Damped filament dispenser

Abstract: A missile data link filament (12) dispenser (10) is located within an enclosure (20) having a single eyelet opening (26) through which the filament feeds on launch. A quantity of a particulate material (28) located within the enclosure (20) is converted to an aerosol mixture by the filament movement on dispense. The aerosol mixture serves to act as a brake on the filament preventing dispense speed exceeding a predetermined desirable maximum.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a filament dispenser for a missile or other moving vehicle, and, more particularly, to a filament dispenser which damps transverse oscillations of the unspooling filament. 2. Description of Related Art A number of missiles remain interconnected with control apparatus upon launch by a filament, either wire or preferably an optical fiber, via which navigational information is exchanged over at least a part of the missile travel path. These filaments are typically wound into a pack carried on the missile, or other vehicle, and care must be taken in the manner of unspooling the filament (dispensing) to prevent damage to the filament. One difficulty encountered on dispensing a wound filament pack, especially at high speeds, is the tendency for the filament to form helical loops of relatively large amplitude extending transversely of the dispensing direction. Such loops require a correspondingly large exit port for filament dispensing which may be undesirable. Also, the loops on leaving the vehicle experience air drag in an amount dependent upon size which is desirably kept to a minimum. Still further, the radar cross-section of the vehicle (i.e., detectability) is accordingly maintained at a size larger than desired. The loops also prevent ducting of dispensed filament prior to release into the ambient airstream. It is, therefore, highly desirable to provide a filament dispensing technique ideally producing a linear trajectory allowing dispense from a small exit port. Also, all of this should be accomplished without subjecting the filament to significant risk of damage, destruction or reduction in signal transmission capabilities. DE-C-867983 describes a thread or fiber dispenser comprising a wound pack of the thread or fiber secured in a container. Thread or fiber from the pack is fed at high speed through an eyelet in a plate above the container. Transverse movement of the thread or fiber is damped by partially filling the container with a liquid, so that the wound pack is immersed in the liquid. DE-C-867983 describes the preamble of independent claims 1 and 2. US-A-2620998 describes a thread anti-balloon device for limiting the lateral movement of a thread being taken off a bobbin at high speed. The device comprises a housing surrounding the bobbin such that contact with an inner surface of the housing exerts a braking action on the thread. An eyelet is provided at one end of the housing, through which the thread is pulled from the housing. The present invention provides an apparatus for dispensing a filament from a wound pack, comprising: wall members defining a hollow enclosure within which the wound pack is fixedly mounted, one of the wall members having a single eyelet opening through which the filament passes on dispensing; and means for damping transverse movement of the filament during dispensing, characterized in that the means for damping comprises a quantity of a pulverulent material located within the enclosure, which material is induced into an aerosol within the enclosure by the filament movement during dispensing. The present invention also provides an apparatus for dispensing a filament from a wound pack, comprising: an enclosure for the wound pack including wall members having a single eyelet opening therein through which the dispensed filament passes on dispensing; and means for damping transverse movement of the filament during dispensing, characterised in that the means for damping comprises: a nozzle mounted in an enclosure wall member and directed into the enclosure interior; and a source of supply of a pressurized aerosol connected to the nozzle, for supplying the aerosol to the enclosure interior during dispensing of the filament. The present invention further provides a missile having mounted therein an apparatus for dispensing a filament according to the above aspects of the invention. Prior to or at the start of the filament dispensing, the enclosure is filled with an aerosol mixture which has sufficient density to damp the unspooling filament transverse kinetic energy so that linear payout results. Not only are the already referenced advantages obtained, but a linear dispense trajectory is advantageous in enabling avoidance of the missile rocket plume which could otherwise destroy or damage the filament. In the accompanying drawings: FIG. 1 is a perspective, partially fragmentary view of a first form of the invention; FIG. 2 is a side elevational view of an alternative embodiment; and FIG. 3 is a side elevational view of yet another embodiment. FIG. 4 depicts general filament dispensing from a missile 34. Turning now to the drawing and particularly FIG. 1, the filament dispensing apparatus of the invention is enumerated generally as 10. More particularly, a filament 12 is wound into a pack 14 on a cylindrical drum 16 which is tapered to a relatively smaller diameter takeoff end 18. A hollow enclosure 20 is cylindrical and of such internal dimensions as to enable coaxially securing the large end of the drum 16 to the closed end wall 22, while at the same time providing space for the filament to be taken off the pack without contacting the enclosure walls. The enclosure end wall 24 opposite the drum small end 18 includes a small opening or eyelet 26 through which the filament 12 passes on dispense. The outer end of the filament 12 interconnects with apparatus located at the launch site (not shown) while the other end of the filament is similarly connected to on-board apparatus (not shown). Neither of these apparatus nor the connections thereto are shown since they are conventional and detailed understanding is not necessary for a full understanding of this invention. A quantity of an aerosol powder 28 is openly positioned within the enclosure 20. Immediately upon the filament beginning dispense, the moving filament agitates to aerosol powder causing it to form an aerosol mixture or suspension within the enclosure. The aerosol mixture is sufficiently dense to act as a brake upon the filament reducing the formation of transverse loops. That is, the aerosol mixture provides an aerodynamic drag to the unspooling filament which damps transverse kinetic energy permitting the filament to exit via eyelet 26 along a substantially linear trajectory. In explanation, it is known that braking of an unspooling filament by contact with a solid surface reduces transverse "ballooning" of the filament. However, such braking is not completely satisfactory in that the filament may be subject to undue abrasion and tensile forces resulting in undesirable bending, kinking or even severing of the filament. In seeking a substitute for mechanical braking, liquids were considered for use in the enclosure, but all were found to be too dense resulting in excessive filament tensile stress on dispense. Failing to find a liquid within the necessary density range, gases were considered; however, no gas could be found having a sufficiently high density to provide satisfactory damping. An aerosol mixture which consists essentially of very fine solid or liquid particulate matter suspended in a gas has been found to possess the required range of density, namely, greater than that of any gas found but less than that of a liquid. Although other aerosol materials and amounts may be found advantageous, for an enclosure having an interior 30 cm long and 15 cm in diameter, 300 gms of molybdenum disulfide powder (sold under the trade designation Z-Powder) will be kept air borne within the enclosure by the filament unspooling movement and at the same time provide the desired filament braking. Although an optimum density of an aerosol containing the above mentioned powder has not been determined as yet, it is clear that an aerosol mixture having a density of less than about 10 times the density of air will be insufficient. On the other hand, an aerosol mixture density of an aerosol containing the above mentioned powder exceeding 100 times that of air is too great for filament safety or to insure satisfactory signal transmission. As an alternative embodiment, the aerosol mixture can be supplied from a pressurized source 30 and selectively injected into the enclosure 20 via a nozzle 32 (FIG. 1). Results obtained are the same as in the first described embodiment. FIG. 4 depicts general filament dispensing from a missile 34. As shown, the filament dispenser 10 is located generally midships and the filament 12 extends outwardly of the missile for connection with apparatus at the launch site (not shown). At launch, the filament unwinds maintaining the interconnection for the required part of the flight path. FIG. 2 shows application of the invention to a filament canister constructed for inside payout which is advisable for certain uses. Also, FIG. 3 shows an embodiment in which the filament is caused to reverse its direction on being taken off the drum before passing through eyelet. In both cases the addition of an aerosol mixture either via a spray nozzle or by filament induced turbulent air movement over a quantity of particulate source material can be used to achieve the desired filament braking. In the practice of the present invention the reduction of filament transverse oscillations acts ultimately to reduce air drag on the dispensing vehicle. Radar cross-section of the vehicle is also reduced. Since filament ducting is possible (e.g., via eyelet) dispensing in a manner to avoid the rocket plume is facilitated. As a result of such ducting, higher speed and longer range missions for the missile are made possible. Although the present invention has been described in connection with a preferred embodiment, it is to be understood that modifications may be made that come within the scope of the appended claims. For example, instead of a single component aerosol, multiple components may be used, certain ones of which provide other and different advantageous operational characteristics (e.g., lubricity).

