Airship docking mechanism

A system and method for docking an airship to a mooring mast includes a thruster that is mounted to the fore end of the airship. When activated, the thruster generates a thrust vector that is substantially perpendicular to the longitudinal axis of the airship and is selectively directional. In particular, the configuration of the thruster can be changed to vary the direction of the thrust vector around the longitudinal axis to maneuver a connector on the thruster into contact with the mooring mast. Engagement of the connector to the mooring mast then docks the airship to the mooring mast.

FIELD OF THE INVENTION

The present invention pertains generally to docking systems for airships. More particularly, the present invention pertains to docking systems that incorporate a thruster, which maneuvers the fore end of an airship into contact with a mooring mast during the docking of the airship. The present invention is particularly, but not exclusively useful as a system and method for docking an airship to a mooring mast wherein the thruster uses elongated airfoil blades to generate aerodynamic thrust for maneuvering the airship.

BACKGROUND OF THE INVENTION

While advances in technology have improved many aspects of airship operations, docking an airship to a mooring mast still remains a labor intensive and operationally difficult task. In fact, the majority of accidents involving lighter-than-air airships occur during a docking procedure.

In general, docking an airship requires releasing mooring lines from the airship, which are then grasped by a ground crew. Next, the ground crew directs the nose section of the airship into an anchoring mechanism on the mooring mast. While this process is time-consuming and difficult under ideal conditions, if winds are gusting or there are significant up and down drafts, docking becomes an ever more difficult process. This is primarily due to the large cross-sectional area of airships and their otherwise limited maneuverability.

In light of the above, it is an object of the present invention to provide a system and method for docking a lighter-than-air airship to a mooring mast that uses a thruster mounted on the fore end of the airship to maneuver the fore end of the airship into position for docking. It is another object of the present invention to reduce the required number of ground crew members by providing additional airborne maneuverability to airships during the docking process. It is yet another object of this invention to make the docking process for airships safer. Still another object of the present invention is to provide a docking system for lighter-than-air airships that is easy to use, relatively simple to implement, and comparatively cost effective.

SUMMARY OF THE INVENTION

The present invention is directed to a docking system that operates to maneuver a lighter-than-air airship into position for docking the airship to a mooring mast. In general, the airship defines a longitudinal axis and it can be of a rigid, semi-rigid, or non-rigid type construction. As envisioned for the present invention, the docking system includes a thruster that is mounted in alignment with the longitudinal axis at the fore end of the airship. When activated, the thruster generates a thrust vector that is substantially perpendicular to the longitudinal axis of the airship. Further, this thrust vector is selectively directional around the longitudinal axis to maneuver the fore end of the airship. Docking of the airship is then accomplished by maneuvering the fore end of the airship with the thruster until a connector, which may be mounted on the thruster, engages with the mooring mast. Engagement of the connecter with the mooring mast then docks the airship to the mooring mast.

Structurally, the thruster of the present invention includes a first hub that defines a hub axis. In its orientation on the airship, the first hub is mounted at the fore end of the airship and its hub axis is collinear with the longitudinal axis of the airship. Additionally, a plurality of equally spaced-apart blade gears are mounted on the periphery of the first hub for rotation with the first hub. Also, an airfoil blade is fixedly attached to each of the blade gears, for movement with the respective blade gear. In more detail, the blades are elongated to define a blade axis, and each blade is mounted With its blade axis substantially perpendicular to the first hub. Thus, each blade extends from the first hub, substantially parallel to the longitudinal axis of the airship. Further, each airfoil also defines a chord line that extends from the leading edge to the trailing edge of the airfoil blade. In this configuration, when the first hub is rotated, each airfoil blade will travel on a circular blade path around the longitudinal axis of the airship and generate aerodynamic forces. The thruster may also include a second hub that is connected to the ends of the airfoil blades, opposite the first hub.

Control over the aerodynamics forces generated by each airfoil blade is provided by a dedicated gear assembly that collectively includes the blade gear mentioned above, a mid-gear, and a center gear. In their relationship to each other, the mid-gear is intermeshed between the blade gear and the center gear. Further, a link interconnects the center of the blade gear to the center of the mid-gear, and another link interconnects the center of the mid-gear to the center of the center gear. In addition, all three gears are substantially the same diameter and are coplanar with each other. Within this assembly, the blade gear, mid-gear, and center gear can be rotated about their respective axes. Thus, when the first hub is rotated, the blade gear urges against the mid-gear, which in turn, urges against the center gear. Meanwhile, the centers of the various gears remain connected by the links, resulting in the simultaneous rotation of all three gears.

As envisioned for the present invention, several gear assemblies will be incorporated into the first hub. The respective center gears will then establish a gear cluster in which all of the center gears rotate about a common center gear axis. For purposes of disclosure, the common center gear axis will always be substantially parallel with the longitudinal axis of the airship.

