Abstract:
A shock absorbing docking spacer for connecting a vessel to a mooring structure and which includes first and second sections relatively telescopically movable longitudinally relative to one another so as to define a variable effective overall length for the docking spacer and wherein one section contains an airtight air bag and the air bag is connected to the other section such that as the first and second sections move relatively inwardly relative to one another the air bag provides a buffer for absorbing impact forces between the first and second sections brought about by ambient conditions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application claiming the filing priority benefit of U.S. Provisional Patent Application Ser. No. 61/630,912, filed Dec. 22, 2011, in the name to the current inventors and the contents of which are incorporated in their entirety herein be reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to shock absorbing spacers or bumpers for connecting a boat or other vessel from a mooring, such as a dock, and more particularly to a spacer having a bag, bladder or other enclosure containing a fluid under pressure for protecting a vessel from impact with a dock, buoy or other mooring structure when the vessel is subjected to forces caused by waves, wind, tide and the like. 
     2. Brief Description of the Related Art 
     U.S. Pat. No. 6,431,104, issued on Aug. 13, 2002, in the name of John T. Webb, the contents of which are also incorporated in the entirety herein by reference, is directed to a shock absorbing spacer which functions to separate a boat tied to a mooring from impacting the mooring. The spacer uses a resilient length of cord, sometimes referred to as a “bungee cord” to act as a buffer or shock absorber as two cylinders are forced toward one another as a vessel secured to the spacer moves toward a mooring due to ambient conditions. One of the cylinders is attached to mooring such as a dock and the other is attached to a vessel such as a boat. The two cylinders are in telescopic relationship with one other and when the boat is subjected to the forces mentioned above, the inner cylinder slides into the outer cylinder thereby shortening the effective overall length of the spacer. The sliding is resisted by the bungee cord so that the spacer is never short enough to allow the boat to come into contact with the mooring. 
     In U.S. Pat. No. 4,043,545, issued Aug. 23, 1977, in the name of Darrell D. Dial et al, another form of cushioning unit or bumper for positioning between a boat or ship and a mooring, such as a dock, is disclosed wherein a piston rod is connected to a piston plate that is movable within a buffering cylinder and divide the buffering cylinder into separate interior portions. As ambient conditions urged a vessel towards its mooring, the piston plate is driven inwardly of the buffering cylinder such that compression of fluid within the buffering cylinder acts as a buffer on the forces being directed between the vessel and the mooring. During this compression period, compressed fluid is bled from the buffering cylinder through a plurality of ports which communicate with the interior of a secondary high pressure cylinder within which the buffering cylinder is mounted. As forces increase within the high pressure cylinder, they will act in an opposite direction to urge the piston face toward an opposite end of the buffering cylinder such that the piston rod is restored to its originally extended position relative to the vessel. 
     Other examples of cushioning or bumper devices used to dissipate forces tending to direct vessels either toward or away from mooring devices are disclosed in U.S. Pat. No. 4,063,526 to Ueda wherein inner and outer pressurized cylinders are used and U.S. Pat. No. 4,066,030 to Milone, wherein a hydraulic cylinder arrangement is provided with a male portion of the arrangement being vertically movable within a vertical guide track so that relative vertical movement of a vessel and a dock or mooring structure is accounted for simultaneously with the buffering of compressive and expansion forces. Another buffering or cushioning device for allowing for vertical movement between a vessel and a mooring structure is disclosed in U.S. Pat. No. 5,014,638 to Ilves et al. 
     SUMMARY OF THE INVENTION 
     A first embodiment of shock absorbing, cushioning device or docking spacer of the present invention for use in securing a boat or similar vessel to a mooring, such as a dock, includes an elongated body having a pair of sections movable longitudinally of each other in telescopic relationship to define a variable effective overall length. One of the sections is adapted to being attached to the boat while the other section is adapted to being attached to the dock. An airtight bag or bladder containing a pressurized fluid, and preferably a gas, is disposed within one section while a connecting rod extends from the bag to the other section. The connecting rod advances toward the bag upon impact of the boat with the shock absorber or docking spacer. 
