Abstract:
An automated system for accurately measuring the thickness of a sample quantity of small items such as oat flakes. The system picks individual oat flakes from a hopper using a vacuum and passes them between two precision rollers. One roller is fixed and has vacuum ports to pick up the flake from the hopper. The second roller is floating. As the flake passes between the rollers, the flake is flattened and the second roller is deflected by an amount equal to the thickness of the flake. A vision system comprising a video camera, a light source and a computer measures the deflection of the floating roller. The vision system obtains an image of the curvature of the floating roller at the point opposite the pinch point of the two rollers. Data from the measurement may be recorded on the computer and processed as desired.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates generally to a system and method for measuring the thickness of a small, thin item, and more specifically to a system and method for measuring the thickness of a flaked food product such as an oat flake.  
       BACKGROUND OF THE INVENTION  
       [0002]     In many manufacturing and food processing environments, it is necessary for quality assurance and other purposes to measure accurately the thickness of a small, thin item. For example, oats are processed into a variety of forms for use as a breakfast cereal, including old-fashioned or large flake rolled oats, quick oat flakes, and instant oatmeal. Old-fashioned oats are made of rolled oat groats (dehulled oat kernels) and are prepared to make oatmeal by cooking in boiling water for up to thirty minutes. Quick oat cereal consists of flakes made by rolling cut groats thinner than old-fashioned oat flakes. Quick oat flakes are prepared by cooking in boiling water for 1 to 15 minutes. Instant oatmeal is similar to quick oats but with additional treatments, such as the addition of a hydrocolloid gum to accelerate hydration. Instant oatmeal is prepared by adding hot water and stirring, without any additional cooking being required. Instant oatmeal may also be prepared by adding cold water and heating the mixture briefly in a microwave oven.  
         [0003]     The production of old-fashioned oats and quick oat flakes is essentially the same, except for the starting material. Old fashioned oats start with whole groats and quick oats start with steel-cut groats. After being steamed, both are then rolled between two metal rollers, the spacing of which is adjusted to produce the flake thickness required for each product. Quick oats are rolled thinner than old-fashioned oats so that they will cook faster. For instant oatmeal, the flakes are rolled even thinner than for quick oats. Generally, quick oats have a thickness in the range of about 0.015 to 0.022 inches, while old-fashioned oats may have a thickness of up to about 0.05 inch.  
         [0004]     For quality assurance purposes, it is necessary to sample oats from a production run and measure their thickness. A fairly uniform flake thickness is desirable in each processed batch of flakes to, for example, assure uniform cooking times and deliver the desired consistency and texture in the final cooked cereal product.  
         [0005]     Previously, measurements of this type were done manually using a micrometer. Since this was done by hand, the process was time-consuming, labor-intensive and inconvenient. Further, measurements were prone to being both inaccurate and inconsistent for several reasons. The micrometer compresses the flake, and depending on the pressure applied could yield inaccurate results. Further, the pressure applied could vary not only from flake to flake, but also due to different techniques used by different human operators. Although some automated approaches have been proposed and represent an improvement over the manual approach, such approaches suffer other shortcomings, such as their inability to handle overlapping flakes and difficulty in accurately measuring curved flakes.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The invention is directed to an automated system for accurately measuring the thickness of a sample quantity of small items such as oat flakes. The system of the invention picks individual oat flakes from a hopper using a vacuum and passes them between two precision rollers. One roller is fixed and has vacuum ports to pick up the flake from the hopper. The second roller is floating. As the flake passes between the rollers, the flake is flattened and the second roller is deflected by an amount equal to the thickness of the flake. A vision system comprising a video camera, a light source and a computer measures the deflection of the floating roller. The vision system obtains an image of the curvature of the floating roller at the point opposite the pinch point of the two rollers. Data from the measurement may be recorded in the memory of the computer and processed as desired. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a front perspective view of the roller assembly of the thickness measuring apparatus of the invention.  
         [0008]      FIG. 2  is a rear perspective view of the roller assembly of  FIG. 1   
         [0009]      FIG. 3  is a partial detailed front perspective view of the roller assembly of the apparatus.  
         [0010]      FIG. 4  is a partial detailed rear perspective view of the roller assembly of the apparatus.  
         [0011]      FIG. 5  is a partial side elevation view of the roller assembly of the apparatus.  
