AU2015200605B2

AU2015200605B2 - Automatic Twistlock

Info

Publication number: AU2015200605B2
Application number: AU2015200605A
Authority: AU
Inventors: Ture Nyholm
Original assignee: Skrin Pty Ltd
Current assignee: Skrin Pty Ltd
Priority date: 2014-02-25
Filing date: 2015-02-07
Publication date: 2017-04-06
Anticipated expiration: 2035-02-07
Also published as: GB201502003D0; GB2523471A8; CN104859975B; AU2015200605A1; GB2523471B; NZ704638A; CN104859975A; GB2523471A

Description

Automatic Twistlock FIELD OF THE INVENTION 2015200605 07 Feb 2015 5 This invention relates to a twistlock having a single cone that is automatic in operation, such that generally vertical forces on the cone of the twistlock can be used both to lock a container in place as well as to unlock the container.

BACKGROUND OF THE INVENTION 10 Twistlocks are used in transport, and are commonly used with shipping containers conforming to ISO regulation (International Standards Organisation). Such twistlocks are predominantly used in shipping where the twistlocks interlock between corner castings of two adjacent containers, or in shipping or rail freight where containers are fixed to fixed castings provided on rail carriages or the deck of a ship. Other uses 15 also exist. Where the term corner casting or container casting are used in this specification they are intended to refer to castings of the type found on corners of shipping container, or fixed on a surface for connection with such containers.

Twistlock have traditionally taken the form of a housing, through which a shaft 20 extends joined to or formed with a respective cone on either end of the shaft and positioned on opposing sides of the housing. The cones are somewhat elongate to fit through the rectangular slot in the corner casting, and to lock within the corner casting on rotation to a position transverse to the slot. Where both cones are locked within a respective casting the two adjacent castings are locked together. 25

Various advances have been made in twistlocks and some of these have been directed at improving the inefficiencies of using manual twistlock. The operation of a manual twistlock requires that a workman unlocks all twistlocks so that the container can be lifted off. For loading the reverse is the case. In shipping containers are 30 stacked so that the worker need also to mount the stack of container to unlock the twistlock and also to remove them. Several proposals have been made for semiautomatic twistlocks to minimise the effort required in loading and unloading and several versions are commercially in use. These semi-automatic twistlocks facilitate loading, in that the cones are biased, for example, by the shafts being spring loaded 2 to a locked position. The lower cones of the twistlock are placed in position either on the bottom container or the fixed casting. The container is lowered onto the cones, which are so formed that the downwards vertical force impart a rotational force on the shaft which forces the cone into a position allowing the cone to pass through a slot in 5 the casting to the inside of the hollow casting, whereupon the cone snaps into the locked position within the container casting by reason of the torsional resistance conferred by the spring. 2015200605 07 Feb 2015

There is still however a considerable amount of work needed in the unloading with 10 such semi-automatic twistlocks because a lever or other device needs to be manually actuated to move the cone to an unlocked position, as a result each twistlock must be separately handled. Automatic twistlock that can be unloaded in a manner similar to that by which it is loaded are currently in use. 15 Automatic twistlocks are in use, particularly in rail transport. These have a cone comprising a lower surface so bevelled that lifting the container causes the cone to turn to the unlocked position thereby allowing release of the cone.

Automatic twistlocks, however, has several disadvantages, the primary disadvantage 20 arises as a result of rough and somewhat careless handling. Where the container is lifted by crane or gantry using a spreader movement is relatively stable with the container being lifted in a more or less even fashion. However, where facilities for lifting containers off of, for example, rail wagons, do not provide for repeatable lifting in an even fashion there is a high risk of jamming of one or more of the twistlock 25 engaging the container. It is practice in some facilities to lift containers off using a forklift and there can be significant tilting along the longitudinal axis of a container as well as rotating through the vertical axis of a container.

