Abstract:
A vibration isolator includes mounting members engaged with an isolator member. The isolator member contains a primary loop and a secondary loop, wherein the primary loop is the point of attachment to the mounting members. The secondary loop provides added symmetry between the compression rate and at least one of the roll spring rate and the shear spring rate of the isolator member. Features of the vibration isolator, such as the number of secondary loops, may be varied to achieve an isolator member with particular characteristics required for individual applications.

Description:
The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of contract No. FCS003548-4JM21 awarded by the U.S. Department of Defense. 
    
    
     BACKGROUND 
     Vibration isolator devices are commonly utilized to absorb vibrations and reduce movement between two structures. A typical vibration isolator contains a vibration attenuation element or an isolator member situated between the two structures. 
     Various configurations of vibration isolators are used in rugged applications where attenuation of vibration inputs is required to meet performance requirements in severe dynamic environments. Cable or wire-rope isolators are generally well-suited for such environments; however, space constraints, installation limitations, as well as cost constraints may diminish the effectiveness of such isolators. 
     SUMMARY OF THE INVENTION 
     The present invention is a vibration isolator using a cable or wire rope isolator. The isolator is wound to have a primary structure, typically in the form of a primary loop, and a secondary structure, typically in the form of a secondary loop. The primary loop has a radius greater than the radius of the secondary loop. This adds symmetry between the compression spring rate, and at least one of the roll spring rate and the shear spring rate of the vibration isolator. In a preferred embodiment, the vibration isolator has two mounting members separated by an isolator member. The mounting members contain a number of holes, through which the isolator member is wound forming a winding path. 
     A number of characteristics of the vibration isolator may be varied to achieve a particular isolator member with specific spring rates. The number of holes in the mounting members may be customized to include a number of primary loops. Additionally, the number of secondary loops within the primary loops, or even each primary loop, may be customized to provide the required symmetry. The isolator member may be a continuous spring member or may be a number of separate segments positioned between the mounting members. Of the segments, only certain segments may contain a secondary loop. 
     The vibration isolator may be manufactured by providing the mounting members with a mechanism for engaging the isolator member. The isolator member has a specific winding path positioned between the two mounting members. The winding path can be wound such that it passes through the mounting members a particular number of times. Additionally, the isolator member can be manufactured to include a differing number of primary loops and secondary loops to achieve the desired effect. 
     The invention will be described in further detail below in conjunction with the attached figures, wherein like reference numerals indicate like components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a standard vibration isolator; 
         FIG. 2  is a perspective view of a vibration isolator with a secondary structure; 
         FIG. 3  is a side view of a vibration isolator with a secondary structure; 
         FIG. 4  is a top view of a vibration isolator with a secondary structure; 
         FIG. 5  is a perspective view of an alternate embodiment of a vibration isolator with a secondary structure; 
         FIG. 6  is a side view of the embodiment depicted in  FIG. 5 . 
         FIG. 7  is a top view of another alternate embodiment of a vibration isolator. 
         FIG. 8  is a top view of yet another alternate embodiment of a vibration isolator. 
     
