Abstract:
A mechanism for decreasing kinetic energy includes a carriage to connect to an object, a first wire passing through a top portion of the carriage, a second wire coterminous with the first wire at a top end and a bottom end, a spreading wheel axially fixed in a center position of the carriage between the first and second wires to plastically deform the first and second wires from a substantially parallel configuration to conform to a circumferential surface on two opposing sides of the spreading wheel as the carriage moves from the top to the bottom end, and a pair of despreading wheels axially parallel to and oriented proximal to the spreading wheel such that the first and second wires are deformed by a circumferential surface of each of the despreading wheels such that they are deformed again as the carriage moves from the top to the bottom end.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application claims priority to Indian Patent Application No. 5703/CHE/2015 filed Oct. 23, 2015, the entire contents of which is incorporated herein by reference. 
         [0002]    The present disclosure relates to energy attenuation systems, and more particularly to a kinetic energy attenuation system with twin wire bending. 
         [0003]    Military aircraft including rotorcraft and helicopters may undergo high vertical accelerations and/or decelerations in fast (hard) landing scenarios. Energy absorption with respect to hard landings may help preserve health and safety of aircraft occupants. Conventional aircraft cockpit seats may include energy attenuation systems designed to absorb vertical accelerations/decelerations. The “wire bender type” is one of the most commonly used mechanisms for energy absorption in seating products. Conventional wire bender-type absorption devices may include two or three rollers and a single wire. The wire is often fixed to the aircraft structure, while the rollers are often connected to the seat bucket. In situations having extreme vertical accelerations/decelerations, the rollers on the wire may plastically deform the wire (cyclically bending and unbending the wire), thereby absorbing the energy from the vertical acceleration/deceleration. The wire often increases in cross section from the top side of the wire that is bent at the beginning of the deceleration to the bottom side of the wire bent at the end of the deceleration. However, due to the limited available stroke length for seat structure, heavier occupants may be difficult to accommodate with conventional systems. 
       SUMMARY OF THE INVENTION 
       [0004]    According to one embodiment, a mechanism for decreasing kinetic energy may include a carriage configured to connect to an object, a first wire passing through a top portion of the carriage, a second wire coterminous with the first wire at a top end and a bottom end, a spreading wheel axially fixed in a center position of the carriage between the first and second wires and configured to plastically deform the first and second wires from a substantially parallel configuration to conform to a circumferential surface on two opposing sides of the spreading wheel as the carriage moves from the top end to the bottom end, and a pair of despreading wheels axially parallel to the spreading wheel and oriented proximal to the spreading wheel such that the first and second wires are plastically deformed by a circumferential surface of each of the despreading wheels such that the first and second wires are deformed again as the carriage moves from the top end to the bottom end. 
         [0005]    According to another embodiment, a method for decreasing kinetic energy can include coupling a carriage configured to connect to an object, passing a first wire through a top portion of the carriage, passing a second wire coterminous with the first wire at a top end and a bottom end, passing the first and second wires around opposing sides of a spreading wheel axially fixed in a center position of the carriage, the spreading wheel, in operation, plastically deforming the first and second wires to conform to a circumferential surface of the spreading wheel when the carriage moves from the top end to the bottom end, and passing the first and second wires between a pair of despreading wheels axially parallel to the spreading wheel and oriented proximal to the spreading wheel such that the first and second wires may be plastically deformed by a circumferential surface of the despreading wheels such that they are closer together than when on opposing sides of the spreading wheel. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0007]      FIG. 1  depicts a front view of a twin wire bending kinetic energy attenuation system according to one embodiment; 
           [0008]      FIG. 2  depicts a detailed view of the system of  FIG. 1 ; 
           [0009]      FIG. 3 a    depicts prior art; 
           [0010]      FIG. 3 b    depicts a front view of a partially actuated twin wire bending kinetic energy attenuation system of  FIG. 1 ; 
           [0011]      FIG. 4 a    is a chart comparing the energy gradient of the system of  FIG. 1  to the energy gradient of existing devices; 
           [0012]      FIG. 4 b    is a chart comparing the strain energy dissipation of the system of  FIG. 1  compared to the strain energy dissipation of existing devices; 
           [0013]      FIG. 4 c    is a chart comparing sliding energy with respect to time of the system of  FIG. 1  compared to sliding energy of existing devices; and 
           [0014]      FIG. 4 d    is a chart comparing total energy with respect to stroke length of the system of  FIG. 1  to that of existing devices. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  depicts a front view of a twin wire bending kinetic energy attenuation system  100 , according to one embodiment. System  100 , as illustrated, includes twin wires  14  and  16  and a carriage  18 . Carriage  18  may be configured to receive wires  14  and  16  through a top portion of the carriage. Wires  14  and  16  may be configured to feed through a configuration of spreading and dispreading wheels (e.g., spreading wheel  20  and dispreading wheels  22  and  24  (depicted in greater detail in  FIG. 2 ). Wires  14  and  16  may be configured to have coterminous and joined ends at top end  10  and bottom end  12 . 
