1. INTRODUCTION A candle handling system is provided at each of the three washout stations in the spray booth. Each system is comprised of the following subsystems. Manual transfer trays Inclined feeder Two candle indexers Candle transfer device
The feeder system precisely aligns each candle in front of the rotating chuck so that the chuck can accurately grip the aft end of the candle. 2. SPECIFICATIONS The MRPP must process the different candles at various rates to generate the required 300 pounds of magnesium powder per shift. Table 1 provides the following information: Percentage of Mg in each type of candle (from drawings). Mg recovered, lbs., from each candle (MRPP recovery efficiency of 96.6%; from mass balance calculations) Processing time available for each candle (based on 7 hours washout time per shift) Time interval between candles exiting MRPP Candle production (8 hour operating shift, and hourly for 7 hour washout period)
The three feeders provide ½ hour accumulation capacity for the 60 mm candles and 1 hour for the remaining candles. Table 2 shows the following: Required total and per station accumulations Required feeder length
Note that each Mk45 candle is cut in half and each half is washed out separately. In the case of the 155mm M118A2, LUU-2, and Mk45 only two washout stations are used to washout the illuminant. The third station is used to prepare the candles for washout. Minimum feeder length is determined by maximum candle O.D., required accumulation capacity, whether there are 2 or 3 stations washing out illuminant, and stacking the candles one row deep at the feeders. The 81 mm M301A2 candles require the longest feeder of 60.3; say 61 inches.
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Table 1: Required Production Rates B Type C D E F Candles Process Time Illuminant Percent Mg Mg (1) Available For Each Each Recovered Each Candle Lbs. (6) Each, Lbs. Minutes (2) (4) 0.500 55.0 0.266 1.12 0.573 55.0 0.304 1.28 1.375 55.0 0.731 3.07 1.410 56.0 0.763 3.20 1.740 48.0 0.807 3.39 1.710 54.6 0.902 3.79 0.000 0.00 2.560 45.0 1.113 4.67 3.310 51.0 1.631 6.85 4.300 56.0 2.326 6.51 5.875 48.5 2.752 11.56 4.370 61.5 2.596 10.90 19.250 61.0 11.343 31.76 16.000 61.0 9.428 26.40 G Interval Between Candles Minutes 0.37 0.43 1.02 1.07 1.13 1.26 1.56 2.28 3.26 3.85 3.63 15.88 13.20 H I Candles (2) Production per 1 Shift Hour (7 Hr period) 1,129 161.3 985 140.8 411 58.7 393 56.2 372 53.1 333 47.5 0.0 270 38.5 184 26.3 129 18.4 109 15.6 116 16.5 26 3.8 32 4.5
60 mm M83A3 60 mm M721 81 mm M301A2(3) 81 mm M853A1 105 mm M314A2 105 mm M314A3 4.2 Inch M335 4.2 Inch M335A1 4.2 Inch M335A2 155 mm M118A2 155 mm M485A2 2.75 In M257 LUU 2B/B Mk 45 (est wt) (7)
Table 2: Required Accumulation and Minimum Feeder Lenghts B Candle C Plant Production per Hour (7 Hr shift) 161.3 140.8 58.7 56.2 53.1 47.5 0.0 38.5 26.3 18.4 15.6 16.5 3.8 4.5 E F Accumulation (3)(4)(5) Required Feeder Total Per Station Length, in. Ea. or Mk 45 1/2-Sect. (minimum) 81.0 27 58.6 71.0 24 52.1 59.0 20 60.3 57.0 19 52.8 54.0 18 51.0 48.0 16 49.0 0.0 0 0.0 39.0 13 48.2 27.0 9 33.7 19.0 10 44.3 16.0 6 25.5 17.0 6 16.5 4.0 2 9.8 10.0 5 23.2 D G H I
60 mm M83A3 60 mm M721 81 mm M301A2 81 mm M853A1 105 mm M314A2 105 mm M314A3 4.2 Inch M335 4.2 Inch M335A1 4.2 Inch M335A2 155 mm M118A2 155 mm M485A2 2.75 In M257 LUU 2B/B Mk 45 (est wt) (7)
Max OD @ spacer = 3.01"
Brakes on OD
Brakes on OD 2 spray booths; Brakes on OD
2 spray booths 2 spray booths
Notes: (1) Mg recovery efficiency, % = 96.6 (from mass balance). (2) Washout hours/shift = 7 8 operating hours/10 hour shift, and 300 pounds Mg recovered/shift. (3) Accumulation: one hour minum for all candles except 60 mm which is 30 minutes. (4) Three washout stations except two when processing 155mm M118A2, Mk 45 & LUU-2. (5) Fractional values rounded up to next whole number. (6) Per drwgs. (minimum). (7) After cut off ends of Mk 45.
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Table 3 is incomplete at this time, but will be used to aid in developing washout cycle times. The washout cycle is separated into chuck loading, washout, and chuck unloading times. The table also shows maximum washout time available, and required production rates. Appendix B “Candle Specifics” provides detailed information on the candle details.
