WO2009000045A1

WO2009000045A1 - Twistlock

Info

Publication number: WO2009000045A1
Application number: PCT/AU2008/000942
Authority: WO
Inventors: Ture Nyholm
Original assignee: Ture Nyholm
Priority date: 2007-06-26
Filing date: 2008-06-26
Publication date: 2008-12-31

Abstract

A twistlock for reversibly engaging with a comer casting of a shipping container to fasten the shipping container on a railway truck The twistlock comprises a housing with a top and a bottom. The bottom of the housing is connected or adapted for connection with a railway truck surface. The twistlock has an upright shaft with a corner casting engaging head on top, the shaft being rotatable relative to the housing between an engaged position and a disengaged position of the head. The head is elongate laterally with respect to the shaft and is in the disengaged position when aligned with a slot in a corner casting in which position it can fit through the corner casting. In the engaged position the head is angled with respect to the slot so that when positioned therein an underneath surface of the head engages with upwardly facing surfaces inside the corner casting to inhibit lifting of the container off of the twistlock. The shaft biased to the engaged position preferably by a spring. The shaft is journalled on the housing to form two bearings, an upper bearing at an upper portion of the shaft and a lower bearing at a lower portion of the shaft.

Description

TWISTLOCK

This invention relates to a fastener known as a twistlock which is used to secure international shipping container. In particular aspects the invention relates to a twistlock suitable for use in rail transport or similar land transport application.

BACKGROUND OF THE INVENTION

Twistlocks are commonly used in fastening International shipping containers either to load bearing surfaces or when placed in a stack fastening one on top of the other.

In particular in rail applications there is a severe limitation with regards to the height of the twistlock. Generally regulatory standards for height of twistlocks is calculated to take into account the minimum clearance allowed for bridges traversing a rail track. Thus the twistlocks for rail transport are low profile, in Australia a clearance from the rail truck surface to the bottom of the container is mandated at 28mm.

Typically rail trucks are multipurpose such that dedicated container transport trucks are not provided, and the twistlocks are removable from the load bearing surface so that other loads do not become snagged on the twistlocks damaging either or both, the load or the twistlock. The means to provide for removability is preferably simple but still provides for reliable and secure positioning of the twistlock on the rail truck surface.

Providing a low profile and removability as well as a sturdy design as required in a rail freight environment results in some design compromises. An example of a twistlock adapted for rail transport bearing in mind these constraints is described in Australian Patent Specification 746207. To maintain the required low profile the shaft of the twistlock described in the above specification is journalled to the housing via just one bearing, and as will be appreciated there is some instability in the shaft with just a single bearing. It will also be seen that the thrust bearing is incorporated relatively inaccessibly within the twistlock housing.

Twistlocks are generally left on rail trucks and as such are susceptible to tampering by vandals or others, and it is desirable that certain features are incorporated in the twistlocks making it more difficult to effect such damage. Additionally it is also desirable, because of the relative lack of visibility that there be provided a visible sign that the twistlock are properly positioned to function.

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

OBJECT OF THE INVENTION

It is an object of the present invention to provide a twistlock that obviates or reduces any one or more of the problems associated with prior art twistlock or at least provides the public with a useful choice.

SUMMARY OF THE INVENTION

The invention may be considered to arise from providing a twistlock for rail applications having a shaft journalled within a housing on an upper and a lower bearing with a spring acting on the shaft therebetween to bias the shaft and integral head into an engaged position.

In an alternative broad form, the invention may be said to reside in a twistlock for reversibly engaging with a corner casting of a shipping container to fasten the shipping container on a railway truck, the twistlock comprising, a housing having a top and a bottom, the bottom connected or adapted for connection with a railway truck surface, an upright shaft having a corner casting engaging head on top, the shaft being rotatable between an engaged position and a disengaged position of the head, the head being elongate laterally with respect to the shaft and being in the disengaged position aligned with a slot in a corner casting in which position it can fit through the corner casting, and in the engaged position being angled with respect to the slot so that when positioned therein an underneath surface of the head engages with upwardly facing surfaces inside the corner casting to inhibit lifting of the container off of the twistlock, the shaft biased to the engaged position, and the shaft bearing on the housing at an upper portion thereof and at a lower portion thereof.