There is usually some sideways movement; it is rare for the corner castings of the 30 container to engage the top cone of the twistlock with only a vertical motion. As a result it is highly likely that the twistlocks may be tilted with respect to the fixed corner casting on loading. As a result the twistlock may become jammed in the corner casting so that the cone cannot rotate to align with the elongate slot of the casting on the container. 3 2015200605 07 Feb 2015

One proposal for addressing this is to facilitate the physically removal of the twistlock from the rail carriage in a manner suggest in US 5632586 by the present inventor. Nevertheless the twistlock will still jam or break where container is tilted of twisted 5 because of the corner casting jams between a downwardly facing surface of the cone of the twistlock and the twistlock housing. Such jamming requires the intervention of a worker to manually remove the twistlock or where the twistlock is broken it requires replacement. 10 It is an object of the present invention to provide an automatic twistlock that reduces jamming or at least provides the public with a useful choice.

For purposes of this specification the word "comprising" means "including but not limited to", and the word "comprises" has a corresponding meaning. Also a 15 reference in this specification to a document is not to be taken as an admission that the disclosure therein constitutes common general knowledge in Australia.

SUMMARY OF THE INVENTION

The present invention resides a twistlock with a cone comprising a downwardly 20 facing surface shaped to provide for an initial lifting phase of a container and a further lifting phase of a container, the initial lifting phase providing for a greater ease of lifting against rotational resistance on the cone compared to the further lifting phase.

In one form the invention could be said to reside in an automatic twistlock comprising 25 a shaft journalled for rotation in a housing, the housing comprising an upper portion for registering with a slot in a corner casting of an international shipping container, the shaft extending out of the top of the upper part of the housing and having a cone fixed thereto for rotation with the shaft, between a disengaged position aligned with the slot and an engaged position straddling the slot, a biasing means acting between 30 the housing and the shaft to bias the shaft and thus the cone to the engaged position, a downwardly facing surface of the cone comprising four lower quadrants defined around a pivot axis of the shaft, at least one lower quadrant comprising a lower contact path for contact with a side of the slot, said lower contact path angled upwardly and laterally outwardly so that on drawing the container upwardly the side 4 of the slot urges the cone and hence the shaft to rotate against the action of the biasing means toward the disengaged position and thus release from the corner casting; 2015200605 07 Feb 2015 the lower contact path comprising an initial lower contact part and a further 5 lower contact part, the initial lower contact part shaped so that more lift of the container is required to give a unit of rotation than the further lower contact part thus requiring less force to lift the container.

The provision of less resistance to lift at an initial phase of the rotation provides for 10 accommodation of some tilting of the container on a longitudinal axis without jamming, by reason of the greater ease of lifting.

In a preferred configuration the cone comprises the two lower contact paths each in a diagonally opposed lower quadrant of the cone. Thus two opposite sides of the slot 15 co-act on the cone to exert a rotational force thereon, and additionally tend to have a balancing effect on the cone to provide stability when the container is lifted off of the cone and thus the twistlock.

The at least one lower quadrant of the cone may comprise a transverse bevel on the 20 downwardly facing surface of the cone thereof, the bevel having an initial slope forming the initial contact part and a further slope forming the further contact part, the initial slope being steeper than the further slope.

In a second, preferable, form the lower surface of the at least one lower quadrant of 25 the cone may be shaped so that the initial lower contact part extends longitudinally along the lower quadrant and the further lower contact part extends laterally of the lower quadrant. The initial lower contact part of this second form provides for rotation of the cone which, in its engaged position, is at an angle to the side of the slot in the corner casting, thus the pressure along the angled cone imparts a rotational pressure 30 against the biasing means.

Preferably a downwardly facing surface of at least two longitudinally adjacent lower quadrants of the cone are angled upwardly longitudinally from a shaft proximal 5 portion towards a free end of the cone, to thereby form a lower cutaway portion of the lowermost surface of the cone and 2015200605 07 Feb 2015 a downwardly facing bevel is formed between a side of the cone in one of said two quadrants and a lateral central portion thereof, a lower cutaway ridge 5 formed at a lowermost portion thereof, the initial lower contact part traversing the lower cutaway ridge.

