US3551925A

US3551925A - Self-stabilizing davit

Info

Publication number: US3551925A
Application number: US760418A
Authority: US
Inventors: John R Reid
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-09-18
Filing date: 1968-09-18
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05

Abstract

A DAVIT HAVING A DAVIT ARM MOUNTED ON THE DECK OF A SHIP, WITH AT LEAST TWO ROPES CONNECTED TO EACH POINT SUSPENSION OF AN OBJECT TO BE HANDLED, ONE OF THE ROPES EXTENDING TO A SHEAVE MOUNTED NEAR THE TOP OF THE ARM, THE OTHER ROPE EXTENDING TO A SHEAVE MOUNTED ON THE ARM AT A CERTAIN DISTANCE FROM THE TOP SHEAVE, SUCH THAT AT EACH POINT OF SUSPENSION THE OBJECT IS SUPPORTED IN THE INBOARD

POSITION OF THE DAVIT ARM BY THE ONE ROPE AND AT THE OUTBOARD POSITION OF THE ARM BY BOTH ROPES.

Description

Jan. 5, 1971y J. R. REID SELF-STABILIZING DAVIT Filed sept. 18. 1968 5 Sheets-Sheet l FIG.

Jan. 5, 1971 J.' R. REID ,SELF-STABILIZING DAVIT 5 Sheets-Sheet 2A Filed Sept. 1a, 196e N .mi

Jan* 5, 197B J. R.RE1D 3,551,925

' sELF-sTAB1L1zmG nAvIT A Filed sept. 1 8, 1968 5 sheets-sheet s FIG. 3

Jan. 5, H971 J. RQREID SELF-STBILIZING DAVIT 5 Sheets-Sheet 4 Filed Sept. 18, 1968 Av @E Jan.. 5, 1971 J. Raam 3,551,925

SELF-STABILIZING DAVIT Filed sept. 1s, 1968 5 sheets-sheet s United States Patent O 3,551,925 SELF-STABILIZING DAVIT John R. Reid, 2871 Sandalwood Drive, Ottawa 8, Ontario, Canada Filed Sept. 18, 1968, Ser. No. 760,418 Int. Cl. B63b 23/06 U.S. Cl. 9-39 4 Claims ABSTRACT F THE DISCLOSURE A davit having a davit arm mounted on the deck of a ship, with at least two ropes connected to each point suspension of an object to be handled, one of the ropes extending to a sheave mounted near the top of the arm, the other rope extending to a sheave mounted on the arm at a certain distance from the top sheave, such that at each point of suspension the object is supported in the inboard position of the davit arm by the one rope and at the outboard position of the arm by both ropes.

The invention relates to a davit for lauching from or for taking on board of a ship, a life boat, a landing craft, a launch, a raft, a buoy, a mine, a torpedo, an ambulance or a similar object, said davit comprising a davit arm for supporting the object, said arm being mounted on the deck of said ship in such a way that it is adapted to take an inboard position for stowing said object and an outboard position for raising or lowering said object, means for bringing said davit arm from the one position in the other and vice versa, means for lowering and raising said object including falls, at least one winch for winding up and paying out said falls and/sheaves for guiding said falls between said object and said winch.

The difficulty in handling such objects with a davit as described is that in the case when the ship is rolling during the raising or lowering of the object it can strike heavily against the ship.

The invention has for its object to provide a davit with which the risk of an accident as a result of the impacts between the object and the ship is minimized. According to the invention at each point of suspension of said object at least two falls are connceted to said object, one of said falls extending from said point to a sheave mounted near the top of said davit arm, the other fall extending from said point to a sheave mounted on said arm at a certain distance from said top sheave, such that in each point of suspension in the inboard position of said arm, said one fall supports said object and in the outboard position of said arm both falls support said object, said one fall extending upwards in a direction away from the ship and said other fall extending upwards towards the ship.

During the lowering and raising of the object the one fall pulls the object away from the ship and the other fall pulls the object towards the ship. Due to this arrangement a swinging movement of the object is prevented or at least damped to a great extent.

