Load balancing system

A load balancing system for a system of rotating elements such as a helicopter rotor or an airplane propeller. The load balancing system includes two or more balancing tubes rotationally attached to blades or props on the system of rotating elements. The balancing tubes are slightly curved and enclose a hollow space containing a quantity of weighted fluid such as mercury. During operation of the system of rotating elements, the weighted fluid disperses throughout the hollow space in the balancing tubes so as to counter any imbalance in the system of rotating elements. Centrifugal forces will cause different dispersal of the weighted fluid throughout the hollow space depending on the overall pulling or pushing forces resulting from any imbalance.

BACKGROUND OF THE INVENTION

The present invention is directed to a load balancing system for rotor blades on a helicopter or similar system of rotating elements. Specifically, the inventive load balancing system includes two or more tubes, each enclosing a quantity of a liquid, attached to a system of rotating elements in opposing or rotationally equally-spaced positions. When the system is at full rotation speed, the quantity of liquid in each tube will reach an equilibrium that counter-balances any irregularities in the system of rotating elements.

Various systems have been developed for properly balancing systems of rotating elements, specifically such as wheel and tire assemblies on vehicles. These prior balancing systems were designed so the tires rotated smoothly and do not wear unevenly shortening the life and tread of the tires. One of the most commonly employed systems for balancing wheel and tire assemblies is the securement of counterbalancing lead weights to the wheel at various positions based on measurements made during rotation. These arrangements are not entirely satisfactory since the weights are fixed and tend to compensate only for a single condition. In the event that condition changes due to tire wear or some other cause, the balancing is no longer effective.

Other systems have been developed for balancing tire and wheel arrangement that rely on the insertion of a plurality of mobile mass elements loosely positioned within the tire. For example, a dynamic wheel balancing system of this type is shown in U.S. Pat. No. 4,179,162 showing such a system. Other systems showing automatic rotation balancing systems for tires and wheel arrangements involve the placement of discrete mass balancing members within some type of raceway or grooveway cavity attachable to the wheel or rim. Typical of these systems are U.S. Pat. Nos. Re 25,383; 3,913,980; and 3,316,021.

The problem that arises with rotating tire wheel assemblies also is common in other systems of rotating elements. One such system is rotor blades, as on a helicopter or similar vehicle. Balancing devices for such rotor blade systems are typically of the types shown in U.S. Pat. Nos. 8,313,296 and 10,526,076. Such prior balancing devices typically have solid weights with limited adjustability and are mounted in close proximity to the axis of rotation. Solid weights with limited adjustability have a limited ability to finely balance an out-of-balance rotor system. Similarly, weights mounted in close proximity to the axis of rotation must have substantial weight to counter-balance forces on such systems of rotating elements.

Due to the foregoing and the many suggested approaches to the problem of balancing a rotating system of elements, it becomes apparent that there is a need for an effective, universal and simplified load balancing device.

Accordingly, there is a need for an improved load balancing device that has improved adjustability for weight balancing and does not require the use of substantial weights. The present invention fulfills these needs and provides other related advantages.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a load balancing system for balancing or equalizing a load on a system of rotating elements about a central axis, particularly in rotors or propellers. The load balancing system of the present invention preferably comprises two or more hollow, close-ended cylinders that define an internal passage within which a flowing fluid mass is contained. The hollow, close-ended cylinders are preferably secured to the system of rotating elements by universal, freely-rotating fasteners, in positions that are oppositely disposed or uniformly spaced around the axis of rotation.

In one particular embodiment, the load balancing system is specially adapted for securement to rotor blades as on a helicopter. The tubes of the load balancing system can be attached at any point along the length of two or more rotor blades, but are particularly effective at the extreme ends of the rotor blades. The tubes are preferably attached by a freely-rotating fastener so as to allow for varying pitch in the rotor blades, while still allowing the tubes to remain parallel to the plane of rotation of the rotor blades. Further, the tubes contain an amount of liquid, preferably mercury or other similarly behaving material, to provide sufficient weight and responsiveness to unbalanced forces.

