The invention described herein relates to an Extendable Beam Structure (EBS) that is relatively lightweight and very compact when stowed, but extendable into a long stiff beam structure for both space and terrestrial applications. The EBS, with a telescoping central beam, is stabilized with a network of cables in tension, and standoff members in compression, like the orthogonal structural stays, known also as spreaders, attached to sailboats masts. These stays hold shroud lines running parallel to but offset from the mast in order to increase its stiffness and prevent the mast from excessive bending in high winds. The telescoping central beam is extended by means of cables and pulleys that extend and contract the beam with motor driven winches, with cables played out from the tips of the stays during the extension process, to maintain stiffness during deployment. A variety of fixed length diagonal cables provide additional lateral stability.
The EBS differs from previous telescoping masts or towers in several important ways. Conventional telescoping masts, antennas or towers utilize a plurality of nested tubes with a larger diameter tube at the base and sequentially decreasing diameter tubes that are stowed within each other then extended through various means to form the mast or tower. Various techniques have been used in the past to extend these mast structures: hydraulic, pneumatic and mechanical. In mechanical systems, cables and pulleys are used to extend and contract the masts. In addition to cylindrical shapes for the nested mast segments, there are a variety of shapes possible, triangular, and rectangular being the most prominent. Some of the extended tower structures are further stabilized structurally with diagonal cables from the top or midsection of the tower to the ground.
The EBS relies on certain elements of the prior art like a telescoping central beam structure, which is extended by means of cables and pulleys, with optional diagonal cables secured to the ground. But the EBS differs in a number of important features that allow for much larger payloads to be supported in the case of a tower, with a central beam design that is relatively light weight compared to other conventional extendable masts. In many descriptions of the prior art only one strand of cable is used to extend the mast. In the EBS, the design allows for many turns of cable in a compound pulley system that allows for substantial forces to be applied to the beam extension.
In traditional extendable masts or towers, the cylindrical, triangular or rectangular telescoping members must be relatively stout in order carry the weight of the payload, but also to prevent bending or flexing since the mast is essentially a long narrow structure with a high length to diameter ratio. This tendency to bend or flex must be countered by the strength of each of the telescoping members, which adds considerable weight. Furthermore, the wall thickness of the telescoping members somewhat limits the number of members that can be embedded one within the other when the system is in a stowed configuration. This limitation is further complicated by the addition of seals in the case of hydraulic or pneumatic systems, and spaces for cables and pulleys in the mechanical system.
In the case of the EBS, central beam is an open system, as will be seen in following figures and discussion. Rather than closed cylinders, triangles or rectangular shaped tubes, the beam segments of the EBS are stiffened plates laid up next to each other with pulleys and cables sandwiched between the plates, such that up to 20 or more segments can easily be accommodated by the designs.
The EBS is unique in that the compressive axial loads are borne by the central beam, but the bending moments on the central beam are countered by the outrigger stays and cables, acting in a manner similar to that utilized on sailboats to lightweight the mast, but also provide necessary strength. The side view of the EBS is similar to that of a typical TV tower with a triangular or rectangular cross section made up of welded pipes or angle irons. In the case of the EBS the outer members are not pipes or angle irons, but rather cables in tension. Therefore, only the central beam need be a substantial stout structure, the rest of the support being a network of relatively light weight cables and stays.
In space applications, the EBS can be deployed robotically to unfold large antennas or solar arrays, and/or provide sub-structural-members for building or extending platforms in space. On the ground, there are numerous terrestrial applications possible, like extendable towers, hereafter referred to as the Power Tower (PT), capable of lifting moderate to heavy payloads to hundreds of feet of altitude. Power Tower can be used for radio or TV broadcasting, signal direction finding, a platform for surveillance cameras, border protection, weather data collection, environmental monitoring, emergency lighting, high altitude firefighting equipment, high altitude scaffolding, and support for wind turbines. Horizontal terrestrial applications include portable bridging. The value of EBS is its portability, in that it can be stowed and deployed within a matter of minutes to perform functions that are normally performed by permanent structures or a scaffold-type structure like very tall vertical cranes that take hours or days to assemble.
The EBS is scalable in terms of size, weight and extension length. For antenna masts with relatively light payloads, the central beam could be very light weight and may not require diagonal anchoring cables. Lighter weight versions could be mounted on a truck or other vehicle as will be seen in later figures with the central beam incorporated in the body of the truck with nested stays incorporated in the roof.