         [0016]    Twin wires  14  and  16  may be plastically deformable wires configured to absorb kinetic energy by their respective deformation. Wires  14  and  16  may be substantially similar or identical, and have coterminous ends with joining means (e.g., a rivet, grommet, etc.). 
         [0017]      FIG. 2  depicts wires  14  and  16  joined at top end  10  with grommet  26  rigidly fixed to system attaching member  28  which are illustrated as a holed lug. In some embodiments, grommet  26  may be configured to securely hold wires  14  and  16  under normal operational conditions (without extreme vertical decelerations, for example). In some aspects grommet  26  may be configured to fail at a certain vertical force that may exceed normal operational conditions. Accordingly, grommet  26  may be configured to activate system  100  to dissipate energy when normal operational force is exceeded. Wires  14  and  16  may also absorb kinetic energy with exertion of frictional forces from spreading wheel  20  and dispreading wheels  22  and  24 . Frictional forces may work in conjunction with wire inertial forces from deformation to absorb kinetic energy from carriage  18 . 
         [0018]    In some embodiments, wires  14  and  16  may have consistent thickness from one end (e.g., top end  10 ) to the other end (e.g., bottom end  12 ). Accordingly, wires  14  and  16  may exert consistent stopping force with respect to carriage  18  thru  28  attached to an object  18   a  traveling along the length of the wires. In other aspects twin wires  14  and  16  may have varying thickness from end to end, which may absorb varying amounts of kinetic energy with respect to a particular thickness at a corresponding portion along the length. For example, a thick section of wire  14  and/or  16  may require greater force to deform than a thinner section, and thus, may absorb a greater quantity of energy at the thick section. In another example, a wire being thicker at the bottom end  12  than the top end  10  may decelerate carriage  18  at a greater rate with respect to time toward bottom end  12  than when traveling closer to top end  10 . In another embodiment, an alternate shape of the cross section of wire  14  and/or  16  may be used in conjunction with complementary shape of spreading wheel  20  and/or dispreading wheels  22  and  24 , which may maximize the energy dissipation. In some aspects, energy dissipation can be maximized with complementary wire and wheel shapes. 