In operation, the thruster is activated by rotating the first hub. Because each blade gear is mounted near the periphery of the first hub, the airfoil blades that are mounted on the blade gears are respectively driven along the blade path around the longitudinal axis of the airship. Rotation of the blade gear along the blade path results in the rotation of the blade gear, mid-gear, and center gear about their respective axes. Further, rotation of the blade gear about the blade gear axis causes the airfoil blade and the chord line of each airfoil blade to rotate as well. Thus, as the first hub rotates, the airfoil blade travels on the blade path and the chord line simultaneously rotates about the blade axis. In this motion, the chord line of the airfoil blade remains substantially tangential to the blade path during the rotation of the first hub.

For thrust and control purposes, cyclical variations of the respective angles of attack for each airfoil blade (i.e. the relationship between the chord line and the blade path) are introduced by moving the cluster of center gears. In greater detail, this movement is accomplished by moving the cluster of center gears omni-directionally in a plane such that the common center gear axis remains substantially parallel to the longitudinal axis of the airship. As a consequence, for each location of the center gear axis, changes in the respective angles of attack of each airfoil blade remain azimuthally uniform as the airfoil blades rotate about the longitudinal axis.

It is well known that when an airfoil passes through a fluid medium at some angle between the airfoil and the relative direction of the passing fluid medium, a force is produced. Lift is the component of the force that is perpendicular to the relative direction of the passing fluid medium. Thus, in the present invention, as the airfoil blades travel along the blade path, each airfoil blade produces a lift force. When the lift forces produced by the various airfoil blades are summed, a single resultant thrust vector is produced. Consequently, the direction of this thrust vector is controlled by cyclically changing the angle of attack of each airfoil blade in the manner previously described.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially toFIG. 1, a docking system in accordance with the present invention is shown and generally designated10. As shown inFIG. 1, the system10includes an airship12and a mooring mast14. As further shown, the airship12includes a fore end16, an aft end18, a longitudinal axis20extending between the fore end16and the aft end18, a propulsion unit22, and mooring lines23a-e. It is to be appreciated that a thruster24(best seen inFIG. 2) is mounted on the fore end16of the airship12for generating a thrust vector (T) that is substantially perpendicular to the longitudinal axis20and selectively directional. Further, the propulsion unit22generates a propulsion force (P). Working together, the propulsion unit22and the thruster24maneuver the airship12until the connecter26, which is attached to the thruster24, engages with the mooring mast14. Engagement of the connector26with the mooring mast14docks the airship12to the mooring mast14.

Referring now toFIG. 2it can be seen that the thruster24includes a hub30. As shown, a plurality of airfoil blades32are rotatably mounted to the periphery of the hub30. As contemplated by the present invention, it is to be appreciated that the blades32a,32b, and32care only exemplary. Further, the airfoil blades32have two ends,34and36, with end34mounted on hub30. As intended in the present invention, the plurality of blades32can be rotated with the hub30about the longitudinal axis20. Another hub40is mounted on the end36of blade32.

Still referring toFIG. 2, each blade32has a blade axis38that generally extends in a direction from the end34to the end36. Using this structure as a base for reference, the aerodynamic properties of the blade32will be better appreciated with reference toFIG. 3.

As shown InFIG. 3, it can be seen that each blade32defines a chord line42extending from the leading edge44of the blade32to its trailing edge46. Depending upon several factors, which include the respective design shapes of the upper surface48and the lower surface50of the blade32, and the angle of attack (α) between the chord line42and the relative wind52, an aerodynamic force (R) will be generated on the blade32in accordance with well known aerodynamic principles. Specifically, as shown inFIG. 3, the components of the force (R) will include lift (L) and drag (D), as well as a moment (M). For purposes of this disclosure, it is sufficient to appreciate that these forces are generated on the blade32in response to a relative wind52, and that these forces can be controlled by properly orienting the blade32with the relative wind52(i.e. by changing the angle of attack, α). How this is accomplished for the present invention is best considered with reference toFIG. 4.

InFIG. 4, it is to be appreciated that a hub gear60is fixedly attached to the hub30. Consequently, the rotation of a drive gear62by a drive shaft64causes the hub30to rotate relative to the airship12. It is also to be appreciated that the blade32is fixed to a blade shaft66, which in turn is held onto the hub30by a pivot mount68. As intended by the present invention, the blade32is driven in rotation about the longitudinal axis20by the hub30while, at the same time, the blade32is free to rotate about the blade axis38.FIG. 4also shows that a blade gear70is attached to the blade shaft66for rotation therewith.