The following EBS description for the sake of convenience is described with reference to the Power Tower where parts of the EBS can be described in terms such as top and bottom, horizontal and vertical. The principals of deployment, however, are the same for the EBS regardless of orientation to gravity as might occur, for example, in a deployment in space or horizontal structures like bridges.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the drawings.
a-e show an overview of the EBS as a vertical tower (Power Tower-PT), with payload.
a shows the PT in stowed transportable confirmation.
b shows the PT in being configured for deployment where packages of nested stays are rotated outward away from the stowed cluster of beam segments.
c shows the payload platform attached and raised up in order to tension the top level beam to stay fixed diagonal cables.
a is a perspective view of two levels of the EBS with all cables and stays deployed.
b illustrates the deployment of a single pair of stays.
c shows the initial deployment phase as shown in
a shows a side view of a cluster of four nested beam segments illustrating the beam extension cable and pull in various stages of extension.
b shows a side view of the same four nested beam segments illustrating how adjacent beam segments are connected together via alignment guides.
a and 4b show a dual opposing central beam system CBS variant in mid and full extension, with extension and retraction cables and winches.
a and 5b are perspective views of four BS segments of an EBS in early and later phases of deployment illustrating the stay-to-stay vertical cable deployment mechanisms.
c and 5d are side views of the nested stays in the stowed position and mid-deployment.
a-d show top views of central beam variant and hardware associated with the central beam.
a is the beam core of the simplest variant, essentially a long flat plate, with alignment tracks.
b shows beam core in the shape of a “V” to improve beam stiffness.
c shows a top view of the upper end of the BS with pulleys and cable attachment points for a “high hat” shaped core.
d is a top view of the lower end of the BS, including the lower beam extension pulleys and stay attachment points.
a-g show views of nested BS and associated pulleys, cables and other hardware.
a is a top view of the upper level of the three nested beam segments similar to that shown in
b shows the top view of the lower level of the three nested beam segments similar to that shown in
c is a front view of the lower beam with pulleys.
d is a side, edge view of the lower beam with pulleys.
e is a frontal view of the upper beam with pulleys.
f is a side view of the upper beam with embedded pulleys.
g is a magnified view of the extension cable crossover points.
a is an exploded view of the beam extension subsystem cables and pulleys illustrated in
b shows a less conventional pulley system, but one that allows a high mechanical advantage with all of the cabling in one plane routed over multiple micro-pulleys.
a shows how three stays per level can be affixed to a single set of nested beam segments shown previously in
b and 11c show with stick models how deployment of the three stay variant occurs without interference of cables and stays.
a shows an alternative three-stay variant with one set of nested stays attached to the top of the nested beam segments.
b and 12c show stick models of the three-stay variant in the pre-deployment state and the deployed state illustrating again non interference of cables and stays.
a and 14b show how four stays per beam segment in a single central beam can be supported with stabilizing cables, without the cables interfering with the stays.
a-h show it is possible to general from the previous examples that there are a number of possible stay configurations with a single central beam.
c, 15e and 15g show a composite top view of the lower platforms.
a and 18b show a truck-mounted version of the EBS with a surveillance camera mounted on the top.
a is the side view of a fully deployed bridge.
b and 19c are front views of two variants of the deployed bridge.
a-d show how the two-beam system is deployed.
a shows a top view of two packages of nested beam segments.
b and 20c show the two packages of beam segments being separated with rigid hinged stays.
d also shows a perspective view of a twin beamed bridge substructure with nested stay structures deployed.
a is a side view of one of the roadbed segments with stiffening structures rotating downward for added support.
b shows a customized shape of the beam segments to support the roadbed segments.
a-c show step-by-step process for deployment of the bridge on-site from a truck, which carries both the EBS superstructure and the roadbed segments to the site.
b illustrates a fully extended bridge prior to its placement on the opposite shore.
c is a side view of the truck illustrating deployment of the roadbed segments.
a-e show the deployment of a large solar array in space using the EBS system.
a is a side view of the stowed package with the rolled up PV membrane and deployment structure.
b is a front view of the stowed array with a rolled up PV membrane, rigid truss beams on each lengthwise side of the drum, EBS structures at each end of the drum, and a roller bearing allowing the drum to rotate during deployment.
c shows the initial deployment of the EBS with robotic rotation of the leading stays and trailing stays at each end of the drum, stretching taut fixed length diagonal cables and extendable cables.
d and e show respectively the solar array system in mid and full deployment.
a-d show an overview of the EBS as a vertical tower (Power Tower-PT), with payload.
In the second phase of pre-deployment, shown in
a is a perspective view of two levels of the EBS showing: two beam segments BS 4 each with four structural stays SS 3 in the same horizontal planes; vertical extendable cables SSE 5 connecting the tips of the stays vertically; fixed diagonal cables BSF 8 connecting stays to adjoining beam segments BS 4; fixed in-plane horizontal cables SSFi 10 connecting the stay tips in the same horizontal plane; fixed out-of-plane diagonal cable SSFo 11 connecting a stay tip at one level, to an adjacent stay tip at the next higher level. The dotted lines and arrows indicate connections to levels above and below the illustrated beam segment.
b illustrates the deployment of a single pair of stays SS3 which are rotated away from a single beam segment BSM4 around rotatable joint 12 to secure the stay in a perpendicular position relative the to BS, by tensioning of the fixed cable BSF 8 at 90 degrees. The figure shows also the stay SS3 in mid rotation as dotted lines with the un-tensioned fixed-length cable BSF 8 shown as a curved dotted line before it is pulled taut.
c illustrates that the EBS is composed of multiple BS 4 and SS 3, which are nested together in parallel in the stowed configuration, then rotated manually or robotically outward in order to accomplish the stabilized beam extension.
