CA1235714A

CA1235714A - Fluidic vibration isolating

Info

Publication number: CA1235714A
Application number: CA000468200A
Authority: CA
Inventors: Dale W. Schubert
Original assignee: Barry Wright Corp
Current assignee: Hutchinson Aerospace and Industry Inc
Priority date: 1984-01-18
Filing date: 1984-11-20
Publication date: 1988-04-26
Also published as: IL73629A0; IT1179500B; IT8449218A1; CH670487A5; GB8429919D0; FR2558231B1; FR2558231A1; JPS60159429A; GB2153042A; NL8403577A; IT8449218A0; GB2153042B; DE3500398A1

Abstract

ABSTRACT
A fluidic vibration isolator has an inverted flower-pot-shaped casing clamped to a base member. The casing has an annular rim depending from the top to which the outside edge of an annular diaphragm is clamped by a clamping ring. The inside edge of the diaphragm is clamped to a load support member formed with a tapered recess by a force-fit and/or bonded sleeve. A supported member has a depending stem that rests in the bottom of the recess. The closed chamber inside the casing contains dichlorotetrafluoroethane in the liquid state at the bottom with heating resistors. The supported member has a depending shutter that allows electromagnetic energy to energize a photocell when the supported member descends to a predetermined level to cause the delivery of electrical energy to the heating resistors.

Description

lZ:~5714 FLUIDIC VIBRATION ISOLATING
The present invention relates in general to fluidic vibration isolating and more particularly con-cerns novel fluidic vibration isolating apparatus and techniques that are characterized by very low trans-missibility and high damping both axially and radially with a relatively inexpensive compact structure.
The present invention represents an improvement over the fluidic vihration isolation system described in U.S. Patent No. 4,057,212 granted November 8, 1977 for FLUIDIC VIBRATION ISOLATOR of Dale W. Schubert. That patent discloses a fluidic vibration isolation system having a chamber containing a fluid in both the liquid and vapor state. A heater selectively heats the liquid to increase the amount of fluid in the vapor state and thereby the pressure in the chamber. A height sensor actuates a switch for regulating the energy to the heater so as to maintain the height of a load supported on the chamber. As the vapor pressure in the chamber increases, the chamber expands to raise the load to a preselected height.
It is an important object of this invention to provide improved fluidic vibration isolating.
According to the invention, there is closed chamber means for enclosing a fluid in both vapor and liquid states. Preferably the closed chamber means in-cludes a casing of relatively rigid material, such as metal or a high temperature thermoplastic, that remains -lZ3S,~14

-2-essentially constant in volume in the presence of internal vapor pressure changes and is r~sistant to the internal biphasal fluid. The closed chamber means also includes load support means for receiving a load sup-porting member. There is flexible diaphragm meansintercoupling the load support means with the casing in fluid-tight relationship. This diaphragm means allows both angular and translatïonal deflection of the load support means from a normally vertical axis in all azimuth directions. The load support means may thus function as a pendulum having a translatable pivot point.
There is load support platform means for supporting a load, such as a work table, having a depending lOâd supporting member for being seated in the load support means. Preferably the load support platform means also includes depending shutter means for altering the flow of electromagnetic energy between a source of electro-- magnetic energy and photoelectric transducing means for selectively controlling the electrical energy delivered to heating means in the closed chamber means so as to maintain the load support platform means at a pre-determined height.
Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompany-ing drawing in which:
FIG. 1 is a diametrical sectional view of a preferred embodiment of the invention; and FIG. 2 is a graphical representation of isola-tion characteristics of the embodiment of FIG. 1.
With reference now to the drawing and moreparticularly FIG. 1 thereof, there is shown a diametrical sectional view of a preferred embodiment of the inven-tion. Because of cylindrical symmetry, this view ade~uately illustrates this embodiment of the invention.
The isolator 11 is bolted to base structure 12 by means, such as nut and bolt assemblies 13, typically six being .. .....

