Showing papers on "Dynamic Vibration Absorber published in 1984"

Optimal Design of a Passive Vibration Absorber for a Truss Beam

Abstract: The selection of the design parameters of passive vibration absorbers attached to a long cantilevered beam is studied. This study was motivated by the need for conducting p arametric analysis of dynamics and control for spaceshuttle-attached l ong beams. An optimization scheme using a quadratic cost f unction is introduced yiedding the optimal sizing of the tip vibration absorber. Analytical s olutions for an optimal absorber are presented for the case of one beam vibrational mode coupled with the absorber dynamics, and results are extended to cover the m ultiple mode case. An algorithm is developed to make an initial estimate of optimal tuning parameters which m inimize the quadratic error cost function. Examples are given to illustrate the design concept.

The cruciform dynamic vibration absorber

Abstract: The cruciform dynamic absorber comprises two free–free beams that are mass loaded at their free ends and that are joined centrally at right angles at a point at which they are attached to the vibrating item or structure of concern. Both a lumped simple system and distributed mechanical systems such as beams and clamped circular plates are considered. The damping of the absorber beams and of the lumped and distributed mechanical systems is assumed throughout to be of the solid type. The branches (arms) of the cruciform dynamic absorber are generally tuned to the fundamental and second or third resonances of the distributed mechanical systems considered. Sometimes, one branch is tuned to the fundamental resonance of the distributed mechanical system concerned while the other branch, with essentially zero damping, is tuned off resonance, for example, to the frequency of a troublesome machinery discrete, thereby generating a pronounced trough in the transmissibility curve with a compensating transmissibility peak at a slightly higher frequency that is not necessarily of predominant magnitude.

An Optimum Design Method for the Dual Dynamic Damper and its Effectiveness

Abstract: In order to eliminate the drawbacks of a conventional dynamic absorber whose damping performance is very sensitive to the variation of parameters, use of a dual dynamic absorber is proposed in this paper. To reduce the transmissibility across a main vibration system at resonance, the optimum design procedure of the dual dynamic absorber is described, and optimum values for its tuning and damping parameters are specified in graphical forms and by formulas for the designing. Utilizing the design formulas, the effectiveness of the dual dynamic absorber in reducing the transmissibility at resonance is studied and shown to be considerably greater than that of the conventional dynamic absorber. Also, it is shown that by use of the dual absorber, it is possible to avoid a decrease of damping performance with the change of the natural frequency of the main vibration system and of damping in its absorbers.

Damped dynamic vibration absorber

Abstract: A pump is disclosed having a damped dynamic vibration absorber for attenuating pump vibration in response to a periodic disturbing force generated when the pump is in operation. The vibration absorber comprises elastic means, an annular mass and an energy dissipative means. The elastic means are arranged around the pump in a plane generally normal to the axis of rotation having one end secured to the pump and one end free to vibrate relative to the pump. The annular mass is secured to the free end and the energy dissipative means comprising a squeeze film damper is secured to the annular mass. The annular mass has a predetermined mass, and the elastic means have a predetermined stiffness and the squeeze film damper has a predetermined damping ratio such that the absorber generates a compensating force acting on the pump out of phase with a periodic disturbing force which acts on the pump and is generated while the pump is operated. The effect of the compensating force is to attenuate vibration of the pump which would otherwise occur as a result of the periodic disturbing force.

Bearing for the drive assembly of a motor vehicle

Abstract: In order to prevent the transmission of vibrations to the vehicle body, the drive assembly of the motor vehicle is elastically suspended on a cross member and the latter likewise elastically connected to the vehicle frame. At the same time, the mass of the cross member and its elastic bearing on the vehicle frame are so matched that the cross member forms a vibration absorber for the vibrations of the drive assembly comprising engine, clutch and gearbox. In a certain speed range the vibration absorber oscillates in the opposite phase to the gearbox so that a noise reduction can be obtained.