Central Beam Extension Subsystem
a and b shows the central beam extension subsystem BES in stowed form, mid deployment, and fully deployed.
When pulleys 13, for example, at the top of BS1, are connected via continuous cable 15 through the pulleys 14 at the opposite end of the adjacent segment BS2, a force is generated to move to the two segments past each other when the BEC is retracted at the base of the EBS until the pulleys at one end of BS1 will meet the pulleys at the opposite end of BS2 at full deployment. The right most drawing in
b shows a different feature of the beam extension subsystem BES, which is the means by which adjacent beam segments are connected to each other with alignment guides at the outer edges of each BS. One set of alignment guides is attached to the top of each BS 17 and the other set at the bottom 18. At the top of
As shown in the
Semi-Autonomous Beam Extension Subsystem (SBES)
As mentioned previously, not all of the features above for the fully autonomous EBS must be incorporated into variants, which for the sake of simplicity and cost would not require the elaborate internal beam extension subsystem.
c though 3f illustrate the sequential elevation process. In
e shows the bottom of BS1 reaching the top of BS2 at which place the BS1 is locked to BS2 via a mechanism shown in
There are many possible locking mechanisms for securing the beam segments.
f shows the process repeated where the bottom of the BS1/BS2 combined segments is locked into the top of BS3.
The retraction process encompasses a reverse process with the bottom of next to last BS unlocked from the top of the BS at the base of the EBS tower, then lowered by the SBES external mechanism to the base, wherein the BS originally third from the bottom is unlocked and lowered to base, and so on until the PT is totally retracted. The SBES system is more labor intensive and would require more manual activity by operators, but may be more cost effective for those situations where elevations and retractions are infrequent since it eliminates the many pulleys and cables associated with the autonomous beam extension system.
Dual Central Beam System
a and 4b shows a dual central beam system CBS variant in mid and full extension. The dual system consists of two extending beams as shown in
In order to maintain tension on all of the cabling being retracted by winch 16, a separate winch 24 is connected to the Beam Retraction Cable (BRC) 25 running directly from the payload level at the top to the base, providing the necessary tension to retract the EBS with cable from winch 16 allowed to play out as BRC 25 is retracted.
This dual beam system allows for 4 stays to be supported at each level as shown in
Extendable Stay to Stay Vertical Cable Subsystem
As illustrated in previous figures there are diagonal cables BSF 8 and fixed in plane horizontal cables SSFi that are stretched taut during the initial deployment phase, and extendable vertical cables SSE 5, and can vary in length depending on degree of elevation of the EBS. The mechanism for extending and contracting the vertical extendable cable SSE 5 is illustrated in
The net result of this mechanical system is to play out SSE 5 cable to lengths which are equal to the lengths in elevation of the beam segments BS 4 as the multiple BS slide past each during the EBS elevation. When the EBS is retracted, the reverse process occurs, that is, the vertical cables SSE 5 contract in direct proportion to the contraction of the beam segments. This mechanical system assures that the stays remain perpendicular to the attached beam segment as the EBS is raised and lowered, and maintains enough tension in the outer cable network to assure that the whole structure is stabile during elevation and retraction of the EBS.
c and 5d are side views of the nested stays in the stowed position (
Stay to Stay Diagonal Cable Subsystem
In order to counteract torsion moments in the fully extended beam structure, it might be advantageous to add diagonal fixed cables from one stay tip to an adjacent stay tip, at different levels as shown in
Integration of Central Beam, Pulleys, Cables and Stays
a-d show top views of central beam variant and hardware associated with the central beam.
a-g shows views of nested BS and associated pulleys, cables and other hardware.
c is a frontal view of the lower beam with pulleys 14, stay attachment tabs 31, rotary joint 12 and stay 3a in the stowed position, and stay 3b in the rotated or deployed position.
d is a side, edge view of the lower beam with pulleys 14, attachment tab 31, and alignment track 19.
e is a frontal view of the upper beam with pulleys 13, continuous cable BEC 15, beam control cable BCC 32, pulleys 33 that rout cable BCC 32 across the top of the upper beam segment 4 reversing its direction, beam crossover point 34 where cable BEC 15 is routed across the BS to the adjacent BS, beam crossover point 35, where BCC 32 is routed across the BS to the adjacent BS, BSF 8 cable, and attachment tabs 30.
f is a side view of the upper beam with embedded pulleys 13, (in the figure hidden from view, but shown as dotted lines), attachment tab 30, and alignment track 19 and crossover point 34.
g is a magnified view of the crossover points 34 and 35, where pulleys 36 allow a low friction transition from one side of the beam segment to the other when cables 15 and 32 are under tension. This transition could be accomplished without the pulleys, but with added friction.
a is an exploded view of the beam extension subsystem cables and pulleys illustrated in
In the 8-pulley system shown in
The importance of mechanical advantage between each BS is important for two reasons. With relatively stout central beam segment system, the EBS can lift heavy payloads with smaller diameter cabling, which is required for pulleys with modest diameters. Furthermore, a large force is required to overcome friction in other pulley systems required to play out the vertical cables at the tips of the stays during EBS extension as described.
b shows a less conventional pulley system, but one that allows a high mechanical advantage with all of the cabling in one plane routed over multiple micro-pulleys 13b and 14b, with different radius of curvature so that turns of the cable with smaller radius of curvature can be nested within curvatures with a greater radius. The advantage of this variant pulley system is as follows. For applications where there are many beam segments, it is advantageous to minimize the space between each beam segment so that the out-of-plane thickness of the beam segment package itself is not too great.