Alternate embodiments are adapted for use on rotor blades having two, three, four or other quantity of blades, with a sufficient number of balancing tubes attached to the blades so as to provide an oppositely disposed or uniformly spaced configuration—or both. Another alternate embodiment might have the load balancing system installed on a propeller system, i.e., a vertically disposed set of props, rather than the previously described rotor system, i.e., a horizontally disposed set of rotors. The principles of the inventive load balancing system would apply equally as well to a propeller system as to a rotor system.

As claimed herein, the present invention is directed to a load balancing system for a system of rotating elements. The load balancing system is designed to be used in a system of rotating elements that has two or more blades on the system of rotating elements. The two or more blade extend away from and are uniformly spaced around an axis of rotation of the system of rotating elements. Two or more balancing tubes are rotationally attached to the two or more blades. Each of the two or more balancing tubes define an enclosed hollow space containing a weighted fluid.

The system of rotating elements may contain two, three, four, five, or more blades as may be reasonably designed. The load balancing system may have a number of balancing tubes that exactly equals the number of blades. Alternatively, the number of balancing tubes may be less than the number of blades, provided however, that the balancing tubes are uniformly spaced around the axis of rotation and uniformly dispersed around the blades so as to be balanced.

The two or more balancing tubes are preferably uniformly spaced around the axis of rotation. The weighted fluid preferably comprises mercury.

The two or more balancing tubes are attached to an end of the two or more blades distal from the axis of rotation. When attached to the end of the blades, the two or more balancing tubes preferably freely rotate relative to the two or more blades to which they are attached.

The two or more balancing tubes preferably have a degree of curvature that is equal to an arc of a circle having a diameter that is at least three times a width of one of the two or more blades. The two or more balancing tubes have an overall length such that each end of the two or more balancing tubes extends beyond a leading edge and a trailing edge of the two or more blades by no more than 5% of the overall length. In a particular embodiment, each end of the two or more balancing tubes extends beyond the leading edge and the trailing edge of the two or more blades by no more than 1½ inches.

Each of the one or more balancing tubes is preferably made of stainless steel. In addition, each of the one or more balancing tubes includes an insulating liner in the enclosed hollow space.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to load balancing system, generally referred to by reference numeral20inFIGS.1-11. The inventive load balancing system20is configured to be used with a system of rotating elements as in a helicopter rotor or similar vehicle. The system20generally includes two or more hollow, closed-ended tubes22freely attached to the system of rotating elements as described below.

FIGS.1and2illustrate a helicopter10having a horizontally oriented rotor12with two blades14a,14bdisposed linearly across an axis of rotation16. In this embodiment, the tubes22of the inventive load balancing system20are attached to the outermost end18of each rotor blade14a,14b. However, as understood by a person of ordinary skill in the art, the balancing system20would function with the tubes22attached at any point along the rotor blades14a,14b, albeit less effective at balancing.

Although this detailed description specifically refers to a helicopter10with two rotor blades14a,14b, the inventive system20will operate on helicopters and other vehicles with rotor or propeller systems having any number of blades. The balancing system20will preferably have tubes22attached to each blade or prop, but may be attached to fewer, so long as the tubes22of the balancing system are uniformly or equally spaced around the axis of rotation of the rotor or propeller system.

FIGS.3and4illustrate an outermost end18of a blade14a,14bshowing a tube22fastened thereto. In one embodiment (FIG.3), the tube22is attached to the blade14a,14bby a straight fastener24having an encircling sleeve26rotationally attached to a base28, preferably with a hex- or other multi-sided shape. The base28is secured to the end18of the blade14a,14bby threaded or other secure connection (not shown). In another embodiment (FIG.4), the tube22is attached to the blade14a,14bby an off-set fastener30having a sleeve32encircling the tube22and an adjacent opening34rotationally secured to a post36fixed to the end18of the blade14a,14b. The rest of the figures illustrate the off-set fastener30, but the balancing system20will function as intended with the straight fastener24or any other securing fastener that allow for rotation as described below.

