Tug/barge Latching Mechanism

Abstract

A self-latching self-releasing mechanism for coupling and releasably locking a marine tug to a barge includes, in a preferred form, a non-powered latching mechanism of the hook type mounted at the aft end of the barge and a power-driven coupling mechanism mounted at the fore end of the tug. The power-driven coupling mechanism includes an eye mounted at the forward end of an elongated tubular nut adapted to be driven forwardly and rearwardly by a power drive screw shaft. The rearward end of the screw shaft is supported for rotation in the housing of the power drive. The power-drive housing is supported on a stub shaft mounted for universal movement in a support housing mounted on the tug. Translational thrust forces are transmitted through the screw shaft and its power-drive housing to the support housing. Self-latching and self-releasing of the latching mechanism is controlled by the direction of the axial movement of the tubular nut on the screw shaft.

Description

BACKGROUND OF THE INVENTION

This invention relates to mechanisms for coupling a marine tug to a barge.

More particularly, the invention relates to mechanisms for coupling together and locking releasably a tug and a barge in tandem arrangement, as distinguished from the alongside arrangement which is frequently used in harbor work.

The invention relates particularly to tug/barge coupling means where the aft end of the barge is provided with a recess or notch for receiving the prow or fore part of a tug which is to be releasably latched to the barge for pulling or pushing the barge which in most instances will be much larger than the tug.

SUMMARY OF THE INVENTION

A principal object of the invention is to provide a self-latching, self-releasing coupling mechanism for connecting a tug and barge together, with all of the power-driven components being located on the tug.

A further object is to provide a latching mechanism of the foregoing type in which the tug and barge, when latched together, are effectively integrated, with no freedom of relative motion between the tug and the barge.

A further object is to provide a power-driven, self-latching, self-releasing coupling mechanism for a tug and a barge for effecting a rigid connection therebetween, but with provision for aligning the component parts of the mechanism located on the tug with that located on the barge.

The foregoing, as well as other objects of the invention, are accomplished, in accordance with a preferred form of the invention, by providing a non-powered hook latch mechanism on the barge and by providing on the tug a power-driven coupling mechanism which includes an eye mounted at the forward end of a tubular nut adapted to be moved in the forward and rearward directions by rotation of a screw driven by a power drive assembly. Self-latching and self-releasing of the latching mechanism is controlled by the direction of axial movement of the tubular nut on the power-driven screw shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational illustration of a marine tug/barge coupling and latching mechanism, according to one embodiment of the present invention, the barge and tug being shown in unlatched positions, with the barge on the left and the tug on the right.

FIG. 2 is a schematic elevational illustration similar to that of FIG. 1 but showing the barge and tug in latched positions.

FIG. 3 is an end view in section, looking along the line 3--3 of FIG. 1.

FIG. 4 is an elevational view, in section, of the coupling mechanism on the tug, as seen looking along the bent line 4--4 of FIG. 3.

FIG. 5 is a view looking down along the line 5--5 of FIG. 4.

FIG. 6 is a perspective illustration of the latching mechanism on the barge, and the forward end of the coupling mechanism on the tug.

FIG. 7 is a plan view of the latching mechanism on the barge.

FIGS. 8, 9 and 10 are a series of schematic views illustrating the latching and unlatching of the tug and barge.

FIGS. 11 through 14 are a series of schematic views illustrating a modified form of latching apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated schematically, at the left-hand side of FIG. 1, is the aft end of a barge B having mounted thereon a non-powered hook-type latching mechanism. Illustrated schematically at the right-hand portion of FIG. 1, is the fore end of a tug T having mounted thereon a power-driven form of coupling mechanism adapted to co-operate with the hook mechanism on the barge B to automatically couple and uncouple the tug and barge vessels. The coupling mechanism on the tug T will be described first.

Referring to FIGS. 3, 4, 5 and 6, as well as to FIG. 1, an eye 45 is threaded or otherwise fitted into the forward end of a tube 42 and pinned against rotation relative to tube 42 as by pin 43. As seen best in FIG. 5, eye 45 includes a self-aligning spherical bearing or ball joint 48 whose function is to allow for mis-alignment of barge and tug components. Supported in spherical bearing 48 is a heavy latch pin 46 which projects laterally beyond each side of eye 45. Mounted in latch pin 46 for pivotal forward movement in a horizontal plane are a pair of legs 47, one on each side of eye 45. Legs 47 may be spring biased into the lateral positions shown in solid line in FIG. 5.

