Showing papers on "Dynamic Vibration Absorber published in 1981"

Wheel tire with noise absorbing means

Abstract: The running characteristics of a tire for a wheel are improved to provide a more quiet run, by attaching to an inner and/or outer surface of the tire vibration absorbing elements. Vibration absorbing elements may even be inserted into the tire material itself. The vibration absorbing elements are secured to the tire surface in a force and moment or torque transmitting manner by vulcanization or by a suitable adhesive. A strap may hold the individual absorbing elements together or the elements may form integral parts of the strap which is secured to the tire surface, for example, by a rubber vulcanizing operation. The vibration absorber elements may be secured to an inner tube instead of to the tire.

Hydraulic-operating shock and vibration absorber and damper

Abstract: The invention relates to a hydraulically-operating shock and vibration absorber or damper, having a cylinder closed at one end, a piston slidable within the cylinder, the piston being connected with a hollow piston rod extending out of the open end of the cylinder. The interior of the piston rod and the cylinder define a chamber filled with an incompressible damping fluid. A space is defined in the piston rod separated from the chamber by a slidable separating piston. The space contains a compressible agent. The damping fluid is pressed out of one portion the chamber, through the control port, into another portion when the shock absorber is under load. The compressible damping agent is air or gas under normal pressure or else pressurized. The imcompressible damping fluid consists of a non-Newtonian, permanently plastic, homogeneous paste of high heat-conducting capacity composed of graphite, a wetting agent, intrinsically viscous agent and polyglycol ether, polyglycol ester and/or a saturated, aromatic or aliphatic ester of caboxylic acid. Into the opening of the piston, a control pin extends which increases or decreases the cross section of the opening when the piston moves in and out.

Vibration absorber for an automotive vehicle

Abstract: A vibration absorber for an automotive vehicle which can prevent the shuddering phenomenon even while the vehicle is gradually accelerated or decelerated. The rubber member thereof is provided with multistep elasticity characteristics such that a first shearing portion of the rubber member is first deformed in shear, a second shearing portion thereof is next deformed in shear, and the other portion thereof is lastly deformed under compression. To achieve the above-mentioned elasticity characteristics, some appropriately sized slots, cavities, or gaps are provided within the rubber member at appropriate positions within the rubber member.

Vibration absorber for a free piston Stirling engine

Abstract: A free piston Stirling engine has a hermetic vessel containing a displacer piston and a power piston coupled to each other and to the vessel by gas springs. An additional mass is coupled to the vessel by a gas spring which is tuned to the operating frequency of the engine geometrically. The vibration absorber is effective at all engine frequencies because the absorber gas spring follows the engine working gas mean pressure and changes the absorber natural frequency as the engine frequency changes.

Application of a Structural-Acoustic Diagnostic Technique to Reduce Boom Noise in a Passenger Vehicle

Abstract: This paper is No. 81011. Body "boom" is a structurally generated noise that can be excited in a passenger vehicle by road roughness or powertrain vibration. It typically occurs in a frequency band below 200 hz and results when the input forces to the body structure are transmitted to the wall panels around the passenger compartment which, in turn, vibrate and excite the acoustic modes of the compartment cavity. This paper concerns the diagnoiss of boom noise which is excited by engine vibration. Several approaches have been described in the literature for reducing engine induced boom noise. These include reducing the input excitation of the engine to the body structure by use of a vibration absorber, adjusting the engine mounts to tune the engine vibration for minimum acoustic participation, and the use of a Helmholtz resonator to modify the acoustic response of the compartment cavity. Another approach, which is the topic of this paper, is to identify and alter the structural wall panels which excite the boom noise. T his approach has been applied successfully to reduce boom noise generated by road input and is based on the use of a finite element model of the compartment cavity to determine the panel participations in exciting the acoustic modes. A diagnostic technique for noise reduction based on the use of the finite element model together with experimental panel vibration data has been developed, and its application is described in this paper. (Author/TRRL)

Gas-filled tyre

Abstract: In a gas-filled vehicle tire are provided for the purpose of reducing the sound radiation to the tire force and moment positively connected vibration absorber (4). The vibration absorber are preferably mounted inside the tire, but can also be attached to the outer side surfaces of the tires. The vibration absorber may be formed, for example, triangular, tubular or crescent-shaped in cross-section.

