Self-forming-boom Storing And Deploying Apparatus

Abstract

Improved apparatus which stores and deploys rolled-up thin, springlike, strip material that self-unwinds and curls outwardly at its edges into a hollow tubular boom when freed of its wound state. Self-adjusting means radially constraining the edges of the outermost winding of the rolled-up strip maintains same compactly wound on the storage reel during self-unwinding, and one-way ball-type centrifugal brake means on the reel stabilizes the strip-unwinding rate while permitting unrestrained reel rotation in the winding direction.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

Deployable boom apparatus in which a thin elongated strip wound in a widthwise flattened state is self-biased to unwind and curl edgewise into an extended hollow cylindrical configuration.

2. Description of the Prior Art

In deployable boom apparatuses which store springlike metal strip in wound widthwise flattened form on a storage reel and are operable to permit self-biased unwinding extension with edgewise curling of such strip into an extensive hollow cylindrical configuration, it has been the practice, as in U.S. Pat. No. 3,144,104 to Weir et al., FIGS. 2 and 3, to so wind the strip onto the reel that its curl-prone edges face radially outward, and to retain the wound turns on the reel by conical keeper discs at opposite ends of the reel that slant inwardly in radially restraining circumferential contact with the edges of the outermost turn of the wound strip. When the reel is freed for turning about its central axis, the tape unwinds from the reel as the outermost turn curls itself edgewise and self-extends into hollow tubular form. Although in Weir et al., the axial separation distance between the conical keeper disc at opposite ends of the reel is adjustable to suit different numbers of initial strip windings, such distance remains fixed after having been adjusted to suit a fully loaded reel with a given number of turns, or windings, so that during subsequent deployment of the boom as the outermost turn of the strip maintains contact with the rotating conical keeper disc on the reel and continuously exits tangentially therefrom, the inner turns progressively expand in diameter, bloom out, and continuously redistribute themselves in the annular space between the central hub of the reel and the keeper discs. This results in a sliding movement between the turns of the strip as same unwinds from the reel and thus departs from a pure unwinding action. At least in the cases where the spring strip edges are notched to provide an interlocking boom seam, as in FIG. 8 of the Weir et al. patent, for example, such relative sliding movement between the spring strip turns during deployment from the reel can interfere with self-unwinding deployment of such strip, so that resort is made to powered arrangements such as in FIG. 7 of Weir et al. patent, where the strip is maintained tensioned on the reel between power-driven pinch rolls that pay out the strip from the reel and a slipping belt and pulley arrangement that sprags rotation on the reel.

SUMMARY

The present invention, in providing a strip storage reel having self-adjusting keeper means which operates to maintain the spring strip turns compactly wound around the reel during deployment, hence results in pure nonslip unwinding of the strip, readily enables the strip to be self-unwound without need for pinch-roll payout, even in the case of notched-edge interlock-seam boom strips. Furthermore, such self-adjusting keeper means affords opportunity for payout control through the medium of a motor on the hub portion of the reel, which may also serve for strip windup. Payout rate control is provided by a centrifugal ball-type friction-braking means on the reel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, in outline, of an improved self-forming and self-deploying extensible boom apparatus embodying the present invention;

FIGS. 2 and 3 are end and side elevation views, respectively, showing in outline one exemplification of a novel strip storage reel of the present invention as employing self-adjusting keeper means for the strip windings;

FIG. 4 is a cross-sectional view in side elevation, showing an alternate construction of a self-adjusting winding keeper reel constructed in accord with features of the present invention;

FIGS. 5 and 6 are plan views, in outline, showing the action of a compound form of self-adjusting strip keeper means of the type shown in FIGS. 2 and 3;

FIG. 7 is an end elevation view, partly in outline and partly in section, of a ball-type centrifugal friction break means for regulating the rotary speed of the strip storage reel during self-energized unwinding deployment of the strip stored on the reel; and

