with reference to the drawings in detail , the preferred embodiment of the invention , as shown in fig5 , and 8 , is designed specifically for placement on billboards ( 3 ) since this embodiment is particularly adapted to facilitate the maintenance of billboards ( 3 ) and the replacement of the signs . however , as one of ordinary skill in the art would realize , the present invention is not limited to the preferred embodiment disclosed herein , nor to the specific field for which it is described . other possible applications of the present invention include , but are not limited to , preventing birds and other animals from perching on or crossing support structures , fences , utility lines , and tree branches . in addition , the present invention is particularly well - suited for use on those portions of offices and other buildings which lack easy access and where birds often land , such as ledges , over - hangs and roof tops . the present invention comprises a plurality of rotatable rings ( 1 ) threaded by a cable ( 4 ) supported above the top frame member ( 2 ) of the billboard ( 3 ). the rotatable rings ( 1 ) are preferably cylindrical in shape to permit free rotational movement upon contact and have a length that may be varied depending on the length of the structure on which they are placed . for a normal size billboard ( 3 ), the rotatable rings ( 1 ) would be approximately three inches long . they are placed on the cable ( 4 ) at a horizontal distance ( 6 ) from each other sufficiently close to prevent a bird from landing on the cable ( 4 ), but far enough from each other to permit uninhibited rotation . referring to fig2 the rotatable rings ( 1 ) have a cylindrical cavity ( 7 ) defined by cylindrical wall ( 8 ), with the cylindrical cavity ( 7 ) having a diameter ( 34 ) large enough relative to the cable ( 4 ) to facilitate rotation of the rotatable rings ( 1 ) upon contact . in order to make it even more difficult for a bird or small animal to balance upon the rotatable rings , the outer cylindrical wall ( 8 ) is preferably provided with an outer diameter of approximately one half inch . this choice for the diameter of the cylindrical wall ( 8 ) is for reference only since the diameter may be varied to suit a particular cable ( 4 ) or to enhance the rotation of the rotatable rings ( 1 ). the rotatable rings ( 1 ) may , in the alternative , be provided with any of multitude of shapes other than that of the cylindrical wall ( 8 ) which will also provide an unstable surface for preventing the perching of birds thereon . the cylindrical wall ( 8 ) of the rotatable rings ( 1 ) may further be provided with a lengthwise incision ( 9 ) running from one end to the other and penetrating through to the inner cylindrical cavity ( 7 ). this lengthwise incision ( 9 ) permits the rotatable rings ( 1 ) to be placed upon existing cables , utility lines or other cylindrical structures , as shown in fig7 by simply pulling the cylindrical wall ( 8 ) open and pressing the rotatable rings ( 1 ) onto the cylindrical structure . in order to permit the deformation of the rotatable rings ( 1 ) in this manner , it is preferable that the rotatable rings ( 1 ) be manufactured from a flexible , but weather resistant , material such as a suitable synthetic polymeric material , which may or may not have an ultraviolet light protective coating for inhibiting deterioration caused by the sun . however , the rotatable rings ( 1 ) are not limited to such polymeric materials , but may also be manufactured from malleable metals or other synthetic materials . in the event the rotatable rings do not have the lengthwise incision ( 9 ), they may be threaded onto one end of the cable ( 4 ) in a consecutive manner . with reference to fig1 to prevent birds from landing on the top frame member ( 2 ) of the billboard ( 3 ), or on any of the other structures noted above , the cable ( 4 ) is stretched along the entire length of the top frame member ( 2 ) and is supported at a vertical distance ( 10 ) above the top frame member ( 2 ) sufficient to preclude a bird from sitting underneath the cable ( 4 ). the cable ( 4 ) is manufactured with a plastic or vinyl coating ( 11 ) ( see fig2 ) which is treated to prevent ultra - violet light deterioration and which provides a smooth surface to reduce friction and prevent fraying of the cable ( 4 ) itself . although the size and construction of the cable ( 4 ) can take many forms , it is preferred that the cable ( 4 ) be three - sixteenths of an inch in diameter and be manufactured by means of seven large strands interwoven with nineteen smaller strands of stainless steel fiber . the preferred embodiment of the present invention , as shown in fig5 and 6 , includes a lower support arm ( 24 ) and an upper support arm ( 25 ) placed