Abstract:
This invention relates to gap/edge bead detection systems. Such structures of this type, generally, employ the use of fiber optic sensor assemblies positioned at the edges of the web and/or between gaps in the sheets in order to detect the absence of material.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to gap/edge bead detection systems. Such structures of this type, generally, employ the use of fiber optic sensor assemblies positioned at the edges of the web and/or between gaps in the sheets in order to detect the absence of material. 
     2. Description of the Related Art 
     Extrusion coating is a process where a moving paper web is coated with a molten polymer layer. The polymer layer usually extends beyond the paper web, thereby creating a “polymer edge bead”. It is important that the polymer bead be present to insure that the entire web has been coated. Some polymers are difficult to control at the extrusion extremities of the paper web and/or sheet. These polymers are subject to occasional and unpredictable “wicking in”, i.e., the edge of the polymer layer moves inside the edge of the paper web. This “wicking in” can be as much as several inches and may continue for just a few seconds or sometimes until corrective action is taken by the operator. Also, the absence of polymer along the entire web is a serious quality defect that can be catastrophic for the customer&#39;s product. 
     It is known to employ detection systems that use cameras to monitor the web. However, these are very expensive and highly sensitive. Also, these systems often require the web to be shielded from the surroundings. 
     It is also known to employ photo sensors to inspect a material edge and control process conditions within tolerances required by production. Exemplary of such prior art is U.S. Pat. No. 4,357,899 (&#39;899) to Jones et al., entitled “Coating Apparatus”. The major focus of the &#39;899 reference is in controlling a liquid coating process through reservoir design tanks. However, the inspection system of the &#39;899 reference cannot be employed on both a sheeting machine where it senses the gap between sheets and on an extrusion coating line where it senses the presence or absence of a polymer coating at the edge of a continuous sheet. 
     Therefore, it is apparent from the above that there exists a need in the art for a highly accurate and economically reliable gap and edge bead detection for a variety of extruded coatings. The detection system should function without regard to material characteristics such as color, temperature, thickness or chemical make-up. The chemical system should also be unaffected by the physical surroundings. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure. 
     SUMMARY OF THE INVENTION 
     Generally speaking, this invention fulfills. these needs by providing an edge bead detection system, comprising a frame means, a length of material having a coating located over a portion of the length of material, a slidable mounting means operatively connected to the frame means, an edge bead detection means operatively connected to the mounting means and located a predetermined distance away from the length of material, and a retaining means operatively connected to the mounting means. 
     In another further preferred embodiment, the detection system is capable of sensing the gap between sheets and the presence or absence of polymer coating along the edge of a continuous sheet without regard to material characteristics such a color, temperature, thickness or chemical make-up. Also, the detection system is unaffected by the physical surroundings. 
     The preferred system, according to this invention, offers the following advantages: lightness in weight; ease of assembly and repair; good stability; good durability; excellent economy; excellent detection characteristics; excellent sensing characteristics; mobility of location and relocation; physical protection; and ability to realign. In fact, in many of the preferred embodiments, these factors of detection, sensing, mobility of location and relocation, physical protection, and ability to realign are optimized to the extent that is considerably higher than heretofore achieved in prior, known detection systems. 
    
    
     The above and other features of the present invention, which will become more apparent as the description proceeds, are best understood by considering the following detailed description in conjunction with the accompanying drawings, wherein like characters represent like parts throughout the several views and in which: 
     A BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a gap/edge bead detection system, according to the present invention; 
     FIG. 2 is an isometric view of the slidable mount which is attached to the gap/edge bead detection means, according to the present invention; 
     FIG. 3 is a side, plain view of the gap/edge bead detection means, according to the present invention; and 
     FIG. 4 is an end view, taken along line  4 — 4  of FIG. 3, of the gap/edge bead detection means. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference first to FIG. 1, there is illustrated an advantageous environment for use of the concepts of this invention. In particular, gap/edge bead detection system  2  is illustrated. System  2  includes, in part, length of material  3 , frame  4 , conventionally extruded coating  5 , bracket  6 , mid support  8 , removable cover  10 , raising/lowering latch mechanism  50 , and gap/edge bead detection mechanism  100 . Preferably, frame  4 , bracket  6 , mid support  8  and cover  10  are constructed of any suitable, durable material. Frame  4  is rigidly attached to bracket  6  and mid support  8  by conventional techniques. Length of material  3  can either be a length of a conventional roll of material or a length of a conventional sheet of material. Cover  10  can be conventionally removed in order to allow ease of frame alignment during installation. 
