Abstract:
Method and apparatus for measuring the liquid fill level in bottles while the bottles are still within the turret section of the filler system. A source of focused light, such as that generated by a laser, is directed onto a series of targets positioned on the turret behind the bottles. The beam is directed back through the bottle neck and detected by a remote camera. The detected image varies depending upon whether the bottle was underfi

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention provides method and apparatus for measuring the fill level in containers, such as transparent bottles and jars, while the bottles are still within the filler turret section of the filler apparatus.  
           [0003]    2. Description of the Prior Art  
           [0004]    Systems for measuring the fill level in bottles have been commercially available for many years. In most modern beverage fillers, the bottles from the infeed starwheel are placed on a bottom stirrup in the filler rotary turret. Each of the stirrups are movable in the vertical direction and are lifted by a mechanism, such as a cam, so that the top of each bottle is engaged into a filling cup. This cup seals the internal volume of the bottle from normal atmospheric conditions. A vacuum is usually applied to each bottle and the filler then allows the beverage to flow into the bottle. By first applying the vacuum, the bottles may be filled faster and minimizes foaming in carbonated beverages. The bottles are filled with liquid and then are lowered by cam down to the same bottom position as they were in the infeed starwheel. As the stirrup is lowered by the cam to the proper position, the bottles are handed off to transition starwheel where they are fed into a bottle capper. Prior to capping, carbonated beverages are usually jetted with some form of liquid or gas that makes them foam-over, allowing the foam to displace any air in the volume between the liquid level and the top of the bottle.  
           [0005]    U.S. Pat. No. 3,133,638 issued to the inventor of the instant application, discloses an inspection apparatus which utilizes two vertically aligned photocells which monitor the light provided through an inspection zone from a source of light. A third photocell provides an indication when the bottle enters the inspection zone. The light from the source passes through the neck area of the bottle and the light diffusing characteristics of the liquid determines where the diffused light is focused on an image plane by a lens. The lens, in turn, focuses the light on either one of two positions at the image plane on either or both, of the vertically aligned photocells depending upon the fill level in the bottle.  
           [0006]    Although the measuring apparatus disclosed in the &#39; 638  patent provides excellent results, the inspection is initiated after the bottles have been capped in a previous operation. Inspecting fill levels after capping and providing the support mechanism for doing so adds to the cost and complexity of the inspection system.  
           [0007]    What is therefore desired is to provide a liquid fill level measuring system wherein the inspection is completed while the bottles are still within the rotary turret section of the filler system.  
         SUMMARY OF THE PRESENT INVENTION  
         [0008]    The present invention provides method and apparatus for measuring the liquid fill level in bottles while the bottles are still within the turret section of the filler system. Measuring the bottles for fill level while they are in the filler turret enables the exact valve number that fills each bottle to be known without complex memory systems tracking the bottle downstream of the filler station to the reject station. As stated hereinabove, in the carbonated beverage industry, the bottles are usually “foamed over” before the capper station to purge any oxygen in the headspace above the liquid to prevent oxidation of their content which can change the true fill point in the bottles. The present invention avoids inaccurate measurements downstream of the capper station by measuring the fill level prior to capping. Further, the newer beverage filler systems have electronic controlled valves that are adjusted, or tuned, to provide the desired bottle fill level. In accordance with the teaching of the present invention, the exact liquid level, as measured by the system optics, is used as a signal for the electronics that control the filler valves enabling the operator to set the desired fill level in the bottles and detect faulty or malfunctioning valves at the early stages of the filling process, thus reducing the number of improperly filled bottles that must be discarded and, in turn, reducing process costs. 
       
    
    
