Patent Publication Number: US-7721631-B2

Title: Combined wrench and marking system

Description:
BACKGROUND INFORMATION 
   1. Field 
   The disclosure relates generally to a method and apparatus for installing fluid fittings and fasteners. More particularly, the present disclosure relates to a self-contained, combined wrench and marking system for installing and marking fluid fittings and fasteners, and to a method for installing and marking fluid fittings and fasteners. 
   2. Background 
   An aircraft includes many movable structures, for example and without limitation, wing flaps, vertical fins and ailerons, that are operated hydraulically. Accordingly, a typical aircraft may include many hydraulic lines that extend throughout the aircraft and that are comprised of numerous line sections joined together by fluid fittings. 
   The fittings are assembled to the line sections using nuts, and it is important that the assembled structures be fluid-tight. In a typical procedure for installing a hydraulic line in an aircraft, a mechanic first loosely attaches one end of a fitting to a line section by hand-tightening the nut at the one end of the fitting, then stretches or compresses the line section so that the opposite end of the fitting can be attached to another line section, again by hand-tightening the nut at the opposite end of the fitting. The mechanic then further tightens the nuts, first at one end and then at the opposite end of the fitting. This process of alternately tightening the nuts at the ends of the fitting may be repeated two or three times until the nuts at both ends of the fitting are fully tightened. 
   A mechanic may install several hundred hydraulic fittings in a day, and to help ensure that all nuts and fittings have been properly tightened, it is often the practice to mark a nut and/or fitting after it has been fully tightened. 
   As a result of the process of alternately and repeatedly tightening the nuts at the opposite ends of a fitting, however, it is not uncommon that the mechanic might inadvertently fail to fully tighten the nut at one or both ends of a fitting, yet still mark the nuts as being fully tightened. 
   All fittings in a hydraulic line of an aircraft are subjected to leak-testing such that any nuts that may have been only hand-tightened or that were otherwise improperly installed will be identified and properly fastened. When a fitting fails leak-testing, however, it is necessary to clean the leaked aviation hydraulic fluid (e.g., Skydrol) from surrounding surfaces, and to then fully tighten any loose nuts prior to retesting of the fitting. In addition to being time consuming, the preferred cleaning agent used to clean the leaked aviation hydraulic fluid is Freon which is a hazardous material and may also cause damage to the surrounding surfaces that requires repair. 
   Thus, it would be desirable to minimize the number of fittings that fail during leak-testing. 
   The typical procedure for marking an assembled hydraulic joint requires the mechanic to apply a colored compound, (e.g., Inspection seal lacquer F925) by squeezing a small tube so that a stripe of the compound, sometimes referred to as a “torque stripe”, covers both the fitting and the nut. This procedure for marking an installed hydraulic joint may be unsatisfactory. 
   One problem, as indicated above, is that the mechanic may inadvertently mark a fitting that has not been fully tightened. Also, these manual marking procedures are time consuming and reduce productivity. Recognizing the inadequacies of manual marking procedures, a marking wrench was developed. The prior art marking wrench both tightens a fastener and then marks the tightened nut with ink to indicate that the nut has been tightened. 
   The prior art marking wrench, however, is still not fully satisfactory. For one thing, the marking wrench only marks the nut and not its mating fitting. It is desirable to have the mark cover both nut and fitting so that it would be known if someone loosened, or tampered with the nut. A misaligned mark on the nut and fitting surfaces flags this condition. The prior art marking wrench is also non-ratcheting which makes operation of the wrench rather slow. Furthermore, the prior art marking wrench contacts the nut with ink impregnated felt, but trials of this wrench found that the felt dried up, rendering its marking capability useless. 
   There is, accordingly, a need for a mechanism for installing fittings and fasteners in hydraulic lines in an aircraft and in other applications that will minimize fluid leaks during leak-testing, and that will also automatically mark installed fittings and fasteners after they have been properly installed. 
   SUMMARY 
   An embodiment of the disclosure provides a self-contained combined wrench and marking system. The self-contained combined wrench and marking system has a wrench that may include a wrench head for rotating a fastener during a fastener tightening operation, a torque measuring mechanism for measuring a torque applied to the fastener during the fastener tightening operation, and an angle measuring mechanism for rotating the fastener to a preset angle during the fastener tightening operation. The self-contained combined wrench and marking system also has a marking system for automatically marking the fastener after the torque is applied to the fastener and after rotating the fastener to the preset angle. 
