Showing papers on "Dynamic Vibration Absorber published in 1987"

Vibration absorber for a racket

Abstract: In construction of a vibration absorber for a racket, a mass is indirectly supported by a visco-elastic member arranged within the grip or the yoke of the racket via an elongated interface so that resonant swing of the interface on receipt of vibration from the head of the racket should cause deformation of the visco-elastic member for thermal diffusion of vibration energy. The visco-elastic member is sandwiched between two elongated leaf springs. One end of the leaf spring is mounted to the wall of the racket handle and the other end of the leaf spring supports the mass. By proper choice of the component, vibration in a specified frequency range can be selectively damped so as to match vibration characteristics of rackets of various types.

The Past and Future of Seismic Effectiveness of Tuned Mass Dampers

Abstract: The tuned mass dampers (TMDs) have been found effective to reduce the wind induced response of tall buildings [5, 6, 13, 14, 15, 16, 21, 22]. The effectiveness of tuned mass dampers under transient type ground excitations such as earthquakes has been studied by several investigators [2, 4, 8, 12, 19, 23, 24, 25]. Grandall and Mark [4] investigated the effect of single-degree-of-freedom tuned mass dampers mounted on single-degree-of-freedom primary structural systems subjected to stationary ideal white noise excitation. They found that as the frequency of the tuned mass damper approaches the frequency of the primary structure, the tuned mass damper is effective in reducing the displacement and acceleration response of the primary structure. Their results show that the acceleration has sharp tuning when the mass ratio µ is small and has broad tuning when µ is large. They have defined the mass ratio µ as the ratio of the mass of the TMD to the mass of the primary structure.

Tuned array vibration absorber

Abstract: A tuned vibration absorber comprises a laminated constrained layer beam formed from at least two rigid plates joined together by a layer of elastomer. One end of the laminated structure is mounted in a rigid base so that the laminated structure forms a cantilever constrained layer beam. The lamianted constrained beam is constructed so as to vibrate normal to the laminated structure at a resonance frequency that is to be dampened. The elastomer layer converts the vibrational kinetic energy into heat so that the heat can be removed. An array of tuned vibration absorbers is formed so as to damp a wide range of frequencies. The resonance frequencies of the tuned vibration absorbers are regularly spaced about the resonance frequency. The tuned array vibration absorber thus absorbs some of the vibrational kinetic energy and disperses the remainder over a wide range of frequencies to reduce the maximum amplitude of the vibrations that occur at any one frequency.

Knife drive centrifugal pendulum vibration absorber

Abstract: A knife drive centrifugal pendulum vibration absorber for an agricultural combine harvester includes a wobble drive assembly 82 with an input drive shaft 132. A flywheel 188 is secured to the wobble drive input drive shaft 132. The flywheel has apertures 192 with walls that are arcs about an axis that are parallel to the axis of rotation of the flywheel 188. A roller 194 is inserted in each aperture 194. The rollers 194 roll along the walls of the apertures 194 in response to changes in the speed of rotation of the flywheel 188 and absorb vibrations induced in the drive shaft 132 by a reciprocating knife assembly 74.

Torsional vibration absorber

Abstract: A torsional vibration absorber utilizes a resilient element comprising a coil spring positioned along relative rotational directions between drive and driven plates The coil spring includes a compressive elastic member loosely positioned within the inner cavity of the coil spring and extending along the axis of the coil spring Resin sheet elements having a diameter larger than the external diameter of the elastic member are provided as being fixed by bonding to each end of the elastic member A metallic seat member is positioned at one end of the coil spring so as to provide contact with a corresponding resin member so as to compress the elastic member only in one of the relative rotational directions of the vibration absorber

Plate spring (disc spring, cup spring, Belleville spring) of plastic, having particular damping properties as functionally integrated structural spring-and-damper (concussion spring) unit

Abstract: Plate-shaped spring elements of thermoplastic, if necessary with additional integrated functions, as replacement for conventional vibration damper (vibration absorber) designs, consisting of a spring and a separate damper (absorber). The object, specifically springing and damping of oscillating systems, is achieved by a single structural element or by a number of identical structural elements. The spring-damper characteristic is, on the one hand, predetermined by the design, but can, on the other hand, also be varied to a large degree during the production of the elements by influencing the manufacturing parameters.

Device for application with use of web vibration absorber

Abstract: A vibration damper for use with an apparatus for applying liquid to both sides of a running web and then drying the web with an air drier. Vibrations induced by the air drier are damped by uniformly blowing air on both sides of the running web between the drier and the liquid application heads. Preferably, the gas ejection surfaces are stepped or tapered so allow larger vibration near the drier but to reduce the allowed vibration nearer the liquid application heads.

