Automated barrel panel transfer and processing system

An automated system for preparing weld land areas of panels to be welded to each other is disclosed. Generally, the system of the present invention includes a system for cleaning contaminants from such weld land areas. In one embodiment, the system for cleaning contaminants includes a system for blasting carbon dioxide granules or pellets against the weld land areas. In instances where the panels comprise aluminum, the system may further include a system for removing at least a first layer of aluminum oxide from the weld land areas. In one embodiment, the system for removing includes a system for moving a plurality of sheets of sand paper over the weld land areas. For purposes of moving the panels relative to the system for cleaning contaminants and/or the system for removing at least the first layer of aluminum oxide, the automated system of the present invention may further include a shuttle system for supporting and moving at least the first panel therethrough.

FIELD OF THE INVENTION
 The present invention generally relates to a system for transporting and
 processing at least a first panel to be welded to a second panel, and in
 particular, to a system for transporting the first panel through a panel
 processing system to prepare portions of the first panel to be welded to a
 second panel.
 BACKGROUND OF THE INVENTION
 Aluminum barrels (e.g., cylinders) are weldable to domes (e.g.,
 hemispheres) to make launch vehicle propulsion (e.g., propellant or fuel)
 tanks. Such barrels may be made from four 90.degree. curved panels that
 are weldable together along longitudinally extending seams in a vertical
 weld fixture or tool. Generally, for purposes of welding the panels to
 form a tank, the panels may be placed on a horizontal turntable of the
 vertical weld fixture and then rotated into clamping bars of the vertical
 weld fixture. Thereafter, a two torch-single pass/variable polarity gas
 tungsten arc system may be used to butt-weld the panels together. For a
 four panel fuel tank, this process is repeated four times to produce a
 complete barrel.
 Prior to butt-welding a first panel to a second panel, the panels are
 typically transported from a loading area to one or more preparation
 areas, manually prepared (e.g., cleaned and sanded by hand) at the
 preparation area(s) in order to enhance the weld, and additionally moved
 from such panel preparation areas to the weld fixture. Current practices
 for both manually preparing and moving panels can be labor intensive, time
 consuming, expensive and inefficient.
 SUMMARY OF THE INVENTION
 In one aspect, the present invention is directed to an automated panel
 transfer and processing system. More specifically, the system of the
 present invention is capable of queuing, handling and processing a
 plurality of aluminum alloy panels (e.g., four panels) which are to be
 welded together to form a cylindrical portion of a propulsion (e.g., fuel
 or propellant) tank for use in launch vehicles. In this regard, the system
 of the present invention is capable of queuing and transporting at least a
 first panel through at least a first weld preparation station which
 functions to (1) clean inner and outer edge wall portions (e.g., weld
 lands) of at least the first panel and to (2) remove a layer comprising
 aluminum oxide therefrom. Thereafter, the system functions to transport at
 least the first panel into a weld fixture, where the side edge wall of the
 first panel may be trimmed (e.g., routed) and then butt-welded to another
 panel (e.g., a second panel) which has been transferred and processed by
 the system of the present invention. This system reduces costs and risks
 associated with manual handling and manual weld land preparation
 processing. In this regard, panel handling and weld land processing are
 now controlled and repeatable processes. The successful automation of this
 process in accordance with the system of the present invention reduces
 cycle time substantially while also reducing total labor costs and avoids
 extra costs by reducing the possibility of rework and risk of damage.
 In another aspect, the present invention is directed to a digital
 radiographic weld inspection system for use on the weld fixture. As noted
 hereinabove, the weld fixture is vertically oriented, and includes a
 router for trimming side edge walls of at least the first panel to remove
 aluminum oxide therefrom, and a two torch-single pass/variable polarity
 gas tungsten arc system for butt-welding the first panel to a second panel
 processed in accordance with the present invention. Of importance, the
 vertical weld fixture further includes the digital radiographic weld
 inspection system. The weld inspection system, which is mountable onto the
 weld fixture, such that the weld inspection system can inspect welds upon
 completion of butt-welding operations, includes a fiber optic scintillator
 (FOS) x-ray to light conversion screen coupled to a high resolution
 charged coupled device (CCD) camera to produce radiographic images of a
 weld area between welded panels of the cylindrical fuel tank (e.g., first
 and second panels). This non-film system allows images of the weld to be
 viewed immediately upon acquisition on a CRT monitor and eliminates
 development of film, which results in simplified image review, storage and
 retrieval of radiographic records. As such, the system provides very fast
 image acquisition and electronic image enhancements not available with
 conventional film techniques. Moreover, the barrel welds can be
 radiographically inspected immediately upon completion of the weld while
 the panels (e.g., first and second panels) are still clamped in the weld
 fixture (e.g., full length weld inspection results within 75 minutes of
 weld completion). This allows improvements in the weld process, with
 attendant reduction of weld defects and weld repairs since each weld
 (e.g., weld connecting first and second panels) may be inspected prior to
 proceeding with the next weld (e.g., weld connecting second and third
 panels). Accordingly, weld parameters may be adjusted prior to starting
 another weld, thereby eliminating recurring weld problems. Additional
 benefits include reduced build cycle-time for assembling a launch vehicle
 propulsion (e.g., fuel or propellant) tank and reduced labor costs
 associated with re-installing a barrel into the weld fixture for a full
 length weld repair if required.