   A further embodiment of the disclosure provides a self-contained combined wrench and marking system. The self-contained combined wrench and marking system has a wrench that may include a wrench head for tightening a fastener during a fastener tightening operation. The self-contained combined wrench and marking system also has a marking system for automatically marking the fastener after tightening the fastener. The marking system may include a marking fluid reservoir containing a marking fluid, a spray nozzle line connected to the marking fluid reservoir for receiving the marking fluid from the marking fluid reservoir, a replaceable gas cartridge containing a gas propellant, and a control valve for delivering the gas propellant from the replaceable gas cartridge to the spray nozzle line for spraying the marking fluid for marking the fastener. 
   A further embodiment of the disclosure provides a method for installing a fitting and for marking automatically an installed fitting. The method may include rotating a fastener to attach the fitting during a fastener tightening operation, measuring a torque applied to the fastener during the fastener tightening operation, and rotating the fastener to a preset angle during the fastener tightening operation. The method may also include marking automatically the installed fitting and the fastener after applying the torque to the fastener and after rotating the fastener to the preset angle. 
   A further embodiment of the disclosure provides a A self-contained combined wrench and marking system. The self-contained combined wrench and marking system has a wrench. The wrench may include a ratcheting wrench head for rotating a fastener during a fastener tightening operation, and a torque measuring mechanism for measuring a torque applied to the fastener during the fastener tightening operation. The torque measuring mechanism may include a strain-beam that is stressed during the fastener tightening operation, and a stress measuring mechanism for measuring an amount of stress on the strain-beam, wherein the amount of stress is related to torque. The wrench may also include an angle measuring mechanism for rotating the fastener to a preset angle during the fastener tightening operation, and the angle measuring mechanism may include a gyroscope. The self-contained combined wrench and marking system also has a marking system for automatically marking the fastener after the torque measuring mechanism determines that the torque applied to the fastener is equal to a preset torque value and after the angle measuring mechanism determines that the fastener is rotated to the preset angle. The marking system may include a marking fluid reservoir containing a marking fluid, a spray nozzle line connected to the marking fluid reservoir for receiving the marking fluid from the marking fluid reservoir, and a replaceable gas cartridge containing a gas propellant. A first control valve may deliver the gas propellant from the replaceable gas cartridge to the marking fluid reservoir for delivering the marking fluid from the marking fluid reservoir to the spray nozzle line, and a second control valve may deliver the gas propellant from the replaceable gas cartridge to the spray nozzle line for spraying the marking fluid for marking the fastener. 
   A further embodiment of the disclosure provides a method for installing a fitting and for marking automatically an installed fitting. The method includes a fastener tightening operation. The fastener tightening operation may include rotating a fastener to attach the fitting, measuring a torque applied to the fastener while rotating the fastener to apply a preset torque to the fastener, and measuring a rotation angle of the fastener while rotating the fastener for rotating the fastener to a preset angle to install the fitting. The method also includes a marking operation for marking automatically the installed fitting and the fastener. The marking operation may include delivering a gas propellant from a replaceable gas cartridge to a marking fluid reservoir for delivering a marking fluid from the marking fluid reservoir to a spray nozzle line, and delivering the gas propellant from the replaceable gas cartridge to the spray nozzle line for spraying the marking fluid from the spray nozzle line. 
   The features, functions, and advantages can be achieved independently in various embodiments or may be combined in yet other embodiments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the embodiments are set forth in the appended claims. The embodiments themselves, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of advantageous embodiments when read in conjunction with the accompanying drawings. 
