GB2145377A - Improvements in or relating to the push towing of barges - Google Patents

Abstract

In a system for releasably interconnecting a tug (3) and a barge (1), the tug is provided with a bow having a predetermined rake and contour and the barge is provided at its stern with a notch (2) having a configuration adapted to receive the bow of the tug in a close-fitting relationship. The barge is provided on each of its wings defining the notch at the stern with a casting (5) having a rail (6), the rails extending from the notch surface of the stern of the barge to form inwardly extending projections. The tug is provided on both sides in its bow region with recesses (9) which are adapted to receive the projections and the tug is further provided, in each said recess in the bow region, with at least one plunger adapted to engage the respective barge rail to force engagement surfaces (7) on the barge projections and tug recesses against one another to hold the tug to the barge in a releasable manner. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the push-towing of barges This invention relates to the push-towing of barges and is particularly concerned with releasable interconnections between tugs and barges.

Numerous proposals have been madeforthe releasable interlocking of tugs and barges and one prior system for this purpose is disclosed in my British Patent Specification No. 2053807. This prior system comprises releasably interlockable tugs and barges in which the tugs and barges are provided at port and starboard with fore-and-aft extending rails and channels so that when a tug is joined to a barge each of said rails fits into a respective complementary one of said channels. Lugs are provided on each side of each tug and complementary slots are provided at each rear of each barge so that when a tug is joined to a barge each of the lugs fits snugly into a respective one of the slots.

A problem with this prior system and with other known rigid coupling systems of this type is to match the draft and trim of the tug to that of the barge. There is a swell even in sheltered harbours and a slight list of either the tug or the barge to port or starboard can cause problems in connecting the tug to the barge. This is because the system depends on the axially disposed rails and channels in horizontal planes being brought into intimate engagement when joining the tug to the barge. The load bearing elements are usually parallel to the central axis of the tug and barge so that the draft, trim and heel of both the tug and barge must be adjusted within close limits prior to attempting connection which can be critical with effects of swell and wind.Draft can be compensated by ballasting adjustments of the tug or by similar means on the barge but this only compensates for the major problem and takes time to accomplish and verify.

Another system which has been proposed is the semi-rigid system of the type known as the ACB Hydropad System which also employs a notch system in the barges for receiving tugs. This system can couple tugs and barges having differences in draft but it relies on the tug being retained in the notch in the barge by means of a very heavily loaded cable system which forces the tug into the bottom of the notch against rubbertyred rollers. The tug is restrained laterally in the notch by a considerable number of hydraulicaily loaded friction pads so that the tug tends to rise and fall vertically with wave action, under normal conditions, until moderate sea-state conditions are exceeded. The tug must then be disconnected and withdrawn from the notch to take the barge under line tow when the weather conditions are least favourable for such a manoeuvre.Alternatively, if the master receives unfavourable weather reports before sailing, and schedules do not permit delay, he has to put the barge on a line at the outset which means a much slower voyage with higher fuel consumption. However, even with the tug fitted in the barge notch, hydrodynamic losses are much higher than with rigid coupling systems because of the tug oscillating in the notch and because the conventional form of the bow of the tug leaves a gap at the bottom of the notch which reduces speed and increases fuel consumption. Moreover, if one of the cables on either the port or starboard side of the interconnected tug/barge system should fail under duress at sea before the tug could be released, the results could be catastrophic for the safety of both the tug and the barge not to mention the danger to any hand on deck on the side where the cable failed.

Thus while the semi-rigid coupling system eliminates the problem of matching the draft of the tug to that of the barge, it creates other problems and cannot be used in the open sea under all weather conditions.

In order to overcome the above-mentioned problems, it was proposed in my British Patent Specification No. 2096065 to provide a system for releasably interlocking a tug and a barge in which the tug was provided with a bow having a predetermined rake and contour and the barge was provided at its stern with a notch having a configuration adapted to receive the bow of the tug in a close-fitting relationship. The barge was provided on each of its wings defining the sides of the notch at the stern with a rail, said rails extending in a transverse plane parallel to the rake of the tug bow, and the tug was provided, in its bow region on both port and starboard sides, with clamping means engageable with the rails to hold the tug to the barge in a releasable manner.The clamping means consisted of clamps pivotally mounted on each of the port and starboard sides of the tug in the bow region thereof.

By means of the clamps on the tugs and the rails on the barges, coupling between a barge and a tug could be accomplished immediately without regard to variations in the draft or trim of the tug in relation to the barge. It was possible for a tug to drop off a fully laden barge and immediately pick up an empty or partially laden barge without any adjustment to the draft of the tug having to be made. Moderate differences in trim or list of the barge did not inhibit coupling because of the relatively short length of axial engagement of the tug.

This prior system did, however, have a disadvantage in that it involved a complicated linkage system in order to operate the clamps and the present invention aims to provide a releasable tug-barge coupling system which has the advantages of the system described in Patent Specification No.

2096065 but which, at the same time, is less complicated.