In order to increase mechanical advantage in the system shown in
Beam Segment Extension Control Subsystem
a and 8b show the beam control cable BCC 32 routed through crossover point 35 and across pulleys 33, descending toward the lower end of the BS.
As can be seen from the drawing, the retraction of cable 32a by winch 36 with BS 4a being stationary elevates BS 4b by the amount of cable length retracted by winch 36. The movement upward of BS 4b in turn retracts fixed length cable 32b, which is anchored at point 38a, such that BS 4c is elevated by a like amount by the retraction of cable 32b attached to BS 4c at point 37c. All BS are in turn elevated by this mechanical linkage, each over adjacent BS by an amount equal to the length retracted by the winch 36.
Thus each BS is raised simultaneously and equally by the action of winch 36. Thus any movement by one of the beam segments will cause or be caused by the retraction of the first length of cable 32 by winch 36. Furthermore, during elevation, Beam Retraction Cable BRC 25 attached to the payload at the topmost BS is played out by winch 24 in length equal to the length of elevation of the EBS during any portion of the upward deployment. These two cable systems thus guarantee that the beam segments will be deployed in a simultaneous but controlled manner such that there is equal distance between each level as it ascends and descends
The action of winch 36 connected to and operates in conjunction with winch 16 in
Citing, for example, the 135 foot tower described above, with 15 ten foot segments at full extension would entail 9 ft. of cable BCC 32 retracted on winch 36, but 15×9 ft.×7=1305 ft. of cable BES 15 retracted on winch 16, where 15 is the number of BS segments, 9 ft. is the amount of elevation of each BS, and 7 is the mechanical advantage of the upper and lower pulley systems 13 and 14, as described previously. Furthermore, the Beam Retraction Cable would be played out 9 ft.×15 or 135 ft. at full EBS extension, but in an amount during deployment, which is proportional to the length required to maintain a restraining force on the whole deployment.
Control of EBS Deployment, Cable Play Out/Retraction Subsystem
Simultaneous and equal extension of the beam segments can be controlled through the simultaneous and integrated play out and retraction of the various cables by the winch subsystem, whether through a mechanically linked integrated winch subsystem described in subsequent paragraphs and a figure or a distributed electronically controlled set of winches. The winch system must simultaneously control the extension and retraction of four cable subsystems: Beam Extension Cable_(BEC) 15, the Beam Retraction Cable (BRC) 25; the Beam Control Cable (BCC) 32: and the External Anchoring Cables (EAC) 6 which is optional for certain applications. This could not be done efficiently and successfully if the beam segments were deployed randomly. Likewise a beam extension strategy described previously where the top most BS is deployed fully, with all other segments locked down, then the next segment deployed fully and so on until the last segment is deployed, though theoretically possible, would be unnecessarily complex, with locking and release systems required, along with a very complex winching system.
The rationale for maintaining control by means of the three essential the Beam Control Subsystem cables and their winches is as follows. The Beam Extension Cable 32 is continuous through all beam segments. If the multiple beam segments were “free floating” that is not controlled by other means, then the contracting force between each BS pair could differ slightly due to frictional losses in the multiple pulley systems, with the upper BS experiencing less friction due to their location. Thus the extension of the EBS would be somewhat haphazard, with some BS pairs experiencing more extension than others.
With the multiple BCC cables in place, the EBS deployment is under control as follows. When the bottom BS pair experiences the force of extension due to the retraction of the BEC 15 cable, the next pair will encounter not only the extension force due to BEC 15, but also the extending force of the BCC 32 cable subsystem, which however, allows only as much extension as is allowed by the length of cable retracted on winch 36. In fact, the BS pair is restrained not to extend further by the BCC 32 cable subsystem. Since all BS pairs are mechanically connected in like manner, this has the effect of controlling the extension of the whole EBS system simultaneous and with equal spacing among the multiple BS pairs. Finally, the total length of the EBS is controlled by the Beam Retraction Cable BRC 25, which limits the upward forces of both extension cable subsystems 15 and 32.
Note, there are different but fixed mechanical advantages in the three cabling systems that exercise control. In the example cited above, the length of cable 15 retracted by winch 16 to fully extend the EBS is 1305 ft. Winch 24 plays out 135 ft. of cable 25 and winch 36 retracts 9 ft. of cable 32. The ratio of the lengths of these three cable either played out or retracted during deployment is 9:135:1305 or 1:15:105. As long as the three winches are configured through winch spool diameters or reduction gears to maintain these ratios, the deployment will be controlled with cable lengths retracted or played out appropriately to maintain the EBS stability.