       FIG. 1  is a flow diagram of aircraft production and service methodology; 
       FIG. 2  is a block diagram of an aircraft; 
       FIG. 3  is an illustration of a perspective plan view of a combined wrench and marking system according to an advantageous embodiment of the disclosure; 
       FIG. 4  is an illustration of an exploded perspective plan view of the combined wrench and marking system of  FIG. 3 ; 
       FIG. 5  is an illustration of the combined wrench and marking system of  FIGS. 3 and 4  with portions removed to show internal features of the combined wrench and marking system according to an advantageous embodiment of the disclosure; 
       FIG. 6  is an illustration of an electronic circuit diagram of the main circuit board shown in  FIG. 5  according to an advantageous embodiment of the disclosure; 
       FIG. 7  is an illustration of a fluid circuit diagram representing a fluid system of the marking system of the combined wrench and marking system of  FIGS. 3-5  according to an advantageous embodiment of the disclosure; 
       FIG. 8  is an illustration showing an enlarged view of the nosepiece body of the combined wrench and marking system of  FIGS. 3-5 ; 
       FIG. 9  is an illustration showing an enlarged view of the display and control panel of the combined wrench and marking system of  FIGS. 3-5 ; 
       FIG. 10  is an illustration of a portion of the combined wrench and marking system of  FIGS. 3-5 , looking in the direction of arrow  8  in  FIG. 3 , to show features of the combined wrench and marking system according to an advantageous embodiment of the disclosure; 
       FIGS. 11A and 11B  are an illustration of a flowchart that shows program logic for installing fluid fittings and fasteners according to an advantageous embodiment of the disclosure; 
       FIG. 12  is an illustration of a Table that describes options that may be selected during the options mode in the flowchart of  FIGS. 11A and 11B  according to an advantageous embodiment of the disclosure; 
       FIG. 13  is an illustration that shows an ink mark sprayed on both a nut and a fitting that has been assembled to a hydraulic line section according to an advantageous embodiment of the disclosure; 
       FIG. 14  is an illustration of a cross-section of a nosepiece body of a combined wrench and marking system according to a further advantageous embodiment of the disclosure; and 
       FIG. 15  is an illustration of an enlarged view of the mixing area shown in  FIG. 14 . 
   

   DETAILED DESCRIPTION 
   Referring more particularly to the drawings, embodiments of the disclosure may be described in the context of an aircraft manufacturing and service method  100  as shown in  FIG. 1  and an aircraft  200  as shown in  FIG. 2 . During pre-production, exemplary method  100  may include specification and design  102  of the aircraft  200  and material procurement  104 . During production, component and subassembly manufacturing  106  and system integration  108  of the aircraft  200  takes place. Thereafter, the aircraft  200  may go through certification and delivery  110  in order to be placed in service  112 . While in service by a customer, the aircraft  200  is scheduled for routine maintenance and service  114  (which may also include modification, reconfiguration, refurbishment, and so on). 
   Each of the processes of method  100  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of venders, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
   As shown in  FIG. 2 , the aircraft  200  produced by exemplary method  100  in  FIG. 1  may include an airframe  202  with a plurality of systems  204  and an interior  206 . Examples of high-level systems  204  include one or more of a propulsion system  208 , an electrical system  210 , a hydraulic system  212 , and an environmental system  214 . Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry. 
   Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method  100 . For example, components or subassemblies corresponding to production process  106  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  200  is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages  106  and  108 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  200 . Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft  200  is in service, for example and without limitation, to maintenance and service  114 . 
   With reference now to  FIG. 3 , an illustration of a perspective plan view of a combined wrench and marking system according to an advantageous embodiment of the disclosure is depicted. The combined wrench and marking system, often referred to herein as a marking wrench, is designated by reference number  300 , and generally includes handle portion  302 , housing portion  304 , nosepiece portion  306  and head portion  308 . 
     FIG. 4  is an illustration of an exploded perspective plan view of the combined wrench and marking system of  FIG. 3 .  FIG. 4  illustrates various components of marking wrench  300 , and may be referred to during the following detailed description to facilitate a clear understanding of the marking wrench and its operation. 
   Returning to  FIG. 3 , handle portion  302  includes handle cap  310  for a user to hold marking wrench  300 . As will be described hereinafter, handle cap  310  may be hollow to define a compartment that contains a CO 2  cylinder to provide pressurized gas for the marking system of the marking wrench. 
   Housing portion  304  may include housing body  312  covered by housing body cover  314 . A display and control panel  316  may be mounted on housing body cover  314 . Display and control panel  316 , which is also illustrated in  FIG. 9  and will be described more fully hereinafter, may include display  318 , On/Set button  320 , mode button  322 , and status lights  324 ,  326  and  328 . 
   Housing body  312  may also include ink refill port  332  for refilling an ink reservoir included in the marking system of marking wrench  300 . 
   Nosepiece portion  306  includes a nosepiece body  534 , which is illustrated in  FIGS. 4 and 5  and will be described more fully hereinafter, that is enclosed in lower and upper nosepiece covers  334  and  336 . A spray nozzle  338  of the marking system may be in the nosepiece body as illustrated in  FIG. 3 . 
