Abstract:
Shock mounts are described that provide improved shock and vibration isolation compared to existing shock mounts. The shock mounts utilize zero-overlap elastomeric mount technology designed to provide more effective shock and vibration isolation. The shock mounts described herein can be used to mount any objects in which it is desired to isolate the objects from shocks and vibrations including, but not limited to, equipment and large mass objects on military and commercial vessels.

Description:
FIELD 
     This disclosure relates to a shock and vibration isolation system for use in isolating equipment from shock and vibration. 
     BACKGROUND 
     The concept of shock and vibration isolation systems is known in the art. In order to protect equipment from shock and vibration forces, it is known to employ elastomeric shock isolators that attenuate shock and vibration to a support structure to protect the equipment carried by the support structure. The shock and vibration isolation requirements of large mass objects, for example objects on naval vessels, are a major challenge to meet. 
     SUMMARY 
     Shock mounts for mounting objects are described that provide improved shock and vibration isolation compared to existing shock mounts. The shock mounts utilize zero-overlap elastomeric mount technology designed to provide more effective shock and vibration isolation. The shock mounts described herein can be used to mount any objects in which it is desired to isolate the objects from shocks and vibrations including, but not limited to, equipment and large mass objects on military and commercial vessels. 
     As used in this application, a zero-overlap elastomeric mount is an elastomeric mount where the mount has no column of elastomeric material from the top to the bottom of the mount, i.e. there is no straight path of material from top to bottom. 
     In one embodiment, the shock mount includes first and second support members that are generally parallel to one another. The first support member includes a load bearing surface designed to engage a load to be supported by the shock mount and the second support member includes a mounting surface designed to engage a mounting structure for the shock mount. In addition, the first and second support members include a load bearing axis. A zero-overlap elastomeric mount is connected to the first and second support members and extends therefrom in a direction generally away from the load bearing axis. The elastomeric mount includes a first end connected to the first support member, a second end connected to the second support member, and a looped section between the first end and the second end. The elastomeric mount forms a non-buckling member that provides shock and vibration attenuation. In addition, the loop forms a secondary mount support when an object supported by the shock mount comes into contact with the loop, which will result in a step-wise increase in shock and vibration attenuation during large displacements of the supported object. 
     In another embodiment, the shock mount includes first and second support members that are generally parallel to one another. The first support member includes a load bearing surface designed to engage a load to be supported by the shock mount and the second support member includes a mounting surface designed to engage a mounting structure for the shock mount. In addition, the first and second support members include a load bearing axis. A zero-overlap elastomeric mount includes a mounting end connected to the side surfaces of the first and second support members and the elastomeric mount extends from the support members in a direction generally away from the load bearing axis where the load bearing axis does not extend through the zero-overlap elastomeric mount. The elastomeric mount is configured to expand in dimension when subjected to a shock event via the first and second support members, wherein the expansion occurs at a location offset from the load bearing axis of the first and second support members. 
     In the case of the mount including a looped section, the energy of a shock event is transferred through a larger distance of elastomeric materials, resulting in greater application of the bulk modulus. In another embodiment, the mount is designed to accomplish shock attenuation through buckling of the geometric shape, for example a hollow truncated cone, resulting is bowing of the walls both inward and outward during a shock event. This buckling will also bring into play the bulk modulus and shear modulus of the material. 
    
    
     
       DRAWINGS 
         FIG. 1  is a perspective view of a shock mount according to a first embodiment. 
         FIG. 2  is a side view of the shock mount of  FIG. 1 . 
         FIG. 3  is a top plan view of the shock mount of  FIG. 1 . 
         FIG. 4  is a perspective view of a shock mount according to a second embodiment. 
         FIG. 5  is a side view of the shock mount of  FIG. 4 . 
         FIG. 6  is an end view of the shock mount of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-3  illustrate a shock mount  10  that supports a load  12  to isolate the load from shock and vibration. The load  12  can be any object requiring isolation from shock and vibration. In one exemplary embodiment, the load  12  is electrical equipment, such as an electrical cabinet that houses electronics, on a military or commercial vessel at sea. In the case of an electrical cabinet, four shock mounts are typically used to support the cabinet. As used herein, the term “shock mount” is a mount that is intended to isolate the load from shock as well as vibration. 
