What are the types of Parker Parker spool type logic components?

There are four basic types of spool-type logic components available, each of which contains multiple gauges, each of which has the same function, but a large gauge has a high flow capacity. The advantage of PARKER Parker's use of logic element technology is that a smaller pilot can be used to control larger flows, resulting in a compact and efficient system. Since the spool position can be modulated, the spool type logic element is typically used for almost any form of pressure or flow control function. However, the spool valve has clearance, so Parker can also provide a valve-type logic element to provide a high-flow 2/2-way function that meets low leakage requirements.
 
The first step in ordering a logic component is to determine if the application requires direction, pressure, or flow control. Directional control is the simplest and most typical function, because the logic element is a two-way device that can be piloted internally or externally. If pressure or flow control is required, the designer has the flexibility to select the appropriate type for the four basic types of spool-type logic components to perform the pressure and flow control functions. The four types described below are based on the four functions of normally open and normally closed, internal control and external control.
 
Type 1: _ _SLC2-A and R_ _E3 series, which are normally closed, externally controlled plug-in, flow direction from port 1 to port 2. Simply put, under normal conditions, the spool is closed by the internal biasing spring to the flow from port 1 to port 2. If an external control pressure is not applied from the pilot port 3 to the bias spring chamber, the flow flows from port 1 to port 2 when the pressure reaches the set value of the bias spring. When a pilot control pressure is applied to port 3, the pressure will be superimposed above the set pressure of the biasing spring. The pilot pressure applied to port 3 is to be provided and/or controlled by an external source of pressure. Typical high flow control functions for this type of logic include: relief valves, sequence valves, priority pressure compensators, unloading and load sensing unloading valves.
 
Type 2: _ _SLC2-B and R_ _F3 series, same as type 1, but with a throttle hole inside the spool, allowing pressure from port 1 to the bias spring chamber and port 3, thus providing An internal pilot control source.
 
Type 3: _ _SLC3-A and R_ _H3 series, which are normally open type, externally controlled plug-in, flow direction is port 2 to port 1. Simply put, under normal conditions, the flow is allowed to flow from port 2 to port 1. If an external control pressure is not applied from the pilot port 3 to the bias spring chamber, the flow from port 2 to port 1 is throttled and limited at the set pressure of the bias spring. When a pilot control pressure is applied to port 3, the pressure will be superimposed above the set pressure of the biasing spring to help keep the spool open. The pilot pressure applied to port 3 is to be provided and/or controlled by an external source of pressure. Typical high flow control functions for this type of logic include: throttling control, pressure compensator, and pressure relief valve.
 
Type 4: _ _SLC3-B and R_ _G3 series, same as type 3, but with a throttle hole inside the spool, allowing pressure from port 1 to the bias spring chamber and port 3, thus providing An internal pilot control source.