Abstract:
A system and method for use in providing a peripheral seal between the case and lid of a MACS modular unit or other workpiece interface, the system including a workpiece holding device for carrying and moving a workpiece of interest in relation to a solvent dispensing system and a solvent dispensing system for dispensing a metered amount of solvent into the interface to be sealed on the workpiece, the solvent dispensing system further including a metering device for dispensing a predetermined known amount of the solvent, a stationary dispensing valve for dispensing solvent supplied from the metering device over a predetermined time, a re-supply system for reloading the metering device of the known amount of liquid solvent; and a control system for controlling the operation of the workpiece holding device and the solvent dispensing system.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to the manufacture of propellant charge systems for large caliber artillery pieces, more particularly, to modular artillery charge systems or MACS, and involves improvements in a load, assembly and packaging process for manufacturing field modular charge units for singular and multi-unit propellant charge systems. Specifically, the invention is directed to an improved solvent application system and method which coordinates the sealing of the lid to the case of a MACS unit with precision. 
     II. Related Art 
     Propellant charges for cannon artillery systems, primarily large caliber weapons systems such as 155 mm howitzers, etc., typically include plurality of coordinating modular charge units serially loaded behind the shell. The individual modular charge units are generally cylindrical in shape, frequently having a length to diameter ratio approaching 1. A central axial opening is provided through each unit to facilitate ignition of that and consecutive units. Such a system concept is illustrated, for example, by Reinelt, et al., in U.S. Pat. No. 4,702,167. 
     Particular embodiments of such modular units are of a three-piece design, which includes a combustible case body, normally nitrocellulose, having a closed end provided with a central bore opening and an open end, a combustible cap or lid, provided with a central bore opening that aligns with that of the case body is adapted to fit or nest in and seal into the open end of the case body, and a combustible central or core tube, which fits over raised rims in the central bores of and connects the central openings provided in the closed ends of both the relatively rigid case body and lid to form a continuous central bore for containing core igniter bags. Top and bottom recesses are provided to accommodate two end igniter bags. This assures proper ignition of a number of serially placed modular charges. Up to eight modular charges may be employed in firing a 155 mm howitzer, for example. 
     The MACS load, assembly and packing process utilizes a series of discreet work stations, each of which is designed to accomplish a specific operation on the case, charge or additive materials. The present invention deals primarily with the provision of a significantly better approach to one difficult manual portion of the process including an operation at one discrete station in which the peripheral interface between the case and lid is sealed by the application of a volatile solvent such as acetone for the case and lid material. 
     This operation requires a specified, metered amount of solvent, normally acetone, to be applied evenly along the joint between the nitrocellulose case body and lid. Upon application, capillary action between the two rather tight fitting pieces draws the acetone along the mating surfaces and produces fusing of the two components together thereby sealing the module. The step further requires a positive shut-off from the solvent to prevent solvent spills and contact with the part other than at the juncture to be sealed. This step of the process has heretofore been accomplished entirely by a hand operation, the consistency of the results resting on the repetitive skill of the individual operator. The operator applied the acetone or other solvent using a hand-held syringe while, at the same time, spinning the module on a turn table. The operation of the table was also controlled by hand. This led to many peripheral inconsistencies in the form of over application and gaps in the application of the acetone, solvent and/or so to inconsistent sealing of the module. The syringe often would leak solvent onto the module rather than stopping abruptly at the end of the step. These drawbacks, in turn, could lead to rejection of the unit. This situation speaks of a definite need to improve this step of the process, to increase the accuracy of the sealing of the case and lid of each module, and also to remove the burden of consistency from the individual operator. 
     Accordingly, it is a primary object of the present invention to provide a system that automatically rotates and seals the case body and lid in a modular artillery charge system. 
     It is a further object of the present invention to provide such a fixture that is capable of consistently metering the exact desired amount of solvent and of insuring a complete solvent shut-off thereafter. 
     A still further object of the present invention is to provide such a system which interlocks the operation of the solvent dispensing with the rotation of the modular unit. 