     As shown in FIG. 2, latch mechanism  50  is illustrated. Mechanism  50  includes, in part, base  52 , guide  54 , arm  56 , arm  58 , extension  60 , stop  62 , pivot base  64 , pivot  66 , arm  68 , pivot  70 , pivot base  72 , arm  74 , gap/edge bead detector holder  76  and gap/edge bead detector mechanism  100 . 
     Preferably, base  52 , guide  54 , arm  56 , arm  58 , extension  60 , pivot base  64 , pivot  66 , arm  68 , pivot  70 , pivot base  72 , arm  74 , and gap/edge bead detector holder  76  are constructed of any suitable, durable material. Stop  62 , preferably, is constructed of any suitable material which, when interacting with frame  4 , prevents mechanism  50  from sliding along the direction of arrow X (FIG.  1 ). 
     The construction of base  52  and guide  54  should be such that it fits over frame  4  and easily slides along the direction of arrow X (FIG.  1 ). Pivot base  64  is rigidly attached to base  52  by conventional techniques. Arms  56  and  58  are conventionally latched to base  64  by latch  66  such that when arm  56  is pulled up away from frame  4 , arm  58  pivots up and raises extension  60  and stop  62  away from frame  4 . In this manner, base  52  is able to slide along frame  4  in the direction of arrow X (FIG.  1 ). 
     Arm  68  is pivotedly attached to arm  74  at pivot  70 . Pivot  70  is conventionally attached to pivot base  72 . Pivot base  72  is conventionally attached to base  52 . In this manner, when arm  68  is pushed down towards frame  4 , this causes gap/edge bead detection mechanism  100  to raise above length of material  3  which is traveling in the direction of arrow Y (FIG.  1 ). 
     FIG. 3 more clearly illustrates gap/edge bead detection mechanism  100 . Mechanism  100  includes, in part, conventional coiled spring  102 , conventional bushing  104 , conventional fiber optic sensor head  106 , and conventional sensor cable head  108 . Sensor cable head  108  is conventionally attached to an electronic control unit (not shown) which controls the coating of length of material  3 . It is to be understood that the control unit can be connected to a conventional alarm system (not shown) to alert the operator if mechanism  100  does not sense any coating. 
     As more clearly shown in FIG. 4, bushing  104  is constructed of an outside diameter which is slightly larger than the inside diameter of coiled spring  102 . This allows bushing  104  to be pressure fitted into the end of coiled spring  102 . The center of bushing  104  is conventionally drilled and tapped to allow sensor head  106  to be screwed into bushing  104 . This provides infinite depth adjustment and a secure mounting for sensor head  106 . 
     The gap/edge bead detection system  2  is manually operated and provides for two detection systems, one on each edge of the paper web. The horizontal location of detection mechanism  100  is infinitely variable. The operator simply slides the detection mechanism  100  to match the edge of length  3  being processed. The vertical gap between detection mechanism  100  and edge bead  5  is fixed and maintained by latch mechanism  50 . Latch mechanism  50  is in working position when lowered. The vertical position is also shown as a manual operation. These two positioning functions can be automated using commercially available position technology and engineering. 
     Sensor mechanism  100  consists of a fiber optic bundle and spring assembly. The purpose of spring  102  is to allow for process upsets, such as web breaks, to occur without destroying detection mechanism  100 . Detection mechanism  100  can bend out of the way if contacted by a portion of length of material  3  during an upset. For example, the tail of the previous roll retained with in the web on a splice can flap into the air and strike detection mechanism  100 . Spring  102  serves as a shield and is self-aligning in that it also brings sensor head  106  back into the proper position to resume gap/edge bead detection. 
     It is to be understood that detection mechanism  100  can also employed to detect gaps between lengths of material  3 . In particular, detection mechanism  100  can be located in one position so as to detect an edge of coating  5  and also to detect when there is a gap between lengths of material  3 . 
     The fiber optic detection mechanism  100  was chosen for several reasons. Sensor head  106  reacts very quickly and is sensitive over a wide range of colors. Sensor head  106  is capable of detecting an object of only 0.001″ thickness even when laying on a solid surface. Sensor head  106  is autoreflective, i.e., it is self-contained, requiring only the present or absence of an object. An opposing light source or reflector of a through beam signal is not required. Finally, detection mechanism  100  is relatively inexpensive and highly reliable for millions of operations. 
     Finally, detection system  2  can be interfaced with any appropriate warning device (e.g., buzzer, lights) which is commercially available. A conventional web and/or sheet marketing system could also be interfaced with the detection system  2  to flag defective product. Also, detection system  2  can be conventionally connected to a conventional coater (not shown). In this manner, if a defect is detected by system  2 , an alarm may sound, the sheet may be marked and/or the coater may be activated to provide coating. 
     Once given the above disclosure, many other features, modifications or improvements will become apparent to the skilled artisan. Such features, modifications or improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.