Referring to FIGS. 1 and 4, tube 42 is an elongated tube which, for assembly purposes, may be externally threaded at its rearward end of receiving an internally threaded collar 41 which is supported on a captive nut 40 mounted on elongated externally threaded shaft or screw 20. The forward end of screw 20 is of reduced diameter and non-threaded, and keyed thereto, as by a key 49, is a sleeve-bushing 44 which supports the forward end of screw 20 within the tube 42. Secured, as by welding, to the underside of tube 42, is a key 50 which is loosely fitted and supported in a slot 51 in a pedestal 52 mounted on the deck of the tug T.

Screw 20 extends rearwardly from tube 42 through the forward portion of a power drive housing 30 and into a rearward portion 130 which is secured, as by bolts, to the forward portion. The rearward portion 130 is secured, as by welding, to a stub shaft 131 which is screwed into a square nut 12 having spherical forward and rearward faces for universal movement in a ball type socket 13 mounted in a support housing 10 on the tug T. A key 132 locks the stub shaft 131 against rotation in the square nut 12, thereby preventing rotational movement of power-drive housing 30 in response to torque forces imposed on the housing 30.

Supported in housing 30 is a power drive which comprises a plurality of electric drive motors 32 (four being shown in FIG. 3) which are connected through suitable couplings 33 to pinions 34 which are engaged at spaced-apart positions with the peripheral teeth of a bull gear 35 mounted on and keyed to screw shaft 20, as by key 36. If desired, a positive brake (not shown) may be applied to one or more of the pinion shafts to lock the screw shaft 20 against rotation when it is not being driven by the power drive.

Screw 20 is adapted for rotation in housing 30 on a roller bearing assembly 39 located forwardly of the bull gear 35, and by thrust bearing assemblies 37 and 38 located rearwardly of the bull gear 35 and retained by a retaining nut 53 screwed on the end of screw shaft 20.

Reference is now made to FIG. 6 which is a perspective illustration of the non-powered latching mechanism mounted at the aft of barge B. Mounted on and strongly secured to the structure of barge B is a block pedestal 80 having a rearwardly extending shelf 81 which is received within a horizontal slot in the forward portion of a block 82 and pinned thereto by vertical pin 83. The rearward portion of block 82 is secured to the closed end of a flat U-shaped plate 84 having a pair of parallel legs 85 which extend rearwardly beyond the rear edge of barge B. The inner edges of legs 85 are outwardly divergent at the rearward ends of the legs, as seen at 86 in FIG. 6.

Welded to the inner edges of the legs 85 are vertical guide plates 87, the rearward end portions of which are divergent and inclined downwardly forming the divergent ramp surfaces 88. A pair of restraining blocks 89 are secured to the surface of barge B and are so positioned as to allow limited pivotal movement of the U-shaped member 84 on pin 83 in the lateral directions while preventing upward or vertical movement of member 84.

Pivotally secured to the rearward portion of block 82, as by a horizontal pivot pin 61, is a bifurcated hook latch member 60, and pivotally secured to the legs of latch member 60, as by pivot pins 63, are a pair of latch support legs 62, one on each side the latch member 60. The lower ends of legs 62 are supported on the ledge of L-shaped pedestal blocks 90, the rearward portion 91 of which projects upwardly to form stop members for the legs 62. Pedestals 90 are secured, as by welding, to legs 85 of the U-shaped plate 84.

OPERATION

To latch tug T to barge B, tug T is maneuvered into a position immediately rearward of barge B. In some instances, barge B will be specially designed and built for a tug connection and will have a notch or slot in its rearward end portion for receiving the bow or forward portion of tug T.

When tug T has been maneuvered into a position in alignment with barge B, which is the position indicated in FIG. 1, drive motors 32 are energized to drive pinions 34 to drive bull gear 35 rotationally, thereby driving rotationally the threaded shaft or screw 20.

Since key 50 in slot 51 of pedestal 52 prevents tube 42 from rotating, it will be seen that when screw 20 is driven rotationally, the tubular nut (comprising nut 40, collar 41 and tube 42) moves axially on screw 20, thereby causing a corresponding forward or rearward movement of eye 45.

