AU2012201899A1

AU2012201899A1 - Boat Lifting Apparatus and Method

Info

Publication number: AU2012201899A1
Application number: AU2012201899A
Authority: AU
Inventors: Grant Mcrobbie
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-03-30
Filing date: 2012-03-30
Publication date: 2012-10-18
Anticipated expiration: 2032-03-30
Also published as: AU2012201899B2

Abstract

Abstract A boat lifting method and apparatus 10 for lifting a boat above the waterline. 5 The apparatus comprises a pair of floatation bodies 12 having sufficient buoyancy when filled with air to support a boat 14 above the waterline, and being adapted to be submerged below the waterline when substantially filled with water. The boat lifting apparatus 10 also comprises a support cradle 16 mounted on the floatation bodies 12 for supporting the boat 14 above the 10 waterline when the floatation bodies 12 are filled with air. A buoyancy control means 18 controls the filling of the floatation bodies with air or water as required. Each floatation body 12 comprises a front buoyancy chamber 20 and a rear buoyancy chamber 22 separated by a baffle 24, the front and rear chambers being in fluid communication with each other wherein, to lift the 15 boat in use, the buoyancy control means 18 fills the rear chamber 22 with air first such that the stern of the boat 14 is first lifted above the water line, then the bow of the boat 14 as the front chamber 20 also subsequently fills with air. 20 Drawing to Accompany Abstract: Figure 1 Cle

Description

ORIGINAL AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention title: "BOAT LIFTING APPARATUS AND METHOD" Applicant: GRANT McROBBIE Associated Provisional Application No.: 2011901177 The following statement is a full description of the invention, including the best method of performing it known to me: 2 "BOAT LIFTING APPARATUS AND METHOD" Field of the Invention The present invention relates to a boat lifting apparatus and method and 5 relates particularly, though not exclusively, to a pontoon-type boat lifting apparatus and method for dry-docking boats on the water. Background to the Invention A number of prior art boat lifting or dry-docking apparatus are known which 10 are designed to lift and/or support a boat above the water-line without necessarily removing the boat from the water. A typical purpose for lifting a boat out of the water in this way is to prevent marine growth from accumulating on the hull while the boat is docked. Various types of boat lifting apparatus are known, including a so-called pontoon-type in which two 15 or more pontoons are raised by buoyancy controls, with the boat hull supported above the pontoons. A typical prior art pontoon-type boat lifting apparatus is described in Australian Patent No 692401. AU692401 describes a docking apparatus in which a pair of spaced apart buoyancy bodies may be filled or partially filled with water to cause the bodies to submerge and allow a 20 boat to be launched or located over the bodies for subsequent lifting. Air is pumped back into the buoyancy bodies to cause them to rise and lift the boat out of the water. Many prior art pontoon-type boat lifting apparatus pump air into the buoyancy bodies in such a manner that the bow of the boat (front) is lifted out of the 25 water first. A problem with this procedure, however, is that because most of the weight of the boat is in the stern, (where the engine(s) is/are located) the bow of the boat tends to be lifted up at a very steep angle. This runs the risk of damaging the boat's engine(s) as there is a real possibility that water may enter the engine(s) via the exhaust pipe(s) during the lifting operation. For 30 this reason, many boat owners do not like to use pontoon-type boat lifting systems as they do not want any risk of damaging the boat's engine(s).