According to the present invention, there is provided a system for releasably interlocking a tug and a barge in which the tug is provided with a bow having a predetermined rake and contour and the barge is provided at its stern with a notch having a configuration adapted to receive the bow of the tug in a close-fitting relationship, the barge being provided on each of its wings defining the notch at the stern with a rail extending in a transverse plane parallel to the rake of the tug bow, wherein the rails extend from the notch surface of the stern of the barge to form inwardly extending projections, wherein the tug is provided on both sides in its bow region with recesses adapted to receive said projections, and wherein the tug is further provided, in each said recess in the bow region, with at least one plunger adapted to engage the respective barge rail to force engagement surfaces on the barge projections and tug recesses against one another to hold the tug to the barge in a releasable manner.

Preferably, each plunger is provided, at the end which is adapted to engage with the respective barge rail, with a spherically seated engagement shoe.

The plunger may each be operated by means of a respective hydraulic ram or a screw jack. in the latter case, the screw jack may be operated hydraulically or electrically.

Preferably, the rake angle of the tug bow and the notch and rails at the stern of the barge is in the region of 25 but this angle is not essential.

The surfaces of the barge rails against which the plungers are adapted to engage preferably extend at an angle of 45" to the longitudinal axis of the barge.

The angle between the engagement surfaces on the barge projections and tug recesses may, however, be steeper.

The invention will now be further described, by way of example, with reference to the drawings, in which: Figure lisa plan view of a tug and a barge interconnected by one embodiment of a system according to the invention; Figure 2 is a side elevation of the interconnected tug and barge shown in Figure 1; and Figure 3 is a section, to an enlarged scale, taken on the line Ill-Ill in Figure 2 in the direction of the arrows.

Referring to the drawings, the stern of a barge 1 has a notch 2 which is shaped to receive the bow of a tug 3. The bottom or forward end of the notch 2 has a rake angle of 25 which is substantially the same as the rake of the bow of the tug 3 as indicated by the dotted lines in Figure 2. If desired the bow of the tug 3 may have a flat surface 4 as shown in Figure 1 instead of the more usual pointed end in order to abut against a corresponding flat surface at the bottom of the notch 2 when the tug and barge are interconnected.

At the end of each wing of the barge defining the notch 2, a casting 5 is provided which has a projection extending inwardly into the notch and provided on its forwardly facing surface with a rail 6 extending at an angle of about 45 to the longitudinal axis of the barge and on its rearwardlyfacing surface 7 with a strip 8 of non-metallic material. The surfaces 7 preferably extend at a steeper angle than 45" to the longitudinal axis of the barge.

The tug is provided, at the sides of its bow region, with a pair of recesses 9 which are adapted to receive the projections at the ends of the wings of the barge. A casting 11 is provided in the region of each recess, each casting having an engagement surface 12 which is adapted to about against the strip 8 of non-metallic material on the respective surface 7 at the stern of the barge when the tug and barge are connected together. A number of plungers extend through respective openings in the tug wall in the region of the recesses to engage with the rails 6 on the barge.

As shown in Figure 3, each plunger is mounted in a tubular sheath 13 which is provided in the casting 11 which is mounted on the wall of the tug 3. The plunger 14 is connected to a piston rod 15 of a hydraulic ram 16 which is mounted on the tug by suitable mounting means (not shown). The outer end of the plunger 14 is provided with a spherical seating for the reception of an engagement shoe 17 of non-metallic material which has a partially spherical inner surface adapted to mate with the spherical seating at the end of the plunger. The shoe 17 is secured to the plunger 14 by a pair of screws 18 which permit limited relative movement between the shoe and the plunger. The outer surface of the shoe 17 is substantially planar for engagement with the rail 6.

The number of plungers deployed on each side of the tug will depend on the relative sizes of the tugs and barges which are to be connected together. The plungers will normally be spaced apart by about one to one and a half metres and the number required will thus largely depend on the depth of the hull. For a barge of 3-400 D.W.T., four sets of plungers will normally be required on each side of the tug.

When it is desired to connect a tug 3 to a barge 1, the tug is manoeuvred into the notch 2 at the stern of the barge 1 and at this stage the plungers 14 are fully retracted to the position indicated by the dotted lines in Figure 3. The tug is advanced into the notch until the engagement surfaces 12 on the tug abut against the strips 8 on the engagement surfaces 7 of the barge. The hydraulic rams 16 are then operated to force the associated plungers 14 outwardly until the engagement shoes 17 engage the rails 6 on the barge. The castings 5 at the stern of the barge 1 are then positively gripped between the engagement shoes 17 and the surfaces 12 to give a rigid coupling between the barge and the tug. The barge can be released simply by operating the rams 16 to retract the plungers 14 and moving the tug astern to take it out of the notch 2 at the stern of the barge.

The angle of the rails 6 to the longitudinal axis of the barge 1 is chosen to be 45" because this is considered to be the best compromise between a secure coupling and undue stress on the barge wings. If the plungers acted outwardly, they would tend to "spread" the wings of the barge and would not be so effective in achieving a rigid connection.