Two case studies in the use of tuned vibration absorbers on foot bridges

Abstract: The work described is part of a research programme into ways of reducing pedestrian-induced vibrations of footbridges, the problem being that these vibrations can cause discomfort to the user. The two case studies presented describe one method by which this has been achieved - the discrete tuned vibration absorber. Results show that an absorber with a low mass value (approximately 0.6% of the bridge superstructure mass) can achieve very worthwhile reductions in vibration levels. This effect is, however, dependent on optimum damping and accurate tuning of the absorber and on minimum dry friction in the absorber movement.(a) (TRRL)

Coulomb-type vibration absorber for suspended cables and suspended cable combined therewith

Abstract: A vibration absorber for attachment to suspended cables such as electrical transmission lines, to suppress vertical aeolian vibrations as well as horizontal subconductor oscillations. A clamp arm has one end attached to a suspended cable and another end rotatably coupled to a frame through two frictionally-engaged elements which provide coulomb friction when the clamp arm is caused to rotate relative to the frame as a result of said vibrations or oscillations. A separate resilient member couples the clamp arm to the frame to restore the initial orientation of the clamp arm.

Vibration absorber for aerially suspended conductors and cables

Abstract: In a vibration absorber for use with aerially suspended conductors and cables, there is described an improved vibration absorber wherein wind or turbulence induced vibrations resulting in travelling waves on conductors cables are absorbed so as to prevent damage to or failure of conductors and related hardware due to fatigue. Known devices, particularly dampers and spacer dampers, attempt to control merely the amplitude of the waves produced on the conductor and are therefore ineffective in preventing the formation of such waves and the damage that may result. In this invention, a vibration absorber comprising a piston and cylinder device whereby a travelling wave displaces the piston orthe cylinder relative to one another causing a fluid contained within the cylinder to be displaced through an orifice in the piston. The absorbing system thus defined has a mechanical dissipative impedance of value R to inhibit the reflection of a wave propagated on the conductor whereby the wave is absorbed. The value of R is in the range of .5 TM to 2.0 TM where T is the tension of the conductor and M is the mass of the conductor per unit length.

Reduction of Hull Vibration in a Landing Craft by Means of a Vibration Absorber

Abstract: Structural problems caused by wave induced hull vibration were experienced by a series of six landing craft operated by the Royal Australian Navy. These craft, of maximum displacement of 520 tonnes, were designed primarily for the transport of cargo from ships off-shore to water terminals and undeveloped beaches, but they have also been operated on long sea voyages, often in rough seas. It was decided to fit a damped vibration absorber in each vessel to increase the structural damping and minimise the vibration response. The absorber used has a mass of 10 tonnes, is supported on air springs, and is installed in the bows of the ship. The paper describes the design and installation of the vibration absorber, and gives the results of evaluation tests carried out in calm seas and in rough seas. Several years of operational experience have now been gained and the absorber has proved to be very effective in reducing hull vibration in these craft. The paper is followed by a discussion.

Device for damping vibrations in the drive train of a motor vehicle

Abstract: The invention indicates a device for damping vibrations in the drive train of a motor vehicle by means of a vibration absorber which, in coaxial arrangement with the propeller shaft of the motor vehicle, comprises an annular oscillatory mass, a supporting flange which can be fixed on the propeller shaft, and a spring body composed of an elastomer which provides the vibrational coupling of the oscillatory mass to the supporting body of the supporting flange. The supporting body of this supporting flange is of circular cylindrical design and the spring body is divided into elements in the form of ring segments which, as seen in the circumferential direction, are connected to one another by reinforcing elements which, as seen in the radial direction, are arranged between slots on the oscillatory-mass side and slots on the supporting-body side. The resonant frequency of the torsional vibration of the vibration absorber can be influenced in a specifically intended way by means of these reinforcing elements. Inserted into the ring segment-shaped spring elements of the spring body are reinforcing elements which are designed as circular cylindrical sheet-metal sleeves by means of which the resonant frequency of the radial vibration of the vibration absorber can be influenced in a specifically intended way to produce an increase.