One can see from the above discussion why the extension subsystem represented by cable 15, pulleys 13, and 14, and winch 16 is the principal force for extending the EBS, and why the EBS can lift very heavy objects. In the case of the 135 ft. tower, if cable 32 was made of ⅛ inch multi-stranded stainless steel wire rope, with a breaking strength 2000 lbs, the maximum force generated between a pair of BS segments given the eight strands of rope in the compound 8 pulley system between each BS pair as illustrated in
With a liberal safety margin, the EBS would be capable of lifting thousands of pounds of payload, in addition to the weight of the EBS system itself, and the necessary force to overcome the substantial friction involved in operation of the other cabling systems like the extension of the vertical cable 5 with its multiple pulleys 27a and 27b and the BCC cables 32 through pulleys 33 and crossover points 34 and 35.
Avoiding Stay/Cable Interference (Four Stay, Dual Central Beam Variant)
One of the key features of the EBS concept is the ability of the rather complex network of stabilizing external cables 5, 8, 10, and 11 to be able to support the EBS extension with out interfering with each other. This is accomplished by design of the cable attachment points at the ends of each stay, and the lengths of the stays themselves allowing clearance for adjacent cables to clear the stay during the deployment process.
Note, the figure is not to scale in the sense that the length of the stays relative to the dual central beam structure in the center are much longer than indicated, as are the stay tip cables 10 in the horizontal plane. Thus in this top view there are break points indicated by wavy lines in the nested stays 3 at point 39 and the multiple stay to stay cables 10 at point 40. This allows for a more magnified view of the stay tips showing how the stays can be deployed without stay/cable interference. Cables 10a are shown attached to the multiple stays the tips 41 which are slightly offset so that no cable overlaps any of the stays. Cables 10b on the other hand do in fact overlap the stays at 42 as shown in the top view of
It is to be noted also that attachment points for the beam to stay fixed cables BSF 8 shown as small triangles at 43 are all positioned inboard from the innermost SSFi 10a and therefore will not interfere with cables 10 during deployment.
Avoiding Stay/Cable Interference (Three Stay, Single Central Beam Variant)
a shows how three stays per level can be affixed to a single set of nested beam segments shown previously in
b and 11c show stick models of the 3-stay variant in the pre-deployment state,
a shows an alternative three-stay variant where two sets of nested stays 3 on the left hand side are attached through rotatable joints 12 to the lower end the stowed beam segments 4, with one set of stays 3 on the right side connected to the upper level through beam segment extensions 44b and deployed upward through rotatable joints 12. Also shown are leading and trailing cables 5a and 5b, with two sets of diagonal fixed length cables BSF 8 connecting the two sets of stays on the left side, with one set of in plane horizontal fixed length cables SSFi 10 connecting the tips of the two sets of stays on the left hand side. On the right hand side, two sets of out-of-plane diagonal fixed length cables SSFo 11 connect the single set of upper stays on the right, to the two sets of stays on the left.
b and 12c show stick models of the three-stay variant in the pre-deployment state,
Note, as with
Cables 10a are shown attached to the multiple stays the tips 41 which are slightly offset so that no cable overlaps any of the stays. Cables 10b on the other hand do in fact overlap the stays at 42. Cables 10c do not overlap stays in the upper left hand portion of the
As in
Avoiding Stay/Cable Interference (Four Stay, Single Central Beam Variant)
a and 14b show how four stays per beam segment in a single central beam can be supported with stabilizing cables, without the cables interfering with the stays as the EBS is extended, using the same principles illustrated in previous figures (
In
b shows a variant where two sets of nested stays SS3, joined to the upper end of the nested beam segments 4 are rotated upward during pre-deployment, and two sets joined to the lower end rotated downward. Here there are no horizontal in-plane cables 10, but rather four sets of out-of-plane stay tip cables SSFo 11, and two sets of diagonal beam to stay cables BSF10.
Generalized Model Showing Stay and Fixed Cable Attachment Points
a-h show it is possible to generalize from the previous examples that there are a number of possible stay configurations with a single central beam 4 using the orthogonal beam extensions or platforms at the ends of the each of the beam segments 4. A platform is any fixed orthogonal extension of the BS, top and bottom, that allows attachment points on three sides for stays or cable attachment tabs. These are shown as 44a and 44b in stylized (not to scale) drawing
c and 14d show the top level composite views of the upper and lower level platform associated with the 3 stay variant in
Likewise,
g represents the upper and lower levels of
In general, a number of other stay cable combinations are possible but not shown, which essentially adhere however to the principles articulated in these single central beam examples, namely, as long as three sides of the upper and lower extensions 44a and 44b, mirror images of each other, are utilized for stay attachment tabs 31 or BSF 8 attachment points, no matter the angle of tab attachment to the central beam within certain limits (e.g., normal to central beam, up to 30 or 45 degrees off normal), an architecture can be devised along with in-plane and out-of-plane stay tip to stay tip cables SSFi and SSFo to stabilize any combination of stays and cables without interference of stays and cables as the EBS is extended.