In a preferred form the lower cutaway portion is angled upwardly from an engaged contact portion of the downwardly facing surface of the cone where there is contact 10 between the downwardly facing surface of the cone and the side of the slot of the corner casting in the engaged position.

Preferably the cone comprises two lower cutaway portions a respective one extending to a respective one of the free ends of the cone. 15

In a preferred form the downwardly facing bevel ridge is adjacent a lateral centre of the cone.

Preferably a downwardly facing lower transverse ridge extends laterally of the at 20 least one lower quadrant of the cone from a free end proximal part of the lower cutaway, the lower transverse ridge being angled outwardly and upwardly of the lower cutaway bevel edge, the further lower contact part traversing the lower transverse ridge. 25 Preferably the lower transverse ridge extends upwardly from the lower cutaway bevel edge such that there is tangential contact between the lower transverse ridge and the edge of the corner casting slot.

Reference is made in this specification to two parts of the lower contact path 30 traversed by the slot of the corner casting which requires two differing amounts of force. There may additionally be provided an intermediate lower contact part requiring an intermediate force to traverse. Furthermore the invention will be understood to encompass two or more intermediate lower contact parts requiring two or more and differing intermediate forces to traverse. 6 2015200605 07 Feb 2015

It is also to be understood that there need not necessarily be two distinct lower parts of the lower contact path requiring two distinct and separate levels of force, instead there optionally may be provided a continuous increase in the force required to lift a 5 container. The lower contact path has a longitudinal component being longitudinal of the cone, a vertical component being vertical of the cone, and a transverse component being transverse of the cone. It will be understood than the greater the transverse component that a part of the lower contact path has the greater the rotational impact lifting against a side of the slot has on the cone, and thus greater 10 force is required to lift the container whilst that part is in contact with the side of the slot. The initial lower contact part thus has less transverse component that the further lower contact part, and thus when contact is made with the initial lower contact part less force is required to lift the container. 15 It is also to be understood that the invention encompasses a lower contact path that is, for example, curved, having a continuously increasing transverse component. It is however to be understood that this need not be increasing over the entire length of the lower contact path. 20 Additionally it will be understood that similar consideration come into play where the variation in force required for traverse is achieved by the slope of the lower contact path. In that case, the initial lower contact part is steeper and thus requires less rotation of the cone than the further lower contact part, and this may be embodied in two discrete lower parts. Alternatively, there may be one or more discrete 25 intermediate lower parts that require one or more intermediate levels of force to traverse. It will be understood that the invention also contemplates a continuous decrease in steepness of the lower contact path.

Further embodiments of the invention contemplate combination of variations of slope 30 together with variation in longitudinal, vertical and transverse components of the lower contact path that provide for an initial lifting phase of the container and a further lifting phase of the container, where the initial lifting phase provide a greater ease of lifting against rotation resistance of the cone compared to the further lifting phase. 7

In a further preferred form the cone comprises a respective lower contact path in all four lower quadrants of the cone. This allows for respective ones of two longitudinally adjacent lower quadrants to optionally contact opposite sides of the slots of the corner casting. The advantage of this configuration is that should the 5 twistlock or container be brought out of alignment such that either needs to be realigned then the lower quadrant that is normally not in contact can engage the opposite side of the slot and act to realign the cone. Such missalignment might occur when there is a missalignment between the shaft and the housing, for example, where a locking pin, limiting the rotation of the shaft in the housing, is 10 dislodged or otherwise disengaged. 2015200605 07 Feb 2015

Another benefit of the configuration of having a respective lower contact path in all four lower quadrants is that of requiring less metal. Additionally the weight of the cone is reduced from what it would otherwise be. 15 A fully automatic twistlock also has the capacity to release from the corner casting of a container, but also has the capacity to engage with a corner casting. Thus typically the upwardly facing surface has a pair of diagonally opposed upwardly facing bevels configured for contact with opposite sides of the slot of the corner casting so as to 20 urge the cone into the disengaged position for insertion through the slot of the corner casting.

