Patent ID: 12240739

DETAILED DESCRIPTION

Wire rope boom extension systems have existed for many years. Within a classic (traditional) wire rope extension system, a series of ropes, that run over sheaves, (a pulley over which a cable wraps around) are positioned throughout the boom. These cables drive each boom section to move synchronously when a single translation apparatus, such as a hydraulic cylinder, is extended. In a typical four section wire rope boom, the rod of the extend cylinder is anchored to the base section of the boom and the barrel is anchored to the back of the second section. When the term rope is used in this disclosure it is contemplated that the term includes cables, synthetic rope, chain, engineered assemblies, or any other flexible components capable of transmitting large forces in tension.

While cranes are extremely versatile, they have limitations that must be carefully observed, or serious mishaps can result.FIG.1reveals a range diagram for a typical extensible boom crane. The chart reveals the limitations that exist on the extension of the boom and the load that can be carried by the boom based on the ability of the crane to carry the desired load without overloading the boom sections which include the ropes, sheaves and typically the hydraulic cylinder that provides the motive force. Additionally, the range diagram establishes limits that prevent tipping of the crane because of overextension of the boom. The information disclosed herein is directed to addressing a system for increasing the load capacity of the boom by reducing the tension carried by the ropes internal to the extension system to keep the boom extended.

It should be appreciated by the reader that in operational embodiments of the system disclosed herein, the wire rope and sheave configurations will be mirrored within each boom section. More precisely, to maximize the load carrying capacity of the wire rope and to capitalize upon the increased bending flexibility of lesser diameter wire rope, two identical wire rope and sheave systems are utilized in production embodiments. These identical wire rope and sheave systems are disposed opposite one another (on each side internal to the boom) in the extensible boom sections.

A single large wire rope with the same load carrying capacity as two smaller diameter ropes has a reduced capacity to flex around the redirection sheaves and hence two smaller, more flexible, wire ropes are preferable in a fully operational context. To facilitate full and clear disclosure of the system, the placement of only one side of the sheave and wire rope system will be discussed herein; however, as noted immediately above, it is contemplated that in a production setting the boom sections will each house two identical rope and sheave systems.

FIG.2illustrates a longitudinal cross-sectional view, detailing the internal ropes and sheaves, of a prior art embodiment of a four-section telescopic boom system. The first boom system embodiment includes a base section, two intermediate sections and a tip section. The boom sections are traditionally fabricated in a wide range of cross-sectional shapes to include, among others, square, rectangular, and circular. Typically, the boom sections are fabricated from high strength steel and may span from six inches to many feet in cross-section and may span in length from a few feet to over thirty feet. The wall thickness of the boom sections must necessarily vary to accommodate the overall size and intended load carrying capacity of the boom system.

The prior art design illustrated inFIG.2includes a hydraulic cylinder HC, also known as the barrel, with an extensible rod ER. The distal end DE of the extensible rod ER is secured to an anchor point AP on or near the first end of the base section BS of the boom system. A proximal end of the hydraulic cylinder HC is securely pinned to the second intermediate section2S of the boom system at a barrel anchor BA proximate the first end of the second section. As the extensible rod is extended outwardly from the cylinder HC under pressure from the hydraulic fluid, it longitudinally translates the second intermediate section2S outwardly from the base section BS.

While the hydraulic cylinder HC and extensible rod ER for the application of translational force are utilized to separate the second section2S from the base section BS, there are other operational elements within the boom sections that cause the other two boom sections3S,4S to undergo translation.FIG.2also illustrates the location of various sheaves that are facilitating extension of the boom sections. As previously discussed, the barrel anchor BA is located proximate the first end of the second intermediate section2S. A first sheave S1is secured to the distal end of the hydraulic cylinder HC and a second sheave S2is secured proximate the second end of the third section3S.