Cable Play Out and Retraction Winches and Tensioning Mechanisms
An essential feature and primary requirement of the EBS is the capability of winches to play out and retract cables precisely and in a controlled manner to maintain adequate structural stiffness during the extension process. Otherwise, bending or buckling could occur, especially in those cases like PT where heavy payloads must be elevated in wind loading environments. This is controlled play out and retraction of cables is accomplished through Motorized Winch(es) and Tensioning Mechanisms, usually in the base of the EBS that plays out and retracts the four cabling systems subject to change during the deployment process. This includes: the Anchoring Cables (AC); the Beam Retraction Cable (BRC); the continuous Beam Extension Cable (BEC); and the Beam Control Cable (BCC). All four cabling systems must be synchronized in terms of the lengths of cable played out and/or retracted. This can be done mechanically with a centrally located winch subsystem as will be described, or with a distributed winch system relying on centralized computer control described.
Centralized, Mechanically Integrated Winch Subsystem
There are several ways that a single motor 47 can control the direction and rate of rotation of the winches, which are required to vary depending on their function and the required mechanical advantage. In one scheme, reversible motor 47 is linked through reduction gears 48 to the common axle through a power train 49 (direct drive of chain drive) embedded in the support structure. The winches rate of rotation is controlled through by means of planetary or other gearing systems embedded around the axle at 50. Or, alternatively, the reversible motor 47 could power a common drive shaft parallel to the axle, embedded in support structure 51, with appropriate gearing within 50 to power the winches at different rates.
What is essential here is that the winches rotate in a coordinated fashion, to extend or contract the EBS with the proper amount of cable dispensed from each winch. The single motor is able to power the multiple winches to extend the EBS or by reversing, power the contraction. The varying amounts of cable played out or retracted by each of the winches is proportional to the height of the tower, length and number of beam segments, and the mechanical advantage of the Beam Extension Subsystem pulleys at each end of the beam segments.
In the examples cited previously, there are varied but fixed mechanical advantages in the three cabling systems that exercise control over EBS extension and retraction. In the previous example of a 135 ft. tower, the length of cable 15 retracted by winch 16 to fully extend the EBS is 1305 ft., while simultaneously, winch 24 plays out 135 ft. of cable 25 and winch 36 retracts 9 ft. of cable 32. The ratio of the lengths of these three cable either played out or retracted during deployment is 9:135:1305 or 1:15:105. As long as the three winches are configured through winch spool diameters or reduction gears to maintain these ratios, the deployment will be controlled with cable lengths retracted or played out appropriately to maintain the EBS stability.
In
The next drum to the left, the Beam Retraction Cable Winch 24 must play out 135 ft. of cable 25 shown in insert 24a as one layer deep. At 3 ft. of play out per revolution of the drum, with cable one layer deep as shown in insert 24a, drum would undergo 45 revolutions for full extension. Note the grooves of the drum are in the form of a helix to assure single layer spacing and a precision lay down of cable. With ¼″ cable and a 1/16″ groove wall, the face of the drum would be approximately 13-14 inches wide. Although not shown on the drawing, a mechanism similar to 52 could be used to aid the lay down of cable.
Minor adjustments can be made in the shape of the drums on winches 36 and 24 each of which has only one layer of cable, versus the nine layers of cable on drum 16, to compensate for variances in the amount of cable played out. If the rate of rotation 36 and 24 are each directly proportional through reduction gears to the rotation of winch 16 there will be a slight mismatch since the inner layers of cable on drum 16 will play out slightly less cable than the outer layers on drum 16. By slightly increasing the radius of the grooves of drums 36 and 24 from one side of the drums to the other (±5%) in a linear fashion across the face of the drum, this variation can be equalized.
Finally, on the far left in the drawing, the three optional anchoring cables AC 45 could be played out from a unique tapered drum which compensates for difference in length of anchoring cables 5 as the tower ascends. The tangent of the angle between anchoring cable 6 and the ground is equal to the height of the tower represented by the length of cable 25 played out by drum 24, and the fixed distance between the base of the tower and the anchoring point of the cable to the side of the tower as shown in
Note there are three cables overlapping each other as shown in inserts 45a and 45b each coming off of the drum at 120 degree angle from each other, then routed through pulleys at the base of the tower (not shown) to the anchoring points at the side of the tower. The radius of the tapering of the helical grooves is designed such that the amount of cable played out equals the hypotenuse the right triangle formed by the length of cable 6, the length of cable 25 and the fixed distance between the tower base and the anchoring point. The length of cable 6 at any point is equal to the square root of the sum of the squares of cable 25 and the distance between the tower base and the anchoring point. Although not required, for the sake of convenience, the grooves in drum 45 can be so designed that one revolution of drum 45 corresponds to one revolution in drum 24, or 115 revolutions for full extension of cable 6.
