Dock fender and shock absorber

An apparatus for protecting a boat from harmful contact with the piling of a dock is provided. The apparatus comprises a generally rigid, vertical, elongated tube, preferably made of PVC pipe and a hollow sleeve. The sleeve is preferably made of concentric layers of resilient and strength imparting material and has a hollow core aligned with the elongated axis of the tube. Lag bolts extend from inside the core of the sleeve, through the sleeve and wall of the tube into a wooden 2.times.4 within the tube. Also, lag bolts extend from inside the core of the sleeve, through the sleeve and into a piling. In this way, the tube is attached to the sleeve which is in turn attached to the piling. A seal and a cap with a vent are attached to the bottom and top of the tube respectively.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The instant invention relates to dock fenders and more particularly to dock 
fenders with a shock absorber-type connection to a piling. 
2. Description of Related Art 
It has long been recognized that it is desirable to cushion the impact 
between a boat and dock piling, which impacts occur as a normal result of 
docking or mooring the boat against the dock piling. Examples of attempts 
to provide such cushioning are given in the following U.S. Pat. Nos.: 
3,145,685, issued to Kulick, Sr., on Aug. 25, 1964 
3,950,953, issued to Matthews, on Apr. 20, 1976 
4,411,556, issued to LeBlanc et al., on Oct. 25, 1983 
4,804,296, issued to Smath, on Feb. 14, 1989

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a perspective view showing the dock fender 24 and sleeve 12 in 
position attached to a piling 10 of a dock 11. Dock fender 24 comprises a 
vertically positioned elongated tube 26 having a cap 30 at the uppermost 
end and a seal 32 at the lowermost end. The lowermost end of tube 26 
preferably extends below the water level, while the uppermost end of tube 
26 containing cap 30 extends a sufficient height above the water so that 
boats contacting dock fender 24 will contact the outer surface of dock 
fender 24 below cap 30. 
As is seen in more detail in FIG. 2, tube 26 preferably is a hollow pipe 
preferably made of polyvinylchloride (PVC) having an inside diameter of 4 
inches. The thickness of the wall of pipe 24 is preferably 1/4 inch but 
may be as thick as 1/2 inch. The typical length of tube 26 is about ten 
feet but may be of variable lengths from a few feet to over twenty feet. 
The dimensions given are merely exemplary and are not intended to be for 
limitation. A dock fender strengthening means 28, which is typically a 
common wooden 2.times.4, extends through the middle of tube 26 to add 
strength to dock fender 24. 
Cap 30 and seal 32 are also made of polyvinylchloride (PVC). Cap 30 fits 
securely over the top of tube 26 and prevents water from entering the top 
of tube 26. To prevent cap 30 from being dislodged, a lag bolt 23 is 
threaded through cap 30 into the dock fender strengthening means 28. 
Because tightening lag bolt 23 into dock fender strengthening means 28 
causes a depression in the top of cap 30 where water may accumulate, lag 
bolt 23 is preferably coated with a silicone sealer, such as is commonly 
used in the marine environment, to prevent water intrusion into tube 26. 
Cap 30 preferably contains a vent 31 for allowing air to enter tube 26. 
Thereafter, the air may circulate within tube 26 around dock fender 
strengthening means 28. Allowing air to enter and circulate within tube 26 
reduces the deterioration of dock fender strengthening means 28 caused by 
moisture within tube 26. Vent 31 may be just a void in cap 30 which void 
may be closable by a hinged covering or any other means for closing 
openings which are common in the boating industry and related fields. 
Seal 32 at the bottom end of tube 26 prevents water from entering tube 26 
at the lower end of tube 26. Seal 32 is a cap which fits securely over the 
bottom of tube 26. Seal 32 is sealingly connected to tube 26 by waterproof 
glue suitable for sealing PVC parts as is well known in the art. This 
waterproof connection prevents water from entering tube 26 through the 
bottom of tube 26. 
Dock fender 24 is attached to piling 10 through sleeve 12. Sleeve 12 is a 
multi-layered tube having about the same exterior diameter as tube 26. 
Sleeve 12 preferably has three concentric layers around a hollow center. 
The inner layer 14 is preferably a one-half inch thick layer of an 
elastomer material such as rubber. Outside inner layer is middle layer 16 
which adds strength to sleeve 12. Preferably, middle layer 16 comprises 
four layers of canvas or nylon to impart strength, as well as a degree of 
resiliency to sleeve 12. Middle layer 16 is also approximately one-half 
inch thick. 
Outside middle layer 16 is outer layer 18 comprising a one-half inch layer 
of elastomer material such as rubber which adds to the shock absorbing 
capacity of the sleeve 12. The outer surface of outer layer 18 is 
preferably colored. This coloring is merely decorative and serves no 
functional purpose. 
