Loss-in-weight feeder system

Claim 1

A loss-in-weight feeder for discharging a flowable substance from a reservoir through a controllable discharge member under regulated conditions, comprising: scale means for developing a weight signal representative of the weight of at least the material being discharged from said reservoir; digital converting means in operative communication with said scale means for sampling said weight signal and developing digital weight signals representative thereof at a predetermined sampling rate; storage means in operative communication with said digital converting means for accumulating said digital weight signals; computing means in operative communication with said digital converting means for developing arithmetic average weight signals from said digital weight signals representative of the actual feed rate from said reservoir; input means, operatively associated with said storage means, for entering a signal representative of the desired feed rate from said reservoir into said storage means; said computing means also being used for developing a correction signal based on a proportioned deviation signal determined as a time-weighted variable which is a function of any deviation between the actual feed rate and the desired feed rate; and feedback means communicating with said computing means for applying said correction signal to said feeder to adjust the actual feed rate through said discharge member.

Claim 20

A method for adjusting the rate in a loss-in-weight feeder comprising the steps of: developing a series of weight signals representative of the average weight of material discharged by said feeder during each of a plurality of time intervals of predetermined length; storing said averaged weight signals in a plurality of rate queues: computing a value representative of the actual rate of said feeder from elements comprising a first of said rate queues; determining the degree of deviation between an operator entered set point and said actual rate; selecting a temporary set point as the lesser of said deviation and an empirically determined value; computing a second rate representative of the instantaneous rate of said feeder based on the values comprising a second of said rate queues; computing an error factor as the difference between said temporary set point and said second rate; computing a proportioning factor as the product of an operator entered variable representative of gain and the difference between said operator entered set point and said actual rate; adding to said proportioning factor an operator entered value representative of minimum gain to determine total gain; comparing said total gain with an operator entered value representative of maximum gain; computing a correction factor as the product of the lesser of said total gain and said maximum gain and said value representative of the difference between said temporary set point and said rate; and generating a signal representative of said correction factor to adjust the rate in said feeder.

Claim 21

A method for adjusting the rate in a loss-in-weight feeder comprising the steps of: developing a series of weight signals representative of the average weight of material discharged by said feeder during each of a plurality of time intervals of predetermined length; storing said averaged weight signals in a plurality of rate queues: computing a value representative of the actual rate of said feeder from elements comprising a first of said rate queues; determining the degree of deviation between an operator entered set point and said actual rate; selecting a temporary set point as the lesser of said deviation and an empirically determined value; computing a second rate representative of the instantaneous rate of said feeder based on the values comprising a second of said rate queues; computing an error factor as the difference between said temporary set point and said second rate; computing a proportioning factor as the product of an operator entered variable representative of gain and the difference between said operator entered set point and said actual rate; adding to said proportioning factor an operator entered value representative of minimum gain to determine total gain; comparing said total gain with an operator entered value representative of maximum gain; computing a correction factor as the product of the lesser of said total gain and said maximum gain and said value representative of the difference between said temporary set point and said rate; and generating a signal representative of said correction factor to adjust the rate in said feeder.