Development of Intelligent Structures Using Finite Control Elements in a Hierarchic and Distributed Control System.

Abstract: : Conclusions drawn from the theoretical optimization of inertial reaction devices. Three different optimization procedures yielded almost identical absorber designs providing confidence in the tuning process. The optimal passive components of the control actuator were found to be equal to those of the optimal absorber. This allows passive damping to be added without significant mass penalty. When using an inertial device to increase damping in several modes, it is desirable to tune the frequency of the device to the lowest mode and adjust the damping accordingly. Experimentally, an inertial reaction device was used effectively as both a passive vibration absorber and a control actuator, passively tuned as an absorber, verifying the results of the tuning analysis that stated that passive tuning compliments active control. This dual purpose device resulted in a mass savings, increased modal controllability, and reduced target mode disturbance transmission. Additional passive damping increases gain margin for feedback systems that are conditionally stable and allows a form of passive damping enhancement in the event of control system failure. These space realizable experiments were found to be important in determining performance limitations due to instrumentation instabilities, friction in relative motion actuators, and actuator saturation at low frequencies. Uniformity in the positive definite, dual feedback matrix allowed better performance before the onset of instrumentation/actuator instabilities because all actuators were able to exert maximum stable feedback.

Earthquake prevention unit.

Abstract: The vibration-free unit comprises a frame which carries an instrument and whose edges are supported by vibration absorption units each consisting of a casing (1), and a disc-shaped vibration absorber (5) made of elastic material, pref. soft rubber. This is supported in the casing and in which there are holes that are symmetrical w.r.t. the absorber's centre and lie on circles that are generally concentric with the absorber's centre. A post (3) which passes through the centre of the absorber and whose bottom is set on a laterally slidable block that consists, e.g. of ball bearings (8) and a bearing holder (9) and rests on a baseboard (2). Central portions of instrument carrying frame are fitted with vertical sliders, coil springs, vibration dampers and an attitude control linkage device.

Motor driven antenna for vehicles

Abstract: A motor driven antenna for vehicles including an antenna element, an antenna housing tube which stores the antenna element and is fixed to a mounting hole of the vehicle body, a motor mechanism mounted on the base of the antenna housing tube, which retracts and extends the antenna element housed in the antenna housing tube, and a coupling mechanism for coupling the casing for the motor mechanism to the antenna housing tube. The coupling mechanism includes a first vibration absorber provided between a housing tube holding section of the motor mechanism casing and the base portion of the antenna housing tube, a second vibration absorber which fits on the antenna housing tube at a position away from the first vibration absorber a specified distance toward the tip of the end of the antenna housing tube and a coupling member for connecting the second vibration absorber and the motor mechanism casing so that the coupling member holds the second vibration absorber therein.

On the Vibration Control of Superstructures of Ships by Means of a Dynamic Vibration Absorber with an Adjustable Mass

Abstract: The reduction of superstructure vibration is essential for securing comfortable accomodation space and for preventing damage of delicate equipment in ships. Superstructure vibration is divided into three categories. The first is the local vibration where decks and walls vibrate locally. The second is the fore-aft vibration of the superstructure where the whole superstructure vibrates in the fore and aft direction at its resonant frequency. And the third is the vibration which is caused by hull girder vibrations. The prevention of fore-aft vibration is the most important, because the cure is difficult and expensive in many cases.The authors have developed a dynamic vibration absorber of which the natural frequency can be controlled by adjusting the location of the mass. The reduction of the superstructure fore-aft vibration by means of the dynamic vibration absorber were studied, and are presented in this paper. Scale model tests and full scale tests were performed. The superstructure and the dynamic vibration absorber were modelled into two degrees of freedom systems with the help of FEM analyses. The experimental results were compared with the results calculated by the simple formula of two degrees of freedom systems. They generally showed good correlation.The vibration of the superstructure of a 40, 000 DWT cargo ship was reduced to one forth of the original vibration level by using the dynamic vibration absorber with a 800 kg weight.The dynamic vibration absorber has the following advantages : (1) The installation requires little change in the vibrating structure, so the installation is economical.(2) The dynamic vibration absorber itself generates no vibration, nor noise, because it requires no power sources.(3) The effect of vibration reduction is constant and reliable.

Practical Experiences in Passive Vibration Control of Chimneys (Conclusions from Wind Tunnel and Full Scale Tests)

Abstract: Cylindrical chimney structures with low structural damping are very susceptible to wind induced oscillations. It is well known that chimneys under wind loading respond dynamically in the across-wind as well as in the along-wind direction. For such structures the dynamic response in the across-wind direction is often greater than along-wind.