In an advantageous embodiment of the invention, said sheaves for guiding said falls from the point of suspension are arranged on said arm at such a distance from each other that in the outboard position of said arm said top sheave lies outside the ship at a distance which is at least corresponding with the width of said object, whereas said other sheave is lying just outside the ship.

Further according to the invention the Winches for winding up and paying out said falls are synchronized.

The invention is elucidated further with reference to the drawing, which illustrates some embodiments of the davit according to the invention.

rice

In the drawing:

FIG. 1 shows a davit according to the invention with a lifeboat in a section across a ship;

FIG. 2 shows the davit of FIG. 1 in a view transverse to the ship;

FIG. 3 shows a davit with a lifeboat in other embodiment in a section across a ship;

FIG. 4 shows the davit of FIG. 3 in a view transverse to the ship; and

FIG. 5 shows a davit with a buoy or the like in a section across a ship.

In FIGS. 1 and 2 a gravity davit is shown which is inserted for pivoting on the deck of a ship. The davit arm 1, 2 can swing out from the inboard position shown in solid lines to the outboard position shown in chain dotted outline at 1', 2' under the influence of gravity, said swinging being controlled by a winch 3 mounted on the arm 1. The winch 3 has two

drums

4, 5 which are mounted on one shaft `6. On the drum 4 a steel rope 7 is wound, said rope 7 being guided by a sheave 8 mounted on the arm 1 and being connected to a fixed point 9 on the deck 10 near the davit arm 1. On the other drum 5 a steel rope 11 is wound, said rope 11 being guided by

sheaves

12, 13, 14 and connected to a xed point 15 on the deck 10 near the davit 2.

The

drums

4, 5 have the sa-me diameter so lthat by operating these

drums

4, 5 the davit arms 1, 2 are moved in synchronized way, therefore the davit arms 1, 2 can be connected by a cross beam 16 which can resist the horizontal forces arising from the pull in the rope 11 between the davit arms 1, 2.

A lowering winch 17 is also mounted on the davit arm 1. On the drum 18 of winch 17 falls 19, 20 are wound. These falls 19, 20 are guided by sheaves 21, 22 resp. 23 mounted on the davit arm 1 and are connected to a ring 24.

On the drum 25 the

falls

26, 27 are wound, which are guided by

sheaves

28, 29, 30, 31 resp. 32, 33, 34 and are connected to a ring 35. The

drums

18, 25 are mounted on one shaft 36 and have the same diameter so that the movement of the

falls

19, 20, 26, 27 is substantiall synchronized. The

sheaves

22, 23 resp. 31, 34 are positioned in such a way that in the inboard position of the arms 1, 2 the one

fall

19, 26 is tensioned and the

other fall

20, 27 is slack.

When the boat 37 is suspended by means of the

rings

24, 35, and is to be launched, it is only necessary to loosen the brake. Preferably the length of the steel ropes 7, 11 is such that in the outboard position of the davit arms 1, 2 the ropes 7, 11 are completely unwound from the

drums

4, 5 but remain connected to these

drums

4, 5 which are stopped in their dead center. In this way no shock will occur when the arms 1, 2 reach the outboard position. In the outboard position of the arm 1 the fall 20 is tensioned due to the rotation of the arm 1. The fall 19" is pulling the ring 24 a'way from the ship whereas the other fall 20l is pulling the ring 24' towards the ship. Similar considerations are true for the arm 2 and the ring 35. So the rings 24', 35' are in a definite position which is adapted for embarkation of the boat 37. Upon a further lowering of the boat to the position shown at 37" the distances 22', 24 and 23', 24' remain the same, so that the distance between the ring 24' and the side of the ship remains also the same.

The lifeboat can rotate around an axis through the rings 24", 35", but remains inside the circle 38 around the rings 24" 35". In this way contact of the iboat 37" with the ship can be prevented for rolling movements which do not exceed the angle 22', 24", 23'. It is easy to imagine that in the case when the ship is very high above the water level and the davit arms 1, 2 are rather short, the

angle

22', 24, 23 will be rather small so that it is possible that the boat 37 strikes against the ship when strong rolling movements occur. In such a Way the arrangement has still its effect. The angle between the falls 19', 20 is great during the rst part of the lowering movement and even when the angle between the falls becomes very small, the swinging movements of the boat are eifectively damped.