This prior art design as illustrated atFIG.2also utilizes ropes under tension to convey translational force to the various boom sections of the system to cause their movement. The prior art system ofFIG.2utilizes an anchor rope AR with first and second ends FE, SE. The anchor rope AR extends over, and partially circumscribes the first sheave S1with the first end FE anchored proximate the first end of the third section3S. The second end SE of the anchor rope AR is anchored at the base section BS at an anchor point.

The second, smaller diameter rope SR, as also illustrated atFIG.2, includes first and second ends fe, se with the first end fe anchored proximate to the first end of the fourth section4S of the system. The smaller diameter rope SR passes around the second sheave S2that is secured proximate to the second end of the third section3S. Finally, the second end (se) of the second smaller rope SR is anchored proximate to the first end of the second section2S of the system.

As noted above, the first and second ropes AR, SR in this prior art configuration are of different thicknesses because the tension carried in the larger anchor rope AR is greater than the tension carried in the second smaller rope SR. When larger ropes are required to carry the specified maximum load then the sheaves over which the load carrying ropes run must also have a greater diameter and thickness. Increasing the dimensions of the sheaves and ropes results in a more densely crowded interior of the boom assembly. A more tightly packed set of boom sections is more challenging for initial fabrication as well as to access for repair and replacement of components internal to the telescoping boom assembly and therefore it is highly desirable to reduce the size of ropes, as well as the width and diameter of sheaves, yet maintain a high load carrying capacity. Larger diameter sheaves are required for larger ropes with greater load carrying capacity because larger ropes simply cannot curve around smaller diameter sheaves as readily as smaller ropes. Larger diameter ropes in turn require larger spacing between cross sections.

Table 1 andFIG.3provide a summary of the forces acting on each element of the previously described prior art telescoping boom assembly. The load for each sheave identifies the load at the anchor point for that specific sheave. As can be seen in Table 1 andFIG.3, the load on Rope2is equivalent to the load applied at the tip (F). The load on Rope1is twice the load applied to the tip section. The load on Rope1is of particular concern because that rope must have a greater capacity to resist the operating load applied to the tip section of the boom. As previously mentioned, larger ropes require larger sheaves and consume more space in the already limited interior of the boom sections thereby complicating boom section fabrication as well as maintenance and repair operations.

TABLE 1LOAD FACTORS BY COMPONENTNo.ElementLoad FactorOperating load applied to the tip sectionF1Sheave 1 (left) S14F2Sheave 2 (right) S22F3Rope 1 AR2F4Rope 2 SRF7Force required to extend the rod from the cylinder3F

To comprehend the new boom extension system disclosed herein, one must appreciate the mechanical advantage provided by a block and tackle system. The system10as disclosed herein provides considerable mechanical advantage as compared to traditional telescoping boom systems. The telescopic boom system10as disclosed herein in its most basic form as illustrated atFIG.4includes two boom sections12,14.

The system10also includes a rope28with anchor point28A that is positioned between the boom sections12,14. A first of these boom sections12is conceptually fixed (also known as the adjacent section) and the second14is extending. The rope28is redirected by a first sheave30mounted to the adjacent section12and is further redirected by a second sheave32mounted to the extending section14. This generalized arrangement of sheaves that directs and then redirects the rope with the sheaves having distinct attachment points provides the mechanical advantage to the multi-section booms that has been missing from prior art designs.

The redirecting of the rope around the sheaves creates what is referred to as parts-of-line (N). The part-of-line term of art requires the counting of the ropes that are either (1) attached to the load or (2) attached to sheaves that translate at the same speed as the load. Each time that the rope28is redirected by a sheave the rope experiences an increase in the number of parts-of-line. As the number of the parts-of-line (N) increases, the tensile load in the rope is reduced.

When the tensile load is decreased because the number of parts of line increases the velocity ratio changes requiring the rope to be pulled farther to achieve the desired extension. This ratio is the same ratio as determined by the number of parts of line (N). The objective of the boom designer is to bring the tension in the rope to below the safe tensile limit of the rope but provide the boom crane with the specified lift capacity.

