Abstract:
A boat lift having a plurality of flotation tanks positioned under each of opposite sides of a frame of the boat lift. Trunk lines receive water through a port near the rear of the trunk lines, and communicate water into a plurality of flotation tanks. Water flow is regulated so that the plurality of the tanks fill relatively evenly to maintain a surface of the boat lift that is generally horizontal at all times. Hingeable connection of the dock to a bulkhead, along with lateral stabilization, participate in maintaining a generally horizontal attitude for the boat lift. Water is expelled from the plurality of flotation tanks by pumping water from the flotation tanks, allowing the frame of the boat lift to rise.

Description:
[0001]    This Application claims the benefit of U.S. Provisional Application No. 61/725,506 filed Nov. 13, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to docks for boats and vessels generally, and is more specifically related to a boat lift. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is desirable to store boats out of the water when not in use. Particularly in salt water environments, water can lead to rapid corrosion of metal parts, and depreciation of other parts of the boat. Further, in many salt water environments, storage of the boat hull in the water leads to fouling of the hull, propellers and through hulls that communicate with boat utilities. Barnacle growth, for example, occurs in many salt water environments, and such fouling reduces performance of the boat hull and propulsion systems. 
         [0004]    In one particular example, barnacles and other growth attributed to storing a boat hull in water occurs in through hulls and other openings in the hull. For example, barnacle growth in water inlets for jet boats that use water for propulsion, or for boats that pump water, such as firefighting vessels, experience fouling in the water intakes. While fouling on a boat hull is undesirable, fouling of water inlets or engine cooling could result in engine failures, and fouling in water inlets of vessels for emergency response can also be disastrous. It is expensive to frequently inspect and remove growth, such as barnacle growth, but is critical to do so if the boat is stored in water. 
         [0005]    There is a need for a drive on boat lift that is reliable, and provides rapid, high lifting capacity, while also allowing the boat to be driven on to the boat lift at a generally horizontal attitude, so that the operator&#39;s vision is not obstructed by an elevated bow during the critical time while the boat is positioned at the dock. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is a boat lift having a plurality of flotation tanks positioned under each of opposite sides of a frame of the boat lift. Trunk lines receive water through a port near the rear of the trunk lines, and communicate water into a plurality of flotation tanks. Water flow is regulated so that the plurality of the tanks fill relatively evenly to maintain a surface of the boat lift that is generally horizontal at all times. Hingeable connection of the dock to a bulkhead, along with lateral stabilization, participate in maintaining a generally horizontal attitude for the boat lift. A catwalk may be provided on the longer side of the dock. 
     
    
     
       BRIEF DRAWING DESCRIPTION 
         [0007]      FIG. 1  is top plan view of the dock demonstrating an attachment of a hinge that attaches the hinged frame section of the lift to a bulkhead. 
           [0008]      FIG. 2  is a top plan view of the dock of  FIG. 1  with the dock in place and the hinged frame section attached to the bulk head. 
           [0009]      FIG. 3  is the top plan view of the dock of  FIG. 2  demonstrating a boat shown in phantom lines entering the boat lift. 
           [0010]      FIG. 4  is an isolation taken essentially as shown in  FIG. 2 , with a lateral stabilizer positioned in the boat lift frame, with the boat lift in a raised, upper position. 
           [0011]      FIG. 5  is an isolation essentially taken as shown in  FIG. 3 , with a lateral stabilizer positioned in the boat lift frame, with the boat lift in a lowered position. 
           [0012]      FIG. 6  is a rear elevation of the boat lift with a boat in position on the boat lift, and the boat lift in a relatively lowered position. 
           [0013]      FIG. 7  is a side elevation of the boat lift and boat of  FIG. 6 . 
           [0014]      FIG. 8  is a rear elevation of the boat lift with a boat in position on the boat lift, and the boat lift in a raised, elevated position. 
           [0015]      FIG. 9  is a side elevation of the boat lift and boat of  FIG. 8 . 
           [0016]      FIG. 10  is a schematic demonstrating operational air and water flow for the boat lift. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    In preferred embodiments, a boat lift comprises a frame  2  or similar sub-structure. The frame may generally have a v-shape to accommodate the common shape for boat hulls, so that the frame is constructed and arranged to receive and hold a boat hull in a stable and generally horizontal position.  FIG. 6 . The frame may be covered with planking  4 , which may be wood, and which may be teak, as demonstrated in the drawing figures. The frame may be covered with other materials, which may be synthetic rubber or other elastomers or polymers that will receive and hold the boat hull without damaging the boat hull other materials of which docks and boat lifts are formed of may be used. 
         [0018]    A hinged frame section  6  of the boat lift connects the frame to a bulkhead. The hinged boat lift section is hingeably connected to the frame and hingeably connected to the bulkhead. The hinged boat lift section may be covered with the planking  4  or other material of which the frame of the boat lift is covered. The bulkhead is intended to be stationary in most cases, and may be a fixture in some manner to real estate. 
