Loose end detector for tobacco articles

Abstract

A device for detecting loose ends in tobacco articles such as cigarettes comprises a stationary cam for positioning the articles prior to reaching a flat sensor surface. A pair of concentric electrodes are arranged on the sensor surface for generating an electric field. Cigarettes are moved through the field so as to create a field disturbance. Deviations from a predetermined field disturbance indicate that a cigarette is defective. A piece of thin glass, of about 5.5 mils, covers the sensor surface and is adhered thereto to protect against wear. Compared to surface protecting members previously used, the glass member significantly extends the wear life of the sensor, improves the sensitivity of the device, improves detection accuracy, and eliminates the need for daily readjustment of the field.

We claim: 
     
       1. In a device for sensing the density of tobacco comprising a flat sensor surface, means for generating a capacitance field emanating from said sensor surface, means for adjusting said capacitance field, means for moving a desired portion of a tobacco article past said sensor surface in contact therewith so as to move through the electric field, and a protective member covering said sensor surface to protect said sensor surface against wear, the improvement wherein said protective member comprises a thin piece of glass plate adhered to said sensor surface, whereby the wear life is extended indefinitely, the sensitivity of the field is enhanced, and variations in positioning the tobacco article in the field, due to localized wear of the protective member, are virtually eliminated. 
     
     
       2. A device according to claim 1, further comprising means for orienting tobacco articles generally perpendicular to said sensor surface and for moving tobacco ends of the articles past said sensor surface, and a stationary cam positioned for engaging tobacco ends of tobacco articles prior to said sensor surface for locating each tobacco end at a predetermined position to contact said sensor surface, wherein said protective member comprises a piece of glass covering both said cam and sensor surface to provide a continuous, smooth guide surface for the tobacco ends along said cam and sensor surface. 
     
     
       3. A device according to claim 2, wherein said glass has a thickness within a range of 4 mils to 40 mils. 
     
     
       4. A device according to claim 3, wherein said means for generating a capacitance field comprises a first electrode and an annular electrode concentrically arranged on said sensor surface. 
     
     
       5. A device according to claim 2, wherein said glass has a thickness of about 5.5 mils. 
     
     
       6. A method for improving the performance and service life of a device for sensing the density of tobacco, the device comprising a flat sensor surface, means for generating a capacitance field emanating from the sensor surface, and means for adjusting the capacitance field, comprising the steps of: providing a thin piece of glass plate; conforming the shape of said glass plate to the sensor surface; applying an adhesive between said glass plate and the sensor surface; and adhering said glass plate to the sensor surface. 
     
     
       7. A method according to claim 6, wherein the steps of applying adhesive and adhering said glass plate comprise applying a UV curing adhesive between said glass plate and the sensor surface; placing the glass plate on the sensor surface; forming a bubble free seal between the glass plate and sensor surface; and placing the device and glass plate under a UV curing light source to cure the adhesive. 
     
     
       8. A method according to claim 6, wherein the device further includes a stationary cam, the cam and sensor surface forming a bevelled surface on the device; wherein said glass plate is provided having a thickness of between 4 and 40 mils; and further comprising the steps of cutting said glass plate to a size to cover both the sensor surface and cam; shaping said glass plate in a bevelled, heated mold conforming to the bevelled surface of the device; and then adhering the bevel-shaped glass plate onto the bevelled surface of he device. 
     
     
       9. A method according to claim 8, wherein the steps of applying adhesive and adhering said glass plate comprise applying a UV curing adhesive to one of said glass plate and the bevelled surface of the device; placing the glass plate on the bevelled surface; forming a bubble free seal between the glass plate and bevelled surface; and placing the device and glass plate under a UV curing light source to cure the adhesive.