It will, of course, be understood that, in the coupling operation, the drive motors 32 are so driven as to drive bull gear 35 and the screw 20 in a direction to cause the tubular nut (40, 41, 42) to move forwardly on the screw 20 in the direction of barge B.

Reference is now made to FIG. 7 which shows that latch pin 46 has a length which is less than the lateral spacing between the latch support legs 62, thereby to allow the latch pin 46 to pass between the legs 62. However, the foldable release legs 47, when in their normal laterally extended positions, shown in full in FIG. 5, are too long to pass between support legs 62.

FIG. 8 shows the action which occurs as eye 45, at the forward end of the tubular nut 40, 41, 42 approaches and engages with the hook type latching mechanism on the barge B. In FIG. 8, latch pin 46, in the right-most phantom position, has just engaged the inclined surfaces of the ramp portions 88 of guide members 87. The latch 60 and the support legs 62 are in the positions shown in phantom. As eye 45 continues to be driven forwardly by the action of the rotating screw 20, the latch pin 46 reaches the second phantom position just beyond the upper end of the ramps 88. Continued forward movement of eye 45 causes the one-way-acting release legs 47 to engage the latch support legs 62, and as eye 45 continues to move forwardly, the latch support legs 62 are pushed forwardly causing them to pivot counterclockwise, as seen in FIG. 8, about the pins 63.

As soon as the lower ends of the latch support legs 62 leave the pedestal 90, the bifurcated latch member 60, being no longer supported, starts to fall downwardly, and in so doing pivots clockwise about the pin 61. Continued forward movement of eye 45 carries latch pin 46 to the position shown in solid line in FIG. 8. In this position, the hook latch 60 has fallen from the phantom to the solid-line position shown in FIG. 8. The forward drive of screw 20 is now stopped, and drive motors 32 are reversed to drive the bull gear 35 in the opposite direction, thereby causing the tubular nut (40, 41, 42) and eye 45 to move rearwardly, in a direction away from barge B and toward the tug T.

Withdrawal of eye 45 and its pin 46 rearwardly in the direction of the tug, from the most forward position shown in solid line in FIG. 8, allows the hook latch member 60 to drop further downwardly into the position indicated in FIG. 9, and, when latch pin 46, riding on the edge surfaces of guide members 87, reaches the position illustrated in FIG. 9, the pin 46 is fully latched in the hook of latch member 60, with eye 45 positioned in the notch between the legs of the latch 60. Continued rotation of screw 20, in the direction to withdraw latch pin 46, now causes the tug T to be pulled toward the barge B until the tug and barge are in tight abutting relationship as illustrated in FIG. 9. Thereafter, the tug and barge operate as an integral unit, at least so far as thrust forces are concerned.

To unlatch the latching mechanism and decouple the tug T from the barge B, screw 20 is driven, by its shaft mounted motor drive, in a direction to cause the tubular nut (40, 41, 42) and latch pin 46 to move forwardly from the latched position shown in FIG. 9, toward the position shown in phantom in FIG. 10. As latch pin 46 is moved forwardly from the position shown in FIG. 9, with pin 46 riding on the edge surfaces of guide members 87, the hook latch member 60 is cammed pivotally upwardly by pin 46 and support legs 62 are cammed pivotally upward by legs 47. When the latch pin 46 reaches the forward position indicated in phantom in FIG. 10, the one-way-acting release legs 47 have been moved beyond the lower ends of latch support legs 62 and these legs 62 now drop pivotally in a counterclockwise direction about pins 63, from the position indicated in phantom in FIG. 10 to the vertical position indicated in solid line in FIG. 10. In this latter position, legs 62 support the hook latch 60 in the raised position shown in solid line in FIG. 10. The shaft-mounted motor drive is then reversed, and screw 20 is rotated in a direction to withdraw tube 42 and eye 45. As the latch pin 46 is withdrawn, the bifurcated latch member 60 remains in the raised position indicated in solid line in FIG. 10, being supported by the latch support legs 62 on the pedestal 90.

When, during the withdrawal of eye 45 and pin 46, the laterally extending release legs 47 reach the vertically positioned latch support legs 62, the legs 62 being prevented from moving counterclockwise by the upstanding stop portion 91 of pedestal 90, force the foldable legs 47 to fold pivotally inwardly, as indicated in phantom in FIG. 5, thereby allowing the eye 45 to be withdrawn. After eye 45 and release legs 47 have fully cleared the support legs 62, the release legs 47, are returned to their outwardly extended positions, shown in solid line in FIG. 5. This return may preferably be by spring means, not shown.