         [0019]    Positioned underneath the boat lift frame is a plurality of flotation tanks  8 . A first plurality of flotation tanks is positioned along one side of the boat lift frame, and a second plurality of tanks is positioned along a second side of the boat lift frame. The tanks are constructed and arranged to be flooded with water, and subsequently to have water evacuated from the tanks to cause submersion of the boat lift frame, and lifting of the boat lift. 
         [0020]    In a preferred embodiment, the flotation tanks are rectangular in cross-section, as shown in drawings. A rectangular cross section may include a square cross section. As shown in  FIG. 6  and  FIG. 8 , the bottom of the flotation tanks is at an angle from horizontal. 
         [0021]    In a preferred embodiment, this angle will be between 10 and 45 degrees from horizontal. As shown particularly in  FIG. 8 , when the tanks are evacuated of water  10 , the remaining water will settle in the lower most portion of the tank, and in a corner thereof due to the angle of the tank. Causing the remaining water to flow to the corner of the generally horizontal tank provides for the most evacuation of water, since the pick up for the conduit to the water pump may be located in this corner. If the tanks are mounted so that the bottom is substantially horizontal, evacuation of the water is not as complete. The rectangular cross section, in many cases, provides a flat top surface for mounting the tanks against the upwardly angled surface of the boat lift frame that is generally v-shaped in the preferred embodiment shown in  FIGS. 6 and 8 . 
         [0022]    In a preferred embodiment, a first trunk line  12  and a second trunk line  14  are positioned between the first plurality of flotation tanks and second plurality of flotation tanks. The first trunk line and a second trunk line are generally parallel to each other, positioned horizontally, and run longitudinally underneath the boat lift frame and between the first plurality of flotation tanks and second plurality of flotation tanks and substantially the length of the frame  2 . 
         [0023]    Each trunk line has a water receiving port  16  positioned in a rear of the trunk line, which is near the rear of the boat lift frame. The rear of the boat lift frame is defined as the end of the boat life frame that is generally adjacent to the stern of a boat  30  when a boat is in position on the boat lift, as shown in the drawing figures. The water receiving port of the trunk lines is preferred to be near the rear of the boat lift, since typically, boats are heavier at the rear. While the device is designed to use multiple complimentary components to submerge and raise the frame at a relatively horizontal and level attitude, it is preferred that the water receiving ports are held under the water by the rearwardly biased weight of most vessels. 
         [0024]    Each trunk line communicates by a flow limiting conduit  18  that connects the associated trunk line to the associated flotation tank. For example, the trunk line associated with the flotation tanks on the left side of the boat lift will have a flow limiting conduit connecting the trunk line to each of the flotation tanks, such that if there are three flotation tanks, there will be three float limiting conduits from the associated trunk line to the left side of the flotation tanks. Similarly, the trunk line on the right side will be connected by a flow limiting conduit from the trunk line to each of the three flotation tanks so that three flow limiting conduits run from the trunk line to the three flotation tanks. Further, a conduit  20  connects the first trunk line to the second trunk line. 
         [0025]    Several elements of the invention permit the boat lift frame to be submerged while maintaining a relatively horizontal position. The use of multiple flotation tanks, each having a flow limiting conduit from a trunk line, regulates the flow of water into each of the tanks. As the valves on the rear of the trunk lines associated with the ports  16  are opened by an actuator ( FIG. 10 ), which is preferably a pneumatic actuator housed in a sealed, water proof housing, water floods the trunk lines. If multiple flotation tanks are not used, the weight of the boat would tend to cause the rear portion of a single tank to flood at rear, preventing the boat lift from descending evenly. The use of the trunk line with the flow limiting conduit means that water is available for each of the conduits from the trunk line in a relatively even volume and relatively even flow rate, so that the plurality of flotation tanks, such as three flotation tanks, fills evenly. Further, having a conduit that communicates water from the first trunk line to the second trunk line also assures that water is available for both trunk lines, and that relatively the same volume of water is present in each of the trunk lines, so that the plurality of tanks on each side of the boat lift frame all fill at generally the same rate, keeping the boat lift at a proper attitude. 
         [0026]    Further, mounting the boat lift frame to the bulkhead  22  or similar stationary mounting allows the boat lift frame to descend with a generally horizontal attitude. By hinging the hinged frame section at the front of the boat lift frame and at the bulkhead or similar stationary mounting, the boat lift frame descends and ascends relatively evenly. 
         [0027]    Mounting of the boat lift to the lateral stabilizers as shown in  FIG. 4  is also important to the boat lift in descending and ascending at a relatively even attitude. Due to the movement of the hinged frame section  6 , the boat lift frame will be moved forward as the boat lift frame descends to the position of  FIG. 7 , and pushed to the rear by the movement of the hinges of the hinged frame section shown in  FIG. 9 . The slotted mounting brackets  24  shown in  FIGS. 4 and 5  permit forward and rearward movement of the boat lift, maintaining the desired attitude. Lateral stabilizers  26  are positioned within the slotted mounting brackets to prevent movement of the boat lift at a right angle to the forward and rearward travel of the boat lift during normal operation. These slots, while permitting movement of the boat lift in one direction, retard movement of the boat lift in other directions. The slots also prevent the boat lift from being pushed to an undesired attitude by wave action striking the side of the boat lift. The lateral stabilizers in a preferred embodiment, are also used as mounting for the catwalk  28 , which may run the length of the boat life frame on one or both sides of the dock. 
