Abstract:
An improved coaxial rotor assembly for a helicopter includes an upper rotor system having a multiple of upper rotor blades each having outer tips and mounted on and extending outwards from a central rotor shaft and a lower rotor system having a multiple of lower rotor blades each having outer tips and mounted on and extending outwards from the central rotor shaft with the upper rotor system spaced an axial distance from the lower rotor system on the central rotor shaft. A rotor blade support ring extends circumferentially around each of the upper and lower rotor systems which movably engages and supports the outer tips of the upper and lower rotor blades in spaced apart relation such that the upper and lower rotor systems rotate in opposite directions and the rotor blade support ring means prevents contact between the upper and lower rotor systems during operation thereof.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates generally to improved rotor designs for helicopters and, more particularly, to an improved coaxial rotor system for helicopters which includes an upper rotor system having a plurality of upper rotor blades which are mounted on and extend outwards from a central rotor shaft, a lower rotor system having a plurality of lower rotor blades extending outwards from and connected to the central rotor shaft and rotating in a direction opposite the upper rotor system, the upper rotor system spaced an axial distance from the lower rotor system, and a circumferential rotor blade support ring which extends around the upper and lower rotor systems and engages the outer ends of each of the upper and lower rotor blades in generally parallel travel planes thereby preventing engagement of the upper rotor system with the lower rotor system during operation of the helicopter. 
         [0003]    2. Description of the Prior Art 
         [0004]    There are many different types of helicopters which are currently in use, including single rotor helicopters, dual rotor helicopters, transverse rotor helicopters, and several other related helicopter-type rotor-based flying aircraft. However, among the different types of helicopters currently being used, it has been found that those with dual rotors are among the most versatile, due to their increased lifting capacity from the increased air flow resulting from the two rotors being used on the aircraft. Primarily, there are three common configurations of dual rotor helicopters which utilize the contra-rotating effect to benefit the rotor craft, the first being a twin rotor design which includes two rotors mounted on the aircraft, one mounted behind the other, the second being intermeshing rotors which are mounted close to each other with the rotor blades intermeshing over the top of the aircraft, and finally a coaxial rotor design which includes two rotors mounted one above the other on the same rotational axis. It has further been found that the coaxial rotor system is generally more cost-effective, as the size of the helicopter does not have to be expanded to accommodate the position of the two rotors as they are positioned one atop another. A further benefit of the coaxial rotor design is that, in forward flight, the lift provided by the advancing ends of each rotor compensates for the retreating half of the other, eliminating one of the key effects of dissymmetry of lift, namely retreating blade stall. 
         [0005]    Unfortunately, however, coaxial rotors have several disadvantages which must be addressed in order to permit the coaxial rotor system to function properly. For example, there is an increased mechanical complexity of the rotor system due to the required linkages and swash plates for a dual coaxial rotor system. Furthermore, because each rotor system needs to be turned in an opposite direction, the central rotor shaft or mast itself is far more complex, and provisions for making pitch changes to the upper rotor system must pass through the lower rotor system. The most significant and potentially deadly problem encountered with coaxial rotor systems, however, is that during extreme aerobatic maneuvers of the helicopter, such as those encountered during combat or the like, the upper rotor system may accidentally contact the lower rotor system during operation thereof, which results in the contacting blades disintegrating due to the high rate of speed at which the upper and lower rotor systems are rotating, and this disintegration of the rotor blades results in rapid disintegration of the remaining elements of the rotor system due to the unbalanced nature of the upper and lower rotor systems, and the entire rotor structure quickly becomes unstable and self-destructs. This, of course, results in the helicopter falling from the sky and further results in the almost certain death of the pilot and crew of the helicopter. There is therefore a need for a system or device which will generally prevent accidental intermeshing of the upper and lower rotor systems. 
         [0006]    There are several examples shown in the prior art which attempt to address and solve this problem with coaxial rotor systems, including such Patents as Scott, U.S. Pat. No. 7,210,651 issued May 1, 2007. Scott discloses a dual coaxial rotor system which includes an upper and lower rotor system with reduced axial rotor separation distance along a common axis by way of rotor tip position sensing and rotor position control to avoid tip contact. In fact, all of the prior art devices currently known follow a similar method of attempting to address and correct the problem of rotor tip contact between upper and lower rotor systems, but, of course, in extreme conditions, these systems can fail resulting in destruction of the upper and lower rotor systems. There is therefore a need for a structural physical system which will accomplish the purpose of separating the upper and lower rotor systems while simultaneously permitting and enhancing operation of the coaxial rotor system. 