Table3: Candle Washout Cycle Time Breakdown B Candle C Chuck Loading 60 mm M83A3 60 mm M721 81 mm M301A2 81 mm M853A1 105 mm M314A2 105 mm M314A3 4.2 Inch M335 4.2 Inch M335A1 4.2 Inch M335A2 155 mm M118A2 155 mm M485A2 2.75 In M257 LUU 2B/B Mk 45 D E F G Washout Cycle Times per Candle, minutes Waterjet Chuck Total Test Estimated Unloading 0.7 0.8 1.2 1.6 3 4.2 2.3 3.8 3.9 5.4 3.7 22.7 9.6 0.7 0.8 1.2 1.6 3 4.2 0 2.3 3.8 3.9 5.4 3.7 22.7 9.6 H Max.Time Available 1.12 1.28 3.07 3.20 3.39 3.79 0.00 4.67 6.85 6.51 11.56 10.90 31.76 26.40 I Candles per 1 Shift 1,129 985 411 393 372 333 0 270 184 129 109 116 26 32
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Figure 1 shows the equipment for one washout station, i.e., feeder, indexers, and transfer device. These components are mounted to a mounting plate that is bolted to the side of the spray booth frame. The plate provides a modular assembly with adjustment and precise alignment, independent of spray booth frame weldment tolerances. The two indexers, transfer device and its gripper are all pneumatically powered. The operator picks up one tray of candles (after shroud lines/wires have been cut off) in the Preparation Area and carries it to one of the feeders. The operator places the end of the tray on the inclined feeder and manually slides the candles onto the feeder while the tray slides out form underneath the candles. Candle first fire (forward) ends are adjacent to the spray booth. The candles roll/slide down to the end of the feeder. Indexer #1 (at the end of the feeder) is extended down and prevents the candles from falling off the end of the feeder (Indexer #2 is retracted). The operator repeats this operation as desired (until feeder capacity is reached). The feeder has two conductive polyethylene plastic strips that support the candles near each end. Two conductive plastic guide rails are provided, one at each end of the candles. The guide rail and strip nearest to the spray booth are fixed. The other guide rail and strip are adjusted to accommodate the various candle lengths. Note that the feeder shown in Figure 1 handles 60mm through 155mm and Mk45 half-lengths. A similar feeder but wider feeder concept, yet to be designed, accommodates the 2.75” rocket warheads and LUU-2s. The feeder is vertically adjustable for the different candle diameters. The centerline of the candle at the bottom end of the feeder is thus always at the same position relative to indexer #1 and the transfer device gripper. The feeder incline angle is also adjustable. The simplest, most trouble free feeder is a single inclined flat guide. The overall feeder length is 61 inches in order to provide a one-hour accumulation for 81mm M301A2 and other candles. (See Table 2, column F.) A zigzag track that rises vertically would require less horizontal distance, but requires a more complicated track and guides and moves the loading point higher above the floor. The zigzag track is more likely to jam and interrupt the feed.
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Figure 1: Candle Handling System
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3.2 Transfer Device
The transfer device is an arm that moves in an arc between the lower end of the feeder and rotating chuck centerline. A pneumatically operated self-centering adjustable force gripper is mounted at the upper end of the arm. The self-centering feature (± 0.001”) compensates for variations in candle diameters and helps assure candle centerline alignment with the rotating chuck axial centerline. The lower end of the transfer arm is clamped and keyed to a support tube. This tube is supported by a pair of ball bearings mounted on a shaft and flange bolted to the mounting plate. As candle lengths change, the arm clamp is loosened, the arm is repositioned along the tube to align the gripper with the middle of the candle, and the clamp is tightened. This allows the gripper to always grip the candles near the midpoint at the candle center of gravity. The transfer arm is powered by a pneumatic cylinder. One end of the cylinder is fixed to a pivot attached to the mounting plate. The other end is attached to an actuating arm welded to the end of the support tube. A self-contained linear hydraulic damper is also attached to this arm so that arm velocity and acceleration are controlled. Magnetic switches are mounted on the air cylinder to indicate arm position at either end of its travel. As the transfer arm and gripper move into position in front of the rotating chuck, the actuating arm pushes against a small hydraulic shock adsorber that decelerates the assembly and candle. The arm comes to rest against an adjustable positive stop that precisely aligns the candle with the chuck. The “home” position for the transfer device is at the lower end of the feeder, with the gripper jaws open and positioned around the candle which is held in place by indexer #1. The closed center position of the gripper jaws is slightly above and away from the candle centerline when it is held by indexer #1. Each candle is loaded into the gripper by the following sequence. Indexer #2 extends, holding the second candle in place. Indexer #1 retracts. The first candle rolls forward slightly against the gripper. As the gripper fingers close, the lower finger lifts the candle slightly. The fingers close, centering the candle between the “vee” shaped fingers. Clamping force is controlled by regulating the air pressure supplied to the gripper. Magnetic switches are mounted on the gripper to signal open/closed positions. The transfer device then moves the candle into position in front of the rotating chuck. The chuck assembly moves forward positioning the chuck fingers over the aft end of the candle. The chuck fingers close on the candle. The transfer device gripper fingers open. The chuck assembly moves back so that the forward end of the candle is clear of the Recovery of Magnesium from Obsolete Pyrotechnic Munitions 50% Design Submittal 6
transfer device. The transfer device returns to its home position at the feeder. The rotating chuck and positioning system then proceed with the washout cycle.