Curved rail pendulum type vibration absorber

Abstract: PURPOSE:To make it possible to obtain a small size vibration absorber having its damping coefficient which is adjustable and a long oscillating period, by disposing a damper between arms attache to a plurality of carrier vehicles oscillating on a plurality of curved rails whose relative positions are adjustable. CONSTITUTION:Carrier vehicles 7, 20 supported by wheels 3, 3a-3c are carried on and guided by curved rails 2, 2a-2d which are secured on bases 1, 1a-1d. The vehicles 7, 20 have pins 8, 8' supporting arms 10, 10a with which the positions of weights 12, 12a may be adjusted by means of screws 15, 15a. Further, a damper 14 is attached between stems provided to the arms 10, 10a, by means of pins 13, 13a-13c.

Bellows type vibration absorber

Abstract: PURPOSE:To reduce resonance magnification greatly by arranging a vibration absorbing column body on the axial center of a bellows, with the upper and lower ends of the column body connected to the inner upper and lower surfaces of the bellows, and providing the bellows with communication holes. CONSTITUTION:A bellows 10 is tightly closed by cover bodies 12 and 13 at the top and bottom of a main body 11. A vibration absorbing column body 20 of a gel-like material is arranged along the axial line of and within the main body 11. The bellows 10 is provided with communication holes 14 to make an inner chamber 15 communicate with outside. Accordingly, since vibrations applied to the bellows 10 are absorbed simultaneously with the elastic deformation of the bellows 10 and the non-elastic deformation of the vibration absorbing column body 20 made of the gel-like material, the repulsive elasticity of the bellows 10 is restrained by the deformation of the vibration absorbing column body 20. Also, since air in the inner chamber 15 is discharged through the communication holes 14 when the bellows 10 contracts, resonance frequencies vary with the diameter of the communication holes 14.

Double acting vibration absorber

Abstract: PURPOSE:To enable the smallness of size to be attained in a damping device, by vibrating the first additional mass to resonate with a main vibrating system while giving the predetermined damping action by the damping device through the second additional mass which is connected so as to resonate, in the case of a vibration absorber for a building or the like. CONSTITUTION:A double acting vibration absorber A, which connects the first additional mass 1 to the roof floor or the like of a structure through springs 3 setting up on to the first additional mass 1 a vibration absorber (a) supporting the second additional mass 2 through springs 4, holds a resistance plate 7, protruding to the bottom side, horizontally in viscous fluid 6 in a viscous fluid tank 5 fixed to a side of the first additional mass 1. And when vibrative external force of earthquake or the like is input to the structure, the first additional mass 1 resonates, further the double acting vibration absorber A, in which the second additional mass 2 tends to resonate in large amplitude, receives viscous resistance of the viscous fluid 6 by the resistance plate 7, absorbing vibrating energy by the damping force of that resistance. In this way, the double acting vibration absorber A, enabling a damping device to be formed in small size while a quick response to be attained for an earthquake and wind or the like, enables the damage of a building or the like to be surely prevented.

Pendulum type dynamic vibration absorber

Abstract: PURPOSE:To effectively absorb vibration with the simple constitution by combining a pendulum in which an additive mass is suspended by suspending members and an attenuating device for attenuating the vibration of the pendulum, in a dynamic vibration absorber for a building CONSTITUTION:As for a dynamic vibration absorber 1, an additive mass 2 in square form is suspended through a connection part 9 such as universal joint onto a supporting frame 4 by four suspending members 3, and a resistance plate 7 whose height can be adjusted is held horizontally by an adjuster 8 using screws, etc, below the additive mass 2, and immersed into the viscous fluid 6 in a viscous fluid tank 5 fixed onto a building When the building is vibrated by an earthquake, wind or the like, the additive mass 2 is vibrated so as to shift slightly upwardly, and the distance between the resistance body 7 and the bottom plate of the viscous fluid tank 5 increases, and the vibration is attenuated by the shearing resistance of the viscous fluid 6 Therefore, the effective absorption for vibration is permitted with the simple constitution which requires a relatively small place

Balance type vibration absorber

Abstract: PURPOSE:To restrain bending and torsional vibration by disposing a spring and a damping device between two main weights balanced with a counterweight positioned at the vertex of an isosceles triangle and a structure in a balance type vibration absorber for a huge structure. CONSTITUTION:A balance 12 supported by a pivot supporting point on a structure 10 comprises a beam 12a supported on a supporting point 11 and a beam 12b fixed at right angle thereto. Main weights 13 are disposed at both ends of the beam 12b and a counterweight 14 is disposed at the forward end portion of the beam 12a in such a manner as to position at the vertex of an isosceles triangle, wherein the respective masses are statically balanced to be horizontal. A spring 15 and a damping device 16 are provided between both end portions of the beam 12b where the main weights 13 are disposed and the structure 10, respectively. In this arrangement, bending and torsional vibration of a huge structure can be restrained by mass of comparatively small main weights and counterweight, and the initial deformation of the spring will not be caused.