         [0007]    Therefore, an object of the present invention is to provide an improved coaxial rotor assembly for a helicopter. 
         [0008]    Another object of the present invention is to provide an improved coaxial rotor system for a helicopter which includes upper and lower rotor systems and a circumferential rotor blade-engaging ring which extends around the upper and lower rotor systems and movably engages and secures the outer ends of the rotor blade of each of the upper and lower rotor systems such that the distance between the upper and lower rotor systems remains generally constant due to the mechanical connections of the upper and lower rotor blades to the circumferential ring thereby substantially eliminating all possibility of physical interaction between the upper and lower rotor systems. 
         [0009]    Another object of the present invention is to provide an improved coaxial rotor system for a helicopter which is extremely strong yet light in weight so that the substantial benefits of use of the circumferential ring of the present invention are not literally outweighed by the added weight included in the system by use of the circumferential ring. 
         [0010]    Finally, an object of the present invention is to provide an improved coaxial rotor assembly for a helicopter which is relatively simple in design, economical to manufacture, and is safe, efficient and effective in use. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention provides an improved coaxial rotor assembly for a helicopter including an upper rotor system having a multiple of upper rotor blades each having outer tips, the upper rotor blades mounted on and extending outwards from a central rotor shaft and a lower rotor system having a multiple of lower rotor blades each having outer tips and mounted on and extending outwards from the central rotor shaft. The upper rotor system is spaced an axial distance from the lower rotor system on the central rotor shaft. Finally, a rotor blade support ring extends circumferentially around each of the upper and lower rotor systems movably engaging and supporting the outer tips of the upper and lower rotor blades in spaced apart relation such that the upper and lower rotor systems rotate in opposite directions and the rotor blade support ring prevents contact between the upper and lower rotor systems during operation thereof. 
         [0012]    The present invention thus provides a substantial improvement over those systems and methods found in the prior art which are designed to prevent the upper and lower rotors of coaxial rotor systems from accidentally interacting. First of all, because the device for maintaining separation of the upper and lower rotor systems provides a structural physical barrier to the interaction of the two rotor systems, it is superior to those devices which are designed to sense improper proximity and only then react to try to prevent the interaction. Such devices can fail, whereas the present invention cannot unless structural failure of the ring occurs. Also, because the present invention provides a circumferential ring which effectively covers the outer tips of the rotor blades, it is safer for persons working on or with the helicopter to be around the helicopter, as accidental contact with the rotating blade tips is prevented. Perhaps most importantly from an operational standpoint, however, the present invention prevents interaction of the upper and lower rotor systems during extreme operation of the helicopter, and as it is during these maneuvers that rotor interaction is most likely to take place, the present invention will permit the operator of the helicopter to concentrate on flying the helicopter and not be concerned about potential interaction between rotor systems. It is therefore seen that the present invention provides a substantial improvement over those systems and methods found on the prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of the improved coaxial rotor system of the present invention on a helicopter; 
           [0014]      FIG. 2  is a detailed side elevational view of the system; 
           [0015]      FIG. 3  is a detailed top plan view of the present invention; 
           [0016]      FIG. 4  is a detailed perspective view of the ring of the present invention; 
           [0017]      FIG. 5  is a detailed side elevational view of the ring and trolleys movably mounted therein; 
           [0018]      FIGS. 6 and 7  are detailed side elevational views of alternative embodiments of the outer ring of the system; and 
           [0019]      FIG. 8  is a perspective view of an alternative embodiment of the improved coaxial rotor system of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    The improved coaxial rotor assembly  10  of the present invention is shown best in  FIGS. 1-5  as including an upper rotor system  12  and a lower rotor system  32  each of which include a plurality of rotor blades, specifically a set of upper rotor blades  14  and a set of lower rotor blades  34 . In the preferred embodiment, the upper and lower rotor systems  12  and  32  would each include approximately three to eight rotor blades  14  and  34 , with the exact number, shape and size of the rotor blades to be determined by the specific design and performance requirements of the helicopter  90  with which the improved helicopter rotor assembly  10  of the present invention is to be used. 