Preferably a thrust bearing acts between the shaft and the housing and more preferably acts at the lowermost portion of the shaft and housing.

Typically a spring is provided to bias the shaft and head in the engaged position, and for simplicity the spring may be an elastomeric block which preferably is flat, perhaps in the form of a disc. Such a flat block, it will be understood, is vertically compact and as such is suitable for rail applications because there are tight constraints in terms of allowable height of the twistlock in rail transport. The shaft is preferably journalled for rotation on the housing either side of the spring, so that shaft bearings are located on both sides of the spring, this provides a more stable arrangement rather than having only one bearing on one side of the spring, with the spring otherwise having a larger capacity to pull the shaft off of a single axis of rotation leading to potential wear problems and, more concerning, a greater risk of jamming of the twistlock.

Preferably the shaft further includes an axial fastener at a bottom end. This is fastened to the shaft to firmly fit into the housing, and to secure it thereto. Preferably the fastener is a shaft nut that is secured to the lower portion of the shaft, the shaft nut being internally screw threaded, and the lower portion of the shaft being complementary screw threaded to that of the shaft nut. A lower portion of the shaft nut forms a flange, being expanded relative to an upper portion of the fastener. The fastener flange, in use, contacts a downwardly facing surface of the housing immediately adjacent the shaft, so that on tightening, the nut can, if required, draw the shaft downwardly into position, and more particularly defines the extent of axial play in the shaft, the fastener flange and downwardly facing surface of the housing thus act as the thrust bearing on rotation of the shaft. Preferably a lowermost shaft nut recess is provided in the housing so that the shaft nut can be accommodated within the housing and does not extend beneath it.

The outer surface of the upper portion of the shaft nut is preferably machined to have a circular cross section so that it can be journalled for rotation in the lower portion of the housing acting as a radial bearing. Shaft nut registering means is preferably provided to register the shaft nut to the shaft so that the two are not subject to relative rotation during use, that may otherwise lead to a loosening or undoing of the shaft nut from the shaft. The shaft nut preferably has a radially extending pin aperture therethrough and the shaft has an identically or similarly configured shaft aperture, bore or groove so that when the pin aperture and shaft aperture bore or groove are aligned a pin may be passed therethrough to secure the two together. The pin and co-aligned grooves or apertures thus jointly act as the registering means.

The provision of the lowermost shaft nut acting as a bearing minimises the height of the twistlock. This is advantageous in that the height restrictions posed on twistlocks for railway trucks can more easily be met whilst at the same time providing for a journal at a lower portion of the housing of the twistlock.

The housing preferably comprises a spring cavity, which spring cavity is formed laterally of the shaft. The spring, as indicated above, preferably comprises an elastomeric block suitably secured to both the housing and the shaft.

The spring may thus comprise an outer inflexible ring, that may be made of metal, and in use is secured to the housing, a ring of elastomer is bonded to the outer ring and extends inwardly thereof, the spring further comprising an inner inflexible ring bonded to the inside of the elastomer ring. The inner ring may also be formed of metal. The inner ring preferably has an inner surface shaped to fit over the shaft, having a shaft registering means to register with the shaft. The inner ring preferably has a close fit to the shaft, the shaft preferably having an irregularity of cross sectional shape onto which the spring is fitted and the inner surface of the inner ring has a complementary shape to act as the shaft registering means to register with the shaft. The irregularity preferably extends downwardly so that the shaft may be guided into the inner ring, before the shaft nut is secured thereto. It will be appreciated that the shaft will typically have a circular cross section to allow it to rotate in the housing, the irregularity in shape preferably takes the form of a flat, or other shaped recess, taken out of the circular cross sectional shape so that the shaft is still able to rotate, particularly at a lower portion thereof. In the alternative a key and keyway may be provided to prevent relative rotation.