Once again, although explicit dimensions for the thickness and number of 
layers has been given, it is to be understood that this is by way of 
example and not by limitation. 
Dock fender 24 is attached to sleeve 12 by means of lag bolts 22 extending 
through brackets 20A disposed on the interior surface of sleeve 12. Lag 
bolts 22 extend through the multiple layers 14, 16, 18 of sleeve 12, 
through the wall of tube 26 and are secured into dock fender strengthening 
means 28 within tube 26. Sleeve 12, in turn, is secured to piling 10 by 
means of lag bolts 22 extending through brackets 20B disposed on the 
interior surface of sleeve 12 opposite brackets 20A, through the layers 
14, 16, 18 of sleeve 12 into piling 10. In this way, dock fender 24 is 
attached to sleeve 12 which in turn is attached to dock piling 10. 
It has been found that the initial tightening of lag bolts 22 into the 
respective dock piling 10 or tube 26 and dock fender strengthening means 
28 creates an effective initially watertight seal between the lag bolts 22 
and sleeve 12. However, because of movement of the dock fender 24, from 
waves or docking and mooring of boats, and because the lowermost sleeve 12 
is sometimes attached to a dock piling 10 so that sleeve 12 is underwater 
at high tide, the initially watertight seal between lag bolts 22 and 
sleeve 12 often leaks water into tube 26. Therefore, a silicone sealer, 
such as is commonly used in the marine environment, is preferably placed 
around lag bolts 22 prior to screwing lag bolts 22 through sleeve 12 into 
the respective dock piling 10 or tube 26 and dock fender strengthening 
means 28. Because the uppermost sleeve 12 is above the water at high tide, 
it may not be necessary to place the silicone sealer around the lag bolts 
22 extending through this sleeve 12, in order to preserve the watertight 
seal. The silicone sealer prevents the intrusion of water into tube 26. 
Brackets 20A, B as well as lag bolts 22 are preferably made of stainless 
steel to prevent rust from exposure to the moisture necessarily present in 
the marine environment. 
In operation, as a boat approaches dock 11 for mooring, when the boat 
contacts dock fender 24, the impact of the boat upon dock fender 24 is 
dissipated through sleeve 12. The impact of the boat on dock fender 24 is 
dissipated primarily due to the resilient, deformable material which 
comprise the layers 14, 16, 18 of sleeve 12. Although most of the shock 
absorbing capacity of the dock fender 24 comes from the resiliency of 
sleeve 12, there is an amount of resiliency inherent in the PVC of tube 
26. This inherent resiliency of tube 26 adds to the overall shock 
absorbing of dock fender 24. 
This absorption of the impact upon dock fender 24 reduces the impact, and 
consequently the effect of the impact on both dock fender 24 and the boat. 
The presence of sleeve 12 provides a cushioning effect to impacts upon 
dock fender 24. Therefore, it is not necessary to replace dock fender 24 
nor repair damage to a boat using dock 11 as often as has been required 
with prior art dock fenders. 
In addition, once a boat has been securely moored to dock 11, the effect of 
the boat's movement and consequent contact with dock fender 24 due to the 
motion of water through wave action or through the wakes of passing boats 
is minimized due to the shock absorbing effect of sleeve 12. The shock 
absorbing effect of sleeve 12 in this context has the same benefits upon 
both dock fender 24 and the boat using dock fender 24 described above. 
An additional benefit of placing sleeve 12 between piling 10 and dock 
fender 24 is that no matter what angle a boat impacts dock fender 24, the 
force of the impact will be dissipated through sleeve 12. This dissipation 
from any angle is due to sleeve 12's resistance to deformability in any 
direction because of the tubular shape of sleeve 12. It is particularly 
important to be able to dissipate the impact of a boat on dock fender 24 
from any direction because a boat is likely to impact dock fender 24 from 
any direction, both as the boat approaches the dock 11 for mooring and as 
the boat is moved by wares and wakes while moored. In this way, both the 
boat and dock fender 24 are protected during impact. 
While the instant invention has been described in connection with the 
specific embodiment, it is to be understood that this description is given 
by means of example and not by means of limitation. For example, the 
composition of sleeve 12, although given as a preferred embodiment, is not 
critical to the operation of the invention. It is within the scope of the 
invention to include any means for resiliently connecting a dock fender 24 
to a piling 10 which can dissipate the force of the impact of a boat on 
dock fender 24 from any direction. 
In addition, the specific structure of dock fender 24, including having a 
wooden 2.times.4 insert as the dock fender strengthening means 28, is not 
critical to the instant invention as long as a fender is provided which 
has sufficient strength to absorb the impact of a boat in the conditions 
for which such dock fenders are found and which has means for connecting 
to sleeve 12. 
It is clear that changes and modifications can be made to the foregoing 
description and still be within the scope of the invention. Further, it is 
understood that obvious changes and modifications will occur to those 
persons skilled in the art.