     Another object of the present invention is the provision of a mechanized processing station that interlocks solvent dispensing with the provision of proper ventilation. 
     Still another object of the present invention is to provide a mechanized processing station that includes a mechanized turn table and adjacent solvent application device that assures complete and proper sealing of the module. 
     Additional objects and advantages regarding the invention will become apparent to those skilled in the art upon familiarization with the specification, drawings and claims contained herein. 
     SUMMARY OF THE INVENTION 
     The present invention solves many problems associated with the prior existing processes by providing automated mechanized discreet workstation system for precisely applying sealing solvent to the lid/body interface of a modular artillery charge system (MACS) unit or other workpiece. This system provides for case rotation and automated precise solvent quantity metering and shut off. Distribution (placement) about the periphery of the interface is also uniform as application is coordinated with turn table rotation. 
     The system is pneumatically-operated and includes a pneumatically driven turn table for mounting and rotating the modular unit to be sealed which is situated in precise relation to a solvent dispensing valve which applies the desired amount of solvent about the circular juncture between the cap and body as the modular unit is rotated. The solvent, normally acetone for a nitrocellulose cap and body, by capillary action is drawn into the joint to provide a complete welded or fused nitrocellulase seal. 
     The solvent dispensing system is contained on a mounting table beneath a ventilation hood and its operation is interlocked with a ventilation fan in the hood. The solvent dispensing system includes a solvent supply tank and a solvent supply dispensing valve which cooperates with a gas-tight measuring syringe connected also to a solvent dispensing valve. The solvent is precisely loaded and discharged by the operation of the measuring syringe. The syringe plunger is operated by a double acting hydraulic cylinder operated by a pair of air over metered fluid supply containers which cooperate with a follower arm-operated limit valve. A precise sequencing control system is also provided to coordinate proper sequencing of dispensing and refilling operations. 
     After a startup timing sequence, the operation is initiated by the operator utilizing a foot valve, or the like, and proceeds thereafter automatically to seal a modular unit placed in the turn table and then precisely reload the gas-tight measuring syringe for the next unit in a manner which is controlled by time-interlocked pneumatic valves and electric relays. Thus, the system and method of the invention for the precise patterned application of a liquid material upon a moving workpiece. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like numerals depict like parts throughout the same: 
     FIG. 1 is a cross section view of an individual propellant charge module of a class suitable to be sealed using the fixture of the system of the invention; 
     FIG. 2 is a perspective view of a center core tube in accordance with the charge module unit of FIG. 1; 
     FIG. 3 is a perspective view of a lid to be sealed to case of the modular unit of FIG.  1 . 
     FIG. 4 is a schematic side elevational view of a work station for the application of sealing solvent in accordance with the present invention including pneumatic connections; and 
     FIG. 5 is a schematic control diagram depicting a method operating the work station of FIG.  4 . 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1-3 depict a typical modular artillery charge system (MACS) charge unit, generally at  8 , usable alone or serially with various numbers of other units in a plurality of propellant-loading configurations as a propellant charge for large cannons such as the 155 mm howitzer. It will occur to those skilled in the art that the system and method associated with the present invention are usable for processing a variety of these types of charges and other similar devices and that the unit of the detailed description is meant as an example and not by way of limitation. 
     The modular charge unit and elements depicted in FIGS. 1-3 is included herein as an illustrative example of a class of charge units which can be solvent sealed using the work station of the present invention. Additional details of such modular charge units are found in U.S. Pat. No. 5,747,723 issued to Gregory Buckalew et al., which is incorporated herein by reference in its entirety. 
     FIG. 1 shows a modular propellant charge unit including a unit body or shell  10 , center core tube  12 , and a cap  14  as the basic parts thereof. As can be seen from the figures, each of these is generally made up of a thin-walled hollow cylinder which, in the case of the center core tube  12 , has two open ends. The body  10  and cap  14  each have an open end and a closed end. As seen in the figures, the open end of cap  14  fits into and seals the open end of the body  10  and the closed ends of both cap  14  and body  10  describe central openings with tubular rim or lip extensions. 