DETAILED DESCRIPTION
 Functionally, the panel transfer and processing system of the present
 invention is capable of acquiring, transporting, processing and locating a
 range of panels vertically into a weld fixture. In the one embodiment, the
 panel transfer system is capable of processing four 90.degree. segments
 having a 10 foot to 13 foot diameter and, in another embodiment,
 processing five 72.degree. segments having a diameter of 13 feet to 14
 feet. Each segment can range from 2 feet to 30 feet in length with a
 maximum weight of 1,000 pounds.
 Referring to FIG. 1, the panel transfer system 10 of the present invention
 includes the following major components: a panel transportation cart 16
 for moving and supporting a plurality of panels from a first location to a
 second location, a panel position shuttle 22 for extracting at least one
 panel from the panel transportation cart 16 at the second location and for
 transporting at least a first panel 28a through the system 10, and a weld
 preparation station 34 for cleaning inner and outer edge wall portions of
 38a, 38b of at least the first panel 28a. The system 10 further includes a
 rail system 44 which interfaces with the panel position shuttle 22 to
 transport at least the first panel 28a from beneath the panel
 transportation cart 16, through the weld preparation station 34 and to the
 vertical weld fixture 50. In addition, for purposes of automating the
 transport and processing of the panels 28a-28d, the system 10 also
 includes at least a first control station 150.
 In particular, in referring to FIG. 2, the panel transfer cart 16 is
 configured to support a plurality of panels 28a-28d which, when cleaned
 and welded together, form a barrel suitable for use in a launch vehicle
 propulsion tank. In order to facilitate and enhance barrel processing
 efficiency, the panel transportation cart 16 includes first and second
 wheel assemblies 18a, 18b which allow for easy movement of the panels
 28a-28d from a first location (e.g., an unloading area) to a second
 location (e.g., the panel transfer and processing area). Referring to
 FIGS. 1 and 3, once the panel transportation cart 16 arrives at the panel
 processing area, the panel transportation cart 16 may be guided into
 tracks 20a, 20b to ensure at least rough alignment of the panels 28a-28d
 with the panel positioning shuttle 22 and the weld preparation station 34.
 Once received within the tracks 20a, 20b, the panel transportation cart 16
 is positionable about the lifts 21 which are capable of lifting the panel
 transportation cart 16 and panels 28a-28d supported thereby, such that the
 panel positioning shuttle 22 may be positioned thereunder to receive at
 least the first panel 28a. Furthermore, the first wheel assembly 18a is
 pivotable about the frame of the panel transportation cart 16 to allow
 passage of the panel positioning shuttle 22 thereunder to retrieve/receive
 one of the panels (e.g., the first panel 28a), as illustrated in FIGS.
 3-4. In addition, the cart 16 includes at least a first alignment bar 23
 which is receivable within slots 29 of the panels 28a-28d to ensure proper
 positioning (e.g., centered) of the panels on the shuttle 22 and alignment
 of the inner and outer edge wall portions 38a, 38b of the panels with the
 weld preparation station 34. A second alignment bar may also be included
 on the opposite end of the cart 16. In one embodiment, the first and
 second alignment bars have first and second different dimensions to ensure
 the panels are correctly oriented and positioned.
