Patent Publication Number: US-6666142-B1

Title: Switch key tool for use in changing switch knob settings on a laser guided bomb

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a hand tool which allows a user to change the switch settings on a laser guided bombs and the like. More particularly, the present invention relates to a hand tool which allows a user to change the switch settings on a laser guided bomb when the PRF (pulse repetition frequency) code switch knobs on a laser guided are broken or lost during flight. 
     2. Description of the Prior Art 
     Laser Guided Bombs and Guided Bomb Units include guided control units, computer control groups or control sections which control the operation of the bombs. Each guided control unit or computer control group has a plurality of Pulse Repetition Frequency (PRF) Code switch knobs which are used to set the pulse repetition frequency for the Laser Guided Bomb. 
     There have been several occurrences in the past where the PRF code switch knobs have either been broken or lost. Without the switch knobs the laser guided bombs are rendered nonoperative since the switch knobs cannot be reattached externally. The PRF switch knobs are fabricated from plastic or other polymer and are secured to the knobs shaft by a retaining set screw. The threaded area of the knob which receives the set screw expands over time which loosens the set screw causing the knob to separate from its shaft and the bomb. 
     In addition, repeated use of the bomb for testing and harsh environments will often cause the switch knobs to separate from their shafts again rendering the laser guided bombs non-operative. 
     Currently, when the switch knobs are missing from a laser guided bomb, the bomb is sent to a rework facility for replacement of the missing switch knobs. Since the bombs have to be dis-assembled to replace the missing switch knobs and there are shipping cost associated with the transfer of a bomb to a rework facility, the cost to replace a bomb&#39;s switch knobs can be several thousand dollars. 
     Accordingly, there is a need to provide an apparatus or tool which will allow a user to set the pulse repetition switch knobs on a laser guided bomb to a pulse repetition code for the laser guided bomb. In addition, the tool needs to have the capability of allowing a user to set the pulse repetition frequency for a laser guided bomb when one or more of the PRF switch knobs are broken or missing. It is also desirable that the tool be inexpensive, easy to fabricate, lightweight and portable. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes some of the disadvantages of the past including those mentioned above in that it comprises a relatively simple in design yet highly effective and efficient switch key tool which allows a user to change the switch knob setting on a laser guided bomb and thereby change the pulse repetition frequency for the bomb. 
     The switch key tool has a cylindrical shaped body, a rectangular shaped member at one end and a “D” shaped opening at the opposite end of the tool. A user inserts the rectangular member into an elongated opening within the switch knob to change the switch knob setting. A first elongated white identification line on the black surface of the housing for switch key tool identifies for the user the current setting of the switch knob and provides a means for the user to set the switch knob to the new/required setting. 
     When the switch knob is missing, the user slides the “D” shaped opening of switch key tool over the shaft for the missing switch knob to change the PRF code setting for the missing knob. A second elongated white identification line on the black surface of the housing for switch key tool identifies for the user the current setting when the switch knob is missing and provides a means for the user to set the switch knob&#39;s shaft to the new/required setting. 
     The switch key tool also has a U shaped handle which allows a user to attach the tool to a utility belt. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a partial sectional view of a laser guided bomb including the switch knobs for setting the pulse repetition frequency code for the bomb; 
     FIGS. 2 and 3 illustrate side views of the switch key tool for use in changing switch knob settings on a laser guided bomb; 
     FIGS. 4 and 5 illustrate end views of the switch key tool depicted in FIGS. 2 and 3; and 
     FIG. 6 is a perspective view of the switch key tool being used to change the pulse repetition frequency for a laser guided bomb 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1,  2  and  3 , laser guide bombs and guided bomb units have a plurality of switch knobs  22  and  24  which allow a user to set the pulse repetition code for the bomb  28  prior to deployment of bomb  28  for testing or some other purpose. Each switch knob  22  and  24  Us recessed within a cylindrical shaped opening  30  extending from the outer surface  32  of the bomb  28  in the manner illustrated in FIG.  1 . Around the periphery of the cylindrical shaped openings  30  are numbers or reference numerals by which a user sets the pulse repetition frequency code for the laser guided bomb  30 . For example, the numbers around switch knob  24  are  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7  and  8 , while the numbers around switch knob  22  are  4 ,  5 ,  6 ,  7  and  8 . There is also a “SKIP  1 ” and “SKIP  2 ” as well as a “STD LGB” around switch knob  22 . 
     The opening  30  with the numbers  5 ,  6  and  7  is empty. Adjacent this opening on the surface  32  of bomb  28  is a circle  33  with a line extending inward. 
     As shown in FIG. 1, the opening  30  between switch knobs  22  and  24  is missing its switch knob leaving only a switch knob shaft  38  within the opening. 