     The remaining portion of the body  10  is shown filled with a propellant material as at  20 . The body, core and lid are generally made of combustible nitrocellulose coated with an environmentally stable protective coating shown about the periphery of FIG. 1 at  22 . Typically, the body  10  and cap  14  each have a wall thickness between 2.0 mm and 2.7 mm. The dimensions and density of the body  10 , core tube  12  and cap  14  must be within a very close tolerance to insure durability, critical functioning of the igniter and complete combustion. A core igniter bag  24  flanked by end igniter bags  26  and  28  is illustrated to make up the igniter system in FIG.  1 . The make up and function of the igniter material is well known to those skilled in the art as is the composition of the main propellant charge and these details do not form a part of the present invention. 
     FIG. 2 depicts the center core tube or ignition tube  12  as a thin-walled cylinder with two open ends. The center core tube  12  typically has a wall thickness slightly less than that of the body  10  (typically 1.3-1.8 mm) may have a diameter of 17.7 mm to 31.8 mm. These dimensions are based on a 155 mm module and the devices have evolved and are designed in accordance with a large amount of accumulated interior ballistic knowledge or lore. 
     The center core tube  12  is positioned longitudinally in the body  10  and receives tubular extension  16  defining the center open portion of the body  10  and tubular extension  18  defining the center open portion of the cap  14  at  18  in the assembled modular unit. As can be seen in FIG. 3, the central portion of the cap  14  continues the hollow-center core ignition system through an opening  40  and includes a conical recessed section  42  and a tubular extension or raised rim  18  which is designed to be accommodated in one end of the center core tube  12 . In this manner, the core tube  12  overlaps and seals the internal junctures with both the module case  10  by overlapping the rim or lip extension  16  at  13  and with the central opening in the cap by overlapping the rim  18  at  19 . The outer rim of  43  of cap  14  further includes a series of protuberances or protrusions  44  spaced equally about the periphery of the open end of the cap and extending radially from the exterior surface. The protrusions  44  are designed to be accommodated or received in a groove  46  located in the body  10  (FIG. 1) so that the lid  14 , when inserted, can be snapped into place. Once installed, a great deal of force is required to remove the lid from the modular body. 
     After the cap is inserted, however, there remains a peripheral gap  48  between the sidewall of the case  10  and the outer rim  43  of the cap  14 . It is in this gap that a solvent, normally acetone for nitrocellulose units, is applied to the outer rim and by capillary action enters the gap  43  and peripherally fuses the lid rim  43  to the case body. Thereafter, the igniters  24 ,  26  and  28  can be added, together with the final weather proofing coat at  29 . 
     FIG. 4 depicts a schematic representation of a work station encompassing the mechanized sealing system in accordance with the invention. The system shown generally at  50  includes a bench or table  52  above which is mounted a molded ventilation hood  54 . The hood is provided to deal with an open front, a rearwall  56 , sidewalls  58  and a top member  60  which is, in turn, attached to a ventilation stack at  62  provided with an exhaust fan  64 . The bench is provided with a turn table station indicated generally by  66  having a driven shaft  68  and a turn table deck  70  which is preferably pneumatically driven. A modular unit similar to that depicted in FIGS. 1-3 is pictured on the turn table and is preferably fixedly mounted on a locking spindle, or the like, attached to the turn table to precisely position the modular unit relative to the solvent applicator valve nozzle. 
     The solvent dispensing system is contained within the ventilation hood  54  and is designed for pneumatic operation. The system includes a solvent storage tank  80 , a solvent supply dispensing valve  82  fixed in the desired spaced and postured relation to the turn table deck  70  as determined by the workpiece of interest to be processed and a dispensing valve  84 . A gas-tight metric needle syringe is provided at  86  operated by a limit valve  88  and an air over double-acting cylinder  90  utilizing a shaped member  92  attached to the rod  94  of the double-acting cylinder  90  and a follower arm system  96  which operates the limit valve  88 . Cylinder operating air over fluid supply containers are shown at  98  and  100  with metering orifices  99  and  101 , respectively. 
