Abstract:
The disclosed roller switch has a roller, a flag arm, and a photoelectric detector. The roller is connected to the flag arm and vertical movement of the roller causes the flag arm to move. The movement of the flag arm causes the photoelectric detector to send a signal. The signal may be used to measure the length of a material passing under the roller. The inventive roller switch has a pair of flag arms, and the roller is mounted on a shaft extending between the pair of flag arms. By providing a pair of flag arms connected by the roller, the roller switch is more robust and durable. The roller switch is also capable of pivoting across a conveyor belt.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to a roller switch. Specifically, the invention is directed to a roller switch for sensing the leading edge of a material on a conveyor belt, which triggers a sensor to determine the length of the material on the conveyor belt.  
         BACKGROUND OF THE INVENTION  
         [0002]    In tire manufacturing, stock material of various types is applied to a building drum. The stock materials are cut to a required length. The cutting of the stock material occurs either at the building drum, or prior to arriving at the building drum. If the stock material is cut at the building drum, the strip length is determined by the tire builder or by a sensor. If the stock material is to be cut automatically, to reduce waste, the length of the stock must be accurately measured.  
           [0003]    One method of measuring stock material is the roller switch  100  illustrated in FIG. 4. The roller switch  100 , mounted along the side of a conveyor belt carrying the stock material, has a mounting bracket  102 , a sensor bracket  104 , a roller  106 , and a flag arm  108 . The roller  106 , which extends only a partial distance across the conveyor, is related to the flag arm  108  and the related roller  106  and arm  108  pivot about a shaft  110 . The flag arm  108  is formed of a lightweight material and is spring biased to maintain its position when the switch  100  is not in operation. The side  112  of the flag arm  108  that is adjacent to a photoeye mounted within the sensor bracket  104  is covered in a reflective tape.  
           [0004]    At the illustrated rest, or non-sensing, position, the flag arm  108  is not directly adjacent to the photoeye. When material travels under the roller  106 , the roller  106  is pushed up, and due to the connection between the roller  106  and the flag arm  108 , the flag arm  108  moves and the side of the arm  112  covered in reflective tape is then positioned adjacent to the photoeye. Due to the reflective taping on the flag arm  112 , light is directed back to the photoeye and a sensor is triggered to indicate that material is now traveling under the roller  106  and measurement of the length of the material is taken.  
           [0005]    While this roller switch  100  has been sufficient, it has not proven to be reliable for extended periods of time due to the following problems. The photoeye is triggered by reflective tape; however, the tape can quickly become dirty and thus unreliable, requiring down time to clean the switch. The unit is also susceptible to being knocked out of adjustment. This can occur if the material traveling on the conveyor gets bunched up or is too thick and hits the roller  106 . Additionally, if the thickness of the material is too great, the flag arm  112  may travel past the photoeye, providing an incorrect indication. Also, the switch is easily knock out of adjustment during the removal of stock. Stock is frequently removed from the conveyor for a variety of reasons.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is designed to overcome the limitations of the known mechanism. The roller switch is more robust than the known conventional roller switches.  
           [0007]    The disclosed roller switch has a roller, a flag arm, and a photoelectric detector. The roller is connected to the flag arm and vertical movement of the roller causes the flag arm to move. The movement of the flag arm causes the photoelectric detector to send a signal. The signal may be used to measure the length of a material passing under the roller. The inventive roller switch has a pair of flag arms, and the roller is mounted on a shaft extending between the pair of flag arms. By providing a pair of flag arms connected by the roller, the roller switch is more robust and durable.  
           [0008]    In one aspect of the invention, to further increase the robust character of the roller switch, a tube extending between the flag arms is located adjacent to the roller. When material passes under the roller switch, the material must first pass under the tube.  
           [0009]    In another aspect of the invention, the vertical movement of the roller cause the upper end of the flag arm to unblock the photoelectric detector.  
           [0010]    In another aspect of the roller switch, the roller switch is capable of pivoting about one end when mounted onto a support structure. Pivoting of the entire unit allows for easier servicing of the roller switch and makes it easier to remove any material from beneath the roller switch.  
