butterfly Valve 2 and the Air Gate will be opened by linkage from the Treadle.
Opening the Air Gate allows pressurized air to pass through it, moving on to the Roller Valve.
Since the Roller Valve’s lever is pressed in, the pressurized air from the Air Gate will pass through the Roller Valve and move on to the Spool Control Port.
When the pressurized air reaches the Spool Control Port, it will push the 4-Way Valve’s Spool to its working position.
As the 4-Way Valve Spool moves, it reconfigures the passageways through the 4-Way Valve, routing the incoming air to the front of the cylinder.
Opening Butterfly Valve 2 opens the exhaust side of the Air Circuit, allowing more pressurized air to enter the front of the Air Circuit through Butterfly Valve 1.
The incoming air (because the Spool has moved to its working position) is routed toward the front of the cylinder.
The Ram comes down as pressurized air rushes into the front of the cylinder.
The cylinder piston pushes the air ahead of the piston out its rear port, on through the 4-Way Valve to the Muffler.
Normal cycling resumes as the roller on the Roller Valve lever moves down the Ramp (as the Ramp is moving down with the Ram) and the lever on the Roller Valve moves out, cutting off the pressurized air from going to the Spool Control Port and releasing the pressure in that hose (which allows the 4-Way Valve’s spool to return to its normal position).
2. Understanding the Performance Gain we get because we use a Check Valve at the air input port on the 4-Way Valve.
The Short Story….
The Check Valve prevents air from being pushed back into the incoming air stream before the Ram changes direction. The trapped air gets compressed even more (as the Ram keeps moving in the same direction for an instant because of momentum) and provides an extra “boost” when the ram finally changes direction.
The Long Story….
It’s easy to understand that… in order for an air cylinder to cycle a Ram…. pressurized air must first be sent to one end of the cylinder, then the other.
Visualize the pressurized air coming into the rear of the cylinder first… It comes rushing in, pushing the piston forward, extending the rod and moving the ram away from the front of the cylinder.
Then…. When it’s time to initiate changing the direction the ram is moving, pressurized air comes into the front of the cylinder, pushing the piston back, retracting the rod and bringing the Ram back toward the front of the cylinder. That was easy. Air going in the rear…. Air going in the front…. each time pushing the piston to move the Ram.
What is less intuitive (to think about) is the air on the other side of the piston. It has to be moved out of the way…. That air is pushed out of the cylinder (through the opposite cylinder port from incoming air), to and through the 4-way Valve and on to the muffler.
What is equally important (for those of us that want to get the best performance), is to understand how to take maximum advantage of EVERYTHING that is happening during this whole cycle.
There is one more dynamic that is significant…. and that is to consider what happens when the 4-Way Valve’s air passageways are reconfigured to accommodate changing which end of the cylinder the air is rushing toward.
That reconfiguration happens in an instant. Air is moving into one end of the cylinder… then a few milliseconds later, it’s moving into the other end of the cylinder.
Also keep in mind that the Ram is moving and has a great deal of momentum.
When the air coming into the cylinder is switched from one end to the other, it initiates the process to reverse the direction the ram is moving. Changing the direction the Ram is moving does not happen instantaneously.
If you are a visual learner (like me), you may need to doodle (sketch) a bit to follow this.
The Ram, due to the momentum it has, continues to move in the same direction for a moment before it reverses direction and heads the other way.
Hmmmm…. A couple milliseconds ago, air was coming into the front of the cylinder, pushing the piston back…. now, an instant later, air is coming into the back of the cylinder trying to push the piston forward… but the piston is still moving toward the back of the cylinder because of the momentum of the Ram…
The incoming air faces a dilemma… for an instant (as long as the Ram keeps moving towards the back of the cylinder) the piston is fighting the incoming pressurized air and trying to push it back OUT the rear port.
The air the piston is pushing into the incoming air stream is at a higher pressure than incoming air (it’s being compressed because it is flowing into an oncoming stream of air). Eventually, the air pressure from the opposing sources will equalize and the Ram will stop and reverse the direction it is moving. Whew!!!
This all takes time. The air that is being pushed back into the incoming air stream pushes air well into the hose (or pipe) before equalization occurs.
Is there a way that process could be sped up?
