Using variable inductance to indicate roller wear

#This invention relates to the method and apparatus for indicating roller wear in a media handling device. Such structures of this type, generally, employ the use of variable inductance to determine roller wear. The media transport roller has a non-conductive surface with a conductive core. Located just above the conductive core is a rod containing a power coil that is driven by AC excitation and a pick-up coil. The pick-up coil is connected to circuitry that measures the inductance. As the media transport roller wears, the conductive core moves closer to an inductive pick-up unit. The measured output voltage from the pick-up unit depends upon the distance between the core and the pick-up unit. This inductance change can then be correlated to media transport roller wear and relayed to the user through the use of an LED or other similar types of graphical/numerical displays.

#Prior to the present invention, as set forth in general terms above and more specifically below, it is known, in the media handling device art, to make use of a device for determining roller wear. Exemplary of such prior art is U.S. Pat. No. 6,055,047 ('047) to A. Schweizer et al., entitled “Device for Determining the Degree of Wear of a Paper Transport Roller.” The '047 reference discloses a paper transport roller which comprises two layers having different degrees of reflection for electromagnetic radiation. When the outer layer is worn, the degree of reflection of the surface of the paper transport roller changes and the user is signaled that paper transport roller must be replaced. However, if a foreign object becomes attached to the transport roller of the '047 reference, this foreign object could adversely affect the reflection characteristics of the device. Also, if the paper transport roller does not wear evenly, one edge of the roller may have a different degree of reflection than the other edge of the roller and, possibly, adversely affect the reflection characteristics of the device. Therefore, a more advantageous paper transport roller wear indication system, then, would be presented if the system did not have to rely on a paper transport roller which comprises two layers having different degrees of reflection.

#It is apparent from the above that there exists a need in the art for a paper transport roller wear indication system which is lightweight through simplicity of parts and uniqueness of structure, and which these equals the wear indication characteristics of the known paper transport roller wear indication systems, but which at the same time employs variable inductance which will alert the user to the worn condition of the paper transport roller. 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.

#FIG. 1 is a schematic illustration of a media transport roller wear indicating system, according to one embodiment of the present invention;

#FIG. 2 is a schematic illustration of a media transport roller wear indicating system, according another embodiment of the present; and

#FIG. 3 is a side view, schematic illustration of a media transport roller wear indicating system, according to still another embodiment of the present invention.

#With reference to FIG. 1, there is illustrated one preferred embodiment for use of the concepts of this invention. Media transport roller wear indicating system 2 for indicating media transport roller wear is illustrated in FIG. 1. System 2 includes, in part, media handling device 3, conventional media transport roller 4, conductive core 6, conventional pick-up unit rod 8, conventional pick-up unit power coil 9, conventional pick-up unit pick-up coil 10, conventional variable inductance measurement means 11, conventional hard stop 12, conventional media transport roller rotation counting means 14, and media transport roller wear indicating/display means 16. It is to be understood that a conventional pick-up unit consists of rod 8, pick-up unit power coil 9, and pick-up coil 10.

#Media handling device 3 can be, but is not limited to, a paper handler, a printer, a copier, a facsimile machine, a printing device or the like. It is to be understood that media transport roller 4, preferably, is a conventional pick-up media transport roller that moves up and down along the directions of arrow A. Conductive core 6 is, preferably, constructed of any suitable, durable, conductive material that is capable of conducting electricity. It is being understood that any suitable, durable, non-conductive material, such as rubber, can be used in media transport roller 4 to conventionally encircle conductive core 6. Hard stop 12, preferably, is constructed of any suitable, durable, non-conductive material, such as a polymeric material, that does not adversely affect the wear characteristics of media transport roller 4.

#is to be understood that hard stop 12 provides a reference point to determine a change in variable inductance. What is meant by this is that media transport roller 4 initially contacts hard stop 12. The initial distance between conductive core 6 and pick-up coil 10 can be measured to provide an initial/reference variable inductance.