   Head portion  308  includes ratcheting head  340  of the marking wrench. Ratcheting head  340  is adapted to grip and rotate a nut, such as hydraulic nut  350  in  FIG. 3 , in order to fasten hydraulic fitting  352  to a section  354  of a hydraulic line. More particularly, marking wrench  300  may be used to tighten hydraulic nut  350  to a preset torque value and to then rotate the nut to a preset angle in order to fully tighten the hydraulic fitting  352  to line section  354 ; and to then mark both the nut and the fitting with ink using the marking system of the marking wrench to indicate that nut  350  has been fully tightened and that hydraulic fitting  352  has been attached to line section  354  in a secure, leak-free manner. 
   In an advantageous embodiment of the disclosure, marking wrench  300  may be used to install and mark hydraulic nuts and fittings to assemble hydraulic lines of an aircraft. It should be understood, however, that the marking wrench may also be used in other fastening applications and it is not intended to limit advantageous embodiments to any particular application. 
   According to an advantageous embodiment, marking wrench  300  may be about 17 inches long and weigh about two pounds. Marking wrench  300  may also be less than one inch thick, and thus provides a narrow profile in the plane of rotation of the marking wrench such that the marking wrench may be used in confined areas. 
     FIG. 5  is an illustration of the combined wrench and marking system of  FIGS. 3 and 4  with portions removed to show internal features of the combined wrench and marking system according to an advantageous embodiment of the disclosure. More particularly,  FIG. 5  illustrates marking wrench  300  with housing body cover  314  and upper nosepiece body cover  336  removed. As shown in  FIG. 5 , marking wrench  300  may include two circuit boards, main circuit board  502  in housing body  312 , and gyroscope circuit board  506 , also referred to as gyroscope  506 , in nosepiece body  534 . By providing a separate gyroscope circuit board, if the gyroscope circuit board  506  goes bad, it may be replaced independently of main circuit board  502 . Main circuit board  502  will be described more fully hereinafter in conjunction with  FIG. 6 . 
   Gyroscope  506  may be used to measure the angle of rotation of a nut being rotated (displaced angle) by marking wrench  300 , for example, hydraulic nut  350  in  FIG. 3 . Gyroscope  506  actually measures the rate of rotation of the nut, however, this measurement is then integrated using a suitable integration numerical method algorithm, such as Simpson&#39;s rule or the trapezoidal rule, in order to determine the angle of rotation of the nut. 
   Also illustrated in  FIG. 5  is strain-beam  508  in nosepiece body  534 . Strain-beam  508  may be used to measure torque. In particular, one end of strain-beam  508  is rigidly attached to nosepiece body  534  and the other end is free, i.e., the strain-beam is in a cantilever configuration. Strain-pin  510  is screwed into the free end of strain-beam  508  and just contacts an inner wall of nosepiece body  534 . This contact may be adjusted by screwing strain-pin  510  further into or further out of strain-beam  508 . 
   Strain-beam  508  senses an amount by which it is bent. Specifically, when marking wrench  300  rotates a nut in a clockwise direction, nosepiece body  534  bends and pushes against strain-pin  510  which, in turn, applies a load onto strain-beam  508  causing it to bend. Through calibration, the amount of stress on the strain-beam as a result of being bent is related to torque, enabling torque to be measured. 
   More particularly, as a result of the bending of strain-beam  508 , a voltage sent to the strain-beam changes, due to the strain-beam&#39;s change in resistance, then an instrumentation amplifier on main circuit board  502  amplifies this signal. The amplified voltage signal, or analog signal, is sent to a suitable microcontroller, such as a Microchip PIC microcontroller, on the main circuit board  502 . The microcontroller has analog-to-digital converter capability so that the analog voltage can be converted to digital format. In digital format, the microcontroller can apply various measured and stored correction factors, such as the calibration factor, to compute torque. 
     FIG. 5  also illustrates vibrating motor  512  in housing body  312 , which may be used for tactile feedback. Vibrating motor  512  may turn on for two seconds after marking wrench  300  has completed rotation of a nut to indicate to a user that the nut is fully tightened so that the user may get ready for the wrench to mark the tightened nut and associated fitting. 