     The mount  10  includes first and second generally parallel support members  14 ,  16 . In the illustrated embodiment the support members  14 ,  16  are generally identical in construction, although they could differ depending upon the mounting requirements. The first support member  14  includes a planar load bearing surface  18  designed to engage the load  12  to be supported by the shock mount. Typically, the surface  18  is upward facing, with the load  12  being vertically above the mount so that the first and second support members  14 ,  16  have a vertical load bearing axis A-A that extends in the Z-direction. However, the surface  18  can have other orientations. The support member  14  also includes a bottom surface  20 , a first side surface  22  and a second side surface  24 . 
     The second support member  16  includes a bottom mounting surface  26  designed to engage a mounting structure  28  for the shock mount, an upward facing surface  30  that faces the bottom surface  20 , a first side surface  32  that faces in the same direction as the side surface  22 , and a second side surface  34  that faces in the same direction as the side surface  24 . 
     The support members  14 ,  16  can be formed of any material that one finds suitable for use in the mount  10 . For example, the support members  14 ,  16  can be made from a metal including, but not limited to, aluminum. The support members  14 ,  16  are provided with a number of mounting holes  17  to receive fasteners used to secure the support members to the load  12  and the mounting structure  28 . 
     At least one zero-overlap elastomeric mount  40  is connected to the first and second support members  14 ,  16 . In the illustrated embodiment, there are a plurality of the mounts  40 , and more specifically three mounts  40 . The mounts  40  are generally identical to each other, so only one mount will be described in detail. In addition, although three mounts  40  are illustrated, a larger or smaller number of mounts can be used depending upon the shock and vibration requirements of the mount  10 . 
     As used in this disclosure and claims, a zero-overlap elastomeric mount is an elastomeric mount where the mount has no column of elastomeric material from the top to the bottom of the mount, i.e. there is no straight path of material from top to bottom. Any type of elastomeric material used in shock mounts can be used as long as the elastomeric material is deemed to satisfy the isolation requirements of the shock mount. For example, the elastomeric mounts  40  can consist essentially of silicon rubber. 
     Each elastomeric mount  40  comprises an elongated strip of elastomeric material, with a first end  42  connected to the side surface  22  of the first support member  14 , a second end  44  connected to the side surface  32  of the second support member  16 , and a looped section  46  between the first end  42  and the second end  44 . The mounts  40  extend from the side surfaces  22 ,  32  in a direction generally away from the load bearing axis A-A. By connecting the ends  42 ,  44  of each mount  40  to the side surfaces  22 ,  32 , rather than to, for example, the surfaces  20 ,  30 , the extent of vertical travel of the support members  14 ,  16  is maximized to accommodate larger vertical displacements of the load  12  without direct engagement between the support members  14 ,  16 . 
     With reference to  FIGS. 1 and 2 , the looped section  46  is generally circular and forms generally half of a figure eight or half of an infinity symbol. The mount  40  is formed by the strip of elastomeric material having a first section  48  that includes the first end  42  that extends from the side surface  22  and curves downward to a second section  50  that is curved upwardly and forms generally a half-circle. The second section  50  is integral with a third section  52  that is curved downwardly opposite the second section  50  and forms generally a half-circle. A fourth section  54  that includes the second end  44  extends from the side surface  32  and curves upwardly to the third section  52 . 
     As seen in  FIG. 3 , the elastomeric mounts  40  are arranged side-by-side and are not directly connected to one another, with the looped sections  46  sharing a common axis Y-Y. The first and second support members  14 ,  16  each have a longitudinal axis that extends in the Y-direction, and for each mount  40 , the first and second ends  42 ,  44  are displaced from each other along the longitudinal axes. 
     As best seen in  FIG. 2 , the bottommost point  60  of the second section  50  and the topmost point  62  of the third section  52  do not project beyond the plane of the bottom mounting surface  26  or above the plane of the load bearing surface  18 . As a result, there is a clearance “d” between the bottom of the load  12  and the topmost point  62  of the looped section, the purpose of which will be described below. 
     In the case of a conventional C-shaped shock mount, the material is compressed which stretches damping material on the back of the mount which tends to cause delaminate. However, during use of the shock mount  10 , due to the shape of the mounts  40 , forces along the load bearing axis A-A will tend to enlarge or expand the openings formed by the loop sections  46  which eliminates stretching. This results in the energy being transferred through a larger distance of elastomeric materials, resulting in greater application of the bulk modulus. Further, the rather long length of the strips forming the mounts  40  increases the area of material available to accommodate stress, which allows for lower strains in the mounts  40  thereby reducing the potential for surface fractures and delamination. The expansion of the looped sections  46  occurs about the axis Y-Y spaced from the load bearing axis A-A of the first and second support members. 