The indexers are pneumatically powered. Their strokes and operating pressures are adjustable. Magnetically operated switches are mounted on the air cylinders to signal position at either end of the indexers travel. The position of indexer #2 is adjustable to accommodate the various candle diameters. Smaller diameter candles cause indexer #2 to be mounted closer to indexer #2, etc. Spacer plates of appropriate thickness are installed between the indexers and the mounting plate to keep the indexers centered along the various candle lengths. A wider feeder is installed and the transfer arm and gripper are appropriately positioned to accommodate the longer lengths of the 2.75 inch rocket warhead and the LUU-2 candles. Otherwise, the feeding and transfer process is as described above.
3.4 Gripper Fingers
The attached drawing 31304-304-04 shows the gripper finger used for the two 155mm and Mk45 candles. Fingers of similar configuration will be designed for the other candle diameters.
3.5 Additional Candle Preparation
The 155mm M118A2, Mk45 and LUU-2 require additional preparation before washout can proceed. The washout station at the very end of the flexible sidewall conveyor will be setup to aid in this preparation.
3.5.1 155mm M118A2
This candle has a 0.05” thick steel retaining disc sandwiched between the 0.050” thick book cover board assembly bonded to the first fire composition and canister at the forward end of the candle. A steel center wire runs through a steel tube the length of the candle. A “hat shaped” sleeve is soldered to the end of this wire, with the “brim” of the hat positioned in front of the retaining disc. The retaining discs cannot be safely removed in the Preparation Area, and they interfere with washout of the illuminant. Therefore, one washout station will be set up to aid in removing the retaining discs. The other two washout stations will washout the illuminant after the retaining discs and center wires have been removed.
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The candles are loaded into the feeder at the first washout station. The waterjet abrades and cuts away the book cover board closing discs and retaining ring that surrounds the retaining disc. The waterjet removes the first fire and illuminant behind the retaining disc by passing through the slots in the retaining disc and the annular area between the disc O.D. and the canister I.D. The illuminant binder is Laminac, thus it will washout easily. The washing action will break the assembly bond to the first fire composition. The water pressure behind the disc may move it and the center wire forward. After the above cycle is completed, the candle is withdrawn from the booth, the transfer device grips the candle, the rotating chuck disengages from the candle and retracts, and the transfer device loads the candle on to an accumulation ramp. This inclined ramp is on the other side of the chuck assemble from the feeder. The candles accumulate on this ramp until removed by the operator. The transfer device is driven by a three position air cylinder i.e., two air cylinders assembled end to end. One cylinder provides the necessary stroke to move the candle from the feeder to the chuck, and the other from the chuck to the accumulation ramp. Magnetic switches mounted on the air cylinders indicate arm position at each end of its travel and at the rotating chuck centerline position. The operator removes each candle from the accumulation ramp and removes and discards the retaining disc and center wire. The candle is then loaded onto one of the feeders at one of the two washout stations.
The forward ends of the LUU-2s are cut off in the Preparation Area to expose the bracket glue lines. The LUU-2s are loaded into the feeder at the first washout station. Each candle is transferred to the rotating chuck which inserts the end of the candle into the spray booth. A “cutoff” waterjet nozzle is positioned perpendicular to the candle O.D. The rotating chuck assembly advances the candle and aligns the glue line with the cutoff waterjet. As the candle rotates, the waterjet cuts the bracket loose. The aluminum bracket drops on to a diverter chute that directs the bracket into a collection container outside the booth. The candle is then removed from the booth and transferred to the accumulation ramp, same as for the 155mm above. The operator then transfers the candles to one of the feeders at one of the two washout stations.
3.5.2 Mk 45
Operational safety requires that the cups at either end of the Mk45 candle be cut off by the “cutoff” waterjet. Also, the wetted cardboard tube can collapse during washout, Recovery of Magnesium from Obsolete Pyrotechnic Munitions 50% Design Submittal 8
interfering with the operation. Thus the candle is cut in half by the “cutoff” waterjet to reduce the cardboard exposure time. These operations may be accomplished several ways. The operator can manually process each candle through the first washout station, making all three cuts before moving onto the next candle. Or a number of candles can be processed using the feeder, transfer device, rotating chuck, and accumulation ramp to cut off the ignition cup with fuze. Then the candles are processed again with the ends reversed, and the suspension cups with explosive bolts are cut off. The candles are then processed a third time to cut them in half.
The half sections are manually loaded onto one of the feeders at the one of the two washout stations. The cutoff cups would be collected the same way as described above for the LUU-2 brackets. Further analysis is required before the final approach is selected. The second approach appears to require less of the operator’s time.
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