The cone thus preferably comprises four upper quadrants defined around the pivot axis of the shaft at least one upper quadrant comprising an upper contact path for 25 contact with a side of the slot, said upper contact path angled outwardly from an uppermost surface of the cone so that on placing the container on the cone, the side of the slot urges the cone and hence the shaft to rotate against the action of the biasing means toward the disengaged position and thus allows entry into the corner casting. 30

The present invention also provides for an upwardly facing surface of the cone to be similarly shaped to the downwardly facing surface of the cone. 8

Preferably the cone comprises two upper contact paths each in a diagonally opposed upper quadrant of the cone. 2015200605 07 Feb 2015

In preference the cone comprises a respective upper contact path in all four upper 5 quadrants of the cone, particularly where the cone comprises a respective lower contact path in all four lower quadrants. This preferable form may provide for a symmetrically shaped cone.

Preferably the cone comprises a transitional path part between the bevel of an upper 10 quadrant and the transverse ridge of a corresponding lower quadrant, the transitional path part defining the widest part of the cone and being curved to facilitate traverse through the slot.

In one form the cone comprises a central aperture passing through from one 15 longitudinal side to the other. The provision of the central aperture results in reduction of weight of the cone.

Preferably an uppermost part of the upwardly facing surface sloping downwardly from the pivot axis of the shaft toward both fee ends of the cone. 20

In a preferred form the cone is integrally formed with the shaft, and is preferably cast as one piece.

The invention in another aspect will be understood to comprise a cone of any one of 25 the forms defined or described herein or any combination of two or more of these forms.

BRIEF DESCRIPTION OF THE DRAWINGS 30 For a better understanding the invention will now be described with reference to the drawings wherein: 9 2015200605 07 Feb 2015

Figure 1 is a side plan view of a twistlock of the illustrated embodiment with the twistlock housing shown in cross sectional view through B-B of figure 2, 5 Figure 2 is a downward plan view through A-A in Figure 1, showing detail of the biasing means and its arrangement in the twistlock housing relative to the shaft, Figure 3 Is a side plan view of a cone according to a illustrated embodiment of 10 this invention, Figure 4 is a bottom plan view of the illustrated embodiment of the cone, Figure 5 15 is a top plan view of the illustrated embodiment of the cone, Figure 6 is an end plan view of the illustrated embodiment of the cone, Figure 7 is a perspective view of the illustrated embodiment of the cone, 20 Figure 8 is a schematic bottom view of the cone in the disengaged position relative to the slot of a corner casting, Figure 9 is a schematic bottom view of the cone in the engaged position straddling the slot of the corner casting, 25 Figure 10 is a top view through a section of a corner casting showing the manner in which the cone straddles the slot in the engaged position. Figure 11 is a perspective view of the cone and an upper portion of the shaft, 30 showing the initial lower contact part and the further lower contact part of the lower contact path between a side of the corner casting and the cone of the twistlock, 10 2015200605 07 Feb 2015

Figure 12 is a side view of a twistlock according to the illustrated embodiment 5 with the cone in the engaged position and the corner casting of an international container, showing in cross sectional view, slightly lifted up from the twistlock, Figure 13 is a view similar to figure 12 except that the container is tilted and thus the contact with the cone of the twistlock is altered, Figure 14 10 is a schematic plan view of the twistlock with the cone in the engaged position, Figure 15 is a schematic top plan view of the twistlock with the cone missaligned and skewed the opposite direction to the usual engaged position, 15 Figure 16 is a somewhat schematic view of the side of the slot of the corner casting bearing against the cone when retrieved from the usual engaged position, Figure 17 20 is a somewhat schematic view of the side of the slot of the corner casting bearing against the cone when in the missaligned position.