To achieve the desired tension load in the rope28which is operable on the extending boom section14, the number of sheaves attached to each of the extending14and adjacent12boom sections must be determined. The number of sheaves secured to each section is determined by the formulas:

For⁢⁢N≥2E=2⁢(N-1)+1+(-1)N4A=2⁢N+1+(-1)N+14

The first end28A of the rope28is anchored to the adjacent section12if N is an even number while the first end28A of the rope28is anchored to the extending section14if N is an odd number. The second end28B of the rope28is anchored to a section as will be determined below in greater detail.N=number of parts of line of the rope operable on the extending sectionA=number of sheaves mounted to the adjacent sectionE=number of sheaves mounted to the extending section

As noted above, the numerical determination of the variables A, E and N is calculated for successive extending and adjacent sections12,14along the entire boom. It should also be understood that the translation of the sheave mounted to the adjacent section12, by the motive force of, for example a hydraulic cylinder, yields a total telescopic translational force applied to the extending section14that is greater than the tension in the rope based upon a multiplication factor equal to the parts-of-line of the system acting on the extending section14.

It is also important to recognize that the translation of the sheaves mounted to the adjacent section12causes the velocity ratio of the extending section14relative to the velocity of the adjacent section12to be other than 1:1 when compared to the velocity ratio of the second end28B of the rope28relative to the velocity of the extending section14. This velocity ratio is N:1, where N is the parts-of-line of the system acting on the extending section. A desired velocity ratio may be achieved by anchoring the second end of the rope to a prior section closer to the base section or redirecting the rope between sections to provide the necessary stroke leaving the adjacent section sheave set. Additional detail on the methodology for anchoring the second end of the rope to achieve the desired velocity ratio is discussed below.

An exemplary embodiment of the system100, as disclosed and illustrated atFIG.5, is comprised of four telescoping sections102,104,106and108. The base section102is the section with the largest cross-sectional area and the tip108is the section with the smallest cross-sectional area. These boom sections102,104,106and108as with the previously detailed prior art design are preferably fabricated from high strength steel with cross-sectional dimensions ranging from a few inches to greater than sixty inches in some larger cranes.

A hydraulic cylinder110with an extensible rod112is secured to the first end114of the second section104. A distal end116of the extensible rod112is anchored to the first end118of the base section102and the barrel120of the hydraulic cylinder110is anchored to the first end114of the second section104at an anchor point124. As the extensible rod112is extended from the barrel120, the second section104telescopes out from the base section102.

Within this embodiment, all four sections contain at least one sheave and at least one rope traverses through each section102,104,106,108. In this embodiment as further illustrated atFIG.5, a first sheave130is anchored proximate the first end118of the first (base), section102. A second sheave134is anchored proximate to the first end114of the second section104. A third sheave138is anchored proximate to the first end140of the third section106while a fourth sheave144is anchored proximate to the second end146of the second section104and is adjacent to a fifth sheave150that is also anchored proximate to the second end146of the second section106. A sixth sheave154is anchored proximate the first end160of the fourth section108and a seventh sheave162is anchored proximate to the second end164of the third section106.

Now that the sheave positions have been identified, the orientation of the ropes in this embodiment is discussed. As illustrated atFIG.5, a first rope170is anchored at a first end172proximate to the first end118of the base section102. This rope170traverses through the base102, as well as the second and third sections104,106. The rope170partially circumscribes the seventh sheave162and is redirected to the sixth sheave154where it partially circumscribes the sixth sheave154and terminates at a second end176proximate the seventh sheave162and is anchored to the third section106.

FIG.6illustrates the forces experienced by all ropes and sheave anchors in the embodiment illustrated atFIG.5. Importantly, the tension within the first rope170is only 1/2F. The first end180of a second rope182is anchored to the base section102preferably between the first and second sheaves130,134. The second rope182extends initially toward the first end132of the second section104and then is redirected by the first sheave134to extend toward the first sheave130. The second rope182then extends away from the first sheave130toward the fourth sheave144. The second rope182is then directed around the fourth sheave144to the third sheave138where it is once again redirected to the fifth sheave150.