By cross-referencingFIG. 4withFIG. 5A, it can be seen that the blade gear70is a component of a gear assembly that is shown inFIG. 5Aand designated71. In detail, the gear assembly71is a combination of the blade gear70as well as a mid-gear72and a center gear74. Further, the gear assembly71includes a link76that interconnects the center of rotation of the blade gear70with the center of rotation of the mid-gear72. Similarly, a link78interconnects the center of rotation of the mid-gear72with the center of rotation of the center gear74. At this point it is to be understood that for the present invention, the hub30preferably includes three separate gear assemblies71. Accordingly, the respective center gears74of the gear assemblies71have been variously designated74a,74b, and74c. However, discussions herein are often made with reference to only a single center gear74. As such, the referenced center gear74may be any one of the gears74a,74b, or74c.

Referring again toFIG. 4, it is shown that the center gear74is fixedly attached to a shaft82. Further, the shaft82and the center gear74are co-axial. Importantly, although the center gear axis80and the longitudinal axis20are parallel, they are not necessarily co-linear. As disclosed in more detail below, relative off-set movements between the center gear axis80and the longitudinal axis20provide control over the angle of attack (α) of the airfoil blade32. Still referring toFIG. 4, an x-y pad84is shown mounted on the airship12so as to be moveable relative to the airship12. Further, a guide86is mounted on the x-y pad84that is used to hold the shaft82stationary relative to the x-y pad84without hindering rotation of the shaft82.

Referring now toFIG. 5A, a gear assembly71is shown at a location90on a blade path88. In greater detail, the blade path88is the circular path that the gear assembly71travels in response to the rotation of the hub30. Further, the gear assembly71is shown with the elements of the gear assembly71, the center gear74, mid-gear72, blade gear70, and links76and78, in a particular configuration. The same gear assembly71is shown at a different location91on the blade path88and is designated71′(shown by dashed lines). Importantly, at all locations on the blade path88, the center gear axis80and the longitudinal axis20of the airship12are substantially, collinear. Within this configuration, it is to be appreciated that at location90, the link76and the link78form an angle (β), and at location91the links76′ and78′ form the same angle (β). Also shown is the orientation of the airfoil blade32at location90. As contemplated by the present invention, the angle of attack (α) is dependent upon the orientation of the chord line42of the airfoil blade32, relative to the blade path88. In this present configuration, the chord line42at location90is substantially parallel to a line92, which is tangent to the blade path88at location90. Consequently, the airfoil blade32has an angle of attack (α) of zero. Similarly, at location91on the blade path88, the angle of attack (α) is zero as well because the chord line42′ is substantially parallel to a line93, which is tangent to the blade path88at location91.

Referring now toFIG. 6with cross reference toFIG. 5B, control over the respective angles of attack (α) for the airfoil blades32is accomplished by collectively moving the cluster of center gears74omni-directionally in a plane such that the center gear axis80remains substantially parallel to the longitudinal axis20of the airship12. In particular, the translational movement of the cluster of center gears74is accomplished by moving the x-y pad84. InFIG. 6it can be seen that to do this, a frame100is mounted on the airship12and a servo102, which is also mounted on the airship12(seeFIG. 1), is connected between the airship12and the frame100to move the frame100in a back-and-forth motion in the x-direction (indicated by the arrow104). Another independently operated servo106is mounted directly on the x-y pad84and is connected to the frame100to move the frame100in a back-and-forth motion on the x-y pad84in the y-direction (indicated by arrow108). As intended for the present invention, movement of the x-y pad84in its x-y plane on the airship12can be accomplished omni-directionally through a distance from the longitudinal axis20that may be as much as one half the diameter of the center gear74.

Referring toFIG. 5Bwith cross reference toFIG. 5A, the center gear axis80has been displaced through a distance “d” from the longitudinal axis20. As a result of this displacement, a changed configuration is shown for gear assembly71at location90. In this configuration, the links76and78form an angle (β′), where β′<β. In addition, the chord line42of airfoil blade32has been rotationally displaced about the blade gear axis38, in the direction indicated by the arrow94. Importantly, the rotation of the chord line42from the line92is the angle of attack (α′) for the airfoil blade32. Similarly, at the location91, the links76′ and78′ now form an angle (β″), where β″>β. Further, the chord line42′ of the airfoil blade32′ has been rotationally displaced about the blade gear axis38′ from line93, in the direction indicated by the arrow95. The rotation of the chord line42′ from the line93defines an angle of attack (α″) for the airfoil blade32′.

In operation, an operator manually or remotely activates the thruster24and moves the center gear axis80through a distance “d” from the longitudinal axis20of the airship12, creating a thrust vector (T). In greater detail, there are two separate movements to consider.