     The air over fluid supplies  98  and  100 , as metered by orifices  99  and  101 , are operated pneumatically by a power valve P 3  via pneumatic lines  102  and  104 . Line  104  is also parallel connected to operate the supply nozzle  82  in refilling the metering syringe  86 , as will be discussed. 
     The solvent tank is further provided with an air supply in line  106  via inlet  108 . A solvent outlet with pressure gauge is shown at  110  to provide solvent to the supply nozzle  82  which, in turn, is metered to the dispensing valve  84  using the metering needle syringe  86 . The dispensing operation is timed and controlled by a 7000 series or equivalent controller pictured at  112  in pneumatic line  114  in series with power valve P 1 . The turn table  66  is operated pneumatically using air supplied via line  115  as controlled by power valve P 2 . The dispensing valve and turn table are supplied from a common line  106 A and parallel with line  106 . A shut-off valve is provided at  116  and is further interlocked with the vent fan  64  via conductor  117  to prevent operation of this system without ventilation. 
     The control system for the solvent sealing process step of the invention is pictured schematically in FIG.  5 . The system includes time delay relays  120 ,  122  and  124 , relay valve contacts  126 ,  126 A and  128  and a foot valve  130 , which controls sequenced events from start to finish in a module sealing cycle including a series of three events at  140 ,  150  and  160  via the main sequencing control module. 
     In operation, once the system is turned on, the timer of time delay relay  120  times out and establishes the enabling or starting point by initiating the switching of relay valve context  126  and  126 A (opening context  126  and closing contacts  126 ). This provides power to the operator-controlled foot valve  130  via relay valve contact  128 . By closing the foot valve  130 , the operator initiates an automatic timed sequence of events which results in the solvent sealing of the module lid as will be discussed next. 
     The closing of foot valve  130  produces a signal at  132  which initiates event  140  by turning on P 1 , P 2  and P 3  introducing air into the system which starts the turn table rotating via P 2  and line  115  at a predetermined speed. It also opens the dispensing valve  84  via P 1  and timing controller  112  through line  114 ; and via P 3  supplies air to line  102  to extend cylinder  90  and via  92  depress the plunger of needle syringe  86  to dispense a measured amount of solvent to dispensing valve  84 . In this manner, as the module is rotated a known radial distance, usually about 2 revolutions a measured amount of solvent is uniformly applied through the dispensing valve  84  using the precise control of an air over oil cylinder system and the needle syringe  86 . 
     During the solvent application, overall control timer  122  is timing out and thereafter this produces a signal at  134  which turns off everything in event  140 . This provides a positive shutoff for the solvent to prevent overuse or spillage-long a problem in the manual step. Signal  134  also initiates event  150  by switching relay valve  2 A thereby opening relay valve contacts  128  thereby dropping out foot valve  130  and switching valve P 3  to initiate a pressurized refill sequence for he solvent dispenser. This pressurizes line  104  which also opens solvent supply dispensing valve  82  and retracts or collapses cylinder  90  via air over operator  98 . This, in turn, raises the plunger and enables the precise refilling of the needle syringe  86  with another measured amount or dose of solvent. When the follower arm  96  reaches its upper limit indicating that the needle syringe is refilled to contain the desired volume of solvent, valve  88  closes producing a signal at  136  that turns off event  150  and initiates event  160 . Timer at  124  turns on, contacts  128  are again closed and contacts  126  and  126 A reset to their normal positions. Once timer  124  times out, a signal at  138  turns off event  160  at  142  thereby ending the cycle. 
     In one embodiment, the electronically controlled solvent dispenser valve  84  and needle syringe  86  cooperate to dispense 1.6 cc of solvent in a 12-second timed sequential step in which an air driven turntable system  66  is controlled at 10 rpm. The electronic dispensing valve  84  controls the rate of disposition of solvent and an electronic timer controls the duration of application rate and duration of application, of course, can be modified as desired. 
     This invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.