Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C27/00—Rotorcraft; Rotors peculiar thereto
  • B64C27/001—Vibration damping devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F7/00—Vibration-dampers; Shock-absorbers
  • F16F7/10—Vibration-dampers; Shock-absorbers using inertia effect
  • F16F7/104—Vibration-dampers; Shock-absorbers using inertia effect the inertia member being resiliently mounted
  • F16F7/116—Vibration-dampers; Shock-absorbers using inertia effect the inertia member being resiliently mounted on metal springs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C27/00—Rotorcraft; Rotors peculiar thereto
  • B64C27/001—Vibration damping devices
  • B64C2027/005—Vibration damping devices using suspended masses

Definitions

• the invention relates in general to the field of vibration cancellation and in particular to a compact assembly for cancellation of vibration in structural members .
• vibration attenuation devices employ various combinations of the mechanical system elements to adjust the frequency response characteristics of the overall system to achieve acceptable levels of vibration in the structures of interest in the system.
• vibration cancellation systems are utilized to cancel mechanical vibrations which are associated with the propulsion system and which are generated by the engine, transmission, propellers, rotors, or proprotors of the aircraft .
• Frahm recognized that the inertial characteristics of a sprung mass could harness out-of-phase acceleration of the auxiliary body to generate counter-balancing forces to attenuate or cancel vibration in a structural member.
• the auxiliary body is excited by the vibration of the structural member to which it is attached.
• the auxiliary body and connecting spring in the Frahm device form a classical spring and mass assembly, the natural frequency, ⁇ n , of which is given by:
• the auxiliary mass incorporates a first set of mounting features disposed on a first set of surfaces facing in a first direction toward the central plane of the mass and a second set of mounting features disposed on a second set of surfaces facing in a second direction substantially opposite the first direction.
• the mass is suspended by a first set of springs acting on the mass through 8 the first set of mounting features and a second set of springs acting on the mass through the second set of mounting features.
• a third embodiment of the present invention is a vibration cancellation device comprising an auxiliary mass having a center, an axis of motion, and a first central plane passing through the center of mass and orthogonal to the axis of motion.
• the auxiliary mass has a second central plane passing through the center of mass and orthogonal to the first central plane and having a first and second side and a third central plane passing through the center of mass and orthogonal to the first and second central planes and having a first and second side.
• This third embodiment of the present invention uses a set of four springs to suspend the auxiliary mass, with one spring being disposed in each of the four quadrants, and the springs disposed in opposite diagonal quadrants acting together in opposition to the remaining two springs .
• a fourth embodiment of the present invention is a vibration cancellation device incorporating a frame having a first and second set of spring pockets .
• the pockets in the first set are shaped and disposed to accept and retain a first set of springs along a first set of spring axes parallel to the axis of motion.
• the pockets in the second set face opposite the first set of spring pockets and are shaped and disposed to accept and retain a second set of springs along a second set of spring axes parallel to the axis of motion.
• Figure 3 is a top view of the embodiment shown in figures 1 and 2 with the lid removed to reveal the internal components;
• Figure 4 is a cutaway side view of the embodiment shown in figures 1-3;
• the present invention disclosed herein comprises an improved vibration cancellation device designed to overcome many of the shortcomings inherent in prior devices .
• the vibration cancellation device is smaller in scale than prior designs, facilitating more versatility with respect to design options .
• the various embodiments of the present invention disclosed herein make use of vibration cancellation devices using offset springs.
• the suspended frame 20 is suspended within the case 12 and lid 14 by two lower springs 32 and two upper springs 34.
• springs 32 and 34 are disposed adjacent to, rather than in line with, the suspended assembly of the suspended frame 20, tuning masses 22, and tuning mass fasteners 24.
• one of the more common arrangements employed paired upper and lower springs axially aligned, rather than being offset as in the present design. Such coaxial alignment has generally been thought necessary in order to provide for fully offset loading and to avoid the impartation of any dynamic moments or angular accelerations to the suspended mass.
• tuning masses 22 are accessible and removable through windows 18 without disassembly of the frahm 10 itself . Accordingly, although the spring stiffness k cannot be easily changed without disassembly of the unit, the mass m can be. This allows for fine-tuning of the natural frequency w of the frahm 10 after assembly, so as to account for manufacturing tolerances or other factors.
• the tuning masses 22 are a set of thin plates secured to the suspended frame 20 by a set of threaded tuning mass fasteners 24. Adjustment of the mass of the suspended assembly can therefore be performed by adding or removing plates, by replacement of heavier plates with lighter plates, or by removal of material from plates already secured in place.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Vibration Prevention Devices (AREA)
• Apparatuses For Generation Of Mechanical Vibrations (AREA)
• Springs (AREA)

Priority Applications (7)

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Publications (2)

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Cited By (3)

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Citations (5)

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• 2001
  • 2001-08-24 US US09/939,127 patent/US6443273B1/en not_active Expired - Lifetime
• 2002
  • 2002-08-26 DE DE02796400T patent/DE02796400T1/de active Pending
  • 2002-08-26 EP EP02796400A patent/EP1419089B1/en not_active Expired - Lifetime
  • 2002-08-26 DE DE60232593T patent/DE60232593D1/de not_active Expired - Lifetime
  • 2002-08-26 BR BR0212061-5A patent/BR0212061A/pt active Search and Examination
  • 2002-08-26 CA CA002457293A patent/CA2457293C/en not_active Expired - Lifetime
  • 2002-08-26 WO PCT/US2002/026633 patent/WO2003018342A2/en not_active Ceased
  • 2002-08-26 JP JP2003522830A patent/JP4339683B2/ja not_active Expired - Fee Related
  • 2002-08-26 AU AU2002332609A patent/AU2002332609B2/en not_active Ceased

Patent Citations (5)

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