DESC:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
INNOVATIVE LAUNCHING OF A DESTROYER CLASS VESSEL UNDER TIDAL CONSTRAINTS

Applicant:
Mazagon Dock Shipbuilders Limited
A company Incorporated in India under the Companies Act, 1956
Under Ministry of Defence,
(A Govt. of India Undertaking)
Having address:
Dockyard Road, Mazagon,
Mumbai - 400010, Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.

CROSS-REFERENCE TO RELATED APPLICATION AND PRIORITY
[001] The present application claims priority from Indian Provisional Application No. 201821043060 filed on 15th November, 2018.
TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to launching of a destroyer class vessel under tidal constraints and more specifically to launching of a destroyer class vessel under tidal constraints by using pontoons.
BACKGROUND
[003] Launching a ship has always been a challenging task as being one of the critical event in ship building process. Launching needs to consider the safety of the high-value vessel and that of the personnel onboard, and therefore needs to factor in adequate safety margins due to technical difficulties and physical laws governing the phenomenon. Launching entails a concerted effort wherein the design needs to be configured, the right kind of materials has to be selected and a controlled exploitation of the natural forces of gravity, buoyancy, water resistance and friction must be orchestrated to achieve the desired result.
[004] Conventionally, the weight at launch of the ship is driven by the tide height which is a natural phenomenon available on a day of the launch. In other words, the vessel may progressively achieve a weight beyond which the vessel may not be held on the slipway and to be necessarily launched. It is to be noted that an amount of weight of the ship during launch is directly proportional to the tide height.
[005] In an example, consider a destroyer ship of weight of 4190 MT is to be launched. The tide height (High Waters) required to support the destroyer ship during launching may be calculated as 5.3 m. The days in one calendar year with tide heights more than 5.0 m listed at below table.
Date Time Height (m)
12 Jan 09 00:59 5.04
13 Jan 09 01:41 5.13
14 Jan 09 02:22 5.09
11 Feb 09 01:14 5.07
23 Jul 09 13:23 5.01
24 Jul 09 14:03 5.05
[006] From the above, it becomes amply evident that a suitable tide window may not be available in the whole year to launch the destroyer ship for the given launch weight of 4190 MT.
SUMMARY
[007] Before the present device is described, it is to be understood that this application is not limited to the particular machine or device, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosures. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce aspects related to launching of a destroyer class vessel under tidal constraints, and the aspects are further elaborated below in the detailed description. This summary is not intended to identify essential features of the proposed subject matter nor is it intended for use in determining or limiting the scope of the proposed subject matter.
[008] The present subject matter describes a device for launching of a marine vessel. The device comprising of a forward pontoon and an aft pontoon. The forward pontoon is attached to a front bottom portion of the marine vessel by a first plurality of brackets. The forward pontoon comprises of a groove to directly engage with a bottom surface of the marine vessel. The aft pontoon is attached to a rear bottom portion of the marine vessel by a second plurality of brackets. The forward pontoon and the aft pontoon are installed to the marine vessel before launching the marine vessel into a water body.
[009] The present subject matter further describes a method of launching a marine vessel. The method of comprising steps of: attaching a forward pontoon with a front bottom portion of the marine vessel by a first plurality of brackets wherein the forward pontoon comprises a groove to directly engage with a bottom surface of the marine vessel, attaching an aft pontoon with a rear bottom portion of the marine vessel by a second plurality of brackets, and sliding the marine vessel on the slip way, wherein the marine vessel is attached to the forward pontoon and the aft pontoon. In one aspect of the present subject matter, the forward pontoon and the aft pontoon are removed from the marine vessel once the marine vessel is fully afloat in a water body.
[0010] It is an object of the present subject matter to launch the marine vessel with the increased launch weight by externally providing the required buoyancy for the launch. To do so, the present invention discloses a novel technique of integrating external buoyancy tanks also known as pontoons with the marine vessel.

BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The foregoing summary, as well as the following detailed description of embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, there is shown in the present document example constructions of the disclosure, however, the disclosure is not limited to the specific methods and device disclosed in the document and the drawings.
[0012] The detailed description is described with reference to the accompanying figures. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[0013] Figure 1 illustrates a view of a device for launching of a marine vessel with attachment of a forward pontoon, in accordance with an embodiment of the present subject matter.
[0014] Figure 2 illustrates an another view of the device for launching of the marine vessel with attachment of the forward pontoon, in accordance with an embodiment of the present subject matter.
[0015] Figure 3 illustrates a view of the device for launching of the marine vessel with attachment of an aft pontoon, in accordance with an embodiment of the present subject matter.
[0016] Figure 4 illustrates an another view of the device for launching of the marine vessel with attachment of the aft pontoon, in accordance with an embodiment of the present subject matter.
[0017] Figure 5 illustrates a method of launching the marine vessel, in accordance with an embodiment of the present subject matter.
[0018] The figure depicts various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
[0019] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any devices and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary, devices and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0020] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein.
[0021] The terms “marine vessel” and “ship” are used interchangeably as the subject matter is described in more details in following disclosure.
[0022] Launching a marine vessel or a ship has always been a fascinating subject and it still remains to be a critical event in the ship building process. Launching needs to consider the safety of the high-value vessel and that of the personnel on-board, and therefore needs to factor in adequate safety margins due to the technical difficulties and the physical laws governing the phenomenon. Launching entails a concerted effort wherein the design needs to be configured, the right kind of materials has to be selected and a controlled exploitation of the natural forces of gravity, buoyancy, water resistance and friction has to be orchestrated to our advantage. In traditional launching method the launch weight is dictated by the tide height available on the day of launch.
[0023] Referring to figure 6, an equilibrium of forces acting on a marine vessel during launching is illustrated in accordance with an embodiment of the present invention. It is to be noted that function of pontoons (buoyancy tanks) fitted at the fore and aft sections of the marine vessel, in the launching process may be explained in conjunction with theory of conventional end launching. Launch dynamics is governed by the dynamic equilibrium of the three main forces acting on the ship during the movement of the ship on the sliding ways, i.e. the force of gravity P, the reaction R of the sliding way and the upward thrust S on the submerged portion of the ship.
[0024] The force of gravity may remain constant in magnitude and direction during the launch and may always be considered to act through the center of gravity of the ship. The other two forces do change the magnitude and also the point of application during the launching and such variations may cause various phenomenon including, but not limited to, stern lift, tipping and dropping of bow typically observed during the launch. A typical end launching process sequentially follows the four stages given below:
1. The start of the launch when the ship on cradle starts sliding down the slipway.
2. The rotation (stern lift) when the ship starts leaving from the slipway.
3. Tipping, when the bow lifts from the slipway together with the cradle.
4. Dropping of bow into the water before leaving the slipway.