     FIG. 6  is an illustration of an electronic circuit diagram of the main circuit board illustrated in  FIG. 5  according to an advantageous embodiment of the disclosure. The electronic circuit is generally designated by reference number  600  and may include a Microchip microcontroller  602 , for example, a PIC16F877A microcontroller operating at 16 MHz, for controlling marking wrench  300 . Microcontroller  602  may contain 8K, 14-bit words of programmable flash memory and 256 X 8 bytes of EEPROM data memory, and may include  30  input/output (I/O) ports. As shown in  FIG. 6 , electronic circuit  600  may also include LED operation components  604  for controlling the operation of status lights  324 ,  326  and  328 , strain-beam amplifier circuit  606  for use in measuring torque, pressure sensor circuit  608  and pressure sensor amplifier circuit  610  for use in the marking system of the marking wrench, LCD integrated circuit  612  for display  318 , membrane switch and debounce circuit  614 , which is needed to assure that buttons  320  and  322  function properly (otherwise pressing a button might turn on then turn off the wrench), buzzer  616 , resettable fuse  618 , which is needed in situations when the batteries are inadvertently installed with reverse polarity, and vibrating motor circuit  620  that includes vibrating motor  512 . 
     FIG. 7  is an illustration of a fluid circuit diagram representing a fluid system of the marking system of the combined wrench and marking system of  FIGS. 3-5  according to an advantageous embodiment of the disclosure. The marking system includes the fluid system, an ink injection system and parts of the marking wrench control system including the pressure sensor  608  and the pressure sensor amplifier  610  (not shown in  FIG. 7 ). 
   The fluid system is generally designated by reference number  700 . CO 2  may be delivered by a disposable 16 gram, or other size, CO 2  cylinder  702  which contains CO 2  at approximately 900 psig. As shown in  FIG. 4 , cylinder  702  may be supported in hollow handle cap  310 . Adjustable high pressure regulator  704  may be preset, by the wrench manufacturer, to output a pressure of about 25 psig from cylinder  702 . Low pressure line  706  from regulator  704  may be split into four lines. One line may be directed to pressure sensor  608 . Here, the control program, using pressure sensor  608  and pressure sensor amplifier  610  monitors the CO 2  pressure of the lines. When the pressure goes below 22 psig or above 30 psig, the control program may signal the user to change the CO 2  cylinder  702 . 
   The control program checks for over pressure as well as for under pressure because when the pressure in CO 2  cylinder  702  drops from use, the low pressure left in the cylinder may cause regulator  704  to increase the outlet pressure to considerably above 25 psig. 
   Two lines of the four lines split from line  706  may supply flow to solenoid-actuated valves  710  and  712 . Valve  710  may be used to operate pilot actuated valve  714  which, in turn, may inject ink into nozzle line  716  via ink line  718 . Solenoid-actuated valve  712  may be used to flood nozzle line  716  with CO 2  so as to propel the ink out spray nozzle  338  during a marking operation. 
   The fourth line split from line  706  may go directly into ink reservoir  720  which may comprise a low volume pump. A piston, schematically shown at  722 , may separate the CO 2  from the ink in reservoir  720  which is always pressurized. The ink should be pressurized so that it will function properly in all orientations of the marking wrench, especially when spraying in an overhead direction. 
   The following sequence of events may occur to actuate an ink spray shot:
         1. Solenoid actuated valve  710  directs CO 2  to pilot actuated valve  714  for a time duration of approximately 10 milliseconds, which is controlled by the control program, to open valve  714 ;   2. Solenoid-actuated valve  710  during the time duration controls the amount of ink injected into nozzle line  716 ;   3. Solenoid-actuated valve  710  is turned off at the end of the time duration;   4. Solenoid-actuated valve  712  directs CO 2  into nozzle line  716  to propel ink to spray nozzle  338 ;   5. Spray nozzle  338  aids in atomizing the ink as the ink is sprayed out of the nozzle and onto a nut and fitting.       