     Each switch knob has a white one digit code identification line  34  on its top surface which identifies the position setting for the switch knob. The identification line  34  for each switch knob extends from the center of the knob to its periphery and is generally engraved into the top surface of switch knob. Each switch knobs also has an elongated slot  36  which is centrally located within each switch knob and is positioned perpendicular to the identification line  34 . A tool, such as the switch key tool comprising the present invention when inserted into slot  34  allows the user to set the switch knob to the desired PRF code bit. 
     The switch knobs  22  and  24  are secured to their shafts by a set screw. The threaded area of the knob which receives the set screw expands over time which loosens the set screw causing the knob to separate from its shaft and the bomb. 
     Referring to FIGS.1,  2  and  3 , the switch key tool, designated generally by the reference numeral  40 , is used to set the switch knobs  22  and  24  to the desired pulse repetition code. In addition, the opening  30  between switch knobs  22  and  24  is missing its switch knob leaving only generally “D” shaped switch knob shaft  38  within the opening  30 . The switch key tool  40  can be used to set the switch knob shaft to the position associated with a one digit PRF code number the user needs to enter to activate the laser guided bomb. 
     Referring to FIGS. 1-5, switch key tool  40  has a cylindrical shaped body  42  which is approximately five inches in length and has a diameter of approximately six tenths of an inch. One end  43  of the cylindrical shaped body  42  of switch key tool  40  has a generally rectangular shaped member  44  which is designed to fit within the elongated slot  36  for each switch knob  22  and  24 . Rectangular shaped member  44  is approximately 0.350 inches wide by 0.100 inches deep which insures that member  44  will fit securely slot  36  for each switch knob  22  and  24 . The other end  45  of the cylindrical shaped body  42  of switch key tool  30  has an opening  46  which is “D” shaped and is designed to slide over the switch knob shaft  38  of a missing switch knob. A portion  47  of each end  43  and  45  is angled at approximately 45° for approximately one tenth of inch to align switch key tool  40  with openings  30 . This makes for easy insertion of the switch key tool  40  into each of the openings  30  within the outer surface  32  of the bomb  28 . 
     At this time it should be noted that switch key tool  40  is fabricated from aluminum. 
     Positioned at the ends of cylindrical shaped body  42  are a pair of engraved code bit identification lines  48  and  50 . Each identification line  48  and  50  is white in color such that the lines  48  and  50  stand out from the body of switch key tool  30 . Lines  48  and  50  are perpendicular to member  44  and are in alignment with the one digit code identification line  34  on each of the switch knobs  22  and  24  when member  44  is inserted in the slot  36  for one of the switch knobs  22  or  24 . Thus, the identification lines function in exactly the same manner as the white one digit code identification line  34  on the switch knobs  22  and  24 . This allows a user to set the pulse repetition frequency (PRF) code for the laser guided bomb regardless of whether or not the switch knobs are broken or missing. 
     The cylindrical shaped body  42  of switch key tool  40  has a flat surface  52  which is indented into the surface of body  42  about one tenth of an inch. Engraved lettering in the flat surface  52  read as follows: “GBU-CCG” and “SWITCH KEY” with “SWITCH KEY” being positioned below “GBU-CCG”. The lettering is white in color to distinguish the lettering from the black of the cylindrical shaped body  42 . The lettering allows the user to identify the tool and its intended use which is to set the PRF code for the laser guided bomb  28 . Positioned 180° from the engraved lettering on flat surface  52  is the part number “1393AS450” for switch key tool  40 . This lettering is also engraved and white in color to distinguish the lettering from the black of the cylindrical shaped body  42 . 
     The switch key tool  40  has a U-shaped handle  54  in proximity to end  43 . U-shaped handle  54  provides a means for a user to carry the switch key tool  40  on a tool belt. 
     Referring to FIG. 6, switch key tool  40  is shown in proximity to the switch knob  24 . The user then inserts member  44  of switch key tool  40  into the elongated slot  36  within switch knob  36  to change the PRF code setting for switch knob  36 . Code bit identification line  48  identifies for the user of switch key code tool  40  the particular setting at which the switch knob  36  currently resides and also allows the user to verify that the new setting for switch knob  36 . Thus, for example, when the user needs to change the setting for knob  24  from its current setting of “ 3 ” (as best seen in FIG. 1) to a setting of “ 6 ” the user will rotate switch key tool  40  clockwise until line  48  is in alignment with the numeral “ 6 ”. 
     From the foregoing it may readily be seen that the present invention comprises a new, unique and exceedingly useful switch key tool for use in changing switch settings on a laser guided bomb which constitutes a considerable improvement over the known prior art. Obviously, many modifications of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims that the invention may be practiced otherwise than as specifically described.