DETAILED DESCRIPTION OF THE ILLUSTRATED AND EXEMPLIFIED EMBODIMENTS 25 The twistlock (10) of the illustrated embodiment comprises a shaft (11) journalled for rotation with a housing (12). The housing comprises an upper portion (15) that registers with a slot (16) in a corner casting (17) of an international shipping container. The shaft extends out of the top of the upper portion (15) of the housing and has a cone (20) attached thereto. The cone rotates with the shaft between a 30 disengaged position aligned with the slot, perhaps best seen in figure 8, and an engaged position as shown in figures 9, 11 and 14. In the engaged position the cone straddles the slot (16). A biasing means (18) in the form of a spring acts between the housing and the shaft to bias the shaft to the engaged position. 11 A downwardly facing surface (21) comprises four lower quadrants (21a, 21b, 21c, 21d) defined around a pivot axis (22) of the shaft. At least one of the four lower quadrants comprises a lower contact path (shown as 25 in figure 11) for contact with a side of the slot, as perhaps best seen in figures 11 and 12. The lower contact path 5 is angled laterally outwardly on the downwardly facing surface (21) of the cone so that on lifting the container upwardly side of the slot urges the cone and hence the shaft to rotate against the action of the biasing means toward the disengaged position and thus release from the corner casting. 2015200605 07 Feb 2015 10 The lower contact path (25) comprises an initial lower contact part (26) and a further lower contact part (27). The initial lower contact part is shaped so that more lift of the container is required to give a unit of rotation than the further lower contact part.

The cone comprises four lower contact paths, one in each of the four lower 15 quadrants (21a, 21b, 21cand 21d). These can be considered in pairs of diagonally opposed quadrants, thus one pair comprises lower contact paths in quadrants 21a and 21 c, and a second pair comprise lower contact paths in quadrants 21b and 21d.

Opposite sides (28, 29) of the slot (16) bear against the contact paths of two opposed 20 quadrants, for example, as illustrated in figure 9 these are quadrants 21b and 21 d, thereby co-acting to exert a rotational force against the cone (20) against the biasing means (18).

In the illustrated embodiment each of the contact paths (25) comprise a initial lower 25 contact part (26) that extends longitudinally along the downwardly facing surface of the cone and thus the respective lower quadrant, and the further lower contact part (27) extends laterally of the downwardly facing surface of the cone and thus the respective lower quadrant. The side of the slot impart a rotational pressure against the initial lower contact part (26) because the cone and hence the initial lower 30 contact part is at an angle to the side of the slot. The angle of the cone to the slot is approximately 45°. A downwardly facing surface of at least two longitudinally adjacent lower quadrants, for example 21a, and 21d or on the other hand 21b and 21c are angled upwardly 12 longitudinally from a shaft proximal portion toward a free end (34) of the cone to thereby form a lower cutaway portion (35) of the lowermost surface of the cone. In the illustrated embodiment two lower cutaway portions (35a, 35b) are angled upwardly to both free ends of the cone. The lower cutaway portion as illustrated is 5 angled upwardly from an engaged contact portion (40) being where there is contact between the side of the slot and the cone in the engaged position. 2015200605 07 Feb 2015 A respective downwardly facing bevel (36a, 36b, 36c, and 36d) is formed in each quadrant between a longitudinally central part and sides of the cone. A lower 10 cutaway bevel ridge (37) is formed at a lowermost portion of the bevel. The initial lower contact part (26) traverses the lower cutaway bevel edge. It can be seen that the bevel (36) for each quadrant does not extend to a lateral centre of the cone.

There is a central strip (38) that is generally flat between longitudinally adjacent bevels, nonetheless the central strip is narrow so the cutaway bevel ridge (37) is 15 adjacent the lateral centre of the cone.

