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BACKGROUND OF THE INVENTION 
     This invention relates to an impact absorbing sign post and, in particular, to a sign post mounted on a bollard-type structure with impact absorbing and quick change-out capabilities. 
     It is well know that sign posts, such as parking lot sign posts in shopping centers, big box stand alone stores, theaters, sporting event stadiums, and airports, carrying numerous signs, such as handicap parking, directional, stop signs, and others, are often struck by vehicles and seriously damaged to such an extent they require replacement or extensive repair. Often the sign posts are struck with such force to be hit out of the vertical position or they are bent from the impact and the damaged post requires replacement of the post and/or resetting of the solid bollard-type structure in concrete. There is considerable cost incurred with both labor and materials to reset or replace the damaged post. 
     A flexible parking sign is disclosed in U.S. Pat. No. 2,164,680 issued Jul. 4, 1939 to H. H. Donovan. The Donovan discloses a flexible parking sign including a spring element attached to the above-ground mounted base so as to permit flexing of the sign post upon impact by a vehicle. 
     A resilient bollard with rotatable collar for alerting vehicles of their location is disclosed in U.S. Pat. No. 5,397,197 issued Mar. 14, 1995 to Dale W. Beavers. The Beavers bollard is made of an elongate member having a lower proximal end biasedly attachable in an upright position to a path surface, an upper distal end, and a longitudinal axis. A collar is attached to the elongate member about its distal end. The collar is rotatable about the longitudinal axis of the elongate member. When the bollard is mounted on or adjacent a vehicle path surface, the bollard is deflectable from its upright position about its proximal end, for example, when contacted by a vehicle. The collar rotates when in contact with the vehicle for following the contour of the vehicle without damaging the vehicle. Mounted atop the bollard may be a light. 
     Another self-uprighting post is disclosed in U.S. Pat. No. 4,806,046 issued Feb. 21, 1989 to Richard O. Clark. The Clark patent discloses a self-uprighting delineator post comprising a base that may be fixed to a stationary object. A load cell is interposed between the base and delineator post and incorporates upper and lower load cells which are in abutment pivotally disposed. The load cell elements are secured by a pair of cables disposed in side-by-side relation and maintained under tensile stress by open or a pair of compression springs which are subjected to predetermined spring preload. The side-by-side cables fit within aligned passages of the upper and lower load cells serve to insure return of the delineator post to its properly oriented upright position after being force toward the horizontal by an impact force. 
     Although the prior art discloses sign posts and bollards with the capability to return to vertical after a vehicle impact, the prior art fails to disclose a sign post with a bollard-type lower portion affixed to the ground which absorbs vehicle impacts while providing quick-change out capability of an interior spring mechanism without requiring removal of the bollard-type lower portion from the ground and without requiring the replacement of the whole sign post structure. 
     SUMMARY OF THE INVENTION 
     The present invention provides an impact absorbing sign post with quick change-out capability that includes an upper sign post for carrying at least one sign or the like. An intermediate hollow bollard post is positioned below the upper sign post in operative arrangement with the sign post. The upper sign post is removably attached to the intermediate hollow bollard post. A lower hollow bollard post has a first portion of predetermined axial length positioned below ground level and attached to the ground to be immovable, and a second portion of the lower hollow bollard of a predetermined axial length substantially less than the first portion is positioned above ground level. 
     A pivot base flexible joint member is provided that has a central opening of predetermined size. The pivot base flexible joint member is removably attached to the lower hollow bollard post proximate the second portion thereof. The pivot base flexible joint member includes a top plate sized to cover the top of the second portion of the lower hollow bollard post and is in contacting and supportive relationship with the intermediate hollow bollard post. A dome portion is centrally affixed to the upper surface of the top plate. The dome portion having a circular base having a diameter a predetermined amount less than the inside diameter of the bottom of the intermediate hollow bollard post. The dome portion may have a semi-toroidal shape. The dome portion in operative contacting arrangement with the intermediate hollow bollard post. The central opening of the pivot base flexible joint member passing through the dome portion and the top plate. A removable attachment means is included for attaching the pivot base flexible joint member to the top of the lower bollard post proximate the second portion thereof. 
     The sign post includes a quick change-out spring kit substantially housed within the lower hollow bollard post. The quick change-out spring kit includes at least one concentric coil spring housed within the lower hollow bollard post in the operative position. The at least one concentric coil spring at the top thereof contacting the bottom surface of the top plate of the pivot base flexible joint member and confined by the pivot base flexible joint member within the lower hollow bollard post. 