After partially circumscribing the fifth sheave150the second rope182is anchored at its second end190proximate the first end140of the third section106. The maximum tension in the second rope182does not exceed 1/2F and therefore a lesser diameter rope182internal to the boom assembly is required, and likewise smaller width sheaves that need only accommodate a load of 1/2F are required.

It is possible to reduce the tension in the rope further by adding sheaves to the system and selectively attaching the rope ends to the appropriate anchor points. Referring again toFIGS.5and6, a force F is applied to the tip section108. There are two parts of line surrounding the sixth sheave154resisting this force F at the rear of the tip section108so the tension in the tip extend rope170is 1/2F and the total load on the rear sheave154attached to the tip section is F.

Three parts of line are acting on anchor point176and sheave162attached to the front end of the third section106with each part under a tension load of 1/2F. Therefore, the total force applied to the front sheave162and the anchor point176is 3/2F. The third sheave138at the rear of the third section106is resisting this force along with anchor point180so the total from this sheave and anchor point must be equivalent to 3/2F. This force is divided into three parts of line therefore the tension in each of the lines is 1/2F.

The tension in the ropes running around the sheaves144,150at the front146of the second section104must be the same as the tension in the ropes at the rear of the third section106which is 1/2F. However, there are now four parts of line coming from this sheave set144,150so the total force applied to the second section104is 2F.

Two redirection sheaves130,134are required to provide enough stroke for the third section106extend rope182. These sheaves130,134are attached respectively to the base section102and the first end114of the second section104. The tension in these ropes is 1/2F. The anchor point of the redirection sheave134at the rear of the second section104is resisting a total force of F.

The extend cylinder110is resisting all the forces attempting to push the second section104into the base section102. These forces are coming from the second sheave134and the sheave set144,150at the front end of the second section104. The total force applied to the extend cylinder110is 2F+F=3F. Table 2 details the loads applied to the sheaves and ropes of the system as disclosed herein and Table 3 provides guidance on the extending section parts of line and the attachment point of the second end of the rope.

TABLE 2LOAD FACTORS BY COMPONENTNo.ElementLoad FactorOperating load applied to the tip sectionF1Sheave 130F2Sheave 134F3Sheave 138F4Sheave 150F5Sheave 144F6Sheave 154F7Sheave 162F8Rope 1701/2F9Rope 1821/2F12Force required to extend the rod from the cylinder3F13Tip Section 108 Extend Force 154AF14Third Section 106 Retract Forces 162A & 1763/2F15Third Section 106 Extend Forces 138A & 1903/2F16Second Section 104 Retract Forces 134A, 144A &3F150A17Second Section 104 Extend Force 1243F

While the discussion above details the methodology for determining the number of sheaves for both the extending and the adjacent boom sections there must be a methodology for determining to where the first and second ends of the ropes used for the adjacent and extending sections are to be anchored. Recall that a primary objective of the system100as disclosed herein is to lower the tension in the ropes utilized in the boom sections. The boom crane designer knows the maximum load to which he wants the extensible boom crane to be able to lift, what he needs to determine is whether the tension in the rope is below its safe tensile limit.

To accomplish the reduction in tension, additional sheaves around which ropes are redirected thereby are used to create parts-of-line in the sheave and rope system. Recall that determining the number (N) of parts-of-line requires the counting of the ropes that are either (1) attached to the load or (2) attached to sheaves that translate at the same speed as the load. Once the number of parts of line (N) are determined the formulas for A and E can be utilized to calculate the number of sheaves in both the adjacent and extending sections.

What remains to be determined are the locations of anchoring of the first and second ends of the rope used in the adjacent and extending sections under assessment. The location of anchoring of the first end of the rope between the extending and adjacent sections is determined by (N) [number of parts-of-line]. If (N) is an even number, then the first end of the rope is anchored to the extending section. If, however, (N) is an odd number the first end of the rope is anchored to the adjacent section.