         [0012]      FIG. 6  is a front view of the roller apparatus mounted on a cart with the computer and display of the thickness measuring system.  
         [0013]      FIG. 7  is an operator interface screen displayed by the system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     With reference to  FIGS. 1 and 2 , the system of the invention includes a roller assembly  2  which is mounted on platform  4 . A hopper  6  for holding a quantity of oat flakes to be sampled is supported above platform  4  by hopper support  8 . A vacuum roller  10  is mounted for rotation in vacuum roller support  12 . A vacuum hose  14  connected to a vacuum pump (not shown) provides a vacuum to vacuum roller  10 . Compression roller  16  is mounted for rotation on one end of pivot arm  18 . The other end of pivot arm  18  is pivotally mounted to pivot arm support  20 . By virtue of this arrangement, compression roller  16  is floating, i.e., free to move up and away from vacuum roller  10  when a flake passes between the two rollers. Vacuum roller  10  and compression roller  16  are preferably made of pre-hardened stainless steel. In a preferred embodiment, compression roller  16  is 5.0 inches in diameter, and vacuum roller  10  is 5.125 inches in diameter. A perimeter plate  22  is coaxially mounted to compression roller  16 . In a preferred embodiment, the perimeter plate  22  is approximately 6.0 inches in diameter.  
         [0015]     A digital camera  24  is supported above platform  4  by camera support  26 . Camera  24  is positioned to view the upper peripheral edge of compression roller  16 . A light source  28  is supported above platform  4  by light support  30 . Light source  28  is positioned to back light the upper edge of perimeter plate  22  vis á vis camera  24 , thus creating a shadow that is detected by camera  24 .  
         [0016]     A motor  32  is supported by motor mount  34 . When motor  32  is energized, it directly rotates motor drive gear  36  which is attached to the shaft of motor  34 . A vacuum roller drive gear  38  is coaxially connected to vacuum roller  10 , and a compression roller drive gear  40  is coaxially connected to compression roller  16 . The respective teeth of motor drive gear  36 , vacuum roller drive gear  38  and compression roller drive gear  40  engage one another such that motor  32  causes all of the gears to rotate, which in turn causes vacuum roller  10  and compression roller  16  to rotate. The teeth of vacuum roller drive gear  38  and compression roller drive gear  40  are of sufficient size that they remain engaged for rotation even when compression roller  16  is deflected by the passage of a flake between the rollers. In operation, the speed of rotation of the rollers is approximately 4 rpm.  
         [0017]     As best seen in  FIGS. 3, 4  and  5 , a vacuum plate  42  is closely positioned against vacuum roller  10  and is urged into contact therewith in clutch-like fashion by springs  44 . Vacuum hose  14  is connected to vacuum plate  42  by fitting  46 . Apertures in the adjacent sides of vacuum plate  42  and vacuum roller  10  (not visible) permit a vacuum to be applied to vacuum roller  10  while permitting vacuum roller  10  to rotate freely. Vacuum plate  42  is preferable made of plastic with a low coefficient of friction to permit vacuum roller  10  to rotate freely. The face of vacuum roller  10  has a series of 18 small holes  48  spaced equally about its perimeter to permit vacuum pickup of flakes. The number and spacing of holes  48  are selected to ensure that only one flake at a time passes between the rollers. The vacuum applied to vacuum roller  10  is in the range of about 4 to 8 inches Hg. A second vacuum hose  50  is positioned to remove excess flakes from compression roller  16 . The vacuum applied to remove excess flakes is in the range of about 5 to 10 inches Hg. Pressurized air at about 15-20 psi is provided via blow-off hose  52  and nozzle  54  to blow compressed flakes off the rollers after measurement.  
         [0018]     For convenience, roller assembly  2  and other system components may be mounted on a cart  56  as shown in  FIG. 6 . Cart  56  also holds computer  58 , display  60  and keyboard  62 , as well as equipment for providing and regulating the required vacuum and pressurized air (not shown in detail) which are housed in cabinet  64 . The system may be connected to a plant compressed air supply which is typically available at a production or testing facility. Preferably, the compressed air supply is at about 80 psi. The flow of air may be controlled by a solenoid valve and the required amount of vacuum or pressurized air may be provided to each part of the system by adjusting a set of pressure regulators (not shown). Alternately, the system can be completely self-contained by providing a compressor and/or vacuum pump with appropriate valves and pressure regulators, which may be located in cabinet  64 .  