[0025] At first stage the force of gravity P and the reaction R of the sliding way are in equilibrium and there is no upward thrust force S on the ship as no portion of the ship is submerged in the water.
[0026] At second stage a portion of the ship enters in the water and an upward thrust force S starts acting and results in the rotation of the ship as shown in figure 6. The ship is supported by its buoyancy and by that portion of the slip ways still in contact with the ship.
[0027] At third stage the bow of the ship starts tipping and the force of gravity P is more than the upward thrust force S and hence results in the rotation in opposite direction as shown in figure 6 which is not favorable condition for safe launching of the ship.
[0028] At fourth stage the bow drops into the water hence reaction of slipway becomes zero and the force of gravity and the upward thrust force are in equilibrium.
[0029] Hence pontoons are attached to the ship to provide extra buoyancy to the ship ensuring that the moment of the buoyancy is always greater than the moment of weight of the ship. Needless to say that higher the weight of the ship to be launched, higher the buoyancy required to avert the tipping.
[0030] Referring now to figure 1 and figure 2, a view of a device 100 for launching of a marine vessel 110 is shown. The device 100 may comprise a forward pontoon 130. The forward pontoon 130 may be attached to a front bottom portion of the marine vessel 110 by a first plurality of brackets 132.
[0031] The forward pontoon 130 may further comprise a groove 134 to engage with a bottom surface 112 of the marine vessel 110. A sonar portion of the marine vessel may be accommodated in the groove 134. In the groove 134, the bottom surface of the marine vessel 110 may engage directly with the forward pontoon 130 and no brackets are used in between the surface of the marine vessel 110 and the forward pontoon.
[0032] In an embodiment of the present subject matter, the first plurality of brackets 132 are engaged to the marine vessel 110 by a joining means selected from the set of welding, bolting and riveting. The engagement of the brackets with the marine vessel 110 is a very critical step as any unsafe means to join the brackets may harm the hull of the marine vessel 110 and may result in leakages.
[0033] Similarly the first plurality of brackets 132 are engaged to the forward pontoon 130 by a joining means selected from the set of welding, bolting and riveting. A precaution needs to be taken while joining the brackets to the forward pontoon 130 so that the pontoons may be retrieved in a good condition for reuse.
[0034] In another embodiment of the present subject matter, the forward pontoon 130 may be made by combining one or more pontoons. As the forward pontoon 130 may be very big based on the dimensions of the marine vessel 110 on which the pontoon is to be attached hence the forward pontoon 130 may be an integrated one pontoon or may be made by combining multiple pontoons together to make a big pontoon.
[0035] In another embodiment of the present subject matter, the forward pontoon 130 may comprise a plurality of manholes and a plurality of ladders for surveying or maintenance purpose.
[0036] Designing of the forward pontoon 130 posed an added challenge owing to the shape of the frame in the forward sections of the vessel 110. The vessel comprises conservative forward sections and a sonar dome is mounted on the bow. The dome per se being an item that may be fitted post launch, the forward pontoon 130 must be built around a mounting flange of the sonar dome.
[0037] In an embodiment of the subject matter, considering the crane and space available for the erection at slipway, the design space for external buoyancy may be split with provision for three pontoons. The forward pontoon 130 may be split into three parts which are joined together to make a single forward pontoon 130. The dimensions of the forward pontoon 130 may vary based on the width, height, weight and buoyancy requirements at the time of the launch of the vessel 110.
[0038] Referring now to figure 3 and figure 4, another view of the device 100 for launching of the marine vessel 110 is shown. The device 100 may further comprise an aft pontoon 340. The aft pontoon 340 may be attached to a rear bottom portion of the marine vessel 110 by a second plurality of brackets 342.
[0039] In an embodiment of the present subject matter, the second plurality of brackets 342 are engaged to the marine vessel 110 by the joining means selected from the set of welding, bolting and riveting. The engagement of the brackets with the marine vessel 110 is a very critical step as any unsafe means to join the brackets may harm the hull of the marine vessel 110 and may result in leakages.
[0040] Similarly the second plurality of brackets 342 are engaged to the aft pontoon 340 by the joining means selected from the set of welding, bolting and riveting. A precaution needs to be taken while joining the brackets to the aft pontoon 340 so that the pontoons may be retrieved in a good condition for reuse.
[0041] In another embodiment of the present subject matter, the aft pontoon 340 may comprise a plurality of manholes and a plurality of ladders for surveying or maintenance purpose.
[0042] The dimensions of the aft pontoon 340 may vary based on the width, height, weight and buoyancy requirements at the time of the launch of the vessel 110.
[0043] It is to be noted that the forward pontoon (130) and the aft pontoon (340) may be made of a material selected from the set of metal, reinforced material and abrasive material.
[0044] The mechanical integration of the pontoons (130, 340) to the frame by way of brackets (132, 342) with integration points may exactly match with the frames of the ship 110. The erection of the pontoon to its final location on the slipway must be undertaken within a restricted space. Since some of the brackets may be too closely placed, there may be issues of welding inaccessibility, which the yard must mitigate. Since the pontoon is a floating structure, structural integrity must be separately proven by a series of pressure tests. Since the pontoons once afloat are prone to corrosion, cathodic protection and an appropriate paint scheme may be drawn-up to check the corrosion potential. It may also be required for the yard to ensure that the integration points of the brackets to the hull falls exactly on the contours of the hull frame to avoid local stress concentration and subsequent rupture during launch.
[0045] The role of pontoons (130, 340) may come to an end when the ship 110 is fully afloat. However, the pontoons (130, 340) are to be dismantled from the hull without damaging both the ship and the pontoons. The removal of the pontoons may be carried out in the wet basin while the ship is afloat or in a Dry dock when the ship is secured on the dock blocks. Removal of the pontoons in a dry-dock is a straightforward solution vis-à-vis when the ship is afloat. The pontoons (130, 340) are removed from the ship without adversely affecting the trim and stability of the vessel and at the same time retrieving the pontoon in good condition for future re-usage.
[0046] Referring to figure 5, a method 500 comprising steps of launching the marine vessel 110 by using the device 100 is shown. The order in which the method is described, is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method or alternate methods. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the subject matter described herein. However, for ease of explanation, in the embodiments described below, the method may be considered to be implemented with the above described device 100.
[0047] The method 500 of launching the marine vessel 110 comprises following steps. Initially at block 502, the forward pontoon 130 may be attached to the front bottom portion of the marine vessel 110 by the first plurality of brackets 132. Further at block 504, the aft pontoon 340 may be attached to the rear bottom portion of the marine vessel 110 by the second plurality of brackets 342. While the forward pontoon 130 and the aft pontoon 340 are attached to the marine vessel 110, at block 506 the marine vessel 110 is made to slide on the slip way.
[0048] Further when the marine vessel 110 is completely afloat in the water body, the forward pontoon 130 and the aft pontoon 340 are removed from the marine vessel 110 and the forward pontoon 130 and the aft pontoon 340 can be reused for launching of another marine vessel.
[0049] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0050] Some object of the present invention provides possibility of a higher percentage of pre-outfitting on the slipway.
[0051] Some object of the present invention enables better utilization of modular construction facilities for example slipways may be loaded with heavier ships.
[0052] Some object of the present invention facilitates reduction in wet basin outfitting and dry docking activities with benefits of time and cost.
[0053] Some object of the present invention facilitates less dependency on tide and provides more tide windows for launching.
[0054] Some object of the present invention facilitates possibility of shipping-in of heavy equipment and machinery pre-launch activities, which were hitherto impossible for this class of vessel.
[0055] Some object of the present invention provides safe and cost-effective solution as the pontoons functions as 'virtual appendages' that can be integrated or dismantled and re-used as required.
[0056] Some object of the present invention enables less deterioration of ship's hull during the launch of the ship.
[0057] Although implementations for the device 100 have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementation for the device 100. ,CLAIMS:
1. A device (100) for launching of a marine vessel (110), wherein the device (100) comprises:
a forward pontoon (130), wherein the forward pontoon (130) is attached to a front bottom portion of the marine vessel (110) by a first plurality of brackets (132) and the forward pontoon (130) comprises:
a groove (134) to engage with a bottom surface (112) of the marine vessel (110) and
an aft pontoon (340) wherein the aft pontoon (340) is attached to a rear bottom portion of the marine vessel (110) by a second plurality of brackets (342);
wherein the forward pontoon (130) and the aft pontoon (340) are installed to the marine vessel (110) before launching the marine vessel (110).
2. The device (100) as claimed in claim 1, wherein the forward pontoon (130) is made by combining more than one pontoons.