Surface grinder incorporating vibration damper

Abstract: PURPOSE:To prevent vibrations harmful to machining from being generated, by a method wherein a vibrator resonating with a vibration at a specified frequency of a frame of a surface grinder is provided at a part of the frame, and a damper oil is intermediately provided between the vibrator and the frame. CONSTITUTION:A pair of reinforcing plates 8 are fixed between a lower part of the rear face of a head 1 and both sides of an intermediate part of a supporting column 2. A vibration absorber 9 is placed on and fixed to the top of the column 2. A damper oil 12 is stored in a casing 11 fixed to the top of the column 2. A leaf spring 14 is fixed by clamping between a pair of clamping bodies 13 fixed to an upper surface of the casing 11, and the vibrator 15 is suspendedly fixed to a lower end part of the spring 14 in the condition of being immersed in the oil 12. When the column 2 and a grinding wheel spindle head 5 are integrally oscillated with a base part of the column 2 as a center, vibration of the column 2 at a specified frequency in forward and backward directions is damped by appropriately regulating the projecting length of the spring 14 and the viscosity and quantity of the oil 12, whereby the column 2 and the wheel spindle head 5 can be restrained from being oscillated.

Mirror vibration absorber

Abstract: A mirror vibration absorber for mirror assemblies mounted on motor vehicles comprises a ballast absorbing the vibration of the mirror assembly and disposed either inside or outside thereof. The position and weight of the ballast can be adjusted to the specific vibration frequency of the mirror assembly. The adjustment of the ballast position is made either by moving the adjustment of rods secured to the ballast relative to the mirror assembly or by moving the ballast relative to the adjustment rod. The ballast absorbs the mirror vibration and thereby reduces the need for reenforcing mounting hardware and braces.

Liquid-dampening vibration absorber

Abstract: © In a vibration absorber, lower and upper holders (10,14) are interconnected by means of an annular elastomeric dampening member (17) and have a throttling disk (18,19) for dividing the interior space of the absorber into two liquid-filled working chambers (24, 25), of which the lower chamber is defined by a rubber elastic membrane (20). The membrane (20) and the throttling disk (18,19) are loosely inserted in the lower holder (14) and held in position therein by a resilient holding device (26, 27, 28) sealingly urging said membrane and said throttling disk against a sealing face (16) on said lower holder (14).

Closed type rotary compressor

Abstract: PURPOSE: To reduce operational vibration in a rotational direction, by mounting a vibration absorber to a compressor. CONSTITUTION: A closed vessel 2 is supported by a vibration isolating rubber 14. A vibration absorber 15 is rotatably supported to a fulcrum shaft 17 of the closed vessel 2. The vibration absorber 15 has a natural frequency equal to a frequency where the compressor 1 is vibrated. The vibration absorber 15 is designed to vibrate with opposite phase to the vibration of the compressor 1 to thereby reduce operational vibration in the rotational direction of the compressor 1. COPYRIGHT: (C)1985,JPO&Japio

Vibration absorber for carrier of serial printer

Abstract: PURPOSE:To suppress the occurrence of resonance sound in the frame structure by absorbing the vibrations of a wire and a motor by supporting a motor to drive the motor pulley wound with a wire for moving a carrier through a buffer CONSTITUTION:A carrier having the printing head of a serial printer is linearly moved through a wire wound around the motor pulley to be driven by a motor 25, the direction of which is changed by a guide pulley and a carrier pulley and both ends of which are supported by the frame Since the motor 25 is supported through a buffer 27 on a base 26, the vibrations of the wire and the motor are absorbed, resonance sound in the frame structure due to the transmission of vibration is suppressed, and therefore, the occurrence of noise can be prevented

Visco-elastically damped torsional vibration absorber with spring-coupled fly-ring

Abstract: Viscously damped torsional vibration absorbers are increasingly being equipped with additional coupling springs or springs which elastically centre the damping ring in the housing. In order to prevent the displacement of the viscous medium by the alternating displacement of spring portions and to keep the space taken up by the viscous medium in the gap between the damper ring and the housing as small as possible, the space occupied by the additional springs is, according to the invention, separated from the gap space containing the viscous medium by elastically dynamically deformable elastomers. As a result, there is greater freedom in the optimisation of the shape of the springs, and the strongly temperature-dependent displacement damping and displacement stiffening by the alternating spring deformation is eliminated.