The remaining unknown is the location of the anchoring of the second end of the rope that extends beyond the adjacent and extending section. Table 3 references the number of parts-of-line (N). The column to the right in Table 3 allows calculation of the anchor point for the second end of the rope. Table 3 provides that based upon there being two parts of line we are to use the formula “n−3.” The variable “n” is in this instance is four (4) because it is the fourth section. The section to which the second end of the extend rope is to be attached is therefore n−3 or 4-3=1. The second end of the rope must be anchored to the first section (the base) to achieve synchronous extension of these boom sections along with the other boom sections of this crane.

A more complicated scenario is a parts-of-line calculation of three (3) in the extending section three (3). Using the formula in the right column of Table 3 yields a n−4 equation or 3-4 equals minus 1. The second end of the rope cannot be anchored to a section with a location of minus nor to a location that is zero. These section numbers do not exist.

The second end of the rope must be redirected by a sheave in the base section (section1) and a sheave in section number2back to anchor to the first end of the base section to satisfy the anchor requirements. To be clear on this, the second end cannot be anchored at the base section because the formula dictates that the second end must be redirected by at least two sections to get past minus one and zero which are imaginary and therefore boom sections to which anchoring cannot occur.

TABLE 3EXTENDING SECTION PARTS OFLINE AND ATTACHMENT POINTSection to which second end ofParts of line in sheaveextend rope must attach assumingset of extending sectionsection “n” is the extending section1n-22n-33n-44n-5

Example 1

The formulas set forth in the paragraphs above are to be utilized for any two adjacent sections of the boom wherein the inner section is extending by ropes to determine the number of sheaves mounted to the two adjacent sections. This should not be confused with the applicability of this formula to sections not extended by the ropes, i.e., the sections directly attached to the cylinder. Presuming a five-section crane is undergoing design and the rope under consideration has a safe tensile limit of 20,000 pounds. The extensible boom crane; however, has an operational capacity of 60,000 pounds.

To reduce the operational tension on the fifth section rope to no greater than 20,000 pounds then the rope in that section must have at least three parts of line (N=3). Three parts of line reduces the tension in the applicable rope from the crane operational load of 60,000 pounds to 20,000 pounds. Using the two formulas referenced above, the number of sheaves “E” mounted to the fifth section equals 1; however, the number of sheaves “A” mounted to the fourth section (the extending section) equals 2. These numerical tools allow the crane designer to determine how best to size the rope and incorporate the appropriate number, and load capacity of sheaves, to achieve the desired operational capabilities for an extensible crane.

Example 2

A designer developing a six-section extensible boom with an operational capacity of 80,000 pounds seeks to employ rope with a 20,000-pound tensile load limit. To reduce the tensile loading of the rope in the fifth extensible section to no greater than 20,000 pounds requires four parts of line (N=4). Utilizing the formulas set forth above, the output of the equation for “A” yields a value of 2 and the output of the equation for “E” also yields a value of 2. Consequently, two sheaves are required in both the adjacent and extending sections of the boom to reduce the tensile load in the rope to the appropriate level.

The number and location of sheaves determined for use in the various sections of an extensible boom while moderating the load carried by the ropes does impact the velocity of extension of the boom sections. The translation of the sheaves mounted to the adjacent section causes the velocity ratio of the extending section relative to the velocity of the adjacent section to be other than 1:1 when compared to the velocity ratio of the second end of the rope relative to the velocity of the adjacent section.

This velocity ratio is determined by the number of parts-of-line (N) and numerically the velocity ratio is N:1. The velocity ratio for synchronous extension of the telescopic boom sections is achieved by anchoring or redirecting the rope around at least one of a redirection sheave, a pulley, or a pin mounted to a prior operatively connected section of the boom as detailed at Table 3.