     An elongated tension means axially passes through the at least one coil spring and the central opening of the pivot base flexible joint member. The elongated tension means includes a tension adjustment means near the top portion thereof. The elongated tension means is removably attached near the top thereof in predetermined position to the intermediate hollow bollard post. 
     A disk-shaped bottom spring contact member having a diameter about equal to or greater than the outer diameter of the bottom coil of the largest of the at least one concentric coil springs is also included. The disk-shaped bottom spring contact member is provided with a second central opening sized to accommodate the passage of the bottom portion of the elongated tension means. A locking member is mounted on the bottom portion of the tension means in cooperative relationship with the disk-shaped bottom spring contact member for enabling the disk-shaped bottom spring member to compress the at least one coil spring against the bottom of the pivot base flexible joint member, 
     The pivot base flexible joint member of the present invention permits the sign post to usually absorb a vehicular impact by flexing the sign post at the pivot base flexible joint member, and in the event the quick change-out spring kit requires replacement, the removable attachment means may be removed and the tension means at the top may be released and the quick change-out spring kit may be removed and replaced with a new quick change-out spring kit. 
     Preferably, the tension means of the present invention comprises a cable or a chain. Also, desirably, in the case of the tension means being a cable, the tension means further includes an upper threaded member attached to the upper end of the cable and a lower threaded member attached to the lower end of the cable in the operative position. 
     The intermediate hollow bollard post desirably further includes an upper tension means support metallic disk member with a third central opening attached to the inner wall of the intermediate hollow bollard post in predetermined position. Preferably, the upper threaded member of the tension means passes through the third central opening of the upper tension means support metallic disk member and the tension adjustment-means preferably is provided with a first adjustment-release nut in operative engagement with the upper threaded member, whereby the tension of the cable may be adjusted. 
     The lower hollow bollard sign post of the present invention may have a square cross section. The top plate is square or rectangular shaped and sized to cover the top of the square lower hollow sign post. The top plate includes side flange mounts extending perpendicularly downwardly over opposite sides of the top of the square hollow lower bollard post in the operative position. Preferably, the side flange mounts have first apertures in alignment with second threaded apertures in the bottom hollow bollard post in the operative position. First bolt means pass through the first apertures of the side mounts and engage the threaded second apertures of the bottom hollow bollard post to maintain the quick change-out spring kit in position. 
     The at least one concentric spring may comprise an inner spring and an outer spring. Preferably, the upper sign post includes an upper sign carrying post attached to a lower sleeve sized to be insertable in the intermediate hollow bollard sign post and removably attached thereto. A sign is attached to the upper sign carrying post. The upper sign carrying post and the lower sleeve desirably consists essentially of an aluminum alloy. 
     The lower threaded member passes through the central opening of the disk-shaped bottom spring contact member to engage the locking member in the operative position. 
     Preferably, in a another embodiment, the tension means includes a chain which further includes a bottom threaded post having a top eyelet. The bottom threaded post passes through the disk-shaped bottom spring contact member with the top eyelet above the top of the disk-shaped bottom spring contact member in the operative position and the chain is in operative engagement with the top eyelet of the bottom threaded post. The tension means further includes a top threaded post having a bottom eyelet. The intermediate hollow bollard post further includes an upper tension means support metallic disk member with a third central opening attached to the inner wall of the intermediate hollow bollard post in predetermined position. The top threaded post upwardly passes through the third central opening of the upper tension means support metallic disk member with the bottom eyelet in operative position below the bottom of the upper chain stop metallic disk member. The chain being in operative engagement with the bottom eyelet of the top threaded post. In this configuration, the tension means includes a second adjustment-release nut in operative engagement with the top threaded post, whereby the tension of the chain may be adjusted. 
     Preferably in the first embodiment using a cable, the central opening has a minimum diameter larger than the diameter of the cable and the central opening at the top of the dome portion is substantially larger than the diameter of the central opening and gradually decreases in a tapered-fashion towards the bottom of the dome portion, whereby any fraying or pinching of the cable is prevented during impact on the sign post. In the second embodiment using a chain, desirably the central opening has a minimum diameter larger than the diameter of the maximum width of any link of the chain and the central opening at the top of the dome portion has a diameter substantially larger than the maximum width of any link of the chain and the diameter of the central opening gradually decreases in a tapered-curved-fashion towards the bottom of the dome portion, whereby any pinching of the chain is prevented during impact on the sign post. 