         [0021]    Of course, the improved helicopter rotor assembly  10  of the present invention would include all of the standard elements found in coaxial rotor assemblies, including the various control elements which control the pitch and yaw of the upper and lower rotor systems  12  and  32  and the power plant  92  operative to drive the upper and lower rotor systems  12  and  32  as mounted on the central rotor shaft  80 . It should be noted that all of the various elements of the helicopter  90  which are provided to power and control the speed, pitch, angle, configuration of the upper and lower rotor systems  12  and  32 , the upper rotor blades  14  and lower rotor blades  34  and the power plant  92  and the remaining operational elements of the helicopter  90  used with the improved helicopter rotor assembly  10  of the present invention would be understood by those skilled in the art of helicopter design, and therefore further discussion of those already well-known features is deemed unnecessary. It should be further noted, however, that although minimal discussion is undertaken in regards to those elements already well known in the prior art, those elements such as the power plant  92  and helicopter  90 , particularly the fuselage  94  of helicopter  90 , may be modified or changed in accordance with the teachings of the prior art to accommodate various purposes and uses as will be determined by manufacturers and users of the present invention. Therefore, such modifications should be understood to be a part of this disclosure. 
         [0022]    The significant inventive feature of the improved helicopter rotor assembly  10  of the present invention is shown best in  FIGS. 1-5  as including an outer circumferential ring  40  which is generally E-shaped in cross-sectional shape and which includes upper and lower channels  42  and  52 , each of which would be substantially identical to one another, as shown best in  FIGS. 2 and 4 . Specifically, upper channel  42  would include a top wall  44  and base wall  46  (which also preferably forms the top wall of lower channel  52 ), each of which would include a wheel channel  48  and  50  formed therein which would preferably be generally rectangular in cross-sectional shape. Each of the upper rotor blades  14  would be connected to an upper rotor blade trolley  60  which, in the preferred embodiment, would include a generally rectangular trolley body  62  and upper and lower wheels  64  and  66  which are mounted on frictionless ball bearings and fit within the top wheel channel  48  and base wheel channel  50  of upper channel  42 , as shown best in  FIGS. 4 and 5 . The connection of the upper rotor blade trolley  60  to upper rotor blade  14  would preferably be via a rotating ball joint  70  which permits the pitch of the upper rotor blade  14  to be modified while maintaining contact and connection between the upper rotor blade  14  and upper rotor blade trolley  60 , and therefore this connecting joint  70  should be constructed of a tungsten-carbide steel material or other such high wear resistance and high strength construction material, as would the other elements of the improved helicopter rotor assembly  10 . 
         [0023]    It should further be noted that the outer circumferential ring  40  would be mounted on the central rotor shaft  80  via a plurality of ring support rods  82  which support the outer circumferential ring  40  in a generally fixed position such that as the upper rotor blade trolleys  60  travel around the outer circumferential ring  40  within upper channel  42 , the arc described forms a perfect circle with a radius equal to the length of the upper rotor blade  14  plus the length of connection joint  70 . Of course, due to the high temperatures and forces involved in the operation of the improved helicopter rotor assembly  10  of the present invention, it is expected that outer circumferential ring  40  would be constructed of an extremely light weight yet extremely durable graphite composite material or other such highly wear-resistant and heat-resistant construction material, as would be the ring support rods  82 . Of course, it should be noted that several different types of construction materials may be used with the outer circumferential ring  40  and ring support rods  82  of the present invention so long as the intended functional features of the present invention are neither significantly degraded nor destroyed. 
         [0024]    In operation, the upper and lower rotor blades  14  and  34  would rotate in opposite directions as per a standard coaxial rotor design, but this is important as there will be some frictional forces resulting from the upper and lower rotor blade trolleys  60  and  68  traveling within the upper and lower channels  42  and  52  of the outer circumferential ring  40 . As these frictional forces will be in opposite directions due to the counter-rotational forces of the upper and lower rotor systems  12  and  32 , the frictional forces should cancel out and the outer circumferential ring  40  should remain generally stable as the upper and lower rotor blades  14  and  34  rotate therewithin. The important consideration of the outer circumferential ring  40  comes into play when extreme aerobatic maneuvers are performed with a helicopter  90  outfitted with the improved helicopter rotor assembly  10  of the present invention. In an ordinary coaxial rotor assembly, the upper and lower rotor systems  12  and  32  would have to be spaced an axial distance to prevent accidental interaction of the upper and lower rotor blades  14  and  34  during such extreme maneuvering. However, with the present invention, specifically outer circumferential ring  40 , the upper and lower rotor systems  12  and  32  will be placed much more closely together than that found in the prior art and this may be done without risking accidental interaction of the upper and lower rotor blades  14  and  34  as they are prevented from traveling anywhere outside of the predetermined plane of rotation as defined by the upper and lower channels  42  and  52  of outer circumferential ring  40 . It is expected that this feature will allow the helicopter  90  to fly at a faster rate of speed and be far more maneuverable than those helicopters with coaxial rotor systems found in the prior art, as the operator need not worry that the extreme maneuvers or high rates of speed being pursued by the helicopter  90  will result in accidental interaction of the upper and lower rotor blades  14  and  34 . This represents a significant and unique improvement over the prior art. 