3 The present invention was developed with a view to providing an improved boat lifting apparatus and method which is less susceptible to the above noted problems with the prior art. References to prior art in this specification are provided for illustrative 5 purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere. Summary of the Invention 10 According to one aspect of the present invention there is provided a boat lifting apparatus for lifting a boat above the waterline, the apparatus comprising: a pair of floatation bodies having sufficient buoyancy when filled with air to support a boat above the waterline, and being adapted to be submerged 15 below the waterline when substantially filled with water; a support cradle mounted on the floatation bodies for supporting the boat above the waterline when the floatation bodies are filled with air; and, buoyancy control means for controlling the filling of the floatation bodies with air or water as required; 20 wherein each floatation body comprises a front buoyancy chamber and a rear buoyancy chamber separated by a baffle, the front and rear chambers being in fluid communication with each other wherein, to lift the boat in use, the buoyancy control means fills the rear chamber with air first such that the stern of the boat is first lifted above the water line, then the bow of the boat 25 as the front chamber also subsequently fills with air. Advantageously the front and rear chambers are in fluid communication with each other through a pipe assembly provided in connection with the baffle. Preferably the pipe assembly comprises an elongate pipe which is connected at one end to an opening in the baffle located a prescribed height above a 4 floor of the floatation body, the pipe extending into the rear chamber a prescribed distance along the floor of the floatation body such that the respective ends of the pipe subscribe a predetermined angle 0* that corresponds substantially to the angle of inclination of the floatation body at 5 which the front chamber begins to be filled with air through the pipe. Preferably the predetermined angle 0 is between 10* and 15* to the horizontal. More preferably the predetermined angle 0 is about 12.50 to the horizontal. Advantageously the baffle is also provided with a small breather hole, near 10 the top of the floatation body, for bleeding air from one buoyancy chamber into the other. Preferably a pair of guide members is provided on the support cradle for guiding the boat into the correct position above the cradle, when the apparatus is fully submerged. Preferably the floatation bodies and guide 15 members are made from high density polyethylene (HDPE). Typically the buoyancy control means comprises a blower for blowing air into the buoyancy chambers via air delivery lines. Preferably each floatation body is of cylindrical configuration and has an air inlet/outlet which opens into the rear buoyancy chamber near the top of the 20 floatation body. Preferably the front buoyancy chamber has a water inlet/outlet provided towards the bottom of the floatation body. Preferably a snorkel is connected to the water inlet/outlet of each floatation body to ensure that water cannot flow back into the water inlet/outlets once the front chambers are filled with air. 25 According to another aspect of the present invention there is provided a boat lifting method for lifting a boat above the waterline, the method comprising the steps of: providing a pair of floatation bodies having sufficient buoyancy when filled with air to support a boat above the waterline, and being adapted to be 5 submerged below the waterline when substantially filled with water, and wherein each floatation body comprises a front buoyancy chamber and a rear buoyancy chamber separated by a baffle, the front and rear chambers being in fluid communication with each other; 5 moving a boat over a support cradle mounted on the floatation bodies for supporting the boat above the waterline when the floatation bodies are filled with air; first filling the rear chamber of each floatation body with air such that the stern of the boat is first lifted above the waterline; and, 10 then filling the front chamber of each floatation body with air such that the bow of the boat is subsequently lifted above the waterline. Preferably the steps of filling the front and rear buoyancy chambers with air involves connecting air delivery lines to air inlets on each floatation body and to a blower, in order to pump air into the buoyancy chambers of the floatation 15 bodies. Typically as air is pumped into the rear chamber via the air inlet, the air pressure within the rear chamber forces the water to be evacuated from this chamber through a pipe connected to an opening in the baffle into the front chamber, and as the water pressure in the front chamber increases the water is forced to be evacuated from this chamber via a water outlet, while 20 the baffle prevents the air from entering the front chamber. Preferably as the rear chamber fills with air its buoyancy increases to the point where the stern of the boat begins to be gradually lifted by the cradle, and wherein the position of the baffle and the location of the opening and pipe controls the angle and speed at which the floatation bodies are lifted 25 above the waterline. Advantageously when the angle of inclination of the floatation body reaches a predetermined angle 0 *, then filling with air of the front chamber of each floatation body commences such that the bow of the boat also begins to be lifted. Typically at the predetermined angle G*, the end of the pipe, located about midway along the floor of the rear chamber, 6 becomes exposed to air and hence air begins to enter the front chamber via the pipe. Throughout the specification, unless the context requires otherwise, the word 5 "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word "preferably" or variations such as "preferred", will be understood to imply that a stated integer or group of integers is desirable but not essential to the 10 working of the invention. Brief Description of the Drawings The nature of the invention will be better understood from the following detailed description of a preferred embodiment of the boat lifting apparatus 15 and method, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a preferred embodiment of a boat lifting apparatus according to the present invention; Figure 2(a) is a top plan view of the boat lifting apparatus of Figure 1; 20 Figure 2(b) is an end elevation of the boat lifting apparatus of Figure 1; Figure 3 is a side elevation of the boat lifting apparatus of Figure 1; Figures 4 to 7 illustrate a sequence of steps in a preferred method of lifting a boat in accordance with the present invention; and, Figures 8 to 11 illustrate a sequence of steps in a preferred method of 25 lowering a boat in accordance with the present invention.