In each quadrant there is also a downwardly facing lower transverse ridge (45a, 45b. 45c, 45d). The lower transverse ridge extends laterally of a respective quadrant, from a free end proximal part (46) of the lower cutaway. The further lower contact 20 part (27) of the contact path traverses the lower transverse ridge (45). Contact between a respective side of the slot of the corner casting and a respective transverse ridge may be tangential.

The illustrated embodiment also has the capacity to engage with a corner casting 25 automatically when the container is lowered on top of it. The cone thus comprises four upper quadrants (50a, 50b, 50c and 50d). Each of the upper quadrants comprise a respective upper contact path for contact with a side of the slot (16) of the corner casting. The sides of the slot on dropping down on the cone urge the cone and the shaft to rotate against the action of the biasing means toward the disengaged 30 position to allow entry of the cone into the corner casting.

The upper contact path comprises a respective bevel (51a, 51b, 51c, 51 d) extending downwardly in each upper quadrant. 13

The upwardly facing surface of at least two longitudinally adjacent upper quadrants, thus 50a and 50d on the one hand and 50b and 50c on the other, are angled downwardly longitudinally from a pivot axis toward a respective free end (34a and 34b) of the cone to thereby form a respective upper sloped portion (52a, 52b). 2015200605 07 Feb 2015 5

The cone also comprises a respective transition path part (53a, 53b, 53c, 53d) between the bevel of an upper quadrant and the transverse ridge of a corresponding lower quadrant. The transitional path part defines the widest part of the cone and is curved to facilitate traverse through the slot. 10

The illustrated embodiment also comprises a central aperture (55) passing through one longitudinal side of the cone to the other.

Figures 1 and 2 show more detail of the working of the illustrated embodiment. Shaft 15 (11) is journalled for rotation with the housing and has two bearings, an upper bearing (60) and a lower bearing (61). Two protrusions (62, 63) extend axially of the shaft, and can be inserted through the top of the housing (12) via a keyway (not shown) and rotated for engagement with a downwardly facing flange (64), that also acts as a bearing to stabilise the shaft relative to the housing whilst retaining the 20 same therein.

The biasing means (18) is a steel spring that comprises a coil, with a first end (71) engaging in a slot (72) extending upwardly from the lowest end of the shaft (73). The coil spring forms an elbow (74) that engages with a spring engaging slot (75) 25 extending from inside to out of the housing. The second end (76) of the spring extends directly from the elbow and abuts a locking pin (77) that is inserted through the housing to act as a stop to prevent the spring from disengaging from the housing. It can be seen that the slot in the shaft and the slot in the housing is aligned in figure 2, and it would thus be appreciated that should the pin be removed, that elbow could 30 be struck for example by a hammer and punch to remove the spring.

Figure 13 shows detail of the accommodation of tilting of the corner casting by the cone of the twistlock. Thus a second of the two sides (29) of the slot in the corner casting is shown lifted relative to the first of the two sides (28), and a top edge of the 14 second side (29) bears against lower cutaway ridge (37). As a result of the greater ease of lifting against rotational resistance the twistlock accommodates uneven lifting more easily and thus jamming of the twistlock is more often avoided than would otherwise be the case. 2015200605 07 Feb 2015 5

Figure 14 to 17 illustrates the benefit of having a lower contact path in four quadrants of the cone. Figures 14 and 16 show the engaged position of the cone (20) when in the normal engaged position where the cone straddles the slot (16) of the corner casting so that ends (34a, 34b) extend over respective sides (28, 29) of the slot. 10 Where locking pin (77) is inadvertently released or broken, then the cone will sometime move to the other way, for example as shown in figure 15. With the present invention instead of jamming by reason of a flat bottom of the cone bearing against an upward facing surface of the corner casting, side (29) of the slot can exert a rotational force against the contact path of the cone for example as shown in 15 figure17 along upper part (45b) of the contact path. Rotation shown by arrows (80, 81) is opposite to normal disengagement rotation.