The outer ring preferably includes an outwardly facing securing bore, the housing including a spring securing aperture with similar or the same dimension as the securing bore on the outer ring of the spring. A spring securing bolt is passed from the outside of the housing through the spring securing aperture and screwed into the bore. The outer ring of the spring may be expanded where the securing bore is formed so that the bore can be made deeper for the bolt to achieve greater purchase than would otherwise be possible.

The bolt comprises a head and a shank, a washer is preferably positioned over the shank, with a spring positioned between the bolt head and the washer, preferably a retainer, more preferably a retainer pin passing through the shank, retains the washer on the bolt shank. This provides a means of tightening the bolt in place with frictional engagement against the housing without the need for frictional engagement by the head of the bolt on an outwardly facing surface of the housing. It will be understood that the spring securing bolt also provides a means for a quick release of the twistlock in the event that that the twistlock becomes jammed and the container cannot be lifted therefrom. Thus the spring securing bolt of the one or more jammed twistlocks can be undone so that the shaft is decoupled from the tension of the spring and can therfore be rotated into the disengaged position and the container can then be lifted off.

In one form a bolt recess is provided in the housing, the spring securing aperture formed through the bottom of the bolt recess, such that when in position the bolt is sunken into the housing. The bolt in this form preferably includes an outwardly accessible socket of angular crossection such as may be engagable by an Allen key, or similar less readily available tool, to thereby make the bolt less readily accessible for tampering with. Alternatively protrusions may extend either side of the bolt head generally at the same level so that when the rail truck moves the bolt head is protected from accidental contact with a stationary object and being sheared off. It is also preferred to provide an indicator means that indicates that the spring is properly fastened and in place. The indicator means can comprise an elongate flexible indicator member secured at an inner end to the outer ring of the spring. An indicator aperture is formed through the housing and aligned tangentially with the outer ring of the spring. The indicator member when in position and fastened to a properly located spring extends out of a front of the housing to be clearly visible from the side of a railway truck. Should the outer ring move, the indicator will also move to indicate to the operator that the ring is not properly held, which fault can be rectified.

Preferably rotation limit means are provided to limit rotation of the shaft within the housing, between the engaged position and the disengaged position. The limit means may comprise a protrusion extending downwardly from the head and a limit passageway formed in the housing adjacent the head, said limit passageway having a respective stop means at both ends, the protrusion extending into the passageway and rotation of the head limited by engagement of the protrusion by a first of the stop means at a first end of the . passageway when in the disengaged position and engagement of the protrusion by a second of the stop means at the second end of the passageway when the head is in the engaged position. It will also be understood that the influence of the spring will bias the protrusion against the second end, that is, when the head is in the engaged position. This arrangement thus provides for a positively limited arc of rotation of the head and shaft.

It will also be appreciated that the rotation limit means may be provided by a protrusion extending upwardly from the housing into a similar passageway in the head, in a similar arrangement.

The twistlock of this invention is preferably a removable twistlock. In one form the twistlock comprises slide means at a lower portion, for engaging with track means, so that the twistlock can be slid into and out of the track means. Preferably, in use, the track, means is fixed to an upwardly facing surface of a railway truck and positioned so the twistlock can be slid lateral to the direction of movement of the railway truck. Preferably also the track means comprise a slide registering means to register with the slide means when in the fully inserted position, to thereby inhibit lateral movement once in place. In one form the track means comprise a pair of spaced apart tracks. In one form these are incorporated into a base, the base comprising a transverse rear member and two forwardly extending spaced apart arms, together forming the generally U shaped base, each one of the pair of tracks is formed on the inside of a respective one of the arms. In a preferred form the arms are undercut perhaps in an approximate reverse bevel so that a ledge is form in an upper part of the arm thus providing an overhang that acts as the track. The overhang may be continuous or may be provided in discrete parts. A ridge, being continuous or in discrete parts, is formed at a lowermost portion of both sides of the housing. The ridge fits under the overhang formed in the arms to enable sliding of the housing into the base, thus acting as the guide. It will be understood that preferably a close fit is formed between the housing ridge and the overhang in the base so that there is minimal transverse, vertical and/or horizontal play therebetween. It will also be understood that the overhang of the sides acts to retain the twistlock housing against a lifting force, so that the twistlock stays on the rail truck when the container is lifted therefrom.

