Application Notes
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comatrol hydraulic cartridge valves

Overview

Logic elements are multi-purpose devices. These valves, when used with other cartridge valves, can create a wide variety of circuits for control of pressure, flow, and direction.

logic-elements-group

Spring Biased, Normally Closed, Differential Sensing Valves

Spring-biased, normally-closed differential sensing valves include: CP700-1, CP701-1, and CP702-1. These valves are normally closed and will modulate based on the spring
control pressure, inlet pressure at port , and pilot pressure at port.

logic-elements-cross-section

Common Applications

  • Load-sensing for a fixeddisplacementpump with single or
    multiple actuators.
  • Bypass-type pressure-compensated flow control.

logic-elements-single-actuator-load-sensing

logic-elements-multiple-actuator-load-sensing

logic-elements-bypass-flow-control

 

Spring-biased, normally-closed, vent-to-open differential sensing valves include: CP700‑2, CP701-2, and CP702-2. These valves are normally closed and will modulate based on the spring control pressure, inlet pressure at port , and pilot pressure at port.

logic-elements-cross-section2

 

Common applications include:
· Pump unloading.
· Pilot-operated relief valve.
· Sequence valve.
· Selector circuit.

logic-elements-pilot-operated-relief logic-elements-pump-unloading
 logic-elements-pilot-operated-seq logic-elements-selector-valve

Logic Elements Poppet-Type Circuit Examples

Poppet-type logic elements provide a multitude ofhydraulic circuit options, as illustrated in the circuit examples below. These poppet designs provide low-leakage and are commonly piloted. to provide the needed functionality, as a pressure relief, check valve, directional valve, or flow control.

logic-elements-5-poppot-circuits

 

Spring Biased, Normally Open, Vent To Close, Differential

 

Spring-biased, normally-open, vent-to-close differential sensing valves include: CP700-3, CP701-3, and CP702‑3.  These valves are normally open and will modulate based on spring control pressure, outlet pressure at port , and pilot pressure at port . One application for this valve is to create a high-flow pressure reducing valve when using a small relief valve (like CP208-1), or a proportional relief valve (like CP558‑20) as a pilot element. logic-elements-spring-biased
logic-elements-dimensions-3
   
Spring Biased, Normally Open, Differential Sensing Valves  
   
Spring-biased, normally-open differential sensing valves include: CP700-4, CP701‑4, and CP702-4. These valves are normally open and will modulate based on spring control pressure, outlet pressure at port , and pilot pressure at port . One application for this valve is as a pressure compensator when used with a fixed or adjustable orifice to create a pressure-compensated flow control. logic-elements-pressure-comp
  logic-elements-dimensions-4
   
Pressure Compensating, Differential Sensing Valves  
Pressure compensators offer the circuit designer capability to add pressure compensation to any fixed or variable orifice. This ensures that flow, and resulting actuator speed, are maintained regardless of system and working pressures. Note that a pressure compensator is required when using Comatrol direct-acting proportional flow controls; see Proportional valve application notes for more information.
   
Restrictive-type
Restrictive-type pressure compensators are three-ported valves that work in series with a fixed or variable control orifice. The pressure compensator is located downstream of the orifice and is spring-biased to an open position as shown. The spool “senses” the pressure on either side of the control orifice and will vary it’s restriction in order to maintain a constant pressure differential across the control orifice, hence maintaining a constant flow rate.
logic-elements-rest-type-pc-op
Priority-type
Priority-type pressure compensators are four-ported valves that work in series with a fixed or variable control orifice.  As with the restrictive-type valves, these valves maintain a constant pressure differential across the control orifice.  However, rather than restricting flow when the differential pressure becomes too high, the priority-type pressure compensators open a fourth bypass port for all flow in excess of that demanded by the control orifice. Note that if the bypass port is blocked, the valve will function as a restrictive-type pressure compensator.
logic-elements-pri-type-pc-op

Summary

All of these circuits are particularly effective to control high flows while using small (e.g. 8 series) solenoid and relief valves as pilot elements. The above examples are typical
circuits but are by no means the only applications for these valves. Effective use of differential sensing valves is a key to designing cost-effective circuits, and is limited only
by the imagination of the designer.

 

 

 

 

 

 

 

 

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