Compressing air back into the line seems like wasted energy. This needs to be stopped so the Ram can reverse direction faster.
......Enter the lowly Check Valve.
A Check Valve is a device that allows air to move freely in one direction only.
OK… We can stop air from being pushed back into the incoming stream. How does that affect the Ram?
Well….. and this is the good part.… The Ram still doesn’t instantly reverse direction.
The Ram still continues to move in the direction is was moving because of the momentum it has. It’s just that it’s moving against air that cannot be pushed out into the incoming air stream (back flow has been stopped).
The air that is trapped (because of the Check Valve) is even further compressed by the moving Ram until that pressure stops the Ram and reverses its direction.
Before the Ram reverses and moves in the opposite direction (the momentum has finally relented), the pressure will have greatly risen and provides a significant “power assist” to propel the Ram forward. Eventually, the air behind the piston drops in pressure and equalizes with the pressure on the other side of the Check Valve, allowing the Check Valve to open and let additional incoming air enter the cylinder to continue pushing the Ram forward…. Whew again!!!
3. Ram Cycling Management using a single Roller Valve.
The Short Story
The Air Circuit takes advantage of Physics. The decision to change the direction the Ram is traveling is made at the center of the stroke. The Roller Valve detects the center of the stroke and initiates changing the direction the Ram is moving (incoming air is immediately directed to the opposite end of the cylinder). The Ram continues to move in the same direction (due to momentum) for a moment, then changes direction. When the Ram again passes the center of the stroke, it all happens again.
The distance the Ram travels away from and back to the center of the stroke is one-half of a cycle.
The Long Story
It’s not necessarily intuitive to understand how ram cycling can be managed using only one Roller Valve.
After all, doesn’t the air circuit need to directly manage exactly when the Ram should change the direction it’s moving…. both at the top and bottom of its cycle?
Not necessarily…. When an air circuit uses just one Roller Valve, the cycle is managed from the Nominal Center of the Stroke. As described in the “Roller Valve Long Story”, the air circuit initiates changing the direction the Ram is moving when the roller (on the Roller Valve) moves the lever (on the Roller Valve) in or out. This happens whenever there is an interaction between the Roller Valve and the Ramp.
I say “initiates changing the direction” because the ram does not change direction immediately. It keeps moving in the same direction for an instant because of its momentum. When incoming pressurized air overcomes that momentum, the Ram will stop and move the other direction toward the center of the stroke. The distance the Ram traveled from the center out, then back will be half of one cycle.
As the Ram is traveling the new direction, the Roller Valve will interact with the Ramp again…. and the air circuit will once again reconfigure the air paths in the 4-Way Valve and initiate changing the direction the Ram is moving. The distance the Ram travels (due to momentum) after that subsequent interaction is the remainder of the cycle.
The distance the ram travels (from the center of the stroke) before it changes direction is dependent upon how far the Treadle has been pushed down (air volume and pressure affect how long the stroke will be).
Two Roller Valve Management. If it is necessary to have a longer stroke than can be effectively managed with a single Roller Valve, a Roller Valve could be installed to initiate the change in direction at each end of the stroke. This would require a different 4-Way Valve (air assist at both ends of the spool) and a redesign of the Cricket in several areas.
4. Single-Hit Capability.
The Single-Hit feature allows the operator to initiate a single strike without the Ram cycling.
Action: The operator presses the Treadle down and the Ram delivers a single strike, after which the Treadle is released and the Ram returns to its upper-most position.
Several things come into play to use this feature.
The Treadle must initially be in its fully-up position.
The Cricket needs to be put in Single-Hit and Clamp mode.
This is accomplished by moving the Stroke Adjustment Assembly to its lowest possible position.
Normal cycling of the Ram is disabled.
When the Stroke Adjustment Assembly has been moved to its lowest possible position, normal cycling is automatically disabled. This occurs because the roller on the Roller Valve has been moved down far enough to always remain on the Dock, regardless of any movement by the Ram. This prevents the roller from interacting with the Ramp, thereby disabling normal cycling..
The 4-Way Valve’s Spool must initially be in its “normal” position.
When the Treadle is in its fully-up position, the Spool will be in its “normal” position because the Air Gate is closed, which prevents pressurized air from being presented at the Spool Control Port, regardless of the position of the lever on the Roller Valve.
