Hydraulic and earth engineering – Marine vessel portage – launching – or removing – Lifting
Reexamination Certificate
2003-02-10
2004-02-24
Will, Thomas B. (Department: 3671)
Hydraulic and earth engineering
Marine vessel portage, launching, or removing
Lifting
C114S044000
Reexamination Certificate
active
06695533
ABSTRACT:
BACKGROUND OF INVENTION
This invention relates to boat hoists, generally, and, more specifically, to a hydraulic lift device for a boat hoist, in which the structure to which the principal components thereof are attached also provides a protective enclosure for those components.
A variety of prior art applications are known related to the function of vertically moving a suspended boat cradle by various means including some hydraulic applications. Such hoists are used in residential, recreational and light commercial settings, to lift a boat out of the water when not in use. In northern locales, these hoists must also be seasonably removable to prevent ice damage of hoist components at or below the water surface.
Prior art applications in the field have included variations of cantilever-style hoists. Many of these employ hydraulic cylinders below the water surface. Some hoists of this type have utilized large winches forward of the hoist to pull the hoist's bed or cradle over its pivot point. There has been limited success, as well, with vertical lifts which utilize hydraulics or large cable winches.
Existing vertical winch lifts, typically may be outfitted with two or more winches, particulary for heavier weight applications, and these multiple winches may run at varying speeds, which may be disadvantageous.
Hydraulic vertical lifts of the existing art often use one cable to lift one corner of the lifting bed or cradle, using multiple leveling cable to equalize lift on all other corners. Existing hydraulic applications, as well, utilize the “pull” of the hydraulic cylinder, rather than the “push”. Because of these factors most existing hydraulic lifting devices have significant load limitations.
Hydraulic cantilever lifts require substantial structure support because of compounded force at bottom of the lifting cycle. Significantly more power is required in the initial portion of the cycle than in the latter. It is also typical of the prior art that the hydraulics are beneath the water surface when the hoist is operated. This creates a number of disadvantages.
Below surface hydraulics are not only difficult to service, but are exposed to harsh elements, including sand, salt (in salt water applications), zebra muscles and barnacles. Below lift mechanical components will also require deeper water, which is a luxury not always available, because the lift bed may not be able to be placed as proximate to the bottom as is optimally desired. Because of their method of operation, and upper configuration, hydraulic cantilever hoists may also be difficult to accessorize with such important additions as canopies and motor and bow stops.
Winch cantilever hoists address some concerns, but present their own problems. Structure size and weight, to address strength requirements, limit mobility of the entire hoist assembly. They are also generally powered by 220 volt electricity which is potentially hazardous in a marine environment.
Representative of the prior art are U.S. Pat. No. 5,934,826 to Mansfield disclosing a combination boat lift apparatus and piling; U.S. Pat. No. 5,522, 671, to Keesling, disclosing a pair of hydraulic cylinders vertically mounted in conjunction with reinforced concrete pilings; U.S. Pat. No. 5,090,841, to Pench, Jr. et al, disclosing a hydraulic pump and cylinder on a manual boat lift; U.S. Pat. No. 4,773,346 to Blanding et al., disclosing vertically mounted hydraulic cylinders, at each corner of a boat hoist; and U.S. Pat. No. 4,641,596 to Reprogle et al., which discloses a combination of vertical hydraulic cylinders and moveable pulley blocks;
Accordingly, a need exists for a boat hoist hydraulic lift device which may be used in conjunction with an easily portable boat hoist to maximize mobility; which allows the lift bed of the hoist to rest as proximate to the bottom of the body of water as possible; which utilizes the “push” as opposed to the “pull” of the hydraulic cylinder unit; which does not require 220 volt electrical power from an external source; which provides equal vertical “lift” directly to both ends of the lift bed; and which is constructed so that the primary mechanical and power components are located above the surface of the water and are otherwise shielded from the elements.
The present invention is so directed.
SUMMARY OF THE INVENTION
The present invention has been designed to the overcome the shortcomings in the prior art as noted above. It is directed to the provision of a significantly improved lifting device for utilization with in-water boat hoists.
More specifically, this invention is directed to a boat hoist hydraulic lift device which may be used in conjunction with currently existing boat hoist frames to provide a portable boat hoist which maximizes mobility.
An additional object of the invention is to provide a boat hoist hydraulic lift device which allows the lift bed of the hoist to rest as approximate as possible to the bottom of the body of water and, further is constructed so that the primary mechanical components are located above the surface of the water, and are shielded from other elements as well.
An additional object of the invention is to provide a hydraulic lift device which maximizes lifting power by utilizing the “push” of a hydraulic cylinder, as opposed to the “pull” thereof. Further, the device is directed to provision of a hydraulic lifting function in an in-water boat hoist application which does not require 220 volt electrical power from an external source and which provides equal vertical lift directly to both ends of the lift bed.
The boat hoist lift device which is a primary object of the invention is utilized in conjunction with in-water boat hoists having a base frame, which is normally adjustable, to rest substantially horizontally on the bottom of a body of water. Such hoists are normally substantially rectangular in shape, with a lower rectangular base, and supporting shoes or skids, which have an adjustment means to level the lower portion of the hoist. The hoist itself has a plurality of stanchions which extend vertically, normally at the corners thereof, and along the sides. Stanchions are not normally provided along the ends of the hoist, as that is where the boat, or other load to be lifted, normally enters and exits.
In conjunction with the type of hoist described, the present invention, in an important feature, may utilize either one hydraulic lift device or a pair of such devices mounted in parallel, on opposite sides of the boat hoist.
According to a further important feature of the invention, each individual hydraulic lift device unit initially includes a support and enclosure unit, extending between upright stanchions of the boat hoist assembly itself, on one side of the boat hoist. This rigid unit provides the dual function of supporting the hydraulic lift device and its primary components, and further, enclosing those components and shielding them from the elements. This rigid support member is essentially a rigid, longitudinal box member, extending between upright boat hoist stanchions and includes joined and enclosed bottom, back, top, and end units. A front cover unit, which is removable, is also provided, for access to the components for service and maintenance.
According to a further feature of the invention, within the support structure enclosure, a hydraulic cylinder, which includes a cylinder body and extendable piston, is secured, in horizontal relationship. The cylinder body itself is located more closely to one end of the enclosure, and the piston rod is extended by hydraulic pressure, outwardly, toward the other end of the enclosure.
A further feature of the invention includes a vertical yoke member which is centered on and attached, by clevis, or other means, to the end of the piston rod. Two separate lift cables extend rearwardly, substantially in parallel, from the yoke at the end of the piston rod, towards the end of the enclosure where the cylinder body is located. One of the lift cables continues such horizontal extension to a point closely approximate to the end of t
Bishop Douglas S.
Mayo Tara L.
Will Thomas B.
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