     A method for replacing the quick change-out spring kit of the present invention is also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference may be made to the accompanying drawings exemplary of the invention, in which: 
         FIG. 1  is an elevation view of the impact absorbing sign post with a cable tension means partially broken away; 
         FIG. 2  is the same as  FIG. 1  but depicting the impact absorbing sign post during impact with maximum flexure of the sign post; 
         FIG. 3  is an elevation view of a portion of the spring change-out kit with a cable; 
         FIG. 4  is a sectional view of the dome portion, 
         FIG. 5  is the same as  FIG. 1 , but with a chain instead of a cable; 
         FIG. 6  is the same as  FIG. 5 , but showing the impact absorbing sign post during impact with maximum flexure; and, 
         FIG. 7  is an elevation view of a portion of the spring change-out kit with a chain. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1  is shown an impact absorbing sign post  10  of the present invention with quick change-out capability. The impact absorbing sign post  10  includes an upper sign post  12  for carrying at least one sign  14 . An intermediate cylindrical hollow bollard post  18  is positioned below the upper sign post  12  in supportive arrangement therewith. The upper sign post  12  is attached by attachment members  16  which may be cooperating bolts and nuts to the intermediate cylindrical hollow bollard post  18 . A lower hollow bollard post  20  has a predetermined axial length such as 24 to 30 inches. It has a first or lower portion  22  having an axial length such as 21 to 30 inches and positioned as shown in  FIG. 1  below ground level  23  and is attached to the ground by concrete  24 , for example, to be immovable. A second or upper portion  26  of the lower hollow bollard post  20  may have an axial length such as 0 to 3 inches and is positioned above ground level  23 . The upper portion  26  could be of negligible height if threaded flanges not shown are attached to the interior of the lower hollow bollard post  20  (not shown) and the pivot base flexible joint member  28  hereinafter described is attached by through bolts (not shown passing through joint member  28 ) engaging the threaded flanges. 
     A pivot base flexible joint member  28  having a central opening  30  predetermined maximum width such as ¾ to 1 inch. The pivot base flexible joint member  28  is removably attached to the lower hollow bollard post  20  proximate the second portion  26  thereof. 
     The pivot base flexible joint member includes a top plate  32  sized to cover the top of the second portion  26  of the lower hollow bollard post  20 . The second or upper portion  26  of the lower hollow bollard  20  may have a square cross-section have the dimensions 5 inches by 5 inches, for example. The top plate  32  may have the dimensions of 5½ inches by 5½ inches and be ¼ inch thick. The top plate  32  is in contacting and supportive relationship with respect to the intermediate hollow bollard post  20 , as depicted in  FIGS. 1 and 2 . A dome portion  34  is centrally affixed to the upper surface  36  of the top plate  32 . The dome portion  34  has a circular base  36  having a diameter such as 3 inches which is less than the inside diameter of the bottom of the intermediate hollow bollard post which is 3¼ inches, for example. The dome portion  34  has a semi-toroidal shape, like the upper half of a doughnut, and is in operative contacting arrangement with the intermediate hollow bollard post  18 , as shown in  FIGS. 1 and 2  for example. The dome portion  34  may be attached to the top plate  32  by dome bolts  35   a ,  35   b , as shown in  FIG. 4 . The dome portion  34  may be made of a solid material such as steel. The central opening  30  of the pivot base flexible joint member  28  passes through the dome portion and the top plate as shown in  FIG. 1 . A removable attachment means  38  for attaching the pivot base flexible joint member  28  to the top of the lower bollard post  20  proximate the second portion  26  is included. 
