Hydraulic and earth engineering – Marine vessel portage – launching – or removing – Lifting
Reexamination Certificate
1999-05-21
2001-11-20
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Marine vessel portage, launching, or removing
Lifting
C114S044000, C114S048000, C254S01000C, C414S678000
Reexamination Certificate
active
06318929
ABSTRACT:
TECHNICAL FIELD
The invention relates to lifting devices, and in particular to devices for lifting watercraft, for example, boats and sea planes.
BACKGROUND OF THE INVENTION
Known is U.S. Pat. No. 5,184,914 issued to the inventor of the present invention which is incorporated herein by reference and discloses a watercraft lifting device having a rectangular stationary base formed of two longitudinal parallel beams and two transverse beams, generally described as front and rear transverse beams. The rectangular base is submersible under water. Pivoting booms connect each of the four corners of the rectangular base to swingable mounting arms positioned parallel to and coplanar with each of the longitudinal beams to form two pairs of pivoting booms, generally described as front and rear pivoting booms. The two pair of pivoting booms form with the mounting arms collapsing parallelograms on which watercraft supports extended a predetermined distance above the mounting arms hold the craft during lifting. A double-acting hydraulic cylinder is pivotally connected to the rear transverse beam and its piston rod is pivotally connected to the two front pivoting booms such that expansive energization of the double-acting hydraulic cylinder extends the piston rod and swings front pair of pivoting booms upward from a collapsed attitude. The parallelogram linkage forces the mounting arms and rear pair of pivoting booms to follow the front pair of pivoting booms. Thus, expansive energization of the double-acting hydraulic cylinder raises the front pair of pivoting booms and lifts the rear pair of pivoting booms, the mounting arms and the watercraft supports attached to the mounting arms upward to lift a watercraft out of the water. Upward movement continues until the pivoting booms pass through a vertical orientation into an overcenter orientation whereby the watercraft is supported above the surface of the water.
Retractive energization of the double-acting hydraulic cylinder retracts the piston rod into the piston jacket of the double-acting hydraulic cylinder and reverses the motion of the pivoting booms. Thus, retractive energization of the double-acting hydraulic cylinder first raises the pivoting booms and lifts the mounting arms and watercraft supports attached to the mounting arms upward. Upward movement causes the pivoting booms to pass back through vertical orientation. Continued retraction of the piston rod into the double-acting hydraulic cylinder combined with the weight of the latching apparatus and the watercraft collapses the parallelograms whereby the watercraft is lowered into the water. The piston rod continues to retract into the double-acting hydraulic cylinder collapsing the parallelograms, including the mounting arms and watercraft supports attached to the mounting arms, until contact between the watercraft supports and the watercraft is broken and the watercraft can float free.
Although the apparatus of the prior art operates effectively in many practical applications, a need exists for a watercraft lifting apparatus which operates effectively in shallow water applications where the typical water depth is minimal and the apparatus of the prior art cannot collapse sufficiently to break contact between the watercraft supports and the watercraft and release the watercraft to float free.
SUMMARY OF THE INVENTION
The present invention resolves limitations of the prior art by providing a low profile watercraft lifting apparatus. The present invention is a watercraft lifting apparatus which includes a generally rectangular base adapted to be submerged under water. The base is formed of two longitudinal beams joined by two transverse beams generally described as front and rear transverse beams. Pivoting booms connect each of the four corners of the rectangular base to swingable mounting arms positioned generally parallel with the longitudinal beams to form two pairs of pivoting booms, generally described as a front pair of pivoting booms and a rear pair of pivoting booms. The pivoting booms form with the mounting arms collapsing mock parallelograms on which watercraft supports hold the craft during lifting.
According to one aspect of the present invention, the low profile lifting apparatus of the present invention provides a self-guiding watercraft entry attitude by providing the pivot points for the rear pair of pivoting booms at a position above the pivot points for the front pair of pivoting booms. Positioning the rear boom pivot points above the pivot points for the front pair of pivoting booms provides a mock parallelogram shape in a side elevation view wherein the rear pair of pivoting booms and thus the rear ends of the mounting arms are positioned at a lower attitude than the front ends of the mounting arms and are angled downwardly from the higher elevation of the front ends of the mounting arms when the lifting apparatus is in a collapsed attitude. In one preferred embodiment, the pivot points for the rear pair of pivoting booms at a position above the centerline of the longitudinal beams of the base.
According to another aspect of the present invention, the self-guiding watercraft entry attitude provided by the positioning of the rear boom pivot points above the front boom pivot points is accentuated by providing the pivot points for the front pair of pivoting booms at a position below the centerline of the longitudinal beams of the base. Positioning the front boom pivot points below the longitudinal beam centerline provides an accentuated mock parallelogram shape in a side elevation view by accentuating the downward angle of the mounting arms when the lifting apparatus is collapsed. Furthermore, varying the lengths of the front and rear pivoting booms by the amount of the off-set between the front and rear boom pivoting points reduces the downward angle of the mounting arms when the booms are fully extended such that mounting arms are essentially parallel with the longitudinal beams of the base when the lifting apparatus is in an upright or extended orientation.
According to yet another aspect of the invention, each pair of pivoting booms are positioned either inward or outward of the two longitudinal beams of the base rather than coplanar with the longitudinal beams. Thus, the booms collapse into a side-by-side orientation with the longitudinal beams of the base providing a lower profile lifting apparatus as compared with the prior art apparatus by providing more complete collapsing of the mock parallelogram.
According to another aspect of the invention, a low profile lifting apparatus is provided by providing one or more convex-shaped cross supports or cross braces joining the pair of rear pivoting booms. The shaped cross supports or cross braces provide a low profile lifting apparatus by reducing the dimension by which the watercraft supports must be extended above the mounting arms to provide a hull-clearing channel portion for shaped boat hulls. At least one cross brace joining the pair of rear pivoting booms is positioned adjacent the pivot points on the longitudinal beams and provides a boom extension projecting downward beneath the level of the pivot points. A double-acting hydraulic cylinder or other suitable actuator is pivotally connected between the downward projecting boom extension on the rear pair of pivoting booms and the front pair of pivoting booms such that expansive energization of the double-acting hydraulic cylinder extends the piston rod and swings both pairs of pivoting booms upward from a collapsed attitude. Thus, expansive energization of the double-acting hydraulic cylinder causes the hydraulic cylinder to exert a first rotational force against the front pair of pivoting booms which rotates the front pair of pivoting booms upward and a second equal and opposite rotational force on the downward projecting boom extension of the cross braces on the rear pair of pivoting booms which acts over a lever arm distance and causes the rear pair of pivoting booms to rotate upward.
According to another aspect of the present invention, pivotally connec
Pechhold Alexandra K.
Seed IP Law Group PLLC
Will Thomas B.
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