at each end of the top frame member ( 2 ). the lower support arms ( 24 ) are affixed to the top frame member ( 2 ), while the upper support arms ( 25 ) are pivotally connected to each of the lower support arms ( 24 ) by means of an axial rod ( 26 ) so that the rotatable tings ( 1 ) threaded by the cable ( 4 ) may be rotated to a side position ( see fig5 ) in order to facilitate maintenance of the billboard ( 3 ). the pivotal connection ( 27 ) between the lower support arms ( 24 ) and the upper support arms ( 25 ) at one end of the top frame member ( 2 ) further includes a gear ( 28 ) and a lever or pawl ( 29 ) working in a cooperative manner to provide for selective adjustment in the rotation of the upper support arms ( 25 ). in order to rotate the upper support arms ( 25 ) from below , a lever string ( 30 ) and an arm string ( 31 ) are used to manipulate the position of the upper support arms ( 25 ). an axial spring ( 32 ) encircling the axial rod ( 26 ) is affixed between the lower support arm ( 24 ) and the upper support arm ( 25 ) to provide tension against the lever ( 29 ) positioned on a lever support ( 33 ). to rotate the upper support arms ( 25 ) downward , the arm string ( 31 ) is pulled against the tension of the axial spring ( 32 ) while the lever ( 29 ) acts to lock the gear ( 28 ) in the desired rotated position . a workman may now place a hooked ladder over the top frame member ( 2 ) of the billboard ( 3 ) without the cable ( 4 ) interfering with the maintenance of the billboard ( 3 ). to cause the upper support arms ( 25 ) to return to their upright position , the lever string ( 30 ) is pulled to release the lever ( 29 ) from the gear ( 28 ). the axial spring ( 32 ) then retracts to its initial position . an alternate embodiment of the present invention , as shown in fig1 is particularly suited for placement on structures other than billboards ( 3 ), such as the ledges , over - hangs and rooftops of offices and other buildings where birds and small animals tend to congregate . this embodiment of the invention makes use of two l - shape support arms ( 5 ) placed at opposite ends of the top frame member ( 2 ) of the billboard ( 3 ). it is noted that the choice of the l - shape support arms ( 5 ) is merely one of convenience for simplicity in description and the specific design is in no way limited to such l - shape support arms ( 5 ). the support arms ( 5 ) may be manufactured out of any material capable of withstanding the tension of the cable ( 4 ) produced when birds attempt to land on the rotatable rings ( 1 ) including , but not limited to aluminum , steel , or hardened plastic . the support arms ( 5 ) are provided with a horizontal member opening ( 12 ) to facilitate attachment of the support arms ( 5 ) to the top frame member ( 2 ). a vertical member opening ( 13 ) passing from an inside surface ( 14 ) to an outside surface ( 15 ) of the support arms ( 5 ) is further provided for attachment of the cable ( 4 ) between the support arms ( 5 ). the top frame member ( 2 ) may be attached by high strength stainless steel bolts having teflon coated lock nuts , or other similar means , extending through the horizontal member opening ( 12 ). as seen most clearly in fig3 the cable ( 4 ) is attached to the support arms ( 5 ) by swedge screws ( 16 ) affixed to each end of the cable ( 4 ), and a stop member ( 17 ) placed on the outside of a helical tension spring ( 18 ), whereby the helical tension spring ( 18 ) is compressed between the stop member ( 17 ) and the outside surface ( 15 ) of one of the support arms ( 5 ). at one end of the top frame member ( 2 ), the cable ( 4 ) is attached to the support arm ( 5 ) by placing the swedge screw ( 16 ) through the vertical member opening ( 13 ) of the support arm ( 5 ) and threading a nut ( 19 ) onto the swedge screw ( 16 ) until tight . at the other end of the top frame member ( 2 ), the cable ( 4 ) is threaded through both the vertical opening ( 13 ) of the support arm ( 5 ) and a central cavity ( 20 ) of the helical tension spring ( 18 ). the stop member ( 17 ) is then secured to the cable ( 4 ) on the outside end of the helical tension spring ( 18 ) by threading a nut ( 19 ) onto the swedge screw ( 16 ). during operation , the vertical distance ( 10 ) ( see fig1 ) between the top frame member ( 2 ) and the cable ( 4 ) may be adjusted by simply loosening or tightening the nut ( 19 ) on the swedge screw ( 16 ) adjacent the stop member ( 17 ) such that the compression on the helical tension spring ( 18 ) is either reduced or increased , respectively . this manner of construction also facilitates maintenance of the billboard ( 3 ) in that the end of a hook ladder may be placed on top of the cable ( 4 ), whereby the helical tension spring ( 18 ) will compress to permit the