In the manner described above, the tug T and barge B are automatically latched together, and automatically released, by power drive mechanism located on the tug T. There is no lifting and lowering of the coupling shaft and hence no shocks to the latching system. No manual adjustments or operations are required. Latching and unlatching is achieved according to the directions of axial movements of the tubular nut. The capability of ramp surfaces 88 of guide members 87 to cam eye 45 upwardly to the necessary latching position accommodates to different levels of tug deck relative to barge deck. The capability of plate 84 and hook latch 60 to pivot laterally, to the limited extent permitted by retaining blocks 89, accommodates to misalignments in the axial or tandem directions. The capability of latch pin 46 to move universally in its spherical bearing 48 in eye 45 accommodates to horizontal and other misalignments. And the capability of screw 20 to apply a strong drawing force on the hook latch 60 enables the mechanism to draw the tug into tight locked engagement with the barge B, as indicated schematically in FIG. 9.

It is to be noted that none of the thrust forces (pull or push) are imposed on the power drive nor on its housing 30. Housing 30 merely rides along with any small axial movement of screw 20. All of the axial thrust forces are taken by the support housing 10. This is an important feature of the shaft-mounted drive disclosed in the present application. FIGS. 11 through 14 are a series of sequential views schematically illustrating a modified form of latching mechanism in which the hook member is on the tug T, at the forward end of the tubular nut, and the eye member is on the barge B. In FIGS. 11-14, a pair of pedestals 100 support therebetween a pivot pin 101 on which are mounted a pair of link arms 102 having at their forward ends a cross pin 103 which functions as the latch pin.

Pivotally supported on latch pin 103 are a pair of latch pin support legs 104, the lower ends of which normally rest on a pair of pedestals 105. Legs 104 are prevented from moving clockwise beyond the vertical position by an upstanding portion 106 of the pedestals 105.

Secured to the forward end of the tubular nut (corresponding to 40, 41, 42 in FIGS. 1-10 but not illustrated in FIGS. 11-14) is a hook latch member 110 having a configuration indicated in FIGS. 11-14. Secured to each side of hook latch member 110 is a fixed bracket 111 having pivotally secured thereto a leg 113 having a roller 112 at the outer end thereof.

When after the tug T and barge B have been brought into tandem alignment, the shaft-mounted motor drive is driven in a direction to move the tubular nut and its hook latch 110 forwardly, in the direction of the barge B. Rollers 112, being in alignment, or substantial alignment, with the latch-pin support legs 104, encounter the legs 104 and move the legs pivotally in a clockwise direction about the pin 103, as indicated in FIG. 11. When this happens, the link arms 102, being no longer supported by the legs 104, drop downwardly in a pivotal movement about support pin 101, and the latch pin 103 is carried down from the position shown in solid line in FIG. 11 to the position shown in phantom. This brings the latch pin 103 into the region of crook 114 of the hook latch member 110.

The shaft-mounted motor drive is now reversed and the screw 20 rotated in the opposite direction to withdraw the tubular nut, thereby to pull the latch pin 103 fully into the crook 114 of the hook latch 110. Continued rotation of screw 20 then pulls the tug T and barge B into tight abutting relation, as indicated in FIG. 12.

To release the latching mechanism of FIGS. 11-14, and uncouple the tug T from the barge B, the shaft-mounted drive mechanism is rotated in a direction to drive screw 20 rotationally in a direction to move the tubular nut 40, 41, 42 and its hook latch 110 forwardly, toward the barge B. When hook latch 110 is so moved, the latch pin 103 is cammed up the slope 115 of the hook latch. When hook latch 110 reaches the position indicated in dot-and-dash lines in FIG. 13, the latch-pin support legs 104 are clear of the rollers 112, and the latch-pin support legs 104 drop pivotally in a counterclockwise direction into a vertical position, up against the stop 106 of pedestal 105, as indicated in solid line in FIG. 13. In this position, the latch pin 103 is supported on the upper edge of the hook latch 110. The motor drive on tug T is then reversed to withdraw the hook latch 110. As soon as the latch pin 103 clears the end of the flat upper edge of the hook latch 110, the latch pin 103 drops down but only until the lower ends of the latch-pin support legs 104 reach the pedestal 105. Thereafter, the latch pin 103 is supported by the legs 104, as seen in FIG. 14.

