# Patent

## Title
Programmable boatlift system with boat position sensor

## Abstract

A programmable boatlift system having a cable extending up from one end of a boatlift cradle, across through a shaft attached to a motor, and down to an opposite end of the boatlift cradle. A position sensor having an idler sheave is placed on the cable, or a position sensor having a collar is placed on the shaft. The motor turns the shaft to cause the cable to move across the roller sheave, or to cause the collar to rotate, to raise or lower the boatlift cradle. The position sensor produces an output signal proportional to the distance the cable travels over the idler sheave or proportional to the number of rotations of the collar. An electronic control circuit uses the output signal to infer the vertical position of the boatlift cradle and to position the boatlift cradle as desired.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of patent application Ser. No. 11/937,937 now U.S. Pat. No. 7,534,069, filed Nov. 9, 2007, which is incorporated herein by reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a programmable boatlift system, and, more particularly, to a boatlift system that indicates the exact position of the boat within the lift system.
2. Technical Background
Programmable boatlift 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 boatlift 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 boatlift, so that a remote, programmable unit can position the boat automatically as desired.
SUMMARY OF THE INVENTION
The present invention is a boatlift 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 boatlift 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.
In an alternate embodiment of the boat position sensor, a collar is fixed circumferentially on the shaft and is fitted with the encoder to produce an electronic signal proportioned to the number of rotations of the collar as the shaft rotates during lifting and lowering of the lift cable.
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 boatlift 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.
FIG. 10 illustrates an alternate embodiment of the boat position sensor consisting of a collar fixed circumferentially to the rotating shaft and its axis.



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 down line 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's 17 final absolute position at power-down in non-volatile memory, so as to eliminate the need to recalibrate the boatlift cradle'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.
An alternate embodiment of the boat position sensor of the present invention is shown in FIG. 10. This boat position sensor 60 is attached to beam 14 by connections to shaft 19 and bracket 29. Boat position sensor 60 has a collar 61 which is fixed circumferentially to shaft 19 and to the axis of shaft 19. Collar 61 rotates in unison with shaft 19. Collar 61 has a plurality of holes 62 for the transmission of infrared (IR) light, similar to idler sheave 25. Position sensor 60 also has a quadrature encoder 63 which is similar to encoder 34 shown in FIG. 4, having IR transmitters and IR receivers. Encoder 63 is attached to a support plate 64 which is attached to bracket 29 so that encoder 63 is held in position over collar 61. Encoder 63 is connected electrically to the motor 18 by wire 65 and to the user keypad interface 27 by wire 66. Encoder 63 is positioned over collar 61 in the same way encoder 34 is positioned over sheave 25 as shown in FIG. 4. The detection of the IR signal through holes 62 in the collar 61, as the collar 61 is rotated by shaft 19, allows the encoder 63 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. As in the encoder 34, the two pairs of IR transmitters and IR receivers are set, preferably, about 165° apart relative to axis of the shaft 19.
The boat or shaft position sensor 60 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 collar 61 position input and user interface/keypad input to control the lift motor on/off and direction. The electronic control circuit 26 is programmable to automatically turn off the motor 18 after a fixed number of rotations of the collar 61 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.
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.

## Claims

1. A programmable boatlift system having a single motor, comprising:
a) a single first cable extending up from one end of a first boatlift cradle, and down to an opposite end of the first boatlift cradle, the single first cable being attached to a shaft therebetween, the shaft being attached to the motor;
b) a collar having a plurality of holes for the transmission of light, said collar fixed concentrically to said shaft and to the axis of said shaft, and rotating in unison with said shaft;
c) a quadrature encoder having two pairs of IR transmitters and IR receivers, said encoder placed over said collar, said two pairs of IR transmitters and IR receivers being set apart about 165 degrees relative to the axis of said shaft;
d) said IR transmitters transmitting infra red light through the holes in said collar and said IR receivers receiving said infra red light so that said encoder produces an electronic output signal in proportion to the number of rotations of said collar, and in proportion to the distance the single first cable travels; and
e) an electronic control circuit having a microcontroller, an in-circuit programming header, and a motor control circuit, said control circuit programmable to use said output signal to infer the exact position of the single first cable and the boatlift cradle without the requirement of a limit switch.

2. The boatlift system of claim 1 wherein said electronic control circuit is programmable to automatically turn off said motor after a fixed number of rotations of said collar in one direction, and after said fixed number of rotations in an opposite direction, and after any amount of rotations therebetween as desired.

3. The boatlift system of claim 1 further comprising a second boatlift cradle and a single second cable, with the single second cable extending up from one end of the second boatlift cradle, across to the shaft, and down to an opposite end of the second boatlift cradle, the single second cable being attached to the shaft.

4. A programmable boatlift system having a single motor, comprising:
a) a single first cable extending up from one end of a first boatlift cradle, and down to an opposite end of the first boatlift cradle, the single first cable being attached to a shaft therebetween, the shaft being attached to a motor;
b) a collar having a plurality of holes for the transmission of light, said collar fixed concentrically to said shaft and to the axis of said shaft, and rotating in unison with said shaft;
c) a quadrature encoder having two pairs of IR transmitters and IR receivers, said encoder placed over said collar, said two pairs of IR transmitters and IR receivers being set apart about 165 degrees relative to the axis of said shaft;
d) said IR transmitters transmitting infra red light through the holes in said collar and said IR receivers receiving said infra red light so that said encoder produces an electronic output signal in proportion to the number of rotations of said collar, and in proportion to the distance the single first cable travels;
e) an electronic control circuit having a microcontroller, an in-circuit programming header, and a motor control circuit, said control circuit programmable to use said output signal to infer the exact position of the single first cable and the boatlift cradle without the requirement of a limit switch; and
f) said electronic control circuit is programmable to automatically turn off said motor after a fixed number of rotations of said collar in one direction, and after said fixed number of rotations in an opposite direction, and after any amount of rotations therebetween as desired; and
g) a second boatlift cradle and a single second cable, with the single second cable extending up from one end of the second boatlift cradle, across to the shaft, and down to an opposite end of the second boatlift cradle, the second cable being attached to the shaft.