In both embodiments of fasteners24,30, the connection between the sleeves26,32and the tube22, and the base28or post36and end18of the blade14a,14b, are each configured to be securely fixed so as to remain rigid and not unintentionally separate from their respective securements. However, the connections between the sleeve26and base28, and the opening24and post26, are both freely rotating so that the tube22is rotational in a plane perpendicular to the blade14a,14b.

FIGS.3and4illustrate the tube22with internal broken lines indicating an internal hollow passageway22abetween closed ends22bthereof. In addition, the tube22is illustrated as extending well beyond the leading edge15aand trailing edge15bof the blades14a,14b. This is exaggerated in the drawings to more clearly illustrate a curvature of the tube22, which curvature allows for differences in distance from the axis of rotation16between the center of the tube22and the ends22b. In a particularly preferred embodiment, when not exaggerated for purposes of illustration, the tube22extends only slightly beyond the leading edge15aand trailing edge15bof the blade14a,14b, while retaining the degree of curvature.

FIGS.5-7illustrate other views of the end18of the blades14a,14bwith the attached tube22and fastener30. As shown inFIG.6, a tube22is attached to the end18of each opposing blade14a,14bin a mirrored configuration. ComparingFIGS.5and7, the freely rotational configuration of the fasteners24,30allow for the tube22to remain in a horizontal plane whether the blade14a,14bis oriented in the horizontal plane or at a pitch angle above or below the horizontal plane.

FIG.8illustrates the balance system20attached to the ends18of the blades14a,14bsimilar to those shown inFIG.5or6. However, the tubes22in this illustration are shown with a quantity of a weighted fluid40within the hollow passage22a. As shown inFIG.8, the weighted fluid40causes the tube22to orient vertically when the rotor12is in a stopped or stationary position. The force of gravity pulls on the weighted fluid40and the freely rotational configuration of the fastener24,30results in the vertical orientation. In an alternative embodiment, the fasteners24,30may include stop limiters (not shown) that prevent the tubes22from rotating away from the plane of rotation42by more than plus or minus 30 degrees.

FIG.9illustrates a configuration similar to that inFIG.8, but shows the start-up rotation of the rotor system12, with the rotor rotating clockwise in the plane of rotation42when looking from the top down. The proximate blade14ais illustrated as having a direction (left to right on the page) and relative speed (slower start-up) of rotation Indicated by arrow44. Although not illustrated by an arrow, because of the overall clockwise rotation, the distal blade14bis rotating in an opposite direction (right to left on the page) at the same relative speed (slower start-up). At this start-up speed, the tubes22will be angled in such a way that the weighted fluid40will slightly trail the direction of rotation44, particularly as the rotor12rotates faster.

As the rotor12reaches full rotation speed, indicated by arrows46the tubes22will level out such that the tubes22are generally parallel to the plane of rotation42. This configuration is shown inFIG.10, which also shows the weighted fluid40differently dispersed in the tubes22depending on the forces acting on the balancing system20. This different dispersion results from the type of unbalanced forces acting on a particular blade as described more fully below.

For purposes of illustration, inFIG.10, the off-set fastener30of tube22on the distal blade14bis flipped opposite from that on the proximal blade14a. This is done to more clearly illustrate the possibility of different dispersions. Although it is preferred that in operation the off-set fasteners30are both oriented in the same direction, the load balancing system20will still function as intended if the off-set fasteners30are oppositely oriented. Because of the rounded nature of the hollow passage22a, the weighted fluid40can adjust its position to compensate for the off-set fasteners30being oppositely oriented.

When stopping the helicopter10, the rotors12begin slowing down as indicated by arrows48inFIG.11. As the speed of rotation of the rotors12decreases, the forces keeping the tubes22parallel to the plane of rotation42lessen and the tubes22begin returning to the vertical orientation ofFIG.8. The weighted fluid40returns from the dispersions in the tubes22mentioned above and flows to the lowest point of each tube22, until finally coming to rest in the bottom end of the tube22when in the vertical position.

