Abstract:
A CATV filter assembled inside a housing has the housing marked by a laser system with indicia relating to specific characteristics of the filter. The housing is thus not mechanically deformed during the step of marking, resulting in unchanged RF characteristics of the filter as a result of the marking

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to the field of cable television (CATV) filters, and more particularly to laser marking for identification of a CATV filter. 
       BACKGROUND OF THE INVENTION 
       [0002]    Cable television (CATV) filters typically block channels from the full spectrum of channels offered to provide a limited or basic service to a subscriber at a lower price. Other CATV filters permit certain channels to pass through the filter while blocking the remainder. Because different models of filters block different groups of premium channels, the model numbers of the CATV filters are permanently printed, typically by roll stamping, into the metal housing of the filter. The filter tube is inserted into a support arbor after which raised hardened metal characters are rolled over the filter tube to leave an impression in the metal filter tube. Printed labels and ink labels are inadequate because of the filters&#39; exposure to the environment and become impossible to read after sufficient exposure to the elements. 
         [0003]    In addition, users are now requesting even more information to be permanently printed onto the filters, e.g., bar codes and/or serial numbers to control better the use of the filters. It is not practical to stamp such information on the filters using roll stamping. 
         [0004]    Furthermore, stamping can deform the housing and change the internal characteristics of the performance of the filter, which fact can cause elaborate work-arounds when fabricating CATV filters. 
       SUMMARY OF THE INVENTION 
       [0005]    Briefly stated, a CATV filter assembled inside a housing has the housing marked by a laser system with indicia relating to specific characteristics of the filter. The housing is thus not mechanically deformed during the step of marking, resulting in unchanged RF characteristics of the filter as a result of the marking. 
         [0006]    According to an embodiment of the invention, a method includes the steps of providing a CATV filter assembled inside a housing; and marking, with a laser system, an outside of the housing with indicia relating to specific characteristics of the filter, wherein the housing is not mechanically deformed during the step of marking, therein resulting in unchanged RF characteristics of the filter as a result of the step of marking 
         [0007]    According to an embodiment of the invention, a marked device includes a CATV fitter assembled inside a housing; and an outside of the housing being laser-marked by a laser system with indicia relating to specific characteristics of the filter, wherein the housing is not mechanically deformed during the marking, therein resulting in unchanged RF characteristics of the filter as a result of the marking. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows a laser system according to an embodiment of the present invention. 
           [0009]      FIG. 2  shows a schematic of the laser and laser control circuitry associated with the embodiment of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]    According to an embodiment of the invention, a workpiece such as an outer shell or sleeve of a cable TV system component, which component preferably being a trap or surface mount product, is marked with indicia relating to specific characteristics of the system component such as the part number or other information, with the indicia preferably being a logo, bar-coding, date-coding, 2-D Matrix, or similar. 
         [0011]    The marking is preferably done with a laser, and preferably an excimer laser or pulsed solid state laser such as the VersaScribe GM Laser Marking System manufactured by Alase Technologies, Inc. According to Alase, VersaScribe GM YAG Laser Engraving Systems are designed to bring precision, reliability, versatility, and speed to the most demanding applications, with WinLase Software allowing for applications ranging from deep engraving to fine surface annealing. 
         [0012]    The VersaScribe YAG laser features q-switched, flash lamp technology for high laser energy densities and proven reliability. The laser preferably operates in TEMoo mode. Because the internal Q-switch is software controlled, the operator has the flexibility to change the laser beam power characteristics for marking materials such as steel, aluminum and soft plastics. The VersaScribe laser is a high performance Nd:YAG Laser Marker, with 80 watts CW at 1064 nm. 
         [0013]    The laser marking is preferably done at 90% power, 4 Khz with a marking speed of 500 mm/sec. This setting is used for both the stainless and brass cases. The etch depth is no greater than 0.0002″ so that the base material is not exposed causing corrosion. 
         [0014]    Referring to  FIG. 1 , an optically enclosed shroud  10  is preferably placed over a laser  12  and workpiece (not shown) such that an operator can view the workpiece through a viewing window  14  laser safety viewing glass. Multiple interlocks to laser  12  preferably prevent operation of laser  12  with shroud  10  out of position. An “Emergency Stop” (not shown) is preferably located on a laser control box PLC ( FIG. 2 ) within easy reach of the operator at all times. A quick-release latching (not shown) on shroud  10  preferably allows access for maintenance. 
         [0015]    To maintain the focal point of etching on the workpiece, a fixture  16  is preferably of the shuttle type with exchangeable inserts to accommodate various sleeve types, with the diameters of the sleeve types ranging from a trap sleeve to a SMT sleeve. Fixture  16  is connected to a fixture plate  18 . Fixture plate  18  is in turn slideably connected via a shuttle groove  20  to a platform  24 . Fixture plate  18  is slideable in and out through an opening  26  in shroud  10  using a slide handle  22 . A large green LED  28  is preferably mounted in shroud  10  to indicate that laser  12  is inactive, with a red LED  30  to identify the active state. 
         [0016]    The process is as follows. The operator inserts the sleeve by hand into fixture  16  on fixture plate  18 . Fixture plate  18  is shuttled into shroud  10  by the operator via slide handle  22  until fixture plate  18  reaches a shuttle stop  36 . Laser  12  is preferably activated by a sensor such as limit switch  32  detecting the presence of fixture plate  18  and the sleeve. Upon completion of the laser etch, laser control PLC preferably activates a solenoid  34  which returns fixture plate  18  and fixture  16  for another unload/load cycle of the sleeve. A schematic for the laser and control circuitry is shown in  FIG. 2 . When the workpiece is a filter assembly which includes a housing and a filter disposed inside the housing, the housing is un-deformed by this laser marking operation. 
         [0017]    While the present invention has been described with reference to a particular preferred embodiment and the accompanying drawings, it will be understood by those skilled in the art that the invention is not limited to the preferred embodiment and that various modifications and the like could be made thereto without departing from the scope of the invention as defined in the following claims.