Patent Publication Number: US-7707955-B1

Title: Transom platform lifting apparatus and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional Applications Ser. No. 60/954,467 filed Aug. 7, 2007 for “Lifting Apparatus and Method,” Ser. No. 60/957,041 filed Aug. 21, 2007 for “Transom Platform and Dinghy Chock Lifting Apparatus and Method,” and Ser. No. 60/981,153 filed Oct. 19, 2007 for “Transom Platform and Dinghy Chock Lifting Apparatus and Method,” the disclosures of which are hereby incorporated by reference herein in their entirety, and all commonly owned. 

   FIELD OF INVENTION 
   The present invention generally relates to mechanical lifting devices and more particularly to lifts useful as a marine accessory. 
   BACKGROUND 
   While dock mounted and transom mounted davits and lifts are well known, improvements have been developed throughout the years as described in U.S. Pat. No. 7,293,521 to Johns, JR. et al. for “Hydraulic Transom Lift,” the disclosure of which is herein incorporated by reference in its entirety. As described in the Johns &#39;521 patent, a transom mounted lift assembly includes a lift arm operable with an actuator for rotating the lift arm. A lift arm extension member has a cradle attached for carrying a watercraft such as a dinghy. Once the watercraft is lifted to a storage position, the lift assembly is locked into position using a latch having a hook rotated onto a latch pin. Both the lift actuator and the latch actuator are driven by a hydraulic power pack. One need for the locking and thus the latch results from typically slow pressure drops in the hydraulic lines feeding fluid and pressure to the actuators. Such need to secure the lift assembly in a stored position is well known in the art, as further illustrated with reference to U.S. Pat. No. 6,327,992 to Martin for “Hydraulic Lift for Small Watercraft Mounted to a Boat Transom,” wherein a locking cylinder actuates a plate having a hook for securing the lifting apparatus in a stored position. The present invention is directed to improving a lift and avoiding the need for added equipment such as the locking latch, by way of example. 
   SUMMARY 
   The present invention may be described as a lifting apparatus comprising a base and a lift arm having a proximal end and a distal end, the proximal end pivotally attached to the base for a generally vertical rotation of the lift arm about a lift arm proximal pivot axis, wherein the lift arm distal end is moveable between a lowered position and a raised position. A crank arm having a proximal end and a distal end may include the proximal end pivotally attached to the base for rotation of the crank arm about a crank arm proximal pivot axis. A connector arm having a proximal end and a distal end may include the proximal end pivotally attached to the lift arm for rotation about a connector arm proximal pivot axis, and the distal end pivotally attached to the distal end of the crank arm for rotation about a common connector arm to crank arm distal pivot axis. An actuator is operable with at least one of the crank arm and the connector arm for rotational movement thereof. 
   One embodiment may comprise the rotation of the connector arm and the crank arm such that in combination the connector arm and the crank arm are movable from a top dead center alignment having the common connector arm to crank arm distal pivot axis in a straight line alignment with both the connector arm proximal pivot axis and the crank arm proximal pivot axis, and wherein the actuator causes movement of the crank arm and the connector arm from the top dead center alignment to lowered over center alignments with the lift arm movable from the lowered position to the raised position during operating positions of the apparatus, to raised over center alignments with limited movement of the lift arm in the raised position during a locking position of the apparatus. Yet further, a stop may be positioned for limiting a range of movement of the lift arm during the raised over center alignment of the connector arm and the crank arm. 
   Associated methods may comprise operating the actuator for rotating the crank arm in a counter clockwise direction, wherein the counter clockwise rotation of the crank arm results in a lowering of the lift arm distal end to a lowered position of the lifting apparatus, and operating the actuator for rotating the crank arm in a clockwise direction, wherein the clockwise rotation of the crank arm results in a raising of the lift arm distal end to a raised position of the lifting apparatus. The crank arm and the connector arm in combination may be rotated through a top dead center alignment, wherein a rotation axis of the pivot pin assembly, a common connector arm to crank arm distal pivot axis, is in a straight line alignment with both the connector arm proximal pivot axis and the crank arm proximal pivot axis, to a raised over center alignment in the raised position, wherein the raised over center alignment results in the pivot pin assembly hitting a stop and thus preventing further clockwise rotation of the crank arm and thus providing a locking position of the apparatus. Yet further, the crank arm may be rotated in a counter clockwise direction for moving the apparatus from the over center position of the locking position through the top dead center alignment, wherein the rotation axis of the pivot pin assembly moves beyond the straight line alignment to a lowered over center alignment permits movement of the lift arm distal end to the lowered position. 