         [0025]      FIGS. 6 ,  7 , and  8  disclose alternative embodiments of the improved helicopter rotor assembly  10  of the present invention which are designed to address and solve problems or concerns which it is believed may arise through use of the present invention. Specifically,  FIG. 6  shows an alternative embodiment of the improved helicopter rotor assembly  10 ′ which replaces the outer circumferential ring  40  with a single circumferential ring plate  100  on which the upper and lower rotor blade trolleys  60 ′ and  68 ′ travel. In this embodiment, upwards deflection of the upper rotor system  12 ′ and downwards deflection of the lower rotor system  32 ′ is permitted, yet interaction between the upper and lower rotor systems  12 ′ and  32 ′ is prevented due to the physical structure of ring plate  100  positioned between the upper and lower rotor blade trolleys  60 ′ and  68 ′. 
         [0026]      FIG. 7  discloses an alternative embodiment of the outer circumferential ring  40 ′ in which the outer wall  56  may move freely relative to the upper and lower rotor blade trolleys  60 ″ and  68 ″, and such a configuration may be desirable in situations where the upper and lower rotor systems  12 ′ and  32 ′ are of sufficient strength and stability to provide independent support for the outer circumferential ring  40 ″ mounted thereon, thereby eliminating the need for the ring support rods  82  as was described previously. 
         [0027]    Finally,  FIG. 8  discloses a third alternative embodiment of the outer circumferential ring  40 ′″ in which the upper and lower channels  42 ′ and  52 ′ may rotate relative to one another. Such a configuration may be desirable when independent speed and rotation of the upper and lower rotor systems  12 ′ and  32 ′ is mandated, and the upper and lower channels  42 ′ and  52 ′ would preferably be separated by spacing wheel units  110  as shown in  FIG. 8 . 
         [0028]    There are several significant advantages available to the helicopter operator when operating a helicopter outfitted with the improved coaxial rotor assembly  10  of the present invention. For example, the helicopter would be to be able to rotate to face any direction, even while standing still in the air. Furthermore, since the improved coaxial rotor assembly  10  substantially prevents not only interaction between the upper and lower rotor systems  12  and  32 , but also prevents the rotor systems  12  and  32  from impacting external objects such as trees, poles, wires, etc., helicopters such as military helicopters can fly in the woods and the jungle between the high trees without fear of rotor impact. The present invention can include increased safety by adding some protective metal rods to the top and bottom of the outer circumferential ring  40  for deflecting tree branches and the like, if so desired. Also, as the present invention uses two rotors instead of one, it generates greater lift so it can use a smaller rotor radius than other helicopters, thus permitting the helicopter to fly in tighter spaces such as between close trees and within narrower passages between buildings. Also, having greater lift capacity means that the helicopter can reach higher altitudes when necessary, like passing over mountain zones in an easier manner than that possible with other helicopters or climbing faster during combat or while undergoing evasive maneuvers. Finally, because the same amount of lift can be generated using lower rotation speeds, as compared with a single rotor helicopter, the operating lifespan for the rotor and helicopter parts will be increased due to the decreased wear and tear on the parts. 
         [0029]    It is to be understood that numerous additions, modifications and substitutions may be made to the improved helicopter rotor assembly  10  of the present invention which fall within the intended broad scope of the appended claims. For example, the size, shape and construction materials used in connection with the improved helicopter rotor assembly  10  may be modified or changed so long as the intended functional features of the present invention are neither significantly degraded nor destroyed. Furthermore, the precise configuration of the outer circumferential ring  40  or ring plate  100  may be modified or changed so long as the intended purpose of maintaining physical separation between the upper and lower rotor systems  12  and  32  via a physical structure is maintained. Finally, although the present invention has been shown as being used in connection with helicopters, the present invention may be used in connection with many different types of rotor-driven aircraft, and such usages would be understood by those skilled in the art of such aircraft design. 
         [0030]    There has therefore been shown and described an improved helicopter rotor assembly  10  which accomplishes at least all of its intended objectives.