Various features of the invention have been particularly shown and described in connection with the exemplified embodiments of the invention, however, it must be 20 understood that these particular arrangements merely illustrate and that the invention is not limited thereto and can include various modifications, which fall within the spirit and scope of the invention. 15

Claims

CLAIMS:

1. An automatic twistlock comprising a shaft journalled for rotation in a housing, the housing comprising an upper portion for registering with a slot in a corner casting of an international shipping container, the shaft extending out of the top of the upper part of the housing and having a cone fixed thereto for rotation with the shaft, between a disengaged position aligned with the slot and an engaged position straddling the slot, a biasing means acting between the housing and the shaft to bias the shaft and thus the cone to the engaged position, a downwardly facing surface of the cone comprising four lower quadrants defined around a pivot axis of the shaft, at least one lower quadrant comprising a lower contact path for contact with a side of the slot, said lower contact path angled upwardly and laterally outwardly so that on drawing the container upwardly the side of the slot urges the cone and hence the shaft to rotate against the action of the biasing means toward the disengaged position and thus release from the corner casting; the lower contact path comprising an initial lower contact part and a further lower contact part, the initial lower contact part shaped so that more lift of the container is required to give a unit of rotation than the further lower contact part thus requiring less force to lift the container over the initial lower contact part than the further lower contact part, the lower surface of the at least one lower quadrant of the cone is shaped so that the initial lower contact part extends longitudinally along the lower quadrant and the further lower contact part extends laterally of the lower quadrant, the cone comprising two lower contact paths each in a diagonally opposed lower quadrant of the cone, wherein a downwardly facing surface of at least two longitudinally adjacent lower quadrants of the cone are angled upwardly longitudinally from a shaft proximal portion towards a free end of the cone, to thereby form a lower cutaway portion of the lowermost surface of the cone, and a downwardly facing bevel is formed between a side of the cone in one of said two quadrants and a lateral central portion thereof, a lower cutaway ridge formed at a lowermost portion thereof, the initial lower contact part traversing the lower cutaway ridge.
2. The automatic twistlock of claim 1 wherein the lower cutaway portion is angled upwardly from an engaged contact portion of the downwardly facing surface of the cone where there is contact between the downwardly facing surface of the cone and the side of the slot of the corner casting in the engaged position.
3. The automatic twistlock of claim 1 or 2 wherein the cone comprises two lower cutaway portions a respective one extending to a respective one of the free ends of the cone.
4. The automatic twistlock of claim 3 further comprising a downwardly facing lower transverse ridge extends laterally of the at least one lower quadrant of the cone from a free end proximal part of the lower cutaway, the lower transverse ridge being angled outwardly and upwardly of the lower cutaway ridge, the further lower contact part traversing the lower transverse ridge.
5. The automatic twistlock of claim 4 wherein the lower transverse ridge extends upwardly from the lower cutaway ridge such that there is tangential contact between the lower transverse ridge and the edge of the corner casting slot.
6. The automatic twistlock of claim 5 wherein the cone comprises four upper quadrants defined around the pivot axis of the shaft, the cone further comprising two upper contact paths each in a diagonally opposed upper quadrant of the cone for contact with downwardly facing sides of the slot, said upper contact path angled outwardly from an uppermost surface of the cone so that on placing the container on the cone, the side of the slot urges the cone and hence the shaft to rotate against the action of the biasing means toward the disengaged position and thus allows entry into the corner casting.
7. The automatic twistlock of claim 6 wherein the cone comprises a respective lower contact path in all four lower quadrants of the cone and wherein the cone comprises a respective upper contact path in all four upper quadrants of the cone and wherein the cone comprises a transitional path part between the bevel of an upper quadrant and the transverse ridge of a corresponding lower quadrant, the transitional path part defining the widest part of the cone and being curved to facilitate traverse through the slot.