An internal spring will push and hold the 4-Way Valve’s Spool in its “normal” position when there is no pressurized air being presented at the Spool Control Port.
The Ram must rise to its upper-most position when the Treadle is fully up.
Since the Spool in the 4-Way Valve is in its normal position, any pressurized air entering Port 1 of the 4-Way Valve will be directed to the rear of the cylinder, raising the Ram.
There is always a very small amount of pressurized air allowed to flow through the 4-Way Valve to move the cylinder… even when the Treadle is fully-up (see the Butterfly Valve 2 discussion). This provides the pressurized air to lift the Ram to its fully-up position.
Allowing the small amount of air (with the Treadle fully up) to continuously enter the 4-Way Valve can be implemented by providing a “stop” the butterfly lever hits before it fully closes as the Treadle is raised (recommended)… Or by adjusting the Treadle linkage to not allow the lever to fully close.
While the 4-Way Valve’s Spool is in its normal position, any pressurized air entering Port 1 of the 4-Way Valve will cause the Ram to rise.
The Ram will rise to its upper-most position and stay there because the 4-Way Valve’s Spool will remain in its normal position.
When the operator presses the Treadle down, several things happen
The Air Gate is opened, allowing pressurized air to move forward from the Air Gate… through the Roller Valve (this path is open because its roller is on the Dock and its lever is pushed in) and on to the Spool Control Port.
The Spool in the 4-Way Valve moves to its "working" position and directs pressurized air entering Port 1 on the 4-Way Valve to flow to the front of the cylinder.... bring the Ram down.
The Ram will deliver a single strike when the operator presses down on the Treadle.
As the operator presses down the treadle, Butterfly Valve 2 is opened (via linkage from the treadle), allowing pressurized air to enter Port 1 of the 4-Way Valve. Since the spool is in its working position, that air will go into the front of the cylinder and pull down the Ram (this is the down stroke).
Since cycling is disabled, (the 4-Way Valve’s Spool remains in its working position) the Ram will stay down after it hits its target.
The Ram will rise to its upper-most position when the operator releases the Treadle.
When the operator releases the treadle to its fully-up position, The Air Gate is closed.
A path is opened through the Air Gate to release the pressurized air that had been forwarded through to the Spool Control Port.
Releasing the pressurized air from the Spool Control Port allows the 4-Way Valve’s Spool to move back to its “normal” position.
The “small amount of pressurized air” entering Port 1 of the 4-Way Valve (that was previously discussed) is directed to the rear of the cylinder, rising the Ram to rise to its upper-most position.
The operator needs to be able to initiate either a “light” or “forceful” strike with the Ram.
The speed the Ram moves downward is directly associated with the volume of pressurized air entering the 4-Way Valve when the operator presses the treadle down.
The volume of air entering the 4-Way Valve is controlled by how far Butterfly Valve 2 is opened.
The further down the treadle is pressed, the more open that valve becomes.
A quick action on the treadle by the operator causes the Ram to descend rapidly, providing a forceful strike.
A slow action on the treadle by the operator causes the Ram to descend slowly, providing a light strike.
While the Cricket is in the Single-Hit and Clamp mode, the Ram can be used to clamp an object between the dies.
On the original Cricket, the force will be about 300 pounds at the recommended operating pressure of 80 PSI.
Force = Pressure times area plus falling weight.
To clamp, the operator
Puts the Cricket in the Single-Hit and Clamp mode.
This is done by moving the Stroke Adjustment Assembly to its lowest position.
Places the object to be clamped on the lower die.
Presses the treadle down slowly, until the Treadle is in its lowest position.
This will bring the ram down to rest on the object on the lower die.
As long as the operator holds the treadle down, the object will be clamped.
To release the clamp, the operator slowly releases the treadle to its upper-most position.
The Ram will rise to its upper-most position and remain there.
The Cricket is then ready for the next object to be clamped…. or a Single-Hit action.
How it works….
Read the “Single Hit Capability” Technical Discussion.
Clamping works exactly the same as the single hit works. The only difference is the operator holds down the Treadle instead of releasing it.
Consider the clamping action as a very light single hit, pushing the Treadle to its lowest-possible position…. after which you do not release the Treadle until you want the clamp released.
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