     FIG. 8  is an illustration showing an enlarged view of the nosepiece body of the combined wrench and marking system of  FIGS. 3-5 . At rest, ink resides in between the inside surface of sleeve  802 , which is made from a flexible plastic tubing such as polyurethane, and the outside surface of nozzle line  716  (note that other components illustrated in  FIG. 8  are shown in phantom lines to better illustrate structural features). Spring  804  maintains positive pressure on the piston  822  which in turn puts pressure on sleeve  802  to maintain a no ink flow condition. When valve  710  (not shown in  FIG. 8 ) is actuated, CO 2  is directed into the cylinder  820  containing piston  822 , causing the piston to compress spring  804 , and to move away from the sleeve  802 , uncovering ink inlet  806  (a small hole) in nozzle line  716 . O-ring  808  maintains a fluid-tight condition between piston  822  and the cylinder  820  as the piston moves within the cylinder. The valve on-time controls the amount of ink injected into nozzle line  716 . 
     FIG. 9  is an illustration showing an enlarged view of the display and control panel of the combined wrench and marking system of  FIGS. 3-5 . As indicated with reference to  FIG. 3 , display and control panel  316  may include display  318 , On/Set button  320 , Mode button  322 , and status lights  324 ,  326  and  328 . 
   Display  318  may be an LCD (liquid crystal display), and may display three seven-segment digits without decimal points which may be used to represent letters or numbers. For example,  FIG. 9  schematically illustrates display  318  displaying the digits “70” which may represent the letters “TO” for “torque”. 
   On/Set button  320  has two functions. The On feature turns marking wrench  300  on and off. The Set feature may be used to set (store) a value into memory. Mode button  322  may be used for selecting a desired function among several available functions as will be described hereinafter. 
   Status lights  324 ,  326  and  328  may comprise LEDs (light emitting diodes) of three different colors. For example light  324  may be green, light  326  may be yellow, and light  328  may be red. According to an advantageous embodiment, green LED  324  may be on during torque measurement, yellow LED  326  may be on during angle measurement, and red LED  328  may go on when angle measurement is complete. In addition, red LED  328  may go on in conjunction with messages being displayed on display  318  to indicate a fault, such as that the battery needs changing, the CO 2  cylinder needs replacing or that the gyroscope needs replacing. 
     FIG. 10  is an illustration of a portion of the combined wrench and marking system of  FIGS. 3-5 , looking in the direction of arrow  10  in  FIG. 3 , to show features of the combined wrench and marking system according to an advantageous embodiment of the disclosure. In particular,  FIG. 10  shows some features on the underside of marking wrench  300 . 
   As shown in  FIG. 10 , marking wrench  300  may be provided with electrical power by batteries  1002 , for example, three AA batteries carried in battery compartment  1004  in housing body  312 . The batteries may be easily replaced when necessary by removing four screws  1006  and removing battery access panel  1008 . 
     FIG. 10  also shows ink supply viewing window  1010 . Ink supply viewing window  1010  enables the current level of the ink in ink reservoir  720  to be monitored. When refilling of reservoir  720  is necessary, the refilling may be easily accomplished by injecting ink into the reservoir through ink refill port  332  (see  FIG. 3 ) using a syringe or the like. Ink refill port may be closed by a plug  402  (see  FIG. 4 ) which may be removed during a refilling operation. 
     FIG. 10  also shows CO 2  cylinder  702  which may be easily replaced by fully unscrewing handle cover  310 . 
     FIGS. 11A and 11B  are an illustration of a flowchart that schematically shows program logic for installing fluid fittings and fasteners according to an advantageous embodiment of the disclosure. More particularly,  FIGS. 11A and 11B  illustrate a method for installing fluid fittings and fasteners using a combined wrench and marking system such as marking wrench  300  in  FIGS. 3-5 . The method is generally designated by reference number  1100 , and begins by turning on the marking wrench (Step  1102 ) for example, by operating On/Set button  320  on display and control panel  316 . The control program then goes through a diagnostic sub-program (Step  1104 ) during which the program checks battery voltage, CO 2  pressure, and gyroscope operation. A determination is made whether any action is needed responsive to the diagnostic tests (Step  1106 ). If an action is required (Yes output of Step  1106 ), LCD display  318  displays appropriate symbols indicating the action that is required, and red LED  328  also lights up (Step  1108 ). After five seconds, the marking wrench will turn off so that the required action(s) may be taken (Step  1110 ). This will prevent a user from ignoring the display. 
   During the diagnostic sub-program (Step  1104 ) the gyroscope baseline may also be determined. The gyroscope baseline may be used to determine the nut angle, and should be determined while the marking wrench is not moving. 
