A manual valve is one operated by a person and a mechanical valve is operated by a machine interface. There are a variety of operators, but the valve functions are those normally seen - 3/2, 5/2 and 5/3.
How do manual or mechanical valves work?
A valve body will consist of a number of ports to provide inlet, outlet(s) and exhaust(s); so, for example, a 5/2 valve as mentioned above, has 5 ports - the first number.
Manual and mechanical valves are of the spool type. In a spool valve, a profiled spool slides within a machined metal bore. As the spool moves in the bore, the profile of the spool either blocks or opens the connection between ports; the second number above - 2 - refers to the number of positions the spool can take.
In all cases, with manual or mechanical valves, there will be an operator which acts to move the spool position. Image 1 shows a manual valve operator; clearly, a person will push the button to operate the valve. Image 2 shows a roller lever mechanical valve; a cam on a machine, or a similar mechanical device, will depress the lever to operate the valve at the appropriate point in a process. So, once the operator has been actioned, how does the valve work to direct the flow of air?
Please refer to Figure 1 which shows a valve with a push-button operator and a spring return. In position '1', port 1 (inlet) is connected to port 2 (12) and air can be passed to, for example, a double acting actuator; exhaust air from the actuator comes back through port 4 and is exhausted from port 5. Port 3 is blocked. In position '2' (see Figure 2), the button is depressed, and supply air is passed through port 1 to port 4; the actuator moves in the opposite direction and air is exhausted through port 2 to port 3, port 5 blocked.
How do I select a manual or mechanical valve?
The first consideration may be, whether it is important for the valve to be operated by a person, or better (or only possible) for a machine to provide the operation; if manual, does a person need to provide the return, or can this be 'automated' by use of a spring or pilot. A good example is an emergency stop valve; clearly, the first operation must be performed by a person, but also the reset. In this case, it is a well marked push button operator, with a twist reset return. The operating force should be checked to be compatible with the method of operation chosen.
The application will determine the function chosen. So, for example, above the 5/2 valve was employed for a double acting cylinder; a 3/2 valve will be suitable for a single acting actuator operation. Types of manual or mechanical valve? Manual valves are available in 3/2, 5/2 and 5/3 functions; mechanical valves are 3/2 and 5/2.
The operator is the mechanism that activates the valve, either by depressing or pulling. Depending on the application, push button, pull button, push and pull, lever, key twist and pedal are popular for manual valves; plunger, roller, roller lever and uni-directional are often seen in mechanical valves. There are also pilot return operated valves available.
Typical applications for manual and mechanical valves?
Manual and mechanical valves are strong, robust and reliable and so the units have multiple uses, which gives rise to their popularity; some typical uses are given below.
A very common application is as an emergency stop button; the red coloured push button has a twist reset and positively breaks the supply in the control circuit to the process. Similarly, to ensure machine safety, a roller valve can be used to create the circuit only on closure of a machine gate protecting the operative from the process. Plunger valves can be used to count the number of travels of a carriage in a repetitive process; key operated valves can ensure that, on removal of the key, a process can continue in operation (or be shut off) without unauthorised interference. There are many more applications.
Do I need anything else for manual and mechanical valves?
The valves will need to be securely mounted and full dimensional drawings are provided. Piping and fittings will be required to connect the valves into the pneumatic system. For new applications, we have a comprehensive range of actuators and cylinders and valves.