Example 3

To further illustrate the advantages of this innovative method of deploying sheaves and ropes to achieve optimal mechanical advantage,FIG.7illustrates an embodiment of a five-section boom comprised of a base section, three intermediate sections and a tip section. With a force F applied to the tip section, the greatest tension in any rope segment, due to the inclusion of multiple sheaves disbursed throughout the various sections with functionally appropriate anchor points does not produce a rope tension exceeding 5/9F, i.e., a fraction of F, the load being applied at the tip section. The loads experienced by all ropes, sheave anchor points and the extension cylinder are detailed inFIG.7.

FIG.8illustrates the same five-section boom embodiment shown inFIG.7with reference numbers utilized instead of load factors.FIG.8represents an exemplary configuration of a five-section boom. There are an immense number of boom rope and sheave configurations that are possible utilizing the system as disclosed herein. These configurations are based upon the boom designer's interest in managing the load in the rope as well as managing space in the boom sections. WhileFIGS.7and8are instructive, they should not be considered limiting in terms of the full scope of rope and sheave configurations that are contemplated by this disclosure.

As illustrated atFIG.8, the base section310includes a double sheave312,314secured at an anchor point316proximate the first end318of the base section310. The two sheaves312,314while anchored at one point316are configured to redirect two separate ropes using two separate grooves on the double sheave312,314. These sheaves312,314while positioned side-by-side are unattached and separately rotatable upon on a single axle and are therefore capable of operating at different rotational speeds. A second sheave324is also anchored near the first end318of the base section310at anchor point324A.

The driving force for this five-section boom is a hydraulic cylinder364having first and second ends366,368. Extending from the hydraulic cylinder364is a piston370with a distal end372. The first end366of the hydraulic cylinder364is anchored366A proximate to the first end332of the second section334while the second end368of the hydraulic cylinder364is unanchored. The distal end372of the hydraulic piston370is anchored at anchor point372A proximate to the first end318of the first section310.

As the boom operator seeks to extend the boom sections, hydraulic fluid is routed to the hydraulic cylinder364causing it to extend the piston370. As the distal end372of the piston370is extended, it pushes against the first end318of the base section310causing the cylinder364which is anchored proximate to the first end332of the second section334to extend outwardly from the base section310. This outward extension of the second section334also causes the separation of sheaves410and312pulling on the first rope400anchor404.

The second end404of the first rope400is anchored at an anchor point406proximate the double sheave312,314. The first rope400is redirected by a sheave410anchored to the first end332of the second section334at anchor point410A. After partially circling the sheave410the first rope400extends around the smaller sheave312and then forward to a collection of three sheaves414,416and418.

The three sheaves are anchored at anchor points414A,416A and418A. The first rope400extends around sheave418that is anchored to the second section334proximate the second end422of the second section334. Upon being redirected by this first sheave418, the first rope400traverses to the second sheave414which is anchored proximate to the first end430of the third section432. After traversing to and being redirected by the third sheave416, which is also anchored proximate to the second end422of the second section334, the first end434of the first rope400is anchored to the third section432at an anchor point434A in proximity to the first sheave414.

As the hydraulic cylinder364extends the piston370outward, the first rope400due to the connection at the anchor point406at the first end318of the base section310pulls the third section432forward because the separation of sheaves312and410. Recall that the second section334is already extending outward because the hydraulic cylinder364is anchored to the first end332of the second section334and it moves in unison with the hydraulic cylinder364.

The boom system as disclosed herein utilizes a second rope500with first and second ends530,504. This second rope500is operable to extend the fourth section360. The second end504of the second rope500is anchored at anchor point506proximate the first end332of the second section334. The second rope500traverses the second coaxial sheave314anchored in the base section310and then traverses to a three-set sheave514,516,518that are anchored at anchor points514A,516A,518A. The second rope500first partially circumscribes the third sheave518that is anchored proximate to the second end522of the third section432.