   Returning to Step  1106 , if an action is not required as a result of the diagnostic tests (No output of Step  1106 ), an options mode may be entered into to select options for operating the marking wrench (Step  1112 ). Entry into the options mode may be accomplished by pressing mode button  322  on display and control panel  316 .  FIG. 12  is an illustration of a Table that describes options that may be selected during the options mode in the flowchart of  FIGS. 11A and 11B  according to an advantageous embodiment of the disclosure. 
   As shown in  FIG. 12 , options that may be selected include ink spray adjustment  1202 , CO 2  spray adjustment  1204 , ink amount  1206 , change or clear ink  1208 , measure angle  1210 , and calibrate  1212 .  FIG. 12  describes each of these options. For example, to change the ink amount (Option  1206 ), the Mode button  322  is pressed to enter into the options mode, then the Mode button is again pressed when IA- is displayed on display  318  to select the ink amount option  1206 . Then the On/Set button  320  is pressed to select and store the amount of ink in each spray. This amount is stored in memory and will not be lost if there is a loss of power to the marking wrench. 
   A similar procedure is used when the other options shown in  FIG. 12  are selected. Certain of the options may require entry of a code to enable the user to make modifications, For example, both the angle measuring option  1210  and the calibrate option  1212  may require the user to enter a code using On/Set button. The calibration option may also be used to store either or both torque and angle preset values. 
   Returning to  FIGS. 11A and 11B , after completion of operations in the options mode (Step  1112 ), the stored torque and angle values are recalled and displayed (Step  1114 ). This is so the user may verify that the wrench is set properly. Display  318  may display the torque value followed by the angle value. The marking wrench then starts measuring torque during a nut-tightening operation. 
   The torque measuring process is generally designated by dashed box  1116 , and begins by display  318  displaying current torque (Step  1118 ). Display  318  may initially display 0 inch-pounds indicating that there is no load on the handle of the marking wrench. Green LED  324  may also turn on indicating that torque is being measured (Step  1120 ). The user then begins tightening a nut, ratcheting if necessary (Step  1122 ). 
   As the nut is tightened, a determination is made whether the measured torque is within a selected percentage of the preset torque value, for example, within 5 inch-pounds of the preset value (Step  1124 ). If the measured torque is not within 5 inch-pounds of the preset torque value (No output of Step  1124 , the method returns to Step  1124  as the nut continues to be tightened. If the torque gets within 5 inch-pounds of the preset torque value (Yes output of Step  1124 ), buzzer  616  on main printed circuit board  502  may beep five times (Step  1126 ) as an indicator. 
   A determination is then made whether the measured torque is equal to the preset torque value (Step  1128 ). If the measured torque does not equal the preset torque value (No output of Step  1128 ), the method returns to Step  1128  as the nut continues to be tightened. If the measured torque equals the preset torque value (Yes output of Step  1128 ), the green LED may turn off and the yellow LED  326  may turn on ending the torque measuring process (Step  1130 ). The method then switches to an angle measuring mode. 
   The angle measuring process is generally designated by dashed box  1132 , see  FIG. 11B . Display  318  may display current angle (Step  1134 ). Initially, display  318  will show 0 degrees. The user continues to tighten the nut, ratcheting if necessary (Step  1136 ). A determination is made whether the measured angle is within 10 percent of the preset angle value (Step  1138 ) If it is determined that the measured angle is not within 10 percent of the preset angle (No output of Step  1138 ), the method returns to Step  1138  and the user continues to tighten the nut. If the measured angle is within 10 percent of the preset angle (Yes output of Step  1138 ) buzzer  616  may beep five times as an indicator (Step  1140 ). 
   A determination is then made whether the measured angle is equal to the preset angle (Step  1142 ). If it is determined that the measured angle is not equal to the measured angle (No output of Step  1142 ), the method returns to Step  1142  and the user continues to tighten the nut. If it is determined that the measured angle is equal to the preset angle (Yes output of Step  1142 ), the red LED may go on to indicate that angle measurement is complete (Step  1144 ). 
   When the preset angle is reached, the wrench may also begin to vibrate (Step  1146 ). This indicates to the user that the wrench is ready to spray. After a time delay of one second, the marking wrench then sprays both the nut and the fitting (Step  1148 ). After the spraying, the marking wrench may automatically turn off (Step  1150 ). 