     In a second embodiment of the invention, as opposed to a rod extending from one section and being connected to a pressurized bag or bladder in the other section, the shock absorbing, cushion device or docking spacer has one section having one end connected to one of a vessel or a mooring structure and another end connected to a first sealed end of a pressurized bag or bladder mounted within a second section of the shock absorber. In this embodiment, as the section connected to the vessel moves toward the mooring device, the first end of the bag or bladder is moved toward a second end thereof thereby building up pressure within the bag or bladder which build up of pressure buffers the force of the vessel moving toward the mooring structure. In this embodiment, a bumper device or resilient material may be provided on an inner end face of the movable section to thereby provide a resilient stop should the forces driving the sections toward one another cause an impact there between. 
     In both embodiments of the invention, the shock absorbing or spacer devices may be mounted to a slidable base secured to a vertical guide track structure which is mounted to a vertical post or other portion of the mooring device so that water levels change relative to the mooring structure, the slidable base will automatically be vertically adjusted. In this manner, transverse stresses on the sections of the shock absorbing or spacer devices will be reduced thereby allowing smoother reciprocal motion between the telescoping sections of the devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the shock absorbing devices or docking spacers of the present invention will be had with reference to the accompanying drawings in which: 
         FIG. 1  is a side elevation view, primarily in section, of a shock absorbing device or docking spacer of a first embodiment of the present invention; 
         FIG. 2  is a front perspective view of the shock absorbing device or docking spacer of  FIG. 1  attached to a mooring structure by way of a vertically movable base; 
         FIGS. 3   a  and  3   b  are illustrational views of the shock absorbing device or docking spacer with adjustable base of  FIG. 2  and showing the relationship between a vessel and the mooring structure at high and low tides, respectively, and illustrating how the sections of the shock absorbing device remain horizontally aligned; and 
         FIG. 4  is a side elevation view, primarily in section, of a shock absorbing device or docking spacer of a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIG. 1 , a first embodiment of shock absorbing device or docking spacer  10  includes first and second hollow sections or cylinders,  11  and  12 , respectively, which are moveable longitudinally of each other in a telescopic relationship along axis A-A of the first section with resulting changes in the effective overall length of the docking spacer. A bushing  14  is disposed between an inner wall  15  of the first section and the outer wall  16  of the second section for reducing friction between the two walls as they slide relative to each other. 
     The first section  11  is connected to a cleat  17  which is attached to a dock  18  while the second section is connected to a cleat  20  which is attached to a boat  21 . Alternatively and with reference to  FIGS. 2 ,  3   a  and  3   b , the first section may be connected to a base slider  22  which is mounted to slide vertically on a track or guide channel such as an I-beam  24 . The I-beam is fastened to a vertical post  26  which is provided adjacent to, or which forms part of, the dock  18 . The docking slider  22  allows the docking spacer  10  to move vertically so that the boat to which the docking spacer is attached is free to move up and down with the tide. This vertical adjustment reduces vertical transverse forces which can be created between the first and second cylinder sections  11  and  12  and the sections remain generally horizontally aligned regardless of the water level as shown in  FIGS. 13A and 13B . Thus the sections will not bind when reciprocally moving relative to one another regardless of wave action. 
     Mounted within the first section  11  is a fluid-containing airtight bag or bladder  32 . A valve  34  is attached to the bag to allow fluid under pressure to flow into the bag and for bleeding the fluid from it. A pressure gauge (not illustrated) measures the pressure within the bag. As shown, the valve  34  extends out from a proximal end of the first section. 
     The fluid flows to the bag from a high pressure cylinder (not illustrated). For reasons of economy, air is the preferred fluid and the air is contained in one or more conventional air cylinders. Other gases such as nitrogen or inert gases may also be used but generally are less suitable than air because of their cost. Liquids such as water can also be used but are generally not very suitable because of the cost of compressing them. 