The transverse rear member of the base acts as a stop to define the maximum extent to which the housing can be inserted into the base. The arms preferably have a retainer aperture transversely therethrough, and a housing retainer pin can pass therethrough to retain the housing to prevent movement along the track. Preferably the arms extend past the slides of the housing, or the housing, so that the retainer pins fit closely against an outer end of the housing when fully inserted, that is, abutting against the transverse rear member of the base.

The twistlock is preferably a fully automatic twistlock, as these are usual in operation for single stack container operations such as used in rail transport. A fully automatic twistlock is one where manual movement of the shaft is not required either for loading or unloading of containers, and rather rely on downwardly or upwardly forces imparted by the corner casting on angled surfaces of the twistlock head to urge the head into the disengaged position against the action of the spring. This use has evolved particularly because any manual operation is labour intensive and the torsional forces of the springs used in rail twistlocks are not that high given that containers are not stacked and therefore the vertical forces on containers carried on trains are not as extreme as might be experienced in, for example, maritime transport.

It will also be understood that the invention may comprise the combination of a twistlock and a base as defined or described herein. Further the invention might encompass a railway truck fitted with a plurality of spaced apart bases with or without twistlocks held therein.

For a better understanding the invention will be described with reference to the drawings of substantially one embodiment of the invention although minor variations of this embodiment may exist between the different drawings. In the drawings

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 : is a combination view of a cross section of the housing taken through I -

I of figure 2 showing the shaft and head (not in cross section) in place,

Figure 2: is a cross sectional view of the housing taken through II - II of figure 1 showing detail of the spring and indicator,

Figure 2a: is a partial cross sectional somewhat schematic view of the spring securing bolt,

Figure 3 : is a perspective view of the shaft and head with shaft nut in place,

Figure 4: is a side view of the shaft and head,

Figure 5 : is a detailed view of a lowermost part of the shaft showing the groove for registering with the shaft nut via a pin,

Figure 6: is a cross sectional view of the shaft nut taken through VI - VI of figure Figure 7: is a cross sectional view of the shaft nut taken through VII - VII of figure 6,

Figure 8: is an end view of the shaft and head,

Figure 9: is a cross sectional view through the head and partially of the shaft taken through IX - IX of figure 11,

Figure 10: is a lateral cross sectional view of the shaft taken through X -X of figure 8 showing detail of circular cross section and the flat for engaging the spring,

Figure 11: is plan view from the top of the head, showing the maximum possible degree of rotation of the head,

Figure 12: is a cross sectional view of the housing taken through XII - XII of figure 15,

Figure 13 : is a cross sectional view of the housing taken through XIII - XIII of figure 15,

Figure 14: is a plan view of housing showing the angular extent of the limit passageway,

Figure 15: is a cross sectional view of the housing taken through XV -XV of figure

12,

Figure 16: is plan view form the open end of the base to capture the twistlock on the rail truck surface, Figure 17: is a cross sectional view through an arm of the base taken through XVII - XVII of figure 18,

Figure 18: is a plan view from above of the base,

Figure 19: is a plan view from the front of the twistlock positioned in the base with the head in the engaged position,

Figure 20: is a plan view from above of the twistlock positioned in the base with the head in the engaged position,

Figure 21 : is a plan view from a side of the twistlock positioned in the base with the head in the disengaged position,

Figure 22: is a plan view from the top of the twistlock positioned in the base with the head in the disengaged position,

Figure 23: is a cross sectional view similar to that of figure 13, except somewhat enlarged, and

Figure 24 is a partial view showing the a horizontal cross section of the shaft, and showing the rotation of the head relative to a slot in the corner casting of a standard international shipping container.

DETAILED DESCRIPTION OF THE ILLUSTRATED AND EXEMPLIED EMBODIMENTS OF THE INVENTION

This invention relates to a twistlock, particularly one suitable for use in rail transport applications, that typically will be of compact vertical dimensions.

