Method for the production of tablets and a tablet press

Claim 1

A method for the production of uniform tablets by means of a tablet press which includes a rotary disc provided with a plurality of dies and pistons engaging from below respective dies, a filling wheel and a metering wheel arranged for simultaneous rotation on the upper surface of the disc in the range of the dies, a vertically adjustable cam track, on which the pistons ride, having a section of less vertical displacement and a section of greater vertical displacement which raises the pistons so that the pressure is exerted by the pistons pressing the tablet forming material against a position of the metering wheel, an electronic device for measuring individual pressing forces in said dies, variations in said pressing forces being caused by, among other factors, fluctuating bulk densities in the tablet-forming material in the die due to the varying of the rotary speeds of the filling and metering wheels, an electronic device which amplifies the electronic measuring device output, a first electronic control device which receives a portion of the amplifier output, compares said output with a predetermined required pressing force value and emits control impulses based upon said amplifier output and said predetermined required pressing force value, an electronic signal averager which receives the remaining portion of said amplifier output and averages said output, a second electronic control device, also emitting control impulses which compares the signal averager output with a predetermined average pressing force valve representing the required average pressing force which is related to the vertical displacement of the pistons as controlled by the vertical position of the cam track, comprising the steps of: (a) adjusting the rotary speed of said wheels in accordance with said control impulses, originating from the first electronic control device, in order to minimize the variations of the pressing forces exerted against the forming tablet in the die due to the action of the cam track; and (b) adjusting the vertical position of said cam track so in response to control impulses generated by either both control devices or solely by the second control device so that the pressure exerted by the piston upon the tablet forming material in the die is altered by raising or lowering the position of the pistons relative to the die according to the difference between an average value of said pressing forces and a predetermined desired value so as to minimize differences in weight of respective tablets.

Claim 2

A method for the production of uniform tablets by means of a tablet press which includes a rotary disc provided with a plurality of dies and pistons engaging from below respective dies, a filling wheel and a metering wheel arranged for simultaneous rotation on the upper surface of the disc in the range of the dies, a vertically adjustable cam track, on which the pistons ride, having a section of less vertical displacement and a section of greater vertical displacement which raises the pistons so that the pressure is exerted by the pistons pressing the tablet forming material against a position of the metering wheel, an electronic device for measuring individual pressing forces in said dies, variations in said pressing forces being caused by, among other factors, fluctuating bulk densities in the tablet-forming material in the die due to the varying of the rotary speeds of the filling and metering wheels, an electronic device which amplifies the electronic measuring device output, a first electronic control device which receives a portion of the amplifier output, compares said output with a predetermined required pressing force value and emits control impulses based upon said amplifier output and said predetermined required pressing force value, an electronic signal averager which receives the remaining portion of said amplifier output and averages said output, a second electronic control device, also emitting control impulses which compares the signal averager output with a predetermined average pressing force valve representing the required average pressing force which is related to the vertical displacement of the pistons as controlled by the vertical position of the cam track, comprising the steps of: (a) adjusting the rotary speed of said wheels in accordance with said control impulses, originating from the first electronic control device, in order to minimize the variations of the pressing forces exerted against the forming tablet in the die due to the action of the cam track; and (b) adjusting the vertical position of said cam track so in response to control impulses generated by either both control devices or solely by the second control device so that the pressure exerted by the piston upon the tablet forming material in the die is altered by raising or lowering the position of the pistons relative to the die according to the difference between an average value of said pressing forces and a predetermined desired value so as to minimize differences in weight of respective tablets.