After partially circumscribing the third sheave518, the second rope500then traverses to the first sheave514that is anchored proximate to the first end526of the fourth section360. Upon partially circumscribing the first sheave514the rope then traverses to the second sheave516that is anchored to the third section432at anchor point516A between the first and third sheaves514,516. After partially circumscribing the second sheave516the first end530of the second rope500is anchored proximate to the first end526of the fourth section532at anchor point530A.

As the hydraulic cylinder364extends the piston370outward the second end504of the third rope500is moved forward thereby pulling the rope500around the sheave314mounted to the base section310. As the second rope500traverses around the three sheaves514,516,518the first end530of the second rope500which is anchored to the fourth section360pulls the fourth section360forward. Recall the third section is already translating forward due to the first rope400and the extension of the hydraulic cylinder364. Synchronous extension with the other two sections334,342is achieved through the hydraulic cylinder364extension by the second rope500anchor point504as well as the translation of sheaves516and518due to the translation of the third section432by the first rope400.

The exemplary five-section boom system as disclosed herein also utilizes a third rope328that includes a first end338and a second end330. The third rope328has a second end330anchored to the first end332of the second section334. The third rope328is then redirected around sheave324anchored at point324A at the first end318of the base section310. The first end338of the third rope328upon being redirected around second sheave324is routed through all boom sections to the tip section342where it is redirected by four sheaves346,348,350,352that are anchored respectively at anchor points346A,348A,350A and352A. Two of the sheaves348,352are anchored to the tip section342while two sheaves346,350are anchored to the fourth section360. After being redirected by sheave352, the first end338of the third rope328is anchored proximate to the second end358of the fourth section360.

Because the second end330of the third rope328is anchored proximate to the first end332of the second section334, the second section334pulls the third rope328attachment point331and the second end330of the third rope328forward when extended by the hydraulic cylinder364. Because the first end338of the first rope328is anchored proximate to the second end358of the fourth section360, the translation of the fourth section360by the second rope500also causes the tip section342to extend. Consequently, under the sheave and rope configuration disclosed in this example as illustrated atFIG.8, the extension of the hydraulic cylinder364causes the third rope328to produce outward movement of the tip section342as well.

As previously detailed atFIG.7, none of the ropes in this five-section boom experience a load greater than 5/9F which is the load on the first rope400in the third section432that is redirected by sheaves414,416and418and anchored at anchor point434A. The three parts-of-line (N) in this first rope400within section three432provide considerable mechanical advantage and reduces the tension to 5/9F from a rope load of 5/3F due to the existence of three parts-of-line.

Because there are three parts of line (N) in this extending section the formula above in Table 3 is used and the formula is n−4, wherein “n” is the number of the extending section, in this instance section three432, so the second end404of the rope400must attach to section “minus one;” however, there is no “minus one” section nor is there a “zero” section. The procedure to address that mathematical disparity is to redirect the rope400as was done with sheave312and one additional time around sheave410attached to the second section334. The redirecting sheave410effectively accounts for another section and allows the second end404of the rope400to be anchored to the base section310at anchor point406.

The rope500in the fourth section360is potentially subject to a load of 5/4F and as with the third section, there are, however, three parts of line (N) due to there being three sheaves514,516,518redirecting the rope resulting in a load reduction to 5/12F. Without the three parts of line (N) the second rope500would experience a load of 5/4F and therefore require a rope with a higher breaking strength and of larger diameter. An undesirable tradeoff. Again, using the formula of n−4 in Table 3 above, and “n” is now the fourth section so application of the formula results in a value of zero. Since there is no section “zero” the second rope500is redirected forward using sheave314with the second end504of the rope500being anchored at anchor point506proximate the first end332of the second section334.