The twistlock comprises a housing (10) with a top (11) and bottom (12), the bottom connected or adapted for connection with a railway truck surface. The twistlock includes an upright shaft (20) that has a head (21) on top of the shaft. The head is rotatable between an engaged position (25) and a disengaged position (26). The head is elongate laterally of the shaft and is in the engaged position when aligned with a slot (30) in a comer casting of a container. A biasing means in the illustrated embodiment comprises a spring (31) that biases the shaft and head to the engaged position. The shaft bears radially on the housing at an upper portion (35) and lower portion (36) thereof, and in the illustrated embodiment the upper portion and lower portion are respectively above and below the spring.

At a lower end the shaft includes a shaft nut (40) (or fastener) that includes an expanded lower portion (41) taking the form of what may be described as a flange and a upper portion (42) of the shaft nut accordingly being narrower. The shaft nut is internally threaded (43), with a lower portion (44) of the shaft being complementary screw threaded (45) so that the shaft nut can be secured thereto (see figure 3). In use (see figure 1) an upper surface (46) the fastener flange (41) contacts a downwardly facing surface (42) of the housing immediately adj acent the shaft, acting as a thrust bearing thereagainst against axial play in the shaft.

An outer surface (47) of the upper portion of the shaft nut is machined in circular cross section so that it acts as a radial bearing against inwardly facing surface (36) of the lower portion of the housing which is machined in complementary fashion. It can be seen that the shaft is journalled for rotation at an upper portion and a lower portion of the housing, and that the spring acts on the shaft between the two axial bearings.

The shaft nut has a pin aperture (50) extending radially therethrough and the shaft has a radially extending groove (51) extending inwardly from a lowermost surface, being of similar dimension to the pin aperture (50), so that when aligned a pin (52) may be passed therethrough to act as a registering means to secure the shaft and shaft nut together to prevent relative rotation, unless withdrawn.

A lower shaft nut recess (55) is provided in a lowermost part of the housing to accommodate the shaft nut which thus does not extend beneath the housing, so that the shaft nut and shaft is thus adapted for support over a rail truck or similar support surface. The housing comprises a spring cavity (56) formed laterally of the shaft, and accommodates the spring (31). The spring comprises an outer inflexible ring (60) an elastomeric block (61) in the form of a central ring and an inner ring (62). The outer ring and the inner ring are made of metal and are bonded to the elastomeric block. The inner surface (63) of the inner ring is generally circular to provide for a close fit over the shaft (20). The shaft has an irregularity of cross sectional shape in the form of a flat (64) cutaway from the otherwise circular cross sectioned shaft. The inner surface of the inner ring has a complementary flat (65) which together with the flat (64) of the shaft act as a register means to register the inner ring on the shaft, perhaps best seen in figure 2. An outwardly facing securing bore (66) is formed into a first expanded portion (67) of the outer ring the securing bore being internally screw threaded. The twistlock housing includes a spring securing aperture (68) with similar or the same dimensions as the securing bore. A spring securing bolt (69) passes from the outside of the housing through the spring securing aperture and is screwed into the securing bore to hold the outer ring in fixed position relative to the housing.

An indicator means comprising an elongate flexible indicator member (70) is secured at an inner end (70a) to a second expanded portion (71) of the outer ring. The indicator member passes through an indicator aperture (72) formed through the housing generally tangentially aligned with the outer ring of the spring. An outer end (70b) of the indicator means extends out of the front of the housing so as to be clearly visible from the side of a railway truck when the spring is in position and indicator is properly fastened.

Rotation limit means (80) acts to limit the extent of rotation of the shaft relative to the housing. Rotation limit means comprise a protrusion (81) extending downwardly from the head (21) and a limit passageway (82) formed in the housing adjacent the head. The limit passageway has a respective stop means at both ends represented by the respective upright end walls (83, 84) of the limit passageway.