7 Detailed Description of Preferred Embodiments A preferred embodiment of a boat lifting apparatus 10 in accordance with the invention, as illustrated in Figures 1 to 3, comprises a pair of floatation bodies 12a and 12b having sufficient buoyancy when filled with air to support a boat 5 14 above the waterline (see Figure 7). The floatation bodies 12a and 12b are also adapted to be submerged below the waterline when substantially filled with water (see Figure 11). The apparatus 10 further comprises a support cradle 16 mounted on the floatation bodies 12 for supporting the boat 14 above the waterline when the floatation bodies 12 are filled with air. 10 Buoyancy control means 18 is provided for controlling the filling of the floatation bodies 12 with air or water as required (see Figure 1). Each floatation body 12 comprises a front buoyancy chamber 20 and a rear buoyancy chamber 22 separated by a baffle 24 (see Figure 3). The front and rear chambers 20 and 22 are in fluid communication with each other through 15 baffle 24. In use, to lift the boat 14, the buoyancy control means 18 fills the rear chamber 22 with air first, such that the stern of the boat 14 is first lifted above the water line. Then the bow of the boat 14 is lifted as the front chamber 20 also subsequently fills with air. The buoyancy control means 18 typically comprises a blower 26 for blowing 20 air into the buoyancy chambers 20 and 22 via air delivery lines 28. Each floatation body 12 is typically of cylindrical configuration and has an air inlet/outlet 30 which opens into the rear buoyancy chamber 22 near the top of the floatation body, as can be seen most clearly in Figure 3. The front buoyancy chamber 20 has a water inlet/outlet 32 provided towards the 25 bottom of the floatation body 12. Typically a snorkel 33 is connected to the water inlet/outlet 32 of each floatation body 12, as shown in Figure 1. The snorkels 33 ensure that water cannot flow back into the water inlet/outlets 32 once the front chambers 20 are filled with air. A rope and pulley system 35 is provided for lifting the ends of the snorkels 33 out of the water during the 30 lifting operation. Preferably caps 37 are also provided for closing off the air inlets 30 on top of the floatation bodies 12.