3. The device (100) as claimed in claim 1, wherein the first plurality of brackets (132) and the second plurality of brackets (342) are engaged to the marine vessel (110) by a joining means selected from the set of welding, bolting and riveting.

4. The device (100) as claimed in claim 1, wherein the first plurality of brackets (132) is engaged to the forward pontoon (130) by the joining means selected from the set of welding, bolting and riveting.

5. The device (100) as claimed in claim 1, wherein the second plurality of brackets (342) is engaged to the aft pontoon (340) by the joining means selected from the set of welding, bolting and riveting.

6. The device (100) as claimed in claim 1, wherein the forward pontoon (130) and the aft pontoon (340) comprise a plurality of manholes and a plurality of ladders for surveying or maintenance purpose.
7. The device (100) as claimed in claim 1, wherein the forward pontoon (130) and the aft pontoon (340) are made of a material selected from the set of metal, reinforced material and abrasive material.

8. The device (100) as claimed in claim 1, wherein the forward pontoon (130) and the aft pontoon (340) are coated with a corrosion resistant material.

9. A method (500) of launching a marine vessel (110), wherein the method (500) comprises steps of:
attaching a forward pontoon (130) with a front bottom portion of the marine vessel (110) by a first plurality of brackets (132) wherein the forward pontoon (130) comprises a groove (134) to engage with a bottom surface (112) of the marine vessel (110);
attaching an aft pontoon (340) with a rear bottom portion of the marine vessel by a second plurality of brackets (342); and
sliding the marine vessel (110) on the slip way wherein the marine vessel (110) is attached to the forward pontoon (130) and the aft pontoon (340).

10. The method (500) as claimed in claim 9, wherein the forward pontoon (130) and the aft pontoon (340) are removed from the marine vessel (110) once the marine vessel (110) is fully afloat in a water body.