The twistlock housing comprises slide means at a lower portion taking the form of two ridges (90, 91) extending laterally from the lowermost edges of either side of the housing, and extending along the full length of both of the sides. A base (95) is provided to be fixed to the surface of a railway truck, generally a plurality of bases will be spaced apart regularly on the surface to coincide with the distance between corner castings on a standard international shipping container. The base (95) comprises a transverse rear member (96) and two forwardly extending spaced apart arms (97, 98) together forming a generally U shaped base. A track means is incorporated into the two arms. The two arms are undercut in an approximate reverse bevel (99) thus provide an overhang (100) that acts as a track. A respective ridge is of a complementary shape and fits under the overhang formed in the arms as perhaps best seen in figure 18, and are thus configured to enable sliding of the housing into the base. A respective retainer aperture (101, 102)) is formed transversely through each of the arms, the arms also extend past the side of the housing when fully inserted. Retainer pins (one of which is shown as 103) are inserted into the retainer aperture and abut a front of the housing to retain the housing within the base. It will be appreciate that the locking pins are not all that apparent to the untutored eye and thus are not obvious targets for vandals.

Typically the base will be welded to the surface of the rail truck, with the opening of the U shaped base facing outwards of the truck so that the twistlock can be slid into the base from the side of the truck.

It can also be seen that a protective wall (140) is provided on arm (97). The protective wall extends upwardly of arm (97) to cover the spring cavity opening (125), and thus prevents unauthorised access once the twistlock is fastened in place. This acts as an anti tamper means.

It will be appreciated that the shaft and the head are unitary in construction and forged or cast from a suitable grade of steel. The shaft is machined to the desired dimension. It can be seen (see particularly figure 3), that the flat (64) machined from the shaft extends from the bottom of the shaft to a position at which the inner ring of the spring engages, approximately two thirds of the way up the shaft. This enables the bottom of the shaft to be inserted into the inner ring of the spring on assembly. It can also be seen (for example figure 8) that the screw threaded (45) portion of the shaft is of somewhat lesser diameter to the remainder of the shaft, so that the shaft nut can be secured and tightened against a seat formed by the slight expansion provided at the upper part of the screw threaded portion.

The protrusion (81) extending downwardly of the head, and outwardly of the remainder of the shaft and is unmachined and is part of the cast product. The head of the twistlock is in this embodiment integrally cast with the shaft, although if wanted it may be separately made and suitably secured to the shaft, this is however not preferable. The head is shaped for fully automatic operation and thus includes diametrically oppositely positioned lower bevels (110, 111) that bear against the inner walls of the corner casting aperture (30) to urge the head and shaft to rotate against the action of the spring when the container is lifted off of the twistlock. Similarly the head includes diametrically oppositely positioned upper bevels (112, 113) to urge the head and shaft to rotate against the action of the spring when the container is placed onto the twistlock.

It can be seen particularly with reference to figure 24, that the head protrusion (81) and limit pathway, provide for a limit (114) to maximum rotation of the head which in the present embodiment is 45°.

The head includes two hollows (115, 116) at either end (see particularly figure 9). This is useful as a means of reducing weight of the head. An alternative in place of the two hollows is simply to provide for a one (or more) apertures through the head, it is however desirable not to do so due to a greater capacity to tamper with the twistlock.

The twistlock housing (10) comprises a lowermost portion (120) that includes slides (90, 91) a central spring containing portion (121) that is somewhat expanded relative to the other parts, and an upper portion (122) that is elongate and dimensioned to fit into the slot of a corner casting.

Internally the twistlock housing comprises a spring cavity (56) that is fully opened at a first side thus having a rectangular spring cavity opening (125). The spring cavity opening allows for access to the spring cavity for placement or removal of the spring (31) which can simply be slid into place when disengaged from the shaft. Similarly the indicator can be attached to the outer ring of the spring through the spring cavity opening.

A shaft bore (128) is provided vertically through an approximate centre of the housing. A surface defining the shaft bore is machined to provide an accurate rotational fit with the shaft, similarly the upper downwardly facing surface (42) of the shaft nut recess (55) is also machined to provide for an accurate rotation fit with the upwardly facing surface of the shaft nut. The shaft bore comprises two portions, an upper portion (35) and a lower portion (36), positioned respectively above and below the spring cavity. It can be seen particularly in figure 12 that the lower portion of the shaft bore is of wider cross sectional dimensions that the upper portion, reflecting the increased diameter of the shaft and shaft nut at the lower portion, the outer surface (47) of the upper portion of which is dimensioned to rotatably bear against the lower portion (36) of the shaft bore.

