Abstract: Methods and apparatus are provided for gauging the thickness or other property of a plastic film such as blown film or other material having a front side, a back side, and characteristics including a substantial transparency to radiation at a reference wavelength and a degree of transparency depending on the value of the property at an absorption wavelength. These methods and apparatus provide a useful measurement of the material property in the presence or absence of detrimental effects such as those caused by a broadband absorbing substance (e.g. carbon black) or scattering substance (e.g. TiO.sub.2) in the material, or variations in the apparent reflectivity of one or both of the surfaces on the front and back sides, as a result, for example, of the minute surface irregularities in high-density polyethylene.

Abstract: A property such as moisture content in a sheet of material such as paper that both absorbs and strongly scatters infrared radiation is measured by passing the sheet through the central region of a substantially spherical cavity formed between a pair of concave mirror-surfaced, specularly reflecting bodies that are spaced apart to form a pass gap of sufficient width to allow substantially free movement of the sheet therethrough while substantially enclosing a first portion of the sheet on both sides. A spot of infrared radiation is projected onto one side of the sheet in the center of the cavity to illuminate a second portion of the sheet included within and substantially smaller than the enclosed first portion. Thus infrared radiation scattered or transmitted by the second portion is reflected from the mirror-surfaced bodies and directed back to the second portion substantially within the area of the sheet defined by the spot.

Abstract: A system for compensating for the backlash of a drive mechanism of an actuator that can be controlled manually or switched to automatic, with the starting position indeterminate. The actuator includes a position transducer for the actuator. Impulses are supplied to the drive mechanism to energize the drive mechanism in discrete steps in a first direction. In response to a change in the actuator position being sensed by the position transducer, the supply of impulses to the drive mechanism is terminated. Because of backlash in gearing included in the drive mechanism, each of the impulses to the drive mechanism does not necessarily result in a change in the actuator position. In response to movement of the actuator being sensed the drive mechanism is energized in a direction opposite to the first direction through a distance equal to the sum of the backlash and the amount of movement of the actuator detected by the position transducer.

Abstract: A property of a thin, infrared radiation-transmissive film of plastic or the like with specular surfaces is measured with substantial freedom from errors caused by wave interference effects, utilizing first and second infrared radiations having wavelengths selected so that one of the radiations is subject to greater absorption in the film material than the other radiation. Beams of each of the radiations are directed from a multiplicity of points as on the diffusively reflective inner surface of a sphere to a surface of the film at a broad spectrum of incidence angles so that the beams traverse a multiplicity of paths through the film constituting a broad spectrum of path lengths. Radiations leaving the film are intercepted and redirected from a multiplicity of points to a surface of the film at a broad spectrum of incidence angles so that the redirected radiations also traverse a multiplicity of paths through the film constituting a broad spectrum of path lengths.

Abstract: Set points for thicknesses of coatings on opposite sides of a sheet are determined in response to measurements of the thickness of each coating. A computer responds to the two thickness measurements to derive indications of the spread of values of the measurements for each coating. The computer derives an additional indication of the spread of values for the total thickness of the two coatings. In response to the indications of the spreads of values for the coatings and the total coating thickness, minimum allowable average values for the two coating thicknesses and the total coating thicknesses are determined. The set point values for the two coating thicknesses are calculated from these minimum values, with consideration given to predetermined maximum and minimum ratios of the two coating thicknesses.

Abstract: A sheet material characteristic monitoring apparatus is provided for use in processes involving the production and contouring of sheet material. In a preferred embodiment, the sheet material characteristic is measured at two or more stationary cross direction locations of the sheet. A digital computer computes a regression equation between the measured values of the sheet characteristic and their respective locations, which equation is evaluated between limits representing the sheet edges to provide a data profile comprising estimated values of the sheet characteristic across the width of the sheet. The data profile may be derived substantially instantaneously. The data profile may further be evaluated between limits representing one or more desired transverse dimensions of the sheet.

Abstract: Specifically disclosed is the combination of a paper making machine and a control system including an automatic arrangement which, on demand of the machine operator, performs a coordinated machine speed increase, maintaining the paper sheet characteristics substantially constant until the dryer steam pressure or the steam valve opening reaches a limit. During the speed increase, a number of other machine variables are compared with set limit values and the speed increase is discontinued when a limit is exceeded for a predetermined time period. When the steam pressure has been at a limit, or the steam valve has been wide open, for a predetermined time period the control system, upon sensing the limit being reached, switches to a dryer limited mode of operation wherein the steam pressure is maintained at the limit or the steam valve is locked open.

Abstract: Thickness of a sheet being produced by an extruder is controlled in response to measurements of: sheet thickness, the speed at which material is fed through a screw of the extruder, as determined by screw speed, and the speed with which material is taken away from the extruder, as determined by sheet speed. Measured thickness is compared with a setpoint for sheet thickness and a determination is made as to whether the thickness is in a predetermined, deadband region relative to the setpoint, or if the sheet is out of the deadband because it is excessively thin or excessively thick. In response to the sheet thickness being in the deadband region, the screw speed is changed in response to a signal indicative of the product of sheet speed error and rate of change of screw speed with respect to sheet speed. Sheet speed is controlled by multiplying sheet speed error by a predetermined constant.

Abstract: A process monitoring and control system is provided for use in a tire calendering system producing a strip of rubber tire material comprising a layer of tire cord laminated between first and second layers of rubber. In a preferred embodiment, the thickness of the first rubber layer is measured by a single point radiation backscatter gauge at a point prior to its lamination with the tire cord and second layer. The thickness of the first layer is controlled to a desired target by means of a control loop including the single point gauge. The total thickness of the combined layers is measured at the calender output by a total thickness gauge. Gauge coordination means, including a delay means, are provided whereby measurements of the thickness of the first layer and of the combined strip are derived over the same longitudinal portion of the strip.