     With reference to  FIGS. 1-3 , for example, a quick change-out spring kit  40  of the present invention substantially housed within the lower hollow bollard post  20 . The quick change-out spring kit  40  includes at least one concentric coil spring  42  housed within the lower hollow bollard post  20 . The coil spring  42  may be a compression spring. The coil spring  42  may comprise two concentric coil springs, i.e., inner spring and outer spring (not shown). In the operative position, the at least one concentric coil spring  42  at the top  44  thereof contacts the bottom surface  46  of the top plate  32  of pivot base flexible joint member  28  and is confined by the pivot base flexible joint member  28  within the lower hollow bollard post  20  in use. An elongated tension means  48  axially passes through the at least one coil spring  42  and the central opening  30  of the pivot base flexible joint member  28 . The elongated tension means  48  includes a tension adjustment means  50  proximate the top portion  52  thereof. The elongated tension means  48  is removably attached proximate the top portion  52  thereof in predetermined position, as shown in  FIG. 1 , to the intermediate hollow bollard post  18 . A disk-shaped bottom spring contact member  54  having a diameter such as 4 inches, which is about equal to or greater than the outer diameter of the bottom coil spring which is of the largest of the at least one concentric coil springs if more then one spring is used. The disk-shaped bottom spring contact member  54  having a second central opening  56  sized to accommodate the passage of the bottom portion  58  of the elongated tension means  48  therethrough. A locking member  60  is mounted on the bottom portion  58  of the tension means in cooperative relationship with the disk-shaped bottom spring contact member  54  for enabling the disk-shaped bottom spring member  54  to compress the at least one coil spring  42  against the bottom surface  46  of top plate  32  of the pivot base flexible joint member  28 . 
     In a first embodiment of the impact absorbing sign post  10  of the present invention, the elongated tension means  48  may comprise a cable  62 , for example. As can be seen in  FIGS. 1-3 , the cable  62  includes an upper threaded member  66   a  and a lower threaded member  66   b . The cable  62  can be a stranded stainless steel wire cable with a maximum diameter of ⅜ inches and can be 22 to 24 inches long, for example. The upper threaded member  66   a  and lower threaded member  66   b  is attached to the cable  62  at it ends  68   a ,  68   b  by welding, for example. The central tapered opening  30  should have a minimum diameter greater than the maximum width of the cable  62  to allow the cable to pass unimpeded through the central tapered opening  30 . The central opening  30  at the top  65  of the dome portion  34  is substantially larger than the diameter of the cable  62 . The diameter of the central opening gradually decreases in a tapered-curved-fashion towards the bottom  75  of the dome portion  34 , so that the dome portion  34  is semi-toroidal shaped, approximating one half of a doughnut shape, whereby any fraying or pinching of the cable is prevented during impact on the sign post. The curvature of the central opening  30  is upwardly tapering away from the center line  31  as shown in  FIG. 4 . 
     The intermediate hollow bollard post  18  also includes an upper tension means support metallic disk member  70  having a third central opening  72  passing through it. The upper tension means support metallic disk member  70  may be made of steel and is welded to the inner surface of the hollow bollard post  18  and positioned as shown in  FIG. 1  for example. 
     With regard to the first embodiment of the invention, with reference to  FIGS. 1-3 , the upper threaded member  66   a  of the tension means  48  passes through the third central opening  72  of the upper tension means support metallic disk member  70 . The tension adjustment means  50  for compressing the coil spring  42  to the desired compression includes a first adjustment-release nut  76  which operatively engages the upper threaded member  66   a . The first adjustment-release nut  76  is tightened to achieve the desired tension on the cable  62  to compress the coil spring  42 . A first locking nut  78  may be engaged on the upper threaded member  66   a  as shown in  FIG. 1  to prevent the first adjustment-release nut  76  from unintentionally loosening. The lower threaded member  66   b  passes through the central opening  30  to engage the locking member nut  60 , in the operative position. A washer  71  may also be included for setting the locking member  60  as shown in  FIG. 1 . In addition a pair of lower locking nuts  73   a ,  73   b  are placed on the lower threaded member  66   b  to act as a stop for locking member  60 . 
     The lower hollow bollard sign post  20  may have a square cross section—not shown. The top plate  32  may be square or square-shaped, not shown, and sized to completely cover the top  20  of the lower hollow sign post. Of course, the lower hollow bollard sign post  20  could have a rectangular, circular, or other type cross-section and the top plate  32  would be designed in accordance with such structure to cover it. In the present embodiments the square-shaped top plate  32  includes side flange mounts  32  extending perpendicularly downwardly over opposite sides of the top  80  of the lower hollow bollard sign post  20  in the operative position. The side flange mounts  82   a ,  82   b  may be attached to the top  80  of the lower hollow sign post  20  by providing first apertures  84   a ,  84   b , respectively, and second threaded apertures  86   a ,  86   b , respectively, are provided in the bottom hollow bollard post  20 . First bolts  88   a ,  88   b  pass through the first apertures  82   a ,  82   b  and engage the second threaded apertures  86   a ,  86   b  to maintain the quick change-out spring kit  40  in position. 