The indicator is made of a highly visible colour and from a flexible plastics material such as polyurethane. The inner end (70a) of the indicator may be fastened to the second expanded portion (71) of the outer ring of the spring by means of a rivet (129) that perhaps is welded thereto by induction welding. The rivet passes through an aperture in the inner end of the indicator. An inner portion of the indicator may be flattened which profile facilitates attachment to the outer ring of the spring. An enlarged outer portion of the indicator is desirable to facilitate visibility.

It can also be seen that the spring securing bolt that hold the spring in place comprises a spring bolt head (130) and a bolt shank (131). A washer (132) is fitted over the bolt shank and held in place by a retaining pin (133). A spring (134) is positioned between the bolt head and the washer, so that on fastening the spring nut frictional engagement is maintained against the outside of the housing. A spring securing bolt recess (135) accommodates the spring securing bolt within the housing so that it is not accessible to tampering or damage occasioned by contact with external objects when the rail truck is moving. Similarly the bolt head includes an outwardly accessible recess of angular cross section (136) such as is engageable by an Allen key. The embodiment with a securing bolt recess is particularly shown in figure 2. In an alternatively embodiment no securing bolt recess is provided, instead the bolt head extends outside of the housing (particularly shown in Figure 20). The central portion of the housing (121) include two outwardly extending protective protrusions (140, 142). These particularly provide protection against transverse striking by an object encountered during travel of the rail truck.

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

Claims

1. A twistlock for reversibly engaging with a corner casting of a shipping container to fasten the shipping container on a railway truck, the twistlock comprising, a housing having a top and a bottom, the bottom connected or adapted for connection with a railway truck surface, an upright shaft having a corner casting engaging head on top, the shaft being rotatable between an engaged position and a disengaged position of the head, the head being elongate laterally with respect to the shaft and being in the disengaged position aligned with a slot in a corner casting in which position it can fit through the corner casting, and in the engaged position being angled with respect to the slot so that when positioned therein an underneath surface of the head engages with upwardly facing surfaces inside the corner casting to inhibit lifting of the container off of the twistlock, the shaft biased to the engaged position, and the shaft journalled on the housing to form two bearings an upper bearing at an upper portion of the shaft and a lower bearing at a lower portion of the shaft.

2. The twistlock of claim 1 further comprising a thrust bearing acting between the shaft and the housing to limit axial movement of the shaft, said thrust bearing acting at the lowermost portion of the shaft and housing.

3. The twistlock of claim 1 wherein the thrust bearing takes the form of a shaft nut that is secured to the lower portion of the shaft, the shaft nut being internally screw threaded, and the lower portion of the shaft being complementary screw threaded to that of the shaft nut, a lower portion of the shaft nut forming a flange, being expanded relative to an upper portion of the shaft nut, the flange contacting a downwardly facing surface of the housing immediately adjacent the shaft to limit the extent of axial movement of the shaft, an outer surface of the upper portion of the shaft nut is machined to have a circular cross section so that it can be journalled for rotation in the lower portion of the housing thus acting as a radial bearing.

4. The twistlock of claim 3 wherein a lowermost shaft nut recess is formed in the housing so that the shaft nut can be accommodated therein.

5. A twistlock as in any one of claims 1 to 4 wherein the biasing means is a spring comprising an elastomeric block, said upper bearing located above the elastomeric block and the lower bearing located below the elastomeric block.

6. A twistlock as in claim 5 wherein the spring comprises an outer inflexible ring secured to the housing, the elastomeric block is formed as an annulus and is bonded to the outer ring and extends inwardly thereof, the spring further comprising an inner inflexible ring bonded to the inside of the elastomeric annulus the inner ring having an inner surface shaped to fit over the shaft, the twistlock further comprising a shaft registering means to register with the shaft.