           [0011]    In another aspect of the roller switch, each flag arm is attached to an end plate. The first end plate is attached to pivoting means and the second end plate is attached to locking tube into which a locking pin is inserted. The roller switch pivots about the first end plate when the locking pin is removed from the tube.  
           [0012]    Also disclosed is a method of measuring the length of a finite length strip material. The method includes the steps of placing the material on a moving conveyor belt, passing the material under a roller, causing the roller to vertically move, pivoting a flag arm in response to the movement of the roller, generating a signal in response to the movement of the flag arm, and measuring the length of the material. In the inventive method disclosed, the material passed under a tube prior to passing under the roller and the flag arm pivots about a shaft extending through the tube. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The invention will be described by way of example and with reference to the accompanying drawings in which:  
         [0014]    [0014]FIG. 1 is a perspective view of the roller switch;  
         [0015]    [0015]FIG. 2 is a cross sectional view of the roller assembly;  
         [0016]    [0016]FIG. 3 is a perspective view of the roller switch from a different view; and  
         [0017]    [0017]FIG. 4 is a cross sectional view of a prior art switch. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    [0018]FIG. 1 illustrates the roller switch  2  of the present invention. The roller switch  2  is mounted on railings  4  astride a conveyor belt  6 . The roller switch  2  has a roller assembly  8 , a photoelectric switch  10 , and a pivot assembly  12 . The roller assembly  8  extends between two end plates  14  mounted on support plates  16 . The support plates  16  are secured to angle brackets  18  that are attached to the railings  4 . Extending between the end plates  14  is a support beam  20 .  
         [0019]    The roller assembly  8  has a roller  22 , a protective tube  24 , and side flag arms  26 . The roller assembly  8  pivots on a pivot shaft  28  that extends through the protective tube  24 . The roller  22  is mounted in a rotatable manner on a roller shaft  30 . The roller shaft  30  and the protective tube  24  are secured to the side flag arms  26 . The protective tube  24  may extend beyond the flag arms  26 . The pivot shaft  28  extends beyond the flag arms  26  and attaches to the end plates  14  to permit the roller assembly  8  to pivot.  
         [0020]    As seen in FIG. 2, each flag arm  26  has a horizontal leg  32  and a vertical leg  34 . The roller shaft  30  and the protective tube  24  are secured at one end of the horizontal leg  32 . Midway along the horizontal leg  32  is an adjustable spring  36  to tension and maintain the position of the roller assembly  8 . The vertical leg  34  extends at approximately ninety degrees from the horizontal leg  32 . Along both legs  32 ,  34 , cut outs  38  reduce the weight of the arms  26 . The size and configuration of the cut outs  38  are selected to reduce the weight while maintaining the structural integrity of the arms  26 . Whatever the placement of the cut outs  38 , the uppermost end  35  of the vertical leg  34  remains solid.  
         [0021]    Mounted on one end of the support beam  20  is a photoeye bracket  40 , see FIG. 3. A photoeye emitter  42  is mounted within in one leg  44  of the bracket  40  and a corresponding receiver is mounted within the opposing leg  44 . The photoeye bracket  40  is positioned so the vertical leg  34  of the flag arm  26  is midway between the bracket legs  44 . The photoeye bracket  40  may be mounted at either end of the beam  20 .  
         [0022]    Stock travels on the conveyor belt  6  in the direction shown by the arrow D. The stock passes under the protective tube  24 , and then contacts the roller  22 . If the stock is not moving smoothly along on the conveyor belt  6 , but is instead bundled up or traveling as a mass instead of a sheet, the stock will hit the protective tube  24  first, instead of the roller  22 .  
         [0023]    As the stock passed under the roller  22 , the roller  22  is vertically raised, causing the roller assembly  8  to pivot about the pivot shaft  28 . As the one end of the horizontal leg  32  is raised, the other end of the leg  32  is lower, pulling the vertical leg  34  of the flag arm  26  down and the uppermost end  35  of the vertical leg  34  out of alignment with the photoeye  42 . Thus, when there is no stock passing under the roller  22 , the photoeye  42  is blocked, and when there is stock passing under the roller  22 , the photoeye  42  is not blocked. Because the vertical leg  34  of the flag arm  26  is pulled down due to the pivoting motion of the roller assembly  8 , regardless of the thickness of the stock passing under the roller  22 , the flag arm  26  will not inadvertently block the photoeye  42 , sending an incorrect signal. When the photoeye  42  is tripped by the movement of the flag arm  26 , a signal is sent to a measuring device (not illustrated), and measurement of the length of the material moving along the conveyor belt  6  begins.  