Beamlike Dynamic Vibration Absorbers

Abstract: Although the concept of the dynamic absorber and its potential for vibration reduction were first discussed in the early part of this century, John Snowdon's comprehensive work in this area was certainly a pioneering effort. By rephrasing the standard equations in terms of complex dynamic moduli, it became possible to treat viscoelastic (rubberlike) absorber damping, as well as the conventional viscous damping. For either type, Dr. Snowdon provided expressions and curves for the socalled optimum tuning and damping conditions, thus placing the solutions to many practical vibration problems within reach. In this paper, the performance of several beamlike dynamic vibration absorbers is analyzed and, in selected cases, confirmed by experiment. The absorbers are employed to suppress the transmissibility at resonance across a simple mass‐spring vibrator, a stanchion, and a simply supported rectangular panel. The absorbers comprise either single or double cantilever beams that are mass loaded at their free ends, or clamped‐clamped beams that are centrally mass loaded. Analyses are based throughout on the Bernoulli‐Euler beam and thin‐plate theories without simplification.

Bellows-type vibration absorber for suspended cables and suspended cable in combination therewith

Abstract: A vibration absorber for attachment to suspended cables such as electrical transmission lines, to suppress vertical aeolian vibrations as well as horizontal subconductor oscillations. A clamp arm has one end attached to a suspended cable and a fulcrum adjacent the other end. The fulcrum is rotatably coupled to a frame, and the end of the clamp arm adjacent the fulcrum is coupled to the frame through two bellows elements which force air through small orifices to provide viscous friction when the clamp arm is caused to rotate relative to the frame as a result of said vibrations or oscillations. Each bellows includes a resilient pleated portion which acts to restore the initial orientation of the clamp arm.

Method and apparatus for testing and/or adjusting vibration absorber for suspended cables

Abstract: A pendulum type vibration absorber tester/adjuster, which enables vibration absorbers to be set to a desired damping in the factory. The test/adjustment is effected by mathematically determining the pendulum weight and arm length, setting the pendulum into motion and recording the motion on a chart recorder, and adjusting the damping of the absorber until a predetermined decrement is obtained.

Feeder for transport facilities

Abstract: PURPOSE:To absorp vibration and prevent a noise, by providing a groove on the peripheral part of the body of a feeder made of an electric conductor and by filling a vibration absorber in the groove. CONSTITUTION:A feeder comprises a feeder body 21 made of an electric conductor of prescribed electric conductivity and a vibration absorber 23 filled in a groove 22 provided on the peripheral part of the body 21. The cross section of the feeder body 21 is shaped as U. A sliding surface 24 for a pantograph shoe is provided on the bottom of the body 21. The groove 22 is located in the body 21. The body 21 is made of iron alloy, aluminum alloy or the like. A solid material such as concrete, a high-molecular substance such as rubber or the like is used as the vibration absorber 23. The feeder is vibrated because a pantograph slides thereon. A solid vibration sound is made by the vibration. Since the vibration energy of the feeder is absorbed by the absorber 23, the magnitude of the vibration is lowered. This results in greatly reducing the solid vibration sound of the feeder itself.

Contact wire for urban traffic facility

Abstract: PURPOSE:To support the contact wire without tilting it or decreasing its damping effect, by constructing the support in the pressing direction of a collector shoe with a vibration absorbing material having a small spring constant, as well as constructing the support in the pressing direction of the tare and the support in the pressing direction of the collector shoe in the separate structure. CONSTITUTION:The contact wire 5, which is movable to the pressing direction by the collector shoe, is suspended byh a track girder 1 through contact wire supporter 2-4. A vibration absorber 6 is provided between a bracket 4 and the track girder 1, so that the movement of the contact wire 5 to the direction of the track girder 1 is restrained, and the contact wire 5 does not tilt to the dead load direction. Besides, the vibration of the contact wire 5 is absorbed, if vibrated by collector shoe as the wire rope 3 is provided in the member to support the contact wire 5 in its tare direction. Moreover, vibration of the contact wire 5 is absorbed by the vibration absorber 6 having a small spring constant, therefore, vibration of the contact wire 5 is prevented from propagating to the track girder 1.

Air cylinder-type vibration absorber for suspended cables and suspended cable in combination therewith

Abstract: A vibration absorber for attachment to suspended cables such as electrical transmission lines, to suppress vertical aeolian vibrations as well as horizontal sub-conductor oscillations. A clamp arm has one end attached to a suspended cable and a fulcrum adjacent the other end. The fulcrum is rotatably coupled to a frame, and the end of the clamp arm adjacent the fulcrum is coupled to the frame through the air cylinder damping element which forces air through a small orifice to provide viscous damping when the clamp arm is caused to rotate relative to the frame as a result of said vibrations or oscillations. A pair of torsion springs or non-rotatably mounted resilient washers acts to restore the initial orientation of the clamp arm.