In FIGS. 3 and 4 similar parts are indicated with the same numerals as in FIGS. 1 and 2.

In this embodiment the boat 37 is suspended on the davit arms 1, 2 which can move by means of rolls 39, 40 along

track

41, 42 which are mounted on the deck of the ship. On the

tracks

41, 42 davit control winch 3 is mounted and the ends of steel ropes 7, 11 are connected to the moving parts at 43, 44 and are directly and indirectly connected with the arms 1, 2. The davit control winch 3 consists of two parts, one with a drum 4 for the davit arm 1 and the other with the drum 5 for the arm 2. Both

drums

4, 5 are synchronized by means of the shaft.

The lowering winch 17 also consists of two parts. The

drums

18, 45 control the

falls

19 and 20, whereas the drums 46, control the

falls

26, 27. The four

drums

18, 45, 46, 25 are synchronized by means of the shaft 47, which moves with the davit arms 1 and 2. In general it can be remarked that the lowering winch 17 can be combined with the davit arm control winch 3.

FIG. 5 shows a single davit for a raft, a buoy a mine or a similar object. The davit arm 1 is hingedly connected to a rotating column 47 which is mounted around a shaft 48 which is mounted on the deck 10. The davit arm 1 is held in position by means of a winch 3 with a drum 4 and a steel rope 7 which is guided by a sheave 8 and is connected to the arm 1.

A lowering winch 17 is mounted on the davit arm 1. On the drum 18 of this winch 17 are wound two falls 19, 20 which are guided by the

sheaves

22 and 23 and are connected at their free ends to a ring 24 which is connected to a buoy 50.

The

sheaves

22, 23 are positioned on the arm 1 in such a Way that upon paying out the falls 19, 20 the ring 24 is lowered substantially parallel to the side of the ship. Small deviations in the path of the ring 24 can be corrected by winding the

falls

19, 20 on drums of a different diameter.

I claim:

1. A davit for launching or for taking on board a ship, a lifeboat, a landing craft, a launch, a raft, a buoy,

a mine, a torpedo, an ambulance or a similar object, said davit comprising a davit arm supporting the object, means mounting said arm on the deck of said ship such that the arm is adapted to take an inboard position for stowing said object and an outboard position for raising or lowering said object, means for bringing said davit arm from one position to the other, means for lowering and raising said object including falls, at least one winch for winding up and paying out said falls and sheaves for guiding said falls between said object and said winch, wherein at each point of suspension of said object at least two separate falls are connected to said object, one of said falls, extending from said point to a sheave tixedly mounted near the top of said davit arm, the other fall extending from said point to a second sheave fixedly mounted on said arm at a distance from said top sheave, such that at each point of suspension in the inboard position of said arm said one fall supports said object and in the outboard position of said arm both falls support said object, said one fall extending upwardly in a direction away from the ship and said other fall extending upwards toward the ship.

2. A davit according to claim 1, wherein said sheaves for guiding said falls from said point of suspension are spacedly arranged on said arm at such a distance from each other that in the outboard position of said arm said top sheave lies outside the ship by a distance which at least corresponds with the width of said object, whereas said other sheave lies just outside the ship.

3. A davit according to claim 1 comprising means connecting the Vwinches which wind up and pay out said falls for synchronized movement.

4. A davit according to claim 1 comprising a ring at each point of suspension secured to said object, the two falls at each point of suspension being connected to said ring thereat.

References Cited UNITED STATES PATENTS 1,833,199 11/1931 Beagle 9-40 2,038,233 4/ 1936 Oppenheim 9-39 FOREIGN PATENTS 27,718 5/1914 Great Britain 9-39 MILTON BUCHLER, Primary Examiner I. E. PITTENGER, Assistant Examiner