Eliminate Stalling While Maintaining Optimum Speed

The cutting device may be a trenching chain, a drill, a grade trimming wheel or a saw. The feed could be a cylinder, a motor or a tractive drive. Typically, an operator will adjust the feed rate so that the cutting device does not stall. The problem with this solution is that when the cutting is easy, productivity is lost. The simple circuits shown below may be better solutions.


Here's how it works:

A counterbalance valve is a direct-acting, pilot-assisted relief valve. Pilot assist at port 3 lowers the effective setting of the relief valve at a rate determined by the pilot ratio. Port 3 of the counterbalance senses the pressure at the cutting device or saw. Port 1 connects to the feed circuit and port 2 goes to tank.

When the pressure required to drive the saw starts to climb too high, the effective setting of the counterbalance is lowered. Feed force will be modulated by relieving the feed circuit to tank, thus preventing the cutting device from stalling.

NOTE: The circuit on the left is all about pressure control as opposed to flow control. Pressure control allows large changes in flow with small changes in pressure. The determining factor in this circuit is the pressure at the cutting device. Don't get too caught up in numbers. There are at least three performance curves involved and trying to predict exactly what will happen is difficult, if not impossible.

The counterbalance valve can also control a remote control pressure reducing valve, PV*B, if the feed/clamping cylinder must have controlled inlet pressure instead of controlled flows.

In order to serve this purpose, the counterbalance valve has to have enough capacity to handle the flow of the feed circuit. The counterbalance valve will probably need a low pilot ratio and a high setting. It is best to select the counterbalance valve that provides a stable interaction between both circuits.

IMPORTANT NOTE: This circuit is presented as one example of how to apply our cartridge valves. It is not a  "This package guarantees that your saw will never stall again" package.

Performance Assurance

All Sun cartridges are individually tested at the factory and preset to specific pressure or flow control settings where indicated. The actual performance of the buyer's equipment can not be reproduced in Sun's testing laboratory, therefore, assurance of suitability of all of Sun's products in the buyer's application is the responsibility of the buyer. This is typically accomplished by manufacturing a prototype system followed by a test or qualification program on the part of the buyer.