FIG. 8 is a section view taken along the line VIII-VIII in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the improved self-forming, self-extending boom apparatus comprises a rigid frame means 10 in which is rotatably mounted a storage reel 11 having a hub portion 12 journaled in the frame for turning about an axis 13 and to which the innermost end of the boom-forming spring strip 14 and around which such strip is wound for storage in a manner in which its self-curling edges face outwardly of the hub and become flattened widthwise of the strip as wound therearound. The strip 14, in accord with prior practice for use as extensible spaced booms, for example, is composed of metal, such as beryllium copper, properly heattreated to have a springlike characteristic that, when wound in coil form around the reel hub 12, is self-biased toward straightening out and curling edgewise into a hollow tubular boom 15 as for projection in space aboard a satellite to obtain gravity gradient stabilization, for example. Opposite side edges of the strip 14 may be notched to form a series of tabs 16 that interlock together during deployment to form a lock seam 17 for the boom 15 formed by such strip. An assemblage of guide rollers 18 and 19, rotatably mounted on the frame 10, cooperate with the inner and outer surfaces of the strip 14, respectively, to direct such strip tangentially from the reel 11 as its edges begin to curl together upon becoming free from such reel en route to assuming the hollow tubular configuration of the boom 17 it self-forms into.

Referring to FIGS. 1, 2, and 3, in accord with a prime feature of the present invention, a self-adjusting keeper means is provided on the reel 11 to maintain the strip windings thereon in a compactly wound state during storage thereon as well as during unwinding of the strip in self-ejecting extension into projecting boom shape. In the illustrative form shown in these figures, the self-adjusting keeper means takes the form of a plurality of spring tabs or fingers 18 of thin elongated form which are secured at an inner radial end to the hub 12 of the reel and which extend radially outward and axially inward of such hub at a number of circumferentially spaced-apart locations at both hub ends. The fingers 18 are made of such as spring steel and shaped to act as flexure springs which exert a radially inward force at the edges of the outermost turn of the spring strip 14 wound on the reel 11. The keeper fingers 18 are so constructed and arranged as to maintain such retaining force against the outer turn edges of the strip 14 during unwinding of the strip from the fully loaded to the fully unloaded states of the reel, as such outer turn unwinds from the reel and becomes progressively closer to the hub 12. Also, the spring fingers 18 are so proportioned relative to the separation distance between the partially curled edges of the strip 14 as it leaves the reel 11 tangentially therefrom, that the maximal inward projection of the ends of such fingers, which occurs when the last several turns of the strip 14 remain on the hub 12 in compactly wound state thereon, will not engage such tangential strip region as the fingers rotate with turning of the reel hub during the strip unwinding. Flat, slotted discs 20 attached to opposite ends of the hub 12 of the storage reel 11, provide for locating the fingers 18 as well as protecting same during handling of the reel, as during assembly of the apparatus.

In FIGS. 5 and 6 is illustrated an extension of the spring finger 18 concept of FIGS. 1 to 3, wherein several circumferential arrays of such fingers are employed at different radial distances away from the hub 12 of the storage reel 11 for the strip 14, to enable accommodation of a greater number of strip turns on the reel without causing interference between the rotating fingers 18 and the edge-curling tangential region of the strip leaving the reel during unwinding deployment. FIG. 5 shows the keeper action of the outermost fingers 18 on a fully loaded reel while the inner fingers 18 are held in retracted readiness by the ends of the strip windings. FIG. 6 shows keeper action of the inner fingers 18 when only several turns of the strip 14 remain on the hub 12, while also showing that the fully projecting idle outer fingers 18 will clear the curling side edges of the tangentially leaving strip 14.

Referring to FIG. 4, the reel 11 of the present invention, embodying self-adjusting keeper means for maintaining the outermost turn of the wound strip 14 clamped at its edges constantly during unwinding of such strip, may take the alternate form as shown, which substitutes, for the fingers 18, a pair of inwardly facing conical rims 22 attached to opposite ends of a telescoping hub 23 biased by a helical compression spring 24 which constantly urges the two rims 22 toward one another to maintain such outer turn contact with the strip.