         [0028]    The preferred catwalks  28  are supported by flotation tanks  32 . The flotation tanks are water tight, but provide a water inlet and/or outlet for filling the tanks or withdrawing water from the tanks. During construction and/or positioning of the dock, catwalks are positioned alongside the boat lift frame. The flotation tanks are filled with water  34  to a level of the flotation tanks that holds the catwalk in the desired position relative to the boat lift frame, so that the top decking  36  of the catwalks, which may be covered similarly or identically to the boat lift frame, are at the desired position relative to the decking of the boat lift frame. Once the water level in the flotation tanks of the catwalks is sufficient to hold the catwalk in the desired position, it should not be necessary to frequently adjust the flotation tanks&#39; water level. In a preferred embodiment, when the boat lift frame has lifted the boat to the full upper position, so that the hull of the boat is out of the water, the decking of the boat lift frame, where it joins the catwalk, and the decking of the catwalk will be relatively even each with the other. Occupants of the boat may ingress and egress the boat by traversing the catwalk or the hinged frame section, without the decking of any of these elements presenting a tripping hazard. 
         [0029]    A preferred schematic of the operational elements is shown in  FIG. 10 . The left side of the schematic represents the rear of the boat lift. Arrows demonstrate water entering the water receiving ports  16  of the preferred parallel trunk lines. A valve is associated with each water receiving port, and the valve may be fully or partially opened, and fully or partially closed, as desired, to allow water to flood the trunk lines. As further demonstrated by arrows between the trunk lines and the flotation tanks, water flows through the flow limiting conduits to the flotation tanks  8 . A conduit also permits flow between each of the trunk lines. Air vents are provided in an upper portion of each of the flotation tanks as shown, to allow air to evacuate the flotation tanks as water floods the flotation tanks. Air vent lines connect the air vents in this embodiment. 
         [0030]    The force of gravity holds the openings of the trunk lines under water, with the water entering the flotation tanks with the valves of the trunk lines open. The valves are controlled by an actuator. The actuator is preferred to be pneumatically controlled with an air compressor providing air pressure for actuating the valve by means of the actuator. When the flotation tanks are filled with water, the boat lift frame, and any associated boat or vessel, is submerged to a depth that allows the boat to float in water, and be driven on or off of the boat lift frame and the decking thereof. 
         [0031]    An air vent communicates with the air vent lines as shown in the schematic. In a preferred embodiment, the air vent is positioned near the front of a boat lift as shown in  FIG. 10 . The air vent has a valve associated with it, and the valve may also have an actuator that operates the valve to a fully opened or fully closed or partially open or partially closed position. The actuator may be pneumatically operated and controlled. By controlling the rate of flow of air out of the air vent, the rate of submersion of the boat lift can be controlled. In a preferred embodiment, the openings of the trunk lines and water flow from the trunk lines into the flotation tank are sufficient to allow the boat lift to travel from fully raised to fully submerge in less than one minute. However, by limiting the degree of opening of the air vent, and thereby limiting the rate of flow of air out of the flotation tanks, the rate of water entering the flotation tanks, and therefore the rate of submersion, may also be controlled. 
         [0032]    The boat lift is raised by evacuating water from the flotation tanks and replacing the water with air. In a preferred embodiment, evacuation of the water is performed by pumping the water from the flotation tanks, using one or more water pumps. To accomplish water evacuation from the flotation tanks, the ports of the trunk lines at the rear of the boat lift are closed by the actuators. Water is then pumped from the flotation tanks and trunk lines and out of the device through water pump out lines that communicate with each of the flotation tanks. 
         [0033]    During the water evacuation process, the air vent will remain open so that air replaces water that is evacuated. The water flow rate may be regulated by partially closing the air vents. However, in most cases, the air vent will remain fully open, since rapid evacuation of water, and the associated lifting action, is desired to occur relatively rapidly. Sensors may be provided so that when there is no water flow to the water pumps, or an individual pump of a plurality of water pumps, operation of the pump or pumps is terminated. 
         [0034]    In a preferred embodiment, a central control panel  40  for operating the boat lift is provided. The control panel may have a simple command selector to raise or lower the boat lift. Other controls may control the rate of flow of water and/or air in and out of the flotation tanks by operation of the valves as discussed herein. In other embodiments, manual controls for actuating the pumps or terminating operations of the pumps may be provided. 
         [0035]    In some embodiments, the boat lift frame is built in a plurality of sections, with one flotation tank positioned on each side of the modular section. The sections of the frame may be attached with fasteners that are removable, such as nuts and bolts, rather than welding the entire length of the frame together. In this manner, a modular boat lift that may be built to a customized length by adding or removing sections is available. As shown in the drawings, three frame sections are connected, with each frame section comprising an associated flotation tank. 
         [0036]    More, or fewer, sections could be used to vary the length of the boat lift.