Abstract:
A transom bracket enclosing a hydraulic power cylinder is mounted to the transom of a watercraft. An actuation rod of the power cylinder moves multiple lift arms connected to a platform bracket supporting a platform for supporting a small auxiliary watercraft. Electrical or manual operation of the power cylinder causes the platform bracket to move in a vertical direction either upwards out of the water or downwards into the water. A lock mechanism operated by a lock cylinder locks the lift apparatus in place when not in operation. Grooves on sides of the transom bracket and transversely extended pins connecting the linkage arms provide a downward stop to movement of the lift apparatus.

Description:
FIELD OF THE INVENTION 
     This invention relates to hydraulic boat lifts. More particularly, it refers to a hydraulic lift mounted on the transom of a watercraft for lifting small auxiliary watercraft from the water, including support means for preventing damage caused by following seas. 
     DESCRIPTION OF THE INVENTION 
     Hydraulic operated boat lifts generally are well known as shown in U.S. Pat. Nos. 4,895,479; 5,184,914; 5,275,505; 5,890,835; and 5,919,000. None of these lift systems is adapted for mounting on the transom of a watercraft. Applicant has previously developed a vessel transom mounted hydraulic lift system for supporting a platform used to cradle an auxiliary watercraft. However, this system had a limitation which prevented practical utilization. During heavy following seas, the impact of water on the platform caused the hydraulic lift system arms to collapse. A hydraulic lift system is needed which will be practical for long term use mounted on the transom of a watercraft for the purpose of lifting small auxiliary watercraft out of the water and withstanding the impact of large waves during following seas. 
     SUMARRY OF THE INVENTION 
     This invention satisfies the need for an efficient and practical hydraulic lift system attached to a transom of a watercraft for lifting small auxiliary watercraft out of the water and withstanding wave action caused by following seas. The hydraulic lifting apparatus includes a transom bracket bolted to a transom of a watercraft, the transom bracket enclosing an hydraulic power cylinder operating multiple link arms causing a platform bracket to move in a vertical direction upwards from the water or down into the water. The platform bracket supports a platform and a boat cradle for supporting a small auxiliary watercraft. A locking plate operated by a hydraulic cylinder and grooves for receipt of a transverse pin lock the platform in an upright position and stops to prevent distortion of the action arms create a stable platform resistant to wave action. 
     The hydraulic power cylinder is either operated electrically or by a manual override connected to a hand pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be best understood by those having ordinary skill in the boat lift art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
     FIG. 1 is an elevational side view of the boat lift apparatus of this invention mounted to a boat transom and showing an auxiliary watercraft in phantom being lifted from the water. 
     FIG. 2 is an elevational side view of the boat lift apparatus according to FIG. 1, but with the boat lift apparatus mounted to a differently configured boat transom. 
     FIG. 3 is an isolated elevational side view of the boat lift apparatus. 
     FIG. 4 is a top plan view of the boat lift apparatus of FIG.  3 . 
     FIG. 5 is an elevational front view of the boat lift apparatus of FIG.  3 . 
     FIG. 6 is an exploded view of the hydraulic boat lift apparatus. 
     FIG. 7 is a schematic of the electrical system operating the hydraulic boat lift apparatus. 
     FIG. 8 is a schematic of the hydraulic system operating two hydraulic lifts for the boat lift apparatus. 
     FIG. 9 is a side elevation view of the manual system for operating the lift apparatus. 
     FIG. 10 is a prospective of a single hydraulic lift for a light duty platform attached to a small boat transom. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Throughout the following detailed description., the same reference numerals refer to the same element in all figures. Turning first to FIGS. 1 and 2, the hydraulic boat lift apparatus  10  is mounted to a boat  14  at its transom  12  or  12 A by a transom bracket  15 . In the boat  14  transom  12  is angled downward towards the waterline  28  and transom  12 A is angled upward. In either case, transom bracket  15  is mounted directly to transom  12  or  12 A. 
     The hydraulic boat lift apparatus  10  has a pair of parallel inboard lift arms  16  and  18 , each having a distal end  17  and  19  respectively mounted within a platform bracket  20 . The platform bracket  20  supports a platform  22  and an auxiliary watercraft cradle  24  on which an auxiliary watercraft  26  is mounted. 
     Turning to FIGS. 3-6, the inboard lift arm  16  has a bore  23  at a proximal end  31  and inboard lift arm  18  has a bore  21  at proximal end  29 . A first transverse pin  52  passes through bores  21  and  23  and extends outwardly from both bores  21  and  23 . 
     A power cylinder  30  has a unitary construction with a transverse bore at the blind end  35  through which a support pin  37  passes. The power cylinder rod  34  has a transverse coupler  50  distal from the power cylinder  30 . A second transverse pin  44  passes through coupler  50  and connects to transverse bores  56  and  58  positioned proximal to bores  23  and  21  respectively on arms  16  and  18  respectively. 
     A hydraulic fluid conduit  60  leads to a lock cylinder  32  attached to a plate  62  having a locking groove  70 . In the locked position groove  70  engages outward transverse projection  72  on a port side outboard lift arm  40 . Actuation of the system  10  as seen in FIGS. 7 and 8 causes plate  62  to pivot and release transverse projection  72 . 
     Another outboard lift arm  42  parallel to lift arm  40 , has a back end  64  containing a transverse bore  66  corresponding to back end  74  containing a transverse bore  76  on lift arm  40 . Bores  66  and  76  have a pin  46  passing therethrough as well as through side elements  80  and  82  of transom bracket  15 . A front end  84  of lift arm  42  has a bore  86  connecting to front end  88  through bore  90  of arm  40  by third pin  110 . Lift arms  42  and  40  respectively engage the ends of pin  52  on a downward movement so that the ends of pin  52  act as a positive stop. In this way, the outboard arms  42  and  40  cannot fold back over center when additional pressure is caused by wave action on the platform  22 . 
     Platform bracket  20  has a slot  92  and  94  on each side through which ends of fourth pin  96  pass. Pin  96  passes through a bore on the proximal end  98  of an adjuster rod  54 . A distal half  100  of the adjuster rod  54  is threaded and a pin  48  moves along the threads to adjust the angle of repose of the platform bracket  20 . The pin  48  is attached to platform bracket  20  at transverse bores  102  and  104 . Links  106  and  108  connect pin  96  to pin  110  which engages bores  90  and  86  respectively on outboard lift arms  40  and  42 . Pin  96  also engages links  108  and  106  to bores  17  and  19  respectively on inboard lift arms  16  and  18 . Third pin  110  also passes through transverse bore  112  and  114  on platform bracket  20 . 
     Operation of the hydraulic lift system  10  shown in FIG. 7 is initiated by a hand held control  116 . Pushing one of the up or down buttons activates the motor  118  which causes the hydraulic pump  120  to cause the lock cylinder  32  to unlock pin  72  and allow movement of the arms by power cylinder  30 . 
     Grooves  122  and  124  on side elements  82  and  80  respectively of the transom bracket engage the ends of second pin  44  to limit the travel of the boat lift apparatus  10  in an upward configuration. 
     As shown in FIG. 9, handle  125  is moved in and out to operate pump  120  and cause a flow of oil in the block manifold  126  to operate the hydraulic lift system manually. 
     While it requires a pair of hydraulic boat lift apparatus to lift platform  22 , a single hydraulic boat lift apparatus as shown in FIG. 10 is sufficient to lift a platform operated by the lift apparatus attached to transom  12 B. 
     Various changes, modifications and alterations can be contemplated by those skilled in the art without departing from the intended spirit and scope thereof. As such, it is intended that the present invention only be limited by the terms of the appended claims.