         [0019]     Computer  58  is programmed with an appropriate operating system and camera application software which controls the operation of the system and, preferably, provides a graphical user interface for the operator via display  60 . A standard computer mouse (not shown) may be provided for use in conjunction with the graphical user interface.  
         [0020]     After computer  58  is booted with all the required operating systems, the operator opens the camera application software, which is pre-configured to the system operation requirements. The operator interface screen  66  which is displayed on display  60  is shown in  FIG. 7 . The operator enters the test data including operator name, process name and product name by clicking on the Setup button  68  shown in  FIG. 7  and selecting the appropriate items from a drop-down menu. The operator places a small amount of screened oat flakes in hopper  6 . The operator then activates the system by clicking on the Start button  70  shown in  FIG. 7 . This will activate the vacuum system by opening a solenoid valve in the compressed air supply line, energize motor  32  to drive the rollers, and activate camera  24  to take pictures.  
         [0021]     Oat flakes are inducted from an opening at the bottom of hopper  6  by the vacuum system. More specifically, individual flakes are picked up by vacuum roller  10  by way of the vacuum present at holes  48  on the face of vacuum roller  10 . Excess flakes are removed by vacuum hose  50 . The individual flakes pass between the rotating rollers. As a flake passes through, compression roller  16  is deflected upwards by a distance equal to the thickness of the flake. Camera  24  views the deflection of perimeter plate  22  which is attached to moveable compression roller  16  from the edge by viewing it against backlight  28 . The camera image  72  of the shadow of perimeter plate  22  is displayed on the operator interface screen  66  as shown in  FIG. 7 . Camera image  72  will move as a flake passes between the rollers and compression roller  16  is deflected, providing the operator with a visual indication of the operation of the system and the relative thickness of the flakes. The accuracy of the system is increased by viewing the curvature of perimeter plate  22  rather than a single point. Perimeter plate  22  is preferably made of a dark, non-reflective material to prevent light reflection from floating compression roller  16 , which might cause an inaccuracy in measurement. Perimeter plate  22  also prevents measuring any extra flakes which were not blown on compression roller  16 . The curvature measurement is positioned directly opposite (i.e., 180° away from) the pinch point of the two rollers. Measurement data for each flake in the sample batch is recorded and stored in the memory of computer  58 . At the end of the batch of flakes the system stops and displays the results, including the minimum, maximum and mean of flake thickness, elapsed time and incremented batch count, as shown in  FIG. 7 . The operator will then remove any leftover flakes from hopper  6  to prepare the system for the next test.  
         [0022]     Preferably, polarizing filters (not shown) are provided on both camera  24  and light  28  to minimize glare and thus further enhance accuracy. Camera  24  preferably operates at a rate in excess of 20 frames per second and has a resolution of approximately 0.00018 inches per pixel, to assure accuracy for flakes having thicknesses in the range of about 0.0145 to 0.050 inches. The image from camera  24  is transmitted to computer  58  and displayed on display  60 . Computer  58  may be a personal computer with a standard operating system and components. Computer  58  is programmed to measure the deflection of compression roller  16  from the camera image and thus obtain the thickness of each flake. Thickness data is stored in memory in computer  58 , which may be connected to a network to permit data to be transferred to a central computer if desired.  
         [0023]     The use of a computer as part of the system affords simple control and great flexibility. The entire process may be operated under computer control. The computer may be programmed to, for example, configure sample data, control the system, perform and desired statistical analysis on the date, archive data, report data to a central computer via a network, and display camera images and data in various formats on the display.  
         [0024]     In a preferred embodiment, camera  24 , light  28 , the polarizing lenses and the camera application software comprise a vision system, preferably the In-Sight machine vision system available from Cognex Corporation of Natick, Mass., which includes Cognex In-Sight Explorer camera application software.  
         [0025]     The system and method of the invention thus have numerous advantages. The process is automatic, reducing significantly the labor and time required for measurements. The measurement is highly accurate, with tests indicating a measurement that is accurate within ±0.001 inches. Although the flakes are compressed and flatted, they are not damaged. While the compression is similar to that of a manual micrometer, it is consistent from flake-to-flake and batch-to-batch.  
         [0026]     Although the invention has been described in terms of a preferred embodiment, numerous variations and modifications will be apparent without departing from the scope and spirit of the invention as defined by the following claims.