8 As can be seen most clearly in Figure 3, the front and rear chambers 20 and 22 are in fluid communication with each other through a pipe assembly 34 provided in connection with the baffle 24. Preferably the pipe assembly 34 comprises an elongate pipe 36 which is connected at one end to an opening 5 38 in the baffle 24 located a prescribed height above a floor of the floatation body 12. The pipe 36 extends into the rear chamber 22 a prescribed distance along the floor of the floatation body 12. Typically the opening 38 is located approximately midway up the baffle 24, and the pipe 36 extends approximately halfway along the length of the rear chamber 22 such that the 10 respective ends of the pipe 36 subscribe a predetermined angle 0*. The angle 0 corresponds substantially to the angle of inclination of the floatation body 12 at which the front chamber 20 begins to be filled with air through the pipe 36 (as will be described in more detail below). Preferably the predetermined angle 90 is between 100 and 150 to the horizontal. More 15 preferably the predetermined angle 0* is about 12.50 to the horizontal. Preferably the baffle 24 is also provided with a small breather hole 40, near the top of the floatation body 12, for bleeding air from one buoyancy chamber into the other, as will be described in more detail below. Preferably a pair of guide members 50 is provided on the support cradle 16 20 for guiding the boat 14 into the correct position above the cradle 16, when the apparatus 10 is fully submerged. The floatation bodies and guide members 50 are preferably made from high density polyethylene (HDPE) cylinders, and the support cradle 16 and other components are likewise made from HDPE sheet and rod material. The various components are fastened 25 together using large plastic bolts. A preferred method of lifting a boat 14 above the waterline, using the apparatus 10, and lowering the boat back down into the water, will now be described with reference to Figures 4 to 11. The method of lifting the boat 14 comprises the step of moving the boat 14 over the support cradle 16 30 mounted on the floatation bodies 12 for supporting the boat above the waterline when the floatation bodies are filled with air. Then the air delivery 9 lines 28 are connected to the air inlets 30 on each floatation body 12, and to the blower 26, in order to pump air into the buoyancy chambers 20 and 22 of the floatation bodies 12. Importantly, the method preferably involves filling the buoyancy chambers 20 and 22 in a particular sequence in order ensure that 5 the stern of the boat 14 is lifted first. Therefore the method further comprises the step of first filling the rear buoyancy chamber 22 of each floatation body 12 with air such that the stern of the boat 14 is first lifted above the waterline. As air is pumped into the rear chamber 22 via inlet 30, the air pressure within the rear chamber 22 forces 10 the water to be evacuated from this chamber through the pipe 36 and opening 38 into the front chamber 20, as shown in Figure 4. The water pressure in front chamber 20 increases and forces the water to be evacuated from this chamber via water outlet 32. At this time baffle 24 prevents the air from entering the front chamber 20, although a small volume of air could 15 enter the front chamber 20 via the breather hole 40. As the rear chamber 22 fills with air its buoyancy increases to the point where the stern of the boat 14 begins to be gradually lifted by the cradle 16. The position of the baffle 24, and the location of the opening 38 and pipe assembly 34 controls the angle and speed at which the floatation bodies 12 are lifted above the waterline. 20 When the angle of inclination of the floatation body 12 reaches the predetermined angle 6*, of about 12.50 to the horizontal, then filling with air of the front chamber 20 of each floatation body 12 commences such that the bow of the boat 14 also begins to be lifted, as shown in Figure 5. At the predetermined angle 0, the end of the pipe 36, located about midway along 25 the floor of the rear chamber 22, becomes exposed to air and hence air begins to enter the front chamber 20 via the pipe 36. As the air continues to be pumped into the rear chamber 22 via air inlet 30, the front chamber 20 continues to fill with air via the breather hole 40 and pipe 36, forcing the water out of front chamber 20 via the water outlet 32. The 30 increasing volume of air in the front chamber 20 increases the buoyancy of the front chamber 20 so that the bow of the boat 14 also gradually begins to 10 be lifted above the waterline on the cradle 16, as shown in Figure 6. Water continues to be evacuated from the front chamber 20 via the water outlet 32, and any remaining water in the rear chamber 22 is also evacuated via pipe 36 into the front chamber 20. The lift is almost complete as the last of the 5 water is removed from the front chamber 20 causing the boat lift apparatus to begin its levelling out process. When the lifting process is complete, as shown in Figure 7, the boat lifting apparatus 10 levels out and any remaining water in both buoyancy chambers is evacuated via the water outlet 32. The water outlets 32 are closed by lifting 10 the snorkels 33 above the waterline using the rope and pulley system 35. The air inlets 30 are closed by disconnecting the air delivery lines 28 and replacing the air caps 37. The boat 14 is now completely out of the water ready to store. The process of lowering the boat 14 back into the water on the boat lift 15 apparatus 10, according to the preferred method of the invention, will now be described with reference Figures 8 to 11. The air inlet/outlet 30 of each floatation body 12 is first opened by removing the air caps 37, and the water outlet/inlet 32 of each floatation body 12 is also opened by lowering the snorkels 33 below the waterline. Water will start to flow into the front 20 buoyancy chamber 20 through water inlet 32, which pushes the air in the front chamber 20 into the rear chamber 22 and out to atmosphere through air outlet 30, as shown in Figure 8. The position of the baffle 24, and the location of the opening 38 and piping assembly 34 also controls the angle and speed at which the floatation bodies 12 will sink below the waterline. 25 The water entering the front chamber 20 creates a counter-weight of water in front of baffle 24 which causes the bow of the boat 14 to begin to be lowered towards the waterline, as shown in Figure 8. As the water level within the front chamber 20 continues to rise, it will eventually reach the level of the opening 38 in the baffle 24 and begin to flow into the rear chamber 22 via the 30 pipe 36, as shown in Figure 9.when the water level within the front chamber 20 reaches the top of the opening 38 in baffle 24, a small air pocket is formed 11 in the front chamber 20 in front of the baffle 24. Air from this air pocket is released into the rear chamber 22 via the breather hole 40. This slows the rate at which water enters the rear chamber 22 and helps to lower the boat 14 in a more controlled manner. 5 As the front chamber 20 continues to fill with water, as shown in Figure 10, the bow of the boat 14 reaches the waterline keeping the boat at an acceptable angle on the cradle 16. Air in the rear chamber 22 continues to be evacuated via the air outlet 30, as more water enters the water inlet 32 and passes through the front chamber 20 and pipe 36 via opening 38 into the rear 10 chamber 22. As more water enters the rear chamber 22 it gradually becomes submerged, easing the stern of the boat 14 into the water. When the front chamber 20 is completely filled with water, as shown in Figure 11, the bow of the boat 14 is lowered below the waterline and the floatation bodies 12 of the boat lift apparatus 10 are completely submerged. The hull of 15 the boat 14 lifts off the cradle 16, and guide members 50 keep the boat in position away from the apparatus 10 so that it can be driven away safely. The boat lifting apparatus 10 may be left submerged, ready for when the boat 14 returns to dock, or it may be refloated by refilling the floatation bodies 12 with air. 20 Now that preferred embodiments of the boat lifting apparatus and method have been described in detail, it will be apparent that the described embodiments provide a number of advantages over the prior art, including the following: (i) The boat lifting method and apparatus ensures the stern of the boat is 25 lifted first, obviating the risk of water entering the engine exhaust. (ii) The provision of front and rear chambers permits lifting and lowering of the boat from and into the water in a controlled manner. (iii) The position and location of the pipe assembly ensures that the angle of inclination of the boat during the lifting and lowering operations does 30 not exceed acceptable limits.

