Extended low frequency range pulsation attenuator

Claim 1

A stock supply system providing reduced low frequency pressure variations in a stock suspension being fed to a paper machine comprising: an attenuator chamber, inlet conduit means arranged to deliver a stock suspension into said attenuator chamber, said attenuator having an air chamber which applies pressure to the stock suspension discharge means receiving the stock suspension discharged from said attenuator chamber, a control system comprising a first sensor for sensing the pressure applied to said suspension and control means for controlling the pressure applied to said suspension in said attenuator chamber, a sump receiving the overflow from said attenuator chamber, discharge means for receiving the stock suspension discharged from said sump discharge control means for controlling the discharge from said sump, second sensing means for sensing the stock pressure in said inlet conduit means upstream of said attenuation chamber, third sensing means arranged to sense the level of stock in said sump, a high pass filter receiving a signal from said second sensing means, a low pass filter receiving a signal from said third sensing means, a summing amplifier receiving the outputs of both said high pass and low pass filters, and said discharge control means receiving the output of said summing amplifier and connected to said discharge means to control operation of said discharge means in response to said output.