Abstract:
A shock isolator having a housing securable to a support structure with the housing containing a bell shaped elastomer having a base secured to the housing and an axially offset apex surface secured to a connector to cantileverly support equipment to be isolated from shock with the cantileverly support of apex surface from the base insuring that any displacement of the connector produces a substantial shearing action in the elastomer to effectively damp the effect of a shock on the shock isolator.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to shock isolators and, more specifically, to a single shock isolator providing damping in three coordinate axis. 
     BACKGROUND OF THE INVENTION 
     The concept of shock isolator is old in the art. Typically, some type of a damping device is placed between two objects to attenuate the force and displacement between the two objects. These type of isolators are useful in many applications and are particularly useful to protect sensitive equipment on board ships or the like. Generally, it is preferred to have a shock isolator that isolates from shocks in all directions, that is a six degree of freedom shock isolator that responds to shock in the x, y, and z axis. 
     When elastomers placed in a compressive condition they are generally not effective in damping or attenuating a shock force However, if the elastomer is place in a shear condition the elastomer is generally more responsive to damping the shock forces. The difficulty in using a single solid or massive elastomer as a shock damping device is that it is difficult to have the single elastomer simultaneously function as both a support and a damping device in all three major axis. 
     The present invention utilizes a single elastomer to provides a low cost shock isolator that simultaneously supports sensitive equipment and attenuate shocks in all three major axis to protect the sensitive equipment supported by the shock isolator. That is, the elastomer is configured so as to provide six degrees of freedom by cantileverly supporting a connector within housing so that regardless of the direction of the displacement of the connector it always places the elastomer in a substantial shear condition where the elastomer is most effective in damping the shock forces to the supported equipment. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention comprises a shock isolator having a cylindrical housing securable to a support structure with the cylindrical housing containing a bell shaped elastomer having a base secured to the cylindrical housing and an axially offset apex surface cantileverly secured to a connector that supports equipment to be isolated form shock with the cantileverly support of the apex surface from the base insuring that any displacement of the connector produces a substantial shearing action in the elastomer to generate effective damping of any shocks or vibrations to the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side view of ship having shock isolators to support control equipment therein; 
     FIG. 2 shows a front view of a support structure holding equipment in a condition isolated from shock in three different axis; 
     FIG. 3 shows a cross sectional view of the shock isolator of the present invention; 
     FIG. 4 show a perspective view of the bell shaped etastomer in the shock isolator shown in FIG. 3; and 
     FIG. 5 illustrates the dynamic response of the bell shaped elastomer. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 Shows a typical use of the present invention in a ship  10 . Ship  10  is shown in side view and having a support structure  11  therein with shock isolators located in the support structure  11  to dampingly support sensitive control equipment located thereon. 
     FIG. 2 shows a front view of a support structure  11  which is supporting sensitive equipment  12  in a condition which isolates equipment  12  from shock n three different axis. A first six degree-of-freedom shock isolator  15  and a second six degree-of-freedom shock isolator  16  are located in a spaced position above equipment  12  and support equipment  12  in structure  11 . Shock isolator  15  and  16  each have one end fixedly secured to structure  11  and the opposite end secured to equipment  12  to suspend the equipment  12  in a spaced condition from structure  11 . The shock isolators  115  and  16  greatly attenuated any shocks to the structure  11  to thereby reduce the chances of the equipment  12  being damaged. 
     FIG. 3 shows a cross sectional view of shock isolator  15  of the present invention. Shock isolator  15  includes a member  17  for fixedly securing a cup-shaped, cylindrical shaped, rigid housing  18  to support structure  11 . Preferably housing  18  is made of metal or the like and maintains its rigid condition. Located within the cylindrical housing  18  is a bell shaped elastomer  19 . Bell shaped elastomer  19  has an annular base  20  that is preferably adhesively secured to an inner surface  18   a  of housing  18 . The width of the zone or band of adhesive securement of the elastomer to the housing  18  is identified as Z a . Bell shaped elastomer  19  also include an apex region  21  having an internal 360 degree apex support surface  22  which is preferably adhesively secured to a first end  23   a  of a rigid connector  23  to enable the elastomer to form a contilevered connection between housing  18  and connector  23 . Connector  23  is located internally to bell shape elastomer  19 . Connector  23  includes a second end  23   b  to support equipment therefrom. The width of the band or the zone of attachment of the apex support surface  22  to the end  23   a  of connector  23  is identified by Z b . A central axis x extends vertically upward and is identified by reference numeral  28 . the zone of attachment Z a  and the zone of attachment Z b  are axially offset from on another along axis  28  so as not to compressively surround connector  23   a  and thereby compressively limit the displacement of connector  23 . 
     FIG. 3 shows isolator  15  in the relaxed condition with the connector in a central position in elastomer  19 . In the embodiment shown, the connector  23  is sufficiently stiff to supporting equipment from connector end  23   b . It is noted that the zones of adhesion Z b  and Z a  are axially offset from one another so that displacement of connector  22  with respect to housing  18  places elastomer  19  in shear. That is, in the embodiment shown in FIG. 3 the elastomer housing  18  provides 360 degree contilevered support between the housing  18  and connector end  23   a . By providing a 360 degree cantilever support the elastomer can be responsive to shocks in any directions by elongation rather than compression of the elastomer. 
     FIG. 3 shows that housing  18  and the elastomer  23  from a closed chamber  35  that prevents external objects from inhibiting displacement of elastomer  19 . That is, normally housing  18  is suspended along a vertical axis  28  with the housing  18  preventing object from accidentally falling into the chamber  35  from the top and elastomer  19  preventing objects from accidentally entering chamber  35  from the bottom. As the bottom of elastomer  19  faces downward objects can not normally be retained therein. Consequently, when isolator  15  is placed in the vertical condition the isolator will remain operable and unaffected by any objects that might accidentally come into contact with isolator  15 . 
     In order to appreciate the operation of the invention reference should be made to FIG. 5 which shows shock isolator  15  with housing  18  angularly displaced with respect to vertical axis  28 . Note, the only connection between connector  23  and housing  18  is through elastomer  19 . Furthermore, the forces between connector  23  and housing  18  are transmitted through the two zones of attachment Z a  and A b . The result is that the elastomer  19  is placed in a substantial shear condition so as to be responsive to shocks to the system. By substantial shear condition it is meant that while there may be some compressive action occurring within elastomer  19  the compressive action is minimized so that the shear or tension response of the elastomer predominates. While the connector is shown being angularly displaced form the x-axis it is apparent that 260 degree contilever support provided by the bell shaped elastomer  19  places the elastomer in a substantial shear condition to effectively damp shocks from any direction. By having the two zones of attachment A a  and A b  axially offset from one another one assures that displacement of the connector  23  with respect to the housing  18  places the elastomer  23  in a shear condition or substantial shear condition that effectively dissipates or attenuates shocks between objects connected thereto in the three major axis. 
     While angular displacement of connector  22  places elastomer  19  in the shear condition any axially displacement of connector  22  along x-axis  28  also places elastomer  19  in a substantial shear or tension condition. Consequently, while connector  22  is free to move in any direction it is tensionally restrained from moving by the contilever support between connector  22  and housing  18 . However, since motion in any direction produces a substantial shear condition the bell shaped elastomer provides effective damping between two objects.