         [0019]    In some embodiments, system  100  may be configured as a kinetic energy attenuation system for slowing a bucket seat (e.g., object  18   a ) of an aircraft in a hard vertical landing scenario. For example, system  100  may be configured to attach to a supporting framework (not shown) at top end  10  and bottom end  12 , where the framework configures wires  14  and  16  are substantially perpendicular to a deck of an aircraft  30 . In some aspects, carriage  18  may be rigidly fixed to a bucket seat (e.g., object  18   a ) such that in operation, the bucket seat rests in a position closest to top end  10 . The bucket seat may float in a vertical position with respect to the rigid frame. In some aspects, object  18   a  may also connect to object  18   a  such that a structure (e.g., an aircraft chassis) supports the object before the proposed mechanism becomes functional due to vertical force that exceeds normal operational conditions. For example, in a hard landing situation, the bucket seat may continue downward travel to the earth at the same velocity as the supporting framework (attached to the deck of the aircraft) and the aircraft. As the aircraft touches the surface of the earth (ship deck, water, etc.), the aircraft and supporting framework may come to an abrupt stop from their collective downward velocity after touch-down. The bucket seat, which was vertically free-floating with respect to the supporting structure, and traveling at the same velocity as the aircraft and supporting structure, may continue to travel toward the earth along the length of system  100 . In the absence of system  100 , the bucket seat would continue to travel toward to the ground at the same rate of travel and come to the same abrupt stop at the same rate as the framework and aircraft. On the other hand, if a seat is configured with system  100 , system  100  may gradually absorb the kinetic energy of the bucket seat (and passenger sitting in the bucket), which may minimize injury and/or damage. As the carriage  18  starts movement from top end  10  of wires  14  and  16  toward bottom end  12 . In some embodiments, system  100  may linearly or progressively diminish the kinetic energy of the carriage (and attached seat) in an increasing rate with respect to the distance traveled from top end  10 . Progressively diminishing the kinetic energy of the seat and carriage may minimize risk of injury to person or property. 
         [0020]    Referring again to  FIG. 2 , a detailed view of a portion of the system  100  is shown. Carriage  18  is depicted near top end  10  of twin wires  14  and  16 . Top end  10  may be configured to attach to an object, such as, for example, a framework fixed to the chassis of an aircraft (e.g., in a helicopter). In some embodiments, twin wires  14  and  16  may fasten at both ends (top end  10  is shown in  FIG. 2 ) to a rigid framework fastened to the chassis. Wires  14  and  16  may be joined at the same location using joining means such as, for example, a grommet. 
         [0021]    Carriage  18  may include a spreading wheel  20  axially fixed to a center position of carriage  18 . Twin wires  14  and  18  may be configured to feed through an opening at the top of carriage  18  and plastically deform around spreading wheel  20 . In some aspects, despreading wheels  22  and  24  may also be axially fastened to carriage  18  and be rotatable about their axes. Despreading wheels  22  and  24  may rotate as carriage  18  traverses along the length of twin wires  14  and  16  from top end  10  to bottom end  12  and deform wires  14  and  16  to be substantially parallel. Spreading wheel  20  may be configured as a rigid body that is not rotatable about its axis. In other embodiments, spreading wheel  20  may be configured to rotate axially. Wires  14  and  16  may feed through an opening at the bottom of carriage  18 , and connect to bottom end  12  in a fashion similar or the same as the connection at the top end  10 . 
         [0022]      FIG. 3 a    depicts an example of a conventional energy dissipation system (e.g., an “existing device”) having a single wire.  FIG. 3 b    depicts an exemplary energy dissipation twin wire energy dissipation system  100 , in accordance with some embodiments. 
         [0023]    Friction may contribute significantly to the overall energy dissipation in the twin wire mechanism as against the existing (conventional) designs.  FIG. 4 a    depicts a chart comparing the energy gradient of the system of  FIG. 3 b    to the energy gradient of existing devices as depicted in  FIG. 3   a.    
         [0024]      FIG. 4 b    depicts a chart comparing the strain energy dissipation of the system of  FIG. 1  compared to the strain energy dissipation of existing devices. 
         [0025]      FIG. 4 c    is a chart comparing sliding energy with respect to time of the system of  FIG. 1  compared to sliding energy of existing devices. and 
         [0026]      FIG. 4 d    depicts a chart comparing total energy with respect to stroke length of the system of  FIG. 1  to that of existing devices. 
         [0027]    Although described with respect to aircraft applications, according to some embodiments, system  100  be functional for energy attenuation in automobiles, machinery, and other applications. 
         [0028]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
         [0029]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. 
         [0030]    Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.