For windup of the strip 14 onto the reel 11, such as an electric motor 27 of FIG. 1, may be employed. Locking means, not shown, is provided for securing the reel hub 12 against rotation, thereby preventing unwinding of the strip until the desired time, when the reel hub 12 will be unlocked to permit its rotation by action of the self-energized unwinding strip 14.

Referring to FIGS. 1, 7, and 8, during self-energized unwinding projection of the spring strip 14 from the reel 11, it becomes important to limit the rate of payout of the tangentially leaving strip. In the present apparatus this is done by a centrifugal ball-type friction brake that imposes a degree of rotary restraint on the hub 12 of the reel according to rate of turning of such hub, thereby to obtain a limited turning rate for such hub during strip payout. A rotary part 30 of the brake means is secured to rotate with the hub 12 of the strip storage reel 11, as by attachment to a common shaft 32 journaled in the frame means 10. Rotary part 30 includes a number of circumferentially spaced-apart sockets or cavities 34 which open outwardly from a circular outer peripheral portion of such part and in which are disposed a number of ball members 36, one in each cavity. Encircling the rotary part 30, there is a stator ring 38 which is secured against rotation to a portion of the frame 10. Stator ring 38 has an annular tapered friction surface 40 that extends radially and axially inward. In the relaxed state of the brake, when the reel hub 12 is not turning, the balls 36 rest only lightly against the surface 40 if at all. During rotation of the part 30, the balls 36 are caused by centrifugal force to travel outwardly of their cavities 34 into rolling and slipping engagement with the tapered annular friction surface 40 of the stator ring 38 and become wedged between such surface 40 and a radial wall 42 in each cavity 34 to impose a restraint to relative rotation between the two parts 30 and 38, thereby between the frame means 10 and the reel hub 12, which varies in degree according to rate of rotation of such hub. This form of centrifugal braking means tends to maintain its effectiveness even in the presence of wear of the friction parts, since the balls 36 will merely assume deeper positions along the tapered annular friction surface as any wear progresses. In the exemplified configuration of FIGS. 1, 7, and 8, such brake means is rendered ineffective during strip windup, by provision of radially extending sloping end walls 44 for the cavities 34 in rotary part 30, which causes the balls 36 to move radially inward away from the tapered annular friction surface on the stator ring 38.

Claims

I claim:

1. Extensible boom apparatus, comprising,

a support frame,

a storage reel having a central hub rotatably mounted in said support frame,

strip guide means mounted on said frame a distance away from said reel,

an elongated spring strip of thin springlike material attached at one end to said hub and wound compactly therearound in a widthwise flattened state and having its opposite end extending tangentially from its reel-wound turns through said guide means,

said strip being inherently biased to unwind and project itself through said guide means while curling itself outwardly at its edges to form itself into a hollow cylindrical configuration,

self-adjusting coil keeper means on said storage reel at opposite ends of said hub exerting a resilient radially inward constraint at the edges of the outermost turn of the spring strip to maintain such strip compactly wound on the reel hub during payout unwinding of the strip from the reel and consequent reduction in diameter of such outer turn, and

a centrifugal friction brake means interposed between said frame and reel to limit the rate at which strip payment is permitted by freedom of reel rotation.

2. Extensible boom apparatus, comprising,

a support frame,

a storage reel having a central hub rotatably mounted in said support frame,

strip guide means mounted on said frame a distance away from said reel,

an elongated spring strip of thin springlike material attached at one end to said hub and wound compactly therearound in a widthwise flattened state and having its opposite end extending tangentially from its reel-wound turns through said guide means,

said strip being inherently biased to unwind and project itself through said guide means while curling itself outwardly at its edges to form itself into a hollow cylindrical configuration,

and self-adjusting coil keeper means on said storage reel at opposite ends of said hub exerting a resilient radially inward constraint at the edges of the outermost turn on the spring strip to maintain such strip compactly wound on the reel hub during payout unwinding of the strip from the reel and consequent reduction in diameter of such outer turn, said turns keeper means comprising rigid inwardly facing conical members at opposite ends of the hub, and

helical compression spring means biasing the two conical members toward one another.