   Embodiments of the present invention directed to a lifting apparatus having a mechanical locking feature are herein described by way of example and may include a lift arms pivotally attached to a base plate, which base plate may be mounted to a transom or supporting structure such as a dock. An actuator such as a hydraulic piston may be operable with linking elements to raise ad lower the lift arm. One linking element includes a crank arm and connector arm operable with the actuator. Operation of the lift arm from a lowermost position through intermediate positions and to an upper position provides the lifting function. As the actuator operates to pull the crank arm upward through the action of the piston rod pulling from the piston rod pivot axis, the connector arm pivot rod is moved beyond an axis or plane for which the connector arm longitudinal axis and the crank arm longitudinal axis are coincident or within the plane. Such an action causes the connector arm pivot axis rod to be biased against the cylinder wall (or alternatively a separate stop element) under gravitational force from the weight of the lift arm. As a result, the hydraulic pressure in the lines feeding the actuator may be released allowing the linking elements to be held in a stored position. When it is time to lower the lift arm, hydraulic pressure is provided to the actuator for moving the piston rod outward and driving the crank arm to a lowering position. A platform may be attached to the lift arm with a leveling arm cooperating with the lift arm to maintain the platform in a generally horizontal position throughout its movement. Yet further, a chock assembly may be carried by the platform. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     For a fuller understanding of the invention, reference is made to the following detailed description, taken in connection with the accompanying drawings illustrating various embodiments of the present invention, in which: 
       FIG. 1  is a perspective view of one embodiment of a lifting apparatus in keeping with the teachings of the present invention; 
       FIGS. 2 and 3  are front and top views, respectively, of the lifting apparatus of  FIG. 1 ; 
       FIGS. 4 and 5  are partial side views illustrating the lifting apparatus of  FIG. 1  is a lowered position and a raised position, respectively; 
       FIG. 6  is a diagrammatical illustration of linkage in a top dead center (TDC) and raised and lowered over center (OC) orientations, respectively; 
       FIG. 7  is a side view of the embodiment of  FIG. 1  illustrating linkage members in a locking position; 
       FIG. 8  is a partial side view of the apparatus of  FIG. 1  illustrated in an intermediate lowered position; 
       FIG. 9  is a perspective view of one embodiment of the invention including a platform carried by the lifting apparatus of  FIG. 1 ; 
       FIGS. 10 and 11  are partial side views illustrating raised and lowered positions of the platform; 
       FIG. 12  illustrates an alternate embodiment of the invention, wherein the platform includes a chock assembly illustrated in a stowed position; 
       FIG. 13  illustrates the chock assembly of  FIG. 12  in a deployed position; and 
       FIG. 14  illustrates the embodiment of  FIG. 12  during a lifting position of the platform having the chock assembly in the deployed position. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   The present invention will now be described more fully with reference to the accompanying drawings in which alternate embodiments of the invention are shown and described. It is to be understood that the invention may be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure may be thorough and complete, and will convey the scope of the invention to those skilled in the art. 
   One embodiment of the present invention is illustrated with reference initially to  FIGS. 1-3  illustrating, by way of example, a lifting apparatus  10  comprising a base  12 . A lift arm  14  is herein described as having a proximal end  16  and a distal end  18 . The proximal end  16  is pivotally attached to the base  12  for a generally vertical rotation of the lift arm  14  about a lift arm proximal pivot axis  20 , wherein the lift arm distal end  18  and thus the apparatus  10  is moveable between a lowered position  22  and a raised position  24 , as illustrated with reference to  FIGS. 4 and 5 , respectively. With continued reference to  FIGS. 1-3 , a crank arm  26  herein described as including a proximal end  28  and a distal end  30  has its proximal end  28  pivotally attached to the base  12  for rotation of the crank arm  26  about a crank arm proximal pivot axis  32 . A connector arm  34  herein described as including a proximal end  36  and a distal end  38  has its proximal end  36  pivotally attached to the lift arm  14  for rotation of the connector arm  34  about a connector arm proximal pivot axis  40 . The distal end  38  of the connector arm  34  is pivotally attached to the distal end  30  of the crank arm  26  for rotation about a common connector arm to crank arm distal pivot axis  42 . For the embodiment herein described by way of example, an actuator  44  is pivotally connected between the base  12  and the crank arm  26 . However, it will be clear to those skilled in the art to connect the actuator  44  to alternate elements such as the connector arm  34  for imparting rotations movement of the arms  14 ,  26 ,  34 , now having the benefit of the teachings of the present invention. For clarity and focus on invention, the above description makes reference to arms  14 ,  26 ,  34  for the apparatus  10 , but as is clear, reference may be made to arm pairs as will be further described later in this section. 