Helicopter airframe variable tune vibration absorber

Abstract: This paper describes a unique helicopter airframe-mounted vibration absorber. It is a tuneable mass-spring absorber with a natural frequency that is automatically controlled. The concept embodies two opposed bifilar pendular mounted masses, acting under controllable spring forces. Internal compression springs were initially position set by an open loop hydraulic servo electronically operated by rotor rpm. Other aircraft requirements and applications include consideration of a self-adaptive configuration using a limited authority closed outer loop control design. The basic absorber has been proven to be highly reliable. It is weight effec- tive for wide range NR applications.

Optimization of space structures

Abstract: Computational methods for the design of structures for specified transient response, truss beam units with specified attached vibration absorbers, and laminates for structural components of large space structures are examined. Equations for the measurement of structural stiffness that are maximized for a specific total mass and that will reduce the structural weight are presented. A model for a cantilevered space truss beam of a specific mass and with a specified tip vibration absorber is explained. Design criteria of the laminates include minimizing the weight as well as frequency, buckling, and global stiffness constraints. Other variables include orientation of the lamina and the thickness of each layer.

Damping of vibrations in an impact mechanism, using a spring shock absorber

Abstract: In planning destructive impact devices, there is definite interest in finding the parameters of a vibration which is transferred to the manipulator during the operation of the impact mechanism. An analogous problem has already been considered [ I] in application to pneumatic-impact ore mechanisms (POM's). However, these studies were conducted without taking the mechanical characteristics into consideration for the system which provides the force of compression. The setup given for this problem corresponds to the presence of an ideal vibration absorber between the POM and the control device. In the present work, a method is proposed for determining the parameters of the force action of the impact mechanism on the manipulator in a general boundary regime [2], with a spring vibration absorber between them. In Fig. I, a sketch is presented which corresponds to the problem posed. The following assumptions are made: the instrument is choked; the resultants of the forces from the air pressures in the operating spaces of the cylinder are the same in size for the stem and striker mechanism and opposite in sign; the resultant of the pressure forces does not depend on the stem vibrations; displacements of the manipulator are negligibly small compared to the swing of the stem vibrations; interaction of the stem and manipulator is accomplished only through the spring.

Head vibrationproof structure of floppy disc device

Abstract: PURPOSE:To attain stably read and write of information to a medium by fitting a dynamic vibration absorber having a high damping effect to a head arm supporting a head of a moving side. CONSTITUTION:The dynamic vibration absorber (viscous damper) 11 having a high damping effect is fitted to a position of a seal plate 9 opposite to a head 2. The dynamic vibration absorber 11 is constituted by putting silicon oil 13 having a viscosity of 500-1,000cst into a case 12 made of a copper plate having a plate thickness of 0.2mm. and including a weight 14 having a weight of about 2g made of copper or lead or the like. Thus, the vibration generated between the medium and head attended with the deterioration of the surface of medium is eliminated through vibration absorption by means of this dynamic vibration absorber 11.

Rotationally vibrating type vibration absorber

Abstract: PURPOSE:To vary freely vibrational frequency and vibrating force applied to a hull during running of a rotationally vibrating type vibration absorber rotating a pair of rotors reversely to each other by providing a deviated weight moved by a hydraulic cylinder. CONSTITUTION:A rotationally vibrating type vibration absorber provided in a hull or the like has rotors 1 respectively secured fixedly to rotary shafts 2 rotating reversely to each other. And when pressurized oil is supplied to the piston rod 7 side in a cylinder hole 5, a deviated weight 4 is attached closely to a rotary support 3 so that the center of gravity of the rotor 1 is on the rotary shaft 2. On the other hand, when pressurized oil from an oil path A1 is supplied to an end of a piston 6 in the cylinder hole 5 through a pilot check valve 9, oil paths A2 and C, the deviated weight 4 is extended. When pressurized oil in oil paths A1, B1 is exhausted, said weight is locked by the valve 9. Thus, the position of the center of gravity of the rotor 1 can be set at will, and vertical vibration is caused by the reverse rotation of both rotors to each other to vary freely the vibration absorbing force to the hull during running.