On the other hand, a smaller angle would create problems in designing the bow of the tug which must be able to pass between the projecting castings 5 at the ends of the wings of the barge and yet still be able to grip said castings between the plungers and the engagement surfaces 12. The angle between the engagement surfaces 7 and 12 is, however, not critical.

It will be appreciated that, by means of the system according to the invention, a tug can be connected to a barge without having to match the trim of the tug to the barge since the clamps on the tug can engage the rails on the barge over a wide difference between the trim of the barge and tug.

By employing what is best defined as a "raked slot", the benefit of "mating" unaffected by draft differences is combined with a hydrodynamically desirable form of bow for the tug. While a prow of truncated form has been depicted in the drawings, this is not essential and a curved prow with tangential flanks may be utilised if desired. The shape of the bow form can be curved on the flanks if desirable because the fundamental principle of a rake slot or notch places no restriction on the choice of "true" form.

In order to reduce the cost of construction, the cross frames are desirable canted to match the rake of the bow so that they are then simply of rectangularform of equal depth. The side plates and bow plate do not require "working" because there are no compound curvatures. If a truncated prow and straight flanks are chosen as shown in the drawings, the bow plate is a rectangular plate and the flanks are flat plates. If a curved prow is desired, the bow plate is rolled to the specified radius and the flanks are flat plates. If an elliptical bow form is desired, the prow can again consist of a rolled bow plate and the flanking plates are simply wrapped around the frames after any necessary pre-rolling which may be required by the curvature. Regardless of the choice of construction, the result is a tug with a bow of acceptable hydrodynamic form.

The system according to the invention provides a canted joint across the principal axis of shear and bending and shares the stress between the barge wings which terminate far enough aft, at their lower extremity, to be near the centre of gravity of the tug which greatly reduces the resultant bending momenu when the tug is temporarily unsupported in heavy seas.

The invention is not restricted to the abovedescribed embodiment but variations and modifications may be made without departing from the scope of the invention. For example, instead of a hydraulic ram, a screw jack may be used to operate each plunger.

Claims (17)

1. A system for releasably interconnecting a tug and a barge in which the tug is provided with a bow having a predetermined rake and contour and the barge is provided at its stern with a notch having a configuration adapted to receive the bow of the tug in a close-fitting relationship, the barge being provided on each of its wings defining the notch at the stern with a rail extending in a transverse plane parallel to the rake of the tug bow, wherein the rails extend from the notch surface of the stern of the barge to form inwardly extending projections, wherein the tug is provided on both sides in its bow region with recesses adapted to receive said projections, and wherein the tug is further provided, in each said recess, in the bow region, with at least one plunger adapted to engage the respective barge rail to force engagement surfaces on the barge projections and tug recesses against one another to hold the tug to the barge in a releasable manner.

2. A system according to claim 1, wherein each plunger is arranged to be operated by means of a respective hydraulic ram.

3. A system according to claim 1, wherein each plunger is arranged to be operated by a screw jack.

4. A system according to claim 3, wherein the or each screw jack is arranged to be operated hydraulically.

5. A system according to claim 3, wherein the or each screw jack is arranged to be operated electrically.

6. A system according to any preceding claim, wherein the rake angle of the tug bow and notch and rails at the stern of the barge is in the region of 25 .

7. A system according to any preceding claim, wherein the surfaces of the barge rails against which the plungers are adapted to engage extend at an angle of 45 to the longitudinal axis of the barge.

8. A system according to any preceding claim, wherein the bow of the tug is provided with a flat surface and wherein the bottom of the notch in the stern of the barge is provided with a corresponding flat surface against which the flat surface of the bow of the tug is arranged to abut when the tug and barge are interconnected.

9. A system according to any preceding claim, wherein each rail of the barge is provided on a casting adapted to be secured to the end of a respective wing of the barge, the rails being provided on forwardly facing surfaces of said castings.

10. A system according to claim 9, wherein each casting is provided with a rearwardly facing surface having applied thereto a strip of non-metallic material to form said engagement surfaces against which part of the bow region of the tug is arranged to abut when the tug and barge are interconnected.

11. A system according to claim 10, wherein the tug is provided, in the region of each recess, with a respective casting having an engagement surface adapted to abut said strip of non-metallic material on the corresponding casting on the barge wings when the tug and barge are interconnected.

12. A system according to claim 11, wherein each plunger is mounted in a respective tubular sheath which is provided in the associated casting which is mounted on a respective wall of the tug in the bow region thereof.

13. A system according to any preceding claim, wherein each plunger is provided, at the end which is adapted to engage with the respective barge rail, with a spherically seated engagement shoe.

14. Asystem according to claim 13, wherein each engagement shoe has a part-spherical inner surface adapted to mate with a spherical seating at the end of the plunger, the shoe being secured to the plunger in such a manner as to permit limited relative movement between the shoe and the plunger.

15. A system according to claim 14, wherein the outer surface of each shoe is substantially planar for engagement with a respective rail on the barge.

16. A system according to any one of claims 13 to 15, wherein the engagement shoes are made of non-metallic material.

17. A system for releasably interconnecting a tug and a barge substantially as described herein with reference to the drawings.