     DESCRIPTION OF THE DRAWING  
       [0009]    For a better understanding of the present invention as well as other objects and further features thereof, reference is made to the following description which is to be read in conjunction with the accompanying drawing therein:  
         [0010]    [0010]FIG. 1 is a schematic of a fill level apparatus modified in accordance with the teachings of the present invention;  
         [0011]    [0011]FIG. 2 is a schematic top view of the optical system of the present invention;  
         [0012]    [0012]FIG. 3 illustrates in more detail how the bottle fill level is detected, the output on a computer monitor being superimposed thereon; and  
         [0013]    [0013]FIG. 4 illustrates the illumination return beam path. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0014]    Referring now to FIG. 1, a top view of a conventional beverage filler system  8  used to fill and measure, or inspect, cola, beer and water bottles is illustrated. The bottles  10  are fed into the rotating filler turret  12  by means of a chain type conveyor  14  moving in the direction of arrow  7 . A timing screw  16  spaces the bottles  10  into the infeed starwheel  18  which then places the bottles  10  into the rotating filler turret  12 . As the bottles  10  travel around the turret  12 , they are filled with the beverage and then placed into the transition starwheel  20  which hands them off to capper  22 . Bottles  10  are fed from capper  22  into the outfeed starwheel  24  which deposits them on the outfeed conveyor  26 . The bottles are precisely indexed from the infeed starwheel  18  through the filler turret  12 , transition starwheel  20 , capper  22  and into the outfeed starwheel  24 . Precise indexing is required since the filler system  8  operates at a high rate of speed ( up to 1200 bottles per minute) and any deviation in bottle placement can cause damage to the bottles and/or filling equipment. The bottles  10  from infeed starwheel  18  are placed on a bottom stirrup in filler turret  12  at position  15 . Each of the stirrups are movable in the vertical direction and are lifted by a mechanism, such as a cam, so that the top of each bottle  10  is engaged into a filling cup at position  21 . The cup seals the internal volume of the bottle from normal atmospheric conditions. A vacuum is applied to each bottle  10  and the filler enables the fluid beverage to flow into the bottle (the vacuum allows the bottles to be filled rapidly and minimizes foaming in the carbonated beverages). The bottles are filled with liquid by the time the bottles reach position  17  and are then lowered by a cam to the same level they were in infeed starwheel  18 . As the stirrup is lowered to the proper position, bottles  10  are handed off to transistion starwheeel  20  and then fed to capper  22 . Prior to capping, carbonated beverages are jetted with liquid or gas that makes the beverage foam, the foam displacing any air in the volume between the liquid level and the top  23  of bottle  10  (headspace).  
         [0015]    In accordance with the teachings of the present invention, the conventional method of measuring bottle fill levels downstream from the capping station is modified by measuring the fill level when the bottles are still positioned on the rotating turret  12 . In particular, a plurality of targets  30 , each comprised of a vertical panel preferably rectangular in shape), are mounted to backplates positioned behind each bottle turret position on filler turret  12  so it overlaps the entire range of fill level positions  13  in the vertical direction (FIGS.  3 ( a )- 3 ( c )). Targets  30  comprise a material that diffuses the incident light beam  9  in such a manner that the image  19  of an illumination source  36  is formed on each target  30  as shown in FIG. 3. In this regard, conventional reflective targets will not function since “backlighting” is needed as a light source for the imaging system of the present invention. Corner-reflective tape, such as those manufactured by the 3M Company, Mineapolis, Minn., or similar material, are the preferred target material. Specifically, the characteristics of the target material are such that it must not reflect a major portion of the incident illumination; otherwise it will not function as the required secondary light source behind the bottles (paper has these characteristics also). A video camera  38  is positioned so its field of view  40  is placed over the fill level range of the bottles  10  being filled. The image of the light source on the target  30  is viewed by the camera  38  as it looks through the neck of each bottle  10  as they are moved pass camera  38  by the turret  12 .  
         [0016]    The light source image  19 , as viewed by camera  38 , appears in different formats depending upon the fill level  13   a ,  13   b  and  13   c  in each bottle  10 . FIGS.  3 ( a )- 3 ( c ) illustrate these images assuming that no image distortion takes place as the light from the bright image on the targets  30  travel through the bottle neck back to the camera  38 . As the bottles  10  pass in front of line of sight between each target  30  and camera  38 , the image  19  of the bottle  10  will sweep across the camera field of view  40 . Since the bottle  10  is cylindrical in shape, the portion containing the liquid acts as a lens and offsets the target image from the bottle centerline  27  based on the liquid level as shown in FIGS.  3  ( a )- 3 ( b ), and  3 ( c ) for an underfilled (image  19 A), properly filled (image  19 B) and an overfilled bottle (image  19 C), respectively. FIG. 4 is a simplified top view illustrating the return beam path when no liquid is present ( 19 A) and when liquid is present ( 19 B and  19 C). The lens action of the liquid in the bottle neck can be clearly seen in FIG. 4 as the beams incident on the liquid are refracted toward the denser medium.  
         [0017]    An intense source of light which can provide a sharply focused beam  9  is preferred since much of the illumination is lost on the type of target that must be used to form the back lighted source for inspection. A laser whose spectral output can be sensed by video camera  38  is the preferred source of illumination. For optimum inspection purposes, the light source  36  is activated at all times since the images of the bottle necks rapidly sweep across the camera field of view  40 . This requirement essentially precludes the use of strobe light sources; other filament sources are not typically bright enough and have limited life.  
         [0018]    The camera field of view  40  may be calibrated so the received image gives the exact fill level in each bottle. The information from this image, after calibration, can be used for graduated fill level measurements and for controlling the filler valves.  
         [0019]    While the invention has been described with reference to its preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its essential teachings.