     Attached to the distal end  35  of the bag which faces the second section  12  is a coupling  36  having a threaded socket  37  which receives one of two threaded ends  39  of a connecting rod or like connector  38 . The opposite end of the connecting rod is threadably attached to a proximal end wall  40  of the second section, relative to the cleat  20 . The connecting rod is also supported in a distal end wall  41  of the second section  12 . 
     In use of the first embodiment, a hooked end member  42  connected to the proximal end of the first section  11  is secured, such as by a rope  43 , to the cleat  17  of the dock  18  and a proximate hooked end member  44  connected to the proximal end of the second section  12  is secured to the cleat  20  of the vessel  21 , also such as by a rope  45 . The pressure within the air bag  32  is adjusted to provide a preferred buffering resistance to movement of the connecting rod  28  as ambient conditions force the second section  12  to move reciprocally relative to the first section. Such ambient conditions include forces caused by waves, wind, tide and the like. The greater the pressure within the air bag the less the buffering resistance to movement of the second section as such higher pressure resists compression of the air bag that is necessary to allow a buffered compression of the air bag to absorb the forces directed from the vessel toward the mooring dock. 
     Also, as shown in the drawings, in some forms of the first embodiment, some clearance  47  may be provided between the air bag  32  and the inner walls of the first section to allow for some initial expansion of the air bag without resistance from the walls of the first section. 
     With reference to  FIG. 4 , a second embodiment of shock absorbing device  90  for connecting between a boat  20  and a mooring device such as a dock  18  is shown including outer and inner cylindrical sections,  91  and  92 , respectively. Spaced bushings  94  and  96  are disposed in an annular gap between the two sections. The bushings act not only to close the gap but also act as guides for ensuring that the direction of the sliding motion of the second section  92  is along a longitudinal axis B-B of the first section  91 . The outward movement of the second section relative to the first section is limited by a circular plate  98  at the distal end of the second section. The plate defines a forward or distal wall of the second section. The plate engages bushing  94  when an effective length of the mooring spacer is greatest. The inward movement the second section is limited by a bumper  100  which contacts proximal end wall  102  of the first section. When contact occurs, the effective length of the mooring spacer is the least. 
     An airtight bag  104  for compressed fluid is disposed within the first section. The bag is closed except for an opening defined by an edge  105  which is attached to plate  98 . Thus as the second section slides inward toward end wall  102  of the first section, the plate draws the circular edge  105  and the air bag  104  inward toward the end wall  102  with resulting compression of fluid within the bag. Fluid may be introduced into the bag or bled from it through a valve  108  adjacent to the proximal end wall  102  of the first section. 
     In use of the second embodiment, a hooked end member  42  connected to the proximal end of the first section  91  is secured, such as by a rope, not shown, to the cleat  17  of the dock  18  and a proximate hooked end member  44  connected to the proximal end of the second section  92  is secured to the cleat  20  of the vessel  21 , also such as by a rope, not shown. The pressure within the air bag  104  is adjusted to provide a preferred buffering resistance to movement of the second section  92  toward the proximal end  102  of the first section  91  as ambient conditions force the second section  92  to move reciprocally relative to the first section  91 . Such ambient conditions include forces caused by waves, wind, tide and the like The greater the pressure within the air bag, the less the buffering resistance to movement of the second section as such higher pressure resists compression of the air bag that is necessary to allow a buffered compression of the air bag to absorb the forces directed from the vessel toward the mooring deck. 
     Also, as shown in the drawings, in some forms of the second embodiment, some clearance  115  may be provided between the air bag  104  and the inner walls of the first section  91  to allow for some initial expansion of the air bag without resistance from the walls of the first section. 
     It will be understood, of course, that modifications can be made in the structure of the shock absorbing devices and docking spacers of the invention without departing from the scope and purview of the invention as defined in the claims that follow.