 FIGS. 5-8 generally illustrate the features of the panel transportation
 cart 16 and panel positioning shuttle 22 which enable the panel
 positioning shuttle 22 to retrieve/receive at least the first panel 28a
 from the panel transportation cart 16. Generally, the lifts 21 function to
 adjust the vertical position of the panels relative to the shuttle 22 by
 vertically adjusting the position of the cart 16. Associated with the
 lifts 21 are servo drives which function to lower/raise the cart 16 such
 that the lower-most panel (e.g., the panel to be processed) is positioned
 at a selected height for retrieval by the shuttle 22. In this regard, the
 servo mechanism is commanded to go to one of four absolute positions. Each
 of these positions puts the belly of the next available panel at a common
 distance from the floor.
 In order to allow retrieval of the lower-most panel and transport the panel
 through the system for processing, the panel positioning shuttle 22 is
 movable along rails 60a, 60b via a drive system having a speed and torque
 controlled motor which drives the rear gears 62a, 62b, which interface
 with the gear racks 61a, 61b of the rails 60a, 60b, respectively. The
 drive system is capable of moving the shuttle 22 along the rails 60a, 60b
 to a position beneath the panel transportation cart 16 and is further
 capable of raising a carriage assembly 70 thereon to a raised position to
 retrieve/receive and lower at least the first panel 28a from the panel
 transportation cart 16, and specifically, from swing-out rollers 17 which
 support the panels at various incremental heights. The shuttle 22 may
 include sensors (e.g., optical, contact, etc.) for slowing and stopping
 the shuttle 22 so that the first panel 28a may be received on the carriage
 or saddle assembly 70 at a selected position. FIG. 7A illustrates one
 embodiment of the swing-out rollers 17, the rollers being capable of
 rotating from a first position supporting a panel to at least a second
 position to allow the panels to be lowered onto the panel transportation
 cart 16. The lower-most panel 28a is located first, and the next lower
 swing-out roller 17 may be rotated to a support position whereupon the
 next panel 28b is lowered and so on. The aforementioned process is done
 manually at a remote cart-loading station and thereafter the swing-out
 rollers 17 are stationary.
 Extraction of at least the first panel 28a is accomplished by first lifting
 the panel 28a off the rollers 17 (e.g., about 1 inch) and moving the first
 panel 28a via the shuttle 22 horizontally until the panel 28a is clear of
 the cart 16. Once the first panel 28a is received onto the carriage 70 of
 the panel position shuttle 22, the first panel 28a may be lowered to the
 appropriate height for preparation at the cleaning station 34. In order to
 secure the panel on the carriage 70, a plurality of translationally
 positionable clamps 72, 74a, 74b are provided on the panel position
 shuttle 22. In particular, and referring to FIGS. 9 and 9A, the clamps
 74a, 74b are capable of translational movement in order to abuttingly
 engage the end wall 39a of the first panel 28a. The clamps 74a, 74b
 additionally function to support the weight of the first panel 28a when
 the panel is being positioned for placement upon the vertical weld
 assembly 50 (to be described in more detail hereinbelow). The panel clamps
 74a, 74b are movable a discrete distance via timed feed rate to engage the
 aft end wall 39a. The panel position shuttle 22 also includes a single
 clamp 72 for engaging the fore or second end wall portion 39b to
 accommodate panels of varying lengths, the clamp 72 being movable along
 the rail 76 of the panel position shuttle 22. Additionally, the clamp 72
 may also include a sensor (e.g., optical, contact) for determining when
 the clamp 72 engages the end wall portion 39b of the first panel 28a
 (e.g., to stop the clamp 72 upon engagement), as illustrated in FIGS. 9
 and 9B. The clamp 72 also functions to support the panel 28a as the panel
 28a is positioned onto the vertical weld fixture 50 and to confirm the
 centerline alignment of the saddles 70 of the shuttle 22.
 As noted in FIG. 10, the system 10 of the present invention further
 includes a weld preparation station 34, which includes a carbon dioxide
 (CO.sub.2) system 80a, 80b for cleaning the inner and outer edge wall
 portions 38, 38b (i.e., weld lands) on both sides of the first panel 28a,
 and a sanding system 90a, 90b for sanding the inner and outer edge wall
 portions 38a, 38b of both sides of the panel 28a to remove at least 0.001
 inch/side of material (e.g., aluminum oxide and aluminum) therefrom.