   With reference again to  FIGS. 4 and 5 , and to  FIG. 6 , the rotation of the connector arm  34  and the crank arm  26  are such that in combination, the connector arm  34  and the crank arm  26  are movable through a top dead center (TDC) alignment  46  having the common connector arm to crank arm distal pivot axis  42  in a straight line  48  alignment with both the connector arm proximal pivot axis  40  and the crank arm proximal pivot axis  32 . With reference to  FIG. 6 , the crank arm  26  is illustrated using a crank arm longitudinal axis  26   a  and the connector arm  34  is illustrated using a connector arm longitudinal axis  34   a . The lift arm  14  is diagrammatically illustrated using an effective lift arm axis  14   a . The actuator  44  moves the crank arm  26  and the connector arm  34  from the top dead center alignment  46  to lowered over center alignments  50 , illustrated with reference to  FIGS. 5 and 6 , with the lift arm  14  movable from the lowered position  22 , illustrated with reference again to  FIG. 4 . By way of example, the lift arm  14  may be raised to the raised position  24 , illustrated with reference again to  FIG. 5 , during operating positions of the apparatus  10  for raising and lowering the lift arm  14  for such events as lifting and lowering a dinghy as earlier described with reference to U.S. Pat. No. 7,293,521 and for raising and lowering a platform as will be described later in this section. 
   With reference again to  FIG. 6  and now to  FIG. 7 , the apparatus  10  as herein described, may be raised to over center alignments, herein referred to as raised over center alignments  52  where there is a restricted and more limited movement of the lift arm  14  for setting the apparatus  10  in a locking position  54 . With reference again to  FIGS. 1 and 7 , a stop  56  may be positioned for limiting a range of movement of the lift arm  14  during the raised over center alignment  52  of the connector arm  26  and the crank arm  26  positioned for receiving the crank arm there against. As later described, the actuator  44  may provide the stop  56 . 
   For the embodiment herein described by way of example, and with reference again to  FIGS. 1 and 2 , and to  FIG. 8 , the actuator  44  comprises a housing  58  such as a cylinder, and a rod  60 , such as a piston rod extendable into and out of the housing  58 . The actuator  44  may comprise well known hydraulic, pneumatic, electric, or the like actuation to the rod  60 . For the embodiment herein described by way of example, the housing  58  is pivotally connected to the base  12  at pivot point  62  and the rod  60  is pivotally connected to the crank arm  26  at pivot point  64 . In one embodiment, an outside surface  66  of the housing  58  may provide the stop  56  earlier described for limiting the movement of the common connector arm to crank arm distal pivot axis  42  with the axis defined by axis assembly  68  contacting the housing  58  when in the raised over center alignment  52 , thus limiting the movement of the lift arm  14  in the raised position in the locking position  54 . As herein illustrated, only a single actuator  44  may be employed. 
   In operation, a user may operate the actuator for rotating the crank arm in a counter clockwise direction, wherein the counter clockwise rotation of the crank arm results in a lowering of the lift arm distal end to a lowered position of the lifting apparatus, and operate the actuator for rotating the crank arm in a clockwise direction, wherein the clockwise rotation of the crank arm results in a raising of the lift arm distal end to a raised position of the lifting apparatus. The crank arm may be rotated so as to rotate the crank arm and the connector arm in combination through a top dead center alignment, wherein a rotation axis of the pivot pin assembly, a common connector arm to crank arm distal pivot axis, is in a straight line alignment with both the connector arm proximal pivot axis and the crank arm proximal pivot axis, to a raised over center alignment in the raised position, wherein the raised over center alignment results in the pivot pin assembly hitting the stop and thus preventing further clockwise rotation of the crank arm for placing the apparatus in the locking position. Rotating the crank arm in a counter clockwise direction may move the apparatus from the over center position of the locking position through the top dead center alignment, wherein the rotation axis of the pivot pin assembly moves beyond the straight line alignment to a lowered over center alignment permits movement of the lift arm distal end to the lowered position. 