Variable vibration absorber with a wide frequency spectrum

Abstract: The invention relates to a device for absorbing system excitation vibrations of machines, machine parts, running gear and bodywork (wherever vibrations are unwanted), the variation of the resonant natural vibration of the device being achieved by variation of the resilient effective surfaces. The device consists of the holder (2) (for rigid introduction of vibrations), at least one mass (1) and at least one spring element (3) arranged between the holder and the mass, the said spring element being connected to at least one spring member (4) in such a way that the resonant natural vibration of the device can be varied relative to the excitation vibration by adjusting the slide (6).

Vibration wave motor

Abstract: PURPOSE:To readily apply an AC voltage by providing conductivity at a vibration plate and a movable body, securing an electro-mechanical energy converter to one side of the plate, and applying an AC voltage to the other side face of the converter and the body CONSTITUTION:A vibration plate 2 is held together with a piezoelectric element plate 1 through a ringlike vibration absorber 4 at a base 5 made of an insulating material A rotatable circular movable body 3 made of a conductor material is supported by bearing 77 through a bush 8 to a stationary shaft 6 The body 3 is contacted with the upper surface of the body 3 in a pressed stage The shaft 6, the bush 8 and the bearing 7 are formed of conductive materials, the shaft 6 is electrically conducted with the body 3 to apply an AC voltage between an electrode film formed on the lower surface of the plate and the body 3

Pendulum type vibration absorber provided with spring

Abstract: PURPOSE:To make it possible to obtain a vibration absorber which has a small size while it has a long oscillating period, by disposing springs between frames and bases, and by providing arms each having a weight, and by providing dampers between the arms. CONSTITUTION:Springs 4, 4A are disposed between frames 3, 3a supported on base 1, 1a by means of rollers 2, 2a through 2i, and the bases 1, 1a. Further, arms 8a, 8a are supported to bearings 7, 7a through 7c secured on the frames 3, 3a, through the intermediary of pins 6, 6a. Further, the arms 8, 8a are provided with weights 9, 9a, and viscoelastic dampers 12, 12a through 12c are disposed between the arms 8, 8a.

Rotating synchronous processing system

Abstract: PURPOSE:To prevent turbulence of synchronization due to vibration by inserting a vibration absorber at least between a tooth portion on passive side of a toothed rotation transmitted and a rotary shaft in a drum type engraving scanner CONSTITUTION:A rotary encoder is coupled to one end of a rotary shaft 2 of a recording drum, and the turning torque given from a motor through a speed reducer is transmitted by engagement of a toothed belt 50 and a toothed pulley 36 The toothed pulley 36 comprises a main body inner ring portion 71 fixed to the shaft 2 and a main body outer ring portion 73 having a tooth portion 74, which is disposed concentrically with a gap 72, wherein ring-shaped vibration absorbers 75, 76 are pressed in the vicinity of a boundary portion between both sides of both ring portions 71, 73 by fitting pressure inner rings 77, 78 to pressure outer rings 79, 80 by bolts 81 and coupled to each other to absorb vibration In this arrangement, the turbulence of a designated processing for a rotated body itself or a processed body interlocking with the rotated body and rotation can be reduced

Effect of Coulomb Friction on a Dynamic Vibration Absorber System with Harmonic Base Excitation (2nd Report, Coulomb Friction in the Main System) : Series C : Vibration, Control Engineering, Engineering for Industry

Abstract: This report presents the effect of Coulomb friction combined with viscous damping in the main system, to which a viscous-damped dynamic vibration absorber is attached. The main system is subjected to harmonic base excitation, and in the analysis, a similar process is used to that explained in the previous report. The conclusions are : -(1) The numerical results of the analytical solution coincide very well with those of digital simulation. (2) Coulomb friction coexisting with the viscous damping in the main system, with a dynamic vibration absorber tuned so as to suppress the resonant response of the system in considering only viscous damping, reduces the maximum amplitudes of the main mass. The features of two equi-height maximums in the resonance curve vanish. (3) Since conventional expressions for the optimum tuning of the absorber do not fit in this case, other new empirical formulae are recommended.