 Specifically, and referring to FIGS. 10A-10B, the carbon dioxide cleaning
 system 80a, 80b of the present invention functions to blast carbon dioxide
 pellets or granules against the inner and outer edge wall portions 38a,
 38b on the side portions of the first panel 28a in order to clean or
 remove contaminants, such as oil, grease or other non-volatile residue and
 particulates (e.g., organics) from these edge wall portions 38a, 38b,
 which can adversely affect the weldability of the edge wall portions to
 similar portions of another panel (e.g., a second panel 28b). In the event
 such contaminants are not removed prior to sanding of the weld lands,
 there is a risk that the contaminants will be smeared into the panel
 during the sanding process, which, in turn, can degrade the weld
 integrity.
 In one embodiment, illustrated in FIGS. 10A, 10B, the carbon dioxide
 cleaning system 80a, 80b each includes first and second nozzles 92a, 92b
 (e.g., venturi-type nozzles) for impacting a plurality of carbon dioxide
 pellets or granules suspended in a high velocity, filtered and heated air
 stream against the weld land area (e.g., inner and outer edge wall
 portions 38a, 38b on both sides of the panel 28a). Such nozzles 92a, 92b
 may be sized to have a width which corresponds to the width of the inner
 and outer edge wall portions 38a, 38b which need to be cleaned for welding
 (e.g., one inch width). In this embodiment, the carbon dioxide pellets
 generally have a dimension of about 0.080 inch. However, the size of such
 pellets may be varied in order to achieve more aggressive cleaning and/or
 removal of material. Of course, the velocity of the shuttle 22 supporting
 the panel 28a may be varied to enhance cleaning of the inner and outer
 edge wall portions 38b, 38b, and, in some instances, may be slowed to not
 only clean the inner and outer edge wall portions 38a, 38b, but also to
 remove at least 0.001 inch/side of material from the inner and outer edge
 wall portions 38a, 38b (e.g., to remove a layer of aluminum oxide) to
 enhance the weldability thereof.
 The carbon dioxide pellets or granules are deliverable through a conduit
 94a, 94b and are entrained in the heated, filtered and compressed air flow
 which is delivered via conduits 96a, 96b. In order to deliver the granules
 of carbon dioxide (e.g., dry ice) against the inner and outer edge wall
 portions 38a, 38b to achieve sufficient cleaning, the air delivered
 through conduits 96a, 96b is filtered and heated to a temperature of about
 70.degree. F. to about 150.degree. F., depending upon the humidity level
 of the room in which the system is contained, and compressed to a pressure
 of about 100 psi, and, in a preferred embodiment, the filtered, compressed
 air is heated to a temperature of about 140.degree. F. and it is
 compressed to about 100 psi. The panel 28a may be fed through the cleaning
 system 80a, 80b at a speed of about 18 inches/minute.
 Since the carbon dioxide granules impact the inner and outer edge wall
 portions 38a, 38b on the sides of the panel 28a and sublimate to dissolve
 the greases and oils while blasting off the non-volatile residue and
 particulates, the carbon dioxide cleaning systems 80a, 80b also include a
 vent or exhaust system 98 (e.g., vacuum) for creating a negative pressure
 environment within the enclosure 91, and further includes wipers to
 inhibit leakage of carbon dioxide gas from within the enclosure 91 to the
 outside environment. The exhaust system 98 thus functions to remove the
 resulting suspended particulates and to inhibit carbon dioxide gas from
 escaping into the surrounding environment, which could result in
 displacement of oxygen in the surrounding atmosphere. The carbon dioxide
 cleaning system 80a, 80b further includes air knives 101 for blowing
 heated, filtered air against the inner and outer edge wall portions 38a,
 38b to dry such portions after cleaning. As a result of this cleaning
 process, the weldability of panels to each other is enhanced due to
 reduced amounts of impurities (e.g., organic materials) thereon. In
 addition, the cleaning process of the present invention reduces cycle-time
 because it can be accomplished in parallel to the actual panel locating
 and welding for three of the four panels. Further, the cleaning process
 requires no actual touch labor.