With the tip section342, the third rope328tension is potentially subject to a load of F but because there are four parts of line (N) that reduces the load F applied to the tip rope328to just 1/4F. Resorting again to the formula in Table 3, with four parts of line (N) the formula for determining the connection point of the rope is n−5. Since n=5 the formula yields a value of “zero.” This is the same outcome as experienced in the paragraph above for the second rope500and the fourth section432. Since there is no section “zero” the third rope328is redirected forward using sheave324with the second end330of the rope328being anchored at anchor point331proximate the first end332of the second section334.

It is quite conceivable that, for example, a lesser or greater number of sheaves could have been employed in any of the five sections to either increase or decrease the tension in the ropes. The formulas for “A” and “E” outlined above provide the methodology to determine the required number of sheaves based upon the number of parts of line. The number of sheaves employed as well as the rope/sheave diameters are dictated by the designer of the extensible boom and are just a subset of the overall extensible boom design considerations.

Additionally, the point of attachment of the second ends of the extension ropes of the boom utilizing the criteria set forth in Table 3 has been extensively expounded upon in the immediately preceding discussion. Finally, as disclosed herein, the first end of the rope in the extending section is anchored to the adjacent section if the number of parts of line (N) is an even number while the first end of the rope is anchored to the extending section if (N) is an odd number.

In Example 3 above, with the five-section boom, because section three432utilizes three parts of line (N) the anchor point434A for the first end434of the first rope400is to the extending section432. Two sheaves416,418are attached to the adjacent section334while the third sheave414is attached to the extending section432. Likewise, with section four360, there are also three parts of line (N) and the anchor point530A for the first end530of the second rope500is also to the extending section360. Two sheaves516,518are attached to the adjacent section432while the third sheave514is anchored to the extending section360.

The tip section342incorporates four parts of line and as referenced immediately above, when there are an even number of parts of line in a section, the first end338of the third rope328is anchored to the adjacent section360, in this example at anchor point338A. As previously discussed, the tip section342employs a total of four sheaves346,348,350,352. Two of those sheaves346,350are anchored to the adjacent section360while two of the sheaves348,352are anchored to the extending section342.

The methodologies as outlined above yield a system that is capable of increased load capacity for the same size of rope diameter and sheave width as extensible boom systems that are currently employed. Consequently, an extensible boom designer may elect to specify a larger load capacity for the extensible boom or reduce the rope diameter and cross-sectional dimension of the boom sections and maintain a similar load capacity.

The disclosed apparatus, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The disclosed apparatus and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present, or problems be solved.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only examples of the disclosure and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope of these claims.

The disclosure presented herein is believed to encompass at least one distinct invention with independent utility. While the at least one invention has been disclosed in exemplary forms, the specific embodiments thereof as described and illustrated herein are not to be considered in a limiting sense, as numerous variations are possible. Equivalent changes, modifications, and variations of the variety of embodiments, materials, compositions, and methods may be made within the scope of the present disclosure, achieving substantially similar results. The subject matter of the at least one invention includes all novel and non-obvious combinations and sub-combinations of the various elements, features, functions and/or properties disclosed herein and their equivalents.

Benefits, other advantages, and solutions to problems have been described herein regarding specific embodiments. However, the benefits, advantages, solutions to problems, and any element or combination of elements that may cause any benefits, advantage, or solution to occur or become more pronounced are not to be considered as critical, required, or essential features or elements of any or all the claims of at least one invention.

Many changes and modifications within the scope of the instant disclosure may be made without departing from the spirit thereof, and the one or more inventions described herein include all such modifications. Corresponding structures, materials, acts, and equivalents of all elements in the claims are intended to include any structure, material, or acts for performing the functions in combination with other claim elements as specifically recited. The scope of the one or more inventions should be determined by the appended claims and their legal equivalents, rather than by the examples set forth herein.

Benefits, other advantages, and solutions to problems have been described herein regarding specific embodiments. Furthermore, the connecting lines, if any, shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the inventions.

The scope of the inventions is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.

In the detailed description herein, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a feature, structure, or characteristic, but every embodiment may not necessarily include the feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a feature, structure, or characteristic is described relating to an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic relating to other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.

Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. § 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.