     The upper sign post  12  may include an upper sign carrying post  90  including a sealing cap  92  attached thereto by welding, for example. The sealing cap  92  is sized to cover top  94  of the intermediate hollow bollard post  18  and have a diameter slightly larger than the diameter of the intermediate hollow bollard post  18  to prevent rain, snow and debris from entering the intermediate hollow bollard post  18 . The upper carrying sign post  90  may be attached proximate the top  94  of the intermediate hollow bollard post  18  by second bolts  96   a ,  96   b  and cooperating threaded holes in the upper sign carrying post  90 , not shown. The upper sign carrying post  90  and the sealing cap  92  can made of various materials, such as metal e.g., steel or aluminum alloy or poly plastic products. 
     In a second embodiment of the invention the tension means  48  includes the chain  64  comprised of links  98 . With regard to this embodiment depicted in  FIGS. 5-7 , like elements of this embodiment are identified by the same numerals as the first embodiment. The tension means  48  includes a bottom threaded post  100   a  having a top eyelet  102   a . The bottom threaded post  100   a  passes through the disk-shaped bottom spring contact member  56  with the top eyelet  102   a  positioned above the top  104  of the disk-shaped bottom spring contact member  56 . The chain  64  is in operative engagement with the top eyelet  102   a  as shown in  FIG. 5 . The tension means  48  also includes a top threaded post  100   b  having a bottom eyelet  102   b . The top threaded post  100   b  upwardly passes through the third central opening  72  with the bottom eyelet operatively positioned below the bottom of the upper support metallic disk member  70 . The tension adjustment means  50  includes a second adjustment-release nut  106  in operative engagement with the top threaded post  100   b . The tension of the chain  64  may be adjusted by tightening or loosening the second adjustment-release nut  106 . 
     With regard to the second embodiment, the central-curved-tapered opening  30  should have a minimum diameter greater than the maximum width of any link  98  of the chain  64  to allow the chain to pass unimpeded through the central tapered opening  30 . 
     The method of the invention for replacing the quick change-out spring kit  40  of the impact absorbing sign post  10 , having a structure as already described, includes the steps of: 
     a. removing the upper sign post  12  from the intermediate hollow bollard post  18 , 
     b. releasing the elongated tension means  48  from the attachment to the intermediate hollow bollard post  18 , 
     c. releasing the pivot base flexible joint member  28  from the top  80  of the lower hollow bollard post  20 , 
     d. removing the quick change-out spring kit  40  from the lower hollow bollard post  20 , 
     e. inserting the replacement quick change-out spring kit  40 , 
     f. re-attaching the pivot base flexible joint member  28  to the top  80  of the lower bollard post, 
     g. attaching the elongated tension means  48  to the intermediate hollow bollard post  18 , and 
     h. re-attaching the upper sign post  12  to the intermediate hollow bollard post  18 . 
     With regard to step a. in order to release the sign post  12  second bolts  96   a ,  96   b  must be removed. With regard to step b. in order to release elongated tension means  48  from the attachment to the intermediate hollow bollard post  18 , the first locking nut  78 , and the first or second adjustment-release nut  76  must be removed. In step c. the first bolts  88   a ,  88   b  are removed from the corresponding second threaded apertures  86   a ,  86   b . In step d. the quick change-out spring kit  40  is removed by lifting the top plate  32  together with the intermediate hollow bollard post  18  completely off the lower hollow bollard post  20 . The tension means  48  with the cable  62  or chain  64  slides through the central aperture  30 , the replacement quick change-out spring kit  40  may not be installed in a reverse manner. 
     It is apparent various modifications can be made to the within described embodiments without departing from the scope of the present invention.

Summary:
An impact absorbing sign post with quick change-out capability and method is provided. The impact absorbing sign post includes an upper sign post for carrying a sign, an intermediate cylindrical hollow bollard post carrying the upper sign post and a lower hollow bollard post mounted immovably in the ground supporting the intermediate cylindrical hollow bollard post. A easily removable pivot base flexible joint member with a dome portion is mounted between the intermediate cylindrical hollow bollard post and the lower hollow bollard post. A quick change-out spring kit is housed substantially with the lower hollow bollard post in includes a coil spring that is compressed by a tension means such as a cable or chain. When the sign post is impacted by a vehicle and the spring kit is damaged a replacement quick change-out spring kit may be easily installed after removal of the original spring kit without the necessity of removing the lower hollow bollard post from the ground.