Patent Publication Number: US-2009220300-A1

Title: Programmable boatlift system with boat position sensor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of pending patent application No. 11/937,937 filed Nov. 9, 2007, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a programmable boatlift system, and, more particularly, to a boat lift system that indicates the exact position of the boat within the lift system. 
     BACKGROUND OF THE INVENTION 
     Programmable boat lift systems are known but they require two cables on each side of the boat, two at the front and two at the rear of the boat. Two motors are required, one for each side of the boat to operate the cables. The use of level sensors is known to stop or start the motors to position the boat as desired, but these sensors must be placed near the boat and move up and down with the boat. They require the use of mercury switches and float switches and can be exposed to water as the boat is placed into the water. The plurality of motors, cables, and sensors in these systems create a need for constant maintenance and repair. A cable system for a boat lift using a single motor is known but it is not suitable for detecting the position of the boat within the lift system. 
     What is needed is a boatlift system that operates with a single motor, with a single cable at the front of the boat, a single cable at the back of the boat, and a simple sensor that measures the actual position of the boat within the boat lift, so that a remote, programmable unit can position the boat automatically as desired. 
     SUMMARY OF THE INVENTION 
     The present invention is a boat lift system having a boatlift structure with a front end, a back end, and vertical and horizontal support beams. Boatlift cradles are positioned among the support beams and are connected to the upper portion of the boatlift structure by a steel cable at the front of the boatlift structure and a steel cable at the back end of the boatlift structure. The cables extend from one side of the cradle upwards towards a pulley, horizontally across the boatlift structure towards a shaft rotated by a motor, through a hole in the shaft, and downward to the lift cradle. An idler sheave is placed on one of the cables on the portion that extends horizontally across the boat lift structure. The sheave is fitted with a quadrature encoder to produce an electronic signal proportioned to the number of rotations of the sheave as the cable moves across the sheave during lifting or lowering of the lift cable. The signal from the encoder is sent to an electronic control circuit which uses the encoder signal to infer the vertical position of the boat or lift cradle within the boatlift structure. The electronic control circuit consists of a microcontroller with non-volatile memory, oscillator, and related circuitry for receiving and sending electronic signals. The electronic control circuit will also receive signals from a user input keypad which allows a user to invoke the end functions of the programmable boatlift system, and the electronic control circuit will send signals to the motor to turn the boat motor on and off, in either direction based upon the programming in the electronic control circuit. Because the boat position sensor provides the exact vertical position of the boat within the boatlift structure, limit sensors, float sensors, moisture sensors, and timers are not required for operation of the boatlift system. 
     An advantage of the present invention is a programmable boatlift system that requires only two cables. 
     Another advantage is a single boat position sensor which determines the exact position of the boat within the boat structure. 
     Another advantage is a single motor to raise and lower the boat. 
     Another advantage is a simple, durable, idler sheave with a quadrature encoder to sense the boat position. 
     Another advantage is a programmable control unit with a remote control to automatically position the boat within the boat lift structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the boatlift structure of the programmable boatlift system of the present invention. 
         FIG. 2  shows the winch mechanism of the present invention. 
         FIG. 3  shows the idler sheave with IR detectors engaging the lift cable. 
         FIG. 4  shows a view of the idler sheave and quadrature encoder viewed along the length of the cable. 
         FIG. 5  shows the electronic components of the programmable boatlift system. 
         FIG. 6  shows the electronic components of the electronic control circuit. 
         FIG. 7  is an electrical schematic of the microcontroller of the electronic control circuit. 
         FIG. 8  is an electrical schematic of the rotary encoder and connector of the boat position sensor. 
         FIG. 9  is an electrical schematic of the user keypad interface. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows the boatlift structure  11  of the boatlift system  10  of the present invention. The boatlift structure  11  has a front end  12  and a back end  13 . The boatlift structure  11  is supported by four vertical beams  14 , and has right side  15  and left side  16 . A boatlift cradle  17  is suspended by a cable  21  from the upper ends of beams  14 . A motor  18  is attached to the upper end of a beam  14  at the back end  13  and left side  16  of the boatlift structure  11 . The motor  18  has shaft  19  that extends from the motor  18  to a bearing  20  attached at the upper end of a beam  14  at the front end  12  and left side  16  of the boatlift structure  11 . Bearing  20  supports shaft  19  as motor  18  rotates shaft  19 . 
     Cable  21  is attached to one side  22  of boatlift cradle  17  and extends upward therefrom to pulley  50 , from there across to shaft  19 , and from there down to the opposite side  23  of boatlift cradle  17 . A boat position sensor  24  is attached to boatlift structure  11  and engages cable  21  by means of an idler sheave  25 . The boat position sensor  24  is connected electrically to motor  18  by a wire  28  and to a user key pad interface  27  by a wire  54 . 