As the shaft-mounted drive mechanism is continued to be rotated in a direction to withdraw the tubular nut 40, 41, 42 and the hook 110, the rollers 112 reach and push against the forward surfaces of the latch-pin support legs 104, as seen in phantom in FIG. 14. This forces rollers 112 and their support arms 113 to pivot inwardly, the arms 113 moving pivotally in the fixed bracket 111. This movement allows rollers 112 to clear the latch-pin support legs 104, as is indicated in FIG. 14. When the hook latch 110 is fully clear of the latch-pin mechanism on the barge B, the arms 113, spring biased by means not shown, move outwardly into the lateral positions indicated in FIGS. 11-13.

While two forms of latching mechanism have been illustrated and described, the preferred form is that illustrated in FIGS. 1-10 wherein the eye of the latch is mounted in a spherical bearing carried at the forward end of the power-driven tubular nut, since this form allows for misalignments between the latching mechanism on the tug and the latch component on the barge.

The invention has been described as particularly suited for latching a tug to a barge, and in such case the power drive, shaft screw and tubular nut are located on the tug. However, the latching mechanism described may also be used for latching together other forms of units, at least one of which is mobile.

The preferred form of drive is that illustrated and described, namely, a screw-and-tubular nut form of drive in which the power drive for the screw shaft is mounted in a housing which embraces the screw shaft, and wherein all of the thrust forces are taken by a ball joint housing mounted on the tug and which supports the power drive housing. The invention contemplates, however, other forms of reversible drive, as for example, a drive in which one of the latch components is mounted at the forward end of an extendible piston which may be driven by hydraulic, pneumatic, or other suitable form of reversible power drive.

In at least some of the tug/barge installations, as well as in other cases where the load demands are very great, it will be necessary or advantageous to install, in parallel, two or more coupling-and-latching mechanisms of the types described herein.

Claims

What is claimed is:

1. Apparatus for releasably coupling and latching together first and second units at least one of which is mobile, said coupling-and-latching apparatus comprising:

A. a first powered mechanism mounted on a first mobile unit, said first mechanism including:

a. an elongated screw shaft;

b. support means supporting the rearward end of said screw shaft on said first mobile unit for limited universal movement;

c. a reversible power drive mounted on and supported by said support means;

d. an elongated tubular nut on said screw shaft;

e. means preventing rotational movement of said nut while allowing axial movement thereof on said screw shaft in response to said nut being driven rotationally by said power drive;

f. a first latch component mounted at the forward end of said tubular nut and adapted to be moved axially forwardly and rearwardly on said screw shaft to effect self-latching and self-unlatching of said coupling-and-latching apparatus;

B. a second non-powered mechanism on a second unit, said second mechanism including:

g. a second latch component fixed mounted on said second unit and adapted to be engaged by said first latch component and to be latched thereto, and to be unlatched therefrom, in response to axial movement of said first latch component on said screw shaft, according to the direction of said axial movement;

h. one of said first and second latch components comprising a hook latch;

i. the other of said latch components comprising a latch pin adapted to be received within the hook of said hook latch when said first latch component is moved axially on said screw shaft into operative engagement with said second latch component.

2. Apparatus according to claim 1 wherein

a. said second mechanism includes a pair of spaced-apart support legs for supporting said second latch component in elevated non-latching position;

b. said first mechanism includes release means on said first latch component operative during forward movement thereof for engaging said support legs and removing the same from support position to allow said second latch component to fall from its elevated position into latching position;

c. said release means during rearward movement of said first mechanism passing by said support legs without disturbing the positions thereof.

3. Apparatus according to claim 2 wherein:

a. said second latch component includes a hook latch;

b. said first latch component includes a latch pin adapted to be received in the hook of said hook latch.

4. Apparatus according to claim 3 wherein:

a. said hook latch is mounted for pivotal movement in a vertical plane;

b. said hook-latch support legs are supported for pivotal movement in said hook latch.

5. Apparatus according to claim 4 wherein:

a. said hook latch is a bifurcated member having a gap;

b. said latch pin is supported in an eye mounted at the forward end of said tubular nut;

c. said eye is received within the gap of said hook latch when said latch pin is received in the hook of said hook latch.