     Further, during a large shock event, the bottom of the load  12  will engage the top of the loop sections  46  if the load displaces downwardly by a distance greater than “d”. Thus, the loop sections  46  form a secondary mount support when load  12  comes into contact with the loop sections  46 , which will result in a step-wise increase in shock and vibration attenuation during large displacements of the load. 
       FIGS. 4-6  illustrate an embodiment of a shock mount  100  that supports a load  102  to isolate the load from shock and vibration. The load  102  can be any object requiring isolation from shock and vibration. In one exemplary embodiment, the load  102  is electrical equipment, such as an electrical cabinet that houses electronics, on a military or commercial vessel at sea. In the case of an electrical cabinet, four shock mounts are typically used to support the cabinet. 
     The mount  100  includes first and second generally parallel support members  104 ,  106 . In the illustrated embodiment the support members  104 ,  106  are generally identical in construction, although they could differ depending upon the mounting requirements. The first support member  104  includes a planar load bearing surface  108  designed to engage the load  102  to be supported by the shock mount. Typically, the surface  108  is upward facing, with the load  102  being vertically above the mount so that the first and second support members  104 ,  106  have a vertical load bearing axis A-A that extends in the Z-direction. However, the surface  108  can have other orientations. The support member  104  also includes a bottom surface  120 , a first side surface  122  and a second side surface  124 . 
     The second support member  106  includes a bottom mounting surface  126  designed to engage a mounting structure  128  for the shock mount, an upward facing surface  130  that faces the bottom surface  120 , a first side surface  132  that faces in the same direction as the side surface  122 , and a second side surface  134  that faces in the same direction as the side surface  124 . 
     The support members  104 ,  106  can be formed of any material that one finds suitable for use in the mount  100 . For example, the support members  104 ,  106  can be made from a metal including, but not limited to, aluminum. The support members  104 ,  106  are provided with a number of mounting holes  136  to receive fasteners used to secure the support members to the load  102  and the mounting structure  128 . 
     A zero-overlap elastomeric mount  140  is connected to the first and second support members  104 ,  106 . Any type of elastomeric material used in shock mounts can be used as long as the elastomeric material is deemed to satisfy the isolation requirements of the shock mount. For example, the elastomeric mount  140  can consist essentially of silicon rubber. 
     In the illustrated embodiment, the mount  140  is shaped generally as a hollow, hexagonal, truncated cone having a mounting end  142  connected to the first and second support members  104 ,  106 . The mount  140  has a first side panel  144  with an edge thereof connected to the side surface  122  of the first support member  104 , a second side panel  146 , a third side panel  148 , a fourth side panel  150  with an edge thereof connected to the side surface  132  of the second support member  106 , a fifth side panel  152 , and a sixth side panel  154 . The edges of the side panels  146 ,  148 ,  152 ,  154  at the mounting end  142  are not directly connected to the first and second support members. 
     As shown in  FIG. 5 , the side panels  144 - 154  taper toward one another as the elastomeric mount  140  extends from the support members  104 ,  106  in a direction generally away from the load bearing axis A-A to a truncated end  156 . The truncated end  156  includes a through-passage  158  having an axis x-x perpendicular to the load bearing axis A-A. In addition, as evident from  FIGS. 4 and 6 , the mounting end  142  of the elastomeric mount  140  has a width dimension d 1  that is greater than a height dimension d 2  thereof. 
     The disclosed shock mount  100  is able to fit into current spaces occupied by many current shock mounts. Further, the design of the elastomeric mount  140  provides controlled buckling that results in effective shock and vibration isolation. During a shock event, the mount  140  is designed to buckle, resulting is bowing of the walls both inward (i.e. panels  144 ,  146 ,  154  and the panels  148 ,  150 ,  152  bow toward each other when viewed in the direction of  FIG. 6 ) and outward (i.e. the panels  146 ,  148  and  152 ,  154  tend to bow outward when viewed in the direction of  FIG. 6 ). This buckling of the mount  140  will also bring into play the bulk modulus and shear modulus of the material forming the mount  140 . Thus, during buckling the mount  140  expands in the Y-direction along the width dimension d 1 , with the expansion occurring along the Y-direction at a location offset from the load bearing axis A-A of the first and second support members. 
     The embodiments disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.