Claims: A filament and an apparatus(10) for dispensing such a filament (12) from a wound pack (14) of said filaments, comprising: wall members defining a hollow enclosure (20) within which the wound pack (14) is fixedly mounted, one of the wall members (24) having a single eyelet opening (26) through which the filament (12) passes on dispensing; and means for damping transverse movement of the filament (12) during dispensing, characterised in that the means for damping comprises a quantity of a pulverulent material (28) located within the enclosure (20), which material is induced into an aerosol within the enclosure (20) by the filament (12) movement during dispensing. A filament and an apparatus (10) for dispensing such a filament (12) from a wound pack (14) of said filaments, comprising: an enclosure (20) for the wound pack including wall members having a single eyelet opening (26) therein through which the dispensed filament (12) passes on dispensing; and means for damping transverse movement of the filament (12) during dispensing, characterised in that the means for damping comprises: a nozzle (32) mounted in an enclosure wall member and directed into the enclosure interior; and a source of supply (30) of a pressurized aerosol connected to the nozzle (32), for supplying the aerosol to the enclosure interior during dispensing of the filament (12). A filament and an apparatus according to claim 1 or 2, in which the enclosure (20) is a hollow cylinder with the wound pack (14) affixed to an inner circular end surface (22) of the enclosure and the eyelet opening (26) is formed in the opposite circular end surface (24). A filament and an apparatus according to claim 1 in which the pulverulent material is molybdenum disulfide. A filament and an apparatus according to claim 1, 3 or 4 in which the pulverulent material (28) is present in an amount sufficient to provide, during dispensing of the filament (12) a density of said aerosol within the enclosure (20) of between 10 and 100 times the density of air. A filament and an apparatus according to claim 2, in which the aerosol provided in the enclosure interior during dispensing of the filament (12) has a density of between 10 and 100 times the density of air. A missile (34) having mounted therein a filament and an apparatus (10) for dispensing a filament (12) from a wound pack according to any preceding claim.

Inventors: CHESLER RONALD B, CHESLER, RONALD B.
Applicants: HUGHES AIRCRAFT CO, HUGHES AIRCRAFT COMPANY
Application year: 1990
Main classification: F42B15
IPC codes: F41G7, F42B15, B65H75, B65H59, B65H63, B65H49