~Z357~4 sufficient. The top 14 of a load, such as a work table, rests on vibration isolated supported mem~er 15, a load support platform, to receive significant vibration isolation in both axial and radial directions.
An inverted flower-pot-shaped supporting member 16 comprises a casing having a baseplate 17 sealed fluid-tight with means including 0-ring 21A. A central load support member 21 is formed with a tapered recess 22 for accommodating stem 23, a load supporting member that is fastened to the center of the underside of supported member 15. A flexible diaphragm 24 intercouples load support member 21 and supporting member 16 in fluid-tight relationship while allowing both angular and trans-lational deflection of member 21 to complete the fluid-tight closed chamber.
A sleeve 25 force fit and bonded to member 21 secures the inside edge of diaphragm 24 to member 21.
The outside edge of diaphragm 24 is clamped between clamping ring 26 and a depending rim of supporting member 16 with 0-ring 28 to establish a fluid-tight seal therebetween. Bolts, such as 27, typically six, fasten ring 26 to supporting member 16 in tapped openings.
Supported member 15 carries a depending stud 23 with a rounded end that nests in the rounded bottom of tapered recess 22. The cross sectional area of stud 23 is slightly less than that of recess 22 at the bottom which is less than-that at the top. Stud 23 is free to move in the open region including bore 29 at the top so that it freely pivots about its bottom. Surface 30 functions às a stop in case of a severe jolt.
Supported member 15 may also carry a depending flag-shaped shutter element 31 secured by screw 32 for allowing photocell 33 to be selectively illuminated by an electromagnetic source (not visible in FIG. 1) when supporting member 15 drops below a predetermined level.
Photocell 33 then provides a switching signal over wires 34 that causes heating resistors 35 above base 17 to .

~Z357~4 -receive ele trical energy tha~ heats the liq~id component 36 of the fluid inside the closed chamber~ This heating increases the vapor pressure therein and causes the load support member 21 to move upward until shutter element 31 interrupts the flow of infrared radiant energy to photocell 33 to thereby cause resistors 35 to be de-energized in substantially the manner as described in U.S. Patent No. 4,057,212.
In a typical application of the invention, a table top may have four supports o~ the type shown in FIG. 1 supporting the table top in four corners. Prefer-ably, the shutter-controlled photoelectric assembly of one of the two rear supports controls the resistors in both rear supports in accordance with known techniques recognizing that three points determine the location of a plane surface. An "OR" circuit can contain two or four members such that the contact point is at the lowest of - the two points. The "OR" circuit thus allows either switch sensing an associated corner dropping below the normal level to effect heating in both isolators until the actuating switch indicates the normal level has been reached.
The invention has a number of features and advantages. It provides high isolation both axially and radially. Load support member 21 comprises a pendulum having a pivot point that flexible diaphragm 24 allows to translate in all azimuth directions. As a result this pendulum has a lower resonant frequency for a given length than a fixed point pendulum. Allowing the lower tip of member 21 to rest in the liquid component 36 of the enclosed fluid as shown helps provide additional radial damping. Axial movement of member 21 and dia-phragm 24 is believed to effect isothermal compression and rarefaction of the vapor component of the enclosed liquid to dissipate significant energy in effecting changes between ~apor and liquid state that provides high damping in the axial direction.
i . . . , ~ ~

~Z3S714 I

Referring to FIG. 2, there is shown a graphical representation of transmissibility as a f~nction of fre-quency of the embodiment of FIG. 1 for an excitation velocity o~ 0.3 in/sec. at resonance. Note that this compact structure is characterized by a resonance signif-icantly below 1. O Hz that is exceptionally broad and of very low resonant amplification because of the high damping characteristics discussed above.
Many specific materials may be used in prac~ic-ing the invention. The hard structures may be made ofmetal or a hard plastic, such as Noryl GFN3. The va-porizable fluid enclosed in the chamber may be, for exam-ple, dichlorotetrafluoroethane. The photoelectric switch may comprise an infrared LED phototransistor switch. The resistors may comprise conventional 10 watt resistors.
An actual embodiment of the invention includes supporting and supported elements less than 4" high and 8" in diameter.
It is evident that those skilled in the art may now make numerous uses and modifications of and depar-tures from the specific embodiments described herein without departing from the inventive concepts. Conse-quently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and sccpe of the appended claims.
What is claimed is:

Claims

-6-

1. Fluidic vibration isolation apparatus com-prising, closed chamber means including a casing for enclosing substantially fluid-tight compressible biphase fluid, said closed chamber means including load sup-port means for supporting a load supporting member in axial and radial vibration isolating relationship, diaphragm means for supporting said load sup-port means on said casing means while allowing said load support means to both rock angularly and translate relative to a predetermined vertical axis of said closed chamber means to exhibit both angular displacement and translation from said predetermined vertical axis passing through said closed chamber means to exhibit pendulum action about a point translatable in any azimuth direc-tion, and fluid means in said closed chamber means for developing pressure on said load support means to provide vertical vibration isolation.

2. Fluidic vibration isolation apparatus in accordance with claim 1 and further comprising, said load supporting member supported by said load support means at a point below said diaphragm means and having a normal vertical axis corresponding to said predetermined axis.

3. Fluidic vibration isolation apparatus in accordance with claim 1 wherein said load supporting member comprises a member formed with a tapered recess with its bottom cross sectional area that is smaller than its top cross sectional area.

4. Fluidic vibration isolation apparatus in accordance with claim 3 and further comprising, said load supporting member comprising a stud seated in said recess of cross sectional area slightly less than said bottom cross sectional area and formed with a rounded end that resides in a mating rounded bottom portion of said recess.

5. Fluidic vibration isolation apparatus in accordance with claim 1 wherein at least a tip portion of said load support means always resides within a liquid component of said fluid at the bottom of said closed chamber means.

6. Fluidic vibration isolation apparatus in accordance with claim 4 wherein said diaphragm means has concentric inside and outside edges and further com-prising, means for securing said inside edge to said load support means near the top thereof, and means for clamping said outside edge to said casing near the top thereof.

7. Fluidic vibration isolation apparatus in accordance with claim 6 wherein said means for clamping said inside edge comprises a sleeve secured to said load support means, and said means for clamping said outside edge comprises a damping ring secured to a rim depending from the top of said fixed support member.

8. Fluidic vibration isolation apparatus in accordance with claim 7 and further comprising, a supported member above said casing, said stud depending from said supported member, shutter means depending from said supported member for selectively regulating the flow of electro-magnetic energy, a source of electromagnetic energy and photoelectric transducing means oppositely aligned for selective interruption by said shutter means and supported in fixed relationship to said casing, and electrically heated elements inside said closed chamber means for heating said fluid in response to a predetermined relationship between said shutter means and said photoelectric transducing means.

9. A method of fluidic vibration isolation which method includes the steps of, enclosing a compressible biphase fluid sub-stantially fluid-tight in a closed chamber means including a casing and load supporting means for sup-porting a load supporting member in axial and radial vibration isolation relationship and diaphragm means for supporting said load support means on said casing, applying vibrational forces to said casing that may cause said load support means to both rock angularly and translate relative to a predetermined vertical axis of said closed chamber means to exhibit pendulum action about a point translatable in any azimuth direction, and developing pressure on said load support means with said compressible biphase fluid to provide vertical vibration isolation.

10. A method in accordance with claim 9 and further including the step of supporting said load supporting member at a point below said diaphragm means so that said load supporting member may rock freely about said point in a predetermined solid angle.

11. A method in accordance with claim 9 and further including the step of maintaining at least a tip portion of said load support means within a liquid component of said fluid.

12. A method in accordance with claim 9 and further including the steps of sensing when said load supporting member departs from a predetermined level, and altering the temperature of said fluid to change said pressure until said predetermined level is attained.