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawings,  FIG. 1  shows a standard prior art vibration isolator  100  includes a first mounting member  102 , a second mounting member  104  and an isolator member  106 . The mounting members  102 ,  104  each have a first side  112 ,  114  and a second side  116 ,  118  respectively. The isolator member  106  further includes a plurality of segments  108 ,  110  positioned between the mounting members  102 ,  104 . The vibration isolator  100  has a specific compression spring rate, a specific roll spring rate, and a specific shear spring rate. The spring rates are dependent on variables such as the composition of the isolator member  106 , the diameter and length of the isolator member  106 . In addition, the angle of the segments  108 ,  110  relative to the mounting members  102 ,  104  may have an effect on the spring rates of the standard vibration isolator  100 . 
     Now referring to  FIGS. 2 ,  3  and  4 , a vibration isolator  200  according to the present invention is detailed. The vibration isolator  200  includes a first mounting member  202 , a second mounting member  204  and an isolator member  206 , wherein the first mounting member  202  is directly opposite the second mounting member  204 . The isolator member  206  is engageable with the first mounting member  202  and the second mounting member  204 . 
     The isolator member  206  further includes a plurality of segments  208  positioned between the mounting members  202 ,  204 . The plurality of segments  208  including at least one segment  208  having a primary structure in the form of primary loop  210  and a secondary structure in the form of secondary loop  212  which are positioned along a winding path. The primary loop  210  is generally envisioned to wrap approximately three hundred and sixty degrees, although in certain embodiments, only one half of a primary loop may be utilized, spanning only from a first mounting member to a second mounting member. In such an embodiment in which the mounting members directly oppose one another, the primary loop would wrap approximately one hundred eighty degrees. Again referring to  FIGS. 2 ,  3  and  4 , the radius of the primary loop  210  is greater than the radius of the secondary loop  212 . The presence of the secondary loop  212  provides more even symmetry between the compression spring rate and at least one of the roll spring rate and the shear spring rate of the isolator member  206  than does the standard vibration isolator  100  depicted in  FIG. 1 . 
     The spring rates may be affected by several factors including the total number of primary loops  210 , the total number of secondary loops  212 , and the placement of both the primary loops  210  and secondary loops  212  relative to the mounting members  202 ,  204 . The vibration isolator  200  has a first side  220  and a second side  222 . The isolator member  206  contains four primary loops  210  and eight secondary loops  212  wherein each primary loop  210  contains two secondary loops  212 . Each primary loop  210  has one secondary loop  216  on the first side  220  and the second side  222 . A standard prior art isolator with four primary loops was found to have a maximum spring rate (in compression) 6.1 times the minimum spring rate (in shear), yielding a maximum resonant frequency 2.5 times the minimum. In comparison, the vibration isolator  200  containing eight secondary loops  212  in addition to four primary loops  210  was found to have a maximum spring rate (in compression) 2.6 times the minimum spring rate (in roll), yielding an improved maximum resonant frequency 1.6 times the minimum. 
     The isolator member  206  detailed in  FIGS. 2-4 , may be one continuous piece of material that enters and exits the first mounting member  202  and the second mounting member  204  at various points  230 . The points  230  include through holes  232  which span the width of the mounting members  202 ,  204 . Alternatively, the primary loops  210  may span only between respective sides of the mounting members  202 ,  204 ; hence the primary loops  210  depicted in  FIGS. 2-4  would be formed by two separate portions. The inclusion of one secondary loop  212  still allows added symmetry to such an embodiment. 
     Other slight modifications to the embodiment shown in  FIGS. 2-4  are possible and still able to produce more even symmetry between the spring rates. The number of primary loops and secondary loops may be varied and the number of primary loops may be equal to or different from the number of secondary loops. In addition, some primary loops or sides may be void of secondary loops. The isolator member may be composed of a spring member or a plurality of spring members. Furthermore, the spring members may be made of cable, wire-rope, wire braid or another material. Overall, the winding patterns and material of the isolator member may take any form that is advantageous for a particular application. 
     Similarly to the potential modifications of the isolator member, modifications to the mounting members  202 ,  204  depicted in  FIGS. 2-4  allow the vibration isolator to be further customized. Preferably the mounting members  202 ,  204  are made of bar stock having a length and a number of holes. The bar stock can be split into separate portions that can be connected together, such as with threaded fasteners, to clamp around the isolator member. The length and number of holes may be varied as well as the orientation of the mounting members relative to one another. Additionally, the isolator member may be wound through each hole or particular holes may be skipped. Furthermore, each mounting member may include two portions that act as clamping members securing the isolator member. The mounting members can also be made of other materials and can have different constructions, including being molded around the isolator member. 
     The embodiment depicted in  FIGS. 5-6  demonstrates some of the available modifications. A vibration isolator  300  according to the present invention includes a first mounting member  302 , a second mounting member  304  and an isolator member  306 . The isolator member  306  is engageable with the first mounting member  302  and the second mounting member  304 . 
     The isolator member  306  further includes a plurality of segments  308  positioned between the mounting members  302 ,  304 . The plurality of segments  308  containing at least one of the segments  308  having a primary structure in the form of a loop  310  and a secondary structure in the form of a loop  312  which are positioned along a winding path. The radius of the primary loop  310  is greater than the radius of the secondary loop  312 . 
     The vibration isolator  300  has a first side  320  and a second side  322 . The first side  320  has several secondary loops  312 , whereas the second side  322  has a different number of secondary loops  312 . The isolator member  306  includes a first spring member  330 , a second spring member  332 , a third spring member  334  and a fourth spring member  336 . The first spring member  330  has one primary loop  310  with two secondary loops  312  on the first side  320  and one secondary loop  312  on the second side  322 . The second spring member  332  has one primary loop  310  with one secondary loop  312  on the first side  320  and one secondary loop  312  on the second side  322 . The third spring member  334  and the fourth spring member  336  each contain three secondary loops  312 . The mounting members  302 ,  304  contain holes  340  which are not used to engage the isolator member  306 . The differences between the vibration isolator  200  and the vibration isolator  300  demonstrate the ability to customize the device for a particular application. While one vibration isolator can be used to isolate a device from vibration, it is also anticipated that two or more vibration isolators can be used in conjunction with one another to isolate the device from vibration. The particular application will dictate the number of vibration isolators and the orientations of the vibration isolators. 
       FIGS. 7 and 8  show other possible embodiments.  FIG. 7  demonstrates a vibration isolator  400  including a first mounting member  402 , a second mounting member  404  and an isolator element  406 . The isolator  400  has a first side  410  and a second side  412 . Only the first side  410  contains a secondary loop  420 . In  FIG. 8 , a vibration isolator  500  includes a first mounting  502 , a second mounting  504  and a vibration isolator  506 . The isolator  500  has a first side  510  and a second side  512  wherein only the first side  510  has a partial primary loop  520  and a secondary loop  522 . The second side  512  is devoid of any primary loops  520  (or portion thereof) and secondary loops  522 . 
     The vibration isolators  200 ,  300  and similar embodiments may be made by providing first and second mounting members with an isolator member positioned between the mounting members. The isolator member is then wound through a particular combination of holes contained within the mounting members. The isolator member must contain at least one primary structure and at least one secondary structure, preferably in the form of a primary loop and secondary loop. 
     Having thus described the invention in connection with the several embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the several embodiments described herein with out departing from the spirit and scope of the invention. It is my intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included with in the scope of the following claims. Any elements of any embodiments disclosed herein can be used in combination with any elements of other embodiments disclosed herein in any manner to create different embodiments.