 Referring to FIGS. 10, 10C and 10D, the system 10 includes sanding systems
 90a, 90b for sanding the inner and outer edge wall portions 38a, 39b on
 both sides of the panel 28a. More specifically, the sanding system 90a
 includes first and second sanding or flapper wheels 112a, 112b, which each
 include a plurality of sheets of sand paper having a grit of 120 or
 greater. Rotation of the sanding or flapper wheels 112a, 112b functions to
 remove at least about 0.001 inch layer comprising aluminum oxide and
 aluminum from the inner and outer edge wall portions 38a, 38b to further
 enhance the weldability of wall panels to each other. In order to remove a
 layer of between about 0.001 inch and about 0.003 inch from the inner and
 outer edge wall portions 38a, 38b on the sides of each panel 28a, the
 sanding or flapper wheels 112a, 112b are rotated such that the sheets of
 sand paper having a grit of 120 or greater have a surface speed across the
 inner and outer edge wall portions 38a, 38b of about 200,000
 inches/minute. Further, the shuttle 22 may move the first panel 28a
 through the sanding system 90a at a velocity of about 18 inches per
 minute. Of course, the speed of the sheets of sand paper and/or the
 shuttle 22 may be varied, depending, among other things, the grit of the
 sand paper used, the material comprising the panel, and the amount of
 material to be removed from the inner and outer edge wall portions of the
 panel. The sander system 90a may further include a vacuum system 116 for
 removing sanding dust during sanding operations. A plurality of brushes
 118 may be further included to engage the inner and outer walls of the
 panel 28a to reduce sanding dust escaping to the surrounding environment.
 The sanding system 90a may further include air knives 120a, 120b for
 blowing filtered, dried air to remove any excess dust remaining on the
 cleaned and sanded inner and outer edge wall portions 38a, 38b on both
 sides of the panel 28a. For purposes of sanding the inner and outer edge
 wall portions 38a, 38b of both sides of the panel 28a when such portions
 are appropriately positioned between the sanding wheels 112a, 112b for
 sanding operations, the sanding system 90a may also include a sensor 119
 (e.g., infrared) which activates and deactivates the sanding wheels 112a,
 112b.
 After the inner and outer edge wall portions 38a, 38b on each side of the
 panel 28a have been sanded, the shuttle 22 may then function to
 verticalize and position the panel 28a on the vertical weld fixture 50.
 More specifically, and referring to FIGS. 11-12, the motorized reels 62a,
 62b of the shuttle 22 are engagable with gear rack 61a, 61b to generally
 drive and to govern the speed of the shuttle 22 as shuttle 22 moves along
 the tracks 60a, 60b from a horizontal to a vertical orientation. In one
 embodiment, the motors 62a, 62b go into a local jogging control mode as
 the panel 28a is verticalized. Thereafter, the lift mechanisms 78 utilized
 to raise the saddle/carriage assembly 70 to extract the panel 28 from the
 panel transportation cart 16 may be utilized to translate the panel 28a
 horizontally such that the panel 28a may be received upon rollers of the
 vertical weld fixture 50. Of note, the clamps 72, 74a, 74b function to
 hold the panel in a vertical position and during actuation to the vertical
 weld fixture 50.
 Of note, the control station 150 of the system 10, illustrated in FIG. 1,
 controls the positioning and attendant functionality of the panel
 positioning shuttle 22 and may control operation of the weld preparation
 station 34. A second control station may also be provided in proximity to
 the vertical weld fixture 50 to allow monitoring and control of the system
 10 therefrom.
 The above-described system 10 may be further utilized for processing of
 panels 28b-28d. In this regard, a second panel 28b may be processed in
 accordance with the features of the present invention, and then positioned
 on the vertical weld fixture 50 adjacent to the first panel 28a for
 routing and welding to the first panel 28a. After such routing and
 welding, the resultant weld of the first and second panels may be
 inspected for defects in accordance with the digital x-ray inspection
 system of the present invention. Generally, the system includes a digital
 radiographic (non-film) system which uses a fiber optic scintillator (FOS)
 x-ray to light conversion screen coupled to a high resolution charged
 coupled device (CCD) camera to produce the radiographic images. The system
 eliminates some of the problems associated with radiographic images. In
 addition, the images from the system can be viewed immediately upon
 acquisition on a CRT monitor. Further, since the system is interconnected
 to the vertical weld machine, the barrel welds can be radiographically
 inspected immediately upon completion of the weld while the panels are
 still clamped in the vertical weld fixture.
 The foregoing description of the present invention has been presented for
 purposes of illustration and description. Furthermore, the description is
 not intended to limit the invention to the form disclosed herein.
 Consequently, variations and modifications commensurate with the above
 teachings, and the skill or knowledge of the relevant art, are within the
 scope of the present invention. The embodiments described hereinabove are
 further intended to explain best modes known for practicing the invention
 and to enable others skilled in the art to utilize the invention in such,
 or other, embodiments and with various modifications required by the
 particular applications or uses of the present invention. It is intended
 that the appended claims be construed to include alternative embodiments
 to the extent permitted by the prior art.