hooks of the ladder to pull the cable ( 4 ) down to the top frame member ( 2 ). in an alternate embodiment of the present invention , shown in fig4 the helical tension spring ( 18 ) is placed on a side frame member ( 21 ) of the billboard ( 3 ) so as to facilitate adjustment of the invention by bringing the helical tension spring ( 18 ) within reach of a person standing on the access deck of the billboard . in this embodiment , the support arm ( 5 ) nearest to the helical tension spring ( 18 ) is affixed to the side frame member ( 21 ) in the same manner as described above . in order to redirect the cable ( 4 ) from above the top frame member ( 2 ) to along the side frame member ( 21 ), a third support arm ( 22 ) is similarly affixed to the end of the top frame member ( 2 ) nearest to the helical tension spring ( 18 ). a pulley ( 23 ) is then affixed to the third support arm ( 22 ) so that the cable ( 4 ) freely rotates around the pulley ( 23 ) to the helical tension spring ( 18 ) below . in another alternate embodiment , as shown in fig8 the cable ( 4 ) passes through a second vertical member opening ( 41 ) of a fourth support arm ( 43 ) and is provided with sufficient length for taut attachment to a first eye hook ( 40 ) affixed to the lower portion of the side frame member ( 21 ). the purpose of this alternate embodiment is to provide a simple , yet efficient means , of removing the cable ( 4 ) from its operating position above the top frame member ( 2 ). this will facilitate maintenance of the billboard ( 3 ) by allowing a workman to place a hooked ladder on the top frame member ( 2 ) without having the cable ( 4 ) caught within the hooks of the ladder . to accomplish this , a second eye hook ( 37 ) is provided adjacent to the top frame member ( 2 ) for guided passage of the cable ( 4 ) along the side frame member ( 21 ). a loop handle ( 49 ) is incorporated into the cable ( 4 ), which will enable the workmen to have a secured grip on the cable ( 4 ) thus allowing the workmen to safely re - connect the cable ( 4 ) to the installed eye hook ( 40 ). below the second eye hook ( 37 ), the end of the cable is attached to a turn buckle ( 38 ) provided with a self - closing hook ( 39 ) for attachment of the cable ( 4 ) to the first eye hook ( 40 ). above the second eye hook ( 37 ), a stop member ( 36 ) is affixed to the cable ( 4 ) to prevent complete passage of the cable ( 4 ) through the fourth support arm ( 43 ) when the cable ( 4 ) is detached from the first eye hook ( 40 ). by use of this structure , a workman can detach the self - closing hook ( 39 ) and allow the weight of the suspended portion of the cable ( 4 ) to pull the cable ( 4 ) through the fourth support arm ( 43 ) until contact is made with the stop member ( 36 ). the suspended portion of the cable ( 4 ), and the rotatable rings ( 1 ) thereon , will move to a hanging position located below the top frame member ( 2 ) and behind the billboard ( 3 ). so that the cable ( 4 ) will freely move to the hanging position behind the billboard ( 3 ), the second vertical member opening ( 41 ) of the fourth support arm ( 43 ), as shown in fig9 is bevelled and de - burred so that the cable is not inhibited by any sharp corners on the second vertical member opening ( 41 ). in addition , to improve its functioning , the fourth support arm ( 43 ) has a horizontal portion ( 44 ) and a vertical portion ( 45 ), with the vertical portion ( 45 ) being twisted such that an inside face ( 46 ) of the vertical portion ( 45 ) points towards the back of the billboard ( 3 ). furthermore , a gusset support ( 47 ) is affixed angularly between the vertical portion ( 45 ) and the horizontal portion ( 44 ) so as to provide extra strength to the fourth support arm ( 43 ). in yet another embodiment , as shown in fig1 , the invention as described in the embodiment depicted in fig8 is further modified to provide a recess ( 48 ) within the side frame member ( 21 ). the recess ( 48 ) is adapted to receive the cable ( 4 ) by means of both eye hooks ( 37 , 40 ) being affixed within the recess ( 48 ) such that the securing means is hidden from view and the cable ( 4 ) is prevented from fluttering during windy conditions .
a bird anti - perching device for preventing birds and other animals from perching , nesting or crossing on billboards and other structures such as utility lines , branches , ledges , roof tops and overhangs . in a preferred embodiment , the device has a plurality of rotatable rings strung consecutively on a cable supported above the top frame member of a billboard . the cable is supported above the top frame member by two support arms placed at opposite ends of the billboard . the support arms incorporate a tightening means for making adjustments in the height and rigidity of the cable .