Spring devices – Resilient shock or vibration absorber – Including energy absorbing means or feature
Reexamination Certificate
2001-10-04
2004-06-08
Graham, Matthew C. (Department: 3683)
Spring devices
Resilient shock or vibration absorber
Including energy absorbing means or feature
C267S136000, C248S638000
Reexamination Certificate
active
06746005
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to methods, apparatuses and systems for isolating vibrations emanating from sources such as machinery, more particularly to those which implement at least one resilient element and which provide support for such sources.
It is environmentally desirable in many contexts to reduce transmission of vibrations to neighboring structure. For example, the U.S. Navy has an interest in attenuating the transmission, via connecting members to supporting structure, of unwanted vibrations from heavy machinery such as ship engines. Devices for reducing such transmission are generally known as vibration “isolators” because they serve to “isolate” the machine's vibration from contiguous structure. A vibration isolator is used to join one object to another and to restrict, to some degree, the transmission of vibration. See, e.g, J. E. Ruzicka, “Fundamental Concepts of Vibration Control,”
Sound and Vibration
, July 1971, pp 16-23, incorporated herein by reference. See also, Eugene (Eygeny) I. Rivin, “Principles and Criteria of Vibration Isolation of Machinery,”
ASME Journal of Mechanical Design
, Transactions of the ASME, Vol. 101, October 1979, pp 682-692, incorporated herein by reference. Both passive and active vibration isolation systems have been known in the art.
Passive vibration isolators have conventionally involved a passive damping arrangement which provides a resilient element (“spring”) along with a damping mechanism (“energy releaser”), and which serves as a support (“mount”), for vibrating machinery or other structure. Passive vibration isolation devices, alternatively referred to as “mounts” or “springs” or “spring mounts” in nomenclature, operate on the principle of low dynamic load transmissibility by a material having a resilient property. Passive mounts are designated “passive” because their function is based upon their inherent property rather than on their ability to, in an “active” manner, react to an in-situ condition.
Passive mounts have been known to use any of various materials for, the resilient element, such as rubber, plastic, metal and air. Elastomeric mounts rely primarily upon the resilience and the damping properties of rubber-like material for isolating vibrations. Mechanical spring mounts implement a helical or other metal spring configuration. Pneumatic, mounts utilize gas and an elastic material (such as reinforced rubber) as resilient elements in a bellows-like pneumatic spring assembly. A pneumatic mount or spring typically comprises a flexible member, which allows for motion, and a sealed pressure container or vessel having one or more compartments, which provides for filling and releasing a gas. Pneumatic springs are conventionally referred to as “air springs” because the gas is usually air. In conventional usage and as used herein the terms “air spring,” “air mount” and “air spring mount” are used interchangeably, and in the context of these terms the word “air” means “gas” or “pneumatic,” wherein “gas” or “pneumatic” refers to any gaseous substance.
Active vibration isolation has more recently become known in the art. Basically, a sensor measures the structure's vibration, an actuator is coupled with the structure, and a feedback loop tends to reduce the unwanted motion. Typically, an output signal, proportional to a measurable motion (such as acceleration) of the structure, is produced by the sensor. Generally speaking, the actuator includes some type of reaction mass. A processor/controller processes the sensor-generated output signal so as to produce a control signal which drives the reaction mass, the actuator thereby producing a vibratory force, whereby the motion (e.g., acceleration) of the structure is reduced.
The three basic components of an active vibration isolation system are a motion sensor (e.g., a motion transducer), a processor/controller and a vibratory actuator. The sensor responds to vibratory motion by converting the vibratory motion into an electrical output signal that is functionally related to, e.g., proportional to, a parameter (e.g., displacement, velocity or acceleration) of the experienced motion. An accelerometer, for example, is a type of sensor wherein the output is a function of the acceleration input; the output is typically expressed in terms of voltage per unit of acceleration. The most common processor/controller is a “proportional-integral-derivative”-type (“PID”-type) controller, a kind of servomechanism, which proportionally scales, and integrates or differentiates, the sensor response. The actuator is essentially a device adapted to transmitting a vibratory force to a structure; such an actuator has been variously known and manifested as an inertia actuator, inertial actuator, proof mass actuator, shaker, vibration exciter and vibration generator; as used herein, the terms “actuator,” “inertia actuator” and “vibratory actuator” are interchangeable and refer to any of these devices. The actuator generates a force, applied to the structure, based on the electrical output signal from the processor/controller.
Incorporated herein by reference are the following two patents: Jen-Houne Hannsen Su U.S. Pat. No. 5,899,443, issued 04 May 1999, entitled “Passive-Active Vibration Isolation”; and, Jen-Houne Hannsen Su U.S. Pat. No. 5,887,858, issued 30 Mar. 1999, entitled “Passive-Active Mount.” Also incorporated herein by reference is Jen-Houne Hannsen Su, “Robust Passive-Active Mounts for Machinery and Equipment,”
Proceedings of DETC '
97, 1997 ASME Design Engineering Technical Conferences, Sep. 14-17, 1997, Sacramento, Calif. (nine pages).
In Su '443 and Su '858, Su discloses inventions which uniquely and efficaciously combine known passive vibration technology with known active vibration technology. According to either Su '443 or Su '858, one or more vibratory actuators are coupled with (e.g., attached to or mounted upon) the bottom attachment plate of a conventional mount. Su '443 and Su '858 further disclose placement of one or more motion sensors (for sensing, e.g., velocity or acceleration) at the bottom attachment plate so that the sensors and actuators are correlated in pairs, each sensor-actuator pair having one sensor and one actuator in a functionally and situationally propinquant relationship. The inventive mount disclosed in Su '443 and Su '858 is styled therein “passive-active” because, proceeding generally downward from the above-mount object to the below-mount foundation, the object's vibration is first reduced passively and then is further reduced actively.
Su '443 and Su '858 each teach the availing of active control so as to, in effect, increase the dynamic stiffness of the below-mount foundation. The impedance inherent in a realistic below-mount foundation falls short of the impedance inherent in an ideally rigid below-mount foundation. According to Su '443 and Su '858, the impedance differential between foundation reality and foundation ideality is largely compensated for by providing one or more inertia actuators on the bottom plate (e.g., retainer plate, mounting plate, backing plate, or end plate) of the mount, for example inside an air mount on its bottom plate.
Su '443 and Su '858 thus provide more effective, yet practical and affordable, vibration isolation methods, apparatuses and systems. Typically, the electronic components will be commercially available; the sensors, actuators and PID-type controllers appropriate for most inventive embodiments according to Su '443 and Su '858 will be “off-the-shelf” items which can be purchased at less than prohibitive costs. In accordance with Su '443 and Su '858, the sensors and actuators can be retrofitted in existing conventional mounts, or the inventive mount can be manufactured or assembled from scratch.
For many applications according to Su '443 and Su '858, the inventive mount will afford superior performance in isolating vibrations of an above-mount structure from a realistic bel
Gallant Robert Joseph
Su Jen-Houne Hannsen
Burch Melody M.
Graham Matthew C.
Kaiser Howard
The United States of America as represented by the Secretary of
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