     FIG. 13  is an illustration that shows an ink mark sprayed on both a nut and a fitting that has been assembled to a hydraulic line section according to an advantageous embodiment of the disclosure. In particular,  FIG. 13  shows an ink mark  1302  sprayed on both nut  1304  and fitting  1306  that have been attached to hydraulic line section  1308  to indicate that the nut and fitting have been properly attached to the line section. 
   Returning to  FIGS. 11A and 11B , marking wrench  300  may include a power off timer that will automatically turn off the wrench after a set time is reached. This timer may be set during torque measuring (Step  1160 ), and may be reset during angle measuring (Step  1170 ). The timer may be set for three minutes although other time periods can also be set if desired. If measured torque or measured angle does not change within the set period of time, the marking wrench automatically turns off (Steps  1162  and  1172 , respectively). 
     FIG. 14  is an illustration showing a cross-sectional view of a nosepiece body of a combined wrench and marking system according to a further advantageous embodiment of the disclosure. More particularly,  FIG. 14  illustrates a marking system in which ink is electronically injected into the ink reservoir rather than by CO 2  deployed ink injection as in the advantageous embodiment described with reference to  FIGS. 3-10 . 
   Nosepiece body  1402  of the combined wrench and marking system may include a stepper motor  1404  with gearbox which is controlled by the microcontroller  602  on the main circuit board of the combined wrench and marking system. The output shaft on the gearbox may be attached to blade coupling  1406  (shaped similar to a blade screwdriver) which is inserted into a blade receptacle (shaped similar to a slotted screw head) on valve stem  1408 . Valve stem  1408  has exterior threads  1430  which mate with interior threads on nosepiece body  1402 . Since connected together, by blade coupling  1406  and blade receptacle, rotation of the output shaft causes the valve stem  1408  to rotate in nosepiece body  1402 . As this rotation occurs, the valve stem  1408  will either extend or retract into the nosepiece body  1402 , depending on the rotation direction of the output shaft. This will cause the blade coupling  1406  to be withdrawn or be further inserted into the blade receptacle. The advantage of this coupling arrangement, is that the thrust force is applied on the threads  1430  and not onto the shaft of the stepper motor  1404 . 
   In operation, ink pressurized to about 5 psig is directed into ink port  1410 . No ink flows, however, until valve stem  1408  is retracted. When the stepper motor  1404  is signaled by the control program to rotate a certain number of steps, valve stem  1408  will rotate in nosepiece body  1402  causing the valve to retract from the front ink seal  1412 . Retraction is dependent on the valve stem screw threads  1430 . 
   At this point, ink is injected into mixing chamber  1414 . The valve stem is then extended forward to seal front ink seal  1412 . Then an electronic valve (not shown in  FIG. 14 , but which functions similarly to valve  712 ) is signaled to inject CO 2  via CO 2  flow line  1418  at about 25 psig into mixing chamber  1414 . The mixing chamber  1414 , is contained within nozzle sleeve  1420 . Ink and CO 2  mix together in chamber  1414 , and the atomized ink is propelled down nozzle sleeve  1420  and out nozzle hole  1422 . 
     FIG. 15  is an illustration of an enlarged view of the mixing area shown in  FIG. 14 .  FIG. 15  illustrates features to eliminate ink clogging. Specifically, the front portion of valve stem  1408  is designed to retain O-ring  1412  and break up any dried ink when the valve stem  1408  is retracted. This is facilitated through the close tolerance hole in the nosepiece and the O-ring retainer design, generally shown at  1510 . 
   A combined wrench and marking system according to advantageous embodiments is completely self-contained and does not require connection to an external air line or to any other external source. As a result it is easy to handle and manipulate. Use of a combined wrench and marking system according to advantageous embodiments may reduce the number of hydraulic leaks that occur during leak-testing of a fitting that has been attached to a hydraulic line section because both the nut and the fitting are automatically marked only after the nut has been properly tightened. This will help ensure that joints that have not been properly assembled will not be inadvertently marked. 
   The combined wrench and marking systems according to advantageous embodiments is light in weight and compact in size. In addition, the combined wrench and marking systems according to advantageous embodiments is less than one inch thick and has no protruding components, and thus provides a narrow profile in the plane of rotation of the marking wrench such that the marking wrench may be used in confined areas. 
   The description of the different advantageous embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different advantageous embodiments may provide different advantages as compared to other advantageous embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.