       FIG. 2  shows the shaft  19  attached to a beam  14  by a bracket  29  at back end  13 , right side  16  of boatlift structure  11 . The shaft  19  is supported by bearings  30 . Shaft  19  has hole  31  through which cable  21  is inserted. As motor  18  turns the portions of cable  21  extending upward from each side  22 ,  23  of boatlift cradle  17  are wound around shaft  19  in the same direction. The portions of the cable attached to sides  22 ,  23  of boatlift cradle  17 , thus, lift or lower boatlift cradle  17  in a level horizontal position. Although not shown, a similar cable and boatlift cradle arrangement is at the front end  12  of boatlift structure  11 , wherein the cable passes through a second hole in shaft  19 . Thus, there are two boatlift cradles, each with its own cable arrangement wherein the cables lift or lower both boatlift cradles in unison as the motor  18  rotates shaft  19  which acts as a winch. With a boatlift cradle at the front of a boat and at the rear of the boat, the rotation of shaft  19  by motor  18  will raise and lower the boat in a level position, both horizontally and vertically. 
       FIG. 3  shows the idler sheave  25  of the boat position sensor  24  in place on cable  21 . Sheave  25  rotates on an axle  51 . Sheave  25  has a plurality of holes for transmission of infrared (IR) light which is detected by IR detectors  53 .  FIG. 4  shows the boat position sensor  24  looking downline along cable  21 .  FIG. 4  further shows a quadrature encoder  34  in place over idler sheave  25  and IR transmitters  52 . The detection of the IR signal through holes  32  in the sheave  25 , as the sheave  25  is rotated by cable  21 , allows the encoder  34  to produce an output signal directly proportional to the distance cable  21  has traveled as it raises or lowers the boatlift cradle  17 . Thus, this output signal is directly proportional to the absolute amount a boat in the boatlift cradle  17  has been raised or lowered by the cables. The two pairs of IR transmitters  52  and receivers  53  are set, preferably, about 165° apart relative to axle  51  of sheave  25 . 
       FIG. 5  shows a block diagram of the electrical and functional components of the programmable boatlift system  10  of the present invention. An AC inlet and power supply circuit  36  interfaces with line voltage and provides for the power requirements of the circuitry. The power supply  36  provides  12  volt line voltage to a motor control circuit  35 . A 5 volt line voltage is supplied to an electronic control circuit  26 . This 5 volt line voltage can operate for a short period of time after external power is removed. This will allow the electronic control circuit  26  to record the boatlift cradle&#39;s  17  final absolute position at power-down in non-volatile memory, so as to eliminate the need to recalibrate the boatlift cradle&#39;s  17  position when power is restored. Motor control relays in the motor control circuit  35  turn the boatlift motor  18  on and off, in either direction, based upon input from the electronic control circuit  26 . 
     The boat or cable position sensor  24  provides an output signal to the electronic control circuit  26  which uses this signal to infer the absolute position of the boatlift cradle  17 . A user interface or keypad  27  allows a user to invoke the function of the programmable boatlift system  10  through keys or push buttons. The electronic control circuit  26  encompasses all logical operations of the circuitry and interfaces with the cable position input and user interface/keypad input to control the lift motor on/off and direction. 
     The components of the electronic control circuit  26  are shown in  FIG. 6 . It consists of a microcontroller  38  with non-volatile memory, an oscillator, and related circuitry to interface with all other parts of the circuitry. Electronic control circuit  26  also contains an in-circuit programming header  37 , a motor control circuit  41 , limit switch circuits  39 , and a buzzer/power loss circuit  40 .  FIG. 7  shows an electrical schematic of a microcontroller  38 .  FIG. 8  shows an electrical schematic of the rotary encoder  34  and connector.  FIG. 9  shows an electrical schematic of the user keypad  27  and connector. A remote control unit can also be used to operate the user keypad  27 . A user can press up, down, or stop keys to make the boatlift cradle  17  go up or down or stop at any desired position. An enter key can be used to program the electronic control circuit  26  to raise and lower the boatlift cradle a desired amount by pressing other keys, such as, for example, keys labeled “winter”, “night”, “water”, etc. The electronic control circuit  26  is programmable to automatically turn off the motor  18  after a fixed number of rotations of the idler sheave  25  in one direction, and after the same fixed number of rotations in an opposite direction, and at any amount of rotations there between. 
     The foregoing description has been limited to specific embodiments of this invention. It will be apparent; however, that variations and modifications may be made by those skilled in the art to the disclosed embodiments of the invention, with the attainment of some or all of its advantages and without departing from the spirit and scope of the present invention. For example, various types of known microprocessing, memory, and programming devices may be used in the electronic control circuit. Various types of rotary encoders known in the art may be used with the idler sheave. Other emitters and detectors may be used in the encoder besides infrared. The electronic control circuit can be programmed to lock after a certain amount of time for security purposes, and a pass code can be entered into the user key pad to unlock the electronic control circuit. The electronic control circuit can be programmed to produce an alarm before the motor is turned on. A wireless remote device can be used to access the electronic control circuit and/or user key pad. One or more limit switches can be used for safety purposes to turn off the motor in case of a malfunction in the system. 
     It will be understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated above in order to explain the nature of this invention may be made by those skilled in the art without departing from the principle and scope of the invention as recited in the following claims.