Referring toFIG. 5A, the first movement is the rotation of the gear assembly71about the center gear axis80on the blade path88. With the rotation of the hub30in the direction shown by the arrow96, the airfoil blade32is moved along the blade path88in the same direction96. This movement causes the blade gear70to urge against the mid-gear72, which in turn, urges against the center gear74. Meanwhile, the centers of the various gears70,72, and74remain connected by the respective links76and78. Further, the center gear axis80is held substantially stationary relative to the blade path88, and collinear with the longitudinal axis20. In this configuration, all of the gears,70,72, and74rotate. Specifically, the blade gear70rotates in the direction of arrow96, the mid-gear72rotates in the direction of arrow97, and the center gear74rotates in the direction of arrow96. In addition, because all of the gears70,72, and74have substantially the same diameter, as the gear assembly71travels along the blade path88, the orientation of the chord line42of airfoil blade32remains substantially the same with respect to the blade path88. For example, as the gear assembly71rotates from location90to location91on the blade path88, the angle of attack (α) of the airfoil32remains substantially zero. Similarly, as the links76and78rotate about the center gear axis80, the angle (β) between the links remains constant. On the other hand, as the center gear axis80is displaced through a distance “d” from the longitudinal axis20, the angle between the links (β), and subsequently the angle of attack (α), no longer remains constant. This is best seen inFIG. 5B.

As shown inFIG. 5Bwith cross reference toFIG. 5A, the second movement is the displacement of the center gear axis80through a distance “d” from the longitudinal axis20. As contemplated by the present invention, the center gear74does not rotate during the displacement. Consequently, at the location90, the angle between links76and78decreases to less than the angle (β). As the angle between the links76and78decreases, the airfoil blade32rotates in the direction of arrow94. Further, at location91, the angle between the links76′ and78′ increases to greater than the angle (β), rotating the airfoil blade32′ in the direction of arrow95. Importantly, the angle of attack (α′) for the airfoil blade32at location90is equal to the difference between the angles (β) and (β′). Similarly, the angle of attack (α″) at location91is equal to the difference between the angles (β″) and (β).

When the two movements are superimposed, the resulting movement is a cyclically varying angle of attack (α) for the airfoil blade32. Still referring toFIG. 5Bwith cross reference toFIG. 5A, as the gear assembly71rotates about the offset center gear axis80and travels along the blade path88, the angle between the links76and78continuously varies. As indicated above, at any given location on the blade path88, the orientation of the chord line42of the airfoil blade32is dependent upon the angle between the links76and78. Thus, when the angle between links76and78is less than the angle (β), the chord line42is oriented in the direction of arrow94. On the other hand, when the angle between the links76and78is greater than the angle (β), the chord line42is oriented in the direction of arrow95. In both cases, the orientation is relative to a line tangent to the blade path88at the given location. This orientation of the airfoil blade32determines the direction of the lift force (L) generated by the airfoil blade32. Specifically, an orientation in the direction of arrow94generates a lift force (L) directed to the longitudinal axis20, and an orientation in the direction of arrow95generates a lift force (L) in the opposite direction.

The displacement of the center gear axis80from the longitudinal axis20determines the maximum angle of attack (α) of the airfoil blade32. Specifically, the further the center gear axis80is displaced from the longitudinal axis20, the greater the maximum deviation of the angle between the links76and78from the angle (β). As described previously, the angle of attack (α) is equal to the difference between the angle between the links76and78, and the angle (β).

In combination, the rotational orientation of the airfoil blade32and the degree of displacement of the center gear axis80from the longitudinal axis20provide control over the magnitude and direction of the thrust vector (T) (best seen inFIG. 7) generated by the thruster24.

As shown inFIG. 7, the hub30(seeFIG. 4) is rotated about the longitudinal axis20in the direction shown by arrow110and simultaneously, the center gear axis80is moved through a distance “d” from the longitudinal axis20. Consequently, as the airfoil blades32travel on the blade path88, each airfoil blade32has a cyclically constant angle of attack (α). Within this configuration, when the lift forces (L) generated by each airfoil blade32at any moment in time are summed, a thrust vector (T) results. For example, at location112, the airfoil blade32agenerates a lift force (La) in a manner described previously. Similarly, at locations114and116, airfoil blades32band32cgenerate lift forces (Lb) and (Lc). When the lift forces (La, Lb, Lc) produced by airfoil blades32a,32b, and32crespectively, at position112,114, and116are summed, a single thrust vector (T), as shown, results.

The direction and magnitude of the thrust vector (T) can be changed by further displacing the center gear axis80. Specifically, with the further displacement of the center gear axis80, the angle of attack (α) of each airfoil blade32is cyclically changed. Accordingly, the lift forces (La, Lb, Lc) produced by airfoil blades32a,32b, and32care changed as well. When the lift forces (La, Lb, Lc) are again summed, a different thrust vector (T) results to accommodate the maneuvering requirements of the airship12during the docking procedure.