12 (iv) The boat lifting apparatus and method are easy to operate and does not require special training or expertise. It will be readily apparent to persons skilled in the relevant arts that various 5 modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. For example, the shape and configuration of the floatation bodies need not be cylindrical as in the illustrated embodiment. Therefore, it will be appreciated that the scope of 10 the invention is not limited to the specific embodiments described.

Claims

1. A boat lifting apparatus for lifting a boat above the waterline, the apparatus comprising: 5 a pair of floatation bodies having sufficient buoyancy when filled with air to support a boat above the waterline, and being adapted to be submerged below the waterline when substantially filled with water; a support cradle mounted on the floatation bodies for supporting the boat above the waterline when the floatation bodies are filled with air; and, 10 buoyancy control means for controlling the filling of the floatation bodies with air or water as required; wherein each floatation body comprises a front buoyancy chamber and a rear buoyancy chamber separated by a baffle, the front and rear chambers being in fluid communication with each other wherein, to lift the boat in use, the 15 buoyancy control means fills the rear chamber with air first such that the stern of the boat is first lifted above the water line, then the bow of the boat as the front chamber also subsequently fills with air.

2. A boat lifting apparatus as defined in claim 1, wherein the front and rear chambers are in fluid communication with each other through a pipe 20 assembly provided in connection with the baffle.

3. A boat lifting apparatus as defined in claim 2, wherein the pipe assembly comprises an elongate pipe which is connected at one end to an opening in the baffle located a prescribed height above a floor of the floatation body, the pipe extending into the rear chamber a prescribed distance along the floor of 25 the floatation body such that the respective ends of the pipe subscribe a predetermined angle 0 that corresponds substantially to the angle of inclination of the floatation body at which the front chamber begins to be filled with air through the pipe. 14

4. A boat lifting apparatus as defined in claim 3, wherein the predetermined angle 0 is between 100 and 150 to the horizontal.