Likewise, as with drum 24, the grooves of drum 45 are in the form of a helix to assure single layer spacing and a precision lay down of cable. With ¼″ cable and a 1/16″ groove wall, the face of the drum 45, like 24 would be approximately 13-14″ wide. Although not shown on the drawing, a mechanism similar to 52 could also be used to aid the lay down of cable.
Distributed, Electronically Controlled Winches and Tensioning Mechanisms
If the winches are not linked mechanically and driven by a common motor and drive system with gearing to compensate for differences in winch rate of rotation, the alternative is a mechanical separation, with multiple motors driving multiple winches, with the control of play out and retraction electronically. This would require each motor to have its own encoder connected to a central microprocessor to record the number of revolutions for each winch with feedback loops to control the rates of revolution of each winch so that the cables are play-out and retracted in a coordinated fashion during EBS deployment. This electronically controlled system would have positive benefits, but also risks and perhaps added cost.
Central computer controlling the operation of distributed winches would assure the proper ratios of cable are played out or retracted in the ratios dictated by the architecture, for example, in the 135 ft. tower case, the ratio of lengths for cables is 9:135:1305 for cables 32, 24, and 15 respectively. The play out of cable 45 could be computed as discussed previously as a length of cable equal to the square root of the sum of the squares of cable 25 and the distance between the tower base and the anchoring point.
Role of the Tensioning Mechanism
Tensioning mechanisms are provided for several reasons for both the mechanically integrated and the electronically integrated winch systems as described. A primary role is to allow the limited loosening of the cables when the EBS is ascending or descending in order to lesson the friction on pulleys and cables as the EBS is lengthen or shortened. When the EBS is extended to the desired length, which need not be the fully extended length, the EBS system can be “locked down” with all of the cables pulled taut and in tension so that the that the EBS system is at maximum rigidity. This is to minimize swaying or vibration of the payload platform, which may be required if it contains optical sensors, optical communications systems or RF transmitters or receivers (radars) requiring stable platforms. When lock down mode is required, the tensioning through the screw drive mechanism can exert thousands of pounds of tension.
The tensioning mechanism can also be used to take up slack if there is a slight variation in the amount of cable the four cabling systems if, in the mechanically integrated system, the winches did not dispense the exact amount of cable based on the mechanical gearing ratios. This can occur through small variations in drum radius, cable elongation due to cable aging, pulley maladjustment, etc. The tensioning mechanism can adjust and compensate for these length variances by adjustment in the slider shown in
In a lockdown situation, both the external cabling network stabilizing the central beam (cables 5, 8 and 11), and the internal cabling systems associated with the central beam extension (15, 25 and 32) must be tensioned. By tensioning cable 5 at the base of the tower as shown in
The tensioning of all of the internal cabling systems can be accomplished by tensioning only cable 15 while other cable drums remain stationary. For the electronically controlled system this can be done by means of computer control. For the mechanically integrated system where all drums are mechanically linked with different fixed gear ratios, the shortening of cable 15 while all other cables remain stationary is accomplished by the tensioning system shown in
Other Applications of the EBS System Concept
Truck Mounted Mobile EBS System
a and 18b show at truck-mounted version of the EBS with a surveillance camera mounted on the top. The payload could as well be a line of sight microwave link as is commonly used by mobile TV news teams dispatched to remote locations to report a events.
To add to the stability of the tower system, as is shown in
b shows a perspective view of the truck itself with a cutaway of the van containing a small control room. The figure shows the feet 62 extending downward with four sets of stays 3 mounted on the top of the van in trays 63, with the beam segments 4 telescoped into a well in the center of the van. In this configuration there is no need to rotate the nested stays into position during the initial deployment since they are already orthogonal to the central beam 4 and in position for extension of the beam. This allows the tower to be erected quickly at the deployment site.
During initial deployment, the beam segment package with payload attached, is elevated robotically during until the fixed diagonal cables 8 secured prior to beam extension in trays 63 are made taut. From this point on, the EBS extension is accomplished in a manner similar to that shown in previous figures, (e.g.,
It is conceivable that a truck mounted EBS type system could be useful in fighting urban fires in tall buildings by extending ladders and water cannons vertically to heights well beyond those attainable with current hood and ladder truck technology. Also in the figure described above, once the feet are deployed, the section of the van shown in
There are non truck-mounted variants of the EBS, which contain features of the system shown in
Portable Bridging Equipment
Bridge Structure and Variants
Up to now, applications have been suggested that relate to a single central beam structure with 3 or 4 stays per level with network of cables to provide central beam stability against bending moments. Since the EBS concept is scalable and modular, it's conceivable that other terrestrial or space applications are possible with orientations that are vertical, horizontal or any orientation in between. Also, multiple central beams can be linked together to provide a variety of geometries that address specific requirements. This would be the case with a bridge application shown in
a is the side view off a fully deployed bridge with stays 3 and networks of fixed length cables 8 and extendable cables 5 providing the stability to the two central beams 4 that provide lateral support for the bridge's roadbed 66.
b and 19c are front views of two variants.
c shows a two-way bridge, which has only the lower stay and cable support system, not the trestle-like structure. The weight of the roadway together with the angled disposition of the outer stays is sufficient to maintain tension in cables 10. Truncated stays 69, with cabling, can provide a side barrier to the roadway.