In reference toFIG.2, the rotor12is illustrated with an unbalanced configuration where the first blade14ais a “light side” of the rotor12with a force arrow48pulling the blade14ainward toward the axis of rotation16. In this same configuration, the second blade14bis a “heavy side” of the rotor12with a force arrow50pushing the blade14boutward away from the axis of rotation16. To be clear, these pulling and pushing forces48,50are not acting separately, but in unison and follow the rotor12around the plane of rotation. Without the load balancing system20described herein, the pulling forces48and pushing forces50cause the rotor12to operate in a constant state of imbalance, resulting in increased wear and tear on the rotor system12.

The tubes22of the load balancing system20operate in unison to counter this state of imbalance. As shown inFIGS.10A and10B, the weighted fluid40reacts differently within the tubes22depending on the particular forces48,50acting on a blade14a,14b.

FIG.10Aillustrates the blade14asubjected to the inward pulling forces48toward the axis of rotation. To counter these pulling forces48, the weighted fluid40will collect closer to the center of the tube22. With the weighted fluid40concentrated in the center of the tube22, the weight is at its most outward point in the plane of rotation, which create greater centrifugal forces.

FIG.10Billustrates the blade14bsubjected to the outward pushing forces50away from the axis of rotation. To counter these pushing forces50, the weighted fluid40will divide its mass between the opposite ends22bof the tube22. With the weighted fluid40split between the ends22bof the tube22and because of the curve of the tube22, the weight of the fluid40is at a more inward point in the plane of rotation when compared to the opposite tube22(FIG.10A), which create smaller centrifugal forces.

The greater centrifugal forces reacting to the pulling forces48(FIG.10A) combined with the lesser centrifugal forces reacting to the pushing forces50(FIG.10B) cooperate to counteract the general state of imbalance. Because of the ability of the weighted fluid40to flow and react to changes in forces, the dispersion of weighted fluid40in each tube22will vary as needed to counter-balance the forces.

The weighted fluid40is preferably a quantity of mercury or similarly behaving non-friction fluid. Although mercury is a toxic material, given its relative density, the amount of mercury needed for the load balancing system20to perform satisfactorily is not significant. It is believed that on a standard helicopter10, each tube22likely only needs to contain 10 grams of mercury at most. At atmospheric temperatures, 10 grams of mercury is only about 0.74 milliliters. A greater quantity of mercury may be needed for rotor systems12of significantly greater weights, but even then it is not significantly more because of the distance between the tubes22and the axis of rotation16.

FIGS.12and12Aillustrate an interior structure of the tube22. The balancing tube22is preferably made from stainless steel or similarly non-reactive material. The hollow space22aof the tube22preferably includes an insulating tube liner22c. The insulating liner22cshould be non-porous, non-reactive, and non-absorbent to the weighted fluid40, particularly mercury.

The insulating tube liner22cis configured to protect the weighted fluid40against extremes of temperature, particularly cold temperatures. If temperatures in the tube22reaches the freezing point of the weighted fluid40, the load balancing system20will not operate as intended. As the weighted fluid40approaches the freezing point, its viscosity will increase thereby decreasing its ability to flow. Once the weighted fluid40reaches the freezing point, it will begin to solidify and lose all ability to flow.

In the case of mercury as the weighted fluid40, its freezing point is approximately −37.89° F. Such a temperature would not likely be reached in most environments. However, in certain extremes and/or at certain altitudes, such a temperature can be reached in ambient conditions on land or even at high rotation speeds during operation. Thus, the insulating tube liner22chelps to prevent the weighted fluid40from reaching the freezing point, particularly when in extreme conditions and/or at higher altitudes.

Various detailed embodiments of the present invention are disclosed herein. However, it should be understood, that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.