         [0024]    The roller assembly  8  is adjusted and tensioned so that when there is no stock on the conveyor belt  6  passing under the roller  22 , the roller  22  is spaced above the surface of the conveyor belt  6 . The spacing between the roller  22  and the surface of the conveyor belt  6  is selected to be less than the thickness of the stock, including any thickness tolerances, that will travel under the roller  22 . The spacing must also be sufficient to permit the end  35  of the vertical leg  34  of the flag arm  26  to move out of alignment with the photoeye  42  when stock passes under the roller  22 . For a stock thickness of 2 to 3 mm, a preferred spacing between the roller  22  and the surface of the conveyor belt  6  is about 0.5 mm.  
         [0025]    The roller  22  is illustrated as having a length of about one half the length of the roller shaft  30 . However, the roller  22  may have any length equal or less than the roller shaft  30 . The roller  22  may also be mounted on the other end of the roller shaft  30  than that which is illustrated, or may be mounted in a central position on the shaft. The primary requirement for the roller position is that the roller  22  be in a location that permits the leading edge of the stock to contact the roller  22 .  
         [0026]    The pivot assembly  12  permits the roller switch  2  to be swung to one side of the conveyor belt  6 . On the pivoting side of the roller switch  2 , the end plate  14  is attached to a support sleeve  46 . Inside the sleeve  46  is a bearing sleeve  48  about which the support sleeve  46  rotates.  
         [0027]    On the locking side of the switch  2 , a vertical sleeve  50  is attached to the other end plate  14 . Extending upwardly from the associated support plate  16  is a sleeve  52 . When the support plate sleeve  52  is aligned with the vertical sleeve  50 , a ball locking pin  54  is inserted therein to prevent movement of the roller switch  2 .  
         [0028]    Located adjacent to the sleeves  50 ,  52  is a raising pin  56 . The pin  56  is inserted into a hole  57  within the end plate  14  and extends through the other side of the plate  14 . The pin  56  extends out from the end plate  14  at a height less than the height of the support plate sleeve  52 . During normal operation of the roller switch  2 , the pin  56  is inserted into the end plate  14  to a depth such that the pin  56  does not interfere with the arm  26 , see also FIG. 2. When the roller switch  2  is to be pivoted, the roller  22  is manually raised, and the pin  56  is pushed further in. The pin  56  is pushed in to a depth so that the pin is under the horizontal arm  32  and the arm  32  rests on the pin  56 , thus moving the roller  22  out of the way during pivoting and any maintenance of the switch  2 . Also, the depth should be such that the end of the pin  56  will pass by the sleeve  52  when the roller switch  2  is pivoted. Should the pin  54  not be pushed in, as the roller switch  2  begins to swing, the pin  56  will contact the support plate sleeve  52 , stopping movement of the roller switch  2 .  
         [0029]    The selection of which side of the roller switch  2  is the locking side and which is the pivoting side is arbitrary and is best determined by ease of operation. The roller switch  2  may be pivoted to one side of the conveyor belt  6  for various reasons such as removal of stock from the conveyor belt  6 , adjusting the tension of the roller assembly  8 , or routine maintenance of the switch  2 .  
         [0030]    By providing the roller switch  2  with support at both ends, as opposed to the cantilever design of the conventional roller switch  100 , the switch  2  is more robust and less susceptible to damage. Furthermore, by extending the roller shaft  30  across the full width of the conveyor belt  6 , the length and the position of the sensing roller  22  may be readily altered for any material width or configuration of material carried on the conveyor belt  6 , such as material with a taped leading edge or adjacent lengths of material.  
         [0031]    Also, by reversing the conventional method of tripping the photoeye  42 , greater accuracy and less false trips in the detection of material beneath the roller switch  2  is achieved.  
         [0032]    Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full-intended scope of the invention as defined by the following appended claims.