Dual Beam Structure and Stay Deployment
a-d shows how the two-beam system is deployed.
d also shows a single foremost stay 3a, which has been referred to previously as the leading stay described in
a is a side view of one of the roadbed segments 66 with stiffening structures 72 that rotate downward around hinge 73 and are locked into place with diagonal struts 74. These stiffening structures allow the road bed to support heavy loads transferring the loads to the beam structures running along the sides of the roadbed segments as shown in
The roadbed segments contain load bearing rollers 75 that carry the load downward to the inner horizontal surfaces of the beam segments 4, with side looking alignment rollers 76 fore and aft that contact the inner side wall of the beam segments to provide lateral forces keeping the roadbed segments properly aligned.
The end view in
Onsite Deployment Process
a-c show step-by-step process for deployment of the bridge on-site from a truck, which carries both the EBS superstructure and the roadbed segments to the site.
A deployment crane is used to providing a lifting force to the end of the bridge as it is deployed across a river or valley and aid placement of the bridge footings on the opposite shore. This deployment crane consists of a deployment cable 77 attached to the leading stay at point 78, routed through pulley 79 attached to a telescoping crane mast 80 and ultimately anchored in winch 81. The winch is able to play out and retract cable as needed in the deployment process.
The crane mast is stowed horizontally during transit to the deployment site, but is elevated and rotated around hinge 82 through hydraulic or other means, with an angle of rotation appropriate for each stage of the deployment process, as the EBS superstructure is extended over the river or other obstacle. A secondary mast cable 83 and independent winching system 84 provides additional restraining force on the mast when it is rotated to the vertical position as shown in
b illustrates a fully extended bridge prior to its placement on the opposite shore, with telescoping mast 80 in a near vertical orientation, the deployment cable approximately horizontal, and the bridge itself being positioned to drop onto the opposing shore.
The front of the truck may be staked to the ground to oppose the rotational forces induced by cable 77 when the bridge superstructure is fully extended and in the near horizontal orientation. But this is probably not necessary. The bridge superstructure is extremely light weight relative to the weight of the roadbed segments which are still loaded in the truck, and make up the largest portion of the overall weight of the bridge, approximately 70-80%. Included also in the moment of force opposing the bridge superstructure moment is the weight of the truck itself, its engine, and weight of the stowed roadbed segments.
c is a side view of the truck illustrating deployment of the roadbed segments 66. Roadbed segments have been rotated 90 degrees in the horizontal plane, exposing the side view of the package of segments, which are alternately hinged 85 and folded like an accordion. During deployment, cables linked to winches on the opposite end of the bridge draw out the hinged roadbed segments onto the tracks of the dual beam support structure, aided by the load bearing rollers 75, and alignment rollers 76. This process continues until the all of the segments are laid out and secured to the bridge superstructure. Alternatively, individual roadbed segments, without hinges, could be stowed horizontally on the truck and dispensed individually onto the tracks of the dual beam support structure.
It should be noted that because of the architecture of the EBS system, that an EBS bridge can be extended to any length short of its maximum extension if, for example, if the river or obstacle to be bridged is not as wide as that shown in the figures. Furthermore, the EBS concept is modular, meaning more than one bridge superstructure can be deployed to double or triple the length of the bridge. This would require a float system or temporary pilings be established in the river at the opposite end of the first bridge superstructure deployed. Another deployment truck, then using the bridge itself could back to the end of the bridge and begin deploying the second bridge superstructure.
Solar Array Deployment in Space
a-e shows the deployment of a large solar array in space using the EBS system. Photovoltaic solar cells attached to a flexible membrane are rolled onto a drum in the stowed configuration. EBS structures along each side of the stowed package provide a controlled extension of the solar array until it is fully deployed.
a is a side view of the stowed package with the rolled up PV membrane 86 and deployment structure 87.
Summary of EBS Principles
Although the applications shown above are quite varied, the fundamental EBS principles are common to each that is: 1) one or more central beam packages contain nested beam segments can be extended by mean of internal pulleys and cables that when retracted, extend the beams; 2) support stays and a network of fixed length and variable length cables that maintain the rigidity of the central beam during and after deployment; 3) winches that play out and retract the various cabling systems as required; 4) in a variant mode of beam extension, described as “Simplified Semiautonomous,” the complex internal cables and pulleys for beam extension and control as described in 1) are replaced by a mechanical system, external to the nested beam segments, which provide an external force to sequentially raise and lower beam segments to extend and retract the EBS.
While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention.
This application claims the benefit of U.S. Provisional Application No. 60/903,516 filed Feb. 27, 2007.
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