6. Apparatus according to claim 3 wherein said second mechanism includes a ramp means for guiding said latch pin into said hook latch.

7. Apparatus according to claim 4 wherein said mounting for said hook latch is adapted for limited pivotal movement laterally.

8. Apparatus according to claim 4 wherein said mounting for said hook latch includes guide members for guiding said latch pin.

9. Apparatus according to claim 4 wherein a stop member is provided to limit the pivotal movement of said support legs in the rearward direction.

10. Apparatus according to claim 3 wherein said release means operative during forward movement of said first latch component includes a pair of lateral legs mounted on said latch pin for pivotal forward movement only, said lateral legs being adapted during forward movement to engage and move said support legs, and during rearward movement to be moved pivotally by said support legs to allow said lateral legs to pass by said support legs.

11. Apparatus according to claim 2 wherein:

a. said first latch component includes a hook latch;

b. said secnd latch component includes a latch pin adapted to be received in the hook of said hook latch.

12. Apparatus according to claim 11 wherein:

a. said latch pin is mounted for pivotal movement in a vertical plane;

b. said support legs are supported for pivotal movement on said latch pin.

13. Apparatus according to claim 12 wherein a stop member is provided to limit the pivotal movement of said support legs in the rearward direction.

14. Apparatus according to claim 13 wherein said release means operative during forward movement of said first latch component includes a pair of lateral legs mounted on said hook latch for pivotal forward movement only, said lateral legs being adapted during forward movement to engage and move said support legs, and during rearward movement to be moved pivotally by said support legs to allow said lateral legs to pass by said support legs.

15. Apparatus for releasably coupling together first and second units at least one of which is mobile, said coupling apparatus comprising:

A. a first powered mechanism mounted on a first mobile unit, said first mechanism including:

a. an extendible elongated rigid member;

b. means supporting the rearward end of said rigid member on said first mobile unit for limited universal movement;

c. a reversible power drive;

d. a first latch component mounted at the forward end of said extendible rigid member and adapted to be moved forwardly and rearwardly by said power drive;

B. a second non-powered mechanism on a second unit, said second mechanism including:

e. a second latch component fix mounted on said second unit and adapted to be engaged by said first latch component and to be releasably latched thereto;

f. one of said first and second latch components comprising a hook latch;

g. the other of said latch components comprising a latch pin adapted to be received within the hook of said hook latch when said first latch component is moved by said power drive into operative engagement with said second latch component;

h. said second mechanism including a pair of spaced-apart support legs for supporting said second latch component in elevated non-latching position;

i. said first mechanism including release means on said first latch component operative during forward movement thereof for engaging said support legs and removing the same from support position to allow said second latch component to fall from its elevated position into latching position;

j. said release means during rearward movement of said first mechanism passing by said support legs without disturbing the positions thereof.

16. Apparatus according to claim 15 wherein:

a. said second latch component includes a hook latch;

b. said first latch component includes a latch pin adapted to be received in the hook of said hook latch.

17. Apparatus according to claim 16 wherein said second mechanism includes a ramp means for guiding said latch pin into said hook latch.

18. Apparatus according to claim 16 wherein said release means operative during forward movement of said first latch component includes a pair of lateral legs mounted on said latch pin for pivotal forward movement only, said lateral legs being adapted during forward movement to engage and move said support legs, and during rearward movement to be moved pivotally by said support legs to allow said lateral legs to pass by said support legs.

19. Apparatus according to claim 16 wherein:

a. said hook latch is mounted for pivotal movement in a vertical plane;

b. said hook-latch support legs are supported for pivotal movement in said hook latch.

20. Apparatus according to claim 19 wherein:

a. said hook latch is a bifurcated member having a gap;

b. said latch pin is supported in an eye mounted at the forward end of said extendible rigid member;

c. said eye is received within the gap of said hook latch when said latch pin is received in the hook of said hook latch.

21. Apparatus according to claim 19 wherein said mounting for said hook latch is adapted for limited pivotal movement laterally.

22. Apparatus according to claim 19 wherein said mounting for said hook latch includes guide members for guiding said latch pin.

23. Apparatus according to claim 19 wherein a stop member is provided to limit the pivotal movement of said support legs in the rearward direction.