   Thus, when the connector arm longitudinal axis and the crank arm longitudinal axis are beyond a coincident alignment and on the cylinder side of the coincident alignment with the connector arm pivot axis skewed upward, the connector arm pivot axis rod is biased against the stop. As a result, under a force of gravity, the connector arm applies a force on the connector arm distal pivot axis resulting in the biasing force of the proximal pivot axis toward the cylinder. In this skewed orientation, there is no need to use the actuator to hold the lift arm and no need for a latch to secure the lift arm in the elevated dinghy storage position. The lift arm will remain in this locked position as a result of gravity alone. Such a “mechanical lock” is a safety feature accommodating, by way of example, an event including a hydraulic breach or failure of a related electrical system. The apparatus remains in a safe and stowed position until a positive action is initiated by a user. 
   With reference now to  FIGS. 9-11 , one embodiment of the invention includes a platform  70  operable with the lifting apparatus  10  above described. The platform  70  is pivotally attached to the distal end  18  of the life arm  14 . A leveling arm  72  is pivotally connected between the platform  70  and the base  12 , wherein the leveling arm  72  and lift arm  14  in combination cause the platform  72  to be maintained in a generally horizontal orientation  74  during movement of the apparatus  10  between the raised position  24  and the lowered position  22  earlier described with reference to  FIGS. 4 and 5 , by way of example. For one embodiment of the invention as herein described, a platform support  76  is secured to a bottom surface  78  of the platform  70 . As illustrated, the platform support  78  includes first and second pivot pins  80 ,  82  with the first pivot pin  80  proximate the platform bottom surface  78  and the second pivot pin  82  further distanced from the bottom surface  78  than the first pivot pin  80 . The distal end  18  of the lift arm  14  is pivotally connected to the first pivot pin  80  and the leveling arm  72  is pivotally connected to the second pivot pin  82 . 
   In one embodiment as illustrated with reference to  FIG. 10 , by way of example, an adjustment element  84  such as a threaded rod, is operable with the leveling arm  72  between the base  12  and the platform support  76  for modifying a length dimension of the leveling arm  72  and thus providing a leveling adjustment to the platform  70 . A fine adjustment in the platform leveling may thus be achieved. 
   As illustrated with reference to  FIGS. 12-14 , one embodiment may comprise the platform  70  having a cavity  86  accessible from a top surface  88  of the platform  70 . A chock assembly  90  is foldable into the cavity  86  during a stowed position  92 , as illustrated with reference to  FIG. 12 , and out of the cavity  86  into a deployed position  94 , as illustrated with reference to  FIG. 13 . As herein illustrated by way of example, two cavities  86  and chock assemblies  90  will typically be employed. 
   The embodiment herein described, by way of example, while reference is made to single elements, includes lift arm pairs forming pivotally attached to a base plate. As illustrated with reference to  FIGS. 9-11 , the base  12  may be mounted to a transom  96  of a boat  98  or supporting structure such as a dock. 
   As a result of the above described apparatus  10 , one of skill in the art will appreciate that pressure in lines feeding a pneumatic or hydraulic actuator, or power to an electric actuator, may be released allowing the lifting apparatus  10  and thus the platform  70  or dinghy being carried by the chock assemble  90  to be held in a stored position, the locking position  54  without concern. When it is time to lower the platform  70 , pressure is provided to the actuator  44  for moving the piston rod  60  outward and driving the crank arm  26  for lowering the lift arm  14 . 
   Depending upon a need, strengthening of the lift arm  14  or other structural supports may be improved using various selected materials and/or gussets, by way of example, and as illustrated with reference again to  FIG. 10 . Consistent with the embodiment illustrated and as above described, the lift arm  14  comprises a lift arm pair having proximal ends pivotally attached to the base  12 , the crank arm  26  comprises a crank arm pair having proximal ends pivotally attached to the base  12 , and the connector arm  34  comprises a connector arm pair having proximal ends pivotally attached to the lift arm pair for rotation about a connector arm proximal pivot pin, and distal ends pivotally attached to the distal ends of the crank arm pair for rotation about a common connector arm to crank arm distal pivot pin. Additional strength may be obtained in such a structure by a cross beam  102 , illustrated by way of example with reference again to  FIGS. 1-3 , wherein the cross beam  102  provides a rigid connection between the lift arms  14  of the lift arm pair. 
   Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and alternate embodiments are intended to be included within the scope of the claims supported by this disclosure.