Method and apparatus for monitoring the diameters of rod-shaped products of the tobacco processing industry

Apparatus for monitoring the diameter of a rod-shaped product of the tobacco processing industry which is deformable by the impinging testing fluid when the pressure of such fluid exceeds a given value, particularly of filter rod having a porous tubular wrapper, comprising means for transporting the product axially along a predetermined path;

• means for establishing between the exterior of the product in a predetermined portion of said path and the atmosphere at least one passage of predetermined cross-sectional area so that the unoccupied portion of such passage varies with deviations of the diameter of the product portion in the passage from a predetermined value;
• a source of compressed gaseous testing fluid;
• means for conveying from said source a stream of testing fluid against the exterior of the product so that the fluid impinges upon the product, including means for confining the fluid to the flow into the atmosphere by way of the unoccupied portion of said passage;
• means for maintaining the pressure of conveyed fluid at an at least substantially constant value, including means for holding the pressure of testing fluid at or below said given value so that the testing fluid does not effect any deformation of the product in said path;
• and means for generating first signals denoting fluctuations of the rate of flow of testing fluid through said passage as a function of deviations of the diameter of the product from said predetermined value.

A method of monitoring the diameter of a rod-shaped product of the tobacco processing industry of the type having a tubular envelope consisting of porous wrapping material, particularly a filter rod having a porous tubular wrapper, comprising the steps of transporting the product axially along a predetermined path;

• establishing between the exterior of the product in a portion of said path and the atmosphere at least one passage of predetermined cross-sectional area so that the unoccupied portion of such passage varies with deviations of the diameter of the product portion in the passage from a predetermined value;
• directing against the exterior of the moving product a stream of gaseous testing fluid so that the fluid impinges upon the product;
• confining such fluid to the flow into the atmosphere at least substantially exclusively by way of the unoccupied portion of the passage;
• maintaining the pressure of the impinging fluid at an at least substantially constant value;
• generating first signals denoting fluctuations of the rate of fluid flow through said passagee as a function of deviations of the diameter of the product from said predetermined value;
• converting the wrapping material into said envelope ahead of said portion of said path;
• ascertaining the porosity of wrapping materail prior to said converting step;
• generating second signals denoting the ascertained porosity;
• and relating the second signals to the respective first signals, including modifying the second signals in accordance with the equation
• d=(Q.sub.10 -Q.sub.1)/Y(Q.sub.2)
• wherein d is the diameter of the product, Q.sub.10 is the rate of fluid flow through said passage when the diameter of the product equals zero, Q.sub.1 is the rate of fluid flow through the passage when the diameter of the product exceeds zero but does not exceed the diameter of the passage, and Y(Q.sub.2) denotes the porosity of the selected wrapping material.