7. The twistlock of claim 6 wherein the inner ring has a close fit to the shaft, the shaft having an irregular cross sectional shape, the inner surface of the inner ring having a complementary shape to fit over the irregular cross sectional shape so as to act as the shaft registering means to register with the shaft, the irregularity extends downwardly to the bottom of the shaft so that the shaft can be guided into the inner ring.

8. The twistlock of either claim 5 or 6 wherein the outer ring includes an outwardly facing securing bore, the housing including a spring securing aperture with similar or the same dimension as the securing bore on the outer ring of the spring, a spring securing bolt is passed from the outside of the housing through the spring securing aperture and screwed into the bore.

9. The twistlock of claim 8 wherein the bolt comprises a head and a shank, a washer is positioned over the shank, with a spring positioned between the bolt head and the washer, a retainer retains the washer on the bolt shank.

10. The twistlock of either claim 8 or 9 wherein a bolt recess is provided in the housing, the spring securing aperture formed through the bottom of the bolt recess, such that when in position the bolt is sunken into the housing.

11. The twistlock of any one of claims 8 to 10 wherein the housing comprises a respective protrusion extending on either side of the bolt head generally at the same level so that when the rail truck moves the bolt head is protected from accidental contact with a stationary object. 5

12. The twistlock of any one of claims 5 to 11 wherein the housing comprises a spring cavity, which spring cavity is formed laterally of the shaft, and said spring cavity being accessible from outside of the housing for insertion of the spring.

10 13. The twistlock of any one of claims 6 to 12 further comprising an indicator means that indicates that the spring is properly fastened and in place, the indicator means comprising an elongate flexible indicator member secured at an inner end to the outer ring of the spring, an indicator aperture being formed through the housing and aligned tangentially with the outer ring of the spring, the indicator member when in position and

15 fastened to a properly located spring extends out of a front of the housing, whereas when not fastened the indicator is retracted.

14. The twistlock of any one of claims 1 to 13 further comprising rotation limit means to limit rotation of the shaft within the housing, between the engaged position and the

20 disengaged position.

15. The twistlock of claim 14 wherein the limit means comprise a protrusion extending downwardly from the head and a limit passageway formed in the housing adjacent the head, said limit passageway having a respective stop means at both ends, the

25 protrusion extending into the passageway and rotation of the head limited by engagement of the protrusion by a first of the stop means at a first end of the passageway when in the disengaged position and engagement of the protrusion by a second of the stop means at the second end of the passageway when the head is in the engaged position.

30 16. The twistlock of any one of claims 1 to 15 further comprising slide means at a lower portion, for engaging with track means, so that the twistlock can be slid into and out of the track means.

17. The twistlock of claim 16 wherein the track means are adapted to be fixed to an upwardly facing surface of a railway truck and positioned so the twistlock can be slid lateral to the direction of movement of the railway truck, the track means further comprising a slide registering means to register with the slide means when in the fully inserted position, to thereby inhibit lateral movement once in place.

18. The twistlock of claim 17 wherein the track means comprise a pair of spaced apart tracks incorporated into a base, the base comprising a transverse rear member and two forwardly extending spaced apart arms, together forming the generally U shaped base, each one of the pair of tracks is formed on the inside of a respective one of the arms.

19. The twistlock of claim 18 wherein the arms have a retainer aperture transversely therethrough, and a housing retainer pin can pass therethrough to retain the housing to prevent movement along the track.

20. The twistlock of claim 19 wherein the transverse rear member of the base acts as a stop to define the maximum extent to which the housing can be inserted into the base, and the arms extend past the slides of the housing, or the housing, and the retainer pins fit closely against an outer end of the housing when inserted maximally.

21. The twistlock of any one of claims 16 to 19 when read through claim 12 wherein access to the spring cavity is through a spring cavity opening in a side of the housing, a protective wall extends upwardly of the one arm of the base adjacent the spring cavity opening, to above a level of the spring cavity to thereby cover the spring cavity opening when the housing is maximally inserted in the base.