5. A boat lifting apparatus as defined in claim 4, wherein the predetermined angle 9*is about 12.50 to the horizontal. 5

6. A boat lifting apparatus as defined in any one of the preceding claims, wherein the baffle is also provided with a small breather hole, near the top of the floatation body, for bleeding air from one buoyancy chamber into the other.

7. A boat lifting apparatus as defined in any one of the preceding claims, 10 wherein a pair of guide members is provided on the support cradle for guiding the boat into the correct position above the cradle, when the apparatus is fully submerged.

8. A boat lifting apparatus as defined in claim 7, wherein the floatation bodies and guide members are made from high density polyethylene (HDPE). 15

9. A boat lifting apparatus as defined in any one of the preceding claims, wherein the buoyancy control means comprises a blower for blowing air into the buoyancy chambers via air delivery lines.

10. A boat lifting apparatus as defined in any one of the preceding claims, wherein each floatation body is of cylindrical configuration and has an air 20 inlet/outlet which opens into the rear buoyancy chamber near the top of the floatation body.

11. A boat lifting apparatus as defined in claim 10, wherein the front buoyancy chamber has a water inlet/outlet provided towards the bottom of the floatation body. 25

12. A boat lifting apparatus as defined in claim 11, wherein a snorkel is connected to the water inlet/outlet of each floatation body to ensure that water cannot flow back into the water inlet/outlets once the front chambers are filled with air. 15

13. A boat lifting method for lifting a boat above the waterline, the method comprising the steps of: providing a pair of floatation bodies having sufficient buoyancy when filled with air to support a boat above the waterline, and being adapted to be 5 submerged below the waterline when substantially filled with water, and wherein each floatation body comprises a front buoyancy chamber and a rear buoyancy chamber separated by a baffle, the front and rear chambers being in fluid communication with each other; moving a boat over a support cradle mounted on the floatation bodies for 10 supporting the boat above the waterline when the floatation bodies are filled with air; first filling the rear chamber of each floatation body with air such that the stern of the boat is first lifted above the waterline; and, then filling the front chamber of each floatation body with air such that the 15 bow of the boat is subsequently lifted above the waterline.

14. A boat lifting method for lifting a boat above the waterline as defined in claim 13, wherein the steps of filling the front and rear buoyancy chambers with air involves connecting air delivery lines to air inlets on each floatation body and to a blower, in order to pump air into the buoyancy chambers of the 20 floatation bodies.

15. A boat lifting method for lifting a boat above the waterline as defined in claim 14, wherein as air is pumped into the rear chamber via the air inlet, the air pressure within the rear chamber forces the water to be evacuated from this chamber through a pipe connected to an opening in the baffle into the 25 front chamber, and as the water pressure in the front chamber increases the water is forced to be evacuated from this chamber via a water outlet, while the baffle prevents the air from entering the front chamber.

16. A boat lifting method for lifting a boat above the waterline as defined in claim 15, wherein as the rear chamber fills with air its buoyancy increases to 16 the point where the stern of the boat begins to be gradually lifted by the cradle, and wherein the position of the baffle and the location of the opening and pipe controls the angle and speed at which the floatation bodies are lifted above the waterline. 5

17. A boat lifting method for lifting a boat above the waterline as defined in claim 16, wherein when the angle of inclination of the floatation body reaches a predetermined angle 6*, then filling with air of the front chamber of each floatation body commences such that the bow of the boat also begins to be lifted. 10

18. A boat lifting method for lifting a boat above the waterline as defined in claim 17, wherein at the predetermined angle 0 , the end of the pipe, located about midway along the floor of the rear chamber, becomes exposed to air and hence air begins to enter the front chamber via the pipe.

19. A boat lifting apparatus for lifting a boat above the waterline substantially 15 as herein described with reference to and as illustrated in any one or more of the accompanying drawings.

20. A boat lifting method for lifting a boat above the waterline substantially as herein described with reference to and as illustrated in any one or more of the accompanying drawings. 20 Dated this 3 0 1h day of March 2012 Grant McRobbie 25 by his Patent Attorneys Janet Stead & Associates